• Title/Summary/Keyword: Source Contribution

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Identification of acrosswind load effects on tall slender structures

  • Jae-Seung Hwang;Dae-Kun Kwon;Jungtae Noh;Ahsan Kareem
    • Wind and Structures
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    • v.36 no.4
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    • pp.221-236
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    • 2023
  • The lateral component of turbulence and the vortices shed in the wake of a structure result in introducing dynamic wind load in the acrosswind direction and the resulting level of motion is typically larger than the corresponding alongwind motion for a dynamically sensitive structure. The underlying source mechanisms of the acrosswind load may be classified into motion-induced, buffeting, and Strouhal components. This study proposes a frequency domain framework to decompose the overall load into these components based on output-only measurements from wind tunnel experiments or full-scale measurements. First, the total acrosswind load is identified based on measured acceleration response by solving the inverse problem using the Kalman filter technique. The decomposition of the combined load is then performed by modeling each load component in terms of a Bayesian filtering scheme. More specifically, the decomposition and the estimation of the model parameters are accomplished using the unscented Kalman filter in the frequency domain. An aeroelastic wind tunnel experiment involving a tall circular cylinder was carried out for the validation of the proposed framework. The contribution of each load component to the acrosswind response is assessed by re-analyzing the system with the decomposed components. Through comparison of the measured and the re-analyzed response, it is demonstrated that the proposed framework effectively decomposes the total acrosswind load into components and sheds light on the overall underlying mechanism of the acrosswind load and attendant structural response. The delineation of these load components and their subsequent modeling and control may become increasingly important as tall slender buildings of the prismatic cross-section that are highly sensitive to the acrosswind load effects are increasingly being built in major metropolises.

Prediction of radioactivity releases for a Long-Term Station Blackout event in the VVER-1200 nuclear reactor of Bangladesh

  • Shafiqul Islam Faisal ;Md Shafiqul Islam;Md Abdul Malek Soner
    • Nuclear Engineering and Technology
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    • v.55 no.2
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    • pp.696-706
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    • 2023
  • Consequences of an anticipated Beyond Design Basis Accident (BDBA) Long-Term Station Blackout (LTSBO) event with complete loss of grid power in the VVER-1200 reactor of Rooppur Nuclear Power Plant (NPP) of Unit-1 are assessed using the RASCAL 4.3 code. This study estimated the released radionuclides, received public radiological dose, and ground surface concentration considering 3 accident scenarios of International Nuclear and Radiological Event Scale (INES) level 7 and two meteorological conditions. Atmospheric transport, dispersion, and deposition processes of released radionuclides are simulated using a straight-line trajectory Gaussian plume model for short distances and a Gaussian puff model for long distances. Total Effective Dose Equivalent (TEDE) to the public within 40 km and radionuclides contribution for three-dose pathways of inhalation, cloudshine, and groundshine owing to airborne releases are evaluated considering with and without passive safety Emergency Core Cooling System (ECCS) in dry (winter) and wet (monsoon) seasons. Source term and their release rates are varied with the functional duration of passive safety ECCS. In three accident scenarios, the TEDE of 10 mSv and above are confined to 8 km and 2 km for the wet and dry seasons, respectively in the downwind direction. The groundshine dose is the most dominating in the wet season while the inhalation dose is in the dry season. Total received doses and surface concentration in the wet season near the plant are higher than those in the dry season due to the deposition effect of rain on the radioactive substances.

Determination of homogeneity index of cementitious composites produced with eps beads by image processing techniques

  • Comak, Bekir;Aykanat, Batuhan;Bideci, Ozlem Salli;Bideci, Alper
    • Computers and Concrete
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    • v.29 no.2
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    • pp.107-115
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    • 2022
  • With the improvements in computer technologies, utilization of image processing techniques has increased in many areas (such as medicine, defence industry, other industries etc.) Many different image processing techniques are used for surface analysis, detection of manufacturing defects, and determination of physical and mechanical characteristics of composite materials. In this study, cementitious composites were obtained by addition of Grounded Granulated Blast-Furnace Slag (GGBFS), Styrene Butadiene polymer (SBR), and Grounded Granulated Blast-Furnace Slag and Styrene Butadiene polymer together (GGBFS+SBR). Expanded Polystyrene (EPS) beads were added to these cementitious composites in different ratios (20%, 40% and 60%). The mechanical and physical characteristics of the composites were determined, and homogeneity indexes of the composites were determined by image processing techniques to determine EPS distribution forms in them. Physical and mechanical characteristics of the produced samples were obtained by applying consistency, density, water absorption, compressive strength (7 and 28 days), flexural strength (7 and 28 days) and tensile splitting strength (7 and 28 days) tests on them. Also, visual examination by using digital microscope, and image analysis by using image processing techniques with open source coded ImageJ program were performed. As a result of the study, it is determined that GGBFS and SBR addition strengthens the adhesion sites formed as it increases the adhesion power of the mixture and helps to get rid of the segregation problem caused by EPS. As a result of the image processing analysis it is demonstrated that GGBFS and SBR addition has positive contribution on homogeneity index.

