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- ItemA risk analysis of autonomous vessels in complex urban waterways(Mahidol University, 2020) Valdez Banda, O.A.; Kujala, P.; Sapsathiarn, Y.; Mokkhavas, O.; Punurai, W.; Suvanjumrat, C.; Priyadumkol, J.Autonomous vessels have become one potential alternative for the concept of urban mobility. In complex urban waterways, autonomous vessels could assist in the transporting of goods and people. The recent development of technologies enabling autonomous systems has supported the initial design of new autonomous vessels concepts. However, before these concepts are further designed and operated, it is necessary to analyze their risks to develop strategies for ensuring the safety of people and the protection of the natural environment. In this study, an initial analysis is elaborated to assess the application of autonomous vessels in Chao Phraya River in Bangkok and Larn island in eastern Thailand. The aim is to provide an initial analysis of the risks of autonomous vessels by developing an initial overview of the application of the autonomous vessels in the mentioned operational context. The capabilities of the proposed process to analyze these risks are also evaluated.
- ItemBuckling of rectangular nanoplates - Advances in Engineering Materials, Structures and Systems: Innovations, Mechanics and Applications(2019) Y.Sapsathiarn; R.K.N.D. RajapakseSize-dependent behaviour is a key characteristic of nanostructures such as nanotubes, nanoplates and nanobeams. The primary reason for size-dependent behavior is the high surface energy of nanomaterials and nanostructures. Atoms near the surfaces of a nanomaterial/nanostructure have different energy compared to atoms in the bulk. Nanoscale plates are used in various nanotechnology devices, such as nano-electromechanical systems (NEMS), resonators, sensors, etc. Mechanical stability of nanostructures is an important issue in both design and fabrication. In this study, buckling response of rectangular nanoplates under compressive in-plane loading is considered by using a modified continuum theory. In classical continuum mechanics, strain energy is stored in the bulk and surface energy is neglected. Size-dependency can be incorporated into modelling by using a modified continuum theory that accounts for surface energy. The governing equations for bucking of rectangular nanoplate are developed by employing the Gurtin-Murdoch continuum model that accounts for surface energy. Analytical techniques are used in the analysis and closed-form solutions are presented for simply-supported rectangular nanoplates under uniaxial and biaxial compression. Selected numerical results are presented for critical loads and buckled shapes, and the influence of surface residual stress and surface elastic properties are investigated.
- Itemการประเมินผลการริเริ่มใช้ระบบจองห้องประชุมออนไลน์ ณ คณะวิศวกรรมศาสตร์ มหาวิทยาลัยมหิดล(2561) มะลิวรรณ พฤฒารา; สมชาย ปฐมศิริ; Maliwan Phuttara; Somchai Pathomsiri; มหาวิทยาลัยมหิดล. คณะวิศวกรรมศาสตร์สถาบันการศึกษาระดับมหาวิทยาลัย มีห้องจำนวนมากสำหรับการประชุม การเรียนการสอน การนำระบบเข้ามาใช้งานสามารถช่วยบริหารจัดการสินทรัพย์ให้มีประสิทธิภาพกองเทคโนโลยีสารสนเทศ มหาวิทยาลัยมหิดล พัฒนาระบบการจองห้องประชุมและใช้งานทดแทนการจองห้องด้วยกระดาษ คณะวิศวกรรมศาสตร์เห็นว่าเป็นแนวความคิดที่ดี และนำมาประยุกต์ใช้ โดยไม่มีต้นทุนเพิ่ม เพียงแต่ปรับบริบทเล็กน้อย จึงริเริ่มนำระบบมาใช้งานปี พ.ศ. 2560 เพื่อเป็นการวัดผลสัมฤทธิ์ของระบบใหม่ จึง ศึกษาวิเคราะห์ประเมินผลประโยชน์ที่ได้รับ 3 ด้าน ได้แก่ การประหยัดค่าใช้จ่ายทางตรง การลดขั้นตอนการทำงาน และความพึงพอใจของผู้ใช้ โดยใช้ข้อมูลระหว่างปี พ.ศ. 2555 – 2559 ประกอบกับการสังเกตการณ์ทำงาน ระหว่างระบบเดิมที่ใช้แบบฟอร์มกระดาษกับระบบใหม่ออนไลน์ และใช้ข้อมูล การสำรวจความพึงพอใจผลการวิเคราะห์พบว่าระบบใหม่ช่วยประหยัด ค่าใช้จ่ายทางตรงได้อย่างชัดเจน ลดขั้นตอนการทำงานจาก 11 เหลือ 7 ขั้นตอน ผู้เกี่ยวข้องลดลงจาก 4 เหลือ 2 คน ใช้เวลาน้อยลงจาก 15 นาที เหลือเพียง 2 นาที โดยที่คุณภาพของงานยังเหมือนเดิม ความพึงพอใจมี ค่าเฉลี่ยเท่ากับ 3.63 (ค่อนข้างมาก)
