自驱动植入式能源收集器件的研究进展

植入式医疗电子器件对于人体健康监测及治疗至关重要,其正常运转需要外界电池供能,而 电池电能耗尽后需要二次手术更换,该过程会对病人身心造成二次伤害并带来沉重的经济负担。人体 运动的机械能和体内的化学能,如心跳、呼吸、血液循环和葡萄糖的氧化还原等,都具有转化为电能 的潜力。近年来,自驱动能源收集技术的不断发展使得体内能量被有效收集后,可为植入式医疗电子 器件供能。自驱动植入式能源收集器件主要包括压电纳米发电机、摩擦纳米发电机、光伏电池、热释 电发电机、自驱动腕表、生物燃料电池和耳蜗内电位收集器等。该文讨论了植入式能源收集器件的种 类、代表性应用及现存的挑战,并对其未来的应用进行了展望。     

圆片级低真空封装的MEMS压电振动能量收集器结构设计

MEMS低真空封装技术能为MEMS器件的可动部分提供低阻尼环境,降低能量损耗,有效提高器件的能量转换效率,具有重要的研究意义和应用前景,是MEMS技术的研究热点和难点。为了进一步提高MEMS压电振动能量收集器的输出性能,提出了圆片级低真空封装的共质量块MEMS压电悬臂梁阵列振动能量收集器新结构,通过有限元分析方法对器件结构参数进行了优化设计,在优化结构参数下仿真器件输出性能：在610 Hz、2 gn加速度下,器件的输出电压为8.88 V,输出功率为1220μW,能满足实际应用需求;根据器件结构设计了加工工艺流程,对低真空封装结构的实现和封装工艺探索具有重要意义。     

基于静电纺丝法制备P(VDF-TRFE) /石墨烯(GR)薄膜的柔性复合压电纳米发电机

提出了一种利用静电纺丝工艺制备P(VDF-TRFE)/石墨烯(Graphene,以下简称GR)复合纳米纤维薄膜的方法并对其压电性能进行了研究。首先,以复合薄膜为功能层设计并制备了柔性压电纳米发电机。使用扫描电镜(SEM)表征了复合纤维薄膜表面的微观形貌。其次,对各纳米发电机样品进行了压电响应对比实验,含0.2%石墨烯的P(VDF-TRFE)/GR纳米发电机的开路输出电压、短路输出电流峰值分别为12.3 V、1.41 μA,比纯P(VDF-TRFE)样品分别增加了大约2.0倍、2.2倍。此外,通过理论分析和周期激振测试探究了纳米发电机电响应输出的影响因素和规律,证实在激振器驱动信号150 mV^300 mV振幅、10 Hz^30 Hz频率的范围内,其开路输出电压随着其振幅和振动频率增大而增大,电容充电效率随其振幅增大而增大。     

一种PWM结合PFM的ZVS准谐振变换器

准谐振变换器可以实现功率器件的零电压或零电流开关,但要得到稳定输出电压需采用脉冲频率调制(PFM),这给功率电路参数设计和系统稳定性带来困难,本文研究一种PFM结合PWM的控制模式来调节准谐振变换器输出电压,并实现其开关管的软开关,该控制方案与电压调节器协调工作,调节功率管驱动信号的脉宽和频率,保证了软开关条件和降低导通损耗,实现高频高效的功率变换。建立了100W升压准谐振变换器样机,实验结果验证了该控制方案的可行性。     

DC/DC开关电源模块并联供电系统均流控制研究

介绍了由两个DC/DC开关电源模块并联构成的供电系统电路结构和工作原理。该系统采用ARM芯片STM32为主控芯片产生驱动功率开关器件MOSFET的PWM脉冲[1],对供电系统的输出电压和各个模块的输出电流均实现了全数字闭环PI控制。系统输出电压稳定,能实现两个模块电流的比例分配,同时具有输出负载短路及延时恢复功能。仿真和实验结果验证了控制技术的正确性和可行性。     

0～50V连续可调开关电源

描述了输出电压从０至５０伏连续可调式开关直流稳压电源的原理，结构。电源采用功率ＶＭＯＳ器件制作，具有驱动功率小，电路结构简单等特点，电路设计了过载保护功能，最大输出功率可达１００Ｗ，输出纹波峰值小于６０ｍＶ，效率达８０％左右。     

转速—电压转换装置

在转速反馈控制系统中,通常由测速发电机来检测电机转速,输出与转速成线性关系的电压作为反馈控制信号。这里介绍的是一种用电子元件组成的测速装置,它具有测边发电机的功能,整个电路结构简单,价格低,耗能少,体积小,重量轻。装置原理如图1所示,在电机轴端上装一个圆盘,在其边缘开有分布均匀的小孔。通过光耦元件(如光电断续器)将电机的转速变成脉冲信号。该脉冲信号的频率正比于电机的转速。然后利用压控电源带通滤波器,将频率量转化成电压量,使它们成线性关系,电路如图2所示。在选择压控电压源通带滤波器的电路元件参数时,尽可能使工作段的频率与输出电压成正比关系,压控电压源通带滤波器的幅频特性如图3所示,工作段在中心频率ω_0以下,并留一定的余量。     

基于八悬臂梁-中心质量块结构MEMS压电振动能量采集器

高能量密度输出、低频范围响应、环境适应性强的自供电振动能量采集器已成为微能源技术领域的一个重要发展方向。提出一种d31型工作模式下MEMS压电式振动能量采集器,设计八悬臂梁-中心质量块结构代替传统的单悬臂梁结构,利用溶胶-凝胶（Sol-Gel）技术在每个悬臂梁上异质集成制备锆钛酸铅（Pb（Zr0.53Ti0.47）O3,PZT）压电功能厚膜层,通过MEMS工艺和引线键合技术完成器件础结构制造。输出性能测试结果表明,器件一阶谐振频率为41 Hz,3 gn加速度激励下输出电压峰峰值为264.00 mV;在器件两端加载3.00 MΩ负载时输出功率最大,为0.72 nW。     

基于高压静电纺丝法制备P(VDF-TrFE)/ZnO/GR复合膜压电性能的研究

提出了一种利用高压静电纺丝法制备P(VDF-TrFE)/ZnO/Graphene(以下简称GR)复合纳米纤维薄膜的方法，并对其压电性能进行了研究。首先，利用扫描电镜（SEM）观测复合薄膜的表面形貌并分析其X射线衍射（XRD）图谱。其次，将薄膜封装为三明治结构的压电纳米发电机(PNG)并研究了其压电性能。结果表明，含10%ZnO、0.1%GR的P(VDF-TrFE)/ZnO/GR复合薄膜压电纳米发电机开路输出电压和短路输出电流峰值为12.6V、7.88μA，约是纯P(VDF-TrFE)薄膜的2.7倍、3.1倍。在激振力大小3.5N，频率为5HZ的条件下P(VDF-TrFE)/ZnO/GR压电纳米发电机的最大瞬时输出功率为33.85μW，持续激振21分钟后，LTC3588-1毫微功率能量收集电源可以稳定输出3.3V电压1.5s。P(VDF-TrFE)/ZnO/GR压电纳米发电机具有良好的压电性能，具有成为自供电设备的潜力。     

基于DSP的离网型永磁同步发电机电压调节器

针对目前离网型永磁同步发电机输出电压不稳定及难以调节的问题,先将输出电压整流成直流电压,再将直流电压逆变为交流电压输出。逆变电路采用SPWM算法,并以DSP作为控制核心。经过整流、逆变后,发电机的输出电压稳定,并且能对输出电压方便地进行调节。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).