Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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An Experimental Study of Different Signal Processing Methods on Ultrasonic Velocity Profiles in a Single Phase Flow
Get PDFUltrasonic velocity profile (UVP) measurement methods have been continuously developed in the field of engineering. A UVP can visualize a fluid flow along a benchmark line. This provides a significant advantage over other conventional methods such as differential pressure, turbine, and vortex. This paper presents an experimental study of using different signal processing methods including autocorrelation (AC), fast Fourier transform (FFT), maximum likelihood estimation (MLE), multiple signal classification (MUSIC), and Estimation of signal parameter via rotational invariance technique (ESPRIT) under diverse situations as the number of pulse repetitions (Nprf), frequency of repetitions (fprf), velocity profiles, computation – time requirements and flowrates. Experimental results express that there is an optimal number and frequency of pulse repetitions for each signal processing method that depended on fprf, Nprf, and flowrate. Moreover, computation-time and statistical tests were verified from experimental results. From the comparisons, MLE was experimentally the best algorithm even though the trade-off of moderate computation-time requirements was realized. However, considering the optimization of both accuracy and computation-time consumption, MLE was determined as the preferred signal processing method based on UVP for estimating flowrate in existing water reactors.  
A Suitable Constitutive Model for Solid Tire Analysis under Quasi-Static Loads using Finite Element Method
Get PDFThe rubber solid tire was built using three different compound layers. In order to develop solid tire, the finite element method (FEM) was employed to model and analyze its performance. The constitutive model was important to describe the simulated results of FEM; therefore, the hyperelastic material models were implemented for each compound of solid tire layers. The second order Ogden model was the most agreement with the compression test of the rubber compound specimens. The R2 of internal, middle and tread compound layer was 0.990, 0.988 and 0.989, respectively. The solid tire model was developed and test with the compressive loads. Particularly, the compressive loads on the solid tire were performed with the experiment regarding to the simulation. The solid tire model which was complied with the Ogden model had good agreements with the experimental results. It had an average error less than 8.49%. The Ogden model which was implemented with the mechanical property of rubber compound of solid tire was found that it will be advantaged to design and develop the novel solid tire in the future work
Particle Motion over the Surface of a Cylinder, which Performs Translational Oscillations in a Vertical Plane
Get PDFGeneralized differential equations of relative particle motion over the internal surface of an inclined cylinder, which performs an oscillating motion, have been formulated. All the points of a cylinder trace ellipses in vertical planes. Such cases of cylinder oscillation, when either semi-axes or one of them is equal to zero, that is to say, a cylinder performs reciprocating motion, have been considered. The equations have been solved applying numerical methods and trajectories of relative particle motion over the surface of a cylinder have been built. Graphs of other kinematic characteristics as a time-varying function have been presented. Certain cases, when a cylinder axis is located horizontally or at an angle to a horizontal plane, have been considered
Flood Mapping along the Lower Mekong River in Cambodia
Get PDFLocated in Southeast Asia, Cambodia is one of the most disaster prone countries, where flooding rank the top of the natural disaster. Flood affects and threatens not only humans’ and animal’s life, properties, infrastructures, but it is also an obstacle to the current development. Furthermore, without having the efficient modern technology to predict flood situation in Cambodia, the disaster in this country become more serious. The objective of this research study is to simulate flood inundation area by using software HEC-RAS. HEC-RAS is a hydraulic model software capable of calculating any hydraulic river study including flood. In this study, the Lower Mekong River with approximately 50 km length was selected to delineate flood map from 2000 until 2013 and also 10-year return period map. The available data are 11 years of the measured water level at the upstream and downstream stations, 18 surveyed cross-sections and DEM with grid cell size 30 m x 30 m were used to understand the recurrence of the floods in the study area. The output from the model was delineated into map including flood extent and flood depth from 2000 until 2013 (without 2009, 2010 and 2012). The results show that flooding varied from year to year; however, the greatest flood was during 2000 and again in 2011. The simulated flood maps were compared with observed data to figure out that the model was accurate for flood mapping. These results will be useful for river engineers, experts, and decision makers to manage river floods
Barriers of Adoption Building Information Modeling (BIM) in Construction Projects of Iraq
Get PDFBuilding Information Modeling (BIM) is a unified and comprehensive system for all that associated with the construction project, which includes a set of effective policies, procedures, and computer applications that increase the level of performance in construction project during its life cycle. Through this study investigate about the potential barriers which facing the adoption of BIM was performed. The quantitative approach was adopted by conducting a questionnaire directed to professionals in the field of construction projects in the public and private sectors. Three hundred copies of the forms were distributed to the private companies and governmental institutions and departments. The data were subjected to the appropriate statistical analysis and the results showed that the three highest potential barriers of using BIM in Iraq are a weakness of the government's efforts, Poor knowledge about the benefits of BIM, and resistance to change
