• Journal of muscle and joint health
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• v.13 no.1
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• pp.7-19
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• 2006

Falls are a major sources of death and injury in elderly people. Aged-related changes in the physiological systems which contribute to the maintenance of balance are well documented in older adults. These changes coupled with age-related changes in muscle and bone are likely to contribute to an increased risk of falls in this population. Regular exercise may be one way of preventing falls and fall-related fractures. However, the optimal exercise prescription to prevent falls has not yet been defined. On the literature review of exercise intervention for fall prevention in the elderly, exercise appeared to be a useful tool in fall prevention by improving fall risk factors. The optimum exercise prescription; moderate intensity frequency of 3-4 times per week, duration of 30-60minutes can contribute to decreased hazards and number of fall. Fall prevention protocol should include safety, falling effect, enjoyment, and easiness to follow for older people. Effective exercise programs suggested for fall prevention were such as weight-bearing exercise, resistance exercise, lower muscle strength with elastic band, swiss ball exercise walking, tai chi, and yoga.

• Journal of environmental and Sanitary engineering
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• v.11 no.1
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• pp.9-15
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• 1996

The purpose of this study was to evaluate the decomposition efficiency of $NH_3$ odor gas using high frequency surface discharge body. The results from this study are as follows; 1, Voltage and frequency of electric elements have effects on removal of $NH_3$ odor. The higher these two elements were set up, the more efficiently deodorizing processing worked. In this experiment, the optimum voltage and frequency applicable were observed around AC 6.0 kVp-p and 24.0 kHz respectively. 2. The temperature, humidity and residence time were observed strong variables for NH$_3$ removal process. Its performance had limits at high temperature and humidity conditions. The longer the residence time continued, the more efficiently deodorization process worked. The experimental results showed that the deodorization was efficiently processed under such conditions as $30.0^{\circ}C$ in temperature, 60rh% in humidity and 0.3 sec in residence time. 3. It was observed that in deodorization experiment, $NH_3$ odor gas was perfectly decomposed under the concentration condition below 15.0ppm. Moreover it was considered as economic and practical in terms of maintenance cost when compared with other deodorization methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.540-546
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• 2013

The induction motor is used for driving the special equipments such as warship and submarine pump due to robust structure and simple maintenance. Domestic and foreign warships use a wide range of voltages and the DC voltage sources mainly from battery. In the low voltage level, the ${\Delta}$-connection operation of induction motor can be used for the maximum power. However, the temperature of the inverter increases because of the high input current. On the other hand, Y-connection operation of the induction motor does not cause a problem of temperature because of the low input current compared to the ${\Delta}$-connection. But the lack of the supply voltage can not be avoided. Therefore, this paper suggests the algorithm of the optimum field weakening control to extend the operating range of the induction motor with maximum power in a limited thermal and DC voltage condition.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.308-316
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• 2008

For the measurement of liquid level in ship's cargo tank, ballast tank, fuel oil tank and fresh water tank, several types of gauge meter are used such as tubular type, magnetic float type, reflex type transparent type and welding pad type. Among them, magnetic float type gauge meter is environmental friendly device because it is free of power source and maintenance. The main obstacle of the device is relatively large error bound. In this paper, finite element method is used to design and analysis of the magnetic float type gauge meter. The operation of reed switch according to the magnetic field has been successfully described and agreed well with experimental measurement. The optimum geometry with combination of permanent magnet and reed switches are designed to achieve 98 % accuracy of fluid level.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.481-484
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• 2009

It has been reported that reckless marine structures located in the coastal zone deteriorate environment and tourism due to industrialization and tourist development. Therefore, it needs to analyze am appropriate remodeling plan for environment, tourism, and safety in current marine structures and then establish the standard for the optimum remodeling design and the guidance for maintenance. Furthermore, it needs a precise simulation program about typhoons and tidal waves for the environment, safety and a three-dimensional positioning and structural modeling currently built in structures. This research has a purpose of suggesting a theoretical method for the establishment of GIS information.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.48-50
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• 2005

