A Precorrected-FFT Method for Coupled Electrostatic-Stokes Flow Problem

We present the application of the boundary integral equation method for solving the motion of biological cell or particle under Stokes flow in the presence of electrostatic field. The huge dense matrix-vector product from the boundary integral method poses a computationally challenging problem for solving the large system of equations generated. In our work, we used the precorrected-FFT (pFFT) method to reduce the computational time and memory usage drastically, so that large scale simulations can be performed quickly on a personal computer. Results on the force field acting on the particle, as well as the behavior of the particle through cell trap are presented.Singapore-MIT Alliance (SMA

Numerical Study of the Poisson-Boltzmann Equation for Biomolecular Electrostatics

Electrostatics interaction plays a very important role in almost all biomolecular systems. The Poisson-Boltzmann equation is widely used to treat this electrostatic effect in an ionic solution. In this work, a simple mixed discrete-continuum model is considered and boundary element method is used to solve for the solution.Singapore-MIT Alliance (SMA

Experimental and numerical studies of acoustical and ventilation performances of glass louver window

The noise attenuation and ventilation performances of the glass louver window were investigated using experimental and numerical methods in order to improve the understanding of this common feature in noise mitigation issue. Sound pressure levels (SPLs) data were measured for frequencies ranging from 100 Hz to 6000 Hz for a room fitted with a louver window. It was found that the louver window was able to attenuate 1.4 %, 5.5 % and 12.0 % of the noise when the panels were partially and fully closed at 30°, 60° and 90°, respectively. For frequencies below 3000 Hz, the best attenuation occurred around 1700 Hz to 2000 Hz for all panel angles. The insertion loss (IL) is similar for frequencies ranging from 3000 Hz to 6000 Hz when the louver window was fully closed at 90°. The velocity magnitude of the air passed through the louver panels increased with increased panel angle. The reduction of the mass flow rate for air passed through the louver window when the panels were partially closed at 30° and 60° are 7.7 % and 46.2 %, respectively

Air Drag on a Stratospheric Balloon in Tropical Regions

Stratospheric balloons are popular for scientific applications as they can carry heavy payloads to perform observations for a long duration. However, for practical applications, a major challenge is the control of the trajectories of the balloons as well as station keeping for a period of time due to severe weather condition such as strong wing at the stratosphere. In order to have a better control of the movement of a stratospheric balloon, we need to have a better understanding of the air flow drag acting on a typical stratospheric balloon. In this paper, numerical simulation studies using the Star CCM+, a computational fluid dynamics software, are carried out to investigate the air drag coefficients of a balloon in the stratosphere in tropical region. By analyzing the weather data provided by the local Meteorological Service for the past three years and considering the balloon size according to the payload capacity, the characteristic Reynolds numbers and flow regime are identified. Thereafter, numerical investigations are performed to study the air drag acting on a pumpkin-shaped stratospheric balloon under typical stratospheric weather conditions in tropical regions, which is justified by referring to the drag force acting on a sphere when a flow past it under those Reynolds numbers that is obtained by using the respective empirical and semi-empirical solutions obtained from experiments

Computational Fluid Dynamics Study of Balloon System Tethered to a Stratosail

In this paper, we present a numerical study of a stratospheric balloon system tethered to a passive device, known as the Stratosail, for station-keeping operation. For scientific applications, stratospheric balloons that operate at altitudes between 15 and 20 km will need to maintain station over a fixed point above the earth for a prescribed period of time. This is a challenging problem due to the limitation of payloads and lack of an energy source. The present study uses computational fluid dynamics (CFD) simulations to analyze the drift velocity of such a balloon-Stratosail system under typical wind conditions in the stratosphere. The Stratosail is attached below the super-pressure helium balloon via a long and thin tether about 10 to 15 km below the balloon, providing a drag force to alter the flight path of the balloon. Its operation depends on the natural differences in the wind speed and wind direction at different altitudes in the atmosphere that act on the balloon and the Stratosail (spaced far apart by 10km to 15 km). In this study, we calculated the drag forces on the balloon and Stratosail for typical wind speeds at various altitudes in the stratosphere. The tether was also modelled as a cable joining the balloon and sail. With this model, the drift velocity of the system was calculated for various altitudes and the angle of attack of the sail

