• Journal of Ocean Engineering and Technology
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• v.30 no.3
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• pp.201-207
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• 2016

In this paper, an aluminum pressure vessel (cylinder) for a 200 m water depth is designed and analyzed. Because of their lack of usage in the deep sea, only a few papers about pressure vessels subjected to external pressures have previously been published. Moreover, the high level of imported external-pressure-vessel products limits the academic pursuit. Yet, research on internal pressure vessels is widely available because of their broad usage at onshore. This paper presents the process of basic designing and modelling of pressure vessels using the design rules of American Standard of Mechanical Engineering (ASME) Section VIII Division 1. To promote understanding, finite element analysis (FEA) result of an existing sample cylinder which was not designed by ASME code is compared with the design obtained in this paper. Several methodologies are used for the finite element analysis, including rectangular, cylindrical, and axisymmetric coordinate, to attain an accurate stress result. Same dimensions except the thickness of the cylinder and loading condition of 0.200 MPa was given for the current study. Finally, a rigorous design procedure is added for the bolt and boundary conditions of the cylindrical body and its ends. The obtained stress level satisfies the allowable design stress value specified in the ASME code.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.280-286
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• 2020

Cards made from PVC and PET materials do not oxidize or decompose readily, so they are generally incinerated or landfilled after use and cause pollution problems, such as environmental hormones and combustion gases during incineration. In addition, there is a problem of environmental pollution because they are discarded as semi-permanent refuse without being decomposed at landfill. This study attempted to solve this problem using polylactic acid (PLA), which is a representative biodegradable material as a substitute material that can solve the issues with these cards. On the other hand, when the thin card core sheet is made from only PLA material, the physical properties of the material are insufficient, such as the low temperature impact strength, high temperature stability, and poor bending properties, so its use is limited. To solve this problem, the compositional ratio of PLA was reviewed, and the optimal biodegradable compound composition was determined through an examination of the compositions, such as crystallization nucleating agents, additives, and nano compound technology. The high functionalization as a biodegradable card was verified through a laminating process using annealing technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.978-984
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• 2008

In this paper, we propose a RFID metal tag antenna with a minimum by size of a metal surface to attach. This proposed tag antenna is a patch antenna which is able to stick on metal surface and designed for very slim structure ($119{\times}30{\times}1.6$ mm) antenna that is matched to a chip impedance. This has a loop coupling feeding and consists of a inner radiator and a outer radiator. The outer radiator activates the current to concentrate on the inner radiator regardless of metal size to attach. Also the tag antenna is designed by CST microwave tool and the performance is measured in the anechoic chamber. The optimum antenna has 3.77 % of the matching bandwidth($S_{11}<-10$ dB). The readable range of the tag antenna is about 2.9 m on metal(max. size $700{\times}700$ mm) and 5.5 m in free space according to the measurement results.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.4
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• pp.335-340
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• 2002

In this paper, the stress induced leakage currents of thin silicon oxides is investigated in the ULSI implementation with nano structure transistors. The stress and transient currents associated with the on and off time of applied voltage were used to measure the distribution of high voltage stress induced traps in thin silicon oxide films. The stress and transient currents were due to the charging and discharging of traps generated by high stress voltage in the silicon oxides. The transient current was caused by the tunnel charging and discharging of the stress generated traps nearby two interfaces. The stress induced leakage current will affect data retention in electrically erasable programmable read only memories. The oxide current for the thickness dependence of stress current, transient current, and stress induced leakage currents has been measured in oxides with thicknesses between 113.4${\AA}$ and 814${\AA}$, which have the gate area $10^3cm^2$. The stress induced leakage currents will affect data retention and the stress current, transient current is used to estimate to fundamental limitations on oxide thicknesses.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.1
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• pp.135-140
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• 2004

Anti-skin aging agent could be have an inhibition effect of ROS production as well as fragmentation and change of collagen cross linkage in collagen molecule. For the monitoring of lipid peroxidation and collagen degradation, the skin of young and old rats were incised and observed 7 days. In the result, the wound closure was observed in the skin from 10 of 11 young rats and in 8 of 11 old rats. And the longer wound length but shorter wound closure, weaker collagen density and thicker epidermis were observed in old rats than in young rats. The level of hydroxyproline as a parameter of collagen synthesis and MDA as a parameter of lipid peroxidation was lower in old group than in young group. The cyst and lacuna between collagen bundle and fibroblast were observed in old rats in contrast to young rats. So that we propose that MDA and hydroxyproline could be used for monitoring of anti-skin aging agent.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.191-192
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• 2010

