基于螺旋波纹波导高增益高效率被动式压缩方法

对一种改进型螺旋波纹波导实现高增益高效率被动式脉冲压缩进行了研究,并利用微扰理论求解出了该波导的损耗特性。结合波导的色散和损耗特性,设计了输入微波的频率调制形式。还对改进型螺旋波纹波导进行了模拟研究,在输入脉冲宽度为66ns的条件下,得到了半高宽为1.9ns的压缩脉冲,增益为21.2倍,脉冲宽度比为34.7倍,压缩效率为61%,这表明改进型螺旋波纹波导应用于被动式脉冲压缩具有高效率高增益特性。

基于深度强化学习的无蜂窝系统无线接入点选择算法

面向以用户为中心的无蜂窝分布式多输入多输出(Multiple-Input Multiple-Output, MIMO)架构,研究利用不完备信道状态信息(Channel State Information, CSI)下实现无线接入点(Access Point, AP)与用户(User Equipment, UE)之间的选择,提出基于深度强化学习(Deep Reinforcement Learning, DRL)的高效分配算法,通过使用不完备CSI快速生成以用户为中心的AP集合,减少了对前馈链路容量的占用。仿真结果表明,与其他传统选择算法相比,所提出的DRL接入点选择算法可以获得至少22.48%的总遍历频谱效率增益;与深度Q网络(Deep-Q-Network, DQN)算法相比,可以获得约14.17%的总频谱效率增益。

线性与非线性传热过程的Curzon-Ahlborn热机在任意功率时的效率

热机性能的优化是热力学领域的一个重要问题,而工质与热源之间的传热过程是热机工作时产生不可逆的主要来源.本文在引入功率增益和效率增益两个重要参数的基础上,基于一个简化的Curzon-Ahlborn热机模型并利用合比分比原理,给出了线性与非线性传热过程的热机在任意功率输出时的效率表达式,结合数值计算详细讨论了热机在任意功率输出时的特性.研究表明,参数ξ作为功率增益δP的函数存在两个分支:在第一分支上(不利情形),效率呈现出单调变化特征;在第二分支上(有利情形),效率随着的δP变化是非单调的且有最大值.随着传热指数的增加,热机的工作区域减小,这源于非线性传热过程包含热辐射所致.进一步发现功率-效率关系曲线存在权衡工作点,热机在该点附近工作能够实现最有效的热功转换.研究结果有助于深入理解具有不同传热过程热机的优化执行.

电站锅炉节能环保关键技术研究

节能环保理念符合当前社会发展需求,电站锅炉作为能源体系的重要组成部分,是非常重要的设备。针对电站锅炉设备开展节能环保研究有着突出意义。就目前的发展态势来看,公众环保意识持续增强,传统的电站锅炉技术无论是运行效能还是污染排放量方面均难以满足目前的节能环保要求。在此基础上做好电站锅炉节能环保技术研究工作就显得格外重要。在本文中,先对电站锅炉节能环保技术效益增率展开初步分析,然后对锅炉节能中需要使用的设备和技术展开分析,最后分析了锅炉节能环保技术的具体应用,以供参考。

一种三绕组零纹波高增益DC/DC变换器

新能源并网发电系统的应用使得零纹波高增益DC／DC变换器成为研究热点。在一种耦合电感型DC／DC变换器的基础上，引入无源零纹波电路，推导得到一种三绕组零纹波高增益DC／DC变换器。三绕组耦合电感实现了高增益的同时，还实现了零纹波功能。倍压电路的使用，使得变换器的电压增益进一步得到提高，还限制了二极管寄生电容与漏感谐振产生的电压尖峰。两个有源开关相互钳位，限制了开关管关断时刻的电压尖峰，还实现了零电压开通。变换器功率器件的电压应力均远低于输‘出电压，可选用低耐压器件来提高变换器效率。最后搭建一台250W、48V／380V的实验样机验证理论分析的正确性。

5～22 GHz平坦高增益单片低噪声放大器

使用0.25μm G aA s PHEM T工艺技术,设计和制造了性能优良的5-22 GH z两级并联反馈单片低噪声放大器。在工作频率5-22 GH z内,测得增益G≥18 dB,带内增益波动ΔG≤±0.35 dB,噪声系数N F≤3.2 dB,输入输出驻波V SW R≤1.7,最小分贝压缩点输出功率P1dB≥10.5 dBm,电流增益效率达2.77 mA/dB。测试结果验证了设计的正确性。

