Evaluating and improving the performance of video content distribution in lossy networks

The contributions in this research are split in to three distinct, but related, areas. The focus of the work is based on improving the efficiency of video content distribution in the networks that are liable to packet loss, such as the Internet. Initially, the benefits and limitations of content distribution using Forward Error Correction (FEC) in conjunction with the Transmission Control Protocol (TCP) is presented. Since added FEC can be used to reduce the number of retransmissions, the requirement for TCP to deal with any losses is greatly reduced. When real-time applications are needed, delay must be kept to a minimum, and retransmissions not desirable. A balance, therefore, between additional bandwidth and delays due to retransmissions must be struck. This is followed by the proposal of a hybrid transport, specifically for H.264 encoded video, as a compromise between the delay-prone TCP and the loss-prone UDP. It is argued that the playback quality at the receiver often need not be 100% perfect, providing a certain level is assured. Reliable TCP is used to transmit and guarantee delivery of the most important packets. The delay associated with the proposal is measured, and the potential for use as an alternative to the conventional methods of transporting video by either TCP or UDP alone is demonstrated. Finally, a new objective measurement is investigated for assessing the playback quality of video transported using TCP. A new metric is defined to characterise the quality of playback in terms of its continuity. Using packet traces generated from real TCP connections in a lossy environment, simulating the playback of a video is possible, whilst monitoring buffer behaviour to calculate pause intensity values. Subjective tests are conducted to verify the effectiveness of the metric introduced and show that the results of objective and subjective scores made are closely correlated.

An evaluation of the effectiveness of intervention strategies for the promotion of health and safety performance in small firms

Recognition of the contribution of small firms to the UK economy has grown considerably since 1995 when this research first began. The poor record of small firms in managing health and safety effectively has caused concern, and efforts made to improve knowledge and awareness of the target group through various initiatives have had some success. This research thesis attempts to identify the range of intervention routes and methods available to reach the target group, and to consider ways of evaluating the outcome of such efforts. Various interventions were tested with small firms, including a Workshop; use of Questionnaires; short postal Reply Slip survey; leading to a closer evaluation of a specific industry- the Licensed Trade. Attitudes and beliefs of the sample were identified, and observations carried out to consider actions taken by workers and others in the workplace. These empirical research findings were used to develop the theme of Primary and Secondary interventions intended to change behaviours, and to confirm assumptions about what small firms currently do to manage health and safety risks. Guidance for small firms was developed as a Secondary intervention tool to support Primary interventions, such as inspection or insurance provision.

Longitudinal dispersion in spiral wound RO modules and its effect on the performance of batch mode RO operations

Operation of reverse osmosis (RO) in cyclic batch mode can in principle provide both high energy efficiency and high recovery. However, one factor that causes the performance to be less than ideal is longitudinal dispersion in the RO module. At the end of the batch pressurisation phase it is necessary to purge and then refill the module. During the purge and refill phases, dispersion causes undesirable mixing of concentrated brine with less concentrated feed water, therefore increasing the salt concentration and energy usage in the subsequent pressurisation phase of the cycle. In this study, we quantify the significance of dispersion through theory and experiment. We provide an analysis that relates the energy efficiency of the batch operation to the amount of dispersion. With the help of a model based on the analysis by Taylor, dispersion is quantified according to flow rate. The model is confirmed by experiments with two types of proprietary spiral wound RO modules, using sodium chloride (NaCl) solutions of concentration 1000 to 20,000 ppm. In practice the typical energy usage increases by 4% to 5.5% compared to the ideal case of zero dispersion.

Was it good for them? Reflections on the use of MENTOR and changes in course design using general performance measures

This paper considers the use of general performance measures in evaluating specific planning and design decisions in higher education and reflects on the students' learning process. Specifically, it concerns the use of the MENTOR multimedia computer aided learning package for helping students learn about OR as part of a general business degree. It includes the transfer of responsibility for a learning module to a new staff member and a change from a single tutor to a system involving multiple tutors. Student satisfaction measures, learning outcome measures and MENTOR usage patterns are examined in monitoring the effects of the changes in course delivery. The results raise some questions about the effectiveness of general performance measures in supporting specific decisions relating to course design and planning.

