Safe Execution Research Articles

Local Planning Semantics: A Semantics for Distributed Real-Time Systems

Design, implementation and verification of distributed real-time systems are acknowledged to be very hard tasks. Such systems are prone to different kinds of delay, such as execution time of actions or communication delays implied by distributed platforms. The latter increase considerably the complexity of coordinating the parallel activities of running components. Scheduling such systems must cope with those delays by proposing execution strategies ensuring global consistency while satisfying the imposed timing constraints. In this paper, we investigate a formal model for such systems as compositions of timed automata subject to multiparty interactions, and propose a semantics aiming to overcome the communication delays problem through anticipating the execution of interactions. To be effective in a distributed context, scheduling an interaction should rely on (as much as possible) local information only, namely the state of its participating components. However, as shown in this paper these information is not always sufficient and does not guarantee a safe execution of the system as it may introduce deadlocks. Moreover, delays may also affect the satisfaction of timing constraints, which also corresponds to deadlocks in the former model. Thus, we also explore methods for analyzing such deadlock situations and for computing deadlock-free scheduling strategies when possible.

Causes of building construction related accident in the south-western states of Nigeria

Within the focus of the final outcome of any construction activity is the realisation of minimal cost, timely delivery and quality oriented structure. Nevertheless, above all is the safe execution of the construction site activities, which is a matter of life, most especially lives of the operatives. The study focuses on the identification of the common types of accident, the level of occurrences, as well as the causes of the identified accidents. Through an extensive literature review, eighteen (18) different types of accident were identified, which were subsequently classified into seven (7) categories. Moreover, well-structured questionnaires were administered to construction participants, with the data analysed descriptively. The outcome revealed the four categories of frequently occurring accidents to be: contact with working tools, vehicle-related, slip and trip, and falls. Some crucial inclusions in the list of causes are failure of edge protection, safety standard violations, overloading of scaffold and crane, wrong placement of ladder, loss of control over body movement, failure in the designs, absence of warning signs, over speeding of vehicle, wrong selection of working tools, non-usage of personal protective equipment, improperly installed equipment, horseplay, and poor housekeeping. However, by exploring the accident process, recommendations based on the findings are put up.

The possible role of interoception in time perception during isometric contraction

Next generation mobile networks are envisioned to provide support for real-time control applications. One of the main aspects of these systems is that the location of the controller may be separated from the location of sensing and actuation. This promises benefits in terms of an increased flexibility, lower costs due to resource sharing, and higher computational capabilities. This paper focuses on one aspect of such systems, specifically, the controller handover. During a controller handover, a control process is moved from one point of computation to another at runtime. A possible reason for performing such a handover is to move the control process to a controller with better channel conditions. The safety of the handover is analyzed using a probabilistic reachability analysis by modeling the handover procedure as a stochastic hybrid system. Based on this safety analysis, a safety-oriented handover triggering rule is proposed. This triggering rule is shown to be dependent on the instantaneous state of the plant, in contrast to handover in mobile networks where it is only dependent on the state of the communication links. A vehicle platoon is considered as an example scenario, which is controlled by a base station of a mobile network. While driving, the platoon will move out of the communication range of the base station, so the control process needs to be moved to the next base station. Simulations illustrate the conditions for a safe execution of so called hard and soft handover protocols.

Nontechnical skills of the operating theatre circulating nurse: An ethnographic study.

This paper aims to uncover circulating nurses' nontechnical skills-namely, the cognitive and social skills that floor nurses need to deliver patient care in the operating room. Previous studies have shown that nontechnical skills play a key role in the safe execution of high-risk health practices, such as anaesthesia, resuscitation, and surgery. Regarding the surgical team, research has thus far focused on the nontechnical skills of anaesthesiologists, surgeons, and scrub nurses, leaving unexplained the cognitive and social skills that circulating nurses need to acquire and use. Ethnographic study. Empirical materials were collected in the operating department of a hospital located in northern Italy, drawing on direct observation, document analysis and informal interviews with the circulating nurses. Data collection lasted 3months, from May - July 2017. Nontechnical skills of circulating nurses can be described using five categories: leadership, situation awareness, task management, communication, and teamwork. This paper explicitly addresses circulating nontechnical skills needed to support the design of educational and training pathways for nurses.

