Randomized Algorithms for Probabilistic Optimal Robust Performance Controller Design

Polynomial-time randomized algorithms were constructed to approximately solve optimal robust performance controller design problems in probabilistic sense and the rigorous mathematical justification of the approach was given. The randomized algorithms here were based on a property from statistical learning theory known as (uniform) convergence of empirical means (UCEM). It is argued that in order to assess the performance of a controller as the plant varies over a pre-specified family, it is better to use the average performance of the controller as the objective function to be optimized, rather than its worst-case performance. The approach is illustrated to be efficient through an example.

A Simple Mix Proportion Design Method Based on Frost Durability for Recycled High Performance Concrete Using Fully Coarse Recycled Aggregate

Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix proportion design method for RHPC using 100 % CRA and natural sand. Five groups of RHPC mixes with five strength grades（40, 50, 60, 70 and 80 MPa） were produced using CRA with four quality classes, and their workability, 28 d compressive strengths and frost resistances（measured by the compressive strength loss ratio and the relative dynamic modulus of elasticity） were tested. Relationships between the 28 d compressive strength, the frost resistance and the CRA quality characteristic parameter, water absorption, were then developed. The criterion of a CRA maximum water absorption limit value for RHPC was suggested, independent of its source and quality class. The results show that all RHPC mixes achieve the expected target workability, strength, and frost durability. The research results demonstrate that the application of the proposed method does not require trial testing prior to use.

PERFORMANCE-BASED INTELLIGENT RESOURCE DESCRIPTION MODEL FOR INTERNET-BASED PRODUCT DESIGN

Issues on intelligent resource description and multiple intelligent resources integration for lntemet based collaborative design are analyzed. A performance-based intelligent resource description model for lnternet-based product design is proposed, which can help to create, store, manipulate and exchange intelligent resource description information for applications, tools and systems in Interact-based product design. A method to integrate multiple intelligent resources to fulfill a complex product design and analysis via lntemet is also proposed. A real project for improving the bearing system design of a turbo-expander with many intelligent resources in prominent universities is presented as a case study.

Satellite constellation design with genetic algorithms based on system performance

Satellite constellation design for space optical systems is essentially a multiple-objective optimization problem. In this work, to tackle this challenge, we first categorize the performance metrics of the space optical system by taking into account the system tasks（i.e., target detection and tracking）. We then propose a new non-dominated sorting genetic algorithm（NSGA） to maximize the system surveillance performance. Pareto optimal sets are employed to deal with the conflicts due to the presence of multiple cost functions. Simulation results verify the validity and the improved performance of the proposed technique over benchmark methods.

Analysis on the development of chemically-improved soil in railway engineering

Purpose-Explore the development trend of chemically-improved soil in railway engineering.Design/methodology/approach–In this paper,the technical standards home and abroad were analyzed.Laboratory test,field test and monitoring were carried out.Findings–The performance design system of the chemically-improved soil should be established.Originality/value–On the basis of the performance design,the test methods and standards for various properties of chemically-improved soil should be established to evaluate the improvement effect and control the engineering quality.

Parametric study on performance of bridge retrofitted by unseating prevention devices

Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper, parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-fault type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the restrainers and concrete shear keys are obtained. Responses obtained from numerical simulations under the Chi-Chi earthquake leaded to new implications to design those devices. Restrainer should not exceed its breaking strain and sufficient unseating length will be needed always. Concrete Shear key was determined by considering both displacement demand of the superstructure and displacement ductility of the column at the same time. Further study is needed to provide optimal design parameters for use in performance based bridge design.

CONSTRUCTION DESIGN AND FLOW ANALYSIS OF CENTRIFUGAL PUMP IMPELLER WITH SUPER-LOW SPECIFIC SPEED

Some commonly used constructions and their design principles of centrifugal pump impeller with super low specific speed are introduced. The internal flow related to pump performance is analysed primarily.

