• Structural Engineering and Mechanics
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• v.39 no.2
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• pp.241-266
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• 2011

The Self Compacting Concrete, SCC is the new generation type of concrete which is not needed to be compacted by vibrator and it will be compacted by its own weight. Since SCC is a new innovation and also the high strength self compacting concrete, HSSCC behavior is like a brittle material, therefore, understanding the strength effect on the serviceability performance of reinforced self compacting concretes is critical. For this aim, first the normal and high strength self compacting concrete, NSSCC and HSSCC was designed. Then, the serviceability performance of reinforced connections consisting of NSSCC and HSSCC were investigated. Twelve reinforced concrete connections (L = 3 m, b = 0.15 m, h = 0.3 m) were simulated, by this concretes, the maximum and minimum reinforcement ratios ${\rho}$ and ${\rho}^{\prime}$ (percentage of tensile and compressive steel reinforcement) are in accordance with the provision of the ACI-05 for conventional RC structures. This study was limited to the case of bending without axial load, utilizing simple connections loaded at mid span through a stub (b = 0.15 m, h = 0.3 m, L = 0.3 m) to simulate a beam-column connection. During the test, concrete and steel strains, deflections and crack widths were measured at different locations along each member. Based on the experimental readings and observations, the cracked moment of inertia ($I_{cr}$) of members was determined and the results were compared with some selective theoretical methods. Also, the flexural crack widths of the members were measured and the applicability for conventional vibrated concrete, as for ACI, BS and CSA code, was verified for SCCs members tested. A comparison between two Codes (ACI and CSA) for the theoretical values cracking moment is indicate that, irrespective of the concrete strength, for the specimens reported, the prediction values of two codes are almost equale. The experimental cracked moment of inertia $(I_{cr})_{\exp}$ is lower than its theoretical $(I_{cr})_{th}$ values, and therefore theoretically it is overestimated. Also, a general conclusion is that, by increasing the percentage of ${\rho}$, the value of $I_{cr}$ is increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3800-3805
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• 2012

Infrared(IR) reflective black cool pigment and paint which is used for interior/exterior materials(IR reflectance >30%) to prevent heat island effect and to increase energy efficiency were studied. Cool pigment was synthesized using mixture of $Fe_2O_3$ and $Cr_2O_3$ with calcination from 900 to $1,200^{\circ}C$. Cool paint was prepared by formulation of cool pigment, acrylic resins, and other additives. Results showed that optimum color fixation of pigment obtained by mole ratio of Fe to Cr was 0.9 with calcination temperature at $1,000^{\circ}C$. The cool paint formulated by 20% pigment and 1.5% dispersive additive with $125{\mu}m$ thickness of coated layer showed optimum IR reflectance. Temperature difference on surface between cool paint and ordinary paint(STD) was $36.5^{\circ}C$ and IR reflectance(TSR) was 39.3% at wavelength from 700 to 2,500nm. And color change was not detected during 500hrs weathering test.

• Korean Journal of Environmental Agriculture
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• v.39 no.4
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• pp.289-296
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• 2020

BACKGROUND: There is a need for a revolutionary method to overcome the problem of biochar, which has relatively low adsorption capacity for existing anion pollutants, along with collectively recycling fallen leaves, a kind of forest by-product. Therefore, the objective of this study was to prepare iron-decorated biochar derived from fallen leaves (Fe-FLB), and to evaluate their adsorption properties to Congo red (CR) as anionic dye. METHODS AND RESULTS: The adsorption properties of CR by fallen leaves biochar (FLB) and Fe-FLB were performed under various conditions such as initial CR concentration, reaction time, pH and dosage with isotherm and kinetic models. In this study, Fe-FLB prepared through iron impregnation and pyrolysis of fallen leaves contained 56.9% carbon and 6.3% iron. Congo red adsorption by FLB and Fe-FLB was well described by Langmuir model and pseudo second order model and the maximum adsorption capacities of FLB and Fe-FLB were 1.1 mg/g and 25.6 mg/g, respectively. In particular, it was found that the adsorption of CR was occurred by chemical adsorption process by the outer boundary layer of Fe-FLB. CONCLUSION: Overall, the production of Fe-FLB using fallen leaves and using it as an anion adsorbent is considered to be a way to overcome the problem of biochar with relatively low anion adsorption in addition to the reduction effect of waste.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.245-253
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• 2006

