Davies Model Research Articles

A soft application for surface solar radiation estimation in Algeria

In this article, we have developed an application of four theoretical models that allows to estimate the solar radiation received on the ground for any region of the Algerian territory. The first model makes it possible to estimate the global solar radiation received on the ground. This model is a spectral model for the determination of direct and diffuse irradiance on a horizontal and sloping surface and for a clear sky. The second model is a Bird & Hulstrom time model that estimates solar radiation at ground level for a certain period (Hours, days, months, … etc.). The third model is the Davies & Hay model, which makes it possible to trace the rates of absorption and diffusion of solar radiation by the various atmospheric constituents as a function of time and make comparisons. The last model is Lacis & Hansen which allows to trace the global radiation for a certain period. These models are based on the determination of the transmission coefficients of the various atmospheric constituents. These coefficients require the availability of current meteorological parameters (relative humidity, ambient temperature, atmospheric pressure, etc.) and geographical parameters of the site (latitude, longitude and altitude). The application developed made it possible to study several models for estimating global solar radiation at a few Algerian sites and to draw a conclusion on the most appropriate models of estimations.

ESTIMATION OF ADULT PATIENT DOSES FOR CHEST X-RAY EXAMINATIONS AND COMPARISON WITH DIAGNOSTIC REFERENCE LEVELS (DRLs).

The aim of this study was to evaluate the radiation doses to patient during chest (posterior anterior/and lateral) examinations. The study was performed in three public hospitals of İstanbul province with a total of 300 adult patients. Entrance surface dose (ESD) measurements were conducted on computed radiography, digital radiography and screen film system. ESD was estimated by using International Atomic Energy Agency (IAEA) model and Davies model which are the common indirect models. Results were compared with diagnostic reference levels from the European Commission, IAEA and National Radiological Protection Board. Although the results are compatible with the international diagnostic reference levels, they present variations between the hospitals. Dose variations for the same type of X-ray examination support the idea that further optimization is possible.

Study on the pressure drop characteristics for the particles across fibres

A comparison of the results obtained from typical pressure drop models of fibrous media to experimental values has been done in the paper. Then, the pressure drop characteristics for different structural and operating parameters would be evaluated. The results show that Davies model instead of Kuwabara, Henry and Happel models fits well with the tested data and gives errors of less than 7.0%. Pressure drop across the media increases with increasing solid fraction, superficial velocity and fibre layer thickness, and decreases with increasing fibre diameter. Fibre diameter in the range of smaller values and solid fraction have more significant effects on the air flow resistance than the other factors.

De la jerarquización funcional continua de los asentamientos a la discreta: el caso de Aragón

Se plantean primero las dificultades que entraña pasar de un modelo jerarquizado continuo a otro discreto y la necesidad de jerarquias discretas para la ordenación del territorio. Para la jerarquización funcional de Aragón se parte del modelo de Davies utilizando 117 variables (licencias fiscales). De la jerarquía continua de centralidades reales se llega a una jerarquía discretade tipo christalleriano dando una serie de pasos: mediante medidas tipificadas, eliminacidn de los municipios del área metropolitana, supresidn en el nivel elemental de índices de atracción negativa con excepciones justificadas (vía ernpírica y estadlstica), consideración de los incrementos medios de centralidad para aceptar las rupturas del "continuum", agrupamientos de niveles jerárquicos en función de una optimación del índice del vecino más próximo.

Suspension of solid particles in vessels agitated by Rushton turbine imperllers

The “just suspended” condition is an important criterion for the design of agitators in solid−liquid mixing processes. This criterion is met when all the particles are in motion on the base of the vessel but not necessarily uniformly distributed throughout the liquid. Grenville et al. (2015) have proposed a new correlation for predicting the just suspension speed of axial flow impellers in standard, baffled vessels with dished bases. It is based on the physical model proposed by Davies (1986) and correlates data taken at three scales over a wide range of physical properties.Many previous workers have measured the just suspension speed for Rushton turbines, which produce a radial primary flow, and forced their data to the correlation proposed by Zwietering (1958) but without testing the statistical fit. The applicability of the Davies (1986) model and Grenville et al. (2015) correlation to radial flow impellers was recognized as an outstanding question and it is addressed in this paper.Chapman (1981) measured the just suspension speed for Rushton turbines at five vessel scales in standard baffled vessels with flat bases under gassed and ungassed conditions. The ungassed data have been successfully fitted to the Grenville et al. (2015) correlation but with a change in geometrical dependencies. The just suspension speed is independent of impeller clearance above the vessel base but strongly dependent on the impeller to vessel diameter ratio. These geometric effects are very different to the ones observed for axial impellers in dished base vessels and this suggests that further work should be carried out to reconcile these differences.

