• Journal of Korea Water Resources Association
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• v.49 no.7
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• pp.615-623
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• 2016

This Study calculated the Submerged Flow Characteristics and Discharge coefficient by the rising angular change of the Improved-Pneumatic-Movable. According to the result, the smaller the ratio of weir height and weir length (L/W) or the weir standing angle, the bigger of the downstream head ($H_2$). The change of discharge reduction factor ($Q_s/Q_1$), by the hight from weir crest to downstream surface and the ratio form weir crest to upstream water height ($h_t/H$), was decreased when the $h_t/H$ closed to number 1. Although the weir water depth of the down-stream was shallower level than the up-stream, the velocity was faster then before. And the more the flow, the less the gab between the upper and lower reaches level. And when the same flow condition, the downstream head ($H_2$) was increased when the L/W was bigger. The Submerged Flow Discharge coefficient of Improved-Pneumatic-Movable weir was made by the upstream approach flow head and the upper lower stream flow condition, not by the physical data of Movable weir.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.2
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• pp.201-208
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• 2013

In this paper, the PTS scheme generate alternative orthogonal frequency frequency division multiplexing (OFDM) signal sequences by multiplying all the time domain samples with phase rotating vectors to find an OFDM signal having the minimum peak-to-average power ratio (PAPR). However, it needs an exhaustive search which causes large computational complexity. In order to solve this problem, we propose two efficient methods based on the crest factor. The first proposed scheme is to select time domain sample with large magnitude to calculate PAPR, and the next scheme is to calculate the absolute value of real and imaginary part of the sample at each subblock. The simulation results show that the proposed schemes achieve better PAPR reduction performance than existing PTS schemes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1108-1113
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• 2000

A condition monitoring methodology for rotating machinery is proposed based on multivariate statistical analysis. The CMS usually are using the vibration signal amplitude such as acceleration RMS, peak and velocity RMS to detect machine faults but the information is not so enough that CMS cannot perform reliable monitoring. So new parameters are added such as shape factor, crest factor, kurtosis and skewness as time domain parameters and spectrum amplitude of rotating frequency, $2^{nd}$ harmonics and gear mesh frequency etc. as frequency domain parameters. Many parameters are combined to represent the machine state using the Hotelling's $T^2$ statistics. The proposed methodology is tested in laboratory and the on-line experiment has shown that the proposed methodology offers a reliable monitoring for rotating machinery.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.237-240
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• 2006

In this paper, a new design using a simulation method was proposed. And to estimate its validity, various electronic and optical data were measured after making a 150[W] electronic ballast for high pressure sodium lamps. Using PSpice 9.1, the best solutions of various parameters such as the resonant frequency, the lamp output voltage, and the current of the electronic ballast were obtained. The power factor of the system was 99.8[%], the crest factor 1.44, the THD 4.99[%], and the weight 0.5[kg]. These are very good characteristics compared with a conventional HPS Lamp ballast.

• Wind and Structures
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• v.38 no.6
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• pp.477-492
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• 2024

This study presents a comprehensive investigation of wind load characteristics and wind-induced responses associated with different wind incidence angles and terrains of the 1000kV UHV substation frame. High-frequency force balance (HFFB) force measurement wind tunnel tests are conducted on the overall and segment models to characterize wind loads characteristics such as the aerodynamic force coefficients and the shape factors. The most unfavorable wind incidence angles and terrains for aerodynamic characteristics are obtained. A finite element model of the substation frame is built to determine the wind-induced response characters based on the aerodynamic force coefficients and bottom forces of the segment models. The mean and root mean square (RMS) values of displacement responses at different heights of the frame structure are compared and analyzed. The influence of wind incidence angle and terrains on wind-induced responses is also examined. The displacement responses in terms of the crest factor method are subsequently transformed into dynamic response factors. The recommended values of dynamic response factors at four typical heights have been proposed to provide a reference for the wind resistance design of such structures.

