Base isolation provides a very effective passive method of protecting the structure from the hazards of earthquakes. The proposed isolation system combines the laminated rubber bearing with the device made of shape memory alloy (SMA). The smart base isolation uses hysteretic behavior of SMA to increase the structural damping of the structure and utilizes the different responses of the SMA at different levels of strain to control the displacements of the base isolation system at various excitation levels. The performance of the smart base isolation is compared with the performance of isolation by laminated rubber bearings to assess the benefits of additional SMA damper for isolation of three story building.

The specific mission was to identify the conditions of atmospheric pressure and ambient temperature under which a so-called empty-Boeing model 747-131 fixed wing jet aircraft center wing tank (CWT), containing a residual fuel loading of about 3 kg/m 3 , less than 100 gallons of aviation kerosene (JetA Athens refinery commercial jet fuel), could form hazardous air/fuel mixtures. The issues are limited to explosion safety concerns relating to certificated fixed wing jet aircraft in regularly scheduled commercial passenger service. It is certain that a combustible mixture does not exist in a fuel tank containing Jet-A type fuel at ambient temperatures below 38°C (100°F), which is the lean limit flash point (LFP) for commercial jet fuel at sea level. Never the less, although not included in this paper, the original study reported by Wyczalek and Suh (1997), identified six highly unlikely, but rationally possible critical conditions which can occur in a combination which may permit a combustible mixture to exist within a jet aircraft fuel tank and pose a potential hazard. The scope of this paper is limited to mathematical modeling concerns related to fixed wing jet aircraft fuel tanks and commercial jet fuels combustible air-fuel mixture ratios. It was further limited to a historical review of the scientific literature in the public domain from 1950 to the present time, which defined the thermodynamic and minimum ignition energy properties of aviation gasoline and commercial jet fuels; and, to comparisons with new thermodynamic data for JetA Athens flight test samples, released by the National Transportation Safety Board (NTSB) during public hearings on the TWA800 event in Baltimore, Maryland in December 1997. The original work reported by Wyczalek and Suh (1997) conclusively demonstrated that the USAF Wright Air Development Center and the US Bureau of Mines conducted and published comprehensive evaluations of the potential hazards relating to jet aircraft fuel tanks as early as 1952. This historical scientific data and the mathematical models for the new jetA and Athens refinery jetA in this paper, are relevant to pending TWA800 related litigation, and to the future implementation of NTSB recommendations resulting from the TWA800 event.

Heat release rates of typical items in fires are needed as a prerequisite for estimating fire growth and temperatures in structural fires. That is, these burning rates are required to be specified by the user as input to single-room and multi-room structural fire computer codes like FPETool, FASTLife and HAZARD. Data are given here that permit burning items to be specified in a useful modeled way, taking a t 2 -fire for the growth and decay periods, with a constant maximum heat release rate between these two periods.

Risk-based design uses severity and occurrence quantification to determine overall system risk and prioritize the most important hazards. To fully understand and effectively mitigate potential risks, the effects of component failures and human errors (acting alone and in tandem) need to be considered early. Then one can determine whether to allocate resources to proactively mitigate human errors in the design process. In previous work, the Human Error and Functional Failure Reasoning (HEFFR) framework was developed to model effects of human errors and component failures in a system, taking critical event scenarios as inputs and producing functional failures, human errors, and their propagation paths as outputs. With automated scenario generation, this framework can model millions of scenarios that cause system critical functions to fail. However, the outputs of this framework do not include any quantifiable measures to assess the risk of the hazards or prioritize fault scenarios. This work addresses these shortcomings by using a scenario probability and cost model to quantify the expected cost of failures in the HEFFR framework. A coolant tank case study is used to demonstrate this approach. The results show that the quantifiable measures enable HEFFR to identify worst-case scenarios, prioritize scenarios with the highest impact, and improve human-product interactions. However, the underlying likelihood and cost models are subject to uncertainties which may affect the assessments.

