68 research outputs found

    Convection Due to Spatially Distributed Heating

    Get PDF
    Convection in an infinite horizontal slot subject to spatially distributed heating has been investigated for a wide range of Prandtl numbers. The primary flow response consists of convection in the form of rolls. When heating wave number alpha is sufficiently large the convection is found to be limited to a layer adjacent to lower wall and a uniform conductive layer emerges at upper section of the slot. Conditions leading to the emergence of secondary convection have been identified using linear stability of the above primary convection. The secondary convection gives rise to longitudinal, or transverse, or oblique rolls; or to oscillatory mode at onset. Three mechanisms of instability have been identified. For small and moderate alpha parametric resonance leads to the pattern of instability that is locked-in with the pattern of heating. The second mechanism is associated with the formation of patterns of vertical temperature gradients and patterns of primary convection currents, operates approximately in the same range of alpha. The third mechanism operates for large alpha where instability is driven by uniform mean vertical temperature gradient created by primary convection and fluid response becoming similar to that found in the case of uniformly heated wall. A rapid stabilization of the oblique rolls is observed when alpha is reduced sufficiently, with the oscillatory mode taking the dominant role. As alpha becomes very small, secondary motions concentrate around the hot spots. When an external flow is introduced into the slot, the heating assists in reduction of the overall drag

    EVALUATION OF POLYUNSATURATED FATTY ACIDS AND β-GLUCAN CONTAINING DIET ON GROWTH PERFORMANCE AND CONDITION FACTOR OF PABDAH CATFISH, OMPOK PABDA (HAMILTON, 1822)

    Get PDF
    Nutritionally balanced diet and selection of appropriate species for culturing environment are important criteria in aquaculture. The present study was conducted to evaluate the effects of polyunsaturated fatty acids (PUFAs) and β-glucan containing diet (PBG) on growth performance, feed utilization, length-weight relationship, and condition factor of Pabdah catfish, Ompok pabda. In this study, squid extracted phospholipid and mushroom powder were used as the source of PUFAs and β-glucan, respectively, and formulated two isonitrogenous diets such as basal or control (CON) diet and PBG diet with maintaining 30% protein levels. During the study period, similar physicochemical conditions of water such as temperature, pH, and dissolved oxygen (DO) were 26.5 ± 2 °C, 7.4 ± 0.2, and 6.7 ± 0.5 ppm, respectively were maintained in each cistern. The results showed that final mean body weight, final mean length gain, food conversion ratio (FCR), specific growth rate (SGR), food conversion efficiency (%), hepato somatic index (HSI), kidney index (KI), and viscerosomatic index (VSI) were significantly (P<0.01 and P<0.05) higher in fish fed the PBG diet than that of fish fed the CON diet. The coefficient of determination showed a significant relationship (R2 = 0.956) between the length and weight of the treatment group. The length-weight relationship and relative condition factor (K) of Ompok pabda were significantly (P<0.05) affected by the PBG diet. The present study shows that the experimental diet more effective and achieves better growth performance, feed utilization, length-weight relationship, and condition factor of Ompok pabda.

    A Small-Sample Randomization-Based Approach to Semi-Parametric Estimation and Misspeci cation in Generalized Linear Mixed Models

    Get PDF
    PhDIn a generalized linear mixed model (GLMM), the random effects are typically uncorrelated and assumed to follow a normal distribution. However, fi ndings from recent studies on how the misspeci cation of the random effects distribution affects the estimated model parameters are inconclusive. In the thesis, we extend the randomization approach for deriving linear models to the GLMM framework. Based on this approach, we develop an algorithm for estimating the model parameters of the randomization-based GLMM (RBGLMM) for the completely randomized design (CRD) which does not require normally distributed random effects. Instead, the discrete uniform distribution on the symmetric group of permutations is used for the random effects. Our simulation results suggest that the randomization-based algorithm may be an alternative when the assumption of normality is violated. In the second part of the thesis, we consider an RB-GLMM for the randomized complete block design (RCBD) with random block effects. We investigate the effect of misspecifi cation of the correlation structure and of the random effects distribution via simulation studies. In the simulation, we use the variance covariance matrices derived from the randomization approach. The misspecifi ed model with uncorrelated random effects is fi tted to data generated from the model with correlated random effects. We also t the model with normally distributed random effects to data simulated from models with different random effects distributions. The simulation results show that misspeci cation of both the correlation structure and of the random effects distribution has hardly any effect on the estimates of the fi xed effects parameters. However, the estimated variance components are frequently severely biased and standard errors of these estimates are substantially higher

    AN APPROACH TO MONITORING DATA QUALTIY - PRODUCT ORIENTED APPROACH -

    Get PDF
    The data asset is increasingly becoming one of the top factors in securing organization success. Recognizing the importance of the quality of data, practitioners and researchers have considered for many years ways to improve data quality. Scientists have worked on mathematical and statistical model to introduce constrain based mechanism to prevent data quality problems. Management of the process of data generation has also attracted many researchers. The practical application of most of the proposed approaches is still very limited. Improving data quality with in the development cycle of information system is rarely integrated. Neither process mapping nor data modeling provides sufficient provision to define the required quality that data must conform to. Furthermore, ongoing monitoring of data for quality conformance is not possible without developing cost and time prohibitive data monitoring system. Recognising this limitation and aiming to provide a practical-orient approach, we propose a process centric information system design incorporating data product quality and conformance. In this paper we consider the benefit of a process centric framework for ongoing data quality monitoring

    Pattern and risk factors of acute poisoning in a tertiary hospital of Central Bangladesh

