Search

The micro-bond test quantifies the interfacial shear strength (IFSS) providing essential information to estimate the failure conditions of fiber-reinforced plastics. The work focuses on achieving a micromechanical understanding of the microbond test, which involves pulling a fiber out of a bead of matrix (i.e. droplet) through a knife-edge, in order to quantify the interfacial fracture properties of fiber-reinforced composites. The micro drop pull-out test is simulated using fracture mechanics concepts under the framework of the finite element (FE) analysis. The FE model takes into account the real elliptical geometry of the droplet as well, as the frictional contact during the detaching due to fracture of fibre/matrix interface. The finite element simulation is carried out using ABAQUS software, the predicted force-displacement curves and IFSS are consistent with those measured by the micro-bond test.The micro-bond test quantifies the interfacial shear strength (IFSS) providing essential information to estimate the failure conditions of fiber-reinforced plastics. The work focuses on achieving a micromechanical understanding of the microbond test, which involves pulling a fiber out of a bead of matrix (i.e. droplet) through a knife-edge, in order to quantify the interfacial fracture properties of fiber-reinforced composites. The micro drop pull-out test is simulated using fracture mechanics concepts under the framework of the finite element (FE) analysis. The FE model takes into account the real elliptical geometry of the droplet as well, as the frictional contact during the detaching due to fracture of fibre/matrix interface. The finite element simulation is carried out using ABAQUS software, the predicted force-displacement curves and IFSS are consistent with those measured by the micro-bond test.

Water is essential to the ecosystem for the energy required to stay alive. Nowadays, rapid development in technology can cause pollution to the environment such as water quality pollution and then faced by society. A dangerous source in wastewater such as dyes poses a severe problem due to its toxicity and it was hard to treat. Based on the adsorption ability, activated carbon from corn cob was made for the removal of dyes in wastewater treatment. Activated carbon from corn cob was developed by using alkaline solution treatment of potassium hydroxide (KOH) with different mass ratios, and then was characterized by FTIR, XRD, and SEM. The synthesized activated carbon was also used for removal of methyl orange from aqueous solution. In this research, the obtained char yield after pre-carbonization at 500 °C was 74.20%, while activated carbon yields were 53.60% to 78.80%, based on its difference mass ratios of KOH. The activated carbon without an activation agent gave adsorption capacities of 14.63%. However, when the char was introduced to KOH, the adsorption was increased from 41.09% to 80.36%. The percentage of dye removal increased when the mass ratios of KOH increased. The produce activated carbon from corn cob by using KOH can be effectively used for wastewater treatment.

LNC-infiltrated La0.8Sr0.2MnO3 (LSM) is studied as oxygen electrode in solid oxide cells (SOCs). Incorporation of small amounts of LNC nanoparticles was found to cause significant increase in the electro-catalytic activity and stability of the LSM oxygen electrodes. In this study, the electrochemical impedance responses of an LSM and LNC-infiltrated LSM electrode were measured at 800 °C in air. Also, activation energy for both LSM and LNC-infiltrated LSM electrodes was measured to be 1.36 eV. Results indicate that polarization resistance (Rp) decreases by increasing temperature and operating in reversible condition. Moreover, infiltrating of LNC nanoparticles decreases the polarization resistance of the LSM oxygen electrode, thus promoting diffusion phenomena.

Composite aluminum alloy (5000 series) and multi-walled carbon nanotubes (MWCNTs) were made using mechanical alloying, cold press and sintering. The quality of interactions between Al powders and CNTs in the metal matrix composite has a significant effect on mechanical properties. Motivated from the properties of functionalized CNTs, the current study use this material rather than the raw type, because of its reactivity. Besides, a poly-vinyl-alcohol pre-mixing is done, the aim of which is to enhance mixing process. The functionalized carbon nanotubes ware made by chemically method through refluxing with nitric acid. By this method functional groups have been created on CNTs surfaces. 1% and 3% functionalized carbon nanotubes were manufactured using the aforementioned method. To provide unbiased comparisons, 1% and 3% with raw CNTs and pure aluminum is produced with same manner. The numerical experiments affirm the superiority of the functionalized carbon nano-tubes in terms of the relative density and hardness of nanocomposites. As a final activity, the Fourier transformation infrared spectroscopy and field emission scanning electron microscopy techniques were used to characterize the carbon nanotubes and the powders.

