Bibliographies: 'Variable transport delay' – Grafiati (2025)

Abstract:

Research aim is to analyze a class of automatic control systems at mining and concentrating facilities, where controlling action is the consumption of fuel or substance by a transporting body in order to develop recommendations on stability and control quality improvement. Research methodology consists in working out a model of automatic control system and studying the infl uence of varying transportation delay on the model, which arises in the process of stabilizing the output value of the system of automatic control. The RMS error of output value control was measured on the system’s model when measuring the delay of the main controlling action. Discussion was carried out by the example of the control process where the output value of the control object is regulated by the conveyor which feeds the ore. It has been shown that when changing the controlling action (ore consumption), time the delivery time also changes at the same time. These facilities refer to the facilities with the varying parameter – delay in control; they are poorly explored. It has been shown that control systems like that cannot adequately operate in the general case. One of the main methods of improving the quality of such control systems is to use the Smith predictor. However, in this case the system of automatic control will operate adequately under constant parameters of the control object, which is highly unlikely in the conditions of mining treatment. Delay in such systems is defi nitely associated with the speed of material feed. It has been proposed to automatically change regulator’s settings depending on the speed of the conveyor. Material can be fed using an assembly with constant speed, as an alternative, while the consumption may be carried out in accordance with the variation of the control object output value by a separate feeder

Abstract:

Introduction: Delays in definitive management of critically ill patients are known to drive poor clinical outcomes. A scarcely studied time period in interfacility transfer is the time between initial patient presentation and the decision to transfer. This study seeks to identify patient, environmental and institutional characteristics associated with delays in decision to transfer critically ill patients by air ambulance to a tertiary care centre. Methods: Patients >18 years old who underwent emergent air ambulance interfacility transport to a tertiary care centre were included. Patient records were located in a provincial air ambulance database. The primary exposure variable was time from patient presentation to initial call to facilitate transfer. Patient, environmental and institutional characteristics were identified using stepwise variable selection at a significance of 0.1. These characteristics were then explored using quantile regression to identify significant factors associated with delay in transport initiation. Results: A total of 11231 patients were included in the analysis. There were 5009 females (44.60%) and 6222 males (55.4%). The median age of patients was 57. The median time to initiate the transfer was 3.05 hours. The variables identified with stepwise selection were gender, category of illness, heart rate, systolic blood pressure, Glasgow coma scale, vasopressor usage, blood product usage, time of day, and type of sending site. The following factors were significantly (p < 0.05) associated with an increase in time to initiate transfer compared to the reference category at the 90th centile of time: cardiac illness (+1.45h), gastrointestinal illness (+3.27h), respiratory illness (+4.90h), sepsis (+3.03h), vasopressors (+2.31h), and an evening hour of transport (+3.67h). The following factors were significantly (p < 0.05) associated with a decrease in time to initiate transfer compared to the reference category at the 90th centile of time: neurologic illness (-1.45h), obstetrical illness (-1.56h), trauma (-3.14h), GCS <8 (-0.98h), blood transfusion (-1.47h), and sending site being a community hospital >100 beds (-2.26h), <100 beds (-4.71h), or nursing station (-10.02h). Conclusion: Time to initiate transfer represents a significant window in a patient's transport journey. In looking at the predictors of early or late initiation of transfers, these findings provide education and quality improvement opportunities in decreasing time to definitive care in critically ill populations.

Abstract:

For this stable process with oscillatory dynamics, characterized with small damping ratio and dominant transport delay, design of the series PID pitch controller is based on the model obtained from the open-loop process step response, filtered with the second-order Butterworth filter Fbw. Performance of the series PID pitch controller, with the filter Fbw, is analyzed by simulations of the set-point and input/output disturbance responses, including simulations with a colored noise added to the control variable. Excellent performance/robustness tradeoff is obtained, compared to the recently proposed PI pitch controllers and to the modified internal model pitch controller, developed here, which has a natural mechanism to compensate effect of dominant transport delay.

Abstract:

The traditional congestion control mechanism of transport control protocol (TCP) has been proved cannot satisfy the wireless scenario. The extensive research has been done to understand the drawback of TCP in wireless networks. In this paper, we proposed a new congestion control algorithms for mobile ad-hoc networks (MANET) at the TCP sender side which efficiently adapts to the maximum transmission rate of a mobile wireless link, the new algorithms follow the idea of FAST TCP which uses delay as congestion measure. However, FAST TCP has limitations when used over a dynamic mobile wireless link with a high frame error ratio (FER) and frequent delay changes due to the variable rate. The new algorithms overcome this shortcoming by improving the congestion signal choice. By using analysis, we proved that the new congestion control mechanism provides superior performance over mobile wireless network environments.