- ItemSynchronized Load Quantification from Multiple Data Records for Analysing High-rise Buildings(2018) Behrendt, Marco; Wonsiri Punurai; Beer, Michael; Mahidol University. Faculty of Engineering. Department of Civil and Environmental Engineering; Universtät Hannover. Institute for Risk and Reliability LeibnizTo analyse the reliability and durability of large complex structures such as high-rise buildings, most realistically, it is advisable to utilize site-specific load characteristics. Such load characteristics can be made available as data records, e.g. representing measured wind or earthquake loads. Due to various circumstances such as measurement errors, equipment failures, or sensor limitations, the data records underlie uncertainties. Since these uncertainties affect the results of the simulation of complex structures, they must be mitigated as much as possible. In this work, the Procrustes analysis, finding similarity transformations between two sets of points in n-dimensional space is used and is extended to uncertainties so that data records can be analysed regarding the uncertainty. To find the best matching of two sets of points the Kabsch algorithm is used. In this manner, a basis is created to simulate and assess the reliability of high-rise buildings under load due to wind and earthquakes.
- ItemProbabilistic seismic hazard assessment for offshore structures in Andaman Sea(2018) T. Ornthammarath; Teraphan Ornthammarath; Mahidol University. Faculty of Engineering. Department of Civil and Environmental EngineeringA set of probabilistic seismic hazard maps for Offshore structures in Andaman sea has been derived using procedures developed for the latest US National Seismic Hazard Maps. In contrast to earlier hazard maps for this region, which are mostly computed using delineated seismic source zone, the presented maps are based on the combination of smoothed gridded seismicity, crustal-fault, and subduction source models. The ground motion hazard map is presented over a 10 km grid in terms of peak ground acceleration and spectral acceleration at 1.0 undamped natural periods and a 5% critical damping ratio for 10 and 2% probabilities of exceedance in 50 years, which have generally been used for Seismic Analysis and Design of Offshore Structures.
- ItemThe fatigue assessment of offshore monopile structure considering corrosion(2019) M.S. Azad; W. Punurai; C. Sinsabvarodom; P. Asavadorndeja; C. Guedes Soares; J. Parunov; Mahidol University. Faculty of Engineering. Department of Civil and Environmental Engineering; Norwegian University of Science and Technology. Department of Marine Technology; Synterra Co. LtdOffshore monopile structures are typically employed in shallow water depths. The structures are embedded into the seabed up to certain depths depending on the soil conditions. Fatigue is a critical problem for the lifespan of existing offshore structures. The salinity of seawater provides a corrosive environment for steel materials. It potentially increases the fatigue damage in the structure. The aim of this research is to dem-onstrate the consequences of fatigue behavior of monopile due to corrosion. The analyses have been per-formed by finite element analysis (FEA) using shell elements to simulate the dynamic responses of monopile structures. Soil springs are applied as foundation system. The hydrodynamic force from ocean waves is consi-dered for estimating the force spectrum. A wave scatter diagram is applied for the long-term sea state of mo-nopile structures. The stress spectrum is determined from the spectral analysis. To investigate the effect of corrosion, experimental SN curves from the previous study are implemented. These experimental curves are included with the effect of corrosion. Three different cases are considered: in air (room temperature), seawater (45°C) and seawater (45°C+diffused air). It was observed that higher amounts of diffused air in the seawater provide higher fatigue damage in the structure.
