The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personn...The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personnel from firing artillery within the cab.To investigate the overpressure characteristics of the FFICC,a foreign trade equipment model was used as the research object,and a numerical model was established to analyze the propagation of muzzle blast from the muzzle to the interior of the crew compartment under extreme firing condition.For comparative verification,the muzzle blast experiment included overpressure data from both the flow field outside the crew compartment(FFOCC)and the FFICC,as well as the acceleration data of the crew compartment structure(Str-CC).The research findings demonstrate that the overpressure-time curves of the FFICC exhibit multi-peak characteristics,while the pressure wave shows no significant discontinuity.The enclosed nature of the cab hinders the dissipation of pressure wave energy within the FFICC,leading to sustained high-amplitude overpressure.The frameskin structure helps attenuate the impact of muzzle blast on the FFICC.Conversely,local high overpressure caused by the convex or concave features of the cab's exterior significantly amplifies the overpressure amplitude within the FFICC.展开更多
In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software ...In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software was used to build a parameterized dynamic model of the saddle ring.A parameter identification method for the ring was proposed based on the particle swarm optimization algorithm.A loading test was designed and performed several times at different elevation angles.The response histories of the saddle ring with different loads were then obtained.The parameters of the saddle ring dynamic model were identified from statistics generated at a 500 elevation angle to verify the feasibility and accuracy of the proposed method.The actual loading history of the ring at a 70°elevation angle was taken as the model input.The response histories of the ring under these working conditions were obtained through a simulation.The simulation results agreed with the actual response.Thus,the effectiveness and applicability of the proposed dynamic model were verified,and it provides an effective method for modeling saddle rings.展开更多
In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the ...In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.展开更多
Deuterated polymer microspheres can be used as a neutron source in conjunction with lasers because thermonuclear fusion neutrons can be produced efficiently by collisions of the resulting energetic deuterium ions.A ne...Deuterated polymer microspheres can be used as a neutron source in conjunction with lasers because thermonuclear fusion neutrons can be produced efficiently by collisions of the resulting energetic deuterium ions.A new type of solid deuterated polymer microsphere with a carbon hydrogen–carbon deuterium(CH-CD)multilayer has been designed for preparing the target for inertial confinement fusion(ICF)experiments.To fabricate these solid CH-CD multilayer microspheres,CH beads are first fabricated by a microfluidic technique,and the CD coating layer is prepared by a plasma polymerization method.Both polystyrene(PS)and poly(α-methylstyrene)(PAMS)are used as the material sources for the CH beads.The effects of the PS and PAMS materials on the quality of the solid CH beads and the resulting CH-CD multilayer polymer microspheres are investigated.The solid PS beads have better sphericity and a smoother surface,but large vacuoles are observed in solid PS-CD multilayer microspheres owing to the presence of residual fluorobenzene in the beads and a glass transition temperature of the solid PS beads that is lower than the temperature of plasma polymerization.Therefore,solidPAMSbeads are more suitable as a mandrel for fabricating solid CH-CD multilayer polymer microspheres.Solid CH-CD multilayer microspheres with specified size have been successfully prepared by controlling the droplet size and the CD deposition rate and deposition time.Compared with the design value,the diameter deviation of the inner CH beads and the thickness deviation of the CD layer can be controlled within 20μmand 2μm,respectively.Thus,an approach has been developed to fabricate solid CH-CD multilayer microspheres that meet the physical design requirements for ICF.展开更多
To improve the quality of deuterated polystyrene(DPS)shells,the synthesis and purification of DPS as well as the fabrication of DPS shells are investigated.The molecular weight and molecular weight distribution,measur...To improve the quality of deuterated polystyrene(DPS)shells,the synthesis and purification of DPS as well as the fabrication of DPS shells are investigated.The molecular weight and molecular weight distribution,measured by GPC-MALLS,are about 350 kg mol^(-1) and less than 2.0,respectively.The results of TG and GC-MS indicate that the residual solvent is almost completely removed.DPS shells with;300 mm–2500 mmdiameter and;10 mm–100mmwall thickness are successfully prepared by a microfluidic device.The monodispersity of the diameter ismuchbetter than that of the wall thickness in a batch ofDPSshells.The vacuoles can be suppressed by both reducing hydrophilic residues in DPS and adding some salts into the outer water phase(W2).The defects appearing during the drying process decrease by heat treatment,ethanol exchange,and lowered drying temperature.The results presented in this work not only provide guidelines for the preparation of DPS shells of better quality,but also indicate challenges for the future.展开更多
