In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measuremen...In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were performed.Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g.The onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and analysed.Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process.During the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant grain.The calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were observed.The dynamic mechanical response process of the dummy propellant grain was analysed in detail.The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.展开更多
BACKGROUND Pancreatic surgery is challenging owing to the anatomical characteristics of the pancreas.Increasing attention has been paid to changes in quality of life(QOL)after pancreatic surgery.AIM To summarize and a...BACKGROUND Pancreatic surgery is challenging owing to the anatomical characteristics of the pancreas.Increasing attention has been paid to changes in quality of life(QOL)after pancreatic surgery.AIM To summarize and analyze current research results on QOL after pancreatic surgery.METHODS A systematic search of the literature available on PubMed and EMBASE was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Relevant studies were identified by screening the references of retrieved articles.Studies on patients’QOL after pancreatic surgery published after January 1,2012,were included.These included prospective and retrospective studies on patients'QOL after several types of pancreatic surgeries.The results of these primary studies were summarized inductively.RESULTS A total of 45 articles were included in the study,of which 13 were related to pancreaticoduodenectomy(PD),seven to duodenum-preserving pancreatic head resection(DPPHR),nine to distal pancreatectomy(DP),two to central pancre-atectomy(CP),and 14 to total pancreatectomy(TP).Some studies showed that 3-6 months were needed for QOL recovery after PD,whereas others showed that 6-12 months was more accurate.Although TP and PD had similar influences on QOL,patients needed longer to recover to preoperative or baseline levels after TP.The QOL was better after DPPHR than PD.However,the superiority of the QOL between patients who underwent CP and PD remains controversial.The decrease in exocrine and endocrine functions postoperatively was the main factor affecting the QOL.Minimally invasive surgery could improve patients’QOL in the early Core Tip:This review summarizes and analyzes current research results on quality of life(QOL)after pancreatic surgery.The article covers the discussion and analysis of the QOL of various pancreatic surgeries.Which kind of surgical procedure has better QOL is controversial.The long-term benefits on QOL of minimally invasive surgery over open surgery are contro-INTRODUCTION The pancreas,located in the retroperitoneum,is a glandular organ with endocrine and exocrine functions.It can be divided into four main parts:Head,neck,body,and tail.Pancreatic surgery can be divided into pancreaticoduoden-ectomy(PD),duodenum-preserving pancreatic head resection(DPPHR),distal pancreatectomy(DP),central pancre-atectomy(CP),and total pancreatectomy(TP).Pancreatic surgery is challenging due to the organ’s complex anatomical structure,peripheral vascularity,and intractable postoperative complications.Following the standardization of surgical steps and improvements in relevant medical techniques and surgical instruments,the safety of pancreatic surgery has significantly improved.Perioperative morbidity,mortality,and other related indicators have become more acceptable.However,owing to the organ’s essential role in digestion,absorption,and blood glucose regulation,changes in the quality of life(QOL)of patients after pancreatic surgery have attracted the attention of surgeons.More patients with non-malignant pancreatic diseases are willing to undergo surgical treatment because of the acceptable safety.In this case,from the perspective of the patient postoperatively,the significance of rehabilitation reflects the traditional perioperative outcome and QOL[1].The QOL is a new concept that extends beyond health.Although there is no consensus on its conception[2],we can consider it a multi-dimensional architecture that incorporates objective and individual subjective views of aspects of one’s physical,psychological,and social well-being[3-5].It includes evaluating physical health,and many subscales,such as emotion,job,culture,family,sociability,economy,cognition,happiness,sex,and some symptoms[6].Since people have realized the importance of QOL,many QOL scales have emerged,including the European Organization for Research and Treatment of Cancer QLQ-C30,European Quality of Life 5-dimension,36-item Short,etc.However,it is challenging to follow up on patients’QOL once they are discharged from the hospital.Consequently,most relevant studies had small sample sizes or lacked long-term follow-up results.Moreover,a summary of studies on QOL after pancreatic surgery is lacking.This study assessed the QOL in patients who underwent PD,DPPHR,DP,CP and TP.We conducted this study to describe the existing findings on the QOL after pancreatic surgery to make it easier for surgeons and patients to decide on a surgical approach.In addition,we attempted to identify controversial results to encourage further targeted research.展开更多
Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted m...Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the parameter optimization in the PSAM scheme. We discuss how the pilot spacing and the length of the Wiener ?lter should be chosen under the constraint of a tradeoff between pilot overhead, estimation accuracy, and receiver complexity. We also formulate an power allocation problem for the considered system. It is shown that the power allocation problem can optimally be solved by means of a gradient search method. Numerical simulations are presented to verify the correctness of the theoretical results and to demonstrate the benefits of the parameter optimization.展开更多
