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Semi-definite programming based pulse waveform design and its further analysis
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作者 王利利 沙学军 吴宣利 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2008年第4期578-581,共4页
In order to provide a judicious pulse waveform design required for ultra-wideband(UWB)communication to enable the UWB spectral mask compatible and coexistent with other existing wireless communication systems,a semi-d... In order to provide a judicious pulse waveform design required for ultra-wideband(UWB)communication to enable the UWB spectral mask compatible and coexistent with other existing wireless communication systems,a semi-definite programming(SDP)based pulse waveform design method for UWB radios is introduced and a further analysis is given in this paper.By using Sedumi and Yalmip toolboxes of Matlab,the procedure of solving the SDP problem is simplified.Simulation results show that this SDP based pulse waveform design method can be used to design pulses that fulfill the Federal Communications Commission(FCC)spectral mask strictly and optimize the power efficiency at the same time.This paper also analyzes the influences of the power efficiency duing to the changes of sampling interval and the number of combined pulses,and then the optimal sampling interval that maximizes the transmission power can be found. 展开更多
关键词 ULTRA-WIDEBAND pulse waveform design FCC spectral mask semi-definite programming
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Programmed cell death induced by modified clay in controlling Prorocentrum donghaiense bloom 被引量:1
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作者 Hena Ji Zhiming Yu +3 位作者 Liyan He Jianan Zhu Xihua Cao Xiuxian Song 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2021年第11期123-134,共12页
Modified clay(MC),an effective material used for the emergency elimination of algal blooms,can rapidly reduce the biomass of harmful algal blooms(HABs)via flocculation.After that,MC can still control bloom population ... Modified clay(MC),an effective material used for the emergency elimination of algal blooms,can rapidly reduce the biomass of harmful algal blooms(HABs)via flocculation.After that,MC can still control bloom population through indirect effects such as oxidative stress,whichwas initially proposed to be related to programmedcell death(PCD)at molecular level.To further study theMC induced cell death in residual bloom organisms,especially identifying PCD process,we studied the physiological state of the residual Prorocentrum donghaiense.The experimental results showed that flocculation changed the physiological state of the residual cells,as evidenced by growth inhibition and increased reactive oxygen species production.Moreover,this research provides biochemical and ultrastructural evidence showing that MC induces PCD in P.donghaiense.Nuclear changes were observed,and increased caspase-like activity,externalization of phosphatidylserine and DNA fragmentation were detected in MC-treated groups and quantified.And the mitochondrial apoptosis pathway was activated in both MC-treated groups.Besides,the features of MC-induced PCD in a unicellular organism were summarized and its concentration dependent manner was proved.All our preliminary results elucidate the mechanism through which MC can further control HABs by inducing PCD and suggest a promising application of PCD in bloom control. 展开更多
关键词 modified clay Prorocentrum donghaiense programmed cell death Harmful algal blooms
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Inner Product Laplacian Embedding Based on Semidefinite Programming
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作者 Xianhua Zeng 《Journal of Signal and Information Processing》 2011年第3期196-204,共9页
This paper proposes an inner product Laplacian embedding algorithm based on semi-definite programming, named as IPLE algorithm. The new algorithm learns a geodesic distance-based kernel matrix by using semi-definite p... This paper proposes an inner product Laplacian embedding algorithm based on semi-definite programming, named as IPLE algorithm. The new algorithm learns a geodesic distance-based kernel matrix by using semi-definite programming under the constraints of local contraction. The criterion function is to make the neighborhood points on manifold as close as possible while the geodesic distances between those distant points are preserved. The IPLE algorithm sufficiently integrates the advantages of LE, ISOMAP and MVU algorithms. The comparison experiments on two image datasets from COIL-20 images and USPS handwritten digit images are performed by applying LE, ISOMAP, MVU and the proposed IPLE. Experimental results show that the intrinsic low-dimensional coordinates obtained by our algorithm preserve more information according to the fraction of the dominant eigenvalues and can obtain the better comprehensive performance in clustering and manifold structure. 展开更多
