• Nuclear Engineering and Technology
• /
• 제30권5호
• /
• pp.416-423
• /
• 1998

Many studies for the perforated plates have been done, especially on the subject of static behavior and stress distribution in the plate. Equivalent elastic properties are one of the successive concepts for this problem. However little effort was taken to get their dynamic characteristics. In this paper finite element modal analysis was performed for the perforated plates having square and triangular hole patterns. An attempt to use existing equivalent elastic properties into the modal analysis of the plate was carried out. To verify feasibility of the finite element models, modal test was also performed on one typical perforated plate. System parameters such as natural frequencies and mode shapes were extracted and compared with the analysis results.

• 대한조선학회논문집
• /
• 제43권6호
• /
• pp.683-692
• /
• 2006

The BEM, known as solving boundary value problems, could have some advantages In solving domain problems which are mostly solved by FEM and FDM. Lately, in the elastic-plastic nonlinear problems, BEM could provide the subdomain approach for the region where the plastic deformation could occur and the unknown nodal displacement of this region are added as the unknown of the boundary integral equation for this approach. In this paper, initial stress method was used to establish the formulation of such BEM approach. And a simple rectangular plate having a circular hole was analyzed to verify the suggested method and the result is compared with that from FEM. It is shown that the result of two methods are showing similar stress-strain curves at the root of perforated plate and furthermore the plastic deformation obtained by BEM shows more reasonable behavior than that of FEM.

• 정보보호학회논문지
• /
• 제25권3호
• /
• pp.559-565
• /
• 2015

USB 메모리에 의한 정보유출 악성코드 유입 등에 대한 방어를 위해 다양한 복사방지 장치제어와 같은 보안기술들이 지속적으로 연구 개발 되고 있다. 하지만, 지난 2014년 Black Hat Security Conference에서 USB의 새로운 취약성으로 제시된 BadUSB에 대해서는 치명적 보안결함으로 인식되고 있음에도 불구하고 대응책이 미흡한 실정이다. 이를 개선하기 위해, BadUSB로 인한 취약성을 대상으로, 기술적 제도적 관리적 측면의 대응방안을 제시하고자 한다.

• 한국전기전자재료학회논문지
• /
• 제17권2호
• /
• pp.212-216
• /
• 2004

In this paper, we have fabricated a triode field emitter using carbon nanotubes (CNTs) directly grown by thermal chemical vapor deposition(CVD) method as an electron omission source. Vertically aligned CNTs have been grown in the center of the gate hole, to the size of 1.5 ${\mu}{\textrm}{m}$ in diameter, with help of a sacrificial layer of a type generally used in metal tip process. By the method of tilling the substrate, we made CNTs emitters both with and without SiO$_2$layer, a sidewall protector, deposited on sidewall of gate. After that we researched the electrical characteristics about two types of emitters. In effect, a sidewall protector can enhance the electrical characteristics by suppressing the problem of short circuits between the gate and the CNTs. The leakage current of an emitter with a sidewall protector is approximately sevenfold lower than that of an emitter without it at a gate voltage of 100 V.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 추계학술발표대회 논문집
• /
• pp.147-152
• /
• 2000

This paper presents the thermoelastic analysis and 3-D failure analysis of the carbon/carbon brake disk. The mechanical properties of the carbon/carbon brake disk were measured for both in-plane and out of plane directions. The mechanical properties were used as the input of the thermoelastic analysis and 3-D stress analysis for the brake disk. The gap between rotor clip and clip retainer was an important parameter in the loading transfer mechanism of the rotor. The change of gap was considered separating the mechanical deformation and thermal deformation. Because the rotor clip and clip retainers were not contacted, the clip retainers and rivets were excluded from the rotor analysis model. The disk was modeled by using the cyclic symmetry condition and the contact problem between the rotor disk and rotor clip was considered. From the results of the 3-D stress analysis, the stress concentration at the key hole of the brake disk was confirmed.

