Estimation of the Squirt-Flow Length Based on Crack Properties in Tight Sandstones

A novel treatment for the stability of a class of linear time invariant (LTI) systems with rationally independent multiple time delays using the Direct Method (DM) is studied. Since they appear in many practical applications in the systems and control community, this class of dynamics has attracted considerable interest. The stability analysis is very complex because of the infinite dimensional nature (even for single delay) of the dynamics and furthermore the multiplicity of these delays. The stability problem is much more challenging compared to the TDS with commensurate time delays (where time delays have rational relations). It is shown in an earlier publication of the authors that the DM brings a unique, exact and structured methodology for the stability analysis of commensurate time delayed cases. The transition from the commensurate time delays to multiple delay case motivates our study. It is shown that the DM reveals all possible stability regions in the space of multiple time delays. The systems that are considered do not have to possess stable behavior for zero delays. We present a numerical example on a system, which is considered “prohibitively difficult” in the literature, just to exhibit the strengths of the new procedure.

Download Full-text

Observations of wave velocity and attenuation in two‐phase media

Geophysics ◽

10.1190/1.1442072 ◽

1986 ◽

Vol 51 (12) ◽

pp. 2193-2199 ◽

Cited By ~ 7

Author(s):

G. W. Purnell

Keyword(s):

Physical Model ◽

Wave Velocity ◽

Wave Attenuation ◽

P Wave ◽

Rubber Matrix ◽

Two Phase ◽

P Wave Velocity ◽

Porosity And Permeability ◽

Dispersion And Attenuation ◽

Scattering Losses

The velocity and attenuation of a wave transmitted through a two‐phase material are functions of the material’s composition. In physical model experiments, I used suspensions of grains in a silicone rubber matrix to reduce or avoid uncertainties about framework elastic constants, porosity, and permeability that result from using fluid‐saturated grain frameworks. I varied the composition to produce materials that are useful in physical seismic modeling. In the tested suspensions, ultrasonic P-wave velocity, velocity dispersion, and attenuation all increase with grain concentration and frequency. I compared seven published mathematical models for wave propagation in two‐phase media. One given by Mehta most closely agrees with the P-wave velocities I observed. The agreement is sufficiently close to merit use of Mehta’s model in the design of physical model materials. The observed P-wave attenuation generally increases approximately linearly with frequency. This approximate linearity leads to reliable constant-Q estimates, ranging from 187 to 16 for grain concentrations from 0 to 0.49. I conclude that relative motion between the grains and the rubber matrix contributes most of the observed attenuation at lower concentrations, whereas scattering losses become much more important at higher concentrations and frequencies.

Download Full-text

Practical Applications of X-Ray Line Profile Analysis

Materials Science and Engineering ◽

10.4018/978-1-5225-1798-6.ch043 ◽

2017 ◽

pp. 1094-1132

Author(s):

Jenő Gubicza

Keyword(s):

Crystallite Size ◽

Twin Boundary ◽

Line Profile ◽

Profile Analysis ◽

Vacancy Concentration ◽

Direct Method ◽

Line Profile Analysis ◽

Line Profiles ◽

X Ray ◽

Practical Applications

In the previous chapters, the theory and the main methods of diffraction peak profile analysis were presented. Additionally, the specialties in the measurement and the evaluation of line profiles in the cases of thin films and single crystals were discussed. In this chapter, some practical considerations are given in order to facilitate the evaluation of peak profiles and the interpretation of the results obtained by this method. For instance, the procedures for instrumental correction are overviewed. Additionally, how the prevailing dislocation slip systems and twin boundary types in hexagonal polycrystals can be determined from line profiles is shown. Besides the dislocation density, the vacancy concentration can also be obtained by the combination of electrical resistivity, calorimetric, and line profile measurements. The crystallite size and the twin boundary frequency determined by X-ray peak profile analysis are compared with the values obtained by the direct method of transmission electron microscopy. Furthermore, the limits of line profile analysis in the determination of crystallite size and defect densities are given. Finally, short overviews on the results obtained by peak profile analysis for metals, ceramics, and polymers are presented.

