• 대기
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• 제32권2호
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• pp.119-133
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• 2022

From 2015 to 2021, high-concentration fine dust episodes with a daily average PM_2.5 concentration of 50 ㎍ m^-3 or higher were selected and classified into 3 types [long range transport (LRT), mixed (MIX) and Local emission and stagnant (LES)] using synoptic chart and backward trajectory analysis. And relationships between the fine particle data (PM_2.5 and PM₁₀ concentration and PM_2.5/PM₁₀ ratio) and meteorological data (PBLH, Ta, WS, U-wind, and Rainfall) were analyzed using hourly observation for the classification episodes on the Korean Peninsula and the Seoul metropolitan area (SMA). In LRT, relatively large particles such as dust are usually included, and in LES, fine particle is abundant. In the Korean peninsula, the rainfall was relatively increased centered on the middle and western coasts in MIX and LES. In the SMA, wind speed was rather strong in LRT and weak in LES. In LRT, rainfall was centered in Seoul, and in MIX and LES, rainfall appeared around Seoul. However, when the dust cases were excluded, the difference between the LRT and other types of air quality was decreased, but the meteorological variables (Ta, RH, Pa, PBLH, etc.) were further strengthened. In the case of the Korean Peninsula, it is difficult to find a clear relationship because regional influences (topographical elevation, cities and coasts, etc.) are complexly included in a rather wide area. In the SMA, it is analyzed that the effects of urbanization such as the urban heat island centered on Seoul coincide with the sea and land winds, resulting in a combination of high concentrations and meteorological phenomena.

• Geomechanics and Engineering
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• 제32권4호
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• pp.427-443
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• 2023

Across the globe, rapid urbanization demands the construction of basements for car parking and sub way station within the vicinity of high-rise buildings supported on piled raft foundations. As a consequence, ground movements caused by such excavations could interfere with the serviceability of the building and the piled raft as well. Hence, the prediction of the building responses to the adjacent excavations is of utmost importance. This study used three-dimensional numerical modelling to capture the effects of twin excavations (final depth of each excavation, H_e=24 m) on a 20-storey building resting on (4×4) piled raft. Because the considered structure, pile foundation, and soil deposit are three-dimensional in nature, the adopted three-dimensional numerical modelling can provide a more realistic simulation to capture responses of the system. The hypoplastic constitutive model was used to capture soil behaviour. The concrete damaged plasticity (CDP) model was used to capture the cracking behaviour in the concrete beams, columns and piles. The computed results revealed that the first excavation- induced substantial differential settlement (i.e., tilting) in the adjacent high-rise building while second excavation caused the building tilt back with smaller rate. As a result, the building remains tilted towards the first excavation with final value of tilting of 0.28%. Consequently, the most severe tensile cracking damage at the bottom of two middle columns. At the end of twin excavations, the building load resisted by the raft reduced to half of that the load before the excavations. The reduced load transferred to the piles resulting in increment of the axial load along the entire length of piles.

• Structural Engineering and Mechanics
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• 제87권3호
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• pp.221-229
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• 2023

