Local Measurement Method Research Articles

Study on Local Measurement Method of Bus Short Circuit Capacity in Substation

The short-circuit capacity of the bus is a key parameter required for the operation and control of the power system. Online measurement of the short-circuit capacity is crucial for the observability and controllability of the power grid. In this paper, it is proposed that the bus voltage disturbance can be caused by switching on and off the parallel capacitor. According to the voltage disturbance, the on-line measurement of the short circuit capacity of the power grid can be performed. Based on the circuit model of the substation, using the substitution theorem and superposition principle of the linear circuit, the accurate calculation method of bus short-circuit capacity measurement is derived. It is revealed that the phase change of the voltage vector caused by the capacitor switching is the key factor affecting the measurement accuracy. It breaks through the approximate formulas of previous studies. The proposed measurement method has high accuracy; an iterative calculation method for the phase difference of the voltage vector is proposed. The method is more convenient and reliable than direct measurement. Based on MATLAB / Simulink, the substation bus and online measurement model are established. Simulation analysis of various scenarios shows that the proposed method has a measurement error of less than 1%, which is technically easy to implement and practically promote.

Development of wall and interfacial friction models for two-dimensional film flow with local measurement methods

Abstract Based on the advancement of computational capability, high-precision analyses of multi-dimensional thermal hydraulic phenomena in nuclear power plants have been carried out. One of the multi-dimensional phenomena is two-phase flow in the upper downcomer. The quantification of momentum transfer between a downward liquid flow and a transverse gas flow in the reflood phase is significant because it determines the bypass flow rate of the emergency core coolant (ECC). Multi-dimensional modules of thermal-hydraulic analysis codes have been used to simulate this multi-dimensional two-phase flow. However, the model and correlations incorporated in the multi-dimensional modules are ones developed from one-dimensional experimental results. Because the characteristics of multi-dimensional phenomena are different from one-dimensional conditions, the implemented models and correlations might produce inaccurate results. Therefore, new models based on multi-dimensional experimental data should be developed. This study involved the twodimensional, two-phase experiments performed using 1/10 and 1/5 scale facilities. These were simplified unfolded downcomers of the Advanced Power Reactor 1400 (APR1400). The local measurement methods, pitot tubes, ultrasonic thickness gauge, and depth-averaged PIV, were applied to measure local variables: air velocity, liquid film velocity, and liquid film thickness. Local experimental data on the two-dimensional film flow were used to produce the wall and to inform interfacial friction factors from two-dimensional, two-phase momentum conservation equations. New wall and interfacial friction models were developed incorporating newly proposed physical concepts.

Experimental study on two-dimensional film flow with local measurement methods

In an accident condition of a nuclear reactor, multidimensional two-phase flows may occur in the reactor vessel downcomer and reactor core. Therefore, those have been regarded as important issues for an advanced thermal-hydraulic safety analysis. In particular, the multi-dimensional two-phase flow in the upper downcomer during the reflood phase of large break loss of coolant accident appears with an interaction between a downward liquid and a transverse gas flow, which determines the bypass flow rate of the emergency core coolant and subsequently, the reflood coolant flow rate. At present, some thermal-hydraulic analysis codes incorporate multidimensional modules for the nuclear reactor safety analysis. However, their prediction capability for the two-phase cross flow in the upper downcomer has not been validated sufficiently against experimental data based on local measurements. For this reason, an experimental study was carried out for the two-phase cross flow to clarify the hydraulic phenomenon and provide local measurement data for the validation of the computational tools. The experiment was performed in a 1/10 scale unfolded downcomer of Advanced Power Reactor 1400 (APR1400). Pitot tubes, a depth-averaged PIV method and ultrasonic thickness gauge were applied for local measurement of the air velocity, the liquid film velocity and the liquid film thickness, respectively. The uncertainty of the depth-averaged PIV method for the averaged velocity of the liquid film was discussed. Also the local velocity profiles of air and liquid film and the liquid film thickness distribution were presented. These local experimental data of two-dimensional film flow which simulated the two-phase cross flow can be used to validate the multidimensional models in the system analysis codes and CFD codes.