Presence of toxic chemicals in food products due to the use of different synthetic materials in food packages may cause long-term health hazard. Addition of chemical components such as phthalate family (for instance, Di(2-ethylhexyl) phthalate, DEHP) to plastics may result in diffusion of these materials in food specially in liquids such as bottled soft drink, water and juice. In this work, we present a chemical sensor that can detect DEHP in orange juice at extremely low concentrations. The sensor is made of two interdigitated electrodes, and electrochemical impedance spectroscopy (EIS) is used for the detection. Sensors with different overall dimensions and finger/gap sizes were fabricated using a polycrystalline silicon standard foundry. For simplification of the experiments, low concentration of citric acid in water (similar to orange juice) is used to represent the orange juice. The sensors are exposed to different concentrations of DEHP and their Nyquist and impedance-frequency plots are studied. The experimental data shows that the sensors can distinctly capture low concentrations of DEHP in the juice solution. An electrical model is developed that can simulate the frequency response of the system containing the sensor and the solution. The model includes dynamic physical parameters such as double-layer capacitance, solution resistance and Warburg impedance that can be used in detection. EIS curves fit to experimental data shows that the model well fits the experimental data.

Swarm robotic search is concerned with searching targets in unknown environments (e.g., for search and rescue or hazard localization), using a large number of collaborating simple mobile robots. In such applications, decentralized swarm systems are touted for their task/coverage scalability, time efficiency, and fault tolerance. To guide the behavior of such swarm systems, two broad classes of approaches are available, namely nature-inspired swarm heuristics and multi-robotic search methods. However, simultaneously offering computationally-efficient scalability and fundamental insights into the exhibited behavior (instead of a black-box behavior model), remains challenging under either of these two class of approaches. In this paper, we develop an important extension of the batch Bayesian search method for application to embodied swarm systems, searching in a physical 2D space. Key contributions lie in: 1) designing an acquisition function that not only balances exploration and exploitation across the swarm, but also allows modeling knowledge extraction over trajectories; and 2) developing its distributed implementation to allow asynchronous task inference and path planning by the swarm robots. The resulting collective informative path planning approach is tested on target search case studies of varying complexity, where the target produces a spatially varying (measurable) signal. Significantly superior performance, in terms of mission completion efficiency, is observed compared to exhaustive search and random walk baselines, along with favorable performance scalability with increasing swarm size.

Noise is one of the major serious issues for planetary gear trains (PGTs). This noise is regarded as a noise hazard in certain cases such as helicopter cabins where the sound level reaches 100dB. Herein, planet gears of several precisions are combined to investigate the influence of tooth precision on meshing noise of PGT. The meshing noise of PGTs is generated by stiffness coefficient excitation and error excitation forces; however, the stiffness coefficient excitation is assumed to be constant in this paper because a slight error on the tooth surface does not affect the meshing stiffness. It was found that maintaining the same precision for all planet gears is the best. If one of the planet gears has a precision that is significantly different from that of the others, the sound pressure level increases. The deviation for the maximum error among all meshing pairs, should be restricted to no more than 3μm in case of module one spur gear.

There is a major push in safety-critical systems to consider system risk early in the design process in order to avoid costly redesign later on. However, existing techniques, which may be labor-intensive and be subject to many sources of uncertainty, rely on failure mode and failure rate data, which can only be estimated in the early design phase. This paper proposes a network-based technique for assessing the consequential importance of a particular component to enable designers to consider hazards in the design of the system architecture without the use of estimated failure rates. Structural consequence analysis represents connectivity between components with a network and provides an explicit representation of risk prevention and mitigation techniques, such as redundancy. The network is augmented with a measure of the consequence of the failure of the “end” components, or sinks, which can be backpropagated through the network to compute the consequence associated with the failure of all components. Based on this consequence, designers can consider mitigation strategies, such as redundancy or increased component reliability. The approach is demonstrated in the design of an electric system to control an aileron of an unmanned aircraft system (UAS). It is found that structural consequence analysis can identify potentially important components without failure rate data, allowing designers to proactively design for risk earlier in the design process.

Unlike an autonomous driving system, a shared control system keeps the driver in the loop to exploit human’s decision-making, path-planning, and control skills in vehicle motion control. In the meantime, a shared control system consistently provides support to the driver in hazardous situations. Typical shared control systems concentrate on altering vehicle steering actions through either active front steering or haptic steering torque. However, an active front steering system requires costly hardware and a haptic steering torque explicitly interferences with the driver hand-wheel steering. To overcome the drawbacks of the steering-based strategies, this paper introduces a driver support system based on direct yaw moment control for highspeed collision avoidance maneuvers. The new system maintains a hierarchical structure with a high-level lateral velocity planner and a low-level lateral velocity governor. In addition, the personally-preferred collision avoidance trajectories of each driver are taken into account to make the controller personalizable. Carsim-Simulink joint simulations demonstrate that this novel shared control system can successfully assist the driver in high-speed collision avoidance maneuvers. Moreover, both physical and mental loads of the driver are substantially reduced in contrast to using an active front steering system.

