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Postoperative complications are vital factors affecting the prognosis of patients with hepatocellular carcinoma (HCC), especially for complex hepatectomy. The present study aimed to compare perioperative complications between laparoscopic and robotic complex hepatectomy (LCH vs. RCH). Patients with solitary HCC after complex hepatectomy were collected from a multicenter database. Propensity score-matched (PSM) analysis was adopted to control confounding bias. Multivariable analysis was performed to determine the prognostic factors. 436 patients were included. After PSM, 43 patients were included in both the LCH and RCH groups. The results showed that compared to LCH, RCH had lower rates of blood loss and transfusion, and lower postoperative 30-day and major morbidity, and post-hepatectomy liver failure (PHLF) (all P < 0.05). Additionally, the length of hospital stay was shorter in the RCH group (P = 0.026). Multivariable analysis showed RCH is an independent protective factor for reducing the 30-day morbidity, major morbidity and PHLF. RCH has advantages over LCH in the minimally invasive treatment of complex HCC, as it can reduce the incidence of postoperative morbidity. Therefore, RCH should be considered for patients with HCC who require complex hepatectomy. [ABSTRACT FROM AUTHOR]

Annotating large-scale datasets to train modern convolutional neural networks is prohibitively expensive and time-consuming for many real tasks. One alternative is to train the model on labeled synthetic datasets and apply it in the real scenes. However, this straightforward method often fails to generalize well mainly due to the domain bias between the synthetic and real datasets. Many unsupervised domain adaptation (UDA) methods were introduced to address this problem but most of them only focused on the simple classification task. This paper presents a novel UDA model which integrates both image and feature level based adaptations to solve the cross-domain object detection problem. We employ objectives of the generative adversarial network and the cycle consistency loss for image translation. Furthermore, region proposal based feature adversarial training and classification are proposed to further minimize the domain shifts and preserve the semantics of the target objects. Extensive experiments are conducted on several different adaptation scenarios, and the results demonstrate the robustness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Object proposal generation, as a preprocessing technique, has been widely used in current object detection pipelines to guide the search of objects and avoid exhaustive sliding window search across images. Current object proposals are mostly based on low-level image cues, such as edges and saliency. However, objectness is possibly a high-level semantic concept showing whether one region contains objects. This paper presents a framework utilizing fully convolutional networks (FCNs) to produce object proposal positions and bounding box location refinement with Support Vector Machine (SVM) to further improve proposal localization. Experiments on the PASCAL VOC 2007 show that using high-level semantic object proposals obtained by FCN, the object recall can be improved. An improvement in detection mean average precision is also seen when using our proposals in the Fast R-convolutional neural network framework. In addition, we also demonstrate that our method shows stronger robustness when introduced to image perturbations, e.g., blurring, JPEG compression, and salt and pepper noise. Finally, the generalization capability of our model (trained on the PASCAL VOC 2007) is evaluated and validated by testing on PASCAL VOC 2012 validation set, ILSVRC 2013 validation set, and MS COCO 2014 validation set. [ABSTRACT FROM PUBLISHER]

Background: The long-term prognosis of patients with hepatocellular carcinoma (HCC) after surgery remains far from satisfactory, especially in patients with microvascular invasion (MVI). This study aimed to evaluate the potential survival benefit from adjuvant lenvatinib for patients with HCC and MVI. Methods: Patients with HCC after curative hepatectomy were reviewed. All patients were divided into 2 groups according to adjuvant lenvatinib. Propensity score matching (PSM) analysis was used to reduce selection bias and make the results more robust. Survival curves are shown by the Kaplan-Meier (K-M) analysis and compared by the Log-rank test. Univariate and multivariate Cox regression analyses were performed to determine the independent risk factors. Results: Of 179 patients enrolled in this study, 43 (24%) patients received adjuvant lenvatinib. After PSM analysis, 31 pairs of patients were enrolled for further analysis. Survival analysis before and after PSM analysis showed a better prognosis in the adjuvant lenvatinib group (all P <.05). The adverse events associated with oral lenvatinib were acceptable. Multivariate Cox regression analysis showed that adjuvant lenvatinib was an independent protective factor for improving overall survival (OS) (hazard ratio [HR] = 0.455, 95% confidence interval [CI] = 0.249-0.831, P =.001) and recurrence-free survival (RFS) (HR = 0.523, 95% CI = 0.308-0.886, P =.016). Conclusions: Postoperative adjuvant targeted therapy can improve the long-term prognosis of patients with HCC and MVI. Therefore, in clinical practice, oral lenvatinib should be recommended for patients with HCC and MVI to decrease tumor recurrence and improve long-term survival. [ABSTRACT FROM AUTHOR]

This study focused on the combined effect of ferrite content and thermal aging on the stress corrosion cracking (SCC) of CF8A by using an alternating current potential drop (ACPD) technique to measure the SCC growth rates in high temperature water environment. The results show that thermal aging and high δ-ferrite content increased the susceptibility to SCC. The SCC susceptibility to the factor of δ-ferrite content of CF8A is greater than that for thermal aging treatment. Furthermore, the SCC mechanisms at the crack tip were investigated using transmission electron microscopy (TEM). The formation of Fe oxide ahead of the crack tip enhanced the crack propagation along γ / δ-ferrite interface. For the specimen with high δ-ferrite content, the δ-ferrites were distributed in continuous networks, which provide continuous SCC-sensitive paths. [ABSTRACT FROM AUTHOR]

Patent claim parsing can contribute in many patent-related applications, such as patent search, information extraction, machine translation and summarization. However, patent claim parsing is difficult due to the special structure of patent claims. To overcome this difficulty, the challenges facing the patent claim parsing were first investigated and the peculiarities of claim syntax that obstruct dependency parsing were highlighted. To handle these peculiarities, this study proposes a new two-level parser, in which a conventional parser is imbedded. A patent claim is pre-processed in order to remove peculiarities before passed to the conventional parser. The process is based on a new dependency-based syntax called Independent Claim Segment Dependency Syntax (ICSDS). This two-lever parser has demonstrated promising improvement for patent claim parsing on both effectiveness and efficiency over the conventional parser. [ABSTRACT FROM AUTHOR]

Abstract: As closed-loop production becomes an increasingly viable strategy for product life cycle management, cost modelling and analytical tools for closed-loop production systems will become increasingly important. Existing tools based on life cycle costing (LCC) methods are lacking an integrated life cycle perspective in their approach – a perspective that cannot be overlooked when modelling closed-loop production systems. In this paper, we aim to solve this lack of integrated life cycle approach by proposing the product structure-based integrated life cycle analysis (PSILA) technique. It allows us to streamline the process of modelling a closed-loop production system for a complex product based on its product structure. Through this technique, we developed a cost model of a closed-loop production system for a flat-panel (FPD) monitor case study. In this case study, the results simulated by the cost model show an increase in the economic performance when closed-loop production is adopted for the FPD monitor. Deeper analysis of the results in the case study indicate that in order to improve the economic performance of the closed-loop production system for the FPD monitor, the best strategy is not to merely focus on the reutilisation of materials. Instead, the option to remanufacture the FPD monitor for the secondary market should be explored to maximise the value reclaimed from the monitors in the EoL phase. The case study demonstrates that the cost model developed through the PSILA technique has the ability to function as a tool for analysing the economic performance of closed-loop production systems. More importantly, it has the ability to provide us with strategic insights on the cost feasibility of adopting closed-loop production strategies. [Copyright &y& Elsevier]