높은 유전상수를 가지는 터널 장벽물질 들은 플래쉬메모리 및 나노 부유게이트 메모리 소자에서 터널의 두께 및 밴드갭 구조의 변형을 통하여 단일층의 $SiO_2$ 터널장벽에 비하여 동작속도를 향상시키고 누설전류를 줄이며 전하보존 특성을 높여줄 수 있다.[1-3] 본 연구에서는 $Al_2O_3/HfO/Al_2O_3$구조의 고 유전체 터널장벽을 사용하여 $WSi_2$ 나노입자를 가지게 되는 metal-oxide-semiconductor(MOS)구조의 커패시터를 제작하여 전기적인 특성을 확인하였다. p형 (100) Si기판 위에 $Al_2O_3/HfO/Al_2O_3$ (AHA)의 터널장벽구조를 원자층 단일 증착법을 이용하여 $350^{\circ}C$에서 각각 2 nm/1 nm/3 nm 두께로 증착시킨 다음, $WSi_2$ 나노입자를 제작하기 위하여 얇은 $WSi_2$ 박막을 마그네트론 스퍼터링법으로 3 - 4 nm의 두께로 증착시켰다. 그 후 $N_2$분위기에서 급속열처리 장치로 $900^{\circ}C$에서 1분간의 열처리과정을 통하여 AHA로 이루어진 터널 장벽위에 $WSi_2$ 나노입자들이 형성할 수 있었다. 그리고 초 고진공 마그네트론 스퍼터링장치로 $SiO_2$ 컨트롤 절연막을 20 nm 증착하고, 마지막으로 열 증기로 200 nm의 알루미늄 게이트 전극을 증착하여 소자를 완성하였다. 그림 1은 AHA 터널장벽을 이용한 $WSi_2$ 나노 부유게이트 커패시터 구조의 1-MHz 전기용량-전압 특성을 보여준다. 여기서, ${\pm}3\;V$에서 ${\pm}9\;V$까지 게이트전압을 점차적으로 증가시켰을 때 메모리창은 최대 4.6 V로 나타났다. 따라서 AHA의 고 유전체 터널층을 가지는 $WSi_2$ 나노입자 커패시터 구조가 차세대 비 휘발성 메모리로서 충분히 사용가능함을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.798-805
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• 2017

This paper presents a low profile multi circular ring with different radius, patch antenna with modified feed line and slotted ground. The size of the antenna is $15{\times}12mm^2$, having electrical dimensions of $0.14{\lambda}{\times}0.12{\lambda}$ (at lower initial frequency) and footprints of $180mm^2$. The proposed antenna covers 3.1 to 12.3 GHz, reflection coefficient up to -38 dB with Bandwidth ratio of 4.13:1 and fractional Bandwidth of 122%. Bandwidth dimension ratio has been calculated (which is 6246) as a proof for compact size. Thin slots introduced on the feed line provide good impedance matching for whole frequency band. Numerical simulations of the proposed antenna are reported in terms of reflection coefficient ${\leq}-10dB$, vswr 2:1, radiation pattern and group delay (ns). The proposed antenna has advantage of very small size along with better impedance match that provides a practical approach to realize it for BW enhancement and UWB applications.

• Design & Manufacturing
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• v.14 no.3
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• pp.44-49
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• 2020

One of display trends today is development of high pixel density. To get high PPI, a small size of pixel must be developed. RGB pixel is arranged by evaporation process which determines pixel size. Normally, a fine metal mask (FMM; Invar alloy) has been used for evaporation process and it has advantages such as good strength, and low thermal expansion coefficient at low temperature. A FMM has been manufactured by chemical etching which has limitation to controlling the pattern shape and size. One of alternative method for patterning FMM is laser micromachining. Femtosecond laser is normally considered to improve those disadvantages for laser micromachining process due to such short pulse duration. In this paper, a femtosecond laser drilling for thickness of 16 ㎛ FMM is examined. Additionally, we introduce experimental results for controlling taper angle of hole by vibration module adapted in laser system. We used Ti:Sapphire based femtosecond laser with attenuating optics, co-axial illumination, vision system, 3-axis linear stage and vibration module. By controlling vibration amplitude, entrance and exit diameters are controllable. Using vibrating objective lens, we can control taper angle when femtosecond laser hole drilling by moving focusing point. The larger amplitude of vibration we control, the smaller taper angle will be carried out.

