5,296 research outputs found
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
Complicated objects: artifacts from the Yuanming Yuan in Victorian Britain
The 1860 spoliation of the Summer Palace at the close of the Second Opium War by British and French troops was a watershed event within the development of Britain as an imperialist nation, which guaranteed a market for opium produced in its colony India and demonstrated the power of its armed forces. The distribution of the spoils to officers and diplomatic corps by campaign leaders in Beijing was also a sign of the British Army’s rising power as an instrument of the imperialist state. These conditions would suggest that objects looted from the site would be integrated into an imperialist aesthetic that reflected and promoted the material benefits of military engagement overseas and foregrounded the circumstances of their removal to Britain for campaign members and the British public.
This study mines sources dating to the two decades following the war – including British newspapers, auction house records, exhibition catalogs and works of art – to test this hypothesis. Findings show that initial movements of looted objects through the military and diplomatic corps did reinforce notions of imperialist power by enabling campaign members to profit from the spoliation through sales of looted objects and trophy displays. However, material from the Summer Palace arrived at a moment when British manufacturers and cultural leaders were engaged in a national effort to improve the quality of British goods to compete in the international marketplace and looted art was quickly interpolated in this national conversation. Ironically, the same “free trade” imperatives that motivated the invasion energized a new design movement that embraced Chinese ornament.
As a consequence, political interpretations of the material outside of military collections were quickly joined by a strong response to Chinese ornament from cultural institutions and design leaders. Art from the Summer Palace held a prominent place at industrial art exhibitions of the postwar period and inspired new designs in a number of mediums. While the availability of Chinese imperial art was the consequence of a military invasion and therefore a product of imperialist expansion, evidence presented here shows that the design response to looted objects was not circumscribed by this political reality. Chinese ornament on imperial wares was ultimately celebrated for its formal qualities and acknowledged links to the Summer Palace were an indicator of good design, not a celebration of victory over a failed Chinese state. Therefore, the looting of the Summer Palace was ultimately an essential factor in the development of modern design, the essence of which is a break with Classical ornament
The Improvement of Multi-Satellite Orbit Determination Through the Incorporation of Intersatellite Ranging Observations
For many satellite remote sensing and communications missions, particularly those involving a formation or constellation of satellites, having precise knowledge of the satellites’ positions in both an absolute and relative sense is essential. However, the capabilities of Global Navigation Satellite Systems (GNSS)-based precise orbit determination (POD) alone may not be enough to fulfill the mission’s requirements. This thesis examines potential gains to POD when additional Intersatellite Range (ISR) observations (range magnitude only, not range direction or rate) are combined with standard GNSS observables. These ISR observations can be obtained from simple radio frequency (RF) or optical sensors. The methodology behind the combination approach is described and illustrated through a series of simulated case studies involving multiple satellites in low Earth orbit (LEO) using realistic hardware-derived (where possible) measurement noise. The results demonstrate that substantial improvements (factor of two or better) in the POD of the constellation satellites can be obtained with even intermittent ranging measurements, and with only millimeter-level ranging precision. This improved positioning capability enables new mission concepts for small-satellite constellations and formations, and makes these multi-satellite systems resilient to disruptions in GNSS signal availability. This GNSS-denial could be due to a variety of factors, such as intermittent or total hardware failure, power-related duty cycling, or ground-based jamming. Results show that under appropriate phasing of periodic GNSS-denial, combined with the new information from the ISR observations, POD levels approaching the non-GNSS-denied case can be achieved. For the cases of region-specific or single-satellite total GNSS-denial, constellations with ISR capability can be designed to completely compensate for the loss of GNSS observations and perform at levels better than with GNSS alone. Furthermore, the GNSS-denied case has an extended application for providing ISR-only POD for constellations around planetary bodies through the inversion of the invariant non-spherical gravity fields. Case studies are presented using high resolution invariant Earth and lunar gravity fields. In these example cases, ISR-only POD is demonstrated at the sub-meter level with the same millimeter precision of ISR. This research provides opportunities for new mission concepts that require precise positioning, improvements to mission operations, and enables new paradigms for orbit determination without access to GNSS.Ph.D
Robust, Energy-Efficient, and Scalable Indoor Localization with Ultra-Wideband Technology
Ultra-wideband (UWB) technology has been rediscovered in recent years for its potential to provide centimeter-level accuracy in GNSS-denied environments. The large-scale adoption of UWB chipsets in smartphones brings demanding needs on the energy-efficiency, robustness, scalability, and crossdevice compatibility of UWB localization systems. This thesis investigates, characterizes, and proposes several solutions for these pressing concerns. First, we investigate the impact of different UWB device architectures on the energy efficiency, accuracy, and cross-platform compatibility of UWB localization systems. The thesis provides the first comprehensive comparison between the two types of physical interfaces (PHYs) defined in the IEEE 802.15.4 standard: with low and high pulse repetition frequency (LRP and HRP, respectively). In the comparison, we focus not only on the ranging/localization accuracy but also on the energy efficiency of the PHYs. We found that the LRP PHY consumes between 6.4–100 times less energy than the HRP PHY in the evaluated devices. On the other hand, distance measurements acquired with the HRP devices had 1.23–2 times lower standard deviation than those acquired with the LRP devices. Therefore, the HRP PHY might be more suitable for applications with high-accuracy constraints than the LRP PHY.
The impact of different UWB PHYs also extends to the application layer. We found that ranging or localization error-mitigation techniques are frequently trained and tested on only one device and would likely not generalize to different platforms. To this end, we identified four challenges in developing platform-independent error-mitigation techniques in UWB localization, which can guide future research in this direction.