关键词 INNER Product semi-definite programming GEODESIC DISTANCE LAPLACIAN Matrix
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A Modified Lagrange Method for Solving Convex Quadratic Optimization Problems
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作者 Twum B. Stephen Avoka John Christian J. Etwire 《Open Journal of Optimization》 2024年第1期1-20,共20页
In this paper, a modified version of the Classical Lagrange Multiplier method is developed for convex quadratic optimization problems. The method, which is evolved from the first order derivative test for optimality o... In this paper, a modified version of the Classical Lagrange Multiplier method is developed for convex quadratic optimization problems. The method, which is evolved from the first order derivative test for optimality of the Lagrangian function with respect to the primary variables of the problem, decomposes the solution process into two independent ones, in which the primary variables are solved for independently, and then the secondary variables, which are the Lagrange multipliers, are solved for, afterward. This is an innovation that leads to solving independently two simpler systems of equations involving the primary variables only, on one hand, and the secondary ones on the other. Solutions obtained for small sized problems (as preliminary test of the method) demonstrate that the new method is generally effective in producing the required solutions. 展开更多
关键词 Quadratic programming Lagrangian Function Lagrange Multipliers Optimality Conditions Subsidiary Equations modified Lagrange Method
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Thiamine-modified metabolic reprogramming of human pluripotent stem cell-derived cardiomyocyte under space microgravity 被引量:1
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作者 Xinglong Han Lina Qu +16 位作者 Miao Yu Lingqun Ye Liujia Shi Guangfu Ye Jingsi Yang Yaning Wang Hao Fan Yong Wang Yingjun Tan Chunyan Wang Qi Li Wei Lei Jianghai Chen Zhaoxia Liu Zhenya Shen Yinghui Li Shijun Hu 《Signal Transduction and Targeted Therapy》 SCIE CSCD 2024年第5期2132-2142,共11页
During spaceflight,the cardiovascular system undergoes remarkable adaptation to microgravity and faces the risk of cardiac remodeling.Therefore,the effects and mechanisms of microgravity on cardiac morphology,physiolo... During spaceflight,the cardiovascular system undergoes remarkable adaptation to microgravity and faces the risk of cardiac remodeling.Therefore,the effects and mechanisms of microgravity on cardiac morphology,physiology,metabolism,and cellular biology need to be further investigated.Since China started constructing the China Space Station(CSS)in 2021,we have taken advantage of the Shenzhou-13 capsule to send human pluripotent stem cell-derived cardiomyocytes(hPSC-CMs)to the Tianhe core module of the CSS.In this study,hPSC-CMs subjected to space microgravity showed decreased beating rate and abnormal intracellular calcium cycling.Metabolomic and transcriptomic analyses revealed a battery of metabolic remodeling of hPSC-CMs in spaceflight,especially thiamine metabolism.The microgravity condition blocked the thiamine intake in hPSC-CMs.The decline of thiamine utilization under microgravity or by its antagonistic analog amprolium affected the process of the tricarboxylic acid cycle.It decreased ATP production,which led to cytoskeletal remodeling and calcium homeostasis imbalance in hPSC-CMs.More importantly,in vitro and in vivo studies suggest that thiamine supplementation could reverse the adaptive changes induced by simulated microgravity.This study represents the first astrobiological study on the China Space Station and lays a solid foundation for further aerospace biomedical research.These data indicate that intervention of thiamine-modified metabolic reprogramming in human cardiomyocytes during spaceflight might be a feasible countermeasure against microgravity. 展开更多
关键词 programming battery modified
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NONLINEAR LAGRANGIANS FOR NONLINEAR PROGRAMMING BASED ON MODIFIED FISCHER-BURMEISTER NCP FUNCTIONS
