2.3–21 GHz broadband and high linearity distributed low noise amplifier

This paper focuses on the design of a 2.3–21 GHz Distributed Low Noise Amplifier (LNA) with low noise figure (NF), high gain (S₂₁), and high linearity (IIP3) for broadband applications. This distributed amplifier (DA) includes S/C/X/Ku/K-band, which makes it very suitable for heterodyne receivers. The proposed DA uses a 0.18 μm GaAs pHEMT process (OMMIC ED02AH) in cascade architecture with lines adaptation and equalization of phase velocity techniques, to absorb their parasitic capacitances into the gate and drain transmission lines in order to achieve wide bandwidth and to enhance gain and linearity. The proposed broadband DA achieved an excellent gain in the flatness of 13.5 ± 0.2 dB, a low noise figure of 3.44 ± 1.12 dB, and a small group delay variation of ±19.721 ps over the range of 2.3–21 GHz. The input and output reflection coefficients S₁₁ and S₂₂ are less than −10 dB. The input compression point (P_1dB) and input third-order intercept point (IIP3) are −1.5 dBm and 11.5 dBm, respectively at 13 GHz. The dissipated power is 282 mW and the core layout size is 2.2 × 0.8 mm².     

Numerical investigation of a convective hybrid nanofluids around a rotating sheet

Hybrid nanofluids are formulated with various kinds of base fluids. They are designed to provide good heat transfer performance. They can achieve this by dispersing various kinds of nanoparticles in the base materials. This new technology of formulating hybrid nanofluids has a wide range of applications in various industries such as solar energy, medical equipment, and aerospace. Keeping these applications in view, this study provides an insight into the effects of convective heat transport on a Hybrid nanofluid, across a rotating sheet with a variable heat source. In this investigation, the governing boundary layer partial differential equations were modified into the ordinary differential equations, by using the proper similarity transformations. Later, they were solved numerically, with the support of the Lobatto IIIA technique in MATLAB. The influence of the Richardson number on flow parameters was studied, and it was discovered that increasing Ri increases the velocity while decreasing temperature and concentration profiles. The impact of various other flow parameters on the flow fields and also on the behavior of Nusselt number, coefficient skin friction, and Sherwood number were studied and represented graphically. The outcomes were found to be in excellent accord when compared with quoted studies.     

Microstructures and properties of nickel-titanium carbide composites fabricated by laser cladding

In this work, Ni/TiC composites were synthesized by the laser cladding technique (LCT). A scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness meter, electrochemical workstation, and friction and wear tester examined the microstructure, surface morphology, phase structure, microhardness, wear, and corrosion resistances of the Ni/TiC composites. These results indicated the Ni/40TiC composite contained finer equiaxed crystals than the Ni and Ni/20TiC composites. In addition, numerous TiC particles in the Ni/40TiC composite impeded growth of the nickel crystals, which resulted in the fine microstructure of the Ni/40TiC composite. The Ni, Ni/20TiC, and Ni/40TiC composites exhibited face-centered cubic (f c c) lattices. The average microhardness values of the Ni/20TiC and Ni/40TiC composites were approximately 748 HV and 851 HV, respectively. The Ni/40TiC composite had the lowest friction coefficient (0.43) among all three coatings, and only some shallow scratches appeared on the surface of the Ni/40TiC composite. The corrosion potential (E) of Ni/40TiC exceeded the Ni/20TiC composite, and both were larger than the Ni composite, which indicated the Ni/40TiC composite had outstanding corrosion resistance and the Ni composite had poor corrosion resistance. The corrosion current densities (i) of Ni, Ni/20TiC, and Ni/40TiC composites were 5.912, 4.405, and 3.248 μA/cm², respectively.     

A hybrid optimization technique for proficient energy management in smart grid environment

Electrical energy is one of the key components for the development and sustainability of any nation. India is a developing country and blessed with a huge amount of renewable energy resources still there are various remote areas where the grid supply is rarely available. As electrical energy is the basic requirement, therefore it must be taken up on priority to exploit the available renewable energy resources integrated with storage devices like fuel cells and batteries for power generation and help the planners in providing the energy-efficient and alternative solution. This solution will not only meet electricity demand but also helps reduce greenhouse gas emissions as a result the efficient, sustainable and eco-friendly solution can be achieved which would contribute a lot to the smart grid environment. In this paper, a modified grey wolf optimizer approach is utilized to develop a hybrid microgrid based on available renewable energy resources considering modern power grid interactions. The proposed approach would be able to provide a robust and efficient microgrid that utilizes solar photovoltaic technology and wind energy conversion system. This approach integrates renewable resources with the meta-heuristic optimization algorithm for optimal dispatch of energy in grid-connected hybrid microgrid system. The proposed approach is mainly aimed to provide the optimal sizing of renewable energy-based microgrids based on the load profile according to time of use. To validate the proposed approach, a comparative study is also conducted through a case study and shows a significant savings of 30.88% and 49.99% of the rolling cost in comparison with fuzzy logic and mixed integer linear programming-based energy management system respectively.     

