Estimating cell loss rates in high-speed networks with leaky bucket controlled sources

This paper deals with high-speed networks, such as the ATM network, over which data is transferred in cells or packets. Results based on asymptotic analysis of stochastic fluid flow models imply that these networks would have to be run at very low utilization to satisfy the stringent performance requirement of very low cell loss rates. Recent papers have quantified that asymptotic approximations can be quite bad with even a modest number of users sending traffic into the network. In this paper it is shown that two more assumptions in the asymptotic analysis may lead to significant overestimation of the cell loss rates. The more significant of these is the use of the underlying exponential ON durations if sources are policed. The second and less significant is the assumption of an infinite buffer. A new approximate nalytic method is then developed for estimating the cell loss rate with sources policed by a leaky bucket type mechanism. This method focuses directly on the problem of measuring cell losses in the presence of many sources simultaneously bursting in a time period small enough to cause buffer overflow. It turns out to be highly accurate even with some rather drastic simplifying assumptions.     

Hydration of propylene oxide using ion-exchange resin catalyst in a slurry reactor

Kinetics of hydration of propylene oxide using an ion-exchange resin catalyst in a slurry reactor was studied. The kinetics of homogeneous, uncatalyzed reaction was studied separately and used to obtain heterogeneous reaction kinetics. The homogeneous reaction was found to be 0.43 order with respect to propylene oxide concentration. The heterogeneous reaction was found to have intraparticle diffusional resistance under certain conditions. The intrinsic kinetic parameters and effective diffusivity were obtained from these data. The heterogeneous reaction was found to be 0.55 order with respect to propylene oxide concentration. The activation energies obtained for homogeneous and heterogeneous reactions were 51.5 and 53.4 kJ/mol, respectively. A theoretical model incorporating all the mass transfer resistances has been proposed.     

Synthesis,characterization, and curing of o-and p-chlorophenol-furfural resins

Polycondensation of furfural, respectively, with o- and p-chlorophenols has been carried out under various reaction conditions. All the resin samples have been characterized by spectral studies, viscometric measurement and by the estimation of the number-average molecular weight. Thermogravimetric analysis (TGA) of selected resin samples has been carried out. The kinetics of curing reaction of selected resin samples has been investigated by differential scanning calorimetry (DSC). The properties of the glass laminates prepared using each of the two types of resins showed that the latter are much less suitable than phenol-furfural resin as matrices for the fabrication of laminates.     

Using Augmented Infinitesimal Perturbation Analysis for Capacity Planning in Intree ATM Networks

Augmented Infinitesimal Perturbation Analysis is used to determine asymptotically unbiased and strong consistent gradient estimates for use in the capacity planning of intree ATM networks. These gradients are used to determine the locally optimal minimum average network delay by applying a steepest descent algorithm with projection and an Armijo line search to solve the capacity assignment (CA) problem. The network capacities are governed by a linear cost constraint. It is assumed that input regulators (e.g., leaky bucket regulators) are used at the source of each virtual circuit. All virtual circuit external arrivals are modeled as independent Poisson processes. Regenerative simulation is used to determine gradient estimates.     

Covalent Assembly of Two-Dimensional COF-on-MXene Heterostructures Enables Fast Charging Lithium Hosts

2D heterostructured materials combining ultrathin nanosheet morphology, defined pore configuration, and stable hybrid compositions, have attracted increasing attention for fast mass transport and charge transfer, which are highly desirable features for efficient energy storage. Here, the chemical space of 2D–2D heterostructures is extended by covalently assembling covalent organic frameworks (COFs) on MXene nanosheets. Unlike most COFs, which are generally produced as solid powders, ultrathin 2D COF-LZU1 grows in situ on aminated Ti₃C₂T_x nanosheets with covalent bonding, producing a robust MXene@COF heterostructure with high crystallinity, hierarchical porosity, and conductive frameworks. When used as lithium hosts in Li metal batteries, lithium storage and charge transport are significantly improved. Both spectroelectrochemical and theoretical analyses demonstrate that lithiated COF channels are important as fast Li⁺ transport layers, by which Li ions can be precisely nucleated. This affords dendrite-free and fast-charging anodes, which would be difficult to achieve using individual components.     

