Characterizing Deformation of Buildings from Videos

We have started to explore the feasibility of extracting useful data on the deformation of buildings and structures based on optical videos, (Taghavi Larigani & Heaton). In the beginning, we look at the characterizations and limitations of the hardware, which is composed of a high-quality digital camera, combined with its optical imaging system capturing a video-footage of the structure under test, and then introduce a straightforward targets-tracking algorithm that produces the time-series displacements of targets that we select on the video. We performed preliminary measurements consisting of testing our targets-tracking algorithm using high definition format videos displaying the structures that we wanted to test. The measurements pertain to a 1) finite-element software-generated video of JPL/NASA principal building, 2) YouTube-video of a seismic dynamic test of a building, 3) YouTube-video of the Millennium London Bridge “Wobbly Bridge”, 4) YouTube-video of a United Boeing 777, 4) YouTube-video of NASA space shuttle rockets during launch. So far, our tests are encouraging. If our approach proves viable, it can be transformative for the field of earthquake engineering and structural health monitoring. Hence, we consider the prospect of using our technique for surveying buildings and other civil structures in high seismic risk urban agglomerations. In parallel, the same technique could be applied for 1) real-time structural health monitoring of civil structures, 2) nuclear plants, 3) oil and gas infrastructures, 4) rail & road networks, 5) aircraft, 6) spacecraft, 7) etc., by simply analyzing the structure-facing camera recorded data

Tunable semiconductor lasers

Tunable semiconductor lasers are disclosed requiring minimized coupling regions. Multiple laser embodiments employ ring resonators or ring resonator pairs using only a single coupling region with the gain medium are detailed. Tuning can be performed by changing the phase of the coupling coefficient between the gain medium and a ring resonator of the laser. Another embodiment provides a tunable laser including two Mach-Zehnder interferometers in series and a reflector coupled to a gain medium

Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations

Optical resonator and laser applications

The invention discloses a semi-ring Fabry-Perot (SRFP) optical resonator structure comprising a medium including an edge forming a reflective facet and a waveguide within the medium, the waveguide having opposing ends formed by the reflective facet. The performance of the SRFP resonator can be further enhanced by including a Mach-Zehnder interferometer in the waveguide on one side of the gain medium. The optical resonator can be employed in a variety of optical devices. Laser structures using at least one SRFP resonator are disclosed where the resonators are disposed on opposite sides of a gain medium. Other laser structures employing one or more resonators on one side of a gain region are also disclosed

Optical resonator

The invention discloses a semi-ring Fabry-Perot (SRFP) optical resonator structure comprising a medium including an edge forming a reflective facet and a waveguide within the medium, the waveguide having opposing ends formed by the reflective facet. The performance of the SRFP resonator can be further enhanced by including a Mach-Zehnder interferometer in the waveguide on one side of the gain medium. The optical resonator can be employed in a variety of optical devices. Laser structures using at least one SRFP resonator are disclosed where the resonators are disposed on opposite sides of a gain medium. Other laser structures employing one or more resonators on one side of a gain region are also disclosed

A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks

A method has been developed for unambiguously measuring the exact magnetic field experienced by trapped mercury ions contained within an atomic clock intended for space applications. In general, atomic clocks are insensitive to external perturbations that would change the frequency at which the clocks operate. On a space platform, these perturbative effects can be much larger than they would be on the ground, especially in dealing with the magnetic field environment. The solution is to use a different isotope of mercury held within the same trap as the clock isotope. The magnetic field can be very accurately measured with a magnetic-field-sensitive atomic transition in the added isotope. Further, this measurement can be made simultaneously with normal clock operation, thereby not degrading clock performance. Instead of using a conventional magnetometer to measure ambient fields, which would necessarily be placed some distance away from the clock atoms, first order field-sensitive atomic transition frequency changes in the atoms themselves determine the variations in the magnetic field. As a result, all ambiguity over the exact field value experienced by the atoms is removed. Atoms used in atomic clocks always have an atomic transition (often referred to as the clock transition) that is sensitive to magnetic fields only in second order, and usually have one or more transitions that are first-order field sensitive. For operating parameters used in the (199)Hg(+) clock, the latter can be five orders of magnitude or more sensitive to field fluctuations than the clock transition, thereby providing an unambiguous probe of the magnetic field strength

