Objective:To analyze the diagnostic value of combined testing of C-reactive protein(CRP)and procalcitonin(PCT)in elderly patients with bacterial pneumonia.Methods:This study included 50 elderly patients with bacterial...Objective:To analyze the diagnostic value of combined testing of C-reactive protein(CRP)and procalcitonin(PCT)in elderly patients with bacterial pneumonia.Methods:This study included 50 elderly patients with bacterial pneumonia as the observation group and 50 patients with non-bacterial pneumonia as the control group,recruited from May 2022 to October 2023.Fasting venous blood samples were collected in the morning from all 100 participants.CRP levels were measured using a fully automated biochemical analyzer,while PCT levels were detected using the immunoturbidimetric luminescence method.Results:CRP and PCT levels were significantly higher in bacterial pneumonia patients[(98.25±11.59)mg/L and(3.57±1.35)μg/L,respectively]compared to the control group[(5.55±2.78)mg/L and(0.25±0.12)μg/L,respectively],with significant intergroup differences(P<0.05).Patients with severe bacterial pneumonia exhibited higher serum CRP and PCT levels compared to those with moderate or mild disease(P<0.05).The combined testing of CRP and PCT showed higher sensitivity and specificity than individual tests.In the observation group,CRP and PCT levels significantly decreased after treatment compared to pre-treatment levels.Conclusion:The combination of CRP and PCT testing provides high diagnostic accuracy for bacterial pneumonia in elderly patients.It effectively differentiates bacterial from non-bacterial infections,offering valuable data to guide clinical treatment.展开更多
This review focuses on current aspects of the novel technology of combined impedance manometry for esophageal motility testing. It presents methodological features, summarizes current results and discusses implication...This review focuses on current aspects of the novel technology of combined impedance manometry for esophageal motility testing. It presents methodological features, summarizes current results and discusses implications for further research. The combined technique assesses simultaneously bolus transport and associated peristalsis, thus allowing detailed analysis of the relationships between bolus transit and esophageal motility. Recent studies demonstrate that combined impedance manometry provides important additional information about esophageal motility as compared to conventional manometry: (1) monitoring of bolus transport patterns, (2) calculation of bolus transit parameters, (3) evaluation of bolus clearance, (4) monitoring of swallow associated events such as air movement and reflux, and (5) investigation of the relationships between bolus transit and LES relaxation. Studies with healthy subjects have identified several useful parameters for comprehensive assessment of eosphageal function. These parameters were found to be pathological in patients with classical achalasia, mild GERD, and ineffective esophageal motility. The technology of combined impedance manometry provides an important new tool for esophageal function testing, advancing both clinical and basic research. However, several important issues remain to be standardized to make the technique suitable for widely clinical use.展开更多
The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound c...The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined method.The results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength test.In addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.展开更多
This paper presents the results of the performance quality testing of polyethylene pipes reinforced with aramid fibers, intended for applications such as discharging and gathering oil pipelines, and describes the test...This paper presents the results of the performance quality testing of polyethylene pipes reinforced with aramid fibers, intended for applications such as discharging and gathering oil pipelines, and describes the test rig specifically designed for this purpose. The pipe specimens are submitted to impact with a device that simulates the collision of a pickaxe, and of a backhoe loader. After the impact, the pipes are tested under combined loading comprising internal pressure, and transverse loading; some pipe specimens without previous impact are tested as well. The results show that the reinforced thermoplastic pipes can fully withstand maximal operating pressure levels in the presence of damage and additional transverse loading.展开更多
For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out s...For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.展开更多
This paper deals with a combined test rig for a traction system in the laboratory environment.An experimental system was designed and implemented to verify the performance of the traction system for a metro train.For ...This paper deals with a combined test rig for a traction system in the laboratory environment.An experimental system was designed and implemented to verify the performance of the traction system for a metro train.For a highly accurate control of the system,a hybrid control algorithm combining vector control and slip frequency control was applied to control the traction inverter.The design method of the flywheels,which represent the equivalent model of the train moment inertia,was elaborated.A train runtime diagnosis system was completed by adopting the multifunction vehicle bus（MVB） protocol.The dynamic performance of the metro power traction system was emulated under the control of the train runtime diagnosis system.Using the combined test rig,the performances of the traction system in traction,braking,temperature rise,etc.,were verified through traction and breaking experiments.展开更多
