Analysis of a Novel Flux-Weakening Structure of High-Speed Permanent-Magnet Motors Based on Soft-Magnetic Ferrite

Soft-magnetic ferrite has advantages of high initial magnetic permeability, high electric resistivity, low loss and low cost in the high-frequency alternating field. Considering the characters of soft-magnetic ferrite, this paper uses a soft-magnetic ferrite ring as stator core and presents a novel field-weakening structure of high speed PM motors. Based on this structure, a novel field-weakening method of PM motors can be presented. The equivalent reluctance of permanent magnetic field circuit can be changed by altering saturation degree of soft-magnetic ferrite core in this method. For the convenience of analysis and calculation, considering the magnetic field distribution in the motors, this paper deduces an equivalent two-dimensional finite element model of three-dimensional magnetic field, by which the field-weakening parameters of high speed PM motor can be conveniently analyzed. The simulation results of finite element model prove: the field-weakening structure of high speed PM motor based on soft-magnetic ferrite, presented in this paper, is valid and feasible, offers a valid and applicative method for field-weakening control of high speed PM motor.     

Finite element modeling of transient heat transfer and microstructural evolution in welds: Part II. Modeling of grain growth in austenitic stainless steels

During welding, structures are subjected to localized heating and cooling cycles, as described in Part I.[1] A mathematical model is proposed to determine the metallurgical changes that occur in austenitic stainless steel due to the welding thermal cycle. The proposed kinetic model computes the austenite grain growth as a function of time and temperature. It is based on a Zener pinning grain growth model. The results obtained indicate that the model is in good agreement with the experimental data reported in the literature. Furthermore, it was observed that rewriting the kinetic constant in the grain growth equation as a function of the peak temperature led to improved results for the majority of the cases examined.     

聚酯纺粘土工布和GCL在垃圾填埋场中的应用

主要介绍了土工布和膨润土防水毯（GCL）在垃圾卫生填埋场应用中的特点和作用，阐述了在卫生填埋场设计中选择土工布和GCL应注意的一些问题。     

Steel protection capacity of polymeric based cement mortars against chloride and carbonation attacks studied using electrochemical polarization resistance

This work analyzes the protection capacity of modified Portland cement mortar with polymers: styrene butadiene, acrylic latex with reinforced plastic fibres and acrylic latex with silica fume, using the electrochemical polarization resistance (R_p) technique to monitor the behaviour of steel bars embedded in the specimens, when placed in environments with CO₂ and chloride. Results indicate that only chemical, physical and mechanical characterizations are not sufficient to classify these materials from the point of view of protection against aggressive agents. There is evidence that material performance depends on workability, chemical composition of squeezed pore solution in addition to the porosity and resistivity which have an important role in the protection against the corrosion of steel bars.     

Weakly non-linear stability of stratified natural convection in a vertical cavity with lateral temperature gradient

Stability of free convection is examined in a vertical cavity with a fixed lateral temperature difference on the walls, which is also heated from the bottom by a constant heat flux causing vertical stratification of the base flow. Weakly nonlinear stability equations are derived, under the assumption of fully developed flow conditions. Critical Rayleigh numbers and Landau coefficients are determined in terms of the Prandtl number and stratification parameter. It is found that critical disturbances are always two-dimensional, for stationary and oscillating instabilities as well. Alternatives are considered for the calculation of the Landau coefficient. Analysis reveals that unstationary instability is the preferred mode at the codimension point.     

Visualisation in architecture,engineering and construction (AEC)

In the architecture, engineering and construction industries, computer visualization usage can cover the whole lifecycle of a product from presentation of initial concepts to the final stages of production and can also extend to maintenance issues. Three-dimensional walkthroughs can be created from hand drawn sketches at the very early stages of the design process. Three-dimensional models can be used by design teams to communicate design intent to client and users and to compare and evaluate design options. During more advanced stages of design, three-dimensional representations can be used to check the integrity of services coordination, accessibility and maintainability. During construction, visualization can facilitate the interpretation of design details by site operatives. The concept of visualization is not limited to modeling physical objects but can extend to the representation of abstract data sets of the type obtained from simulation programs used in performance assessment or from Computation Fluid Dynamics (CFD) applications. This paper will review the application of visualization in the process of design and construction and then present findings from three research projects that made use of some of these techniques at various stages of the process: for collaborative working during concept design stage, for design development and marketing in the house building sector, and for the modeling of design details during the construction stage.     

