The characteristics and development situation of electric vehicles are briefly introduced. Large specific weight and high specific price electric are characteristics of electric vehicles, and cost, life and weight are the key points to the development of electric vehicles. Some unreasonable phenomea in electric car industry were pointed out. It is proposed that developing small and efficient electric vehicles is the strategic choice of China’s automobile industry. Finally, the line of electric vehicles development is given: market guiding, supporting small and helping large, taking low-end as cut point, and diverse development.
With the rapid development of long span bridges in China, this paper focused on some engineering projects related to wind resistance challenges on three types of long span bridges, including flutter instability and control of suspension bridges, wind induced vibration of cable-stayed bridges and control of wind-rain induced cable vibration, vortex shedding vibration and control of arch bridges, and the refinements on aerodynamic flutter and buffeting of super long span bridges. It can be concluded that the intrinsic limit of span length due to aerodynamic stability is about 1 500 m for a traditional suspension bridge, and beyond or even approaching this limit, designers should be prepared to improve aerodynamic stability. The long-span cable-stayed bridges with a 1 000 m main span have high enough critical flutter speed, but the main aerodynamic concern is rain-wind induced vibration of long stay cables. Except one example of vortex-induced vibration, long-span arch bridges have no wind resistance problems. The fundamental research on wind resistance of long-span bridges was also introduced with the full-mode flutter analysis method as 3D bridge flutter precise analysis, the bridge buffeting frequency-domain analysis under skew wind action, the bridge flutter and buffeting reliability evaluation method based on second order theory and first passage theory, and the unveiling of bridge flutter evoluation process, generation mechanism and control law.
A study on the anti-sliding stability of hydraulic structures on subbed soil has been made. Using the anti-sliding test results of dragged concreting pressure plate in foundation pits, the decreased value of anti-sliding bearing capacity after spring back influenced of subbed soil is determined; envelope of anti-sliding shear stress and friction coefficient are also quantitatively determined. It is suggested to use the maximum compressive stress σmax of eccentric load to predict structure displacement, sliding and creepy slippage of subbed soil, to determine sliding contour creep, and limit the maximum compressive of subbed soil. Two built hydraulic structures are reviewed and calculated by drafted method, and the results are accord with real conditions.
This paper discusses the fundamental issues for wind energy focusing on civil engineering, including reducing construction cost, establishing relevant standards and codes, measuring wind speed and forecasting energy output and mapping wind resources. This paper concludes that as China will have a long period for wind energy development and project construction, it is important to establish guidelines of civil engineering for wind projects, to develop wind measuring and forecasting technique with proprietary intellectual property rights of China, and to survey wind resources and to map the results in nation-scale and province-scale. This paper also prospects researches and land usage for wind projects in accordance with conditions of China and characteristics of wind projects which are beneficial for wind energy development in China.
Focusing on F1 weathered trough which has maximum water inflow and great difficulty in construction in Xiamen Xiang'an Subsea Tunnel,full-sectional grouting reinforcement and waterproofing,5 m grouting inside heading, 70 m along longitudinal direction of tunnel and superfine cement single-fluid grouting as major grouting material were applied according to poor geological conditions and the character of sudden water inflow. Meanwhile,the corresponding parameters of grouting were established after drillings for grouting were conducted. The results of field monitoring and numerical calculation during construction show that the grouting-effect meets the qualifications of design and construction of Xiamen Xiang'an Subsea Tunnel. The research results can provide technical reference for similar projects in grouting and waterproofing.
The ELF (extremely low frequency) engineering project for underground exploration is one of the major national science and technology infrastructure projects approved by Chinese government,which will apply to resource exploration, earthquake predication and other frontier sciences. The background, construction content, key technology and test results are introduced. On the basis of which, the application prospect of the project are expected.
PV is never limited by resources and production materials and is the main alternative energy sources in the future. China is now the largest producer of PV modules in the world and has made remarkable cost reduction in recent years.It is expected that PV will reach "grid-parity" within 5~10 years and become market competitive with conventional electricity.Large scale utilization of PV domestically will give great help to realize the target of GHG reduction and energy sustainable development in China.We still need great efforts in incentive policies, financing and grid-connection.
This paper prescribes a movable voltage-variable & frequency-variable on shore power supply system which successfully provids on shore power for container vessel at port. The high-voltage power supply (10 kV/50 Hz/2 000 kV·A) for the Quay Cranes is used as the power input of the system after frequency and voltage converting (450 V/60 Hz),and then was put out and supplied to vessel. This system is flexible with positive effect on energy-saving and emission reduction. Besides, there is no need of civil reconstruction to container terminals, which is suitable for the busy ports in China.
The aim of this paper is to find out regularity of comb-type water reducers effect on early hydration of cement and to guide engineering applications of comb-type water reducers. Microstructures of early hydrates of cement superplasticized by three typical polycarboxylates were observed by SEM, and the electronic characteristic data of cement hydrates were analyzed. It is found that comb-type water reducers can accelerate hydration rate of cement minerals. Moreover, acrylic acid based copolymer promotes formation of ettringite, and maleic anhydrite based copolymer speeds up formation of monosulfoaluminate. Therefore, early hydration of cement and engineering properties of concrete are dominated by the kind of comb-type water reducers. Suitable choice should be made according to application requirements of concrete engineering, and modification should be done by blending retarders, air entraining agent or defoaming agent if needed.