Methodology for assessment of operational limits including uncertainties in wave spectral energy distribution for safe execution of marine operations

Marine operations need to be executed in a cost-effective and safe manner. Safety depends on safety margins that are included in the operational limits. These operational limits are normally given in terms of sea state parameters, i.e. significant wave height (Hs) and peak period (Tp), here denoted as Hs(Tp). Safety margins on Hs(Tp) should account for various sources of uncertainties in weather forecasts, wave spectral shape, numerical models, etc. Wave spectra at an offshore site may be multi-modal and not necessarily resemble analytical spectra, such as Joint North Sea Wave Project (JONSWAP) or Pierson-Moskowitz (PM) models. Since floating vessels are sensitive to wave spectral energy distribution, Hs(Tp) operational limits should account for this source of uncertainty. This paper provides a general methodology to assess the uncertainty in Hs(Tp) limits due to variability in wave spectral energy distribution. This is important for safe execution of marine operations. The methodology uses response-based operational limits, directional (2D) hindcast wave spectra and dynamic coupled models of marine operation activities. A case study of an offshore wind turbine transition piece installation is shown to illustrate the proposed methodology.

High Angle-of-Attack Pitching Moment Characteristics of Slender-Bodied Reusable Rocket

The development of a fully reusable vertical-takeoff, vertical-landing rocket is indispensable for reducing space transportation costs. However, there are many technical issues associated with such vehicles, such as the safe execution of a turnover maneuver during return flight. It is known that a relatively desirable pitching moment characteristic for turnover can be accomplished by employing a slender-body configuration, but the reason for this is not well understood. In this study, a delayed detached-eddy simulation on the aerodynamic characteristics of such a slender-bodied reusable rocket is carried out for angles of attack between 0 and 180 deg using unstructured compressible computational fluid dynamics. Inviscid calculations are also conducted to distinguish the pitching moment contribution of the body configuration itself from the effects of viscosity and turbulence. It was found that two types of vortices were formed at 0–90 deg, and these vortices affected the pitching moment distribution. Three types of vortices generated at 90–180 deg were also observed. Combined with the results of the inviscid simulation, it is concluded that the pitching moment characteristic is greatly impacted by the behaviors of these vortices and bubbles.

Velox VM: A safe execution environment for resource-constrained IoT applications

We present Velox, a virtual machine architecture that provides a safe execution environment for applications in resource-constrained IoT devices. Our goal with this architecture is to support developers in writing and deploying safe IoT applications, in a manner similar to smartphones with application stores. To this end, we provide a resource and security policy framework that enables fine-grained control of the execution environment of IoT applications. This framework allows device owners to configure, e.g., the amount of bandwidth, energy, and memory that each IoT application can use. Velox's features also include support for high-level programming languages, a compact bytecode format, and preemptive multi-threading.In the context of IoT devices, there are typically severe energy, memory, and processing constraints that make the design and implementation of a virtual machine with such features challenging. We elaborate on how Velox is implemented in a resource-efficient manner, and describe our port of Velox to the Contiki OS. Our experimental evaluation shows that we can control the resource usage of applications with a low overhead. We further show that, for typical I/O-driven IoT applications, the CPU and energy overhead of executing Velox bytecode is as low as 1–5% compared to corresponding applications compiled to machine code. Lastly, we demonstrate how application policies can be used to mitigate the possibility of exploiting vulnerable applications.

Problems and solutions in IGRT for cervical cancer.

The contribution of Image-guided Radiotherapy (IGRT) to modern radiotherapy is undeniable, being the way to bring into daily practice the dosimetric benefits of Intensity-Modulated Radiotherapy (IMRT). Organ and target motion is constant and unpredictable at the pelvis, thus posing a challenge to the safe execution of IMRT. There are potential benefits of IMRT in the radical treatment of cervical cancer patients, both in terms of dose escalation and decrease of toxicity. But it is essential to find IGRT solutions to control the aspects that can lead to geographic miss targeting or organs at risk (OAR) overdose. This review seeks to describe the problems and possible solutions in the clinical implementation of IMRT/IGRT protocols to treat intact cervical cancer patients.

