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Generally, humanoid robots usually suffer significant impact force when walking or running in a non-predefined environment that could easily damage the actuators due to high stiffness. In recent years, the utilization of passive compliant series elastic actuators (SEA) for driving humanoid's joints has proved the capability in many aspects so far. However, despite being widely applied in the biped robot research field, the stable control problem for a humanoid powered by the SEAs, especially in the walking process, is still a challenge. This paper proposes a model reference adaptive control (MRAC) combined with the back-stepping algorithm to deal with the parameter uncertainties in a humanoid's lower limb driven by the SEA system. This is an extension of our previous research (Lanh et al., 2021).

Firstly, a dynamic model of SEA is obtained. Secondly, since there are unknown and uncertain parameters in the SEA model, a Model Reference Adaptive Controller (MRAC) is employed to guarantee the robust performance of the humanoid's lower limb. Finally, an experiment is carried out to evaluate the effectiveness of the proposed controller and the SEA mechanism.

This paper proposes an effective control algorithm that can be widely applied for the humanoid-SEA system. Besides, the effect of the coefficients in the control law is analyzed to further improve the response's quality.

Even though the simulation shows good results with stable system response, the practical experiment has not been implemented to fully evaluate the quality of the controller.

The MRAC is applied to control the humanoid's lower limb and the back-stepping process is utilized to combine with an external SEA system but still maintain stabilization. The simplified model of the lower-limb system proposed in the paper is proven to be appropriate and can be taken for further research in the future.

Humanoid robots have been utilized in many fields such as medical, construction, and disaster response. While humanoid robots nowadays can achieve great capabilities, the one-leg balancing task still poses a challenging problem. This paper aims to propose a novel approach to solve the problem.

To aid the balance of one leg in humanoid robot, an external balance mechanism is inserted to the back of the humanoid robot. First, a dynamic model of the humanoid robot with balance mechanism and its simplified model are introduced. Second, a backstepping-based control method is utilized to build the proposed controller for one-leg stance system through two steps. For the first step, a minimum observer-based controller with a virtual control input is used to control the first sub-system reaching the desired reference input. For the second step, a virtual control input is considered as a reference input of a second sub-system, then a model reference adaptive controller (MRAC) is employed to control the second sub-system reaching the virtual control input in presence of uncertainties. By using the external balance mechanism, the sideway balancing task is separated from normal walking function. Furthermore, the utilization of the balance mechanism ensures the humanoid robot's hip adduction does not exceed the threshold of a human when walking. Finally, a simulation study is carried out to evaluate the effectiveness of the proposed method.

This paper proposes a model reference adaptive control using state observer for balancing one leg of humanoid robot in stance phase that extends our previous research (Tran et al., 2021).

The main research contents have been introduced.

This study aims to evaluate blast loads on and the response of submerged structures.

An arbitrary Lagrangian–Eulerian method is developed to model fluid–structure interaction (FSI) problems of close-in underwater explosions (UNDEX). The “fluid” part provides the loads for the structure considers air, water and high explosive materials. The spatial discretization for the fluid domain is performed with a second-order vertex-based finite volume scheme with a tangent of hyperbola interface capturing technique. The temporal discretization is based on explicit Runge–Kutta methods. The structure is described by a large-deformation Lagrangian formulation and discretized via finite elements. First, one-dimensional test cases are given to show that the numerical method is free of mesh movement effects. Thereafter, three-dimensional FSI problems of close-in UNDEX are studied. Finally, the computation of UNDEX near a ship compartment is performed.

The difference in the flow mechanisms between rigid targets and deforming targets is quantified and evaluated.

Cavitation is modeled only approximately and may require further refinement/modeling.

The results demonstrate that the proposed numerical method is accurate, robust and versatile for practical use.

Better design of naval infrastructure [such as bridges, ports, etc.].

To the best of the authors’ knowledge, this study has been conducted for the first time.

The purpose of this study is to explain the poor informativeness of earnings in dual-class firms by examining the quality of earnings and the information environment.

The earnings informativeness, earnings quality and information environment of dual-class firms are compared with a matched sample of single-class firms. The authors have performed the returns-earnings association tests, examine the quality of earnings by using proxies for discretionary accruals, and examine the information environment by employing four empirical constructs: the analyst forecast dispersion, absolute forecast errors, Amihud’s (2002) illiquidity measure, and the bid-ask spread.

