• Journal of the Korean Geographical Society
• /
• v.48 no.2
• /
• pp.167-183
• /
• 2013

This paper aimed to investigate the Asian dust source region and climatic condition of source region by the case of Asian dust in south Korea. In order to analyze the weather condition of source region, observed the Asian dust days data and weather data in China were used. The Asian dust days originating from inner-Mongolia were the most frequent. The Asian dust days originating from all the source regions except Loess plateau were increased recently and occurred over the country. In case of Loess plateau, the frequency of the Asian dust days in 1960s was the highest and only the southern region of the south Korea was mostly affected. The relationship between the Asian dust days of Korea and climatic factors of spring and April of source region was significant. The relationship between the Asian dust days originating from the inner Mongolia and sea level pressure of April and relative humidity of spring was negative. The Asian dust days from Gobi had positive relationship with wind gust days and negative relationship with sea level pressure in April. The Asian dust days from Manchuria had negative relationship with precipitation and sea level pressure in April. The Asian dust days from Loess plateau had positive relationship with maximum wind speed and negative relationship with sea level pressure in April.

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2003.10a
• /
• pp.78-79
• /
• 2003

Effects of dietary lipid level and source (squid liver oil being rich in n-3 HUFA, soybean oil being rich in 18:2n-6, and linseed oil being rich in 18:3n-3) in fishmeal-based diet on growth and body composition of grower sunshine bass raised in seawater were investigated. Fifteen grower (an initial weight of 146.8$\pm$0.23 g) sunshine bass were randomly distributed into 27 of 250 L fiber reinforced plastic flow-through tanks. Fish were hand-fed to satiety twice daily for 6 days a week throughout the feeding trial. Survival was over 97% and not significantly affected by either dietary lipid level or lipid source (n-3 highly unusaturated fatty acid, HUFA). Weight gain of fish tended to improve with dietary n-3 HUFA level up to 2.9%, but sharply decreased at 3.5%. The best weight gain was obtained in fish fed the diet supplemented with 6% squid liver oil and 3% soybean oil. FER and PER were not significantly affected by either dietary lipid level or dietary lipid source. The lowest moisture content of the whole body was observed in fish fed the diet supplemented with 12% squid liver oil and highest for the diet supplemented with 9% linseed oil, respectively. Protein content of fish was not significantly affected by either dietary lipid level or dietary lipid source. However, lipid content of the whole fish tended to increase with an increase of either dietary lipid level or dietary n-3 HUFA level, except for fish fed the diet supplemented with 9% linseed oil. Ash content of fish fed the diet with no supplementation of oil was highest and lowest for the diet supplemented with 9% soybean oil, respectively. Significant differences in saturated fatty acids (16:0, 18:0 and 24:0), monoene (18:1n-9), 18:2n-6, 20:5n-3 and sum of n-3 HFUA of fish were observed. In considering these results, it could be concluded that supplementation of 9% oil combined with 6% squid liver oil and 3% soybean oil into fishmeal-based diet was the most recommendable for growth of grower sunshine bass raised in seawater.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.9
• /
• pp.1312-1318
• /
• 2002

A feeding trial using sows and their neonates was conducted to determine the effects of source and level of organic trace mineral supplementation on reproductive performance of sows and the subsequent performance of their neonates through 2 wk post weaning. A total of 16 gestating sows ($Landrace{\times}$Yorkshire) in parities 2 to 4 were randomly assigned to 4 dietary treatments following a $2{\times}2$ factorial arrangement in a completely randomized design. One of the two factors evaluated the effect of the source (inorganic vs organic), and the second factor evaluated the effect of the level (low vs high) of trace minerals added to the diet. The trace mineral premixes were formulated to provide a low concentration of trace minerals (50 ppm Fe/87.5 ppm Fe, 17.5 ppm Cu/85 ppm Cu, 45 ppm Zn/60 ppm Zn, and 20 ppm Mn/17.5 ppm Mn), and a high concentration of trace minerals (100 ppm Fe/175 ppm Fe, 35 ppm Cu/170 ppm Cu, 90 ppm Zn/120 ppm Zn, 40 ppm Mn/35 ppm Mn), when included at 0.20% in sows'/weaned pigs' diets, respectively. The total number born, total born alive and weaned, and the average neonate weight at birth were affected neither by the dietary source nor by the level of trace minerals (p>0.05), but an interaction effect (p<0.05) between the source and level of trace minerals was observed on the average weight at weaning. The neonates from sows fed the low level of organic trace minerals gained weight at an equal rate compared with those farrowed by sows fed the high level of inorganic trace minerals. Sows fed the organic trace minerals nursed their young with milk higher in Fe and Zn (p<0.05) compared with those fed diets with inorganic trace minerals. Consequently, the weaned pigs receiving the organic form of trace minerals tended to grow at a faster rate, consumed less feed and tended to utilize their feed more efficiently (p<0.10). It was further observed that the organic trace minerals significantly increased (p<0.05) Fe contents in the liver and serum, and Zn in the serum and bone. In conclusion, sows and neonates fed the organic minerals at low level showed similar performance compared with those fed the inorganic minerals at high level as specified in this study.

