• Journal of information and communication convergence engineering
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• 제2권2호
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• pp.61-66
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• 2004

This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia Wireless LAN system. The presented method is a comparative analysis between a case where parameter a for time average is 0.3.1 with consideration of channel presumption with two types of rms delayed spread, which is 50nsec. 150nsec, for the performance analysis of STTC (Space-Time Trellis Code) adopting time-space ciphering method appropriate for MIMO channel, and performance in the case where presumed channel value from long training column section is applied to according frame in a single frame. The result showed that BER brought SNR improvement of l.0dB in $10^{-3}$ when a was 0.3 than adopting only the long training column, and showed increase of general performance improvement for the sake of time average rather than the case without.

• Design & Manufacturing
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• 제16권1호
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• pp.62-69
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• 2022

In the present study, the injection molding optimization of a large thick LH type elastic frames for the reduction of warpage was performed. Two kinds of fine and coarse finite element models were prepared to investigate the efficiency of analysis time and quality on simulation results. In order to derive injection molding conditions that can minimize distortion of parts, it was investigated that the effects of mold temperature, resin temperature, injection time, hold pressure switching time, holding pressure and the hold time on deformation characteristics using the design of experiments. The main influential factors on the warpage were found from the optimization simulation and the geometry data of the warpage result was converted into an initial model for injection simulation. It was shown that a coarse model with good mesh quality could be adapted for mold design since the total analysis time using the proposed model was reduced to 1/10. The suggested inversed warpage model produced the best minimized result of warpage.

• 한국통신학회논문지
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• 제30권6C호
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• pp.423-433
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• 2005

다중 반송자를 사용하는 CDMA 통신 시스템에서 주파수 영역의 전력과 시간 영역의 전송율을 적응적으로 사용하는 시스템을 분석하였다. 수신단으로 부터 얻는 이상적인 채널상태 정보를 가정하고, 주파수 영역에서는 각 사용자의 부채널 중에서 가장 채널상태가 좋은 한 대역을 선택하고, 시간영역에서는 목표 수신 품질을 만족하도록 전송율을 조정한다. 단일 사용자의 경우에 평균 BER을 최소화 할 수 있는 최적의 전송 방식의 식을 유도하였다. 채널 상태 역수 법이 사용 대역의 수나, 평균 전송양이 증가할 때 최적의 알고리듬이라는 사실 또한 증명하였다. 수학적 분석과 시뮬레이션 결과 제안된 주파수 시간 적응 알고리듬을 사용한 방식이 주파수영역에서만 선택적인 방법을 사용하는 MC-CDMA 방식과 비교하여 현격히 좋은 성능을 보임을 보였다. 또한 제안된 적응형 MC-CDMA 전송방식과 기존의 RAKE 수신기를 사용하고 시간 영역에서 적응적 방식을 사용하는 DS-CDMA 시스템과 성능을 비교하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.3-3
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• 2001

Recently TiN, TiAlN, CrN hardcoatings have adapted many industrial application such as die, mold and cutting tools because of good wear resistant and thermal stability. However, in terms of high speed process, general hard coatings have been limited by oxidation and thermal hardness drop. Especially in the case of PCB drill, high speed cutting and without lubricant process condition have not adapted these coatings until now. Therefore more recently, superhard nanocomposite coating which have superhard and good thermal stability have developed. In previous works, WC-TiAlN new nanocomposite film was investigated by cathodic arc ion plating system. Control of AI concentration, WC-TiAlN multi layer composite coating with controlled microstructure was carried out and provides additional enhancement of mechanical properties as well as oxidation resistance at elevated temperature. It is noted that microhardness ofWC-TiA1N multi layer composite coating increased up to 50 Gpa and got thermal stability about $900^{\circ}C$. In this study WC-TiAlN nanocomposite coating was deposited on PCB drill for enhancement of life time. The parameter was A1 concentration and plasma cleaning time for edge sharpness maintaining. The characteristic of WC-TiAlN film formation and wear behaviors are discussed with data from AlES, XRD, EDS and SEM analysis. Through field test, enhancement of life time for PCB drill was measured.

• 한국가축번식학회지
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• 제16권4호
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• pp.353-361
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• 1993

