Global Design Method Research Articles

Optimal Design and Analysis of a High-Load Supersonic Compressor Based on a Surrogate Model

To explore the internal flow mechanism and improve the performance of a supersonic compressor, an efficient global optimization design method was developed for an axial flow compressor and applied in the optimization design of a prototype supersonic compressor. Based on the multiple circular arc (MCA) blade parameters, the method can be used to parameterize the elementary stage of the blade. The optimized solution is obtained by changing the elementary stage and stacking lines of the blade during the optimization process. It has the advantages of fewer optimization variables, strong physical intuition, and a smooth surface. The optimization results show that a change in the rotor blade shape parameters has a significant effect on the compressor efficiency under design conditions, while a change in the skewed-swept parameters of the stator is the main factor that improves the compressor’s performance under near-stall conditions. Further numerical results show that the optimized rotor changes the form of the shock, weakens the degree of shock boundary layer interference, inhibits the radial migration flow of the supersonic rotor, reduces the loss of the rotor blade top, and improves the performance of the compressor under design conditions. The stator’s optimization restrains the generation of a concentrated shedding vortex at the root of the blades and greatly improves the stall margin of the compressor. Finally, the total pressure ratio and flow rate are less than 1% of the values based on the prototype operating conditions, the design mass flow of the optimized high-load supersonic compressor is increased by 0.25%, the isentropic efficiency is increased by 1.05%, and the stall margin is enhanced by 3.5%, thus verifying the effectiveness of the optimization method.

Development of 0.34 THz Sub-Harmonic Mixer Combining Two-Stage Reduced Matching Technology with an Improved Active Circuit Model

In this paper, a high-performance 0.34 THz sub-harmonic mixer combining two-stage reduced matching technology with an improved active circuit model is established and analyzed. The mixer’s improved active circuit model is realized by decomposing passive functional models into basic transmission line units and their impedance matching and filtering are realized through automatic optimization. The improved active circuit model takes out the RF (radio frequency) transition model separately to set an optimization goal instead of operating directly in the mixing circuit. Compared with traditional active circuit models in the SDM (subdivision design method) and GDM (global design method), it provides a massive optimization space, larger working bandwidth, and better results. In the RF frequency range of 320–360 GHz, the SSB (single sideband) conversion loss of the 0.34 THz sub-harmonic mixer is below 9.5 dB and the RF return loss is less than 12 dB.

The Development of Frequency Multipliers for Terahertz Remote Sensing System

This paper summarizes the development of novel Schottky-diode-based terahertz frequency multipliers. The basic structure and manufacturing process of planar Schottky barrier diodes (SBDs) are reviewed, along with other diode structures that have been proposed in the literature. A numerical modeling method for the novel diodes in the context of terahertz frequency multipliers is presented, which includes 3D electromagnetic (EM) modeling, electro-thermal modeling and modeling of physical non-ideal effects. Furthermore, a general design methodology for developing terahertz frequency multipliers is introduced, involving a sub-division design method (SDM), a global design method (GDM) and a half-sub-division and half-global design method (HS-HGDM). These methods are summarized and compared for 110 GHz and 220 GHz frequency multipliers in the context of communication and imaging applications. Laboratory measurements of these multipliers show good agreement with numerical simulations. Finally, several classic terahertz remote sensing systems are reviewed, and a 220 GHz remote sensing system established using novel frequency multipliers for security inspection purposes is presented along with associated imaging results.

Multi-mode vortex-induced vibration control of long-span bridges by using distributed tuned mass damper inerters (DTMDIs)

Tuned mass damper inerter (TMDI) has been proved to be a feasible device for vibration control of long-span bridges due to its excellent space performance. However, existing design method for TMDI is conducted mode-by-mode. When applied to multi-mode control of the bridge through multiple TMDIs, it cannot consider the synergistic effect among the TMDIs and thus leading to a suboptimum design result. This paper presents an efficient method for multi-mode vortex-induced vibration (VIV) control of long-span bridges by using spatially distributed TMDIs (DTMDIs). The governing equations of the bridge-DTMDIs system are established in modal coordinate. A global optimization method considering the synergistic effect among the DTMDIs is proposed and compared with conventional mode-by-mode approach through a numerical case study. The robustness of the control schemes against variations in structural and aerodynamic parameters is investigated. The influence of inerter span length on the control efficiency is also discussed. The results show that the proposed global design method can achieve a better control efficiency with even less TMDIs as compared with conventional mode-by-mode approach. The proposed method can also be extended to VIV control of some other line-like structures.

