Four novel amphoteric surfactants of N-(2-alkylamidoethyl)-N, N-dimethyl ammonioacetates were synthesized. The each reaction between four saturated fatty acids containing 10, 12, 14 and 16 carbon atoms and N, N-dimethylethylene diamine permitted to give the intermediate products, N-(2-alkylamidoethyl)-N, N-dimethylamines. Quaterinzation of these intermediates was permitted to form N-(2-alkylamidoethyl)-N, N-dimethyl, ammonioacetates, whose sturctures were identified by CC, TLC, elemental analysis, IR pectrophotometry and 1HNMR spectrometry. The products yielded from 48% to 58%. The isoelectric points were shown in the range of 4.30~6.64. It showed a tendency to learn to the acidic site and its range was broadened as increase of the hydrophobic group length. Surface tensions of the aqueous solution in the 10-6~10-1mol/l of amidobetaines were measured. and the critical micell concentration(cmc) were shown in the range of 8.37×10-6~8.96×10-2mol/l, and γcmc were reduced to 32.3~38.2 dyne/cm. A linear relationship between log cmc and the number of carbon in the hydrophobic alkyl chain was presented by the formula of log cmc=2.38-0.5n, and the contribution-rate of n on the standard free energy change in micellization ɘ(δG0m)/ɘn, was calulated as -0.5RT.

This paper investigates the impact of monetary policy independence shock on bond yield by allowing for heterogeneous coefficients in the model based on panel data for 19 developing countries using quarterly data from 1991 to 2016. First, we estimate the model using conventional panel VAR estimation with the assumption of homogeneous coefficients across countries. Second, by performing Chow and Roy-Zellner tests to check the homogeneity assumption, we find that the assumption does not hold in the model. Third, we apply a meangroup estimation for panel VAR as a solution for heterogeneity panel model. The results reveal that central bank independence is effective in reducing bond yield with the maximum at period 6 after the shock. Shock one standard deviation bond yield has a negative effect on consumption and investment. We determine that central bank independence has a contradictory effect on real activity; a negative effect on consumption but a positive influence on investment for the first two years after the shock. Additionally, we split our sample into three groups to make the subgroups pool. Our empirical result shows that monetary policy independence shock reduces bond yield. Meanwhile, the response of economic activity to bond yield varies for all three groups.

This empirical research aims to identify the relationship between fiscal and financial macroeconomic fundamentals and the volatility of government bonds’ borrowing cost in an emerging country - Vietnam. The study covers the period from July 2006 to December 2019 and it is based on a sample of 1-year, 3-year, and 5-year government bonds, which represent short-term, medium-term and long-term sovereign bonds in Vietnam, respectively. The Generalized AutoRegressive Conditional Heteroskedasticity (GARCH) model and its derivatives such as EGARCH and TGARCH are applied on monthly dataset to examine and suggest a significant effect of fiscal and financial determinants of bond yield volatility. The findings of this study indicate that the variation of Vietnam government bond yields is in compliance with the theories of term structure of interest rate. The results also show that a proportion of the variation in the yields on Vietnam government bonds is attributed to the interest rate itself in the previous period, base rate, foreign interest rate, return of the stock market, fiscal deficit, public debt, and current account balance. Our results could be helpful in the macroeconomic policy formulation for policy-makers and in the investment practice for investors regarding the prediction of bond yield volatility.

본 연구에서는 코어직경에 따른 시멘트 모르타르의 부착강도 변동 특성을 분석하기 위하여, 코어직경 50mm 부착강도 13개 데이터와 코어직경 75mm 부착강도 17개 데이터를 활용하여 분석하였다. 부착강도의 평균값을 비교하면 코어직경 75mm의 값이 코어직경 50mm의 값에 비해 10.5% 정도 크게 나타났으며, 코어직경에 따른 부착강도의 변동계수(Coefficient of Variation) 값을 비교·분석한 결과 코어직경 75mm의 변동계수가 모든 시험 회차에서 상대적으로 작게 나타났다. 그러므로, 코어 직경에 따른 부착강도의 변동성을 최소화 하기 위해서는 코어직경 75mm를 사용하는 것이 바람직할 것으로 판단된다.

