• Advances in concrete construction
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• v.8 no.4
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• pp.269-276
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• 2019

The cracking and spalling caused by fracture of concrete lining have adverse impacts on serviceability and durability of the tunnel, and the subsequent maintenance work for damaged structure needs to be specific to the damaging causes. In this paper, a particular case study of an operational tunnel structure is presented for the serious cracking and spalling behaviours of concrete lining, focusing on the multi-factors inducing lining failure. An integrated field investigation is implemented to characterize the spatial distribution of damages and detailed site situations. According to results of nondestructive inspection, insufficient lining thickness and cavity behind lining are the coupled-inducement of lining failure bahaviors. To further understanding of the lining structure performance influenced by these multiple construction deficiencies, a reliable numerical simulation based on extended finite element method (XFEM) is performed by using the finite element software. The numerical model with 112 m longitudinal calculation, 100 m vertical calculation and 43 m vertical depth, and the concrete lining with 1450 solid elements are set enrichment shape function for the aim of simulating cracking behavior. The numerical simulation responses are essentially in accordance with the actual lining damaging forms, especially including a complete evolutionary process of lining spalling. This work demonstrates that the serious lining damaging behaviors are directly caused by a combination of insufficient thickness lining and cavity around the surrounding rocks. Ultimately, specific maintenance work is design based on the construction deficiencies, and that is confirmed as an efficient, time-saving and safe maintenance method in the operational railway tunnel.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.152-163
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• 1995

This experiment was performed to observe the adhesion pattern and microleakage in the gingival margin according to variation in the resin cement thickness which results from thickness of Die spacer. which is considered to effect the adaptability of the composite resin inlays. Clearfil CR inlays were fabricated on stone models with CR Sep applicated once and Nice fit twice, 4 times, and 6 times each. After 2nd curing within the CRC-100 oven, CR inlays were cemented with CR inlay cement. Dye(2% methylene blue) penetration and adhesion pattern were evaluated after sectioning of gingival margin into :3 pieces. The results were as follows ; 1. The thickness of resin cement showed unevenchanging pattern with that of die spacer, namely, it was increased until 4 times' application of Nice-Fit but was decreased with 6 times' application of that. 2. The degree of dye penetration wasn't affected by cement thickness within a limited value. 3. Most of dye penetration was shown through the interface between cement and enamel rather than the interface between cement and CR inlay. This shows that the affinity of resin cement for CR inlay was superior to the adhesive strength with tooth structure. 4. No gap was found at the interface between enamel and cement but some showed separation between dentin and cement. It is concidered that the contraction force of cement was less than the bond strength with the enamel. 5. Lots of voids were found in the CR inlay and resin cement. There was a pooling tendency of bonding agent and cement in the axiogingival line angle portion. 6. In some specimens, cracks were shown in enamel margin. From this it could be considered that cavity preparation and surface treatment weakened the tooth structure.

• Restorative Dentistry and Endodontics
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• v.13 no.2
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• pp.265-282
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• 1988

The pulp response of posterior composite resins in relation to the thickness of remaining dentin was studied with 120 teeth from 6 dogs, Class V. cavities were prepared on the cervical area of facial surfaces. The thickness of remaining dentin was controlled with Caries Meter$^{(R)}$. The cavities of group A were prepared to show the electrical impedance of 22-26$K{\Omega}$(thickness of remaining dentin:0.4-0.5mm). The cavities of group B, 50-55$K{\Omega}$(thickness of remaining dentin: 0.8-0.9mm). Zinc - Oxide Eugenol cement, Estilux$^{(R)}$ posterior, Heliomolar$^{(R)}$ radiopaque, P-30$^{(R)}$ and Scotchbond$^{(R)}$+P-30$^{(R)}$ were filled in each cavity. After 3days, 1 week, 2 weeks, 4 weeks, 9 weeks and 13 weeks, the teeth and pulp tissue were processed routinely and stained with Hematoxylin and Eosin. Pathological tissue changes were observed with light microscope. The following results were obtained. I. The pulp response of group A cavties was severer than that of group B cavities. 2. In the pulp of group A cavities which were filled with Zinc-Oxide Eugenol Cement, only vascular changes were observed after 3 days and 1 week, severe acute inflammation after 4 weeks, moderate acute inflammation after 9 weeks, and chronic inflammation and formation of granulation tissue after 13 weeks. 3. In the pulp of group A cavities which were filled with Estilux$^{(R)}$ posterior, only vascular changes were observed after 3 days and 1 week. But the inflammatory response has became much severer with the elapsed experimental period. 4. In the pulp of group A cavities which were filled with Heliomolar$^{(R)}$ radiopaque, the inflammatory response with the elapsed experimental period was not severer than that of the pulp of group A cavities which were filled with other materials. 5. In the group B cavities, the difference of pulp response by filling materials was not recognizable. In the group A cavities, the pulp response of Estilux$^{(R)}$ posterior was severest and in order P-30$^{(R)}$, Heliomolar$^{(R)}$ radiopaque was slighter.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.34-42
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• 2003

This paper presents a rigid-plastic finite element method to handle the frictional contact problem between two deformable bodies experiencing large deformation. The variational formulation combined with incremental quasi-static model is employed for treating the contact boundary condition. The frictional behavior of the model obeys Coulomb's law of friction. The proposed contact algorithms are classified into two categories, one for searching contacting nodes and the other for calculating contact forces at the contact surface. A slave node and master contact segment are defined using the geometric condition of finite elements on the contact interface. The penalty parameter is used to limit the penetration between contacting bodies, and the finite elements are coupled with contact boundary elements.us gates and cavity thicknesses. Through this study we have observed that the jetting is related to the die swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Korean Journal of Veterinary Research
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• v.36 no.2
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• pp.289-296
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• 1996

