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Showing records 1 to 25 of 1594. [First] Page: 1 2 3 4 5 Last
Highly Selective Syngas/H2 Production via Partial Oxidation of CH4 Using (Ni, Co and Ni−Co)/ZrO2−Al2O3 Catalysts: Influence of Calcination Temperature
Anis Hamza Fakeeha, Yasir Arafat, Ahmed Aidid Ibrahim, Hamid Shaikh, Hanan Atia, Ahmed Elhag Abasaeed, Udo Armbruster, Ahmed Sadeq Al-Fatesh
July 17, 2019 (v1)
Keywords: Al2O3, bimetallic catalyst, methane, partial oxidation, Syngas, ZrO2
In this study, Ni, Co and Ni−Co catalysts supported on binary oxide ZrO2−Al2O3 were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic system was then tested for syngas respective H2 production via partial oxidation of methane at 700 °C and 800 °C. The influence of calcination temperatures was studied and their impact on catalytic activity and stability was evaluated. It was observed that increasing the calcination temperature from 550 °C to 800 °C and addition of ZrO2 to Al2O3 enhances Ni metal-support interaction. This increases the catalytic activity and sintering resistance. Furthermore, ZrO2 provides higher oxygen storage capacity and stronger Lewis basicity which contributed to coke suppression, eventually leading to a more stable catalyst. It was also observed that, contrary to bimetallic catalysts, monometallic catalysts exhibit higher activity with higher calcination temperatur... [more]
On the Use of Starch in Emulsion Polymerizations
Shidan Cummings, Yujie Zhang, Niels Smeets, Michael Cunningham, Marc A. Dubé
July 17, 2019 (v1)
Keywords: emulsion, graft, polymerization, polysaccharide, Starch
The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is a water-based process. It can be made even more attractive as a green alternative with the addition of starch, a renewable material that has proven to be extremely useful as a filler, stabilizer, property modifier and macromer. This work provides a critical review of attempts to modify and incorporate various types of starch in emulsion polymerizations. This review focusses on the method of initiation, grafting mechanisms, starch feeding strategies and the characterization methods. It provides a needed guide for those looking to modify starch in an emulsion polymerization to achieve a target grafting performance or to incorporate starch in latex formulations for the replacem... [more]
Air-Core-Liquid-Ring (ACLR) Atomization: Influences of Gas Pressure and Atomizer Scale Up on Atomization Efficiency
Marc O. Wittner, Heike P. Karbstein, Volker Gaukel
July 17, 2019 (v1)
Subject: Other
Keywords: ACLR, efficiency, high viscous feeds, pneumatic atomization, scale up
Air-core-liquid-ring (ACLR) atomizers present a specific type of internal mixing pneumatic atomizers, which can be used for efficient atomization of high viscous liquids. Generally, atomization efficiency is considered as a correlation between energy input and resulting droplet size. In pneumatic atomization, air-to-liquid ratio by mass (ALR) is commonly used as reference parameter of energy input. However, the pressure energy of the atomization gas is not considered in the calculation of ALR. In internal mixing ACLR atomizers, it can be assumed that this energy contributes to liquid disintegration by expansion of the gas core after exiting the atomizer. This leads to the hypothesis that droplet sizes decrease with increasing gas pressure at constant ALR. Therefore, the use of volumetric energy density (EV) as a reference parameter of energy input was investigated at different gas pressures between 0.4 and 0.8 MPa. Furthermore, scale up-related influences on the atomization efficiency... [more]
The Flotation Process Can Go Green
George Z. Kyzas, Kostas A. Matis
July 17, 2019 (v1)
Keywords: adsorptive floatation, biosurfactants, floatation, green approach, wastewater treatment
In today’s world of environmental strain, wastewater treatment has become a, more or less, conventional application of flotation—as for instance, in the oil, food, or chemical industries, and in potable water treatment. In this paper, different flotation methods (such as ion, adsorbing colloid, and adsorptive flotation, including biosorption) and techniques will be reviewed; and, in order to explain them further, several applications of these from the laboratory (General and Inorganic Chemical Technology) at Aristotle University of Thessaloniki, Greece (AUTh) will be presented and analyzed, with the main focus on sustainability. The application of flotation as a separation process, when applied in pollution control or during water treatment, was often criticized due to the possible toxicity of the applied collectors; however, the use of biosurfactants may alleviate this concern and enhance its further acceptability.
