介质阻挡放电的分段负载模型和断续模式能量压缩方法

为优化大气压介质阻挡放电表面处理效果,提出了一种向放电负载注入断续电流实现能量压缩的方法。根据负载介质等效电容在放电和不放电阶段的不同形成机理,对传统负载模型的介质电容进行拆分,建立了一种分段负载模型及其参数测量方法。然后,利用断续电流模式谐振变换器的状态运行轨迹,并结合分段负载模型,推导出了谐振电感对有效放电时间的控制函数。最后,搭建了一台350 W谐振电源样机进行实验,实验结果表明：分段负载模型比传统负载模型更准确地描述了负载有效放电时间和能量压缩特性;通过调节断续电流模式谐振变换器的谐振电感,在功率为250 W和350 W、频率为20～40 kHz范围内实现了可控的能量压缩;在各个能量密度和工作频率下,被处理材料的表面亲水性随有效放电时间的缩短而增强。

实现全功率范围能量压缩的电流源谐振型等离子体驱动源

针对大气压介质阻挡放电材料表面处理应用,提出一种电流源谐振型等离子体驱动源。通过构建并-串联结构的谐振网络,在全功率范围内实现单周期能量传输时间的压缩,从而提高各个功率下的表面处理效果,并推导出一种判断能量压缩状态在全功率范围内稳定性的方法。然后,通过在逆变器上增加旁路辅助电容,建立电流旁路通路,从而实现开关管的零电压开关,保证了电源高效运行,并推导出辅助电容的选取原则。最后,搭建了一台350W电流源谐振型电源样机,实验结果验证了理论分析的正确性,表明电流源并-串联谐振型等离子体驱动源是一种适合于表面处理应用的有效方案。

电磁导波能量压缩式脉冲激励方法研究

电磁导波检测技术因其非接触耦合特性而被广泛应用于各种类型金属管道的损伤检测,但较低的激发效率却导致电磁导波信号能量传递范围有限,限制了其在长管道和结构复杂管道方面的应用。为提高电磁导波换能效率,本文摒弃了脉冲发生器和功率放大器相组合的激励源结构,提出了一种以能量压缩原理为核心的脉冲激发方法,在空间和时间上压缩存储于电容中的能量来提高激发信号强度,并确定了脉冲形成回路参数的选取规则。实验证明该方法可以有效增加电磁导波激发信号幅值。

利用能量压缩后的MBPD检测低信噪比声音事件

针对低信噪比下的声音事件检测问题,提出基于能量压缩和灰度增强的多频带能量分布图的声音事件检测方法。将声音数据的gammatone频谱转成能量谱,对不同频带的能量进行不同比例的能量压缩,计算其多频带能量分布图,并对其进行灰度增强;对调整后的多频带能量分布图进行8×8的分块,对每一子块进行奇异值分解,提取主要数值作为声音事件的特征;利用随机森林分类器对特征建模与检测。实验结果表明,在低信噪比环境下,该方法具有良好的检测效果。

压缩空气能量的度量基准探讨

为了对压缩空气进行节能,必须有衡量压缩空气具有多少能量的度量基准。本文从热力学基本概念出发,提出用总机械能来衡量静止压缩空气可以作机械功的能量。用总流动功率来衡量流动的压缩空气所具有的机械能。给出了简便的计算总机械能及总流动功率的公式。给出了测定总机械能及总流动功率的方法。这样,对任何复杂的充排气回路,都可以测定它们在一定时间内压缩空气所消耗的能量,从而进行节能分析和运行成本核算等工作。

压缩感知伪随机动态功率信号的电能测量方法

针对压缩感知检测方法不能准确测量伪随机动态测试信号电能量值的问题,该文首先分析了动态测试信号的频域稀疏性,证明动态测试信号满足压缩感知检测的条件;然后采用系统稳态优化的方法,构造了一种确定型压缩感知测量矩阵,证明其符合限制等距特性(RIP)条件,最后提出了一种新型压缩感知动态测试信号电能量的测量方法。实验结果表明:该文压缩感知测量方法的理论相对误差优于传统的采样功率电能测量方法,能够实现m序列动态测试信号的电能量值准确测量。

