A study on the carbon dioxide recovery from 2 ton-CO2/day pilot plant at LNG based power plant

A pilot plant of 2 ton-CO₂/day for CO₂ recovery from flue gas emitted from 250 MW LNG based power plant was tested with aqueous absorbents. The absorbent tested were of different nature such as primary amine (MEA), blend of primary, secondary, tertiary and sterically hindered amine such as MDEA + HMDA, AEPD + DPTA, and TIPA + DPTA. We have studied the CO₂ recovery as function of temperature, concentration, and flow rate of absorbent, pressure and temperature of stripper, and flow rate and temperature of flue gas. It was observed that while CO₂ recovery increases with increase in flow rate and concentration of absorbent, it decreases with increase in temperature and flow rate of flue gas. The CO₂ recovery ratio increases with increase in stripper temperature and decrease in stripper pressure. CO₂ loading (mol CO₂/mol amine) also decreases with increase in stripper temperature.For the absorbent flow rate greater than 2.4 N m³/h, the carbon dioxide recovery ratio follows the sequence: MEA > MDEA + HMDA > AEPD + DPTA > TIPA + DPTA.     

Physiological Imaging Methods for Evaluating Response to Immunotherapies in Glioblastomas

Glioblastoma (GBM) is the most malignant brain tumor in adults, with a dismal prognosis despite aggressive multi-modal therapy. Immunotherapy is currently being evaluated as an alternate treatment modality for recurrent GBMs in clinical trials. These immunotherapeutic approaches harness the patient’s immune response to fight and eliminate tumor cells. Standard MR imaging is not adequate for response assessment to immunotherapy in GBM patients even after using refined response assessment criteria secondary to amplified immune response. Thus, there is an urgent need for the development of effective and alternative neuroimaging techniques for accurate response assessment. To this end, some groups have reported the potential of diffusion and perfusion MR imaging and amino acid-based positron emission tomography techniques in evaluating treatment response to different immunotherapeutic regimens in GBMs. The main goal of these techniques is to provide definitive metrics of treatment response at earlier time points for making informed decisions on future therapeutic interventions. This review provides an overview of available immunotherapeutic approaches used to treat GBMs. It discusses the limitations of conventional imaging and potential utilities of physiologic imaging techniques in the response assessment to immunotherapies. It also describes challenges associated with these imaging methods and potential solutions to avoid them.     

Multiple orifice synthetic jet for improvement in impingement heat transfer

Synthetic jet is potentially useful for cooling of electronic components and its utility has been investigated in previous studies. Synthetic jet will become further attractive if additional cooling can be obtained without a corresponding increase in the input power. In this context, we explore the use of multiple orifice single-cavity synthetic jet employed in direct impingement mode of cooling. Experiments are conducted for different configurations with a center orifice surrounded by multiple satellite orifices. The Reynolds number is in the range of 1000–2600 while the normalized axial distance is varied in the range of 1–30 in this study. The maximum heat transfer coefficient with multiple orifice synthetic jet is approximately 12 times that of the natural heat transfer coefficient and up to 30% more as compared to that obtained with a conventional single orifice jet. Interestingly, the average Nusselt number gets maximized at two axial distances-the two peaks can be of comparable magnitude. The appearance, location and magnitude of the two peaks depend on the number of satellite orifices and the pitch circle radius on which the satellite holes lie. It is proposed that a transition in flow behavior from multiple-jet to a combined-jet occurs, which leads to the appearance of this additional peak. The additional peak (at the smaller axial distance) can be utilized in the design of cooling solutions for compact devices. The input power reduces slightly in the multi-orifice case with respect to the conventional design. The average velocity at the surface is also obtained with the help of hot-wire anemometry. The use of multiple orifice synthetic jet does not appear to have been explored earlier and the results are expected to be useful in several practical applications.     

