• Journal of the Korean Data and Information Science Society
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• 제18권1호
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• pp.195-210
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• 2007

This paper develops a consistent nonparametric test for Granger causality in the context of strong-mixing process, which covers a large class of stationary processes including ARMA and ARCH models. The previously proposed tests require absolute regularity ($\beta$-mixing) more stringent than the strong-mixing condition. We prove the consistency of the test under a high level assumption on the approximation error of U statistic by its projection. Due to the sample splitting, the test statistic we propose is asymptotically normally distributed under the null.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.412-419
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• 2009

Large quantity of extra soils discharged from excavation site in Songdo area can be treated by hardening agents and utilized in surface stabilized layer overlying thick reclaimed soft soil deposit. Though surface layer stabilization method using cement or lime for very soft soils has been studied in recent years, but studies on moderately soft clayey silt has not been tried. The purpose of this research is to investigate optimum mixing condition for stabilizing Songdo marine soil with low plasiticity. The optimum mixing conditions of hardening agents with Songdo soil such as kind of agents, mixing ratio, initial water content and curing time are investigated by uniaxial compression test and laboratory vane test. The results indicate that strength increases with high mixing ratio and long curing time, while decreases drastically under certain water content before mixing. Finally, optimum mixing condition considering economic efficiency and workability with test results was proposed.

• 한국농촌건축학회논문집
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• 제24권2호
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• pp.45-52
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• 2022

Of the 17,106 domestic reservoirs(as of December 2020), 14,611 are older than 50 years, and these old reservoirs will gradually increase over time. The injection grouting method is most applied to the reinforcement method of the aging reservoir. However, the injection grouting method is not accurate in uniformity and reinforced area. An laboratory model test was conducted to evaluate the applicability of the deep mixing method, which compensated for these shortcomings, as a reservoir reinforcement method. As a result of calculating the hydraulic conductiveity for each method through the model test results, the injection grouting method was calculated as a hydraulic conductiveity value that was about 7.5 times larger than that of the deep mixing method. As a result of measuring the water level change in the laboratory model test, it was found that the water level change decreased in the injection method and deep mixing method compared to the non-reinforcement method. In addition, deep mixing method showed a water level change of about 15% based on 40 hours compared to the injection method, indicating that the water-reducing effect was superior to that of the injection method.

• 한국지반환경공학회 논문집
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• 제25권6호
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• pp.5-12
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• 2024

현재 저수지 제체의 차수성 및 안전성 확보를 위해 약액을 저압으로 주입하여 제체 손상을 최소화하는 그라우팅 공법이 보편적으로 사용되고 있으나, 내구성 확보와 체계적인 고화재의 배합비 결정방법이 정립되어 있지 않은 문제들이 있다. 본 연구에서는 원지반과 고화재를 다양한 중량비율로 교반·혼합하였을 경우 혼합체의 투수계수와 강도를 실내시험을 통해 확인하였으며, 시험결과들의 분석을 통해 최적 배합비를 제안하였다. 실내실험을 위한 공시체는 고화재의 배합량을 고려하여 제작하였다. 투수시험용 공시체는 사질토와 점성토 별 고화재 배합량 1.5kN/m³에 대해 제작하였으며, 투수시험 결과 차수 성능이 확보되어 각종 설계기준을 만족하는 것을 확인하였다. 강도시험을 위한 공시체는 점성토의 경우 5가지, 사질토는 3가지 배합비로 각각 3개 총 24개의 시편을 제작하였으며, 시험 결과 사질토와 점성토 모두 배합량 2.0kN/m³ 이하에서는 일축압축강도가 재령일이 증가함에 따라 선형적으로 증가하는 경향을 나타냈다. 따라서 현장에 적용되는 최적의 배합비는 고화재 배합량을 1.5kN/m³ 및 2.0kN/m³으로 결정하였다. 또한 현재 운영 중인 노후 저수지 개보수사업 설계사례를 대상으로 실험성과를 반영한 수치해석을 실시한 결과 저수지 제체의 차수 및 안전성 증대 효과를 확인하였다.

• KIEAE Journal
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• 제7권4호
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• pp.119-126
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• 2007

In this study, we processed two procedures of application test of filler for fire-resistance utility that are new application methods of aerated concrete and properties test of aerated concrete according to mixing ratio because we investigated the better use of aerated concrete as filler for fireproof safety and we proposed basic data about standardization of mixing of aerated concrete. We measured flow and volume change of aerated concrete. And if its volume doesn't change, we added measuring unit weight and compressive strength. To test application of aerated concrete as filler for fireproof safety, we filled up aerated concrete to fireproof safety according to suitable mixing ratio. Then we measured maximum temperature of inner part of fireproof safety in accordance with the standard test of fireproof. According to the results, aerated concrete as filler for fireproof safety could be possibly used. So when we make aerated concrete, we should consider using an adding agent as well as a foaming agent.

• KIEAE Journal
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• 제9권2호
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• pp.65-71
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• 2009

Results from tests for what mixing rate of soil and sand is proper for the rammed earth and for how much additives are optimum are as under. 1) In the test to evaluate what mixing rate of soil and sand is desirable, peptizing property and surface sticking rate are found similar in its degree, but compression strength is found most stable when the ratio of soil and sand mixing shows 30:70 which indicates the best mixing rate of soil and sand. 2) In a test to add hydrated lime, compression strength, peptizing property, and surface sticking rate are found best when the mixing rate of soil and sand shows 23:7. 3) In a test to add sea weeds, the peptizing property goes down at 75% of sea weeds input a little bit more than at 100%, but compression strength shows best at 75% which is thought to be the best rate. 4) In a drop test, more soil powder mixed, the sticking strength gets better and more sands are contained, the sticking strength gets far worse to be scattered in powder type. 5) As concluding all results mentioned in the above item, the most desirable mixing rate of soil, sand, and hydrated lime is found to be 23:7:70 for the rammed earth where compression strength, peptizing property, and surface sticking rate are best.

