• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.1-6
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• 2009

An Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor used for collecting overtopping waves and converting the water pressure head into electric power through hydro turbines installed in a vertical duct affixed to the sea bed. A numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. The Reynolds Averaged Navier-Stokes equation and two-phase VOF model are utilized to generate the 2D numerical linear propagating waves, which are validated by the overtopping experiment results. Calculations are made for several incident wave conditions and shape parameters for the overtopping device. Both the incident wave periods and heights have evident effects on the overtopping performance of the OWEC device. The computational analysis demonstrates that the present overtopping device is more compatible with longer incident wave periods.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.168-176
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• 2006

Nowadays, Three dimensional printing (3DP) technique that is one of solid freeform fabrication (SFF) technology has been notable issue, and has been applied by various fields. The SFF system can fabricate three dimensional objects of solid freeform with high speed and low cost using ink jet printing technology. In this research, a SFF system to analyze 3DP process technology is developed. We applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm and minimized position error to the developed SFF system. We analyzed and optimized process variables such as jetted volume, layer thickness, powder bed and so on experimentally. Also. the dimensional error of a developed SFF system is evaluated. Finally, the feasibility of application to bio manufacturing is presented through successful fabrication of teeth and cranium model.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.7
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• pp.80-89
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• 2000

Driving simulators provide engineers with a power tool in the development and modification stages of vehicle models. One of the most important factors to realistic simulations is the fidelity obtained by a motion bed and a real-time visual image generation algorithm. Virtual reality technology has been widely used to enhance the fidelity of vehicle simulators. This paper develops the virtual environment for such visual system as head-mounted display for a vehicle driving simulator. Virtual vehicle and environment models are constructed using the object-oriented analysis and design approach. Based on the object model, a three-dimensional graphic model is completed with CAD tools such as Rhino and Pro/ENGINEER. For real-time image generation, the optimized IRIS Performer 3D graphics library is embedded with the multi-thread methodology. The developed software for a virtual driving simulator offers an effective interface to virtual reality devices.

• The Journal of Internal Korean Medicine
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• v.27 no.4
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• pp.822-826
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• 2006

Objectives : Essential hyperhidrosis is a socially and occupationally disabling disorder. There are many suggestions that hyperhidrosis is associated with the autonomic nervous system, especiallythe sympathetic system. This study was designed to investigate the autonomic nerve system in patients with essential hyperhidrosis and healthy controls by the frequency domain analysis of heart rate variability (HRV). Methods : 17 head-hyperhidrosis patients in the ambulatory care were investigated. All were inspected at the first medical examination. using the PSA of HRV. HRV was measured for minutes after 5 minutes bed rest. We checked the frequency domain analysis of HRV (i.e. TP, VLF, LF, HF) which were transformed into natural logarithm of patients against the standard measures of the HRV components. Then we compared the values of patients with means of normal Korean subjects. Results : The values of natural logarithmic measure of HRV (LnTP, LnHF, LnLF, LnVLF) of patients With head-hyperhidrosis we examined were $6.85{\pm}1.61$, $4.93{\pm}$2.00, $5.40{\pm}1.83$, and $6.13{\pm}1.37$, respectively. None of these values were higher than means of normal subjects. Conclusions : This study suggests that the function of the autonomic nervous system does not increase in patients with head-hyperhidrosis.

• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.1
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• pp.3293-3301
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• 1974

