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The Gifford-McMahon cryocoolers are considered to be prominent candidates for the cooling of high-temperature superconducting magnets, liquefaction of permanent gases, helium recondensation in magnetic resonance imaging machines, cooling of superconducting quantum interference device, etc. In this paper, multi-dimensional numerical simulation is performed to visualize the oscillating heat and fluid flow processes that happen in a mechanically driven GM cryocooler. Influence of the ideal gas equation and real gas equation of states on the cooling behaviour is explained. The minimum achievable refrigeration temperature of a uniform mesh regenerator is compared with a multi-mesh regenerator. It is noticed that a multi-mesh regenerator produces a lower refrigeration temperature as compared to a uniform mesh regenerator. In addition to this, a one-dimensional simulation is conducted and results are compared with multi-dimensional numerical simulation. The no-load temperature value calculated by the one-dimensional model and multi-dimensional model with ideal gas is lower than that of real gas equations. Additionally, the refrigerating capacity calculated by the one-dimensional model and multi-dimensional model with the ideal gas equation is higher than those of the real gas equation of state. [ABSTRACT FROM AUTHOR]

One of the most significant challenges in describing the drying of porous materials is the realistic integration of internal transport phenomena into mathematical models, coupled with the external free flow. However, the intricacies of pore-scale geometry make experimentation and observation very difficult in practice, thereby making modeling techniques a useful tool for the analysis of the drying process. Among the many modeling techniques developed for drying, the lattice Boltzmann method (LBM)-based modeling approach has gained favor in recent years due to its ability to incorporate realistic geometry and transport at the pore scale. Our previous works on Shan–Chen LBM for drying of capillary porous media were based on the Bhatnagar–Gross–Krook collision operator and diffusion interface boundary conditions. This study elucidates the drying of a capillary porous medium under the influence of convection–diffusion boundary conditions at the gas side, using Shan–Chen LBM. The pore-scale effects of convection–diffusion conditions during the drying process are presented in relation to the macroscale drying kinetics. Moreover, the differences between the convection–diffusion kinetics and purely diffusion–dominated kinetics of the drying process are also presented here. This work also aims to incorporate the convection–diffusion transport phenomena into the drying process of a porous medium under the influence of an imposed thermal gradient, establishing and studying the phenomena of stabilization and destabilization of the drying front under the influence of a temperature gradient, thereby extending the lattice Boltzmann method of modeling for the simulation of convection–diffusion drying, both for the isothermal case and the imposition of a thermal gradient. [ABSTRACT FROM AUTHOR]

In this article, a numerical analysis is conducted for a miniature coaxial pulse tube cryocooler including the effect of an axial conduction enhanced term. This term is a representative of supplementary energy loss, which happens because of turbulent conduction, mixing, and thermal dispersion. The complex physical domain of cryocooler is modeled intelligently in one-dimensional model by splitting the total computational domain into two subsections. The individual subsections of the cryocooler have been discretized into a number of small control volumes. Both subsections are merged together to make a complete computational domain for the cryocooler. The conservative form of the nonlinear, coupled partial differential equations demonstrating its heat and fluid flow aspects have been discretized into algebraic equations by utilizing the finite volume technique. Final discretized algebraic equations have been solved iteratively to predict its heat and fluid flow behaviors. Suitable relaxation factors have been incorporated to accelerate the convergence of the simulation. Moreover, the variation of mean cyclic energy, enthalpy, and exergy flow have been visualized along its physical domain with and without fluid axial conduction enhancement loss processes. Influences of different length of inertance tube, outer to inner radius ratio of annular passage, and length to radius ratio of pulse tube on no-load temperature is studied for with and without fluid axial conduction heat loss. [ABSTRACT FROM AUTHOR]

Emerging nanoscale devices, including memristors, have been extensively studied to implement biological synaptic functions such as learning and plasticity, which are the fundamental building blocks of brain-inspired neuromorphic computing. The memristor with analog switching ability exhibits linear tuning of weight during neural network training is a desirable synaptic device behavior. The importance of inserting a HfO x sandwiched layer in a TaO x /HfO x /TaO x memristor is to achieve analog set/reset operation along with improved spatial/temporal switching uniformity. The optimal resistive switching (RS) behavior can be attributed to asymmetric oxygen vacancy distribution in the stacked structure leading to the formation of an hourglass-shaped conductive filament. Furthermore, confining filament formation/rapture in the narrow fixed region displays superior endurance characteristics (dc cycles >2000 and ac cycles > 106) and uniform resistive switching with the set (reset) voltage variation constrained to 1.8 (2.9) %. Paired-pulse facilitation (PPF), a form of short-term synaptic plasticity is stimulated to replicate bio-synapse behavior. The stable long-term potentiation (LTP) and depression (LTD) behavior for more than 1000 epochs (>105 pulses) with excellent symmetry and linearity is achieved with 50 ns voltage pulse stimulation. The pattern recognition accuracy of 93% was achieved for an image of size 10 × 10 pixels after 13 epochs by deploying 100 synapses in Hopfield Neural Network (HNN) simulation. This comprehensive study demonstrates that the HfO x -inserted TaO x memristor has tremendous potential for application in future neuromorphic computing. [ABSTRACT FROM AUTHOR]

In this paper, an experimental investigation is conducted to investigate the cool-down behavior of single-stage Gifford-McMahon type pulse tube cryocooler. Nine different cold head configurations of pulse tube cryocooler have been fabricated with different aspect ratios of regenerator and pulse tube to investigate their effect on the cooling process. Additionally, experimental investigation have been conducted to conceive the impact of operating parameters like mean pressure, pressure ratio on minimum refrigeration temperature, and cooling capacity. The influence of orifice and double-inlet valve opening rates on the performance parameters of pulse tube cryocooler has been investigated. A transient one-dimensional computational model of the pulse tube cryocooler is adopted to predict the theoretical refrigeration performance. In the one-dimensional computational model, the governing equations for compressible flow are solved iteratively to predict the basic fluid flow and heat transfer behaviors. It is noticed that the optimum value of the orifice valve opening to achieve maximum cooling capacity and minimum refrigeration temperature strongly depends on the geometrical parameters. The minimum refrigeration temperature and maximum cooling capacity occur at different values of orifice valve opening in each configuration. The orifice valve opening is found to be a more influential parameter on cooling capacity over the double inlet valve opening. [ABSTRACT FROM AUTHOR]