Study on Mass Transfer Kinetics of Sugar Extraction from Sweet Sorghum Biomass via Diffusion Process and Ethanol Yield Using SSF
Nana Baah Appiah-Nkansah, Jun Li, Ke Zhang, Meng Zhang, Donghai Wang
July 17, 2019 (v1)
Subject: Biosystems
Keywords: bioethanol, diffusion, ethanol fermentation, kinetic model, mass transfer, sweet sorghum juice
Sweet sorghum juice, a potential bioethanol feedstock, can be incorporated into the dry-grind ethanol process to improve sugar utilization efficiency, thereby enhancing ethanol yields. The juice is normally obtained by pressing the stalk through roller mills in tandem. Juice extraction by this process is known to be labor intensive, less efficient, and susceptible to considerable fermentable sugar loss due to microbial activities when stored at room temperature. Sweet sorghum juice extraction via diffusion has recently been proposed to improve sugar recovery efficiency. In this study, extraction kinetics based on the optimized diffusion parameters (8% grain loading, 85 °C, and 120 min) were determined to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Diffusion parameters obtained from previous studies were used to extract free sugars and convert them into ethanol using granular starch hydrolyzing enzymes (GSHE) and traditional enzymes. Ethan... [more]
An Experimental Approach on Industrial Pd-Ag Supported α-Al2O3 Catalyst Used in Acetylene Hydrogenation Process: Mechanism, Kinetic and Catalyst Decay
Ourmazd Dehghani, Mohammad Reza Rahimpour, Alireza Shariati
July 17, 2019 (v1)
Keywords: acetylene hydrogenation, catalyst decay, kinetic model, process modeling
The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al2O3 catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET (Brunauer−Emmett−Teller), SEM, TEM, and DTG analyses. The XRD results show that the dispersed palladium particles on the support surface experience an agglomeration during the reaction run time and mean particle size approaches from 6.2 nm to 11.5 nm. In the second step, the performance of Pd-Ag supported α-Al2O3 catalyst is investigated in a differential reactor in a wide range of hydrogen to acetylene ratio, temperature, gas hourly space velocity and pressure. The full factorial design method is used to determine the experiments. Based on the experimental results ethylene, ethane, butene, and 1,3-butadiene are produced through the acetylene hydrogenation. In the third step, a detailed reaction network is pr... [more]
Measurement and Correlation of the Solubility of β-Cyclodextrin in Different Solutions at Different Temperatures and Thermodynamic Study of the Dissolution Process
Shanshan Jin, Xuewei Cui, Yingping Qi, Yongfeng Shen, Hua Li
July 11, 2019 (v1)
Subject: Other
Keywords: Apelblat equation, simplified Apelblat equation, solubility, β-Cyclodextrin, λh equation
A new improved formulation was studied to improve the rehydration properties of freeze-dried dumplings. To provide basic data for industrial applications, the solubility capabilities of β-Cyclodextrin in sucrose, NaCl, and a mixed solution were measured at temperatures ranging from 303.15 to 353.15 K using a laser monitoring method. The experimental values indicated that the solubility of β-Cyclodextrin in solvents increased with increasing temperature. The simplified Apelblat model, Apelblat model, and λh model were employed to analyze the experimental results using correlation tests. The relative average deviation (RAD) values between the experimental and calculated values were less than 0.095, 0.075, and 0.103 for the simplified Apelblat equation, Apelblat equation, and λh equation, respectively. Apparent thermodynamic analysis of β-Cyclodextrin dissolution was also performed at the mean temperature using the model parameters of Apelblat equation. Furthermore, thermodynamic properti... [more]
Computational Fluid Dynamics (CFD) Simulations and Experimental Measurements in an Inductively-Coupled Plasma Generator Operating at Atmospheric Pressure: Performance Analysis and Parametric Study
Sangeeta B. Punjabi, Dilip N. Barve, Narendra K. Joshi, Asoka K. Das, Dushyant C. Kothari, Arijit A. Ganguli, Sunil N. Sahasrabhude, Jyeshtharaj B. Joshi
July 11, 2019 (v1)
Keywords: Energy, impedance, inductively-coupled plasma, plasma
