Parallel-series Model Research Articles

Study on Thermal Conductivity of Reinforced Concrete Plate

By the heat flow meter method, the thermal conductivity of reinforced concrete was experimental studied for the energy conservation design of reinforced concrete composite wall as building envelop. The steel bars were arranged as horizontal one-way, horizontal two-way and vertical in the reinforced concrete plates with different reinforcement volume ratio. Based on the test results, the effects of arrangement of steel bar and reinforcement volume ratio on thermal conductivity of reinforced concrete were analyzed. It can be concluded that the thermal conductivity of reinforced concrete was higher than that of concrete and increased with the reinforcement volume fraction, the steel bars in horizontal two-way arrangement brought the reinforced concrete with greater thermal conductivity than that in one-way arrangement, the vertical steel bar made the reinforced concrete with significantly higher thermal conductivity. The series-parallel model and parallel-series model are proposed for predicating the thermal conductivity of reinforced concrete with horizontal steel bars.

Capacitive humidity sensor with a coplanar electrode structure based on anodised porous alumina film

A simple and new relative humidity (RH) capacitive sensor with a two-layer planar structure based on anodic aluminium oxide (AAO) film serving as a sensing layer has been fabricated. A pair of separated tantalum thin films under the AAO layer served as two coplanar electrodes. AAO film was fabricated by anodising deposited aluminium thin film in oxalic acid. The influence of the pore size and thickness of the AAO film, and the electrode spacing, on the performance of the sensor was investigated. The RH sensor with a thicker AAO film and narrower electrode spacing was more sensitive. By pore widening, the sensitivity of the sensor can be improved. The achieved average sensitivity as high as ∼3.57 pF/RH% was obtained for sensors with an AAO layer of 2 µm thickness and 80 nm pore size. These results were explained using the partial capacitance method and parallel-serial model. In addition, under the humidity range of 20–80%, sensors with 70 nm pores had the highest sensitivity, which was interpreted in terms of effective permittivity and anion concentration. This study provides an easy method to fabricate high-performance humidity sensors with very simple structures for practical applications.

Theoretical and experimental study of the thermal conductivity of nanoporous media

The nanoparticle thermal conductivity and nanoscale thermal contact resistance were investigated by molecular dynamics (MD) simulations to further understand nanoscale porous media thermal conductivity. Macroscale porous media thermal conductivity models were then revised for nanoporous media. The effective thermal conductivities of two packed beds with nanoscale nickel particles and a packed bed with microscale nickel particles were then measured using the Hot Disk. The measured results show that the nano/microscale porous media thermal conductivities were much less than the thermal conductivities of the solid particles. Comparison of the measured and calculated results shows that the revised combined parallel-series model and the revised Hsu-Cheng model can accurately predict the effective thermal conductivities of micro- and nanoparticle packed beds.

An analytical model for combined radiative and conductive heat transfer in fiber-loaded silica aerogels

An improved analytical model for the total thermal conductivity of fiber-loaded silica aerogels was developed based on the complex refractive index, size, orientation, volume fraction and morphology of the fibers and silica aerogel. A cubic array of spherical porous secondary nanoparticles and a modified parallel-series model were proposed to model the combined solid and gaseous thermal conductivities. An anomalous diffraction theory (ADT) was used to predict the fiber extinction coefficient. Five common fiber types in the composites were studied including amorphous SiO2 glass, silicon glass, common float glass, soda lime silica glass and borosilicate glass. The results show that the total extinction coefficient of the silica aerogel system is largest by loading with the common float glass fiber and lowest by loading with the soda lime silica glass among the five fiber types. The model provides theoretic guidelines for material designs with optimum parameters, such as the type, inclination angle, volume fraction and diameter of the fibers as well as the aerogel nanoparticle and pore sizes. The optimum fiber for improved thermal insulation should have a large spectral complex refractive index throughout the infrared region.

Risk Study on Subway Construction Based on Reliability Theory

This paper described the present risks existing in subway construction and proposed the idea that reliability theory can be applied in the field of subway construction. Based on this, a parallel-series model of risk control system was established. According to the required target of system reliability, combining with the reliability distribution theory, the reliabilities of each subsystem that constituted the parallel-series model can be determined. Aiming at the basic events that constituted the subsystem, average allocation method was taken to solve the basic events reliabilities and an example was given. This studies showed that reliability theory can be successfully applied in the field of subway construction and can fulfill the optimization of construction safety under a given security target.

