Improving the performance of swift-water rescue quick release harnesses

This paper considered the effectiveness of empathic design modifications to quick release harness design. It was found that the critical element in effecting a rapid and efficient release was the tape length distal to the buckle/back-bar components. We have concluded that the length of tape pulled through the buckle and the loading of the buckle/ tri-glide are critical to ensure an effective release. Physical separation of tape and buckle mechanism when the harness is released is crucial to the effective release. We then considered the problems this may pose in multiple user situations such as ‘call out’ teams or training use and we propose that the adaptation utilised in the research harness to facilitate testing may provide a simple and low cost solution to the multiple user problem allowing easy adjustment of the harness to ensure the separation of buckle and tape on release. We conclude by outlining the design adaptations and recommendations for the training and use of the quick release harness and make recommendations for the training of QRH use

Design of a baggage handling system

In a previous paper we have shown how the design of an object processing system can be reduced to a graph embedding problem. Now we apply the transformations found there to a particular system, namely a Baggage Handling System (BHS) of airports, focusing especially on the sorting processors area, as one of the main challenging points. By means of an historical case study, we demonstrate how the method can be successfully applied

Confidence: Its role in dependability cases for risk assessment

Society is increasingly requiring quantitative assessment of risk and associated dependability cases. Informally, a dependability case comprises some reasoning, based on assumptions and evidence, that supports a dependability claim at a particular level of confidence. In this paper we argue that a quantitative assessment of claim confidence is necessary for proper assessment of risk. We discuss the way in which confidence depends upon uncertainty about the underpinnings of the dependability case (truth of assumptions, correctness of reasoning, strength of evidence), and propose that probability is the appropriate measure of uncertainty. We discuss some of the obstacles to quantitative assessment of confidence (issues of composability of subsystem claims; of the multi-dimensional, multi-attribute nature of dependability claims; of the difficult role played by dependence between different kinds of evidence, assumptions, etc). We show that, even in simple cases, the confidence in a claim arising from a dependability case can be surprisingly low

Honeywell Enhancing Airplane State Awareness (EASA) Project: Final Report on Refinement and Evaluation of Candidate Solutions for Airplane System State Awareness

The loss of pilot airplane state awareness (ASA) has been implicated as a factor in several aviation accidents identified by the Commercial Aviation Safety Team (CAST). These accidents were investigated to identify precursors to the loss of ASA and develop technologies to address the loss of ASA. Based on a gap analysis, two technologies were prototyped and assessed with a formative pilot-in-the-loop evaluation in NASA Langleys full-motion Research Flight Deck. The technologies address: 1) data source anomaly detection in real-time, and 2) intelligent monitoring aids to provide nominal and predictive awareness of situations to be monitored and a mission timeline to visualize events of interest. The evaluation results indicated favorable impressions of both technologies for mitigating the loss of ASA in terms of operational utility, workload, acceptability, complexity, and usability. The team concludes that there is a feasible retrofit solution for improving ASA that would minimize certification risk, integration costs, and training impact

Noise shaping Asynchronous SAR ADC based time to digital converter

Time-to-digital converters (TDCs) are key elements for the digitization of timing information in modern mixed-signal circuits such as digital PLLs, DLLs, ADCs, and on-chip jitter-monitoring circuits. Especially, high-resolution TDCs are increasingly employed in on-chip timing tests, such as jitter and clock skew measurements, as advanced fabrication technologies allow fine on-chip time resolutions. Its main purpose is to quantize the time interval of a pulse signal or the time interval between the rising edges of two clock signals. Similarly to ADCs, the performance of TDCs are also primarily characterized by Resolution, Sampling Rate, FOM, SNDR, Dynamic Range and DNL/INL. This work proposes and demonstrates 2nd order noise shaping Asynchronous SAR ADC based TDC architecture with highest resolution of 0.25 ps among current state of art designs with respect to post-layout simulation results. This circuit is a combination of low power/High Resolution 2nd Order Noise Shaped Asynchronous SAR ADC backend with simple Time to Amplitude converter (TAC) front-end and is implemented in 40nm CMOS technology. Additionally, special emphasis is given on the discussion on various current state of art TDC architectures.Electrical and Computer Engineerin

Low-Jitter Clock Multiplication: a Comparioson between PLLs and DLLs

This paper shows that, for a given power budget, a practical phase-locked loop (PLL)-based clock multiplier generates less jitter than a delay-locked loop (DLL) equivalent. This is due to the fact that the delay cells in a PLL ring-oscillator can consume more power per cell than their counterparts in the DLL. We can show that this effect is stronger than the notorious jitter accumulation effect that occurs in the voltage-controlled oscillator (VCO) of a PLL. First, an analysis of the stochastic-output jitter of the architectures, due to the most important noise sources, is presented. Then, another important source of jitter in a DLL-based clock multiplier is treated, namely the stochastic mismatch in the delay cells which compose the DLL voltage-controlled delay line (VCDL). An analysis is presented that relates the stochastic spread of the delay of the cells to the output jitter of the clock multiplier. A circuit design technique, called impedance level scaling, is then presented which allows the designer to optimize the noise and mismatch behavior of a circuit, independently from other specifications such as speed and linearity. Applying this technique on a delay cell design yields a direct tradeoff between noise induced jitter and power usage, and between stochastic mismatch induced jitter and power usage

True high-order VCO-based ADC

A novel approach to use a voltage-controlled oscillator (VCO) as the first integrator of a high-order continuous-time delta-sigma modulator (CT-DSM) is presented. In the proposed architecture, the VCO is combined with a digital up-down counter to implement the first integrator of the CT-DSM. Thus, the first integrator is digital-friendly and hence can maximally benefit from technological scaling

Reliability Analysis of a Fire Alarm System

AbstractSafety instrumented systems (SIS) are used in different industrial areas and household applications in order to protect humans, the environment and assets. This article presents a fire warning system, which is a typical SIS application, in a student apartment. And the paper focus on the reliability assessment of the alarm system. Such reliability assessment is important to ensure the safety critial systems. Standard reiability parameters and two reliabiility measures PFD and spurious trip rate analyses of the system are carried out for each safety instrumented function. Based on the calculated result, system configuration of such system can be selected. And decision of implementing such a system or not can be made. From the reliability analysis of a fire alarm system, both the risk reduction effect and side effect of using such a system can be better understood. It is acceptable for use in an apartment. Thereafter several risk reducing measures are introduced. No big change is needed

Optimization of safe introduction of the mixture air + fuel into an industrial boiler, complying with the SIL2 safety level

Industrial boilers are mainly used in the industries of energy and oil&gas, concretely in refineries and thermal or solar power stations, in order to boil water and use the resultant steam to make the turbines rotate so that electricity is produced. This process of boiling water involves a combustion that has to be both safe and efficient. This means that a control of the mixture air-fuel has to be carried out: the less amount of gas per unit of amount of air, the less efficient the combustion is; but an excess of fuel in the mixture can produce an uncontrolled burst that could cause an accident. Traditionally, when developing the control system of a boiler, the actions of modulating itself would be developed with analog equipments (continuous). The start and stop sentences, as well as interlocks, are digital (all/nothing) that might imply digital equipments. Nowadays, due to advances in microprocessor-based systems, it is possible to achieve safety function with analog equipments that permit to evaluate different setting points in a unique device as well as provide a continuous measure of the variables in the whole operating range.Ingeniería Electrónica Industrial y Automátic