Xiao-Bo Wang, Wen-Jie Xu, Bing-Yin Zhang and Qi-Cheng Sun
Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large…
Abstract
Purpose
Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large particles – hence the term rock-fill. Mass stability of these dams results from friction and particle interactions rather than through a cementing agent binding the particles together. However, high-stress conditions and prolonged exposure to the elements can severely damage rock-fill. Therefore, understanding and modeling rock-fill breakage is important for dam engineering. The purpose of this paper is to improve discontinuous deformation analysis (DDA) techniques for modeling rock-fill breakage, proving the new method using simulations of spherical particle crushing.
Design/methodology/approach
This work models rock-fill as bonded ellipsoid particles, and develops an improved DDA method to model the breakage of particle assemblies. The paper starts by describing the principles of three-dimensional DDA for spherical particles, and then derives the submatrices for normal contact, shear contact, and frictional force. The new algorithm incorporates a bond model with a revised open-close iteration algorithm into the DDA method to simulate particle crushing. To validate the improved DDA method, calculated particle contacts and movements are validated against theoretical results. Finally, this work performs a series of point-loading experimental tests for cement ellipsoid particles of both high and low compression strengths, with the test results compared against the results from corresponding DDA simulations.
Findings
In particle crushing tests, the force and displacement show an approximately linear relationship until the crushing point, at which point low compression ellipsoid particles split into several large pieces while the high-compression particles break into many small fragments. The DDA simulation results are in good agreement with the crushing tests, demonstrating the validity of the DDA method for solving particle crushing problems. Although the improved DDA model is applicable to rock-fill particle crushing studies, some issues remain, particularly in increasing calculation efficiency and performing large-scale computations and long real-time simulations. Future research should address these issues.
Originality/value
A bond model with a revised open-close iteration algorithm is incorporated into the DDA method. The simulated results shed insight into rock-fill crushing mechanisms, an element of concern in engineering practices.
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Amirreza Kosari, Alireza Sharifi, Alireza Ahmadi and Masoud Khoshsima
Attitude determination and control subsystem (ADCS) is a vital part of earth observation satellites (EO-Satellites) that governs the satellite’s rotational motion and pointing. In…
Abstract
Purpose
Attitude determination and control subsystem (ADCS) is a vital part of earth observation satellites (EO-Satellites) that governs the satellite’s rotational motion and pointing. In designing such a complicated sub-system, many parameters including mission, system and performance requirements (PRs), as well as system design parameters (DPs), should be considered. Design cycles which prolong the time-duration and consequently increase the cost of the design process are due to the dependence of these parameters to each other. This paper aims to describe a rapid-sizing method based on the design for performance strategy, which could minimize the design cycles imposed by conventional methods.
Design/methodology/approach
The proposed technique is an adaptation from that used in the aircraft industries for aircraft design and provides a ball-park figure with little engineering man-hours. The authors have shown how such a design technique could be generalized to cover the EO-satellites platform ADCS. The authors divided the system requirements into five categories, including maneuverability, agility, accuracy, stability and durability. These requirements have been formulated as functions of spatial resolution that is the highest level of EO-missions PRs. To size, the ADCS main components, parametric characteristics of the matching diagram were determined by means of the design drivers.
Findings
Integrating the design boundaries based on the PRs in critical phases of the mission allowed selecting the best point in the design space as the baseline design with only two iterations. The ADCS of an operational agile EO-satellite is sized using the proposed method. The results show that the proposed method can significantly reduce the complexity and time duration of the performance sizing process of ADCS in EO-satellites with an acceptable level of accuracy.
Originality/value
Rapid performance sizing of EO-satellites ADCS using matching diagram technique and consequently, a drastic reduction in design time via minimization of design cycles makes this study novel and represents a valuable contribution in this field.