Risk of Epidural Hematoma After Neuraxial Techniques in Thrombocytopenic Parturients: A Report From the Multicenter Perioperative Outcomes Group

(Anesthesiology. 2017;126(6):1053–1063) Thrombocytopenia is a relative or even absolute contraindication to neuraxial techniques for labor analgesia and cesarean delivery due to a potential increased risk of epidural hematoma, which can cause permanent neurological injury. Consensus on an acceptable platelet count needed for safe execution of neuraxial techniques and risk stratification of this complication by platelet count are unclear. This retrospective cohort study aimed at using the Multicenter Perioperative Outcomes Group (MPOG) database to define the risk of epidural hematoma requiring surgical decompression stratified by platelet count after neuraxial techniques in thrombocytopenic parturients. A systematic review was also done to combine the resulting data with existing literature reporting neuraxial techniques in thrombocytopenic pregnant women.

Erector spinae plane block for radical mastectomy: A new indication?

The erector spinae plane block is a technique recently described by Forero et al. in September 2016. It has applications in the control of chronic pain with neuropathic component of the chest wall, and for pain control in thoracoscopic surgery. In this article, we describe the use of this technique as part of a multimodal analgesic approach in a 40-year-old woman, who underwent radical mastectomy due to breast cancer. By performing this block before anesthetic induction, we have achieved an opioid sparing effect, avoiding a possible immunomodulatory effect, although not yet proven in humans. During hospitalization, the patient reported no pain (0/10 in numeric scale), without resorting to rescue analgesia. The easy, fast and safe execution of erector spinae plane block makes it a promising technique in the context of surgical pain during radical mastectomy.

Priority-free conditionally-preemptive scheduling of modular sporadic real-time systems

For a real-time system (RTS) processing both sporadic and (multiple-period) periodic tasks, this study presents a novel modular modeling framework to describe the parameters of tasks, conforming to the pertinent concepts and techniques of discrete-event systems (DES). A task is represented by an automaton synchronized by the modular models corresponding to its parameters. As a consequence, a DES model depicting the RTS is synchronized by the DES representing these tasks. Based on supervisory control theory, priority-free conditionally-preemptive (PFCP) real-time scheduling is solved by finding all the safe execution sequences. Finally, the PFCP scheduling is illustrated by real-world examples.

Accident Causal Factors on the Building Construction Sites: A Review

The concerns for cost, quality and timely delivery of projects have been in existence from time immemorial, whereas the passion for these should be extended to safe execution of site works by the construction participants, as safety of life is very paramount. However, high level of commitment that is essential for the safe execution of site works has become a taboo. Hence, a plethora of accidents takes place on the site ranging from falls from height, contact with working tools, vehicle-related, slip and trip, collapse, exposure to harmful substances, to lifting and handling object accidents. It is pertinent to know that, responsibility for accidents on site cuts across all project participants (clients, consultants, contractors, workers), as well as the construction site environment. Recognition of the construction participants and site environmental factors as agents of accident is the focus of this research. Through extensive review of literature, a copious number of factors were identified and subsequently grouped under five factors as client-related, consultant-related, contractor-related, construction workers-related, and construction site-related. However, there has been a dearth of research in the grouping of accident contributing factors. The identification and understanding of these factors will go a long way in mitigating construction accidents, coupled with proven measures taken in positively addressing them. Efforts to prevent these causative factors include inter alia elimination of hazards from design, effective safety management, adequate planning of activities and employment of seasoned professionals by the client. The contractors are to embark on staff safety auditing, set up safety committees, conduct regular training for staff, use innovative technology, uphold housekeeping and report accident occurrence, while strict adherence to safety regulations must be adopted by all construction operatives.

Anchored piles in Santiago's gravel: modeling results for displacement curve

This study describes the method of discontinuous and anchored machine bored piles. The main advantage of this method is its faster and safer execution in comparison with hand-dug piles (rectangular section), the most widely used method for soil retaining in the gravel of Santiago. This paper shows the results of displacement versus height obtained by a numerical modeling (software Plaxis 2D), in the case of anchored machine bored piles used for the construction of the Faculty of Physical and Mathematical Sciences, Universidad de Chile. As part of monitoring of excavation, measurements of displacements were obtained for two piles at different stages by preinstalled inclinometers in the piles. Furthermore, the study shows the results for the displacement using rod construction module (software GGU-Retain), and through Winkler's theory (software CYPE: Embedded retaining walls), considering the most representative stages and the redistribution of soil pressure that is indicated in the Chilean Norm NCh.3206 for the model done on GGU-Retain. The results of the performed modellings are graphically compared with the measured field values.

