Journal articles on the topic 'Non-uniform transient environments'

Thermal comfort evaluation for vehicle occupants is very complicated due to the transient nature and non-uniformity of the vehicle interior. The thermal sensation of an automotive occupant is affected by the surrounding environment. More than this, the actual standard is proposing three evaluation indexes and was developed for steady state and controlled conditions and some of the indexes are not adapted for this complex environment. In this article the three standardized indexes values are compared in term of thermal comfort, in a vehicle passenger in summer season. The results are showing that the mean values of PMV/PPD model calculated in a single point with Comfort Sense equipment are far from the TSV mean values which was collected in questionnaires, while the teq index which was calculated with an advanced thermal manikin are closer to the TSV comfort votes. This may be explained by the fact that the TSV and teq consider the sensation for each body part at the local level. For a correct evaluation of the thermal comfort in non-uniform and transient environments like in the vehicles, is not enough to measure in a single point and the results to be considered in all the ambiance. The main conclusion is that the PMV/PPD indexes are not very well adapted to the vehicle environment.

This paper provides an analysis of the non-Darcian effect on transient natural convection of a vertical flat plate embedded in a high-porosity medium. The plate surface is either maintained at an uniform wall temperature (UWT), or subjected to an uniform heat flux (UHF), and convective, boundary and inertia effects are considered. The local volume-averaged principles and certain empirical relations have been utilized to establish the governing equations. The coupled nonlinear partial differential equations are solved with a numerical integration technique using a cubic spline. Along with transient mean and local Nusselt numbers at the plate, representative transient velocity and temperature profiles are presented. Both effects for non-Darcian flow model are shown to be more pronounced in high-porosity medium and, hence, reduce the heat transfer rate.

The severe aerodynamic heating on the surface of modern hypersonic flight vehicle, that can bring high temperature and large temperature gradients in the structure of the vehicle, will be a challenge for the vehicles design and multidisciplinary optimization. The transient thermal environment consists of high temperature and large temperature gradients will generate two important problems related to vehicle structure, namely: 1) the material property, such as elastic modulus, will be degraded at elevated temperature, and 2) the non-uniform thermal stress cased by large temperature gradients will change the stiffness distribution of wing structure, which can make the modal frequencies and shapes of structure changed remarkably. Firstly, the theory and methodology of structure modal analysis in transient thermal environment is outlined. Subsequently, the transient temperature field of structure considering aerodynamic heating is obtained by employing computational technology of aerodynamic heating/structure heat transfer coupling program. Finally, the modal frequencies and shapes of vehicle structure under transient temperature field is calculated based on finite element method (FEM). Based on the analysis and investigation of the simulation results, the influence of the transient thermal environment on structure modal frequency and shape is determined. Furthermore, the investigation of wing structure modal analysis considering aerodynamic heating is an important basis of aerothermoelastic simulation.

The effect of a non-uniform solar temperature field on the cable-net structure of the reflector of a five-hundred-meter aperture spherical radio telescope-FAST was analyzed using the thermal analysis module of ANSYS. The integral parametric finite element model of the reflector structure with its measured landform was built, and the boundary conditions of periodic air temperature, solar radiation, long-wave radiation and shadows of surrounding environment, etc, were computed at intervals of half an hour under a cloudless sky on a summer day, as one of the worst-case climate conditions. The transient structural temperatures were then analyzed under sunshine which lasted for several days with a rational initial structural temperature distribution until the whole set of structural temperatures converged to the results obtained the day before. The corresponding structural analysis was then carried out. The results indicate that the highest local temperature difference goes up to 11° and the maximum r.m.s. error of fitting of the reflector geometry is about 2.2mm.

Thermal environment in residential kitchen in China is transient and non-uniform and with strong radiation asymmetry from gas stove. Due to the complexity of kitchen thermal environment, it is not sure if previous thermal comfort models can accurately predict the thermal comfort in residential kitchens. In order to evaluate if existing thermal comfort models can be applied for Chinese kitchens, this investigation conducted human subject tests for 20 cooks when preparing dishes in a kitchen. The study measured skin temperatures of the cooks and environmental parameters and used questionnaires to obtain their thermal sensation votes at the same time. The actual thermal sensation votes were compared with the predicted ones by four thermal comfort models: predicted mean vote (PMV) model, dynamic thermal sensation (DTS) model, the University of California at Berkeley (UCB) model, and the transient outdoor thermal comfort model from Lai et al. The results showed that all the models could predict the trend of the thermal sensations but with errors. The PMV model overpredicted the thermal sensations. The UCB and Lai’s models showed a slower change in thermal sensation votes (TSV) after turning on the stove. The DTS model was more accurate than the others in predicting the mean thermal sensation, but with a large variation in predicting individual thermal sensation votes. A better thermal comfort model should be developed for Chinese residential kitchens.

The aim of the paper is to present a three dimensional transient cooling analysis of an automobile cabin with a virtual manikin under solar radiation. In the numerical simulations the velocity and the temperature distributions in the automobile cabin as well as around the human body surfaces were computed during transient cooling period. The surface-to-surface radiation model was used for calculations of radiation heat transfer between the interior surfaces of the automobile cabin and a solar load model that can be used to calculate radiation effects from the sun's rays that enter from the glazing surfaces of the cabin was used for solar radiation effects. Inhomogeneous air flow and non-uniform temperature distributions were obtained in the automobile cabin and, especially in ten minutes of cooling period, high temperature gradients were computed and measured and high temperature values were obtained for the surfaces which were more affected from the sunlight. Validations of the numerical results were performed by comparing numerical data with the experimental data presented in this study. It is shown that the numerical results were good agreement with the experimental data.

Mesh adaptation has proven to be very efficient for simulating transient multiphase computational fluid dynamics applications. In this work, we present a new parallel anisotropic mesh adaptation technique relying on an edge based error estimator. It provides a high level of accuracy while substantially reducing the computational effort. This technique enables a good capture of physical phenomena, boundary layers, interfaces, free surfaces and even multiphase turbulent flows, and has a great potential to simulate a large variety of applications. Current investigations explore the performance of the new algorithm on massively parallel resources. In this paper, we show that the developed adaptive meshing works very well in a parallel environment involving topological mesh modifications and dynamic repartitioning of parallel slots. It is also shown that the proposed methodology provides an additional gain in terms of computational cost due the production of a non-uniform mesh size distribution. Runs performed on national and European supercomputers will show the scalability and pertinence of our developments.

