Search results

The purpose of this paper is to explore the operation strategies of a manufacturer who produces brown and green product simultaneously.

The authors establish three models to examine the joint decisions of pricing and advertising. Three advertising strategies are: non-advertising investment (NA), advertising investment for brown product (BA) and advertising investment for green product (GA).

The theoretical analysis shows that advertising investment can substantially increase the product greening level and manufacturer's profit. More importantly, we find that the GA strategy is more likely to be the best strategy as the advertising investment efficiency increases. The BA strategy is more likely to be preferred as the R&D cost increases. Finally, the modeling results are verified by numerical experiments, and more insights are obtained.

This paper considers the case in which a single manufacturer produces the brown and green product simultaneously. In fact, many manufacturers in the market produce brown and green product at the same time. Furthermore, in addition to advertising investment for brown product and green product, manufacturers can also invest in advertising for brands.

The paper contributes to the investigations on green production and advertising decisions of a manufacturer who produces brown and green products simultaneously.

The weld joint of large thin-wall metal parts which deforms in manufacturing and clamping processes is very difficult to manufacture for its shape is different from the initial model; thus, the space normals of the part surface are uncertain.

In this paper, an effective method is presented to calculate cutter location points and to estimate the space normals by measuring some sparse discrete points of weld joint. First, a contact-type probe fixed in the end of friction stir welding (FSW) robot is used to measure a series of discrete points on the weld joint. Then, a space curve can be got by fitting the series of points with a quintic spline. Second, a least square plane (LSP) of the measured points is obtained by the least square method. Then, normal vectors of the plane curve, which is the projection of the space curve on the LSP, are used to estimate the space normals of the weld joint curve. After path planning, a post-processing method combing with FSW craft is elaborated.

Simulation and real experiment demonstrate that the proposed strategy, which obtains cutter locations of welding and normals without measuring the entire surface, is feasible and effective for the FSW of large thin-walled complex surface parts.

This paper presents a novel method which makes it possible to accurately weld the large thin-wall complex surface part by the FSW robot. The proposed method might be applied to any multi-axes FSW robot similar to the robot studied in this paper.

Uncertainty can arise for a manipulator because its motion can deviate unpredictably from the assumed dynamical model and because sensors might provide information regarding the system state that is imperfect because of noise and imprecise measurement. This paper aims to propose a method to estimate the probable error ranges of the entire trajectory for a manipulator with motion and sensor uncertainties. The aims are to evaluate whether a manipulator can safely avoid all obstacles under uncertain conditions and to determine the probability that the end effector arrives at its goal area.

An effective, analytical method is presented to evaluate the trajectory error correctly, and a motion plan was executed using Gaussian models by considering sensor and motion uncertainties. The method used an integrated algorithm that combined a Gaussian error model with an extended Kalman filter and a linear–quadratic regulator. Iterative linearization of the nonlinear dynamics was used around every section of the trajectory to derive all of the prior probability distributions before execution.

Simulation and experimental results indicate that the proposed trajectory planning method based on the motion and sensor uncertainties is indeed highly convenient and efficient.

The proposed approach is applicable to manipulators with motion and sensor uncertainties. It helps determine the error distribution of the predefined trajectory. Based on the evaluation results, the most appropriate trajectory can be selected among many predefined trajectories according to the error ranges and the probability of arriving at the goal area. The method has been successfully applied to a manipulator operating on the Chinese Space Station.

Time slot allocation in world interoperability for microwave access (WiMax) mesh networks is controlled by a centralized scheduling algorithm, as specified in the IEEE standard 802.16. The scheduling algorithm should be able to minimize the total transmission time for all traffic flows. The purpose of this paper is to investigate the multi‐channel scheduling problem in WiMax mesh networks, in order to explore the potential of simultaneous transmissions and thus minimize the total transmission time.

The paper first analyzes how many channels are sufficient for the avoidance of interference, then presents an efficient scheduling algorithm along with the channel assignment strategy for time slot allocation. Particularly, for networks with chain topology, the paper provides an optimal solution to minimize the total transmission time.

The simulation results show that this scheme can improve the system performance substantially as compared with the single‐channel system. Also, it is observed that double‐channel settings may provide a performance similar to the multiple channels.

The algorithm presented in this paper is conformed to the IEEE standard 802.16‐2004; so it is suitable for WiMax mesh networks.

The paper is of value in presenting a scheduling and channel assignment schema for multi‐channel WiMax mesh networks. The work is also important for the study of time division multiple access (TDMA)‐based multi‐channel wireless mesh networks.

Abnormal vibrations often occur in the liquid oxygen kerosene transmission pipelines of rocket engines, which seriously threaten their safety. Improper handling can result in failed rocket launches and significant economic losses. Therefore, this paper aims to examine vibrations in transmission pipelines.

