Pearl City, HI, United States
Pearl City, HI, United States

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Person M.J.,Massachusetts Institute of Technology | Dunham E.W.,Lowell Observatory | Bosh A.S.,Massachusetts Institute of Technology | Levine S.E.,Massachusetts Institute of Technology | And 47 more authors.
Astronomical Journal | Year: 2013

On 2011 June 23, stellar occultations by both Pluto (this work) and Charon (future analysis) were observed from numerous ground stations as well as the Stratospheric Observatory for Infrared Astronomy (SOFIA). This first airborne occultation observation since 1995 with the Kuiper Airborne Observatory resulted in the best occultation chords recorded for the event, in three visible wavelength bands. The data obtained from SOFIA are combined with chords obtained from the ground at the IRTF, the U.S. Naval Observatory Flagstaff Station, and Leeward Community College to give the detailed state of the Pluto-Charon system at the time of the event with a focus on Pluto's atmosphere. The data show a return to the distinct upper and lower atmospheric regions with a knee or kink in the light curve separating them as was observed in 1988, rather than the smoothly transitioning bowl-shaped light curves of recent years. The upper atmosphere is analyzed by fitting a model to all of the light curves, resulting in a half-light radius of 1288 ± 1 km. The lower atmosphere is analyzed using two different methods to provide results under the differing assumptions of particulate haze and a strong thermal gradient as causes for the lower atmospheric diminution of flux. These results are compared with those from past occultations to provide a picture of Pluto's evolving atmosphere. Regardless of which lower atmospheric structure is assumed, results indicate that this part of the atmosphere evolves on short timescales with results changing the light curve structures between 1988 and 2006, and then reverting these changes in 2011 though at significantly higher pressures. Throughout these changes, the upper atmosphere remains remarkably stable in structure, again except for the overall pressure changes. No evidence of onset of atmospheric collapse predicted by frost migration models is seen, and the atmosphere appears to be remaining at a stable pressure level, suggesting it should persist at this full level through New Horizon's flyby in 2015. © 2013. The American Astronomical Society. All rights reserved.

Nordkvist N.,Leeward Community College | Crouch P.E.,University of Hawaii at Manoa | Bloch A.M.,University of Michigan | Sanyal A.K.,New Mexico State University
Proceedings of the IEEE Conference on Decision and Control | Year: 2011

In this paper we define a class of optimal control problems which we denote "embedded optimal control problems". These are not true optimal control problems since the control system is not locally controllable on the manifold on which it is defined. Despite this, they allow for a well defined associated optimal control problem which does not admit abnormal extremals. We apply Pontryagin's maximum principle to the embedded optimal control problem to derive the generating differential equations for the normal and abnormal extremals. We show that the normal extremal generating equations in a sense contain the extremal generating equations for the associated optimal control problem. We show that this is not the case for the abnormal extremal generating equations. This has applications to the study of the optimal control of systems constrained to a given submanifold of a configuration space, for example the sphere or hypersphere. We apply the theory to three examples in order to illustrate its applicability and to show how it relates to well known results. © 2011 IEEE.

Sanyal A.K.,New Mexico State University | Nordkvist N.,Leeward Community College
Journal of Guidance, Control, and Dynamics | Year: 2012

A state estimation scheme that does not depend on the statistical distribution of bounded measurement noise is presented. This scheme is used to provide state estimates for feedback in an attitude tracking control scheme that exhibits almost global asymptotically stable tracking of a desired attitude trajectory with perfect state measurements. The control and estimation schemes use the global, unique representation of rigid body attitude provided by rotation matrices. Attitude and angular velocity state estimate updates are obtained from discrete multirate measurements using a deterministic filtering scheme. Propagation of discrete state estimates is carried out with a Lie group variational integrator, which preserves the orthogonality of rotation matrices during numerical propagation without reprojection. This integrator is also used to numerically simulate the feedback system. The performance of this attitude tracking control scheme is then compared with that of a recently reported quaternion observer-based continuous feedback attitude tracking scheme. This quaternion-based attitude tracking scheme is shown to exhibit unstable, unwinding behavior. Numerical simulation results for both these feedback tracking schemes are obtained for a satellite in circular Earth orbit tracking an oscillating angular velocity spin maneuver. These numerical results are then compared for control effort and time taken for the tracking errors to converge to the desired trajectory. © 2011 by Amit K. Sanyal.

Aeby G.S.,Hawaii Institute of Marine Biology | Aeby G.S.,University of Hawaii at Manoa | Callahan S.,Hawaii Institute of Marine Biology | Callahan S.,University of Hawaii at Manoa | And 10 more authors.
Diseases of Aquatic Organisms | Year: 2016

