• Journal of Magnetics
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• 제3권2호
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• pp.44-48
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• 1998

Scanning Electron Microscopy with Polarization Analysis (SEMPA) was used to image the surface magnetic domain structure of the 100 ${\mu}{\textrm}{m}$ thick 3% Si-Fe sheet. The thin-gauged 3% Si-Fe strips with magnetic induction ($B_{10}$) from 1.98 to 1.57 Tesla were prepared via conventional metallurgical processes including melting, hot-and cold-rolling, intermediate annealing and final annealing. Using SEMPA, it was observed that the $B_{10}$ (1.98 T) Tesla sample was almost composed of 180$^{\circ}$ stripe domains which are parallel to rolling direction. On the other hand the 3% Si-Fe sheet with $B_{10}$ (1.57 T) Tesla was composed of large 180$^{\circ}$stripe domains that are slanted about 30$^{\circ}$to the rolling direction and complex magnetic domain structures like tree and zigzag pattern. The 180$^{\circ}$stripe domains, which covered a major part of the sample, had (110)<001> Goss texture parallel to the rolling direction. The domain walls between 180$^{\circ}$stripe domains were the conventional Bloch type walls. On the other hand, the 90$^{\circ}$domains, which covered minor part on edge of the sample, were observed in (200) grains. The domain walls between 90$^{\circ}$domains were the Neel type walls. In high magnification, the elliptical singularity at the Neel walls was clearly observed.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.380-387
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• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• Advances in nano research
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• 제10권5호
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• Journal of Biosystems Engineering
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• 제31권6호
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• pp.489-499
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• 2006

Since the application of chemicals in confined spaces under the canopy of an orchard is hazardous work, it is needed to develop an autonomous guidance system for an orchard sprayer. The autonomous guidance system developed in this research could steer the vehicle by tracking an overhead guidance rail, which was installed on an existing frame structure. The autonomous guidance system consisted of an 80196 kc microprocessor, an inclinometer, two interface circuits of actuators for steering and ground speed control, and a fuzzy control algorithm. In addition, overhead guidance rails for both straight and curved paths were devised, and a trolley was designed to move smoothly along the overhead guidance rails. Evaluation tests showed that the experimental vehicle could travel along the desired path at a ground speed of 30 $\sim$ 50 cm/s with a RMS error of 5 cm and maximum deviation of less than 12 cm. Even when the vehicle started with an initial offset or a deflected heading angle, it could move quickly to track the desired path after traveling 2 $\sim$ 3 m. The vehicle could also complete turns with a curvature of 1 m. However, at a ground speed of 50 cm/s, the vehicle tended to over-steer, resulting in a zigzag motion along the straight path, and tended to turn outward from the projected line of the guidance rail.

• 한국실내디자인학회논문집
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• 제20권3호
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• pp.190-197
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• 2011

The purpose of this study is to examine the characteristics of space design appearing in facade and interior composition factors of buildings in the colonial period in Indonesia. Research method is a field study, and subjects of the study is 14 buildings built in the colonial period located in Jakarta. The research result is as follows. First, Facade is divided into C type (colonial style), CT type (colonial style + traditional style), CA type (colonial style + art deco style), and CTA type (colonial style + traditional style + art deco style). Among them, CT type which shows both a colonial style and traditional style accounts for the most. As for Java traditional style mainly shows Joglo roof style and bratticing decoration on top of gates, and the colonial style presents both an Amsterdam canal housing style such as narrow Facade and unusual Gable, and a classical style such as pediment, entablature, and columns. Second, interior space is divided into C type (colonial style), CT type (colonial style + Indonesian traditional style), A type (art deco style), and CA type (colonial style + art deco style). Among them, CT type was also accounted for the most. Selected traditional style is a shape of bratticing decoration on top of gates and a shape of tenon of Joglo housing structure. Colonial style showed classical style such as exposed crossbeams, columns, and pilasters, and as for unique decoration, there are Ancona decoration and Delft tile decoration. On one hand, art deco style used typical art deco factors such as contrast of various materials and complementary color or golden color use as well as zigzag or vertical lines and geometric ornament by combining with colonial style or traditional style. It is expected that such research result will be a practical reference data when Korean construction companies or interior design companies advance Indonesia.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3749-3754
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• 2013

Two 3D isomorphous and isostructural complexes, namely, $[Zn(BDOA)(bpy)(H_2O)_2]_n$ (1) and $[Cd(BDOA)-(bpy)(H_2O)_2]_n$ (2); (BDOA = Benzene-1,4-dioxyacetic acid, bpy = 4,4'-bipyridine) were synthesized under hydrothermal conditions and characterized by means of elemental analyses, thermogravimetric (TG), infrared spectrometry, and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the triclinic system, space group P-1 and each metal ion in the complexes are six-coordinated with the same coordination environment. In the as-synthesized complexes, $BDOA^{2-}$ anions link central metal ions to form a 1D zigzag chain $[-BDOA^{2-}-Zn(Cd)-BDOA^{2-}-Zn(Cd)-]_{\infty}$, whereas bpy pillars connect metal ions to generate a 1D linear chain $[-bpy-Zn(Cd)-bpy-Zn(Cd)-]_{\infty}$. Both infinite chains are interweaved into 2D grid-like layers which are further constructed into a 3D open framework, where hydrogen bonds play as the bridges between the adjacent 2D layers. Luminescent properties of complex 1 showed selectivity for $Hg^{2+}$ ion.

