Implicit Safety Research Articles

Virtually coupled train set control subject to space-time separation: A distributed economic MPC approach with emergency braking configuration

The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set (VCTS) at a minimal but safe distance. To guarantee collision avoidance, the safety distance should be calculated using the state-of-the-art space-time separation principle that separates the Emergency Braking (EB) trajectories of two successive units during the whole EB process. In this case, the minimal safety distance is usually numerically calculated without an analytic formulation. Thus, the constrained VCTS control problem is hard to address with space-time separation, which is still a gap in the existing literature. To solve this problem, we propose a Distributed Economic Model Predictive Control (DEMPC) approach with computation efficiency and theoretical guarantee. Specifically, to alleviate the computation burden, we transform implicit safety constraints into explicitly linear ones, such that the optimal control problem in DEMPC is a quadratic programming problem that can be solved efficiently. For theoretical analysis, sufficient conditions are derived to guarantee the recursive feasibility and stability of DEMPC, employing compatibility constraints, tube techniques and terminal ingredient tuning. Moreover, we extend our approach with globally optimal and distributed online EB configuration methods to shorten the minimal distance among VCTS. Finally, experimental results demonstrate the performance and advantages of the proposed approaches.

An efficient method for computing slope reliability calculation based on rigorous limit equilibrium

Abstract Traditional rigorous limit equilibrium methods satisfy all equilibrium conditions and usually have high accuracy, however, which are less efficient for slope reliability analysis. The main reason is that the limit state functions are highly nonlinear implicit functions of safety factor. Complex numerical iterations are required, which may sometimes lead to computational convergence problems. A new method for computing slope reliability calculation with high efficiency and accuracy was proposed. This method was based on the rigorous limit equilibrium method by modifying normal stresses over the slip surface. The critical horizontal acceleration factor K c {K}_{c} , which can be expressed explicitly, was used to replace the implicit safety factor as a representation of slope stability. The difference between K c {K}_{c} and the known value K c 0 {K}_{c0} was used as the limit state function. Two slope examples were analyzed. The results showed that the calculation results of this method were in good agreement with those of the traditional Morgenstern–Price limit equilibrium method, but the computational efficiency was significantly improved. When this method was combined with the subset simulation method, the calculation time was only a few seconds. Therefore, this method can be used for rapid calculation of slope reliability.

Reinforcement Learning with Dual Safety Policies for Energy Savings in Building Energy Systems

Reinforcement learning (RL) is being gradually applied in the control of heating, ventilation and air-conditioning (HVAC) systems to learn the optimal control sequences for energy savings. However, due to the “trial and error” issue, the output sequences of RL may cause potential operational safety issues when RL is applied in real systems. To solve those problems, an RL algorithm with dual safety policies for energy savings in HVAC systems is proposed. In the proposed dual safety policies, the implicit safety policy is a part of the RL model, which integrates safety into the optimization target of RL, by adding penalties in reward for actions that exceed the safety constraints. In explicit safety policy, an online safety classifier is built to filter the actions outputted by RL; thus, only those actions that are classified as safe and have the highest benefits will be finally selected. In this way, the safety of controlled HVAC systems running with proposed RL algorithms can be effectively satisfied while reducing the energy consumptions. To verify the proposed algorithm, we implemented the control algorithm in a real existing commercial building. After a certain period of self-studying, the energy consumption of HVAC had been reduced by more than 15.02% compared to the proportional–integral–derivative (PID) control. Meanwhile, compared to the independent application of the RL algorithm without safety policy, the proportion of indoor temperature not meeting the demand is reduced by 25.06%.

Dual-Attitude Decision-Making Processes of Construction Worker Safety Behaviors: A Simulation-Based Approach.

