• Title, Summary, Keyword: decay

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A comparative study for the decay of chlorine residual using EPANET2.0 and an experimental pipeline system (EPANET 2.0과 관망실험을 통한 배수관망 염소농도 감쇄 비교연구)

  • Baek, Dawon;Kim, Hyunjun;Kim, Sanghyun
    • Journal of Korean Society of Water and Wastewater
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    • v.32 no.5
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    • pp.411-419
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    • 2018
  • The residual chlorine concentration is an essential factor to secure reliable water quality in the water distribution systems. The chlorine concentration decays along the pipeline system and the main processes of the reaction can be divided into the bulk decay and the wall decay mechanisms. Using EPANET 2.0, it is possible to predict the chlorine decay through bulk decay and wall decay based on the pipeline geometry and the hydraulic analysis of the water distribution system. In this study, we tried to verify the predictability of EPANET 2.0 using data collected from experimental practices. We performed chlorine concentration measurement according to various Reynolds numbers in a pilot-scale water distribution system. The chlorine concentration was predicted using both bulk decay model and wall decay model. As a result of the comparison between experimental data and simulated data, the performance of the limited $1^{st}$-order model was found to the best in the bulk decay model. The wall decay model simulated the initial decay well, but the overall chlorine decay cannot be properly predicted. Simulation also indicated that as the Reynolds number increased, the impact of the wall.

Prediction of residual chlorine using two-component second-order decay model in water distribution network (이변량 감소모델을 적용한 배급수관망에서의 잔류염소농도 예측 및 이의 활용)

  • Kim, Young Hyo;Kweon, Ji Hyang;Kim, Doo Il
    • Journal of Korean Society of Water and Wastewater
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    • v.28 no.3
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    • pp.287-297
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    • 2014
  • It is important to predict chlorine decay with different water purification processes and distribution pipeline materials, especially because chlorine decay is in direct relationship with the stability of water quality. The degree of chlorine decay may affect the water quality at the end of the pipeline: it may produce disinfection by-products or cause unpleasant odor and taste. Sand filtrate and dual media filtrate were used as influents in this study, and cast iron (CI), polyvinyl chloride (PVC), and stainless steel (SS) were used as pipeline materials. The results were analyzed via chlorine decay models by comparing the experimental and model parameters. The models were then used to estimate rechlorination time and chlorine decay time. The results indicated that water quality (e.g. organic matter and alkalinity) and pipeline materials were important factors influencing bulk decay and sand filtrate exhibited greater chlorine decay than dual media filtrate. The two-component second-order model was more applicable than the first decay model, and it enabled the estimation of chlorine decay time. These results are expected to provide the basis for modeling chlorine decay of different water purification processes and pipeline materials.

A Study on the Error Associated with Ventilation Rate Calculation Using Different Sampling Intervals (측정시간에 따른 거주주택의 환기량 계산 오류에 관한 연구)

  • 양원호;배현주;이기영;정문호
    • Journal of Environmental Health Sciences
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    • v.26 no.3
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    • pp.50-54
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    • 2000
  • Ventilation rates can be measured directly by a tracer decay method, although little is known of the effects of different sampling intervals on decay rte calculations. This study determined variations in decay rates calculated by three techniques using residential ozone decay data. The calculation techniques were a regression technique, decay techniques using half-life and average-life, and finite difference techniques using two different time intervals. Variation associated with regression technique calculations for residential ozone decay rates based on data from both sample intervals were within 10% (2.81$\pm$1.88 hr-1). However, both half-life and finite difference technique calculations using a shorter-time interval were significantly different from those obtained with the regression technique(p<0.05). Therefore, the use of short sampling intervals in tracer decay may cause significant error in decay rate calculations.

