• Journal of Korean Society of Disaster and Security
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• v.16 no.3
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• pp.17-26
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• 2023

Prestressed Concrete (PSC) girders are divided into pre- and post-tension types as prestressing method, and I- and U-type as cross-sectional shape. There are both advantages and disadvantages depending on each prestressing method and cross-sectional shape, and each method is applied to bridge construction sites. In this study, a new girder design was attempted to develop that overcomes its shortcomings by using the pretension method and U-type cross sectional shape. Its structural performance was verified in this study. Pretension type girders are mainly manufactured in factories because they require a reaction arm and related facilities, and have the disadvantage of being limited in weight and span length for road transportation. In addition, in the case of the U-type cross-section, structural stability is very reliable during construction against overturning, but its own weight is relatively large comparing to I-type, and the post-tension method is mainly applied after on-site production. In this study, a PSC girder manufacturing method using the field pretension was proposed and a span length of 40 m real-scale test specimen was manufactured and verified its structural performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1C
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• pp.102-110
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• 2004

In this paper, we propose a VLSI structure of real-time image compression and reconstruction processor using 2-D discrete wavelet transform and implement into a hardware which use minimal hardware resource using ASIC library. In the implemented hardware, Data path part consists of the DWT kernel for the wavelet transform and inverse transform, quantizer/dequantizer, the huffman encoder/huffman decoder, the adder/buffer for the inverse wavelet transform, and the interface modules for input/output. Control part consists of the programming register, the controller which decodes the instructions and generates the control signals, and the status register for indicating the internal state into the external of circuit. According to the programming condition, the designed circuit has the various selective output formats which are wavelet coefficient, quantization coefficient or index, and Huffman code in image compression mode, and Huffman decoding result, reconstructed quantization coefficient, and reconstructed wavelet coefficient in image reconstructed mode. The programming register has 16 stages and one instruction can be used for a horizontal(or vertical) filtering in a level. Since each register automatically operated in the right order, 4-level discrete wavelet transform can be executed by a programming. We synthesized the designed circuit with synthesis library of Hynix 0.35um CMOS fabrication using the synthesis tool, Synopsys and extracted the gate-level netlist. From the netlist, timing information was extracted using Vela tool. We executed the timing simulation with the extracted netlist and timing information using NC-Verilog tool. Also PNR and layout process was executed using Apollo tool. The Implemented hardware has about 50,000 gate sizes and stably operates in 80MHz clock frequency.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.489-500
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• 2004

Statement of problem: The use of zirconia prostheses fabricated with CAD/CAM system is on an increasing trend in dentistry. However, evaluation of the fit related to internal relief and marginal reproducibility of zirconia has not been reported. Purpose : This study was to evaluate the fit related to internal relief and marginal reproducibility of zirconia core fabricated with CAD/CAM system. Materials and methods: The evaluation was based on 30 zirconia cores and 5 IPS-Empress2 cores. Zirconia cores were fabricated in different conditions of internal relief(0, 10, 20, 30, 40 and $50{\mu}m$), and IPS-Empress2 cores were fabricated in accordance with the manufacturer's instructions. Before cementation, the marginal discrepancies or cores were measured on metal die. And then, each core was cemented to stone die, embedded in an acrylic resin and sectioned in two planes(mesiodistally and labiopalatally). The internal gaps were measured at the margin and axial surface. Measurements for the marginal discrepancies, the internal marginal gaps and the internal axial gaps were performed under a measuring microscope(Compact measuring microscope STM5; Olympus, Japan) at a magnification of ${\times}100$. In addition, the marginal conagurations of metal die, zirconia core and IPS-Empress2 core were examined with SEM(S-2700, Hitachi, Japan). Results : Within the limits of this study the results were as follows. 1. Compared with IPS-Empress2 cores, the marginal discrepancies of zirconia cores had no significant differences. the internal marginal gaps were statistically smaller and the internal axial gaps were statistically larger in each condition of internal relief. 2. The marginal discrepancies and the internal marginal gaps of zirconia cores had no significant differences related to the conditions of internal relief(P>0.05). 3. The internal axial gaps of zirconia cores with $0{\sim}20{\mu}$m for internal relief were significantly larger than that with $50{\mu}m$ (P<(0.0001). 4. SEM micrographs showed favorable marginal reproducibility of zirconia core and smooth texture on the milling surface. Conclusion: The marginal discrepancy and the internal gaps of zirconia core were clinically acceptable and the milling surface was showed smooth texture. For fabrication of the durable esthetic restoration, further investigations on complex design of core, milling accuracy, compatability of enamel porcelain and porcelain firing seems to be needed.

