Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Explicit Energy-Minimal Short-Term Path Planning for Collision Avoidance in Crowd Simulation
Get PDFIn traditional crowd simulation methods, global path planning (GPP) and local collision avoidance (LCA) were mostly used to advance pedestrians toward their own goals without colliding. However, we found that using those methods in bidirectional flows can force a pedestrian to get stuck among the incoming people, walk through the congestion, or even unintentionally occupy in a dense area, although more comfortable passageway exists. These odd behaviors are usually produced and simply noticeable in bidirectional case. This paper aims at reducing these artifacts to achieve more behavioral fidelity, by adding the explicit metabolic-energy-minimal short-term path planning (MEM) in between GPP and LCA. For energy analysis, the optimal control theory with the objective energy function from the study of biomechanics was employed, which finally leads to the useful optimal walking characteristics for the pedestrians. The simulation results show that the pedestrians with MEM can adapt their moving to avoid the congestion, resulting in more promising lane changing and overtaking behaviors. Even though MEM was mainly developed to deal with the artifacts in bidirectional flows, it can be extended with a little modification and can produce significant behavioral improvement for multi-directional case as shown in the last part of the paper
Polyethylene/Bacterial-Cellulose Biocomposite Synthesized via In Situ Polymerization with Zirconocene/MMAO Catalyst
Get PDFIn this study, the polyethylene filled celluloses regarded as biocomposites was produced via in situ polymerization with zirconocene/MMAO catalyst. Three types of celluloses including microcrystalline cellulose (MCC), bacterial cellulose prepared from pineapple shell extract (BCP), and bacterial cellulose prepared from coconut (BCC) were used as fillers and also catalytic support in the polymerization system. It was found that the presence of cellulose fillers slightly decreased catalytic activity of the polymerization system, but it was still higher compared with that of other natural fillers such as coir dust. This is caused by the lower impurity of cellulose. The MCC provided the highest catalytic activity among all cellulose fillers. The obtained biocomposites were characterized with different techniques including scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). It was observed that all obtained biocomposites exhibited good morphology compared with the neat polyethylene. Thermal stability of the polymers was improved with the cellulose fillers
Fe and Co-doped (Ba, Ca)TiO3 Perovskite as Potential Electrocatalysts for Glutamate Sensing
Get PDFBarium titanate (BaTiO3) and calcium titanate (CaTiO3) are renown perovskite-structured dielectric materials. Nevertheless, utilization of BaTiO3 and CaTiO3 in sensing applications has not been extensive. This study, therefore, aims at examining potential usage of BaTiO3 and CaTiO3 as enzyme-less sensors. BaTiO3, CaTiO3, Fe-doped BaTiO3, Co-doped BaTiO3, Fe-doped BaTiO3, and Co-doped CaTiO3 (with Fe and Co 5 at%) were synthesized by solution combustion technique, compositionally and microstructurally examined, and tested for their electrocatalytic activities. All powders consisted of submicrometer-sized particles. Measurements of electrocatalytic activities in 0.01 M glutamate solution by cyclic voltammetry were performed. It was found that oxidation peaks occurred at applied voltage close to 0.6 V. Peak currents, which denoted electrocatalytic performance, were prominent in doped powders. Electrocatalytic activities of the powders were discussed with respect to chemical composition, microstructure, and electronic characteristic of the materials
Transformation Optical User-Friendly Interface for Designing Metamaterials
Get PDFTransformation optics offers a procedure to design the structures of metamaterials to find the material parameters needed in various applications. However, a methodology of a transformation optics is too complicated. To help users who are beginning to study metamaterials and transformation optics, a transformation optical user-friendly interface is developed. The interface is implemented based on the free-form touch transformation. By combining various transformation templates, a fully arbitrary transformation can be realized. Transformation templates are created by basic functions. The interface provides both the input method as well as the real-time visualization of the space. The program uses model-view-controller architecture. Three examples from the touch interface are verified by the FDFD simulation
Central Nervous System (CNS) Based Motion Control
Get PDFMotion simulators are widely used in several applications ranging from research to commercial training and entertainment in order to replicate real movement situation. These motions can be sensed by human perception organ called Central Nervous System (CNS). This research presents a novel control algorithm called Central Nervous System (CNS) based control that aims to create realistic perception of vehicle simulation. CNS-based motion control was evaluated by computer simulation to classical, adaptive and optimal washout filter. In addition, comparisons of human motion perception are performed on Force Dynamics 301 simulator for longitudinal acceleration driving test of all four washout filters. The subjects were seated in the simulator. Their motion perceptions were measured through vestibulo-ocular reflex (VOR) using EyeSeeCam vHit camera and compared to the estimated VOR from CNS model. The results revealed that CNS-based motion control can crucially reduce the workspace and provide realistic motion sensation.
