Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Effects of Concrete Mix Proportion and Chloride Content on Electrochemical Properties of Reinforcing Steel in Concrete
Get PDFCorrosion of steel in concrete has been considered as a major cause reducing the lifespan of reinforced concrete (RC) structures. Evaluation of corrosion rate is crucial to determine service life and maintenance plaining for RC structures. Electrochemical properties of corrosion of embedded steel in concrete, including the Tafel slope, corrosion potential and corrosion current density, are significant parameters predicting corrosion rate. The objective of this paper was to quantitatively evaluate electrochemical properties of steel in different compositions of concrete. Varied parameters include the water to binder ratio of concrete, type of binder and chloride content. The electrochemical properties were evaluated at three periods of exposure. Experimental results reveal that the electrochemical properties of reinforcing steel depend on water to binder ratio, type of binder and chloride content. An increase in chloride content significantly decreases the corrosion potential and increases the corrosion rate of steel. The anodic equilibrium potential is lower with an increase in chloride content. The varied concrete mix proportion significantly influence the cathodic polarization. This is due to the effects of concrete porosity on oxygen concentration, which is influenced by the concrete mix proportions. The results can be used to predict corrosion rate of steel in various concrete mix proportion for determining service life and repairing of RC structures
Trajectory Tracking Control Design for Dual-Arm Robots Using Dynamic Surface Controller
Get PDFThis paper presents a dynamic surface controller (DSC) for dual-arm robots (DAR) tracking desired trajectories. The DSC algorithm is based on backstepping technique and multiple sliding surface control principle, but with an important addition. In the design of DSC, low-pass filters are included which prevent the complexity in computing due to the “explosion of terms”, i.e. the number of terms in the control law rapidly gets out of hand. Therefore, a controller constructed from this algorithm is simulated on a four degrees of freedom (DOF) dual-arm robot with a complex kinetic dynamic model. Moreover, the stability of the control system is proved by using Lyapunov theory. The simulation results show the effectiveness of the controller which provide precise tracking performance of the manipulator
Modelling and Simulation of Acid Extraction of Lanthanum from Indonesian Low Grade Bauxite using Fixed-Bed Extractor
Get PDFDemand on lanthanides is growing rapidly due to significant growth of the utilization of advanced materials for industries. Efficient and large scale extraction process of lanthanide from their sources is studied. In this sense, extraction of lanthanum from Indonesian low grade bauxite using a fixed-bed cylindrical extractor with dimension of 30 × 3 cm was modelled and simulated. This simulation model would provide the optimum conditions, extraction time, and cost of extraction, useful for industrial application. A mathematical modelling and simulation was also used to investigate the effects of several parameters, such as particle size, fluid velocity, and acid concentration, on extraction yield of lanthanum. The simulation suggested that the maximum amount of lanthanum sulfate extracted from the low grade bauxite was as high as 6.6 mg after an extraction time of 300 min. The extraction yield can be increased when particle size was decreased, sulfuric acid flow rate was decreased, and concentration of sulfuric acid was increased
Design of an Acoustic-Based Nondestructive Test (NDT) Instrument to Predict the Modulus of Elasticity of Wood
Get PDFModulus of elasticity (E) can predict the mechanical characteristics, as well as grade the quality of wood. The Destructive Test (DT) method is the more commonly used, where the wood sample is split up when being tested. This research used the NDT method based on the longitudinal stress wave method (LSWM) whilst utilizing handheld instruments. The calculated E-dynamic (Ed) from the NDT method was compared with the E-static (Es) from the DT method to validate the technique. Six different wood types were tested with ten samples of each kind. An average R-value of 0.898 was obtained, indicating a high correlation between the Ed values and Es values. The LSWM method requires reliable hardware and software to record the impulse response. It starts by hitting the wood with a hammer to create an impulse, finding the resonance frequency (f0), and later calculating the Ed. A more practical and easy-to-use handheld mobile instrument was developed using a Raspberry Pi-2 microcomputer as the signal processor, an LCD touchscreen, a USB soundcard, and a dynamic microphone that covers 0.1-5kHz and -64 ± 3dB. An internal telecommunication system is provided to support measurements conducted at lumber mills. The software includes band-pass filtering of the recorded spectrum where the f0 is depicted. A time-domain envelope fitting is then applied to the filtered spectrum to obtain the R2envelope. A low R2envelope value indicates an inadequate impulse response, and therefore, the test should be redon
The Design of Experimental Production of Briquette Solid Fuel from Oil Palm Fiber and Kernel Meal Residual