• Journal of radiological science and technology
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• v.42 no.6
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• pp.447-454
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• 2019

In order to improve and supplement the shielding method for electron beam treatment, we designed a patient-specific shielding method using a 3D printer, and evaluated the usefulness by comparing and analyzing the distribution of electron beam doses to adjacent organs. In order to treat 5 cm sized superficial tumors around the lens, a CT Simulator was used to scan the Alderson Rando phantom and the DICOM file was converted into an STL file. The converted STL file was used to design a patient-specific shield and mold that matched the body surface contour of the treatment site. The thickness of the shield was 1 cm and 1.5 cm, and the mold was printed using a 3D printer, and the patient customized shielding block (PCSB) was fabricated with a cerrobend alloy with a thickness of 1 cm and 1.5 cm. The dosimetry was performed by attaching an EBT3 film on the surface of the Alderson Rando phantom eyelid and measuring the dose of 6, 9, and 12 MeV electron beams on the film using four shielding methods. Shielding rates were 83.89%, 87.14%, 87.39% at 6, 9, and 12 MeV without shielding, 1 cm (92.04%, 87.48%, 86.49%), 1.5 cm (91.13%, 91.88% with PSCB), 92.66%) The shielding rate was measured as 1 cm (90.7%, 92.23%, 88.08%) and 1.5 cm (88.31%, 90.66%, 91.81%) when the shielding block and the patient-specific shield were used together. PCSB fabrication improves shielding efficiency over conventional shielding methods. Therefore, PSCB may be useful for clinical application.

• Journal of Dental Rehabilitation and Applied Science
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• v.40 no.2
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• pp.72-81
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• 2024

Purpose: This study aimed to assess the marginal and internal fit of 3-unit monolithic zirconia fixed partial dentures (FPDs) fabricated via computer-aided design and computer-aided manufacturing (CAD/CAM) from solid working casts and removable die system. Materials and Methods: The tooth preparation protocol for a zirconia crown was executed on the mandibular right first premolar and mandibular right first molar, with the creation of a reference cast featuring an absent mandibular right second premolar. The reference cast was duplicated using polyvinyl siloxane impression, from which 20 working casts were fabricated following typical dental laboratory procedures. For comparative analysis, 10 FPDs were produced from a removable die system (RD group) and the remaining 10 FPDs from the solid working casts (S group). The casts were digitized using a dental desktop scanner to establish virtual casts and design the FPDs using CAD. The definitive 3-unit monolithic zirconia FPDs were fabricated via a CAM milling process. The seated FPDs on the reference cast underwent digital evaluation for marginal and internal fit. The Mann-Whitney U test was applied for statistical comparison between the two groups (α = 0.05). Results: The RD group showed significantly higher discrepancies in fit for both premolars and molars compared to the S group (P < 0.05), particularly in terms of marginal and occlusal gaps. Color mapping also highlighted more significant deviations in the RD group, especially in the marginal and occlusal regions. Conclusion: The study found that the discrepancies in marginal and occlusal fits of 3-unit monolithic zirconia FPDs were primarily associated with those fabricated using the removable die system. This indicates the significant impact of the fabrication method on the accuracy of FPDs.

• Archives of Plastic Surgery
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• v.33 no.5
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• pp.612-615
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• 2006

Purpose: An ideal bony construct can be divided into two broad categories: (1) the design and fabrication of biodegradable, biomimetic scaffolds that provide correct signals to induce osteogenesis: (2) the identification of an ideal source of osteoprogenitor cells to seed onto the scaffold. We selected poly-glycolic acid as a synthetic scaffold among various scaffolds because of these properties. Meanwhile, culture medium is supplemented with fetal bovine serum(FBS): such serum contains essential elements such as proteins, hormones, growth factors and trace minerals. The composition of FBS can be ideal for various cell growth in vitro. We supposed that we could enhance bone growth at a fractured site if FBS was mixed with synthetic scaffold-PGA. Methods: We cultured human osteoblasts in five different prepared culture dishes made with FBS and PGA mixture. The mixtures contained different ratio of FBS, that is, 0, 1.5, 3, 7, and 10%. We cultured human osteoblasts for seven days and examined the growth and attachment of the cells at the 1st, 3rd, 5th, 7th days, respectively. Results: In the mixture of 0% FBS and PGA, the growth of the cells lasted for one day. In 1.5 and 3% FBS and PGA, the growth of the cells was examined at the 3rd day, then minimally declined at the 5th and 7th days. In 7% FBS and PGA, the growth of the cells lasted for 5 days, then declined at the 7th day. In 10% FBS and PGA, the growth of the cells lasted for 5 days, then declined at the 7th day. Staining status of the osteoblasts with alkaline phosphatase showed pale pink color in 0% FBS and PGA groups, but bright pink color in 1.5, 3, 7, 10% FBS and PGA groups, especially in 3%, 7%. Conclusion: In consequence, the growth of human osteoblast was higher in the mixture of FBS and PGA groups than in pure PGA ones. It is assumed that the mixture of FBS and PGA affects the proliferation of human osteoblasts.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.153-160
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• 2010