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Experimenting biochemical oxygen demand decay rates of Malaysian river water in a laboratory flume

  • Nuruzzaman, Md.;Al-Mamun, Abdullah;Salleh, Md. Noor Bin
    • Environmental Engineering Research
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    • v.23 no.1
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    • pp.99-106
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    • 2018
  • Lack of information on the Biochemical Oxygen Demand (BOD) decay rates of river water under the tropical environment has triggered this study with an aim to fill the gap. Raw sewage, treated sewage, river water and tap water were mixed in different proportions to represent river water receiving varying amounts and types of wastewater and fed in a laboratory flume in batch mode. Water samples were recirculated in the flume for 30 h and BOD and Carbonaceous BOD (CBOD) concentrations were measured at least six times. Decay rates were obtained by fitting the measured data in the first order kinetic equation. After conducting 12 experiments, the range of BOD and CBOD decay rates were found to be 0.191 to 0.92 per day and 0.107 to 0.875 per day, respectively. Median decay rates were 0.344 and 0.258 per day for BOD and CBOD, respectively, which are slightly higher than the reported values in literatures. A relationship between CBOD decay rate and BOD decay rate is proposed as $k_{CBOD}=0.8642_{k_{BOD}}-0.0349$ where, $k_{CBOD}$ is CBOD decay rate and $k_{BOD}$ is BOD decay rate. The equation can be useful to extrapolate either of the decay rates when any of the rates is unknown.

Fatigue characteristics of distributed sensing cables under low cycle elongation

  • Zhang, Dan;Wang, Jiacheng;li, Bo;Shi, Bin
    • Smart Structures and Systems
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    • v.18 no.6
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    • pp.1203-1215
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    • 2016
  • When strain sensing cables are under long-term stress and cyclic loading, creep may occur in the jacket material and each layer of the cable structure may slide relative to other layers, causing fatigue in the cables. This study proposes a device for testing the fatigue characteristics of three types of cables operating under different conditions to establish a decay model for observing the patterns of strain decay. The fatigue characteristics of cables encased in polyurethane (PU), GFRP-reinforced, and wire rope-reinforced jackets were compared. The findings are outlined as follows. The cable strain decayed exponentially, and the decay process involved quick decay, slow decay, and stabilization stages. Moreover, the strain decay increased with the initial strain and tensile frequency. The shorter the unstrained period was, the more similar the initial strain levels of the strain decay curves were to the stabilized strain levels of the first cyclic elongation. As the unstrained period increased, the initial strain levels of the strain decay curves approached those of the first cyclic elongation. The tested sensing cables differed in the amount and rate of strain decay. The wire rope-reinforced cable exhibited the smallest amount and rate of decay, whereas the GFRP-reinforced cable demonstrated the largest.

Analysis of Delay-Bandwidth Normalization Characteristic in Decay Usage Algorithm of UNIX (UNIX의 Decay Usage 알고리즘에서의 지연시간-사용량 정규화 특성 분석)

  • Park, Kyeong-Ho;Hwang, Ho-Young;Lee, Chang-Gun;Min, Sang-Lyul
    • Journal of KIISE:Computer Systems and Theory
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    • v.34 no.10
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    • pp.511-520
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    • 2007
  • Decay usage scheduling algorithm gives preference to processes that have consumed little CPU in the recent past. It has been widely-used in time-sharing systems such as UNIX, where CPU-intensive processes and interactive processes are mixed. However, there has been no sound understanding about the mixed effects of decay usage parameters on the service performance. This paper empirically analyzes their effects in terms of the resulting service bandwidth and delay Based on such empirical analysis, we derive the clear meaning of each parameter. Such analysis and understanding provides a basis of controlling decay usage parameters for desirable service provision as required by applications.

Observation of Soft-Rot Wood Degradation Caused by Higher Ascomyceteous fungi

  • Lee, Yang-Soo
    • Mycobiology
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    • v.28 no.1
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    • pp.47-50
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    • 2000
  • The capability of higher ascomyceteous fungi to cause typical soft-rot decay for wood under laboratory conditions is reviewed and discussed. Fungi tested were extremely active in the decomposition of timbers. Scanning electron micrographs illustrated typical soft-rot decay pattern of higher wood decay ascomycetes, with the exception of H. trugodes that caused white-rot decay. Most of the fungi tested could be grouped as soft-rot fungi that showed typical soft-rot type II. Hypha confined primarily to the resin canals in softwoods or vessel elements in hardwoods and spread tracheid to tracheid via pits of cell wall to cell wall with mechanical force.

