Universal Theoretical Model Research Articles

A novel simulation calculation model based on photosynthetic electron transfer for microalgal growth prediction in any photobioreactor

The microalgal research field is currently lacking a unified theoretical computing system to explain various experimental results related to microalgal growth. Thus a novel universal theoretical model was created to predict microalgal growth with carbon dioxide (CO2) fixation in any cultivation system. First, a new “light-effect colorimetric method” was proposed to estimate the actual f2 value of suspended microalgal cells during regular experimentation using a formula explaining the photosynthetic effective electron transfer rate (ETR = PFD·ΦII·f1·f2), which only requires the use of a simple spectrophotometer. A mathematical relationship between photosynthetic electron transfer and the microalgal growth rate was then identified based on this modified ETR by simplifying factors influencing the cultivation conditions (e.g., nutrients and CO2) into the slope and intercept of this formula. Subsequently, software was written to allow the above relationship to stimulate any 3-D microalgal cultivation system. Many example cases were conducted to clarify the significance and application of this theoretical model. It was found that the average ETR of a cultivation system describes microalgal tolerance to high CO2 concentrations. A photobioreactor at any given location under a certain light condition has a theoretical maximum yield of microalgal biomass, irrespective of how the other cultivation conditions change. A new concept of “biological similarity” is proposed as a basic principle for scaling up microalgal experiments with photosynthetic CO2 fixation to perform a repeated growth curve with < 5 % error. Finally, a “multi-batch dilution method” was demonstrated to increase the microalgal biomass yield by 64.4 % over a short cultivation period. General application of this calculation model would change the empirical status of microalgal engineering designs.

Theoretical and practical guide for an axial superresolved focus via Gouy phase steering

Achieving an axial superresolved focus with a single lens by simply inserting a modulation mask in the pupil plane is preferred due to its compact configuration and general applicability. However, lack of a universal theoretical model to manifest the superresolved focusing mechanism vastly complicates the mask design and hinders optimal resolution. Here we establish an interference model and find out that the axial resolution closely relates to the Gouy phase gradient (GPG) at the focal point. Using a GPG tuning-based optimization approach, the axial resolution of a ring-mask-modulated beam is readily improved to attain superresolved focal depth for multiple types of pupil function and polarization. In experiment, a focus with an axial resolution of 27% improved from the diffraction limit and 11% finer than the previously reported record is demonstrated for the radially polarized beam. In simulations, a spherical focus with 3D isotropic resolution and a superoscillation-like axial modulation behavior toward extremely high axial resolution is also presented. This approach can be applied for varied types of pupil function, wavelength, and polarization, and can be easily transferred to other traditional or superresolution microscopes to upgrade their axial resolution.

Theoretical Prediction Model of the Explosion Limits for Multi-Component Gases (Multiple Combustible Gases Mixed with Inert Gases) under Different Temperatures

Combustible gases often lead to fire and explosion accidents due to their unsafe characteristics. Furthermore, their explosion limits are influenced by various factors. In the industrial production process, the operating unit is often in a high-temperature environment, and the multi-component gas explosion limits under this condition are difficult to determine. Therefore, it is urgent to have a universal theoretical prediction model to rapidly predict the multi-component gas explosion limits at high temperatures. This paper proposes a theoretical prediction model for the lower explosion limit of multi-combustible gases containing inert gases at different temperatures based on the heat balance equation and radiation heat loss, which can be used to solve the lower explosion limit of the “multiple combustible gases + multiple inert gases” mixture at different temperatures. It solves the explosion limits of methane, ethylene, propane, and propylene mixed with nitrogen with relative errors of 2.66%, 5.98%, 6.82%, and 5.88%, respectively, compared with experimental data. It also obtained theoretically predicted gas explosion limits for methane, ethylene, propane, and propylene mixed with carbon dioxide, with relative errors of 3.24%, 5.13%, 6.19%, and 5.58%, respectively. Although the reference experimental data made the model validation somewhat limited, validation with data for multiple single gases and temperatures still gave the model considerable reliability.

