• Environmental Analysis Health and Toxicology
• /
• 제26권
• /
• pp.1.1-1.6
• /
• 2011

Plasmodium vivax malaria has occurred annually in the Republic of Korea (ROK) since its re-emergence in 1993. P. vivax malaria in ROK has been strongly influenced by infected mosquitoes originating from the Democratic People's Republic of Korea. Korean P. vivax malaria has shown typical characteristics of unstable malaria transmitted only during the summer season, and displays short and long incubation periods. The changing pattern of the transmission period can be predicted by analyzing the seasonal characteristics of early primary attack cases with a short incubation period. Such cases began to gradually occur earlier in the 1990s after the re-emergence. Most of the malaria cases after mid-August are presumed to be early primary attack, short incubation period cases. Only primary transmission was possible until the early 2000s, whereas up to fourth or fifth transmission occurred in the mid-2000s. The results indicate that the length of transmission period has been gradually extending, which may be ascribed to a climate change-mediated temperature rise. Malaria and climate data should be integrated to analyze and predict the influence of climate change on malaria occurrence in ROK.

• 한국기계가공학회지
• /
• 제19권1호
• /
• pp.108-113
• /
• 2020

Pinions are generally heavy and integrated with a shaft. Thus, fabricating a pinion is a material- and machining-intensive task characterized by low productivity. Contact of the output pinion with a sliding surface or a cloud contact causes loss of power because of friction. Consequently, the output pinion undergoes considerable wear and tear at its ends, which adversely affects the overall transmission efficiency of decelerators. To improve transmission efficiency and extend gear life, an optimum output pinion design is required. To this end, in this study, an output pinion for worm gear decelerators was designed and optimized by means of product verification through prototyping and performance evaluation to improve gear life and productivity. The optimized design was validated and subjected to structural analysis.

• 한국기계가공학회지
• /
• 제18권12호
• /
• pp.15-21
• /
• 2019

The worm reducer is capable of quadrature power transmission when the shafts are disposed at right angles to each other. Since a large reduction ratio can be obtained of up to approximately 1/100 and a sliding movement is performed during operation compared with other gears, the noise and vibration are small, and there is the advantage that reverse rotation can be prevented. On the other hand, severe wear and damage are displayed on the gear and worm tooth surface, and many defects, such as intense heat generation of the reducer, occur. In the reducer case, the four-piece casing method was selected to solve the problems of heat generation, transmission efficiency, and assemblability. In this paper, we analyzed the problems of the worm and worm wheel (the core parts of a 5-Ton worm reducer) and casing through these methods and researched how to solve them.

• 한국기계가공학회지
• /
• 제18권4호
• /
• pp.93-99
• /
• 2019

A cross drilling/milling Unit is an important mechanical part which is widely used in many kinds of machining tool, and various gear trains with good accuracy and reliability features are widely used in power transmission systems. A study on a novel power transmission optimization method for driving gear trains in cross drilling/milling units is presented in this paper. A commercial program for gear system simulation, Romax Designer, was used in this research to intuitively observe the gear meshing and the load distribution conditions on the gear teeth. We obtained the optimal modification value through comparing the results of repeated experiments. For validation, optimized gears were fabricated and then measured with a precision tester.

• Advances in aircraft and spacecraft science
• /
• 제5권5호
• /
• pp.533-550
• /
• 2018

Detonation transmission between propane/oxygen (donor) and propane/air (acceptor) with an abrupt area change is experimentally studied. In the donor, there are two types of incident detonation waves: A self-sustained Chapman-Jouguet (CJ) detonation wave and an overdriven detonation wave that is a result of the difference in the initial donor pressure ratios. The piston work is used to characterize the strength of the incident detonation wave. For an incident CJ detonation wave, the re-initiation of a detonation wave in the acceptor depends on the initial pressure in the donor and the expansion ratio. The axisymmetric and non-axisymmetric soot patterns respectively correspond to direct detonation and detonation re-initiation. For an incident overdriven detonation wave, the re-initiation of a detonation wave in the acceptor strongly depends on the degree of overdrive.

• Journal of the Optical Society of Korea
• /
• 제12권4호
• /
• pp.337-345
• /
• 2008

This article presents the RSOA-based re-modulation schemes for practical application to the WDM-PON link. Emphasis is put on the three methods for reducing the residual downstream signal in the upstream transmission; the simplest one is to use the RSOA gain-saturation property, the second uses selective filtering of the adiabatic-chirped DFB-LD output spectrum, and the last uses a dynamic RSOA gain control by varying its driving current according to the incident binary signal. The reflection sensitivity in the proposed re-modulation link is also qualitatively presented in the cases of using two different types of seed light: coherent light from DFB-LD array and spectrum-sliced incoherent ASE light. We show experimental results of an error-free bidirectional gigabit transmission over 20 km at -30 dB reflection with the spectrum-sliced ASE seed light.

• 한국컴퓨터정보학회논문지
• /
• 제11권3호
• /
• pp.49-56
• /
• 2006

P2P 분산 시스템의 가장 큰 특징은 해당 피어들이 항상 온라인 상태일 것이라는 보장이 없다는 것이다. 즉 P2P 시스템을 이용할 때에는 해당 피어로부터 파일을 다운로드받다가 다운로드 되지 않는 경우가 발생하게 된다. 이를 해결하기 위한 연구의 대부분은 재전송이라는 방법에 의존하고 있다. 이는 P2P 시스템의 성능 저하의 원인이 되므로 이에 대한 해결책이 필요하다. 본 연구에서는 해당 P2P 시스템을 이용하는 사용자의 평균 이용 시간대의 분석 자료를 자원 제공자 선택의 기준으로 적용하여 자원 전송 보장성을 높이고, 또한 인기도 높은 자원에 대해서 자료 전송 기회를 높여주는 역할의 기존의 분산 객체 리플리케이션 기법들과의 조합에 의한 분산 객체 전송률이 향상된 검색 알고리즘을 제안한다.

• 한국기계가공학회지
• /
• 제14권2호
• /
• pp.14-18
• /
• 2015

In recent years, world is faced with a transportation energy dilemma, and the transportation is almost dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle (HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error (T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. In this paper, the analysis of gear tooth profile and lead modification is firstly presented, and then, the different transmission error of no mesh misalignment and mesh misalignment under one loaded torque for the 1st gear pair of HEV gearbox was investigated and compared. At last, the appropriate tooth modification was used to minimize and compare the transmission error of the gear pair with mesh misalignment under the loaded torque.

• International Journal of Precision Engineering and Manufacturing
• /
• 제7권2호
• /
• pp.3-7
• /
• 2006

We propose a new concept of transmission-tribology design based on the investigation of development and existing problems of the gear drive and tribology. The content of transmission-tribology and transmission-tribology design is probed. Some effective methods of transmission-tribology design is probed. Some effective methods of transmission-tribology design are put forward. Partial achievements in this research are introduced tersely. Mechanical transmission, which is represented by the gear drive, and tribology are two main branches of mechanical engineering. They have their own definite research field. In recent years, we have been doing our utmost to suggest combining mechanical transmission-tribology and transmission-tribology design. Partial achievements in this research area are obtained.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2006년도 임시총회 및 하계학술연구발표회
• /
• pp.104-105
• /
• 2006