• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.12
• /
• pp.6060-6065
• /
• 2013

Minimizing the height of the die roll is very important for maximizing the size of effective shear planes. In this study, the die roll change was investigated for the change in the amounts and clearance of the V-ring indentation. Shear analysis and experiments were conducted with the V-ring distance fixed to 2mm. Fine blanking die was applied to the die insert with different clearances. Several specimens were analyzed about the height of the die roll. As a result, the pressure of V-ring effectively inhibited the flow of materials. And the height of the die roll was lowest when the clearance between the die and punch was 1% of the material thickness.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.51 no.3
• /
• pp.134-140
• /
• 2002

Deep submicron NMOSFETs with elevated source/drain can be fabricated using self-aligned selective epitaxial growth(SEG) of silicon for enhanced device characteristics with shallow junction compared to conventional MOSFETs. Shallow junctions, especially with the heartily-doped S/D residing in the elevated layer, give hotter immunity to Yt roll off, drain-induced-barrier-lowering (DIBL), subthreshold swing (SS), punch-through, and hot carrier effects. In this paper, the characteristics of both deep submicron elevated source/drain NMOSFETs and conventional NMOSFETs were investigated by using TSUPREM-4 and MEDICI simulators, and then the results were compared. It was observed from the simulation results that deep submicron elevated S/D NMOSFETs having shallower junction depth resulted in reduced short channel effects, such as DIBL, SS, and hot carrier effects than conventional NMOSFETs. The saturation current, Idsat, of the elevated S/D NMOSFETs was higher than conventional NMOSFETs with identical device dimensions due to smaller sheet resistance in source/drain regions. However, the gate-to-drain capacitance increased in the elevated S/D MOSFETs compared with the conventional NMOSFETs because of increasing overlap area. Therefore, it is concluded that elevated S/D MOSFETs may result in better device characteristics including current drivability than conventional NMOSFETs, but there exists trade-off between device characteristics and fate-to-drain capacitance.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.2
• /
• pp.139-145
• /
• 2014

Control of threshold voltage ($V_T$) by ground-plane (GP) technique for planar tunnel field-effect transistor (TFET) is studied for the first time using TCAD simulation method. Although GP technique appears to be similarly useful for the TFET as for the metal-oxide-semiconductor field-effect transistor (MOSFET), some unique behaviors such as the small controllability under weak ground doping and dependence on the dopant polarity are also observed. For $V_T$-modulation larger than 100 mV, heavy ground doping over $1{\times}10^{20}cm^{-3}$ or back biasing scheme is preferred in case of TFETs. Polarity dependence is explained with a mechanism similar to the punch-through of MOSFETs. In spite of some minor differences, this result shows that both MOSFETs and TFETs can share common $V_T$-control scheme when these devices are co-integrated.

• Korean Journal of Human Ecology
• /
• v.18 no.2
• /
• pp.491-500
• /
• 2009

This study was carried out to investigate the preference for traditional food of university students through the analysis of their daily meal types. Questionnaires were collected from a total of 197 students from December 2007 to February 2008 in Chungnam Province. The results are as follows; 148 of the respondents (73.0%) prefer Korean traditional meal as their favorite food. The significant differences are found in both gender groups and major groups (p<.05). 178 of the respondents (90.4%) answered that the traditional foods are excellent and good. However, the foods were significantly (p<.05) evaluated that major students consider them to be 'excellent' foods, while non-major students consider them to be 'good' foods. 136 of respondents (69.0%) answered that the traditional foods have beneficial influences on their health. In the survey on intake frequency of traditional meals, 137 of respondents (65.9%) have traditional foods more than twice a day. The ratio of traditional meal intake of male students is a significantly higher level (p<.05) than that of female students. Their preference for traditional rice cake, fermented rice punch, and juice mixed with fruits is a very high level of the average of 4.19, 4.22 and 4.34, respectively. The preference for Kimchi, Bulgoki, boiled beef slices, sundae and jelly was a relatively high level of the average of 4.43, 4.65, 4.14, 4.30, and 4.05, respectively. Concludingly, the research shows the majority of students enjoy korean traditional food and expect Korean food as favorite food to be developed and to be inherited.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.1
• /
• pp.55-60
• /
• 2002

For the development of a new creep test technique, the availability of SP-Creep test is discussed for 1Cr-0.5Mo boiler header material. And some results are also compared with those of 2.25Cr- 1Mo steel which widely uses as boiler superheater tube. The results can be summarized as follows. The load exponents(n) obtained by SP-Creep test for 1Cr-0.5Mo steel are decreased with increasing creep temperature and the values are 15.67, 13.89, and 17.13 at 550$^{circ}C$ ,575$^{circ}C$ and 600$^{circ}C$, respectively. The temperature dependence of the load exponent is given by n = 107.19 - 0.1108T. This reason that load exponents show the extensive range of 10∼16 is attributed to the fine carbide such as M$_{23}$C$_{6}$ in lath tempered martensitic structures. At the same creep condition, the secondary creep rate of 1Cr-0.5Mo steel is lower than the 2.25Cr-1Mo steel1 due to the strengthening microstructure composed by normalizing and tempering treatments. Through a SEM observation, it can be summarized that the primary, secondary, and tertiary creep regions of SP-Creep specimen are corresponding to plastic bending, plastic membrane stretching, and plastic instability regions among the deformation behavior of four steps in SP test, respectively.y.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.10
• /
• pp.438-442
• /
• 2005

