• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.415-423
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• 2006

As the shortage of natural & good quality aggregate for concrete, it is needed development of alternative aggregate. At the present time, the crushed sand is widely used among the alternation aggregate, and the usage of crushed sand will be increased more and more. Generally, crushed sud is produced with wet process in domestic, but some manufacturing companies which are handicapped with local restrict are produced by dry process. In this study, analyzing the facilities of dry crushed sand, the quality properties of dry crushed sand was done by Korean Industrial Standards. Based on the quality results of dry crushed sand, the experiment of concrete with the dry crushed sand which is substitute for sea sand was done. As the results of basic qualities, the amount of 0.08 mm sieve passing ratio was over KS criteria, and the fineness modulus was higher than sea sand, and the other physical properties of dry crushed sand was similar to sea sand. The results of concrete experiment, according to the substitutive ratio of dry crushed sand is increased, the slump and air content of concrete was decreased by increase of fine particles of dry crushed sand, and the unit weight content, compressive & tensile strength of concrete were increased on the contrary. The physical properties of concrete used dry crushed sand were showed same tendency without relation to W/B. Consequently, if the fine particle contents of dry crushed sand was lower, it is judged that dry crushed sand is no problem to use for concrete aggregate and the amount of usage will be increased.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06c
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• pp.265-267
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• 2006

사용목적(Purpose)은 최근 개인 프라이버시 보호와 관련하여 데이타 수집과 수집 후 보안관리에 있어서 중요한 요소로 사용되고 있다. W3C(World Wide Web Consortium)는 데이타 제공자가 자신이 방문한 웹 사이트에 개인정보를 제공하는 것을 통제할 수 있도록 하는 표준을 제시하였다. 그러나 데이타 수집 후 유통과정에서 개인정보에 대한 보안관리에 대한 언급이 없다. 현재 히포크라테스 데이타베이스(Hippocratic Databases), 사용목적기반 접근제어(Purpose Based Access Control)등은 W3C의 데이타 수집 메커니즘을 따르고 있으며, 데이타 수집 후 보안관리에 대하여 사용목적 관리와 접근제어 기법을 사용하여 관리를 하고 있으나 사용목적에 대한 표현과 사용목적 관리의 미흡함으로 인하여 그에 따르는 개인정보의 프라이버시 보호에 있어서 효과적인 해결책을 제시하지 못하고 있다. 본 논문은 사용목적의 표현력을 향상시키면서. 사용목적의 효과적인 관리기법을 제시한다. 또한 개인의 프라이버시 보호를 위한 방법으로 사용목적의 분류화를 통해 최소권한의 원칙을 따르는 접근제어 기법을 제시한다. 본 논문에서는 사용목적을 상속적, 시간적 그리고 독립적 구조로 분류화하였으며, 이렇게 분류화된 사용목적에 대한 각기 다른 관리기법을 제시한다. 또한 접근제어의 유연성을 위해 RBAC의 역할계층 구조를 사용하였으며, 일의 최소 단위인 태스크(task)의 최소권한을 얻기 위한 조건으로 몇몇 특성의 사용목적을 사용하여 만족할 경우 태스크를 처리하기 위한 기존 모델보다 향상된 최소사용권한을 제공하는 기법을 제시한다. Interference Contrast)에 의한 내부구조 관찰이 최종 동정기준이 되어야할 것으로 나타났다.cillus로 구성되었다. 한편, DAL세균군(42균주)은 high G+C 및 low G+C gram positive 계통군 이외에도 proteobacteria -subdivision에 속하는 Afipia와 Ralstonia, proteobacteria -subdivision에 속하는 Variovorax, proteobacteria $\beta$-subdivision에 속하는Pseudomonas로 구성되어 계통학적으로 다양한 세균임이 확인되었다. 40%까지 대체가 가능하였으며, 아울러 높은 라이신 부산물의 대체 수준에 있어서 사료효율과 단백질 전환효율을 고려한다면 아미노산 첨가(라이신과 아르지닌)와 중화 효과에 좋은 결과가 있을 것으로 사료된다.의한 적정 양성수용밀도는 각고 5~6cm 크기의 경우 10~15개체가 적합하였다. 수증별 성장은 15~20 m 수층에서 빨랐으며, 성장촉진과 폐사를 줄이기 위해서는 고수온이 지속되는 7~10월에는 20~30m수층으로 채롱을 내려 양성하고 그 외 시기에는 15 m층 내외가 좋은 것으로 나타났다. 상품으로 출하 가능한 크기 인 각고 10 cm이상, 전중량 140 g 내외로 성장시 키기까지는 채묘후 22개월이 소요되었고, 출하시기는 전중량 증가가 최대에 이르는 3월에서 4월 중순이 경제적일 것으로 판단된다.er 90 % of good relative dynamic modulus of elasticity due to fineness of formation caused by the