The production of Indo-Pacific monochrome drawn glass beads in the Sasanian Empire: Insights from Xinjiang,northwest China

Indo-Pacific glass beads are produced by the drawn technique, which originates from South Asia, and their chemical compositions are unique in South and Southeast Asia. However, a small number of Indo-Pacific beads with Sassanian glass compositions are excavated in Asia and Africa after the 3rd c. CE, and their production sites in South/Southeast Asia or in the Sassanian region remain controversial. In this study, 15 drawn glass beads with various colours from Astana necropolis (ca. the 4th-8th c. CE) in Xinjiang, northwest China were investigated by using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Scanning Electron Microscope, Raman spectroscopy and visible to near-infrared spectroscopy to characterize the production technology and origins. The results show that most Astana glass beads share similar chemical compositions with the glassware from Veh Arda?īr, a famous Sasanian site. Furthermore, Sasanian glass compositions predominate in Indo-Pacific beads in Xinjiang during the 4th-8th c. CE, while popular glass recipes in contemporary South/Southeast Asia are infrequently found; thus, it is deduced that the drawn method should have been mastered by Sasanian craftsmen. Moreover, the cobalt materials in Sasanian glass were imported from further western regions and changed over time. The popular Sasanian glass across central Eurasia reflects the trade monopoly of Sasanian in West and Central Asia, and the land glass bead trade is distinct from the contemporary maritime trade in the Indian and Pacific Oceans.     

卤醇脱卤酶催化合成(R)-1-氯-3-苯氧基-2-丙醇的工艺优化

以卤醇脱卤酶重组湿菌体E. coli BL21（pET28a-HHDH）为催化剂，催化外消旋的1-氯-3-苯氧基-2-丙醇的动力学拆分可以获得光学纯的(R)-1-氯-3-苯氧基-2-丙醇。本文系统地研究了卤醇脱卤酶催化合成光学纯(R)-1-氯-3-苯氧基-2-丙醇的影响因素，对反应pH、反应温度、菌体浓度、亲核试剂 {\mathrm{N}}_{\mathrm{3}}^{-} 浓度和底物浓度进行了探究。结果表明，卤醇脱卤酶催化合成(R)-1-氯-3-苯氧基-2-丙醇的最佳工艺条件为：pH为7.0，反应温度为28℃，菌体浓度为22.5g/L，亲核试剂NaN₃的浓度为50mmol/L，底物外消旋1-氯-3-苯氧基-2-丙醇的浓度为10mmol/L。在此工艺条件下，(R)-1-氯-3-苯氧基-2-丙醇的ee值和收率分别为100%和16.97%。     

Fabrication and characterization of electrospun Plantago major seed mucilage/PVA nanofibers

Electrospinning is a well-known technique for producing nanofibers using synthetic and natural polymers like mucilage. In this study, Plantago major Mucilage (PMM) was blended with polyvinyl alcohol (PVA) as a nontoxic adding agent, in order to produce electrospun nanofiber. Electrospinning parameters (voltage, tip-to-collector distance, feed rate, and PMM/PVA ratio) were optimized and solution properties were analyzed. The morphology of nanofibers was investigated using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET). Mechanical strength of nanofibers was determined, and cell viability on nanofibers was discussed by MTT assay. The results of SEM indicated that the PMM/PVA (50/50) nanofibers obtained with average diameter of 250 nm. Viscosity, electrical conductivity, and surface tension of PMM/PVA solution were 550 Cp, 575 μS/cm, and 47.044 mN/m, respectively. FTIR and XRD results verified the exiting PMM in produced nanofibers and no chemical reaction between PMM and PVA. Improvement in mechanical strength and cell viability of nanofibers by adding PMM to PVA nanofibers indicated the potential application of PMM-based nanofibers for medical and food industries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47852.     

单晶硅表层机械力学特性的各向异性分析

为探究挠性筋结构单晶硅材料的各向异性特性以及KOH腐蚀工艺对其力学性能的影响规律,进行纳米压痕实验,并结合原子力显微镜观察单晶硅表层3个主晶面上压痕裂纹形貌随晶向的变化规律,分析单晶硅材料表层弹性模量、硬度、断裂韧性等机械力学特性参数在(001)、(110)及(111)3个主要晶面上沿各个晶向的变化规律;分析挠性筋结构单晶硅材料(001)晶面的KOH腐蚀工艺对其材料表面机械特性的影响规律.结果表明:挠性筋单晶硅在(001)晶面上弹性模量的各向异性变化幅度明显,硬度及断裂韧性各向异性的变化幅度不大;挠性筋单晶硅在(110)晶面弹性模量和断裂韧性的各向异性变化幅度明显,硬度各向异性变化幅度不大;挠性筋单晶硅在(111)晶面硬度值、弹性模量及断裂韧性参数的变化幅度幅值均较小;确定了单晶硅表层3个晶面裂纹最易扩展的晶向方向,KOH腐蚀工艺使得单晶硅表面质量降低,腐蚀后暴露的表面微裂纹、缺陷等会使得单晶硅(001)晶面表层硬度、断裂韧性降低,从而降低了挠性筋结构的实际断裂强度.     

Joining zirconia with nickel-based superalloys for extreme applications by using a pressure-free high-temperature resistant adhesive

In order to meet the high demand for joining ceramic/superalloy composite structure in extreme environments, a novel high-temperature resistant adhesion technique was developed for joining ZrO₂ and Inconel 625 by applying an aluminum phosphate emulsion/zirconium sol based adhesive. With increasing temperature, a series of reactions occurred in adhesive, and its high-temperature bonding was attributed to the formation of a composite structure containing various ceramics and intermetallics. The adhesive after RT curing could find direct applications in extreme environments, and provide bonding strength no less than 2.5 MPa in the temperature range of RT-1100 °C. The bonding strength was higher than 4 MPa in the temperature range of 800–1000 °C, which was further attributed to the formation of an effective CTE-gradient relationship among ZrO₂, adhesive and Inconel 625, as well as the interfacial reactions between the two substrates. The work broadened the application of adhesion technique and brought new ideas for joining dissimilar engineering materials.