• Advances in concrete construction
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• 제6권1호
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• pp.29-45
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• 2018

This paper investigates the effect of inclusion of glass fibers on mechanical and fracture properties of binary blend geopolymer concrete produced by using fly ash and ground granulated blast furnace slag. To study the effect of glass fibers, the mix design parameters like binder content, alkaline solution/binder ratio, sodium hydroxide concentration and aggregate grading were kept constant. Four different volume fractions (0.1%, 0.2%, 0.3% and 0.4%) and two different lengths (6 mm, 13 mm) of glass fibers were considered in the present study. Three different notch-depth ratios (0.1, 0.2, and 0.3) were considered for determining the fracture properties. The test results indicated that the addition of glass fibers improved the flexural strength, split tensile strength, fracture energy, critical stress intensity factor and critical crack mouth opening displacement of geopolymer concrete. 13 mm fibers are found to be more effective than 6 mm fibers and the optimum dosage of glass fibers was found to be 0.3% (by volume of concrete). The study shows the enormous potential of glass fiber reinforced geopolymer concrete in structural applications.

• Computers and Concrete
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• 제18권6호
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• pp.1065-1082
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• 2016

The main aim of this study is to predict the compressive and flexural strengths of self-compacting mortar (SCM) containing $nano-SiO_2$, $nano-Fe_2O_3$ and nano-CuO using wavelet-based weighted least squares-support vector machines (WLS-SVM) approach which is called WWLS-SVM. The WWLS-SVM regression model is a relatively new metamodel has been successfully introduced as an excellent machine learning algorithm to engineering problems and has yielded encouraging results. In order to achieve the aim of this study, first, the WLS-SVM and WWLS-SVM models are developed based on a database. In the database, nine variables which consist of cement, sand, NS, NF, NC, superplasticizer dosage, slump flow diameter and V-funnel flow time are considered as the input parameters of the models. The compressive and flexural strengths of SCM are also chosen as the output parameters of the models. Finally, a statistical analysis is performed to demonstrate the generality performance of the models for predicting the compressive and flexural strengths. The numerical results show that both of these metamodels have good performance in the desirable accuracy and applicability. Furthermore, by adopting these predicting metamodels, the considerable cost and time-consuming laboratory tests can be eliminated.

• Computers and Concrete
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• 제15권2호
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• pp.215-229
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• 2015

The emerging technology of self compacting concrete, fiber reinforcement together reduces vibration and substitute conventional reinforcement which help in improving the economic efficiency of the construction. The objective of this work is to find the regression model to determine the response surface of mix proportioning Steel Fiber Reinforced Self Compacting Concrete (SFSCC) using statistical investigation. A total of 30 mixtures were designed and analyzed based on Design of Experiment (DOE). The fresh properties of SCC and mechanical properties of concrete were studied using Response Surface Methodology (RSM). The results were analyzed by limited proportion of fly ash, fiber, volume combination ratio of two steel fibers with aspect ratio of 50/35: 60/30 and super plasticizer (SP) dosage. The center composite designs (CCD) have selected to produce the response in quadratic equation. The model responses included in the primary stage were flowing ability, filling ability, passing ability and segregation index whereas in harden stage of concrete, compressive strength, split tensile strength and flexural strength at 28 days were tested. In this paper, the regression model and the response surface plots have been discussed, and optimal results were found for all the responses.

• Journal of Pharmaceutical Investigation
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• 제30권3호
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• pp.167-172
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• 2000