Patient-specific three-dimensional printing for Kommerell's diverticulum

BackgroundKommerell's diverticulum is a complex congenital malformation of aorta. Three-dimensional (3D) printing is an innovative manufacturing process that allows computer-assisted conversion of 3D imaging data into physical “printouts.” The aim of this study was to explore the feasibility and impact of using patient-specific 3D-printed cardiac prototypes derived from computed tomography data on surgical decision-making and preoperative planning for Kommerell's diverticulum. MethodsFrom April to August 2017, five patients with Kommerell's diverticulum were diagnosed and chosen for study. Cardiac computed tomography was done for all patients. One case was diagnosed with left aortic arch, and another four cases presented right-sided aortic arch and aberrant left subclavian artery. In addition, one patient complicated with aortic dissection. Data were used to generate patient-specific 3D models. All cases were reviewed along with their models, and the impact on surgical decision-making and preoperative planning was assessed. ResultsAccurate life-sized 3D models were successfully printed for all patients. These models enabled improved understanding of aortic malformation and preoperative planning. 3D models also allowed real-time intraoperative guidance for surgeons. Conclusions3D printed models can improve the understanding of anatomy and allow anticipation of surgical technique challenges, which could radically assist surgical planning, and safe execution of surgery for Kommerell's diverticulum. The combination of 3D printing technique and surgical procedure is a promising perspective for treatment of complex aortic malformation.

Methodology of Dynamic Monitoring of Structures in the Vicinity of Hydrotechnical Works – Selected Case Studies

Abstract The constant development of geotechnical technologies imposes the necessity of monitoring techniques to provide a proper quality and the safe execution of geotechnical works. Several monitoring methods enable the preliminary design of work process and current control of hydrotechnical works (pile driving, sheet piling, ground improvement methods). Wave parameter measurements and/or continuous histogram recording of shocks and vibrations and its dynamic impact on engineering structures in the close vicinity of the building site enable the modification of the technology parameters, such as vibrator frequency or hammer drop height. Many examples of practical applications have already been published and provide a basis for the formulation of guidelines, for work on the following sites. In the current work the author’s experience gained during sheet piling works for the reconstruction of City Channel in Wrocław (Poland) was presented. The examples chosen describe ways of proceedings in the case of new and old residential buildings where the concrete or masonry walls were exposed to vibrations and in the case of the hydrotechnical structures (sluices, bridges).

Методические аспекты функционирования единой системы аттестации руководителей и специалистов строительного комплекса Российской Федерации

The article considers the components of the Unifi ed Certifi cation System for managers and specialists of the construction complex of the Russian Federation, as well as the principles of its functioning, technical and methodological assessment tools. The objectives of the fi nal certifi cation, which are established by the legislation on education (control of the assimilation of new knowledge) and qualifi cation and job certifi cation, established by labor legislation (confi rmation of compliance with the position held) are not aimed at achieving the self-regulation goals in construction defi ned by the Town Planning Code of the Russian Federation. A Unifi ed system of attestation, developed by the All-Russian branch association of employers “National Association of Self-Regulating Organizations Based on the Membership of Building Persons” (NOSTROY), aims to confi rm the qualifi cation of a specialist in terms of knowledge of the norms of technical regulation of works in the fi eld of construction — norms that provide a safe execution of the kind of construction work on which this specialist is declared upon obtaining a certifi cate of admission to work aff ecting safety of objects of capital construction in Russia.

In-situ medical simulation for pre-implementation testing of clinical service in a regional hospital in Hong Kong.

The implementation of a new clinical service is associated with anxiety and challenges that may prevent smooth and safe execution of the service. Unexpected issues may not be apparent until the actual clinical service commences. We present a novel approach to test the new clinical setting before actual implementation of our endovascular aortic repair service. In-situ simulation at the new clinical location would enable identification of potential process and system issues prior to implementation of the service. After preliminary planning, a simulation test utilising a case scenario with actual simulation of the entire care process was carried out to identify any logistic, equipment, settings or clinical workflow issues, and to trial a contingency plan for a surgical complication. All patient care including anaesthetic, surgical, and nursing procedures and processes were simulated and tested. Overall, 17 vital process and system issues were identified during the simulation as potential clinical concerns. They included difficult patient positioning, draping pattern, unsatisfactory equipment setup, inadequate critical surgical instruments, blood products logistics, and inadequate nursing support during crisis. In-situ simulation provides an innovative method to identify critical deficiencies and unexpected issues before implementation of a new clinical service. Life-threatening and serious practical issues can be identified and corrected before formal service commences. This article describes our experience with the use of simulation in pre-implementation testing of a clinical process or service. We found the method useful and would recommend it to others.

