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1 – 10 of over 5000Chenglong Yu, Zhiqi Li, Dapeng Yang, Hong Liu and Alan F. Lynch
This study aims to propose a novel method based on model learning with sparsity inducing norms for estimating dynamic gravity terms of the serial manipulators. This method is…
Abstract
Purpose
This study aims to propose a novel method based on model learning with sparsity inducing norms for estimating dynamic gravity terms of the serial manipulators. This method is realized by operating the robot, acquiring data and filtering the features in signal acquisition to adapt to the dynamic gravity parameters.
Design/methodology/approach
The core principle of the method is to analyze the dictionary composition of the basis function of the model based on the dynamic equation and the Jacobian matrix of an arm. According to the structure of the basis function and the sparsity of the features, combined with joint-angle and driving-torque data acquisition, the effective features of dynamic gravity parameters are screened out using L1-norm optimization and learning algorithms.
Findings
The theoretical analysis revealed that training data obtained based on joint angles and driving torques could rapidly update dynamic gravity parameters. The simulation experiment was carried out by using the publicly available robot model and compared with the previous disassembly method to evaluate the feasibility and performance. The real 7-degree of freedom (DOF) industrial manipulator was used to further discuss the effects of the feature selection. The results show that this estimation method can be fully operational and efficient in industrial applications.
Research limitations/implications
This approach is applicable to most serial robots with multi-DOF and the dynamic gravity parameters of the robot are estimated through learning and optimization. The method does not require prior knowledge of the robot arm structure and only requires joint-angle and driving-torque data acquisition under low-speed motion. Furthermore, as it is a data-driven-based method, it can be applied to gravity parameters updating.
Originality/value
Different from previous general robot dynamic modelling methods, the sparsity of the analytical form of dynamic equations was exploited and model learning was formulated as a convex optimization problem to achieve effective gravity parameters screening. The novelty of this estimation approach is that the method does not only require any prior knowledge but also does not require a specifically designed trajectory. Thus, this method can avoid the laborious work of parameter calibration and the induced modelling errors. By using a data-driven learning approach, the new parameter updating process can be completed conveniently when the robot carries additional mass or the end-effector changes for different tasks.
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Bassem Kahouli and Samir Maktouf
– This paper aims to use the approach based on the application of the law of gravity for the study of the flows of export and the effects of the RTAs.
Abstract
Purpose
This paper aims to use the approach based on the application of the law of gravity for the study of the flows of export and the effects of the RTAs.
Design/methodology/approach
In this paper, the authors evaluate the effects of RTAs on exports between members and non-members taking into account the Vinerian specification. The authors also try to estimate the impact of the recent economic crisis on the flows of export and the success of the RTAs. The authors use a model of static and dynamic gravity for 40 countries and six RTAs during the period 1980-2011.
Findings
Definitely the proliferation of RTAs will continue to be one of the driving forces that will constitute the political system and the global economy in the following years. It indicates a process that implies the merger of economies separated in bigger regions of free trade. Regional integration is seen as beneficial in many senses and is the major economic objectives in addition to presenting a stabilizing factor in international relations.
Originality/value
The gravity model is estimated using the last techniques of panel data which takes into account the endogeneity of the effects of integration and the existence of dynamic effect.
Economists have had problems interpreting the gravity model, particularly as applied to migration behaviour. Its physical analogy is unappealing and theories of economic behaviour…
Abstract
Economists have had problems interpreting the gravity model, particularly as applied to migration behaviour. Its physical analogy is unappealing and theories of economic behaviour do not generally give rise to gravity laws. Some years ago Niedercorn and Bechdolt (1969) published a paper in which they provide a derivation of the gravity model using utility theory. Their approach is, however, much more applicable to other flows of human interaction across space, such as travel or communication flows, than it is to migration flows. The major purpose of this paper is to indicate a set of assumptions which might underlie a gravity model of migration and to show that these assumptions are quite severe. One important implication is that we should fully expect any real world migration pattern to deviate from the predictions of a gravity model. Nevertheless, the gravity specification may be a useful starting point in the analysis of migration behaviour, as it imposes restrictions on the formulation of the estimating equations. Thus we may fruitfully study how and why the real world migration patterns diverge from gravity flows.
Gour Gobinda Goswami, Md. Rubaiyath Sarwar and Md. Mahbubur Rahman
The main objective of this paper is to examine the impact of COVID-19 on the tourism flows of eight Asia-Pacific Countries: Australia, Hong Kong, Malaysia, New Zealand, the…
Abstract
Purpose
The main objective of this paper is to examine the impact of COVID-19 on the tourism flows of eight Asia-Pacific Countries: Australia, Hong Kong, Malaysia, New Zealand, the Philippines, Singapore, Taiwan and Thailand.
Design/methodology/approach
Using monthly data from 2019M1 to 2021M10 and 48 origin and eight destination countries in a panel Poisson pseudo-maximum likelihood (PPML) estimation technique and gravity equation framework, this paper finds that after controlling for gravity determinants, COVID-19 periods have a 0.689% lower tourism inflow than in non-COVID-19 periods. The total observations in this paper are 12,138.
