共查询到20条相似文献，搜索用时 171 毫秒
1.
A two-stage method is developed to solve a new class of multi-storage tank multi-source （MTMS） systems. In the first stage, the optimal storage policy of each tank is determined according to the electricity tariff, and the ground-level storage tank is modeled as a node. In the second stage, the genetic algorithm, combined with a repairing scheme, is applied to solve the pump scheduling problem. The objective of the pump scheduling problem is to ensure that the required volume is adequately provided by the pumps while minimizing the operation cost （energy cost and treatment cost）. The decision variables are the settings of the pumps and speed ratio of variable-speed pumps at time steps of the total operational time horizon. A mixed coding methodology is developed according to the characteristics of the decision variables. Daily operation cost savings of approximately 11% are obtained by application of the proposed method to a pressure zone of S. Y. water distribution system （WDS）, China. 相似文献
2.
A practical method for computing the one-way rectangular orthotropicplate(isotropic plate as a special case)is suggested in this paper.The supported condi-tions in two opposite edges may be simply supported,continuous or supportednonsymmetrically and the other two opposite edges are slide-supported or free.A series ofsimplified formulas are given for calculating the bending moments along the cross section(loaded section),in which the acting point of the concentrated load or the center of a rec-tangular uniform load is located.The valid range and accuracy of these formulas were stud-ied and the approximate results were examined and compared extensively with those by thetriangular series solution or finite element method. 相似文献
3.
Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth. 相似文献
4.
The reinforcement effect of a reconstruction scheme for a steel factory building was investigated using finite element method and dynamic performance test. The workshop concerned is a portal frame structure with four spans and two slope roofs, of which ten columns need cutting for expanding span. The design and reconstruction pro- ject of column-cut supported by joist were introduced, which includes column reinforcement, connection rebuilding between brackets and crane beams, and the changing of rigid joint into hinge joint. The construction scheme was put forward in the light of the characteristics of the reinforcement and reconstruction. Spot test of dynamic performance on the workshop and comparison with theoretical analysis results show that the column-cut supported by joist design is effective and the reconstruction project is successful. 相似文献
5.
The characteristics of acoustic emission(AE)signals given off in the course of the failure of a concrete structure is explored based on the laboratory experiments with concrete specimens.It is observed that the failure of a concrete structure experiences three stages divided by two inflexion points on the AE event curve,which are sequentially no damage,damage initiation and propagation,and major failure stages.In the first stage,existing micro cracks and defects are compacted by loading. but no damage propagated,hence few AE signals are detected,and it appears that there exists a nearly linear relationship between the relative stress and relative strain.In the second stage,the AE event frequency increases implying that micro cracks begin to emerge inside the concrete structure,which is consistent with the damage mechanics.When the load is over 80% of that breaks the structure,i.e.the maximum load,there is a vertical jump on the AE event count curve,which suggests that the failure propagation speeds up.After the second inflexion point,the AE event density increases faster than before,and there is another jump just before breaking,which indicates a quick propagation stage.These findings are valuable for evaluating the damage situations,and for studying and monitoring the dynamic process of the failure behaviors of a concrete structure. 相似文献
6.
Thermal-mechanical behavior of functionally graded thick plates, with one pair of opposite edges simply supported, is investigated based on 3D thermoelasticity. As for the arbitrary boundary conditions, a semi-analytical solution is presented via a hybrid approach combining the state space method and the technique of differential quadrature. The temperature field in the plate is determined according to the steady-state 3D thermal conduction. The Mori-Tanaka method with a power-law volume fraction profile is used to predict the effective material properties including the bulk and shear moduli, while the effective coefficient of thermal expansion and the thermal conductivity are estimated using other micromechanics-based models. To facilitate the implementation of state space analysis through the thickness direction, the approximate laminate model is employed to reduce the inhomogeneous plate into a homogeneous laminate that delivers a state equation with constant coefficients. The present solutions are validated by comparisons with the exact ones for both thin and thick plates. Effects of gradient indices, volume fraction of ceramics, and boundary conditions on the thermomechanical behavior of functionally graded plates are discussed. 相似文献
7.
This paper proposes a hybrid optimization to solve the scheduling of household power consumption for Step and Time-of-Use (TOU) tariff system. The target function is the cost of electricity, and the optimization object is total instantaneous power within a billing period. The control variables are starting moments of each household appliance. The optimization procedure is divided into two stages. Firstly, the prerequisite for minimal cost is calculated through mathematical analysis and generalized function theory. Secondly, the solution is obtained by using a heuristic algorithm in which the result of the first stage is considered to reduce the searching space. And an evaluation methodology is deduced to evaluate the optimization. The computer simulation demonstrates that the proposed approach can reduce the cost of electricity evidently in the sense of probability. The approach shows great value for embedded applications. 相似文献
8.
