Optical time-domain reflectometer specifications and performance testing

From a researcher's as well as a user's point of view, it is highly desirable to adopt a common basis for specifying optical time-domain reflectometer performance parameters. This paper proposes some procedures and test methods which permit these devices to be characterized in a consistent way. Passive test fixtures are also described which may facilitate measurements of dynamic range and other reflectometer properties.     

Optical communication noise rejection using correlated photons

This paper describes a completely new way to perform noise rejection using a two-photon sensitive detector and taking advantage of the properties of correlated photons to improve an optical communications link in the presence of uncorrelated noise. In particular, a detailed analysis is made of the case where a classical link would be saturated by an intense background, such as when a satellite is in front of the sun, and identifies a regime where the quantum correlating system has superior performance.     

太赫兹时域谱的动物皮革光学特性

利用THz时域谱技术对猪皮、牛皮、羊皮在0.2~1.7 THz波段的吸收特性进行了研究.精确测量其折射率、吸收系数等光学参数用于对皮革成分分析以及质量评价,获得了三种皮革样品的吸收峰位置.该研究成果表明,THz-TDS技术可以用于对皮革成分快速检测.     

Fabrication and performance improvement of Ag grid transparent conducting films using selective laser ablation

Journal of Materials Science: Materials in Electronics - Silver (Ag) grid transparent conducting films (TCFs) were firstly fabricated by selective laser ablation of Ag thin films prepared by radio...     

Experimental study on the improvement of CO2 air conditioning system performance using an ejector

Several preceding researches have evidenced that the transcritical air conditioning system using CO₂ as a refrigerant has an inherent inefficiency resulting in degraded steady-state system performance of a CO₂ air conditioning system compared with that of a conventional air conditioning system. As a practical improvement, two-phase ejector was considered in place of expansion device in this study. The two-phase ejector for CO₂ air conditioning system was designed and developed considering the non-equilibrium state for evaluating the sonic velocity and the critical mass flux. The experiments of performance with respect to variation of ejector geometry such as the motive nozzle throat diameter, mixing section diameter and the distance between motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. Experiments showed that the coefficient of performance of the system using an ejector was about 15% higher than that of the conventional system.     

Simulation and performance evaluation of shunt hybrid power filter using fuzzy logic based non-linear control for power quality improvement

This paper deals with design and simulation of a three-phase shunt hybrid power filter consisting of a pair of 5th and 7th selective harmonic elimination passive power filters connected in series with a conventional active power filter with reduced kVA rating. The objective is to enhance the power quality in a distribution network feeding variety of non-linear, time-varying and unbalanced loads. The theory and modelling of the entire power circuit in terms of synchronously rotating reference frame and leading to a non-linear control scheme is presented. This work involves introduction of individual fuzzy logic controllers for d and q axis current control and for voltage regulation of the DC link capacitor. The simulation schematic covering the power and control circuits have been developed taking into account severe harmonic distortion caused by non-linear and unbalanced loads. The effectiveness of the fuzzy logic controller for the compensation of harmonics and reactive power has been verified by successive simulation runs and analysis of the results. The proposed controller is also able to compensate the distortion generated by the voltage- and current-fed non-linear loads, unbalanced and dynamically varying loads. Further, excellent regulation of the DC link voltage is accomplished, which significantly contributes to improvement of power quality.     

Amélioration de la performance des machines frigorifiques á absorption par l'utilisation de cycles à absorption et désorption étagésPerformance improvement of absorption cooling systems by using staged absorption and desorption cycles

This study deals with staged absorption and desorption cooling systems which increase the performance of absorption cycles that are driven by only low-grade energy, particularly when the working fluids are NH₃---H₂0. Instead of working with only one absorber, these systems use a cascade of absorbers composed by one operating at the evaporator pressure, followed by a series of absorbers operating at staged pressures P_j, between P_ev and P_c In the same way, a cascade of generators is used for desorption. For the same operating parameters for other equipment and the same COP, the systems that we propose permit the generators to run at temperatures below those of all other systems offered up to now and using the same working fluids. When T_ev = −10°C, T_a = T_c = 30°C, the temperature of the generators can be as low as 65°C while the COP of the system is 0.258 and the COP_ex 0.317. By increasing the temperature of generators to 85°C while maintaining the other parameters at the same values, COP becomes 0.374 and the COP,, 0.336. These results improve the performance of absorption systems using only low-grade energy (T < 100°C). Particularly, they are better than the performance of two-stage absorption systems which consist of two single-stage absorption cycles coupled with each other through the evaporator of the first cycle and the absorber of the second cycle. With the same operating parameters indicated above for our system at the evaporator, the condenser, and the absorber, these coupled cycles need temperatures at generators of 80 and 100°C, whereas they give a COP of only 0.270