Modelling the coordination of the controls of stomatal aperture, transpiration, leaf growth, and abscisic acid: update and extension of the Tardieu-Davies model.

Stomatal aperture, transpiration, leaf growth, hydraulic conductance, and concentration of abscisic acid in the xylem sap ([ABA]xyl) vary rapidly with time of day. They follow deterministic relations with environmental conditions and interact in such a way that a change in any one of them affects all the others. Hence, approaches based on measurements of one variable at a given time or on paired correlations are prone to a confusion of effects, in particular for studying their genetic variability. A dynamic model allows the simulation of environmental effects on the variables, and of multiple feedbacks between them at varying time resolutions. This paper reviews the control of water movement through the plant, stomatal aperture and growth, and translates them into equations in a model. It includes recent progress in understanding the intrinsic and environmental controls of tissue hydraulic conductance as a function of transpiration rate, circadian rhythms, and [ABA]xyl. Measured leaf water potential is considered as the water potential of a capacitance representing mature tissues, which reacts more slowly to environmental cues than xylem water potential and expansive growth. Combined with equations for water and ABA fluxes, it results in a dynamic model able to simulate variables with genotype-specific parameters. It allows adaptive roles for hydraulic processes to be proposed, in particular the circadian oscillation of root hydraulic conductance. The script of the model, in the R language, is included together with appropriate documentation and examples.

Effects of Y on hot tearing susceptibility of Mg–Zn–Y–Zr alloys

The hot tearing susceptibility of MgZn2.5YxZr0.5 (x=0.5, 1, 2, 4, 6) alloys was evaluated by thermodynamic calculations based on Clyne–Davies model. The microstructure and morphology of hot tearing regions of the alloys were observed by X-ray diffraction and scanning electron microscopy. The solidification temperature and shrinkage stress during the solidification of MgZn2.5YxZr0.5 alloys in the “T” type hot tearing permanent-mold were acquired with the attached computer. The effect factors of hot tearing susceptibility of MgZn2.5YxZr0.5 alloys, such as the solidification temperature interval, the variation of solid fraction in vulnerable region, the residual liquid fraction in the final stage, the type of the second phase of the alloys were discussed based on the above calculation and observation. The results demonstrated that the hot tearing susceptibility in the investigated alloys was found as follows–MgZn2.5Y2Zr0.5>MgZn2.5Y0.5Zr0.5>MgZn2.5Y4Zr0.5>MgZn2.5Y6Zr0.5>MgZn2.5Y1Zr0.5. The highest hot tearing susceptibility of MgZn2.5Y2Zr0.5 alloy related to the following reasons: the largest freezing range, the biggest changing of the variation of solid fraction in vulnerable region, the least liquid film in the final stage of solidification, the formation of the second phase which worsens the liquid flow and interdendritic feeding after dendrite coherency.

Exploring Factors that Influence Talent Management Competency of Academics in Malaysian GLC’s and Non- Government Universities

The aim of this research is to investigate the nature and extent of talent management related factors on talent management competencyforAcademics in threeMalaysian universities. The study explored the literature and identified a broad theorized model by (Davies & Davies, 2010) further by undertaking a literature review from the extant literature some common factors associated to Talent Management the authors developed indicators and multi-item measures to preliminarily test and propose Davies & Davies model to a survey instrument(sample N= 166 with an 80% response rate).The study found that, Academic’s perception of talent identification, talent development and talent management culture relevance are the most important contributors to talent management competency for Academics. The findings also suggest that talent management competency levels for Academics are significantly higher when management have integrated HR systems that identify value, measure team and individual performance, assess and develop careers, give honest formal feedback and a culture of rewarding high performance. The study concludes that utilizing a more comprehensive model that incorporates the TM whole lifecycle beyond recruitment and selection and using methodology with multi-item measures has unearthed nuances in the data that confirm and extend the extant literature of talent management in higher education. In particular organizations that embark on a ‘one size fits all’ TM strategy by ignoring these job related factors could eventually face further problems such as high staff turnover, poor morale and associated costs and potential sacrificial client/customer service strategies that will impact on the bottom line and the organizations reputation. Indexterms: Talent Management –identification; development; culture, Exploratory Factor Analysis Faculty of Business &Law, Swinburne University of Technology, Hawthorn. Melbourne, Australia. Email: jannakis@swin.edu.au Faculty of Business &Law, Swinburne University of Technology, Hawthorn. Melbourne, Australia. Email: mdass@swin.edu.au Lecturer, College of Business Management and Accounting, UNITEN, Sultan Haji Ahmad Shah Campus. Contact No: 09-4552020 ext:3128, E-mail: aerni@uniten.edu.my 164 Journal of International Business and Economics, Vol. 2(4), December 2014

