884 resultados para Cross-ecosystem analysis
Resumo:
There is increasing awareness that integrating gender into development frameworks is critical for effective implementation of development strategies. In working to alleviate rural poverty, the CGIAR Research Program on Aquatic Agricultural Systems (AAS) recognizes that “business as usual” gender integration approaches will not deliver lasting and widespread improvements in agricultural productivity, poverty reduction and food security. In response, AAS operationalized a gender transformative approach. The approach is informed by conceptual frameworks that explicitly recognize the potent influence of social relations on creating and perpetuating gender inequalities. In this way, AAS aims to address the underlying causes of rural poverty and gender inequality in Zambia’s Barotse Floodplain, where people rely extensively on riverine and wetland ecosystems for food and livelihood security. A central question guiding the research program is “How do social norms and gendered power relations influence agricultural development outcomes?” The findings presented in this report provide insights that help answer this question. The report presents a review of literature relevant to livelihoods, ecosystem services, and gender and social relations in Zambia, with a specific focus on Western Province, where AAS is currently implemented. It also presents a synthesis of findings of a social and gender analysis conducted in 2013 in 10 focal communities situated in and around the Barotse Floodplain.
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This study analyses competition in the wholesale and retail fish marketing system in Kisumu, which is Kenya's largest fish market. It is based on cross sectional and time series primary data collected in a survey involving 88 retailers and 47 wholesale traders of fish in the town. Stratified random sampling method was used in selecting the respondents, Concentration ratios, Lorenz curves and Gini coefficients are derived and evaluated for both markets. They demonstrate that market shares are unequally distributed among the wholesalers and retailers. The Gini coefficients are 0.37 and 0.45 for the whole and retail markets respectively. Based on a Gini coefficient cut-off level of 0.4, it is concluded that the wholesale fish market exhibits effective competition while the retail outlet has oligopolistic tendencies. The implication of this level of competition to price efficiency is discussed. Intervention measures to enhance competition in the market are recommended.
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To meet targeted reductions in CO 2 emissions by 2050, demand for metal must be cut, for example through the use of lightweight technologies. However, the efficient production of weight optimized components often requires new, more flexible forming processes. In this paper, a novel hot rolling process is presented for forming I-beams with variable cross-section, which are lighter than prismatic alternatives. First, the new process concept is presented and described. A detailed computational and experimental analysis is then conducted into the capabilities of the process. Results show that the process is capable of producing defect free I-beams with variations in web depth of 30-50%. A full analysis of the process then indicates the likely failure modes, and identifies a safe operating window. Finally, the implications of these results for producing lightweight beams are discussed. © 2012 Elsevier B.V. All rights reserved.
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The Particle Image Velocimetry (PIV) technique is an image processing tool to obtain instantaneous velocity measurements during an experiment. The basic principle of PIV analysis is to divide the image into small patches and calculate the locations of the individual patches in consecutive images with the help of cross correlation functions. This paper focuses on the application of the PIV analysis in dynamic centrifuge tests on small scale tunnels in loose, dry sand. Digital images were captured during the application of the earthquake loading on tunnel models using a fast digital camera capable of taking digital images at 1000 frames per second at 1 Megapixel resolution. This paper discusses the effectiveness of the existing methods used to conduct PIV analyses on dynamic centrifuge tests. Results indicate that PIV analysis in dynamic testing requires special measures in order to obtain reasonable deformation data. Nevertheless, it was possible to obtain interesting mechanisms regarding the behaviour of the tunnels from PIV analyses. © 2010 Taylor & Francis Group, London.
