• Journal of Magnetics
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• 제21권1호
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• pp.125-132
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• 2016

High gradient magnetic separation (HGMS) is the most commonly used magnetic cell separation technique in biomedical science. However, parameters determining target cell capture efficiencies in HGMS are still not well understood. This limitation leads to loss of information and resources. The present study develops a bead-capture theory to predict capture efficiencies in HGMS. The theory is tested with CD3- and CD14-positive cells in combination with paramagnetic beads of different sizes and a generic immunomagnetic separation system. Data depict a linear relationship between normalized capture efficiency and the bead concentration. In addition, it is shown that key biological functions of target cells are not affected for all bead sizes and concentrations used. In summary, linear bead-capture theory predicts capture efficiency ($E_t$) in a highly significant manner.

• 한국산업보건학회지
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• 제16권3호
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• pp.290-301
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• 2006

A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank. Efficiency of push pull hood system is affected by various parameters, such as, cross draft, vessel shapes, tank surface area, liquid temperature. A previous work assisted by flow visualization technique qualitatively showed that a strong cross draft blown from the pull hood to push slot could destroy a stable wall-jet on the surface of tank, resulting in the abrupt escape of smoke from the surface. In this study, the tracer gas method was applied to determine the effect of cross-draft on the capture efficiency qualitatively. A new concept of capture efficiency was introduced, that is, linear efficiency. This can be determined by measuring the mass of tracer gas in the duct of pull hood while the linear tracer source is in between push slot and pull hood. By traversing the linear tracer source from the push slot to the pull hood, it can be found where the contaminant is escaped from the tank. Total capture efficiency can be determined by averaging the linear efficiencies. Under the condition of cross-draft velocities of 0, 0.4, 0.75, 1.05 and 1.47m/s, total capture efficiencies were measured as 97.6, 95.4, 94.6, 92.7 and 70.5% respectively. The abrupt reduction of efficiency with cross-draft velocity of 1.47m/s was due to the destruction of tank surface wall-jet by the counter-current cross-draft. The same phenomenon was observed in the previous flow visualization study. As an alternative to overcome this abrupt efficiency drop, the 20% increase of hood flow rates was tested, resulting in 20% efficiency increase.

• 한국해양공학회지
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• 제35권3호
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• pp.216-228
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• 2021

In the present study, the performance of a floating oscillating water column (OWC) device has been studied in regular waves. The OWC model has the shape of a hollow cylinder. The linear potential theory is assumed, and a matched eigenfunction expansion method(MEEM) is applied for solving the diffraction and radiation problems. The radiation problem involves the radiation of waves by the heaving motion of a floating OWC device and the oscillating pressure in the air chamber. The characteristics of the exciting forces, hydrodynamic forces, flow rate, air pressure in the chamber, and heave motion response are investigated with various system parameters, such as the inner radius, draft of an OWC, and turbine constant. The efficiency of a floating OWC device is estimated in connection with the extracted wave power and capture width. Specifically, the piston-mode resonance in an internal fluid region plays an important role in the performance of a floating OWC device, along with the heave motion resonance. The developed prediction tool will help determine the various design parameters affecting the performance of a floating OWC device in waves.

• 한국수산과학회지
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• 제26권4호
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• pp.369-379
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• 1993

1992년 동계에 췌셰픽만의 꽃게자원에 대하여 예망을 사용한 연속채집법에 의한 어획 효율성을 조사하였다. 일반선형모델 분석에 따르면 26회에 걸친 야외시험 결과 어획효율성은 저질이나 수심, 사용된 조사선박에 따라 통게학적으로 유의한 차이가 나타나지 않았다. 예망효율(즉, 어획율)은 Leslies방법과 단순히 개조된 방법 등의 두 방법을 사용하여 추정하였다. 평균 어획율은 0.26 (표준오차:0.03)으로 추정되었는데 이는 한번의 예망을 사용하여 채집장소에 존재하고 있는 꽃게 가운데 단지 $26\%$($95\%$ 신뢰한계 : $20{\sim}32\%$)를 잡을 수 있다는 의미이다. 예망효율은 꽃게의 밀도가 증가함에 따라 지수적으로 감소하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.127-130
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• 2004

