• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.411-418
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• 2018

This paper introduces a new method of ice load generation in the time domain for the station-keeping performance evaluation of Arctic offshore structures. This method is based on the ice load spectrum and mean ice load. Recently, there has been increasing interest in Arctic offshore technology for the exploration and exploitation of the Arctic region because of the better accessibility to the Arctic ocean provided by the global warming effect. It is essential to consider the ice load during the development of an Arctic offshore structure. In particular, when designing a station-keeping system for an Arctic offshore structure, a consideration of the ice load acting on the vessel in the time domain is essential to ensure its safety and security. Several methods have been developed to consider the ice load in the time domain. However, most of the developed methods are computationally heavy because they consider every ice floe in the sea ice field to calculate the ice load acting on the vessel. In this study, a new approach to generate the ice load in the time domain with computational efficiency was suggested, and its feasibility was examined. The ice load spectrum and mean ice load were acquired from a numerical analysis with GPU-event mechanics (GEM) software, and the ice load with the varying heading of a vessel was reconstructed to show the feasibility of the proposed method.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.156-163
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• 2009

Statement of problem: Recently, there have been increased esthetic needs for posterior dental restorations. The failure of posterior dental ceramic restoration are possible not only by the characters of the component materials but also by the type of food. Purpose: The research aim was to compare the in vitro fracture resistance of simulated first molar crowns fabricated using 4 dental ceramic systems, full-porcelain-occlusal-surfaced PFG, half-porcelain-occlusal-surfaced PFG, Empress 2, Ice Zirkon and selected Korean foods. Material and methods: Eighty axisymmetric crowns of each system were fabricated to fit a preparation with 1.5- to 2.0-mm occlusal reduction. The center of the occlusal surface on each of 15 specimens per ceramic system was axially loaded to fracture in a Instron 4465, and the maximum load(N) was recorded. Afterwards, selected Korean foods specimens(boiled crab, boiled chicken with bone, boiled beef rib, dried squid, dried anchovy, round candy, walnut shell) were prepared. 15 specimens per each food were placed under the Instron and the maximum fracture loads for them were recorded. The 95% confidence intervals of the characteristic failure load were compared between dental ceramic systems and Korean foods. Afterwards, on the basis of previous results, 14Hz cyclic load was applied on the 4 systems of dental ceramic restorations in MTS. The reults were analyzed by analysis of variance and Post Hoc tests. Results: 95% confidence intervals for mean of fracture load 1. full porcelain occlusal surfaced PFG Crown: 2599.3 to 2809.1 N 2. half porcelain occlusal surfaced PFG Crown: 3689.4 to 3819.8 N 3. Ice Zirkon Crown: 1501.2 to 1867.9 N 4. Empress 2 Crown: 803.2 to 1188.5 N 5. boiled crab: 294.1 to 367.9 N 6. boiled chicken with bone: 357.1 to 408.6 N 7. boiled beef rib: 4077.7 to 4356.0 N 8. dried squid: 147.5 to 190.5 N 9. dried anchovy: 35.6 to 46.5 N 10. round candy: 1900.5 to 2615.8 N 11. walnut shell: 85.7 to 373.1 N under cyclic load(14Hz) in MTS, fracture load and masticatory cycles are: 1. full porcelain occlusal surfaced PFG Crown fractured at 95% confidence intervals of 4796.8-9321.2 cycles under 2224.8 N(round candy)load, no fracture under smaller loads. 2. half porcelain occlusal surfaced PFG Crown fractured at 95% confidence intervals of 881705.1-1143565.7 cycles under 2224.8 N(round candy). no fracture under smaller loads. 3. Ice Zirkon Crown fractured at 95% confidence intervlas of 979993.0-1145773.4 cycles under 382.9 N(boiled chicken with bone). no fracture under smaller loads. 4. Empress 2 Crown fractured at 95% confidence intervals of 564.1-954.7 cycles under 382.9 N(boiled chicken with bone). no fracture under smaller loads. Conclusion: There was a significant difference in fracture resistance between experimental groups. Under single load, Korean foods than can cause fracture to the dental ceramic restorations are boiled beef rib and round candy. Even if there is no fracture under single load, cyclic dynamic load can fracture dental posterior ceramic crowns. Experimental data with 14 Hz dynamic cyclic load are obtained as follows. 1. PFG crown(full porcelain occlusion) was failed after mean 0.03 years under fracture load for round candy(2224.8 N). 2. PFG crown(half porcelain occlusion) was failed after mean 4.1 years under fracture load for round candy(2224.8 N). 3. Ice Zirkon crown was failed after mean 4.3 years under fracture load for boiled chicken with bone(382.9 N). 4. Empress 2 crown was failed after mean 0.003 years under fracture load for boiled chicken with bone(382.9 N).

