• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.57-65
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• 2011

Numerical simulations by three-dimensional Particle Flow Code($PFC^{3D}$, Itasca) considering distinct element method (DEM) were carried out for prediction of triaxial compression test with sand material. The effect of scale conditions for numerical model and distinct material on final prediction results was analyzed by numerical models under various scale conditions, and following observations were made from the numerical experiments. It is very useful to model the initial material condition without any porosity conversion from 2-D to 3-D DEM. Numerical experiments have shown that in all cases considered, 3D distinct element modeling could provide good agreement on stress-strain behavior, volume change and strength properties with laboratory testing results. It was important thing to assess reasonable scale ratio of numerical model and distinct elements for saving calculation time and securing calculation efficiency under condition with accuracy and appropriateness as numerical laboratory. As results of DEM simulations under various scale conditions, most of results show that shear strength properties as cohesion and internal friction angle are similar in condition of $D_{mod}/D_{gmax}$ < 10. It shows that 3-D distinct element method could be used as efficient tool to assess strength properties by numerical laboratory technique.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.1
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• pp.19-30
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• 2012

For digital data compression, the quantization is the main part of the lossy source coding. In order to improve the performance of quantization, the vector quantizer(VQ) can be employed. The encoding complexity, however, exponentially increases as the vector dimension or bit rate gets large. Much research has been conducted to alleviate such problems of VQ. Especially for high bit rates, a constrained VQ, which is called the sample-adaptive product quantizer(SAPQ), has been proposed for reducing the hugh encoding complexity of regular VQs. SAPQ has very similar structure as to the product VQ(PQ). However, the quantizer performance can be better than the PQ case. Further, the encoding complexity and the memory requirement for the codebooks are lower than the regular full-search VQ case. Among SAPQs, 1-SAPQ has a simple quantizer structure, where each product codebook is symmetric with respect to the diagonal line in the underlying vector space. It is known that 1-SAPQ shows a good performance for i.i.d. sources. In this paper, a study on designing 1-SAPQ for the first-order Markov process. For an efficient design of 1-SAPQ, an algorithm for the initial codebook is proposed, and through the numerical analysis it is shown that 1-SAPQ shows better quantizer distortion than the VQ case, of which encoding complexity is similar to that of 1-SAPQ, and shows distortions, which are close to that of the DPCM(differential pulse coded modulation) scheme with the Lloyd-Max quantizer.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.259-276
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• 2006

In rock mass subject to high in-situ stresses, the failure process of rock is dominated by the stress-induced fractures growing parallel to the excavation boundary. When the ratio of in situ stresses compared to rock strength is greater than a certain value, progressive brittle failure which is characterized by popping and spatting of rock debris occurs due to stress concentration. Traditional constitutive model like Mohr-Coulomb usually assume that the normal stress dependent frictional strength component and the cohesion strength component are constant, therefore modelling progressive brittle failure will be very difficult. In this study, a series of numerical analyses were conducted for surrounding rock mass near crude oil storage cavern using CW-FS model which was known to be efficient for modelling brittle failure and the results were compared with those of linear Mohr-Coulomb model. Further analyses were performed by varying plastic shear strain limits on cohesion and internal friction angle to find the proper values which yield the matching result with the observed failure in the oil storage caverns. The obtained results showed that CW-FS model could be a proper method to characterize essential behavior of progressive brittle failure in competent rock mass.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.3
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• pp.171-174
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• 2022

Cosmetic packing materials tend to be difficult to recycle when discarded due to the cosmetic industry's pursuit of aesthetics, functionality, and high value-added design. Pump packaging, which is widely used for the good preservation and discharge of cosmetics contents, is difficult to be separated and recycled because of a metal spring, which is in charge of pump resilience. In this study, a polypropylene spring was developed to replace the existing metal spring to improve the recyclability of the pump packaging for cosmetics, and was uni-materialized by applying to the cosmetic packing materials with 0.2 ml of discharge amount. In addition, performance test was conducted to verify the equivalence with the existing metal spring pumps as grounds for the commercialization of metal-free uni material pump packaging. The decompression leak test showed no leakage and displayed 14.8~17.5 N of pressing strength, 2.3~8.8 % of deviation in dispensing volume, and 4 occasions of pumping for initial discharge.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.148-148
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• 2000