Workplace accidents are of great concern in the construction industry. Most of those accidents are caused by unsafe behavior in the workplace. Many previous studies have analyzed the causes of workers' unsafe behaviors, but few have investigated workers' feelings of insecurity from the perspective of systematic psychological theory. This study developed an attitude-behavior-intervention feedback loop mechanism of construction workers and used the dual-attitude theory to explain the occurrence mechanisms of unsafe behavior. Using this mechanism, an active-intervention system-dynamics model and a passive-intervention system-dynamics model were designed and simulated. The coefficient of the system dynamics equation in the simulation model involved meta-analysis to combine the correlation coefficients of existing studies, which increased the sample size and improved the statistical test efficiency. The results show that an implicit safety attitude has a more significant impact on safety behavior, and the effect of an active intervention is stronger than that of a passive intervention. Based on these results, this paper presents some feasible suggestions to reduce the probability of unsafe worker behaviors occurring.

The mere sight of loved ones does not inhibit psychophysiological defense mechanisms when threatened

Looking at pictures of loved ones, such as one's romantic partner or good friends, has been shown to alleviate the experience of pain and reduce defensive reactions. However, little is known about such modulatory effects on threat and safety learning and the psychophysiological processes involved. Here, we explored the hypothesis that beloved faces serve as implicit safety cues and attenuate the expression of fear responses and/or accelerate extinction learning in a threatening context. Thirty-two participants viewed pictures of their loved ones (romantic partner, parents, and best friend) as well as of unknown individuals within contextual background colors indicating threat-of-shock or safety. Focusing on the extinction of non-reinforced threat associations (no shocks were given), the experiment was repeated on two more test days while the defensive startle-EMG, SCR, and threat ratings were obtained. Results confirmed pronounced defensive responding to instructed threat-of-shock relative to safety context (e.g., threat-enhanced startle reflex and SCR). Moreover, threat-potentiated startle response slowly declined across test days indicating passive extinction learning in the absence of shocks. Importantly, neither a main effect of face category (loved vs. unknown) nor a significant interaction with threat/safety instructions was observed. Thus, a long-term learning history of beneficial relations (e.g., with supportive parents) did not interfere with verbal threat learning and aversive apprehensions. These findings reflect the effects of worries and apprehensions that persist despite the repeated experience of safety and the pictorial presence of loved ones. How to counter such aversive expectations is key to changing mal-adaptive behaviors (e.g., avoidance or stockpiling), biased risk perceptions, and stereotypes.

The differential dynamic model for the implicit safety culture dissemination in nuclear power plants

This paper evaluates the implicit safety culture (ISC) and the dissemination among staff in a nuclear power plant. The Schein’s cultural hierarchy theory was adopted to compare implicit aspects of different organizational cultures, and to explore the application of both explicit and implicit cultures, to define the ISC of a nuclear plant and to summarize its characteristics. The dissemination system and the mechanism of the ISC was scrutinized based on dynamic and superimposing effects, which are regarded as a unity of opposites. A differential dynamic model of the ISC dissemination of the nuclear power plant was established by this study. Results of the model indicated that the ISC could be disseminated freely within the power plant when the dissemination was at an unstable equilibrium point. However, the ISC would not disseminate effectively and might disappear gradually in the power plant when the dissemination was at an asymptotic equilibrium point. The application of ISC is a crucial issue to improve the safety and benefit of the management of the nuclear power plant, including measures such as intensifying the collaboration and communication of departments, and setting a special department for the ISC dissemination and some incentive protocols in the nuclear power plant.

What's cooking in your mind? Implicit and explicit safety evaluations of unprocessed and processed foods.

What's cooking in your mind? Implicit and explicit safety evaluations of unprocessed and processed foods.

Safety culture transformation-The impact of training on explicit and implicit safety attitudes.

