• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 8
  • 7
  • 5
  • 5
  • 5
  • 1
  • 1
  • 1
  • Tagged with
  • 47
  • 19
  • 12
  • 11
  • 10
  • 10
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 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

A graph-theory-based C-space path planner for mobile robotic manipulators in close-proximity environments

Wall, D G 10 August 2016 (has links)
In this thesis a novel guidance method for a 3-degree-of-freedom robotic manipulator arm in 3 dimensions for Improvised Explosive Device (IED) disposal has been developed. The work carried out in this thesis combines existing methods to develop a technique that delivers advantages taken from several other guidance techniques. These features are necessary for the IED disposal application. The work carried out in this thesis includes kinematic and dynamic modelling of robotic manipulators, T-space to C-space conversion, and path generation using Graph Theory to produce a guidance technique which can plan a safe path through a complex unknown environment. The method improves upon advantages given by other techniques in that it produces a suitable path in 3-dimensions in close-proximity environments in real time with no a priori knowledge of the environment, a necessary precursor to the application of this technique to IED disposal missions. To solve the problem of path planning, the thesis derives the kinematics and dynamics of a robotic arm in order to convert the Euclidean coordinates of measured environment data into C-space. Each dimension in C-space is one control input of the arm. The Euclidean start and end locations of the manipulator end effector are translated into C-space. A three-dimensional path is generated between them using Dijkstra’s Algorithm. The technique allows for a single path to be generated to guide the entire arm through the environment, rather than multiple paths to guide each component through the environment. The robotic arm parameters are modelled as a quasi-linear parameter varying system. As such it requires gain scheduling control, thus allowing compensation of the non-linearities in the system. A Genetic Algorithm is applied to tune a set of PID controllers for the dynamic model of the manipulator arm so that the generated path can then be followed using a conventional path-following algorithm. The technique proposed in this thesis is validated using numerical simulations in order to determine its advantages and limitations.
2

Improvised explosive devise [device] placement detection from a semi-autonomous ground vehicle

Miller, Benjamin D. 12 1900 (has links)
Improvised Explosive Devices (IEDs) continue to kill and seriously injure military members throughout the Iraqi theatre. Autonomous Ground Vehicle (AGV) seeks to identify the human presence placing the IED and then report that contact to a unit of action. This research developed a semi-autonomous platform that can navigate to waypoints, avoid obstacles, investigate possible threats and then detect motion that triggers a visual camera. The information is then relayed back to the user and can trigger a variety of actions. AGV has been tested in a numerous environments with a wide range of success. It is limited by the communication range from its standard 802.11G router and the continuous availability of the global positioning system. Terrain with extensive peaks and valleys is not ideal for the current platform. However, for detecting the human presence that is consistent with IED placement, AGV is well suited.
3

"EOD, Up!" how explosive ordnance disposal forces can best support special operations forces

Draper, Stephen R. 06 1900 (has links)
U.S. special operations forces (SOF) are likely to undertake missions against terrorists, insurgents, and other enemies where they will encounter explosive hazards. Identification, detection, and neutralization of weapons of mass destruction, improvised explosive devices, booby-traps, and similar weapons requires the support of technicians trained in explosive ordnance disposal (EOD), an expertise that is not resident in SOF units. Consequently, there is a need for EOD technicians with SOF capabilities who can readily integrate with them. This thesis employs a variety of methodologies, from an analysis of required capabilities to an application of game theory, to determine how SOF can be best supported by existing EOD forces and how the supporting command structures and relationships may be improved. It concludes that the Navy's EOD force is best suited to provide support to SOF, and should be included in all special operations planning documents. Those Navy EOD units tasked to provide support to SOF should be consolidated into one organization dedicated to that mission. Finally, when supporting SOF, the Navy should replace its current eight-person EOD operational element with a two-man team that will better match SOF operational requirements. / US Navy (USN) author.
4