• KIEAE Journal
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• 제4권3호
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• pp.195-202
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• 2004

This study focuses on the impacts of apartment building arrangements on the outdoor and indoor air quality - the efficiency of natural ventilation in the outside/inside area of an apartment with consideration to the characteristics of an air flow in outside area depending on the types of the arrangements, the main direction of the wind, and the outside wind pressure on the building facade. As indices to evaluate the efficiency of natural ventilation, the concepts of "Age of Air" and "Purging Flow Rate(PFR)" were used in this study. As indices to classify the efficiency of indoor natural ventilation, the mean values of the wind pressure differences between the front and the back elevations of an apartment building were used. The research showed that the PFR of each apartment building arrangement ranges from 0.867 to 3.253. The "minus-shaped" arrangement showed the highest PFR, 2.306; the "zigzag-shaped" arrangement measured 1.889; the "angle-shaped" arrangement measured 1.465, and the "square-shaped" arrangement measured 1.241. Depending on the direction of the wind, the pressure differences range extremely, with variations from 170% to 2300%. Thus, the indoor natural ventilation efficiency can be changed by the pressure differences of the wind, which are sensitive to the main direction of the wind even though the structure and planning of the apartment complexes are the same. Despite the same direction of the wind, even the efficiency can be diverse. This study showed how to predict the most beneficial apartment building arrangement for the profitable natural ventilation efficiency in each direction of the wind.

• 조명전기설비학회논문지
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• 제16권4호
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• pp.64-72
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• 2002

산업의 발달에 따라 선형 직류 모터의 용용이 확대되고 있다. 본 연구에서는 가동차석형 양측식 다분할 여자 LDM의 해석을 연구대상으로 하였다. 본 LDM의 구조에서 가동자는 큰 추력을 얻도록 영구지석 6개를 사용하였으며, 고정자는 철심의 포화를 억제 하도록 다 분할형 권선을 성층하였다. 또한 양측 여자 권선은 지그재그형으로 성 층하여 추력의 리플을 억제하고, 정추력을 발생할 수 있도록 설계하였다. 여기에 다 분할시 영구자석대 권선 폭의 비가 중요하므로 본 연구에서는 똑비를 1 : 1, 1 : 0.84 및 1 : 0.5의 3개 부분으로 나누어 해석하였다. 해석 방법은 복잡한 수치해석의 유한요소법 보다는 퍼미언스 및 자기저항 법을 이용하여 파라며터를 계산하였다. 제작된 실험장 치를 통하여 추력을 측정한 결과는 전 변위에 대해서 정추력이 발생함을 알 수 있었다.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.109-118
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• 2018

현재 개발 중에 있는 2열 겹침주열말뚝은 대심도 굴착 시 적용을 위해 2열의 말뚝을 통해 강성을 크게 증대시키고 말뚝 간 엇갈림 겹침부를 통한 연속성 확보로 추가의 그라우팅이 없이 차수벽 역할을 할 수 있도록 고안된 흙막이 벽체이다. 이 벽체는 기존의 주열말뚝벽체에 비해 2열 엇갈림 말뚝 시공으로 단면 형상이 복잡하여 기존의 주열말뚝벽체들에 비해 휨 강성 등 단면 조건에 좌우되는 설계인자의 결정이 용이하지 않다. 본 연구에서는 2열 겹침주열말뚝의 다양한 단면 조건들에 대해서 이론적 방법과 통계적 분석을 통해 간단한 단면 제원, 즉, 말뚝의 직경과 말뚝 간 겹침길이를 이용해 흙막이 벽체의 중요 설계 인자인 휨 강성을 간편하게 산정할 수 있는 계산식을 유도하였다. 개발된 간편 휨강성 산정식은 정밀하게 계산된 휨 강성과 비교해 오차율 3% 이하인 것으로 나타났다.

• Applied Microscopy
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• 제49권
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• pp.3.1-3.7
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• 2019

Graphene, which is one of the most promising materials for its state-of-the-art applications, has received extensive attention because of its superior mechanical properties. However, there is little experimental evidence related to the mechanical properties of graphene at the atomic level because of the challenges associated with transferring atomically-thin two-dimensional (2D) materials onto microelectromechanical systems (MEMS) devices. In this study, we show successful dry transfer with a gel material of a stable, clean, and free-standing exfoliated graphene film onto a push-to-pull (PTP) device, which is a MEMS device used for uniaxial tensile testing in in situ transmission electron microscopy (TEM). Through the results of optical microscopy, Raman spectroscopy, and TEM, we demonstrate high quality exfoliated graphene on the PTP device. Finally, the stress-strain results corresponding to propagating cracks in folded graphene were simultaneously obtained during the tensile tests in TEM. The zigzag and armchair edges of graphene confirmed that the fracture occurred in association with the hexagonal lattice structure of graphene while the tensile testing. In the wake of the results, we envision the dedicated preparation and in situ TEM tensile experiments advance the understanding of the relationship between the mechanical properties and structural characteristics of 2D materials.