Using tree stems in multi-temporal terrestrial lidar scanning data to monitor landslides on vegetated slopes     

van Veen  Megan  Porter  Michael  Lato  Matt  Mitchell  Andrew  Fish  Colleen  Van Gassen  Wim 《Landslides》2022,19(4):829-840

Landslides - Terrestrial lidar scanning (TLS) has become a widely accepted expert tool for monitoring geohazards on bare or sparsely vegetated slopes through change detection. While trees can be an...  相似文献   

Nonlinear behavior simulation of soil-structure interaction system via real-time hybrid testing     

Tang  Zhenyun  Liu  Hao  Dietz  Matt  Chatzigogos  Charisis T.  Du  Xiuli 《Bulletin of Earthquake Engineering》2022,20(11):6109-6128

Bulletin of Earthquake Engineering - Soil-structure interaction (SSI) can potentially compromise structures that are subjected to seismic excitation. In recent years, real-time hybrid testing...  相似文献   

GI Expertise          下载免费PDF全文

Matt Duckham 《Transactions in GIS》2015,19(4):499-515

This article concerns the identification of the expertise that GI scientists have in common. Rather than attempt to be exhaustive, the approach is to identify a minimal set of expert topics shared across GI science. In this article, a set of five expert topics is proposed for this purpose: structure, uncertainty, dynamism, language and cognition, and design with geographic information. The article then examines the extent to which the literature lends support for these five topics, using two analyses: first, a qualitative analysis of the papers found in the 2006 Classics from IJGIS; and second a citation analysis investigating the occurrences of keywords related to the proposed expert topics. The results suggest that these five areas of expertise do indeed tend to distinguish research in GI science from that in other fields, and in particular where the expert topics occur in combination. The establishment of an acknowledged core of shared expertise should assist in interdisciplinary research and teaching collaboration, usually founded on a shared understanding of what expertise different partners can contribute.  相似文献   

The diapcynal nutrient flux and shear-induced diapcynal mixing in the seasonally stratified western Irish Sea   总被引：1，自引：0，他引：1  

Tom P. Rippeth  Phil Wiles  Matt R. Palmer  Jonathan Sharples  Jacqueline Tweddle 《Continental Shelf Research》2009

We estimate the diapcynal nitrate flux in the seasonally stratified western Irish Sea using the dissipation method. By comparing the divergence of the reported benthic and diapcynal nitrate fluxes, we are able to explain much of the observed annual summer decline in deep-water nitrate at this location. We then show that the new production, fuelled by the diapcynal nitrate flux, is of a similar magnitude to that associated with the spring bloom. This suggests that the physical processes responsible for the diapcynal nitrate flux will set the limit on new production at this location. High-resolution mid-water column ADCP measurements show an average thermocline gradient Richardson number of 1, thus suggesting episodes of enhanced shear could result in shear instability, and therefore mixing within the thermocline. Bulk shear measurements reveal episodes of enhanced shear in the form of spikes, during which time the bulk shear vector takes the form of a clockwise rotating vector which has a period close to the local inertial period. The episodes of shear spikes are correlated to the wind and are consistent with observations made elsewhere. Estimates of profiles of the rate of dissipation of turbulent kinetic energy, based on microstructure velocity measurements, show that during a shear spike the dissipation rate within the thermocline, and therefore the buoyancy (and nitrate) flux, is enhanced by a factor of 4 when compared to periods with no shear spikes. Intermittent shear spikes are, therefore, an important mechanism for enhancing mixing across the shelf sea seasonal thermocline, and therefore delivery of nitrate to the euphotic zone, at this location.  相似文献   

Tidal gravity variations revisited at Vostok Station, Antarctica     

Koichiro Doi  Kazuo Shibuya  Anja Wendt  Reinhard Dietrich  Matt King 《Polar Science》2009,3(1):1-12

In 1969, prior to the discovery of the subglacial Lake Vostok, an Askania Gs-11 gravimeter was operated at Vostok Station (78.466°S, 106.832°E; 3478 m asl) to observe tidal gravity variations. To gain a better understanding of the lake's tidal dynamics, we reanalyzed these data using a Bayesian Tidal Analysis Program Grouping method (BAYTAP-G and -L programs). The obtained phase leads for the semidiurnal waves M2 (6.6 ± 2.1°) and S2 (10.1 ± 4.2°) are more pronounced than those of the diurnal waves, among which the largest phase lead (for K1) was 5.0 ± 0.5°. The obtained δ factor for M2 was 0.890 ± 0.032, significantly less than the theoretical value of 1.16. For three global ocean tide models (NAO99b, FES2004, and TPXO6.2), the estimated load tides on waves Q1, O1, P1, K1, M2, and S2 range from 0.1–0.2 μGal (Q1 and S2) to 0.6–0.7 μGal (K1). The difference in amplitude among the three models is less than 0.14 μGal (M2), and the difference in phase is generally less than 10°. In calculating the residual tide vectors using the ocean models, the TPXO6.2 model generally gave the smallest residual amplitudes. Our result for the K1 wave was anomalously large (1.36 ± 0.25 μGal), while that for the M2 wave was sufficiently small (0.37 ± 0.17 μGal). The associated uncertainty is half that reported in previous studies. It is interesting that the residual K1 tide is approximately 90° phase-leaded, while the M2 tide is approximately 180° phase-leaded (delayed). Importantly, a similar reanalysis of data collected at Asuka Station (71.5°S, 24.1°E) gave residual tides within 0.2–0.3 μGal for all major diurnal and semidiurnal waves, including the K1 wave. Therefore, the anomalous K1 residual tide observed at Vostok Station must be linked to the existence of the subglacial lake and the nature of solid–ice–water dynamics in the region.  相似文献   

