Effect of Flue Gas Recirculation on Multi-Cyclones Performance in Reducing Particulate Emission from Palm Oil Mill Boiler

The effect of recirculating the flue gas on the performance of a multi-cyclones unit as particulate collector in an actual plant scale was studied. The existing multi-cyclones unit was modified by connecting a recirculation duct between the inlet and outlet gas stream of the multi-cyclones attached with an external induced (ID) fan. The particulate samplings were done following the U.S. EPA method at boiler outlet (before multi-cyclones), stack (after multi-cyclones) and recirculation duct. Result shows that the amount of recirculated particulates increases with ID fan suction power. The collection efficiency increased slightly from 68% (0% or without recirculation) to 74% (at 11% recirculation) and dropped to 67% (at 17% recirculation). Moreover, the amount of the fine particulate size fraction emitted able to be reduced one fold at 11% recirculation flow rate. However, high amount of recirculated particulates results in re-entrainment of particulates into the outlet of the multi-cyclones, hence, results in increase of particulate emission in the stack.     

Modelling area-wide count outcomes with spatial correlation and heterogeneity: an analysis of London crash data

Count models such as negative binomial (NB) regression models are normally employed to establish a relationship between area-wide traffic crashes and the contributing factors. Since crash data are collected with reference to location measured as points in space, spatial dependence exists among the area-level crash observations. Although NB models can take account of the effect of unobserved heterogeneity (due to omitted variables in the model) among neighbourhoods, such models may not account for spatial correlation areas. It is then essential to adopt an econometric model that takes account of both spatial dependence and uncorrelated heterogeneity simultaneously among neighbouring units. In studying the spatial pattern of traffic crashes, two types of spatial models may be employed: (i) classical spatial models for higher levels of spatial aggregation such as states, counties, etc. and (ii) Bayesian hierarchical models for all spatial units, especially for smaller scale area-aggregations. Therefore, the primary objectives of this paper is to develop a series of relationships between area-wide different traffic casualties and the contributing factors associated with ward characteristics using both non-spatial models (such as NB models) and spatial models and to identify the similarities and differences among these relationships. The spatial units of the analysis are the 633 census wards from the Greater London metropolitan area. Ward-level casualty data are disaggregated by severity of the casualty (such as fatalities, serious injuries, and slight injuries) and by severity of the casualty related to various road users. The analysis implies that different ward-level factors affect traffic casualties differently. The results also suggest that Bayesian hierarchical models are more appropriate in developing a relationship between area-wide traffic crashes and the contributing factors associated with the road infrastructure, socioeconomic and traffic conditions of the area. This is because Bayesian models accurately take account of both spatial dependence and uncorrelated heterogeneity.     

Distribution of reinforcement particles in surface composite fabrication via friction stir processing: Suitable strategy

Fabrication of metal matrix surface composites (SCs) is an emerging trend of friction stir processing applications. Key factors affecting the properties of SCs are process parameters, tool geometry, tool dimensions and reinforcement strategies. In this research, effects of different reinforcement strategies and varying tool offset positions on dispersion of reinforcement particles in the base matrix are investigated. The experiments were performed in two phases using AA6063 as base metal at constant process parameters of 1120?rpm rotational speed, 40?mm/min traverse speed and 2.5° tilt angle. In the first phase, effect of six different reinforcement strategies on the reinforcement particles distribution and defect formation was studied. It was found that groove method with tool offset in retreating side (RS) exhibited better homogeneity in reinforcement distribution out of the six reinforcement strategies considered. In the second phase, effect of variation of tool offset in RS was investigated. Results from second phase of experimentation reflected that the best dispersion of reinforcement powder with larger stir zone area was found with 1.5?mm tool offset which is numerically half of the tool pin radius. The results were supported by macro and microstructural images obtained from the optical microscope and scanning electron microscope.     

An adaptive EWMA control chart for monitoring the process mean in Bayesian theory under different loss functions

The Shewhart control chart is used for detecting the large shift and an exponentially weighted moving average (EWMA) control chart is used for detecting the small/moderate shift in the process mean. A scheme that combines both the Shewhart control chart and the EWMA control chart in a smooth way is called the adaptive EWMA (AEWMA) control chart. In this paper, we proposed a new AEWMA control chart for monitoring the process mean in Bayesian theory under different loss functions (LFs). We used informative (conjugate prior) under two different LFs: (1) squared error loss function and (2) linex loss function for posterior and posterior predictive distributions. We used the average run length and standard deviation of run length to measure the performance of the AEWMA control chart in the Bayesian theory. A comparative study is conducted for comparing the proposed AEWMA control chart in Bayesian theory with the existing Bayesian EWMA control chart. We conducted a Monte Carlo simulation study to evaluate the proposed AEWMA control chart. For the implementation purposes, we presented a real-data example.     

