Underwater Ranging

The paper deals with underwater laser ranging system, its principle of operation and maximum depth capability. The sources of external noise and methods to improve signal-to-noise ratio are also discussed

Why Do Cascade Sizes Follow a Power-Law?

We introduce random directed acyclic graph and use it to model the information diffusion network. Subsequently, we analyze the cascade generation model (CGM) introduced by Leskovec et al. [19]. Until now only empirical studies of this model were done. In this paper, we present the first theoretical proof that the sizes of cascades generated by the CGM follow the power-law distribution, which is consistent with multiple empirical analysis of the large social networks. We compared the assumptions of our model with the Twitter social network and tested the goodness of approximation.Comment: 8 pages, 7 figures, accepted to WWW 201

Critical Analysis of Background Subtraction Techniques on Real GPR Data

Ground penetrating radar (GPR) is used to detect the underground buried objects for civil as well as defence applications under varying conditions of soil moisture content. The capability of detection depends upon soil moisture, target characteristics and subsurface characteristics, which are mainly responsible for contaminating the GPR images with clutter. Researchers earlier have used averaging, mean, median, Eigen values, etc. for subtracting the background from GPR images. To analyse the background subtraction or clutter reduction problems, in this paper, we have experimentally reviewed background subtraction techniques with or without target conditions to enhance the target detection under variable soil moisture content. Indigenously developed GPR has been used to collect the data for different soil conditions and several background subtraction signal processing techniques were critically reviewed like, mean, median, singular value decomposition (SVD), principal component analysis (PCA), independent component analysis (ICA) and training methods. The signal to clutter ratio (SCR) measurement has been used for performance evaluation of each technique. The relative merits and demerits of each technique has also been analysed. The background subtraction techniques have been appliedto experimental GPR data and it is observed that in comparison of mean, SVD, median, ICA, PCA, the training method shows the highest SCR with buried target. Finally, this review helps to select the comparatively better background subtraction technique to enhance the detection capability in GPR

Starbursts versus Truncated Star Formation in Nearby Clusters of Galaxies

We present long-slit spectroscopy, B and R bandpass imaging, and 21 cm observations of a sample of early-type galaxies in nearby clusters which are known to be either in a star-forming phase or to have had star formation which recently terminated. From the long-slit spectra, obtained with the Blanco 4-m telescope, we find that emission lines in the star-forming cluster galaxies are significantly more centrally concentrated than in a sample of field galaxies. The broadband imaging reveals that two currently star-forming early-type galaxies in the Pegasus I cluster have blue nuclei, again indicating that recent star formation has been concentrated. In contrast, the two galaxies for which star formation has already ended show no central color gradient. The Pegasus I galaxy with the most evident signs of ongoing star formation (NGC7648), exhibits signatures of a tidal encounter. Neutral hydrogen observations of that galaxy with the Arecibo radiotelescope reveal the presence of ~4 x 10^8 solar masses of HI. Arecibo observations of other current or recent star-forming early-type galaxies in Pegasus I indicate smaller amounts of gas in one of them, and only upper limits in others.Comment: to be published in Astronomical Journa

Future demand for primary hip and knee arthroplasty in Scotland

ACKNOWLEDGEMENTS The authors are grateful to the Scottish Arthroplasty Project for the data utilised in this manuscript. No funding was received for this study.Peer reviewedPublisher PD

Radial Color Gradients in K+A Galaxies in Distant Clusters of Galaxies

Galaxies in rich clusters with z $\gtrsim$ 0.3 are observed to have a higher fraction of photometrically blue galaxies than their nearby counterparts. This raises the important question of what environmental effects can cause the termination of star formation between z $\approx$ 0.3 and the present. The star formation may be truncated due to ram-pressure stripping, or the gas in the disk may be depleted by an episode of star formation caused by some external perturbation. To help resolve this issue, surface photometry was carried out for a total of 70 early-type galaxies in the cluster Cl1358+62, at z $\sim$ 0.33, using two-color images from the Hubble Archive. The galaxies were divided into two categories based on spectroscopic criteria: 24 are type K+A (e.g., strong Balmer lines, with no visible emission lines), while the remaining 46 are in the control sample with normal spectra. Radial color profiles were produced to see if the K+A galaxies show bluer nuclei in relation to their surrounding disks. Specifically, a linear gradient was fit to the radial color profile of each galaxy. We find that the K+A galaxies on average tend to have slightly bluer gradients towards the center than the normals. A Kolmogorov-Smirnov two-sample test has been applied to the two sets of color gradients. The result of the test indicates that there is only a $\sim$2% probability that the K+A and normal samples are drawn from the same parent distribution. There is a possible complication from a trend in the apparent magnitude vs. color gradient relation, but overall our results favor the centralized star formation scenario as an important process in the evolution of galaxies in dense clusters.Comment: 16 pages, 12 figures, accepted for publication in A