지금까지 반도체 표면에 대한 연구는 주로 (1000, (111) 표면 등 낮은 밀러 지표를 가진 표면에 대해 이루어져 왔다. 이에 반해 밀러 지표가 높은 Si 면은 불안정하고, 가열하면 다른 표면, 즉 지표가 낮은 면으로 재배열하는 경향이 있는 것으로 알려져 있는데 아직 이들 높은 밀러 지표를 가진 표면에 대한 연구는 미미한 상태이다. 그러나, Si(113)면은 밀러 지표가 높으면서도 안정하기 때문에 Si(113)의 구조를 정확하게 알 수 있다면 밀러 지표가 낮은 Si 표면이 안정한 이유를 이해할 수 있을 것이다. 따라서 본 연구에서는 TOF-CAICISS 장치(Time of Flight - CoAxial Impact Collision Ion Scattering Spectroscopy) 장비와 RHEED(Reflection High Energy Electron Diffrction)를 이용하여 Si(113) 표면의 구조와 Si(113) 표면의 온도에 따른 구조 변화를 관찰하였다. TOF-CAICISS 실험결과를 보면 (3$\times$2)에서 (3$\times$1)으로 상변환하면서 Si(113) 표면에 오각형을 이루는 dimer 원자들과 adatom 원자들간의 높이차가 작아짐을 알 수 있다. RHEED 실험결과와 전산 모사 결과로부터 상온에서 Si(113)(3$\times$2) 구조를 가지다가 45$0^{\circ}C$~50$0^{\circ}C$에서 Si(113) (3$\times$1) 구조로 상변환한다는 것을 알 수 있다. 그러나, 아직 상전이 메카니즘은 명확하게 밝혀지지 않았다. 실험결과를 전산 모사와 비교함으로써 Si(113) 표면에 [33]방향으로 이온빔을 입사시켰을 경우 dabrowski 모델과 Ranke AI 모델이 적합하지 않다는 것을 알 수 있다./TEX>, shower head의 온도는 $65^{\circ}C$로 설정하였다. 증착된 Cu 박막은 SEM, XRD, AFM를 통해 제작된 박막의 특성을 비교.분석하였다. 초기 plasma 처리를 한 경우에는 그림 1에서와 같이 현저히 증가한 초기 구리 입자들이 관측되었으며, 이는 도상 표면에 활성화된 catalytic site의 증가에 기인한다고 보여진다. 이러한 특성은 Cu films의 성장률을 향상시키고, 또한 voids를 줄여 전기적 성질 및 surface morphology를 향상시키는 것으로 나타났다. 결과 필름의 잔류 응력과 biaxial elastic modulus는 필름의 두께가 감소함에 따라 감소하는 경향을 나타냈으며, 같은 두께의 필름인 경우, 식각 깊이에 따른 biaxial elastic modulus 의 변화를 통해 최적의 식각 깊이를 알 수 있었다.도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.는 현저하게 향상되었다. 그 원인은 SB power의 인가에 의해 활성화된 precursor 분자들이 큰 에너지를 가지고 기판에 유입되어 치밀한 박막이 형성되었기 때문으로 사료된다.을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품 개발에 따른 새로운 수요 창출과 수익률 향상, 기존의 기능성 안료를 나노(nano)화하여 나노 입자를 제조, 기존의 기능성 안료에 대한 비용 절감 효과등을 유도 할 수 있다. 역시 기술적인 측면에서도 특수소재 개발에 있어 최적의 나노 입자 제어기술 개발 및 나노입자를 기능성 소재로 사용하여 새로운 제품의 제조와 고압 기상 분사기술의 최적화에 의한 기능성 나노 입자 제조 기술을 확립하고 2차 오염 발생원인 유기계 항균제를 무기계 항균제로 대체할 수 있다.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.2
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• pp.106-113
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• 2011

The object of this clinical study was to evaluate the short-term outcome of modified resin-bonded fixed partial dentures which utilizes the original tooth undercuts and different path of insertion of components. Materials and methods: 71 units of modified RBFPDs that were used in 21 patients at the Department of Prosthodontics, College of Dentistry, Yonsei University were evaluated. The follow-up period was up to 25 months, the mean being 7 months. Survival rate, mobility, percussion, probing depth, bleeding on probing, plaque index was recorded and radiographs were taken to monitor alveolar bone loss. Results & Conclusion: Within the limits of this short term retrospective study, it was concluded that: 1. No mechanical failure such as debonding or fracture of the framework was found during the follow-up period. 2. The periodontal apparatus was stable and no clinical change was observed after prosthetic treatment. 3. No significant marginal bone loss was found in the radiographic evaluation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.83-94
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• 2008

