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Development of a High-Resolution Multiscale Modeling and Prediction System for Bay of Bengal, Part II: An Application to October 2008  [PDF]
Arun Chakraborty, Avijit Gangopadhyay
Open Journal of Marine Science (OJMS) , 2016, DOI: 10.4236/ojms.2016.61012
Abstract: A high-resolution (10 km × 10 km) multiscale ocean modeling system was developed for the Bay of Bengal (BOB) region for short-term ocean hindcasts/forecasts. A physical validation of this system that was based on climatological initialization and short-term simulations was presented in Part I of this series of studies. Realistic structures for prevalent eddies, fronts and gyres were reasonably reproduced and validated for three individual months (February, June and October). In this study, we present an application and synoptic validation of the system for October 2008 in a hindcast mode. The system is based on the Regional Ocean Modeling System (ROMS), which assimilates satellite andin-situmeasurements within the background climatology using an objective analysis to produce the synoptic initial condition for the model and/or to produce an estimation of the current ocean state. A meteorological forecast is then input into this synoptic three-dimensional ocean model to produce the ocean hindcast/forecast. The high-density Array for Real-time Geotropic Oceanography (ARGO) observations, and the Tropical Rain Measuring Mission (TRMM) satellite’s microwave imager (TMI) passes during the beginning of the month of October 2008, provided a unique opportunity for the system to assimilate thesein-situobservations at initialization. Then, the ARGO and TMI observations during the later part of October 2008 were used for the statistical validation of the system’s fidelity. The validation shows that the hindcast/forecast system can reasonably predict the ocean currents, temperature and salinity. The forecast error increases as the forecast time window increases, although the system has a reasonable predictability for up to seven to ten days. The assimilation of both
Development of a High-Resolution Multiscale Modeling and Prediction System for Bay of Bengal, Part I: Climatology-Based Simulations  [PDF]
Arun Chakraborty, Avijit Gangopadhyay
Open Journal of Marine Science (OJMS) , 2016, DOI: 10.4236/ojms.2016.61013
Abstract: A high-resolution (10 km × 10 km) multiscale ocean modeling system was developed for short-term (1 - 2 weeks) ocean state hindcasting/forecasting in the Bay of Bengal (BOB) region. This paper is Part I of a two-part series of studies. The Regional Ocean Modeling System (ROMS) was implemented and initialized with Levitus 1/4° climatological fields for short-term forecasting. The results from these climatology-based model simulations for three representative months (February, June and October) in three different seasons (winter, summer and autumn) are discussed herein. This high-resolution model implementation simulates most of the observed dominant circulation features. The multiscale features during February include an anticyclonic basin-scalegyre with a strong western boundary current (WBC) in the western basin, the formation of several shallow mesoscale eddies in the head of the Bay and a cyclonic sub-basin-scale Myanmar Gyre in the northeast. During June, no well-defined boundary current is simulated along the Indian coast; instead, alternating cyclonic and anticyclonic eddies appear along the east coast with cross-basin eastward flow to support a deep cyclonic Andaman Gyre. In October, a basin-scale cyclonic gyre with a continuous well-defined East India Coastal Current (EICC), weak inflow from the Malacca Strait to the Andaman Sea and advection of BOB water into the Arabian Sea via the Palk Strait are simulated well by the model. A number of mesoscale eddies appear on the eastern half of the basin during October. Physical pattern of simulated eddies and transports across selected sections are validated against available drifter climatology, ARGO data and previous observations. Application of this system to synoptic short-term predictions for October 2008 will be presented in
ISO 50001: Are the Auditors Equipped Enough?  [PDF]
Avijit Choudhury
Open Journal of Energy Efficiency (OJEE) , 2012, DOI: 10.4236/ojee.2012.13006
Abstract: This paper tries to address the issue of expertise and awareness level of ISO-50001 [1] certification auditors in judging the efficacy of existing energy management (EnMS) and suggest the methodology to ensure continual improvement in EnMS. This article also tells about the need of thorough understanding of legal & other mandatory requirements which need to be addressed properly before framing the energy policy and setting up objectives & targets for the organization. Particularly SMEs, while implementing any standard or adopting any new system, largely depend on the consultant/ system auditor because of their limited knowledge and resources. In such cases the auditors need to play a larger role by making appropriate ENCON recommendations and guide them how to achieve the compliance. Further in India, most of the companies have got poor metering system. Even crucial energy data like flow rate of LPG, natural gas, FO, steam etc are quoted from judgment or past experience. Meters are not there to measure motor power, liquid temp or gas prss. In such cases auditors need to guide the clients how to establish the energy monitoring & targeting system and how to establish proper M&V (Measurement & Verification) protocol. In nut shell the ISO-50001 auditor needs to play the role of a friend, philosopher & guide to ensure that at the end of the day his client has complied with all the energy regulations and at the same time achieved some significant reduction in energy consumption.