We evaluated the relations among exposure and urinary levels of Cr, folate, vitamin $B_{12}$ and Hcy levels in the workers chronically exposure to Cr. Subjects were 104 male employees, 65 workers exposed to Cr in 9 electroplating plants and 39 office workers who had never been occupationally exposed to hazardous substances including Cr. The geometric mean(GM) of Cr in workplace was $0.069{\pm}0.101mg/m^3$ and urinary Cr was $0.483{\pm}0.394mg/g$ creatinine and airborne Cr concentration was significantly correlated to the urinary concentration of Cr(r=0.900, p=0.000). The geometric mean concentration of urinary Cr in control group was $0.301{\pm}0.255mg/g$ creatinine. In comparing the workers exposed to Cr with controls, significantly higher mean plasma levels were found of Hcy($11.3{\pm}4.9$ vs $9.4{\pm}4.7{\mu}mol/{\ell}$, p=0.05), but vitamin $B_{12}$ levels ($181.8{\pm}68.7$ vs $216.0{\pm}64.3nmol/{\ell}$, p=0.01) was significantly decreased. Hcy concentrations correlated positively with airborne Cr concentrations(r=0.287, p=0.004) and urinary Cr concentrations(r=0.244, p=0.015) but folate concentrations correlated negatively with airborne(r=-0.234, p=0.020) and urinary Cr concentrations(r=-0.640, p=0.090), respectively. No correlations were observed between vitamin $B_{12}$, airborne and urinary Cr concentrations. Also, Hcy concentrations correlated positively with vitamin $B_{12}$(r=0.295, p=0.0020 and negatively with folate concentrations(r=-0.196, p=0.046). The various biological(i.e. age and serum indicates) or lifestyle factors(i.e. medication, smoking, alcohol and coffee intake), also taken into account as potential confounders, did not influence the correlations found. Thus, this study found evidence that Cr might be associated with elevated plasma levels of Hcy. Furthermore, elevated plasma levels of Hcy were significantly associated with folate and vitamin $B_{12}$ concentration.

• Journal of radiological science and technology
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• v.31 no.4
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• pp.415-417
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• 2008

This study is to measure the radiation dose of neutrons generated by the particle accelerator during X-ray (photon) treatment with a neutron detection method by using CR-39, and to research how the generation of neutrons may incur problems associated with radiation doses for patient treatment when using high energy photons for cancer treatment as a clinical application. The findings are summarized as follows : The results showed that average 0.35mSv was measured with exposure of 1Gy photon in case of fast neutron, 0.65mSv with exposure of 2Gy photon, 1.82mSv exposure of 5Gy, 0.26mSv with exposure of 1Gy photon in case of thermal neutron, 0.56mSv with exposure of 2Gy photon, and 1.23mSv with exposure of 5Gy of photon. By measuring the occurrence of neutron by using Wedge Filter, it has been confirmed that the occurrence of neutrons increased when using Wedge Filter. The results also showed that more neutrons were detected over the existing experiments when using an SRS Cone requiring high doses of radiation. Total 2.85mSv neutrons were found on the average with exposure of 5Gy photon in case of fast neutron and 1.37mSv neutrons were found on the average with exposure of 5Gy photon in case of thermal neutron. During the general treatment, about 1.6 times more neutrons over 5Gy photon were found in case of fast neutron and about 1.12 time more neutrons over 5Gy photon were found in case of thermal neutron.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.55-60
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• 2010

Purpose: We investigated the changes of plastic lens after etching of coating films by comparing uncoated lens. Methods: CR-39, middle index and high index lenses of 0 (zero) diopter were etched at $80^{\circ}C$ and room temperature using a coating remover, and then changes of refractive power, transmittance and surface morphology were investigated. Results: There were no differences in refractive power and transmittance between uncoated and etched lenses. The etching rate was similar in both CR-39 and middle index lens, but in the case of high index lens, it was slower and less steady than the others. From the SEM observation of lens surface, etching damage was found out on the surface of etched lens. It was shown the least damage in middle index lens but the most damage in high index lens. Conclusions: If the etching of coating films is demanded on condition that the surface of ophthalmic lenses are not damaged, a using of most adequate coating remover based on lens material should be considered, and a caution for proper etching conditions is required.

