• 한국통신학회논문지
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• 제30권7B호
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• pp.481-488
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• 2005

멀티미디어 응용 서비스에 대한 요구가 증대됨에 따라 멀티미디어 혼잡제어 알고리즘에 대한 연구가 더욱 중요시되고 있다. 그러나 기존에 제안된 혼잡제어 알고리즘들은 혼잡 상황 판단을 위하여 RTT를 사용하기 때문에 데이터 전송 경로의 혼잡 상황과 회신 정보 회신 경로의 혼잡 상황을 정확히 구분하지 못하는 단점이 있다. 본 논문에서는 OTT를 사용하여 네트워크 혼잡 상황을 판단하도록 제안된 RRC-OTT(Receiver-based Rate Control with One-way Trip Time) 알고리즘의 장점을 활용하여 데이터 전송 경로와 회신 정보 회신 경로의 혼잡 상황 판단을 분리하도록 하였고, 특히 회신 경로의 혼잡 상황이 데이터 전송 경로에 미치는 영향을 최소화하는 알고리즘을 제안하였다. 제안된 알고리즘의 성능 평가를 통하여 기존 혼잡제어 알고리즘과 달리 RRC-OTT 알고리즘은 회신 경로의 혼잡 상황에 영향을 받지 않고 일정한 성능을 보임을 입증하였다.

• IMMUNE NETWORK
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• 제2권4호
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• pp.183-188
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• 2002

Gradual attrition of telomere to a critical short length elicits successive cellular response of cellular senescence and crisis. Cancer cells evade this process by maintaining functional telomeres via one of two known mechanisms of telomere maintenance. The first and most frequent mechanism involves reactivation of enzyme activity of telomerase, a ribonucleoprotein complex mainly via transcriptional up-regulation of TERT, a catalytic subunit of telomerase complex. The second mechanism utilizes telomerase-independent way termed ALT (for Alternative Lengthening of Telomere), which possibly involves recombination pathways. Thus master key for cellular immortalization is supposed to possess adequate telomere reserves. Indeed, telomerase can alone induce the immortalization under culture on feeder cell layers without generally known inactivation mechanism of tumor suppressor genes. Including this phenomena, this review will focus on telomerase and telomere-associated proteins, thereby implication of these proteins for cellular immortalization processes.

• 한국전자거래학회지
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• 제6권3호
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• pp.41-61
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• 2001

Many markets are forecast to see significant changes due to the growth of electronic commerce made possible by the internet. The way of doing business with internet affects the market mechanism. It is now over 10 years since Malone et al(1987) set out their hypothesis on electronic markets, and electronic hierarchies. An electronic market is an interorganizational information system through which multiple buyers and sellers interact to accomplish one or more of the following market-making activities. And they predicted that markets evolve toward electronic markets, by reducing search cost, which may result in significantly. higher price competition among sellers and therefore lower prices for buyers. And the degree of two factors; asset specificity and uncertainty, affect the market mechanism. Products with low asset specificity and low uncertainty are compatible with a market relationship while the greater the asset specificity and uncertainty, the more likely it is to favour a hierarchical structure. Based on the these researches, we observed and analyzed a case study of market mechanism in Internet business. We found the fact that even though Internet could make the business environment in which lots of buyers and suppliers participate, electronic market will evolve market mechanism. 1 analyzed two factors, which affected market evolution. First, When Asset specificity is low in electronic commerce, market structure should be preferred to hierarchical structure. Second, When transaction uncertainty is low in electronic commerce, market structure should be preferred In hierarchical structure. This research covers conceptual and empirical aspects on electronic market structure. Future research should be variously done about the influential factors of electronic market mechanism.

