Theoretical Design Method Research Articles

Theoretical description and design of nanomaterial slab waveguides: application to compensation of optical diffraction.

Planar optical waveguides made of designable spatially dispersive nanomaterials can offer new capabilities for nanophotonic components. As an example, a thin slab waveguide can be designed to compensate for optical diffraction and provide divergence-free propagation for strongly focused optical beams. Optical signals in such waveguides can be transferred in narrow channels formed by the light itself. We introduce here a theoretical method for characterization and design of nanostructured waveguides taking into account their inherent spatial dispersion and anisotropy. Using the method, we design a diffraction-compensating slab waveguide that contains only a single layer of silver nanorods. The waveguide shows low propagation loss and broadband diffraction compensation, potentially allowing transfer of optical information at a THz rate.

Multiobjective Design Optimization Using Dual-Level Response Surface Methodology and Booth's Algorithm for Permanent Magnet Synchronous Generators

This paper studies a dual-level response surface methodology (DRSM) coupled with Booth's algorithm using a simulated annealing (BA-SA) method as a multiobjective technique for parametric modeling and machine design optimization for the first time. The aim of the research is for power maximization and cost of manufacture minimization resulting in a highly optimized wind generator to improve small power generation performance. The DRSM is employed to determine the best set of design parameters for power maximization in a surface-mounted permanent magnet synchronous generator with an exterior-rotor topology. Additionally, the BA-SA method is investigated to minimize material cost while keeping the volume constant. DRSM by different design functions including mixed resolution robust design, full factorial design, central composite design, and box-behnken design are applied to optimize the power performance resulting in very small errors. An analysis of the variance via multilevel RSM plots is used to check the adequacy of fit in the design region and determines the parameter settings to manufacture a high-quality wind generator. The analytical and numerical calculations have been experimentally verified and have successfully validated the theoretical and multiobjective optimization design methods presented.

Optimal control of noninstantaneous impulsive differential equations

In this paper, we study optimal control problems for a new class of noninstantaneous impulsive differential equations arising from the dynamics of evolution processes in pharmacotherapy. We construct a suitable control function, which allows us to characterize the structure of controllability by using the terminal time subinterval instead of the global time interval. We apply fixed point approach to show the controllability results that are the foundation of optimal control theory. Next, we study existence of optimal control problems for a certain quadratic functional acting as the performance index. In addition, we design ILC updating laws for deterministic impulsive systems to generate a sequence of control functions to approximate the optimal control function. Further, we extend the deterministic results to random case by designing ILC updating laws with randomly varying trial length. Finally, several examples are given to demonstrate the validity of theoretical results and design methods. Here, we remark that ILC updating algorithm is adopted to find a desired optimal control for impulsive systems, which provides another effective way to solve optimization problem via computer techniques.

Theoretical investigation of the compression limits of sealing structures in complex load transferring between subsea connector components

This paper provides a theoretical method for calculating the compression limits of a subsea connector's sealing structure to prevent natural gas leakages. The amount of compression deformation is related to the compressive load between contact surfaces. Because of the different compressive loads on the gasket under preloading and operation conditions, the amount of compression will change. Therefore, the load transmission relations between subsea connector components are first analyzed under different working conditions, and the relationship between the sealing contact load and the locking force is obtained. Secondly, a contact model between the lenticular gasket ring and hubs is established on the basis of Hertz contact theory. An analytical equation for the amount of compression is deduced. Considering the demands for sealing and strength, compression limit equations are put forward. In order to apply the compression limits equations, an optimization model is built for a locking mechanism, and the structure design parameters of one certain subsea connector are optimized. This study provides a theoretical method and guidance for the structural design of subsea connectors with a metallic lenticular gasket.

Electromagnetic–thermal–structural coupling analysis of the ITER edge localized mode coil with flexible supports

In a fusion reactor, the edge localized mode (ELM) coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature, high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil (with flexible supports) of ITER (the International Thermonuclear Fusion Reactor), an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.

Decoupling Design and Verification of a Free-Piston Linear Generator

This paper proposes a decoupling design approach for a free-piston linear generator (FPLG) constituted of three key components, including a combustion chamber, a linear generator and a gas spring serving as rebounding device. The approach is based on the distribution of the system power and efficiency, which provides a theoretical design method from the viewpoint of the overall power and efficiency demands. The energy flow and conversion processes of the FPLG are analyzed, and the power and efficiency demands of the thermal-mechanical and mechanical-electrical energy conversion are confirmed. The energy and efficiency distributions of the expansion and compression strokes within a single stable operation cycle are analyzed and determined. Detailed design methodologies of crucial geometric dimensions and operational parameters of each key component are described. The feasibility of the proposed decoupling design approach is validated through several design examples with different output power.