A universal theoretical model for hybrid structure sensor with proximity and large-range contact force sensing

Human-robot collaboration (HRC) is highly relied on the multi-information from the environment, especially for the external object approaching and large-range contact force perception. The information collected by the sensor with only a single-function will make the system complex and hard to achieve. Herein, we propose a universal theoretical model for hybrid structure sensor with multi-information perception capacity, which combines the capacitive and piezoresistive mechanisms for proximity and large-range contact force detection, respectively. The capacitor from the complex hybrid structure is decomposed into several ones with a single dielectric constant, which can simplify the model. The change of equivalent relative dielectric constant is response for the change of sensor output during the object approaching and contact in a tiny force. The bulk and interface resistance of the composite film will extend the sensitive range of contact force. Furthermore, the theoretical model is solved via numerical method and verified by experimental results. Finally, the maximum error is only 0.57%, 3.07% and 3.83% for object approaching, contacting force in 0–20 N and in 20–120 N, respectively. It indicates the accuracy and validity of the model, which can provide a promising method for designing integrated sensor for proximity and contact sensing and active safety control on HRC.

Theoretical modeling and dynamic characteristics analysis of piezoelectric inertial actuator

The converse wiring method of piezoelectric inertial actuator (PIA) based on asymmetrically clamping principle is used to overcome backward motion phenomenon, which is essential for improving the stability and positioning accuracy of actuator. However, the theoretical researches performed for the driving technology with the novel converse wiring method is scarce at present. To remedy this shortage, a theoretical model of the above-mentioned method is proposed to analyze its dynamic characteristics and output performances comprehensively by comparing the theoretical model with traditional direct wiring method for the first time. In this work, the physical models, mathematical models and simulation models of the actuator under two wiring methods are established and analyzed. LuGre friction model using in Simulink has been further modified to simulate the frictional force of the actuator more accurately. With a series of experimental results of output characteristics, the simulation models and each internal subsystem are verified. On this basis, the relationships between resultant force and velocity, frictional force and velocity are revealed theoretically. Besides, the essential mechanism that the actuator can achieve no backward motion and high stability under the converse wiring method is explained from a theoretical perspective. This work provides theoretical guidance for the design and optimization of actuators, contributing to the exploration of internal mechanism and the establishment of a systematic and universal theoretical model for PIA.

Piezoelectric Energy Harvesting Technology: From Materials, Structures, to Applications

The piezoelectric energy harvesting is a promising, interesting and complex technology. Herein, the aim is to review the key groups of parameters that contribute to the performance of energy harvesting and to offer a guideline for the future development. For this purpose, a universal theoretical model is developed. According to the model, the parameters are divided into six groups. Each group is then discussed. First, a discussion on the piezoelectric materials status, advantages and disadvantages of ceramics, polymers, single crystals, composites, nanomaterials, and lead‐free materials are summarized. The orientation of materials is also discussed. Second, the structure designs, including off‐resonance, on‐resonance, and impact design were introduced. Third, typical sources of excitations and vibrations are given, including direct contact force, low vibration force, hydraulic, pneumatic power, and acoustic power. The fourth consideration is on the effect of frequency and speed is discussed, focusing on the high‐frequency and high‐speed conditions. This is followed by the effect of electrical load on the output power of an energy harvester was discussed. Last, the parameters of energy accumulation effect and methods are also introduced. Following the above discussion, some examples are provided to show the potential applications, including the areas of structural health monitoring, vibration engines, pavement road energy harvesting, wireless sensor nodes, and human gait power. Finally, at the end of the review, the future challenges are addressed.

Aspects of Selecting Appropriate Conveyor Belt Strength

Breaks in the so-called “continuous” (unspliced) belt sections, and not in the spliced areas, are infrequent but do happen in practice. This article presents some aspects, which may account for such breaks in conveyor belts. It indicates the so-called “sensitive points” in design, especially in the transition section of the conveyor belt and in identifying the actual strength of the belt. The presented results include the influence of the width of a belt specimen on the identified belt tensile strength. An increase in the specimen width entails a decrease in the belt strength. The research involved develops a universal theoretical model of the belt on a transition section of a troughed conveyor in which, in the case of steel-cord belts, the belt is composed of cords and layers of rubber, and in the case of a textile belt, of narrow strips. The article also describes geometrical forces in the transition section of the belt and an illustrative analysis of loads acting on the belt. Attention was also devoted to the influence of the belt type on the non-uniform character of loads in the transition section of the conveyor. A replacement of a conveyor belt with a belt having different elastic properties may increase the non-uniformity of belt loads in the transition section of the conveyor, even by 100%.

Shift of the Infrared Absorption and Emission Spectra of Transition Metal Ions in Solid Solutions of Semiconductor Compounds

A universal theoretical model is proposed that explains the observed shift of IR absorption and emission bands in the spectra of transition metal ions in solid solutions of semiconductor compounds. The model has been used for estimating the long-wavelength shift of luminescence bands in the spectra of semiconductor solid solutions with increasing concentration in application to crystals of the ternary systems ZnMgSe(Cr2+) and CdMnTe(Fe2+). Description of the phenomenon is generalized to the case of multicomponent solid solutions.

