Accelerated dry-stack masonry construction is seen all over the world in the last two decades. Intense investigation on structural behaviour of dry-stack masonry is also seen worldwide. This research work, presents an investigation of the structural behaviour of Hydraform drystack masonry developed in South Africa. Unit compressive strength, masonry wall compressive strength and flexural resistance of dry-stack masonry/reinforced concrete beams were investigated. Due to the interlocking mechanism nature of Hydraform dry-stack blocks, three different unit compressive testing methods were investigated. The methods are described as: - Shoulder test; - Centre test; - Cube test. Tests were carried out under different humidity conditions: - Dry; - Wet; - Normal. Influence of different cement contents within the block units and moisture contents were investigated. The study made proposal of Hydraform block unit grads to be used for design. Compressive strength of dry-stack masonry walls was experimentally investigated. Dry-stack masonry wall specimens made by different block grades were subjected to in-plane vertical uniformly distributed load. Test results were used to establish dry-stack masonry characteristic compressive strength for several block grades. Flexural strength of dry-stack masonry/reinforced concrete composite beams was investigated. Series of beams were tested for flexural resistance. Applicability of conventional reinforced masonry flexural analysis philosophy was established.

According to the previous experimental fact that an interdigitated single PEMFC has a better performance than other flow type single PEMFC, therefore this research is aimed to predict a two-cell stack interdigitated PEMFC via a numerical simulation. Investigation the effects of the cell temperature, the cell operating pressure, the fuel flow rate and the air flow rate are performed. This research can provide design reference for application of interdigitated PEMFC stack.

The present research analyzes random porous thermoacoustic stack systems analytically, experimentally, and numerically with a primary objective to develop a comprehensive analytical porous media modeling for random porous (such as Reticulated Vitreous Carbon (RVC) foams) environment. Mathematical models are developed for flow, thermal, and energy fields within the random porous medium stack. The Darcy and Brinkman-Forchheimer-extended Darcy models are used for modeling the momentum equation and local thermal equilibrium assumption between the porous matrix and trapped fluid in the void space for energy equation. The expressions of temperature, energy flux density, and acoustic work absorbed or produced by a thermoacoustic device are compared with existing literature and observed good agreements. After obtaining the flow and thermal fields’ information, the present study examines the entropy generation distribution within the stack. One important item revealed in this study is that entropy generation inside the porous medium completely follows the trend of the imaginary part of Rott’s first function profile. Another major contribution of this research is to identify the location of maximum entropy generation which is identical to the location of maximum thermoacoustic heat and work transport. The expression of Nusselt number for steady flow cannot be used in oscillatory random porous medium because of the phase difference between the temperature gradient at the wall and the temperature difference between the wall and the space averaged temperature. The present research experimentally examines novel stack configuration by considering “alternating conducting and insulating materials” as stack in thermoacoustic devices. The objective of considering such stack arrangement is to reduce the conduction heat transfer loss from the hot end of the stack to the cold end, thereby increasing the performance of the stack. Eight different heterogeneous stack arrangements are studied in this research. The performance of the heterogeneous stack arrangement is compared with the typical homogeneous stacks. This research shows that heterogeneous stacks can be used in thermoacoustic devices particularly in small (millimeter) scale thermoacoustic devices. Numerically the present study investigates the influence of working fluid, geometric, and operating conditions on stack performance by solving the full Navier-Stokes, mass, energy equation, and equation of state.

The amount of interest in asteroids, particularly near-Earth asteroids, has been slowly increasing the last few years. Early on, it was the fear of the potential hazards of an asteroid impact (which still remains); now, science and exploration are driving the motivation for detecting asteroids. By incorporating a process that attempts to remove stars from images, known as difference image analysis, into the shift and stack method for finding moving objects, an algorithm that searches for asteroids in series of images was created. When tested on previously discovered asteroids, the algorithm was able to detect 73% (104 out of 142) of the asteroids, with a false positive occurring in roughly one in six runs. Two of the test asteroids found by the algorithm were not found using a different shift and stack technique. Almost all of the asteroids that the algorithm could not detect were either slow moving, faint or both. The detection capability of the algorithm can easily be improved to be more successful at detecting slow and/or faint asteroids. This can be achieved by using a better method for masking the star residuals or by increasing the time between successive images when searching for asteroids with velocities of 2.4

