Critical Point Data Research Articles

Development of a monitoring system for disassembled towers with internal suspension poles

The traditional construction monitoring methods of suspended pole-mounted decomposed towers are mostly manual monitoring. The monitoring personnel has multiple blind spots, and the possibility of misjudgment based on personal experience is relatively large. It is difficult to ensure the construction safety of the suspended pole decomposing tower. For this reason, combined with the current power Internet of Things technology, this paper develops an intelligent monitoring system for suspended pole-mounted decomposing towers. According to the construction technology and its safety requirements of inner suspension derrick for transmission tower erection in sections, this system is classified into intellisense layer, wireless transport layer and information integration layer. According to the physical characteristics of the seven major risk points of the inner suspension pole group tower, the intellisense layer developed corresponding sensing equipment to obtain risk information. In the wireless transport layer, the ZigBee and 4G communication technologies are selected to interconnect self-constituted LAN and 4G wide area networks, to complete on-site data interaction and long-distance transmission. In the information integration layer, the force of cable, the inclination and height of derrick, and the distance between derrick and tower are determined. The system has been verified by the 500 kV delivery project of Fujian Zhouning Pumped Storage Power Station. The average error of critical monitoring point data is 4.14%, and the average data transmission delays in the far and near fields of the system are 18 ms and 176 ms.

Estimating polystyrene equation of state (EOS) parameters using the cloud and critical points of polystyrene + hydrocarbon mixtures*

AbstractThree polystyrene parameters for the modified Sanchez‐Lacombe equation of state were estimated by performing a correlation of the cloud and critical point data for six well defined polystyrene + hydrocarbon mixtures. The volume shift, a fourth parameter, was adjusted to the polystyrene pressure‐volume‐temperature (PVT) data. A parameterization of the modified Sanchez‐Lacombe equation of state is used to estimate the hydrocarbon parameters given their critical temperature, critical pressure, and acentric factor, but these properties are not available for the polymer. The original polystyrene parameters estimated solely on the pure component PVT data results have difficulty representing the slope and curvature of the cloud points of binary polystyrene + hydrocarbon mixtures. A previous technique for adjusting one of the polystyrene parameters to match the cloud points with the remainder fit to the PVT data results in an improved match over the pure component PVT data alone. Adjusting three polystyrene parameters can better match the cloud points of a binary polystyrene + hydrocarbon mixture, while only increasing the absolute average deviation in pure polystyrene density by 0.07%. The polystyrene parameters obtained by fitting the cloud points were used to correlate the bubble points of polystyrene in other solvents.

Morse inequalities for orbifold Borel homology

Using a notion of Morse function on classifying spaces for finite groups, we define Morse numbers relating the critical point data of an orbifold Morse function to the homology of an associated Borel construction. In particular, we establish Morse inequalities relating our numbers to integral equivariant homology, generalizing the inequalities for manifold Morse functions due to E. Pitcher. To showcase the sharpness of these new inequalities, we will provide a complete classification of all closed, orientable, two-dimensional orbifolds for which equality may be achieved. For three-dimensional orbifolds with singular circles, we prove partial results in this direction, with an emphasis on singular knots in orbifold three-spheres.

System Identification of a Soil Tunnel Based on a Hybrid Artificial Neural Network–Numerical Model Approach

