Strain Improvement Through UV and Chemical Mutagenesis for Enhanced Citric Acid Production in Molasses-Based Solid State Fermentation

Aspergillus niger was subjected to UV radiation and chemical mutagenesis to develop its hyper-producing mutants for enhanced citric acid production. Ethyl methane sulfonate (EMS) and Ethidium bromide (EB) were used for chemical mutagenesis of Aspergillus niger. UV, and chemically treated mutants of Aspergillus niger were identified by using 2-deoxy, D-glucose as selective marker. The selected mutants were cultured in solid state fermentation (SSF) of sugarcane molasses medium (10%) using corn cobs, banana stalk, sugarcane bagasse, wheat straw, and wheat bran as carrier substrates. After pH adjustment and sterilization, the triplicate flasks were inoculated with 5 mLof homogenous spore suspensions of selected mutants of A. niger and the flasks were subjected to SSF under still culture conditions. The mutant EB-3 (treated with 1 mg/mL ethidium bromide for 120 min) giving highest citric acid yield (64.2 mg/mL) in 72 h was selected as hyper-producing mutant. Citric acid production process using EB-3 mutant was then optimized to enhance citric acid production by the mutant in SSF. Aspergillus niger EB-3 mutant could produce 67.72 mg/mL citric acid in 72 h using banana stalks as support material under optimum conditions of pH (pH 6), incubation temperature (35°C) and inoculum size (5 mL) in SSF.     

Energy and exergy analysis of a 747-MW combined cycle power plant Guddu

ABSTRACT

The paper presents a detailed study based on the energy and exergy analysis of a combined cycle power plant (CCPP) Guddu having triple pressure heat recovery steam generator (HRSG). The energy loss and the energy efficiency of each plant component with HRSG as a whole is calculated. The exergy destruction of these components and the sub-parts of the HRSG are also found out. All the three stages of the steam turbine are analysed individually. The combustion chamber is found to have the maximum share of exergy destruction while the condenser is having a maximum of energy loss. The total net power output, energy and exergy efficiency of the whole plant is calculated as 737.8?MW, 59.12% and 58.24%, respectively. The error in getting the designed power output of 747?MW is 3.16%. The thermal efficiency of the Brayton and Rankine cycle is 62.01% and 56.38%, respectively.     

Influence of absorber doping in a-SiC：H/a-Si：H/a-SiGe：H solar cells

This work deals with the design evaluation and influence of absorber doping for a-Si:H/a-SiC:H/a-SiGe:H based thin-film solar cells using a two-dimensional computer aided design (TCAD) tool. Various physical parameters of the layered structure, such as doping and thickness of the absorber layer, have been studied. For reliable device simulation with realistic predictability, the device performance is evaluated by implementing necessary models (e.g., surface recombinations, thermionic field emission tunneling model for carrier transport at the heterojunction, Schokley-Read Hall recombination model, Auger recombination model, bandgap narrowing effects, doping and temperature dependent mobility model and using Fermi-Dirac statistics). A single absorber with a graded design gives an efficiency of 10.1% for 800 nm thick multiband absorption. Similarly, a tandem design shows an efficiency of 10.4% with a total absorber of thickness of 800 nm at a bandgap of 1.75 eV and 1.0 eV for the top a-Si and bottom a-SiGe component cells. A moderate n-doping in the absorber helps to improve the efficiency while p doping in the absorber degrades efficiency due to a decrease in the V_OC (and fill factor) of the device.     

Crystallization kinetics and structure of poly(trimethylene terepthalate)/monolayer nano-mica nanocomposites

In this work, the structure of poly(trimethylene terepthalate) (PTT)/monolayer nano-mica (MNM) nanocomposites are investigated by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and scanning electron microscope (SEM). In the PTT nanocomposites, the crystallization induces the segregation of MNM in which three morphologies, including interlamellar, interfibrillar, and interspherulitic segregations, are observed with changing the MNM content. Avrami analysis of isothermal crystallization demonstrates that MNM enhances the bulk crystallization rate in the nanocomposites. Moreover, the non-integral values of Avrami exponent n between 2 and 4 with increasing crystallization temperature indicate the mixed growth and nucleation mechanisms. The analysis of secondary nucleation theory for neat PTT and the PTT nanocomposites exhibit the same regime transition of crystallization behaviour in which the classical transition temperatures of regime I to II and regime II to III take place at 488 K and 468 K, respectively. The growth rate of spherulites of the PTT nanocomposites is twofold larger than that of neat PTT in regime III, implying that MNM plays an effective role as a nucleating agent, since the addition of MNM enormously reduces the activation energy of nucleation, folding surface free energy and average work of chain folding for PTT nucleation. However, experimental results show that the MNM content below 1 wt% is the most effective for nucleation of PTT crystallization.     

