scholarly journals A constrained optimization solution for Caughey damping coefficients in seismic analysis

2017 ◽  
Vol 34 (3) ◽  
pp. 682-708
Author(s):  
Danguang Pan ◽  
Chenfeng Li
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Programming Approach ◽  
Content Type ◽  
Practical Applications ◽  
Damping Coefficients ◽  
Modal Damping ◽  
Orthogonality Conditions ◽  
Optimal Damping ◽  
Damping Model

Purpose Extended from the classic Rayleigh damping model in structural dynamics, the Caughey damping model allows the damping ratios to be specified in multiple modes while satisfying the orthogonality conditions. Despite these desirable properties, Caughey damping suffers from a few major drawbacks: depending on the frequency distribution of the significant modes, it can be difficult to choose the reference frequencies that ensure reasonable values for all damping ratios corresponding to the significant modes; it cannot ensure all damping ratios are positive. This paper aims to present a constrained quadratic programming approach to address these issues. Design/methodology/approach The new method minimizes the error of the structural displacement peak based on the response spectrum theory, while all modal damping ratios are constrained to be greater than zero. Findings Several comprehensive examples are presented to demonstrate the accuracy and effectiveness of the proposed method, and comparisons with existing approaches are provided whenever possible. Originality/value The proposed method is highly efficient and allows the damping ratios to be conveniently specified for all significant modes, producing optimal damping coefficients in practical applications.

scholarly journals Taking into Account Material Damping in Seismic Analysis of Structures

2020 ◽  
Vol 14 (1) ◽  
pp. 55-59
Author(s):  
Maria S. Barabash ◽  
Bogdan Y. Pysarevskyi ◽  
Yaroslav Bashynskyi
Keyword(s):  
Seismic Analysis ◽  
Time History ◽  
Physical And Mechanical Properties ◽  
Time History Analysis ◽  
Material Damping ◽  
Damping Coefficients ◽  
Modal Damping ◽  
History Analysis ◽  
Earthquake Load ◽  
Displacement Speed

The purpose of this paper is to justify that it is necessary to take into account physical and mechanical properties of soil and different materials of erected structures for damping vibrations in dynamic loads, and to suggest tools for modelling the damping effect (natural or engineering induced) between foundation and soil. A technique is suggested for modelling the behavior of structure in time history analysis taking into account material damping. When solving this problem, the following results were obtained: the physical meaning of material damping was described; Rayleigh damping coefficients were computed through modal damping coefficients. Numerical analysis was carried out for the structure together with soil in earthquake load. Time history analysis was carried out for the problem. Peak values of displacement, speed and acceleration at the roof levels were compared. Analysis results were compared (with and without taking into account material damping). Significant influence of damping on the stress-strain state of the structure has been confirmed.

Zn diffusion and reflow behaviour of Sn-9Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga solders on a Ni/Cu substrate under IR reflow

2014 ◽  
Vol 26 (2) ◽  
pp. 87-95 ◽  
Author(s):  
J. Mittal ◽  
K.L. Lin
Keyword(s):  
Theoretical Calculations ◽  
Research Work ◽  
Content Type ◽  
Diffusion Behavior ◽  
Zn Diffusion ◽  
Cu Substrate ◽  
Practical Applications ◽  
Substrate Interface ◽  
Solder Balls ◽  
Practical Implications

Purpose – This paper aims to compare the reflow and Zn diffusion behaviors in Sn-Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (5E) solders during soldering on a Ni/Cu substrate under infrared (IR) reflow. The study proposes a model on the effect of various elements particularly Zn diffusion behavior in the solders on the formation of intermetallic compounds (IMCs). Design/methodology/approach – The melting activities of two solders near their melting points on copper substrates are visualized in an IR reflow furnace. Reflowed solder joints were analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy. Findings – Reflow behaviors of the solders are similar. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Both solders show a reduced amount of Zn in the solder. Theoretical calculations demonstrate a higher Zn diffusion in the 5E solder; however, the amount of Zn actually observed at the solder/substrate interface is lower than Sn-9Zn solder due to the formation of ZnAg3 in the solder. A thinner IMC layer is formed at the interface in the 5E solder than the Sn-Zn solder. Research limitations/implications – The present work compares the 5E solder only with Sn-Zn solder. Additional research work may be required to compare 5E solder with other solders like Sn-Ag, SnAgCu, etc. to further establish its practical applications. Practical implications – The study ascertains the advantages of 5E solder over Sn-Zn solder for all practical applications. Originality/value – The significance of this paper is the understanding of the relation between reflow behavior of solders and reactivity of different elements in the solder alloys and substrate to form various IMCs and their influence on the formation of IMC layer at solder/substrate interface. Emphasis is provided for the diffusion behavior of Zn during reflow and respective reaction mechanisms.

