In this paper, a mathematical model for topology optimization oftruss structures with constraints of displacement and systemreliability under multiple loading cases is constructed. In order toavoid the difficulty of c...In this paper, a mathematical model for topology optimization oftruss structures with constraints of displacement and systemreliability under multiple loading cases is constructed. In order toavoid the difficulty of computing the structure's system reliability,a solving approach is presented in which the failure probability ofsystem is divided into the sum of a all bars' failures probability bymeans of reliability distribution. In addition, by drawing into thereliability safety factor and the fundamen- tal relationship instructural mechanics, all probability constraints of displacement andstress are equiv- alently displayed as conventional form and linearfunction of the design variables.展开更多
The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A...The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.展开更多
BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first u...BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first underwent a total hip arthro-plasty(THA)using a metal-on-metal bearing due to hip arthrosis.Follow-up visits revealed no complications after the procedure.Two years after the THA,acetabular component loosening occurred due to subsequent trauma of the opposite hip,necessitating a revision THA using a ceramic-on-ceramic bearing.CASE SUMMARY We aim to illustrate a rare case where the primary reason for undergoing THA revision was not only incomplete bone graft incorporation but also improper limb load distribution.Following the revision arthroplasty,a 9-year follow-up visit revealed improvements in all evaluation measures on questionnaire compared to the state before surgery:Harris Hip Score(before surgery:15;after surgery:95),Western Ontario and McMaster Universities Arthritis Index(before surgery:96;after surgery:0),and Visual Analogue Scale(before surgery:10;after surgery:1).CONCLUSION Opposite-hip trauma caused a weight transfer to the limb after a THA procedure.This process led to a stress shielding effect,resulting in acetabular component loosening.展开更多
The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the sel...The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the self-equilibrium of fixed stresses field is analyzed. Elastic shakedown and plastic shakedown conditions are presented based on the fixed stresses field. The theorem is convenient to evaluate the shakedown limit of structures under cyclical variable multiloadings through solving positive scalar fields and fixed stresses field factors at a series of dangerous positions of the structure, and tedious computations are avoided. Finally the theorem is applied to a thick-walled cylindrical tube under variable pressure and temperature, and the rolling contact problem. The results are in good agreement with some computational results.展开更多
To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three speci...To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three specimens with different cross section shape and different heat treatment condition. According to the experimental results, using numerical calculation software program and the numerical simulation with finite element analysis （FEA）, the relationships among the maximal load and displacement on cross section shape with each step bend loading, the loading stroke with the heat treatment condition, and the loading stroke with cross section shape were gained, and also those curves were discussed qualitatively. Finally, the contrast results between the numerical simulation and experiment were carried out to study the influence about the multi-step loading on specimen. It is put forward that enlightenment for the straightening stroke in the precision linear guide rail manufacture process.展开更多
Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional c...Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.展开更多
BACKGROUND Because immediate implant surgery is not recommended for patients who have been diagnosed with periodontitis,researchers have treated these patients with a variety of methods,including combining orthodontic...BACKGROUND Because immediate implant surgery is not recommended for patients who have been diagnosed with periodontitis,researchers have treated these patients with a variety of methods,including combining orthodontic and periodontal surgeries as well as implantation.However,these treatments cost time and money for the patient.Although it has been reported that temporary implants released a severe gag reflex in 1 case,only a few studies have documented using temporary implants to treat patients diagnosed with severe periodontitis.CASE SUMMARY The patient was a 49-year-old female who was missing the majority of her teeth and had gingival atrophy and severe alveolar bone atrophy.After being diagnosed with severe periodontitis,the patient underwent staged load applied implant restoration therapy.The first load-bearing stage was carried out immediately by inserting temporary Osstem mini implants.Maxillary teeth were extracted by using the guided bone regeneration technique,and lateral maxillary sinus lifting was conducted on both sides.During the second load-bearing stage,temporary implants were removed,and permanent implants were placed.The resin bridge was segmented during the third load-bearing stage.During the fourth load-bearing stage,the permanent prosthesis was positioned in the patient’s mouth.CONCLUSION By conducting the load-bearing treatment in stages,the patient’s mouth contained restorations throughout the procedure,thus guaranteeing basic function and appearance.展开更多
