Nonlinear Physical Properties Research Articles

Study of the Thermal-Hydraulic Characteristics of a Printed Circuit Heat Exchanger Using a Novel Iterative Inversion Method Combined with Genetic Algorithm

Printed circuit heat exchangers are getting more and more applications in various energy systems. Detailed data monitoring is essential to understand their operation situations in real time. Nevertheless, the commonly monitored parameters are inadequate to evaluate the local flow and heat transfer characteristics when the fluid undergoes an obvious property variation in the channel. In this work, a measurement system for printed circuit heat exchangers similar to those in industrial applications was set up to study the thermal-hydraulic characteristics of supercritical CO2 with non-linear physical properties. The experimental results show that the heat transfer coefficient can be increased by 82.9–109.6% when the mass flow rate increases from 0.15 to 0.42 kg/s. By comparison, the heat transfer coefficient can be increased by 70.7% when the fluid state approaches the critical point. A novel iterative inversion method was proposed to deduce the coefficients of the heat transfer and friction factor correlations based on the collected fundamental parameters. The deviations of the heat transfer rate and friction coefficient between the measured data and the predicted results by the derived correlations were both within 10%, indicating the feasibility and reliability of the inversion method.

Effect of Frictional Slipping on the Strength of Ribbon-Reinforced Composite.

A numerical–analytical approach to the problem of determining the stress–strain state of bimaterial structures with interphase ribbon-like deformable inhomogeneities under combined force and dislocation loading has been proposed. The possibility of delamination along a part of the interface between the inclusion and the matrix, where sliding with dry friction occurs, is envisaged. A structurally modular method of jump functions is constructed to solve the problems arising when nonlinear geometrical or physical properties of a thin inclusion are taken into account. A complete system of equations is constructed to determine the unknowns of the problem. The condition for the appearance of slip zones at the inclusion–matrix interface is formulated. A convergent iterative algorithm for analytical and numerical determination of the friction-slip zones is developed. The influence of loading parameters and the friction coefficient on the development of these zones is investigated.

High-Temperature and Large-Polarization Ferroelectric with Second Harmonic Generation Response in a Novel Crown Ether Clathrate.

Molecular ferroelectrics of high-temperature reversible phase transitions are very rare and have attracted increasing attention in recent years. In this paper is described the successful synthesis of a novel high-temperature host-guest inclusion ferroelectric: [(C6 H5 NF3 )(18-crown-6)][BF4 ] (1) that shows a pair of reversible peaks at 348 K (heating) and 331 K (cooling) with a heat hysteresis about 17 K by differential scanning calorimetry measurements, thus indicating that 1 undergoes a reversible structural phase transition. Variable-temperature PXRD and temperature-dependent dielectric measurements further prove the phase-transition behavior of 1. The second harmonic response demonstrates that 1 belongs to a non-centrosymmetric space group at room temperature and is a good nonlinear optical material. In its semiconducting properties, 1 shows a wide optical band gap of about 4.43 eV that comes chiefly from the C, H and O atoms of the crystals. In particular, the ferroelectric measurements of 1 exhibit a typical polarization-electric hysteresis loop with a large spontaneous polarization (Ps ) of about 4.06 μC/cm2 . This finding offers an alternative pathway for designing new ferroelectric-dielectric and nonlinear optical materials and related physical properties in organic-inorganic and other hybrid crystals.

On-chip erbium-doped lithium niobate microring lasers.

Lithium niobate on insulator (LNOI), regarded as an important candidate platform for optical integration due to its excellent nonlinear, electro-optic, and other physical properties, has become a research hotspot. A light source, as an essential component for an integrated optical system, is urgently needed. In this Letter, we reported the realization of 1550 nm band on-chip LNOI microlasers based on erbium-doped LNOI ring cavities with loaded quality factors higher than 1 million at ∼970nm, which were fabricated by using electron beam lithography and inductively coupled plasma reactive ion etching processes. These microlasers demonstrated a low pump threshold of ∼20µW and stable performance under the pump of a 980 nm band continuous laser. Comb-like laser spectra spanning from 1510 to 1580 nm were observed in a high pump power regime, which lays the foundation of the realization of pulsed laser and frequency combs on a rare-earth ion-doped LNOI platform. This Letter effectively promotes the development of on-chip integrated active LNOI devices.