In this article, electrical characteristics of a high-power inductively-coupled plasma (ICP) torch operating at 3 MHz are determined by direct measurement of radio-frequency (RF) current and voltage together with energy balance in the system. The variation of impedance with two parameters, namely the input power and the sheath gas flow rate for a 50 kW ICP is studied. The ICP torch system is operated at near atmospheric pressure with argon as plasma gas. It is observed that the plasma resistance increases with an increase in the RF-power. Further, the torch inductance decreases with an increase in the RF-power. In addition, plasma resistance and torch inductance decrease with an increase in the sheath gas flow rate. The oscillator efficiency of the ICP system ranges from 40% to 80% with the variation of the Direct current (DC) powers. ICP has also been numerically simulated using Computational Fluid Dynamics (CFD) to predict the impedance profile. A good agreement was found between the... [more]
Simulating Stochastic Populations. Direct Averaging Methods
Vu Tran, Doraiswami Ramkrishna
July 11, 2019 (v1)
Keywords: direct averaging, drug resistance, stochastic simulation, transfer
A method of directly computing the average behavior of stochastic populations is established, which obviates the time-consuming process of generating detailed sample paths. The method relies on suitably discretized time intervals in which nonlinearities are quasi-linearized to produce random variables with known expectations and variances. The pair of equations is directly solved to obtain the average behavior of the system at the end of a time interval based on its knowledge at the beginning of the interval. The sample path requirement for this process is considerably lower than that for the process over the entire simulation period. The efficiency of the method is demonstrated on the transfer of antibiotics resistance between two bacterial species which is a problem of mounting concern in fighting disease.
A Glucose-Dependent Pharmacokinetic/ Pharmacodynamic Model of ACE Inhibition in Kidney Cells
Minu R. Pilvankar, Hui Ling Yong, Ashlee N. Ford Versypt
July 11, 2019 (v1)
Subject: Biosystems
Keywords: benazepril, diabetic kidney disease, diabetic nephropathy, PK/PD, podocytes, renin-angiotensin system
Diabetic kidney disease (DKD) is a major cause of renal failure. Podocytes are terminally differentiated renal epithelial cells that are key targets of damage due to DKD. Podocytes express a glucose-stimulated local renin-angiotensin system (RAS) that produces angiotensin II (ANG II). Local RAS differs from systemic RAS, which has been studied widely. Hyperglycemia increases the production of ANG II by podocyte cells, leading to podocyte injury. Angiotensin-converting enzyme (ACE) is involved in the production of ANG II, and ACE inhibitors are drugs used to suppress elevated ANG II concentration. As systemic RAS differs from the local RAS in podocytes, ACE inhibitor drugs should act differently in local versus systemic contexts. Experimental and computational studies have considered the pharmacokinetics (PK) and pharmacodynamics (PD) of ACE inhibition of the systemic RAS. Here, a PK/PD model for ACE inhibition is developed for the local RAS in podocytes. The model takes constant or dyn... [more]
Determination of KOSGEB Support Models for Small- and Medium-Scale Enterprises by Means of Data Envelopment Analysis and Multi-Criteria Decision Making Methods
Ali Sevinç, Tamer Eren
July 11, 2019 (v1)
Keywords: AHP, data envelopment analysis, KOSGEB, productivity, SME, TOPSIS
Small- and Medium-Scale Enterprises (SMEs) act as catalysts in the general economy with regard to their added value. Support programs have been designed by the government through the Small and Medium Enterprises Development and Support Administration KOSGEB) and other institutions in order to further the general economic contributions of such enterprises. However, there is no method for using support models according to a productivity and effectiveness principle. This causes serious wastes of both resources and time. In this study, the problem of applying support models to improve the most critical problems of SMEs was discussed. As a place of application, 82 firms registered to the Konya Chamber of Industry were selected for the automotive supplier industry. Firstly, a productivity evaluation of companies was performed by a data envelopment analysis (DEA). Firms were grouped into A, B1, B2, C1, and C2 according to their activity scores. Using an Analytical Hierarchy Process (AHP), the... [more]
High Nitrate and Phosphate Ions Reduction in Modified Low Salinity Fresh Water through Microalgae Cultivation
Ahmad Rozaimee Mustaffa, Ku Halim Ku Hamid, Mohibah Musa, Juferi Idris, Roslina Ramli
July 11, 2019 (v1)
Subject: Biosystems
Keywords: biodiesel, Carbon Dioxide, fresh water, low salinity, nitrate ions, phosphate ions, Spirogyra sp., Tetraspora sp.