The present research analyzes random porous thermoacoustic stack systems analytically, experimentally, and numerically with a primary objective to develop a comprehensive analytical porous media modeling for random porous (such as Reticulated Vitreous Carbon (RVC) foams) environment. Mathematical models are developed for flow, thermal, and energy fields within the random porous medium stack. The Darcy and Brinkman-Forchheimer-extended Darcy models are used for modeling the momentum equation and local thermal equilibrium assumption between the porous matrix and trapped fluid in the void space for energy equation. The expressions of temperature, energy flux density, and acoustic work absorbed or produced by a thermoacoustic device are compared with existing literature and observed good agreements. After obtaining the flow and thermal fields’ information, the present study examines the entropy generation distribution within the stack. One important item revealed in this study is that entropy generation inside the porous medium completely follows the trend of the imaginary part of Rott’s first function profile. Another major contribution of this research is to identify the location of maximum entropy generation which is identical to the location of maximum thermoacoustic heat and work transport. The expression of Nusselt number for steady flow cannot be used in oscillatory random porous medium because of the phase difference between the temperature gradient at the wall and the temperature difference between the wall and the space averaged temperature. The present research experimentally examines novel stack configuration by considering “alternating conducting and insulating materials” as stack in thermoacoustic devices. The objective of considering such stack arrangement is to reduce the conduction heat transfer loss from the hot end of the stack to the cold end, thereby increasing the performance of the stack. Eight different heterogeneous stack arrangements are studied in this research. The performance of the heterogeneous stack arrangement is compared with the typical homogeneous stacks. This research shows that heterogeneous stacks can be used in thermoacoustic devices particularly in small (millimeter) scale thermoacoustic devices. Numerically the present study investigates the influence of working fluid, geometric, and operating conditions on stack performance by solving the full Navier-Stokes, mass, energy equation, and equation of state.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / This paper discusses simulating iNET's protocol stack using OPNET Modeler. It shows an example of a custom protocol simulated in OPNET Modeler, and how to model the test article, and ground station as reusable components for future simulation. Network simulation is a critical tool for iNET as it enables design decisions that cannot be made analytically due to the complexity of the problem. This work addresses the incorporation of iNET's protocol stack into the OPNET Modeler tool set as this piece of iNET is unique and is not available in OPNET Modeler.

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There is an increasing demand for reliable wireless communication in embedded real time systems.  Various communication requirements make the development and deployment of applications that rely on the existence of a protocol stack a challenging research and industrial field of activity. Suitable protocol stacks need to be designed and implemented on new hardware platforms and software structures. Applications that exchange packets over a wireless medium have to deal with time constraints, error checks and have to be aware of energy consumption.   PIE (Platform for Intelligent Embedded Systems) is an experimental platform developed at Halmstad University for educational purposes.  It is a robotic vehicle with wireless communication capabilities that can be used to experiment with traffic scenarios where the vehicles communicate in order to cooperate, for example to avoid hazards or to build platoons.   This thesis addresses the design and implementation of a protocol stack suitable for the PIE platform in the area of vehicle alert systems. Requirements include low latencies along with low packet loss ratios.  The thesis addresses also experimenting with reactive objects for programming network software.

In this thesis, a portable PEMFC stack, which can directly power or charge 3C products, will be developed. The stack is developed for portable applications, so the structure of the stack is simplified as possible as we can. The PEMFC stack is made with 32 carbon fiber bunches for current collectors and two 8-cell banded-type MEAs which are made with 8 sets of electrodes on a piece of membrane. The stack can develop a high voltage by serially connecting 8 cell or 16 cell outside of the reaction chamber. The resistance of each carbon bunch assembling with carbon cloth is measured before they are assembled into the stack. Under assembly pressure 3 bar, the total resistance is about 8.7m£[ or 11m£[¡Ecm2. The resistance is about one half of that graphite plate assembling with carbon cloth. Without being compressed greatly in diffusion layer, the fluid can easily flow through the gaps between carbon fiber and within diffusion layers, and then the reactive region will react more uniformly. In addition, the connecting wires are assembled to a wire collecting board, so that the stack is look more neat, and it easier assemble or dissemble. In this thesis, the volume of the developed 16-cell hydrogen fuel cell stack is about 9.6 cm*6.3 cm*2.2 cm. The total electrode area is 50 cm2 (16-cell¡Ñ3.15 cm2 per cell). When the stack is operating at room temperature and air-breathing, an 8-cell stack in series connection can generate 3.7V voltage. Its power at voltage 3.7V is about 3.6W. It can directly power PDAs, mobile phones or digital cameras. A 16-cell stack in series connection can generate 7.2V voltage. Its power at this voltage can offer 7W. The 16-cell stack can directly power digital single-lens reflex cameras. If two or more of this stack are connected in series, it will be able to power a notebook or other more power products.

In this thesis, a PEMFC stack, which can be self-humidification of passive portable hydrogen fuel cell, will be developed. The stack is developed for portable applications, so the structure of the stack is simplified as possible as we can. As the cathode directly exposed under the atmosphere, so in a long time, the membrane easily lead to excessive evaporation of water, so that performance degradation. The traditional humidifier is more complex applications are not suitable for portable, so this thesis stack developed by the use of cotton capillarity, the water from the tanks transferred to the membrane, and then by cotton and a good touch to the membrane humidifier effect, this structure without an increase in large equipment, in line with the principles of portability. The PEMFC stack is made with carbon fiber bunches for current collectors and two 8-cell banded-type MEAs, the stack can develop a high voltage by serially connecting outside of the reaction chamber. 16-cell in series when the current density is greater than 110mA/cm2, use humidification to avoid long time operation, due to water cause a voltage drop. Humidification is not only to help transfer of hydrogen ions, and the role of a cooling stack, the cells temperature is too high will not cause transpiration rate of speed. Current density greater than 250mA/cm2, although humidity can still be effective, but insufficient humidification single cotton, one hour after, the voltage drop of about 20% longer cell performance, such as humidity will be no more have a more significant decline phenomenon, more cotton or additional external humidification humidifier can maintain a long-time stable operation. Therefore, the performance of the cells in order to avoid a recession, should pay attention to in a long time when working conditions and operating range.