• Journal of the Society of Naval Architects of Korea
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• v.57 no.2
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• pp.80-87
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• 2020

As the Arctic sea ice decreases due to various reasons such as global warming, the demand for ships and offshore structures operating in the Arctic region is steadily increasing. In the case of sea ice, the anisotropy is caused by the uncertainty inside the material. For most of the research, nevertheless, estimating the ice load has been treated deterministically. With regard to this, in this paper, a four-point bending strength analysis of an ice specimen was attempted using a stochastic finite element method. First, spatial distribution of the material properties used in the yield criterion was assumed to be a multivariate Gaussian random field. After that, a direct method, which is a sort of stochastic finite element method, and a sensitivity method using the sensitivity of response for random variables were proposed for calculating the probabilistic distribution of ice specimen strength. A parametric study was conducted with different mean vectors and correlation lengths for each material property used in the above procedure. The calculation time was about ten seconds for the direct method and about three minutes for the sensitivity methods. As the cohesion and correlation length increased, the mean value of the critical load and the standard deviation increased. On the contrary, they decreased as the friction angle increased. Also, in all cases, the direct and sensitivity methods yielded very similar results.

• Journal of Advanced Marine Engineering and Technology
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• v.14 no.4
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• pp.57-66
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• 1990

In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air conditioning systems are being operated during daytime in summer season, which inevitably entails the construction of an additional electric power plant. This study is aimed to carry out a basic experiment for the development of a cooling air conditioning system using the ice energy by the surplus electric power during the night-time. The experimental apparatus consists of four major parts; (1) the heating section consisting of the air duct and I.D. fan, (2) the cold section with the ice chamber, (3) the bundle of heat pipes made in a form of the staggered arrangement with ${C_y}/{d_o}$=2.0 and ${C_x}/{d_o}$=1.73, (4) the refrigerator system to cool down the ice chamber. This study involves an intensive experiment concerning the convective heat transfer of the air flow surrounding the bundle of heat pipes. This major experimental parameters are the amount of working fluid, the velocity of air and the working temperature. The major findings of the present study are as follows; (1) The optimum amount of the working fluid necessary for the horizontal heat pipes is much more than that for the vertical type. (2) The convective heat transfer coefficients of the air are coincided with the empirical equations of Grimson and ${\breve{Z}ukauskas}$. (3) The equation of the mean heat transfer coefficient obtained in the present study is ${N_um}=0.32 {Re_max^{0.63}}$.

• Journal of Nutrition and Health
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• v.43 no.5
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• pp.500-512
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• 2010

The relationship between food and nutrient intake, glycemic index (GI), glycemic load (GL), and body weight was investigated with high school girls residing in Seoul. As subjects, 159 girls were divided into a normal weight (NW) group (18.5 kg/$m^2$ $\leq$ BMI < 23 kg/$m^2$, n = 110) and an overweight (OW) group (BMI $\geq$ 23kg/$m^2$, n = 49) by body mass index (BMI). The food and nutrient intake data obtained by the 3-day food record were analyzed by Can pro 3.0 software. Anthropometric measurements were collected from each subject. Daily dietary GI (DGI) and dietary GL (DGL) were calculated from the 3-day food record. Body weights and BMI of NW were 52.4 kg and 20.4 kg/$m^2$ and those of OW were 65.2 kg and 25.4 kg/$m^2$, respectively. Total food, animal food, and other food intakes of NW were higher than those of OW, and vegetable food intakes of NW were lower than those of OW. Sugars intake of NW was significantly higher than OW. Nutrient intakes were not different between the two groups. Dietary fiber, calcium, and folate intakes of NW and OW were under 65% of the dietary reference intakes (DRIs). Major food sources of energy intake for both groups were rice, pizza, ice cream, pork, instant noodle, and chicken. Mean adequacy ratio (MAR), an index of overall dietary quality, was higher in NW (0.82) than in OW (0.80). Mean daily DGI of NW and OW was 66.5 and 66.4, respectively. Mean daily DGL of NW and OW was higher in NW (162.0) than in OW (155.9). DGI and DGL adjusted to energy intake were not significantly correlated with anthropometric data.

• Journal of Technologic Dentistry
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• v.35 no.1
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• pp.19-27
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• 2013

Purpose: The aim of this research was to evaluate the shear bond strength of different zirconia veneering ceramics with and without liner glass materials to yttria partially-stabilized tetragonal zirconia polycrystalline(Y-TZP). Methods: Five co mmercial zirconia veneering ceramics were used in this study, E-Max(EM), Creation ZI(CR), Cercon ceram kiss(CE), Triceram(TR) and Zirkonzahn ICE(ZI). All samples were prepared according to manufacturer's instructions. Experimental industrially manufactured Y-TZP ceramic blocks(diameter: 2.7 mm; height: 13.5 mm) were used in this study. Shear bond strength between zirconia ceramic coping and zirconia veneering ceramics were evaluated by the push-shear bond test. The fracture load data were analyzed using ANOVA and Scheffe's test(${\alpha}$=0.05). The fractured surfaces of zirconia core ceraimc and zirconia veneering ceramics were observed using a scanning electron microscope(SEM). Results: The mean shear bond strengths ranged from 20 MPa ($20.12{\pm}6.34$ MPa) to 66.6 MPa ($66.62{\pm}10.01$ MPa). The Triceram(TRG) showed the highest value and Creation ZI(CR) showed the lowest value. In all groups, Zirconia liner and glass material groups was significantly higher shear bond strength than without liner(P<0.05), with the exception of Cercon ceram kiss(CE)groups. Conclusion: Zirconia bonding materials may have the advantage of improved bond strength between zirconia ceramic core and veneering ceramics.