• Korean Journal of Environment and Ecology
• /
• v.7 no.2
• /
• pp.181-186
• /
• 1994

The Shindae resting place-Jibong valley forest in Tokyusan area was studied to investigate forest structure in relation to altitude and part of slope. Forty eight quadrats were set up in the valley forest along altitude of 750m to 1,247m and part of the slope. Density of trees in tree strata decreased as increasing elevation, and mean DBH of trees in tree strata increased as increasing elevation. With increasing elevation the importance values of Quercus mongolica, Acer mono, Fraxinus mandshurica increased, while those of Quercus serrate, Betula schmidtii decreased. As going from lower part to upper part of the slope, the importance values of Quercus mongolica and Symplocos chinensis for. pilosa increased while those of Cornus controversa and Fruxinus mandshurica decreased. The number of species, species diversity and evenness tended to decreased as increasing elevation. The range of similarity indices between elevation belts, and parts of the slope were 55.3~67.1％ and 36.8~71.7%, respectively. According to importance value and cluster analysis, the studied valley forest was classified into four forest communities of Quercu serrata community of lower part of slope of low elevation belt, Quercus mongolica-Quercus serrata community of middle and upper part of slope of low elevation belt, Quercus mongolica-deciduous tree species community of middle and high elevation belt and Quercus mongolica-Rhododendron schzippinbachii community of the top area.

• Journal of Astronomy and Space Sciences
• /
• v.29 no.4
• /
• pp.343-349
• /
• 2012

The solar proton telescope (SPT) is considered as one of the scientific instruments to be installed in instruments for the study of space storm (ISSS) which is determined for next generation small satellite-1 (NEXTSat-1). The SPT is the instrument that acquires the information on energetic particles, especially the energy and flux of proton, according to the solar activity in the space radiation environment. We performed the simulation to determine the specification of the SPT using geometry and tracking 4 (GEANT4). The simulation was performed in the range of 0.6-1,000 MeV considering that the proton, which is to be detected, corresponds to the high energy region according to the solar activity in the space radiation environment. By using aluminum as a blocking material and adjusting the energy detection range, we determined total 7 channels (0.6~5, 5~10, 10~20, 20~35, 35~52, 52~72, and >72 MeV) for the energy range of SPT. In the SPT, the proton energy was distinguished using linear energy transfer to compare with or discriminate from relativistic electron for the channels P1-P3 which are the range of less than 20 MeV, and above those channels, the energy was determined on the basis of whether silicon semiconductor detector (SSD) signal can pass or not. To determine the optimal channel, we performed the conceptual design of payload which uses the SSD. The designed SPT will improve the understanding on the capture and decline of solar energetic particles at the radiation belt by measuring the energetic proton.

• Journal of Astronomy and Space Sciences
• /
• v.35 no.3
• /
• pp.195-200
• /
• 2018

The present paper describes the design of a Solid State Telescope (SST) on board the Korea Astronomy and Space Science Institute satellite-1 (KASISat-1) consisting of four [TBD] nanosatellites. The SST will measure these radiation belt electrons from a low-Earth polar orbit satellite to study mechanisms related to the spatial resolution of electron precipitation, such as electron microbursts, and those related to the measurement of energy dispersion with a high temporal resolution in the sub-auroral regions. We performed a simulation to determine the sensor design of the SST using GEometry ANd Tracking 4 (GEANT4) simulations and the Bethe formula. The simulation was performed in the range of 100 ~ 400 keV considering that the electron, which is to be detected in the space environment. The SST is based on a silicon barrier detector and consists of two telescopes mounted on a satellite to observe the electrons moving along the geomagnetic field (pitch angle $0^{\circ}$) and the quasi-trapped electrons (pitch angle $90^{\circ}$) during observations. We determined the telescope design of the SST in view of previous measurements and the geometrical factor in the cylindrical geometry of Sullivan (1971). With a high spectral resolution of 16 channels over the 100 keV ~ 400 keV energy range, together with the pitch angle information, the designed SST will answer questions regarding the occurrence of microbursts and the interaction with energetic particles. The KASISat-1 is expected to be launched in the latter half of 2020.

• Journal of Animal Environmental Science
• /
• v.12 no.1
• /
• pp.21-28
• /
• 2006

This study was carried out to measure and analyze the characteristics of noise and vibration, and to analyze their effects on the productivity of layers, mechanical troubles, and abnormal wear-out failure of facilities and equipment of the layer house. The measurements of noise and vibration were taken at 13 layer farms nationwide for the operations of feed supplier system, feed distribution system, automatic egg collection system, ventilation system, blot conveyer for layer feces, and fur the case of with and without their operation by a sound level meter and a vibration measuring system in the layer house equipped with upright multi-tier cages. Measurement results showed that normal times were noise(N) 82 dB and vibration(V) 0.2072 cm/s, feed supplier system were 90 dB(N) and 2.8560 cm/s(V), feed distribution system were 90 dB(N) and 2.0222 cm/s(V), automatic egg collection system were 87 dB(N) and 0.1865 cm/s(V), ventilation system 88 dB(N) and 2.5364 cm/s(V), belt conveyer fur layer feces were 88 dB(N) and 0.2387 cm/s(V), and then maximum values of noise and vibration were 90 dB and 2.8560 cm/s, respectively, when feeding systems(feed supplying system and feed distribution system) were operated. Based on these results, an experiment is being conducted to find out the effect of noise and vibration on the productivity of layers in the layer house equipped with upright multi-tier cages.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.18 no.5
• /
• pp.179-183
• /
• 2008

