• Title, Summary, Keyword: Quantitative fluctuation

Search Result 69, Processing Time 0.041 seconds

Sea-level Change and Coastal Erosion (해수면 변화와 해안 침식)

  • Jeon, Dong-Chull
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.7 no.4
    • /
    • pp.289-304
    • /
    • 1995
  • Time series of the relative sea levels at the selected tide-gauge stations in the North Pacific and historical aerial photographs in the Hawaiian Islands are analyzed. Long-term rising trend of sea level ranges from +1 to +5 mm/yr at most of the stations, which is primarily due to global warming and tectonic motion of the plates. The annual and interannual fluctuations of sea level result from the thermal expansion/contraction of sea-surface layer due to the annual change of the solar radiation and possibly from a coupled ocean-atmosphere phenomenon associated with an ENSO event, respectively. Sea-level changes in three different time-scales (linear trend. annual oscillation, and interannual fluctuation) and their quantitative contribution to the shoreline changes as a result of long-term cross-shore sediment transport arc hypothesized.

  • PDF

Adaptive Absolute Delay Differentiation in Next-Generation Networks (차세대 네트워크에서의 적응형 절대적 지연 차별화 방식)

  • Paik, Jung-Hoon
    • Convergence Security Journal
    • /
    • v.6 no.1
    • /
    • pp.55-63
    • /
    • 2006
  • In this paper, an algorithm that provisions absolute differentiation of packet delays is proposed with an objective for enhancing quality of service (QoS) in future packet networks. It features an adaptive scheme that compensates the deviation for prediction on the traffic to be arrived continuously. It predicts the traffic to be arrived at the beginning of a time slot and measures the actual arrived traffic at the end of the time slot, and derives the deviation between the two quantity. The deviation is utilized to the delay control operation for the next time slot to offset it. As it compensates the prediction error continuously, it shows superior adaptability to the bursty traffic as well as the constant rate traffic. It is demonstrated through simulation that the algorithm meets the quantitative delay bounds and shows superiority to the traffic fluctuation in comparison with the conventional mechanism.

  • PDF

Properties of the variations of volumetric water content on the saturated/unsaturated media by water-level fluctuations (수위변동에 따른 포화/불포화 매질의 체적함수비 변화 특성 평가)

  • Kim, Man-Il;Lim, Heon-Tae;Kim, Hyoung-Soo
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • /
    • pp.1076-1082
    • /
    • 2006
  • This study measured the change of media properties using Time domain Reflectometry (TDR) and Tensionmeter (TM) to measure volumetric water content of soil affecting in land subsidence and pollutant diffusion under saturation/unsaturated condition by water-level fluctuations. Also, actual water content compared their changes aspect by dry oven test for quantitative determinations of these measured values. In the case of TM, initial unsaturated condition confirmed that range in dimension of each other different according to their establishment depth, but measured values of TM can know that is shown measured value in almost similar measuring range under drain condition after the first injection. Also, the results of TDR showed that can measure enough change of volumetric water content in saturation/unsaturated condition by water-level fluctuations. Therefore, we are judged that TDR measurement equipment is very effective to measure the variations of volumetric water content and water-level being caused in groundwater level fluctuations.

  • PDF

Geotechnical Diagnosis System for Preventing a Ground Subsidence Relating with Cultural Heritage (석조문화재관련 지반침하 방지를 위한 지반진단시스템)

  • Kim Man-Il;Yang Dong-Yoon;Lee Kyu-Shik;Jeong Gyo-Cheol
    • The Journal of Engineering Geology
    • /
    • v.16 no.3
    • /
    • pp.301-306
    • /
    • 2006
  • Damages of cultural properties is caused by subsidence of foundation relating stone structures. To prevent of these structures, ground monitoring should be achieved certainly. Representative ground subsidence cause is saturated and unsaturated condition that is produced repeatedly by groundwater level fluctuations. It controls role that decrease porosity or effective porosity of soil media. Estimation of physical properties can predict from reaction of dielectric constant. Variations of dielectric constants are measured from physical characteristics change of pore, soil particle, air and water which are consisted to ground. Therefore, ground subsidence monitoring is thought that quantitative measurement is available using dielectric response of media.