Comparing the Effects of Different Daily and Sub-Daily Downscaling Approaches on the Response of Urban Stormwater Collection Systems

Water Resources Management - Change in the spatiotemporal pattern of precipitation is one the most important effects of climate change. This may result in considerable changes in urban flooding and...     

Converting Daily Rainfall Data to Sub-daily—Introducing the MIMD Method

One of the most important analysis in many hydrological and agricultural studies is to convert the daily rainfall data into sub-daily (hourly) because in many rainfall stations, only the daily rainfall data are available and for a comprehensive rainfall analysis, these data should be converted to sub-daily. Many experimental and analytical methods are available for this conversion but one of the simplest yet accurate ones has been proposed by the Indian Meteorological Department (IMD). Since the IMD method has shown low accuracy in some regions, in this study, the IMD method is modified to a single parameter equation, called Modified Indian Meteorological Department (MIMD) in order to improve the accuracy of the conversion. For this reason, the parameter is calibrated so that the maximum correlation between observed and estimated values is achieved. Five stations in different regions with different climatic conditions were selected so that the daily and sub-daily rainfall data were available in each of them. Then, the parameter of the MIMD method was derived for each station. The results were compared with both observed data and IMD method and it was shown that the mean correlation coefficient of MIMD and IMD methods were 0.9 and 0.73 respectively for 12-h rainfall depth which indicated that the accuracy of the MIMD method in estimation of sub-daily rainfall depths was significantly increased. Moreover, the results showed that the accuracy of the MIMD method decreases as rainfall duration decreases.

     

Applying dual-tree complex discrete wavelet transform and gamma modulating function for simulation of ground motions

The aim of this paper is to develop a stochastic-parametric model for the generation of synthetic ground motions (GMs) which are in accordance with a real GM. In the proposed model, the dual-tree complex discrete wavelet transform (DT-CDWT) is applied to real GMs to decompose them into several frequency bands. Then, the gamma modulating function (GMF) is used to simulate the wavelet coefficients of each level. Consequently, synthetic wavelet coefficients are generated using extracted model parameters and then synthetic GM is extracted by applying the inverse DT-CDWT to synthetic wavelet coefficients. This model simulates the time–frequency distribution of both wide-frequency and narrow-frequency bandwidth GMs. Besides being less time consuming, it simulates several dominant frequency peaks at any moment in the time duration of GM, because each frequency band is separately simulated by the gamma function. Moreover, the inelastic response spectra of synthetic GMs generated by the proposed model are a good estimate of target ones. Using the random sign generator in the proposed model, it is possible to generate any number of synthetic GMs in accordance with a recorded one. Because of these advantages, the proposed model is suitable for using in performance-based earthquake engineering.

     

Querying a building information model for construction-specific spatial information

The design and construction community has shown increasing interest in adopting building information models (BIMs). The richness of information provided by BIMs has the potential to streamline the design and construction processes by enabling enhanced communication, coordination, automation and analysis. However, there are many challenges in extracting construction-specific information out of BIMs. In most cases, construction practitioners have to manually identify the required information, which is inefficient and prone to error, particularly for complex, large-scale projects. This paper describes the process and methods we have formalized to partially automate the extraction and querying of construction-specific information from a BIM. We describe methods for analyzing a BIM to query for spatial information that is relevant for construction practitioners, and that is typically represented implicitly in a BIM. Our approach integrates ifcXML data and other spatial data to develop a richer model for construction users. We employ custom 2D topological XQuery predicates to answer a variety of spatial queries. The validation results demonstrate that this approach provides a richer representation of construction-specific information compared to existing BIM tools.