BACKGROUND： Recent advancements in gene therapy have provided new methodology for treating ischemia in lower extremities. Gene transfer of angiogenic factors to ischemic tissues may promote local proliferation of new...BACKGROUND： Recent advancements in gene therapy have provided new methodology for treating ischemia in lower extremities. Gene transfer of angiogenic factors to ischemic tissues may promote local proliferation of new vessels and form collateral circulation. OBJECTIVE： To observe histopathological changes in the femoral and intramuscular nerve three months after intramuscular injection of hepatocyte growth factor （HGF） into the peripheral skeletal muscle in a canine model of lower limb ischemia. DESIGN： Randomized occlusion modelled and verification animal study. SETTING： Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA. MATERIALS： This study was performed at Animal Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA from September to November 2006. A total of eight male mongrel dogs, weighing 12–15 kg and 1.5–3 years of age, were selected for this study. This experimental study was in accordance with local ethics standards. Recombinant plasmid carrying HGF （pUDKH） and occlusion model plasmid （pUDK） were provided by the Third Laboratory of Radiation Medical Institute, Academy of Military Medical Sciences of PLA. METHODS： Grouping and model establishment： under anesthesia, complete vascular occlusion models were established on the left lower extremities. The experimental dogs were randomly divided into a model group and a pUDKH treatment group, with four dogs in each group. Dogs in the pUDKH group were injected with 0.15 mg/kg pUDKH. Ten minutes later, intramuscular injections were performed at three spots into the peripheral skeletal muscle of the left hind limb, as well as lateral injections at two spots. The injection volume at each spot was 0.2 mL. Dogs in the model group were injected with pUDK, and dosage and injection method were identical to the treatment group. MAIN OUTCOME MEASURES： Histopathological changes in the femoral nerve, as well as internal and external intramuscular nerve tissues in the hind limb of dogs three months after plasmid injection under optic microscope. RESULTS： （1） Histopathological changes in the femoral nerve： tiny nerves from the femoral nerve to the intramuscular nerve exhibited marked degeneration in the model group. The degenerating features included neurites, myelin sheaths, and Schwann cell nuclei. Neuropathy in the pUDKH treatment group was not detected. （2） Histopathological changes of the intramuscular nerve： large and irregular vacuoles were present on several longitudinal sections of intramuscular nerve fibers in the model group, as well as annular-shaped blank regions on transverse sections of peripheral neurites. In the pUDKH treatment group, large, blank regions were present in several segments of partial nerve fibers of the longitudinal intramuscular nerve region, but only a few nerve fibers exhibited annular-shaped blank regions on the transverse section of peripheral neurites. CONCLUSION： Local pUDKH injection may relieve or block femoral and intramuscular nerve tissue injury in a canine mocel of lower limb ischemia.展开更多
Objective: More than half of human glioblastomas show EGFR gene amplification and mutation, but EGFR inhibitors have not been effective in treating EGFR-positive glioblastoma patients.The mechanism behind this type of...Objective: More than half of human glioblastomas show EGFR gene amplification and mutation, but EGFR inhibitors have not been effective in treating EGFR-positive glioblastoma patients.The mechanism behind this type of primary resistance is not well understood.The aim of this study was to investigate gefitinib resistance in glioblastoma, and explore ways to circumvent this significant clinical problem.Methods: MTT method was used to test the cell viability after EGFR-positive glioblastoma cells were treated with indicated drugs;real-time quantitative PCR method was included to detect the TNFα mRNA levels in glioma tissues and cell lines.ELISA was introduced to measure the TNFα protein levels in cell culture supernatant of glioblastoma cells treated with gefitinib.Western blot was used to detect the activity change of intracellular kinases in drug-treated glioblastoma cells.Two mouse xenograft tumor models were carried out to evaluate the in vivo effects of a combination of EGFR and TNFα inhibitors.Results: We found that glioblastoma resistance to gefitinib may be mediated by an adaptive pro-survival TNFα-JNK-Axl signaling axis, and that high TNFα levels in the glioblastoma microenvironment may further intensify primary resistance.A combination of the TNFα-specific small-molecule inhibitor C87 and gefitinib significantly enhanced the sensitivity of glioblastoma cells to gefitinib in vitro and in vivo.Conclusions: Our findings provide a possible explanation for the primary resistance of glioblastoma to EGFR inhibitors and suggest that dual blockade of TNFα and EGFR may be a viable therapeutic strategy for the treatment of patients with chemotherapy-refractory advanced glioblastoma.展开更多
