Search

Percutaneous sacroiliac screw is one of the main methods to treat unstable posterior pelvic ring injury. However, complexity of pelvic anatomical structure increases the difficulty and risk with freehand operation. Besides, S2 screw fixation began to receive attention. The purpose of the current study was to evaluate the safety, accuracy, efficiency and clinical outcome of robot-assisted S2 screw fixation for posterior pelvic ring injury.We reviewed 128 cases of unstable posterior pelvic ring injury treated by percutaneous sacroiliac screw fixation in our hospital from January 2016 to January 2020. All cases were divided into robot-assisted S1 group (RAS1), robot-assisted S2 group (RAS2), freehand group S1 group (FHS1) and freehand group S2 group (FHS2). The mean times of fluoroscopy per screw and adjustment per guide wire were used to evaluate radiation exposure and the efficiency of screw placement, respectively. The final position of the screw was evaluated with postoperative CT to illustrate security and accuracy. 108 patients (84.38%) were followed up for 5~24 months and the Majeed scores were compared among groups.A total of 180 screws were inserted. In comparison of the mean times of fluoroscopy per screw and adjustment per guide wire, RA group was significant less than FH group, further comparison revealed that freehand S2 placement need more fluoroscopy and adjustment times compared with freehand S1 placement, but for robot-assisted procedure, there was no difference between placing S1 and S2. Screw penetration was found in the FHS1(3/48) and FHS2(2/14) and none in RAS1 or RAS2, which means robot-assisted groups were more safety and accurate (P0.001). The mean Majeed score in RAS1 (83.33±13.47) and RAS2 (82.32±11.42) was higher than in FHS1 (80.43±12.25) and FHS2 (75.08±18.47), but this difference failed to reach significant.Compared with the freehand operation, TiRobot increased the safety and accuracy, reduced radiation exposure, and improved the efficiency. TiRobot could reduce the risk of S2 placement and provide a safe and feasible way for clinical practice.

Manufacturers are pursuing energy-efficient production in response to the fluctuating energy price, growing global competition, rigorous international laws, and severe environmental crisis. This article proposes to boost the energy efficiency of production systems by controlling the production. It extends the existing energy-saving control research by presenting integrated modeling, analyzing, and controlling approaches. The work starts from the modeling of the production systems and establishes an analytical model to systematically quantify the production loss resulted from energy-saving control and the various disruptions. A dynamic control algorithm is proposed to reduce energy consumption and maintain desirable productivity. Simulation studies are utilized to demonstrate the application of the proposed method and verify its effectiveness.

Nonexponential relaxations are universal characteristics for glassy materials. There is a well-known hypothesis that nonexponential relaxation peaks are composed of a series of exponential events, which have not been verified. In this Letter, we discover the exponential relaxation events during the recovery process using a high-precision nanocalorimetry, which are universal for metallic glasses and organic glasses. The relaxation peaks can be well fitted by the exponential Debye function with a single activation energy. The activation energy covers a broad range from α relaxation to β relaxation and even the fast γ/β′ relaxation. We obtain the complete spectrum of the exponential relaxation peaks over a wide temperature range from 0.63 T g to 1.03 T g , which provides solid evidence that nonexponential relaxation peaks can be decomposed into exponential relaxation units. Furthermore, the contribution of different relaxation modes in the nonequilibrium enthalpy space is measured. These results open a door for developing the thermodynamics of nonequilibrium physics and for precisely modulating the properties of glasses by controlling the relaxation modes.

Alternating magnetic fields (AMFs) are recently demonstrated as a promising strategy to promote the electrochemical catalytic reactions. However, the underlying mechanisms are still an open question. In this work, we systematically investigated the influence of AMFs on the hydrogen evolution reaction (HER) by using a Fe-Co-Ni-P-B magnetic catalyst. The HER catalytic efficiency is boosted significantly by AMFs, with 27% increase in current density at 20 mT. This is attributed to the enhancement of charge-transfer efficiency by Lorentz interaction with a minor contribution from the heating effect. The high magnetic permeability and skin effect of electromagnetic eddy current for the Fe-Co-Ni-P-B electrode can magnify the Lorentz effect. These findings clarify the mechanism of AMF-enhanced HER catalytic activities and open a door for designing a high-efficiency electrocatalysis system.

