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1.
In modern control engineering and simulations,it is perferable to get the governing equationsby an easier way,so that state equations have been widely used.There are many rules to select statevariables,but the uses of these rules may have different forms of limitations and exceptions,yet afully argumented bond graph can be processed in proper way to select the state variables and toyield the state equations.The state variables are usually related to the energy-storing elements.State equations can easily be derived from bond graph by means of constitutive relations and struc-tural relations.  相似文献   

2.
INTRODUCTIONAt present fifty sorts chemical substances have been determined to influence endocrine system, half of which are chlorides, such as dioxins. The structure of these substances is similar with biologic hormone. When they are taken in body of human, they can destroy hormone balance of biology and result in endocrine disorder, the more serious problem is that they lead to heteroplasia and procreant unconventionality. As people pay more attention to water environment and understand…  相似文献   

3.
Constraint pushing techniques have been developed for mining frequent patterns and association rules. How ever, multiple constraints cannot be handled with existing techniques in frequent pattern mining. In this paper, a new algorithm MCFMC (mining complete set of frequent itemsets with multiple constraints) is introduced. The algorithm takes advantage of the fact that a convertible constraint can be pushed into mining algorithm to reduce mining research spaces. By using a sample database, the algorithm develops techniques which select an optimal method based on a sample database to convert multiple constraints into multiple convert ible constraints, disjoined by conjunction and/or, and then partition these constraints into two parts. One part is pushed deep inside the mining process to reduce the research spaces for frequent itemsets, the other part that cannot be pushed in algorithm is used to filter the complete set of frequent itemsets and get the final result. Results from our detailed experi ment show the feasibility and effectiveness of the algorithm.  相似文献   

4.
A genetic algorithm to solve the set covering problem proposed in the literature had some improvements which gave better solutions, i.e., better chromosomes in the first starting population, taking full account of domain specific knowledge with sound programming skill. We have further investigated the input data dependency of their genetic algorithm, i.e., the dependency on costs and density. We have found that for input problem data sets with densities greater than or equal to 3%, our genetic algorithm is still practical both in computing time and approximation ratio.  相似文献   

5.
By means of first-principles calculations,we have investigated the effects of rare earth elements (REEs) on the structures and mechanical properties of magnesium.The lattice parameters,elastic constants,bulk moduli,shear moduli,Young’s moduli and anisotropic parameter of these solid solutions have been calculated and analyzed.The nearest-neighbor distance between Mg and the REEs is also analyzed to explore the correlation with the bulk moduli.The results show that the 4f-electrons and atomic radii play an important role in the strengthening process.The anomalies of the lattice parameters and mechanical properties at Eu and Yb are due to the half-filled and full-filled 4f-electron orbital states.Finally,the increase of directional bonding character near the alloying elements may account for the anisotropy and brittleness of these magnesium alloys.  相似文献   

6.
MA Ting 《科技信息》2007,(34):155-158
This paper mainly illustrates the important role TCFL teachers play in the process of teaching Chinese as a foreign language and the requirement that has been imposed on the teachers to be equipped with a set of professional knowledge structure and skill structure.The characteristics of TCFL determine the special teaching content and teaching methodology of this field,which require the teachers to have special knowledge and unique skills.  相似文献   

7.
Partner selection is a fundamental problem in the formation and success of a virtual enterprise. The partner selection problem with precedence and due date constraint is the basis of the various extensions and is studied in this paper. A nonlinear integer program model for the partner selection problem is established. The problem is shown to be NP-complete by reduction to the knapsack problem, and therefore no polynomial time algorithm exists. To solve it efficiently, a particle swarm optimization (PSO) algorithm is adopted, and several mechanisms that include initialization expansion mechanism, variance mechanism and local searching mechanism have been developed to improve the performance of the proposed PSO algorithm. A set of experiments have been conducted using real examples and numerical simulation, and have shown that the PSO algorithm is an effective and efficient way to solve the partner selection problems with precedence and due date constraints.  相似文献   

8.
As for the theory and method in garment structural design according to human figures, a principle for garment design, i. e. body-fitting without added allowance, and a combination of draping and planar design (DPD hereunder) for young ladies has been put forward, and, also, a DPD garment prototype for them has been established. And the applied formulae for extensively-practicing operation have been set up, which proves to be, with actual samples, a systematic and practical garment structural designing theory and approach.  相似文献   

