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M Jackson - One of the best experts on this subject based on the ideXlab platform.
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fast forge a new cost effective Hybrid Processing route for consolidating titanium powder into near net shape forged components
Journal of Materials Processing Technology, 2017Co-Authors: N S Weston, M JacksonAbstract:Reducing the high cost of titanium to a level where it can compete with currently used commodity metals offers opportunities to many industries to exploit its excellent combination of properties to improve performance or reduce weight. The key to decreasing cost is to reduce the number of Processing steps to go from ore to component, as well as material wastage from excessive machining. This paper describes a new solid-state Hybrid manufacturing route, termed by the authors as FAST-forge, for converting titanium alloy powder into components with wrought properties in two steps; utilising field assisted sintering technology (FAST) to produce a shaped preform billet that is finished to near net shape by a one-step precision hot forge. The route has been demonstrated at the laboratory scale using Ti-6Al–4V hydride-dehydride powder by producing fully consolidated, microstructurally homogeneous, double truncated cone specimens directly through FAST, which were then upset forged at a range of temperatures and strain rates. The microstructural evolution and forging behaviour of the Ti-6Al–4V after FAST consolidation is similar to conventional melt, multi-step forged product. Break up of primary α at high strains was observed at 950°C and 0.01 s−1, 0.1 s−1, and 1 s−1. There is good agreement between finite element modelling of the hot forging and the experimental data, which will enable more complex shaped geometries to be produced via the proposed FAST-forge route in future. Such a route could be used to consolidate powder from a lower-cost alternative extraction method to become a disruptive technology that will enable a step-change in the economics of titanium components.
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FAST-forge − A new cost-effective Hybrid Processing route for consolidating titanium powder into near net shape forged components
Journal of Materials Processing Technology, 2017Co-Authors: N S Weston, M JacksonAbstract:Reducing the high cost of titanium to a level where it can compete with currently used commodity metals offers opportunities to many industries to exploit its excellent combination of properties to improve performance or reduce weight. The key to decreasing cost is to reduce the number of Processing steps to go from ore to component, as well as material wastage from excessive machining. This paper describes a new solid-state Hybrid manufacturing route, termed by the authors as FAST-forge, for converting titanium alloy powder into components with wrought properties in two steps; utilising field assisted sintering technology (FAST) to produce a shaped preform billet that is finished to near net shape by a one-step precision hot forge. The route has been demonstrated at the laboratory scale using Ti-6Al–4V hydride-dehydride powder by producing fully consolidated, microstructurally homogeneous, double truncated cone specimens directly through FAST, which were then upset forged at a range of temperatures and strain rates. The microstructural evolution and forging behaviour of the Ti-6Al–4V after FAST consolidation is similar to conventional melt, multi-step forged product. Break up of primary α at high strains was observed at 950°C and 0.01 s−1, 0.1 s−1, and 1 s−1. There is good agreement between finite element modelling of the hot forging and the experimental data, which will enable more complex shaped geometries to be produced via the proposed FAST-forge route in future. Such a route could be used to consolidate powder from a lower-cost alternative extraction method to become a disruptive technology that will enable a step-change in the economics of titanium components.
N S Weston - One of the best experts on this subject based on the ideXlab platform.
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fast forge a new cost effective Hybrid Processing route for consolidating titanium powder into near net shape forged components
Journal of Materials Processing Technology, 2017Co-Authors: N S Weston, M JacksonAbstract:Reducing the high cost of titanium to a level where it can compete with currently used commodity metals offers opportunities to many industries to exploit its excellent combination of properties to improve performance or reduce weight. The key to decreasing cost is to reduce the number of Processing steps to go from ore to component, as well as material wastage from excessive machining. This paper describes a new solid-state Hybrid manufacturing route, termed by the authors as FAST-forge, for converting titanium alloy powder into components with wrought properties in two steps; utilising field assisted sintering technology (FAST) to produce a shaped preform billet that is finished to near net shape by a one-step precision hot forge. The route has been demonstrated at the laboratory scale using Ti-6Al–4V hydride-dehydride powder by producing fully consolidated, microstructurally homogeneous, double truncated cone specimens directly through FAST, which were then upset forged at a range of temperatures and strain rates. The microstructural evolution and forging behaviour of the Ti-6Al–4V after FAST consolidation is similar to conventional melt, multi-step forged product. Break up of primary α at high strains was observed at 950°C and 0.01 s−1, 0.1 s−1, and 1 s−1. There is good agreement between finite element modelling of the hot forging and the experimental data, which will enable more complex shaped geometries to be produced via the proposed FAST-forge route in future. Such a route could be used to consolidate powder from a lower-cost alternative extraction method to become a disruptive technology that will enable a step-change in the economics of titanium components.
