Shuang-Gao Li, Wenmin Chu, Xiang Huang and Jinggang Xu
In the digital assembly system of large aircraft components (LAC), the docking trajectory of LAC is an important factor affecting the docking accuracy and stability of the LAC…
Abstract
Purpose
In the digital assembly system of large aircraft components (LAC), the docking trajectory of LAC is an important factor affecting the docking accuracy and stability of the LAC. The main content of docking trajectory planning is how to move the LAC from the initial posture and position to the target posture and position (TPP). This paper aims to propose a trajectory planning method of LAC based on measured data.
Design/methodology/approach
First, the posture and position error model of the wing is constructed according to the measured data of the measurement points (MPs) and the fork lug joints. Second, the particle swarm optimization algorithm based on the dynamic inertia factor is used to optimize the TPP of the wing. Third, to ensure the efficiency and stability of posture adjustment, the S-shaped curve is used as the motion trajectory of LAC, and the parameters of the trajectory are solved by the generalized multiplier method. Finally, a series of docking experiments are carried out.
Findings
During the process of posture adjustment, the motion of the numerical control locator (NCL) is stable, and the interaction force between the NCLs is always within a reasonable range. After the docking, the MPs are all within the tolerance range, and the coaxiality error of the fork lug hole is less than 0.2 mm.
Originality/value
In this paper, the measured data rather than the theoretical design model is used to solve the TPP, which improves the docking accuracy of LAC. Experiment results show that the proposed trajectory method can complete the LAC docking effectively and improve the docking accuracy.
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Yang Liu, Xiang Huang, Shuanggao Li and Wenmin Chu
Component positioning is an important part of aircraft assembly, aiming at the problem that it is difficult to accurately fall into the corresponding ball socket for the ball head…
Abstract
Purpose
Component positioning is an important part of aircraft assembly, aiming at the problem that it is difficult to accurately fall into the corresponding ball socket for the ball head connected with aircraft component. This study aims to propose a ball head adaptive positioning method based on impedance control.
Design/methodology/approach
First, a target impedance model for ball head positioning is constructed, and a reference positioning trajectory is generated online based on the contact force between the ball head and the ball socket. Second, the target impedance parameters were optimized based on the artificial fish swarm algorithm. Third, to improve the robustness of the impedance controller in unknown environments, a controller is designed based on model reference adaptive control (MRAC) theory and an adaptive impedance control model is built in the Simulink environment. Finally, a series of ball head positioning experiments are carried out.
Findings
During the positioning of the ball head, the contact force between the ball head and the ball socket is maintained at a low level. After the positioning, the horizontal contact force between the ball head and the socket is less than 2 N. When the position of the contact environment has the same change during ball head positioning, the contact force between the ball head and the ball socket under standard impedance control will increase to 44 N, while the contact force of the ball head and the ball socket under adaptive impedance control will only increase to 19 N.
Originality/value
In this paper, impedance control is used to decouple the force-position relationship of the ball head during positioning, which makes the entire process of ball head positioning complete under low stress conditions. At the same time, by constructing an adaptive impedance controller based on MRAC, the robustness of the positioning system under changes in the contact environment position is greatly improved.
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Shan Chen, Fuli Zhou, Jiafu Su, Longxiao Li, Biyu Yang and Yandong He
The paper investigates firms' optimal pricing policies and green strategies in a dynamic green supply chain with consideration of different retail service strategies. The purpose…
Abstract
Purpose
The paper investigates firms' optimal pricing policies and green strategies in a dynamic green supply chain with consideration of different retail service strategies. The purpose of the paper is to address the following research questions: (1) What are the optimal pricing policies and green strategies of the dynamic decentralized supply chain with the competitive or supportive retail service? (2) How does the dynamic consumer's perception of green product affect these equilibrium solutions?
