Bubble growth model and its influencing factors in a polymer melt under nonisothermal conditions

Traditionally, in order to simplify the bubble growth process in a polymer melt, an isothermal model is typically used. In fact, the temperature of the polymer melt is changing during the foaming process. In order to accurately study the growth mechanism of bubbles in polymer melts, we build a physical and mathematical model of bubble growth in a polymer melt under nonisothermal conditions. The parameters of pressure, zero-shear viscosity, relaxation time, Henry's constant, diffusion coefficient, and surface tension were determined. The fourth-order Runge–Kutta method was used to solve the nonisothermal bubble model in the polymer melt. A computational program is developed to find the dimensional change during the bubble growth process, and the correctness of the model is verified. The nonisothermal growth mechanism of and factors influencing bubbles in the polymer melt are analyzed. Combined with the design of experiment (DOE) analysis method, the transfer function of the bubble radius and the maximum growth rate of bubbles with the process parameters were obtained, such as cooling rate, system pressure, and gas concentration. The results show that system pressure has the most significant effect on bubble growth. At the same time, a bubble growth prediction model is built, which can be used to predict the growth of bubbles. Through optimization analysis, it can be used to control the growth of bubbles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47210.     

Intra‐spacecraft optical communication solutions using discrete transceiver

The ever‐decreasing size of the small satellites with more demanding payloads has opened new research areas to investigate innovative onboard data‐handling solutions. This paper presents the use of optical intra‐satellite communication using discretely designed transceivers. The transceiver can handle large variations in the received photocurrents and implements filtration against the ambient light. The designed transceiver has been tested with selected optical components including infrared diodes, photo detectors, and optical guides to validate its functionality. The displacement damage testing on selected optical components was performed to validate their suitability for use in space. The experimental communication schemes have been presented for free space as well as glass fiber‐based intra‐spacecraft communication.     

Distributed Reed-Muller Coded-Cooperative Spatial Modulation

Wireless Personal Communications - This paper proposes distributed Reed-Muller coded spatial modulation (DRMC-SM) scheme based on Kronecker product (KP) construction. This special construction...     

Analysis of the High Frequency Field Expressions at the Caustic Region of a Spherical Reflector Placed in Chiral Medium

High frequency field expressions are derived around the caustic region of a spherical reflector placed in a homogenous, isotropic and reciprocal chiral medium. Firstly Geometrical Optics (GO) field expressions are derived for the spherical reflector placed in chiral medium. As the GO approximation fails at the vicinity of the caustic therefore, Maslov’s method has been used to find the field expressions which are also valid around the caustic region. Present work is an extension of previous work from two dimensional to three dimensional reflector. Some numerical results including line plots around the focal region of spherical reflector placed in chiral medium are obtained using the derived expressions.     

Decolorisation of Remazol vinyl sulphone reactive dyes by potassium permanganate

Three Remazol vinyl sulphone‐based reactive dyes were selected to investigate their decolorisation by potassium permanganate, in relation to pH, concentration of potassium permanganate and time. The amount of colour removal was measured by ultraviolet–visual spectrometry and it was found that potassium permanganate only partially degraded the dye solution; this was also proved by the percent removal of chemical oxygen demand and total organic carbon. Decolorisation was observed to increase when the pH of the dye solution was decreased. Up to a pH level of 5, the decolorisation efficiency is very much slower, but as the pH level shifts towards 2 the rate of decolorisation becomes relatively faster, while a further decrease in pH results in a rapid change in decolorisation. The concentration of potassium permanganate also showed significant effects on the decolorisation. Rapid decolorisation was observed within 10 min for all three dyes, but after that time the decolorisation became slower.     

Fiber-optic tunable multiwavelength variable attenuator and routing module designs that use bulk acousto-optics

A compact fiber-coupled bulk acousto-optical multiwavelength variable optical attenuator module design that uses a retroreflective double-pass geometry within a single bulk acousto-optic tunable filter device is presented. The proposed attenuator module demonstrates a high 17-dB notch dynamic range at a low 100-mW drive power and uses a single bulk collinear-interaction acousto-optic tunable-filter device. Experiments show a low (<1.8-dB) fiber-to-fiber insertion loss with a fast 34-micros speed within a wide 1520-1640-nm agile multinotch band. The basic broadband attenuator module design is extended to allow for efficient architectures for routing modules such as agile drop filters, analog hitless tap filters, and digital add-drop switches.     

