应用自动分析仪测定天然橡胶标准胶NR中的氮含量

试验研究自动分析仪测定NR中氮含量，结果表明，自动分析仪测定NR中的氮含量，结果与凯氏法（国标方法）测定结果基本相同，两者无显著性差异，自动分析仪法测定氮含量缩短了消化时间，减少了人为因素的影响，具有自动化程度高，简便，快捷的优点。     

Time-dependent universal conductance fluctuations in IrO2 nanowires

Single-crystalline iridium dioxide nanowires show the time-dependent universal conductance fluctuations (TUCFs) at cryogenic temperatures. The conductance fluctuations persist up to temperature T as high as nearly 10 K. The root-mean-square TUCF magnitudes increase with decreasing T, reaching approximately 0.1 e² / h at 1.7 K. We ascribe these conductance fluctuations to originating from the conduction electrons scattering upon mobile defects (moving scattering centers). Our measured TUCF characteristics are satisfactorily explained in terms of the existing TUCF theory in its three-dimensional form. The extracted electron dephasing length L_φ(1.7 K) ≃90 nm is smaller than the diameter (≈ 180 nm) of our nanowires.     

Improved tracking of shunt active power filter by sliding mode control

An improved tracking technique of the reference current waveform in a shunt type active power filter is proposed in this paper using sliding mode control and feedback linearization. Feedback linearization approach helps to reduce the complexity of the controller. Excellent tracking is achieved in both for steady state and dynamic performance. A three-phase four-wire system is considered. The proposed algorithm is simulated first in MATLAB/SIMULINK. An experimental prototype using a dspace1104 based controller is also produced in the laboratory. Results from simulation match well with the corresponding results from experimental prototype confirming the usefulness of the proposed technique.     

Steady-state thermal heat conductivity in rotor of ball asynchronous motor

The problem of how to develop a mathematical model of the heat processes that take place in the rotor of a spherical asynchronous motor under the influence of internal heat sources is considered. An analytic model of the process is suggested that makes it possible to solve the problems of determination of the extreme thermal modes of a motor and is well suitable for the searching procedures of the construction optimization problems.     

Thermoeconomic considerations in the allocation of heat transfer inventory for irreversible refrigeration and heat pump systems

In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in irreversible refrigeration cycles and heat pumps with finite thermal capacitances. Investigation is made with respect to specified rate of cooling and heating for the refrigeration cycle and heat pump, respectively. Exact expressions are obtained without the use of an internal irreversibility parameter. The optimum hot-to cold-end unit cost ratio resulted in unequal division of heat exchanger conductances for the heat pump in contrast to the endoreversible case where they were the same. At a constant evaporator to condenser fluid temperature ratio, the COP of both refrigeration and heat pump systems was found to vary in an almost asymptotic manner in contrast to the endoreversible case where it was constant. In conclusion, it is best to measure the effect of internal dissipation by deriving exact mathematical expressions as the effect on some performance parameters could be lost due to the averaging effect of the internal irreversibility parameter.     

电导-紫外串联离子色谱法测定海水中的溴、碘离子

建立了电导-紫外串联离子色谱法测定海水中溴、碘离子的分析方法。样品采用滤膜净化处理,选用TSK Super ICA HR保护柱(4 mm×50 mm)和TSK gel Super IC-HR高性能分析柱(4 mm×250 mm),3.2 mmol/L Na2CO3-1.0 mmol/L Na HCO3为淋洗液。抑制电导和紫外检测器同时检测,碘离子使用紫外法检测以消除氯离子干扰。在优化条件下,整个分析过程8 min内完成。溴离子的方法检出限为2.2μg/L,碘离子的方法检出限为3.6μg/L,相对标准偏差(n=8)分别为1.36%~7.38%、1.97%~8.89%。采用加标法测定,回收率分别为94.5%~105.0%、94.9%~106.1%。     

火花塞陶瓷绝缘体高温分流电阻的研究

火花塞陶瓷绝缘体的高温分流电阻会影响火花塞的使用性能和寿命,笔者研究了氧化铝中Na2O含量、配方组成和烧结温度对火花塞陶瓷绝缘体高温分流电阻的影响。结果表明:随着氧化铝原材料中Na2O含量的增加,试样的高温分流电阻逐渐降低;在配方组成中,当CaO的含量由33%增加至40%,氧化铝原材料中Na2O含量为0.1%时,试样在500℃时的分流电阻由517MΩ提升至1 192MΩ;烧结温度低于1 580℃时,试样的高温分流电阻较低。     

35～1000kV线路绝缘子污闪电压值的估算

针对目前绝缘子污闪电压缺乏系统研究的现状,建立了35~1 000 kV输电线路用普通型绝缘子交流污闪电压的计算模型即展开普通型绝缘子成平面模型后分析交流污闪条件,计算出绝缘子在不同表面污层电导率条件下的临界污闪电压值;对35~1 000 kV输电线路用5种不同吨位的普通型绝缘子进行交流人工污秽试验,获其在各盐密下的50%污闪电压;通过计算值和试验值的对比,可将绝缘子表面污层电导率转化为盐密,从而算出各普通型绝缘子在不同盐密下的交流污闪电压值。试验验证计算结果误差小,说明该模型能够有效估算代表普通型绝缘子的50%污闪电压情况。该研究结果可供各电压等级输电线路外绝缘选择参改。     

阀控式"免维护"蓄电池组监控和故障预测

阀控式蓄电池虽被冠以"免维护"的称号,但并非"不用维护",事实证明了正确使用和维护好阀控式蓄电池,做好蓄电池的监控和故障预测工作,对保证设备状态及寿命是非常重要的.     

提高电容器外保护用熔断器的可靠性

围绕提高并联电容器外保护用熔断器的可靠性问题,提出合理选择电容器组接线方式和正确选用熔断器的额定电压、采用X-R控制图对熔丝加工工序进行质控、按照国标GB/T2828.1实施抽检计划,以及对工艺结构采取改进措施等,以期对熔断器的生产与应用有所裨益。