Functionality of amorphous multicomponent systems largely depends upon the miscibility among components, especially in systems such as amorphous drugs and electrolytes. An in-depth understanding of mixing behaviors of various constituents is necessitated. Here, we applied the small- and wide-angle X-ray scattering (SWAXS) technique to monitor the mixing behaviors in three typical glass-forming binary systems imposed by varied heat of mixing. It is found that the Porod invariant (

Manipulation of the internal architecture is essential for electromagnetic interference (EMI) shielding performance of metal-based coatings, which can address the electromagnetic pollution in large-size, complex geometries, and harsh environments. In this work, oriented segregated structure with conductive networks embedded in magnetic matrix was achieved in Fe-based amorphous coatings via Ni–Cu–P functionalization of (Fe0.76Si0.09B0.1P0.05)99Nb1 amorphous powder precursors and then thermal spraying them onto aluminum (Al) substrate. Benefiting from the unique magnetic-electric structure, the coating@Al composite delivered prominent EMI shielding performance. The EMI shielding effectiveness (SE) of modified coating@Al composite is ~41 dB at 8–12 GHz, doubling the value of Al substrate and is 15 dB greater than that of Ni–Cu–P-free coating@Al composite. Microstructure analysis showed that the introduced Ni−Cu−P insertions forcefully suppress the serious oxidation of the magnetic precursors during thermal spraying and form a dense conductive network in the magnetic matrix. Electron holography observation and electromagnetism simulation clarified that the modified coating can effectively trap and attenuate the incident radiations because of the electric loss from Ni−Cu−P conductive network, magnetic loss from Fe-based amorphous coating, and the electromagnetic interactions in the oriented segregated architectures. Moreover, the optimized thermal isolation and mechanical properties brought by structural improvement enable the coating to shield complex parts in thermal shock and mechanical loading environments. Our work gives an insight on the design strategies for metal-based EMI shielding materials and enriches the fundamental understanding of EMI shielding mechanisms.

This work investigates a scheduling problem of deadlock-prone flexible manufacturing systems modeled by place-timed Petri nets. It proposes an anytime branch and bound (AB&B) algorithm for it to minimize system makespan based on the branch tree of a net model and a highly permissive deadlock controller. The proposed algorithm searches a sequence of transitions in the branch tree that evolves the model from the initial marking to the final one. In order to prune the branch tree and increase search speed, this work develops two pruning rules, a lower bound of makespan, and a novel branching strategy. Their usage ensures AB&B’s high search efficiency. Experimental results demonstrate that the proposed algorithm surpasses the state-of-the-art ones. Note to Practitioners —In practice, scheduling is one of the most important issues for production managers to address. Existing approaches to deadlock-prone flexible manufacturing system (FMS) scheduling have multiparameters. Their settings can impact the scheduling results greatly. Since their turning is a challenging task, it is difficult to find the best parameter settings. This article proposes an anytime branch and bound (AB&B) algorithm for minimizing the makespan of deadlock-prone FMSs. It has only one parameter, i.e., maximal CPU time, which needs no turning. When it is highly tight, AB&B can output a feasible and decent schedule. If it is larger and larger, AB&B can output a better and better schedule. Comparison studies show that AB&B outclasses existing ones significantly. It is suitable for real-time scheduling cases in which satisfied schedules must be offered in a very short time.

Predictive maintenance (PM) and quality management help to improve the business bottom line by alleviating the system performance degradation caused by unscheduled machine breakdown and product qua...

The advance of new generation of IT and sensor technologies results in data enriched production environment. However, there is a lack of an effective utilization of the data to improve productivity while reducing quality management cost. Therefore, this paper proposes a systematic method to analyze the production dynamics, and presents an event-based method to quantitatively evaluate the impact of various disruptions on system throughput, including machine breakdown and quality failure. It is proved that the impact of the events can be measured with system loss which is the summation of the production loss of the slowest machine and the overall number of defective parts produced in the subsystem where the slowest machine locates in. The data-driven method is integrated into an optimization method to exploit the optimal quality inspection allocations. In the method, a non-linear optimization problem is formulated and solved with an adaptive genetic algorithm to trade off the penalty cost of production loss and the investment cost of quality inspection. The research results in a comprehensive understanding of production dynamics subject to quality inspection and rework. It is of critical importance to boost productivity with better quality inspection allocations. Simulation studies are performed to validate the proposed methods.

