Articles de revues : « Primary delay modelling »

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Indhu, B., et K. Yogeswari. « Structural Equation Modelling (SEM) Approach On Inappropriate Construction Equipment Delay Factors ». Civil Engineering Journal 7, n^o 7 (1 juillet 2021) : 1156–68. http://dx.doi.org/10.28991/cej-2021-03091717.

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The advancement of construction equipment is a trend in the construction industry, with numerous benefits. However, using inappropriate construction equipment causes delays in construction projects, affecting the firm's reputation. A number of research studies on overall delay have been conducted globally. Even so, there is a lack of research on construction delays caused by inappropriate construction equipment. The aim of this paper is to investigate the inappropriate construction equipment delay factors and their effects on the firm's reputation. Based on the issues identified in the focus group interviews and the literature survey, a questionnaire survey was conducted to assess the impact of these factors on the progress of Indian construction projects. The primary constraint was that all 300 responses were collected in person from construction professionals to avoid lethargic responses that could skew the results. Pearson correlation coefficients were used to determine the positive strength of each factor's relationship. A t-test was used to see if there was a significant difference between the respondents' firm categories. Structural Equation Modeling (SEM) was used to validate the effective relationship between the causes of delays due to inappropriate construction equipment and its impact on company's reputation. All of the factors examined by the SEM analysis evidenced that the inappropriate construction equipment factors are correlated among themselves and combined to impact the reputation of the company. Recommendations are made to overcome the inappropriate equipment delay factors. Doi: 10.28991/cej-2021-03091717 Full Text: PDF

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Meyer, Matthias R., Alain M. Bernheim, David J. Kurz, Crochan J. O’Sullivan, David Tüller, Rainer Zbinden, Thomas Rosemann et Franz R. Eberli. « Gender differences in patient and system delay for primary percutaneous coronary intervention : current trends in a Swiss ST-segment elevation myocardial infarction population ». European Heart Journal : Acute Cardiovascular Care 8, n^o 3 (8 novembre 2018) : 283–90. http://dx.doi.org/10.1177/2048872618810410.

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Background: Women with ST-segment elevation myocardial infarction (STEMI) experience greater delays for percutaneous coronary intervention-facilitated reperfusion than men. Whether women and men benefit equally from current strategies to reduce ischaemic time and whether there are gender differences in factors determining delays is unclear. Methods: Patient delay (symptom onset to first medical contact) and system delay (first medical contact to percutaneous coronary intervention-facilitated reperfusion) were compared between women ( n=967) and men ( n=3393) in a Swiss STEMI treatment network. Trends from 2000 to 2016 were analysed, with additional comparisons between three time periods (2000–2005, 2006–2011 and 2012–2016). Factors predicting delays and hospital mortality were determined by multivariate regression modelling. Results: Female gender was independently associated with greater patient delay ( P=0.02 vs. men), accounting for a 12% greater total ischaemic time among women in 2012–2016 (median 215 vs. 192 minutes, P<0.001 vs. men). From 2000–2005 to 2012–2016, median system delay was reduced by 18 and 25 minutes in women and men, respectively ( P<0.0001 for trend, P=n.s. for gender difference). Total occlusion of the culprit artery, stent thrombosis, a Killip class of 3 or greater, and presentation during off-hours predicted delays in men, but not in women. A Killip class of 3 or greater and age, but not gender or delays, were independently associated with hospital mortality. Conclusions: STEMI-related ischaemic time in women remains greater than in men due to persistently greater patient delays. In contrast to men, clinical signs of ongoing chest discomfort do not predict delays in women, suggesting that female STEMI patients are less likely to attribute symptoms to a condition requiring urgent treatment.

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Shakeel, Atif, Riaz Hussain, Adeel Iqbal, Irfan Latif Khan, Qadeer ul Hasan et Shahzad Ali Malik. « Analysis of Efficient Spectrum Handoff in a Multi-Class Hybrid Spectrum Access Cognitive Radio Network Using Markov Modelling ». Sensors 19, n^o 19 (23 septembre 2019) : 4120. http://dx.doi.org/10.3390/s19194120.

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Cognitive radio networks (CRNs) rely on sensing of the licensed spectrum of a primary network to dynamically ascertain underutilized portion of the spectrum, thus affording additional communication opportunities. In a CRN, a single homogeneous spectrum access, such as interweave only deprives the secondary users (SUs) of channel access during handoff, particularly at high primary network traffic. Therefore, providing quality-of-service (QoS) to multi-class SUs with diverse delay requirements during handoff becomes a challenging task. In this paper, we have evolved a Markov-based analytical model to ascertain the gain in non-switching spectrum handoff scheme for multi-class SUs employing hybrid interweave-underlay spectrum access strategy. To satisfy the QoS requirements of the delay-sensitive traffic, we have analyzed the impact of hybrid spectrum access scheme for prioritized multi-class SUs traffic. The results show substantial improvement in spectrum utilization, average system throughput and extended data delivery time compared to conventional CRN using interweave only spectrum access. This demonstrates the suitability of the proposed scheme towards meeting QoS requirements of the delay-sensitive SU traffic while improving the overall performance for delay-tolerant SU traffic as well.

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Gao, Jing, Changchuan Yin et Xi Han. « End-to-End Delay Analysis in Cognitive Radio Ad Hoc Networks with Different Traffic Models ». Mobile Information Systems 2015 (2015) : 1–9. http://dx.doi.org/10.1155/2015/157659.

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Delay and throughput are important metrics for network performance. We analyze the end-to-end delay of cognitive radio ad hoc networks for two traffic models: backlogged and geometric, respectively. By modelling the primary users as a Poisson point process and the secondary network deploying multihop transmissions, we derive the closed-form expression for the end-to-end delay in secondary networks. Furthermore, we optimize the end-to-end delay in terms of the hop number and the secondary transmission probability, respectively. The range of the optimal hop number and the equation satisfied by the optimal transmission probability are obtained for backlogged source models. The equation met by the optimal hop number is presented for geometric source models.

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Keck, David N., et Mark A. McKibben. « Abstract stochastic integrodifferential delay equations ». Journal of Applied Mathematics and Stochastic Analysis 2005, n^o 3 (1 janvier 2005) : 275–305. http://dx.doi.org/10.1155/jamsa.2005.275.

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We investigate a class of abstract stochastic integrodifferential delay equations dependent upon a family of probability measures in a separable Hilbert space. We establish the existence and uniqueness of a mild solution, along with various continuous dependence estimates and Markov (weak and strong) properties of this solution. This is followed by a convergence result concerning the strong solutions of the Yosida approximations of our equation, from which we deduce the weak convergence of the measures induced by these strong solutions to the measure induced by the mild solution of the primary problem under investigation. Next, we establish the pth moment and almost sure exponential stability of the mild solution. Finally, an analysis of two examples, namely a generalized stochastic heat equation and a Sobolev-type evolution equation, is provided to illustrate the applicability of the general theory.

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Elsayed, Ahmed, Ahmed Sedeek, Mohamed Doma et Mostafa Rabah. « Vertical ionospheric delay estimation for single-receiver operation ». Journal of Applied Geodesy 13, n^o 2 (26 avril 2019) : 81–91. http://dx.doi.org/10.1515/jag-2018-0041.

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Abstract An apparent delay is occurred in GPS signal due to both refraction and diffraction caused by the atmosphere. The second region of the atmosphere is the ionosphere. The ionosphere is significantly related to GPS and the refraction it causes in GPS signal is considered one of the main source of errors which must be eliminated to determine accurate positions. GPS receiver networks have been used for monitoring the ionosphere for a long time. The ionospheric delay is the most predominant of all the error sources. This delay is a function of the total electron content (TEC). Because of the dispersive nature of the ionosphere, one can estimate the ionospheric delay using the dual frequency GPS. In the current research our primary goal is applying Precise Point Positioning (PPP) observation for accurate ionosphere error modeling, by estimating Ionosphere delay using carrier phase observations from dual frequency GPS receiver. The proposed algorithm was written using MATLAB and was named VIDE program. The proposed Algorithm depends on the geometry-free carrier-phase observations after detecting cycle slip to estimates the ionospheric delay using a spherical ionospheric shell model, in which the vertical delays are described by means of a zenith delay at the station position and latitudinal and longitudinal gradients. Geometry-free carrier-phase observations were applied to avoid unwanted effects of pseudorange measurements, such as code multipath. The ionospheric estimation in this algorithm is performed by means of sequential least-squares adjustment. Finally, an adaptable user interface MATLAB software are capable of estimating ionosphere delay, ambiguity term and ionosphere gradient accurately.

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Lv, Yangyang, Lijuan Chen, Fengde Chen et Zhong Li. « Stability and Bifurcation in an SI Epidemic Model with Additive Allee Effect and Time Delay ». International Journal of Bifurcation and Chaos 31, n^o 04 (30 mars 2021) : 2150060. http://dx.doi.org/10.1142/s0218127421500607.

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In this paper, we consider an SI epidemic model incorporating additive Allee effect and time delay. The primary purpose of this paper is to study the dynamics of the above system. Firstly, for the model without time delay, we demonstrate the existence and stability of equilibria for three different cases, i.e. with weak Allee effect, with strong Allee effect, and in the critical case. We also investigate the existence and uniqueness of Hopf bifurcation and limit cycle. Secondly, for the model with time delay, the stability of equilibria and the existence of Hopf bifurcation are discussed. All the above show that both additive Allee effect and time delay have vital effects on the prevalence of the disease.

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Chadee, Aaron, Hanna Ali, Sihara Gallage et Upaka Rathnayake. « Modelling the Implications of Delayed Payments on Contractors’ Cashflows on Infrastructure Projects ». Civil Engineering Journal 9, n^o 1 (1 janvier 2023) : 52–71. http://dx.doi.org/10.28991/cej-2023-09-01-05.

