Strain‐rate‐dependent mechanical properties of polypropylene separator for lithium‐ion batteries

The mechanical integrity of battery separators is critical for battery safety and durability. A comprehensive study of strain‐rate‐dependent tensile and puncture properties of a polypropylene lithium‐ion battery separator is presented here with a new model. Due to anisotropy of the polymeric membrane, tensile testing was conducted for different directions. Results showed that tensile strength and elastic modulus were increased 1000% and 500%, respectively, for different directions. It was also demonstrated that tensile strength changed 10 to 25% with strain rate (1.67 × 10^?4 to 1.67 × 10^?1 s^?1) for different directions. An equation was obtained for the first time for flow stress versus strain rate at varied tensile directions with respect to machine direction. Moreover, puncture testing was performed and it was shown that puncture strength was increased 140% with increasing strain rate from 0.25 to 250 mm min^?1. Two failure modes were also observed in puncture samples. Finally, Eyring's model was used to calculate activation enthalpy of the porous polypropylene separator. © 2020 Society of Chemical Industry     

Stable haptic rendering in interactive virtual control laboratory

Stable control of haptic interfaces is one of the most important challenges in haptic simulations, because any instability of a haptic interface can cause it to get far from the realistic sense. In this paper, the control strategies employed for a stable haptic rendering in an interactive virtual control laboratory are presented. In this interactive virtual laboratory, there are different scenarios to teach the control concepts, in which a haptic interface is used in the two cases of force control and position control. In this regard, two control strategies are employed to avoid instability. An energy-compensating controller is utilized to remove energy leakage. Besides, a fuzzy impedance control is used along with the energy-compensating controller for the position control scenarios. The results obtained indicate the proposed approaches practically guarantee the stability of the haptic interface for an educational application in practice.     

Evaluation of driver drowsiness using respiration analysis by thermal imaging on a driving simulator

In this paper, a new non-intrusive driver drowsiness detection method is introduced based on respiration analysis using facial thermal imaging. Drowsiness is the cause of many driving accidents all over the world. Drivers’ respiration system undergoes significant changes from wakefulness to drowsiness and can be used to detect drowsiness. Current respiration measurement methods are intrusive and uncomfortable making respiration the least measured vital sign during driving. In this paper, a new method is presented based on facial thermal imaging to analyze drivers’ respiration signal non-intrusively. Thirty subjects are tested in a car simulator. They are fully awake at the beginning and experience drowsiness during the tests. The mean and the standard deviation of the respiration rate and the inspiration-to-expiration time ratio are extracted from the subjects’ respiration signal. To detect drowsiness, the Support Vector Machine (SVM) and the K-Nearest Neighbor (KNN) classifiers are used. The Observer Rating of Drowsiness method is used for scoring the drowsiness level and validating the proposed method. The performance and the results of both methods are presented and compared. The results indicate that drowsiness can be detected with the accuracy of 90%, sensitivity of 92%, specificity of 85%, and precision of 91%.

     

An algorithm on sign words extraction and recognition of continuous Persian sign language based on motion and shape features of hands

Sign language is the most important means of communication for deaf people. Given the lack of familiarity of non-deaf people with the language of deaf people, designing a translator system which facilitates the communication of deaf people with the surrounding environment seems to be necessary. The system of translating the sign language into spoken languages should be able to identify the gestures in sign language videos. Consequently, this study provides a system based on machine vision to recognize the signs in continuous Persian sign language video. This system generally consists of two main phases of sign words extraction and their classification. Several stages, including tracking and separating the sign words, are conducted in the sign word extraction phase. The most challenging part of this process is separation of sign words from video sequences. To do this, a new algorithm is presented which is capable of detecting accurate boundaries of words in the Persian sign language video. This algorithm decomposes sign language video into the sign words using motion and hand shape features, leading to more favorable results compared to the other methods presented in the literature. In the classification phase, separated words are classified and recognized using hidden Markov model and hybrid KNN-DTW algorithm, respectively. Due to the lack of proper database on Persian sign language, the authors prepared a database including several sentences and words performed by three signers. Simulation of proposed words boundary detection and classification algorithms on the above database led to the promising results. The results indicated an average rate of 93.73 % for accurate words boundary detection algorithm and the average rate of 92.4 and 92.3 % for words recognition using hands motion and shape features, respectively.     

Improved passivity criterion in haptic rendering: influence of Coulomb and viscous friction

In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5?cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific trajectory is designed and the movement of the haptic robot is investigated on this trajectory to validate and compare this passivity criterion with the previous criteria.     

