• Title, Summary, Keyword: Local measurement

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Analysis of the Local Air-Change Effectiveness by Field Measurement (실험을 통한 환기시스템의 국소적 환기효율 분석)

  • Choi, Younhee;Song, Doosam
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.2
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    • pp.63-67
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    • 2017
  • The purpose of this study is to analyze the Age of Air and the Local Air-change Effectiveness of by field measurement. The indexes of Age of Air and Local Air-change Effectiveness are used to analyze the local ventilation effectiveness of multiple locations and are mainly evaluated using the computational fluid dynamics (CFD) method. In this study, measurement of the Local Air-change Effectiveness was based on ASHRAE 129. The performance of Local Air-change Effectiveness and the dependence of the outlet location on Local Air-change Effectiveness were analyzed. The results showed that a greater air-change rate (ACH) may not guarantee better local ventilation effectiveness.

Measurement of local wall temperature and heat flux using the two-thermocouple method for a heat transfer tube

  • Ahn, Taehwan;Kang, Jinhoon;Jeong, Jae Jun;Yun, Byongjo
    • Nuclear Engineering and Technology
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    • v.51 no.7
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    • pp.1853-1859
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    • 2019
  • The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

On the Local Identifiability of Load Model Parameters in Measurement-based Approach

  • Choi, Byoung-Kon;Chiang, Hsiao-Dong
    • Journal of Electrical Engineering and Technology
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    • v.4 no.2
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    • pp.149-158
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    • 2009
  • It is important to derive reliable parameter values in the measurement-based load model development of electric power systems. However parameter estimation tasks, in practice, often face the parameter identifiability issue; whether or not the model parameters can be estimated with a given input-output data set in reliable manner. This paper introduces concepts and practical definitions of the local identifiability of model parameters. A posteriori local identifiability is defined in the sense of nonlinear least squares. As numerical examples, local identifiability of third-order induction motor (IM) model and a Z-induction motor (Z-IM) model is studied. It is shown that parameter ill-conditioning can significantly affect on reliable parameter estimation task. Numerical studies show that local identifiability can be quite sensitive to input data and a given local solution. Finally, several countermeasures are proposed to overcome ill-conditioning problem in measurement-based load modeling.

Local Flow Speed Measurement Using Tunable AC Thermal Anemometry

  • Chung Won Seok;Kwon Ohmyoung;Lee Joon Sik;Choi Young Ki;Park Seungho
    • Journal of Mechanical Science and Technology
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    • v.19 no.7
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    • pp.1449-1459
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    • 2005
  • This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.

Electrical Spin Transport in n-Doped In0.53Ga0.47As Channels

  • Park, Youn-Ho;Koo, Hyun-Cheol;Kim, Kyung-Ho;Kim, Hyung-Jun;Han, Suk-Hee
    • Journal of Magnetics
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    • v.14 no.1
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    • pp.23-26
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    • 2009
  • Spin injection from a ferromagnet into an n-doped $In_{0.53}Ga_{0.47}As$ channel was electrically detected by a ferromagnetic detector. At T = 20 K, using non-local and local spin-valve measurements, a non-local signal of $2\;{\mu}V$ and a local spin valve signal of 0.041% were observed when the bias current was 1 mA. The band calculation and Shubnikov-de Haas oscillation measurement in a bulk channel showed that the gate controlled spin-orbit interaction was not large enough to control the spin precession but it could be a worthy candidate for a logic device using spin accumulation and diffusion.