Rainfall prediction is a challenging problem in the meteorological department around the world due to the accurateness of prediction. This paper studies on data mining techniques to predict rainfall using meteorological data of Subang Weather Station collected from January 2009 to December 2016. The data preparation process involves five weather factors which are maximum temperature, minimum temperature, evaporation, wind speed and cloud with 2922 observations. Predictive Decision Tree model, Artificial Neural Network model and Naive Bayes model are developed for rainfall prediction and comparison. Surprisingly, results show that the performance of Decision Tree model is better as compared to the other predictive models with the misclassification rate of 0.15 and RMSE=0.35. Given enough set of data, rainfall can be predict using the data mining techniques.

Nanostructured plate-like manganese cobalt oxide (MCO) was synthesized as the anode material for lithium-ion batteries. Under basic conditions and using a molar ratio of OH− /NO3−= 1.5, crystallite size of 14 nm was found for samples calcined at 350°C. The electrodes were fabricated by mixing MCO as the active material, Super P carbon as the conducting material and polyvinylidene fluoride (PVDF) as the binder in N-methyl-2-pyrrolidone (NMP) solvent. The slurry was coated onto a copper foil substrate. The aim of this investigation is the assessment of deposition parameters on different plausible defects (such as agglomeration/blisters, pinholes/divots, cracks and non-uniform coating) and also electrical behavior of the deposited layer. Because of high degree of agglomeration, mortar method was found to be ineffective while mixing using magnetic stirrer was proved to be more appropriate in terms of final rheology. The optimum value for the binder was found to be 2.73 wt% of the NMP solvent. Effective drying...

This study investigates and analyzes the long run and short run relationships between Bursa Malaysia Composite index (KLCI) and nine macroeconomic variables in a VAR/VECM framework. After regression analysis seven out the nine macroeconomic variables are chosen for further analysis. The use of Johansen–Juselius Cointegration and Vector Error Correction Model (VECM) technique indicate that there are long run relationships between the seven macroeconomic variables and KLCI. Meanwhile, Granger causality test shows that bidirectional relationship between KLCI and oil price. Furthermore, after 12 months the shock on KLCI are explained by innovations of the seven macroeconomic variables. This indicate the close relationship between macroeconomic variables and KLCI.

This study relates the Poisson, mixed Poisson (MP), generalized Poisson (GP) and finite Poisson mixture (FPM) regression models through mean-variance relationship, and suggests the application of these models for overdispersed count data. As an illustration, the regression models are fitted to the US skin care count data. The results indicate that FPM regression model is the best model since it provides the largest log likelihood and the smallest AIC, followed by Poisson-Inverse Gaussion (PIG), GP and negative binomial (NB) regression models. The results also show that NB, PIG and GP regression models provide similar results.

This paper introduces a new two-parameter mixed Poisson distribution, namely the Poisson-weighted Lindley (P-WL), which is obtained by mixing the Poisson with a new class of weighted Lindley distributions. The closed form, the moment generating function and the probability generating function are derived. The parameter estimations methods of moments and the maximum likelihood procedure are provided. Some simulation studies are conducted to investigate the performance of P-WL distribution. In addition, the compound P-WL distribution is derived and some applications to insurance area based on observations of the number of claims and on observations of the total amount of claims incurred will be illustrated.

In this work, a switched and impulsive controller is designed to control the Endocrine Disruptor Diethylstilbestrol mechanism which is usually modeled as a singular system. Then the exponential stabilization property of the proposed switched and impulsive singular model is discussed under matrix inequalities. A design algorithm is given and applied for the physiological process of endocrine disruptor diethylstilbestrol model to illustrate the effectiveness of the results.

