• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.101-105
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• 2001

For high voltage XLPE power cables, semiconducting layers have been applied to prevent discharge at the interface between conductor and insulation, and/or insulation and external shielding layer. The semiconducting layers may be also effective to release electrical stress in the interface. The property of semiconducting layers are significantly related to the quality and reliability of power cables. Generally, these semiconducting layers are formed by extruding, the conductibility of the material is given by the carbon black mixed with base polymer. The life of power cables is depended on the smoothness of the interface between insulation and semiconducting layer. If the smoothness is no good, the life of power cables is shorter because the electrical stress and water tree is increased. The causes of no good smoothness are the void of the interface, the protrusions, the contaminants and impurities of the semiconducting layer. The selection and dispersion of the Carbon Black is the significant factor to determine the life of power cable in the manufacturing of semiconducting compound.

• Journal of Digital Convergence
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• v.9 no.5
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• pp.225-233
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• 2011

Internet telephony is an Internet service which supports voice telephone using VoIP technology on the IP-based Internet. It has some advantages in that voice telephone services can be accompanied with multimedia services such as video communication and messaging services. Recently, the introduction of smart phones has led to a growth in social networking services and thus, the research and development of Internet telephony has been actively progressed and has the potential to become a replacement for the telephone service that is currently being used. In this paper we designed and implemented a recording system which records voice data of SIP-based Internet telephone's voice calls. It is developed on the linux system and has some features such as audio mixing of two in/out voice channels, live packet sniffing, and the ability to transfer mixed audio files to the log file server. These functions are implemented using various open source softwares. Afterwards, this VoIP recording system will be applied as a base technology to advanced services like a VoIP-based call center system.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.408-420
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• 2016

This study proposes an alternative approach for the use of chitosan silver-based dressing for the control of foot infection with multidrug-resistant bacteria. Sixty-five bacterial isolates were isolated from 40 diabetic patients. Staphylococcus aureus (37%) and Pseudomonas aeruginosa (18.5%) were the predominant isolates in the ulcer samples. Ten antibiotics were in vitro tested against diabetic foot clinical bacterial isolates. The most resistant S. aureus and P. aeruginosa isolates were then selected for further study. Three chitosan sources were tested individually for chelating silver nanoparticles. Squilla chitosan silver nanoparticles (Sq. Cs-Ag⁰) showed the maximum activity against the resistant bacteria when mixed with amikacin that showed the maximum synergetic index. This, in turn, resulted in the reduction of the amikacin MIC value by 95%. For evaluation of the effectiveness of the prepared dressing using Artemia salina as the toxicity biomarker, the LC₅₀ was found to be 549.5, 18,000, and 10,000 μg/ml for amikacin, Sq. Cs-Ag⁰, and dressing matrix, respectively. Loading the formula onto chitosan hydrogel dressing showed promising antibacterial activities, with responsive healing properties for the wounds in normal rats of those diabetic rats (polymicrobial infection). It is quite interesting to note that no emergence of any side effect on either kidney or liver biomedical functions was noticed.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.3
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• pp.169-180
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• 2015

Recently, scheduling problems with position-dependent processing times have received considerable attention in the literature, where the processing times of jobs are dependent on the processing sequences. However, they did not consider cases in which each processed job has different learning or aging ratios. This means that the actual processing time for a job can be determined not only by the processing sequence, but also by the learning/aging ratio, which can reflect the degree of processing difficulties in subsequent jobs. Motivated by these remarks, in this paper, we consider a two-agent single-machine scheduling problem with linear job-dependent position-based learning effects, where two agents compete to use a common single machine and each job has a different learning ratio. Specifically, we take into account two different objective functions for two agents: one agent minimizes the total weighted completion time, and the other restricts the makespan to less than an upper bound. After formally defining the problem by developing a mixed integer non-linear programming formulation, we devise a branch-and-bound (B&B) algorithm to give optimal solutions by developing four dominance properties based on a pairwise interchange comparison and four properties regarding the feasibility of a considered sequence. We suggest a lower bound to speed up the search procedure in the B&B algorithm by fathoming any non-prominent nodes. As this problem is at least NP-hard, we suggest efficient genetic algorithms using different methods to generate the initial population and two crossover operations. Computational results show that the proposed algorithms are efficient to obtain near-optimal solutions.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.149-162
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• 2003

Moisturizing the skin is one of the most important functions of skincare cosmetics, because water plays a significant role in keeping the skin healthy. There are various humectants including polyol (glycerin and 1,3-butylene glycol), water-soluble polymers, and botanical extracts. It is well known that the increased amount of polyol in lotion for obtaining high moisturizing effect gives a sticky feeling to the skin. Therefore, a few humectants that can give high moisturizing effect without a sticky feeling for lotion formula is available. On the other hand, oil-based lipstick is well known to have a difficulty to contain a large amount of hydrophilic humectants, because the humectants is unable to be mixed well into oil-based lipsticks and give the lips a peculiar taste. There are newly developed humectants, polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) that can solve these problems describable above. EPDME is a random copolymer of ethylene oxide and propylene oxide. EPDME gives a low sticky feeling with a high moisturizing effect when it is used in lotion. As a remarkable character, EPDME can show not only a preventing effect on rough and dry skin, but also a improving effect upon the use for 1-4 weeks. EPDME can show a synergistic effect with glycerin on preventing to rough and dry skin. Since EPDME can be dissolved in oil-based formulation and used as an ingredient of lipsticks, EPDME can give a moisturizing effect that allows lip to be healthy condition. EPDME can also give no peculiar taste even upon the use of a large amount. EPDME is a useful cosmetic ingredient that can show a good skin care effect in both water-based formula and oil-based formula. EPDME of which polarity can be controllable is expected to be used for various cosmetic applications in near future.

