A study of Skype over IEEE 802.16 networks: voice quality and bandwidth usage

Skype, one of the popular VoIP applications, has its own redundancy mechanism to mitigate the impact of packet loss at the expense of additional bandwidth usage. However, the benefit of voice quality improvement through redundancy is reduced greatly in the case of consecutive loss of Skype packets. When Skype is running over wireless networks, the high likelihood of having consecutive packet loss in a noisy wireless environment could lead to an interesting scenario: using more bandwidth for a lower voice quality. In this thesis, we study the impact of the HARQ retransmission mechanism of WiMAX to the voice quality of Skype. Two key parameters for the HARQ mechanism of WiMAX (i.e. Maximum numbers of retransmission and the delay of sending ACK) and their interplay with voice quality are investigated in this research. While HARQ retransmission may reduce the redundancy usage in Skype, it introduces additional bandwidth usage during the retransmission. The overhead of WiMAX retransmission with different HARQ parameters and overall bandwidth usage of Skype are also discussed in this thesis. Numerical analysis and simulation of voice quality and bandwidth usage of Skype over WIMAX are presented. Results show that HARQ retransmission can reduce the impact of bursty noise and improve the voice quality of skype up to 22%. The overall bandwidth consumption can be reduced by 76% when HARQ is engaged. Combining our studies on voice quality and bandwidth usage, we attempt to obtain the optimal HARQ parameters that can lead to the highest voice quality over bandwidth usage ratio for Skype over WiMAX

Laser Cooling of 85Rb Atoms to the Recoil Temperature Limit

We demonstrate the laser cooling of 85Rb atoms in a two-dimensional optical lattice. We follow the two-step degenerate Raman sideband cooling scheme [Kerman et al., Phys. Rev. Lett. 84, 439 (2000)], where a fast cooling of atoms to an auxiliary state is followed by a slow cooling to a dark state. This method has the advantage of independent control of the heating rate and cooling rate from the optical pumping beam. We operate the lattice at a Lamb-Dicke parameter eta=0.45 and show the cooling of spin-polarized 85Rb atoms to the recoil temperature in both dimension within 2.4 ms with the aid of adiabatic cooling

Non-autoregressive Transformer-based End-to-end ASR using BERT

Transformer-based models have led to a significant innovation in various classic and practical subjects, including speech processing, natural language processing, and computer vision. On top of the transformer, the attention-based end-to-end automatic speech recognition (ASR) models have become a popular fashion in recent years. Specifically, the non-autoregressive modeling, which can achieve fast inference speed and comparable performance when compared to conventional autoregressive methods, is an emergent research topic. In the context of natural language processing, the bidirectional encoder representations from transformers (BERT) model has received widespread attention, partially due to its ability to infer contextualized word representations and to obtain superior performances of downstream tasks by performing only simple fine-tuning. In order to not only inherit the advantages of non-autoregressive ASR modeling, but also receive benefits from a pre-trained language model (e.g., BERT), a non-autoregressive transformer-based end-to-end ASR model based on BERT is presented in this paper. A series of experiments conducted on the AISHELL-1 dataset demonstrates competitive or superior results of the proposed model when compared to state-of-the-art ASR systems

DEVELOPING A MODEL OF BACKPACKERS’ EXPLORATORY CURIOSITY

Purpose – While curiosity is a critical factor in motivating human exploratory behaviors across domains, past studies are yet to explore the exploratory curiosity construct in the context of backpacking. This study aims to conceptualize backpackers’ exploratory curiosity and, importantly, developing a scale for the construct. Design/Methodology – A survey questionnaire is first designed on the basis of a literature review and in-depth interviews. Then, two surveys are conducted using sample sizes of 228 and 276. The scale, along with its four factors (i.e., excitement, new destinations, social contact, and new tourism events) and 18 items, was determined as reliable and valid by the implementation of a rigorous instrument development process. Approach – This study identifies the characteristics of backpacker exploratory curiosity, and then generates fundamental constructs with detailed descriptions and explanations for a questionnaire. Subsequently, to understand the characteristics of such curiosity and how they can be applied to explain backpacker behaviors. Findings – This study extended the application of the curiosity concept to the tourism industry, and offered a new perspective, namely, exploratory behaviour individuals display in response to novelty, excitement, and changes in their environment can be used as variables to measure their curiosity level, and then the BECS can be utilized by tourism management organizations to help increase the number of potential clients. Originality of the research – The study contributed to a theoretical enhancement of the current level of knowledge on the existing literature on backpackers’ exploratory behavior and developed a reliable and valid scale for measuring backpacker exploratory curiosity

The study of roadway sustainability in Texas : a case study with the use of the Greenroads rating system

textIn the state of Texas, the roadway network consists of approximately 313,228 miles of roads (Federal Highway Administration, 2013), accounting for 7.61% of the public roads in the United States. To put it in perspective, this is equal to 12.6 times the circumference of Earth. In order to manage this network, the state and local transportation agencies use millions of tons of natural resources to construct and maintain these facilities. If these resources are not being properly used, Texas might end up wasting them, producing more pollutants, and imposing threats to its natural environment. Moreover, there is no way to quantify and record the efforts made by the Texas transportation community in becoming sustainable. Thus, there is a need to promote and keep track of ongoing sustainability efforts. In this study, we explore the trend of roadway sustainability in Texas, and propose a Texas version of sustainability rating system that is based on Greenroads. The Greenroads sustainability rating system is a third-party rating system developed by the University of Washington and aimed at recognizing sustainable practices in roadway projects. First, two of its projects in Texas are selected as the case study for the purpose of understanding the system. Second, 1,594 pavement projects are extracted from Texas highway construction database called Site Manager that is maintained by the Texas Department of Transportation (TxDOT) to understand the state of practice. Third, some material data that comes from TxDOT division engineers is included as well. Together with them, a Greenroads-based sustainability rating system, especially adapted in terms of material selection and pavement technology, is proposed. As a result, the implementation of this system is expected to spark more pursuits of roadway sustainability in Texas.Civil, Architectural, and Environmental Engineerin

The Effectiveness of Corporate Advertising in a Collegiate Fitness Center

The purpose of this research is to examine the effectiveness of the corporate advertisements in a collegiate fitness center in Hong Kong. In this study, a survey questionnaire was utilized to examine whether participants’ demographic information influenced the consumers’ attitude and purchase intention toward the product. A total of 112 valid samples were collected. The result showed there was a significant difference between genders in product purchase intention. And the research also found that participants’ exercise time can make a significant difference on the attitude and purchase intention toward the products. Compared with non-sport product, the sport related products received higher scores of attitude and purchase intention from participants in the collegiate sport center. There existed some limitations (sample size, time, gender ratio) during the research process. The result indicated there is potential commercial value hidden in the Hong Kong collegiate fitness clubs