Download Full-text

Practical Applications of X-Ray Line Profile Analysis

X-Ray Line Profile Analysis in Materials Science ◽

10.4018/978-1-4666-5852-3.ch009 ◽

2014 ◽

pp. 271-318

Keyword(s):

Crystallite Size ◽

Twin Boundary ◽

Line Profile ◽

Profile Analysis ◽

Vacancy Concentration ◽

Direct Method ◽

Line Profile Analysis ◽

Line Profiles ◽

X Ray ◽

Practical Applications

In the previous chapters, the theory and the main methods of diffraction peak profile analysis were presented. Additionally, the specialties in the measurement and the evaluation of line profiles in the cases of thin films and single crystals were discussed. In this chapter, some practical considerations are given in order to facilitate the evaluation of peak profiles and the interpretation of the results obtained by this method. For instance, the procedures for instrumental correction are overviewed. Additionally, how the prevailing dislocation slip systems and twin boundary types in hexagonal polycrystals can be determined from line profiles is shown. Besides the dislocation density, the vacancy concentration can also be obtained by the combination of electrical resistivity, calorimetric, and line profile measurements. The crystallite size and the twin boundary frequency determined by X-ray peak profile analysis are compared with the values obtained by the direct method of transmission electron microscopy. Furthermore, the limits of line profile analysis in the determination of crystallite size and defect densities are given. Finally, short overviews on the results obtained by peak profile analysis for metals, ceramics, and polymers are presented.

Download Full-text

Person Search via Deep Integrated Networks

Applied Sciences ◽

10.3390/app10010188 ◽

2019 ◽

Vol 10 (1) ◽

pp. 188

Author(s):

Ju-Chin Chen ◽

Cheng-Feng Wu ◽

Chun-Huei Chen ◽

Cheng-Rong Lin

Keyword(s):

Accuracy Rate ◽

Integrated Networks ◽

Practical Applications ◽

Detection And Identification ◽

Person Search ◽

Background Clutter ◽

Manual Processing ◽

Active Research ◽

Bounding Boxes ◽

Problem Setting

This study proposes an integrated deep network consisting of a detection and identification module for person search. Person search is a very challenging problem because of the large appearance variation caused by occlusion, background clutter, pose variations, etc., and it is still an active research issue in the academic and industrial fields. Although various studies have been proposed, following the protocols of the person re-identification (ReID) benchmarks, most existing works take cropped pedestrian images either from manual labelling or a perfect detection assumption. However, for person search, manual processing is unavailable in practical applications, thereby causing a gap between the ReID problem setting and practical applications. One fact is also ignored: an imperfect auto-detected bounding box or misalignment is inevitable. We design herein a framework for the practical surveillance scenarios in which the scene images are captured. For person search, detection is a necessary step before ReID, and previous studies have shown that the precision of detection results has an influence on person ReID. The detection module based on the Faster R-CNN is used to detect persons in a scene image. For identifying and extracting discriminative features, a multi-class CNN network is trained with the auto-detected bounding boxes from the detection module, instead of the manually cropped data. The distance metric is then learned from the discriminative features output by the identification module. According to the experimental results of the test performed in the scene images, the multi-class CNN network for the identification module can provide a 62.7% accuracy rate, which is higher than that for the two-class CNN network.

Download Full-text

Analysis on the Dynamic Wave Attenuation Properties of Metaconcrete Considering a Quasi-Random Arrangement of Inclusions

Frontiers in Materials ◽

10.3389/fmats.2020.615189 ◽

2021 ◽

Vol 7 ◽

Author(s):

Deborah Briccola ◽

Anna Pandolfi

Keyword(s):

