Range Of Centimeters Research Articles

Distributed fiber optic shape sensing along shotcrete tunnel linings: Methodology, field applications, and monitoring results

Deformation monitoring and structural reliability assessment are key components in modern conventional tunneling. The state-of-the-art monitoring design is usually based on displacement measurements of geodetic targets using total stations paired with pointwise geotechnical sensors inside the tunnel lining. In recent years, distributed fiber optic sensing (DFOS) has become more popular in tunneling applications. DFOS measurements basically deliver internal strain and temperature distributions, but no direct relation to the tunnel shape’s behavior. This paper introduces a novel sensing and evaluation concept, which combines DFOS strain measurements and geodetic displacement readings for distributed shape assessment along curved structures, such as tunnel cross-sections. The designed system was implemented into shotcrete tunnel cross-sections as well as shaft linings and enables the determination of displacement profiles with high spatial resolution in the range of centimeters. Evaluations of continuous monitoring campaigns over several weeks as well as epoch-wise measurements performed by different DFOS sensing units in combination with stochastic analysis demonstrate the high potential of the developed approach and its capability to extend traditional monitoring methods in tunneling.

High-Quality UAV-Based Orthophotos for Cadastral Mapping: Guidance for Optimal Flight Configurations

During the past years, unmanned aerial vehicles (UAVs) gained importance as a tool to quickly collect high-resolution imagery as base data for cadastral mapping. However, the fact that UAV-derived geospatial information supports decision-making processes involving people’s land rights ultimately raises questions about data quality and accuracy. In this vein, this paper investigates different flight configurations to give guidance for efficient and reliable UAV data acquisition. Imagery from six study areas across Europe and Africa provide the basis for an integrated quality assessment including three main aspects: (1) the impact of land cover on the number of tie-points as an indication on how well bundle block adjustment can be performed, (2) the impact of the number of ground control points (GCPs) on the final geometric accuracy, and (3) the impact of different flight plans on the extractability of cadastral features. The results suggest that scene context, flight configuration, and GCP setup significantly impact the final data quality and subsequent automatic delineation of visual cadastral boundaries. Moreover, even though the root mean square error of checkpoint residuals as a commonly accepted error measure is within a range of few centimeters in all datasets, this study reveals large discrepancies of the accuracy and the completeness of automatically detected cadastral features for orthophotos generated from different flight plans. With its unique combination of methods and integration of various study sites, the results and recommendations presented in this paper can help land professionals and bottom-up initiatives alike to optimize existing and future UAV data collection workflows.

Magnetic Field-Assisted Self-Wound 3-D Nanomembrane Capacitors Bridge the Gap Between MLCC and Trench Capacitor Technologies

This letter reports the transformation of large-area planar metal–insulator–metal (MIM) nanomembrane capacitors into compact tubular 3-D architectures. By combining the powerful approach of strain-induced nanomembrane self-assembly with an external magnetic field, a stable winding process over a large distance in the range of centimeters is demonstrated. A wet release platform based on encapsulated methyl cellulose allows to release the planar structures with rates of several $100~\mu \text{m}$ /s from their substrate. Footprint shrinkage factors up to 230 are shown by assembling 24-mm long planar structures into 3-D architectures having 82- $\mu \text{m}$ diameter and ~120 windings. The fabricated capacitors feature a capacitance per footprint up to $1.3~\mu \text{F}$ /mm2 for a 15-nm Al2O3 dielectric with less than 100-nA/ $\mu \text{F}$ leakage at 6 V and improved frequency characteristics. This technology is a promising candidate for bridging the gap between discrete multilayer ceramic capacitor (MLCC) and ON-chip trench capacitor technologies.

The smallest known Palaeozoic mantis shrimp specimen, and possibilities for where to find more

Mantis shrimps are fierce predatory crustaceans in modern day oceans. Fossils of mantis shrimps are still a rarity. They occurred back in the Carboniferous, 300 million years ago, but already with quite a diversity of different forms. Interestingly, all these fossils are comparably large, usually several centimetres body length. From the Mesozoic, numerous mantis shrimp fossils have also been reported, the largest specimens being far in the centimetre range as well, but the smallest specimens being only about 4–5 mm. With this data set, we can reconstruct aspects of the life history for (at least some) Mesozoic mantis shrimps, but not for Palaeozoic forms. We report here a new fossil mantis shrimp specimen from the Carboniferous Bear Gulch limestones, USA. The specimen is quite small, in its rolled-up position about 10 mm across the laterally preserved body, but 25 mm in estimated total length. This is considerably shorter than any mantis shrimp so far known from the Palaeozoic. Hence, the specimen provides an important data point. Furthermore, it provides some indications where we could possibly find more specimens of comparable or even smaller size: The specimen resembles certain co-occurring fossils, representatives of Cyclida, in some aspects, suggesting that among the material of Cyclida we might find more small-sized mantis shrimps.

