Deep‐Ultraviolet Hyperbolic Metacavity Laser

Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum‐well (MQW), deep‐ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.     

中碳多元合金钢破碎机锤头的研制

对采用Cr、Mo、Ni及Mn等元素多元合金化中碳合金钢锤式破碎机锤头的组织、力学性能及耐冲击磨损性能进行了试验研究。锤头采用自硬树脂砂工艺铸造 ,对所研制的锤头进行了现场装机试验。试验结果表明 :合金元素含量分别为 :w(Cr) =4～ 5 %、w(Mo) =0 5～ 0 7%、w(Ni) =0 3～ 0 5 %、w(Mn) =0 6～ 0 9% ,含碳量为 :w(C) =0 4～ 0 5 %的中碳多元合金钢锤头具有高耐冲击磨损和良好韧性相结合的特点 ,其工作寿命为高锰钢锤头的 1 5 5倍     

Green Adeptness in the Synthesis and Stabilization of Copper Nanoparticles: Catalytic,Antibacterial, Cytotoxicity,and Antioxidant Activities

Copper nanoparticles (CuNPs) are of great interest due to their extraordinary properties such as high surface-to-volume ratio, high yield strength, ductility, hardness, flexibility, and rigidity. CuNPs show catalytic, antibacterial, antioxidant, and antifungal activities along with cytotoxicity and anticancer properties in many different applications. Many physical and chemical methods have been used to synthesize nanoparticles including laser ablation, microwave-assisted process, sol-gel, co-precipitation, pulsed wire discharge, vacuum vapor deposition, high-energy irradiation, lithography, mechanical milling, photochemical reduction, electrochemistry, electrospray synthesis, hydrothermal reaction, microemulsion, and chemical reduction. Phytosynthesis of nanoparticles has been suggested as a valuable alternative to physical and chemical methods due to low cytotoxicity, economic prospects, environment-friendly, enhanced biocompatibility, and high antioxidant and antimicrobial activities. The review explains characterization techniques, their main role, limitations, and sensitivity used in the preparation of CuNPs. An overview of techniques used in the synthesis of CuNPs, synthesis procedure, reaction parameters which affect the properties of synthesized CuNPs, and a screening analysis which is used to identify phytochemicals in different plants is presented from the recent published literature which has been reviewed and summarized. Hypothetical mechanisms of reduction of the copper ion by quercetin, stabilization of copper nanoparticles by santin, antimicrobial activity, and reduction of 4-nitrophenol with diagrammatic illustrations are given. The main purpose of this review was to summarize the data of plants used for the synthesis of CuNPs and open a new pathway for researchers to investigate those plants which have not been used in the past.

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Graphical abstract Proposed Mechanism for Antibacterial activity of copper nanoparticles.

     

High birefringence photonic crystal fiber with a complex unit cell of asymmetric elliptical air hole cladding

High birefringence induced by elliptical air hole photonic crystal fibers (EHPCFs) is analyzed numerically using the finite-element method. Statistical correlations between the birefringence and the various parameters are obtained. We found that the complex elliptical air hole is better than that of a circular one to obtain high birefringence in photonic crystal fibers. Our suggested structures can considerably enhance the birefringence in EHPCFs and show that the birefringence can be as high as 1.1294 x 10(-2), which is higher than the birefringence obtained from conventional step-index fiber (5 x 10(-4)), circular air holes PCF (3.7 x 10(-3)), and elliptical hollow PCF (2.35 x 10(-3)).     

Applied and Emerging Methods for Meat Tenderization: A Comparative Perspective

The tenderization process, which can be influenced by both pre‐ and post‐slaughter interventions, begins immediately after an animal's death and is followed with the disruption of the muscle structure by endogenous proteolytic systems. The post‐slaughter technological interventions like electrical stimulation, suspension methods, blade tenderization, tumbling, use of exogenous enzymes, and traditional aging are some of the methods currently employed by the meat industry for improving tenderness. Over the time, technological advancement resulted in development of several novel methods, for maximizing the tenderness, which are being projected as quick, economical, nonthermal, green, and energy‐efficient technologies. Comparison of these advanced technological methods with the current applied industrial methods is necessary to understand the feasibility and benefits of the novel technology. This review discusses the benefits and advantages of different emerging tenderization techniques such as hydrodynamic‐pressure processing, high‐pressure processing, pulsed electric field, ultrasound, SmartStretch^?, Pi‐Vac Elasto‐Pack® system, and some of the current applied methods used in the meat industry.     