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作者 Yonghong Ren Fangfang Guo Yang Li 《Journal of Computational Mathematics》 SCIE CSCD 2015年第4期396-414,共19页
This paper proposes nonlinear Lagrangians based on modified Fischer-Burmeister NCP functions for solving nonlinear programming problems with inequality constraints. The convergence theorem shows that the sequence of p... This paper proposes nonlinear Lagrangians based on modified Fischer-Burmeister NCP functions for solving nonlinear programming problems with inequality constraints. The convergence theorem shows that the sequence of points generated by this nonlinear La- grange algorithm is locally convergent when the penalty parameter is less than a threshold under a set of suitable conditions on problem functions, and the error bound of solution, depending on the penalty parameter, is also established. It is shown that the condition number of the nonlinear Lagrangian Hessian at the optimal solution is proportional to the controlling penalty parameter. Moreover, the paper develops the dual algorithm associ- ated with the proposed nonlinear Lagrangians. Numerical results reported suggest that the dual algorithm based on proposed nonlinear Lagrangians is effective for solving some nonlinear optimization problems. 展开更多
关键词 nonlinear Lagrangian nonlinear programming modified Fischer-BurmeisterNCP function dual algorithm condition number
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Effects of Plasticizers,Antioxidants and Burning Rate Modifiers on Aging Performance of the HTPB/HMDI Composite Solid Propellant
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作者 Ahmed M Enew Ehab Abadir +1 位作者 Sahar Elmarsafy Karim K Elsharkawy 《含能材料》 EI CAS CSCD 北大核心 2019年第1期21-27,90,共8页
The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were expl... The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime. 展开更多
关键词 polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)composite solid PROPELLANT plasticizers ANTIOXIDANTS burning rate modifiERS aging program
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THE PRIMAL-DUAL POTENTIAL REDUCTION ALGORITHM FOR POSITIVE SEMI-DEFINITE PROGRAMMING
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作者 Si-ming Huang(Institute of Policy and Management, Academy of Mathematics and System Sciences, Chinese Academy of Sciences, Beijing 100080, China) 《Journal of Computational Mathematics》 SCIE CSCD 2003年第3期339-346,共8页
In this paper we introduce a primal-dual potential reduction algorithm for positive semi-definite programming. Using the symetric preserving scalings for both primal and dual interior matrices, we can construct an alg... In this paper we introduce a primal-dual potential reduction algorithm for positive semi-definite programming. Using the symetric preserving scalings for both primal and dual interior matrices, we can construct an algorithm which is very similar to the primal-dual potential reduction algorithm of Huang and Kortanek [6] for linear programming. The complexity of the algorithm is either O(nlog(X0 · S0/ε) or O(nlog(X0· S0/ε) depends on the value of ρ in the primal-dual potential function, where X0 and S0 is the initial interior matrices of the positive semi-definite programming. 展开更多
关键词 Positive semi-definite programming Potential reduction algorithms Complexity.
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Fuzzy Multi-Objective Semi-Definition Programming
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作者 Rui LIU Ke Cun ZHANG 《Journal of Mathematical Research and Exposition》 CSCD 2010年第4期599-609,共11页
This paper first applies the fuzzy set theory to multi-objective semi-definite program-ming (MSDP), and proposes the fuzzy multi-objective semi-definite programming (FMSDP) model whose optimal efficient solution i... This paper first applies the fuzzy set theory to multi-objective semi-definite program-ming (MSDP), and proposes the fuzzy multi-objective semi-definite programming (FMSDP) model whose optimal efficient solution is defined for the first time, too. By constructing a membership function, the FMSDP is translated to the MSDP. Then we prove that the optimal efficient solution of FMSDP is consistent with the efficient solution of MSDP and present the optimality condition about these programming. At last, we give an algorithm for FMSDP by introducing a new membership function and a series of transformation. 展开更多
关键词 fuzzy multi-objective semi-definite programming membership function optimality efficient solution efficient solution optimality condition.