Design/methodology/approach
The paper establishes the dynamic game models and then derives a firm's instantaneous and steady-state feedback equilibrium solutions in three scenarios as follows: (1) the integrated supply chain; (2) the decentralized supply chain with competitive retail service and (3) the decentralized supply chain with supportive retail service. Finally, we conduct numerical analyses to compare the firm's instantaneous and steady-state equilibrium solutions and profit in the three scenarios.
Findings
The theoretical and numerical analysis results suggest that the supportive retail service is less inefficient than the competitive retail service in the decentralized supply chain and that the types of retail service have no influence on the green strategy. Moreover, a firm's myopia leads to lowering the greenness degree, retail service level and severe price competition, resulting in economic losses. Consumers’ initial perception of greenness degree determines whether the retailer should adopt the skimming pricing strategy or penetration pricing strategy. Furthermore, only when consumers’ perception of greenness degree is higher than a threshold, will the manufacturer produce green product with positive greenness degree.
Originality/value
This is one of few studies on the effect of different types of retail service on horizontal competition in green supply chain. The extension of the static study by adopting differential game approaches provides researchers with a deeper understanding of the application of retail service in green supply chain.
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Meng H. Lean and Wei-Ping L. Chu
The purpose of this paper is to describe a rapid and robust axisymmetric hybrid algorithm to create dynamic temporal and spatial charge distributions, or charge map, in the…
Abstract
Purpose
The purpose of this paper is to describe a rapid and robust axisymmetric hybrid algorithm to create dynamic temporal and spatial charge distributions, or charge map, in the simulation of bipolar charge injection using Schottky emission and Fowler-Nordheim tunneling, field-dependent transport, recombination, and bulk and interfacial trapping/de-trapping for layered polymer films spanning the range from initial injection to near breakdown.
Design/methodology/approach
This hybrid algorithm uses a source distribution technique based on an axisymmetric boundary integral equation method (BIEM) to solve the Poisson equation and a fourth-order Runge-Kutta (RK4) method with an upwind scheme for time integration. Iterative stability is assured by satisfying the Courant-Friedrichs-Levy (CFL) stability criterion. Dynamic charge mapping is achieved by allowing conducting and insulating boundaries and material interfaces to be intuitively represented by equivalent free and bound charge distributions that collectively satisfy all local and far-field conditions.
Findings
Charge packets cause substantial increase of electric stress and could accelerate the breakdown of polymeric capacitors. Conditions for the creation of charge packets are identified and numerically demonstrated for a combination of impulsive step excitation, high charge injection, and discontinuous interface.
Originality/value
Metallized bi-axially oriented polypropylene (BOPP) dielectric thin film capacitor with self-clearing and enhanced current carrying capability offer an inexpensive and lightweight alternative for efficient power conditioning, energy storage, energy conversion, and pulsed power. The originality is the comprehensive physics and multi-dimensional modeling which span the dynamic range from initial injection to near breakdown. This model has been validated against some empirical data and may be used to identify failure mechanisms such as charge packets, gaseous voids, and electroluminescence. The value lies in the use of this model to develop mitigation strategies, including re-designs and materials matching, to avoid these failure mechanisms.
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Md. Anwarul Abedin and Rajib Shaw
The contamination of groundwater by natural arsenic is currently a worldwide epidemic. Arsenic-contaminated groundwater has been reported in Argentina, Chile, Mexico, China…
Abstract
The contamination of groundwater by natural arsenic is currently a worldwide epidemic. Arsenic-contaminated groundwater has been reported in Argentina, Chile, Mexico, China, Hungary, West Bengal in India, Bangladesh, and Vietnam. Of these regions, Bangladesh and West Bengal are the most seriously affected in terms of the size of the population at risk and magnitude of health problems. Hence, chronic exposure to arsenic >50′′μg/L in drinking water can result in serious health problems. Common symptoms of arsenic-related ailments are skin, cardiovascular, renal, hematological, and respiratory disorders. Therefore, this chapter focuses on nature, origin, and extent of groundwater arsenic contamination, probable causes, and its impacts on food, drinking water, and social coverage. It further discloses mitigation approaches proposed and practiced by the different research groups to combat this problem and finally concludes.