Besides the cross-platform compatibility, localization error-mitigation techniques raise another concern: most of them rely on extensive data sets for training and testing. Such data sets are difficult and expensive to collect and often representative only of the precise environment they were collected in. We propose a method to detect and mitigate non-line-of-sight (NLOS) measurements that does not require any manually-collected data sets. Instead, the proposed method automatically labels incoming distance measurements based on their distance residuals during the localization process. The proposed detection and mitigation method reduces, on average, the mean and standard deviation of localization errors by 2.2 and 5.8 times, respectively.
UWB and Bluetooth Low Energy (BLE) are frequently integrated in localization solutions since they can provide complementary functionalities: BLE is more energy-efficient than UWB but it can provide location estimates with only meter-level accuracy. On the other hand, UWB can localize targets with centimeter-level accuracy albeit with higher energy consumption than BLE. In this thesis, we provide a comprehensive study of the sources of instabilities in received signal strength (RSS) measurements acquired with BLE devices. The study can be used as a starting point for future research into BLE-based ranging techniques, as well as a benchmark for hybrid UWB–BLE localization systems.
Finally, we propose a flexible scheduling scheme for time-difference of arrival (TDOA) localization with UWB devices. Unlike in previous approaches, the reference anchor and the order of the responding anchors changes every time slot. The flexible anchor allocation makes the system more robust to NLOS propagation than traditional approaches. In the proposed setup, the user device is a passive listener which localizes itself using messages received from the anchors. Therefore, the system can scale with an unlimited number of devices and can preserve the location privacy of the user. The proposed method is implemented on custom hardware using a commercial UWB chipset. We evaluated the proposed method against the standard TDOA algorithm and range-based localization. In line of sight (LOS), the proposed TDOA method has a localization accuracy similar to the standard TDOA algorithm, down to a 95% localization error of 15.9 cm. In NLOS, the proposed TDOA method outperforms the classic TDOA method in all scenarios, with a reduction of up to 16.4 cm in the localization error.Cotutelle -yhteisväitöskirj
New Signal Priority Strategies to Improve Public Transit Operations
Rapid urbanization is causing severe congestion on road transport networks around the world. Improving service and attracting more travellers could be part of the solution. In urban areas, improving public transportation efficiency and reliability can reduce traffic congestion and improve transportation system performance. By facilitating public buses' movement through traffic signal-controlled intersections, a Transit Signal Priority (TSP) strategy can contribute to the reduction of queuing time at intersections. In the last decade, studies have focused on TSP systems to help public transportation organizations attract more travellers. However, the traditional TSP also has a significant downside; it is detrimental to non-prioritized movements and other transport modes.
This research proposes new TSP strategies that account for the number of passengers on board as well as the real-time adherence of buses to their present schedules. Two methods have been proposed. First, buses are prioritized based on their load and their adherence to their schedules, while in the second method, the person delay at an intersection is optimized. The optimization approach in the first method uses a specific priority for public transit, while additional parameters are considered in the second method, like residual queue and arrival rate at the intersection. One of this research's main contributions is providing insight into the benefits of these new TSP methods along a corridor and on an isolated signalized intersection. The proposed methods need real-time information on transit operations, traffic signals status and vehicular flows. The lack of readily available infrastructure to provide all these data is compensated by using a traffic simulator, VISSIM, for an isolated intersection and an arterial corridor. The study area simulation results indicated that the new TSP methods performed better than the conventional TSP. For the investigated study area, it was shown that the second method performed better in an isolated signalized intersection, while the first method reduced traffic and environmental indices when used for an arterial corridor.
Future research can investigate the effects of the proposed methodology on the urban network by using macrosimulation to see the effects of the proposed TSP on the network. Also, considering conflicting TSP requests in these methodologies could be another area for further research
Patenting Genetic Information
The U.S. biotechnology industry got its start and grew to maturity over roughly three decades, beginning in the 1980s. During this period genes were patentable, and many gene patents were granted. University researchers performed basic research— often funded by the government—and then patented the genes they discovered with the encouragement of the Bayh-Dole Act, which sought to encourage practical applications of basic research by allowing patents on federally funded inventions and discoveries. At that time, when a researcher discovered the function of a gene, she could patent it such that no one else could work with that gene in the laboratory without a license. She had no right, however, to control genes in nature, including in human bodies. Universities licensed their researchers’ patents to industry, which brought in significant revenue for further research. University researchers also used gene patents as the basis for obtaining funding for start-up enterprises spun out of university labs. It was in this environment that many of today’s biotechnology companies started. In 2013, the Supreme Court held that naturally occurring genes could no longer be patented. This followed a 2012 decision that disallowed patents on many diagnostic processes. These decisions significantly changed the intellectual property protections in the biotechnology industry. Nevertheless, the industry has continued to grow and thrive. This Article investigates two questions. First, if some form of exclusive rights still applied to genes, would the biotech industry be even more robust, with more new entrants in addition to thriving, well-established companies? Second, does the current lack of protection for gene discoveries incentivize keeping such discoveries secret for the many years that it can take to develop a therapeutic based thereon—to the detriment of patients who could benefit from knowledge of the genetic associations, even before a treatment is developed? The Article concludes by analyzing what protection for discovering genetic associations, if any, will most increase social welfare
2023-2024 Undergraduate Academic Catalog
https://digitalcommons.cedarville.edu/academic_catalogs/1128/thumbnail.jp
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