Findings
A 1% increase in COVID-19 transmission in the origin country leads to a 0.037% decline in tourism flow in the destination country, while the reduction is just 0.011% from the destination. On the mortality side, the corresponding decline in tourism flows from origin countries is 0.030%, whereas it is 0.038% from destination countries. A 1% increase in vaccine intensity in the destination country leads to a 0.10% improvement in tourism flows, whereas vaccinations at the source have no statistically significant effect. The results are also robust at a 1% level in a pooled OLS and random-effects specification for the same model.
Research limitations/implications
The findings provide insights into managing tourism flows concerning transmission, death and vaccination coverage in destination and origin countries.
Practical implications
The COVID-19-induced tourism decline may also be considered another channel through which the global recession has been aggravated. If we convert this decline in terms of loss of GDP, the global figure will be huge, and airline industries will have to cut down many service products for a long time to recover from the COVID-19-induced tourism decline.
Social implications
It is to be realized by the policymaker and politicians that infectious diseases have no national boundary, and the problem is not local or national. That’s why it is to be faced globally with cooperation from all the countries.
Originality/value
This is the first paper to address tourism disruption due to COVID-19 in eight Asia-Pacific countries using a gravity model framework.
Highlights
Asia-Pacific countries are traditionally globalized through tourism channels
This pattern was severely affected by COVID-19 transmission and mortality and improved through vaccination
The gravity model can be used to quantify the loss in the tourism sector due to COVID-19 shocks
Transmission and mortality should be controlled both at the origin and the destination countries
Vaccinations in destination countries significantly raise tourism flows
Asia-Pacific countries are traditionally globalized through tourism channels
This pattern was severely affected by COVID-19 transmission and mortality and improved through vaccination
The gravity model can be used to quantify the loss in the tourism sector due to COVID-19 shocks
Transmission and mortality should be controlled both at the origin and the destination countries
Vaccinations in destination countries significantly raise tourism flows
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Alessandro Antimiani and Valeria Costantini
The purpose of this paper is to analyse the role of the enlargement process of the European Union as a factor fostering international competitiveness of EU Member States. The…
Abstract
Purpose
The purpose of this paper is to analyse the role of the enlargement process of the European Union as a factor fostering international competitiveness of EU Member States. The paper argues that the economic integration process has reduced the technological gap between old and new EU Member States, and this pattern of technological innovation can partially explain the strong impulse on the export dynamics of European countries.
Design/methodology/approach
The paper builds an augmented gravity model by including the role of technological innovation, proxied by the stock of knowledge at the sector level. The authors gather together information on patents applied to international offices and bilateral export flows available from COMTRADE dataset.
Findings
By using a dynamic panel data estimator the authors find three main empirical evidences. First, the enlargement process has produced an overall larger positive impact on export flows for new Members than for old ones, and more importantly that sectors with the higher technological content have received the strongest impulse. Second, the augmented gravity model allows shaping the crucial role of technological innovation in fostering export competitiveness. Third, this impact seems to be stronger for old EU Member States than for new ones.
Research limitations/implications
The major limitation concerns time span adopted in this work. By expanding the dataset to further years it could be possible to better disentangle the effects also related to the new wave of the EU enlargement.
Social implications
The policy implication derived is that the more the new EU Members catch up technologically as a result of the integration process, the more they will benefit in terms of economic development.
Originality/value
The major originality of this paper is the construction of an augmented gravity model by including the role of technological innovation, applied to distinguished manufacturing sectors in a dynamic panel setting.
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Junshan Hu, Xinyue Sun, Wei Tian, Shanyong Xuan, Yang Yan, Wang Changrui and Wenhe Liao
Aerospace assembly demands high drilling position accuracy for fastener holes. Hole position error correction is a key issue to meet the required hole position accuracy. This…
Abstract
Purpose
Aerospace assembly demands high drilling position accuracy for fastener holes. Hole position error correction is a key issue to meet the required hole position accuracy. This paper aims to propose a combined hole position error correction method to achieve high positioning accuracy.
Design/methodology/approach
The bilinear interpolation surface function based on the shape of the aerospace structure is capable of dealing with position error of non-gravity deformation. A gravity deformation model is developed based on mechanics theory to efficiently correct deformation error caused by gravity. Moreover, three solution strategies of the average, least-squares and genetic optimization algorithms are used to solve the coefficients in the gravity deformation model to further improve position accuracy and efficiency.
Findings
Experimental validation shows that the combined position error correction method proposed in this paper significantly reduces the position errors of fastener holes from 1.106 to 0.123 mm. The total position error is reduced by 43.49% compared with the traditional mechanics theory method.
Research limitations/implications
The position error correlation method could reach an accuracy of millimeter or submillimeter scale, which may not satisfy higher precision.
Practical implications
The proposed position error correction method has been integrated into the automatic drilling machine to ensure the drilling position accuracy.
Social implications
The proposed position error method could promote the wide application of automatic drilling and riveting machining system in aerospace industry.
