万东程控X线机旋转阳极电路硬件和软件的故障及改进方法

万东程控X线机在中小医院里面的装机量很大,由于该机型在旋转阳极启动电路[1]中的硬件和软件设计上存在一定的改进余地,故本文对该部分电路提出了具体的改进方法,可以使该电路工作的更加稳定高效。

Sytec 2000i旋转阳极电路故障分析与诊断

1 Sytec 2000i旋转阳极电路原理经全波整流后的直流电源＋Vcc和-Vcc约276V,作为inverter模块的输入电源。inverter模块的作用是逆变,即把直流电再次整流成交流电,是由两块IGBT构成,其作用类似于晶匝管,在门控信号的作用下导通或是关断。正常的工作流程是：

Effect of gas bubble on cell voltage oscillations based on equivalent circuit simulation in aluminum electrolysis cell

A method to investigate the effect of gas bubble on cell voltage oscillations was established. The whole aluminum electrolysis cell was treated as a resistance circuit, and the dynamic simulation of the cell equivalent circuit was modeled with Matlab/Simulink simulation software. The time-series signals of cell voltage and anode current were obtained under different bubble conditions, and analyzed by spectral and statistical analysis methods. The simulation results show that higher bubble release frequency has a significant effect on the cell voltage oscillations. When the bubble coverage of one anode block exceeds 80%, the cell voltage may exceed its normal fluctuation amplitude. The simulation also proves that the anode effect detected by computer in actual production is mainly the whole cell anode effect.

Improvement of Electrical Performance of SOI-LIGBT by Resistive Field Plate

The electrical performance including breakdown voltage and turn-off speed of SOI-LIGBT is improved by incorporating a resistive field plate (RFP) and a p-MOSFET.The p-MOSFET is controlled by a signal detected from a point of the RFP.During the turning-off of the IGBT,the p-MOSFET is turned on,which provides a channel for the excessive carriers to flow out of the drift region and prevents the carriers from being injected into the drift region.At the same time,the electric field affected by the RFP makes the excessive carriers flow through a wider region,which almost eliminates the second phase of the turning-off of the SOI-LIGBT caused by the substrate bias.Faster turn-off speed is achieved by above two factors.During the on state of the IGBT,the p-MOSFET is off,which leads to an on-state performance like normal one.At least,the increase of the breakdown voltage for 25% and the decrease of the turn-off time for 65% can be achieved by this structure as can be verified by the numerical simulation results.

Corrosion pathways in aluminium alloys

The corrosion pathways in AA2024-T3, AA5083-O and AA6082-T6 alloys have been investigated. The objective of the investigation is to further the understanding of the complex localised corrosion mechanism in aluminium alloys. The investigation was carried out by examining the corroded surfaces of the alloys after potentiodynamic polarization tests in a 3.5% NaCl solution with the aid of a scanning electron microscope, and by analysing the flow of anolyte solution using the scanning vibrating electrode technique. The results revealed that the overall corrosion pathways in the alloys are distinctively different and are influenced by the flow of anolyte solution. Also revealed, was the fact that corrosion propagates in two ways （particularly in the AA5083-O and AA6082-T6 alloys）： an overall pathway in the corrosion front （filiform-like pathway in the AA5083 alloy and organized linear pathways in AA6082 alloy）; and the crystallographic channelling along the （100） directions. These are dependent on the grain distinct features of the AA5083-O and AA6082-T6 alloys and are not influenced by the presence of coarse second phase particles in these alloys, compared with the AA2024-T3 alloy, where the corrosion pathways are more dependent on the presence of second phase particles and grain boundary character.