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FAST-forge − A new cost-effective Hybrid Processing route for consolidating titanium powder into near net shape forged components
Journal of Materials Processing Technology, 2017Co-Authors: N S Weston, M JacksonAbstract:Reducing the high cost of titanium to a level where it can compete with currently used commodity metals offers opportunities to many industries to exploit its excellent combination of properties to improve performance or reduce weight. The key to decreasing cost is to reduce the number of Processing steps to go from ore to component, as well as material wastage from excessive machining. This paper describes a new solid-state Hybrid manufacturing route, termed by the authors as FAST-forge, for converting titanium alloy powder into components with wrought properties in two steps; utilising field assisted sintering technology (FAST) to produce a shaped preform billet that is finished to near net shape by a one-step precision hot forge. The route has been demonstrated at the laboratory scale using Ti-6Al–4V hydride-dehydride powder by producing fully consolidated, microstructurally homogeneous, double truncated cone specimens directly through FAST, which were then upset forged at a range of temperatures and strain rates. The microstructural evolution and forging behaviour of the Ti-6Al–4V after FAST consolidation is similar to conventional melt, multi-step forged product. Break up of primary α at high strains was observed at 950°C and 0.01 s−1, 0.1 s−1, and 1 s−1. There is good agreement between finite element modelling of the hot forging and the experimental data, which will enable more complex shaped geometries to be produced via the proposed FAST-forge route in future. Such a route could be used to consolidate powder from a lower-cost alternative extraction method to become a disruptive technology that will enable a step-change in the economics of titanium components.
Shi Jin - One of the best experts on this subject based on the ideXlab platform.
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Hybrid Processing design for multipair massive mimo relaying with channel spatial correlation
IEEE Transactions on Communications, 2019Co-Authors: Milad Fozooni, Hien Quoc Ngo, Michail Matthaiou, Shi Jin, George C AlexandropoulosAbstract:Massive multiple-input multiple-output (MIMO) avails of simple transceiver design which can tackle many drawbacks of relay systems in terms of complicated signal Processing, latency, and noise amplification. However, the cost and circuit complexity of having one radio frequency (RF) chain dedicated to each antenna element are prohibitive in practice. In this paper, we address this critical issue in amplify-and-forward (AF) relay systems using a Hybrid analog and digital (A/D) transceiver structure. More specifically, leveraging the channel long-term properties, we design the analog beamformer which aims to minimize the channel estimation error and remain invariant over a long timescale. Then, the beamforming is completed by simple digital signal Processing, i.e., maximum ratio combining/maximum ratio transmission (MRC/MRT) or zero forcing (ZF) in the baseband domain. We present analytical bounds on the achievable spectral efficiency taking into account the spatial correlation and imperfect channel state information at the relay station. Our analytical results reveal that the Hybrid A/D structure with ZF digital processor exploits spatial correlation and offers a higher spectral efficiency compared to the Hybrid A/D structure with MRC/MRT scheme. Our numerical results show that the Hybrid A/D beamforming design captures nearly 95% of the spectral efficiency of a fully digital AF relaying topology even by removing half of the RF chains. It is also shown that the Hybrid A/D structure is robust to coarse quantization, and even with 2-bit resolution, the system can achieve more than 93% of the spectral efficiency offered by the same Hybrid A/D topology with infinite resolution phase shifters.