Modeling gravitational wave detection with atom interferometry

The atom interferometry is a promising tool for the detection of the gravitational wave (GW) in the mid-frequency band ranging from 0.01 Hz to 10 Hz. Particularly, the multi-arm atom interference detectors can help to extract better data with the removal of fake detection. The existing models for GW detection with atom interferometry, however, are mainly focused on the one-dimensional situation, and cannot be directly applied to the multi-arm frame of the GW detection. In this work, we develop a universal theoretical model for GW detectors based on atom interferometry, in which the eikonal equation under general relativity is adopted to calculate the perturbation of the GW on light propagation, and the dependence of the response function on the azimuth is also discussed. We further analyze the dominant noise sources, which limits the detection capabilities of detector. This work provides a complete model for GW detection with atom interferometry, with the ability to analyze the performance of the multi-arm atom interference detectors.

Бизнес и социальное предпринимательство: обзор основных теоретических моделей

В статье представлен обзор основных подходов западных авторов к пониманию социального предпринимательства. Исследовательский интерес в этой сфере заключается в выявлении возможных вариантов сочетания коммерческой (деловой) и некоммерческой (благотворительной) активности предприятий в условиях современной экономики. Историческое развитие социального предпринимательства изначально проходило в двух различающихся логиках – англо-американской и западноевропейской (континентальной), – что способствовало возникновению двух разных теоретических моделей. Выявляются характерные черты и сущностные особенности каждой из моделей. Отмечается, что в Великобритании и США издавна существуют традиции предпринимательства населения как эффективного средства решения социальных проблем, в то время как в континентальных странах Западной Европы, в рамках романо-германской системы права, значительную часть решения таких проблем берет на себя государство, хотя католические и протестантские церковные приходы также отчасти выполняли социальную миссию. Исходя из этих различий, складываются разные традиции в развитии организационных, управленческих, ценностных форм социального предпринимательства. Авторами отмечается, что в современных условиях происходит конвергенция двух теоретических моделей, прослеживается формирование универсальной (синтетической) модели, основанной на стирании существенных различий в практиках развития социального предпринимательства. Внимание уделяется анализу современных форм социального предпринимательства, в частности, выявлению ориентаций предпринимательства, его миссии и целей. Анализ исследований показывает, что, с одной стороны, в современных экономических условиях преобладающее большинство социальных предприятий вынужденно или по доброй воле включаются в коммерческую деятельность. С другой стороны, все коммерческие предприятия для достижения долгосрочного успеха и процветания должны в своей деятельности ориентироваться на выполнение социально значимых задач и достижение социального эффекта. Делается вывод, что современное социальное предпринимательство имеет гибридные формы организации, опирается на социально-ориентированную цель (миссию), ориентируется на производство социального изменения и решение социальных проблем посредством деятельности, приносящей доход и построенной на основе использования бизнес-технологий.

Many-Body Decay of the Gapped Lowest Excitation of a Bose-Einstein Condensate.

We study the decay mechanism of the gapped lowest-lying axial excitation of a quasipure atomic Bose-Einstein condensate confined in a cylindrical box trap. Owing to the absence of accessible lower-energy modes, or direct coupling to an external bath, this excitation is protected against one-body (linear) decay, and the damping mechanism is exclusively nonlinear. We develop a universal theoretical model that explains this fundamentally nonlinear damping as a process whereby two quanta of the gapped lowest excitation mode couple to a higher-energy mode, which subsequently decays into a continuum. We find quantitative agreement between our experiments and the predictions of this model. Finally, by strongly driving the system below its (lowest) resonant frequency, we observe third-harmonic generation, a hallmark of nonlinear behavior.

Сдвиг инфракрасных спектров поглощения и излучения ионов переходных металлов в твердых растворах полупроводниковых соединений

A universal theoretical model explaining the effect of the shift of absorption and emission bands of transition metal ions in solid solutions of semiconductor compounds is proposed. By the example of ternary compounds Zn1-xMgxSe:Cr2+ and Cd1-xMnxTe:Fe2+, an estimate of the typical parameters of the long-wavelength shift of absorption and luminescence in the mid-infrared range with increasing of concentration of solid solution is performed. A generalization of the effect to the case of multicomponent solid solutions is considered.

