국내 고농도의 초미세먼지 발생 빈도 증가와 함께 그 전구물질인 NH3와 관련한 연구가 활발히 진행 중이다. NH3 배출에 있어 농업의 기여율이 높은 것은 자명한 사실이다. 그러나 비료 사용이 농경지 대기 중 NH3 농도에 장기간 미치는 영향에 관련한 연구는 미비한 실정이다. 따라서 본 연구에서는 수동식 NH3 확산형 포집기를 활용해 11개월 간 농경지 대기 중 NH3 농도를 관측하였다. 그 결과 비료 살포 직후 한 달 동안 NH3 배출의 영향이 가장 큰 것으로 나타났다. 그 이후 여름철 기온 상승으로 NH3 휘발이 촉진되어 대기 중 농도가 증가할 것으로 예상하였으나, 54일간의 지속적인 강우로 인하여 대기 중 높은 암모니아 농도는 관측되지 않았다. 그 후 NH3 농도는 가을과 겨울을 거치면서 점차 감소하였다. 비료의 영향력이 감쇠한 시점 이후에는 기온이 감소할수록, 그리고 강수량이 증가할수록 NH3 농도는 감소하는 것을 상관분석을 통해 확인할 수 있었다. 종합해 보면, 국내 NH3 배출량에서 비료의 기여율을 연구하는 데 있어 비료 살포 직후 최소 한 달 동안은 집중적으로 살펴보아야 할 것이며, 현장 연구 시 강수량과 무강우 일수 등의 기상 정보도 함께 고려해야 할 것이다.

Structure behaviors resulting from an earthquake are experimentally simulated mainly through a shaking table test. As for large-scale structures, however, size effects over a miniature may make it difficult to assess actual behaviors properly. To address this problem, research on the hybrid simulation is being conducted actively. This method is to implement numerical analysis on framework members that affect the general behavior of the structure dominantly through an actual scale experiment and on the rest parts by applying the substructuring technique. However, existing studies on hybrid simulation focus mainly on Slow experimental methods, which are disadvantageous in that it is unable to assess behaviors close to the actual level if material properties change depending on the speed or the influence of inertial force is significant. The present study aims to establish a Real-time hybrid simulation system capable of excitation based on the actual time history and to verify its performance and applicability. The hybrid simulation system built up in this study utilizes the ATS Compensator system, CR integrator, etc. in order to make the target displacement the same with the measured displacement on the basis of MATLAB/Simulink. The target structure was a 2-span bridge and an RC pier to support it was produced as an experimental model in order for the shaking table test and Slow and Real-time hybrid simulations. Behaviors that result from the earthquake of El Centro were examined, and the results were analyzed comparatively. In comparison with the results of the shaking table test, the Real-time hybrid simulation produced more similar maximum displacement and vibration behaviors than the Slow hybrid simulation. Hence, it is thought that the Real-time hybrid simulation proposed in this study can be utilized usefully in seismic capacity assessment of structural systems such as RC pier that are highly non-linear and time-dependent.

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and . The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

Pretreatment of eliminating FFA is needed to make biodiesel from animal fat recovered from leather wastes because its acid value is high. This study was carried out to investigate the influence of 4 different pretreatment methods, which are heterogeneous catalyst method, ion exchange resin method, low pressure.high temperature method, and alkali method on the eliminating FFA and fatty acid composition. The results showed that the rate of eliminating FFA increased in the order of alkali method > catalyst method > low pressure high temperature method > ion exchange method. In the case of pretreatment of alkali method using NaOH, the rate of eliminating FFA appeared more than 86% regardless of acid value. Therefore, it was considered that alkali method using NaOH was the most effective in the view of economical and productive aspects, taking it into account that the acid value of animal fat recovered from fleshing scrap generated during leather making processes was 7 to 8.

Fleshing scrap is a kind of wastes produced during leather making process and used in the test of manufacturing biodiesel. The early step of manufacturing biodiesel is fat recovery from fleshing scrap. Hence, we investigated the influence of the way of fat recovery on the fatty acid composition. We used three different recovery ways, that is chemical method by protein decomposition with acid/fat recovering, physical method by protein denaturalization with heat and vacuum/fat pressing, and biodiesel method by protein decomposition/fat recovering. The biological method yielded the best results in terms of appearance transparency. It was most effective to lower acid value. Also the recovered fat by biological method would be favorable methyl-ester reaction raw material for biodiesel because it contains more than 5% of oleic acid among unsaturated fatty acid.