An Longitudinal Analysis of Changing Beliefs on the Use in IT Educatee by Elaboration Likelihood Model (정교화 가능성 모형에 의한 IT 피교육자 신용 믿음 변화의 종단분석)

  • Lee, Woong-Kyu
    • Asia pacific journal of information systems
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    • v.18 no.3
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    • pp.147-165
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    • 2008
  • IT education can be summarized as persuading the educatee to accept IT. The persuasion is made by delivering the messages for how-to-use and where-to-use to the educatee, which leads formulation of a belief structure for using IT. Therefore, message based persuasion theory, as well as IT acceptance theories such as technology acceptance model(TAM), would play a very important role for explaining IT education. According to elaboration likelihood model(ELM) that has been considered as one of the most influential persuasion theories, people change attitude or perception by two routes, central route and peripheral route. In central route, people would think critically about issue-related arguments in an informational message. In peripheral route, subjects rely on cues regarding the target behavior with less cognitive efforts. Moreover, such persuasion process is not a one-shot program but continuous repetition with feedbacks, which leads to changing a belief structure for using IT. An educatee would get more knowledge and experiences of using IT as following an education program, and be more dependent on a central route than a peripheral route. Such change would reformulate a belief structure which is different from the intial one. The objectives of this study are the following two: First, an identification of the relationship between ELM and belief structures for using IT. Especially, we analyze the effects of message interpretation through both of central and peripheral routes on perceived usefulness which is an important explaining variable in TAM and perceived use control which have perceived ease of use and perceived controllability as sub-dimensions. Second, a longitudinal analysis of the above effects. In other words, change of the relationship between interpretation of message delivered by IT education and beliefs of IT using is analyzed longitudinally. For achievement of our objectives, we suggest a research model, which is constructed as three-layered. While first layer has a dependent variable, use intention, second one has perceived usefulness and perceived use control that has two sub-concepts, perceived ease of use and perceived controllability. Finally, third one is related with two routes in ELM, source credibility and argument quality which are operationalization of peripheral route and central route respectively. By these variables, we suggest five hypotheses. In addition to relationship among variables, we suggest two additional hypotheses, moderation effects of time in the relationships between perceived usefulness and two routes. That is, source credibility's influence on perceived usefulness is decreased as time flows, and argument quality's influence is increased. For validation of it, our research model is tested empirically. With measurements which have been validated in the other studies, we survey students in an Excel class two times for longitudinal analysis. Data Analysis is done by partial least square(PLS), which is known as an appropriate approach for multi-group comparison analysis with a small sized sample as like this study. In result. all hypotheses are statistically supported. One of theoretical contributions in this study is an analysis of IT education based on ELM and TAM which are considered as important theories in psychology and IS theories respectively. A longitudinal analysis by comparison between two surveys based on PLS is also considered as a methodological contribution. In practice, finding the importance of peripheral route in early stage of IT education should be notable.

Estimation of Nitrate-nitrogen Contamination Sources in Cheju Island Groundwater using $\delta$$^{15}$ N Values ($\delta$$^{15}$ N값을 이용한 제주도 지하수중의 질산성질소 오염원추정에 관한 연구)

  • 오윤근;현익현
    • Journal of the Korean Society of Groundwater Environment
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    • v.4 no.1
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    • pp.1-4
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    • 1997
  • This study was carried out to find out the source of nitrate-nitrogen (NO$_3$-N) contamination in the groundwater in Cheju Island. Among the sites which have exceeded or may exceed the criterion level (10 mg/L) of NO$_3$-N in drinking water, seven sampling sites including two reference sites were chosen. The former regions are mainly agricultural ones (A-1 to A-6) and residential (R). The latter regions are forest (F-1 and F-2). The predicted major source and its contribution to NO$_3$-N concentration at each site, using $\delta$$\^$15/N and NO$_3$-N concentration, were as follow; Those at A-1, R and F-1 was 61.1%, 50.0% and 20.0% to manure or domestic sewage, 27.8%, 45.7% and 40.0% to chemical fertilizers and 11.1%, 4.3% and 40.0% to natural soil, respectively. Those at A-2 to A-6 were 37.8%, 25.0%, 40.9%, 26.2% and 35.7% to manure or domestic sewage, 59.6%, 71.7%, 53.0%, 71.5% and 60.2% to chemical fertilizers and 2.6%, 3.3%, 6.1%, 2.3% and 4.1% to natural soil, respectively.