高比强多孔铝合金的压缩变形性能

采用渗流法制备了新型多组元、高比强多孔铝合金,研究了合金的单向压缩变形特征和能量吸收性能,讨论了孔壁厚度均匀性、孔隙率和强化热处理对性能的影响。结果表明;提高多孔铝合金的孔壁厚度的均匀度和强化热处理都显著提高多孔铝合金的压缩吸能性能;随着孔隙率的降低多孔铝合金的压缩强度增加。

大功率半导体激光器驱动电源的设计

高能激光系统通常需要多种输出模式的驱动电源，现有电源存在输出模式单一的问题。采用能量压缩技术和电流串联负反馈技术实现了多输出模式半导体激光器驱动电源。分析了特殊设计高输入阻抗差分运算电路作为负反馈网络的工作原理，推导出了精确的参考电压与输出电流的关系式。最后，将所研制的驱动电源应用于国内首台400W工业级光纤激光器系统中，驱动电源实现了0—26A连续可调、稳定度优于0．15％。的连续电流和准连续电流输出。测试结果验证了设计思路的可行性，实现了半导体激光器驱动电源的多输出模式和高电流稳定度。

高功率窄脉宽半导体激光激励器设计

为了获得高功率窄脉宽半导体激光,设计了半导体激光器相应的激励单元,论述MOSFET作为高速开关的工作机理,分析基于MOSFET作为高速开关产生窄的大电流脉冲的电路模型。为了使MOSFET开关速度尽可能快,根据前述分析,提出推挽式MOSFET栅极驱动方式并设计了触发窄脉冲的发生电路。当激光二极管接入放电回路时,实验表明:激光二极管输出光的峰值功率可达67.5 W,脉宽约为20 ns。最后,简要分析了影响光脉冲宽度的因素。

图像编码中的快速矢量变换算法

对图像采样数据进行矢量变换是实现图像矢量编码的重要组成部分 .本文针对矢量变换算法中存在着由矢量构成矩阵的维数和变换核矩阵维数不相等的问题 ,提出了一种新的矢量变换算法并对该算法的解相关能力和能量压缩能力进行了统计分析 .仿真实验结果表明该算法能较大地提高计算效率 .

Influence of hydrogen content on room temperature compressive properties of Ti-6Al-4V alloy at high strain rate

Electromagnetic forming tests were done at room temperature to reveal the influence of hydrogen content on the compressive properties of Ti-6Al-4V alloy at high strain rate. Microstructure was observed to reveal the mechanism of hydrogen-enhanced compressive properties. The experimental results indicate that hydrogen has favorable effects on the compressive properties of Ti-6Al-4V alloy at high strain rate. Compression of Ti-6Al-4V alloy first increases up to a maximum and then decreases with the increase of hydrogen content at the same discharge energy under EMF tests. The compression increases by 47.0% when 0.2% (mass fraction) hydrogen is introduced into Ti-6Al-4V alloy. The optimal hydrogen content for cold formation of Ti–6Al–4V alloy under EMF was determined. The reasons for the hydrogen-induced compressive properties were discussed.

数码涡旋多联机性能指标评价方法分析

针对近年来在市场上推出的以数码涡旋压缩机为主机的多联式空调(热泵)机组的工作原理和能量调节特征,基于不同能量调节方式下机组制冷量和输入功率随时间变化的实验研究,提出了以一定采样时间周期内机组总冷量和总输入功以及两者之比评价数码涡旋机组能量及效率指标的方法,为这类机组的性能测定和相关指标对比提供了有价值的参考.

一种适用于非连续工作状态的脉冲功率激励源

提出了一种应用于非连续工作状态的脉冲功率激励源的设计方案,该方案以功率场效应管为开关器件构成全桥功率放大电路,采用储能电容压缩能量提高功率,基于幅相调制方法调节输出功率,具有频率范围广、输出效率高和输出功率调节方便的特点,解决了仪器供电电源输出电流有限和要求激励源大功率输出之间的矛盾。

房间空气调节器实际运行性能测量方法研究

房间空气调节器的现场运行性能一直受到行业和用户的关注,亟待研发通用性强、精度较高、反映其实际使用状态的空调器运行性能参数的测量方法。本文提出了基于压缩机能量平衡法的各类空调器的现场性能测量方法及其精度改善措施,实验结果表明,该方法具有良好的制冷量、制热量及能效比测量精度。本研究为房间空调器的现场性能测量及其评价标准体系的构建提供了基础条件。

基于新阈值函数的小波阈值降噪方法

小波阈值降噪方法中,传统硬阈值函数连续性差,传统软阈值函数过于光滑,本文针对传统方法的缺点提出一种基于压缩能量思想的阈值函数。通过Matlab仿真表明,改进的阈值函数使用minimaxi阈值效果较好,改进的方案比传统的软、硬、半软阈值降噪能得到较高的信噪比,使信号得到较好的滤波效果。

Parametric Study of Two-Body Floating-Point Wave Absorber

In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber （FPA） with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter＇s efficiency when considering specific conditions.

