• 농촌계획
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• 제24권4호
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• pp.15-25
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• 2018

This study was designed to understand the change of rural landscape and to consider problems followed by development restrictions lifted for Neobiul Village in Ansan City, Korea. Physical landscape changes were comprehended by a field study and interview with local residents, and the residents' perception regarding the landscape changes were analyzed with the REP investigation method. The results can be summarized into the following three points: First, due to the lift of development restrictions and the deregulation of land use, the number of factories and warehouses for rent increased, which became a new source of income for the village. Second, the residents' complaints increased due to the increased traffic volume and waste from a sudden influx of factories and warehouses, which could not be handled by a small farming village. Third, a mix of landscape combining both city and farming village was formed due to the influx of external capital and the need of rental income, although the residents rather wanted Neobiul Village to become a residential village than a factory location. Furthermore, even in the farmlands near the village where development restrictions have not been lifted, the level of dependence on the farming industry has decreased as a consequence of the increase in farmland rent and weekend farms. This paper confirmed that the change of rural landscape followed by lifted development restrictions affects the everyday life of residents living in Neobiul Village. This study has significant implications in that it suggests a case showing the effects of national policies such as lifting development restrictions for rural villages in suburban areas.

• 한국재료학회지
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• 제29권8호
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• pp.469-476
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• 2019

A lead-free bulk ceramic having a chemical formula $Ba_{0.8}Ca_{0.2}(Ti_{0.8}Zr_{0.1}Ce_{0.1})O_3$ (further termed as BCTZCO) is synthesized using mixed oxide route. The structural, dielectric, impedance, and conductivity properties, as well as the modulus of the synthesized sample are discussed in the present work. Analysis of X-ray diffraction data obtained at room temperature reveals the existence of some impurity phases. The natural surface morphology shows close packing of grains with few voids. Attempts have been made to study the (a) effect of microstructures containing grains, grain boundaries, and electrodes on impedance and capacitive characteristics, (b) relationship between properties and crystal structure, and (c) nature of the relaxation mechanism of the prepared samples. The relationship between the structure and physical properties is established. The frequency and temperature dependence of the dielectric properties reveal that this complex system has a high dielectric constant and low tangent loss. An analysis of impedance and related parameters illuminates the contributions of grains. The activation energy is determined for only the high temperature region in the temperature dependent AC conductivity graph. Deviation from the Debye behavior is seen in the Nyquist plot at different temperatures. The relaxation mechanism and the electrical transport properties in the sample are investigated with the help of various spectroscopic (i.e., dielectric, modulus, and impedance) techniques. This lead free sample will serve as a base for device engineering.

• Current Applied Physics
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• 제18권11호
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• pp.1280-1288
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• 2018

In this work, we pointed out that Sr substitution for Ca leads to modify the magnetic and magnetocaloric properties of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds. Analyzing temperature dependence of magnetization, M(T), proves that the Curie temperature ($T_C$) increased with increasing Sr content (x); $T_C$ value is found to be 130-260 K for x = 0.0-0.3, respectively. Using the phenomenological model and M(T,H) data measured at several applied magnetic field, the magnetocaloric effect of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds has been investigated through their temperature and magnetic field dependences of magnetic entropy change ${\Delta}S_m$(T,H) and the change of the specific heat change ${\Delta}C_P$(T,H). Under an applied magnetic field change of 10 kOe, the maximum value of $-{\Delta}S_m$ is found to be about $3J/kg{\cdot}K$, and the maximum and minimum values of ${\Delta}C_P$(T) calculated to be about ${\pm}60J/kg{\cdot}K$ for x = 0.3 sample. Additionally, the critical behaviors of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds around their $T_C$ have been also analyzed. Results suggested a coexistence of the ferromagnetic short- and long-range interactions in samples. Moreover, Sr-doping favors establishing the short-range interactions.

• 한국분말재료학회지
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• 제28권3호
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• pp.239-245
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• 2021

The SnSe single crystal shows an outstanding figure of merit (ZT) of 2.6 at 973 K; thus, it is considered to be a promising thermoelectric material. However, the mass production of SnSe single crystals is difficult, and their mechanical properties are poor. Alternatively, we can use polycrystalline SnSe powder, which has better mechanical properties. In this study, surface modification by atomic layer deposition (ALD) is chosen to increase the ZT value of SnSe polycrystalline powder. SnSe powder is ground by a ball mill. An ALD coating process using a rotary-type reactor is adopted. ZnO thin films are grown by 100 ALD cycles using diethylzinc and H₂O as precursors at 100℃. ALD is performed at rotation speeds of 30, 40, 50, and 60 rpm to examine the effects of rotation speed on the thin film characteristics. The physical and chemical properties of ALD-coated SnSe powders are characterized by scanning and tunneling electron microscopy combined with energy-dispersive spectroscopy. The results reveal that a smooth oxygen-rich ZnO layer is grown on SnSe at a rotation speed of 30 rpm. This result can be applied for the uniform coating of a ZnO layer on various powder materials.

