数学中的“并联电阻”(高一、高二、高三)

并联电路的总电阻R与分支电路的电阻R1,R2存在如下关系:两1/R1+1/R2=1/R.在数学中也有类似的关系式.1.

A Novel High Output Resistance Current Source Based on Negative Resistance

This paper presents a novel scheme for enhancing resistance that utilizes an equivalent negative resistance. Adopting this novel scheme in the proposed current source could remarkably boost its output resistance without requiring increased power supply. Simulation with 0.6μm CMOS process models shows that the output resistance of the novel current source can reach the order of 10^9Ω with a 1.04GHz bandwidth and only 10.6ppm/℃ in the range of -40～145℃.

Design of Parallel Electrical Resistance Tomography System for Measuring Multiphase Flow

ERT(electrical resistance tomography) is effective method for visualization of multiphase flows,offering some advantages of rapid response and low cost,so as to explore the transient hydrodynamics.Aiming at this target,a fully programmable and reconfigurable FPGA(field programmable gate array)-based Compact PCI(peripheral component interconnect) bus linked sixteen-channel ERT system has been presented.The data acquisition system is carefully designed with function modules of signal generator module;Compact PCI transmission module and data processing module(including data sampling,filtering and demodulating).The processing module incorporates a powerful FPGA with Compact PCI bus for communication,and the measurement process management is conducted in FPGA.Image reconstruction algorithms with different speed and accuracy are also coded for this system.The system has been demonstrated in real time(1400 frames per second for 50 kHz excitation) with signal-noise-ratio above 62 dB and repeatability error below 0.7%.Static experiments have been conducted and the images manifested good resolution relative to the actual object distribution.The parallel ERT system has provided alternative experimental platform for the multiphase flow measurements by the dynamic experiments in terms of concentration and velocity.

Measuring Method for Shunt Resistance of Solar Cell

Shunt resistance of solar cell must be monitored for large area solar cell manufactured with conventional process.A measuring method for the shunt resistance is derived from direct-current model.The shunt resistance of solar cell is obtained only by treating a part of I-V data.

Investigation of shunt solar cells’ currents based on equivalent circuit model

In view of the universality of the parallel connection of solar cells and their mismatch problem, in the present paper, we select two shunt solar cells (connected in parallel) as our research object, and use the equivalent one-diode circuit of the solar cell and the analysis of the two-body model. At first, the equations of current and voltage are deduced from the related electrical laws and the circuit diagram of the two solar cells connected in parallel. Then, according to the experimentally measured data of typical single-crystalline silicon solar cells (125 mm×125 mm), we select the appropriate simulation parameters. Following this, by using the photo-generated current, the shunt resistance, and the serial resistance of one of the shunt solar cells and the load resistance as independent variables, in turn, the changing characteristics of each branch current in the two shunt solar cells are numerically discussed and analyzed for these four cases for the first time. At the same time, we provide a simple physical explanation for the modeling results. Our analyses show that these parameters have different impacts on the internal currents of solar cells connected in parallel. These results provide a reference to solve the problem of connecting solar cells and to develop higher efficiency solar cells and systems. Meanwhile, the results will contribute to a better comprehension of the reasons for efficiency loss of solar cells and systems, and deepen the understanding of the electrical of solar cells behavior for high performance photovoltaic applications.

End Effect on the Twin-Wire Depth Probe

The end effect on the output voltage of a twin-wire depth probe was investigated both theoretically and ex- perimentally.It was found that the contribution of the end of the probe to the output voltage depends upon the distance between the boundary and the end of the probe and the geometrical configuration of the probe. By mounting a piece of plate to the end of the electrodes,the end effect can be reduced.However,the size of the plate required to eliminate completely this effect is much larger than that usually mounted on commercially available probes.Comparison between theoretical and experimental results was made.Reasonable agreement was obtained.