Temperature–dependent linear and non-linear optical and physical properties of borosilicate 7059 glasses using ellipsometry

Vacuum temperature-dependent ellipsometric studies on borosilicate 7059 glasses and across a temperature range of 111 to 473 K are reported. The refractive index (n), reflection loss (RL), molar refraction (Rm), electronic polarizability (αe), thermo optic coefficient (δn/δT), coefficient of temperature dependence of density (δρ/δT), metallization criterion (Ḿ), optical band gap (Eg), oxide ion polarizability (αo2), optical basicity (A) and electronegativity values are computed. Both the non-linear susceptibility (χ(3)) and non-linear refractive index (n2) are also evaluated over the reported range of temperature. The values of n, RL and Rm are decreased from 1.5317 to 1.5283, from 0.3097 to 0.3079 and from 7.035 to 6.994, respectively over the temperature range 111 - 473 K. The measured values of Ḿ and Eg are increased from 0.6903 to 0.6920 and from 9.53 to 9.58 eV, respectively over the same temperature range. It is noted that the value of αe is decreased from 2.791 to 2.775 × 10−24 cm3, but both δn/δT and δρ/δT are increased from -1.189 to -0.791 × 10−5 K−1 and from -5.212 to -3.46 × 10−5g cm−3 K−1, respectively over the temperature range 111-473 K. Similarly, both n and Eg based oxide ion polarizability {α02-(n)andα02-(Eg)} values are decreased from 1.4326 to 1.4374 and from 1.4275 to 1.44191, respectively. Both the optical basicities, A(n) and A (Eg) are also decreased from 0.5082 to 0.5013 and from 0.5002 to 0.4932, respectively over the reported temperature range. Next, the values of electronegativity (ζ1av) measured using Zahid model on the base of αO2-(n) and A(n) are increased from 5.002 to 5.011 and from 4.7855 to 4.8396, respectively over the temperature range 111-473 K. The values of (ζ1av) measured using Reddy model on the base of αO2-(n) and A(n) are increased from 4.9558 to 4.9691 and from 4.7468 to 4.7771, respectively over the same temperature range. Both χ(3) and n2 are decreased from 1.31620 to 1.27347 × 10−14 esu and from 1.5654 to 1.5274 × 10−14 esu, respectively over the temperature range 111-473 K. Analysis of the above new findings indicates that all the evaluated values of n, RL and Rm, αe,α02-(n)andα02-(Eg), A(n) and A (Eg), have decreasing trend with increasing temperature causing a small increase in Eg values. Further, both the refractive index and energy band gap based Ḿ values are found to be less than one, so, the reported glasses exhibit insulating behaviour over the temperature range 111-473 K. In addition, the rigorous structural changes have not occurred in the glass network over the reported temperature range. Next, due to the low values of δn/δT and δρ/δT, borosilicate 7059 glasses are less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shocks. Also, the calculated values of electronegativity show that these glasses have an ionic character. The new findings also indicate that the generated values for both third-order nonlinear optical susceptibility and non-linear refractive index are very small which don't support the nonlinearity phenomena in these glasses.

The Research of the Repolarization Process in Solid Solutions (Rb1 – xKx)2ZnCl4 by the Harmonic Analysis Method

The reactive component $${{J}_{c}}(t)$$ and the active component $${{J}_{g}}(t)$$ time dependences by the harmonic analysis method of the current density $${{J}_{x}}(t)$$ time dependences arising in the repolarization process in the studied samples in the ferroelectric phase under the action of an electric field $$E(t)$$, whose amplitude is higher than the coercive one, are obtained. Obtained dependences analysis showed general regularities in the dynamics of the (Rb1 – xKx)2ZnCl4 crystals domain boundaries. The regularities of the defects influence on the nonlinear physical properties associated with the domain structure dynamics are revealed.

Comprehensive modeling for geometric optimization of a thermoelectric generator module

This paper develops a one-dimensional simulation model of a thermoelectric module aiming at its characteristic exploration and output performance prediction. Almost all related effects are considered including Seebeck, Peltier, Thomson effects, the spatial- and temperature-dependent thermoelectric material properties, as well as the other irreversible factors. In order to ensure its high accuracy and computational efficiency, the differential equations built for components of non-linear physical properties, and analytical equations for the others of constant properties are jointly solved by numerical methods and implemented in MATLAB integrated development environment. A small deviation of 1.44% exists between its calculated output power and that by a previously reported three-dimensional model under a specific wide load range (0–250 Ω), validating its accuracy of this model. Besides, it indicates that both the proportions of heat leakage through the occupied air zone and its maximum output power to the input total heat flow have the same order of magnitude. A rising proportion for the former has to be paid attention in case of a higher temperature difference applied. The assumption of regarding its electrical contact resistance as an identical external resistance connected with the load in series is computationally proved to generate a negligible discrepancy in terms of TEM characteristics and its output performance. Furthermore, with respect to the impacts of TEM geometry, the pre-set fixed substrate area weakens the equivalence of regarding a thermoelectric module with larger cross-section area of thermoelectric legs as multiple identical modules with smaller leg areas connected in parallel. It accounts for the better linearity of rising output power by a long leg than that by a short leg as the leg area increases. A long thermoelectric leg means an increased induced electrical potential and inner resistance as well, thus leading to a single peak of the output power as the leg length increases. Finally, a thermoelectric geometric optimization approach abased on the Hill-climbing algorithm is introduced and first applied for the maximum output. Its accuracy and efficiency are validated and analyzed detailedly by supplying different variables as initial search point. All the methods and conclusions in this paper can assist thermoelectric generators’ performance estimation and guide the geometric optimizations regarding their large-scale applications in the future.

