Evaluating households’ preferences regarding reducing power outages in rural areas: cases in the Ganges Floodplain in Bangladesh

This paper investigates household preferences regarding an improved supply of electricity in rural Bangladesh, where the expansion of stable electricity is an urgent policy issue. The paper examines household preferences regarding reductions in the frequency and duration of power outages. It also examines prior notification mechanisms that do not necessarily provide an increased supply of electricity but that allow households to prepare for potential power failures. A questionnaire survey designed as a choice experiment was applied to households to elicit preferences. The econometric analysis reveals that villagers prefer a reduction in both the frequency and duration of power outages and a 1-day prior notification of power outages. There are slight disparities in preferences according to the season and the timing of improvements (e.g., summer or winter and all day or peak hours). Thus, the present study may be beneficial for policymakers when considering the provision of electricity supply improvements in rural areas in exchange for slight increases in electricity tariffs.     

Modeling the current-voltage characteristics of thin-film silicon solar cells based on photo-induced electron transfer processes

Power conversion efficiency of p-i-n type microcrystalline silicon (c-Si:H) solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. The effect of the excitonic state on the charged carrier generation has been studied compared to a conventional scheme in which only charged carriers are taken into account for the operation of the solar cells. A numerical model has been developed to calculate current-voltage characteristics of solar cells on the basis of two types of charged carrier generation processes (exciton process and charged carrier process). The light trapping effect due to a textured back surface reflector (BSR) was embedded in the numerical model by using the effective medium theory in combination with the matrix method in the field of the electromagnetic theory of light. As an application of this modeling, it was found that the reported data of the power conversion efficiency were not explained by the conventional charged carrier process model and that the combined model of the charged carrier process with the exciton process well explains the performance of the p-i-n type c-Si:H solar cells. In this way, the typical power conversion efficiencies were estimated to be 10.5% for the device (i-layer thickness: 1.8 m) with the BSR (period: 600 nm; height: 250 nm) and 8.6% for the device with the flat reflector under the condition that the fractions of the exciton process and charged carrier process were 60% and 40%, respectively.     

Modeling the current-voltage characteristics of thin-film silicon solar cells based on photo-induced electron transfer processes

Power conversion efficiency of p-i-n type macrocrystalline silicon (µc-Si:H) solar cells has been analyzed in terms of sequential processes of photo-induced electron transfer. The effect of the excitonic state on the charged carrier generation has been studied compared to a conventional scheme in which only charged carriers are taken into account for the operation of the solar cells. A numerical model has been developed to calculate current-voltage characteristics of solar cells on the basis of two types of charged carrier generation processes (exciton process and charged carrier process). The light trapping effect due to a textured back surface reflector (BSR) was embedded in the numerical model by using the effective medium theory in combination with the matrix method in the field of the electromagnetic theory of light. As an application of this modeling, it was found that the reported data of the power conversion efficiency were not explained by the conventional charged carrier process model and that the combined model of the charged carrier process with the exciton process well explains the performance of the p-i-n type μc-Si:H solar cells. In this way, the typical power conversion efficiencies were estimated to be 10.5% for the device (i-layer thickness: 1.8 μm) with the BSR (period: 600 nm; height: 250 nm) and 8.6% for the device with the flat reflector under the condition that the fractions of the exciton process and charged carrier process were 60% and 40%, respectively.     

Indirect identification of an unstable intermediate in γ-HCH degradation by Pseudomonas paucimobilis UT26

While a postulated intermediate, 1,3,4,5-tetrachlorocyclohexa-1,4-diene(1,4-TCDN), is one of the key-compounds in γ-hexachlorocyclohexane(γ-HCH) degradation by Pseudomonas paucimobilis UT26(UT26), it has neither been isolated nor identified yet. Thus, an indirect identification was attempted to demonstrate its existence by a chemical oxidation of the microbial degradation products in situ.

1,2,4,5-Tetrachlorobenzene(1,2,4,5-TeCB) was newly produced by the chemical oxidation with hydrogen peroxide under iron(II) of W medium containing degradation products in situ of γ-1,3,4,5,6-pentachlorocyclohexene(γ-PCCH) by Escherichia coli MV1184(E. coli) which possesses the dehydrochlorinating activity of UT26. The chemical oxidation required the preceding enzymatic reactions to γ-PCCH by E. coli for the production of 1,2,4,5-TeCB. In facts, 1,2,4,5-TeCB was not produced from γ-PCCH by either of the chemical or enzymatic reaction alone.

Considering these results and the fact that hydrogen peroxide is known to dehydrogenate chemical compounds, it was concluded that 1,2,4,5-TeCB was produced directly from the unstable intermediate, 1,4-TCDN, on yielded from γ-PCCH by an enzymatic dehydrochlorination.     

