Surrogate-based optimization of a BioMEMs microfluidic weir

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.Includes bibliographical references (p. 127-130).BioMEM microfluidic weirs enable biologists to study biological processes at the cell level. A novel substrate-affixed microfluidic array of weirs allows active sorting of cells via control electrodes. The ability of the weirs to retain cells hydrodynamically is vital to the functionality of the substrate-affixed array of weirs. The objective of this thesis is to give insight using numeric tools to the microfluidic weir designer on how to improve the ability of the microfluidic weir to retain cells. Simulations of the interactions between the cell and the weir were performed using a computer simulation of Stokes flow. The computational approach uses a pre-corrected Fast Fourier Transform Boundary Element Method to evaluate the drag forces acting on the cell and a rigid body physics library to handle rigid body collision dynamics between the cell and the weir. This model was used to address two research questions which are the two main discussions of the thesis. The first discussion studies in detail the mechanisms behind the 'Around The Side' (ATS) and 'Over The Top' (OTT) modes of escape that were observed experimentally. A model example was studied for each mode. The forces and torques experienced by the cell when it escaped through either mode are explained in detail. Each mode was segmented into time periods and the mechanisms behind these modes of escape were discussed to give insight to the microfluidic weir designer. The second discussion focuses on design space exploration and optimization of the ability of the microfluidic weir to retain the cell. In order to make design optimization computationally tractable a surrogate is derived; that is, a model that provides an accurate approximation to the input/output map of the simulation but that is much cheaper computationally to evaluate.(cont.) The surrogate was built using the Support Vector Machine (SVM) algorithm and was then used for the design space exploration and optimization. The weir geometry and flow rate were used as design variables to maximize the ability of the microfluidic weir to retain cells in the design optimization problem. Results from the design space exploration and optimization showed that a minimal depth of the mouth of the weir is required for the weir to be able to retain any beads. However, the ability of the weir to retain beads is more sensitive to the width of the mouth than the depth.by Boon Hooi Ooi.S.M

Design of Field Experiments for Adaptive Sampling of the Ocean with Autonomous Vehicles

Due to the highly non-linear and dynamical nature of oceanic phenomena, the predictive capability of various ocean models depends on the availability of operational data. A practical method to improve the accuracy of the ocean forecast is to use a data assimilation methodology to combine in-situ measured and remotely acquired data with numerical forecast models of the physical environment. Autonomous surface and underwater vehicles with various sensors are economic and efficient tools for exploring and sampling the ocean for data assimilation; however there is an energy limitation to such vehicles, and thus effective resource allocation for adaptive sampling is required to optimize the efficiency of exploration. In this paper, we use physical oceanography forecasts of the coastal zone of Singapore for the design of a set of field experiments to acquire useful data for model calibration and data assimilation. The design process of our experiments relied on the oceanography forecast including the current speed, its gradient, and vorticity in a given region of interest for which permits for field experiments could be obtained and for time intervals that correspond to strong tidal currents. Based on these maps, resources available to our experimental team, including Autonomous Surface Craft (ASC) are allocated so as to capture the oceanic features that result from jets and vortices behind bluff bodies (e.g., islands) in the tidal current. Results are summarized from this resource allocation process and field experiments conducted in January 2009.Singapore. National Research Foundatio

Multi-layer model simulation and data assimilation in the Serangoon Harbor of Singapore

In June of 2009, a sea trial was carried out around Singapore to study and monitor physical, biological and chemical oceanographic parameters. Temperature, salinity and velocities were collected from multiple vehicles. The extensive data set collected in the Serangoon Harbour provides an opportunity to study barotropic and baroclinic circulation in the harbour and to apply data assimilation methods in the estuarine area. In this study, a three-dimensional, primitive equation coastal ocean model (FVCOM) with a number of vertical layers is used to simulate barotropic and baroclinic flows and reconstruct the vertical velocity structures. The model results are validated with in situ ADCP observations to assess the realism of the model simulations. EnKF data assimilation method is successively implemented to assimilate all the available ADCP data, and thus correct for the model forecast deficiencies.Singapore. National Research FoundationSingapore-MIT AllianceSingapore-MIT Alliance. Center for Environmental Sensing and Monitorin

Curbing Bribe-Giving in Malaysia: The Role of Attitudes and Parents

© The Author(s). Published with license by Taylor & Francis Group, LLC. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/).One of the main challenges developing nations face is curbing bribery. While there are many efforts to curb bribery, most focused at macro level, such as law, while little has been examined at the micro level, e.g., individual behavior and intention. Those who did investigate at the micro level tend to focus on the recipients rather than the ones giving the bribe. We explored eight factors that influence Malaysian young adults’ bribe giving intention based on the Reasoned Action Approach (RAA). A total of 345 respondents (M age = 20.68, SD = 2.01, 189 are females) completed questionnaires about all RAA variables. Partial Least Squares Structural Equation Modelling (PLS-SEM) was carried out using smartPLS3.0 to analyze the result. The result revealed that out of the eight variables, four variables—Instrumental attitudes, Experiential Attitudes, Parents’ descriptive norms and Capacity—explain 74% of the variance in bribe giving intention. An important take-away is that young adult’s perception of whether their parents gave or did not give bribes in a given situation is important in influencing their bribe giving intention. Bribe giving prevention messages must be targeted explicitly toward parents, where they play a crucial role in curbing this dishonesty.Peer reviewe

