• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.251-254
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• 2001

In this paper, we analyzed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC 600[V] wire. Messurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflaming pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds genalated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of $2.5{\pm}0.04[w/cm^{2}]$ for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 25.2 to 37.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomplete combustion of FR-PVC which has high content of carbon in compound.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.74-81
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• 2002

Recently tube hydroforming has been widely applied to the automotive industries due to its several advantages over conventional methods. In this paper, attention is paid to comparison of an implicit and an explicit finite element method widely used for numerical simulation of a hydroforming process. For an explicit FEM, a huge amount of computational time is required because of the very small time increment to solve a quasi-static problem. Hence, when an explicit FEM is used fDr a hydroforming process, it is general to convert the real problem to a virtual problem with a different processing time and mass density by appropriate scaling factor. However it is difficult to figure out how large the scaling should be adopted enough to ignore the dynamic effects and maintain the desired accuracy. In this paper, the comparison of the results obtained from both methods focus on the accuracy of the predicted geometrical shape and the stress with various scaling factors which are applied to analyze hydroforming process of an automobile lower arm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1609-1620
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• 1993

A Study on the trombe wall system, a kind of passive solar systems, has been performed numerically. The system is treated as a two-dimensional steady turbulent natural convection including constant heat source per unit area. The numerical code, "PHOENICS, " was employed to analyze this conduction-convection conjugated heat transfer. The general mode of the flow field was examined, and the exchange of mass between two recirculating flows is found to be the major mechanism of the heat transfer. It is shown that the performance is affected by the changes in the geometrical factors-the thickness of the wall, the width between the windowand the wall, and size of the vents. Further analysis has been performed to show the optimal geometry with regard to the last two factors.o factors.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.50-59
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• 2010

In this paper, two kind of free-form progressive addition lenses (PALs) were designed with Zernike polynomial surface and anatomically accurate finite presbyopic schematic eyes which have aspheric cornea, aspheric GRIN crystalline lens, aspheric retina, and Gaussian apodization factor. Geometrical and diffraction MTFs were used for the optimization process in sequence. 5th orders of Zernike polynomials were used for the evaluation of progression zones of the two examples. The target MTF was set as 0.22 at 100 lp/mm which satisfies the standard visual resolution. These examples were fabricated with a CNC diamond turning machine controlled by slow tool servo (STS). After polishing process, the wavefront aberrations were measured with a laser interferometer on the ten test points across the progression zones and then compared with three current commercially available PALs on the optical performance. Astigmatic aberrations of the examples are very lower than the three selected PALs and have more increased stabilized progressive intermediate zones and near zones. It is expected to give better clear and comfortable distance, intermediate and near visions than other conventional PALs and to improve the adaptability of presbyopic patients to PALs.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.98-104
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• 2001

A dynamic fracture toughness test method with a chevron notched ceramic specimens is proposed. The notch angles of the chevron specimens were 90, 100$^{\circ}$and 110$^{\circ}$. Finite element analysis(FEA) were done to determine the geometrical properties of chevron-notch specimens according to notch angles. The static fracture toughness of the chevron notched alumina specimen was 3.8MP$\alpha$√m similar to that of the general fracture specimen with a precrack. Dynamic fracture toughness was 4.5 MP$\alpha$√m slightly higher than the static one. These research showed the possibility of the split Hopkinson pressure bar test method using the newly proposed chevron notched specimens to get the dynamic fracture toughness of extremely brittle materials such as ceramics.

• Journal of Biosystems Engineering
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• v.37 no.2
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• pp.90-99
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• 2012

Purpose: This study was conducted to investigate the optimal sorting factors in establishing an efficient sorting technology for brown rice. Methods: The brown rice varieties used in this study were Il Pum, Chu Cheong, Dong Jin, Un Gwang, Nam Pyeong, and Dae An. These were classified into whole grain, unriped grain, and green dead rice. The shape factors were analyzed based on length, width and thickness of the grains. Results: The results revealed that the maximum length among whole grain, unriped grain, and green dead rice was observed in Dae An variety while Chu Cheong variety showed the minimum. Further more, Il Pum brown rice showed the maximum width while Dong Jin variety showed the minimum. In the case of thickness, the maximum was observed in Un Gwang variety and that of the minimum among Nam Pyeong variety for both whole grain and unriped grain. Conclusions: The length and width can be used as determinants in sorting factors of whole grain and green dead rice, and the thickness can be considered as optimum sorting factor of whole grain and unriped grain.