Measured natural periods of concrete shear wall buildings: insights for the design of Canadian buildings

2012 ◽  
Vol 39 (8) ◽  
pp. 867-877 ◽  
Author(s):  
Damien Gilles ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Shear Wall ◽  
Mode Shapes ◽  
Design Stage ◽  
Base Shear ◽  
Period Equation ◽  
Input Load ◽  
Structural Engineers

Structural engineers routinely use rational dynamic analysis methods for the seismic analysis of buildings. In linear analysis based on modal superposition or response spectrum approaches, the overall response of a structure (for instance, base shear or inter-storey drift) is obtained by combining the responses in several vibration modes. These modal responses depend on the input load, but also on the dynamic characteristics of the building, such as its natural periods, mode shapes, and damping. At the design stage, engineers can only predict the natural periods using eigenvalue analysis of structural models or empirical equations provided in building codes. However, once a building is constructed, it is possible to measure more precisely its dynamic properties using a variety of in situ dynamic tests. In this paper, we use ambient motions recorded in 27 reinforced concrete shear wall (RCSW) buildings in Montréal to examine how various empirical models to predict the natural periods of RCSW buildings compare to the periods measured in actual buildings under ambient loading conditions. We show that a model in which the fundamental period of RCSW buildings varies linearly with building height would be a significant improvement over the period equation proposed in the 2010 National Building Code of Canada. Models to predict the natural periods of the first two torsion modes and second sway modes are also presented, along with their uncertainty.

scholarly journals A typology of personal factor attributes among shoppers

2014 ◽  
Vol 18 (4) ◽  
pp. 394-412 ◽  
Author(s):  
Yue Teng Wong ◽  
Syuhaily Osman ◽  
Aini Said ◽  
Laily Paim
Keyword(s):  
Hierarchical Cluster ◽  
Measurement Model ◽  
Shopping Behavior ◽  
Personal Factors ◽  
Shopping Malls ◽  
Personal Factor ◽  
Content Type ◽  
Practical Applications ◽  
Confirmatory Factor ◽  
Klang Valley

Purpose – The purpose of this paper is to derive a comprehensive model with integrated dimensions of trait constructs to understand the shoppers’ dispositional traits in consumption. This study endeavors to gain empirical validation of a motivational network of shoppers’ traits in consumption as well as to ascertain different shoppers’ typology from the configurations of personal factor attributes. Design/methodology/approach – Store-intercept method was used to collect data from a sample of 600 apparel adult shoppers at five shopping malls in Klang Valley, Malaysia. The factor structure of personal factors was achieved using confirmatory factory analysis. The hierarchical and non-hierarchical cluster analysis was employed to develop the shoppers’ typology. Findings – A relatively good fit in confirmatory factor analysis validates the applicability of the conceptualized personal factor attributes measurement model. The constitution of personal factor attributes results in three shoppers typology of Confident, Enthusiastic Shoppers; Moderate, Pragmatic Shoppers and Self-Confined, Apathetic Shoppers. Practical implications – The study provides an understanding of the personal attribute factors and disseminates insightful information about profile of shoppers’ typology. Accordingly, the implementation of the strategy which involving the personality and psychological desires of the consumers, is now possible. Originality/value – This paper stipulates new insights to discern other dimensions in personality traits to examine the personal factor attributes, by considering the elemental traits, compound traits, situational traits and surface traits in a holistic manner. The findings of this study advance the knowledge on personal factor attributes that shape shopping behavior along with practical applications.

Robot obstacle avoidance system using deep reinforcement learning

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaojun Zhu ◽  
Yinghao Liang ◽  
Hanxu Sun ◽  
Xueqian Wang ◽  
Bin Ren
Keyword(s):  
Reinforcement Learning ◽  
Collision Avoidance ◽  
Obstacle Avoidance ◽  
Learning Algorithm ◽  
Optimal Path ◽  
Environmental Parameters ◽  
Working Environment ◽  
Content Type ◽  
Practical Applications ◽  
Human Operators

