The geological strength index(GSI) system,widely used for the design and practice of mining process,is a unique rock mass classification system related to the rock mass strength and deformation parameters based on the...The geological strength index(GSI) system,widely used for the design and practice of mining process,is a unique rock mass classification system related to the rock mass strength and deformation parameters based on the generalized Hoek-Brown and Mohr-Coulomb failure criteria.The GSI can be estimated using standard chart and field observations of rock mass blockiness and discontinuity surface conditions.The GSI value gives a numerical representation of the overall geotechnical quality of the rock mass.In this study,we propose a method to determine the GSI quantitatively using photographic images of in situ jointed rock mass with image processing technology,fractal theory and artificial neural network(ANN).We employ the GSI system to characterize the jointed rock mass around the working in a coal mine.The relative error between the proposed value and the given value in the GSI chart is less than 3.6%.展开更多
A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simul...A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simultaneously,which frequently occur in wideband Synthetic Aperture Radar(SAR) systems.Based on the time-frequency relation of the chirp signal and the analyses of the channel errors in wideband SAR,joint multiple subpulses processing method is adopted to separate the image frequency component due to the I/Q channel error.Then,the complete description of the channel error is acquired for building the correction function,which is used to correct the radar raw echo in frequency domain.The validity and capability of this method are demonstrated by the experiments of the channel error correction on the high resolution SAR system with the effective bandwidth of 500 MHz.展开更多
The scope of this project was to investigate the possibility of application of Image Processing Technique in the field of Shaft Alignment process. Misalignment of shaft using image processing software Visionbuilder wa...The scope of this project was to investigate the possibility of application of Image Processing Technique in the field of Shaft Alignment process. Misalignment of shaft using image processing software Visionbuilder was calculated. The further purpose of this project was to check whether the image processing technique can be used in bone transplant surgery. The model of the hip was used for the experimentation purpose. Image processing software Visionbuilder was used to match the profiles of the bone before implant and bone after implant.展开更多
Effects of friction stir spot processing(FSSP)on the microstructures and microhardness of tungsten inert gas(TIG)welded TA15titanium alloy joints were investigated.The macro/micro structural observation and microhardn...Effects of friction stir spot processing(FSSP)on the microstructures and microhardness of tungsten inert gas(TIG)welded TA15titanium alloy joints were investigated.The macro/micro structural observation and microhardness evaluation of the TA15alloy sheets and TA15TIG welded joints were carried out using optical microscope and microhardness tests.The results show that FSSP effectively improves the microstructure and increases the microhardness of the TA15sheets.As for the TIG welded joints,FSSP also effectively improves the microstructure of joints.And the average microhardness value in weld nugget zone is improved significantly,while a small increase of this value in heat affected zone is observed.The hardness in stirring zone is significantly higher than that in the base metal.Two peak values of hardness appear along the width direction in stirring zone.After FSSP,the average hardness of the weld zone of TA15TIG welded joint is significantly higher than that before FSSP.Under the present process parameters,both the surface oxidation in TA15sheets and in TIG welded joints after FSSP are not evident,while the surface forms the bright white layer,which is composed of a great multitude of fine grains.展开更多
In order to study the application of laser shock processing(LSP) as a post weld treatment technology and a strengthening technology, a series experiments and analysis were taken in this paper. The hardness of the lase...In order to study the application of laser shock processing(LSP) as a post weld treatment technology and a strengthening technology, a series experiments and analysis were taken in this paper. The hardness of the laser shock processed zone of Al-Li alloy was measured, and the microstructure and mechanical properties of the welded joints of the Ni-based superalloy GH30 and the Austenitic stainless steel !Crl8Ni9Ti were compared with those without LSP in this paper. The results showed that the size of strengthened zone was similar to that of laser spot and strengthened layer was about 1mm deep, and the high intense dislocations and twins produced in the shocked zone. Plastic strain also gained surface residual compress stress, which is benefit for the fatigue properties of welded zones. In this test , the surface hardness of welding zone of the superalloy GH30 improved obviously and tensile strength increased by 12%, but the improvement of fatigue life was not obvious; Martensite phase is formed in plasma welding !Crl8Ni9Ti, which reduced the effect of strain deformation martensite induced by laser shock processing, but the surface residual compress stress gained by laser shock processing can obviously improve the fatigue life of !Crl8Ni9Ti welded joints.展开更多
Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s...Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.展开更多
