• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4102-4110
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• 2022

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m². Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 ℃, much below the permissible value of tungsten material (~1200 ℃). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.

• Journal of the Korean Society of Radiology
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• v.17 no.5
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• pp.751-759
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• 2023

Breast ultrasonography is difficult to image in fatty breasts and to find micro-calcification, but the discovery of micro-calcification is very important for breast cancer screening. Among the color Doppler artifact of ultrasound, twinkle artifact mainly occur on strong reflectors such as stones or calcification in images, and evaluation methods using them are clinically being used. In this study, we are conducting experiments on the color Doppler settings of ultrasound equipment, such as repetition frequency, ensemble, persist, wall filtering, smoothing, linear density, and dissociation value, by producing a breast simulation phantom using the largest amount of calcium phosphate among breast implants. The purpose of this study was to improve the contrast of twinkle artifact in breast ultrasound examinations and to maximize their use in clinical practice. As a result, the pulse repetition frequency occurred in the range of 3.6 kHz to 7.2 kHz, and did not occur above 10.5 kHz. For ensembles, twinkle artifact occurred in all sizes of calcification under low conditions, and in threshold settings, the twinkle artifact increased slightly only under 80 to 100 conditions, and did not occur in 1 mm size calcification. Persist, wall filter, smoothing, and line density settings did not have much meaning in the setting variable because conditions did not increase by condition, and pulse repetition frequency, ensemble, and thresholds had the greatest impact on the twinkling artifact image. This study is expected to help examiners select optimal conditions to effectively increase twinkle artifact by adjusting color Doppler settings.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.211-218
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• 2007

In this study, we investigated the spatial distribution of macrozoobenthos in the estuarine sandy flat, the Bongam tidal flat located in Masan Bay during March, 2004. A total 13 species were identified at 12 stations within the tidal flat. The mean density was $20,267\;ind./m^2$, and mean biomass was $228.1g/m^2$. Dominant species in the Bongam tidal flat were all polychaetes: Prionospio japonicus ($11,716\;ind./m^2$, 57.8%) and Polydora ligni ($3,929\;ind./m^2$, 19.4%) of spionoid polychaete, and Neanthes succinea ($3,425\;ind./m^2$, 16.9%) of nereid polychaete. The most dominant species, P. japonicus distributed evenly all stations in the tidal flat. But N. succinea showed high density at the upper area of the tidal flat. Species diversity index (H') was in the range of 0.6 to 1.2 which is relatively low due to the prominent of P. japonicus and few species richness at each station. The study area was divided into two station groups (group A and B) based on the cluster analysis and MDS ordination, and the spatial distribution of macrozoobenthos on the Bongam tidal flat seemed to be in the influence of exposure duration from tidal levels and specific geological topography.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.67-72
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• 2009

Purpose: ISCD (International Society for Clinical Densitometry) requests that users perform mandatory Precision test to raise their quality even though there is no recommendation about patient selection for the test. Thus, we investigated the effect on precision test by measuring reproducibility of 3 bone density groups (normal, osteopenia, osteoporosis). Materials and Methods: 4 users performed precision test with 420 patients (age: $57.8{\pm}9.02$) for BMD in Asan Medical Center (JAN-2008 ~ JUN-2008). In first group (A), 4 users selected 30 patient respectively regardless of bone density condition and measured 2 part (L-spine, femur) in twice. In second group (B), 4 users measured bone density of 10 patients respectively in the same manner of first group (A) users but dividing patient into 3 stages (normal, osteopenia, osteoporosis). In third group (C), 2 users measured 30 patients respectively in the same manner of first group (A) users considering bone density condition. We used GE Lunar Prodigy Advance (Encore. V11.4) and analyzed the result by comparing %CV to LSC using precision tool from ISCD. Check back was done using SPSS. Results: In group A, the %CV calculated by 4 users (a, b, c, d) were 1.16, 1.01, 1.19, 0.65 g/$cm^2$ in L-spine and 0.69, 0.58, 0.97, 0.47 g/$cm^2$ in femur. In group B, the %CV calculated by 4 users (a, b, c, d) were 1.01, 1.19, 0.83, 1.37 g/$cm^2$ in L-spine and 1.03, 0.54, 0.69, 0.58 g/$cm^2$ in femur. When comparing results (group A, B), we found no considerable differences. In group C, the user_1's %CV of normal, osteopenia and osteoporosis were 1.26, 0.94, 0.94 g/$cm^2$ in L-spine and 0.94, 0.79, 1.01 g/$cm^2$ in femur. And the user_2's %CV were 0.97, 0.83, 0.72 g/$cm^2$ L-spine and 0.65, 0.65, 1.05 g/$cm^2$ in femur. When analyzing the result, we figured out that the difference of reproducibility was almost not found but the differences of two users' several result values have effect on total reproducibility. Conclusions: Precision test is a important factor of bone density follow up. When Machine and user's reproducibility is getting better, it’s useful in clinics because of low range of deviation. Users have to check machine's reproducibility before the test and keep the same mind doing BMD test for patient. In precision test, the difference of measured value is usually found for ROI change caused by patient position. In case of osteoporosis patient, there is difficult to make initial ROI accurately more than normal and osteopenia patient due to lack of bone recognition even though ROI is made automatically by computer software. However, initial ROI is very important and users have to make coherent ROI because we use ROI Copy function in a follow up. In this study, we performed precision test considering bone density condition and found LSC value was stayed within 3%. There was no considerable difference. Thus, patient selection could be done regardless of bone density condition.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.11
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• pp.6-12
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• 2010

