PURPOSES : Recently, air pollution due to fine particulate matter has been increasing in Korea. Nitrogen oxides (NOx) are particulate matter precursors significantly contributing to air pollution. Increasing efforts have been dedicated to NOx removal from air, since it is particularly harmful. Application of titanium dioxide (TiO2) for concrete road structures is a suitable alternative to remove NOx. As the photocatalytic reaction of TiO2 is the mechanism that eliminates NOx, the ultraviolet rays in sunlight and TiO2 in existing concrete structures need to be contacted for the reaction process. For the application of vertical concrete road structures such as retaining walls, side ditches, and barriers, a pressurized TiO2 fixation method has been developed considering the pressure and pressurization time. In this study, longterm serviceability and repeatability were investigated on concrete specimens applying the dynamic pressurized TiO2 fixation method. Additionally, the environmental hazards of nitrate adsorbed on TiO2 particles were evaluated. METHODS : Concrete specimens to simulate roadside vertical concrete structures were manufactured and used to evaluate the long-term serviceability and repeatability of the dynamic pressurized TiO2 fixation method. The NOx removal efficiency was measured using NOx evaluation equipment based on ISO 22197-1. In addition, the nitrate concentration was measured using a comprehensive water quality analyzer for evaluating environmental hazards. RESULTS : As the experiment to evaluate the NOx removal efficiency of the dynamic pressurized TiO2 fixation method progressed from one to seven cycles, the nitrate concentration increased from 2.35 mg/L to 3.06 mg/L, and the NOx removal efficiency decreased from 53% to 25%. After seven cycles of NOx removal efficiency evaluation, the average nitrate concentration was 3.06 mg/L. The nitrate concentration collected immediately after the NOx removal efficiency test for each cycle was in the range of 2.51 to 2.57 mg/L. By contrast, it was confirmed that the nitrate concentration was lowered to approximately 2.1 mg/L when the surface was washed with water. CONCLUSIONS : The NOx removal efficiency was maintained at over 25% even after seven cycles of NOx removal efficiency evaluation, securing long-term serviceability. In addition, the harmful effects on the environment and human health are insignificant, since the nitrate concentration was less than 10 mg/L, in accordance with domestic and foreign standards. Practical applicability of the pressurized TiO2 fixation method was established by evaluating the long-term serviceability, repeatability, and environmental hazards.

3D 프린팅 콘크리트는 임의의 형상을 자유롭게 적층하여 제작할 수 있다는 장점을 가지고 있지만, 노즐의 구조 및 형상에 따라 곡선부의 출력 품질이 달라진다. 또한, 공기중에서 출력한 경우와 수중에 서 출력한 경우 그 품질이 달라진다. 본 연구에서는 고정 마감날을 가진 사각형 노즐을 이용하여 3D 프린팅 모르타르를 수중에서 곡선 형태로 출력하고 적층한 후 출력성능, 적층성능, 및 역학적성능을 평가하였다. 30 × 30 mm 사각형 개구부를 가지고 있고 노즐 끝 양 측면에 고정 마감날이 설치된 노 즐을 사용하였다. 사전 직선 출력시험에서 선정된 조건인 호퍼 회전속도 14 rpm, 노즐 이동 속도 2000 mm/min을 적용하여 출력하였고, 1층 높이를 30mm로 출력하여 5층 적층하였다. 출력 및 적층 결과, 직선부분의 표면은 양호한 반면 곡면부분, 특히 곡률이 큰 곡선부분의 바깥쪽에서 표면균열이 관찰되었다. 직선부분의 치수 일관성은 양호한 반면, 곡률 반경이 작은 곡선부분의 폭 차이가 나타났 다. 곡선부분의 밀도와 압축강도는 직선부분보다 낮았다. 이는 곡선부에서 직사각형 노즐 회전에 따른 재료 토출이 불균일하기 때문인데, 이러한 문제점을 보완할 수 있는 제어 기술 개발이 필요하다.