BACKGROUND Lumbar facet joint syndrome(LFJS)is a pain condition arising from lumbar facet joint diseases.Treatments of LFJS includes patient education,oral medication,bed rest,physical therapy,and procedural intervent...BACKGROUND Lumbar facet joint syndrome(LFJS)is a pain condition arising from lumbar facet joint diseases.Treatments of LFJS includes patient education,oral medication,bed rest,physical therapy,and procedural interventions.For some refractory cases that fail conservative therapies,dorsal ramus medial brunch radiofrequency ablation is warranted.However,as nerve fibers can regenerate,their efficacy is impermanent,and the recurrence rate is relatively high.Considering synovial impingement is a paramount pathogenesis of LFJS,in this case,we removed the culprit hyperplastic articular capsule and the articular process partially through a spinal endoscope.As the culprit hyperplastic joint capsule was excised,it is supposed to generate more prolonged efficacy and a lower recurrence rate than radiofrequency treatment.CASE SUMMARY A 40-year-old female patient was diagnosed with LFJS.She complained of low back pain and right buttock pain for half a year.The patient was placed in the prone position.After disinfection and draping,a 25-cm 18-gauge needle was inserted into the dorsal surface of the right L5 articular process.Subsequently,a guidewire,dilating tubes,and a working cannula was inserted successively.The spinal endoscope was positioned in the working cannula.Under the endoscope,the microvascular tissue,muscle tissue attached on the L5 inferior articular process and S1 superior articular process,as well as the capsule and minor portion of the inferior articular process were removed.After the joint space was clear and no bleeding points existed,the endoscope and working cannula were shifted,and the incision was sutured.After treatment,the symptoms were completely relieved.The patient was pain-free during the follow-up period of 6 mo.CONCLUSION The endoscopic partial joint capsule and articular process excision is an effective procedure for LFJS,especially for cases caused by synovial impingement.展开更多
We give an extension result of Watanabe’s characterization for 2-dimensional Poisson processes. By using this result, the equivalence of uniqueness in law and joint uniqueness in law is proved for one-dimensional sto...We give an extension result of Watanabe’s characterization for 2-dimensional Poisson processes. By using this result, the equivalence of uniqueness in law and joint uniqueness in law is proved for one-dimensional stochastic differential equations driven by Poisson processes. After that, we give a simplified Engelbert theorem for the stochastic differential equations of this type.展开更多
Joint inversion of teleseismic body-wave data and strong ground motion waveforms was applied to determine the rupture process of the 2010 Mentawai earthquake. To obtain stable solutions, smoothing and non-negative con...Joint inversion of teleseismic body-wave data and strong ground motion waveforms was applied to determine the rupture process of the 2010 Mentawai earthquake. To obtain stable solutions, smoothing and non-negative constraints were introduced. A total of 33 teleseismic stations and 5 strong ground motion stations supplied data. The teleseismic and strong ground motion data were separately windowed for 150 s and 250 s and bandpass filtered with frequencies of 0.001e1.0 Hz and 0.005e0.5 Hz, respectively. The finitefault model was established with length and width of 190 km and 70 km, and the initial seismic source parameters were set by referring to centroid moment tensor(CMT) solutions. Joint inversion results indicate that the focal mechanism of this earthquake is thrust fault type, and the strike, dip, and rake angles are generally in accordance with CMT results. The seismic moment was determined as 5.814 1020Nm(Mw7.8) and source duration was about 102 s, which is greater than those of other earthquakes of similar magnitude. The rupture nucleated near the hypocenter and then propagated along the strike direction to the northwest, with a maximum slip of 3.9 m. Large uncertainties regarding the amount of slip retrieved using different inversion methods still exist; however, the conclusion that the majority of slip occurred far from the islands at very shallow depths was found to be robust. The 2010 Mentawai earthquake was categorized as a tsunami earthquake because of the long rupture duration and the generation of a tsunami much larger than was expected for an earthquake of its magnitude.展开更多
The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clin...The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clinical guidelines.This review aims to elucidate the available approaches for TMJ reconstruction,with a particular emphasis on recent groundbreaking advancements.The current spectrum of TMJ reconstruction integrates diverse surgical techniques,such as costochondral grafting,coronoid process grafting,revascularized fibula transfer,transport distraction osteogenesis,and alloplastic TMJ replacement.Despite the available options,a singular,universally accepted‘gold standard’for reconstructive techniques or materials remains elusive in this field.Our review comprehensively summarizes the current available methods of TMJ reconstruction,focusing on both autologous and alloplastic prostheses.It delves into the differences of each surgical technique and outlines the implications of recent technological advances,such as 3D printing,which hold the promise of enhancing surgical precision and patient outcomes.This evolutionary progress aims not only to improve the immediate results of reconstruction but also to ensure the long-term health and functionality of the TMJ,thereby improving the quality of life for patients with end-stage TMJ disorders.展开更多
The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,co...The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.展开更多
Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges. The dependence of cracking process of jointed rock masses on the two important g...Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges. The dependence of cracking process of jointed rock masses on the two important geometrical parameters, joint orientation and joint persistence, was studied systematically by carrying out a series of uniaxial compression tests on gypsum specimens with regularly arranged multiple parallel pre-existing joints. According to crack position, mechanism and temporal sequence, seven types of crack initiations and sixteen types of crack coalescences, were identified. It was observed that both tensile cracks and shear cracks can emanate from the pre-existing joints as well as the matrix. Vertical joints were included and coplanar tensile cracks initiation and coalescence were observed accordingly. For specimen with joint inclination angle ,8=75~, it was found that collinear joints can be linked not only by coplanar shear cracks but also by mixed tensile-shear cracks, and that a pair of them can form a small rotation block. Seven failure modes, including axial cleavage, crushing, crushing and rotation of new blocks, stepped failure, stepped failure and rotation of new blocks, shear failure along a single plane and shear failure along multiple planes, were observed. These modes shift gradually in accordance with the combined variation of joint orientation and joint persistence. It is concluded that cracking process and failure modes are more strongly affected by joint orientation than by joint persistence, especially when joint inclination angle is larger than 45~. Finally, variations of macroscopic mechanical behaviors with the two geometrical parameters, such as patterns of the complete axial stress-axial strain curves, peak strength and elastic modulus, are summarized and their mechanisms are successfully explained according to their different cracking process.展开更多
Interoperability plays an important role in the joint command, control, communication, computer, intelligence, surveillance, reconnaissance(C4 ISR) operations. Coordinating and integrating operational processes to ful...Interoperability plays an important role in the joint command, control, communication, computer, intelligence, surveillance, reconnaissance(C4 ISR) operations. Coordinating and integrating operational processes to fulfill a common mission are challenged by the ever-changing battlefield and hence requires a cross-organizational process management that produces an autonomous, flexible and adaptable architecture for collaborative process evolution. The traditional business process collaboration pattern is based on the predefined "public-view" perspective and cannot meet the requirement of the joint task operations. This paper proposes a flexible visibility control mechanism and a dynamic collaboration framework for modeling and generating collaborative processes. The mechanism allows collaborators to define a set of visibility rules to generate different views of the private processes for different collaborations, which gives a great flexibility for the collaboration initiator to decide on an appropriate collaboration pattern. The framework supports collaborators to dynamically and recursively add a new process or even a new organization to an existing collaboration. Moreover, a formal representation of the processes and a set of generation algorithms are provided to consolidate the proposed theory.展开更多
With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircr...With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.展开更多
Four process parameters, pad diameter, stencil thickness, ball diameter and stand-off were chosen as four control factors. By using an L25 （5^6 ） orthogonal array the ceramic ball grid array （ CBGA ） solder joints...Four process parameters, pad diameter, stencil thickness, ball diameter and stand-off were chosen as four control factors. By using an L25 （5^6 ） orthogonal array the ceramic ball grid array （ CBGA ） solder joints which have 25 different combinations of process parameters were designed. The numerical models of all the 25 CBGA solder joints were developed using the Sugrace Evolver. Utilizing the sugrace coordinate exported from the 25 CBGA solder joints numerical models, the finite element analysis models were set up and the nonlinear finite element analysis of the CBGA solder joints under thermal cycles were pegrormed by ANSYS. The thermal fatigue life of CBGA solder joint was calculated using Coffin-Manson equation. Based on the calculated thermal fatigue life results, the range analysis and the variance analysis were pegrormed. The results show that the fatigue life of CBGA solder joint is affected by the pad diameter, the stencil thickness, the ball diameter and the stand-off in a descending order, the best combination of process parameters results in the longest fatigue life is 0.07 mm stand-off, 0.125 mm stencil thickness of, 0.85 mm ball diameter and 0. 89 mm pad diameter. With 95% confidence the pad diameter has a significant effect on the reliability of CBGA solder joints whereas the stand-off, the stencil thickness and the ball diameter have little effect on the reliability of CBGA solder joints.展开更多
For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the b...For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the bondedparticle model. The microscopic parameters which can reflect the macroscopic mechanical properties and failure behavior of artificial jointed specimens are firstly calibrated. Then, the influence of joint inclination and confining pressure on stress-strain curves, crack patterns, and contact force distributions of jointed rock are investigated. The simulation results show that both the compressive strength and elastic modulus of the specimens increase with increasing confining pressure, and these two mechanical parameters decrease first and then increase with the increase of joints inclination. The sensitivity of strength and elastic modulus to confining pressure is not the same in different joints inclinations, which has the least impact on specimens with α=90°. Under low confining pressure, the failure modes are controlled by the joint inclination. As the confining pressure increased, the initiation and propagation of tensile crack are gradually inhibited, and the failure mode is transferred from tensile failure to shear-compression failure. Finally, the reinforcement effect of prestressed bolt support on engineering fractured rock mass is discussed.展开更多
Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polari...Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.展开更多
For the tunnel crossing active fault,the damage induced by fault movement is always serious.To solve such a problem,a detailed anti-faulting tunnel design process for Urumqi subway line 2 was introduced,and seven thre...For the tunnel crossing active fault,the damage induced by fault movement is always serious.To solve such a problem,a detailed anti-faulting tunnel design process for Urumqi subway line 2 was introduced,and seven three-dimensional elastic-plastic finite element models were established.The anti-faulting design process included three steps.First,the damage of tunnel lining from different locations of fault rupture surfaces was analyzed.Then,the analysis of the effect on tunnel buried depth was given.Finally,the effect of the disaster mitigation method on the flexible joint was verified and the location of the flexible joint was discussed.The results show that when the properties of surrounding rock at the tunnel bottom grows soft,the tunnel deformation curve is smoother and tunnel damage induced by fault movement is less serious.The vertical displacement change ratio of secondary linings along the tunnel axis may be the main factor to cause shear damage to the tunnel.The interface between the hanging wall and fracture zone is defined as the most adverse fault rupture surface.The tunnel damage was reduced with the decrease in the tunnel buried depth as more energy was dissipated by overburden soil and the differential uplift zone of soil became more diffuse.The method of the flexible joint can reduce the tunnel damage significantly and the disaster mitigation effect of different locations on the flexible joint is different.The tunnel damage is reduced by the greatest degree when the flexible joint is located on the fault rupture surface.展开更多
Columnar jointed basalt(CJB) widely distributes in the dam site of the Baihetan Hydropower Station.The columnar joint structure and fracture development of CJB have significant influence on the mechanical properties o...Columnar jointed basalt(CJB) widely distributes in the dam site of the Baihetan Hydropower Station.The columnar joint structure and fracture development of CJB have significant influence on the mechanical properties of rock mass,and the mechanical properties of CJB are of great significance to the Baihetan Hydropower Project.Therefore,in-situ direct shear tests were carried out on ten test adit at different locations in the dam site area to study the shear behavior of CJB.In this study,21 sets of in-situ direct shear tests were conducted for rock types of type Ⅱ_(2),type Ⅲ_(1)and type Ⅲ_(2),with horizontal and vertical shear planes and two different specimen sizes of CJB.Shear strength parameters of CJB were obtained by linear fitting of in-situ direct shear test results based on the Mohr-Coulomb strength criterion.The results indicate that the shear strength parameters of CJB with horizontal shear plane increase as the increase of rock type grade.The shear strength parameters of CJB show obvious anisotropy and the friction coefficient of the horizontal shear plane is greater than the vertical shear plane.The friction coefficient in the horizontal direction of the shear plane is 1.27 times that in the vertical direction of the shear plane.With the increase of rock type grade,the difference of friction coefficient becomes larger.However,the cohesion changes little whether the shear plane is horizontal or vertical.In addition,the size effect of CJB in this area is significant.The shear strength parameters of large size(100 cm × 100 cm) specimens are lower than those of regular size(50 cm × 50 cm) specimens.The reduction of cohesion is greater than that of the friction coefficient.For rock type Ⅲ_(2),the cohesion of large-size specimens is 0.637 of the regular-size specimens.The reduction percentage of the friction coefficient for type Ⅲ_(2)is 1.66 times that of type Ⅲ_(1).The reduction percentage of the cohesion for type Ⅲ_(2)is 1.27 times that of type Ⅲ_(1).The size effect decreases with the increase of rock type grade.The research results of this study can provide an important basis for the selection of rock mechanics parameters in the dam site area of Baihetan Hydropower Station and the stability analysis of the dam foundation and rocky slopes.展开更多
文摘The geological strength index(GSI) system,widely used for the design and practice of mining process,is a unique rock mass classification system related to the rock mass strength and deformation parameters based on the generalized Hoek-Brown and Mohr-Coulomb failure criteria.The GSI can be estimated using standard chart and field observations of rock mass blockiness and discontinuity surface conditions.The GSI value gives a numerical representation of the overall geotechnical quality of the rock mass.In this study,we propose a method to determine the GSI quantitatively using photographic images of in situ jointed rock mass with image processing technology,fractal theory and artificial neural network(ANN).We employ the GSI system to characterize the jointed rock mass around the working in a coal mine.The relative error between the proposed value and the given value in the GSI chart is less than 3.6%.
