• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1120-1131
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• 2006

This paper describes the numerical analysis techniques using the Combined Integration/Matrix Method to calculate ground potential rise which can be occurred in the various grounding systems. Combined Integration/Matrix Method is used to reduce the error and computation time with the analytical integration equation and the proper segmentaion of earth embedded conductor. To do it, optimal segmentaion method for the buried conductors is presented through error analysis which is capable of applying the practical scaled various grounding systems. The optimum length of segmented element is much co-related with the buried depth of grounding electrode and the maximum length of buried electrode. As a result, less 3 precent errors was obtained by proposed model. The proposed model is applied to verify an effect of multi-grounding problems which was aroused much controversy with separated or common grounding between the high power grounding system and low power grounding system such as signal and telecommunication grounding.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.11
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• pp.612-620
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• 2017

Power consumption in Southeast Asia is steadily increasing due to industrialization and the effects of hot and humid climates. However, there are not enough energy generation facilities and infrastructures to meet the growing demand because it is difficult to secure the construction and operation costs of the transmission and distribution systems. This study aims to develop a gas engine driven heat pump system that supplies heating, cooling and electric power to buildings. This system, besides its normal function to produce heat, has the capacity to generate electricity on a household level. This paper investigates similar cases overseas before developing the system. Through the investigation of commercialized similar systems, the level of technology and market trend of development system were identified. Features and specifications of commercial and industrial systems will be used for system development.

• International Journal of Control, Automation, and Systems
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• v.5 no.5
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• pp.539-546
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• 2007

The important field of research in ship operation is related to the high efficiency of transportation, the convenience of maneuvering ships and the safety of navigation. For these purposes, many intelligent technologies for ship automation have been required and studied. In this paper, we propose an intelligent voice instruction-based learning (VIBL) method and discuss the building of a ship's steering control system based on this method. The VIBL system concretely consists of two functions: a text conversion function where an instructor's inputted voice is recognized and converted to text, and a linguistic instruction based learning function where the text instruction is understood through a searching process of given meaning elements. As a study method, the fuzzy theory is adopted to build maneuvering models of steersmen and then the existing LIBL is improved and combined with the voice recognition technology to propose the VIBL. The ship steering control system combined with VIBL is tested in a ship maneuvering simulator and its validity is shown.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.177-182
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• 2009

The purpose of this study is to investigate planning of urban energy supply systems configuration and operating conditions for the district heating and cooling system using combined heat and power system. Generally the district heating and cooling system has been known to one of the effective way for energy saving, cost reduction and demand side management of energy. Economical analyses were carried out and operating characteristics for some systems were examined in terms of GER factor which represents to the ratio of gas and electricity costs. Rates of the energy consumption and the $CO_2$ emission were compared from the system configuration of the energy supply system with new district cooling system with the conventional one.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.1
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• pp.7-12
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• 2008

A GNSS(Global Navigation Satellite System) using GPS provides us with very useful information concerning the positioning of users in many sectors such as transportation, social services, the justice system and customs services, public works, search and rescue systems and leisure. A GNSS using the Galileo satellite is due to work in 2008 and expected to be used in various fields such as aviation, marine transportation, land surveying, resources development precise agriculture, telemetics, and so on. In this paper, we discuss the implementation and testing of a combined GPS/Galileo receiver which we named KSTAR V1.0. Each tracking module of GPS/Galileo dual mode correlator has the five track arms which consist of Very Early code, Early code, Prompt code, late code, and Very late code. Each of 24 tracking modules can be assigned to GPS and/or Galileo signal by changing mode selection register. The basic correlator integration dump period is set to 1ms for GPS C/A code and fast Galileo signal tracking. The performance of the developed combined GPS/Galileo receiver was tested and evaluated using the IF (Intermediated Frequency)-level GPS/Galileo signal generator.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.132-139
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• 2011

We investigate theoretically the combined effect of fiber chromatic dispersion and self-phase modulation (SPM) on multi-channel subcarrier multiplexed (SCM) optical transmission systems in terms of the detected RF carrier power and SPM-induced power gain after transmission over single-mode fiber (SMF) links. According to the calculated power gain due to the SPM effect at the transmission distance of P3dB using the detected radio-frequency (RF) carrier power after photo-detection, the power gain is significantly degraded with large optical modulation index (OMI), small SCM channel spacing, and large fiber launching power because of the increased interaction between subcarrier channels. The nonlinear phase shift due to linear and nonlinear fiber characteristics is investigated to explain these results in detail. The numerical simulation results show that the OMI per SCM channel has to be smaller than 10 % for the fiber launching power of 10 dBm to guarantee prevention of SPM-induced power gain degradation below 0.5 dB for the SCM system with the channel spacing of 100 MHz. This result is expected to be utilized for the optical transmission systems using the SCM technology in future radio-over-fiber (RoF) networks.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.40-44
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• 2010

A layered coding scheme is one of the adaptive receiving techniques for unidirectional services such as multimedia broadcasting and multicasting services (MBMS), where we cannot utilize feedback information. The layered coding scheme can be used with hierarchical modulations by combining suitable code rates and modulation orders of each. In addition, it has been reported that hybrid and/or integrated satellite systems can effectively achieve transmit diversity gains by appropriate utilization of space time coding combined with turbo codes. This paper proposes a layered turbo coding schemes for hybrid and/or integrated satellite systems. We first introduce the system architecture and operational principle of the proposed scheme, and discuss the applicability.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.369-372
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• 2006

Flat plate slab systems have been commonly used as a gravity force resisting systems, which should be constructed with lateral force resisting systems such as shear walls and moment resisting frame. ACI 318(2005) allows the Direct design method, the equivalent frame method (ACI-EFM) under gravity loads and the finite-element models, effective beam width models and equivalent frame models under lateral loads. ACI-EFM can be used for gravity loads as well as lateral loads analysis. But the method may not predict the behavior of flat plate slabs under lateral loads. Thus Previous study developed a Modified equivalent frame method(Modified-EFM) which could give more precise answer for flat plate slab under lateral loads. This study is to verified the accuracy of a Modified-EFM under combined lateral and gravity loads. The accuracy of this model is verified by comparing the results using the Modified-EFM with the results of finite element analysis. For this purpose, 7 story building is considered. The analysis results of other existing models are included. The analysis results show that Modified-EFM produces comparable drift and slab internal moments with those obtained from finite element analysis.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.737-750
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• 2022

Timber-Concrete Composite construction system consists of combining timber beam or deck and concrete with different connectors. Different fastener types are used in Timber-Concrete Composite systems. In this paper, the effects of two types of fasteners on structural behavior are compared. First, the notches were opened on timber beam, and combined with reinforced concrete slab by fasteners. This system is called as Notched Connection System. Then, timber beam and reinforced concrete slab were combined by new type designed fasteners in another model. This system is called as Notched-Slab Approach. Two laboratory models were constructed and bending tests were performed to examine the fasteners' effectiveness. Bending test results have shown that heavy damage to concrete slab occurs in Notched Connection System applications and the system becomes unusable. However, in Notched-Slab Approach applications, the damage concentrated on the fastener in the metal notch created in the slab, and no damage occurred in the concrete slab. In addition, non-destructive experimental measurements were conducted to determine the dynamic characteristics. To validate the experimental results, initial finite element models of both systems were constituted in ANSYS software using orthotropic material properties, and numerical dynamic characteristics were calculated. Finite element models of Timber-Concrete Composite systems are updated to minimize the differences by manual model updating procedure using some uncertain parameters such as material properties and boundary conditions.

• Tribology and Lubricants
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• v.38 no.4
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• pp.121-127
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• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.