A new decision making structure for managing arriving orders in MTO environments

In order to improve the quality of decision about orders incoming to make to order (MTO) company, an effective evaluation approach is essential. So, in this paper a comprehensive decision making structure is presented for acceptance or rejection of incoming orders. The aim of the proposed structure is to manage the arriving orders so that the MTO system just proceeds to produce those arriving orders which are feasible and profitable for the system. The proposed structure composed of three phases. At the first phase, arriving orders are prioritized into high and low priority orders, considering characteristics of order and customer and utilizing technique for order performance by similarity to ideal solution (TOPSIS). At the second phase, rough-cut capacity was calculated for each order regarding priority level and so, acceptance or rejection decision is taken based on it. Finally, at the third phase, the previous phase accepted orders are evaluated based on their due dates and material arrival times and final decisions for orders are made. At the end, the effectiveness of the proposed structure is demonstrated through a case study.     

Particle motion and modes of wear in the dry sand–rubber wheel abrasion test

In the dry sand–rubber wheel test, the particles are free to move between the wheel and testpiece. The particles may either roll as they pass through the contact, or they may temporarily embed in the rubber wheel and groove the sample; the motion of the particles will govern the modes of deformation of the sample and thus the dominant mechanisms of wear. In experiments concerning the abrasion of a range of steels with widely varying hardnesses, it has been shown that the motion of the particles through the contact depends not only upon the details of the testing conditions (for example particle feedrate, particle size and shape, applied load) but also upon the testpiece material properties themselves, such as hardness. Such a dependence upon testpiece material properties is a cause for concern for those who use the test, and indicates that observations of the mechanisms of wear are an essential part of this test methodology. Particle rolling through the contact is favoured by low applied loads and low testpiece hardness whereas particle sliding through the contact is favoured by high applied loads and high testpiece hardness. The wear coefficients in situations where particle sliding (grooving) occurs are not significantly higher than those for situations where particle rolling occurs and it is argued that this is associated with the way in which grooving particles orient themselves with respect to the testpiece as they pass through the contact. This is in contrast to fixed-particle grooving abrasion (such as might be observed in tests using abrasive papers), and as such, it is argued that what is commonly termed two-body abrasion should be subcategorised into “fixed-particle grooving abrasion” and “free-particle grooving abrasion”. The paper then proceeds to provide an analysis of the motion of particles in the dry sand-rubber wheel abrasion test, and seeks to understand the mechanics controlling their motion, and thus the dependence of particle motion upon external factors, focussing on the effects of testpiece hardness and applied load. The effect of hardness on particle rotation is well predicted by the model, but the effect of the applied load on particle motion observed experimentally is opposite to that which is predicted by the model. The shortcomings of the model are discussed, and the model has been qualitatively modified to account for this discrepancy. The modifications centre around the significant changes in rubber wheel–particle contact geometry as the applied load is changed; such changes are difficult to model analytically due to the large strains associated with such a contact, and it is suggested that finite element modelling may be required to fully understand and model the complex contacts occurring in this simple and widely employed test method.     

Isolation of a novel mutant strain of Saccharomyces cerevisiae by an ethyl methane sulfonate-induced mutagenesis approach as a high producer of bioethanol

In order to obtain mutant strains showing higher bioethanol production than wild-type strains, a commercial Saccharomyces cerevisiae type was subjected to mutagenesis using ethyl methane sulfonate (EMS). After adding EMS to a shaken yeast suspension, the viability of yeast cells was assessed by diluted sample inoculation to solid yeast-extract peptone glucose (YEPG) medium at 15-min intervals. At 45 min, the viability of yeast cells was estimated to be about 40%. Mutagenized cells were recovered from YEPG broth after incubation at 30 degrees C for 18 h. After this period, EMS-treated yeast cells were grown on solid aerobic low-peptone (ALP) medium containing 2-12% (v/v) ethanol. All plates were incubated at 30 degrees C for 2-6 d in order to form colonies. The mutant strains that tolerated high concentrations of ethanol were selected for bioethanol production in microfuge tubes containing fermentation medium. Formation of bioethanol in small tubes was detected by the distillation-colorimetric method. In addition, trehalose content and invertase activity were determined in each mutant strain. Among many isolated mutant strains, there were six isolated colonies that grew on ALP medium supplemented with 10% (v/v) ethanol and one of them produced bioethanol 17.3% more than the wild type.     

Multispectral particle filter tracking using adaptive decision-based fusion of visible and thermal sequences

Multimedia Tools and Applications - One of the main challenges of detection and tracking of objects in video monitoring is the lighting conditions of the scene under surveillance and its...     

Isolation of a flocculating Saccharomyces cerevisiae and investigation of its performance in the fermentation of beet molasses to ethanol

The present study aims at evaluating the performance of the relative importance of different types of interactions in yeast cell flocculation. The yeasts isolated from several sources, purified and identified by morphological and biochemical methods. About 50 strains of yeast were isolated on PDA medium, among those strains six strains were flocculent and one of them was identified as Saccharomyces cerevisiae. The influence of different additives on the flocculation was investigated and it was shown that pistacia gum (turpentine) increases the flocculation up to 93.8%. Addition of ammonium sulfate (0.2 g l⁻¹) increases the production of alcohol to 6.19%.