Urbanization and industrialization have significantly increased the amount of solid waste produced in recent decades, posing considerable disposal problems and environmental burdens. The practice of waste utilization in concrete has gained popularity among construction practitioners and researchers for the efficient use of resources and the transition to the circular economy in construction. This study employed Lytag aggregate, an environmentally friendly pulverized fuel ash-based lightweight aggregate, as a substitute for natural coarse aggregate. At the same time, fly ash, an industrial by-product, was used as a partial substitute for cement. Concrete mix M20 was experimented with using fly ash and Lytag lightweight aggregate. The percentages of fly ash that make up the replacements were 5%, 10%, 15%, 20%, and 25%. The Compressive Strength (CS), Split Tensile Strength (STS), and deflection were discovered at these percentages after 56 days of testing. The concrete cube, cylinder, and beam specimens were examined in the explorations, as mentioned earlier. The results indicate that a 10% substitution of cement with fly ash and a replacement of coarse aggregate with Lytag lightweight aggregate produced concrete that performed well in terms of mechanical properties and deflection. The cementitious composites have varying characteristics as the environment changes. Therefore, understanding their mechanical properties are crucial for safety reasons. CS, STS, and deflection are the essential property of concrete. Machine learning (ML) approaches have been necessary to predict the CS of concrete. The Artificial Fish Swarm Optimization (AFSO), Particle Swarm Optimization (PSO), and Harmony Search (HS) algorithms were investigated for the prediction of outcomes. This work deftly explains the tremendous AFSO technique, which achieves the precise ideal values of the weights in the model to crown the mathematical modeling technique. This has been proved by the minimum, maximum, and sample median, and the first and third quartiles were used as the basis for a boxplot through the standardized method of showing the dataset. It graphically displays the quantitative value distribution of a field. The correlation matrix and confidence interval were represented graphically using the corrupt method.

• 한국음향학회지
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• 제26권7호
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• pp.353-360
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• 2007

급속한 도시화와 인구밀도의 증가로 도시의 주거지역은 점점 고층화, 고밀화 되어가는 추세이다. 그로 인하여 인구의 공간적 집중으로 발생하는 교통수요를 감당하기 위하여 도시내부 도로는 점차 증가하였으며, 주거지역은 도로에 바로 인접하여 개발되고 있다. 이에 따라 도로에 연접한 주거지역의 도로교통소음 문제를 해결하기 위하여 방음벽에 의존하는 실정이었으나, 경관저해, 소음차단성능저해 등 다양한 역기능이 발생하고 있다. 본 연구에서는 방음벽의 역기능을 해소하고 바람직한 개선방안을 제시하기 위하여 도로변에 위치한 주거지역의 현장측정을 통하여 시뮬레이션의 정확도를 검증한 후 방음시설별 성능평가 및 전체 지역을 분석하였다. 그리고 개선방안으로 건축물의 배치형태 변화와 도로단으로부터의 이격거리를 20m 증가시켰다. 분석 결과 도로변과 평행한 공동주택의 피해가 가장 심각하였고, 시설별 분석에서는 방음벽의 성능이 우수하였으며, 건물 배치형태는 $30^{\circ}$ 배치가 우수하며, 이격거리가 증가함에 따라 교통소음이 감소하는 것으로 나타났다.

• 상하수도학회지
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• 제37권6호
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• pp.335-345
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• 2023

In Korea, as part of the Green New Deal project toward a carbon-neutral society, it is necessary to build a climate-resilient urban environment to green the city, space, and living infrastructure. To this end, SWMM-ING was improved and the model was modified to analyze the carbon reduction effect. In addition, I plan to select target watersheds where urbanization is rapidly progressing and evaluate runoff, non-point pollution, and carbon reduction effects to conduct cost estimation and optimal design review for domestic rainwater circulation green infrastructure. In this study, green infrastructure facilities were selected using SWMM-ING. Various scenarios were presented considering the surface area and annual cost of each green infrastructure facility, and The results show that the scenario derived through the APL2 method was selected as the optimal scenario. In this optimal scenario, a total facility area of 190,517.5 m² was applied to 7 out of 30 subwatersheds to achieve the target reduction. The target reduction amount was calculated a 23.50 % reduction in runoff and a 26.99 % reduction in pollutant load. Additionally, the annual carbon absorption was analyzed and found to be 385,521 kg/year. I aim to achieve additional carbon reduction effects by achieving the goal of reducing runoff and non-point pollution sources and analyzing annual carbon absorption. Moreover, considering the scale-up of these interventions across the basin, it is believed that an objective assessment of economic viability can be conducted.