The present paper investigates the changeability of safety culture elements such as explicit and implicit safety attitudes by training. Therefore, three studies with different time frames, training durations, and settings will be presented. In the first study, the short‐term attitude change of students from an international environmental sciences study program was measured after safety training in a chemical laboratory. In the second study, the medium‐term attitude change was assessed after a Crew Resource Management training for German production workers in the automotive industry. In the third study, the long‐term attitude changes were measured after safety ethics training in a sample of German occupational psychology and business students. Different self‐report measures were used to evaluate the training effectiveness of explicit safety attitudes. The change of implicit safety attitudes was assessed by Implicit Association Tests. The results of all three studies revealed a significant training effect on the explicit safety attitudes, but not on the implicit ones. Besides the training effect on the explicit attitudes, there was no effect of time frame (short‐, medium‐, long‐term), training duration (2 h, 2 days, 12 weeks), and setting (chemical laboratory, automotive industry, safety ethics study program) on the attitude change. Based on the results, conceptual, methodological, and practical implications for training effectiveness and safety culture transformation are discussed.

N-version programming approach with implicit safety guarantee for complex dynamic system stabilization applications

Safety-critical systems are widely used in many sectors to prevent fatal accidents and prevent loss of life, damage of property, or deterioration of the environment. Implementation of software safety standards as part of the development of safety-critical software is generally considered an essential element of any safety program. Therefore, it has become more critical to produce highly reliable software to meet the safety requirements established by functional safety standards, such as IEC 61508, ISO 26262, and EN 50128. IEC 61508 supports well-known safety mechanisms such as design diversity like N-version (multi-version) programming. N-version (multi-version) programming is a method where multiple functionally equivalent programs are independently developed from the same software specifications. N-version (multi-version) programming is particularly an effective approach to increase the quality of software in a safety-critical system. In this paper, one of the well-known and widely used algorithms in the field of N-version (multi-version) programming, the majority voting algorithm, has been modified with an online stability checker where the decisions of the voter are judged against the stability of the underlying system. The plant where all the theoretical results are implemented is a tilt-rotor system with the proposed N-version (multi-version) programming–based controller. The experimental results show that the modified majority voter-based N-version (multi-version) programming controller provides more reliable control of the plant.

What is the safety case for health IT? A study of assurance practices in England

ObjectiveHealth IT (HIT) systems are increasingly becoming a core infrastructural technology in healthcare. However, failures of these systems, under certain conditions, can lead to patient harm and as such the safety case for HIT has to be explicitly made. This study focuses on safety assurance practices of HIT in England and investigates how clinicians and engineers currently analyse, control and justify HIT safety risks. MethodsThree workshops were organised, involving 34 clinical and engineering stakeholders, and centred on predefined risk-based questions. This was followed by a detailed review of the Clinical Safety Case Reports for 20 different national and local systems. The data generated was analysed thematically, considering the clinical, engineering and organisational factors, and was used to examine the often implicit safety argument for HIT. ResultsTwo areas of strength were identified: establishment of a systematic approach to risk management and close engagement by clinicians; and two areas for improvement: greater depth and clarity in hazard analysis practices and greater organisational support for assuring safety. Overall, the dynamic characteristics of healthcare combined with insufficient funding have made it challenging to generate and explain the safety evidence to the required level of detail and rigour. ConclusionImprovements in the form of practical HIT-specific safety guidelines and tools are needed. The lack of publicly available examples of credible HIT safety cases is a major deficit. The availability of these examples can help clarify the significance of the HIT risk analysis evidence and identify the necessary expertise and organisational commitments.

Natural language indicators of differential gene regulation in the human immune system