FRP 복합재 중 CFRP(Carbon Fiber Reinforcement Plastic)는 현재 Rebar, Plate, Grid 등 다양한 형태로 RC 구조물에 내‧외부 보강재로써 사용되고 있다. 이 중 CFRP Grid의 경우 국내에서 상용화가 되지 않아 다른 형태의 보강재보다 성능 분석 및 평가 기준이 미흡한 실정이다. 이에 따라 본 연구에 서는 Grid의 Strand, 경계조건, ASTM 고정장치의 유무 등 다양한 실험을 통하여 CFRP 그리드의 인 장 성능평가를 진행하였다. 선행 연구에서는 CFRP Grid의 인장시험 고정단의 경계조건에 따른 영향 성 분석을 위해 ASTM D7205 및 ASTM D6637에 따라 Tap-Tap (Type 1), Tap-Mortor (Type 2) 로 구성하여 인장시험을 수행하였으며, 시편의 파단 형상 및 시험 결과값이 가장 안정적인 Type 2를 CFRP Grid의 고정단 경계조건으로 설정하였다. 이러한 선행 연구를 바탕으로 고온 노출에 따른 CFRP 그리드의 인장 성능시험 평가를 진행하였으며, 인장시험은 만능재료시험기 및 고성능 카메라를 활용하여 최대 응력과 탄성계수를 도출하였다. 온도는 FRP의 전이온도인 150℃ 이내의 130℃에서 각 Case 별 5개의 시편을 70분(Case 2), 100분(Case 3), 120분(Case 4), 150분(Case 5) 노출한 후, 고온 에 노출하지 않은 시편(Case 1)과 비교하였다. 실험 결과, Case 5와 Case 1을 비교하여 인장강도와 탄성계수는 각각 최대 51.32%, 44.4% 감소하였다. 결론적으로 고온 환경에서 지속적으로 노출될 경 우, CFRP Grid의 성능이 최대 절반 수준으로 감소 되며 RC 부재 내‧외부에 보강 시에 고온 조건을 면밀히 검토하여 성능 감소를 최소화할 필요가 있다고 판단된다.

Restraints of Branch Lines are used as earthquake-resistant support devices for fire-fighting pipes along with sway brace devices. The central types are aligned and fixed in a straight line with center of the pipe, but the eccentric types are fixed to on side of the pipe, so a bending moment occurs. In this study, three specimens each of central type and eccentric type were installed at an angle of 45° from the vertical and a monotonic compression load of 1340N was applied. All central type samples satisfied 17.8mm of the allowable displacement, but all eccentric type samples failed to meet the target load and buckled. Therefore, when considering the performance of eccentric type restraints, both compressive load and bending moment must be considered. Even through material mechanics calculations, the yield stress of eccentric type - 3/8 inch all threaded steel bolt - exceeds 320Mpa of the allowable stress. A experiment standards need to be established for eccentric type restraints.

PURPOSES : As the number of fixed traffic enforcement equipments increase rapidly, it is necessary to improve efficient operation and management plans. The aim of this study is to evaluate the factors influencing fixed traffic enforcement equipment failure. METHODS : This study utilized binary logistic regression analysis using the database provided by the Korean Road Traffic Authority to evaluate the factors affecting the failure of fixed traffic enforcement equipment. RESULTS : As a result of the evaluation of this study, the main factors affecting failure were red-light camera, old equipment, Jeju, National expressways, and equipment with low speed limits. CONCLUSIONS : This study can be used as basic data on the improvement of operation management plas for maintenance of traffic enforcement equipment. Through this study, it will be possible to establish a step-by-step plan with high efficiency comapared to the input of required manpower.

효소 고정화 막 생물반응기(EMBRs)는 폐수 내의 염료를 처리하는 새로운 방법입니다. 이 분야는 효소의 효능과 환경에 대한 높은 저항성 때문에 많은 양의 연구가 진행되었습니다. 효소 자체와 해당 효소의 구조를 모두 포함하는 다양한 방법이 EMBR에 접근할 수 있습니다. 생물반응기 자체는 염료 제거의 필요에 맞게 변형될 수 있습니다. 효소적 생물반응기 부터 산화 그래핀 또는 탄소 나노튜브와 같은 나노구조를 사용하는 것까지 다양합니다. 또한 TiO2와 같은 나노입자는 EMBR 을 더욱 향상시키기 위해 사용될 수 있습니다. 폴리머 기반의 막 지지 구조는 또한 효능 증가의 문제에 접근하는 다양한 방 법을 포함합니다. 본 바와 같이, 지난 수십 년 동안 EMBR을 사용하는 이 문제에 대한 다양한 접근법이 수행되었습니다. 이 검토는 방법론을 요약하고 EMBR에 대한 다양한 개선 사항을 설명하는 것을 목표로 합니다.