본 연구는 철근 콘크리트 내 강제 부식된 철근의 단조가력(Monotonic loading) 부착성능을 파악하고, 추후 해석모델 검증을 위한 데이터를 확보하기 위한 것이다. 이를 위해 이전 연도에 진행된 연구(철근 콘크리트의 가속 부식 실험 방법 정립 및 부식 특성 분석)를 바탕으로 제작된 철근 콘크리트 부재의 부식이 진행되었다. 철근의 직경, 철근 부식도, 콘크리트 압축 강도가 실험 변수로 지정되었고, 선행 연구를 바탕으로 자체 제작한 인발 시험기를 활용하여 실험 변수에 따른 철근의 콘크리트 인발 거동을 실험하였다.

포스트텐션 프리캐스트콘크리트(Precast Concrete, PC) 보-기둥 접합부에서는 프리스트레스가 도입된 긴장재가 접합부 내부를 관통하기 때문에, 기존의 철근콘크리트(Reinforced Concrete, RC) 보-기둥 접합부와 다른 거동을 나타내며, 포스트텐션 PC 접합부의 정확한 해석 및 설계를 위해서는 먼저 긴장재의 부착특성 및 그에 따른 접합부 거동이 명확히 규명 되어야 한다. 이 연구에서는 포스트텐션 PC 보-기둥 접합부에서 긴장재의 부착특성을 분석하고, 그에 따른 보의 거동 및 파괴모드를 규명함으로써 이를 추후 보-기둥 접합부 모델링에 활용하고자 한다.

GFRP 보강근과 콘크리트의 부착성능은 접착력, 부착력 및 지압력으로 발휘되며 보강근의 표면처리 방식이나 외피형상에 따라 발휘되는 부착저항력의 종류와 크기는 다르다. GFRP 부착 해석모델에 대한 선행연구를 살펴보면 철근의 부착 해석모델을 일부 수정하여 발전시키거나 수치해석을 통한 매개변수의 수가 많은 복잡한 해석식을 제안하였다. 전자의 경우에는 규격화된 마디형상을 갖는 철근과 달리 구성재료, 배합방법, 제조방법에 따라 다양한 외피형상을 가지는 GFRP 보강근의 특성을 포괄적으로 제안하는 데는 제약이 있으며 후자의 경우에는 수치해석으로 인한 수학적 관계식으로 GFRP 보강근의 부착거동과의 역학적인 관계를 고려하기에는 어려움이 있다. 따라서 이 연구에서는 GFRP 보강근의 콘크리트와의 외피형상에 따라 달라지는 부착메커니즘을 반영한 부착 해석모델을 제안하고자 하였다. 제안한 부착 해석모델에 대한 적합성 검증을 위하여 타 연구자가 수행한 실험값과 비교하였으며 기존의 부착 해석모델인 BPE 부착 해석모델과 CMR 부착 해석모델과의 비교연구도 수행하였다. 비교결과 이 연구에서 제안한 부착 해석모델이 실제 거동에 가장 근사하게 평가하였다.

콘크리트 구조물은 시공 후 다양한 원인에 의해 물리적, 화학적 변형을 통해 물리적인 성능이 저하된다. 이러한 콘크리트 구조물의 성능저하는 사용수명을 감소하기 때문에 합리적인 보수보강이 필요하다. 최근 콘크리트 구조물의 효율적인 보수을 위해, 부착성능을 향상시킨 하이브리드 보수재료에 대한 연구가 활발히 수행되어오고 있다. 본 연구에서는 기존콘크리트와의 부착성능 및 수밀성을 향상시키기 위해 초속경 시멘트에 PVA 분말수지, 나일론 섬유, 라텍스를 혼입 한 하이브리드 보수재를 개발하였다. 보수재료의 성능평가를 위해 압축강도, 건조수축, 부착강도 실험을 수행하였다. 또한 미리 손상이 발생한 시험체를 제작한 후 보수 전후의 휨부착 성능평가를 수행하였다. 휨강도 평가결과, 기존의 초속경시멘트만 혼입한 시험체를 제외한 모든 실험체에서 110%~150%정도 휨강도가 크게 나타났고, 휨강도에 의해 발생된 균열패턴은 모든 실험체가 기존 콘크리트와 일체 거동하는 것으로 나타났다.

The purpose of this study was to evaluate the mechanical properties and bond performance of epoxy paint containing graphene materials. Experiment result, it was confirmed that graphene materials are effective to improve the mechanical properties of the epoxy paint, but it is not effective to improve the bond performance.