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Chwo-Ming J. Yu, Hsiao-Wen Lin and Hui-Yun Chiu
In recent years, many firms from developing countries (LDCs) have engaged in foreign direct investment (FDI). Interestingly some of these firms locate their investments in…
Abstract
In recent years, many firms from developing countries (LDCs) have engaged in foreign direct investment (FDI). Interestingly some of these firms locate their investments in developed countries (DCs) (i.e., upstream FDI), instead of in countries economically similar to or less than their home countries (i.e., downstream FDI). However, only a few researchers have examined the issues related to upstream FDI. Furthermore, when examining FDI, most studies have focused on manufacturing subsidiaries but paid less attention to sales subsidiaries. Due to the differences in nature, management of manufacturing and sales subsidiaries should be different. Using a case study approach and focusing on the behaviors of Taiwanese firms, we address two research questions: (1) what are the channel strategies adopted by the sales subsidiaries of Taiwanese high-tech firms (i.e., multinational corporations (MNCs) from LDCs (LDCMNCs)) in DCs? and (2) how do these subsidiaries manage their channels in DCs? Our findings are: (1) LDCMNCs tend to use multiple sales channels, to work with large national distributors, and to adopt high touch channels to market products in DCs; (2) to reduce channel conflict, less powerful LDCMNCs tend to adopt multiple independent channel system, instead of dual channel system; and (3) due to limited resources, LDCMNCs make more effort on designing channel conflict prevention mechanisms than designing channel conflict resolution mechanisms, emphasize more on building relationships with distributors and tend to use financial incentives/high-power incentives than use other types of incentives to motivate distributors. The findings of this study are helpful for LDC firms to operate their sales subsidiaries more effectively in DCs.
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During the operation of Wendelstein 7-X (W7-X), any mechanical disturbance such as stick-slip may cause quenching of superconducting (SC) coils. The friction behavior of MoS2…
Abstract
Purpose
During the operation of Wendelstein 7-X (W7-X), any mechanical disturbance such as stick-slip may cause quenching of superconducting (SC) coils. The friction behavior of MoS2 lubrication (thin film) for narrow support elements between the SC coils in W7-X is rather important, as there is a design requirement for a coefficient of friction (COF) 0.05 between the sliding surfaces to control the stress contribution (from friction).
Design/methodology/approach
The author has carried out intensive calibrations or verifications using verified models considering previous friction tests on various samples which measured the COF in 4.2 K, 77 K and room temperature conditions (at high vacuum) to simulate the actual working condition.
Findings
The author has given useful explanations and diagnosis for previous anomalous scattered data. To improve the performance of MoS2, the author has predicted its better COF (0.002 via tuning of the activation volume), which could be a superlubricating state for MoS2 thin films considering the long-term operation requirement W7-X.
Originality/value
In this paper, the author has adopted Eyring’s approach to predict the low COF (0.002 via tuning of the activation volume), which could be a superlubricating state for MoS2 thin films considering the long-term operation requirement W7-X. Finally, some recent progresses about the possible few-layer MoS2 role in the electromagnetic loads have been provided.
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In 1968, Garrett Hardin identified a class of common goods that suffer under traditional market mechanisms. As a result, institutions become pivotal in defining acceptable…
Abstract
In 1968, Garrett Hardin identified a class of common goods that suffer under traditional market mechanisms. As a result, institutions become pivotal in defining acceptable consumption behavior. This paper describes the results of an agent-based computer simulation used to study how institutional forces shape consumption patterns. The results suggest common-interested behaviors support a greater population at a higher quality of living; however, exclusively common-interested behaviors result in underutilized commons, and the whole is generally less well off. Overall, when populations generally act in the common-interest, the commons, the population and individuals all experience higher quality outcomes than when they act in generally or exclusively self-interested ways. The paper frames further applications in terms of managing growth for long-term sustainability.
