Proceedings. The 21st Digital Avionics Systems Conference
During flight, aircraft avionics transmit and receive RF signals to/from antennas over coaxial ca... more During flight, aircraft avionics transmit and receive RF signals to/from antennas over coaxial cables. As the density and complexity of onboard avionics increases, the electromagnetic interference (EMI) environment degrades proportionately, leading to decreasing signal-to-noise ratios (SNRs) and potential safety concerns. The coaxial cables are inherently lossy, limiting the RF signal bandwidth while adding considerable weight. To overcome these limitations, we have investigated a fiber optic communications link for aircraft that utilizes wavelength division multiplexing (WDM) to support the simultaneous transmission of multiple signals (including RF) over a single optical fiber. Optical fiber has many advantages over coaxial cable, particularly lower loss, greater bandwidth, and immunity to EMI. In this paper, we demonstrate that WDM can be successfully used to transmit multiple RF signals over a single optical fiber with no appreciable signal degradation. We investigate the transmission of FM and AM analog modulated signals, as well as FSK digital modulated signals, over a fiber optic link (FOL) employing WDM. We present measurements of power loss, delay, SNR, carrier-to-noise ratio (CNR), total harmonic distortion (THD), and bit error rate (BER). Our experimental results indicate that WDM is a fiber optic technology suitable for avionics applications.
Pneumatosis coli is an uncommon medical condition which, if not recognized, may result in unneces... more Pneumatosis coli is an uncommon medical condition which, if not recognized, may result in unnecessary surgical intervention. This case highlights the link between pneumatosis coli and other conditions affecting the large bowel, as well as demonstrating its association with chronic obstructive airways disease.
Synthetic biology aims to systematically design and construct novel biological systems that addre... more Synthetic biology aims to systematically design and construct novel biological systems that address energy, environment, and health issues. Herein, we describe the development of a synthetic genetic system, which comprises quorum sensing, killing, and lysing devices, that enables Escherichia coli to sense and kill a pathogenic Pseudomonas aeruginosa strain through the production and release of pyocin. The sensing, killing, and lysing devices were characterized to elucidate their detection, antimicrobial and pyocin release functionalities, which subsequently aided in the construction of the final system and the verification of its designed behavior. We demonstrated that our engineered E. coli sensed and killed planktonic P. aeruginosa, evidenced by 99% reduction in the viable cells. Moreover, we showed that our engineered E. coli inhibited the formation of P. aeruginosa biofilm by close to 90%, leading to much sparser and thinner biofilm matrices. These results suggest that E. coli carrying our synthetic genetic system may provide a novel synthetic biology-driven antimicrobial strategy that could potentially be applied to fighting P. aeruginosa and other infectious pathogens. Molecular Systems Biology 7: 521;
International Journal of Communication Systems, 2002
Continued progress in both civil and military radio-frequency (RF) digital avionics applications ... more Continued progress in both civil and military radio-frequency (RF) digital avionics applications is overstressing the capabilities and reliability of existing RF communication networks based on coaxial cables on board modern aircrafts. Future avionics systems will require high-bandwidth on-board communication links that are lightweight, immune to electromagnetic interference, and highly reliable. Fibre-optic networks can meet all these challenges in a cost-effective manner. Recently, on-board fibreoptic communication systems, where a fibre-optic network acts like a local area network (LAN) for digital data communications, have become a topic of extensive research and development. However, modern digital avionics systems require a system capable of transporting microwave and millimeter-wave RF signals that carry digital data on board an aircraft. Such optical networks transporting RF signals are completely different from the digital fibre-optic communication systems. Recent advances in optoelectronics technology, including linear optoelectronic devices and wavelength division multiplexing (WDM), have opened a number of possibilities for designing on-board fibre-optic networks, including all-optical networks for digital avionics RF signal communication. The objective of this paper is to present a number of optical network architectures for transmitting RF signals carrying digital data in an aircraft. In this paper, we investigate a number of different approaches, including all optical architectures, for building an optical network using fibre-optic transmission of on-board VHF and UHF RF signals. The relative merits and demerits of the network architectures are discussed, and the suitability of the architectures for particular applications is presented.
Suspected spinal cord or cauda equina pathology is an emergency that must be dealt with swiftly, ... more Suspected spinal cord or cauda equina pathology is an emergency that must be dealt with swiftly, with appropriate referral and investigations. Constipation is a clinical diagnosis of exclusion, but should not be forgotten as a cause of major morbidity when severe in nature. It can mimic an acute abdomen, sepsis and even spinal cord pathology. We describe a case of cauda equina syndrome in a young man. The pathology responsible was found to be constipation with faecal impaction, once nerve and bony pathology were excluded. When treated, there was almost immediate resolution of the neurologic signs and urinary retention.
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Papers by Hung Nguyen