Electromagnetic interference assessment of a train-network-pipeline coupling system based on a harmonic transmission model

The harmonics and resonance of traction power supply systems(TPSSs)aggravate the electromagnetic interference(EMI)to adjacent metallic pipelines(MPs),which has aroused widespread concern.In this paper,an evaluation method on pipeline interference voltage under harmonic induction is presented.The results show that the Carson integral formula is more accurate in calculating the mutual impedance at higher frequencies.Then,an integrated train-network-pipeline model is established to estimate the influences of harmonic distortion and resonance on an MP.It is revealed that the higher the harmonic cur-rent distortion rate of the traction load,the larger the interference voltage on an MP.Particularly,the interference voltage is amplified up to 7 times when the TPSS resonates,which is worthy of attention.In addition,the parameters that affect the variation and sensitivity of the interference voltage are studied,namely,the pipeline coating material,locomotive position,and soil resistivity,indicating that soil resistivity and 3PE(3-layer polyethylene)anticorrosive coating are more sensitive to harmonic induction.Field test results show that the harmonic distortion can make the interference voltage more serious,and the protective measures are optimized.

Heat and Mass Transfer by Natural Convection during Transpiration trough a Porous Plate

Cooling by evaporation through transpiring porous walls is expanding in various industrial applications such as air conditioning. It is also used to cool water in a clay jug. This process deserves to be studied, understood and valued. This paper deals with the transpiration phenomenon through a saturated porous plate coupled with heat and mass transfer by natural convection. Conservation Equations (mass, momentum, energy and concentration), associated with adequate boundary conditions, have been numerically solved using an implicit finite difference iterative method. The numerical model has been validated by experimental measurements from holographic interferometry. The used method to obtain temperature and concentration profiles was explained. They are evaluated from the refractive index of moisture air in the boundary layer. The main numerical results presented are: Nusselt and Sherwood numbers, temperature, humidity, and velocity profiles within the boundary layer as well as the different heat fluxes exchanged between the plate and the surrounding environment. Besides, the present model allows showing the important effect of the equivalent thermal conductivity and the surface emissivity on temperature and heats flux.

The First-Order Comprehensive Sensitivity Analysis Methodology (1^st-CASAM) for Scalar-Valued Responses: II. Illustrative Application to a Heat Transport Benchmark Model

This work illustrates the application of the 1st-CASAM to a paradigm heat transport model which admits exact closed-form solutions. The closed-form expressions obtained in this work for the sensitivities of the temperature distributions within the model to the model’s parameters, internal interfaces and external boundaries can be used to benchmark commercial and production software packages for simulating heat transport. The 1st-CASAM highlights the novel finding that response sensitivities to the imprecisely known domain boundaries and interfaces can arise both from the definition of the system’s response as well as from the equations, interfaces and boundary conditions that characterize the model and its imprecisely known domain. By enabling, in premiere, the exact computations of sensitivities to interface and boundary parameters and conditions, the 1st-CASAM enables the quantification of the effects of manufacturing tolerances on the responses of physical and engineering systems.

Breaking efficiency limit of thermal concentrators by conductivity couplings

The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break this upper limit by considering the couplings of thermal conductivities and improve the concentrating efficiency of thermal concentrators. For this purpose, we first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by its geometric configuration. To go further, we explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or by adding the second shell with an isotropic thermal conductivity, thereby making the concentrating efficiency completely free from the geometric configuration. Nevertheless, apparent negative thermal conductivities are required, and we resort to external heat sources realizing the same effect without violating the second law of thermodynamics. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide guidance to other diffusive systems such as static magnetic fields and dc current fields for achieving similar behaviors.

Sensitive Determination of Five Priority Haloacetic Acids by Electromembrane Extraction with Capillary Electrophoresis

A method for sensitive determination of five priority haloacetic acids in drinking water has been developed for the first time based on electromembrane extraction(EME)prior to CZE with capacitively coupled contactless conductivity detection(CZE-C^(4)D).The target analytes were extracted from 10 mL of the sample solution(donor phase),through the supported liquid membrane(using a polypropylene membrane supporting 1-octanol),and into 10μL of 50 mmol/L NaAc solution(acceptor phase).The extracted solution was directly analyzed by CZE-C^(4)D without de-rivatization.Several factors that affect separation,detection and extraction efficiency were investigated.Under the optimum conditions,five haloacetic acids(monochloroacetic acid,dichloroacetic acid,trichloroacetic acid,mono-bromoacetic acid,and dibromoacetic acid)could be well separated from other components coexisting in water samples within 23 min,exhibiting a linear calibration over two orders of magnitude(r≥0.9943);the enrichment factors at 430-671 were obtained in a 30 min of extraction,and the limits of detection were in the range of 0.17-0.61 ng/mL.The intraday relative standard deviations for peak areas investigated at 10 ng/mL were between 1.2%and 9.7%for the combined EME-CZE-C^(4)D procedure.This approach offers an attractive alternative to the officially proposed method for purified drinking water analysis,which requires derivatization procedure prior to gas chromatography analysis.

Simple and cost-effective determination of ciprofloxacin hydrochloride by electrical micro-titration

By employing an electrical micro-titration system, in which a capacitively coupled contactless conductivity detector（C^4D） was used to monitor the reaction process in real time, herein a novel method for determining ciprofloxacin hydrochloride（CIPHCl） was developed for the first time. Mode 1： Standard CIPHCl solutions at different concentrations were loaded into reaction cells, respectively, and were titrated with standard Ag^＋. Upon the titration, the formation of a precipitate alters the number of ions in the solution, raising the change of conductivity, which was monitored by a special C-4 D to construct a titration curve. The endpoint of the titration was located from the peak of the curve. Between the elapsed time and the initial concentration of titrand, a linear relationship was established over the range of2.0–8.0 mmol/L. Mode 2： Standard Fe^3＋ took the place of Ag^＋, and was used as titrant to recognize ciprofloxacin contributed to the formation of complexation, which also resulting a change of solution conductivity. Under optimized conditions, a working range of 1.0–5.0 mmol/L CIPHCl was found. Because the reaction solutions were isolated from the working electrodes, this pioneer work shows significant simplicity and cost-effectiveness, by eliminating the requirements for detector exchange/renewal between different measurements, and by involving no auxiliary chemicals. Both of the two approaches were applied successfully to determine CIPHCl in tablet samples. And the results were in good agreement with those obtained by reference method.