AbstractWe examine theoretically the transient displacement flow and density stratification that develops within a ventilated box after two localized floor-level heat sources of unequal strengths are activated. The heat input is represented by two non-interacting turbulent axisymmetric plumes of constant buoyancy fluxes ${B}_{1} $ and ${B}_{2} \gt {B}_{1} $. The box connects to an unbounded quiescent external environment of uniform density via openings at the top and base. A theoretical model is developed to predict the time evolution of the dimensionless depths ${\lambda }_{j} $ and mean buoyancies ${\delta }_{j} $ of the ‘intermediate’ $(j= 1)$ and ‘top’ $(j= 2)$ layers leading to steady state. The flow behaviour is classified in terms of a stratification parameter , a dimensionless measure of the relative forcing strengths of the two buoyant layers that drive the flow. We find that $\mathrm{d} {\delta }_{1} / \mathrm{d} \tau \propto 1/ {\lambda }_{1} $ and $\mathrm{d} {\delta }_{2} / \mathrm{d} \tau \propto 1/ {\lambda }_{2} $, where $\tau $ is a dimensionless time. When $\hspace{0.167em} \hspace{0.167em} \ll \hspace{0.167em} \hspace{0.167em} $1, the intermediate layer is shallow (small ${\lambda }_{1} $), whereas the top layer is relatively deep (large ${\lambda }_{2} $) and, in this limit, ${\delta }_{1} $ and ${\delta }_{2} $ evolve on two characteristically different time scales. This produces a time lag and gives rise to a ‘thermal overshoot’, during which ${\delta }_{1} $ exceeds its steady value and attains a maximum during the transients; a flow feature we refer to, in the context of a ventilated room, as ‘localized overheating’. For a given source strength ratio $\psi = {B}_{1} / {B}_{2} $, we show that thermal overshoots are realized for dimensionless opening areas $A\lt {A}_{oh} $ and are strongly dependent on the time history of the flow. We establish the region of $\{ A, \psi \} $ space where rapid development of ${\delta }_{1} $ results in ${\delta }_{1} \gt {\delta }_{2} $, giving rise to a bulk overturning of the buoyant layers. Finally, some implications of these results, specifically to the ventilation of a room, are discussed.

Rammed earth construction provides an efficient alternative construction material to limit energy consumption and CO2 emission. It possesses various characteristics of a sustainable material, but its mechanical capacity is sensitive to humidity variations. It is, therefore, important to better understand water transport within rammed earth when subjected to varying ambient conditions. In this context, the present work aims to analyze the hydraulic behavior of a reduced piece of rammed earth wall consisting of a column of size 14cm x 14cm x 30cm subjected to drying from the initial compaction water content in an indoor environment. The columns had transient non-uniform relative humidity, which was measured in-situ. Thermo-hydraulic coupled numerical modeling was developed using realistic atmospheric boundary conditions. The material and hydric parameters were chosen from an experimental study previously performed at the material scale. A parametric study was performed in order to evaluate the sensitivity of the modeling to both material parameters and boundary conditions. The results of the numerical simulations were highly sensitive to parameter values used for the water retention curve and the surface mass transfer coefficient, with a satisfactory matching of experimental results only achieved after adjusting initial estimates of relevant parameter values.

The advancement of material technology has contributed to the variation of high-performance composites with good electrical insulation and mechanical properties. Their usage in electrical applications has grown since then. In Malaysia, the composite made of Glass Fiber Reinforced Polymer (GFRP) has been adopted for crossarm manufacturing and has successfully served 275 kV lines for a few decades. However, the combination of extreme conditions such as lightning transient and tropical climate can impose threats to the material. These issues have become major topics of discussion among the utilities in the Southeast Asian (SEA) region, and also in previous research. In Malaysia, more than 50% of total interruptions were caused by lightning. Limited studies can be found on the composite crossarm, especially on the square tube GFRP filled crossarm used in Malaysia. Therefore, this paper proposes to study the behavior of the particular GFRP crossarm, by means of its insulation characteristics. Experimental and simulation approaches are used. Throughout the study, the GFRP specimen is known to have an average breakdown strength at 7.2 kV/mm. In addition, the CFO voltages of the crossarm at different lengths are presented, whereby the behavior under dry and wet conditions is comparably discussed. At the same time, the polarity effect on the CFO voltages is highlighted. The maximum E-fields at the immediate moment before breakdown are analyzed by adopting the finite element method (FEM). Non-uniform distribution of E-fields is witnessed at different parts of the crossarm structure. Simultaneously, the maximum field localized on the crossarm immediately before the breakdown is also presented.

Abstract It is widely known that the accumulation of solid matter forming a cake layer on the membrane surface is one of the major limitations of the filtration performance in submerged membrane bioreactors (SMBR). This study is focused on the influence of the cake porosity of different particle microscopic packed structures on the filtration performance of hollow fiber systems. An integrated model based on the finite element method to simulate numerically the flow in an SMBR is presented. The model coupled the Navier–Stokes and Darcy Brinkman equations to simulate a complete filtration run. The cake growth took into consideration not only the deposition with local filtration velocity but also the effect of aeration scouring. A novel solution of mesh deformation was adopted to investigate transient cake growth along the fiber. Comparisons between simulations and experiments are in good agreement. The results show that a higher porosity particle packed structure causes non-uniform filtration and cake thickness but also higher permeate flux. Meanwhile, the proportion of cake resistance to total resistance increases with the decrease of porosity.

Abstract The operating condition of bus transit system has not been efficient in most cities of Iran, and many management methods such as regular bus scheduling, assigning exclusive bus lanes, etc., which are necessary for increasing the efficiency of this system, were not regarded enough. Thus, achieving a method for locating the bus stops and optimizing the number of such stops based on a non-homogeneous spatial and temporal distribution of passengers as well as the local traffic patterns are important to be investigated. As such, the present study aims to investigate the modeling of a bus transit system corridor according to the non-homogeneous spatial and temporal distribution of passengers throughout the route aiming at optimization of the number of attracted passengers to the bus. For this purpose, the 8-km route from Vali-e-asr roundabout to Gas roundabout in the city of Rasht in the north of Iran is selected for modeling. Hammersley sampling method, as well as two heuristic optimization techniques, including a Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) algorithm, are used for generating a non-uniform population and solving the optimization model. Therefore, the results of this analysis are compared to the optimization results by using the probabilistic analysis without considering the reference uncertainty. Finally, the PSO is selected as the superior algorithm for modeling and locating the bus stops due to its results in less travel time, and the validity of robust optimization model is shown due to its higher accuracy and adaptation to the real-world environment. Overall, although the optimization results based on indeterminate analysis in comparison to determinate analysis brought about more average travel time, more population sets were covered by the new introduced stops during 18 active hours of the bus transit system.