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This paper reports the design and numerical analysis of a three-dimensional biochip plasma blood separator using computational fluid dynamics techniques. Based on the initial configuration of a two-dimensional (2D) separator, five three-dimensional (3D) microchannel biochip designs are categorically developed through axial and plenary symmetrical expansions. These include the geometric variations of three types of the branch side channels (circular, rectangular, disc) and two types of the main channel (solid and concentric). Ignoring the initial transient behaviour and assuming that steady-state flow has been established, the behaviour of the blood fluid in the devices is algebraically analysed and numerically modelled. The roles of the relevant microchannel mechanisms, i.e. bifurcation, constriction and bending channel, on promoting the separation process are analysed based on modelling results. The differences among the different 3D implementations are compared and discussed. The advantages of 3D over 2D separator in increasing separation volume and effectively depleting cell-free layer fluid from the whole cross section circumference are addressed and illustrated. © 2011 John Wiley & Sons, Ltd.
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This paper presents an analytical modeling technique for the simulation of long-range ultrasonic guided waves in structures. The model may be used to predict the displacement field in a prismatic structure arising from any excitation arrangement and may therefore be used as a tool to design new inspection systems. It is computationally efficient and relatively simple to implement, yet gives accuracy similar to finite element analysis and semi-analytical finite element analysis methods. The model has many potential applications; one example is the optimization of part-circumferential arrays where access to the full circumference of the pipe is restricted. The model has been successfully validated by comparison with finite element solutions. Experimental validation has also been carried out using an array of piezoelectric transducer elements to measure the displacement field arising from a single transducer element in an 88.9-mm-diameter pipe. Good agreement has been obtained between the two models and the experimental data.
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An existing hybrid finite element (FE)/statistical energy analysis (SEA) approach to the analysis of the mid- and high frequency vibrations of a complex built-up system is extended here to a wider class of uncertainty modeling. In the original approach, the constituent parts of the system are considered to be either deterministic, and modeled using FE, or highly random, and modeled using SEA. A non-parametric model of randomness is employed in the SEA components, based on diffuse wave theory and the Gaussian Orthogonal Ensemble (GOE), and this enables the mean and variance of second order quantities such as vibrational energy and response cross-spectra to be predicted. In the present work the assumption that the FE components are deterministic is relaxed by the introduction of a parametric model of uncertainty in these components. The parametric uncertainty may be modeled either probabilistically, or by using a non-probabilistic approach such as interval analysis, and it is shown how these descriptions can be combined with the non-parametric uncertainty in the SEA subsystems to yield an overall assessment of the performance of the system. The method is illustrated by application to an example built-up plate system which has random properties, and benchmark comparisons are made with full Monte Carlo simulations. © 2012 Elsevier Ltd. All rights reserved.
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BGCore reactor analysis system was recently developed at Ben-Gurion University for calculating in-core fuel composition and spent fuel emissions following discharge. It couples the Monte Carlo transport code MCNP with an independently developed burnup and decay module SARAF. Most of the existing MCNP based depletion codes (e.g. MOCUP, Monteburns, MCODE) tally directly the one-group fluxes and reaction rates in order to prepare one-group cross sections necessary for the fuel depletion analysis. BGCore, on the other hand, uses a multi-group (MG) approach for generation of one group cross-sections. This coupling approach significantly reduces the code execution time without compromising the accuracy of the results. Substantial reduction in the BGCore code execution time allows consideration of problems with much higher degree of complexity, such as introduction of thermal hydraulic (TH) feedback into the calculation scheme. Recently, a simplified TH feedback module, THERMO, was developed and integrated into the BGCore system. To demonstrate the capabilities of the upgraded BGCore system, a coupled neutronic TH analysis of a full PWR core was performed. The BGCore results were compared with those of the state of the art 3D deterministic nodal diffusion code DYN3D (Grundmann et al.; 2000). Very good agreement in major core operational parameters including k-eff eigenvalue, axial and radial power profiles, and temperature distributions between the BGCore and DYN3D results was observed. This agreement confirms the consistency of the implementation of the TH feedback module. Although the upgraded BGCore system is capable of performing both, depletion and TH analyses, the calculations in this study were performed for the beginning of cycle state with pre-generated fuel compositions. © 2011 Published by Elsevier B.V.
