光通信中的功率计算与通信距离等效验证

光通信具有设备体积小、重量轻等优点, 为了保证长距离通信的顺畅进行, 需要对发射功率进行安全系数较高的计算。分析了发射功率、光束发散角和接收灵敏度对系统通信距离与性能的限制。针对光通信中发射功率计算提出了一种安全系数更高的计算公式, 计算公式表明需要求出最小探测功率, 当通信所要求的误码率确定时, 探测器所需最小探测功率可以通过信噪比与接收器所需最小探测功率的关系计算得出, 在实际通信系统中, 探测灵敏度可以测出, 实际通信系统的透过率也可以测出, 探测器所需最小探测功率也可以通过检测得出, 通过实践验证两者结果吻合, 从而验证了发射功率计算公式的可行性。通过计算公式对安全系数最大情况下所能达到的通信距离进行了模拟验证。     

Optimization Algorithms for Joint Power and Sub-Channel Allocation for NOMA-Based Maritime Communications

This paper investigates resource optimization schemes in a marine communication scenario based on non-orthogonal multiple access (NOMA). According to the offshore environment of the South China Sea, we first establish a Longley–Rice-based channel model. Then, the weighted achievable rate (WAR) is considered as the optimization objective to weigh the information rate and user fairness effectively. Our work introduces an improved joint power and user allocation scheme (RBPUA) based on a single resource block. Taking RBPUA as a basic module, we propose three joint multi-subchannel power and marine user allocation algorithms. The gradient descent algorithm (GRAD) is used as the reference standard for WAR optimization. The multi-choice knapsack algorithm combined with dynamic programming (MCKP-DP) obtains a WAR optimization result almost equal to that of GRAD. These two NOMA-based solutions are able to improve WAR performance by 7.47% compared with OMA. Due to the high computational complexity of the MCKP-DP, we further propose a DP-based fully polynomial-time approximation algorithm (DP-FPTA). The simulation results show that DP-FPTA can reduce the complexity by 84.3% while achieving an approximate optimized performance of 99.55%. This advantage of realizing the trade-off between performance optimization and complexity meets the requirements of practical low-latency systems.     

语音能量给手机供电的可行性分析

测试手机通话和待机的能耗,通话声波能量和说话气流能量,结果表明在现有手机耗能状况下,通话中的能量即使转化效率达100%也远不足以维持手机正常工作。有关说话声能为手机供电的报道不足为信。     

孔径平均对自由空间光通信误码率的影响

研究了接收端孔径平均效应对自由空间光通信误码率的影响。对数辐射方差是反映接收孔径上某一点闪烁起伏的参量。如果自由空间光通信的误码率仅仅是和对数辐射方差有关,那么得到的就是点接收器的结果。对数辐射的协方差是与接收平面上某两点间距离有关的闪烁起伏参量。孔径平均效应意味着要将误码率和对数辐射的协方差联系起来。文中共考虑了两种模型:球面波和平面波,并假设接收孔径直径等于第一菲涅耳区尺度。分析的结果显示,孔径平均后的误码率有明显的减小。     

Energy Efficiency of User-Centric,Cell-Free Massive MIMO-OFDM with Instantaneous CSI

In the user-centric, cell-free, massive multi-input, multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) system, a large number of deployed access points (APs) serve user equipment (UEs) simultaneously, using the same time–frequency resources, and the system is able to ensure fairness between each user; moreover, it is robust against fading caused by multi-path propagation. Existing studies assume that cell-free, massive MIMO is channel-hardened, the same as centralized massive MIMO, and these studies address power allocation and energy efficiency optimization based on the statistics information of each channel. In cell-free, massive MIMO systems, especially APs with only one antenna, the channel statistics information is not a complete substitute for the instantaneous channel state information (CSI) obtained via channel estimation. In this paper, we propose that energy efficiency is optimized by power allocation with instantaneous CSI in the user-centric, cell-free, massive MIMO-OFDM system, and we consider the effect of CSI exchanging between APs and the central processing unit. In addition, we design different resource block allocation schemes, so that user-centric, cell-free, massive MIMO-OFDM can support enhanced mobile broadband (eMBB) for high-speed communication and massive machine communication (mMTC) for massive device communication. The numerical results verify that the proposed energy efficiency optimization scheme, based on instantaneous CSI, outperforms the one with statistical information in both scenarios.     

