Antenna integration for wireless and sensing applications

As integrated circuits become smaller in size, antenna design has become the size limiting factor for RF front ends. The size reduction of an antenna is limited due to tradeoffs between its size and its performance. Thus, combining antenna designs with other system components can reutilize parts of the system and significantly reduce its overall size. The biggest challenge is in minimizing the interference between the antenna and other components so that the radiation performance is not compromised. This is especially true for antenna arrays where the radiation pattern is important. Antenna size reduction is also desired for wireless sensors where the devices need to be unnoticeable to the subjects being monitored. In addition to reducing the interference between components, the environmental effect on the antenna needs to be considered based on sensors' deployment. This dissertation focuses on solving the two challenges: 1) designing compact multi-frequency arrays that maintain directive radiation across their operating bands and 2) developing integrated antennas for sensors that are protected against hazardous environmental conditions. The first part of the dissertation addresses various multi-frequency directive antennas arrays that can be used for base stations, aerospace/satellite applications. A cognitive radio base station antenna that maintains a consistent radiation pattern across the operating frequencies is introduced. This is followed by multi-frequency phased array designs that emphasize light-weight and compactness for aerospace applications. The size and weight of the antenna element is reduced by using paper-based electronics and internal cavity structures. The second part of the dissertation addresses antenna designs for sensor systems such as wireless sensor networks and RFID-based sensors. Solar cell integrated antennas for wireless sensor nodes are introduced to overcome the mechanical weakness posed by conventional monopole designs. This can significantly improve the sturdiness of the sensor from environmental hazards. The dissertation also introduces RFID-based strain sensors as a low-cost solution to massive sensor deployments. With an antenna acting as both the sensing device as well as the communication medium, the cost of an RFID sensor is dramatically reduced. Sensors' strain sensitivities are measured and theoretically derived. Their environmental sensitivities are also investigated to calibrate them for real world applications.Ph.D.Committee Chair: Tentzeris, Emmanouil; Committee Member: Akyildiz, Ian; Committee Member: Allen, Mark; Committee Member: Naishadham, Krishna; Committee Member: Peterson, Andrew; Committee Member: Wang, Yan

Signature features with the visibility transformation

The signature in rough path theory provides a graduated summary of a path through an examination of the effects of its increments. Inspired by recent developments of signature features in the context of machine learning, we explore a transformation that is able to embed the effect of the absolute position of the data stream into signature features. This unified feature is particularly effective for its simplifying role in allowing the signature feature set to accommodate nonlinear functions of absolute and relative values

Gender Differences in Pathways to Compulsive Buying in Chinese College Students in Hong Kong and Macau

The addictive nature of compulsive buying implies that mood disturbances, stress, and cognitive biases that underlie compulsive buying might operate in ways similar in both genders. In the current study, we aimed to test hypothetical pathways of mood compensation and irrational cognitions, which may explain compulsive buying tendencies. We also examined potential gender differences in these pathways. Methods Two-hundred and thirty-two male (age: M = 20.30, SD = 1.74) and 373 female Chinese college students (age: M = 19.97, SD = 1.74) in Hong Kong and Macau completed measures assessing compulsive buying, psychological distress, avoidance coping, materialism, and buying-related cognitions. Mediation analyses via a structural equation modeling approach explained by Cheung (2007, 2009) were conducted, with gender as a grouping variable. Results There was a gender difference in the mood compensation pathway; avoidance coping partially mediated the link between psychological distress and compulsive buying severity in females only. On the other hand, the irrational cognitive pathway, in which irrational buying-related cognitions fully mediated the link between materialism and compulsive buying severity, was supported for both genders. There was no gender difference in the extent of mediation within the irrational cognitive pathway, and the mediation effect within the irrational cognitive pathway was larger than that within the mood compensation pathway for both genders. Conclusions Mood compensation processes in compulsive buying might be female specific, and secondary to irrational cognitions, which were gender invariant. Gender-dependent mechanisms and irrational cognitions should be emphasized in compulsive buying treatment

The Role of IFN-α/β in Host Antiviral Response to T3D Mammalian Orthoreovirus

The antiviral activity of Type 1 Interferon (IFN) has been extensively studied and recognized, especially in regards to Hepatitis and HIV; however the IFN antiviral activity has not been specifically analyzed in reoviral infection. In this study, a mouse model of reoviral encephalitis was used to determine the role of Type 1 Interferon (IFN) in host antiviral activity. Six mice deficient in IFN-α/β receptor (IFNAR) function were inoculated with Type 3 Dearing (T3D) mammalian orthoreovirus intracranially at 15 days of age and showed signs of clinical illness, lethargy, hunched posture, and dull hair coat at day 7 post infection. Mice were humanely euthanized and tissues were harvested for histologic evaluation on days 8 and 9 post infection. Pathologic lesions including meningoencephalitis, hydrocephalus, rhinitis, hepatitis, interstitial pneumonia and marked lymphoid depletion were identified on routine histologic exam. Further investigation utilizing immunohistochemistry (IHC) for Reovirus, CD3 cells, B220 cells, and F4/80 was performed on the affected tissues. Reovirus was detected in the brain, liver and lung. In the brain there was a robust T-cell (CD3) and macrophage (F4/80) response. In the spleen Caspase-3 immunohistochemistry confirmed marked apoptosis in the lymphoid tissue. Pathologic lesions were not present in the gastrointestinal tract, heart, or kidneys. This study shows that IFNAR deficient mice are susceptible to reovirus infection at post natal day 15 with morbidity and mortality due to reovirus induced meningoencephalitis, hepatitis, and interstitial pneumonia