All oxide-based transparent flexible memristor is prioritized for the potential application in artificially simulated biological optoelectronic synaptic devices. SnOx memristor with HfOx layer is found to enable a significant effect on synaptic properties. The memristor exhibits good reliability with long retention, 104 s, and high endurance, 104 cycles. The optimized 6 nm thick HfOx layer in SnOx-based memristor possesses the excellent synaptic properties of stable 350 epochs training, multi-level conductance (MLC) behaviour, and the nonlinearity of 1.53 and 1.46 for long-term potentiation and depression, respectively, and faster image recognition accuracy of 100% after 23 iterations. The maximum weight changes of -73.12 and 79.91% for the potentiation and depression of the synaptic device, respectively, are observed from the spike-timing-dependent plasticity (STDP) characteristics making it suitable for biological applications. The flexibility of the device on the PEN substrate is confirmed by the acceptable change of nonlinearities up to 4 mm bending. Such a synaptic device is expected to be used as a vision photo-receptor. [ABSTRACT FROM AUTHOR]

Continuous effort is made on Gifford-McMahon cryocoolers (GMC) to amplify its refrigeration power, so they can be used to cool the cryopumps, high Tc magnets and development of efficient small-scale hydrogen liquefiers, etc. The fluidic-driven GMC is considered to be more reliable and prominent candidate than the mechanically-driven GMC due to its structural simplicity and reliability. Nonetheless, cooling mechanism of the fluidic-driven GMC is complicated, as the displacer motion inside the displacer cylinder is simultaneously controlled by the pressure difference between drive chamber and compression/expansion chamber. Different paths of displacer can be traced inside the displacer cylinder for different drive-chamber discharging process, hence, pressure–volume power of compression and expansion chambers, and refrigeration power changes. A theoretical study is conducted in present paper to visualize the influence of drive-chamber discharging process on the thermodynamic characteristics of fluidic-driven GMC for the first time. Thermodynamic cycles are drawn at the expansion chamber of the fluidic-driven GMC for different values of drive-chamber discharging process for two types of valve timing arrangements. Energy and work loss behaviors in different components of the GMC are also analysed. Adequate experimental investigations have also been carried out on a fluidic-driven displacer type GMC to verify the simulation results. [ABSTRACT FROM AUTHOR]

In GM refrigerator and GM-type pulse tube refrigerator, a rotary valve is located in between the compressor and cold head to generate the pressure pulse. In a typical rotary valve, the rotor rotates over the stator plane of the valve stator plate to generate the pulsating pressure wave. Thus, a surface contact occurs between the stator plane and rotor, which leads to the formation of wear between them. If the generated wear particles will flow to the cold head unit with helium, it will be stacked in the regenerator wire meshes, and hence deteriorates its thermal performance. Also, these worn out particles may be stacked within the orifice and double inlet valves and thereby changes their flow coefficient. Thus, good quality materials having better tribological and mechanical properties are essential for smooth operation of those refrigerators. In this paper, an experimental investigation is conducted by taking different grades of Polytetrafluoroethylene (PTFE) materials, and the wear rates and coefficient of friction have been determined. Different materials used in this investigation are Glass-filled PTFE, Rulon- filled PTFE, Molybdenum disulfide bronze (MoS2)-filled PTFE, and Graphite-filled PTFE, and it is observed that the wear rate of Rulon-filled PTFE is smaller than the remaining materials. Furthermore, the analysis is extended to investigate the tribological behavior of materials by varying different parameters like load, speed and sliding distance. It is evident that with an increase in load, the wear rate increases. Also, the wear rate rises with a rise in the sliding distance. The Vickers hardness number and Brinell hardness number of different materials is also tested in this investigation. [ABSTRACT FROM AUTHOR]

In this study, the Shan Chen Lattice Boltzmann method (LBM) is implemented to simulate pore-scale physics of drying porous media. The pore-scale mechanisms responsible for multiphase fluid transport in drying porous media are revisited, and the physical effects such as capillary valve effect and Haines jumps are delineated. Fluctuations observed in drying rate curves are realized to be caused by Haines jumps during the fast invasion of the gas phase into the complex geometry of the pore space. Furthermore, it is observed that the fluctuations are significant in the initial period of drying and diminish as the drying front recedes into the porous medium. The observed fluctuations in drying rate curves render the inspiration to reconcile LBM and pore network model as a hybrid pore-scale technique to track the micro–macro interactions in drying porous media. [ABSTRACT FROM AUTHOR]

Anodic porous transport layer (PTL) plays a pivotal role in the performance of the polymer electrolyte membrane (PEM) water electrolyser. In this study, Shen-Chen Lattice Boltzmann Method (SC-LBM) is implemented to study the invasion patterns (IP) of O 2 in a water saturated anodic PTL. Multiphase flow patterns in anodic PTL obtained with the LBM simulations are validated with the experiment results. Simulations are conducted for varied Capillary number (Ca) and Bond number (Bo) to study the competitiveness between the capillary, viscous forces and gravity. A dimensionless number (φ) is defined to develop a set of optimized parameters to enhance O 2 removal. The O 2 saturations along the normalized length reveal importance of void space microstructure in PTL. Thus, positive and negative porosity gradients are implemented from catalyst layer (CL) to water flow channel to understand invasion patterns. The results inspire to consider a random micro porous layer (MPL) near the CL to minimize the accumulation of O 2. Such parametric analysis and pore structure studies is a promising technique for the optimisation of the O 2 removal process. • Shan Chen LBM implementation for O 2 invasion in anodic porous transport layer of PEM electrolyser. • Validation of O 2 invasion patterns with experiments and PNM simulations. • Two-phase immiscible displacement characterized by Capillary number and Bond number. • Parametric optimisation of void space for better PTL i.e. for lower breakthrough saturation of O 2. [ABSTRACT FROM AUTHOR]

In this paper, simultaneous influence of low and high pressure of helium compressor, frequency, opening coefficient of orifice valve and waiting time of rotary valve on the cooling capacity and "coefficient of performance" (COP) of a single-stage orifice pulse tube refrigerator is studied. "Box–Behnken design" model is opted here to create a design data matrix by utilizing the above design variables and responses (i.e., cooling capacity and COP). A numerical model is used to estimate the responses from the design variables, and effects of each design variable on the responses are studied through "analysis of variance." Finally, input variables are ranked according to their ability to change the outputs by using the sensitivity analysis. A regression equation, which establishes a functional relationship between the design variables and response, is maximized by using "particle swarm optimization" method. ANN model is also applied to find the relationship between design variables and responses. Furthermore, by using the optimal range of inputs, an experimental investigation is carried out. Novelty of this article includes the study of simultaneous influences of aforementioned input variables on COP and cooling capacity, and also the sensitivity analysis. It has been observed that the cooling power and COP are increased by 10.8% and 0.76%, respectively, after optimization within the range of selected input parameters. [ABSTRACT FROM AUTHOR]

