• Journal of Korean Institute of Industrial Engineers
• /
• v.16 no.1
• /
• pp.115-122
• /
• 1990

Kanban, a pull system for inventory control is in direct contrast to conventional push systems. In the pull system, the kind and quantity of items needed by the succeeding stage are withdrawn from the preceding stage, only at the rate and at the time they are consumed. In this paper, lot size models are formulated in two special cases of practical interests and simple solution procedures are adapted to minimize the total cost of the kanban system. An numerical example is solved to illustrate the method.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.5
• /
• pp.462-466
• /
• 2008

This paper proposes a stable gain scheduling method of linear time invariant controllers for tracking servo system. In order to read and write the data on the optical disc, the pick-up head should be moved to the exact track quickly and follow the track immediately. Two different controllers are used for each moving and track-following. In pull-in period, a transition period from moving to track-following, the head might slip and miss the target track. This brings on another searching process and increases the total time. One way to avoid slipping is to extend the bandwidth of the track-following controller. But, extending the bandwidth could degrade the following performance. More prevalent way is to use one more controller in this pull-in period and switch to the following controller. In general, however, switching or scheduling of stable controllers cannot guarantee the stability. This paper suggests an scheduling method guaranteeing the overall stability not only in a generalized form but also in special form for SISO system. The sufficient condition is derived from the fact that Q factor of a stable controller should be stay in $RH_{\infty}$ space. In the experiment, the proposed method shows better performance than the switching method such as shorter time and lower current consumption.

• Journal of Power Electronics
• /
• v.12 no.3
• /
• pp.418-428
• /
• 2012

It is very important to improve the overall efficiency of systems with a source of power that has low-voltage high-current terminal characteristics such as fuel cells. A resonant converter is required for high efficiency systems. However, the peak value of the switches current is large in a resonant converter. This peak current requires a large number of switches and results in system failures. In this paper, an analysis and experiments of a resonant isolation push-pull converter are performed. A switching loss analysis is performed in order to compare losses between a resonant push pull converter and a hard switching push-pull converter. Specially, the conduction loss is studied based on the ratio between the resonant frequency and the switching frequency. In addition, a method for improving the efficiency is implemented with conventional HF insolation converters.

• Journal of Satellite, Information and Communications
• /
• v.12 no.2
• /
• pp.33-37
• /
• 2017

This paper suggests a new reliable push pull converter. The proposed push-pull converter have additional two diodes comparing with conventional push-pull converter. When one of two MOSFETs of the push-pull converter is on state, the other MOSFET is automatically off state due to adding additional diodes. Therefore, the converter is under electric noise environments, the converter avoids short circuit due to turning on of two MOSFETs. In this paper, the suggested converter has been simulated by PLECS software for 100 kHz switching frequency. In simulation, the current of the converter switches increases about 10 % for $20{\mu}sec$ electric noise environments. However, the converter operates very reliably without any short circuit conditions.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
• /
• 2002.05a
• /
• pp.63-68
• /
• 2002

This study performed to evaluated musculoskeletal disorders(MSDs) during sitting work. The musculskeletal system is affected by various work factors such as strength, weight, posture, repetition, duration and exertion. Ergonomic study on sitting work is necessary to evaluate these factors affecting human body. But the strength and work load data by the work factors are insufficient in Korea. Therefore, this study evaluated the work load using the elcctromyogram(EMG) and measured the arm strength by arm posture and push pull work during sitting work. to evaluated muscle load, the vertical height and horizontal angle of arm were adjusted around acromion. And EMG data were recorded on pc during the test.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.405-411
• /
• 2008

The pressurized grouting soil nailing method using rubber membrane packer system was developed for recycling materials to minimize environmental pollution and reducing construction costs. For this purpose, field pull-out tests were performed to evaluate the characteristics of soil nailing by measuring tensile stresses and axial displacements.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.15 no.25
• /
• pp.63-74
• /
• 1992

This study proposes D- shortage control system which is a convenient tool for cooperative companies to reduce shortages which frequently break out between the manufacturing companies and the cooperative companies. On the ground of theoretical analysis of MRP and JIT system, D- shortage control system sets up a schedule that secures the delivery date by precedent scheduling( D-) comparing with MRP It also syncronizes business, production and release, and builds the pull system comparing with JIT. The factors causing shotages are the scheduling absurdity and the controlling absurdity. The scheduling absurdity can be settled by the calculating required quantity method of MRP and the controlling absurdity can be settled by daily control of business, production and pruchasing fuctions by the pull system of JIT. And the inventory and the WIP can be reduced by the operating of PULL system and by the settlement of D- shortage control practices. The Application of D- shortage control system, therefore, enables the rationalization of logistics and reduces the inventory And it leads to the reinforced competitiveness and the security of subsistence of manufacturer by the cost ruduction, the reduction of financial difficulty, and the insurance of the delivery date.

• Proceedings of the Safety Management and Science Conference
• /
• 2011.11a
• /
• pp.557-561
• /
• 2011

The study proposes three types of production lead time according to the production or demand pattern. First of all, it discusses the difference of three lead times. While pitch time and cycle time are used in push system with process stock and mass conveyor production, the tact time is used in pull system like as JIT based lean production system.

• Tunnel and Underground Space
• /
• v.20 no.5
• /
• pp.332-343
• /
• 2010

This study aims to evaluate the supporting effect of a spiral bolt that is superior to a rock bolt in terms of constructability, stability, environmental and economic aspects as a support system. This study thus analyzed the mechanical properties of a rock bolt which is widely used as a support and a spiral bolt. In addition, laboratory pull-out tests were conducted for the evaluation of properties of the supports such as displacement, pull-out load, confining pressure etc. Moreover, the differences between a rock bolt and a spiral bolt were drawn by comparing the two results of laboratory pull-out tests and in-situ pull-out tests. Then, the differences of the supporting effect of the two supports were analysed by comparing the results of the two pull-out tests with a numerical analysis using FLAC3D.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.5
• /
• pp.51-57
• /
• 2011

Parametric studies based on analysis of lubrication system of a four cylinder gasoline engine are illustrated system in this paper. In development process of engine lubrication system, parts of failure cases are related with oil pull over and oil churning phenomenon. The crankcase & head system pressure by oil churning phenomenon are gradual increased. It cause oil pull over phenomenon at engine breather line and oil over-consumption. In order to improve oil reduction and oil pull over phenomenon are also considered in the developing state. For this study, the characteristics of engine lubrication system are measured at various tilting angle and drain hole sizes. In addition, the oil flow & oil quantity are tested by blow by meter and catch jar. Results are presented to stabilize the oil supply system at sever driving condition. The data from present study are available for the engine lubrication system.