Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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An Extreme Vertices Mixture Design Approach to Optimization of Tyrosinase Inhibition Effects
Get PDFThe objective of this study is to optimize the tyrosinase inhibition effects of three mixtures included Emblica extract, L-Ascorbic acid, and Kojic acid. Tyrosinase is a copper-containing oxidase, which has activity for both catechol and cresol. It is responsible for browning reactions. Mushroom tyrosinase was used in this study as the tyrosinase source and L-DOPA was used to activate the browning activity. The seventeen formulations were conducted by extreme vertices mixture design. To specify the lower and upper limit, prior study for each ingredient was experimented. Ten and thirty-three percentage of inhibition were proposed to specify the lower and upper limit of each ingredient. The result of experiment shown the difference tyrosinase inhibition effects of seventeen formulations. The analysis of variance for result was significant for all pairs and all of components with 92.89 percentage of R-square adjusted. To optimize the best combination, used of response optimization by setting up the target to 80, 85, 90, and 95 percentage of tyrosinase inhibition effect. The optimum combination with 90%inhibition target is 3.1541 mg./ml. of Emblica extract, 0.1420 mg./ml. of L-Ascorbic acid, and 0.0297 mg./ml. of Kojic acid, this formula unlike the formula that was experimented on.The objective of this study is to optimize the tyrosinase inhibition effects of three mixtures included Emblica extract, L-Ascorbic acid, and Kojic acid. Tyrosinase is a copper-containing oxidase, which has activity for both catechol and cresol. It is responsible for browning reactions. Mushroom tyrosinase was used in this study as the tyrosinase source and L-DOPA was used to activate the browning activity. The seventeen formulations were conducted by extreme vertices mixture design. To specify the lower and upper limit, prior study for each ingredient was experimented. Ten and thirty-three percentage of inhibition were proposed to specify the lower and upper limit of each ingredient. The result of experiment shown the difference tyrosinase inhibition effects of seventeen formulations. The analysis of variance for result was significant for all pairs and all of components with 92.89 percentage of R-square adjusted. To optimize the best combination, used of response optimization by setting up the target to 80, 85, 90, and 95 percentage of tyrosinase inhibition effect. The optimum combination with 90% inhibition target is 3.1541 mg/ml of Emblica extract, 0.1420 mg/ml of L-Ascorbic acid, and 0.0297 mg/ml of Kojic acid, this formula unlike the formula that was experimented on
Spur and Helical Gear Sliding Loss Model with Load Distribution Pattern on Gear Tooth Surface
Get PDFThe model for estimation of spur and helical gear sliding loss with load distribution pattern on gear tooth surface is presented in this paper. The load distribution for the spur gear is considered to distribute uniformly along the line of contact. During double teeth meshing, load sharing ratio between meshing teeth is considered to be 33:67 percent or 45:55 percent. For the helical gear the load distribution can be calculated by the method proposed by Niemann and Richter. The contour plots of load distribution conform to the tooth contact patterns obtained experimentally. The sliding losses estimated from the presented method are compared with the estimations done by the former model and also the experimental results. It is found that the sliding losses calculated from the presented method are closer to the experimental results than the estimations from the former model. The effects of the helix angle and pressure angle on the sliding loss can also be estimated correctly by the presented method.The model for estimation of spur and helical gear sliding loss with load distribution pattern on gear tooth surface is presented in this paper. The load distribution for the spur gear is considered to distribute uniformly along the line of contact. During double teeth meshing, load sharing ratio between meshing teeth is considered to be 33 : 67 percent or 45 : 55 percent. For the helical gear the load distribution can be calculated by the method proposed by Niemann and Richter. The contour plots of load distribution on gear tooth surface conform to the tooth contact patterns obtained experimentally. The sliding losses estimated from the presented method are compared with the estimations done by the former model and also the experimental results. It is found that the sliding losses calculated from the presented method are closer to the experimental results than the estimations from the former model. The effects of the helix angle and pressure angle on the sliding loss can also be estimated correctly by the presented method
Synthesis of Mesoporous TiO2 with a Template Free One Step Reaction of Acid-Catalyzed TiC
Get PDFMesoporoustitania (TiO2) having high specific surface areas of 163 to 306 m2/g was prepared by a template-free one step reaction between TiC precursor and aqueous nitric acid (HNO3) solution. The effects of reaction parameters including acid concentration, reaction time and temperature were investigated. The properties of the prepared TiO2 induced by those parameters were characterized by various techniques such as thermal gravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD). It was found that the TiC was completely oxidized to TiO2 at reaction time of 8 h, 70°C with 5 M HNO3. At this condition, the obtained TiO2 composed a mixed phase of 45% anatase and 55% rutile and showed the highest pore volume of 0.239 cm3/g with specific surface area of 306 m2/g. Moreover, all the anatase was transformed into the rutile when the reaction time reached 48 h. The rates of the rutile transformation increased with increasing the acid concentrations but decreased with increasing the reaction temperatures. The pore volumes and the specific surface areas were reduced by increasing the acid concentrations or the reaction temperatures. It is possibly because at the conditions of the high acid concentrations or the high temperatures, the mesoporous framework of TiO2 was collapsed. Based on the acid conditions, a peptization process was adopted to describe the effects of all investigated parameters
