Variable Elasticity Research Articles

On the motion/stiffness decoupling property of articulated soft robots with application to model-free torque iterative learning control

This article tackles the problem of controlling articulated soft robots (ASRs), i.e., robots with either fixed or variable elasticity lumped at the joints. Classic control schemes rely on high-authority feedback actions, which have the drawback of altering the desired robot softness. The problem of accurate control of ASRs, without altering their inherent stiffness, is particularly challenging because of their complex and hard-to-model nonlinear dynamics. Leveraging a learned anticipatory action, iterative learning control (ILC) strategies do not suffer from these issues. Recently, ILC was adopted to perform position control of ASRs. However, the limitation of position-based ILC in controlling variable stiffness robots is that whenever the robot stiffness profile is changed, a different input action has to be learned. Our first contribution is to identify a wide class of ASRs, whose motion and stiffness adjusting dynamics can be proved to be decoupled. This class is described by two properties that we define: strong elastic coupling, relative to motors and links of the system and their connections; and homogeneity, relative to the characteristics of the motors. Furthermore, we design a torque-based ILC scheme that, starting from a rough estimation of the system parameters, refines the torque needed for the joint positions tracking. The resulting control scheme requires minimum knowledge of the system. Experiments on variable stiffness robots prove that the method effectively generalizes the iterative procedure with respect to the desired stiffness profile and allows good tracking performance. Finally, potential restrictions of the method, e.g., caused by friction phenomena, are discussed.

Effects of renewable and non‐renewable energy consumption on CO2 emissions in India: Empirical evidence from disaggregated data analysis

In this paper, we examined the relationship between renewable and non‐renewable energy consumption on CO2 emissions in India by taking disaggregated data from 1965 to 2018. In order to determine the effect of long‐run elasticity of independent variables on dependent variables, we have used ARDL bound testing approach. The directions of causality of the variables are investigated by Toda–Yamamoto Granger causality test. The long‐run results reveal that hydro energy consumption has a positive impact on CO2 emissions but not significant. However, nuclear energy consumption indicates that there is a negative effect on CO2 emissions. It reveals that all non‐renewable energy consumption sources have positive and significant effect on CO2 emissions.

Does remittance inflow influence human development in south Asian countries? An empirical insight

AbstractThis article investigate the relationship between human development, remittance inflows, and other macroeconomic variables like life expectancy, human capital, FDI, CPI, economic growth, and financial development in South Asia during 1990–2018. The Fisher residual co‐integration test confirms that there is a co‐integration among the variables. The VECM approach also indicates that there is a long run relationship among the variables. We apply FMOLS and DOLS to show the long run elasticity of explanatory variables in this article. Remittance indicates positive and significant effect on human development. We find that there is a positive effect between government expenditure and human development. Similarly, life expectancy rate and human capital has a positive effect on human development. There is a unidirectional causality between remittance and human development in South Asian region. We can suggest that public policies can be conceived to promote health, education, and income, thereby encouraging and enhancing human development.

Macroeconomic Growth in Vietnam Transitioned to Market: An Unrestricted VES Framework

The Vietnamese economy has increased at high speed over the transformation decades; however, most recent studies on the economic growth of this country used the Cobb-Douglas or CES (Constant Elasticity of Substitution) production functions, which are unable to explore the relationship between the elasticity of capital-labour substitution and development process, and hence, are not relevant to accessing a dynamic economic system. For that reason, this study is conducted to specify an unrestricted VES (Variable Elasticity of Substitution) production function in a one-sector growth model of Vietnam, highlighted by two characteristics: successful transition from plan to market and rapid progress. The VES is given preference over the CES and the Cobb-Douglas having the elasticity of substitution between capital and labour varying with economic development. By employing a Bayesian nonlinear regression through MCMC methods, the study reported the following findings: (1) the above-unity variable elasticity of capital-labour substitution in an aggregate unrestricted VES function specified for Vietnam shows that the model generates the possibility of endogenous economic growth; (2) the capital share tends to increase, while the labour share faces a downward trend along with the development of Vietnam; (3) the VES is empirically proven through a Bayes factor test to be superior to the CES and Cobb-Douglas for analysis of the growth process of Vietnam, an emerging transition economy.

