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Filter pruning is a compression and acceleration method for deep convolutional neural network models that operates at a large scale. Many researchers have studied this approach and made significant progress, but the problem remains an open research topic. In this paper, we propose a DCNN structure optimization method for filter order–information structure similarity graph clustering with global pruning rate control, which considers the mapping strength distribution of convolution kernels in filters and the influence of equivalent convolution kernels on filter similarity. In this method, the relative strengths of the mappings between different convolution kernels in a filter determine the overall type of information combined in the output channel through the superposition filtering of information extracted from different input channels. The structural differences between the equivalent convolution kernels of different filters reflect the differences between the types of information extracted from the same input channel in the convolutional layer. By combining these two factors, we construct a measure of filter order–information structure similarity and then construct a filter similarity graph for the convolutional layer. For the pruning strategy, we establish a convolutional layer filter number allocation model with global pruning rate control using the scaling factors of batch normalization (BN) layers in sparse network. Then, in the filter similarity graph, we perform filter pruning by clustering subgraphs according to the given filter number allocation model for each convolutional layer. This yields an optimized structure for the pruned DCNN model. The experimental results and analysis demonstrate that our proposed method achieves effective pruning. In particular, on the ImageNet dataset, when pruning ResNet-50, the acceleration ratio and compression ratio of the model are 5.31x and 3.78x, respectively, while the model's classification accuracy decreases only slightly. Our method outperforms several state-of-the-art methods. [ABSTRACT FROM AUTHOR]

As studied in previous works, dynamic compliance presents widespread antiresonances in its spectrum, which could trap gradient-based topology optimization for minimum dynamic compliance and cause the optimization procedure to converge prematurely. In order to solve this problem, a novel method for predicting the frequencies that correspond to points of antiresonance in dynamic compliance spectrum is presented in this paper. By leveraging this eigenvalue formulation method, a strategy for introducing antiresonant frequency constraint is developed to solve one-material topology design for minimum dynamic compliance under high-frequency (above the first resonance of the initial design) excitations. In order to facilitate the exploitation of antiresonances, accurate track and eigenvalue sensitivity analysis for the prescribed antiresonant frequency are also discussed in detail. Numerical results show that the proposed method can achieve well-defined topologies with excellent dynamic performance. [ABSTRACT FROM AUTHOR]

This paper presents a topology optimization approach for the surface flows on variable design domains. Via this approach, the matching between the pattern of a surface flow and the 2-manifold used to define the pattern can be optimized, where the 2-manifold is implicitly defined on another fixed 2-manifold named as the base manifold. The fiber bundle topology optimization approach is developed based on the description of the topological structure of the surface flow by using the differential geometry concept of the fiber bundle. The material distribution method is used to achieve the evolution of the pattern of the surface flow. The evolution of the implicit 2-manifold is realized via a homeomorphous map. The design variable of the pattern of the surface flow and that of the implicit 2-manifold are regularized by two sequentially implemented surface-PDE filters. The two surface-PDE filters are coupled, because they are defined on the implicit 2-manifold and base manifold, respectively. The surface Navier-Stokes equations, defined on the implicit 2-manifold, are used to describe the surface flow. The fiber bundle topology optimization problem is analyzed using the continuous adjoint method implemented on the first-order Sobolev space. Several numerical examples have been provided to demonstrate this approach, where the combination of the viscous dissipation and pressure drop is used as the design objective. [ABSTRACT FROM AUTHOR]

Acute promyelocytic leukemia (APL) stands out as a distinctive form of acute leukemia, exhibiting a higher occurrence of thrombotic events when contrasted with other leukemia subtypes. Since thrombosis is a relatively rare but unfavorable condition with poor prognostic implications, it is crucial to determine the risk factors for thrombotic events in APL(thrombosis in large venous or arterial from onset to differentiation therapy in 30d). We performed a retrospective study involving 950 APL patients between January 2000 and October 2022, from which 123 were excluded by younger than 16 years of age, 95 were excluded by incomplete data, and 6 were excluded by thrombosis related to CVC or PICC. A total of 23 APL patients with thrombosis for inclusion in our analysis were performed a 1:5 ratio matching based on sex (perfect match) and age (within 5 years) to patients without thrombosis. These patients were continuously monitored in the outpatient department over a period of 5 years. We meticulously examined clinical and laboratory data to pinpoint the risk factors related to thrombotic events in APL. Our primary clinical endpoints were all-cause mortality and achieving complete remission, while secondary clinical outcomes included APL relapse. Thrombotic events were observed in 2.4% (23/950) of APL patients. Compared to patients without thrombosis, patients with thrombosis had higher lactate dehydrogenase (LDH) [313 (223, 486) vs. 233 (188, 367) U/L, p = 0.020], higher indirect bilirubin [11.2 (7.4, 18.6) vs.8.3 (6.0, 10.7) umol/L, p = 0.004], higher creatinine [72 (62, 85) vs. 63 (54, 74) umol/L, p = 0.026], higher CD2 expression (65.2 vs. 15.2%, p < 0.001), higher CD15 expression (60.9 vs. 24.3%, p = 0.001), and PML/RARαisoforms (p < 0.001). Multivariate-logistic-regression analysis revealed several factors that were markedly related to thrombosis, including LDH (OR≈1.003, CIs≈1.000–1.006, p = 0.021), indirect bilirubin (OR≈1.084, CIs≈1.000–1.188, p = 0.043), CD2 expression positive (OR≈16.629, CIs≈4.001–62.832, p < 0.001), and CD15 expression positive (OR≈7.747, CIs≈2.005–29.941, p = 0.003). The S-type (OR≈0.012, CIs≈0.000–0.310, p = 0.008) and L-type (OR≈0.033, CIs≈0.002–0.609, p = 0.022) PML/RARα isoforms were negatively associated with thrombosis. Kaplan–Meier curves indicated that the survival rates were remarkably varied between APL patients with and without thrombosis (HR:21.34, p < 0.001). LDH and indirect bilirubin are variables significantly associated with thrombosis in APL, S-type and L-type PML/RARαisoforms exhibit a negative association with thrombotic events. The thrombotic events of APL can predict the subsequent survival of thrombosis. The findings of our study have the potential to facilitate early detection of thrombosis and enhance the prognosis for individuals with APL who develop thrombosis. Further validation of our findings will be essential through future prospective or multicenter studies. [ABSTRACT FROM AUTHOR]

