To pursue FexCoy-PANI/CNT catalysts for oxygen reduction reaction in acid medium with controlled molecular self-assembly method

The mainstream of pyrolyzed transitional metal-nitrogen-carbon (M-N-C) catalysts for ORR still confront difficulty in PEMFC application. To pursue M-N-C structure from wet chemistry at ambient temperature, this paper prepares Fe_xCo_y-PANI/CNT porous structures composed of amorphous Fe and Co NPs into PANI layer on CNT surface, supported by the controlled molecular self-assembly mechanism (MS). For their ORR behaviors in acid medium, all Fe_xCo_y-PANI/CNT catalysts demonstrate similar features as Pt-based catalyst in low current density region, and 4e pathway and active sites in pore utilization in high current density region. Specifically, we disclosed nitrogen in PANI matrix dominates specific activity for ORR, and a little transitional metal attain mass activity at maximum. The active sites mounted into PANI matrix and 4e pathway help catalysts to achieve high durability. Thus, we extend a new type of platinum-free catalyst and develop a bottom-up approach for preparation-structure-activity, expecting to drive PEMFC remarkably.     

The phase change thermoelastic analysis of biological tissue with variable thermal properties during cryosurgery

Abstract

In this work, the coupling phase change heat transfer process and thermal stress behavior of biological tissue during cryosurgery are studied in the context of a generalized thermoelastic theory. The nonlinear governing equations are constructed while considering the variable thermal properties and solved by a time-domain finite element method based on the effective heat capacity formulation. A 2-D tumor and normal tissue model is adopted for simulating the freezing process in cryosurgery. The effects of temperature-dependent thermal properties and relaxation time on the responses of biological tissue are discussed and illustrated graphically.     

Enhanced thermoelectric properties of atomic-layer-deposited Hf:Zn16O/18O superlattice films by interface-engineering

This study examines three novel approaches for enhancing the thermoelectric (TE) properties of atomic-layer-deposited (ALD) ZnO thin films: 1) Hf-doping, which preserved the crystallinity of ZnO and provided effective phonon scattering owing to Hf's similar atomic radius to and large mass difference with Zn, leading to high power factor (PF) and low thermal conductivity (κ); 2) controlling the distribution of Hf into an alternating scattered phase/clustered phase superlattice, which balanced the high PF of the scattered phases with the low κ of the clustered phases, while providing significant energy-filtering effect to raise the Seebeck coefficient; 3) introducing ¹⁸O/¹⁶O periodicity into the Hf:ZnO films—by alternately using H₂¹⁶O and H₂¹⁸O as oxidants in the ALD processes, which further suppressed κ without compromising PF. The combination of the three approaches resulted in a maximum improvement in ZT of ~1600% over that of the undoped ZnO.     

Using fuzzy MCDM technique to find the best location in Qatar for exploiting wind and solar energy to generate hydrogen and electricity

Hydrogen has been a promising energy carrier to meet the world's energy needs as well as reduce pollutant emissions. Although many countries have policies and programs to expand hydrogen production, the potential for hydrogen production in different regions of Qatar has not yet been evaluated. Therefore, this paper, for the first time, evaluates the possibility of an average annual cogeneration of 14 kWh of electricity and 85 kg/day of hydrogen by a home-scale solar-wind system connected to the grid in Qatar. NASA's 20-year average of meteorological data, the electricity tariff and gasoline price in 2018, along with annual real interest rate, were used as inputs to HOMER software. The techno-econo-enviro analysis was done over a one-year period hour by hour. From the results, it was found that the lowest prices of hydrogen and electricity generated, with $ 2.092/kg and $ 11.495/kWh, were related to Grid and PV-Wind-Grid scenarios, respectively. Also, results indicated that Ar-Ruways station and PV-Wind-Grid scenario were the most environmentally suitable options that resulted in a CO₂ emission rate of 1434 kg annually. To select just one station among five areas, a fuzzy method was deployed as a prioritization technique. Its results suggested that Doha Intl Airport site is the most suitable one for constructing solar-wind hybrid energy generation system.     

Simulation of integrated novel PSA/EHP/C process for high-pressure hydrogen recovery from Coke Oven Gas