Control of production operations is one of the most cost-effective methods to improve energy efficiency in production lines. Although many research efforts have been devoted to utilizing production control to boost production energy efficiency, it is not clear how production dynamics change in reaction to the energy saving operations, which is important to capture energy saving opportunities. In this paper, an optimal energy saving control method based on N-policy is introduced to reduce the system energy consumption while only slightly decreasing productivity. A Markov chain model is established to interpret the dynamics of serial production lines with N-policy. The analytical formulas of production rate and energy consumption are derived. Then, an energy-efficient control model is formulated to balance the productivity and energy consumption. For two-machine production lines, the monotonicity property of the model is proved, and the analytical N-policy is derived. For longer production lines, an adaptive genetic algorithm is utilized to solve the energy-efficient control model. Case studies validate the effectiveness of the proposed optimal energy saving control method.

Objective A bone defect rat model was established to investigate the osteogenic effect of local delivery two antibiotics (vancomycin and tobramycin powder) on bone regeneration. Methods Twenty‐four Sprague–Dawley (SD) male rats (6 to 8 weeks, 200 to 250 g) were used in this study. All these rats were randomly divided into four groups. Based on dose conversion between rat and human via body surface area, the rat dose of two antibiotics was 88μg/g and 176 μg/g for vancomycin and tobramycin, respectively. Con group (no antibiotic), Van group (vancomycin, 88 μg/g), Tob group (tobramycin 176 μg/g), and Van+Tob group (vancomycin 88μg/g combined with tobramycin 176 μg/g). A 5.0‐mm full‐thickness standardized mandibular bone defect was performed with a drill in each rat and different antibiotic powders were placed over the bone defect space, respectively. All these animals were sacrificed after 12 weeks post‐operation. The mandible bones were harvested for further radiographic and histologic analysis. The bone volume/total volume (BV/TV) ratio, bone volume (BV), and bone fractional area (BFA) in the defect area via micro‐computed tomography (μCT scanning) were further analyzed. Then, we performed a histological assessment via hematoxylin and eosin (H&E) and Masson's trichrome staining to analyze bone regeneration and also analyze the number of osteoblasts per filed. Results There were no postoperative deaths, signs of vancomycin‐related or tobramycin‐related toxicity, or signs of systemic illness in any of the four groups. All wounds healed well, and no complications or surgical site infection were observed in all rats. From the μCT scans analyses, there was less bone regeneration in the Van group than in the Con group (BV/TV: F = 64.29, R 2 = 0.9602; P = 0.0052; BFA: F = 76.17, R 2 = 0.9662, P = 0.0007; BV: F = 194.4, R 2 = 0.9865, P = 0.0022). However, when the tobramycin and vancomycin were combined, an increase in bone defect re‐ossification was found in the Van+Tob group than in the Van group (BV/TV: F = 64.29, R 2 = 0.9602, P = 0.0033; BFA: F = 76.17, R 2 = 0.9662, P = 0.0006; BV: F = 194.4, R 2 = 0.9865, P = 0.0033). Routine H&E and Masson staining supported the finding of μCT scanning. Quantitative indices confirmed that both the bone regeneration and the number of osteoblasts per filed in the defect area was higher in the Van+Tob group than in the Van group (percentage of bone tissue: F = 145.7, R 2 = 0.9562, P = 0.0008; number of osteoblasts per file; F = 67.3, R 2 = 0.9098, P 0.9999). Conclusion For bone defect, local application of vancomycin combined with tobramycin was recommended over vancomycin alone. This animal study presents data suggesting that the use of local delivery of vancomycin and tobramycin should be investigated further in clinical studies., Bone defect rat model was established and vancomycin and/or tobramycin were local delivered to investigate their osteogenic effect. We performed μCT scanning and histological assessment to analyse bone regeneration. Local application of vancomycin combined with tobramycin was recommended other than vancomycin alone.