This study was taken to examine external changes, behavioral changes, and endocrine changes such as estradiol-17$\beta$, progesterone, T4 and T3 of female Oreochromis niloticus living in 0$\textperthousand$, 10$\textperthousand$, 20$\textperthousand$, and 30$\textperthousand$ salt concentrations, respectively. The results obtained in these experiments were summarized as follows. In seawater obtained in these experiments were summarized as follows. In seawater challenge test, any fish didn't die in each group such as 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, external body color of fish changed from dark-striped to light-grey color. At the same time, thyroxine and triiodothyronine concentrations significantly(P<0.05) increased, and then were at the highest level in 30 salinity. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, feed intake of fish started from the fourth day. From 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, estradiol-17$\beta$ levels were increased gradually. When fish was adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, the levels of each progesterone didn't show significant change, and especially showed the lowest peak in 20$\textperthousand$. The greatest thyroxine activity(T4) was observed in 30$\textperthousand$. The levels of and triiodothyronine(T3) significantly changed in all salinities, and its level was at the highest peak in 30$\textperthousand$ salinity. Correlation coefficients between serum progesterone and triiodothyronine in 10$\textperthousand$ and 30$\textperthousand$ were ＋0.677 and ＋0.843, respectively. Correlation coefficient of serum thyroxine(T4) and triiodothyronine(T3) individuals in 10$\textperthousand$ was ＋0.768, and ＋0.843, respectively.

• 한국식생활문화학회지
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• 제12권1호
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• pp.87-96
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• 1997

The purpose of this study is, to examine current foodservice management practices at free meal service organization for elderly people and, to evaluate the attitude of recipients about the service and their ecological background. 6 meal service center as well as randomly selected 120 recipients at Sungnam area were surveyed and interviewed and result were summarized as follow. The cost of each meal (lunch) was ranged from 1,300 won to 1,500 won and number of attendant at meal service were ranged from 50 to 200 persons. Meal time for lunch begins from 10:30 am to noon because greater portion of people (elderly) didn't take breakfast frequently. Most of the center adapted self-service system. Standard recipe was not developed and meal preparation was controlled under the experiences of volunteer’s. Recording system of, nutrition management, production control, storage and inventory control was not well adapted by most of the center. In order to measure the level of storage, sanitation etc., scorin system in survey was adapted in this study and result are as follow: The score of sanitation of kitchen was lower than dinning area and that of food storage was lowest score. It was suggested that not only financial but also systematical support on management by local government may be necessary to meet the goal of supply nutritionally balanced food at the center. The score given by the recipient on the satisfaction of meal service was rate as 4.8 at the 5-point maximum scale. Meeting friends and share social relationship was major reason (41.6% of the total) of visiting to the center. It is suggested that in order to meet the changes of the patterns of change of social and family structure, the service of the center should be extended in urban area and it is necessary to develop systematic management models for the center.

• 한국미생물·생명공학회지
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• 제44권4호
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• pp.529-534
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• 2016

해조류 중 갈조류인 미역으로부터 분리당화발효(SHF)를 위한 전처리 및 효소당화를 검토하고, 기존의 분리당화발효(SHF)를 개선하기 위해 공배양발효(co-culture)를 수행하였다. 비순치 효모와 고농도 mannitol에 순치(adaptive evolution)한 효모를 이용한 공배양발효를 실시한 결과 발효 72시간에 12.2 g/l의 에탄올과 에탄올 수율($Y_{EtOH}$) 0.41을 나타내었다. 이러한 기존의 분리당화발효(SHF)를 개선한 공배양발효를 통해 에탄올 생산 수율이 0.23에서 0.41로 35.2% 증가하였으며, 에탄올 발효시간도 108시간에서 72시간으로 33.3% 감소하였다. 이러한 연구결과는 해양 바이오매스인 해조류로부터 바이오연료 생산과정에 있어 유용한 정보를 제공하는 것으로 판단된다.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.315-323
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• 2010

This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in prototype with different speeds of sound as well as in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics. Furthermore, in compressible simulation the amplification of pressure fluctuations is observed from the inlet of stay vane channels to the spiral case wall. Finally, the procedure is applied to a three-dimensional pump configuration in model scale with adapted speed of sound. Normalized Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1997년도 추계학술대회발표논문집; 홍익대학교, 서울; 1 Nov. 1997
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• pp.117-120
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• 1997

In this paper, we analyze Inventory Strategy of our country middle-small Company which are ordered form large Company which product using JIT(just in time) System. Until now, we have not found a good inventory strategy for middle small Company which such like above. In this paper, we first simply survey product lead time, lot size and safety inventory in continuous product system which idea can be adapted our object. We try to mathematical modelling of product lead time, total inventory cost of bur country middle-small Company. We suggest inventory strategy for middle-small Company.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.129-134
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• 2012

As application-specific requirements for wireless sensor networks emerge, both real-time and reliable communications become major research challenges in wireless sensor networks due to the many constraints on nodes and wireless links. To support these services, several protocols have been proposed. However, since most of them were designed as well as developed for general purpose applications, it is not recommended that they be directly adapted to applications with special requirements. In this paper, we propose a way to extend the current reliable transport protocol to cover a special real-time service, the (m,k)-firm deadline stream, in wireless sensor networks. While the proposed scheme is basically built on the PSFQ protocol for reliability, some features have been newly developed to support the (m,k)-firm stream efficiently. Finally, simulation results are given to demonstrate the feasibility of the proposed scheme in high traffic and with failed links.