• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.263-270
• /
• 1996

Noise control of a plate structure with multiple disk shaped piezoelectric actuators is studied. The plate is excited by an acoustic pressure field produced by a noise source located below the plate. Finite element modeling is used for the plate structure that supports a combination of three dimensional solid, flat shell and transition elements. The objective function, in the optimization procedure, is to minimize the sound energy radiated onto a hemispherical surface of given radius and the design parameters are the locations and sizes of the piezoelectric actuators as well as the amplitudes of the voltages applied to them. Automatic mesh generation is addressed as part of the modeling procedure. Numerical results for both resonance and off resonance frequencies show remarkable noise reduction and the optimal locations of the actuators are found to be close to the edges of the plate structure. The optimized result is robust such that when the acoustic pressure pattern is changed, reduction of radiated sound is still maintained. The robustness of an optimally designed structure is also tested by changing the frequency of the noise source using only the actuator voltages as design parameters.

• Journal of the Korean Society of Physical Medicine
• /
• v.11 no.3
• /
• pp.55-58
• /
• 2016

PURPOSE: This study was measured the differences in the flexor and extensor muscle activities of the elbow joints based on the tire pressure of wheelchairs during propulsion, investigating the optimal tire pressure for improving occupants' propulsion and avoiding related injury. METHODS: Ten healthy volunteers (10 men aged $23.1{\pm}1.9years$, weight: $67.9{\pm}3.4kg$, height: $175.1{\pm}2.7cm$) took part in the study. The mean values used in the statistical process were obtained from values measured while a subject sitting on a wheelchair propelled himself forward for 10 meters on a flat floor at maximum speed. The tire pressure of the wheelchairs was set at 100 psi, 50 psi, and 25 psi. All of the subjects performed wheelchair propulsion for each pressure. This study was measured the activation of the biceps brachii and triceps brachii muscles on the dominant side during wheelchair propulsion. The measured data was analyzed using one-way analysis of variance (ANOVA) via the statistical package for the social sciences (SPSS) version 12.0 for Windows to compare the muscle activity. RESULTS: The muscle activities of the biceps brachii and triceps brachii were significant differences between each pressure group. The post hoc test found statistically significant differences between 100 psi and 50 psi and 100 psi and 25 psi for the biceps brachii and triceps brachii muscles, respectively. CONCLUSION: The maintaining proper tire pressure in a wheelchair may help to prevent overuse syndrome in the occupant's elbow joints.

• The KIPS Transactions:PartC
• /
• v.13C no.5 s.108
• /
• pp.601-606
• /
• 2006

Decode-and-forward cooperative communications protocol (DFP) allows single-antenna users in wireless medium to obtain the powerful benefits of multi-antenna systems without physical antenna arrays. For this protocol, so far the relays have used SNR to evaluate the reliability of the received signal before deciding whether to forward the decoded data so as to prevent their unsuccessful detection. However, SNR only characterizes the long-term statistic of Gaussian noise and thus leading to inaccurate assesment. Therefore, we propose using log-likelihood ratio (LLR) which accounts for the instantaneous noise in the received signal as an alternative to SNR. A variety of simulation results reveal the significant superiority of the SNR-based DFP to the SNR-based DFP regardless of threshold level and relay position under the flat Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.4 no.3
• /
• pp.146-155
• /
• 1992

It has been conventional to treat the land boundary as a fixed one in numerical modeling of tidal flows, particularly in the finite element scheme. However conventional models using the fixed land boundary result in unrealistic tidal flows in inter-tidal zones which exist over wide coastal area in Korea. In this study, a 2-dimensional hydrodynamic model, using finite element method for moving boundary problems was developed. The performance of the model was tested in a rectangular channel with an open boundary at one end and a moving boundary at the other end. The model was applied to calculate the tidal currents in Maro Hae, located in the southwestern part of Korea where wide tidal flats develop. The behavior of tidal currents in the Udolmok and near the tidal flats in the study area was satisfactory when compared with the observed data. Variation of tidal currents due to the construction of Kochunam sea-dyke which barrages large area of tidal flat was presented. The results of this study confirm the efficiency of moving boundary treatment in coastal numerical models.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.26 no.6
• /
• pp.901-910
• /
• 2002

This study is to classify somatotypes of the upper class boys in elementary school. The study is conducted through anthoropometric measurements and photometric measurements. The subjects are 320 boys in the age group of 10 to 11 years old. The following conclusions are drawn from this study. 1. The height items are increased along with age increase. The increases in the factors, which specify vertical sizes such as height and length, are a little larger than those of breadth, depth, and girth, which specify ; horizontal sizes. 2. The factor analysis on anthropometric measurements and photometric measurements reveals five somatic composition factors and those factors comprised 79.60% of total variance. 3. The torso shapes of the upper class boys in elementary school are classified into three categories. The first type is taller and heavier than the average elementary school upper class boys and has the highest rising shoulders. The shape of the back is about average and the chest is developed above average. The curvature of the lower back is gentle and lower abdomen protrudes the most of the three types. The second type is tall and slightly heavier than average and shoulders are raised a little. The shoulder blades protrude about average and the curvature of lower back is the most developed of all. The cheat is developed about average and the abdomen is a little protruding. The third type is the most common with the smallest height of the three and skinny with dropped shoulders. The chest is somewhat flat and the shoulder blades protrude about average.