 
The Reuse of Waste Glass as Aggregate Replacement for Producing Concrete Bricks as an Alternative for Waste Glass Management on Sichang Island
Get PDFThe objective of this research is to manage waste glass in Koh Sichang, Chonburi province, used as a partial fine aggregate replacement in concrete brick production according to the Thai Industrial Standard (TIS) 57-2533. An experimental approach aimed to determine the level of waste glass replacement for the optimal compressive strength. Five samples of 0, 10, 20, 30, and 100% waste glass aggregates by weight were tested at 7, 14, and 28 days. The microstructure and mineralogical phases of the concrete bricks were investigated by scanning electron microscopy and X-ray diffractometry, respectively. The experimental results showed that the compressive strength was improved by increments in replacing waste glass up to 20%; in contrast, the compressive strength was decreased with an increase of waste glass of over 20% in concrete bricks. The optimum compressive strength of concrete brick was 20% by weight, which had the highest values (46.51, 47.41, and 48.49 MPa at 7, 14, and 28 days, respectively) and lowest water absorption. Therefore, waste glass can be used as a partial fine aggregate for producing concrete bricks, and it can be employed as an alternative material for waste glass management
In-situ Observation of Martensite Decomposition in HAZ of Cr-Mo Steel Weldment
Get PDFIn-situ observation of martensite decomposition at Heat Affected Zone (HAZ) was investigated on a dissimilar joining between 2.25Cr-0.5Mo grade T22 as base material and ER90S-B9 as filler metal using GTAW process using LEEM at a synchrotron facility. A post weld heat treatment (PWHT) cycle was simulated on a welded specimen in high vacuum chamber by heating cartridge and electron bombardment. Both effects PWHT duration and weld areas were studied for comparisons. At the simulated PWHT between 690oC -700oC in CGHAZ, martensite started to decompose by the dissolution of carbide flakes. The prior-austenite grain boundaries were also shown during the process. The same phenomena were also observed in FGHAZ with different extent. In un-affected base material, ferrite and new pearlite grains presented and grew at the expense of old pearlite. Longer PWHT duration resulted in more ferrite formed in all weld areas. Raising PWHT temperature to 730oC could push the reaction above Eutectoid temperature as the new austenite formed at grain boundaries. The proposed mechanism for martensite decomposition would be in steps as dissolution of carbide followed by formation of ferrite and growth as PWHT proceeded
Development of a Realistic Driving Cycle Using Time Series Clustering Technique for Buses: Thailand Case Study
Get PDFRealistic driving cycles for Thailand’s road conditions were studied only for the pollution problems of passenger cars and light-duty trucks in urban areas of the metropolitan region. Such driving cycles did not cover rural areas and the in-use operation of buses. Furthermore, such created methods of the driving pattern were very irregular and complicated for chassis dynamometer operation. To propose a new method for a realistic driving cycle, the development of the route traffic for bus transportation in rural areas using a time series clustering technique is indicated. As a case study, this method was applied to collect the driving data on the 323 route in Kanchanaburi province using on-board measurement. The selection procedure of suitable speed and interval time for driving cycle construction was revealed. Similarity of driving characteristics was identified with clustering technique for each time duration to decide the best driving cycle. In conclusion, the frequency of speed ranges from entire trips is 30-40 km/h with the highest ratio of deceleration time to the entire trip. Furthermore, discrete average speeds at each time point with 40 seconds of interval time are the best choice related to the real driving condition in this case study
Alternative Software for Evaluating Preliminary Rock Stability of Tunnel Using Rock Mass Rating (RMR) and Rock Mass Quality (Q) on Android Smartphone
Get PDFNowadays, tunneling is applied to a variety of constructions such as subway station, water supply tunnel and underground mine. Tunnel safety is one of the most important factors of construction. Most tunneling is operated in remote area that is difficult to reach. This research aims to develop an alternative software for Android smartphone, which use for estimating preliminary rock mass stability and suggesting support method for the early state tunnel. Suitable rock mass classifications for tunnel are rock mass rating (RMR) and rock mass quality (Q system). They are applied to the application. Android operating system is chosen because it is the most popular operating system in the world. The application is programmed by the official programming software from Google, the Android Studio. PSU-RQ is the name of this application. PSU-RQ is easy to use because it reduced the complexity of the theories by numerical logic. The application results are verified by comparing with Excel standard worksheet. PSU-RQ is reliable and accurate. The application is tested in a tunneling case study as an example. Whenever a smartphone is available, the user can estimate preliminary rock mass stability and support method of tunnel instantly. However, long-term stability investigation is necessary
Monitoring of Hot Corrosion Behaviors for Alloys and Aluminide Coatings under Molten Sulfate Film with Thermal Cycles
Get PDFIn this study, a thin molten sulfate film was formed on the metallic samples and their corrosion processes have been monitored by electrochemical impedance technique under thermal cyclic condition. Inconel 600, nickel and aluminide diffusion coatings were used as samples. 50 mol%Na2SO4- 50 mol%Li2SO4 was used for preparing the molten sulfate film. Two kinds of specially designed electrochemical cells have been used in this study. One is three-electrode configuration and another is two-electrode configuration. Electrochemical impedance measurements were used for monitoring the degradation processes for all samples tested. It was found that both corrosion resistance and the change of molten sulfate film has been monitored successfully during 6 thermal cycles. In every thermal cycle, the corrosion resistance increased when the temperature shifted to lower values and decreased with the rising of temperature. Also, A drastic increase in corrosion resistance and the resistance of the molten salt film was observed when the temperature decreased below the melting point of the mixed molten sulfate film. Although both three-electrode and two-electrode configurations were usable for electrochemical measurements under molten sulfate film, it was concluded that the newly designed two-electrode configuration is more suitable under thermal cyclic condition