In this paper,we establish a delayed predator-prey model with nonlocal fear effect.Firstly,the existence,uniqueness,and persistence of solutions of the model are studied.Then,the local stability,Turing bifurcation,and...In this paper,we establish a delayed predator-prey model with nonlocal fear effect.Firstly,the existence,uniqueness,and persistence of solutions of the model are studied.Then,the local stability,Turing bifurcation,and Hopf bifurcation of the constant equilibrium state are analyzed by examining the characteristic equation.The global asymptotic stability of the positive equilibrium point is investigated using the Lyapunov function method.Finally,the correctness of the theoretical analysis results is verified through numerical simulations.展开更多
Through analyzing the roll model of the integrated system of fin and anti-rolling tank, this paper uses binomial equation to simplify the module and check how the approximate parameters simulate the original function....Through analyzing the roll model of the integrated system of fin and anti-rolling tank, this paper uses binomial equation to simplify the module and check how the approximate parameters simulate the original function. Based on the simplified module, the influence of fin and anti-rolling tank on the coefficient items of the roll module is discussed, and the influencing factors between fin and anti-rolling tank are analysed. And through simulation, the influence of action between fin and anti-rolling tank on the static characteristics, and the integrated stabilization effect, are analyzed.展开更多
Objective To investigate the preventive effect of probiotics on pediatric food allergy. Methods From MEDLINE bibliographical database, we searched and reviewed all randomized controlled trials on the preventive effect...Objective To investigate the preventive effect of probiotics on pediatric food allergy. Methods From MEDLINE bibliographical database, we searched and reviewed all randomized controlled trials on the preventive effects of probiotics on pediatric food allergies up to September 2013 and excluded the studies that do not meet inclusion criteria and extracted the data. Meta-analysis for the results of homogenous studies was performed using RevMan 5.0 and the co-effect was pooled by using fixed-effects model of relative risk(RR) ratios. Results Ten trials published between 2007 and 2012 including 2701 cases were included. Meta-analysis based on included data showed that the preventive effect of prenatal and postnatal probiotic supplementation on food allergies was not significant with the RR=0.88(95% CI: 0.76-1.03). Conclusion Present evidences cannot show in unequivocal terms that prenatal and postnatal probiotic supplementation will prevent food allergic diseases.展开更多
In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on ...In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on permeability and porosity.The time lag effect of rock deformation illustrating the relationship between changes in permeability and steady time was studied.Permeability reduction ratios were measured under different stress loading rates which were achieved by different pump rate settings.The results show that permeability and porosity gradually decrease with increases in effective pressure.Permeability at high effective pressure attains stability quickly.Steady times at low effective pressure are very long.Reduction in permeability at lower stress loading rates is small,while,in contrast,it is large at high stress loading rates.展开更多
Background Low responsiveness to clopidogrel （LRC） is associated with increased risk of ischemic events. This study was aimed to explore the feasibility of tailored antiplatelet therapy according to the responsivene...Background Low responsiveness to clopidogrel （LRC） is associated with increased risk of ischemic events. This study was aimed to explore the feasibility of tailored antiplatelet therapy according to the responsiveness to clopidogrel. Methods A total of 305 clopidogrel naive patients with acute coronary syndromes （ACS） undergoing coronary stenting were randomly assigned to receive standard （n = 151） or tailored （n = 154） antiplatelet therapy. The ADP-induced platelet aggregation tests by light transmission aggregometry were performed to identify LRC patients assigned to the tailored group. The standard antiplatelet regimen was dual antiplatelet therapy with aspirin and clopidogrel. The tailored antiplatelet therapy was standard regimen for non-LRC patients and an additional 6-month cilostazol treatment for LRC patients. The primary efficacy outcome was the composite of cardiovascular death, myocardial infarction or stroke at one year. Results LCR was present in 26.6% （41/154） of patients in the tailored group. The percentage platelet aggregation for LCR patients was significantly decreased at three days after adjunctive cilostazol treatment （77.5% ± 12.1% vs. 64.5% ± 12.1%, P 〈 0.001）. At one year follow-up, a non-significant 37% relative risk reduction of primary events were observed in the tailored group as compared to the standard group （5.8% vs. 9.3%, P = 0.257）. There were no differences in the rates of stent thrombosis and hemorrhagic events between the two groups. Conclusions Tailored antiplatelet therapy for ACS patients after coronary stenting according to responsiveness to clopidogrel is feasible. However, its efficacy and safety need further confirmation by clinical trials with larger sample sizes.展开更多
Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground...Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.展开更多
Objective To evaluate the clinical efficacy of incising spinal pia mater to relieve pressure and unilateral open-door laminoplasty with internal screw fixation for treatment of the dated spinal cord injury. Methods Fr...Objective To evaluate the clinical efficacy of incising spinal pia mater to relieve pressure and unilateral open-door laminoplasty with internal screw fixation for treatment of the dated spinal cord injury. Methods From March, 2009 to July, 2010, 16 cases with chronic cervical cord injury underwent spinal dura mater incision and unilateral open-door laminoplasty with internal screw fixation. Nerve functions of preand postoperation were evaluated by Frankel classification and the Japanese Orthopaedic Association (JOA) scale. The improvement rate of JOA score at the indicated time was recorded. Results Postoperative Frankel classification rating of 16 patients improved obviously. JOA scores at the 1st month, 3rd month, 6th month, and 12th month after surgery were 7.9±2.3, 8.5±1.6, 8.9±2.1, and 12.4±2.5, respectively, and significantly increased compared with that prior to surgery (5.5±0.6). At the end of follow-up period, JOA score was significantly higher than that of pre-treatment (P<0.05). The recovery was relatively rapid during the first 3 months following the surgery, then entered a platform period. Conclusion It is effective for patients with dated spinal cord injury to undergo spinal decompression and laminoplasty.展开更多
Objective． An internal fixation apparatus—— distraction reduction fixation system(DRFS) was designed to satisfy the clinical needs for spondylolisthesis. Methods. Since 1996, 53 patients were treated with DRFS. Amo...Objective． An internal fixation apparatus—— distraction reduction fixation system(DRFS) was designed to satisfy the clinical needs for spondylolisthesis. Methods. Since 1996, 53 patients were treated with DRFS. Among them, 35 had spondylolisthesis, 12 had lumbar canal stenosis accompanied with instability, 2 had vertebral tumors and 4 suffered from spinal fracture. The average age was 53.6 years old (ranged 24～ 72yrs). The mean time for follow- up was 30.6 months (16～ 44 months). Results． The slip rate was 0.15± 0.10 before operation, and decreased to 0.09± 0.07 after operation. Entire slip reposition was achieved in 19 cases (54.3％ ). The change in height of the intervertebral space within the fixation segments was 0.7± 0.17. Conclusion． DRFS achieved better results for spondylolisthesis less II degree and no other adverse effects were found. Compared with other foreign and domestic techniques, it had advantages in less implants, less operation gears required and ease to utilize in operation. It was proved to be an ideal internal fixation apparatus.展开更多
The stress combination method for the fatigue assessment of the hatch comer of a bulk carrier was investigated based on equivalent waves. The principles of the equivalent waves of ship structures were given, including...The stress combination method for the fatigue assessment of the hatch comer of a bulk carrier was investigated based on equivalent waves. The principles of the equivalent waves of ship structures were given, including the determination of the dominant load parameter, heading, frequency, and amplitude of the equivalent regular waves. The dominant load parameters of the hatch comer of a bulk carrier were identified by the structural stress response analysis, and then a series of equivalent regular waves were defined based on these parameters. A combination method of the structural stress ranges under the different equivalent waves was developed for the fatigue analysis. The combination factors were obtained by least square regression analysis with the stress ranges derived from spectral fatigue analysis as the target value. The proposed method was applied to the hatch comer of another bulk carrier as an example. This shows that the results from the equivalent wave approach agree well with those from the spectral fatigue analysis. The workload is reduced substantially. This method can be referenced in the fatigue assessment of the hatch comer of a bulk carrier.展开更多
Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating effici...Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating efficiency, performance, safety, and habitability of a vessel and its subsystems. In the following research, the life cycle of vessels was divided into 9 phases, and 15 research subjects were also identified from among these phases. The 15 subjects were systemized, and then the man-machine-environment engineering system application model for vessels was developed using the ICAM definition method 0 (IDEF0), which is a systematical modeling method. This system model bridges the gap between the data and information flow of every two associated subjects with the major basic research methods and approaches included, which brings the formerly relatively independent subjects together as a whole. The application of this systematic model should facilitate the application of man-machine-environment system engineering in vessels, especially at the conceptual and embodiment design phases. The managers and designers can deal with detailed tasks quickly and efficiently while reducing repetitive work.展开更多
In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and ...In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and then established the flow rules after failure. The condition under which states of deformation convert is presented and the manner in which these convert is proposed. In the end, the process of gas outbursts is explained in detail. It shows that a gas outburst is a process in which the boundaries of coal seams are variable because of coal failure. If the fractures are not connected or even closed owing to coal/rock stress, fractured zones will retain a certain level of carrying capacity because of the self-sealing gas pressure. When the accumulation of gas energy reaches its limit, coal seams will become unstable and gas outbursts take place.展开更多
In locally convex Hausdorff topological vector spaces,ε-strongly efficient solutions for vector optimization with set-valued maps are discussed.Firstly,ε-strongly efficient point of set is introduced.Secondly,under ...In locally convex Hausdorff topological vector spaces,ε-strongly efficient solutions for vector optimization with set-valued maps are discussed.Firstly,ε-strongly efficient point of set is introduced.Secondly,under the nearly cone-subconvexlike set-valued maps,the theorem of scalarization for vector optimization is obtained.Finally,optimality conditions of ε-strongly efficient solutions for vector optimization with generalized inequality constraints and equality constraints are obtained.展开更多
Prandtl’s lifting line theory was generalized to the lifting problem of a three-dimensional hydrofoil in the presence of a free surface. Similar to the classical lifting theory, the singularity distribution method wa...Prandtl’s lifting line theory was generalized to the lifting problem of a three-dimensional hydrofoil in the presence of a free surface. Similar to the classical lifting theory, the singularity distribution method was utilized to solve two-dimensional lifting problems for the hydrofoil beneath the free surface at the air-water interface, and a lifting line theory was developed to correct three-dimensional effects of the hydrofoil with a large aspect ratio. Differing from the classical lifting theory, the main focus was on finding the three-dimensional Green function of the free surface induced by the steady motion of a system of horseshoe vortices under the free surface. Finally, numerical examples were given to show the relationship between the lift coefficient and submergence Froude numbers for 2-D and 3-D hydrofoils. If the submergence Froude number is small free surface effect will be significant registered as the increase of lift coefficient. The validity of these approaches was examined in comparison with the results calculated by other methods.展开更多
We propose a method to improve positioning accuracy while reducing energy consumption in an indoor Wireless Local Area Network(WLAN) environment.First,we intelligently and jointly select the subset of Access Points(AP...We propose a method to improve positioning accuracy while reducing energy consumption in an indoor Wireless Local Area Network(WLAN) environment.First,we intelligently and jointly select the subset of Access Points(APs) used in positioning via Maximum Mutual Information(MMI) criterion.Second,we propose Orthogonal Locality Preserving Projection(OLPP) to reduce the redundancy among selected APs.OLPP effectively extracts the intrinsic location features in situations where previous linear signal projection techniques failed to do,while maintaining computational efficiency.Third,we show that the combination of AP selection and OLPP simultaneously exploits their complementary advantages while avoiding the drawbacks.Experimental results indicate that,compared with the widely used weighted K-nearest neighbor and maximum likelihood estimation method,the proposed method leads to 21.8%(0.49 m) positioning accuracy improvement,while decreasing the computation cost by 65.4%.展开更多