Abstract:

With the expansion of cities, district heating (DH) networks are playing an increasingly important role. The energy consumption due to the time delay caused by the transport of the medium in the DH network is enormous, especially in large networks. The study of time delay is necessary for the operation and optimization of DH networks. Compared with previous studies of constant flow rates and ideal pipeline (without regard to branches, elbows, variable pipe diameters, etc), this paper simulates a DH network in Tianjin University, China, by establishing the actual engineering model in a Computational Fluid Dynamics (CFD) method to analyze the time delay. The CFD model has great advantages in terms of computational cost and application range compared to theoretical calculations. The peak-valley method was used to verify the correctness of the time delay simulation model. Results show that the time delay calculated by the CFD model is consistent with the actual time delay obtained from the measured data. Based on this model, the parameters that affect the time delay are furtherly analyzed. Four key parameters, including flow rate, pipe length, pipe diameter, and water supply temperature are summarized. The results show that the flow rate, pipe length and pipe diameter have a great influence on the time delay of the DH network, while the temperature has little effect on the time delay. The time delay of the DH network system has a significant impact and can provide services for optimal control of the system.

Abstract:

NS-2 is a tool to simulate networks and events that occur per packet sequentially based on time and are widely used in the research field. NS-2 comes with NAM (Network Animator) that produces a visual representation it also supports several simulation protocols. The network can be tested end-to-end. This test includes data transmission, delay, jitter, packet-loss ratio and throughput. The Performance Analysis simulates a virtual network and tests for transport layer protocols at the same time with variable data and analyzes simulation results based on the network simulator NS-2.

Abstract:

Under many circumstances, when providing full bus priority methods, urban transport officials have to operate buses in mixed traffic based on their road network limitations. In the case of Istanbul's Metrobus lane, for instance, when the route comes to the pre-designed Bosphorus Bridge, it has no choice but to merge with highway mixed traffic until it gets to the other side. Much has been written on the relative success of implementing Ramp Metering (RM), for example ALINEA (‘Asservissement line´ aire d’entre´ e autoroutie’) and Variable Speed Limits (VSL), two of the most widely-used “merging congestion” management strategies, in both a separate and combined manner. However, there has been no detailed study regarding the combination of these systems in the face of high bus volume. This being the case, the ultimate goal of this study is to bridge this gap by developing and proposing a combination of VSL and RM strategies in the presence of high bus volume (VSL+ALINEA/B). The proposed model has been coded using microscopic simulation software—VISSIM—and its vehicle actuated programming (VAP) feature; referred to as VisVAP. For current traffic conditions, the proposed model is able to improve total travel time by 9.0%, lower the number of average delays of mixed traffic and buses by 29.1% and 81.5% respectively, increase average speed by 12.7%, boost bottleneck throughout by 2.8%, and lower fuel consumption, Carbon Monoxide (CO), Nitrogen Oxides (NOx), and Volatile Organic Compounds (VOC) emissions by 17.3% compared to the existing “VSL+ALINEA” model. The results of the scenario analysis confirmed that the proposed model is not only able to decrease delay times on the Metrobus system but is also able to improve the adverse effects of high bus volume when subject to adjacent mixed traffic flow along highway sections.

Abstract:

AbstractAcute pulmonary embolism (PE) is frequently a fatal disease. The clinical presentation of PE is variable and frequently nonspecific, and there is commonly a diagnostic delay. We aimed to investigate factors associated with the delay in the diagnosis of PE.Data from patients with PE were collected from January 2011 to December 2013 in an acute care teaching hospital. Time-to-diagnosis, evaluated by obtaining a diagnostic computed tomography scan, was then analyzed by the Cox proportional hazard model for examining factors associated with time to the diagnosis of PE. Independent variables included age, gender, activities of daily living, means of transport to the hospital, body temperature, hypoxemia, typical symptoms for PE, serum C-reactive protein (CRP) concentrations, infiltration on chest radiograph, Wells score, classification of patients with PE based on early mortality risk, patients referred from other specialties, daytime versus nighttime arrival, diagnosed by an emergency physician, and diagnosed by a medical resident.Sixty patients were included. The time to diagnosis was significantly delayed in low-risk patients (hazard ratio [HR], 2.2; 95% CI, 1.2–4.1) and in patients who did not use an ambulance (HR, 1.9; 95% CI, 1.0–3.7). In an analysis of the latter subgroup, higher serum CRP concentrations were associated with a delayed diagnosis (HR, 1.1; 95% CI, 1.0–1.2).The time to the diagnosis of PE was delayed in low-risk patients and in patients who attended the hospital by means other than an ambulance. In such patients, a delayed diagnosis was associated with higher serum CRP concentrations.