An Extended Theoretical Method Used for Design of Sheet Beam Electron Gun

An extended theoretical method based on Pierce theory is investigated in this paper to provide a reliably support and direct approaches for the design of the general sheet beam electron gun. First, the general characteristics of the sheet beam electron gun are discussed by dividing the gun into three investigation parts, and the design curves are derived theoretically, which are quite different from the curves for circular beam gun. The valid range of curvature radius ratio of cathode to anode R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> for sheet beam gun is achieved as 1.879 <; R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> <; 2.79 with the compression factor M of 1.879 <; M <; 30, which can make the sheet beam gun more stable and reliable. Then, the theoretical design method based on the design curves for sheet beam gun is deduced, and the reconstruction of anode aperture and the correction of cylindrical aberration are considered thoroughly, which may improve the design method more accurate and practical. Based on the theoretical calculation and parameters analysis, two types of sheet beam gun models with different M of 4 and 10 are constructed and simulated by the 3-D software, respectively, with the same beam voltage of 22 kV, a beam current of 3.50 A, and the beam cross section of 6 mm×0.24 mm. The results achieve the good agreement and verification with the theoretical expectation for the both the two sheet beam gun.

Quantitative Supervisory Control Game for Discrete Event Systems

We formulate an optimal supervisory control problem for quantitative non-terminating discrete event systems (DESs) modeled by finite weighted automata. The control performance of a supervisor is evaluated by the worst-case limit-average weight of the infinite sequences generated by the supervised DES. An optimal supervisor is a supervisor that avoids deadlocks and maximizes the control performance. We propose a game theoretical design method for an optimal supervisor using a two-player turn-based mean-payoff game automaton. As the first player, the objective of the supervisor is to maximize the worst-case limit-average weight of the generated sequences; as the second player, the DES aims to minimize it. We show that an optimal supervisor can be computed from an optimal strategy (of the first player) for this game. Then, we propose an algorithm to compute an f-minimally restrictive optimal supervisor, which is a finite-memory optimal supervisor that enables as many sequences as possible and can be represented by an optimal strategy for a finite version of the two-player game.

Design of natural frequency adjustable electromagnetic actuator and active vibration control test

An important issue in inertia electromagnetic actuator is that the best performance of device is limited to a very narrow bandwidth around the natural frequency. In order to overcome this issue of the conventional inertia electromagnetic actuator, an inertia electromagnetic actuator capable of adjusting the natural frequency is introduced. This paper presents theoretical investigation, design method, and experimental tests of the natural frequency adjustable electromagnetic actuator. The optimal design scheme is obtained by using ANSOFT software and experimental tests are conducted to examine the practical property of natural frequency adjustable electromagnetic actuator. Following the results obtained by property experiments, a series of active vibration control tests are carried out and experimentally verified that although the measured natural frequencies at different positions cannot satisfy the theoretical values perfectly, natural frequency adjustable electromagnetic actuator still works very well at test frequencies and reduces the vibration from 18.3 dB to 11.3 dB at frequency of 26.25 Hz.

Experimental and numerical study of full-scale scissor type bridge

Mobile Bridge™ is a deployable bridge that uses a scissors mechanism to achieve its useful structural form. The bridge has a compact size in its undeployed state and can be transported easily to where it is needed. Its rapid deployment makes this type of bridge very useful in areas struck by natural disasters by enabling vehicles to cross terrain that has been made impassable. In previous research, experiments and analyses were conducted on a small-scale bridge designed for pedestrians. In order to consider a bridge of increased size, it is necessary to assess whether design and analysis techniques of the small scale bridge are applicable to the full-scale one. In this paper, we consider a full-scale deployable bridge with a lower deck and two scissor units, that allows for a light vehicle to pass across. We have carried out a light vehicle loading test in order to investigate its basic structural characteristics. Furthermore, the paper presents the theoretical design method and numerical models based on the experimental work followed by validation and comparison with the obtained experimental values.