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基于早期预警评分建立的骨科术后患者程序化监护方案的应用价值研究 被引量:23
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作者 彭伶丽 杨佳琪 金惠 《中国全科医学》 CAS CSCD 北大核心 2012年第3期335-337,共3页
目的探讨基于早期预警评分(MEWS)的骨科术后患者程序化监护方案的应用价值。方法将骨科术后患者随机分为对照组(110例)和实验组(109例)。对照组采用传统的监测方案即根据医生医嘱进行监测,实验组采用根据MEWS评分设计的程序化监护方案... 目的探讨基于早期预警评分(MEWS)的骨科术后患者程序化监护方案的应用价值。方法将骨科术后患者随机分为对照组(110例)和实验组(109例)。对照组采用传统的监测方案即根据医生医嘱进行监测,实验组采用根据MEWS评分设计的程序化监护方案。对比分析两组意外事件发生率、30 d内病死率、ICU转入率、平均住院日及患者的满意度。结果实验组在意外事件发生率、30 d内病死率、ICU转入率、平均住院日均明显低于对照组,差异有统计学意义(P<0.05);实验组患者满意度明显高于对照组,差异有统计学意义(P<0.05)。结论基于MEWS评分建立的骨科术后患者程序化监护方案具有较好的应用价值,能降低骨科手术后患者风险的发生,有利于医护之间的合作,提高了患者的满意度,增强了护士的主动服务意识。 展开更多
关键词 早期预警评分 骨科 整体护理 程序化监护
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石墨炉升温程序的灰化技术 被引量:15
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作者 吴华 李绍南 《中国环境监测》 CAS CSSCI CSCD 北大核心 1998年第3期32-34,共3页
本文以测定铅为例,研究了石墨炉升温程序的灰化技术,包括基体干扰的消除,基体改进剂和L’vov平台的应用。
关键词 石墨炉升温程序 大气监测 灰化技术
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基于微观和流变分析的岩沥青改性沥青性能评价 被引量:30
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作者 黄刚 何兆益 +1 位作者 胡诚 黄涛 《东南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2010年第2期367-372,共6页
采用埃索70#沥青,以不同掺量的青川天然岩沥青为改性剂制备岩沥青改性沥青.通过红外光谱和差示扫描热量法(DSC)对天然岩沥青及岩沥青改性沥青的微观结构进行分析,研究其改性机理.采用SHRP试验对岩沥青改性沥青的高温、低温和抗疲劳性能... 采用埃索70#沥青,以不同掺量的青川天然岩沥青为改性剂制备岩沥青改性沥青.通过红外光谱和差示扫描热量法(DSC)对天然岩沥青及岩沥青改性沥青的微观结构进行分析,研究其改性机理.采用SHRP试验对岩沥青改性沥青的高温、低温和抗疲劳性能进行研究,并对不同掺量的岩沥青改性沥青进行了SHRP-PG分级.微观研究证明,天然岩沥青沥青质的杂原子基团含量高,芳香性和极性强.经过改性,基质沥青的微观结构发生了变化,岩沥青改性沥青的感温性降低,温度稳定性和水稳定性得到增强.流变特性分析表明岩沥青改性沥青的黏度明显提高,高温稳定性和抗疲劳性得到显著改善,可用于非极端低温的环境. 展开更多
关键词 岩沥青改性沥青 微观结构分析 改性机理 SHRP试验 性能
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基于动态规划算法的增程式电动汽车能量管理策略优化 被引量:24
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作者 席利贺 张欣 +1 位作者 耿聪 薛奇成 《交通运输工程学报》 EI CSCD 北大核心 2018年第3期148-156,共9页