• Proceedings of the Korean Information Science Society Conference
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• 2006.06c
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• pp.274-276
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• 2006

e-seal은 RFID(Radio Frequency IDentification) 기술을 사용하여 원격에서 자동으로 봉인상태를 확인할 수 있는 컨테이너 봉인 장치를 말한다. RFID의 특징상 반도체 칩에 기록된 정보를 제 삼자가 쉽게 판독 및 변조할 수 있다는 취약점으로 인하여 활성화되지 못하고 있는 실정이다. ISO에서는 RFID의 취약점을 보안하기 위한 표준작업(ISO 18185)을 진행 중이다. 이 중, ISO 18185-4는 e-seal에 저장되는 자료나 리더와의 RF통신에서 데이터 보호를 위한 표준이다. 이와 관련된 연구로는 인증 프로토콜과 ISO 18185-4를 위한 보고서로 제출된 보안 프로토콜이 있다. 제안된 e-seal 보안 프로토콜을 적용하기 위해서는 e-seal과 리더 간의 데이터를 암/복호화할 키가 필요하지만, 키 서버를 통해 전달받은 마스터 키를 데이터 암/복호화 키로 바로 사용하는 것은 보안 상의 문제점을 야기할 수 있기 때문에 PRF(Pseudo Random Function)을 이용하여 마스터 키로부터 MTK(Mutual Transient Key)를 유도하고, MTK를 암/복호화 키로 사용해야 한다. 기존의 PRF는 일방향 해시 함수(MD5, SHA 등)를 기반으로 하는 HMAC[2. 3]을 일반적으로 사용하였다. 그러나 일방향 해시 함수는 e-seal과 같은 제한된 자원을 갖는 환경에 적합하지 않다. 따라서, 본 논문에서는 e-seal 보안 프로토콜을 위한 효율적인 PRF을 제안한다. 기존의 일방향 해시 함수 기반이 아닌 블록 암호화 알고리즘을 기반으로 하는 MAC을 이용하여 PRF을 보다 효율적으로 구현하였고, 블록 암호화 알고리즘은 AES를 선택 합성체 $GF((2^4)^2)$을 통해 하드웨어 모듈을 최적화 하였다. AES를 기반으로 하는 MAC은 HMAC에 비해 면적 및 처리율에서 뛰어난 결과를 보여주었다.<0.01).이상의 연구 결과, cook-chill생산 시 녹차 추출물의 첨가가 미생물적 품질유지에 효과가 있다고 사료되는 바 본 연구결과를 기초로 급식소에서 음식 생산 시 녹차 추출물 및 천연 항균성 물질 첨가에 따른 미생물적 품질 및 관능적 품질검사를 통한 레시피 개발에 관한 지속적인 연구가 수행되어야 하겠다.다.다리다보니 점심시간을 활용할 수 없게 되는 문제점에 대한 재검토가 필요하다. 따라서 차후 학교급식의 안전성 확보를 위한 급식환경 개선의 일환으로 식당공간 확보 시 신속한 시간 내에 급식이 가능하도록 넓은 공간과 쾌적한 환경의 식당 조성에 대해 관심을 기울여야 할 것으로 사료된다. 이상 여부를 반영하는 임상증상의 빈도가 높은 청소년기 남녀 중학생의 경우 아침과 저녁의 결식빈도 및 외식과 간식의 빈도가 높았고, 아침식사의 질과 체형만족도가 낮은 것으로 나타나 청소년의 건강과 식습관 및 체형만족도가 상호 관련성이 높은 것으로 나타났다. 따라서 본 연구 결과는 성장기 청소년의 건강 유지를 위하여 바람직한 식습관의 중요성을 재인식할 수 있었으며, 올바른 식습관 확립을 위한 영양교육의 중요성이 재확인되었다.경제적일 것으로 판단된다.er 90 % of good relative dynamic modulus of elasticity due to fineness of formation caused by the increase of the unit powder content and the improvement of flowability, without regard to the replacement of crushed stone fines. Therefore, it can be said that the usage of crushed stone fines can control the strength of super flowing concrete by replacement and re

