• 치위생과학회지
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• 제14권3호
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• pp.349-355
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• 2014

본 연구는 최근 치의학계 전반적으로 치과용 캐드캠 시스템의 사용이 증가함에 따라 새로운 재료의 개발도 활발히 이루어지고 있는 현실을 반영하였다. 최근 새롭게 개발된 고정성 보철물의 제작 재료인 연질금속재료를 이용하여 제작된 고정성 보철물의 변연 간격을 평가하여 봄으로써 신재료의 임상적 허용 가능성을 변연 간격을 기준으로 가늠하여보고자 하였으며, 나아가서는 치과의사, 치과위생사 및 치과기공사 등 해당 분야 임상가들에게 참고자료를 제시하고자 하였다. 연구 결과에 따르면 연질금속블록을 가공하여 제작된 집단이 전통적인 방식에 의해 제작된 집단보다 우수한 변연간격을 보였으나, 통계적으로 유의하지 않았다. 또한 연질금속블록을 가공하여 제작된 보철물들의 변연 간격이 임상적 허용 수치로 제시되고 있는 $120{\mu}m$를 넘지 않는 것으로 보아 변연 간격을 기준으로 하였을 때 임상적으로 허용이 가능할 것으로 생각된다.

• Advances in materials Research
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• 제11권2호
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• pp.147-164
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• 2022

This study aims to investigate the influence of scoria aggregate (SA) and silica fume (SF) as a replacement of conventional aggregate and ordinary Portland cement (OPC), respectively. Three types of concrete were prepared namely normal weight concrete (NWC) using limestone aggregate (LSA) and OPC (control specimen), lightweight concrete (LWC) using SA and OPC, and LWC using SA and partial SF (SLWC). The representative workability and compressive strength properties of the developed concrete were evaluated, and the results were correlated with non-destructive ultrasonic pulse velocity and Schmidt hammer tests. The LWC and SLWC yielded compressive strength of around 30 MPa and 33 MPa (i.e., 78-86% of control specimens), respectively. The findings indicate that scoria can be beneficially utilized in the development of structural lightweight concrete. Present renewable sources of aggregate will preserve the natural resources for next generation. The newly produced eco-friendly construction material is intended to break price barriers in all markets and draw attraction of incorporating scoria based light weight construction in Saudi Arabia and GCC countries. Findings of the SWOT analysis indicate that high logistics costs for distributing the aggregates across different regions in Saudi Arabia and clients' resistant to change are among the major obstacles to the commercialized production and utilization of lightweight concrete as green construction material. The findings further revealed that huge scoria deposits in Saudi Arabia, and the potential decrease in density self-weight of structural elements are the major drivers and enablers for promoting the adoption of lightweight concrete as alternative green construction material in the construction sector.

• 생명과학회지
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• 제19권10호
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• pp.1368-1373
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• 2009

본 연구는 미국 유타주에 거주하는 10-15세 어린이와 청소년들의 허리둘레가 electronic pedometer (전자 보수계)의 타당성과 신뢰성에 미치는 영향을 분석하기 위하여 비만집단 10명(HWC, BMI $28.91\pm3.07$)과 일반집단 10명 (LWC, BMI $18.05\pm1.55$)으로 총 20명(14 Hispanic and 6 Caucasian)의 어린이와 청소년들을 대상으로 실시하였다. Electronic pedometer 의 신뢰성을 측정하기 위하여 각 어린이는 Yamax SW-701 electronic pedometer 를 허리에 차고 15계단 오르기와 15계단 내리기를 3 sets 실시한 결과, HWC 집단이 LWC 집단보다 더 많은 보수를 기록했으나 오르기와 내르기 시행의 주 효과는 유의한 차이가 없었고, 또 두 집단간의 상호작용에도 유의한 차이가 없었다. 보수를 측정하여 pedometer의 타당성에 허리둘레가 미치는 영향을 분석하기 위하여 각자의 보행 속도에 따라 400 m를 걷게 한 결과 주 효과는 두 집단 간에 유의한 차이가 있었으나 counting technique (hand-counted vs. pedometer counted)의 주 효과는 유의한 차이가 없었으며, 또 400 m 걷기의 시기와 group별 시기의 상호작용도 유의한 차이가 없었다. 이러한 결과는 pedometer가 walking steps 측정에 HWC 집단과 LWC 집단에 동일하게 타당도가 있음을 나타내고 있다. 추후의 연구에서는 어린이들의 walking speed, pedometer tilt angle, leg length, 및 stride length 등을 고려한 연구가 필요하다고 사료된다.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.123-136
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• 2008