Evaluation of Combustion Instability in a Model Gas Turbine Adopting Flame Transfer Function and Dynamic Mode Decomposition (화염 전달함수 및 DMD 기법을 이용한 모형 가스터빈의 연소불안정성 평가)

  • Son, Jinwoo;Sohn, Chae Hoon;Yoon, Jisu;Yoon, Youngbin
    • Journal of the Korean Society of Combustion
    • /
    • v.22 no.2
    • /
    • pp.1-8
    • /
    • 2017
  • To evaluate the combustion instability of a gas turbine combustor, the DMD technique was applied. The mode frequency results for each fuel composition were compared with FFT(Fast Fourier Transform) results. The damping coefficient, which is a quantitative parameter for combustion instability, was evaluated for 5 experimental cases. The flame transfer function (FTF) was calculated in the most unstable test case. In deriving the FTF, gain and phase were calculated using DMD technique. As a result of the analysis of the OH radical perturbation of the DMD, the heat release fluctuation was the highest at 100 Hz, at which the highest value of gain is observed. The frequency of FFT and FTF were different. In order to clarify the reason for this, FTF for various resonance frequencies was performed and it shows that the pattern of gain was similar to FFT.

Variations in Marine Environments and Phytoplankton Community around Mokpo Harbour (목포항 주변해역의 수질 및 식물플랑크톤 변동 특성)

  • Cho, Eun-Seob
    • Journal of Environmental Science International
    • /
    • v.19 no.11
    • /
    • pp.1323-1336
    • /
    • 2010
  • This study was carried out to determine marine environments and phytoplankton community around Mokpo harbour on March to November during the period of 2004-2009. The remarkable fluctuations of marine environments were shown around Mokpo harbour depending on monthly and yearly. Among seasons, summer was a great that was associated with extremely releasing the freshwater from Youngsan River Weir, contributing to effect the fluctuations of water quality. Nevertheless of monthly and yearly, the molecular ratio of N:P was always shown in above 16 that was mainly attributed to freshwater discharge on March to November. This indicates that phosphorus playes an important role in limiting factor as growth in phytoplankton. During this study, Skeletonema costatum was found to be richer than the other groups of diatoms in terms of abundance and species number. Mokpo harbour, with the presence of a narrow avenue for exchange with offshore waters, has limited growth in phytoplankton, but this species is able to well adapt and fast grow under even high level of suspended solid and low intensity of light compared with other species. The discharge of freshwater is associated with significantly fluctuation of marine environments in this region, but it does not affect the quantitative and qualitative distribution of phytoplankton. It is necessary to persistently monitor based on water quality and phytoplankton community.

Assessment for Propagation Behavior and Fracture Surface of Mixed-mode Fatigue Crack by Fracture Surface-Roughness Induced Crack Closure (파면거칠기 유도 균열닫힘에 의한 혼합모드 피로균열의 전파거동 및 파면에 대한 평가)

  • Seo, Ki-Jeong;Lee, Jeong-Moo
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.31 no.4
    • /
    • pp.432-440
    • /
    • 2007
  • In this study, we have investigated the closure behavior of fatigue cracks in SAPH440 steel plates under a mixed-mode I+II loading. A crack image capturing system as a direct measuring method was used to measure the closure levels at a crack tip. The crack closure levels in the fluctuation and stable sections were increased with the increase of the mode mixture ratio. The mode mixture ratio independent fatigue crack propagation rates equation was calculated by considering mixed-mode crack closure levels. The equation was examined according to the application method of crack opening ratio. The fracture surface analysis by C-scan method was also performed in order to investigate the closure mechanism and propagation mode of crack under the mixed-mode I+II loading. The crack closure under the mixed mode I+II is confirmed as a surface roughness closure by the quantitative analysis of fracture surface using the proposed surface roughness parameter.

