• Food Science and Preservation
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• v.17 no.1
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• pp.16-22
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• 2010

To maintain the storage quality of agricultural products, temperature uniformity during cold storage, which is affected by fan flow rate and product arrangement, is important. We simulated and validated a CFD (Computational Fluid Dynamics) model that can predict both airflow and temperature distribution in a cold storage environment. Computations were based on a commercial code (FLUENT 6.2) and two turbulence models. The standard k-$\varepsilon$ model and the Reynolds stress model (RSM) were chosen to improve the accuracy of CFD prediction. To obtain comparative data, the temperature distribution and velocity vector profiles were measured in a full-scale cold storage facility and in a 1/5 scale model. The agricultural products domain in cold storage was modeled as porous for economical computation. The RSM prediction showed good agreement with experimental data. In addition, temperature distribution was simulated in the cold storage rooms to estimate the uniformity of temperature distribution using the validated model.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.8 no.1
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• pp.70-82
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• 1997

Objective：This study was performed to identify and understand the characteristics of adolescents who had a history of police arrest and/or were adjudicated unruly/delinquent by the juvenile court. Method：The study employed a retrospective reivew of coumputer-recorded data set on 210 consecutive admissions to an adolescent psychiatric inpatient unit. Three groups(No Police Contact, N=115；Police Contact Only, N=60；Adjudicated, N=35) were compared on the areas of a) cognitive and educational performance b) emotion：anxiety, depression, suicidality c) personality d) family and life experiences. Standardized assessments were administered to all subjects using WISC-Ⅲ, Kaufman Test of Educational Achievement, Millon Adolescent Personality Inventory, Reynolds Adolescent Depression Scale, Revised-Chilren’s Manifest Anxiety Scale, Suicide Ideation Questionnarie, Suicide Behavior Interive, Life Events Checklist, and Family Environmental Scale. A subgroup of the subjects, 60 cases also received a standardized interview by Child Assessment Schedule. Results：The characteristic findings of the delinquent group(the police contact only and adjudicated subjects combined) included (1) a high rate of adoption, sexual promiscuity, out of home placement, and repeated psychiatric hospitalization, (2) low verbal IQ scores and educational achievements, (3) high impulsivity, low social conformity, and high forcefulness in personality inventory, (4) low activityrecreation orientation and low moral religious emphasis in family environment, (5)a high frequency of adverse life experiences, (6) among 3 groups, the Police Contact Only group showed the lowest depression, anxiety and suicidal ideation scores, (7) a high diagnostic frequency of conduct disorder, ODD, and ADHD. Conclusions：The adolescent psychiatric inpatients with a delinquent history presented with a certain clinical, family, psychometric characteristics that warrant specific clinical intervention strategies for their cognitive deficits, an impulsive personality style, family dysfunction with adverse life experiences and disruptive behavioral disorders, different from the rest of adolescent psychiatric inpatients.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.15 no.2
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• pp.168-177
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• 2004

Objectives : This study was done to develop Korean form of Reynolds' SIQ-JR(Suicidal Ideational Questionnaire-Junior). Through this study we evaluated reliability and validity of Korean form SIQ-JR. Methods : Subjects were 1,160 middle and high school students and 114 adolescent psychiatric patients. SIQ-JR and 8 self-reporting scales highly related with suicidal ideation and suicide behaviors were applied to them. Results : In reliability aspect of Korean form of SIQ-JR, internal consistency, test-retest reliability and item-total correlation were statistically significant results. In factor analysis, concerning about other person was extracted as a indepenedent factor. This results reflect our cultural characteristics. There were statistical differences of SIQ-JR scores in groups by sex and age. Clinical group showed significantly(P<0.01) higher scores than general population. Among the 8 suicidal relating scales, depression(r=0.42), aggression(r=0.36), trait anxiety(r=0.35), and anger-in(r=0.31) were highly related with suicidal ideation but impulsivity and hopelessness were not significantly related with suicidal ideation. Conclusion : Korean form of SIQ-JR was useful instrument in reliability and validity. We hope that this instrument widely used in school mental health, community psychiatry and clinical setting for screening tool.