Resumo:
Coupled Monte Carlo depletion systems provide a versatile and an accurate tool for analyzing advanced thermal and fast reactor designs for a variety of fuel compositions and geometries. The main drawback of Monte Carlo-based systems is a long calculation time imposing significant restrictions on the complexity and amount of design-oriented calculations. This paper presents an alternative approach to interfacing the Monte Carlo and depletion modules aimed at addressing this problem. The main idea is to calculate the one-group cross sections for all relevant isotopes required by the depletion module in a separate module external to Monte Carlo calculations. Thus, the Monte Carlo module will produce the criticality and neutron spectrum only, without tallying of the individual isotope reaction rates. The onegroup cross section for all isotopes will be generated in a separate module by collapsing a universal multigroup (MG) cross-section library using the Monte Carlo calculated flux. Here, the term "universal" means that a single MG cross-section set will be applicable for all reactor systems and is independent of reactor characteristics such as a neutron spectrum; fuel composition; and fuel cell, assembly, and core geometries. This approach was originally proposed by Haeck et al. and implemented in the ALEPH code. Implementation of the proposed approach to Monte Carlo burnup interfacing was carried out through the BGCORE system. One-group cross sections generated by the BGCORE system were compared with those tallied directly by the MCNP code. Analysis of this comparison was carried out and led to the conclusion that in order to achieve the accuracy required for a reliable core and fuel cycle analysis, accounting for the background cross section (σ0) in the unresolved resonance energy region is essential. An extension of the one-group cross-section generation model was implemented and tested by tabulating and interpolating by a simplified σ0 model. A significant improvement of the one-group cross-section accuracy was demonstrated.
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High conversion LWRs concepts typically rely on a heterogeneous core configuration, where fissile zones are interspersed with fertile blanket zones in order to achieve a high conversion ratio. Modeling such a heterogeneous structure of these cores represents a significant challenge to the conventional reactor analysis methods. It was recently suggested to overcome such difficulties, in particular, for the case of axially heterogeneous reduced moderation BWRs, by introducing an additional set of discontinuity factors in axial direction at the interfaces between fissile and fertile fuel assembly zones. However, none of the existing nodal diffusion core simulators have the capability of accounting for discontinuity of homogeneous nodal fluxes in axial direction since the fuel composition of conventional LWRs is much more axially uniform. In this work, we modified the nodal diffusion code DYN3D by introducing such a capability. The new version of the code was tested on a series of reduced moderation BWR cases with Th-U233 and U-Pu-MA fuel. The library of few-group homogenized cross sections and the data required for the calculation of discontinuity factors were generated using the Monte Carlo transport code Serpent. The results obtained with the modified version of DYN3D were compared with the reference Monte Carlo solutions and were found to be in good agreement. The current analysis demonstrates that high conversion LWRs can in principle be modeled using existing nodal diffusion core simulators. © 2013 Elsevier Ltd. All rights reserved.
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A novel gene-K23, differentially expressed in cross-subfamily cloned embryos, was isolated by RACE-PCR technique. It had 2580 base pairs (bp) in length, with a 1,425 bp open reading frame (ORF) encoding a putative protein of 474 amino acids (aa). Bioinformatic analysis indicated that K23 had 22 phosphorylation sites, but it had no signal peptides. Developmental expression analysis in zebrafish showed that K23 transcripts were maternally expressed in ovum and the amount of K23 transcripts increased gradually from zygote to pharyngula period. Subcellular localization analysis revealed that K23 protein was homogeneously distributed both in nuclei and cytoplasm. Taken together, our findings indicate that K23 gene is a novel gene differentially expressed in fish cross-subfamily cloned embryos.