This paper introduces a novel Coke Oven Gas (COG) hydrogen purification/compression system based on the technologies of Pressure Swing Adsorption (PSA) and Electrochemical Hydrogen Purification and Compression (EHP/C). As the EHP/C tolerates O₂, N₂ and CH₄ impurities, PSA can be utilized solely for CO and CO₂ removal (other COG impurities were not considered in this work). A relaxation of PSA hydrogen purity could significantly enhance its recovery rate. In this study, the suitability of traditional hydrogen PSA as part of the hybrid PSA/EHP/C approach was investigated. Aspen Adsorption and Matlab were used to model the PSA and EHP/C systems, respectively. The effect of adsorption pressure, purge-to-feed-ratio (P/F-ratio) and adsorption time within cycle on PSA performance is reported. This study found that breakthrough of non-detrimental components is typically accompanied with poisonous CO. Hence, the CO removal with traditional H₂-PSA resulted into high purity product. In a two-bed PSA, 36.3% of hydrogen was recovered at 99.9988% purity and 0.18 ppm CO. Subsequently, as a result, the EHP/C purification capability was merely utilized, but polished this hydrogen to >99.999% purity. Simultaneously, hydrogen was isothermally compressed to 20 MPa, consuming a marginal 2.42 kWh/kg. Compared to mechanical compression, this is 31.6% more energy efficient. Recovering hydrogen from by-product COG was found to save 0.5 kg CO₂/kg H₂ compared to hydrogen produced from natural gas. Conventional hydrogen PSA, utilizing 70% Activated Carbon and 30% Molecular Sieve 5A, was found not to be effective to target the removal of CO specifically. To increase synergy between PSA and EHP/C, the PSA requires adequate design and operation using appropriate adsorbents and cycle steps to target elimination of CO. An increased EHP/C catalyst tolerance for CO also contributes to higher flexibility.     

Arabic sign language intelligent translator

ABSTRACT

Arabic sign language (ArSL) is method of communication between deaf communities in Arab countries; therefore, the development of systemsthat can recognize the gestures provides a means for the Deaf to easily integrate into society. In this research we implemented a computational structurefor an intelligent interpreter that automatically recognizes the isolated dynamic gestures. The proposed system recognizes and translates gesturesperformed with one or both hands. It comprises five subsystems, building dataset, video processing, feature extraction, mapping between ArSL and Arabictext, and text generation. To apply the system, 100-signs of ArSL was used, which was applied on 1500 video files. It's were divided into five classes:alphabet, numbers, "prepositions, pronouns and question words", Arabic life expressions, and "nouns and verbs". The evaluation indicated that thesystem automatically recognizes and translates isolated dynamic ArSL gestures by highly accurate manner. The results showed that the system accuracy is 95.8%.     

Food recognition using neural network classifier and multiple hypotheses image segmentation

ABSTRACT

This paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance.     

A Novel Beam Search to Improve Neural Machine Translation for English-Chinese

Neural Machine Translation (NMT) is an end-to-end learning approach for automated translation, overcoming the weaknesses of conventional phrase-based translation systems. Although NMT based systems have gained their popularity in commercial translation applications, there is still plenty of room for improvement. Being the most popular search algorithm in NMT, beam search is vital to the translation result. However, traditional beam search can produce duplicate or missing translation due to its target sequence selection strategy. Aiming to alleviate this problem, this paper proposed neural machine translation improvements based on a novel beam search evaluation function. And we use reinforcement learning to train a translation evaluation system to select better candidate words for generating translations. In the experiments, we conducted extensive experiments to evaluate our methods. CASIA corpus and the 1,000,000 pairs of bilingual corpora of NiuTrans are used in our experiments. The experiment results prove that the proposed methods can effectively improve the English to Chinese translation quality.     

Spin reorientation,normal and inverse magnetocaloric effects in heavy rare-earth iron garnets

Experiments for heavy rare-earth iron garnets Ho₃Fe₅O₁₂ and Er₃Fe₅O₁₂ show a compensation effect characterized by a near zero magnetization at 134 K and 80 K, respectively. The magnetic entropy change calculated according to the Maxwell's relation is shown to be positive and negative, indicating both normal and inverse magnetocaloric effects exist in the sample. The critical temperature (134 K for Ho₃Fe₅O₁₂, 80 K for Er₃Fe₅O₁₂) of the two types of magnetocaloric effect occurs at almost the same temperature as the compensation point. However, the compensation effect is attributed to the multiple exchange interactions among the octahedral sites Fe³⁺, the tetrahedral sites Fe³⁺ and the dodecahedral sites R³⁺, while the reversal of the magnetocaloric effect is originated from the spin reorientation. The maximum magnetic entropy change of the normal magnetocaloric effect is 4.72 J kg⁻¹ K⁻¹ for Ho₃Fe₅O₁₂ at 34 K and 4.94 J kg⁻¹ K⁻¹ for Er₃Fe₅O₁₂ at 24 K, respectively. Moreover, all the positive slopes of basic Arrott plots suggest only the second-order phase transition existing in Ho₃Fe₅O₁₂ and Er₃Fe₅O₁₂.     

Influence of Chemical Reaction on Mass Transport in Yield Stress Exhibiting Flow Regime

Theoretical Foundations of Chemical Engineering - In this study, the simulations for first-order chemical reactions (constructive and destructive) in the flow of the Casson fluid with...