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 ThermoCalc, the amounts of specific elements (C, B, and Zr) in liquid phase during solidification, cracking susceptibility coefficients (CSC) and cracking criterion based on
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Abstract values ($$\left {{\text{d}}T/{\text{d}}f_{{\text{s}}}^{1/2} } \right$$ $\left(\text{d}T/\text{d}{f}_{\text{s}}^{1/2}\right)$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 values provided a better prediction for cracking resistance.$$\left {{\text{d}}T/{\text{d}}f_{{\text{s}}}^{1/2} } \right$$ $\left(\text{d}T/\text{d}{f}_{\text{s}}^{1/2}\right)$Graphical abstract 
Free, publiclyaccessible full text available June 1, 2023

Elastic actuation can improve humanrobot 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 levelground human walking. When the winding Joule heating losses are dominant withmore »

A Boolean {\em $k$monotone} function defined over a finite poset domain ${\cal D}$ alternates between the values $0$ and $1$ at most $k$ times on any ascending chain in ${\cal D}$. Therefore, $k$monotone functions are natural generalizations of the classical {\em monotone} functions, which are the {\em $1$monotone} functions. Motivated by the recent interest in $k$monotone functions in the context of circuit complexity and learning theory, and by the central role that monotonicity testing plays in the context of property testing, we initiate a systematic study of $k$monotone functions, in the property testing model. In this model, the goal is to distinguish functions that are $k$monotone (or are close to being $k$monotone) from functions that are far from being $k$monotone. Our results include the following: \begin{enumerate} \item We demonstrate a separation between testing $k$monotonicity and testing monotonicity, on the hypercube domain $\{0,1\}^d$, for $k\geq 3$; \item We demonstrate a separation between testing and learning on $\{0,1\}^d$, for $k=\omega(\log d)$: testing $k$monotonicity can be performed with $2^{O(\sqrt d \cdot \log d\cdot \log{1/\eps})}$ queries, while learning $k$monotone functions requires $2^{\Omega(k\cdot \sqrt d\cdot{1/\eps})}$ queries (Blais et al. (RANDOM 2015)). \item We present a tolerant test for functions $f\colon[n]^d\to \{0,1\}$ with complexity independent ofmore »