The article established a modelling that predicted and measured the quenching and pre-stretching stress in 7050 aluminum alloy thick plate in order to make the alloy suitable enough for manufacturing in the aerospace industries. The results show that both the rolling direction component stress and the transverse direction component stress have a “M” distribution along the plate thickness of 7050 aluminum alloy thick plate, but the level is slightly different, but the level is slightly different. The maximum value of quenching residual stress is about 187MPa in the 80mm thick of 7050 plate. Pre-stretching of the heat treated and quenched alloy to 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% and 3.5% to reduce the residual stresses. It has been recorded that more than 90% reduction of residual stresses were observed in a pre-stretching rage of 2-3%. Measuring the surface residual stresses of the alloy by ultrasonic methods and measuring the internal residual stresses of the alloy by crack compliance methods. The two methods are used to verify the model. The difference between the measurement and the simulation is within 40MPa. The experimental data of the ultrasonic and the crack compliance methods were found to correspond well with the simulated models. This shows that the simulation model can effectively predict the evolution of residual stress in 7050 aluminum alloy thick plate, and the simulation model can also be reconstructed and inspected through the experimentally measurement.

Recent fragile-to-strong crossover (FSC) concept in the crystallization kinetics study of phase-change supercooled liquids (PCLs) is attractive for screening the high-performance phase-change materials. It is important to search the FSC behavior in confined PCLs, like the two-dimensional confined PCLs, which is believed has fast crystallization and good thermal stability. Together with the ultrafast differential scanning calorimetry measurement and the generalized Mauro-Yue-Ellison-Gupta-Allan viscosity model, we here studied the crystallization kinetics of two-dimensional confined GeTe PCLs. It was found such confined PCLs has distinct FSC with large crossover magnitude is 2, confirming two-dimensional confinement can trigger the FSC behavior in PCLs.

Aggregation method has been widely utilized to evaluate the performance measures of production lines. However, traditional aggregation method (TAM) has low prediction accuracy in production lines with multiple bottlenecks, such as “inverted bowl” lines and “oscillatory” lines. Therefore, the root causes of the low prediction accuracy are first investigated. Extensive numerical studies indicate that $\Lambda $ -units are one of the major causes, where a $\Lambda $ -unit is defined as the subsystem between two consecutive bottlenecks. Then, an improved aggregation method (IAM) is proposed to improve the prediction accuracy of TAM. IAM is established by extending the traditional two-machine aggregation building blocks to general multimachine aggregation building blocks in $\Lambda $ -units. Specifically, for a small-scale $\Lambda $ -unit, an aggregation building block is established for all the machines and buffers in the $\Lambda $ -unit. For a large-scale $\Lambda $ -unit, a heuristic rule is proposed to divide the $\Lambda $ -unit into several small-scale production line segments, where an aggregation building block is established for each segment. Numerical studies indicate that IAM can effectively improve the estimation accuracy of the aggregation method while maintaining a reasonable computational efficiency. Note to Practitioners— Bottleneck machines refer to the machines whose performance impedes the production systems in the strongest manner. They have been widely utilized to improve productivity, energy efficiency, and so on. However, there are few efforts devoted to the impacts of bottlenecks on the aggregation method. The numerical studies indicate that the traditional aggregation method (TAM) has lower estimation accuracy in production lines with multiple bottlenecks. Therefore, in this article, improved aggregation method (IAM) is established to improve the performance of the aggregation method in the production lines. The research contributes to the literature with a generalized aggregation method that is very effective in production lines with and without bottlenecks. It can be utilized by production managers to evaluate production performance, predict the impacts of system changes, and accelerate control and investment decision-making.

This paper studies a two-agent scheduling problem on mixed batch machines in parallel. A mixed batch machine can process several jobs simultaneously as a batch, as long as the number of jobs in the...

The dynamics and thermodynamics of the Debye and structural (α) relaxations in isomeric monoalcohols near the glass transition temperature Tg are explored using dielectric and calorimetric techniques. The α relaxation strength at Tg is found to correlate with the heat capacity increment, but no thermal signals can be detected to link to the Debye relaxation. We also observed that the activation energy of the Debye relaxation in monoalcohols is quantitatively correlated with that of the α relaxation at the kinetic Tg, sharing the dynamic behavior of the Rouse modes found in polymers. The experimental results together with the analogy to the Rouse modes in polymers suggest that the Debye process in monoalcohols is an entropic process manifested by the total dipole fluctuation of the supramolecular structures, which is triggered and driven by the α relaxation.

