Integrated analysis of error detection and recovery

An integrated modeling and analysis of error detection and recovery is presented. When fault latency and/or error latency exist, the system may suffer from multiple faults or error propagations which seriously deteriorate the fault-tolerant capability. Several detection models that enable analysis of the effect of detection mechanisms on the subsequent error handling operations and the overall system reliability were developed. Following detection of the faulty unit and reconfiguration of the system, the contaminated processes or tasks have to be recovered. The strategies of error recovery employed depend on the detection mechanisms and the available redundancy. Several recovery methods including the rollback recovery are considered. The recovery overhead is evaluated as an index of the capabilities of the detection and reconfiguration mechanisms

Software safety : a definition and some preliminary thoughts

Software safety is the subject of a research project in its initial stages at the University of California Irvine. This research deals with critical real-time software where the cost of an error is high, e.g. human life. In this paper software techniques having a bearing on safety are described and evaluated. Initial definitions of software safety concepts are presented along with some preliminary thoughts and research questions

The class action as sheriff: private law enforcement and remedial roulette

In a recent conference paper,1 Jeff Berryman expressed dismay about the “piecemeal” undermining of the compensation principle. The compensation principle requires that the plaintiff should as nearly as possible get the sum of money that will place him in the same position as if he had not suffered a wrong.2 Berryman argues that the principle has occupied a central position in modern private law “as a justification for who (victim) is allowed to commence an action in court, and for what (compensation), and as a limiting mechanism on the limits of what courts may justifiably do. But its justificatory and limiting roles are becoming frayed.”3 He describes the demise of the principle as “death by a thousand cuts”. Some of the deepest cuts have been inflicted by the modern class action. In this essay I will explore the effect of developments in class action law and practice upon remedial law, and investigate the state of health of the compensation principle. My focus will be upon class actions in Australia, Canada, and the US, in descending order. I will concentrate on compensatory, and to a lesser extent restitutionary remedies; leaving discussion of punitive, exemplary and treble damages for another occasion

Automated Mixed Traffic Vehicle (AMTV) technology and safety study

Technology and safety related to the implementation of an Automated Mixed Traffic Vehicle (AMTV) system are discussed. System concepts and technology status were reviewed and areas where further development is needed are identified. Failure and hazard modes were also analyzed and methods for prevention were suggested. The results presented are intended as a guide for further efforts in AMTV system design and technology development for both near term and long term applications. The AMTV systems discussed include a low speed system, and a hybrid system consisting of low speed sections and high speed sections operating in a semi-guideway. The safety analysis identified hazards that may arise in a properly functioning AMTV system, as well as hardware failure modes. Safety related failure modes were emphasized. A risk assessment was performed in order to create a priority order and significant hazards and failure modes were summarized. Corrective measures were proposed for each hazard

The United States Climate Change Policies and COVID-19: Poisoning the Cure

Climate change is complex during the best of times. It is commonly conceptualized as the quintessential global collective action problem: it affects those who do not contribute to it while the benefits of climate change mitigation measures are not restricted to those who pursue such measures. This conceptualization illustrates the high transaction costs involved in domestic policies as well as in international agreements addressing climate change, and it is of academic and practical interest. As such, this Article discusses the current challenges that climate change policies face, focusing on the linkages between the climate change policies of the Trump administration and the COVID-19 pandemic and on the effects of those linkages, both in the United States and globally. Specifically, this Article addresses the Trump administration’s attacks on climate science and its deregulatory climate agenda, as well as the United States’ withdrawal from the Paris Agreement on Climate Change. In addition, it discusses principles of international law and the challenges related to state liability for environmental harms in the context of the COVID-19 crisis. This Article also assesses how the United States’ climate policies are likely to aggravate inequalities both domestically, as well as globally, in the aftermath of the pandemic. This Article offers several original contributions. First, it provides a unique assessment of how the deregulatory climate policies implemented nationally and internationally by the Trump administration have magnified the COVID-19 crisis. Second, the law and economics methodology used in this Article validates the claim that improving environmental quality is connected to optimizing early regulatory action. Third, this Article discusses the challenges of state liability for climate harms in the aftermath of the United States’ withdrawal from the Paris Agreement and concurrent COVID-19 pandemic. Finally, this Article offers relevant insights for the literature on climate change that are likely to be applicable to critical future situations, whether they are health-related, a global economic crisis, or climate-related emergencies. Ultimately, this Article concludes that, in the aggregate, all such climate change policies have contributed to increased pollution, including elevated greenhouse gas emissions that have aggravated pre-pandemic inequalities embedded within the United States and among countries. Consequently, the domestic and international policy choices of the Trump administration are worsening the impact of the pandemic, particularly for those in more vulnerable positions, as well as indelibly poisoning the global commons. Keywords: climate change, climate policy, international environmental law, international law, international energy law, COVID-19, pandemic, deregulation, Trump administration, Paris Agreement, international liability, climate harm, inequality