Full-face excavation of large tunnels in difficult conditions

Following a few preliminary remarks on the tunneling methods at the beginning of the 20th century, thesuccessful applications of the full-face method also in difficult conditions are underlined. The attention isposed on the use of a systematic reinforcement of the face and of the ground, by means of fiber-glasselements. A selection of tunnels where this method was used successfully is reported with the purposeof illustrating the wide spectrum of ground conditions where it has been applied. Then, following adescription of the main concepts behind the method, the attention moves from the so-called “heavymethod”, where deformations are restrained, to the “light method”, where deformations are allowedwith the intention to decrease the stresses acting on the primary and final linings. The progress in theapplication of the “light method” is underlined, up to the development of a novel technique, which relieson the use of a yielding support composed of top head steel sets with sliding joints and specialdeformable elements inserted in the primary lining. The well-known case study of the Saint Martin LaPorte access adit, along the Lyon-Turin Base Tunnel, is described. In this tunnel, a yield-control supportsystem combined with full-face excavation has been adopted successfully in order to cope with the largedeformations experienced during face advance through the Carboniferous formation. The monitoringresults obtained during excavation are illustrated, together with the modeling studies performed whenpaying attention to the rock mass time-dependent behavior.

Aerodynamic design optimization of helicopter rotor blades including airfoil shape for hover performance

This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight. A new geometry representation algorithm which uses the class function/shape function transformation （CST） is employed to generate airfoil coordinates. With this approach, airfoil shape is considered in terms of design variables. The optimization process is constructed by integrating several programs developed by author. The design variables include twist, taper ratio, point of taper initiation, blade root chord, and coefficients of the airfoil distribution function. Aerodynamic constraints consist of limits on power available in hover and forward flight. The trim condition must be attainable. This paper considers rotor blade configuration for the hover flight condition only, so that the required power in hover is chosen as the objective function of the optimization problem. Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance. The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%, which is a good improvement for rotor blade design.

Design and Performance of an Improved Trapped Vortex Combustor

A trapped vortex combustor （TVC） has been a very promising novel concept for it offers improvements in lean blow out, altitude relight, operating range, as well as a potential to decrease NOx emissions compared to conventional combustors. The present paper discusses the improved designs of the new combustor over the prior ones of our research group, including that：a） the over-all dimensions, both axial and radial, are reduced to those of an actual aero-engine combustor; b） the air flow distribution is optimized, and especially 15% of the air is fed into the liner as cooling air; c） a straight-wall diffuser with divergence angle 9°is added. A series of experiments （cavity-fueled only, under atmospheric pressure） has been conducted to investigate the performance of the improved TVC. Experimental results show that at the inlet temperature of 523 K, the inlet pressure of 0.1 MPa, stable operation of the TVC test rig is observed for the Mach number 0.15-0.34, indicating good flame stability; the combustion efficiency obtained in this paper falls into the range of 60%-96%; as the total excess air ratio increases, the combustion efficiency decreases, while the increase of the inlet temperature is beneficial to high combustion efficiency; besides, the optimal Mach numbers for high combustion efficiency under different inlet conditions are confirmed. The outlet temperature profiles feature a bottom in the midheight of the exit. This paper demonstrates the feasibility for the TVC to be applied to a realistic aero-engine preliminarily and provides reference for TVC design.

终压变动对变转速汽轮机功率的影响

本文讨论变转速汽轮机终压变动时其功率变化的规律.通过在汽轮机机组上的试验,验证了导出的公式,这些公式具有推广意义.结论指出:变转速汽轮机功率的变化只受终压的影响.

Expected Sliding Distance of Vertical Slit Caisson Breakwater

Evaluating the expected sliding distance of a vertical slit caisson breakwater is proposed. Time history for the wave load to a vertical slit caisson is made. It consists of two impulsive wave pressures followed by a smooth sinusoidal pressure. In the numerical analysis, the sliding distance for an attack of single wave was shown and the expected sliding distance during 50 years was also presented. Those results were compared with a vertical front caisson breakwater without slit. It was concluded that the sliding distance of a vertical slit caisson may be over-estimated if the wave pressure on the caisson is evaluated without considering vertical slit.