For the quality control of the industrial products, an automatic hole measuring system has been developed. The measurement device allows X-Y movement due to contact forces between a hole and its own circular cone and the device is attached to an industrial robot. Its measurement accuracy is about 0.04mm. This movement of the plate is measured by two LVDT sensor system. But this system using the LVDT sensors is restricted by high cost and precision of measurement and correspondence of environment so particularly, a vision system with CCD-Camera is discussed in this paper for the above mentioned purpose. The device consists of two of two links jointed with hinge pins basically and, they guarantee free movement of the touch prove attached on the second link in the same plane. These links are returned to home position by the spring plungers automatically after each process for the next one. On the surface of the touch prove, it has a circular white mark for camera recognition. The system detect and notify the center coordinate of capture mark image through the image processing. Its measuring accuracy has been proved to be about $\pm$0.01mm through the repeated implementation over 200 times. This technique will shows the advantage of touch-indirect image capture idea using cone-shaped touch prove in various symmetrical shaped holes particulary, like tapped holes, chamfered holes, etc As a result, we attained our object in a view of the accuracy, economical efficiency, and functionality

• 한국산업보건학회지
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• 제18권2호
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• pp.161-170
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• 2008

푸쉬-풀 환기시스템은 도금조와 같이 흡인해야 할 거리가 상대적으로 긴 경우에 많이 사용되고 있다. 그러나, 창문이나 출입문을 통한 방해기류가 푸쉬-풀 환기시스템의 오염물질 제어효율을 심각하게 훼손시키고 있다고 추측하고 있으나 이에 대한 세부적인 연구가 부족한 상태에 있다. 따라서, 본 연구에서는 전산유체역학(Computational fluid dynamics)을 이용하여 푸쉬-풀 환기시스템에서의 방해기류의 방향과 세기가 흡인효율에 어떠한 영향을 미치는지에 대해 평가해 보았다. 선형흡인효율(Linear capture efficiency) 방법을 이용하여 푸쉬-풀 환기시스템에서 가상의 개방조에서 발생한 오염물질이 푸쉬-풀 시스템에 의하여 포집되지 못하고 누출되는 구역이 어딘지를 찾아낼 수 있었다. 전산유체역학 컴퓨터시뮬레이션은 AIRPAK2.1 (FLUENT CODE) 소프트웨어를 사용하였다. 푸쉬-풀 후드시스템에 방해기류가 강하게 작용하면 상대적으로 강한 와류가 발생하는데, 일반적인 난류모델인 ${\kappa}-{\varepsilon}$모델은 와류현상을 충분히 보여주지 못한 반면에 RNG 모델을 사용했을 때 실험결과를 적절히 모사해낼 수 있었다. RNG 모델을 이용하여 세가지 방향, 즉 푸쉬에서 풀 방향으로, 풀에서 푸쉬 방향으로 그리고 그에 수직되는 방향으로 방해기류가 있을 때의 푸쉬-풀 환기시스템의 흡인효율을 분석하였다. 방해기류가 0.25m/s이하일 때에는 흡인효율이 거의 떨어지지 않았으나, 방해기류가 0.6m/s에서 흡인효율이 40-70%로 떨어짐을 알 수 있었다. 따라서, 방해기류를 감소시킬 수 있는 방안에 대해서도 연구를 해야 되겠지만, 방해기류 존재 하에서 충분한 흡인 효율을 유지할 수 있는 푸쉬-풀 후드 설계기준에 대한 연구도 필요할 것으로 판단된다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2005년도 춘계공동학술대회 발표논문
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• pp.1114-1116
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• 2005

Shop floor control systems (SFCS) are used to make real-time planning and scheduling decisions to optimize the efficiency of manufacturing shops. These shops exhibit a non-linear, dynamic evolution caused by 1) the concurrent flows of disparate parts following complex routings, 2) a variety of machines that breakdown at random times, 3) stochastic arrivals of new parts with different priorities, and 4) jobs that have probabilistic processing times and transportation times. Because of their ability to capture that evolution faithfully, simulation models are often used in the aforementioned decisions. In this paper, various types of decision-making problems encountered in a shop floor have been investigated and categorized into process related problems and resource related problems for shop floor simulation.