A Novel Method for Simultaneous and Continuous Determination of Thermal Properties during Phase Transition Applied to Calanus finmarchicus

The thermal properties of a product are the most important parameters for practical engineering purposes and models in food science. Calanus finmarchicus is currently being examined as a marine resource for uncommon aquatic lipids and proteins. Thermal conductivity, specific heat, enthalpy and density were measured over the temperature range from -40 to +20 degrees C. The initial freezing point was determined to be -2.3 degrees C. The thermal properties were recorded continuously on 4 samples using a new method, and the results were compared with predictive models. The accuracy of the new method is demonstrated by different calibration runs. Significant differences in the thermal conductivity of the frozen material were found between the parallel-series model and the data, whereas the model of Pham and Willix (1989) or the Maxwell-Euken adaption showed better agreement. The measured data for specific heat, enthalpy, and density agreed well with the model. Practical Application: The thermal data obtained can be used directly in food engineering and technology applications, for example, in a thin layer model for freezing food for which precise thermal data for each layer are now available, enabling the more accurate prediction of freezing times and temperature profiles. Dimensionless numbers (such as the Biot number) can also be based on measured data with minor deviations compared to more general modeled thermal properties. Future activities will include the generation of a comprehensive database for different products.

Relationship of Parallel Model and Series Model for Permanent Magnet Synchronous Motors Taking Iron Loss Into Account

This paper investigates the relationship of parallel model and series model for permanent magnet synchronous motor taking iron loss into account. The expressions of flux linkage, terminal voltage, and electromagnetic torque are compared. It follows from the investigation that the parallel and series models are mathematically the same. In addition, the properties of the models are exhibited. The parallel model is superior in understanding the physical meaning to the series model. The series model is superior in low order of the state variables to the parallel model.

Elastic property estimates of a unidirectional discontinuous fibre composite

A simple modification of the Ward/Wilczynski series-parallel and parallel-series models is used to examine the elastic properties of a unidirectional discontinuous-fibre composite. Whilst not a rigorous bounding procedure, this method allows a rapid evaluation of all the elastic properties and has proved very useful for examining the effects of fibre aspect ratio, interfibre spacing and fibre end-to-end distance on the composite elastic properties. In addition the method can deal with both an anisotropic fibre and an anisotropic matrix. Simple finite-element techniques are used to evaluate these model composites and hence investigate the most appropriate connectivity régimes. The simulations show that only the longitudinal modulus of the composite is significantly modified by the variations in fibre aspect ratio and geometry.

Estimation of system reliability for redundant stress-strength model

The reliability and an estimate for it are derived for series-parallel and parallel-series stress-strength model under assumption that all components are subjected to a common stress. We also obtain the asymptotic normal distribution of the estimate.

Modelling the thermal conductivity of starch-water gels

The thermal conductivity of starch gels, ranging in water content from 51 to 97% by mass, was measured using the thermal probe method and the thermal conductivity of starch itself was determined using a revised analysis of the null point method of Sakiyama et al. (1993), taking into account the effect of hydration. The thermal conductivity of hydrated starch (mass fraction of water = 0.22) was found to be 0.364, 0.386 and 0.388 W m −1K −1 at 10, 50 and 80 °C, respectively, and its density at 20 °C was estimated to be 1.38 × 10 3 kg m −3. The corresponding effective thermal conductivities and density of dry starch were estimated as: 0.293, 0.305 and 0.301 W m −1 K −1 and 1.54 kg m −3, respectively. The measured thermal conductivities of starch gels followed quite closely intermediate models such as the Maxwell model or the parallel-series model, but were inconsistent with either the parallel or series models alone.

Fine structure and tensile properties of ramie fibres in the crystalline form of cellulose I, II, III I and IV I

This study focuses on the change in the fine structure and tensile properties of ramie fibres by the treatment for crystalline conversion. Through the conversion from cellulose I into II, III I and IV I, the integral crystallinity index and the crystallite size decreased and the internal surface area increased while Young's modulus of the fibre decreased and the ultimate strain increased. Two phase parallel, series and parallel-series models which comprise two kinds of springs with different constants representing the crystalline and amorphous components, respectively, were applied to the tensile force-strain relationship of the fibres. The parallel model could not be applied to the samples because the crystal lattice strains were smaller than the fibre strains; the former strains were less than one fourth of the latter ones, at any given tensile load. On the basis of the series model, Young's modulus of crystalline component of cellulose III I was the highest and the next was that of cellulose I, followed by II and IV I. Young's modulus of amorphous component of cellulose I was the highest and the next was that of II, followed by III I and IV I. Applying a parallel series model, the values for Young's moduli of crystalline and amorphous components were found to depend both on the feature of crystalline component and the density of amorphous region.