Both crystallization and relaxation are intrinsic characteristics that derive from the metastable nature of metallic glasses. However, the interactions between the two reactions are not understood fully. In this paper, enthalpy evolution and phase existence diagrams composed of liquid, glass and crystal are established to illustrate the phase transitions upon heating and cooling a metallic glass-forming material. We find that metallic glasses located in different enthalpy levels in the diagrams exhibit quite different resistance to crystallization. The crystal nucleation rate for the fast-cooled glass is smaller compared to the slow-cooled glass, which is verified to be correlated with the larger amount of β relaxation in the fast-cooled sample. These findings provide new evidence for the inheritance between glass and liquid, and suggest that modulating the glassy state is a new route to control the crystallization kinetics of supercooled liquids.

An electrode with low performance or limited endurance for water splitting hydrogen generation has been the key limitation for application of hydrogen in contemporary clean-energy technologies. In this paper, an Al80Ni6Co3Mn3Y5Au3 metallic glass ribbon with outstanding catalytic activity in the hydrogen evolution reaction (HER) in acidic solutions is fabricated for the first time. Its overpotential is about 70 mV @ 10 mA cm−2 and Tafel slope is about 39 mV dec−1, which are comparable to those of commercial noble Pt/C electrodes (33 mV @ 10 mA cm−2 and 38 mV dec−1). Such a high catalytic reactivity is attributed to the synergic effect of multiple elements that disperse atomically homogeneously on the nanoporous surface. The outstanding catalytic activity persists and even becomes much better over a long-time reaction, which is attributed to the formation of a protective Au-rich layer in the interface. The Al-based metallic glass ribbon is flexible with high yield strength, large elasticity and good electrical conductivity, which are desirable and promising characteristics for a free-standing catalytic electrode in the HER.

Stress relief can improve the soft magnetic properties of Fe-based metallic glasses (MGs) and is vital for industrial applications. In this work, we investigated the evolution of soft magnetic properties, relaxation dynamics, and mechanical properties of Fe-based MGs under different applied tensile strains and stress relaxation times. We found that stress relaxation can significantly reduce coercivity Hc by 95% compared with as-quenched state. Furthermore, the coercivity Hc, apparent activation volume Vact and time constant tr all show analogous two-stage variation with annealing time, accompanied by approximate crossovers. This suggests that the microstructure change emerges, further verified by the domain wall motion and the transition from elastic to plastic. These results are helpful in preparing Fe-based MGs with excellent soft magnetic and mechanical properties by controlling the stress relaxation condition.

Cache-type phase-change random-access memory is a remaining challenge on the path to universal memory. The recently designed Sc0.2Sb2Te3 (SST) alloy is one of the most promising phase-change materi...

This paper studies a new mixed batch scheduling problem that arises in vacuum heat treatment. A mixed batch machine can process at most a given number of jobs simultaneously. The processing time of a batch is the weighted sum of the maximum processing time and the total processing time of jobs in the batch. The objective is to minimize the makespan. We first prove that the problem on a single machine can be solved in polynomial time, while the problem on multiple identical machines is NP-hard. Then, we develop a pseudopolynomial time exact algorithm when the number of machines is fixed. Further, we analyze the worst-case performance ratio of a full batch longest processing time algorithm and design Algorithm LPT-Greedy with improved worst-case performance.

In this paper, development of coupled codes using two-group neutron diffusion kinetics code and computational fluid dynamics (CFD) solver Fluent has been introduced. Way of coupling, time step control algorithm and spatial mesh overlays have been summarized in detail which are basic components and challenges of the coupling methodologies. The implement and verification of coupled code have been modeled on integral pressurized water reactor (IPWR) IP200 with hexagonal fuel assembly in the core and once-through steam generators. The steam line break core transient was analyzed in coupled code simulation of a core boundary conditions derived from system code simulation results. The results presented transient three-dimensional distribution of the key operation parameters such as reactor power and coolant temperature, also demonstrated the inherent safety features of IP200. The current work will bring about the ability to explore multi-scale and multi-dimensional safety transient evaluations and give more precise neutronics/thermal-hydraulics mapping.