A novel light responsive nanosphere was constructed,and it was used as a drug carrier to investigate the loading and release properties of the Quercetin(QU).In this paper,mesoporous silica nanoparticles(MSN)were used ...A novel light responsive nanosphere was constructed,and it was used as a drug carrier to investigate the loading and release properties of the Quercetin(QU).In this paper,mesoporous silica nanoparticles(MSN)were used as a substrate,and 3-aminopropyl triethyoxysilane was used as a surface modification agent to introduce—NH_(2),and the azobenzene-4,4’-dicarboxylic acid(AZO)was used as light responsive agent to introduce the group of—N=N—,and thenβ-cyclodextrin(β-CD)was combined with AZO through host-guest interaction to construct light responsive nanoparticles(MSN@β-CD).The structure and properties of the carrier were analyzed by FTIR,BET,XPS,TGA,XRD,SEM and TEM.In vitro drug release studies showed the release rate of QU@MSN@β-CD(dark)was 12.19%within 72 h,but the release rate of QU@MSN@β-CD(light 10 min)was 26.09%,exhibiting a light-responsive property.The CCK8 tests demonstrated that MSN@β-CD could significantly decrease the toxicity of QU.Therefore,the controllable light-responsive drug delivery system has great application prospects.展开更多
Unraveling the diversification mechanisms of organisms is a fundamental and important macroevolutionary question regarding the diversity,ecological niche, and morphological divergence of life. However, many studies ha...Unraveling the diversification mechanisms of organisms is a fundamental and important macroevolutionary question regarding the diversity,ecological niche, and morphological divergence of life. However, many studies have only explored diversification mechanisms via isolated factors. Here,based on comparative phylogenetic analysis, we performed a macroevolutionary examination of horseshoe bats(Chiroptera: Rhinolophidae:Rhinolophus), to reveal the inter-relationships among diversification, intrinsic/extrinsic factors, and climatic ecological niche characteristics. Results showed a general slowing trajectory during diversification, with two dispersal events from Asia into Southeast Asia and Africa playing key roles in shaping regional heterogeneous diversity. Morphospace expansions of the investigated traits(e.g., body size,echolocation, and climate niche) revealed a decoupled pattern between diversification trajectory and trait divergence, suggesting that other factors(e.g., biotic interactions) potentially played a key role in recent diversification. Based on ancestral traits and pathway analyses, most Rhinolophus lineages belonging to the same region overlapped with each other geographically and were positively associated with the diversification rate, implying a competitive prelude to speciation. Overall, our study showed that multiple approaches need to be integrated to address diversification history. Rather than a single factor, the joint effects of multiple factors(biogeography, environmental drivers, and competition) are responsible for the current diversity patterns in horseshoe bats, and a corresponding multifaceted strategy is recommended to study these patterns in the future.展开更多
Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(...Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(3)(x=0,0.1-0.4)and CaTi_(0.7)Co_(0.3)O_(3) catalysts were prepared by using citric acid complexation method to promote the synthesis of ethanol.It was found that Mo species in the perovskite lattice can regulate the Co^(0) and Co^(2+)ratio through the domain-limiting effect of perovskite and the degree of Co reduction could be adjusted by changing the Co/Mo molar ratio.Among these investigated catalysts,the total selectivity of alcohols over the catalyst with the optimal Co/Mo ratio CaTi_(0.6)Co_(0.3)Mo_(0.1)O_(3) reached 39.1%,with ethanol accounting for 74.7%,which was ascribed to the moderate and tightly bound ratio of dissociative to non-dissociative adsorption sites on the surface and the balance of CH_(x)-CH_(y) coupling and C^(O) insertion.展开更多
In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state informa...In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state information(CSI)can be obtained at the transmitter(Alice),while eavesdropper's(Eve's)CSI is unknown.Firstly,the analytical expression of the achievable ergodic rate at Bob is obtained.Then,by exploiting Bob's statistical CSI,we jointly design the transmit covariance matrix at Alice and the phase shift matrix at the RIS to minimize the transmit power of the information signal under the quality-of-service(QoS)constraint of Bob.Finally,we propose an artificial noise(AN)-aided method without Eve's CSI to enhance the security of this system and use the residual power to design the transmit covariance for AN.Simulation results verify the convergence of the proposed method,and also show that there exists a trade-off between the secrecy rate and QoS of Bob.展开更多
文摘In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were performed.Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g.The onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and analysed.Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process.During the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant grain.The calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were observed.The dynamic mechanical response process of the dummy propellant grain was analysed in detail.The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.
基金National Natural Science Foundation of China,No.82273442 and No.82273438.
