• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.309-313
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• 2014

The volume fraction of the coarse aggregate in the conventional plastic concrete is controlled relatively low to ensure a required workability. In this paper, a new type of coarse aggregate interlocking concrete with strength ranging from C30 to C80 was prepared with scattering-filling aggregate process. The strength of concrete prepared with this method increases obviously whereas the shrinkage decreases significantly, the cement dosage in the concrete decreased 20 % at the same time. The microhardness of the ITZ between the cement paste and scattering-filling aggregate is higher than that of the original aggregate, the ITZ become narrower and tighter also. The interlocking and more even distribution of the coarse aggregate and the water absorption of the addition of extra amount of coarse aggregates contribute to the strength and performance improvement of the concrete prepared with scattering-filling aggregate process.

• Computers and Concrete
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• 제16권3호
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• pp.343-356
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• 2015

1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

• 한국환경보건학회지
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• 제8권2호
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• pp.13-31
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• 1982

Factors affecting on dewatering characteristics of anaerobically digested or/and elutriated sludges were examined from 15 January 1982 to 30 April 1982, results obtained were as follows 1. Sludges, either anaerobically digested or/and elutriated sludges, which were produced at the Joong Rang Cheon Sewage Treatment Plant wore found to be compressive in its nature, coefficient of compressibility ranged from 0.83 for unelutriated and 1.10 for elutriated. 2. Dosage of FeC13 for the anaerobically digested sludges were difficult to establish for the most favorable dosage rate, though the filterability indicated linear improvement with increased dosage from dosing rate excess of over 15% in terms of dry solids by weight, under the conditions of this examination. Optimum filterability were obtained with 9~11% of $FeCl_3$ for elutriated sludges, and required CaO, as aids, were appeared to be 2.5~3.5 times that of the $FeCl_3$ at that point by weight. 3. The specific resistances for anaerobically digested sludges showed higher value than the elutriated one, being $11 \times 10^{12} ~ 20 \times 10^{12}$ cm/g with no chemical conditioning, and $2 \times 10^{12} ~ 11 \times 10^{12}$ cm/g with conditioned ($FeCl_3$ + CaO) contrast to $0.5 \times 10^{12} ~ 2.0 \times 10cm/g$ for the elutriated. 4. The strength of the alkalinities before and after elutriation were measured to 10,000 ~ 15,000 mg/l and 1,500 ~ 2,000mg/l respectively. These alkalinities affected greatly on the filterabilities together with concentration of the organic matters in the sludges. 5. The yields with 11% $FeCl_3$, by weight to the DS, on the elutriated sludges averaged to $14.7 kg/m^2.hr$, and $3.2kg/m^2.hr$ for unelutriated sludges. Which was 4.6 times of not elutriated sludges. Elutriated sludges without chemical conditioner added showed much better filterabilities than with 15% of $FeCl_3$ added to the anaerobically digested and unelutriated sludges.

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.26-33
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• 2012

본 연구는 알칼리 활성화 슬래그에서 혼합 활성화제에 관한 것이다. 본 연구에서는 수산화나트륨(NaOH, A Case), 수산화칼슘($Ca(OH)_2$, B Case), 수산화마그네슘($Mg(OH)_2$, C Case), 수산화알루미늄($Al(OH)_3$, D Case), 그리고 수산화칼륨(KOH, E Case)의 5가지 수산화계열 활성화제를 사용했다. 이 5가지 수산화계열 활성화제와 탄산나트륨($Na_2CO_3$)를 혼합하였다. 5가지 수산화계열 활성화제의 농도는 3M로 하고, 탄산나트륨은 1M, 2M, 3M로 하였다. 플로우와 응결 특성은 탄산나트륨의 혼합에 따라 감소하는 결과가 나타났다. 그러나 압축응력은 탄산나트륨의 혼합 농도에 따라 증가하는 결과를 나타내었다. 이것은 수산화계열 활성화제와 탄산나트륨의 혼합은 알칼리 활성화 슬래그 모르타르의 특성에 효과적인 것으로 판단된다.