New environment change of electric power system focused in consumer's energy supply and demand. But electric power reliability preservation and reliability improvement countermeasure also need for long-term. It is need that change equipments that is composing electric power system in well-timed time and by maintaining, prevent breakdown beforehand and prevent consumer's power interruption by equipment fail. However, as only quantitative estimation is available by reliability estimation method that is presented in existing, it is no to use in dictionary fault prevention. Therefore, applied optimum reliability preservation through existent equipment fault data analysis of electric power system in equipment replace side, and this when maintain equipment replace of electric power system for reliability preservation using responsiveness analysis to base ordering evaluate. In existing about main equipment plain that this paper is power system the valued failure rate use this by score and precedence of electric power system equipment for replace of system considered expense.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.217-218
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• 2012

A load motor used for warship or submarine is with limited volume and weight, also specific environmental tests like impact, vibration, noise, temperature and EMC/EMI have to be satisfied. Induction motors, synchronous motors, BLDC motor and etc, are used depending on the purpose of using military equipment. Induction Motors are used for a number of military equipment more commonly due to the robust structure and simple maintenance. Domestic and foreign warships have a wide range of voltages as the DC voltage sources with battery are mainly used for them. The ${\Delta}-connection$ operation of the induction motor is required to make the maximum power in a low voltage level. But the elements' temperature of the inverter increases due to high input current when it is in the ${\Delta}-connection$ operation. Therefore, the induction motor must be driven with the Y-connection. The lack of voltage needs to be with the field weakening control. This paper suggests the optimum field weakening control algorithm to drive the induction motor with maximum power in a limited thermal and DC voltage condition.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.4
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• pp.59-74
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• 1987

In this dissertation, a complete model of commutatorless static Kramer type slip power recovery system of 3.phi. induction motor has been designed and tested in the laboratory, and the experimental results are compared with the numerical values. The main results of this study are summerized as follows. (1) Maintenance and repair of the mechanical commutator is obviated by adopting a thyristor commutator in place of the mechanical commutator in the conventional Kramer system. (2) The experimental results of developed torque, and stator current are generally coincided with the numerical values obtained by the derived equation, proving their validity. (3) This system is simulated and the following operational characteristics are obtained with suitable design values : (a) The speed control range of 7:1 is obtained when the turn ratio of induction motor is lowered to about 3:1 to 4:1 and the generating constant of auxiliary synchronous motor is increased to 120-175 range. (b) Its efficiency can be increased to 75-85%, the range for static Scherbius system and its power factor takes values in the range of 65-85%, which is twice of the range for static Scherbius system.

• Journal of Industrial Technology
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• v.5
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• pp.59-64
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• 1985

The remarkable economic growth achived during 1960-1980 in Korea inevitablely demanded the expansion and maintenance of the harbors and their auxiliary seashore facilities. One of the most important elements in the basic besign for the expasion of a harbor and its auxiliary facilities is, of course, the proper determination of the design wave which reflects the major characteristics of the seashore under consideration. In this study, the parameters of significant waves for the industrial harbors on East Coast, Muck-Ho and Po-Hang, are first computed by means of computer programming using S.M.B and P.N.J methods, respectively. Then the design waves with the return periods of 5-200 years were estimated by frequency analysis of the significant waves. A comparison of the design waves with the observed wave data during the past 10 years made it possible to determine the optimum value of design wave at the two harbors. The important results of this study can be summarized as follows; 1) It seems appropriate to take the design wave hieghts with the return period of 50 years at Muck-Ho and Po-Hang as 6.9 and 5.8 meters respectively. 2) It was found that for the determination of design waves on East Coast of Korean Peninsula P.N.J method works better than S.M.B method in predicting the significant wave, and the Log-Normal distribution fits best to the wave data which were put to frequency analysis.