Get PDFThe objective of this research was to study the experimental design for the production of briquette solid fuel from oil palm fiber and kernel meal residue by Factorial Design. Independent variables consisted of mixture ratio of oil palm fiber to oil palm kernel meal residue, percent of coordinate volume and the briquette forming pressure whereas the dependent variables were composed of compression resistance value, impact resistance value and combustion rate. The results of the experimental design showed that at 20 tons of forming pressure, the mixture ratio of kernel meal residue to oil palm fiber 80:20 and 20 percent of coordinate volume provided the best compression resistance value of 2,636 Newton with 85.75% impact resistance value, combustion rate of 1.71 Grams/Minute, heating value of 4386.3 Calories/Gram and the density of 700 Kilograms/Cubic Meter
Improvement in Photocatalytic Effects of Dye Sensitized Titanium Dioxide by Hydroxyapatite Coating
Get PDFApplying photocatalytic n-semiconductor effect of titanium dioxide, performance of TiO2 anode with copper oxides cathode as a wet solar cell in seawater is being studied. This research aimed to study photocatalytic effects of dye sensitized TiO2 electrode coated by hydroxyapatite (HAp). TiO2 electrode was manufactured double layered by screen printing method and copper oxides electrode by vacuum deposition on Type 329J4L stainless steel base substrate. N719 Ruthenizer dye was used for sensitizing on TiO2 electrode and HAp was coated on the electrode surface by squeegee printing method. Four types of TiO2 electrodes were studied; TiO2 electrode, dye-sensitized TiO2, HAp coated TiO2, and dye-sensitized TiO2 with HAp coating. Cell voltage and current density was measured under irradiated and dark conditions. The power densities of electrode with HAp coating was found higher than other electrodes without HAp. The current flow was enhanced by introducing HAp coating while dye sensitizing reduced current flow. Cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) analysis were performed. EIS analysis showed HAp coating increased capacitance values of each electrodes. The surface of electrodes analysed by Scanning Electron Microscope (SEM) and Electron Dispersion X-ray Spectroscopy (EDS) indicated that HAp was dispersed on TiO2 surface but was not formed as a layer
Iris-based Image Processing for Cholesterol Level Detection using Gray Level Co-Occurrence Matrix and Support Vector Machine
Get PDFSerious illnesses such as strokes and heart attacks can be triggered by high levels of cholesterol in human blood that exceeds ideal conditions, where the ideal cholesterol level is below 200 mg/dL. To find out cholesterol levels need a long process because the patient must go through a blood sugar test that requires the patient to undergo fasting for 10–12 hours first before the test. Iridology is a branch of science that studies human iris and its relation to the wellness of human internal organs. The method can be used as an alternative for medical analysis. Iridology thus can be used to assess the conditions of organs, body construction, and other psychological conditions. This paper proposes a cholesterol detection system based on the iris image processing using Gray Level Co-Occurrence Matrix (GLCM) and Support Vector Machine (SVM). GLCM is used as the feature extraction method of the image, while SVM acts as the classifier of the features. In addition to GLCM and SVM, this paper also construct a preprocessing method which consist of image resizing, segmentation, and color image to gray level conversion of the iris image. These steps are necessary before the GLCM feature extraction step can be applied. In principle, the GLCM method is a construction of a matrix containing the information about the proximity position of gray level images pixels. The output of GLCM is fed to the SVM that relies on the best hyperplane. Thus, SVM performs as a separator of two data classes of the input space. From the simulation results, the system built was able to detect excess cholesterol levels through iris image and classify into three classes, namely: non–cholesterol (< 200 ), risk of cholesterol (200–239 ) and high cholesterol (> 240 ). The accuracy rate obtained was 94.67% with an average computation time of 0.0696 . It was using each of the 75 training and test data, with the second-order parameters used are contrast–correlation–energy–homogeneity, pixel distance = 1, quantization level = 8, Polynomial kernel types and One Against One Multiclass.
Iris has specific advantages which can record all organ conditions, body construction and psychological conditions. Therefore, Iridology as a science based on the arrangement of iris fibers can be an alternative for medical analysis. In this paper proposes a cholesterol detection system through the iris using Gray Level Co-occurence Matrix and Support Vector Machine. Input system is an iris image that will be processed by pre-processing and then extracted features with the Gray Level Co-Occurrence Matrix method which is a matrix containing information about position the proximity of pixels that have a certain gray level. And then classified with the Support Vector Machine method that relies on the best hyper lane which functions as a separator of two data classes in the input space.