Can I Get a Volunteer: Contemporary Improvised Theatre and the Audience

McLean, Jonas 26 April 2019 (has links)
In this thesis I present a new dramaturgical model for understand improvised theatre. Improvised theatre is a field full of experimentation, and the art form has recently been evolving faster than the theories used to understand it. Rather than relying on colloqiual terms such as “short form” and “long form”, I propose a new terminilogy based on Chris Johnston’s notion of “Restrictions”. I explain the use of the Restrictions: Location, Role, Narrative, Game, and Materials, and how to meassure the “Scope” of Restrictions by the Number of affected performers and Duration. I explain how Restrictions affect four elements of improvised performance: Space, Time, Speech, and Physicality. By creating a rubric to illustrate the interaction between Restrictions and these elements, I move towards a new foundation for understanding improvised theatre. In addition, I propose four metrics to meassure audience participation: Number of participants, Method of participation, Agency of the participat, and Duration of the participation. Using my Restriction rubric and audience participation metrics, I analyse four case studies. Each case study is a recent piece of improvised theatre. I attended each piece multiple times and interviewed the artists behind eacch production with a questionnaire. These are Blind Date and Undercover by Spontaneous Theatre, Quest Friends Forever, and GRIMprov’s Guided Roleplay. Each production features audience participation, the effects of which I explain using Erika Fischer-Lichte’s notion of the autopoietic feedback loop.By analysing these contemporary productions I demostrate the efficacy of my new rubrics and terminilogy.
5

Detection and Monitoring of Improvised Explosive Device Education Networks Through the World Wide Web.

Stinson, Robert T. III 06 1900 (has links)
As the information age comes to fruition, terrorist networks have moved mainstream by promoting their causes via the World Wide Web. In addition to their standard rhetoric, these organizations provide anyone with an Internet connection the ability to access dangerous information involving the creation and implementation of Improvised Explosive Devices (IEDs). Unfortunately for governments combating terrorism, IED education networks can be very difficult to find and even harder to monitor. Regular commercial search engines are not up to this task, as they have been optimized to catalog information quickly and efficiently for user ease of access while promoting retail commerce at the same time. This thesis presents a performance analysis of a new search engine algorithm designed to help find IED education networks using the Nutch open-source search engine architecture. It reveals which web pages are more important via references from other web pages regardless of domain. In addition, this thesis discusses potential evaluation and monitoring techniques to be used in conjunction with the proposed algorithm.
6

A graph-theory-based C-space path planner for mobile robotic manipulators in close-proximity environments

Wall, D. G. January 2016 (has links)
In this thesis a novel guidance method for a 3-degree-of-freedom robotic manipulator arm in 3 dimensions for Improvised Explosive Device (IED) disposal has been developed. The work carried out in this thesis combines existing methods to develop a technique that delivers advantages taken from several other guidance techniques. These features are necessary for the IED disposal application. The work carried out in this thesis includes kinematic and dynamic modelling of robotic manipulators, T-space to C-space conversion, and path generation using Graph Theory to produce a guidance technique which can plan a safe path through a complex unknown environment. The method improves upon advantages given by other techniques in that it produces a suitable path in 3-dimensions in close-proximity environments in real time with no a priori knowledge of the environment, a necessary precursor to the application of this technique to IED disposal missions. To solve the problem of path planning, the thesis derives the kinematics and dynamics of a robotic arm in order to convert the Euclidean coordinates of measured environment data into C-space. Each dimension in C-space is one control input of the arm. The Euclidean start and end locations of the manipulator end effector are translated into C-space. A three-dimensional path is generated between them using Dijkstra’s Algorithm. The technique allows for a single path to be generated to guide the entire arm through the environment, rather than multiple paths to guide each component through the environment. The robotic arm parameters are modelled as a quasi-linear parameter varying system. As such it requires gain scheduling control, thus allowing compensation of the non-linearities in the system. A Genetic Algorithm is applied to tune a set of PID controllers for the dynamic model of the manipulator arm so that the generated path can then be followed using a conventional path-following algorithm. The technique proposed in this thesis is validated using numerical simulations in order to determine its advantages and limitations.
7