Infrastructure for mobile sensor network in the Singapore coastal zone

URL to conference page. Scroll down to 2010 conference, click on "Paper and session list," and search the PDF for Patrikalakis.Singapore is an island nation located at southern tip of the Malaysian Peninsula. She is at a strategic location along major shipping routes and therefore has one of the busiest harbors in the world. Having a safe and secure harbor environment is vital to maintain trade and growth in the country and region. To help build and maintain a safe harbor environment, the Center of Environmental Sensing and Modelling (CENSAM) under the Singapore-MIT Alliance for Research and Technology (SMART) is developing a mobile sensor network in the Singapore coastal zone

Bullying, Eating Disorders and Coping Strategies among Adolescents in Malaysia

Understanding how bullying leads to eating disorders can help develop effective intervention strategies. This phenomenological study examines the relationship between bullying and coping strategies Malaysian adolescents diagnosed with eating disorders use. Using the snowball sampling technique, 12 Kuala Lumpur participants, six females and six males aged 10 to 19, responded to interview questions based on the literature reviews, theories, and a published questionnaire. By using thematic analysis, the researcher found out that all 12 participants with EDs were bullied about their weight or size. Most of the bullying and teasing were verbal or via online platforms. The findings suggest that bullying can be a significant cause of the development of eating disorders among adolescents in Malaysia. Proper coping strategies can be essential in overcoming the trauma of being bullied and treating eating disorders

PATH PLANNING FOR MULTIPLE TYPES OF AUTONOMOUS VEHICLES

Master'sMASTER OF SCIENCE IN COMPUTATIONAL ENGINEERIN

Examining Social Presence and Online Learning Satisfaction Among Malaysian University Students During the COVID-19 Pandemic

This study aimed to investigate the relationship between social presence and online learning satisfaction among 257 university students (Mage=19.89years, SDage=1.93) during the COVID-19 pandemic. The partial least square (PLS) algorithm was used to examine the association and the prediction of the proposed relationship. This study employed a cross-sectional research design with convenience sampling. Participants completed an online survey questionnaire which consisted of a Social Presence Scale and Satisfaction Scale in March 2022. All scales included in the present study reported a satisfying level of reliability and validity coefficient. The PLS regression tests showed that social presence was positively associated with online learning satisfaction (β = 0.717, p < 0.01). Additionally, social presence reported a medium level of prediction power towards online learning satisfaction which shed light on the underlying mechanisms that explain students’ online learning satisfaction during the COVID-19 pandemic. The results also demonstrate the singifiant contribution of teaching and learning approach, programme or intervention to facilitate social presenc. It is also essential to promote a greater sense of online satisfaction among university students

Measurement accuracy and reliability of self-reported versus measured weight and height among adults in Malaysia: Findings from a nationwide blood pressure screening programme.

Most studies reporting prevalence of obesity use actual weight and height measurements. Self-reported weight and height have been used in epidemiological studies as they have been shown to be reliable, convenient, and inexpensive alternatives to actual measurements. However, the accuracy of self-reported weight and height might vary in different regions because of the difference in health awareness and social influences. This study aims to determine the accuracy and reliability of self-reported weight and height compared to actual measured weight and height among adults in Malaysia. This was a cross-sectional study conducted at the community level during blood pressure screening campaigns. Participants self-reported their weight and height in a questionnaire survey. Their weight and height were validated using measurements by researchers on the same setting. Body mass index (BMI) was defined as underweight (<18.5kg/m2), normal (18.5-22.9 kg/m2), overweight (23-27.4 kg/m2) and obesity (≥27.5 kg/m2). Bland-Altman analysis, intraclass correlation coefficients and weighted Kappa statistics were used to assess the degree of agreement between self-reported and measured weight and height. A total of 2781 participants were recruited in this study. The difference between the mean self-reported and measured weight and height were 0.4 kg and 0.4 cm respectively. Weighted Kappa statistics analysis showed that there was a substantial agreement between the BMI classifications derived from self-reported and actual measurement (ҡ = 0.920, p<0.001). There was no marked difference in the sensitivity and specificity of self-reported BMI among Malaysian adults by gender. We observed substantial agreement between self-reported and measured body weight and height within a sample of Malaysian adults. While self-reported body weight showed weaker agreement with actual measurements particularly for obese and overweight individuals, BMI values derived from self-reported weight and height were accurate for 88.53% of the participants. We thus conclude that self-reported height and weight measures may be useful for tracking and estimating population trends amongst Malaysian adults