CPE Model Research Articles

Description and prediction of stress-strain curve of loess

The accurate description of the stress-strain relationships of rock and soil is very important to analyze its mechanical properties, but the forms of stress-strain curves are different, which can be softening, hardening, or ideal elastoplastic. With the change of confining pressure, they can be transformed into each other. Taking one of loess as the research object, consolidated drained triaxial tests of undisturbed loess under different confining pressures are carried out. The stress-strain relationship obtained is described by the composite power exponential model (CPE model). According to the results, the critical confining pressure during the transformation of the stress-strain curve and the stress-strain relationship under a given confining pressure are predicted. The comparison with the experimental data shows that the CPE model has high accuracy in description and prediction, and the predicted critical confining pressure can correctly judge the type of stress-strain curve of undisturbed loess under different confining pressures. The predicted ideal elastic-plastic stress-strain curve and the curves under given confining pressures conform to the curve change law, which can reflect the real characteristics of loess. Finally, the stress-strain curves of coral clay, silica sand and cement mortar are described and predicted by the CPE model, and then compared with the experimental data. The high consistency between the two further verifies the wide applicability of the CPE model. It provides a method to infer the results under other conditions from a limited number of test results, which will help to correctly analyze the mechanical properties of loess, clay, sand, cement mortar and other materials in practical projects, and to be realized in numerical analysis.

Modulation of soluble guanylate cyclase ameliorates pulmonary hypertension in a rat model of chronic thromboembolic pulmonary hypertension by stimulating angiogenesis.

Acute pulmonary embolism (PE) does not always resolve after treatment and can progress to chronic thromboembolic disease (CTED) or the more severe chronic thromboembolic pulmonary hypertension (CTEPH). The mechanisms surrounding the likelihood of PE resolution or progress to CTED/CTEPH remain largely unknown. We have developed a rat model of CTEPH that closely resembles the human disease in terms of hemodynamics and cardiac manifestations. Embolization of rats with polystyrene microspheres followed by suppression of angiogenesis with the inhibitor of vascular endothelial growth factor receptor 2 (VEGF‐R2) SU5416 results in transient, acute pulmonary hypertension that progresses into chronic PE with PH with sustained right ventricular systolic pressures exceeding 70 mmHg (chronic pulmonary embolism [CPE] model). This model is similar to the widely utilized hypoxia/SU5416 model with the exception that the “first hit” is PE. Rats with CPE have impaired right heart function characterized by reduced VO2Max, reduced cardiac output, and increased Fulton index. None of these metrics are adversely affected by PE alone. Contrast‐mediated CT imaging of lungs from rats with PE minus SU5416 show large increases in pulmonary vascular volume, presumably due to an angiogenic response to acute PE/PH. Co‐treatment with SU5416 suppresses angiogenesis and produces the CTEPH‐like phenotype. We report here that treatment of CPE rats with agonists for soluble guanylate cyclase, a source of cGMP which is in turn a signal for angiogenesis, markedly increases angiogenesis in lungs, and ameliorates the cardiac deficiencies in the CPE model. These results have implications for future development of therapies for human CTEPH.

Electrical impedance spectroscopy of a PET chip sandwiched between two disk electrodes: understanding the contribution of the polymer/electrode interface.

This work is devoted to the understanding of the dielectric impedance response of a semi-crystalline polyethylene terephthalate (PET) membrane sandwiched between two disk electrodes under alternate voltage excitation in the frequency range between 1 MHz and 25 mHz. Experimental results obtained for various PET thicknesses (36, 50 and 100 μm) highlighted the influence of the contact resistance at the electrode/polymer interface. For a better understanding of the PET/electrode interface behaviour, the experiments were compared with simulations performed for three different descriptions: the direct use of electrical equivalent circuits, an analytical model accounting for a power-law distribution of resistivity, and a numerical model (finite element simulations of the whole cell). The results highlight that the resistivity distribution obtained using the power-law model provided an appropriate description of the system in the frequency range investigated while the use of the CPE model is only consistent for low-frequencies (below 1 Hz).