A sigma-delta modulator based class-D audio amplifier is presented. Parallel digital input is serialized to two-bit output by a fourth-order digital sigma-delta noise shaper. The output of the digital sigma-delta noise shaper is applied to a fourth-order analog sigma-delta modulator whose three-level output drives power switches. The pulse density modulated (PDM) output of the power switches is low-pass filtered by an LC-filter. The PDM output of the power switches is fed back to the input of the analog sigma-delta modulator. The first integrator of the analog sigma-delta modulator is a hybrid of continuous-time (CT) and switched-capacitor (SC) integrator. While the sampled input is applied to SC path, the continuous-time feedback signal is applied to CT path to suppress the noise of the PDM output. The class-D audio amplifier is fabricated in a standard $0.13-{\mu}m$ CMOS process and operates for the signal bandwidth from 100-Hz to 20-kHz. With 4-${\Omega}$ load, the maximum output power is 18.3-mW. The total harmonic distortion plus noise and dynamic range are 0.035-% and 80-dB, respectively. The modulator consumes 457-uW from 1.2-V power supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.4 s.346
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• pp.8-15
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• 2006

In this paper, the 94 GHz, low conversion loss, and high isolation single balanced mixer is designed and fabricated using GaAs-based metamorphic high electron mobility transistors (MHEMTs) with 70 nm gate length and the hybrid ring coupler with the micromachined transmission lines, dielectric-supported air-gapped microstrip lines (DAMLs). The 70 nm MHEMT devices exhibit DC characteristics with a drain current density of 607 mA/mm an extrinsic transconductance of 1015 mS/mm. The current gain cutoff frequency ($f_T$) and maximum oscillation frequency ($f_{max}$) are 320 GHz and 430 GHz, respectively. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of $3.57{\pm}0.22dB$ and the transmission loss of $3.80{\pm}0.08dB$ in the measured frequency range of 85 GHz to 105 GHz. This mixer shows that the conversion loss and isolation characteristics are $2.5dB{\sim}>2.8dB$ and under -30 dB, respectively, in the range of $93.65GHz{\sim}94.25GHz$. At the center frequency of 94 GHz, this mixer shows the minimum conversion loss of 2.5 dB at a LO power of 6 dBm To our knowledge, these results are the best performances demonstrated from 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.380-384
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• 1988

The coefficients of the hot-air and freeze dried garlic isotherms and the critical water activities of these were estimated to be 0.85-0.94 by the linear regression and 0.58-0.60 by the sensory evaluation and ${\Delta}E$ value. Water adsorption rate(K) of hot-air dried garlic packaged with $48{\mu}m$ low density polyethylene(LDPE) decreased from $0.12g\;H_2O/100g/day\;to\;0.093g\;H_2O$/100g/day with decreasing the package dimension from $0.051m^2\;to\;0.029m^2\;at\;40^{\circ}C$ and 75% RH, and that of freeze dried one decreased from $0.17g\;H_2O/100g/day\;to\;0.12g\;H_2O$/100g/day as the filling weight increased from 50g to 10g in the package of $0.051m^2$. Shelf-life of hot-air dried garlic packaged with $80{\mu}m$ LDPE were 99days at $40^{\circ}C,\;283day\;at\;30^{\circ}C\;and\;455\;days\;at\;15^{\circ}C$ in the 75% RH. The differences of water contents between predicted data with water vapor permeability of the conventional method and experimental data were 0-1.5% in the water content range of around 13-18%, but about 2 in the water content range of around 8-11%.