Laser Range Sensors

This paper presents the design aspects of laser range finders and proximity sensors beingdeveloped at IRDE for different applications. The principle used in most of the laser rangefinders is pulse echo or time-of-flight measurement. Optical triangulation is used in proximitysensors while techniques like phase detection and interferometry are employed in instrumentsfor surveying and motion controllers where high accuracy is desired. Most of the laser rangefinders are designed for ranging non-cooperative targets

Analysis of Image Transmission using MIMO-Alamouti Space-Time Encoding

Rapid increase in requirements of high speed transmission of multi-media information resulted in development of MIMO systems. MIMO systems have emerged as the most efficient methodology for the high speed robust data transmission. In this paper, the performance of Alamouti Space-time block coded MIMO system is analysed using the metric of efficient image transmission over the Rayleigh fading channel. The transmitted image is modulated using M-PSK modulation technique, and its reconstructed version is plotted as an output function. Zero-forcing equalization is done for the detection of the original symbols from the received symbols which are influenced by the multipath fading and the channel noise. The results for image transmission using 2×1 and 2×2 Alamouti STBC are evaluated for different SNR values. The inverse relationship between the SNR and BER in the results depict that the high value of SNR and receiver antenna leads to enhanced system efficiency with reduced BER and distortion less recovery of image. It is very evident from the analysis of the received images that as we increase the SNR or the number of the antennas at the receiving side, the quality of the received image improves for the same channel environment. During the analysis, it is also found that increasing the number of bits forming one symbol in M-PSK modulation increase the BER which is undesirable. Thus, trade-off between the number of antenna, SNR and the M value of PSK is an essential requirement for achieving enhanced performance

Antenatally diagnosed congenital anomalies-trend in tertiary care hospital

Background: Antenatally diagnosed, congenital abnormalities of the fetus are frequently offered antenatal surgical consultation in all tertiary care hospitals to adequately counsel prospective parents. We aimed to assess the current trends in antenatally diagnosed congenital malformations of fetus in patients who had presented to our hospital for reassessment or surgical consultation and these patients were counselled and prognosticated after confirmation of anomaly at our centre accordingly.Methods: This was a retrospective study of all the cases diagnosed antenatally with fetal abnormalities. All cases were referred to either pediatric surgery outpatient department or fetal medicine subunit of a tertiary care centre from January 2017-December 2018. The complete records of these pregnant women were perused, presence and type of anomaly confirmed at our centre and trends about types of anomalies analysed.Results: A total of 209 women were analyzed for antenatal anomalies, out of these patients medical termination of pregnancy was offered to 27 (12.9%) patients, in which 38 anomalies were detected and in 182 (87%) patients pregnancy was continued to delivery. A total of 223 anomalies were detected in this group with some patients having fetuses with more than one anomaly. Gastrointestinal abnormalities were present in 94 (51.6%) patients of those who delivered and accounted for the most common anomaly followed by CNS abnormality which accounted for 39 (21.4%) of total abnormalities and genitourinary abnormalities contributed to 28 (13.3%) of abnormalities. A total of 85.2% of patients were referred after 20 weeks.Conclusions: The significant number of patients with major congenital anomalies are still diagnosed at a date later than permissible time for termination of gestation (20 weeks). There were cases where anomaly scan was done at a later gestation and then there were others where inadequate counselling made patient to present late for prognostication. However, there are certain anomalies that are picked up late and are likely to be missed in the routine anomaly scan. Therefore, antenatal detection and early referral helps in offering early counselling and better outcome for pregnancy.

New observational method framework and application

© 2017 19th ICSMGE Secretariat. All rights reserved. This paper introduces the new holistic Observational Method (OM) framework described in Ciria C760 -the new revision to the Embedded Retaining Wall Design Guide. This new OM framework is described by four approaches and these are explained with reference to case histories. Maximum benefit is achieved by back analyzing case histories in similar ground conditions to derive the most probable soil parameters. These parameters can then be used in an ab initio design to maximize saving in the wall thickness, toe embedment, and propping forces. A contingency plan is based on conventional characteristic design parameters and this involves additional propping. The term ipso tempore is introduced to cover wall redesign after construction starts. This may be to achieve saving in propping where movements are smaller than predicted. Alternatively, additional propping or ground treatment may be required and this is consistent with Peck's 'best way out' approach.Ove Arup Lt