独立双池受激布里渊散射系统中能量转换效率的研究

利用瞬态包含泵浦抽空的SBS理论模型对独立双池受激布里渊散射系统进行数值模拟，给出了能量转换效率随泵浦功率密度的变化规律。实验验证，理论值与实验结果相吻合。     

可再生能源下燃煤电站-碳捕集优化调度

燃煤电站集成碳捕集技术在实现碳减排的同时可以提升电站灵活性,帮助电网消纳风光;而可再生能源网络可以提供富余能量来满足碳捕集的需求,提升电站碳捕集系统的经济性能。为此,本文提出了一种可再生能源背景下超临界燃煤电站-碳捕集系统的整体优化调度方法。该方法将深度学习与启发式计算融合,综合考虑机组运行约束和电网功率平衡约束,以降低运行成本和最大消纳风光为目标,对电站-碳捕集系统整体运行优化。结果表明,碳捕集系统的引入可以消纳51%的弃风弃光量,降低35%的碳捕集成本。通过比较,自由捕集率约束模式具有最好的优化调度空间,而平均捕集率约束模式在满足电网指定碳排放要求的同时能够保证良好的经济性。     

激光功率和能量计量技术的现状与展望

功率和能量是激光器的两个基本参数,激光功率和能量测量一直是激光参数计量中最基础的测量工作.总结了美国标准技术研究院(NIST)、英国国家物理实验室(NPL)以及中国国家计量院(NIM)在激光功率能量计量方面的技术现状,重点介绍了国防科工委光学计量一级站激光功率能量计量方面已具备的条件,详细说明了所采用的测量原理以及所达到的测量范围和测量不确定度等技术指标.提出了激光功率和能量计量的发展趋势和发展方向.     

On the Optimal Choice of Coefficients in a Truncated Wild Sum and Approximate Solutions for the Kac Equation

We study an approximate solution of the Boltzmann problem for Kac's caricature of a Maxwellian gas by using a truncated and modified expansion of Wild type. We choose the coefficients in the Wild sum approximation using a criterion based on exactly reproducing the behavior of the leading modes.     

Bounds of Efficiency at Maximum Power for Normal-, Sub- and Super-Dissipative Carnot-Like Heat Engines

The Carnot-like heat engines are classified into three types (normal-, sub- and, super-dissipative) according to relations between the minimum irreversible entropy production in the "isothermal" processes and the time for completing those processes. The efficiencies at maximum power of normal-, sub- and super-dissipative Carnot-like heat engines are proved to be bounded between η C /2 and η C /(2 η C ), η C /2 and η C , 0 and η C /(2 η C ), respectively. These bounds are also shared by linear, sub- and super-linear irreversible Carnot-like engines [Tu and Wang, Europhys. Lett. 98 (2012) 40001] although the dissipative engines and the irreversible ones are inequivalent to each other.     

BGO高能γ探测器性能测定与效率模拟

实验测定了两套新制作的φ75×100 BGO高能γ探测器的能量分辨与时间分辨,根据BGO晶体中Ge的热中子俘获所释放的2条高能γ射线对γ能谱作能量刻度.模拟计算了4—30MeV能量区间BGOγ探测器的全能峰效率、单逃逸率与双逃逸率,计算了入射γ光子在0—30MeV区间均匀分布时BGO探测器的实际计数响应与计数效率随γ光子能量的变化,分析了γ光子在探测介质中的能损向下延展造成的能谱扭曲.     

湍流大气光通信系统误码率分析与实验研究

自由空间光通信(FSO)系统的性能由于受大气湍流影响会产生剧烈波动。根据系统和大气参数评估系统差错性能的研究具有现实意义。以大气湍流信道和光电探测两个模型为基础,建立了FSO系统差错性能的数学仿真模型,提出了湍流条件下系统误码率计算公式。对仿真结果与弱湍流条件下获得的实验数据进行了比较,并依据此模型对光强起伏和背景噪声等因素的影响进行仿真。仿真结果表明,基于该模型的仿真结果与实验数据一致,光强起伏是引起系统性能波动的主要因素,最优判决阈值需根据实际大气条件进行调整。该模型可有效评估湍流条件下FSO系统性能,并为相关理论研究提供参考。     

平衡和非平衡方法计算相对结合自由能的精度和效率比较

Estimation of protein-ligand binding affinity within chemical accuracy is one of the grand challenges in structure-based rational drug design. With the efforts over three decades, free energy methods based on equilibrium molecular dynamics (MD) simulations have become mature and are nowadays routinely applied in the community of computational chemistry. On the contrary, nonequilibrium MD simulation methods have attracted less attention, despite their underlying rigor in mathematics and potential advantage in efficiency. In this work, the equilibrium and nonequilibrium simulation methods are compared in terms of accuracy and convergence rate in the calculations of relative binding free energies. The proteins studied are T4-lysozyme mutant L99A and COX-2. For each protein, two ligands are studied. The results show that the nonequilibrium simulation method can be competitively as accurate as the equilibrium method, and the former is more efficient than the latter by considering the convergence rate with respect to the cost of wall clock time. In addition, Bennett acceptance ratio, which is a bidirectional post-processing method, converges faster than the unidirectional Jarzynski equality for the nonequilibrium simulations.     