In this study, a three-dimensional high-pressure pipeline model composed of corrugated pipes, multi-section bent pipes, and other auxiliary structures was established. The fluid–solid coupling method was used to analyse vibration characteristics of the pipeline under various external excitations. The simulation results were visualised using MATLAB, and their validity was verified via a thermal test.

In this study, the vibration mechanism of a complex high-pressure pipeline was examined via a visualisation method. The results showed that the low-frequency vibration of the pipe was caused by fluid self-excited pressure pulsation, whereas the vibration of the engine system caused a high-frequency vibration of the pipeline. The excitation of external pressure pulses did not significantly affect the vibrations of the pipelines. The visualisation results indicated that the severe vibration position of the pipeline thermal test is mainly concentrated between the inlet and outlet and between the two bellows.

The results of this study aid in understanding the causes of abnormal vibrations in rocket engine pipelines.

The causes of different vibration frequencies in the complex pipelines of rocket engines and the propagation characteristics of external vibration excitation were obtained.

This paper aims to present an overview of the challenges encountered in integrating visual search interfaces into digital libraries and repositories. These challenges come in various forms, including information visualisation, the use of knowledge organisation systems and metadata quality. The main purpose of this study is the identification of criteria for the evaluation and integration of visual search interfaces, proposing guidelines and recommendations to improve information retrieval tasks with emphasis on the education-al context.

The information included in this study was collected based on a systematic literature review approach. The main information sources were explored in several digital libraries, including Science Direct, Scopus, ACM and IEEE, and include journal articles, conference proceedings, books, European project reports and deliverables and PhD theses published in an electronic format. A total of 142 studies comprised the review.

There are several issues that authors did not fully discuss in this literature review study; more specific, aspects associated with access of digital resources in digital libraries and repositories based on human computer interaction, i.e. usability and learnability of user interfaces; design of a suitable navigation method of search based on simple knowledge organisation schemes; and the use of usefulness of visual search interfaces to locate relevant resources.

The main steps for carrying out a systematic review are drawn from health care; this methodology is not commonly used in fields such as digital libraries and repositories. The authors aimed to apply the fundamentals of the systematic literature review methodology considering the context of this study. Additionally, there are several aspects of accessibility that were not considered in the study, such as accessibility to content for disabled people as defined by ISO/IEC 40500:2012.

No other systematic literature reviews have been conducted in this field. The research presents an in-depth analysis of the criteria associated with searching and navigation methods based on the systematic literature review approach. The analysis is relevant for researchers in the field of digital library and repository creation in that it may direct them to considerations in designing and implementing visual search interfaces based on the use of information visualisation.

The paper aims to present a tracked robot comprised of several biochemical sampling instruments and a universal control architecture. In addition, a dynamic motion planning strategy and autonomous modules in sampling tasks are designed and illustrated at length.

Several sampling instruments with position tolerance and sealing property are specifically developed, and a robotic operation system (ROS)-based universal control architecture is established. Then, based on the system, two typical problems in sampling tasks, i.e. arm motion planning in unknown environment and autonomous modules, are discussed, implemented and tested. Inspired by the idea of Gaussian process classification (GPC) and Gaussian process (GP) information entropy, three-dimensional (3D) geometric modeling and arm obstacle avoidance strategy are implemented and proven successfully. Moreover, autonomous modules during sampling process are discussed and realized.

Smooth implementations of the two experiments justify the validity and extensibility of the robot control scheme. Furthermore, the former experiment proves the efficiency of arm obstacle avoidance strategy, while the later one demonstrates the time reduction and accuracy improvement in sampling tasks as the autonomous actions.

The proposed control architecture can be applied to more mobile and industrial robots for its feasible and extensible scheme, and the utility function in arm path planning strategy can also be utilized for other information-driven exploration tasks.

Several specific biochemical sampling instruments are presented in detail, while ROS and Moveit! are integrated into the system scheme, making the robot extensible, achievable and real-time. Based on the control scheme, an information-driven path planning algorithm and automation in sampling tasks are conceived and implemented.

The purpose of this paper was to solve the shortage of carrying energy in probing robot and make full use of wind resources in the Antarctic expedition by designing a four-wheel land-yacht. Land-yacht is a new kind of mobile robot powered by the wind using a sail. The mathematical model and trajectory of the land-yacht are presented in this paper.

The mechanism analysis method and experimental modeling method are used to establish a dual-input and dual-output mathematical model for the motion of land-yacht. First, the land-yacht’s model structure is obtained by using mechanism analysis. Then, the models of steering gear, servomotors and force of wing sail are analyzed and validated. Finally, the motion of land-yacht is simulated according to the mathematical model.

The mathematical model is used to analyze linear motion and steering motion. Compared with the simulation results and the actual experimental tests, the feasibility and reliability of the proposed land-yacht modeling are verified. It can travel according to the given signal.

This land-yacht can be used in the Antarctic, outer planet or for harsh environment exploration.

A land-yacht is designed, and the contribution of this research is the development of a mathematical model for land-yacht robot. It provides a theoretical basis for analysis of the land-yacht’s motion.