• 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.

• 대한약리학회지
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• 제7권1호
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• pp.67-76
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• 1971

The excretion of uric acid in man has been of great interest because of its importance as an end product in purine metabolism as well as of its role in causing gout. There are many differences in the modes of renal handling of urate among various species of animals. Uric acid actively secreted by the renal tubules of most vertebrate including amphibians, reptiles, and birds. On the other hand, in most mammals net tubular reabsorption of urate appears to be occurred with some exception, such, as Dalmatian dog. In the rabbits, however, the mechanism of renal excretion of uric acid has long been a subject of controversial results. Within a given group it was possible to find individuals with either net secretion or net reabsorption of urate depend on the experimental conditions. Excretion of urate can be depressed or enhanced by a variety of drugs belonging mainly to the aromatic acid group. Diodrast, probenecid, cinchophen and salicylates have been reported as uricosuric agents, on the other hand, lactate, benzoate, pyrazinoic acid, acetazolamide and chlorothiazide are known to be contraindicated to use for the patient with gout since these agents depress the excretion of uric acid from the kidney. However, complex and sometimes the paradoxical effects on the urate excretion by those above mentioned drugs are not uncommon. The experiments were designed to investigate the mechanisms of renal handling of urate as well as the effects of variety of drugs on the tubular transport of uric acid in the rabbits. Male or female white rabbits, from 1.5 to 2.5 kg in weight, were used. The experimental methods used in these studies were clearance, stop-flow, and retrograde injection techniques. The effects of saline, salicylate, chlorothiazide and probenecid were investigated in each experimental conditions. Results of the experiments were summarized as follows; 1. In the rabbits, the rate of urate clearance was always lower than the rate of inulin clearance. The filtration fraction of the urate was one third on an average, therefore, it is estimated that approximately two thirds of filtered urate was reabsorbed. 2. In the kidneys of rabbits, the urate clearance was increased significantly by administration of chlorothiazide and decreased by probenecid. The administration of salicylate had no effect on the rate of urate clearance. The filtration fraction of urate was increased by chlorothiazide and decreased by probenecid. 3. In the stop-flow studies, the U/P ratio of urate was higher than the U/P ratio of inulin in the proximal region, indicating the secretion of uric acid in the proximal tubules. The proximal peak was increased by chlorothiazide and inhibited by probenecid.4. In the retrograde injection studies, the reabsorption of urate in the proximal region was observed, and these reabsorptive transport of urate was depressed by either probenecid or by chlorothiazide. 5. No distal tubular activity was observed under any of these experimental conditions concerning urate transport. The results of these experiments show that probenecid inhibits both secretory and reabsorptive transport of uric acid in the kidney of the rabbits. The enhancement of secretory transport of urate by chlorothiazide in the clearance study was due to the secondary action of chlorothiazide which inhibits the reabsorptive transport of urate in the proximal tubules. It is evident that the urate transport in the kidneys of rabbits is bidirectional nondiffusive flux both secretory and reabsorptive directions in the proximal tubules.

• 한국통신학회논문지
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• 제31권7B호
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• pp.608-618
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• 2006

멀티미디어 스트리밍 서비스의 증가는 인터넷 콘텐츠의 새로운 국면으로 나타나고 있다. 특히, 무선이동통신망에서 증가하는 멀티미디어 응용에 대한 QoS 제공은 무엇보다 중요하다. 서비스 제공자는 클라이언트 가까이에 있는 프락시에서 자주 억세스되어지는 멀티미디어 스트림의 초기 세그먼트를 캐슁함으로써 성능을 향상 시킬 수 있다. 프락시는 서버로부터 스트림의 나머지 부분을 요구함과 동시에 클라이언트에 전송을 시작할 수 있다. 본 논문에서는 IETF의 RTSP 환경에서 프리픽스 캐슁 서비스를 무선망에 적용시키고, 무선 상황이나 핸드오프 시에 네트 워크 상황에 적응적으로 대응하고 단절현상을 줄일 수 있는 효과적인 RTSP 핸들링 기법을 제안 한다. 또한 캐슁 프락시의 성능을 향상시키기 위해 트래픽 기반 캐슁 기법(TSLRU)을 제안한다, TSLRU는 트래픽을 세 종류로 분류하여 캐슁하며, 교체 대상 결정시 여러 요소(traffic types, recency, frequency, object size)를 반영함으로써 캐슁 프락시의 성능을 향상 시킨다. 모의실험에서 캐슁 알고리즘은 byte hit Rate와 startup latency에서 높은 성능을 보였으며, 제안한 RTSP 핸들링 기법 역시 throughput에서 좋은 성능을 보였다.