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.311-320
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• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.252-260
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• 2015

The aim of this research is providing the fundamental data for treating and recycling the byproducts by using the wet processed bottom ash as a fine aggregate replacement for cement-based extruded panel. Although the cement-based extruded panel was used mainly as a cladding component with its high strength and outstanding durability, it was hardly spread because of low economic feasibility due to the high cost of additives or fibers which were used to achieve 14 MPa of flexural strength as a cladding material. As a solution of this drawback, by the previous research, it was possible to replace cement by fly ash up to 80 % by decreasing quality criteria with restricting the application to indoor purpose. In this research, based on the previous research, by using the bottom ash as a replacement of fly ash, improvement of shape retention performance is tried. As a result of the experiment on evaluating the optimum content and PSD of bottom ash, as the fineness modulus and content of bottom ash was increased, the extruding performance was decreased and penetration resistance was increased. Additionally, the optimum content and the maximum particle size was found as 20 %, and 0.3 mm, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.77-86
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• 2013

This study investigates the fundamental properties of the water-binder (W/B) ratio and fine aggregate-binder (F/B) ratio in the alkali-activated slag cement (AASC) mortar. The W/B ratios are 0.35, 0.40, 0.45, and 0.50, respectively. And then the F/B ratios varied between 1.00 and 3.00 at a constant increment of 0.25. The alkali activator was an 2M and 4M NaOH. The measured mechanical properties were compared, flow, compressive strength, absorption, ultra sonic velocity, and dry shrinkage. The flow, compressive strength, absorption, ultra sonic velocity and dry shrinkage decreased with increases W/B ratio. The compressive strength decreases with increase F/B ratio at same W/B ratio. Also, at certain value of F/B ratio significant increase in strength is observed. And S2 (river sand 2) had lower physical properties than S1 (river sand 1) due to the fineness modulus. The results of experiments indicated that the mechanical properties of AASC depended on the W/B ratio and F/B ratio. The optimum range for W/B ratios and F/B ratios of AASC is suggested that the F/B ratios by 1.75~2.50 at each W/B ratios. Moreover, the W/(B+F) ratios between 0.13 and 0.14 had a beneficial effect on the design of AASC mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.116-121
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• 2019

In order to evaluating applicability of RAP (recycled aggregate powder) in mortar, in this study, physical and mechanical tests was carried out. Material characteristics of recycled aggregate and RAP were evaluated and the mechanical properties of mortar replaced with RAP were analyzed. Test result of sieve analysis showed that as the milling time increased the fineness modulus was decreased and the distribution of 0.6 mm particle size was found to increase. The fluidity of mortar mixture substituted with RAP tended to increase than Plain mixture. It was result that the increasing fluidity was affected by unreacted surplus water in the mortar as the binder was replaced with RAP. From the compressive strength result of the mortar subjected to RAP, it was found that the RAP was able to replace up to about 10% of unit binder weight although the compressive strength of mortar was decreased as the RAP replacement increased. From the above study, it can be concluded that the physical properties of RAP satisfied the quality standard of aggregate for replacement with fine aggregate. Moreover, in case of the RAP was replaced up to 10% of unit cement weight, it was able to be possible to improve fluidity and compressive strength of mortar.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.649-659
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• 2022