• The Journal of the Korea Contents Association
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• v.10 no.11
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• pp.228-234
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• 2010

Ni-Cr and Co-Cr alloy uncontained Be element for using as dental porcelain alloy were analyzed the mechanical properties through bonding strength and fracture test after the bonding with porcelain. The bonding strengths between alloy and ceramic were measured through the shear bond strength test. Consequently, the T-3 group contained Be element that had shear strength of 41.13(${\pm}5.11$)MPa was showed the highest shear strength than the other groups. The second highest group was a verabond contained Be element that had shear strength of 40.72(${\pm}5.98$)MPa. The results of the other groups according to the shear strength were Wirobond(38.40(${\pm}9.66$)MPa) belonged to Co-Cr alloy, and Verabond 2V(32.77(${\pm}4.31$)MPa), Bellabond N(28.63(${\pm}6.39$)MPa), Bellabond plus(24.97(${\pm}6.13$)MPa), Argeloy N.P. Star(22.69(${\pm}3.41$)MPa) uncontained Be element, respectively. The morphological aspects of the fracture surface between alloys and ceramic were observed that all groups were caused mixed failure as conformation attached ceramic fragments to metallic surface by fracture process.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.61-68
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• 2007

Interfacial fracture energy(${\Gamma}$) between $Al_2O_3$ thin film deposited by Atomic Layer Deposition(ALD) and sputter deposited Cu electrode for embedded PCB applications is measured from a $90^{\circ}$ peel test. While the interfacial fracture energy of $Cu/Al_2O_3$ is very poor, Cr adhesion layer increases the interfacial fracture energy to $39.8{\pm}3.2g/mm\;for\;Ar^+$ RF plasma power density of $0.123W/cm^2$, which seems to come from the enhancement of the mechanical interlocking and Cr-O chemical bonding effects.

• Journal of Navigation and Port Research
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• v.39 no.4
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• pp.335-344
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• 2015

This study aims to assess the effectiveness of zeolite, montmorillonite, and steel slag as capping materials to block the release of heavy metals from marine sediment depending on their depths. The results showed that all capping materials used this study were not effective in interrupting release of As. Zeolite had negative effect on the block of Cr release but it was significantly reduced to 5 cm by montmorillonite capping. In contrast to As and Cr, Cd, Ni, and Pb were not released even from uncapped sediments. Cu and Zn were the heavy metals those were most significantly influenced by the capping conditions. Cu release from marine sediments were effectively blocked by more than 1 cm depth of montmorillonite and more than 3 cm depth of zeolite. All capping materials were found to be effective in interrupting release of Zn from marine sediments. It was concluded that the zeolite, montmorillonite, and steel slag could be used as a potential capping material for interrupting the release of Cr, Cu, and Zn from the contaminated marine sediments.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.39-42
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• 1999

1) 서울 지역 도로가 퇴적물에서는 특히 Cu와 Zn의 오염이 도심 지역을 중심으로 심각하게 진행되고 있으며. Pb는 무연 휘발유의 사용량 증가와 더불어 감소 추세이나 여전히 높은 함량을 나타내고 있다. 2) Pb와 Cr의 함량은 공간적 지배가 강하여 Pb는 주로 교통 혼잡 지역, Cr은 공구상 밀집 지역에서 높게 나타난다. 반면, Cu, Cd, Zn 함량은 시간적 및 공간적 변화를 모두 보여주어 금속 산업 밀집도 및 강우량 변화에 따라 변화된다. 3) 특히 오염이 심화되고 있는 지역의 도로가 퇴적물이 하수계로 직접 유입되지 못하도록 차단하는 적절한 시설이 필요하며, 아울러 오염된 퇴적물을 집적하여 처분할 때는 주변 토양의 오염에 유의해야 할 것이다.