Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Facile Fabrication of Chitosan/Starch Composite Films with Fumed Silica as an Additive
Get PDFChitosan/cassava starch (CS/ST) composite films with different CS:ST (w/w) ratios were prepared by solution casting and investigated as a support for fumed silica (fSiO2) dispersion. The CS, as a 1% (w/v) solution in 1% (w/v) acetic acid, and gelatinized ST, as a 3% (w/v) solution in 1% (w/v) acetic acid, were mixed at the appropriate volume ratios with a homogenizer, and then fSiO2 at 1, 3, or 5% (w/w of CS) was added and cast as films. The morphology, tensile strength, contact angle, X-ray diffraction (XRD) pattern, and surface functional groups of the films were investigated. The external morphology of the CS/ST composite film revealed that the fSiO2 particles were homogeneously dispersed into the polymer matrix. The water absorption and surface hydrophobicity of the composite film increased with increasing ST or CS contents. The hydrophobic acetyl groups of CS caused a notable reduction in the wettability as well as the water adsorption ability, which are preferable for a packaging film application. The CS/ST film with a high fSiO2 content had a higher tensile strength due to the reinforcement effect of the fSiO2 nanoparticles. The XRD patterns of the CS/ST films revealed that the 2q of the crystalline region of CS were slightly changed when including the fSiO2. The shift in the ST diffraction peak was probably due to the change in its chain orientation caused by hydrogen-bonding interactions between CS and ST molecules, resulting in their good adhesion
Micro Cup Drawing without Wrinkles Using a Bulged Punch
Get PDFA novel Bulged Punch (BP) was successfully performed for wrinkle elimination in micro cup drawings of AA1235 foils. BP was used to create a specific enlarged gradual punch profile before wrinkles began to occur until the end of the stroke, with fully annealing of AA1235 occurring before accumulative roll bonding (ARB), asymmetric rolling (AR), and stress relieving of a rolled blank, and deep drawing. The research purpose is to create a micro cup without wrinkles. The method was studied via experimentally deep drawing a blank thickness of 300 mm with pairs of dies-BPs supported by a press tool. Blanks were processed under (a) ARB 4 and 6 cycles, (b) combined ARB with AR and (c) post-heat-treatment. The process was selected when a force (F) from the simulation matched with the measured value. The results showed that BP can simultaneously eliminate the occurrence of wrinkles at the cup edge, reduce the earing occurrence, increase cup corner thickness, and decrease the edge thickness. Simulation models were built using the finite element method software LS Dyna, which supports experimental evidence. The findings imply that BP can successfully eliminate wrinkles at the cup edge
Numerical Investigation of Two Double Swirl/Vortex Chamber Configurations for Turbine Blade Leading Edge Cooling
Get PDFThe objective of this work is to numerically assess the cooling performance of two double swirl/vortex chamber configurations (DSC and M-DVC). The predictive capability of five turbulence models is critically evaluated on fine and good-quality mesh for impinging and swirling flows. The averaged second norm is employed to quantitatively measure the simulation error from each turbulence model compared to the experimental data. The RNG turbulence model with enhanced wall treatment is found to be the most accurate and suitable for the simulation of impinging and swirling flows. Various key physical and dimensionless parameters, including thermal performance factor, turbulence kinetic energy and vorticity, are used to comparatively assess the cooling performance of DSC and M-DVC under the laboratory testing condition and the real operating condition at base load. The results reveal that DSC can enhance better heat transfer due to higher turbulence kinetic energy. Also, much more uniform Nusselt number distribution is obtained by DSC owing to more symmetric and uniformly distributed velocity and vorticity. With the real operating condition, DSC even performs much better than M-DVC
Self-healing Behavior of Expansive Mortars with Fly Ash and Bottom Ash
Get PDFIn this paper, the effectiveness of fly ash (FA) and bottom ash (BA) on the self-healing (S-H) behavior of expansive concrete was experimentally investigated by using the crack closing ratio and water flow rate as indicators of the self-healing ability. To heal cracks that may be caused by shrinkage, high CaO-SO3-free lime fly ash (FAB), high CaO fly ash (FAA), and low CaO fly ash (FAR), and one type of expansive additive were used as the partial binder replacement materials. A pre-soaked bottom ash with high water retainability was used as a water-providing agent for the internal curing (IC) technique, to reduce shrinkage and enhance long-term hydration. Pre-cracked mortar samples were prepared in a disc shape with a fixed crack width of 0.1 mm. After crack creation, the crack width ratio and water flow rate were monitored every 7 days for 3 months. It was observed that expansive mortars with 30% fly ash showed significant improvement in the self-healing ability when compared to the non-fly ash mortar. The use of 10% bottom ash showed enhanced self-healing ability in expansive mortar. Moreover, using both fly ash and bottom ash showed significant improvement in the self-healing behavior