Objective:To study the clinical effects of multigene combination test to guide chemotherapy combined with targeted therapy in patients with advanced gastrointestinal tumors.Methods:The samples were selected from 60 pa...Objective:To study the clinical effects of multigene combination test to guide chemotherapy combined with targeted therapy in patients with advanced gastrointestinal tumors.Methods:The samples were selected from 60 patients with advanced gastrointestinal tumors admitted to our hospital from March 2019 to July 2020,and were divided into a study group and a control group using a random number table model;patients in the control group did not undergo genetic testing and FOLLOX4+PD-1 chemotherapy,while patients in the study group underwent TYMS,ERCC1,EGFR,and KRAS and VEGF gene expression levels test,and the sensitive treatment plan was determined based on the test results,and the clinical indexes were compared between the two groups.Results:By comparing the total effective rate,survival time,and time to disease progression of chemotherapy in the two groups,the study group has a significant advantage(P<0.05).Conclusion:The combination of chemotherapy and targeted therapy for advanced gastrointestinal tumor patients can improve the efficiency of chemotherapy and prolong the time of disease progression and survival,which is worthy of comprehensive promotion.展开更多
High-speed railway combined modulation and test system is mainly aimed at high-speed railway system to carry out a complete test system. The reliability, safety and usability (RAMS) of the high speed rail system are e...High-speed railway combined modulation and test system is mainly aimed at high-speed railway system to carry out a complete test system. The reliability, safety and usability (RAMS) of the high speed rail system are evaluated under normal load and edge and boundary load conditions by testing the initial connection of the system. At present, some researches mainly focus on the analysis of RAWS for the subsystems of high-speed railway system and most of them use qualitative analysis and research. The main purpose of this paper is to explore the reliability of the high-speed railway combined commissioning and testing system in the way of quantitative analysis.展开更多
Rock bolts are subjected to different loading conditions along their lengths such as axial,bending,and/or shear forces,which can cause failure at lower loads than those considered for design purposes.The common existi...Rock bolts are subjected to different loading conditions along their lengths such as axial,bending,and/or shear forces,which can cause failure at lower loads than those considered for design purposes.The common existing methodologies do not consider the actual loading of the rock bolts and assume it is only pure axial or pure shear.This study was conducted to investigate the un-grouted rock bolt performance under combined load conditions.Two loading regimes were evaluated:the effect of initial shear displacement on axial load capacity and displacement,and the effect of axial displacement on the shear load capacity.The first regime was also conducted for shear with a gap,when there is a spacing between the shear interfaces.The results of this study showed that the rock bolt can resist higher axial loads than shear under pure or combined load conditions.Under combined load conditions,the rock bolt capacity decreased significantly for both regimes.However,when applying the shear load with a gap,the rock bolt load capacity was not affected significantly.Also,the total bar deformation was improved for shear and axial.The findings of this study show the need to improve the rock bolt design considering the complex loading conditions in situ with/without a gap.展开更多
With the continuous development of deep oil and gas,minerals,geothermal resources,and other resources,there are increasingly more stringent requirements for equipment.In particular,the ultra-highpressure dynamic seals...With the continuous development of deep oil and gas,minerals,geothermal resources,and other resources,there are increasingly more stringent requirements for equipment.In particular,the ultra-highpressure dynamic seals of deep mining device need to be developed.Therefore,considering the use of dynamic seals in unique deep mining environments,an ultra-high-pressure rotating combined dynamic seal was designed and developed and its sealing performance was experimentally measured and analyzed.The results show that the experimental device can operate stably under a pressure of up to150 MPa and a rotating speed of 76 r/min,and can also operate normally under a rotating speed of up to 140 r/min and a sealing pressure of 120 MPa.During the operation of the ultra-high-pressure rotating combined dynamic seal,the sealing ring does not show obvious damage,which vouches for its sealing performance.No leakage of flow and pressure was detected in the all seal structures within the sealing pressure range of 0-150 MPa.Therefore,the dynamic sealing performance of the device is intact under ultra-high-pressure conditions and can be applied in deep mining environments at a certain depth.The research and development of this device can aid future deep energy exploration and exploitation.展开更多