The general consensus among academics is that the spatio-temporal humidity distribution is more or less uniform in an indoor space. This has, for the large part, not yet been proven by an academic study; subsequently, this paper aims to demonstrate that this is not always true. The paper makes use of a validated transient CFD model, which uses the Low Reynolds Number k-ϵ turbulence model. The model simulates people in a room at a constant skin temperature and emitting a constant source of humidity using source terms in the species equation. The model is eventually used to predict the implications of having a high source of humidity, in the form of occupancy, on the micro-climate’s spatio-temporal humidity distribution. The results for the high-occupancy case show that different locations experience various amounts of humid air, with a 31% difference between the lowest and highest locations. The amount of water vapor in each person’s proximity is deemed to be highly dependent on the flow of the inlet jet, with the people farthest from the jet having an overall less mass of water vapor in their proximity over the two-hour experimental period. This paper has concluded that there are, in fact, cases where the humidity non-uniformity inside an interior environment becomes substantial in situations of high occupancy. The results of this paper may be useful to improve the design of HVAC systems.

To date, discrete event stochastic simulations of large scale biological reaction systems are extremely compute-intensive and time-consuming. Besides, it has been widely accepted that spatial factor plays a critical role in the dynamics of most biological reaction systems. The NSM (the Next Sub-Volume Method), a spatial variation of the Gillespie’s stochastic simulation algorithm (SSA), has been proposed for spatially stochastic simulation of those systems. While being able to explore high degree of parallelism in systems, NSM is inherently sequential, which still suffers from the problem of low simulation speed. Fine-grained parallel execution is an elegant way to speed up sequential simulations. Thus, based on the discrete event simulation framework JAMES II, we design and implement a PDES (Parallel Discrete Event Simulation) TW (time warp) simulator to enable the fine-grained parallel execution of spatial stochastic simulations of biological reaction systems using the ANSM (the Abstract NSM), a parallel variation of the NSM. The simulation results of classical Lotka-Volterra biological reaction system show that our time warp simulator obtains remarkable parallel speed-up against sequential execution of the NSM.I.IntroductionThe goal of Systems biology is to obtain system-level investigations of the structure and behavior of biological reaction systems by integrating biology with system theory, mathematics and computer science [1][3], since the isolated knowledge of parts can not explain the dynamics of a whole system. As the complement of “wet-lab” experiments, stochastic simulation, being called the “dry-computational” experiment, plays a more and more important role in computing systems biology [2]. Among many methods explored in systems biology, discrete event stochastic simulation is of greatly importance [4][5][6], since a great number of researches have present that stochasticity or “noise” have a crucial effect on the dynamics of small population biological reaction systems [4][7]. Furthermore, recent research shows that the stochasticity is not only important in biological reaction systems with small population but also in some moderate/large population systems [7].To date, Gillespie’s SSA [8] is widely considered to be the most accurate way to capture the dynamics of biological reaction systems instead of traditional mathematical method [5][9]. However, SSA-based stochastic simulation is confronted with two main challenges: Firstly, this type of simulation is extremely time-consuming, since when the types of species and the number of reactions in the biological system are large, SSA requires a huge amount of steps to sample these reactions; Secondly, the assumption that the systems are spatially homogeneous or well-stirred is hardly met in most real biological systems and spatial factors play a key role in the behaviors of most real biological systems [19][20][21][22][23][24]. The next sub-volume method (NSM) [18], presents us an elegant way to access the special problem via domain partition. To our disappointment, sequential stochastic simulation with the NSM is still very time-consuming, and additionally introduced diffusion among neighbor sub-volumes makes things worse. Whereas, the NSM explores a very high degree of parallelism among sub-volumes, and parallelization has been widely accepted as the most meaningful way to tackle the performance bottleneck of sequential simulations [26][27]. Thus, adapting parallel discrete event simulation (PDES) techniques to discrete event stochastic simulation would be particularly promising. Although there are a few attempts have been conducted [29][30][31], research in this filed is still in its infancy and many issues are in need of further discussion. The next section of the paper presents the background and related work in this domain. In section III, we give the details of design and implementation of model interfaces of LP paradigm and the time warp simulator based on the discrete event simulation framework JAMES II; the benchmark model and experiment results are shown in Section IV; in the last section, we conclude the paper with some future work.II. Background and Related WorkA. Parallel Discrete Event Simulation (PDES)The notion Logical Process (LP) is introduced to PDES as the abstract of the physical process [26], where a system consisting of many physical processes is usually modeled by a set of LP. LP is regarded as the smallest unit that can be executed in PDES and each LP holds a sub-partition of the whole system’s state variables as its private ones. When a LP processes an event, it can only modify the state variables of its own. If one LP needs to modify one of its neighbors’ state variables, it has to schedule an event to the target neighbor. That is to say event message exchanging is the only way that LPs interact with each other. Because of the data dependences or interactions among LPs, synchronization protocols have to be introduced to PDES to guarantee the so-called local causality constraint (LCC) [26]. By now, there are a larger number of synchronization algorithms have been proposed, e.g. the null-message [26], the time warp (TW) [32], breath time warp (BTW) [33] and etc. According to whether can events of LPs be processed optimistically, they are generally divided into two types: conservative algorithms and optimistic algorithms. However, Dematté and Mazza have theoretically pointed out the disadvantages of pure conservative parallel simulation for biochemical reaction systems [31]. B. NSM and ANSM The NSM is a spatial variation of Gillespie’ SSA, which integrates the direct method (DM) [8] with the next reaction method (NRM) [25]. The NSM presents us a pretty good way to tackle the aspect of space in biological systems by partitioning a spatially inhomogeneous system into many much more smaller “homogeneous” ones, which can be simulated by SSA separately. However, the NSM is inherently combined with the sequential semantics, and all sub-volumes share one common data structure for events or messages. Thus, directly parallelization of the NSM may be confronted with the so-called boundary problem and high costs of synchronously accessing the common data structure [29]. In order to obtain higher efficiency of parallel simulation, parallelization of NSM has to firstly free the NSM from the sequential semantics and secondly partition the shared data structure into many “parallel” ones. One of these is the abstract next sub-volume method (ANSM) [30]. In the ANSM, each sub-volume is modeled by a logical process (LP) based on the LP paradigm of PDES, where each LP held its own event queue and state variables (see Fig. 1). In addition, the so-called retraction mechanism was introduced in the ANSM too (see algorithm 1). Besides, based on the ANSM, Wang etc. [30] have experimentally tested the performance of several PDES algorithms in the platform called YH-SUPE [27]. However, their platform is designed for general simulation applications, thus it would sacrifice some performance for being not able to take into account the characteristics of biological reaction systems. Using the similar ideas of the ANSM, Dematté and Mazza have designed and realized an optimistic simulator. However, they processed events in time-stepped manner, which would lose a specific degree of precisions compared with the discrete event manner, and it is very hard to transfer a time-stepped simulation to a discrete event one. In addition, Jeschke etc.[29] have designed and implemented a dynamic time-window simulator to execution the NSM in parallel on the grid computing environment, however, they paid main attention on the analysis of communication costs and determining a better size of the time-window.Fig. 1: the variations from SSA to NSM and from NSM to ANSMC. JAMES II JAMES II is an open source discrete event simulation experiment framework developed by the University of Rostock in Germany. It focuses on high flexibility and scalability [11][13]. Based on the plug-in scheme [12], each function of JAMES II is defined as a specific plug-in type, and all plug-in types and plug-ins are declared in XML-files [13]. Combined with the factory method pattern JAMES II innovatively split up the model and simulator, which makes JAMES II is very flexible to add and reuse both of models and simulators. In addition, JAMES II supports various types of modelling formalisms, e.g. cellular automata, discrete event system specification (DEVS), SpacePi, StochasticPi and etc.