• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.585-589
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• 2002

본 연구에서는 소프트웨어의 출시 이후 주기적인 보수(periodic maintenance)를 고려한 출시 시기 결정 방법을 제시하였다. 출시시기 결정방법에 관한 연구는 소프트웨어의 신뢰성 확보, 사용자 편의성 등에 관한 연구와 더불어 중요한 연구 분야로 여겨지는 분야이다. 일반 적으로 소프트웨어는 출시 이후에도 패치(patch), 서비스팩(service pack)등을 통해 지속적인 보수가 이루어지기 때문에, 출시 이후의 보수를 고려하여 출시시기를 결정하는 방법론이 필요하다. 이를 위해, 출시 이후의 보수정책을 반영한 소프트웨어 신뢰성 성장 모형(software reliability growth model)을 도출하였다. 위 모형을 기반으로 하여 비용과 신뢰성에 근거한 소프트웨어 출시 시점을 결정해 보았다. 제시된 모형의 타당성을 검증하기 위해 예제를 통해 기존의 논문에서 제시되었던 결과들과 비교분석을 해 보았다. 본 연구의 결과는 기존 연구에서 고려되지 않았던 보수 정책을 고려함으로써, 보다 현실에 가까운 모형을 제시하였다는 점에서 의의를 찾을 수 있고, 출시 후 보수 시점, 보수 정책 등의 결정에도 기여할 수 있을 것이다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.407-407
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• 2004

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.850-855
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• 2013

This paper proposes a novel design for a compact, high-isolation WCDMA indoor repeater antenna. The proposed antenna consists of a patch antenna and metamaterial absorber. The required WCDMA bandwidth is obtained by utilizing the coupling between the main and the parasitic patches. In addition, high isolation is achieved using the metamaterial absorber, which has an absorption of about 98% at 2.1 GHz. Overall, the proposed antenna has a gain of over 7 dBi, a Voltage Standing Wave Ratio (VSWR) of less than 2, more than 85 dB of isolation between the service and donor antennas over the WCDMA band and a total volume of the proposed antenna only $70mm{\times}70mm{\times}43.8mm$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.777-779
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• 2009

Study for VoIP in MANET is mainly focused on transmission performance or voice quality of VoIP traffic as single traffic. In this study, VoIP performance is analyzed of MANET which has several types of traffics. Diffserv scheme is used to process the traffics. It is showed that VoIP traffic performance is improved by differv scheme, as a result of analysis for VoIP and FTP traffic. Simulator, which is implemented with NS-2 package and VoIP patch, is used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1343-1351
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• 2010

In this paper, a novel patch antenna based on the metamaterial CRLH(Composite Right- and Left-Handed) structure is designed, implemented, and measured. Contrary to the standard microstrip patch's fundamental resonance mode of half-wavelength or its positive multiple, the proposed antenna shows the in-phase electric field over the entire antenna. The proposed antenna has a desired omni-directional field pattern which is typical characteristic of $\lambda/4$ monopole antenna, and also shows the merit of low profile. HFSS(High Frequency Structure Simulator) of Ansoft which is based on the FEM(Finite Element Method) is used to simulate the proposed antenna. FR-4 substrate of thickness 1.6 mm and relative permitivity 4.4 is used for the proposed antenna implementation. The implemented antenna showed VSWR (Voltage Standarding Wave Ratio)$\leq$2 for the frequency band from 2.63 GHz to 2.655 GHz which is used for S-DMB (Satellite-Digital Multimedia Broadcasting) service. And measured peak gain and efficiency are 2.65 dBi and 81.14 %, respectively.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.235-243
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• 2002