Noise has been recognized as a serious health hazard in modern society. Among various noise reduction ways, control of the transmission path from the source to the receiver is a feasible option for both existing and new facilities. More specifically, acoustic barriers and reactive or dissipative mufflers are two characteristic measures. The performance of a noise barrier or a muffler always depends on geometries. For the former, the key geometry is the barrier height; for the latter, the key geometries are the shape and size of the expansion chamber or resonance tubes. Conventional barriers and mufflers are scarcely capable of altering their key geometries, and hence, their performance based on requirements, nor possessing adequate versatility to adapt to variable noise conditions. In this research, we show that origami, the ancient art of paper folding, provides abundant inspiration for developing reconfigurable noise controlling devices, exemplified by Miura-ori noise barrier, modular-origami silencer, Miura-ori quarter-wavelength tube, and origami-ball expansion chamber. We show that the shape and characteristic geometries of these devices can be significantly altered via folding with a single degree of freedom, which can be exploited for tuning their attenuation performances. Then the modular-origami silencer is employed to exemplify the folding-induced advantages. Finite element studies reveal that folding could reconfigure the silencer such that the sound attenuation bandwidth can be effectively tuned. In addition, by incorporating multiple origami layers in a silencer and by programming their geometries, prescribed noise control requirement can be achieved. Overall, with the modular-origami silencer as a proof-of-concept example, we demonstrate that origami could inspire new innovation in designing noise control devices with the long-desired shape re-configurability and acoustic tunability.

Structural control systems, including passive, semi-active and active damping systems, are used to increase structural resilience to multi-hazard excitations. While semi-active and active damping systems have been investigated for the mitigation of multi-hazard excitations, their requirement for real-time controllers and power availability limit their usefulness. This work proposes the use of a newly developed passive variable friction device for the mitigation of multi-hazard events. This passive variable friction device, when installed in a structure, is capable of mitigating different hazards from wind and ground motions. In wind events, the device ensures serviceability, while during earthquake events, the device reduces the building’s inter-story drift to maintain strength-based motion requirements. Results show that the passive variable friction device performs better than a traditional friction damper during a seismic event while not compromising any performance during wind events.

Hydrogen is a carbon-free fuel expecting to be used in either combustion devices or fuel cells. However, high diffusivity and reactivity of hydrogen may result in potential hazards of flame flash back in conventional combustion systems, which greatly restricts the wide application of hydrogen fuel in engines. In this study, an inherently safe technique of rapidly mixed tubular combustion is adopted to attempt the hydrogen combustion, in which fuel and oxidizer are individually injected into the cylindrical combustor. Two methods of fuel and oxidizer feeding are tested: (1) hydrogen and air are separately injected from fuel and oxidizer inlets, respectively. Measurements are conducted by varying air flow rate and equivalence ratio ( Φ ), in which a steady tubular flame can only be obtained below Φ = 0.35, above which the flame becomes unsteady. (2) N 2 is adopted as the diluent in both H 2 and O 2 streams. By adding N 2 in the fuel stream to approach the same mean injection velocity as that of N 2 and O 2 mixture in the oxidizer inlet, fuel/oxidizer mixing is much enhanced, and a steady tubular flame has been achieved at Φ = 0.5. Then the oxygen content in the overall mixture of N 2 and O 2 is gradually reduced from 0.21 to investigate the combustion characteristics. Flame structure, lean extinction limit, flame stability and laminar burning velocity as well as temperature are investigated under various oxygen contents and equivalence ratios. The results provide a useful guide to the safe operation of hydrogen combustion in the rapidly mixed tubular flame burner.

Teams of small (mm-to-cm scale) robots, often known as swarm-bots, can provide unique functionality owing to their small form factor, distributed sensing capabilities, resilience to disruptions and agent-loss, and likely low cost. Such swarm-bots are being increasingly touted to support various indoor surveillance, hazard detection, and search and rescue missions. This paper presents the conceptual design, fabrication, and testing of a new cm-scale wheeled swarm-bot. Simulated investigation of a simple particle-swarm-inspired approach to coordinated path planning for these swarm-bots is also presented. The swarm bot is developed around a modular platform, comprising snap-on (3D printed) structural components, a stepper-motor actuated wheel system, a Raspberry Pi computing node, a wireless radio module, a Lipo battery, and proximity sensors; all components are readily detachable, thereby allowing reconfiguration flexibility. Through three design generations, a stable prototype offering >20cm/s speed and ∼50 min endurance, was developed, assembled and tested. A virtual simulated environment is developed by combining MATLAB-based modules and a V-Rep environment, in order to simulate the coordinated operation of these swarm-bots. A 78% rate of success in completing target (light source) search missions was observed during the numerical experiments, and performance robustness was observed to improve with increasing swarm size.