Recent Progress in NIR-II Contrast Agent for Biological Imaging.

Fluorescence imaging technology has gradually become a new and promising tool for in vivo visualization detection. Because it can provide real-time sub-cellular resolution imaging results, it can be widely used in the field of biological detection and medical detection and treatment. However, due to the limited imaging depth (1–2 mm) and self-fluorescence background of tissue emitted in the visible region (400–700 nm), it fails to reveal biological complexity in deep tissues. The traditional near infrared wavelength (NIR-I, 650–950 nm) is considered as the first biological window, because it reduces the NIR absorption and scattering from blood and water in organisms. NIR fluorescence bioimaging's penetration is larger than that of visible light. In fact, NIR-I fluorescence bioimaging is still interfered by tissue autofluorescence (background noise), and the existence of photon scattering, which limits the depth of tissue penetration. Recent experimental and simulation results show that the signal-to-noise ratio (SNR) of bioimaging can be significantly improved at the second region near infrared (NIR-II, 1,000–1,700 nm), also known as the second biological window. NIR-II bioimaging is able to explore deep-tissues information in the range of centimeter, and to obtain micron-level resolution at the millimeter depth, which surpass the performance of NIR-I fluorescence imaging. The key of fluorescence bioimaging is to achieve highly selective imaging thanks to the functional/targeting contrast agent (probe). However, the progress of NIR-II probes is very limited. To date, there are a few reports about NIR-II fluorescence probes, such as carbon nanotubes, Ag2S quantum dots, and organic small molecular dyes. In this paper, we surveyed the development of NIR-II imaging contrast agents and their application in cancer imaging, medical detection, vascular bioimaging, and cancer diagnosis. In addition, the hotspots and challenges of NIR-II bioimaging are discussed. It is expected that our findings will lay a foundation for further theoretical research and practical application of NIR-II bioimaging, as well as the inspiration of new ideas in this field.

Satellite based Navigational System Errors

When two or more signals of the satellite signals arrives through a GPS antenna with different tracks it leads to multipath phenomenon. The two main classifications of multipath phenomenon are specular and diffuse multipath. In the multipath pertaining to specular phenomenon the signals of GPS are reverberated through relatively sleek surfaces resulting in unsystematic errors within both pseudorange and carrier phase measurements. In contrast, diffuse phenomenal multipath is considered when the signal of GPS is incidental along a rough exterior where the reverberated signals are dispersed in various directions and generally they are unrelated in time period domain and it is noisy in activity. The stated unsystematic in-accurateness tin to be significant and leads to misconceptions of meters in the range in regard of pseudo range and for phase measurements at a range of a few centimeters . As the positioning mechanism needs to be be precised needs the straight path betwixt the satellites and a receiver, as the phenomenon of multipath doesn’t exist. The phenomenal multipath occurrences for the associated misconceptions in a GPS apparents eventually evidences for navigational misconceptions. Topical studies on GPS and its applications stimulate the necessitate for an improved multipath characterization techniques, to have an increased admiration for the spatial complexity and sequential of specific- position multipath environments.

Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu

C-type asteroids are among the most pristine objects in the Solar System, but little is known about their interior structure and surface properties. Telescopic thermal infrared observations have so far been interpreted in terms of a regolith-covered surface with low thermal conductivity and particle sizes in the centimetre range. This includes observations of C-type asteroid (162173) Ryugu1–3. However, on arrival of the Hayabusa2 spacecraft at Ryugu, a regolith cover of sand- to pebble-sized particles was found to be absent4,5 (R.J. et al., manuscript in preparation). Rather, the surface is largely covered by cobbles and boulders, seemingly incompatible with the remote-sensing infrared observations. Here we report on in situ thermal infrared observations of a boulder on the C-type asteroid Ryugu. We found that the boulder’s thermal inertia was much lower than anticipated based on laboratory measurements of meteorites, and that a surface covered by such low-conductivity boulders would be consistent with remote-sensing observations. Our results furthermore indicate high boulder porosities as well as a low tensile strength in the few hundred kilopascal range. The predicted low tensile strength confirms the suspected observational bias6 in our meteorite collections, as such asteroidal material would be too frail to survive atmospheric entry7. The MASCOT lander observed a boulder on the surface of asteroid Ryugu up close. The boulder’s low thermal inertia is closer to fine regolith or comets rather than stony boulders, indicating high porosity and low tensile strength. Orbit measurements confirm that Ryugu’s surface is covered with similar boulders.