PURPOSES : The increase in particulate matter due to increased air pollutant emissions has become a significant social issue. According to the Ministry of Environment, air pollutants emitted from large-scale businesses in 2022 increased by 12.2% compared to the previous year, indicating that air pollution is accelerating owing to excessive industrialization. In this study, TiO2, which is used to reduce airborne particulate, was used. The TiO2 coating fixation and dynamic pressure coating-type TiO2 fixation methods were used to solve the material peeling phenomenon caused by gravity, which is a limitation when the TiO2 penetration method is applied to a vertical concrete structure along the road. The long-term durability and performance were analyzed through environmental resistance and NOx removal efficiency evaluation experiments. These analyses were then assessed by comparing the NOx removal efficiency with the dynamic pressure permeationtype TiO2 fixation method used in previous studies. METHODS : To evaluate the long-term durability and performance of the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation method for vertical concrete structures, specimens were manufactured based on roadside vertical concrete structures. Environmental resistance tests such as the surface peeling resistance test (ASTM C 672) and freeze-thaw resistance test (KS F 2456) were conducted to evaluate the long-term durability. To evaluate the long-term performance, the NOx removal efficiency of TiO2 concrete owing to road surface deterioration during the environmental resistance test was evaluated using the NOx removal efficiency evaluation equipment based on the ISO 22197-1 standard. This evaluation was compared and analyzed using the dynamic pressure infiltration TiO2 fixation method. RESULTS : The long-term durability of the TiO2 coating fixation and dynamic pressure coating TiO2 fixation methods were evaluated using environmental resistance tests. During the surface peeling resistance test, the TiO2 material degraded and partially detached from the concrete. However, the NOx removal efficiency was ensured by the non-deteriorated and fixed TiO2 material. The long-term performance was confirmed through a freeze-thaw resistance test to evaluate the NOx removal efficiency after 300 cycles of surface deterioration. The results showed that when the TiO2 coating fixation and dynamic pressure infiltration TiO2 fixation methods were applied to vertical concrete structures, the durability of the structure was not compromised. In comparison to the dynamic pressure infiltration TiO2 fixation method, the NOx removal efficiency observed during the surface peeling resistance test was lower, while the freeze-thaw test exhibited notably higher removal efficiency. CONCLUSIONS : To solve the material peeling phenomenon caused by gravity, the long-term durability and performance were evaluated by applying the TiO2 coating fixation and dynamic pressurized coating TiO2 fixation methods to vertical concrete specimens. Long-term durability was confirmed through environmental resistance tests, and long-term utility was secured by measuring the NOx removal efficiency according to surface degradation. These findings show that implementing the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation methods on-site effectively reduce NOx.

국제유가가 배럴당 85달러에서 하반기에는 최대 100달러까지 오를 것으로 예상하여 세계 시장에서 해양플랜트 발주가 늘어 날 가능성이 크다. 해양플랜트의 주요 특징 중 한 가지는 탑사이드에 대형 헬리데크가 위치하며 경량화 및 내부식성을 위하여 알루미 늄 합금을 구조의 기본 재료로 사용하고 있다. 선주사는 긴급 상황 발생 시 신속한 인명 대피를 위하여 헬리콥터 크기를 대형화하는 추세이고, 헬리콥터를 데크에 안정적으로 고박할 수 있는 장치의 안전사용하중도 증가가 필요하다. 알루미늄 재질의 특성상 용접에 의 한 구조 강도 저하가 크기 때문에, 고정 장치는 데크에 매립하여 볼트로 고정하는 방식으로 설계가 필요하다. 본 연구에서는 대형 헬 리데크(직경=28m)에 사용이 가능한 헬리콥터 고정 장치를 개발하기 위하여 알루미늄 합금 6082-T6를 적용한 모델을 개발하였다. 개발 된 고정 장치는 실제 고박에 사용하는 하중 조건을 만족하도록 비선형구조 강도 계산을 통하여 검증하였다. 45도 경사각을 갖는 하중 조건은 국부적인 소성 붕괴로 인하여 90도 조건에 비해 낮은 최종강도를 나타냈다. 최종 모델에 대한 비선형 구조 붕괴 거동은 강도 실험과 경향이 유사하게 나타났다. 본 연구에서 도출한 주요 내용은 유사 알루미늄 기자재의 구조 강도 검토 시 참고 문헌이 될 것으 로 판단된다.

