Analysis of asymptotically tight approximation SER for cooperative NOMA systems

The closed-form formula derivation of the power domain cooperative non-orthogonal multiple access(NOMA) system is of great significance for further improving the performance of the system.However,the system performance formulas of the channel capacity and the paired bit error rate pairwise error probability(PEP) are too complicated,which have increased the difficulty in system performance optimization.Therefore,based on the amplify forward(AF) relay cooperative NOMA model,the signal interference noise ratio(SINR) formulas of the two user nodes are constructed.Through the assumption of that,the symbol error rate(SER) of each user is fair,the simplification condition of moment generating function(MGF) with the harmonic mean form is satisfied.Combined with the SER calculation formula of MGF,the system SER asymptotically tight approximation formula with simple structure is derived at high signal-to-noise ratio(SNR).The Monte Carlo simulation results show that,the formula can accurately describe the SER performance of the power domain cooperative NOMA system with the non-ideal successive interference cancellation(SIC) system when SNR is high.Under the condition of certain total power,the optimal power allocation factor is solved in order to minimize the total system SER.     

The Life-Cycle Model with Optimal Retiring Age and Simulation

In this paper, a life-cycle model with retirement is set up to study how an individual chooses the optimal retiring age on account of wage growth rate, longevity and healthy state. It is proved that there exists optimal retiring age under given conditions. The numerical simulations are given to show how wage growth rate, longevity and healthy state affect retiring age.     

Mechanical and corrosion properties of low-carbon steel prepared by friction stir processing

Low-carbon steel plates were successfully subjected to normal friction stir processing(NFSP) in air and submerged friction stir processing(SFSP) under water, and the microstructure, mechanical properties, and corrosion behavior of the NFSP and SFSP samples were investigated. Phase transformation and dynamic recrystallization resulted in fine-grained ferrite and martensite in the processed zone. The SFSP samples had smaller ferrites(5.1 μm), finer martensite laths(557 nm), and more uniform distribution of martensite compared to the NFSP samples. Compared to the base material(BM), the microhardness of the NFSP and SFSP samples increased by 19.8% and 27.1%, respectively because of the combined strengthening effects of grain refinement, phase transformation, and dislocation. The ultimate tensile strengths(UTSs) of the NFSP and SFSP samples increased by 27.1% and 38.7%, respectively. Grain refinement and martensite transformation also improved the electrochemical corrosion properties of the low-carbon steel. Overall, the SFSP samples had better mechanical properties and electrochemical corrosion resistance than the NFSP samples.     

COVERING TWO DIGRAPHS WITH ARBORESCENCES

Let G_1 and G_2 be finite digraphs,both with vertex set V.Suppose that each vertexv of V has nonnegative integers f(v) and g(v) with f(v)≤g(v),and each arc e of G_4 hasnonnegative integers a_i(e) and b_i(e) with a_i(e)≤b_i(e),i=1,2.In this paper we give anecessary and sufficient condition for the existence of k arborescences in G_4 covering each are(?) of G_i at least a_i(e) and at most b_i(e) times,i=1,2,and satisfying the condition that foreach v in Vf(v)≤r_1(v)=r_2(v)≤g(v)where r_4(v) denote the number of the arborescences in G_(?) rooted at v.     

基于区域叠合有限元技术预测三维编织复合材料弹性性能

本文基于区域叠合有限元技术预测三维四向编织复合材料弹性性能。在该方法中,分别建立相互独立的纤维增强相有限元模型和复合材料整体区域(包括所有增强相和基体相所占几何空间)有限元模型,两相模型在空间叠合组成复合材料模型,运用节点自由度耦合技术使两相模型满足变形协调关系,通过对两相模型赋予适当的材料属性以使所建复合材料模型具有与实际复合材料等效的力学特性。该方法较传统方法显著缩短了建模时间,降低了建模难度。区域叠合法的数值模拟结果与传统方法预测结果一致。本文的研究为进一步研究编织复合材料非线性宏观力学特性和渐进损伤过程模拟奠定基础。     

粘性液体-颗粒物料在斜轴式滚筒中的混合试验

分析了液体物料在滚筒中的运动模式,得到了液体物料的运动轨迹.应用自行研制的斜轴式滚筒混合机,进行白乳胶和建筑用黄砂的混合实验,对混合过程中的混合时间、筒体倾斜角和旋转速度等工艺参数进行系统研究,从中得到一些改善混合质量的因素.同时确定了上述工艺参数的参考值.通过视频采集分析了高粘度物料的混合过程.试验结果可供在斜轴式滚筒混合机用于粘性液体与固体颗粒的混合借鉴.     

New Develoopment of the Basic Theory of Extenics

In this paper,the new development of three basic theories of Extenics,incluing basic-element theory,extension set theory and extension logic theory ,has been introduced.And the new theoretical frame of Extenics has also been set forth.     

确定平面应力状态主应力方向的四个解析法

本文综合应力圆和解析法求平面应力状态主应力方向的两种方法,从不同的角度提出了四种由主平面方位角公式直接确定主应力方向的方法。     

对数域电流模式带通滤波器的频率限制

基于对数域积分器误差函数分析方法，分别导出了带通滤波器的中心频率、品质因数与积分器误差函数幅值和相位之间的关系式，得到了中心频率、品质因数与晶体管非理想参数RE、RB、有限电流增益β值和Early电压VA值的关系式。研究结果表明，寄生电阻RE和RB主要影响滤波器的中心频率，有限β值对中心频率和品质因数均有影响，有限VA对滤波器的影响相对较小。给出的电子补偿方法，可以显著地改善非理想对数域带通滤波器的性能。SPICE仿真分析验证了理论分析结果，所得结果可为对数域滤波器的精确设计和应用提供理论依据。     

联合多址系统中扩频码的分配算法

在基于码分多址(CDMA)和空分多址(SDMA)技术的联合多址系统中, 扩频码的分配应根据移动用户空间向量的正交性来进行.文中给出一扩频码的分配算法.应用该算法,相同的扩频码可分配给同一小区内不同SDMA信道的用户,进而提高CDMA系统的通信容量.