A 560 GHz Sub-Harmonic Mixer Using Half-Global Design Method

In this paper, a 560 GHz terahertz sub-harmonic mixer using a new half-global design method is reported. This method combines the advantages of the subdivision design method and the global design method, and greatly enhances the abilities of the optimization of matching variables while retaining the portability of the unit circuit. When the local oscillator (LO) frequency was fixed with 3 mW power at 280 GHz, average up-conversion double sideband (DSB) conversion loss of 8 dB with intermediate frequency (IF) power of −5 dBm was achieved.

The Design of Terahertz Monolithic Integrated Frequency Multipliers Based on Gallium Arsenide Material.

A global design method for a terahertz monolithic integrated frequency multiplier is proposed. Compared with a traditional independent design, the method in this paper adopts overall optimization and combines the device with the circuit design. The advantage is that it provides a customized design for frequency multipliers according to specifications. On the basis of the gallium arsenide process of the Institute of Microelectronics, Chinese Academy of Sciences, two types of Schottky diodes have been developed to meet the needs of different designs. On the one hand, a Schottky diode with a 3 μm junction’s diameter was used in the design of the 200 GHz balanced doubler and, on the other hand, a diode with a 5 μm diameter was used in the 215 GHz unbalanced tripler. The measured results indicated that the output power of the doubler was more than 250 μW at 180~218 GHz, and the maximum was 950 μW at 198 GHz when driven with 12.3 mW, whereas that of the tripler was above 5 mW at 210~218 GHz and the maximum exceeded 10 mW. Such frequency multiplier sources could be widely used in terahertz imaging, radiometers, and so on.

Small-Signal Modeling and Parameter Optimization Design for Photovoltaic Virtual Synchronous Generator

With the continuous proliferation of renewable energy generation, distributed photovoltaic inverters operating at a maximum power point reduce the inertia of power systems, degrading system frequency stability and potentially causing severe oscillations in systems after being disturbed. The virtual synchronous generator (VSG) control method, which causes photovoltaic inverters to possess inertia and damping, now plays an important role in the field of distributed generation. However, while introducing the advantages of synchronous machines, problems with oscillations are also introduced and the stochastic fluctuation characteristic of photovoltaics results in the stochastic drifting of the operating point. This paper presents an adaptive controller parameter design method for a photovoltaic-VSG (PV-VSG) integrated power system. Firstly, a small-signal model of the PV-VSG is built and a state space model is deduced. Then, the small-signal stability and low frequency oscillation characteristics of the photovoltaic power generation system are analyzed. Finally, considering the limitations of system oscillations and the stochastic drifting of the operating point, a global optimization design method for controller parameters used to improve system stability is proposed. The time domain simulation shows that an optimized PV-VSG could provide sufficient damping in the case of photovoltaic power output changes across a wider range.

A 200–240 GHz Sub-Harmonic Mixer Based on Half-Subdivision and Half-Global Design Method