• 한국정보통신학회논문지
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• 제2권4호
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• pp.559-573
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• 1998

정보통신 표준화 기구들은 최근 동 분야가 국가 및 시장 경쟁력제고에 있어 전략적 수단으로 부상됨에 따라 더 많은 새롭고 복잡한 표준들을 보다 짧은 시간 내에 개발해야 한다는 문제에 직면하고 있으며, 이러한 문제 의 해결을 위해 이들은 표준개발절차의 많은 부분들을 전자화 시킨 소위 전자적 표준개발시스템 혹은 전자적 문서처리시스템의 구현을 꾀하고 있다. 본 논문에서는 이러한 정보통신분야의 환경변화에 효율적으로 대처하기 위해 국내 표준화 환경 및 표준화 순기(표준(안)연구개발표준(안)제안의견수렴표준화위원회 승인표준(안)확정)에 따른 Workflow기반 표준(안) 개발 환경을 WWW상에서 설계 구현한 표준정보유통망(SICN : Standards Information Cooperation Network) 시스템을 소개한다 구현된 온라인 표준개발 시스템은 기존의 인터라넷(Intranet)기반의 시스템과는 달리 개념적으로 인터넷의 제3물결이라 할 수 있는 엑스트라넷(Extranet) 개념의 Workflow 기반 시스템이라 할 수 있으며, 이는 향후 '가 상 표준 개발망(VSDN : Virtual Standards Development Network)'으로 확장 구현될 예정이다.

• 한국위성정보통신학회논문지
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• 제11권3호
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• pp.65-71
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• 2016

현재 한국항공우주연구원에서 개발 중인 차세대 저궤도 위성의 탑재컴퓨터는 높은 성능을 위해 LEON2-FT/AT697F 프로세서를 사용하며 SpaceWire, 1553B, DMAUART, CAN Master 등의 다양한 통신을 지원하기 위해 별도의 FPGA 기반의 통신칩이 개발되었다. 프로세서와 통신칩간의 통신은 PCI 버스를 통해서 이루어지며, 탑재소프트웨어에서 직접 PCI 버스를 통해 각종 디바이스를 제어 및 통신을 수행한다. 차세대 탑재컴퓨터에서는 기존 1553B 통신을 위해 사용되었던 VASI IP1553B 컨트롤러 대신 Actel 1553BRM 코어를 사용하며 통신칩의 AMBA 버스상에 연결을 위해 Aeroflex Gaisler에서 개발 된 B1553BRM Wrapper를 사용한다. 본 논문에서는 차세대 저궤도 위성에서의 PCI기반의 1553B 통신 소프트웨어의 구조와 통신방법에 대해서 기술하고 탑재소프트웨어 레벨의 태스크를 통한 1553B 처리방식에 대해서 설명한다. 그리고 시뮬레이터 및 실제 하드웨어에서 테스트 된 결과에 대해 설명한다.

• 지능정보연구
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• 제15권3호
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• pp.119-136
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• 2009

컨테이너 물동량 증가와 컨테이너선의 대형화에 따라서 항만 하역장비는 지속적으로 변화하고 있다. 본 연구는 항만 하역장비 가운데 컨테이너크레인의 기계적 생산성을 상세히 평가하기 위해 개발된 시뮬레이션 모델을 소개한다. 모델은 컨테이너크레인의 메커니즘으로 싱글 및 듀얼 트롤리 방식을, 스프레더 유형으로 싱글, 트윈, 탠덤 방식을 고려하고 컨테이너크레인의 규모와 속도 등에 관련된 세부 사양을 입력받아 기구학적 특성을 구현한다. 또한 외부의 물리적 제약으로 선박의 크기, 컨테이너의 적재위치와 무게를 고려한다. 본 모델은 다양한 입력변수가 파라미터 (parameter)로 분리되어 실험 조건을 편리하게 설정할 수 있으며, 객체 지향적으로 설계 개발되어 향후 새롭게 개발되는 장비 유형이나 기존 장비의 변화를 유연하게 수용할 수 있다.

• 정보처리학회논문지D
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• 제11D권5호
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• pp.1177-1188
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• 2004

