Characterization of wall dispersive and attenuative effects on UWB radar signals     

Ali Muqaibel  Ahmad Safaai-Jazi 《Journal of The Franklin Institute》2008,345(6):640-658

This paper addresses the potentials of ultra-wideband (UWB) through-wall imaging radars compared with conventional narrowband systems. The challenges that limit the utilization of high precision UWB systems are examined with the aim of mitigating them. These challenges include multi-path, pulse dispersion, and antenna effects on the pulse shape due to angles of transmission and arrival. The propagation of UWB signals through walls is a crucial factor in determining the success of UWB radar technology. UWB signals, when propagating through walls, not only suffer attenuation but also distortion due to dispersive properties of the walls. This paper examines time- and frequency-domain techniques for measuring the electromagnetic properties of construction materials in the UWB frequency range. The measured parameters provide valuable insights in appreciating the capabilities and limitations of the UWB technology. Special attention is paid to time gating as a mean to extract the direct-path signal from the multi-path components. Both single-pass and multi-pass models are discussed. Multi-pass models account for the multiple reflections within the wall while the single-pass model assumes the possibility of gating out a single transmission. The partition-dependent narrowband propagation model is modified to account for the ultra-wide bandwidth of the signal. The paper illustrates the application of the modified model in indoor environments. The modified model is helpful in estimating the link power budget. It is also useful in studying the performance of UWB systems for indoor communication and positioning applications.  相似文献   

A new method for performance evaluation of bit decoding algorithms using statistics of the log likelihood ratio     

Ali Abedi  Amir K. Khandani 《Journal of The Franklin Institute》2008,345(1):60-74

This paper presents a new method for the performance evaluation of bit decoding algorithms. The method is based on estimating the probability density function (pdf) of the bit log likelihood ratio (LLR) by using an exponential model. It is widely known that the pdf of the bit LLR is close to the normal density. The proposed approach takes advantage of this property to present an efficient algorithm for the pdf estimation. The moment matching method is combined with the maximum entropy principle to estimate the underlying parameters. We present a simple method for computing the probabilities of the point estimates for the estimated parameters, as well as for the bit error rate. The corresponding results are used to compute the number of samples that are required for a given precision of the estimated values. It is demonstrated that this method requires significantly fewer samples as compared to the conventional Monte-Carlo simulation.  相似文献   

Adjustments of serum lactate dehydrogenase isoenzymes and their significance in monitoring the treatment in patients with tubercular pyothorax     

Riaz Ahmad  Mumtaz Alam  M. Faisal Siddiqui  Absar-ul Hasnain 《Indian journal of clinical biochemistry : IJCB》2008,23(2):181-185

The adjustments and diagnostic significance of polyacrylamide gel electrophoretic (PAGE) profiles of lactate dehydrogenase isoenzymes (LDH: 1.1.1.27) was evaluated in the sera and pleural fluid of patients with tubercular pyothorax. Sera and pleural fluid samples were randomly collected from 72 and 18 patients respectively at two different timings; first, when patients were admitted to the Hospital and second, after an intensive phase of treatment. Sera of 20 healthy individuals served as control. Our results demonstrate significant differences in sera LDH (sLDH) and pleural fluid LDH (pfLDH) isoenzymes. In patients the order of LDH isoenzyme in sera and pleural fluid followed: LDH−5>−4>−2>−3>−1 and LDH-5>−4>−3>−2>−1 respectively. The ranking of activity levels in control was LDH−2>−1>−3>−5>−4. In the second phase of sampling from 31 patients, values of sLDH isoenzymes showed recovery and resembled profiles of controls. Therefore, the sLDH zymograms of patients can be used as the prognostic marker, since they tend to reach the normal level during recovery signifying the effect of chemotherapy in hospitalized patients. Moreover, according to the present findings on LDH-PAGE profiles, the levels of LDH-5 and-4 rise in pyothorax patients significantly (P<0.05). This elevation along with the rise in total LDH activity may, therefore, be used in the diagnosis and monitoring of tubercular pyothorax.  相似文献   

Orthogonal Polynomials and Padé Approximation     

Faiz Ahmad 《上海大学学报(英文版)》1998,(2)

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅＰａｄéａｐｐｒｏｘｉｍａｔｉｏｎｉｓａｔｙｐｅｏｆｒａｔｉｏｎａｌｆｒａｃｔｉｏｎａｐｐｒｏｘｉｍａｔｉｏｎｔｏａｆｕｎｃｔｉｏｎ．Ｌｅｔｆｂｅｒｅｐｒｅｓｅｎｔｅｄｂｙａｐｏｗｅｒｓｅｒｉｅｓｆ（ｘ）＝∑∞ｉ＝０ｃ...  相似文献   

Interpreting Cues of Goodness: Thin Sliced Judgment of Malaysians and Chinese towards Political Leaders     

Madiha A. Hashmi  Ezhar Tamam  Moniza Waheed  Abdul Muati Ahmad 《Journal of Intercultural Communication Research》2016,45(5):419-436