Software configuration testing is used to test a piece of software with all kinds of hardware to ensure that it can run properly on them.This paper generates test cases for configuration testing with several common me...Software configuration testing is used to test a piece of software with all kinds of hardware to ensure that it can run properly on them.This paper generates test cases for configuration testing with several common methods,such as multiple single-factor experiments,uniform design,and orthogonal experiment design used in other fields.This paper analyzes their merits and improves the orthogonal experiment design method with pairwise testing,and decreases the testing risk caused by incomplete testing with a method of multiple-factors-covering.It presents a simple factor cover method which can cover all the factors and pairwise combinations to the greatest degree.Some comparisons of these methods are made on the aspects of test suite scale,coverage,and usability,etc..展开更多
A recently developed friction self-piercing riveting(F-SPR)technique based on the combination of fric-tion stir processing and riveting has been reported to possess both solid-state bonding and mechanical fastening ch...A recently developed friction self-piercing riveting(F-SPR)technique based on the combination of fric-tion stir processing and riveting has been reported to possess both solid-state bonding and mechanical fastening characteristics.However,there is still a lack of quantitative understanding of the hybrid en-hancement mechanism,hindering its engineering application.To fill in this gap,the current research investigated the microstructure evolution,microhardness distribution,and miniature-tensile performance of the aluminum alloy AA7075-T6 F-SPR joints by experiments.An accurate numerical simulation model was established to quantitatively evaluate the individual contributions of microstructure,local bonding strength,and macro interlocking to the performance of the joint,which could well explain the experi-mental results.It was found that due to the friction stirring of the rivet,solid-state bonding driven by dynamic recrystallization is realized between the trapped aluminum in the rivet cavity and the bottom aluminum sheet.The solid-state bonding zone has 75%yield strength,81%ultimate tensile strength,and 106%elongation compared to the base material.This solid-state bonding enables the internal interlock-ing between the trapped aluminum and the rivet to withstand the additional load,which forms a novel dual-interlock fastening mechanism and increases the peak cross-tension force by 14.3%compared to the single-interlock joint.展开更多
In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerody...In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerodynamic performance by both simulations and experiments.The basic flow field employed by proposed method is a combined flow named IBB,which is combined by Internal Conical Flow A(ICFA),truncated Busemann flow I(BI)for external section,and truncated Busemann flow II(BII)for internal section.The model configuration is generated by streamline tracing method from basic flow field,in which the forebody section is traced from ICFA and BI flows,and the inlet as well as strut section is traced from BII flow.The simulations in Mach number 4,5,and 6 demonstrate uniform starting flow fields with relatively high total pressure recovery,which agree well with experiments in wind tunnel.Additionally,in low Mach number cases,this inlet could start at Mach number 3 while it is unstarted at Mach number 2.7;in high Mach number cases,a uniform flow could still exist in Mach number 6.5 while a relatively strong shock wave boundary layer interaction is found in cowl area of Mach number 7 case,indicating the inlet designed by proposed method works in a relatively wide Mach number range.展开更多
A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tes...A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tests were carried out for the study of mechanical properties of NCSLD using electro-hydraulic servo press-shear machine. Processing technology of the damper was improved. Shaking table tests under two-dimensional excitation on structural aseismic control of a one-story structure model were carried out using the small size NCSLD; parameters of the structure and shaking table were also introduced. Results indicate that process improvement is beneficial to the implementation of working mechanism of the damper,NCSLD has full hysteresis loop which takes on bilinearity,NCSLD has obvious energy dissipation effect and it can control structural seismic response effectively.展开更多
Ultra-high molecular weight polyethylene(UHMWPE)fiber composite has been extensively used to construct lightweight protective structures against ballistic impacts,yet little is known about its performance when subject...Ultra-high molecular weight polyethylene(UHMWPE)fiber composite has been extensively used to construct lightweight protective structures against ballistic impacts,yet little is known about its performance when subjected to combined blast and fragment impacts.Built upon a recently developed laboratory-scale experimental technique to generate simulated combined loading through the impact of a fragment-foam composite projectile launched from a light gas gun,the dynamic responses of fullyclamped UHMWPE plates subjected to combined loading were characterized experimentally,with corresponding deformation and failure modes compared with those measured with simulated blast loading alone.Subsequently,to explore the underlying physical mechanisms,three-dimensional(3D)numerical simulations with the method of finite elements(FE)were systematically carried out.Numerical predictions compared favorably well with experimental measurements,thus validating the feasibility of the established FE model.Relative to the case of blast loading alone,combined blast and fragment loading led to larger maximum deflections of clamped UHMWPE plates.The position of the FSP in the foam sabot affected significantly the performance of a UHMWPE target,either enhancing or decreasing its ballistic resistance.When the blast loading and fragment impact arrived simultaneously at the target,its ballistic resistance was superior to that achieved when subjected to fragment impact alone,and benefited from the accelerated movement of the target due to simultaneous blast loading.展开更多