基金Supported by the National High-Tech Research and Development Plan of China(No.2007AA120302)
文摘A novel method,referred to as joint multiple subpulses processing,is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/demodulate systems simultaneously,which frequently occur in wideband Synthetic Aperture Radar(SAR) systems.Based on the time-frequency relation of the chirp signal and the analyses of the channel errors in wideband SAR,joint multiple subpulses processing method is adopted to separate the image frequency component due to the I/Q channel error.Then,the complete description of the channel error is acquired for building the correction function,which is used to correct the radar raw echo in frequency domain.The validity and capability of this method are demonstrated by the experiments of the channel error correction on the high resolution SAR system with the effective bandwidth of 500 MHz.
文摘The scope of this project was to investigate the possibility of application of Image Processing Technique in the field of Shaft Alignment process. Misalignment of shaft using image processing software Visionbuilder was calculated. The further purpose of this project was to check whether the image processing technique can be used in bone transplant surgery. The model of the hip was used for the experimentation purpose. Image processing software Visionbuilder was used to match the profiles of the bone before implant and bone after implant.
基金Project(51405389) supported by the National Natural Science Foundation of ChinaProject(3102015ZY024) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2014003) supported by the Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures,China
文摘Effects of friction stir spot processing(FSSP)on the microstructures and microhardness of tungsten inert gas(TIG)welded TA15titanium alloy joints were investigated.The macro/micro structural observation and microhardness evaluation of the TA15alloy sheets and TA15TIG welded joints were carried out using optical microscope and microhardness tests.The results show that FSSP effectively improves the microstructure and increases the microhardness of the TA15sheets.As for the TIG welded joints,FSSP also effectively improves the microstructure of joints.And the average microhardness value in weld nugget zone is improved significantly,while a small increase of this value in heat affected zone is observed.The hardness in stirring zone is significantly higher than that in the base metal.Two peak values of hardness appear along the width direction in stirring zone.After FSSP,the average hardness of the weld zone of TA15TIG welded joint is significantly higher than that before FSSP.Under the present process parameters,both the surface oxidation in TA15sheets and in TIG welded joints after FSSP are not evident,while the surface forms the bright white layer,which is composed of a great multitude of fine grains.
文摘In order to study the application of laser shock processing(LSP) as a post weld treatment technology and a strengthening technology, a series experiments and analysis were taken in this paper. The hardness of the laser shock processed zone of Al-Li alloy was measured, and the microstructure and mechanical properties of the welded joints of the Ni-based superalloy GH30 and the Austenitic stainless steel !Crl8Ni9Ti were compared with those without LSP in this paper. The results showed that the size of strengthened zone was similar to that of laser spot and strengthened layer was about 1mm deep, and the high intense dislocations and twins produced in the shocked zone. Plastic strain also gained surface residual compress stress, which is benefit for the fatigue properties of welded zones. In this test , the surface hardness of welding zone of the superalloy GH30 improved obviously and tensile strength increased by 12%, but the improvement of fatigue life was not obvious; Martensite phase is formed in plasma welding !Crl8Ni9Ti, which reduced the effect of strain deformation martensite induced by laser shock processing, but the surface residual compress stress gained by laser shock processing can obviously improve the fatigue life of !Crl8Ni9Ti welded joints.
基金financially supported by the National Natural Science Foundation of China (Nos. 90915012 and 41090291)the Research Project in Earthquake Science, CEA (No.201108002)
文摘Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.