提出了一种动态规划改进算法,根据约束条件确定未来可达状态序列,通过计算离散状态点间的转移代价,在保证求解精度的同时,降低了离线优化计算量;利用改进动态规划算法设计了增程式电动汽车能量管理策略,根据能量管理优化问题特点,建立... 提出了一种动态规划改进算法,根据约束条件确定未来可达状态序列,通过计算离散状态点间的转移代价,在保证求解精度的同时,降低了离线优化计算量;利用改进动态规划算法设计了增程式电动汽车能量管理策略,根据能量管理优化问题特点,建立了动力系统模型和适用于全局优化求解的系统状态方程,并确定了以动力电池荷电状态为系统状态量和增程器发电功率为系统控制量;在迭代计算过程中,将发动机燃油费用和动力电池电能费用之和作为目标函数,构建了基于北京主干道不同行驶里程仿真工况,得到了驱动电机需求功率最优分配结果;提取了增程器启停状态与动力电池荷电状态和驱动电机需求功率二者之间的控制规则,利用最小二乘法对增程器功率分流比与驱动电机需求功率的分布规律进行拟合,建立了基于优化规则的能量管理策略。仿真结果表明:对于行驶里程为100km的仿真工况,动态规划改进算法计算时间为7 239s,与经典动态规划算法相比计算效率提高了78.2%;基于优化规则的能量管理策略能够获得类似动态规划改进算法的控制效果,2种控制策略的动力电池荷电状态误差小于2.5%;相比实车电能消耗-电能维持型控制策略,基于优化规则的控制策略能够使整车经济性提高5.4%,使燃油经济性提高7.9%。 展开更多
关键词 汽车工程 增程式电动汽车 能量管理策略 动态规划 改进算法 燃油经济性
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非线性二次规划贝叶斯叠前反演 被引量:69
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作者 杨培杰 印兴耀 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2008年第6期1876-1882,共7页
叠前反演的目的是基于弹性波理论从地震数据中获得地层参数的可靠估计,进而用于描述地层的流体和岩性特征.然而叠前反演问题都是高维的和非适定的,并且容易受各种噪声和采集过程中不确定因素的影响,因此,为了获得稳定可靠的解必需对反... 叠前反演的目的是基于弹性波理论从地震数据中获得地层参数的可靠估计,进而用于描述地层的流体和岩性特征.然而叠前反演问题都是高维的和非适定的,并且容易受各种噪声和采集过程中不确定因素的影响,因此,为了获得稳定可靠的解必需对反演过程加以合理的约束.本文提出了一种基于非线性二次规划的叠前三参数反演方法.首先基于贝叶斯参数估计理论,假设似然函数服从高斯分布,并使待反演的参数服从于改进的Cauchy分布,从而提高了反演结果的分辨率;其次用协方差矩阵来描述参数间的相关程度,进一步提高了反演结果的稳定性;最后将问题转化为一个非线性二次规划的求解问题,并在多种约束下得到问题的解.仿真实验和实际应用皆已表明,本文提出的反演方法运算速度快捷,既使在信噪比很低的情况下也可获得较好的反演结果,为储层的进一步识别提供更多的物性参数. 展开更多
关键词 叠前反演 非线性二次规划 贝叶斯理论 协方差矩阵 改进的Cauchy分布
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功能梯度材料飞轮转子优化设计 被引量:11
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作者 闫晓磊 钟志华 +2 位作者 查云飞 莫旭辉 孙光永 《机械工程学报》 EI CAS CSCD 北大核心 2011年第2期72-79,共8页