In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses...In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.展开更多
Many conventional methods of testing strong and pulsed electromagnetic fields,the ones used in radars for example,had deficiencies due to the difficulty in obtaining simultaneous information about the electromagnetic ...Many conventional methods of testing strong and pulsed electromagnetic fields,the ones used in radars for example,had deficiencies due to the difficulty in obtaining simultaneous information about the electromagnetic field's peak both in the time domain and in the frequency domain.With regard to this problem,after analyzing the time-domain and the frequency-domain characteristics of radar pulsed signals,we propose a new time-frequency combination test method based on the correction of the test parameters,as well as its correction method at different bandwidths.The test method is applied in a quick test of a high-power pulsed radar signal,and the corrected results have error less than 1 dB in both the time domain and the frequency domain,which indicates that the proposed time-frequency combined method is effective in testing strong and pulsed electromagnetic fields.展开更多
The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covere...The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.展开更多
On the basis of EST (Equivalent STate hashing) algorithm, this paper researches a kind of test generation algorithm based on search state dominance for combinational circuit. According to the dominance relation of the...On the basis of EST (Equivalent STate hashing) algorithm, this paper researches a kind of test generation algorithm based on search state dominance for combinational circuit. According to the dominance relation of the E-frontier (evaluation frontier), we can prove that this algorithm can terminate unnecessary searching step of test pattern earlier than the EST algorithm through some examples, so this algorithm can reduce the time of test generation. The test patterns calculated can detect faults given through simulation.展开更多
In this paper the structure-based test generation algorithm has been studied for the problem that test patterns are obtained by determined finite faults set in the past. This Algorithm can find out all test patterns o...In this paper the structure-based test generation algorithm has been studied for the problem that test patterns are obtained by determined finite faults set in the past. This Algorithm can find out all test patterns one tithe, so faults detection is very convenient. By simulation, the smallest test patterns set can be obtained and faults coverage rate is 100%.展开更多
文摘Objective:To analyze the diagnostic value of combined testing of C-reactive protein(CRP)and procalcitonin(PCT)in elderly patients with bacterial pneumonia.Methods:This study included 50 elderly patients with bacterial pneumonia as the observation group and 50 patients with non-bacterial pneumonia as the control group,recruited from May 2022 to October 2023.Fasting venous blood samples were collected in the morning from all 100 participants.CRP levels were measured using a fully automated biochemical analyzer,while PCT levels were detected using the immunoturbidimetric luminescence method.Results:CRP and PCT levels were significantly higher in bacterial pneumonia patients[(98.25±11.59)mg/L and(3.57±1.35)μg/L,respectively]compared to the control group[(5.55±2.78)mg/L and(0.25±0.12)μg/L,respectively],with significant intergroup differences(P<0.05).Patients with severe bacterial pneumonia exhibited higher serum CRP and PCT levels compared to those with moderate or mild disease(P<0.05).The combined testing of CRP and PCT showed higher sensitivity and specificity than individual tests.In the observation group,CRP and PCT levels significantly decreased after treatment compared to pre-treatment levels.Conclusion:The combination of CRP and PCT testing provides high diagnostic accuracy for bacterial pneumonia in elderly patients.It effectively differentiates bacterial from non-bacterial infections,offering valuable data to guide clinical treatment.
文摘This review focuses on current aspects of the novel technology of combined impedance manometry for esophageal motility testing. It presents methodological features, summarizes current results and discusses implications for further research. The combined technique assesses simultaneously bolus transport and associated peristalsis, thus allowing detailed analysis of the relationships between bolus transit and esophageal motility. Recent studies demonstrate that combined impedance manometry provides important additional information about esophageal motility as compared to conventional manometry: (1) monitoring of bolus transport patterns, (2) calculation of bolus transit parameters, (3) evaluation of bolus clearance, (4) monitoring of swallow associated events such as air movement and reflux, and (5) investigation of the relationships between bolus transit and LES relaxation. Studies with healthy subjects have identified several useful parameters for comprehensive assessment of eosphageal function. These parameters were found to be pathological in patients with classical achalasia, mild GERD, and ineffective esophageal motility. The technology of combined impedance manometry provides an important new tool for esophageal function testing, advancing both clinical and basic research. However, several important issues remain to be standardized to make the technique suitable for widely clinical use.