The purpose of this study is to develop a transurethral liquid suppository containing prostaglandin $E_1\;(PGE_1)-loaded$ microemulsion, which undergoes a phase transition to gels at body temperature. The effects of oils, ethanol as solvent and HCl as pH-controlling agent on the physicochemical properties of liquid suppositories composed of poloxamer P 407, P 188 and carbopol was investigated. The stability of $PGE_1$ and release of $PGE_1$ from liquid suppository were evaluated. Oils such as Neobee and soybean oil significantly decreased the gelation temperature but increased the gel strength of liquid suppository due to their strongly binding with the components of liquid suppository base. However, ethanol slightly did the opposite. The pH of liquid suppositories hardly affected the gelation temperature and gel strength due to addition of very small HCl (0.005-0.01%). A liquid suppository [$PGE_1/P$ 407/P 188/carbopol/Neobee/ethanol/HCl (0.2/14/14/0.4/7/2/0.005%)], which had the gelation temperature $(34.2{\pm}0.6^{\circ}C)$ and gel strength $(31.35{\pm}4.37\;sec)$ suitable for liquid suppository system, was easily administered and not leak out from the body. About 60% of $PGE_1$ was released out within 2 h from this formulation. It was shown that the release of $PGE_1$ was proportional to the square root of time, indicating that $PGE_1$ might be released from the suppository by Fickian diffusion. It was stable at $4^{\circ}C$ for at least 2 months. The results suggest that transurethral liquid suppository containing prostaglandin $E_1-loaded$ microemulsion is thought to be a convenient, safe and effective dosage form for $PGE_1$. However, it should be further developed as a more convenient and stable dosage form for $PGE_1$.

• 한국전문물리치료학회지
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• 제14권3호
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• pp.72-80
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• 2007

The purpose of this study was to verify the effects on fine motor, muscle strength (hand-grip), explosive muscular strength (vertical jump) and muscular endurance (sit-up) after ingesting coffee. Hence this study targeted a sample group of 38 healthy men in their twenties, without cardiac disorders and muscle disorders and none of them were hypersensitive to caffeine with symptoms such as palpitation and dyspnea. Nineteen of them ingested coffee, whereas the other nineteen men ingested decaffeinated coffee at the same amount. The amount of coffee was controlled by weight so as to regulate intake to 6 mg caffeine per kg. Research material was evaluated through O'Conner's finger dexterity test, hand-grip strength test, vertical jump test and sit-up test. The data were analyzed by means of paired t-test and ANCOVA. The material was then, analyzed by means of two-way ANOVA in order to verify the effect of one or two cups of coffee on fine motor and hand-grip strength. All parameters were measured by an independent observer. The results were as follows: There were no significant differences to fine motor, hand-grip strength, vertical jump, sit-up before and after drinking decaffeinated coffee, but there was a difference to those before and after drinking caffeine coffee. There was no significant difference to hand dexterity and hand-grip strength in one or two cups of coffee. Intake of a certain dosage of caffeine effects activation of muscles working in a short period based on the results. As a consequence, intake of certain dosages of caffeine was beneficial to enhance efficiency of activity during exercises, but it is will be difficult to obtain the desired result with only one or two cups of coffee.

• Geomechanics and Engineering
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• 제33권1호
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• pp.29-40
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• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.

• 자원리싸이클링
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• 제27권1호
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• pp.45-54
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• 2018

플라이애시의 부유선별 과정에서 교반속도와 공기주입량과 같은 기계적 요소 변화에 따른 영향을 알아보고자 본 연구를 실시하였다. 본 연구에서는 미연탄소 함량이 약 3.4 ~ 3.7% 수준인 화력발전소 플라이애시를 사용하였다. 대표적인 부유선별의 선별 요소인 pH, 교반속도, 포수제 첨가량, 기포제 첨가량 변화에 따른 영향을 살펴보았을 때, Safflower oil을 포수제로 사용하여 첨가량을 800 g/ton, pH 7, 교반속도 1,200 rpm, 기포제 첨가량이 400 g/ton였을 때, 미연탄소 회수율과 미연탄소 함량이 각각 63%, 34%로 나타났다. 이 때 부상물 SEM/EDS 분석을 통해 알아본 결과, 구형의 플라이애시 미립자가 미연탄소 내에 고용되거나, 광액 내에 가라앉지 못하고 기포와 함께 부유함으로써 미연탄소의 함량을 낮추는 것으로 나타났다. 교반속도와 공기주입량과 같은 기계적 요소를 변화시킨 실험에서는 공기주입량 8L/min, 교반 속도 900 rpm에서 미연탄소 회수율 74%, 미연탄소 함량 67%인 것으로 나타났다. 이는 낮은 교반속도와 추가 공기주입으로 인하여 광액 내 와류의 강도가 낮아져, 미립의 플라이애시 입자가 미연탄소와 함께 부유되는 현상을 방지됨으로써, 미연탄소 회수율과 미연탄소 함량이 향상된 것으로 나타났다. 또한, 교반속도와 공기주입량을 각각 800 rpm, 6 L/min으로 설정하였을 때 미연탄소 회수율과 미연탄소 탄소함량이 각각 80%, 70%로 향상되어 가장 우수한 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제19권3호
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• pp.39-47
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• 2015

