• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.145-148
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• 2002

This paper has been studied a predistorter which is able to linierizing of RF amplifier using schottkey. If input signal level is low, input signal is delivered directly. And if input signal level is high, input signal Is delivered with decreasing. So RF amplifier always works at saturation region .When this predistorter is used to simplified C-class RF amplifier, we have concluded that efficiency is improved about 3%.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2000년도 제15회 학술강연회논문초록집
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• pp.10-10
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• 2000

For low Earth orbit, the atmosphere causes orbit altitude to decrease, If this decrease is not corrected by the satellite propulsive unit, the orbit decoys continuously unit reaches the dense atmosphere and satellite life ends. If active orbit maintenance is mode by satellite propulsive unit then fuel consumption is necessary, which must be considered in the satellite design. Especially interesting is the method for evaluating the fuel consumption role for maintenance of elliptical orbit developed in this paper.(omitted)

• 대한수학회보
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• 제58권5호
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• pp.1247-1260
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• 2021

We introduce the notion of barycentric transformation of Fano polytopes, from which we can assign a certain type to each Fano polytope. The type can be viewed as a measure of the extent to which the given Fano polytope is close to be Kähler-Einstein. In particular, we expect that every Kähler-Einstein Fano polytope is of type B_∞. We verify this expectation for some low dimensional cases. We emphasize that for a Fano polytope X of dimension 1, 3 or 5, X is Kähler-Einstein if and only if it is of type B_∞.

• 디지털융복합연구
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• 제15권11호
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• pp.167-174
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• 2017

최근 우리나라 기업의 회계투명성에 대한 불신이 심각한 상황이다. 회계투명성에 대한 불신은 기업의 자본조달비용을 증가시키므로 수익성을 악화시킨다. 감사업계는 낮은 회계투명성의 원인을 감사인과 피감사기업 간의 수의계약으로 보고 있다. 피감사기업이 감사인을 고용하면서 낮은 감사보수를 요구하며, 이론적으로 낮은 감사보수는 감사자원 투입의 저하를 초래하여 감사품질을 감소시킨다. 그러나 이에 대한 실증적 증거는 전무한 상황이다. 본 연구에서는 연도-산업별로 감사보수가 평균보다 낮은 감사인을 저가수임 감사인으로 선정하고, 이러한 감사인들의 감사품질이 상대적으로 낮은지를 검증하였다. 연구 결과, 저가수임 감사인으로부터 감사를 받은 피감사기업의 재량적 발생액이 상대적으로 높은 것으로 나타났다. 이러한 결과는 저가수임이 감사품질에 부정적 영향을 미치는 것으로 해석할 수 있다. 본 연구는 감사보수와 관련된 여러 정책개발에 실증적 증거로 제시될 수 있다.

• 정보보호학회논문지
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• 제14권1호
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• pp.79-89
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• 2004

Mobile IP Low Lattency Handoffs Mobile IP 등록 요청 절차를 처리하는데 발생하는 지연을 최소화시켜 실시간 서비스를 가능하게 해준다. 그러나 인증, 권한 검증, 과금을 지원하는 AAA 기반의 Mobile IP 망에서는 매 지역등록이 일어날 때마다 새로운 세션 및 세션 키가 필요하며. 이를 위해 홈 망까지 등록 절차가 수행되어야 한다. 이로 인해, 이동 노드 재인증 절차와 방문 망에서 홈 망까지의 트랜잭션으로 인한 통신 지연이 발생한다. 이러한 지연을 줄이기 위해서 본 논문에서는 홈 망의 AAA 서버를 관여시키지 않고, 이전에 할당된 세션 키론 재사용 하여 Low Latency Handoffs를 수행하는 기법을 제안한다. 이 기법에서는 이전 방문 에이전트와 새로운 방문 에이전트가 세션 키를 교환하는 단계에서 발생하는 보안 취약점을 해결하기 위하여 게이트웨이 방문 에이전트로 하여금 신뢰할 수 있는 제3자 역할을 수행하도록 하고 이를 통해 키를 공유한다. 제안한 기법에 의하면 홈 망까지의 트랜잭션이 필요 없고, 세션 키의 기밀성과 무결성이 보장되므로 이동 노드가 빠르고 안전하게 핸드오프를 수행할 수 있다.

• 한국소음진동공학회논문집
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• 제19권10호
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• pp.1028-1033
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• 2009

To detect faults and monitor thinning on a pipe, many people use ultra sonic sensors that are operated in high frequency range. Because there are many modes in high frequency range, it is difficult to find faults and monitor pipe thinning on a structure. If we deal with signals in a low frequency range which include only A0 wave and S0 wave, the information of monitoring and diagnosis can be easily obtained. In this paper, the technique for exciting low frequency range using ultra sonic sensors is proposed. The main idea of the proposed method comes from the beat phenomenon. The beat frequency is equal to the absolute value of the difference in frequency of the two waves. If the beat frequency is tuned by two ultra waves, we can excite A0 mode and S0 mode of structures. To verify the proposed method, we have performed a steel plate and pipe experiments. Experimental results show that two ultra sonic sensors can well excite low frequency range.

