Science Letters:A power divider based on a new kind of composite right/left-handed transmission line (CRLH TL) unit

INTRODUCTION Wave propagation in a material with negative magnetic permeability and negative electric permit- tivity was first theoretically analyzed by Veselago (1968). In such a left-handed material (LHM), the electric field E, the magnetic field H and the wave vector k of electromagnetic wave propagation obey the left-hand rule (instead of the right-hand rule for usual materials). After Smith et al.(2000) demon- strated simultaneously negative permeability and permittivity, using cop…     

Novel resonator based on composite right/left-handed transmission lines

INTRODUCTION Left-handed materials (LHMs) are characterized by simultaneously negative permittivity and perme- ability. It was first investigated theoretically by Ve- selago (1968). The experimental realization of LHM with resonance structures was demonstrated by Smith et al.(2000). Since then, LHM has gained significant interest and started to be integrated into novel mi- crowave and optical applications. The transmis- sion-line (TL) approach was recently proposed to realize LHMs …     

Science Letters:Dual structure of composite right/left-handed transmission line

INTRODUCTION An artificial dielectric medium that exhibits si- multaneously negative electric permittivity and magnetic permeability, also known as a left-handed (LH) material, was first envisaged by Veselago, who theoretically predicted that such a medium would exhibit a negative refractive index (NRI) (Veselago, 1968). An artificial NRI medium exhibiting back- ward-wave propagation characteristics (and therefore a negative refractive index) was first realized ex- perimentally in (She…     

Dual structure of composite right/left-handed transmission line

A dual structure of composite right/left handed （CRLH） transmission line （TL） is analyzed in which an inductance LR is in parallel with a capacitance CL and a shunt capacitance CR is in series with an inductance LL. Both the distributed and lumped cases are considered. The dispersion diagram and transmission properties of the dual CRLH TL are given and compared with those of a standard CRLH TL. Contrary to the frequency response of a standard CRLH TL, a dual CRLH TL has a left-handed （negative phase shift） band at higher frequencies and a right-handed （positive phase shift） band at lower frequencies. A novel dual-band balun is presented as an application.     

A tunable dual-broad-band branch-line coupler utilizing composite right／left-handed transmission lines

INTRODUCTION Veselago (1968) theoretically analyzed the wave propagation in a left-handed (LH) material which has simultaneously a negative magnetic permeability and a negative electric permittivity. The electric field, the magnetic field, and the wave vector of an electro-magnetic wave propagating in such a material obey the left-hand rule (instead of the right-hand rule for usual materials). Such an LH material was first real-ized in 2001 in microwave region with an array of metallic …     

A new broadband differential phase shifter fabricated using a novel CRLH structure

Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90° in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90° broadband differential phase shifter are presented.     

平面天线阵列馈电网络应用教学探讨

在综合分析了微带平面天线阵列馈电网络的两种传统馈电方式的基础上,提出了一种在微波工程应用中实际使用的一种新型馈电网络,提高学生理论知识与实践相结合的能力,更好的掌握最新技术发展。其新型馈电网络由一种左-右手混合微带传输线构成,可以获得高于传统并联馈电网络的天线阵列增益;同时,可以修正传统串联馈电网络的天线阵列辐射方向图的波束偏移,给出了一个工作频率为35GHz的2×2微带面阵的馈电网络设计案例,验证了其理论的正确性。     

A video structural similarity quality metric based on a joint spatial-temporal visual attention model

Objective video quality assessment plays a very important role in multimedia signal processing. Several extensions of the structural similarity （SSIM） index could not predict the quality of the video sequence effectively. In this paper we propose a structural similarity quality metric for videos based on a spatial-temporal visual attention model. This model acquires the motion attended region and the distortion attended region by computing the motion features and the distortion contrast. It mimics the visual attention shifting between the two attended regions and takes the burst of error into account by introducing the non-linear weighting fimctions to give a much higher weighting factor to the extremely damaged frames. The proposed metric based on the model renders the final object quality rating of the whole video sequence and is validated using the 50 Hz video sequences of Video Quality Experts Group Phase I test database.     