Trust-Tech based Parameter Estimation and its Application to Power System Load Modeling

  • Choi, Byoung-Kon;Chiang, Hsiao-Dong;Yu, David C.
    • Journal of Electrical Engineering and Technology
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    • v.3 no.4
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    • pp.451-459
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    • 2008
  • Accurate load modeling is essential for power system static and dynamic analysis. By the nature of the problem of parameter estimation for power system load modeling using actual measurements, multiple local optimal solutions may exist and local methods can be trapped in a local optimal solution giving possibly poor performance. In this paper, Trust-Tech, a novel methodology for global optimization, is applied to tackle the multiple local optimal solutions issue in measurement-based power system load modeling. Multiple sets of parameter values of a composite load model are obtained using Trust-Tech in a deterministic manner. Numerical studies indicate that Trust-Tech along with conventional local methods can be successfully applied to power system load model parameter estimation in measurement-based approaches.

The Effect of Local Basis Weight on Local Strain (지역 평량이 지역 변형률에 미치는 영향)

  • 남원석;백기현
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.3
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    • pp.105-109
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    • 1999
  • The purpose of this experiment was to see the effect of local basis weight on the local strain during changing moisture content in handsheets. The averaged strain value of the whole size of paper sheet did not give more valuable information to explain non uniform deformation in the paper sheet. The combination of intact strain measurement system KISA (Linear Image Strain Analysis) and local basis weight measurement method using a scanner made it possible to compare local basis weight with local strain to explain moisture induced paper deformation . Usually higher basis weight local area showed higher moisture induced local strain. However, the hygro-induced strain values were highly affected by the behavior of neighbor local areas. Well distributed local basis weight paper would give more uniform local strains than those of non-uniformed local basis weight paper.

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A Study on the Use of Results and Measurement Case of Productivity of the Public Organization (공공조직 생산성 측정사례 및 결과 활용에 관한 연구 : 지방자치단체 생산성지수 중심)

  • Kim, Wan Pyong
    • Journal of the Korea Society of Digital Industry and Information Management
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    • v.10 no.4
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    • pp.225-236
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    • 2014
  • Productivity of public organizations was far older due to issue more difficult to measure than private organizations. Unlike the private sector, the public sector is a diverse and sometimes conflicting objectives (efficiency, effectiveness, equity, democracy, etc.) exist, it is difficult to measure productivity in a single index. Many departments of government is intricately interrelated and sometimes produced by the joint efforts, it is difficult to allocate performance, incentives and accountability to among departments. And there is the difficulty of collecting data on the productivity indicators of public organizations. Despite these difficulties, we developed a productivity index system and measuring method to systematically introduce the concept of productivity in the local administration. In this paper, the productivity and the productivity index measurement practices of local governments conducted annually from 2011 on was deep into research. First, the report found examples of the governments of the developed countries, productivity measurement, then the way MOPAS(Ministry of Public Administration and Security) measure productivity index of local governments, success factors, the implications were in-depth analysis. Finally, in order to enhance productivity and competitiveness municipalities studied ways to take advantage of the productivity index.

The Local Fatigue Strain Distribution Near a Crack Tip by Using Fine Dot Grid Strain Measurement Method (微小圓形格子變形率 測定法을 利용한 龜裂先端의 局所疲勞變形率分布)

  • 박영철;오세욱;김광영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.1
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    • pp.209-217
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    • 1991
  • We have carried out a preliminary study to search for the new fracture mechanics parameter which can effectively estimate the fatigue life. In this study, the distribution of local fatigue strains near a fatigue crack tip was detailedly revealed using by fine dot grid strain measurement method. From these results, a single parameter (.DELTA.A), which characterize local fatigue strain field, was nearly proposed by the authors.

A Suggestion of New Approach for Measurement of Remaining Prestress (잔존프리스트레스 측정을 위한 새로운 접근법 제안)

  • 이창수;김승익;김현겸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.835-840
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    • 2001
  • The new approach is a kind method of restoring temporary defect. Here, it is important for the defect not to occur problems of both local effect and global system. A basic concept is that it measures remaining prestress of PSC structures during the defect is restored. This study suggested new approach for measurement of remaining prestress. Two important results are obtained. First, safety problems, local stress concentration and global system, are very satisfied. Second, measurement value exists within error bound $\pm$ 1% in comparison with known value.

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