Band Limited Signals Observed Over Finite Spatial and Temporal Windows: An Upper Bound to Signal Degrees of Freedom

The study of degrees of freedom of signals observed within spatially diverse broadband multipath fields is an area of ongoing investigation and has a wide range of applications, including characterising broadband MIMO and cooperative networks. However, a fundamental question arises: given a size limitation on the observation region, what is the upper bound on the degrees of freedom of signals observed within a broadband multipath field over a finite time window? In order to address this question, we characterize the multipath field as a sum of a finite number of orthogonal waveforms or spatial modes. We show that (i) the "effective observation time" is independent of spatial modes and different from actual observation time, (ii) in wideband transmission regimes, the "effective bandwidth" is spatial mode dependent and varies from the given frequency bandwidth. These findings clearly indicate the strong coupling between space and time as well as space and frequency in spatially diverse wideband multipath fields. As a result, signal degrees of freedom does not agree with the well-established degrees of freedom result as a product of spatial degrees of freedom and time-frequency degrees of freedom. Instead, analogous to Shannon's communication model where signals are encoded in only one spatial mode, the available signal degrees of freedom in spatially diverse wideband multipath fields is the time-bandwidth product result extended from one spatial mode to finite modes. We also show that the degrees of freedom is affected by the acceptable signal to noise ratio (SNR) in each spatial mode.Comment: Submitted to IEEE Transactions on Signal Processin

Analysis of Degrees of Freedom of Wideband Random Multipath Fields Observed Over Time and Space Windows

In multipath systems, available degrees of freedom can be considered as a key performance indicator, since the channel capacity grows linearly with the available degrees of freedom. However, a fundamental question arises: given a size limitation on the observable region, what is the intrinsic number of degrees of freedom available in a wideband random multipath wavefield observed over a finite time interval? In this paper, we focus on answering this question by modelling the wavefield as a sum of orthogonal waveforms or spatial orders. We show that for each spatial order, (i) the observable wavefield is band limited within an effective bandwidth rather than the given bandwidth and (ii) the observation time varies from the given observation time. These findings show the strong coupling between space and time as well as space and bandwidth. In effect, for spatially diverse multipath wavefields, the classical degrees of freedom result of "time-bandwidth" product does not directly extend to "time-space-bandwidth" product.Comment: 9 pages, 2 figures, Accepted in 2014 IEEE Workshop on Statistical Signal Processin

Using decoys to block SPIT in the IMS

Includes bibliographical references (leaves 106-111)In recent years, studies have shown that 80-85% of e-mails sent were spam. Another form of spam that has just surfaced is VoIP (Voice over Internet Telephony) spam. Currently, VoIP has seen an increasing numbers of users due to the cheap rates. With the introduction of the IMS (IP Multimedia Subsystem), the number of VoIP users are expected to increase dramatically. This calls for a cause of concern, as the tools and methods that have been used for blocking email spam may not be suitable for real-time voice calls. In addition, VoIP phones will have URI type addresses, so the same methods that were used to generate automated e-mail spam messages can be employed for unsolicited voice calls. Spammers will always be present to take advantage of and adapt to trends in communication technology. Therefore, it is important that IMS have structures in place to alleviate the problems of spam. Recent solutions proposed to block SPIT (Spam over Internet Telephony) have the following shortcomings: restricting the users to trusted senders, causing delays in voice call set-up, reducing the efficiency of the system by increasing burden on proxies which have to do some form of bayesian or statistical filtering, and requiring dramatic changes in the protocols being used. The proposed decoying system for the IMS fits well with the existing protocol structure, and customers are oblivious of its operation

Antibacterial efficacy of raw and commercially available honey

In vitro antibacterial activity of raw and commercially available honey was tested against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Shigella spp. and Salmonella spp.). Both types of honey showed antibacterial activity against test organisms with the zone of inhibition ranging from 8.13 to 30.85 mm, while E. coli, S. aureus, and Shigella spp. showed sensibility towards both types of honey. Raw honey possesses more inhibitory activity against S. aureus and Shigella spp., than commercially available honey. On the other hand, commercially available honey possesses more inhibitory activity than raw honey against E. coli. Both types of honey showed no effects on Salmonella spp. The potency of honey at 100% concentration was found to be higher than all other concentrations tested. However, no effect was observed at concentration of 6.25% v/v honey in the case of both samples.Key words: Honey, antibacterial activity, raw honey, commercially available honey, minimum inhibitory concentration (MIC)

Development of Time Measuring Technique to Measure the Shock Speed during the Propagation in the Free Atmosphere