Drying of porous media sounds simple yet complicated to study the multiphase flow counterparts in porous media with intricate pore geometries. In the past, we have discussed the Lattice Boltzmann Model (LBM) as a powerful multiphase solver for the drying of porous media. In this study, we extend our previous work on the Shan Chen representation of the multiphase LBM to drying of porous media with imposed thermal gradients. A linearly varied stationary temperature profile is imposed concerning the depth of the porous medium, i.e., free evolution of temperatures due to the phase change is neglected. The preferential heating is divided into two kinds of gradients: First, the positive thermal gradient where temperatures varies linearly on an increasing order from top to bottom (e.g., the contact heating mode of drying). Second, the negative thermal gradient opposite the former (e.g., convective mode of heating). It is observed that the thermal gradient can lead to stabilizing and destabilizing drying fronts, where the latter situation incurs two drying fronts in a later period of drying. The novelty of this work is the establishment of thermal aspects to the previously discussed LBM and introduces the concepts of evaporation–condensation of trapped clusters and liquid bridges. The characteristics of thermal drying for stabilized and destabilized drying fronts is re-established at a magnified level of study using the developed LBM. [ABSTRACT FROM AUTHOR]

Incorporation of rice-husk-ash (RHA), an agricultural waste, in situ during the synthesis of MIL-101(Cr) resulted in a significant improvement in the CO2 adsorption properties over the synthesized RHA-MIL-101(Cr). The newly synthesized RHA-MIL-101(Cr) composite exhibited an enhancement of 14–27% in CO2 adsorption capacity as compared to MIL-101(Cr) at 25 °C and 1 bar. The content of RHA incorporated in RHA-MIL-101(Cr) fine tuned the CO2 capture performance to achieve high working capacity (0.54 mmol g−1), high purity (78%), superior CO2/N2 selectivity (18) and low isosteric heat of adsorption (20–30 kJ mol−1). The observed superior CO2 adsorption performance of RHA-MIL-101(Cr) is attributed to the fine tuning of textural characteristics—enhancement of 12–27% in BET surface area, 12–33% in total pore volume and 18–30% in micropore volume—upon incorporation of RHA in MIL-101(Cr). [ABSTRACT FROM AUTHOR]

In the present article, a methodology is suggested to enhance the cooling performance of a double inlet pulse tube refrigerator (DIPTR), which is affected by multiple operating and geometrical parameters, using artificial intelligence methods. A procedure based on artificial intelligence method is adopted to generate the optimum range of inputs to achieve the maximum obtainable performance of the DIPTR. Artificial neural network (ANN) is developed using three different activation functions at the outer layer. It is observed that purelin and tansig activation functions predict the results (cooling power and percentage Carnot respectively) more accurately in accordance with the numerical results. In addition, it is observed that the particle swarm optimization (PSO) of the weights and bias of ANN is capable of representing the non-linear mathematical relationship among inputs and outputs more accurately in case of a DIPTR. It is further observed that the hybrid scheme of the artificial-neuro-fuzzy-inference system (ANFIS) can estimate both cooling capacity and percentage Carnot apparently more precise than the backpropagation algorithm. A numerical model is developed, based on the finite volume discretization of the governing equations with ideal gas assumption to generate the data matrix, which is essential to develop the ANN and ANFIS. Finally, an experimental analysis is conducted to validate the optimum range of inputs (low and high-pressures of compressor, waiting time of rotary valve and frequency) obtained from artificial intelligence models. [ABSTRACT FROM AUTHOR]

The thermodynamic process parameters such as cooling capacity and percentage Carnot efficiency of an orifice pulse tube refrigerator are maximized using a novel hybrid statistical simulation approach. With the help of a one-dimensional numerical model, the inside gas flow and thermal processes responsible for the production of cooling effect inside the tube have been solved. Subsequently, the thermodynamic process parameters are calculated as a function of input geometrical parameters of the regenerator, pulse tube, and orifice valve. Response surface methodology is thereupon applied to investigate the influence of input factors on outputs. Desirability method is finally adopted to maximize both cooling capacity and percentage Carnot efficiency. A sensitivity investigation has been undertaken to find out the degree of influence of each input on the output. An experimental investigation has been conducted at the optimal set of parameters so as to validate the proposed methodology. The investigation shows that, there exists an almost linear relationship among the geometrical parameters of the pulse tube on outputs, and a nonlinear quadratic relationship among the geometrical parameters of regenerator on outputs. Finally, possible combination of input parameters have been generated by the model at which both the outputs are maximum. [ABSTRACT FROM AUTHOR]

Radial inflow turbine and nozzle among the other components of the cryogenic turboexpander has a significant effect on the efficiency of the system. This study proposes an effective one-dimensional design approach of a radial turbine by introducing different loss correlations. The methodology also describes the effect of non-dimensional design variables on the performance of the turbine. These variables (blade speed ratio, pressure ratio, hub and shroud to turbine inlet radius ratio) undergo artificial intelligence-based model to predict their optimal range for better efficiency and power output of the turbine. Based on these optimal ranges, two turbine and nozzle models are generated. The results of the optimized configuration show that the turbine total-to-static efficiency and power output are higher by 4% and 18.9% respectively as compared to the existing literature. Thereafter, the three-dimensional computational fluid dynamics (CFD) analysis is carried out to visualize the fluid flow and thermal characteristics at different inlet temperatures in the flow passage using ANSYS CFX®. The study also focuses to identify the flow separation zone, tip leakage flow, vortex formation, secondary losses and its reasons at different spans of the turbine. An experimental platform is also established to validate the CFD results of a case study. The experimental results show that the mass flow rate and rotational speed has major effect on temperature drop and isentropic efficiency of the turboexpander. The study highlights the importance of the design methodology, the estimation capability of artificial intelligence models, the experimental techniques and benchmarking model for numerical analysis at different cryogenic temperature. [ABSTRACT FROM AUTHOR]

In this study, a particle swarm optimization method is employed to find the optimal operating parameters and geometrical parameters, which maximize the coefficient of performance (COP) of an inertance pulse tube refrigerator (IPTR). The considered decision variables of the IPTR are the charging pressure, which varies from 15 to 25 bar, operating frequency varying from 20 to 60 Hz, geometrical parameters, such as diameter varying from 15.0 to 25.00 mm, and length varying from 40.0 to 70 mm of the regenerator; diameter varying from 12.0 to 20.00 mm and length varying from 40.0 to 80 mm of the pulse tube; and diameter varying from 2.0 to 6.00 mm and length varying from 1.0 to 3.0 m of the inertance tube. A 1D numerical model, based on the finite volume discretization of governing equations has been selected to build the initial design matrix and solve the governing continuity, momentum, and energy equations. Analysis of variance is performed using the result obtained from the numerical simulation to visualize the variations of COP as a combination of various input parameters. It is observed that after optimizing the input parameters, the COP of the IPTR increases by 15.14%. [ABSTRACT FROM AUTHOR]