Development of an Antenna Grid of a Centimetric Range in the MIMO System for Determining Coordinates of Objects

In this work, a block diagram of a system to determine the location of a moving object or objects, which is using the technology of the MIMO (Multiple Input Multiple Output), is proposed. For this system, a microstrip antenna array was modeled and manufactured as an emitter. The numerical modeling of the lattice was carried out using the CADFEKO software package. Based on the obtained simulation results, the operative embodiment was made of the antenna array.

COMPARISON OF DIVER-OPERATED UNDERWATER PHOTOGRAMMETRIC SYSTEMS FOR CORAL REEF MONITORING

Abstract. Underwater photogrammetry is a well-established technique for measuring and modelling the subaquatic environment in fields ranging from archaeology to marine ecology. While for simple tasks the acquisition and processing of images have become straightforward, applications requiring relative accuracy better then 1:1000 are still considered challenging. This study focuses on the metric evaluation of different off-the-shelf camera systems for making high resolution and high accuracy measurements of coral reefs monitoring through time, where the variations to be measured are in the range of a few centimeters per year. High quality and low-cost systems (reflex and mirrorless vs action cameras, i.e. GoPro) with multiple lenses (prime and zoom), different fields of views (from fisheye to moderate wide angle), pressure housing materials and lens ports (dome and flat) are compared. Tests are repeated at different camera to object distances to investigate distance dependent induced errors and assess the accuracy of the photogrammetrically derived models. An extensive statistical analysis of the different systems is performed and comparisons against reference control point measured through a high precision underwater geodetic network are reported.

Streamer and leader breakdown in air at atmospheric pressure in strongly non-uniform fields in gaps less than one metre

The breakdown in synthetic air at 100 kPa in rod-plane arrangements at 50 mm gap and in atmospheric air in the range of a few centimeters to some ten centimeters was investigated at positive polarity. Different shapes of the rods (spherical and sharp cut) were used to investigate the influence of the details of the electric field at the tips. Optical diagnostics using an image intensifier and a photomultiplier tube was applied to determine the relevant breakdown mechanisms. Streamer crossing was observed at typical average fields of about 4 to 5 kV/cm. Breakdown occurred at significantly higher fields via leader propagation or streamer-to-spark transition. The experimental results are compared to a simple 1D leader model and to breakdown data from literature. A reasonable description of experimental values by the leader model is seen.

Nonvisible satellite estimation algorithm for improved uav navigation in mountainous regions

Global Navigation Satellite System (GNSS) is one of the most used technologies around the world for navigation. This technology is integrated in aircraft, ship, and submarine guidance systems; it is available in cell phones and cars, and also used to monitor Earth surface movements. The system accuracy spans from a range of a few centimeters up to meters. This variation is related to different sources of error such as the receiver clock error, Earth's ionospheric and tropospheric signal delay [1], or multipath effect in semiobstructed areas. If the surrounding objects have highly reflective surfaces, the error magnitude might surge to several hundred meters due to multiple reflections that the signal experiences before reaching the receiving antenna. A further source of error is present when the same signal is received more than once. As the present work is focused only on the effect of nonvisible satellites, multipath effect is not further investigated.