• Korean Journal of Agricultural Science
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• v.39 no.3
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• pp.427-439
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• 2012

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the behaviour of failure due to overtopping. The pore water pressure, earth pressure and settlement by high water level, a rapid drawdown and overtopping were compared and analyzed. Also, seepage analysis and slope stability analysis were performed for steady state and transient conditions. The pore water pressure and earth pressure for inclined core type showed high value at the base of the core, but they showed no infiltration by leakage. The pore water pressure and earth pressure by overtopping increased at the upstream slope and core, it is considered a useful data that can accurately estimate the possibility of failure of the reservoir. The behavior of failure due to overtopping was gradually enlarged towards the downstream slope from reservoir crest, and the inclined core after the raising embankment was influenced significantly to prevent the reservoir failure. The pore water pressure distribution for steady state and transient condition showed positive (+) pore water pressure on the upstream slope, it was gradually changed negative (-) pore water pressure on the downstream slope. The pore water pressure by overtopping showed a larger than the high water level at the downstream slope, it was likely to be the piping phenomenon because the hydraulic gradients showed largely at the inclined core and reservoir crest. The safety factor showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.41-49
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• 2010

Stepped weir of this study was suggested a type of natural type structures. Unique flow, such as Wave type flow, at downstream of mild slope stepped occurs. WTF(Wave type flow) is different with hydraulic jump occurred at Round crest weir. WTF is phenomenon to rise the water level by recirculation area occurred by step height at downstream of mild slope stepped. Wave height of WTF condition is higher than tailwater level and maximum velocity of WTF condition occurs in area of water surface. In this results, WTF presents to be important factor for design of join area of weir with levee. This study got and analyzed hydraulic condition occurred of WTF, scales of WTF and velocity profiles on flow patterns using experiments. WTF was not consider to stepped weir design and this results can be important data for design of stepped weir and structures.

• Ocean and Polar Research
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• v.26 no.2
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• pp.219-230
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• 2004

The aims of this study are to construct database using geostatistics and Geographic Information System (GIS), and to derive the spatial relationships between manganese nodule abundance and each factor affecting nodule abundance, such as metal grade, slope, aspect, water depth, topography, and acoustic characteristics of the subbottom using the GIS and probability methods. The greater is the copper and nickel grade, the higher is the rating. The distribution pattern of nickel grade is similar to that of copper grade. The slopes are generally less than $3^{\circ}$, excluding seamounts and cliff areas. There is no increment in the rating with increasing slope. The rating is highest for slopes between 2.5 and $3.5^{\circ}$ in block B2 and between 3 and $6^{\circ}$ in block C1. The topography is classified into five groups: seamount, hill crest, hill slant, hill base or plain, and seafloor basin or valley. The ratings prove lowest for seamount and hill crest. The results of the study show a decrease in the rating with an increase in water depth in the study area. There was a poor relationship between manganese nodule abundance and the thickness of the upper transparent layer in block C1. Using GIS, it is possible to analyze a large amount of data efficiently, and to maximize the practical application, to increase specialization, and to enhance the accuracy of the analyses.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.1
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• pp.31-36
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• 2019

As the number of elderly population increases, the proportion of edentulous patients is increasing, and the demand for traditional dentures will also increase. Arranging the artificial teeth according to the relationship and shape of the upper and lower alveolar ridge is an important factor increasing the stability of the denture. This case is a 79 year old female patient who wishes to make denture covered by national health insurance for psychological and economical reasons. With the alveolar bone severely atrophic, the dental CAD software was used for accurate diagnosis and the posterior teeth were arranged in a cross bite according to the interalveolar crest line angle by the program. After completion, the denture showed adequate stability and maintenance in periodic examinations and treatment, and the patient also expressed high satisfaction.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.209-217
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• 1999

This study was concerned with comparing the measured values of labial alveolar bone through the lateral cephalometric radiography and mandibular incisor cross-sectional tomogram between two groups, one group of mandibular prognathism patients who needed an orthognathic surgery as an experimental group and the other group who had normal molar relationships as a control group. The purpose of the study was to find out the predisposing factor of bone resorption and gingival recession before orthodontic treatment. The results were as follows: 1. The cross-sectional area of labial alveolar bony plate in mandibular prognathism was significantly smaller than that of control group. 2. In mandibular prognathism, the distance between cementoenamel junction and alveolar crest was significantly greater than control group. 3. There were negative correlations between area of labial alveolar bony plate and distance from cementoenamel junction to alveolar crest, and positive correlations between area of labial alveolar bony plate and distance from alveolar crest to root apex. 4. In mandibular prognathism, there were positive correlations between IMPA and thickness of symphysis, and negative correlations between IMPA and the alveolar bony height. The results of the present study suggest the mandibular prognathism patients are prone to the gingival recession due to the small amount of labial alveolar bone around lower incisors.