• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1459-1462
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• 2002

Emergence of the fourth generation mobile communication system (4G system) is now in its dawn. This paper pro- poses a perspective framework on the 4G system, and discusses system aspects of radio access technologies. The focus of the paper is to define the scope and features of the 4G system in an overall system/network viewpoint. From the foreseeable development trends, it is highly expected that whatever emerges in the 4G system will be some kind of constantly evolving and grand recursive concatenation of all the existing system/network developments.

• Journal of Information Technology Applications and Management
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• 제16권4호
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• pp.205-222
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• 2009

Considering time-lag in the performance evaluation of information system (IS) investment is important because its effect reveals after certain period of time passed. Particularly it is more in the systems of e-government informatization projects which the amount of investment and the scale of business are huge. Many methods to solve this issue have been proposed such as system dynamics methods, simulations, structural equations etc. However, it is still difficult and unsolved problem because collecting practical data for time-lag analysis is very hard. In this paper, we analyze IS time-lag effect through factor analysis using the accumulated practical operational DB data. For the performance evaluation of the G4C system, the representative e-government web portal, we selected eleven factors reflecting time passing in G4C DB data. With these factors this paper conduct time-lag analysis in four view points. First, we conducted 'Stabilizing of G4C system' and got a result that IS is needed about three years for the stabilization. Second, we conducted 'Utilization of G4C system' and got a result that the utilization reaches appropriate level after in three years later after the introduction of G4C system. Third, we conducted 'Cost reduction effect' and got a result that cost reduction is stable in the third year after the introduction of G4C system. Lastly, we conducted 'System maturity effect' and got a result that the system reaches to the quality level that users expect after third to fourth years. According to the results of this research, we found that performance of IS improv continuously not immediately, and it needs three or four years of time-lag.

• Journal of Communications and Networks
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• 제4권4호
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• pp.321-335
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• 2002

Emergence of the fourth generation mobile communication system (4G system) is now in its dawn. This article proposes a perspective framework on the 4G system, and discusses various kinds of system aspects and technological requirements in terms of novel service features, spectrum management, radio access technologies, wired access integration, core network, and mobile terminal. The focus of the article is to define the scope and features of the 4G system in an overall system/network viewpoint. From the foreseeable development trends, it is highly expected that whatever emerges in the 4G system will be some kind of constantly evolving and grand recursive concatenation of all the existing system/network developments.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.29-33
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• 2015

In this paper, we propose the method to improve the performance of the antenna system that contains three bands, such as Lte3G, WLAN and Lte4G. This antenna has an advantage that can cover the three different frequency bands 2.1GHz, 2.4GHz and 2.6GHz through one antenna design. The design and simulations are done using CST Microwave Studio 2014 program. The antenna is designed by using the FR-4 (lossy) substrate with the dielectric constant of er=4.3 and dielectric loss tangent 0.025. The substrate dimensions are the following; Thickness[h] is 1.6mm, Length is 90mm, and Width is 40mm. The ground is designed by using the PEC material with h=0.035mm. The patch is designed by using the copper with h=0.035mm. In the near future, we will fabricate the antenna, which we have designed, and then apply this antenna to the mobile communication system. And we will test this mobile communication system for the diverse environments.

• KSBB Journal
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• 제13권5호
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• pp.547-553
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• 1998

For the efficient production of a new exo-polysaccharide from Ganoderma lucidum ASI 7004, the optimum conditions and methods in submerged cultivation were investigated with an airlift fermenter system. The optimum aeration rate was 2.5 Wm at the initial pH 5.0 and 28$^{\circ}C$. The increase of dissolved oxygen concentration by pure oxygen supply during cultivation did not improved the exo-polysaccaride production and the mycelial growth. The maximum exo-polysaccharide production and the mycelial growth under the optimum culture condition were obtained in media of glucose 60g/L, yeast extract 6g/L, (NH4)2HPO4 1g/L and KH2PO4 0.5g/L. Under these optimum medium and culture conditions, about 7.15g/L of exo-polysaccharide and 13.9g/L of mycelial growth were producted, respectively.