• Journal of Digital Convergence
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• v.15 no.4
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• pp.451-459
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• 2017

This study investigates the usage of smartphones in English listening activities. 71 students answered the 10-item questionnaire after doing listening activity using their own smartphone for one semester in the course of Practical English listening and reading. The findings show that listening activity done with smartphone enhanced students' interest in English listening and improved their English listening skills because smart phones made customized learning possible. However, the major limitation of using smart phone is that students are distracted during activity by smart phones' other functions such as SMS and messenger. To reduce such distraction, I suggest that individual listening activity with smart phones be mixed with instructor-led activity using a classroom computer in about 50 to 50 ratio. The ratio might vary depending on the level of students' English listening skills. These findings will make a contribution to the boost of digital convergence English learning.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.33-38
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• 2009

Recently most of A/V devices are being adopted hi-tech of A VRCP and changed to mobile environment. AVRCP is designed to provide a standard interface to control A/V devices, hi-fi equipment, or others to allow a single remote control or other device to control all the A/V equipment to which a user has access. It may be used in concert with A2DP or VDP. The AVRCP defines two roles, that of a controller and target device. In AVRCP, the controller translates the detected user action to the A/V control signal, and then transmits it to a remote Bluetooth enabled device. It can be small and mixed mobile devices using bluetooth technologies. The functions available for a conventional infrared remote controller can be realized in this protocol. The remote control described in this protocol is designed specifically for A/V control only. We designed new DSP using Adaptive Acoustic Echo Canceller for bluetooth hands free based this AVRCP standard specifications.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.179-190
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• 2010

This paper describes a new stochastic heuristic algorithm in engineering problem optimization especially in power system applications. An improved particle swarm optimization (PSO) called adaptive particle swarm optimization (APSO), mixed with simulated annealing (SA), is introduced and referred to as APSO-SA. This algorithm uses a novel PSO algorithm (APSO) to increase the convergence rate and incorporate the ability of SA to avoid being trapped in a local optimum. The APSO-SA algorithm efficiency is verified using some benchmark functions. This paper presents the application of APSO-SA to find the optimal location, type and size of flexible AC transmission system devices. Two types of FACTS devices, the thyristor controlled series capacitor (TCSC) and the static VAR compensator (SVC), are considered. The main objectives of the presented method are increasing the voltage stability index and over load factor, decreasing the cost of investment and total real power losses in the power system. In this regard, two cases are considered: single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC). Using the proposed method, the locations, type and sizes of FACTS devices are obtained to reach the optimal objective function. The APSO-SA is used to solve the above non.linear programming optimization problem for better accuracy and fast convergence and its results are compared with results of conventional PSO. The presented method expands the search space, improves performance and accelerates to the speed convergence, in comparison with the conventional PSO algorithm. The optimization results are compared with the standard PSO method. This comparison confirms the efficiency and validity of the proposed method. The proposed approach is examined and tested on IEEE 14 bus systems by MATLAB software. Numerical results demonstrate that the APSO-SA is fast and has a much lower computational cost.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.1
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• pp.32-40
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• 2001

The purpose of designing Haebaragi park, legally designated as children park, is to make a place for children including residents performing outdoor recreation, various social interactions, and cultural activities. Design concept for space plan have twofold; the one is a positive and creative playing space and facilities for children, escaped from a monotonous playground, and the other is a cultural and social space for neighboring communities. The site having the area of 1,316.7 square meters, located in Nowon-Dong, Buk-Gu, Daegu metropolitan City, is just like a vest pocket park. The adjacent area had been developed a slum area with mixed ad visually conflicting land use patterns and low income groups. The children and residents living in the area do not have any public space suitable for playing and/or rest. After analyzing such locational characteristic as accessibility, land use of the communities, and potentials for park development, and such design concept as arrangement of facilities, efficient use of site, and functional allocation of park space, We have mad a plan for composition of spaces for various activities, provision of facilities based on estimation of user-demand and activities, and planting. In the design process, we have tried to harmonize functional spaces with facilities, and to organize all the functions as a whole. To improve urbanity and aesthetic shape of park design, we have introduced a central plaza, design of a pave floor, a torrent, large trees for shade, colonnades and so on. From this design project, we can develop the site as a children park for increasing creativities and various playing opportunities, and as a resident space for rest, cultural activities. In the future, it is required that many attempt to design and develop urban small space as a park for children and residents.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.70-71
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• 2002

Exchange-coupled cluster of transition-metal ions are relevant to many different scientific areas, ranging from chemistry to solid-state physics, biology, material science and has been the subject of much research in recent years(1,2). Single crystal EPR spectroscopy works as a very effective tool for the measurement of J values for small exchange interactions. This makes EPR technique very suitable for detection of weak exchange coupling transmitted over long distances via extended atomic and melecular bridges. Large polyoxometallates (3) may provide ideal structural environments for the study of interactions between paramagnetic ions. The detailed nature of magnetic interaction (positive sign and magnitude of J~0.006 $cm^{-1}$ /) was clearly determined for di-copper(II) system by single crystal EPR spectroscopy (4). The single-triplet (S-T) transitions are forbidden by different symmetries of the wave functions. However, when the singlet ground state is mixed into triplet states, the S-T transitions can be allowed and observed as weak lines. These weak S-T lines are positioned symmetrically with respect to the main transitions in the distance equals to 2J from the center of the spectrum. This lines allow one to determine the J-value with very high accuracy when │J│ ＜ hv 0.32 $cm^{-1}$ /. Unfortunately, the S-T transitions in the single crystal were detected by EPR method only in a few complexes until now. We have measured single-triplet transition lines for several magnetically coupled cluster systems and determined their J values accurately. The temperature dependency of J was studied by monitoring the changes in S-T.