Cooperative Secret Communication with Artificial Noise in Symmetric Interference Channel

We consider the symmetric Gaussian interference channel where two users try to enhance their secrecy rates in a cooperative manner. Artificial noise is introduced along with useful information. We derive the power control and artificial noise parameter for two kinds of optimal points, max-min point and single user point. It is shown that there exists a critical value $P_c$ of the power constraint, below which the max-min point is an optimal point on the secrecy rate region, and above which time-sharing between single user points achieves larger secrecy rate pairs. It is also shown that artificial noise can help to enlarge the secrecy rate region, in particular on the single user point.Comment: 3 pages, 3 figures, to appear in IEEE Communications Letter

Hydrogenated microcrystalline silicon germanium material and photovoltaic devices prepared using ECR PECVD

High quality muc-SiGe:H is a very promising alternative for high efficiency photovoltaic device. The preparation of this material requires very high hydrogen dilution ratio in PECVD system. The deposition rate was greatly limited by this high hydrogen ratio. In this work, ECR PECVD technique is used to deposit muc-SiGe:H material. The growth rate can be greatly enhanced by taking advantage of the high plasma density and low ion energy features of ECR and extremely high hydrogen dilution ratios are no longer necessary for muc-SiGe:H growth. Films with good crystallinity were prepared at hydrogen dilution ratio as low as 1:15. An intensive study has been completed for the muc-SiGe:H with 0 to over 75% Ge incorporated. The optical bandgap shrinks with the incorporation of Ge into the material. Raman spectra and the increase of activation energy and photosensitivity indicates the deterioration of crystallinity by adding Ge to the Si structure. Solar cell devices using muc-SiGe:H as the active layer were deposited on stainless steel substrates. Fill factors over 55% were achieved for muc-SiGe devices with less than 35% Ge. An muc-Si buffer layer between n+ and muc-SiGe:H n layer was used in the device design and this buffer layer revealed to be very beneficial to the device performance and the growth rate of muc-SiGe:H active layer. C-V measurements showed that the accidental oxygen leakage can raise the doping level to the order of 1E17cm-3 ppm level TMB can be mixed in the source gas to very effectively reduce the N-type doping brought by oxygen. Short circuit current was increased by the TMB counter doping. The minority carrier diffusion length was estimated from reversed bias QE and C-V measurements. In the muc-SiGe:H devices fabricated by ECR PECVD, the hole diffusion length is several tenth micrometers. The accidental doping in the muc-SiGe:H deteriorates the device performance by decreasing the minority carrier diffusion length. Compensating doping of TMB can increase minority carrier diffusion length Lp and improve short circuit current, and hence improve the conversion efficiency of solar cell device

Effects of process parameters on mechanical properties of abrasive-assisted electroformed nickel

AbstractA cathode mandrel with translational and rotational motion, which was supposed to obtain uniform friction effect on surface, was employed in abrasive-assisted electroforming for revolving parts with complex profile. The effects of current density, translational speed and rotational speed on the deposit properties were studied by orthogonal test. The tensile strength, elongation and micro hardness value were measured to find out how the factors affected the properties. The optimized results show that changes of current density affect the tensile strength of nickel layer most, while translational speed has the most remarkable influences on both elongation and micro hardness. The low rotational speed affects the properties least. In this experiment, a smooth nickel layer with tensile strength 581MPa, elongation 17% and micro hardness 248HV is obtained by the orthogonal test

Impact of the Collective Forest Right System Reform on Poverty Reduction and Income Growth for Forest Farmer in Mountain Area - A Case Study of Jiangxi Province, China

Despite being a strong advocate for children’s rights in the international community, Sweden has received critique from the Committee on the Rights of the Child regarding the high number of children who have been removed from their families and that are currently living in foster homes. Previous research has not dealt with the issue of children’s rights in foster care placement processes in Sweden, nor has it included Sweden in discourse analyses on children’s rights, or sufficiently explored the relationship between discourse and implementation of the UNCRC. I use theories on discourse and translation in order to provide a comparative analysis of the articulations of children’s rights relevant for foster care placement processes in the UNCRC, and on the national and local level in Sweden. The analysis points to both similarities and differences in the discourses and identifies six aspects of the Swedish discourse that make certain activities in foster care placement processes possible, desirable and inevitable