This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass ...This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.展开更多
Objective To analyze the problems of China’s pharmacovigilance organization system,and to provide targeted suggestions for improving it.Methods The relevant literature at home and abroad was reviewed to compared the ...Objective To analyze the problems of China’s pharmacovigilance organization system,and to provide targeted suggestions for improving it.Methods The relevant literature at home and abroad was reviewed to compared the differences in pharmacovigilance organizations in the United States,the European Union,Japan and China.Then,the problems of China’s pharmacovigilance organization management were found out.Results and Conclusion China’s pharmacovigilance organizational system has problems such as inadequate organizational setup,immature institutional construction,no coordination mechanism for pharmacovigilance practice,and industry associations of third-party organizations having no role to play.It is recommended to carry out theoretical and methodological research on the pharmacovigilance organizational system to provide practical guidance for optimizing the system with Chinese characteristics.展开更多
Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the...Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the-fly unsteady adjoint-based aerodynamic and aeroacoustic optimization methodology is developed,which maintains the fidelity of the Navier-Stokes solution for unsteady flow and of the moving-medium Ffowcs Williams-Hawkings(FW-H)formulation for capturing tonal noise.Furthermore,this on-the-fly approach enables a unified architecture for discreteadjoint sensitivity analysis encompassing both aerodynamics and aeroacoustics,facilitating effective multi-objective weighted optimizations.Subsequently,this proposed methodology is applied to perform trade-off optimizations between aerodynamics and aeroacoustics for a propeller by employing varying weighting factors to comprehend their influence on optimal configurations.The results demonstrate a positive correlation between efficiency and noise sensitivities,and thus indicate an inherent synchronicity where pursing noise reduction through purely aeroacoustic optimization inevitably entails sacrificing aerodynamic efficiency.However,by effectively incorporating appropriate weighting factors(recommended to range from 0.25 to 0.5)into the multi-objective function combined with both aerodynamics and aeroacoustics,it becomes feasible to achieve efficiency enhancement and noise reduction simultaneously.Key findings show that reducing blade planform size and equipping“rotated-S”shaped airfoil profiles in the tip region can effectively restrain noise levels while maintaining aerodynamic performance.展开更多
Objective To analyze the problems of China’s pharmacovigilance legislation,and to provide some suggestions for improving it.Methods Relevant literature at home and abroad were studied to compare the laws and regulati...Objective To analyze the problems of China’s pharmacovigilance legislation,and to provide some suggestions for improving it.Methods Relevant literature at home and abroad were studied to compare the laws and regulations of the United States,the European Union,Japan and China.Then,the problems of China’s pharmacovigilance legislation were analyzed.Results and Conclusion The Chinese pharmacovigilance legislation has such problems as nontransparent formulation process,poor dynamic adaptability,insufficient use of the attention mechanism,fragmentation of laws and regulations,and poor connection of laws and regulations,which should be optimized.It is recommended to carry out theoretical and methodological research on pharmacovigilance legislation to provide practical guidance for optimizing pharmacovigilance legislation with Chinese characteristics.展开更多
Simultaneously,reducing an acoustic metamaterial’s weight and sound pressure level is an important but difficult topic.Considering the law of mass,traditional lightweight acoustic metamaterials make it difficult to c...Simultaneously,reducing an acoustic metamaterial’s weight and sound pressure level is an important but difficult topic.Considering the law of mass,traditional lightweight acoustic metamaterials make it difficult to control noise efficiently in real-life applications.In this study,a novel optimization-driven design scheme is developed to obtain lightweight acoustic metamaterials with a strong sound insulation capability for additive manufacturing.In the proposed design scheme,a topology optimization method for an acoustic metamaterial in the acoustic-solid interaction system is implemented to obtain an initial cross-sectional topology of the acoustic microstructure during the conceptual design phase.Then,in the detailed design phase,the parametric model for a higher-dimensional design is formulated based on the topology optimization result.An adaptive Kriging interpolation approach is proposed to accurately reformulate a much easier surrogate model from the original parameterization formulation to avoid repeating calls for nonlinear analyses in the 3D acoustic-structure interaction system.A surrogate model was used to optimize a ready-to-print acoustic metamaterial with improved noise reduction performance.Experimental verification based on an impedance tube is implemented.Results demonstrate characteristics of the devised metamaterial as well as the proposed method.展开更多