An experimental work was conducted by using a laboratory-made model dryer to investigate the effect of the rate of natural forced-air on the drying rate of rough rice which was deposited in the deep-bed. The dryer consisted of 8 cylinderical containers with grain holding screen at their bottoms, each of which having 30cm in diameter and 15cm in height. The containers were sacked vertically with keeping them air-tight by using paper tape during dryer operation. Two separate layers of containers were operated in the same time to have two replications. The moisture contents of grains within each bins after predetermined period of dryer operation were determined indirectly by measuring the weight of the individual containers. The air-rates were maintained at 6 levels, or 5, 8, 10, 15, 18 and 20 millimenters of static head of water. The roomair conditions during dryer operation were maintained in the range of 10-l5$^{\circ}C$ in temperature and 40-60% in relative humidity. The results of the study are summarized as follows: 1. Drying characteristics of the grains in the bottom layers were approximately the same regardless of airdelivery rates, giving the average drying rate as about 0.35 percent per hour after 40-hour drying period, during which moisture content (w. b.) reduced from 24 percent to about 10 percent. 2. After about 40-hour drying period, the mean drying rates increased from 0.163 percent per hour to 0.263 percent per hour as air-flow rates increased from 5mm to 87.16mm of static head of water. In the same time, the moisture differences of grains between lower and upper layers varied from 12.7 percent at the air rate of 5mm of water head to 7.5 percent at the air-flow rate of 20mn of water head. Thus, the greater the air-flow rate was, the more overall improvement in drying performance was. Additionally, from the result of ineffectiveness of drying grain positioned at 70cm depth or above by the air rate of 5mm of static head of water it may be suggested in practical application that the height of grain deposit would be maintained adequately within the limits of air-rates that may be actually delivered. 3. Drying after layer-turning operation was continued for about 30 hours to test the effectiveness of reducing moisture differences in the thick layers. As a result of this layer-turning operation, moisture distribution through layers approached to narrow ranges, giving the moisture range as about 7 percent at air-flow rate of 5mm head of water, about 3 percent at 10mm head about 2 percent at 15mm head, and less than 1 percent at 20mm head. In addition, from the desirable results that drying rate was rapid in the lower layers and dully in the upper layers, layer-turning operation may be very effective in natural air drying with deep-layer grain deposit, especially when the forced air was kept in low rate. 4. Even though the high rate of air delivery is very desirable for deep-layer natural-air drying of rough rice, it can be happened that the required air delivery rate could not be attained because of limitation of power source available on farms. To give a guide line for the practical application, the power required to perform the drying with the specified air rate was analyzed for different sizes of drying bin and is given in Table (5). If a farmer selects a motor of which size is 1 or {{{{1 { 1} over {2 } }}}} H.P. and air-delivery rate which ranges from 8~10mm of head, the diameter of grain bin may be suggested to choose about 2.4m, also power tiller or other moderate size of prime motor may be recommended when the diameter of grain bin is about 5.0m or more for about 120cm grain deposit.

• Journal of Home Health Care Nursing
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• v.5
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• pp.84-99
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• 1998

The objectives of this study are to identify the actual educational contents of management for head nurse and to propose the educational subjects according to identity the needs of head, charge, and staff nurses. The subjects were investigated the actual Management Development Programs and educational needs of head nurses and prospective nurse manager(charge nurse, staff nurse with a lot of clinical experiences) in general hospitals. The tools were composed of two questionnaires: One was developed from the literature review for making items to measure actual situation. The other was revised Katz's model for measurement of educational needs. The first respondents of actual situation were 27 general hospitals with over 400 beds in Seoul and the second respondents were 89 head nurses, 67 charge nurses and 136 nurses at 3 hospitals by convenient sampling out of 27 general hospitals. Data were collected by telephone interview, mail questionnaire and visiting from 7th of October through 30th of November in 1997. In data analysis, general characteristics of the respondents and actual status of Management Development Programs were analyzed by frequency and percentage. Educational needs according to general characteristics were analyzed by ANOVA The results were as follows: 1. Actual situation of Management Development Program 1) Seven hospitals(26%) had Management Development Program for prospective managers and 14 hospitals (52%) for head nurses. 2) Education Department existed in 14 hospitals (52%). 3) One hospital(4%) had top level managers took part in the Management Development. 4) Two hospitals selected head nurse, who had finished courses of Management Development. Eight hospitals(30%) assessed educational needs. The assessment tools consisted of making a question via questionnaire(75%), determining at department meeting(12%) and interview(13%). 5) Educational programs had 3 types: 10 lecture type, 7 discussion type and 4 role play type programs. 6) One hospital evaluated the change of learner's attitude. 7) Four hospitals scored educational point, but that was measured only by attending. 8) Actual Management Development Programs were as follows. parenthesis indicates the number of hospitals. (1) Management Development Programs for Prospective manager. Role perception of Middle level Manager (1) . Role reconstruction of Nurse Manager (1). Workshop for Charge Nurse (1). Nursing Delivery System and Nursing Process (1). Communication (1). Motivation (1) (2) Management Development Programs for Head nurse.. Head nurse's Role (5). Administrative Work (7). Service Education (4). Prevention and Countermeasure of Nursing Incidence (3). Appraisal (3) 2. The results of needs on Management Development subject 1) The educational needs of all respondents on 3 skill domains showed positive agreement to strongly positive agreement. 2) High priority(more than 4.5) items were 12 of 24 Human skill items(50%), 1 of 6 Technical skill items(16%), and 2 of 13 Conceptual skill items (15%). 3) Out of high priority items, 8 items were instituted. 4) All respondents showed high needs on 3 skill domains regardless of 3 positions (head nurse, charge nurse, and nurse). Educational needs of Human skill domain, according to position were 108. S, 108.7, 106.8 (mean score = 72) , needs of Technical skill domain were 26.5, 26.6, 26.I(mean score=18), and needs of Conceptual skill domains were 56.9,56.7, 55.1(mean score=39). 5) Needs of 3 skill domains according to clinical career showed significant difference. Out of respondents, nurses with career of over 16years showed lowest degree of needs in Human skill domains(F=4.47, P=.004) and Conceptual skill domain(F=2.93, P=.034). 6) Educational needs according to educational background were not significant difference. But out of respondents, nurses educated at 3-year junior college relatively showed lowest needs in all of the 3 skill domains. With the above-mentioned findings, further study is necessary for generalization of this study at hospitals with different bed size and location. Also it is needed to study about management skill of nurse and charge nurse, and effective educational method.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.878-883
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• 2006