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The consideration of payments to contractors is not only a legal obligation but a necessity for assuring the continuity and completion of a construction project. However, consistent payments to facilitate project cash flows are uncommon in the construction industry. Within the context of a small island developing state, this paper aims to uncover leading risks factors the contributing to implications of delayed payments, on contractors’ cash flows and uncover any causalities and effects on relationships among these factors. A two-tiered quantitative approach was adopted. Firstly, a compiled list of delay factors was collated from the literature review. Semi-structured interviews were conducted with experienced construction professionals to determine the factors’ relevance and applicability in Trinidad and Tobago. A closed-ended survey questionnaire was subsequently developed and administered to primary construction stakeholders. Secondly, the responses obtained were collated, validated, and ranked using the relative importance index. A confirmatory factor analysis (CFA) was carried out using SPSS, and thereafter, SPSS Amos was used to determine the best-fit Structural Equation Model (SEM). The results strongly indicate that the issue of delayed payments is very prevalent within public sector projects. Unstable political climates and the delay in employers’ issuance of variation orders were found to be the main causes of delayed payments within the industry. Delays in sub-contractor and supplier payments as well as an increase in the contractor’s debt are the leading effects of delayed payments on the contractor’s cash flows. Based on these findings, a risk response framework was outlined to assist small to medium-contracting enterprises cope with payment delays, both locally and internationally. This research contributes to the advancement of construction management knowledge by informing construction professionals and policy makers of the implications of delaying approved payments, the consequential causes and effects, and a risk response technique to mitigate the negative effects on contractors’ cash flows. Doi: 10.28991/CEJ-2023-09-01-05 Full Text: PDF

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Wang, Yichen, et K. J. Ray Liu. « Statistical Delay QoS Protection for Primary Users in Cooperative Cognitive Radio Networks ». IEEE Communications Letters 19, n^o 5 (mai 2015) : 835–38. http://dx.doi.org/10.1109/lcomm.2015.2412123.

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Leong, Lee Vien, et Kwang Yew Tan. « Volume-Delay Function in Trip Assignment ». Applied Mechanics and Materials 802 (octobre 2015) : 351–56. http://dx.doi.org/10.4028/www.scientific.net/amm.802.351.

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Four-stage demand models are the most popular travel demand forecasting models. Trip assignment which is the last stage in the four-stage demand modelling is a key element in travel demand forecasting process. Traffic assignment model is used to assign travel demands into the road network and predict network flows that are associated with future planning scenarios based on the estimates of link travel times. In order to calculate travel time between origin and destination, a function presenting the relationship between link delays and link flows is used. This function is known as Volume-Delay Function (VDF) and it is the fundamental component of equilibrium trip assignment models. This study aims to investigate and improve VDFs for heterogeneous traffic at different type of arterial roads in Malaysia by using the road network in Balik Pulau, Penang as a case study. Primary data such as traffic volume and speed are collected at three types of arterial roads, which are the principal arterial, minor arterial and collectors to derive the parameters required in the VDFs. In this study, the most well-known and most widely-used volume-delay function which is known as the BPR function developed by the U.S. Bureau of Public Roads was investigated and calibrated using the transportation planning software, EMME 4.1.3. The calibrated functions are then validated with field data. The output from this research is very important as better understanding of VDFs can produce better estimate of link travel times and hence better planning for future scenarios.

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Detollenaere, Jens, Amelie Van Pottelberge, Lise Hanssens, Wienke Boerma, Stefan Greß et Sara Willems. « Patients’ Financially Driven Delay of GP Visits : Is It Less Likely to Occur in Stronger Primary Care Systems ? » Medical Care Research and Review 75, n^o 3 (6 décembre 2016) : 292–311. http://dx.doi.org/10.1177/1077558716682170.

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Available evidence has suggested that strong primary care (PC) systems are associated with better outcomes. This study aims to investigate whether PC strength is specifically related to the prevalence of patients’ financially driven postponement of general practitioner (GP) care. Therefore, data from a cross-sectional multicountry study in 33 countries among GPs and their patients were analyzed using multilevel logistic regression modelling. According to the results, the variation between countries in the levels of patients’ postponement of seeking GP care for financial reasons was large. More than one third of these cross-country differences could be explained by characteristics of the health care system and the GP practices. In particular, PC systems with good accessibility and those systems that offer comprehensive care were associated with lower levels of financially driven delay. Consequently, we can conclude that well-organized PC systems can compensate for the negative influence of individual characteristics (socioeconomic position) on the care-seeking behaviors of patients.

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Zhang, Yanxia, Long Li, Junjian Huang et Yanjun Liu. « Stability and Hopf Bifurcation Analysis of a Vector-Borne Disease Model with Two Delays and Reinfection ». Computational and Mathematical Methods in Medicine 2021 (7 juin 2021) : 1–18. http://dx.doi.org/10.1155/2021/6648959.

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In this paper, a vector-borne disease model with two delays and reinfection is established and considered. First of all, the existence of the equilibrium of the system, under different cases of two delays, is discussed through analyzing the corresponding characteristic equation of the linear system. Some conditions that the system undergoes Hopf bifurcation at the endemic equilibrium are obtained. Furthermore, by employing the normal form method and the center manifold theorem for delay differential equations, some explicit formulas used to describe the properties of bifurcating periodic solutions are derived. Finally, the numerical examples and simulations are presented to verify our theoretical conclusions. Meanwhile, the influences of the degree of partial protection for recovered people acquired by a primary infection on the endemic equilibrium and the critical values of the two delays are analyzed.

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Leung, A. Y. T., H. X. Yang et P. Zhu. « Bifurcation of a Duffing Oscillator Having Nonlinear Fractional Derivative Feedback ». International Journal of Bifurcation and Chaos 24, n^o 03 (mars 2014) : 1450028. http://dx.doi.org/10.1142/s021812741450028x.

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Active feedback control is commonly used to attenuate undesired vibrations in vibrating machineries and structures, such as bridges, highways and aircrafts. In this paper, we investigate the primary resonance and 1/3 subharmonic resonance of a harmonically forced Duffing oscillator under fractional nonlinear feedback control. By means of the first order averaging method, slow flow equations governing the modulations of amplitude and phase of the oscillator are obtained. An approximate solution for the steady state periodic response is derived and its stability is determined by the Routh–Hurwitz criterion. We demonstrate that appropriate choices on the control strategies and feedback gains can delay or eliminate the undesired bifurcations and reduce the amplitude peak both of the primary and subharmonic resonances. Analytical results are verified by comparisons with the numerical integration results.

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Liu, Chunxia, Yan Yan et Wen-Quan Wang. « Application of nonlocal continuum theory to the primary resonance analysis of an axially loaded nano beam under time delay control ». Applied Mathematical Modelling 85 (septembre 2020) : 124–40. http://dx.doi.org/10.1016/j.apm.2020.03.039.

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Zeng, Liang. « Forecasting the primary energy consumption using a time delay grey model with fractional order accumulation ». Mathematical and Computer Modelling of Dynamical Systems 27, n^o 1 (2 janvier 2021) : 31–49. http://dx.doi.org/10.1080/13873954.2020.1859547.

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Gillies, R. G., G. C. Hussey, H. G. James, G. J. Sofko et D. André. « Modelling and observation of transionospheric propagation results from ISIS II in preparation for ePOP ». Annales Geophysicae 25, n^o 1 (1 février 2007) : 87–97. http://dx.doi.org/10.5194/angeo-25-87-2007.

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Abstract. The enhanced Polar Outflow Probe (ePOP) is scheduled to be launched as part of the Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer (CASSIOPE) satellite in early 2008. A Radio Receiver Instrument (RRI) on ePOP will receive HF transmissions from various ground-based transmitters. In preparation for the ePOP mission, data from a similar transionospheric experiment performed by the International Satellites for Ionospheric Studies (ISIS) II satellite has been studied. Prominent features in the received 9.303-MHz signal were periodic Faraday fading of signal intensity at rates up to 13 Hz and a time of arrival delay between the O- and X-modes of up to 0.8 ms. Both features occurred when the satellite was above or south of the Ottawa transmitter. Ionospheric models for ray tracing were constructed using both International Reference Ionosphere (IRI) profiles and local peak electron density values from ISIS ionograms. Values for fade rate and differential mode delay were computed and compared to the values observed in the ISIS II data. The computed values showed very good agreement to the observed values of both received signal parameters when the topside sounding foF2 values were used to scale IRI profiles, but not when strictly modelled IRI profiles were used. It was determined that the primary modifier of the received signal parameters was the foF2 density and not the shape of the profile. This dependence was due to refraction, at the 9.303-MHz signal frequency, causing the rays to travel larger distances near the peak density where essentially all the mode splitting occurred. This study should assist in interpretation of ePOP RRI data when they are available.

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Spillane, Emma, Shawn Walker et Christine McCourt. « Optimal time intervals for vaginal breech births : a case-control study ». NIHR Open Research 2 (16 septembre 2022) : 45. http://dx.doi.org/10.3310/nihropenres.13297.2.

