515 research outputs found
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
Preparation and characterization of mixed matrix membrane based on Polysulfone (PSF) and Lanthanum Orthoferrite (LaFeO3) for gas separation
The aim of this study is to investigate the effects of polysulfone (PSF) and lanthanum orthoferrite (LaFeO3) incorporated mixed matrix membrane (MMM) on gas permeation and selectivity properties. PSF/LaFeO3 MMMs were prepared with various weights loading of LaFeO3. The membranes obtained were characterized using scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and Fourier-transform infra-red (FT-IR). The gas transport properties of MMM were measured using single gas permeation set up (CO2, CH4, O2 and N2) at ambient temperature, and feed pressure of 2, 4 and 6 bar. The permeation test showed that the mixed matrix membrane exhibited high permeability. With increasing LaFeO3 weight loading to 1.0%, the highest permeability values were 47.74 GPU for CO2, 29.85 GPU for CH4, 57.56 GPU for O2, and 40.66 GPU for N2. The results also showed that by incorporating 1.0wt% of LaFeO3 into PSF matrix, the highest CO2/CH4 and O2/N2 selectivity of 1.60 and 1.42 respectively were obtained. Overall, all the resultants MMM showed higher permeability and selectivity compared to pure PSF membrane
Contrast of Bayesian and Classical Sample Size Determination
Sample size determination is a prerequisite for statistical surveys. A comprehensive overview of the Bayesian approach for computation of the sample size, and a comparison with classical approaches, is presented. Two surveys are taken as example to illustrate the accuracy and efficiency of each approach, and to make recommendations about which method is preferred. The Bayesian approach of sample size determination may require fewer subjects if proper prior information is available
Percentage composition of Brachyuran larvae collected during 1994 in Manora Channel, Karachi, Pakistan
Brachyuran larvae are the most common zooplankton component of the Manora Channel, Karachi, Pakistan. The identification of these larvae would assist in the assessment of brachyuran species and provide information on percentage composition, occurrence, abundance and breeding habits of the brachyuran species in the Manora Channel area. However plankton caught larvae is not easily identified. An accurate identification of such material is only possible by the comparison with larvae reared under laboratory conditions and documented with illustrations. The identifications for this present study were based on the works of Gurney (1938); Atkins (1954); Chhapgar (1955); Raja Bai (1960); Hashmi (1969, 1970a, b); Baba and Miyata (1971); Kakati and Sankolli (1975); Rice (1975); Kakati (1977); Lim and Tan (1981); Yatsuzuka and Sakai (1984); Fielder, et al (1984); Amir (1989, M. Phil thesis unpublished); Ingle (1992); Siddiqui and Tirmizi (1992); Tirmizi et al (1993); Bano (1999, M. Phil thesis unpublished); Ghory and Siddiqui (2001); Ghory (2002, M. Phil thesis unpublished); Ghory and Siddiqui (2002)
Survey on Cyber Attacks and Initial methods for its avoidance
A survey paper on the cyber crime which effected so many digital systems as we are very much depending upon internet for so many things in our daily life. It describes about the various cyber attacks around the world.In the early days of personal computing, malware threats like the infamous Brain virus, was distributed using floppy disk and were easily localized and handled. But after long time because of the Internet the cybercrime was massively distributed. From there we have seen methods of attacking increased drastically which became more prevalent. One of the most difficult things to counter about all of these cyber threats is that they are now truly personal. The one such example is ransomeware which will attack the victim’s system and demand him to pay money called ransome. Unless until he pay’s the attacker will not resume the system from his control. Recently we had heard that so many banking systems were hacked due to this cyber threat ransome, In this paper I am giving some of the examples of different kinds of cyber attacks
Occurrence and abundance of brachyuran larvae in the Manora Channel (Karachi, Pakistan) during 1993
The present paper investigates the occurrence and abundance of
brachyuran larvae in the Manora Channel during August- December 1993. The fortnightly planktonic sampling was carried out in Manora Channel which is bordered by mangroves, during day time from surface and subsurface waters at shallow depth using Bongo net of 300 micron mesh size. Analysis of samples revealed presence of brachyuran larvae of 12 species belonging to 6 families. Of these 4 species are confirmed: Serenella indica, Dotilla blanfordi,
Metopograpsus thukuhar and Clistocoeloma lanatum, 2 provisionally identified species are: Pilumnus ?karachiensis and Pinnotheres ?pisum, 2 species are identified upto generic level: Philyra sp. and Pinnotheres sp., and 1 Ocypodid species and 3 Xanthid species are identified upto family level.
This study based on identification, occurrence and abundance of brachyuran larvae in the area, also gives percentage composition of brachyuran larvae collected during 1993, in the Manora Channel
Distributional patterns of brachyuran larvae in Manora Channel (Karachi, Pakistan) collected during 1995
This study gives an account of distributional patterns of Brachyuran larvae in the Manora Channel from January to November 1995. The planktonic sampling was carried out during day time from surface and sub-surface waters of station I and II (certain sites) at shallow depths (15'-20') using Bongo net of 300 micron mesh size. In all 19527 larvae were obtained through fourteen sampling. These brachyuran larvae belonged to nine families and twenty four species: Ebalia sagittifera, Philyra sp., Philyra scabriuscula (Leucosiidae), Schizophyris aspera (Majidae), Charybdis annulata, Charybdis sp. (Portunidae), Xanthid sp A., B. and C. (Xanthidae), Pilumnus karachiensis, Pilumnus sp. (Pilumnidae), Menippe rumphii (Oziidae), Pinnotheres sp. A, and B. (Pinnotheridae), Nasima dotilliforme, Serenella indica, Macrophthalmus (Mareotis) depressus, Macrophthalmus sp., Dotilla blanfordi, Ocypodid sp. A., B. and C. (Ocypodidae), Metopograpsus thukuhar and Clistocoeloma lanatum (Grapsidae). This study is based on identification, occurrence, distributional patterns along Manora Channel and percentage composition of brachyuran larvae in the area, collected during 1995
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