• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4121-4128
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• 2010

A probe card is used in testing semiconductor wafers. It must maintain a precise location tolerance for a fine pitch due to highly densified chips. However, high heat transferred from its lower chuck causes thermal deformations of the probe card. Vertical deformation due to the heat will bring contact problems to the pins in the probe card, while horizontal deformation will cause positional inaccuracies. Therefore, probe cards must be designed with proper materials and structures so that the thermal deformations are within allowable tolerances. In this paper, heat transfer analyses under realistic loading conditions are simulated using ANSYS$^{TM}$ finite element analysis program. Thermal deformations are calculated based on steady-state temperature gradients, and an optimal structure of the probe card is proposed by adjusting a set of relevant design parameters so that the deformations are minimized.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.9
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• pp.1131-1138
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• 2019

The importance of coatings has been increasing for different purposes such as prevention of static electricity of auto parts or products, improvement of abrasion and corrosion resistance, and enhancement of esthetics. As a method for measuring the thickness of a coating film, a contact method with probe is commonly used. However, it is problematic that accuracy of the sensor is degraded due to sensor output distortion or load phenomenon, which is caused by a change in magnetic permeability of the core. In this study, we propose a method to reduce the measurement error of the coating film by applying the optimized circuit design and the thickness measurement algorithm to the problems caused by the nonlinear characteristics. The tests result which have been taken with different thickness coating samples show that the measurement accuracy is within ${\pm}2%$.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.4
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• pp.307-321
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• 2020

Purpose : A person infected by SARS-CoV2 may present various symptoms such as fever, pain in lower respiratory tract, and pneumonia. Measuring body temperature is a simple method to screen patients. However, changes in the surrounding environment may cause errors in infrared measurement. Hence, a non-contact thermometer controls this error by setting a correction value, but it is difficult to correct it for all environments. Therefore, we investigate device error values according to changes in the surrounding environment (temperature and humidity) and propose guidelines for reliable patient detection. Methods : For this study, the temperature was measured using three types of non-contact thermometers. For accurate temperature measurement, we used a water bath kept at a constant temperature. During temperature measurement, we ensured that the temperature and humidity were maintained using a thermo-hygrometer. The conditions of the surrounding environment were changed by an air conditioner, humidifier, warmer, and dehumidifier. Results : The temperature of the water bath was measured using a non-contact thermometer kept at various distances ranging from 3~10 cm. The value measured by the non-contact thermometer was then verified using a mercury thermometer, and the difference between the measured temperatures was compared. It was observed that at normal surrounding temperature (24 ℃), there was no difference between the values when the non-contact thermometer was kept at 3 cm. However, as the distance of the non-contact thermometer was increased from the water bath, the recorded temperature was significantly different compared with that of mercury thermometer. Moreover, temperature measurements were conducted at different surrounding temperatures and the results obtained significantly varied from when the thermometer was kept at 3 cm. Additionally, it was observed that the effect on temperature decreases with an increase in humidity Conclusion : In conclusion, non-contact thermometers are lower in lower temperature and dry weather in winter.

• Korean Journal of Social Welfare Studies
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• v.41 no.4
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• pp.345-368
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• 2010

The purpose of this study is to develop the School Multicultural Climate(SMC) scale for students and to evaluate its reliability and validity. This study comprises of both qualitative and quantitative research. Preliminary items were developed based on the theoretical literature and interviews with students. The scale was evaluated with students in grades 4 through 6 in the seven elementary schools. Exploratory factor analysis was determined that the scale was composed of four components: Equal Status, Mutual Cooperation, Friendly Relations, Supportive Norms. The scale demonstrated that Cronbach's alpha=.943 for the internal consistency of total items. And the standard error of the measurement, another way of evaluating reliability, was 3.33. Criteria-related validity was evaluated by showing that the differences of the students' recognition of the school multicultural climate level, which depend on the availability of the multiculture-related policy, was statistically significant. The correlation analysis for the convergent validity was performed with the theoretically related variables such as self esteem and school adjustment. It was found that the SMC scale was a reliable and valid measure for evaluating the multicultural climate level of elementary school.

