• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.255-261
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• 2022

In this work, the strain-amplitude independent and strain-amplitude dependent damping capacities of Mg-5%Sn alloy have been investigated as a function of its age-hardening response. The hardness increased with an increase in aging time, reached a peak value after 48 h, and then it gradually decreased. The damping capacities of the Mg-5%Sn alloy exhibited a decreasing tendency in the order of solution-treated, under-aged, peakaged, and over-aged states in the strain-amplitude dependent region, whereas they increased continuously with aging time in the strain-amplitude independent region. The microstructural examination during aging revealed that the lower concentration of Sn solutes in the α-(Mg) matrix and the lower density of the Mg₂Sn precipitate particles may well be the crucial factors for better damping values in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.2
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• pp.313-319
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• 1999

We devise the 3 models of Multilayered Recurrent Prediction Neural Network(MLRPNN), which are obtained by modifying the Multilayered Perceptron(MLP) with 4 layers. We experimentally study the speech recognition performance of 3 models by a comparative method, according to the variation of the prediction order, the number of neurons in two hidden layers, initial values of connecting weights and transfer function, respectively. By the experiment, the recognition performance of each MLRPNN is better than that of MLP. At the model that returns the output of the upper hidden layer to the lower hidden layer, the recognition performance shows the best value. All MLRPNNs, which have 10 or 15 neurons in the upper and lower hidden layer and is predicted by 3rd or 4th order, show the improved speech recognition rate. On learning, these MLRPNNs have a better recognition rate when we set the initial weights between -0.5 and 0.5, and use the unipolar sigmoid transfer function in the lower hidden layer.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.2
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• pp.237-248
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• 2001

The purpose of this study was to compare the comfort sensation depending on four different kinds of denim blue jeans: cotton, cotton/tencel, tencel, cotton/pp. The objective and subjective experiments were conducted to measure the comfort of blue jeans. To investigate the objective comfort, physical properties related to thermal insulation, moisture properties and hand were measured. For subjective comfort measurement, 5 healthy female college students were taken as subjects. The outcomes of the experiments are as follows: The higher the air permeability and bulk density of the denim, the lower the thermal insulation, the thicker the denim, the higher the thermal insulation. Tencel blending denim showed the higher bulk density, the lower air contents, and consequently the lower thermal insulation than the other denims. Tencel showed the highest moisture regain, and cotton/tencel blend showed the highest water vapor permeability. Tencel denim had relatively better flexibility, shape stability and elastic recovery than the other denims. The total hand values of the denims by KES-FB system were not significantly different. Cotton and cotton/pp denims raised the subjects body temperature after excercise more than tencel or cotton/tencel denims. Average skin temperature was found to have a correlation with micro climate temperature and micro climate humidity. The correlation coefficients were 0.749 and 0.767, respectively. However, average skin temperatures were not significantly different among the materials. Pulse rate was found to be the highest when wearing cotton/pp and the lowest in case of cotton/tencel denim. The energy was consumed in order of cotton>cotton/pp>tencel>cotton/tencel. There was no significant difference in preference before excercise, but, after the excercise, the order of preference changed as the following; cotton/tencel>tencel>cotton/pp>cotton.

• Journal of Korean society of Dental Hygiene
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• v.9 no.2
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• pp.45-56
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• 2009