Objective:Multiple brain metastases are a severe condition for cancer patients.To date,no general consensus exists regarding the optimal treatment procedure for multiple brain metastases.Radiotherapy is the most commo...Objective:Multiple brain metastases are a severe condition for cancer patients.To date,no general consensus exists regarding the optimal treatment procedure for multiple brain metastases.Radiotherapy is the most commonly used treatment option.The role of surgical resection for multiple brain metastases is unclear.The aim of this study was to compare the outcomes of patients with multiple brain metastases treated with either surgery or stereotactic radiosurgery(SRS).Methods:The medical records of 279 consecutive adult patients with multiple brain metastases treated with either surgery(26 patients)or SRS(253 patients)were retrospectively reviewed.Propensity score matching was conducted to correct for discrepancies in the baseline characteristics,and 78 patients(26 receiving surgery and 52 receiving SRS)were chosen for comparison of outcomes,such as overall survival,local tumor control rate,and symptom improvement.Results:The tumor size in the surgery group was significantly greater than that in the SRS group after propensity score matching.However,the neurological recovery rate,incidence of leptomeningeal metastasis after surgery,1-year local tumor control rate,and overall survival were not significantly different between groups.Conclusions:Our data demonstrate that surgery and radiosurgery have identical overall survival and local tumor control rates in patients with 2 to 4 brain metastases.Although SRS remains the primary and standard option for patients with brain metastasis,surgery offers several distinct advantages,such as establishing a diagnosis or relieving mass effects,and may additionally be beneficial in carefully selected patients with 2–4 brain metastases.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U2341269)。
文摘The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personnel from firing artillery within the cab.To investigate the overpressure characteristics of the FFICC,a foreign trade equipment model was used as the research object,and a numerical model was established to analyze the propagation of muzzle blast from the muzzle to the interior of the crew compartment under extreme firing condition.For comparative verification,the muzzle blast experiment included overpressure data from both the flow field outside the crew compartment(FFOCC)and the FFICC,as well as the acceleration data of the crew compartment structure(Str-CC).The research findings demonstrate that the overpressure-time curves of the FFICC exhibit multi-peak characteristics,while the pressure wave shows no significant discontinuity.The enclosed nature of the cab hinders the dissipation of pressure wave energy within the FFICC,leading to sustained high-amplitude overpressure.The frameskin structure helps attenuate the impact of muzzle blast on the FFICC.Conversely,local high overpressure caused by the convex or concave features of the cab's exterior significantly amplifies the overpressure amplitude within the FFICC.
基金supported by National Natural Science Foundation of China(11472137)the Natural Science Foundation of Jiangsu Province,China(BK20140773)。
文摘In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software was used to build a parameterized dynamic model of the saddle ring.A parameter identification method for the ring was proposed based on the particle swarm optimization algorithm.A loading test was designed and performed several times at different elevation angles.The response histories of the saddle ring with different loads were then obtained.The parameters of the saddle ring dynamic model were identified from statistics generated at a 500 elevation angle to verify the feasibility and accuracy of the proposed method.The actual loading history of the ring at a 70°elevation angle was taken as the model input.The response histories of the ring under these working conditions were obtained through a simulation.The simulation results agreed with the actual response.Thus,the effectiveness and applicability of the proposed dynamic model were verified,and it provides an effective method for modeling saddle rings.
基金supported by the Key Basic Research Projects of Basic Strengthening Plan under Grants 2017-JCJQ-ZD-004
文摘In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.
基金funding from the National Natural Science Foundation of China(Grant Nos.51703212 and 52073264)the Open Project of the State Key Laboratory of Environment-Friendly Energy Materials(Grant Nos.18kfhg03 and 19kfhg02)a project supported by the CAEP Foundation(Grant No.PY20200117).
