• Journal of the Korea Concrete Institute
• /
• v.29 no.3
• /
• pp.259-266
• /
• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that reinforces shear force. CFP pile (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) developed in this study increases the shear stress by placing composite shear connector and filling the concrete into hollow part of the pile. By placing the reinforcement (H13-8ea) and the reinforcement (H19-8ea) into hollow section inside of PHC piles, it also improves the shear strength due to increasing steel ratio. It reinforces shear strength effectively by dowel force that is generated by putting reinforcement (H13-8) into the holes of composite shear connectors for the composite behavior of filled concrete and PHC pile. The study was reviewed and compared the calculated result of the shear strength by limit state design method highway bridge design standards (2012) and experiment result of the shear strength by KS F 4306. We can design the shear strength reasonably as the safety ratio of 2.20, 2.15, 2.05 is shown comparing to design shear strength, according to design shear strength on each cross sections and the experiment results of the CFP pile.

• Journal of the Korea Concrete Institute
• /
• v.29 no.3
• /
• pp.249-257
• /
• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that make up for the defects of PHC piles. CFP (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) piles developed in this study increases the compressive stress through enlarged cross section by rearranging composite shear connectors and filling the hollow part of PHC pile with concrete. And it improved shear and bending performance placing the rebar (H13-8ea) within the PHC pile and the hollow part of PHC pile of rebar (H19-8ea). In addition, the composite shear connectors were placed for the composite behavior between PHC pile and filled concrete. Placing Rebars (H13-8ea) of PHC pile into composite shear connector holes are sleeve-type mechanical coupling method that filling the concrete to the gap of the two members. Nonlinear finite element analyzes were performed to verify the performance of shear and bending moments and it deduced the spacing of the composite shear connectors. Through a various interpretation of CFP piles, it's proved that the CFP pile can increase the shear and bending stiffness of the PHC pile effectively. Therefore, this can be utilized usefully on the construction sites.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.43 no.9
• /
• pp.1407-1414
• /
• 2014

Physicochemical properties of rice-based expanded snacks extruded with rice flour, high amylose starch, and isolated soy protein were investigated using a twin-screw extruder. The ingredients were extruded at various feed moisture contents (19~23%) and screw speeds (200~400 rpm) at a constant feed rate (43.4 kg/hr). Bulk density and apparent density of rice snacks were 0.06~0.21, and 0.55~0.65 respectively. Bulk density, apparent density, water absorption index, and breaking strength of rice snacks increased with increasing feed moisture content and decreasing screw speed. However, expansion and water solubility index of rice snacks increased with decreasing feed moisture content and increasing screw speed. Hunter's color L values of rice snacks was lower with increasing screw speed at feed moisture contents of 19% and 21%, but was not significantly different from a feed moisture content of 23%. On the other hand, a and b values of rice snacks were higher with increasing screw speed a feed moisture content of 19%. X-ray diffraction intensity of rice snacks decreased with decreasing feed moisture content and increasing screw speed. X-ray diffraction of rice snacks was V-type at feed moisture contents of 19% and 21% and screw speeds of 300, and 400 rpm. In the microstructure of the cross section of rice snacks, air cells in rice snacks were not well formed, and cell walls were thicker with increasing feed moisture content and decreasing screw speed.

• Journal of the Korean Ceramic Society
• /
• v.39 no.5
• /
• pp.479-483
• /
• 2002

Silicon dioxide thick film using silica optical waveguide cladding was fabricated by Plasma Enhanced Chemical Vapor Deposition(PECVD) method, at a low temperature ($320^{\circ}$C) and from $(SiH_4+N_2O)$ gas mixtures. The effects of deposition parameters on properties of $SiO_2$ thick films were investigated by variation of $N_2O/SiH_4$ flow ratio and RF power. After the deposition process, the samples were annealed in a furnace at $1150^{\circ}$C, in N2 atmosphere, for 2h. As the $N_2O/SiH_4$ flow ratio increased, deposition rate decreased from 9.4 to 2.9 ${\mu}m/h$. As the RF power increased, deposition rate increased from 4.7 to 6.9 ${\mu}m/h$. The thickness and the refractive index measurements were measured by prism coupler. X-ray Photoelectron Spectroscopy(XPS) and Fourier Transform-infrared Spectroscopy(FT-IR) were used to determine the chemical states. The cross-section of films was observed by Scanning Electron Microscopy(SEM).

• Journal of Korean Society of Forest Science
• /
• v.42 no.1
• /
• pp.67-73
• /
• 1979

In order to observe the anatomical phenomena of root formation in the hypocotyl cuttings of maples, the hypocotyls of Acer palmatum. Acer micro-sieboldianum, and Acer saccharinum were used as the materials. The rooted portions were sectioned by a microtom and doubly stained by safranin and fast green. The results obtained are summarized as follows; 1. A cross section structure of hypocotyl cuttings of Acer sp. is consist of epidermis, cortex, vascular bundle and pith from the outside. The vascular bundle makes circular shape forming polyarch in A. saccharinum and tetrarch in both A. palmatum and A. micro-sieboldianum. 2. An adventitious root of A. saccharinum originated in phloem parenchyma, while that of A. palmatum and A. micro-sieboldianum originated in interfascicular parenchyma related with phloem cells. 3. The hypocotyl cuttings of Acer sp. is commonly composed of parenchyma tissue having vigorous differentiation capability. Therefore, the originated root grow easily through the cortex and epidermis breaking their tissues.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.19 no.6
• /
• pp.318-323
• /
• 2009