In this study, a general nonlinear restoring force (NRF) identification approach using structural dynamic response measurements and complete excitations is proposed at first. In this approach, the least-squares technique is employed to identify the parameters of an equivalent linear system of the nonlinear structure model based on the external excitations and the corresponding response measurements. The proposed approach is developed when the structure to be identified is incompletely excited. Both of the approaches are validated with a 4-story frame structure equipped with smart devices of magneto-rheological (MR) damper to simulate nonlinear performance. The identified NRF of the structure is compared with the test measurements. Results show that the proposed data-based approaches are capable of identifying the nonlinear restoring behavior of engineering structures and have the potential to be employed to evaluate the damage initiation and development procedure of engineering structures under dynamic loads.
The mainstream of development in knowledge discovery is researching on new high-performance and high-scalability mining algorithm. In fact, the research of process model and inner mechanism reflecting the law of knowledge discovery system or process and determining model and algorithm is more important, which has not got enough attention. This paper proposed a new independent knowledge discovery system framework, which combines those three elements: mechanism, model and algorithm. Through the cross-integration and comprehensive integration of several "systems framework", a kind of knowledge discovery theory based on inner cognitive mechanism(KDTICM) has been constructed. Researches and experimental results show that this high-starting point and high-level researches on the construction methodology are likely to form high-performance mining system methodology and new research direction; this researches on the KD(knowledge discovery) construction methodology can substantively involve domain knowledge long unresolved into "the solution to these important issues such as knowledge discovery process" and "dynamic real-time maintenance" of knowledge base; by exposing the essence, the regularity and complexity of KD would react on the mainstream development. Finally, the paper gave strong evidence of effectiveness of such construction methodology.
A series of research on mechanical behaviors of big pipe-roof in shallow large-span loess tunnel was made on Wenxiang Tunnel in Zhengzhou-Xi'an Special Passenger Railway. The longitudinal deformations of the pipe-roofs are monitored and the mechanical behaviors of the pipe-roofs are researched at the test section. The force-deformation law of big pipe roof in loess tunnel was obtained: in front of the excavating face about 15 m, the pipe roof started to bear the load; after the excavating face about 15 m,the load became stable; the longitudinal deformation of the whole pipe-roofs was groove-shaped distribution; the largest force of pipe-roofs was at the excavating face. The conclusions can provide reference for the design parameter optimization and the construction scheme selection of pipe-roofs and had been verified in the result of numerical analysis software FLAC3D and deformation monitoring.
Based on the truss arch of Xiangtan 4th Bridge, we made fatigue property test on concrete filled steel pipe K-joints of three different specifications, and calculated the amplitude of fatigue load of concrete filled steel pipe K-joints with hot-spot stress approach in this paper, which presented that hot-spot stress approach can be used to assess fatigue life of concrete filled steel pipe, and fatigue property of concrete filled steel pipe K-joints was obviously better than that of steel pipe K-joints. Moreover, the S—N curve of concrete filled steel pipe K-joints proposed by this paper would be of referential significance for building design criterion of fatigue life of concrete filled steel pipe K-joints.
The dehumidified adsorption system of expanded perlite in a closed space was designed and orthogonal experiments of three-factor and three-level and single factor for current velocity of wet air, sorbent layer, laid density of sorbent were processed. The effect of the above diversified factor on dehumidification performances was analyzed. The experimental results show that dehumidified velocity increases with air current, and dehumidified time decreases accordingly, higher current velocity of wet air is adopted within a certain scope, which increases dehumidification efficiency. And dehumidification ability improves with adsorbent layer increment. With laid density of adsorbent increment, the ability of heat and mass transfer between wet air and adsorbent grain has improved. Dehumidification velocity increases, and consuming time decreases correspondingly.
Combining with the characters of the practicing qualification personnel in construction market, evaluation method based on the self-organizing nerural network is brought out to analyze the credit classification of the practicing qualification personnel. And the impact factors on the credit classification of the practicing qualification personnel, such as the number of neurons, the training steps, the dimension of neurons and the field of winning neurons are studied. Then a self-organizing competitive neural network is built. At last, a case study is conducted by taking practicing qualification personnel as an example. The research result reveals that the method can efficiently evaluate the credit of the practicing qualification personnel; thus,it could provide scientific advice to the construction enterprise to prevent relevant discreditable behaviors of practicing qualification personnel.
Along with the time and the environment unceasing change and enterprise technology innovation competence's more requests, the technology innovation competence can not satisfy enterprise technology new requests, and therefore technology innovation competence renewal is enterprise's one kind of competence behaviors under the new requests.This article studied enterprise technology innovation competence renewal method under the new requests based on rough set theory, acquiring the renewal order with the minimal expense. The validity of the algorithm was given in the end.
This Issue
Sep 2011, Volume 13 Issue 9