This paper presents an optimal production model for manufacturer in a supply chain with a fixed demand at a fixed interval with respect to the learning effect on production capacity. An algorithm is employed to find t...This paper presents an optimal production model for manufacturer in a supply chain with a fixed demand at a fixed interval with respect to the learning effect on production capacity. An algorithm is employed to find the optimal delay time for production and production time sequentially. It is found that the optimal delay time for production and the production time are not static, but dynamic and variant with time. It is important for a manufacturer to schedule the production so as to prevent facilities and workers from idling.展开更多
The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required ...The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.展开更多
Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the cha...Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the channel capacity.Indeed fortunately,the latter researchers found some practical channel codes approaching the channel capacity with insignificant losses of spectral efficiency under ignorable bit error rate(BER).The authors note,in general,that bits of the channel codes are not independent of each other in code space.Further,we note that the modulated symbols are not independent among them,as well,in Euclidean Space.By exploiting a usage of the dependencies jointly to signal design,we can transmit two independent signal streams through an additive white Gaussian channel and separate them in Euclidean space at the receiver.The capacity of this approach is found larger than that of Shannon capacity in the same channel assumptions.The numerical results confirm the theoretical procedures.展开更多
This work studied the effect of increasing degree of metamorphism on the properties of rocks.The properties investigated are the physical,mechanical and dynamic parameters.They are important inputs in the design of ma...This work studied the effect of increasing degree of metamorphism on the properties of rocks.The properties investigated are the physical,mechanical and dynamic parameters.They are important inputs in the design of many mining and civil engineering techniques such as in tunnelling,slope stability and dynamic activities associated with seismicity and fragmentation.This work compared the degree of metamorphism examined through petrographic studies of the Transvaal Sequence in South Africa with the properties of the rocks.The study shows that as the effect metamorphism increases,the state of stress,compaction of grains,cementation and the brittleness of the rocks increases.In addition,increase in the metamorphic effect increases the value of the rock property.The degree of metamorphism of an outcrop is the key factor influencing its property value.Therefore the metamorphism effect of an outcrop may act as a guide to its engineering properties.展开更多
基金supported by the National Natural Science Foundation of China (No.12271261)the National Undergraduate Training Program for Innovation and Entrepreneurship (No.202310300044Z)。
文摘In this paper,we establish a delayed predator-prey model with nonlocal fear effect.Firstly,the existence,uniqueness,and persistence of solutions of the model are studied.Then,the local stability,Turing bifurcation,and Hopf bifurcation of the constant equilibrium state are analyzed by examining the characteristic equation.The global asymptotic stability of the positive equilibrium point is investigated using the Lyapunov function method.Finally,the correctness of the theoretical analysis results is verified through numerical simulations.
基金Supported by National Defense Basement Research Foundation Under Grant No. 10106-04030104.
文摘Through analyzing the roll model of the integrated system of fin and anti-rolling tank, this paper uses binomial equation to simplify the module and check how the approximate parameters simulate the original function. Based on the simplified module, the influence of fin and anti-rolling tank on the coefficient items of the roll module is discussed, and the influencing factors between fin and anti-rolling tank are analysed. And through simulation, the influence of action between fin and anti-rolling tank on the static characteristics, and the integrated stabilization effect, are analyzed.
文摘Objective To investigate the preventive effect of probiotics on pediatric food allergy. Methods From MEDLINE bibliographical database, we searched and reviewed all randomized controlled trials on the preventive effects of probiotics on pediatric food allergies up to September 2013 and excluded the studies that do not meet inclusion criteria and extracted the data. Meta-analysis for the results of homogenous studies was performed using RevMan 5.0 and the co-effect was pooled by using fixed-effects model of relative risk(RR) ratios. Results Ten trials published between 2007 and 2012 including 2701 cases were included. Meta-analysis based on included data showed that the preventive effect of prenatal and postnatal probiotic supplementation on food allergies was not significant with the RR=0.88(95% CI: 0.76-1.03). Conclusion Present evidences cannot show in unequivocal terms that prenatal and postnatal probiotic supplementation will prevent food allergic diseases.