Abstract:

Left-turn bays are often installed on the road segment between paired intersections. Such left-turn bays may reduce the approach capacities and impact on one another. Four optimization models are put forward for uncoordinated paired intersections with left-turn bays. The phase effective green times and the left-turn bay lengths are the decision variables, maximizing the intersection capacities, minimizing the intersection delays and both of them are respectively regarded as different objective functions, and minimizing the total delay for paired intersections is viewed as another objective function. The total capacity-to-delay ratio is defined to evaluate the operations of paired intersections as a whole. Using the field data, the sensitivities of the optimized outcomes to the weighting factors of the objective functions are analysed. To clarify the influences of different scenarios on traffic stream operations, seven scenarios are tested using VISSIM. The interval estimation and hypothesis testing are used to analyse the simulated data. Three concrete models are recommended to apply in practice with the procedure of model application being provided. The achievements can be applied to optimally assign the temporal-spacial resources for paired intersections when left-turn bays need to be installed and coordinated signals do not need to be considered.

Abstract:

SummaryDespite the guidance published in revised Codes of Practice and by the Royal College of Psychiatrists, implementation of Section 136 of the Mental Health Act 1983 is still variable. Government funding in England to establish places of safety in psychiatric facilities has been effective but custody suites are still used excessively, especially for those who are brought in intoxicated. Patients feel criminalised by this use of custody suites and by the use of police vehicles rather than ambulance transport for conveyance to the place of safety. There is often a delay in commencing the assessment and the first doctor does not always have Section 12 approval as recommended in the Codes of Practice. The importance of the local Section 136 group tasked with developing and overseeing the implementation of local policy and monitoring is highlighted. There is a need for monitoring locally, but ideally in a form that can be used nationally for benchmarking and research.

Abstract:

Ma thèse en automatique s’inscrit dans la thématique de recherche «Transport» du LAMIH. L’objectif est d’améliorer le fonctionnement des moteurs thermiques (essence), notamment en réduisant la consommation et la pollution. Face à cet enjeu écologique et économique, et compte tenu des nouvelles normes et des stratégies court-termistes de l’industrie (scandale Volkswagen...), de nouveaux contrôleurs doivent être conçus pour piloter l’arrivée d’air et d’essence au sein du moteur. En considérant l’aspect hautement non-linéaire du système, la représentation Takagi-Sugeno et le background théorique du LAMIH sont utilisés. Un premier contrôleur est synthétisé pour régler le problème de la vitesse de ralenti du moteur. Cependant, la complexité du système impose l’utilisation d’un contrôleur très coûteux d’un point de vue computationnel. Un contrôleur alternatif est donc synthétisé afin d’être implémenté dans l’ordinateur embarqué du moteur. Un second contrôleur est obtenu pour maintenir la richesse en proportions stoechiométriques afin de réduire la pollution. Ce système étant sujet à un retard de transport variable, un changement de domaine est réalisé afin de rendre ce retard constant, et de concevoir un contrôleur simple et efficace. Des essais réels sur le banc d’essai moteur du LAMIH sont réalisés afin de valider la méthodologie présentée<br>My PhD in Automatic Control is part of the research theme “Transport” of the LAMIH. The objective is to improve the functioning of the gasoline engines, mainly by reducing the fuel consumption and the pollution. With this ecologic and economic challenge, and taking into account the new norms and the short-term strategies of the industry (scandal of Volkswagen...), new controllers have to be designed to control the air valve and the fuel injection inside the engine. Considering the highly nonlinear aspect of the system, the Takagi-Sugeno representation and the theoretical background of the LAMIH have been used. A first controller is designed to solve the problem of idle engine speed. However, the complexity of the system forces the use of a controller that is very costly from a computational point of view. An alternative controller is then designed in order to be implemented inside the embedded computer of the engine. A second controller is obtained to maintain the air-fuel ratio in stoichiometric proportions in order to reduce the pollution. This system being subject to a variable transport delay, a change of domain is realized to make this delay constant, and to design a simple and efficient controller. Real-time experiments have been realized on the engine test bench of the LAMIH in order to validate the presented methodology