Beam features of variable cross-sections are developed in this paper for topology optimization based on feature-driven method. As beam structures are extensively used and mostly hold standard cross-sections in engineering practice, this work is aimed at the simultaneous design of beam layout and beam cross-section. The H-shaped cross-section is taken as general design primitive owing to its flexible evolution into T-shaped, C-shaped, and L-shaped cross-sections. Meanwhile, it is represented by means of the level-set functions (LSFs) with design variables consisting of the beam position, rotation angles, cross-section sizes, and cross-section configurations. Through the continuous change of defined cross-section configuration variables, different specifications of standard cross-sections with normed size values can be obtained and selected from the parts library. Fixed-mesh technique is also implemented for structural analysis and sensitivity analysis. Several numerical examples are presented to demonstrate the effectiveness and merits of the proposed method. [ABSTRACT FROM AUTHOR]

Hemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory syndrome with high mortality mediated by an unbridled and persistent activation of cytotoxic T lymphocytes and natural killer cells. However, the influence factors of early death in adult sHLH patients are still not fully elucidated, which need further investigating. We have conducted an observational study of adult HLH patients between January 2016 and December 2022. All patients are enrolled according to HLH-2004 criteria. Clinical manifestations, laboratory data, treatments, and outcomes have been recorded. Influence factors associated with prognosis are calculated by using logistic regression models. Overall, 220 patients enrolled in this study. The etiologies of HLH were divided into five groups including autoimmune-associated hemophagocytic syndrome (AAHS) (n = 90, 40.9%), malignancies (n = 73, 33.2%), EBV-HLH (n = 18, 8.2%), infection excluded EBV (n = 24, 10.9%), and other triggers (n = 15, 6.8%). Among them, EBV-HLH had the highest mortality (77.8%), and AAHS had the lowest mortality (14.4%). Multivariate analysis indicated that age (≥ 38 years old), cytopenia ≥ 2 lines, platelets (≤ 50 × 109/L), aspartate aminotransferase (≥ 135U/L), prothrombin time (≥ 14.9 s) and activated partial thromboplastin time (≥ 38.5s), EBV, and fungal infection are independent risk factors for poor prognosis of HLH. Adult HLH patients with elder age, cytopenia ≥ 2 lines, levels of decreased platelets, increased AST, prolonged PT and APTT, EBV, and fungal infection tend to have a poor prognosis. [ABSTRACT FROM AUTHOR]

Study objective: This study aims to investigate the characteristics of patients with an initial diagnosis of systemic lupus erythematosus (SLE) in an emergency department (ED) and their outcomes. Methods: A total of 147 SLE patients (119 females and 28 males, mean age 26 ± 19 years) who visited the ED of the Peking University People's Hospital between January 2017 and June 2022 were enrolled in the study. Data on demographic information, clinical characteristics, comorbidities, therapy, and outcomes were collected. Results: Most patients visit ED because of symptoms related to SLE (74.8%, 110/147). The remaining 37 patients (25.2%) visited ED due to infection (43.2%, 16/37), gastrointestinal bleeding (10.8%, 4/37), coronary heart or cerebrovascular disease (18.9%, 7/37), macrophage activation syndrome or thrombotic microangiopathy (18.9%, 7/37), leukemia (5.4%, 2/37), and hepatic encephalopathy (2.7%, 1/37). Of the patients, 54.4% (80/147) were first diagnosed with SLE at the time of their ED visit. Thrombocytopenia events occurred significantly more frequently in this group of patients (OR 3.664, 95% CI 1.586–8.464, p = 0.002). Pulse steroid therapy was administered to 32.5% (26/80) of the patients with an initial diagnosis of SLE, and 26.3% (21/80) of these patients also received IVIG therapy during their ED visit. SLEDAI scores were significantly decreased after 6 months of therapy. The rate of mortality was 6.8% (10/147) in the 6-month follow-up period, and all the ten deaths happened in patients with disease-established SLE. The main causes of death were infections (two patients) and SLE flare (four patients). Conclusion: Understanding disease patterns can contribute to physicians providing accurate diagnosis and efficient care for SLE patients in ED. Key Points • Systemic lupus erythematosus, a complex autoimmune disorder, can have either a chronic or a relapsing and remitting disease course. The disease can involve acute events or severe comorbidities, and frequent visits to the emergency department (ED) are inevitable. • It is essential to better understand which comorbidities can lead to emergency department visits. Accurate clinical diagnosis and appropriate interventions from ED physicians can have a strong impact on the prognosis of the disease. • Hematologic compromise attributed to SLE flare is the most common reason for ED visits. Owing to aggressive treatments, the clinical outcomes in patients with initial diagnosis of SLE have improved notably. • Our study highlights that early recognition and appropriate management of SLE-related conditions and other comorbidity in ED are crucial. [ABSTRACT FROM AUTHOR]

This work presents a topology optimization method for prestressed cable-truss structures considering geometric nonlinearity. Based on the large deformation kinematics theory, we establish a multi-node cable element model, which can fully take into account the geometric nonlinearity caused by external loads and prestress. Besides, nonlinear hyperelasticity principles are used to deal with cable materials’ unidirectional stress characteristics. To consider the impact of prestress on the global structural stiffness, we carried out the rebalancing of prestress and construct an objective function of prestress-modified compliance. Then, we equate the cable-truss structure as a particular two-phase material structure and realize the material interpolation based on a discrete material optimization-like method. Finally, we perform the adjoint sensitivity analysis of the objective function and solve the optimization problem through the gradient-based algorithm. Therefore, we establish a topology optimization method for prestressed cable-truss structures with stiffness as the objective, continuous density/size parameters as variables, and mass fraction as constraints. This method’s feasibility and reliability are demonstrated in 2D and 3D numerical examples. [ABSTRACT FROM AUTHOR]

This work develops a topological optimization framework for parametric lattice structure design under harmonic load based on the scale-dependent multiscale finite element method (MsFEM). Two different design variables are introduced and optimized simultaneously in the topology optimization, i.e., the control parameters represent the lattice cell’s material consumption and the configuration. To improve analysis accuracy and efficiency, the MsFEM with periodic boundary condition is used for structures with strong periodicity and the MsFEM with six nodes on each edge of the coarse element is used for those with weak periodicity, respectively. Then the scale-dependent lattice cell’s equivalent stiffness and mass matrices can be established. The surrogate model of the relationship between the lattice control parameters and stiffness matrices and mass matrices is built based on the proper orthogonal decomposition and diffusion approximation methods. Therefore, sensitivity analysis of the dynamic responses concerning the control parameters can be performed. Finally, numerical examples and vibration testing results are presented to show the validity of the optimization framework using gradient lattice structures to suppress vibration under frequency band loading and its potential application in engineering practice. [ABSTRACT FROM AUTHOR]