• 한국건축시공학회지
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• 제18권4호
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• pp.313-319
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• 2018

전 세계적으로 폭발성 물질 사용 증가와 폭탄테러 등으로 인명 및 재산 피해가 증가하고 있는 추세이다. 이에 중요 건축물이나 군사시설에 방호 방폭 성능을 향상시킬 목적으로 섬유보강 고성능 시멘트 복합체(HPFRCC)에 대한 연구가 진행되고 있다. 그러나, HPFRCC의 자기수축 문제를 해결하기 위해 ERCO를 혼입하게 되면 높은 점성 및 지방분의 시멘트 알칼리와의 조기반응으로 유동성, 공기량 및 강도 등 품질저하의 문제점이 발생한다. 이에 본 연구에서는 기존에 도출된 HPFRCC의 최적 배합에 ERCO 혼입시기 및 혼입율 변화에 따른 HPFRCC의 자기수축저감 및 기초적 특성에 대해 분석하였다. 그 결과 모르타르 믹싱완료 후 ERCO를 0.5% 혼입하는 후혼입 방법이 유동성, 강도 및 자기수축저감 등의 HPFRCC의 품질 향상에 가장 효과적인 것으로 밝혀졌다.

• The Journal of Korean Physical Therapy
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• 제26권5호
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• pp.331-343
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• 2014

Purpose: The purpose of this study is to assess the effectiveness of short-wave therapy (SWT) for treatment of knee osteoarthritis (OA) as compared to placebo and control, and to assess the question of whether the effects are related to the mode, dosage, and application method. Methods: We searched randomized, placebo-controlled trials using electronic databases. We also manually reviewed sources in order to identify additional relevant studies. Results: Eight studies (597 participants) with OA were included in the meta-analysis. Pulse SWT had a significant effect on pain relief compared with control treatment, while did not favour compared with the placebo group. Pulse SWT had a significant effect on functional improvement compared with control and placebo treatment. Continuous SWT had no effect on pain relief and functional improvement. Capacitive SWT a significant effect on pain relief, functional improvement, and muscle strength. Continuous and capacitive SWT had increased muscle strength significantly. We found no clinical significance of all outcomes except pain and functional improvement in pulsed SWT with low dose. There was no difference in adverse events. None of the participants experienced any serious adverse events. Conclusion: Low dose pulsed SWT provided a short-term clinical benefit for pain relief and functional improvement. Pulsed SWD with low and high dose had effects on pain and function. There seems to be a placebo effect. We found significant effects on pain and function in capacitive SWT. Despite some positive findings, this analysis lacked data on how effectiveness is affected by mode, dosage, and application method of SWT. Further well-designed clinical studies are required in order to confirm the effectiveness of SWT.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.727-732
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• 2002

Steel Fiber Reinforced Shotcrete(SFRS) has been prevalently used in lining to stabilize tunnel structures as temporary or permanent support. In recent, it is one of the major elements of tunnel construction, and so the quality control of SFRC should be clarified to guarantee the safety. The experimental study has been performed to verify the possible correlations in several chracteristics related to quality of SFRC and examine the applicability of round panel test for in field. The test variables were the type and dosage of accelerator, aspect ratio of fiber, and fiber content. The test results such as compressive strength, flexural strength, flexural toughness, and energy absorption capacity, were exmained and analyzed scrutinizingly.

• International Journal of Safety
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• 제8권1호
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• pp.14-17
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• 2009

The $Co^{60}$ $\gamma$-ray irradiation effects on the electrical and thermal characteristics of low density polyethylene crosslinked by Dicumyl peroxide (DCP) were investigated. We experimented on electrical properties as following; electrical tree inception and growing type for applying AC step voltage, AC breakdown strength, volume resistivity with increasing dosage. Also, chemical analyses were performed TGA, gel fraction. These electrical properties changed depending upon its crosslinking degree and byproducts from crosslinking reactions. Crosslinking reactions were considered causing by $\gamma$-ray irradiation and DCP had contained in low density polyethylene.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.207-210
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• 1999

This experimental study was carried out to estimate the effects of mixing dosage rate and blaine on the mechanical properties of concrete admixed with ground granulated blast-furnace slag (BFS) powder. According to the test results, compressive strength of concrete admixed with slag not more than 35% was at least 80% of compressive strength of OPC concrete at 3 days age, and much bigger than that of OPC concrete at 28 days age. Consequently, in order to apply the BFS to the concrete is demanded, and rigorous construction management should be followed.

• 펄프종이기술
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• 제38권1호통권113호
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• pp.34-44
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• 2006

A new composition of paper coating adhesives was prepared by using a nano-filler of an organically-modified montmorillonite (O-MMT). The new O-MMT coating adhesives were applied to the paper, and the properties of coated papers including surface morphology, optical and physical properties, and printing properties were investigated. The use of O-MMT improved the mechanical properties, such as folding endurance, tearing strength, and tensile strength, while the surface smoothness decreased. It decreased especially when the dosage was high enough, approximately above 6 parts. The printing properties such as wet- and dry-pick were enhanced with addition of O-MMT.