Adaptive B-spline volume representation of measured BRDF data for photorealistic rendering

Measured bidirectional reflectance distribution function (BRDF) data have been used to represent complex interaction between lights and surface materials for photorealistic rendering. However, their massive size makes it hard to adopt them in practical rendering applications. In this paper, we propose an adaptive method for B-spline volume representation of measured BRDF data. It basically performs approximate B-spline volume lofting, which decomposes the problem into three sub-problems of multiple B-spline curve fitting along u-, v-, and w-parametric directions. Especially, it makes the efficient use of knots in the multiple B-spline curve fitting and thereby accomplishes adaptive knot placement along each parametric direction of a resulting B-spline volume. The proposed method is quite useful to realize efficient data reduction while smoothing out the noises and keeping the overall features of BRDF data well. By applying the B-spline volume models of real materials for rendering, we show that the B-spline volume models are effective in preserving the features of material appearance and are suitable for representing BRDF data

A General Synthetic Route to Atomically Dispersed Catalysts for Revealing Their Catalytic Trends in Oxygen Reduction Reaction

MAT.P-356 A General Synthetic Route to Atomically Dispersed Catalysts for Revealing Their Catalytic Trends in Oxygen Reduction Reaction Jae Hyung Kim, Hyungjun Kim1, Sang Hoon Joo2,* School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Korea 1 Korea Advanced Institute of Science and Technology, Korea 2 Division of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Korea Area: Material Chemistry Type: Poster Presentation Code: MAT.P-356 Location: Exhibition Hall 1 Date: THU 11:00~12:30 Atomically dispersed catalysts have recently emerged as a research frontier in catalysis with their maximum atom efficiency and unusual catalytic reactivity. However, a generic strategy toward atomically dispersed catalysts of wide range of compositions is still lacking, which has often limited systematic studies that can unravel the catalytic origins of atomically dispersed catalysts. In the work, we present a generalized synthetic route to atomically dispersed catalysts of precious metals, which consists of ???trapping??? of precious metal precursors and ???stabilizing??? them with SiO2 layers. Through mass spectrometry analyses during activation processes of catalysts, we demonstrated that the ???trapping-and-stabilizing??? method is capable of impeding the decomposition of a metal precursor, preserving atomically dispersed sites. Five atomically dispersed precious metals (Os, Ru, Rh, Ir, and Pt) catalysts were obtained and served as model catalysts for unravelling reactivity trends of atomically dispersed catalysts for oxygen reduction reaction (ORR). Combining experimental results and density functional theory calculations, we revealed that higher H2O2 selectivity was shown in atomically dispersed catalysts compared to their nanoparticle counterparts, which originates from abnormally weakened oxygen binding energies and isolated geometric configurations of atomically dispersed sites. Furthermore, the relative binding energies of *OOH and *O species were identified as determinants that dictate the ORR selectivity of atomically dispersed catalysts. This rational approach for preparing atomically dispersed catalysts can aid in enhancing the understanding their universal catalytic behaviors for ORR

Distributional Prototypical Methods for Reliable Explanation Space Construction

As deep learning has been successfully deployed in diverse applications, there is an ever increasing need to explain its decision. To explain decisions, case-based reasoning has proved to be effective in many areas. The prototype-based explanation is a method that provides an explanation of the model’s prediction using the distance between an input and learned prototypes to effectively perform case-based reasoning. However, existing methods are less reliable because distance is not always consistent with human perception. In this study, we construct a latent space which we call an $explanation space$ with distributional embedding and latent space regularization. This explanation space ensures that similar (in terms of human-interpretable features) images share similar latent representations, and therefore provides a reliable explanation for the consistency between distance-based explanation and human perception. The explanation space also provides additional explanation by transition, allowing the user to understand the factors that affect the distance. Throughout extensive experiments including human evaluation, we have shown that the explanation space provides a more human-understandable explanation

Unravelling Catalytic Trends of Atomically Dispersed Precious Metal Catalysts for Oxygen Reduction Reaction