Morphing aircraft can adaptively regulate their aerodynamic layout to meet the demands of varying flight conditions, improve their aerodynamic efficiency, and reduce their energy consumption. The design and fabrication of high-performance, lightweight, and intelligent morphing structures have become a hot topic in advanced aircraft design. This paper discusses morphing aircraft development history, structural characteristics, existing applications, and future prospects. First, some conventional mechanical morphing aircraft are examined with focus on their morphing modes, mechanisms, advantages, and disadvantages. Second, the novel applications of several technologies for morphing unmanned aerial vehicles, including additive manufacturing for fabricating complex morphing structures, lattice technology for reducing structural weight, and multi-mode morphing combined with flexible skins and foldable structures, are summarized and categorized. Moreover, in consideration of the further development of active morphing aircraft, the paper reviews morphing structures driven by smart material actuators, such as shape memory alloy and macro-fiber composites, and analyzes their advantages and limitations. Third, the paper discusses multiple challenges, including flexible structures, flexible skins, and control systems, in the design of future morphing aircraft. Lastly, the development and application of morphing structures in the aerospace field are discussed to provide a reference for future research and engineering applications. [ABSTRACT FROM AUTHOR]

In this work, a novel optimization method is proposed to pursue high-performance 3D-braided composite structure under thermo-mechanical loads, which optimizes structural topology and braiding parameters concurrently. To realize such design under affordable computational cost, we decompose the optimization method into offline and online stages. In the offline stage, a parameterized geometric model controlled by two braiding parameters, i.e., fiber volume fraction and braiding angle, is established to characterize the microstructure of composite. Subsequently Energy-based Homogenization Method is applied to calculate equivalent composite properties including elastic tensor, thermal conductivity tensor, and Coefficient of Thermal Expansion. A surrogate model based on Radial Basis Network is established to map braiding parameters to equivalent material properties. In the online stage, the surrogate model is integrated into Rational Approximation of Material Properties to build a systematic design scheme for structural topology and braiding parameters. Taking manufacturability into account, the proposed method is combined with stiffener layout design to obtain easy-to-manufacture braided composite structures. Finally, several numerical examples are provided to demonstrate the effectiveness of the proposed optimization method, indicating that braiding parameters have essential impacts on the composite structural design and performance. [ABSTRACT FROM AUTHOR]

To fully utilize the in-situ resources on the moon to facilitate the establishment of a lunar habitat is significant to realize the long-term residence of mankind on the moon and the deep space exploration in the future. Thus, intensive research works have been conducted to develop types of 3D printing approach to adapt to the extreme environment and utilize the lunar regolith for in-situ construction. However, the in-situ 3D printing using raw lunar regolith consumes extremely high energy and time. In this work, we proposed a cost-effective melting extrusion system for lunar regolith-based composite printing, and engineering thermoplastic powders are employed as a bonding agent for lunar regolith composite. The high-performance nylon and lunar regolith are uniformly pre-mixed in powder form with different weight fractions. The high-pressure extrusion system is helpful to enhance the interface affinity of polymer binders with lunar regolith as well as maximize the loading ratio of in-situ resources of lunar regolith. Mechanical properties such as tensile strength, elastic modulus, and Poisson’s ratio of the printed specimens were evaluated systematically. Especially, the impact performance was emphasized to improve the resistance of the meteorite impact on the moon. The maximum tensile strength and impact toughness reach 36.2 MPa and 5.15 kJ/m2, respectively. High-pressure melt extrusion for lunar regolith composite can increase the effective loading fraction up to 80 wt.% and relatively easily adapt to extreme conditions for in-situ manufacturing. [ABSTRACT FROM AUTHOR]

Cellular infill structures such as honeycomb have been widely used in the field of light weighting. In recent years, the emergence of additive manufacturing technologies has provided a new solution to fabricate complicated cellular infill structures. This paper presents a continuous printing path planning method for gradient honeycomb structures. Given a 2D filling region represented by a polygon, a honeycomb graph that covers the filling area is trimmed to generate an infill pattern. Then an algorithm is proposed to transform the honeycomb filling pattern into an Eulerian graph, which can be traversed by a single-stroke printing path. For each honeycomb, double-spiral paths are used to generate gradient honeycomb structures with varying wall thicknesses. Later, the 2D honeycomb infills are generalized to 3D cases that are suitable for multi-axis printing. First, three mutually orthogonal vector fields that are embedded on the tetrahedral mesh of the printed part are generated by considering the support-free condition. Then the three vector fields are used to calculate three monotonically increasing scalar distance fields, which span a non-Euclidean space. Finally, the 2D honeycomb infills are generated in the non-Euclidean space with parallel sliced layers, which are then mapped back to the Euclidean space to obtain the real self-supporting 3D honeycomb infills. The proposed 2D/3D honeycomb infill structures generation algorithms have been verified by both simulation and experimental tests. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMA) are an ideal class of metallic materials for reusable energy dissipation structures because of pseudo-elasticity. This paper presents a density-based topology optimization framework for the design of SMA structures utilizing pseudo-elastic behaviors to dissipate large amounts of energy under prescribed design constraints. A phenomenological constitutive model is adopted to accurately simulate the mechanical behaviors of SMA, and the corresponding material interpolation scheme is developed via SIMP method. Numerical instability caused by excessive distortion of low-density elements is alleviated by super element method. The degree of phase transformation, which is related to the energy dissipation, is characterized by strain energy and end compliance. Sensitivities are derived via adjoint method. A number of optimized simple-supported beam structures and 2D lattice structures with different energy dissipation performance and stiffness capacity are tailored. In addition, the load dependency and initial design dependency for the optimization of SMA energy dissipation structures are discussed. [ABSTRACT FROM AUTHOR]