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Keywords
Peilin Cheng, Yuze Ye, Bo Yan, Yebo Lu and Chuanyu Wu
Soft grippers have safer and more adaptable human–machine and environment–machine interactions than rigid grippers. However, most soft grippers with single gripping postures have…
Abstract
Purpose
Soft grippers have safer and more adaptable human–machine and environment–machine interactions than rigid grippers. However, most soft grippers with single gripping postures have a limited gripping range. Therefore, this paper aims to design a soft gripper with variable gripping posture to enhance the gripping adaptability.
Design/methodology/approach
This paper proposes a novel soft gripper consisting of a conversion mechanism and four spring-reinforced soft pneumatic actuators (SSPAs) as soft fingers. By adjusting the conversion mechanism, four gripping postures can be achieved to grip objects of different shapes, sizes and weights. Furthermore, a quasi-static model is established to predict the bending deformation of the finger. Finally, the bending angle of the finger is measured to validate the accuracy of the quasi-static model. The gripping force and gripping adaptability are tested to explore the gripping performance of the gripper.
Findings
Through experiments, the results have shown that the quasi-static model can accurately predict the deformation of the finger; the gripper has the most significant gripping force under the parallel posture, and the gripping adaptability of the gripper is highly enhanced by converting the four gripping postures.
Originality/value
By increasing the gripping posture, a novel soft gripper with enhanced gripping adaptability is proposed to enlarge the gripping range of the soft gripper with a single posture. Furthermore, a quasi-static model is established to analyze the deformation of SSPA.
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Jianliang Yang, Hanping Hou, Yong Chen and Lu Han
Based on the context of the Internet of Things (IoT), the territorial public emergency supplies will be networked, platform-based management, unified emergency dispatch. The…
Abstract
Purpose
Based on the context of the Internet of Things (IoT), the territorial public emergency supplies will be networked, platform-based management, unified emergency dispatch. The problem of supplies dispatching in the “last kilometer” of emergency is solved, and the supplies needed in the disaster area are promptly delivered to the hands of the victims so that they can quickly be rescued after the disaster and to save valuable time for rapid rescue, which can greatly decrease casualties and property losses. This paper aims to discuss these issues.
Design/methodology/approach
By analyzing the shortage of existing emergency supplies dispatching research and taking all factors such as disaster area demand, social reserve, road conditions, mode of transport, loading limit, disaster area satisfaction rate and road capacity into consideration under the background of IoT, a variety of the territorial emergency supplies dispatching model with more rescue points, more affected areas are constructed. The objective function of the model is to aim in finding the shortest rescue time, giving the solution algorithm, and finally simulating the simulation case.
Findings
Based on the context of the IoT, the territorial public emergency supplies will be networked, platform-based management, unified emergency dispatch. Considering factors such as road conditions, modes of transport and road capacity, the authors construct a number of emergency rescue plans, multiple disaster scenarios and various emergency supplies dispatching models. The authors simulate the situation through simulation cases with the shortest time being the ultimate goal. The problem of supplies dispatching in the “last kilometer” of emergency is solved, and the supplies needed in the disaster area are promptly delivered to the hands of the victims so that they can quickly be rescued after the disaster and to save valuable time for rapid rescue, which can greatly decrease casualties and property losses.
Originality/value
This paper provides little research on the dispatch of emergency supplies. The problems of direct dispatch from the rescue point to the affected area and dispatch of supplies without relying on the arrival of emergency supplies at the rear are addressed. Therefore, this study does not focus on the arrival of emergency supplies at the rear but on direct dispatching issues during territorial public emergency supplies from the rescue point to the disaster point.