Photoelectric characteristics of an inverse U-shape buried doping design for crosstalk suppression in pinned photodiodes

A design of an inverse U-shape buried doping in a pinned photodiode （PPD） of CMOS image sensors is proposed for electrical crosstalk suppression between adjacent pixels. The architecture achieves no extra fill factor consumption, and proper built-in electric fields can be established according to the doping gradient created by the injections of the extremely low P-type doping buried regions in the epitaxial layer, causing the excess electrons to easily drift back to the photosensitive area rarely with a diffusion probability; the overall junction capacitance and photosensitive area extensions for a full well capacity （FWC） and internal quantum efficiency （IQE） improving are achieved by the injection of a buried N-type doping. By considering the image lag issue, the process parameters of all the injections have been precisely optimized. Optical simulation results based on the finite difference time domain method show that compared to the conventional PPD, the electrical crosstalk rate of the proposed architecture can be decreased by 60%-80% at an incident wavelength beyond 450 nm, IQE can be clearly improved at an incident wavelength between 400 and 600 nm, and the FWC can be enhanced by 107.5%. Furthermore, the image lag performance is sustained to a perfect low level. The present study provides important guidance on the design of ultra high resolution image sensors.

Cyclone separation in a supercritical water circulating fluidized bed reactor for coallbiomass gasification： Structural design and numerical analysis

A new concept of a supercritical water （SCW） circulating fiuidized bed reactor is proposed to produce hydrogen from coal/biomass gasification. The cyclone is a key component of the reactor system, in this paper, cyclones with a single circular inlet （SCI） or a double circular inlet （DCI） were designed to adapt to the supercritical conditions. We evaluated the separation performance of the two cyclones using numerical simulations. A three-dimensional Reynolds stress model was used to simulate the turbulent flow of the fluid, and a stochastic Lagrangian model was used to simulate the particle motion. The flow fields of both cyclones were three-dimensionally unsteady and similar to those of traditional gas-solid cyclones. Secondary circulation phenomena were discovered and their influence on particle separation was estimated. Analyzing the distribution of the turbulence kinetic energy revealed that the most intensive turbulence existed in the zone near the vortex finder while the flow in the central part was relatively stable. The particle concentration distribution was non-uniform because of centrifugal forces. The distribution area can be divided into three parts according to the motion of the particles. In addition, the separation efficiency of both cyclones increased with the inlet SCaN velocity. Because of its perturbance flow, the DCI separator had higher separation efficiency than the SCI separator under comparable simulations. However, this was at the expense of a higher pressure drop across the cyclone.

Sustainability of steel structures:towards an integrated approach to life-time engineering design

Nowadays,the construction sector is more and more oriented toward the promotion of sustainability in all its activities.The goal to achieve is the optimization of performances,over the whole life-cycle,with respect to environmental,economic and social requirements.According to the latest advances,the concept of sustainability applied to constructions covers a number of branches such as life-cycle costing,ecology,durability and even structural design.Several procedures and design tools have been implemented in the framework of international research.Indeed the current trend in civil engineering research is moving towards life-time engineering,with the aim to implement integrated methodologies to consider as a whole all the sustainability requirements according to time-dependent multi-performance-based design approaches.Following a general introduction of the concept of sustainability applied to constructions,this paper presents an overview of life-time engineering methodologies according to the current state-of-the-art.In particular the methods currently received by International Standards are discussed.A special focus is devoted to the durability design of metal structures with respect to the degradation phenomena able to impair the structural capacity over time.Finally a proposal towards an integrated approach to life-time engineering design of steel structures and needs for further advances are presented.