基金Projects 2008ZX05009-004 supported by the National Key Sci-Tech Major Special Item2006CB705805 by the National Basic Research Program of Chinasupported by the National Basic Research Program of China and "enhanced oil recovery basic theory for low permeability reservoirs" under grant 2002CCA00700
文摘In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on permeability and porosity.The time lag effect of rock deformation illustrating the relationship between changes in permeability and steady time was studied.Permeability reduction ratios were measured under different stress loading rates which were achieved by different pump rate settings.The results show that permeability and porosity gradually decrease with increases in effective pressure.Permeability at high effective pressure attains stability quickly.Steady times at low effective pressure are very long.Reduction in permeability at lower stress loading rates is small,while,in contrast,it is large at high stress loading rates.
文摘Background Low responsiveness to clopidogrel （LRC） is associated with increased risk of ischemic events. This study was aimed to explore the feasibility of tailored antiplatelet therapy according to the responsiveness to clopidogrel. Methods A total of 305 clopidogrel naive patients with acute coronary syndromes （ACS） undergoing coronary stenting were randomly assigned to receive standard （n = 151） or tailored （n = 154） antiplatelet therapy. The ADP-induced platelet aggregation tests by light transmission aggregometry were performed to identify LRC patients assigned to the tailored group. The standard antiplatelet regimen was dual antiplatelet therapy with aspirin and clopidogrel. The tailored antiplatelet therapy was standard regimen for non-LRC patients and an additional 6-month cilostazol treatment for LRC patients. The primary efficacy outcome was the composite of cardiovascular death, myocardial infarction or stroke at one year. Results LCR was present in 26.6% （41/154） of patients in the tailored group. The percentage platelet aggregation for LCR patients was significantly decreased at three days after adjunctive cilostazol treatment （77.5% ± 12.1% vs. 64.5% ± 12.1%, P 〈 0.001）. At one year follow-up, a non-significant 37% relative risk reduction of primary events were observed in the tailored group as compared to the standard group （5.8% vs. 9.3%, P = 0.257）. There were no differences in the rates of stent thrombosis and hemorrhagic events between the two groups. Conclusions Tailored antiplatelet therapy for ACS patients after coronary stenting according to responsiveness to clopidogrel is feasible. However, its efficacy and safety need further confirmation by clinical trials with larger sample sizes.
文摘Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.
文摘Objective To evaluate the clinical efficacy of incising spinal pia mater to relieve pressure and unilateral open-door laminoplasty with internal screw fixation for treatment of the dated spinal cord injury. Methods From March, 2009 to July, 2010, 16 cases with chronic cervical cord injury underwent spinal dura mater incision and unilateral open-door laminoplasty with internal screw fixation. Nerve functions of preand postoperation were evaluated by Frankel classification and the Japanese Orthopaedic Association (JOA) scale. The improvement rate of JOA score at the indicated time was recorded. Results Postoperative Frankel classification rating of 16 patients improved obviously. JOA scores at the 1st month, 3rd month, 6th month, and 12th month after surgery were 7.9±2.3, 8.5±1.6, 8.9±2.1, and 12.4±2.5, respectively, and significantly increased compared with that prior to surgery (5.5±0.6). At the end of follow-up period, JOA score was significantly higher than that of pre-treatment (P<0.05). The recovery was relatively rapid during the first 3 months following the surgery, then entered a platform period. Conclusion It is effective for patients with dated spinal cord injury to undergo spinal decompression and laminoplasty.
文摘Objective． An internal fixation apparatus—— distraction reduction fixation system(DRFS) was designed to satisfy the clinical needs for spondylolisthesis. Methods. Since 1996, 53 patients were treated with DRFS. Among them, 35 had spondylolisthesis, 12 had lumbar canal stenosis accompanied with instability, 2 had vertebral tumors and 4 suffered from spinal fracture. The average age was 53.6 years old (ranged 24～ 72yrs). The mean time for follow- up was 30.6 months (16～ 44 months). Results． The slip rate was 0.15± 0.10 before operation, and decreased to 0.09± 0.07 after operation. Entire slip reposition was achieved in 19 cases (54.3％ ). The change in height of the intervertebral space within the fixation segments was 0.7± 0.17. Conclusion． DRFS achieved better results for spondylolisthesis less II degree and no other adverse effects were found. Compared with other foreign and domestic techniques, it had advantages in less implants, less operation gears required and ease to utilize in operation. It was proved to be an ideal internal fixation apparatus.