The Analysis and Calculation on ECRH Anode Circuit on the HL-2A Tokamak

In the last year, ECRH system has been built in the HL-2A and the testing of gyrotron is also finished. In the project testing, one of the problems is current-peak occurring in the anode circuit of gyrotron. The current-peak is much larger than that of the value set in protection circuit. The frequent current-peak frequently occurring in the rising of anode-voltage often caused the protection circuit to mistaken trigger. The mistaken triggering often halted the normal gyrotron-testing. A set of equations of anode circuit are derived for analysis the phenomena of the current-peak. The calculation based on the deduced formula shows that value of the current-peak strongly depends on the inductance L, capacitance C and the ramp-time of anode voltage in the anode circuit. The conductance L and capacitance C are the characteristic inductance and capacitance of the cable that is used for anode HV power supply. The numerical calculation is exactly consistent with waveform of the current peak recorded by oscillograph, that means the derived formula are correct. In order to decrease the value of the current-peak, we should decrease capacitance C, and increase inductance L and ramp-time of anode voltage.

Solar-Powered Direct-Current Loads in Small Buildings

Traditional light bulbs （e.g., incandescent, fluorescent） use too much electricity, convert very little energy into light of sufficient quality and in their production use toxic contaminants. During the last few years, a new type of light source, LED （light emitting diode） bulb, has gained increasing popularity and its costs are set to plunge even further. LED bulbs offer many advantages over traditional sources, and they can be used as a direct replacement to existing lighting. This paper will use a spreadsheet-based analysis with hourly solar data supplied by Ecotect to show that, the efficiency of LED installations can be increased when used in conjunction with photovoltaic modules, as the two generate （and use） DC （direct-current） electricity, thereby eliminating intermediate-level losses in the electronic circuitry. If a storage battery is included, the solar panels generate electricity during the times when the occupants are not necessarily using the lighting, but the stored electricity can be used to power the lighting when the energy is required. The latest results demonstrate that, a slight reduction in the required floor area to be lit allows the solar-battery-LED system to be implemented in small buildings using a storage battery size that is within the range of present commercial devices.

二极管整流器的演示实验

高三物理课第五章电子管整流器一节的教材比较抽象,学生不容易理解,有如下几个难点: 1.二极电子管具有单向导电性,学生对此缺乏具体了解,实际意义更体会不深刻。2.当加在二极电子管上的板压一定时,改变灯丝电压,板流改变。当灯丝电压一定时,改变板压,板流也跟着改变。

意大利Odel血管机故障检修两则

故障现象一开机，做冠状动脉造影时，控制台发出报警声。同时台面显示“ANODESAFETY”字样。透视及曝光无射线。关机重启，故障依旧。故障分析与检修根据显示的“ANODESATETY”（阳极安全）信息可初步判断该故障与球管的旋转阳极和相关的保护电路有关。由电原理图分析得知，该旋转阳极电路是采用两组大功率可控硅模块（IGBT）组成的独立全桥逆变器为其提供电源，通过改变提高定子绕组中的电流频率来高速启动x线管旋转，使达到10000转／分以上。该电路处于高压高频状态下工作，首先应对其检查。

SnO_2 nanosheet as a photoanode interfacial layer for dyesensitized solar cells

SnO2 nanosheet films about 200 nm in thickness are successfully fabricated on fluorine-doped tin oxide （FTO） glass by a facile solution-grown approach. The prepared SnO2 nanosheet film is appfied as an interfacial layer between the nanocrystalline TiO2 film and the FTO substrate in dye-sensitized solar cells （DSCs）. Experimental results show that the introduction of a SnO2 nanosheet film not only suppresses the electron back-transport reaction at the electrolyte/FTO interface but also provides an efficient electron transition channel along the SnO2 nanosheets, and as a result, increasing the open circuit voltage and short current density, and finally improving the conversion efficiency for the DSCs from 3.89% to 4.62%.

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.

Study of crystalline silicon solar cells with integrated bypass diodes

This paper reported a novel method of integrating bypass diodes into crystalline silicon solar cells.Bypass diodes which have the opposite p-n junction were formed by printing specific paste on the local surface of solar cells using screen printing,while infrared laser was applied to isolate the diode from the cell after firing.A module of crystalline silicon solar cells with integrated bypass diodes was fabricated and the I-V characteristics were measured under different shade conditions.The experimental results clearly showed that the integrated bypass diodes can effectively stabilize module's short circuit current while reduce the module power loss when shaded as well.