In this investigation, the response surface methodology is implemented to analyze the influences of high and low pressure of the compressor, frequency and waiting time of the rotary valve on the cooling capacity and COP of Gifford-McMahon (GM) cryorefrigerator. A one-dimensional numerical model based on finite volume discretization method (FVM) of the governing equations is employed to calculate the cooling capacity and COP of the Gifford-McMahon cryorefrigerator. Analysis of variance (ANOVA) is performed to visualize the impact of the aforementioned input parameters on both cooling capacity and COP. Finally, the particle swarm optimization (PSO) method is opted to optimize the regression equations so obtained from the response surface analysis, to maximize the cooling capacity and COP of the Gifford-McMahon cryorefrigerator. Results reveal that both COP and cooling capacity are not able to produce maximum performance at a particular combination of those input parameters. At a lower pressure ratio, the COP is maximum, while at a higher pressure ratio the cooling capacity is maximum. Furthermore, at a nominal value of waiting time, the cooling capacity is maximum and a higher value of waiting time the COP is maximum. It is observed that, after optimizing the parameters by PSO, the cooling power increases by 11.3% and COP increases by 6.43%. [ABSTRACT FROM AUTHOR]

The nonradiative rate in 3-aminoquinoline is found to exhibit anomalous solvent dependence, being rather fast in nonpolar solvents and remarkably slower in more polar and especially, more protic ones. The cause of such behavior is investigated by studying the dependence of fluorescence spectral and temporal parameters on the solvent properties such as polarity and hydrogen bonding ability. Complementary quantum mechanical calculations have been performed and the picture that emerges from these studies is that of an excited state with a short radiative lifetime due to the flipping of the amino group. This state is selectively populated in nonpolar, nonhydrogen bonding solvents, but is destabilized with respect to the more polar intramolecular charge transfer (ICT) state in polar solvents and even more so in protic solvents and dimethylsulfoxide. The slower nonradiative rates in the ICT state is attributed to the more restricted motion of the amino group in this state. The role of hydrogen bonding of the amino group and the ring nitrogen in stabilization/destabilization of the ICT state and therefore on the nonradiative rate is also explored. [ABSTRACT FROM AUTHOR]

Abstract Differential co-expression is a cutting-edge approach to analyze gene expression data and identify both shared and divergent expression patterns. The availability of high-throughput gene expression datasets and efficient computational approaches have unfolded the opportunity to a systems level understanding of functional genomics of different stresses with respect to plants. We performed the meta-analysis of the available microarray data for reoviridae and sequiviridae infection in rice with the aim to identify the shared gene co-expression profile. The microarray data were downloaded from ArrayExpress and analyzed through a modified Weighted Gene Co-expression Network Analysis (WGCNA) protocol. WGCNA clustered the genes based on the expression intensities across the samples followed by identification of modules, eigengenes, principal components, topology overlap, module membership and module preservation. The module preservation analysis identified 4 modules; salmon (638 genes), midnightblue (584 genes), lightcyan (686 genes) and red (562 genes), which are highly preserved in both the cases. The networks in case of reoviridae infection showed neatly packed clusters whereas, in sequiviridae, the clusters were loosely connected which is due to the differences in the correlation values. We also identified 83 common transcription factors targeting the hub genes from all the identified modules. This study provides a coherent view of the comparative aspect of the expression of common genes involved in different virus infections which may aid in the identification of novel targets and development of new intervention strategy against the virus. Highlights • The present work describes the potential of differential co-expression approach. • Our study provides a detailed procedure of computational methods combined to get insight into gene expression profiles. • Virus infection has not been studied much in the form of meta-analysis till date. • The present study identified important transcription factors and genes in the virus infected rice. [ABSTRACT FROM AUTHOR]

Highlights • Drying of capillary porous media using Lattice Boltzmann Method. • Dynamic invasion patterns during of capillary porous media. • Simulating the effect of void space intersections, i.e. representation of Haines Jumps. • Effect of sharp edges in the porous media found to entrap liquid and rate of invasion. • First of its kind in simulating drying of capillary porous media using Lattice Boltzmann Method. Abstract Drying of capillary porous media involves coupled heat and mass transfer in complex void space geometry, which makes it very difficult to model and simulate invasion patterns. Thus far, modeling of drying was done using either continuum methods or pore network models (PNM), both of which have some limitations on representing the geometry of void space and underlying transport mechanism. Pore network models were in general applied to reconstructed void space, therefore, dynamic invasion patterns, cluster formations and dependency on drying kinetics may not be accurate. Alternatively, Lattice Boltzmann Method (LBM) is ideal for simulation of drying in capillary porous media as it can incorporate complex effects in a simple and natural way. In this work, the Lattice Boltzmann Method (LBM) using Shan Chen multiphase representation is used to simulate invasion patterns during the drying of four different void space computation domains, differing in both pore and throat geometries. The dynamics of invasion patterns and cluster formation were captured in all four computation domains. Due to the complex geometries present in porous media, capillary instabilities are often observed which leads to sudden jumps in the fluid-fluid interface. In this work, the effects of such instabilities on the liquid distribution are studied. The invasion patterns are compared to identify the dependence of capillary instabilities on the pore structure. It was observed that fluid-fluid interface motion could be classified into two types- evaporation-diffusion invasion, which constituted of slow invasion of voids by diffusion, and Haines jumps, which involved fast invasion of voids due to capillary instabilities. It was observed that some types of porous media exhibited an abundance of the former, particularly in irregular pore structures. However, regular pore structures showed a combination of both evaporation-diffusion invasions and Haines jumps. Lastly, it was observed that the rate of invasion of pores depends on its structure. Pores with sharp edges take a considerably longer period to invade due to a liquid holdup at the edges. This work emphasizes the advantages of using the LBM to simulate the drying of porous media for complex regular/irregular geometries. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Slug-flow range & Mass Transfer rates are dependent on channel diameter & geometry. • Flow rates of liquid pairs governs mass transfer coefficient. • Enhanced Mass Transfer in Microdomain. • Helical channel- the best option for higher mass transfer & slug-flow range. • Optical microscopy employed to visualize the flow dynamics. Abstract An exhaustive study of various flow patterns that occurs in liquid-liquid flow along with detailed mass transfer study in micro-domain has been presented. Experimental studies on mass transfer have been performed using a hydrocarbon phase (toluene) from which extraction of acetic acid was done using water as a solvent in co-current flow. The same liquid-liquid systems (toluene-acetic acid-water) have been used for flow pattern study. Two channel diameters (0.15 mm and 0.25 mm) have been considered in the study with three different microchannel geometries, i.e. straight channel, helical channel and a gradual 90-degree bend. The microchannels used in this study are developed by the non-lithographic method. The present study unravels various flow patterns and their transitions in such small diameter microchannels with very high enhancement in mass transfer rates. The range of flow rates is varied from 10 to 90 μ L/min and mass transfer co-efficients are obtained in the range of 0.0053 – 0.7952 s−1 for all channel geometries. The Reynold number mixture for all the flowrates have been evaluated and it varies from 7 to 50 which clearly indicates that the flow lies in the laminar regime. The study may find useful application in pharmaceutical and fine-chemical industries. [ABSTRACT FROM AUTHOR]

Nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs), the first line of defense, are the cytosolic pattern recognition receptors (PRRs) that regulate the inflammatory activity in response to invading pathogens. NLRs are the members of AAA+ ATPase superfamily that comprises of N-terminal EBD(s), a centrally positioned NOD/NACHT and varying range of LRRs towards the C-terminal end. Due to the lack of structural data, the functional aspects of NLRP-signaling mechanism, which includes pathogen recognition, nucleotide-binding, and sensor-adaptor-effector interactions, are not fully understood. In this study, we implemented structural bioinformatics approaches including protein modeling, docking, and molecular dynamics simulations to explore the structural-dynamic features of ADP-/ATP-Mg2+ binding in NLRPNACHT models. Our results indicate a similar mode of ATP-Mg2+ binding in all NLRPNACHT models and the interacting residues are found consistent with reported mutagenesis data. Accompanied by the key amino acids (proposed to be crucial for ATP-Mg2+ coordination), we further have noticed that some additional conserved residues (including ‘Trp’ of the PhhC motif, and ‘Phe’ and ‘Tyr’ of the GxxxxRxxF motif) are potentially interacting with ATP during dynamics; which require further experimentation for legitimacy. Overall, this study will help in understanding the ADP-/ATP-Mg2+ binding mechanisms in NLRPs in a broader perspective and the proposed ATP-binding pocket will aid in designing novel inhibitors for the regulation of inflammasome activity. [ABSTRACT FROM AUTHOR]

The search for a cost-effective fabrication method for cross-linked polydimethylsiloxane (PDMS) based microreactors remains an attractive area of research. In this work, a simple and cost-effective method for fabricating microchannel with different geometrical configurations such as straight, helical and straight channel with gradual 90° bend has been offered. In order to construct the microchannels slender copper wire of 0.21 mm diameter has been planted inside a block of PDMS and then it has been easily drawn out by applying a little tensile force. Two different types of inlet sections (L and T types) have been constructed for each type of microchannel. Moreover, detailed flow visualization studies (flow patterns) using a biphasic system, toluene-water-acetic acid have been performed for straight and helical microchannels for mass transfer application. The flow patterns have been observed by varying a wide range of inlet velocities of both the phases from 0.0079 to 0.047 m/s. The effect of surface and viscous forces are dominant over other forces such as inertia and gravity, which is evident from the range of slug flow in both the microchannels. The overall volumetric mass transfer coefficient is found to be in the range of 0.06–0.6 s −1 , which is significantly higher than the reported results. This copper wire-based non-lithographic technique is flexible and convenient in comparison with conventional lithographic methods and may enable the production of miniature components for chemical and biochemical systems, involving continuous flow systems usually comprising of two or more phases. [ABSTRACT FROM AUTHOR]

Black gram (Vigna mungo) seeds are a rich source of digestible proteins, however, during storage these seeds are severely damaged by bruchids (Callosobruchus spp.), reducing seed quality and yield losses. Most of the cultivated genotypes of black gram are susceptible to bruchids, however, few tolerant genotypes have also been identified but the mechanism of tolerance is poorly understood. We employed Suppression Subtractive Hybridization (SSH) to identify specifically, but rarely expressed bruchid egg induced genes in black gram. In this study, Suppression Subtractive Hybridization (SSH) library was constructed to study the genes involved in defense response in black gram against bruchid infestation. An EST library of 277 clones was obtained for further analyses. Based on CAP3 assembly, 134 unigenes were computationally annotated using Blast2GOPRO software. In all, 20 defense related genes were subject to quantitative PCR analysis (qPCR) out of which 12 genes showed up-regulation in developing seeds of the pods oviposited by bruchids. Few major defense genes like defensin, pathogenesis related protein (PR), lipoxygenase (LOX) showed high expression levels in the oviposited population when compared with the non-oviposited plants. This is the first report on defense related gene transcript dynamics during the bruchid-black gram interaction using SSH library. This library would be useful to clone defense related gene(s) such as defensin as represented in our library for crop improvement. [ABSTRACT FROM AUTHOR]

The effect of a defect concentration-modified top electrode on the bipolar resistance switching of transparent Al-doped ZnO/ZnO/ITO [AZO(TE)/ZnO/ITO(BE)] devices was investigated. Different oxygen vacancy concentrations in the top electrode, Al-doped ZnO, can be simply controlled by modulating the sputtering working pressure condition from 1.2 to 12 mTorr. The oxygen vacancy concentration between AZO and ZnO may trigger oxygen diffusion at the interface and affect the switching characteristic. High oxygen release from a ZnO resistive layer caused by excessive oxygen vacancy concentration at the top electrode is responsible for reducing the memory window as a result of reduced oxygen available to rupture the filament. Top electrode based on lower oxygen vacancy concentration has a higher memory window and an asymmetric resistive switching characteristic. However, all set of devices have excellent endurance of more than 10 cycles. This study showed that an Al-doped ZnO top electrode helps not only to achieve a transparent device but also to enhance memory properties by providing a suitable oxygen vacancy concentration. [ABSTRACT FROM AUTHOR]

The influence of single and double forming on the switching stability of AZO/ZnO1-x/ITO transparent resistive memory devices was investigated. Devices that underwent single forming exhibited severe switching instability, where as those that underwent double forming exhibited excellent switching uniformity. The quantity of conducting filaments can be limited by applying the two-step forming process. Consequently, the set/reset process can be controlled, enhancing switching stability. Satisfactory endurance with an acceptable ON/OFF ratio of 10² and satisfactory retention behavior of 104s at room temperature confirmed the reliability of optimized devices. Furthermore, highly transparent devices (transparency of approximately 85% in visible range) have been fabricated. [ABSTRACT FROM AUTHOR]

The influence of single and double forming on the switching stability of AZO/ZnO1-x/ITO transparent resistive memory devices was investigated. Devices that underwent single forming exhibited severe switching instability, where as those that underwent double forming exhibited excellent switching uniformity. The quantity of conducting filaments can be limited by applying the two-step forming process. Consequently, the set/reset process can be controlled, enhancing switching stability. Satisfactory endurance with an acceptable ON/OFF ratio of 10² and satisfactory retention behavior of 104 s at room temperature confirmed the reliability of optimized devices. Furthermore, highly transparent devices (transparency of approximately 85% in visible range) have been fabricated. [ABSTRACT FROM AUTHOR]

