Papers by Shahinur Rahman
Energies
The increase in penetration levels of inverter-based resources (IBRs) is changing the dynamic per... more The increase in penetration levels of inverter-based resources (IBRs) is changing the dynamic performance of power grids of different parts of the world. IBRs are now being more and more integrated into the grid at a single connection point as an IBR plant. Due to the complex nature and dynamicity of each inverter model, it is not realistic to build and analyze full complex models of each inverter in the IBR plant. Moreover, simulating a large plant including detailed models of all the IBRs would require high computing resources as well as a long simulation time. This has been the main issue addressed in the new IEEE Std 2800-2022. This paper proposes a novel approach to model an IBR plant, which can capture the transient nature at the plant level, detailed IBR control at the inverter level, interactions of multiple IBR groups in a plant structure, and a collector system connecting the IBRs to the grid. The IBRs in the plant use a voltage source inverter topology combined with a gri...
POM (Polyoxymethylene) polymer has been a focus of great attention in the field of polymer due to... more POM (Polyoxymethylene) polymer has been a focus of great attention in the field of polymer due to its promising properties i.e. low coefficient of friction, high abrasion resistance, high heat resistance and self-lubricating. It is widely used to make small gear wheels, ball bearings, precision parts, automotive and consumer electronics. The Polyoxymethylene (POM) polymer samples were irradiated with 1 MeV electron beam in two doses (100 and 200 KGy) and 165 KeV electron beam in two doses (100 & 200 KGy) under N2 atmosphere. The tribological and physico-chemical (morphological and structural) properties of electron beam irradiated POM have been analyzed using pin on disk tribometer (under dry friction conditions), raman spectroscopy and optical microscopy. Tribotesting demonstrates that electron irradiation at a dose of 1MeV, 100 KGy resulted in a decrease of the friction coefficient, whereas 1MeV (200 KGy) and 165 KeV (100 and 200 KGy) resulted in increase of the friction coefficient as compared to pure POM, respectively. It has been denoted that electron irradiation may induce a sort of defects on POM due to chain scission and cross linking as demonstrated from raman spectroscopy analysis which is also ascertained by optical microscopy observation. The electron irradiation transferred the wear system of unirradiated POM sample from the abrasive wear, adhesive wear and scraping to mild scraping for the treated one which can be concluded from optical microscopy observation. The degree of improvement of tribological attribute relies on the optimum irradiated fluence conditions (energy and dose rate).
Advances in Intelligent Systems and Computing, 2018
Data is not meaningful unless its information could be extracted. In every second in this world, ... more Data is not meaningful unless its information could be extracted. In every second in this world, we are generating millions of data over the Internet in different form. Most of them are in text format. Usually, data is written based on any topic, or sometimes on few topics. Following this, identifying topic of any text data is very important. Topic identification may help text summarization tools, text classification tool, etc. Machine learning applications may need less training on their data, only if once the topic of text is identified. Therefore, the demand of topic modeling is higher than ever right now. Data scientists are working day and night to make it more effective and accurate using different methods. Topic modeling focuses on the keywords that can express or identify the topic discussed in the document. Topic modeling can save a lot of time by releasing its user from page-to-page manual reviewing. In this paper, a model has been proposed to find out topic of a document....
Anwer Khan Modern Medical College Journal, 2017
It has been established that laparoscopic cholecystectomy could be performed at a treatment cost ... more It has been established that laparoscopic cholecystectomy could be performed at a treatment cost that is equal to or slightly less than that of open cholecystectomy, and with substantial cost savings to the patient and society due to the reduced loss of time from work 3. The cost of laparoscopic cholecystectomy and open cholecystectomy has been compared in some randomized controlled trials with divergent results 4. The aim of this study was to analyze and compare the perioperative results of patients undergoing laparoscopic and open cholecystectomy concerning to duration of operation, complications, hospital stay and cost.
