Transceiver Optimization for Two-Hop AF MIMO Relay Systems With DFE Receiver and Direct Link

In this paper, we consider precoding and receiving matrices optimization for a two-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay system with a decision feedback equalizer (DFE) at the destination node in the presence of the direct source-destination link. By adopting the minimum mean-squared error (MMSE) criterion, we develop two new transceiver design algorithms for such a system. The first one employs an iterative procedure to design the source, relay, feed-forward, and feedback matrices. The second algorithm is a non-iterative suboptimal approach which decomposes the optimization problem into two tractable subproblems and obtains the source and relay precoding matrices by solving the two subproblems sequentially. Simulation results validate the better MSE and bit-error-rate (BER) performance of the proposed algorithms and show that the non-iterative suboptimal method has a negligible performance loss when the ratio of the source node transmission power to the relay node transmission power is small. In addition, the computational complexity analysis suggests that the second algorithm and one iteration of the first algorithm have the same order of complexity. As the first algorithm typically converges within a few iterations, both proposed algorithms exhibit a low complexity order

A unified constitutive model for asymmetric tension and compression creep-ageing behaviour of naturally aged Al-Cu-Li alloy

A set of unified constitutive equations is presented that predict the asymmetric tension and compression creep behaviour and recently observed double primary creep of pre-stretched/naturally aged aluminium-cooper-lithium alloy AA2050-T34. The evolution of the primary micro- and macro-variables related to the precipitation hardening and creep deformation of the alloy during creep age forming (CAF) are analysed and modelled. Equations for the yield strength evolution of the alloy, including an initial reversion and subsequent strengthening, are proposed based on a theory of concurrent dissolution, re-nucleation and growth of precipitates during artificial ageing. We present new observations of so-called double primary creep during the CAF process. This phenomenon is then predicted by introducing effects of interacting microstructures, including evolving precipitates, diffusing solutes and dislocations, into the sinh-law creep model. In addition, concepts of threshold creep stress σth and a microstructure-dependant creep variable H, which behave differently under different external stress directions, are proposed and incorporated into the creep model. This enables prediction of the asymmetric tension and compression creep-ageing behaviour of the alloy. Quantitative transmission electron microscopy (TEM) and related small-angle X-ray scattering (SAXS) analysis have been carried out for selected creep-aged samples to assist the development and calibration of the constitutive model. A good agreement has been achieved between the experimental results and the model. The model has the potential to be applied to creep age forming of other heat-treatable aluminium alloys

Effects of Grazing Management on Grassland Production and Animal Performance

Five grazing treatments with a set of design for evaluation of seasonal grazing influencing grassland conditions and animal performance have been conducted across northern and western China, in order to identify the key solutions for degradation of grazing grasslands. Here, the effects of seasonal grazing within two systems-one based on current ‘survival’ practices and the other taking more of a ‘production’ focus in Bashang grasslands were reported. The experiment involved a factorial combination of alternative practices (survival vs. production systems) in spring, summer and autumn with a layout of 15 plots and 1.5 ha per plot. Results of consecutive two years studies showed that the vegetation composition changed significantly across grazing treatments, and spring rest treatments can significantly improve grassland production but with low LWG across all grazing seasons. Animal lost live weight on all grazing treatments in autumn indicating that the quality of grassland was lower and need supplementary feed in this season. In the meantime, the average LWG is lowest across the whole grazing season in the continuous survival grazing treatments, but highest in the continuous production treatment. In conclusion, spring rest is most important for grassland quality maintenance, and the continuous production grazing is more appropriate for animal production

Experimental studies and constitutive modelling of anelastic creep recovery during creep age forming

This paper presents a study of anelastic creep recovery during creep-ageing of an aluminium alloy AA7050-TAF. Uniaxial Creep-Ageing and Recovery Test (CART) was used to characterise the influence of anelastic creep strain on total creep deformation for determining the actual amount of springback in creep age forming (CAF) process. CART was performed on aluminium alloy AA7050-TAF at 174°C between the stress levels of 137.5 to 162.5 MPa. A constitutive model was developed for the prediction of the creep-ageing and recovery response of material in creep age forming. A 'back stress' variable was used to represent the net effect of the internal stresses of the material which causes anelastic creep recovery. Other microstructural variables were introduced to model complex micro-mechanisms and hardening effects including solid solution hardening, dislocation hardening, and age hardening. It has been found that the permanent strain after creep-ageing depends not only on total creep strain but also on anelastic strain. Simulation results from the constitutive model developed in this study show a good agreement with experimental data

Influence of Fermion Velocity Renormalization on Dynamical Mass Generation in QED3_3

We study dynamical fermion mass generation in (2+1)-dimensional quantum electrodynamics with a gauge field coupling to massless Dirac fermions and non-relativistic scalar bosons. We calculate the fermion velocity renormalization and then examine its influence on dynamical mass generation by using the Dyson-Schwinger equation. It is found that dynamical mass generation takes place even after including the scalar bosons as long as the bosonic compressibility parameter $\xi$ is sufficiently small. In addition, the fermion velocity renormalization enhances the dynamically generated mass.Comment: 6 pages, 3 figures, Chinese Physics Letter, Vol 29, page 057401(2012

Pure multiplicative stochastic resonance of anti-tumor model with seasonal modulability

The effects of pure multiplicative noise on stochastic resonance in an anti-tumor system modulated by a seasonal external field are investigated by using theoretical analyses of the generalized potential and numerical simulations. For optimally selected values of the multiplicative noise intensity quasi-symmetry of two potential minima and stochastic resonance are observed. Theoretical results and numerical simulations are in good quantitative agreement.Comment: 5 pages, 5 figure

High Dimensional Apollonian Networks

We propose a simple algorithm which produces high dimensional Apollonian networks with both small-world and scale-free characteristics. We derive analytical expressions for the degree distribution, the clustering coefficient and the diameter of the networks, which are determined by their dimension

The development of ovary in quail’s embryo

The experiment was conducted to study the development of ovary in quails’ embryos which were incubated for 4 to 17 days and incubated out for 1 day. The quails’ embryos or gonads were cut out and HE staining was carried out. The results showed that when embryo was hatched for 4 days, lots of primordial germ cells (PGCs) clustered in the region where gonad would be formed. On the 5th day of hatching, the gonad of the embryo began to be formed and exhibited the feature of ovary or testis. On the 7th hatching day, the right ovary began to degenerate, just a few PGCs began to differentiate into oogonia. On the 10th day, there were many oogonia in the ovary, some of which were surrounded by some other cells distributed like circles. On the 11th day, there were more oogonia, the skinniness became thicker while the medulla was thinner. On the 13th day, the division between skinniness and medulla was obvious and the ovary formed the early original ovum. On the 14th day, more original ovums were seen in the skinniness. On the 17th hatching day and on the 1st day of hatching out, the shape of ovary tended to be mature, also the ovum was clear and more; the medulla was full of vessels. On the 5th hatching day, gonad began to differentiate. On the 7th hatching day and later, thedifferentiation of gonad was obvious; the right ovary began to degenerate. On the 13th hatching day, early original ovum began to be formed in the skinniness of ovary. The results established groundwork for the research of the development of gonads of quail and other poultry.Key words: Quail, embryo, gonad, ovary