We modified the optical system of 500 mm wide-field telescope of which point spread function showed an irregularity. The telescope has been operated for Near Earth Space Survey (NESS) located at Siding Spring Observatory (SSO) in Australia, and the optical system was brought back to Korea in January 2008. After performing a numerical simulation with the tested value of surface figure error of the primary mirror using optical design program, we found that the surface figure error of the mirror should be fabricated less than root mean square (RMS) $\lambda$/10 in order to obtain a stellar full width at half maximum (FWHM) below $28\;{\mu}m$. However, we started to figure the mirror for the target value of RMS $\lambda$/20, because system surface figure error would be increased by the error induced by the optical axis adjustment, mirror cell installation, and others. The radius of curvature of the primary mirror was 1,946 mm after the correction. Its measured surface figure error was less than RMS $\lambda$/20 on the table of polishing machine, and RMS $\lambda$/15 after installation in the primary mirror cell. A test observation performed at Daeduk Observatory at Korea Astronomy and Space Science Institute by utilizing the exiting mount, and resulted in $39.8\;{\mu}m$ of stellar FWHM. It was larger than the value from numerical simulation, and showed wing-shaped stellar image. It turned out that the measured-curvature of the secondary mirror, 1,820 mm, was not the same as the designed one, 1,795.977 mm. We fabricated the secondary mirror to the designed value, and finally obtained a stellar FWHM of $27\;{\mu}m$ after re-installation of the optical system into SSO NESS Observatory in Australia.

• Macromolecular Research
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• v.11 no.4
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• pp.207-223
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• 2003

For last five years, we are developing the novel local drug delivery devices using biodegradable polymers, especially polylactide (PLA) and poly(D,L-lactide-co-glycolide) (PLGA) due to its relatively good biocompatibility, easily controlled biodegradability, good processability and only FDA approved synthetic degradable polymers. The relationship between various kinds of drug [water soluble small molecule drugs: gentamicin sulfate (GS), fentanyl citrate (FC), BCNU, azidothymidine (AZT), pamidronate (ADP), $1,25(OH)_2$ vitamin $D_3$, water insoluble small molecule drugs: fentanyl, ipriflavone (IP) and nifedipine, and water soluble large peptide molecule drug: nerve growth factor (NGF), and Japanese encephalitis virus (JEV)], different types of geometrical devices [microspheres (MSs), microcapsule, nanoparticle, wafers, pellet, beads, multiple-layered beads, implants, fiber, scaffolds, and films], and pharmacological activity are proposed and discussed for the application of pharmaceutics and tissue engineering. Also, local drug delivery devices proposed in this work are introduced in view of preparation method, drug release behavior, biocompatibility, pharmacological effect, and animal studies. In conclusion, we can control the drug release profiles varying with the preparation, formulation and geometrical parameters. Moreover, any types of drug were successfully applicable to achieve linear sustained release from short period ($1{\sim}3$ days) to long period (over 2 months). It is very important to design a suitable formulation for the wanting period of bioactive molecules loaded in biodegradable polymers for the local delivery of drug. The drug release is affected by many factors such as hydrophilicity of drug, electric charge of drug, drug loading amount, polymer molecular weight, the monomer composition, the size of implants, the applied fabrication techniques, and so on. It is well known that the commercialization of new drug needs a lot of cost of money (average: over 10 million US dollar per one drug) and time (average: above 9 years) whereas the development of DDS and high effective generic drug might be need relatively low investment with a short time period. Also, one core technology of DDS can be applicable to many drugs for the market needs. From these reasons, the DDS research on potent generic drugs might be suitable for less risk and high return.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1233-1237
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• 2011

Insertion loss, ripple, and return loss were -1.7093dB, 0.9162dB, and -24.762dB with Cellular Rx(824~849 MHz), -1.8021dB, 0.9615dB, and -22.258 with Tx(869~894 MHz), repectively. On the other hand, insertion loss, ripple, and return loss were -2.0149dB, 1.5163dB, and -34.046 dB with DCS Rx(1710~1785 MHz), -1.5894dB, 2.3742dB, and -33.058dB with Tx(1805~1880 MHz), respectively. In the particular, the attenuations in 5MHz edge of band width were -9.1399dB and -14.336dB with Cellular Rx, -7.0343dB and -5.2943dB with Cellualr Tx, respectively. The attenuations of DCS Rx from the relative Tx were -58.298dB and -65.644dB, respectively. On the other hand, those of DCS Tx from the relative Rx were -70.659dB and -50.488dB, respectively. From the aboved results, the dielectric filters for Celluar and DCS band with Isolator showed the good skirt and ripple characterics.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.65-74
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• 2013

The through-silicon via (TSV) technology is essential for 3-dimensional integrated packaging. TSV technology, however, is still facing several reliability issues including interfacial delamination, crack generation and Cu protrusion. These reliability issues are attributed to themo-mechanical stress mainly caused by a large CTE mismatch between Cu via and surrounding Si. In this study, the thermo-mechanical reliability of copper TSV technology is investigated using numerical analysis. Finite element analysis (FEA) was conducted to analyze three dimensional distribution of the thermal stress and strain near the TSV and the silicon wafer. Several parametric studies were conducted, including the effect of via diameter, via-to-via spacing, and via density on TSV stress. In addition, effects of annealing temperature and via size on Cu protrusion were analyzed. To improve the reliability of the Cu TSV, small diameter via and less via density with proper via-to-via spacing were desirable. To reduce Cu protrusion, smaller via and lower fabrication temperature were recommended. These simulation results will help to understand the thermo-mechanical reliability issues, and provide the design guideline of TSV structure.