GFP Pattern Recognition in Raman Spectra by Modified VGG Networks for Localisation Tracking in Living Cells
Get PDFThe coupling between Raman spectroscopy and green fluorescent protein (GFP) labelling informs chemical compositions at the specific sites. This information leading to study that explain core knowledge of living organism and eventually advance our conventional technique of medical diagnosis. In order to achieve these purposes, the precise interpretation is required. A massive number of Raman/GFP spectra as well as identification of GFP contribution in each spectrum are arroaches to achieve those goals. In the paper, CNN is proposed to classify the spectra with and without GFP signal. The dataset of GFP-positive and GFP-negative spectra were created with various size and background color. The feature extraction and classification are conduced with VGG networks. To increase the performance of VGG network, the modified VGG13 and modified VGG19 were designed. These two models extend fully-connected layer from 3 (the original VGG model) to 5 layer for better classification task. Batch normalization is also added at the end of feature extraction units to reduce unpredicted shifting of parameters. The original VGG16, VGG19, and ResNet50 are used as comparison models. The results show that both of our modified VGG models significantly enhances training accuracy of the network comparing to the original VGG. The accuracy of original VGG can be increased when applied pre-trained weight, but the accuracies are yet slightly lower than modified models. Training on ResNet, deeper network, gave the comparable accuracy with our modified models
A Field Survey of Thermal Comfort in Air-conditioned Space in Songkhla’s Hot Humid Climate
Get PDFThis paper reports the study results from a field comfort survey of people in hot humid climate of Songkhla, a province in southern Thailand (latitude 7.20°N and longitude 100.59°E). Thermal sensation, thermal acceptability, and thermal preference were assessed from the observations of three hundred subjects in air-conditioned spaces in buildings. The analysis showed that the operative temperature for the thermal neutrality (TVS=0) was 26.3°C, and the acceptable temperature range (TVS=±0.5) was 25.6-27.1°C. The air movement played a key role to improve the people thermal sensation and preference, but the relative humidity performed less impact. In our study case, the PMV model could not well applied to Songkhla’s people as it predicted the neutral temperature one and a half degree colder than the actual, and underestimated the hyper-sensitivity of the thermal sensation to the temperature
Mo and Mn Co-doping for Isoproturon Degradation under Visible Light
Get PDFThis research focused on the improvement of the catalytic efficiency of titanium dioxide using transition metals for isoproturon degradation under visible light. Molybdenum and manganese were varied at 0.5% by weight and 1% by weight. Mo/Mn doped TiO2 was synthesized using sol-gel method and compared with the undoped TiO2 to find out the most suitable doping metal and doping amount for the degradation of isoproturon, a pesticide generally used in agricultural sites. The characterization techniques for all doped TiO2 included N2 physical adsorption/desorption (BET), X-Ray diffraction Spectroscopy (XRD), Ultra Violet -Visible Spectroscopy (UV-VIS), Photoluminescence Spectroscopy (PL), and SEM (Scanning Electron Microscope) –EDX (Energy Dispersive X-ray Diffraction). For each TiO2 catalyst, the photocatalytic degradation of 10 ppm isoproturon was carried out under visible light and the catalytic efficiency was determined using UV-VIS to measure the residual concentration of isoproturon. According to the results, doping molybdenum and manganese assists in reducing the band gap energy, increasing the surface area of catalysts, and enhancing the photocatalytic activity. In case of manganese, it also minimizes the recombination of photogenerated electrons and holes, which leads to better photocatalytic performance. The optimum isoproturon degradation is appeared with the co-doped Mo and Mn at 1% by weight
The Impact of Building Façade Reflectivity on Pedestrian Visual Comfort with the Application of Bayesian Structural Equation Modeling