For the terahertz harmonic mixer, a design model based on Half-Subdivision and Half-Global Design Method (HS-HGDM) with a single functional unit is proposed. The single functional unit circuit of the mixer, such as LO or IF Low Pass Filter (LPF), is designed by Subdivision Design Method (SDM), and the rest circuits of the mixer are designed by Global Design Method (GDM). The harmonic mixer based on this model is characterized by simple circuit structure, low conversion loss, small circuit size and high stability. In this paper, an improved Compact Suspended Micro-strip Resonators (CSMRs) filter is developed for the IF part of sub-harmonic mixer. The remaining circuits consist of some basic transmission units, such as the High-Z Low-Z impedance Transmission Lines (H-Z L-Z TLs) applied for main circuit, and full/reduced height WR4.3/WR8 applied for providing RF/LO signal. In RF frequency range 200–240 GHz, a Single Sideband (SSB) conversion loss of 7.36±0.76 dB operating at IF frequency 1.8 GHz, and a Double Sideband (DSB) noise temperature below 1034 K with the LO power of 2–5 mW and the LO frequency of 107 GHz were achieved. This broadband sub-harmonic mixer operates at room temperature, which makes it applicable to sub-millimeter wave or terahertz wireless communication systems and imaging inspection systems.

The Global Stability Performance and Design Method of the Mono-Overhanging Steel Beam

Abstract This article presents a research and design method for the global stability of the mono-overhang steel beam, which is very different from other kinds of beams. First, the total potential energy equation of the mono-overhanging beam is deduced by energy method. Then, the critical bending moment formula of the global stability is deduced based on its boundary conditions. Second, by introducing the equivalent calculated length coefficient, the critical bending moment equation is transformed into the form that is the same as that of a simply supported beam subjected to the uniform moment. This transformation can make stable design more convenient. At last, the impact factors of the calculated length coefficient of the global stability are determined. Furthermore, the formulas of the equivalent calculated length coefficients are proposed, which reflect the comprehensive interrelation between the equivalent calculated length coefficient and its impact factors. These formulas are continuous functions so that the calculation results are more precise and practical than before because in the previous method, the calculated length coefficient is taken as a piecewise constant value, which has led to a large error in the past.

Multiphysics Global Design and Experiment of the Electric Machine With a Flexible Rotor Supported by Active Magnetic Bearing

Electric machine with a flexible rotor has unique advantages and extensive applications in industry, but it has been studied in the theoretical and experimental stage for decades because of its multidisciplinary feature, difficulty of realization, and lacking suitable design method. In this paper, a multiphysics global design method was proposed, and an electric machine with a flexible rotor supported by active magnetic bearing was developed based on this method to resolve a series of actual engineering problems for future industrial air blower application. The design process involves electromagnetic field, force field, flow field, and temperature field. The validity of the industrial prototype system was verified by the relevant experiments, and the proposed design method can be used for the development of the similar complex machine with the characteristics of multidisciplines or multiphysics.

Design of 199 to 238 GHz broadband subharmonic mixer combining two‐stage reduced matching technology with Global Design Method

AbstractTerahertz technology is widely used in communications, radar, electronic countermeasures, precision guidance, and biomedical applications. In this paper, a 199 to 238 GHz broadband subharmonic mixer combining two‐stage reduced matching technology with Global Design Method is designed, fabricated, measured, and analysed successfully. Compared with traditional single‐stage reduced matching technology and Subdivision Design Method, the two‐stage reduced matching technology is applied for terahertz mixer's Radio Frequency (RF) waveguide and Local Frequency (LO) waveguide, while the LO/Intermediate Frequency (IF) Low‐Pass Filter of terahertz mixers is not necessary to design separately. The core of Global Design Method is that the whole mixer circuit, including LO/RF waveguide, is divided into basic transmission units, which match and filter circuit simultaneously with more optimization variables. When LO driven power is 3.1 mW, LO frequency is 108, 112 GHz. The measured single‐sideband (SSB) conversion loss ranges from 7.84 to 12.4 dB with RF frequency 199 to 238 GHz. The measured double‐sideband (DSB) noise temperature varies between 580 and 1059 K with LO driven power 2 to 5 mW. The multi‐stage reduced matching technology and Global Design Method is general, effective, accurate, can reduce circuit size, simplify circuit structure, broaden frequency band, and can be applied for terahertz harmonically mixers.