文摘BACKGROUND Lumbar facet joint syndrome(LFJS)is a pain condition arising from lumbar facet joint diseases.Treatments of LFJS includes patient education,oral medication,bed rest,physical therapy,and procedural interventions.For some refractory cases that fail conservative therapies,dorsal ramus medial brunch radiofrequency ablation is warranted.However,as nerve fibers can regenerate,their efficacy is impermanent,and the recurrence rate is relatively high.Considering synovial impingement is a paramount pathogenesis of LFJS,in this case,we removed the culprit hyperplastic articular capsule and the articular process partially through a spinal endoscope.As the culprit hyperplastic joint capsule was excised,it is supposed to generate more prolonged efficacy and a lower recurrence rate than radiofrequency treatment.CASE SUMMARY A 40-year-old female patient was diagnosed with LFJS.She complained of low back pain and right buttock pain for half a year.The patient was placed in the prone position.After disinfection and draping,a 25-cm 18-gauge needle was inserted into the dorsal surface of the right L5 articular process.Subsequently,a guidewire,dilating tubes,and a working cannula was inserted successively.The spinal endoscope was positioned in the working cannula.Under the endoscope,the microvascular tissue,muscle tissue attached on the L5 inferior articular process and S1 superior articular process,as well as the capsule and minor portion of the inferior articular process were removed.After the joint space was clear and no bleeding points existed,the endoscope and working cannula were shifted,and the incision was sutured.After treatment,the symptoms were completely relieved.The patient was pain-free during the follow-up period of 6 mo.CONCLUSION The endoscopic partial joint capsule and articular process excision is an effective procedure for LFJS,especially for cases caused by synovial impingement.
文摘We give an extension result of Watanabe’s characterization for 2-dimensional Poisson processes. By using this result, the equivalence of uniqueness in law and joint uniqueness in law is proved for one-dimensional stochastic differential equations driven by Poisson processes. After that, we give a simplified Engelbert theorem for the stochastic differential equations of this type.
基金supported by National Natural Science Foundation of China (41304046)
文摘Joint inversion of teleseismic body-wave data and strong ground motion waveforms was applied to determine the rupture process of the 2010 Mentawai earthquake. To obtain stable solutions, smoothing and non-negative constraints were introduced. A total of 33 teleseismic stations and 5 strong ground motion stations supplied data. The teleseismic and strong ground motion data were separately windowed for 150 s and 250 s and bandpass filtered with frequencies of 0.001e1.0 Hz and 0.005e0.5 Hz, respectively. The finitefault model was established with length and width of 190 km and 70 km, and the initial seismic source parameters were set by referring to centroid moment tensor(CMT) solutions. Joint inversion results indicate that the focal mechanism of this earthquake is thrust fault type, and the strike, dip, and rake angles are generally in accordance with CMT results. The seismic moment was determined as 5.814 1020Nm(Mw7.8) and source duration was about 102 s, which is greater than those of other earthquakes of similar magnitude. The rupture nucleated near the hypocenter and then propagated along the strike direction to the northwest, with a maximum slip of 3.9 m. Large uncertainties regarding the amount of slip retrieved using different inversion methods still exist; however, the conclusion that the majority of slip occurred far from the islands at very shallow depths was found to be robust. The 2010 Mentawai earthquake was categorized as a tsunami earthquake because of the long rupture duration and the generation of a tsunami much larger than was expected for an earthquake of its magnitude.
基金supported by NSFC(82370932)Research and Develop Program of West China Hospital of Stomatology Sichuan University(RD-03-202102,LCYJ2019-20)Natural Science Foundation of Sichuan Province(2023NSFSC1512,2024NSFSC1588)。
文摘The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clinical guidelines.This review aims to elucidate the available approaches for TMJ reconstruction,with a particular emphasis on recent groundbreaking advancements.The current spectrum of TMJ reconstruction integrates diverse surgical techniques,such as costochondral grafting,coronoid process grafting,revascularized fibula transfer,transport distraction osteogenesis,and alloplastic TMJ replacement.Despite the available options,a singular,universally accepted‘gold standard’for reconstructive techniques or materials remains elusive in this field.Our review comprehensively summarizes the current available methods of TMJ reconstruction,focusing on both autologous and alloplastic prostheses.It delves into the differences of each surgical technique and outlines the implications of recent technological advances,such as 3D printing,which hold the promise of enhancing surgical precision and patient outcomes.This evolutionary progress aims not only to improve the immediate results of reconstruction but also to ensure the long-term health and functionality of the TMJ,thereby improving the quality of life for patients with end-stage TMJ disorders.
基金funded by the National Natural Science Foundation of China(52478138).
文摘The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.