Get PDFThe rapid urban development promotes the need for skyscrapers, which vastly adopt a modern architecture design using reflective materials on the façade of the building, particularly for the aesthetic purpose. Nevertheless, outdoor glare or reflected daylight from a highly reflective building façade may cause visual and thermal discomforts for the residents in the neighborhood buildings and outdoor pedestrians. This might cause uncomfortable glare for individuals outside the building. The amount of glare will be higher as a result of greater solar radiation obtained all year round in tropical countries. Regression and presently structural equation modeling are the best-known statistical modeling in approximating the connection between building facade reflectivity and pedestrian’s visual performance. Nevertheless, those methodologies have their own limitations. The primary aim of this research is to compare the effect of building facade reflectivity on pedestrian visual comfort by using four core statistical approximation approaches which include regression, partial least square, structural equation modeling with maximum likelihood estimator, and structural equation modeling with Bayesian estimator. The present study introduces a novel as well as practical modeling and predicting concepts for investigators and specialists in the building façade reflectivity study field
Confirmatory Factor Analysis of the Life Cycle Costing Sub-Cost Distribution for Industrialised Building System using SEM-PLS
Get PDFIndustrialised Building System (IBS) contributes a great shift in sustainable construction, however previous studies have proven that one of the hindrances in promoting sustainable in IBS, is a high cost for pre-cast material components, thus effected the overall cost. In addition, the introduction of Life Cycle Costing (LCC) leads in providing a better and comprehensive cost estimation; as well as provides a significant advantage in the preparation of cost estimates, hence it provides a better baseline for decision making. The lacking application of LCC in IBS is still in trivial impact, where Malaysia experiences a slower progress of IBS construction, even though robust steps has been taken by the Government to influence construction players to accommodate LCC in projecting a comprehensive cost estimates, especially for IBS projects. This paper highlights an outcome of study that simulate the causal effect relationship between IBS Cost Factors and LCC Cost Distribution. A questionnaire survey was used to associate the IBS cost factors and LCC cost distribution and followed by Structural Equation Modelling (SEM) analysis which validate the relationships between the factors. The result of analysis was developed based on findings from 102 responded questionnaires which were distributed to Quantity Surveyors from various agencies. There were 5 LCC cost distribution factors used in this research and 43 IBS Cost Factors to get associated with. SEM-PLS was used to eliminate the cost association by eliminating factors recorded a loading value less than 0.70. From 43 IBS Cost Factors used earlier, only 15 cost factors were retain for further analysis and the development of a cost estimates using LCC approach. The outcome of this analysis is expected to guide the construction players to achieve more practical cost estimates and feasible alternatives for decision making in IBS construction, by focusing on the critical cost contributed to the overall cost of IBS project in Malaysia
The Downstream of a Density-Stratified Sphere Wake
Get PDFThe objective of the present work is to access moderately-stratified wake statistics into the far downstream. This is accomplished via a continuation of the solution from the stratified-wake, body-inclusive, large-eddy simulation of Chongsiripinyo & Sarkar (TSFP10) by a temporal-model, direct numerical simulation. Simulation of stratified wake at Re = U∞D/ν = 10^4 and Fr = U∞/ND = 3 is performed; U∞, D, and N are sphere velocity, sphere diameter, and buoyancy frequency. Three findings are as follows. 1) In the late-NEQ regime, centerline mean streamwise velocity deficit continues to decay with the power-law exponent U0 ∝ t^{−0.4} and while the progression of horizontal wake span is at LH ∝ t^{1/3}, vertical wake extent remains stagnant (LV ∝ t^0). 2) The beginning of NEQ-Q2D transitioning is found to be where the mean wake is geometrically most anisotropic, that is the ratio LV /LH is at a minimum. The transitioning is a gradual process that lasts 50 ≤ N t ≤ 250. 3) In the Q2D regime, vertical profile of the mean streamwise defect velocity (Ud) exhibits self-similarity. This self-similar state is not of Gaussian-type but better fitted with individual plane-wake self-similarity solution. The centerline defect velocity rapidly decays at a rate U0 ∝ t^{−3/4}. Horizontal extension growth rate is reduced to be LH ∝ t^{1/4} and the exponential growth rate of wake height is found to be LV ∝ t^{1/2}, an indication of the dominating viscous diffusion process