一种带反馈的高效功率放大器设计

文中提出了一种带有反馈电路结构的宽带高效连续F类功率放大器,该正反馈电路被用来补偿功率放大器在高频段的增益和效率恶化。因此,功率放大器能够在宽带内具有较为平坦的增益和效率性能。该放大器同时使用K渐变线作为输入匹配以改善宽带性能和减少功率损耗。测量结果表明,该功率放大器在1.6 GHz~2.6 GHz频段具有65.1%~75.3%的功率附加效率(Power-Added Efficiency,PAE)和10.1 dB~12 dB的增益。

Improvements on High Current Performance of Static Induction Transistor

Methods for improving the high current performance of static induction transistor （SIT） are presented.Many important factors,such as ＂trans-conductance per unit channel width＂ θ, ＂gate efficiency＂ η, ＂sensitivity factor＂ D,and ＂intrinsic static gain＂ μ0,that may be used to describe different aspects of the electrical performance of an SIT are first defined.The dependences of electrical parameters on the structure and technological process of an SIT are revealed for the first time.The packaging technologies are so important for the improvement of high power performance of SITs that they must be paid attention.Testing techniques and circuits for measuring frequency and power parameters of SITs are designed and constructed.The influence of packaging processes in technological practice on the electrical performance of SITs is also discussed in depth.

Cherenkov型自由电子激光器中介电系数选择的研究

计算了Cherenkov型自由电子激光器中介质的介电系数的变化对激光器输出性能的影响,结果表明,偏大或偏小的介电系数不仅会降低效率,而且对增益特性产失严重的影响。

基于信息运动模型的信息作用机理研究

本文通过考察信息运动模型和信息约束,建立信息作用模型,揭示信息作用必须遵从物理层次和信息层次的5个匹配规则,提出信息作用机理,并应用作用机理从人类信息活动和组织系统两方面考察信息作用效应,提出信息增益效率理论。

面向磁阻传感器的MEMS磁通汇聚器优化设计研究

微机电(micro electro mechanical systems,MEMS)磁阻传感器由于小体积、低功耗和高灵敏度在许多领域得到了广泛应用,然而其在测量低频弱磁场时受到1/f的影响,严重限制了其低频弱磁场的检测分辨率。为了减小1/f噪声的影响,MEMS磁通汇聚器被用于放大弱磁场,并将低频弱磁场调制到高频区域以抑制1/f噪声。使用拓扑优化对给定尺寸的磁通汇聚器进行优化,以提高其磁场增益,最后使用优化后的塔形磁通汇聚器比较了变间隙调制、扭转调制、垂直运动调制和压电悬臂梁调制的调制效率和增益效率积。结果表明,垂直运动调制具有较高的增益效率积和较高的磁场检测分辨率,是现有调制方式中的最优调制方式。

A Novel High Spectral Efficiency Waveform Coding-OVFDM

Based on the Overlapped Multiplexing Principle[12],a frequency domain OVFDM(Overlapped Frequency Domain Multiplexing) Coding is proposed.By the data weighted shift overlapped version of any band-limited Multiplexing Transfer Function H(f) the coding gain and spectral efficiency are both achieved.The heavier the overlap of the data weighted Multiplexing Transfer Function H(f),the higher the coding gain and spectral efficiency as well as the closer the output to the optimum complex Gaussian distribution.The bit error probability performance is estimated.The time domain OVTDM(Overlapped Time Domain Multiplexing) Coding,the dual of OVFDM in time domain is incidentally proposed as well.Both theoretical analysis and testified simulations show that OVFDM(OVTDM) is suitable for high spectral efficiency application and its spectral efficiency is only roughly linear to SNR rather than the well-known logarithm to SNR.

Effects of Stocking Density on Water Quality,Growth and Economic Benefits of Chinese Softshelled Turtle Pelodiscus sinensis in Ponds