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Background: Breech births are associated with a high rate of hypoxic injury, in part due to cord occlusion during emergence. Maximum time intervals and guidelines oriented toward earlier intervention have been proposed in a Physiological Breech Birth Algorithm. We wished to further test and refine the Algorithm for use in a clinical trial. Methods: We conducted a retrospective case-control study in a London teaching hospital, including 15 cases and 30 controls, during the period of April 2012 to April 2020. Our sample size was powered to test the hypothesis that exceeding recommended time limits is associated with neonatal admission or death. Data collected from intrapartum care records was analysed using SPSS v26 statistical software. Variables were intervals between the stages of labour and various stages of emergence (presenting part, buttocks, pelvis, arms, head). The chi-square test and odds ratios were used to determine association between exposure to the variables of interest and composite outcome. Multiple logistic regression was used to test the predictive value of delays defined as non-adherence the Algorithm. Results: Logistic regression modelling using the Algorithm time frames had an 86.8% accuracy, a sensitivity of 66.7% and a specificity of 92.3% for predicting the primary outcome. Delays between umbilicus and head >3 minutes (OR: 9.508 [95% CI: 1.390-65.046] p=0.022) and from buttocks on the perineum to head >7 minutes (OR: 6.682 [95% CI: 0.940-41.990] p=0.058) showed the most effect. Lengths of time until the first intervention were consistently longer among the cases. Delay in intervention was more common among cases than head or arm entrapment. Conclusion: Emergence taking longer than the limits recommended in the Physiological Breech Birth algorithm may be predictive of adverse outcomes. Some of this delay is potentially avoidable. Improved recognition of the boundaries of normality in vaginal breech births may help improve outcomes.

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Spillane, Emma, Shawn Walker et Christine McCourt. « Optimal time intervals for vaginal breech births : a case-control study ». NIHR Open Research 2 (4 août 2022) : 45. http://dx.doi.org/10.3310/nihropenres.13297.1.

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Background: Breech births are associated with a high rate of hypoxic injury, in part due to cord occlusion during emergence. Maximum time intervals and guidelines oriented toward earlier intervention have been proposed in a Physiological Breech Birth Algorithm. We wished to further test and refine the Algorithm for use in a clinical trial. Methods: We conducted a retrospective case-control study conducted in a London teaching hospital, including 15 cases and 30 controls, during the period of April 2012 to April 2020. Our sample size was powered to test the hypothesis that exceeding recommended time limits is associated with neonatal admission or death. Data collected from intrapartum care records was analysed using SPSS v26 statistical software. Variables were intervals between the stages of labour and various stages of emergence (presenting part, buttocks, pelvis, arms, head). The chi-square test and odds ratios were used to determine association between exposure to the variables of interest and composite outcome. Multiple logistic regression was used to test the predictive value of delays defined as non-adherence the Algorithm. Results: Logistic regression modelling using the Algorithm time frames had an 86.8% accuracy, a sensitivity of 66.7% and a specificity of 92.3% for predicting the primary outcome. Delays between umbilicus and head >3 minutes (OR: 9.508 [95% CI: 1.390-65.046] p=0.022) and from buttocks on the perineum to head >7 minutes (OR: 6.682 [95% CI: 0.940-41.990] p=0.058) showed the most effect. Lengths of time until the first intervention were consistently longer among the cases. Delay in intervention was more common among cases than head or arm entrapment. Conclusion: Emergence taking longer than the limits recommended in the Physiological Breech Birth algorithm is predictive of adverse outcomes. Some of this delay is potentially avoidable. Improved recognition of the boundaries of normality in vaginal breech births may help improve outcomes.

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Samaranayaka, Chamil, Ari Samaranayaka, Dave Barson et RK De Silva. « Factors influencing trends in trauma-associated orbital cavity reconstruction procedures and time delay : New Zealand national data 2000–2014 ». Trauma 20, n^o 4 (18 juillet 2017) : 258–67. http://dx.doi.org/10.1177/1460408617719477.

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Aim Surgical reconstructions of orbital fractures due to trauma are increasing worldwide. This study identifies characteristics of patients facing such procedures, possible causes for increasing trends, and factors associated with the duration from trauma to surgical procedures. Methods Trauma-related orbital reconstruction procedures in New Zealand over a 15-year period were identified from Ministry of Health hospital discharge data. Age-standardised rates for each year and age-specific rates for each gender were calculated using age, sex and year-specific population data from New Zealand population censuses. The contribution of these procedures to total trauma-related maxillofacial procedures was assessed. Descriptive statistics were used to identify demographic, trauma-related, and procedure-related characteristics associated with higher frequency and increasing trends. Characteristics independently associated with time delay from trauma to surgery were identified by multivariable Cox regression modelling. Results Orbital procedures are most common among males and the young to middle aged, and trends in frequency and rates of procedures are sharply increasing outnumbering other types of trauma-related maxillofacial procedures, with interpersonal violence being a major contributor to this increase. Younger age and higher number of injuries are associated with less time delay from injury to procedure while Asian ethnicity, motor vehicle accidents, non-maxillofacial primary diagnoses, and higher number of medical comorbidities are associated with longer delay. Conclusion The first three findings are consistent with international literature, and could be considered by policy makers when deriving preventive measures. The findings related to time delay are new and could contribute information towards forming clinical guidelines if similar patterns were identified elsewhere.

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Gutierrez-Amo, Ruben, Unai Fernandez-Gamiz, Iñigo Errasti et Ekaitz Zulueta. « Computational Modelling of Three Different Sub-Boundary Layer Vortex Generators on a Flat Plate ». Energies 11, n^o 11 (10 novembre 2018) : 3107. http://dx.doi.org/10.3390/en11113107.

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Flow separation is the source of several problems in a wind turbine including load fluctuations, lift losses, and vibrations. Vortex generators (VGs) are passive flow control devices used to delay flow separation, but their implementation may produce overload drag at the blade section where they are placed. In the current work, a computational model of different geometries of vortex generators placed on a flat plate has been carried out throughout fully meshed computational simulations using Reynolds Averaged Navier-Stokes (RANS) equations performed at a Reynolds number of R e θ = 2600 based on local boundary layer (BL) momentum thickness θ = 2.4 mm. A flow characterization of the wake behind the vortex generator has been done with the aim of evaluating the performance of three vortex generator geometries, namely Rectangular VG, Triangular VG, and Symmetrical VG NACA0012. The location of the primary vortex has been evaluated by the vertical and lateral trajectories and it has been found that for all analyzed VG geometries the primary vortex is developed below the boundary layer thickness δ = 20 mm for a similar vorticity level ( w x m a x ). Two innovative parameters have been developed in the present work for evaluating the vortex size and the vortex strength: Half-Life Surface S 05 and Mean Positive Circulation Γ 05 + . As a result, an assessment of the VG performance has been carried out by all analyzed parameters and the symmetrical vortex generator NACA0012 has provided good efficiency in energy transfer compared with the Rectangular VG.

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Chen, Mark IC, Iain BH Tan et Yih-Yng Ng. « Modelling the Utility of Body Temperature Readings From Primary Care Consults for SARS Surveillance in an Army Medical Centre ». Annals of the Academy of Medicine, Singapore 35, n^o 4 (15 avril 2006) : 236–41. http://dx.doi.org/10.47102/annals-acadmedsg.v35n4p236.

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Introduction: There is interest in surveillance systems for outbreak detection at stages where clinical presentation would still be undifferentiated. Such systems focus on detecting clusters of syndromes in excess of baseline levels, which may indicate an outbreak. We model the detection limits of a potential system based on primary care consults for the detection of an outbreak of severe acute respiratory syndrome (SARS). Materials and Methods: Data from an averaged-sized medical centre were extracted from the Patient Care Enhancement System (PACES) [the electronic medical records system serving the Singapore Armed Forces (SAF)]. Thresholds were set to 3 or more cases presenting with particular syndromes and a temperature reading of ≥38o C (T ≥38). Monte Carlo simulation was used to insert simulated SARS outbreaks of various sizes onto the background incidence of febrile cases, accounting for distribution of SARS incubation period, delay from onset to first consult, and likelihood of presenting with T ≥38 to the SAF medical centre. Results: Valid temperature data was available for 2012 out of 2305 eligible syndromic consults (87.2%). T ≥38 was observed in 166 consults (8.3%). Simulated outbreaks would peak 7 days after exposure, but, on average, signals at their peak would consist of 10.9% of entire outbreak size. Under baseline assumptions, the system has a higher than 90% chance of detecting an outbreak only with 20 or more cases. Conclusions: Surveillance based on clusters of cases with T ≥38 helps reduce background noise in primary care data, but the major limitation of such systems is that they are still only able to confidently detect large outbreaks. Key words: Communicable diseases, Emerging, Epidemiology, Military medicine, Syndrome

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Tiwari, Pankaj Kumar, Sudip Samanta, Jocirei D. Ferreira et Arvind Kumar Misra. « A Mathematical Model for the Effects of Nitrogen and Phosphorus on Algal Blooms ». International Journal of Bifurcation and Chaos 29, n^o 10 (septembre 2019) : 1950129. http://dx.doi.org/10.1142/s0218127419501293.

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The increase of nutrients in lakes typically stimulates the growth of algae in this environment. Therefore, it is important to understand the connection between nutrient concentration and algal biomass to manage the water pollution caused by excessive plant nutrients. It is worth observing that phosphorus and nitrogen are often considered as the principal limiting nutrients for aquatic algal production due to their short supply compared to cellular growth requirements. In freshwaters, phosphorus is the least abundant among the nutrients needed in large quantity by photosynthetic organisms, hence this is the primary nutrient that limits their growth. The purpose of this work is to compare the effects of nitrogen and phosphorus on the growth of algae in lakes. By using a sensitivity analysis technique, we found that the sources of phosphorus provide a greater risk for bloom of algae than that of nitrogen. Therefore, to reduce the occurrence of algal bloom more attention should be paid for the control of phosphorus input into the lake but the inflow of nitrogen cannot be ignored. The existence of a transcritical bifurcation is discussed and its direction is investigated by applying the projection method technique. Further, to make the system more realistic, time delay involved in the conversion of detritus into nutrients is considered. We show that for increasing values of time delay, the system undergoes an Andronov–Hopf-bifurcation. Some simulations are presented to verify the analytical findings. The results of our study can be helpful for the policy makers to mitigate algal blooms from lakes.

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Walker, J. J., F. Spiga, R. Gupta, Z. Zhao, S. L. Lightman et J. R. Terry. « Rapid intra-adrenal feedback regulation of glucocorticoid synthesis ». Journal of The Royal Society Interface 12, n^o 102 (janvier 2015) : 20140875. http://dx.doi.org/10.1098/rsif.2014.0875.

