Sensitivity of the stability assessment of a deep excavation to the material characterisations and analysis methods

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Mohsen Ghadrdan ◽  
Tahereh Shaghaghi ◽  
Ali Tolooiyan
Keyword(s):  
Stability Assessment ◽  
Deep Excavation ◽  
Analysis Methods ◽  
The Stability

Model Test Techniques Developed to Investigate the Wind Heeling Characteristics of Sailing Vessels and Their Response to Gusts

1991 ◽  
Author(s):  
Barry Deakin
Keyword(s):  
Wind Tunnel ◽  
Model Test ◽  
Wind Tunnels ◽  
Stability Assessment ◽  
Tunnel Floor ◽  
The Stability ◽  
Scaled Models ◽  
Scale Data ◽  
Heeling Moment ◽  
Gust Response

During the development of new stability regulations for the U.K. Department of Transport, doubt was cast over many of the assumptions made when assessing the stability of sailing vessels. In order to investigate the traditional methods a programme of work was undertaken including wind tunnel tests and full scale data acquisition. The work resulted in a much improved understanding of the behaviour of sailing vessels and indeed indicated that the conventional methods of stability assessment are invalid, the rules now applied in the U.K. being very different to those in use elsewhere. The paper concentrates on the model test techniques which were developed specifically for this project but which will have implications to other vessel types. The tests were of two kinds: measurement of the wind forces and moments on a sailing vessel; and investigation of the response of sailing vessels to gusts of wind. For the force and moment measurements models were mounted in a tank of water on a six component balance and tested in a large boundary layer wind tunnel. Previous tests in wind tunnels have always concentrated on performance and the heeling moments have not normally been measured correctly. As the measurements of heeling moment at a range of heel angles was of prime importance a new balance and mounting system was developed which enabled the above water part of the vessel to be modelled correctly, the underwater part to be unaffected by the wind, and the interface to be correctly represented without interference. Various effects were investigated including rig type, sheeting, heading, heel angle and wind gradient. The gust response tests were conducted with Froude scaled models floating in a pond set in the wind tunnel floor. A mechanism was installed in the tunnel which enabled gusts of various characteristics to be generated, and the roll response of the models was measured with a gyroscope. These tests provided information on the effects of inertia, damping, rolling and the characteristics of the gust. Sample results are presented to illustrate the uses to which these techniques have been put.

scholarly journals Сombined ships stability analysis at the stage of design study

2021 ◽  
pp. 29-35
Author(s):  
Ilya A. Gulyaev Gulyaev ◽  
Evgeniy P. Ronnov
Keyword(s):  
Stability Analysis ◽  
Optimization Problems ◽  
Mutual Influence ◽  
Static Stability ◽  
Wind Effect ◽  
Stability Assessment ◽  
Design Study ◽  
Hull Design ◽  
The Stability ◽  
Russian River

. A method of stability analysis for combined ship (oil carrier/platform ship type) at the stage of design study is presented. It should be noted that not all of ship’s main seaworthiness and operational characteristics are the result of a simple addition of the characteristics of an oil carrier and a platform ship. Their mutual influence takes place, which should be taken into account when analysing the stability in the multivariant optimization problems of internal and external design of such ships. This leads to the requirement to adjust the known methods of stability analysis at the initial stages of ship design, which was the purpose of the present work and its originality. Taking into account the multivariance of the task and the hull design type, the stability assessment will be carried out through the analysis of the metacentric height extreme value on the assumption that the requirements of Russian River Register for admissible heeling angle at static wind effect are met. In order to account for nonlinearity of static stability curve when inclining up to the angles of deck immersion into water and emergence of bilge, it is suggested to apply an approximate method of metacentric radius determination. The proposed method of combined ship stability assessment is recommended to apply at the stage of justification and analysis of ship’s key elements as a limitation in the problems of mathematical modeling of optimization of such type of ships. The method allows to exclude from further consideration at the design study stage the possible options that do not meet the requirements of seaworthiness.

A Survey of Fractional-Order Neural Networks

2017 ◽  
Author(s):  
Shuo Zhang ◽  
YangQuan Chen ◽  
Yongguang Yu
Keyword(s):  
Neural Networks ◽  
Stability Analysis ◽  
Fractional Order ◽  
Computational Science ◽  
General Introduction ◽  
Analysis Methods ◽  
Recent Trends ◽  
The Stability

In this paper, the literature of fractional-order neural networks is categorized and discussed, which includes a general introduction and overview of fractional-order neural networks. Various application areas of fractional-order neural networks have been found or used, and will be surveyed and summarized such as neuroscience, computational science, control and optimization. Recent trends in dynamics of fractional-order neural networks are presented and discussed. The results, especially the stability analysis of fractional-order neural networks, are reviewed and different analysis methods are compared. Furthermore, the challenges and conclusions of fractional-order neural networks are given.