功能梯度材料(Functionally graded materials,FGMs)是一种材料属性在空间位置上连续变化的新型材料。与均匀材料相比,高速储能飞轮转子采用FGMs可以有效地减少应力集中,充分发挥材料性能,从而改善转子的工作性能。针对飞轮转子轴向厚... 功能梯度材料(Functionally graded materials,FGMs)是一种材料属性在空间位置上连续变化的新型材料。与均匀材料相比,高速储能飞轮转子采用FGMs可以有效地减少应力集中,充分发挥材料性能,从而改善转子的工作性能。针对飞轮转子轴向厚度相对较厚时平面应力方法误差较大的问题,通过将转子离散为有限个等厚匀质微环的方法,推得变厚度FGMs飞轮转子的三维半解析解——修正平面应力(Modified plane stress,MPS)解,并采用有限元法验证其精确性。应用序列二次规划(Sequential quadratic programming,SQP)优化方法,以飞轮转子的厚度、材料体积分数和转速为设计变量,以最大化转子的储能密度为目标函数,对FGMs飞轮转子的形状和材料分布进行优化设计,并分析材料性能参数对结果的影响。计算结果表明,合理的转子形状与材料分布可以使转子应力分布更加均匀,大大提高飞轮的储能性能。 展开更多
关键词 飞轮转子 功能梯度材料 修正平面应力 序列二次规划
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有限推力下时间最优轨道转移 被引量:12
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作者 梁新刚 杨涤 《航天控制》 CSCD 北大核心 2007年第1期46-51,共6页
研究了一种有限推力作用下的时间最优轨道转移计算方法。以非奇异根素形式的高斯行星摄动方程为基础,由庞德里亚金极小值原理导出正则方程组,通过将最优控制问题转化为协状态初值为待优化参数的参数优化问题,并通过非线性规划求解得到... 研究了一种有限推力作用下的时间最优轨道转移计算方法。以非奇异根素形式的高斯行星摄动方程为基础,由庞德里亚金极小值原理导出正则方程组,通过将最优控制问题转化为协状态初值为待优化参数的参数优化问题,并通过非线性规划求解得到的参数优化问题,从而避开求解两点边值问题的困难。文章最后给出2个算例,分别计算了零倾角零偏心率最优轨道转移和大倾角改变最优轨道转移。计算过程及结果表明本文所用方法对协状态初值猜测敏感性小,收敛迅速;零倾角零偏心率情况下无奇异;所得控制轨线光滑。 展开更多
关键词 轨道优化 非奇异根素 非线性规划
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氯化镁改性硅胶的吸水等温线及脱附性能 被引量:11
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作者 朱培怡 王海增 李溪 《硅酸盐学报》 EI CAS CSCD 北大核心 2010年第4期735-740,共6页
用氯化镁改性硅胶制备复合干燥剂,在相对湿度为20%~90%的条件下研究氯化镁改性硅胶对水蒸气的吸附,采用FHH(Frenkel–Halsey–Hill)模型研究复合干燥剂表面的粗糙程度,测定水在改性硅胶上的程序升温脱附曲线,考察复合干燥剂的再生温度... 用氯化镁改性硅胶制备复合干燥剂,在相对湿度为20%~90%的条件下研究氯化镁改性硅胶对水蒸气的吸附,采用FHH(Frenkel–Halsey–Hill)模型研究复合干燥剂表面的粗糙程度,测定水在改性硅胶上的程序升温脱附曲线,考察复合干燥剂的再生温度、再生次数及氯化镁改性对硅胶吸湿性能和水的脱附活化能的影响。结果表明:在相同条件下,氯化镁含量为1%时,改性硅胶的吸水量约为未改性硅胶的10倍,改性硅胶吸水符合第Ⅳ型等温线。通过FHH模型分析说明改性后硅胶的大片状固体颗粒被部分破坏,形成更为精细的孔隙分布,硅胶表面更加粗糙和不规则。程序升温脱附研究表明氯化镁改性硅胶的脱附活化能较小,脱附容易进行。脱附再生3次后,改性硅胶仍具有较高的吸水量,复合干燥剂具有较好的再生性能。 展开更多
关键词 改性硅胶 氯化镁 复合干燥剂 程序升温脱附 吸附等温线 干燥剂再生
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变围压循环下低渗透致密砂岩有效应力方程研究 被引量:20
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作者 郑玲丽 李闽 +1 位作者 钟水清 肖文联 《石油学报》 EI CAS CSCD 北大核心 2009年第4期588-592,共5页
