Transition-zone models for 2-dimensional boundary layers: A review

Models for the laminar-turbulent transition zone have in recent years become increasingly important, especially in technological applications where the design is driven by peak heat-transfer rates or extensive regimes of laminar or transitional flow. Models in current use can be classified into three types, namely linear-combination, algebraic and differential. The first type based on the principle of combining mean laminar and turbulent velocities, in proportions determined by the intermittency, is shown to be both successful and relatively easy to implement, especially if recent improvements in estimating turbulent spot formation rates and ideas concerning the possibility of sub-transitions within the transition zone are incorporated. Algebraic models, where the eddy viscosity is released by the intermittency, and differential models involving fairly elaborate schemes for determining the kinetic energy of turbulent fluctuations and their length scale, are found to require further development for handling flows with large pressure gradients. The authors wish to express their appreciation to Prof. A Prabhu for support through the project ‘Transition and turbulence in shear flows’ sponsored by the Department of Science and Technology.     

Pluronic‐based dual‐stimuli sensitive polymers capable of thermal gelation and pH‐dependent degradation for in situ biomedical application

Thermo‐sensitive hydrogels are considered ideal for applications in the biomedical fields for their biocompatibility, flexibility, tissue‐like water content, and reversible gelation property. By adjusting sufficient hydrophilic–hydrophobic balance in block copolymer structure, thermogel's critical gelation temperature (CGT) can be modified to be near the physiological temperature, which makes it an appealing candidate for in situ gel depot. In this study, we report successful syntheses of novel multiple block copolymer compounds, denoted as dual‐stimuli sensitive polymers (DSSPs), by copolymerizing Pluronic P104 (7100 Da) and 2,2‐bis(aminoethoxy)propane (BAP) using diisocyanate linkers, l ‐lysine ethyl ester diisocyanate (DSSP‐1), and 1,6‐hexamethylene diisocyanate (DSSP‐2). Through effective elongation of polymer chain lengths (DSSP‐1: 41,760 Da, DSSP‐2: 41,230 Da), Pluronic P104's reversible thermal gelation properties were enhanced, as demonstrated by lowered CGTs (DSSP‐1: 36 °C, DSSP‐2: 38.7 °C; 15 wt %) that is near the physiological temperature. Furthermore, integration of acid‐labile BAP allowed rapid pH‐dependent degradation of the polymer, which was displayed by gel permeation chromatography and release profiles of nile red and irinotecan from polymeric micelles and gels, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46552.     

Molding and casting behavior of ferro chrome slag as a mold material in ferrous and non-ferrous foundry industries

In the present investigation, efforts are made to use Ferro Chrome (Fe-Cr) slag as a mold material for the replacement of silica sand in the foundry industry. The sodium silicate-Fe–Si process is adopted for evaluating the same. The process parameters considered for this investigation are % of sodium silicate, % of Fe–Si powder as a binder, and mold setting time. A series of sand tests are carried out on sand, slag individually, and for various combinations of these two. Three types of molds are made with sand, slag individually, and combination of these two with 6% sodium silicate and 1.5% Fe–Si. Various ferrous and non-ferrous castings are performed on these newly developed slag molds. The results reveal that the Fe-Cr slag with mold permeability, compression, and shear strength is a suitable candidate for either partial or full replacement of silica sand. During casting neither fusing, dripping, nor collapse of the mold walls is observed in slag molds; this is true for both ferrous and non-ferrous castings. Castings with good surface finish and no surface defects are made by slag molds. Faster heat transfer in slag molds enable to obtain castings with enhanced metallurgical and mechanical properties.     

