538 research outputs found
Treatment of Subject Descriptors on Children in Twenty Three DDC Editions
Full text linkThe study explores the treatment of subject descriptors on children and its correlated subjects in the 23 DDC editions by adopting an assessment and evaluation study. Authors found that the Home and family management (640) class holds the maximum subject descriptors on children
A new balloon dissector for totally extraperitoeneal hernia repair
No full textBackground: Balloon dissectors (BD) find their use in totally extraperitoneal (TEP) and retroperitoneoscopic procedures. Commercial BD is prohibitively expensive. The author uses an indigenously assembled BD and describes the same. Material and Methods: The author assembles the BD by tying glove-fingers on an NG tube and then tying this assembly in the concavity of a Kelly′s clamp, premounted with peanut gauze (KC-BD). Results: The author has used it in the last 75 cases of TEP. A large working space is created, without any iatrogenic injuries or balloon rupture. This cheap indigenous BD can be assembled easily and in no time at all. Conclusions: KC-BD offers several advantages because of its unique design. It is effective, totally nontraumatic, inexpensive, and easy to assemble
Techniques for the performance analysis of queueing networks
No full textETDs are only available to UIUC Users without author permissionU of I OnlyAnalyzing the performance of queueing networks that do not admit a product form solution is a challenging problem. In this thesis we present some tools for doing so. Our attention is restricted to Markovian queueing networks.We first present a technique for bounding the performance of such networks. Assuming a steady state for functionals of the state, we obtain linear programs which bound the performance. This technique is illustrated using quadratic functionals to bound the performance of a class of Markovian queueing networks called reentrant lines. We also show how this technique may be applied to bound throughput and blocking probabilities in networks with buffer capacity constraints. In some cases bounds obtained using multimedial functional of the state are shown to approach the exact value when the degree of the multimedial increases.We also study another important technique for the analysis of queueing networks, namely, the fluid limit approach. This approach is used to establish the stability of a class of policies called Fluctuation Smoothing policies for open reentrant lines. We also show how the fluid limit approach can be used to obtain the asymptotic performance of closed queueing networks in heavy traffic. We then use fluid limits to establish the efficiency of Fluctuation Smoothing policies for closed reentrant lines, as well as the Harrison-Wein policy for two station closed reentrant lines.Made available in DSpace on 2011-05-07T14:22:46Z (GMT). No. of bitstreams: 2
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Efficient uniformly convergent numerical methods for singularly perturbed parabolic reaction–diffusion systems with discontinuous source term
No full textFinanciación de acceso abierto proporcionada por los Fondos Europeos FEDER y la Junta de Castilla y León en el marco de la Estrategia de Investigación e Innovación para la Especialización Inteligente (RIS3) de Castilla y León 2021-2027[EN] This article is concerned with the construction and analysis of efficient uniformly convergent methods for a class of parabolic systems of coupled singularly perturbed reaction–diffusion problems with discontinuous source term. Due to the discontinuity in the source term, the solution to this problem exhibits interior layers along with boundary layers, which are overlapping and interacting in nature. To achieve an efficient numerical solution for the coupled system under consideration, at interior points (excluding the interface point) we employ a special finite difference scheme in time (where the components of the approximate solution are decoupled at each time level) and the central difference scheme in space; for mesh points on the interface, a special finite difference scheme decoupling the components of the approximate solution is developed. A rigorous error analysis is provided, establishing the method’s uniform convergence. In terms of computational cost, our numerical methods are more efficient than existing approaches for solving this class of problems. Finally, we provide numerical results to substantiate the theory and showcase the efficiency of our methods.The first author expresses gratitude to the Indian Institute of Technology (BHU) for
the assistance provided during the work tenure. Sunil Kumar extends thanks to the Science and Engineering
Research Board (SERB) for awarding the research support grant CRG/2023/003228 for this work
Two approaches to the hierarchical solution of constraint satisfaction problems
No full textConstraint Satisfaction Problems (CSPs) involve assigning values to a finite set of variables from their finite domains such that a finite set of constraints is satisfied. Graph coloring, Scheduling and Time-table design are some of the commonly occurring CSPs. All general solution procedures for CSPs are based upon a combinatorial enumeration of variable bindings, with the addition of clever devices to reduce the number of nodes explored in the corresponding search tree. CSPs, however, are NP-hard, and general-purpose search algorithms are slow. This research explores the application of problem decomposition to construct faster CSP solvers
Previous applications of Problem Decomposition to CSPs have been based upon the representation of a CSP as a Constraint Graph, where nodes represent variables, and arcs represent constraints. A tree-shaped constraint graph, after some preprocessing on the nodes, can be solved without backtrack (Freuder, 82). Researchers have proposed different methods for reducing a constraint graph into a tree of node-clusters, with the cost of solution dependent on the size of the largest such cluster.