DOES INFLATION ON ADMINISTERED PRICES AND VOLATILE FOODS COMMODITIES REDUCE THE HOUSEHOLDS WELFARE IN ACEH, INDONESIA?

High inflation is closely related to poverty. Inflation for volatile food is one of the causes of decreasing in household welfare. Volatile food commodities such as; rice, meat, fish, red chili, and shallot contributed to the inflation in the last three years. Likewise, administered price commodities such as LPG (liquefied petroleum gas), electricity, gasoline and water also contributed to high inflation. This study analyzes the effect of inflation on commodity-based welfare by analyzing the elasticity of demand for these commodities. The data used are cross section data obtained from the 2018 National Social Economic Survey (Susenas) of Aceh. The model used is the Almost Ideal Demand System (AIDS) model regressed with the Seemingly Unrelated Regression (SUR) approach. The results show that that most of the coefficient of the price has a negative and significant effect. The coefficient is used to calculate the elasticity of price variables, income elasticity, family size elasticity and education elasticity as control variables. The elasticity results indicates that prices greatly affect the decline in household welfare, displayed by the elastic value of demand for administrated and volatile food commodities while income elasticity, family size elasticity, and education elasticity shows an inelastic value. Therefore, it is recommended for Bank Indonesia and the government (in this case the Regional Inflation Control Team) to continue to pursue a commodity-based inflation control policy in Aceh. It is also necessary for the government to encourage more superior commodities, especially for volatile food commodities such as rice, meat, fish, red chili, and shallot. Producing more of the volatile food commodities will be important to maintain the price and quantity of food. In addition, the government must also provide symmetrical information about developments and plans to increase prices, thus not to cause excessive inflation expectations.

Nanobeam Theory Taking Into Account Physical Nonlinearity

In this paper, we construct a new theory of nanobeams taking into account the dependence of the material properties on the stress state. The theory is based on the Euler–Bernoulli kinematic model in the first approximation. The beam material is isotropic but heterogeneous. For the first time, the physical nonlinearity and the dependence of the material properties on the temperature are taken into account in the study of nanobeams, and the theory is developed for arbitrary materials. It is based on the theory of small elasticplastic strains and on the the modified torque theory of elasticity. The stationary temperature field is determined by solving the three-dimensional Poisson equation with boundary conditions of orders 1–3. The initial equations are derived from the Hamilton–Ostrogradskii principle. The desired system of partial differential equations is reduced to the Cauchy problem by the finite difference method of the second order of accuracy, and the Cauchy problem is solved by the Runge–Kutta or Newmark method. At each time step, an iterative procedure is developed by the Birger method of variable elasticity parameters. The stationary solution follows from the dynamic solution of the problem obtained by the method of determination (the method of the parameter position). The convergence of the solution is investigated depending on the number of points of partition along the length and thickness of the beam in the finite difference method as well as on the method of solving the Cauchy problem and the size-dependent parameter, i.e., the solution of the problem is considered to have almost infinite number of degrees of freedom. Numerical examples are given for a beam rigidly clamped at the ends with the stress-strain diagram for aluminum. Accounting for the size-dependent parameter in the nanobeam theory significantly affects the load-carrying capacity of nanobeams.

Asymptotic behavior of the solution of an axisymmetric problem of elasticity theory for a sphere with variable elasticity modules

In the paper the axisymmetric problem of elasticity theory is studied for the radially inhomogeneous sphere of small thickness that does not contain any of the poles 0 and . Here the case is considered when the elasticity modules vary linearly with respect to the radius. It is assumed that the lateral surface of the sphere is free of stresses, and at the ends of the sphere (at the conical sections) the stresses are set, leaving it in equilibrium. A characteristic equation is obtained and, based on its asymptotic analysis, the existence of three groups of roots is established with respect to the small parameter characterizing the thickness of the sphere. The corresponding homogeneous solutions are constructed, depending on the roots of the characteristic equation. It is shown that the penetrating solution corresponds to the first group of roots. The second group of roots corresponds to the solution of the edge effect type, similar to the edge effect in the applied theory of shells. The third group of roots corresponds to the boundary layer type solution localized in the conical sections. The solution corresponding to the first and second groups of roots determines the internal stress–strain state of the sphere. In the first term of the asymptotic, they can be considered as a solution in the applied theory of shells. The question of satisfying the boundary conditions at the ends (on the conical sections) of the sphere is considered using the variational Lagrange principle.