Abstract: Sustainable product development has become an important consideration by many product manufacturers in recent years. Manufacturers are adopting the life cycle approach in the development of products by incorporating the End-of-Life stage considerations at the design stage. To achieve this, however, there is the need to fill up the knowledge gap between the End-of-Life stage and design stage. Tools and methodologies for Design for End-of Life are required to assist designers to design products with better End-of-Life performance. In this paper, a novel Design for End-of-Life methodology is proposed. The methodology captures, represents and analyses the knowledge from the End-of-Life stage into a product End-of-Life Index. The index enables designers to make informed decision on design alternatives for optimal product End-of-Life performance using information from the End-of-Life stage. A case study illustrating the application of this End-of-Life Index on a power tool is subsequently presented. From the discussion, it was shown that the index was able to help to assess the End-of-Life performance of the design and also the changes made subsequently. In essence, this work done here has been demonstrated to be of assistance to designer to adopt Design for End-of-Life. [Copyright &y& Elsevier]

Background & aims: The benefit of postoperative adjuvant transcatheter arterial chemoembolization (pTACE) for patients with hepatocellular carcinoma (HCC), especially those with Child-Pugh (CP) B, remains controversial. This study aimed to assess the survival benefit of pTACE for HCC patients with CP B. Methods: Data from 297 HCC patients with CP B7 or B8 were analyzed, dividing them into groups with and without pTACE (70, 23.6% vs. 227, 76.4%). Propensity score matching (PSM) was used to control for confounding bias, and competing-risk regression was applied to address bias from non-cancer-specific death (NCSD). Results: Preliminary findings suggest that pTACE did not increase the incidence of severe complications in HCC patients with CP B7 or B8. Survival analysis indicated that the group receiving pTACE had better overall survival and recurrence-free survival than the group without pTACE after PSM. Furthermore, competitive risk analysis revealed that pTACE was an independent prognostic factor associated with reduced cancer-specific death incidence (subdistribution hazard ratio [SHR] 0.644, 95%CI: 0.378–0.784, P = 0.011) and recurrence (SHR 0.635, 95% CI: 0.379–0.855, P = 0.001). Importantly, pTACE did not increase NCSD. Subgroup analysis corroborated these results. Conclusion: Adjuvant TACE demonstrates the potential to significantly enhance the long-term prognosis of HCC patients with CP B7 or B8 following hepatectomy, particularly those with multiple tumors, large tumor size, macrovascular or microvascular invasion, and narrow resection margin. Hence, pTACE should be considered for patients at high risk of recurrence following thorough evaluation. [ABSTRACT FROM AUTHOR]

Abstract: The placement of micro-implants is a common but relatively new surgical procedure in clinical dentistry. This paper presents a haptics-based simulation framework for the pilot drilling of micro-implants surgery to train orthodontists to successfully perform this essential procedure by tactile sensation, without damaging tooth roots. A voxel-based approach was employed to model the inhomogeneous oral tissues. A preprocessing pipeline was designed to reduce imaging noise, smooth segmentation results and construct an anatomically correct oral model from patient-specific data. In order to provide a physically based haptic feedback, an analytical drilling force model based on metal cutting principles was developed and adapted for the voxel-based approach. To improve the real-time response, the parallel computing power of Graphics Processing Units is exploited through extra efforts for data structure design, algorithms parallelization, and graphic memory utilization. A prototype system has been developed based on the proposed framework. Preliminary results show that, by using this framework, proper drilling force can be rendered at different tissue layers with reduced cycle time, while the visual display has also been enhanced. [Copyright &y& Elsevier]

This study investigated the effects of dendrite axis and fusion boundary (FB) on the stress corrosion cracking (SCC) of 308 L/304 L welds by using an alternating current potential drop (ACPD) technique to measure the SCC growth rates in a simulated boiling water reactor environment. The results show that the ferrite/austenite interfaces are more susceptible to SCC in the SS 308 L welds. Furthermore, the angle between the applied load and the dendrite axis affects the SCC growth rate, and as this angle approached 90°, the SCC crack growth rate increases. The SCC cracks in the heat affected zone (HAZ) are mainly intergranular and some cracks propagate transgranularly. Furthermore, the primary crack in the HAZ propagates along the FB; when reaching FB, some secondary cracks are arrested at the FB. The residual strain caused by weld shrinkage is the crucial factor for the increase in SCC susceptibility in HAZ. [ABSTRACT FROM AUTHOR]

• The mechanism in scratching of CaF 2 with magneto-plasticity is uncovered. • A magnetic field significantly suppresses surface damage. • Brittle fracture is reduced by lower scratching stress with magneto-plasticity. • Dislocation nucleation and mobility are enhanced under a magnetic field. • A novel analysis of energy criterion and crystal plasticity is proposed. Magnetic field-tuned dislocation plasticity (i.e., magneto-plasticity) has attracted growing attention for assistance to limit the damage evolution of brittle ceramics in the material removal process. However, the mechanism controlling material removal of brittle ceramics with magneto-plasticity remains far from clear. Therefore, combined stress field modeling and molecular dynamics (MD) simulations were performed for scratching of a ceramic material, calcium fluoride (CaF 2), to investigate the magneto-plasticity mechanism during the material removal process of brittle ceramics. The stress field calculation with magneto-plasticity was first conducted, which suggests a general reduction in scratching stress on the subsurface under the magnetic field effect. It is also found that the degree of reduction in scratching stress is significantly influenced by the magnetic field intensity and direction as well as strain rate. The reduced scratching stress is responsible for the suppressed formation and evolution of cracks and defects in scratching. Subsequently, MD simulations in scratching of CaF 2 show that the application of a magnetic field can facilitate dislocation nucleation, enlarge the range of dislocation propagation, and regularize the dislocation distribution, indicating the advancement in elastic-plastic transition and dislocation mobility. From the views of energy criterion and crystal plasticity, a magnetic field can decrease the required work and resolved shear stress for dislocation slip, which results in a lower scratching stress level. The combined theoretical method of this study broadens the comprehension of magneto-plasticity on deformation mechanism in the material removal process of ceramics and offers theoretical direction for the application of magnetic field assistance in ceramic processing. [Display omitted] [ABSTRACT FROM AUTHOR]

Multi-label learning methods can be categorised into algorithm adaptation, problem transformation and ensemble methods. Some of these methods depend on a base classifier and the relationship is not well understood. In this paper the sensitivity of five problem transformation and two ensemble methods to four types of classifiers is studied. Their performance across 11 benchmark datasets is measured using 16 evaluation metrics. The best classifier is shown to depend on the method: Support Vector Machines (SVM) for binary relevance, classifier chains, calibrated label ranking, quick weighted multi-label learning and RAndom k -labELsets; k -Nearest Neighbours (k -NN) and Naïve Bayes (NB) for Hierarchy Of Multilabel classifiERs; and Decision Trees (DT) for ensemble of classifier chains. The statistical performance of a classifier is also found to be generally consistent across the metrics for any given method. Overall, DT and SVM have the best performance–computational time trade-off followed by k -NN and NB. [ABSTRACT FROM AUTHOR]