文摘Deuterated polymer microspheres can be used as a neutron source in conjunction with lasers because thermonuclear fusion neutrons can be produced efficiently by collisions of the resulting energetic deuterium ions.A new type of solid deuterated polymer microsphere with a carbon hydrogen–carbon deuterium(CH-CD)multilayer has been designed for preparing the target for inertial confinement fusion(ICF)experiments.To fabricate these solid CH-CD multilayer microspheres,CH beads are first fabricated by a microfluidic technique,and the CD coating layer is prepared by a plasma polymerization method.Both polystyrene(PS)and poly(α-methylstyrene)(PAMS)are used as the material sources for the CH beads.The effects of the PS and PAMS materials on the quality of the solid CH beads and the resulting CH-CD multilayer polymer microspheres are investigated.The solid PS beads have better sphericity and a smoother surface,but large vacuoles are observed in solid PS-CD multilayer microspheres owing to the presence of residual fluorobenzene in the beads and a glass transition temperature of the solid PS beads that is lower than the temperature of plasma polymerization.Therefore,solidPAMSbeads are more suitable as a mandrel for fabricating solid CH-CD multilayer polymer microspheres.Solid CH-CD multilayer microspheres with specified size have been successfully prepared by controlling the droplet size and the CD deposition rate and deposition time.Compared with the design value,the diameter deviation of the inner CH beads and the thickness deviation of the CD layer can be controlled within 20μmand 2μm,respectively.Thus,an approach has been developed to fabricate solid CH-CD multilayer microspheres that meet the physical design requirements for ICF.
基金We gratefully acknowledge funding from the National Natural Science Foundation of China(51703212)State Key Laboratory of Environment-friendly Energy Materials(18kfhg03).
文摘To improve the quality of deuterated polystyrene(DPS)shells,the synthesis and purification of DPS as well as the fabrication of DPS shells are investigated.The molecular weight and molecular weight distribution,measured by GPC-MALLS,are about 350 kg mol^(-1) and less than 2.0,respectively.The results of TG and GC-MS indicate that the residual solvent is almost completely removed.DPS shells with;300 mm–2500 mmdiameter and;10 mm–100mmwall thickness are successfully prepared by a microfluidic device.The monodispersity of the diameter ismuchbetter than that of the wall thickness in a batch ofDPSshells.The vacuoles can be suppressed by both reducing hydrophilic residues in DPS and adding some salts into the outer water phase(W2).The defects appearing during the drying process decrease by heat treatment,ethanol exchange,and lowered drying temperature.The results presented in this work not only provide guidelines for the preparation of DPS shells of better quality,but also indicate challenges for the future.
基金the Foundation of High-Tech Key Project of the National 863 Program, No. 2001AA217061
文摘BACKGROUND： Recent advancements in gene therapy have provided new methodology for treating ischemia in lower extremities. Gene transfer of angiogenic factors to ischemic tissues may promote local proliferation of new vessels and form collateral circulation. OBJECTIVE： To observe histopathological changes in the femoral and intramuscular nerve three months after intramuscular injection of hepatocyte growth factor （HGF） into the peripheral skeletal muscle in a canine model of lower limb ischemia. DESIGN： Randomized occlusion modelled and verification animal study. SETTING： Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA. MATERIALS： This study was performed at Animal Experimental Center, Lanzhou General Hospital of Lanzhou Military Area Command of Chinese PLA from September to November 2006. A total of eight male mongrel dogs, weighing 12–15 kg and 1.5–3 years of age, were selected for this study. This experimental study was in accordance with local ethics standards. Recombinant plasmid carrying HGF （pUDKH） and occlusion model plasmid （pUDK） were provided by the Third Laboratory of Radiation Medical Institute, Academy of Military Medical Sciences of PLA. METHODS： Grouping and model establishment： under anesthesia, complete vascular occlusion models were established on the left lower extremities. The experimental dogs were randomly divided into a model group and a pUDKH treatment group, with four dogs in each group. Dogs in the pUDKH group were injected with 0.15 mg/kg pUDKH. Ten minutes later, intramuscular injections were performed at three spots into the peripheral skeletal muscle of the left hind limb, as well as lateral injections at two spots. The injection volume at each spot was 0.2 mL. Dogs in the model group were injected with pUDK, and dosage and injection method were identical to the treatment group. MAIN OUTCOME MEASURES： Histopathological changes in the femoral nerve, as well as internal and external intramuscular nerve tissues in the hind limb of dogs three months after plasmid injection under optic microscope. RESULTS： （1） Histopathological changes in the femoral nerve： tiny nerves from the femoral nerve to the intramuscular nerve exhibited marked degeneration in the model group. The degenerating features included neurites, myelin sheaths, and Schwann cell nuclei. Neuropathy in the pUDKH treatment group was not detected. （2） Histopathological changes of the intramuscular nerve： large and irregular vacuoles were present on several longitudinal sections of intramuscular nerve fibers in the model group, as well as annular-shaped blank regions on transverse sections of peripheral neurites. In the pUDKH treatment group, large, blank regions were present in several segments of partial nerve fibers of the longitudinal intramuscular nerve region, but only a few nerve fibers exhibited annular-shaped blank regions on the transverse section of peripheral neurites. CONCLUSION： Local pUDKH injection may relieve or block femoral and intramuscular nerve tissue injury in a canine mocel of lower limb ischemia.