The results show that the quality of earnings is better while the quality of the information environment is worse in dual-class firms compared to single-class firms. Overall, the results suggest that an inferior information environment is a plausible explanation for the low informativeness of dual-class firms’ earnings.

The results provide empirical support for Dechow et al. (2010) that the use of the earnings-returns association measure to draw conclusions about the quality of earnings is not appropriate in the presence of a poor information environment.

This is the first study to empirically show that low earnings informativeness in dual-class firms can be explained by the inferior quality of the information environment.

The purpose of this paper is to carry out free vibration and buckling analysis of functionally graded material (FGM) plate.

Equilibrium and stability equations of FGM rectangular plate under different boundary conditions are derived using finite element method-based inverse trigonometric shear deformation theory (ITSDT). Eight-noded rectangular plate element with seven degrees of freedom at each node is used for the present analysis. The power-law distribution method has been considered for the continuously graded variation in composition of the ceramic and metal phases across the thickness of a functionally graded plate.

The finite element formulation incorporated with ITSDT and provisions of the constitutive model of FGM plate has been implemented in a numerical code to obtain the natural frequency and critical buckling load under uniaxial and biaxial compressive load. The influence of material gradation, volume fraction index, span to thickness ratio and boundary constraints over free vibration and buckling response has been studied.

Development and validation of finite element methodology using ITSDT to predict the structural response of the FGM plates under different loading, geometric and boundary conditions.

The paper aims to estimate the factors affecting Vietnam's export in rice and coffee, the two most important agricultural products, especially in exploring the role of “behind-the-border” constraints.

The paper applies the stochastic frontier gravity model, which models the aggregate effect of “behind-the-border” factors for Vietnam's export in rice and coffee.

The paper finds that the impact of “behind-the-border” constraints is statistically significant, suggesting that Vietnam's exports in rice and coffee may be prevented from reaching their export potential by such factors. Moreover, technical efficiency and potential export suggest that Vietnam has a lot of potential to increase its exports in rice and coffee with its major trading partners. The Association of Southeast Asian Nations group continues to be the major market of Vietnamese rice and coffee. Vietnam can also take advantage of the opportunity to export these commodities to the European Union (EU) (not including the UK), and Comprehensive and Progressive Agreement for Trans-Pacific Partnership, especially in coffee to the EU.

The study cannot identify specific “behind-the-border” factors due to the limitation of data availability.

Many existing studies suggest that export in agricultural products of Vietnam, especially in rice, is significantly affected by natural factors and “explicit beyond-the-border” constraints. They ignore the impact of “behind-the-border” constraints in Vietnam and its trading partners. My study proved the significant impact of such constraints. Therefore, Vietnam needs more policies to remove the “behind-the-border” constraints to promote export in rice and coffee.

Drawing from institutional theory and organizational learning perspectives, the purpose of this paper is to examine how social norms of corruption in home countries and those in host localities influence firm bribery behavior. It also investigates factors that moderate the influence of these norms.

The study is based on survey data of foreign invested firms (FIFs) in Vietnam, conducted by the Vietnam Chamber of Commerce and Industry between 2010 and 2018 along with Transparency International’s Corruption Perception Index. The authors run ordinary least squares regressions to test the hypotheses.

The study provides evidence that social norms of corruption in both home countries and host localities influence firms’ bribery behavior, but their effects are moderated by different sets of factors. Specifically, the use of local leadership augments the impact of the host province’s corruption norms on the firm’s bribe payments. By contrast, the relationship between the home country’s corruption norms and a FIF’s bribe payment is weaker if local leadership is used, and stronger if the FIF’s home country belongs to the Organization for Economic Co-operation and Development.

Repeated cross-sectional data do not allow us to genuinely keep track of the changing roles of home country and host province corruption norms over time. In addition, the use of perception measures for corruption norms is subject to potential biases.

As the hiring of local executives weakens the impact of the home country’s norms which are embedded in the MNCs’ general practices, a stronger learning measure and regular review of the headquarters’ policies and practices is needed to ensure the overseas branch’s compliance. For policymakers, it is critical to recognize that local corruption plays a role in shaping FIFs’ bribery behavior.