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The hypothalamic–pituitary–adrenal axis is a vital neuroendocrine system that regulates the secretion of glucocorticoid hormones from the adrenal glands. This system is characterized by a dynamic ultradian hormonal oscillation, and in addition is highly responsive to stressful stimuli. We have recently shown that a primary mechanism generating this ultradian rhythm is a systems-level interaction where adrenocorticotrophin hormone (ACTH) released from the pituitary stimulates the secretion of adrenal glucocorticoids, which in turn feedback at the level of the pituitary to rapidly inhibit ACTH secretion. In this study, we combine experimental physiology and mathematical modelling to investigate intra-adrenal mechanisms regulating glucocorticoid synthesis. Our modelling results suggest that glucocorticoids can inhibit their own synthesis through a very rapid (within minutes), presumably non-genomic, intra-adrenal pathway. We present further evidence for the existence of a short time delay in this intra-adrenal inhibition, and also that at the initiation of each ACTH stimulus, this local feedback mechanism is rapidly antagonized, presumably via activation of the specific ACTH receptor (MC2R) signalling pathway. This mechanism of intra-adrenal inhibition enables the gland to rapidly release glucocorticoids while at the same time preventing uncontrolled release of glucocorticoids in response to large surges in ACTH associated with stress.

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Yang, S., et R. D. Reitz. « Improved combustion submodels for modelling gasoline engines with the level set G equation and detailed chemical kinetics ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 223, n^o 5 (1 mai 2009) : 703–26. http://dx.doi.org/10.1243/09544070jauto1062.

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Five combustion submodels have been improved for modelling gasoline engines with the level set G equation and detailed chemical kinetics. These combustion submodels include a transport equation residual model, the introduction of a Damkohler criterion model for assessing the combustion regime of flame-containing cells, the precise calculation of ‘primary heat release’ based on the subgrid scale unburned or burned volumes of flame-containing cells, the modelling of flame front quenching in highly stratified mixtures, and a recently developed primary reference fuel (PRF) mechanism. In the transport equation residual model a fictitious species concept is introduced to account for the residual gases in the cylinder, which have a great effect on the laminar flame speed. The residual gases include carbon dioxide (CO2), water (H2O), and nitrogen (N2) remaining from the previous engine cycle or introduced using exhaust gas recirculation (EGR). This pseudo-species is described by a transport equation. The transport equation residual model differentiates between CO2 and H2O from the previous engine cycle or EGR and that which is from the combustion products of the current engine cycle. The Damkohler criterion model is based on a comparison between a laminar flame propagation timescale and the chemical kinetics timescale to determine whether the level set G-equation model or chemical kinetics should be used for assessing the combustion processes in flame-containing cells. The results from implementation of the Damkohler model range between the G-equation model and pure chemistry, depending on the conditions. The improved primary-heat-release calculation model precisely considers the chemical kinetics heat release in unburned regions of flame-containing cells and thus is thought to be physically reasonable. The simulation results show that the flame-front-quenching model effectively captures the flame quench phenomenon in highly stratified mixtures which are typical in gasoline direct-injection engines. Validation of the new PRF mechanism shows that the calculated ignition delay matches shock tube data very well over a wide range of conditions. The integrated model was used to simulate the combustion process in a gasoline turbocharged direct-injection engine, and the same set of combustion model parameters for both high loads and low loads were used. For both high-load and low-load operating conditions, good agreement with the experimental in-cylinder pressure, heat release rates, and mass fraction burned data was obtained.

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B A Sujatha Kumari, Ankitha D V, Anupama N, Keerthana D et Poonam K S. « Comparative Analysis of Network Parameters using Noxim Simulator ». international journal of engineering technology and management sciences 6, n^o 6 (28 novembre 2022) : 435–41. http://dx.doi.org/10.46647/ijetms.2022.v06i06.077.

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In the field of Network-on-Chip, simulation is one of the primary techniques used to examine and evaluate novel ideas. It is necessary to have simulation tools available that are frequently restricted to modelling particular network configurations in order to evaluate the performance and power figures of NoC and WiNoC systems. This article introduces Noxim, a SystemC-developed open, extendible, customizable, cycle-accurate NoC simulator that enables the analysis of the performance and power statistics of both established wired NoC and new WiNoC designs. The Noxim simulator stands out among the many simulators that can be discovered in the literature. A lot of scholars use it since it supports wifi and is open-source. Hybrid wired-wireless networks aim to combine the finest aspects of the two strategies. In this study, investigation on various optimal configurations are carried out considering various test scenarios. Different parameters like Throughput, delivered packets, delay, and battery consumption and Packet Injection Rate are considered for optimisation. The findings demonstrate that the test cases utilised only require a small number of wireless routers, enhancing the metrics desired.

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Fagergren, Anders, Örjan Ekeberg et Hans Forssberg. « Control Strategies Correcting Inaccurately Programmed Fingertip Forces : Model Predictions Derived From Human Behavior ». Journal of Neurophysiology 89, n^o 6 (juin 2003) : 2904–16. http://dx.doi.org/10.1152/jn.00939.2002.

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When picking up a familiar object between the index finger and the thumb, the motor commands are predetermined by the CNS to correspond to the frictional demand of the finger-object contact area. If the friction is less than expected, the object will start to slip out of the hand, giving rise to unexpected sensory information. Here we study the correction strategies of the motor system in response to an unexpected frictional demand. The motor commands to the mononeuron pool are estimated by a novel technique combining behavioral recordings and neuromuscular modelling. We first propose a mathematical model incorporating muscles, hand mechanics, and the action of lifting an object. A simple control system sends motor commands to and receives sensory signals from the model. We identify three factors influencing the efficiency of the correction: the time development of the motor command, the delay between the onset of the grip and load forces (GF-LF-delay), and how fast the lift is performed. A sensitivity analysis describes how these factors affect the ability to prevent or stop slipping and suggests an efficient control strategy that prepares and corrects for an altered frictional condition. We then analyzed fingertip grip and load forces (GF and LF) and position data from 200 lifts made by five healthy subjects. The friction was occasionally reduced, forcing an increase of the GF to prevent the object being dropped. The data were then analyzed by feeding it through the inverted model. This provided an estimate of the motor commands to the motoneuron pool. As suggested by the sensitivity analysis the GF-LF-delay was indeed used by the subjects to prevent slip. In agreement with recordings from neurons in the primary motor cortex of the monkey, a sharp burst in the estimated GF motor command (NGF) efficiently arrested any slip. The estimated motor commands indicate a control system that uses a small set of corrective commands, which together with the GF-LF-delay form efficient correction strategies. The selection of a strategy depends on the amount of tactile information reporting unexpected friction and how long it takes to arrive. We believe that this technique of estimating the motor commands behind the fingertip forces during a precision grip lift can provide a powerful tool for the investigation of the central control of the motor system.

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Yıldız Bölükbaşı, Esra, Sara Mumtaz, Muhammad Afzal, Ute Woehlbier, Sajid Malik et Aslıhan Tolun. « Homozygous mutation in CEP19, a gene mutated in morbid obesity, in Bardet-Biedl syndrome with predominant postaxial polydactyly ». Journal of Medical Genetics 55, n^o 3 (10 novembre 2017) : 189–97. http://dx.doi.org/10.1136/jmedgenet-2017-104758.

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BackgroundBardet-Biedl syndrome (BBS) is a ciliopathy with extensive phenotypic variability and genetic heterogeneity. We aimed to discover the gene mutated in a consanguineous kindred with multiple cases of a BBS phenotype.MethodsSNP genotype data were used for linkage analysis and exome sequencing to identify mutations. Modelling and in silico analysis were performed to predict mutation severity.ResultsPatients had postaxial polydactyly plus variable other clinical features including rod-cone dystrophy, obesity, intellectual disability, renal malformation, developmental delay, dental anomalies, speech disorder and enlarged fatty liver. The 4.57 Mb disease locus harboured homozygous, truncating CEP19 c.194_195insA (p.Tyr65*) mutation. We also found glioma-associated oncogene homolog 1(GLI1) c.820G>C (p.Gly274Arg) in the homozygous state in most patients. In silico modelling strongly suggests that it is damaging. Also, different combinations of four possible modifier alleles in BBS-related genes were detected. Two are known modifier alleles for BBS, splicing variant CCDC28B c.330C>T and missense MKKS/BBS6 p.Ile339Val, and the others are C8ORF37/BBS21 p.Ala178Val and TMEM67/BBS14 modifier p.Asp799Asp. Some patients carry all those five known/possible modifier alleles. Such variants are highly significantly more abundant in our patients than in a control group.ConclusionCEP19 encodes a centrosomal and ciliary protein, as all BBS genes do. Another truncating mutation p.Arg82* has been reported as responsible for morbid obesity in a family; however, in the family we present, not all homozygotes are obese, although some are severely obese. The variant in GLI1, encoding a transcription factor that localises to the primary cilium and nucleus and is a mediator of the sonic hedgehog pathway, possibly exacerbates disease severity when in the homozygous state.

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Malysz, Pawel, et Shahin Sirouspour. « Trilateral teleoperation control of kinematically redundant robotic manipulators ». International Journal of Robotics Research 30, n^o 13 (22 mars 2011) : 1643–64. http://dx.doi.org/10.1177/0278364911401053.