Abstract:

<p>This master’s thesis describes the development of a model of the catalystsystem aiming at control by an MPC. A well functioning model, which is suitable in control purpose, is important while emission legislation become more and more hard to fulfill for the car manufacturers. Much research has been done in the field of physical modeling of the system, but in this work a linear adaptive time discrete ARX-model is developed and validated.</p><p>The systems tendency to change its dynamic during usage implies that the model must be adaptive. The developed model proved to be well functioning and shows promising conditions for the MPC design. The system and the model are analyzed in the time- and frequency domains and the model is both implemented and validated in a Saab 9-5.</p><p>The work has been performed both at Saab Automobile Powertrain AB in Södertälje and in Vehicular Systems Dept. of Electrical Engineering at Linköpings University.</p>

Abstract:

In this dissertation, an assessment is conducted of the potential benefits of combined heat and power (CHP) based district energy (DE) grids in energy systems of different scale having significant fossil fuel fired electrical generation capacity. Three studies are included in the research.In the first study, the potential benefits of expanding CHP-based DE grids in a large scale energy system are investigated. The impacts of expanding wind power systems are also investigated and a comparison between these technologies is made with respect to fossil fuel utilization and CO2 emissions. A model is constructed and five scenarios are evaluated with the EnergyPLAN software taking the province of Ontario, Canada as the case study. Results show that reductions in fuel utilization and CO2 emissions of up to 8.5% and 32%, respectively, are possible when switching to an energy system comprising widespread CHP-based DE grids. In the second study, a high temporal resolution numerical model (i.e. the SS-VTD model) is developed that is capable of rapidly calculating distribution losses in small scale variable flow DE grids with low error and computational intensity. The SS-VTD model is validated by comparing simulated temperature data with measured temperature data from an existing network. The Saanich DE grid, located near Victoria, Canada, is used as the case study for validation.In the third study, the potential benefits of integrating high penetrations of renewable energy via a power-to-heat plant in a small scale CHP-based DE grid are investigated. The impacts of switching to a CHP-based DE grid equipped with an electric boiler plant versus a conventional wave power system are compared with respect to fossil fuel utilization and CO2 emissions. The SS-VTD model is used to conduct the study. The energy system of the Hot Springs Cove community, located on the west coast of Vancouver Island, Canada is used as the case study in the analysis. Results show that relative to the conventional wave power system, reductions in fuel utilization and CO2 emissions of up to 47% are possible when switching to a CHP-based DE grid.<br>Graduate

Abstract:

This chapter deals with industrial networked control systems. These systems are the most modern means of industrial control. The current approach contains several problems. Mostly discussed problem in the control theory is a network-caused variable transport delay problem. On the software point of view there is problem of the system latency, which limits time period of the discrete control. State of art research in hardware part of the system shows that latency source and transport delay variations are caused by unpredictable hardware behavior as well. Another problem is the control system security. This was the case of the Mexico gulf oil rig disaster in 2010, as well as Iran nuclear program three months later the same year, caused by worm attack at its centrifuges. Therein lies the question; how can security issues be avoided? The authors demonstrate how via using GNU/Linux, which solves timing correctness by their project of the plasma cutting machine design.

Abstract:

The VANET (Vehicular Ad hoc Network) is a collection of mobile nodes forming a temporary network on variable topology, operating without base station and without centralized administration. Communication is possible between vehicles within each other's radio range as well as with fixed components on road side infrastructure. The characteristics of VANET network that distinguishes it from other ad hoc networks, such as high mobility and communication with the infrastructure to support security or comfort applications, have prompted researchers to develop models and mobility specific protocols. The main goal of this chapter is firstly to compare the performance of three Ad hoc routing protocols: OLSR, AODV and DSDV, and secondly to examine the impact of varying mobility, density and pause time on the functionality of these protocols. The results of this chapter demonstrate that AODV have better performance in terms of Throughput and Packets Delivery Rate (PDR), whereas OLSR have best performance in terms of Packet Delivery Time (Delay).

Abstract:

This chapter investigates adaptive control for uncertain multi-input LTI systems with distinct discrete actuator delays. In parallel with the single-input case in the third chapter, four types of basic uncertainties come with multi-input LTI time-delay systems. Different combinations of the four uncertainties above result in different design difficulties. For example, when the full-state measurement of the transport PDE state is available, the global stabilization is acquired, whereas when the actuator state is not measurable and the delay value is unknown at the same time, the problem is not solvable globally, since the problem is not linearly parameterized. The chapter then summarizes the different collections of uncertainties for the multi-input case. When some of the four variables are unknown or unmeasured, the basic idea of certainty-equivalence-based adaptive control is to use an estimator (a parameter estimator or a state estimator) to replace the unknown variables in the PDE-based framework in the previous chapter, and carefully select their adaptive update laws based on Lyapunov-based analysis.

