TEMPERED BAINITE EMBRITTLEMENT IN SOME STRUCTURAL STEELS

The variations of microstructures and mechanical properties of steels 15CrMnMoV,18Mn2CrMoB,18Cr2Ni4W,30CrMnSi,30CrMnSiNi2 and 40CrMnSiMoV,which weretempered at different temperatures after austempering and continuous cooling at given rates,have been investigated.Based on the experimental results,the behaviour and mechanism oftempered bainite embrittlement(TBE)have been discussed.Finally,the theoretical and prac-tical basis for selecting the optimum tempering temperature of steels with bainite structure af-ter heat treatment are proposed.     

SHORT-RANGE ORDER STRUCTURES OF Fe-Ge AMORPHOUS THIN FILMS

The short-range order structures of Fe_xGe_(1-x) amorphous thin films,(x=8.7,19.1 and28.5%)have been studied by means of X-ray absorption spectrum.The nearest neighborsaround a Ge or an Fe atom are constituted by two coordinate sub-shells with a very short dis-tance,In two films with lower Fe content,structural parameters of the nearest neighborsaround a Ge atom are very near to that in amorphous germanium,and the positions of Fe at-oms are randomly substitutional.But when x=28.5%,some great changes occur on theshort-range order structure of a-Fe_xGe_(1-x) film:its structure deviates from continuous ran-dora network and tends toward dense random packing of atoms.Meanwhile,there is a strong-er interaction between near neighboring Fe-Ge atoms in a-Fe_xGe_(1-x) films.     

GROWTH OF Bi(Pb)-Sr-Ca-Cu-O SUPERCONDUCTING WHISKERS

Amorphous Bi(Pb)-Sr-Ca-Cu-O strips of types(1112)and(2212)were made by means ofnon-equilibrium solidification of melt-quenching method,On the surface of glassy strip,theflexible(2212)superconducting whiskers have been obtained.The growth and feature ofsuperconducting whiskers were studied in detail.     

A new chip-thickness model for performance assessment of silicon carbide grinding

The chip-thickness models, used to assess the performance of grinding processes, play a major role in predicting the surface quality. In the present paper, an attempt has been made to develop a new chip-thickness model for the performance assessment of silicon carbide grinding by incorporating the modulus of elasticities of the grinding wheel and the workpiece in the existing basic chip-thickness model to account for elastic deformation. The new model has been validated by conducting experiments, taking the surface roughness as a parameter of evaluation .     

MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAl ALLOY POWDER

The rapidly solidified powder of Ti-34Al-2Mn alloy was obtained by means of ultrasonicgas atomisation (USGA) technique.The tupical size of the powder is 27 μm.X-ray diffractionresults show that the powder consists of major α_2-phase and minor γ-phase.Under opticalmicroscope both equiaxed and dendritical microstructure features were observed on RS pow-der sections.After annealing at 900 ℃/for 2 h in vacuum,most of α_2-phase transforms intoγ-phase,resulting in refinement of structure.     

STUDY OF INTERFACES AND SURFACES OF YBa_2Cu_3O_(7-x)-Ag

Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDXand AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observedfor 0.4 mol Ag doped YBCO.AES analysis indicated that Ag segregated on surfaceof YBCO and resulted in decrease of YBCO-metal lead resistance.In addition,solutionand segregation of Ag as elemental state were often appeared on interfaces and surfacesof high temperature annealed YBCO,whether elemental Ag or compound Ag_2O andAgNO_3 adopted as doping material.     

CONTROL OF CONSTRUCTION ACTIVITIES: III. FUZZY-BASED CONTROLLER

In this paper, a real-time fuzzy-based controller of construction activities is proposed. Because of the numerous uncertainties associated with construction activities, their control requires a different approach than the traditional feedback methods. These methods are essentially based on the knowledge of a transfer function that models the input/output relationships for the controlled system. For a highly complex and uncertain system such as a construction activity, a fuzzy-based control strategy was found to be a suitable and effective approach. The proposed control system is built in two main levels, the process and the activity levels. Each level comprises two main units, namely, the fuzzy controller and the self learning algorithm. The implementation of the control actions can be performed by either manipulating the states of the variables for the purpose of improving the process output, or changing the process behavior function for the same purpose. Practical examples are presented wherever possible to illustrate the proposed control strategy.     

SCHEDULING OF NONSERIAL LINEAR PROJECTS WITH MULTIPLE NON-OVERLAPPED LOOP STRUCTURES

Existing dynamic programming formulations are utilized for the scheduling of serial linear projects. These formulations cannot, however, be used for the scheduling of nonserial linear projects. The intent of this paper is to present a nonserial dynamic programming formulation for the scheduling of linear projects with multiple non-overlapped loop structures. The objective of the nonserial dynamic programming solution is to provide for the selection of resources, interruptions, and lags for production activities that lead to the minimum project duration. The advantages of this nonserial dynamic programming approach include its ability to handle work interruption and variable production rates. In addition, the developed system produces a graphical representation of the project schedule of minimum duration. A nonserial linear project is treated herein using the proposed method.     

Power,Society,and Living Space: Evolution and Formation Mechanism of Urban Streets in China

Being one of the most important elements of urban public space, streets have contained rich social lives as well as the social and political connotations in Chinese cities with specific local characteristics, while most of them have been long neglected in the researches focusing on grand narratives and center-based perspectives. The paper retrospectively analyzes the evolution process of urban streets in China, dividing it into four critical periods. With the perspective of socio-spatial analysis, the unique formation mechanisms of Chinese urban streets are summarized in different contexts including power system, social domain, and living space, thus to provide references for the exploration of street development mode and revitalization mechanism facing the multiple challenges of globalization, modernity, as well as local social and cultural traditions.     

Experimental‐numerical research on the seismic performance of URM buildings made of lightweight AAC blocks / Experimentell‐numerische Untersuchung zum seismischen Verhalten von unbewehrten Mauerwerksgebäuden aus Porenbetonblöcken

Masonry walls constructed with lightweight AAC blocks and thin‐layer mortar meet the increasingly strict requirements of energy efficiency and sustainability. In this sense, they represent an excellent solution for modern buildings, not only for external cladding but also as loadbearing elements. Despite the possible advantages of using lightweight AAC masonry, a specific assessment of its seismic performance is mandatory in order to set design recommendations allowing to reach safety levels consistent with those required for other masonry types complying with EN 1998 standard requirements. A comprehensive study on the seismic performance of unreinforced masonry buildings made of lightweight AAC was carried out in an integrated experimental‐numerical approach. The experimental campaign provided the necessary information to setup a reliable numerical model to be extensively used to assess the seismic performance of a number of prototype AAC masonry buildings with different characteristics, by means of both linear and nonlinear static (pushover) analysis. The results of this systematic numerical assessment were eventually used to draft design recommendations, to set parameters (behaviour factors) to be used in linear analysis and to calibrate rules for simple buildings.