In this paper,an adaptive cubic regularisation algorithm based on affine scaling methods(ARCBASM)is proposed for solving nonlinear equality constrained programming with nonnegative constraints on variables.From the op...In this paper,an adaptive cubic regularisation algorithm based on affine scaling methods(ARCBASM)is proposed for solving nonlinear equality constrained programming with nonnegative constraints on variables.From the optimality conditions of the problem,we introduce appropriate affine matrix and construct an affine scaling ARC subproblem with linearized constraints.Composite step methods and reduced Hessian methods are applied to tackle the linearized constraints.As a result,a standard unconstrained ARC subproblem is deduced and its solution can supply sufficient decrease.The fraction to the boundary rule maintains the strict feasibility(for nonnegative constraints on variables)of every iteration point.Reflection techniques are employed to prevent the iterations from approaching zero too early.Under mild assumptions,global convergence of the algorithm is analysed.Preliminary numerical results are reported.展开更多
The numerical dispersion phenomenon in the finite-difference forward modeling simulations of the wave equation significantly affects the imaging accuracy in acoustic reflection logging.This issue is particularly prono...The numerical dispersion phenomenon in the finite-difference forward modeling simulations of the wave equation significantly affects the imaging accuracy in acoustic reflection logging.This issue is particularly pronounced in the reverse time migration(RTM)method used for shear-wave(S-wave)logging imaging.This not only affects imaging accuracy but also introduces ambiguities in the interpretation of logging results.To address this challenge,this study proposes the use of a least-squares difference coefficient optimization algorithm aiming to suppress the numerical dispersion phenomenon in the RTM of S-wave reflection imaging logging.By optimizing the difference coefficients,the high-precision finite-difference algorithm serves as an effective operator for both forward and backward RTM processes.This approach is instrumental in eliminating migration illusions,which are often caused by numerical dispersion.The effectiveness of this optimized algorithm is demonstrated through numerical results,which indicate that it can achieve more accurate forward imaging results across various conditions,including high-and low-velocity strata,and is effective in both large and small spatial grids.The results of processing real data demonstrate that numerical dispersion optimization effectively reduces migration artifacts and diminishes ambiguities in logging interpretations.This optimization offers crucial technical support to the RTM method,enhancing its capability for accurately modeling and imaging S-wave reflections.展开更多
An ant colony optimization （ACO）-simulated annealing （SA）-based algorithm is developed for the target assignment problem （TAP） in the air defense （AD） command and control （C2） system of surface to air missi...An ant colony optimization （ACO）-simulated annealing （SA）-based algorithm is developed for the target assignment problem （TAP） in the air defense （AD） command and control （C2） system of surface to air missile （SAM） tactical unit. The accomplishment process of target assignment （TA） task is analyzed. A firing advantage degree （FAD） concept of fire unit （FU） intercepting targets is put forward and its evaluation model is established by using a linear weighted synthetic method. A TA optimization model is presented and its solving algorithms are designed respectively based on ACO and SA. A hybrid optimization strategy is presented and developed synthesizing the merits of ACO and SA. The simulation examples show that the model and algorithms can meet the solving requirement of TAP in AD combat.展开更多
Rotor noise is one of the most important reasons for restricting helicopter development;hence,the optimization design of rotor blade considering aeroacoustic and aerodynamic performance at the same time has always bee...Rotor noise is one of the most important reasons for restricting helicopter development;hence,the optimization design of rotor blade considering aeroacoustic and aerodynamic performance at the same time has always been the focus of research attention.For complex rotor design problems with a large number of design variables,the efficiency of the traditional Kriging model needs to be improved.Thus,Hierarchical Kriging(HK)model is employed in this study for rotor optimization design.By using the validated RANS solver and acoustic method based on the FWHpds equation,an efficient aerodynamic/aeroacoustic optimization method for high-dimensional problem of rotors in hover based on HK model is developed.By using present HK model and new infill-sampling criteria,the number of design variables is increased from less than 20-53.Results of two analytical function test cases show that the HK model is efficient and accurate in calculation.Subsequently,the helicopter rotor blade is optimally designed for aerodynamic/aeroacoustic performance in hover based on the HK model with high dimensional design variables.The objective function is adopted to improve the rotational noise characteristics by reducing the absolute peak of the acoustic pressure.In addition,the constraints of thrust,hover efficiency,solidity,and airfoils thickness are strictly satisfied.Optimization results show that the Kriging model finds the objective of reducing the noise by 2.87 dB after 248 iterations while the HK model does it only after 164 iterations.The optimization efficiency of the HK model is significantly higher than that of the traditional Kriging model.In the case analyzed,the HK model saves 35%of the time used by the Kriging model.展开更多