Capital and asset structures and their influence on the performance of Egyptian nationalised industries:an application of financial statement analysis and survey

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Impact of the fiber type and dispersion management on the performance of a NRZ 16 x 40 Gb/s DWDM transmission system

We examine the impact of the fiber type and dispersion management on the performance of a 16 × 40 Gb/s dense wavelength-division-multiplexing nonreturn-to-zero transmission system. The transmission line is composed of G.652 or G.655 fiber with periodic dispersion compensation and hybrid Raman erbium-doped fiber amplifier amplification.

The influence of socio-cultural environments on the performance of nascent entrepreneurs:an instrumental variable approach

The importance of informal institutions and in particular culture for entrepreneurship is a subject of ongoing interest. Past research has mostly concentrated on cross-national comparisons, cultural values, and the direct effects of culture on entrepreneurial behavior, but in the main found inconsistent results. The present research adds a fresh perspective to this research stream by turning attention to community-level culture and cultural norms. We hypothesize indirect effects of cultural norms on venture emergence. Specifically that community-level cultural norms (performance-based culture and socially-supportive institutional norms) impact important supply-side variables (entrepreneurial self-efficacy and entrepreneurial motivation) which in turn influence nascent entrepreneurs’ success in creating operational ventures (venture emergence). We test our predictions on a unique longitudinal data set (PSED II) tracking nascent entrepreneurs venture creation efforts over a 5 year time span and find evidence supporting them. Our research contributes to a more fine-grained understanding of how culture, in particular perceptions of community cultural norms, influences venture emergence. This research highlights the embeddedness of entrepreneurial behavior and its immediate antecedent beliefs in the local, community context.

Impact of the fiber type and nonlinear management over the performance of a 16x40 Gb/s DWDM transmission system

We examine impact of the fiber type and nonlinear management over the performance of a 16x40Gb/s DWDM NRZ transmission system. The line is constituted of 3x100km of G.652 or G.655 fiber with hybrid Raman-EDFA amplification.

Founders' human capital and the performance of UK new technology based firms

This paper investigates the role of entrepreneurs' general and specific human capital on the performance of UK new technology based firms using a resource based approach to the entrepreneurship theory. The effect of entrepreneurial human capital on the performance of NTBFs is investigated using data derived from a survey of 412 firms operating in both high-tech manufacturing and the services sectors. According to the resource based theory it is found that specific human capital is more important for the performance of NTBFs in relation to general. More specifically individual entrepreneurs or entrepreneurial teams with high levels of formal business education, commercial, managerial or same sector experience are found to have created better performing NTBFs. Finally it is found that the performance of a NTBF can improve through the combination of heterogeneous but complementary skills, including, for example, technical education and commercial experience or managerial technical and managerial commercial experience. © 2010 Springer Science+Business Media, LLC.

The influence of organizational and national culture on new product performance

The authors conduct a meta-analysis on the combined influence of organizational and national culture on new product performance. For this purpose, they refer to the effectiveness of value congruency and develop a conceptual model describing the fit between organizational culture types as suggested by the competing values framework and national culture, as described by Hofstede's cultural dimensions. The meta-analysis is based on 489 effect sizes taken from 123 manuscripts. The findings show that organizations with a market culture show the highest new product performance, while hierarchy-type organizations show the lowest performance. The influence of national culture variables supports the effect of value congruency, and shows that in individualistic cultures the impact of a clan culture decreases, the impact of an adhocracy culture type decreases with uncertainty avoidance, and the influence of a hierarchy culture type increases with power distance. The superior effect of a market culture type can be matched by other organizational orientations, but in particular national cultures only. The combined findings underline the importance for firms that seek to improve the success rate of new products on international markets to consider the fit of a national culture with a firm's organizational culture.