• Journal of Microbiology and Biotechnology
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• 제4권4호
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• pp.333-337
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• 1994

In order to develop the whey beverage, we examined the optimum conditions for alcohol fermentation by Kluyveromyces tragilis ATCC 46537. The optimum conditions for alcohol production by K. fragilis ATCC 46537 were as follows; pH 4.5, $30^{\cir}C$, with a supplement of 50 g/l of lactose. To develop a continuous production of alcohol from whey, we compared batch fermentation with continuous iermentation in conjunction with UF system. Batch fermentation produced 11.0 g/l of alcohol, whereas pseudocontinuous and continuous fermentation with UF system produced 8.5 g/l of alcohol. To increase the alcohol production, we added 50 g/l of lactose to both fermentations. Batch fermentation with lactose supplement produced 15.7 g/l of alcohol and continuous fermentation with lactose supplement in conjunction with UF system produced 15.0 g/l of alcohol. These results clearly demonstrate that the UF system can be used to increase the alcohol production from whey, supplemented with exogenous lactose.

• KSBB Journal
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• 제16권5호
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• pp.511-515
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• 2001

TCE및 TCE 분해산물의 높은 독성으로 인하여 TCE 분해 효소 및 세포 불활성화가 일어나서 장기간 안정되게 반응기 운전이 어렵다는 단점을 극복하고, TCE와 성장기질사이의 경쟁적 저해관계로 인한 처리효율 감소도 막기 위하여 TCE분해단계와 세포 및 효소 재활성화 단계를 구분시킨 2단계 CSTR/TBF 시스템을 개발하였다. B. ceapcia G4를 분해 미생물로 사용하였으며, 탄소원인 phenol과 공기 및 배지가연속적으로 공급되는 CSTR에서 효소 및 세포 재활성를 도모하고, TBF에서는 폐가스에 포함된 기사의 TCE를 공기와 함께 공급하여 B. cepcia G4 미생물막에의한 TCE가 분해되도록 구성하였다. 2단계 CSTR/TBF 시스템은 유입 TCE 농도가 15pp $m_{v}$까지도 100% 수준의 처리 효율을 보여주었으며, 고농도의 TCE를 안정적으로 장기간 처리할 수 있었다.다.

• 한국축산시설환경학회지
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• 제4권1호
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• pp.21-28
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• 1998

This study was carried out to estimate the economic impacts on operation cost and curtail the bulking agent between two kinds of plants in swine farms. Bulking agents and Plants have a variety of roles in the fields of the composting for livestock manure and also represent an economic problem in terms of plant operation costs and compost production. Two farms which have rotary(size of reactor : 10${\times}$35${\times}$1.5m) or bucket(size of reactor : 10${\times}$68${\times}$2m) plants were used for 24 weeks for bucket conveyor system, which are composed of refilling rice hull as a bulking agent every 3 weeks till decreasing volume, for 4 weeks for rotary conveyor system, which has continuous compost production system without refilling rice hull, respectively. Composts was produced in 24 weeks in the bucket conveyor system, in 4 weeks in the rotary conveyor system, respectively. The results are as follows : 1. The tissue change of Rice hull at the composts of 45 days pursuant to composting steps was more crumbling in bucket conveyor system than in rotary conveyor system. 2. Microbial counts of the final composts for safety and quality showed that total bacteria counts was 1.01${\times}$108 cfu/g in bucket conveyor system, 2.82${\times}$108 cfu/g in rotary conveyor system, Salmonella was 0.3${\times}$102 cfu/g in bucket conveyor system, 7.6${\times}$102 cfu/g in rotary conveyor system, colifom bacteria was 0.5${\times}$106 cfu/g in bucket conveyor system, 1.5${\times}$106cfu/g in rotary conveyor system, fungi 1.24${\times}$106 cfu/g in bucket conveyor system, 0.01${\times}$106 cfu/g in rotary conveyor system, respectively. However, Any system used in this trial could not be met the regulation of A grade compost of EPA and USA. 3. C:N ratio according to the composting was more rapidly changed in bucket conveyor system with 64.5 of 5 days compost to 25.4 of final products than in rotary conveyor system with 26.7 of 5 days compost to 25.9 of final products. 4. Based on the mechanical characteristics of plants used in trial and compared with Rotary conveyor system, the Bucket conveyor system in which has 0.72 ㎥/㎥ of bulking agent capacity per slurry could be curtailed 1.78 ㎥of rice hull for disposal of waste, 1㎥. It was proper facilities to produce composts quantitative in Rotary conveyor system, and to treat waste quantitative and obtain good results in compost quality in Bucket conveyor system.