Large cooling capacity single-stage GM cryocoolers are in an enormous demand in their widespread application domains like cooling of high-temperature superconducting magnets, cryopumps, etc., nevertheless, their efficiency needs to be enhanced considerably for industrial purposes. A mathematical model is considered to be a reliable guide for the performance optimization of GM cryocooler, as it demonstrates the complex physical processes happening inside gas chambers to generate the cooling effect. In this paper, thermodynamic analysis and gas dynamic studies of a single stage mechanical drive and pneumatic drive GM cryocooler is conducted. Influence of the quiet time on the performance parameters of both types of cryocooler is demonstrated. Pressure-volume diagrams are drawn at the expansion chamber of both mechanical drive and pneumatic drive GM cryocoolers to explain the thermodynamic processes. The reason for the deviation of theoretical model pressure-volume plot from ideal pressure-volume plot is elaborated. The flow characteristics of the rotary valve on the performance parameters have been investigated. It is revealed that, the P-V power at the expansion chamber of both types GM cryocooler decreases with rise in the quiet time. However, with an increase in the quiet time, the specific cooling power of GM cryocooler increases up to certain extent. An experimental investigation is performed on a pneumatic drive GM cryocooler to substantiate the theoretical results. • Thermodynamic aspects of both mechanical drive and pneumatic drive GM cryocooler are investigated. • A mathematical model is adopted to illustrate the displacer dynamics of both types of GM cryocoolers. • The influence of quiet time on the performance characteristics of both cryocoolers is examined. • A portable vacuum chamber and GM cryocooler are built and experimental investigation is conducted. • The building procedure of the physical model of the pneumatic drive GM cryocooler is elaborated. [ABSTRACT FROM AUTHOR]

Cellulase reduces silver ions in both aqueous and methanolic media yielding stable narrow-sized silver nanoparticles (Ag-NP) at room temperature. The synthesized nanoparticles have been characterized by various spectroscopic, microscopic methods. The redox potentials of tyrosine residues and protein backbone play an instrumental role to reduce the metal ions. The average size of nanoparticles formed in aqueous medium is of 5.04 ± 3.50 nm. Post-synthesis of Ag-NP secondary structure of enzyme is completely lost whereas upon incubation with chemically synthesized Ag-NP a significant gain in secondary structure is observed. Cellulase as a capping ligand stabilizes the silver nanoparticles even in methanol. [ABSTRACT FROM AUTHOR]

Numerous metal-insulator-metal systems demonstrate electrically induced resistive switching effects and have therefore been proposed as the basis for future nonvolatile memories. They combine the advantages of flash memories and dynamic random access memories while avoiding their drawbacks, such as operation speed, power consumption and device integration and scalable issues. The RRAM devices primarily operate at different resistance values to store the digital data and can keep the resistance state without any power supply. Recent advances in the understanding of the resistive switching mechanism are explained by a thermal or electrochemical redox reaction near the interface between the oxide and the top active metal electrode. Here we review the ongoing research and development activities on the perovskite based resistive switching memory devices. The possible switching mechanisms for the resistive switching are described. The effects of crystal structure, dopants, doping concentrations, annealing temperature, device structures and thickness of the active oxide layer on the resistive switching characteristics and consequently the memory performances are also discussed. From this insight, we take a brief look into different effect on the switching of the perovskite material systems. [ABSTRACT FROM AUTHOR]

• One-dimensional numerical simulation of an inertance pulse tube cryocooler is performed. • The influence of gas axial heat conduction on the oscillating flow behaviour is evaluated. • The effect of thermal dispersion in porous media and turbulent conduction in turbulent flow regimes are considered with the help of gas-axial-conduction-enhancement factor. • It is seen that the gas-axial-conduction-enhancement factor creates a phase shift in all oscillating physical quantities at all locations. • It is also noticed that inclusion of gas axial conduction enhancement factor produces an adverse effect on the refrigeration process of the cryocooler. Most one-dimensional simulation models developed so far to estimate the theoretical performance of pulse tube cryocoolers ignore the effect of heat loss arising out of thermal dispersion in porous media and turbulent conduction in pipes. In this paper one-dimensional numerical simulation of an inertance type pulse tube cryocooler has been carried out to illustrate the effect of thermal dispersion and turbulent conduction on the oscillating gas flow and heat transfer behavior. The study has been conducted under three conditions: simulation of cryocooler without considering gas axial heat conduction effects, simulation of cryocooler with gas axial heat conduction but neglecting the influence of thermal dispersion and turbulent conduction, and simulation of the cryocooler with gas axial heat conduction including the influence of thermal dispersion and turbulent conduction. The effect of thermal dispersion and turbulent conduction in the gas phase has been expressed in terms of an axial-conduction-enhancement-factor in the gas energy equation. It is revealed that the inclusion of axial-conduction enhancement factor in the porous media and tubes of the pulse tube cryocooler creates a positive phase shift in all oscillating physical quantities. This phase change causes an adverse effect on the cooling mechanism of the pulse tube cryocooler. It is found that, the coefficient of performance decreases by 8.6% and the minimum cooling temperature increases by 6.67% when the axial-conduction enhancement factor is included in the one-dimensional simulation model. [ABSTRACT FROM AUTHOR]

Abstract: The endogenous small non-coding functional microRNAs (miRNAs) are short in size, range from ~21 to 24 nucleotides in length, play a pivotal role in gene expression in plants and animals by silencing genes either by destructing or blocking of translation of homologous mRNA. Although various high-throughput, time consuming and expensive techniques like forward genetics and direct cloning are employed to detect miRNAs in plants but comparative genomics complemented with novel bioinformatic tools pave the way for efficient and cost-effective identification of miRNAs through homologous sequence search with previously known miRNAs. In this study, an attempt was made to identify and characterize conserved miRNAs in garlic expressed sequence tags (ESTs) through computational means. For identification of novel miRNAs in garlic, a total 3227 known mature miRNAs of plant kingdom Viridiplantae were searched for homology against 21,637 EST sequences resulting in identification of 6 potential miRNA candidates belonging to 6 different miRNA families. The psRNATarget server predicted 33 potential target genes and their probable functions for the six identified miRNA families in garlic. Most of the garlic miRNA target genes seem to encode transcription factors as well as genes involved in stress response, metabolism, plant growth and development. The results from the present study will shed more light on the understanding of molecular mechanisms of miRNA in garlic which may aid in the development of novel and precise techniques to understand some post-transcriptional gene silencing mechanism in response to stress tolerance. [Copyright &y& Elsevier]

One-dimensional (1D) zinc oxide (ZnO) nanostructures have been extensively and intensively studied for several decades not only for their extraordinary chemical and physical properties, but also for their current and future different electronic and optoelectronic device applications. This review provides a brief overview of the progress of different synthesis methods and applications of 1D-ZnO nanostructures. Morphology of ZnO nanostructures grown by various methods and progress in the optical properties are briefly described. Using low-temperature photoluminescence (LTPL) study, detailed informations about the defect states and impurity of such nanostructures are reported. Improvement of field emission properties by modifying the edge of 1D-ZnO nanostructures is briefly discussed. Applications such as different sensors, field effect transistor, light-emitting diodes (LEDs), and photodetector are briefly reviewed. ZnO has large exciton binding energy (60 meV) and wide band gap (3.37 eV), which could lead to lasing action based on exciton recombination. As semiconductor devices are being aggressively scaled down, ZnO 1D nanostructures based resistive switching (RS) memory (resistance random access memory) is very attractive for nonvolatile memory applications. Switching properties and mechanisms of Ga-doped and undoped ZnO nanorods/NWs are briefly discussed. The present paper reviews the recent activities of the growth and applications of various 1D-ZnO nanostructures for sensor, LED, photodetector, laser, and RS memory devices. [ABSTRACT FROM AUTHOR]