Comparing the characteristics of thrombotic thrombocytopenic purpura (TTP) and TTP-like syndrome patients at admission will allow early differentiation of TTP from TTP-like syndrome and help tailor initial treatment. The medical records of 78 patients with suspected TTP in the Emergency Department of Peking University People's Hospital in the past 5 years were retrospectively analyzed and divided into TTP and TTP-like syndrome groups based on ADAMTS13 activity and ADAMTS13 antibody titer. There were 25 and 53 patients in the TTP group and the TTP-like syndrome group, respectively. The neutrophil-to-lymphocyte ratio (P = 0.025) was tremendously higher, and albumin (P = 0.002) was lower in the TTP-like syndrome group, indicating a more severe inflammation. Compared with the TTP-like syndrome group, the TTP group had an approximately two-fold to three-fold higher prevalence of central nervous system dysfunction (P < 0.001). Also, hemolysis was more substantial in the TTP group as evidenced by higher schistocytes (P < 0.001), reticulocyte (P < 0.001), total bilirubin (P = 0.002), indirect bilirubin (P < 0.001), lactate dehydrogenase (P = 0.007) and cell-free hemoglobin (P < 0.001), simultaneously lower platelet (P < 0.001), haptoglobin (P = 0.044), and ADAMTS13 activity (P < 0.001). The Kaplan–Meier survival analysis showed that the TTP group significantly predicted poor prognosis (log-rank test: X2 = 5.368, P = 0.021). TTP and TTP-like syndrome are two kinds of distinct phenotypes with different hemolysis statuses and illustrated differentiated inflammatory reactions, target organ damage (TOD), and the clinical outcome. [ABSTRACT FROM AUTHOR]

In this paper, a B-spline parameterized density method is proposed to simultaneously optimize the structural topology and the build direction for additive manufacturing (AM). B-spline parameterization is used to represent the structural density field together with Heaviside projection and Boolean operation. Two constraints and a novel filtering scheme relevant to AM are presented: The overhang angle constraint constructed based on the density gradient with build direction included as design variables. The boundary gradient constraint constructed for possible V-shaped cross-section features of 3D problems in various build directions. The gradient filtering scheme adopted to eliminate the V-shaped areas by computing the global overhang angle at all structural boundaries. Representative 2D and 3D problems are dealt with to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Autonomous landing in non-cooperative environments is a key step toward full autonomy of unmanned aerial vehicles (UAVs). Existing studies have addressed this problem by finding a flat area of the ground as the landing place. However, all these methods have poor generalization ability and ignore the semantic feature of the terrain. In this paper, we propose a well-designed binocular-LiDAR sensor system and a robust terrain understanding model to overcome these deficiencies. Our model infers both morphologic and semantic features of the ground by simultaneously performing depth completion and semantic segmentation. Moreover, during the inference phase, it self-evaluates the accuracy of the predicted depth map and dynamically selects the LiDAR accumulation time to ensure accurate depth prediction, which greatly improves the robustness of the UAV in completely unknown environments. Through extensive experiments on our collected low-altitude aerial image dataset and real UAVs, we verified that our model effectively learned two tasks simultaneously and achieved better performance than existing depth estimation-based landing methods. Furthermore, the UAV can robustly select a safe landing site in several complex environments with about 98% accuracy. [ABSTRACT FROM AUTHOR]

Purpose: To summarize the clinical characteristics and surgical option of Robert's uterus. Methods: We reported a rare case of Robert's uterus with severe uterine adhesion with successive laparoscopic and hysteroscopic surgery. To our knowledge, such a case has not been reported previously. We also performed a systematic literature review from the PubMed, Embase, and Cochrane databases. Results: Our patient with Robert's uterus with severe uterine adhesions was successfully treated with hysteroscopic septal resection and hysteroscopic adhesiolysis, and the intractable dysmenorrhea disappeared after the hysteroscopic septal resection. In our study, we analyzed the selected 22 reported cases, 10/22 cases (45.5%) were diagnosed before age 20; 20/22 cases (90.91%) experienced dysmenorrhea, 19/22 cases (86.36%) were with hematometra. 5/22 cases (22.73%) underwent re-operation or a third surgery before diagnosis and management. Conclusion: Robert's uterus, a rare congenital abnormality of Mullerian duct development, consists of an oblique septum and non-communicating asymmetrical uterine hemi-cavity. The main symptoms are the presence of hematometra and severe dysmenorrhea. Septal resection is the main surgical procedure; however, the rarity and difficulty obtaining a pre-operative diagnosis lead to a high rate of misdiagnosis and second surgery. [ABSTRACT FROM AUTHOR]

Radar cross section (RCS) reduction for cavities is essential in flight vehicle design. As a conventional method to reduce the RCS, coating radar absorbing materials has been widely employed in engineering. Nevertheless, radar absorbing coatings (RAC) will additionally increase the structural weight. In this paper, a topology optimization approach is introduced for the layout design of RAC on the inner cavity walls. The objective of this problem is to minimize the mean value of RCS under the prescribed incident angles. A SIMP-like model is employed to represent the relative impedance of areas of intermediate density. The design variable is iteratively updated during the optimization process using a gradient-based algorithm. The RCS of the cavity is computed by the iterative physical optics method, which is utilized for the subsequent analytical gradient derivation. The validity of the proposed method is demonstrated by optimizing the RAC layout of two different shaped cavities. In both numerical examples, when optimizing the RCS in both planes with a weight of 1:1 and a volume fraction of 50%, the highest RCS loss rate in both horizontal and pitch planes is 18.02% and the lowest is only 6.89%. The optimization results indicate that the proposed method can be employed as a design procedure to consider both weight cost and cavity RCS reduction when coating the absorbing materials, instead of the classical experience-based RAC distributions. [ABSTRACT FROM AUTHOR]

Deep neural network pruning is an effective model compression and acceleration method. In the initial pruning stage, maintaining the integrity of the input channel of the convolution layer is very important to improve the performance of the pruning model. This paper proposes a two-stage multi-strategy progressive kernel pruning method with adjustable input channels. First, a Hybrid Norm Sparse Index (HNSI) is defined as the basis for selecting the number of retained kernels, and then a two-stage progressive pruning technique is adopted. In the first stage, HNSI is used in the groups for moderate kernel pruning. HNSI in the group can reserve at least one kernel in each group, allowing the input channel information of each layer to be mapped to the next layer and ensuring better network optimization through moderate pruning. In the second stage, HNSI is used in the layers for adjustable full kernel pruning. At this stage, the HNSI of each layer is the basis of preserving the kernel number, and the pruning process is divided into two strategies. The first strategy is kernel pruning in the low-level layer. On the basis of the overall kernel pruning in the layer, each group is forced to retain at least one kernel, thus ensuring that the primary feature of each input channel can be transmitted to the next layer. The second strategy is kernel pruning in the high-level layer. Because of the stronger information abstraction ability in the high-level layer, only the valid input channel information can be passed to the next layer, no longer forcing each group to retain the kernel, which can greatly improve the efficiency of network pruning. Model analysis and experiments show that the two-stage kernel pruning can not only obtain better network optimization direction under moderate pruning but also obtain better network performance under a higher pruning rate. [ABSTRACT FROM AUTHOR]

