A 24-GHz Patch Array with a Power Amplifier/Low-Noise Amplifier MMIC

This paper presents an active patch array designed at 24 GHz. It can be used as a front-end component for a phased array. A series resonant array structure is chosen which is compact and easy excite. With 5 elements, the array proved a 12-dB antenna gain. A power amplifier and a low noise amplifier are designed on a single GaAs chip (PALNA). Bias switch is used in the PALNA, which greatly reduces the switch loss in a transceiver and increases the efficiency. 20-dB small signal gain is achieved in both power amplifier and low noise amplifier. The active patch array is built by the combination of the patch array and PALNA. The measured active gain of this antenna is 35-dB for the PA mode and 31-dB for the LNA mode. This active patch array can obtain an EIRP of 34 dBm with a total radiated power of 22dBm and a maximum PAE of 32%. To check the noise performance, we applied sources at both normal temperature and 77K (liquid nitrogen) and extracted the noise figure (3.5 dB) of the active antenna by the Y factor method. The results proved that the active antenna is working efficiently as both a transmitting and receiving antenna.     

Rapid prototyping of 5356-aluminum alloy based on variable polarity gas tungsten arc welding: process control and microstructure

This paper concentrates on rapid prototyping of a 5356-aluminum alloy based on a new deposition process of variable polarity gas tungsten arc welding (VPGTAW), and describes the microstructure and geometrical properties of the deposited layers. The wettability and distortion tendency of the deposited layers is effectively improved by preheating the substrate up to 118°C, monitoring the arc-length, and adjusting the arc current during the deposition process. The relationships between the geometry of the deposited layers and the welding parameters are developed. The surface roughness of the deposited parts is found to be in the order of 2 μm. The deposited layers exhibit equiaxed dendrites at the top layer, fine equiaxed grains at the middle, and bottom of a deposited wall together with some precipitates distributed at the grain boundary regions, and coarse columnar grains at the bonding zone between the deposited wall and the substrate. The residual microstructure such as grain size and distribution of precipitates is highly dependent on the related locations in the deposited wall. The deposited samples possess a maximum hardness at the top layer and exhibit a slight decreasing trend towards the middle and bottom of the fabricated part due to the heat effects of the material that occurs during the deposition. By understanding these relationships between parameters and their effect on the process output, the process can be used more effectively and the quality be improved as well.     

Life Beyond Bases: The Advent of Frames (Part II)

While the first part of this article presented most of the basic theoretical developments of frames, this part is more user friendly. It covers a large number of known frame families (harmonic tight frames, equiangular frames, unit-norm tight frame, Gabor frames, cosine-modulated frames, double-density frames, multidimensional frames, filter bank frame) as well as those applications where frames made a difference.     

Modeling of the influence of the abrasive waterjet cutting parameters on the depth of cut based on fuzzy rules

Currently, the abrasive waterjet cutting parameters for the milling operation have to be determined by a combination of prior experience and trial and error. It is shown that the selection of the abrasive waterjet cutting parameters for a required depth of cut in the given material can be effectively done by applying the principles of the fuzzy set theory. This approach will eliminate the need for extensive experimental work in order to select the magnitudes of the most influential abrasive waterjet parameters on the depth of cut. Fuzzy logic provides a methodology and imitation of a human's way of making decisions which is very useful in such applications where the mathematical model of the process does not exist, and one of such processes is indeed abrasive waterjet cutting. A number of case studies are performed to verify the validity of the proposed methodology for selecting the abrasive waterjet cutting parameters in order to achieve the predetermined depth of cut.     

High pressure waterjet cooling/lubrication to improve machining efficiency in milling

The efficiency of the metal cutting operations depends upon the thermal/frictional conditions at the tool-chip interface. The use of high pressure waterjet as a coolant/lubricant to improve the thermal/frictional conditions in milling operations was studied here. The influence of high pressure waterjet delivered into tool-chip interface in two different methods, namely, waterjet injected directly into the tool-chip interface through a hole in the tool rake face, and waterjet injected into tool-chip interface through an external nozzle, was explored in this study. The effectiveness of these developed methods was evaluated in terms of cutting force, surface finish, chip shape and tool wear.     