A preliminary study of the effect of urea in the preservation of meat

An investigation was undertaken on the effect of urea in the preservation of meat. It was observed that there was always a lag period in the early stages of microbial spoilage of meats at different temperatures, due to the non-availability of required nutrients, and subsequent rapid growth of microorganisms was attributed to the utilisation of amino acids released due to autolytic changes. Dry urea salt was employed in the present study to denature or retard the activity of enzymes of the meat in order to extend the shelflife of meat by preventing spoilage. Parameters such as ERV, pH and TPC were studied during meat spoilage. It appears from the present studies that autolytic changes were responsible for the ultimate spoilage of meat. When urea was applied in the meat, the microbial lag phase and the shelflife of meat were extended. It seems that urea checked the autolytic changes in meat and thereby microbial growth was delayed due to the non-availability of nutrients from the autolytic changes.     

Experimental investigations on the SiO<Subscript>2</Subscript> flux-assisted GTA welding of super-austenitic stainless steels

Analyzed in this paper are barrier properties of wood specimens treated by ball burnishing. For the purpose of experimental investigation, special device was designed which allows continuous monitoring of the volume of water absorbed by specimen within particular time intervals. The device allows water pressurized at 3 bar to efficiently penetrate specimen internal structure over its burnished/non-burnished surface interface. The experimental investigation encompassed six types of wood—beech, acacia, walnut, oak, linden, and ash tree. Comparative analysis was performed to establish relative resistance to water penetration in burnished and non-burnished specimens, as well as the quantities of water volume absorbed over time. The results indicate that ball burnishing is capable of enhancing barrier properties in all of the examined types of wood.     

Enhanced Co-Scheduling: A Software Pipelining Method Using Modulo-Scheduled Pipeline Theory

Instruction scheduling methods which use the concepts developed by the classical pipeline theory have been proposed for architectures involving deeply pipelined function units. These methods rely on the construction of state diagrams (or automatons) to (i) efficiently represent the complex resource usage pattern; and (ii) analyze legal initiation sequences, i.e., those which do not cause a structural hazard. In this paper, we propose a state-diagram based approach for modulo scheduling or software pipelining, an instruction scheduling method for loops. Our approach adapts the classical pipeline theory for modulo scheduling, and, hence, the resulting theory is called Modulo-Scheduled pipeline (MS-pipeline) theory. The state diagram, called the Modulo-Scheduled (MS) state diagram is helpful in identifying legal initiation or latency sequences, that improve the number of instructions initiated in a pipeline. An efficient method, called Co-scheduling, which uses the legal initiation sequences as guidelines for constructing software pipelined schedules has been proposed in this paper. However, the complexity of the constructed MS-state diagram limits the usefulness of our Co-scheduling method. Further analysis of the MS-pipeline theory, reveals that the space complexity of the MS-state diagram can be significantly reduced by identifying primary paths. We develop the underlying theory to establish that the reduced MS-state diagram consisting only of primary paths is complete; i.e., it retains all the useful information represented by the original state diagram as far as scheduling of operations is concerned. Our experiments show that the number of paths in the reduced state diagram is significantly lower—by 1 to 3 orders of magnitude—compared to the number of paths in the original state diagram. The reduction in the state diagram facilitate the Co-scheduling method to consider multiple initiations sequences, and hence obtain more efficient schedules. We call the resulting method, enhanced Co-scheduling. The enhanced Co-scheduling method produced efficient schedules when tested on a set of 1153 benchmark loops. Further the schedules produced by this method are significantly better than those produced by Huff's Slack Scheduling method, a competitive software pipelining method, in terms of both the initiation interval of the schedules and the time taken to construct them.     

Synthesis and characterization of partially crystalline nanosized ZSM-5 zeolites

Partially crystalline nanosize ZSM-5 with high surface area (678 m²/g) was synthesized successfully without using organic template by a two-step temperature process. Aluminum nitrate was used as aluminum source for the first time to synthesize ZSM-5 materials. The presence of MFI structure of the materials was analyzed by XRD, FTIR, Raman spectroscopy and TEM techniques. Addition of commercial HZSM-5 as a seeding agent to the reactants resulted an increase in crystallinity of the ZSM-5 sample and subsequent decrease in specific surface area. The partially crystalline samples exhibited low microporosity and remarkably high meso/macropore volume with pore diameters around 30 nm.