Controlling excessive waiting times in emergency departments: an extension of the ISA algorithm.

In an emergency department (ED), the demand for service is not constant over time. This cannot be accounted for by means of waiting lists or appointment systems, so capacity decisions are the most important tool to influence patient waiting times. Additional complexities result from the relatively small system size that characterizes an ED (i.e. a small number of physicians or nurses) and the presence of customer impatience. Assuming a single-stage multiserver M(t)/G/s(t) + G queueing system with general abandonment and service times and time-varying demand for service, we suggest a method inspired by the simulation-based Iterative Staffing Algorithm (ISA) proposed by Feldman and others (2008) as a method to set staffing levels throughout the day. The main advantage of our extension is that it enables the use of performance measures based on the probability of experiencing an excessive waiting time, instead of the common focus on delay probability as a performance metric.Emergency department; Personnel planning; Time-varying arrival rate;

Editors\u27 Notebook

Editorial introduction to The Goose Volume 16, Issue 2 (2018)

Cross-scale modelling of transpiration from stomata via the leaf boundary layer

Background and Aims Leaf transpiration is a key parameter for understanding land surface-climate interactions, plant stress and plant structure-function relationships. Transpiration takes place at the microscale level, namely via stomata that are distributed discretely over the leaf surface with a very low surface coverage (approx. 0·2-5 %). The present study aims to shed more light on the dependency of the leaf boundary-layer conductance (BLC) on stomatal surface coverage and air speed. Methods An innovative three-dimensional cross-scale modelling approach was applied to investigate convective mass transport from leaves, using computational fluid dynamics. The gap between stomatal and leaf scale was bridged by including all these scales in the same computational model (10−5-10−1 m), which implies explicitly modelling individual stomata. Key Results BLC was strongly dependent on stomatal surface coverage and air speed. Leaf BLC at low surface coverage ratios (CR), typical for stomata, was still relatively high, compared with BLC of a fully wet leaf (hypothetical CR of 100 %). Nevertheless, these conventional BLCs (CR of 100 %), as obtained from experiments or simulations on leaf models, were found to overpredict the convective exchange. In addition, small variations in stomatal CR were found to result in large variations in BLCs. Furthermore, stomata of a certain size exhibited a higher mass transfer rate at lower CRs. Conclusions The proposed cross-scale modelling approach allows us to increase our understanding of transpiration at the sub-leaf level as well as the boundary-layer microclimate in a way currently not feasible experimentally. The influence of stomatal size, aperture and surface density, and also flow-field parameters can be studied using the model, and prospects for further improvement of the model are presented. An important conclusion of the study is that existing measures of conductances (e.g. from artificial leaves) can be significantly erroneous because they do not account for microscopic stomata, but instead assume a uniform distribution of evaporation such as found for a fully-wet leaf. The model output can be used to correct or upgrade existing BLCs or to feed into higher-scale models, for example within a multiscale framewor

Quality and reliability of LES of convective scalar transfer at high Reynolds numbers

Numerical studies were performed to assess the quality and reliability of wall-modeled large eddy simulation (LES) for studying convective heat and mass transfer over bluff bodies at high Reynolds numbers (Re), with a focus on built structures in the atmospheric boundary layer. Detailed comparisons were made with both wind-tunnel experiments and field observations. The LES was shown to correctly capture the spatial patterns of the transfer coefficients around two-dimensional roughness ribs (with a discrepancy of about 20%) and the average Nusselt number (Nu) over a single wall mounted cube (with a discrepancy of about 25%) relative to wind tunnel measurements. However, the discrepancy in Re between the wind tunnel measurements and the real-world applications that the code aims to address influence the comparisons since Nu is a function of Re. Evaluations against field observations are therefore done to overcome this challenge; they reveal that, for applications in urban areas, the wind-tunnel studies result in a much lower range for the exponent m in the classic Nu∼Re m relations, compared to field measurements and LES (0.52–0.74 versus≈ 0.9). The results underline the importance of conducting experimentalor numerical studies for convective scalar transfer problems at a Re commensurate with the flow of interest, and support the use of wall-modeled LES as a technique for this problem that can already capture important aspects of the physics, although further development and testing are needed

Nondestructive measurement of fruit and vegetable quality

We review nondestructive techniques for measuring internal and external quality attributes of fruit and vegetables, such as color, size and shape, flavor, texture, and absence of defects. The different techniques are organized according to their physical measurement principle. We first describe each technique and then list some examples. As many of these techniques rely on mathematical models and particular data processing methods, we discuss these where needed. We pay particular attention to techniques that can be implemented online in grading lines

Influence of urban form on the performance of road pavement solar collector system: symmetrical and asymmetrical heights

Recent works have highlighted the importance of mitigating the urban heat island effect using innovative technologies. Several studies have emphasised the capabilities of the road pavement solar collector system to dissipate high temperature from the pavement/road surfaces not only to expand its lifecycle but also to reduce the Urban Heat Island effect. This study builds on previous research combining an urban configuration and a road pavement solar collector system in Computational Fluid Dynamics in order to understand the complicated connection of the urban environment and the road pavement. This study investigates the impact of the urban form on the performance of the road pavement solar collector focusing on comparing symmetrical and asymmetrical height of the urban street canyon. A tridimensional de-coupled simulation approach was used to simulate a macro domain (urban environment) and micro domain, which consists of road pavement solar collector pipes. ANSYS Fluent 15.0 was employed with the solar load model, Discrete Ordinate radiation model and Reynold Averaged Navier Stokes with standard k-epsilon equation. The simulation was carried out based on the summer month of June in Milan urban centre, Italy. Results showed a significant variation in the temperature results of road surface in comparing the three configurations. It was also found that there was a significant reduction in the road pavement solar collector system performance when taller building row was behind the first approaching building row. The method presented in this research could be useful for studying the system integration in various urban forms

The Rwandan Genocide in Film, and A Sunday in Kigali: Watching with a Pierced Eye

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