文摘BACKGROUND Pancreatic surgery is challenging owing to the anatomical characteristics of the pancreas.Increasing attention has been paid to changes in quality of life(QOL)after pancreatic surgery.AIM To summarize and analyze current research results on QOL after pancreatic surgery.METHODS A systematic search of the literature available on PubMed and EMBASE was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Relevant studies were identified by screening the references of retrieved articles.Studies on patients’QOL after pancreatic surgery published after January 1,2012,were included.These included prospective and retrospective studies on patients'QOL after several types of pancreatic surgeries.The results of these primary studies were summarized inductively.RESULTS A total of 45 articles were included in the study,of which 13 were related to pancreaticoduodenectomy(PD),seven to duodenum-preserving pancreatic head resection(DPPHR),nine to distal pancreatectomy(DP),two to central pancre-atectomy(CP),and 14 to total pancreatectomy(TP).Some studies showed that 3-6 months were needed for QOL recovery after PD,whereas others showed that 6-12 months was more accurate.Although TP and PD had similar influences on QOL,patients needed longer to recover to preoperative or baseline levels after TP.The QOL was better after DPPHR than PD.However,the superiority of the QOL between patients who underwent CP and PD remains controversial.The decrease in exocrine and endocrine functions postoperatively was the main factor affecting the QOL.Minimally invasive surgery could improve patients’QOL in the early Core Tip:This review summarizes and analyzes current research results on quality of life(QOL)after pancreatic surgery.The article covers the discussion and analysis of the QOL of various pancreatic surgeries.Which kind of surgical procedure has better QOL is controversial.The long-term benefits on QOL of minimally invasive surgery over open surgery are contro-INTRODUCTION The pancreas,located in the retroperitoneum,is a glandular organ with endocrine and exocrine functions.It can be divided into four main parts:Head,neck,body,and tail.Pancreatic surgery can be divided into pancreaticoduoden-ectomy(PD),duodenum-preserving pancreatic head resection(DPPHR),distal pancreatectomy(DP),central pancre-atectomy(CP),and total pancreatectomy(TP).Pancreatic surgery is challenging due to the organ’s complex anatomical structure,peripheral vascularity,and intractable postoperative complications.Following the standardization of surgical steps and improvements in relevant medical techniques and surgical instruments,the safety of pancreatic surgery has significantly improved.Perioperative morbidity,mortality,and other related indicators have become more acceptable.However,owing to the organ’s essential role in digestion,absorption,and blood glucose regulation,changes in the quality of life(QOL)of patients after pancreatic surgery have attracted the attention of surgeons.More patients with non-malignant pancreatic diseases are willing to undergo surgical treatment because of the acceptable safety.In this case,from the perspective of the patient postoperatively,the significance of rehabilitation reflects the traditional perioperative outcome and QOL[1].The QOL is a new concept that extends beyond health.Although there is no consensus on its conception[2],we can consider it a multi-dimensional architecture that incorporates objective and individual subjective views of aspects of one’s physical,psychological,and social well-being[3-5].It includes evaluating physical health,and many subscales,such as emotion,job,culture,family,sociability,economy,cognition,happiness,sex,and some symptoms[6].Since people have realized the importance of QOL,many QOL scales have emerged,including the European Organization for Research and Treatment of Cancer QLQ-C30,European Quality of Life 5-dimension,36-item Short,etc.However,it is challenging to follow up on patients’QOL once they are discharged from the hospital.Consequently,most relevant studies had small sample sizes or lacked long-term follow-up results.Moreover,a summary of studies on QOL after pancreatic surgery is lacking.This study assessed the QOL in patients who underwent PD,DPPHR,DP,CP and TP.We conducted this study to describe the existing findings on the QOL after pancreatic surgery to make it easier for surgeons and patients to decide on a surgical approach.In addition,we attempted to identify controversial results to encourage further targeted research.
文摘Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the parameter optimization in the PSAM scheme. We discuss how the pilot spacing and the length of the Wiener ?lter should be chosen under the constraint of a tradeoff between pilot overhead, estimation accuracy, and receiver complexity. We also formulate an power allocation problem for the considered system. It is shown that the power allocation problem can optimally be solved by means of a gradient search method. Numerical simulations are presented to verify the correctness of the theoretical results and to demonstrate the benefits of the parameter optimization.
