Normalization of the Background Independent Open String Field Theory Action

It has been shown recently that the background independent open string field theory provides an exact description of the tachyon condensation on unstable D-branes of bosonic string theory. In this analysis the overall normalisation of the action was chosen so that it reproduces the conjectured relations involving tachyon condensation. In this paper we fix this normalisation by comparing the on-shell three tachyon amplitude computed from the background independent open string field theory with the same amplitude computed from the cubic open string field theory, which in turn agrees with the result of the first quantised theory. We find that this normalisation factor is in precise agreement with the one required for verifying the conjectured properties of the tachyon potential.Comment: LaTeX file, 8 pages, references adde

Unbiased homomorphic system and its application in multiplicative noise reduction

Noise of a multiplicative nature is encountered in many applications such as coherent imaging, remote sensing and signal processing for communication systems. This thesis is concerned with the problem of reducing the multiplicative noise corrupting a signal. A generalization of the existing sampled function weighted order (SFWO) filter is proposed by relaxing the symmetry condition for the probability density function (PDF) of the noise to the filter. This generalized SFWO (GSFWO) filter is then used within a homomorphic system to reduce the multiplicative noise. It is shown that the output from such a system is biased, and hence, a suitable bias compensation technique is suggested. An unbiased homomorphic system, whose design is based on the PDF of the corrupting multiplicative noise, is proposed to reduce the noise. Images and videos generated by coherent imaging systems are always corrupted by speckle, which is a multiplicative noise having a lognormal distribution. A filter called the mean median (MM) filter to reduce additive white Gaussian noise (AWGN) is first proposed and this filter is then used within the unbiased homomorphic system to reduce the speckle in images. Fast filters to reduce AWGN in videos are also proposed in this thesis. Novel techniques for temporal estimation employing a change detection technique to determine the interframe motion are developed for their use in these filters. A new method is proposed to appropriately combine the spatial and spatiotemporal estimates of the original signal in order to obtain the final output. Finally, the MM-filter along with a novel temporal estimation scheme are used within the unbiased homomorphic system to reduce the speckle in videos. The effectiveness of the various proposed algorithms is demonstrated and compared with that of some of the existing schemes through extensive simulation

Hematological profile including alkali resistant hemoglobin of neonates at birth using cord blood in relation to gestational age and maternal diseases

Background: The importance of complete hemogram along with the hematological indices in the diagnosis of neonatal health cannot be overemphasized. There is a severe paucity of relevant data regarding neonatal hematological profile in relation to gestational age and maternal diseases in this part of the country. With this perspective, the authors intended to do a pilot study to analyse the haematological profile of neonates of different gestational ages and different maternal diseases born in a teriary care hospital in Eastern India.Methods: This is a cross sectional study design based on cord blood sample of newborns and their mothers recruited from those admitted in the gynae and obstetric department in IPGME&R. The umbilical cord blood was collected from the newborn babies and then examined for different haematological parameters. The data obtained was statistically analysed.Results: While there has been a sequential rise of fetal red cell count, hemoglobin and the total white cell count neutrophils with gestational age, the mean corpuscular cell volume decreased. All these values were comprised to varying degrees in maternal diseases except for nucleated rell blood cells which conspicuously increased in neonates of diabetic mothers.Conclusions: In this study, a small attempt was made to assess the haematological profile (including alkali resistant hemoglobin) of the newborns in relation to gestational age and maternal diseases in the population attending a tertiary care hospital in Eastern India

Transmission Map and Atmospheric Light Guided Iterative Updater Network for Single Image Dehazing

Hazy images obscure content visibility and hinder several subsequent computer vision tasks. For dehazing in a wide variety of hazy conditions, an end-to-end deep network jointly estimating the dehazed image along with suitable transmission map and atmospheric light for guidance could prove effective. To this end, we propose an Iterative Prior Updated Dehazing Network (IPUDN) based on a novel iterative update framework. We present a novel convolutional architecture to estimate channel-wise atmospheric light, which along with an estimated transmission map are used as priors for the dehazing network. Use of channel-wise atmospheric light allows our network to handle color casts in hazy images. In our IPUDN, the transmission map and atmospheric light estimates are updated iteratively using corresponding novel updater networks. The iterative mechanism is leveraged to gradually modify the estimates toward those appropriately representing the hazy condition. These updates occur jointly with the iterative estimation of the dehazed image using a convolutional neural network with LSTM driven recurrence, which introduces inter-iteration dependencies. Our approach is qualitatively and quantitatively found effective for synthetic and real-world hazy images depicting varied hazy conditions, and it outperforms the state-of-the-art. Thorough analyses of IPUDN through additional experiments and detailed ablation studies are also presented.Comment: First two authors contributed equally. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible. Project Website: https://aupendu.github.io/iterative-dehaz