A Tangential Induction Sensor for 3-D Analyses of Peripheral Flux Distributions in Transformer Cores

This paper concerns the detection of local magnetic induction in peripheral regions of transformer cores. Induction distributions are important for the interpretation of local losses and magnetostriction. Most authors use advanced numerical modeling-like FEM for the computation of local induction values. However, effective estimations tend to be impossible due to non-linearity, extreme anisotropy, and complex effects of hysteresis. As an alternative to FEM, the conventional method for local measurements is to use arrays of single-turn search coils. However, this method is laborious, and it affects the measured values in strong ways due to the thickness of the arranged wires and artifacts from the drilled holes. This paper presents a novel approach for peripheral core regions based on measurements with a tangential induction coil, i.e., a field coil with a ferromagnetic core. The sensor was tested on a model transformer core stacked from three packages of different widths of grain-oriented electrical steel, for the nominal induction of 1.7 T. As an advantageous effect, the sensor does not cause any interlaminar air gaps and detects the amplitude of the induction not only in planar, but also in lateral positions. Results from $\boldsymbol {\sim }100$ measuring positions are presented. They show that the induction distribution is inhomogeneous with variations up to $\boldsymbol {\sim }15$ %. High induction values were measured in the widest main package of the core, in contrast to much lower ones in the outer packages. On the other hand, the corners, yokes, and T-joints show much more uniformly flux distribution. The findings of this paper can be assumed to be relevant for industry in order to optimize the construction of cores for the purpose of their uniform utilization.

Body composition measurement methods and their clinical application

Body composition measurement could significantly facilitate evaluating the content of various body components, getting information about the health status and assessing the diagnosis, treatment, test, and prognosis of several diseases. Human health will be seriously affected by the imbalance of body composition. Body composition measurement methods are generally divided into local measurement methods and general measurement methods. The former ones include skinfold thickness measurement, ultrasonic measurement, computed tomography and nuclear magnetic resonance measurement; while the latter ones include anthropometry, underwater weighing measurement, air displacement measurement, biological resistance measurement, near infrared absorption measurement, dual-energy X-ray absorptiometry measurement, isotope dilution measurement, potassium isotope measurement and three-dimensional body scanning measurement, etc. This article reviews a variety of body composition measurement methods and their clinical application. Key words: Human body composition measurement method; Clinical application; Body fat

Practical Identifiability Analysis for the Characterization of Mass Transport Properties in Migration Tests

The common assumption of considering external mass transfer resistance as negligible can lead to a systematic bias that underestimates the actual diffusivity value. In this context, the suitability of two methods and the possible experimental setups (global or local concentration measurements) for determination of both diffusivity and mass transfer coefficient are discussed. The assessment was based on the experimental results of the desorption of Uvitex OB from low density polyethylene into the food simulant Miglyol 829. A practical identifiability analysis performed for each of the methods and experimental setups demonstrated that the increased amount of information provided by local measurement methods allows a better identifiability of the parameters, thereby reducing the experimental work and providing an unbiased method for determination of diffusivity.

A CO2 tracer-gas method for local air leakage detection and characterization

A method for local measurement of air leakage rate is presented that can be used to accurately and quickly assess leakage rates across a surface, such as around a valve or hatch in a pressurized gas tank or a window in a building. The method uses a small local enclosure with constant volume placed about a region on the structure under investigation (e.g., a window), which is depressurized and injected with a small concentration of carbon dioxide as a tracer gas. The time variation of the pressure and carbon dioxide concentration inside the enclosure are monitored and used to quantify the leakage flow rate as a function of pressure difference. This method uses a small enclosure with internal mixing so that a quasi-steady-state condition is quickly achieved. Because of the small size of the enclosure, advanced data processing techniques are necessary to reduce uncertainty in determination of the rate of change of the carbon dioxide concentration that arises from sensor variability. Results of a laboratory demonstration of the proposed leakage detection and characterization device are reported for the problem of leakage through a circular hole in a plate with prescribed pressure differences. Experimental results from the laboratory tests are found to be in excellent agreement with results of a numerical simulation of leakage flow through a hole, as well as predictions from a number of empirical equations for this problem found in the literature.