能量传递制冷机制中激光制冷的最佳泵浦频率和最大制冷效率

在能量传递型激光制冷中,对于非均匀线宽比较窄的情况,引起最大制冷效率的激发光频率不随温度的变化而变化最大制冷效率与温度呈三次暴的关系。对于非均匀线宽比较宽的情况。随着温度的降低,最佳激发光频率与非均匀线形的中心频率差越来越大,并在较低的温度下迅速拉大它们间的距离。由能量传递机制所引起的荧光制冷最大效率也随着温度的降低而越来越低,并在最后趋于零。它们随温度的降低而降低的规律与实验中得到的结论相符合。     

Joint Optimization of Control Strategy and Energy Consumption for Energy Harvesting WSAN

With the rapid development of wireless sensor technology, recent progress in wireless sensor and actuator networks (WSANs) with energy harvesting provide the possibility for various real-time applications. Meanwhile, extensive research activities are carried out in the fields of efficient energy allocation and control strategy design. However, the joint design considering physical plant control, energy harvesting, and consumption is rarely concerned in existing works. In this paper, in order to enhance system control stability and promote quality of service for the WSAN energy efficiency, a novel three-step joint optimization algorithm is proposed through control strategy and energy management analysis. First, the optimal sampling interval can be obtained based on energy harvesting, consumption, and remaining conditions. Then, the control gain for each sampling interval is derived by using a backward iteration. Finally, the optimal control strategy is determined as a linear function of the current plant states and previous control strategies. The application of UAV formation flight system demonstrates that better system performance and control stability can be achieved by the proposed joint optimization design for all poor, sufficient, and general energy harvesting scenarios.     

Optimal power allocation for maximizing the energy efficiency of NOMA enabled full-duplex coordinated direct and relay transmission (CDRT) system with SWIPT

In this paper, we investigate the energy efficiency (EE) performance of non-orthogonal multiple access (NOMA) enabled full-duplex (FD) coordinated direct and relay transmission (CDRT) system (i.e., NOMA-FD-CDRT system). Firstly, we consider a two-user scenario, where the base station (BS) can directly communicate with the near user, while it requires the help of a dedicated FD relay node to communicate with the far user. In the second part, we consider that there are two near users and two far users in the system. To improve the EE, we consider integrating the simultaneous wireless information and power transfer (SWIPT) technique at the FD relay. We formulate an analytical expression for the overall EE of the SWIPT-assisted NOMA-FD-CDRT system. We determine optimal power allocation (OPA) for the downlink users at the BS that maximizes the EE. An iterative algorithm based on Dinkelbach method is proposed to determine the OPA vector. With the help of detailed numerical and simulation investigations, it is demonstrated that the proposed OPA can provide significant enhancement of EE of the considered SWIPT-assisted NOMA-FD-CDRT system.     

闪电成像仪虚警率和探测率模拟计算

在明确虚警率和探测率概念基础上,建立了虚警率和探测率与信噪比之间相互关系的定量模型,通过模拟计算给出信噪比对虚警率和探测率的影响.计算结果表明:要使虚警率控制在10%以内,信噪比应该达到5.0以上;要使探测率达到90%,信噪比应该达到5.2～5.7.     

Power and Thermal Efficiency Optimization of an Irreversible Steady-Flow Lenoir Cycle

Using finite time thermodynamic theory, an irreversible steady-flow Lenoir cycle model is established, and expressions of power output and thermal efficiency for the model are derived. Through numerical calculations, with the different fixed total heat conductances (UT) of two heat exchangers, the maximum powers (Pmax), the maximum thermal efficiencies (ηmax), and the corresponding optimal heat conductance distribution ratios (uLP(opt)) and (uLη(opt)) are obtained. The effects of the internal irreversibility are analyzed. The results show that, when the heat conductances of the hot- and cold-side heat exchangers are constants, the corresponding power output and thermal efficiency are constant values. When the heat source temperature ratio (τ) and the effectivenesses of the heat exchangers increase, the corresponding power output and thermal efficiency increase. When the heat conductance distributions are the optimal values, the characteristic relationships of P-uL and η-uL are parabolic-like ones. When UT is given, with the increase in τ, the Pmax, ηmax, uLP(opt), and uLη(opt) increase. When τ is given, with the increase in UT, Pmax and ηmax increase, while uLP(opt) and uLη(opt) decrease.     

槽道流POD重构及湍流动能耗散率分析

采用二维粒子图像测速仪（2DPIV）对槽道内涡波流场进行实验研究,用POD技术对2DPIV瞬态速度矢量场进行主导模态重构,得到槽道内的平均流速和湍流动能分布;采用大涡PIV方法对湍流动能耗散率分布进行计算.结果表明：重构流场表征了原始流场的主导结构,剔除了噪声等干扰信息;大涡PIV方法能有效地估算动能耗散率的分布;湍流动能在壁面附近较小,在接近槽道中心区域湍流动能越来越大,呈现出射流的特征;动能耗散率的峰值出现在壁面附近和槽道中心区域,动能耗散率随着远离壁面程度的增加先降低后逐渐增加直至达到峰值.