汉语是联合国官方正式使用的6 种同等有效语言之一。请不要歧视汉语! Chinese is one of the six equally effective official languages of the United Nations. Not to discriminate against Chinese, please! 关于集成电路中研制可变电阻的建议 在集成电路中,目前已有场效应晶体管( field effect transistor )可以作为电压控制的可变线性电阻使用。 在实时性要求高的场合,可以将复杂的程序(软件)转换成相应的硬件集成电路,以提高计算的速度。 随着集成电路的集成度提高,导线(导体)之间的空间距离越来越近。这样分布参数的作用会越来越明显。在还没有达到量子力学性质占主导地位的情况下,直接使用导体之间的“场”传输信号时(即变废为宝),有可能制作出“半路、半场”类型的集成电路。这样,需要研制可变参数的元件(如可变电阻、电容和电感等),以实现相应的集成电路硬件内部参数的自动调节,实现对应软件中的“参数优化”功能。 如支持向量机、人工神经网络等,目前流行的普遍是软件。这样,它们的计算时间,特别是用于训练的时间会降低实时性。当采用相应的集成电路硬件后,预期训练时间和运算时间会明显减少,从而极大地扩展它们的使用范围。 需要高性能“可变参数元件”的硬件集成电路,还应包括“线性 PID 控制”、“模糊控制”等各种有广泛实际应用价值的集成电路。 除了现有的电压控制“可变参数电阻”外,还应该研制“电流控制的可变参数电阻”等。因为电流控制的元件,可能会有更高的抗干扰能力。在“半路、半场”类型的集成电路,电流控制元件有可能会降低设计的难度。把“场”更多地留给“信号传输”,把“电流/‘路’”尽可能留给元件。 参考资料: Moore Samuel K. 4 strange new ways to compute . IEEE Spectrum, 2018, 55(1): 10-11. https://ieeexplore.ieee.org/document/8241695 闵应骅,2018-01-12,放开思路,重振计算科学技术 (180112) http://blog.sciencenet.cn/blog-290937-1094444.html Macha Naveen Kumar, Chitturi Vinay, Vijjapuram Rakesh, 等. A new concept for computing using interconnect crosstalks . 2017 IEEE International Conference on Rebooting Computing (ICRC), Washington, NOV 08-09, 2017: 46-47. https://ieeexplore.ieee.org/document/8123636 杨正瓴. 关于“互容”概念的意义 . 电工教学,1995, 17(4): 35-39. 杨正瓴. 互容的定义和模型 . 科学通报,1990, 35(12): 960. 感谢您的指教! 感谢您指正以上任何错误! 感谢您提供更多的相关信息 !
上面两个动画是以电位为z轴做出来的,一个是单相情况,一个是双相情况。电路图如下: 其实电阻可以直接用正弦函数算,为了和前面统一还是把相量写出来吧。 图中已知条件为: (1). u S - u G = 60.0Sin →60.0 ∠ 0° (用最大值做相量); (2) . X 为电阻,则: Z=13.66→13.66 ∠ 0.0° , 所以 i 总 → 4.39 ∠ 0.0° ;然后可以利用电流算出分压: u BG →22.0 ∠ 0.0° ; u AB →22.0 ∠ 0.0° ; u SA →16.1 ∠ 0.0° ; 1. 单相情况 单相情况 u G =0 ,电压相位相同。 下图是相量及正弦动画: 正弦函数的横坐标与标示的不同, 4π 对应60,否则波形太密集了。 2. 双相情况 双相情况类似差分放大电路里的差模信号,可设 u O = ( u S + u G ) /2=0 ,则: u SO →30.0 ∠ 0.0° ; u GO →30.0 ∠ 180.0° ; u AO = u SO - u SA →13.9 ∠ 0.0° ; u AB →22.0 ∠ 0.0° ; u BO = u GO + u BG →8.0 ∠18 0.0° ; 下图是相量及正弦动画:
Journal of Power Sources Volume 256 , 15 June 2014, Pages 449–456 Bulk and contact resistances of gas diffusion layers in proton exchange membrane fuel cells Donghao Ye a , b , Eric Gauthier a , Jay B. Benziger a , , , Mu Pan b a Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA b State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China Received 23 October 2013, Revised 14 January 2014, Accepted 17 January 2014, Available online 24 January 2014 http://dx.doi.org/10.1016/j.jpowsour.2014.01.082 Get rights and content Highlights • Direct measurement of gas diffusion layer bulk and contact resistances. • Teflon treatment increases GDL contact resistance with no change of bulk resistance. • Microporous layer decreases contact resistance. • Uneven compression under channels and ribs deforms GDL, breaking electrical contact. Abstract A multi-electrode probe is employed to distinguish the bulk and contact resistances of the catalyst layer (CL) and the gas diffusion layer (GDL) with the bipolar plate (BPP). Resistances are compared for Vulcan carbon catalyst layers (CL), carbon paper and carbon cloth GDL materials, and GDLs with microporous layers (MPL). The Vulcan carbon catalyst layer bulk resistance is 100 times greater than the bulk resistance of carbon paper GDL (Toray TG-H-120). Carbon cloth (CCWP) has bulk and contact resistances twice those of carbon paper. Compression of the GDL decreases the GDL contact resistance, but has little effect on the bulk