Infections by Cronobacter spp. are hazardous to infants since they can lead to neonatal meningitis, bacteremia, and necrotizing enterocolitis. Cronobacter spp. are frequently resistant to 13-1actam derivatives, macrol...Infections by Cronobacter spp. are hazardous to infants since they can lead to neonatal meningitis, bacteremia, and necrotizing enterocolitis. Cronobacter spp. are frequently resistant to 13-1actam derivatives, macrolides, and aminoglycosides. In addition, multi-resistant strains have also been detected. In China, the isolation rate of Cronobacter spp. from commercial powdered infant formula （PIF） or follow-up formula （FUF） is relatively high. Nevertheless, clinical cases of Cronobacter infection have been ignored to date. Here we describe two cases of Cronobacter infection detected at the Wuhan Women and Children Medical Care Center Hospital （Wuhan City, China）. We provide the genomic analysis of the isolates and the antibiotic-resistance profiles of the two strains. The Cronobacter strains identified in this study were not susceptible to third-generation cephalosporins, aminoglycoside, and/or trimethoprim-sulfamethoxazole. Whole genome sequencing revealed various genes known to encode antibiotic resistance. Future studies are needed to determine whether the genes predicted in this study are functional. As with Enterobocter spp., the antibiotic resistance of Cronobocter is a serious issue that requires more attention.展开更多
BACKGROUND Odontogenic infection is one of the common infectious diseases in oral and maxillofacial head and neck regions.Clinically,if early odontogenic infections such as acute periapical periodontitis,alveolar absc...BACKGROUND Odontogenic infection is one of the common infectious diseases in oral and maxillofacial head and neck regions.Clinically,if early odontogenic infections such as acute periapical periodontitis,alveolar abscess,and pericoronitis of wisdom teeth are not treated timely,effectively and correctly,the infected tissue may spread up to the skull and brain,down to the thoracic cavity,abdominal cavity and other areas through the natural potential fascial space in the oral and maxillofacial head and neck.Severe multi-space infections are formed and can eventually lead to life-threatening complications(LTCs),such as intracranial infection,pleural effusion,empyema,sepsis and even death.CASE SUMMARY We report a rare case of death in a 41-year-old man with severe odontogenic multi-space infections in the oral and maxillofacial head and neck regions.One week before admission,due to pain in the right lower posterior teeth,the patient placed a cigarette butt dipped in the pesticide"Miehailin"into the"dental cavity"to relieve the pain.Within a week,the infection gradually spread bilaterally to the floor of the mouth,submandibular space,neck,chest,waist,back,temporal and other areas.The patient had difficulty breathing,swallowing and eating,and was transferred to our hospital as an emergency admission.Following admission,oral and maxillofacial surgeons immediately organized consultations with doctors in otolaryngology,thoracic surgery,general surgery,hematology,anesthesia and the intensive care unit to assist with treatment.The patient was treated with the highest level of antibiotics(vancomycin)and extensive abscess incision and drainage in the oral,maxillofacial,head and neck,chest and back regions.Unfortunately,the patient died of septic shock and multiple organ failure on the third day after admission.CONCLUSION Odontogenic infection can cause serious multi-space infections in the oral and maxillofacial head and neck regions,which can result in multiple LTCs.The management and treatment of LTCs such as multi-space infections should be multidisciplinary led by oral and maxillofacial surgeons.展开更多
Load distribution is a key technology in hot strip rolling process, which directly influences strip product quality. A multi-objective load distribution model, which takes into account the rolling force margin balance...Load distribution is a key technology in hot strip rolling process, which directly influences strip product quality. A multi-objective load distribution model, which takes into account the rolling force margin balance, roll wear ratio and strip shape control, is presented. To avoid the selection of weight coefficients encountered in single objective optimization, a multi-objective differential evolutionary algorithm, called MaximinDE, is proposed to solve this model. The experimental results based on practical production data indicate that MaximinDE can obtain a good pareto-optimal solution set, which consists of a series of alternative solutions to load distribution. Decision-makers can select a trade-off solution from the pareto-optimal solution set based on their experience or the importance of ob- iectives. In comparison with the empirical load distribution solution, the trade-off solution can achieve a better per- formance, which demonstrates the effectiveness of the multi-objective load distribution optimization. Moreover, the conflicting relationship among different objectives can be also found, which is another advantage of multi-objective load distribution optimization.展开更多
Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benef...Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benefits of seawater desalination, the desalination load can be combined with renewable energy sources such as solar energy, wind energy, and ocean energy or with the power grid to ensure its effective regulation. Utilizing energy internet(EI) technology, energy balance demand of the regional power grid, and coordinated control between coastal multi-source multi-load and regional distribution network with desalination load is reviewed herein. Several key technologies, including coordinated control of coastal multi-source multi-load system with seawater desalination load, flexible interaction between seawater desalination and regional distribution network, and combined control of coastal multi-source multi-load storage system with seawater desalination load, are discussed in detail. Adoption of the flexible interaction between seawater desalination and regional distribution networks is beneficial for solving water resource problems, improving the ability to dissipate distributed renewable energy, balancing and increasing grid loads, improving the safety and economy of coastal power grids, and achieving coordinated and comprehensive application of power grids, renewable energy sources, and coastal loads.展开更多
This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water disch...This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales： 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.展开更多
The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number o...The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.展开更多
This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of re...This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies,a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities(LMIs). Finally,a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.展开更多
The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator cont...The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.展开更多
Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on a...Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.展开更多
The thermomechanical fatigue behaviour of different high temperature alloys has been investigated and is under investigation respectively. The creep-fatigue behaviour of heat resistant steels was investigated by long-...The thermomechanical fatigue behaviour of different high temperature alloys has been investigated and is under investigation respectively. The creep-fatigue behaviour of heat resistant steels was investigated by long-term service-type strain cycling tests simulating thermomechanical fatigue (TMF-) loading conditions at the heated surface of e.g. turbine rotors. Single-stage as well as three-stage cycles leads to similar results at the application of the damage accumulation rule. Life prediction which simulates typical combinations of cold starts, warm starts and hot starts has been established successfully for isothermal service-type loading and will be exceeded for thermomechanical loading. Long-term thermomechanical fatigue testing of Thermal Barrier Coating systems show typical delamination damage. An advanced TMF cruciform testing system enables complex multiaxial loading.展开更多
BACKGROUND Uncovered stents used for malignant obstructions in the biliary tree, especially in the hilar area, are prone to obstruction by tumor ingrowths. In comparison, however, covered stents may block bile duct br...BACKGROUND Uncovered stents used for malignant obstructions in the biliary tree, especially in the hilar area, are prone to obstruction by tumor ingrowths. In comparison, however, covered stents may block bile duct branches and are at risk of migration. We have developed a multi-hole self-expandable metallic stent (MHSEMS), with a hole in each cell, to prevent the obstruction of bile duct branches. In addition, the holes may prevent migration due to small ingrowths by reducing the tension of the membrane. CASE SUMMARY MHSEMS were placed in five patients with a malignant obstruction and one with post-endoscopic sphincterotomy bleeding. Each MHSEMS was successfully deployed in all cases. Patients showed no complications. Two cases were reviewed. Case 1: A 74-year-old male presented with jaundice and was diagnosed with a sigmoid colon cancer and giant liver metastases in the right liver lobe. A MHSEMS was placed in the left bile duct. The jaundice improved and peroral cholangioscopy was performed. Case 2: A 90-year-old female was admitted to hospital for jaundice and diagnosed with cholangiocarcinoma. A MHSEMS was placed in the left bile duct but after 8 months the stent became obstructed by tumor ingrowth. We treated the patient by ablation therapy. A silicone cover separated the internal bile duct from the surrounding tissue, protecting the latter from thermal injury during treatment by endobiliary ablation of the reobstruction. CONCLUSION A MHSEMS is a new choice of stent for biliary tract diseases.展开更多
The CBR (Case-Based Reasoning) usually is been used to accomplish customized products by variant design or reusable design.In the CBR,retrieve is very important.A simple case retrieval method is been brought forward t...The CBR (Case-Based Reasoning) usually is been used to accomplish customized products by variant design or reusable design.In the CBR,retrieve is very important.A simple case retrieval method is been brought forward to retrieve a opti- mal prototype based on using inputted multi-parameters,it can be programmed easily.An example has been proved this method can find optimal prototype for new design task efficiently.展开更多
基金the National Natural Science Foundation of China
文摘In this paper, a mathematical model for topology optimization oftruss structures with constraints of displacement and systemreliability under multiple loading cases is constructed. In order toavoid the difficulty of computing the structure's system reliability,a solving approach is presented in which the failure probability ofsystem is divided into the sum of a all bars' failures probability bymeans of reliability distribution. In addition, by drawing into thereliability safety factor and the fundamen- tal relationship instructural mechanics, all probability constraints of displacement andstress are equiv- alently displayed as conventional form and linearfunction of the design variables.