본 연구는 MgO를 0~16% 사용한 알칼리 활성화 슬래그 시멘트 (AASC)의 강도와 건조수축 특성에 관안 연구이다. 고로슬래그 미분말 (GGBFS)는 KOH를 활성화제로 사용하였고, 활성화제의 농도는 2M과 4M이다. MgO는 GGBFS의 중량에 대해 치환하였고 물-결합재 비 (w/b)는 0.5이다. 실험결과, 높은 MgO 치환율은 높은 수화반응으로 모든 재령에서 높은 압축강도를 나타내었다. 압축강도와 초음파속도 (UPV)는 MgO의 양이 증가함에 따라 증가되었다. AASC의 건조수축은 MgO의 양이 증가함에 따라 감소하였다. SEM 결과를 통해 높은 양의 MgO 시험체는 치밀한 반응 생성물질이 만들어 진 것을 확인할 수 있다.

• 한국건설순환자원학회논문집
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• 제4권3호
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• pp.299-306
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• 2016

본 연구에서는 동일 작업성 조건에서 저품질 잔 굵은 골재가 콘크리트의 공학적 특성에 미치는 영향을 실험적으로 분석 하고자 하였는데, 그 결과를 요약하면 다음과 같다. 먼저, 슬럼프 및 공기량을 단위수량과 AE제 혼입량 변화로 동일하게 배합설계 하였다. 따라서, 양호한 품질의 골재를 사용한 배합에 비해 저품질의 골재 사용시 불량의 입도 및 미립자량 등의 영향으로 단위수량 및 AE제 혼입량이 각각 약 18%, 98% 증가하는 경향이 나타났다. 압축강도의 경우는 양호한 품질의 부순 굵은 골재를 사용한 배합에 비해 저품질의 발파석 굵은 골재를 사용한 배합에서 특히, 발파석 마사토 및 해사와 같은 저품질 잔골재와 복합될 때 20~35% 까지 저하하는 결과를 나타내었다. 또한, 저품질 잔 굵은 골재를 사용한 콘크리트인 경우는 압축강도뿐만 아니라 탄성계수와 내구성으로 동결융해, 건조수축, 탄산화 및 염해저항성 측면에서도 크게 저하하여 그 심각이 문제시 되었다. 따라서 저품질 골재를 순환자원으로 활용하고자 할 때에는 물씻기, 혼합골재에 의한 입도 조정 등 별도의 처리를 거쳐 사용하거나 혹은 사용을 철저히 규제하는 특별한 대책이 수립 되어야 할 것으로 사료된다.

• 펄프종이기술
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• 제43권5호
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• pp.43-48
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• 2011

Filler loading at thick stock was carried out in order to verify if the dual addition of filler can be used as a means to reduce the detrimental effects of filler on the strength properties of paper. PCC was added to 3.5% pulp slurry blended with HwBKP, BCTMP and SwBKP. Cationic starch was used as a fixing agent. The mixture of PCC and pulp was stirred for 5, 10 and 20min. at 1,000 rpm. The remaining PCC was washed out before handsheet making. PCC particles were flocculated and fixed on the pulp fiber and/or space between fibers. It is expected that the flocculation and inclusion of PCC can be helpful to improve the strength properties of paper due to the reduction of detrimental effect in fiber bonding. The distinct tendency in PCC flocculation and fixing on pulp fiber was not observed by the change of cationic starch dosage and treatment time.