A 220 GHz Broadband Sub-Harmonic Mixer Based on Global Design Method

A terahertz mixer is one of terahertz key components and widely used on terahertz wireless communication, remote sensing, aerospace exploration, and biomedical system. The performance of the terahertz mixer has a great effect on the entire terahertz transceiver system performance. This paper proposes a 220 GHz broadband sub-harmonic mixer based on global design method (GDM), which is different from the traditional subdivision design method of which the mixer circuit is composed of functional unit circuits. Instead, the GDM adopts the overall performance of the mixer (conversion loss) as an optimization goal. The continuous structures of the circuit are described by ideal transmission line models and waveguide models, meanwhile, the S-parameters of the de-embedded model are used to describe the discontinuous structures. The measured single-sideband (SSB) conversion loss is basically consistent with the simulation results, which verifies the accuracy and reliability of the GDM. When local oscillator (LO) frequency is fixed at 110 GHz, the measured SSB conversion loss is less than 10 dB with the average value of 8.1 dB from 198 to 238 GHz. The minimum conversion loss of the mixer is 6.35 dB at 207 GHz. The measured double-sideband noise temperature of the mixer is less than 924 K at an intermediate frequency of 1.6 GHz. The GDM has the characteristics with a wide frequency band, small circuit size, simple structure, low LO power, and stable performance, and can also be applied to other terahertz components.

A computational approach based on a multiaxial fatigue criterion combining phase transformation and shakedown response for the fatigue life assessment of Nitinol stents

Self-expanding stents made of Nitinol, a Nickel–Titanium shape memory alloy, are used in standard medical implants for the treatment of cardiovascular diseases. Despite the increasing success, clinical studies have reported stent failure after the deployment in the human body, thus undermining patient’s safety and life. This study aims to fill the gap of reliable assessment of the fatigue life of Nitinol stents. We propose a global computational design method for preclinical validation of Nitinol stents, which can be extended to patient-specific computations. The proposed methodology is composed of a mechanical finite element analysis and a fatigue analysis. The latter analysis is based on a novel multiaxial fatigue criterion of the Dang Van type, combining the shakedown response of the stent and the complexity of phase transformation taking place within the material. The method is implemented in the case of a carotid artery stent. The implant configuration as well as the applied cyclic loading are shown to affect material phase evolution as well as stent lifetime. The comparison with the results obtained by applying a strain-based constant-life diagram approach allows to critically discuss both fatigue criteria and to provide useful recommendations about their applicability.

Buckling mechanism of steel core and global stability design method for fixed-end buckling-restrained braces

Based on theoretical analyses, the development of buckling mode of steel core is revealed for buckling restrained braces (BRBs) with fixed ends. The formulae are derived for the bending moments of the stiffening part of the core and restraining member of BRBs. Then a global stability design method of fixed-end BRBs is proposed. The results of the contact force, flexural response and buckling half wavelength with finite-element analysis agree with the theoretical analysis. The design criteria as well as the buckling half wavelength were validated by the quasi-static tests of five BRBs. Compared to existing methods, the proposed design approach can ensure a proper safety margin of the stiffening part.

Life cycle cost based optimization design method for an integrated cooling system with multi-operating modes

Cooling system is a primary concern in data centers, since the energy consumption of cooling system accounts for a large proportion of the total. This paper proposes a global optimization design method to reduce the life cycle cost for an integrated cooling system which is a combination of thermosyphon loop and vapor compression refrigeration cycle. The integrated cooling system has three different operating modes corresponding to different outdoor conditions, and the optimization design method establishes the physical model for the cooling system with multi-operating modes. Considering minimizing the life cycle cost of the system as the objective function, the main parameters of each component are optimized and designed by sequential quadratic programming. The optimization results show a remarkable energy saving effect, and the optimized cooling system reduces the life cycle cost by approximate 10% compared with the existing system.