PURPOSES : Advancements in science and technology caused by industrialization have led to an increase in particulate matter emissions and, consequently, severity of air pollution. Nitrogen oxide (NOx), which accounts for 58% of road transport pollutants, adversely affects both human health and the environment. A test-bed was constructed to determine NOx removal efficiency at the roadside. TiO2, a material used to reduce particulate matter, was used to remove NOx. It was applied to a vertical concrete structure using the dynamic pressurized penetration TiO2 fixation method, which can be easily applied to vertical concrete structures. This study was conducted to evaluate the NOx removal efficiency of the dynamic pressurized-penetration TiO2 fixation method in a test-bed under real roadside conditions. METHODS : A test-bed was constructed in order to determine the NOx removal efficiency using the dynamic pressurized penetration TiO2 fixation method on the roadside. The dynamic pressurized-penetration TiO2 fixation method was applied by installing a vertical concrete structure. NOx was injected into the test-bed using an exhaust gas generator. By installing a shading screen, the photocatalytic reaction of TiO2 was suppressed to a maximum concentration of 1000 ppb along the roadside. The removal efficiency was evaluated by measuring NOx concentrations. In addition, illuminance was measured using an illuminance meter. RESULTS : From the results of the analysis of the NOx removal efficiency in the test-bed which the dynamic pressurized type TiO2 fixation method was applied to, an average removal efficiency ranging from 18% to 40% was achieved, depending on the illuminance. Similarly, according to the results of the evaluation of the NO removal efficiency, an average of removal efficiency ranging from 20% to 62% was achieved. Thus, the NOx removal efficiency increased when the illuminance was high. CONCLUSIONS : From the results of the experiment conducted, the efficiency of NOx removal per unit volume was obtained according to the illuminance of TiO2 concrete along an actual road. Field applicability of the dynamic pressurized-penetration-type TiO2 fixation method to vertical concrete structures along roads was confirmed.

The records system is believed to have started in Italy in the 14th century in line with trade developments in Europe. In 1491, Luca Pacioli, a mathematician, and an Italian Franciscan monk wrote the first book that described double-entry accounting processes. In many countries, including Korea, the government accounting standards used single-entry bookkeeping rather than double-entry bookkeeping that can be aggregated by account subject. The cash-based and single-entry bookkeeping used by the government in the past had limitations in providing clear information on financial status and establishing a performance-oriented financial management system. Accordingly, the National Accounting Act (promulgated in October 2007) stipulated the introduction of double-entry bookkeeping and accrual accounting systems in the government sector from January 1, 2009. Furthermore, the Korean government has also introduced International Financial Reporting Standards (IFRS), and the System of National Accounts (SNA). Since 2014, Korea owned five national accounts. In Korea, valuation began with the 1968 National Wealth Statistics Survey. The academic origins of the valuation of national wealth statistics which had been investigated by due diligence every 10 years since 1968 are based on the 'Engineering Valuation' of professor Marston in the Department of Industrial Engineering at Iowa State University in the 1930s. This field has spread to economics, etc. In economics, it became the basis of capital stock estimation for positive economics such as econometrics. The valuation by the National Wealth Statistics Survey contributed greatly to converting the book value of accounting data into vintage data. And in 2000 National Statistical Office collected actual disposal data for the 1-digit asset class and obtained the ASL(average service life) by Iowa curve. Then, with the data on fixed capital formation centered on the National B/S Team of the Bank of Korea, the national wealth statistics were prepared by the Permanent Inventory Method(PIM). The asset classification was also classified into 59 types, including 2 types of residential buildings, 4 types of non-residential buildings, 14 types of structures, 9 types of transportation equipment, 28 types of machinery, and 2 types of intangible fixed assets. Tables of useful lives of tangible fixed assets published by the Korea Appraisal Board in 1999 and 2013 were made by the Iowa curve method. In Korea, the Iowa curve method has been adopted as a method of ASL estimation. There are three types of the Iowa curve method. The retirement rate method of the three types is the best because it is based on the collection and compilation of the data of all properties in service during a period of recent years, both properties retired and that are still in service. We hope the retirement rate method instead of the individual unit method is used in the estimation of ASL. Recently Korean government’s accounting system has been developed. When revenue expenditure and capital expenditure were mixed in the past single-entry bookkeeping we would like to suggest that BOK and National Statistical Office have accumulated knowledge of a rational difference between revenue expenditure and capital expenditure. In particular, it is important when it is estimated capital stock by PIM. Korea also needs an empirical study on economic depreciation like Hulten & Wykoff Catalog A of the US BEA.

