Safety Verification for Neural Networks Based on Set-boundary Analysis

Neural networks (NNs) are increasingly applied in safety-critical systems such as autonomous vehicles. However, they are fragile and are often ill-behaved. Consequently, their behaviors should undergo rigorous guarantees before deployment in practice. In this paper we propose a set-boundary reachability method to investigate the safety verification problem of NNs from a topological perspective. Given an NN with an input set and a safe set, the safety verification problem is to determine whether all outputs of the NN resulting from the input set fall within the safe set. In our method, the homeomorphism property of NNs is mainly exploited, which establishes a relationship mapping boundaries to boundaries. The exploitation of this property facilitates reachability computations via extracting subsets of the input set rather than the entire input set, thus controlling the wrapping effect in reachability analysis and facilitating the reduction of computation burdens for safety verification. The homeomorphism property exists in some widely used NNs such as invertible NNs. Notable representations are invertible residual networks (i-ResNets) and Neural ordinary differential equations (Neural ODEs). For these NNs, our set-boundary reachability method only needs to perform reachability analysis on the boundary of the input set. For NNs which do not feature this property with respect to the input set, we explore subsets of the input set for establishing the local homeomorphism property, and then abandon these subsets for reachability computations. Finally, some examples demonstrate the performance of the proposed method.Comment: 19 pages, 7 figure

Verifying Safety of Neural Networks from Topological Perspectives

Neural networks (NNs) are increasingly applied in safety-critical systems such as autonomous vehicles. However, they are fragile and are often ill-behaved. Consequently, their behaviors should undergo rigorous guarantees before deployment in practice. In this paper, we propose a set-boundary reachability method to investigate the safety verification problem of NNs from a topological perspective. Given an NN with an input set and a safe set, the safety verification problem is to determine whether all outputs of the NN resulting from the input set fall within the safe set. In our method, the homeomorphism property and the open map property of NNs are mainly exploited, which establish rigorous guarantees between the boundaries of the input set and the boundaries of the output set. The exploitation of these two properties facilitates reachability computations via extracting subsets of the input set rather than the entire input set, thus controlling the wrapping effect in reachability analysis and facilitating the reduction of computation burdens for safety verification. The homeomorphism property exists in some widely used NNs such as invertible residual networks (i-ResNets) and Neural ordinary differential equations (Neural ODEs), and the open map is a less strict property and easier to satisfy compared with the homeomorphism property. For NNs establishing either of these properties, our set-boundary reachability method only needs to perform reachability analysis on the boundary of the input set. Moreover, for NNs that do not feature these properties with respect to the input set, we explore subsets of the input set for establishing the local homeomorphism property and then abandon these subsets for reachability computations. Finally, some examples demonstrate the performance of the proposed method.Comment: 25 pages, 11 figures. arXiv admin note: substantial text overlap with arXiv:2210.0417

An economic evaluation of a primary care-based technology-enabled intervention for stroke secondary prevention and management in rural China : a study protocol

Introduction: Secondary prevention of stroke is a leading challenge globally and only a few strategies have been tested to be effective in supporting stroke survivors. The system-integrated and technology-enabled model of care (SINEMA) intervention, a primary care-based and technology-enabled model of care, has been proven effective in strengthening the secondary prevention of stroke in rural China. The aim of this protocol is to outline the methods for the cost-effectiveness evaluation of the SINEMA intervention to better understand its potential economic benefits. Methods: The economic evaluation will be a nested study based on the SINEMA trial; a cluster-randomized controlled trial implemented in 50 villages in rural China. The effectiveness of the intervention will be estimated using quality-adjusted life years for the cost-utility analysis and reduction in systolic blood pressure for the cost-effectiveness analysis. Health resource and service use and program costs will be identified, measured, and valued at the individual level based on medication use, hospital visits, and inpatients' records. The economic evaluation will be conducted from the perspective of the healthcare system. Conclusion: The economic evaluation will be used to establish the value of the SINEMA intervention in the Chinese rural setting, which has great potential to be adapted and implemented in other resource-limited settings

Better PROMs and higher return-to-sport rate after modular bicompartmental knee arthroplasty than after total knee arthroplasty for medial and patellofemoral compartment osteoarthritis

BackgroundTheoretical advantages of bicompartmental knee arthroplasty (BKA) over total knee arthroplasty (TKA) for bicompartmental (medial combined with patellofemoral) osteoarthritis (OA) are still unclear. This study aimed to compare patient-reported outcome measures (PROMs) and return-to-sport (RTS) rate between modular BKA and TKA in early follow-up.MethodsTwenty-five consecutive modular BKA cases with a minimum 2-year follow-up were matched with 50 TKA cases at 1:2 ratio. Demographic data and preoperative functional scores, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Scores (KSSs), were analyzed to ensure comparability. Postoperative WOMAC score, KSS, range of motion (ROM), Forgotten Joint Score-12 (FJS-12), and RTS rates were compared. Operative time and blood loss were also analyzed.ResultsSignificant differences in the WOMAC-function (median 97.1 vs. 89.7, p < 0.001) and KSS-function (median 90.0 vs. 80.0, p = 0.003) scores were identified between the BKA and TKA groups. ROM was significantly greater in the BKA group than in the TKA group (median 125.0° vs. 120.0°, p = 0.004), in addition to the FJS-12 (median 89.6 vs. 53.1, p < 0.001). The overall RTS rate was significantly higher in the BKA group than in the TKA group (71.6% vs. 56.5%, p = 0.039). Operative time was significantly longer in the BKA group than in the TKA group (median 105.0 vs. 67.5 min, p < 0.001), but blood loss was similar (median 557.6 vs. 450.7 ml, p = 0.334).ConclusionModular BKA demonstrated better functional recovery, better joint perception, and higher RTS rate than TKA; thus, modular BKA can be a good alternative for bicompartmental OA

