• Journal of Navigation and Port Research
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• v.32 no.4
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• pp.295-304
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• 2008

In order to achieve a sustainable competitive advantage in the expanding maritime transportation market, most shipping companies are making every effort to reduce transportation costs. Likewise, the car shipping companies, which carry more than 80% of total car import and export logistics volume, also do their utmost for transportation cost saving. Until now many researches have been made for efficient maritime transportation, but studies for car shipping companies have rarely been made. For this reason, this study has tried to develop a maritime transportation planning support system which can help to save logistics costs and increase a competitive power of car shipping companies. To this end, instead of manual effort to solve the routing problem of car carrier vessels, this study has used an integer programming model to make an optimal transportation planning at the minimum cost. Also in response to the frequent changes both in the car production schedule and ship's arrival schedule after the completion of transportation planning, this research has developed a decision support system of maritime transportation, so that users can easily modify their existing plans.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6258-6263
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• 2014

The LDC (Low Voltage DC-DC Converter) used for hybrid vehicles and electric vehicles was utilized to supply the electric apparatus load with a voltage and to charge the auxiliary batteries by receiving a high DC voltage from the high voltage battery. The LDC has a long-time load test during the manufacturing process. On the other hand, it has the disadvantage of considerable energy consumption because it has the structure to release the power as 100% heat during a load test. Therefore, in this paper, a recycling load test method was proposed and 75~90% energy saving was realized.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.823-825
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• 2003

A sensor system was designed to measure real time vibro displacement of civil structure. The He-Ne laser is used for the displacement measuring method, because it guarantees short time stabilization, long time output power stability. Also, it guarantees simple maintenances and repairs under actual using condition. The line CCD image sensor(Tcd-142d) is used to detect the displacement of Ne-Ne laser responding to the vibro of civil structure. For accurate measurement and comparison, CDP-50 is used. Usually CDF-50 (Strain type displacement device) is used for the standard correction device of optical measurement equipments. The data processing part is consists of Optical sensor part, Wireless data transmission device, DAQp-1200, and LapView program. The displacement data of vibro from optical sensor part inputted to wireless data transmission device and then transmitted to DAQp-1200 in main control room. DAQp-1200 performs A/D conversion for the receiving data. After that the converted data inputted to computer system using LapView program for user display. The significance of this paper is to develope a convenient, accurate and lost saving real time displacement measurement system for the civil structure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3921-3944
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• 2015

Currently Energy-Saving (ES) methods in cellular networks could be improved, as compensation method for irregular Base Station (BS) deployment is not effective, most regional ES algorithm is complex, and performance decline caused by ES action is not evaluated well. To resolve above issues, a low-complexity energy efficient BS cooperation mechanism for Long Time Evolution (LTE) networks is proposed. The mechanism firstly models the ES optimization problem with coverage, resource, power and Quality of Service (QoS) constraints. To resolve the problem with low complexity, it is decomposed into two sub-problems: BS Mode Determination (BMD) problem and User Association Optimization (UAO) problem. To resolve BMD, regional dynamic multi-stage algorithms with BS cooperation pair taking account of load and geographic topology is analyzed. And then a distributed heuristic algorithm guaranteeing user QoS is adopted to resolve UAO. The mechanism is simulated under four LTE scenarios. Comparing to other algorithms, results show that the mechanism can obtain better energy efficiency with acceptable coverage, throughput, and QoS performance.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.207-214
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• 2012

This paper is to improve an identification ratio of tags by analyzing Slotted ALOHA, Dynamic Slotted ALOHA, Binary-tree and Query-tree and shortening the tag identification time in mobile RFID. Also, it enables the stable information transmission of tags by saving backscattering power of tags through shortening of identification time. As a result, this increases the available time of the battery and accessibility to a RFID service. For this, we proposed the energy-efficient tag anti-collision protocol for mobile RFID. The proposed scheme shows advanced result in identification time and collision counts. This scheme may be the first attempt for the mobile anti-collision.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.874-880
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• 2006

The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

• Annual Conference of KIPS
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• 2012.04a
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• pp.79-82
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• 2012