Recently, many methods have been proposed to deal with the problem of cross-domain semantic segmentation. Most of them choose to conduct domain adversarial training either on the high-level convolutional neural network (CNN) features or on the output segmentation maps. Typically, a relatively small weight is given to the adversarial training loss to avoid the problem of mode collapse. However, one potential weakness of these methods is that low-level CNN layers may receive little gradients for domain adaptation, especially when the network is deep. To address this problem, we propose to conduct an auxiliary adversarial training on the fused multi-level CNN features. Gradients for domain adaptation can thus flow into low-level CNN layers more easily along a shorter path. Experiments are conducted on the dataset of Cityscapes with using the source datasets of GTA5 and SYNTHIA, respectively. Quantitative and qualitative results certify the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to detect the printing failures (such as warpage and collapse) in material extrusion (MEX) process effectively and timely to reduce the waste of printing time, energy and material. Design/methodology/approach: The approach is designed based on the frequently observed fact that printing failures are accompanied by abnormal material phenomena occurring close to the nozzle. To effectively and timely capture the phenomena near the nozzle, a camera is delicately installed on a typical MEX printer. Then, aided by the captured phenomena (images), a smart printing failure predictor is built based on the artificial neural network (ANN). Finally, based on the predictor, the printing failures, as well as their types, can be effectively detected from the images captured by the camera in real-time. Findings: Experiments show that printing failures can be detected timely with an accuracy of more than 98% on average. Comparisons in methodology demonstrate that this approach has advantages in real-time printing failure detection in MEX. Originality/value: A novel real-time approach for failure detection is proposed based on ANN. The following characteristics make the approach have a great potential to be implemented easily and widely: (1) the scheme designed to capture the phenomena near the nozzle is simple, low-cost, and effective; and (2) the predictor can be conveniently extended to detect more types of failures by using more abnormal material phenomena that are occurring close to the nozzle. [ABSTRACT FROM AUTHOR]

Additively manufactured lattice structures enable the realisation of light-weight, multi-functional, structures. For example, lattices can be used for high stiffness and buckling resistance in sandwich structures or as support material for additive manufacturing. Topology optimisation and additive manufacturing are two technologies that allow the design, optimisation and manufacture of complex lattice designs. In this work, a new lattice optimisation methodology is presented that tailors the size, shape and orientation of individual lattice trusses in three-dimensional space by using principal strain fields obtained from topology optimisation. This new method of generating functionally graded lattices is shown both numerically and experimentally to be capable of generating lattice structures with greatly improved stiffness and strength when compared to lattice structures with a uniform lattice infill. Upper and lower relative density thresholds and minimum truss member sizes are included in the optimisation workflow to ensure that the optimised lattice designs are compatible with additive manufacturing process constraints. The functional grading method is also shown to be capable of generating conformal lattice structures in three dimensions, even for complex loading conditions and arbitrary volume boundaries. • A novel lattice infill methodology creates optimally aligned lattice structures. • Lattice structures are automatically generated using principal strain trajectories. • The lattices conform to arbitrary 3D design space volumes. • Optimally aligned lattice structures have higher stiffness and strength. • Additively manufactured lattices validate the optimisation predictions. [ABSTRACT FROM AUTHOR]

Abstract 3D bioprinting is a pioneering technology that enables fabrication of biomimetic, multiscale, multi-cellular tissues with highly complex tissue microenvironment, intricate cytoarchitecture, structure-function hierarchy, and tissue-specific compositional and mechanical heterogeneity. Given the huge demand for organ transplantation, coupled with limited organ donors, bioprinting is a potential technology that could solve this crisis of organ shortage by fabrication of fully-functional whole organs. Though organ bioprinting is a far-fetched goal, there has been a considerable and commendable progress in the field of bioprinting that could be used as transplantable tissues in regenerative medicine. This paper presents a first-time review of 3D bioprinting in regenerative medicine, where the current status and contemporary issues of 3D bioprinting pertaining to the eleven organ systems of the human body including skeletal, muscular, nervous, lymphatic, endocrine, reproductive, integumentary, respiratory, digestive, urinary, and circulatory systems were critically reviewed. The implications of 3D bioprinting in drug discovery, development, and delivery systems are also briefly discussed, in terms of in vitro drug testing models, and personalized medicine. While there is a substantial progress in the field of bioprinting in the recent past, there is still a long way to go to fully realize the translational potential of this technology. Computational studies for study of tissue growth or tissue fusion post-printing, improving the scalability of this technology to fabricate human-scale tissues, development of hybrid systems with integration of different bioprinting modalities, formulation of new bioinks with tuneable mechanical and rheological properties, mechanobiological studies on cell-bioink interaction, 4D bioprinting with smart (stimuli-responsive) hydrogels, and addressing the ethical, social, and regulatory issues concerning bioprinting are potential futuristic focus areas that would aid in successful clinical translation of this technology. [ABSTRACT FROM AUTHOR]

Purpose: Laparoscopic liver resection (LLR) for hepatocellular carcinoma (HCC) remains controversial, especially for tumors larger than 5 cm. We compared the short- and long-term outcomes of laparoscopic and open liver resection (OLR) for large HCC. Methods: Patients with large HCC after curative hepatectomy were enrolled. To compare the short-term outcomes, propensity score matching (PSM) and inverse probability treatment weighting (IPTW) were performed to reduce the effect of confounding factors, respectively. Subsequently, Cox-regression analyses were conducted to identify the independent risk factors associated with decreased recurrence-free survival (RFS) and poor overall survival (OS). Result: There were 265 patients enrolled in the final analysis: 146 who underwent OLR and 119 who underwent LLR. There was no significant difference between the OLR and LLR groups according to PSM and IPTW analysis (all P > 0.05). Multivariable analysis revealed that LLR was not independently associated with poorer OS (HR 1.15, 95% CI 0.80–1.67, P = 0.448) or RFS (HR 1.22, 95% CI 0.88–1.70, P = 0.238). Conclusion: There were no significant differences in perioperative complications or long-term prognosis between LLR and OLR for large HCC, which provides evidence for standard laparoscopic surgical practice with adequate surgeon experience and careful patient selection. [ABSTRACT FROM AUTHOR]

Functionally graded lattice core structures show a gradual and localised variation in their mechanical properties with the aim of improving structural performance whilst minimising weight. We present a novel approach to generate optimised functionally graded lattice core structures. Firstly, topology optimisation is performed to return the optimal core density distribution to minimise the structure's compliance subject to a mass constraint. A series of isostatic lines are then constructed with respect to the local principal stresses to generate a lattice structure spatially graded with respect to lattice cell size, aspect ratio and orientation. To validate this novel approach, optimisation is performed on a sandwich core structure subject to three point bending. Experimental tests confirm the greatly improved stiffness and strength properties (101% and 172% respectively) of the core as a result of spatially grading the lattice cells when compared to a benchmark core with uniform cell size of the same density. The new approach also significantly outperforms lattice structures with graded diameters as optimised by state-of-the-art commercial software packages. Non-dimensional core performance indices are formulated to express the relative specific stiffness and strength properties of the core for the three design approaches. [ABSTRACT FROM AUTHOR]

In a previous work, the Product Structure-based Integrated Life cycle Analysis (PSILA) technique was developed to conduct cost modelling and analysis of closed-loop production systems. In this paper, we expand the utility of this technique into carbon footprint (CFP) modelling and analysis of closed-loop production systems – enabling companies to make informed decisions on whether to adopt closed-loop production based not only on economic but also environmental performance. A description of the PSILA technique applied for carbon footprint modelling and analysis is explained, followed by a case study of closed-loop production of a flat-panel display (FPD) monitor to validate the technique. We verified the CFP result simulated by the model built through the PSILA technique, or PSILA-CFP model in short, against the result generated by a model built through the conventional Life Cycle Assessment (LCA) method. A benchmarking analysis was then conducted to compare the closed-loop production system against the linear production system. Through this analysis, we demonstrated how the CFP result can be broken down based on the product structure, thus enabling us to granularise the result and trace the impact of implementing a closed-loop production system to the individual modules, components and materials that are recovered, reutilised or treated in the system. The results were able to show that the implementation of the closed-loop production system for the FPD monitor can potentially result in an overall CFP reduction of 39.91 million kg CO 2 e, of which 90.03% is contributed by the closed-loop recycling of ABS. The other significant contributors of CFP reduction are from the closed-loop material recycling of the aluminium, which accounts for 8.13 million kg CO 2 e or 20.37% of the total CFP reduction. A sensitivity analysis was also carried out to investigate the effects of data uncertainties, which may invalidate assumptions made in the case study. In summary, we have successfully adapted the PSILA technique so as to provide decision support in the form of analytical insights on how a closed-loop production system will perform in terms of carbon footprint, why it performs this way and what to look out for if the decision is made to implement such a system. [ABSTRACT FROM AUTHOR]