With the exploration of the ocean, underwater acoustic communication has attracted more and more attention in recent years. The underwater acoustic channel is considered to be one of the most complicated channels beca...With the exploration of the ocean, underwater acoustic communication has attracted more and more attention in recent years. The underwater acoustic channel is considered to be one of the most complicated channels because it suffers from more serious multipath effect, fewer available bandwidths and quite complex noise. Since the signals experience a serious distortion after being transmitted through the underwater acoustic channel, the underwater acoustic communication experiences a high bit error rate （BER）. To solve this problem, carrier waveform inter- displacement （CWlD） modulation is proposed. It has been proved that CWlD modulation is an effective method to decrease BER. The linear frequency modulation （LFM） carrier-waves are used in CWlD modulation. The performance of the communication using CWID modulation is sensitive to the change of the frequency band of LFM carrier-waves. The immune particle swarm optimization （IPSO） is introduced to search for the optimal frequency band of the LFM carrier-waves, due to its excellent performance in solving complicated optimization problems. The multi-objective and multi- peak optimization nature of the IPSO gives a suitable description of the relationship between the upper band and the lower band of the LFM carrier-waves. Simulations verify the improved perfor- mance and effectiveness of the optimization method.展开更多
Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise ...Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise reduction. Based upon the mode analysis method of sound propagation in a circular duct with multiple liners, a flexible tolerance method is used to optimize the acoustic parameters(impedance), geometric structure parameters(such as open area ratio, cavity depth and hole diameter) and operating condition parameters(such as blade passing frequency). The mathematical models for these kinds of optimization are presented here. The optimum values of the design variables are determined when the in-duct sound suppression approaches a maximum. It can be derived from the optimum results that the emphasis of the engineering optimization design of the perforated plate honey-comb structure should be placed on the optimum choice of the open area ratio and cavity depth. Some reference criteria for the engineering design of the multi-linings are also provided.展开更多
In this paper,a design method for an acoustic cloak in the presence of background mean flows is proposed by using topology optimization,which enables the associated fabrication of the cloaking design.The density-based...In this paper,a design method for an acoustic cloak in the presence of background mean flows is proposed by using topology optimization,which enables the associated fabrication of the cloaking design.The density-based topology optimization method is used to allocate the designated materials,thus providing the structure of the cloak.The optimization problem is efficiently solved with the gradient-based globally convergent method of moving asymptotes,which utilizes the derivative information from the finite element simulation studies of the linearized acoustic potential equation.This paper introduces the whole design method first then numerically demonstrates the corresponding performance,which shall constitute the main contribution of the present work.展开更多
The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution s...The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution spatial differential method for large eddy simulation(LES),which can guarantee accuracy and efficiency.The aeroacoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings(FW-H)integration formula.Fidelity of calculation is verified by standard models.Method of streamline-based Euler simulation(MSES)is used to obtain the aerodynamic characters.Based on the confirmation of numerical methods,detailed research has been conducted for the leading edge slat on multi-element airfoils.Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.展开更多
Reducing the operation and maintenance (O & M) cost is one of the potential actions that could reduce the cost of energy produced by offshore wind farms. This article attempts to reduce O & M cost by improving...Reducing the operation and maintenance (O & M) cost is one of the potential actions that could reduce the cost of energy produced by offshore wind farms. This article attempts to reduce O & M cost by improving the utilization of the maintenance resources, specifically the efficient scheduling and routing of the maintenance fleet. Scheduling and routing of maintenance fleet is a non-linear optimization problem with high complexity and a number of constraints. A heuristic algorithm, Ant Colony Optimization (ACO), was modified as Multi-ACO to be used to find the optimal scheduling and routing of maintenance fleet. The numerical studies showed that the proposed methodology was effective and robust enough to find the optimal solution even if the number of offshore wind turbine increases. The suggested approaches are helpful to avoid a time-consuming process of manually planning the scheduling and routing with a presumably suboptimal outcome.展开更多