A network-aware error-resilient method using prioritized intra refresh for wireless video communications

We propose a novel prioritized intra refresh method for the wireless video communication. The proposed method considers the characteristics of the human visual system, the error-sensitivity of the bitstream, and the state of the time-varying wireless channel jointly. An expected perceptual distortion model was used to adjust the intra refresh rate adaptively. This model consists of the perceptual weight map based on an attention model, the bit error probability map based on bitstream size, and the dynamic channel state information （CSI）. Experimental results indicate that, compared with other intra refresh methods that consider only the content of the video or the CSI, the proposed method improves the average peak signal-to-noise ratio （PSNR） of the whole frame by about 0.5 dB, and improves the average PSNR of the attention-area by about 0.8 dB.     

A network condition classification scheme for supporting video delivery over wireless Internet*

INTRODUCTION Real-time video transport over wireless Internet faces many challenges due to the heterogeneous en- vironment including wireline and wireless networks. Fig.1 shows a typical end-to-end video transport in- volving wireline and wireless networks. The video transport may suffer from many problems such as wireline network congestion and wireless multi-path fading, resulting in high packet loss-rate, and causing severe video quality degradation. To maintain the optimal video quali…     

一种高吞吐率JPEG2000 9/7离散小波变换VLSI设计(英文)

为提高JPEG2000系统中离散小波变换的计算并行度,设计了一种高吞吐率二维9/7离散小波变换VLSI架构.其行变换核采用翻转结构,并根据行列变换核输入数据流的差异,在行变换核基础上增加输入选择器和数据缓存模块得到列变换核.对行列变换的归一化过程进行融合以节省乘法器,并论证了其合理性.通过多路选择器重排4个行变换核的输出,使每个列变换核处理的数据量减半,实现四路输入、四路输出.对一幅N×N的灰度图像进行一层9/7小波变换,计算时间为0.25N2+1.5N个周期,关键路径延迟为1个乘法器延迟,且只需5N存储空间.FPGA后仿真结果表明,时钟频率可达136 MHz,吞吐率达到544M sample/s,可以满足高速率应用的要求.     

定价多资产美式期权的半线性Black-Scholes偏微分方程的唯一解

In this paper, by using the optimal stopping theory, the semilinear Black-Scholes partial differential equation （PDE） was invesigated in a fixed domain for valuing two assets of American （call-max/put-min） options. From the viscosity solution of a PDE, a unique viscosity solution was obtained for the semilinear Black-Scholes PDE.     

A cross-cultural collaborative: creating textbooks and learning materials and a sustainable partnership for African children

Abstract

This article describes a case study of the South Carolina State University (SCSU)-Zanzibar Textbook and Learning Materials Program (TLMP). A Needs Assessment Plan (NAP), consisting of interviews, observations and debriefings, and including a Rapid Needs Assessment (RNA), was implemented to determine the need for textbooks and learning materials. The purpose of the collaborative was to support capacity building in Zanzibar and provide textbooks and learning materials for children in this Sub-Saharan African region. The outcomes were achieved by developing, publishing, and delivering approximately one million culturally relevant textbooks for secondary students, as well as supplementary learning materials. Some of the Education For All (EFA) goals served as a guide for the TLMP's commitment to improve education and social awareness (i.e., gender, HIV/AIDS), and professional development through textbooks. Methodological considerations were framed by case study processes for a) describing, monitoring and analyzing causal effects, and b) a participatory research approach. The methods promoted an equitable process, giving voice to all participants. Consistent with the findings, results were culturally relevant textbooks and improved capacity for Zanzibari participants. Thus, a comprehensive process evolved, resulting in a sustainable partnership between SCSU and Zanzibari stakeholders. The success of the project was confirmed at an historic ceremonial event, Biology textbooks and learning materials were delivered in January 2008, and Physics, Chemistry, and Mathematics textbooks are scheduled to be delivered in September 2008.