Product appearance is one of the crucial factors that influence consumers' purchase decisions. The attractiveness of product appearance is mainly determined by the inherent aesthetics of the design composition related to the arrangement of visual design elements. Hence, it is critical to study and improve the arrangement of visual design elements for product appearance design. Strategies that apply aesthetic design principles to assist designers in effectively arranging visual design elements are widely acknowledged in both academia and industry. However, applying aesthetic design principles relies heavily on the designer's perception and experience, while it is rather challenging for novice designers. Meanwhile, it is hard to measure and quantify design aesthetics in designing artefacts when designers refer to existing successful designs. In this regard, this study aims to introduce a method that assists designers in applying aesthetic design principles to improve the attractiveness of product appearance. Furthermore, formulas for aesthetic measurement based on aesthetic design principles are also developed, and it makes an early attempt to provide quantified aesthetic measurements of design artefacts. A case study on camera design was conducted to demonstrate the merits of the proposed method where the improved strategies for the camera appearance design offer insights for concept generation in product appearance design based on aesthetic design principles. [ABSTRACT FROM AUTHOR]

Concept validation plays a critical role in product design especially in the early design phase of market-driven product design. Due to the presence of ambiguous information, arbitrary interpretation of user needs, and so on, design concept validation remains a challenging task. In this work, we aim to involve customers in the conceptual design phase so that understanding about customer needs, expectations, and satisfaction can be better altered through customer--design interaction. A framework for concept validation using digital prototyping is proposed to actively involve customers in three major validation tasks, i.e., specification solicitation, concept selection, and concept refinement. Technical challenges of involving customers in conceptual design using digital prototyping are discussed. Our experimental study based on smartphone dimension design reveals the capabilities of the proposed framework. Experimental results suggest when interacting through digital prototyping, customer satisfaction on design concepts can be enhanced by making alterations to customer needs, expectations, and satisfaction. [ABSTRACT FROM AUTHOR]

It is known that hydrophobic microfiltration membranes can be used for demulsification of oil-in-water (o/w) emulsion due to coalescence of oil droplets in membrane pores. This study demonstrates that a hydrophilic polymer membrane can be used for the demulsification of surfactant-stabilized water-in-oil (w/o) emulsions. The success of demulsification is dependent on the type of emulsions and membrane used. Membrane pore size and transmembrane pressure were found to affect demulsification efficiency (DM), while other factors, such as membrane thickness and initial water content have slight or almost no effect. A coalescence mechanism of the demulsification phenomenon is also discussed. The separation process is not based on sieving effects due to a difference in membrane pore size, but is determined by droplet interactions with membrane surface. [Copyright &y& Elsevier]

Chromia-forming ferritic stainless steel (FSS) is a highly promising interconnect material for application in solid oxide fuel cells. In this study, initial oxidation of chromium oxides was performed at 500–800 °C to understand the evolution of materials at an early stage. The structural variations in oxide scales were analyzed through scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffractometry (XRD), laser confocal microscopy (LSCM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Surface electrochemical properties were investigated through electrochemical impedance spectroscopy to understand how the heat treatment temperature affected surface impedance. Treatment temperatures higher than 700 °C facilitate the diffusion of Cr and Mn, thus allowing ferritic spinels to form on the surface and leading to high electrical conductivity. [ABSTRACT FROM AUTHOR]

The development of the Internet of things has prompted an exponential increase in the demand for flexible, wearable devices, thereby posing new challenges to their integration and conformalization. Additive manufacturing facilitates the fabrication of complex parts via a single integrated process. Herein, the development of a multinozzle, multimaterial printing device is reported. This device accommodates the various characteristics of printing materials, ensures high‐capacity printing, and can accommodate a wide range of material viscosities from 0 to 1000 Cp. Complete capacitors, inclusive of the current collector, electrode, and electrolyte, can be printed without repeated clamping to complete the preheating, printing, and sintering processes. This method addresses the poor stability issue associated with printed electrode materials. Furthermore, after the intercalation of LiFePO4 with Na ions, X‐ray photoelectron spectroscopy and X‐ray diffraction results reveal that the Na ions permeate the interlayer structure of LiFePO4, enhancing the ion migration channels by increasing the ion transmission rate. A current rate of 2.5 mAh ensures >2000 charge/discharge cycles, while retaining a charge/discharge efficiency of 96% and a discharge capacity of 91.3 mAh g−1. This manufacturing process can provide conformal power modules for a diverse range of portable devices with various shapes, improving space utilization. [ABSTRACT FROM AUTHOR]

Metallic lattice structures are well known for having high specific elastic moduli and strength. However, very little is understood about their resistance to fracture. In this work Ti–6Al–4V lattice structures are additively manufactured by selective laser melting and their fracture toughness characteristics are investigated. Resistance to fracture was determined under Mode-I loading at static rates using an extended compact tension (EC(T)) specimen, modified to contain lattice cells. The lattices consist of octet cells with a 3.5 mm edge length and relative densities ranging from 25% to 56%. Toughness is shown to increase by a power law with relative density and this trend was also obtained with finite element models. A new functional grading optimisation methodology is also presented for increasing fracture toughness. The size optimisation results in a functionally graded lattice whereby lattice truss diameters become the design variables. After size optimisation, initiation fracture toughness increases by up to 37%. Image 1 • Novel optimisation method for generating lattices with high fracture toughness. • Crack size effect on toughness is suppressed by tailoring lattice truss diameters. • Additively manufactured lattices validate FE models with good agreement. [ABSTRACT FROM AUTHOR]

Additive manufacturing enables the fabrication of periodic ceramic lattices with controllable micro-architectures. Many studies reported their catastrophic brittle fracture behaviour. However, ceramic lattices may fail by a layer-by-layer pseudo-ductile fracture mode, by controlling micro-architectures and porosities. Moreover, their fracture behaviour can be optimised by introducing strut/wall thickness gradients. This paper investigates the fracture behaviour and the fracture mode transition of ceramic triply periodic minimal surface (TPMS) structures. Alumina TPMS structures with relative densities of 0.14-0.37 are fabricated by ceramic stereolithography. Quasi-static compression tests validate a transition density range for non-graded samples: low (<0.21) and moderate (>0.25) relative density samples show layer-by-layer pseudo-ductile and catastrophic brittle fracture modes, respectively. The pseudo-ductile failure mode increases the energy absorption performance, enabling load-bearing capacity for a compressive strain up to 50%. With appropriate thickness gradients, graded structures exhibit significant increase of energy absorption without a decrease of fracture strength compared to their non-graded counterparts. [ABSTRACT FROM AUTHOR]

