It is difficult to determine the effective reservoir rock compressibility,aquifer volume and water influx of high pressure and ultra-high pressure gas reservoirs,so when the traditional apparent reservoir pressure and...It is difficult to determine the effective reservoir rock compressibility,aquifer volume and water influx of high pressure and ultra-high pressure gas reservoirs,so when the traditional apparent reservoir pressure and cumulative gas production curve extrapolation method and its modified version are used to calculate the initial gas in-place of such gas reservoirs,the calculation accuracy is lower.The material balance equation in the form of power function for such gas reservoirs was established based on Gonzalez method to improve the accuracy and reliability of reserve evaluation.Then,based on 20 high pressure and ultra-high pressure reservoirs that had been developed abroad,the empirical value of the power exponent was defined,and the influences of the depletion degree of apparent reservoir pressure and the degree of reserve recovery on the reliability of reserve calculation were analyzed.Besides,the critical value of the key parameter affecting the reliability of reserve evaluation(depletion degree of apparent reservoir pressure)was determined and compared with the critical value of the two-linear trends.Finally,an example calculation was carried out.And the following research results were obtained.First,the empirical value of the power exponent calculated using the material balance method in the form of power function is 1.02847,with an upper limit of 1.11567.Second,the depletion degree of apparent reservoir pressure corresponding to the inflection point of the classical two-linear trends ranges from 0.14 to 0.38 with an average of 0.23,while that corresponding to the extrapolation point of the second straight line is between 0.23 and 0.50 with an average of 0.33,and the corresponding degree of reserve recovery is in the range of 33%-65%with an average of 45%.Third,the reserves of such high pressure gas reservoirs calculated with this new method has an error rate less than 10%if the depletion degree of apparent reservoir pressure is greater than 0.33.In conclusion,for such high pressure gas reservoirs and the stress-sensitive fractured gas reservoirs,the material balance method in the form of power function proposed in this paper can avoid the uncertainty parameters(e.g.effective reservoir rock compressibility,aquifer volume and water influx)and it is advantageous with simple calculation process,better practicability and small error.展开更多
Based on the independent, continuous and map- ping （ICM） method and homogenization method, a research model is constructed to propose and deduce a theorem and corollary from the invariant between the weight filter f...Based on the independent, continuous and map- ping （ICM） method and homogenization method, a research model is constructed to propose and deduce a theorem and corollary from the invariant between the weight filter func- tion and the corresponding stiffness filter function of the form of power function. The efficiency in searching for op- timum solution will be raised via the choice of rational filter functions, so the above mentioned results are very important to the further study of structural topology optimization.展开更多
A new exact and universal conformal mapping is proposed. Using Muskhelishvili＇s complex potential method, the plane elasticity problem of power function curved cracks is investigated with an arbitrary power of a natu...A new exact and universal conformal mapping is proposed. Using Muskhelishvili＇s complex potential method, the plane elasticity problem of power function curved cracks is investigated with an arbitrary power of a natural number, and the general solutions of the stress intensity factors （SIFs） for mode I and mode II at the crack tip are obtained under the remotely uniform tensile loads. The present results can be reduced to the well-known solutions when the power of the function takes different natural numbers. Numerical examples are conducted to reveal the effects of the coefficient, the power, and the projected length along the x-axis of the power function curved crack on the SIFs for mode I and mode II.展开更多
The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real...The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real-power is used to Combined with the global properties of the noise-free system, the evolutionary process of the tran- sient PDFs is revealed. The results show that stochastic P-bifurcation occurs when the system parameter varies in the response analysis and the stationary PDF evolves from bimodal to unimodal along the unstable manifold during the bifurcation.展开更多
当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在...当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在明确基于DSP的串联式中频电源主电路拓扑结构,利用混合灵敏度方法建立中频电源控制器,选取合适的加权函数,提高中频电源的跟踪能力,消除其中不确定因素,实现鲁棒性能的提升。实验结果表明,经由所提方法控制后,串联式中频电源的输出电压波形整体较为稳定,没有发生较为突出的波动,整体电源总谐波失真值小,具有优秀的稳定性和鲁棒性。展开更多
针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信...针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信与目标探测的双功能雷达通信一体化波形设计进行了简要介绍。首先,以总功率与PAPR为约束条件,以多用户干扰(Multi-User Interference,MUI)能量与雷达波形相似度加权和为目标函数,并引入加权因子ρ动态调整通信雷达性能偏好。其次,采用标准交替方向乘子(Alternating Direction Multiplier Method,ADMM)算法,并引入增广拉格朗日函数,通过变量分裂实现优化求解。最后,对所提方法的通信误码率和雷达分辨率等性能进行了仿真。结果表明,所提方法相较于传统方法实现了动态场景下通信和速率的提升,且与恒模约束相比和速率增幅达4.5%,雷达探测概率在低信噪比时达到0.8以上,并最终趋于稳定值1。展开更多
基金Project supported by Major Special Science and Technology Project of PetroChina Company Limited“Study and application of key technologies for developing deepeultra-deep gas in Kuqa depression”(No.:2018E-1803).