• 천문학회보
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• 제44권2호
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• pp.48.4-48.4
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• 2019

We studied the metal-distribution of isolated Milky-way mass galaxy using various hydrodynamic solvers and investigated the difference of the result between AMR and SPH codes. In particle-based codes, physical quantities like mass or metallicity defined in each particle are conserved unless being injected explicitly by the effect of the supernova, whereas in the Eulerian codes the diffusion is simply accomplished by hydro-equation. Therefore, without including explicit physics of diffusion on the SPH- codes, the metal mixing in the galaxy or CGM only can be accomplished by the direct motion of the particles, however, the standard-SPH codes depress the instability of the turbulent fluid mixing. In this work, we simulated under common initial conditions, common gas-physics like cooling-heating models, and star-formation feedback using ENZO(AMR) GIZMO and GADGET-2 codes. We additionally included a metal-diffusion algorithm on the SPH-codes, which follows the subgrid-turbulent mixing model investigated by Shen et al. (2010) and compared the effect of the metal-outflow on the halo region of the galaxy in different hydro-solvers. We also found that for the implementation of the diffusion scheme in the SPH-codes, the existence of a sufficient number of the gas-particles, which is the carrier of the metals, is necessary. So we tested a new initial condition for proper implementation of the diffusion scheme on the SPH simulations. By comparing the metal-contamination of the circumgalactic medium with different hydrodynamics models, we quantify the diffusion strength of AMR codes using diffusion parameterization of the SPH codes and also suggest the calibration solutions in the different behavior of codes in metal-outflow.

• 로봇학회논문지
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• 제18권4호
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• pp.385-391
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• 2023

In the elderly population, sarcopenia occurs due to physical aging, leading to movement restrictions and loss of function. This results in dependence on daily activities and limitations in participation, ultimately decreasing the overall quality of life. In this study, we propose an algorithm designed to enable patients with sarcopenia to perform sit-to-stand and stand-to-sit movements seamlessly in their daily lives. The algorithm incorporates a wearable robot for muscle support and includes algorithms for standing and seated muscle strength support. To validate the algorithm's performance, EMG sensors were attached to the Rectus Femoris and Biceps Femoris muscles. The participants underwent two scenarios: one without wearing the device and one with the device providing muscle strength support, performing sit-to-stand and stand-to-sit motions for one minute in each case. The results showed a 16% increase in the EMG peak value of the Rectus Femoris muscle during standing motion (p=0.009). On the right side, there was a roughly 20% decrease (p=0.018) during standing and a 21% decrease (p=0.014) during sitting motion. In the future, we aim to gather additional data to further refine the algorithm. Our goal is to develop an optimal muscle strength support algorithm based on this data, making it applicable for real-life use by patients with sarcopenia.

• 한국해양학회지:바다
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• 제13권3호
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• pp.246-251
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• 2008

심해저 망간단괴 집광시스템(이하, 집광시스템)의 개념설계가 공리적 설계(Axiomatic Design)의 관점에서 평가되었다. 또한 이미 수행된 집광시스템의 개념설계에 대해 기능적 영역의 기능요구와 물리적 영역의 설계파라미터가 구체화되었다. 기능요구와 설계파라미터의 상호관계는 첫 번째 수준 계층에서 하위 수준 계층으로 순차적으로 분석되었다. 이러한 상호관계는 설계행렬의 형태로 표현되었고 기능요구와 설계파라미터 사이의 독립성을 판단하기 위한 지표로 사용되었다. 설계행렬의 분석결과 본 집광시스템은 설계파라미터간에 연성이 되지 않는 비연성화된 설계임이 확인되었다. 결과적으로, 본 집광시스템은 독립공리(Independence Axiom)를 만족하는 잘된 설계임이 개념적으로 입증되었다.

• International Journal of Computer Science & Network Security
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• 제24권4호
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• pp.206-210
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• 2024