• Multi-material printing interpenetrating phase composites with controlled mechanical properties. • Stable mechanical reponse for energy absorption, damage tolerance and fracture tougness. • Strengthening and toughening mechanisms of IPCs. Under external load, lightweight cellular solids are often associated with localized deformation that would lead to their catastrophic failure. Cellular solids are thus often infilled with a soft secondary material, constituting interpenetrating phase composites. Owing to highly interconnected porous architectures and controllable smooth surfaces, the triply periodic minimal surface structures based on interpenetrating phase composites are investigated in this paper. Samples are fabricated via polyjet multi-material printing, with the hard material taking on the primitive lattice and the soft material taking on its inverse. Quasi-static compression and three-point bending tests were performed on the fabricated composites. Results show that the combination of high stiffness, strength, and prolonged smooth plateau stress endows the composites to be promising for lightweight materials and energy absorbers. The designed composites can exhibit an excellent fracture toughness of 0.51 MPa•m1/2. Moreover, the designed interpenetrating architectures and stiff-contrast materials intrinsically control the strengthening and toughening mechanisms. The findings presented here demonstrate the potential to obtain enhanced mechanical properties by combining the advantages of the multi-material printing technique and interpenetrated design. [ABSTRACT FROM AUTHOR]

Stress shielding is one of the main problems that lead to bone resorption and revision surgery after implantation. Most of the commercially available metallic non-porous bone implants have a much greater stiffness than the native human bones and are prone to cause stress-shielding. With an open cell structure and intricate architecture, hyperbolic minimal surfaces offer several advantages such as less stress concentration, high permeability and high surface area to volume ratio, thus providing an ideal environment for cell adhesion, migration, and proliferation. This paper explores the use of porous bone implant design based on Triply Periodic Minimal Surfaces (TPMS) which is additively manufactured with ceramic material (Alumina) using Lithography-based Ceramics Manufacturing (LCM) technology. A total of 12 different primitive surface structure unit cells with pore size in the range of 500–1000 μm and porosity above 50% were considered. This is one of the earliest studies reporting the 3D printing of TPMS-based structures using ceramic material. Our results suggest that the choice of material and a porous TPMS-based design led to fabrication of structures with a much lesser compressive modulus comparable with the native bone and hence could potentially be adopted for bone implant design to mitigate the stress-shielding effect. Unlabelled Image • 3D-printed ceramic hyperbolic surface structures exhibit Young's modulus values between 2-5.5 GPa comparable to native bone • The open cell structure & intricate architecture offer conducive cell-microenvironment (high surface area to volume ratio) • Difficulty in slurry removal with smaller unit cell sizes (<2 mm) resulted in greater mass deviations (up to 100%) • An equation is derived to find the theoretical Young's modulus of the printed structures for proprietary materials • A functionally-graded structure for the trochanter region of hip implant is designed to mitigate stress-shielding effects [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hierarchical scaffold contains aligned fibers in micro-size and thin film with nano-sized pores. • Aligned fibers of scaffold guide the orientation and induce the elongation of fibroblasts. • The film of scaffold increases cell adhesion area, hence, improving cell proliferation. Abstract Specific structures of esophagus play an important role in specific functions. However, current esophageal tissue engineering scaffolds replicate them poorly. To address this issue, the objective of this study is to fabricate a hierarchical PCL/F127 scaffold inspired by the natural esophageal structure. The hierarchical scaffold consists of aligned fibers in micro-size and thin film with nano-sized pores through combining E-jetting and E-spraying. The aligned fibers of scaffold guide the orientation and induce the elongation of fibroblasts, mimicking the uniformly oriented esophageal muscles. Furthermore, the film functioned as a protective barrier to replicate the esophageal mucosa. Meanwhile, the film also increases cell adhesion area, hence, improving cell proliferation. These two features of the fabricated hierarchical scaffold mimic the structure of natural esophagus. Moreover, fabricated hierarchical scaffold possesses comparable mechanical properties to natural esophagus. These results prove the potential of fabricated scaffold for esophagus tissue repair. [ABSTRACT FROM AUTHOR]

The incidence of peripheral nerve injuries is on the rise and the current gold standard for treatment of such injuries is nerve autografting. Given the severe limitations of nerve autografts which include donor site morbidity and limited supply, neural guide conduits (NGCs) are considered as an effective alternative treatment. Conductivity is a desired property of an ideal NGC. Reduced graphene oxide (rGO) possesses several advantages in addition to its conductive nature such as high surface area to volume ratio due to its nanostructure and has been explored for its use in tissue engineering. However, most of the works reported are on traditional 2D culture with a layer of rGO coating, while the native tissue microenvironment is three‐dimensional. In this study, PCL/rGO scaffolds are fabricated using electrohydrodynamic jet (EHD‐jet) 3D printing method as a proof of concept study. Mechanical and material characterization of the printed PCL/rGO scaffolds and PCL scaffolds was done. The addition of rGO results in softer scaffolds which is favorable for neural differentiation. In vitro neural differentiation studies using PC12 cells were also performed. Cell proliferation was higher in the PCL/rGO scaffolds than the PCL scaffolds. Reverse transcription polymerase chain reaction and immunocytochemistry results reveal that PCL/rGO scaffolds support neural differentiation of PC12 cells. [ABSTRACT FROM AUTHOR]

Abstract NGCs are considered as an alternative treatment method for treating peripheral nerve injuries in place of nerve autografts. Biomimicry, conductivity, and biodegradability are the properties expected of an ideal NGC. PCL/PAA NGCs with three different concentrations of PAA (2.5, 5 and 7.5%) were fabricated using EHD-jet 3D printing. The mechanical properties of the PCL/PAA NGCs mimic the native human nerve properties (ultimate tensile strength of 6.5 to 11.7 MPa) and the conductivity match that of the amphibian motor nerve fiber myelin sheath (10−6 S/cm). The in vitro degradation studies reveal that they are biodegradable and injury/site-specific biodegradability can be obtained by tuning the PCL/PAA concentration ratio. In addition, PAA being a polyanionic polymer has the potential to act as a cation-exchanger, mimicking the functions of the nerve cortical gel layer, thereby influencing the electrophysiological phenomena called nerve excitation and conduction. Neural differentiation studies with PC12 cells assessed by the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunocytochemistry showed enhanced gene expression with the presence of PAA. Our results suggest that the EHD-jet 3D printed porous conductive PCL/PAA NGCs has the potential to be used in the treatment of peripheral nerve injuries. Graphical abstract Unlabelled Image Highlights • Ideal Nerve Guide Conduits with biomimicry and conductivity were fabricated using Electrohydrodynamic Jet 3D Printing • The mechanical properties and conductivity of the scaffolds mimic the native human nerve properties • Poly(acrylic acid) as cation-exchanger mimics nerve cortical gel layer functions, influencing nerve excitation & conduction • PC12 in vitro neural differentiation studies showed enhanced gene expression with the presence of Poly(acrylic acid) • Can potentially be used to treat peripheral nerve injuries & neurodegenerative conditions (Alzheimer's and Parkinson's) [ABSTRACT FROM AUTHOR]

