Dual-tracking multi-constellation GNSS front-end for high-performance receiver applications

This paper presents the design and implementation of a dual–tracking Radio Frequency (RF) front–end for a multi–constellation Global Navigation Satellite Systems (GNSS) receiver. The RF frond–end is based on the direct RF conversion architecture, which employs sub–Nyquist sampling (also known as subsampling) at RF. The dual–tracking RF front–end is composed of a few RF components that are duplicated to form the two RF channels. Employing a dual–channel Analogue–to–Digital Converter (ADC) enables synchronisation of the RF channels and minimises the errors resulting from the differences in the satellite clocks and the propagation delay between the two RF channels. The digitised GNSS signals are processed by two separate acquisition and tracking engines that are driven by the front–end’s master clock. This setup provides two synchronised receivers that are integrated onto one piece of hardware. The hardware is intended to be used for research applications such as multipath mitigation, scintillation assessment, and advanced satellite clock and spatial frame transformation modelling.

Special Section Guest Editorial: Image/Video Quality and System Performance

Rapid developments in display technologies, digital printing, imaging sensors, image processing and image transmission are providing new possibilities for creating and conveying visual content. In an age in which images and video are ubiquitous and where mobile, satellite, and three-dimensional (3-D) imaging have become ordinary experiences, quantification of the performance of modern imaging systems requires appropriate approaches. At the end of the imaging chain, a human observer must decide whether images and video are of a satisfactory visual quality. Hence the measurement and modeling of perceived image quality is of crucial importance, not only in visual arts and commercial applications but also in scientific and entertainment environments. Advances in our understanding of the human visual system offer new possibilities for creating visually superior imaging systems and promise more accurate modeling of image quality. As a result, there is a profusion of new research on imaging performance and perceived quality.

Drink availability is associated with enhanced examination performance in adults

While dehydration has negative effects on memory and attention, few studies have investigated whether drinking water can enhance cognitive performance, and none have addressed this in a real-world setting. In this study we explored the potential benefits of the availability of water for undergraduates. The exam performance of students who brought drinks in to exams was compared with those that did not for three cohorts of undergraduates (N = 447). We employed earlier coursework marks as a measure of underlying ability. Students who brought water to the exam achieved better grades than students who did not. When coursework marks were covaried, this effect remained statistically significant, suggesting that this finding was not simply due to more able students being more likely to bring in water. This implies that water consumption may facilitate performance in real-world settings, and, therefore, have specific implications for the assessment of undergraduate learners under examination conditions, but further research is required to evaluate this hypothesis.

An assessment of manager/subordinate perceptions of performance appraisal effectiveness

This study postulates that performance appraisal will be effective to the extent that managers and subordinates have a shared perception of its purpose and function and the degree to which it meets the needs of both groups. A two part research project was conducted to: 1) identify manager/subordinate perceptions of the purposes served by the formal performance appraisal process; 2) determine the extent to which these purposes are being satisfied in organizational practice; and 3) assess if managers and subordinates have a shared perception of the effectiveness of the appraisal process. The sample for the study included 36 managers and 143 subordinates from a division of a large Midwest service organization. The results were mixed with regard to the appraisal system effectively accomplishing its diverse goals. However, in general, there was support for the notion that both managers and subordinates find the appraisal process to be a worthwhile organizational practice. Approximately 70% of the respondents indicated that they would participate in the appraisal program whether they were required to do so or not.