By the application of life cycle assessment（LCA） methodology, this paper estimates the environmental impacts of production and disposal of traction motors used in electric vehicles in China. The results show that the total energy use, the criteria emissions and the greenhouse gases（GHG） emissions of a traction motor production and disposal are about 2,899,MJ, 4.5,kg and 259.5,kg per motor, respectively. Among the regulated emissions, the SOxemission ranks first by total mass, followed by CO, PM10, NOx, PM2.5, and volatile organic compound（VOC）. The motor material production stage accounts for most of the energy consumption and emissions, followed by the assembly stage and the end-of-life disposal stage. In this study, the environmental performance analysis is extended to the comparison between the use of secondary material and primary material for the material production stage. It is found that using 100% secondary material results in a 52.9% reduction in energy consumption, a 49.8% reduction in regulated emissions, and a 49.3% reduction in GHG emissions compared with the use of 100% primary material. 相似文献
9.
A low-power three-stage amplifier for driving large capacitive load is proposed. The feedback path formed by the active-feedback Miller capacitor leads to a high frequency complex-pole but a high Q-value, which significantly deteriorates the stability of the amplifier. The serial RC stage introduced as the second stage output load can optimize the resistor Rz and the capacitor Cz under fixed power and small compensation capacitor Ca, which brings about a suitable Q-value of the complex-pole and the gain-bandwidth product extension of the amplifier. The amplifiers were designed and implemented in a standard 65 nm CMOS process with capacitive loads of 500 p F and 2 n F, respectively. The post-layout simulation results show that the amplifier driving the 500 p F capacitive load can achieve a gain of 113 d B, a phase margin of 50.6° and a gain-bandwidth product of 5.22 MHz while consuming 24 μW from a 1.2 V supply. For the 2 n F capacitive load, the amplifier has a gain of 102 d B, a phase margin of 52.8°, a gain-bandwidth product of 4.41 MHz and a power of 43 μW. The total compensation capacitors are equal to 1.13 p F and 1.03 p F. The better figures-of-merits are 108 750 and 205 113(MHz×p F/m W). The layout areas are 0.064 mm×0.026 mm and 0.063 mm×0.027 mm. Compared with the CFCC scheme, the gainbandwidth product is extended by 1.6 times at CL=500 p F and Ca=1.1 p F. 相似文献
10.
For reconstructing a freeform feature from point cloud, a deformation-based method is proposed in this paper. The freeform feature consists of a secondary surface and a blending surface. The secondary surface plays a role in substituting a local region of a given primary surface. The blending surface acts as a bridge to smoothly connect the unchanged region of the primary surface with the secondary surface. The secondary surface is generated by surface deformation subjected to line constraints, i.e., character lines and limiting lines, not designed by conventional methods. The lines are used to represent the underlying information of the freeform feature in point cloud, where the character lines depict the feature＇s shape, and the limiting lines determine its location and orientation. The configuration of the character lines and the extraction of the limiting lines are discussed in detail. The blending surface is designed by the traditional modeling method, whose intrinsic parameters are recovered from point cloud through a series of steps, namely, point cloud slicing, circle fitting and regression analysis. The proposed method is used not only to effectively and efficiently reconstruct the freeform feature, but also to modify it by manipulating the line constraints. Typical examples are given to verify our method. 相似文献
11.
The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA. The influences of pile non-linearity and soil non-linearity on impact force, ship crush depth and the cap displacement of pile supported protective system are discussed. It's shown that for both severe impact case and non-severe impact case, the non-linearity of pile material influence the impact force history, ship crush depth. The non-linearity of pile material and soil has remarkable influence on the cap displacement especially for severe impact case. These issues should not be ignored in the analysis of pile supported protective system subjected to ship impact. 相似文献
12.
In this paper, the axisymmetric general solutions of transversely isotropic magnetoelectroelastic media are expressed with
four harmonic displacement functions at first. Then, based on the solutions, the analytical three-dimensional solutions are
provided for a simply supported magnetoelectroelastic circular plate subjected to uniform loads. Finally, the example of circular
plate is presented.
Project supported by the National Natural Science Foundation of China (No. 10172075) and Ningbo Natural Science Foundation
for Young Scientist (No. 02J20102-13) 相似文献
13.
