Robertson Model Research Articles

Prediction of aircraft cabin noise by statistical energy analysis

The noise level in the aircraft cabin is an important indicator on market competitiveness, and it is a considerable challenge to reduce the noise in the cabin at a relatively small cost, so efficient and accurate forecasting tools are required. In the aviation industry, Statistical Energy Analysis (SEA) is widely used to predict mid- and high-frequency noise in aircraft cabins. It has the advantages of simple method and low requirement of structure details. This paper models the cabin of a certain type of aircraft, and uses statistical energy methods to predict the noise level in the cabin during ground and cruise conditions. Among them, the prediction result of the cabin noise on the ground is in good agreement with the test results above 250Hz, which verifies the correctness of the model. During cruise, the pressure fluctuation on the outer surface of the front fuselage is dominated by turbulent boundary layer noise. The analysis shows that the Robertson model can predict turbulent boundary layer noise well, and the difference between the predicted single-point spectrum and the experimental value is less than 1dB. The cabin noise predicted by only loading the turbulent boundary layer noise source is consistent with the experimental results, but the sound pressure level in some frequency bands is low.

Platoon dispersion model in the mixed traffic environment

To describe the phenomenon of platoon dispersion in the mixed traffic environment and provide a theoretical basis for signal timing optimization in the mixed traffic environment. Based on Robertson’s platoon dispersion model, this paper fully considers the characteristics of mixed traffic conditions, and models the platoon dispersion in the mixed traffic environment. Firstly, considering the influence of the percentage of non-motor vehicles on the platoon dispersion, the functional relationship between the percentage of non-motor vehicles and the parameters of the platoon dispersion model is derived, and the parameters of the Robertson platoon dispersion model are calibrated. Secondly, through the data collected from Zitai Road in the city of Kunming, the required model parameters are calculated, and the arrival flow rate distribution downstream of the intersection is obtained. Finally, according to the measured data, the proposed model is compared with the classical Robertson model. The results show that compared with the Robertson model, the average prediction mean square error of the proposed model is reduced by 5.89%, which can better describe the dispersion law of the mixed traffic under the influence of different percentage of non-motorized vehicles.

Multi-Model Approach on Growth Estimation and Association With Life History Trait for Elasmobranchs

Age and growth information is essential for stock assessment of fish, and growth model selection may influence the accuracy of stock assessment and subsequent fishery management decision making. Previous descriptions of the age and growth of elasmobranchs relied mainly on the von Bertalanffy growth model (VBGM). However, it has been noted that sharks, skates and rays exhibit significant variety in size, shape, and life history traits. Given this variation, the VBGM may not necessarily provide the best fit for all elasmobranchs. This study attempts to improve the growth estimates by using multi-model approach to test four growth models—the VBGM, the two-parameter VBGM, the Robertson (Logistic) and the Gompertz models to fit observed or simulated length-at-age data for 38 species (44 cases) of elasmobranchs. The best-fit growth model was selected based on the bias corrected Akaike’s Information Criterion (AICc), the AICc difference, the AICc weight, the Bayesian Information Criterion (BIC), and the Leave-one-out cross-validation (LOOCV). The VBGM and two-parameter VBGM provide the best fit for species with slow growth and extended longevity (L∞ > 100 cm TL, 0.02 < k < 0.25 yr–1), such as pelagic sharks. For fast-growing small sharks (L∞ < 100 cm TL, kr or kg > 0.2 yr–1) in deep waters and for small-sized demersal skates/rays, the Robertson and the Gompertz models provide the best fit. The best-fit growth models for small sharks in shallow waters are the two-parameter VBGM and the Robertson model. Although it was found that the best-fit growth models for elasmobranchs were associated with their life history trait, exceptions were also noted. Therefore, a multi-model approach incorporating with the best-fit model selected for each group in this study was recommended in growth estimation for elasmobranchs.