The case of using multiple streams in streaming

Off-chip replacement （capacity and conflict） and coherent read misses in a distributed shared memory system cause execution to stall for hundreds of cycles. These off-chip replacement and coherent read misses are recurring and forming sequences of two or more misses called streams. Prior streaming techniques ignored reordering of misses and not-recently-accessed streams while streaming data. In this paper, we present stream prefetcher design that can deal with both problems. Our stream prefetcher design utilizes stream waiting rooms to store not-recently-accessed streams. Stream waiting rooms help remove more off-chip misses. Using trace based simulation% our stream prefetcher design can remove 8% to 66% （on average 40%） and 17% to 63% （on average 39%） replacement and coherent read misses, respectively. Using cycle-accurate full-system simulation, our design gives speedups from 1.00 to 1.17 of princeton application repository for shared-memory computers （PARSEC） workloads running on a distributed shared memory system with the exception of dedup and swaptions workloads.     

Ensemble Learning for Fetal Health Classification

: Cardiotocography (CTG) represents the fetus’s health inside the womb during labor. However, assessment of its readings can be a highly subjective process depending on the expertise of the obstetrician. Digital signals from fetal monitors acquire parameters (i.e., fetal heart rate, contractions, acceleration). Objective:: This paper aims to classify the CTG readings containing imbalanced healthy, suspected, and pathological fetus readings. Method:: We perform two sets of experiments. Firstly, we employ five classifiers: Random Forest (RF), Adaptive Boosting (AdaBoost), Categorical Boosting (CatBoost), Extreme Gradient Boosting (XGBoost), and Light Gradient Boosting Machine (LGBM) without over-sampling to classify CTG readings into three categories: healthy, suspected, and pathological. Secondly, we employ an ensemble of the above-described classifiers with the over-sampling method. We use a random over-sampling technique to balance CTG records to train the ensemble models. We use 3602 CTG readings to train the ensemble classifiers and 1201 records to evaluate them. The outcomes of these classifiers are then fed into the soft voting classifier to obtain the most accurate results. Results:: Each classifier evaluates accuracy, Precision, Recall, F1-scores, and Area Under the Receiver Operating Curve (AUROC) values. Results reveal that the XGBoost, LGBM, and CatBoost classifiers yielded 99% accuracy. Conclusion:: Using ensemble classifiers over a balanced CTG dataset improves the detection accuracy compared to the previous studies and our first experiment. A soft voting classifier then eliminates the weakness of one individual classifier to yield superior performance of the overall model.     

Distributed polar-coded OFDM based on Plotkin’s construction for half duplex wireless communication

A Plotkin-based polar-coded orthogonal frequency division multiplexing (P-PC-OFDM) scheme is proposed and its bit error rate (BER) performance over additive white gaussian noise (AWGN), frequency selective Rayleigh, Rician and Nakagami-m fading channels has been evaluated. The considered Plotkin’s construction possesses a parallel split in its structure, which motivated us to extend the proposed P-PC-OFDM scheme in a coded cooperative scenario. As the relay’s effective collaboration has always been pivotal in the design of cooperative communication therefore, an efficient selection criterion for choosing the information bits has been inculcated at the relay node. To assess the BER performance of the proposed cooperative scheme, we have also upgraded conventional polar-coded cooperative scheme in the context of OFDM as an appropriate bench marker. The Monte Carlo simulated results revealed that the proposed Plotkin-based polar-coded cooperative OFDM scheme convincingly outperforms the conventional polar-coded cooperative OFDM scheme by 0.5 ~ 0.6 dBs over AWGN channel. This prominent gain in BER performance is made possible due to the bit-selection criteria and the joint successive cancellation decoding adopted at the relay and the destination nodes, respectively. Furthermore, the proposed coded cooperative schemes outperform their corresponding non-cooperative schemes by a gain of 1 dB under an identical condition.