Browsing by Author "Chen, S."

Now showing 1 - 8 of 8
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    Boundary Effects on Population Dynamics in Stochastic Lattice Lotka-Volterra Models
    Heiba, B.; Chen, S.; Täuber, Uwe C. (2017-08)
    We investigate spatially inhomogeneous versions of the stochastic Lotka-Volterra model for predator-prey competition and coexistence by means of Monte Carlo simulations on a two-dimensional lattice with periodic boundary conditions. To study boundary effects for this paradigmatic population dynamics system, we employ a simulation domain split into two patches: Upon setting the predation rates at two distinct values, one half of the system resides in an absorbing state where only the prey survives, while the other half attains a stable coexistence state wherein both species remain active. At the domain boundary, we observe a marked enhancement of the predator population density. The predator correlation length displays a minimum at the boundary, before reaching its asymptotic constant value deep in the active region. The frequency of the population oscillations appears only very weakly affected by the existence of two distinct domains, in contrast to their attenuation rate, which assumes its largest value there. We also observe that boundary effects become less prominent as the system is successively divided into subdomains in a checkerboard pattern, with two different reaction rates assigned to neighboring patches. When the domain size becomes reduced to the scale of the correlation length, the mean population densities attain values that are very similar to those in a disordered system with randomly assigned reaction rates drawn from a bimodal distribution.
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    Evaluation of UV Disinfection Performance in Recirculating Systems
    Zhu, S.; Saucier, B. B.; Chen, S.; Durfey, J. E. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2002-06-01)
    The use of ultraviolet (UV) disinfection devices has become increasingly popular in wastewater and aquaculture industries. Although the effectiveness of UV disinfection has been well documented for flowthrough operation regimes in wastewater treatment, research focusing on water recirculating systems is still limited. In this study, the performance of single-lamp UV devices were tested on a recirculating system for fecal coliform (FC) disinfection. Experimental results indicated that UV power input, recirculating flow rate and water UV transmittance were three important factors determining UV disinfection efficiency. An UV disinfection model for a recirculating system was developed based on theoretical analysis and experimental data. A key model parameter, namely the first-order inactivation rate constant (k), was determined to be 0.0062 m2 J-1 for FC disinfection. Simulation using the model provided useful information for design and operation of recirculating UV disinfection systems. The model prediction of disinfection process for other microorganisms is also capable of using reported values of the inactivation rate constant.
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    Evolutionary dynamics and competition stabilize three-species predator-prey communities
    Chen, S.; Dobramysl, U.; Täuber, Uwe C. (2017-11-15)
    We perform individual-based Monte Carlo simulations in a community consisting of two predator species competing for a single prey species, with the purpose of studying biodiversity stabilization in this simple model system. Predators are characterized with predation efficiency and death rates, to which Darwinian evolutionary adaptation is introduced. Competition for limited prey abundance drives the populations' optimization with respect to predation efficiency and death rates. We study the influence of various ecological elements on the final state, finding that both indirect competition and evolutionary adaptation are insufficient to yield a stable ecosystem. However, stable three-species coexistence is observed when direct interaction between the two predator species is implemented.
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    Input choices in agriculture: Is there a gender bias?
    Bhagowalia, P.; Chen, S.; Shively, Gerald E. (West Lafayette, IN: Purdue University, Department of Agricultural Economics, 2007)
    This study analyzes the effect of child gender on the use of agricultural inputs in rural India. Results indicate that households with boys use fertilizers, irrigation services, and insecticides to a greater extent than households with girls. One reason for this may be that boys provide a sense of social security and provide more assurance that the farm will stay in the family, therefore more effort is put into the farm to keep it productive. Examining gender biases and how they affect the behavior of farmers in a household is important to addressing agricultural productivity and food security.
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    The Intermediate Neutrino Program