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The Importance of groundwater discharge for environmental assessment of Chinhae Bay (진해만 환경평가를 위한 해저지하수의 중요성)

  • Chung Chong Soo;Hong Gi Hoon;Kim Suk Hyun;Kim Young Il;Moon Duk Soo;Park Jun Kun;Choi Jun Sun;Yang Dong Beom
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.3 no.4
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    • pp.23-36
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    • 2000
  • Bottom sea waters in eight stations including from inner bay to outer bay to understand the importance of the submarine groundwater discharge for the environmental assessment of Chinhae Bay was collected in August 1999 and January 2000. Generally, /sup 222/Rn is very useful tracer to assess the submarine groundwater discharge because it is 2-4 orders of magnitude more concentrated in groundwater compared to surface water. The /sup 222/Rn activities ranged between about 33 to 182 dpm/100kg within the bay. Higher activities more than 100 dpm/100kg were found at the inner bay. The /sup 226/Ra activities, its parent, however, were little different between stations. /sup 222/Rn activities at the same station varied with season. It suggests that the major source of /sup 222/Rn is not from the bottom sediment, but from the change of submarine groundwater discharge by precipitation. The contents of Cl/sup -/ and SO/sub 4//sup 2-/ in the groundwater of Wonjeon-ri were very high as 1,312 and 369 ppm, respectively, indicating that this groundwater along the Chinhae coast was affected by seawater. Therefore, the submarine groundwater in the inner Bay may discharge to the overlying water. It indicates that these submarine groundwater discharges may play an important role as another important source of nutrients in the Chinhae Bay, because groundwater around the Chinhae Bay showed high concentration of dissolved inorganic nutrients (average , nitrate>174 μM, silicate>262 μM). Therefore, further studies are required to assess the contribution by the submarine groundwater discharge in the biogeochemical processes of the Chinhae Bay.

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On the Support Region of a Minimum Mean-Square Error Scalar Quantizer for a Weibull Source (Weibull 신호원에 최적인 양자기의 지지역에 관한 연구)

  • Lim, Sil-Kyu;Na, Sang-Sin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.1C
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    • pp.129-139
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    • 2004
  • This paper studies the support region of an optimum (minimum mean-squre error) fixed-rate scalar quantizer for a Weibull source. The support region is defined to be the interval determined by the outermost thresholds of a quantizer and plays an important role in its performance, and hence it motivates this study. The paper reports the following specific results. First, approximation formulas are derived for the outermost thresholds of optimum scalar quantizers for a Weibull distributions. Second, in the case of Rayleigh and exponential distributions the derived approximation formulas are compared for the evaluation of their accuracy with the true values of optimum quantizers. Numerical results show that the formula for the leftmost threshold stays within 1% of the true value for 128 and 256 quantization points or more, for Rayleigh and exponential distribution, respectively, while that for the rightmost threshold does so for 512 and 32 quantization points or more. These formulas exhibit increased accuracy with the number of quantization points. In conclusion, the formulas have high accuracy. The contribution of the paper consists in the derivation of closed accurate formulas for the support of optimum.

Characteristics of Air Quality in the West Coastal Urban Atmosphere; Characteristics of VOCs Concentration Measured from an Industrial Complex Monitoring Station at Gunsan and a Roadside Station at Jeonju (서해연안 도시지역의 대기질 특성 연구: 군산시 산업단지와 전주시 도로변에서 VOCs 농도분포 특성 연구)

  • Ryoo, Jae-Youn;Kim, Deug-Soo;Chae, Soo-Cheon;Nam, Tu-Cheon;Choi, Yang-Seock
    • Journal of Korean Society for Atmospheric Environment
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    • v.26 no.6
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    • pp.633-648
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    • 2010
  • The study was performed to elucidate the characteristics of VOCs at distinct monitoring sites in urban atmosphere; one is at a roadside in downtown inland city of Jeonju, and the other is at an industrial site in Gunsan near coastal area. The ambient samples were collected for 24 hours in two-bed adsorbent tubes by using MTS-32 sequential tube sampler equipped with Flex air pump every 16 days in a roadside and a industrial complex from February to November in 2009. VOCs were determined by thermal desorption coupled with GC/MSD. Major individual VOCs in roadside samples were shown as following order in magnitude: toluene>m,p-xylene>ethyl benzene>decanal; and those in the industrial complex samples were as follows: toluene>ethanol>ethyl acetate>decanal>m,pxylene. High benzene concentration in the roadside was more frequently occurred than in the industrial complex. However ambient level of toluene in the industrial complex was higher than that in the road side. Results from roadside sample analysis showed that nonane and 1,2,4-trimethylbenzene were very frequently observed with higher concentrations than those in the industrial complex. It seems that nonane and 1,2,4-trimethylbenzene could be the source characteristics for the roadside air. From the diurnal variation, it was found that concentrations of benzene, ethylbenzene, xylene, nonane and 1,2,4-trimethylbenznene in the roadside were higher during rush hours; but those in the industrial complex were higher from 10 to 16 LST when the industrial activities were animated. On weekly base, the concentration of benzene, toluene, ethylbenzene and m,p-xylene in the roadside were higher specifically on Wednesday, but those in the industrial complex were higher on Sunday. It was found that the general trends of VOCs levels at both sites significantly influence on seasonal changes. The results of factor analysis showed that the VOCs in the roadside were mainly affected by the emission of vehicles and the evaporation of diesel fuel, meanwhile those in the industrial complex were influenced by the evaporation of solvents and vehicular emission.