Journal of Armed Forces Medical College, Bangladesh, 2015
The number of chest trauma patients has rapidly increased in this 21 st century of high speed tra... more The number of chest trauma patients has rapidly increased in this 21 st century of high speed travel, violence, natural and manmade disasters. Most of the patients present with haemothorax and/or haemopneumothorax. Drainage of haemothorax and/or haemopnumothorax by tube thoracostomy is the main stay of treatment. Even timely insertion of chest tube sometimes fails to drain haemothorax adequately and results in clotted haemothorax for which surgical management is needed. Application of continuous low pressure suction through chest tube hastens evacuation of blood and reduces incidence of clotted haemothorax and thoracotomy. Objective: The aim of this study is to find out the effectiveness of continuous low pressure suction in evacuation of blood and air from pleural cavity, in early re-expansion of lung and reduction of clotted haemothorax in comparison with simple chest tube drainage. Methods: This randomized controlled clinical trial was conducted at Combined Military Hospital (CMH) Dhaka and National Institute of Diseases of the Chest and Hospital (NIDCH), Mohakali, Dhaka from April 2012 to March 2013. A total of 60 patients with blunt and penetrating chest trauma fulfilling the selection criteria enrolled in this study. Patients were allocated into two groups. Patients who received continuous low pressure suction on their chest tubes were leveled as group-I and patients who received only chest tube drainage were leveled as group-II. Data were collected by interview, observation, clinical examination and investigation results. Data were processed and analyzed by using statistical test.
Bangladesh Journal of Endosurgery, 2014
Backgraound: Open appendectomy (OA) has been the treatment of choice for acute appendicitis since... more Backgraound: Open appendectomy (OA) has been the treatment of choice for acute appendicitis since its introduction by Mc-burney in 1884. Laparoscopic appendectomy(LA) though widely practiced, has not gained universal approval. LA was first described in 1983. Some early studies showed equivocal results about benefit of LA. Recent studies showed overall benefit in favour of LA. So far no such a large study was done in any Bangladeshi hospital. So, we decided to do this study with a view to evaluate the therapeutic benefit of LA by comparing with conventional OA. Materials and methods: We collected data of 763 appendectomies done in Jahurul Islam medical college hospital from July 2007 to June 2012 for a period of 5 years. Out of them 448 had conventional OA and 315 had LA. We compared the mean operation time, time of first oral feeding, narcotic analgesic requirement, duration of post operative hospital stay. Results: We found that mean operation time was 33±5.8 minute and 37± 7.5 minute in LA and OA respectively. Duration of post operative hospital stay was 1.2 days shorter in Laparoscopic group. LA required 1.1 shots of less analgesic than OA. Oral feeding was resumed 21 hours earlier following LA compared to OA. Laparoscpic appendectomy was safely performed in paediatric patient without any adverse effect. We also found that, in female patient, concurrent ovarian cysts, tubal pregnancy and endometriosis can be diagnosed and managed laparoscopically in the same sitting. Conclusion: Our study found that laparoscopic appendectomy is an effective and safe procedure irrespective of age and sex of the patient. LA has added advantage of early return of bowel movement, less post-op hospital stay and less requirement of narcotic analgesic.
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010
The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in... more The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in June 2009. The instrument combines microchannel plate detector technology with fiber-fed integral field spectroscopy on an unstable stratospheric balloon gondola platform. This unique combination poses a series of calibration and data reduction challenges that must be addressed and resolved to allow for accurate data analysis. We discuss our approach and some of the methods we are employing to accomplish this task.
SPIE Proceedings, 2010
We are designing the Keck Cosmic Web Imager (KCWI) as a new facility instrument for the Keck II t... more We are designing the Keck Cosmic Web Imager (KCWI) as a new facility instrument for the Keck II telescope at the W. M. Keck ObselVatory (WMKO). KCWI is based on the Cosmic Web Imager (CWI), an instrument that has recently had first light at the Hale Telescope. KCWI is a wide-field integral-field spectrograph (IFS) optimized for precision sky limited spectroscopy of low surface brightness phenomena. KCWI will feature high throughput, and flexibility in field of view (FOV), spatial sampling, bandpass, and spectral resolution. KCWI will provide full wavelength coverage (0.35 to 1.05 !lm) using optimized blue and red channels. KCWI will provide a unique and complementary capability at WMKO (optical band integral field spectroscopy) that is directly connected to one of the ObselVatory's strategic goals (faint object, high precision spectroscopy), at a modest cost and on a competitive time scale, made possible by its simple concept and the prior demonstration of CWI.