Purpose Most manufacturing plants choose the easy way of completely separating human operators from robots to prevent accidents, but as a result, it dramatically affects the overall quality and speed that is expected from human–robot collaboration. It is not an easy task to ensure human safety when he/she has entered a robot’s workspace, and the unstructured nature of those working environments makes it even harder. The purpose of this paper is to propose a real-time robot collision avoidance method to alleviate this problem. Design/methodology/approach In this paper, a model is trained to learn the direct control commands from the raw depth images through self-supervised reinforcement learning algorithm. To reduce the effect of sample inefficiency and safety during initial training, a virtual reality platform is used to simulate a natural working environment and generate obstacle avoidance data for training. To ensure a smooth transfer to a real robot, the automatic domain randomization technique is used to generate randomly distributed environmental parameters through the obstacle avoidance simulation of virtual robots in the virtual environment, contributing to better performance in the natural environment. Findings The method has been tested in both simulations with a real UR3 robot for several practical applications. The results of this paper indicate that the proposed approach can effectively make the robot safety-aware and learn how to divert its trajectory to avoid accidents with humans within the workspace. Research limitations/implications The method has been tested in both simulations with a real UR3 robot in several practical applications. The results indicate that the proposed approach can effectively make the robot be aware of safety and learn how to change its trajectory to avoid accidents with persons within the workspace. Originality/value This paper provides a novel collision avoidance framework that allows robots to work alongside human operators in unstructured and complex environments. The method uses end-to-end policy training to directly extract the optimal path from the visual inputs for the scene.

Development of a direct NGM(1,1) prediction model based on interval grey numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ye Li ◽  
Yuanping Ding ◽  
Yaqian Jing ◽  
Sandang Guo
Keyword(s):  
Genetic Algorithm ◽  
Markov Model ◽  
Prediction Model ◽  
Real Number ◽  
Content Type ◽  
Optimal Weight ◽  
Practical Applications ◽  
Number Sequences ◽  
Integral Development ◽  
Grey Number

PurposeThe purpose of this paper is to construct an interval grey number NGM(1,1) direct prediction model (abbreviated as IGNGM(1,1)), which need not transform interval grey numbers sequences into real number sequences, and the Markov model is used to optimize residual sequences of IGNGM(1,1) model.Design/methodology/approachA definition equation of IGNGM(1,1) model is proposed in this paper, and its time response function is solved by recursive iteration method. Next, the optimal weight of development coefficients of two boundaries is obtained by genetic algorithm, which is designed by minimizing the average relative error based on time weighted. In addition to that, the Markov model is used to modify residual sequences.FindingsThe interval grey numbers’ sequences can be predicted directly by IGNGM(1,1) model and its residual sequences can be amended by Markov model. A case study shows that the proposed model has higher accuracy in prediction.Practical implicationsUncertainty and volatility information is widespread in practical applications, and the information can be characterized by interval grey numbers. In this paper, an interval grey numbers direct prediction model is proposed, which provides a method for predicting the uncertainty information in the real world.Originality/valueThe main contribution of this paper is to propose an IGNGM(1,1) model which can realize interval grey numbers prediction without transforming them into real number and solve the optimal weight of integral development coefficient by genetic algorithm so as to avoid the distortion of prediction results. Moreover, the Markov model is used to modify residual sequences to further improve the modeling accuracy.

Shariah-compliant equities and Shariah screening: need for convergence of ethical screening of stocks with Shariah screening

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tauhidul Islam Tanin ◽  
Abu Umar Faruq Ahmad ◽  
Aishath Muneeza
Keyword(s):  
Original Research ◽  
Screening Process ◽  
Screening Criteria ◽  
Content Type ◽  
Practical Applications ◽  
Qualitative Research Methodology ◽  
Qualitative Descriptive ◽  
Stock Screening ◽  
Descriptive Approach ◽  
Practical Implications

PurposeThis study explores the practical application of the Shariah screening process and how it could be enhanced by converging the same with the ethical screening of stocks.Design/methodology/approachThis study adopts a qualitative research methodology by combining the qualitative descriptive approach and content analysis.FindingsThe findings of this research suggest that there is scope to converge ethical screening of stocks with Shariah Screening as the lex loci applicable to Shariah screening is derived from Shariah, which considers ethics as part of determining its rules.Practical implicationsThe data from this study reveal several practical applications, the ultimate goal of which is to help the policymakers and stakeholders understand the relevance of the Shariah screening of stocks and get a streamlined screening process, paving the way to enhance the same using ethical screening criteria to develop its function to become much more relevant irrespective of the denomination of faiths.Originality/valueThis is original research, which is expected to contribute to understanding the extent to which Shariah screening can be enhanced by integrating the ethical stock screening dimension to it.