采用了修正的析因设计方案,对低渗透致密砂岩进行了有效应力方程的实验研究。实验方案中包含多个循环,每个循环都是在孔隙流体压力不变,增加和降低围压的方式下进行。用稳态法采集各测点的渗透率,并用响应面法进行数据处理分析。结果表... 采用了修正的析因设计方案,对低渗透致密砂岩进行了有效应力方程的实验研究。实验方案中包含多个循环,每个循环都是在孔隙流体压力不变,增加和降低围压的方式下进行。用稳态法采集各测点的渗透率,并用响应面法进行数据处理分析。结果表明,有效应力系数随着围压的增加而减小,随着孔隙流体压力的增加而增大。在实验研究范围内,有效应力系数的最大值不超过0.88,当围压大、孔隙流体压力小时,有效应力系数远小于1.0,表明孔隙流体压力对渗透率变化的影响变得很小。用响应面方法获取的有效应力系数确定了有效应力,建立了渗透率与有效应力的关系,与传统有效应力的概念相吻合。 展开更多
关键词 低渗透致密砂岩 渗透率 有效应力 有效应力系数 响应面法 修正的析因设计
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湿度对油烟中易挥发有机化合物吸附的影响 被引量:4
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作者 李晶 肖文清 +1 位作者 李忠 奚红霞 《化学工程》 CAS CSCD 北大核心 2010年第8期73-77,共5页
主要研究了甲醛、乙醛和苯在有机硅烷KH560和1706改性活性炭(AC)表面的脱附活化能,并通过透过曲线实验测定了不同湿度对三者在改性活性炭上吸附的影响,最后用光电子能谱(XPS)分析材料表面的亲水基团和憎水基团比例的变化。结果表明... 主要研究了甲醛、乙醛和苯在有机硅烷KH560和1706改性活性炭(AC)表面的脱附活化能,并通过透过曲线实验测定了不同湿度对三者在改性活性炭上吸附的影响,最后用光电子能谱(XPS)分析材料表面的亲水基团和憎水基团比例的变化。结果表明,采用有机硅烷改性活性炭可提高材料的憎水性,在较高湿度下(RH〉60%),三者在未改性活性炭固定床穿透时间减少得最多,1706/AC固定床次之,KH560/AC固定床最小;程序升温脱附(TPD)实验表明,用有机硅烷改性活性炭可以削弱水和活性炭表面的结合力,增强与甲醛、乙醛和苯的结合力。通过XPS分析,与未改性活性炭相比,经有机硅烷改性的活性炭,其憎水性得到提高。 展开更多
关键词 程序升温脱附 透过曲线 改性活性炭 脱附活化能 XPS
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基于程序流敏感的自修改代码混淆方法 被引量:5
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作者 何炎祥 陈勇 +4 位作者 吴伟 陈念 徐超 刘健博 苏雯 《计算机工程与科学》 CSCD 北大核心 2012年第1期79-85,共7页
自修改代码混淆方法是一种隐藏程序重要信息的有效技术。为减少代码混淆造成的额外开销而又不影响代码混淆的质量,利用程序流敏感分析方法选择比较重要的指令进行混淆。为提高代码混淆的质量,有效地防止反汇编,提出一个二步比较混淆模... 自修改代码混淆方法是一种隐藏程序重要信息的有效技术。为减少代码混淆造成的额外开销而又不影响代码混淆的质量,利用程序流敏感分析方法选择比较重要的指令进行混淆。为提高代码混淆的质量,有效地防止反汇编,提出一个二步比较混淆模型。该模型包括两个子混淆器,混淆器1采用程序流敏感分析方法获得混淆的指令并产生两个混淆代码文件和一个混淆代码映射文件。混淆器2通过比较两个混淆代码文件精确地定位混淆指令在二进制代码中的位置,然后利用混淆代码映射文件对二进制代码进行混淆,以进一步提高代码混淆的质量。通过实验分析,混淆后二进制文件的额外开销只占整个代码的3%左右,并且混淆后的反汇编代码明显异于原始的反汇编代码,甚至出现了一些无法识别的错误指令。 展开更多
关键词 程序流敏感 自修改代码 代码混淆 二进制数据定位 代码保护
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