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Hybrid Processing design for multipair massive mimo relaying with channel spatial correlation
arXiv: Information Theory, 2018Co-Authors: Milad Fozooni, Hien Quoc Ngo, Michail Matthaiou, Shi Jin, George C AlexandropoulosAbstract:Massive multiple-input multiple-output (MIMO) avails of simple transceiver design which can tackle many drawbacks of relay systems in terms of complicated signal Processing, latency, and noise amplification. However, the cost and circuit complexity of having one radio frequency (RF) chain dedicated to each antenna element are prohibitive in practice. In this paper, we address this critical issue in amplify-and-forward (AF) relay systems using a Hybrid analog and digital (A/D) transceiver structure. More specifically, leveraging the channel long-term properties, we design the analog beamformer which aims to minimize the channel estimation error and remain invariant over a long timescale. Then, the beamforming is completed by simple digital signal Processing, i.e., maximum ratio combining/maximum ratio transmission (MRC/MRT) or zero-forcing (ZF) in the baseband domain. We present analytical bounds on the achievable spectral efficiency taking into account the spatial correlation and imperfect channel state information at the relay station. Our analytical results reveal that the Hybrid A/D structure with ZF digital processor exploits spatial correlation and offers a higher spectral efficiency compared to the Hybrid A/D structure with MRC/MRT scheme. Our numerical results showcase that the Hybrid A/D beamforming design captures nearly 95% of the spectral efficiency of a fully digital AF relaying topology even by removing half of the RF chains. It is also shown that the Hybrid A/D structure is robust to coarse quantization, and even with 2-bit resolution, the system can achieve more than 93% of the spectral efficiency offered by the same Hybrid A/D topology with infinite resolution phase shifters.
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spectral and energy efficiency of multi pair massive mimo relay network with Hybrid Processing
arXiv: Information Theory, 2017Co-Authors: Jian Liu, Shi Jin, Xiaodai DongAbstract:We consider a multi-pair massive multiple-input multiple-output (MIMO) relay network, where the relay is equipped with a large number, N, of antennas, but driven by a far smaller number, L, of radio frequency (RF) chains. We assume that K pairs of users are scheduled for simultaneous transmission, where K satisfies 2K = L. A Hybrid signal Processing scheme is presented for both uplink and downlink transmissions of the network. Analytical expressions of both spectral and energy efficiency are derived with respect to the RF chain number under imperfect channel estimation. It is revealed that, under the condition N > 4L^2/pi, the transmit power of each user and the relay can be respectively scaled down by 1=sqrt(N) and 2K=sqrt(N) if pilot power scales with signal power, or they can be respectively scaled down by 1=N and 2K=N if the pilot power is kept fixed, while maintaining an asymptotically unchanged spectral efficiency (SE). While regarding energy efficiency (EE) of the network, the optimal EE is shown to be achieved when Pr = 2KPs, where Pr and Ps respectively refer to the transmit power of the relay and each source terminal. We show that the network EE is a quasi-concave function with respect to the number of RF-chains which, therefore, admits a unique globally optimal choice of the RF-chain number. Numerical simulations are conducted to verify our observations.
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spectral and energy efficiency of multi pair massive mimo relay network with Hybrid Processing
IEEE Transactions on Communications, 2017Co-Authors: Jian Liu, Shi Jin, Xiaodai DongAbstract:We consider a multi-pair massive multiple-input multiple-output relay network, where the relay is equipped with a large number, $N$ , of antennas, but driven by a far smaller number, $L$ , of radio-frequency (RF) chains. We assume that $K$ pairs of users are scheduled for simultaneous transmission, where $K$ satisfies $2K=L$ . A Hybrid signal Processing scheme is presented for both uplink and downlink transmissions of the network. Analytical expressions of both spectral efficiency (SE) and energy efficiency (EE) are derived with respect to the RF chain number under imperfect channel estimation. It is revealed that, under the condition $N>\left \lfloor{ 4L^{2}/\pi }\right \rfloor $ , the transmit power of each user and the relay can be, respectively, scaled down by $1/\sqrt {N}$ and $2K/\sqrt {N}$ if pilot power scales with signal power, or they can be, respectively, scaled down by $1/N$ and $2K/N$ if the pilot power is kept fixed, while maintaining an asymptotically unchanged SE. While regarding EE of the network, the optimal EE is shown to be achieved when $P_{r} = 2K P_{s}$ , where $P_{r}$ and $P_{s}$ , respectively, refer to the transmit power of the relay and each source terminal. We show that the network EE is a quasi-concave function with respect to the number of RF-chains which, therefore, admits a unique globally optimal choice of the RF-chain number. Numerical simulations are conducted to verify our observations.