ДИНАМИКА ГЕОМЕТРИЧЕСКИ И ФИЗИЧЕСКИ НЕЛИНЕЙНОГО ЧУВСТВИТЕЛЬНОГО ЭЛЕМЕНТА НАНОЭЛЕКТРОМЕХАНИЧЕСКОГО ДАТЧИКА В ВИДЕ НЕОДНОРОДНОЙ НАНОБАЛКИ, НАХОДЯЩЕЙСЯ В ТЕМПЕРАТУРНОМ И ШУМОВОМ ПОЛЯХ

Актуальность исследования. Наноэлектромеханические системы,будучи высокочувствительными датчиками, имеющими малыеразмеры, и надежными в эксплуатации, находят все более широкое применение в нефтегазовой промышленности для мониторинга различных процессов в нефтедобыче – от разведки до повышения нефтеотдачи, а также при бурении скважин, очистке, фракционировании и переработке до вывода их из эксплуатации. Одним из примеров применения наноэлектромеханических систем является сейсмические исследование месторождений. Применениенаноэлектромеханических систем позволяет улучшить производительность в дополнение к существенной экономии средств и времени для широкого спектра технологий нефтегазовой промышленности. Благодаря возможности непрерывного контроля эти технологии могут стать основой «умных» месторождений. Цель: построение математической модели, наиболее полно описывающей нелинейную динамику чувствительного элемента наноэлектромеханического датчика под действием знакопеременной нагрузки. Для этогонеобходимо учесть наиболее распространённые в настоящее время кинематические гипотезы, масштабные эффекты с помощью моментной теории упругости,нелинейную зависимость между напряжениями и деформациями, неоднородность материала, шумовые и тепловые поля.А также исследовать характер сложных нелинейных колебаний и выявитьзакономерности перехода их от гармонических к хаотическим. Объекты: геометрически и физически нелинейная нанобалка, описываемая кинематической моделью первого приближения, на которую воздействует равномерно распределенная знакопеременная поперечная нагрузка с гармонической составляющей, температурное поле и аддитивный внешний шум. Методы: вариационные методы,метод конечных разностей второго порядка точности для сведения системы нелинейных дифференциальных уравнений в частных производных к задаче Коши, метод Ньюмарка для решения задачи Коши, метод переменных параметров упругости Биргерадля решения физически нелинейной задачи, метод вариационных итераций для получения аналитического решения двумерного уравнения теплопроводности. Результаты.Для получения аналитического решения теплопроводности применяется метод вариационных итераций. Построенаматематическая модельколебаний чувствительного элемента наноэлектромеханического датчика в виде размерно-зависимой балки, на которую действует равномерно распределенная поперечная нагрузка с гармонической составляющей. Помимо переменной нагрузки учитывалось влияние температурного поля и аддитивного внешнего шумового воздействия. Геометрическая нелинейность принята по теории Теодора фонКармана (связь между деформациями и перемещениями). Для учета физической нелинейностиматериалабалки применяются деформационная теория пластичности и метод переменных параметров упругости. Уравнения движения элемента механической системы, а также соответствующие граничные и начальные условия выведены исходя из принципа Остроградского–Гамильтона на базе модифицированной моментной теории с учетом гипотезы Эйлера–Бернулли.Выявлено,что температурное и шумовое поляуменьшают нагрузку, при которой происходит переход в хаотическое состояние системы. Переход от гармонических колебаний к хаотическим происходит по сценарию Рюэля–Такенса–Ньюхауза.

Perioperative Quality Initiative (POQI) consensus statement on fundamental concepts in perioperative fluid management: fluid responsiveness and venous capacitance

BackgroundOptimal fluid therapy in the perioperative and critical care settings depends on understanding the underlying cardiovascular physiology and individualizing assessment of the dynamic patient state.MethodsThe Perioperative Quality Initiative (POQI-5) consensus conference brought together an international team of multidisciplinary experts to survey and evaluate the literature on the physiology of volume responsiveness and perioperative fluid management. The group used a modified Delphi method to develop consensus statements applicable to the physiologically based management of intravenous fluid therapy in the perioperative setting.DiscussionWe discussed the clinical and physiological evidence underlying fluid responsiveness and venous capacitance as relevant factors in fluid management and developed consensus statements with clinical implications for a broad group of clinicians involved in intravenous fluid therapy. Two key concepts emerged as follows: (1) The ultimate goal of fluid therapy and hemodynamic management is to support the conditions that enable normal cellular metabolic function in order to produce optimal patient outcomes, and (2) optimal fluid and hemodynamic management is dependent on an understanding of the relationship between pressure, volume, and flow in a dynamic system which is distensible with variable elastance and capacitance properties.