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Yusuf Arayici, Ghassan Aouad and Vian Ahmed
Collaborative working using Information and Communication Technologies (ICT) systems in construction has become a reality as many activities are performed globally with actors…
Abstract
Collaborative working using Information and Communication Technologies (ICT) systems in construction has become a reality as many activities are performed globally with actors located in various geographical locations. Computer Integrated Construction (CIC) is the type of ICT system that binds a fragmented and geographically distributed set of construction stakeholders collaborating together. Although the concept of CIC has been the subject of research for many years, its uptake has been very limited due to the development of the technology and its effective implementation. Research in this area is still premature and does not pay much attention to the development and implementation of the prototypes in the industry. As a result, the research developments have remained as prototypes although they have captured industrial interest. However, ongoing research within the field of construction IT is stressing that it is crucial to define research methodologies for human centred and adaptive CIC developments through industry‐wide knowledge sharing. The aim of this paper, through triangulated research strategy of interviews, surveys and case study is to justify the need for a requirements engineering process as a CIC development methodology for adaptive and user‐centred systems developments and as a guideline to bridge the gap between industry and the research community. The case study project is the DIVERCITY system development undertaken by researchers and practitioners across Europe to develop a shared virtual construction design and briefing environment that enables the construction industry to better undertake the client briefing and design review phases of a construction project.
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Zongyao Yang, Yong Shan and Jingzhou Zhang
This study aims to investigate the effects of exhaust direction on exhaust plume and helicopter infrared radiation in hover and cruise status.
Abstract
Purpose
This study aims to investigate the effects of exhaust direction on exhaust plume and helicopter infrared radiation in hover and cruise status.
Design/methodology/approach
Four exhaust modes are concerned, and the external flow field and fuselage temperature field are calculated by numerical simulation. The infrared radiation intensity distributions of the four models in hovering and cruising states are computed by the ray-tracing method.
Findings
Under the hover status, the exhaust plume is deflected to flow downward after it exhausts from the nozzle exit, upon the impact of the main-rotor downwash. Besides, the exhaust plume shows a “swirling” movement following the main-rotor rotational direction. The forward-flight flow helps prevent the hot exhaust plume from a collision with the helicopter fuselage generally for the cruise status. In general, the oblique-upward exhaust mode provides moderate infrared radiation intensities in all of the viewing directions, either under the hover or the cruise status. Compared with the hover status, the infrared radiation intensity distribution alters somewhat in cruise.
Originality/value
Illustrating the influences of exhaust direction on plume flow and helicopter infrared radiation and the differences of helicopter infrared radiation under hover and cruise statuses are identified. Finally, an appropriate exhaust mode is proposed to provide a better IR signature distribution.
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Keywords
Yarima Sallau Lawal, Aliyu Makarfi Ibrahim, Mu'awiya Abubakar, Ziyadul Hassan Ishaq and Mohammed Mustapha Sa'ad
Building developments are often capital intensive, have a long payback period and many associated risks and uncertainties. This makes investments in building projects to be a big…
Abstract
Purpose
Building developments are often capital intensive, have a long payback period and many associated risks and uncertainties. This makes investments in building projects to be a big challenge. This study aims to develop a computerized simulation-based binomial model (CSBBM) for building investment appraisal with a view to improving the economic sustainability of proposed building projects.
Design/methodology/approach
Mathematical equations and algorithms were developed based on the binomial method (BM) of real options analysis and then implemented on a computer system. A hybrid algorithm that integrates Monte Carlo simulation (MCS) and BM was also developed. A real-life project was used to test the model. Sensitivity analysis was also conducted to explore the influence of input variables on development option value (DOV).
Findings
The test result shows that the model developed provides a better estimate of the value of an investment when compared with traditional net present value technique, which underestimate the value. Moreover, inflation rate (i) and rental value (Ri) are the most sensitive variables for DOV. An increase in i and Ri by just 5% causes a corresponding increase in DOV by 202% and 132%, respectively. While the least sensitive variable is the discount rate (r), as an increase in r by 5% causes a corresponding decrease in DOV by just 9%. The CSBBM is capable of determining the optimal time of development of buildings with an accuracy of 80.77%.
Practical implications
The hybrid model produces higher DOV than that of only the BM because MCS considers randomness in uncontrollable variables. Thus, building investment decision-makers should always use MCS to complement the BM in an investment analysis.
Originality/value
There is limited evidence on the use of this kind of hybrid model for determining DOV in practice.
