Three dimensional turbulent wall jets

Jets issuing tangentially to an impermeable flat surface from orifices of finite aspect ratio are termed three-dimensional wall jets. The turbulent flow of viscous incompressible fluid associated with such wall jets has been investigated analytically. Results are presented for the wall jets issuing from orifices of various shapes and several aspect ratios. The maximum velocity shows three regions of decay. The potential core region is followed by a characteristic decay region where maximum velocity decays in a manner dependent on the shape and aspect ratio of the orifice. Following this region, there is a radial wall jet type maximum velocity decay region. All three-dimensional wall jets issuing from any arbitrary cross-sectional orifice decay in a similar manner in this radial decay region. The half-velocity width grows faster in the transverse direction than in a direction normal to the flat surface. The analytical results agree reasonably well with existing experimental results.     

Experimental modelling of copper foams processed through powder metallurgy route using a compressible space holder material

The present work is focused on the processing of open cellular copper foams through space holder technique without the use of binders. In this work, moderate pressures were used during the cold compaction of the powders. The main objective was to obtain dense cell walls by limiting the use of binders and use a compressible and lubricant type of space holder material. It has been shown in this study that the use of high compaction pressure helps to decrease/limit the quantity of binder required and this, in turn, yields relatively dense cell walls necessary for better mechanical strength of foams. Using 2N factorial method, mathematical models have been developed to express the final porosity and pore size as functions of the various processing parameters viz compaction pressure, sintering temperature/ time and space holder content. The most significant sintering parameters influencing the porosity and pore size of the processed foams have also been found out.     

Combined sorbent/catalyst media for destruction of halogenated VOCs

Several chromium modified zeolites have been developed and tested for their ability to physisorb chlorinated VOCs (CVOCs) at ambient and then catalytically destroy them at elevated temperatures (ca. 300°C). These dual function materials, which act as both sorbents and catalysts, are believed to be the key to implementing a new energy efficient process for the destruction of low concentration level CVOC streams. Data showing catalytic activity, sorptivity and other physical properties for Y and ZSM-5 zeolites based media are presented. A chromium exchanged ZSM-5 (Cr-ZSM-5) medium which showed superior performance catalytically (> 95% TCE and MeCl₂ destruction at 300°C) and adequate sorption capacity (0.074 g TCE/g sorbent, 0.064 g MeCl₂/g sorbent at 23°C in the presence of humid air) was chosen for subsequent dual function tests. These tests showed that ambient temperature fixed bed sorption of CVOCs followed by periodic heating of the upper portion of the bed to catalytic temperatures (ca. 35°C) with slow temperature ramping of the lower portion to desorb trapped CVOCs, produced a highly energy efficient cyclic process for their destruction. A Cr-ZSM-5 bed, which alternately stored and then destroyed CVOC from a humid 110 ppm TCE stream at a space velocity of 2400 h⁻¹, was shown to operate over a 1460 min cycle which required heating for only 7% of the time.     

Novel Low-Temperature Synthesis of Ferroelectric Neodymium-Doped Bismuth Titanate Nanoparticles

In this study, we report on the synthesis of nanopowders of ferroelectric Bi_3.5Nd_0.5Ti₃O₁₂ ceramic at temperatures below 500°C via a simple chemical method using citric acid as a solvent. The calcined powders were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Heating the as-dried powders in air first leads to crystallization of the Bi₂Ti₂O₇ phase at ∼310°C, followed by crystallization of the perovskite Nd-doped Bi₄Ti₃O₁₂ phase at ∼490°C as suggested by the peaks in the DSC analysis and confirmed by the evolution of phases in XRD patterns of the powders calcined at various temperatures. TEM of particles calcined at 550°C for 1 h in air showed an average particle size of 50–60 nm. The temperature dependence of capacitance of nanopowders calcined at 700°C for 1 h in air showed a Curie temperature of ∼615°C evincing a ferroelectric transition.     

Improved scheduler for multi-core many-core systems

Over the years, presence of heterogeneous system has dominated the area of concurrent job execution. Heterogeneous system is the natural choice as it can be designed with the legacy system. Scheduling, on such systems, is an important activity as it affects the job execution characteristic. Heterogeneity introduces many challenges for the efficient job execution. Heterogeneity in core architecture introduces the possibility of heterogeneous memory architecture in many/multi core heterogeneous system. This makes it often impossible to determine for the same instruction if a high frequency core has low or high memory latency in comparison to the low frequency core and vice-versa. The work proposes an improved scheduler for such systems in which both core and memory are heterogeneous. It defines average effective time ( \(\hbox {AE}_\mathrm{t}\) ) as the base parameter for this purpose. Priorities of each thread (workload) and the core are dynamically generated using \(\hbox {AE}_\mathrm{t}\) for effective mapping. Experimental results, on the benchmark data, reveal that the proposed scheduler performs much better in terms of cores utilization, speedup and efficiency in comparison to other similar models.     

Synthesis of some organic poly(aminium phosphate)s: 4

Poly(aminium phosphate)s were prepared by precipitation from aqueous solution. The composition of these derivatives was established by analysing for nitrogen and phosphorus. Weight average molecular weights were determined by intrinsic viscosity determination. The intrinsic viscosity has been determined by replacing the usual extrapolation of specific viscosity to zero concentration ($\text{η}{}_{\mathrm{<mtext>sp</mtext>}}\text{C}$ vs. CO) with the extrapolation of linear transformation. G = AF + B where $\text{G =}\text{y}\text{α ? x}$, $\text{F =}\text{x}\text{α ? x}$ and α = x_M + x_m (where $\text{y =}\text{η}{}_{\mathrm{<mtext>sp</mtext>}}\text{C}$ and x_m and x_M denote concentration). The values for Huggins constants (k′ + k″) were also calculated and found to be characteristic of linear chain polymers. The R_g values for poly(aminium phosphate)s have been determined in New Ebel's solvent, by a paper chromatographic technique. A linear relationship between degree of polymerization and R_g values is indicative of the linear chain polymeric character of these derivatives. The polyelectrolyte behaviour of these polymers has also been established by conductivity measurements.     