System identification of structures is the primary goal of this study. Numerical simulation using methods such as finite element modelling or finite difference modelling is the practical solution to model the structure based on some accurate parameter values that are essential to identify the behaviour law of the structures. An optimisation method integrated with the numerical model (NM) can solve an inverse problem to provide a calibrated parameter set to improve the modelling. For this purpose, an application of artificial neural networks (ANNs) integrated with an NM with the title “hybrid ANN–NM” approach is proposed in this study so that the parameters and resulted deformations of a developed NM of the structure would enter to a designed ANN for training the network. The developed hybrid ANN–NM method to identify the system of a tunnel excavated in the soil is applied and reported in this paper. A set of variable material parameters with a set of displacement and strain data (in $$x$$ and $$y$$ directions) of critical points of the tunnel which obtained from 2D FDM in FLAC 7.00 software is provided to train the ANN. This study is divided into two methods: (1) fitting model to the displacements and strains to show the deformation behaviour of the tunnel related to the parameter changing, and (2) fitting model to the parameters related to the displacements and strains to estimate the optimum parameters for the NM. For the first method, the parameter dataset as input and the displacements and strains as the ANN’s output in one approach separately and in another approach altogether are considered to train the ANN. In the second method, the displacements and strains as input and the physical parameters of the NM as output are submitted to train the ANN. The MSE convergence of implemented ANN shows the power of ANN to model the behaviour of structure based on the token data. Also, the RMSE of residuals refers to the success of the proposed method for the fitting model. Besides, this method was able to provide the optimum parameters for the numerical model in minimum computing time regarding the implementation of the second method.

Density of Liquid Niobium and Tungsten and the Estimation of Critical Point Data

Density as a function of temperature was measured for the liquid transition metals niobium and tungsten by means of ohmic pulse-heating. The generated data are extensively compared to the existing literature data, and the uncertainty is critically assessed according to the guide to the expression of uncertainty in measurement (GUM). Starting from the obtained liquid-phase density regression, the phase diagram, and the critical point, i.e., critical temperature T_{mathrm {c}} and critical density rho _{mathrm {c}} of niobium and tungsten are estimated. The so-obtained critical point for these two high-melting metals is compared to the data available in the existing literature.

Possibility of pressure crossover prediction by classical DFT for sparingly dissolved compounds in scCO2

A new method of solubility estimations, applied to sparingly dissolved compounds in supercritical carbon dioxide has been introduced in this paper. The method is based on determination of solubility contributions along the thermodynamic path consisting of sublimation and solvation processes. The contribution of the sublimation process is taken from the experiment, while the free energy of solvation is calculated from the classical density functional theory based on the fundamental measure theory. The parameterization of potential was performed using the Weeks-Chandler-Anderson procedure, where the Lennard-Jones parameters were obtained from the thermodynamics data of solute and solvent critical points. The introduced method can efficiently predict the pressure crossover on solubility curve of sparingly dissolved compounds in supercritical carbon dioxide.

Density of Liquid Tantalum and Estimation of Critical Point Data

In order to determine the density of tantalum over the entire liquid phase (at the pressure applied) and several hundred K into the super-heated region, the method of ohmic pulse-heating was applied. For this purpose, images of the thermal radial expansion of the resistively heated sample wires were taken with an adapted CCD system. A newly integrated high-power photoflash and improved triggering of the experiment allowed the acquisition of high-contrast shadow images of the expanding wires. To reduce the uncertainty arising from simultaneous pyrometric temperature measurement, the change in normal spectral emissivity as a function of temperature was additionally taken into account. In this work, the density versus temperature relationship of tantalum is reported and compared to existing literature data. From the newly obtained liquid-phase density, critical point data of tantalum, such as critical temperature and critical density, were estimated via an extrapolation procedure. Furthermore, an estimate of the phase diagram in the density versus temperature plane is given. The work is concluded by a rigorous density uncertainty estimation according to the guide to the expression of uncertainty in measurement (GUM).

Consistency Analysis and Data Consultation of Gas System of Gas-Electricity Network of Latvia

Abstract In the present research, the main critical points of gas transmission and storage system of Latvia have been determined to ensure secure and reliable gas supply among the Baltic States to fulfil the core objectives of the EU energy policies. Technical data of critical points of the gas transmission and storage system of Latvia have been collected and analysed with the SWOT method and solutions have been provided to increase the reliability of the regional natural gas system.

Crowd Simulations and Determining the Critical Density Point of Emergency Situations.