Objective: To explore the significance of Fluorine-18 labeled fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in diagnosing connective tissue diseases (CTDs) in fever of unknown origin (FUO) or inflammation of unknown origin (IUO) patients. Methods: Clinical and image data of 242 consecutive FUO/IUO patients who underwent PET/CT examination and eventually diagnosed CTDs were retrospectively analyzed, including distribution of diseases, clinical characteristics, and PET/CT imaging findings. The role of FDG PET/CT in differential diagnosis of CTDs was evaluated through clinical questionnaire survey. Results: Patients diagnosed as CTDs accounted for 48.1% of FUO/IUO patients. Among them, adult-onset Still's disease was most frequently diagnosed. Other common diseases included systemic vasculitis, undifferentiated connective tissue disease, rheumatoid arthritis, idiopathic inflammatory myopathy, systemic lupus erythematosus, and polymyalgia rheumatica. On FDG PET/CT examination, 97.9% of the patients had positive findings. Inflammatory lesions were detected in 66.5% and non-specific abnormal uptakes were found in 31.4%. Detected lesions distributed consistently with corresponding susceptible organs and tissues in various diseases. Clinical questionnaire results shown that FDG PET/CT excluded malignant tumors, focal infections, or other typical CTDs in 45.5% of the patients; indicated important diagnostic clues or appropriate biopsy sites in 20.6% of patients; and directly suggested the diagnosis of a CTD in 33.1% of patients. Conclusion: FDG PET/CT could reveal inflammatory lesions in organs and tissues that reflect the clinical characteristics in different CTDs, thus providing an objective evidence for differential diagnosis, classification, and treatment decision of these diseases. Key Points • FDG PET/CT is a useful tool for differential diagnosing connective tissue diseases among patients with fever of unknown origin/inflammatory of unknown origin. [ABSTRACT FROM AUTHOR]

Hyperferritinemia comes to light frequently in general practice. However, the characteristics of COVID-19-associated hyperferritinemia and the relationship with the prognosis were not well described. The retrospective study included 268 documented COVID-19 patients. They were divided into the hyperferritinemia group (≥ 500 µg/L) and the non-hyperferritinemia group (< 500 µg/L). The prevalence of fever and thrombocytopenia and the proportion of patients with mechanical ventilator support and in-hospital death were much higher in the hyperferritinemia group (P < 0.001). The hyperferritinemia patients showed higher median IL-6, D-dimer, and hsCRP (P < 0.001) and lowered FIB level (P = 0.036). The hyperferritinemia group had a higher proportion of patients with AKI, ARDS, and CSAC (P < 0.001). According to the multivariate analysis, age, chronic pulmonary disease, and hyperferritinemia were found to be significant independent predictors for in-hospital mortality [HR 1.041 (95% CI 1.015-1.068), P = 0.002; HR 0.427 (95% CI 0.206-0.882), P = 0.022; HR 6.176 (95% CI 2.447-15.587), P < 0.001, respectively]. The AUROC curve was 0.88, with a cut-off value of ≥ 971 µg/L. COVID-19 patients with hyperferritinemia had a high proportion of organ dysfunction, were more likely to show hyper-inflammation, progressed to hemophagocytic lymphohistiocytosis, and indicated a higher proportion of death. [ABSTRACT FROM AUTHOR]

Aiming at the exploration and resource utilization activities on the Moon, in situ resource utilization and in situ manufacturing are proposed to minimize the dependence on the ground transportation supplies. In this paper, a laser-assisted additive manufacturing process is developed to fabricate lunar regolith composites with PA12/SiO2 mixing powders. The process parameters and composite material compositions are optimized in an appropriate range through orthogonal experiments to establish the relationship of process—structure—property for lunar regolith composites. The optimal combination of composite material compositions and process parameters are mixing ratio of 50/50 in volume, laser power of 30 W, scanning speed of 3500 mm/s, and scanning hatch space of 0.2 mm. The maximum tensile strength of lunar regolith composites reaches 9.248 MPa, and the maximum depth of surface variation is 120.79 µm, which indicates poor powder fusion and sintering quality. Thereafter, the mechanical properties of laser-sintered lunar regolith composites are implemented to the topology optimization design of complex structures. The effectiveness and the feasibility of this laser-assisted process are potentially developed for future lightweight design and manufacturing of the solar panel installed on the lunar rover. [ABSTRACT FROM AUTHOR]

The electromagnetic performance of flight vehicles has been attracting considerable interest in recent years. As one of the important indicators of this performance, radar cross section (RCS) has been extensively studied. A significant limitation on the RCS of flight vehicles lies in the fact that tiny gaps will transform into steps during structural deformation, where the local RCS will be significantly affected. This study investigates a topology optimization method to minimize the RCS of step structures when subjected to external loads. To ensure that the structure discretized by shell elements in the mechanical finite element analysis can still simulate the wave reflection of step structures, artificial step elements are defined to simulate the generation of steps during structural deformation. Then, the conventional method of moments is utilized to calculate the RCS. To implement the gradient-based optimization, the sensitivity of RCS with respect to the design variables is derived analytically by the adjoint method. An extended compliance-based topology optimization is performed to determine a stiffness constraint. Then, together with a structural volume limitation, the average RCS of target incident angles will be set as the object to obtain the structural topology. The superiority compared with the general structural design method and the validity have been demonstrated with numerical examples. [ABSTRACT FROM AUTHOR]

In this work, a novel concurrent optimization framework based on multiscale finite element method is proposed to pursue superior-performance hierarchical structures with parameterized lattice. Distinguished with conventional homogenization-based optimization method, this framework gets rid of the assumption of scale separation while optimizing hierarchical structures. Firstly, a multi-parameter description is presented to generate a family of parameterized lattice cells that share similar geometric features. In order to balance structural performance and computational cost, we decompose the optimization framework into offline and online stages. In the offline stage, the equivalent stiffness matrix of lattice is calculated with the help of multiscale finite element method. A surrogate model based on general regression neural network (GRNN) is established to map lattice parameters to equivalent stiffness matrix. Besides, the discrete topological variables are introduced to determine the distribution of lattice. Discrete material optimization (DMO) model is employed to integrate such two kinds of design variables into a material interpolation model. Hence, the concurrent optimization framework can optimize the macroscopic distribution and their spatially varying lattice configurations simultaneously at an affordable computation cost. Finally, numerical examples are presented to illustrate the effectiveness of the proposed concurrent optimization framework, indicating that lattice size, relative density, and configuration have essential impacts on the hierarchical structural design and performance. [ABSTRACT FROM AUTHOR]

