A BIM-based value for money assessment in public-private partnership: an overall review

Public-private partnerships (PPPs) have proliferated and adapted to public development in recent decades; within it, the value for money (VfM) assessment defines the feasibility of the project procurement model as one of the essential components of PPP. However, evaluating the VfM in PPPs remains problematic. Given concerns about PPP profitability, a more integrated VfM evaluation is urgently needed to manage multiple indicators along the project lifecycle. Building information management (BIM), popular in architecture, engineering, and construction, provides resources that could support the VfM to a great extent. This paper uses a review approach to identify the current issues that are affecting VfM assessments and suggests that BIM, functioning throughout the PPP lifecycle, could support decision-making in VfM processes in order to satisfy service targets

1-D P- and S-wave velocity models for the collision zone between the northern Tianshan mountain and the Junggar basin based on local earthquake data

We have developed crustal minimum 1-D P- and S-wave velocity models of the collision zone between the northern Tianshan mountain and the Junggar basin (86°E–89°E, 43°N–44.5°N). These two models were created through inversion of 1 370 P- and 1 396 S-wave travel times from 173 well-constrained local earthquakes recorded by the Ürümqi sparse local seismic network and temporary seismic arrays. In contrast to previous models, our results indicate relatively low velocity at both shallow (<10 km) and deep (30–45 km) depths. The shallow zone is interpreted to be the result of thick surficial sedimentary deposits, whereas the deeper anomaly is interpreted to result from ductile shearing and lower crustal flow. Additionally, we detected several transition layers under the lower crust, which may imply structural complexity of the uppermost mantle in this region. The improved models reduce the RMS residual of earthquake locations by 41.7% from 1.2 to 0.5 seconds. The more accurately located hypocenters appear to correlate with prominent local over-thrusts, which underlie an anticlinal fold belt and several blind faults. Positive station corrections are observed near the Junggar basin, which likely reflects low wave velocity; negative corrections near the Tianshan mountain and Bogda mountain suggest high wave velocity.National Natural Science Foundation (China) (Grant 41204037)China Earthquake Administration (Basic Research Project Grant 2012IES010103

Conjugate fault deformation revealed by aftershocks of the 2013 Mw6.6 Lushan earthquake and seismic anisotropy tomography

The Lushan seismic dataset used in the manuscript entitled 'Conjugate fault deformation revealed by aftershocks of the 2013 Mw6.6 Lushan earthquake and seismic anisotropy tomography ' submitted to Geophysical Research Letters

Study on dynamic characteristics of gas films of spherical spiral groove hybrid gas bearings

According to the gas film force variation law, when the bearing axis is slightly displaced from the static equilibrium position, displacement and velocity disturbance relation expressions for the gas film force increment are constructed. Moreover, combined with the bearing rotor system motion equation, calculation model equations for the gas film stiffness and damping coefficients are established. The axial and radial vibration and velocity of the gas bearings during operation are collected. The instantaneous stiffness and damping coefficients of the gas film are calculated by the rolling iteration algorithm using MATLAB. The dynamic changes in the gas film stiffness and damping under different motion states are analyzed, and the mechanism of the gas film vortex and oscillation is studied. The results demonstrate the following: (1) When the gas bearing is running in the linear steady state in cycle 1, the dynamic pressure effect is enhanced and the stability is improved by increasing the eccentricity; when the gas supply pressure is increased, the static pressure effect is enhanced and the gas film vortex is reduced, but the oscillation is strengthened. (2) With the increase in rotational speed, the gas film vortex force gradually exceeds the gas film damping force, and the stability gradually worsens, causing a fluctuation in the gas film stiffness and damping, following which singularity occurs and a half-speed vortex is formed. Meanwhile, the gas film oscillation is intensified, and the rotor enters the nonlinear stable cycle 2 state operation. (3) As the fluctuation of the film force increases, the instantaneous stiffness and damping oscillation of the film intensifies, most of the stiffness and damping coefficients exhibit distortion, and the rotor operation will enter a chaotic or unstable state. Therefore, the gas bearing stiffness and damping variation characteristics can be used to study and predict the gas bearing operating state. Finally, measures for reducing the vortex and oscillation of the gas film and improving the stability of the gas bearing operation are proposed