HVAC vs Geothermal Heat Pump—Myth & Truth  [PDF]
Avijit Choudhury
Open Journal of Energy Efficiency (OJEE) , 2013, DOI: 10.4236/ojee.2013.21007
Abstract: In India energy auditors in some cases have recommended ground water based heat pump in place of common HVAC system to achieve better efficiency. However the users were made to understand that heat pumps are not suitable for Indian climatic condition and it produces no better result than the conventional system. This article tries to find answer to this debate thru an impartial analysis with the available data. First the concept is tested thermodynamically to compare the derived COPs and next from the experimental data on specific energy consumption.
Energy Audit Methodology of Sponge Iron Manufacturing Units Using DRI Process  [PDF]
Avijit Choudhury
Open Journal of Energy Efficiency (OJEE) , 2014, DOI: 10.4236/ojee.2014.33005
Abstract: Conducting complete energy audit (both process and utility) of a sponge iron unit is challenging as there is no laid down procedure to audit the process side. Further, the average heat to power ratio (kWth/kWe) of sponge iron plants ranges from (25:1) to (31:1). This shows that the manufacturing process mostly uses thermal energy and application of electrical energy is insignificant. The main & only source of thermal energy is coal and the entire coal is fed to the rotary kiln. Therefore we find that “Kiln” is the “Black-Box” of this industry and the success of energy efficiency is hidden in the kiln process chemistry. This article tries to establish detailed energy audit methodology of sponge iron manufacturing process or kiln operation with a view to finding out major energy saving potential of the unit. In the research work we find that it is the incomplete reaction of coal that causes the major energy inefficiency in the process. Substantial amount of un-reacted carbon comes out with the char (by-product) which has virtually zero commercial value. The article also puts a question mark on the justification of using high-grade imported coal in such energy inefficient industries.
A Study of Porosity Effect on Tribological Behavior of Cast Al A380M and Sintered Al 6061 Alloys  [PDF]
Avijit Sinha, Zoheir Farhat
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2015, DOI: 10.4236/jsemat.2015.51001
Abstract: Due to their light weight, high corrosion resistance and good heat conductivity, aluminium alloys are used in many industries today. They are suitable for manufacturing many automotive components such as clutch housings. These alloys can be fabricated by powder metallurgy and casting methods, in which porosity is a common feature. The presence of pores is responsible for reducing their strength, ductility and wear resistance. The present study aims to establish an understanding of the tribological behavior of high pressure die cast Al A380M and powder metallurgy synthesized Al 6061. In this study, dry sliding wear behavior of Al A380M and Al 6061 alloys was investigated under low loads (1.5 N – 5 N) against AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration and frequency of 10 Hz. Wear mechanisms were studied through microscopic examination of the wear tracks. This study revealed that due to combined effect of real area of contact and subsurface cracking, wear rate increased with increasing porosity content. The difference in friction and wear behavior between received Al A380M and Al 6061 is attributed to their hardness differences.