ROCK GLACIER MONITORING USING AERIAL PHOTOGRAPHS: CONVENTIONAL VS. UAV-BASED MAPPING – A COMPARATIVE STUDY

Abstract. Rock glaciers are creep phenomena of mountain permafrost. Typically, these landforms look like lava flows from a bird’s eye view. Active rock glaciers move downslope with flow velocities in the range of few centimeters to several meters per year. Thus, large masses of rock and ice can be gradually transported down-valley. In this paper we present a comparative study analyzing surface change for Tschadinhorn rock glacier, a relatively fast moving rock glacier located in the Hohe Tauern Range of the Austrian Alps. Aerial photographs (1954–2017) of both metric (conventional) and non-metric (UAV-based) aerial surveys were compared to derive multi-annual to annual flow vector fields and surface height change. For each time interval given we computed a single representative value for flow velocity and, if applicable, also for area-wide surface height change, i.e. volume change. The velocity graph obtained represents the temporal evolution of the kinematics of the rock glacier with good discrimination. Volume change was difficult to quantify since temporal changes were rather small and close to insignificance. The precision and accuracy of the results obtained were numerically quantified. Our study showed that for the Tschadinhorn rock glacier UAV-based aerial surveys can substitute conventional aerial surveys as carried out by national mapping agencies, such as the Austrian Federal Office of Metrology and Surveying (BEV). Thus, UAV-based aerial surveys can help to bridge the data gap between regular aerial surveys. The high accuracy of the UAV-derived results would even allow intra-annual change detection of flow velocity.

Interdigitated cantilever array topology for low frequency MEMS vibration energy harvesting

Micro-fabricated vibration energy harvesters enable merits such as miniaturisation, economies of scale for manufacturing, and ease of integration with semiconductor IC technologies. However, the frequency range of ambient vibration is generally low (10’s Hz to 100’s Hz). Existing MEMS vibration energy harvesters that target these frequencies typically are in the centimetre scale range. This sacrifices the miniaturisation aspect as well as introducing new challenges in packaging and integration for the unconventionally large MEMS devices. This paper proposes a new interdigitated fork cantilever array topology, which allows for up to about a third reduction in resonant frequency compared to the classical cantilever topology, for the same design area and without compromising on power optimisation. Further resonant frequency reduction is also possible, but at the expense of power optimisation. This opens up design flexibility to achieve low frequency MEMS resonators that are more suitable to practically target ambient vibration, without sacrificing the aforementioned merits of MEMS technology.

Contribution of UAS to the monitoring at the Lärchberg-Galgenwald landslide (Austria)

ABSTRACTIn April 2001, a rock fall occurred at the landslide Lärchberg-Galgenwald, Austria. The movement of this landslide has been under observation for decades, but the methods used so far have several disadvantages. This article aims to show that unmanned aerial systems (UAS) provide a reasonable alternative in terms for monitoring the landslide. At the landslide, we focused on the most active area to (i) record changes of the landslide’s surface, (ii) assess the accuracy of the resulting data, (iii) assess whether the number of ground control points (GCPs) could be reduced in subsequent UAS surveys, and (iv) conclude whether UAS-based recording is favourable compared to common terrestrial methods. UAS imagery, acquired under challenging site conditions in November 2015 and May 2016, were processed to digital elevation models and orthophotos with a ground sampling distance of 0.04 m, which should display expected changes of up to ~0.17 m (relating to previously reported movements of up to 30 cm a−1) for the same period of time. Using DEM differencing, we calculated a vertical difference that was in the range of a few centimetres in most cases with only a few localized areas of much larger change. The latter are mainly related to single objects moving such as rock blocks or tree trunks. Apart from that, no general surface elevation lowering (a threshold of 0.27 m was used to distinguish significant from insignificant changes) could be detected. Based on the resulting orthophotos, we calculated vectors of horizontal displacement, which confirmed that the changes are related to single objects and revealed that in upcoming flight campaigns the number of GCPs can be generously reduced with an acceptable loss of positional accuracy. Therefore, the suitability of UAS for expanding the monitoring approaches used at Lärchberg-Galgenwald landslide is described.

Accurate millimetre and submillimetre rest frequencies for cis- and trans-dithioformic acid, HCSSH

Context. A better understanding of sulphur chemistry is needed to solve the interstellar sulphur depletion problem. A way to achieve this goal is to study new S-bearing molecules in the laboratory, obtaining accurate rest frequencies for an astronomical search. We focus on dithioformic acid, HCSSH, which is the sulphur analogue of formic acid. Aims. The aim of this study is to provide an accurate line list of the two HCSSH trans and cis isomers in their electronic ground state and a comprehensive centrifugal distortion analysis with an extension of measurements in the millimetre and submillimetre range. Methods. We studied the two isomers in the laboratory using an absorption spectrometer employing the frequency-modulation technique. The molecules were produced directly within a free-space cell by glow discharge of a gas mixture. We measured lines belonging to the electronic ground state up to 478 GHz, with a total number of 204 and 139 new rotational transitions, respectively, for trans and cis isomers. The final dataset also includes lines in the centimetre range available from literature. Results. The extension of the measurements in the mm and submm range lead to an accurate set of rotational and centrifugal distortion parameters. This allows us to predict frequencies with estimated uncertainties as low as 5 kHz at 1 mm wavelength. Hence, the new dataset provided by this study can be used for astronomical search.

