• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.102-108
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• 2006

In this paper, we propose an interference cancellation(IC) scheme using a partial Rake(PRAKE) combining in ultra-wideband(UWB) multipath fading channels. In this IC scheme, differently from the conventional transmitter model, which employs a guard interval between each frame, the guard interval is employed between each slot for estimating the multiple access interference(MAI). The UWB systems using the proposed IC scheme have little performance degradation without regard to the number of user, while the conventional UWB systems have a significant performance degradation according to the number of user. In order to reduce the receiver complexity, the PRAKE combining of post-canceled signal and the partial user IC scheme are also proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.485-492
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• 2003

This paper proposes a transmission probability control scheme for guaranteeing fair packet transmissions in CDMA slotted ALOHA system. In CDMA slotted ALOHA system, the packets transmitted in the same slot act as multiple access interference, so that unsuccessful packet transmissions are caused entirely by multiple access interference. Therefore, in order to maximize the system throughput, the number of simultaneously transmitted packets should be kept at a proper level. In the proposed scheme, the base station calculates the packet transmission probability of mobile stations in the next slot according to the offered load and then broadcasts this probability to all the mobile stations. Mobile stations, which have a packet to transmit, attempt to transmit packet with the received probability. Simulation results show that the proposed scheme can offer better system throughput and average delay than the conventional scheme, and guarantee a good fairness among all mobile stations regardless of the offered load.

• YAKHAK HOEJI
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• v.54 no.4
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• pp.316-321
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• 2010

Adefovir dipivoxil which was originally developed by Gilead Sciences has been used as treatments of HIV and HBV, especially a therapeutics for HBeAg positive and negative chronic patients. We developed highly efficient purification method using reverse phase column chromatography for mass production and a stable amorphous Adefovir dipivoxil using solid dispersion method. Reverse phase column chromatography led to highly pure product, more than 99.7% by HPLC and can be used for mass production compared with normal column chromatography. Solid dispersion method containing watersoluble polymer and Isomalt showed improved stability of amorphous Adefovir dipivoxil against heat and moisture.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.2
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• pp.107-113
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• 2018

Maintaining adequate residual chlorine concentration is an important criteria to provide secure drinking water. The chlorine decay can be influenced by unstable flow due to the transient event caused by operation of hydraulic devices in the pipeline system. In order to understand the relationship between the transient event and the chlorine decay, the probability density function based on the water demand curve of a hypothetical water distribution system was used. The irregular transient events and the same number of events with regular interval were assumed and the fate of chlorine decay was compared. The chlorine decay was modeled using a generic chlorine decay model with optimized parameters to minimize the root mean square error between the experimental chlorine concentration and the simulated chlorine concentration using genetic algorithm. As a result, the chlorine decay can be determined through the number of transients regardless of the occurrence intervals.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.184-189
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• 2001

The design of an ultra fast ellipsometer is suggested. It adopts the division-of-amplitude-photopolarimeter (DOAP) as the polarization state detector. It does not utilize any moving part such as the rotating polarizer(analyzer) or even any electronic modulation part like the piezo-electric phase modulator. Hence the time resolution of the present system is limited only by the response time of the photo-detector and electronic circuit as well as the analog-digital converter. The feasibility of the suggested ultra fast ellipsometer was tested and the response time with nano-second time resolution has been verified. Its future application to the investigation of kinetics including that of the phase-change optical recording media like GezSb2 Tes is discussed. ussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.729-739
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• 1994

In a centralized spread-spectrum packet radio network, a random assignment -transmitter-based spreading code protocol(RA-T) is proposed which permits the contention mode only in the trasmission of a preamble while avoiding collision during the data packet transmission by assigning near-orthogonal spreading codes to each user. Compared to the conventional transmitter-based code scheme, this scheme allows reduction in receiver complexity when only a small number of distinct spreading codes are employed for the preamble transmission. Throughout theoretical and simulation results, it is shown that the use of the RA-T scheme with just two or three distinct codes for the preamble packet achieves most of the performance gain.

• Survey Research
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• v.11 no.3
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• pp.115-137
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• 2010

This article challenges necessity for applications of ethnography principles to marketing research in the field. Since ethnography collects in-depth data about consumers' experiences and behavioral patterns, it can provide useful informations for marketers' decision making. Therefore this study introduces ethnography principles that need to be applied to marketing research, summarizes its usage values in the fields, and introduces case projects that were conducted under the guideline of ethnography principles. Finally, this study identifies the reasons why marketers hesitate using ethnography when they conduct marketing research and provides suggestions for more active applications of ethnography in the field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1126-1132
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• 1999

In this paper, we consider the superposed 16-QAM CDMA system for subband coded (SBC) image transmissions. We divide the SBC image bit into two group according to its significance. First, we investigate the average bit error rate (BER) of the overall system when the significance of bits is ignored. Next, we investigate the optimal signal constellation and processing gain that maximizes the peak signal-to-noise ratio (PSNR) of SBC image, subject to a fixed power and bandwidth constraint. We examine the performance improvement over the conventional equal distane, equal processing gain system, and the equal error protection (EEP) system.

• Fashion & Textile Research Journal
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• v.5 no.5
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• pp.453-464
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• 2003

This study is to analyze that the pluralism is the main aspect of the modem fashion which examines the definition and the character of the pluralism. This will also consider the pluralism that appeared on the modern fashion which is based on them. The main point of pluralism is that the world is necessarily aware of plural and difference. Also many values which is focused on the previous generation, for instance disorganize of westernism, androcentrictrism, christianism and powerful nationalism, what is called unfamiliar, heterogeneous, the others and the circumference things. As these were rehabilitated, morality, ethics, religion or politics were all became possible to choose for one's taste. The pluralism expressed in modern fashion can be divided as collapse of genre, grafting the lower and higher orders cultivation, variety way of approaching in time, internationalism. The result for the consideration is that the pluralism has candid attitude for everything so that in the modern fashion is importing variety range of artistic definition. Namely, it is not only containing previous pure art, elegance art and element of artistic sublime beauty, but also has aesthetics of ugliness, deconstructive art and anti-fashion so that the definition of the art is getting vagueness and diverse.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.244-247
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• 2018

Lecithin, a zwitterionic phospholipid, forms spherical reverse micelles in organic solvents such as decane. The addition of multivalent ions like calcium chloride to lecithin organosols induces the transformation of organosols into organogels. A variety of applications of such organogels were found in gelation of fuels, food processing and drug delivery. Here, we investigated the effect of temperature on their rheological properties. In particular, the organogels showed a distinct melting temperature (${\sim}95^{\circ}C$) and their elastic properties decreased with increasing temperature. This is maybe due to the fact that the electrostatic interaction between lecithin and calcium chloride could be weaken with increasing temperature.