Atomically dispersed catalysts have emerged as a research frontier in catalysis, however a general strategy for atomically dispersed catalysts of wide compositional range is still lacking, which has impeded systematic studies unveiling the catalytic origins of atomically dispersed catalysts. In the work, we present a generalized synthetic strategy toward atomically dispersed precious metal catalysts, which consists of ???ldquo;trapping???rdquo; of precious metal precursors and ???ldquo;immobilizing???rdquo; them with SiO2 layers. Five atomically dispersed precious metals (Os, Ru, Rh, Ir, Pt) catalysts were prepared and served as model catalysts for revealing reactivity trends of atomically dispersed catalysts for oxygen reduction reaction (ORR). We found that higher H2O2 selectivity was shown in atomically dispersed catalysts compared to their nanoparticle counterparts, which originates from abnormally weakened oxygen binding energies and isolated geometric configurations of atomically dispersed sites. Furthermore, the relative binding energies of *OOH and *O species were identified as determinants that dictate the ORR selectivity of atomically dispersed catalysts

Pt-Based Intermetallic Nanostructures: Activity Origin and Multifunctionality for Efficient Electrocatalysis

Pt-based intermetallic nanostructures have demonstrated superior electrocatalytic performances compared to random alloy structures. However, the origin of their enhanced catalytic properties remains elusive. Furthermore, a robust synthetic strategy for well-defined intermetallic nanostructures represents a challenge. In this work, we reveal by combining theoretical and experimental results that the activity enhancement in intermetallic structures for oxygen reduction reaction (ORR) originates from the intensified ligand effect. We prepared well-defined model nanocatalysts via confined nanospace-directed synthesis using mesoporous silica templates, which allows precise control over the size and shape of nanostructures. Importantly, this method can transform disordered alloy nanostructures into intermetallic analogues without agglomeration, enabling decoupling of an atomic ordering effect in catalysis. The prepared ordered intermetallic Pt3Co nanowires (O-PtCo NWs) can benefit from the intensified ligand effect, Pt-skin layer, and aggregation-tolerant contiguous structure, which lead to their superior ORR activity and durability to disordered alloy Pt3Co nanowires (D-PtCo NWs) and Pt/C catalysts. The multifunctionality of O-PtCo NWs is demonstrated with their higher activity and durability in alkaline hydrogen evolution reaction and acidic methanol oxidation reaction than D-PtCo NWs and Pt/C catalysts. Furthermore, the O-PtCo NWs-based cathode in proton exchange membrane fuel cell (PEMFC) shows much better durability than a Pt/C-based PEMFC

Unveiling Catalytic Trends of Atomically Dispersed Precious Metal Catalysts for Oxygen Reduction Reaction

Atomically dispersed catalysts have emerged as a research frontier in catalysis, however a general strategy for atomically dispersed catalysts of wide range of compositions is still lacking, which has limited systematic studies unravelling the catalytic origins of atomically dispersed catalysts. In the work, we present a generalized synthetic strategy to atomically dispersed catalysts of precious metals, which consists of ???trapping??? of precious metal precursors and ???immobilizing??? them with SiO2 layers. Five atomically dispersed precious metals (Os, Ru, Rh, Ir, Pt) catalysts were prepared and served as model catalysts for revealing reactivity trends of atomically dispersed catalysts for oxygen reduction reaction (ORR). We found that higher H2O2 selectivity was shown in atomically dispersed catalysts compared to their nanoparticle counterparts, which originates from abnormally weakened oxygen binding energies and isolated geometric configurations of atomically dispersed sites. Furthermore, the relative binding energies of *OOH and *O species were identified as determinants that dictate the ORR selectivity of atomically dispersed catalysts

Reversible Ligand Exchange in Atomically Dispersed Catalysts for Modulating the Activity and Selectivity of the Oxygen Reduction Reaction

Rational control of the coordination environment of atomically dispersed catalysts is pivotal to achieve desirable catalytic reactivity. We report the reversible control of coordination structure in atomically dispersed electrocatalysts via ligand exchange reactions to reversibly modulate their reactivity for oxygen reduction reaction (ORR). The CO-ligated atomically dispersed Rh catalyst exhibited ca. 30-fold higher ORR activity than the NHx-ligated catalyst, whereas the latter showed three times higher H2O2 selectivity than the former. Post-treatments of the catalysts with CO or NH3 allowed the reversible exchange of CO and NHx ligands, which reversibly tuned oxidation state of metal centers and their ORR activity and selectivity. DFT calculations revealed that more reduced oxidation state of CO-ligated Rh site could further stabilize the *OOH intermediate, facilitating the two- and four-electron pathway ORR. The reversible ligand exchange reactions were generalized to Ir- and Pt-based catalysts