In modern societies, crowds and mass gatherings are recurrent. A combination of inadequate facilities and inefficient population management can lead to injury and death. Simulating people's behavior in crowds and mass gatherings can assist in the planning and management of gatherings, especially in emergency situations. We aimed to determine the crowd pattern and the critical density point in the grand bazaar of Kerman in Iran. We collected data by use of a census method with a questionnaire. To determine the critical density point, height and weight data were placed in the equation $\,s\,{\equals}\,\sqrt {{{L{\vskip -1.5pt \,\,\asterisk\,\,}M} \over {3600}}} $ and the outer body surface of all the individuals in the bazaar was calculated. The crowd was simulated by use of flow-based modeling. Flow rate was determined by using the equation (flow rate=density * speed). By use of SketchUp Pro software (version 8; Trimble, Sunnyvale, CA), the movement of each person and the general flow rate were simulated in the three-dimensional environment of Kerman bazaar. Our findings showed that the population critical density point in Kerman bazaar would be 6112 people. In an accident, the critical density point in Kerman bazaar would be created in about 1 minute 10 seconds after the event. It seems necessary to identify and provide solutions for reducing the risk of disasters caused by overcrowding in Kerman bazaar. It is suggested that researchers conduct studies to design safe and secure emergency evacuation of Kerman bazaar as well as proper planning for better and faster access of aid squads to this location. (Disaster Med Public Health Preparedness. 2017;11:674-680).

Atomic energy analysis of cooperativity, anti-cooperativity, and non-cooperativity in small clusters of methanol, water, and formaldehyde

The local and regional stabilities in clusters of water, methanol, and formaldehyde up to the tetramers have been analyzed from an atomic energy perspective. We optimize structures at the MP2/6-311++G(d,p) level with some CCSD(T)/6-311++G(d,p) single point energies, and then decompose the electronic densities into atomic parts using the atoms in molecules (AIM) approach. We consider the changes in atomic energy in the clusters vs. the isolated monomer. This method of analysis allows us to reveal the variety of stabilities within these hydrogen-bonded clusters, including indications of cooperative, anti-cooperative, and non-cooperative interactions. Cooperatively interacting clusters have increasing stability at the atomic level as the cluster size grows. This is not observed in the anti- and non-cooperative arrangements of water and formaldehyde clusters. The cooperativity in methanol clusters is dominated by the OH regions, with negligible energy change in the methyl regions. Formaldehyde clusters, including the lowest minimum “bucket” cluster, do not show significant cooperativity. Atomic energy analysis is supported with bond critical point data as well as charge and geometric values. We represent the local stability in the clusters using a simple visual approach that allows areas of increased or decreased stability to be easily interpreted.

Modelling of Integrating Processes with Time Delay Using a Relay Response Curve

This paper presents a technique to identify integrating processes based on time domain analysis of the relay response curve. Explicit analytical expressions are provided for first- and second-order integrating process models in terms of a few critical point data. Models with up to three parameters are estimated by means of a single symmetrical relay experiment without solving any nonlinear equations. The procedure requires less time for the autotuning test as it uses only half-output limit cycle data. Simulation examples illustrate the simplicity of the presented method.

Prediction of vapour–liquid coexistence data of Phenylacetylcarbinol

Phenylacetylcarbinol (PAC) is an important chiral molecule, the R-isomer of which is used in the manufacture of several pharmaceutical products and is currently produced by means of biotransformation. The knowledge of thermodynamic properties of PAC is essential to improve the process involving the separation of PAC from the organic solvent, used in the biotransformation process to extract PAC from the aqueous broth. In spite of its importance, limited experimental vapour pressure data is available on PAC in the literature. Hence, in this study, the physical and thermodynamic properties of PAC are predicted using structure property correlations combined with equations of state, and also molecular simulation as the first step to optimize the process design for the production of PAC. The properties predicted include liquid and vapour densities at co-existence, enthalpy of vaporization, saturation pressure, critical point and normal boiling point. The liquid and vapour densities at coexistence and the critical point data from both the methods are found to be in agreement.