文摘A novel light responsive nanosphere was constructed,and it was used as a drug carrier to investigate the loading and release properties of the Quercetin(QU).In this paper,mesoporous silica nanoparticles(MSN)were used as a substrate,and 3-aminopropyl triethyoxysilane was used as a surface modification agent to introduce—NH_(2),and the azobenzene-4,4’-dicarboxylic acid(AZO)was used as light responsive agent to introduce the group of—N=N—,and thenβ-cyclodextrin(β-CD)was combined with AZO through host-guest interaction to construct light responsive nanoparticles(MSN@β-CD).The structure and properties of the carrier were analyzed by FTIR,BET,XPS,TGA,XRD,SEM and TEM.In vitro drug release studies showed the release rate of QU@MSN@β-CD(dark)was 12.19%within 72 h,but the release rate of QU@MSN@β-CD(light 10 min)was 26.09%,exhibiting a light-responsive property.The CCK8 tests demonstrated that MSN@β-CD could significantly decrease the toxicity of QU.Therefore,the controllable light-responsive drug delivery system has great application prospects.
基金supported by the National Natural Science Foundation of China(31970394,32192421,31300314)Special Foundation for National Science and Technology Basic Research Program of China(2021FY100303)。
文摘Unraveling the diversification mechanisms of organisms is a fundamental and important macroevolutionary question regarding the diversity,ecological niche, and morphological divergence of life. However, many studies have only explored diversification mechanisms via isolated factors. Here,based on comparative phylogenetic analysis, we performed a macroevolutionary examination of horseshoe bats(Chiroptera: Rhinolophidae:Rhinolophus), to reveal the inter-relationships among diversification, intrinsic/extrinsic factors, and climatic ecological niche characteristics. Results showed a general slowing trajectory during diversification, with two dispersal events from Asia into Southeast Asia and Africa playing key roles in shaping regional heterogeneous diversity. Morphospace expansions of the investigated traits(e.g., body size,echolocation, and climate niche) revealed a decoupled pattern between diversification trajectory and trait divergence, suggesting that other factors(e.g., biotic interactions) potentially played a key role in recent diversification. Based on ancestral traits and pathway analyses, most Rhinolophus lineages belonging to the same region overlapped with each other geographically and were positively associated with the diversification rate, implying a competitive prelude to speciation. Overall, our study showed that multiple approaches need to be integrated to address diversification history. Rather than a single factor, the joint effects of multiple factors(biogeography, environmental drivers, and competition) are responsible for the current diversity patterns in horseshoe bats, and a corresponding multifaceted strategy is recommended to study these patterns in the future.
基金National Natural Science Foundation of China(21872101,21962014)Science and Technology Program of Zungeer County,Inner Mongolia(2020YY-12)。
文摘Selective synthesis of ethanol from syngas under the Co-based catalysts is still challenging due to the hard of regulating the active site Co^(0) and Co^(2+)ratio.In this work,a series of CaTi_(0.9-x)Co_(x)Mo_(0.1)O_(3)(x=0,0.1-0.4)and CaTi_(0.7)Co_(0.3)O_(3) catalysts were prepared by using citric acid complexation method to promote the synthesis of ethanol.It was found that Mo species in the perovskite lattice can regulate the Co^(0) and Co^(2+)ratio through the domain-limiting effect of perovskite and the degree of Co reduction could be adjusted by changing the Co/Mo molar ratio.Among these investigated catalysts,the total selectivity of alcohols over the catalyst with the optimal Co/Mo ratio CaTi_(0.6)Co_(0.3)Mo_(0.1)O_(3) reached 39.1%,with ethanol accounting for 74.7%,which was ascribed to the moderate and tightly bound ratio of dissociative to non-dissociative adsorption sites on the surface and the balance of CH_(x)-CH_(y) coupling and C^(O) insertion.
基金supported in part by the National Key Research and Development Program of China under Grant 2020YFB1804900in part by the National Natural Science Foundation of China under Grant 92067201,U1805262,62071247,62071249,62171240+2 种基金in part by the Jiangsu Provincial Key Research and Development Program of China under Grant BE2020084-5in part by Special Funds of the Central Government Guiding Local Science and Technology Development under Grant 2021L3010in part by Key provincial scientific and technological innovation projects under Grant 2021G02006.
文摘In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state information(CSI)can be obtained at the transmitter(Alice),while eavesdropper's(Eve's)CSI is unknown.Firstly,the analytical expression of the achievable ergodic rate at Bob is obtained.Then,by exploiting Bob's statistical CSI,we jointly design the transmit covariance matrix at Alice and the phase shift matrix at the RIS to minimize the transmit power of the information signal under the quality-of-service(QoS)constraint of Bob.Finally,we propose an artificial noise(AN)-aided method without Eve's CSI to enhance the security of this system and use the residual power to design the transmit covariance for AN.Simulation results verify the convergence of the proposed method,and also show that there exists a trade-off between the secrecy rate and QoS of Bob.