Report of a pilot study of quality improvement in nursing homes led by healthcare aides

Objective: Healthcare aides (unregulated care providers), who deliver the majority of direct care in Canadian nursing homes, have high levels of emotional exhaustion and cynicism. However, they also have remarkably high levels of job efficacy. Strategies to empower this workforce may reduce cynicism and draw on their high levels of job efficacy. The primary objective of this study was to act as proof-of-principle to determine whether quality improvement teams led by healthcare aides could be established in nursing homes and function on a daily basis. Methods: This study was a pilot test of a complex intervention using a mixed methods approach. We used a combination of education, networking and coaching to engage staff teams in quality improvement in 1 of 3 areas (pain control, skin care or behaviour management). We measured healthcare aides’ quality of work life, informal communication and research (best practice) use before and after the intervention. To understand the effect of quality of care at the bedside we used risk-adjusted quality indicators derived from Resident Assessment Instrument - Minimum Data Set 2.0 data. Results: A total of 10 teams participated in the intervention. At least 70% of the teams succeeded in learning and applying the improvement model and methods for local measurement. For 50% of the teams, data showed measurable improvement in the clinical areas. There were no significant differences between pre and post measures of survey variables. Conclusions: We have demonstrated the ability of healthcare aides to engage in quality improvement initiatives at the bedside in a collaborative environment and advance our results as an important contribution to person-centered healthcare.

Discrete Spectral Local Measurement Method for Testing Solar Concentrators

In order to compensate for the inconvenience and instability of outdoor photovoltaic concentration test system which are caused by the weather changes, we design an indoor concentration test system with a large caliber and a high parallelism, and then verify its feasibility and scientificity. Furthermore, we propose a new concentration test method: the discrete spectral local measurement method. A two-stage Fresnel concentration system is selected as the test object. The indoor and the outdoor concentration experiments are compared. The results show that the outdoor concentration efficiency of the two-stage Fresnel concentration system is 85.56%, while the indoor is 85.45%. The two experimental results are so close that we can verify the scientificity and feasibility of the indoor concentration test system. The light divergence angle of the indoor concentration test system is 0.267° which also matches with sunlight divergence angle. The indoor concentration test system with large diameter (145 mm), simple structure, and low cost will have broad applications in solar concentration field.

Pyroelectric scanning probe microscopy: A method for local measurement of the pyroelectric effect in ferroelectric thin films

This work demonstrates a surface scanning method for the quantitative determination of the local pyroelectric coefficient in ferroelectric thin films. It allows generating a map of the pyroelectric response with very high spatial resolution. In domains of previously aligned dipole moments (achieved by tip-assisted poling) small heat fluctuations are achieved by laser diode excitation from the sample's bottom side thus inducing changes in the surface potential due to the pyroelectric effect. Simultaneously, the surface potential variations are detected by scanning surface potential microscopy thus forming the base for the pyroelectric coefficient map. The potential of the method is demonstrated on the basis of ferroelectric semicrystalline copolymer thin films yielding local maxima of the pyroelectric coefficients up to $40\text{ }\ensuremath{\mu}\text{C}/{\text{m}}^{2}\text{ }\text{K}$. Another promising feature is the ability to visualize ``screened'' polarization thus enabling in-depth profiling of polarization distributions and domain formation and to study the composition dependence of ferroelectric nanodomains.

Micro-mechanical testing of SiLK by nanoindentation and substrate curvature techniques

Advanced micro-mechanical characterization methods provide material properties of thin films for modeling thermo-mechanical behavior of thin films for micro-electronic applications. Here, we focus on the local measurement method of nanoindentation for finding visco-elastic properties, and a global method of substrate curvature testing that provides linear elastic properties. Our specimen SiLK, Dow chemicals, is a low- k dielectric thin polymer film with a thickness of 400 nm, 6 and 8 μm, deposited on Si substrate. Our results show temperature dependent linear elastic and linear visco-elastic material properties for thin film materials.