Removal efficiency of As(III) was investigated with a pilot-scale filtration system packed with an equal amount(each 21.5 kg) of manganese-coated sand(MCS) in the bottom and iron-coated sand(ICS) in the top. Height and diameter of the used column was 200 cm and 15 cm, respectively. The As(III) solution was introduced into the bottom of the filtration system with a peristaltic pump at a speed of $5{\times}10^{-3}$ cm/s over 148 days. Breakthrough of total arsenic in the mid-sampling position(end of the MCS bed) and final-sampling position(end of the ICS bed) was started after 18 and 44 days, respectively, and then showed a complete breakthrough after 148 days. Although the breakthrough of total arsenic in the mid-sampling position was started after 18 days, the concentration of As(III) in this effluent was below 50 ppb up to 61 days. This result indicates that MCS has a sufficient oxidizing capacity to As(III) and can oxidize 92 mg of As(III) with 1 kg of MCS up to 61 days. When a complete breakthrough of total arsenic occurred, the removed total arsenic by MCS was calculated as 79.0 mg with 1 kg MCS. As variation of head loss is small at each sampling position over the entire reaction time, it was possible to operate the filtration system with ICS and MCS for a long time without a significant head loss.

• Journal of Radiation Protection and Research
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• v.36 no.3
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• pp.160-167
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• 2011

This study conducts cross-comparison through verification of treatment planning of using beam spoiler and bolus, according to the dose variation of different tumor bed and metastatic lymph node cancers, against ionization and optically stimulated luminescence detectors(OSLDs), in head and neck radiotherapy. Verification of treatment planning examined the feasibility of inserting detectors through simulated solid dry water slabs under identical irradiated conditions from treatment planning system to measure beam spoiler and 0.5, 1 cm bolus. In addition, two detectors were cross-compared for verification of treatment planning accuracy and reliability within ${\pm}$2%. The study found that, given a beam spoiler thickness of 0.5 cm and beam spoiler-to-skin distance of 10 cm subjected to optimal dose distribution given for metastatic lymph node cancers, the bolus low-level skin dose was less, and the tumor bed dose reduced slightly. Additionally, two detectors were cross-compared for accuracy within ${\pm}$1%. Accordingly, The use of beam spoiler was determined that reduces skin side effects and can deliver an optimal dose distribution for tumor, and to apply to future clinical studies should be performed.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.267-267
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• 2019

Driftwood is one of serious problems in a river environment. In several countries, such as Indonesia, Japan, and Italy, the driftwood frequently appears in a river basin, and it can alter the channel bed, flow configuration by wood deposition and jam formation. Therefore, the studies related to driftwood have been actively conducted by many researchers to understand the mechanism of driftwood dynamics. In particular, wood motion by collision is one of the difficult issues in the numerical simulation because the calculation for wood collision requires significantly expensive calculation time due to small time step. Thus, this study conducted the numerical simulation in consideration of the wood motion by water flow and wood collision to understand the wood dynamics in terms of computation. We used the 2D (two-dimensional) depth-averaged velocity model, Nays2DH, which is a Eulerian model to calculate the water flow on the generalized coordinate. A Lagrangian type driftwood model, which expresses the driftwood as connected sphere shape particles, was employed to Nays2DH. In addition, the present study considered root wad effect by using larger diameter for a particle at a head of driftwood. An anisotropic bed friction was considered for the sliding motion dependent on stemwise, streamwise and motion directions. We particularly considered changeable draft at each particle and projection area by an angle between stemwise and flow directions to precisely reproduce the wood motions. The simulation results were compared with experimental results to verify the model. As a result, the simulation results showed good agreement with experimental results. Through this study, it would be expected that this model is a useful tool to predict the driftwood effect in the river flow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.195-202
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• 1987

The flow characteristics in the shallow open channel bends are investigated, whose total angles were 30, 60, 90, 120, 150 and 180 in degree, and whose bed frictions were relatively rough(C=30) and smooth(C=60), respectively. The terms analyzed in this study are the water surface profile, the distribution of velocity and the flow direction, relating to the various total angles in the bends. The maximum depth in the bends could be found at the outside section of the location of $15^{\circ}$ local angle from the bend inlet, having no relation to the total angle and bed friction. It is supposed that the path of maximum velocities is especially influenced by the bottom friction when the total angles are bigger than 150 in degree, approximately. The ratio of the superelevation to the velocity head seems to increase as the total angle of the bends increases. The flow direction is skewed to the inner side at the bend inlet, and skewed to the outside at the bend outlet, regardless of their total angles.