• Animal Bioscience
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• 제37권4_spc호
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• pp.730-741
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• 2024

Pig production is one of the viable enterprises of the livestock sub-sector of agriculture. It contributes significantly to the economy and animal protein supply to enhance food security in Africa and globally. This article explored the present status of pig production in Africa, the challenges, prospects and potentials. The pig population of Africa represents 4.6% of the global pig population. They are widely distributed across Africa except in Northern Africa where pig production is not popular due to religio-cultural reasons. They are mostly reared in rural parts of Africa by smallholder farmers, informing why majority of the pig population in most parts of Africa are indigenous breeds and their crosses. Pig plays important roles in the sustenance of livelihood in the rural communities and have cultural and social significance. The pig production system in Africa is predominantly traditional, but rapidly growing and transforming into the modern system. The annual pork production in Africa has grown from less than a million tonnes in year 2000 to over 2 million tonnes in 2021. Incidence of disease outbreak, especially African swine fever is one of the main constraints affecting pig production in Africa. Others are lack of skills and technical know-how, high ambient temperature, limited access to high-quality breeds, high cost of feed ingredients and veterinary inputs, unfriendly government policies, religious and cultural bias, inadequate processing facilities as well as under-developed value-chain. The projected human population of 2.5 billion in Africa by 2050, increasing urbanization and decreasing farming population are pointers to the need for increased food production. The production systems of pigs in Africa requires developmental research, improvements in housing, feed production and manufacturing, animal health, processing, capacity building and pig friendly policies for improved productivity and facilitation of export.

• Smart Structures and Systems
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• 제33권4호
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• pp.291-300
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• 2024

Uncertainty of the model, system delay and drive dynamics can be considered as normal uncertainties, and the main source of uncertainty in the seismic control system is related to the nature of the simulated seismic error. In this case, optimizing the management strategy for one particular seismic record will not yield the best results for another. In this article, we propose a framework for online management of active structural management systems with seismic uncertainty. For this purpose, the concept of reinforcement learning is used for online optimization of active crowd management software. The controller consists of a differential controller, an unplanned gain ratio, the gain of which is enhanced using an online reinforcement learning algorithm. In addition, the proposed controller includes a dynamic status forecaster to solve the delay problem. To evaluate the performance of the proposed controllers, thousands of ground motion data sets were processed and grouped according to their spectrum using fuzzy clustering techniques with spatial hazard estimation. Finally, the controller is implemented in a laboratory scale configuration and its operation is simulated on a vibration table using cluster location and some actual seismic data. The test results show that the proposed controller effectively withstands strong seismic interference with delay. The goals of this paper are towards access to adequate, safe and affordable housing and basic services, promotion of inclusive and sustainable urbanization and participation, implementation of sustainable and disaster-resilient buildings, sustainable human settlement planning and manage. Simulation results is believed to achieved in the near future by the ongoing development of AI and control theory.

• Advances in concrete construction
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• 제17권1호
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• pp.13-26
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• 2024

Due to its capacity to address urgent environmental challenges connected to urbanization and stormwater management, pervious concrete, a sustainable and innovative material, has attracted a lot of attention recently. The aim of this study was to find the engineering characteristics of pervious concrete made from recycled aggregate (RA) at various aggregate-to-cement ratios (A/C) and the addition of 5% (by weight of total aggregate) of both natural and recycled fine aggregate to produce a very sustainable concrete product for a variety of applications. The three distinct aggregate-to-cement ratios, 6, 5, and 4, were used to produce pervious concrete using recycled aggregate in the research approach. The ratio of water to cement (w/c) was maintained at 0.3. Pervious concrete was created using single-sized recycled aggregate that passed through a 12.5 mm sieve and was held on a 9.5 mm sieve, as well as natural and recycled sand that passed through a 4 mm sieve. The production of twelve distinct concrete mixtures resulted in the testing of each concrete sample for dry density, abrasion resistance, compressive and splitting tensile strengths, porosity, and water permeability. A statistical method called GLM-ANOVA was also used to assess the characteristics of pervious concrete made using recycled aggregate. According to the experimental results, lowering the aggregate-to-cement ratio enhances the pervious concrete's overall performance. Additionally, a modest amount of fine aggregate boosts mechanical strength while lowering void content and water permeability. However, it was noted that such concretes' mechanical qualities were adversely affected to some extent. The results of this study offer insight into the viability of using recycled aggregates in order to achieve both structural integrity and environmental friendliness, which helps to optimize pervious concrete compositions.