Chemical Composition and Features of Asian Dust Observed in Korea (2000~2002) (2000~2002년 우리나라에서 관측된 황사의 화학 조성 및 특성)

  • Shin S.A;Han J.S;Hong Y.D;Ahn J.Y;Moon K.J;Lee S.J;Kim S.D
    • Journal of Korean Society for Atmospheric Environment
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    • v.21 no.1
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    • pp.119-129
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    • 2005
  • The ambient TSP data measured at Seoul, Incheon. Taean, Daegu, Busan in Korea were used to explain the chemical composition and general features of Asian Dust (AD) observed in Korea. 9 episodes out of 19 were sampled from 2000 through May 2002, and measurements were conducted covering ionic and metal components with mass concentration. The results showed that daily averaged mass concentration (TSP) during the AD episodes was 458 $\mu\textrm{g}$/㎥, and ionic and metal concentrations were 27.93 $\mu\textrm{g}$/㎥ and 71.7 $\mu\textrm{g}$/㎥, respectively, accounting for 6.1 % and 15.5% of the total aerosol mass. TSP concentrations during episodes were varied from 120 to 1742 $\mu\textrm{g}$/㎥ according to the impact of Asian Dusts and had a tendency of showing higher values at sites in the west side of Korea, which can be explained by the effect of diffusion and deposition. In this study, ionic components like Ca (NO$_3$)$_2$, CaSO$_4$, NaNO$_3$, Na$_2$SO$_4$ were prominent types in secondary aerosol during AD periods and also indicated that V, Co as well as soil elements such as Ca, Fe, Mg, Mn, K correlated well with Al, while Cu, Cd, Pb, Zn didn't agree well with it. In addition, enrichment factors (EFs) for each metal component were obtained to provide simple information about source contribution of Asian Dust, and the results were compared with those from other AD studies. In this study, the results showed that aerosol properties in Korea during the Asian Dust were considerably different from those of general atmospheric condition and specially varied from case to case rather than site to site, which implies that there are certain variations in the soil of source region, pathways of air mass, and meteorological condition. For the enhanced study, those factors should be combined with the features of Asian Dust resolved from this study.

Determination of EMCs for Rainfall Ranges from Transportation Landuses (교통관련 토지이용에서의 강우계급별 EMC 산정)

  • Lee, So-Young;Maniquiz, Marla C.;Choi, Ji-Yeon;Kim, Lee-Hyung
    • Journal of Wetlands Research
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    • v.11 no.2
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    • pp.67-76
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    • 2009
  • The contribution of pollutant loadings from non-point source (NPS) to the four major rivers in Korea exceeded 22~37 % of the total loadings in 2004 and is expected to reach 60 % in 2020. Most of NPS loadings are coming from urban areas, especially from paved areas. Because of high imperviousness rate, many types of NPS pollutant are accumulating on the surface during dry periods. The accumulated pollutants are wash-off during a storm and highly degrading the water quality of receiving water bodies. For this reason, the Korean Ministry of Environment (MOE) developed the Total Maximum Daily Load (TMDL) program to protect the water quality by managing the point source and NPS loadings. NPS has high uncertainties during a storm because of the characteristics of rainfall and watershed areas. The rainfall characteristics can affect on event mean concentrations (EMCs), mass loadings, flow rate, etc. Therefore, this research was performed to determine EMCs for rainfall ranges from transportation landuses such as road and parking lot. Two sites were monitored over 45 storm events during the 2006/06 through 2008/10 storm seasons. Mean TSS EMCs decrease as rainfall ranges increase and highest at less than 10mm rainfall. The results of this study can be used to determine the efficient scale of BMP facility considering specific rainfall range.

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