On the Dielectric Properties of Human Skin

Electrochemical impedance spectroscopy has become a powerful tool to assess the response of human skin to external stimuli. Two approaches have been taken to analyze the skin impedance data. The skin properties have been assumed to be independent of spatial position but dependent on frequency,[1] and, alternatively, skin properties have been assumed to be independent of frequency but dependent on spatial position.[2] Recent data published by White et al.[3] provides a unique opportunity to assess the validity of the two distinct approaches. The data used in the present study were part of a larger study intended to correlate changes in the flux of p-chloronitrobenzene and 4-cyanophenol in response to physical and chemical damage. Split-thickness human cadaver skin (300-400 microns thick) from the back was purchased from the National Disease Research Interchange (NDRI, Philadelphia, PA). The skin was collected within 24 h post mortem, frozen immediately, and stored at temperatures less than -60 C until used. The protocol described by White et al.[4] was used to ensure that skin samples had sufficient integrity for meaningful measurements of in-vitro chemical permeability.The impedance was measured in the four-electrode configuration, in which two Ag/AgCl (In Vivo Metric, Healdsburg, CA) reference electrodes were used to sense the potential drop across the skin, and two Ag/AgCl working electrodes were used to drive the current. The skin was exposed on both sides for roughly eight hours to a phosphate buffered saline solution (PBS) (0.01 M, pH 7.4, Sigma P-3813) prepared in de-ionized water. The impedance measurements were collected with a 10 mV potential perturbation after two eight-hour long, permeation experiments in which 4-cyanophenol-saturated PBS was placed in the donor chamber and PBS was placed in the receptor chamber. After the first 4-cyanophenol permeation experiment, the frame holding the skin was removed from the diffusion cell, the skin was pierced by a 26 gauge needle (with a 464 micron outside diameter), the cell was reassembled, and the donor and receptor chambers refilled with fresh 4-cyanophenol-saturated PBS and PBS, respectively, for the second permeation experiment. Before perforation with a needle, the impedance diagrams showed a capacitive loop with a depressed semi-circle, consistent with a CPE model. The impedance measured after perforation with the needle could be fit by a CPE model, but the capacitive loop was substantially smaller. Perforation by a needle also caused a substantial shift in the characteristic frequency. These data were used to evaluate models for the impedance response of skin under the hypothesis that perforation by a needle introduces an additional parallel pathway for current to flow, but should not change the dielectric properties of the skin. Under the assumption that skin properties are a function of frequency, this hypothesis means that the frequency-dependent dielectric response should not be altered by perforation of the skin. The observed frequency shift provides a means of assessing different proposed distributions of skin properties. The analysis presented in this paper supports the hypothesis that skin may be described as a system with frequency-independent properties that are functions of position within the skin. The frequency-dependent relative permittivity and resistivity were changed substantially by perforation of the skin. References S. Grimnes and O­. G. Martinsen, Bioimpedance and Bioelectricity Basics, 3rd edition (Amsterdam: Academic Press, 2015). M. E. Orazem, B. Tribollet, V. Vivier, S. Marcelin, N. Pebere, A. L. Bunge, E. A. White, D. P. Riemer, I. Frateur, and M. Musiani, J. Electrochem. Soc., 160 (2013) C215-C225. E. A. White, M. E. Orazem, and A. L. Bunge, Pharm. Res., 30 (2013), 2036-2049. E. A. White, M. E. Orazem, and A. L. Bunge, J. Electrochem. Soc., 159 (2012) G161-G165.

Electrochemical Double Layer Capacitors (supercapacitors) Ageing Impacts and Comparison on Different Impedance Models

Electrochemical Double Layer Capacitors (EDLC) are energy storage devices known for their higher lifetime and higher power density than batteries. They use double layer electrostatic effect between ionic and electronic charges. This articles deals with impedance models used for EDLC modeling. Firstly this article presents EDLC ageing causes through a literature review. Then it is shown by experimental results that ageing mainly affects EDLC impedance. Secondly the article presents the classical models used for EDLC impedance modeling (single pore model, CPE model) with the physical meaning of their parameters. The newest model called multipore model (MP) allows to classify porous structure EDLC by pore time constants. Then every impedance models are compared in term of fitting precision with experimental results.

