Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Conceptual Design and Analysis of Small Power Station for Supporting Unmanned Aerial Vehicle (UAV) Deployment
Get PDF“Flight time” of unmanned aerial vehicle (UAV) or drone flying robot is the key component for supporting industrial activities. In practice, most battery-powered drones can fly 20 - 30 minutes for a single charging cycle. When the battery depleted, the drone is forced to come back to the station to recharge, or swap in a charged battery. However, these tasks are manually done by human multiple times. Aside from the inconvenience, human error and inappropriate force application may damage the socket compartment or loosen the locking system between battery and socket, making higher risk of the battery accidentally fall off from the socket during the flight. This research presents a “Small power station” to automatically load and unload battery from the drone’s mainframe with a constant force. The station has two main functions: drone positioning, and six-slot-battery exchange mechanism. Product design and development (PDD) and Kano analysis method were applied to properly list necessary compartments of the designed station. Finite element analysis (FEA) and kinematic calculation were applied to virtually check whether or not the developed platform was designed in the safety boundary. “DJI Matrice 100” drone was applied as the case study to demonstrate the proposed approach
Pulsed Discharge Plasma in Slug-flow Reactor System for Water Pollutant Removal and Nanoparticle Synthesis
Get PDFThe water pollutants removal and the metal nanoparticles synthesis were demonstrated by the applying high voltage discharge plasma at room temperature. The experiments were performed in continuous system by the flowing liquid and gas phases simultaneously in a glass capillary tube, where various gas types were employed as a gas phase. The optical emission spectroscopy (OES) equipment identified that the reactive oxidation species were obviously observed at each gas type. The generation rate of them can be enhanced significantly by changing the reactor type from straight to helical form. The water pollutants removal rate has order from oxygen > air > nitrogen > argon > helium. Furthermore, the silver or gold nanoparticles can be synthesized by this plasma reactor system. The transmission electron microscopy (TEM) images indicated that the particle products had spherical morphology with a diameter size smaller than 10 nm. It was deduced that the process presented here is an innovative and applicable in practice, and it can lead to advanced organic compounds degradation and nanoparticles synthesis technology
Experiment Investigation and Optimization for Slider Bonding Process to Enhance the Shear Strength of Epoxy Adhesive Joint
Get PDFThe shear strength of adhesive bonding between the slider and suspension greatly affects the quality of the hard disk drive. Therefore, this paper intends to determine the optimal slider bonding parameters which can maximize the shear strength of the adhesive joint. The response surface methodology (RSM) and optimization are employed to investigate the effects of five process parameters to the shear strength of the adhesive joint. Next, the central composite design which is a RSM is conducted. The analysis of variance is used to identify the significant terms of the quadratic regression model. Then, the optimization approach is utilized to determine the optimal process parameters with the mean shear strength of 257.62 gf. The confirmation experiment to validate the quadratic model reveals that the prediction error is only 1.6% which is acceptable. Next, the regression model is also used to define the optimal process conditions under the capacity constraint. In this case, the regression model can provide the accurate prediction of the shear strength with 1.14% error. In conclusion, the RSM and optimization approach can effectively yield the optimal process parameters that can enhance the shear strength of the adhesive joint to achieve the appropriate quality level
An Automated Framework for BPMN Model Verification Achieving Branch Coverage
Get PDFBPMN model is used in software development process that the procedural logics of software are described in term of graphical representation. Formal verification using colored Petri net (CPN) can be used to prove whether a designed BPMN model is frees of undesirable properties such as deadlock and unreachable task, and meets user requirements or not. Although there are many researches providing the transformation rules and frameworks for automating and verifying the CPN model, the CPN markings determination covering all execution paths is quite cumbersome. This paper proposes an automated BPMN verification framework that integrates the BPMN modeling tool and the CPN model checker together. The designed BPMN model is transformed into a CPN model and control flow graph (CFG). The CFG is used to create the execution paths and to find the interleaved activities. The interleaved activities are then considered for creating the CPN port places and markings by an applying of the branch coverage testing technique. Behaviors of the CPN model are analyzed by using a state space analysis based on the CPN model and automated markings. Our framework has been implemented as an Eclipse BPMN modeler plugin, and it is tested with the five case studies. The results show that our framework is practical. It can automate the CPN models from the BPMN model and guide the designers regarding the CPN markings determination to achieve branch coverage criteria
Machine Vision based Grabbing Objects with Manipulator System Design
Get PDFIn recent years, machine vision technology and robot control technology have attracted lots attention of the researchers. They provide people with fast and efficient services in many fields, which have an increasingly important impact on the modern manufacturing industry and the inspection industry. In this paper, a mechanical vision-based grab control system based on machine vision is developed and analyzed accordingly. This design employs industrial cameras with Gigabit Ethernet ports, six-degree-of-freedom servo drive robots. The Host computer control software is designed on the development platform provided by Microsoft and processed in machine vision image processing. The software has implemented an image processing algorithm. It aims to combine machine vision, robot control and other technologies to achieve precise positioning, recognition and capture of targets. In the end, the proposed method is displayed in the upper computer accordingly
Compressive Behaviors of Micropillar Patterns Made of PDMS Material using the Finite Element Method