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Teleoperation control of kinematically redundant robots requires a strategy for resolving their redundancy. A trilateral two-master/one-slave control approach is proposed for delay-free applications in which the first master controls a primary task control frame, e.g. the slave end-effector frame; meanwhile, another master device can manipulate a secondary task frame attached to the slave robot, e.g. to avoid collision with obstacles in the task environment. Any remaining degrees of motion are resolved autonomously. Teleoperation control is achieved in three steps employing joint-space Lyapunov-based adaptive motion/force controllers, a velocity-level redundancy resolution method, and task-space coordinating reference commands. Priority can be given to either the primary or secondary control frame so that the high-priority task can be transparently carried out without interference from the other task. Whenever applicable, the lower-priority task control frame would be restricted to the natural constraints imposed by prioritization or otherwise, decoupling between the tasks is achieved with the use of an arbitrarily weighted pseudo-inverse. Experiments with a planar teleoperation system consisting of two master devices controlling a closed-chain four degree-of-motion redundant slave robot show the feasibility of the approach.

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Portal-Porras, Koldo, Unai Fernandez-Gamiz, Iñigo Aramendia, Daniel Teso-Fz-Betoño et Ekaitz Zulueta. « Testing the Accuracy of the Cell-Set Model Applied on Vane-Type Sub-Boundary Layer Vortex Generators ». Processes 9, n^o 3 (11 mars 2021) : 503. http://dx.doi.org/10.3390/pr9030503.

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Vortex Generators (VGs) are applied before the expected region of separation of the boundary layer in order to delay or remove the flow separation. Although their height is usually similar to that of the boundary layer, in some applications, lower VGs are used, Sub-Boundary Layer Vortex Generators (SBVGs), since this reduces the drag coefficient. Numerical simulations of sub-boundary layer vane-type vortex generators on a flat plate in a negligible pressure gradient flow were conducted using the fully resolved mesh model and the cell-set model, with the aim on assessing the accuracy of the cell-set model with Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) turbulence modelling techniques. The implementation of the cell-set model has supposed savings of the 40% in terms of computational time. The vortexes generated on the wake behind the VG; vortical structure of the primary vortex; and its path, size, strength, and produced wall shear stress have been studied. The results show good agreements between meshing models in the higher VGs, but slight discrepancies on the lower ones. These disparities are more pronounced with LES. Further study of the cell-set model is proposed, since its implementation entails great computational time and resources savings.

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Freeman, Walter J. « A Neurobiological Theory of Meaning in Perception Part II : Spatial Patterns of Phase in Gamma EEGs from Primary Sensory Cortices Reveal the Dynamics of Mesoscopic Wave Packets ». International Journal of Bifurcation and Chaos 13, n^o 09 (septembre 2003) : 2513–35. http://dx.doi.org/10.1142/s0218127403008156.

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Domains of cooperative neural activity called "wave packets" have been discovered in the visual, auditory, and somatomotor cortices of rabbits that were trained to discriminate conditioned stimuli in these modalities. Each domain forms by a first order state transition, which strongly resembles a phase transition from vapor to liquid. In this view, raw sense data injected into cortex by sensory axons drive cortical action potentials in swarms like water molecules in steam. The increased activity destabilizes the cortex. Within 3 to 7 milliseconds of transition onset, the activity binds together into a state resembling a scintillating rain drop, which lasts ~80 to 100 milliseconds, then dissolves. Wave packets form at rates of 2 to 7/second in all sensory areas, overlapping in space and time. Results of sensory information processing are seen in spatial patterns of amplitude modulation (AM) of wave packets with carrier waves in the gamma range (20 to 80 Hz in rabbits). The AM patterns correspond to categories of CSs that the rabbits can discriminate. The patterns are found in electroencephalographic (EEG) potentials generated by dendrites and recorded with high-density electrode arrays. The state transitions by which AM patterns form are manifested in the spatial pattern of phase modulation (PM), which have the radial symmetry of a cone. The apex of a PM cone marks the site of nucleation of an AM pattern. The phase gradient gives a soft boundary condition, where the axonal delay in spread gives sufficient phase dispersion to reach the half-power level. The size of the wave packets (10 to 30 mm in diameter in rabbits) is determined largely by the conduction velocities of intracortical axons through which the neural cooperation is maintained. The findings show that significant cortical activity takes the form of mesoscopic interactions of millions of neurons in broad areas of cortex, which are more clearly detected in graded dendritic potentials than in action potentials. The distinction is analogous to the difference between statistical mechanical and thermodynamic descriptions of particle behavior. Both types of neural activity show spatial and temporal discontinuities but at distinctive scales of microns and msec versus mm and tenths of a second. The aim of measurement here is to establish the wave packet as the information carrier at the mesoscopic level in brain dynamics, comparable to the role of the action potential as the information carrier at the microscopic level in neuron dynamics.

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Grazia, Carlo Augusto, Natale Patriciello, Martin Klapez et Maurizio Casoni. « Transmission Control Protocol and Active Queue Management together against congestion : cross-comparison through simulations ». SIMULATION 95, n^o 10 (30 novembre 2018) : 979–93. http://dx.doi.org/10.1177/0037549718814626.

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Most Internet traffic is carried by the Transmission Control Protocol (TCP) nowadays, even in the case of real-time services. Detecting and mitigating the congestion is one of the primary tasks of this protocol, in fact, different TCP versions are defined by their congestion control algorithms. Furthermore, Active Queue Management (AQM) algorithms share the same goal of congestion mitigation with TCP; in particular, the most efficient congestion control occurs when AQM and TCP work together. This paper presents a brief survey and a cross-comparison of the latest and most important TCP and AQM variants, then provides an evaluation of a different kind of performance on the ns-3 network simulator over various types of environments (multiple Round Trip Time, long delay, different congestion levels, etc.). In any shared bottleneck, the choice of the TCP-AQM couple to adopt is crucial. We will show that the results are not univocal and the “one size fits all” solution does not exist. Moreover, the proper couple depends on the performance that we want to boost and on the environment that we have to deal with.

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Monk, Ruth, et Bronwen Connor. « Cell Reprogramming to Model Huntington’s Disease : A Comprehensive Review ». Cells 10, n^o 7 (22 juin 2021) : 1565. http://dx.doi.org/10.3390/cells10071565.

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Huntington’s disease (HD) is a neurodegenerative disorder characterized by the progressive decline of motor, cognitive, and psychiatric functions. HD results from an autosomal dominant mutation that causes a trinucleotide CAG repeat expansion and the production of mutant Huntingtin protein (mHTT). This results in the initial selective and progressive loss of medium spiny neurons (MSNs) in the striatum before progressing to involve the whole brain. There are currently no effective treatments to prevent or delay the progression of HD as knowledge into the mechanisms driving the selective degeneration of MSNs has been hindered by a lack of access to live neurons from individuals with HD. The invention of cell reprogramming provides a revolutionary technique for the study, and potential treatment, of neurological conditions. Cell reprogramming technologies allow for the generation of live disease-affected neurons from patients with neurological conditions, becoming a primary technique for modelling these conditions in vitro. The ability to generate HD-affected neurons has widespread applications for investigating the pathogenesis of HD, the identification of new therapeutic targets, and for high-throughput drug screening. Cell reprogramming also offers a potential autologous source of cells for HD cell replacement therapy. This review provides a comprehensive analysis of the use of cell reprogramming to model HD and a discussion on recent advancements in cell reprogramming technologies that will benefit the HD field.

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Shi, Xi, Jian Sun et Zijun Xiao. « Investigation on River Thermal Regime under Dam Influence by Integrating Remote Sensing and Water Temperature Model ». Water 13, n^o 2 (8 janvier 2021) : 133. http://dx.doi.org/10.3390/w13020133.

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River water temperature (RWT), a primary parameter for hydrological and ecological processes, is influenced by both climate change and anthropogenic intervention. Studies on such influences have been severely restricted due to the scarcity of river temperature data. This paper proposed a three-stage method to obtain long-term daily water temperature for rivers and river-type reservoirs by integrating remote sensing technique and river water temperature modelling. The proposed three-stage method was applied to the Three Gorges Reservoir (TGR) and validated against in situ measured RWTs in the two study sites, Cuntan and Huanglingmiao. The result showed improvements in the method: the quadrate window selection and RWT correction jointly reduce RMSE from 1.8 to 0.9 °C in Cuntan and from 2.1 to 1.2 °C in Huanglingmiao. As a whole, the estimated daily RWT has a consistent RMSE of 1.1–1.9 °C. Meanwhile, by analysing the Landsat-derived daily RWT, we demonstrated that the TGR had a significant impact on the outflow’s thermal regime. At the downstream reach of TGR, an apparent increase in RWT in the cold season and interannual thermal regime delay compared to inflow were found with the increasing water level after the dam construction. All the results and analyses indicate that the proposed three-stage method could be applied to obtain long time series of daily RWT and provide a promising approach to qualitatively analyse RWT variation in the poorly gauged catchment for river water quality monitoring and management.

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Shi, Xi, Jian Sun et Zijun Xiao. « Investigation on River Thermal Regime under Dam Influence by Integrating Remote Sensing and Water Temperature Model ». Water 13, n^o 2 (8 janvier 2021) : 133. http://dx.doi.org/10.3390/w13020133.

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River water temperature (RWT), a primary parameter for hydrological and ecological processes, is influenced by both climate change and anthropogenic intervention. Studies on such influences have been severely restricted due to the scarcity of river temperature data. This paper proposed a three-stage method to obtain long-term daily water temperature for rivers and river-type reservoirs by integrating remote sensing technique and river water temperature modelling. The proposed three-stage method was applied to the Three Gorges Reservoir (TGR) and validated against in situ measured RWTs in the two study sites, Cuntan and Huanglingmiao. The result showed improvements in the method: the quadrate window selection and RWT correction jointly reduce RMSE from 1.8 to 0.9 °C in Cuntan and from 2.1 to 1.2 °C in Huanglingmiao. As a whole, the estimated daily RWT has a consistent RMSE of 1.1–1.9 °C. Meanwhile, by analysing the Landsat-derived daily RWT, we demonstrated that the TGR had a significant impact on the outflow’s thermal regime. At the downstream reach of TGR, an apparent increase in RWT in the cold season and interannual thermal regime delay compared to inflow were found with the increasing water level after the dam construction. All the results and analyses indicate that the proposed three-stage method could be applied to obtain long time series of daily RWT and provide a promising approach to qualitatively analyse RWT variation in the poorly gauged catchment for river water quality monitoring and management.