Bayesian EWMA control charts based on Exponential and transformed Exponential distributions

In this paper, we proposed the Bayesian exponentially weighted moving average (EWMA) control charts for mean under the nonnormal life time distributions. We used the time between events data which follow the Exponential distribution and proposed the Bayesian EWMA control charts for Exponential distribution and transformed Exponential distributions into Inverse Rayleigh and Weibull distributions. In order to develop the control charts, we used a uniform prior under five different symmetric and asymmetric loss functions (LFs), namely, squared error loss function (SELF), precautionary loss function (PLF), general entropy loss function (GELF), entropy loss function (ELF), and weighted balance loss function (WBLF). The average run length (ARL) and the standard deviation of run length (SDRL) are used to check the performance of the proposed Bayesian EWMA control charts for Exponential and transformed Exponential distributions. An extensive simulation study is conducted to evaluate the proposed Bayesian EWMA control chart for nonnormal distributions. It is observed from the results that the proposed control chart with the Weibull distribution produces the best results among the considered distributions under different LFs. A real data example is presented for implementation purposes.     

Exploring the Relationship Between Multi-Dimensional Top Management Support and Project Success: An International Study

Abstract

The role of top management support in achieving project success has gained much attention in research and practice. A number of studies on single dimensional top management support have been conducted. In the engineering management literature, top management support has rarely been studied as a multi-dimensional construct. This research examines the relationship between multiple dimensions of top management support and project success. Different data analysis methods were employed to test the research hypotheses and to validate the multi-dimensionality of top management support. Findings indicate a significant and positive relationship between multi-dimensional top management support and project success.     

Rheology of high flowing mortar and concrete

Rheology of high flow mortar and concrete was studied using coaxial cylinder rheometer and lifting sphere viscometer. The tests results were compared with the traditional test methods of high flowing mortar and concrete. Generalized equations for viscosity and yield stress of the mortar and concrete were then developed based on this investigation. The Farris model was used to calculate the viscosity and a new model was proposed to calculate the yield stress for the generalized equations. These models were validated using test results of different high flow mortar and concrete. The study also revealed that the rheology values obtained using the coaxial cylinder rheometer and lifting sphere viscometer test are significantly different.

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Résumé La rhéologie de mortiers et bétons ayant un écoulement élevé a été étudiée à l'aide d'un rhéomètre à cylindre coaxial et d'un viscosimètre soulevant une sphère. Les résultats des essais ont été comparés aux méthodes d'essai traditionnelles des mortiers et bétons à écoulement élevé. Les équations généralisées pour la viscosité et la contrainte d'écoulement des mortiers et bétons ont été développées à partir de cette investigation. Le modèle de Farris a été utilisé pour calculer la viscosité et un nouveau modèle a été proposé pour calculer la contrainte d'écoulement dans les équations généralisées. Ces modèles ont été validés au moyen des résultats des essais portant sur différents mortiers et bétons ayant un écoulement élevé. L'étude a aussi révélé que les valeurs rhéologiques obtenues en utilisant le rhéomètre à cylindre coaxial et lors de l'essai du viscosimètre soulevant une sphère sont considérablement différentes.

     

Effect of Temperature and Starch Concentration on the Intrinsic Viscosity and Critical Concentration of Sago Starch (Metroxylon sagu)

Intrinsic viscosity and critical concentration of sago starch dispersions were studied at different temperatures and presence of solutes (sodium chloride, glucose and sucrose). Ubbelohde capillary viscometer was used to measure relative viscosity. Intrinsic viscosity decreases with an increase in temperature but the critical concentration remained fairly constant over the range of temperature studied. Sodium chloride enhanced the intrinsic viscosity but sugars somehow reduced it. Critical concentration is defined as the point where the starch molecules start to entangle with each other and abruptly enhance viscosity. Sodium chloride enhanced the molecular entanglement and lowered the critical concentration.     

Enzymic Extraction of Native Starch from Sago (Metroxylon sagu) Waste Residue

Residual native starch was extracted from sago pith residue using two types of commercial cell‐wall degrading enzymes, Pectinex Ultra SP‐L and Ultrazyme 100G. The first increased starch yield with a shorter incubation period than the second. The superior effect of Pectinex Ultra SP‐L was observed already at 0.5 h, where a wide granule size distribution (8—87 μm) was obtained. A slight increase in the release of granules ranging from 30—60 μm was noted within a 2 h incubation period. However, upon further incubation, the distribution pattern was similar to that of untreated samples. Samples treated with Ultrazyme 100G exhibited a unimodal distribution pattern, with larger granules, ranging from 40—70 μm, being released upon further incubation within a 2 h incubation period. However, all samples exhibited a bimodal distribution upon further incubation.