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Studies on Chlorine Demand and Its Decay Kinetics in Chlorinated Sewage Effluents (하수의 염소 소독시 총잔류염소 감소 특성에 관한 연구)

  • Beck, Youngseog;Sohn, Jinsik
    • Journal of Korean Society on Water Environment
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    • v.21 no.2
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    • pp.176-183
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    • 2005
  • Chlorination of wastewater is recently practiced in Korea. While many researchers have studied the kinetics of aqueous chlorine(HOCl) with nitrogeneous compounds and other organic/inorganic contaminants in drinking water, the researches of wastewater chlorination are relatively few. The purpose of this study was to investigate the chlorine decay kinetics and parameters on wastewater chlorination. Chlorine decay rate increased with increasing initial chlorine concentration. The parameters affecting chlorine decay rate were different in each wastewater treatment plant. One of the most important parameters affecting chlorine decay was initial chlorine concentration, and other parameters such as $NH_3-N$, total coliform, $UV_{254}$ and Fe were also affected. The decay ratio of chlorine was decreased with increasing initial chlorine concentration, and the disinfection efficiency showed good correlation with the decay ratio.

Efficient Computation of Radioactive Decay with Graph Algorithms

  • Yoo, Tae-Sic
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.1
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    • pp.19-29
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    • 2020
  • This paper gives two graph-based algorithms for radioactive decay computation. The first algorithm identifies the connected components of the graph induced from the given radioactive decay dynamics to reduce the size of the problem. The solutions are derived over the precalculated connected components, respectively and independently. The second algorithm utilizes acyclic structure of radioactive decay dynamics. The algorithm evaluates the reachable vertices of the induced system graph from the initially activated vertices and finds the minimal set of starting vertices populating the entire reachable vertices. Then, the decay calculations are performed over the reachable vertices from the identified minimal starting vertices, respectively, with the partitioned initial value over the reachable vertices. Formal arguments are given to show that the proposed graph inspired divide and conquer calculation methods perform the intended radioactive decay calculation. Empirical efforts comparing the proposed radioactive decay calculation algorithms are presented.

Reduction in Mechanical Properties of Radiata Pine Wood Associated with Incipient Brown-Rot Decay (초기(初期) 갈색부후(褐色腐朽)에 따른 라디에타소나무의 역학적(力學的) 성질(性質) 감소(減少))

  • Kim, Gyu-Hyeok;Jee, Woo-Kuen;Ra, Jong-Bum
    • Journal of the Korean Wood Science and Technology
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    • v.24 no.1
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    • pp.81-86
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    • 1996
  • This study was performed to evaluate the reduction in bending properties of radiata pine sapwood associated with incipient brown-rot decay. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested destructively. Brown-rot decay by T. palustris and G. trabeum caused serious reduction in bending properties at very early stages of decay, with about 30 percent decrease in bending strength observed for only 1~2 percent weight loss. In general, the reduction in bending properties caused by T. palustris was somewhat greater than that by G. trabeum. Work to maximum load was reduced most severely and rapidly from the onset of decay, while modulus of elasticity showed a much more moderate rate of reduction. Modulus of rupture was affected by decay to a greater extent than was modulus of elasticity. Since a relatively strong correlation between weight loss and bending strength was observed, the residual strength of decayed wood can be predicted by weight loss due to decay. The results of this study indicate that very early stages of brown-rot decay reduce the bending strength significantly. Thus, it is recommended that all load-bearing members in wooden structures, especially those that are periodically wetted, should be inspected regularly to prevent a sudden failure even though there are no definite signs of decay.

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