• 한국컴퓨터정보학회논문지
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• 제16권5호
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• pp.23-31
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• 2011

컴퓨팅 시스템의 부팅 시간 지연 문제는 시스템 소프트웨어 분야에서 중요한 이슈로 부각되어 왔다. 최근 임베디드 시스템 환경에서도 리눅스의 부팅 속도 개선에 많은 관심이 집중되고 있다. 본 연구에서는 임베디드 리눅스 시스템의 대안적인 부팅 방식으로써 하이버네이션을 기반으로 하는 부팅 방식에 주목한다. 본 논문은 다음의 두 가지 측면에서 그 의의를 찾을 수 있다. 첫째, 실제 모바일 전자기기에 널리 활용되는 ARM 임베디드 개발 보드에서 리눅스 버전 2.6.21에 하이버네이션 기반 부팅 방식을 구현한다. 둘째, 하이버네이션 기반 부팅 과정을 시간대 별로 관찰하고 부팅 속도 개선의 여지에 대해서 논의한다. 실제 구현을 통한 부팅 과정 분석 결과, 다양한 최적화 기법이 적용될 경우 하이버네이션 기반 부팅 방식은 전통적인 부팅 방식보다 최대 3.1배 정도 빠른 부팅을 제공할 수 있을 것으로 기대된다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.II
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• pp.489-497
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• 2000

Since Chinese cabbages weigh 3 to 5kgf and are big in size at the time of harvest, handling operations such as harvesting, loading and unloading including transportation require the highest labor demand among all other cultivation processes. Recently, though several cabbage harvesters were developed in Japan and Europe, those harvesters were not suitable for Chinese cabbages cultivated in Korea because of the size and shape. The cabbage harvester is almost meaningless without any proper cabbage piling and pallet unloading mechanism. Most harvesters developed so far adopted a sort of slide and free falling way in collecting cabbages into the pallet. Three or four labors are usually required for cleaning incoming cabbages and loading those in the pallet. Because of the required time for piling cabbages without severe damage and the required space capacity to carry empty and loaded pallets, harvesting speed should be adjusted in accordance with time required for consecutive operations. Up to now, any automatic or semi-automatic collecting device has not been developed in the world to pile cabbages on the layer one by one into the pallet in the ordered way with little damage and to unload pallet from the harvester continuously during the harvest process. To compromise system expenses and function, Semi-automatic cabbage piling and pallet unloading mechanism was devised and it required one labor. The foldable mesh pallet with a size of 1050mm x 1050mm x 1000mm and holding capacity of around 70 cabbages was utilized. The prototype for piling and unloading mechanism was composed of three parts such as feeding device, automatic piling device with retractable bellows, and pallet unloading device. Prior to developing the prototype, the geometric properties and the amount of the damage of the cabbage caused during the piling operation were investigated. Considering the height of the pallet, a series of cabbage carrying plates were mounted to the bracket chain to lift and to carry cabbages to the loading device. Indoor laboratory experiments showed that the cabbage carrying chain conveyor worked successfully. Considering the conveying speed 0.46m/sec of the pull up belt from the cabbages on the ground, the speed of cabbage carrying chain conveyor worked property in the range of 0.26m/sec to 0.36m/sec. The system allowed the operator to modify the position of cabbage slightly. Overall system worked successfully resulting into almost same capacity without severe damage to the cabbage as human did.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.99-104
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• 2004

Micro/meso cutting is getting more important in the fields of precision machining technology. A micro-turning lathe is one of parts to consist the Micro Factory. It accepts stepwise motion actuators that are used for feeding system instead of the conventional mechanism. It is consisted of two Piezoelectric ceramics; one is for feeding the slider, and the other is for clamping the slider in the guide way of the body. The linearity and positional accuracy of the actuators are good enough for high precision motion. The spindle unit is operated with DC motor on the top of the slider. The motion is communicated with miniaturized linear encoder attached on each side of axis. A mono crystal diamond tool is used for cutting tool. This micro-lathe has been made a machining experiment to see the characteristics of micro-machining.

• 생물정신의학
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• 제8권1호
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• pp.162-166
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• 2001

The mirtazapine is a relatively new antidepressant that has noradrenergic and specific serotonin antagonist action(NaSSAs). This has been known as one of the most safest drugs because of its few side effects. Until now, there have been only one case report that mirtazapine causes a EPS side effect(restless leg syndrome). But the peculiar mechanism of this drug makes it impossible to explain the exact reasons why the mirtazapine could induce EPS symptoms. Authors observed three cases of mirtazapine induced akathisia. We could not explain the phenomenon the other way except akathisia. So here we presents the three case of mirtazapine induced akathisia and a few possible hypothesis of this phenomenon.