Adverse social conditions have been linked to a conserved transcriptional response to adversity (CTRA) in circulating leukocytes that may contribute to social gradients in disease. However, the CNS mechanisms involved remain obscure, in part because CTRA gene-expression profiles often track external social-environmental variables more closely than they do self-reported internal affective states such as stress, depression, or anxiety. This study examined the possibility that variations in patterns of natural language use might provide more sensitive indicators of the automatic threat-detection and -response systems that proximally regulate autonomic induction of the CTRA. In 22,627 audio samples of natural speech sampled from the daily interactions of 143 healthy adults, both total language output and patterns of function-word use covaried with CTRA gene expression. These language features predicted CTRA gene expression substantially better than did conventional self-report measures of stress, depression, and anxiety and did so independently of demographic and behavioral factors (age, sex, race, smoking, body mass index) and leukocyte subset distributions. This predictive relationship held when language and gene expression were sampled more than a week apart, suggesting that associations reflect stable individual differences or chronic life circumstances. Given the observed relationship between personal expression and gene expression, patterns of natural language use may provide a useful behavioral indicator of nonconsciously evaluated well-being (implicit safety vs. threat) that is distinct from conscious affective experience and more closely tracks the neurobiological processes involved in peripheral gene regulation.

Will TLAC regulations fix the G-SIB too-big-to-fail problem?

The efficacy of the Financial Stability Board's proposed requirement for minimum “total loss absorbing capacity” (TLAC) at global systemically important banks (G-SIBs) is assessed using a stylized model of a bank holding company and an equilibrium asset pricing model to value financial claims. I identify a number of G-SIB strategies that satisfy minimum TLAC requirements but fail to reduce implicit safety net subsidies that accrue to G-SIB shareholders or increase the resources available to recapitalize a failing G-SIB subsidiary. To meet the FSB's stated goals, TLAC requirements must impose minimum TLAC at all subsidiaries and restrict how TLAC funds can be invested. An equivalent, but much simpler solution is to significantly increase regulatory capital requirements on systemically important bank subsidiaries.

Will TLAC Regulations Fix the G-SIB Too-Big-To-Fail Problem?

The efficacy of the Financial Stability Board’s proposed requirement for minimum “total loss absorbing capacity” (TLAC) at global systemically important banks (G-SIBs) is assessed using a stylized model of a bank holding company and an equilibrium asset pricing model to value financial claims. I identify a number of G-SIB strategies that satisfy minimum TLAC requirements but fail to reduce implicit safety net subsidies that accrue to G-SIB shareholders or increase the resources available to recapitalize a failing G-SIB subsidiary. To meet the FSB’s stated goals, TLAC requirements must impose minimum TLAC at all subsidiaries and restrict how TLAC funds can be invested. An equivalent, but much simpler solution is to significantly increase regulatory capital requirements on systemically important bank subsidiaries.

Predictive Effect of Implicit Safety Attitudes on Safety Performance in Aviation Safety Culture

The fundamental feature of safety culture is represented by safety attitudes. In terms of measuring safety cultures, many researchers have mainly focused on explicit safety attitudes and generally relied on specific survey instruments. It is questionable, however, whether self-report measures can capture all aspects of organizational safety culture. Instead of getting direct answers, it is necessary to introduce implicit measures and the implicit safety attitudes test into safety culture evaluation. The basic hypothesis of this study was that while various enterprises share different safety culture, the structure and intensity of implicit and explicit safety attitudes differ for employees. The present study was aimed at investigating the complete model of aviation safety culture and the importance of implicit safety attitudes by detecting the relationship between explicit and implicit safety attitudes as well as the prediction effect of implicit safety attitudes.The Flight Management Attitudes Questionnaire(FMAQ 2.0, international version) was adopted in this study which was based on the work characteristics of modern airlines pilots. With the purpose of evaluating explicit safety attitudes under the background of aviation safety culture, FMAQ 2.0 is comprised of three subscales, including basic organizational attitudes, cockpit work attitudes, and flight automation attitudes. Moreover, Evaluative Implicit Association Test and Affective Implicit Association Test were developed for aviatic implicit safety attitudes test. 134 pilots were involved in the investigation, 126 valid cases were obtained. Safety performance were obtained from airline company on four dimensions, including safety regulation, flight style, flight skill and organizational management was applied for validity criterion. The results showed that(1) IAT of aviation safety attitudes indicated a high effect value, aviation safety led to more positive evaluation and feelings while flight risk and adventure were more connected with negative evaluation and emotion.(2) Implicit and explicit safety attitudes were both relevant and relative separation. There was a positive relation between evaluative implicit safety attitudes and cockpit work attitudes. Affective implicit safety attitudes showed significant positive correlation with cockpit work attitudes and flight automation attitudes. And the model data showed that implicit and explicit safety attitudes were separation structure.(3) Both the flight management attitudes and implicit safety attitudes were able to predict safety performance. The former were doing better on predicting flight style, flight skill and organizational management, while the latter had higher prediction rate on safety regulation. The common prediction model fitted well. The study demonstrated a high intensity of aviation safety attitudes. IAT can be used as an effective evaluation tool for implicit safety attitudes. Explicit and implicit safety attitudes are both unified and separated structure. The explicit safety attitudes, implicit safety attitudes and safety performance together constitute a complete model of aviation safety culture. And in this model, the outer layer is aviation safety performance, the middle layer is explicit safety attitudes which can be measured directly, the inner layer is implicit safety attitudes which can be evaluated by indirect measurement methods.