9.
Based on observations of earthquakes that have occurredin theplains of eastern China during recent yeas, the characteristics origins, classification and distribution patterns of earthquake landforms in alluvial plains are discussed. In such flat areas, earthquakes are capable of complete reversal of topographic gradients; minor hills can be replaced by hollows and depressions can experience uplift. The major factors influencing the development of such landforms in alluvial plain are the force of the earthquake, surface and sub-surface characteristics, the thicknesses of different subsurface layers, the height of the groundwater table and the relief. Earthquake hndforms in alluvial plains may be classified hto three main groups (1) Landforms directly associated with the liquefaction of sand hyers; (2) Landforms associated with the passage of earthquake waves; and (3) Landforms associated with earthquake structures. In turn, these categories can be further sub-divided. Through analysis of the Tangshan earthquake landforms, several characteristics of the distribuinn patterns of earthquake landforms in allu vial plains have been recognised.  相似文献   

10.
Gallium, Ge, V, and U are the associated valuable elements in coal. From the 1950s to the 1970s, some researchers in the departments of coal industry and mineral resources of China investigated these elements in coal during geological explorations. The enrichment mechanism and the environmental influence of trace elements in coal have been deeply studied in recent twenty years. With respect to the ore-forming theories and practical utilizations of metals in coal, germanium was furthest studi…  相似文献   

11.
The theoretical research on function-structure relationships of chemicals responsible for carcinogenesis at the very molecular level has begun, so far as Ⅰ know, by Otto Schmidt (1) in the years from 1938 to 1941, with quantum chemistry considerations. This german pioneer author, who was dead probably during the world war Ⅱ, put forth the hypothesis that π. electrons in the polycyclic aromatic hydrocarbons (PAH), in particular their charge density distribution within the molecule, might explain the ir carcinogenic behavior. Since then, many attempts have been made to find correlations between the carcinogenecity of a polycyclic hydrocarbon and certain of its molecular properties. These latter can be obtained by experimental determinations or by quantum chemistry calculations. Correlation research, which is essentially statistical in nature(2), calls for many numerical data to be analyzed. So, quantum chemistry has played and continue to play an important part in this theoretical research, because evaluation of a molecular property of a chemical carcinogen or noncarcinogen by experimental mays takes months, while the attainment of the same measure does not take but only days or even hours. Thus, although reactivity indices of PAH can be determined by exper. imental devices, the famous K- and L-region theory( 3 , 4 ), which is the first successful acquisition in this line, has been built upon analysis of computational data. As K- and L-region theory constitutes a remarkable milestone in the evolution of the theoretical research on chemical carcinogenesis, a brief recall of its essential elements will be given below.  相似文献   

12.
The compatibility and phase morphology of poly (phenylcne oxide) (PPO) multi-componenet blends with poly (ethylene terephthalate) (PET) and polystyrene (PS) were studied using differentialscanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microsopy (SEM) methods. The effect of glycidyl methacrylate-styrene copolymer (GMS), as a compatibilizer, on the morphology of the PPO blends has also been studied in detail. The influence of the moiecular weight of PET and the synergetic effect of the compatibilizers of GMS and phenoxy on the morphology were examined. The DSC and DMA results show that there are two distinct glass transitions correspondinig to PET and PPO existed, however, the Tg of PPO shifts toward lower temperature region due to the addition of GMS and PS. The SEM results reveal that PET component is as dispersed phases in the PPO matrix, part of which is located at the interfaces due to the interaction with GMS while PS is miscible in the PPO matrix. A significant  相似文献   

13.
To facilitate users to access the desired information, many researches have dedicated to the Deep Web (i.e. Web databases) integration. We focus on query translation which is an important part of the Deep Web integration. Our aim is to construct automatically a set of constraints mapping rules so that the system can translate the query from the integrated interface to the Web database interfaces based on them. We construct a concept hierarchy for the attributes of the query interfaces, especially, store the synonyms and the types (e.g. Number, Text, etc.) for every concept At the same time, we construct the data hierarchies for some concepts if necessary. Then we present an algorithm to generate the constraint mapping rules based on these hierarchies. The approach is suitable for the scalability of such application and can be extended easily from one domain to another for its domain independent feature. The results of experiment show its effectiveness and efficiency.  相似文献   

14.
Describe some new fully automatic instruments for the measurements of the blood capillary pressure (Pcap) and arterial elastic properties in human fingers using a photoelectric plethysmographic technique. With these instruments, the value of Pcap was in good agreement with those reported by other investigators, the arterial elastic properties in human fingers have been successfully measured. The measurements of Peap and arterial elasticity are now required in clinics because they provide useful and important information for evaluating vascular haemodynamics.  相似文献   

