Search results

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.

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.

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.

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.

Multi-protocol label switching (MPLS) networks are basically packet-based networks. There are various advantages of MPLS, such as better utilization of the network, reduction in the network latency, and the ability to adhere to the strict and stringent quality of service (QoS) criteria of incoming traffic. Since most of the applications are moving towards the packet-based networks, this move is mounting a pressure on the network providers for changing and upgrading their existing systems. There are various innovations and upgrades which are under progress and being improvised. These innovations and improvements will ensure that the networks can provide the ever-growing and rising demand of bandwidth. This research study captures the review of the concepts of MPLS networks and innovative technologies like traffic engineering, differentiated services, protection, and restoration. This research study also captures MPLS transport profile and its applications. As per the recent literature review, new protocols and designs of MPLS should be handled with care, and designers should exercise caution while recommending and proposing new designs and protocols. Most of the universities need to converge their networks to a single infrastructure in order to reduce operational costs and provide better network with improvised QoS to the students and faculties. Most of the universities and colleges are migrating to internet protocol (IP)/MPLS-based infrastructure. This will help in providing better networks to students studying and staying in universities. IP/MPLS is highly scalable and can be deployed end to end to accommodate the needs of any network size.

Purpose: This study aims to identify communication speech acts and transaction terms in online stores (Olshop) during live streaming on Facebook amid the COVID-19 pandemic and to understand communication patterns between sellers and buyers when shopping on Facebook live streaming in Indonesia.

The Need for Research: This research is motivated by the skill gap arising from increasing buying and selling transactions through live streaming on Facebook. Cultural and demographic shifts, along with the widespread availability of modern technologies and marketing 2.0 have resulted in the global population adopting social media at rates far beyond our use of the Internet, making a compelling case by example and analogy that social media has the potential to level the playing field and is effective in reaching their target market.

Methodology: The type of research is descriptive-qualitative using corpus data instruments. The data collection technique in this study was carried out by reading and observing the data and listening to speeches about buying and selling women’s equipment from various online stores on Facebook. Then select and sort the data designated as forms, strategies, and functions of speech acts in buying and selling transactions during live streaming on Facebook. The data analysis technique has three steps: (1) reducing the amount of data; (2) presenting the data; and (3) concluding.

Findings: The results show that there are four types of speech acts between sellers and buyers in the live-streaming online shop on Facebook, namely, assertive, directive, expressive, and commissive speech acts.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

This study aims to investigate the effects of exhaust direction on exhaust plume and helicopter infrared radiation in hover and cruise status.

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.

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.

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.

The 2019 coronavirus disease (COVID-19) pandemic has profoundly affected family and school life. Evidence demonstrates how pandemic-induced online learning and home confinement can influence family dynamics and, consequently, students’ mental health and quality of life. This chapter extends the literature by building upon the perspective of family systems theory and focusing the analysis on graduate students who are underrepresented in COVID-19 research. Drawing from an online survey among 337 graduate students enrolled in a state university in the Philippines during the second year of the pandemic, this study examines the three family relationship domains (cohesion, expressiveness, and conflict), their predictive relationships with life satisfaction, and the mediating role of mental well-being on these relationships. Findings indicate favorable levels of cohesion, expressiveness, and conflict in the family. Respondents’ age, sex assigned at birth, and marital status were significantly correlated with at least one domain of family relationship. Cohesion and expressiveness yielded significant positive predictive relationships on mental well-being and life satisfaction. Furthermore, findings indicate the partial mediation of mental well-being on the relationship between cohesion and life satisfaction and full mediation on expressiveness and life satisfaction.