Journal of Paediatric Surgeons of Bangladesh, 2014
Introduction: Bronchogenic cysts are congenital anomalies caused by abnormal bronchial developmen... more Introduction: Bronchogenic cysts are congenital anomalies caused by abnormal bronchial development from the primitive ventral foregut, which arises from cells isolated from the main pulmonary branching when lung bud separates from the primitive gut.Materials & Methods: We reviewed all pediatric patients with bronchogenic cyst who underwent surgery in our thoracic surgical unit- III during 2007-2009. They comprised 1 male and 5 female patients, with an age range of 2 to 17 years (mean age 5.66 years).Results: Symptoms were present in 5 patients (83%), cough was the most common symptom. Other symptoms included purulent sputum, chest pain, fever, dyspnea, anorexia and/or weight loss, and haemoptysis. All patients underwent chest x-ray posteroanterior and lateral view and CT scan of chest for diagnostic purpose. Two of the cysts were mediastinal and rests were intraparenchymal. Surgery performed were resection (2), lobectomy (4). Complications of bronchogenic cysts occurred in 4 patient...
SPIE Proceedings, 2008
FIREBall (Faint Intergalactic Redshifted Emission Balloon) had a successful first engineering fli... more FIREBall (Faint Intergalactic Redshifted Emission Balloon) had a successful first engineering flight in July of 2007 from Palestine, Texas. Here we detail the design and construction of the spectrograph. FIREBall consists of a 1m telescope coupled to a fiber-fed ultraviolet spectrograph flown on a short duration balloon. The spectrograph is designed to map hydrogen and metal line emission from the intergalactic medium at several redshifts below z=1, exploiting a small window in atmospheric oxygen absorption at balloon altitudes. The instrument is a wide-field IFU fed by almost 400 fibers. The Offner mount spectrograph is designed to be sensitive in the 195-215nm window accessible at our altitudes of 35-40km. We are able to observe Ly , as well as OVI and CIV doublets, from 0.3 < z < 0.9. Observations of UV bright B stars and background measurements allow characterization of throughput for the entire system and will inform future flights.
SPIE Proceedings, 2010
\\'c describe the Cosmic Web hlJagcr (C\\'[), a UV-VIS integral field sped mgrnph desiglwd for th... more \\'c describe the Cosmic Web hlJagcr (C\\'[), a UV-VIS integral field sped mgrnph desiglwd for thl' Hall' 2()()," telescope at the Palolllar ObSNvatory. CV;l has bl'clI built sp('cificallv for the observation of diffuse radiatioll. The illSt.nllTlCllt lipId of vicw is tit)" x 10" with spectral f(~solvillg power of R~S(J()() alld secillg lilllitl'd spat ial resolutioll. It utilizes volullle phase holographic gratillgs amI is illtl'lId('d to cover the sjH'ctral rallge :lSO()A to !JS()()A with all illstalltalH'olls balldwidth of ~;lS0A. (,WI SilW first light ill .July :20W), alld cOlldnct('(1 it.s firsl succcssful scil'lIt ific observal iOlls ill l'vLrv 20 10.
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010
The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in... more The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in June 2009. The instrument is a 1 meter class balloon-borne telescope equipped with a vacuum-ultraviolet integral field spectrograph intended to detect emission from the inter-galactic medium at redshifts 0.3 < z < 1.0. The scientific goals and the challenging environment place strict constraints on the pointing and tracking systems of the gondola. In this manuscript we briefly review our pointing requirements, discuss the methods and solutions used to meet those requirements, and present the aspect reconstruction results from the first successful scientific flight.