Measurements of local interfacial area: application of bi-optical fibre technique

Local mean interfacial area in gas–liquid bubbly flow is experimentally investigated; data is obtained from the experiments carried out with a double optical sensor intrusive probe and analysed by statistical methods. Local variables are measured in the riser of an external loop airlift reactor in air/water medium. The results are presented in the form of the radial profiles of void fraction, bubble diameter and local average interfacial area at superficial gas velocities ranging from 0.003 to 0.11 m/ s . The axial variations of the same parameters are also investigated. The values of local interfacial area obtained from the classical equation ( a i t=6ε g/ d 32 ) and from bubble velocity statistical treatment methods agree reasonably well. This shows that the double optical probe is a reliable method for local measurements of interfacial area. Eventually, the maximum angle α 0 between the probe vertical direction and bubble velocity vector at the piercing point is evaluated and the influence of gas superficial velocity on α 0 is demonstrated.

Generalized theory of ion impact broadening in magnetized plasmas and its applications for tokamaks.

A generalized semiclassical theory of ion impact broadening in high-temperature, magnetized plasmas is developed that is free from a shortcoming of the standard semiclassical theories of Stark broadening, which were intrinsically divergent at small impact parameters. The convergence of the present theory is achieved by taking into account, on equal footing, both the "dynamic" splitting of Stark sublevels, caused by one of the components of the ion microfield, and the Zeeman splitting. The results are applied to a novel spectroscopic method for local measurements of an effective charge in tokamaks.

Electromagnetic refining of aluminum alloys by the CREM process: Part I. Working principle and metallurgical results

In the first part of this paper, the working principle of a new electromagnetic continuous casting process is described. The main peculiarities of this process are (1) the presence in the sump of a strong electromagnetically driven forced convection, which promotes the production of a fine equiaxed structure, and (2) the fact that the thickness of the segregation zone tends toward zero. Local measurement methods are applied to the study of electromagnetic and hydrodynamic phe-nomena inside the sump of aluminum alloy billets. Further, the evolution of both the grain size and the thickness of the segregated surface layer with the electric power input is presented. In summary, this new technology presents the advantages of avoiding the addition of grain refiners and substantially reducing the scalping operation.

Analysis for reflection from coaxial end attached to lossy sheet and its application to nondestructive measurement

AbstractIn this paper we proposed a nondestructive local measurement method for lossy sheet materials which are widely used as radiowave absorbers. We used a coaxial waveguide to measure the reflection coefficient at its end with an attached flange which touches the lossy sheet backed by a metallic foil. We showed an analytical solution for it and several experimental results. For the analytic analysis, we considered isotropic lossy sheets of both dielectric and magnetic materials. We derived definite integrals for the mutual admittance among multiple modes and the reflection coefficient for the coaxial TEM mode. These formulas were evaluated by numerical integrations. Solutions of these integrations generate errors due to terminated matrix operation for a certain finite limit (naturally they are of infinite dimensions). We showed that the precision of the solution was improved by applying Aitken's acceleration method. In practice we used two magnetic lossy sample materials whose dielectric constants and permeabilities were known. Through experimental measurements for these samples we confirmed the validity of the present analysis. Next we applied the present measurement method for dielectric constants for lossy samples with unknown dielectric constants. We indicated that the measurements by the present method had a higher reliability than those by the existing destructive method by using waveguide standing waves.

Local cytoplasmic calcium gradients in living mitotic cells

Cytoplasmic free calcium has been proposed as a regulator of many microtubule-mediated processes, including mitosis. It has been difficult to test this hypothesis because methods for local measurement of free Ca2+ in the living cell have not been available. We have used the fluorescent calcium indicator dye Quin-2 (methoxyquinoline-1bis(o-aminophenoxy)ethane-N,N,N',N' -tetra acetic acid), which allows such observations to be made by digital processing of fluorescent images from the light microscope. Here we report the application of this technique to the study of local Ca2+ concentrations in mitotic endosperm cells of Haemanthus sp., and show that there is transient increase in free Ca2+ at the mitotic spindle poles during anaphase. This locally high Ca2+ may provide a mechanism for the regional control of microtubules and other cytoskeletal elements during anaphase.