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m Background: Cross-species nuclear transfer has been shown to be a potent approach to retain the genetic viability of a certain species near extinction. However, most embryos produced by cross-species nuclear transfer were compromised because that they were unable to develop to later stages. Gene expression analysis of cross-species cloned embryos will yield new insights into the regulatory mechanisms involved in cross-species nuclear transfer and embryonic development. Results: A novel gene, K31, was identified as an up-regulated gene in fish cross-subfamily cloned embryos using SSH approach and RACE method. K31 complete cDNA sequence is 1106 base pairs (bp) in length, with a 342 bp open reading frame (ORF) encoding a putative protein of 113 amino acids (aa). Comparative analysis revealed no homologous known gene in zebrafish and other species database. K31 protein contains a putative transmembrane helix and five putative phosphorylation sites but without a signal peptide. Expression pattern analysis by real time RT-PCR and whole-mount in situ hybridization (WISH) shows that it has the characteristics of constitutively expressed gene. Sub-cellular localization assay shows that K31 protein can not penetrate the nuclei. Interestingly, over-expression of K31 gene can cause lethality in the epithelioma papulosum cyprinid (EPC) cells in cell culture, which gave hint to the inefficient reprogramming events occurred in cloned embryos. Conclusion: Taken together, our findings indicated that K31 gene is a novel gene differentially expressed in fish cross-subfamily cloned embryos and over-expression of K31 gene can cause lethality of cultured fish cells. To our knowledge, this is the first report on the determination of novel genes involved in nucleo-cytoplasmic interaction of fish cross-subfamily cloned embryos.
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Cross-species nuclear transfer (NT) has been used to retain the genetic viability of a species near extinction. However, unlike intra-species NT, most embryos produced by cross-species NT were unable to develop to later stages due to incompatible nucleocytoplasmic interactions between the donor nuclei and the recipient cytoplasm from different species. To study the early nucleocytoplasmic interaction in cross-species NT, two laboratory fish species (zebrafish and rare minnow) from different subfamilies were used to generate cross-subfamily NT embryos in the present study. Suppression subtractive hybridization (SSH) was performed to screen out differentially expressed genes from the forward and reverse subtractive cDNA libraries. After dot blot and real-time PCR analysis, 80 of 500 randomly selective sequences were proven to be differentially expressed in the cloned embryos. Among them, 45 sequences shared high homology with 28 zebrafish known genes, and 35 sequences were corresponding to 22 novel expressed sequence tags (ESTs). Based on functional clustering and literature mining analysis, up-and down-regulated genes in the cross-subfamily cloned embryos were mostly relevant to transcription and translation initiation, cell cycle regulation, protein binding, etc. To our knowledge, this is the first report on the determination of genes involved in the early development of cross-species NT embryos of fish. (C) 2007 Elsevier Inc. All rights reserved.
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Microcystin analysis in sediments and soils is considered very difficult due to low recovery for extraction. This is the primary limiting factor for understanding the fate of toxins in the interface between water and sediment in both the aquatic ecosystem as well as in soils. In the present study, a wide range of extraction solvents were evaluated over a wide range of pH, extraction approaches and equilibration time to optimize an effective extraction procedure for the analysis of microcystins in soils and lake sediments. The number of extractions required and acids in extraction solutions were also studied. In this procedure, EDTA-sodium pyrophosphate solution was selected as an extraction solvent based on the adsorption mechanism study. The optimized procedure proved to be highly efficient and achieved over 90% recovery. Finally, the developed procedure was applied to field soil and sediment sample collected from Chinese lakes during bloom seasons and microcystins were determined in six of ten samples. (c) 2005 Elsevier Ltd. All rights reserved.
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An n-InP-based InGaAsP multiple-quantum-well wafer was bonded with p-Si by chemical surface activated bonding at 70 degrees C, and then annealed at 450 degrees C. Different thermal expansion coefficients between InP and Si will induce thermal stresses in the bonded wafer. Planar and cross-sectional distributions of thermal stress in the bonded InP-Si pairs were analyzed by a two-dimensional finite element method. In addition, the normal, peeling, and shear stresses were calculated by an analytic method. Furthermore, x-ray double crystalline diffraction was applied to measure the thermal strain and the strain caused by the mismatching of the crystalline orientation between InP (100) and Si (100). The wavelength redshift of the photoluminescence (PL) spectrum due to thermal strain was investigated via the calculation of the band structure, which is in agreement with the measured PL spectra.