The treatment of nitrate and phosphate ions in fresh water such as streams, rivers, lakes, reservoirs, and wetlands through biological treatment has been getting more crucial and popular in recent years. This paper reports the reduction of nitrate and phosphate ions in modified low salinity fresh water via the cultivation of a microalgae strain, e.g., Tetraspora sp. and Spirogyra sp. The low salinity fresh water (9054 to 9992 ppm) was modified with the addition of organic fertiliser (VermiCompost Tea) and used as the cultivation medium to grow microalgae. The microalgae strains were grown under controlled conditions in an indoor laboratory for 14 days. The initial concentrations of nitrate and phosphate ions in the modified fresh water sample were 1.17 mg/L and 0.10 mg/L, respectively. The reduction of nitrate and phosphate ions associated with the effect of cultivation of Tetraspora sp. and Spirogyra sp. in ambient air (0.03% of CO2) and 15% of CO2 was investigated. In ambient air, th... [more]
Mixed Ionic-Electronic Conducting Membranes (MIEC) for Their Application in Membrane Reactors: A Review
Alba Arratibel Plazaola, Aitor Cruellas Labella, Yuliang Liu, Nerea Badiola Porras, David Alfredo Pacheco Tanaka, Martin Van Sint Annaland, Fausto Gallucci
July 11, 2019 (v1)
Subject: Materials
Keywords: fluorite, membrane, membrane reactor, MIEC, oxygen separation, perovskite
Mixed ionic-electronic conducting membranes have seen significant progress over the last 25 years as efficient ways to obtain oxygen separation from air and for their integration in chemical production systems where pure oxygen in small amounts is needed. Perovskite materials are the most employed materials for membrane preparation. However, they have poor phase stability and are prone to poisoning when subjected to CO2 and SO2, which limits their industrial application. To solve this, the so-called dual-phase membranes are attracting greater attention. In this review, recent advances on self-supported and supported oxygen membranes and factors that affect the oxygen permeation and membrane stability are presented. Possible ways for further improvements that can be pursued to increase the oxygen permeation rate are also indicated. Lastly, an overview of the most relevant examples of membrane reactors in which oxygen membranes have been integrated are provided.
Effect of the Freeze-Drying Process on the Physicochemical and Microbiological Properties of Mexican Kefir Grains
Alicia Águeda Conde-Islas, Maribel Jiménez-Fernández, Denis Cantú-Lozano, Galo Rafael Urrea-García, Guadalupe Luna-Solano
July 11, 2019 (v1)
Subject: Biosystems
Keywords: freeze-drying, kefir grains, operating parameters, probiotic, properties
The purpose of this study was to investigate how the properties of Mexican kefir grains (MKG) are affected by the operating parameters used in the freeze-drying process. The factors investigated were the freezing time (3−9 h), freezing temperature (−20 to −80 °C), pressure (0.2−0.8 mbar), and lyophilization time (5−20 h). The maximum range of change and one-way analysis of variance showed that lyophilization time and freezing time significant affects (p < 0.05) the response variables, residual moisture content and water activity, and pressure had a significant effect on the color difference and survival rate of probiotic microorganisms. The best drying conditions were a freezing time of 3 h, a freezing temperature of −20 °C, a pressure of 0.6 mbar, and a lyophilization time of 15 h. Under these conditions, we obtained a product with residual moisture content below 6%, water activity below 0.2, and survival rates above 8.5 log cfu per gram of lactic acid bacteria and above 8.6 log fo... [more]
Water−Organic Solvent Extraction of Phenolic Antioxidants from Brewers’ Spent Grain
Antonio Zuorro, Annalaura Iannone, Roberto Lavecchia
July 11, 2019 (v1)
Subject: Biosystems
Keywords: brewers’ spent grain, phenolic compounds, solvent extraction, waste valorization
Brewers’ spent grain (BSG) is the most abundant by-product of the brewing process. BSG is currently disposed of or used as a supplement for animal feed, although it contains significant amounts of bioactive compounds of great interest to the pharmaceutical, cosmetic and food sectors. In this study we investigate the feasibility of using a simple solvent extraction procedure to recover phenolic antioxidants from BSG. Acetone−water and ethanol−water mixtures were used as extraction solvents. Phenolic extracts obtained by treatment of BSG with the two solvent systems were characterized in terms of total phenolics and antioxidant activity. For both systems, the extraction yield was maximum at 60% (v/v) organic solvent concentration. At all solvent compositions, mixtures containing acetone provided higher extraction yields. As suggested by the strong correlation between the antioxidant activity of BSG extracts and their phenolic content, the antioxidant capacity of the extracts can be mainl... [more]