• Korean Journal of Childcare and Education
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• v.5 no.2
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• pp.43-71
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• 2009

This study is aimed at performing art therapy and looking into the effect on declining depression and anxiety and improving self-esteem, targeting at maladaptive behavior child in home and school living. So, this study made an application of fine art programs 2 session a week, for 50minutes each, total 24 sessions, targeting at elementary 1st girl graders(7 years old in full) in J city. In the end-term, this study performed a fine art therapy for 6 sessions together with mother-children. This study used a Korean-style Children Depression Inventory(CDI) developed by Kovacs and Beak(1977) and adapted by Jo Su Cheol and Lee Young Sik(1990) to look into children's decline in depression and anxiety and Revised Child Manifest Anxiety Scale(RCMAS) produced by Reynolds and Richmond(1978) and adapted by Jo Su Cheol and Choi Jin Suk(1990) to look into improvement of self-esteem. This study performed and analyzed KHTP, KFD painting examination, prior as well as post, to perform children's emotional appraisal and analyzed, classified with sessions, children's change in the progress of programs. The results of this study were as follows: First, fine art therapy was effective in declining children's depression and anxiety. Second, fine art therapy was effective in improving children's self-esteem. Third, children changed their emotional stability affirmatively in KHTP, KFD painting tests. Family affinity and cohesion were strengthened and changed into friendly family. Fourth, in the progress of programs, classified with sessions, children inclined their depression and anxiety and improved their self-esteem. This study leads to the result that art therapy inclines depression and anxiety in maladaptive behavior child and has an affirmative effect on improving self-esteem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1139-1146
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• 2012

An alternative approach for topology optimization of steady incompressible Navier-Stokes flow problems is presented by using P1 nonconforming finite elements. This study is the extended research of the earlier application of P1 nonconforming elements to topology optimization of Stokes problems. The advantages of the P1 nonconforming elements for topology optimization of incompressible materials based on locking-free property and linear shape functions are investigated if they are also valid in fluid equations with the inertia term. Compared with a mixed finite element formulation, the number of degrees of freedom of P1 nonconforming elements is reduced by using the discrete divergence-free property; the continuity equation of incompressible flow can be imposed by using the penalty method into the momentum equation. The effect of penalty parameters on the solution accuracy and proper bounds will be investigated. While nodes of most quadrilateral nonconforming elements are located at the midpoints of element edges and higher order shape functions are used, the present P1 nonconforming elements have P1, {1, x, y}, shape functions and vertex-wisely defined degrees of freedom. So its implentation is as simple as in the standard bilinear conforming elements. The effectiveness of the proposed formulation is verified by showing examples with various Reynolds numbers.

• Wind and Structures
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• v.20 no.4
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• pp.549-564
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• 2015

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations and k-${\varepsilon}$ double equations turbulent model were used to investigate the effect on the measurements of anemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat the moving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriage gaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the present numerical method was validated to be used for further study. In addition, the difference of slipstream between three-car and eight-car grouping models was analyzed, and a series of numerical simulations were carried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and the directions of the induced slipstream on the measurements of the anemometers. The results show that the influence factors of the train-induced slipstream are the passing head car and tail car. Using the three-car grouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstream velocity tend to reduce as the height of the anemometer increases. With the train speed increasing, the relationship between $V_{train}$ and $V_{induced\;slipstream}$ can be expressed with linear increment. In the absence of natural wind conditions, from the head car arriving to the tail car leaving, the induced wind direction changes about $330^{\circ}$, while under the crosswind condition the wind direction fluctuates around $-90^{\circ}$. With the crosswind speed increasing, the peaks of $V_X,{\mid}V_{XY}-V_{wind}{\mid}$ of the head car and that of $V_X$ of the tail car tend to enlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effect on the measurements of anemometers due to the train-induced slipstream.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.5
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• pp.406-414
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• 2017

An experimental study in a recirculating water channel was carried out to investigate the effect of large coherent structures to the skin friction on a flat plate. Particle Image Velocimetry (PIV) technique was used to quantify characteristic features of coherent structures growing to the boundary layer. In the PIV measurement, it is difficult to calculate the friction velocity near the wall region due to laser deflection and uncertainty so that Clauser fitting method at the logarithmic region was adopted to compute the friction velocity and compared with the one directly measured by the dynamometer. With changing the free-stream velocity from 0.5 m/s to 1.0 m/s, the activity of coherent structures in the logarithmic region was increased over three times in terms of Reynolds stress. The flow field was separated by Variable Interval Time Averaging (VITA) technique into the weak and the strong structure case depending on the existence large coherent structures in order to validate its effectiveness. The stream-wise velocity fluctuation was scanned through at the boundary thickness whether it had a large deviation from background flow. With coherent structures connected from near-wall to the boundary layer, mean wall shear stress was higher than that of weak structure case. Proper Orthogonal Decomposition (POD) analysis was also applied to compare the energy budget between them at each free-stream velocity.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1217-1224
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• 2014