Xiaodai Dong - One of the best experts on this subject based on the ideXlab platform.
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Near-Optimal Hybrid Processing for Massive MIMO Systems via Matrix Decomposition
IEEE Transactions on Signal Processing, 2017Co-Authors: Xiaodai DongAbstract:For practical implementation of massive multiple-input multiple-output (MIMO) systems, the Hybrid Processing (precoding/combining) structure is promising to reduce the high implementation cost and power consumption rendered by large number of radio frequency (RF) chains of the traditional Processing structure. The Hybrid Processing is realized through low-dimensional digital baseband Processing combined with analog RF Processing enabled by phase shifters. We propose to design Hybrid RF and baseband precoders/combiners for multistream transmission in massive MIMO systems, by directly decomposing the predesigned unconstrained digital precoder/combiner of a large dimension. This approach is fundamental and general in the sense that any conventional full RF chain precoding solution of a MIMO system configuration can be converted to a Hybrid Processing structure by matrix decomposition. The constant amplitude constraint of analog RF Processing results in the matrix decomposition problem nonconvex. Based on an alternate optimization technique, the nonconvex matrix decomposition problem can be decoupled into a series of convex subproblems and effectively solved by restricting the phase increment of each entry in the RF precoder/combiner within a small vicinity of its preceding iterate. A singular value decomposition-based technique is proposed to secure an initial point sufficiently close to the global solution of the original nonconvex problem. Through simulation, the convergence of the alternate optimization for such a matrix decomposition-based Hybrid Processing (MD-HP) scheme is examined, and the performance of the MD-HP scheme is demonstrated to be near-optimal.
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spectral and energy efficiency of multi pair massive mimo relay network with Hybrid Processing
arXiv: Information Theory, 2017Co-Authors: Jian Liu, Shi Jin, Xiaodai DongAbstract:We consider a multi-pair massive multiple-input multiple-output (MIMO) relay network, where the relay is equipped with a large number, N, of antennas, but driven by a far smaller number, L, of radio frequency (RF) chains. We assume that K pairs of users are scheduled for simultaneous transmission, where K satisfies 2K = L. A Hybrid signal Processing scheme is presented for both uplink and downlink transmissions of the network. Analytical expressions of both spectral and energy efficiency are derived with respect to the RF chain number under imperfect channel estimation. It is revealed that, under the condition N > 4L^2/pi, the transmit power of each user and the relay can be respectively scaled down by 1=sqrt(N) and 2K=sqrt(N) if pilot power scales with signal power, or they can be respectively scaled down by 1=N and 2K=N if the pilot power is kept fixed, while maintaining an asymptotically unchanged spectral efficiency (SE). While regarding energy efficiency (EE) of the network, the optimal EE is shown to be achieved when Pr = 2KPs, where Pr and Ps respectively refer to the transmit power of the relay and each source terminal. We show that the network EE is a quasi-concave function with respect to the number of RF-chains which, therefore, admits a unique globally optimal choice of the RF-chain number. Numerical simulations are conducted to verify our observations.