Employing screen printing technology, aluminum is applied to the back side of the n-type silicon wafer to see the effect of the heat treatment parameters on the Voc of the solar cell, Heat treatment at $850^{\circ}C$ produces the highest Voc among various heat treatment conditions. Heat treatment at the temperatures higher than $850^{\circ}C$ results in lower Voc, which is due to the destruction of the Al-Si alloy emitter layer. The destruction of Al-Si layer observed to be caused by the vigorous movement of silicon atoms toward aluminum layer during the heat treatment.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.1
• /
• pp.86-94
• /
• 1984

In order to improve the rotational performances of NC lathe spindle system in high speed range, a new type(Floating-type driven by V-belt)spindle system was optimally designed and experimented. Through the results of the experiments, the rotational performances of the new type spindle system was discussed and compared with the three equivalent conventional lathe spindle systems. The spindle rotational accuracy( radial error motion of spindle axis), the accelation and the temperature rise of the front spindle bearings for the non-cutting operation were considered as the spindle rotational performances. The radial error motion of the spindle axis was measured by applying the modified L.R.L. method. Compared with the equivalent conventional spindle systems, the following results were obtained. (1) The new type spindle system reduces the radial error motion of the spindle axis in high speed range(1800rpm-2000rpm). (2) The new type spindle system reduces the acceleration and the temperature rise of the spindle bearings considerably with increasing the spindle speed. It is also confirmed that, by this new type spindle system, the max. allowable speed can be increased with satisfying the spindle rotational performances.

• Journal of Power Electronics
• /
• v.11 no.4
• /
• pp.527-532
• /
• 2011

Due to the need for improved fuel consumption and the trend towards increasing the electrical content in automobiles, integrated starter generator (ISG) systems are being considered by the automotive industry. In this paper, in order to change the conventional generator of a vehicle, a belt driven integrated starter generator is considered. The overall ISG system, the design considerations for the claw pole type AC electric machine and a low voltage very high current power stage implementation are discussed. Test data on the low voltage claw pole type machine is presented, and a large current voltage source DC/AC inverter suitable for low voltage integrated starter generator operation is also presented. A metal based PCB (Printed Circuit Board) power unit to attach the 4-parallel MOS-FETs is used to achieve extremely high current capability. Furthermore, issues related to the torque assistance during vehicle acceleration and the generation/regeneration characteristics are discussed. A prototype with the capability of up to 1000 A and 27 V is designed and built to validate the kilo-amp inverter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.530-533
• /
• 2005

Recently, modern reciprocating air compressors tend to be smaller and lighter. But, as the development of performance, they have many problems for noise and vibration. For this reason, many researches are processing for the reduction of noise and vibration by arranging cylinders with V/W type. Especially, noise and vibration problems of reciprocating air compressor cause a rotating unbalance of crankshaft, so it needs a change of crankshaft parameters appropriately. Hence in this study, we changed crankshaft parameters to solve the rotating unbalance and compared results in order to verify the noise and vibration reduction between new and original air compressor. According to modify a crankshaft parameter, the improvements of noise and vibration were showed results of spectrum measured at selected points of the air compressor crankshaft housing and sound intensity contours measured at a belt left side, table that figure out characteristics of noise. Furthermore, we analyzed objective sound quality metrics with recording data of systems. The results showed that, the new design has improved the level of the first harmonic of vibration displacement, noise and objective sound quality metrics.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.12
• /
• pp.1265-1273
• /
• 2015

A coal handling machine is a type of equipment used for loading coal, the main material in a steam power plant, along a conveyer belt from a ship, and is placed after the driving chain bucket. However, studies on the boom hoisting cylinder, which is a hydraulic system used to control the angle of the boom based on loading location, indicate that domestic models are insufficient, and are thereby often substituted with a foreign product. In this study, a technique for analyzing the contact pressure in a thick-walled cylinder was established by comparing the contact pressure, which is calculated theoretically based on the results obtained from FEM simulation, and by checking whether the working oil is leaking from the boom hoisting cylinder using a v-seal. In addition, the driving motion was simulated according to the strokes of the cylinder, and the structural stability was verified under the maximum output conditions.

• Journal of Biosystems Engineering
• /
• v.16 no.2
• /
• pp.124-132
• /
• 1991

This study was carried out to obtain the information needed in the development of forward speed control system and the improvement of combine performance. The effects of variety, grain moisture content and forward speed on the combine load characteristics were investigated through experiments. The results of this study are summarized as follows. 1. A data acquisition system was developed to measure the engine speed and the torques and speeds of the threshing cylinder, dean-grain auger and tailings-return auger. The system consisted of transducers, signal conditioner, interface board and microcomputer. The system accuracy is better than ${\pm}2.3%$ full scale. 2. Linear regression equations were obtained for the torque, speed and power requirement of threshing cylinder for different paddy varieties, grain moisture contents and feed rates. 3. The maximum value of relative frequency for threshing cylinder torque decreased as the increase in feed rate and moisture content. The range of torque fluctuation was 1.2~3.7 and 1.2~1.9 times the average and maximum torque, respectively. The maximum value of power spectrum density (PSD) appeared to be about 11 Hz regardless of paddy variety, grain moisture content and feed rate. 4. The speed of tailings return thrower decreased rapidly at below 900rpm, and it fell to near zero about 3 seconds after that time. When the travelling of combine harvester was stopped immediately after sensing the overload, it took about 7 seconds for a full recovery of the no-load speed of tailings return thrower.