文摘The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined method.The results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength test.In addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.
文摘This paper presents the results of the performance quality testing of polyethylene pipes reinforced with aramid fibers, intended for applications such as discharging and gathering oil pipelines, and describes the test rig specifically designed for this purpose. The pipe specimens are submitted to impact with a device that simulates the collision of a pickaxe, and of a backhoe loader. After the impact, the pipes are tested under combined loading comprising internal pressure, and transverse loading; some pipe specimens without previous impact are tested as well. The results show that the reinforced thermoplastic pipes can fully withstand maximal operating pressure levels in the presence of damage and additional transverse loading.
文摘For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.
基金supported by the Innovation Funds for Technology Based Firms (09C26214301971)
文摘This paper deals with a combined test rig for a traction system in the laboratory environment.An experimental system was designed and implemented to verify the performance of the traction system for a metro train.For a highly accurate control of the system,a hybrid control algorithm combining vector control and slip frequency control was applied to control the traction inverter.The design method of the flywheels,which represent the equivalent model of the train moment inertia,was elaborated.A train runtime diagnosis system was completed by adopting the multifunction vehicle bus（MVB） protocol.The dynamic performance of the metro power traction system was emulated under the control of the train runtime diagnosis system.Using the combined test rig,the performances of the traction system in traction,braking,temperature rise,etc.,were verified through traction and breaking experiments.
文摘Objective:To study the clinical effects of multigene combination test to guide chemotherapy combined with targeted therapy in patients with advanced gastrointestinal tumors.Methods:The samples were selected from 60 patients with advanced gastrointestinal tumors admitted to our hospital from March 2019 to July 2020,and were divided into a study group and a control group using a random number table model;patients in the control group did not undergo genetic testing and FOLLOX4+PD-1 chemotherapy,while patients in the study group underwent TYMS,ERCC1,EGFR,and KRAS and VEGF gene expression levels test,and the sensitive treatment plan was determined based on the test results,and the clinical indexes were compared between the two groups.Results:By comparing the total effective rate,survival time,and time to disease progression of chemotherapy in the two groups,the study group has a significant advantage(P<0.05).Conclusion:The combination of chemotherapy and targeted therapy for advanced gastrointestinal tumor patients can improve the efficiency of chemotherapy and prolong the time of disease progression and survival,which is worthy of comprehensive promotion.
文摘High-speed railway combined modulation and test system is mainly aimed at high-speed railway system to carry out a complete test system. The reliability, safety and usability (RAMS) of the high speed rail system are evaluated under normal load and edge and boundary load conditions by testing the initial connection of the system. At present, some researches mainly focus on the analysis of RAWS for the subsystems of high-speed railway system and most of them use qualitative analysis and research. The main purpose of this paper is to explore the reliability of the high-speed railway combined commissioning and testing system in the way of quantitative analysis.
基金The authors would like to thank Mining3,Minerals Research Institute of Western Australia,Curtin University and Peabody Energy for funding this research project.They also wish to thank Minova Global and its personnel who assisted in completing all the tests conducted at their facility in Nowra,NSW and for providing the rock bolts for testing.
文摘Rock bolts are subjected to different loading conditions along their lengths such as axial,bending,and/or shear forces,which can cause failure at lower loads than those considered for design purposes.The common existing methodologies do not consider the actual loading of the rock bolts and assume it is only pure axial or pure shear.This study was conducted to investigate the un-grouted rock bolt performance under combined load conditions.Two loading regimes were evaluated:the effect of initial shear displacement on axial load capacity and displacement,and the effect of axial displacement on the shear load capacity.The first regime was also conducted for shear with a gap,when there is a spacing between the shear interfaces.The results of this study showed that the rock bolt can resist higher axial loads than shear under pure or combined load conditions.Under combined load conditions,the rock bolt capacity decreased significantly for both regimes.However,when applying the shear load with a gap,the rock bolt load capacity was not affected significantly.Also,the total bar deformation was improved for shear and axial.The findings of this study show the need to improve the rock bolt design considering the complex loading conditions in situ with/without a gap.