Wave Attenuation ◽

Plain Concrete ◽

Concrete Specimen ◽

Longitudinal Direction ◽

Inclusion Type ◽

Practical Applications ◽

Random Arrangement ◽

Resonant Behavior ◽

Dynamic Wave ◽

Positive Quality

The mitigation properties of metaconcrete cast with two types of resonant inclusions are assessed through wave transmission tests. Three cylindric metaconcrete specimens of regular size (20 cm height, 10 cm diameter), containing an equal number of different type of inclusions disposed in a semi-regular lattice, are tested in the longitudinal direction within the sonic range of frequencies. Inclusions, bi-material spheres consisting of a heavy core coated with a soft material, are characterized by a resonant behavior, evaluated numerically with a finite element modal analysis of a unit metaconcrete cell. Each metaconcrete specimen contains six layers consisting of six engineered aggregates of different type. Inclusions are disposed by rotating each layer with respect to the adjacent ones, as so as to create a pseudo-random arrangement. Specimens are excited by a sinusoidal signal of linearly growing frequency, sweeping a range centered at the translational eigenfrequency of the resonant inclusion. A standard plain concrete specimen is used as reference to define a transmissibility coefficient, that facilitates the quantification of the attenuation properties. With respect to plain concrete, all metaconcrete specimens show a marked (up to 80–90%) attenuation of the transmitted signal in proximity of the numerically estimated eigenfrequency of the inclusion. The intensity of the attenuation is weakly dependent on the type of the inclusion, while the frequency where the attenuation is observed depends markedly on the inclusion type. As a very positive quality in the view of practical applications, experimental results confirm that the attenuation effectiveness of metaconcrete is not related to the ordered microstructural arrangement.

Download Full-text

Discovery of a shoal-controlled karst dolomite reservoir in the Middle Permian Qixia Formation, northwestern Sichuan Basin, Southwest China

Energy Exploration & Exploitation ◽

10.1177/0144598717733592 ◽

2017 ◽

Vol 36 (4) ◽

pp. 686-704 ◽

Cited By ~ 5

Author(s):

Di Xiao ◽

Benjian Zhang ◽

Xiucheng Tan ◽

Hong Liu ◽

Jirong Xie ◽

...

Keyword(s):

Sichuan Basin ◽

Middle Permian ◽

Karst Water ◽

Karst System ◽

Reservoir Properties ◽

Parent Rocks ◽

Porosity And Permeability ◽

The Sichuan Basin ◽

Intercrystalline Pores

The dolomites of the Middle Permian Qixia Formation have been important targets of natural gas exploration in the Sichuan Basin for decades. However, more and more exploration and research indicate that the formation of the reservoir might be related to karstification. To testify this hypothesis, we conduct comprehensive outcrop, core, and logging analyses based on a case study in the representative northwestern Sichuan Basin, which has obtained exploration breakthroughs recently. Results show that the Qixia dolomite reservoirs are mainly developed within fine-crystalline dolomites formed by a series of diagenetic modifications, which can be further divided into three types according to the macro- and micro-occurrences of dolomites: euhedral-subhedral crystalline dolomites in the quasi-stratiform karst system (mean porosity and permeability is 3.51% and 3.11 mD, respectively), euhedral-subhedral crystalline dolomites in the leopard porphyritic karst system (mean porosity and permeability is 3.36% and 1.22 mD, respectively), and allotriomorphic mosaic crystalline dolomites with residual parent rock fabrics (mean porosity and permeability is 0.94% and 0.92 mD, respectively). Their reservoir qualities decrease along the order. The formation mechanism of the reservoir is shoal-controlled karst. The preservation of residual intergranular pores within the thin-layer grainstones of shoal facies provides favorable channels for karst water. In the vadose zone, the heterogeneous dissolution within grainstones leads to the formation of leopard porphyritic dissolution features. In the phreatic zone, the karst water flowing along the stratiform grainstones results in the formation of quasi-stratiform dissolution features. The karst system is filled with loose carbonate sands and gravels, whose reservoir properties are far superior to parent rocks, and they can provide migration channels for the hydrothermal fluids with rich Mg2+ in the burial stage. The replacement of hydrothermal fluid results in the redistribution of pores and vugs of inter-fillings within karst system and the formation of intercrystalline pores and residual vugs, but the reservoir space of parent rocks keeps the same as the original condition. Therefore, the exploration of the Qixia dolomite reservoir should be changed to shoal-controlled karst.