基金Supported by the National Natural Science Foundation of China （50809019）.
文摘The stress combination method for the fatigue assessment of the hatch comer of a bulk carrier was investigated based on equivalent waves. The principles of the equivalent waves of ship structures were given, including the determination of the dominant load parameter, heading, frequency, and amplitude of the equivalent regular waves. The dominant load parameters of the hatch comer of a bulk carrier were identified by the structural stress response analysis, and then a series of equivalent regular waves were defined based on these parameters. A combination method of the structural stress ranges under the different equivalent waves was developed for the fatigue analysis. The combination factors were obtained by least square regression analysis with the stress ranges derived from spectral fatigue analysis as the target value. The proposed method was applied to the hatch comer of another bulk carrier as an example. This shows that the results from the equivalent wave approach agree well with those from the spectral fatigue analysis. The workload is reduced substantially. This method can be referenced in the fatigue assessment of the hatch comer of a bulk carrier.
基金Supported by the Fundamental Research Program of CSTIND under Grant No.GF2007004Harbin Engineering University Central Foundation under Grant No.HEUCF100718
文摘Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating efficiency, performance, safety, and habitability of a vessel and its subsystems. In the following research, the life cycle of vessels was divided into 9 phases, and 15 research subjects were also identified from among these phases. The 15 subjects were systemized, and then the man-machine-environment engineering system application model for vessels was developed using the ICAM definition method 0 (IDEF0), which is a systematical modeling method. This system model bridges the gap between the data and information flow of every two associated subjects with the major basic research methods and approaches included, which brings the formerly relatively independent subjects together as a whole. The application of this systematic model should facilitate the application of man-machine-environment system engineering in vessels, especially at the conceptual and embodiment design phases. The managers and designers can deal with detailed tasks quickly and efficiently while reducing repetitive work.
基金financial support from the National Basic Research Program of China (No.2005CB221500)the National Natural Science Foundation of China (Nos.50534049,50674087 and 50974107)the Natural Science Foundation of Jiangsu Province (No.BK2007029)
文摘In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and then established the flow rules after failure. The condition under which states of deformation convert is presented and the manner in which these convert is proposed. In the end, the process of gas outbursts is explained in detail. It shows that a gas outburst is a process in which the boundaries of coal seams are variable because of coal failure. If the fractures are not connected or even closed owing to coal/rock stress, fractured zones will retain a certain level of carrying capacity because of the self-sealing gas pressure. When the accumulation of gas energy reaches its limit, coal seams will become unstable and gas outbursts take place.
基金Foundation item： Supported by the Natural Science Foundation of China（10871216） Supported by the Natural Science Foundation Project of CQ CSTC（2008BB0346, 2007BB0441） Supported by the Excellent Young Teachers Program of Chongqing Jiaotong University（EYT08-016） Acknowledgement The author would like to thank the anonymous referee for the valuable remarks that helped considerably to correct and to improve the presentation.
文摘In locally convex Hausdorff topological vector spaces,ε-strongly efficient solutions for vector optimization with set-valued maps are discussed.Firstly,ε-strongly efficient point of set is introduced.Secondly,under the nearly cone-subconvexlike set-valued maps,the theorem of scalarization for vector optimization is obtained.Finally,optimality conditions of ε-strongly efficient solutions for vector optimization with generalized inequality constraints and equality constraints are obtained.