Response Surface Method in the Optimization of a Rotary Pan-Equipped process for Increased Efficiency of Slow-Release Coated Urea
Farahnaz Eghbali Babadi, Robiah Yunus, Ali Abbasi, Salman Masoudi Soltani
July 5, 2019 (v1)
Keywords: coated urea, design of experiments, process optimisation, slow-release urea
The high solubility of urea in water and its consequent leaching into the soil adversely prevents its full assimilation by plants. An improved slow-release process could effectively minimise the loss of fertilizer material and thus mitigate the associated environmental pollution. In this study, the effects of the operational variables on the efficiency of the urea coating process in a rotary pan have been systematically analysed. A mixture of gypsum-sulphur was used as the coating material with refined water as a binder. In order to comprehensively investigate the impact of each process variable on the efficiency and any potential interactions between them, the effects of particle size, coating material percentage, rotational speed of the pan, spray flow rate and the amount of sprayed water were investigated and analysed via a central composite design of experiments (DoE). The second-order polynomial model provided the best correlation for the experimental data. The predictive model wa... [more]
A Novel Method for Gas Turbine Condition Monitoring Based on KPCA and Analysis of Statistics T2 and SPE
Li Zeng, Wei Long, Yanyan Li
July 5, 2019 (v1)
Keywords: kernel function, KPCA, SPE statistical model, T2 statistical model
Gas turbines are widely used all over the world, in order to ensure the normal operation of gas turbines, it is necessary to monitor the condition of gas turbine and analyze the tested parameters to find the state information contained in parameters. There is a problem in gas turbine condition monitoring that how to locate the fault accurately if failure occurs. To solve the problem, this paper proposes a method to locate the fault of gas turbine components by evaluating the sensitivity of tested parameters to fault. Firstly, the tested parameters are decomposed by the kernel principal component analysis. Then construct the statistics of T2 and SPE in the principal elements space and residual space, respectively. Furthermore, the thresholds of the statistics must be calculated. The influence of tested parameters on faults is analyzed, and the degree of influence is quantified. The fault location can be realized according to the analysis results. The research results show that the propo... [more]
Integration of Membrane Bioreactor and Nanofiltration for the Treatment Process of Real Hospital Wastewater in Ho Chi Minh City, Vietnam
Thanh Tran, Thanh Binh Nguyen, Huu Loc Ho, Duc Anh Le, Tri Duc Lam, Duy Chinh Nguyen, Anh Tuan Hoang, Trung Sy Do, Luong Hoang, Trinh Duy Nguyen, Long Giang Bach
July 5, 2019 (v1)
Keywords: chemical oxygen demand, hospital wastewater, membrane bioreactor, nanofiltration, nitrogen compounds, pathogen contents, total phosphorus
Hospital wastewater contains pharmaceutical residues, chemicals, and pathogens that cause coloration and nourish pathogenic microorganisms. The objective of the study was to evaluate the effectiveness of a medical wastewater treatment system at Military Hospital 175 (Ho Chi Minh City, Vietnam) that combined a membrane bioreactor (MBR) system with nanofiltration (NF). The influent of the system was the wastewater discharged from the operating rooms of the hospital. The system has a capacity of 50 L/day and operates at three organic load rates (OLR) of 0.5, 1.5 and 2.5 kgCOD/m3day (COD: Chemical oxygen demand), in which each load rate operates for 40 days. The results showed that most nutritional criteria generally achieved positive results. Specifically, the average COD removal was shown to be consistently high throughout the three phases at 94%, 93.3%, and 92.7%, respectively. For removal of nitrogen, the system demonstrated efficiencies of 75%, 79%, and 83%, respectively, to three pha... [more]
Effects of Caustic Extraction on Properties of Viscose Grade Dissolving Pulp
Cindy Friebel, Robert H. Bischof, Gabriele Schild, Karin Fackler, Ireen Gebauer