Tree-clustering based methods of decomposition fail on CSPs with global constraints, where any cluster including the global constraint has to include all the problem's variables. This thesis proposes reducing redundant constraint-checks as an alternative motivation for problem decomposition in CSPs. The decomposition algorithms developed here are applicable to CSPs unrestricted on constraint arity.
There are three major components to this research. The first is the development of a framework, named bottom-up solution, for solving a CSP through its decomposition. It is aimed at handling decompositions that do not completely partition a problem into independent components. The framework allows for the efficient handling of problem components dependent upon other subproblems. The bottom-up solution framework has been implemented on top of the basic Backtrack and Forward-Check search algorithms.
The thesis then introduces two problem decomposition algorithms aimed directly at reducing redundant constraint checks. The main insight here is that redundant constraint tests are caused by artificial dependencies of constraints on non-argument variables, set up by the serial nature of combinatorial enumeration used as the basis for search algorithms. The decomposition algorithms seek to reduce artificial dependencies in a problem, and the resulting decompositions can be solved in the bottom-up solution framework.
The third component of this thesis focuses on global and high-arity constraints. The complexity of a class of problems with a particular constraint topology is defined by the highest arity of its constraint set. This is reflected in the inability of search algorithms to take advantage of global constraints to reduce the size of the explored search space. This thesis proposes a procedure for the syntactic decomposition of a global constraint in a problem. This decomposition is used to define an abstract problem layer, and a new hierarchical problem which is equivalent to the original problem, and in which the global constraint is replaced with a set of smaller arity constraints.
The problem decomposition techniques are evaluated on random problems and on some sample application domains. In general the decomposition is shown to be more beneficial for problems which, when solved in their original form, exhibit high artificial serial dependencies and produce bushier search trees. Global constraint decomposition is demonstrated on some sample application domains, and shown to significantly reduce search effort.
Constraint satisfaction problems are difficult enough that there do not exist any reliable and effective general purpose problem solving heuristics and evaluation functions. It is therefore significant that the DOI decomposition algorithm proposed in this research is guaranteed never to make the problem harder to solve.
The primary contribution of this research is in the form of new problem solving methods for general constraint satisfaction problems which significantly improve performance, particularly for harder problems. It also extends the current understanding of what makes constraint satisfaction problems difficult to solve and where search algorithms spend their effort. On the more general side, this thesis promotes a deeper understanding of the application and benefits of problem decomposition as a problem solving strategy.Technical report LCSR-TR-25
Techno-Economic Analysis of 2,3-Butanediol Production from Sugarcane Bagasse
Full text linkSugarcane bagasse (SCB) is a significant agricultural residue generated by sugar mills based on sugarcane crop. Valorizing carbohydrate-rich SCB provides an opportunity to improve the profitability of sugar mills with simultaneous production of value-added chemicals, such as 2,3-butanediol (BDO). BDO is a prospective platform chemical with multitude of applications and huge derivative potential. This work presents the techno-economic and profitability analysis for fermentative production of BDO utilizing 96 MT of SCB per day. The study considers plant operation in five scenarios representing the biorefinery annexed to a sugar mill, centralized and decentralized units, and conversion of only xylose or total carbohydrates of SCB. Based on the analysis, the net unit production cost of BDO in the different scenarios ranged from 1.13 to 2.28 US/kg. Use of the hemicellulose fraction alone was shown to result in an economically viable plant; however, this was dependent on the condition that the plant would be annexed to a sugar mill which could supply utilities and the feedstock free of cost. A standalone facility where the feedstock and utilities were procured was predicted to be economically feasible with a net present value of about 72 million US$, when both hemicellulose and cellulose fractions of SCB were utilized for BDO production. Sensitivity analysis was also conducted to highlight some key parameters affecting plant economics
Life Cycle Assessment of Microbial 2,3-Butanediol Production from Brewer’s Spent Grain Modeled on Pinch Technology
Full text linkMicrobial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer’s spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO2/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production
Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology
