Search for: All records

Creating believable virtual agents has long been the focus of artists and scientists. A believable agent enables the audience to be emotionally involved in a narrative, willingly suspending their disbelief for the pleasure of appreciating literacy, drama, film, etc. In the past few decades, believability has become the goal of virtual reality developers and researchers. In the realm of virtual reality, it is commonly accepted that a believable virtual agent should have personality, emotion, agency, intelligence, and more. Despite its seemingly complicated requirements, believability is a fragile product that can be easily jeopardized by missing one or more of these elements. In this paper, we review the questionnaires that past researchers have used on the topic of virtual agents' believability. Based on the prevailing questions identified in the relevant studies, we propose a scale-aiming at standardizing one-for measuring the believability of virtual agents. We recommend that future research involving virtual agents refer to this scale to evaluate the level of their believability. 

This paper examined the effect of Si addition on the cracking resistance of Inconel 939 alloy after laser additive manufacturing (AM) process. With the help of CALculation of PHAse Diagrams (CALPHAD) software Thermo-Calc, the amounts of specific elements (C, B, and Zr) in liquid phase during solidification, cracking susceptibility coefficients (CSC) and cracking criterion based on$$\left| {{\text{d}}T/{\text{d}}f_{{\text{s}}}^{1/2} } \right|$$$\left(\text{d}T/\text{d}{f}_{\text{s}}^{1/2}\right)$values (T: solidification temperature,f_s: mass fraction of solid during solidification) were evaluated as the indicators for composition optimization. It was found that CSC together with$$\left| {{\text{d}}T/{\text{d}}f_{{\text{s}}}^{1/2} } \right|$$$\left(\text{d}T/\text{d}{f}_{\text{s}}^{1/2}\right)$values provided a better prediction for cracking resistance.

Graphical abstract

 

In this work we study d-dimensional majorant properties. We prove that a set of frequencies in $\mathbb{Z}^d$ satisfies the strict majorant property on $L^p([0,1]^d)$ for all p > 0 if and only if the set is affinely independent. We further construct three types of violations of the strict majorant property. Any set of at least d + 2 frequencies in $\mathbb{Z}^d$ violates the strict majorant property on $L^p([0,1]^d)$ for an open interval of $p \not\in 2\mathbb{N}$ of length 2. Any infinite set of frequencies in $\mathbb{Z}^d$ violates the strict majorant property on $L^p([0,1]^d)$ for an infinite sequence of open intervals of $p \not\in 2\mathbb{N}$ of length 2. Finally, given any p > 0 with $p \not\in 2\mathbb{N}$, we exhibit a set of d + 2 frequencies on the moment curve in $\mathbb{R}^d$ that violate the strict majorant property on $L^p([0,1]^d).$

 

Elastic actuation can improve human-robot interaction and energy efficiency for wearable robots. Previous work showed that the energy consumption of series elastic actuators can be a convex function of the series spring compliance. This function is useful to optimally select the series spring compliance that reduces the motor energy consumption. However, series springs have limited influence on the motor torque, which is a major source of the energy losses due to the associated Joule heating. Springs in parallel to the motor can significantly modify the motor torque and therefore reduce Joule heating, but it is unknown how to design springs that globally minimize energy consumption for a given motion of the load. In this work, we introduce the stiffness design of linear and nonlinear parallel elastic actuators via convex optimization. We show that the energy consumption of parallel elastic actuators is a convex function of the spring stiffness and compare the energy savings with that of optimal series elastic actuators. We analyze robustness of the solution in simulation by adding uncertainty of 20% of the RMS load kinematics and kinetics for the ankle, knee, and hip movements for level-ground human walking. When the winding Joule heating losses are dominant with respect to the viscous losses, our optimal PEA designs outperform SEA designs by further reducing the motor energy consumption up to 63%. Comparing to the linear PEA designs, our nonlinear PEA designs further reduced the motor energy consumption up to 31%. From our convex formulation, our global optimal nonlinear parallel elastic actuator designs give two different elongation-torque curves for positive and negative elongation, suggesting a clutching mechanism for the final implementation. In addition, the different torque-elongation profiles for positive and negative elongation for nonlinear parallel elastic actuators can cause sensitivity of the energy consumption to changes in the nominal load trajectory. 

Using a Lewis acid-quenched CF2Ph- reagent, we show C–C bond formation through nucleophilic addition reactions to prepare molecules containing internal –CF2– linkages. We demonstrate C(sp2)–C(sp3) coupling using both SNAr reactions and Pd-catalysis. Finally, C(sp3)–C(sp3) bonds are forged using operationally simple SN2 reactions that tolerate medicinally-relevant motifs.