In this paper, we propose a fiber Bragg grating (FBG) interrogation system for high resolution sensor application based on radio frequency (RF) generation technique by beating a single longitudinal mode (SLM) fiber ring laser with an external tunable laser source (TLS). The external TLS provides a constant wavelength (CW), functioning as the reference signal for the frequency beating technique. The TLS used has a constant output power and wavelength over time. The sensor signal is provided by the reflected wavelength of a typical fiber Bragg grating (FBG) in the SLM fiber ring laser, which consists of a 1 m long highly doped Erbium doped fiber as the gain medium. The key to ensure the SLM laser oscillation is the role of graphene as saturable absorber which is opposed to the commonly used unpumped erbiumdoped fiber and this consequently contributes to the simple and short cavity design of our proposed system. The signal from the SLM fiber ring laser, which is generated by the FBG in response to external changes, such as temperature, strain, air humidity and air movement, is heterodyned with the CW signal from the TLS at a 6 GHz photodetector using a 3-dB fused coupler to generate the frequency beating. This proposed system is experimentally demonstrated as a temperature sensor and the results shows that the frequency response of the system towards the changes in temperature is about 1.3 GHz/°C, taking into account the resolution bandwidth of 3 MHz of the radio frequency spectrum analyzer (RFSA).

Poisson regression model has been considered as a standard method for modeling count data. However, count data often display overdispersion, and thus, negative binomial (NB) regression model has been suggested for handling overdispersed count data. In addition, generalized Poisson (GP) regression model has been proposed for handling both over- and underdispersed count data. This study proposes the score test for testing Poisson regression against GP alternatives and proves that it is equal to the score test for testing Poisson regression against NB alternatives. The advantage of score test over other alternative tests such as likelihood ratio and Wald is that the score test can be used to determine whether a more complex model is appropriate without fitting the more complex model. Application of the proposed score test on the Malaysian private car claim count data is illustrated.

Fully developed turbulent flow analysis in cylindrical pipe needs highly accurate turbulence model in the smallest scale. This kind of model will enable us to explore the behaviour of wall pressure fluctuation. This study aims to investigate the pressure fluctuation on a pipe wall using Large Eddy Simulation (LES) model in the fully developed flow region. Case studies with several flow rates and pipe diameters were modelled to determine the relationship under unsteady flow conditions. All flows were assumed to be incompressible in rigid pipe wall. Periodic boundary conditions were imposed for the outlet. All models were solved using FLUENT software. The results clearly show non-uniform pressure distribution on the pipe wall for all cases studied. The results also show nonlinear correlation between flow rates and pressure fluctuations along and around the pipe wall. Overall, the results indicate that smaller pipe diameter can only accommodate small range of flow rates before it reached relatively high maximum pressure.

Integrated Computational Fluid Dynamic as a simulation tool for optimization of ship and offshore designs have been developed with higher reliability and accuracy by many institutions. The Department of Marine Technology at the Faculty of Mechanical Engineering, University Teknologi Malaysia has recently developed an integrated CFD simulation tool using potential theory, which intends to upgrade student's level understanding the application of fluid dynamic to ship and offshore structure designs. This paper discusses the application of integrated Naval Architecture and Offshore (NAO) CFD simulation tool for hull performance analysis in term of wave resistance. Detailed discussion on pressure distribution around the hull and generated wave profile by the hull are also presented. As a case study, hull performance of VLCC tanker is simulated using the tool.

Many factors such as: stern hull shape, length, draught, trim, propulsion system and external forces affecting the drift angle influence rate of turn and size of turning circle of ships. This paper discusses turning circle characteristics of U and V stern hull shape of Very Large Crude Oil Carrier (VLCC) ships. The ships have same principal dimension such as length, beam, and draught. The turning circle characteristics of the VLCC ships are simulated at 35 degree of rudder angle. In the analysis, firstly, turning circle performance of U-type VLCC ship is simulated. In the simulation, initial ship speed is determined using given power and rpm. Hydrodynamic derivatives coefficients are determined by including effect of fullness of aft run. Using the obtained, speed and hydrodynamic coefficients, force and moment acting on hull, force and moment induced by propeller, force and moment induced by rudder are determined. Finally, ship trajectory, ratio of speed, yaw angle and drift angle are determined. Results of simulation results of the VLCC ship are compared with the experimental one as validation. Using the same method, V-type VLCC is simulated and the simulation results are compared with U-type VLCC ship. Results shows the turning circle of U-type is larger than V-type due to effect stern hul results of simulation are.