Adaptive Input Traffic Prediction Scheme for Absolute and Proportional Delay Differentiated Services in Broadband Convergence Network

  • Paik, Jung-Hoon;Ryoo, Jeong-Dong;Joo, Bheom-Soon
    • ETRI Journal
    • /
    • v.30 no.2
    • /
    • pp.227-237
    • /
    • 2008
  • In this paper, an algorithm that provides absolute and proportional differentiation of packet delays is proposed with the objective of enhancing quality of service in future packet networks. It features an adaptive scheme that adjusts the target delay for every time slot to compensate the deviation from the target delay, which is caused by prediction error on the traffic to arrive at the next time slot. It predicts the traffic to arrive at the beginning of a time slot and measures the actual arrived traffic at the end of the time slot. The difference between them is utilized by the delay control operation for the next time slot to offset it. Because the proposed algorithm compensates the prediction error continuously, it shows superior adaptability to bursty traffic and exponential traffic. Through simulations we demonstrate that the algorithm meets the quantitative delay bounds and is robust to traffic fluctuation in comparison with the conventional non-adaptive mechanism. The algorithm is implemented with VHDL on a Xilinx Spartan XC3S1500 FPGA, and the performance is verified under the test board based on the XPC860P CPU.

  • PDF

Effect of low H2 content in natural gas on the Combustion Characteristics of Gas Turbine (천연가스 내 미량의 수소함량이 가스터빈의 연소특성에 미치는 영향)

  • Lee, Min Chul;Park, Seik;Kim, Sungchul;Yoon, Jisoo;Joo, Sungpeel;Yoon, Youngbin
    • 한국연소학회:학술대회논문집
    • /
    • /
    • pp.109-110
    • /
    • 2013
  • This paper describes gas turbine combustion characteristics of synthetic natural gas which contains a small amount hydrogen content. By conducting ambient pressure high temperature combustion test at gas turbine relevant combustor geometry, the combustion characteristics such as combustion instability, NOx and CO emission, temperatures at turbine inlet, nozzle and dump plane, and flame structure from high speed OH chemiluminescence images were investigated when changing hydrogen content from zero to 5%. From the results, qualitative and quantitative relationships are derived between key aspects of combustion performance, notably NOx/CO emission and combustion instability. Natural gas containing hydrogen up to 5% does not show significant difference in view of all combustion characteristics except combustion instability. Only up to 1% hydrogen addition could not change the pressure fluctuation and phase gas between fluctuations of pressure and heat release. From the results, it can be concluded that synthetic national gas which contains 1% of hydrogen can be guaranteed for the stable and reliable operation of natural gas firing gas turbine.

  • PDF

Microbial Activity of Ammonia Oxidizing Bacteria and Ammonia Oxidizing Archaea in the Rice Paddy Soil in Wang-gung Area of Iksan, Korea (익산 왕궁지역 논 토양에서의 질산화 세균과 질산화 고세균의 미생물학적 작용)

  • Kim, Hyun-su
    • Journal of Soil and Groundwater Environment
    • /
    • v.21 no.4
    • /
    • pp.50-59
    • /
    • 2016
  • Spatial and temporal changes in nitrification activities and distribution of microbial population of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) in paddy soils were investigated. Soil samples were collected in March and October 2015 from rice paddy with and without the presence of confined animal feeding operations. Incubation experiments and quantitative polymerase chain reaction showed that AOA's contribution to nitrification kinetics was much higher in locations where organic nitrogen in animal waste is expected to significantly contribute to overall nitrogen budget, and temporal variations in nitrification kinetics were much smaller for AOA than AOB. These differences were interpreted to indicate that different microbial responses of two microbial populations to the types and concentrations of nitrogen substrates were the main determining factors of nitrification processes in the paddy soils. The copy numbers of ammonium monooxygenase gene showed that AOA colonized the paddy soils in higher numbers than AOB with stable distribution while AOB showed variation especially in March. Although small in numbers, AOB population turned out to exert more influence on nitrification potential than AOA, which was attributed to higher fluctuation in AOB cell numbers and nitrification reaction rate per cells.