Air Drag on a Stratospheric Balloon in Tropical Regions

Stratospheric balloons are popular for scientific applications as they can carry heavy payloads to perform observations for a long duration. However, for practical applications, a major challenge is the control of the trajectories of the balloons as well as station keeping for a period of time due to severe weather condition such as strong wing at the stratosphere. In order to have a better control of the movement of a stratospheric balloon, we need to have a better understanding of the air flow drag acting on a typical stratospheric balloon. In this paper, numerical simulation studies using the Star CCM+, a computational fluid dynamics software, are carried out to investigate the air drag coefficients of a balloon in the stratosphere in tropical region. By analyzing the weather data provided by the local Meteorological Service for the past three years and considering the balloon size according to the payload capacity, the characteristic Reynolds numbers and flow regime are identified. Thereafter, numerical investigations are performed to study the air drag acting on a pumpkin-shaped stratospheric balloon under typical stratospheric weather conditions in tropical regions, which is justified by referring to the drag force acting on a sphere when a flow past it under those Reynolds numbers that is obtained by using the respective empirical and semi-empirical solutions obtained from experiments

iProgVR: Design of a Virtual Reality Environment to Improve Introductory Programming Learning

Currently, there are a plethora of solutions developed to help students learn the basics of programming. However, there is a relative paucity of solutions that cater to problems students face when learning programming that is mainly caused by the abstract nature of programming, misconceptions of programming concepts, and lack of motivation. Hence, in this study, a framework to address the abstract nature of programming and common programming misconceptions is developed. The framework consists of three modules that correspond to each issue, powered by a simulation engine. The first module is developed to address the abstract nature of programming by representing programming concepts with concrete objects in the virtual environment. The second module employs simulation techniques such as interactions and player perspectives to address common programming misconceptions. Lastly, the third module employs elements in the virtual environment to engage students when learning through the system. To evaluate the system, 60 participants were randomly divided into the control group (N = 30) and the experimental group (N = 30). Participants in the control group were taught using a video lecture while participants in the experimental group were taught using the developed VR intervention. Evaluation results gathered quantitatively indicated that the VR intervention was able to significantly increase programming concepts comprehension and address programming misconceptions. Participants also rated the developed VR intervention to be significantly more engaging than the video lecture

Haptic Interfaces for Virtual Reality: Challenges and Research Directions

The sense of touch (haptics) has been applied in several areas such as tele-haptics, telemedicine, training, education, and entertainment. As of today, haptics is used and explored by researchers in many more multi-disciplinary and inter-disciplinary areas. The utilization of haptics is also enhanced with other forms of media such as audio, video, and even sense of smell. For example, the use of haptics is prevalent in virtual reality environments to increase the immersive experience for users. However, while there has been significant progress within haptic interfaces throughout the years, there are still many challenges that limit their development. This review highlights haptic interfaces for virtual reality ranging from wearables, handhelds, encountered-type devices, and props, to mid-air approaches. We discuss and summarize these approaches, along with interaction domains such as skin receptors, object properties, and force. This is in order to arrive at design challenges for each interface, along with existing research gaps

Experimental and numerical studies on the design of a sonic crystal window

Four sets of numerical models were created to study the effects of shapes, staggering patterns, Helmholtz resonators and array configurations on the acoustical performance of sonic crystals (SCs) in order to design an efficient SC window to mitigate the traffic noise level at a room in a student hostel of NUS. Rectangular SCs consistently obtained highest transmission loss for frequencies ranging from 300 Hz to 3000 Hz compared to diamond and semi-circle SCs. Fully staggered pattern performed better than non-staggered and 50 % staggered patterns for frequencies below 1700 Hz. Helmholtz resonators were useful for enhancing low frequency noise mitigation. The prototype of the final designed SC window was fabricated and tested in order to validate the simulation result. Generally, numerical and experimental results were in similar trends. Maximum transmission loss of the SC window was found to be occurred at 900 Hz which was about 18 dB

A Color Based Touchless Finger Mouse

People work with computers almost anytime, everywhere  in the current trend. However, continuously controlling a computer with mouse for a long time might cause much strains to people’s wrist. This work proposes a touchless finger mouse using webcam. A marker with different colours representing different actions is used. The webcam will capture the information on the marker and trigger the associated actions. This prototype is proven to be able to perform most of the actions a normal mouser can perform