    Get PDF
    Objective: Acute poisoning is a common cause of hospital admission in Bangladesh. But, risk factors and characteristics of victims of different modes of poisoning have not been evaluated for possible intervention strategies. So, in this study we aimed to describe the pattern of acute poisoning in central Bangladesh as well as identifying risk factors for various mode of poisoning. Methods: A prospective observational study was undertaken in Dhaka Medical College Hospital in 2015. Consenting adult acute poisoning victims were included as study subjects. A pretested structured case record form was used to systematically record the cases. The poisoning cases were defined by clinical toxidrome (sympathomimetic, antimuscarinic, opioids, cholinergic, sedative, etc) during acute presentation with suspected poisoning and groups accordingly. SPSS 20 was used for data analysis and statistical tests including mean ± standard division (SD), percentage, t test and chi-square were used accordingly. Results: Total poisoning cases were 1155. Suicidal (62.25%, n=719), commuter poisoning (24.16%, n=279) and accidental poisoning (12.38%, n=143) were main types of poisoning. Risk factors of suicidal poisoning were young females of 11 to 30 years, married, housewives and students (P<0.0001). Stressful relationship was the commonest reason of suicidal poisoning. Pesticides and sedatives were frequently chosen for easy availability. Commuter poisoning was common in males and urban areas (P<0.0001). Accidental poisoning was more in males and rural areas (P<0.0001) and snake envenomation was the main cause. Conclusion: Poisoning burden is high in central Bangladesh. Identified risk factors will help develop poisoning prevention strategies. Keywords: Bangladesh, Poisoning, Suicide, Preventio

    A survey of the Islamic insurance literature – takaful

    Get PDF

    Assessing the Awareness on Occupational Health Hazards Among Dentists of Different Private Dental Clinics in Dhaka, Bangladesh

    Get PDF
    To determine if dentists in and around Dhaka are aware of certain workplace hazards and what precautions they take to avoid them. The current study was done with the help of a self-administered questionnaire that was distributed to 30 dentists in and around Dhaka. Personal information such as age, gender, position (student or faculty), years of experience, and number of working hours per day were also included in the questionnaire. Only those who thoroughly filled out the questionnaire form and were willing to participate were considered for the study. PSPP open source latest version was used to analyze the data. 30.0 percent of the participants had worked in the dental field for more than 10 years, while 26.7 percent of dentists worked for less than 8 hours. General practitioners made up 66.7 percent of the participants, and 43.3 percent of them see nearly 10 to 20 patients per day. In clinical practice, 40.0 percent of them had a needle stick injury. In our study, 0.0 percent of dentists reported to getting some form of litigation from their patients. The current study found that the occupational hazards, biological hazards awareness, and preventive actions observed by dentists in Dhaka are generally consistent with published infection control guidelines and previous studies. The bulk of the dental professionals were in pain in their neck or back muscles. Regular training and workshops can aid in the reduction of such issues. Keywords: Dentists, Private Clinics, Health hazards. DOI: 10.7176/JBAH/12-18-02 Publication date:September 30th 202

    Muscle spindles provide servo-assistance to jaw-closing muscles for chewing hard foods

    Get PDF
    The fundamental pattern of chewing induced by the network of neurons called central pattern generator has been reported to be modified by the information arising from the various oro-facial sensory receptors including muscle spindles of jaw closing muscles. The cell bodies of primary afferent neurons from these muscle spindles lie in mesencephalic trigeminal nucleus (MTN) in the brainstem. The aim of the study was to understand whether muscle spindles from jaw-closing muscles play any role in hard food chewing. Single neuronal discharge of muscle spindle afferents was recorded from the MTN simultaneous with jaw-movement and electromyograpic (EMG) activities of the left masseter (jaw-closing) muscle during chewing soft and hard foods (apple and pellet) in awake rabbits. Ten consecutive chewing cycles were taken for analysis. Discharge of nineteen muscle spindles from seven rabbits was successfully recorded. Muscle-spindle discharge was significantly higher during the closing phase of jaw-movement for the hard food chewing than for the soft food. The jaw-closing muscle EMG activity was significantly higher during hard food chewing compared to soft food. The spindle discharge was higher when the masseter muscle activity was greater for chewing hard food. Significant positive (r=0.822, p=<0.001) correlation was found between the difference of muscle activity between apple and pellet and the difference of spindle discharge between apple and pellet. Above findings suggest that the increase of spindle discharge during hard food chewing may play a role for facilitating jaw-closing muscle activities and thereby provides servo-assistance to jaw-closing muscles to compensate the hardness of food

    Design and Simulation of a Zero Crossing VSC Based Phase Synchronous Inverter for Microgrid System

    Get PDF
    A microgrid is a system which consists of the transmission line and loads capable of operating in parallel with the national grid and distributed power sources such as power generation, storage and demand management. However, to connect the wind, solar and electrostatic power generation system together with microgrid, a phase synchronisation issue arises. For the electrostatic system, generated DC voltage needs to be converted into AC to connect with the transformer-less microgrid system. This process inherently produces very low output current and also degrades the phase synchronization of the system. To counter these issues, a zero-crossing voltage source controller based phase synchronous inverter system has been designed and implemented in this paper. In addition, an active LCL filter has been designed to reduce the high harmonic distortion. Moreover, to verify the result, MATLAB2014a software has been used. In this design, input DC voltage of 10kV, switching frequency of 1.65 kHz, grid frequency of 50Hz and balanced grid loads of star configuration (00, 1200, and 2400 degree) are considered. The simulated result has shown that inverter inversion efficiency is 96.8% and phase angle error is only 3.50 degrees
    corecore