• Journal of Korea Water Resources Association
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• v.53 no.1
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• pp.15-27
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• 2020

Streamflow discharge as a fundamental riverine quantity plays a crucial role in water resources management, thereby requiring accurate in-situ measurement. Recent advances in instrumentations for the streamflow discharge measurement has complemented or substituted classical devices and methods. Among various potential methods, surface current meter using microwave has increasingly begun to be applied not only for flood but also normal flow discharge measurement, remotely and safely enabling practitioners to measure flow velocity postulating indirect contact. With minimized field preparedness, this method facilitated and eased flood discharge measurement in the difficult in-situ conditions such as extreme flood in active ways emitting 24.125 GHz microwave without relying on natural lights. In South Korea, a rectangular shaped instrument named with Microwave Water Surface Current Meter (MWSCM) has been developed and commercially released around 2010, in which domestic agencies charging on streamflow observation shed lights on this approach regarding it as a potential substitute. Considering this brand-new device highlighted for efficient flow measurement, however, there has been few noticeable efforts in systematic and comprehensive evaluation of its performance in various measurement and riverine conditions that lead to lack in imminent and widely spreading usages in practices. This study attempted to evaluate the MWSCM in terms of instrumen's monitoring configuration particularly regarding tilt and yaw angle. In the middle of pointing the measurement spot in a given cross-section, the observation campaign inevitably poses accuracy issues related with different tilt and yaw angles of the instrument, which can be a conventionally major source of errors for this type of instrument. Focusing on the perspective of instrument configuration, the instrument was tested in a controlled outdoor river channel located in KICT River Experiment Center with a fixed flow condition of around 1 m/s flow speed with steady flow supply, 6 m of channel width, and less than 1 m of shallow flow depth, where the detailed velocity measurements with SonTek micro-ADV was used for validation. As results, less than 15 degree in tilting angle generated much higher deviation, and higher yawing angle proportionally increased coefficient of variance. Yaw angles affected accuracy in terms of measurement area.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.5
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• pp.399-407
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• 2009

Laser induced breakdown spectroscopy(LIBS) is an simple analysis method for directly quantifying many kinds of soil micro-elements on site using a small size of laser without pre-treatment at any property of materials(solid, liquid and gas). The purpose of this study were to find an optimum condition of the LIBS measurement including wavelengths for quantifying soil elements, to relate spectral properties to the concentration of soil elements using LIBS as a simultaneous un-breakdown quantitative analysis technology, which can be applied for the safety assessment of agricultural products and precision agriculture, and to compare the results with a standardized chemical analysis method. Soil samples classified as fine-silty, mixed, thermic Typic Hapludalf(Memphis series) from grassland and uplands in Tennessee, USA were collected, crushed, and prepared for further analysis or LIBS measurement. The samples were measured using LIBS ranged from 200 to 600 nm(0.03 nm interval) with a Nd:YAG laser at 532 nm, with a beam energy of 25 mJ per pulse, a pulse width of 5 ns, and a repetition rate of 10 Hz. The optimum wavelength(${\lambda}nm$) of LIBS for estimating soil and plant elements were 308.2 nm for Al, 428.3 nm for Ca, 247.8 nm for T-C, 438.3 nm for Fe, 766.5 nm for K, 85.2 nm for Mg, 330.2 nm for Na, 213.6 nm for P, 180.7 nm for S, 288.2 nm for Si, and 351.9 nm for Ti, respectively. Coefficients of determination($r^2$) of calibration curve using standard reference soil samples for each element from LIBS measurement were ranged from 0.863 to 0.977. In comparison with ICP-AES(Inductively coupled plasma atomic emission spectroscopy) measurement, measurement error in terms of relative standard error were calculated. Silicon dioxide(SiO2) concentration estimated from two methods showed good agreement with -3.5% of relative standard error. The relative standard errors for the other elements were high. It implies that the prediction accuracy is low which might be caused by matrix effect such as particle size and constituent of soils. It is necessary to enhance the measurement and prediction accuracy of LIBS by improving pretreatment process, standard reference soil samples, and measurement method for a reliable quantification method.

