• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1343-1356
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• 2022

Clouds or shadows are the most problematic when monitoring crops using optical satellite images. To reduce this effect, a composite algorithm was used to select the maximum Normalized Difference Vegetation Index (NDVI) for a certain period. This Maximum NDVI Composite (MNC) method reduces the influence of clouds, but since only the maximum NDVI value is used for a certain period, it is difficult to show the phenomenon immediately when the NDVI decreases. As a way to maintain the spectral information of crop as much as possible while minimizing the influence of clouds, a Score-Based Composite (SBC) algorithm was proposed, which is a method of selecting the most suitable pixels by defining various environmental factors and assigning scores to them when compositing. In this study, the Sentinel-2A/B Level 2A reflectance image and cloud, shadow, Aerosol Optical Thickness(AOT), obtainging date, sensor zenith angle provided as additional information were used for the SBC algorithm. As a result of applying the SBC algorithm with a 15-day and a monthly period for Dangjin rice fields and Taebaek highland cabbage fields in 2021, the 15-day period composited data showed faster detailed changes in NDVI than the monthly composited results, except for the rainy season affected by clouds. In certain images, a spatially heterogeneous part is seen due to partial date-by-date differences in the composited NDVI image, which is considered to be due to the inaccuracy of the cloud and shadow information used. In the future, we plan to improve the accuracy of input information and perform quantitative comparison with MNC-based composite algorithm.

• Korean Journal of Remote Sensing
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• v.38 no.6_4
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• pp.1935-1943
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• 2022

The development and application of a high-resolution soil moisture mapping method using satellite imagery has been considered one of the major research themes in remote sensing. In this study, soil moisture mapping in the test area of Jeju Island was performed. The soil moisture was calculated with optical images using linearly adjusted Synthetic Aperture Radar (SAR) polarization images and incident angle. SAR Backscatter data, Analysis Ready Data (ARD) provided by Google Earth Engine (GEE), was used. In the soil moisture processing process, the optical image was applied to normalized difference vegetation index (NDVI) by surface reflectance of KOMPSAT-3 satellite images and the land cover map of Environmental Systems Research Institute (ESRI). When the SAR image and the optical images are fused, the reliability of the soil moisture product can be improved. To validate the soil moisture mapping product, a comparative analysis was conducted with normalized difference water index (NDWI) products by the KOMPSAT-3 image and those of the Landsat-8 satellite. As a result, it was shown that the soil moisture map and NDWI of the study area were slightly negative correlated, whereas NDWI using the KOMPSAT-3 images and the Landsat-8 satellite showed a highly correlated trend. Finally, it will be possible to produce precise soil moisture using KOMPSAT optical images and KOMPSAT SAR images without other external remotely sensed images, if the soil moisture calculation algorithm used in this study is further developed for the KOMPSAT-5 image.

• Journal of the Korean Geotechnical Society
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• v.22 no.9
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• pp.37-43
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• 2006

Dynamic numerical analysis of geotechnical problems requires a way to simulate the decrease of energy as the domain of interest gets larger. This phenomenon is usually referred to as radiation damping or geometric attenuation and it is distinguished from material damping in which elastic energy is actually dissipated by viscous, hysteretic, or other mechanism. The fact that the domain of analysis in numerical modeling must be chosen, however, causes a need for special attention at the boundary. This observation leads directly to the idea of determining the dynamic response of the interior region from a finite model consisting of the interior region subjected to a boundary condition which ensures that all energy arriving at the boundary is absorbed. This paper presents a simple methodology to simulate transmitting boundaries condition using viscoelastic infinite elements within the recently developed "OpenSees" finite element code. The methodology used here provides that the level of absorption for traveling waves is efficient enough for practical purposes, but unsatisfactory for the case of sharp incident angles. The effectiveness of the infinite elements for the absorption of incident waves at boundaries is evaluated via example analysis.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1015-1022
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• 2023

In this paper, we propose DLP(Dual Linear Polarization) antenna with aperture coupled feeding structure for private network. The proposed antenna has general aperture coupled structure and design two port between top and bottom layer to obtain the enhanced isolation. Also, The size of each substrate(top and bottom layer) is 34.0 mm(W)×34.0 mm(L), which is designed on the FR-4 substrate which thickness (h) is 1.0 mm, and the dielectric constant is 4.4. Also, the size of patch antenna is 12.70 mm(W2)×14.60 mm(L3), and it is located on the top layer. The size of feeding line is 24.0 mm(W2)×1.6 mm(L3), and is located at the bottom layer Also, rectangular slot is located on the ground plane between top layer and bottom layer. From the fabrication and measurement results, bandwidths of 300 MHz (4.52 to 4.82 GHz) for feeding port 1, and 170 MHz (4.65 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -30 dB. Also, cross polarization isolation between each feeding port obtained