Enhancing the performance of intelligent control systems in the face of higher levels of complexity and uncertainty

Modern advances in technology have led to more complex manufacturing processes whose success centres on the ability to control these processes with a very high level of accuracy. Plant complexity inevitably leads to poor models that exhibit a high degree of parametric or functional uncertainty. The situation becomes even more complex if the plant to be controlled is characterised by a multivalued function or even if it exhibits a number of modes of behaviour during its operation. Since an intelligent controller is expected to operate and guarantee the best performance where complexity and uncertainty coexist and interact, control engineers and theorists have recently developed new control techniques under the framework of intelligent control to enhance the performance of the controller for more complex and uncertain plants. These techniques are based on incorporating model uncertainty. The newly developed control algorithms for incorporating model uncertainty are proven to give more accurate control results under uncertain conditions. In this paper, we survey some approaches that appear to be promising for enhancing the performance of intelligent control systems in the face of higher levels of complexity and uncertainty.

The impact of ageing and gender on visual mental imagery processes:a study of performance on tasks from the Complete Visual Mental Imagery Battery (CVMIB)

In this study we aim to evaluate the impact of ageing and gender on different visual mental imagery processes. Two hundred and fifty-one participants (130 women and 121 men; age range = 18–77 years) were given an extensive neuropsychological battery including tasks probing the generation, maintenance, inspection, and transformation of visual mental images (Complete Visual Mental Imagery Battery, CVMIB). Our results show that all mental imagery processes with the exception of the maintenance are affected by ageing, suggesting that other deficits, such as working memory deficits, could account for this effect. However, the analysis of the transformation process, investigated in terms of mental rotation and mental folding skills, shows a steeper decline in mental rotation, suggesting that age could affect rigid transformations of objects and spare non-rigid transformations. Our study also adds to previous ones in showing gender differences favoring men across the lifespan in the transformation process, and, interestingly, it shows a steeper decline in men than in women in inspecting mental images, which could partially account for the mixed results about the effect of ageing on this specific process. We also discuss the possibility to introduce the CVMIB in clinical assessment in the context of theoretical models of mental imagery.

A comparison of the teacher efficacy and performance of traditionally and alternatively certified first -year teachers

The purpose of this study was to compare the efficacy and performance evaluations of alternatively certified first-year teachers to traditionally certified first-year teachers. The participants were 25 first-year teachers in the Broward County Public School District (FL) who completed the Transition to Teaching alternative certification program and a comparison group of 32 first-year teachers in the same school district who completed a traditional university teacher preparation program. ^ The study was a mixed methods design (Creswell, 2003; Tashakkori & Teddlie, 1998). The quantitative data were collected during the 2002–2003 school year using the Teachers' Sense of Efficacy Scale (Tschannen-Moran & Hoy, 2001) and the Florida Performance Measurement System formative and summative instruments. The qualitative data consisted of focus group interviews that were conducted at the end of the 2002–2003 school year. ^ Data were analyzed using independent samples t tests to compare the means of the two populations on their efficacy scores and performance evaluations. Paired samples t tests and analysis of covariance (ANCOVA) were used to compare the efficacy scores for each certification type at the beginning of the school year to the efficacy scores at the end of the school year. A repeated measures analysis of variance (ANOVA) was used to compare the change in the efficacy scores of the teachers from the beginning of the school year to the end of the school year. Focus group interviews were conducted and transcribed, and the content was analyzed and categorized based on the four sources of self-efficacy described by Bandura (1986, 1997). ^ The results of this study revealed that no statistically significant differences existed between the two groups of teachers in their teacher efficacy or performance evaluations and that they reported similar sources of their efficacy. These findings add to the research base that supports alternative certification as a viable and effective pathway into teaching. ^

The effects of semantic and syntactic instruction on user performance and satisfaction in search user interface design

The design of interfaces to facilitate user search has become critical for search engines, ecommercesites, and intranets. This study investigated the use of targeted instructional hints to improve search by measuring the quantitative effects of users' performance and satisfaction. The effects of syntactic, semantic and exemplar search hints on user behavior were evaluated in an empirical investigation using naturalistic scenarios. Combining the three search hint components, each with two levels of intensity, in a factorial design generated eight search engine interfaces. Eighty participants participated in the study and each completed six realistic search tasks. Results revealed that the inclusion of search hints improved user effectiveness, efficiency and confidence when using the search interfaces, but with complex interactions that require specific guidelines for search interface designers. These design guidelines will allow search designers to create more effective interfaces for a variety of searchapplications.