A model of quantum thermoacoustic refrigeration micro-cycle(QTARMC)is established in which heat leakage is considered.A single particle contained in a one-dimensional harmonic potential well is studied,and the system ...A model of quantum thermoacoustic refrigeration micro-cycle(QTARMC)is established in which heat leakage is considered.A single particle contained in a one-dimensional harmonic potential well is studied,and the system consists of countless replicas.Each particle is confined in its own potential well,whose occupation probabilities can be expressed by the thermal equilibrium Gibbs distributions.Based on the Schrodinger equation,the expressions of coefficient of performance(COP)and cooling rate for the refrigerator are obtained.Effects of heat leakage on the optimal performance are discussed.The optimal performance region of the refrigeration cycle is obtained by the using ofΩobjective function.The results obtained can enrich the thermoacoustic theory and expand the application of quantum thermodynamics.展开更多
An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling envir...An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling environments with high temperature and pressure, as well as strong collar drilling vibration during the drilling process. Aimed to improve the transmitting performance, numerical and experimental studies for the transducer optimization are conducted. The impact of location and length of the piezoelectric stack on resonance characteristics arid effective electromeehanical coupling coefficient is calculated and analyzed. Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments, and the results are compared with simulated ones. It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies. This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging, especially in acoustic logging while drilling.展开更多
[ Objective] This study aimed to establish an optimized suspension culture for hairy roots of Aconitum coreanum （Levi.） Raipaics. [ Method ] Hairy root of Aconitum coreanum （ Levl. ） Raipaics A0489 was selected as...[ Objective] This study aimed to establish an optimized suspension culture for hairy roots of Aconitum coreanum （Levi.） Raipaics. [ Method ] Hairy root of Aconitum coreanum （ Levl. ） Raipaics A0489 was selected as experimental material, to screen the optimal medium for suspension culture. [ Result] Aconitum coreanum （Levl.） Raipaics hairy roots showed different growth conditions in various liquid medium; salt concentration, nitrogen content, sugar content, rotation speed and room temperature had great influences on the growth of Aconitum coreanum （Levi.） Raipaics hairy roots. [ Conclusion] The optimal suspension culture system for Aconitum coreanum （ Levi. ） Raipaics hairy roots was established ： B5 was used as basic medium, culture temperature was 20℃ under dark conditions, rotation speed was 140 r/m in the first 15 d and 110 r/m in the latter 15 d.展开更多
文摘This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.
文摘Objective To analyze the problems of China’s pharmacovigilance organization system,and to provide targeted suggestions for improving it.Methods The relevant literature at home and abroad was reviewed to compared the differences in pharmacovigilance organizations in the United States,the European Union,Japan and China.Then,the problems of China’s pharmacovigilance organization management were found out.Results and Conclusion China’s pharmacovigilance organizational system has problems such as inadequate organizational setup,immature institutional construction,no coordination mechanism for pharmacovigilance practice,and industry associations of third-party organizations having no role to play.It is recommended to carry out theoretical and methodological research on the pharmacovigilance organizational system to provide practical guidance for optimizing the system with Chinese characteristics.
基金supported by the National Science and Technology Major Project,China(No.Y2019-I-0018-0017)the National Natural Science Foundation of China(No.11602200)+1 种基金Hunan Innovative Province Construction Special Fund,China(No.2021GK1020)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘Propeller design is a highly intricate and interdisciplinary task that necessitates careful trade-offs between radiated noise levels and aerodynamic efficiency.To achieve efficient trade-off designs,an enhanced on-the-fly unsteady adjoint-based aerodynamic and aeroacoustic optimization methodology is developed,which maintains the fidelity of the Navier-Stokes solution for unsteady flow and of the moving-medium Ffowcs Williams-Hawkings(FW-H)formulation for capturing tonal noise.Furthermore,this on-the-fly approach enables a unified architecture for discreteadjoint sensitivity analysis encompassing both aerodynamics and aeroacoustics,facilitating effective multi-objective weighted optimizations.Subsequently,this proposed methodology is applied to perform trade-off optimizations between aerodynamics and aeroacoustics for a propeller by employing varying weighting factors to comprehend their influence on optimal configurations.The results demonstrate a positive correlation between efficiency and noise sensitivities,and thus indicate an inherent synchronicity where pursing noise reduction through purely aeroacoustic optimization inevitably entails sacrificing aerodynamic efficiency.However,by effectively incorporating appropriate weighting factors(recommended to range from 0.25 to 0.5)into the multi-objective function combined with both aerodynamics and aeroacoustics,it becomes feasible to achieve efficiency enhancement and noise reduction simultaneously.Key findings show that reducing blade planform size and equipping“rotated-S”shaped airfoil profiles in the tip region can effectively restrain noise levels while maintaining aerodynamic performance.