In March 2010 and January 2012, we documented 2 widespread and severe coral disease outbreaks on reefs throughout Kāne'ohe Bay, Hawai'i (USA). The disease, acute Montipora white syndrome (aMWS), manifested as acute and progressive tissue loss on the common reef coral M. capitata. Rapid visual surveys in 2010 revealed 338 aMWS-affected M. capitata colonies with a disease abundance of (mean ± SE) 0.02 ± 0.01 affected colonies per m of reef surveyed. In 2012, disease abundance was significantly higher (1232 aMWS-affected colonies) with 0.06 ± 0.02 affected colonies m-1 . Prior surveys found few acute tissue loss lesions in M. capitata in Kāne'ohe Bay; thus, the high number of infected colonies found during these outbreaks would classify this as an emerging disease. Disease abundance was highest in the semi-enclosed region of south Kāne'ohe Bay, which has a history of nutrient and sediment impacts from terrestrial runoff and stream discharge. In 2010, tagged colonies showed an average tissue loss of 24% after 1 mo, and 92% of the colonies continued to lose tissue in the subsequent month but at a slower rate (chronic tissue loss). The host-specific nature of this disease (affecting only M. capitata) and the apparent spread of lesions between M. capitata colonies in the field suggest a potential transmissible agent. The synchronous appearance of affected colonies on multiple reefs across Kāne'ohe Bay suggests a common underlying factor. Both outbreaks occurred during the colder, rainy winter months, and thus it is likely that some parameter(s) associated with winter environmental conditions are linked to the emergence of disease outbreaks on these reefs. © The authors 2016. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited.

Shahhaidar E.,University of Hawaii at Manoa | Shahhaidar E.,Incube Labs | Padasdao B.,University of Hawaii at Manoa | Padasdao B.,Leeward Community College | And 3 more authors.
IEEE Journal of Biomedical and Health Informatics | Year: 2015

Remote health monitoring is increasingly recognized as a valuable tool in chronic disease management. Continuous respiratory monitoring could be a powerful tool in managing chronic diseases, however it is infrequently performed because of obtrusiveness and inconvenience of the existing methods. The movements of the chest wall and abdominal area during normal breathing can be monitored and harvested to enable self-powered wearable biosensors for continuous remote monitoring. This paper presents human testing results of a light-weight (30 g), wearable respiratory effort energy harvesting sensor. The harvester output voltage, power, and its metabolic burden, are measured on twenty subjects in two resting and exercise conditions each lasting 5 min. The system includes two off-the-shelf miniature electromagnetic generators harvesting and sensing thoracic and abdominal movements. Modules can be placed in series to increase the output voltage for rectification purposes. Electromagnetic respiratory effort harvester/sensor system can produce up to 1.4 V, 6.44 mW, and harvests 30.4 mJ during a 5-min exercise stage. A statistical paired t-test analysis of the calculated EE confirmed there is no significant change (P>0.05) in the metabolic rate of subjects wearing the electromagnetic harvester and biosensor. © 2014 IEEE.

Bloch A.M.,University of Michigan | Crouch P.E.,University of Hawaii at Manoa | Nordkvist N.,Leeward Community College
Journal of Geometric Mechanics | Year: 2013

In this paper we define "embedded optimal control problems" which prescribe parametrized families of well defined associated optimal control problems. We show that the extremal generating Hamiltonian equations for an embedded optimal control problem and any associated optimal control problem are simply related by a projection. Furthermore normal extremals project to normal extremals and similarly for abnormal extremals. An interesting class of embedded optimal control problems consists of Clebsch optimal control problems. We provide necessary conditions for a Clebsch optimal control problem to describe a variational problem and thereby a mechanical system. There may be many advantages to analyzing an embedded optimal control problem instead of a particular associated optimal control problem, for example the former being defined on a linear space and the latter on a nonlinear space. The continuous analysis is paralleled by a similar discrete analysis. We define a discrete embedded/Clebsch optimal control problem along with associated discrete optimal control problems and we show results that are analogous to the continuous results. We apply the theory, both in the continuous and the discrete setting, to two example systems: mechanical systems on matrix Lie groups and mechanical systems on n-spheres. © American Institute of Mathematical Sciences.

Xu J.,University of Hawaii at Manoa | Gao X.,University of Hawaii at Manoa | Padasdao B.E.,Leeward Community College | Boric-Lubecke O.,University of Hawaii at Manoa
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2015

Doppler radar physiological sensing has been studied for non-contact detection of vital signs including respiratory and heartbeat rates. This paper presents the first micrometer resolution Wi-Fi band Doppler radar for sub-millimeter physiological displacement measurement. A continuous-wave Doppler radar working at 2.4GHz is used for the measurement. It is intended for estimating small displacements on the body surface resulting from physiological activity. A mechanical mover was used as target, and programmed to conduct sinusoidal motions to simulate pulse motions. Measured displacements were compared with a reference system, which indicates a superior performance in accuracy for having absolute errors less than 10μm, and relative errors below 4%. It indicates the feasibility of highly accurate non-contact monitoring of physiological movements using Doppler radar. © 2015 IEEE.

Nordkvist N.,Leeward Community College | Crouch P.E.,University of Hawaii at Manoa | Bloch A.M.,University of Michigan
Proceedings of the IEEE Conference on Decision and Control | Year: 2012

In this paper we analyze a class of discrete optimal control problems. These systems are discretizations of a class of optimal control problems defined on invariant submanifolds which we denote embedded optimal control problems. We analyze a particular subset of these called discrete Clebsch optimal control problems where the invariant manifolds are group orbits. The generating Hamiltonian equations for such systems are analyzed. The analysis provides a large class of geometric integrators for mechanical systems. We apply the theory to two example systems: mechanical systems on matrix Lie groups and mechanical systems on the n-sphere. © 2012 IEEE.

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