基金Supported by the National Natural Science Foundation of China under Grant No.50921001973 Program under Grant No. 2010CB83270
文摘Prandtl’s lifting line theory was generalized to the lifting problem of a three-dimensional hydrofoil in the presence of a free surface. Similar to the classical lifting theory, the singularity distribution method was utilized to solve two-dimensional lifting problems for the hydrofoil beneath the free surface at the air-water interface, and a lifting line theory was developed to correct three-dimensional effects of the hydrofoil with a large aspect ratio. Differing from the classical lifting theory, the main focus was on finding the three-dimensional Green function of the free surface induced by the steady motion of a system of horseshoe vortices under the free surface. Finally, numerical examples were given to show the relationship between the lift coefficient and submergence Froude numbers for 2-D and 3-D hydrofoils. If the submergence Froude number is small free surface effect will be significant registered as the increase of lift coefficient. The validity of these approaches was examined in comparison with the results calculated by other methods.
基金the High-Tech Research and Development Program of China，the National Seience Foundation for Young Scientists of China，the China Postdoctoral Science Foundation funded project
文摘We propose a method to improve positioning accuracy while reducing energy consumption in an indoor Wireless Local Area Network(WLAN) environment.First,we intelligently and jointly select the subset of Access Points(APs) used in positioning via Maximum Mutual Information(MMI) criterion.Second,we propose Orthogonal Locality Preserving Projection(OLPP) to reduce the redundancy among selected APs.OLPP effectively extracts the intrinsic location features in situations where previous linear signal projection techniques failed to do,while maintaining computational efficiency.Third,we show that the combination of AP selection and OLPP simultaneously exploits their complementary advantages while avoiding the drawbacks.Experimental results indicate that,compared with the widely used weighted K-nearest neighbor and maximum likelihood estimation method,the proposed method leads to 21.8%(0.49 m) positioning accuracy improvement,while decreasing the computation cost by 65.4%.
基金Funded by National Social Sciences Fund for Young Scholar ( No.020JY027)
文摘This paper presents an optimal production model for manufacturer in a supply chain with a fixed demand at a fixed interval with respect to the learning effect on production capacity. An algorithm is employed to find the optimal delay time for production and production time sequentially. It is found that the optimal delay time for production and the production time are not static, but dynamic and variant with time. It is important for a manufacturer to schedule the production so as to prevent facilities and workers from idling.
基金financial support from National Basic Research Program of China (No.2013CB227903)the National Natural Science Foundation of General Program of China (No.51574244)the Joint Funds of the National Natural Science Foundation of China (No.U1361209) are greatly appreciated
文摘The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.
基金supported by two Programs of National Natural Science Foundation of China(No.61271203 and No.61531004)
文摘Shannon channel capacity theorem poses highest bit-rate of error free transmission over additive white Gaussian noise channel.In addition,he proved that there exists channel code that can theoretically achieve the channel capacity.Indeed fortunately,the latter researchers found some practical channel codes approaching the channel capacity with insignificant losses of spectral efficiency under ignorable bit error rate(BER).The authors note,in general,that bits of the channel codes are not independent of each other in code space.Further,we note that the modulated symbols are not independent among them,as well,in Euclidean Space.By exploiting a usage of the dependencies jointly to signal design,we can transmit two independent signal streams through an additive white Gaussian channel and separate them in Euclidean space at the receiver.The capacity of this approach is found larger than that of Shannon capacity in the same channel assumptions.The numerical results confirm the theoretical procedures.
基金The School of Mining Engineering,University of the Witwatersrand South Africa is acknowledged for providing support towards the success of this researchSpecifically the Centennial Trust Fund for Rock Engineering is appreciated for funding part of this research
文摘This work studied the effect of increasing degree of metamorphism on the properties of rocks.The properties investigated are the physical,mechanical and dynamic parameters.They are important inputs in the design of many mining and civil engineering techniques such as in tunnelling,slope stability and dynamic activities associated with seismicity and fragmentation.This work compared the degree of metamorphism examined through petrographic studies of the Transvaal Sequence in South Africa with the properties of the rocks.The study shows that as the effect metamorphism increases,the state of stress,compaction of grains,cementation and the brittleness of the rocks increases.In addition,increase in the metamorphic effect increases the value of the rock property.The degree of metamorphism of an outcrop is the key factor influencing its property value.Therefore the metamorphism effect of an outcrop may act as a guide to its engineering properties.