文摘Objective To analyze the problems of China’s pharmacovigilance legislation,and to provide some suggestions for improving it.Methods Relevant literature at home and abroad were studied to compare the laws and regulations of the United States,the European Union,Japan and China.Then,the problems of China’s pharmacovigilance legislation were analyzed.Results and Conclusion The Chinese pharmacovigilance legislation has such problems as nontransparent formulation process,poor dynamic adaptability,insufficient use of the attention mechanism,fragmentation of laws and regulations,and poor connection of laws and regulations,which should be optimized.It is recommended to carry out theoretical and methodological research on pharmacovigilance legislation to provide practical guidance for optimizing pharmacovigilance legislation with Chinese characteristics.
基金supported by the National Key Research and Development Program of China(No.2023YFB4604800)the National Natural Science Foundation of China(No.52075195)the Inelligent Manufacturing Equipment and Technology Open Foundation(No.IMETKF2023016).
文摘Simultaneously,reducing an acoustic metamaterial’s weight and sound pressure level is an important but difficult topic.Considering the law of mass,traditional lightweight acoustic metamaterials make it difficult to control noise efficiently in real-life applications.In this study,a novel optimization-driven design scheme is developed to obtain lightweight acoustic metamaterials with a strong sound insulation capability for additive manufacturing.In the proposed design scheme,a topology optimization method for an acoustic metamaterial in the acoustic-solid interaction system is implemented to obtain an initial cross-sectional topology of the acoustic microstructure during the conceptual design phase.Then,in the detailed design phase,the parametric model for a higher-dimensional design is formulated based on the topology optimization result.An adaptive Kriging interpolation approach is proposed to accurately reformulate a much easier surrogate model from the original parameterization formulation to avoid repeating calls for nonlinear analyses in the 3D acoustic-structure interaction system.A surrogate model was used to optimize a ready-to-print acoustic metamaterial with improved noise reduction performance.Experimental verification based on an impedance tube is implemented.Results demonstrate characteristics of the devised metamaterial as well as the proposed method.
基金Supported by the National Natural Science Foundation of China(12071133)Natural Science Foundation of Henan Province(252300421993)Key Scientific Research Project of Higher Education Institutions in Henan Province(25B110005)。
文摘In this paper,an adaptive cubic regularisation algorithm based on affine scaling methods(ARCBASM)is proposed for solving nonlinear equality constrained programming with nonnegative constraints on variables.From the optimality conditions of the problem,we introduce appropriate affine matrix and construct an affine scaling ARC subproblem with linearized constraints.Composite step methods and reduced Hessian methods are applied to tackle the linearized constraints.As a result,a standard unconstrained ARC subproblem is deduced and its solution can supply sufficient decrease.The fraction to the boundary rule maintains the strict feasibility(for nonnegative constraints on variables)of every iteration point.Reflection techniques are employed to prevent the iterations from approaching zero too early.Under mild assumptions,global convergence of the algorithm is analysed.Preliminary numerical results are reported.
基金supported by Scientific Research and Technology Development Project of CNPC(2021DJ4002,2022DJ3908).
文摘The numerical dispersion phenomenon in the finite-difference forward modeling simulations of the wave equation significantly affects the imaging accuracy in acoustic reflection logging.This issue is particularly pronounced in the reverse time migration(RTM)method used for shear-wave(S-wave)logging imaging.This not only affects imaging accuracy but also introduces ambiguities in the interpretation of logging results.To address this challenge,this study proposes the use of a least-squares difference coefficient optimization algorithm aiming to suppress the numerical dispersion phenomenon in the RTM of S-wave reflection imaging logging.By optimizing the difference coefficients,the high-precision finite-difference algorithm serves as an effective operator for both forward and backward RTM processes.This approach is instrumental in eliminating migration illusions,which are often caused by numerical dispersion.The effectiveness of this optimized algorithm is demonstrated through numerical results,which indicate that it can achieve more accurate forward imaging results across various conditions,including high-and low-velocity strata,and is effective in both large and small spatial grids.The results of processing real data demonstrate that numerical dispersion optimization effectively reduces migration artifacts and diminishes ambiguities in logging interpretations.This optimization offers crucial technical support to the RTM method,enhancing its capability for accurately modeling and imaging S-wave reflections.
