A Conduction–Radiation Mixture Model for Laser-Assisted Phase Change of Semitransparent Material

A one-dimensional transient coupled conduction-radiation numerical model is developed to investigate the laser melting of semitransparent material under a continuous collimated laser pulse in a convective cooling environment. The medium is considered absorbing, emitting, and scattering. The thermophysical properties are taken to be different for different phase fields. Volumetric radiation is incorporated in the proposed model. The radiation information is obtained by solving the equation of transfer. The temperature field is obtained by solving the energy equation with internal radiation source. The finite-volume method is used to discretize both the equation of transfer and the energy equation. The enthalpy formulation is adopted to capture the continuously evolving solid–liquid interface during the phase change. The laser source is approximated with the collimated radiation source. Collimated intensity is captured directly (without splitting the total intensity into two parts: diffuse and collimated) by adjusting the control angles. The present model is first validated with the existing phase-change model in the literature. Then the effects of different parameters such as optical thickness, scattering albedo, and the conduction–radiation parameter on the liquid fractions and temperature distribution in the medium are studied. It is observed that when the radiation is dominant, the temperature in the medium is high and hence the liquid fraction is more, in contrast to conduction-dominated phase change.     

Study of Damage and Fracture Toughness Due to Influence of Creep and Fatigue of Commercially Pure Copper by Monotonic and Cyclic Indentation

Fracture toughness is the ability of a component containing a flow to resist fracture. In the current study, the Ball indentation (BI) test technique, which is well acknowledged as an alternative approach to evaluate mechanical properties of materials due to its semi-nondestructive, fast, and high accurate qualities is used to estimate damage and the fracture toughness for copper samples subjected to varying levels of creep and fatigue. The indentation fracture toughness shows the degradation of Cu samples when they are subjected to different creep conditions. Axial fatigue cycling increases the strength at the mid-gauge section compared to other regions of the samples due to initial strain hardening. The advancement of indentation depth with indentation fatigue cycles experiences transient stage, i.e., jump in indentation depth has been observed, which may be an indication of failure and followed by a steady state with almost constant depth propagation with indentation cycles.     

Optimal spatiotemporal reduced order modeling, Part II: application to a nonlinear beam

A geometrically nonlinear, simply supported beam under the influence of time-dependent external forcing serves as a testbed to demonstrate application of the optimal spatiotemporal reduced order modeling (OPSTROM) framework proposed in Part I of this work. Fully resolved simulations, which are relatively expensive to perform, are used to accurately predict the beam response for a few forcing parameters. More affordable simulations are achieved with a conventional finite-difference scheme by coarsening the computational grid in space and time. Discretization errors are reduced with OPSTROM as subgrid-scale models are designed to account for the underlying space-time statistical structure using principles of mean-square error minimization, conditional expectations and stochastic estimation. When included in the under-resolved simulations, these optimal subgrid-scale models are shown to significantly improve the accuracy of predictions for both periodic and chaotic response types. This improved accuracy is further demonstrated through a set of numerical experiments designed to capture the complex bifurcation behavior of the beam response.     

The potential of a renewable energy technology for rural electrification in Nepal: A case study from Tangting

Nepal, one of the least developed countries, is characterized by low per capita energy consumption and hugely dominated by traditional energy sources. Despite having enormous potential of hydro-electricity, only 50% of the total population has access to grid electricity. Firewood is the primary energy source for domestic purposes in rural environments. Due to geographical remoteness, a scattered consumer, higher costs of supply and maintenance, low consumption and low level of households’ income linking the rural areas to national electricity grid is difficult and implausible. In order to solve the energy problem in rural areas, Nepal’s government has initiated the production and distribution of several renewable energy technologies. Among several renewable technologies, micro-hydropower has been one of the most promising and widely adopted decentralized technologies to distribute electricity in rural areas. This article begins with a general overview of energy situation in Nepal. Present status and perspective of micro-hydro plants have also been discussed. Similarly, the dynamics of the relationship between electricity and socio-economic development has been analyzed by means of a typical rural electrification project in Tangting, Nepal by assessing the impacts of electricity on health, education, environment, and income in the village. The community has greatly benefitted from the arrival of environment friendly and affordable electricity. It has been concluded that the task of providing electricity to more remote and isolated villages is still challenging in Nepal. More systematic and comprehensive study supported by research and development is required to extend micro-hydro based electricity in more remote and poor communities of Nepal.     