Enhancing Therapeutic Efficacy of Combined Cancer Phototherapy by Ultrasound‐Mediated In Situ Conversion of Near‐Infrared Cyanine/Porphyrin Microbubbles into Nanoparticles

Nanoparticles (NPs)‐based diagnosis and phototherapy are emerging as the cutting‐edge technologies for detection and treatment of cancer but their applications are still limited since insufficient and heterogeneous NPs accumulation in cancer often causes recurrence. To overcome these limitations, multifunctional microbubbles (MBs) were constructed with 1, 1‐dioctadecyl‐3, 3, 3, 3‐tetramethylindotricarbocyanine iodide (DiR) and porphyrin grafted lipid (PGL). Both DiR and PGL self‐assembled as microbubbles, the as‐designed PGL‐DiR MBs possess remarkably high drug loading contents (5.8% PGL and 10.38% DiR) and stable co‐delivery drug combinations. In vivo experiments showed PGL‐DiR MBs could serve as an excellent ultrasound contrast agent to enhance ultrasound imaging greatly for identifying the location and size of the tumors. Upon exposure to ultrasound, in situ conversion of PGL‐DiR MBs into nanoparticles resulted in a remarkable increase in fluorescence intensity (~5 folds) in tumor compared with PGL‐DiR NPs, validating the enhanced tumor accumulation and cellular uptake of therapeutic agents. PGL‐DiR MBs showed complete tumor ablation without recurrence in vivo, while PGL‐DiR NPs showed only 72.6% tumor growth inhibition at the same dose. We believe that PGL‐DiR MBs will soon reach their full potential as an important class of phototherapeutic formulations and will contribute to remarkable advances in cancer treatments.     

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide(CO_2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite(TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine(CHMA) and trimesoyl chloride(TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO_2/CH_4 separation performance. For CO_2/CH_4 mixture gas(30/70 by volume) test, the membrane(PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO_2 permeance of 25 GPU and the best CO_2/CH_4 selectivity of 28 at stage cut of 0.1. The high CO_2/CH_4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.     

Highlights from the literature on risk assessment techniques adopted in the mining industry:A review of past contributions,recent developments and future scope

In this paper a comprehensive review is presented of risk assessment techniques adopted in the mining industry worldwide;those techniques applied in other hazardous industries and potential techniques which are robust,mature and holistic and can be implemented for the Indian mining industry in future to enhance workplace safety are also presented.Findings from the review are indicative of the fact that socio-technical complexity of industrial systems has increased.Recent developments in the area of risk management highlight the need for implementation of the latest robust techniques of risk assessment in the mining sector.In consideration of the present scenario,the development of a model for risk analysis having an interface between hazard identification and risk assessment,along with an interface between risk assessment and accident causation to predict if an accident will occur under given conditions,has become dire necessity.This will increase hazard awareness and enable mine management to select and prioritize problem areas and identify safety system weaknesses in both underground and surface mining.This will ultimately help decision makers,risk analysts and safety managers make a major contribution in the development of workplace safety with a near-to-zero accident rate.     

Performance of a bubble column reactor for oxidation of ethylene (wacker process)

An experimental investigation of the performance of a bubble column reactor for the liquid-phase catalytic oxidation of ethylene to acetaldehyde (Wacker Process) has been carried out by varying the different operating parameters, such as the inlet gas velocity and catalyst concentration. It has also been shown that, for a given set of conditions, a certain critical ratio of partial pressure of O₂ to that of ethylene in the reactor inlet is required for the overall catalytic cycle to work with maximum efficiency under steady state. The agreement between the experimental results and the predictions of a theoretical reactor model developed herein was found to be excellent.     

Corrosion protective poly(o-ethoxyaniline) coatings on copper

Poly(o-ethoxyaniline) (POEA) coatings were synthesized on copper (Cu) by electrochemical polymerization of o-ethoxyaniline in aqueous salicylate solution by using cyclic voltammetry. These coatings were characterized by cyclic voltammetry, UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The performance of POEA as protective coating against corrosion of Cu in aqueous 3% NaCl was assessed by the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results of the potentiodynamic polarization and EIS studies demonstrate that the POEA coating has ability to protect the Cu against corrosion. The corrosion potential was about 0.330 V versus SCE more positive in aqueous 3% NaCl for the POEA coated Cu than that of uncoated Cu and reduces the corrosion rate of Cu almost by a factor of 140.