Study of the Interfacial Bond Behavior between CFRP Grid–PCM Reinforcing Layer and Concrete via a Simplified Mechanical Model

This paper presents the results of pull-out tests conducted to investigate the interfacial bond behavior between a carbon-fiber-reinforced polymer (CFRP) grid–polymer cement mortar (PCM) reinforcing layer and existing concrete, and proposes a simplified mechanical model to further study the interface bond mechanism. Four specimens composed of a CFRP grid, PCM, and concrete were tested. The influence of the type of CFRP grid and the grid interval on the interface bond behavior was discussed. The failure patterns, maximum tensile loads, and CFRP grid strains were obtained. The change process of interface bond stress was investigated based on the grid strain analysis. In addition, the simplified mechanical model and finite element model (FEM) were emphatically established, and the adaptability of the simplified mechanical model was validated through the comparative analysis between the FEM results and the test results. The research results indicate that a CFRP grid with a larger cross-sectional area and smaller grid interval could effectively improve the interface bond behavior. The tensile stress was gradually transferred from the loaded edge to the free edge in the CFRP grid. The interface bond behavior was mainly dependent on the anchorage action of the CFRP grid in the PCM, and the bond action between the PCM and the concrete. The FEM results were consistent with the test results, and the simplified mechanical model with nonlinear springs could well describe the interface bond mechanism between the CFRP grid–PCM reinforcing layer and concrete.

The Community Velocity Model V.1.0 of Southwest China, Constructed from Joint Body- and Surface-Wave Travel-Time Tomography

Southwest China, located at the southeastern margin of the Tibetan plateau, plays an important role for the plateau growth and its material extrusion. It has complicated tectonic environment and strong seismic activities including the 2008 Wenchuan great earthquake. Numerous geophysical studies have been conducted in southwest China. However, a community velocity model (CVM) in this region is still not available, which makes it difficult to have a consistent catalog of earthquake locations and focal mechanisms and a consistent velocity model for simulating strong ground motions and evaluating earthquake hazards. In this study, we aim at building a high-resolution CVM (both VP and VS) of the crust and uppermost mantle in southwest China along with earthquake locations by joint inversion of body- and surface-wave travel-time data. In total, we have assembled 386,958 P- and 372,662 S-wave first arrival times and nearly 8100 Rayleigh-wave dispersion curves in the period band of 5–50 s. A multigrid strategy is adopted in the joint inversion. A coarser horizontal grid interval of 0.5° is first used and then a finer grid interval of 0.25° is used with initial models interpolated from the coarser-grid inverted velocity models. The spatial resolution of both VP and VS models can reach up to 0.5° horizontally and 10 km vertically according to the checkerboard tests. The comparisons of our inverted VP and VS models with those from other studies show general consistency in large-scale features. The inverted models are further validated by P-wave arrival times from active sources and Rayleigh-wave data. In general, our velocity models show two low-velocity zones in the middle-lower crust and a prominent high-velocity region in between them. Our new models have been served as the first version of the CVM in southwest China (SWChinaCVM-1.0) for future studies.

Minimising the computational time of a waveform based location algorithm

<p>Accurate and fast localisation of microseismic events is a requirement for a number of applications, e.g. mining, enhanced geothermal systems. New methods for event localisation have been proposed over the last decades. The waveform-based methods are of the most recent developed ones and their main advantage is the ability to locate weak seismic events. Despite this, these methods are demanding in terms of computational time, making real-time seismic event localisation very difficult. In this work, we further develop a waveform-based method, the Multichannel coherency migration method (MCM), to improve the computational time. The computational time for the MCM algorithm has been reported to linearly depend on several parameters, such as the number of stations, the length of the waveform time window, the computer architecture, and the volume of the area we are searching for the hypocentre. To minimise the computational time we need to decrease one or more of the above parameters without compromising the accuracy of the result. We break the localisation procedure into several steps: (1) we locate the event with a relatively large spatial grid interval which will give less potential hypocentral locations and less calculations as a result. (2) Based on the results of step (1) and the locations of maximum coherencies we decrease the grid volume to a quarter of the original volume and the spatial interval to half the original, focusing only around the area identified in step (1). Step (2) is repeated several times for decreased grid volumes and spatial intervals until the hypocentral location does not significantly change any more. We tested this approach on both synthetic and real data. We find that while the accuracy of the hypocentre is not compromised, the computational time is up to  125,000 times shorter.    </p>

Reliable Time Propagation Algorithms for PMF and RBPMF

This paper addresses the reliable time propagation algorithms for Point Mass Filter (PMF) and Rao–Blackwellized PMF (RBPMF) for the nonlinear estimaton problem. The conventional PMF and RBPMF process the probability diffusion for the time propagation with the direct sampled-values of the process noise. However, if the grid interval is not dense enough, it fails to represent the statistical characteristics of the noise accurately so the performance might deteriorate. To overcome that problem, we propose time propagation convolution algorithms adopting Moment Matched Gaussian Kernel (MMGK) on regular grids through mass linear interpolation. To extend the dimension of the MMGK that can accurately describe the noise moments up to the kernel length, we propose the extended MMGK based on the outer tensor product. The proposed time propagation algorithms using one common kernel through the mass linear interpolation not only improve the performance of the filter but also significantly reduce the computational load. The performance improvement and the computational load reduction of the proposed algorithms are verified through numerical simulations for various nonlinear models.