Volumetric properties of ionic liquids from cubic equation of state: Application to pure and mixture

In this work, we developed a cubic equation of state (CEOS) for modeling the volumetric properties of various ionic liquids (ILs). Two temperature-dependent parameters presented in the CEOS, have been determined from two sets of corresponding states correlations which are based on the critical point data or the surface tension of ILs. The predicted densities of pure ILs were compared with the experimental data over a broad pressure range from 1 to 100MPa. The total average absolute deviations (AADs) of the calculated densities of 948 data points from the experimental data are 1.82% using the critical property and 0.96% using the surface tension and liquid density as scaling parameters. Furthermore, the proposed CEOS was successfully extended to mixtures including IL+IL and IL+solvent systems. 1282 literature data points for mixtures were taken to check the reliability of the mixture version of the proposed CEOS. The AAD of the calculated densities of the mixtures using the surface tension and liquid density as scaling parameter is 0.37%. Furthermore, the excess molar volumes (VE) of the studied binary mixtures have been successfully computed by the use of the proposed CEOS.

Liquid–Liquid Equilibria of Polyvinylpyrrolidone + Several Ammonium Salts + Water Aqueous Two-Phase Systems: Experimental and Correlation

Phase equilibrium behaviors of polyvinylpyrrolidone (PVP) + (NH4)2HPO4, (NH4)2SO4, (NH4)2CO3, (NH4)2C4H4O6, and (NH4)2HC6H5O7 + H2O aqueous two-phase systems (ATPS's) were determined at 298.15 K. A series of common phase-forming ammonium salts and the corresponding anions were discussed. Meanwhile, the temperature effect on phase equilibrium behavior for PVP (K30) + (NH4)2HPO4 + H2O ATPS was investigated at (288.15, 298.15, and 308.15) K. It was found that phase-forming abilities of the salts are in the order: (NH4)2HPO4 > (NH4)2SO4 > (NH4)2C4H4O6 > (NH4)2HC6H5O7 > (NH4)2CO3. Furthermore, a third-order polynomial equation was used to correlate the binodal data, while a simple two-parameter equation along with the Othmer–Tobias and Bancroft equations was used to correlate the tie-lines data. All equations used above were proved to be valid for the experimental data. At last, the data of critical points were obtained by an extrapolation method.

Bonding Trends Traversing the Tetravalent Actinide Series: Synthesis, Structural, and Computational Analysis of AnIV(Aracnac)4Complexes (An = Th, U, Np, Pu;Aracnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-tBu2C6H3)

A series of tetravalent An(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An((Ar)acnac)(4) (An = Th (1), U (2), Np (3), Pu (4); (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group C2/c. Analysis of the bond lengths reveals shortening of the An-O and An-N distances arising from the actinide contraction upon moving from 1 to 2. The shortening is more pronounced upon moving from 2 to 4, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U-O versus Pu-O orbital interactions previously observed in the comparison of UI(2)((Ar)acnac)(2) and PuI(2)((Ar)acnac)(2) bis-complexes. Computational analysis of models for 1, 2, and 4 (1a, 2a, and 4a, respectively) concludes that both the An-O and the An-N bonds are predominantly ionic for all three molecules, with the An-O bonds being slightly more covalent. Molecular orbital energy level diagrams indicate the largest 5f-ligand orbital mixing for 4a (Pu), but spatial overlap considerations do not lead to the conclusion that this implies significantly greater covalency in the Pu-ligand bonding. QTAIM bond critical point data suggest that both U-O/U-N and Pu-O/Pu-N are marginally more covalent than the Th analogues.

Dynamic simulation of pipelines containing dense phase/supercritical CO2-rich mixtures for carbon capture and storage

Carbon dioxide mixtures from separation plants contain usually some impurities. Major impurities include nitrogen, argon, hydrogen and oxygen, depending on the capture technology used for the removal of CO2. The mixture composition determines the critical point data, and the values of critical pressure and critical temperature define, in turn, the limits of dense phase/supercritical pipeline operating conditions. The simulation of dynamic behaviour of three dense phase/supercritical CO2-rich mixtures was carried out in this study. The pipeline CO2 flow model was formulated with the assumption of one-dimensional, nonisothermal flow condition. An illustration of the performance of the model by an example of a fictive but realistic onshore CO2 pipeline is given. The results show that the type and quantity of impurities have a significant influence on the hydraulics of the pipeline transportation system under transient conditions. They also indicate that the transportation costs vary and are dependent on the capture technology used.