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Keywords
M.N. Sun and K.P.S. Cheng
The fine gauge plain weft knitted fabrics knitted from cotton Sirospun1 yarns are more durable and suitable for summer wear. It was found that they have considerable bursting…
Abstract
The fine gauge plain weft knitted fabrics knitted from cotton Sirospun1 yarns are more durable and suitable for summer wear. It was found that they have considerable bursting strength, superior abrasion resistance, superior pilling resistance, greater air resistance, cooler hand‐feel and greater thermal conductivity than the fabrics knitted from two‐fold yarns. The plain weft knitted fabric composed of coarser Sirospun1 yarn is also better in terms of hand‐feel measured by KES instruments.
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Yot Amornkitvikai, Charles Harvie and Piyapong Sangkaew
The objectives of this study are to investigate the role of wages, skills development and R&D on the productivity of Thai manufacturing firms, using data from the 2017 Industrial…
Abstract
Purpose
The objectives of this study are to investigate the role of wages, skills development and R&D on the productivity of Thai manufacturing firms, using data from the 2017 Industrial Census of Thailand.
Design/methodology/approach
The paper uses two-stage least squares (2SLS) to examine the role of wages, skills development and R&D, as well as other vital factors, impacting productivity as measured by labour productivity and total factor productivity.
Findings
Thai manufacturing firms' technology in aggregate exhibits decreasing returns to scale. Increasing wages and skills development promote the labour productivity and total factor productivity (TFP) of Thai manufacturers. R&D is also shown to be vital in promoting the labour productivity and TFP of large firms, but not small firms. Foreign direct investment (FDI) and government support can significantly increase large and medium-sized firms' labour productivity and TFP. Financially constrained firms tend to perform more productively. However, older firms, larger firms, labour supply shortages and political instability adversely affect labour productivity and TFP.
Practical implications
Upskilling and improving HRD policies could move Thailand towards a knowledge-based and high-income country in the future. Intellectual property protection should be strengthened to boost the country's R&D. The government should consider lifting restrictions on FDI to encourage international openness. The Thai Board of Investment’s promotion should target Thai manufacturing firms and FDI.
Originality/value
This study is the first to examine in detail the role of wages, skills development and R&D on the productivity of Thai firms based on the 2017 Thailand Industrial Census.
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Dan-Andrei Sitar-Taut and Daniel Mican
This paper investigates if the existing degree of students' acceptance and use of mobile or m-learning may face the online shift determined by SARS-CoV-2. Based on the extended…
Abstract
Purpose
This paper investigates if the existing degree of students' acceptance and use of mobile or m-learning may face the online shift determined by SARS-CoV-2. Based on the extended unified theory of acceptance and use of technology (UTAUT2), a new comprehensive model, SD-UTAUT (social distancing-UTAUT), is developed to better understand relationships between the original constructs, plus personal innovativeness (PI) and information quality (IQ). It identifies the key factors affecting behavioral intention (BI) and use by examining the influence of revaluated hedonic motivation (HM) and learning value (LV) importance as mediators.
Design/methodology/approach
The paper opted for an exploratory study involving 311 learners, using partial least squares structural equation modeling (PLS-SEM).
Findings
SD-UTAUT can be a new m-learning model in higher education. It has high predictive power and confirmed 15 out of 16 hypotheses. The most powerful relationship is between performance expectancy (PE) and HM. IQ affected LV the most, since HM the behavioral use (BU). HM impacts the use behavior (UB) more than LV, but habit (HT) affects it the most.
Research limitations/implications
Because of the pandemic context, output may lack generalizability and reproducibility.
Practical implications
To improve usage, staff must provide better support, course creators emphasize the objectives and competencies and developers integrate innovation. The joy and pleasure of m-learning use may stimulate the LV through interesting and interactive content, like incorporating gamification.
Originality/value
The model set-up and circumstances are previously unseen. SD-UTAUT confirms ten new hypotheses and introduces the student's grade point average (GPA) as a moderator.
Peer review
The peer review history for this article is available at https://publons.com/publon/10.1108/OIR-01-2021-0017