July 5, 2019 (v1)
Subject: Biosystems
Keywords: caustic extraction, cellulosic fibres, dissolving pulp, pulp, textile fibres, viscose, wood
Viscose, a cellulose-based commodity fibre, is produced by pulping and bleaching of wood, yielding a high quality “dissolving pulp” which is then spun. During pulping and bleaching, effective hemicellulose extraction is required to allow fibre production. We present a design of experiments (DoE) approach to optimise caustic extraction in a total chlorine free (TCF) bleaching sequence (O-CE-Z-P) of beech wood sulphite pulp. Temperature and sodium hydroxide concentration were varied to identify highest xylan extraction yield, and a maximum xylan removal of 83% was achieved at 20 °C and 120 g/L NaOH. Additionally, caustic extraction conditions were derived from the DoE model that led to pulps with high yield, high alpha cellulose content or uniform cellulose molecular weight distribution. Pulps from verification experiments exhibited good reactivity in viscose application tests. Hence, the presented O-CE-Z-P bleaching sequence can be considered as suitable for integrated viscose fibre pro... [more]
Computational Evaluation of Mixing Performance in 3-D Swirl-Generating Passive Micromixers
Mahmut Burak Okuducu, Mustafa M. Aral
July 5, 2019 (v1)
Keywords: Computational Fluid Dynamics, false diffusion, finite volume method, micromixer, numerical diffusion, swirl
Computational Fluid Dynamics (CFD) tools are used to investigate fluid flow and scalar mixing in micromixers where low molecular diffusivities yield advection dominant transport. In these applications, achieving a numerical solution is challenging. Numerical procedures used to overcome these difficulties may cause misevaluation of the mixing process. Evaluation of the mixing performance of these devices without appropriate analysis of the contribution of numerical diffusion yields over estimation of mixing performance. In this study, two- and four-inlet swirl-generating micromixers are examined for different mesh density, flow and molecular diffusivity scenarios. It is shown that mesh densities need to be high enough to reveal numerical diffusion errors in scalar transport simulations. Two-inlet micromixer design was found to produce higher numerical diffusion. In both micromixer configurations, when cell Peclet numbers were around 50 and 100 for Reynolds numbers 240 and 120, the numer... [more]
Realizing Energy Savings in Integrated Process Planning and Scheduling
Liangliang Jin, Chaoyong Zhang, Xinjiang Fei
July 5, 2019 (v1)
Keywords: carbon emission, energy saving, integrated process planning &, MILP models, multi-objective optimization, Scheduling, TOPSIS
The integration of scheduling and process planning can eliminate resource conflicts and hence improve the performance of a manufacturing system. However, the focus of most existing works is mainly on the optimization techniques to improve the makespan criterion instead of more efficient uses of energy. In fact, with a deteriorating global climate caused by massive coal-fired power consumption, carbon emission reduction in the manufacturing sector is becoming increasingly imperative. To ease the environmental burden caused by energy consumption, e.g., coal-fired power consumption in use of machine tools, this research considers both makespan as well as environmental performance criteria, e.g., total power consumption, in integrated process planning and scheduling using a novel multi-objective memetic algorithm to facilitate a potential amount of energy savings; this can be realized through a better use of resources with more efficient scheduling schemes. A mixed-integer linear programmi... [more]
Mechanistic Models of Inducible Synthetic Circuits for Joint Description of DNA Copy Number, Regulatory Protein Level, and Cell Load
Lorenzo Pasotti, Massimo Bellato, Davide De Marchi, Paolo Magni
July 5, 2019 (v1)
Subject: Biosystems
Keywords: bottom-up design, cell load, copy number, inducible promoter, mathematical modeling, mechanistic model, synthetic biology
Accurate predictive mathematical models are urgently needed in synthetic biology to support the bottom-up design of complex biological systems, minimizing trial-and-error approaches. The majority of models used so far adopt empirical Hill functions to describe activation and repression in exogenously-controlled inducible promoter systems. However, such equations may be poorly predictive in practical situations that are typical in bottom-up design, including changes in promoter copy number, regulatory protein level, and cell load. In this work, we derived novel mechanistic steady-state models of the lux inducible system, used as case study, relying on different assumptions on regulatory protein (LuxR) and cognate promoter (Plux) concentrations, inducer-protein complex formation, and resource usage limitation. We demonstrated that a change in the considered model assumptions can significantly affect circuit output, and preliminary experimental data are in accordance with the simulated ac... [more]