• Computers and Concrete
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• 제13권6호
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• pp.781-798
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• 2014

Estimating the workability of self-compacting concrete (SCC) is very important both in laboratories and on construction site. A method using visual information during the mixing process was proposed in this paper to estimate the workability of SCC. First, fourteen specimens of concrete were produced by a single-shaft mixer. A digital camera was used to record all the mixing processes. Second, employing the digital image processing, the visual information from mixing process images was extracted. The concrete pushed by the rotating blades forms two boundaries in the images. The shape of the upper boundary and the vertical distance between the upper and lower boundaries were used as two visual features. Thirdly, slump flow test and V-funnel test were carried out to estimate the workability of each SCC. Finally, the vertical distance between the upper and lower boundaries andthe shape of the upper boundary were used as indicators to estimate the workability of SCC. The vertical distance between the upper and lower boundaries was related to the slump flow, the shape of the upper boundary was related to the V-funnel flow time. Based on these relationships, the workability of SCC could be estimated using the mixing process images. This estimating method was verified by three more experiments. The experimental results indicate that the proposed method could be used to automatically estimate SCC workability.

• Computers and Concrete
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• 제31권6호
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• pp.501-511
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• 2023

The strengthening efficiency of biopolymer treated soil depends on biopolymer type, concentration ratio, soil type, initial water content, curing time and mixing method. In this study, the physical and mechanical properties of xanthan gum (XG) treated kaolinite were investigated through compaction test, Atterberg limit test, triaxial test and unconfined compression test. The results indicated that the optimum water content (OWC) increased from 30.3% of untreated clay to 33.5% of 5% XG treated clay, while the maximum dry density has a slight increase from 13.96 kg/m³ to 14 kg/m³ of 0.2% XG treated clay and decrease to 2.7 kg/m³ of 5% XG treated clay. Meanwhile, the plastic limit of XG treated clay increased with the increase of XG concentration, while 0.5% XG treated clay can be observed the maximum liquid limit with 79.5%. Moreover, there are the ideal water content about 1.3-1.5 times of the optimum water content achieving the maximum dry density and curing time to obtain the maximum compressive strength for different XG contents, which the UCS is 1.52 and 2.07 times of the maximum UCS of untreated soil for 0.5% and 1% XG treated clay, respectively. In addition, hot-dry mixing can achieve highest UCS than other mixing methods (e.g., dry mixing, wet mixing and hot-wet mixing).

• 한국조경학회지
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• 제38권5호
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• pp.93-101
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• 2010

탄성포장은 보행자의 만족감이 매우 높아 수요가 지속적으로 증가할 것으로 예상되나, 탄성포장의 재료 배합기준 즉, 합성고무 칩(EPDM chip)과 폴리우레탄 바인더의 적정배합기준이 미비하여 시공 시 많은 시행착오를 겪고 있는 실정이다. 따라서, 본 연구는 조경용 탄성포장의 폴리우레탄 바인더 배합비에 따른 결합력과 반발탄성의 변화를 실험을 통해 분석하고, 이를 바탕으로 적정한 재료배합 비율을 제시하고자 하였으며, 실험결과는 다음과 같다. 인장실험에서는 시료 B와 시료 C가 바인더 배합비율과 인장강도 간에 강한 양의 상관관계가 있는 것으로 나타나, 배합비율이 증가하면 인장강도가 증가한다는 것을 알 수 있다. 경도실험에서는 시료 A,시료 B,시료 C모두 바인더 배합비율과 경도 간에 통계적으로 상관관계가 없는 것으로 나타나, 탄성포장재의 경도는 바인더의 배합비율에 따라 달라지지는 않는 것으로 판단된다. 반발탄성실험에서는 시료 A와 시료 B가 배합비율과 반발탄성 간에 강한 음의 상관관계가 있는 것으로 나타나, 배합비율이 증가하면 반발탄성이 낮아진다는 것을 알 수 있다. 실험결과를 바탕으로 적정배합비율을 분석해 보면 인장강도의 경우, 인장강도의 증가가 둔화되거나 오히려 감소하는 배합비율 포인트는 20%이며, 반발탄성의 경우, 반발탄성이 급격하게 감소하는 배합비율 포인트는 22%이다. 따라서 두가지 요인을 감안할 때, 적정 배합비는 20~22% 사이로 판단된다. 본 연구의 결과는 조경용 탄성포장 시공 시 결합력과 탄성을 제고할 수 있는 재료배합의 지침을 제공할 수 있을 것으로 기대된다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.319-321
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• 2014

The homogeneity and the long term stability for HCNG(CNG composed of about 20 % hydrogen) have been studied. The homogeneity by using ANOVA shows that the HCNG mixing gas is homogeneous ; the relative uncertainty of homogeneity is 0.0375 %. The long term stability for HCNG mixing gas by using F-test and t-test shows that HCNG mixing gas is stable ; the relative uncertainty of the long term stability is 0.0682 % for seven months.