Converse Barrier Certificates for Finite-time Safety Verification of Continuous-time Perturbed Deterministic Systems

In this paper, we investigate the problem of verifying the finite-time safety of continuous-time perturbed deterministic systems represented by ordinary differential equations in the presence of measurable disturbances. Given a finite time horizon, if the system is safe, it, starting from a compact initial set, will remain within an open and bounded safe region throughout the specified time horizon, regardless of the disturbances. The main contribution of this work is to uncover that there exists a time-dependent barrier certificate if and only if the system is safe. This barrier certificate satisfies the following conditions: negativity over the initial set at the initial time instant, non-negativity over the boundary of the safe set, and non-increasing behavior along the system dynamics over the specified finite time horizon. The existence problem is explored using a Hamilton-Jacobi differential equation, which has a unique Lipschitz viscosity solution

Fast High Dynamic Range Radiance Fields for Dynamic Scenes

Neural Radiances Fields (NeRF) and their extensions have shown great success in representing 3D scenes and synthesizing novel-view images. However, most NeRF methods take in low-dynamic-range (LDR) images, which may lose details, especially with nonuniform illumination. Some previous NeRF methods attempt to introduce high-dynamic-range (HDR) techniques but mainly target static scenes. To extend HDR NeRF methods to wider applications, we propose a dynamic HDR NeRF framework, named HDR-HexPlane, which can learn 3D scenes from dynamic 2D images captured with various exposures. A learnable exposure mapping function is constructed to obtain adaptive exposure values for each image. Based on the monotonically increasing prior, a camera response function is designed for stable learning. With the proposed model, high-quality novel-view images at any time point can be rendered with any desired exposure. We further construct a dataset containing multiple dynamic scenes captured with diverse exposures for evaluation. All the datasets and code are available at \url{https://guanjunwu.github.io/HDR-HexPlane/}.Comment: 3DV 2024. Project page: https://guanjunwu.github.io/HDR-HexPlan

UR4NNV: Neural Network Verification, Under-approximation Reachability Works!

Recently, formal verification of deep neural networks (DNNs) has garnered considerable attention, and over-approximation based methods have become popular due to their effectiveness and efficiency. However, these strategies face challenges in addressing the "unknown dilemma" concerning whether the exact output region or the introduced approximation error violates the property in question. To address this, this paper introduces the UR4NNV verification framework, which utilizes under-approximation reachability analysis for DNN verification for the first time. UR4NNV focuses on DNNs with Rectified Linear Unit (ReLU) activations and employs a binary tree branch-based under-approximation algorithm. In each epoch, UR4NNV under-approximates a sub-polytope of the reachable set and verifies this polytope against the given property. Through a trial-and-error approach, UR4NNV effectively falsifies DNN properties while providing confidence levels when reaching verification epoch bounds and failing falsifying properties. Experimental comparisons with existing verification methods demonstrate the effectiveness and efficiency of UR4NNV, significantly reducing the impact of the "unknown dilemma".Comment: 11 pages, 4 figure

On-Line Adaptive Radiation Therapy: Feasibility and Clinical Study

The purpose of this paper is to evaluate the feasibility and clinical dosimetric benefit of an on-line, that is, with the patient in the treatment position, Adaptive Radiation Therapy (ART) system for prostate cancer treatment based on daily cone-beam CT imaging and fast volumetric reoptimization of treatment plans. A fast intensity-modulated radiotherapy (IMRT) plan reoptimization algorithm is implemented and evaluated with clinical cases. The quality of these adapted plans is compared to the corresponding new plans generated by an experienced planner using a commercial treatment planning system and also evaluated by an in-house developed tool estimating achievable dose-volume histograms (DVHs) based on a database of existing treatment plans. In addition, a clinical implementation scheme for ART is designed and evaluated using clinical cases for its dosimetric qualities and efficiency

Tungsten Nanoparticles Accelerate Polysulfides Conversion: A Viable Route toward Stable Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries are arousing great interest in recent years. Their practical applications, however, are hindered by several intrinsic problems, such as the sluggish kinetic, shuttle effect, and the incomplete conversion of sodium polysulfides (NaPSs). Here a sulfur host material that is based on tungsten nanoparticles embedded in nitrogen-doped graphene is reported. The incorporation of tungsten nanoparticles significantly accelerates the polysulfides conversion (especially the reduction of Na2S4 to Na2S, which contributes to 75% of the full capacity) and completely suppresses the shuttle effect, en route to a fully reversible reaction of NaPSs. With a host weight ratio of only 9.1% (about 3–6 times lower than that in recent reports), the cathode shows unprecedented electrochemical performances even at high sulfur mass loadings. The experimental findings, which are corroborated by the first-principles calculations, highlight the so far unexplored role of tungsten nanoparticles in sulfur hosts, thus pointing to a viable route toward stable Na–S batteries at room temperatures

Trade and Investment Among BRICS: Analysis of Impact of Tariff Reduction and Trade Facilitation Based on Dynamic Global CGE Model

So far, there are few researches based on GTAP model focusing on the inter-regional trade activities among BRICS countries. Specifically, few studies have paid special attention to tariff exemption or trade facilitation scenario analysis. On the other hand, these topics broadly exist in global, multilateral and bilateral trade agreements and dialogues. One of the most prominent issues calling for in-depth study is the dynamic changing characteristics of emerging economies’ trade activities. BRICS countries differ greatly with respect to their trade volume, structure, dependence and environment, which lead to diversified sensitivities to tariff and trade facilitation. As the largest export-oriented emerging economy, China is more sensitive to tariffs and trade facilitation due to its large trade volume of manufactured goods and primary goods. Brazil and Russia are traditional resources exporter and thus they are less sensitive to tariffs and trade facilities because of the monopoly power. India is more dependent on service trade and commodity trade market is usually protected. However, since all of the BRICS counties have joined WTO and the global trade context is transforming, we need to involve the political and economic dynamics into global trade model to simulate the economic impacts. In this paper, we established a dynamic global CGE model to analyze the effects of free trade and trade facilitation in BRICS countries. In the settings of our model, we use adaptive expectation other than pure rational expectation to reflect the situation that BRICS countries are in the midst of transformation. The results show that the dynamic trade changing paths of these countries are quite different from those of developed countries. When trade facilitation increases, the results of China show that China’s agricultural products will see a huge growth in the future. One reason is that agricultural products are very sensitive to trade facilitation, especially sensitive to factors like custom clearance time. Car trade will also see a huge growth under the scenario that car tariffs are reduced

AniDraw: When Music and Dance Meet Harmoniously

In this paper, we present a demo, AniDraw, which can help users practice the coordination between their hands, mouth and eyes by combing the elements of music, painting and dance. Users can sketch a cartoon character through multitouch screens and then hum songs, which will drive the cartoon character to dance to create a lively animation. In technical realization, we apply the mechanism of acoustic driving in which AniDraw extracts time-domain acoustic features to map to the intensity of dances, frequency-domain ones to map to the style of dances, and high-level ones including onesets and tempos to map to start, duration and speed of dances. AniDraw can not only stimulate users’ enthusiasm in artistic creation, but also enhance their esthetic ability on harmony