Full text linkLactic acid (LA) is a vital platform chemical with diverse applications, especially for biodegradable polylactic acid. Bread waste (BW) is sugar-rich waste biomass generated in large quantities in residential and commercial operations. Recently, we evaluated the potential of BW for LA production by Bacillus coagulans under non-sterile conditions. This work presents a techno-economic and profitability analysis for valorizing 100 metric tons of BW per day to alleviate environmental pollution with concurrent production of LA and biomethane. We compared two fermentation approaches: acid-neutral (Scenario I) and low pH (Scenario II). Traditional esterification with methanol, followed by hydrolysis of methyl lactate, was employed for downstream separation to obtain polymer-grade LA. High-pressure steam was generated from solid debris via anaerobic digestion to complement energy demands partly. Energy consumption was further attenuated by process integration using pinch technology, with around 15% and 11% utility cost savings for Scenario I and II, respectively. These processes were capital-intensive, with 42-46% of LA production cost stemming from direct and indirect costs. Utilities were the major cost-contributing factor (19-21%) due to energy-intensive water evaporation from dilute fermentation broth. Due to additional processing steps, capital investment and operating costs were slightly higher in Scenario I than in Scenario II. LA manufacturing cost was thus more for Scenario I (1.82 per kg). The minimum LA selling price for Scenario I and II were 3.22 per kg, respectively, with five-year payback periods and 8.5% internal rates of return. LA was slightly more expensive for decentralized BW processing than the market price
Pattern of Cancer in Nepal from 2003 to 2011
Full text linkCorrection: On 15th January 2017, the authors Sunil Kumar Sah and Naval Kishor Yadav were added to the author list.Cancer is global burden of disease in developed and developing countries. It is one of the main causes of death. The environmental factor and life styles are major causes of cancer.This hospital based retrospective study was carried out using data retrieved from the register maintained at seven cancer centers. The most common basis of diagnosis were microscopic (histopathological and cytopathological examination). The diagnosis was also based on clinical examination, radiological examination, endoscopy, biochemical and immunological tests.Most of the cancer cases were diagnosed at BPKMCH (23908) followed by BPKIHS (9668) and BH (5959) and few cases from KCH (518) in 2003 to 2011. The total number of cancer cases were increasing from 2003 to 2011 and it become double in 2011. Out of 75 district of Nepal, more number of cancer cases was found in Kathmandu, Sunsari, Morang, Chitwan, Lalitpur, Jhapa, Kaski, Nawalparasi, Rupendehi and Kavrepalchowk in 2010. Similarly, in 2011 more number of cancer cases was found in Kathmandu, Morang, Jhapa, Sunsari, Chitwan, Lalitpur, Rupendehi, Kaski, Saptari, Bhaktapur. Lung cancer was the common cancer and similarly, other prevalent cancers were cervical, breast, stomach, ovarian and colo-rectum cancer in 2003 to 2011. The common cancers were lung, cervical, breast, stomach, ovarian and colo-rectum. The number of patients is increasing, which may be due to change in life style and lack of education
Hydrodeoxygenation of Stearic Acid Over Supported Metal Catalysts for the Production of Green Diesel
No full textThe renewable energies have been attracted considerable attention throughout the world due to the rapid depletion of fossil fuels and the continuous degradation of the environment by greenhouse gases. The transportation fuels are the leading energyconsuming sector - accounting for about 28% of global energy. Biomass is the promising carbon-neutral renewable energy source in the globe. It also has tremendous potentials to provide renewable transportation fuels commonly known as bio-fuels. The bioethanol and biodiesel are the promising bio-fuels at the moment. The poor fuel properties of these bio-fuels, however, limit their application for blending with petrol and diesel, respectively, up to 15-20% only in the unmodified combustion engine. Therefore, there is a need for the production of hydrocarbon analogous bio-fuels from biomass commonly known as hydrocarbon bio-fuel. Triglycerides are the promising feedstock for the production of hydrocarbon biofuels because of their lower oxygen content and long carbon chain length compared to cellulosic and starchy biomass. Besides, the triglycerides are composed of C8-C24 fatty acids with the majority of C16 and C18 fatty acids. Therefore, the removal of oxygen from triglycerides results in the formation of diesel-range hydrocarbon biofuel generally known as green diesel. The hydrodeoxygenation (HDO) is the promising technology for the removal of oxygen from triglycerides and fatty acids. This technology produces green diesel with high yield and minimal carbon loss. The HDO is a catalytic process and carried out in the presence of hydrogen over supported metal catalysts. The catalysts thus play a vital role in this process. The present work is thus focused on HDO of stearic acid as a model fatty acid over alumina-supported transition metal (Ni, Co, NiMo, and CoMo) catalysts. In