基金supported by the Program for Guangdong Introducing Innovative and Enterpreneurial Teams(Grant No.2019ZT08G315)the National Natural Science Foundation of China(Grant No.51827901)
文摘With the continuous development of deep oil and gas,minerals,geothermal resources,and other resources,there are increasingly more stringent requirements for equipment.In particular,the ultra-highpressure dynamic seals of deep mining device need to be developed.Therefore,considering the use of dynamic seals in unique deep mining environments,an ultra-high-pressure rotating combined dynamic seal was designed and developed and its sealing performance was experimentally measured and analyzed.The results show that the experimental device can operate stably under a pressure of up to150 MPa and a rotating speed of 76 r/min,and can also operate normally under a rotating speed of up to 140 r/min and a sealing pressure of 120 MPa.During the operation of the ultra-high-pressure rotating combined dynamic seal,the sealing ring does not show obvious damage,which vouches for its sealing performance.No leakage of flow and pressure was detected in the all seal structures within the sealing pressure range of 0-150 MPa.Therefore,the dynamic sealing performance of the device is intact under ultra-high-pressure conditions and can be applied in deep mining environments at a certain depth.The research and development of this device can aid future deep energy exploration and exploitation.
基金The Natronal Natural Science Foundation of China(No.60373066)Opening Foundation of State Key Laboratory of Software Engineering in Wuhan UniversityOpening Foundation ofJiangsu Key Laboratory of Computer Information ProcessingTechnology in Soochow University.
文摘Software configuration testing is used to test a piece of software with all kinds of hardware to ensure that it can run properly on them.This paper generates test cases for configuration testing with several common methods,such as multiple single-factor experiments,uniform design,and orthogonal experiment design used in other fields.This paper analyzes their merits and improves the orthogonal experiment design method with pairwise testing,and decreases the testing risk caused by incomplete testing with a method of multiple-factors-covering.It presents a simple factor cover method which can cover all the factors and pairwise combinations to the greatest degree.Some comparisons of these methods are made on the aspects of test suite scale,coverage,and usability,etc..
基金support of the National Natural Science Foundation of China(Grant Nos.52025058 and U1764251)the State Key Laboratory of Mechan-ical System and Vibration(Grant No.MSVZD202111)+1 种基金the Japan Society for the Promotion of Science(JSPS)KAKENHI(Grant No.21K14439)Shanghai Jiao Tong University.
文摘A recently developed friction self-piercing riveting(F-SPR)technique based on the combination of fric-tion stir processing and riveting has been reported to possess both solid-state bonding and mechanical fastening characteristics.However,there is still a lack of quantitative understanding of the hybrid en-hancement mechanism,hindering its engineering application.To fill in this gap,the current research investigated the microstructure evolution,microhardness distribution,and miniature-tensile performance of the aluminum alloy AA7075-T6 F-SPR joints by experiments.An accurate numerical simulation model was established to quantitatively evaluate the individual contributions of microstructure,local bonding strength,and macro interlocking to the performance of the joint,which could well explain the experi-mental results.It was found that due to the friction stirring of the rivet,solid-state bonding driven by dynamic recrystallization is realized between the trapped aluminum in the rivet cavity and the bottom aluminum sheet.The solid-state bonding zone has 75%yield strength,81%ultimate tensile strength,and 106%elongation compared to the base material.This solid-state bonding enables the internal interlock-ing between the trapped aluminum and the rivet to withstand the additional load,which forms a novel dual-interlock fastening mechanism and increases the peak cross-tension force by 14.3%compared to the single-interlock joint.