[14]. Besides, a well-defined simulator selection mechanism is designed and developed in JAMES II, which can not only automatically choose the proper simulators according to the modeling formalism but also pick out a specific simulator from a serious of simulators supporting the same modeling formalism according to the user settings [15].III. The Model Interface and SimulatorAs we have mentioned in section II (part C), model and simulator are split up into two separate parts. Thus, in this section, we introduce the designation and implementation of model interface of LP paradigm and more importantly the time warp simulator.A. The Mod Interface of LP ParadigmJAMES II provides abstract model interfaces for different modeling formalism, based on which Wang etc. have designed and implemented model interface of LP paradigm[16]. However, this interface is not scalable well for parallel and distributed simulation of larger scale systems. In our implementation, we accommodate the interface to the situation of parallel and distributed situations. Firstly, the neighbor LP’s reference is replaced by its name in LP’s neighbor queue, because it is improper even dangerous that a local LP hold the references of other LPs in remote memory space. In addition, (pseudo-)random number plays a crucial role to obtain valid and meaningful results in stochastic simulations. However, it is still a very challenge work to find a good random number generator (RNG) [34]. Thus, in order to focus on our problems, we introduce one of the uniform RNGs of JAMES II to this model interface, where each LP holds a private RNG so that random number streams of different LPs can be independent stochastically. B. The Time Warp SimulatorBased on the simulator interface provided by JAMES II, we design and implement the time warp simulator, which contains the (master-)simulator, (LP-)simulator. The simulator works strictly as master/worker(s) paradigm for fine-grained parallel and distributed stochastic simulations. Communication costs are crucial to the performance of a fine-grained parallel and distributed simulation. Based on the Java remote method invocation (RMI) mechanism, P2P (peer-to-peer) communication is implemented among all (master-and LP-)simulators, where a simulator holds all the proxies of targeted ones that work on remote workers. One of the advantages of this communication approach is that PDES codes can be transferred to various hardwire environment, such as Clusters, Grids and distributed computing environment, with only a little modification; The other is that RMI mechanism is easy to realized and independent to any other non-Java libraries. Since the straggler event problem, states have to be saved to rollback events that are pre-processed optimistically. Each time being modified, the state is cloned to a queue by Java clone mechanism. Problem of this copy state saving approach is that it would cause loads of memory space. However, the problem can be made up by a condign GVT calculating mechanism. GVT reduction scheme also has a significant impact on the performance of parallel simulators, since it marks the highest time boundary of events that can be committed so that memories of fossils (processed events and states) less than GVT can be reallocated. GVT calculating is a very knotty for the notorious simultaneous reporting problem and transient messages problem. According to our problem, another GVT algorithm, called Twice Notification (TN-GVT) (see algorithm 2), is contributed to this already rich repository instead of implementing one of GVT algorithms in reference [26] and [28].This algorithm looks like the synchronous algorithm described in reference [26] (pp. 114), however, they are essentially different from each other. This algorithm has never stopped the simulators from processing events when GVT reduction, while algorithm in reference [26] blocks all simulators for GVT calculating. As for the transient message problem, it can be neglect in our implementation, because RMI based remote communication approach is synchronized, that means a simulator will not go on its processing until the remote the massage get to its destination. And because of this, the high-costs message acknowledgement, prevalent over many classical asynchronous GVT algorithms, is not needed anymore too, which should be constructive to the whole performance of the time warp simulator.IV. Benchmark Model and Experiment ResultsA. The Lotka-Volterra Predator-prey SystemIn our experiment, the spatial version of Lotka-Volterra predator-prey system is introduced as the benchmark model (see Fig. 2). We choose the system for two considerations: 1) this system is a classical experimental model that has been used in many related researches [8][30][31], so it is credible and the simulation results are comparable; 2) it is simple but helpful enough to test the issues we are interested in. The space of predator-prey System is partitioned into a2D NXNgrid, whereNdenotes the edge size of the grid. Initially the population of the Grass, Preys and Predators are set to 1000 in each single sub-volume (LP). In Fig. 2,r1,r2,r3stand for the reaction constants of the reaction 1, 2 and 3 respectively. We usedGrass,dPreyanddPredatorto stand for the diffusion rate of Grass, Prey and Predator separately. Being similar to reference [8], we also take the assumption that the population of the grass remains stable, and thusdGrassis set to zero.R1:Grass + Prey ->2Prey(1)R2:Predator +Prey -> 2Predator(2)R3:Predator -> NULL(3)r1=0.01; r2=0.01; r3=10(4)dGrass=0.0;dPrey=2.5;dPredato=5.0(5)Fig. 2: predator-prey systemB. Experiment ResultsThe simulation runs have been executed on a Linux Cluster with 40 computing nodes. Each computing node is equipped with two 64bit 2.53 GHz Intel Xeon QuadCore Processors with 24GB RAM, and nodes are interconnected with Gigabit Ethernet connection. The operating system is Kylin Server 3.5, with kernel 2.6.18. Experiments have been conducted on the benchmark model of different size of mode to investigate the execution time and speedup of the time warp simulator. As shown in Fig. 3, the execution time of simulation on single processor with 8 cores is compared. The result shows that it will take more wall clock time to simulate much larger scale systems for the same simulation time. This testifies the fact that larger scale systems will leads to more events in the same time interval. More importantly, the blue line shows that the sequential simulation performance declines very fast when the mode scale becomes large. The bottleneck of sequential simulator is due to the costs of accessing a long event queue to choose the next events. Besides, from the comparison between group 1 and group 2 in this experiment, we could also conclude that high diffusion rate increased the simulation time greatly both in sequential and parallel simulations. This is because LP paradigm has to split diffusion into two processes (diffusion (in) and diffusion (out) event) for two interactive LPs involved in diffusion and high diffusion rate will lead to high proportional of diffusion to reaction. In the second step shown in Fig. 4, the relationship between the speedups from time warp of two different model sizes and the number of work cores involved are demonstrated. The speedup is calculated against the sequential execution of the spatial reaction-diffusion systems model with the same model size and parameters using NSM.Fig. 4 shows the comparison of speedup of time warp on a64X64grid and a100X100grid. In the case of a64X64grid, under the condition that only one node is used, the lowest speedup (a little bigger than 1) is achieved when two cores involved, and the highest speedup (about 6) is achieved when 8 cores involved. The influence of the number of cores used in parallel simulation is investigated. In most cases, large number of cores could bring in considerable improvements in the performance of parallel simulation. Also, compared with the two results in Fig. 4, the simulation of larger model achieves better speedup. Combined with time tests (Fig. 3), we find that sequential simulator’s performance declines sharply when the model scale becomes very large, which makes the time warp simulator get better speed-up correspondingly.Fig. 3: Execution time (wall clock time) of Seq. and time warp with respect to different model sizes (N=32, 64, 100, and 128) and model parameters based on single computing node with 8 cores. Results of the test are grouped by the diffusion rates (Group 1: Sequential 1 and Time Warp 1. dPrey=2.5, dPredator=5.0; Group 2: dPrey=0.25, dPredator=0.5, Sequential 2 and Time Warp 2).Fig. 4: Speedup of time warp with respect to the number of work cores and the model size (N=64 and 100). Work cores are chose from one computing node. Diffusion rates are dPrey=2.5, dPredator=5.0 and dGrass=0.0.V. Conclusion and Future WorkIn this paper, a time warp simulator based on the discrete event simulation framework JAMES II is designed and implemented for fine-grained parallel and distributed discrete event spatial stochastic simulation of biological reaction systems. Several challenges have been overcome, such as state saving, roll back and especially GVT reduction in parallel execution of simulations. The Lotka-Volterra Predator-Prey system is chosen as the benchmark model to test the performance of our time warp simulator and the best experiment results show that it can obtain about 6 times of speed-up against the sequential simulation. The domain this paper concerns with is in the infancy, many interesting issues are worthy of further investigated, e.g. there are many excellent PDES optimistic synchronization algorithms (e.g. the BTW) as well. Next step, we would like to fill some of them into JAMES II. In addition, Gillespie approximation methods (tau-leap[10] etc.) sacrifice some degree of precision for higher simulation speed, but still could not address the aspect of space of biological reaction systems. The combination of spatial element and approximation methods would be very interesting and promising; however, the parallel execution of tau-leap methods should have to overcome many obstacles on the road ahead.AcknowledgmentThis work is supported by the National Natural Science Foundation of China (NSF) Grant (No.60773019) and the Ph.D. Programs Foundation of Ministry of Education of China (No. 200899980004). The authors would like to show their great gratitude to Dr. Jan Himmelspach and Dr. Roland Ewald at the University of Rostock, Germany for their invaluable advice and kindly help with JAMES II.ReferencesH. Kitano, "Computational systems biology." Nature, vol. 420, no. 6912, pp. 206-210, November 2002.H. Kitano, "Systems biology: a brief overview." 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PurposeRecent studies have found that the high demand for air-conditioning usage in tropical countries has affected the thermal adaptability of building occupants to hot weather, and increased building energy consumption. This pilot study aims to investigate the effects of transient thermal environment changes on participants' sensory and physiological responses.Design/methodology/approachThe change of thermal perceptions, skin temperatures and core temperatures when exposed to transient thermal environments (cool-warm-cool) from 10 college-aged female participants during a simulated daily commute by foot to class in a tropical university campus were investigated. Subjective measurements were collected in real-time every 5 min.FindingsThe main finding suggests that participants were acclimatised to cool air-conditioned indoor environments, despite exhibiting significant mean skin temperature differences (p < 0.05). In addition, exposure to uniform air conditioning from 17 to 18°C for 20 min was thermally unacceptable and reduced concentration during given tasks.Research limitations/implicationsThe study focused on thermal comfort conditions in a uniform air-conditioned lecture hall, and the findings may not be applicable for residential and other private building spaces. The distinct temperature difference between indoor and outdoor in the tropical built environment resulted in high dependence on air-conditioning usage. The building occupants' well-being and energy conservation implications of the findings are discussed.Practical implicationsThis study provides the platform for discussion on the dynamics of occupants' comfort level and adopting a more variable thermal environment in tropical spatial transient thermal environments among architects and building management system managers. The findings from this study may contribute to the Malaysian Standards for Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings (MS1525).Originality/valueA knowledge gap in adaptive thermal comfort due to exposure from transient conditions in tropical university campus for energy efficiency revision has been investigated.