Safety Analysis for Controller Handover in Mobile Systems

Next generation mobile networks are envisioned to provide support for real-time control applications. One of the main aspects of these systems is that the location of the controller may be separated from the location of sensing and actuation. This promises benefits in terms of an increased flexibility, lower costs due to resource sharing, and higher computational capabilities. This paper focuses on one aspect of such systems, specifically, the controller handover. During a controller handover, a control process is moved from one point of computation to another at runtime. A possible reason for performing such a handover is to move the control process to a controller with better channel conditions. The safety of the handover is analyzed using a probabilistic reachability analysis by modeling the handover procedure as a stochastic hybrid system. Based on this safety analysis, a safety-oriented handover triggering rule is proposed. This triggering rule is shown to be dependent on the instantaneous state of the plant, in contrast to handover in mobile networks where it is only dependent on the state of the communication links. A vehicle platoon is considered as an example scenario, which is controlled by a base station of a mobile network. While driving, the platoon will move out of the communication range of the base station, so the control process needs to be moved to the next base station. Simulations illustrate the conditions for a safe execution of so called hard and soft handover protocols.

Monitoring and Validation of the Global Replacement of tOPV with bOPV, April-May 2016.

The phased withdrawal of oral polio vaccine (OPV) associated with the Polio Eradication and Endgame Strategic Plan 2013-2018 began with the synchronized global replacement of trivalent OPV (tOPV) with bivalent OPV (bOPV) during April - May 2016, a transition referred to as the “switch.” The World Health Organization’s (WHO) Strategic Advisory Group of Experts (SAGE) on Immunization recommended conducting this synchronized switch in all 155 OPV-using countries and territories (which collectively administered several hundred million doses of tOPV each year via several hundred thousand facilities) to reduce risks of re-emergence of vaccine-derived polioviruses. Safe execution of this switch required implementation of an associated independent monitoring strategy, the primary objective of which was verification that tOPV was no longer available for administration post-switch. This strategy had to be both practical and rigorous such that tOPV withdrawal could be reasonably employed and confirmed in all countries and territories within a discreet timeframe. Following these principles, WHO recommended that designated monitors in each of the 155 countries and territories visit all vaccine stores as well as a 10% sample of highest-risk health facilities within two weeks of the national switch date, removing any tOPV vials found. National governments were required to provide the WHO with formal validation of execution and monitoring of the switch. In practice, all countries reported cessation of tOPV by 12 May 2016 and 95% of countries and territories submitted detailed monitoring data to WHO. According to these data, 272 out of 276 (99%) national stores, 3,741 out of 3.968 (94%) regional stores, 16,144 out of 22,372 (72%) district level stores, and 143,050 out of 595,401 (24%) of health facilities were monitored. These data, along with field reports suggest that monitoring and validation of the switch was efficient and effective, and that the strategies used during the process could be adapted to future stages of OPV withdrawal.

Imaging of human vertebral surface using ultrasound RF data received at each element of probe for thoracic anesthesia

Epidural anesthesia is a common technique for perioperative analgesia and chronic pain treatment. Since ultrasonography is insufficient for depicting the human vertebral surface, most examiners apply epidural puncture by body surface landmarks on the back such as the spinous process and scapulae without any imaging, including ultrasonography. The puncture route to the epidural space at thoracic vertebrae is much narrower than that at lumber vertebrae, and therefore, epidural anesthesia at thoracic vertebrae is difficult, especially for a beginner. Herein, a novel imaging method is proposed based on a bi-static imaging technique by making use of the transmit beam width and direction. In an in vivo experimental study on human thoracic vertebrae, the proposed method succeeded in depicting the vertebral surface clearly as compared with conventional B-mode imaging and the conventional envelope method. This indicates the potential of the proposed method in visualizing the vertebral surface for the proper and safe execution of epidural anesthesia.