Hyperswitch communication network

The Hyperswitch Communication Network (HCN) is a large scale parallel computer prototype being developed at JPL. Commercial versions of the HCN computer are planned. The HCN computer being designed is a message passing multiple instruction multiple data (MIMD) computer, and offers many advantages in price-performance ratio, reliability and availability, and manufacturing over traditional uniprocessors and bus based multiprocessors. The design of the HCN operating system is a uniquely flexible environment that combines both parallel processing and distributed processing. This programming paradigm can achieve a balance among the following competing factors: performance in processing and communications, user friendliness, and fault tolerance. The prototype is being designed to accommodate a maximum of 64 state of the art microprocessors. The HCN is classified as a distributed supercomputer. The HCN system is described, and the performance/cost analysis and other competing factors within the system design are reviewed

Patient-specific resurfacing implant knee surgery in subjects with early osteoarthritis results in medial pivot and lateral femoral rollback during flexion: a retrospective pilot study

Purpose: Metallic resurfacing implants have been developed for the treatment of early, small, condylar and trochlear osteoarthritis (OA) lesions. They represent an option for patients who do not fulfill the criteria for unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) or are too old for biological treatment. Although clinical evidence has been collected for different resurfacing types, the in vivo post-operative knee kinematics remain unknown. The present study aims to analyze the knee kinematics in subjects with patient-specific episealer implants. This study hypothesized that patient-specific resurfacing implants would lead to knee kinematics close to healthy knees, resulting in medial pivot and a high degree of femoral rollback during flexion. Methods: Retrospective study design. Fluoroscopic analysis during unloaded flexion-extension and loaded lunge was conducted at > 12 months post-surgery in ten episealer knees, and compared to ten healthy knees. Pre- and post-operative clinical data of the episealer knees were collected using a visual analog scale (VAS), the EQ 5d Health, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaires. Results: A consistent medial pivot was observed in both episealer and healthy knees. Non-significant differences were found in the unloaded (p = 0.15) and loaded (p = 0.51) activities. Although lateral rollback was observed in both groups, it was significantly higher for the episealer knees in both the unloaded (p = 0.02) and loaded (p = 0.01) activities. Coupled axial rotation was significantly higher in the unloaded (p = 0.001) but not in the loaded (p = 0.06) activity in the episealer knees. Improved scores were observed at 1-year post-surgery in the episealer subjects for the VAS (p = 0.001), KOOS (p = 0.001) and EQ Health (p = 0.004). Conclusion: At 12 month follow-up, a clear physiological knee kinematics pattern of medial pivot, lateral femoral rollback and coupled axial external femoral rotation during flexion was observed in patients treated with an episealer resurfacing procedure. However, higher femoral rollback and axial external rotation in comparison to healthy knees was observed, suggesting possible post-operative muscle weakness and consequent insufficient stabilization at high flexion

PRIMARY FLEXION AXIS SELECTION IN TOTAL KNEE REPLACEMENTS USING COMPUTATIONAL ANALYSIS

Total knee replacements (TKR) are one of the most frequently implanted medical devices, with over 600,000 procedures performed in the United States in 2012. In order to ensure TKR longevity, wear tests are frequently conducted on these implants prior to patient implantation. Variations in implant geometry, material, and surface treatments are all tested, however, TKR alignment may also play a role in the long-term success of the knee implant. When testing knee designs with complex tibial and femoral geometries it is essential that the implant be aligned as the implant manufacturers intended so as to best represent the function of the implant system. Although critical, a key alignment variable that is largely overlooked is femoral axis selection. Currently, femoral axis alignment is simply selected so as to minimize its effect on implant mechanics during walking simulation; a result that might completely misrepresent the implant designer\u27s intent. The purpose of this study was to create a computational model to determine the effect of femoral axis selection on contact-point bearing migration prior to simulator fixation and examine trends in femoral axis selection based on implant geometry. Using 3D optical scans of seven femurs, 3Matic STL for model remeshing, and COMSOL Multiphysics for simulation this study recreated the single-axis rotation of each femoral component in a wear simulator. The lowest femoral contact point was then tracked between 0º and 120º flexion over four hundred possible femoral axes alignment options. The computational model was verified statistically and calculated the location of the ideal axes of rotation for all seven femurs. Reduction of P/D lowest contact-point translation during simulator flexion was found to be dependent on the range of flexion. Single-axis knee designs were found to exhibit a lower tolerance to varied femoral axes of rotation, but still maintained lower mean P/D displacements. Anterior/posterior translation patterns during simulator flexion were found to vary significantly with femoral axis selection. Interestingly, A/P translation patterns were more consistent between varying flexion axes in implants with multiple axes of curvature compared to single-axis designs. TKR alignment in single-axis simulators clearly affects proximal/distal and anterior/posterior lowest contact-point migration and thus possibly implant mechanics during functional testing. An implant that incorporates a geometry that is minimally affected by malalignment should enhance clinical outcomes and provide more consistent functional measures during simulation and use