Si nanocrystal (Si NC) memory device has several advantages such as better retention, lower operating voltage, reduced punch-through and consequently a smaller cell area, suppressed leakage current. However, the physical and electrical reasons for this behavior are not completely understood but could be related to interface states of Si NCs. In order to find out this effect, we characterized electrical properties of Si NCs embedded in a SiO$_{2}$ layer by scanning probe microscopy (SPM). The Si NCs were generated by the laser ablation method with compressed Si powder and followed by a sharpening oxidation. In this step Si NCs are capped with a thin oxide layer with the thickness of 1$\~$2 nm for isolation and the size control. The size of 51 NCs is in the range of 10$\~$50 m and the density around 10$^{11}$/cm$^{2}$ It also affects the interface states of Si NCs, resulting in the change of electrical properties. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift due to the trapped charges were monitored. The results were compared with C-V characteristics of the conventional MOS capacitor structure.

• Journal of Ocean Engineering and Technology
• /
• v.29 no.2
• /
• pp.175-185
• /
• 2015

Jack-up type WTIV(Wind Turbine Installation Vessel) is used to avoid the effects of waves when installing wind turbines in the Southwest Sea of South Korea. During the preloading procedure, unexpected penetration may cause some risks such as excessive penetration or punch-through failure. To ensure the safety of the WTIV during preloading, the bearing capacities should be evaluated based on the soil data at each borehole. Eight boreholes (OW-1 to -8) have been drilled in the Southwest Sea of South Korea. The bearing capacities of a spudcan designed to be used in this district are calculated using both a conventional analysis and finite element analysis with the soil properties of OW-1 to -8. A finite element analysis is carried out for OW-1, -3, and -4 to gain an in-depth understanding of the soil behavior during the penetration. OW-1, -3, and -4 are representative boreholes for a strong layer overlying a soft layer, a general soft layer, and a soft layer overlying a strong layer, respectively. The resultant bearing capacity curves versus the depth of the numerical analysis are compared with the conventional method. The results show that the conventional analysis is conservative. Case studies for different spudcan areas and shapes are also conducted to seek an appropriate spudcan type for the Southwest Sea of South Korea. Finally, a spudcan with a rectangular shape and a bearing area of $112.8m^2$ is selected.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.6
• /
• pp.3667-3671
• /
• 2015

Through experiment that does not cause wrinkles in the forming process for the primary purpose for install PCB(Printed circuit board) the thickness variation of the material was investigated. Experimental results was showed that the forming height of the first process had Influence Material thickness variation in the second process, in the first process, the Entrance corner of the die must have round of the product height of 50%, and The height of forming should be as high as the thickness of the material than the original forming. Also as do implement the forming shape in the first process, the thickness of the material is thinned to 85%, Restriking in the second process was that The thickness of the material is thinned to 80%. Therefore, In order to implement a precise shape, Thinking that the material thinning, The die was maintain the shape of the original product, and It was obtain the effect of the compression that the punch is to be longer, as the sum of more than 20% of the material thickness in the depth of the original product.

• Archives of Plastic Surgery
• /
• v.36 no.5
• /
• pp.519-524
• /
• 2009

Purpose: This study was conducted to establish the most effective method of cell therapy by comparing and analyzing the level of wound healing after various cell delivery methods. Methods: Human mesenchymal stem cells were administered using 5 different methods on full thickness skin defects which were deliberately created on the back of 4 - week old mice using a 8 mm punch. Different modes of administration, cell suspension, local injection, collagen GAG matrix seeding, fibrin, and hydrogel mix methods were used. In each experiment group, $4{\times}105$ mesenchymal stem cells were administered according to 5 deferent methods, and were not for the corresponding control group. Results: The wound healing rate was fastest in the local injection group. The wound healing rate was relatively slow in the collagen matrix group, however, the number of blood vessels or VEGF increased most in this group. Conclusion: For rapid wound healing through wound contraction, it is advantageous to administer MSC by the local injection method. For the healing process of a wide area, such as a burn, the seeding of cells to collagen matrix is thought to be effective.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.1
• /
• pp.67-75
• /
• 2013

The flow stress of zircaloy-4 used in the spacer grid supporting a nuclear fuel rod was determined by the Johnson-Cook model, and model parameters were determined using reverse engineering. Parameters such as A, B, n and $\dot{\varepsilon}_0$ were determined by the tensile test result. To obtain the parameters C and m, a slot milling test and numerical simulation were performed. The objective functions were defined as the difference between the experimental and the simulation results, and then, the parameters were determined by minimizing the objective function. To verify the validity of the determined parameters, cross-verification for each case was conducted through a shearing test and simulation. The results tend to show agreement with the experimental results, such as the features of sheared edges and maximum punch force, with the correlation coefficients exceeding at least 0.97.