Industrial facilities that use modern IT technologies require the ensured reliability and security of information in automated enterprise management. Concurrently, so as to ensure a high quality of communication, it is necessary to expand the bandwidth of communication channels, which are limited by the physical parameters of the radio frequency spectrum. In order to overcome this contradiction, we propose the application of technology fundamental to ultra-wideband signals, in which the ratio between the bandwidth and its central part is greater than "one". For this reason, the information signal is emitted without a carrier frequency - simultaneously within the entire frequency band - provided that the signal level is lower than the noise level. For the transmission of information content, the method of positional-time coding is used, in which each information bit is encoded by hundreds of ultrashort pulses that arrive within a certain sequence. Mathematical models of signals and values observed in wireless communication systems with autocorrelation reception of modulated ultra-wideband signals are furthermore recommended. These assist in identifying features of the dependence of the error probability on the normalized signal-to-noise ratio and the signal base. Comparative analysis has shown that the best noise immunity of the systems considered in this paper is the communication system, which uses the time separation of the reference and information signals. During the first half of the bit interval, the switch closes the output of the transmitter directly to the generator of the ultra-wideband signal - forming a reference signal. In the middle of the bit interval, the switch alternates the output to one of two possible positions depending on the encoding signal - "zero" or "one", forming the information part of the ultra-wideband signal. It should also be noted that systems with autocorrelation reception and separate transmission of reference and information signals, provide a high level of structural signal secrecy. Furthermore, they provide the reliable transmission of digital information, especially in interference conditions.

• 한국자기학회지
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• 제17권2호
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• pp.81-85
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• 2007

분자선 증착법을 이용하여 MnTe 박막을 Si(100):B 및 Si(111) 기판 위에 성장시켰다. 두개의 K-cell을 사용하여 기판온도 $400^{\circ}C$ 및 Te가 풍부한 조건에서 MnTe 합성이 잘 이루어졌다. 이 경우 증착속도는 $1.1 {\AA}/s$이었고 성장된 층의 두께는 $700{\AA}$ 정도이었다. 합성된 MnTe 박막들에 대하여 X선회절, 초전도 양자 간섭계, Physical Property Measurement System, 홀효과 측정 등을 사용하여 그 구조적, 자기적, 전기적 특성들을 조사하였다. X선회절 측정 결과 Si(100) : B및 Si(111)기판 위에 성장된 MnTe는 다결정성의 hexagonal 구조를 나타내었으며, 자기적, 전기적 특성 측정 결과 분말형태의 MnTe와 비교하여 매우 다른 특성을 나타내었다. Zero-field-cooling(ZFC) 및 field-cooling(FC) 조건에서 취해진 자화율 측정에서 다결정 박막은 21 K, 49K, 210K 근처에서 자기적 전이 현상을 보였으며, ZFC와 FC 자화율 사이의 큰 불가역성이 나타났다. MnTe박막의 5K와 300K에서의 자기이력곡선은 강자성 상태를 나타내었으며 잔류자화값과 보자력은 5 K에서 $M_R= 3.5emu/cm^3$와 $H_c=55Oe$를, 300 K에서 $M_R= 2.1emu/cm^3$와 $H_c=44Oe$로 나타났다. 전기수송 특성 측정 결과, 온도에 따른 비저항은 저온에서 Mott variable range hopping 전도특성을 나타내는 전형적인 반도체 성질을 보여주었다.

• 한국산학기술학회논문지
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• 제12권12호
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• pp.5518-5524
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• 2011

사람이 서있는 동안의 안정성 감소는 낙상에 영향을 끼치는 요인 중 하나이다. 따라서 본 논문은 낙상 발생률이 높은 65세 이상의 노인여성을 대상으로 균형기능 검사를 실시하고, 성인여성의 연령대별 비교를 통해 균형능력이 노화에 따라 변화해가는 정형외과 및 신경학적 요인들을 밝혀 낙상을 예방하고자 한다. 연구 대상자는 보조기나 약물복용 없이 독립보행이 가능한 65세 이상의 신체 건강한 노인여성 10명(평균연령: 71.9세)과 성인여성 10명(평균연령: 23.2세)으로 하였다. 균형능력 평가장치(Tetrax)를 이용하여 8가지 자세에 대한 안정성 지수(Stability Index, ST), 푸리에 지수(Fourier index, F), 체중분표(Weight Distribution (%), WD), 체중분포율 지수(Weight Distribution Index, WDI), 동기화 지수(Synchronization Index, SI), 낙상율지수(fall index, FI)를 측정하였다. 그 결과, 안정성 지수(ST)는 노인여성과 성인여성간 PO를 제외한 모든 자세에서 통계적으로 유의한 차이를 나타냈다(p<.01) 푸리에지수는 낮은주파수(low, F1)에서 PO를 제외한 모든 자세에서 노인여성과 성인여성은 유의한 차이를 나타냈다(p<.01). 또한 중간낮은 주파수(middle-low, F2-F4), 중간높은주파수(middle-high, F5-F6), 높은주파수(high, F7-F8) 모두에서 노인여성이 성인여성보다 통계적으로 유의하게 높은 수치를 나타냈다. 모든 자세에서 노인여성의 체중분포율지수가 더 높게 나타났으나, PO와 PC에서만 통계적으로 유의했다. 이는 노화에 따른 생리학적 변화로 체성감각기관, 전정기관, 중추신경계등 전반적인 부분에서 능력이 저하됨에 따라 나타난 것으로 사료된다.