• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.796-802
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• 2013

In this study, we investigates active control technology to reduce the noise transmitted to the outside through the opening of enclosures. A numerical model based on acoustic boundary element method is first established. Using the numerical model, the acoustic transfer functions of the field points over the opening to the primary source at arbitrary locations are estimated. The feedforward control to minimize the acoustic power through the opening is then numerically implemented. The controller generates the secondary source to destructively interfere the noise transmission through the opening. Finally, a parametric study is conducted to evaluate the effects of the location and the number of the microphones on the control performance. Furthermore, the effects of the location of the secondary source on the performance of active noise control are investigated. It is followed that the control system implemented in this study leads to a significant reduction of about 35dB in sound power through the open using only on secondary source located at the optimized position.

• 상하수도학회지
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• 제21권5호
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• pp.581-587
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• 2007

In order to suggest the methodology for improving the equality of flow distribution in a distribution channel, wet tests were carried out for pilot plant which was scaled down to 1/8 of full scale distribution channel being operated in domestic K_water treatment plant. The correlation between various hydraulic variables and their effects on the equality of flow distribution was evaluated through wet tests using pilot plant. From the results of wet tests, the longitudinal baffle with orifices was installed in the distribution channel, the equality of flow distribution was improved on the condition that the Froude number in pilot plant was similar with that in the full scale channel. Also, the opening ratio of the orifices on the longitudinal baffled did not have influence on the performance of the equality of flow distribution when the average flow velocity and Froud number were relatively low (Froude number ${\fallingdotseq} 0.01$). In the other hand, the performance of the equality of flow distribution was improved with increasing the opening ration of on the longitudinal baffle under conditions of relatively high average flow velocity and high Froud number(${\gtrsim}0.1$)

• 한국정밀공학회지
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• 제19권3호
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• pp.131-136
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• 2002

A design system of dies for hot extrusion of structural shapes such as Z's, L's, T's, U's and H's from aluminium alloys was developed in this study. The developed design system of dies is based of estimated die design rule system. The design rules for die design are obtained from the handbooks, plasticity theories and relevant references. The environment of the system is AutoCAD and AutoLISP, the graphic programming language was used for the configuration of the system. This system includes five major modules such as section shape design module, die opening number module, die opening layout module, die correction module and die bearing design module that are used to determine design variables. This system would be used to design of dies for hot extrusion from aluminum alloys and widely used in manufacturing course.

• Geomechanics and Engineering
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• 제16권6호
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• pp.619-626
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• 2018

A simple prediction procedure was investigated for calculating the stresses and displacements of a circular opening. Unlike existed approaches, the proposed approach starts each step with a radius increment. The stress for each annulus could be obtained analytically, while strain increments for each step can be determinate numerically from the compatility equation by finite difference approximation, flow rule and Hooke's law. In the successive manner, the distributions of stresses and displacements could be found. It should be noted that the finial radial stress and displacement were equal to the internal supporting pressure and deformation at the tunnel wall, respectively. By assuming different plastic radii, GRC and the evolution curve of plastic radii and internal supporting pressures could be obtained conveniently. Then the real plastic radius can be calculated by using linear interpolation in the evolution curve. Some numerical and engineering examples were performed to demonstrate the accuracy and validity for the proposed procedure. The comparisons results show that the proposed procedure was faster than that in Lee and Pietrucszczak (2008). The influence of annulus number and dilation on the accuracy of solutions was also investigated. Results show that the larger the annulus number was, the more accurate the solutions were. Solutions in Park et al. (2008) were significantly influenced by dilation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.324-329
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• 2004

In this study, an application of crack morphology variables in the Leak-Before-Break(LBB) evaluation for nuclear piping systems is investigated, including influences on the leakage crack size and crack instability loads. The crack surface roughness and the number of flow turns as a function of the crack opening displacement are applied to LBB evaluations for KSNP pressurizer surge line, for which fatigue and stress corrosion cracking are considered as failure mechanisms. As a result, there would be a significant impact on safety margins to acceptance criteria for the surge line if crack morphology variables are applied additionally to the current regulatory guide without re-analyses for justification of safety factors being applied on the leakage crack size and piping loads for evaluations.

• 한국유체기계학회 논문집
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• 제9권3호
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• pp.22-28
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• 2006

The discharge coefficient in segmental wedge haying ninety degrees yeller angle for the five kinds of opening ratio with differential pressure taps located at both upstream and downstream of one diameter of pipe was measured. Main purpose of this work is placed on specifying the characteristic of discharge coefficient of a segmental wedge used as a primary element of flow metering devices, and suggestion for the fixed location of pressure taps useful. Although the range of the opening ratio over this work is more expanded than previous studies. The opening ratios of segmental wedge, namely 0.3, 0.4, 0.5, 0.6 and 0.7 were investigated. The Reynolds number based on the spool inside diameter ranges from 12,000 to 380,000.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.687-708
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• 2020

