• Journal of the Korean housing association
• /
• v.27 no.4
• /
• pp.13-22
• /
• 2016

The long term plan for apartment housing has a important role to make a decision making whether a repair work should be done or not. But, items for repair works are so various that field workers could not understand the context or plan the repair cost and time. These difficulties are drawn from the number of repair items, duplicated application and meaning, new material application and technology time-gap. Therefore, it needs to change or coordinate the repair items to improve the repair condition, reflecting the current material level or repair technologies. In this paper, it aimed at coordination of the repair items through the repair recording sheet which was surveyed in 22 metropolitan areas of Seoul, conducted between 2011 and 2014. The surveyed data are classified into six categories such as building exterior, building interior and so on, according to long term repair plan and the number of data are 1,918. It analyzed the appearing word for repair-concerned and compared the existing items of the long term plan. Items of building exterior are proposed as roof, exterior wall and painting. Building interior has a little meaning to propose the repair items. The water supply facilities are proper to keep the existing repair items. Items of the outdoor facilities could not need a sign board, drainage root and PVC sheath. Through this study, we can coordinate the repair items in apartment and provide the repair item and cost level.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.11
• /
• pp.2000-2006
• /
• 2011

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. Where calculation method of protection settings and Logic for Protection of Generator Asynchronization will be recommended, A distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, Zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection this paper describes an improved backup protection coordination scheme using a new Logic that will be suggested.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.2
• /
• pp.269-278
• /
• 2016

In order to maintain customer voltages within allowable limit($220{\pm}13V$) as much as possible, tap operation strategy of SVR(Step Voltage Regulator) installed in distribution system is very important, considering the scheduled delay time(30 sec) of SVR. However, the compensation of BESS(Battery Energy Storage System) during the delay time of SVR is being required because the customer voltages in distribution system interconnected with PV(Photovoltaic) system have a difficultly to be kept within allowable limit. Therefore, this paper presents the optimal voltage stabilization method in distribution system by using coordination operation algorithm between BESS and SVR. It is confirmed that customer voltage in distribution system can be maintained within allowable limit($220{\pm}13V$).

• Journal of KIISE:Information Networking
• /
• v.36 no.5
• /
• pp.456-469
• /
• 2009

We develop a new wireless link quality metric, ECOT(Estimated Channel Occupancy Time) that enables a high throughput route setup in wireless mesh networks. The key feature of ECOT is to be applicable to diverse mesh network environments where IEEE 802.11 MAC (Medium Access Control) variants are used. We take into account the exact operational features of 802.11 MAC protocols, such as 802.11 DCF(Distributed Coordination Function), 802.11e EDCA(Enhanced Distributed Channel Access) with BACK (Block Acknowledgement), and 802.11n A-MPDU(Aggregate MAC Protocol Data Unit), and derive the integrated link metric based on which a high throughput end-to-end path is established. Through extensive simulation in random-topology settings, we evaluate the performance of proposed link metric and present that ECOT shows 8.5 to 354.4% throughput gain over existing link metrics.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.1
• /
• pp.768-776
• /
• 2021

Current protection-coordination methods use the reverse time characteristics of the T-C curve, which is not effective for a LVDC distribution system because the protective operation time of converters and DC circuit breakers is much faster than AC protection devices. Therefore, an algorithm is proposed for fault-section isolation using the fault current slope to minimize the blackout region and coordinate between converters and protection devices in a rapid and accurate manner. The method deals with the slope characteristics of a fault current, which may depend on the fault location in an LVDC distribution system. Thus, an LVDC distribution system can be operated in a stable manner by isolating the fault section selectively before the shutdown of the main converter using slope characteristics, which change in proportion to the line impedance and fault location. A 1.5-kV LVDC distribution system was modeled to verify the effectiveness of the proposed algorithm using PSCAD/EMTDC. The system is composed of a distribution substation, LVDC converter, and distribution lines. The simulation results confirm that the proposed algorithm is a useful tool for minimizing the fault section in an LVDC distribution system.

• The Journal of the Korea Contents Association
• /
• v.5 no.1
• /
• pp.73-79
• /
• 2005

Recent advances on wireless technology are enabling the design and deployment of real-time traffic in wireless LAN. Point Coordination Function (PCF) mode of Wireless LAN is defined to provide QoS of real time traffic, such as voice, video in wireless LANs. The service polling scheduling plays an important role in real-time traffic services of wireless LAN. This paper proposes a multicast polling scheme to increase the maximum number of conversations by reducing the amount of empty polls in IEEE 802.11 PCF mode. Our simulation studies show that our scheme may improve performance of the PCF in terms of the average transfer delay and packet discard ratio.

• Industrial Engineering and Management Systems
• /
• v.15 no.3
• /
• pp.278-288
• /
• 2016

Automation ensures accurate and well-organized container transportation in container terminals. This paper addresses operational issues such as equipment scheduling and the coordination between various pieces of equipment in a rail-based automated container terminal. Containers are relayed using multiple types of equipment from road trucks to a vessel and vice versa. Therefore, handshaking is required during a container transfer between different pieces of equipment. Synchronization between the schedules of all the equipment is important to reduce equipment waiting times and the time required for transporting containers, which results in a short turnaround time for a vessel. This paper proposes an integrated control system with the objective of synchronizing the operations of different types of equipment, provides a list of decisions to be made by the control module of each type of equipment, and shows all the required information transfers between control modules. A scheme for the integrated scheduling of multiple types of equipment is proposed. The decisions made by each control module in a real-time fashion are listed with detailed explanations, and the information transfer between managers in a real-time situation at the proposed terminal is described.

• Korean Journal of Materials Research
• /
• v.15 no.4
• /
• pp.252-256
• /
• 2005

We removed the bluish of the natural ruby successfully by vacuum annealing, and measured the color evolution with annealing time and temperature. We varied the anneal temperature and time $800\~1500^{\circ}C$ and $3\~26$ hrs, respectively. The color evolution of rubies with annealing condition was recorded by a digital camera and a color coordination visible spectrometer. We determined the optimum bluish eliminating annealing condition was $1500^{\circ}C-3hr$, which conserving the natural inclusions. We suggest the bluish shrink with diffusion coefficient of $D=(5\times10^{-3}){\exp}(-200.000/RT)[cm^2/s]$. We propose the color of ruby may be determined as the identical red color if the color difference between two samples are less than 1.0, and the color difference nay be an auxiliary standard to evaluate the color of rubies.

• Proceedings of the Korean Information Science Society Conference
• /
• 2004.10c
• /
• pp.322-324
• /
• 2004

IEEf 802.11 Point Coordination Function (PCF) mode is defined to support time bounded traffic, such as VoIP in wireless LANs. The poll scheduling plays an important role in IEEE 802.11 PCF mode operation. This paper proposed a Multicast Polling Scheme to increase the performance of wireless LANs. Moreover, we proposed a polling schedule scheme for our proposed multipoll to serve real-time traffic. The results show that the proposed mechanism is more efficient than the original IEEE 802.11 PCF.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.6
• /
• pp.47-52
• /
• 2012

DAS(Distribution Automation System) is equipped with several software applications such as service restoration, loss minimization, and protective relay coordination. The software applications of DAS are very sensitive to the amount of section load being carried by a particular section of distribution lines. Moreover, each software application requires a different parameter of the section load according to its purpose. Therefore, This paper proposes a new section load management method using real-time measurement data of the distribution lines. In order to provide accurate data to DAS applications, this method considers section loads in terms of the relationship of power versus time. In order to establish that the proposed method is feasible, a performance-testing simulator was developed, and case studies were conducted for a modified real distribution network.