Improving energy harvesting by stochastic resonance in a laminated bistable beam

This paper presents a bistable energy harvesting device as piezoelectric beam acted upon by a harmonic axial load and a transverse random excitation. A comprehensive analytical study for stochastic resonance in the bistable mechanical system is carried out, from which the system can harvest energy at a high efficiency. The bistable electromechanical model is set up and the corresponding equations are derived by extended Hamilton principle. The condition for occurrence of stochastic resonance is derived by Kramers rate. Numerical simulation is carried out and results are obtained. Stochastic resonance is proved and observed when the system is excited by a Gaussian white noise. The output voltage and power conversion in the condition of stochastic resonance is noticeably higher than those in other conditions. These results can provide a theoretical method for preliminary design and optimization of parameters, which can improve the efficiency of energy harvester.

A Theoretical Method for Structural Design and Analysis of Crankshafts

The crankshaft is the crucial mechanical component in many machines and engines and its fatigue assessment is often very time consuming and expensive. The machine designer usually needs a simple theoretical model that would allow choosing the best material and the dimensions of the component in a quick and reliable way. The numerical finite element simulation of crankshafts should follow the first step of theoretical dimensioning with the aim of evaluating the stress-strain behaviour at the notched area to verify the component against fatigue failure. The development of an intermediate theoretical model would prove effective to reduce the time needed to reach a second approximation design of the crankshaft. The aim of this paper is to give the designer a theoretical procedure that allows determining the strain and stress state for verification of crankshafts. The model was developed in the case of crankshafts with two connecting rods and validated by means of numerical finite element modelling and analysis.

트라이볼로지 손상을 억제하기 위한 구조물 모서리부 설계: 제1부 - 설계공식 개발

This paper describes a design method for the corner radius of a contacting body using the theoretical approach of contact mechanics. A complete contact, as in the case of a sharp-cornered punch, produces singular contact traction: whereas, in an incomplete contact, the singular contact traction disappears because of the rounded corners, and the contact edges are within the rounded regions. The design method aims to determine the conditions of the contact force as well as the material properties in an incomplete contact. The incomplete contact changes into the complete contact again when the contact edges exceed the rounded regions owing to either an increased contact force or the compliance of the materials. The contact length of a rounded punch is used as a parameter to derive the required conditions. As a result, a design formula is obtained, which provides a minimum allowable radius when the materials, normal contact force, and the length of a flat region of the punch are predetermined. This work consists of two parts: Part I includes a theoretical background, design method, and formula, and Part II describes the actual process with the investigation of design parameters.

Designing the Amplifon. A locative sound medium to supplement DAB radio

Radio has always had communicative concern for its listeners. It is characterized by personal address, liveness and acoustic moods that reach audiences in a variety of listening situations. Radio's communicative concern should be available for all citizens, but in fact there is rather bad reception for DAB and FM in cities due to narrow streets and other physical interference, and in addition the prominent iPhone lacks both DAB- and FM-receivers. The design project reported here aims to increase sound media's communicative concern in urban settings by 1) replacing one-way FM and DAB with two-way mobile data, 2) replacing loudspeakers with headphones, and 3) replacing the temporal news agenda with one that is locative. The article reports on the theoretical basis, design methods and empirical findings of the Amplifon prototype.

Shear resistance of reinforced concrete beams in dependence on concrete strength in compressive struts

In the current European Code EN 1992-1-1 a truss model with variable inclination angle of concrete compressive struts with a quite wide range of inclination angle, from 21, 8 degrees to 45degrees, is intended for use for shear design of reinforced concrete beams. However, some researches and recommendations indicate special attention when choosing the lower bound of inclination angle of the concrete compressive struts, due to the reduced compressive strength of cracked concrete. This work reviews theoretical background and shear design methods of reinforced concrete beams. Relation of the shear resistance to crushing of the compressive struts as a function of their inclination angle has been investigated through a parametric study, where three different approaches have been used in order to limit stresses in the compressive struts. Based on the comparison of results from the analysis a recommendation for shear resistance calculation of reinforced concrete beams in dependence on concrete strength in compressive struts of the truss model is given.