Effect of Surface Porosity on Tribological Properties of Sintered Pure Al and Al 6061  [PDF]
Avijit Sinha, Zoheir Farhat
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.66059
Abstract: Due to light weight, high specific strength, high corrosion resistance and good heat transfer ability, aluminium alloys are becoming attractive for critical structural applications. These alloys can be manufactured using powder metallurgy techniques in which porosity is a common characteristic. The presence of pores is responsible for decreasing effective load bearing cross sectional area and inducing stress concentration sites for strain localization and damage, decreasing both strength and ductility. The present study aims to establish a better understanding of the relationship between surface porosity and corresponding wear behavior. In this study, porous specimens were produced using powder metallurgy technique and the extent of wear damage and the type of wear was investigated under low load range of 1.5 - 5 N against AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration and frequency of 10 Hz. Scanning electron microscopy of the wear tracks and wear debris was carried out to understand wear mechanisms. This study revealed that due to combined effect of high stress intensity and subsurface cracking, wear rate increases with increasing porosity content. The friction and wear behavior of pure Al and Al 6061 as a function of porosity content can be attributed to their hardness and corresponding wear mechanism.
A Short Report on Decompression Sickness Incidents in Andaman and Nicobar Islands  [PDF]
Sheeba Ahmed, Avijit Roy
Journal of Biosciences and Medicines (JBM) , 2016, DOI: 10.4236/jbm.2016.41012
Abstract: Objectives: Due to presence of extensively fascinating coral reef ecosystem in the continental shelf of Andaman and Nicobar Islands, people from all over the world visit these islands of India to indulge in recreational diving. An increased participation figure has also elevated the number of divers at risk for Decompression Sickness (DCS). Despite this, no scientific data are available on DCS incidents from India. Present study is aimed to evaluate the DCS incidents reported in these islands, treatment provided, and the outcome of the treatment. An attempt has also been made to calculate the approximate frequency of DCS in comparison to the participation figure. Methods: Study design is retrospective data analyses of a recompression chamber. Naval Diving Unit Port Blair has the only active decompression chamber available in the islands, and Govind Ballabh Pant Hospital Port Blair was used to collect information on DCS incidents that occurred during the mentioned period. Due to lack of authenticated generalized documents of divers’ health history and dive logs, the scanty information was gathered from the dive centres on the basis of personal interviews/communications among the SCUBA diving instructors. Results: A total of nine cases were reported during the span of last four and half years, and thus approximate frequency of DCS in Andamans was 0.2/10000 divers year. All of the patients recovered completely after receiving the Hyperbaric Oxygen Therapy (HBOT), with no residual symptoms. Conclusions: Incident rate of DCS in Andamans is lower than that in many other parts of the world; possible reason could be under-reporting of less severe DCS cases. During the study period, the number of DCS type II incidents presented for the treatment was higher than that of DCS type I incidents. HBOT proved a complete success in treating DCS cases in the island.
A New Algorithm of Self Organization in Wireless Sensor Network  [PDF]
Hemanta Kumar KALITA, Avijit KAR
Wireless Sensor Network (WSN) , 2010, DOI: 10.4236/wsn.2010.21006
Abstract: Self organization is one of the most important characteristics in an Ad-hoc Sensor Network. Thousands of Sensors are deployed in a geographical area randomly without considering the location factor. After deployment, sensors are to self organize themselves to form a network of their own. How well the network is formed determines the life of the whole network as well as the quality of data transmission. Self organization based on clustering has proven to be very useful in this regard. Since hierarchical clustering reduces energy consumption by routing data from one node to another. In this paper, we discuss a new algorithm for self organization of sensors deployed in a geographical area. The algorithm forms clusters of sensors by ordering them using a unique triangulation method. This algorithm not only considers all sensors but also groups them so that their inherent clustering property is preserved.
Performance Analysis and Formulation of Turbo Coded OFDM over Rayleigh & Rician Fading Channel
Avijit Patel
International Journal of Electronics Communication and Computer Technology , 2012,
Abstract: In wireless communication, to attain high throughput and better transmission quality, there is a need of better system design . Orthogonal Frequency Division Multiplexing (OFDM) is a techniques for parallel transmission. The performance of OFDM can be improved by using some kind of channel coding. This form of OFDM is called coded-OFDM (COFDM). In this paper Turbo code is used as channel coding with OFDM, called Turbo coded OFDM .This paper compares the performance of Turbo coded OFDM using binary phase shift keying (BPSK) , Quadrature Phase Shift Keying (QPSK) , Quadrature Amplitude Modulation (QAM) modulation technique for different Rayleigh and Rician fading channel . Results is formulated that a combination fading channel and modulation technique gives better performance.
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