基金supported by the National Natural Science Foundation of China(Nos.12072157,51776096)China Postdoctoral Science Foundation(Nos.2019TQ0147,2020M671472)。
文摘In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerodynamic performance by both simulations and experiments.The basic flow field employed by proposed method is a combined flow named IBB,which is combined by Internal Conical Flow A(ICFA),truncated Busemann flow I(BI)for external section,and truncated Busemann flow II(BII)for internal section.The model configuration is generated by streamline tracing method from basic flow field,in which the forebody section is traced from ICFA and BI flows,and the inlet as well as strut section is traced from BII flow.The simulations in Mach number 4,5,and 6 demonstrate uniform starting flow fields with relatively high total pressure recovery,which agree well with experiments in wind tunnel.Additionally,in low Mach number cases,this inlet could start at Mach number 3 while it is unstarted at Mach number 2.7;in high Mach number cases,a uniform flow could still exist in Mach number 6.5 while a relatively strong shock wave boundary layer interaction is found in cowl area of Mach number 7 case,indicating the inlet designed by proposed method works in a relatively wide Mach number range.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 50508012)Science &Technology Plan Project of Guangdong Province(Grant No. 20055190030)+1 种基金Key Basic Research Project of Science and Technology Ministry (Grant No. 2004CCA03300)Science &Technology Project of Guangzhou Education Bureau(Grant No.08C05)
文摘A new combined steel lead damper (NCSLD) was presented. Construction and working mechanism of NCSLD were introduced,pseudo-static tests of the small size dampers which would be used in the subsequent shaking table tests were carried out for the study of mechanical properties of NCSLD using electro-hydraulic servo press-shear machine. Processing technology of the damper was improved. Shaking table tests under two-dimensional excitation on structural aseismic control of a one-story structure model were carried out using the small size NCSLD; parameters of the structure and shaking table were also introduced. Results indicate that process improvement is beneficial to the implementation of working mechanism of the damper,NCSLD has full hysteresis loop which takes on bilinearity,NCSLD has obvious energy dissipation effect and it can control structural seismic response effectively.
基金supported by the National Natural Science Foundation of China(Grant No.12032010,11902155 and 12072250)by the Natural Science Foundation of Jiangsu Province(Grant No.BK20190382)+2 种基金by the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Grant No.MCMS-I-0222K01)by the Fund of Prospective Layout of Scientific Research for NUAAby the Foundation for the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Ultra-high molecular weight polyethylene(UHMWPE)fiber composite has been extensively used to construct lightweight protective structures against ballistic impacts,yet little is known about its performance when subjected to combined blast and fragment impacts.Built upon a recently developed laboratory-scale experimental technique to generate simulated combined loading through the impact of a fragment-foam composite projectile launched from a light gas gun,the dynamic responses of fullyclamped UHMWPE plates subjected to combined loading were characterized experimentally,with corresponding deformation and failure modes compared with those measured with simulated blast loading alone.Subsequently,to explore the underlying physical mechanisms,three-dimensional(3D)numerical simulations with the method of finite elements(FE)were systematically carried out.Numerical predictions compared favorably well with experimental measurements,thus validating the feasibility of the established FE model.Relative to the case of blast loading alone,combined blast and fragment loading led to larger maximum deflections of clamped UHMWPE plates.The position of the FSP in the foam sabot affected significantly the performance of a UHMWPE target,either enhancing or decreasing its ballistic resistance.When the blast loading and fragment impact arrived simultaneously at the target,its ballistic resistance was superior to that achieved when subjected to fragment impact alone,and benefited from the accelerated movement of the target due to simultaneous blast loading.
基金supported by the National Natural Science Foundation of China(Nos.51927807,52074164,42277174,42077267 and 42177130)the Natural Science Foundation of Shandong Province,China(No.ZR2020JQ23)China University of Mining and Technology(Beijing)Top Innovative Talent Cultivation Fund for Doctoral Students(No.BBJ2023048)。
文摘In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.
文摘Many conventional methods of testing strong and pulsed electromagnetic fields,the ones used in radars for example,had deficiencies due to the difficulty in obtaining simultaneous information about the electromagnetic field's peak both in the time domain and in the frequency domain.With regard to this problem,after analyzing the time-domain and the frequency-domain characteristics of radar pulsed signals,we propose a new time-frequency combination test method based on the correction of the test parameters,as well as its correction method at different bandwidths.The test method is applied in a quick test of a high-power pulsed radar signal,and the corrected results have error less than 1 dB in both the time domain and the frequency domain,which indicates that the proposed time-frequency combined method is effective in testing strong and pulsed electromagnetic fields.
文摘The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.
文摘On the basis of EST (Equivalent STate hashing) algorithm, this paper researches a kind of test generation algorithm based on search state dominance for combinational circuit. According to the dominance relation of the E-frontier (evaluation frontier), we can prove that this algorithm can terminate unnecessary searching step of test pattern earlier than the EST algorithm through some examples, so this algorithm can reduce the time of test generation. The test patterns calculated can detect faults given through simulation.
文摘In this paper the structure-based test generation algorithm has been studied for the problem that test patterns are obtained by determined finite faults set in the past. This Algorithm can find out all test patterns one tithe, so faults detection is very convenient. By simulation, the smallest test patterns set can be obtained and faults coverage rate is 100%.