Nickel nanocrystals (NCs) embedded flash memory structure with SiO2tunnelling and pulsed laser deposition grown Al2O3blocking oxide is reported here. The post-deposition thermal annealing of an ultrathin (∼5 nm) nickel film evaporated on thermally grown SiO2tunnelling barrier has been performed to form the nickel NCs. The formation of tiny nickel NCs is confirmed from the high-resolution transmission electron microscope micrographs. The electrical capacitance–voltage (C–V) characteristics of the optimised 1000°C, 5 min annealed sample shows a large memory window of 20 V at ±20 V sweeping voltage. The charge storage properties are found to be significantly improved as compared to control samples. The frequency dependent C–V measurements indicate the dominant charge trapping in Ni NCs, making the memory structure attractive for use in future nanoscale high-performance applications. [ABSTRACT FROM PUBLISHER]

Abstract: In the advancement of complementary metal-oxide-semiconductor device technology, SiO2 was used as an outstanding dielectric and has dominated the microelectronics industry for the last few decades. However, with the recent size downscaling, ultrathin SiO2 is no longer suitable. ZrO2 has been introduced as a high-k dielectric to replace SiO2. This paper reviews recent progress of ZrO2 thin films as dielectric layers for volatile dynamic random access memory (DRAM) applications and as a gate dielectric for CMOS devices. Materials and electrical properties of ZrO2 films obtained by different deposition methods are compared. The effects of different top and bottom electrodes, and different doping elements, on ZrO2 dielectric properties are described. Applications discussed include the use of ZrO2 in Ge and SiGe nanocrystal-embedded nonvolatile flash memory devices. ZrO2 films as charge trapping layers in SOZOS (poly-Si/SiO2/ZrO2/SiO2/Si) and TAZOS (TaN/Al2O3/ZrO2/SiO2/Si) based nonvolatile flash memory stacks, and bipolar, unipolar, and nonpolar ZrO2-based resistive switching memory devices are also briefly discussed. The impact of electrode materials, metal nanocrystals, metal implantation, metal doping, metal layers, and oxide ion conductor buffer layer on resistive switching properties and switching parameters of emerging ZrO2-based resistive switching memory devices for high speed, low power, nanoscale, nonvolatile memory devices are briefly reviewed. A roadmap of the applications of ZrO2 thin film in future low power, nanoscale microelectronic device applications is realized from this review. [Copyright &y& Elsevier]

Abstract: The rate and extent of photoinduced electron transfer change significantly as a result of confinement in nanovolumes. Study of such processes is an active area of research in physical chemistry. The effect is most interesting when the molecules that participate in PET are charged. In the present article, the modulation of PET has been studied for two anionic fluorophores: Lucifer Yellow CH and chlorin p6 with Methylviologen dication. PET, manifested in the quenching of fluorescence of the fluorophores, has been modulated by incorporating the molecules in organized assemblies like micelles, reverse micelles and supramolecular hosts. The dynamics of the process has been monitored in the femtosecond to nanosecond timescale. The modulation of the electron transfer has been found to be occurring mainly due to the disruption of contact ion pairs formed between the fluorophores and the quencher. [Copyright &y& Elsevier]

Metalloregulators regulate transcription In response to metal ions. Many studies have provided insights into how transcription is activated upon metal binding by MerR-family metalloregulators. In contrast, how transcription is turned off after activation is unclear. Turning off transcription promptly is important, however, as the cells would not want to continue expressing metal resistance genes and thus waste energy after metal stress is relieved. Using single-molecule FRET measurements we studied the dynamic interactions of the copper efflux regulator (CueR), a Cu+-responsive MerR-family metalloregulator, with DNA. Besides quantifying its DNA binding and unbinding kinetics, we discovered that CueR spontaneously flips its binding orientation at the recognition site. CueR also has two different binding modes, corresponding to interactions with specific and nonspecific DNA sequences, which would facilitate recognition localization. Most strikingly, a CueR molecule coming from solution can directly substitute for a DNA-bound CueR or assist the dissociation of the incumbent CueR, both of which are unique examples for any DNA-binding protein. The kinetics of the direct protein substitution and assisted dissociation reactions indicate that these two unique processes can provide efficient pathways to replace a DNA-bound holo-CueR with apo-CueR, thus turning off transcription promptly and facilely. [ABSTRACT FROM AUTHOR]

Resistive switching behavior of the Ti/HfO2:NiSi:HfO2/Pt memory structure is investigated. Auger electron spectroscopy analysis indicates no metal diffusion from the electrodes and silicide layer on high-k film. Cross-sectional transmission electron microscopic micrographs revealed the thicknesses of the HfO2 and silicide layer. Significant decrease of forming voltage is observed for the 550 °C, 1 min annealed device embedded with nickel silicide (NiSi) layers. Entire device shows bipolar switching properties with very low set/reset voltage. The optimized annealed device with NiSi embedded layer exhibits improved memory performances such as good on/off ratio (>102), long retention more than 104 s, and reasonable endurance (>103 cycles). A conducting filament model based on two stacks structure is employed to well explain the switching behaviors. [ABSTRACT FROM AUTHOR]

Abstract: Electronic absorption and fluorescence spectroscopic techniques reveal that the pKb for neutral form (N) of 3-aminoquinoline (3AQ) is 5–5.7, in the ground as well as the first electronically excited state. However, the case is quite different for the second pKb, involving the monocation and the dication. The emissive state is found to be monocationic, even in highly acidic conditions and in nafion membrane, where the ground state of the molecule is predominantly dicationic. This indicates that the dication loses a proton in its electronically excited state, possibly due to the delocalization of the lone pair on the amino nitrogen atom over the ring, due to an intramolecular charge transfer. The pKb values have been computed using density functional theory (DFT) for the equilibria of neutral⇆monocation and monocation⇆dication respectively and found to be reasonably in good agreement with the experimental observations. [Copyright &y& Elsevier]