Cycle Time Reduction in Trapped Mercury Ion Atomic Frequency Standards

The use of the mercury ion isotope (201)Hg(+) was examined for an atomic clock. Taking advantage of the faster optical pumping time in (201)Hg(+) reduces both the state preparation and the state readout times, thereby decreasing the overall cycle time of the clock and reducing the impact of medium-term LO noise on the performance of the frequency standard. The spectral overlap between the plasma discharge lamp used for (201)Hg(+) state preparation and readout is much larger than that of the lamp used for the more conventional (199)Hg(+). There has been little study of (201)Hg(+) for clock applications (in fact, all trapped ion clock work in mercury has been with (199)Hg(+); however, recently the optical pumping time in (201)Hg(+) has been measured and found to be 0.45 second, or about three times faster than in (199)Hg(+) due largely to the better spectral overlap. This can be used to reduce the overall clock cycle time by over 2 seconds, or up to a factor of 2 improvement. The use of the (201)Hg(+) for an atomic clock is totally new. Most attempts to reduce the impact of LO noise have focused on reducing the interrogation time. In the trapped ion frequency standards built so far at JPL, the optical pumping time is already at its minimum so that no enhancement can be had by shortening it. However, by using (201)Hg(+), this is no longer the case. Furthermore, integrity monitoring, the mechanism that determines whether the clock is functioning normally, cannot happen faster than the clock cycle time. Therefore, a shorter cycle time will enable quicker detection of failure modes and recovery from them

Airfoil shape optimization using improved simple genetic algorithm (ISGA)

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.To study the efficiency of genetic algorithms (GAs) in the optimization of aerodynamic shapes, the shape of an airfoil was optimized by a genetic algorithm to obtain maximum lift to drag ratio and maximum lift. The flow field is assumed to be two dimensional, Invicsid, transonic and is analyzed numerically. The camber line and thickness distribution of the airfoil were modeled by a fourth order polynomial. The airfoil chord length was assumed constant. Also, proper boundary conditions were applied. A finite volume method using the first order Roe’s flux approximation and time marching (explicit) method was used for the flow analysis. The simple genetic algorithm (SGA) was used for optimization. This algorithm could find the optimum point of this problem in an acceptable time frame. Results show that the GA could find the optimum point by examining only less than 0.1% of the total possible cases. Meanwhile, effects of parameters of GA such as population size in each generation, mutation probability and crossover probability on accuracy and speed of convergence of this SGA were studied. These parameters have very small effects on the accuracy of the genetic algorithm, but they have a sensible effect on speed of convergence. The parameters of this genetic algorithm were improved to obtain the minimum run time of optimization procedure and to maximize the speed of convergence of this genetic algorithm. Robustness and efficiency of this algorithm in optimizing the shape of the airfoils were shown. Also, by finding the optimum values of its parameters, maximum speed and minimum run time was obtained. It is shown that for engineering purposes, the speed of GAs is incredibly high, and acceptable results are sought by a fairly low number of generations of computations.cs201

Theory, Fabrication and Applications of a Novel Archetype Semi-Ring Fabry-Perot (SRFP) Resonator and New Tiltmeters