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Mazauric, Anne-Laure, Pierre Sciora, Vincent Pascal, Jean-Baptiste Droin, Yvon Bésanger, Nouredine Hadjsaïd et Quoc Tuan Tran. « Approach for the adaptations of a nuclear reactor model towards more flexibility in a context of high insertion of renewable energies ». EPJ Nuclear Sciences & ; Technologies 8 (2022) : 15. http://dx.doi.org/10.1051/epjn/2022005.

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The massive penetration of renewable energy sources (RES) that are variable and not “dispatchable”, may weaken the power system supply-demand balance. Nuclear power plants (NPP) contribute in part to this daily and seasonal balance thanks to the “load-following” mode in France for example, but there are still limits to their use. These limits prevent a nuclear power modulation as efficient and quickly as the conventional thermal power plants. The need in terms of power ramps for nuclear in a constrained power system has been quantified in previous studies. Nuclear may compensate for the removal of thermal power plants, in order to fulfill energetic strategies of CO2 reduction. The possibility that nuclear reactors can achieve power ramps of significant values (>5%Pn/min) is put forward and could make possible to replace the services currently provided by thermal power plants. The objective of the study is then to use these power system requirements as the main input parameter for the modelling of a current simplified nuclear reactor capable of responding to frequency control within a specific hypothesis framework. In this paper, a French 1300 MW pressurized water reactor is modelled. Parametric studies are carried out in order to reveal technical and technological constraints when increasing electric power ramp. The study explores ways of design, which may influence reactor flexibility, such as the neutron parameter, Doppler coefficient, or the thermohydraulic parameter, delay in the primary loop.

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Romeyn, Rowan, Alfred Hanssen, Bent Ole Ruud, Helene Meling Stemland et Tor Arne Johansen. « Passive seismic recording of cryoseisms in Adventdalen, Svalbard ». Cryosphere 15, n^o 1 (20 janvier 2021) : 283–302. http://dx.doi.org/10.5194/tc-15-283-2021.

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Abstract. A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by cross-correlation beamforming dispersion imaging. The dispersion images are highly analogous to surface wave studies of pavements and display a complex multimodal dispersion pattern. Supported by theoretical modelling based on a highly simplified arrangement of horizontal layers, we infer that a ∼3.5–4.5 m thick, stiff, high-velocity layer overlies a ∼30 m thick layer that is significantly softer and slower at our study site. Based on previous studies we link the upper layer with syngenetic ground ice formed in aeolian sediments, while the underlying layer is linked to epigenetic permafrost in marine-deltaic sediments containing unfrozen saline pore water. Comparing events from spring and autumn indicates that temporal variation can be resolved via passive seismic monitoring. The transient seismic events that we record occur during periods of rapidly changing air temperature. This correlation, along with the spatial clustering along the elevated river terrace in a known frost polygon, ice-wedge area and the high proportion of surface wave energy, constitutes the primary evidence for us to interpret these events as frost quakes, a class of cryoseism. In this study we have proved the concept of passive seismic monitoring of permafrost in Adventdalen, Svalbard.

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Jin, Tae-Hwan, Ki-Yeol Shin, Mo Chung et Geon-Pyo Lim. « Development and Performance Verification of Frequency Control Algorithm and Hardware Controller Using Real-Time Cyber Physical System Simulator ». Energies 15, n^o 15 (6 août 2022) : 5722. http://dx.doi.org/10.3390/en15155722.

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Frequency stability is a critical factor in maintaining the quality of the power grid system. A battery energy storage system (BESS) with quick response and flexibility has recently been used as a primary frequency control (PFC) resource, and many studies on its control algorithms have been conducted. The cyber physic system (CPS) simulator, which can perform virtual physical modelling and verification of many hardware systems connected to the network, is an optimal solution for the performance verification of control algorithms and hardware systems. This study introduces a large-scale real-time dynamic simulator that includes the national power system. This simulator comprises a power grid model, an energy management system (EMS) model, a BESS system model, and a communication model. It performs the control algorithm performance evaluation and the hardware controller’s response performance evaluation. The performance of the control algorithm was evaluated by tracking the power system’s characteristic trajectory in the transient state based on the physical response delay time between the output instruction of the frequency regulation controller (FRC), a hardware controller, and the output response of the BESS. Based on this, we examined the response performance evaluation results by linking them to the optimally designed actual FRC. As a result, we present an analysis of the BESS’s characteristic trajectories in the transient state, such as frequency, power system inertia, and power grid constant, and provide FRC response performance evaluation results at a level of 163 ms, by connecting the BESS installed at the actual site with the CPS simulator.

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Akhtar, Mansoor, Mohamed Boshnaq et Sathyan Nagendram. « Quality improvement measures : effects on rectal cancer tissue biopsy process ». International Journal of Health Care Quality Assurance 31, n^o 7 (13 août 2018) : 775–83. http://dx.doi.org/10.1108/ijhcqa-06-2017-0097.

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Purpose Delay in histologically confirming rectal cancer may lead to late treatment as histological confirmation is required prior to chemo-radiotherapy or surgical intervention. Multidisciplinary colorectal meetings indicate that there are patients who require multiple tissue biopsy episodes prior to histologically confirming rectal cancer. The purpose of this paper is to examine a quality improvement (QI) measure’s impact on tissue biopsy process diagnostic yield. Design/methodology/approach The authors performed the study in two phases (pre- and post-QI), between February 2012 and April 2014 in a district general hospital. The QI measures were derived from process mapping a rectal cancer diagnostic pathway. The primary outcome was to assess the tissue biopsy process diagnostic yield. The secondary outcome included total breaches for a 62-day target in the pre- and post-QI study phases. Findings There was no significant difference in demographics or referral mode in both study phases. There were 81 patients in the pre-QI phase compared to 38 in the post-QI phase, 68 per cent and 74 per cent were referred via the two-week wait urgent pathway, respectively. Diagnostic tissue biopsy process yield improved from 58.1 to 77.6 per cent after implementing the QI measure (p=0.02). The 62-day target breach was reduced from 14.8 to 3.5 per cent (p=0.42). Practical implications Simple QI measures can achieve significant improvements in rectal cancer diagnostic tissue biopsy process yields. A multidisciplinary approach, involving process mapping and cause and effect modelling, proved useful tools. Originality/value A process mapping exercise and QI measures resulted in significant improvements in diagnostic yield, reducing the episodes per patient before histological diagnosis was confirmed.

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Maas, Willemijn J., Maarten M. H. Lahr, Maarten Uyttenboogaart, Erik Buskens et Durk-Jouke van der Zee. « Expediting workflow in the acute stroke pathway for endovascular thrombectomy in the northern Netherlands : a simulation model ». BMJ Open 12, n^o 4 (avril 2022) : e056415. http://dx.doi.org/10.1136/bmjopen-2021-056415.

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ObjectiveThe objective of this study is to identify barriers for the timely delivery of endovascular thrombectomy (EVT) and to investigate the effects of potential workflow improvements in the acute stroke pathway.DesignHospital data prospectively collected in the MR CLEAN Registry were linked to emergency medical services data for each EVT patient and used to build two Monte Carlo simulation models. The ‘mothership (MS) model’, reflecting patients who arrived directly at the comprehensive stroke centre (CSC); and the ‘drip and ship’ (DS) model, reflecting patients who were transferred to the CSC from primary stroke centres (PSCs).SettingNorthern region of the Netherlands. One CSC provides EVT, and its catchment area includes eight PSCs.Participants248 patients who were treated with EVT between July 2014 and November 2017.Outcome measuresThe main outcome measures were total delay from stroke onset until groin puncture, functional independence at 90 days (modified Rankin Scale 0–2) and mortality.ResultsBarriers identified included fast-track emergency department routing, prealert for transfer to the CSC, reduced handover time between PSC and ambulance, direct transfer from CSC arrival to angiography suite entry, and reducing time to groin puncture. Taken together, all workflow improvements could potentially reduce the time from onset to groin puncture by 59 min for the MS model and 61 min for the DS model. These improvements could thus result in more patients—3.7% MS and 7.4% DS—regaining functional independence after 90 days, in addition to decreasing mortality by 3.0% and 5.0%, respectively.ConclusionsIn our region, the proposed workflow improvements might reduce time to treatment by about 1 hour and increase the number of patients regaining functional independence by 6%. Simulation modelling is useful for assessing the potential effects of interventions aimed at reducing time from onset to EVT.

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Huntingford, Chris, Rebecca J. Oliver, Lina M. Mercado et Stephen Sitch. « Technical note : A simple theoretical model framework to describe plant stomatal “sluggishness” in response to elevated ozone concentrations ». Biogeosciences 15, n^o 17 (12 septembre 2018) : 5415–22. http://dx.doi.org/10.5194/bg-15-5415-2018.

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Abstract. Elevated levels of tropospheric ozone, O3, cause damage to terrestrial vegetation, affecting leaf stomatal functioning and reducing photosynthesis. Climatic impacts under future raised atmospheric greenhouse gas (GHG) concentrations will also impact on the net primary productivity (NPP) of vegetation, which might for instance alter viability of some crops. Together, ozone damage and climate change may adjust the current ability of terrestrial vegetation to offset a significant fraction of carbon dioxide (CO2) emissions. Climate impacts on the land surface are well studied, but arguably large-scale modelling of raised surface level O3 effects is less advanced. To date most models representing ozone damage use either O3 concentration or, more recently, flux-uptake-related reduction of stomatal opening, estimating suppressed land–atmosphere water and CO2 fluxes. However there is evidence that, for some species, O3 damage can also cause an inertial “sluggishness” of stomatal response to changing surface meteorological conditions. In some circumstances (e.g. droughts), this loss of stomata control can cause them to be more open than without ozone interference. To both aid model development and provide empiricists with a system on to which measurements can be mapped, we present a parameter-sparse framework specifically designed to capture sluggishness. This contains a single time-delay parameter τO3, characterizing the timescale for stomata to catch up with the level of opening they would have without damage. The larger the value of this parameter, the more sluggish the modelled stomatal response. Through variation of τO3, we find it is possible to have qualitatively similar responses to factorial experiments with and without raised O3, when comparing to reported measurement time series presented in the literature. This low-parameter approach lends itself to the inclusion of ozone-induced inertial effects being incorporated in the terrestrial vegetation component of Earth system models (ESMs).