Ternary cobalt-nickel silicide/n-Si Schottky diodes have been fabricated by sputtering using an equiatomic cobalt-nickel alloy target. A minimum sheet resistivity of the ternary silicide is found to be 5-7 Ω/sq. Grazing-incidence X-ray diffraction shows the formation of ternary silicide phases. Cross-sectional TEM micrograph shows a fairly uniform diffusion of metals into Si with the formation of fully silicided film. Selected-area electron diffraction pattern exhibits the crystalline nature of the silicide layer. Temperature-dependent electrical current-voltage measurements have been used to characterize an optimized Schottky diode formed by annealing at 450 °C. The room-temperature barrier height and ideality factor are found to be 0.656 eV and 1.6, respectively, from the I-V characteristics. The series resistance of the diode has been calculated and is found to be 1-11.8 Ω The variation of barrier height has been attributed to the inhomogeneity in Schottky junction. [ABSTRACT FROM AUTHOR]

Abstract: The interactions of epicocconone with two supramolecular hosts, α- and β-cyclodextrin have been investigated using fluorescence spectroscopic techniques. 1:1 and 1:2 complexes formed with both the cyclodextrins are marked by the enhancement of fluorescence of epicocconone. A significantly greater fluorescence enhancement is observed with α-CD than with β-CD. This observation fortifies the contention that microviscosity has a significant influence on the excited state dynamics of epicocconone, as the space available for the fluorophore within its complex with α-CD is significantly lesser than that available in its complexes with β-CD, even though the fluorophore is shielded from water in both the cases. [Copyright &y& Elsevier]

Synchronous fluorescence and time-resolved fluorescence spectroscopic studies that reveal the interaction of epicocconone with human serum albumin is significantly different from its interaction with surfactant assemblies. This observation, along with steady-state fluorescence data, indicates ground-state interaction between the fluorophore epicocconone and the protein. Similarity in fluorescence properties with the adduct of the fluorophore with n-butylamine indicates that bonding occurs at the N-terminus of the protein. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of the fluorescent probe 3-phenylureidoquinoline with surfactant assemblies has been investigated using fluorescence spectroscopic and computational techniques. The non-radiative deactivation rates are found to be suppressed in micelles. In the negatively charged SDS micelle, the cation is found to form, leading to a marked shift in fluorescence. This is explained by a consideration of the local pH and altered pK a of the fluorophore. In reverse micelle the gradual addition of water remarkably enhances the rate of non-radiative depopulation. [Copyright &y& Elsevier]

Abstract: This is a computational study of 2-(2′-pyridyl)benzimidazole (2PBI), which has experimentally been found to undergo an excited state proton transfer (ESPT) in the protonated form. In this Letter, the structures of the different forms of this fluorophore have been optimized and CIS calculations have been performed in order to investigate the corresponding excited states. The results help explain some of the experimental observations made earlier by our group as well as by others. [Copyright &y& Elsevier]

• Shan Chen Lattice Boltzmann Method (SC LBM) for multiphase representation of drying in capillary porous media. • First of its kind to employ LBM to showcase micro–macro interactions during drying of porous media. • The mechanistic description of micro-scale-dynamics such as capillary pumping, film flow and Haines jumps. • Effect of Péclet number and size distribution on invasion patterns and drying kinetics. • Hydrodynamics of film flows and film classification i.e. hydraulic film and adsorbed film. The fundamental understanding of the multiphase phenomena involved in drying of porous media is still a challenging task. Pore network models (PNMs) reveal the micro–macro interactions. However, PNMs have shortfalls in using true geometry, and in revealing capillary instabilities and film-effects. In this work, Shan Chen representation of Lattice Boltzmann Method (LBM) is applied to elucidate such complicated multiphase phenomena, i.e. micro-scale-dynamics evolution during drying. In a bundle of capillaries, liquid transport is explained with two pressure gradients. First, the pressure gradient between capillaries leading to capillary pumping, second, the pressure gradient within each capillary along the liquid–gas interface resulting in formation of hydraulic films. Transformation of hydraulic films to adsorbed films is revealed in irregular pore structures. Péclet number is employed to elucidate the effect of boundary layer thickness and temperature on drying kinetics. Characteristics of drying are re-established using the LBM for pore structures with bimodal size distribution. [ABSTRACT FROM AUTHOR]

The drying phenomena of an initially filled perfectly wetting liquid in a square internal cross-sectional tube are studied. The conditions are such that the liquid films develop along the tube internal corners under the effect of capillary forces until the bulk meniscus recedes in the tube. In this work, the Shan-Chen Lattice Boltzmann method (SC-LBM) is implemented to elucidate the complex multiphase phenomena involved in the isothermal drying of the square capillary tube. The SC-LBM is validated with Stefan-Maxwell diffusion relation and the simulated drying kinetics are in very good agreement with the commonly observed drying phenomena, which are the constant rate period (CRP) followed by the falling rate period (FRP). The computed capillarity along the liquid-gas interface at the internal corners of the tube results in the formation of extended corner films and surface films. Further, the pinning and the depinning phenomena as well as the variations of the corner film width are studied in detail. Based on the roughness factor of the tube, the characteristics of drying kinetics are studied and compared with the smooth square capillary tube. [ABSTRACT FROM AUTHOR]

In this study, the influences of flow control characteristics of a flow control valve (either a rotary valve or electrically operated solenoid valves) on the refrigeration performance of a GM cryocooler is investigated numerically. A rotary valve is a flow control device that generates the pressure wave in association with the helium compressor for a GM cryocooler. A one-dimensional numerical model based on nodal analysis is developed with suitable initial and boundary conditions to capture the inside flow physics of the single stage GM cryocooler. By using the numerical model, the effect of the waiting period, opening angle differences of high and low-pressure valves on the refrigeration capacity and COP of the cryocooler is studied. It is perceived that both cooling power and COP are unable to dispense the best performance at a particular waiting period. COP is able to attain its maximum value at about 70° of waiting period whereas, refrigeration capacity is maximum at about 10° of the waiting period. • A one-dimensional numerical model is developed to compute the performance of GM cryocooler. • Effect of waiting time on cooling power and COP is studied. • Effect of opening angle difference between HPV and LPV of rotary valve on cooling power and COP is studied. [ABSTRACT FROM AUTHOR]

Stirling pulse tube cryocoolers (PTC) are widely used in aerospace applications for the cooling of infrared sensors and for filtering background thermal noise in the astro-imaging devices, etc. Present investigation aims to use numerical methods to demonstrate the nonlinear fluid flow, heat transfer, and vortex generation phenomena in a two-stage coaxial type inertance pulse tube cryocooler. The numerical simulation is conducted using commercially available Fluent® code for both single-stage and multi-stage configurations to show nonlinear processes with varying heat load conditions. It has been noticed that the width of the vortex produced inside the pulse tube grows with an increase in heat load capacity. This undesirable flow conditions yields an adverse effect in the cooling behavior and reduces overall performance of cryocooler with higher heat load. Additionally, streamlines, stream function, pressure and temperature variation plots are given for both stages with different heat load capacity to substantiate our results. [ABSTRACT FROM AUTHOR]