• 한국인터넷방송통신학회논문지
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• 제16권6호
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• pp.15-23
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• 2016

본 논문에서는 오픈 환경에서 4G 보안 모델에 대한 연구이다. 4G 네트워크는 여전히 많은 보안 문제를 가지고 있고 전문가가 주시해야할 많은 문제들이 존재한다. 본 논문에서는 기대하지 못한 서비스를 일으키는 많은 보안 위험에 대해서 알아본다. 4G는 IP 기반과 이종 네트워크로 이루어져 있어 많은 문제를 일으키는 주된 요인이다. 본 연구에서는 4G 표준안에서 보안 문제와 취약성에 대해서 다루고 있다. 또한 WiMax 와 3GPP LTE구조에서 수행될 수 있는 여러개의 구조에 본 연구에서 제공되는 문제점과 취약성에 대해서 테스트를 하였다. 마지막으로 본 연구에서는 미래취약성에 대한 잠재적인 영역과 경고 주의가 있는 4G 평가 영역에 대해서도 다루고 있다 이 연구를 4G 네트워크 취약성에 대한 문제에 적용시켜 보다 좋은 네트워크 구조를 개발하면 학습도 보다 빠르게 이루어져 빅데이터 분석에 유용하다.

• 유기물자원화
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• 제24권1호
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• pp.31-40
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• 2016

본 연구에서는 침출수 재순환 시스템을 적용한 중온 혐기성소화를 이용하여 음식물류 폐기물을 분해하여 메탄가스를 생산하였다. 실험은 $36^{\circ}C$로 유지되는 항온수조 내에 생물반응조와 침출수 저장조로 구성된 2개의 동일한 시스템(System A, System B)을 사용하였고, 생물반응조 하단 30 mm위에는 스크린이 있어 고액분리를 하여 침출수 저장조로 침출수를 이송하였다. 침출수 재순환은 매일 수행하였으며, 침출수 재순환 시에는 생물반응조 하단에서 침출수 저장조로 2.5 L를 30분간 이송한 뒤 다시 침출수 저장조에서 생물반응조 상부로 2.5 L를 30분간 주입하였다. 주입된 음식물류 폐기물은 수집되기 전 한 번 세척하였으며 반응조에 주입되기 전에 $36^{\circ}C$로 온도를 올렸다. System A에 49.1 g VS, System B에 54.0 g VS을 2주 간격으로 투입하였다. 저해인자로 측정된 항목은 $NH_4{^+}-N$과 염도였으며, 두 가지 항목의 농도 모두 시스템에 끼친 영향은 없는 것으로 나타났다. System A는 112일간, System B는 140일 동안 운전하였는데, 각 시스템에서 인발된 슬러지는 없었다. 음식물류 폐기물의 혐기성 소화를 통한 평균 메탄 발생량은 System A의 경우 0.439 L $CH_4/g$ VS, System B의 경우 0.368 L $CH_4/g$ VS로 나타났다.