Abstract Based on the measured injection rates obtained from the spray momentum experiment, the three-dimensional computational fluid dynamics simulation study on the effect of injection rate from each nozzle hole on spray characteristics and combustion process was conducted for a one-cylinder diesel engine. The simulation model was successfully verified by the data of the experiment. The results show that at the beginning and mid-stages of injection, the nozzles with a higher transient injection rate exhibit higher jet velocity, bigger spray penetration distance, and wider equivalence ratio distribution. Besides, the disturbance induced by fuel injection on their surrounding gas is higher. Due to the difference in injection rates from each nozzle hole in the cylinder, gas–fuel mixtures are non-uniform. In the case of measured injection rates from each nozzle hole, Hole 4 records the highest instantaneous injection rate. This results in the injection of more fuel during ignition delay. More heat generated from thermal chain reactions raises fuel spray temperatures and quicker ignition of mixtures. In the case of uniform simulated injection rate (injection quantity values are the same as in the previous case), more uniform flow fields and stronger small swirl motions were generated that enhance fuel atomization and mixture formations. At the later stages of injection and combustion, quicker diesel fuel burning rate with a centralized exothermic reaction process occurs due to in-cylinder uniform fuel distribution and air motion. In the case of simulating uniform injection rate from three holes and non-injection from one (same injection quantity values as previous cases), uneven fuel distribution that occurs in the cylinder will result in poor mixture formations and subsequently poor combustion, and more afterburning will occur.