Photon signatures for standoff bomb detection

Loschke, Kyle W. January 1900 (has links)
Master of Science / Department of Mechanical and Nuclear Engineering / William L. Dunn / The purpose of this research was to develop a technology to quickly identify hidden explosive materials. The developed method needs to be performed at a standoff distance of approximately two meters or more, must have high sensitivity (low false-negative rate) and good specificity (low false-positive rate), and should be able to detect a minimum amount of approximately one gallon (15 lbs) of explosive material. In an effort to meet these goals, a template-matching procedure to aid in the rapid detection of hidden improvised explosive devices was investigated. Multiple photon-scattered responses are being used as a part of a multidimensional signature-based radiation scanning (SBRS) approach in an attempt to detect chemical explosives at safe, standoff distances. The SBRS approach utilizes both neutron and photon interrogation to determine if a target contains explosive material, but the focus of this thesis is on photon interrogation. Beams of photons are used to create back-streamed responses called signatures, which are dependent on the density and the composition of the target. These signatures are compared to templates, which are collections of the same signatures if the interrogated volume contained a significant amount of explosives. The signature analysis produces a single figure-of-merit. A low figure-of-merit indicates an explosive might be present in the target. Experiments have been conducted that show an explosive surrogate (fertilizer) can be distinguished from several inert materials using these photon signatures, proving these signatures to be very useful in this particular method of chemical explosive detection.
8

Guided standoff weapons a threat to expeditionary air power

Vish, Jeffrey A. 09 1900 (has links)
The Air Base has long been a potential target of attack for enemy planners. An effective way to attack the United States Air Force (USAF) is to avoid its usual dominance in the air and use an asymmetrical approach, attacking air bases with ground forces inserted into the Joint Rear Area. The history of airbase ground attacks from 1942 to 1994, documented in the book Snakes in the Eagles' Nest, shows that the dominant strategy employed by air base attackers has been the standoff attack. Roughly, 75 percent of all airbase attacks have been through the use of rockets or mortar fire from outside the airbase's perimeter defenses. In Vietnam, where the defenses against penetrating ground attacks were emphasized, this percentage rose to 96 percent. Historically, robust main operating bases, with passive defensive measures such as hardened facilities and redundant systems, have been able to withstand standoff attacks. The relative inaccuracy of the attacker's standoff systems and their limited ability to sustain fire on the air base minimized damage. Times have changed and the USAF finds itself operating in an expeditionary mode across the globe. Expeditionary Air Forces cannot depend on the luxury of operating off airfields with the robust infrastructure of main operating bases. In addition, the emergence of man portable, guided munitions for mortars and guided anti-tank missiles has increased the accuracy of potential standoff weapons. Finally, the sophistication of Improvised Explosive Devices in Iraq and of modern radio-controlled model aircraft suggests the potential for attackers to build their own guided standoff weapons. The potential for a "one shot, one kill" standoff weapon is here today, negating the effectiveness of passive hardening measures. Disrupting these attacks will take new strategies. Understanding current Joint and USAF doctrine is the first step. Areas for further study include disrupting the enemy forces before they launch a standoff attack, intercepting the standoff round in flight and mitigating the damage on impact are discussed.
9

Improving Outcomes after Repetitive Mild Traumatic Brain Injury from Shock Wave Exposure or Stretch Injury