• Coupled systems mechanics
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• 제7권2호
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• pp.111-139
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• 2018

A successful methodology for modelling controlled destruction and progressive collapse of 2D reinforced concrete frames is presented in this paper. The strategy is subdivided into several aspects including the failure mechanism creation, and dynamic motion in failure represented with multibody system (MBS) simulation that are used to jointly capture controlled demolition. First phase employs linear elasto-plastic analysis with isotropic hardening along with softening plastic hinge concept to investigate the complete failure of structure, leading to creation of final failure mechanism that behaves like MBS. Second phase deals with simulation and control of the progressive collapse of the structure up to total demolition, using the nonlinear dynamic analysis, with conserving/decaying energy scheme which is performed on MBS. The contact between structure and ground is also considered in simulation of collapse process. The efficiency of the proposed methodology is proved with several numerical examples including six story reinforced concrete frame structures.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2317-2323
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• 2024

Medical linear accelerators with an energy of 8 MV or higher are radiated owing to photonuclear reactions and neutron capture reactions. It is necessary to quantitatively evaluate the concentration of radioactive isotopes when replacing or disposing them. HPGe detectors are commonly used to identify isotopes and measure radioactivity. However, because the detection efficiency is generally calibrated using a standard material with a density of 1.0 g/cm³, a self-absorption effect occurs if the density of the measured material is high. In this study, self-absorption correction factors were calculated for tungsten, lead, copper, and SUS-303, which are the main materials of medical linear accelerator head parts, for each gamma-ray energy using MCNP 6.2 code. The self-absorption effect was more pronounced as the energy of the emitted gamma rays decreased and the density of the measured materials increased. These correction factors were applied to the radioactivity measurements of the in-built and portable HPGe detectors. Furthermore, compared to the surface dose rate measured by the survey meter, the accuracy of the measurements of radioactivity improved by an average of 124.31 and 100.53 % for inbuilt and portable HPGe detectors, respectively. The results showed a good agreement, with an average difference of 3.70 and 5.24 %.

• Journal of Biosystems Engineering
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• 제40권3호
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• pp.296-304
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• 2015

Purpose: The balance between miscanthus production and its cost effectiveness depends greatly on its moisture content during post processing. The objective of this research was to measure the moisture content using a non-destructive and non-contact methodology for in situ applications. Methods: The moisture content of comminuted miscanthus was controlled using a closed chamber, a humidifier, a precision weigher, and a real-time monitoring software developed in this research. A CMOS sensor equipped with $50{\times}$ magnifier lens was used to capture magnified images of the conditioned materials with moisture content level from 5 to 30%. The hypothesis is that when light is incident on the comminuted particles in an inclined manner, higher moisture content results in light being reflected with a higher intensity. Results: A linear regression analysis for an initiative hypothesis based on general histogram analysis yielded insufficient correlations with low significance level (<0.31) for the determination coefficient. A significant relationship (94% confidence level) was determined at level 108 in a reverse accumulative histogram proposed based on a revised hypothesis. A linear regression model with the value at level 108 in the reverse accumulative histogram for a magnified image as the independent variable and the moisture content of comminuted miscanthus as the dependent variable was proposed as the estimation model. The calibrated linear regression model with a slope of 92.054 and an offset of 32.752 yielded 0.94 for the determination coefficient (RMSE = 0.2%). The validation test showed a significant relationship at the 74% confidence level with RMSE 6.4% (n = 36). Conclusions: To compensate the inconsistent significance between calibration and validation, an estimation model robust against various systematic interferences is necessary. The economic efficiency of miscanthus, which is a promising energy resource, can be improved by the real-time measurement of its crucial material properties.