Terri Bourke John Lidstone 《Discourse: Studies in the Cultural Politics of Education》2015,36(6):833-853
Many governments in Western democracies conduct the work of leading their societies forward through policy generation and implementation. Despite government attempts at extensive negotiation, collaboration and debate, the general populace in these same countries frequently express feelings of disempowerment and undue pressure to be compliant, often leading to disengagement. Here we outline Plan B: a process for examining how policies that emerge from good intentions are frequently interpreted as burdensome or irrelevant by those on whom they have an impact. Using a case study of professional standards for teachers in Australia, we describe how we distilled Foucault's notions of archaeology into a research approach centring on the creation of ‘polyhedrons of intelligibility’ as an alternative approach by which both policy-makers and those affected by their policies may understand how their respective causes are supported and adversely affected. 相似文献
14.
INTRODUCTIONInelasticity ,theproblemofasimplysup portedcircularplatesubjectedtouniformloadsisaclassicone .Timoshenkoetal.(1970 )pre sentedasolutionforanisotropiccircularplate .Dingetal.(2 0 0 0 ;2 0 0 1)obtainedtheanalyti calthree dimensionalsolutionforat… 相似文献
15.
水驱油效率一直是石油领域研究的热点问题,随着注水开发进入特高含水期,提高驱油效率日益受到人们的重视。在参阅国内外相关文献的基础上,对目前驱油效率的影响因素、计算方法进行归纳,对驱油效率的影响因素进行划分;总结了驱油效率计算方法的适用范围,提出了计算水驱油效率的改进方法。 相似文献
16.
唐元锋 《福建工程学院学报》2002,(4)
采用弹塑性有限元方法对一土钉支护边坡工程实例进行详细分析 ,给出边坡侧向变形、土钉应力随边坡开挖过程的变形 ,并且在各个开挖阶段中都进行土工安全系数计算 相似文献
17.
A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was pro- posed. The track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping elements. The general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain, according to the Duhamel integral and the dynamic reciprocity theorem. In the case of the periodic curved track structure subjected to moving loads, the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the integral. The transfer function for the curved track was expressed in the form of a transfer matrix. Single and series moving loads were involved in the calculation program. For the verification of the analytical model, the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the reference. The research results indicate that： under the same moving loads, the displacement response of the curved track decreases slightly with the increasing track radius, and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track; the frequency spectrum of the curved track is more abundant than that of the straight track, which may result in more wheel-rail resonance and rail corrugation in the curved lines. 相似文献
18.
In piezoelectric problems, the form of the general solution is dependent on the eigenvalues of the material. The singular
stress field and electrical displacement field near the interface edge were deduced in this study. The results showed that
the stress field and the electrical displacement field have the same singularity; and that the singularity depends not only
on the mechanical properties and shape of the interface edge, but also on the piezoelectric properties of the composite material.
Project (19972060) supported by Natural Science Foundation of China. 相似文献
19.
Pierre Coirier Caroline Golder 《European Journal of Psychology of Education - EJPE》1993,8(2):169-181
The development of argumentative writing is studied here by examining the structural organization of argumentative texts. It is assumed that the ability to construct supporting relationships, that is, a conclusion statement supported by argument statements, is acquired gradually with age. The following stages of acquisition are postulated: (1) a preargumentation stage, where at first no explicit position is stated, and then an explicit position is stated but is not supported by an argument; (2) a minimal argumentation stage, where a position is explicitly taken and supported by one argument; and (3) an elaborated argumentation stage, where at least two unrelated supporting arguments are used, and then two related arguments are used. Two corpora were gathered under similar conditions: collective debate in the classroom, followed by individual essays written on the chosen topic. The first corpus was produced by 147 children aged 7 to 14, and a group of 34 college students. The second corpus included the protocols of 92 children aged 11 to 16 the essays were graded for the presence or absence of each structural level, and then classified at the highest structural level exhibited. The resulting classification largely confirmed the hypothesized order for the stages of argumentative development. The minimal argumentative structure (standpoint + one supporting argument) was mastered by nearly 90% of the 7 and 8 year-olds. The most elaborate structural level in our model (two related arguments) was attained later: less than one out of four 7–8 year olds versus three out of four beyond age 14. Techniques involving more complex argumentative relations such as refutations and counterarguments, or restriction of one argument by another, are mastered even later and seem to be strongly linked to the nature of the issues under debate. Three main conclusions can be drawn from these results: precocious argumentative skills exist in children before age 11 or 12, argumentative discourse complexity continues to increase up to age 14 and beyond, and the characteristics of the referential domain of argumentation have an impact on this structural elaboration process. 相似文献
20.
This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy. The fine stage is arranged in series with a coarse stage. The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness. We designed the toggle mechanism for reduction of the displacement to suppress signal noises, The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor, respectively. The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm. 相似文献