文摘It is difficult to determine the effective reservoir rock compressibility,aquifer volume and water influx of high pressure and ultra-high pressure gas reservoirs,so when the traditional apparent reservoir pressure and cumulative gas production curve extrapolation method and its modified version are used to calculate the initial gas in-place of such gas reservoirs,the calculation accuracy is lower.The material balance equation in the form of power function for such gas reservoirs was established based on Gonzalez method to improve the accuracy and reliability of reserve evaluation.Then,based on 20 high pressure and ultra-high pressure reservoirs that had been developed abroad,the empirical value of the power exponent was defined,and the influences of the depletion degree of apparent reservoir pressure and the degree of reserve recovery on the reliability of reserve calculation were analyzed.Besides,the critical value of the key parameter affecting the reliability of reserve evaluation(depletion degree of apparent reservoir pressure)was determined and compared with the critical value of the two-linear trends.Finally,an example calculation was carried out.And the following research results were obtained.First,the empirical value of the power exponent calculated using the material balance method in the form of power function is 1.02847,with an upper limit of 1.11567.Second,the depletion degree of apparent reservoir pressure corresponding to the inflection point of the classical two-linear trends ranges from 0.14 to 0.38 with an average of 0.23,while that corresponding to the extrapolation point of the second straight line is between 0.23 and 0.50 with an average of 0.33,and the corresponding degree of reserve recovery is in the range of 33%-65%with an average of 45%.Third,the reserves of such high pressure gas reservoirs calculated with this new method has an error rate less than 10%if the depletion degree of apparent reservoir pressure is greater than 0.33.In conclusion,for such high pressure gas reservoirs and the stress-sensitive fractured gas reservoirs,the material balance method in the form of power function proposed in this paper can avoid the uncertainty parameters(e.g.effective reservoir rock compressibility,aquifer volume and water influx)and it is advantageous with simple calculation process,better practicability and small error.
基金supported by the National Natural Science Foundation of China(11172013)Foundation of National Key Laboratory for Structural Analysis of Industrial Equipment in Dalian University of Technology Foundations(GZ1008)
文摘Based on the independent, continuous and map- ping （ICM） method and homogenization method, a research model is constructed to propose and deduce a theorem and corollary from the invariant between the weight filter func- tion and the corresponding stiffness filter function of the form of power function. The efficiency in searching for op- timum solution will be raised via the choice of rational filter functions, so the above mentioned results are very important to the further study of structural topology optimization.
基金supported by the National Natural Science Foundation of China(Nos.10932001,11072015, and 10761005)the Scientific Research Key Program of Beijing Municipal Commission of Education (No.KZ201010005003)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20101102110016)the Ph.D.Innovation Foundation of Beijing University of Aeronautics and Astronautics(No.300351)
文摘A new exact and universal conformal mapping is proposed. Using Muskhelishvili＇s complex potential method, the plane elasticity problem of power function curved cracks is investigated with an arbitrary power of a natural number, and the general solutions of the stress intensity factors （SIFs） for mode I and mode II at the crack tip are obtained under the remotely uniform tensile loads. The present results can be reduced to the well-known solutions when the power of the function takes different natural numbers. Numerical examples are conducted to reveal the effects of the coefficient, the power, and the projected length along the x-axis of the power function curved crack on the SIFs for mode I and mode II.
基金Project supported by the National Natural Science Foundation of China(Nos.11172233,11302169,11302170,and 11472212)the Fundamental Research Funds for the Central Universities(No.3102014JCQ01079)
文摘The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real-power is used to Combined with the global properties of the noise-free system, the evolutionary process of the tran- sient PDFs is revealed. The results show that stochastic P-bifurcation occurs when the system parameter varies in the response analysis and the stationary PDF evolves from bimodal to unimodal along the unstable manifold during the bifurcation.
文摘当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在明确基于DSP的串联式中频电源主电路拓扑结构,利用混合灵敏度方法建立中频电源控制器,选取合适的加权函数,提高中频电源的跟踪能力,消除其中不确定因素,实现鲁棒性能的提升。实验结果表明,经由所提方法控制后,串联式中频电源的输出电压波形整体较为稳定,没有发生较为突出的波动,整体电源总谐波失真值小,具有优秀的稳定性和鲁棒性。
文摘针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信与目标探测的双功能雷达通信一体化波形设计进行了简要介绍。首先,以总功率与PAPR为约束条件,以多用户干扰(Multi-User Interference,MUI)能量与雷达波形相似度加权和为目标函数,并引入加权因子ρ动态调整通信雷达性能偏好。其次,采用标准交替方向乘子(Alternating Direction Multiplier Method,ADMM)算法,并引入增广拉格朗日函数,通过变量分裂实现优化求解。最后,对所提方法的通信误码率和雷达分辨率等性能进行了仿真。结果表明,所提方法相较于传统方法实现了动态场景下通信和速率的提升,且与恒模约束相比和速率增幅达4.5%,雷达探测概率在低信噪比时达到0.8以上,并最终趋于稳定值1。