基金Project(11102224)supported by the National Natural Science Foundation of ChinaProject(201206370124)supported by the China Scholarship Council,China
文摘The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.
文摘BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first underwent a total hip arthro-plasty(THA)using a metal-on-metal bearing due to hip arthrosis.Follow-up visits revealed no complications after the procedure.Two years after the THA,acetabular component loosening occurred due to subsequent trauma of the opposite hip,necessitating a revision THA using a ceramic-on-ceramic bearing.CASE SUMMARY We aim to illustrate a rare case where the primary reason for undergoing THA revision was not only incomplete bone graft incorporation but also improper limb load distribution.Following the revision arthroplasty,a 9-year follow-up visit revealed improvements in all evaluation measures on questionnaire compared to the state before surgery:Harris Hip Score(before surgery:15;after surgery:95),Western Ontario and McMaster Universities Arthritis Index(before surgery:96;after surgery:0),and Visual Analogue Scale(before surgery:10;after surgery:1).CONCLUSION Opposite-hip trauma caused a weight transfer to the limb after a THA procedure.This process led to a stress shielding effect,resulting in acetabular component loosening.
文摘The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the self-equilibrium of fixed stresses field is analyzed. Elastic shakedown and plastic shakedown conditions are presented based on the fixed stresses field. The theorem is convenient to evaluate the shakedown limit of structures under cyclical variable multiloadings through solving positive scalar fields and fixed stresses field factors at a series of dangerous positions of the structure, and tedious computations are avoided. Finally the theorem is applied to a thick-walled cylindrical tube under variable pressure and temperature, and the rolling contact problem. The results are in good agreement with some computational results.
基金Funded by the Open Research Foundation of State Key Lab of Digital Manufacturing Equipment & Technology in Huazhong University of Science & Technology (No. DMETKF2009016)the Hubei Province Science Founda-tion (No.2008CDB274)+1 种基金the Wuhan High-Tech Development Project Founda-tion (No.200812121559)the International Collaborative Research Funds of Chonbuk National University, 2008
文摘To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three specimens with different cross section shape and different heat treatment condition. According to the experimental results, using numerical calculation software program and the numerical simulation with finite element analysis （FEA）, the relationships among the maximal load and displacement on cross section shape with each step bend loading, the loading stroke with the heat treatment condition, and the loading stroke with cross section shape were gained, and also those curves were discussed qualitatively. Finally, the contrast results between the numerical simulation and experiment were carried out to study the influence about the multi-step loading on specimen. It is put forward that enlightenment for the straightening stroke in the precision linear guide rail manufacture process.
基金supported by the National Natural Science Foundation of China(Grant No.11822203and 11702026)。
文摘Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.
文摘BACKGROUND Because immediate implant surgery is not recommended for patients who have been diagnosed with periodontitis,researchers have treated these patients with a variety of methods,including combining orthodontic and periodontal surgeries as well as implantation.However,these treatments cost time and money for the patient.Although it has been reported that temporary implants released a severe gag reflex in 1 case,only a few studies have documented using temporary implants to treat patients diagnosed with severe periodontitis.CASE SUMMARY The patient was a 49-year-old female who was missing the majority of her teeth and had gingival atrophy and severe alveolar bone atrophy.After being diagnosed with severe periodontitis,the patient underwent staged load applied implant restoration therapy.The first load-bearing stage was carried out immediately by inserting temporary Osstem mini implants.Maxillary teeth were extracted by using the guided bone regeneration technique,and lateral maxillary sinus lifting was conducted on both sides.During the second load-bearing stage,temporary implants were removed,and permanent implants were placed.The resin bridge was segmented during the third load-bearing stage.During the fourth load-bearing stage,the permanent prosthesis was positioned in the patient’s mouth.CONCLUSION By conducting the load-bearing treatment in stages,the patient’s mouth contained restorations throughout the procedure,thus guaranteeing basic function and appearance.