15.
The Benjamin-Bona-Mahony (BBM) equationu_1+UU_x-u_(xxt)=0and the Korteweg-de Vries (KdV) equationu_1+uu_z+u_(xxx)=0have both been proposed as models for long waves in nonlinear dispersive systems and the Cauchy's problemwas studied for the above equations.1 We consider the periodic boundary value problem for the system of n-dimensional generalized BBMequationswhere be a n-dimensional cube with21 in each direction,and _0(x) is a n-dimensional periodic functional  相似文献   

16.
1 Results Several methods have been elaborated in this laboratory allowing preparation of macromolecules with phosphodiester bonds,and having sequence of atoms similar as in the chains of biomacromolecules - nucleic or teichoic acids (TA),namely:-(C)n-O-PO-,where n=2 (for teichoic acids) or 3.These methods,to be discussed in the lecture,are based on the ring-opening polymerization,transesterification,and recently elaborated direct addition of phosphoric acid to diepoxides.For the first time an attempt has been made to directly reacting phosphoric acid with diols in the presence and absence of catalysts.The major side reaction,preventing high molar mass polymers formation,results from dealkylation,i.e.nucleophilic attack of the OH groups on the C atom,instead attack on the P atom.The other two methods allowed reaching high molar mass macromolecules,with Mn up to 105.Following these studies phosphorylation of polymers with side groups containing -OH groups were studied and a series of diblock copolymers with ionic and nonionic blocks were prepared.  相似文献   

17.
By analysis of the conserved elements in yeast U14 boxC/D snoRNA. the conserved elements in rice U14 boxC/D snoRNA have been speculated. Through computer search of the international rice genome database, two rice U14 snoRNA gene candidates are obtained. These two putative U14 snoRNA genes are closely linked on rice chromosome 2. The coding sequences of these two snoR-NAs exhibit the hallmark structure of boxC/D antisense snoRNA. They both have conserved boxC and boxD sequences and a 14nt-long complement to the sequence between 414nt and 427nt of rice 18S rRNA (according to GenBank accession no. X00755). The experimental evidence shows that these two snoRNAs are involved in the methylation of the complementary sequence of rice 18S rRNA. The existence and localization of these two snoRNAs are proved by RT-PCR and Northern blot. Further analysis shows that both of the newly found rice snoRNAs have high homology with maize U14 snoRNA. and they are named rice U14.1 snoRNA and U14.2 snoRNA respectively. The gene sequence encoding these two snoRNAs has been deposited in the GenBank database under accession number of AF332622.  相似文献   

18.
According to the mass action law and the coexistence theory of metallic melts, the mass action concentrations of Cu-Mg, Bi-Tl and Ni-Al melts involving compound formation have been calculated. The calculated results show that, except the ultimate case of pure element, when two elements are present in the melts, all structural units (atoms and molecules) without exception will be present in the melts, i.e., their concentrations may change from great to small, but they will not vanish into nothing, and only under such conditions, the calculated results both agree with practice and obey the law of mass action. In view of that over considerable wide composition range, the activities of both elements of the three solid binary alloys mentioned above have been measured, this seems in contradiction with the present relevant phase diagrams, in which the structural units are determined by composition range, so the latter needs further investigation and consideration.  相似文献   

19.
Two multigene superfamilies, named V1R and V2R, encoding seven-transmembrane-domain G-protein coupled receptors (GPCRs) have been identified as pheromone receptors in mammals. Three V2R gene families have been described in mouse and rat. Here we screened the updated mouse genome se- quence database and finally retrieved 63 putative functional V2R genes including three newly identified genes which formed a new additional family. We described the genomic organization of these genes and also characterized the conservation of mouse V2R protein sequences. These genomic and se- quence information we described are useful as part of the evidence to speculate the functional domain of V2Rs and should give aid to the functionality study in the future.  相似文献   

20.
Seeing that some commercial gas adsorption instrument still uses a too rough method for cal-culation of mesopore size distribution, we reviewed some practical methods of calculation so farproposed in the literature. We have found that most of these methods and many books have someincorrectness in the geometric factor Q_i used for the calculation of pore volume △V_i from corevolume △V_i~k. It has been proved that the correct expression for Q_i should be[_i/(_i~k+1/2△t_i)]~2for cylindrical pores, _i,/(_i~k+1/2△t_i)for slit-shaped pores. On the basis of this correct Q_i,these methods were applied to the desorption isotherms. The results were compared and analyzed.  相似文献   

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