• 한국기계가공학회지
• /
• 제11권6호
• /
• pp.195-200
• /
• 2012

In this study, parameters and requirements of an 120kW class monorail planetary gearbox was analysed and the adaptive planetary gearbox design was selected. The specification of the sun gear, planetary gear and carrier was set and the profile & lead was optimized. The mechanical efficiency of the optimized one and the original one was observed. Dynamo-tester system was used to observe the mechanical efficiency of the planetary gearbox. A dynamo unit was connected with the planetary gearbox which straightened through the motor by a coupling. The standard tooth shape planetary gearbox and modified tooth shape planetary gearbox were used as test pieces and the rotation speed was set from 600 to 6000rpm with 600rpm, 2.5min one step. In order to check the mechanical efficiency of the planetary gearbox, the tests were done as follows. 1) The power loss between driving motor and dynamo tester. 2) Temperature variation by different rotation speeds. 3) Noise variation by different rotation speeds.

• Nuclear Engineering and Technology
• /
• 제48권1호
• /
• pp.200-210
• /
• 2016

The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes, General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. The East Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutron radiography, which sits beneath a large hot cell and is primarily used for neutron radiography of highly radioactive objects. Additional fuel elements were added to the NRAD core in 2013 to increase the excess reactivity of the reactor, and may have changed some characteristics of the neutron beamline. This report discusses characterization of the neutron beamline following the addition of fuel to the NRAD. This work includes determination of the facility category according to the American Society for Testing and Materials (ASTM) standards, and also uses an array of gold foils to determine the neutron beam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. Gold foil activation experiments show that the average neutron flux with length-to-diameter ratio (L/D) = 125 is $5.96{\times}10^6n/cm^2/s$ with a $2{\sigma}$ standard error of $2.90{\times}10^5n/cm^2/s$. The neutron beam profile can be considered flat for qualitative neutron radiographic evaluation purposes. However, the neutron beam profile should be taken into account for quantitative evaluation.

• Tribology and Lubricants
• /
• 제34권6호
• /
• pp.325-331
• /
• 2018

Automobiles and systems requiring high gear ratios and high power densities generally use worm gears. In particular, as worm gears have a small volume and self-locking function, home appliances such as refrigerators and washers consist of worm gears. We can classify worm gears into cylindrical worms and rectangular worms. According to the AGMA standard, there are four types of cylindrical worms, ZA, ZN, ZK and ZI, depending on the machining of the worm shaft. It is preferable to use a ZI-type worm shaft, which is a combination of a worm wheel having an involute helical tooth surface and a conjugate tooth surface. However, in many cases, industries mostly use ZK, ZN, and ZA worm shafts because of the ease of processing. This paper presents numerical approaches to produce ZI and ZA worm surfaces and worm wheel. For the analysis of the transmission error of a worm gear system, this study (1) generates surface profile functions of ZI profile worm gear and worm shaft based on the common rack theory, (2) adopts the Newton-Raphson method for the analysis of the gear surface contact condition, and (3) presents and compares the corresponding transmission errors of ZI and ZA worm gears.

• Journal of Nutrition and Health
• /
• 제24권3호
• /
• pp.189-198
• /
• 1991

This study was performed to examine the effect of excess vitamin A feeding on lipid profile and vitamin A content of rats. 12 male Sprague-Dawley rats. weighing 114.1$\pm$0.9g, were divided into control and excess vitamin A group, and fed experimental diet for 6 weeks. In the excess vitamin A group, the level of vitamin A was 400, 000 1.U./kg diet(100 times of standard level). It was observed that vitamin A excess group had higher levels of plasma total lipid, total cholesterol, and trighlyceride and lower HDL ratio, indicating a high risk to coronary heart disease. In the liver, total CHOL and TG content were also high, and fatty liver was produced by excess Vitamin A. Vitamin A contents of organs were higher when excess vitamin A was given. These results suggested that excess vitamin A could be a dietary factor increasing the lipid contents of plasma and liver. Therefore, it could be said that vitamin A megadose can be one of the risk factors to coronary heart disease.

• 한국유체기계학회 논문집
• /
• 제6권1호
• /
• pp.23-29
• /
• 2003

Three-dimensional flow through a tubular centrifugal fan with airfoil type blades is analyzed, and the effects of turbulence model and numerical scheme on the results are investigated. Standard $k-{\epsilon}$ model and k - w model are tested as turbulence closures. The numerical schemes for convection terms, i.e., Upwind Differencing Scheme (UDS), Mass Weighted Skewed upstream differencing scheme (MWS), Linear Profile Skewed upstream differencing scheme (LPS), and Modified Linear Profile Skewed upstream differencing scheme (MLPS) are also tested, and the performances of these schemes coupled with two turbulence models are evaluated. The static pressure distributions are compared with experimental data obtained in this work, which shows that the $k-{\epsilon}$ model gives better results than the k-w model.

• 치과방사선
• /
• 제3권1호
• /
• pp.29-34
• /
• 1973

The study was made on the facial profile of the normal Korean adults using the roentgenographic cephalograms. The subjects ccnsisted of 50 males and 50 females with the normal occlusion. The measurements were made of the facial angles in skeletal pattern and depth, height and the length in the soft tissue profile. The mean and standard deviations from the subjects were calculated and compared with the samples of male and female. The authors have drawn the conclusions as follows: 1. Compared with the angulation in skeletal patterns, there were no differences between both sexes. 2. Individual variations of the lower face were larger than the upper face in most measuring points. 3. Generally, facial heights were lesser than facial depth in sexual differences. 4. Most dimensions of the facial depth, height and length of the male were larger than those of female.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.28-31
• /
• 2002

In this study, we develop automatic design program, which create 3D model of spur gear and helical gear used VisuaILISP and create helical gear in the CATIA using 2D profile of gear. This model become the standard model, which give not only in itself mold information but also computer processed product with measuring date. Spur gear require mathematical examination of involute curve and trocoidal fillet curve. Automatic design program, which have a mathematical development create the profile of spur gear.

• 한국생산제조학회지
• /
• 제8권5호
• /
• pp.96-101
• /
• 1999

This study suggests an algorithm for tooth profile generation of free from curve involute gear, a special gear of which the pitch line is a free curve instead of a circular one. For the first, a methodology for calculation of the tooth curve is developed and formulated Then the formulated algorithm, is programmed for manufacturing and verified by computer graphics. Next the calculated results as changed in to NC codes to apply to wire electric discharge machine(WEDM). Finally, the machined gear is examined in engagement with a standard involute gear.

• 터널과지하공간
• /
• 제10권1호
• /
• pp.33-44
• /
• 2000

이 연구에서는 지하공동의 점진적인 붕락이 지표침하에 미치는 영향을 조사하기 위하여, 주문진산 표준사를 이용하여 모형지반을 구성하였으며, 공동의 심도를 달리하는 6가지 모델에 대하여 실내 모형실험을실시하였다. 여기서 공동의 심도와 붕락구간의 크기에 따른 침하발생양상을 조사하였다. 또한 NCB 방법, 지수함수를 이용한 윤곽함수법 영향함수법 등의 침하예측방법을 이용하여 모형실험으로부터 측정된 수직 및 수평변위를 해석하였으며, 모래지반에 적합한 침하예측방법을 제안하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.591-594
• /
• 2002

In this study, we develop automatic design program, which create 3D model of spur gear and helical gear used VisualLISP and create helical gear in the CATIA using 2D profile of gear. This model become the standard models which give not only in itself mold information but also compare processed product with measuring date. Spur gear require mathematical examination of involute curve and trocoidal fillet curve. Automatic design program, which have a mathematical development create the profile of spur gear.