the present work, Ni, NiMo, Co, and CoMo catalysts were prepared by incipient wetness impregnation and co-impregnation method. The catalysts were characterized by BET, temperature programmed reduction (TPR), temperature programmed desorption of NH3 (NH3-TPD), pulse chemisorption, powder XRD, and Raman and UV-vis-NIR spectroscopy to identify the catalytically active different surface species. HDO of stearic acid was conducted in a high-pressure batch reactor using n-dodecane as a solvent. The products of the liquid sample were identified by GC-MS and quantified by GC-FID. The gaseous products were quantified by GCTCD. In this work, C15-C18 alkanes, octadecanol (C18-OH), and octadecanal (C17- CHO) were observed as the products during HDO of stearic acid. In this reaction, the stearic acid first reduces to C18-OH in the presence of hydrogen over supported metal catalysts. The C18-OH then undergoes further chemical transformation following two different pathways. In the first pathway, C18- OH undertakes dehydrogenation followed by decarbonylation reaction (elimination of CO) to form C17 alkane (decarbonylation pathway). This reaction pathway was dominant over the alumina-supported Ni catalyst. In the second pathway, C18-OH undergoes dehydration followed by hydrogenation reaction to form C18 alkane (HDO pathway). This reaction pathway was dominant over HZSM-5 supported Ni and alumina-supported NiMo and CoMo catalysts. Both the reaction pathway was, however, significant over the alumina-supported Co catalyst. A suitable kinetic model was further established based on the reaction mechanism for aluminasupported Ni, NiMo, and CoMo catalyst. The calcination temperature plays a vital role in the performance of supported metal catalysts. HDO of stearic acid was investigated over alumina-supported Ni, NiMo, Co, and CoMo catalysts at different calcination temperatures to understand the role of calcination temperature on the catalytic performance of these catalysts. With increasing calcination temperature, the metal dispersion was increased for Ni, NiMo, and CoMo catalyst (up to 973 K) and decreased for Co catalyst. With increasing calcination temperature, the catalytic activity was thus increased for Ni and NiMo catalyst and decreased for Co catalyst. The activity of CoMo catalyst was, however, enhanced with rising calcination temperature up to 973 K and declined slightly after that. The optimum calcination temperature for Ni, NiMo, Co, and CoMo catalyst was found to be 1023 K, 973 K, 773 K, and 973 K. The reaction followed the decarbonylation route over active metallic centers (Ni and Co) and the HDO route over oxophilic M2+.MoO2 (M=Ni/Co) and reducible cobalt oxide species. HDO of stearic acid was also investigated over SiO2, -Al2O3, and HZSM-5 supported Ni catalysts. Characterization studies revealed that only dispersed NiO was present up to 3.4 mmol Ni loading on -Al2O3. The acidity of calcined catalysts was increased with increasing Ni loading up to 3.4 mmol. The catalytic activity and selectivity to products for HDO of stearic acid depend strongly on the acidity of the supports. The conversion of stearic acid was decreased in the order of 2.2NiZSM>2.2NiAl~2.2NiSi. The 2.2NiZSM-5 showed about 85% conversion of stearic acid compared to only ~41% for 2.2NiAl and 2.2NiSi at 360 min of reaction time. The conversion of stearic acid was increased with increasing reaction time, Ni loading on -Al2O3, temperature, and catalyst loading. The complete conversion of stearic acid was accomplished with more than 80% selectivity to C17 alkane at 563 K over 3.4 mmol Ni/-Al2O3 catalyst. HDO of stearic acid was further studied to depicts the role of Ni/Mo mole ratio in the performance of alumina-supported NiMo catalysts. Both Ni and NiMo alloy co-exist in the NiMo catalysts depending on the Ni and Mo content. With increasing Ni/Mo mole ratio, the NiMo alloy content in the catalyst was increased with the simultaneous decrease in the Ni content. The activity of NiMo catalysts was thus enhanced with increasing Ni/Mo mole ratio. C17 and C18 alkanes are thus observed as the dominating hydrocarbon product over Ni and NiMo alloy-rich catalysts, respectively. The activity of the NiMo catalyst was further enhanced with the increasing reaction temperature and metals loading. The selectivity to alkanes was, however, not affected by metal loading. HDO of stearic acid was also extended to ascertain the role of Co/Mo mole ratio on the catalytic performance of alumina-supported CoMo catalysts. The calcined CoMo catalysts showed the presence of Mo, Co, and mixed metal oxides depending on the relative metal content. The reduced CoMo catalysts were gradually enriched with CoMo alloy with increasing Co content up to 2.4 mmol and slightly decreased for 3.1 mmol Co. The catalytic activity of CoMo catalysts was thus enhanced with increasing Co content. The reaction follows the HDO mechanism over CoMo alloy and reducible Co oxide species. The selectivity to C18 alkane was enhanced with increasing Co content up to 2.4 mmol due to the enrichment of CoMo alloy in the catalyst. The catalytic activity of CoMo catalysts was further enhanced with increasing reaction temperature and metals loading without affecting the selectivity to alkanes much
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