• Clean Technology
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• v.26 no.3
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• pp.186-195
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• 2020

The isothermal adsorption, dynamic, and thermodynamic parameters of Acid black (AB) and Quinoline yellow (QY) adsorption by activated carbon were investigated using the initial concentration, contact time, temperature, and pH of the dyes as adsorption parameters. The adsorption equilibrium data fits the Freundlich isothermal adsorption model, and the calculated Freundlich separation factor values found that activated carbon can effectively remove AB and QY. Comparing the kinetic data showed that the pseudo second order model was within 10% error in the adsorption process. The intraparticle diffusion equation results were divided into two straight lines. Since the slope of the intraparticle diffusion line was smaller than the slope of the boundary layer diffusion line, it was confirmed that intraparticle diffusion was the rate-controlling step. The thermodynamic experiments indicated that the activation energies of AB and QY were 19.87 kJ mol^-1 and 14.17 kJ mol^-1, which corresponded with the physical adsorption process (5 ~ 40 kJ mol^-1). The adsorption reaction was spontaneous because the free energy change in the adsorption of AB and QY by activated carbon was negative from 298 to 318 K. As the temperature increased, the free energy value decreased resulting in higher spontaneity. Adsorption of AB and QY by activated carbon showed the highest adsorption removal rate at pH 3 due to the effect of anions generated by dissociation. The adsorption mechanism was electrostatic attraction.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.141-149
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• 2009

This study was conducted to investigate the causes that induce the T-shape cracks at the joints in the jointed concrete pavements(JCPs). The finite element models of JCP including dowel bars were developed and the stress distribution in the slab was investigated under environmental loads. To investigate the effect of dowel bars on the transverse stresses at the joints that induce the T-shape cracks, the slab curling behavior was analyzed with and without dowel bars. In addition, the stress concentration was investigated when the dowel bar was not installed at the mid-depth of the slab. The results of this study showed that the transverse stresses were not affected by the dowel bars if the dowel bars were installed at the mid-depth of the slab. However, if the dowel bars were not installed at the mid-depth, the transverse stresses were concentrated at the dowel bar locations when the slab curled. The stress concentration was dependent on the contact characteristics between the dowel bar and concrete, and was significantly large when the dowel bar not installed at the mid-depth was located far from the edge of the slab. Therefore, to mitigate T-shape cracking in JCP, dowel bars should be very carefully installed and leveled at the proper locations.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.197-206
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• 2002

The purpose of this study was to investigate the putter head movement during the putting strokes. Highly skilled 5 golfers(less than 3 handicaps) and 5 novice golfers(having no golf experience) participated in this study. A target distance was 3 m. Movements of the putter head were recorded at 60 Hz with two video cameras. The results showed that the novice golfers moved the club significantly longer than the expert golfers(p<.0001). Accoring to a movement time, novice golfers moved their club significantly faster than the expert golfers(p<0.001). Novice golfers could not control the club head effectively, and could not hit the ball correctly. Based on the impact zone movement, sweet spot of novice golfers moved faster(along the line of putt), higher(along the vertical line), and wider(along the side to side line) than that of expert golfers.

• Journal of the Korean Geotechnical Society
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• v.32 no.4
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• pp.5-14
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• 2016

Numerical simulation of dynamic soil-pile-structure interaction embedded in a dry sand was carried out. 3D model of the dynamic centrifuge model tests was formulated in a time domain to consider nonlinear behavior of soil using the finite difference method program, FLAC3D. As a modeling methodology, Mohr-Coulomb criteria was adopted as soil constitutive model. Soil nonlinearity was considered by adopting the hysteretic damping model, and an interface model which can simulate separation and slip between soil and pile was adopted. Simplified continuum modeling (Kim et al., 2012) was used as boundary condition to reduce analysis time. Calibration process for numerical modeling results and test results was performed through the parametric study. Verification process was then performed by comparing numerical modeling results with another test results. Based on the calibration and validation procedure, it is identified that proposed modeling method can properly simulate dynamic behavior of soil-pile system in dry condition.