A new plastic-damage constitutive model applicable to lightweight concrete (LWC) and normal weight concrete (NWC) is proposed in this paper based on both continuum damage mechanics and plasticity theories. Two damage variables are used to represent tensile and compressive damage independently. The effective stress is computed in the Drucker-Prager multi-surface plasticity framework. The stress is then computed by multiplication of the damaged part and the effective part. The proposed model is coded as a user material subroutine and incorporated in a finite element analysis software. The constitutive integration algorithm is implemented by adopting the operator split involving elastic predictor, plastic corrector and damage corrector. The numerical study shows that the algorithm is efficient and robust in the finite element analysis. Experimental investigation is conducted to verify the proposed model involving both static and dynamic tests. The very good agreement between the numerical results and experimental results demonstrates the capability of the proposed model to capture the behaviors of LWC and NWC structures for static and impact loading.

• 한국항공우주학회지
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• 제39권8호
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• pp.689-701
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• 2011

본 연구에서는 착빙 환경 요소와 결빙 형상 파라미터의 관계를 자가조직도와 분산분석을 활용하여 분석하였다. 결빙 형상에 영향을 미치는 외기 조건으로 자유류 속도, 대기온도, 대기중 물방울 함유량(LWC), 액적의 평균 직경(MVD)을 선정하였다. 그리고 결빙 형상의 특징이 되는 파라미터로 최대 두께, 결빙한계(Icing limit), 결빙 진행 방향, 결빙면적을 선정하였다. 자가 조직도의 결과는 결빙형상 파라미터에 관계가 있는 외기 조건에 대한 정성적인 관계를 제시하였고 분산분석의 결과는 형상 파라미터에 대한 외기 조건의 영향력의 상대적인 크기와 순위를 정량적으로 제시하였다.

• 대한치과기공학회지
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• 제44권4호
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• pp.126-131
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• 2022

Purpose: The purpose of this study is to evaluate the quality of dental fixed prostheses fabricated by 3DP (three-dimensional printing). Methods: Ten main models were prepared for the study. Ten specimens were printed by 3DP (3DP group). Ten specimens were fabricated by the lost wax technique and casting method to complete the control group (LWC group). The marginal fit was measured for 20 specimens. The measurement of marginal fit was performed using the silicon replica technique. Finally, the marginal fit of 10 specimens from each group was calculated. An independent sample t-test was run to see if the calculated averages for the two groups were mutually significant (α=0.05). Results: According to the experimental results, the mean marginal fit of the 3DP group was 71.9 ㎛, and the LWC group was 55.3 ㎛. The means of the two groups were found to be significantly different (p<0.001) in the results of the independent sample t-test. Conclusion: The marginal fit of fixed dental prostheses produced by 3DP technology was examined with values greater than those fabricated by traditional technology. However, as it appeared to be a value within the range of clinically acceptable range recommended by numerous studies, it was determined that clinical application would be feasible.