The simultaneous improvement of mechanical and functional properties of Ti alloys is of considerable significance for their diverse applications and service life. Incorporating graphene with Ti is hoping to realize that, however, it is challenging to achieve the improvement because of the poor chemical stability of carbon/Ti systems. This challenge becomes particularly significant when using high carbon-content reinforcements, as the reinforcement agglomeration is considered to adversely affect composite performances. In this work, an efficient powder metallurgy method was developed to fabricate titanium matrix composites reinforced by a high content of graphene nanosheets (GNSs). Quasi-continuous GNSs were arranged in a 3D network and were surrounded by in-situ TiC. The results revealed that the load-transfer and solid-solution strengthening factors contributed to the high mechanical strength of the composites. Moreover, the GNS networks conduced to the improvement of thermal conduction, reduced the total weight, and enhanced the anti-wear performance of the composites via self-lubrication. Furthermore, the proposed approach can be applied to other carbon/metal composites for achieving significant improvements in their performance. [Display omitted] • An overall improved property is realized in high-contents graphene/Ti composites. • Load transfer and solid solution factors strengthen the compressive yield strength. • Dense-agglomerated graphene nanosheets build a channel for thermal energy transfer. • Self-lubrication of graphene decreases coefficient of friction and wear loss. • The proposed approach and mechanism can be applied to other carbon/metal systems. [ABSTRACT FROM AUTHOR]

Lightweight lattice structures are an important class of cellular structures with high potentials for multi-functional applications. Considering load-bearing requirements, truss buckling is one of the main failure mechanisms for low density and slender lattice structures. Critical buckling loads can be increased by modifying the profile of a truss. In this paper, we present a shape design method to optimize the critical buckling loads for lattice cores with free-form trusses. The free-form truss is represented by Fourier series and implicit surfaces, having smooth truss diameter variations and truss joints. The optimized truss profile is obtained by solving a parametric shape optimization problem with Fourier series coefficients as design variables. The method is used for designing optimized 1D columns and 3D Kagome lattice cores for sandwich panels. The numerical results predict 26.8% and 20.4% improvements of the critical buckling loads for 1D columns and 3D Kagome lattice cores compared to their uniform counterparts of the same mass, respectively. The optimized structures include complex smooth and curved geometries that are well suited for additive manufacturing because of the greater design freedom. Finally, the initial and optimized lattice cores are additively manufactured and tested. The experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

• A magneto-plastic predictive model of ductile-brittle transition is presented. • The model reveals the relationship between magneto-plasticity and strain rate. • MD simulations identify anisotropic dislocation slip and subsurface stress. • Enhanced ductile-brittle transition across magnetic field and crystal orientations. • Magnetic field improves dislocation-dominant lateral and tangential plastic flow. The micro-cutting of brittle ceramics starts with elastic-plastic deformation followed by severe brittle fracture, which significantly restricts the machinability and application of these materials. Magnetic field-enhanced plasticity (i.e., magneto-plasticity) has shown a positive potential to augment the ductile-brittle transition and machinability but the material removal mechanism of brittle ceramics with magneto-plasticity and its dependence on strain rate remains unclear. In this study, a deformation energy-based model was developed to bring light to the deformation mechanisms affecting the ductile-brittle transition under magneto-plasticity and the corresponding dependency on strain rate. MD simulations assisted the analytical modeling by deriving the orientation-dependent dislocation movement and stress distribution that contribute to single-crystal anisotropy in the surface formation and ductile-brittle transitions during scratching. The proposed model accurately predicted the improvement in ductile-brittle transition under various magnetic field intensities and orientations as confirmed in the experimental magnetic field-enhanced micro-scratching tests on single-crystal calcium fluoride (CaF 2). Scratched surface morphologies, acoustic emission (AE) signals, and critical loading conditions demonstrated the improvements in ductile-brittle transition with magneto-plasticity. Additionally, the progression of lateral slip trace and tangential surface pile-up under various magnetic field conditions confirm the direct influence of magneto-plasticity on dislocation mobility and the change in surface formation mechanism of brittle ceramics. This study not only deepens the understanding of the manifestation of magneto-plasticity during the deformation of brittle ceramics, but also opens new avenues for the integration of magnetic field-assisted technology in manufacturing processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Ensuring the removability of support structure and improving the surface quality of assembly interface are two key requirements to guarantee a model a valid fabrication and promote its kinematic performance in a product. Generally, determining a suitable fabrication orientation for the model is an effective way to meet those requirements. Accordingly, a novel validity- and kinematics-aware approach for optimizing fabrication orientation is proposed in this work. Viewing that it is effective and efficient (in an optimizing process) to evaluate whether a fabrication orientation will take unremovable support structures to a model by checking whether they contact the model on its inaccessible surface regions, a new voxel-based surface-accessibility analysis method is proposed. In detail, to analyze the accessibility (by a cleaning tool) of each surface region accurately, the input model and its bounding box are voxelized together first and represented by using a new voxel-adjacency graph. Then, integrating rapid individual-single-accessibility analysis, voxel-layer-scan analysis, and accessible direction reuse, a parallelable variable-neighborhood-search method is put forward based on the above graph. With this method, all inaccessible surface regions (if any) of the model can be effectively and efficiently identified at once. Moreover, the above-mentioned key requirements are usually two conflicting goals (especially for a model having two or more assembly interfaces) in determining suitable fabrication orientations. To make those goals reconcile with each other, a multi-objective optimization problem is first formulated to explore a set of pareto-optimized fabrication orientations. Here, two new functions are elaborately designed to evaluate the removability of support structures (by counting the number of inaccessible surface regions that appear support structures) and the surface quality of assembly interfaces, respectively. Finally, a greedy method is adopted to recommend one from these compromising fabrication orientations to the uses as the best-suitable fabrication orientation. Experiments are presented to demonstrate the characteristics, effectiveness, and efficiency of the approach. The methodological comparisons also show that the approach has several advantages in AM applications where support structures are mainly removed manually and the models are fabricated for mechanisms. • Optimizing fabrication orientation by reconciling validity with kinematics. • Smart and efficient accessible analysis by parallelable variable neighborhood search. • Rapid finding accessible surface regions by voxel-layer scan in voxel-adjacency graph. [ABSTRACT FROM AUTHOR]

Micro-selective laser melting fabricated triply periodic minimal surface sheet lattice and epoxy interpenetrating phase composites (IPCs) are investigated in this paper. To achieve superior specific energy absorption (SEA) enhancements in the composites, an optimised Schwarz primitive lattice (P-lattice) structure is proposed by redefining the shell opening diameter with a shape parameter. Also, the influences of fabrication directions, along the [100], [110], and [111] lattice directions, on the mechanical responses of the P-lattices and IPCs are presented. Compression results reveal that the modified P-lattices outperform the original P-lattices with superior compressive strength and SEA. The P-lattices also display the lowest strength and SEA along [100] as compared to that of [110] and [111]. The compressive strength and SEA of modified P-lattice along [111] are 123.66% and 64.63% higher than its [100], respectively. As for the IPCs, up to a 52% increase, from the linear addition of the two-component phases has been achieved for SEA. The IPCs also exhibit a superior specific energy absorption of 49.6 J/g, a 1109% improvement from that of the pure lattice, which is attributed to the high strength and large plateau strain of the composites. The simulation results show that the internal energy of both lattice and epoxy in composites is 136% and 21%, respectively, higher than that of single structures due to the interaction effects. • Schwarz Primitive lattice (P-lattice) and epoxy-infilled interpenetrating-phase composites. • High strength and long plateau stress for energy absorption. • Enhanced strength of IPCs when embedded in modified lattices. [ABSTRACT FROM AUTHOR]

