In military applications, underwater vehicles do not communicate with each other. They use sonar systems to detect enemy vehicles that are trying hard not to make any sound or noise. In autonomous/unmanned underwater ...
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In military applications, underwater vehicles do not communicate with each other. They use sonar systems to detect enemy vehicles that are trying hard not to make any sound or noise. In autonomous/unmanned underwater vehicles (AUVs, UUVs), sonar systems are usually employed to detect or avoid underwater obstacles. With the emergence of sQuba, a new breed of car that can be driven both on land and underwater, we explore a new sonar problem. How can an underwater moving vehicle verify the location of senders? As conventional sonar techniques are not appropriate for our purpose, we present a hybrid sonar algorithm that can help underwater vehicles locate target vehicles.
Retinal detachment results in visual loss and requires surgical treatment. The risk of retinal detachment depends, among other factors, on the vitreous rheology, which varies with age. To date, the viscoelasticity of ...
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Retinal detachment results in visual loss and requires surgical treatment. The risk of retinal detachment depends, among other factors, on the vitreous rheology, which varies with age. To date, the viscoelasticity of the vitreous body has only been measured in cadaver eyes. However, the ex vivo and in vivo viscoelasticity may differ as a result of the effect of intravitreal membranes. Therefore, an MRI method and appropriate postprocessing tools were developed to determine the vitreous deformation and viscoelastic properties in the eyes of living humans. Nineteen subjects (eight women and 11 men;mean age, 33years;age range, 14-62years) gazed at a horizontal sinusoidal moving target during the segmented acquisition of complementary spatial modulation of magnetization images. The center of the lens and the scleral insertion of the optic nerve defined the imaging plane. The vitreous deformation was tracked with a dedicated algorithm and fitted with the commonly used viscoelastic model to determine the model parameters: the modified Womersley number a and the phase angle b. The vitreous deformation was successfully quantified in all 17 volunteers having a monophasic vitreous. The mean and standard deviation of the model parameters were determined to be 5.5 +/- 1.3 for a and -2.3 +/- 0.2 for b. The correlation coefficient (-0.76) between a and b was significant. At the eye movement frequency used, the mean storage and loss moduli of the vitreous were around 3 +/- 1hPa. For two subjects, the vitreous deformation was clearly polyphasic: some compartments of the vitreous were gel-like and others were liquefied. The borders of these compartments corresponded to reported intravitreal membrane patterns. Thus, the deformation of the vitreous can now be determined in situ, leaving the structure of the intravitreal membranes intact. Their effect on vitreous dynamics challenges actual vitreous viscoelastic models. The determination of the vitreous deformation will aid in the quant
The North Pacific is an area where sub-synoptic Polar Lows frequently form during the cold season, especially over the Bering Sea, Gulf of Alaska and Japan Sea. So far, a multi-decadal climatology of such Polar Lows b...
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The North Pacific is an area where sub-synoptic Polar Lows frequently form during the cold season, especially over the Bering Sea, Gulf of Alaska and Japan Sea. So far, a multi-decadal climatology of such Polar Lows based on individual cases has not been assembled. Here, we consider dynamical downscaling method for realistically constructing the formation and life cycles of such lows over the past 6 decades without exploiting sub-synoptic information in initial fields. To do so, a regional climate model is conditioned by large-scale information of NCEP re-analyses. We test the approach by examining its skill in simulating ten known cases of North Pacific Polar Lows. Three of these are discussed in some detail. The signatures of all storms emerge in the simulations with additional sub-synoptic details. The tracks of the simulated Polar Lows closely follow the tracks derived from satellite imagery. We conclude that the suggested method is suitable for constructing multi-decade climatologies, including trends and variability, of Polar Lows in the North Pacific by dynamically downscaling NCEP re-analyses.
With the wide application of photoelectric equipments in military and civilian areas such as aviation, arms control etc., high-speed image acquisition and real-time processing attracted more and more attention. In ord...