• Current Optics and Photonics
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• 제4권3호
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• pp.174-185
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• 2020

Multiscattering occurs when a laser transmits into dense atmosphere targets (e.g. fogs, smoke or clouds), which can cause depolarization effects even though the scattering particles are spherical. In addition, multiscattering effects have additional information about microphysical properties of scatterers. Thus, multiscattering can be utilized to study the microphysical properties of the liquid water cloud. In this paper, a Monte Carlo method was used to simulate multi-scattering transmission properties of Lidar signals in the cloud. The results showed the slope of the degree of linear polarization (SLDLP) can be used to invert the extinction coefficient, and then the cloud effective size (CES) and the liquid water content (LWC) may be easily obtained by using the extinction coefficient and saturation of the degree of linear polarization (SADLP). Based on calculation results, a microphysical properties inversion method for a liquid cloud was presented. An innovative multiscattering polarization Lidar (MSPL) system was constructed to measure the LWC and CES of the liquid cloud, and a new method based on the polarization splitting ratio of the Polarization Beam Splitter (PBS) was developed to calibrate the polarization channels of MSPL. By analyzing the typical observation data of MSPL observation in the northern suburbs of Nanjing, China, the LWC and CES of the liquid water cloud were obtained. Comparisons between the results from the MSPL, MODIS and the Microwave radar data showed that, the microphysical properties of liquid cloud could be retrieved by combining our MSPL and the inversion method.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.464-467
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• 2010

Ice accretion on aircraft surface in icing condition induces external shape changes that may result in a hazard factor for aircraft safety. In case of aircraft main wing with high lift equipment, ice accretion is observed around leading edge and flap. During the design phase, location of ice accretion and associated aerodynamic characteristics must be investigated. In this study, icing effects on aerodynamic characteristics of the main wing section of KC-100 aircraft are investigated using an Eulerian-based FENSAP-ICE code in various icing conditions.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.505-508
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• 2006

Talc has been used as coating pigments for gravure printing paper and light weight coated paper (LWC) in Europe for 30 years and the use of talc has been significantly increased every year. Currently, talc is used for about 15% of pigments for paper coating. Especially more than 50% of the coating pigments for gravure printing paper and web printing paper (web off-set) is applying talc. The use of talc improves printability, smoothness, and the coverage of base paper, and showed a significant effect on reducing the coated paper basis weight. In addition, it improves compressibility of the coating layer, influencing the gravure printability.

• Asian-Australasian Journal of Animal Sciences
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• 제19권10호
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• pp.1455-1463
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• 2006

Effects of different levels of molasses in a concentrate supplement on milk yield of cows grazing Setaria grass pastures were investigated. Thirty Friesian cows, 6-7 years old with mean pre-experimental body weight of $428{\pm}6.5$ kg, in early stage of lactation were randomly allotted to five dietary treatments in a completely randomized design experiment that lasted for 126 days. Experimental dietary treatments were forage alone and forage/concentrate mixtures with molasses included at 0, 5, 10 or 15% levels designated as $T_1$, $T_2$, $T_3$, $T_4$ and $T_5$, respectively. The parameters studied were voluntary dry matter (DM) intake, average daily live weight change (LWC), milk yield, body condition score (BCS) and apparent nutrient digestibility coefficients. The DM and energy contents of Setaria grass were low compared to the concentrate diets. Fibre fractions-NDF, ADF, ADL, hemicellulose and cellulose; and gross energy were higher in concentrate mixtures than in the forage. Total DM intake (forage+concentrate mixtures) was significantly higher (p<0.001) in cows on the concentrate mixtures. LWC was not significantly different (p>0.05) between the cows. Average milk yields were significantly different (p<0.05) between cows. Fat corrected milk (FCM) was similar among cows in the treatments. BCS was better (p<0.001) in cows on concentrate mixtures. Digestibilities of DM, CP, NDF, ADF, ADL, OM, and energy were significantly higher (p<0.001) in cows on $T_2$, $T_3$, $T_4$ and $T_5$ than in those on $T_1$. There were no significant differences in the digestibility of DM, CP, NDF, ADF and ADL (p>0.001) in cows on concentrate mixtures. This study therefore demonstrated that lactating dairy cows in Fiji need a level of readily fermented energy source such as molasses in their diets; however, a level above 10% is not nutritionally suitable for lactating dairy cows. Based on data on production parameters-milk yield, fat corrected milk, body condition score and apparent nutrient digestibility coefficients-molasses levels that range between 5-10% are recommended, however, 10% is the best and therefore recommended for inclusion in the concentrate mixture of lactating dairy cows on a basal diet of Setaria sphacelata in Fiji.