기존의 서버 전원 모드 제어에는 서버를 Off할 때 정적 종료 방식을 사용하는 관계로 서버가 사용자 요청을 모두 처리하는 최적의 종료 시간을 찾는데 시간이 많이 걸리는 단점을 가진다. 이 시간이 짧게 되면 사용자 QoS를 보장할 수 없고, 반대로 이 시간이 길게 되면 전력 절감을 기대할 수 없다. 본 논문에서는 정적 종료 방식의 단점을 극복하는 동적 종료 방식을 제안한다. 제안된 방식은 최적의 종료 시간을 찾을 필요 없이 각 서버가 사용자의 요청을 모두 처리하였을 때 자동적으로 서버를 Off한다. 제안된 방법은 최적의 시간을 자동적으로 찾아내기 때문에 사용자 QoS를 보장하고, 전력을 절감한다. 실험은 30대의 PC 클러스터를 이용하여 수행되었고, 실험을 통하여 제안하는 동적 종료 방법이 기존의 정적 종료 방법에 비해 운영자의 수고 없이 자동적으로 전력 절감 및 사용자 QoS에 기여함을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.4
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• pp.1884-1903
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• 2019

Device-to-Device (D2D) communications can provide proximity based services in the future 5G cellular networks. It allows short range communication in a limited area with the advantages of power saving, high data rate and traffic offloading. However, D2D communications may reuse the licensed channels with cellular communications and potentially result in critical interferences to nearby devices. To control the interference and improve network throughput in overlaid D2D cellular networks, a novel channel assignment approach is proposed in this paper. First, we characterize the performance of devices by using Poisson point process model. Then, we convert the throughput maximization problem into an optimal spectrum allocation problem with signal to interference plus noise ratio constraints and solve it, i.e., assigning appropriate fractions of channels to cellular communications and D2D communications. In order to mitigate the interferences between D2D devices, a cluster-based multi-channel assignment algorithm is proposed. The algorithm first cluster D2D communications into clusters to reduce the problem scale. After that, a multi-channel assignment algorithm is proposed to mitigate critical interferences among nearby devices for each D2D cluster individually. The simulation analysis conforms that the proposed algorithm can greatly increase system throughput.

• Journal of the Semiconductor & Display Technology
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• v.18 no.2
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• pp.48-52
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• 2019

Virtual metrology, which is one of APC techniques, is a method to predict characteristics of manufactured films using machine learning with saving time and resources. As the photoresist is no longer a mask material for use in high aspect ratios as the CD is reduced, hard mask is introduced to solve such problems. Among many types of hard mask materials, amorphous carbon layer(ACL) is widely investigated due to its advantages of high etch selectivity than conventional photoresist, high optical transmittance, easy deposition process, and removability by oxygen plasma. In this study, VM using different machine learning algorithms is applied to predict the thickness of ACL and trained models are evaluated which model shows best prediction performance. ACL specimens are deposited by plasma enhanced chemical vapor deposition(PECVD) with four different process parameters(Pressure, RF power, $C_3H_6$ gas flow, $N_2$ gas flow). Gradient boosting regression(GBR) algorithm, random forest regression(RFR) algorithm, and neural network(NN) are selected for modeling. The model using gradient boosting algorithm shows most proper performance with higher R-squared value. A model for predicting the thickness of the ACL film within the abovementioned conditions has been successfully constructed.

• International Journal of Computer Science & Network Security
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• v.21 no.6
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• pp.252-257
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• 2021

The application of the principle of trigeneration allows to simultaneously provide electricity to power electronic devices, as well as heat and cold to create the necessary microclimate of the premises and increase efficiency compared to separate cooling and heating systems. The use of Peltier thermoelectric modules (TEM) as part of trigenerative systems allows for smooth and precise control of the temperature regime, high manufacturability and reliability due to the absence of moving parts, resistance to shock and vibration, and small weight and size parameters of the system. One of the promising areas of improvement of trigenerative systems is their modeling and optimization based on the automatic control theory. A block diagram and functional model of an energy-saving trigenerative climate control system based on Peltier modules are developed, and the transfer functions of an open and closed system are obtained. The simulation of the transient characteristics of the system with varying parameters of the components is performed. The directions for improving the quality of transients in the climate control system are determined, as well as the prospects of the proposed methodology for modeling and analyzing control systems operating in substantially nonlinear modes.