基金supported by the National Aviation Science Foundation of China(20090196002)
文摘An ant colony optimization （ACO）-simulated annealing （SA）-based algorithm is developed for the target assignment problem （TAP） in the air defense （AD） command and control （C2） system of surface to air missile （SAM） tactical unit. The accomplishment process of target assignment （TA） task is analyzed. A firing advantage degree （FAD） concept of fire unit （FU） intercepting targets is put forward and its evaluation model is established by using a linear weighted synthetic method. A TA optimization model is presented and its solving algorithms are designed respectively based on ACO and SA. A hybrid optimization strategy is presented and developed synthesizing the merits of ACO and SA. The simulation examples show that the model and algorithms can meet the solving requirement of TAP in AD combat.
基金sponsored by the National Natural Science Foundation of China(Nos:11772261,11972305)"111"Project of China(No.:B17037).
文摘Rotor noise is one of the most important reasons for restricting helicopter development;hence,the optimization design of rotor blade considering aeroacoustic and aerodynamic performance at the same time has always been the focus of research attention.For complex rotor design problems with a large number of design variables,the efficiency of the traditional Kriging model needs to be improved.Thus,Hierarchical Kriging(HK)model is employed in this study for rotor optimization design.By using the validated RANS solver and acoustic method based on the FWHpds equation,an efficient aerodynamic/aeroacoustic optimization method for high-dimensional problem of rotors in hover based on HK model is developed.By using present HK model and new infill-sampling criteria,the number of design variables is increased from less than 20-53.Results of two analytical function test cases show that the HK model is efficient and accurate in calculation.Subsequently,the helicopter rotor blade is optimally designed for aerodynamic/aeroacoustic performance in hover based on the HK model with high dimensional design variables.The objective function is adopted to improve the rotational noise characteristics by reducing the absolute peak of the acoustic pressure.In addition,the constraints of thrust,hover efficiency,solidity,and airfoils thickness are strictly satisfied.Optimization results show that the Kriging model finds the objective of reducing the noise by 2.87 dB after 248 iterations while the HK model does it only after 164 iterations.The optimization efficiency of the HK model is significantly higher than that of the traditional Kriging model.In the case analyzed,the HK model saves 35%of the time used by the Kriging model.
基金supported by the National Natural Science Foundation of China(61172070,61111130122)the Innovative Research Team of Shaanxi Province(2013KCT-04)the Specialized Research Fund for the Doctoral Program of Higher Education(20126118110008)
文摘With the exploration of the ocean, underwater acoustic communication has attracted more and more attention in recent years. The underwater acoustic channel is considered to be one of the most complicated channels because it suffers from more serious multipath effect, fewer available bandwidths and quite complex noise. Since the signals experience a serious distortion after being transmitted through the underwater acoustic channel, the underwater acoustic communication experiences a high bit error rate （BER）. To solve this problem, carrier waveform inter- displacement （CWlD） modulation is proposed. It has been proved that CWlD modulation is an effective method to decrease BER. The linear frequency modulation （LFM） carrier-waves are used in CWlD modulation. The performance of the communication using CWID modulation is sensitive to the change of the frequency band of LFM carrier-waves. The immune particle swarm optimization （IPSO） is introduced to search for the optimal frequency band of the LFM carrier-waves, due to its excellent performance in solving complicated optimization problems. The multi-objective and multi- peak optimization nature of the IPSO gives a suitable description of the relationship between the upper band and the lower band of the LFM carrier-waves. Simulations verify the improved perfor- mance and effectiveness of the optimization method.
文摘Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise reduction. Based upon the mode analysis method of sound propagation in a circular duct with multiple liners, a flexible tolerance method is used to optimize the acoustic parameters(impedance), geometric structure parameters(such as open area ratio, cavity depth and hole diameter) and operating condition parameters(such as blade passing frequency). The mathematical models for these kinds of optimization are presented here. The optimum values of the design variables are determined when the in-duct sound suppression approaches a maximum. It can be derived from the optimum results that the emphasis of the engineering optimization design of the perforated plate honey-comb structure should be placed on the optimum choice of the open area ratio and cavity depth. Some reference criteria for the engineering design of the multi-linings are also provided.