基金Project(11102224)supported by the National Natural Science Foundation of ChinaProject(2009QL05)supported by the Fundamental Research Funds for the Central Universities of China
文摘Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges. The dependence of cracking process of jointed rock masses on the two important geometrical parameters, joint orientation and joint persistence, was studied systematically by carrying out a series of uniaxial compression tests on gypsum specimens with regularly arranged multiple parallel pre-existing joints. According to crack position, mechanism and temporal sequence, seven types of crack initiations and sixteen types of crack coalescences, were identified. It was observed that both tensile cracks and shear cracks can emanate from the pre-existing joints as well as the matrix. Vertical joints were included and coplanar tensile cracks initiation and coalescence were observed accordingly. For specimen with joint inclination angle ,8=75~, it was found that collinear joints can be linked not only by coplanar shear cracks but also by mixed tensile-shear cracks, and that a pair of them can form a small rotation block. Seven failure modes, including axial cleavage, crushing, crushing and rotation of new blocks, stepped failure, stepped failure and rotation of new blocks, shear failure along a single plane and shear failure along multiple planes, were observed. These modes shift gradually in accordance with the combined variation of joint orientation and joint persistence. It is concluded that cracking process and failure modes are more strongly affected by joint orientation than by joint persistence, especially when joint inclination angle is larger than 45~. Finally, variations of macroscopic mechanical behaviors with the two geometrical parameters, such as patterns of the complete axial stress-axial strain curves, peak strength and elastic modulus, are summarized and their mechanisms are successfully explained according to their different cracking process.
基金supported by the National Natural Science Foundation of China(61273210)the National High Technology Research and Development Program of China(863 Program)(2007AA01Z126)
文摘Interoperability plays an important role in the joint command, control, communication, computer, intelligence, surveillance, reconnaissance(C4 ISR) operations. Coordinating and integrating operational processes to fulfill a common mission are challenged by the ever-changing battlefield and hence requires a cross-organizational process management that produces an autonomous, flexible and adaptable architecture for collaborative process evolution. The traditional business process collaboration pattern is based on the predefined "public-view" perspective and cannot meet the requirement of the joint task operations. This paper proposes a flexible visibility control mechanism and a dynamic collaboration framework for modeling and generating collaborative processes. The mechanism allows collaborators to define a set of visibility rules to generate different views of the private processes for different collaborations, which gives a great flexibility for the collaboration initiator to decide on an appropriate collaboration pattern. The framework supports collaborators to dynamically and recursively add a new process or even a new organization to an existing collaboration. Moreover, a formal representation of the processes and a set of generation algorithms are provided to consolidate the proposed theory.
基金supported by the Fundamental Research Funds for the Central Universities(NS2015072)
文摘With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.
基金This work was supported by Science Foundation of Guangxi Zhuang Autonomous Region (Contract No. 02336060).
文摘Four process parameters, pad diameter, stencil thickness, ball diameter and stand-off were chosen as four control factors. By using an L25 （5^6 ） orthogonal array the ceramic ball grid array （ CBGA ） solder joints which have 25 different combinations of process parameters were designed. The numerical models of all the 25 CBGA solder joints were developed using the Sugrace Evolver. Utilizing the sugrace coordinate exported from the 25 CBGA solder joints numerical models, the finite element analysis models were set up and the nonlinear finite element analysis of the CBGA solder joints under thermal cycles were pegrormed by ANSYS. The thermal fatigue life of CBGA solder joint was calculated using Coffin-Manson equation. Based on the calculated thermal fatigue life results, the range analysis and the variance analysis were pegrormed. The results show that the fatigue life of CBGA solder joint is affected by the pad diameter, the stencil thickness, the ball diameter and the stand-off in a descending order, the best combination of process parameters results in the longest fatigue life is 0.07 mm stand-off, 0.125 mm stencil thickness of, 0.85 mm ball diameter and 0. 89 mm pad diameter. With 95% confidence the pad diameter has a significant effect on the reliability of CBGA solder joints whereas the stand-off, the stencil thickness and the ball diameter have little effect on the reliability of CBGA solder joints.