The Chinese soft-shelled turtle Pelodiscus sinensis is a high-valued freshwater species cultured in China.This study investigated the effects of stocking density on water quality,growth performance and economic return of Pelodiscus sinensis cultured in ponds.P.sinensis were stocked at densities of 1 ind./m^2(LD:low stocking density) and 2 ind./m^2(HD:high stocking density) in 3 000-m^2 ponds,with three replicate ponds for each density.P.sinensis juveniles were fed with a commercial dry pellet feed of 46% crude protein and minced fillet of silver carp ans cultured for 122 days.The results showed that the levels of total nitrogen(TN),total phosphorous(TP),Chlorophyll-a(Chl.a) and turbidity in LD treatment were significantly lower than those in HD treatment(P<0.05).The mean TN and TP concentration in LD treatment was 29.3% and 35.7% lower compared to the HD treatment at the end of the experiment,respectively.Mean survival rates,final weight,average growth rates and PER were significantly higher in LD treatment compared with the HD treatment(P<0.05),respectively.Production was significantly affected by stocking density,which was higher in HD treatment,but the net income was higher in LD treatment.The results suggest that turtles with mean weight 55.6 g rearing at a low stocking density(1 ind./m^2) in ponds had a positive effect on overall economic return and was effective at improving turtle growth performance and water quality.

Matching between mechanics and thermodynamics among 4 individual strokes in a 4-stroke engine by non-circular gear mechanism

The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical simulation.The inherent mismatching between the mechanical behaviors and the thermodynamic process in internal combustion engine is identified,which is believed to be one of the important limiting factors of energy efficiency for conventional engines available in the current market.An approach for engine efficiency improvement through optimal matching between mechanics and thermodynamics(OMBMT)is proposed.An ideal matching model is defined and the conflicts due to the constraints among the mapping strokes in a 4-stroke engine are analyzed.A novel mechanical model is built for approaching optimal matching among all 4 individual strokes in a 4-stroke spark-ignition engine,which is composed of non-circular gears(NCG)and integrated with conventional slider crank engine mechanism.By means of digital mechanical model and numerical simulation,the matching gains among all 4 strokes are defined and calculated for quantifying the NCG engine efficiency improvement by comparing with a baseline engine.The potentials with the OMBMT implemented and the enhancements made by NCG mechanism for engines in terms of overall engine efficiency are reported.Based on the results achieved,it is recommended that the feasibility studies and the experimental validations should be conducted to verify the engine matching concept and effectiveness of the NCG mechanism engine model proposed,and the engine performance and NCG design parameters should be further optimized.

High-speed corner detection based on fuzzy ID3 decision tree

A high-speed comer detection algorithm based on fuzzy ID3 decision tree was proposed. In the algorithm, the Bresenham circle with 3-pixel radius was used as the test mask, overlapping the candidate comers with the nucleus. Connected pixels on the circle were applied to compare the intensity value with the nucleus, with the membership function used to give the fuzzy result. The pixel with maximum information gain was chosen as the parent node to build a binary decision tree. Thus, the comer detector was derived. The pictures taken in Fengtai Railway Station in Beijing were used to test the method. The experimental results show that when the number of pixels on the test mask is chosen to be 9, best result can be obtained. The comer detector significantly outperforms existing detector in computational efficiency without sacrificing the quality and the method also provides high performance against Poisson noise and Gaussian blur.

C波段单泵浦光子晶体光纤拉曼放大器

为了克服传统光纤的拉曼增益效率系数低,而且极不平坦给光纤拉曼放大器设计带来的复杂性和制造成本的提高,本文提出了一种新型双芯光子晶体光纤,通过对该光子晶体光纤横截面结构的合理设计,可使该光子晶体光纤在一定的波长范围内具有比传统光纤更高和更平坦的拉曼增益效率系数谱.利用该光子晶体光纤设计了一个波长范围在1530～1565nm的C波段拉曼放大器,数值计算结果表明,仅用一个泵浦的情况下,该光子晶体光纤拉曼放大器的平均增益可达8.7dB,且增益波动小于0.9dB,比标准单模光纤构成的拉曼放大器性能有非常大的提高.

Characteristics of on-chip dipole antenna using diamond for intra-chip wireless interconnect

In this paper,a 2-mm long on-chip dipole antenna pair on silicon substrate is simulated to investigate the transmission characteristics.A novel technique is proposed by employing a 0.35-mm thick diamond layer between silicon substrate and heat sink to improve antenna performance.The simulated transmission gain of this antenna pair with 1 mm separation on a 10-Ω cm silicon substrate increases by 9 dB at 20 GHz.A modified plane wave model involving diamond layer is also presented to explain gain improvement.Effects of dielectric variety,diamond thickness,substrate resistivity and antenna pair separation on transmission gain have been studied.The results indicate that thinner diamond layer along with high resistivity substrate is preferred.Our method makes integrated dipole antennas well suitable for intra-chip wireless interconnection which is known as a future solution to replace critical wiring interconnection.