This paper provides a practical scaling method to solve an old problem for scaling and developing the speed and resistance of a model to full-scale submarine in fully submerged underwater test. In every experimental test in towing tank, water tunnel and wind tunnel, in the first step, the speed of a model should be scaled to the full-scale vessel (ship or submarine). In the second step, the obtained resistance of the model should be developed. For submarine, there are two modes of movement: surface and submerged mode. There is no matter in surface mode because, according to Froude's law, the ratio of speed of the model to the full-scale vessel is proportional to the square root of lengths (length of the model on the length of the vessel). This leads to a reasonable speed and is not so much for the model that is applicable in the laboratory. The main problem is in submerged mode (fully submerged) that there isn't surface wave effect and therefore, Froude's law couldn't be used. Reynold's similarity is actually impossible to implement because it leads to very high speeds of the model that is impossible in a laboratory and inside the water. According to Reynold's similarity, the ratio of speed of the model to the full-scale vessel is proportional to the ratio of the full-scale length to the model length that leads to a too high speed. This paper proves that there is no need for exact Reynold's similarity because after a special Reynolds, resistance coefficient remains constant. Therefore, there is not compulsion for high speeds of the model. For proving this finding, three groups of results are presented: two cases are based on CFD method, and one case is based on the model test in towing tank. All these three results are presented for three different shapes that can show; this finding is independent of the shapes and geometries. For CFD method, Flow Vision software has been used.

• Journal of Korea Water Resources Association
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• v.45 no.6
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• pp.545-555
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• 2012

A numerical modeling has become increasingly popular and more important to the study of water waves with a rapid advancement of computer technology. However, different types of problems are induced during simulating wave motion. One of the key problems is re-reflection to a computation domain at the incident boundary. The internal wave generating-absorbing boundary conditions have been commonly used in numerical wave models to prevent re-reflection. For the Navier-Stokes equations model, the internal wave maker using a mass source function of the continuity equation has been used to generate various types of waves. Nonetheless, almost every numerical experiment is performed in two dimensions and only a few tests have been expanded to three dimensions. More recently, a momentum source function of the Boussinesq equations is applied to generate essentially directional waves in the three dimensional Navier-Stokes equations model. In this study, the internal wave maker using a momentum source function is employed to generate targeted linear waves in the three-dimensional LES model.

• KSTLE International Journal
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• v.7 no.2
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• pp.27-34
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• 2006

Knudsen number is the ratio of molecular mean free path versus mm thickness and the criterion to determine the flow form. When its value is lower than 0.01, the flow can be assumed to has no slip boundary condition. And in the case that the value is between 0.01 and 10, then the flow has slip boundary condition at both the adjacent walls. The condition of the air flow between the rotating journal and top foil in the air foil bearing is determined by the rotating speed and load, and the Knudsen number is also varied by those values. Because the molecular mean free path is variable to the pressure and temperature, more exact formulation is necessary to understand and analyze the flow regime. In this study, the analysis considering Knudsen number formulated with those variables (pressure, temperature and mm thickness) was executed. The approximate value was examined using the equation to confirm whether the flow has the slip or no-slip boundary condition. From the analytic investigation, it was decided to range approximately 0.01 to 1.0 and the flow can be supposed to have the slip boundary condition. Under the condition of the slip flow, the static characteristics of the air foil bearing were examined using modified Reynolds equations. The results were compared with those considering no slip condition. It shows that the slip condition makes the flow decelerates and the load carrying capacity decreases compared with no slip condition. And as the bearing number and eccentricity ratio increase, the load carrying capacity also increased at both the cases. From this result, it can be supposed that the bearing torque also increases. In the analysis of the dynamic characteristics, the perturbed Knudsen number was taken into consideration. Because the Knudsen number is expressed as the terms of each variable, the perturbed equation can be simply derived. The results of both cases considering and not considering Knudsen number were compared each other. In the case of the direct terms of the stiffness and damping coefficients, the difference between both cases was little and increased as the bearing number and eccentricity ratio increased. And the cross terms have less or more differences.