APOLLO: the Apache Point Observatory Lunar Laser-ranging Operation: Instrument Description and First Detections

A next-generation lunar laser ranging apparatus using the 3.5 m telescope at the Apache Point Observatory in southern New Mexico has begun science operation. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) has achieved one-millimeter range precision to the moon which should lead to approximately one-order-of-magnitude improvements in the precision of several tests of fundamental properties of gravity. We briefly motivate the scientific goals, and then give a detailed discussion of the APOLLO instrumentation.Comment: 37 pages; 10 figures; 1 table: accepted for publication in PAS

Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Most Likely Separation of Intensity and Warping Effects in Image Registration

This paper introduces a class of mixed-effects models for joint modeling of spatially correlated intensity variation and warping variation in 2D images. Spatially correlated intensity variation and warp variation are modeled as random effects, resulting in a nonlinear mixed-effects model that enables simultaneous estimation of template and model parameters by optimization of the likelihood function. We propose an algorithm for fitting the model which alternates estimation of variance parameters and image registration. This approach avoids the potential estimation bias in the template estimate that arises when treating registration as a preprocessing step. We apply the model to datasets of facial images and 2D brain magnetic resonance images to illustrate the simultaneous estimation and prediction of intensity and warp effects

Feature based estimation of myocardial motion from tagged MR images

In the past few years we witnessed an increase in mortality due to cancer relative to mortality due to cardiovascular diseases. In 2008, the Netherlands Statistics Agency reports that 33.900 people died of cancer against 33.100 deaths due to cardiovascular diseases, making cancer the number one cause of death in the Netherlands [33]. Even if the rate of people affected by heart diseases is continually rising, they "simply don’t die of it", according to the research director Prof. Mat Daemen of research institute CARIM of the University of Maastricht [50]. The reason for this is the early diagnosis, and the treatment of people with identified risk factors for diseases like ischemic heart disease, hypertrophic cardiomyopathy, thoracic aortic disease, pericardial (sac around the heart) disease, cardiac tumors, pulmonary artery disease, valvular disease, and congenital heart disease before and after surgical repair. Cardiac imaging plays a crucial role in the early diagnosis, since it allows the accurate investigation of a large amount of imaging data in a small amount of time. Moreover, cardiac imaging reduces costs of inpatient care, as has been shown in recent studies [77]. With this in mind, in this work we have provided several tools with the aim to help the investigation of the cardiac motion. In chapters 2 and 3 we have explored a novel variational optic flow methodology based on multi-scale feature points to extract cardiac motion from tagged MR images. Compared to constant brightness methods, this new approach exhibits several advantages. Although the intensity of critical points is also influenced by fading, critical points do retain their characteristic even in the presence of intensity changes, such as in MR imaging. In an experiment in section 5.4 we have applied this optic flow approach directly on tagged MR images. A visual inspection confirmed that the extracted motion fields realistically depicted the cardiac wall motion. The method exploits also the advantages from the multiscale framework. Because sparse velocity formulas 2.9, 3.7, 6.21, and 7.5 provide a number of equations equal to the number of unknowns, the method does not suffer from the aperture problem in retrieving velocities associated to the critical points. In chapters 2 and 3 we have moreover introduced a smoothness component of the optic flow equation described by means of covariant derivatives. This is a novelty in the optic flow literature. Many variational optic flow methods present a smoothness component that penalizes for changes from global assumptions such as isotropic or anisotropic smoothness. In the smoothness term proposed deviations from a predefined motion model are penalized. Moreover, the proposed optic flow equation has been decomposed in rotation-free and divergence-free components. This decomposition allows independent tuning of the two components during the vector field reconstruction. The experiments and the Table of errors provided in 3.8 showed that the combination of the smoothness term, influenced by a predefined motion model, and the Helmholtz decomposition in the optic flow equation reduces the average angular error substantially (20%-25%) with respect to a similar technique that employs only standard derivatives in the smoothness term. In section 5.3 we extracted the motion field of a phantom of which we know the ground truth of and compared the performance of this optic flow method with the performance of other optic flow methods well known in the literature, such as the Horn and Schunck [76] approach, the Lucas and Kanade [111] technique and the tuple image multi-scale optic flow constraint equation of Van Assen et al. [163]. Tests showed that the proposed optic flow methodology provides the smallest average angular error (AAE = 3.84 degrees) and L2 norm = 0.1. In this work we employed the Helmholtz decomposition also to study the cardiac behavior, since the vector field decomposition allows to investigate cardiac contraction and cardiac rotation independently. In chapter 4 we carried out an analysis of cardiac motion of ten volunteers and one patient where we estimated the kinetic energy for the different components. This decomposition is useful since it allows to visualize and quantify the contributions of each single vector field component to the heart beat. Local measurements of the kinetic energy have also been used to detect areas of the cardiac walls with little movement. Experiments on a patient and a comparison between a late enhancement cardiac image and an illustration of the cardiac kinetic energy on a bull’s eye plot illustrated that a correspondence between an infarcted area and an area with very small kinetic energy exists. With the aim to extend in the future the proposed optic flow equation to a 3D approach, in chapter 6 we investigated the 3D winding number approach as a tool to locate critical points in volume images. We simplified the mathematics involved with respect to a previous work [150] and we provided several examples and applications such as cardiac motion estimation from 3-dimensional tagged images, follicle and neuronal cell counting. Finally in chapter 7 we continued our investigation on volume tagged MR images, by retrieving the cardiac motion field using a 3-dimensional and simple version of the proposed optic flow equation based on standard derivatives. We showed that the retrieved motion fields display the contracting and rotating behavior of the cardiac muscle. We moreover extracted the through-plane component, which provides a realistic illustration of the vector field and is missed by 2-dimensional approaches