• 상하수도학회지
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• 제8권1호
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• pp.34-43
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• 1994

It is well known that the adsorption character of activated carbon is dependent on the specific surface area and pore volume, but the relationship between the surface-chemical structure and the adsorption character has not been studied very often. The purpose of this study is to investigate the effect of the acidic surface functional groups of activated carbon and the adsorption characteristics of low concentration phenol. So three types of activated carbons and four different treatments were introduced to this isotherm experiment. These treatments were nontreatment, 1N $HNO_3$ treatment, 6N $HNO_3$ treatment, $H_2O_2$ treatment. The conclusions of this study are as followings. If the initial concentration of phenol is high as 5mg/l, the adsorption is dependent on the specific surface area. If the initial concentration of phenol is low as $100{\mu}g/l$, the adsorption is dependent on the average pore volume. The acidic surface functional groups prevent the adsorption of phenol molecules to activated carbon. And the adsorbed amount decreases more for $HNO_3$ treatment than for $H_2O_2$ treatment and more for concentrated $HNO_3$ treatment than for dilute $HNO_3$ treatment.

• 한국조경학회지
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• 제27권1호
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• pp.122-131
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• 1999

Indoor environments are usually less than optimal for the growth of ferns, especially in regards to the water condition. These studies were performed to investigate responses involved in causing growth of ferns and presume management plan against the water deficit under indoor conditions. The effect of air humidity and soil moisture on the ferns was examined in Adiantume raddianum and Selaginella kraussiana. Results of experiments are as follows; 1. Under a low humidity condition, having a 25-50% RH. ornamental value of ferns decreased much more than under a 90% RH. Under a low soil moisture, such as sand treatment, ornamental value of ferns also decreased. 2. Leaf chlorophyll content, water content and stomata situations increased as air humidity and soil moisture went up. 3. Even if air humidity and soil water were not enough for ferns growth, the extending of irrigation cycle was helpful. 4. Under extremely low air humidity conditions, some water management, namely, using water holding soil or extending of irrigation cycle was desirable. Other methods of increasing air humidity, including water instruments such as ornamental pools, waterfalls, or fountains, grouping plants together were also helpful. But spraying water on leaves increased injury to ferns growth because of excess evaporation from the leaves. Though these studies, we learn that ferns are susceptible to water condition such as air humidity, soil water and water management. If other environmental factos are maintained with optimal conditions, water condition plays an important role in ferns growth in indoor environments.

• 한국도로학회논문집
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• 제17권3호
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• pp.1-12
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• 2015

PURPOSES : This paper presents a description of the current issues facing road managers regarding the surface-type conversion of low-volume roads for cost savings. METHODS: The paper reviews previous works conducted toward this end, acknowledges gaps in the current research, and lays out what information is needed for further studies. RESULTS : If the cost to maintain an unsurfaced road is less than the cost of maintaining a surfaced road, then there is potential for cost savings for the management agency. However, the problem is bigger than simply maintaining the roads that already exist. If unsurfaced roads prove to be more economical than surfaced roads, then the cost to convert from a surfaced to an unsurfaced roadway, and vice versa, when necessary, must also be examined. CONCLUSIONS : No other studies have addressed the un-surfacing of a road for cost savings, and it is therefore unknown whether substantial savings can be realistically obtained by converting from a surfaced to an unsurfaced road. To determine whether a conversion policy would be a viable option, additional data and research are needed.

• 천문학회지
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• 제34권4호
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• pp.313-315
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• 2001

Some authors have concluded that spiral structures and shocks do not develop if an adiabatic index $\gamma$ > 1.16 is adopted in accretion disc modelling, whilst others have claimed that they obtained well defined spirals and shocks adopting a $\gamma$ = 1.2 and a $M_2/ M_1$ = 1 stellar mass ratio. In our opinion, it should be possible to develop spiral structures for low compressibility gas accretion discs if the primary component is a black hole. We considered a primary black hole of 8M0 and a small secondary component of 0.5M$\bigodot$ to favour spiral structures formations and possible spiral shocks via gas compression due to a strong gravitational attraction. We performed two 3D SPH simulations and two 2D SPH simulations and characterized a low compressibility model and a high compressibility model for each couple of simulations. 2D models reveal spiral structures existence. Moreover, spiral shocks are also evident in high compressibility 2D model at the outer disc edge. We believe that we could develop even well defined spiral shocks considering a more massive primary component.