Abstract Fluid migration behind casings is a well integrity problem that can result in sustained casing pressure, undetected leaks to the environment, and potentially very challenging remediation attempts. Understanding the geometric dimensions and extent of annular migration paths is important for diagnosing and effectively treating fluid migration and sustained casing pressure problems in wells. In this study, permeability and micro-annuli sizes in two full-scale cemented annulus test sections are measured using transient pressure-pulse-decay and steady-state seepage measurements. One of the studied sections is a cemented 9 5/8-in. and 13 3/8-in. casing section from a 30 years old Norwegian North Sea production well. A model for predicting the transient pressure decay in annular sections with non-uniform permeability is presented and the permeabilities of the two sections are determined by fitting the transient model to pressure measurements at either side of the test sections and at selected axial positions. For both sections, measured micro-annulus sizes are within the range of effective wellbore permeabilities based on sustained casing pressure records and previous vertical interference tests from other wells. The test sections display measurable axial permeability variations with the bottom part of these vertical sections having the lower permeability. For the retrieved casing section, the axial permeability variation occurs close to the middle of the test section and is attributed to the top-of-cement. Increasing internal casing pressure is found to slightly reduce the equivalent micro-annulus size, indicative of fracture-like response of the migration paths. Using two independent test protocols, we have measured effective permeabilities as well as local permeability variations in full-scale test sections and found consistent results. The study suggests that the transient test procedure can be used to more effectively characterize low-permeable annular cement where it is otherwise time-consuming or difficult to establish steady-state flow conditions.

To bridge the gap between 2D cell culture and tissue, various 3D cell culture approaches have been developed for the investigation of cardiac myocytes (CM) and fibroblasts (CF), but limitations still exist. The goal of this study was to develop a scaffold-free cardiac culture that could easily and inexpensively create many uniform cardiac microtissues that mimic the cellular distribution and functional behavior of CM and CF in tissue. Using micromolded non-adhesive agarose hydrogels containing 822 concave recesses (800 λm deep x 400 λm wide), we demonstrate that neonatal rat ventricular CM and CF, when seeded alone or in combination, self-assembled into viable (Live/Dead® stain) spherical-shaped microtissues. Importantly, when CM and CF were seeded simultaneously or sequentially, they self-sorted to be highly interspersed, reminiscent of their distribution in ventricular tissue, as shown by cell type-specific CellTracker TM or antibody labeling. Depending on their cellular composition, microtissues expressed extracellular matrix and calcium handling proteins (including SERCA2a), featured typical I K1 and I Ca-L current densities and IV relationships, and formed functional cell-cell connections (as evidenced by spontaneous action potentials, contractions and connexin 43 expression). Microelectrode recordings and optical mapping showed characteristic triangular action potentials (AP) with a resting membrane potential of -66±7 mV (n=4) in spontaneously contracting CM microtissues. Under pacing, optically mapped AP duration at 90% repolarization and conduction velocity were 100±30 ms and 18.0±1.9 cm/s, respectively (n=5 each). The presence of CF led to a prolongation of both AP and calcium transients in CM:CF microtissues (1:1). Furthermore, cell-type-specific adenoviral gene transfer was achieved, with no impact on microtissue formation or cell viability. In conclusion, we have developed a novel scaffold-free cardiac 3D culture model, in which more than 800 homotypic (CM or CF) or heterotypic (CM:CF) microtissues can be formed in a 6-well with ease, analyzed functionally and subjected to cell-type-specific gene transfer, paving the way for future in vitro investigations of CM and CF behavior and their interactions in a 3D environment.