In this study, the bond strength of FRP reinforced inorganic adhesive developed in previous studies was exposed to high temperature. As a result of the experiment, it was confirmed that the bond strength was increased at room temperature in the range of 100 to 200 ° C, but the width gradually decreased with increasing temperature.

기존의 정수처리 방법으로는 제거되지 않는 물질이 발생함에 고도정수 처리 시설의 도입이 증가하고 있다. 그러나 오존을 이용한 고도정수처리 시설의 내부 방수·방식재는 오존의 산화력에 의해 열화되며 콘크리트까지 영향을 미쳐 내구성 저하의 원인이 된다. 본 연구에서는 내오존성 및 내화학성이 뛰어난 금속 패널을 기존의 시공법 보다 손쉬운 방법으로 시공하기 위한 방법으로 금속용사 공법을 이용하여 수처 리 시설 콘크리트 구조물의 열화를 원천적으로 방지하기 위한 마감공법 개발 연구의 일원으로 용사금속 종류 및 피막의 표면처리 방법에 따른 내오존성 평가를 실시하였으며, 오존처리 후의 부착강도를 평가하였다. 실험결과 용사금속 Ti이 용사 후에도 내오존성이 뛰어난 것으로 나타 났으며 표면처리 방법으로는 테프론계 봉공처리제를 사용하여 마감하는 것이 내오존성 및 부착성능 확보에 가장 적합한 방법이라 판단된다.

In this study, presents the mechanical bond strength properties of mortar using bio polymer in seaweed. The evaluation was based on the method presented in KS F 2762. It was confirmed that the resistance performance all levels of biopolymer using mortar excellent performance with bond strength over 1.0 MPa as defined in KS F 4042 『Polymer-cement mortar for Concrete Structures』.

The purpose of this paper is to assess the effect of surface characteristic of GFRP rebar on concrete-reinforcement bond behavior. For sample preparation, 10 GFRP rebar with two types of surface conditions were used to fabricate 15×15×15cm sized GFRP reinforced concrete. Then, pull-out test was carried out on each concrete samples until the maximum bond strength was achieved. From the test result, it was found that the maximum bond strength at the lattice type is 1.38 times higher than that for unidirectional surface.

In this study, the compressive force is evaluated for the SMA surface reinforcement member which is to improve the bond capacity at cold-joint in PC member. As a result, the total compressive force can be estimated according to the number of wires.

The vegetation-based spraying method has been used as a revegetation measure for protecting slopes. However, after the method is applied to the fields, the collapse due to deteriorated bond performance of artificial slopes and defective vegetation growth bases prevent it from displaying its proper function. Therefore, research and application technologies for revegetation measures that can achieve both the reinforcement of slopes and the ecological restoration at the same time are necessary. Accordingly, in this study, fundamental research was conducted regarding the bond properties of slopes, according to the addition of additives based on bonding materials for improving bond performance.

In this paper, the bond stress of Fe based Shape Memory Alloy(Fe-SMA) with near surface mounted strengthening was investigated. An lab-shear test using Fe-SMA strips glued with cementitious matrix was performed to evaluate bond stress. Bond length (250 mm, 350 mm, 450 mm) was considered as experimental variable. The bond stress and utilization of Fe-SMA are 1.487MPa and 80%, respectively, at the bond length of 450 mm.

To examine the practical potentials of V-ties to provide a confinement to a strengthening jacket section of existing reinforced concrete members, direct bond tests were conducted under a parameter of the V-tie details. Test results showed that V-ties with headed-end had a higher bond strength than those with the other details.

This research developed the fiber pullout impact test machine to investigate interfacial bond strength between fiber and cement based matrix under high velocity. To achieve the goal, firstly the existing pullout test machines were investigated. And then, these drawback were comprehended. Finally, Fiber pullout impact test machine base on strain energy frame impact machine was proposed.

The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, curing ages of 7-day, and coating thickness of 100㎛ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is also high bond strength at coating thicknesses of 75㎛ and 100㎛ compared with 150㎛ and 250㎛. It is apparent in this study that the coating thickness is very important factors to improve the bond strength of PCS-coated rebar to cement concrete.

Characteristics of bond strength between AR-glass textile and fine concrete was performed through pull-out test with various transverse reinforced methods as number of lateral reinforced textile and transverse development length. In the both case of change in reinforcing method, bond strength was increased sharply in the first case.