Small Height Changes Research Articles

Radar Interferometry as a Comprehensive Tool for Monitoring the Fault Activity in the Vicinity of Underground Gas Storage Facilities

Underground gas storage facilities are an important element of the natural gas supply system. They compensate for seasonal fluctuations in natural gas consumption. Their expected lifetime is in tens of years. Continuous monitoring of underground gas storage is therefore very important to ensure its longevity. Periodic injection and withdrawal of natural gas can cause, among other things, vertical movements of the terrain surface. Radar interferometry is a commonly used method for tracking changes in the terrain height. It can register even relatively small height changes (mm/year). The primary aim of our research was to verify whether terrain behavior above a relatively deep underground gas storage can be monitored by this method and to assess the possibility of detecting the occurrence of anomalous terrain behavior in an underground gas storage area such as reactivation of faults in the area. The results show a high correlation between periodic injection and withdrawal of natural gas into/from the underground reservoir and periodic changes in terrain height above it (the amplitude of the height changes is in centimeters), which may allow the detection of anomalous phenomena. We documented special behavior of storage structures in the Vienna Basin: the areas adjacent to the underground gas storages show exactly the opposite phase of vertical movements, i.e., while the terrain above the underground reservoirs rises as natural gas is injected, the adjacent areas subside, and vice versa. Based on the analysis of geological conditions, we tend to conclude that this behavior is conditioned by the tectonic fault structure of the studied area.

Estimation of height changes of GNSS stations from the solutions of short vectors and PSI measurements

Abstract Time series of weekly and daily solutions for coordinates of permanent GNSS stations may indicate local deformations in Earth’s crust or local seasonal changes in the atmosphere and hydrosphere. The errors of the determined changes are relatively large, frequently at the level of the signal. Satellite radar interferometry and especially Persistent Scatterer Interferometry (PSI) is a method of a very high accuracy. Its weakness is a relative nature of measurements as well as accumulation of errors which may occur in the case of PSI processing of large areas. It is thus beneficial to confront the results of PSI measurements with those from other techniques, such as GNSS and precise levelling. PSI and GNSS results were jointly processed recreating the history of surface deformation of the area of Warsaw metropolitan with the use of radar images from Envisat and Cosmo-SkyMed satellites. GNSS data from Borowa Gora and Jozefoslaw observatories as well as from WAT1 and CBKA permanent GNSS stations were used to validate the obtained results. Observations from 2000–2015 were processed with the Bernese v.5.0 software. Relative height changes between the GNSS stations were determined from GNSS data and relative height changes between the persistent scatterers located on the objects with GNSS stations were determined from the interferometric results. The consistency of results of the two methods was 3 to 4 times better than the theoretical accuracy of each. The joint use of both methods allows to extract a very small height change below the level of measurement error.

114 PTFE/金属繊維積層材の引張りに伴う表面微小高度変化(材料力学III)

114 PTFE/金属繊維積層材の引張りに伴う表面微小高度変化(材料力学III)

Stability Analysis of a New Frame Formwork Support

Considering the structural characteristics of high-rise residential with regular plane design, simple load condition and small height change of standard floor, a new frame formwork support is proposed. According to eigenvalue buckling analysis, the research proves its stability bearing capacity and mechanics properties. MF1225 bearing capacity is determined by the out-of-plane stiffness. Ledger and bottom reinforcing tube improves the longitudinal stiffness and integrity in frame system.

High precision semiautomated computed tomography measurement of lumbar disk and vertebral heights

Evaluation of treatments of many spine disorders requires precise measurement of the heights of vertebral bodies and disk spaces. The authors present a semiautomated computer algorithm measuring those heights from spine computed tomography (CT) scans and evaluate its precision. Eight patients underwent two spine CT scans in the same day. In each scan, five thoracolumbar vertebral heights and four disk heights were estimated using the algorithm. To assess precision, the authors computed the differences between the height measurements in the two scans, coefficients of variation (CV), and 95% limits of agreement. Intraoperator and interoperator precisions were evaluated. For local vertebral and disk height measurement (anterior, middle, posterior) the algorithm was compared to a manual mid-sagittal plane method. The mean (standard deviation) interscan difference was as low as 0.043 (0.031) mm for disk heights and 0.044 (0.043) mm for vertebral heights. The corresponding 95% limits of agreement were [-0.085, 0.11] and [-0.10, 0.12] mm, respectively. Intraoperator and interoperator precision was high, with a maximal CV of 0.30%. For local vertebral and disk heights, the algorithm improved upon the precision of the manual mid-sagittal plane measurement by as much as a factor of 6 and 4, respectively. The authors evaluated the precision of a novel computer algorithm for measuring vertebral body heights and disk heights using short term repeat CT scans of patients. The 95% limits of agreement indicate that the algorithm can detect small height changes of the order of 0.1 mm.