Formulation of optimized excavatable cement treated materials using a new punching test apparatus

Classical techniques for backfilling of trenches use unbounded materials. Unfortunately, they have been presenting several drawbacks regarding compaction such as noise disturbance, time of implementation and long-term settlement. In that context, controlled low strength materials could be a good alternative solution thanks to their fluidity and cementitious setting, provided that they remain excavatable, even manually with a pick. In fact, it is essential to ensure a rapid and easy permanent access to the underlying networks, in case of emergency or maintenance. Yet, the excavatability was not well defined, nor well measured so far. A fortiori, no mix design process is available to control the excavatability of these materials. It is the purpose of this article to develop one. Recently, a new approach based on a simple punching test in laboratory was proposed to provide a quantitative characterization of cement treated materials excavatability, accounting for the pick impact energy (Morin in Study of cementitious material excavatability, 2009; Morin et al. in Eur J Environ Civ Eng 17(10):935–955, 2013; Can Geotech J, 2017. https://doi.org/10.1139/cgi-2016-0534 ). The present paper first briefly describes how, in the continuation of this study, the testing set-up was improved, the approach was validated and the underlying theoretical models were calibrated on an important campaign of manual excavation on real scale trenches, in parallel with laboratory punching tests. Once the laboratory method developed, it was possible to proceed a large parametric campaign at the laboratory stage to identify the mix design parameters that influence the excavatability of cementitious materials. The second part of the paper describes the methodology used and the empirical model deduced to link the mix proportions of a cementitious material to its excavatability. Finally, manual excavations were realized on real scale trenches to confirm the relevance of the model. In conclusion, a global mix design method is proposed for excavatable cement treated materials, with a brief economical simulation.

Buckling mechanism and global stability design method of buckling-restrained braces

Design formulae of buckling-restrained braces, considering the stiffening part of the core and the effect of friction, are proposed, based on theoretical analyses of the buckling mechanism of the steel core in the presence of a gap between the core and the restraining member. The theoretical analyses are validated by finite element analyses. Compared to existing methods, the results of the proposed analyses are generally better and show the closest correlation with the results of the finite element analysis.

Cartographic continuum rendering based on color and texture interpolation to enhance photo-realism perception

Graphic interfaces of geoportals allow visualizing and overlaying various (visually) heterogeneous geographical data, often by image blending: vector data, maps, aerial imagery, Digital Terrain Model, etc. Map design and geo-visualization may benefit from methods and tools to hybrid, i.e. visually integrate, heterogeneous geographical data and cartographic representations. In this paper, we aim at designing continuous hybrid visualizations between ortho-imagery and symbolized vector data, in order to control a particular visual property, i.e. the photo-realism perception. The natural appearance (colors, textures) and various texture effects are used to drive the control the photo-realism level of the visualization: color and texture interpolation blocks have been developed. We present a global design method that allows to manipulate the behavior of those interpolation blocks on each type of geographical layer, in various ways, in order to provide various cartographic continua.

Global Optimized Design of an Electric Variable Transmission for HEVs

A way to improve existing hybrid vehicles is by globally optimizing the design of their components in relation to their actual use. This paper proposes a global optimal design method for power-split hybrid electric vehicles (PS-HEVs) equipped with an electric variable transmission (EVT). A genetic algorithm is used to optimize system parameters. The process includes discrete dynamic programming (DDP) for optimal energy management. The optimization focuses on minimizing fuel consumption and the number of battery cells. Pareto fronts are depicted and compared for different drive cycles, and they show the existence of a possible tradeoff between fuel consumption and battery size.

A practical and unified global stability design method of buckling-restrained braces: Discussion on pinned connections

The end bending moment induced by brace end rotation was recently found to have a negative effect on the global stability of buckling-restrained braces (BRBs). The proposed bending moment functions for the BRBs with traditional pinned connections, however, were found to be too complicated from practical view. Also, the relationship between the flexural behavior of BRBs and the brace end details has not yet been well understood, possibly resulting in misevaluation of BRB global stability capacity in design. In this paper, a moment amplification factor (MAF) method is proposed to simplify the bending moment function of the BRBs with traditional pinned connections, followed by parametric study on the key parameters affecting the MAF and presentation of the proposed simplified function. A unified global stability design method is proposed and implemented to the BRBs with pin-ended connections. Several future research needs for BRB global stability are presented finally.