Mid-Term Stability Assessment of Jiangxi Power Grid

2013 ◽  
Vol 732-733 ◽  
pp. 882-887
Author(s):  
Yong Chun Su ◽  
Hao Wei Jia
Keyword(s):  
Power System ◽  
Power Grid ◽  
Assessment Method ◽  
Control Measures ◽  
Assessment Process ◽  
Jiangxi Province ◽  
Stable Operation ◽  
Stability Assessment ◽  
Term Stability ◽  
The Stability

Mid-term stability assessment is an important work to support power system operation in a province power grid of China every year. The stability assessment method and process was introduced in this paper. As an example, the stability of Jiangxi province power system was evaluated in the following two years. Weak area and weak transmission line were found out in each power supply area. Prevention and control measures were proposed. According to problems among the assessment process and using the state monitoring data, an approach was discussed to increase the assessment result accuracy. The analysis conclusion provides the reference to the safe and stable operation of Jiangxi power system.

scholarly journals The Stability Analysis of a Multi-Port Single-Phase Solid-State Transformer in the Electromagnetic Timescale

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2250 ◽  
Author(s):  
Rui Wang ◽  
Qiuye Sun ◽  
Qifu Cheng ◽  
Dazhong Ma
Keyword(s):  
Stability Analysis ◽  
Solid State ◽  
Single Phase ◽  
Control Strategies ◽  
Current Source ◽  
Practical Stability ◽  
Stability Assessment ◽  
Solid State Transformer ◽  
The Stability ◽  
Signal Sinusoïdal

This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses the stability assessment of the MS3T in detail. First and foremost, the structure of the MS3T and its three stage control strategies are proposed. Furthermore, the stability analysis of each of the MS3T’s subsystems is achieved through the closed loop transfer function of each subsystem, respectively, including an AC-DC front-end side converter, dual active bridge (DAB) with a high-frequency (HF) or medium-frequency (MF) transformer, and back-end side incorporating DC-AC and dc-dc converters. Furthermore, the practical impedance stability criterion in the electromagnetic timescale, which only requires two current sensors and one external high-bandwidth small-signal sinusoidal perturbation current source, is proposed by the Gershgorin theorem and Kirchhoff laws. Finally, the overall stability assessment, based on a modified impedance criterion for the MS3T is investigated. The overall practical stability assessment of the MS3T can be validated through extensive simulation and hardware results.

Torsional failure of water-filled carbon nanotubes

2015 ◽  
Vol 25 (1) ◽  
pp. 87-97 ◽  
Author(s):  
Hongfei Ye ◽  
Rui Li ◽  
Yonggang Zheng ◽  
Zhongqiang Zhang ◽  
Zhi Zong ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Failure Behavior ◽  
Stability Assessment ◽  
Water Density ◽  
Failure Angle ◽  
Water Filling ◽  
The Stability ◽  
Dynamics Simulations ◽  
Density Of Water ◽  
Torsional Property

The failure behavior of water-filled carbon nanotubes under the torsional moment is investigated by molecular dynamics simulations. The computational results indicate that the shear modulus can be slightly increased but the critical buckling angle can be greatly enhanced by the water filling as compared to the empty carbon nanotubes. The enhancement in the critical buckling angle is almost comparable to that induced by the copper filling. However, the critical failure angle of carbon nanotubes decreases with the increase in the packing density of water, and it is reduced by about 50% when the water density reaches 1.2 g/cm3. Moreover, the researches on the defective water-filled carbon nanotubes reveal that the torsional property of the carbon nanotubes can be influenced by the density and distribution of the Stone–Wales defects. The present findings can provide a theoretical guidance for the stability assessment of nanochannels and the potential application for the drug delivery and release.