Using flower pollinating with artificial bees (FPAB) technique to determine machinable volumes in process planning for prismatic parts

Process planning (PP) has an important role in manufacturing systems design and operations. Volume decomposition and machinable volumes (MVs) or machining features determination is the core activity in process planning. This process requires extraction of elementary volumes (EVs), merging or clustering EVs to construct feasible MVs and finally selecting an optimal combination of MVs. Development of MVs is an important activity, so that better solution is obtained by better developed MVs. Generation of limited number of MVs or machining features, which is often performed by experts may miss the optimal solution. Also, using exact methods such as combinatorial optimization not only generate infeasible MVs, but also require an excessive amount of computational time. In this research, the meta-heuristic procedure of flower pollinating by artificial bees (FPAB) is used in manufacturing context to generate and assess the feasibility of MVs. Furthermore, a set-covering method is used to select the optimal solution. The performance of the proposed model is assessed through some numerical examples. The encouraging results of the numerical examples demonstrate good performance of the proposed method in machining feature or machinable volumes determination problem (MVDP).     

Sulfonation of graphene nanosheet-supported platinum via a simple thermal-treatment toward its oxygen reduction activity in acid medium

The sulfonated graphene nanosheet-supported platinum (s-Pt/GNS) catalyst synthesized via a simple thermal-treatment in the presence of concentrated sulfuric acid was reported in this study. Influence of sulfonation on its structural, surface, morphological and catalytic characteristics of as-prepared s-Pt/GNS was explored using X-ray diffractometer, Raman spectrometry, zeta potential analyzer, scanning and transmission electron microscopes, and cyclic voltammetry. For the oxygen reduction reaction, the current density generated from the s-Pt/GNS at 0.6 V was approximately 32.5 A g⁻¹ Pt, which was about 193% higher than that of original Pt/GNS.     

Microstructural Characterization of Co-Based ODS Alloys

Co-based ODS alloys, strengthened by nanosized oxide dispersion and γ′ precipitates, are potential high-temperature structural materials. The characteristics of the mechanically alloyed powder and the microstructural evolution of the Co-based ODS alloys were investigated. The results revealed that mechanical alloying had induced the formation of supersaturated solid solution in immiscible Co-Al-W-based alloys, originating mainly from extensive grain boundary region, high dislocation density, and ample point defect. Chemical compositions of mechanically alloyed Co-Al-W-based ODS alloys easily deviate from the γ/γ′ two-phase region, leading to the existence of Al _x Co, Co₃W, Co₇W₆, and W phases in addition to the γ and γ′ phases. Nonuniform distribution of alloying elements brings about the differences in morphologies and sizes of γ′ precipitates. Microstructural formation process is impelled by spinodal decomposition mode, and spinodal decomposition behavior has been accelerated in the fine-grained alloy because of the presence of short-circuited diffusion paths for atomic movement.     

Radioactivity levels in some sediment samples from Red Sea and Baltic Sea

Levels of 22?,22?Ra, 232Th, 21?Pb, 21?Po and ??K in sediments from four monitoring areas, El Hamraween and Ras El Behar (Red Sea, Egypt) and LL3A and JML (Baltic Sea, Finland), have been investigated using alpha and gamma spectrometry. The average activity concentrations were 238±4 Bq kg?1 (22?Ra), 215±11 Bq kg?1 (21?Pb) and 311±18 Bq kg?1 (21?Po) for El Hamraween area. In Ras El Behar area, the corresponding values were 16±0.4, 18±1 and 20±5 Bq kg?1, respectively. The activity concentrations for 22?Ra, 21?Pb and 21?Po (uranium series) in El Hamraween bottom sediment are much high compared with those in Ras El Behar area, which indicates the enhanced levels due to the activities of phosphate mining and shipment operations in El Hamraween area. Excluding the influence of phosphate mining activities, it can be concluded that the levels of radioactivity in Baltic Sea sediments are higher than those in Red Sea sediments.     

Re-realization of the NIS National Viscosity Scale and Its Range Extension up to 250,142?mm2/s

A wide-range viscosity standard system has generally been realized with capillary viscometers, which are calibrated by the stepping-up method on the basis of viscosity value of distilled water at 20?°C. As per recommendation of Bureau International des Poids et Mesures (BIPM), the national primary viscosity scale must be realized every 10?years. The present work is an attempt to re-realize the existing scale and extend it to from 70,000 to 250,142?mm²/s. This would enable NIS to calibrate different types of viscometers with the highest constant. The NIS viscosity scale was first realized in 2001 [1] using glass capillary viscometers in the range from 1 to 70,000?mm²/s. From the present calibration results of the NIS viscometers, the present scale is realized with an uncertainty of about 0.07?% at low viscosities (0.9?mm²/s) rising to about 0.25?% at higher viscosities (250,142?mm²/s).