High-resolution additive manufacturing (AM) facilitates engineering applications of cellular lattices with complex geometries. The unique layer-by-layer process of AM causes the mechanical performance of as-fabricated lattice structures to deviate from the ideal value. In this study, the AM process-induced material anisotropy and geometric inaccuracy are integrated into the mechanical evaluation and topology optimization of lattice structures. Specifically, effective mechanical properties of typical strut-based and shell-based lattices are evaluated by the homogenization method combined with the process-induced features. The equivalent stiffness parameters of ideal and as-fabricated lattices are integrated into the topology optimization algorithm to adaptively obtain corresponding macrostructures. Based on the knowledgebase of unit cells and optimized results, the threshold of the variation for microstructure is extracted to guide design and process parameter selection. The proposed design guidelines and evaluation-adjustment framework can be widely applied to various lattices fabricated by AM technologies. [ABSTRACT FROM AUTHOR]

For reaching deterministic self-stabilising distributed synchronisation with commercial-off-the-shelf (COTS) Ethernet, this paper explores the Wire-Adapted Linker-Decoupled EtherNet (WALDEN) architecture with the integration of several mass-produced COTS products. Upon this architecture, basic strategies of distributed synchronisation are discussed. Self-stabilising algorithms are presented and formally analysed. Besides, a prototype system is realised with COTS switches, PHY chips, and low-end ARM series under the WALDEN architecture with a minimum hardware modification. The experimental result shows that a sub-microsecond synchronisation precision can be achieved with this prototype implementation even in the presence of low-quality switch with non-queuing delay-jitters of several microseconds. Among existing solutions, this work features in considering the distributed synchronisation, backward-compatibility, and self-stabilisation problems as a whole. [ABSTRACT FROM AUTHOR]

Multidisciplinary topology optimization (TO) for additive manufacturing (AM) exhibits unprecedented design and manufacturing freedom as an effective lightweight methodology. In order to fully utilize the AM advantages of materialized arrangement in spatial and voxel-by-voxel digitalized printing, multidisciplinary TO for AM requires a full understanding of the process-structure-property-performance (PSPP) relationship to establish the quantitative correlation of part property and multiple process factors, including laser-, process-, and material-related parameters. This study incorporates the PSPP relationships of laser sintered material with topology optimizer so as to provide a guideline for TO collaborative AM design. The proposed workflow involves mapping functions of PSPP relationships via a data-driven approach and then optimizes the multiple process parameters and structural topology by the gradient-based algorithm. Compared with conventional optimization approaches, three case-dependent optimizations demonstrate the effectiveness of the proposed approach yielding encouraging improvements of lightweight performance. The multidisciplinary TO can be generally applied to types of AM technologies, establishing a strong linkage of physical product and digital design. [ABSTRACT FROM AUTHOR]

In this paper, chiral metamaterials (CMM) were optimized from conceptual design to fine design with the effective elastic constants unchanged under finite strain. First, through calculation and comparison of examples, the unit cell method was selected to compute the effective elastic properties of the periodic chiral metamaterials under finite strain. Secondly, the conceptual design of chiral metamaterials with prescribed Poisson's ratios under finite strain was realized through density-based and feature-driven topology optimization. Then, the method of moving asymptotes (MMA) was used to solve the optimization problems. Based on the optimal configuration, chiral metamaterials with prescribed Poisson's ratios and Young's moduli under finite strain were carefully designed through shape optimization. Genetic algorithm was used to solve the optimization problem. Finally, the optimal models were fabricated by 3D printing. The optimal design was validated by tensile test results, i.e., the designed chiral metamaterials can maintain effective elastic properties under large deformation, and the invariance of the effective elastic properties depends on the nonlinearity of the flexible chiral metamaterials. [ABSTRACT FROM AUTHOR]

This paper presents a thermomechanical model for pseudoelastic shape memory alloys (SMAs) accounting for internal hysteresis effect due to incomplete phase transformation. The model is developed within the finite-strain framework, wherein the deformation gradient is multiplicatively decomposed into thermal dilation, rigid body rotation, elastic and transformation parts. Helmholtz free energy density comprises three components: the reversible thermodynamic process , the irreversible thermodynamic process and the physical constraints of both. In order to capture the multiple internal hysteresis loops in SMA, two internal variables representing the transition points of the forward and reverse phase transformation, ϕ s f and ϕ s r , are introduced to describe the incomplete phase transformation process. Evolution equations of the internal variables are derived and linked to the phase transformation. Numerical implementation of the model features an Euler discretization and a cutting-plane algorithm. After validation of the model against the experimental data, numerical examples are presented, involving a SMA-based vibration system and a crack SMA specimen subjected to partial loading–unloading case. Simulation results well demonstrate the internal hysteresis and free vibration behavior of SMA. [ABSTRACT FROM AUTHOR]

Backgrounds: Angiopoietin-2 (Ang-2) is a new predictor for acute pancreatitis (AP). Aims: To assess the predictive value of Ang-2 in determining the progress of AP and the subsequent acute gastrointestinal injury (AGI). Methods: This was a prospective study that enrolled 170 patients with AP and 100 healthy controls. Blood samples were collected within 24 h of the onset of AP. Results: The majority (108) of the patients were categorized as having MAP with the rest (62) classified as suffering from SAP. Considering AGI grading, there were 118 grade 1 and 12 grade 4 patients; in grades 2 and 3, there were 20 patients each. AP was accompanied by MODS and pancreatic necrosis in 46 and 24 cases, respectively. Eighty patients were admitted to the ICU, while mortality was reported among 7.1% patients. The plasma Ang-2 levels were higher among patients with AP than in controls. A similar trend prevailed, in patients with SAP compared to those with MAP. Ang-2 was significantly increased from AGI grade 1 through to grade 4, showing a desirable positive predictive accuracy. Moreover, Ang-2 also showed strong correlations with intestinal permeability as evaluated by d-lactate (DLA), diamine oxidase (DAO), and intestinal fatty acid binding proteins (I-FABPs). Tools (Ranson and APACHE II scores, CRP), which are used more conventionally, could not effectively distinguish the various grades of AGI. Furthermore, Ang-2 predicted poor prognosis and adverse outcomes, including mortality, among patients with AP. Conclusions: This study showed Ang-2 to be an accurate early predictor for SAP, AGI, and intestinal barrier dysfunction, outperforming conventional biomarkers. Ang-2 levels also predicted the adverse outcomes and mortality due to AP. [ABSTRACT FROM AUTHOR]