Nonlinear performance evaluation model for throughput of AQM scheme using full factorial design approach

The performance of active queue management (AQM) is measured in terms of throughput, delay, queue size, and loss rate. We have carried out the optimized performance measure of throughput for AQM scheme random early detection (RED) using full factorial design (FDD) technique that is a new approach of performance analysis particularly for congestion control algorithms. We have considered the input factors, viz, buffer size, maximum threshold, and the number of file transfer protocol (FTP) sources for the evaluation of RED that can be used for other AQM schemes, viz, adaptive RED, three‐section RED (TRED), and adaptive queue management with random dropping (AQMRD). The effect of each input factor as well as their interactions are evaluated using factorial design technique that results to obtain the nonlinear equation for performance measure in terms of input factors buffer size, maximum threshold, and the number of FTP sources. Finally, we show the contour plots for variation of performance measure throughput (steady state) from minimum to maximum values with respect to the different setting of input parameters.     

High Power Factor Operation of a Three-Phase Rectifier for an Adjustable-Speed Drive

This paper presents a novel approach to improve the power factor (PF) and reduce the harmonics generated by an adjustable-speed drive (ASD). A high-frequency (HF) current injection technique is used to improve the PF and harmonic performance. The HF current at the same switching frequency (33 kHz) is injected into the input of a front-end rectifier from the output of an HF inverter. The main feature of the circuit is that it does not require any additional active devices for current injection. The inverter driving the induction motor is operated using a sinusoidal pulsewidth-modulation technique. The circuit simulation and experimental prototype results are presented for 67-hp (50 kW) and 3-hp three-phase induction motors, respectively.     

On the Joint Synchronization of Clock Offset and Skew in RBS-Protocol

Motivated by the necessity of having a good clock synchronization amongst the nodes of wireless ad-hoc sensor networks, the joint maximum likelihood (JML) estimator for clock phase offset and skew under exponential noise model for reference broadcast synchronization (RBS) protocol is formulated and found via a direct algorithm. The Gibbs sampler is also proposed for joint clock phase offset and skew estimation and shown to provide superior performance relative to JML- estimator. Lower and upper bounds for the mean-square errors (MSE) of JML-estimator and Gibbs Sampler are introduced in terms of the MSE of the uniform minimum variance unbiased (UMVU) estimator and the conventional best linear unbiased estimator (BLUE), respectively.     

Studies on the growth and stability of silver nanoparticles synthesized by electron beam irradiation

Stable Ag nanoparticles have been synthesized by irradiating an aqueous solution of AgNO₃ and Poly-vinyl alcohol (PVA) with 8 MeV electrons from a Microtron. The rate of formation of nanoparticles could be controlled by changing either the irradiation dosage or the relative concentration of the precursors. The size, shape, and the rate of formation of the nanoparticles depend on the final dosage, as well as the weight ratio of AgNO₃ and PVA. The formation of Ag nanoparticles and their size were established through UV–Vis spectroscopy and Transmission electron microscopy (TEM) analysis, respectively. Increasing the irradiation dosage seem to favour the formation of polygonal nanostructures. Differential scanning calorimetry (DSC) measurements show that there exists a strong interaction between the PVA matrix and the Ag nanoparticles.     

Bidirectional segmented-memory recurrent neural network for protein secondary structure prediction

The formation of protein secondary structure especially the regions of β-sheets involves long-range interactions between amino acids. We propose a novel recurrent neural network architecture called segmented-memory recurrent neural network (SMRNN) and present experimental results showing that SMRNN outperforms conventional recurrent neural networks on long-term dependency problems. In order to capture long-term dependencies in protein sequences for secondary structure prediction, we develop a predictor based on bidirectional segmented-memory recurrent neural network (BSMRNN), which is a noncausal generalization of SMRNN. In comparison with the existing predictor based on bidirectional recurrent neural network (BRNN), the BSMRNN predictor can improve prediction performance especially the recognition accuracy of β-sheets.     

A multiple-scale analysis of grating-assisted couplers

Optical directional couplers with longitudinal periodic perturbations or gratings are analyzed by a multiple-scale solution to the coupled-mode equations. The use of two length scales in the analysis becomes the key to obtaining globally valid analytic solutions, which are shown to be in excellent agreement with the exact numerical solutions. Because of the nonorthogonality of the coupled modes in the structure, two different coupling lengths, a maximum power transfer length and a zero crosstalk length, are predicted for the power exchange. The spectral properties of the coupler are also studied through a generalized multiple scale method