본 논문에서는 교량 모니터링 시스템의 일부분으로 서해대교에 설치된 교량 하중측정 시스템(BWIM system)으로부터 획득한 신호를 분석하여 통행차량의 정보를 추출하기 위한 알고리즘의 개발과정과 이를 위해 수행한 현장 차량주행시험에 대하여 기술하였다. 개발된 BWIM 시스템은 포장층에 매설하는 축감지기가 없는 형태로, 바닥판과 가로보에 설치된 변형률계로부터 측정한 시간이력 변형률신호만을 이용하였다. 이들 측정신호로부터 추출하고자 하는 차량의 정보는 통과차로, 통과속도, 차 축수 및 총 중량이며, 이들 정보의 추출을 위해 패턴인식기법의 일종인 인공신경망(Aritificial Neural Network, ANN) 기법을 사용하였다. 현장 차량주행시험을 통하여 기지차량 및 미지차량 통행시의 BWIM 응답 데이터를 측정하였으며, 이들 실측데이터를 사용하여 인공신경망의 학습 및 성능검증을 수행하였다. 개발된 기법을 사용하여 추출되는 차량의 정보들은 현재의 교량상태 및 피로수명 평가시 활용될 수 있을 것이며, 향후 설계트럭 하중모델의 개정시 기초자료로도 활용될 수 있을 것으로 기대된다.

Flesh wasters from tannery create major environmental problems. Despite their considerable fat content, these waster do not find important usage. Their disposal is also troublesome and costly. We have investigated the possible use of this fat as the production of biodiesel(fatty acid methyl esters) by transesterification using with fossil fuels. The fat released the waste by boiling water under the optimal condition (i.e., temperature, 120℃; decompression, 200mbar) and used to dry without refining for the production of fatty acid methyl esters. Under the optimal condition, the experimental value of biodiesel yield was about 96%. The result of the chemical and GC analysis showed fatty acid composition and characteristics of biodiesel. Evaluation of the product indicated that it was suitable for use as a biodiesel fuel. In result of this experiment oil extract from fleshing process can be transformed into an environmentally affination fuel, to provide economical and ecological profits.

공용 중인 교량의 건전성을 파악하고 유지관리에 활용하기 위해 서해대교 사장교 구간에는 구조건전성모니터링(structural health monitoring) 시스템이 설치되어 있다. 이를 통해 바람, 지진과 같은 작용하중(applied loads)과 함께 진동, 형상변화, 신축, 부재력, 응력(변형률)과 같은 구조응답(structural response)을 모니터링하고 있다. 2000년 준공 이후 현재까지 장기간 축적된 구조응답 데이터를 기반으로 분석 및 평가를 수행한 결과, 상시 거동뿐만 아니라 다양한 재난상황 시에도 교량 구조계의 거동은 건전한 상태임을 확인할 수 있었다.

This paper discusses the loads on bridges based on long-term measurements. Applied Loads such as winds, earthquakes, temperature variations and traffic effects have been monitored on an existing bridge from the completion of the structure to now. It is confirmed that the monitoring results are within the design values.

Life expectancy of bridges may be reduced mainly due to leakage, freeze-and-thaw, de-icing chemicals, and traffic volumes, which results in early deteriorations. This study suggests the bridge management strategies to extend the service life.

To suggest the preliminary data for effective maintenance of bridge structures, the damage patterns of expressway bridges are quantitatively analyzed in the present study. The defects are the primary damage, and the deterioration occurred around the joint.

Concrete has been considered as a semi-permanent structural material in construction industry. However, durability of concrete member is affected by carbonation, chloride attack, and water, etc. Therefore, to avoid the deterioration of concrete surface treatment materials are applied. This study discusses the long-term performance and desirable quality of surface protection materials for expressway concrete structures.

교량의 설계에 있어서 정확한 하중의 산정은 교량의 안전성 확보에 가장 핵심적인 사항이며 향후 유지관리 측면에서도 매우 중요하다. 교량구조물에서 차량에 의한 하중효과는 주로 활하중(충격하중 포함) 및 피로하중으로 나타난다. 이들 하중의 정형화를 위해서는 실제 교량상을 주행하는 중차량의 중량 및 통행특성을 정확히 파악하는 것이 중요하다. 이를 위해서 주행중인 차량을 정지시키지 않고 중량을 계측할 수 있는 시스템(Bridge Weigh-In-Motion, BWIM)의 개발이 필요하다. 본 연구에서는 다양한 기능을 갖는 BWIM시스템을 국내실정에 맞게 개발하고 이를 고속도로상의 교량에서 검증하였다.