WIND TUNNEL EXPERIMENT ON THE BUILDING HEIGHT DESIGN TO IMPROVE THE VENTILATION RATE IN A BUILT-UP AREA

In densely built-up area, the wind in the canopy layer is very weak, that causes the discomfort condition at the pedestrian level. In this paper, the possibility to improve the ventilation rate by changing the building height locally was investigated using the wind tunnel experiments. The ventilation rate in the narrow street was estimated by the mass transfer velocity in canyon wall that was measured by the originally devised water evaporation technique using filter paper. It was found that only small height change of wing-end building leads to the remarkable increase of ventilation rate over the whole traverse path.

DNA-tile-directed self-assembly of quantum dots into two-dimensional nanopatterns.

DNA-tile-directed self-assembly of quantum dots into two-dimensional nanopatterns.

Mesoscopic details of crack tip deformation field by application of differential interference contrast method

An experimental method is developed to examine the near tip deformation at the mesoscopic scale level. The differential interference contrast (DIC) method is used by application of the Nomarski prism in polarized microscope for measuring the out of surface deformation. The method is very sensitive to small height changes detected by different interference color. Discussed are results for the crack tip deformation field.

Noncontact Near-Field Scanning Optical Microscopy Imaging Using an Interferometric Optical Feedback Mechanism

An interferometric optical feedback mechanism is explored for tip-sample distance control in near-field scanning optical microscopy. An optical signal, based on the interference between the light exiting the tip aperture and that reflecting off the sample surface, is used to implement a feedback scheme to regulate tip-sample distance. The noncontact nature of this feedback mechanism may provide greater flexibility in imaging soft or fragile samples. To characterize the performance of the optical feedback mechanism, images are analyzed of a calibration standard, fluorescently doped lipid monolayers, latex spheres, and fixed cells. Images taken of these samples using optical feedback and the standard tapping-mode feedback are comparable in quality. These samples also demonstrate the ability of optical feedback to follow both large and small height changes and accurately reflect the sample topography. In a nonscanning mode, the interferometric signal can be used to noninvasively probe small dynamic height changes of sample with nanometric spatial resolution. Using a piezo ceramic bimorph to simulate sample movement, we show that nanometric height changes can be detected with millisecond time resolution. This may provide a unique way to probe protein conformational changes free of tip-sample interactions.

Single molecule detection and underwater fluorescence imaging with cantilevered near-field fiber optic probes

Tapping-mode near-field scanning optical microscopy (NSOM) employing a cantilevered fiber optic probe is utilized to image the fluorescence from single molecules and samples in aqueous environments. The single molecule fluorescence images demonstrate both the subdiffraction limit spatial resolution and low detection limit capabilities of the cantilevered probe design. Images taken as a function of tip oscillation drive amplitude reveal a degradation in the resolution as the amplitude is increased. With all cantilevered probes studied, however, a minimum plateau region in the resolution is reached as the drive amplitude is decreased, indicating that the tapping mode of operation does not reduce the optical resolution. Images of fluorescently doped lipid films illustrate the ability of the probe to track small height changes (<1.5 nm) in ambient and aqueous environments, while maintaining high resolution in the fluorescence image. When the tip is immersed in water (1.3 mm), the cantilevered NSOM tip resonance, 25–50 kHz, shifts approximately 100–150 Hz, the amplitude dampens less than 40% and the Q factor is reduced from 300–500 to 100–200.

Topographical analysis in the SEM using an automatic focusing technique

SUMMARYA novel technique for automated topographical analysis in the SEM has been investigated. It utilizes a 16‐bit minicomputer arranged to act as an automatic focusing unit. The computer is coupled to the objective lens of the microscope, by means of a digital to analogue converter, and may regulate the excitation of the lens under program control. Further digital‐to‐analogue converters allow the computer to act as a programmable scan generator by applying ramp waveforms to the scan amplifiers, permitting the beam to be swept over a small sub‐region of the field of interest. The video signal is sampled and applied to an analogue‐to‐digital converter; the resultant binary numbers are stored in computer memory as an array of values representing relative image intensities within a subregion. A differencing algorithm applied to the collected data allows the level of objective lens excitation to be found at which the sharpness of the image is optimized, and the excitation may be related to the working distance for that subregion through a previous calibration experiment. The sensitivity of the method for detecting small height changes is theoretically of the order of 1 μm.