• 대한방사선기술학회지:방사선기술과학
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• 제30권4호
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• pp.391-397
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• 2007

목 적: 담낭 결석은 담도계의 가장 흔한 질환이며 우리나라에서 점차적으로 늘어나고 있는 추세이다. 이와 같은 변화는 서구화된 식이요인이 변화되었기 때문이다. 본 연구는 식이요인에 따른 담낭 운동성과 담낭결석과의 관계를 알아보고자 하였다. 대상 및 방법: 전라북도 위도에서 69명과 경기도 남양주시에서 60명 등 총 129명을 대상으로 하였다. 남양주 시에서 60명 중 9명(남: 2, 여: 7)에서 담석이 발견되었는데 9명을 담석증군으로 하였다. 위도에서 69명 중 단 한 명도 담석이 발견되지 않아 단순 무작위 표본추출로 18명(남: 6, 여: 12)을 담석이 없는 대조군으로 하였다. 담석 및 당뇨가 없는 20대 4명(남: 2, 여: 2)을 추가로 실험 대상자로 설정하여 각각 생선 섭취 후 담낭의 박출 계수와 육류 섭취 후 담낭의 박출 계수를 구하였다. 결 과: 생선과 육류 섭취 후 담낭의 박출 계수율이 차이가 있었다. 생선 섭취 후 120분에 담낭의 박출 계수율이 가장 높게 나타났으며 육류 섭취 후 210분에 담낭의 박출 계수율이 가장 높게 나타났다. 결 론: 생선 섭취 후 보다 육류 섭취 후 담낭 내 담즙이 오래 정체되어 담낭 결석이 형성된다. 본 연구의 결과 담낭의 운동성이 담낭 결석의 형성에 중요한 역할을 한다.

• 한국환경복원기술학회지
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• 제24권4호
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• pp.15-29
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• 2021

Urban green spaces offer a variety of benefits to living things and humans. However, existing green spaces have been reduced and fragmented due to urbanization, and there is a limit to creating new large green spaces in densely developed cities. Street trees have fewer restrictions on land use, which can be a measure to secure green areas in cities. In Korea, excessive pruning is being done on some street trees for reasons such as blocking of building signboards, contact with electric wires, and restrictions on sidewalk widths. Therefore, it is necessary to quantitatively understand the relationship between the benefits provided by street trees and their structures to come up with an efficient and systematic planning and management plan for urban street trees. In this study, we quantitatively analyzed the relationship between the thermal comfort improvement by the shades of street trees and the vertical structure, planting environment, and types of street trees. To calculate the thermal comfort felt by human body, we calculated UTCI (Universal Thermal Climate Index) of each street tree. For the vertical structure of street trees, we used Terrestrial LiDAR and the point clouds of street tree's crown was sliced vertically at 1m intervals. We conducted a multiple regression analysis on the thermal comfort improvement using the variables we obtained from fields. As a result, in the case of a street tree's vertical structure, the lager the volume of tree's crown located 3-4m (β=0.298, p<.05) and 6-7m (β=0.568, p<.001) above clear length, the better the cooling effect. In addition, the thermal comfort improvement was assessed to decrease as the DBH increased (β=-0.435, p<.001). In general, the crown diameter and DBH are positively correlated, with a cooling effect occurring as crown diameter increases. In this study, the opposite result was obtained due to the small number of trees measured, so additional research is needed by increasing the number of tree samples. In the case of the planting environment, the effect of improving thermal comfort was higher in the shaded area of trees planted to the south (β=-0.541, p<.001). Since unsystematic management of street trees can deteriorate the function of them, quantitative evaluations of the vertical structure of street trees are required, which can provide specific measures for planning and management of urban street trees with thermal comfort effect.