• Journal of the Korea Computer Graphics Society
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• v.6 no.4
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• pp.35-42
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• 2000

3D texture mapping generates highly natural visual effects in which objects appear carved from lumps of materials rather than laminated with thin sheets as in 2D texture mapping. Storing 3D texture images in a table for fast mapping computations, instead of evaluating procedures on the fly, however, has been considered impractical due to the extremely high memory requirement. Recently, a practical real-time 3D texture mapping technique was proposed in [11], where they attempt to resolve the potential texture memory problem by compressing 3D textures using a wavelet-based encoding method. In this paper, we consider two other encoding schemes that could also be applied to the compression-based 3D texture mapping. In particular, we extend the vector quantization and FXT1 for 3D texture compression, and compare their performance with the wavelet-based encoding scheme.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.148-148
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• 2010

플래시 메모리로 대표되는 비휘발성 메모리는 IT 기술의 발달에 힘입어 급격한 성장세를 나타내고 있지만, 메모리 소자의 크기가 작아짐에 따라서 그 물리적 한계에 이르러 차세대 메모리에 대한 요구가 점차 높아지고 있는 실정이다. 따라서, 이러한 문제점에 대한 대안으로서 고속 동작 및 정보의 저장 시간을 향상 시킬 수 있는 nano-floating gate memory (NFGM)가 제안되었다. Nano-floating gate에서 사용되는 nanocrystal (NCs) 중에서 Si nanocrystal은 비휘발성 메모리뿐만 아니라 발광 소자 및 태양 전지 등의 매우 다양한 분야에 광범위하게 응용되고 있지만, NCs의 크기와 밀도를 제어하는 것이 가장 중요한 문제로 이를 해결하기 위해서 많은 연구가 진행되고 있다. 또한, 소자의 소형화가 이루어지면서 기존의 플래시 메모리 한계를 극복하기 위해서 터널베리어에 관한 관심이 크게 증가했다. 특히, 최근에 많은 주목을 받고 있는 개량형 터널베리어는 크게 VARIOT (VARIable Oxide Thickness) barrier와 CRESTED barrier의 두 가지 종류가 제안되어 있다. VARIOT의 경우에는 매우 얇은 두께의low-k/high-k/low-k 의 적층구조를 가지며, CRESTED barrier의 경우에는 반대의 적층구조를 가진다. 이와 같은 개량형 터널 베리어는 전계에 대한 터널링 전류의 감도를 증가시켜서 쓰기/지우기 특성을 향상시키며, 물리적인 절연막 두께의 증가로 인해 데이터 보존 시간의 향상을 달성할 수 있다. 본 연구에서는 박막의 $SiO_2$와 $Si_3N_4$를 적층한 VARIOT 타입의 개량형 터널 절연막 위에 전하 축적층으로 $SiN_x$층의 내부에 Si-NCs를 갖는 비휘발성 메모리 소자를 제작하였다. Si-NCs를 갖지 않는 $SiN_x$전하 축적층은 Si-NCs를 갖는 전하 축적층보다 더 작은 메모리 윈도우와 열화된 데이터 보존 특성을 나타내었다. 또한, Si-NCs의 크기가 감소됨에 따라 양자 구속 효과가 증가되어 느린 지우기 속도를 보였으나, 데이터 보존 특성이 크게 향상됨을 알 수 있었다. 그러므로, NFGM의 빠른 쓰기/지우기 속도와 데이터 보존 특성을 동시에 만족하기 위해서는 Si-NCs의 크기 조절이 매우 중요하며, NCs크기의 최적화를 통하여 고집적/고성능의 차세대 비휘발성 메모리에 적용될 수 있을 것이라 판단된다.