A COMPARATIVE MORPHOLOGICAL STUDY OF THE KOS-NISYROS-TILOS VOLCANOSEDIMENTARY BASINS

A swath bathymetric map of Kos-Nisyros-Tilos Volcanic field was created with 50m grid interval, with 10 m isobaths at a scale 1:100.000 using SEABEAM 1180 (180 kHz) multibeam system for depths <500m and SEABEAM 2120 (20 kHz) multibeam system for depths >500m. Five basins have been distinguished in the circum-volcanic area of Nisyros: 1)Eastern Kos basin, the larger and deeper one, with an average sea-bottom depth of 630m. Submarine canyons within the basin occur along the southern coastline of Kos cutting the isobaths from 150 up to 400m depth. A shallow crater with relative topography of ±70m has been discovered at the bottom of the basin (600-670m) 2)Western Kos basin with average depth of 520m. The basin is separated from the Eastern Kos Basin by a rise between Yali and Kos at 400m depth. This basin is separated from the Western Nisyros basin by the Kondeliousa rise. 3)The Western Nisyros basin is located between Kondeliousa rise and western Kos platform with depths of 550m. 4)The Southern Nisyros basin constitutes the northern end of the large Karpathos basin which reaches more than 2000m depth towards the south. 5)The Tilos basin with depths of 600m occurs southeast of Nisyros Island, separated from South Nisyros Basin through a rise of less than 400m depth. The Pachia-Pergoussa and Yali-Nisyros basins are shallow structures within the intra-volcanic relief of Nisyros and surrounding islets. The geometrty of each basin is discussed in relation to the volcanic and tectonic structure of the graben between Kos and Tilos.The intensity of the active geodynamic acrtivity is demonstrated by the creation of a volcanic relief of 1400m in the Nisyros volcanic field.

Designing a Sample of Cores to Estimate the Number of Features at a Site

Previous literature dealing with designing samples of points on a grid focuses on finding all the targets in a sample area, as would be the case when shovel-testing to discover features or sites within an impact zone. That goal will be achieved most efficiently using offset-square or hexagonal grid patterns. However, if the goal is to estimate the number of features based on a probability sample, the optimum design is actually a square grid with a grid interval greater than the target diameter. This surprising but welcome result is due to the interaction of several nonlinear relationships between the grid interval, the target size, the number of sample points, and the probability of intersecting a feature, combined with the fact that square grids can avoid edge-effect biases more efficiently than the other designs. The square also requires the lowest total travel time. Substantial additional cost-efficiency can be gained by using a cluster design with at least five clusters.

A Method of Optimized Utilization of Point-Wise Data Format in Monte Carlo Code

Monte Carlo codes are powerful and accurate tools for reactor core calculation. Most Monte Carlo codes use the point-wise data format, in which the data are given as tables of energy-cross section pairs. When calculating the cross sections at an incident energy value, it should be determined which grid interval the energy falls in. This procedure is repeated so frequently in Monte Carlo codes that its contribution in the overall calculation time can become quite significant. In this paper, the time distribution of Monte Carlo method is analyzed to illustrate the time consuming of cross section calculation. By investigation on searching and calculating cross section data in Monte Carlo code, a new search algorithm called hash table is elaborately designed to substitute the traditional binary search method in locating the energy grid interval. The results indicate that in the criticality calculation, hash table can save 5%∼17% CPU time, depending on the number of nuclides in the material, as well as complexity of geometry for particles tracking.

Mountain-Wave-Like Spurious Waves Associated with Simulated Cold Fronts due to Inconsistencies between Horizontal and Vertical Resolutions

A newly developed global nonhydrostatic model is used for life cycle experiments (LCEs) of baroclinic waves, and the resolution dependency of frontal structures is examined. LCEs are integrated for 12 days with horizontal grid intervals ranging from 223 to 3.5 km in a global domain. In general, fronts become sharper and corresponding vertical flow strengthens as horizontal resolution increases. However, if the ratio of vertical and horizontal grid intervals is sufficiently small compared to the frontal slope s, the overall frontal structure remains unchanged. In contrast, when the ratio of horizontal and vertical grid intervals exceeds 2s − 4s, spurious gravity waves are generated at the cold front. A linear model for mountain waves quantitatively explains the mechanism of the spurious waves. The distribution of the basic wind is the major factor that determines wave amplitude and propagation. The spurious waves propagate up to a critical level at which the basic wind speed normal to the front is equal to the propagation speed of the front. Results from the linear model suggest that an effective way to eliminate spurious waves is to choose a stretched grid with a smaller vertical grid interval in lower layers where strong horizontal winds exist.

Applicability of Large-Scale Convection and Condensation Parameterization to Meso-γ-Scale HIRLAM: A Case Study of a Convective Event

This paper presents a case study of a single cold air outbreak event with widespread convective precipitation over southern Finland on 25 May 2001. The purpose of the study is to investigate the applicability of the convection and condensation scheme of the High-Resolution Limited Area Model (HIRLAM) on meso-γ-scales. The study concentrates on the issue of grid-size-dependent convection parameterization. An explicit approach without the convection scheme is also examined. At the same time, the performance of an experimental nonhydrostatic version of HIRLAM is evaluated. Model simulations are conducted with three different horizontal grid spacings: 11, 5.6, and 2.8 km. Model results are compared to observed radar reflectivity data utilizing a radar simulation model, which calculates radar reflectivities from three-dimensional model output. The best results are obtained using nonhydrostatic dynamics and a grid-size-dependent convection scheme with a 5.6-km grid interval. However, even the best configuration still overestimates the area of strong reflectivity (intense precipitation). All the other combinations produce even stronger reflectivity. The grid-size-dependent convection parameterization is evidently beneficial at smaller grid spacings than 5.6 km. The nonhydrostatic model clearly outperforms its hydrostatic counterpart at the 5.6- and 2.8-km grid spacings, whereas with an 11-km grid interval, both models perform equally well.