• Korean Journal of Agricultural Science
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• v.24 no.1
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• pp.1-5
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• 1997

This study was conducted to obtain basic information for the improvement of garlic cultivars. Local varieties of garlic were collected from 4 major production area in Korea and ecological characteristics were compared. The number of cloves per bulb showed a great variation in the range from 4 to 15. However, more than 70% of examined garlics had 6~8 cloves per bulb. Clove weight also differred between local varieties, thus, the range of clove weight was distributed from 1.0g to 7.6g and this tendency was also similar within a same local variety. Although clove weight was relatively higher in bulbs containing 6~8 cloves, bulb weight was higher in bulbs containing more cloves.

• 한국해양학회지
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• v.20 no.1
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• pp.22-30
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• 1985

The mean sea level(MSL) along the coast of Korea is high in summer and low in winter, mainly due to the inverse barometric effect and the steric departure. The MSL associated with the inverse barometric effect is spatially uniform and has an amplitude of 8.5$\pm$0.8cm. The thermal departure, with amplitude of 4~8cm, is most dominant in the Yellow Sea. The MSL in the South Sea of Korea is strongly affected by the haline departure, which has an amplitude up to 5cm. The annual range of MSL along the western and eastern coasts of Korea are about 40 and 20cm, respectively. The spatial inhomogeneity of the annual range of MSL arises mainly due to the influence of the Asian monsoon, which amplifies (weakens) the annual MSL along the western (eastern) coast of Korea.

• Environmental Engineering Research
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• v.25 no.1
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• pp.123-128
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• 2020

Non-point source pollutant load reductions were calculated using the Hydrologic Simulation Program-Fortran (HSPF) model under the assumption that landuse pattern was changed according to land purchases. Upon the simulation of non-point pollutant and areas with high land purchase ratios to select a buffer zone, the Namgang dam Reach 11, Imha dam Reach 10, and the Reach 136 watershed of the main river were found to rank high for the construction of buffer zones. Assuming that the forms of the purchased lands were changed to wetlands, biological oxygen demand (BOD) loads were changed through the HSPF model. No changes of BOD were present in the Namgang dam and the Imha dam watersheds. BOD loads in Reach 136 according to landuse change were analyzed through a flow duration analysis based on the total maximum daily loads of the United States. The flow duration analyses undertaken to examine changes in BOD of main river Reach 136 watershed indicated a shift of 0.64 kg/d from 3.16 to 2.52 during high flow. The change of BOD under the conditions of moist, mid-range and dry were 11.9%, 9% and 4.5%. At the low flow condition, the variation range in the BOD load was from 0.58 kg/d to 0.41 kg/d.

• Proceedings of the KSRS Conference
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• v.1
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• pp.17-20
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• 2006

Three HF ocean radar stations were installed at the Soya/La Perouse Strait in the Sea of Okhotsk in order to monitor the Soya Warm Current. The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are 3 km and $5^{\circ}$, respectively. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and short-term variations of the Soya Warm Current. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m $s^{-1}$, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.615-621
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• 2005

The electrical stability against surge stress of varistors, which are composed of Zn-Pr-Co-Cr-Y oxide system, were investigated at different sintering times. As sintering time increases, the varistor voltage and nonlinear exponent decreased in the range of $279.6\~179.1$ and $52.5\~24.9$, respectively. On the contrary, the leakage current and dielectric dissipation factor increased in the range of $1.2\~9.8\;{\mu}A$ and 0.0461\~0.0651 with increase of sintering time. For all varistors, the variation rates of V-I characteristic parameters against surge stress were more strongly affected in order of varistor voltage ${\rightarrow}nonlnear$ $exponent{\rightarrow}leakage$ current. On the whole, the electrical stability against surge stress increased with increasing sintering time. Conclusively, it is assumed that the varistors sintered for 2 h exhibited comparatively good characteristics, in view of overall characteristics.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Geomechanics and Engineering
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• v.21 no.3
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• pp.279-288
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• 2020