An Integrated Delphi-AHP and Fuzzy TOPSIS Approach toward Ranking and Selection of Renewable Energy Resources in Pakistan
Yasir Ahmed Solangi, Qingmei Tan, Nayyar Hussain Mirjat, Gordhan Das Valasai, Muhammad Waris Ali Khan, Muhammad Ikram
June 18, 2019 (v1)
Subject: Energy Policy
Keywords: analytical hierarchy process, Delphi, fuzzy technique for order of preference by similarity to ideal solution techniques, renewable energy (RE) resources, sustainable energy planning
Pakistan has long relied on fossil fuels for electricity generation. This is despite the fact that the country is blessed with enormous renewable energy (RE) resources, which can significantly diversify the fuel mix for electricity generation. In this study, various renewable resources of Pakistan—solar, hydro, biomass, wind, and geothermal energy—are analyzed by using an integrated Delphi-analytical hierarchy process (AHP) and fuzzy technique for order of preference by similarity to ideal solution (F-TOPSIS)-based methodology. In the first phase, the Delphi method was employed to define and select the most important criteria for the selection of RE resources. This process identified four main criteria, i.e., economic, environmental, technical, and socio-political aspects, which are further supplemented by 20 sub-criteria. AHP is later used to obtain the weights of each criterion and the sub-criteria of the decision model. The results of this study reveal wind energy as the most feasib... [more]
Availability Assessment of IMA System Based on Model-Based Safety Analysis Using AltaRica 3.0
Haiyong Dong, Qingfan Gu, Guoqing Wang, Zhengjun Zhai, Yanhong Lu, Miao Wang
June 18, 2019 (v1)
Subject: Other
Keywords: AltaRica 3.0, availability assessment, integrated modular avionics, model-based safety analysis
The integrated modular avionics (IMA) system is widely used in all classes of aircraft as a result of its high functional integration and resource utilization in developing advanced avionics systems. However, a series of challenges related to safety assessment exist in the background of the logical architecture for multi-message interactions of the IMA system. Traditional safety assessment methods are mainly based on engineering experience, and are difficult to reuse, incomplete, and even error-prone. Here we propose a method to assess the availability of the IMA system based on the thinking of model-based safety analysis. To aid the proposed method, we implement a tool to generate a AltaRica 3.0 file used to assess the IMA system model. The simulation results show that the proposed method makes the availability assessment fast, efficient, and effective. Moreover, we apply this method to the modification analysis of the IMA system under the condition of satisfying the safety requiremen... [more]
Development of 3D Finite Element Method for Non-Aqueous Phase Liquid Transport in Groundwater as Well as Verification
Wei Yu, Hong Li
June 18, 2019 (v1)
Keywords: finite element method, FLAC, mixed-form formulation, non-aqueous phase liquid, two-phase flow
Groundwater contamination previously occurred at a broad range of locations in present-day China. There are thousands of kinds of contaminants which can be divided into soluble and insoluble categories in groundwater. In recent years, the non-aqueous phase liquid (NAPL) pollution that belongs to the multi-phase seepage flow phenomenon has become an increasingly prominent topic due to the challenge brought by groundwater purification and its treatment. Migrating with seepage flow and moving into the potable water sources, these contaminants directly endanger people’s health. Therefore, it is necessary to research how these contaminants not only migrate, but also are then accordingly remedied. First, as an analysis means, an effective numerical method is necessary to be built. A three-dimensional finite element method program for analyzing two-phase flow in porous media, which can be applied to the immiscible contaminant transport problem in subsurface flow has been developed in this pap... [more]
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