신재생에너지로서 수소에 대한 수요가 증가하고 있으나 기존의 화석 연료와 달리 수소는 연료 공급을 위한 전용 충전소가 필 요하며, 이러한 인프라 확보를 위해서 수소충전소의 위험성 평가가 선행되어야 한다. 따라서 본 연구에서는 정성적 위험성평가와 정량적 위험성 평가로 구분하여 수소충전소에 대한 위험성평가를 수행하였다. 정성적 평가는 Hazard and Operability Analysis(HAZOP) 기법을 사용 하여 Dispenser Module을 두 개의 Node로 평가하였으며, Criticality Estimation Matrix에 따라 Filter의 막힘으로 인한 사고와 고압 사고의 위험 도가 High Level로 평가되었다. 정량적 위험성 평가는 Hydrogen Korea Risk Assessment Module(Hy-KoRAM)을 사용하여 화재의 형상과 피해영 향범위를 나타냈고, 개인적 위험도와 사회적 위험도에 대한 평가를 수행하였다. 개인적 위험도는 수소충전소로부터 약 100m 떨어진 공공 시설 부근까지 추가적인 안전조치가 고려되는 As Low As Reasonably Practicable(ALARP) 구간의 위험도를 보였고, 사회적 위험도 역시 약 10명의 사망자가 발생할 사고빈도가 1E-04/year로 도출되며 ALARP 구간 내에 나타났다. 정성적·정량적 위험성 평가 결과, 공정 단계의 추 가적인 안전 조치와 수소충전소 부근의 제한구역 설정을 통하여 안전성 향상 방안을 제시하였다.

A fixed-point iteration is proposed to integrate the stress and state variables in the incremental analysis of plastic deformation. The Conventional Newton–Raphson method requires a second-order derivative of the yield function to generate a complicated code, and the convergence cannot be guaranteed beforehand. The proposed fixed-point iteration does not require a second-order derivative of the yield function, and convergence is ensured for a given strain increment. The fixed-point iteration is easier to implement, and the computational time is shortened compared with the Newton–Raphson method. The plane-stress condition is considered for the biaxial loading conditions to confirm the convergence of the fixed-point iteration. 3-dimensional tensile specimen is considered to compare the computational times in the ABAQUS/explicit finite element analysis.

A new clamped mechanical splice system was proposed to develop structural performance and constructability for precast concrete connections. The proposed mechanical splice resists external loading immediately after the engagement. The mechanical splices applicable for both large-scale rebars for plants and small-scale rebars for buildings were developed with the same design concept. Quasi-static lateral cyclic loading tests were conducted with reinforced and precast concrete members to verify the seismic performance. Also, shaking table tests with three types of seismic wave excitation, 1) random wave with white noise, 2) the 2016 Gyeongju earthquake, and 3) the 1999 Chi-Chi earthquake, were conducted to confirm the dynamic performance. All tests were performed with real-scale concrete specimens. Sensors measured the lateral load, acceleration, displacement, crack pattern, and secant system stiffness, and energy dissipation was determined by lateral load-displacement relation. As a result, the precast specimen provided the emulative performance with RC. In the shaking table tests, PC frames’ maximum acceleration and displacement response were amplified 1.57 - 2.85 and 2.20 - 2.92 times compared to the ground motions. The precast specimens utilizing clamped mechanical splice showed ductile behavior with energy dissipation capacity against strong motion earthquakes.