基金supported by National Basic Research Program of China (Grant No.2015CB964903)Natural Science Foundation of Tianjin (Grant No.15JCQNJC44800 and 18JCQNJC81300)+3 种基金National Natural Science Foundation of China (Grant No.81702481, 81701224, 81802873 and 81600083)CAMS Innovation Fund for Medical Sciences (Grant No.201612M-1-003 2017-12M-1-015)the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (Grant No.2017PT31033, 2018RC31002, 2018PT32034)
文摘Objective: More than half of human glioblastomas show EGFR gene amplification and mutation, but EGFR inhibitors have not been effective in treating EGFR-positive glioblastoma patients.The mechanism behind this type of primary resistance is not well understood.The aim of this study was to investigate gefitinib resistance in glioblastoma, and explore ways to circumvent this significant clinical problem.Methods: MTT method was used to test the cell viability after EGFR-positive glioblastoma cells were treated with indicated drugs;real-time quantitative PCR method was included to detect the TNFα mRNA levels in glioma tissues and cell lines.ELISA was introduced to measure the TNFα protein levels in cell culture supernatant of glioblastoma cells treated with gefitinib.Western blot was used to detect the activity change of intracellular kinases in drug-treated glioblastoma cells.Two mouse xenograft tumor models were carried out to evaluate the in vivo effects of a combination of EGFR and TNFα inhibitors.Results: We found that glioblastoma resistance to gefitinib may be mediated by an adaptive pro-survival TNFα-JNK-Axl signaling axis, and that high TNFα levels in the glioblastoma microenvironment may further intensify primary resistance.A combination of the TNFα-specific small-molecule inhibitor C87 and gefitinib significantly enhanced the sensitivity of glioblastoma cells to gefitinib in vitro and in vivo.Conclusions: Our findings provide a possible explanation for the primary resistance of glioblastoma to EGFR inhibitors and suggest that dual blockade of TNFα and EGFR may be a viable therapeutic strategy for the treatment of patients with chemotherapy-refractory advanced glioblastoma.
基金This study was supported by research grants from the Tianjin Municipal Science and Technology Commission(Grant No.18JCYBJC27600).
文摘Objective:Multiple brain metastases are a severe condition for cancer patients.To date,no general consensus exists regarding the optimal treatment procedure for multiple brain metastases.Radiotherapy is the most commonly used treatment option.The role of surgical resection for multiple brain metastases is unclear.The aim of this study was to compare the outcomes of patients with multiple brain metastases treated with either surgery or stereotactic radiosurgery(SRS).Methods:The medical records of 279 consecutive adult patients with multiple brain metastases treated with either surgery(26 patients)or SRS(253 patients)were retrospectively reviewed.Propensity score matching was conducted to correct for discrepancies in the baseline characteristics,and 78 patients(26 receiving surgery and 52 receiving SRS)were chosen for comparison of outcomes,such as overall survival,local tumor control rate,and symptom improvement.Results:The tumor size in the surgery group was significantly greater than that in the SRS group after propensity score matching.However,the neurological recovery rate,incidence of leptomeningeal metastasis after surgery,1-year local tumor control rate,and overall survival were not significantly different between groups.Conclusions:Our data demonstrate that surgery and radiosurgery have identical overall survival and local tumor control rates in patients with 2 to 4 brain metastases.Although SRS remains the primary and standard option for patients with brain metastasis,surgery offers several distinct advantages,such as establishing a diagnosis or relieving mass effects,and may additionally be beneficial in carefully selected patients with 2–4 brain metastases.