Analytical investigation of collector optimum tilt angle at low latitude

An analytical investigation on the optimum tilt angle for solar collectors at low latitude, a case study of Universiti Teknologi PETRONAS (UTP), 4.39°N and 100.98°E, Malaysia is presented in this work. The study employed Hay, Davies, Klucher, and Reindl (HDKR) anisotropic sky model to evaluate the available hourly solar radiation on inclined surface using the location metrological data. The tilt angles considered were 0° to 30° in step of 3° with the inclusion of the location latitude angle. The study employed the ratio of global solar radiation on tilted surface to the global solar radiation on horizontal surface in the decision of the optimum tilt. The system equations were converted to MATLAB codes to solve for the optimum tilt angles. The results show that the optimum tilt varies monthly but gave zero degree for south facing collector for the months of April to August; thus, the investigation also considered north facing orientation for the months of April to September. The optimum annual tilt angle for the location using the tilt to horizontal radiation ratio was found to be equal to the location latitude angle. Using the conventional average of the monthly optimum tilt angles, the annual optimum tilt angle was found to be 9.75° for south facing collector. Considering seasonal optimum tilt angle for the location using the tilt to horizontal radiation ratio, 18° facing south was found to be the optimum tilt angle for rainy season (September to March) and 15° facing north for dry season (April to August). Employing the average of monthly optimum tilt method, the seasonal optimum tilt angle was found to be 17° for rainy season and 12° facing north dry season. The effect of dust on the collector was considered with reference to literature and the annual tilt angle of 15° facing south was recommended for the location in the case of large solar collector that cannot be monthly or seasonally adjusted.

Evaluation of the currency of the Davies and Oberle (1990) model of supportive care in specialist and specialised palliative care settings in England

To evaluate the extent to which the Davies and Oberle (1990) model of supportive nursing has currency across specialist and specialised care settings in England. The model describes attributes of palliative nursing for practice and associated educational curricula. It is influential but predates introduction of specialist/specialised care. Its applicability in contemporary care settings has not been evaluated. Evaluation was undertaken using sequential mixed methods, predominantly qualitative. Data collected during 2008-2009. Four stages: (1) focus groups involving hospital and community palliative clinical nurse specialists and nurses from three hospice settings (total = 25) to identify setting-specific characteristics, (2) survey of nurses (n = 48 respondents/31%) with follow-up interviews (n = 25) to identify congruence with the model, (3) interviews with patients (n = 6) and carers (n = 13) for practice evidence and (4) reconvened focus groups (n = 19 nurses) for confirmation. All major dimensions were evidenced. 'Connecting' had reduced emphasis in the hospital setting where specialist nurses spend limited time with patients, but diminishing time to 'connect' with patients and carers as service develops could potentially become problematic across all settings. Two new dimensions ('Displaying expertise' and 'Influencing other professionals') with subdimensions (e.g. 'Advanced communication skills') are proposed as additions to reflect advanced practice. Further new subdimensions ('Making the assessment', 'Prioritising', 'Agreeing the plan') are suggested to be best aligned with the existing dimension 'Connecting'. A revised model of supportive care incorporating dimensions of advanced nursing has currency in contemporary specialist/specialised care settings, although evaluation is required as to the actual impact of the model on care outcomes. 'Connecting' is currently being affected by pace of work and lateness of referrals. 'Spending time' is increasingly difficult to sustain so challenging nurses as to how they may continue to 'connect' with patients as service delivery continues to change.

Noise analysis of qubits implemented in triple quantum dot systems in a Davies master equation approach

We analyze the influence of noise for qubits implemented using a triple quantum dot spin system. We give a detailed description of the physical realization and develop error models for the dominant external noise sources. We use a Davies master equation approach to describe their influence on the qubit. The triple dot system contains two meaningful realizations of a qubit: We consider a subspace and a subsystem of the full Hilbert space to implement the qubit. We test the robustness of these two implementations with respect to the qubit stability. When performing the noise analysis, we extract the initial time evolution of the qubit using a Nakajima-Zwanzig approach. We find that the initial time evolution, which is essential for qubit applications, decouples from the long time dynamics of the system. We extract probabilities for the qubit errors of dephasing, relaxation and leakage. Using the Davies model to describe the environment simplifies the noise analysis. It allows us to construct simple toy models, which closely describe the error probabilities.