Focal Mechanism Determination using High Frequency, Full Waveform Information

In this research, we use high frequency waveform information to determine the focal mechanisms of small local earthquakes at an oil reservoir. During the waveform inversion, we maximize both the phase and amplitude matching between the observed and synthetic waveforms. In addition, we use the polarities of the first P-wave arrivals and the S/P amplitude ratios to better constrain the matching between the synthetic and observed waveforms. The objective function is constructed to include all four criteria. Due to the complexity in the objective function, it is almost impossible to directly perform an inversion with derivative techniques. Instead, an optimized grid search method is used to search over all possible ranges of fault strike, dip and rake, as well as a predetermined range of earthquake locations. To speed up the algorithm, a library of Green‟s functions is pre-calculated for each of the moment tensor components and possible earthquake locations. Careful optimizations in filtering and cross-correlation are performed to further improve the grid search algorithm, such that no filtering and cross correlations are performed in searching through the parameter space of strike, dip, and rake. Consequently, speed is boosted tenfold by these optimizations in filtering and cross correlation. We apply the new method to induced seismic events in an oil reservoir. Satisfactory matching between synthetic and observed seismograms is obtained, as well as reasonable focal mechanisms, considering the local geological structure and possible causes for induced seismicity.Massachusetts Institute of Technology. Earth Resources Laborator

Homography Estimation Based on Order-Preserving Constraint and Similarity Measurement

Copyright 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.Homography is an important concept that has been extensively applied in many computer vision applications. However, accurate estimation of the homography is still a challenging problem. The classical approaches for robust estimation of the homography are all based on the iterative RANSAC framework. In this paper, we explore the problem from a new perspective by finding four point correspondences between two images given a set of point correspondences. The approach is achieved by means of an order-preserving constraint and a similarity measurement of the quadrilateral formed by the four points. The proposed method is computationally efficient as it requires much less iterations than the RANSAC algorithm. But this method is designed for small camera motions between consecutive frames in video sequences. Extensive evaluations on both synthetic data and real images have been performed to validate the effectiveness and accuracy of the proposed approach. In the synthetic experiments, we investigated and compared the accuracy of three types of methods and the influence of the proportion of outliers and the level of noise for homography estimation. We also analyzed the computational cost of the proposed method and compared our method with the state-of-the-art approaches in real image experiments. The experimental results show that the proposed method is more robust than the RANSAC algorithm

Focal Mechanism Determination Using High Frequency Waveform Matching and Its Application to Small Magnitude Induced Earthquakes

We present a new method using high frequency full waveform information to determine the focal mechanisms of small, local earthquakes monitored by a sparse surface network. During the waveform inversion, we maximize both the phase and amplitude matching between the observed and modeled waveforms. In addition, we use the polarities of the first P-wave arrivals and the average S/P amplitude ratios to better constrain the matching. An objective function is constructed to include all four criteria. An optimized grid search method is used to search over all possible ranges of source parameters (strike, dip and rake). To speed up the algorithm, a library of Green’s functions is pre-calculated for each of the moment tensor components and possible earthquake locations. Optimizations in filtering and cross-correlation are performed to further speed the grid search algorithm. The new method is tested on a 5-station surface network used for monitoring induced seismicity at a petroleum field. The synthetic test showed that our method is robust and efficient to determine the focal mechanism when using only the vertical component of seismograms in the frequency range of 3 to 9 Hz. The application to dozens of induced seismic events showed satisfactory waveform matching between modeled and observed seismograms. The majority of the events have a strike direction parallel with the major NE-SW faults in the region. The normal faulting mechanism is dominant, which suggests the vertical stress is larger than the horizontal stress.Massachusetts Institute of Technology. Earth Resources Laborator