resistance. Treatment of the GDL with polytetrafluoroethylene (PTFE) increases the contact resistance, but has little effect on the bulk resistance. A microporous layer (MPL) added to the GDL decreases the contact resistance, but has little effect on the bulk resistance. An equivalent circuit model shows that for channels less than 1 mm wide the contact resistance is the major source of electronic resistance and is about 10% of the total ohmic resistance associated with the membrane electrode assembly. Graphical abstract Keywords Contact resistance; Lateral resistance; Gas diffusion layer; Catalyst layer; PEMFC
24 岁研究生 Edwin H. Hall 于 1879 年的发现:在磁场中的载流导体上会出现横向电势差。这称作 Hall 效应。 1. Hall 效应的应用 可通过上下底面的电势高低来判断载流子的类型(电子或空穴); 可计算载流子的浓度(单位体积内载流子的个数); 可比较精确的测量磁场强度。 2. Hall 效应的推广 Klitzing 发现磁场强度 B 一定大 (比如 5 到 15 T )时, Hall 电阻并非与 B 成正比 (Hall 效应说 Hall 电阻与 B 成正比),而是“量子”的。据此,其获得 1985 年 Nobel 物理学奖; D.C. Tsui (崔琦) 与 H.L. Stomer 发现在磁场强度更强 (比如 20 到 30 T)时,Klitzing 的“量子”可以是分数,而荣获 1998 年的 Nobel 物理学奖。
传统铜线局限性之一就是由于金属电阻引起的电线发热,而导致一部分电能由于导线发热而损失。然而,由超导材料组成的导线因为不存在电阻,所以可以传导电能更有效。而以前在超导材料方面的尝试已经证明,其脆性和成本昂贵是其致命弱点。但是,以色列特拉维夫大学(Tel Aviv University)的研究人员现在已经研制了一种新型的超导材料,他们声称,在同样粗细的情况下,超导电线携带的电能是铜线的40倍。 特拉维夫大学的研究团队他们研制的超导线,是由蓝宝石单晶光纤以及陶瓷混合物等制成。每根导线比人的头发略粗一些,尽管他们能转移大量的电,但是他们为了维持超导状态必须不断冷却。冷却的责任是由一自带冷却系统来完成,以廉价液氮作为制冷剂。Boaz Almog博士是特拉维夫大学的研究团队成员之一,是他们研发出超导电线,相信这项技术将会使遥远的可再生能源,传输到城市电网。高功率超导电缆占用空间少,载能效率高,是部署整个城市电网的理想材料。也可以实现以最有效的方法收集可再生能源如太阳能和风能。超导线也可以用于储能,使设备强化电网的稳定性。 Read more at Gizmag Emerging Technology Magazine 但是特拉维夫大学制成的蓝宝石纤维超导电缆,其中也有美国橡树林国家实验室( Oakridge National Lab )的功劳,使用的蓝宝石纤维是由 Sapphire Systems 公司提供,蓝宝石材料其实就是alpha-Al 2 O 3 , 属于三方晶系,其相关性质如下: Properties of Sapphire Thermal Melting Point: 2053°C (3727°F) Maximum-Use Temperature: 2000°C Specific Heat: 0.18 cal/g-K (25°C), 0.3 cal/g-K (1000°C) Thermal Conductivity:40 watts/m-K (25°C),10 watts/m-K (1000°C) Thermal Expansion Coefficient (25 - 1000°C): 8.8 x 10 -6 K -1 parallel to C-axis, 7.9 x 10 -6 K -1 normal to C-axis Physical/Mechanical Density: 3.97 g/cm 3 (25°C) Young's Modulus (parallel to C axis): 435 GPa (63 x 10 6 psi)at 25°C, 386 GPa (56 x 10 6 psi)at 1000°C Shear Modulus: 175 GPa (26 x 10 6 psi) Poisson's Ratio: 0.27 - 0.30 Flexural Strength: 1035 MPa (150 ksi) parallel to C axis (25°C), 760 MPa (110 ksi) normal to C axis (25°C) Compressive Strength: 2 GPa (300 ksi) 25°C Hardness: 9 Moh's scale. 1900 Knoop (parallel to C axis), 2200 Knoop (normal to C axis) Optical Uniaxial Negative Refractive Index (parallel to C axis): Ordinary rayN o = 1.768, Extraordinary ray N e = 1.760, Birefringence = 0.0087 Temperature Coefficient of Refractive Index: 13 x 10 -6 K -1 (visible range) Spectral Emittance: 0.1 (1600°C) Spectral Absorption Coefficient: 0.1 - 0.2 cm -1 (25 - 1600°C) Electrical Volume Resistivity (ohm-m): 10 16 at 25°C, 10 10 at 500°C, 10 7 at 1000°C Dielectric Strength: 480,000 volts/cm (1,200 volts/mil) Dielectric Constant (25°C, 10 3 - 10 9 Hz): 11.5 parallel to C axis; 9.3 normal to C axis Loss Tangent ( 10 10 Hz, 25°C): 8.6 x 10 -5 parallel to C axis, 3.0 x 10 -5 normal to C axis Magnetic Susceptibility: 0.21 x 10 -6 parallel to C axis; 0.25 x 10 -6 normal to C axis Chemical Weathering Resistance: Unaffected by atmospheric exposure Sea Water Resistance: Unaffected by marine exposure Biological Resistance: Unaffected by in-vivo exposure; non-thrombogenic; non-reactive with body fluids AF Tel Aviv University