While the effect of social norms of corruption on firm bribery behavior has been recognized, to the best of the authors’ knowledge, this is the first study that examines the learning processes FIFs may take to make sense of and cope with these norms, and also the first one to specify factors that moderate the influence of these norms.

The purpose of this article is to carry out the thermal buckling analysis of power and sigmoid functionally graded material Sandwich plate (P-FGM and S-FGM) under uniform, linear, nonlinear and sinusoidal temperature rise.

Thermal buckling of FGM Sandwich plates namely, FGM face with ceramic core (Type-A) and homogeneous face layers with FGM core (Type-B), incorporated with nonpolynomial shear deformation theories are considered for an analytical solution in this investigation. Effective material properties and thermal expansion coefficients of FGM Sandwich plates are evaluated based on Voigt's micromechanical model considering power and sigmoid law. The governing equilibrium and stability equations for the thermal buckling analysis are derived based on sinusoidal shear deformation theory (SSDT) and inverse trigonometric shear deformation theory (ITSDT) along with Von Karman nonlinearity. Analytical solutions for thermal buckling are carried out using the principle of minimum potential energy and Navier's solution technique.

Critical buckling temperature of P-FGM and S-FGM Sandwich plates Type-A and B under uniform, linear, non-linear, and sinusoidal temperature rise are obtained and analyzed based on SSDT and ITSDT. Influence of power law, sigmoid law, span to thickness ratio, aspect ratio, volume fraction index, different types of thermal loadings and Sandwich plate types over critical buckling temperature are investigated. An analytical method of solution for thermal buckling of power and sigmoid FGM Sandwich plates with efficient shear deformation theories has been successfully analyzed and validated.

The temperature distribution across FGM plate under a high thermal environment may be uniform, linear, nonlinear, etc. In practice, temperature variation is an unpredictable phenomenon; therefore, it is essential to have a temperature distribution model which can address a sinusoidal temperature variation too. In the present work, a new sinusoidal temperature rise is proposed to describe the effect of sinusoidal temperature variation over critical buckling temperature for P-FGM and S-FGM Sandwich plates. For the first time, the FGM Sandwich plate is modeled using the sigmoid function to investigate the thermal buckling behavior under the uniform, linear, nonlinear and sinusoidal temperature rise. Nonpolynomial shear deformation theories are utilized to obtain the equilibrium and stability equations for thermal buckling analysis of P-FGM and S-FGM Sandwich plates.

An anisotropic modelling of hollow porous cylinders under harmonic axial loading is proposed to simulate the in vivo behavior of structural elements of cortical bone called osteons. The peripheral surface of the medium is supposed to be impermeable, except on possible existing cracks. Numerical tests are performed by analytical and finite element methods based on the Biot poroelastic theory. The influence of microcracks on the fluid flow is numerically investigated. The findings show that the existence of peripheral cracks directly modifies the stimulation of the mechano‐sensitive network of the bone. Thus, this study attempts to propose a likely mechanism by which bone can sense changes of the surrounding mechanical environment.

This study covers all banks listed on the Amman Stock Exchange. It used (1) dividend-paying status, dividend changes and dividend persistence to measure dividend quality, (2) a checklist instrument consisting of 40 items to measure financial disclosure quality, (3) nationality and (4) the percentage of females and males on the board of directors to measure board diversity. Hierarchical regression analysis was employed to investigate the influence of the board diversity on the relationship between financial disclosure quality and dividend quality.

This study investigates the relationship between financial disclosure quality and dividend quality among Jordanian-listed banks. Moreover, it examines the moderating effect of board diversity on the relationship between financial disclosure quality and dividend quality.

The results in this work imply that banks with high financial disclosure quality have high-quality dividends. Furthermore, nationality and females on the board of directors play a main role as moderators that influence managers' motivations toward the quality of financial disclosure practices and bank dividends. This paper shows that the boards in Jordanian banks have not changed dividend policies and tend to follow a long-term fixed strategy for paying earnings.

Because of the limited number of practical research on the nexus between financial disclosure quality and dividends quality, this study fills a gap in the literature by examining the relationship between them. In addition, a lack of research exists on the effects of board diversity on the nexus of financial disclosure quality and dividends quality. Therefore, this study makes an original contribution to the literature by using nationality and females and males on the board of directors as moderating variables to investigate the effects of board diversity on the relationship between financial disclosure quality and dividend quality among Jordanian banks.