Heat Transfer in Open Cell Foam Insulation

Heat transfer in open cell foam insulation occurs by conduction through the solid material and through the gas in the cell interior and by thermal radiation, which propagates through the structure. The conductive process within these media is described using a simple parallel-series model. Spectral volumetric absorption and scattering coefficients as well as the spectral phase function are predicted using a combination of geometric optics laws and diffraction theory to model the interaction of radiation with the particles forming the foam. The particles considered are both struts formed at the juncture of three cells and strut junctures. The radiative properties can then be utilized to obtain a weighted extinction coefficient, which can be used in the Rosseland equation to obtain the radiative flux. The innovative part of the work lies in the radiative properties predictive model. This new model is compared with simpler ones.

Tearing behavior of blends of isotactic polypropylene and nitrile rubber: influence of blend ratio, morphology and compatibilizer loading

Tearing behavior of blends of isotactic polypropylene (PP) and nitrile rubber (NBR) has been investigated with special reference to the effect of blend ratio and addition of compatibilizing agents. It has been observed that the tear strength of blends depends on the rubber concentration. Attempts have been made to correlate the tear strength with the morphology of the blends. Various composite models such as parallel model, series model, Halpin-Tsai equation and Coran's model have been used to fit the experimental values. The effect of addition of phenolic modified polypropylene (Ph-PP) as a compatibilizer on the tear strength of PP/NBR blend was investigated. The observed increase in tear strength with increase of Ph-PP concentration has been explained in terms of the reduction in particle size of dispersed NBR domains.

Molecular deformation processes in gel-spun polyethylene fibres

The structure/property relationships in the PE fibres have been interpreted quantitatively using a microfibrillar model and the low-strain mechanical properties have been analysed using the Takayanagi models. Information obtained from Raman spectroscopy in the previous paper has been analysed to determine the molecular deformation behaviour of the gel-spun polyethylene (PE) fibres. It is demonstrated that there is a bimodal distribution of stress in the crystalline regions due to the two-phase microstructure of the fibres and it has been shown that the molecular deformation behaviour can be interpreted quantitatively using a parallel-series model. It is found that the Young's modulus of the crystalline regions increases with the degree of chain extension and for the highest-modulus fibres may be close to the theoretical modulus of polyethylene. The fibre modulus is reduced by the presence of low-modulus non-crystalline material in parallel with the crystals.

Bounds for the elastic constants of a unidirectional fibre composite: a new approach

Series-parallel and parallel-series models are used to calculate upper and lower bounds for a unidirectional fibre composite. It is shown that this simple approach produces comparatively close bounds which agree well with those calculated from more sophisticated analytical methods. This approach may be used for initial estimates of composite properties, e.g. when characterizing a new material. In some cases this may be sufficient for the design of simple composite structures.

Kinetic models of cell shape changes and other optically-detected responses to stimulation

Certain cellular responses to stimulation can be described as a continuous series of virtually infinite but real transient states generated by reactions occurring at the molecular level within the cell. While any particular state can in principle be isolated and examined by using appropriate methods to stop or freeze the reaction, adjacent or nearby states will generally be indistinguishable from one another by kinetic means. In favorable cases, however, the progress curves can be fitted to comparatively very simple kinetic models involving a limited number of steps, which accurately describe the real-time response within the limitations of the experimental setup. The simple series models have their origins in the continuous myriad-state or "microscopic" series description, and the observable or "macroscopic" kinetic rate constants are statistically related to the rate constants describing the transitions between the real states of the ongoing response. This indicates that different aspects of stimulus-response coupling, e.g., shape changes, alterations in cytosolic calcium levels and so forth, can be compared in a self-consistent fashion by modeling the individual responses in terms of simple parallel series models.

Anistropic thermal expansion of oriented crystalline polymers

The linear thermal expansitivity of oriented high-density polyethylene (HDPE) and polypropylene (PP) with draw ratio between 1 and 18 has been measured between 120 and 300 K. The expansivity perpendicular to the draw direction z ̂ (α ⊥) increases with λ, because of the alignment of the crystallite chain axes along ẑ; the expansivity parallel to z ̂ (α ) decreases very sharply with λ, becoming negative at about λ = 3 for HDPE and λ = 7 for PP — a consequence of the negative expansivity of the crystalline phase along its chain axis and the constraining effect of the stiff intercrystalline bridges. A model treating the drawn crystalline polymer as a composite consisting of partly aligned crystallites embedded in an isotropic amorphous matrix is adequate for explaining the behaviour of α ⊥, whereas a parallel-series model can give reasonable estimates of α  for ultra-oriented samples, which is largely independent of λ and decreases with increasing temperature. However, neither model can account for the behaviour of α  at low draw ratio.