From the simulation results, the system built was able to detect excess cholesterol levels through iris image and classify into three classes are: risk of cholesterol, high cholesterol and non–cholesterol with an accuracy rate of 96.47% and average computation time was 0.0696 using each of the 75 training and test data, with the second-order parameters used are contrast–correlation–energy–homogeneity, pixel distance = 1, quantization level = 8, Polynomial kernel types and One Against One Multiclas
Flexural Response of CFRP-Strengthened Steel Beams with Initial Bond Defects
Get PDFThis paper presents the flexural behavior of steel beams strengthened with partial-length adhesive-bonded carbon fiber-reinforced polymer (CFRP) plates under static four-point bending. An initial bond defect was intentionally introduced in the constant moment region of the CFRP-strengthened steel beams. In the experimental program, the test variables included the size of the initial bond defect, FRP modulus, FRP plate length, and condition of the steel beam before installation of the FRP plate (undamaged and pre-yielded conditions). Based on the test results, the presence of the initial bond defect changed the failure mode of FRP-strengthened steel beam from the fiber rupture to intermediate plate debonding. With the initial bond defect, the effectiveness of the FRP strengthening scheme decreased as FRP modulus increased. The stiffness, strength, and ductility index of the CFRP-strengthened beam with the initial bond defect decreased as the defect size increased. However, the initial bond defect had no detrimental effect on the maximum load capacity and ductility index of the strengthened beams. The strengthening effectiveness in terms of stiffness, strength, and ductility enhancement was more pronounced in the case of the pre-damaged steel beam, of which the bottom flange had already yielded before installation of the CFRP plate, than the undamaged steel beam
The Action of Vibrating Foundation on Adjacent Static – Load Foundation Having Rectangular Shape: Action of Vibrating Foundation on Adjacent Static – Load Foundation Having Rectangular Shape
No full textThis paper presents an experimental study on the dynamic response of the rectangular foundation, under effect of dynamic load which results from an adjacent footing called (the source of vibration), having square shape and excited by a well-known source of vibration put on the top it. The purpose being to study the effect of dynamic motion on a nearby foundation called a second foundation. Both foundations are founded on collapsible soil (gypseouse soil) with a content of gypsum 60%. The research is conducted in dry and soaked conditions with a large experimental program. The first basis (source vibration) and the second base are made out of steel, respectively in the sizes (80x80x40), (160x40x40) mm (L/ B= 4). After that the soil had been prepared in layers in steel containers with (1000x 500x500) mm, then the two foundations positioned centrally over the ground. The first footing excited by the rotating mass type mechanical oscillator to generate vertical harmonic loading, produces a comparable impact of dynamic loads and the second base is loaded with only static weight under dynamic excitement. The tests are conducted under dynamic response for three frequencies (10, 20, 30) Hz, Displacement amplitude and acceleration of the second foundation are examined, at a different distance between the foundation (1B, 2B, 3B). The results have shown that, when the distance between the foundation increases, the amplitude and the acceleration for the second foundation decreases. Furthermore, the value of these parameters at dry state is higher than their value at soaked state
Laboratory Investigation on Durability of Nano Clay Modified Concrete Pavement
Get PDFToday, one can take a strategy to improve durability in concrete coatings by using modern materials, especially nano-materials. Nano clay is one of the nanoparticles that increases mechanical properties and strength in concrete. With respect to very rich deposits for clay sources in properties of concrete it seems necessary to conduct studies in this regard. Nano clay was utilized with percentages of 1wt%, 2wt% and 3wt% in this study. The effects of both types of water curing and plastic cover curing were examined. The results indicate that using nano clay may increase compressive strength, flexural strength and tensile strength and reduce water penetration and absorption percentage. The best mix design belongs to replacement of 1wt% nano clay. Under water curing conditions in this mix design, rates of compressive strength (35%), flexural strength (31%) and tensile strength (34%) versus control specimen increased, while penetration (35%) and absorption percent (54%) were reduced. The mechanism, nano clay, therefore increases strength and durability in concrete in such a way that the existing Al2SiO5 in nano clay may involve in hydration process and reduce large crystals Ca(OH)2 and accelerate C–S–H gel formation. As a result, dense C–S–H gel is produced and cement mortar and paste will have a more compressed structure. Following the increase in quantity of nano clay up to 2wt% and 3wt%, it is added to the rates of compressive and flexural strengths versus control sample, but in nano clay specimen (1wt%), compressive and flexural and tensile strengths are reduced while water penetration and absorption percentage are increased. It was characterized by analysis on curing methods that showed water curing method was followed by higher strength and durability than in plastic cover curing technique