In the study of wave propagation in the free atmosphere, it is desirable to obtain time measurements to an accuracy of microsecond level. An experiment has been conducted to measure the wave speed during the propagation in the free atmosphere by the present technique. Due to sudden rupture of the diaphragm for the chamber pressure of 4.2 kg/cm2 and a wave generating in a shock tube travels with subsonic speed and the measured incident wave Mach number is 0.8 which leaves the shock tube in the free atmosphere. The measured travelling time of the incident wave to travel 61.5 cm distance in the shock tube is 2200 μsec and the same technique can apply to measure the shock wave speed. Several trigger points are installed at the exit of the shock tube in the open atmosphere to measure the strength of the wave propagation. It is observed that the wave strength decreases during the wave propagation in free atmosphere. Due to spherical expansion behind the wave, the pressure across the wave decreases. A numerical simulation is also conducted on supersonic shock wave to determine the shock speed and the travelling time in the free atmosphere. The pressures across shock wave at different locations of the shock wave are determined by solving the Euler equations and the simulation results indicate that the shock speed decreases during the propagation in the free atmosphere. In both experimental and numerical results, it is observed that the strength of the wave propagation in the free atmosphere decreases continuously due to spherical expansion.  The present technique can also be used to measure the supersonic jet velocity, the velocity of bullet and any particle velocity in subsonic or supersonic ranges

Capacity of Solid Waste Management of the Municipalities in North-West Region of Bangladesh: A Far Cry with Sustainable Development

The study addresses the overall waste management and drainage system of the Municipalities of Bangladesh. It also endeavors to compare the existing system with the requirements of making a sustainable city following the targets of SDG. It tries to highlight the shortcomings of the existing system of waste management and argues that this is never able to confine sustainability in the environment and the habitats of the Municipalities. The study is empirical in nature mainly based on primary data. Data have been collected from the officials and stakeholders of the three selected Municipalities of a North-west district of Bangladesh- Rajshahi through face to face interview and Focus Group Discussion. This paper identifies the fragile solid waste management capacity of the Municipalities of Bangladesh and argues that current practice is nothing but an inevitable setback for the country to achieve sustainable development

Choices:Future trade-offs and plausible pathways

Policy development and management of deltas in the Anthropocene involves the consideration of trade-offs and the balancing of positive and negative consequences for delta functions and the societies that rely on them. This assessment outlines policy-driven and spatial trade-offs that dominate the landscape of choice. It highlights examples of such trade-offs using plausible delta futures and the governance choices associated with them. The analysis is based on modelling broad-scale processes and individual adaptive actions. It highlights how policy choices to maximise economic growth can, for example, have unforeseen consequences such as diminished well-being for some populations. Hence the chapter concludes that trade-offs are a crucial governance challenge for future sustainability of deltas

CAN MINOR FRUIT CULTIVATION CHANGE THE LIVELIHOOD OF THE MARGINAL PEASANTS? A CASE STUDY FROM BANGLADESH

Abstract Lemon (lebu) cultivation, a minor fruit production activity, is increasingly becoming popular among the marginal peasants. The present study aimed at exploring the potentials of lemon production and its impact on the changes in the livelihood pattern of the rural farmers as well as its impact on women empowerment. Based on qualitative and quantitative data collected from Mymensingh district in Bangladesh in 2015, this paper argues that life and livelihood of the citrus producer has significantly changed over the last decade. Income from the sale of lemon is the principal livelihood means and gender non-differentiated participation in the production process further enhanced the sustainability of the livelihoods. It also contributed to employment generation for those who are not directly involved in the lemon cultivation such as power tiller driver, irrigation pump driver, fertilizer & pesticide retailer, small lemon collector, lemon supplier in the study area. Moreover, increased participation of women in the citrus cultivation has changed not only their economic well-being but also social status, honor, planning and decision making power, and self-esteem. This study also shows that marginal and vulnerable poor women including landless women, female member of women headed household and widows significantly benefited from citrus cultivation. Yet, lack of cooperative society, financial support, credit facility, technical support, storage facility and marketing support are identified as the potential problems to achieve a sustainable growth of lemon production activity

Application of the world health organization quality of life instrument, short form (WHOQOL-BREF) to patients with endometriosis

Objective Endometriosis, a common hormone-dependent chronic inflammatory disease causes various symptoms including pelvic pain, which affect the physical and psychological quality of life in women of reproductive age. The present study aimed to assess the quality of life of Iranian women with endometriosis using the World Health Organization Quality of Life Instrument, Short Form (WHOQOL-BREF) questionnaire. Methods This cross-sectional study performed in Tehran between October 2014 and July 2016 included 70 Iranian women with endometriosis. The Iranian version of the WHOQOL-BREF questionnaire was used to measure quality of life in these women. The Pearson's correlation coefficient, the paired and the independent t-tests, and a linear regression model were used to statistically analyze the data using the SPSS software version 16.0. Results The total mean score of the WHOQOL-BREF questionnaire was 80.58. The highest and the lowest mean scores were observed in the environmental (28.15) and the physical health domains (10.59), respectively. A multiple linear regression model (backward method) showed that insurance coverage was associated with the total WHOQOL-BREF score, whereas age, insurance coverage, and income level were associated with domains 1 through 4, respectively (P < 0.05). Conclusion Endometriosis affects various aspects of the quality of life of Iranian women who therefore require holistic management focused on both, the physical and psychological aspects of treatment. © 2018 Korean Society of Obstetrics and Gynecology