Performance of various sub-grid scale models in large-eddy simulations of turbulent flow over complex terrain

Turbulent flow over a two-dimensional steep hill was analyzed by large-eddy simulations (LES). Here, six LES computations were carried out using four different sub-grid scale (SGS) models and two different ground surface conditions. The accuracy of these computations was assessed by comparing the results with those from an experiment by Ishihara et al. (An experimental study of turbulent boundary layer over a steep hill, Proceedings of the 15th National Symposium on Wind Engineering, 1998, pp. 61–66; J. Wind Eng. 89 (2001) 573). The results of the dynamic SGS models were in very poor agreement with those of the experiment. The poor prediction accuracy was mainly caused by the inaccurate estimation of the model coefficient near the ground surface. In order to improve the prediction accuracy of the dynamic SGS models, a hybrid SGS model, i.e., a combination of the standard Smagorinsky model and the dynamic Smagorinsky model, was introduced. The hybrid model provided very accurate predictions and produced the best results of the four SGS models compared here.     

MM5 simulations for air quality modeling: An application to a coastal area with complex terrain

A series of modifications were implemented in MM5 simulation in order to account for wind along the Santa Clarita valley, a north–south running valley located in the north of Los Angeles. Due to high range mountains in the north and the east of the Los Angeles Air Basin, sea breeze entering Los Angeles exits into two directions. One branch moves toward the eastern part of the basin and the other to the north toward the Santa Clarita valley. However, the northward flow has not been examined thoroughly nor simulated successfully in the previous studies. In the present study, we proposed four modifications to trigger the flow separation. They were (1) increasing drag over the ocean, (2) increasing soil moisture content, (3) selective observational nudging, and (4) one-way nesting for the innermost domain. The Control run overpredicted near-surface wind speed over the ocean and sensible heat flux, in an urbanized area, which justifies the above 1st and 2nd modification. The Modified run provided an improvement in near-surface temperature, sensible heat flux and wind fields including southeasterly flow along the Santa Clarita valley. The improved MM5 wind field triggered a transport to the Santa Clarita valley generating a plume elongated from an urban center to the north, which did not exist in MM5 Control run. In all, the modified MM5 fields yielded better agreement in both CO and O₃ simulations especially in the Santa Clarita area.     

Quantitative analysis of microbial biomass yield in aerobic bioreactor

We have studied the integrated model of reaction rate equations with thermal energy balance in aerobic bioreactor for food waste decomposition and showed that the integrated model has the capability both of monitoring microbial activity in real time and of analyzing biodegradation kinetics and thermal-hydrodynamic properties. On the other hand, concerning microbial metabolism, it was known that balancing catabolic reactions with anabolic reactions in terms of energy and electron flow provides stoichiometric metabolic reactions and enables the estimation of microbial biomass yield (stoichiometric reaction model). We have studied a method for estimating real-time microbial biomass yield in the bioreactor during food waste decomposition by combining the integrated model with the stoichiometric reaction model. As a result, it was found that the time course of microbial biomass yield in the bioreactor during decomposition can be evaluated using the operational data of the bioreactor (weight of input food waste and bed temperature) by the combined model. The combined model can be applied to manage a food waste decomposition not only for controlling system operation to keep microbial activity stable, but also for producing value-added products such as compost on optimum condition.     

Stable C and N isotope analysis elucidated the importance of zooplankton in a tropical seagrass bed of Santiago Island,Northwestern Philippines

The role of zooplankton in a tropical seagrass ecosystem was investigated in milkfish farms pollution-impacted and -unimpacted seagrass beds in Santiago Island coral reefs, Northwestern Philippines. The aim was to compare between the two sites: (1) abiotic factors and zooplankton community parameters, and (2) the trophic structure using C and N stable isotopes. Low water (98–119?mV) and sediment (–121 to ?138?mV) Oxidation Reduction Potential values indicated a reducing environment in the impacted site. Zooplankton in the impacted site showed the typical community response to eutrophication (low diversity, but high total abundance due to the dominance of the cyclopoid copepod Oithona oculata), generally few elevated δ¹⁵N values, but a significant shift towards depleted ¹³C due to the organic enrichment of fish-farm feeds. Apart from suggesting a highly complex food web with POM and zooplankton as main food sources in the unimpacted site, the Bayesian mixing model simulation generated reduced complexity in feeding interactions between basal sources, zooplankton, and fish including adults of a key fish species, Siganus fuscescens, in the impacted sites. In this study, C and N stable isotope analysis has clarified the importance of zooplankton as fish prey in a seagrass bed food web.