GTAW of Zinc-Coated Steel and Aluminum Alloy
Get PDFIn this study, effect of zinc-coated layer on steel sheet of dissimilar metals welding between SCGA270C steel and A5052 aluminum alloy by GTAW was investigated. In the experiments, two types of self-brazing welding; 1) welding between non-zinc-coated steel/aluminum alloy, and 2) welding between zinc-coated steel/aluminum alloy, were carried out. The lap joint configuration in which steel was lying on top of aluminum alloy was applied. From the results of zinc-coated steel case, the reaction between the low-melting-point zinc with both molten and solid aluminum alloy provided larger welding width between two metal sheets. Moreover, zinc, which is heavier than aluminum alloy, was fallen down but not well mixed into molten aluminum alloy. Consequently, thick intermetallic compound layer near welding interface between steel/aluminum alloy was formed. Comparison of load resistance between non zinc-coated case and zinc-coated steel case, the wider welding width which consequently improvement the load resistance of the welds was obtained, when using low heat input. However, when applying higher, significant contraction of aluminum welding pool promoted crack along the non-uniform chemical composition zone in case of zinc-coated steel. These cracks were the cause of reduction of load resistance of the welds between zinc-coated steel/aluminum alloy.  
New Approach for Identification of Suitable Vibration Attenuation Relationship for Underground Blasts
Get PDFFor construction and mining activities, excavation in hard or weathered rock or even hard soil, is often performed with the help of blasting. As a safety practice the blasting operation has to be designed such that the existing structures in the vicinity are not adversely affected due to the blasting activity. Blast vibration attenuation relationship for the ground media becomes necessary for the design of blasting. In India, the relevant IS code specifies an attenuation relationship (Power expression) between the peak particle velocity, the charge weight and the distance of the monitoring point from the blast. However, the empirical coefficients are provided in IS code for only two categories - hard rock and weathered rock / soil. Hence they result in uneconomical and sometimes unviable blasting design. The alternate option is to establish site specific attenuation relationship for the location and use the same for design of blasting operation. Industrial practice is to find the empirical constants for the same Power expression (as IS code) from the site trial blast data. For this purpose, the same dataset is used for parameter estimation as well as evaluation of the suitability of the estimated parameters. In this study it is demonstrated that evaluation of performance with a different dataset alters the conclusions. Further, expressions other than the commonly adopted Power expression might be more suitable for the relationship. In this article, two other expressions, namely, Reciprocal expression and Weibull model were identified which could be equally good. Exponents for scaled distance calculation, other than the popularly adopted 0.5, were found to be applicable in the case study. Trail blast data from a site was used to demonstrate the same. It was concluded that while developing site specific attenuation relationship, various expressions with different exponents may be examined for their suitability and this should be done with a fresh dataset. The best expression identified for the site should be finally adopted for further activities
Effect of Process Parameters on Yield of Biofuel Production from Waste Virgin Coconut Oil
Get PDFThis research aimed to determine the influence of process parameters on yields of biofuel production by hydrocracking of waste virgin coconut oil using HZSM-5 zeolite catalyst and to determine statistical relationship of yields of biofuels with the parameters by Pearson’s correlation. The various operating parameters in batch reactor were a reaction temperature (350-400°C), an initial hydrogen pressure (20-40 bar), and a reaction time (1-3 h). The highest yields of gasoline (6.79 wt%) and kerosene (31.38 wt%) were achieved under a temperature at 400°C, initial hydrogen pressure at 40 bar, and a reaction time of 3 h. The highest yield of diesel of 58.62 wt% was achieved at a reaction time of 1 h under temperature 400°C and initial hydrogen pressure 40 bar. The experimental data were analyzed by input-output model with the coefficient of determination (R2) of yield prediction ranging from 0.86 to 0.92. The Pearson’s correlation coefficients show strong dependence of reaction temperature and time on hydrocarbon chains of various length. Yields of shorter hydrocarbon chains such as gasoline and kerosene required higher reaction temperature and longer reaction time and vice versa. Pressure dependence on yields of biofuels was insignificant
Experimental Study of Particles Induced by Screw Tightening Process for Hard Disc Drive Assembly: Effects of ‘Bit’ Speed
