• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1092-1100
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• 2005

In the present study, characteristics of steady state laminar flows of a straight duct connected to a 180$^{o}$ curved duct were examined in the entrance region through experimental and numerical analyses. For the analysis, the governing equations of laminar flows in the Cartesian coordinate system were applied. Flow characteristics such as velocity profiles and secondary flows were investigated numerically and experimentally in a square cross-sectional straight duct by the PIV system and a CFD code(STAR CD). For the PIV measurement, smoke particles produced from mosquito coils. The experimental data were obtained at 9 points dividing the test sections by 400 3m. Experimental and numerical results can be summarized as follows. 1) Reynolds number, Re was increased, dimensionless velocity profiles at the outer wall were increased due to the effect of the centrifugal force and secondary flows. 2) The intensity of a secondary flow became stronger at the inner wall rather than the outer wall regardless of Reynolds number. Especially, fluid dynamic phenomenon called conner impact were observed at dimensionless axial position, x/D$_{h}$=50.

• Journal of Preventive Medicine and Public Health
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• v.46 no.2
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• pp.82-88
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• 2013

Objectives: Unprotected leisure time exposure to ultraviolet radiation from the sun or artificial tanning beds is the most important environmental risk factor for melanoma, a malignant skin cancer with increasing incidences over the past decades. The aim of the present study was to assess the impact of skin health information provided by several sources and different publishing issues on knowledge, risk perception, and sun protective behavior of sunbathers. Methods: A cross-sectional questionnaire survey was conducted among Austrian residents (n=563) spending leisure time outdoors in August 2010. Results: Print media, television, and family were perceived as the most relevant sources of information on skin health, whereas the source physician was only ranked as fourth important source. Compared to other sources, information provided by doctors positively influenced participants' knowledge on skin risk and sun protective behavior resulting in higher scores in the knowledge test (p=0.009), higher risk perception (p<0.001), and more sun protection (p<0.001). Regarding gender differences, internet was more often used by males as health information source, whereas females were more familiar with printed information material in general. Conclusions: The results of this survey put emphasis on the demand for information provided by medical professionals in order to attain effective, long-lasting promotion of photoprotective habits.

• Journal of Preventive Medicine and Public Health
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• v.51 no.4
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• pp.196-204
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• 2018

Objectives: To determine urinary mercury levels in e-waste workers in Southern Thailand and the airborne mercury levels in the e-waste shops where they worked, to describe the associations between urinary and airborne mercury levels, and to evaluate the prevalence of mercury exposure-related health effects among e-waste workers. Methods: A cross-sectional study was conducted by interviewing 79 workers in 25 e-waste shops who lived in Nakhon Si Thammarat Province, Thailand. Information on general and occupational characteristics, personal protective equipment use, and personal hygiene was collected by questionnaire. Urine samples were collected to determine mercury levels using a cold-vapor atomic absorption spectrometer mercury analyzer. Results: The e-waste workers' urinary mercury levels were $11.60{\mu}5.23{\mu}g/g$ creatinine (range, 2.00 to $26.00{\mu}g/g$ creatinine) and the mean airborne mercury levels were $17.00{\mu}0.50{\mu}g/m^3$ (range, 3.00 to $29.00{\mu}g/m^3$). The urinary and airborne mercury levels were significantly correlated (r=0.552, p<0.001). The prevalence of self-reported symptoms was 46.8% for insomnia, 36.7% for muscle atrophy, 24.1% for weakness, and 20.3% for headaches. Conclusions: Personal hygiene was found to be an important protective factor, and should therefore be stressed in educational programs. Employers should implement engineering measures to reduce urinary mercury levels and the prevalence of associated health symptoms among e-waste workers.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.4
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• pp.237-240
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• 2000

This experiment was conducted to evaluate the effect of split application of nitrogen(N) on development of vascular bundle(VB) and yield components of rice. Two cultivars were used in this study; IR58, an indica type and Shinunbongbyeim a japonica type. The number and total cross sectional area of the VB in the peduncle and leaf blade were more and bigger in N split application than 100 percent basal fertilizer. Nitrogen split application at necknode differentiation stage increased the number and size of the VB. Nitrogen split application resulted in increased panicle number with application of N before transplanting and at tillering stage; increased spikelets number with N application at necknode differentiation stage; and increased spikelet fertility and 1000 grain weight with N application at necknode differentiation and heading stages. Grain yield increased 7-10% in N split as compared to all basal application. The total cross sectional area of VB in peduncle closely correlated with the number of spikelets per panicle. Nitrogen management can have an impact on spikelet differentiation through more and bigger VB and increase grain yield potential.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.4
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• pp.615-621
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• 2010

Purpose : The purpose of this study was to compare chronic LBP patients and asymptomatic subjects on measures of multifidus size (cross-sectional area;CSA, thickness) and symmetry (proportional difference of relatively larger side to smaller side). Methods : Data were obtained from 12 asymptomatic subjects without a prior history of LBP (8 females, 4 males), and a retrospective audit was undertaken of records from 12 chronic low back pain patients (8 females, 4 males). CSA and Thickness of the lumbar multifidus muscles was measured from axial T1-weighted magnetic resonance images(MRI). Results : The results of the analysis showed that chronic LBP patients had significantly smaller multifidus CSA and thickness than asymptomatic subjects at L4-5 vertebral levels(p<.05). The asymmetry between sides was seen at L4- L5 vertebral level in patients with chronic low back pain presentations(p<.05). Conclusions : MRI provided a quantitative measure of change between asymptomatic subjects and chronic low back pain patients of multifidus muscle. MRI identified significant differences in cross-sectional area and thickness and helps to evaluate clinically and plan the treatment modalities of LBP.

• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.59-65
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• 2003

In order to achieve the desired lightweight and robust design of a structure, it is preferable to design a structure and its control system, simultaneously, which is termed the combined optimal design. A constant-cross-sectional area cantilever beam was chosen as the optimum design method, An initial load and a time-varying disturbance were applied at the free end of the beam. Sliding mode control was selected, due to its insensitivity to the disturbance, compared with other modes. It is known that the sliding mode control is robust to the disturbance and is uncertain, only if a matching condition is met, after giving a switching hyper plane. In this study, the optimum method was used for the design of the switching hyper plane, and the objective function of the optimum switching hyper plane was assumed to be the objective of the control system. The total weight of the structure was treated as a constraint, and the cross sectional areas of the beam were considered as design variables, the result being a nonlinear programming problem. To solve it, the sequential linear programming method was applied. As a result of the optimum design, the effect of attenuating vibrations has been substantially improved. Moreover, the lightweight design of the structure became possible as a result of the relationship of the weight of the structure to the control objective function.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.679-685
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• 2014

For the measurements of surface shape milled using FIB (focused ion beam), the silicon bulk, $Si_3N_4/Si$, and Al/Si samples are used and observed the shapes milled from different sputtering rates, incident angles of $Ga^+$ ions bombardment, beam current, and target material. These conditions also can be influenced the sputtering rate, raster image, and milled shape. The fundamental ion-solid interactions of FIB milling are discussed and explained using TRIM programs (SRIM, TC, and T-dyn). The damaged layers caused by bombarding of $Ga^+$ ions were observed on the surface of target materials. The simulated results were shown a little bit deviation with the experimental data due to relatively small sputtering rate on the sample surface. The simulation results showed about 10.6% tolerance from the measured data at 200 pA. On the other hand, the improved analytical model of damaged layer was matched well with experimental XTEM (cross-sectional transmission electron microscopy) data.

• 한국어정보학회:학술대회논문집
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• 2017.10a
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• pp.281-284
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• 2017

On the basis of studies that show multi-word combinations, that is the field of phraseology, this study aims to examine relationship between the quality of text and phraseological competence in L2 English writing, following Yves Bestegen et al. (2014). Using two different association scores, t-score and Mutual Information(MI), which are opposite ways of measuring phraseological competence, in terms of scoring frequency and infrequency, bigrams from L2 writers' text scored based on a reference corpus, GloWbE (Corpus of Global Web based English). On a cross-sectional approach, we propose that the quality of the essays and the mean MI score of the bigram extracted from YELC, Yonsei English Learner Corpus, correlated to each other. The negative scores of bigrams are also correlated with the quality of the essays in the way that these bigrams are absent from the reference corpus, that is mostly ungrammatical. It indicates that increase in the proportion of the negative scored bigrams debases the quality of essays. The conclusion shows the quality of the essays scored by MI and t-score on cross-sectional approach, and application to teaching method and assessment for second language writing proficiency.

• Computers and Concrete
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• v.9 no.6
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• pp.469-486
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• 2012

This paper presents Neuro-Fuzzy (NF) based empirical modelling of torsional strength of RC beams for the first time in literature. The proposed model is based on fuzzy rules. The experimental database used for NF modelling is collected from the literature consisting of 76 RC beam tests. The input variables in the developed rule based on NF model are cross-sectional area of beams, dimensions of closed stirrups, spacing of stirrups, cross-sectional area of one-leg of closed stirrup, yield strength of stirrup and longitudinal reinforcement, steel ratio of stirrups, steel ratio of longitudinal reinforcement and concrete compressive strength. According to the selected variables, the formulated NFs were trained by using 60 of the 76 sample beams. Then, the method was tested with the other 16 sample beams. The accuracy rates were found to be about 96% for total set. The performance of accuracy of proposed NF model is furthermore compared with existing design codes by using the same database and found to be by far more accurate. The use of NF provided an alternative way for estimating the torsional strength of RC beams. The outcomes of this study are quite satisfactory which may serve NF approach to be widely used in further applications in the field of reinforced concrete structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1005-1014
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• 2004

Experiments were done for the three dimensional unsteady flow in a counter-rotating axial flow fan under peak efficiency operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the 45$^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. It has been found that the radial and tangential velocity components disappeared, while the axial velocity component highly increased as soon as the tip vortex was generated. It has been observed that secondary flow and turbulence intensity which were increased by the front rotor were dissipated passing through the rear rotor. As the result the energy loss of the counter rotating axial flow fan decreased at the downstream of rear rotor. Also, it has been verified that tip vortex pattern of the rear rotor was dampened because the tip vortex generated by front rotor was mixed with that of the rear rotor.