The lightweight aggregates made of bottom ash (70 wt%) and dredged soil (30 wt%) were prepared to investigate the property differences at various sintering atmospheres. The green aggregates were sintered at $1150^{\circ}C$ and $1200^{\circ}C$ with oxidized, neutralized and reduced atmospheres. The aggregates sintered with oxidized atmosphere showed a clear border between shell and black core area. However, the aggregates sintered with a reduced atmosphere showed only black core area in the entire cross-section of the aggregates. The black core area of the aggregates sintered with a neutralized atmosphere increased with increasing $N_2$ gas flow rates. It was determined that the sintering atmosphere was similar to that of rotary kiln when the CO gas flow was 100 cc/min to make a reduced atmosphere in tube furnace. The water absorption rates of both aggregates from tube furnace with reduced atmosphere and rotary kiln were very similar to each other.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.5
• /
• pp.235-242
• /
• 2017

In order to prepare porous scaffolds capable of pore control, PMMA powder serving as a pore-forming agent was added to HA powder to synthesize a slurry containing TBA as a solvent. And then, porous HA scaffolds where pillarshaped pore channels interconnected with each other were fabricated by freeze-casting and sintering. The crystal structure of the HA scaffolds according to the addition amount of PMMA powder was measured by XRD and the surface and inner cross section of the scaffolds were analyzed through SEM. It was found that removal of PMMA during sintering affects the internal structure of the scaffolds and the crystallinity of the HA powder. Furthermore, through evaluating the physical and mechanical properties of the scaffolds, it was confirmed that the porosity, pore size and compressive strength can be controlled by controlling the addition amount of the pore-forming agent. It was also found that the HA scaffolds produced in this study were similar in structure and properties to the natural cancellous bone. This suggests that porous HA scaffolds with PMMA can be used as an alternative to autogenous bone for tissue engineering as an artificial bone scaffold.

• KDI Journal of Economic Policy
• /
• v.14 no.4
• /
• pp.51-62
• /
• 1992

The purpose of this paper is to estimate the ratio of under-reported business income and related tax to that which is actually reported. The business income and tax are vulnerable to being under-reported. Information about the business income and thus income tax is private information. Without information costs, the tax agency cannot collect all the information about the business income and income tax. In Korea there are more than 600,000 proprietors. Therefore, the costs to investigate the accuracy of the taxpayes' reports are substantial. The tax agency sets a level over which proprietors should report income ratio to total sales, which induces the under-report. To estimate the ratio of under-reported tax, the expenditure method is employed. By this method, the under-reported income can be easily presumed based on expenditures since expenditures are closely related to income. First, the consumption function is estimated by using cross-section data of 1986-89. Generally, the estimation results show the expected sign of the coefficients of the explanatory variables such as income, wealth, and family size. Second, the extent of under-reported business income and related tax is estimated by using the estimation results. The estimated ratios of under-reported tax and income to the actual tax and income fall in the range of 13~39% and 8~25% respectively. This estimation confirms the increasing tendency of the tax detection ratio in previous studies. However, it should be noted that this study is not based on data of the tax report but those of the urban household survey. Therefore, there still remains the possibility that the ratio of under-reported tax could be underestimated.

• Journal of the Korea Concrete Institute
• /
• v.15 no.4
• /
• pp.594-605
• /
• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By investigating existing experiments and numerical results, it was found that flexural pinching which has no relation with shear action appears in RC members subject to axial compression force. However, members with specific arrangement and amount of re-bars, have the same energy dissipation capacity regardless of the magnitude of the axial force applied even though the shape of the cyclic curve varies due to the effect of the axial force. This indicates that concrete as a brittle material does not significantly contribute to the energy dissipation capacity though its effect on the behavior increases as the axial force increases, and that energy dissipation occurs primarily by re-bars. Therefore, the energy dissipation capacity of flexure-dominated member can be calculated by the analysis on the cross-section subject to pure bending, regardless of the actual compressive force applied. Based on the findings, a practical method and the related design equations for estimating energy dissipation capacity and damping modification factor was developed, and their validity was verified by the comparisons with existing experiments. The proposed method can be conveniently used in design practice because it accurately estimates energy dissipation capacity with general design parameters.

• Journal of the Korea Concrete Institute
• /
• v.28 no.1
• /
• pp.59-65
• /
• 2016

Commercial synthetic resins with great amount of hydrogen atoms were investigated for neutron shielding aggregates. Total three types of resins were considered in this study: high density polyethylene (HDPE), polypropylene (PP), and ultra molecular weight polyethylene (UPE). When these resins replaced 20, 40, 60 vol% of fine aggregates, mechanical properties were first evaluated including compressive and tensile strengths, and then image/microstructure analyses such as cross-section analysis, SEM, and X-ray CT were performed. The results showed that the compressive and tensile strengths decreased with the increase of replacement ratio of HDPE and PP, which was found through image analysis that it was closely related to the distribution of resins at the failure surface of test specimens. The strength reduction of UPE was quite small compared to HDPE and PP but it abruptly increased when the replacement level exceeded 60 vol%. The results of microstructure analyses indicated that the replacement level significantly affected the amount of air void so that it is critical to determine the reasonable amount of UPE to make cementitous materials for neutron shielding.