A p–y curve model for laterally loaded XCC pile in soft clay

This paper presents a p–y curve model for laterally loaded X-sectional cast-in-place concrete (XCC) piles, which are a type of non-circular cross-sectional pile, in soft clay. The recently developed empirical solutions for the elastic stiffness and the ultimate lateral resistance of the two-dimensional laterally loaded X-shaped cross-sectional pile segment–soil system by the authors using the complex variable elasticity theory and finite element limit analysis are used as the two key parameters in constructing the p–y curve. An elastic–perfectly plastic p–y curve is immediately obtained with the linear elastic state described by the elastic stiffness of the two-dimensional system, and the perfectly plastic state is controlled by the ultimate lateral resistance. Furthermore, to consider the nonlinear behaviour, a more robust model using the hyperbolic function is selected for producing the p–y curve with the elastic stiffness and the ultimate lateral resistance incorporated. Subsequently, the p–y model is introduced to the Winkler model to generate solutions for the response of laterally loaded XCC piles. The proposed model considers the non-circular cross-sectional effect of the XCC pile and can also be regarded as a simple method for constructing the p–y curve for other non-circular cross-sectional piles.

The Spatial Distribution, Influencing Factors, and Development Path of Inbound Tourism in China—An Empirical Analysis of Market Segments Based on Travel Motivation

According to China’s tourism statistics, the inbound tourism market is composed of eight types of travel motivations (sightseeing, leisure, business meeting (business-m), visiting relatives and friends (visiting-rf), shopping, religious worship (religious-w), culture and sports (culture-s), and health care (health-c)), and the spatial distribution of each type of travel motivation is significantly different. Four inbound sub-markets (foreigners, Hong Kong, Macao, and Taiwan) were selected as our research object. Through empirical analysis of the variable elasticity of eight different inbound motive market segments, we found that the sensitivities (elasticity) of the influencing factors (traffic conditions (traffic-c), destination image (destination-i), industry structure (industry-s), infrastructure, consumer price index (CPI), resource endowment (resource-e), and dressing index (ICL)) are different. Therefore, investment options in the target market can have differential treatment based on the rate of marginal return on investment. In accordance with the characteristics of different market segments, we suggest more feasible development paths and countermeasures, providing a decision-making basis for the accurate development of the inbound tourism market.

On the Correctness of the Well-Known Mathematical Model of Irradiation-Induced Swelling with the Influence of Stresses in the Problems of Elastic-Plastic Deformation Mechanics

The paper provides results of the study of correctness of the mathematical model that includes the influence of stresses on irradiation-induced swelling of metal in the problems of elastic-plastic deformation mechanics. The present-day approaches to modeling irradiation-induced swelling, which take into account a damaging dose, irradiation temperature, and the effect of the stress state on the swelling deformation, are discussed. The constitutive equations that describe the elasticplastic deformation processes allowing for the influence of a stress mode on the irradiation-induced swelling in metal are put forward. Analysis of these equations has made it possible to find the conditions that ensure correctness of the plasticity equations considered and to make a lower-bound estimate of the maximum permissible value of free swelling and irradiation dose. A priori estimates of the maximum permissible value of free swelling and damaging dose are given for 08Kh18N10T steel under various irradiation temperatures. In the practice of strength design such estimates are needed at the stage of problem formulation in order to analyze adequacy of input data, for they enable one to assess a prior the possibility of solving the problem for a given temperature and irradiation dose. The boundary-value problem that describes non-isothermal processes of elasticplastic deformation including swelling strains has been defined in the form of a nonlinear operator equation. Based on the findings regarding the correctness of the constitutive equations, we have established the existence and uniqueness of the generalized solution and its continuous dependence on applied loads, thermal strains and swelling strains. The convergence of the method of elasticity solutions and the method of variable elasticity parameters has been studied as applied to a thermoplasticity problem including irradiation-induced swelling strains.