基金This work was supported by the Beijing Municipal Science&Technology Commission(Grant Z181100001018030)the National Natural Science Foundation of China(Grant 11561130148)the Newton Advanced Fellowship from the Royal Society(Ref.NA14081).
文摘In this paper,a design method for an acoustic cloak in the presence of background mean flows is proposed by using topology optimization,which enables the associated fabrication of the cloaking design.The density-based topology optimization method is used to allocate the designated materials,thus providing the structure of the cloak.The optimization problem is efficiently solved with the gradient-based globally convergent method of moving asymptotes,which utilizes the derivative information from the finite element simulation studies of the linearized acoustic potential equation.This paper introduces the whole design method first then numerically demonstrates the corresponding performance,which shall constitute the main contribution of the present work.
文摘The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution spatial differential method for large eddy simulation(LES),which can guarantee accuracy and efficiency.The aeroacoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings(FW-H)integration formula.Fidelity of calculation is verified by standard models.Method of streamline-based Euler simulation(MSES)is used to obtain the aerodynamic characters.Based on the confirmation of numerical methods,detailed research has been conducted for the leading edge slat on multi-element airfoils.Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.
文摘Reducing the operation and maintenance (O & M) cost is one of the potential actions that could reduce the cost of energy produced by offshore wind farms. This article attempts to reduce O & M cost by improving the utilization of the maintenance resources, specifically the efficient scheduling and routing of the maintenance fleet. Scheduling and routing of maintenance fleet is a non-linear optimization problem with high complexity and a number of constraints. A heuristic algorithm, Ant Colony Optimization (ACO), was modified as Multi-ACO to be used to find the optimal scheduling and routing of maintenance fleet. The numerical studies showed that the proposed methodology was effective and robust enough to find the optimal solution even if the number of offshore wind turbine increases. The suggested approaches are helpful to avoid a time-consuming process of manually planning the scheduling and routing with a presumably suboptimal outcome.
基金Project(51176143)supported by the National Natural Science Foundation of ChinaProject(K201919)supported by the Scientific Research Foundation of Wuhan Institute of TechnologyChina。
文摘A model of quantum thermoacoustic refrigeration micro-cycle(QTARMC)is established in which heat leakage is considered.A single particle contained in a one-dimensional harmonic potential well is studied,and the system consists of countless replicas.Each particle is confined in its own potential well,whose occupation probabilities can be expressed by the thermal equilibrium Gibbs distributions.Based on the Schrodinger equation,the expressions of coefficient of performance(COP)and cooling rate for the refrigerator are obtained.Effects of heat leakage on the optimal performance are discussed.The optimal performance region of the refrigeration cycle is obtained by the using ofΩobjective function.The results obtained can enrich the thermoacoustic theory and expand the application of quantum thermodynamics.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41474160 and 11304347
文摘An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling environments with high temperature and pressure, as well as strong collar drilling vibration during the drilling process. Aimed to improve the transmitting performance, numerical and experimental studies for the transducer optimization are conducted. The impact of location and length of the piezoelectric stack on resonance characteristics arid effective electromeehanical coupling coefficient is calculated and analyzed. Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments, and the results are compared with simulated ones. It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies. This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging, especially in acoustic logging while drilling.
基金Supported by Project of Applied Basic Research from the Institute of Special Wild Economic Animal and Plant Science,Chinese Academy of Agricultural Sciences(tcs2004-08)Project of Jilin Science and Technology Bureau(201222306)
文摘[ Objective] This study aimed to establish an optimized suspension culture for hairy roots of Aconitum coreanum （Levi.） Raipaics. [ Method ] Hairy root of Aconitum coreanum （ Levl. ） Raipaics A0489 was selected as experimental material, to screen the optimal medium for suspension culture. [ Result] Aconitum coreanum （Levl.） Raipaics hairy roots showed different growth conditions in various liquid medium; salt concentration, nitrogen content, sugar content, rotation speed and room temperature had great influences on the growth of Aconitum coreanum （Levi.） Raipaics hairy roots. [ Conclusion] The optimal suspension culture system for Aconitum coreanum （ Levi. ） Raipaics hairy roots was established ： B5 was used as basic medium, culture temperature was 20℃ under dark conditions, rotation speed was 140 r/m in the first 15 d and 110 r/m in the latter 15 d.