Download Full-text

State Switching of a Multistable Impacting System using PDLike Control

MATEC Web of Conferences ◽

10.1051/matecconf/201814810001 ◽

2018 ◽

Vol 148 ◽

pp. 10001

Author(s):

Boying Liu ◽

Wai-keung Fung ◽

Yang Liu

Keyword(s):

Direct Method ◽

Numerical Results ◽

Control Signal ◽

Control Law ◽

Intermittent Control ◽

Lyapunov Direct Method ◽

Practical Applications ◽

State Switching ◽

A Current

A new PD-like control law is proposed in this paper to control a multistable impacting system. This control law can switch the system from a current, undesired state to a desired one by using the differences of the displacement and velocity between the current and desired states. The control law can control the multistable system without affecting its original dynamics, and its stability is proved by using the Lyapunov direct method. Numerical results are compared with the results obtained by using the intermittent control studied in [1]. The proposed PD-like control shows a better performance in terms of the smoothness of its control signal, which is easier to be implemented in practical applications.

Download Full-text

Acoustic Absorption Performance Research of Coir Density Board

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.549.589 ◽

2012 ◽

Vol 549 ◽

pp. 589-592

Author(s):

Jia Yao ◽

Li Li Ma ◽

Lu Wei ◽

Li Wei Jiang ◽

Ya Qin Li

Keyword(s):

Absorption Coefficient ◽

Sound Absorption ◽

Optimization Design ◽

Morphological Characteristics ◽

Wave Impedance ◽

Sound Absorption Coefficient ◽

Coir Fiber ◽

Tropical Fruit ◽

Practical Applications ◽

Absorption Performance

Coir fiber is one of the tropical fruit fibers, the effective use of coir is not comprehensive now and the phenomenon of resources waste still exists. Full study of the advantage characteristics of coir has important significance for the expansion of the application field of coir resources. This article determines the light porous characteristics of coir from the micro-morphological characteristics. Through the prediction model research of the sound absorption coefficient of the porous fiber materials, the optimization density and the optimization thickness ranges can be got for the coir density board, so as to guide the optimization design of the sound absorption performance of coir density board. The changing rule of the sound absorption coefficient of the coir density board has been got by adopting the wave impedance tube method and the sound absorption coefficients by adding 5cm air gap has also been researched. The results of the experiments confirm that coir density board can be used as a secondary noise absorption material; the practical applications of coir density board are as the lightweight wall, the car interior trim or seat filling materials and the shipping cabins materials, to reduce the corresponding environment noise.

Download Full-text

Regularized Multitask Learning for Multidimensional Log-Density Gradient Estimation

Neural Computation ◽

10.1162/neco_a_00844 ◽

2016 ◽

Vol 28 (7) ◽

pp. 1388-1410 ◽

Cited By ~ 1

Author(s):

Ikko Yamane ◽

Hiroaki Sasaki ◽

Masashi Sugiyama

Keyword(s):

Density Gradient ◽

Density Estimation ◽

Direct Method ◽

Multitask Learning ◽

Statistical Problem ◽

Density Estimate ◽

Gradient Estimation ◽

Step Method ◽

Practical Applications ◽

Better Than

Log-density gradient estimation is a fundamental statistical problem and possesses various practical applications such as clustering and measuring nongaussianity. A naive two-step approach of first estimating the density and then taking its log gradient is unreliable because an accurate density estimate does not necessarily lead to an accurate log-density gradient estimate. To cope with this problem, a method to directly estimate the log-density gradient without density estimation has been explored and demonstrated to work much better than the two-step method. The objective of this letter is to improve the performance of this direct method in multidimensional cases. Our idea is to regard the problem of log-density gradient estimation in each dimension as a task and apply regularized multitask learning to the direct log-density gradient estimator. We experimentally demonstrate the usefulness of the proposed multitask method in log-density gradient estimation and mode-seeking clustering.

Download Full-text