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ISBN:
(纸本)9780819488350
With the wide application of photoelectric equipments in military and civilian areas such as aviation, arms control etc., high-speed image acquisition and real-time processing attracted more and more attention. In order to acquire the accurate position information of beacon in photoelectric tracking system quickly, a embedded high frame-rate CMOS beacon position system based on davinci technology was presented. This system could detect the beacon and acquire its position information with high-speed. Using CMOS sensor MT9M001 as detector, this system could capture image and calculated centroid at different speed. It used centroid algorithm based on double gate object tracking strategy to acquire the spot centroid and can process image of 600x550 resolution at 130fps. The system was characterized by dynamic reconfiguration and high efficiency of computation. It could be applied in photoelectric tracking and space laser communication.
This paper presents an assistive robotic system, for which the user can interact with a mobile robot using a haptic interface, for senior and disabled people. The system consists of a nonholonomic PeopleBot mobile rob...
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This paper presents an assistive robotic system, for which the user can interact with a mobile robot using a haptic interface, for senior and disabled people. The system consists of a nonholonomic PeopleBot mobile robot and a Phantom Omni haptic interface. Several technical problems related to the system are addressed and solved. Specifically, the backstepping technique is used, and a new tracking algorithm is developed for the robot to follow the user on a 2-D space. An adaptive fuzzy logic-based windowing method is proposed to solve the velocity estimation problem in the controller. A simple haptic rendering algorithm is designed to generate the haptic feedback based on the position error. Experiments show that the user can guide the movement of the robot quite easily and smoothly using the haptic interface.
A custom designed and manufactured gimbal with a wide field-of-view and fast response time is developed. This enhanced custom design is a 24 volt system with integrated motor controllers and drivers which offers a ful...
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ISBN:
(纸本)9780819484604
A custom designed and manufactured gimbal with a wide field-of-view and fast response time is developed. This enhanced custom design is a 24 volt system with integrated motor controllers and drivers which offers a full 180 degrees field-of-view in both azimuth and elevation;this provides a more continuous tracking capability as well as increased velocities of up to 479 per second. The addition of active high-frequency vibration control, to complement the passive vibration isolation system, is also in development. The ultimate goal of this research is to achieve affordable, reliable, and secure air-to-air laser communications between two separate remotely piloted aircraft. As a proof-of-concept, the practical implementation of an air-to-ground laserbased video communications payload system flown by a small Unmanned Aerial Vehicle (UAV) will be demonstrated. A numerical tracking algorithm has been written, tested, and used to aim the airborne laser transmitter at a stationary ground-based receiver with known GPS coordinates;however, further refinement of the tracking capabilities is dependent on an improved gimbal design for precision pointing of the airborne laser transmitter. The current gimbal pointing system is a two-axis, commercial-off-the-shelf component, which is limited in both range and velocity. The current design is capable of 360 degrees of pan and 78 degrees of tilt at a velocity of 60 degrees per second. The control algorithm used for aiming the gimbal is executed on a PC-104 format embedded computer onboard the payload to accurately track a stationary ground-based receiver. This algorithm autonomously calculates a line-of-sight vector in real-time by using the UAV autopilot's Differential Global Positioning System (DGPS) which provides latitude, longitude, and altitude and Inertial Measurement Unit (IMU) which provides the roll, pitch, and yaw data, along with the known Global Positioning System (GPS) location of the ground-based photodiode array recei
A thermally driven mushy cell tracking algorithm for phase-change problems with a moving boundary is presented. The equation used to track the moving boundary is based on energy balance over the mushy cell and is appl...
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A thermally driven mushy cell tracking algorithm for phase-change problems with a moving boundary is presented. The equation used to track the moving boundary is based on energy balance over the mushy cell and is applied to advance a moving front in a cell-by-cell manner. The efficacy of the tracking algorithm is demonstrated on specific problems solved using the finite volume method. An implicit scheme is adopted to ensure that the numerical solution is unconditionally stable in time. A preconditioned conjugated gradient (P-CG) solver is implemented to ensure that solutions converge in a finite number of iterations. Four benchmark cases are used to validate the algorithm including solidification in one dimensional space (two-region problem), melting of pure aluminum in two-dimensional (2D) space, solidification with periodic boundary conditions, and solidification of one-region problem. The results obtained show that the current algorithm is capable of converging to accurate solutions for moving fronts and the numerical predications are in excellent agreement with corresponding analytical solutions.
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