scholarly journals Inertial mass damper for vibration control of cable with sag

2018 ◽  
Vol 39 (3) ◽  
pp. 749-760 ◽  
Author(s):  
Zhi-Hao Wang ◽  
Hui Gao ◽  
Bu-qiao Fan ◽  
Zheng-Qing Chen
Keyword(s):  
Inertial Mass ◽  
Damping Coefficient ◽  
Stay Cables ◽  
Modal Damping ◽  
Optimal Damping ◽  
Mass Damper ◽  
Negative Effect ◽  
Supplemental Damping ◽  
Antisymmetric Vibrations ◽  
General Dynamic

It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an inertial mass damper. This paper extends previous studies to investigate the effect of the cable sag on the efficiency of an inertial mass damper. The general dynamic characteristics of an inclined sag cable with an inertial mass damper installed close to the cable end are theoretically investigated. The parametric analysis of the inertial mass and the damping coefficient of the inertial mass damper are conducted to evaluate the control performance of the cable with different sags. The results show that the inertial mass damper can alleviate the negative effect induced by the cable sag, and the cable sag can even increase modal damping ratios provided by the inertial mass damper. Sags of stay cables used in actual bridges only affect nearly symmetric vibrations of cables, while having little impact on nearly antisymmetric vibrations. The effect of cable sags will reduce the optimal damping coefficient and inertial mass of the inertial mass damper for the first symmetric mode of the cable.

scholarly journals Conceptualizing a circular framework of supply chain resource sustainability

2017 ◽  
Vol 37 (10) ◽  
pp. 1520-1540 ◽  
Author(s):  
S.C. Lenny Koh ◽  
Angappa Gunasekaran ◽  
Jonathan Morris ◽  
Raymond Obayi ◽  
Seyed Mohammad Ebrahimi
Keyword(s):  
Supply Chain ◽  
Decision Support ◽  
Complex Adaptive Systems ◽  
Adaptive Systems ◽  
Decision Rules ◽  
Theory Building ◽  
Theory Of Constraints ◽  
Content Type ◽  
Practical Applications ◽  
Resource Sustainability

Purpose In response to calls for conceptual frameworks and generic theory building toward the advancement of sustainability in supply chain resource utilization and management, the purpose of this paper is to advance a circular framework for supply chain resource sustainability (SCRS), and a decision-support methodology for assessing SCRS against the backdrop of five foundational premises (FPs) deduced from the literature on resource sustainability. Design/methodology/approach Taking a conceptual theory-building approach, the paper advances a set of SCRS decision-support criteria for each of the theoretical premises advanced, and applies the theory of constraints to illustrate the conceptual and practical applications of the framework in SCRS decision making. Findings This study uses recent conceptualizations of supply chains as “complex adaptive systems” to provide a robust and novel frame and a set of decision rules with which to assess the interconnectedness of environmental, economic, and social capital of supply chain resources from pre-production to post-production. Research limitations/implications The paper contributes to theory building in sustainability research, and the SCRS decision framework developed could be applied in tandem with existing quantitative hybrid life-cycle and input-output approaches to facilitate targeted resource sustainability assessments, with implications for research and practice. Originality/value The novel SCRS framework proposed serves as a template for evaluating SCRS and provides a decision-support methodology for assessing SCRS against the five theorized FPs.

Stability characteristics of lubricating film in mill oil-film bearings

2018 ◽  
Vol 70 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Jianmei Wang ◽  
Zhixiong Li ◽  
Sadoughi Mohammadkazem ◽  
Min Cai ◽  
Jianfeng Kang ◽  
...  
Keyword(s):  
Influential Factors ◽  
Film Stability ◽  
High Rotational Speed ◽  
Content Type ◽  
Oil Film ◽  
Practical Applications ◽  
Lubricating Film ◽  
Operation Conditions ◽  
Comparison Results ◽  
The Stability

Purpose The stability characteristics of an oil film directly influence the safety and service life of mill oil-film bearings. However, very limited work has been done to address the stability characteristics of mill oil-film bearings. To this end, this paper aims to investigate the stability characteristics of mill oil-film bearings through theoretical and experimental analysis. Design/methodology/approach For the first time, a special designed experiment platform was developed to investigate the stability characteristics of mill oil-film bearings. In addition, a theoretical model of lubricating film of the tested bearings was established to analyze the oil-film stability. The theoretical results were compared with the experimental results. Findings The comparison results demonstrate that the critical influential factors on the bearing stability were the eccentricity ratio and the ratio of bearing length to diameter. The mill bearing was likely to be unstable under a small load and at a high rotational speed. Practical implications The paper includes implications for suitable operation conditions in practical use of mill oil-film bearings. Originality/value This paper fulfills an identified need to investigate oil-film stability of mill bearings for practical applications.

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