• Title/Summary/Keyword: lag-phase

Search Result 406, Processing Time 0.031 seconds

A Theoretical Study for the Thermal Diffusivity Measurement of Solid Material using Photothermal Displacement Method (광열변위법을 이용한 재료의 열확산계수 측정에 대한 이론적 연구)

  • Jeon, Pil-Soo;Lee, Eun-Ho;Lee, Kwang-Jai;Yoo, Jai-Suk;Kim, Ki-Hyun
    • Proceedings of the KSME Conference
    • /
    • 2000.04b
    • /
    • pp.132-137
    • /
    • 2000
  • A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in solid materials. The influence of parameters - radius and modulation frequency of pump beam and thickness of material - on the phase lag was studied. The phase decreases up to a certain position, then starts to increase and does have an asymptotic value. The position, where phase has the minimum value, is a function of thermal diffusion length thickness of sample, and radius of pump beam. A new method based on minimum phase lag is described to determine the thermal diffusivity of solid material.

  • PDF

Stoneley wave propagation in nonlocal isotropic magneto-thermoelastic solid with multi-dual-phase lag heat transfer

  • Lata, Parveen;Singh, Sukhveer
    • Steel and Composite Structures
    • /
    • v.38 no.2
    • /
    • pp.141-150
    • /
    • 2021
  • In the present paper we have investigated the Stoneley wave propagation at the interface of two dissimilar homogeneous nonlocal magneto-thermoelastic media under the effect of hall current applied to multi-dual-phase lag heat transfer. The secular equations of Stoneley waves have been derived by using appropriate boundary conditions. The wave characteristics such as attenuation coefficients, temperature distribution and phase velocity are computed and have been depicted graphically. Effect of nonlocal parameter and hall effect are studied on the attenuation coefficient, phase velocity, temperature distribution change, stress component and displacement component. Also, some particular cases have been discussed from the present study.

Aerodynamic Analysis of a Rectangular Wing in Flapping with Lead-Lag Motion using Unsteady VLM (직사각형 평판날개의 리드래그 운동이 조합된 날개짓에 대한 비정상 VLM 공력 해석)

  • Kim, Woo-Jin;Kim, Hark-Bong
    • Journal of the Korean Society for Aviation and Aeronautics
    • /
    • v.14 no.2
    • /
    • pp.39-44
    • /
    • 2006
  • The unsteady vortex lattice method is used to model lead-lag in flapping motions of a rectangular flat plate wing. The results for plunging and pitching motions were compared with the limited experimental results available and other numerical methods. They show that the method is capable of simulating many of the features of complex flapping flight. The lift, thrust and propulsive efficiency of a rectangular flat plate wing have been calculated for various lead-lag motion and reduced frequency with an amplitude of flapping angle(20o). To describe a motion profile of wing tip such as elliptic, line and circle, the phase difference of flapping and lead-lag motion was changed. And the effects of the motion profile on the aerodynamic characteristics of the flapping wing are discussed by examination of their trends.

  • PDF

Effect of operational pH on anaerobic hydrogen fermentation of food waste (음식폐기물의 혐기성 수소 발효시 운전 pH의 영향)

  • Lee, Chae-Young;Lee, Se-Wook
    • Journal of the Korea Organic Resources Recycling Association
    • /
    • v.19 no.3
    • /
    • pp.73-78
    • /
    • 2011
  • The pH is one of the most important factors affecting metabolism pathway and activity of hydrogen producing bacteria. The effect of operational pH on anaerobic hydrogen fermentation of food waste was evaluated at mesophilic condition. In this batch experiment, the initial pH was 8.0 and the operational pH was controlled at 4.7~7.0 by the addition of 5N KOH solutions. At the operational pH of 4.7, the lag phase and the maximum hydrogen production were 47.9h and 534.4 mL, respectively. The lag phase and the maximum hydrogen production were decreased as the operational pH increased. At the operational pH of 7.0, the lag phase and the maximum hydrogen production were 4.2 h and 213.8 mL, respectively.