    Adams, C.; Alonso, J. R.; Ankowski, Artur M.; Asaadi, J. A.; Ashenfelter, J.; Axani, S. N.; Babu, K. S.; Backhouse, C.; Band, H. R.; Barbeau, P. S.; Barros, N.; Bernstein, A.; Betancourt, M.; Bishai, M.; Blucher, E.; Bouffard, J.; Bowden, N. S.; Brice, S.; Bryan, C.; Camilleri, Leslie; Cao, J.; Carlson, J.; Carr, R. E.; Chatterjee, A.; Chen, M.; Chen, S.; Chiu, M.; Church, E. D.; Collar, J. I.; Collin, G.; Conrad, Janet M.; Convery, M. R.; Cooper, R. L.; Cowen, D.; Davoudiasl, H.; Gouvea, A. D.; Dean, D. J.; Deichert, G.; Descamps, F.; DeYoung, T.; Diwan, M. V.; Djurcic, Zelimir; Dolinski, M. J.; Dolph, J.; Donnelly, B.; Dwyer, D. A.; Dytman, S.; Efremenko, Y.; Everett, L. L.; Fava, A.; Figueroa-Feliciano, E.; Fleming, B.; Friedland, A.; Fujikawa, B. K.; Gaisser, T. K.; Galeazzi, M.; Galehouse, D. C.; Galindo-Uribarri, A.; Garvey, G. T.; Gautam, S.; Gilje, K. E.; Gonzalez-Garcia, M.; Goodman, M. C.; Gordon, H.; Gramellini, E.; Green, M. P.; Guglielmi, A.; Hackenburg, R. W.; Hackenburg, A.; Halzen, F.; Han, K.; Hans, S.; Harris, D.; Heeger, K. M.; Herman, M.; Hill, R.; Holin, A.; Huber, Patrick; Jaffe, D. E.; Johnson, R. A.; Joshi, J.; Karagiorgi, Georgia S.; Kaufman, L. J.; Kayser, B.; Kettell, S. H.; Kirby, B. J.; Klein, J. R.; Kolomensky, Y. G.; Kriske, R. M.; Lane, C. E.; Langford, T. J.; Lankford, A.; Lau, K.; Learned, J. G.; Ling, J.; Link, Jonathan M.; Lissauer, D.; Littenberg, L.; Littlejohn, B. R.; Lockwitz, S.; Lokajicek, M.; Louis, W. C.; Luk, K.; Lykken, J.; Marciano, W. J.; Maricic, Jelena; Markoff, D. M.; Caicedo, D. A. M.; Mauger, C.; Mavrokoridis, K.; McCluskey, E.; McKeen, D.; McKeown, R.; Mills, G.; Mocioiu, I.; Monreal, B.; Mooney, M. R.; Morfin, J. G.; Mumm, P.; Napolitano, J.; Neilson, R.; Nelson, J. K.; Nessi, M.; Norcini, D.; Nova, F.; Nygren, D. R.; Orebi Gann, G. D.; Palamara, O.; Parsa, Z.; Patterson, R.; Paul, P.; Pocar, A.; Qian, X.; Raaf, J. L.; Rameika, R.; Ranucci, G.; Ray, H.; Reyna, D.; Rich, G. C.; Rodrigues, P.; Romero, E. R.; Rosero, R.; Rountree, S. D.; Rybolt, B.; Sanchez, Maria Cristina; Santucci, G.; Schmitz, D.; Scholberg, K.; Seckel, D.; Shaevitz, Marjorie Hansen; Shrock, R.; Smy, M. B.; Soderberg, M.; Sonzogni, A.; Sousa, A. B.; Spitz, Joshua; John, J. M. S.; Stewart, J.; Strait, J. B.; Sullivan, G.; Svoboda, R.; Szelc, A. M.; Tayloe, R.; Thomson, M.; Toups, M.; Vacheret, A.; Vagins, M. R.; Water, R. G. V. D.; Vogelaar, R. Bruce; Weber, M.; Weng, W.; Wetstein, M.; White, C.; White, B. R.; Whitehead, L.; Whittington, D. W.; Wilking, M. J.; Wilson, R. J.; Wilson, P.; Winklehner, D.; Winn, D. R.; Worcester, E.; Yang, L.; Yeh, M.; Yokley, Z. W.; Yoo, J.; Yu, B.; Yu, J.; Zhang, C. (2015-04-01)
    The US neutrino community gathered at the Workshop on the Intermediate Neutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 to explore opportunities in neutrino physics over the next five to ten years. Scientists from particle, astroparticle and nuclear physics participated in the workshop. The workshop examined promising opportunities for neutrino physics in the intermediate term, including possible new small to mid-scale experiments, US contributions to large experiments, upgrades to existing experiments, R&D plans and theory. The workshop was organized into two sets of parallel working group sessions, divided by physics topics and technology. Physics working groups covered topics on Sterile Neutrinos, Neutrino Mixing, Neutrino Interactions, Neutrino Properties and Astrophysical Neutrinos. Technology sessions were organized into Theory, Short-Baseline Accelerator Neutrinos, Reactor Neutrinos, Detector R&D and Source, Cyclotron and Meson Decay at Rest sessions.This report summarizes discussion and conclusions from the workshop.
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    Non-equilibrium relaxation in a stochastic lattice Lotka-Volterra model
    Chen, S.; Täuber, Uwe C. (IOP, 2016-04-01)
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    Search for massive neutrinos in the decay pi -> e nu
    Aoki, M.; Blecher, Marvin; Bryman, D. A.; Chen, S.; Ding, M.; Doria, L.; Gumplinger, P.; Hurst, C.; Hussein, A.; Igarashi, Y.; Ito, N.; Kettell, S. H.; Kurchaninov, L.; Littenberg, L.; Malbrunot, C.; Numao, T.; Poutissou, R.; Sher, A.; Sullivan, T.; Vavilov, D.; Yamada, K.; Yoshida, M.; Pienu Collaboration (American Physical Society, 2011-09-06)
    Evidence of massive neutrinos in the pi(+) -> e(+)nu decay spectrum was sought with the background pi(+) -> mu(+) -> e(+) decay chain highly suppressed. Upper limits (90% C. L.) on the neutrino mixing matrix element vertical bar U(ei)vertical bar(2) in the neutrino mass region 60-129 MeV/c(2) were set at the level of 10(-8).
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    Short-term investments in agriculture: Is there a gender bias?
    Bhagowalia, P.; Chen, S.; Shively, Gerald E. (2007)
    Most developing countries strive to improve agricultural productivity by relaxing credit constraints, supplying better inputs, improving marketing and distribution. However the efficacy of these reforms needs to be examined in the context of the behavioral responses of farming households. This study examines gender biases within households that affect short-term input allocation decisions in agriculture. The study utilizes data from ICRISAT's village level studies in India (1975-85) to highlight the effects of child gender on the use of agricultural inputs. The main finding is that households with boys tend to use purchased inputs such as fertilizers and insecticides more intensively compared with households with girls. In general, household with boys also tend to have larger land holdings, and use animal and human labor to a greater extent than household with girls.