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Squire, Geoffrey R., Mark W. Young et Cathy Hawes. « Solar Radiation Flux Provides a Method of Quantifying Weed-Crop Balance in Present and Future Climates ». Plants 10, n^o 12 (3 décembre 2021) : 2657. http://dx.doi.org/10.3390/plants10122657.

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A systematic approach to quantifying the weed–crop balance through the flux of solar radiation was developed and tested on commercial fields in a long-established Atlantic zone cropland. Measuring and modelling solar energy flux in crop stands has become standard practice in analysis and comparison of crop growth and yield across regions, species and years. In a similar manner, the partitioning of incoming radiation between crops and the in-field plant community may provide ‘common currencies’ through which to quantify positive and negative effects of weeds in relation to global change. Here, possibilities were explored for converting simple ground-cover measures in commercial fields of winter and spring oilseed rape in eastern Scotland, UK to metrics of solar flux. Solar radiation intercepted by the crops ranged with season and sowing delay from 129 to 1975 MJ m−2 (15-fold). Radiation transmitted through the crop, together with local weed management, resulted in a 70-fold range of weed intercepted radiation (14.2 to 963 MJ m−2), which in turn explained 93% of the corresponding between-site variation in weed dry mass (6.36 to 459 g m−2). Transmitted radiation explained almost 90% of the variation in number of weed species per field (12 to 40). The conversion of intercepted radiation to weed dry matter was far less variable at a mean of 0.74 g MJ−1 at both winter and spring sites. The primary cause of variation was an interaction between the temperature at sowing and the annual wave of incoming solar radiation. The high degree of explanatory power in solar flux indicates its potential use as an initial predictor and subsequent monitoring tool in the face of future change in climate and cropping intensity.

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Ivanković, Igor, Ksenija Žubrinić-Kostović, Ana Kekelj, Zoran Bunčeć, Per Andersson et Jan Eric Larsson. « Advanced and Rapid Tool in Control Room to Determine the Cause and Location of Events in Transmission Network ». Journal of Energy - Energija 69, n^o 4 (30 décembre 2020) : 25–29. http://dx.doi.org/10.37798/202069449.

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Operating personnel in control room act on SCADA alarm generated on data from station computer. Using new technologies and advanced technical solutions assistance tool can be designed. This tool provides quick help in busy situations for operator. For this new tool with three types of case studies insight will be given in this paper. Introduction part has short information about numbers of alarms and events in Control centre, and their distribution during one month period. Basic principles for alarm handling in SCADA system is given with all limitations. New tool, Intelligent Alarm Processing system is designed and implemented in control room. It has connection to SCADA system with standard data exchange format CIM/XML and run in real time, with only few seconds delay. This system based on Multilevel Flow Model has root cause analyses implemented for power system. Detail fault location algorithm description with block scheme for this Intelligent Alarm Processing system is part of third chapter. Special attention must be paid for modelling protection data in SCADA system which are sent to this new tool. Demonstration of Intelligent Alarm Processing system operation is reported in fourth chapter. Three characteristic disturbances in transmission network were elaborated. Most complex and challenging disturbances for operator in control room is cascading event. This case study is presented in detail in four sequences through graphical user interface. Second case study is also challenging for operators, heavy winter storm with numerous isolated events. In this case study very effective graphical presentation and alarm list with three types, primary event, consequences and detail list for this events were demonstrated. This list pointed out exactly and clearly what happened in the network. Last case study presents common disturbances which appears on daily basis, where this tool is of great assistance because it points on transmission elements very fast.

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Pęczkowski, Grzegorz, Tomasz Kowalczyk, Katarzyna Szawernoga, Wojciech Orzepowski, Romuald Żmuda et Ryszard Pokładek. « Hydrological Performance and Runoff Water Quality of Experimental Green Roofs ». Water 10, n^o 9 (4 septembre 2018) : 1185. http://dx.doi.org/10.3390/w10091185.

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Within the scope of the conducted experiment the authors analysed the efficiency of runoff reduction by the system of extensive type green roofs. The observations were based on storm events in the area of Lower Silesia at the Agro and Hydrometeorology Station Wrocław-Swojec. The authors analysed the thickness of plant substrate, and also estimated the quality of runoff waters under the conditions of periodic atmospheric deposition. Also considered were such indicators as electrolytic conductivity, N, NO3−, NO2−, NH4+, P, PO43−. The experiment included roof substrates designed in two variants, with known hydraulic and physical properties of the soil material. The analysis was performed for models with vegetation layer based on pumice and zelolite, covered with five plant species from the sedum family. The modelling of the hydraulic properties was conducted with variably saturated medium, using the Hydrus 1D software. The performance of systems with primary layer thickness of 11 cm and 9, 8, 7, 6 and 5 cm was estimated. The designed models reduced the average peak flows to 89%, and in addition they caused a delay in the initiation of the runoff which was dependent on the intensity and distribution of rainfalls in time, and on the initial moisture of the profiles. Simulations, performed for variable substrate thickness, permit the conclusion that in the case of thin-layer profiles (5 cm), the relative retention index was decidedly lower and amounted to 35.9% for the substrate with zeolite (originally 60.6%) and 41% for the substrate with pumice (originally 65.7%). In the case of total nitrogen and phosphates, statistical analysis revealed significant differences (p < 0.05) in relation to specific concentrations in the rainwater and in the control surface. The total nitrogen in the runoff from the green roof was nearly twice as high as that in the rainwater and amounted to, on average, 8.3 mg L−1.

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Henze, Larissa, Uwe Walter, Hugo Murua Escobar, Christian Junghanss, Robert Jaster, Rüdiger Köhling, Falko Lange et al. « Towards biomarkers for outcomes after pancreatic ductal adenocarcinoma and ischaemic stroke, with focus on (co)-morbidity and ageing/cellular senescence (SASKit) : protocol for a prospective cohort study ». BMJ Open 10, n^o 12 (décembre 2020) : e039560. http://dx.doi.org/10.1136/bmjopen-2020-039560.

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IntroductionAgeing-related processes such as cellular senescence are believed to underlie the accumulation of diseases in time, causing (co)morbidity, including cancer, thromboembolism and stroke. Interfering with these processes may delay, stop or reverse morbidity. The aim of this study is to investigate the link between (co)morbidity and ageing by exploring biomarkers and molecular mechanisms of disease-triggered deterioration in patients with pancreatic ductal adenocarcinoma (PDAC) and (thromboembolic) ischaemic stroke (IS).Methods and analysisWe will recruit 50 patients with PDAC, 50 patients with (thromboembolic) IS and 50 controls at Rostock University Medical Center, Germany. We will gather routine blood data, clinical performance measurements and patient-reported outcomes at up to seven points in time, alongside in-depth transcriptomics and proteomics at two of the early time points. Aiming for clinically relevant biomarkers, the primary outcome is a composite of probable sarcopenia, clinical performance (described by ECOG Performance Status for patients with PDAC and the Modified Rankin Scale for patients with stroke) and quality of life. Further outcomes cover other aspects of morbidity such as cognitive decline and of comorbidity such as vascular or cancerous events. The data analysis is comprehensive in that it includes biostatistics and machine learning, both following standard role models and additional explorative approaches. Prognostic and predictive biomarkers for interventions addressing senescence may become available if the biomarkers that we find are specifically related to ageing/cellular senescence. Similarly, diagnostic biomarkers will be explored. Our findings will require validation in independent studies, and our dataset shall be useful to validate the findings of other studies. In some of the explorative analyses, we shall include insights from systems biology modelling as well as insights from preclinical animal models. We anticipate that our detailed study protocol and data analysis plan may also guide other biomarker exploration trials.Ethics and disseminationThe study was approved by the local ethics committee (Ethikkommission an der Medizinischen Fakultät der Universität Rostock, A2019-0174), registered at the German Clinical Trials Register (DRKS00021184), and results will be published following standard guidelines.

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Speak, Thomas H., Mark A. Blitz, Daniel Stone et Paul W. Seakins. « A new instrument for time-resolved measurement of HO<sub>2</sub> ; radicals ». Atmospheric Measurement Techniques 13, n^o 2 (20 février 2020) : 839–52. http://dx.doi.org/10.5194/amt-13-839-2020.

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Abstract. OH and HO2 radicals are closely coupled in the atmospheric oxidation and combustion of volatile organic compounds (VOCs). Simultaneous measurement of HO2 yields and OH kinetics can provide the ability to assign site-specific rate coefficients that are important for understanding the oxidation mechanisms of VOCs. By coupling a fluorescence assay by gaseous expansion (FAGE) laser-induced fluorescence (LIF) detection system for OH and HO2 with a high-pressure laser flash photolysis system, it is possible to accurately measure OH pseudo-1st-order loss processes up to ∼100 000 s−1 and to determine HO2 yields via time-resolved measurements. This time resolution allows discrimination between primary HO2 from the target reaction and secondary production from side reactions. The apparatus was characterized by measuring yields from the reactions of OH with H2O2 (1:1 link between OH and HO2), with C2H4∕O2 (where secondary chemistry can generate HO2), with C2H6∕O2 (where there should be zero HO2 yield), and with CH3OH∕O2 (where there is a well-defined HO2 yield). As an application of the new instrument, the reaction of OH with n-butanol has been studied at 293 and 616 K. The bimolecular rate coefficient at 293 K, (9.24±0.21)×10-12 cm3 molec.−1 s−1, is in good agreement with recent literature, verifying that this instrument can measure accurate OH kinetics. At 616 K the regeneration of OH in the absence of O2, from the decomposition of the β-hydroxy radical, was observed, which allowed the determination of the fraction of OH reacting at the β site (0.23±0.04). Direct observation of the HO2 product in the presence of oxygen has allowed the assignment of the α-branching fractions (0.57±0.06) at 293 K and (0.54±0.04) at 616 K, again in good agreement with recent literature; branching ratios are key to modelling the ignition delay times of this potential “drop-in” biofuel.