Abstract:

The fate and transport of a variety of chemicals migrating from industrial and municipal waste disposal sites, or applied to agricultural lands, is increasingly becoming a concern. Once released into the subsurface, these chemicals arc subject to a large number of simultaneous physical, chemical, and biological processes, including sorption-desorption, volatilization, and degradation. Depending upon the type of organic chemical involved, transport may also be subject to multiphase flow that involves partitioning of the chemical between different fluid phases. Many models of varying degree of complexity and dimensionality have been developed during the past several decades to quantify the basic physicochemical processes affecting transport in the unsaturated zone. Models for variably saturated water flow, solute transport, aqueous chemistry, and cation exchange were initially developed mostly independently of each other, and only recently has there been a significant effort to couple the different processes involved. Also, most solute transport models in the past considered only one solute. For example, the processes of adsorption- desorption and cation exchange were often accounted for by using relatively simple linear or nonlinear Freundlich isotherms such that all reactions between the solid and liquid phases were forced to be lumped into a single distribution coefficient, and possibly a nonlinear exponent. Other processes such as precipitation-dissolution, biodegradation, volatilization, or radioactive decay were generally simulated by means of simple first- and/or zero-order rate processes. These simplifying approaches were needed to keep the mathematics relatively simple in view of the limitations of previously available computers. The problem of coupling models for water flow and solute transport with multicomponent chemical equilibrium and nonequilibrium models is now increasingly being addressed, facilitated by the introduction of more powerful computers, development of more advanced numerical techniques, and improved understanding of the underlying transport processes. One major frustrating issue facing soil scientists and hydrologists in dealing with the unsaturated zone, both in terms of modeling and experimentation, is the overwhelming heterogeneity of the subsurface environment.

Abstract:

We extend the recently developed delay-compensated “Bang-Bang” control design methodology for control of the nozzle output flow rate of isothermal screw-extruder-based 3D printing processes to the non-isothermal case, in which, the viscosity of the material that convects in the extruder chamber varies with time, resulting in periodic fluctuations of the material’s transport speed. We model the dynamics of the material convection in the extruder chamber with a nonlinear system with an input delay that simultaneously depends on the state and the time variable to account for the time variations of the transport speed. By combining a nominal, piecewise exponential feedback controller, which achieves global exponential stability in the nominal delay-free case, with nonlinear predictor feedback, the compensation of the time- and state-dependent input delay of the extruder model is achieved. Global asymptotic stability of the closed-loop system under the Bang-Bang predictor feedback is established when certain conditions, which are easy to verify, related to the extruder design and the material properties, as well as to the magnitude and frequency of the material’s transport speed variations, are satisfied. Simulations results are presented to illustrate the effectiveness of the proposed control design.

Abstract:

Soils at waste sites must be evaluated for the potential of residual soil contamination to leach and migrate to the groundwater beneath the disposal area. If migration to the aquifer occurs, contaminants can travel vast distances and pollute drinking water wells, thus exposing human receptors to harmful levels of toxins and carcinogens. To prevent groundwater contamination, a contaminant fate and transport analysis is necessary to assess the migration potential of residual soil contaminants. This type of migration analysis is usually performed using a vadose zone model to account for complex geotechnical and chemical variables including: decay processes, infiltration rate, soil properties, vadose zone thickness, and chemical behavior. The distinct advantage of using a complex model is that less restrictive, but still protective, soil threshold levels may be determined avoiding the unnecessary and costly remediation of marginally contaminated soils. However, the disadvantage of such modeling is the additional cost for data collection and labor required to apply these models. In order to allay these higher costs and to achieve a less restrictive but still protective clean-up level, a multiple contaminant and multi layered soil column equilibrium partitioning model was developed which is faster, simpler and less expensive to use.