The first instinct of any animal (including human) is surviving, which implies security. It impacts how we perceive the whole universe. The best way of satisfying this need, consists of being able to control situations in which we are immersed. One way of doing so, consists of predicting future events. That is why we perceive and model our environment based on cyclic and periodic events, going back to the earliest civilizations. Few examples of such periodic events are: The rotation of earth around the sun, which illustrates a spatial cyclic event. The alternate of day and night, which illustrates a temporal cyclic event. So modeling any sort of event happening in our environment by repetitive events allows us to enforce a secure feeling, since (periodic, cyclic) events have the advantage of being able to be foreseen, which provides the advantage of being well understood. Most of the devices fabricated by human beings are inspired by the perception of its environment, and somehow in most cases we just copy nature. Few examples are: Airplanes are similar to birds. Submarines are similar to whales or sharks. That is why basic tools of many applied and engineering sciences are resonators, which are engineered devices that generate or sustain periodic or cyclic events. One example of a resonator is a guitar. The string can just take a certain finite number of shapes since it is bounded on its two extremes. Any excitation of the string can be decomposed as the excitation of each one of these shapes, which would repeat itself after one round trip. These shapes are called the resonant mode of the string. Each note (the music coming out of it) of the guitar corresponds to one of its resonant modes. The same way that we use a basis to describe a vector (for example x and y in the case of two dimensional vector), we can use the resonant modes as a basis to describe any intensity within the resonator. Therefore in the case of the guitar, any vibration of the string can be decomposed on a set of vibrations of each resonator mode, where the intensity of vibration of each mode is independent of the others. What differentiates any vibration of the string from another is the intensity with which this vibration couple, to each resonant mode. The same way that the guitar is a mechanical resonator, we can think of an electromagnetic resonator. The same way an electromagnetic resonator has different resonant modes, and each intensity couple to the resonator can be decomposed on a set of intensity of each resonant mode. Another example is at the atomic scales, where the atoms within a molecule have specific repetitive vibration and rotation patterns, which are called the resonant modes. The overall concept of a resonator is the same whether it is mechanical or electromagnetic one. The basic concept of a resonator is based upon a feedback, which guarantees the repetition of an event. At the root there are no more than two ways of obtaining such feedback. 1. The first idea consists of forcing the feedback. Due to this feed back the same event would happen at the same time if it is a temporal event or at the same location if it is a spatial event. By confining the event within a (temporal or spatial) barrier, and by being sure that the event would bounce back at that barrier, we would have created such a feedback. Such a specific barrier is often called a reflector. In the case of a mechanical resonator, such a reflector could be a wall. As an example, when someone talks within a confined structure, their voice gets echoed or resonates and in some cases the voice generated by the speaker would get back to him. This is a resonant phenomenon. Another example is if someone who is confined in a medium separated by two walls throws a ball to one of the walls. In a specific case, where the trajectory of the ball repeats itself, we talk about resonance. The same structure is also used in an electromagnetic resonator where the two reflectors are now electromagnetic reflectors. In the case of optics, the reflectors would be mirrors. In that case, the feedback would be obtained by confining an optical medium (a waveguide) within two optical reflectors (mirrors). Such a structure is the most basic archetype resonator in optics and was invented 100 years ago, and was named after its inventors Fabry-Perot. Fundamentally, this structure is very similar to the mechanical resonator obtained with the help of two walls. 2. Another way of thinking of such a feedback is by assuring that either the temporal or spatial path used by the events would be repeated. This can be obtained if the path shape is closed. An example of such structure is a circular shape. In this thesis, we present a completely novel resonator that in addition to having both the advantages of the first and the second types of resonators, has its own specific features. We have called this resonator a Semi-Ring Fabry-Perot (SRFP) resonator. In order to better understand this resonator we will focus ourselves in the field of optics, which emphasizes the best on the wave particularity of resonators. As we will see almost all optical resonators could be modeled as combinations of Fabry-Perot and ring resonators. These devices are the most important letter of the alphabet of the optics, where any device behaves like a word obtained with the combinations of the letters composing the alphabet, similar to introducing a new letter to the alphabet. Thus, we can with the use of this new letter create new words, which are new devices and could be useful. The benefit of the novel resonator that we introduce is beyond the scope of this thesis, where mostly optical applications of the resonator have been introduced. At the end of the thesis, we will introduce a novel way of measuring the incidence tilt of a field using a resonator.</p

An Archetype Semi-Ring Fabry-Perot (SRFP) Resonator

We introduce and demonstrate the generation of a novel resonator, termed Semi-Ring Fabry-Perot (SRFP), that exhibits unique features, such as, its use of one plane mirror, allowing the SRFP to be easily fabricated as a symmetrical device. In addition to its unique features, it exhibits advantages of ring and Fabry-Perot resonators: 1) compared to a ring resonator that only allows a transmitted intensity, the Semi-Ring Fabry-Perot (SRFP) supports standing waves, allowing both a reflected and transmitted intensity; 2) the reflected light spectrum of the SRFP resonator is much narrower than similar Fabry-Perot, implying higher finesse