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.294-302
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• 2023

Ni-Mn-Zn ferrite, Ni_0.5-xMn_xZn_0.5Fe₂O₄ (0 ≤ x ≤ 0.5), was synthesized using the sol-gel method to investigate the crystal structure, microstructure, magnetic properties, high-frequency characteristics, and electromagnetic (EM) wave absorption characteristics as a function of Mn substitution. As the Mn content increased, a continuous decrease in saturation magnetization (M_S) was observed with little change in coercivity (H_C). Samples for each composition (x) exhibited strong EM wave absorption performance with first and second strong EM wave absorption regions satisfying minimum reflection loss, RL_min < -40 dB in the 1.5~2.5, 6~11 GHz range, respectively. The EM wave absorption in Ni-Mn-Zn ferrite depends on magnetic loss, and adjusting µ' and µ'' spectra by Mn substitution or H field allows control of the EM wave absorption frequency.

• Advanced Industrial SCIence
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• v.3 no.2
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• pp.31-37
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• 2024

This paper presents a single and 2-patch microstrip array antenna operated on a frequency of 10.3GHz(x-band). It outlines the process of designing a microstrip patch array antenna using CST MWS. Initially, a single microstrip antenna was designed, followed by optimization using CST MWS to attain optimal return losses and gain. Subsequently, the design was expanded to create a 2×1 microstrip inset-fed array antenna for the X-band applications. The construction material is Roger RO4350B, with specific dimensions (h=0.79mm, 𝜖_r = 3.54). The achieved results include an S11 of -18dB at the resonant frequency (10.3GHz), a gain of 9.82dBi, a bandwidth of 0.165GHz, and a 3-dB beamwidth of 30°, 121° in Az(𝜑=0) and El(𝜑=90) plane, respectively. The future plan involves the fabrication of this array antenna and further expansion to a 4×4 array of microstrip antennas. It is then incorporated on the X-band applications for practical uses.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• Clinical and Experimental Pediatrics
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• v.50 no.4
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• pp.340-347
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• 2007

Purpose : The purpose of this study is to investigate the material in middle school and high school textbooks covering child care and children's health for medically inaccurate content and to make sure that the correct information is given to students. Methods : We have examined 47 kinds of textbooks on the subjects 'Home economics' and 'Technology and home economics' published in 2007 to find out how much importance is placed on children's health and childcare and to search for incorrect definitions, inaccurate facts or insufficient explanations. We have also analyzed the credentials of the writers of these textbooks. Results : Textbooks of middle school cover psychological and physical changes during adolescence and nutrition, and those of high school cover marriage and childcare. These materials covering health made up 27.5%, 11.7% of middle & high school texts. Age definitions of neonate and infant were incorrect. Inaccurate facts were mostly about fontanelles, primitive reflexes, breastfeeding and weaning. There also were wrong informations on the umbilical cord care and developmental milestones during infancy. The childhood immunization schedules and the growth curves were not up to date. Most of the authors major in home economics and the others were school teachers. There was no evidence of any review by a medical society or an expert. Conclusions : When writing about children's health and childcare in textbooks, a board-certified pediatrician or The Korean Pediatric Society should be consulted to provide accurate medical information to middle and high school students.

• Journal of Preventive Medicine and Public Health
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• v.26 no.1 s.41
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• pp.110-125
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• 1993

This study was designed to determine whether non-violent criminal and normal control on the basis of concentration of levels of trace mineral and toxic metal by analysis of human scalp hair. The subjects were selected 87 nonviolent criminal from a prison population and 120 normal control from periodic health checks for study. Hair samples were taken from the napes and Minnesota Multiple Personality Inventory (MMPI) was performed also. Five trace mineral (Zn, Cu, Mg, Fe, Na) and two toxic metal (lead, cadmium) contents were determined by an atomic absorption spectrometer. The contents of zinc and magnesium in hair of non-violent criminal were significantly lower than the control group (p<0.01). In the case of lead and cadimum, mean value of criminal group was significantly higher than control group. Significantly higher T-score of MMPI was seen in non-violent criminal group fur psychopathic deviate (Pd), paranoia scale (Pa), and Mania scale (Ma) than control group, but T-score of depression scale (D) was significantly higher in the control group. In the non-violent criminal group, the content of copper inversely proportion to T-score of Hs, D, Hy, Pd, Mf, Pa, Pt, Sc, Si except Ma, also Zinc inversely proportion to T-score of Hy, Mf, Pa, Pt. These results suggest that difference of some hair mineral contents exist between criminal and normal control group. Thus further studies are necessary to determine whether violent and nonviolent criminal group attributed biochemical imbalance with carefully constructed and controlled studies.