The purposes of this study were to investigate the relationships between the degree of physical pain and the knowledge and preventive actions of musculoskeletal diseases among dental hygiene students with a potential risk of contracting those diseases and thus to help them prevent them. A survey was taken among 207 sophomores and juniors specializing in dental hygiene at S1 and S2, Gyeonggi Province in the area of physical pain, knowledge of musculoskeletal diseases, and preventive actions against them. The findings were as follows: 1. The mean scores of the sophomore in the knowledge of musculoskeletal diseases were $6.20{\pm}2.21$, and those of the juniors were $6.72{\pm}2.29$. The mean scores of the sophomores and juniors in the preventive actions against musculoskeletal diseases were $22.50{\pm}2.37$ and $22.29{\pm}3.01$, respectively. 2. The subjects displayed severe physical pain in the lower back, shoulder, and neck in the descending order and medium physical pain in the neck, shoulder, and lower back in the descending order. 3. The higher level knowledge of musculoskeletal diseases they had, the less physical pain they felt. And there were significant differences among the shoulder, lower back, hip, ankle, and foot. 4. There were relationships between physical pain and the preventive actions against musculoskeletal diseases in "placing the hands at the height of the elbows during treatment", "reducing such positions as bending and extending during treatment", "narrowing the distance with the patient", "taking regular breaks during treatment for recovery", "trying not to incline the neck, back, arm, and wrist as much as possible", and "trying to keep the torso in the neutral position." 5. As for the education about musculoskeletal diseases, 74 sophomores(88.10%) and 102 juniors(89.74%) answered they received no such education. The results suggest that there should be some instructions to help dental hygiene students practice the preventive actions against musculoskeletal diseases and further prevention programs against those diseases.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.803-810
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• 1997

Ba0.5Sr0.5TiO3 thin films were deposited by RF magnetron sputliring method in order to clarify the anneal condition and doping effect on loakage current Nb and Al were selected as electron donor and acceptor dopants respectively, in the BST films because they have been known to have nearly same ionic radii as Ti and thought to substitute Ti sites to influence the charge carrier and the acceptor state adjacent to the gram boundary. BST thin films prepared in-situ at elevated temperature showed selatively high leakage current density and low breakdown voltage. In order to achieve smooth surface and to improve electrical properties, BST thin films were deposited at room temperature and annealed at elevated temperature. Post-annealed BST thin films showed smoother surface morphology and lower leakage current density than in-situ prepared thin films. The leakage current density of Al doped thin films was measured to be around 10-8A/cm2, which is much lower than those of undoped and Nb doped BST films. The result clearly demonstrates that higher Schottky barrier and lower mobile charge carrier concentration achieved by annealing in the oxygen atmosphere and by Al doping are desirable for reducing leakage current density in BST thin films.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.51-56
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• 2016

High brittleness is a characteristic of glass, and in many cases it is broken during the process of machining due to processing problems, such as scratches, chipping, and notches. Machining defects occur due to the vibration of the equipment. Therefore, design techniques are needed that can control the vibration generated in the equipment to increase the strength of tempered glass. The natural frequency of the machine tool via vibration analysis (computer simulation) must be accurately understood to improve the design to ensure the stability of the machine. To accurately understand the natural frequency, 3D modeling, which is the same as actual apparatus, was used and a constraint condition was also applied that was the same as that of the actual apparatus. The maximum speeds of ultrasonic and high frequency, which are 15,000 rpm and 60,000 rpm, respectively, are considerably faster than those of typical machine tools. Therefore, an improved design is needed so that the natural frequency is formed at a lower region and the natural frequency does not increase through general design reinforcement. By restructuring the top frame of the glass processing, the natural frequency was not formed in the operating speed area with the improved design. The lower-order natural frequency is dominant for the effects that the natural frequency has on the vibration. Therefore, the design improvement in which the lower-order natural frequency is not formed in the operating speed area is an optimum design improvement. It is possible to effectively control the vibrations by avoiding resonance with simple design improvements.

• Korean Journal of Organic Agriculture
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• v.7 no.2
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• pp.1-16
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• 1999