황환원 세균의 quorum-sensing 유사 현상

  • Park, Ji-Eun;Jang, Deok-Jin
    • 한국생물공학회:학술대회논문집
    • /
    • 2001.11a
    • /
    • pp.545-548
    • /
    • 2001
  • Microbiologically influenced corrosion (MIC) of metal is common in the natural environment and sulfate reducing bacteria are representative microorganisms for MIC. We found that biofilm fomlation by SRB on the metal surface might be controlled by quorum sensing, which is a cell density dependent regulation of cell metabolism. As cell free culture fluids (spent media) of Desulfovibrio vulgaris and D. desulfuricans were tested for quontrn sensing related test strains, it was found that spent media of two SRB induced increased luminescence of Vibrio harveyi BB886 (sensor 1+, sensor 2-) and BB170 (sensor 1-, sensor 2+). Quorum activities of D. vulgaris and D. desulfuricans appeared to be parallel to growth patterns, i.e., it was low in the lag phase, highly increased in the exponential phase, and reached maximum in the stationary phase. Interestingly, however, luminescence of V. harveyi BB886 and BB170 induced by a unit cell mass of the SHB showed a maximal peak in the late lag phase. Hence, it was suspected that quorum sensing of these two SHB play unknown roles in shifting cells from dormant to growth stages.

  • PDF

Hybridal Analysis of High-Frequency Combustion Instability with Pressure-Coupled Combustion Response Model (압력섭동과 연관된 연소응답모델에 기초한 고주파 연소불안정의 이론-수치적 고찰)

  • 윤웅섭;이길용
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2003.05a
    • /
    • pp.253-257
    • /
    • 2003
  • Theoretical-numerical analysis of wave instability is conducted with parametric response function model. Fluctuating instantaneous mass evaporation rate functionally coupled with pressure perturbations with phase lag is assumed to examine the validity of the method. With sufficiently large amplitude and less phase lag to perturbation, combustion response is resonant to pressure waves, unstable waves are amplified, and the system is driven to instability. Magnitude of response is a crucial instability parameter in the determination of a stability margins and makes a critical change of balancing conditions between the amplifying and damping acoustic energies. In the phase regime the unstable waves are amplified, whereas, the acoustic waves are attenuated in the out-of-phase regime. In the intermediate regime, no distinct tendency of unstable waves was determined.

  • PDF

Nutritional Studies on the Growth of the Rapamycin-Producing Streptomyces hygroscopicus

  • Kim, Wan-Seop;Davis, Sean;Wong, Grace;Demain, Arnold-L.
    • Journal of Microbiology and Biotechnology
    • /
    • v.13 no.4
    • /
    • pp.560-563
    • /
    • 2003
  • During our previous studies on the relationship between nutrient requirements of S. hygroscopicus C9 and rapamycin biosynthesis, we developed chemically-defined media containing among other nutrients, aspartic acid, arginine, histidine, or ammonium sulfate. However, these media (“Cheng et al. medium” and “Lee et al. medium”) showed very slow growth characterized by a very long lag phase of growth. In an attempt to develop a chemically-defined or semi-defined medium to support more rapid growth and increased cell production, we have carried out studies to shorten the lag phase. Of the various additives tested, vitamin-free casein acid hydrolysate was the most significant by shortening the lag phase by 2-3 days. Mixtures of amino acids failed to replace casein acid hydrolysate. The active principle passed through an ultrafilter with a molecular weight cutoff of 1,000 and thus may be a peptide. The present work has yielded a semi-defined medium which should be useful for further growth studies on S. hygroscopicus C9.

Biogas Production Performance Based on Carbon Number and Double Bond Count of Long-chain Fatty Acids