Dynamic platoon dispersion model based on real‐time link travel time

Adaptive signal control system aims to improve the operation efficiency of intersections, in which the platoon dispersion model is one of the key component modules. The problem of the traditional Robertson's model is that they are based on historical data, which cannot effectively capture the dynamic characteristics of traffic flow and be further applied to adaptive signal control systems. Thanks to the unprecedented availability of real-time travel time data provided by the modern intelligent transportation systems, there is an opportunity to calibrate Robertson's model online using real-time travel time data. This study proposes a dynamic Robertson's platoon dispersion model based on real-time travel times. Then, based on field observations, the prediction error and computational efficiency of the traditional Robertson's model, the Gaussian model, and the proposed model are compared and analysed. The results show that the proposed model can better capture the law of dynamic dispersion for traffic flow. The reduced average mean square error of prediction can be as much as 16.86 and 7.07% compared with the traditional Robertson's model and the Gaussian model, respectively. In addition, the average computational time of the proposed model is 0.46 s, which can be applied in the dynamic predictive signal control systems.

Development of Dynamic Platoon Dispersion Models for Predictive Traffic Signal Control

As the development of traffic detection technology, recent research is directed to a new generation of signal control systems supported by new traffic data. One of these directions is dynamic predictive control by incorporating short-term prediction capability. This paper focuses on investigating dynamic platoon dispersion models which could capture the variability of traffic flow in a cross-sectional traffic detection environment. The dynamic models are applied to predict the evolution of traffic flow, and further used to produce signal timing plans that account not only for the current state of the system but also for the expected short-term changes in traffic flows. We investigate factors affecting model accuracy, including time-zone length, position of upstream traffic detection equipment, road section length, traffic volume, turning percentages, and computation time. The impact of these factors on the model’s performance is illustrated through a simulation analysis, and the computation performance of models is discussed. The results show that both the dynamic speed-truncated normal distribution model and dynamic Robertson model with dynamics outperform their respective static versions, and that they can be further applied for dynamic control.

Can Randall\u2019s plug composed of calcium oxalate form via the free particle mechanism?

BackgroundThe likelihood of a Randall’s plug composed of calcium oxalate monohydrate (COM) forming by the free particle mechanism in a model of kidney with a structure recently described by Robertson was examined at the most favourable conditions for the considered mechanism.MethodsThe Robertson model of the kidney is used in the following development. The classical theory of crystallization was used for calculations.ResultsInitial COM nuclei were assumed to form at the beginning of the ascending loop of Henle where the supersaturation with respect to COM has been shown to reach the threshold level for spontaneous nucleation. Nucleation proceeds by a heterogeneous mechanism. The formed particles are transported in the nephron by a laminar flow of liquid with a parabolic velocity profile. Particles travel with a velocity dependent on their position in the cross-section of the nephron assumed to be straight tubule with smooth walls and without any sharp bends and kinks. These particles move faster with time as they grow as a result of being surrounded by the supersaturated liquid. Individual COM particles (crystals) can reach maximum diameter of 5.2 × 10−6 m, i.e. 5.2 μm, at the opening of the CD and would thus always be washed out of the CD into the calyx regardless of the orientation of the CD. Agglomeration of COM crystals forms a fractal object with an apparent density lower than the density of solid COM. The agglomerate that can block the beginning of the CD is composed of more crystals than are available even during crystaluria. Moreover the settling velocity of agglomerate blocking the opening of the CD is lower than the liquid flow and thus such agglomerate would be washed out even from upward-draining CD.ConclusionsThe free particle mechanism may be responsible for the formation of a Randall’s plug composed by COM only in specific infrequent cases such as an abnormal structure of kidney. Majority of incidences of Randall’s plug development by COM are caused by mechanism different from the free particle mechanism.

Heterogeneous platoon flow dispersion model based on truncated mixed simplified phase‐type distribution of travel speed

SummaryExisting research on platoon dispersion models either describe homogeneous traffic flow feature, or are in lack of analytical solutions. By analyzing the field data, the truncated mixed simplified phase‐type distribution is proved to be capable of capturing the characteristics of heterogeneous traffic flow with an excellent fitting result. In light of this, we derive a generic heterogeneous platoon dispersion model with truncated mixed simplified phase‐type of speed in the forms of integrable functions. Numerical case studies are conducted to compare the performance of the proposed model and the conventional models (i.e., the Robertson model and truncated mixed Gaussian model). The results show that the proposed model not only better captures the platoon dispersion laws of heterogeneous traffic flow, but also presents higher computational efficiency, which provides practical implications on traffic signal control. Copyright © 2017 John Wiley & Sons, Ltd.