Ni-base superalloys are used extensively in industry, both in aeroengines and land based turbines. About 60% by weight of most modern gas turbine engine structural components are made of Ni-base superalloys. To satisfy practical demands, the efficiency of gas turbine engines has been steadily and systematically increased by design modifications to handle higher turbine inlet or firing temperatures. However, the increase in operating temperatures has lead to a decrease in the life of components and increase in costs of replacement. Moreover, around 80% of the large frame size industrial/utility gas turbines operating in the world today were installed in the mid-sixties to early seventies and are now 25 to 30 years old. Consequently, there are greater opportunities now to repair and refurbish the older models. Basically, there are two major factors influencing the weldability of the cast alloys: strain-age cracking and liquation cracking. Susceptibility to strain-age cracking is due to the total Ti plus AI content of the alloy; Liquation cracking is due either to the presence of low melting constituents or constitutional liquation of constituents. Though Rene 41 superalloy has 4.5wt.% total Ti and Al content and falls just below the safe limit proposed by Prager et al., controlled grain size and special heat treatments are needed to obtain crack-free welds. Varying heat treatments and filler materials were used in a laboratory study, then the actual welding of service parts was carried out to verity the possibility of crack-tree weld of components fabricated from Rene 41 superalloy. The microstructural observations indicated that there were two kinds of carbides in the FCC matrix. MC carbides were located along the grain boundaries, while M$_{23}$C$_{6}$ carbide was located both inter and intra granularly. Two kinds of filler materials, Rene 41 and Hastelloy X were used to gas tungsten arc weld a patch into the sheet metal, along with varying pre-weld heat treatments. The microstructure, hardness and tensile tests were determined. The service distressed parts were categorized into three classes: with large cracks, with medium cracks and with small or no visible cracks. No significant difference in microstructure among the specimens was observed. Specimens were cut from the corner and the straight edge of the patch repair, away from the corner. The only cracks present were found to be associated with inadequate surface preparation to remove oxidation. Guidelines for oxide removal and the welding procedures developed in the research enabled crack-free welds to be produced.d.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.145-151
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• 2008

In this paper, a dual band microstrip antenna with similar radiation pattern for the satellite internet service is proposed. The proposed antenna has two Y-shaped slots on the microstrip patch that is fabricated on RO4003 substrate with a dielectric constant of 3.38 and a thickness of 0.508 mm, and operates in the 2 GHz and 5 GHz bands. The size of the antenna is $50\times47.5\times6.5\;mm^3$, and fed by coaxial cable. The measured bandwidths of the antenna are 2.398$\sim$2.507 GHz and 5.458$\sim$5.972 GHz for VSWR<2. The measured gains are 8.92 dBi and 7.74 dBi, respectively, for the lower and upper bands.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4103-4121
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• 2018

Quality of Service (QoS) awareness is recognized as a key point for the success of Internet of Things (IOT).Realizing the full potential of the Internet of Things requires, a real-time task scheduling algorithm must be designed to meet the QoS need. In order to schedule tasks with diverse QoS requirements in cloud environment efficiently, we propose a task scheduling strategy based on dynamic priority and load balancing (DPLB) in this paper. The dynamic priority consisted of task value density and the urgency of the task execution, the priority is increased over time to insure that each task can be implemented in time. The scheduling decision variable is composed of time attractiveness considered earliest completion time (ECT) and load brightness considered load status information which by obtain from each virtual machine by topic-based publish/subscribe mechanism. Then sorting tasks by priority and first schedule the task with highest priority to the virtual machine in feasible VMs group which satisfy the QoS requirements of task with maximal. Finally, after this patch tasks are scheduled over, the task migration manager will start work to reduce the load balancing degree.The experimental results show that, compared with the Min-Min, Max-Min, WRR, GAs, and HBB-LB algorithm, the DPLB is more effective, it reduces the Makespan, balances the load of VMs, augments the success completed ratio of tasks before deadline and raises the profit of cloud service per second.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.919-930
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• 2001

This paper presents a wideband technique of impedance and axial-ratio bandwidth which uses the stacked planar array structure through optimum design of sub-polarization generating sections and parasitic patch. So, the effect of the dual-resonance characteristic can contribute to the bandwidth expansion of single fed planar array antenna using circular polarization which doesn\`t hire previous bandwidth expansion technique. The antenna can be used as a dual-band antenna by adjusting the resonance frequencies as well, and then the antenna is designed and fabricated in the frequency band of domestic satellite-TV service. This antenna has the performance of 9.7 % impedance bandwidth and 24 dBi of antenna gain. And it has also 2.8 % and 1.4 % of 3 dB Axial-ratio bandwidth at 11.4 GHz and 11.8 GHz respectively.

• Journal of the Korean Graphic Arts Communication Society
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• v.26 no.1
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• pp.51-64
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• 2008

In this paper, an experiment was done where the input(scanner, digital still camera) and monitor(CRT, LCD) device used the linear multiple regression and the GOG (Gain-Offset-Gamma) characterization model to perform a color transformation. Also to color conversion method of the digital printer it used the LUT(Look Up Table), 3dimension linear interpolation and a tetrahedron interpolation method. The results are as follows. From color reappearance of digital printing case of monitor, the XYZ which it converts in linear multiple regression of input device it multiplied the inverse matrix, and then it applies the inverse GOG model and after color converting the patch of the result most which showed color difference below 5 at monitor RGB value. Also, The XYZ which is transmitted from the case input device which is a printer it makes at LAB value to convert an extreme, when the LAB value which is converted calculating the CMY with the LUT and tetrahedral interpolations the color conversion which considers the black quantity was more accurate.