• Journal of Korean Society of Industrial and Systems Engineering
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• v.6 no.8
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• pp.81-91
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• 1983

In this study the methods of the overhead standard setting and the overhead variance analysis, which raise problems especially in business practice in case that small businesses introduce the standard cost accounting system, were examined by hypothetical examples. As the result of this study small businesses are advised to take the following in setting the overhead cost. (1) To divide the mixed cost into variable overhead and fixed overhead, it is desirable to take Beast square method. (2) In setting the overhead standard, it is desirable to fake the flexible budget system and to make a budget by the inspection method, after dividing the overhead into variable overhead and fixed overhead. (3) After dividing the overhead variance into variable overhead variance and fixed overhead variance, it is desirable to analyze them as follows. (A) Variable overhead variance is analyzed into spending variance and efficiency variance. (B) Fixed overhead valiance is analyzed into budget variance and denominator variance.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.395-398
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• 1996

In this study, when the nonlinear overhead crane which allows simultaneously travel and traverse motion moves a desired transport route, the object suspended the end of rope does undesirable swing motion. Nonlinear overhead crane pertubes in the vicinity of an operating point, therefore the nonlinear overhead crane is modified to linear overhead crane for the operating point. The linear overhead crane was controlled to swing angles of the object by the ratio of torque inputs to motors of the girder and the trolley. As a basis for the result of the linear overhead crane, the nonlinear overhead crane was controlled swing angles of the object and positions of the overhead crane without collision with environmental equipment by partial state feedback control.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1641-1643
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• 1998

In recent the maximum voltage of overhead power transmission lines in Korea was upgraded to 765kV. In general a overhead ground wire is installed for protecting overhead power transmission lines from lightning. For the 765kV line, Composite Overhead Ground Wire with Optic Fiber (OPGW) is applied as a overhead ground wire and have a function of the communication line between substations. In this paper, the construction and properties of OPGW, and its installation methods are discribed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.26-33
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• 2013

Femto-cells are low power/cost, micro-base stations and are main components in heterogeneous networks. However, some of technical issues arise when femto-cells are initially installed. One approach to resolve the problems is to control the transmission (TX) power autonomously via SON(Self-Organized Network) scheme. By controlling the femto-cell TX power, the system throughput performance can be improved or the system overhead is highly reduced. Generally, the TX power for maximizing the system throughput and that for reduced system overhead may not be identical. Therefore, we propose a TX power control scheme by which we can improve the system throughput and reduce the system overhead, simultaneously. When we apply the proposed method, the simulation results show that the system overhead can be reduced by up to 41% compared to the performance of the method which maximizes throughput performance only, and the throughput performance can be improved by up to 63% compared to that of the method which only optimizes the coverage area.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.191-196
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• 2010

The electricity distribution system in Korea is adopting a multi-grounding system. Protection of this distribution system against lightning is performed by installing overhead ground wires over the high voltage wires, and connecting the overhead ground wires to the ground every 200 m. The ground resistance in this system is limited not to exceed $50\Omega$ and overhead ground wire and neutral wire are multiple parallel lines. Although overhead ground wire and neutral wire are installed in different locations on the same pole, this circuit configuration has duplicated functions of providing a return path for unbalanced currents and protecting the distribution system against induced lightning. Therefore, the purpose of this study is to analyze the induced lightning shielding effect according to the neutral wire installation structure of a 22.9kV distribution line in order to present a new 22.9kV distribution line structure model and characteristics. This study calculated induced lightning voltage by performing numerical analysis when an overhead ground wire is present in the multi-grounding type 22.9kV distribution line structure, and calculated the induced lightning shielding effect based on this calculated induced lightning voltage. In addition, this study proposed and analyzed an improved distribution line model allowing the use of both overhead wire and neutral wire to be installed in the current distribution lines. The result of MATLAB simulation using the conditions applied by Yokoyama showed almost no difference between the induced lightning voltage developed in the current line and that developed in the proposed line. This signifies that shielding the induced lightning voltage through overhead wire makes no difference between current and proposed distribution line structures. That is, this study found that the ground resistance of the overhead wire had an effect on the induced lightning voltage, and that the induced lightning shielding effect of overhead wire is small.