The Impact of Zakat on Economic Growth in 5 State in Indonesia

This study aims to reveal the impact of zakat distribution on macroeconomic in 5 state In Indonesia, by using ECM analysis. The motivation of the current research lies on the belief of a large number of economists that zakat does not affect macro economy because 2.5 percent is perceived insignificant. This issue leads to a high curiosity about the impact of zakat distribution in Indonesia. This study finds that zakat has a significant and positive relationship with economic growth. The results of the ECM analysis show that the distribution of zakat positively influences on economic growth. The long-run elasticity of zakat variable is positive and significant.

The Variable Elasticity of Substitution Function and Endogenous Growth: An Empirical Evidence from Vietnam

Purpose: To specify a Variable Elasticity of Substitution function (VES), in which the estimated Elasticity of Substitution (ES) can give some implications for the tendency of economic growth in the Vietnames manufacturing sector. Design/Methodology/Approach: The contribution and the relevant methodology is based on the Bayesian approach having some advantages over the frequentist method: (i) the simulation and prediction results are more reliable in Bayesian analysis due to combining prior knowledge about parameters with obverved data to compose a posterior model, whereas the frequentist approach is based only on available data; (ii) in probability sense, Bayesian credible intervals have a straightforward interpretation compared to frequentist confidence intervals. The Bayesian nonlinear regresion performed is suitable for fitting production functions and depicting economic growth. Findings: The specified VES function has the ES greater than one and this finding contradicts many previous empirical studies in the growth theory. This result points to the possibility of unbounded endogenous growth in the Vietnamese manufacturing sector. Practical implications: Based on the empirical results, in order to realize the possibility of endogenous growth for the studied Vietnamese manufacturing sector, policies of enforcing investment are needed. To raise the level of science and technique, as well as human capital of the Vietnamese enterprises, at the same time, there is great necessity to encourage R&D activities in both the private and public sectors. Originality/Value: Although this study organically builds upon recent studies about the link between the VES, the elasticity of factor subsitution and economic growth, its results proved that the VES is more appropriate than the Cobb-Douglas and the Constant Elasticity of Substitution (CES) to explain economic growth in the view of capital-labor relationship.

DETERMINAN ISLAMIC HUMAN DEVELOPMENT INDEX (IHDI) PROVINSI JAWA TIMUR TAHUN 2001-2016

This study aimed to determine the effect of economic growth, government expenditure, and ZIS distribution on IHDI in East Java in 2001-2016. The research method using quantitative approach by usingOrdinary Least Square (OLS) to see the elasticity of independent variables to dependent variables. The result of statistical test analysis showed that three of four independent variables had a positive and significant value on IHDI, which were: economic growth, goverment expenditure on education, and government expenditure on health. Zakat, infaq, sadaqah variables have nosignificant effect on IHDI.Keywords: Economic Growth, Education Expenditure, Health Expenditure, ZIS Distribution, Islamic Human Development Index

Variable export price elasticity, product quality, and credit constraints: Theory and evidence from Greek firms

We propose a simple model with endogenous quality, additive non-homothetic preferences and credit constraints. A unique data set of Greek manufacturing firms with firm-level exports, credit scores and other financial variables supports the model’s main predictions. Specifically, we establish that less credit-constrained Greek exporters with higher credit scores face export demand curves with lower price elasticity, charge higher export prices, and export higher-quality products.

Capital - Energy Substitution: Does Energy Sources Matter for the Elasticity of Substitution? An Empirical Investigation for OECD Countries

Energy and other factors of production are the primary inputs in the context of sustainable economic growth. This makes energy relatively strategic in the development stage and in the energy importers economies. In this study, the effect of elasticity of substitution on economic growth is investigated for 31 OECD countries over the period from 1990-2014. Although the effect of elasticity of substitution between capital and aggregate energy consumption on economic growth has been examined in many studies, the issue of how this effect changes between the different sources of energy has not been adequately addressed. The research is aimed at contributing to the related literature in this regard. The effect of elasticity of substitution between capital and different energy sources on economic growth is examined within the neoclassical Solow-Swan Growth model. In this model, technology is defined by a variable elasticity of substitution (VES) production function. The empirical model is estimated by the non-linear least squares (NLLS) method. The results show that oil and primary energy consumption are substitutes; natural gas, coal, and hydroelectricity consumption are the complement in the final production of output.