基金supported by the National Natural Science Foundation of China(No.81501799)
文摘Infections by Cronobacter spp. are hazardous to infants since they can lead to neonatal meningitis, bacteremia, and necrotizing enterocolitis. Cronobacter spp. are frequently resistant to 13-1actam derivatives, macrolides, and aminoglycosides. In addition, multi-resistant strains have also been detected. In China, the isolation rate of Cronobacter spp. from commercial powdered infant formula （PIF） or follow-up formula （FUF） is relatively high. Nevertheless, clinical cases of Cronobacter infection have been ignored to date. Here we describe two cases of Cronobacter infection detected at the Wuhan Women and Children Medical Care Center Hospital （Wuhan City, China）. We provide the genomic analysis of the isolates and the antibiotic-resistance profiles of the two strains. The Cronobacter strains identified in this study were not susceptible to third-generation cephalosporins, aminoglycoside, and/or trimethoprim-sulfamethoxazole. Whole genome sequencing revealed various genes known to encode antibiotic resistance. Future studies are needed to determine whether the genes predicted in this study are functional. As with Enterobocter spp., the antibiotic resistance of Cronobocter is a serious issue that requires more attention.
文摘BACKGROUND Odontogenic infection is one of the common infectious diseases in oral and maxillofacial head and neck regions.Clinically,if early odontogenic infections such as acute periapical periodontitis,alveolar abscess,and pericoronitis of wisdom teeth are not treated timely,effectively and correctly,the infected tissue may spread up to the skull and brain,down to the thoracic cavity,abdominal cavity and other areas through the natural potential fascial space in the oral and maxillofacial head and neck.Severe multi-space infections are formed and can eventually lead to life-threatening complications(LTCs),such as intracranial infection,pleural effusion,empyema,sepsis and even death.CASE SUMMARY We report a rare case of death in a 41-year-old man with severe odontogenic multi-space infections in the oral and maxillofacial head and neck regions.One week before admission,due to pain in the right lower posterior teeth,the patient placed a cigarette butt dipped in the pesticide"Miehailin"into the"dental cavity"to relieve the pain.Within a week,the infection gradually spread bilaterally to the floor of the mouth,submandibular space,neck,chest,waist,back,temporal and other areas.The patient had difficulty breathing,swallowing and eating,and was transferred to our hospital as an emergency admission.Following admission,oral and maxillofacial surgeons immediately organized consultations with doctors in otolaryngology,thoracic surgery,general surgery,hematology,anesthesia and the intensive care unit to assist with treatment.The patient was treated with the highest level of antibiotics(vancomycin)and extensive abscess incision and drainage in the oral,maxillofacial,head and neck,chest and back regions.Unfortunately,the patient died of septic shock and multiple organ failure on the third day after admission.CONCLUSION Odontogenic infection can cause serious multi-space infections in the oral and maxillofacial head and neck regions,which can result in multiple LTCs.The management and treatment of LTCs such as multi-space infections should be multidisciplinary led by oral and maxillofacial surgeons.
基金Item Sponsored by National Natural Science Foundation of China(50974039)
文摘Load distribution is a key technology in hot strip rolling process, which directly influences strip product quality. A multi-objective load distribution model, which takes into account the rolling force margin balance, roll wear ratio and strip shape control, is presented. To avoid the selection of weight coefficients encountered in single objective optimization, a multi-objective differential evolutionary algorithm, called MaximinDE, is proposed to solve this model. The experimental results based on practical production data indicate that MaximinDE can obtain a good pareto-optimal solution set, which consists of a series of alternative solutions to load distribution. Decision-makers can select a trade-off solution from the pareto-optimal solution set based on their experience or the importance of ob- iectives. In comparison with the empirical load distribution solution, the trade-off solution can achieve a better per- formance, which demonstrates the effectiveness of the multi-objective load distribution optimization. Moreover, the conflicting relationship among different objectives can be also found, which is another advantage of multi-objective load distribution optimization.