Variations In Ice Flow And Glaciers Over Time And Space

Thesis (Ph.D.) University of Alaska Fairbanks, 2003Ice flows and glaciers change over many time and spatial scales. Glacier surfaces evolve over decades, and this change affects the glacier-climate interaction. When a mass balance is computed using an outdated map, that computation does not reveal actual mass change. We present a method by which a mass balance computed with an outdated map can be transformed into actual mass change. While the actual volume change of a glacier is relevant to hydrological studies, the change that would have occurred on a static surface is more relevant to certain glacier dynamics problems and most climate problems. We term this the reference-surface balance and propose that such a balance is better correlated to climatic variations than the conventional one. Ice responds to stresses over time scales from seconds to millennia. We observed this using two independent strain-gauge systems to measure the strain rates as functions of depth and time at Siple Dome, Antarctica. One system employed optical fibers to measure annual strain rates over 175 m depth intervals. The other used one-meter resistance wires to measure strain approximately hourly at discrete depths. The long-term average strain rates from the two systems agreed to within 16%. The time-dependent strain rates measured beneath the divide by the resistance-wire gauges included intermittent strain events lasting up to 24 hours. We used the results from each system to compute an age-depth relationship assuming a time-independent ice flow geometry. Equilibrium line altitudes are related to climate, and they vary from year to year and among neighboring glaciers. We measured a regional pattern of equilibrium lines using remote sensing. Our goals were to evaluate the accuracy of such measurements, and to assess the spatial and temporal variability of the resulting data. Individual glacier equilibrium line altitudes varied by 100 m relative to a smoothed surface, and inter-annual variations in equilibrium line altitudes at one glacier were 74 m. A map of the regional pattern of equilibrium line altitudes shows variations of 1000 meters from the south to the north side of the range, but no major trend from east to west

Oceanus.

v. 42, no. 1 (2000

Hydromechanical Well Testing Using a 3D Fiber Optic Extensometer

Some fractured rock formations hold important resources, such as water, hydrocarbons or heat, whereas others are good candidates for waste disposal. Hydromechanical well tests have been developed to improve characterization of formation properties and parameter distributions by measuring displacement along with pressure while stressing a well. The displacement that occurs during a well test depends on the geometry of fractures or other sources of permeability, as well as the distribution of compliance or elastic modulus. Current methods of hydromechanical well testing, measures axial displacements along a wellbore, which may cause ambiguity in interpretations when 3-D components of deformation are present. The objectives of this research are to develop an instrument that can measure deformation of rock enveloping wells in three dimensions using technology that will facilitate applications over a wide range of conditions, and demonstrate the performance of this device during well tests in shallow wells in fractured rock. The approach is to use fiber optic strain gauges attached to a flexible coupling, which can move through 5 degrees of freedom. The device that was developed, which will be called the 3DX, has the capability to be lowered in a borehole, anchored into a desired section for testing, and deployed in a different location or removed from the borehole. Transverse displacement is calculated by taking the difference of strain measured between two opposing gauges, whereas axial displacement is calculated from the average displacement of the gauges. The RMS noise level of a 5-minute sample at 1 Hz is 80 nm in the axial direction, and 250 nm in the transverse direction based on field data and calibration factors determined in the lab. Field tests were conducted in Japan in the summer of 2011, and in Clemson, SC and Trenton, NJ during summer, 2012. The field tests show that the 3DX compressed axially approximately 3 to 6 per meter of drawdown and extended axially when the pressure increases. The transverse displacement was approximately 6 to 12 towards the south-southeast during the tests at Clemson in fractured gneiss at a depth of 25m. This is similar to the tilt direction from tiltmeters, providing a field validation of the measurements. The interpretation is that tilting is caused by a fracture that strikes roughly E-W and dips to the south. During ambient conditions in an open borehole the 3DX responds to changes in barometric pressure by closing approximately 0.15 with a 2 cm change in head when the water level rises and opening similarly when the water level drops. The results suggest that 3D displacement can be measured during pumping and ambient monitoring in a rock enveloping borehole. The inclusion of the transverse displacement signal allows fracture orientation to be evaluated