Plastic Classification with X-ray Absorption Spectroscopy Based on Back Propagation Neural Network

2017 ◽  
Vol 71 (11) ◽  
pp. 2538-2548 ◽  
Author(s):  
Qian Wang ◽  
Xiaomei Wu ◽  
Lingcong Chen ◽  
Zheng Yang ◽  
Zheng Fang
Keyword(s):  
Absorption Spectroscopy ◽  
Recognition Rate ◽  
Back Propagation ◽  
Principal Component ◽  
Back Propagation Neural Network ◽  
X Ray ◽  
Analysis Methods ◽  
Average Recognition Rate ◽  
The Stability ◽  
X Ray Absorption

Currently, spectral analysis methods used in the classification of plastics have limitations that do not apply to opaque plastics or the stability of experimental results is not strong. In this paper, X-ray absorption spectroscopy (XAS) has been applied to classify plastics due to its strong penetrability and stability. Fifteen kinds of plastics are selected as specimens. X-ray, which is excited by a voltage of 60 kV, penetrated these specimens. The spectral data acquired by CdTe X-ray detector are processed by principal component analysis (PCA) and other data analysis methods. Then the back propagation neural networks (BPNN) algorithm is used to classify the processed data. The average recognition rate reached 96.95% and classification results of all types of plastic results were analyzed in detail. It indicates that XAS has the potential to classify plastics and that XAS can be used in some fields such as plastic waste sorting and recycling. At the same time, the technology of XAS, in the future, can also be used to classify more substances.

scholarly journals Stability Assessment of Earth Retaining Structures under Static and Seismic Conditions

2019 ◽  
Vol 4 (2) ◽  
pp. 15
Author(s):  
Nimbalkar ◽  
Pain ◽  
Ahmad ◽  
Chen
Keyword(s):  
Retaining Wall ◽  
Earth Pressure ◽  
Accurate Estimation ◽  
Engineering Practice ◽  
Active Earth Pressure ◽  
Stability Assessment ◽  
Linear Distribution ◽  
Backfill Soil ◽  
The Stability ◽  
Seismic Earth Pressure

An accurate estimation of static and seismic earth pressures is extremely important in geotechnical design. The conventional Coulomb’s approach and Mononobe-Okabe’s approach have been widely used in engineering practice. However, the latter approach provides the linear distribution of seismic earth pressure behind a retaining wall in an approximate way. Therefore, the pseudo-dynamic method can be used to compute the distribution of seismic active earth pressure in a more realistic manner. The effect of wall and soil inertia must be considered for the design of a retaining wall under seismic conditions. The method proposed considers the propagation of shear and primary waves through the backfill soil and the retaining wall due to seismic excitation. The crude estimate of finding the approximate seismic acceleration makes the pseudo-static approach often unreliable to adopt in the stability assessment of retaining walls. The predictions of the active earth pressure using Coulomb theory are not consistent with the laboratory results to the development of arching in the backfill soil. A new method is proposed to compute the active earth pressure acting on the backface of a rigid retaining wall undergoing horizontal translation. The predictions of the proposed method are verified against results of laboratory tests as well as the results from other methods proposed in the past.

scholarly journals Impedance-Based Interactions in Grid-Tied Three-Phase Inverters in Renewable Energy Applications

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 464 ◽  
Author(s):  
Teuvo Suntio ◽  
Tuomas Messo ◽  
Matias Berg ◽  
Henrik Alenius ◽  
Tommi Reinikka ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Experimental Measurements ◽  
Stability Assessment ◽  
Transient Performance ◽  
Energy Applications ◽  
Impedance Ratio ◽  
Three Phase ◽  
The Cross ◽  
And Performance ◽  
The Stability

Impedance-ratio-based interaction analyses in terms of stability and performance of DC-DC converters is well established. Similar methods are applied to grid-connected three-phase converters as well, but the multivariable nature of the converters and the grid makes these analyses very complex. This paper surveys the state of the interaction analyses in the grid-connected three-phase converters, which are used in renewable-energy applications. The surveys show clearly that the impedance-ratio-based stability assessment are usually performed neglecting the cross-couplings between the impedance elements for reducing the complexity of the analyses. In addition, the interactions, which affect the transient performance, are not treated usually at all due to the missing of the corresponding analytic formulations. This paper introduces the missing formulations as well as explicitly showing that the cross-couplings of the impedance elements have to be taken into account for the stability assessment to be valid. In addition, this paper shows that the most accurate stability information can be obtained by means of the determinant related to the associated multivariable impedance ratio. The theoretical findings are also validated by extensive experimental measurements.

scholarly journals A Macroelement Approach for the Stability Assessment of Trees

2019 ◽  
pp. 417-426 ◽  
Author(s):  
G. Dattola ◽  
M. O. Ciantia ◽  
A. Galli ◽  
L. Blyth ◽  
X. Zhang ◽  
...  
Keyword(s):  
Stability Assessment ◽  
The Stability
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