Get PDFThe morphology of particles generated during screw tightening process in hard disc drive assembly was studied using a media installing tool kit under a class 100 clean room condition. The screws were made of martensitic 410 stainless steel and the ‘bit’ was made of S2 tool steel. The ‘bit’ speeds used during the screw tightening process can be divided into two steps: the beginning and the final speeds. The effect of both speeds on the morphology of particles generated was investigated. The studied parameters were the aspect ratio and the appearance cross-sectional area of particles. Particles with different sizes were found suggesting that there were different wear mechanisms. Small particles were caused by adhesive wear, while the larger particles were generated by fatigue wear. The appearance cross-sectional area of particles was found to decrease with increase in both speeds within the speed of 250 r/min, after which the appearance crosssectional area appeared to be constant. The effect of cold-weld at asperities was obvious resulting in an increase in aspect ratio at a higher speed. The understanding of the effect of bit speed on the particles morphology during the screw tightening processes could be very useful in the design of the cleaning system in hard disc drive production.The morphology of particles generated during screw tightening process in hard disc drive assembly was studied using a media installing tool kit under a class 100 clean room condition. The screws were made of martensitic 410 stainless steel and the ‘bit’ was made of S2 tool steel. The ‘bit’ speeds used during the screw tightening process can be divided into two steps: the beginning and the final speeds. The effect of both speeds on the morphology of particles generated was investigated. The studied parameters were the aspect ratio and the appearance cross-sectional area of particles. Particles with different sizes were found suggesting that there were different wear mechanisms. Small particles were caused by adhesive wear, while the larger particles were generated by fatigue wear. The appearance cross-sectional area of particles was found to decrease with increase in both speeds within the speed of 250 r/min, after which the appearance crosssectional area appeared to be constant. The effect of cold-weld at asperities was obvious resulting in an increase in aspect ratio at a higher speed. The understanding of the effect of bit speed on the particles morphology during the screw tightening processes could be very useful in the design of the cleaning system in hard disc drive production
Test and Finite Element Analysis of Gravity Load Designed Precast Concrete Wall Under Reversed Cyclic Loads
Get PDFThis research studies the lateral behavior of precast concrete wall panel applicable for a 2-story building. The specimens consist of precast and cast in-situ reinforced concrete bearing wall with 3/4 scaled. The precast wall panel was designed for gravity load only. The specific connection in this study was the welded connection between dowel bar and steel plate embedded in precast wall which was the famous one of the connection for precast bearing wall system in Thailand. The specimens are tested under reversed cyclic loadings through hydraulic actuator in laboratory. The tested results reveal that the precast concrete wall can resist maximum lateral load and show almost the same behavior as cast in-situ RC wall. The cracks of precast wall panel are concentrated around the connection while cast in-situ RC wall are flexural and shear cracks dominant 500 millimeters above the footing of wall. The superimposed technique of the element in FEM analysis is used to model the connection of precast wall. The prediction by FEM analysis for cyclic behavior, hysteretic loop and maximum load are matched with the test results for both specimens
Corrosion Behavior of Ni Steels in Aerated 3.5-wt.% NaCl Solution at 25ºC by Potentiodynamic Method
Get PDFThis work studied the corrosion behaviors of 15Ni, 23Ni, 31Ni and 40Ni steels in aerated 3.5% NaCl solutions at pH 2, 7, 10 and temperature of 25ºC. The observed microstructures of 15 and 23 wt.% Ni steels were partially martensite, but those of 31 and 40 wt.% Ni steels were fully austenite. Polarization curves of the nickel steels were measured by potentiodynamic technique. The corrosion potential (Ecorr), corrosion current density (Icorr), from which the corrosion rate (Rmpy) was calculated, pitting potential (Ep), primary passive potential (Epp) and passive current density (Ip) were evaluated form the polarization curves. The results showed that increasing nickel content increased the corrosion potentials but decreased the corrosion current density or the corrosion rate. Only pH 10, the passive characteristics of the 23Ni, 31Ni and 40Ni steels were observed. The pitting potentials and primary passive potentials of those three steels increased with nickel contents, but the passive current density decreased. Nickel improved general corrosion and pitting corrosion resistances of the tested steels in basic, neutral and acid 3.5% NaCl solutions. The effects of nickel and solution pH on general corrosion resistances of nickel steels were discussed
Influences of Moisture Content on Resilient Modulus of Unbound Crushed Limestone
Get PDFThe design method of pavement structure is evolving to the new Mechanistic-Empirical (M-E) approach. A major benefit of M-E approach is being able to identify the distress patterns and the progress rate of a given pavement structure. This is possible by the knowledge of mechanistic characteristics of pavement materials responding to the repeated loads and environmental changes. Resilient modulus of the unbound granular material is the fundamental parameter needed in the mechanistic analysis of pavement structure. The resilient modulus behavior responding to moisture changes is the key contribution to the structural strength of conventional pavement in Thailand. This study investigated the resilient modulus of the road base materials for the M-E approach. In this research, a set of laboratory tests were conducted on unbound crushed limestone. Two gradations of the limestone were selected to determine the resilient modulus using the repeated-load tri-axial test according to AASHTO T307. Test results revealed that water content played a significant influence to the resilient modulus value. The resilient modulus characteristic of limestone UGM observed from these tests can be employed in Mechanistic-Empirical Pavement Design