Radiocephalic arteriovenous fistula (RCAVF) at wrist is the chosen access for hemodialysis. Most studies describe access complications without considering the effect of the anastomosis angle. In the present investigation, eighteen three-dimensional, simplified models of RCAVF were used to analyze the hemodynamic effect of anastomosis angle under fixed flow rate of 900 ml/min, corresponding to Reynolds number 950. EFD. Lab software was used in the flow simulation with steady flow conditions. The results show that high pressure drop was observed for RCAVF with smaller anastomosis angle. However, for cases with anastomosis angle larger than 45°, pressure drop became relatively constant. The results also show that large vortices appeared in cases with angle smaller than 30°. For cases with angle larger than 60°, low flow zone appeared at the inner wall that may lead to promotion of intimal thickening and formation of stenosis. Overall, for average flowrate, it is recommended that anastomosis angle should be maintained between 45° and 60° to minimize adverse effects.

Tracheal stenosis is known to disturb the flow dynamics in human airway which may lead to breathing difficulties. In order to understand the tracheal stenosis effects to the flow behavior, this work investigates the presence of stenosis at different locations along the trachea wall and explores on how significant the flow could possibly be altered. The stenosis was patched to the healthy trachea models at five regular locations proposed by medical practitioners. All of the models were then subjected to moderate breathing conditions with inhalation flow rate of 45 l/min (Reynolds number 3012). The changes in the flow behavior due to the different locations of the stenosis were then examined to determine the pattern of breathing difficulties. K-epsilon model was used to model the turbulent flow conditions. The results show that the presence of stenoses was proven to produce moderate to severe pressure drop as the locations of the stenoses moved closer to the bifurcation region. For all cases studied, significant change in the velocity pattern was observed which suggests distorted flow rates into the bifurcations. The overall conclusion confirms that the presence of stenosis closer to the bifurcation area will have greater effect to the flow dynamics.

In the deep drawing of cups, the earing defects are caused by planar anisotropy in the sheet. Several methods have been developed to predicting the optimal blank to avoid the formation of ears. In the deep drawing processes, the use of an optimal blank shape not only saves the material but also it may reduce the occurrence of defects e.g. wrinkling and tearing. In addition, finding the desirable flange contour, eliminate the trimming step in the deep drawing of parts with flange. In this study, a systematic method based on sensitivity analysis has been used to find the optimal blank to obtain a desirable flange contour for a cylindrical cup by hydromechanical deep drawing process. With the aid of a well‐known dynamic explicit analysis code ABAQUS; optimum initial blank shape has been obtained. With the predicted optimal blank, both computer simulation and experiment are performed and the effect of blank shape on the some parameters such as thickness distribution and blank holder force during the forming process were investigated. It is shown that formed cup with an optimum blank shape has a better thickness distribution in the both rolled and perpendicular of rolled direction. And it was shown that the blank holder force of modified blank is higher than circular blank.

In our previous works [1–7] we used both symmetrical (no diquark) core quark distribution and asymmetrical (diquark‐quark) core quark distribution along with pseudoscalar mesons and vector mesons to calculate polarized [1,5,6] and unpolarized [2–4,7] nucleon structure functions. For the asymmetrical distribution we considered the superposition of spin‐0, isospin‐0 and spin‐0, isospin‐1 along with spin‐0, isospin‐0 and spin‐1 isospin‐1 states. It turned out that for unpolarized structure functions only the quark‐diquark model was able to reproduce experimental results reasonably well [2–4,7]. Also, one needs the contribution of vector mesons to reproduce the observed Gottfried sum‐rule violation [13]. However, for the polarized case the results were rather mixed. For some case the symmetrical model was more agreeable with observation [1,5,6]. Our objective here is to have a core quark distribution that can reproduce observation equally well, whether it is for the polarized structure function or the unpolarized structure function. To achieve this goal we have added the other two possible states to the diquark state. Namely, spin‐1, isospin‐0 and spin‐1, isospin‐1 and the contribution of both pseudoscalar mesons and vector mesons. The calculation is performed in the light‐cone frame. The dressed nucleon is assumed to be a superposition of the bare nucleon plus virtual light‐cone Fock states of baryon‐meson pairs. For bare nucleon we consider both the case of diquark‐quark model which is now the superposition of all four diquark states and the case which there is no quark clustering inside the nucleon. The initial distributions are evolved using DGLAP equations. The final results are compared with experimental results and other theoretical predictions.