(Invited) Macro and Microstructure Biomimetic Hydrogel for Biotechnology

In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. Advancements in biomaterial science have resulted in materials having cellular and tissue biocompatibility. Hydrogel materials have especially attracted a great deal of attention because of their unique biocompatibility, advantageous physical characteristics, and innate structural similarities to the extracellular matrix. Recent advances in hydrogel chemistries are enabling researchers to create hydrogels that can act as encapsulation of cells, 3D ex vivo tissue models, allowing them to explore fundamental questions in cell biology by replicating tissues' dynamic and nonlinear physical properties. Herein, we introduce a simple and novel 3D - printed device to prepare hydrogel beads and multi-properties gel sheet. We also prepared special hydrogel pattern for 3D ex-vivo organ culture. Regenerative medicine is a multidisciplinary field that aims to regenerate or replace diseased tissues or organs, restoring or maintaining their normal function. Given that every organ in the human body can be prone to failure or to injury, the field of regenerative medicine has expanded. Our data are invaluable in understanding how a hydrogel-based technology help us to understand the basic process of tissue development and has explored the applications of these technologies in the fields of materials science, soft robotics, biotechnology and medical treatment. Reference: Kazi GAS, Rahman KA, Farahat M, Matsumoto T. Fabrication of single gel with different mechanical stiffness using three-dimensional mold. J Biomed Mater Res A. 2018, ‘Accepted Article’, doi: 10.1002/jbm.a.36455.Sathi GA, Kenmizaki K, Yamaguchi S, Nagatsuka H, Yoshida Y, Matsugaki A, Ishimoto T, Imazato S, Nakano T, Matsumoto T. Early initiation of endochondral ossification of mouse femur cultured in hydrogel with different mechanical stiffness. Tissue Eng Part C Methods. 2015; 21:567-75.Kazi Ar, Sathi Ga, Taketa H, Farahat M, Okada M, Torii Y, Matsumoto T. Novel 3d Printed Device For The Simple Preparation Of Hydrogel Beads. 3d Printing And Additive Manufacturing. 2(1): 5-11:2015.

Exploiting Advanced Hydrogel Technologies to Address Key Challenges in Regenerative Medicine.

Regenerative medicine aims to tackle a panoply of challenges from repairing focal damage to articular cartilage to preventing pathological tissue remodeling after myocardial infarction. Hydrogels are water‐swollen networks formed from synthetic or naturally derived polymers and are emerging as important tools to address these challenges. Recent advances in hydrogel chemistries are enabling researchers to create hydrogels that can act as 3D ex vivo tissue models, allowing them to explore fundamental questions in cell biology by replicating tissues' dynamic and nonlinear physical properties. Enabled by cutting edge techniques such as 3D bioprinting, cell‐laden hydrogels are also being developed with highly controlled tissue‐specific architectures, vasculature, and biological functions that together can direct tissue repair. Moreover, advanced in situ forming and acellular hydrogels are increasingly finding use as delivery vehicles for bioactive compounds and in mediating host cell response. Here, advances in the design and fabrication of hydrogels for regenerative medicine are reviewed. It is also addressed how controlled chemistries are allowing for precise engineering of spatial and time‐dependent properties in hydrogels with a look to how these materials will eventually translate to clinical applications.

High-speed deformation of a high-strength coated thin plate

The punch with cone-shaped working part impact into aluminum alloy thin-walled structures is mathematical modelled applying thermo-mechanical coupling of the physical processes during their deformation. The nonlinear physical properties contain a nonlinear stress-strain rate dependence of temperature. To solve the contact problem the sliding boundary conditions (friction) on moving bodies introduced. Numerical simulation of impact process performed using the finite element method and the independent Lagrange-Euler approach for two variants of the thin-walled box structure. The solution of the dynamic viscous plastic contact problem allowed to determine and to design the stress-strain fields in the thin-walled box section. For comparison, the deformation process of the similar aluminum construction with an additional rib considered when the punch with the conical working part impact. Analysis of stress-strain state for two various types of structural geometries demonstrated that mounting the additional medial rib into its design let redistribute the stress fields and significantly reduce the plastic deformation area during the impact because of four fold increasing in its contact stiffness. Such modification of the structure rigidity may improve the strength properties of the entire composite security device applying changes only to its part.