Reliability-based design recommendations for sinusoidal-web beams subjected to lateral-torsional buckling

Developments and advances in fabrication technology have led to a new generation of structural shapes, among them, the sinusoidal-web girder. Due to easy execution and potential for structural efficiency, the use of sinusoidal-web girder has been increasing significantly in several segments of civil engineering construction such as bridges, pedestrian walkways, hangars and industrial buildings. In spite of the advantages this type of structural component may offer, there are no design standards or specifications dealing with all the phenomena involved in the behavior of such beams, such as the resistance against lateral-torsional buckling (LTB). As a result, there is a need to develop design recommendations that properly address the flexural capacity of these elements. Following the current trend of semi-probabilistic codes (e.g. load and resistance factor design format), these recommendations shall be developed within the concepts and methods of Structural Reliability. In this paper, reliability-based design recommendations for sinusoidal-web beams for the limit state of LTB are presented. To this end: (i) an experimental investigation on the resistance of sinusoidal-web beams has been performed, (ii) a finite-element model has been developed and validated by experimental results, (iii) a theoretical model for the sinusoidal-web beam resistance prediction is proposed, (iv) a comprehensive program was established toward the assessment of both physical and epistemic uncertainties related to the basic variables, (v) reliability analyses are performed using First Order Reliability Method (FORM), and (vi) resulting implicit reliability levels are checked against current practice. It is shown that the implicit safety levels in the proposed recommendations are in agreement with current trends in structural engineering practice.

How Safe is Hydrologic Infrastructure Design? Analysis of Factors Affecting Extreme Flood Estimation

AbstractThis study evaluates the implicit safety level in hydrologic infrastructure design, performed in common practice with the calculation of the peak-flow frequency curve for high return periods (100<return period<10,000 years) through use of single-peak hyetographs in a semidistributed hydro-meteorological event-based model. Through consideration of two basins located in mainland Spain, the paper studies the effect on the peak-flow frequency curve of (1) the shape of the design hyetograph defined by the alternating blocks (AB) method or through applying a Monte Carlo (MC) procedure; (2) the catchment area (ranging from 140 to 1,800 km2); and (3) the extent of disaggregation in the hydro-meteorological model (varying from 14 to 66 subbasins). The effect on hydrologic safety was measured through using the ratio R=QmaxAB/QmaxMC, with QmaxAB, the peak flows obtained with the AB method and QmaxMC, the application of MC. The paper finds the following: (1) that the degree of safety decreases as the basin ...