A Two-Step Adaptive Noise Cancellation System for Dental-Drill Noise Reduction
Get PDFThis paper introduces a two-step dental-drill Noise Reduction (NR) technique based upon the Adaptive Noise Cancellation (ANC) system. The proposed technique is particularly designed for the NR headphone, which the patients should be wearing while having their dental treatment. In the first step, a tone-frequency extraction algorithm is proposed to estimate the main sinusoidal frequency of the dental-drill noise. The estimated sinusoidal signal is therefore removed significantly from the dental-drill noise by the use of the ANC system. Then, by using another ANC system and a high-pass filter in the second step, the residual high-frequency components of the dental-drill noise are eliminated sufficiently. Computer simulations based on recorded dental-drill sounds and real speech signals demonstrate the efficiency of the proposed two-step ANC system for dental-drill noise reduction, both in terms of the noise attenuation performance and the speech quality of the enhanced speech signal, as compared to the conventional two-microphone ANC system under ideal situation. Moreover, results of a subjective listening test with 15 listeners are also given to guarantee satisfied speech quality of the enhanced speech signal employing the proposed two-step dental-drill NR technique
Tire-Suspension-Steering Hardware-in-the-Loop Simulation
Get PDFSafety and performance have always been important factors in automotive testing. These factors are highly dependent on the tires and suspensions, which should be simulated and tested throughout the development process. During development, Hardware-In-the-Loop (HIL) simulations may be used so that testings and tunings can be done earlier in the process. In this paper, designs and configurations of a newly developed tire-suspension-steering HIL are shown. An actual wheel assembly with suspension and steering components can be installed for testing with dynamic models of the rest of the car. The slip angle of the tire can be imposed in the test rig while actual tire forces can be measured and used in the dynamic model. Comparisons of HIL simulations and real experiments using the skidpad test and the step steering test are given using Formula SAE race cars. It was found that the HIL simulation results are more accurate compared to non-HIL simulations
Flex Performances of Epoxy Aluminium Particulate Composites
No full textPolymers are characterised with lightness, ease of formability and resistance to chemical attack but their modulus and strength are low. Epoxy was reinforced with aluminium particles of different sizes. Bond, functional group and chemical formulae of the composite phases were examined using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffractometer. The flexural test was also conducted on the developed composites via three-point method. Analysis of variance (ANOVA) was performed using aluminium percentage by weight (wt%) and sizes (Ps) as the predictor variables. Results indicated different chemical formulae of the composite phases. A maximum of 124.44 % increase in flexural modulus was found at 12 wt% reinforcement addition. Probability value, 0.000 for each of wt% and Ps affirm evenly significant influence of both variables on flexural modulus of the composites. Hence, the model can be used for predicting the flexural modulus of epoxy particulate composites within and outside the scope of experiment.
 
Factors of Operation Affecting Performance of a Short Axial-flow Soybean Threshing Unit
Get PDFThis study aimed at investigating the operational factors that affect the performance of a short axial-flow soybean unit. The result would be applied in developing a soybean combine harvester to be installed with a small tractor. The axial-flow soybean threshing unit is composed of a rotor of 0.48 mm diameter and 0.70 m length, peg tooth clearance (PC) of 41.4 mm, concave clearance (CC) of 20 mm, and guide vane inclination (GI) of 80°. The investigated factors included grain moisture content (MC), rotor speed (RS), and feed rate (FR). The split-plot experiment was planned by setting the main plots of soybean moisture contents at three levels, i.e., 14.94, 23.55 and 36.04%wb and the sub-plot of 3 x 3 factorial RCBD treatment: the rotor speed as the first factor having 3 levels, i.e., 7.54, 10.01 and 12.56 m/s; and the feed rate as the second factor with 3 levels, i.e., 100, 150 and 200 kg/h. The experiment demonstrated that the MC and the RS significantly affected the threshing efficiency, unthreshed loss, separating loss, total loss, and percentage of breakage. The FR was found to significantly affect threshing efficiency and percentage of breakage but not on unthreshed loss, separating loss and total loss. The short axial-flow soybean threshing unit is recommended for soybean moisture content of not over 16%wb and rotor speeds between 10 to 12 m/s, while feed rates should not exceed 150 kg/h
Periodic-Review Policy for a 2-Echelon Inventory Problem with Seasonal Demand
Get PDFThis paper studies a two-level inventory system with one warehouse and n retailers under seasonal demand. All locations apply periodic review base-stock policy with echelon stock concept. The objective is to determine the inventory policy with minimum inventory cost respected to required service level. Three alternatives to determine inventory policies are proposed which are upper, lower and EOQ alternatives. Among these alternatives, it is found that, in case of positive ordering cost, upper-alternative policies give the lowest cost which is around 11% lower than other policies. In case of zero ordering cost, EOQ-alternative policies give the lowest cost which is around 20% lower than other policies. However, lower-alternative policies lead to the lower demand loss, its average loss is 0.07% while other policies’ loss can be as high as 0.22%