Get PDFHydrophobic surface is a surface having the ability of water repellent which is frequently coated on medical devices and marine structures. This hydrophobic surface can fabricate from micro-pattern sheets consisting of groups of micropillars arranged into unique micro-patterns which are normally made of low surface energy materials. Thai Microelectronics Center (TMEC) has fabricated micropillar sheets from PDMS for various micropillar array patterns from soft lithography techniques. However, these micropillar sheets were relatively weak under pushing forces. This research aimed to understand compressive behaviors of rectangular prism micropillars having different aspect ratios (ratio of width to length of a rectangular cross-section) and micro-patterns consisting of micropillars having rectangular cross-section and square cross-section by using ANSYS Mechanical APDL program. We found that the aspect ratio of prism micropillars had not influents on both elastic stiffness and compressive strength under compressive loading. The lateral collapse of micropillars were observed on all micro-patterns during compressive loading. Furthermore, the sharklet micro-pattern had the highest compressive strength with maximum compressive pressure of 9.87 kPa. Finally, as loading contact area of micro- patterns increases, the compressive strength increases while the water contact angle decreases
Can Member Check Be Verified in Real Time? Introducing ARC (Asking, Record, Confirm) for Member Checking Validation Strategy in Qualitative Research
Get PDFMember checking involves a process to allow the data to be validated to ensure the credibility of the sources. It is also used to confirm the accuracy of the data and normally returned to the participant after the event or the session. However, it is almost common to find that the data could be lost or misinterpreted after being transcribed and analyzed by the researcher. This paper argues that validation post analysis is time-consuming and involves data lost in the making. Therefore, in this paper, ARC technique (ask, record, confirm) was employed to assist data collection and validation in real-time for qualitative research. Feedback from respondents during the focus group session was reconfirmed on post-it notes and later pasted on A1 sized sheet paper as open coding. This paper presents the steps it took to formulate challenges and opportunities on Building workforce for the future in the Architecture profession to illustrate the nature of the ARC technique. The research demonstrates how the data later transferred to ATLAS.ti 8 for thematic analysis. In the nutshell, the issue on the traditional approach can be addressed through the ARC intervention. Prior work on member checking does not address the issue to be resolved in a real-time. ARC technique will benefit a qualitative researcher to obtain reliable results for their qualitative inquiry
Green Diesel Production from Oleic Acid Deoxygenation Using Subcritical Water under Hydrogen-Free Condition
Get PDFGreen diesel or bio-hydrogenated diesel (BHD) is a second generation renewable liquid fuel that can be produced from several types of renewable sources such as triglyceride in vegetable oils or animal fats, free fatty acid in waste from refining palm oil industry, and their derivatives via a catalytic reaction involving hydrogenation and deoxygenation provided n-alkanes as a main product. In this work, the aim was to investigate the effect of reaction time and catalyst type on green diesel production in a batch mode without H2 feed. The green diesel was produced from oleic acid using activated carbon and commercial catalyst at reaction temperature of 250 °C and total pressure of 40 bars under DI water as a hydrogen source. The results showed that 100% oleic acid conversion was obtained by using both type of catalysts. Pentadecane was the main product with 96% percentage at 3 h reaction time for commercial catalyst and 100% percentage at 5 h reaction time for activated carbon. In addition, the products in gas phase were CO2 and CO for both types of catalyst and CH4 only appeared when commercial catalysts were used. 
Experimental Demonstration of Non-Hermitian Symmetry for DC-SC-FDM in UOWC Systems
Get PDFThis study demonstrates the high spectrum efficiency of DC offset single-carrier frequency division multiplexing (DC-SC-FDM) for underwater optical wireless communications (UOWC). I and Q components were separately transmitted using dual lasers. As a result, the requirement of Hermitian symmetry is alleviated, and the computation time latency is reduced. The Gram–Schmidt orthogonalization procedure was adopted to address the I and Q orthogonality. The system comprises a 1024-point inverse fast Fourier transform (IFFT), a cyclic prefix of 32 samples, and a digital-to-analog converter (DAC) of 400 Msps, and laser diodes possess a wavelength of 553 nm with a power of 150 mW. The study includes real transmissions in a freshwater communication channel and reports experimental results. In addition, the bit error rate has been evaluated. The results show that at the forward error correction (FEC) limit, a communication distance of 10 m can be achieved. A peak-to-average power ratio reduction of 4.96 dB is reached
Laboratory Evaluation of Alkali-Activated Slag Concrete Pavement Containing Silica fume and Carbon Nanotubes
Get PDFEngineers and contractors strive to find the best type of concrete pavement for use in various conditions and applications due to poor performance of asphalt pavements in different climatic conditions, rapid erosion of pavement, poor durability and change in performance characteristics during operation and being non-economic during the period of operation compared to concrete pavements, and not being consistent with the sustainable development principles due to the use of oil-based adhesives. The most common use for portland cement is in the production of concrete that has led to production of greenhouse gases, including carbon dioxide, and global warming has been one of its consequences. More attention has been paid to alkali-activated concrete pavement as a solution because of these effects. The present study has investigated the behavior of alkali-activated slag (AAS) concrete pavement containing silica fume and carbon nanotubes (CNTs). For this purpose, silica fume and CNTs were used as additive for active alkali slag concrete, respectively. The flexural strength, compressive strength, tensile strength, chloride ion charge passed and durability against freeze-thaw cycles was decreased and water penetration was increased by adding silica fume and the use of CNTs in concrete has increased flexural strength, compressive strength, tensile strength, chloride ion charge passed and durability against freeze-thaw cycles and decreased water penetration. The addition of CNTs should have an optimum amount of 5%, so that the mechanical properties and durability of concrete will be decreased by adding more of this additive. The best mix design is for alkali activated slag carbon nanotubes (AASN5) sample, the properties of flexural strength (9%), compressive strength (15%), tensile strength (15%) and chloride ion charge passed (38%) of the AASN5 sample have increased compared to AAS for 28-day curing and penetration (33%) and weight loss decreased after freeze-thaw cycle