멀티 에이전트 시스템은 분산 환경에서 독립된 소프트웨어 개체들의 지능형 협력 작업을 지원하기 위해 개발되었으며 많은 응용 환경에서 사용되어지고 있다. 멀티 에이전트 시스템의 협력을 위해서는 에이전트간에 미리 협의된 형태의 프로토콜인 대화 정책(Conversation Policy; Interaction Protocol)이 사용된다. 현재의 동적인 인터넷 전자시장 환경에서는 거래의 형태가 변화함에 따라 대화 정책이 자주 바뀔 수 있으며 따라서 Ad Hoc한 형태의 대화 정책의 중요성이 커지고 있다. 기존의 에이전트 플랫폼은 몇 개의 표준 혹은 미리 정해진 대화 정책만을 허용함으로써 Ad Hoc한 대화 정책에 대해서는 에이전트 시스템을 일부 새로 구현해주어야 하는 번거로움과 비효율성이 존재한다. 본 연구에서는 그러한 Ad Hoc한 대화 정책을 지원하는 에이전트 플랫폼을 설계하며 그 프로토타입 시스템을 제시한다. 제시된 시스템은 교환 및 해석을 위한 대화 정책 모델, 새로운 대화 정책을 처리하기 위한 메타 대화 처리 부분, 그리고 대화 정책을 런타임시에 교환하고 해석하여 실제 에이전트들이 적응성 있는 상거래 및 협력을 할 수 있도록 하는 메커니즘을 포함한다.

• International Journal of Internet, Broadcasting and Communication
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• 제8권2호
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• pp.49-54
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• 2016

Data delivery is very challenging in VANETs because of its unique characteristics, such as fast topology change, frequent disruptions, and rare contact opportunities. This paper tries to explore the scope of 3G-assisted data delivery in a VANET within a budget constraint of 3G traffic. It is started from the simple S_Random (Srand) and finally reached the 3GSDD, i.e., the proposed algorithm. The performance evaluation of different algorithms is done through the two metrics delivery ratio and average delay. A third function utility is created to reflect the above two metrics and is used to find out the best algorithm. A packet can either be delivered via multihop transmissions in the VANET or via 3G. The main challenge is to decide which set of packets should be selected for 3G transmissions and when to deliver them via 3G. The aim is to select and send those packets through 3G that are most sensitive and requiring immediate attention. Through appropriate communication mechanism, these sensitive information are delivered via VANET for 3G transmissions. This way the sensitive information which could not be transmitted through normal VANET will certainly find its destination through 3G transmission unconditionally and with top priority. The delivery ratio of the packets can also be maximized by this system.

• Molecules and Cells
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• 제26권6호
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• pp.558-565
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• 2008

Although the fertilizing ability of spermatozoa is greatly reduced after freezing, complete understanding of alterations induced by cryopreservation has not been elucidated. The present study evaluates the effects of cryopreservation on the $Ca^{2+}$ handling of boar spermatozoa using several sperm activators. Intracellular $Ca^{2+}$ signals from single spermatozoa were measured using confocal $Ca^{2+}$ imaging of unfrozen samples and of other spermatozoa after having been frozen. Elevation of the external $K^{2+}$ concentration elicited a three times larger $Ca^{2+}$ increase in fresh spermatozoa than in cryopreserved spermatozoa. Caffeine elicited $Ca^{2+}$ transients with some oscillations in the fresh spermatozoa, but not in the thawed spermatozoa. Depletion of the $Ca^{2+}$ store with thapsigargin induced a rapid rise in $Ca^{2+}$ in the control but generated a smaller increase of $Ca^{2+}$ after thawing. Exposure to progesterone induced a biphasic rise of the $Ca^{2+}$ level in the fresh spermatozoa only. Sperm viability was reduced by cryopreservation. Resting $Ca^{2+}$ levels in fresh and cryopreserved spermatozoa were similar. Longer incubation (2.5 h) of thawed spermatozoa partly recovered the $Ca^{2+}$ response to the interventions. These results suggest that cryopreservation reduces the responsiveness of spermatozoa to depolarization, modulators of the internal $Ca^{2+}$ store and progesterone in terms of the $Ca^{2+}$ signal, thus providing a possible mechanism for reduced fertility observed in cryopreserved boar spermatozoa.

• Archives of Plastic Surgery
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• 제43권5호
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• pp.466-469
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• 2016

External volume expansion of the recipient site by suction has been proposed as a way of improving fat graft survival. The objective of this study was to present an innovative and simple intraoperative external expansion system to enhance small-volume autologous fat grafting (40-80 mL) and to discuss its background and its mechanism of action. In this system, expansion is performed using a complete vacuum delivery system known as the Kiwi VAC-6000M with a PalmPump (Clinical Innovations). The recipient site is rapidly expanded intraoperatively 10 times for 30 seconds each with a negative pressure of up to 550 mm Hg before autologous fat injection. During this repetitive stimulation, the tissues become grossly expanded, developing macroscopic swelling that regresses slowly over the course of hours following the cessation of the stimulus. The system sets various mechanisms in motion, including scar release, mechanical stimulation, edema, ischemia, and inflammation, which provide an environment conducive for cell proliferation and angiogenesis. In order to maintain the graft construct in its expansive state, all patients are encouraged postoperatively to use the Kiwi three times daily for one minute per session over the course of three days. The handling of this system is simple for both the patients and the surgeon. Satisfactory clinical outcomes have been achieved without significant complications.