Femoral neck fractures are among the most common fractures in orthopaedics. There are many surgical methods for the treatment of femoral neck fracture. Percutaneous cannulated lag screw fixation for the treatment of femoral neck fractures is favored by orthopaedic doctors because of its characteristics of being minimally invasive, with less bleeding and firm fixation. However, traditional freehand screw placement is limited by many factors, and the screw malposition rate is very high, which directly leads to the reduction of its biomechanical stability, and even leads to the ischemic necrosis of the femoral head caused by damage to blood vessels. In addition, excessive attempts to drill holes can damage cancellous bone and affect the screw's holding force, which reduces the stability of internal fixation and increases the risk of failure. At the same time, too much radiation exposure to medical personnel and patients also causes great damage to the body. Robot-assisted orthopaedic surgery combines the mechanical "eye" (an infrared ray tracking device) and the mechanical "hand" (six degrees of freedom mechanical arm), and through the process of preoperative planning, intraoperative assistance in screw placement, and postoperative confirmation, provides a more minimally invasive and precise treatment method for this kind of surgery, and significantly reduces radiation exposure. This guide uses the TiRobot system as an example to describe the robot surgery in detail, aiming at standardizing the application of robots in orthopaedic surgery.

In this letter, we report clear correlations between the glass transition temperature Tg, the crystallization temperature Tx, the Curie temperature TC and the electronegativity based on statistically analyzing more than 200 kinds of soft magnetic Fe-based amorphous alloys. The underlying physical origin of these correlations is discussed. Based on these correlations, the influences of various alloying elements are classified. These results are helpful for designing new soft magnetic amorphous alloys with high thermal stability.

Cloud manufacturing (CMfg) can make mass manufacturing resources more widely accessible to clients in the form of manufacturing services with their available time slots and the associated prices. In decentralized cases, clients can select optimal services to fulfill their individual demand. This paper proposes that clients can coordinate with each other for the exchange and reutilization of their booked resources. Via client coordination cost savings are derived from the post-optimization of the initial uncoordinated solution of all clients at the planning horizon. The optimization problem, which is a service booking and scheduling problem, has been proved to be strong NP-hard. Besides, we consider manufacturing synchronization (MfgSync) when scheduling a client's job on multiple resources, which includes simultaneity of completing the sub-tasks of a client's manufacturing job and punctuality of fulfilling the job. Optimal solution algorithms based on dynamic programming are proposed for two common cases. Considering the selfishness of each client, the success of the coordination depends on whether every participant can be better off than to act independently. We develop a cooperative game for client coordination and propose a core cost savings allocation scheme with which every client can get benefits through coordination. Based on the allocation scheme, clients tend to form a grand coalition. The computational results show that our approach can make substantial cost savings for clients.

Based on research of the low temperature fracture property of high grade steel pipe, it shows that X70, X80 steel pipe and X80 tee have high Charpy impact toughness. However, as the wall thickness increases, the shear area of DWTT decreases rapidly, and the thickness effect is significant. The research results show that the original wall thickness impact specimen fracture of steel pipe may not be ductile, for design temperature less than -30°C and wall thickness greater than 40mm. The brittle fracture was caused by structural factors. The Charpy impact energy, which just reflects the toughness of materials, does not show the fracture appearance as it would occur in service, because of the different specimen geometry and high rate of impact. The brittle fracture can occur at low temperature and low stress even with a high Charpy impact energy, the conditions of brittle fracture should be established under combination of the wall thickness, temperature and other factors. In this work, it is clarified that measurement of the fracture toughness under service temperature should be used to control low stress brittle fracture, besides the Charpy impact energy to ensure the material toughness.

We report the formation of a Gd10Tb10Dy10Ho10Er10Y10Ni10Co10Ag10Al10 denary high entropy metallic glass (HEMG). The magnetocaloric effect studies show that the denary HEMG possess large magnetic entropy changes over a wide temperature range, and thus a large refrigerant capacity. Combined with the simple alloy design of high entropy alloys and atomic level homogeneous single phase nature of metallic glasses, the magnetocaloric properties of HEMGs can be easily adjusted by changing the elements or configurational entropy. Our works show that the HEMG is a promising candidate material as the magnetic refrigerant.

Aiming at Bernoulli serial lines with batching machines and finite buffers, this study develops analytical methods for performance analysis and system-theoretic properties. Batching machines can pr...