• Korean Journal of Remote Sensing
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• v.15 no.1
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• pp.9-20
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• 1999

The use of climatic information is essential in the industial society. More specialized weather servies are required to perform better industrial acivities including agriculture. Especially, crop models require daily weather data of crop growing area or cropping zones, where routine weather observations are rare. Estimates of the spatial distribution of daily climates might complement the low density of standard weather observation stations. This study was conducted to estimate the spatial distribution of daily minimum and maximum temperatures in Korean Peninsula. A topoclimatological technique was first applied to produce reasonable estimates of monthly climatic normals based on 1km $\times$ 1km grid cell over study area. Harmonic analysis method was then adopted to convert the monthly climatic normals into daily climatic normals. The daily temperatures for each grid cell were derived from a spatial interpolation procedure based on inverse-distance weighting of the observed deviation from the climatic normals at the nearest 4 standard weather stations. Data collected from more than 300 automatic weather systems were then used to validate the final estimates on several dates in 1997. Final step to confirm accuracy of the estimated temperature fields was comparing the distribution pattern with the brightness temperature fields derived from NOAA/AVHRR. Results show that differences between the estimated and the observed temperatures at 20 randomly selected automatic weather systems(AWS) range from -3.$0^{\circ}C$ to + 2.5$^{\circ}C$ in daily maximum, and from -1.8$^{\circ}C$ to + 2.2$^{\circ}C$ in daily minimum temperature. The estimation errors, RMSE, calculated from the data collected at about 300 AWS range from $1.5^{\circ}C$ to 2.5$^{\circ}C$ for daily maximum/minimum temperatures.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.70-77
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• 1998

Ni/SiC Schottky diodes have been fabricated using epitaxial 4H-SiC and 6H-SiC wafers. The epitaxial n-type layers were grown on $n^{+}$ substrates, with a doping density of 4.0$\times$10$^{16}$ c $m^{-3}$ and a thickness of 10${\mu}{\textrm}{m}$. Oxide-termination has been adopted in order to obtain high breakdown voltage and low leakage current. The fabricated Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes show excellent rectifying characteristics up to the measured temperature range of 55$0^{\circ}C$. In case of oxide-terminated Schottky barrier diodes, breakdown voltage of 973V(Ni/4H-SiC) and 920V(Ni/6H-SiC), and a very low leakage current of less than 1nA at -800V has been observed at room temperature. On non-terminated Schottky barrier diodes, breakdown voltages were 430V(Ni/4H-SiC) and 160v(Ni/6H-SiC). At room temperature, SBH(Schottky Barrier Height), ideality factor and specific on-resistance were 1.55eV, 1.3, 3.6$\times$10$^{-2}$ $\Omega$.$\textrm{cm}^2$ for Ni/4H-SiC Schottky barrier diodes, and 1.24eV, 1.2, 2.6$\times$10$^{-2}$$\Omega$.$\textrm{cm}^2$/ for Ni/SH-SiC Schottky barrier diodes, respectively. These results show that both Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes are very promising for high-temperature and high power applications.s..

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.2
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• pp.171-178
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• 2015

This research is the first research on developing the speed limit select model and also it is the result of the research on the importance of each element and consideration factors when selecting the speed limit. For the consideration factor discrimination and calculation of the importance, the delphi method and AHP method was used. The delphi survey was processed through third round survey, 5 high consideration factor(Level 1) and 23 low consideration factor(Level 2) was discriminated. During the process of the third delphi survey, when the CVR cost was in the range between 0.4~1.0 it was treated as the consideration factor when selecting the speed limit and less than 0.4 cost was eliminated. In the process of the second delphi survey, 33 consideration factors were discriminated but was reordered into 23 categories through the third survey. Based on the 23 categories earned through the third delphi analysis, the AHP survey was processed. The result of the AHP survey was that out of the importance of the 5 high consideration factor(Level 1), the traffic condition was evaluated as the number one factor and the vessel condition, waterway condition, environment condition, supporting condition and etc. conditions were evaluated following the traffic condition. Out of the 23 low consideration factor(Level 2) consideration, the visibility was evaluated to be the first important and the performance of the vessel steering, objective factors within the harbor, amount of traffic and density, distance between the passing vessel, speed of the steering capacity and tidal current were the following evaluated factors.