• 한국기계가공학회지
• /
• 제5권4호
• /
• pp.79-85
• /
• 2006

Multi-filament hydrostatic extrusion was developed as a fine wire manufacturing process and wire forming experiments were conducted. Also, single wire stretch forming process was proposed in the possibility of obtaining long wire with constant cross-section. In the multi filament extrusion since the workpiece, die and forming facility are in the macro forming circumstance, fine wire and fine hole structure with less than a few micrometer can be easily obtained. Although stretch forming does not use a die in order to avoid the friction problem between the workpiece and the die, it is necessary to have high level of technology to maintain cross-sectional shape and measure in longitudinal direction.

• 설비공학논문집
• /
• 제12권2호
• /
• pp.181-189
• /
• 2000

The scroll compressor used for heat pump has a wide range of operation condition. To cover both heating and cooling modes, the operating Pressure ratio ranges from 1.5 to 6.8. Since the scroll compressor, however, is a type of compressor whose pressure ratio is fixed, some loss in the compression work is caused by the operation at the pressure ratio different from the built-in pressure ratio. A way of avoiding this problem is to introduce by-Pass holes in compression chambers, so that the compressed gas of pressure higher than the discharge pressure, yet not reached to the discharge port can be released earlier through the by-Pass holes. In this paper, an optimum Positioning of the by-Pass hole and the effect of the by-pass valve on the compressor performance are studied.

• 반도체디스플레이기술학회지
• /
• 제3권3호
• /
• pp.5-9
• /
• 2004

A new wafer level packaging scheme is presented as an alternative to MEMS package. The proof-of-concept structure is fabricated and evaluated to confirm the feasibility of the idea for MEMS wafer level packaging. The scheme of this work is developed using an electroplated tin (Sn) solder. The critical difference over conventional ones is that wafers are laterally bonded by solder reflow after LEGO-like assembly. This lateral bonding scheme has merits basically in morphological insensitivity and its better bonding strength over conventional ones and also enables not only the hermetic sealing but also its electrical interconnection solving an open-circuit problem by notching through via-hole. The bonding strength of the lateral bonding is over 30 Mpa as evaluated under shear and the hermeticity of the encapsulation is 2.0$\times10^{-9}$mbar.$l$/sec as examined by pressurized Helium leak rate. Results show that the new scheme is feasible and could be an alternative method for high yield wafer level packaging.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 B
• /
• pp.702-704
• /
• 2003

In this paper, analysis of bobbin probe signal in steam generator tube with bulge defect on CE system 80 nuclear power plant is represented. The CE system 80 steam generator is adopted in ULJIN-4 nuclear power plant. From Maxwell's equation, the electromagnetic governing equation for eddy current problem is derived and by performing the finite element formulation the 3-dimensional finite element code with brick element is developed. For the ease of the comparison the numerical results with experimental ones, the calculated signals are adjusted by using the ASME standard 100[%] through hole signal. For analysis of the effect of variation of the bulge depth on the impedance signal 0.2[mm] and 0.4[mm] depth of bulge defect signals are calculated and analyzed. As the depth of the bulge defect is increased, the magnitude of the signal is increased, too. But the rate of the increment of the signal is less than that of the depth of defect. From the result of this paper, we can obtained the information of the effect of bulge defect on the impedance signal.

• 센서학회지
• /
• 제25권6호
• /
• pp.399-405
• /
• 2016

Scent diffuser using micro-pore piezo actuator achieved a commercial success because of its cheap production cost, but it is easy to be use for IT-based contents due to difficulty of scent intensity control. To solve this problem, we control the emission amount of scent diffuser by changing amplitude and frequency of input voltage applied to micro-pore piezo actuator. And, we analyzed the effect of density of cotton core on emission amount and a relationship between hole-size of mesh in piezo actuator and viscosity of scents to design a mechanically optimal scent device.