In this study an effective stress analysis was performed to evaluate liquefaction potential and ground settlement for reclaimed sites. The effective stress model can simulate the stiffness degradation due to excess pore pressure and resulting ground deformation. It is applicable to a wide range of strain. An equivalent linear analysis suitable for low strain levels was also carried out to compare the effective stress analysis. Shear stress ratio calculated from an equivalent linear analysis was used to determine SPT blow count to prevent liquefaction. Depending on the magnitude of potential earthquake and fine contents, the SPT blow count was converted into an equivalent cone tip resistance. It was compared with the measured cone tip resistance. The measured elastic shear wave velocity and cone tip resistance from two reclaimed sites in Incheon were used to perform liquefaction analyses. Two liquefaction evaluation methods showed similar liquefaction potential which was evaluated continuously. The predicted excess pore pressure ratio of upper 20 m was between 40% and 70%. The calculated post-shaking settlement caused by excess pore pressure dissipation was less than 10 cm.

• Progress in Medical Physics
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• v.20 no.2
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• pp.80-87
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• 2009

Phase transformation, superelastic characteristics and variation of surface residual stress were studied for Nitinol shape memory alloy through application of UNSM technology, and life extension methods of stent were also studied by using elastic resilience and corrosion resistance. Nitinol wire of ${\phi}1.778$ mm showed similar surface roughness before and after UNSM treatment, but drawing traces and micro defects were all removed by UNSM treatment. It also changed the surface residual stress from tensile to compressive values, and XRD result showed less intensive austenite peak and clear martensite and additional R-phase peaks after UNSM treatment. Fatigue resistance could be greatly improved through removal of surface defects and rearrangement of surface residual stress from tensile to compressive state, and development of surface modification system to improve not only bio-compatability but also resistance to corrosion and wear will make it possible to develop vascular stent which can be used for circulating system diseases which run first cause of death of recent Koreans.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.15-26
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• 2004

Based on an estimating method for post-cyclic strength and stiffness with cyclic triaxial tests proposed by one of the authors, cyclic Direct Simple Shear (DSS) tests were carried out to confirm whether the method can be adapted to DSS test on fine-grained soils: silty clay, plastic silt, and non-plastic silt. Results from cyclic and post-cyclic DSS tests were interpreted by a modified method as adopted for cyclic and post-cyclic triaxial tests. In particular, influence of plasticity index for fine-grained soils and initial static shear stress (ISSS) was emphasised. Findings obtained from the present study are: (i) liquefaction strength ratio of fine-grained soils decreases with decreasing plasticity index and increasing ISSS; (ii) plasticity index and ISSS did not markedly influence relation between equivalent cyclic stiffness and shear strain relations; (iii) the higher the plasticity index of fine-grained soils is, the less the strength ratio decreases with increment of a normalcies excess pore water pressure (NEPWP); (iv) stiffness ratio of plastic silt has large activity decrease rapidly with increasing excess pore water pressure; and (v) post-cyclic strength and stiffness results from DSS tests agree well with those predicted by the method modified from a procedure used for triaxial test results.

• Korean journal of applied entomology
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• v.43 no.4 s.137
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• pp.305-310
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• 2004

The development of Myzus persicae (Sulzer) was studied at temperatures ranging from 15 to $32.5^{\circ}C$ under $70{\pm}5\%$ RH, and a photoperiod of 16:8 (L:D). Mortality of 1st-2nd nymph was higher than that of 3rd-4th nymph at the most temperature ranges whereas at high temperature of $32.5^{\circ}C$, more 3-4nymph stage individuals died. The total developmental time ranged from 12.4 days at $15^{\circ}C$ to 4.9 days at $27.5^{\circ}C$, suggesting that higher the temperature, faster the development. However, at higher end temperature ranges of 30 and $32.5^{\circ}C$, the development took 5.0 and 6.3 days, respectively. The lower developmental threshold temperature and effective accumulative temperatures for the total immature stage were $4.9^{\circ}C$ and 116.5 day-degrees. The nonlinear shape of temperature related development was well described by the modified Sharpe and DeMichele model. When the normalized cumulative frequency distributions of developmental times for each life stage were fitted to the three-parameter Weibull function, attendance of shortened developmental times was apparent with pre-nymph, post-nymph, and total nymph stages in descending order. The coefficient of determination $r^2$ ranged between 0.87 and 0.94.