Autonomous systems operating in dangerous and hard-to-reach environments such as defense systems deployed into enemy territory, petroleum installations running in remote arctic and off-shore environments, or space exploration systems operating on Mars and further out in the solar system often are designed with a wide operating envelope and deployed with control systems that are designed to both protect the system and complete mission objectives, but only when the on-the-ground environment matches the expected and designed for environment. This can lead to overly conservative operating strategies such as preventing a rover on Mars from exploring a scientifically rich area due to potential hazards outside of the original operating envelope and can lead to unanticipated failures such as the loss of underwater autonomous vehicles operating in Earth’s oceans. This paper presents an iterative method that links computer simulation of operations in unknown and dangerous environments with conceptual design of systems and development of control system algorithms. The Global to Local Path Finding Design and Operation Exploration (GLPFDOE) method starts by generating a general mission plan from low resolution environmental information taken from remote sensing data (e.g.: satellites, plane fly-overs, telescope observations, etc.) and then develops a detailed path plan from simulated higher-resolution data collected “in situ” during simulator runs. GLPFDOE attempts to maximize system survivability and scientific or other mission objective yield through iterating on control system algorithms and system design within an in-house-developed physics-based autonomous vehicle and terrain simulator. GLPFDOE is best suited for autonomous systems that cannot have easy human intervention during operations such as in the case of robotic exploration reaching deeper into space where communications delays become unacceptably large and the quality of a priori knowledge of the environment becomes lower fidelity. Additionally, in unknown extraterrestrial environments, a variety of unexpected hazards will be encountered that must to be avoided and areas of scientific interest will be found that must be explored. Existing exploratory platforms such as the Mars Exploratory Rovers (MERs) Curiosity and Opportunity either operate in environments that are sufficiently removed from immediate danger or take actions slowly enough that the signal delay between the system and Earth-based operators is not too great to allow for human intervention in hazardous scenarios. Using the GLPFDOE methodology, an autonomous exploratory system can be developed that may have a higher likelihood of survivability, can accomplish more scientific mission objectives thus increasing scientific yield, and can decrease risk of mission-ending system damage. A case study is presented in which an autonomous Mars Exploration Rover (MER) is generated and then refined in a simulator using the GLPFDOE method. Development of the GLPFDOE methodology allows for the execution of more complex missions by autonomous systems in remote and inaccessible environments.

The current markets are characterized by an increasing demand for individual products, increasing product complexity and stricter safety regulations. This results in large hazard and safety analysis efforts for each individual product variant. One possible solution to reduce these efforts is the automation of analyses and a preliminary assessment of individual changes. Therefore, several approaches are published to e.g. model safety aspects or evaluate change propagations. However, the approaches fail to directly establish the connection between product changes and safety aspects by a common model. This paper develops a method to identify and assess the potential hazard impact of product changes through a common static model. It builds on a graph-based product model and graph-rewriting. From the state of the art, suitable methods tools and principles are identified and evaluated. Based on this, requirements are derived. The capabilities of existing methods are assessed and the most suitable ones adapted and integrated to the method to assess the potential hazard impact of product changes (MBHPA). The MBHPA reduces the complexity by providing two independent interconnected analyses. To evaluate the product changes, a static propagation analysis is provided. It uses defined graph-rewriting patterns to trace propagations and extract a propagation tree. The affected components in a second step can then be evaluated on their hazard potential. Again graph-rewriting patterns are applied to identify the connected hazards which are visualized in a hazard potential portfolio. The MBHPA is implemented and evaluated with the industrial case of an automated coffee machine. The evaluation underlines that the MBHPA successfully identifies possible propagations and their effect on hazards from a static perspective. It helps to improve safety awareness and traceability and reduces the required experience.