In the contemporary urban environment of mass transit, it falls to a small group of public officers to keep large number of travellers safe. The small size of their force and the often limited powers they exert mean that these public safety ‘transit officers’ must project more authority and control than they really have. It is this ambience of authority and control which, in most situations they encounter and seek to influence, is enough to keep the public safe. This paper examines the ambience of a group of transit officers working on the railway lines of an Australian capital city. We seek to show how transit officers are both influenced by, and seek to influence, the ambience of their workplace and the public spaces they inhabit whilst on duty, and here we take ambience to apply to the surrounding atmosphere, the aura, and the emotional environment of a place or situation: the setting, tone, or mood. For these transit officers to keep the public safe, they must themselves remain safe. A transit officer who is disabled in a confrontation with a violent offender is unable to provide protection to his or her passengers. Thus, in the culture of the transit officers, their own workplace safety takes on a higher significance. It affects not just themselves. The ambience exuded by transit officers, and how transit officers see their relationship with the travelling public, their management and other organisational work groups, is an important determinant of their work group’s safety culture. Researching the Working Lives of Transit Officers in Perth Our discussion draws on an ethnographic study of the working lives and communication cultures of transit officers (TOs) employed by the Public Transport Authority (PTA) of Western Australia (WA). Transit officers have argued that to understand fully the challenges of their work it is necessary to spend time with them as they undertake their daily duties: roster in, roster out. To this end, the research team and the employer organisation secured an ARC Linkage Grant in partnership with the PTA to fund doctoral candidate and ethnographer Christine Teague to research the workers’ point of view, and the workers’ experiences within the organisation. The two-hundred TOs are unique in the PTA. Neither of the other groups who ride with them on the trains, the drivers and revenue protection staff (whose sole job is to sell and check tickets), experiences the combination of intense contact with passengers, danger of physical injury or group morale. The TOs of the PTA in Perth operate from a central location at the main train station and the end stations on each line. Here there are change lockers where they can lock up their uniforms and equipment such as handcuffs and batons when not on duty, an equipment room where they sign out their radios, and ticket-checking machines. At the main train station there is also a gym, a canteen and holding cells for offenders they detain. From these end stations and central location, the TOs fan out across the network to all suburbs where they either operate from stations or onboard the trains. The TOs also do ‘delta van’ duty providing rapid, mobile back-up support for their colleagues on stations or trains, and providing transport for arrested persons to the holding cell or police lock up. TOs are on duty whenever the trains are running–but the evenings and nights are when they are mainly rostered on. This is when trouble mostly occurs. The TOs’ work ends only after the final train has completed its run and all offenders who may require detaining and charging have been transferred into police custody. While the public perceive that security is the TOs’ most frequent role, much of the work involves non-confrontational activity such as assisting passengers, checking tickets and providing a reassuring presence. One way to deal with an ambiguous role is to claim an ambience of power and authority regardless. Various aspects of the TO role permit and hinder this, and the paper goes on to consider aspects of ambience in terms of fear and force, order and safety, and role confusion. An Ambience of Fear and Force The TOs are responsible for front-line security in WA’s urban railway network. Their role is to offer a feeling of security for passengers using the rail network after the bustle of the work day finishes, and is replaced by the mainly recreational travels of the after hours public. This is the time when some passengers find the prospect of evening travel on the public transport rail network unsettling–so unsettling that it was a 2001 WA government election promise (WA Legislative Council) that every train leaving the city centre after 7pm would have two TOs riding on it. Interestingly, recruitment levels have never been high enough for this promise to be fully kept. The working conditions of the TOs reflect the perception, and to an extent, the reality that some late night travel on public transport involves negotiating an edgy ambience with an element of risk, rubbing shoulders with people who may be loud, rowdy, travelling in a group, and or drug and alcohol affected. As Fred (all TO names are pseudonyms) comments: You’re not dealing with rational people, you’re not dealing with ‘people’: most of the people you’re dealing with are either drunk or under the influence of drugs, so they’re not rational, they don’t hear you, they don’t understand what you’re saying, they just have no sense of what’s right or wrong, you know? Especially being under the influence, so I mean, you can talk till you’re blue in the face with somebody who’s drunk or on drugs, I mean, all you have to say is one thing. ‘Oh, can I see your ticket please’, ‘oh, why do I need a fucking ticket’, you know? They just don’t get simple everyday messages. Dealing with violence and making arrest is a normal part of this job. Jo described an early experience in her working life as a TO:Within the first week of coming out of course I got smacked on the side of the head, but this lady had actually been certified, like, she was nuts. She was completely mental and we were just standing on the train talking and I’ve turned around to say something to my partner and she was fine, she was as calm as, and I turned around and talked to my partner and the next thing I know I ended up with her fist to the side of my head. And I went ‘what the hell was that’? And she went off, she went absolutely ballistic. I ended up arresting her because it was assault on an officer whether she was mental or not so I ended up arresting her.Although Jo here is describing how she experienced an unprovoked assault in the early days of her career as a TO, one of the most frequent precursors to a TO injury occurs when the TO is required to make an arrest. The injury may occur when the passenger to be arrested resists or flees, and the TO gives chase in dark or treacherous circumstances such as railway reserves and tunnels, or when other passengers, maybe friends or family of the original person of concern, involve themselves in an affray around the precipitating action of the arrest. In circumstances where capsicum spray is the primary way of enforcing compliance, with batons used as a defence tool, group members may feel that they can take on the two TOs with impunity, certainly in the first instance. Even though there are security cameras on trains and in stations, and these can be cued to cover the threatening or difficult situations confronting TOs, the conflict is located in the here-and-now of the exchanges between TOs and the travelling public. This means the longer term consequence of trouble in the future may hold less sway with unruly travellers than the temptation to try to escape from trouble in the present. In discussing the impact of remote communications, Rubert Murdoch commented that these technologies are “a powerful influence for civilised behaviour. If you are arranging a massacre, it will be useless to shoot the cameraman who has so inconveniently appeared on the scene. His picture will already be safe in the studio five thousand miles away and his final image may hang you” (Shawcross 242). Unfortunately, whether public aggression in these circumstances is useless or not, the daily experience of TOs is that the presence of closed circuit television (CCTV) does not prevent attacks upon them: nor is it a guarantee of ‘civilised behaviour’. This is possibly because many of the more argumentative and angry members of the public are dis-inhibited by alcohol or other drugs. Police officers can employ the threat or actual application of stun guns to control situations in which they are outnumbered, but in the case of TOs they can remain outnumbered and vulnerable until reinforcements arrive. Such reinforcements are available, but the situation has to be managed through the communication of authority until the point where the train arrives at a ‘manned’ station, or the staff on the delta vehicle are able to support their colleagues. An Ambience of Order and Safety Some public transport organisations take this responsibility to sustain an ambience of order more seriously than others. The TO ethnographer, Christine Teague, visited public transport organisations in the UK, USA and Canada which are recognised as setting world-class standards for injury rates of their staff. In the USA particularly, there is a commitment to what is called ‘the broken windows’ theory, where a train is withdrawn from service promptly if it is damaged or defaced (Kelling and Coles; Maple and Mitchell). According to Henry (117): The ‘Broken Windows’ theory suggests that there is both a high correlation and a causal link between community disorder and more serious crime: when community disorder is permitted to flourish or when disorderly conditions or problems are left untended, they actually cause more serious crime. ‘Broken windows’ are a metaphor for community disorder which, as Wilson and Kelling (1982) use the term, includes the violation of informal social norms for public behaviour as well as quality of life offenses such as littering, graffiti, playing loud radios, aggressive