1-Bit Massive MIMO Downlink Based on Constructive Interference

In this paper, we focus on the multiuser massive multiple-input single-output (MISO) downlink with low-cost 1-bit digital-to-analog converters (DACs) for PSK modulation, and propose a low-complexity refinement process that is applicable to any existing 1-bit precoding approaches based on the constructive interference (CI) formulation. With the decomposition of the signals along the detection thresholds, we first formulate a simple symbol-scaling method as the performance metric. The low-complexity refinement approach is subsequently introduced, where we aim to improve the introduced symbol-scaling performance metric by modifying the transmit signal on one antenna at a time. Numerical results validate the effectiveness of the proposed refinement method on existing approaches for massive MIMO with 1-bit DACs, and the performance improvements are most significant for the low-complexity quantized zero-forcing (ZF) method.Comment: 5 pages, EUSIPCO 201

Lemons on the Web: A Signalling Approach to the Problem of Trust in Internet Commerce

Asymmetric information is at the heart of situations involving trust. In the case of B2C Internet commerce, the information asymmetry typically relates to the difficulty that consumers have of distinguishing between "trustworthy" and "untrustworthy" Web merchants. The impasse can be resolved by the use of signals by trustworthy Web merchants to differentiate themselves from untrustworthy ones. Using an experimental design where subjects are exposed to a series of purchase choices, we investigate three possible signals, an unconditional money-back guarantee, branding, and privacy statement, and test their efficacy. Our empirical results confirm the predictions suggested by signalling theory.trust (social behaviour), consumer behaviour

An Investigation Of The Leadership Styles Of Principals In Selected Secondary Schools In The District Of Muar, Johor

Much has been written about educational administration. It appears that secondary school principals have different styles of leadership. There are 4 distinct types of leadership posited by Hersey and Blanchard(l976, 1982, 1993), that is, "Telling", "Selling", "Participating" and "Delegating". Each style is appropriate and effective depending on the situation and the maturity of the work group (Bersey and Blanchard, 1982). The purpose of the study was to investigate the leadership styles of principals in selected secondary schools in the district of Muar, Johor. Specifically, it was to determine the extent to which the principals demonstrate the leadership styles of "Telling", "Selling", "Participating" and "Delegating" as delineated in The Leader Effectiveness and Adaptability Description (LEAD) designed by Hersey in 1989. The study also looked into the perceptions of teachers of the leadership styles of their principals by gender, qualification, working experience, grade and location of schools. Data was analyzed using the "Leader Effectiveness and Adaptability Description" (Hersey, 1989) and scores were then analyzed using descriptive statistics. Respondents in the study were 20 principals and 388 teachers. Based on the findings, it was found that principals chose "Selling" as the dominant primary leadership style and "Participating" as the dominant secondary leadership style. They demonstrated high flexibility in "Selling and Participating but rather low style adaptability in general. It was found that the perceptions of principals and teachers were similar on the dominant primary leadership style but differed concerning secondary leadership style(s), style range and style adaptability. It was also found that teachers' perceptions of primary leadership styles of principals differed by gender and qualification but there was no difference in the leadership style adaptability, by qualification of teachers, grade and location of schools. The results appear to indicate that principals still lack the ability to adapt their styles of leader behavior to meet the particular situations and needs of their teachers

A Study On The Characteristics Of Chitosan As An Immobilization Matrix For Biosensors [QP702.C5 A581 2007 f rb ].

Dua jenis kitosan (FCHIT dan SCHIT) telah diselidik sebagai matriks immobilisasi bagi pembuatan biosensor glukosa. Kelikatan-purata berat molekul bagi FCHIT and SCHIT telah ditentukan iaitu 981.80 kD dan 398.61 kD masing-masing. Two chitosan samples (FCHIT and SCHIT) were investigated as an enzyme immobilization matrix for the fabrication of glucose biosensor. The viscosityaverage molecular weight of FCHIT and SCHIT were determined to be 981.80 kD and 398.61 kD respectively

Universal Scaling and Signatures of Nodal Structures in Electron Tunneling from Two-Dimensional Semimetals

We present the theory of out-of-plane electron thermal-field emission from 2D semimetals. We show that the current($\mathcal{J}$)-field($F$)-temperature($T$) characteristic is captured by a universal scaling law applicable for broad classes of 2D semimetals, including monolayer and few-layer graphene, nodal point semimetals, nodal line semimetals and Dirac semimetals at the verge of topological phase transition. The low-temperature scaling takes the universal form, $\log\left( \mathcal{J}/F^\gamma \right) \propto -1/F$ with $\gamma = 1$ for 2D semimetals, which is in stark contrast to the classic Fowler-Nordheim scaling of $\gamma = 2$ for 3D metals. Importantly, the Fermi level dependence of the tunneling currents depends sensitively on the nodal structure through the electronic density of states, thus serving as a probe for detecting the various possible nodal structures of 2D semimetals. Our findings provide a theoretical basis for the understanding of tunneling charge transport phenomena in solid/vacuum and solid/solid interfaces, critical for the development of 2D-material-based vacuum and solid-state electronic devices.Comment: 8 pages, 2 figure

Injection-Limited and Space-Charge-Limited Conduction in Wide Bandgap Semiconductors with Velocity Saturation Effect

Carrier conduction in wide bandgap semiconductors (WBS) often exhibits velocity saturation at the high-electric field regime. How such effect influences the transition between contact-limited and space-charge-limited current in a two-terminal device remains largely unexplored thus far. Here, we develop a generalized carrier transport model that includes contact-limited field-induced carrier injection, space charge, carrier scattering and velocity saturation effect. The model reveals various transitional behaviors in the current-voltage characteristics, encompassing Fowler-Nordheim emission, trap-free Mott-Gurney (MG) SCLC and \emph{velocity-saturated SCLC}. Using GaN, 6H-SiC and 4H-SiC WBS as examples, we show that the velocity-saturated SCLC completely dominates the high-voltage ($10^2 \sim 10^4$ V) transport for typical sub-$\mu$m GaN and SiC diodes, thus unravelling velocity-saturated SCLC as a central transport mechanism in WBG electronics.Comment: 8 pages, 5 figure