A unified model for determining fracture strain of metal films on flexible substrates

Failure strain determination of polymer-supported thin films is a key for the design of the flexible devices. A theoretical model R/R0=(L/L0)2 (R, L are the electrical resistance and the length of the stretched film, respectively. R0, L0 are the corresponding initial values.) has been widely used to determine the fracture strain of thin films on flexible substrates. However, this equation loses its function in some special cases. Here, a simple and universal theoretical model was proposed to determine the fracture strain of metal thin films on flexible substrates in more generally situations. With this model, we investigated the thickness-dependent failure strains of Cu-5 at.% Al films with thickness of 10 nm, 200 nm, 1000 nm, and Ti films with thickness of 50 nm, 100 nm, 300 nm. This model was also employed to study the published data available. The results showed that the new model provided a fairly good prediction of the failure strains of different films.

VISION OF INTEGRATIVE APPROACH TO TEACHING STUDENTS OF PHILOLOGY IN HIGHER TECHNICAL EDUCATIONAL INSTITUTIONS

Vision of integrative approach in higher education as the methodological basis of teaching students at universities has been carried out. It was highlighted that to learn foreign languages technical higher institutions are chosen by applicants. Based on domestic and foreign science’s investigations educational perspective to integrative approach in education has been described. It was summarized that integrative approach fixed in time and place in the context of scientific redefinition and revival of theoretical multiplicity of pedagogy assimilates traditional content of modern education, provides the quality of modernized education. It has been highlighted that integrative approach is the basis of the unity of sectoral knowledge and foreign language competence as the asset of student’s knowledge. It is emphasized that integrative approach is the conceptual element of universal theoretical model of higher education that regulate: educational curricula within the specialty; integrative training courses; textbooks and training manuals in translation. All these factors further to get transferable abilities. It has been proved that there is a great number of components integrate in teaching students of philology: great deal of content (foreign language, sectoral vocabulary, translation, methods of teaching English in higher and secondary education, psychological and pedagogical knowledge); innovative methods and techniques of providing foreign and translation competence; informative content; legal and legislative support etc. These components denote the perspectives of integrative approach as an object of scientific investigation. It has been investigated that young people, choosing philological education in higher technical educational institutions, evaluate advantages of transferable abilities, which strengthen the competitiveness of professional, expand the sphere of demand for the professional, assist to fulfil the ambitions

Radial Distribution Functions for Molecules in the Universal Equation of State Model for Gaseous/Fluid/Condensed Systems

Analytical expressions and a numerical method for calculation of distribution functions of hard spheres gij(r) based on inverting the Laplace transform for functions rgij(r) obtained from the Percus—Yevick equation are obtained. The method for calculation of radial distribution functions is applicable for any distances between hard spheres; it is verified by comparison of numerical results and Monte Carlo simulations. The application of the developed method for calculation of the radial distribution functions of metal atoms is demonstrated. Distribution functions are required to construct a universal theoretical model of equation of state capable of describing both dense multicomponent gas and condensed substances (liquid or solid phases) with high accuracy which is substantially faster than computer experiments (Monte Carlo and molecular dynamics methods).

Universal modeling of unsteady airflow in different hoistway structures and analysis of the effect of ventilation hole parameters

Accounting for the strong flow field in a hoistway during the operation of an ultra-high-speed elevator and reasonable ventilation in engineering practice, installation of ventilation holes (VH) is important. First, based on Bernoulli’s principle for unsteady flow, the unsteady airflow in hoistways without VH, with one pair of VH, and with two pairs of VH were modeled theoretically. Based on these three models, a universal theoretical model of unsteady airflow in a hoistway with multiple VH was deduced. The validity of the theoretical model was verified by comparing the theoretical velocity coefficients with those obtained experimentally in an elevator test tower. Finally, the influence of different VH parameters on the airflow were analyzed. The results showed that the weakening trend of the airflow movement in the hoistway decreased gradually when the cross-sectional areas of the VH increased. The change in the VH length had little effect on the airflow movement in the hoistway, and the change in the opening position of the VH had a significant effect on the airflow in the hoistway. With the increase in the number of VH with the same cross-sectional areas, the weakening trend of the airflow in the hoistway was gradually reduced.