PEMFC Fault Diagnosis, Modeling, and Mitigation

This paper introduces fault diagnosis and separation, mitigation, and modeling of a proton exchange membrane fuel cell (PEMFC). Experimental tests of a single PEMFC were performed during this study. Flooding and drying faults were implemented to be detected from the cell voltage and impedance response of the cell. The impedance response at low frequency was used to identify the cause of the fault. The slope of the magnitude and/or the negative phase response of the cell impedance at low frequency were observed to allow separation of a fault. A cell impedance model based on resistive capacitive (C model) and resistive constant-phase-element (CPE model) circuits is developed. The CPE model has a better approximation of the cell impedance. However, the C model is easy to implement since it is well known in most simulation tools (MATLAB/Simulink or PSpice). A power electronic control is designed and tested to mitigate the faults. Pulsing the cell current at low frequency was seen to increase the cell power by 8% during drying.

Positron impact ionization of molecular nitrogen

We have carried out distorted wave calculations of positron ionization of molecular nitrogen in order to compare with recent experimental measurements. In this work, the nitrogen molecule was represented by a Gaussian wave function. We find that our CPE model gives the better agreement with the measurements in spite of its simplicity.

Positron impact ionization of molecular nitrogen

We have carried out distorted wave calculations of positron ionization of molecular nitrogen in order to compare with recent experimental measurements. In this work, the nitrogen molecule was represented by a Gaussian wave function. We find that our CPE model gives the better agreement with the measurements in spite of its simplicity.

Positron impact ionization of molecular oxygen

We have carried out distorted wave calculations of positron ionization of molecular oxygen in order to compare with experimental measurements. In this work the oxygen molecule was represented by a Gaussian wave function which includes contributions from alpha and beta electrons. We find that our CPE model produces results which are in good agreement with the combined measurements for total ionization and positronium formation.

The effect of target representation in positron-impact ionization of molecular hydrogen

Ionization cross sections for positron collisions with hydrogen molecules have been calculated using a two-center molecular representation. The results are compared with our previous work which used sphericaly averaged H 2 wavefunctions as well as with existing experimental results. The use of a two-centre wave function for the molecular target, either of the Heitler–London type or a Gaussian representation, produces results which lie between the two most recent sets of experimental data. We find that our CPE4 model produces results in better agreement with experiment over the whole energy range than our CPE model.

Leadership behaviours as predictors of cost and change effectiveness

In this study it is assumed that different leadership behaviours affect organisational outcomes in different ways. Leadership has been measured using the CPE model, which embraces three types of leadership centring on change production and employees, respectively. Scales were constructed to measure effectiveness with respect to change and cost. The study was carried out in an international Swedish industrial company. A total of 49 departments were included representing 363 respondents. The data were collected at the individual level. However, all the data were aggregated and analysed at the organisational level. The main results are twofold. First, relation-orientated management is significantly related to both outcomes. Second, there are various combinations of behaviours for specific outcomes. The regression analyses revealed that the best combination for cost effectiveness consists of behaviour orientated towards relations and production. The best combination for effectiveness in dealing with change is an orientation towards relations and change behaviour. These two combinations explain about 30% of the variance in the respective criteria of effectiveness.