Study on triaxial test method and failure criterion of asphalt mixture

Asphalt mixture is the most widely used pavement material all over the world. In China, more than 90% of service expressways are asphalt pavement. However, current asphalt pavement design method still has irrationality. Even though maximum tensile stress theory is used as failure criterion, pavement structure under the effects of wheel load is in three-dimensional complex stress state. Obviously, one-dimensional strength theory cannot reflect the failure characteristics and the resistance of pavement structure. So it is necessary to study the failure criterion of asphalt mixture under three-dimensional complex stress state. Due to limitations of test equipment, there are almost no studies in related area. Under this background, this paper develops a new triaxial test method, according to the investigation of strength characteristics of asphalt mixture under complex stress state through plane isobaric/axial tensile test, plane isobaric/axial compression test, plane tensile and compression/axial tensile test, to reveal the general rules of asphalt mixture's strength failure. The failure mode is divided into three types: tensile failure, shear failure and rheological failure. The tensile meridian and compression meridian in the stress space and strength envelope in the π plane where hydrostatic pressure is greater than zero are obtained, and the failure criterion of asphalt mixture under complex stress state is established, providing theoretical method and scientific basis for structure design as well as strength check of asphalt pavement under three-dimensional stress state.

Structure Analysis and Optimization for Compacting System of Asphalt Paver

Compound motion of double-tamper mechanism causes an impact force on the frame of flatiron-box, which affects the quality of the load when the asphalt paver is running. Different from the previous simplified model, in this paper, the double-tamper mechanism with two parallel slider-cranks is considered. According to the analysis of the structure and principle of the mechanism, and considering the size and mass distribution of each component, the inertia force balance optimization for the double vibrating mechanism is calculated. According to the results of optimization, the vibration experiments were carried out on real screed. The experimental results show that, the harmful inertial force produced by the dual tamping mechanism has been significantly reduced, and the stability of vibration can be effectively improved when screed is paving. The research could provide reliable theoretical method and basis for design, manufacturing and use of asphalt concrete paver.

A modified method for the design of pervious concrete mix

As a new material type for pavement, pervious concrete should be designed to maintain both porosity and the structural strength. The actual mix proportions for pervious concrete depend on the application, the mechanical properties required and the materials used. Actually, the mix proportions of pervious concrete were determined for locally available materials based frequently on trial batching and experience. Another analytical method should be developed to facilitate the concrete producers. Based on the assumption that the cement paste only plays a role of coating, it does not fulfill the void among the grains of gravel; this paper focuses on one modified method for the design of the pervious concrete. The volume cement paste is divided by the surface area of the aggregates to determine the thickness of the excess paste. A scaling factor has been defined to evenly distribute the cement paste toward the size of gravel. Moreover, a binder drainage test is proposed to determine the critical w/c ratio towards to prevent the flow of cement paste to the lower layers of concrete under the action of vibration or compaction. The pervious concrete has been formulated according to this method to validate it. The mechanical and hydraulic tests are performed to characterize the pervious concrete. The obtained pervious concrete presents a large sufficient permeability (1mms−1) for draining rainwater and good mechanical resistance (Rc=28.6MPa) with regard to typical pervious concrete applications such as parking lots, walkways and low-traffic roadways. In addition, the mechanical strength of pervious concrete in this research is found higher than that generally reported by other authors. The results indicate that the theoretical mix design method is a successful theory for an optimizing composition of pervious concrete.

A Design Method for the Asymmetric Artificial Network With an Asymmetrical Transformer

Conducted asymmetric disturbances are measured at telecommunication ports of equipment under test using an asymmetric artificial network (AAN). Therefore, theoretical investigations are carried out to characterize an AAN with a mode-impedance matrix, introducing the common-mode and differential-mode impedances. By referring to this matrix, a theoretical design method is developed for the AAN with an asymmetrical transformer to satisfy the requirements for the mode impedances and the longitudinal conversion loss. By using this design method, two different prototype AANs are assembled: one meets the CISPR 22 specifications, and the other is used in power line telecommunication modem tests. A detailed experimental examination of the assembled AANs validates the proposed theoretical design method.

Design of an enhanced sensitivity FBG strain sensor and application in highway bridge engineering

The theoretical design method of enhanced sensitivity fiber grating (FBG) strain sensors was given, and moreover high qualified strain sensors were developed and fabricated, whose sensing properties were good for practical applications. The strain sensor with cylindrical shell encapsulation contained three tubular structures, due to the uneven surface structure, in the area of the strain concentration, improving the sensitivity. It could achieve the embedment strain measurement and surface measurement and had the advantages of the easy installation. The good agreement was obtained between the measurements and theoretical simulation results. After each calibration test, twenty-four FBG strain sensors and six FBG temperature compensation sensors have been installed on the undersurface of the box girder of Diaoshuiyan bridge in Yongtaiwen highway. Finally, we built up a long-term structure health system for the highway bridge.