Object proposal is essential for current state-of-the-art object detection pipelines. However, the existing proposal methods generally fail in producing results with satisfying localization accuracy. The case is even worse for small objects, which, however, are quite common in practice. In this paper, we propose a novel scale-aware pixelwise object proposal network (SPOP-net) to tackle the challenges. The SPOP-net can generate proposals with high recall rate and average best overlap, even for small objects. In particular, in order to improve the localization accuracy, a fully convolutional network is employed which predicts locations of object proposals for each pixel. The produced ensemble of pixelwise object proposals enhances the chance of hitting the object significantly without incurring heavy extra computational cost. To solve the challenge of localizing objects at small scale, two localization networks, which are specialized for localizing objects with different scales are introduced, following the divide-and-conquer philosophy. Location outputs of these two networks are then adaptively combined to generate the final proposals by a large-/small-size weighting network. Extensive evaluations on PASCAL VOC 2007 and COCO 2014 show the SPOP network is superior over the state-of-the-art models. The high-quality proposals from SPOP-net also significantly improve the mean average precision of object detection with Fast-Regions with CNN features framework. Finally, the SPOP-net (trained on PASCAL VOC) shows great generalization performance when testing it on ILSVRC 2013 validation set. [ABSTRACT FROM PUBLISHER]

• An improved Schwarz primitive lattice structure with small openings was proposed. • Compression tests and FE simulations were conducted to evaluate their performances. • The compressive strength and energy absorption of new lattices have greatly increased. • A rigid-plastic hardening model was introduced to predict the mechanical response. Triply periodic minimal surface (TPMS) sheet lattice structures are composed of continuous and smooth shells, enabling the achievement of a high surface-to-volume ratio and pore interconnectivity, which represent an emerging solution for lightweight applications. In this study, an improved Schwarz primitive lattice (P-lattice) structure was proposed by redefining the original opening diameter with a shape parameter. Prototypes of different configurations, such as the original P-lattice (OP) structure, modified P-lattice structure with a small opening diameter (SP), and modified P-lattice structure with a big opening diameter (BP) were fabricated via micro-selective laser melting using 316 L stainless steel. Quasi-static compression tests were performed on the fabricated samples. The experimental results indicated that the Young's modulus, compressive strength, and energy absorption of the SP lattice were increased by 25.84%, 15.63%, and 33.02%, respectively, compared with those of the OP structure. A finite element model was established to investigate the mechanical properties and energy absorption of all the designed configurations, and the results showed good agreement with the experimental observations. A rigid–plastic hardening model was also introduced to macroscopically predict the mechanical response and energy absorption of the as-designed lattice structures. The mechanical properties and energy absorption of the SP structure outperformed those of the OP and BP structures. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we first describe the construction of a finite element model of the human spine that may be used to assist the investigation of clinical problems by predicting its biomechanical behaviour. A beam finite element (FE) spine model for haptic interaction is built based on a solid FE spine model, which is created in an offline finite element analysis (FEA) software. The mechanical properties of the beam FE spine model are tuned so that its deformation behaviour is very similar to that of the offline solid spine model. Furthermore, the online beam FE spine model is greatly simplified as compared to the offline solid FEA model and hence more appropriate for real-time simulations. Haptic feedback is provided in the real-time simulation of the beam FE spine model, in order to enhance the human–computer interaction. Based on the results of spine deformation obtained from the haptic online FE simulator, the offline FEA spine model again is used to reproduce the same deformation and hence to provide more detailed deformation and vertebrae’s stress/strain information, which the haptic beam FE model is not capable to provide. Then, we present a tetrahedral mass–spring system to model intervertebral discs, which are interposed between vertebrae, and the offline simulation can be run to achieve deformation responses of these intervertebral discs. In our research, combining the haptic beam FE model and the intervertebral disc model can be useful for studying biokinematics of the spine as well as assessing medical conditions in the spine or the biomechanical behaviour of new designs of artificial intervertebral discs. [ABSTRACT FROM AUTHOR]

Apparent anisotropies have been found in the microstructure and mechanical properties of selective laser melted (SLM) Ti–6Al–4V alloy, which will significantly influence the comprehensive performance of the SLM parts. In this study, the effect of scanning strategies on material anisotropy, including surface morphology, microstructure, microhardness, quasi-static and dynamic mechanical properties, were comprehensively investigated with 0°, 67.5°, and 90° scanning strategies. The SLM Ti6Al4V alloy prepared by the 0° scanning strategy exhibited the most pronounced anisotropy. The size of the primary columnar crystals on the front surface (158–173 μm) is approximately 1.8–3.2 times larger than that of the top surface (54–88 μm), and the microhardness at the top surface is ∼30% higher than that of the front surface. In addition, the modified Johnson-Cook constitutive model for the SLM Ti6Al4V alloy is developed based on the results of quasi-static compression and dynamic compression with the average absolute relative error controlled within 10%. This provides a reliable solution and an effective material constitutive model for modelling and simulation of the machining SLM parts with higher accuracy and enhanced physical meaning. [ABSTRACT FROM AUTHOR]

• A novel method for stiffness modeling of industrial robots is proposed. • The effects of link weights and gravity compensator are considered in the model. • The compliance of each link includes the deformation in all directions. • The deflections caused by different factors can be explicitly separated. • The correctness of the proposed model is experimentally verified. In the robotic machining process, the external force due to cutter-workpiece interactions and gravity force due to link weights can cause considerable deviations of the desired trajectory. Besides, gravity compensators can be found in many heavy-duty industrial robots to balance the gravity force. However, the effects of gravity force and balancing force are rarely considered in the deflection analysis. This paper proposes an effective method for the stiffness modeling of heavy-duty industrial robots by taking account of the joint/link compliances, link weights and gravity compensator. Firstly, the static equilibrium equations of each substructure are formulated to derive the expressions of reaction force exerted on each joint. Secondly, a linear map of linear/angular deflections between the joints/links and the end-effector is developed. Finally, the stiffness model of the whole robot is formulated by integrating the joint/link compliances. The robot deflections at several configurations are analyzed, and the deflection distributions throughout the workspace are demonstrated. With this model, it is possible to analytically evaluate the contributions of external force, link weights and gravity compensator to the total deflections. The correctness of the proposed model is also experimentally verified by comparing the calculated and the measured deflections under the same conditions. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is generally characterized by the brief laser-powder interaction time, highly localized heat intensity and input distributions, steep temperature gradients and high cooling rate. It was admitted that the mechanical properties of as-built SLMed components exhibit significantly anisotropic due to different heat history and microstructures in different directions. Post-processing of additively manufactured parts is generally considered an essential operation due to poor surface quality and dimensional accuracy. In this paper, comprehensive research is conducted about the influence of material anisotropy of additively manufactured Ti-6Al-4V alloys on machining performance in ultra-precision micromachining. The machining performance of SLMed Ti-6Al-4V alloys was derived from two cutting directions (parallel/perpendicular to the laser scanning direction), two machining surfaces (top/front surface) and three laser scanning strategies (0°-line scanning, 67.5°/90°- rotation scanning). Surface topography, roughness, microstructure and microhardness were assessed to characterize the material anisotropy of SLMed titanium alloy. The machining results showed that the anisotropic mechanical properties and microstructure feature of the Ti-6Al-4V alloys are the fundamental reasons for the anisotropic machining performance in terms of cutting force and surface roughness. The machining properties of SLMed Ti-6Al-4V alloys are affected by the microstructure, machining surfaces, cutting directions and cutting parameters. Both the magnitude and fluctuation of dynamic cutting force produced on the front surfaces are obviously larger than those generated on the top surfaces. Significant improvement in surface roughness ranging from Sa = 80–100 nm could be achieved along the laser scanning direction for 0°-line SLMed Ti-6Al-4V sample when cutting depth was from 1 to 15 μm at v c = 50 mm/min. In addition, some typical SLMed defects appear on the machined surface and produced chips. This research is applicable to assist manufacturers in choosing the appropriate machining method for SLMed components in ultra-precision machining. Image 1 • The material anisotropy of selective laser melted (SLMed) Ti6Al4V alloy is characterized by EBSD, XRD and microhardness. • The effect of material anisotropy on the machinability of SLMed Ti6Al4V alloy is studied in ultra-precision machining. • The influences of cutting directions, machining surfaces and laser scanning strategies on machining performance are investigated. [ABSTRACT FROM AUTHOR]

