Edem Wornyo

Uses of mobile phones in post-conflict Liberia

Liberia is a country emerging from years of protracted and devastating civil conflict. Left without any fixed line telephone infrastructure, it relies solely on the mobile phone for telephony. This study investigates the usage of mobile phones in this immediate post-conflict setting. In particular, we adopt the uses and gratifications approach to media research, giving focus to both instrumental and intrinsic motivations for use. Mobile phone users in both the capital city of Monrovia and in various rural areas were surveyed using the Q methodology, which identified distinct perspectives within these urban and rural groups. Participants were then sorted into groups where each group contained users with similar perspectives on their mobile phones. These identified groups included sets of users who saw their phones as productivity enhancers, means of connectivity to family and friends, essential business tools, technological curiosities, and sources of personal security. The idea of a phone as a stylish object was markedly rejected, especially in rural areas. We contrast these Q-sort results from Liberia with previous work from Kigali, Rwanda, finding differences especially as related to security.

Post-conflict communications: the case of Liberia

Liberia, founded in 1847 by freed African slaves from the U.S. is a relatively small country with approximately 3.3 million inhabitants (see Figure 1). Unrest has been common within Liberia for more than 25 years, with two major civil wars in this time period. These years of conflict have seen nearly one-third of the population displaced and taken the lives of approximately 250,000 people. Recently, a prominent warlord turned Liberian President, Charles Taylor, ruled with violence both at home and regionally. In 2003, as his government struggled under domestic and international pressure, the civil war entered the capital Monrovia. By the end of that year Taylor was forced to resign and sought asylum in Nigeria. Taylor has since been arrested and removed to The Hague where he faces charges of war crimes and crimes against humanity. With Taylor’s departure, a

Modeling and Optimization of the Deposition of Shape Memory Polymers for Information Storage Applications

Shape memory polymers are of interest as high-capacity information storage media. This paper seeks to understand the effects of processing conditions on diethylene glycol dimethacrylate (DEGDMA) and bisphenol A ethoxylate dimethacrylate. Full factorial experiments are performed to characterize the impact of the following parameters: spin speed, spin time, and nitrogen flow rate. A total of ten experiments are conducted. The measured responses are film thickness, uniformity, hardness and modulus. Analysis of variance reveals the above input parameters are significant with respect to the output responses. The full factorial experiment is augmented by a central composite face centered (CCF) design to facilitate process modeling. Neural network models are developed to examine relationships. The average predictability of the models is better than 2% for training and less than 15% in testing. Genetic algorithms are used in optimizing recipes for the two materials.

Thickness and Uniformity Modeling of the Deposition of Shape Memory Polymers for Information Storage Applications

Shape memory polymers are of interest as high-capacity information storage media. This research seeks to understand the effects of processing conditions on the following candidate polymers: diethylene glycol dimethacrylate (DEGDMA), tertbutyl acrylate (tBA), and bisphenol. Full factorial experiments were performed using three input factors: spin speed, spin time, and nitrogen flow rate. A total of ten experiments were conducted. The measured responses were film thickness, uniformity, hardness and modulus of the materials. Analysis of variance revealed that all input parameters were significant with respect to the film thickness. The full factorial experiments were augmented to a central composite face (CCF) design to enable response surface modeling. Neural network models were developed to examine relationships between the spin speed and thickness of spin coated films. The average predictability of the model was better than 2% for training and less than 15% in testing. This research is expected to aid in understanding the use of these materials in information storage.

Shape memory capacitors for next generation embedded actives

Integral discrete passives occupy nearly 45% of the board real estate. By embedding passives we have the following advantages: improving packaging efficiency & electrical performance, reducing the use of printed wiring board real estate, eliminating assembly to board, minimizing solder joint failure and enhanced reliability. Embedded systems are getting more attention in digital area applied to noise reduction and system performance vs cost enhancement while maintaining EMI suppression. Decoupling capacitors play an important role in high speed system due to the inductance associated with the lead free interconnects. Decoupling can be achieved using embedded capacitance materials that make use of the capacitance of closely spaced power and ground planes. The approach improves electrical performance, frees surface real estate, and eliminates solder connections, which can lead to improved reliability. RF circuits embedded capacitors play a critical role in determining the resonant frequency. Drift in resonant frequency results in distortion in signal quality. In order to over come this frequency drift due to temperature and other environmental conditions, we propose a novel embedded shape memory capacitor (SMC) which can vary with applied stimulus, and subsequently the RF circuit can be tuned. In this paper, we characterize the performance of a novel embedded shape memory capacitor fabricated using shape memory polymers dielectric material, with one metal electrode fabricated on a low strength back plane to allow the electrode to flex . The shape memory dielectric contracts and expands when heated. A step by step process is adopted to transfer the shape memory dielectric to the electrode using lithography technology. A variable frequency DC current is applied to platinum electrode fabricated above the top capacitor plate. The DC voltage not only provides a resonance current, it also allows the platinum electrode to heat the capacitor. The heat deforms the shape memory dielectric thereby changing the capacitance. This variable capacitor is tuned by changing the current and applied frequency. The compression effect on the shape memory also causes a thickness variation there by making the already submicron thick dielectric vary in thickness. The thinner dielectric makes it suitable for high frequency capacitance application. By changing the thickness of the dielectric and varying the frequency, the capacitor becomes very suitable to work over a broad range of RF frequencies and capacitances. In this paper we model, characterize the shape memory dielectric, fabricate and test the novel shape memory capacitor. The data collected from a test bed used to implement this novel capacitor for RF frequency tuning. This characteristics including material components and construction, dielectric properties and topography at metal-dielectric interfaces are optimized for a wide frequency band width. Attention is given to frequency dependence of the different material properties. Effects of the material characteristics on electrical performance, including capacitance and power and ground plane impedance, are examined. Finally, processing and fabrication issues are discussed. A detail description of how it is implemented in RF circuits was presented