Self-Localization Based on Visual Lane Marking Maps: An Accurate Low-Cost Approach for Autonomous Driving

Autonomous driving in public roads requires precise localization within the range of few centimeters. Even the best localization systems based on GNSS cannot always reach this level of precision, especially in an urban environment, where the signal is disturbed by surrounding buildings and artifacts. Recent works have shown the advantage of using maps as a precise, robust, and reliable way of localization. Typical approaches use the set of current readings from the vehicle sensors to estimate its position on the map. The approach presented in this paper exploits a short-range visual lane marking detector and a dead reckoning system to construct a registry of the detected back lane markings corresponding to the last 240 m driven. This information is used to search in the map the most similar section, to determine the vehicle localization in the map reference. Additional filtering is used to obtain a more robust estimation for the localization. The accuracy obtained is sufficiently high to allow autonomous driving in a narrow road. The system uses a low-cost architecture of sensors and the algorithm is light enough to run on low-power embedded architecture.

Self-localization based on visual lane marking maps

Autonomous driving in public roads requires precise localization within the range of few centimeters. Even the best localization systems based on GNSS cannot always reach this level of precision, especially in an urban environment, where the signal is disturbed by surrounding buildings and artifacts. Recent works have shown the advantage of using maps as a precise, robust, and reliable way of localization. Typical approaches use the set of current readings from the vehicle sensors to estimate its position on the map. The approach presented in this paper exploits a short-range visual lane marking detector and a dead reckoning system to construct a registry of the detected back lane markings corresponding to the last 240 m driven. This information is used to search in the map the most similar section, to determine the vehicle localization in the map reference. Additional filtering is used to obtain a more robust estimation for the localization. The accuracy obtained is sufficiently high to allow autonomous driving in a narrow road. The system uses a low-cost architecture of sensors and the algorithm is light enough to run on low-power embedded architecture.

Measurements of partially lubricated contacts on different scales

AbstractThis paper focuses on experimental investigations for lubricated contacts with partially filled gaps. The measurements are performed on two different scales. A pin‐on‐disc test bench represents the microscopic scale whereas a novel test bench with asperities in the range of centimeters corresponds to a rather macroscopic scale. The results are compared and conclusions towards the tribological properties are drawn. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Numerical simulation of electric field enhancement at the contact of positive and negative streamers in relation to the problem of runaway electron generation in lightning and in long laboratory sparks

The hypothetical mechanism of electric field amplification at contact of positive and negative streamers in a streamer corona up to magnitudes required for the generation of runaway electrons and secondary Bremsstrahlung in the x-ray range, observed in long spark discharges in the open atmosphere, is analyzed. The development of two streamers, moving towards each other in interelectrode gaps of the centimetre range, is numerically simulated at applied voltages from 73 to 250 kV. It is shown that the size of the domain with strong electric field, with intensity sufficient for the thermal electron runaway, is of 1–2 mm. The mean field intensity in this domain increases up to magnitudes of ≈250–280 kV cm−1. The maximum energy, to which electrons are capable of energizing in such field, is in the range of 20–70 keV. However, the electron energy is limited by an extremely small life-time of the strong field domain (less than 20 ps).

A Low Cost Sensors Approach for Accurate Vehicle Localization and Autonomous Driving Application.

Autonomous driving in public roads requires precise localization within the range of few centimeters. Even the best current precise localization system based on the Global Navigation Satellite System (GNSS) can not always reach this level of precision, especially in an urban environment, where the signal is disturbed by surrounding buildings and artifacts. Laser range finder and stereo vision have been successfully used for obstacle detection, mapping and localization to solve the autonomous driving problem. Unfortunately, Light Detection and Ranging (LIDARs) are very expensive sensors and stereo vision requires powerful dedicated hardware to process the cameras information. In this context, this article presents a low-cost architecture of sensors and data fusion algorithm capable of autonomous driving in narrow two-way roads. Our approach exploits a combination of a short-range visual lane marking detector and a dead reckoning system to build a long and precise perception of the lane markings in the vehicle’s backwards. This information is used to localize the vehicle in a map, that also contains the reference trajectory for autonomous driving. Experimental results show the successful application of the proposed system on a real autonomous driving situation.