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spectral and energy efficiency of multi pair massive mimo relay network with Hybrid Processing
IEEE Transactions on Communications, 2017Co-Authors: Jian Liu, Shi Jin, Xiaodai DongAbstract:We consider a multi-pair massive multiple-input multiple-output relay network, where the relay is equipped with a large number, $N$ , of antennas, but driven by a far smaller number, $L$ , of radio-frequency (RF) chains. We assume that $K$ pairs of users are scheduled for simultaneous transmission, where $K$ satisfies $2K=L$ . A Hybrid signal Processing scheme is presented for both uplink and downlink transmissions of the network. Analytical expressions of both spectral efficiency (SE) and energy efficiency (EE) are derived with respect to the RF chain number under imperfect channel estimation. It is revealed that, under the condition $N>\left \lfloor{ 4L^{2}/\pi }\right \rfloor $ , the transmit power of each user and the relay can be, respectively, scaled down by $1/\sqrt {N}$ and $2K/\sqrt {N}$ if pilot power scales with signal power, or they can be, respectively, scaled down by $1/N$ and $2K/N$ if the pilot power is kept fixed, while maintaining an asymptotically unchanged SE. While regarding EE of the network, the optimal EE is shown to be achieved when $P_{r} = 2K P_{s}$ , where $P_{r}$ and $P_{s}$ , respectively, refer to the transmit power of the relay and each source terminal. We show that the network EE is a quasi-concave function with respect to the number of RF-chains which, therefore, admits a unique globally optimal choice of the RF-chain number. Numerical simulations are conducted to verify our observations.
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Near-Optimal Hybrid Processing for Massive MIMO Systems via Matrix Decomposition
arXiv: Information Theory, 2015Co-Authors: Xiaodai DongAbstract:For the practical implementation of massive multiple-input multiple-output (MIMO) systems, the Hybrid Processing (precoding/combining) structure is promising to reduce the high cost rendered by large number of RF chains of the traditional Processing structure. The Hybrid Processing is performed through low-dimensional digital baseband Processing combined with analog RF Processing enabled by phase shifters. We propose to design Hybrid RF and baseband precoders/combiners for multi-stream transmission in point-to-point massive MIMO systems, by directly decomposing the pre-designed unconstrained digital precoder/combiner of a large dimension. The constant amplitude constraint of analog RF Processing results in the matrix decomposition problem non-convex. Based on an alternate optimization technique, the non-convex matrix decomposition problem can be decoupled into a series of convex sub-problems and effectively solved by restricting the phase increment of each entry in the RF precoder/combiner within a small vicinity of its preceding iterate. A singular value decomposition based technique is proposed to secure an initial point sufficiently close to the global solution of the original non-convex problem. Through simulation, the convergence of the alternate optimization for such a matrix decomposition based Hybrid Processing (MD-HP) scheme is examined, and the performance of the MD-HP scheme is demonstrated to be near-optimal.
Yupei Huang - One of the best experts on this subject based on the ideXlab platform.
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preparation of tio2 thin films on glass surfaces with self cleaning characteristics for solar concentrators
Surface & Coatings Technology, 2013Co-Authors: Kowei Weng, Yupei HuangAbstract:Abstract High concentration photovoltaic (HCPV) systems improve their long-term stability in terms of sunlight concentration by using silicone-on-glass (SOG) composite optic lenses with glasses. Due to dust pollution, reflectance of the concentrator glasses significantly decreases the output power efficiency of a solar power system. Titanium dioxide (TiO 2 ) films are known for their hydrophilic and photocatalytic characteristics. This study investigates the effects of introducing third elements in a-TiO 2 films by implantation, to enhance the photocatalytic and hydrophilicity properties, as well as widen the wavelength sensitization range. TiO 2 -based hydrophilic and photocatalytic films on glass for self-cleaning purposes were prepared. The implant elements are Fe, Cr, and V. The samples are prepared by a Hybrid system consisting of physical vapor deposition (PVD) and metal plasma ion implantation (MPII). High quality TiO 2 films are first fabricated by r.f. magnetron sputtering system, followed by metal plasma ion implantation of Fe. Experimental results indicate that the Hybrid Processing method significantly increases the activation and sunlight absorption rate of TiO 2 thin films with the addition of third elements. Moreover, the proposed TiO 2 –Fe thin film exhibits superior hydrophilicity properties with a contact angle of 9.95 ° and reduces the optical bandgap to 3.33 eV.