Patrick Lo, Allan Cho, Man-hon Leung, Dickson K.W. Chiu, Eddie H.T. Ko and Kevin K.W. Ho
– The purpose of this paper is to explore art and design students’ use of smartphones for accessing library services and learning at the Hong Kong Design Institute (HKDI).
Abstract
Purpose
The purpose of this paper is to explore art and design students’ use of smartphones for accessing library services and learning at the Hong Kong Design Institute (HKDI).
Design/methodology/approach
A questionnaire survey involving 51 HKDI students was conducted to examine the students’ utilization of apps and the internet on mobile devices to find information for the purpose of academic learning, social networking, and collaborative learning.
Findings
Survey results showed that while the HKDI students were all smartphone owners and active users of such mobile communication devices, only a minority of them “frequently” use these mobile devices for formal learning purposes. They demonstrated a keen preference to use search engines, social communications, and other diverse use of smartphones. Except for research and image/audio-visual needs, the rest of their needs and usage behaviour is similar to mainstream university students.
Practical implications
The results suggest opportunities for the libraries to develop services and facilities that could better fulfil students’ information needs, and to improve the network coverage outside the library.
Originality/value
This is probably the first study of its kind to explore art and design students’ use of smartphones for learning needs. In particular, the recent capability of smartphones and mobile internet speed are comparable with desktops, it is vital to re-examine the much changed environment and user needs.
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The rapid urbanization of China brings in large number of migrant workers coming from rural areas. With the perspective of social integration, this study reviews the findings…
Abstract
Purpose
The rapid urbanization of China brings in large number of migrant workers coming from rural areas. With the perspective of social integration, this study reviews the findings about economic livelihood, social integration and health related to migrant workers since China initiated economic reform. We show that (1) though the economic wellbeing of migrant workers has been improved significantly after they moved to cities, their economic standing is still lower than local residents; (2) though there is progress of social integration between migrant workers and local residents, conflicts and challenges due to the competitions in employment and the sharing of community resource are still commonly found; (3) the disadvantaged status of health is very common among migrant workers and (4) women and the new generation in migration have more disadvantages in the social transition. We suggest that issues of equal rights between migrant workers and local residents should be discussed in the future as more migrant workers intend to stay in cities for long-term.
Design/methodology/approach
The methodology is literature reviews based on the current studies about migrant, migration and policy. The first category of literature is the research field on China's migration and urbanization to describe the whole context of migrant workers. The second is research field on detailed issues about migrant workers and the last field is policy issues about the welfare and needs among migrant workers.
Findings
We find that (1) though the economic wellbeing of migrant workers has been improved significantly after they moved to cities, their economic standing is still lower than local residents; (2) though there are progress of social integration between migrant workers and local residents, conflicts and challenges due to the competitions in employment and the sharing of community resource are still commonly found; (3) the disadvantaged status of health is very common among migrant workers and (4) women and the new generation in migration face more disadvantages in the social transition.
Research limitations/implications
There are some limitations in the current research: (1) the review focuses on the majority of migrant workers to reveal the general picture about the living, developing and rights among migrant workers, but is still lacking in dealing with some special and disadvantaged groups. (2) More international issues related to migrant workers should be discussed in the future considering that China's labor market is becoming more and more global.
Social implications
First, the conclusion about the economic and social integration among migrant workers indicates that more equal welfare services, including resident services, commence services, medical services etc. should be included in the municipal managements considering that Chinese cities will be the combination of local residents and migrant residents. Second, the conclusion about the women and children indicates that the future public services targeted at the disadvantaged population should focus on migrant members due to the second generation of migrant workers will be one of the mainstream population in future China's cities.
Originality/value
This study gives general views on migrant workers in current China. The findings in this review conclude the main development and improvements among tens of millions of migrant workers in Chinese cities. Meanwhile, we also conclude that there are still many disadvantaged and marginalized sub-groups in migration who are suffering from less welfares and rights in urban lives. More detailed and equal rights and public services should be considered and implemented in the fast urbanization taking place.