Numerical-analytical method for investigating the stability of the axisymmetric motion of bodies of revolution in soil media

A method for investigating the stability of the axisymmetric motion of a body of revolution in a compressible soil medium with allowance made for the nonlinear physical and mechanical properties of the soil and the effects of two-dimensional flow is presented.

A new multimodel ensemble method using nonlinear genetic algorithm: An application to boreal winter surface air temperature and precipitation prediction

AbstractA new multimodel ensemble (MME) method that uses a genetic algorithm (GA) is developed and applied to the prediction of winter surface air temperature (SAT) and precipitation. The GA based on the biological process of natural evolution is a nonlinear method which solves nonlinear optimization problems. Hindcast data of winter SAT and precipitation from the six coupled general circulation models participating in the seasonal MME prediction system of the Asia‐Pacific Economic Conference Climate Center are used. Three MME methods using GA (MME/GAs) are examined in comparison with a simple composite MME strategy (MS0): MS1 which applies GA to single‐model ensembles (SMEs), MS2 which applies GA to each ensemble member and then performs a simple composite method for MME, and MS3 which applies GA to both MME and SME. MS3 shows the highest predictability compared to MS0, MS1, and MS2 for both winter SAT and precipitation. These results indicate that biases of ensemble members of each model and model ensemble are more reduced with MS3 than with other MME/GAs and MS0. The predictability of the MME/GAs shows a greater improvement than that of MS0, particularly in higher‐latitude land areas. The reason for the more improved increase of predictability over the land area, particularly in MS3, seems to be the fact that GA is more efficient in finding an optimum solution in a complex region where nonlinear physical properties are evident.

Effect of interaction in the Ga–As–O system on the morphology of a GaAs surface during molecular-beam epitaxy

A thermodynamic analysis of processes of interphase interaction in the Ga–As–O system has been performed and their theoretical laws have been determined, taking into account nonlinear thermal physical properties of the compounds, the oxide film compositions, and modes of molecular-beam epitaxy of GaAs. The processes of interaction of the native oxide of GaAs with the substrate material and also with Ga and As4 from a vapor gaseous phase have been studied experimentally. The experimental results correlate with the results of the thermodynamic analysis. The laws of influence of the removal of the proper oxide on the evolution of the GaAs surface morphology under conditions of the molecular-beam epitaxy have been proposed.

A numerical investigation of flow boiling of non-azeotropic and near-azeotropic binary mixtures

The flow and heat transfer characteristics of binary refrigerant mixtures in a heated horizontal tube were investigated numerically. The pressure drop, temperature profile, and heat transfer coefficient for non-azeotropic and near-azeotropic mixtures of different bulk compositions were obtained. It is found that the non-linear physical properties of the mixtures strongly affect the pressure drop characteristics. Both the fluid properties and mass transfer resistance are responsible for the heat transfer characteristics. The mass transfer resistance has a more significant influence on the nucleate boiling than the convective evaporation for non-azeotropic mixtures, while the resistance can be neglected for near-azeotropic mixtures.

Heat exchanger network retrofit with a fixed network structure

Finding cost effective retrofits for heat exchanger networks remains a challenge. Whilst it is often straightforward to find retrofit changes to an existing network that can improve energy performance, in practice such changes are most often uneconomic. This paper will present an approach to heat exchanger network retrofit around a fixed network structure. Network energy performance is improved through the selective use of heat transfer enhancement. A sensitivity analysis is used to find the most effective heat exchangers to enhance in order to improve the performance of the overall network. The sensitivity analysis used is an extension of a previous sensitivity analysis that was introduced to study network flexibility. The proposed method is applicable for heat exchanger networks involving streams with linear or non-linear physical properties. The enhancement of the most sensitive heat exchangers and avoiding new equipment, together with piping and civil engineering costs, allow much more cost-effective heat exchanger network retrofit.