Development of a New Platoon Dispersion Model considering Turning Vehicles in Urban Road Environment

By considering turning vehicles of a platoon that travels on arterial link, a new procedure for calibrating dispersion parameter α of Robertson's model is proposed. Upstream edge of channelized section is served as the boundary and the link between two adjacent intersections is divided into two sections, which are road section and channelized section. Typical investigation site is selected in Changchun city and data are collected to study the relationship between α and internal frictions, such as traffic volume and turning proportion. Double Gaussian function and logistic function are used to fit the curves among optimum values of α and internal frictions in the two sections, respectively, which allow the determination of α that varies as the volumes and turning proportions change. The study results are of great importance for arterial progression because Robertson's model can depict platoon movements more accurately using the calibrated values of α.

Studying Platoon Dispersion Characteristics Under Heterogeneous Traffic in India

Platoons are created by signalized intersections which control travel patterns of vehicles. It is common for platoons to disperse during normal traffic operations. While platoon dispersion has been studied extensively under homogenous and lane disciplined traffic conditions, this characteristic under heterogeneous conditions has not been addressed adequately. This study will be one of the first steps in this direction and will lead to better understanding and simulation of platoon dispersion under Indian conditions.Data describing platoon dispersion was collected with video recording systems along an arterial in Chennai, India. The Robertson's model parameters calibrated for this data was found to be very different from those obtained in previous studies by other researchers. This could be attributed to the highly heterogeneous traffic existing on Indian roads. Dispersion characteristics were studied by taking each platoon individually. The study will augment the understanding of platoon dispersion by discussing the issue of heterogeneous conditions.

Mixed Platoon Flow Dispersion Model Based on Speed-Truncated Gaussian Mixture Distribution

A mixed traffic flow feature is presented on urban arterials in China due to a large amount of buses. Based on field data, a macroscopic mixed platoon flow dispersion model (MPFDM) was proposed to simulate the platoon dispersion process along the road section between two adjacent intersections from the flow view. More close to field observation, truncated Gaussian mixture distribution was adopted as the speed density distribution for mixed platoon. Expectation maximum (EM) algorithm was used for parameters estimation. The relationship between the arriving flow distribution at downstream intersection and the departing flow distribution at upstream intersection was investigated using the proposed model. Comparison analysis using virtual flow data was performed between the Robertson model and the MPFDM. The results confirmed the validity of the proposed model.

Secondary production of sandy beach macrofauna: An evaluation of predictive models

During the last three decades, several predictive models have been developed to estimate the somatic production of macroinvertebrates. Although the models have been evaluated for their ability to assess the production of macrobenthos in different marine ecosystems, these approaches have not been applied specifically to sandy beach macrofauna and may not be directly applicable to this transitional environment. Hence, in this study, a broad literature review of sandy beach macrofauna production was conducted and estimates obtained with cohort-based and size-based methods were collected. The performance of nine models in estimating the production of individual populations from the sandy beach environment, evaluated for all taxonomic groups combined and for individual groups separately, was assessed, comparing the production predicted by the models to the estimates obtained from the literature (observed production). Most of the models overestimated population production compared to observed production estimates, whether for all populations combined or more specific taxonomic groups. However, estimates by two models developed by Cusson and Bourget provided best fits to measured production, and thus represent the best alternatives to the cohort-based and size-based methods in this habitat. The consistent performance of one of these Cusson and Bourget models, which was developed for the macrobenthos of sandy substrate habitats (C&BSS), shows that the performance of a model does not depend on whether it was developed for a specific taxonomic group. Moreover, since some widely used models (e.g., the Robertson model) show very different responses when applied to the macrofauna of different marine environments (e.g., sandy beaches and estuaries), prior evaluation of these models is essential.

Robertson's model: a framework for exploration of World War II conservation consumption policy influence on fashion in the US

