• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.889-901
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• 2003

In this paper, we consider the optimal replacement policies following the expiration of the combination warranty. The combination warranty can be divided into the renewing combination warranty and the non-renewing combination warranty. The criterion used to determine the optimal replacement period is the overall value function based on the expected cost and the expected downtime. Thus, we obtain the expected cost rate per unit time and the expected downtime per unit time for our model. And then the overall value function suggested by Jiagn and Ji(2002) is applied to obtain the optimal replacement period. The numerical examples are presented for illustrative purpose.

• Bulletin of the Korean Mathematical Society
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• v.41 no.4
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• pp.641-646
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• 2004

A convex combination of two products with same degree of finitely many finite geometric series with each having even degree does not always have all its zeros on the unit circle. However, in this paper, we show that a polynomial obtained by just adding a finite geometric series multiplied by a large constant to such a convex combination has all its zeros on the unit circle.

• Journal of Korean Neurosurgical Society
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• v.59 no.4
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• pp.334-340
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• 2016

Objective : The aim of our study was to evaluate the neuroprotective functions of the combination therapy using methylprednisolone (MP) and tranilast (TR) after spinal cord injury (SCI) in adult rats. Methods : Spinal cord compression injury model was achieved using Yasargil aneurysm clip. Rats were divided into control group, MP group, TR group, and combination therapy group using TR and MP. Rat models were assessed for locomotor functional recovery using Basso, Beattie, and Bresnahan (BBB) score, spinal cord water content and myeloperoxidase (MPO) activity 24 hours post SCI, haematoxylin and eosin staining and glial fibrillary acid protein (GFAP) staining at 7 and 14 days post SCI. Results : The spinal cord water content and MPO activity in the combination therapy group was significantly lower than the control group and the individual therapy groups p<0.05. The combination therapy group had significantly higher BBB scores than control group and individual therapy groups (p<0.05). At one week after SCI, GFAP expression in the combination group was significantly lower than the control group (p<0.05) but there was no significant difference compared to the individual therapy groups (p>0.05). At 2 weeks after SCI there was a slight decrease in GFAP expression compared to the first week but the difference was not statistically significant (p>0.05), GFAP expression between the groups was not statistically significant p>0.05. Conclusion : Combining MP and TR is therapeutically more effective in improving functional recovery, inhibiting inflammation and glial scar formation after acute SCI.

• International Journal of Reliability and Applications
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• v.3 no.3
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• pp.113-124
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• 2002

This paper suggests the optimal periodic preventive maintenance policies after the combination warranty is expired. After the combination warranty is expired, a repairable system undergoes PM periodically and is minimally repaired at each failure. And also the system is replaced by a new system at the N th PM. In this case, we derive the mathematical formula for the expected cost rate per unit time. The optimal number and period for the periodic PM that minimize the expected cost rate per unit time are obtained. Some numerical examples are presented for illustrate purpose.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4197-4203
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• 2013

In order to investigate the heating performance of multi-heat pump applying an inverter compressor, the experiment on heat pump with 3 indoor units was performed under the heating standard and heating low-temperature conditions. The performance data of heat pump with 3 indoor units were measured by the multi-psychrometric calorimeter. The operation characteristics and the behavior of the refrigerant cycle of the heat pump with 3 indoor units were understood from the heating capacity, heating COP, and P-h diagram by indoor-unit combination. The present experimental results show that the operating load and performance of the multi-heat pump depends on the indoor-unit combination. The heating capacity and heating COP of the low temperature condition were smaller than those of the standard one. Also the refrigerant cycles on indoor-unit combination were analyzed by using P-h diagram.

• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.79-89
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• 2016

In this paper, we proposed the object classification method using genetic and dynamic random forest consisting of optimal combination of unit tree. The random forest can ensure good generalization performance in combination of large amount of trees by assigning the randomization to the training samples and feature selection, etc. allocated to the decision tree as an ensemble classification model which combines with the unit decision tree based on the bagging. However, the random forest is composed of unit trees randomly, so it can show the excellent classification performance only when the sufficient amounts of trees are combined. There is no quantitative measurement method for the number of trees, and there is no choice but to repeat random tree structure continuously. The proposed algorithm is composed of random forest with a combination of optimal tree while maintaining the generalization performance of random forest. To achieve this, the problem of improving the classification performance was assigned to the optimization problem which found the optimal tree combination. For this end, the genetic algorithm methodology was applied. As a result of experiment, we had found out that the proposed algorithm could improve about 3~5% of classification performance in specific cases like common database and self infrared database compare with the existing random forest. In addition, we had shown that the optimal tree combination was decided at 55~60% level from the maximum trees.

• The Journal of Korean Physical Therapy
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• v.24 no.1
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• pp.1-6
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• 2012

Purpose: The grip strength is influenced by various factors, such as position of the upper extremity, characteristics of the hand, and general physical condition. In this study, we investigated whether abdominal muscle activity in combination with the abdominal drawing-in maneuver has any effect on the grip strength in healthy young adults. Methods: This study included 31 healthy subjects (16 males, 15 females). We used surface electromyography and pressure bio-feedback unit for this experiment. All Subjects were placed in a cock-lying position with comfort and the grip strength was measured. On the following day, the pressure bio-feedback unit was placed beneath their fifth lumbar vertebra, and the, grip strength was measured again. This time, the measurement was taken while drawing-in their abdomen below the navel gently and gradually, while maintaining a neutral pelvic position. Results: The grip strength was significantly increased when subjects performed the drawing-in maneuver than when they were comfortable (p<0.05). In addition, activations of the rectus abdominal muscles significantly increased (p<0.05). Conclusion: In the current study, we found that abdominal muscle activity, in combination with the abdominal drawing-in maneuver, affected the grip strength, positively. Therefore, we suggest that this result should be considered when evaluating the grip strength.

• Journal of architectural history
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• v.28 no.5
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• pp.19-26
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• 2019

The subjects of this study were limited to Silla buddhist temple remains in the 6~8th century, where the excavation survey report was published and the details of the remains of the corridor are revealed. Since the corridor completes the structure of temple and is involved in formation of the space, the building plan for corridors is thought to have an intention linked to the entire temple. Thus, more closer study is required for this construction plan to identify the role of corridors. The corridor is a building that has a low architectural hierarchy and completes the layout and composition of the temple. In the unit planning of the corridor, unit were designed to be of a certain size in the temple layout. Then, the overall scale was made by adding the fixed size of unit. The combination of corridors are the combined points of paths and were used as visual points. The structure of the corridor was constructed to be adjusted according to the size of the main compartment of the building to which it was connected and inserted under the roof of the building. The adjustment of the unit changed in the range of 0.5 to 2 of Silla's system of measurement. The usage of embedded pillar in the corridor presents a new perspective on Silla architecture.

• Bulletin of the Korean Mathematical Society
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• v.44 no.3
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• pp.461-473
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• 2007

For integral self-reciprocal polynomials P(z) and Q(z) with all zeros lying on the unit circle, does there exist integral self-reciprocal polynomial $G_r(z)$ depending on r such that for any r, $0{\leq}r{\leq}1$, all zeros of $G_r(z)$ lie on the unit circle and $G_0(z)$ = P(z), $G_1(z)$ = Q(z)? We study this question by providing examples. An example answers some interesting questions. Another example relates to the study of convex combination of two polynomials. From this example, we deduce the study of the sum of certain two products of finite geometric series.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.296-297
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• 2011

Many applications involving induction motors that are controlled using variable frequency drives require the ability to stop quickly. These applications include emergency stops, quick stopping of fans, centrifuges, presses, etc. The technique that is widely accepted in the industry for achieving quick stopping makes use of brake resistors in series with a power semiconductor switch. The switch-resistor combination (brake-unit) is applied across the dc bus. The fastest decelerating time achievable depends on the size of the resistors and the switch employed. In this paper, the authors propose a novel method of achieving quick stopping times without the use of any brake-unit. Experimental test results with and without this method on a large inertia motor-load combination show that the proposed stopping method is able to reduce the stopping time significantly compared to normal decelerated stop without the need for a braking unit.