Three-objective subgraph mining using multiobjective evolutionary programming

The existing methods for graph-based data mining (GBDM) follow the basic approach of applying a single-objective search with a user-defined threshold to discover interesting subgraphs. This obliges the user to deal with simple thresholds and impedes her/him from evaluating the mined subgraphs by defining different “goodness” (i.e., multiobjective) criteria regarding the characteristics of the subgraphs. In previous papers, we defined a multiobjective GBDM framework to perform bi-objective graph mining in terms of subgraph support and size maximization. Two different search methods were considered with this aim, a multiobjective beam search and a multiobjective evolutionary programming (MOEP). In this contribution, we extend the latter formulation to a three-objective framework by incorporating another classical graph mining objective, the subgraph diameter. The proposed MOEP method for multiobjective GBDM is tested on five synthetic and real-world datasets and its performance is compared against single and multiobjective subgraph mining approaches based on the classical Subdue technique in GBDM. The results highlight the application of multiobjective subgraph mining allows us to discover more diversified subgraphs in the objective space.     

A new continuous-time formulation for scheduling crude oil operations

In today's competitive business climate characterized by uncertain oil markets, responding effectively and speedily to market forces, while maintaining reliable operations, is crucial to a refinery's bottom line. Optimal crude oil scheduling enables cost reduction by using cheaper crudes intelligently, minimizing crude changeovers, and avoiding ship demurrage. So far, only discrete-time formulations have stood up to the challenge of this important, nonlinear problem. A continuous-time formulation would portend numerous advantages, however, existing work in this area has just begun to scratch the surface. In this paper, we present the first complete continuous-time mixed integer linear programming (MILP) formulation for the short-term scheduling of operations in a refinery that receives crude from very large crude carriers via a high-volume single buoy mooring pipeline. This novel formulation accounts for real-world operational practices. We use an iterative algorithm to eliminate the crude composition discrepancy that has proven to be the Achilles heel for existing formulations. While it does not guarantee global optimality, the algorithm needs only MILP solutions and obtains excellent maximum-profit schedules for industrial problems with up to 7 days of scheduling horizon. We also report the first comparison of discrete- vs. continuous-time formulations for this complex problem.     

Investigations on mechanical and structural aspects of ultrasonic hybrid polymer mixture welding for industrial applications

Two-dimensional C_f/Al composites were fabricated by liquid-solid extrusion following vacuum infiltration technique (LSEVI), and defects were studied and analyzed through optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope(TEM), and the tests of ultimate tensile strength (UTS). Through research, it was found that gas impurities were the main factors to generate hole defects within the 2D-C_f/Al composites, so vacuum level of the test system should be higher than 0.09 MPa. The infiltration of composites would not be sufficient and uniform under the low squeeze pressure of 50 MPa and low squeeze temperature of 590 °C. However, when squeeze pressure was larger than 90 MPa, fiber damage appeared, and macro internal cracks even occurred if it was over 100 MPa. Poor tensile behavior of composites between carbon fibers and matrix might arise because of the inappropriate process parameters. Brittle tensile fracture of composites was observed under the higher preform preheating temperature of 640 °C, and Al₄C₃ was found. Separated fibers and aluminum alloy of tensile fracture might occur under the lower preheating temperature of 580 °C. These defects hindered the improvement of property of C_f/Al composites greatly, and they should be avoided. Through contrast of UTS, internal cracks and poor tensile behavior were the most detrimental factors. Their UTSs were 45 and 117 MPa, respectively, which were less than 120 MPa of matrix. Improved process parameters were used to prepare the 2D-C_f/Al composite, and its defects were seldom found, so UTS of composite was improved 93.3 % than that of matrix.     

Molecular Engineering of Highly Efficient Small Molecule Nonfullerene Acceptor for Organic Solar Cells

A new molecularly engineered nonfullerene acceptor, 2,2′‐(5,5′‐(9,9‐didecyl‐9H‐fluorene‐2,7‐diyl)bis (benzo[c][1,2,5]thiadiazole‐7,4‐diyl)bis (methanylylidene))bis (3‐hexyl‐1,4‐oxothiazolidine‐5,2‐diylidene))dimalononitrile ( BAF‐4CN ), with fluorene as the core and arms of dicyano‐n‐hexylrhodanine terminated benzothiadiazole is synthesized and used as an electron acceptor in bulk heterojunction organic solar cells. BAF‐4CN shows a stronger and broader absorption with a high molar extinction coefficient of 7.8 × 10⁴m ^?1 cm^?1 at the peak position (498 nm). In the thin film, the molecule shows a redshift around 17 nm. The photoluminescence experiments confirm the excellent electron accepting nature of BAF‐4CN with a Stern–Volmer coefficient (K _sv) of 1.1 × 10⁵m ^?1. From the electrochemical studies, the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of BAF‐4CN are estimated to be ?5.71 and ?3.55 eV, respectively, which is in good synchronization with low bandgap polymer donors. Using BAF‐4CN as an electron acceptor in a poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3″′‐di(2‐octyldodecyl) 2,2′;5′,2″;5″,2″′‐quaterthiophen‐5,5″′‐diyl)] based bulk‐heterojunction solar cell, a maximum power conversion efficiency of 8.4% with short‐circuit current values of 15.52 mA cm^?2, a fill factor of 70.7%, and external quantum efficiency of about 84% covering a broad range of wavelength is achieved.