Reventador Volcano 2005: Eruptive activity inferred from seismo-acoustic observation     

Jonathan M. Lees  Jeffrey B. Johnson  Mario Ruiz  Liliana Troncoso  Matt Welsh 《Journal of Volcanology and Geothermal Research》2008

Reventador Volcano entered an eruptive phase in 2005 which included a wide variety of seismic and infrasonic activity. These are described and illustrated: volcano-tectonic, harmonic tremor, drumbeats, chugging and spasmodic tremor, long period and very long period events. The recording of this simultaneous activity on an array of three broadband, seismo-acoustic instruments provides detailed information of the state of the conduit and vent during this phase of volcanic eruption. Quasi-periodic tremor at Reventador is similar to that observed at other volcanoes and may be used as an indicator of vent aperture. Variations in the vibration modes of the volcano, frequency fluctuations and rapid temporal fluctuations suggest the influx of new material, choking of the vent and possible modification of the conduit geometry during explosions and effusion over a period of six weeks.  相似文献   

Numerical simulation of dynamic soil–structure interaction in shaking table testing     

Dimitris Pitilakis  Matt Dietz  David Muir Wood  Didier Clouteau  Arezou Modaressi 《Soil Dynamics and Earthquake Engineering》2008,28(6):453-467

This paper provides an insight into the numerical simulation of soil–structure interaction (SSI) phenomena studied in a shaking table facility. The shaking table test is purposely designed to confirm the ability of the numerical substructure technique to simulate the SSI phenomenon. A model foundation–structure system with strong SSI potential is embedded in a dry bed of sand deposited within a purpose designed shaking-table soil container. The experimental system is subjected to a strong ground motion. The numerical simulation of the complete soil–foundation–structure system is conducted in the linear viscoelastic domain using the substructure approach. The matching of the experimental and numerical responses in both frequency and in time domain is satisfying. Many important aspects of SSI that are apparent in the experiment are captured by the numerical simulation. Furthermore, the numerical modelling is shown to be adequate for practical engineering design purposes.  相似文献   

Measuring accelerometer dynamic range from seismic data using Allan deviation          下载免费PDF全文

Matt McDonald  Patrik Stigborg 《Geophysical Prospecting》2018,66(5):934-941

We propose a new approach for calculating the dynamic range of an accelerometer based on an Allan deviation analysis of production seismic data. This test is intended as a field audit technique and does not require an unconditioned dataset from a low‐noise environment. We first show that Allan deviation can measure white noise levels using two commercial accelerometers. The analysis accurately captures the manufacturing noise density specifications and known relationships between white noise, preamplifier gain, and group forming. We then show that a production seismic dataset is suitable for an Allan deviation analysis because the results are not critically affected by a recording filter. Finally, we illustrate the proposed technique by calculating the dynamic range of an accelerometer channel in a seismic streamer using a production dataset.  相似文献   

Experimental and computational synergy for modelling an advanced gas-cooled reactor core under seismic excitation     

Luiza Dihoru  Olafur Oddbjornsson  Ben Cannell  Adam J. Crewe  Tony Horseman  Matt Dietz  Colin A. Taylor 《地震工程与结构动力学》2020,49(13):1308-1328

The advanced gas-cooled reactors (AGRs) are the backbone of the United Kingdom's nuclear generation fleet, producing approximately 17% of the country's electricity. Their safety cases are supported by thorough inspection and monitoring of their graphite cores and extensive theoretical, analytical, and experimental studies. This paper presents a unique, highly innovative and technically challenging earthquake engineering project that has provided vital evidence to underpin the seismic safety assessments of the AGRs. Two modelling approaches, one experimental (a multilayer array physical model), and one numerical (a SOLFEC nonsmooth contact dynamics computational model) have been developed to investigate the seismic behaviour of an aged graphite core. The synergetic relationship between the two approaches is a product of insightful collaborative learning between the University of Bristol and Atkins, with the experiments providing material parameters and validation data and the computer simulations feeding array design and test schedule recommendations to the physical model. The predictive capabilities of the physical and the numerical models are tested by direct comparison and the good agreement between the results has increased the confidence in both. The model's versatility allows a variety of core scenarios to be tested that can explore in detail the AGR core behaviour in seismic conditions.  相似文献   

Migration Propensities,Patterns, and the Role of Human Capital: Comparing Mexican,Cuban, and Puerto Rican Interstate Migration, 1985–1990     

Matt Foulkes  K. Bruce Newbold 《The Professional geographer》2000,52(1):133-145

This paper expands the human capital model to compare the migration propensities of Cubans, Mexicans, and Puerto Ricans within the U.S. between 1985 and 1990. Using the 5% PUMS from the 1990 U.S. Census, both aggregate migration streams and micro‐level migration propensities are estimated for Cubans, Mexicans, and Puerto Ricans. The effects of personal factors, the economic environment, and the presence of fellow nationals are examined in the context of larger geographic patterns, and discussed in terms of each nationality's immigration history and cultural context. While many factors effect migration behavior similarly, there are notable differences in the way education, English fluency, and unemployment rate affect migration propensity of the native‐born and foreign‐born of each nationality. Differences are also apparent at the macro‐level. Puerto Ricans show signs of dispersing out of New York; Mexicans are redistributing within the Southwest; and Cubans are re‐concentrating in Florida. Both levels of analysis point to how immigration history, settlement patterns, and cultural context influence migration behavior. The results demonstrate the benefits of using an expanded human capital approach to explain migration differences, and highlight the diversity of population redistribution occurring within Hispanic nationalities.  相似文献