• 산업경영시스템학회지
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• 제23권54호
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• pp.77-85
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• 2000

One form of job shop scheduling problem in contemporary automated manufacturing such as flexible manufacturing systems (FMS's) is presented which we call the FMS dispatching priority problem. The FMS dispatching priority problem seeks the best dispatching priority of parts and operations, and is essentially a combinatorial optimization problem. Because of the complicated mechanism of the system, the performance of a given dispatching priority must be evaluated via simulation. Simulated annealing have been applied to the problem, and it is found that appropriate parameter setting will be desirable to get good, if not the optimal, solutions within a limited amount of time under the presence of heavy computational burden due to simulation. More specifically, experiments reveal that initial temperature is the single most important factor among other parameters and factors, and that the appropriate initial temperature depends on the allowable computer time in such a way that the less time one can afford to spend, the lower the appropriate initial temperature should be.

• Steel and Composite Structures
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• 제32권1호
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• pp.1-19
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• 2019

The aim of the paper is the prediction of the seismic collapse mode of steel storage pallet racks under seismic loads. The attention paid by the researchers on the behaviour of the industrial steel storage pallets racks is increased over the years thanks to their high dead-to-live load ratio. In fact, these structures, generally made by cold-formed thin-walled profiles, present very low structural costs but can support large and expensive loads. The paper presents a prediction of the seismic collapse modes of multi-storey racks. The analysis of the possible collapse modes has been made by an approach based on the kinematic theorem of plastic collapse extended to the second order effects by means of the concept of collapse mechanism equilibrium curve. In this way, the dissipative behaviour of racks is determined with a simpler method than the pushover analysis. Parametric analyses have been performed on 24 racks, differing for the geometric layout and cross-section of the components, designed in according to the EN16618 and EN15512 requirements. The obtained results have highlighted that, in all the considered cases, the global collapse mechanism, that is the safest one, never develops, leading to a dangerous situation that must be avoided to preserve the structure during a seismic event. Although the studied racks follow all the codes prescriptions, the development of a dissipative collapse mechanism is not achieved. In addition, also the variability of load distribution has been considered, reflecting the different pallet positions assumed during the in-service life of the racks, to point out its influence on the collapse mechanism. The information carried out from the paper can be very useful for designers and manufacturers because it allows to better understand the racks behaviour in seismic load condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.406-423
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• 2014

The recent advances in wireless communication systems and semiconductor technologies are paving the way for new applications over wireless sensor networks. Health-monitoring application (HMA) is one such emerging technology that is focused on sensing and reporting human vital signs through the communication network comprising sensor devices in the vicinity of the human body. The sensed vital signs can be divided into two categories based on the importance and the frequency of occurrence: occasional emergency signs and regular normal signs. The occasional emergency signs are critical, so they have to be delivered by the specified deadlines, whereas the regular normal signs are non-critical and are only required to be delivered with best effort. Handling the occasional emergency sign is one of the most important attributes in HMA because a human life may depend on correct handling of the situation. That is why the underlying network protocol suite for HMA should ensure that the emergency signs will be reported in a timely manner. However, HMA based on IEEE 802.15.4 might not be able to do so owing to the lack of an appropriate emergency-handling mechanism. Hence, in this paper, we propose a new emergency-handling mechanism to reduce the emergency reporting delay in IEEE 802.15.4 through the modified superframe structure. A fraction of an inactive period is modified into three new periods called the emergency reporting period, emergency beacon period, and emergency transmission period, which are used opportunistically only for immediate emergency reporting and reliable data transmission. Extensive simulation is performed to evaluate the performance of the proposed scheme. The results reveal that the proposed scheme achieves improved latency and higher emergency packets delivery ratio compared with the conventional IEEE 802.15.4 MAC.