Application of the CBSM method for selected ternary and pseudo-ternary L + L systems, and novel criterion for extractants capability

This paper presents the Component Binding by Saturation Model (CBSM) method for correlation of LLE phase composition data for 23 ternary systems and 1 pseudo-ternary system, including both polar and non-polar solutes. In focus on extraction water systems, partition and binding isotherms are proposed, and their parameters are found. Tie-line data are correlated, and critical point data for the example LLE are estimated. To select suitable extractants for the example extraction systems, particularly for the group of water+ethanol+extractant systems, the integral and relative integral capacity criterion is introduced and applied. To assess and/or predict the concentration extent of extractants using, the integral capacity is defined. To predict the capability of the extractants to bind the partitioning component, the relative integral capacity is defined. For the systems with a basic partition mechanism, the general relationship between relative integral capacity and partition constant is expressed and verified. For the extraction systems with associative partition mechanism from the ethanol group ternaries, the empirical relation between the multiparametric variable formed from the partition isotherm parameters and the relative integral capacity is found.

Upward extrapolation of saturated liquid densities

The design of new energy conversion processes requires equations of state for the working fluids. For their construction saturated liquid densities are needed which are not available for some potential working fluids at higher temperatures. Hence, we investigate how Rackett-type equations behave in extrapolations from saturated liquid densities in the temperature range 0.5 ≤ T/ T c ≤ 0.75 up to the critical temperature T c. Extrapolation methods with different inputs from the critical point are used: (a) no critical point data, (b) critical temperature, (c) critical temperature and pressure, and (d) critical temperature and compression factor. It is found that upward extrapolations of the saturated liquid densities without using critical point data can be done with some care and that the additional use of the critical temperature improves the quality of the predictions substantially.

Simulation of Fluid Phase Equilibria in Square-Well Fluids: From Three to Two Dimensions

We study the influence of geometric restrictions on vapour/liquid coexistence properties and critical data of square-well fluids. Starting with three-dimensional bulk systems, we model the confinement by slit-like pores with decreasing slit widths arriving finally at planar (two-dimensional) fluid layers. For both bulk and confined fluids, we use a uniform approach performing series of canonical ensemble Monte Carlo simulations with Widom-like (virtual) particle insertions to estimate chemical potential versus density isotherms. By estimating the corresponding vapour/liquid coexistence densities using a Maxwell-like equal area rule for the subcritical chemical potential isotherms, we are able to study the influence of the confinement not only on chemical potentials but also on the coexistence properties. Critical point data are calculated from the coexistence densities by means of scaling relations. In particular, we study the change of the critical temperature and critical density varying the slit width and including the two- and three-dimensional bulk fluids as limiting cases. While the difference between the bulk and the slit critical temperature is found to decay exponentially with an exponent reciprocal to a linear function in the slit width, no comparable simple relation describing the influence of the confinement on the critical density is found.

Thermodynamic study on phase equilibrium of epoxy resin/thermoplastic blends

The experimental phase diagrams (cloud point curves) of three series of epoxy/thermoplastic blends, namely, epoxy/polystyrene (PS), epoxy/poly(ether sulfone) (PES), and epoxy/poly(ether imide) (PEI) as a function of molar mass and composition have been analysed from a thermodynamic point of view. A model based on the Flory–Huggins lattice theory considering the concentration dependence of the interaction parameter as predicted by Koningsveld was employed to determine the equilibrium compositions, and concentration and temperature dependent interaction parameters. Binodal, spinodal, and critical point data have been computed and show good agreement with experimental data.