Safety margins for unsystematic biometric risk in life and health insurance

In multistate life and health insurances, the pattern of states of the policyholder is random, thus exposing the insurer to an unsystematic biometric risk. For this reason safety margins are added on premiums and reserves. But in contrast to non-life insurance, traditionally the safety margins are not chosen explicitly but implicitly in form of a valuation basis of first order. If we define the implicit margins bottom-up, we are not able to control the level of safety that we finally reach for premiums and reserves. If we use a top-down approach, that means that we directly calculate explicit margins for premiums and reserves and then choose implicit safety margins that correspond to the explicit margins, we are able to control the total portfolio risk, but we have the problem that it is unclear how to allocate the total margin to partial margins for different transitions at different ages. Although the allocation of the total margin to the partial (implicit) margins is not relevant for the total portfolio risk, we have to pay attention since it can have a great effect on the calculation of surplus. In this paper we calculate asymptotic probability distributions for premiums and reserves of second order by using the functional delta method. As a result, we can not only determine the actual level of safety that is induced by given implicit safety margins, but we can also linearly decompose the total randomness of a portfolio to contributions that the different transition rates at different ages make to the total uncertainty. As a result we do not only get new insight into the sources of unsystematic biometric risk, but we also obtain a useful tool that allows to construct reasonable principles for the allocation of the total safety margin to implicit margins with respect to transitions and ages.

Probabilistic Fire Safety Assessment of Passenger Ships

A probabilistic framework is proposed for the assessment of passenger ship fire safety that is based on a structured generation of "design fires." The aim is to establish a rational and practical means for evaluating design selections (materials, geometry, sensors, and suppressors) that influence fire safety with reference to the implicit safety objectives attended by the current regulations. Thus, alternative design solutions could be evaluated more comprehensively. Fire growth intensity, restriction of heat release rate resulting from ventilation shortage, occurrence of flashover, and the final decay are key processes modeled in the current approach. They are interfaced with fire suppression triggered by detection. The effect of manual intervention is also assessed. An application is included based on uniform distributions of selected random parameters. Justification for the considered ranges is provided. The effect of assuming different probability distributions is considered. The methodology can be used for producing the probability of containment and extinguishment of fires as well as for judging the performance of an overall or partial ship design solution.

Multistate models in health insurance

We illustrate how multistate Markov and semi-Markov models can be used for the actuarial modeling of health insurance policies, focusing on health insurances that are pursued on a similar technical basis to that of life insurance. In the first part, we give an overview of the basic modeling frameworks that are commonly used and explain the calculation of prospective reserves and net premiums. In the second part, we discuss the biometric insurance risk, focusing on the calculation of implicit safety margins. We present new results on implicit margins in the semi-Markov model and on biometric estimation risk in the Markov model, and we explain why there is a need for future research concerning the systematic biometric risk.

Federal Liquidity Options: Containing Runs on Deposit-Like Assets Without Bailouts and Moral Hazard

In response to the 2008 runs on deposit-like assets, namely repo and money market funds, the Fed created new liquidity facilities for nonbanking institutions and the Treasury guaranteed certain money market fund balances. These extraordinary actions, while justified by officials as necessary to preserve the financial system, did rescue nonbanks by exposing the public to unprecedented risks. Since 2008, despite legislation and regulation, deposit-like assets are still vulnerable to runs. The fallback policy to contain such runs is still ad hoc lending by the Fed. Bailouts, though officially outlawed, may very well be justified and used again. Finally, because the implicit safety net of government action is still in place, moral hazard remains a feature of the financial landscape. This paper proposes that the Fed auction Federal Liquidity Options (FLOs) as the exclusive means of providing liquidity to nonbanks in a crisis. Having issued FLOs that encompass a sufficient quantity and breadth of collateral, authorities will be able to claim, with credibility, that no additional emergency lending programs or bailouts will be required to safeguard the viability of solvent nonbanks. In the resulting policy regime, the Fed does not rescue individual firms or industries but fulfills its contractual obligations under options previously sold at market-determined prices. Furthermore, with the cost of contingent liquidity internalized by the purchasers of FLOs, and with other extraordinary provisions of liquidity credibly renounced, moral hazard will drop significantly.