Abstract:

This paper continues our effort to study the dynamics of deterministic stresses in a multistage turbomachine using experimental data. Here we focus on the tip and hub regions and compare them to mid span data obtained in previous studies. The analysis is based on data obtained in PIV measurements performed in the second stage of a two-stage turbomachine. A complete data set is obtained using blades and fluid with matched optical index of refraction. Previous measurements at mid span have shown that at mid span and close to design conditions, the deterministic kinetic energy is smaller than the turbulent kinetic energy. The primary contributor to the deterministic stresses at mid span is the interaction of a blade with the upstream wakes. Conversely, we find that the tip vortex is the dominant source of phase-dependent unsteadiness and deterministic stresses in the tip region. Along the trajectory of the tip vortex, the deterministic kinetic energy levels are more than one order of magnitude higher than the levels measured in the hub and mid-span, and are of the same order of magnitude as the turbulent kinetic energy levels. Reasons for this trend are explained using a sample distribution of phase-averaged flow variables. Outside of the region affected by tip vortex transport, within the rotor-stator gap and within the stator passages, the turbulent kinetic energy is still 3–4 times higher than the deterministic kinetic energy. The deterministic and turbulent shear stress levels are comparable in all spanwise locations, except for the wakes of the stator blades, where the turbulent stresses are higher. However, along the direction of tip vortex transport, the deterministic shear stresses are about an order of magnitude higher than the turbulent shear stresses. The decay rates of deterministic kinetic energy in the hub and mid-span regions are comparable to each other, whereas at the tip, the decay rate is higher. The decay rates of turbulent kinetic energy are much smaller than those of the deterministic kinetic energy. The paper also examines terms in the deterministic kinetic energy transport equation. The data indicate that “Deterministic Production” and a new term, called here “Dissipation due to Turbulence” are the dominant source/sink terms. Regions with alternating signs of Deterministic Production indicate that the energy transfer between the phase-averaged and average-passage flow fields can occur in both directions. The divergence of the Pressure-Velocity correlation, obtained from a balance of all the other terms, is dominant and appears to be much larger than the deterministic production (source/sink) term. This trend indicates that there are substantial deterministic pressure fluctuations in the flow field, especially within the rotor-stator gap and within the stator passage.

Abstract:

A lethality zone due to an ignited natural gas release is often used to characterize the consequences of a pipeline rupture. A 1% lethality zone defines a zone where the lethality to a human is greater than or equal to 1%. The boundary of the zone is defined by the distance (from the point of rupture) at which the probability of lethality is 1%. Currently in the gas pipeline industry, the most detailed and validated method for calculating this zone is embodied in the PIPESAFE software. PIPESAFE is a software tool developed by a joint industry group for undertaking quantitative risk assessments of natural gas pipelines. PIPESAFE consequence models have been verified in laboratory experiments, full scale tests, and actual failures, and have been extensively used over the past 10–15 years for quantitative risk calculations. The primary advantage of using PIPESAFE is it allows for accurate estimation of the likelihood of lethality inside the impacted zone (i.e. receptors such as structures closer to the failure are subject to appropriately higher lethality percentages). Potential Impact Radius (PIR) is defined as the zone in which the extent of property damage and serious or fatal injury would be expected to be significant. It corresponds to the 1% lethality zone for a natural gas pipeline of a certain diameter and pressure when thermal radiation and exposure are taken into account. PIR is one of the two methods used to identify HCAs in US (49 CFR 192.903). Since PIR is a widely used parameter and given that it can be interpreted to delineate a 1% lethality zone, it is important to understand how PIR compares to the more accurate estimation of the lethality zones for different diameters and operating pressures. In previous internal studies, it was found that PIR, when compared to the more detailed measures of the 1% lethality zone, could be highly conservative. This conservatism could be beneficial from a safety perspective, however it is adding additional costs and reducing the efficiency of the integrity management process. Therefore, the goal of this study is to determine when PIR is overly conservative and to determine a way to address this conservatism. In order to assess its accuracy, PIR was compared to a more accurate measure of the 1% lethality zone, calculated by PIPESAFE, for a range of different operating pressures and line diameters. Upon comparison of the distances calculated through the application of PIR and PIPESAFE, it was observed that for large diameters pipelines the distances calculated by PIR are slightly conservative, and that this conservativeness increases exponentially for smaller diameter lines. The explanation for the conservatism of the PIR for small diameter pipelines is the higher wall friction forces per volume transported in smaller diameter lines. When these higher friction forces are not accounted for it leads to overestimation of the effective outflow rate (a product of the initial flow rate and the decay factor) which subsequently leads to the overestimation of the impact radius. Since the effective outflow rate is a function of both line pressure and diameter, a simple relationship is proposed to make the decay factor a function of these two variables to correct the excess conservatism for small diameter pipelines.