The effects of trace MoSi 2 addition on the microstructure evolution, mechanical properties and fracture behavior of Ti–6Al–4V wall via cold metal transfer additive manufacturing (CMTAM) were investigated. After the addition of trace MoSi 2 powder, trace (β-Ti, Mo) phase and SiO 2 particles were obtained and partly prior-β→α' phase transformation was suppressed. Compared with the as-built Ti–6Al–4V wall, the prior-β grains changed from columnar to the equiaxed or near-equiaxed after the addition of trace MoSi 2. The tensile analysis result revealed that the addition of trace MoSi 2 could improve the average strain while reduce anisotropy. All specimens showed dimples corresponding to ductile failure mode. The possible thermal cycles for the trace-MoSi 2 -addition specimens during the CMTAM process were analyzed. • Ti–6Al–4V walls with trace MoSi 2 addition were manufactured via CMTAM. • The prior-β grains changed from columnar to the (near-)equiaxed and refined by MoSi 2. • The prior-β.→ α′ phase transformation was suppressed by MoSi 2 several times during CMTAM. • Elongation can be improved owing to grain refinement of prior-β and reduction in acicular α′ martensite. • Anisotropy can be reduced due to grain refinement of prior-β. [ABSTRACT FROM AUTHOR]

Overlapping melting trajectories and partially-melted powders result in poor surface morphology and high surface roughness values (Ra = ~13.34 μm) of selective laser melted (SLMed) Ti6Al4V alloy. Secondary processing of SLMed components is thus an essential finishing operation to produce functional SLMed parts in precision engineering. This paper investigates the effects of laser scanning strategies (0°, 67.5° and 90° laser scanning schemes) and machining surfaces (top and front surfaces) on the machining performance of SLMed Ti6Al4V alloy in milling, compared with that of annealed ASTM B265 Ti6Al4V alloy. High degree of anisotropy of SLMed Ti6Al4V alloy is reflected in cutting force, surface morphology and surface roughness on different machining surfaces. The machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy, where the anisotropy weakens following the sequence of 0°, 90° and 67.5° SLMed samples. It is verified that high cutting speed can improve machining anisotropy features of SLMed titanium alloy. The chip shape of SLMed Ti6Al4V alloy is a typical conical spiral chip, and the bending degree and length of chips produced by SLMed Ti6Al4V alloy are larger than those produced by annealed Ti6Al4V alloy. Unlabelled Image • Grain on top surface of SLMed Ti6Al4V is close to {2 1 ¯ 1 ¯ 0} while that on front surface is inclined to {10 1 ¯ 0} and {0001}. • Machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy. • Surface quality on top surfaces of 0° and 90° SLMed Ti6Al4V is significantly better than that on front surfaces. • The bending degree and length of SLMed Ti6Al4V alloy chips are larger than those of annealed Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

This paper aims to improve the surface quality of 316L stainless steel parts manufactured by selective laser melting (SLM) using dry mechanical-electrochemical polishing (DMECP). DMECP is an advanced surface finishing method combining the advantages of both mechanical and electrochemical polishing techniques in a more environmentally friendly manner. In this paper, the SLM process-related defects causing poor surface quality are analysed first. The material removal mechanism of DMECP is investigated to continuously remove the oxide layers formed during polishing. Surface morphology and roughness evolution under different polishing conditions are characterised. The top surface roughness can be reduced by over 91% from 8.72 μm to 0.75 μm compared to side surface by over 93% from 12.10 to 0.80 μm. The material removal on the top surface is more efficient than that on the side surface under the same polishing condition. The secondary defects formed during polishing can be removed using mechanical polishing mode. The chemical element composition of the polished surface exhibits almost identical content to the initial 316L powders. Compared with the initial dark and rough surfaces, the results validate the capability of DMECP as an effective tool to improve the SLM surface quality and achieve a mirror finish. Unlabelled Image • Dry mechanical-electrochemical polishing (DMECP) is applied to finish selective laser melted (SLMed) surfaces. • The submicron-level surface roughness is achieved on SLMed metal parts. • Defects on SLMed 316L stainless steel are analysed and removed. • The relationship between polishing parameters and surface quality is established. • The material removal cycle and mechanism of DMECP are elucidated. [ABSTRACT FROM AUTHOR]

The prevalence of peripheral nerve injuries resulting in loss of motor function, sensory function, or both, is on the rise. Artificial Nerve Guide Conduits (NGCs) are considered an effective alternative treatment for autologous nerve grafts, which is the current gold-standard for treating peripheral nerve injuries. In this study, Polycaprolactone-based three-dimensional porous NGCs are fabricated using Electrohydrodynamic jet 3D printing (EHD-jetting) for the first time. The main advantage of this technique is that all the scaffold properties, namely fibre diameter, pore size, porosity, and fibre alignment, can be controlled by tuning the process parameters. In addition, EHD-jetting has the advantages of customizability, repeatability, and scalability. Scaffolds with five different pore sizes (125 to 550 μm) and porosities (65 to 88%) are fabricated and the effect of pore size on the mechanical properties is evaluated. In vitro degradation studies are carried out to investigate the degradation profile of the scaffolds and determine the influence of pore size on the degradation rate and mechanical properties at various degradation time points. Scaffolds with a pore size of 125 ± 15 μm meet the requirements of an optimal NGC structure with a porosity greater than 60%, mechanical properties closer to those of the native peripheral nerves, and an optimal degradation rate matching the nerve regeneration rate post-injury. The in vitro neural differentiation studies also corroborate the same results. Cell proliferation was highest in the scaffolds with a pore size of 125 ± 15 μm assessed by the PrestoBlue assay. The Reverse Transcription-Polymerase Chain Reaction (RT-PCR) results involving the three most important genes concerning neural differentiation, namely β3-tubulin, NF-H, and GAP-43, confirm that the scaffolds with a pore size of 125 ± 15 μm have the highest gene expression of all the other pore sizes and also outperform the electrospun Polycaprolactone (PCL) scaffold. The immunocytochemistry results, expressing the two important nerve proteins β3-tubulin and NF200, showed directional alignment of the neurite growth along the fibre direction in EHD-jet 3D printed scaffolds. [ABSTRACT FROM AUTHOR]

In this study, polycaprolactone/mineral trioxide aggregate (PCL/MTA) scaffolds were successfully fabricated via an electrohydrodynamic jet (or E-jet) 3D printing system developed by our group. The viscosity of the composited solutions and the key process parameters (i.e. applied voltage and feed rate) were investigated to achieve an optimal process condition. To investigate the potential of PCL/MTA scaffolds to support regeneration ability for dentin related tissue, we seeded dental pulp stem cells on the scaffolds, and compared the results with cell-seeded PCL scaffolds. Assessment of cell viability and proliferation using live/dead cell staining and MTS assay showed compatibility of PCL and PCL/MTA scaffolds for cellular attachment and growth. These scaffolds could be used for fabrication of three-dimensional tissues and in future could be applied to dentin and periodontal tissue engineering applications. [ABSTRACT FROM PUBLISHER]