음용수 속 암모니아의 존재는 인간의 건강에 매우 해롭다. 농작물에서의 비료 사용, 산업 폐수, 화석 연료의 연소 와 같은 활동으로 인해 가용성 암모니아는 지하수를 오염시킨다. 물에 존재하는 암모니아 농도가 낮더라도 해양생물 등의 수 생환경을 훼손한다. 막 기술은 암모니아를 물로부터 효과적으로 제거하기 위한 매우 중요한 과정이다. 평평한 시트 막, 막 접 촉기, 그리고 막 증류법은 암모니아를 제거하여 물을 정화하는 데 사용되는 방법들 중 하나이다. 막 접촉기는 막 증류법과는 달리 상변화 없이 액체와 가스 간의 또는 액체와 액체간의 질량 전달을 통해 암모니아를 제거하는 효율적인 공정이다. 다만 이 방법은 pH가 매우 높아 암모니아 제거에 비용이 많이 든다. 제올라이트는 우수한 이온 교환 능력을 가지고 있는데, 이는 암모니아와의 상호작용을 향상시켜 폐수로부터 흡착하는 능력을 향상시킨다. 제올라이트를 함유한 혼합 매트릭스 막은 암모 니아 흡착 및 폐수로부터의 분리 효율을 향상시킨다. 이 리뷰에서는 위에서 소개된 내용이 자세히 논의될 것이다.

생체 내 변화에서 효소는 중요한 촉매이다. 효소의 안정성과 재사용성은 촉매 과정에서 중요한 요소이다. 적합한 기질에 효소 고정화는 특정 미세환경의 조성을 통해 효소 활동성을 높인다. 다양한 종류의 분리막이 각각의 생체적합성과 막 표면의 친수성/소수성 조절 용이도에 따라 기질로 사용되었다. 본 논문에서는 셀룰로스, 폴리아크릴로니트릴(PAN), 폴리디메 틸실록산(PDMS), 폴리비닐리덴플루오라이드(PVDF), 폴리에테르설폰(PES) 고분자 분리막이 소개되고 토의되었다. 고정화 효소를 이용한 유기오염물의 생물적 분해는 제약 회사 및 섬유 회사 등에서 발생하는 오염물질을 친환경적으로 감소할 수 있는 방법이다. 효소 고정화 생물반응기(EMBR)로 기름의 가수분해를 제어할 수 있고 이를 통해 탄소 배출량 감소 및 환경오염을 줄일 수 있다. EMBR로 만들 수 있는 바이오에탄올과 바이오디젤은 화석 연료의 대체제이다.

본 연구에서는 환경, 재료 물성 및 제작 등에서의 불확실성을 고려하여 130m급 고정식 해양구조물의 신뢰성 기반 최적설계를 수행 하였다. 구조물의 구조건전성을 엄밀하게 반영하기 위해 작용 및 허용 응력의 비인 UC 값을 신뢰성 해석 및 신뢰성 기반 최적설계의 제약조건으로 고려하였다. 해양구조물의 제작비용을 저감하기 위해 자켓형 지지구조물의 중량을 최소화하였다. 불확실성의 통계적 특성은 문헌 등을 참고하여 관측되거나 측정된 데이터를 기반으로 정의하였다. 자켓형 해양구조물의 신뢰성 해석과 신뢰 기반 최적 설계는 부재 수가 많아 계산 부담이 큼으로 문제의 차원을 축소하기 위해 응답의 중요성을 기준으로 설계변수를 선별할 수 있는 방법 을 제안한다. 또한 효율적인 계산을 위해 신뢰성 기반 최적설계를 수행하기 전 결정론적 최적설계를 먼저 수행하였다. 마지막으로, 도 출된 최적설계(안)을 기존 각 급 규정 기반 설계와 안전성 및 경제성 측면에서 비교 분석하였다.