Quantifying Plant Age and Available Water Effects on Soybean Leaf Conductance

Given the ever‐present threat of drought and the knowledge that water availability is the strongest limiting factor in vegetation growth, it is important to characterize the effect of water limitations on agricultural production. In this study, a small field plot technique for controlling soil moisture content suitable for physiological research in moist, humid areas was tested. We characterized the effect of water stress on total leaf conductance (gl) for two distinct determinate soybean [Glycine max (L.) Merr.] genotypes. Based on these findings, a model of gl as a function of plant age and soil moisture content was formulated and validated. The dependency of gl on plant age was well represented by a parabolic function that increased throughout the vegetative period, peaked around anthesis, and decreased throughout the reproductive period and senescence. A sigmoidal function explained the relation of gl to plant‐available soil water content. This new empirical model effectively quantifies the response of gl to plant‐available soil water and plant age with a functional form similar to the abscisic acid related Tardieu–Davies model.

Hot tearing susceptibility of binary Mg–Y alloy castings

The influence of Y content on the hot tearing susceptibility (HTS) of binary Mg–Y alloys has been predicted using thermodynamic calculations based on Clyne and Davies model. The calculated results are compared with experimental results determined using a constrained rod casting (CRC) apparatus with a load cell and data acquisition system. Both thermodynamic calculations and experimental measurements indicate that the hot tearing susceptibility as a function of Y content follows the “λ” shape. The experimental results show that HTS first increases with increase in Y content, reaches the maximum at about 0.9wt.%Y and then decreases with further increase the Y content. The maximum susceptibility observed in Mg–0.9wt.%Y alloy is attributed to its coarsened columnar microstructure, large solidification range and small amount of eutectic at the time of hot tearing. The initiation of hot cracks is monitored during CRC experiments. It corresponds to a drop in load increment on the force curves. The critical solid fractions at which the hot cracks are initiated are in the range from 0.9 to 0.99. It is also found that it decreases with increasing the content of Y. The hot cracks propagate along the dendritic or grain boundaries through the interdendritic separation or tearing of interconnected dendrites. Some of the formed cracks are possible to be healed by the subsequent refilling of the remained liquids.

Airborne and satellite remote sensing of the mid-infrared water vapour continuum

Remote sensing of the atmosphere from space plays an increasingly important role in weather forecasting. Exploiting observations from the latest generation of weather satellites relies on an accurate knowledge of fundamental spectroscopy, including the water vapour continuum absorption. Field campaigns involving the Facility for Airborne Atmospheric Measurements research aircraft have collected a comprehensive dataset, comprising remotely sensed infrared radiance observations collocated with accurate measurements of the temperature and humidity structure of the atmosphere. These field measurements have been used to validate the strength of the infrared water vapour continuum in comparison with the latest laboratory measurements. The recent substantial changes to self-continuum coefficients in the widely used MT_CKD (Mlawer-Tobin-Clough-Kneizys-Davies) model between 2400 and 3200 cm(-1) are shown to be appropriate and in agreement with field measurements. Results for the foreign continuum in the 1300-2000 cm(-1) band suggest a weak temperature dependence that is not currently included in atmospheric models. A one-dimensional variational retrieval experiment is performed that shows a small positive benefit from using new laboratory-derived continuum coefficients for humidity retrievals.

Comparison of UV-B Broadband Brewer Measurements with Irradiances from Surface-Based and Satellite-Based Models

UV-B irradiance can be estimated from surface meteorological data or from satellite measurements. This paper compares irradiance estimates from the Davies surface-based radiation model and the Canada Centre for Remote Sensing (CCRS) satellite model with Brewer spectrophotometer measurements for all sky conditions at six Canadian stations (Edmonton, Regina, Winnipeg, Montreal, Halifax and Toronto). The Davies model is applied with both the discrete ordinate radiative transfer (DISORT) and the delta-Eddington algorithms to solve the radiative transfer equation. Both models’ estimates are compared with instantaneous Brewer measurements. Both perform similarly with mean bias errors within 6% of the mean measured irradiance for the measurement period and root mean square errors between 25% and 30%.