Boundary adaptation in grid generation for CFD analysis of screw compressors

This paper describes some aspects of an advanced grid generation method used, with Computational Fluid Dynamics (CFD) procedures, to model three‐dimensional flow through screw compressors. The increased accuracy of the flow predictions thus derived, enable such machines to be designed with improved performance and for lower development costs. To achieve this, a wholly original boundary adaptation procedure has been developed, in order to allow for convenient mapping of the internal grid points of a screw compressor, which is sufficiently flexible to fit any arbitrary rotor profile. The procedure includes a practical transformation method, which adapts the computationally transformed region to produce a regular boundary distribution on the mesh boundaries. It also allows for subsequent generation of an algebraic grid, which enables the three‐dimensional domain of a screw compressor to be mapped regularly even in regions where the flow patterns are complex and the geometrical aspect ratio is high. This procedure enables more efficient use of a CFD solver for the estimation of the flow parameters within both oil free and oil injected screw compressors, with either ideal fluids or real fluids, with or without change of phase. Copyright © 2005 John Wiley & Sons, Ltd.     

The contribution of glomalin-related soil protein to Pb and Zn sequestration in polluted soil

The distribution of lead and zinc in glomalin-related soil protein (GRSP), a widespread glycoprotein presumably produced by arbuscular mycorrhizal fungi (AMF) in soil, and in some other soil fractions (soil organic matter - [SOM], carbonates, phosphates, etc.) was studied in soils from an area near a lead smelter that differed in SOM, carbonates and heavy metal (HM) content. Total GRSP represented 5.4-21.2% of the SOM and was positively correlated with the soil Pb and Zn concentrations (r=0.57 and 0.66, p=0.007 and p=0.001 for Pb and Zn, respectively). Pb and Zn were predominantly bound to carbonates and organic matter. The amount of lead bound to GRSP varied between 0.69 and 23.4 mg g(-1) DW GRSP which is 0.8-15.5% of the total soil Pb. The amount of GRSP-bound metal was positively correlated with the total concentration in the case of Pb (r=0.90, p=0.000) but the opposite was found for Zn (r=-0.41, p=0.048), indicating that GRSP predominantly binds Pb. The percentages of HM-GRSP in HM-SOM were variable and were not correlated with SOM content.     

PARTICLE-SIZE DISTRIBUTION INFLUENCE IN HIGH-SPEED EROSION OF ALUMINIUM

The paper discusses the influence of the abrasive particle-size distribution on typical high speed abrasive-waterjet erosion parameters. The size distributions of the used abrasive particles are modelled by a Rosin-Rammler-Sperling (RRSB) grain-size distribution containing the distribution parameters D and n. Both parameters are independently varied to characterise different particle-size distributions. Aluminium specimens are eroded by abrasive-waterjets at velocities of 320 m/s, and the erosion depth, depth distribution, and the surface roughness are measured. The depth distribution and the surface roughness are very sensitive to the particle-size distribution parameters, whereas the average erosion depth is not influenced significantly. These results offer the possibility to select an “optimum” grain-size distribution for maximum surface quality at fixed kinematics conditions.     

Computer simulation and experimental investigation of sheet metal bending using laser beam scanning

Computer simulation and experimental investigation of the sheet metal bending into a V-shape by the laser beam scanning without an external force exerted onto it have been performed. A 3-D FEM simulation has been carried out, which includes a non-linear transient indirect coupled thermal-structural analysis accounting for the temperature dependency of the thermal and mechanical properties of the materials. The bending angle, distribution of stress–strain, temperature and residual stresses have been obtained from the simulations. The sheet metal bending had been performed for different materials, thicknesses, scanning speeds and laser powers. The measurement of real-time temperature and bending angle was carried out. The bending angle is affected by the mechanical and thermal properties of the sheet metal material, the process parameters, and the output of laser energy. The bending angle is increased with the number of laser beam scanning passes and is the function of the laser power and the laser beam scanning speed. The simulation results are in agreement with the experimental results.     

Cost-effectiveness analysis of algae energy production in the EU

Today’s society relies heavily on fossil fuels as a main energy source. Global energy demand increase, energy security and climate change are the main drivers of the transition towards alternative energy sources. This paper analyses algal biodiesel production for the EU road transportation and compares it to the fossil fuels and 1st generation biofuels. A cost-effectiveness analysis was used to aggregate private and external costs and derive the social cost of each fuel. The following externalities were internalized: emissions (GHG and non-GHG), food prices impact, pesticides/fertilizers use and security of supply. Currently the social cost of producing algal biodiesel at 52.3 € GJ⁻¹ is higher than rapeseed biodiesel (36.0 € GJ⁻¹) and fossil fuels (15.8 € GJ⁻¹). Biotechnology development, high crude oil prices and high carbon value are the key features of the scenario where algal biodiesel outcompetes all other fuels. A substantial investment into the biotechnology sector and comprehensive environmental research and policy are required to make that scenario a reality.