Nonlinear acoustic time reversal imaging using the scaling subtraction method

Lab experiments have shown that the imaging of nonlinear scatterers using time reversal acoustics can be a very promising tool for early stage damage detection. The potential applications are however limited by the need for an extremely accurate acquisition system. In order to let nonlinear features emerge from the background noise it is necessary to enhance the signal-to-noise ratio as much as possible. A comprehensive analysis to determine the nonlinear components in a recorded time signal, an alternative to those usually adopted (e.g. fast Fourier), is proposed here. The method is based on the nonlinear physical properties of the solution of the wave equation and takes advantage of the deficient system response scalability with the excitation amplitude. In this contribution, we outline the adopted procedure and apply it to a nonlinear time reversal imaging simulation to highlight the advantages with respect to traditional imaging based on a fast Fourier analysis of the recorded signals.

FE Simulation of Vacuum Hot Bulge Forming Process of BT20 Ti-Alloy Cylindrical Workpiece

The vacuum hot bulge forming has been used in aerospace industry to manufacture cylindrical workpiece with improved mechanical properties and reduced fabrication cost. Vacuum hot bulge forming is based on the material soften and the stress relaxation theory. Different from other metal forming techniques, deformation of the workpiece takes place well below yield point and the amount of plastic deformation is directly relaxed to heating temperature and holding time. In this paper, a two-dimension thermo-mechanical coupled finite element model was developed. In this model, nonlinear radiation heat transfer and thermal physical properties of material depending on temperature were considered. This paper carried out numerical simulation of vacuum hot bulge forming of BT20 Ti-alloy cylindrical workpiece by using finite element software MSC.Marc. The temperature field, deformation field and stress field of hot bulge forming of BT20 Ti-alloy cylindrical workpiece were calculated. Numerical simulation results were accorded with experimental ones, which provided for the practice production as theory bases.

Flow-Induced Corrosion Simulation on a Plate by Finite Element Methods

Flow-induced localized corrosion is regarded as one of the main degradation mechanisms of materials. As an initial step of the simulation of a pipe, a plate is chosen to simplify the problem. In this paper, finite element method is used to simulate the corrosion process in the plate by employing nonlinear geometry and physics equations of the material to describe the quasi-static process. An elastic modulus iterative procedure was performed to obtain the material parameters in consideration of the nonlinear physical properties of corrosion. The effect of corrosion is then considered by introducing a criterion between depth and time, calculating corrosion depth at progressive given time. Dead and live finite elements are employed to consider the invalidation of the material. Thus the movable boundary conditions can be taken into account and the dynamic status of corrosion can be simulated. Stress corrosion process under flowing fluid condition is analyzed and then the results of representative examples are compared with published results.

Simulation of cerebral hemodynamics for preoperative risk assessment

Background: An important part of the medical treatment of many cerebrovascular diseases is the occlusion of brain supplying arteries. Until now, the risk of this intervention can only be estimated by invasive diagnostics including the risk of cerebrovascular accidents. Methods and results: As a supporting tool, a computer model of the circle of Willis was designed. The model is based upon linear differential equations describing electrotechnical circuits extended non-linearly. By these means, time continuous simulations of different states and the online observation of all calculated state variables such as blood pressure and blood flow in every modeled vessel became feasible. For individual simulations, model parameters were determined by MR-angiography and boundary values by simultaneous Duplex-measurements in both carotid and vertebral arteries. State variables generated by the model behaved physiologically and the reaction of individual cerebrovascular systems in critical situations could be investigated by special scenarios. Inaccuracies concerning the determination of model parameters and boundary values of the used differential equations are likely to be resolved in the near future through a more careful and technically improved determination of these values. Conclusions: Computer models of subjects were created taking in account the individual anatomical and non-linear physical properties of real vascular systems supplying the brain. Thereby information could be obtained concerning the hemodynamic effects of an iatrogenic vascular occlusion.

Phase Portrait Modeling of a Nonlinear System with a Dynamic Fuzzy Network

Fuzzy logic and neural networks are two important technologies for modeling and control of dynamical systems and have been constrained by the non-dynamical nature of their some popular architectures. There exist problems such as large rule bases (i.e., curse of dimensionality), long training times, the need to determine buffer lengths. This article proposes to overcome these major problems in phase portrait modeling of a nonlinear system with a dynamic fuzzy network (DFN) with unconstrained connectivity and with dynamic fuzzy processing units called “feurons”. Nonlinear physical system properties can be encapsulated by DFN. As an example, DFN has been used as the modeler for some nonlinear physical system such as chaotic, limit cycle, oscillator. The minimization of an integral quadratic performance index subject to dynamic equality constraints is considered for a phase portrait modeling application. For gradient computation adjoint sensitivity method has been used. Its computational complexity is significantly less than direct sensitivity method, but it requires a backward integration capability. We used first and approximate second order gradient-based methods including Broyden–Fletcher–Golfarb–Shanno algorithm to update the parameters of the dynamic fuzzy networks yielding faster rate of convergence