A detailed analysis of the path traversed by the rear wheels of the bus is useful in highway design, and in the placement of curbs at intersections. In fact, when a bus turns a corner, the rear wheel could move into the path of a passing motorist or pedestrian by generating an hazard situation, as in the cases of traffic circles and changing lanes. Of course, the same problems regard long trucks, semi-trailer trucks and articulated vehicles, but also bicycles (tandem) and motorbikes. In particular, the path of the rear wheels of a bus or a long vehicle in general, is a tractrix or equi-tangential curve, which is different by that traced by the front wheels. The planar motion of the chassis of the vehicle can be represented by means of the centrodes, which are traced by the instant center of rotation on the ground (fixed centrode) and on the moving plane that is attached to the vehicle (moving centrode), respectively. Thus, the pure-rolling motion of the moving centrode that is represented by the axis of the rear wheel, on the fixed centrode (catenary) can reproduce the planar motion of the chassis. This paper deals with the formulation of a suitable algorithm for the kinematic analysis of the planar motion of vehicles that travel corners, traffic circles and changing lanes. The tractrix is considered as the involute of the fixed centrode (catenary), which takes also the rule of evolute. The inflection and the cuspidal or return circles, along with the Euler-Savary equation and the Aronhold Theorems, give other useful information on the planar motion of the chassis.

Two-wheeled inverted pendulums can be used as personal transporters. Their maneuverability and small footprint give them some desirable properties for this application. However, given the unstable mechanical design and the complicated control system that is required, inverted pendulums make complex and unexpected motions in response to both movements of the rider and disturbances from the operating environment. These complex motions lead to dynamic hazards that may cause the rider to fall off or the device to fall over. To better understand some of the complex motions, the response of a two-wheeled inverted-pendulum transporter traveling over bumps of various sizes is studied. Three effects of riding over bumps are demonstrated through an experimental investigation. When striking a bump, the transporter may bounce in the vertical direction, depending on the approach speed and size of the bump. Bumps also cause the transporter to pitch forward. When striking a bump with one wheel, the transporter turns towards the bump. All three effects can act to destabilize the machine and rider.

When crane payloads are lifted off the ground, the payload may unexpectedly swing sideways. This occurs when the hoist cables are at an angle relative to vertical and the payload is not directly beneath the hoist. Because the hoist point is far above the payload, it is difficult for crane operators to know if the hoist cable is perfectly vertical before they start to lift the payload. Some amount of horizontal motion of the payload will always occur at lift off. If an off-centered lift results in significant horizontal motion, then it creates a hazard for the human operators, the payload, and the surrounding environment. This paper develops dynamic models of off-centered lifts and presents experimental verification of the theoretical predictions. To mitigate the detrimental effects of off-centered lifts, autonomous-centering solutions are proposed.

One of the manufacturing steps involved in fabricating semiconductor devices is encapsulation, whose function is to protect the semiconductor device by sealing the package from environmental hazards such as heat, humidity and vibration. Transfer moulding , as an encapsulation technique, offers various advantages over other techniques such as injection moulding. In most cases it is difficult to foresee the effect of a design decision on a complex semiconductor process such as transfer moulding, since process robustness is rarely a function of a single property and is affected by several different parameters. A literature review reveals that whilst support has been developed to help relevant stakeholders to detect and rectify problems associated with fabrication of semiconductors, such as die design, photolithography and ion implantation, support aimed at guiding process engineers and other relevant stakeholders to rapidly deal with transfer moulding defects, are lacking. Within this context, the research reported in this paper is aimed at developing a methodology relevant to transfer moulding which guides stakeholders in identifying and rectifying mouldability problems concerning new semiconductor devices. The proposed methodology is aimed at capitalizing efforts on the production preparation phase of the Integrated Product Development model before problematic semiconductor products reach the execution phase. The methodology is the key contribution of this paper. The evaluation results collectively provide a degree of evidence that the developed methodology helps relevant stakeholders in this direction.

This paper discusses the use of the proposed Material Information Model (MIM) [1] in assessing the sustainability of the Injection Molding (IM) process, and clarifies how to use the material information (based on the characteristics of different types of polymers) to quantify the material impacts. The assessment criteria include energy/water consumption and waste (pollution) production during the process and the effects of other materials during production (like the use of additives) that may add to environmental burdens. This paper addresses issues mainly at the IM process level taking the followings into account — pollution and manufacturing cost, energy and water consumption, waste management, operation safety, hazards to the plastic manufacturing personnel and other environmental impacts — to develop requisite process metrics for measuring the sustainability performances of the IM process. The ideas discussed in the paper lead to the development of computational approaches for selecting the “best” process-material combination.