• Progress in Medical Physics
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• v.13 no.4
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• pp.234-241
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• 2002

The depth electrode technique, especially using the occipito-temporal route is widely used in the clinic, since it is known to be the most precise method about the invasive study of the mesial temporal lobe epilepsy. The depth electrode with the occipito-temporal route has been applied with manual calculation of MR images. Inherently there are some factor causing significant errors due to geometrical axis alignment, such as miss alignment of horizontal or vertical cutting line. In order to correct it in manually, it takes a long time. In this study, authors has developed the software for automate calculation of MRI wording for instance calculation and for the no time delaying operation. Authors could show that this software is useful for the clinic after applying if for 33 cases of the patients.

• Journal of the Korean Solar Energy Society
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• v.25 no.2
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• pp.27-33
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• 2005

To improve the performance of the top-positioning space in buildings, we suggested the environment-friendly system integrating various design techniques in the previous paper. This work discussed to calculate the length of PV considering a part of metallic radiators for radiative cooling, an critical element of the whole system, for shading not to prevent the PV on roof from generating electricity. In the process of calculating the shading area, we used the geometrical relationship between the sun-rays and the variable roof. For general applications, we utilized DL, the ratio of the length of PV and that of metallic radiator on roof, as a design factor, and then used the maximum insolation and the specific insolation($200W/m^2$) to decide the distance off the axis of rotation. As a result, for DL, we found out the reasonable value of 1.0 with full covering, 1.2 with 90%, and 2.0 with 70% in PV covering.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.277-286
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• 2013

Cross-shore sediment transport is very important factor in the design of coastal structures, and the beach profile is mainly affected by a number of parameters, such as wave height and period, beach slope, and the material properties of the bed. In this study cross-shore sediment movement was investigated using a physical model and various offshore bar geometric parameters were determined by the resultant erosion profile. The experiments on cross- shore sediment transport carried out in a laboratory wave channel for initial base slopes of 1/8, 1/10 and 1/15. Using the regular waves with different deep-water wave steepness generated by a pedal-type wave generator, the geometrical of sediment transport rate and considerable characteristics of beach profiles under storm conditions and bar parameters affecting on-off shore sediment transport are investigated for the beach materials with the medium diameter of $d_{50}$=0.25, 0.32, 0.45, 0.62 and 0.80 mm. Non-dimensional equations were obtained by using linear and non-linear regression methods through the experimental data and were compared with previously developed equations in the literature. The results have shown that the experimental data fitted well to the proposed equations with respect to the previously developed equations.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.4
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• pp.255-261
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• 2005

With the advent of sub-90nm technologies, the system-on-chip (SoC) and system-in-package (SiP) are becoming the trend in delivering low-cost, low-power, and small-form-factor consumer electronic systems running at multiple GHz. The shortened transistor channel length reduces the transistor switching cycles to the range of several picoseconds, yet the time-of-flights of the critical on-chip and off-chip interconnects are in the range of 10 picoseconds for 1.5mm-long wires and 100 picoseconds for 15mm-long wires. Designers realize the bottleneck today often lies at chip-to-chip interconnects and the industry needs a good model to compute the inductance in these parts of circuits. In this paper we propose a new method for extracting accurate equivalent inductance circuit models for SPICE-level circuit simulations of system-on-chip (SoC) and system-in-package (SiP) designs. In our method, geometrical meshes are created and numerical methods are used to find the solutions for the electromagnetic fields over the fine meshes. In this way, multiple-GHz SoC and SiP designers can use accurate inductance modeling and interconnect optimization to achieve high yields.