  • Kim, Soo-Ah;Kim, Sang-Hun
    • Journal of Biosystems Engineering
    • /
    • v.43 no.1
    • /
    • pp.37-44
    • /
    • 2018
  • Purpose: The objective of this study was to investigate the high-efficiency anaerobic digestion of organic wastes with high fat content. Specifically, the analysis focused on biogas production performance with a focus on carbon number and the double bond count of the long-chain fatty acids (LCFAs), which are hydrolysis products of triglycerides. Methods: Experiments were performed under mesophilic anaerobic conditions with a feed-to-microorganism ratio (F/M) of 1.0. Biogas production performance was analyzed through biogas production patterns, lag-phase, and the time required for 90% biogas production (T90). Results: Biogas production increased when the content of unsaturated LCFAs (containing relatively large numbers of carbon atoms) increased. In substrate containing LCFAs with four or more double bonds, although the initial lag-phase in biogas production was shortened, development of a three-step lag-phase resulted in decreased biogas production. These results suggest that high rates of anaerobic digestion are possible when the LCFAs have high unsaturated fatty acid content with three or fewer double bonds. Conclusions: When various types of LCFAs are digested anaerobically, biogas production performance can be improved if the unsaturated fatty acid content and number of double bonds are optimized for maximum production.

Measurement of Optical Parameters of Biological Tissues by Using the Frequency-Domain Spectroscopy (주파수 영역 분광법을 이용한 생체의 광학계수 측정법 연구)

  • Jeon, K.J.;Yoon, G.;Kim, H.S.;Kim, W.K.;Yi, J.H.;Park, S.H.;Kim, U.
    • Proceedings of the KOSOMBE Conference
    • /
    • v.1997 no.05
    • /
    • pp.379-382
    • /
    • 1997
  • A method for measuring optical properties of biological medium was investigated by using the frequency domain spectroscopy. When amplitude-modulated light with the frequency of several tens up to several hundred MHz propagates through a scattering medium, the phase lag and the amplitude reduction occur. The phase lag depends on the average of optical path lengths. The amplitude reduction with respect to the radial distance is influenced by the penetration depth. The mean of optical path length and penetration depth are related to optical coefficients. The phase lag and the amplitude reduction were measured based on the heterodyne detection method. The experimental data were fitted with the theoretical curves derived from diffusion theory and the absorption and scattering coefficients were calculated.

  • PDF

Numerical study on flux of cohesive sediment by asymmetric oscillatory flow (비대칭 진동흐름에 의한 점착성 유사의 이동량 수치연구)

  • Son, Min-Woo;Jung, Tae-Hwa;Baek, Kyong-Oh;Cho, Sung-Won
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2012.05a
    • /
    • pp.505-509
    • /
    • 2012
  • 본 연구의 목적은 천해 환경에서의 파형이 점착성 유사의 이동량에 미치는 영향을 살펴보는 것이다. 이를 위하여 이상적인 진동흐름(Oscillatory Flow)을 가정하고 점착성 유사의 이동에 적합한 1DV 모형을 적용하였다. 이상적인 진동흐름을 가정할 때는 다양한 파형을 고려하기 위해 왜곡되거나 비대칭적인 조건을 적용하였다. 크기와 밀도가 변화하는 점착성 유사의 응집현상을 고려하기 위해 기존에 개발된 응집현상 모형을 1DV 모형에 결합하였다. 2차 스토크스파 조건을 모사하기 위해 왜곡된 진동흐름, 톱니파를 모사하기 위해 비대칭 진동흐름 조건을 선택하였다. 수치모의 결과, 왜곡된 진동흐름 조건에서의 점착성 유사 이동량은 흐름의 왜곡도에 큰 영향을 받는 것으로 나타났다. 반면 가는 비점착성 유상의 경우는 왜곡도와 주목할 만한 관계를 보이지 않았다. 비대칭 진동흐름의 경우는 점착성 유사와 비점착성 유사가 서로 다른 방향을 나타내었다. 앞쪽으로 기운 비대칭 진동흐름 조건에서 점착성 유사의 이동량이 뒤쪽 방향으로 발생하는 반면 비점착성 유사는 흐름이 기운 방향과 동일한 방향으로 유사량을 나타내었다. 이러한 현상의 원인으로는 Phase-lag 효과가 고려되었다. 유사의 침강속도와 농도 프로파일의 변화, 물의 유동 조건 등은 복합적인 상호작용을 통해 Phase-lag 효과를 강화시키고 점착성 유사와 비점착성 유사의 이동량이 서로 다른 특성을 나타내게 하는 것으로 고려된다.

  • PDF