To date, sealing structures have been widely used in aerospace vehicles. This paper presents a normalized and systematic procedure realizing lightweight design for a square bolt-flange sealing structure of a rocket engine. To measure the sealing behavior, the contact force on the sealing interface is obtained by a nonlinear analysis of node-to-node contact. The topology optimization is established to achieve sufficient contact forces in the sealing area by acquiring the Kreisselmeier-Steinhauser (KS) function to condense multiple contact force constraints into a global sealing constraint. A three-field projection scheme is also adopted to obtain a clear result and a semi-analytical perturbation scheme is proposed to realize the sensitivity calculation. Then, the square flange cover is optimized by the proposed optimization framework and a lightweight design with a clear load-carrying path is obtained. The optimized design is reconstructed and further optimized in detail. Compared with several traditional designs, it shows better leakproofness under inner liquid pressure, which can be directly fabricated by additive manufacturing and used in the rocket engine. The optimization procedure is proved effective and practical in designing sealing structures for aerospace vehicles. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results. [ABSTRACT FROM AUTHOR]

The new outbreak of Coronavirus Disease 2019 (COVID-19) has emerged as a serious global public health concern. A more in-depth study of blood coagulation abnormality is needed. We retrospectively analyzed 147 consecutive patients with COVID-19 who were admitted to three ICUs in Wuhan from February 9th, 2020 to March 20th, 2020. The baseline coagulation and other characteristics were studied. Our results showed that the prolonged PT, FDP, DD were positively correlated with the levels of neutrophils, ferritin, LDH, total bilirubin, multi-inflammation cytokines, and negatively correlated with the lymphocytes level (p < 0.01). The level of ATIII was significantly negatively correlated with the levels of neutrophils, ferritin, LDH, total bilirubin, IL2R, IL6 and IL8 (p < 0.05). The patients in the ARDS group had a more prominent abnormality in PT, FDP, DD and ATIII, while the patients in the AKI group had more prolonged PT, more severe FDP and DD level, more inferior ATIII and Fib level than those in the non-AKI group (p < 0.01). The value of PT, DD and FDP were positively correlated with the classical APACHE II, SOFA and qSOFA scores, while the ATIII was negatively correlated with them (p < 0.001). The high levels of PT, FDP and DD were correlated with in-hospital mortality (p < 0.001). In conclusion, blood coagulation disorder was prominent in ICU patients with COVID-19 and was correlated with multi-inflammation factors. The abnormality of blood coagulation parameters could be an adverse prognostic indicator for ICU patients with COVID-19. [ABSTRACT FROM AUTHOR]

This work grew out of rapid developments of topology optimization approaches and emerging industry trends of "3D printing" techniques, the latter bridging to a large extent the gap between innovative design and advanced manufacturing. In the present work, we first make an application-oriented review of topology optimization approaches in an attempt to illustrate their efficacy in the design of high-performance structures. Subsequently, a broad panorama of additive manufacturing is provided with a particular interest in its application in the automotive and the aerospace sectors. Taking an aerospace bracket as an example, we further go through an entire procedure from topology optimization design to additive manufacturing, then to performance verification. In the interest of cultivating a long-term partnership upon this combination, we finally examine, in face of present and near future, limitations of additive manufacturing in the loss of geometric accuracy and performance deterioration, and provide a roadmap for future work. [ABSTRACT FROM AUTHOR]

This paper presents the topology optimization of hierarchical microtextures for wetting behavior in the Cassie-Baxter mode, considering a structural unit of the hierarchical microtexture composed of base and secondary structures. The geometrical configuration of the considered structural unit can be described as a fiber bundle composed of an external surface of the base structure and the pattern of the secondary structures. Thus, two design variables are defined, one for the external surface of the base structure, and the other for the pattern of the secondary structures. The Young-Laplace equation, including a term depending on the mean curvature of the external surface, is used to describe the liquid/vapor interface imposed with a surface tension in the Cassie-Baxter mode. To overcome the difficulty of numerically computing the second-order derivative of the external surface, two partial differential equation filters are sequentially applied to the design variable of the base structure to ensure the numerical accuracy and feasibility of using an efficient linear-element-based finite element method to solve the Young-Laplace equation. To improve the performance of the hierarchical microtextures, the volume of the liquid bulges suspended at the liquid/vapor interface in the Cassie-Baxter mode, before the transition into the Wenzel mode, is minimized to optimize the match between the external surface of the base structure and the pattern of the secondary structures. In the topology optimization process, penalization of the material density of the surface tension is achieved by an artificial Marangoni phenomenon. In numerical examples, solid surfaces are tiled into textures with axial symmetry, radial symmetry, chirality, and quasiperiodicity; and structural units are derived consisting of base structures with peak shapes and dense secondary structures surrounding the crests of the peaks. The optimized performance of the derived structural units has been confirmed by comparisons. [ABSTRACT FROM AUTHOR]

Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat dissipation. In this work, by combining experimental and numerical methods, we investigate the compressive behavior and energy absorption of lattices made through the stereolithography apparatus process. Four types of lattice structures are considered: (i) Uniform body-centered-cubic (U-BCC); (ii) graded body-centered-cubic (G-BCC); (iii) uniform body-centered-cubic with z-axis reinforcement (U-BCCz); and (iv) graded body-centered-cubic with z-axis reinforcement (G-BCCz). We conduct compressive tests on these four lattices and numerically simulate the compression process through the finite element method. Analysis results show that BCCz has higher modulus and strength than BCC. In addition, uniform lattices show better energy absorption capabilities at small compression distances, while graded lattices absorb more energy at large compression distances. The good correlation between the simulation results and the experimental phenomena demonstrates the validity and accuracy of the present investigation method. [ABSTRACT FROM AUTHOR]

Thermal stress is an important design factor that will influence structural responses and cause local warping deformations. In this paper, such temperature variation effect is considered in the structural optimization and the shape preserving design approach is extended into thermo-elastic problems to prevent local thermal damages. Based on the weak-coupled thermo-elastic system, nonlinear structural responses at large thermo-mechanical loads are accurately analyzed. The complementary elastic work is minimized to obtain a reasonable rigid structure. Corresponding integrated deformation energy is utilized to calculate the warping deformation accumulated in the incremental thermo-mechanical loading process. Shape preserving effect is then achieved by an additional constraint on the local deformation energy. Through the adjoint method, sensitivity analysis is derived in the coupled field with design-dependent heat conduction and geometrical nonlinearity. In the numerical implementation, an energy interpolation scheme is applied to circumvent numerical instability in low stiffness regions and further modified for multi-material design. Optimization results show that local distortions in thermo-elastic structures are effectively eliminated by the proposed shape preserving design approach. [ABSTRACT FROM AUTHOR]