基金Projects(52004145,51904164)supported by the National Natural Science Foundation of ChinaProject(ZR2020QE119)supported by the Natural Science Foundation of Shandong Province,ChinaProject(SICGM202107)supported by the Open Fund of the Key Laboratory of Mining Disaster Prevention and Control,China。
文摘For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the bondedparticle model. The microscopic parameters which can reflect the macroscopic mechanical properties and failure behavior of artificial jointed specimens are firstly calibrated. Then, the influence of joint inclination and confining pressure on stress-strain curves, crack patterns, and contact force distributions of jointed rock are investigated. The simulation results show that both the compressive strength and elastic modulus of the specimens increase with increasing confining pressure, and these two mechanical parameters decrease first and then increase with the increase of joints inclination. The sensitivity of strength and elastic modulus to confining pressure is not the same in different joints inclinations, which has the least impact on specimens with α=90°. Under low confining pressure, the failure modes are controlled by the joint inclination. As the confining pressure increased, the initiation and propagation of tensile crack are gradually inhibited, and the failure mode is transferred from tensile failure to shear-compression failure. Finally, the reinforcement effect of prestressed bolt support on engineering fractured rock mass is discussed.
文摘Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.
基金The National Natural Science Foundation of China(No.41572276)the National Key Research and Development Program of China(No.2017YFC0805400).
文摘For the tunnel crossing active fault,the damage induced by fault movement is always serious.To solve such a problem,a detailed anti-faulting tunnel design process for Urumqi subway line 2 was introduced,and seven three-dimensional elastic-plastic finite element models were established.The anti-faulting design process included three steps.First,the damage of tunnel lining from different locations of fault rupture surfaces was analyzed.Then,the analysis of the effect on tunnel buried depth was given.Finally,the effect of the disaster mitigation method on the flexible joint was verified and the location of the flexible joint was discussed.The results show that when the properties of surrounding rock at the tunnel bottom grows soft,the tunnel deformation curve is smoother and tunnel damage induced by fault movement is less serious.The vertical displacement change ratio of secondary linings along the tunnel axis may be the main factor to cause shear damage to the tunnel.The interface between the hanging wall and fracture zone is defined as the most adverse fault rupture surface.The tunnel damage was reduced with the decrease in the tunnel buried depth as more energy was dissipated by overburden soil and the differential uplift zone of soil became more diffuse.The method of the flexible joint can reduce the tunnel damage significantly and the disaster mitigation effect of different locations on the flexible joint is different.The tunnel damage is reduced by the greatest degree when the flexible joint is located on the fault rupture surface.
基金supported by the National Key Research and Development Program of China (No.2017YFC1501302)the National Natural Science Foundation of China (No.41630643)+1 种基金the Fundamental Research Funds for the Central Universities (No.CUGCJ1701)the Scientific research project of China Three Gorges Corporation Ltd。
文摘Columnar jointed basalt(CJB) widely distributes in the dam site of the Baihetan Hydropower Station.The columnar joint structure and fracture development of CJB have significant influence on the mechanical properties of rock mass,and the mechanical properties of CJB are of great significance to the Baihetan Hydropower Project.Therefore,in-situ direct shear tests were carried out on ten test adit at different locations in the dam site area to study the shear behavior of CJB.In this study,21 sets of in-situ direct shear tests were conducted for rock types of type Ⅱ_(2),type Ⅲ_(1)and type Ⅲ_(2),with horizontal and vertical shear planes and two different specimen sizes of CJB.Shear strength parameters of CJB were obtained by linear fitting of in-situ direct shear test results based on the Mohr-Coulomb strength criterion.The results indicate that the shear strength parameters of CJB with horizontal shear plane increase as the increase of rock type grade.The shear strength parameters of CJB show obvious anisotropy and the friction coefficient of the horizontal shear plane is greater than the vertical shear plane.The friction coefficient in the horizontal direction of the shear plane is 1.27 times that in the vertical direction of the shear plane.With the increase of rock type grade,the difference of friction coefficient becomes larger.However,the cohesion changes little whether the shear plane is horizontal or vertical.In addition,the size effect of CJB in this area is significant.The shear strength parameters of large size(100 cm × 100 cm) specimens are lower than those of regular size(50 cm × 50 cm) specimens.The reduction of cohesion is greater than that of the friction coefficient.For rock type Ⅲ_(2),the cohesion of large-size specimens is 0.637 of the regular-size specimens.The reduction percentage of the friction coefficient for type Ⅲ_(2)is 1.66 times that of type Ⅲ_(1).The reduction percentage of the cohesion for type Ⅲ_(2)is 1.27 times that of type Ⅲ_(1).The size effect decreases with the increase of rock type grade.The research results of this study can provide an important basis for the selection of rock mechanics parameters in the dam site area of Baihetan Hydropower Station and the stability analysis of the dam foundation and rocky slopes.