panhandling, and vandalism.This theory implies that the physical ambience of the train, and by extension the station, may be highly influential in terms of creating a safe working environment. In this case of ‘no broken window’ organisations, the TO role is to maintain a high ‘quality of life’ rather than being a role predominantly about restraining and bringing to justice those whose behaviour is offensive, dangerous or illegal. The TOs in Perth achieve this through personal means such as taking pride in their uniforms, presenting a good-natured demeanour to passengers and assisting in maintaining the high standard of train interiors. Such a priority, and its link to reduced workforce injury, suggests that a perception of order impacts upon safety. It has long been argued that the safety culture of an organisation affects the safety performance of that organisation (Pidgeon; Leplat); but it has been more recently established that different cultural groupings in an organisation conceive and construct their safety culture differently (Leith). The research on ‘safety culture’ raises a problematic which is rarely addressed in practice. That problematic is this: managers frequently engage with safety at the level of instituting systems, while workers engage with safety in terms of behaviour. When Glendon and Litherland comment that, contrary to expectations, they could find no relationship between safety culture and safety performance, they were drawing attention to the fact that much managerial safety culture is premised upon systems involving tick boxes and the filling in of report forms. The broken window approach combines the managerial tick box with managerial behaviour: a dis-ordered train is removed from service. To some extent a general lack of fit between safety culture and safety performance endorses Everett’s view that it is conceptually inadequate to conceive organisations as cultures: “the conceptual inadequacy stems from the failure to distinguish between culture and behavioural features of organizational life” (238). The general focus upon safety culture as a way of promoting improvements in safety performance assumes that compliance with a range of safety systems will guarantee a safe workplace. Such an assumption, however, risks positioning the injured worker as responsible for his or her own predicament and sets up an environment in which some management officials are wont to seek ways in which that injured worker’s behaviour failed to conform with safety rules or safety processes. Yet there are roles which place workers in harm’s way, including military duties, law enforcement and some emergency services. Here, the work becomes dangerous as it becomes disorderly. An Ambience of Roles and Confusion As the research reported here progressed, it became clear that the ambience around the presentation of the self in the role of a TO (Goffman) was an important part of how ‘safety’ was promoted and enacted in their work upon the PTA (WA) trains, face to face with the travelling public. Goffman’s view of all people, not specifically TOs, is that: Regardless of the particular objective which the individual has in mind and of his motive for having this objective, it will be in his interests to control the conduct of the others, especially their responsive treatment of him. This will largely be through influencing the perception and definition that others will come to formulate of him. He will influence them by expressing himself in such a way that the kind of impression given off will lead them to act voluntarily in accordance with his own plan. (3)This ‘influencing of perception’ is an important element of performing the role of a TO. This task of the TOs is made all the more difficult because of confusions about their role in relation to two other officers: police (who have more power to act in situations of public safety) and revenue project officers (who have less), as we now discuss. The aura of the TO role borrows somewhat from those quintessential law and order officers: the police. TOs work in pairs, like many police, to support each other. They have a range of legal powers including the power of arrest, and they carry handcuffs, a baton and capsicum spray as a means of helping ensure their safety and effectiveness in circumstances where they might be outnumbered. The tools of their trade are accessibly displayed on heavy leather belts around their waists and their uniforms have similarities with police uniforms. However, in some ways these similarities are problematic, because TOs are not afforded the same respect as police. This situation underlines of the ambiguities negotiated within the ambience of what it is to be a TO, and how it is to conduct oneself in that role. Notwithstanding the TOs’ law and order responsibilities, public perceptions of the role and some of the public’s responses to the officers can position these workers as “plastic cops” (Teague and Leith). The penultimate deterrent of police officers, the stun gun (Taser), is not available to TOs who are expected to control all incidents arising on duty through the fact that they operate in pairs, with capsicum spray available and, as a last resort, are authorised to use their batons in self defence. Furthermore, although TOs are the key security and enforcement staff in the PTA workforce, and are managed separately from related staff roles, they believe that the clarity of this distinction is compromised because of similarities in the look of Revenue Protection Officers (RPOs). RPOs work on the trains to check that passengers have tickets and have paid the correct fares, and obtain names and addresses to issue infringement notices when required. They are not PTA employees, but contracted staff from an outside company. They also work in pairs. Significantly, the RPO uniform is in many respects identical to that of the TO, and this appears to be a deliberate management choice to make the number of TOs seem greater than it is: extending the TO ambience through to the activities of the RPOs. However, in the event of a disturbance, TOs are required and trained to act, while RPOs are instructed not to get involved; even though the RPOs appear to the travelling public to be operating in the role of a law-and-order-keeper, RPOs are specifically instructed not to get involved in breaches of the peace or disruptive passenger behaviour. From the point of view of the travelling public, who observe the RPO waiting for TOs to arrive, it may seems as if a TO is passively standing by while a chaotic situation unravels. As Angus commented: I’ve spoken to quite a few members of public and received complaints from them about transit officers and talking more about the incident have found out that it was actually [RPOs] that are dealing with it. So it’s creating a bad image for us …. It’s Transits that are copping all the flak for it … It is dangerous for us and it’s a lot of bad publicity for us. It’s hard enough, the job that we do and the lack of respect that we do get from people, we don’t need other people adding to it and making it harder. Indeed, it is not only the travelling public who can mistake the two uniforms. Mike tells of an “incident where an officer [TO] has called for backup on a train and the guys have got off [the train at the next station] and just stood there, and he didn’t realise that they are actually [revenue protection] officers, so he effectively had no backup. He thought he did, but he didn’t.” The RPO uniform may confer an ambience of power borrowed from TOs and communicated visually, but the impact is to compromise the authority of the TO role. Unfortunately, what could be a complementary role to the TOs becomes one which, in the minds of the TO workforce, serves to undermine their presence. This effect of this role confusion is to dilute the aura of authority of the TOs. At one end of a power continuum the TO role is minimised by those who see it as a second-rate ‘Wannabe cop’ (Teague and Leith 2008), while its impact is diluted at the other end by an apparently deliberate confusion between the TO broader ‘law and order’ role, and the more limited RPO revenue collection activities. Postlude To the passengers of the PTA in Perth, the presence and actions of transit officers appear as unremarkable as the daily commute. In this ethnographic study of their workplace culture, however, the transit officers have revealed ways in which they influence the ambience of the workplace and the public spaces they inhabit whilst on duty, and how they are influenced by it. While this ambient inter-relationship is not documented in the organisation’s occupational safety and health management system, the TOs are aware that it is a factor in their level at safety at work, both positively and negatively. Clearly, an ethnography study is conducted at a certain point in time and place, and culture is a living and changing expression of human interaction. The Public Transport Authority of Western Australia is committed to continuous improvement in safety and to the investigation of all ways and means in which to support TOs in their daily activities. This is evident not only in their support of the research and their welcoming of the ethnographer into the workforce and onto the tracks, but also in their robust commitment to change as the findings of the research have progressed. In particular, changes in the ambient TO culture and in the training and daily practices of TOs have already resulted from this research or are under active consideration. Nonetheless, this project is a cogent indicator of the fact that a safety culture is critically dependent upon intangible but nonetheless important factors such as the ambience of the workplace and the way in which officers are able to communicate their authority to others. References Everett, James. “Organizational Culture and Ethnoecology in Public Relations Theory and Practice.” Public Relations Research Annual. Vol. 2. Eds. Larissa Grunig and James Grunig. Hillsdale, NJ, 1990. 235-251. 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