Turmeric nanofiber-encapsulated natural product formulation act as a phytogenic feed additive—A study in broilers on growth performance,biochemical indices of blood,and E. coli in cecum

A phytogenic feed additive (PFA) formulation was prepared with bioactive molecules—curcuminoids, gingerol, and carvacrol by encapsulating in nanofiber isolated from turmeric spent (turmeric nanofiber, TNF). This formulation was completely characterized by scanning electron microscope, ultra performance liquid chromatography, and gas chromatography and evaluated for its efficacy. PFA-encapsulated TNF (PFA@TNF) considerably increased mean body weight, decreased cholesterol level, mortality rate, and reduced Escherichia coli content of broilers than antibiotic growth promoter (AGP). The depth of crypts in the ileum of broilers was considerably reduced by the inclusion of PFA@TNF in diets compared with the AGP.     

Hexamethylenetetramine: A New Fuel for Solution Combustion Synthesis of Complex Metal Oxides

Hexamethylenetetramine, (CH₂)₆N₄ (HMT) has been employed as a fuel for the first time to synthesize several binary, ternary, and quaternary oxides by the solution combustion method. Technologically important oxides, namely, zirconia, ceria, and their solid solutions, -Al₂O₃, Cr³⁺-doped -Al₂O₃, spinels, MAl₂O₄ (M = Ca, Mg, Zn and Ni), perovskites, LaMO₃ (M = Mn, Cr and Al), La_0.67Sr_0.33MnO₃, and La_0.67Ca_0.33MnO₃, have been synthesized. The oxides synthesized are characterized by X-ray powder diffraction, resistivity, fluorescence spectra, particle size, and surface area measurements. Decomposition of nickel nitrate-HMT complex has been investigated by TG, DTA, TPD, and evolved-gas analysis to elucidate the mechanism.     

Evaluation of the behavior of shrouded plasma spray coatings in the platen superheater of coal-fired boilers

Nickel- and cobalt-based coatings were formulated by a shrouded plasma spray process on boiler tube steels, namely, ASTM-SA210-grade A1 (GrA1), ASTM-SA213-T-11 (T11), and ASTM-SA213-T-22 (T22). The Ni-22Cr-10Al-1Y alloy powder was sprayed as a bond in each case before the final coating. The degradation behavior of the bared and coated steels was studied in the platen superheater of the coal-fired boiler. The samples were inserted through the soot blower dummy points with the help of stainless steel wires. The coatings were found to be effective in increasing resistance to degradation in the given boiler environment. The maximum protection was observed in the case of Stellite-6 (St-6) coating.     

Improved design procedure for double‐ridged waveguides

This article presents a novel methodology for designing double‐ridged waveguides by numerically optimizing their geometric shape such that they sustain the two prescribed lowest order modes. The field solution to the problem is obtained by using the finite element method. The performance of the microgenetic algorithm and the quasi‐Newton methods is studied for carrying out geometry optimization. This generalized formulation is capable of handling inhomogeneous material fillings in the guide, and computational results are presented to demonstrate the versatility of the proposed technique. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 530–539, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10053     

Unfolding of multimeric proteins in presence of denaturants. A case study of helianthinin from Helianthus annuus L

Helianthinin (11S), a multisubunit protein from Sunflower Seeds (Helianthus annuus L.) dissociates to its monomer (2S) through a trimeric (7S) intermediate as a function of guanidine hydrochloride (GuHCl) and guanidine thiocyanate (GuHSCN) concentration. Measurements of viscosity, velocity sedimentation patterns and spectroscopic parameters of the protein in presence of these denaturants both at equilibrium and as a function of time clearly suggest that the dissociation, unfolding and aggregation of this multimeric protein occur sequentially. The unfolding of the protein in guanidinium salts has two transitions with the first transition occurring between native to intermediate and the second transition occurring between intermediate state and unfolded state. The midpoint concentration for the major transition is 1.75 M for GuHCl and 0.8 M for GuHSCN. Evaluation of this data suggests that during the process of denaturation the simultaneous unfolding of acidic and basic subunits of the protein takes place. At intermediate concentrations of denaturant namely 1.6 M of GuHCl or 1.1 M of GuHSCN the aggregation of the protein was found to be maximum. The results suggests the possibility of a mechanism for the dissociation, denaturation and unfolding of multimeric proteins in presence of the chemical denaturants.