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Meisinger, Christa, Jakob Linseisen, Inge Kirchberger, Wolfgang von Scheidt et Thomas M. Berghaus. « Long-term outcomes in patients with acute pulmonary embolism after in-hospital treatment : study protocol of the prospective Lungenembolie Augsburg Studie (LEA study) ». BMJ Open 9, n^o 10 (octobre 2019) : e031411. http://dx.doi.org/10.1136/bmjopen-2019-031411.

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IntroductionAcute pulmonary embolism (PE) is a frequent life-threatening event and an important cause of hospitalisation, morbidity and mortality worldwide. Limited information on the long-term course of PE patients is available so far. The Lungenembolie Augsburg study will provide a view on the predisposing and PE-provoking factors, diagnostic procedures and short as well as long-term treatment options. Especially, the data on the long-term course of the disease—in combination with omics data obtained in biospecimens—will generate new knowledge regarding triggers, disease progression, treatment, long-term sequelae, prognosis and prevention of disease recurrence.Methods and analysisIn this prospective study, we will include about 1000 patients admitted to the university hospital of Augsburg, aged 18 years and older with a confirmed diagnosis of acute PE. At baseline, demographic information, symptoms on presentation, delay in diagnosis, predisposing and PE-provoking factors, comorbidity, quality of life, symptoms of anxiety and depression, information on invasive and non-invasive treatment procedures, complications and laboratory parameters will be collected. During the hospital stay, 30 mL blood will be collected from the patients, processed, aliquoted and frozen at −80°C. In a subgroup of patients, an eight-channel polygraphy will be carried out to assess sleep-disordered breathing. All study participants will be followed up for 60 months via postal questionnaires or telephone interviews after hospital discharge. Long-term survival, bleeding complications and PE recurrence during the follow-up are the primary study outcomes. To identify risk factors and determinants associated with these outcomes, confounder-adjusted Cox-regressions will be used for modelling and to estimate relative risks. Effect modification by age and sex will be examined.Ethics and disseminationThe study protocol was approved by the Ethics Committee of the Ludwig-Maximilians-Universität München (Date of approval: 1 August 2017, Reference number: 17-378). Study results will be presented at national and international conferences and published in peer-reviewed scientific journals.

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Avcioglu, E., S. Sözen, D. Orhon et M. C. M. van Loosdrecht. « Experimental assessment and modelling of nitrate utilisation for primary sludge ». Water Science and Technology 46, n^o 1-2 (1 juillet 2002) : 313–17. http://dx.doi.org/10.2166/wst.2002.0494.

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Electron acceptor utilisation potential of filtered primary sludge under anoxic conditions was experimentally investigated. Major kinetic and stoichiometric parameters were assessed by means of model evaluation of nitrate profile obtained in batch reactors. ASM1, modified for endogenous decay, and ASM3 were used for model simulation. Both models provided consistent interpretation of experimental data. ASM1 yielded μ`H and YHD values of 6.1 d−1 and 0.64 g cell COD(g COD)−1 respectively for heterotrophic anoxic growth. The corresponding storage mechanism associated with ASM3 could be characterised by a kSTO of 13 g COD (g COD d)−1 and a YSTO of 0.78 g COD(g COD)−1. The high kSTO value suggests re-evaluation of the concept of readily biodegradable substrate as defined in ASM3 and tested in the study.

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Hall, E. J. « Aerodynamic modelling of multistage compressor flow fields Part 2 : Modelling deterministic stresses ». Proceedings of the Institution of Mechanical Engineers, Part G : Journal of Aerospace Engineering 212, n^o 2 (1 février 1998) : 91–107. http://dx.doi.org/10.1243/0954410981532162.

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The primary purpose of this study was to investigate improved numerical techniques for predicting flows through multistage compressors. The vehicle chosen for this study was the Pennsylvania State University Research Compressor (PSRC). The PSRC facility consists of a 3 1/2-stage axial flow compressor which shares design features which are consistent with embedded stages of modern gas turbine engine axial flow compressors. In Part 2 of this two-part paper, time-dependent predictions of rotor- stator-rotor aerodynamic interactions are employed to quantify the levels and distribution of deterministic stresses resulting from the average-passage flow field description. Details of the spanwise and blade-to- blade distributions of the velocity correlations are examined and compared with results based on physical deterministic flow structures such as blade wakes and clearance flows. The predicted ‘apparent’ wake profile decay resulting from the interaction of the wake through a downstream blade row is presented and compared with test data. This ‘apparent’ wake profile decay is employed to define a simplified model for deterministic stress correlations in a steady state flow field prediction scheme which retains the ‘mixing- plane’ methodology. Calculations based on this proposed model are described and predicted results are compared with both time-dependent predictions and test data. The resulting prediction strategy is computationally efficient and also contains sufficient physical realism to permit its use in design studies.

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Garner, Katelyn, Sarah Zavala, Kate Pape, Todd A. Walroth, Melissa A. Reger, Brittany Kiracofe, Wendy L. Thomas, Beatrice Adams et David M. Hill. « 10 A Multi-center Study Analyzing Association of Vitamin D Deficiency and Replacement with Infectious Outcomes in Patients with Burn Injuries ». Journal of Burn Care & ; Research 42, Supplement_1 (1 avril 2021) : S12—S13. http://dx.doi.org/10.1093/jbcr/irab032.015.

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Abstract Introduction Vitamin D (25OHD) deficiency has been associated with poor outcomes in intensive care populations. A recent single-center, burn study found a high incidence of 25OHD deficiency. A difference was noted in infectious complications, but was underpowered. The primary objective of this multi-center study was to determine if 25OHD deficiency is associated with infectious outcomes in adult burn patients. Methods Adult patients were eligible for inclusion in this 7 center, retrospective study if admitted January 1, 2016 - July 25, 2019 and had a 25OHD concentration drawn within the first 7 days of admission. Patients were excluded if admitted for a non-burn injury, had total body surface area (TBSA) burned of less than 5%, a readmission, pregnant, incarcerated, or made comfort care or expired within 48 hours of admission. Expecting a 3:1 enrollment, goal was at least 250 total patients to be appropriately powered (β = 0.2; α = 0.05) to detect a 33% difference in composite infectious outcome (bacteremia, pneumonia, urinary tract infection, wound infection, graft loss, or death) between patients with 25OHD deficiency (< 20 ng/mL) and control (≥ 20 ng/mL). Generalized linear mixed modelling was used to control for center effect, % TBSA, age, and presence of inhalation injury and find the most predictive model. Results A total of 1147 patients were initially included. After exclusions, 234 (56.8%) in the deficient and 178 in the control group remained. Patients in the control group had their concentration drawn earlier (p < 0.001), were more likely to be male (p = 0.006), Caucasian (p < 0.001), lower body mass index (p = 0.009), lower % TBSA burn (p = 0.002), and taking a 25OHD supplement prior to admission (p < 0.001). Deficient patients were more likely to have an infectious outcome (52.1% vs 36.0%, p = 0.002), acute kidney injury requiring renal replacement therapy (p = 0.009), less ventilator free days in the first 28 days (p < 0.001), and more days requiring vasopressors (p = 0.008). After controlling for center, % TBSA, age, and inhalation injury the best model also included presence of deficiency (odds ratio = 2.425 [1.035 - 1.252]), days until 25OHD supplement initiation (1.139 [1.035 - 1.252]), and choice of cholecalciferol over ergocalciferol 2.112 [1.151 - 3.877]). Conclusions Dilution concerns were controlled by including %TBSA in the regression model. Even if low 25OHD concentrations were an acute reaction to burn injury and not representative of true deficiency, low concentrations and delay in supplementation were independently associated with increased risk of an infectious outcome.

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Chi, Yeong Nain. « Time Series Forecasting of Global Price of Soybeans using a Hybrid SARIMA and NARNN Model ». Data Science : Journal of Computing and Applied Informatics 5, n^o 2 (31 juillet 2021) : 85–101. http://dx.doi.org/10.32734/jocai.v5.i2-5674.

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Global price of soybeans has a big impact because of the trade war between the U.S. and China. Under this circumstance, price forecast is vital to facilitate efficient decisions and will play a major role in coordinating the supply and demand of soybeans globally. Hence, the primary purpose of this study was to demonstrate the role of time series models in predicting process using the time series data of monthly global price of soybeans from January 1990 to January 2021. The SARIMA and NARNN models are good at modelling linear and nonlinear problems for the time series, respectively. However, using the hybrid model, a combination of the SARIMA and NARNN models has both linear and nonlinear modelling capabilities, can be a better choice for modelling the time series. The comparative results revealed that the Hybrid-LM model with 8 neurons in the hidden layer and 3 time delays yielded higher accuracy than the NARNN-LM model with 8 neurons in the hidden layer and 3 time delays, and the SARIMA, ARIMA(0,1,3)(0,0,2)12, model, according to its lowest MSE in this study. Thus, this study may provide an integrated modelling approach as a decision-making supportive method for formulating price forecast of soybeans for the global soybean market.

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