Progrès récents en métrologie diphasique

Click to increase image sizeClick to decrease image sizeThis review of recent progress in two-phase metrology is by no means exhaustive, having deliberately been limited to the description of a few methods and techniques developed in France during the last few years. Some of these have already been presented at Author's Seminary on Two-Phase Metrology (see special issue of La Houille Blanche No. 5, 1978). In this report, recent developments are discussed under the following headings : I. Measurement of interface areas and material transfer coefficients by a chemical method This method was developed and first applied by Charpentier, Laurent and Prost at the 'Ecole Nationale des Industries Chimiques' in Nancy. It is a global method for determining interface area and material transfer coefficients. A gas-liquid absorption process can take place without a chemical reaction (diffusion) or with one. Transfer coefficients can be determined from the former process, interface area from one with reaction. II. Measurement of two-phase flow boundary friction by an electro-chemical method This method was designed and tested by Cognet, Lebouche and Souhar at the 'Laboratoire d'Energétique et de Mécanique Théorique et Appliquée' in Nancy. It is an instantaneous, local measurement method based on the principle of the mass transfer equivalent of heat transfer applied in anemometry. The limit of electrolytic current produced by contact of two electrodes embedded in a pipe wall is a simple function of the local velocity gradient at the boundary. By using two electrodes, the direction of flow can be determined. III. Determination of the phase-indicating function in finely-dispersed two phase flow by an optical refraction method This method was developed by Danel in the 'Assistance Industrielle Dauphinoise' Company's laboratory. It is an extension of an earlier method designed by Danel and Delahaye (C.E.N.G.), using more efficient, miniaturized 40 µ diameter probes (20 µ at the sensitive tip) with a 1/10th microsecond response. IV. Determination of air-bubble or water droplet size by an optical diffusion method This method was designed and developed by Avellan and Resch at the 'Institut de Mécanique Statistique de la Turbulence' of Aix-Marseilles University. The prototype was produced by the A.I.D. Company. This is a local measurement method of the dimensions of bubbles or droplets passing through the measurement space. The flux diffused by each bubble or droplet in a perpendicular direction to the incident ray depends solely on the bubble or droplet diameter. The particle diameter detection range is from a few microns up to approximately a millimetre. V. Numerical processing of a hot-film anemometer output signal in cavity flow This study was carried out by Abel and Resch at Toronto University under a joint French-Canadian cooperation scheme. The method is a numerical method whereby gas and liquid phases in cavity flow (or mixed flow with bubbles and cavities) can be identified by processing the output signal from a hot-film anemometer in the flow.

Bone Density of the Ulna

Actual mineral content of 32 ulnae was determined by weighing the defatted and dehydrated bones and measuring their volume pycnometrically. The physical density of the distal cancellous part of the bone was calculated and the radiographic density of the distal cancellous part of the bone was determined using silver analysis of roentgen film and densitometry. The results were compared with those obtained earlier by a simple measurement of cortical thickness. The best results were obtained from densitometric scanning of the distal part of the bone but simple cortical measurement gave practically the same accuracy. Because none of the local measurement methods furnish a reliable estimate of mineral content in single cases, a simple cortical measurement is recommended in comparisons of large populations since the other local methods do not give more information in spite of their complexities.

Low-Frequency Microscopic Fluctuations in a Bounded Plasma

Low-frequency electron density fluctuations of a bounded homogeneous plasma are determined at large wavelengths. It is shown that, when the wavelengths are large, the frequency spectrum of fluctuation is determined by the mean square displacement of an electron in a time interval t, 〈Δ(t)2〉. Using a Brownian motion model for 〈Δ(t)2〉 which is exact at large t (as well as at small t), the frequency spectrum can then be evaluated by the method of steepest descents. The resulting spectrum is exact at zero frequency and provides a method for local measurements of diffusion cofficients by light scattering or direct probe measurement techniques. The results are valid regardless of the number of particles in a Debye sphere or of the extent of ionization.