A case of schistosomus reflexes in Korean native female calf was observed macroscopically and radiographically. The results were summarized as follows. 1. The abdominal visceral organs were exposed. 2. The vertebral column bent laterally to the left, and the sacrum approached to the cranium by reflected caudal lumber vertebrae, presenting S-shaped lateral twisting of the vertebrae. 3. The right ribs reflected laterally and dorso-cranially from the 7th rib to 13th rib. The left ribs bent caudally from 8th rib to 13th rib. 4. The length of rudimentary 6th right rib was one half of normal size and the 7th right rib was one third. 5. The sternum was bifid split from the fourth sternebra through the xyphoid cartilage. 6. The diaphragm was intact and thoracic cavity was reduced in size. The lung and heart severely deformed in shape and size. 7. The liver markedly deformed in shape and thickness. 8. The pelvic cavity was reduced in size by compression laterally to the left. 9. The uterus horn, ovary, urinary bladder, and urethra were severely deformed in the shape and position.

• Journal of Chest Surgery
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• v.28 no.3
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• pp.228-232
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• 1995

Computed tomography[CT is an effective technique for the evaluation of the thorax following blunt trauma. To evaluate multiply injured 30 patients who were diagnosed as hemothorax in emergency room, computed tomography of thorax was done. The thickness of slice was one centimeter and the entire pleural cavity from the apex to the costophrenic angle was included in the evaluation. Integration and addition of the hemothorax area for each CT slice was made and amount of blood in the pleural cavity was estimated. The slice which showed largest area of hemothorax was selected and the height and width of the hemothorax area were measured. The number of slices which showed radiographic evidence of hemothorax was counted. Regression analysis was done and measured amount of hemothorax, the height and width of the hemothorax area for each slice and number of slices were put as variables. And following equation was derived. V=108.3A-0.8B-7.4C+84.7 [R2=0.74 [ V: amount of hemothorax, A: height, B: width, C: number of slices Total amount of blood from thoracic drainage was compared to the measured amount by computed tomography and the relation between the two values was statistically significant.[p=0.001 In conclusion, quantitative estimation of size of hemothorax was possible by the above equation and the process was very helpful for determination policy of treatment of individual patient.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.950-954
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• 2003

This paper presents the delivered power and reflection coefficient in metallic shielding enclosure excited by the interior source, which are evaluated with the method of moments, and describes a method for reducing the radiation of electromagnetic fields in the cavity by putting lossy dielectric material in one inside wall. In this paper we introduce carbon polystyrene-foam as lossy dielectric material and observe it's effects of reduction when the thickness and permittivity of lossy dielectric material are changed. The results show that the reduction of the electromagnetic radiation can be achieved by controlling the amount of carbon in lossy dielectric material. The theoretical analysis is verified by the measured delivered power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.958-962
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• 2002

This paper reports on the fabrication of free-standing microstructures by DRIE (deep reactive ion etching). SOI (Si-on-insulator) structures with buried cavities are fabricated by SDB (Si-wafer direct bonding) technology and electrochemical etch-stop. The cavity was formed the upper handling wafer by Si anisotropic etch technique. SDB process was performed to seal the formed cavity under vacuum condition at -760 mmHg. In the SDB process, captured air and moisture inside of the cavities were removed by making channels towards outside. After annealing (100$0^{\circ}C$, 60 min.), the SDB SOI structure with a accurate thickness and a good roughness was thinned by electrochemical etch-stop in TMAH solution. Finally, it was fabricated free-standing microstructures by DRIE. This result indicates that the fabrication technology of free-standing microstructures by combination SDB, electrochemical etch-stop and DRIE provides a powerful and versatile alternative process for high-performance bulk micromachining in MEMS fields.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.600-606
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• 2008

In closed-die hot forging, a billet is formed in dies such that the flow of metal from the die cavity is restricted. Some parts can be forged in a single set of dies, whilst others, due to shape complexity and material flow limitations, must be shaped in multi sets of dies. The purpose of a performing operation is to distribute the volume of the parts such that material flow in the finisher dies will be sound. This study focused on the design of preforms, flash thickness and land width by theoretical calculation and finite element analysis, to manufacture the super hot forging product, 70MC type piston crown used in marine engine. The optimal design of preforms by the finite element analysis and the design experiment achieves adequate metal distribution without any defects and guarantees the minimum forming load and fully filling of the cavity of the die for producing the large piston crown. The maximum loads obtained by finite element analysis are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. Results obtained using DEFORM-2D enable the designer and manufacturer of super hot forging dies to be more efficient in this field.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.423-427
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• 2013

We present the preparation and characteristics of liquid-phase sensors based on nano-porous silicon multilayer structures for determination of organic content in gasoline. The principle of the sensor is a determination of the cavity-resonant wavelength shift caused by refractive index change of the nano-porous silicon multilayer cavity due to the interaction with liquids. We use the transfer matrix method (TMM) for the design and prediction of characteristics of microcavity sensors based on nano-porous silicon multilayer structures. The preparation process of the nano-porous silicon microcavity is based on electrochemical etching of single-crystal silicon substrates, which can exactly control the porosity and thickness of the porous silicon layers. The basic characteristics of sensors obtained by experimental measurements of the different liquids with known refractive indices are in good agreement with simulation calculations. The reversibility of liquid-phase sensors is confirmed by fast complete evaporation of organic solvents using a low vacuum pump. The nano-porous silicon microcavity sensors can be used to determine different kinds of organic fuel mixtures such as bio-fuel (E5), A92 added ethanol and methanol of different concentrations up to 15%.