AbstractThis paper studies pertinent materials related to the conservation of textile apparel and textile‐related natural resources that appeared in poster campaign communications published during the Second World War in the US. An examination of World War II poster campaign communications conveying the need for conservation efforts and rationing as communicated to consumers infers the historical context of the era. These poster campaign communications asked consumers to utilize fully of limited resources while maintaining a sense of individuality and trend‐setting creativity and fashion. World War II shortages and allocations influenced fashion innovations in women's apparel in the US. This paper provides a retrospective examination of innovative trends and the various conservation themes associated with women's fashion identify themes used to influence and to inspire Americans to reuse and recycle in support of the war effort. At no other time in history was voluntary textile conservation as prevalent in mainstream American culture as it was during the 1940s.Content analysis reveals reoccurring themes that appeared in the advertisements developed by the War Advertising Council in the 1940s and used in their poster campaign advertisements. Themes and conservation activities identified in their poster campaign communications included ‘America's New Role as Fashion Arbiters’; ‘Conserve Time, Money, Materials for National Defense Program’; ‘War Production Board General Limitations Order L‐85 – Fabric Conservation on Silhouette Dimensions’; ‘Fashion for Victory’; ‘Beauty in Peace and War’; ‘Fabric Conservation’; ‘Teaching Consumers How to Conserve’; ‘You're In the War Too’; ‘Wearing Clothes More’; ‘Changing Materials for War [Nylon]’. In addition, print communications were categorized according to Robertson's adoption process model. This study found evidence that supports that Robertson's adoption process model was a useful tool in studying these poster campaign communications relative to Robertson's decision‐making process.

Raman studies on nanocomposite silicon carbonitride thin film deposited by r.f. magnetron sputtering at different substrate temperatures

AbstractRaman studies of nanocomposite SiCN thin film by sputtering showed that with increase of substrate temperature from room temperature to 500 °C, a transition from mostly sp2 graphitic phase to sp3 carbon took place, which was observed from the variation of ID/IG ratio and the peak shifts. This process resulted in the growth of C3N4 and Si3N4 crystallites in the amorphous matrix, which led to increase in hardness (H) and modulus (E) obtained through nanoindentation. However, at a higher temperature of 600 °C, again an increase of sp2 C concentration in the film was observed but the H and E values showed a decrease due to increased growth of the graphitic carbon phase. The whole process got reflected in a modified four‐stage Ferrari–Robertson model of Raman spectroscopy. Copyright © 2010 John Wiley & Sons, Ltd.

High conductivity a-C:N thin films prepared by electron gun evaporation

By employing electron beam evaporation, amorphous carbon nitride (a-C:N) thin films, with a low nitrogen content (∼ 1%), were prepared on Si(110) and glass substrates at about 150 °C. The source was a graphite target and an ambient of N 2 was introduced into the growing chamber. The source-substrate distance (SSD) was the main parameter that was intentionally varied. Electron dispersion spectroscopy measurements indicate the nitrogen concentration in the layer as ∼ 1%. The dark electrical conductivity ( σ) of layers was very sensitive to SSD variation, changing up to six orders of magnitude when this parameter was varied from 10.5 to 23.5 cm. A maximum value of σ = 1 × 10 3 Ω − 1 cm − 1 at room temperature was obtained when the SSD was equal to 15.5 cm. We have deduced that, in accordance with the Ferrari–Robertson model (FRM), our samples are localized in the second stage of the amorphization trajectory of FRM. When the SSD increases the C atoms have more probability to collide with N 2 molecules, and the content of nitrogen in the a-C film increases. The amorphization trajectory followed by the films with an SSD increase is from nanocrystalline graphite to amorphous carbon. The changes in the amorphization are due to the nitrogen content in the layers.

ISO 9001:2000 in small organisations

PurposeThe aim of the study is to investigate and to understand the practice of implementing and operating the QMS in an organisational context, providing an analysis of the way ISO 9001:2000 was implemented and operated and focusing on identifying factors which have negatively or positively influenced the effects of the quality management system (QMS).Design/methodology/approachThree case studies of small organisations were examined. The methodological approach was based on Porras and Robertson's model. The data collection methods included interviews, a questionnaire survey of all employees and document studies.FindingsISO 9001:2000 was implemented and operated with minimum effort and little change was experienced. QMS was not perceived as a tool for managing processes, but as a tool for handling documentation. Consequently, this was reflected in the benefits achieved. Despite the external benefits which followed from obtaining the certificates, only minor internal benefits were found. Internal motivation, engaged and trained employees, a competent quality manager, committed CEO and development‐oriented auditors were identified as critical, influencing the effects from ISO 9000. In general, in the way ISO 9001:2000 was implemented and operated many opportunities for improvement were lost.Research limitations/implicationsThe choice of small organisations for the case studies has important implications for the results. Small organisations often lack resources, which limits the initiatives that they can take.Practical implicationsThe QMS and its effects are not determined by the ISO 9001 requirements, but by the organisational context and the way the system is implemented and operated.Originality/valueThe paper provides an explanation why organisations achieve very different results from ISO 9001 implementation. It also shows that certification bodies may have an important role for the effectiveness of the QMS.