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010
FIREBALL (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope co... more FIREBALL (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph. FIREBALL is designed to study the faint and diffuse emission of the intergalactic medium, until now detected primarily in absorption. FIREBALL is a path finding mission to test new technology and make new constraints on the temperature and density of this gas. We report on the first successful science flight of FIREBALL, in June 2009, which proved every aspect of the complex instrument performance, and provided the strongest measurements and constraints on IGM emission available from any instrument.
SPIE Proceedings, 2006
We are developing the Cosmic Web Imager (CWI) to detect and map emission from the intergalactic m... more We are developing the Cosmic Web Imager (CWI) to detect and map emission from the intergalactic medium (IGM). CWI will observe the strong, redshift UV resonance lines of Lyα 1216, CIV 1550, and OVI 1033 over 3600-9000 Å to trace IGM at 1 < z < 7. CWI is an integral-field spectrograph designed for the Hale Telescope at Palomar Observatory. CWI combines in a novel way three mature and extensively used instrumental techniques. The Integral Field Unit (IFU) provides a wide 2D field of view of 60 x 40 arcsec2 for observing extended emission over a large region. The spectrograph using Volume-Phase Holographic gratings have high peak diffraction efficiency and are tunable for covering a large bandpass with a single grating. A low read noise CCD combined with source/background shiftand-nod allowing control of systematics and Poisson-limited sky subtraction to observe the low surface brightness universe. With a resolution of R=10,000 CWI is sensitive to limiting surface brightness ranging from 25-27.5 mag/arcsec2 (10 min-8 hours integration). Recent high resolution simulations predict Lyα Fluorescence from IGM at 100-1000 LU1. CWI with sensitivity of ~200 LU improves the current observational effort by an order of magnitude and enables us to explore wide range of overdensity (δ ~ 30-104) testing the standard model of structure formation in the universe. CWI also serves as the counter part to the balloon borne integral-field spectrograph Faint Intergalactic medium Redshifted Emission Balloon (FIREBALL) currently being built and planned to be launched in Summer 2007. FIREBALL will observe Lyα Fluorescence from IGM at z = 0.7. CWI combined with FIREBALL will enable us to observe the evolution of IGM and the low surface brightness universe.
The Astrophysical Journal, 2014
The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale s... more The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter-(CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on-and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 10 11 M , and the dark halo mass is at least 2 × 10 12 M. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas have significant and coaligned angular momentum, strengthening the case for their association.
Macromolecules, 2008
The synthetic strategy employs classical anionic polymerization using high-vacuum techniques and ... more The synthetic strategy employs classical anionic polymerization using high-vacuum techniques and utilizes a difunctional linking agent 4-(dichloromethylsilyl)diphenylethylene (DCMSDPE). The synthesis involves (a) growing a living PBd chain using s-BuLi as initiator in benzene at room temperature, (b) titration of DCMSDPE with living PBdLi, (c) addition of s-BuLi to activate the double bond of DPE, (d) subsequent addition of butadiene to generate a living " 1 / 2 H", which has two arms and half of the final crossbar , and (e) finally coupling the two " 1 / 2 H" molecules with dichlorodimethylsilane to produce an H-PBd, which has two arms attached to each end of the crossbar. The weight-average molecular weight, number-average molecular weight, molecular weight distribution, intrinsic viscosity, and radius of gyration were characterized by multidetector size exclusion chromatography (SEC) coupled with a refractive index detector, a two-angle (15°and 90°) light scattering detector, and a Viscotek differential viscometer in tetrahydrofuran at 40°C. The H-PBds showed narrow and symmetrical molecular weight distributions (polydispersity indices, PDI) 1.03-1.06). Furthermore, the use of light scattering detectors showed that there were no detectable high molecular weight, more highly branched components present in these materials. This is an important advantage of this novel approach over previous synthetic routes to H-polymers. The values of the branching parameters g (0.58-0.77) and g′ (0.60-0.75) in the thermodynamically good solvent, tetrahydrofuran, are consistent with values reported previously by Roovers and Toporowski for H polystyrenes in the good solvent toluene. Effects of architecture on the branching parameters are elucidated.
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Papers by Shahinur Rahman