The permeation grouting is a commonly used technique to improve the engineering geology condition of the soft ground. It is of great significance to predict the permeation range of the grout so as to ensure the effects of grouting. This paper conducts a theoretical analysis of jet-grouting effects in ground improvement and rotary grouting pile installation by utilizing deformation-permeation coupled poroelastic solutions based on Biot's theory and Laplace-Fourier integral transform technique. The exponential function and the intermittent trigonometric function are chosen to represent time-dependent grouting pressure usually encountered in ground improvement and rotary grouting pile installation process, respectively. The results, including the radial displacement, the hoop stress, the excess pore fluid pressure, the radial discharge, and the permeation radius of grout, are presented for different grouting time, radial positions and grouting lengths. Parametric study is conducted to explore the effects of variation of the exponent in the exponential grouting pressure-time relationship on grouting-induced responses. It is expected that the proposed solutions can be used to estimate the permeation range of grouting in ground improvement and rotary grouting pile installation.

• Smart Structures and Systems
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• v.24 no.1
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• pp.1-14
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• 2019

Transmission tower-line system is one of most critical lifeline systems to cities. However, it is found that the transmission tower-line system is prone to be damaged by earthquakes in past decades. To mitigate seismic demands, this study introduces a tuned-mass damper (TMD) using superelastic shape memory alloy (SMA) spring for the system. In addition, considering the dynamic characteristics of both tower-line system and SMA are affected by temperature change. Particular attention is paid on the effect of temperature variation on seismic behavior. In doing so, the SMA-TMD is installed into the system, and its properties are optimized through parametric analyses. The considered temperature range is from -40 to $40^{\circ}C$. The seismic control effect of using SMA-TMD is investigated under the considered temperatures. Interested seismic performance indices include peak displacement and peak acceleration at the tower top and the height-wise deformation. Parametric analyses on seismic intensity and frequency ratio were carried out as well. This study indicates that the nonlinear behavior of SMA-TMD is critical to the control effect, and proper tuning before application is advisable. Seismic demand mitigation is always achieved in this wide temperature range, and the control effect is increased at high temperatures.

• Journal of the Korean Wood Science and Technology
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• v.17 no.2
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• pp.26-33
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• 1989

The acoustic absorption coefficient and acoustic impedance of 5 species of softwood(sonamoo, sam namoo, gusang namoo, hwaback, sitka spruce) and 5 species of hardwood (Mulgusul namoo, Italian popular, white meranti, red meranti, kalantas) were measured by the standing wave method. which is simple in the setup and gives more accurate result than does any other measuring method. The dependence of the absorption coefficient and complex acoustic impedance on the wood sections. thickness of the sample itself and the back air gap was investigated experimentally in the frequency range from 200Hz to 1800Hz, and the result are as follows: 1. The acoustic absorption coefficient of wood sections was higher on the cross section than radial and tangential sections. 2) The acoustic absorption coefficient were higher in the frequency range from 400Hz to 600Hz, but decreased in the frequency above 600Hz. 3. The genenal tendency of the variation of the normal acoustic impedance was increased according to the frequency. 4. The acoustic absortion coefficient was increased in the to 7mm-thick sample and decreased in 9mm-thick sample. 5. The higher acoustic absorption coefficient was shown in the case with the backing an gap than in the case without the gap.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.257-262
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• 2002

Numerical model introduced in this study combines wave refraction-diffraction, breaking, bottom friction, lateral mixing, and critical shear stress and three sub-models for simulating waves, currents, and bottom change were briefly discussed. Simulations of beach processes and harbor sedimentation were also described at the coast neighboring Bangpo Harbor, Anmyundo, Chungnam, where the area has suffered from accumulation of drifting sand in a small fishing harbor with a wide tidal range. We also made model test for the case of a narrow tidal range at Nakdong river's estuary area to understand the effect of water level variation on the littoral drift. Simulations are conducted in terms of incident wave direction and tidal level. Characteristics of wave transformation, nearshore current, sediment transport, and bottom change are shown and analyzed. We found from the simulation that the tidal level impact to the sediment transport is very important and we should apply the numerical model with different water level to analyze sediment transport mechanism correctly. Although the model study gave reasonable description of beach processes and harbor sedimentation mechanism, it is necessary to collect lots of field observation data, including waves, tides and bottom materials, etc. for better prediction.