Model formulation and solution algorithm of traffic signal control in an urban network

The existing network traffic signal optimization formulations usually do not include traffic flow models, except for control schemes such as SCOOT (Split, Cycle, and Offset Optimization Technique) system that uses simulation for heuristic optimization. Other conventional models normally use isolated intersection optimization with traffic arrival prediction using detector information, or optimization schemes based on green bandwidth approach such as MAXBAND (Maximal Bandwidth). In this paper we present a complete formulation of the problem that includes explicit constraints to model the movement of traffic along the streets between the intersections in a time-expanded network, as well as constraints to capture the permitted movements from modern signal controllers. The platoon dispersion model used is the well-known Robertson's model, which forms linear constraints. Thus it is a rare example of a traffic simulation being analytically embedded in an optimization formulation. The formulation is an integer-linear program, and does not assume fixed cycle lengths or phase sequences. It assumes full information on external inputs, but can be incorporated in a sensor-based environment, as well as in a feedback control framework. The formulation is an integer-linear program that may not be efficiently solved with standard simplex and branch and bound techniques. We discuss network programming formulations to handle the linear platoon dispersion equations and the integer constraints at the intersections. A special-purpose network simplex algorithm for fast solution is also mentioned.

Chain mobility in the amorphous region of nylon 6 observed under active uniaxial deformation

A specially designed solid-state deuterium nuclear magnetic resonance probe was used to examine the effect of uniaxial elongation on the chain mobility in the amorphous region of semicrystalline nylon 6. In measurements conducted near the glass transition temperature, there was measurable deformation-induced enhancement of the mobility of the amorphous chains up to the yield point. This enhanced mobility decayed once deformation was stopped. Enhanced mobility was not observed in deformation at room temperature. The mechanics of deformation can be explained by the Robertson model for glassy polymers near the glass transition temperature, which states that applied stress induces liquid-like behavior in the polymer chains.

Theoretical consideration of the growth kinetics for GaAs and GaSb

An extended MOMBE growth kinetics model is proposed, based on the Robertson model, to explain both the GaAs growth rate variation and modulated beam mass spectroscopy data reported by Martin and Whitehouse. In this model, we assume that (1) MEGa molecules react with ethyl-radicals to form DEGa, (2) excessive group-V molecules on the surface suppress the decomposition of DEGa and enhance the desorption of DEGa, (3) reaction of DEGa with ethyl-radicals to form TEGa is negligible, and (4) effective surface coverage of excessive group-V atoms during growth is determined by the double layer adsorption model including desorption parameters for group-V molecules. The first assumption (1) is found to be a dominant process to explain the behaviour of DEGa desorption at high temperatures. This model can reproduce the dependences of both growth rate and desorbing rate of Ga alkyls on substrate temperature during GaAs MOMBE growth. The use of Sb instead of As produces a significant change in the growth rate variation with substrate temperature and group-V flux for the growth of GaSb, in spite of the use of the same TEGa flow rate. This can be rationalized by the difference in the desorption parameters for Sb and As.

Offspring Quality and the Polygyny Threshold: A New Model for the "Sexy Son" Hypothesis

Recent models for the evolution of polygyny in territorial birds predict that a female should choose to mate polygynously only if her expected number of off-spring is equal to or greater than her expected number if she mated monogamously. A recent model by Weatherhead and Robertson (1979) suggests that polygynous females can, in fact, tolerate lower reproductive success relative to available monogamous breeding situations if their sons inherit from their fathers an enhanced tendency to mate polygynously. Weatherhead and Robertson's model contains several inconsistencies that lead to misleading numerical predictions. These problems are indicated and a new model is presented. The model supports Weatherhead and Robertson's qualitative expectations. It predicts that an increase in the adult sex ratio, the average harem size, the frequency of polygynous males, or the degree of father-son resemblance in pairing success will all increase the size of the initial reproductive loss that can eventually be recovered. Consideration of the effect of reproduction over subsequent generations indicates that there is a limit to the number of generations over which a polygynously mated female can recoup an initial reproductive loss. A method is suggested by which the model may be applied to field studies of natural populations. Finally, limitations on the value of nongenetical approaches in modeling the evolution of female choice are discussed.