Thin slice studies have demonstrated that quick personality inferences of unknown others can be made fairly accurately. Utilizing focus group interviews, the current study examines thin sliced judgments and perceptions of six leaders in the context of goodness. Findings revealed that perceivers were able to form relatively accurate impressions of some leaders based on brief glimpses of nonverbal footage. Across all groups (Malaysian and Chinese) paralinguistic cues, dynamic cues and static cues were instrumental in the formation of positive perceptions of leaders in the context of goodness. These findings have implications for the areas of nonverbal behaviour, political communication, and personality judgement.  相似文献   

Conversational functions for knowledge building communities: a coding scheme for online interactions     

Stefano Cacciamani  Vittore Perrucci  Ahmad Khanlari 《Educational technology research and development : ETR & D》2018,66(6):1529-1546

The aim of this study was to develop a coding scheme rooted in the Knowledge Building model, named Conversational Functions for Knowledge Building (CF4KB), to analyze students’ interactions in an online undergraduate course. In order to develop the coding scheme, we analyzed students discourse and identified the kinds of “Conversational Functions” students performed. Connecting these identified functions with Knowledge Building Model principles, we developed the coding scheme to analyze knowledge building [In the present article, we used “Knowledge Building” to indicate the theoretical model and “knowledge building” to refer to the activity of the community members.] activity. Applying the resulting coding scheme, two independent judges coded 186 messages posted into Knowledge Forum by 26 students (5 men and 21 women) attending the online course of Educational Psychology at University of Valle d’Aosta to develop the coding scheme. The inter-coder agreements obtained were 77.3 and 78.0%, with Cohen’s K?=?0.68 and 0.66, respectively for Specific and Global Conversational Functions level. The theoretical implications and possible uses in different contexts for future inquiry of this instrument are discussed.  相似文献   

Efficacy of a Preventive Counseling Program for Improving Psychological Hardiness and the Positive Use of Social Network Sites among Students at Risk     

Abdallah Salem Farhan Almahaireh  Anas Saleh Rabi Aldalaeen  Suhib Khaled Ahmad Takhaineh 《International journal for the advancement of counseling》2018,40(2):173-186

The purpose of this study was to investigate the efficacy of a preventive counseling program for improving psychological hardiness (PsyH) and the positive use of social network sites (SNSs). The sample consisted of 30 students from Mu’tah University in Jordan who were randomly assigned into either an experimental group (15) or a control group (15). Two constructed scales - the PsyH scale and the Positive Use of SNSs scale - were administered to both groups pre-test and post-test, and a one-month follow-up measure was also administered to the experimental group. The findings revealed that the preventive counseling program significantly improved the level of PsyH and the positive use of SNSs and seemed to have sustained efficacy.  相似文献   

Students’ ‘uses and gratification expectancy’ conceptual framework in relation to E-learning resources     

Makingu Mondi  Peter Woods  Ahmad Rafi 《Asia Pacific Education Review》2007,8(3):435-449

This paper presents the systematic development of a ‘Uses and Gratification Expectancy’ (UGE) conceptual framework which is able to predict students’ ‘Perceived e-Learning Experience. ’ It is argued that students’ UGE as regards e-learning resources cannot be implicitly or explicitly explored without first examining underlying communication theories and learning perspectives. As such, the theoretical framework is grounded in the confluence of theories from communication theories and learning perspectives. The integration of Expectancy-value Theory, and the Uses and Gratification Theory serves to accommodate the suggestion that elearning resources offer gratifications that are expected and valued by students. The key theoretical and practical assumptions of the UGE approach are highlighted and consistently implemented in the conceptual edifice.  相似文献   

College students’ attitudes towards sexually themed science content: a socioscientific issues approach to resolution     

Jamil Mikhail Yahaya  Ahmad Nurulazam  Mageswary Karpudewan 《International Journal of Science Education》2016,38(7):1174-1196

A socioscientific issues integrated instruction was used in the study to resolve college students attitude towards sexually-themed science content. Some 200 college students participated in the study as experimental and control groups. The former consisting of 98 students from one college was taught the content using the socioscientific issues integrated instruction. The later with 102 students from another college was taught the same content using a traditionally teacher dominated lectures. Both groups were taught over a period of eight weeks. Qualitative and quantitative data were obtained before and after the intervention. The quantitative data were analysed using analysis of covariance. The results revealed that there was a significant difference between the experimental and the control groups (F (1, 247) = 426.97, p = .00, partial eta squared = 0.64) where the experimental group showed a significant change in attitude towards the content studied. The qualitative data obtained some experimental group students showed a change in attitude the second interview. It was concluded that the use of the approach has significantly made the college students feel comfortable and confident to learn and teach the content.  相似文献   

Classroom     

Sandhya Mishra  Ankit Namdev  Munindra Bisen  Jeeshan Ahmad  Vishal Mishra 《Resonance》2016,21(10):937-947

In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. “Classroom” is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science.  相似文献