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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

CICADA-INSPIRED SOUND GENERATOR WITH DUAL RESONATORS

Song, Xiaolei January 2022 (has links)
Male cicada’s superior sound producing ability has been well studied by entomologists and ethologists. The secret behind the loud sound is the dual-resonator structure: the primary resonator is a series of buckled ribs/beams on its tymbal organ, while the secondary resonator is a large air cavity in the abdomen with a pair of openings. However, the understanding of the dual-resonator structure is incomplete, and few endeavors have been reported on developing cicada-inspired novel acoustic devices. To this end, this dissertation research aims to achieve a fundamental understanding of the cicada-inspired sound generating structures, and to apply the knowledge to develop a dual-resonator system with superior sound generating ability.First, a clamped-clamped buckled beam – the fundamental vibration source of the dual-resonator system – is modeled and tested for free vibration responses during the snap-through process between its bistable positions. It is found that the free vibration of the buckled beam is independent from actuation. In terms of the natural frequencies and the vibrational mode shapes, the free vibration is determined only by the geometry and material properties of the buckling beam. The experiment provides a comprehensive insight of the snap-through process and the induced free vibrations. Second, both analytical and experimental methods are used to investigate the buckling beam from an energy perspective, including the force needed for actuating the buckled beam, the work by the actuation force, the elastic energy of the buckling beam, and the sound radiation characteristics. Results show that although the actuation forces depend on its acting locations, the work by the force remains constant, which is equal to the elastic energy difference between the first symmetric buckling mode and the first anti-symmetric buckling mode. Acoustic analysis shows that the sound radiation is mostly generated from the first symmetric vibrational mode. Third, the dual-resonator system consisting of a buckling beam and a Helmholtz resonator is proposed. Considered as an equivalent two-degree-of-freedom vibration system, the dual-resonator system is modeled and studied for optimal sound output. Finally, a dual-resonator system is fabricated with the optimal parameters. Experimental characterization shows superior sound outputs of the dual-resonator system similar to what are observed in male cicadas. This dissertation sheds new lights on the structural-acoustic interaction of buckling beam and Helmholtz resonator that is found in the sound-producing organs of male cicadas and develops a cicada-inspired dual-resonator system for the first time. Findings from this research not only enhance the existing knowledge on male cicadas, but also pave the way for its engineering applications that require highly efficient sound radiation. / Mechanical Engineering
2

Bradford Non-Lethal Weapons Research Project (BNLWRP). Research Report No. 7.

Davison, N., Lewer, N. January 2005 (has links)
yes / The length of this Bradford Non-Lethal Weapons Research Project Report No.7 again reflects the interest related to non-lethal weapons from academics, research institutes, policy makers, the police and the military. A number of reports, particularly concerning the Taser electro-shock weapon, have been published from these sectors since our last BNLWRP Report No.6 in October 2004. Some, such as the Amnesty International (U.S. and Canada) have again raised, and stressed, the concerns about the safety of the weapon and the number of deaths associated with its use. Others, such as the Joint Non-Lethal Weapons Human Effects Center of Excellence (HECOE), Human Effectiveness and Risk Characterization of the Electromuscular Incapacitation Device ¿ A Limited Analysis of the TASER. (March 2005) concluded that the Taser was relatively safe, but that further research was needed into potential bio-effects, and for continual development into a safer weapon. Reaction to these reports was mixed. Some US legislators called for limitations on the use of Tasers, more accountability, and the detailed recording of incidents in which they were used.1 Others called for a ban on their use until more testing was carried out regarding their potentially harmful effects. A number of US police forces stopped the use of Taser, slowed down the deployment and ordering of the weapons, reviewed their rules of engagement and reporting, and revisited their operational guidelines. The International Association of Chiefs of Police (IACP) published the Electro- Muscular Disruption Technology (EMDT). A Nine-Step Strategy For Effective Deployment. (April 2005) as a response to these growing concerns. Certain elements of the media, especially The Arizona Republic2 and others, took a hostile view of what they considered the scandal of the number of deaths and associated serious injuries caused by the Taser. Taser International challenged allegations that their weapon was directly responsible for these deaths and quoted reports, such as the Madison Police Department report (February 2005), the study by McDaniel, W & Stratbucker, R & Nerheim, M & Brewer, J. Cardiac Safety of Neuromuscular Incapacitating Defensive Devices (January 2005), and the U.K. DOMILL Statement (March 2005) to support their view. The controversy continues. Other than Tasers, there are still few reports of the newer non-lethal technologies actually being deployed in operations. The exception to this is the Long Range Acoustic Device (LRAD), which is now in widespread use in Iraq. Little additional information has appeared regarding the `active denial¿ weapon we have described in previous reports.
3

Evaluation of the Littoral Combat Ship (LCS) and SPARTAN SCOUT as Information Operations (IO) assets

Bromley, Joseph M. 03 1900 (has links)
Approved for public release, distribution is unlimited / This thesis will address the planned configuration of Lockheed Martin's Flight Zero, Module Spiral Alpha Littoral Combat Ship (LCS) and the ongoing development of the SPARTAN SCOUT, one of the Navy's Unmanned Surface Vessels (USV). Technology currently available as well as developmental technologies will be recommended for implementation in order to make the LCS and SCOUT assets to Information Operations (IO) objectives. Specific technology will include Outboard, TARBS, HPM, Loudspeakers, LRAD and Air Magnet. This thesis will include an evaluation of the current policy for authorizing Information Operations missions, specifically in the areas of Psychological Operations (PSYOP) and Electronic Warfare (EW). / Lieutenant, United States Navy
4

Bradford Non-Lethal Weapons Research Project (BNLWRP). Research Report No. 6.

Davison, N., Lewer, N. January 2004 (has links)
yes / New non-lethal technologies (weapons and delivery systems) continue to make the news, both for their civil and military applications. Technologies which were considered to be in the realm of science fiction a few years ago, are now beginning to undergo field trials or, in some cases, are being deployed with police and soldiers on active service. As this, and our previous reports have highlighted, the development of acoustic weapons (Long Range Acoustic Device) and microwave weapons (Active Denial System) have proceeded rapidly as have advances in robotic, unmanned vehicles for the delivery of both lethal and non-lethal weapons. We repeat our concern that there is a danger of these new non-lethal technologies being `rushed¿ into service (1) without thorough testing for harmful health effects, (2) without a deeper consideration of civil and human rights, (3) without full discussion of their impact on arms control treaties and conventions, and (4) without further study of their social and cultural impact. Since many such weapons will have a rheostatic capacity along the non-lethal to lethal continuum, it is important that weapons developers and manufacturers, and those charged with the responsibility of using them, are held clearly accountable and have transparent rules of engagement. Of particular concern are a new generation of biological and chemical weapons. With respect to the health impact, NATO has a panel working on NLW human effects, the Human Factors and Medicine (HFM) Panel 073, which is due to report later this year (2004) on the Human Effects of Non-Lethal Technologies.1

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