• Asian-Australasian Journal of Animal Sciences
• /
• v.20 no.6
• /
• pp.948-953
• /
• 2007

The relative performance and immune response was evaluated in White Leghorn layers fed liquid DL-methionine hydroxyl analogue-free acid (MHA-FA) relative to dry DL-methionine (DLM) in maize-soybean-sunflower based diets. Three graded levels of methionine (Met) from DLM or MHA-FA were added to the basal diet containing 0.27% Met on an equimolar basis to achieve 0.30, 0.36 and 0.42% Met in the diet. Each diet was fed ad libitum to 25 replicates of one bird (individual feeding) each, from 24 to 40 weeks of age. A regime of 16 h light was provided and all the layers were kept under uniform management throughout the experimental period. None of the parameters studied were influenced by the interaction between source and level of Met in diets. Similarly, the majority of parameters, except for daily feed consumption and immune response (influenced by level) and egg specific gravity and shell thickness (influenced by source), were not affected by either source or level of Met in the diets. Feed consumption was significantly lower in the birds fed a diet containing 0.42% Met compared to those fed lower levels of Met. The cutaneous basophilic hypersensitivity response to PHA-P and antibody titre (32 and 40 wk) to inoculation of sheep red blood cells increased significantly by increasing the concentration of Met in the diet from 0.30 to 0.36%. Thus, the Met requirement for immune competence was higher than for optimum production. The source of Met significantly influenced the egg specific gravity and shell thickness. The specific gravity and shell thickness of eggs increased significantly when MHA-FA was used as the source of Met in the diet compared to DLM. From the study it is concluded that Met requirement for immune competence (360 mg/b/d) is higher than for optimum production (300 mg/b/d). MHA-FA was comparable with DLM as a source of Met for production performance and immunity, when the bioavailability of MHA-FA was considered as 88% of DLM. Further, MHA-FA improved egg shell quality compared to DLM.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.8
• /
• pp.1170-1179
• /
• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to $r^{-2}$ in the near field and $r^{-1}$ in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.1
• /
• pp.78-90
• /
• 2017

This paper presents the design of closed loop controllers operating a single-phase AC-DC three-level converter for improving power quality at AC mains. Closed loop inhibits outer voltage controller and inner current controller. Simulations of three level converter with three different voltage and current controller combinations such as PI-Hysteresis, Fuzzy-Hysteresis and Fuzzy tuned PI-Hysteresis are carried out in MATLAB/Simulink. Performance parameters such as input power factor and source current total harmonic distortion (THD) are considered for comparison of the three controller combinations. The fuzzy-tuned PI voltage controller with hysteresis current controller combination provides a better result, with a source-current THD of 0.93% and unity power factor without any source side filter for the three level converter. For load variations of 25% to 100%, a THD of less than 5% is obtained with a maximum value of only 1.67%. Finally, the fuzzy-tuned PI voltage with hysteresis controller combination is implemented in a Xilinx Spartan-6 XC6SLX25 FPGA board for experimental validation of power quality enhancement. A prototype 100 W, 0-24-48 V as output converter is considered for the testing of controller performance. A source-current THD of 1.351% is obtained in the experimental study with a power factor near unity. For load variations of 25% to 100%, the THD is found to be less than 5%, with a maximum value of only 2.698% in the experimental setup which matches with the simulation results.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.2
• /
• pp.209-215
• /
• 2018

This paper present a 7-level PWM inverter adopting voltage balancing control to series-connected input capacitors. The prior proposed 7-level PWM inverter consists of dc input source, three series-connected capacitors, two bidirectional switch modules, and an H-bridge. This circuit topology is useful to increase the number of output voltage levels, however it fails to generate 7-level in output voltage without consideration for voltage balancing among series-connected capacitors. Capacitor voltage imbalance is caused on the different period between charging and discharging of capacitor. To solve this problem, we uses the amplitude modulation of carrier wave, which is used to produce the center output voltage level. To verify the validity of the proposed control method, we carried out computer-aided simulation and experiments using a prototype.

• Journal of The Korean Astronomical Society
• /
• v.28 no.1
• /
• pp.1-13
• /
• 1995

A list of radio sources in the field of Abell 2256 is presented at 1420 MHz. Also presented is the source count based on the list. This source count is taken with the sources above $7\sigma$ level at 1420 MHz. The overall characteristics of the count is consistent with that of a field where no galaxy cluster presents. The excess of radio sources due to the cluster is examined in the source count but it turned out to be unnoticiable as expected.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.8
• /
• pp.93-98
• /
• 2004

A low power SRAM using elevated source level memory cells is proposed to save the write power of SRAM. It reduces the swing voltages of the bit lines and data bus by elevating the source level of the memory cells from GND to $V_{T}$ and lowering the precharge level of the bit lines and data bus from $V_{DD}$ to $V_{DD}$ - $V_{T}$. It saves the write power of SRAM without area overhead and speed degradation. An SRAM with 8K${\times}$32bits is fabricated in a 0.25um CMOS process. It saves 45% of the power in write cycles at 300MHz with 2.5V. The maximum operating frequency is 330MHz.

• The Journal of the Acoustical Society of Korea
• /
• v.34 no.1
• /
• pp.52-59
• /
• 2015

In the conventional model for the prediction of the railway environmental noise, one used an empirical formula of the total noise level at specific distances. Only a function of the distance to the source was also used to calculate the noise level near the railway bridges. However, the noise varies depending on the position of the receiver as well as the distance from the source especially at concrete bridges. In this paper, a noise propagation model in the railway concrete bridge was derived by considering the diffraction at the bridge deck and the ground effect and applying the ISO 9613-2 noise propagation model. We compared the predicted and measured values of environmental noise at a high-speed railway bridge, and it was confirmed that this prediction model gives relatively small errors.