A B-spline multi-parameterization method (MPM) is presented in this paper for topology optimization of thermoelastic structures. As thermoelastic topology optimization belongs to a kind of design-dependent problems that are complicated to deal with, this method is aimed to solve thermoelastic problems with multiple materials by means of B-spline parameterization that integrates together the recursive multiphase material interpolation (RMMI) and the uniform multiphase material interpolation (UMMI) schemes. The commonly used discrete pseudo-density variables related to the finite element model are thus replaced with continuous pseudo-density fields dominated by control parameters in the B-spline space. In this sense, B-spline multi-parameterization is used for the first time to represent multiple pseudo-density fields and multi-material properties including elasticity matrix and thermal stress coefficient. Compared with traditional pseudo-density method, the current method has the advantage of not only attaining a reduction of design variables in number but also achieving a regularized distribution of pseudo-density fields with a clear material layout over the whole structure domain. Numerical results show that the stable convergences are achieved with the avoidance of gray elements, checkerboards, and multi-material overlapping owing to the high continuity of B-spline preserved for multi-material distributions. Besides, it is found that the RMMI scheme distributes less stiff materials around stiff materials, while the UMMI scheme tends to gather less stiff materials together. [ABSTRACT FROM AUTHOR]

In this work, a novel design and modeling method is proposed to obtain hierarchical structures with non-uniform lattice microstructures based on density-based topology optimization. First of all, a parametric concept is proposed to generate a family of parameterized lattice microstructures that present similar topological features. In order to balance the structural performance and computational efficiency, we construct a Parameterized Interpolation for Lattice Material (PILM) model and the mathematical formulation incorporates two new design variables. At the macroscale, the relative density variable is applied to describe material volume fraction in the design domain, instead of using the pseudo-density in the Solid Isotropic Material with Penalization (SIMP) model. At the microscale, each macroelement is regarded as an individual microstructure controlled by an aspect ratio variable. The equivalent properties of parameterized lattice microstructures can be derived by interpolating the effective elastic matrixes of several typical microstructure unit cells, which avoid expensive iterative homogenization calculations during optimization procedure. Hence, the multiscale concurrent design method can optimize the macroscopic distribution and their spatially varying microstructural configurations simultaneously at an affordable computation cost. Several numerical examples are presented to demonstrate the effectiveness of the proposed approach. Furthermore, the obtained hierarchical structures with non-uniform lattice microstructures show good manufacturability and remarkably improved structural performance by means of the additive manufacturing and experimental testing, compared to the designs with uniform lattice microstructures. [ABSTRACT FROM AUTHOR]

Two-step pressureless sintering processing was used to prepare high density (97.6%) Ca3Co4O9 thermoelectric ceramics. A duplex structure was observed and channel paths for charge carriers were formed between the grains. Oxygen vacancies were identified by fitting of XPS spectra, and the effect of the oxygen vacancies on thermoelectric properties was investigated. The electrical resistivity of samples decreased from 17.5 to 11.7 mΩ·cm and Seebeck coefficient decreased from 197.5 to 181.4 μV/K at 1073 K with increasing of the first-step sintering temperature. Furthermore, a low thermal conductivity of 0.94 W/(m·K) and the peak ZT of 0.30, which was 1.3 times larger than previous work, were obtained at 1073 K when the first-step sintering temperature was 1373 K. [ABSTRACT FROM AUTHOR]

This paper introduces BAZAR, a collaborative robot that integrates the most advanced sensing and actuating devices in a unique system designed for the Industry 4.0. We present BAZAR's three main features, which are all paramount in the factory of the future. These features are: mobility for navigating in dynamic environments, interaction for operating side-by-side with human workers, and dual-arm manipulation for transporting and assembling bulky objects. [ABSTRACT FROM AUTHOR]

Conclusion: In this study, the robust transition trajectory optimization was conducted for tail-sitter UAVs. The correlated stochastic uncertainties are different from existing deterministic optimal transition studies and are considered for the first time. Simulation results show that the robustness of the derived transition trajectories is improved. In the future, we will study more complicated unknown uncertainties. In addition, the robust control law for the tail-sitter transition phases will also be studied. [ABSTRACT FROM AUTHOR]

This paper documents an energy-based analysis of temperature oscillation during cyclic stress-induced phase transformation in shape memory alloys (SMAs). The conversion of total hysteresis work into dissipated heat and stored energy in SMAs is discussed, and the temperature oscillation at the shakedown state in cyclically loaded SMAs is modeled. To validate the theoretical model, both strain and stress-controlled tensile tests on pseudoelastic NiTi wires are performed under cyclic loading and an infrared camera is used to record the surface temperature of the wire. The results show that depending of the loading type, strain or stress-controlled loading, the amplitude of temperature oscillation during cyclic stress-induced phase transformation evolves differently with the frequency: The amplitude of the temperature oscillation under strain-controlled loading gradually reaches a saturated value independent of the frequency; however, for stress-controlled loading, the saturated temperature amplitude is frequency-dependent since it reduces significantly if the frequency is increased. [ABSTRACT FROM AUTHOR]

Spatial gradient information of density field in SIMP (solid isotropic material with penalization) topology optimization is very useful for imposing overhang angle and minimum length (size) manufacturing constraints or achieving shell-infill optimization. However, the computation of density gradient is an approximation since the design space is discretized. There are several operators for this purpose, which arise from the image processing field. This note compares different gradient operators in the context of SIMP topology optimization method and suggests a new computation strategy to improve the accuracy of gradient estimation. We take a case study of spatial gradient-based minimum size constraints. New structural indicator functions are proposed to improve the general applicability of previous gradient-based minimum length constraints. This study is carried out in 2D structure examples to validate the methodology. [ABSTRACT FROM AUTHOR]

Subparts of load carrying structures like airplane windows or doors must be isolated from distortions and hence structural optimization needs to take such shape preserving constraints into account. The paper extends the shape preserving topology optimization approach from simple linear load cases into geometrically nonlinear problems with practical significance. Based on an integrated deformation energy function, an improved warpage formulation is proposed to measure the geometrical distortion during large deformations. Structural complementary elastic work is assigned as the objective function. The average distortion calculated as the integrated deformation energy accumulated in the incremental loading process is accordingly constrained to obtain warpage control. In the numerical implementation, an energy interpolation scheme is utilized to alleviate numerical instability in low stiffness regions. An additional loading case avoids isolation phenomena. Optimization results show that shape preserving design is successfully implemented in geometrically nonlinear structures by effectively suppressing local warping deformations. [ABSTRACT FROM AUTHOR]