Effgen, Gwen Brink January 2016 (has links)
The prevalence of injuries from improvised explosive devices (IEDs) in recent U.S. military conflicts has highlighted the lack of knowledge of the acute and long-term consequences of blast exposure. Real-world blast exposure is complex and multi-phasic. It is unclear whether the shock wave component of blast exposure (primary blast) can cause traumatic brain injury (TBI); however, other blast components, such as tertiary blast (inertial loading mechanics), have known potential to injure the brain. Clinical and in vivo studies suggest that complex blast loading of the whole body and head can result in acute and delayed behavioral deficits and neurodegeneration, yet tertiary blast exposure or injury to the body can initiate a systemic response that complicates understanding of this pathology. To set safe thresholds for primary blast exposure and design headgear that can guard against primary blast, tolerance criteria for primary blast specific to brain must be defined. We developed and validated a model of primary blast injury for use with in vitro organotypic hippocampal slice cultures (OHSCs) and determined that primary blast without concomitant tertiary blast loading or systemic response can injure isolated brain samples. This work was the first to define a cell death tolerance criterion for OHSCs to primary blast and report that the threshold for deficits in neuron function was below the threshold for cell death. Mild TBI (mTBI) or concussion, by definition, results in an altered mental state that can include loss of consciousness (LOC) for less than 30 minutes, dizziness, confusion, and retrograde amnesia. These symptoms typically subside within a week after injury; however, for some patients who experience multiple concussions over a relatively short period, these symptoms can persist for a year or longer; persistence of mTBI symptoms is called post-concussion syndrome (PCS). Studies suggest an initial mechanical trauma to the brain can initiate a period of time during which the brain is more vulnerable to additional injury. Little is known about this phenomenon; therefore the current standard of care for patients suffering from concussion is rest and removal from activities with a risk of additional brain trauma. During combat deployment, over 89% of service members reported an incidence of altered mental state and over 86% reported LOC following 2 or more exposures to blast. We evaluated the response of OHSCs to repetitive primary blast (shock wave loading) and repetitive tertiary blast (stretch injury) separately, characterizing the period of vulnerability that follows an initial insult to define safe rest-periods after blast-exposure and better understand pathologies of more complex injuries, i.e. combined primary and tertiary blast. Long-term potentiation (LTP) was significantly reduced by 2 primary blast exposures delivered 24 hours apart. An initial shock wave exposure increased tissue vulnerability to subsequent exposure, which lasted as long as 72 hours but not longer than 144 hours. Repetitive primary blast exposure also increased microglial activation. Similarly, a single mild stretch injury initiated a period of heightened vulnerability to subsequent mild stretch that lasted at least 72 hours but not longer than 144 hours long. Repetitive stretch injury significantly increased cell death, nitrite concentration, and astrogliosis and significantly reduced LTP. We also tested delayed administration of memantine as a treatment for repetitive stretch injury. Memantine is approved by the Food & Drug Administration for the treatment of Alzheimer’s disease, and preclinical studies suggest memantine may be neuroprotective following TBI. Cell death was reduced and LTP was rescued by delayed memantine treatment. Along with further preclinical and clinical investigation of repetitive primary and tertiary blast exposure, these studies may aid in setting safe rest periods and identifying new therapies for service members exposed to blast. This research has shown that primary and tertiary blast exposure can injure OHSCs causing cell death, altering neuron function, and increase vulnerability to a subsequent exposure. These studies expand our understanding of the neuropathology of primary and tertiary blast loading and evaluate methods to improve outcome after repetitive injuries with complementary strategies including rest periods and drug-treatment.
10

Analytical inverse model for post-event attribution of plutonium

Miller, James Christopher 15 May 2009 (has links)
An integral part of deterring nuclear terrorism is the swift attribution of any event to a particular state or organization. By quickly being able to identify the responsible party after a nuclear event, appropriate people may be held accountable for their actions. Currently, there is a system in place to determine the origin of nuclear devices and materials from post-event data; however, the system requires significant time to produce an answer within acceptable error margins. Described here is a deterministic approach derived from first principles to solve the inverse problem. The derivation starts with the basic change rate equation and ends in relationships for important nuclear concentrations and device yield. This results in a computationally efficient and timely method for producing an estimate of the material attributes. This estimate can then be used as a starting point for other more detailed methods and reduce the overall computation time of the post-event forensics. This work focused on a specific type of nuclear event: a plutonium improvised nuclear device (IND) explosion. From post-event isotopic ratios, this method determines the device’s pre-event isotopic concentrations of special nuclear material. From the original isotopic concentrations, the field of possible origins for the nuclear material is narrowed. In this scenario, knowing where the nuclear material did not originate is as important as knowing where it did. The derived methodology was tested using several cases of interest including simplified and realistic cases. For the simplistic cases, only two isotopes comprised the material being fissioned. In the realistic cases, both Weapons Grade and Reactor Grade plutonium were used to cover the spectrum of possible fissile material to be used by terrorists. The methodology performed very well over the desired energy range. Errors were under two percent from the expected values for all yields under 50 kT. In the realistic cases, competing reactions caused an increase in error; however, these stayed under five percent. As expected, with an increased yield, the error continued to rise, but these errors increased linearly. A sensitivity analysis was performed on the methodology to determine the impact of uncertainty in various physical constants. The result was that the inverse methodology is not overly sensitive to perturbations in these constants.

Page generated in 0.0623 seconds