This study examined the granite, quartzite, phyllite, schist, and gneiss as aggregate resources among the original rock distributed in the Chungju-Goesan area. The granite distributed in the study area is mainly composed of Jurassic biotite granite, and the quartzite layer is from the Daehyangsan quartzite Formation distributed on the upper part of the Gyemyeongsan Formation and the Hyangsan-ri dolomitic limestone Formation. In addition, phyllite is pophyrytic phyllite-schist from the Hwanggangri Formation of the Okcheon group, schist is chlorite schist, from the Munjuri Formation of the Okcheon group, and gneiss is porphyroblastic gneiss which is the upper part of the Seochangri Formation. Aggregate quality evaluation factors of these rocks included fineness modulus, absorption, unit weight, absolute dry density, solid content, porosity, resistance to abrasion, and soundness. In the case of granite, it was found to be partially unsatisfactory in terms of unit weight, solid content, porosity, and resistance to abrasion. Gneiss was found to be out of the standard values in resistance to abrasion and schist in porosity and solid content. As for the overall quality of aggregate resources, it was analyzed that quartzite, gneiss, and phyllite showed excellent quality. Aggregate quality tests are performed simply for each rock, but the rock may vary depending on the morphology of the mineral. Therefore, when analyzing and utilizing the quality evaluation of aggregate resources, it will be possible to use them more efficiently if the rock-mineralological research is performed together.

• Advances in nano research
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• v.16 no.4
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• pp.375-394
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• 2024

The extensive utilization of concrete has given rise to environmental concerns, specifically concerning the depletion of river sand. To address this issue, waste deposits can provide manufactured-sand (MS) as a substitute for river sand. The objective of this study is to explore the application of machine learning techniques to facilitate the production of manufactured-sand concrete (MSC) containing stone nano-powder through estimating the splitting tensile strength (STS) containing compressive strength of cement (CSC), tensile strength of cement (TSC), curing age (CA), maximum size of the crushed stone (Dmax), stone nano-powder content (SNC), fineness modulus of sand (FMS), water to cement ratio (W/C), sand ratio (SR), and slump (S). To achieve this goal, a total of 310 data points, encompassing nine influential factors affecting the mechanical properties of MSC, are collected through laboratory tests. Subsequently, the gathered dataset is divided into two subsets, one for training and the other for testing; comprising 90% (280 samples) and 10% (30 samples) of the total data, respectively. By employing the generated dataset, novel models were developed for evaluating the STS of MSC in relation to the nine input features. The analysis results revealed significant correlations between the CSC and the curing age CA with STS. Moreover, when delving into sensitivity analysis using an empirical model, it becomes apparent that parameters such as the FMS and the W/C exert minimal influence on the STS. We employed various loss functions to gauge the effectiveness and precision of our methodologies. Impressively, the outcomes of our devised models exhibited commendable accuracy and reliability, with all models displaying an R-squared value surpassing 0.75 and loss function values approaching insignificance. To further refine the estimation of STS for engineering endeavors, we also developed a user-friendly graphical interface for our machine learning models. These proposed models present a practical alternative to laborious, expensive, and complex laboratory techniques, thereby simplifying the production of mortar specimens.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.1
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• pp.13-20
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• 2005

The effects of pectin on obesity was studied using 3T3-L1 pre-adipocytes and rats fed 20% high fat diets. The concentration of leptin released from 3T3-L1 adipocytes in the presence of pectin was significantly decreased by 85% compared to that of the control (p<0.05), however, glycerol concentration was not changed. These data indicate that pectin seems to inhibit lipids accumulation in the adipocytes rather than enhance the lipolytic activity. Forty Sprague Dawley rats were fed 20% high fat diet for 8 weeks to induce obesity and then divided equally into four groups. Experimental groups were normal diet group (ND), high fat diet group (HFD), HDF with 10% pectin group (HFP10), and HDF with 20% pectin group (HFP20). Diet for the each group was prepared to be iso-caloric following AIN-76 guideline. After obesity was induced, rats were placed on an restricted diet for 9 weeks. The body weight of HFD increased 50% (p<0.05) compared to the ND, while it was decreased by 12% and 16% for HFP10 and HFP20, respectively (p<0.05). The relative amount of visceral fats for HFDl0 and HFD20 were decreased by 45% and 59% compared to that of HDF (130%), respectively (p<0.05). Pectin seems to have a greater effect on reducing visceral fats accumulation than weight reduction. Significantly increased level of triglyceride, total cholesterol or LDL-cholesterol in the plasma of HFD was returned to the normal or even below the normal by pectin diet, while the level of HDL-cholesterol increased. Lipid lowering effect was also observed in the liver and heart. These effects of pectin were dosedependent. In conclusion, the beneficial effect of pectin on the obesity was observed from cell culture experiment and animal study in terms of inhibiting the accumulation of lipids in the adipocytes.