• Journal of Fashion Business
• /
• v.22 no.4
• /
• pp.118-129
• /
• 2018

The purpose of this study is to develop ECG electrode materials for the heart rate monitoring smart band, a smart device used for ECG and heart rate measurement. The purpose of the evaluation is to assess properties and conductivity of electrodes of the existing heart rate monitoring smart band, and to determine suitability through a representative conductive sample. Because level of thickness does not differ significantly from value of conductive specimen from thickness of the smart band, it can be used as a conductive electrode. Surface conductivity of conductive samples and smart bands, is expected to be available as electrodes except for conductive film. Also, since the knit have conductivity only in the metal processing layer, it is necessary to use electrodes on the part of the metal processing layer that is conductive when applying the knit. Tensile strength and electrical conductivity of the tensile were generally revealed to have a tendency. Thickness of the specimen that can be used as an electrode for the smart band is suitable for all samples, electrical resistance, conductive woven, conductive knit, and conductive cord. In the case of conductive cord, however, the electrode attached to the human body will not conform to the flat shape of the electrode attached to the human body. Therefore, the conductive woven and the conductive knit will be available as an electrode.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.59 no.4
• /
• pp.109-117
• /
• 2017

Coastal reclamation has created large flat lands, part of which is an attractive site to construct greenhouse complexes for the horticulture industry. Wind environments over these coastal lands are entirely different from those of the inland area, and demand increased structural safety. The objective of this study is to evaluate the structural safety of two single-span greenhouses, peach type and even-span type, under the wind characteristics of coastal reclaimed lands. The wind pressure coefficients acting on the walls and roofs of two greenhouses were measured by wind tunnel experiments, and those acting on the roofs were approximately two times larger than those suggested by the existing design guidelines. Consequently, structural analysis conducted by SAP2000 showed that greenhouse structures designed by the existing guidelines might lead to structural failure under coastal wind conditions because their maximum allowable wind speeds were lower than the design wind speed. Especially, the peach type greenhouse constructed in a reclaimed land could be damaged by approximately 48 % of the design wind speed and needed improvement of structural designs. This study suggested increasing the spacing of rafters with thicker pipes for the peach type greenhouse to enhance economic feasibility of the building under strong wind conditions of reclaimed lands.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.42 no.6
• /
• pp.683-694
• /
• 2009

High-resolution (Chirp and Sparker system) seismic profiles were analyzed to investigate the sedimentary sequence and distribution pattern of the late Holocene deposits in Gyunggi Bay, the Yellow Sea. The bay is located in the western part of Korea, east of the Yellow Sea. The sedimentary sequence divided into three units bounded by erosional bounding surface: (1) acoustically parallel to subparallel reflectors with cross bedding structures (Unit 1); (2) confused inner reflectors and top of unit exposed partially at the seafloor (Unit 2); and (3) approximately parallel reflections and regressive to transgressive incision-fills (Unit 3). On the basis of seafloor morphology, surface bedforms, and subbotom acoustic characters, echo types in the study area were identified following the schemes of Chough et al. (2002); (1) flat seafloor with sharp bottom echoes (echo types 1-1, 1-2 and 1-3; transgressive sediment sheets or relict sands), (2) mounded seafloor with either smooth surface or superposed bedforms (echo types 2-1 and 2-2; tidal ridges), and (3) various-scale eroded seafloor (echo types 3-1 and 3-2; channels). Suspect features of acoustic turbid zones which is related to gas charged sediment are reported.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.9 no.2
• /
• pp.79-84
• /
• 2006

The present study deals with the flow over a flat plate with repeated roughness elements of 2-dimensional rectangular shape, which can be applied into the study on the natural geographical roughness and the turbulent flow on roughened solid surface. Experiment was performed using PIV technique in the circulating water channel. Results showed that the flow over roughness elements was characterized by the high shear flow emanating from top of roughness element and the recirculating region formed at the trough of two roughness elements. In general, the ratio between the spacing and the height of roughness elements plays a crucial role in developing the flow pattern near wall surface.

• The KIPS Transactions:PartD
• /
• v.12D no.2 s.98
• /
• pp.247-258
• /
• 2005

Protein structure is highly related to its function and comparing protein structure is very important to identify structural motif, family and their function. In this paper, we construct an integrated database system which has all the protein structure data and their literature. The structure queries from the web interface are compared with the target structures in database, and the results are shown to the user for future analysis. To constructs this system, we analyze the Flat-File of Protein Data Bank. Then we select the necessary structure data and store as a new formatted data. The literature data related to these structures are stored in a relational database to query the my kinds of data easily In our structure comparison system, the structure of matched pattern and RMSD valure are calculated, then they are showed to the user with their relational documentation data. This system provides the more quick comparison and nice analyzing environment.