- ItemAdaptive meta-heuristic to predict dent depth damage in the fixed offshore structures(2018) W. Punurai; M.S. Azad; N. Pholdee; C. Sinsabvarodom; Mahidol University. Faculty of Engineering. Department of Civil and Environmental Engineering; Khon Kaen University. Faculty of Engineering. Department of Mechanical Engineering; Norwegian University of Science and Technology. Department of Marine TechnologyThe jacket structures are often employed in the range of shallow-moderate water depth. The bracing systems and jacket legs typically use the circular section in order to compromise the hydrodynamic resistance and high torsional rigidity However, under lateral impact, these tabular bracing members are susceptible to local denting due to ship collisions or through impact of falling objects and that can weaken overall performance of the entire platform. It is a great significance for forecasting dent depth of these members accurately. This paper investigates the use of adaptive meta-heuristics algorithm to provide an automatic detection of denting damage in an offshore structure. A model is developed combining with the percentage of the dent depth of damaged member diameter and is used to assess the performance of the method. It is demonstrated that the small changes in stiffness of individual damaged bracing members are detectable from measurements of global structural motion.
- ItemA Novel Application of System Survival Signature in Reliability Assessment of Offshore Structures(2018) Regenhardt TE.; Azad M.S.; Punurai W; Beer M.; Vasant P.; Zelinka I.; Weber GW.; Leibniz University HanoverHanover Germany. Institute for Risk and Reliability; Mahidol University. Faculty of Engineering. Department of Civil and Environmental EngineeringOffshore platforms are large structures consisting of a large number of components of various types. Thus a variety of methods are usually necessary to assess the structural reliability of these structures, ranging from Finite-Elements-methods to Monte-Carlo-Simulations. However, often reliability information is only available for the members and not for the overall, complex, system. The recently introduced survival signature provides a way to separate the structural analysis from the behaviour of the individual members. Thus it is then possible to use structural reliability methods to obtain information about how the failure of several constituent members of the offshore platform leads to overall system failure. This way it is possible to separate the structural from time-dependent information, allowing flexible and computationally efficient computation of reliability predictions.
- ItemResponse of Monopile Offshore Wind Turbine Structure Subjected to Seismic Loads and Degradation(2018) Yeter, Baran; Garbatov, Yordan; Guedes Soares, Carlos; Wonsiri Punurai; M.S. Azad; Mahidol University. Faculty of Engineering. Department of Civil and Environmental Engineering; Universidade de Lisboa. Instituto Superior Técnico. Centre for Marine Technology and Ocean Engineering (CENTEC)The objective of this work is to analyse a monopile offshore wind turbine structure subjected to the coupled loads originating from wind, soil interactions and possible seismic activities. The monopile support structure is designed to be installed at 25 m water depth to support a 5MW wind turbine. The structural assessment is performed based on the finite element method accounting for the nonlinearities associated with the geometry and material. The nonlinear structural response of the monopile structure during the seismic activity is assessed accounting for the time-variant degradation of the load-carrying capacity due to corrosion. The nonlinear response of the degrading structures at different years of the service life is presented.
- ItemOn the Development of Using the Non-Invasive Blood Oxygen Level Sensor for Quantifying Hemoglobin Concentration(2013) Khunawat Luangrat; Yunyong Punsawad; Prapat Suriyaphol; Yodchanan Wongsawat; Mahidol University. Faculty of Engineering. Department of Biomedical Engineering; Mahidol University. Faculty of Medicine Siriraj Hospital; Mahidol University. Center for Emerging and Neglected Infectious DiseasesIn this paper, we propose the non-invasive method for detecting hemoglobin concentration. Our hypothesis is that, for the patients who have high hemoglobin concentration, the average pulse amplitudes should be different from their normal condition. To verify our assumption, we diluted the blood of normal subjects by letting them drink the water. According to our experiment, 80% of the subjects had higher pulse amplitude.