In this study, questionnaire were made to environment-friendly producers of apples regarding farm management methods in low-input production method. utilizing organic materials, production and marketing of apples with lower agricultural chemical residues. Besides, five apples farms were visited to find out their management situation by employing the low-input production method in order to protect the environment as well as consumer's health. Those five low-input apple farms were scattered in Kyungbuk, Chungnam, and Chonnam Provinces, There were not many low-input apple farms across the nation from the beginning and, as a result, increasing the sample size was basically very difficult. Most of these farms were using 140hrs of labor per 10a, of which 30hrs in pre-season management, 25hrs in plowing and weed control, 15hrs in disease and pest control, 20hrs in harvest and marketing and 50hrs in miscellaneous activities. Relatively, pest control takes much time in that they would spray pesticides 7-10 times a season to control the apple disease, 9 times on the average. The average gross revenue of low-input apple farms was about \2,000,000/10a, and their average yield was 2,000kg/10a, which are 25% and 13% lower, respectively, than the ordinary apple production case. This means the low-input farmers are inefficient in marketing their products. On the other hand, their production costs were 20.4% higher than the ordinary apple farms on the average. Since the imported foreign fruits including apples must use various agricultural chemicals on their way to the export markets, the domestic low-input apples have competitive edge over them in therms of food safety. In order to improve the low-input apple industry, active cooperation is needed among the producers, government and researchers more than ever. Among other things, production cost reduction and quality improvement with lower chemical residues are part of the urgent matters to be done.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1442-1447
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• 2005

Based on the field measuring data obtained from excavation sections in Inchon International Airport project, the relationships between the horizontal displacement of sheet-pile walls and the deformations of soft ground around the excavation were investigated. The horizontal displacements of walls according to supporting method are largely occurred in order of anchors, anchors with struts, and struts. The depths of maximum horizontal displacement are varied with supporting systems. If the stability number shows lower than ${\pi}$, the maximum horizontal displacement and the velocity of maximum horizontal displacement are respectively developed less than 1% of excavation depth and 1mm/day. When the stability number shows lower than ${\pi}+2$, the maximum horizontal displacement and the velocity are respectively developed less than 2.5% of excavation depth and 2mm/day. Also, when the stability number shows more than ${\pi}+2$, the maximum horizontal displacement and the velocity are rapidly increased.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.7
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• pp.711-717
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• 2007

Location information will become increasingly important for future Pervasive Computing applications. Location tracking system of a moving device can be classified into two types of architectures: an active mobile architecture and a passive mobile architecture. In the former, a mobile device actively transmits signals for estimating distances to listeners. In the latter, a mobile device listens signals from beacons passively. Although the passive architecture such as Cricket location system is inexpensive, easy to set up, and safe, it is less precise than the active one. In this paper, we present a passive location system using Cricket Mote sensors which use RF and ultrasonic signals to estimate distances. In order to improve accuracy of the passive system, the transmission speed of ultrasound was compensated according to air temperature at the moment. Upper and lower bounds of a distance estimation were set up through measuring minimum and maximum distances that ultrasonic signal can reach to. Distance estimations beyond the upper and the lower bounds were filtered off as errors in our scheme. With collecting distance estimation data at various locations and comparing each distance estimation with real distance respectively, we proposed an equation to compensate the deviation at each point. Equations for proposed algorithm were derived to calculate relative coordinates of a moving device. At indoor and outdoor tests, average location error and average location tracking period were 3.5 cm and 0.5 second, respectively, which outperformed Cricket location system of MIT.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.51-61
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• 1983

By using local earthquake data, the Korean crust model and travel-time tables were determined. The upper crustal earthquakes (Hongsung event and Ssanggyesa event) were considered as auxiliary information, and the lower crustal earthquakes (Uljin event and Pohang event) played an important role in determining model parameters. The possible existence of Low Velocity Layer (LVL) in the upper mantle was suggested by discrepancy in the arrival times of Sariwon earthquake which occurred below Moho discontinuity. Computer program for the determination of the model parameters was developed in order to screened out the optimum parameters by comparing the travel times of observed data with theoretical ones. We found that the discontinuities of Conrad, Moho, and upper and lower boundaries of LVL have their depth of 15, 32, 55 and 75 Km, respectively. The velocities of P-and S-wave in the layers between those discontinities were found to be (1) 5.98, 3.40 Km/sec (2) 6.38, 3.79 Km/sec (3) 7.95, 4.58 Km/sec (4) unknown (5) 8.73, 5.05 Km/sec, respectively from the top layer. Travel-time tables were also computed for the inter-local earthquakes which have their direct wave paths above the LVL.