• Health Policy and Management
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• v.10 no.4
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• pp.116-143
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• 2000

Considerable attention has been devoted in the accounting literature to identify the factors that cause or drive the costs of overhead activities. This paper extends recent cost driver research to the health care provider. In various case studies, it has been suggested that overhead costs are driven by volume and complexity variables. This paper investigates the significance of these variables in determining hospital overhead costs, how they are structurally related and how the cost impacts of these variables can be estimated in practice. This paper analyzes the determinants of hospital costs using the sample of South Korea hospitals for seven year during the period 1952－1997. The paper focuses on the extent to which hospital overhead costs depend on complexity, efficiency in addition to depending on more conventional volume based measures of hospital activity. The results of regression analysis suggest that volume and complexity factors positively and significantly affect overhead costs in the hospital industry. The results show that the complexity-related cost drivers strongly affected on the overhead costs in tile health care provider industry more than manufacturing industry which is mainly affected by volume-related cost drivers. That means each Industry may have different cost structures. Therefore it Is Important to find their proper cost structures and cost drivers and use them. Futhermore identification of overhead or indirect cost drivers is likely to be particularly useful in heath care. The identification of cost drivers can be of benefit to all health care stakeholders because these facilitates more efficient management of the national resources devoted to health care. While this study has documented that the level of service complexity is a significant determinant of hospital overhead costs, caution should be exercised in interpreting this as supportive of the cost accounting procedures associated with ABC. It is an open question whether even a well-designed ABC system will provide suitable proxies for marginal costs for decision making purposes.

• Journal of Communications and Networks
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• v.6 no.4
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• pp.331-342
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• 2004

We study the problem of controlling data overhead of mesh-based multicast ad hoc routing protocols by adaptively adding redundancy to the minimal data overhead multicast mesh as required by the network conditions. We show that the computation of the minimal data overhead multicast mesh is NP-complete, and we propose an heuristic approximation algorithm inspired on epidemic algorithms. In addition, we propose a mobility-aware and adaptive mesh construction algorithm based on a probabilistic path selection being able to adapt the reliability of the multicast mesh to the mobility of the network. Our simulation results show that the proposed approach, when implemented into ODMRP, is able to offer similar performance results and a lower average latency while reducing data overhead between 25 to 50% compared to the original ODMRP.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.90-97
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• 2017

Overhead cranes are the most widely used and have been identified as one of the main causes of fatal accidents. Although structural, mechanical and electrical safety standards for overhead cranes have been established to some extent, ergonomic standards related to crane controllers are rarely established. As a result, many crane accidents are reported to be caused by operator's error. To investigate the actual use of crane controllers in the industrial field, we surveyed 82 overhead cranes in 15 workplace and interviewed workers operating them. This study has presented the ergonomic problems related to the crane controllers in the field. As a result of investigation, it was found that the direction control signs, the sign language, and the button layout on the pendant switches and remote controllers are not standardized, which can cause a human error. To reduce human errors in overhead crane operation, ergonomic standards for controllers should be reflected on the government legislation or standards.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.128-135
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• 2005

Overhead crane systems consist of trolley, girder, rope, objects, trolley motor, girder motor, and hoist motor. The dynamic system of these systems becomes a nonlinear state equations. These equations are obtained by the nonlinear equations of motion which are derived from transfer functions of driving motors and equations of motion for objects. From these state equations, Lyapunov functions of overhead crane systems are derived from integral method. These functions secure stability of autonomous overhead crane systems. Also constraint equations of driving motors of trolley, girder, and hoist are derived from these functions. From the results of computer simulation, it is founded that overhead crane systems is secure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.112-117
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• 1997

This paper presents a GA(Genetic Algorithms)-Optical control strategy for the control of the swing motion and the transverse position of the overhead crane. The overhead crane system is defined uncertain due to unknown system parameters such as payload and trolly mass. To control the overhead crane. the GA-Optimal control scheme is suggested. which transfers a trolly to a desired place as fast as possible and minimizes the swing of the payload during the transfer. The genetic algorithms are applied to fine digital optimal feedback gains. A computer simulation demonstrate the performance of the proposed the GA-digital optimal controller for the overhead crane.