Originality/value
A combined position error correction method and the complete roadmap for error compensation are proposed. The position accuracy of fastener holes is reduced stably below 0.2 mm, which can fulfill the requirements of aero-structural assembly.
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Gour Gobinda Goswami and Nisit Panthamit
Political risk factors play a pivotal role in determining the bilateral trade flow of Asian countries in general and the Association for Southeast Asian Nations (ASEAN) countries…
Abstract
Purpose
Political risk factors play a pivotal role in determining the bilateral trade flow of Asian countries in general and the Association for Southeast Asian Nations (ASEAN) countries in particular. The main purpose of this research paper is to examine the impact of disaggregated political risk in lowering the bilateral trade flow of Thailand, a prominent member of ASEAN, vis-à-vis her 132 trading partners.
Design/methodology/approach
Using panel data of Thailand with her partner countries for the period 1984–2015, this paper uses four different panel specifications named pooled ordinary least squares and random effects estimations (estimated generalized least squares estimation) of three types by controlling for cross-sectional heteroscedasticity, time-wise heteroscedasticity and contemporaneous correlation.
Findings
Holding other gravity-based determinants constant, for one unit increase in the ranking of indicator of military in politics at home and abroad, trade flow decreases by 5–9% of the total trade flow of Thailand per year. For other types of political risks like government instability at home and abroad, difficulties in investment profile at home and abroad and internal and external conflict at home and abroad, the decrease is also substantial and most statistically significant. The magnitude of loss due to the military channel at home and abroad can amount to US$9.38–US$16.88 bn per year for Thailand, after controlling for other gravity variables.
Research limitations/implications
The reasons for risk originating from different political channels could be explored at the regional or global level to understand their global and local dimensions.
Practical implications
Policymakers should attempt to resolve the political risks at home and abroad in an amicable manner, through dialogue, so that bilateral trade flow is not inhibited.
Social implications
By taking economic reforms only, the trading problem cannot be resolved until and unless Thailand involves her society, politics and administrative mechanisms in a conducive manner to facilitate her trade. A dialogue among bureaucracy, political authority and military is beneficial in mitigating political risks.
Originality/value
The paper is unique in the sense that it makes a solid attempt to identify the potential channels of disaggregated political risk in affecting trade flow negatively, in a gravity framework, by controlling for different kinds of error structure.
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This study attempts to explore the determinants of tourism demand that impact tourist arrivals in Australia from Asia using an augmented panel gravity model.
Abstract
Purpose
This study attempts to explore the determinants of tourism demand that impact tourist arrivals in Australia from Asia using an augmented panel gravity model.
Design/methodology/approach
The augmented panel gravity model was utilised to analyse the demand for Australian tourism from 15 major countries of Asia over the period 1991 to 2018. Tourist arrivals were the dependent variable while per capita gross domestic product (GDP) and weighted distance were important explanatory variables. Further other indicators like population, money supply, globalisation, price index, exchange rate, uncertainty and two dummy variables were added as control variables.
Findings
The results demonstrate based on the novel methodology of Pesaran (2006), namely CCE (common correlated effects) that tourist arrivals are impacted positively and significantly by per capita GDP of both the country of origin and destination country, globalisation also impacts tourist flows positively. However, tourist arrivals are adversely affected by distance and prices confirming the economic theory.
Originality/value
Gravity models have been intensively used in the recent literature on tourism; however, this study has attempted to explore tourism demand from Asia into Australia which is indeed an unexplored area further the study has used the CCE methodology which takes care of the problems of cross-sectional dependence unlike the earlier methods widely used in the literature like the DOLS and the FMOLS. Last by utilising a wide-ranging set of macro factors the study contributes a novel assessment to the recent literature on tourism demand model.
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Diego Agudelo, Galia Julieta Benítez and Lawrence S. Davidson
This study presents evidence of increasing regionalization of international trade among 10 South American countries from 1980 to 2001. Regionalization of trade in South America is…
Abstract
This study presents evidence of increasing regionalization of international trade among 10 South American countries from 1980 to 2001. Regionalization of trade in South America is best described as an increasing trade among Spanish-speaking countries and increasing trade within the two regional agreements, the Andean Community and Mercosur. There is also evidence of border erosion in the continent, especially among the Mercosur members. These results emerge from a simple statistical analysis and are also economically significant when tested in a consistent gravity equation that controls for a set of macroeconomic and geographic variables.
Wen Yu, Xiaoou Li and Roberto Carmona
– This paper aims to address a new iterative tuning method of PID control for robot manipulators.
Abstract
Purpose
This paper aims to address a new iterative tuning method of PID control for robot manipulators.
Design/methodology/approach
This tuning method uses several properties of the robot control, such as any PD control can stabilize a robot in regulation case, the closed-loop system of PID control can be approximated by a linear system, the control torque to the robot manipulator is linearly independent of the robot dynamic.
Findings
Compared with the other PID tuning methods, this novel method is simple, systematic, and stable. The transient properties of this PID control are better than the other normal PID controllers.
Originality/value
In this paper, a new systematic tuning method for PID control is proposed. The paper applies this method on an upper limb exoskeleton, and real experiment results give validation of our PID tuning method.