Estimating the recreational values of forest park using the contingent valuation method (case study: Kabudval Forest Park, Golestan Province of Iran)

Forest parks are the main tourism sources in Iran. Growing population, traditional patterns changing, urban environmental contamination and emergent need of leisure times highlighted the importance of this issue. This study aimed to estimate the willingness to pay (WTP) and non-market values of Kabudval Forest Park of Golestan province. For this purpose, the contingent valuation (CV) method based on the maximum likelihood logit regression model was used. The required data were obtained from 152 visitors to the park that were randomly selected in different seasons. Results indicated that the average of WTP for each individual to protect the park was calculated to be 34,850 Rials. Also, considering the total area of the park to be 109 hectares and 400,000 annual visitors, the recreational value of each hectare has been obtained 12,787,400 Rials annually. Also, the elasticities of income, education, age, and household size variables showed a significant effect on the WTP for the recreational use of the aforementioned study area. The location of the Negarestan storage dam and the Kabudval full moss waterfall in this park has increased the attractiveness of this park compared to other forest parks.

Role of nanofibers on MSCs fate: Influence of fiber morphologies, compositions and external stimuli.

In regenerative medicine, self-regulated tissue regeneration is perceived by Mesenchymal Stem Cells (MSCs) fate due to their tissue-specific differentiation, which is an emerging yet promising tool for therapeutics. MSCs with their innate nature like secretion of bioactive molecules, multilineage differentiation and proliferation supported tissue repair. MSCs interact with extracellular matrix (ECM) components like collagen, glycosaminoglycans (GAGs), proteoglycans and various proteins that are present in the form of nanofibers representing variable matrix elasticity along with topographies and bioactive cues. Synthetic nanofibers also showed to mimic native tissue microenvironment and supported regeneration owing to structural resemblance with ECM for anchorage-dependent cells. Different nanofibers generated using various polymer precursors and their resultant scaffolds, architectures, compositions etc. were studied for their influence on MSCs activities to improvise cell-cell and cell-material interactions. Electrospinning, popular nanotechnology for fiber formation based on electrohydrodynamic theory, is widely used for many applications due to its simplicity, efficacy and environmentally friendliness. Electrospun nanofibers were extensively investigated to understand the influence of material towards manipulating stem cells based on regenerative medicine. Subsequently, the influence of different solutions and process parameters were studied for nanofiber structure repeatability and emphasized on fiber properties such as diameter, mechanical properties, degradation rate, and porosity. Recent approaches towards scale-up for nanofiber production by electrospinning and other novel techniques are also presented briefly. The fate of MSCs, while seeded on nanofibers under external stimuli viz. electrical, mechanical, magnetic and electromagnetic field, is reviewed to find the niche for differentiation pathways. Further, several external stimuli presented as important factors motivating cellular differentiation in combination with specific conditions without the use of any chemical cues.

Magnetic Elastomers with Smart Variable Elasticity Mimetic to Sea Cucumber.

A magnetic-responsive elastomer consisting of magnetic elastomer and zinc oxide with a tetrapod shape and long arms was fabricated mimetic to the tissue of sea cucumber in which collagen fibrils are dispersed. Only the part of magnetic elastomer is active to magnetic fields, zinc oxide plays a role of reinforcement for the chain structure of magnetic particles formed under magnetic fields. The magnetic response of storage modulus for bimodal magnetic elastomers was measured when the magnetic particle was substituted to a nonmagnetic one, while keeping the total volume fraction of both particles. The change in storage modulus obeyed basically a mixing rule. However, a remarkable enhancement was observed at around the substitution ratio of 0.20. In addition, the bimodal magnetic elastomers with tetrapods exhibited apparent change in storage modulus even at regions with a high substitution ratio where monomodal magnetic elastomers consist of only magnetic particles with less response to the magnetic field. This strongly indicates that discontinuous chains of small amounts of magnetic particles were bridged by the nonmagnetic tetrapods. On the contrary, the change in storage modulus for bimodal magnetic elastomers with zinc oxide with irregular shape showed a mixing rule with a substitution ratio below 0.30. However, it decreased significantly at the substitution ratio above it. The structures of bimodal magnetic elastomers with tetrapods and the tissue of sea cucumber with collagen fibrils are discussed.