Editing landscapes:Experimental frameworks for territorial-based robotic fabrication

With the advent of on-site robotic tools,they can be deployed for editing landscapes e defined as the modulation of grounds with a high degree of sensitivity to matter and form.The paper contributes a theoretical grounding and two experimental frameworks for territorial-based robotic fabrication.Each experimental framework supports a robotic capacity for informing and forming grounds,demonstrated in relation to extreme territories using simulation setups.The frameworks include(1)a layer-sensitive modulation for protecting topsoil and(2)a performance-based robotic forming for creating wind barriers.For each framework,the paper proposes a setup,an exploration method,and an evaluation process.Drawing on the presented frameworks,the paper outlines three potentials of territorialbased robotic fabrication:the capability to modulate grounds vertically,the possibility to perform cross-scalar forming,and the opportunity to form dynamic,performative landscapes.The paper concludes with potential ways in which robotic tools could be leveraged for advancing precise landscape editing across scales.

What is going on in magnesium alloys？

China has been developed into one of the most active regions in terms of both fundamental and applied research on magnesium （Mg） and its alloys in the world from a solid base laid by its prominent metallurgist and materials scientists over the past decades. Nowadays, a large number of young-generation researchers have been inspired by their predecessors and become the key participants in the fields of Mg alloys, which consequently led to the establishment of China Youth Scholar Society for Magnesium Alloys Research in 2015. Since then, the first two China Youth Scholars Symposiums on Mg Alloys Research had been held at Harbin （2015） and Chongqing （2016） China, respectively. A number of crucial research inter- ests related to fundamental and applied Mg research were discussed at the conferences and summarized in this short perspective, aiming to boost far-reaching initiatives for development of new Mg-based materials to satisfy the requirements for a broad range of industrial employments. Herein, four main aspects are included as follows： i） Plastic deformation mechanism and strengthening strategy, ii） Design and development of new Mg-based materials, iii） Key service properties, and iv） New processing technologies.

On the technologies of Hα imaging spectrograph for the CHASE mission

The Hα imaging spectrograph(HIS) is the scientific payload of the first solar space mission, the Chinese Hα solar explorer(CHASE), supported by the China National Space Administration(CNSA). The CHASE/HIS achieves, for the first time in space, Hα spectroscopic observations with high spectral and temporal resolutions. Separate channels for the raster scanning mode(RSM) and continuum imaging mode(CIM) are integrated into one, and a highly integrated design is achieved through multiple folding of the optical path and ultra-light miniaturized components. The design of HIS implements a number of key technologies such as high-precision scanning of the optical field of view(FOV), high-precision integrated manufacturing inspection, a large-tolerance pre-filter window, and full-link solar radiation calibration. The HIS instrument has a pixel spectral resolution of 0.024 ? and can complete a full-Sun scanning within 46 s.

Potential of South African road technology for application in China

One of the main problems with roads and highways in China is the reflection cracking caused by the cement stabilized subbase layers passing through the overlying asphaltic layers. The cracks permit the ingress of moisture which softens the layers below the subbase resulting in loss of support and accelerated breakdown of the subbase layer and reduction in the tiding quality. The aim of this paper is to present the use of South African pavement design approach of deep structure and thin surfacing to overcome the existing problems. The deep pavement structure provides good long-term support and avoids the influence of moisture ingress, which means that only surfacing damage needs to be repaired. An unbound crushed stone base layer which is an integral component of the pavement structure limits reflection cracking. The paper first deals with the South African pavement design procedure and contrast this with the Chinese pavement design method. The inherent weaknesses of these methods are discussed and flowing from this discussion proposals for adapting the South African approach to China is presented. The resultant proposals have a high likelihood of success and will counteract the influences of extreme climate and rampant overloading that occurs on the Chinese roads.

Fault Detection for a Class of Impulsive Switched Systems

The problem of fault detection for a class of nonlinear impulsive switched systems is investigated in this paper. Fault detection filters are designed such that the augmented systems are stable, and the residual error signal generated by the filters guarantees the H∞ performance for disturbances and faults. Sufficient conditions for the design of fault detection(FD) filters are presented by linear matrix inequalities. Moreover, the filter gains are characterized according to a solution of a convex optimization. Finally, an example derived from a pulse-width-modulation-driven boost converter is given to illustrate the effectiveness of the FD design approach.