A meshfree interpolation method for the numerical solution of the coupled nonlinear partial differential equations

This paper formulates a simple classical radial basis functions (RBFs) collocation (Kansa) method for the numerical solution of the coupled Korteweg-de Vries (KdV) equations, coupled Burgers’ equations, and quasi-nonlinear hyperbolic equations. Contrary to the mesh oriented methods such as the finite-difference and finite element methods, the new technique does not require mesh to discretize the problem domain, and a set of scattered nodes provided by initial data is required for realization of solution of the problem. Accuracy of the method is assessed in terms of the error norms $L_2,L_{\infty }$, number of nodes in the domain of influence, time step length, parameter free and parameter dependent RBFs. Numerical experiments are performed to demonstrate the accuracy and robustness of the method for the three classes of partial differential equations (PDEs).     

Bio-based unsaturated polyester/layered silicate nanocomposites: Characterization and thermo-physical properties

Proper stiffness–toughness balance along with enhancement in other thermo-physical properties can be obtained by incorporating layered silicates (nanoclay) in bio-based resins, defined as blends of functionalized vegetable oils and petroleum-based resins. Bio-based polymer nanocomposites with varying clay concentration and varying bio-resin (epoxidized soy bean oil) content in unsaturated polyester resins were manufactured. Thermo-physical properties such as tensile modulus and strength, coefficient of thermal expansion, moisture absorption, toughness, and glass transition temperatures were studied. Fracture surface morphologies and characterization of nanocomposites were performed using electron microscopy. The resulting bio-blend nanocomposites exhibit promising results for use in structural applications.     

Reliability Enhancement in Nondestructive Evaluation: Development of Practical Rules for Vacuum Type Helium Leak Tests

In helium leak testing, reliability is an important factor and while attempting to improve this, lot of challenges are being faced. There are contributors for bringing in variations in leak meter readings obtained during system sensitivity check and actual leak test which ultimately affect the final measured leakage rate of test object and they need to be controlled for obtaining reliable results. Response times of leaks are affected by vacuum side volumes, contaminations in vacuum side, leaked gas travel path restrictions on vacuum side and nature of actual leak paths and their gas flow impedances. Hence, actual consideration of real responses of leaks is to be practiced for a reliable test. The traditional concept of using estimate for percentage helium concentration in test hoods is modified by a novel method for its exact determination which improves reliability in tests. Also, practical rules are derived for the reliable identification of leak locations from response time concept. Spurious indications caused by leaks in temporary test rig joints or due to leaks from joints or passages not in the scope of test are other impediments for a reliable test. The response of system changes instantly by spurious indications and hence they require elimination by adopting innovative methods.     

Chitosan/CNTs nanocomposite as green carrier material for pesticides controlled release

Chitosan-based nanocomposites containing gamma-treated carbon nanotubes (CNTs) were developed for controlled release of pesticide. The CNTs were irradiated under gamma irradiation in air at different doses. The transmission electron microscopic images of gamma-treated CNTs showed disentanglement of the tubes without distorting their tubular structure which effectively increased the dispersion properties of CNTs in nanocomposites. X-ray diffraction analysis of CNTs showed some structural changes, and an irradiation dose of 150 kGy is the most effective. Azinphos methyl (AZM) was selected as a model drug, and its release was studied using HPLC technique. Controlled release response of CNTs-based nanocomposites opens a new avenue for pesticides applications because it requires less quantity of pesticides. As a result, the side effects of pesticide in our environment are minimized.     

Heterogeneous Reactor Modeling of an Industrial Multitubular Packed‐Bed Ethylene Oxide Reactor

The one‐dimensional heterogeneous model of an industrial multitubular packed‐bed ethylene oxide (EO) reactor was developed using the equation‐oriented platform Aspen Custom Modeler. Reactor operation was optimized in terms of maximized EO production and selectivity and enhanced safety related to the presence of oxygen in the EO reactor. Good agreement was found between the model results during validation against the available information under identical operating conditions. The model predicts the behavior of the EO reaction and demonstrates the extent of catalyst utilization with product distribution, product yield, by‐product formation, temperature and concentration profiles, over time and along the length of the reactor or catalyst bed. The model sensitivity studies compute the optimum feed flow, oxygen concentration, feed pressure, etc. and suggest the best operational philosophy.     

A Study on the FTIR Spectroscopy of Polylactide Doped with Nano-Aluminium Oxide and Nano-Cupric Oxide

Elucidation of the structure of naturally existing or synthesized substances is an important criterion in the study of materials to predict the application of the substance. In this study, polylactide was doped with nano-aluminium oxide and nano-cupric oxide with 1 and 3 mg of concentration variants. The interaction between the polymer matrix and the nanoparticles has been studied using Fourier transform infrared. Successful doping of the polymer has been observed. Attention has been drawn to check the intermolecular bonding in films having varying thicknesses, films prepared at higher sonication temperatures, and chemical homogeneity of the doped polymer films.