Mechanical properties and energy absorption properties of aluminum foam-filled square tubes

Longitudinal and transverse mechanical properties and energy absorption properties of foam-filled square tubes under quasi-static loading conditions were studied.The foam-filled thin-walled square tube was fabricated with aluminum tube as its shell and closed-cell Al-Mg alloy foam as its core.The results indicated that the plateau region of the load-displacement curve exhibited a marked fluctuant serration which was clearly related to the formation of folds.The longitudinal deforming mode of foam-filled square tube was the same as that of the empty tube,but the fold number of foam-filled square tube was more than that of the empty tube.The longitudinal compression load and energy absorption value of foam-filled square tube were higher than the sum of that of aluminum foam (alone) and empty tube (alone) due to the interaction between tube and filler.In transverse direction,the compression load and energy absorption ability of foam-filled square tubes were significantly lower than those in longitudinal direction.

Effect of thermal treatment on energy dissipation of granite under cyclic impact loading

High temperature treatment causes thermal damage to rocks in deep mining.To study the thermal effect on the energy dissipation of rocks during the dynamic cyclic loading,cyclic impact loading experiments of heat-treated rocks were carried out using the splitting Hopkinson pressure bar(SHPB)experimental system.The correlations among the energy dissipation,energy dissipation rate,impact times,accumulated absorbed energy per volume,failure mode and temperature were analyzed.The results show that the reflected energy under the first impact increases and finally exceeds the absorbed energy when the temperature increases;however,the total reflected energy decreases above 200℃.The absorbed energy under the first impact and the total absorbed energy all decrease as the temperature increases,the rates of which decrease accordingly.And the same phenomenon appears for the transmitted energy and the rate of the transmitted energy.On the contrary,the rate of the reflected energy increases with the rising temperature.When the temperature increases,the fewer impact times are needed to destroy the sample.In addition,the failure modes are different when the rock is treated at different temperatures;that is,when the temperature is high,even though the absorbed energy is low,the sample breaks into powder after several impacts.

Rock excavation using surface miners: An overview of some design and operational aspects

Surface miner, a continuous mining machine, is being manufactured in India and abroad owing to enhanced demand of production in various mining industries like coal, limestone, gypsum, bauxite etc. Different types of surface miners are manufactured today based on cutting drum placement and design specifications. Selective mining without drilling and blasting, high production and small size products are some of the prominent attractive features obtained with these moving marvels. This machine can be used with good efficiency in soft to medium hard rock (100-120 MPa). This paper synthesizes the different applications, equipment models, features offered, operating methods, cutting performance assessment models as well as typical production performance of surface miner in coal and limestone mines of India. Engine hour metre reading, diesel and pick consumptions are linearly influenced by production. The emphasis for future research is also brought out.

Experimental investigation of effect of refrigerant gases,compressor lubricant and operating conditions on performance of a heat pump

In the field of heat pumps,there are a number of parameters that affect the performance and efficiency of the apparatus,which have been the subject of studies by individual researchers in the literature.This study describes an experimental method in order to investigate the effects of some significant parameters on heat pump performance.In this regard,a laboratory heat pump setup has been utilized to operate in different working conditions for achieving an appropriate estimation to find out effects of mentioned parameters such as refrigerant type and charge amount,compressor oil viscosity,compressor cooling fan,secondary fluids temperature and flow rate.Different refrigerants have been selected and used as circulating fluid in the installed heat pump.Although this work has been devoted to a detailed attempt to recognize the effects of various parameters on the coefficient of performance(COP) value,an appropriate method has been carried out to survey the obtained results by using economic analysis.It was revealed that one of the main parameters is refrigerant charge amount which has a notable effect on COP.The temperature of the heat source was also tested and the performance of the system increased by more than 11% by employing mentioned modifications and various operating conditions.In addition,by selecting a low viscosity compressor oil,the system performance increased by 18%.This improvement is more than 6% for the case that cooling fan is installed to cool the compressor element.