Characterization of Total Dot Gain by Microscopic Image Analysis

Characterization of total dot gain gives a good insight to the study of paper and print. In this article, we propose three approaches based on the Murray–Davies model to obtain total dot gain. In the first approach, the total gain is approximated by minimizing the root-mean-square between the calculated spectrum and the reflected spectrum measured by the spectrophotometer. The other two approaches are based on microscale images captured by a high resolution camera. These two approaches differ in their schemes on how to obtain the gray tone of the full-tone ink. By the use of microscale images, the authors also illustrate the shape of the effective dot area for the investigated paper substrate. They also study the histograms of the reflected and transmitted microscale images. This comparison shows that although the transmitted image has less optical dot gain compared to the reflected image, the transmittance also incorporates some small amount of optical dot gain.

Two-Dimensional Stability Analysis of Interrupted High-Speed Milling

Significant research has been made regarding chatter stability of milling operations. This paper presents a 2 degree of freedom stability analysis model (2 DOF model) for interrupted cutting. The cutting process is divided into two parts namely “free vibration” and “forced vibration” considering the flexibility in x and y directions. Calculating the solutions of the two parts, a four-dimensional-single-variation discretization map is established and the eigenvalues of the Jacques Matrix are checked at the fixed point on the Floquet unit circle. The two Neimark-Sacker and flip bifurcations are evaluated. The research work shows that the up milling is more stable than the down milling under the same operating parameters. The comprison of the proposed 2 DOF model with Davies one degree of dimensional model (1 DOF Davieas model) has been made in the paper which shows that the area of stable region in the proposed model is greater than the stable region in the 1 DOF Davies model. In the last the results of the experiments support the proposed model has been verified by experimentation.

SAD Computers and Two Versions of the Church–Turing Thesis

Recent work on hypercomputation has raised new objections against the Church–Turing Thesis. In this paper, I focus on the challenge posed by a particular kind of hypercomputer, namely, SAD computers. I first consider deterministic and probabilistic barriers to the physical possibility of SAD computation. These suggest several ways to defend a Physical version of the Church–Turing Thesis. I then argue against Hogarth's analogy between non-Turing computability and non-Euclidean geometry, showing that it is a non-sequitur. I conclude that the Effective version of the Church–Turing Thesis is unaffected by SAD computation. 1 SAD Computability1.1 The basic idea of SAD computation 1.2 Avoiding supertasks 1.3 Davies's model of SAD computation 1.4 Hogarth's model of SAD computation 1.5 Generalizing SAD computers 2 Physical Computability2.1 The Physical Church–Turing Thesis 2.2 Deterministic barriers to physical computation 2.3 Probabilistic barriers to physical computation 3 Effective Computability3.1 The Effective Church–Turing Thesis 3.2 Hogarth's challenge to the Effective Church–Turing Thesis 3.3 Arguing from SAD computability is a non-sequitur 3.4 SAD computability is built from finitary computability 4 Concluding Remarks

Two-phase composite modeling of polyurea/wood interfaces

The flexural modulus of oak and pine boards suffused with polymeric methylene diphenyl diisocyanate (pMDI) was measured as a function of the amount of pMDI imbibed. The resulting modulus values were compared to predicted values calculated by assuming a relationship between the composite phases. Specifically, the measured flexural moduli were compared to values obtained from a Kerner model, in which the composite phase consists of isolated and spherical particulate isotropically arranged in the major phase. Results were also compared to a Davies model, in which the two phases exist in a bonded co-continuous morphology. The measured data was shown to be well fit to the Kerner model and not well described by the Davies model, despite the fact that the Davies model is more physically descriptive of the filled wood pore structure. This incongruous result indicates that the pMDI/wood interface is weak, and the resulting tensile properties are not significantly different from the wood–air composite in the absence of pMDI. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Viscoelasticity of epoxy resin/silica hybrid material prepared via sol–gel process: Considered in terms of morphology

AbstractWe investigated the relationship between the morphology and viscoelasticity of epoxy/silica hybrid materials manufactured via two different processes: simultaneous formation of epoxy and silica phases and sequential formation of silica phase in the prepared epoxy phase. The glass transition phenomena of the hybrid materials mostly depended on their silica structure. The particular structure did not affect Tg much, while the silica chain structure greatly raised Tg of the hybrid samples. The storage modulus E′ depended on the volume fraction of the silica phase ζ, rather than the silica structure. In the glassy state, E′ of the hybrid samples slightly decreased when compared with the neat epoxy samples. Lack of chemical reaction between the silica and the epoxy phases could be attributed to this decrease at which the silica structure could have worked as a flaw. In the rubbery state, E′ greatly increased with increasing silica content ζ regardless of the silica structure, and this behavior well agreed with that predicted by the Davies model, because the physical interaction worked very well in the rubbery region. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008