Theoretical prediction model and experimental investigation of detonation limits in combustible gaseous mixtures

Propagation limits in gaseous detonation are an important problem in industrial chemical processes due to safety protections and precautions. Propagation limits are also of great significance for developing new-concept detonation engines. Due to the complex phenomena of near-limit detonation and the multiple competing mechanisms between the properties of mixtures and boundary conditions, development of a universal theoretical prediction model that can satisfactorily estimate the detonation velocity deficit (the difference between the actual detonation velocity and the theoretical CJ detonation velocity) near the limits is still extremely challenging. This work focuses on the essential relation between the detonation structure and prediction models. By analyzing the chemical length scales in the detonation structure of the ZND model, it is found that ΔI (induction length) and ΔR (exothermic length) are important length scales and that they are related to the reaction zone thickness (x) by: x = C·(ΔI + α·ΔR). In combination with Fay’s boundary layer theory, a modified theoretical prediction model (MF) is proposed. The MF model is also compared with previous Fay models and experimental results. To verify the reliability of the MF model, three combustion mixtures (CH4-2O2, 2H2-O2 and C2H4-6N2O) and tubes with three different inner diameters (d = 36, 14 and 4 mm) are investigated. The results show that the MF model satisfactorily predicts the detonation deficit at the near-limit conditions. In the macroscale tube (d = 36 mm), the maximum difference with the experiment data is 9.3%. In the microscale tube (d = 4 mm), the maximum difference is 10.7%. If experimental measurement error is considered, the prediction of the MF model has reasonable accuracy. The results confirm that the detonation structure has an important impact on detonation limit predictions.

Factors influencing dividend payout decisions: Evidence from South Africa

Background: Dividend payout is one of the most debated contemporary corporate finance issues. No universal theoretical model describes the factors that corporate managers consider in dividend payout decisions. This study extends previous South African empirical research on dividend payout trends and motivations for Johannesburg Stock Exchange (JSE)-listed industrial companies over the period 1999–2014. The study period coincides with the introduction of share repurchases as an alternative distribution method, covers multiple dividend distribution regulatory amendments and overlaps the global financial crisis of 2008. Objectives: The aim of this study was to ascertain whether the global financial crisis of 2008 affected dividend payouts and to identify factors that influenced dividend payout decisions of JSE-listed industrial companies over the period 1999–2014. Method: Descriptive statistics and a fixed-effects panel regression analysis were applied to dividend data extracted from published annual reports of JSE-listed industrial companies over the period 1999–2014. Results: Dividend distributions of JSE-listed industrial companies increased over the study period in contrast to declining global dividend distribution trends. A significant increase in dividend payout was found when comparing pre- and post-recession periods, in line with the positive impact of dividend distribution regulatory reforms. Company size (+), profitability (+), sales growth (−) and free cash flow (−) were identified as significant factors that influence dividend distributions of JSE-listed industrial companies.

Prediction and optimization of stress distribution in bonded anchors for CFRP tendons

This study proposed a universal theoretical model for predicting the stress distributions in bonded anchors for carbon fibre reinforced polymer (CFRP) tendons based on the elasticity theory. The proposed model is adaptable for predicting the stress distributions of straight anchors as well as anchors with different conical angles, and it was validated by experimental results. A parametric analysis was conducted to examine the effect of the structural form of anchors, conical degree and bonding material on the stress distributions in the anchor zone based on the developed theoretical model. The results reveal that the resistance against the slippage of the tendon increases with respect to the conical degree. However, by having a high conical degree, serious stress concentrations as well as a high risk of shear and compressive damage appear in the anchor zone. The conical degree from 3° to 4° is suggested for the anchors with a conical length of no less than 200 mm. The straight segment at the free end in a straight-conical-straight anchor has little effect on the stress distributions whereas the straight segment at the loading end reduces significantly the stress concentration and even out the stress distribution in the anchor zone. It is suggested that the length ratio of the conical to the straight segment at the loading end be kept in between 4:1 to 2:1, which has a positive effect on the stress distributions by reducing the maximum stress as well as transferring the tensile load from the loading end towards the free end more efficiently. The bonding medium influences the stress distributions as well. A homogeneous bonding medium with a lower modulus produces better stress distributions in the anchor zone. An improvement in the stress distributions becomes more distinct with the application of a bonding medium with a gradually decreasing modulus from the free end to the loading end. A thicker bonding medium generates a more uniform stress distributions in the anchor zone, but the increase of the thickness has to be limited due to a larger deformation appearing simultaneously in the bonding medium.

Effect of Structural Parameters on the Stiffness of Truss Structure

Stiffness is an important parameter during the designment of truss structure. A finite element model (FEM) was put forward to calculate the stiffness of truss structure. The proposed FEM was compared with the universal theoretical model to verify the rationality of FEM. The verified FEM was further used to research the effect of structural parameters on the stiffness of truss structure. The variations of stiffness with length of truss, size of cross section, and spacing of cell were illustrated. The calculated results showed a nonlinear relationship between stiffness and structural parameter. At last, the underlying mechanism of the nonlinear relationship was discussed.