Energy Efficiency Analysis of MISO-OFDM Communication Systems Considering Power and Capacity Constraints

In this paper, the energy efficiency of multi-input single-output and orthogonal frequency division multiplexing (MISO-OFDM) communication systems with power and capacity constraints is investigated. By formulating the power allocation problem of MISO-OFDM communication systems, the minimum subchannel transmission power is analyzed with power and capacity constraints. Simulation results indicate that there exists a specific minimum subchannel capacity threshold. Moreover, the energy efficiency of MISO-OFDM communication systems starts to increase only when the minimum subchannel capacity exceeds the specific threshold.     

市售商品补钙制剂的补钙效果观察

本文以大鼠为模型，研究不同化学形式钙以及市售数种钙剂的补钙效果。１．不同化学形式钙的补钙效果：选用三周龄断乳Ｗｉｓｔａｒ大鼠５６只，雌雄各半，喂饲３周缺钙饲料后，按体重随机把大鼠分成４组，即缺钙饲料、补充碳酸钙、活性钙或乳酸钙饲料（３０００ｍｇＣａ／ｋｇ），实验期为１２周。２．市售补钙制剂的补钙效果：选用动物及实验期同实验１，动物数为８４只，按体重随机把大鼠分成７组，即缺钙饲料组，其它６组为补充碳酸钙、钙尔奇－Ｄ、盖天力、活性钙、壮骨宝、巨人补钙饲料（３０００ｍｇＣａ／ｋｇ）。补钙各组大鼠终体重和身长均非常显著高于对照组。补充不同化学形式钙或商品钙制剂组的血浆、红细胞和肝脏中钙含量均显著高于缺钙对照组，补钙各组间无显著差异。多数钙制剂对雄性肾脏钙存留的影响不显著，只有盖天力显著增加雄性肾脏钙存留；补钙对雌性肾脏钙存留的影响非常显著。补充的三种化学形式钙和商品钙剂均显著增加骨矿物质含量，但是碳酸钙和乳酸钙的效果优于活性钙，巨人补钙和活性钙的效果似不如其它钙制剂。按效果价格比，目前碳酸钙仍是最好的钙源。     

聚能切割索切割能力仿真及试验研究

为深入研究聚能切割索的切割能力,采用数值仿真和试验的手段研究了聚能切割索（Flexible Linear Shaped Charge,FLSC）切割不同材料铝板的切割效果。仿真和试验结果表明：材料的屈服强度对侵彻性能影响最大,随着被切割对象屈服强度的增大,侵彻深度降低。     

DGTD用于RCS计算的初步研究

时域离散伽辽金法(Discontinuous Galerkin Time Domain, DGTD)同时具有时域有限元算法(FiniteElement Time Domain, FETD)非结构网格剖分和时域有限差分算法(Finite Difference Time Domain, FDTD)显式迭代的优点,是一种非常有前途的电磁计算方法,该文首先描述了基于矢量基函数的时域离散伽辽金法的基本原理.然后,给出了DGTD处理散射问题时平面波入射加入的具体实现方法.最后,给出了金属球、介质球和金属弹头宽带散射的算例,算例结果的比较表明了该文算法的正确性和有效性.该文的研究,为复杂目标雷达散射截面RCS的准确预估打下了坚实的基础.      

双链路故障时的共享路径保护

在波长路由光网络中,网络的存活性已经受到越来越多的重视.对单链路故障时的保护已经不能满足某些关键性业务对网络存活性的要求,因而研究了双链路故障时的共享路径保护技术.在动态业务下,将共享路径保护问题归结为整数线性规划.在节点无波长转换能力的情况下,分别提出了为当前业务计算最优路径和固定路径两种策略下的整数线性规划.数值结果表明,相对于专用保护,双链路故障时的共享路径保护能够节约30%左右的波长链路资源.     

Low-Dose X-ray CT Reconstruction via Dictionary Learning

Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures.     

Enhanced Elastic Migration of Magnesium Cations in alpha-Manganese Dioxide Tunnels Locally Tuned by Aluminium Substitution

The harsh conditions of large hydrated ion radius of Mg²⁺ cations and the strong electrostatic interaction with the host material put forward higher requirements for high-performance aqueous magnesium ion (Mg²⁺) energy storage devices. Herein, substituted aluminium ions (Al³⁺) doped α-MnO₂ materials are prepared. The introduction of Al³⁺ cations adjust the local chemical environment inside the tunnel structure of α-MnO₂ and precisely regulates the diffusion behavior of inserted Mg²⁺ cations. The shortened oxygens’ distance and abundant oxygen defects result in a substantially enhanced elastic migration pattern of Mg²⁺ cations driven by strengthened electrostatic attraction, which brings the lower diffusion energy barrier, improved reaction kinetics, and adaptive volume expansion as evidenced by Climbing Image-Nudged Elastic Band density function theory calculations coupled with experimental confirmation in X-ray photoelectron spectroscopy, electron paramagnetic resonance, and galvanostatic intermittent titration technique. As a result, this rationally designed cathode exhibits a high reversible capacity of 197.02 mAh g^-1 at 0.1 A g^-1 and stable cycle performance of 2500 cycles with 82% retention. These parameters are among the best of Mg-ion capacitors reported to date. This study offers a detailed insight into the local tunnel structure tunning effect and opens up a new path of modification for tunnel-type structural materials.     

Dual mode wideband band-pass filter with notched band for communication system

This paper presents a planar microstrip wideband dual mode Band-Pass Filter (BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz. The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at ?? =90° and ?? =0°, respectively. A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity. By using a parallel-coupled feed line, a narrow notched band is introduced at the required frequency and its Fractional BandWidth (FBW) is about 5%. The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic, the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz (calculated from 1.959 GHz with ?34.43 dB to 2.065 GHz with ?2.93 dB) and 228.10 dB/GHz (calculated from 3.395 GHz with ?2.873 dB to 3.507 GHz with ?28.42 dB). This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz. Having been presented in this article, the measurement results agree well with the simulation results, which validates our idea.     

A Stochastic Approximation Approach to the Power-Control Problem

This paper proposes and analyzes a new distributed power-control algorithm based on the theory of stochastic approximation. The power-control problem is first converted into a stochastic approximation problem in which the zero point of a specific function is determined. A distributed power-control algorithm is then derived and its convergence properties are analyzed using standard techniques. In the distributed algorithm, each user iteratively updates its power level by using estimates of the inverse of the signal-to-interference ratio (SIR) of its channel. No knowledge of the channel gains or state information of other users is required. Moreover, the algorithm is robust in the sense that it can handle errors in the bit-error rate estimates, and hence, can be used in practical scenarios. Convergence of the algorithm is analyzed in the almost-sure sense     

灰岩含水饱和度对纵、横波速度变化影响的实验研究

该实验是以灰岩作为试样,用超声岩石参数测定仪测量此试样在不同的含水饱和度下纵、横波传播的速度,获得了纵、横波速度和纵、横波速度比与含水饱和度的关系：①纯灰岩和泥质条带灰岩的纵波速度V_P与含水饱和度S_W之间成正比关系;②横波速度V_S与含水饱和度S_W之间成反比关系;③当灰岩试样饱含水时,V_P/S_S的值均大于2;④当灰岩试样饱含气时,V_P/V_S的值均小于2;⑤在试样含水饱和状态时,纯灰岩(孔隙率小)的V_P/V_S值大于泥质条带灰岩(孔隙率大)的V_P/V_S值。我们利用上述关系,可鉴别地层中的流体含量。对岩石固结程度差的地层,还可用纵、横波速度比与含水饱和度的关系划分出油、气、水层。