Positron impact ionization of krypton and xenon

Several distorted-wave models for positron ionization of krypton and xenon are investigated. Our previous CPE (Coulomb plus Plane waves -- full Energy range) model produces reliable cross sections for krypton. For xenon, at high positron energies, the CPE results fall below experiment. We have proposed an alternate model DCPE4 that works well for both krypton and xenon. A common feature of both of these models is that the free electron and positron are treated differently.PACS No.: 34.90.+q

On the ideal polarisability of electrodes displaying cpe-type capacitance dispersion

Abstract The relevance of the concept of ideal polarisability to solid electrodes displaying constant phase angle behaviour (constant phase element (cpe)) is reconsidered in the context of the recent dispute in this Journal [Zoltowski, 443 (1998) 149; Lang and Heusler, 457 (1998) 257]. It is shown that the cpe as a model of the electrochemical interface is ‘unphysical’ due, first of all to unattainability of the steady state after potential or current perturbation. It is also concluded that the thermodynamic equations governing the equilibria of an ideally polarisable electrode cannot be applied to an electrode modelled by cpe because the notions of the charge and double layer capacitance (Cd) are irrelevant in the framework of the cpe model. As a consequence, procedures of calculation of Cd from impedance data modelled by cpe are unjustified.

Globalization, Comparative Political Economy and the Economic Policies of the Blair Government

This paper critically examines attempts to revitalize the comparative political economy model in contrast to analyses based on a globalization perspective. The organized market economy approach of Peter Hall is seen as a more inviting version of the CPE model. The political dilemmas facing national governments in an era of globalization are examined through a discussion of the economic policies of the Blair Government in Britain.

Positron-impact ionization of molecular hydrogen

Two ionization models containing realistic descriptions of the final state of the system, but employing only plane and Coulomb waves, are applied to positron ionization of molecular hydrogen. In addition, spherically averaged wavefunctions are used to simplify the complexity of the molecular geometry. The theoretical cross sections are compared with the measurements of Fromme et al and Moxom et al. The agreement between the experiment of Moxom et al and the CPE model with a reasonably accurate representation is similar to the agreement shown by Campeanu et al for positron ionization of noble gases. These results suggest that relatively accurate spherical representations of the molecular wavefunction can be used successfully in distorted-wave calculations of positron-impact ionization of molecular targets.

Control or Decontrol? Theoretical arguments for policy making in transition

After a period of reform of the CPE model, some fundamental issues remain interesting, such as how to treat markets and planning, and how to reform. The historical debates between the ‘Disequilibrium School’ and the ‘Shortage School’ have never been clearly concluded. The chronic-excess-demand hypothesis has by no means been shown to be correct. Some literature overlooks the important differences between CPEs and RCPEs in terms of the nature and functioning of economic institutions. Actually, financial crisis in CPEs and RCPEs are outcomes of a set of complex factors, notably the decontrolling of the financial and banking systems. To address the extreme importance of financial control in transition, econometrics still looks not so powerful.

Street Ministry CPE: An Experiment in the Haight-Ashbury

Describes a non-institutional Clinical Pastoral Education program focusing on street people and the ways CPE students discovered for ministering to them. Argues that the advantages of this CPE model include (1) a unique context for ministry, (2) greater growth in pastoral identity through less identification with institutional authority and more identification with those ministered to, and (3) a different perspective for ethical and theological reflection than is usually found in more traditional CPE programs.

Screening and distortion effects in positron impact ionisation of helium

Total cross sections for positron impact ionisation of helium are calculated within a distorted-wave formalism. By using various physical models the authors found that those which include complete screening of the residual ion are capable of reproducing the experimental data. The inclusion of distortion of the outgoing waves brings the authors CPT and CPE model results into very good agreement with the measurements of Fromme et al (1986) up to 300 eV.

Use of the CPE Model in Developing Congregational Campus Ministry

Use of the CPE Model in Developing Congregational Campus Ministry

Pastoral supervision today

The introduction of clinical pastoral education as a prerequisite to many forms of ministry and the initiation of D. Min. programs in theological schools call for a reappraisal of the process and substance of pastoral supervision. Effective models of supervision for D. Min. programs have not yet been identified, yet a CPE model is inherent in the requirements for the degree. The meaning, goals, content, and styles of supervision are discussed. A scale is included to assist students and supervisors to evaluate supervisory conferences.