Openings in steel plate shear walls (SPSWs) are usually used for decorative designs, crossing locations of multiple utilities and/or structural objectives. However, earlier studies showed that generating an opening in an SPSW has a negative effect on the cyclic performance of the SPSW. Therefore, this study proposes tripling or doubling the steel-sheet-plate (SSP) layer and stiffening the opening of the SPSW to provide a solution to undesirable opening effects, improve the SPSW performance and provide the infill option of potential strengthening measures after the construction stage. The study aims to investigate the impact of SSP doubling with a stiffened opening on the cyclic behaviour, expand the essential data required by structural designers and quantify the SPSW performance factors. Validated numerical models were adopted to identify the influence of the chosen parameters on the cyclic capacity, energy dissipation, ductility, seismic performance factors (SPF) and stiffness of the suggested method. A finite Element (FE) analysis was performed via Abaqus/CAE software on half-scale single-story models of SPSWs exposed to cyclic loading. The key parameters included the number of SSP layers, the opening size ratios corresponding to the net width of the SSP, and the opening shape. The findings showed that the proposed assembly method found a negligible influence in the shear capacity with opening sizes of 10, 15, 20%. However, a deterioration in the wall strength was observed for openings with sizes of 25% and 30%. The circular opening is preferable compared with the square opening. Moreover, for all the models, the average value of the obtained ductility did not show substantial changes and the ultimate shear resistance was achieved after reaching a drift ratio of 4.36%. Additionally, the equivalent sectional area of the SSP in the twin and triple configuration of the SPSWs demonstrated approximately similar results. Compared with the single SSP layer, the proposed configuration of the twin SSP layer with a stiffened opening suggest to more sufficiency create SSP openings in the SPSW compared to that of other configurations. Finally, a tabular SPF quantification is exhibited for SPSWs with openings.

• Journal of Preventive Medicine and Public Health
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• 제34권3호
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• pp.219-227
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• 2001

Objectives : To understand the current status of the opening, closing and relocation of primary medical institutes in Korea and identify the underlying decision factors. Methods : Sources of analyzed data included the medical institutional master file at the National Health Insurance Corporation(1998, 2000) and Regional Statistic Annual Bulletins. To investigate changes including the opening, closing and relocation, a total of primary medicalinstitutions(16,757 in 1998, 19,267 in 2000) were analysed. Results : Between 1998 and 2000, there was a 15.0%(2,510) increase in the number of primary medical institutions and the rate of increase in the rural area was higher than the urban area, and higher for specialty clinics than primary practice. However, these findings did not suggestany improvement in the maldistribution of primary medical institutions. During the time period studied, newly opened and closed primary medical institutions numbered 4,085 and 1,573, respectively. Additionally, institutions thatrelocated numbered 2,729, or 16.3% of all primary medical institutions in operation in 1998. These openings and closings were more frequent among young doctors. As a result of our analysis on the underlying regional factors forrelocation, the factors that were statistically significant were local per capita tax burden and the number of schools per ten thousand persons. !n, the case of institutional factors, movements were significantly associated with gender and the location of primary medical institutions. Conclusions : In order to establish effective long-term intervention for primary medical institutions, further study and monitoring of primary medical institutions and the identification of factors influencing opening location and relocation is necessary.

• 대한인간공학회지
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• 제20권2호
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• pp.83-97
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• 2001

Korea has become an aged society according to the UN specifications. The number of the aged population will increase drastically, and the number of single aged people will also increase. Products used in our daily life are manufactured within the normal capabilities of people. Thus, aged people have encountering problems in using them. Numerous products are used in our daily lives. The purpose of this study is to find the acceptable torque for aged people to open the caps of processed food containers. Depending on the size and shape of the opening hand, hand operation has been classified into three categories. A total of one hundred and nine people participated in this study. Fifty nine people in the 20-30 year old range and fifty people in their 60-70's. Results of the study are as follows: 1) For all categories the acceptable cap torque data for the aged people are established. To satisfy 95% of the aged people, it was found that $74N{\cdot}cm$ for type A caps, and $141N{\cdot}cm$ for B type caps. and $214N{\cdot}cm$ for type C were the acceptable torque levels. 2) The appropriate level of torque for opening the cap was found to be 70% of the maximum torque for the aged people.(71.4% for type A. 71.4% for type B. 72.2% for type C). 3) Capabilities of the 70's drops sharply in function related to opening cap (maximum torque, gripping force, and wrist movement range). 4) Among aged subjects, 65.0% for type A, 42.0% for type B, and 68.8% for type C, had difficulties in opening the container caps.

• Journal of Oral Medicine and Pain
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• 제41권2호
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• pp.35-40
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• 2016

Purpose: This study aimed to investigate the characteristics of the symptoms of temporomandibular disorders (TMD) in Korean children and adolescents using representative samples and questionnaires. Methods: A survey involving the interview of 10-, 12-, and 15-year-old children and adolescents regarding the symptoms of TMD was conducted as a part of the 2010 National Oral Health Surveys. The study population included 18,112 subjects (male, 9,734; female, 8,378). The interview involved three questions related to the symptoms of TMD. The prevalence of symptoms of TMD, correlation of the symptoms with sex and age, and the difference in the number of symptoms according to sex and age were analyzed. Results: Among the symptoms of TMD in children and adolescents, the prevalence of temporomandibular joint (TMJ) sounds during mouth opening was 13.0%, while those of TMJ pain and limitation were 3.1% and 4.3%, respectively. While the prevalence of TMJ sounds during mouth opening did not show any statistically significant difference between the sexes, the rates of prevalence of TMJ pain and limitation of mouth opening in were higher in the female subjects than the male (p<0.05). It was also observed that the older the subjects, the higher the prevalence of TMJ sounds, TMJ pain, and limitation of mouth opening (p<0.05). The number of symptoms of TMD was found to be increased among female subjects as well as the older ones (p<0.05). Conclusions: There are variations in the prevalence of symptoms of TMD among Korean children and adolescents according to sex and age, which is consistent with the results of previous studies. It is necessary to conduct a national cohort study to evaluate the risk factors for TMD in children and adolescents.