基金Supported by National Natural Science Foundation of China （60674039, 60704004） and Innovation Fund for Outstanding Scholar of Henan Province （084200510009 ）
基金supported by the State Grid Science and Technology Project, “Study on Multi-source and Multiload Coordination and Optimization Technology Considering Desalination of Sea Water” (No. SGTJDK00DWJS1800011)
文摘Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benefits of seawater desalination, the desalination load can be combined with renewable energy sources such as solar energy, wind energy, and ocean energy or with the power grid to ensure its effective regulation. Utilizing energy internet(EI) technology, energy balance demand of the regional power grid, and coordinated control between coastal multi-source multi-load and regional distribution network with desalination load is reviewed herein. Several key technologies, including coordinated control of coastal multi-source multi-load system with seawater desalination load, flexible interaction between seawater desalination and regional distribution network, and combined control of coastal multi-source multi-load storage system with seawater desalination load, are discussed in detail. Adoption of the flexible interaction between seawater desalination and regional distribution networks is beneficial for solving water resource problems, improving the ability to dissipate distributed renewable energy, balancing and increasing grid loads, improving the safety and economy of coastal power grids, and achieving coordinated and comprehensive application of power grids, renewable energy sources, and coastal loads.
基金National Natural Science Foundation of China, No.41271026
文摘This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales： 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.
基金supported by Shandong Provincial Natural Science Foundation of China(Grant No.ZR2010EL003)
文摘The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.
基金supported in part by the National Natural Science Foundation of China(61673161)the Natural Science Foundation of Jiangsu Province of China(BK20161510)+2 种基金the Fundamental Research Funds for the Central Universities of China(2017B13914)the 111 Project(B14022)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies,a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities(LMIs). Finally,a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.
文摘The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.
文摘Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.
基金supported by the Deutsche Forschungsgemeinschaft(DFG),Project No.BE1890,16-1the Forschungs-vereinigung der Arbeitsgemeinschaften der Eisen und Metall verarbeitenden Industrie e.V.(AVIF),Project No.A166+1 种基金the FKM Forschungskuratorium Maschinenbau e.V.Project No.052510the Arbeitsgemeinschaft industrieller Forschungsvereinigungen(AiF)and the VDEh-Gesellschaft zur Forderung der Eisenforschung mbH,Project No.11200 N.
文摘The thermomechanical fatigue behaviour of different high temperature alloys has been investigated and is under investigation respectively. The creep-fatigue behaviour of heat resistant steels was investigated by long-term service-type strain cycling tests simulating thermomechanical fatigue (TMF-) loading conditions at the heated surface of e.g. turbine rotors. Single-stage as well as three-stage cycles leads to similar results at the application of the damage accumulation rule. Life prediction which simulates typical combinations of cold starts, warm starts and hot starts has been established successfully for isothermal service-type loading and will be exceeded for thermomechanical loading. Long-term thermomechanical fatigue testing of Thermal Barrier Coating systems show typical delamination damage. An advanced TMF cruciform testing system enables complex multiaxial loading.
文摘BACKGROUND Uncovered stents used for malignant obstructions in the biliary tree, especially in the hilar area, are prone to obstruction by tumor ingrowths. In comparison, however, covered stents may block bile duct branches and are at risk of migration. We have developed a multi-hole self-expandable metallic stent (MHSEMS), with a hole in each cell, to prevent the obstruction of bile duct branches. In addition, the holes may prevent migration due to small ingrowths by reducing the tension of the membrane. CASE SUMMARY MHSEMS were placed in five patients with a malignant obstruction and one with post-endoscopic sphincterotomy bleeding. Each MHSEMS was successfully deployed in all cases. Patients showed no complications. Two cases were reviewed. Case 1: A 74-year-old male presented with jaundice and was diagnosed with a sigmoid colon cancer and giant liver metastases in the right liver lobe. A MHSEMS was placed in the left bile duct. The jaundice improved and peroral cholangioscopy was performed. Case 2: A 90-year-old female was admitted to hospital for jaundice and diagnosed with cholangiocarcinoma. A MHSEMS was placed in the left bile duct but after 8 months the stent became obstructed by tumor ingrowth. We treated the patient by ablation therapy. A silicone cover separated the internal bile duct from the surrounding tissue, protecting the latter from thermal injury during treatment by endobiliary ablation of the reobstruction. CONCLUSION A MHSEMS is a new choice of stent for biliary tract diseases.
基金Funded by the Scientific Foundation of Shanghai Automobile Industry(No.0212).
文摘The CBR (Case-Based Reasoning) usually is been used to accomplish customized products by variant design or reusable design.In the CBR,retrieve is very important.A simple case retrieval method is been brought forward to retrieve a opti- mal prototype based on using inputted multi-parameters,it can be programmed easily.An example has been proved this method can find optimal prototype for new design task efficiently.