Correlation between tibial valgus deformity and aspect ratio of resected tibial surface in female Chinese patients undergoing total knee arthroplasty

BackgroundMorphology of the resected tibial surface is the reference for tibial component design, selection, and implantation in total knee arthroplasty (TKA). This comparative study sought to answer whether valgus deformity of the tibia would affect the morphology of the resected tibial surface in TKA.MethodsThirty-one female Chinese patients with valgus tibias were retrospectively and consecutively identified from a single-center registration database. Thirty-one patients with well-aligned tibias were matched in terms of gender, height, and weight. Weight-bearing full-length radiographs and computed tomography images of the whole lower limb were obtained for every case. Tibial resection was mimicked perpendicular to the mechanical axis of the tibia in the frontal plane with 3° of posterior slope and a cut level individualized by the actual intraoperative cut. On the resected surface, mediolateral dimension (MLD), medial anteroposterior dimensions (mAPD), and lateral anteroposterior dimensions (lAPD) were measured, and aspect ratios (AR) were calculated. We compared the AR between the two groups.ResultsThe aspect ratio of resected tibial surface positively correlated with tibial valgus alignment. Patients with valgus tibias had significantly smaller AR (MLD/mAPD) for the medial plateau (1.50 ± 0.06 vs. 1.54 ± 0.07, P = 0.032). However, the AR for the lateral plateau was similar between the two groups (1.63 ± 0.08 vs. 1.65 ± 0.07, P = 0.328).ConclusionThis difference in morphology of resected tibial surface between valgus and well-aligned tibias should be considered in tibial component design, as well as in the selection and placement of TKA implants for knees with valgus tibias

From traitor to martyr: drawing lessons from the death and burial of Wang Jingwei, 1944

Based on recently re-opened files and publications in Nanjing, as well as published and newsreel accounts from the 1940s, this paper represents the first scholarly analysis of the rituals surrounding the death and burial of Wang Jingwei in Japanese-occupied China. Rather than locating this analysis purely in the literature on the history of the Second Sino-Japanese War (1937-1945), however, this paper asks what Wang Jingwei's Re-organized National Government might tell us about personality cults in the political culture of modern China. While Wang's burial was one which drew heavily on the precedent of Sun Yat-sen's funerals of the 1920s, it also presaged later spectacles of public mourning and post-mortem commemoration, such as Chiang Kai-shek's funeral in 1975 in Taipei. In focusing on this one specific event in the life of a "puppet government" then, this paper hopes to re-ignite scholarly interest in the study of "dead leaders" and their posthumous lives in modern Chinese history more generally

Variation of physicochemical parameters of coal during low temperature oxidation under different oxygen concentrations

In order to explore the effect of different oxygen concentrations in mine goaf on the microscopic characteristics of coal during low temperature oxidation process, we simulated coal oxidation at low temperature under different oxygen concentrations. Through BEL-Max automatic specific surface/pore analysis, steam adsorption instrument and electron spin resonance spectrometer (ESR), the change characteristics of pore distribution and free radicals during low temperature oxidation of coal under different oxygen concentrations were obtained. The experimental results show that with the increase of oxygen concentration and oxidation temperature, moisture, volatile matter, BET specific surface area and free radical concentration change in stages. After 130 ℃, the recombination rate of coal and oxygen is accelerated, and the continuous decrease of moisture and volatile matter leads to the development of coal pores, increases the active surface contact area between oxygen and coal, activates the original inactive primary free radicals, participates in the reaction and produces more new free radicals. In the heating range of 200 ℃, the concentration of free radicals (21%) increased by 12.77 × 1017/g

Robotic-assisted differential total knee arthroplasty with patient-specific implants: surgical techniques and preliminary results

Abstract Objective In total knee arthroplasty (TKA), achieving soft-tissue balance while retaining acceptable lower limb alignment is sometimes difficult and may lead to patient dissatisfaction. Theoretically, patient-specific implants can bring great benefits, while the lack of precise surgical tools may hinder the improvement of outcomes. The objective of this study was to illustrate surgical techniques and evaluate kinematics and early clinical outcomes of robotic-assisted TKA using patient-specific implants. Methods Based on preoperative CT scan, femoral and tibial components were 3D printed. Medial and lateral tibial liners were separate with different thicknesses, posterior slopes and conformity. TiRobot Recon Robot was used for surgery, and was armed with smart tools that quantify gap, force and femoral-tibial track. We collected data on demographics, intraoperative gap balance and femoral-tibial motion. In the follow-up, we evaluated the range of motion, Visual Analogue Scale (VAS), forgotten joint score (FJS), Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) score. Radiological data were also harvested. Results Fifteen patients (17 knees) were enrolled with a mean age of 64.6 ± 6.4 (53–76) years. In 5 knees, we used symmetric tibial liners, the rest were asymmetric. After surgery, the average alignment was 1.6 ± 2.0 (-3–5) degrees varus. The average follow-up lasted 6.7 ± 4.2 (1–14) months. The mean visual analogue scale was 0.8 ± 0.7 (0–2), FJS was 62.4 ± 25.3 (0–87), KOOS was 86.5 ± 9.4 (57–97). 11 patients were “very satisfied”, 3 were “satisfied" with the result, and one patient was neutral due to restricted extension and unsatisfactory rehabilitation at five months’ follow-up. Conclusions With patient-specific implants and robotics, TKA could be performed by a mathematical way, which was dubbed a “differential” TKA. Intraoperative kinematics was excellent in terms of gap-force balancing and femoral-tibial relative motion. Preliminary clinical outcomes were overall satisfactory