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刘昀 《科技信息》2007,(32):138
A Streetcar Named Desire is a tragedy.Blanche,a beautiful woman,finally goes insane.She has an indecent past.She tells lies and is indulgent in her behavior toward men.All these seem to suggest that she deserves such a consequence.However,the fact is that Blanche once was a pure girl who dreamed of true love and happy family.It is the cruel reality that results in her tragedy.Compared with her,Stella's tragedy is a tragedy of toleration.Unlike Blanche,Stella prefers to tolerate when confronting with the reality.The tragedy of Blanche and Stella is typical of the time in which women cannot enjoy the same rights as men.  相似文献   

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Study on the Universality of the Normal Cloud Model   总被引:6,自引:0,他引:6  
The distribution function is an important tool in the study of the stochastic variances. The normal distribution is very popular in the nature and our society. The idea of membership functions is the foundation of the fuzzy sets theory. While the fuzzy theory is widely used, the completely certain membership function that has no any fuzziness at all has been the bottleneck of the applications of this theory.Cloud models are the effective tools in transforming between qualitative concepts and their quantitative expressions. It can represent the fuzziness and randomness and their relations of uncertain concepts. Also cloud models can show the concept granularity in multi-scale spaces by the digital characteristic Entropy (En). The normal cloud model not only broadens the form conditions of the normal distribution but also makes the normal membership function be the expectation of the random membership degree. In this paper, the universality of the normal cloud model is proved, which is more superior and easier, and can fit the fuzziness and gentleness of human cognitive processing.It would be more applicable and universal in the representation of uncertain notions.  相似文献   

4.
By studying the variations of balloon height and of wind-ing radius in any one winding layer of ring spinning, the formula for determining the winding tension in any layer is derived, and then the overall tension variation throughout all winding layers can be computed. A meth-od of measuring the winding tension is also introduced here, with the measured results agreeing with the com-puted ones, and so the reliable relationship between winding tension, speed and ring traveller weight can be thus obtained. The highest allowable spindle speed is also discussed.  相似文献   

5.
Subliminal Channels in the NTRU and the Subliminal-Free Methods   总被引:1,自引:0,他引:1  
The construetion and destruction of subliminal channel are important problems in the information hiding. The subliminal channel can send secret information without notice. Two subliminal-free methods named weak (strong) subliminal-free on public-key cryptosystem (PKC) are proposed in this paper using the combinatorial method. The first method can only free the subliminal information with any minor probability and the second can free all. Moreover, the "traitor problem" which is same as the model of the subliminal channel in PKC is given. Two subliminal channels are embedded in N-th degree truncated polynomial ring (NTRU) cryptosystem, and their subliminal-free methods are also be obtained by the action of surveillant.  相似文献   

6.
Analysis of the taxonomy and stratigraphic distribution of the Early Cambrian eodiscoid trilobites of the Yangtze Platform indicates that species of Tsunyidiscus and Hupeidiscus can be used for biostratigraphic correlation. T. aclis occurs only in the lower Qiongzhusian, T. armatus occurs in the lower and middle Qiongzhusian, while T. niutitangensis and T. tingi occur mainly in the middle and upper Qiongzhusian, with only T. tingi extending upward into the lower Canglangpuian. H. orientalis first appears in the upper Qiongzhusian, reaching peak abundance in the lower Canglangpuian and becoming extinct above the Drepanuroides Zone. Biostratigraphic and lithostratigraphic correlations indicate that the limestone in the lower part of the Mingxinsi Formation, the Upper Member of Jiumenchong Formation, and the upper part of the Middle Member of the Huangbailing Formation, can be correlated with each other as Hupediscus, an index fossil of the lower Canglangpuian, is abundant in all these units. The lower part of the Niutitang and Jiumenchong formations in eastern Guizhou, which mainly represent Qiongzhusian strata, can be correlated with the Lower Member of the Huangbailing Formation. The basal part of the Niutitang Formation, which may be equivalent to the Upper Meishucunian Shiyantou Formation in eastern Yunnan, is very condensed. Well-preserved sponge faunas and non-mineralized fossils in the lower part of the Niutitang and Hetang formations are not older than Qiongzhusian in age.  相似文献   

7.
According to the Wide Area Network model,we formulate Internet flow control as a constrained convex programming problem,where the objective is to maximize the total utility of all sources over their transmission rates,Based on this formulation,flow control can be converted to a normal unconstrained optimization problem through the barrier function method.so that it can be solved by means of a gradient projection algorithm with properly rate iterations.We prove that the algorithm converges to the global optimal point,which is also a stable proportional fair rate allocation point,provided that the step size is properly chosen.The main difficulty facing the realization of iteration algorithm is the distributed computation of congestion measure.Fortunately,Explicit Congestion Notification (ECN) is likely to be used to improve the performance of TCP in the near future.By using ECN,it is possible to realize the iteration algorithm in IP networks.Our algorithm is divided into two parts,algorithms in the router and in the source.The router marks the ECN bit with a probability that varies as its buffer occupancy varies,so that the congestion measure of links can be communicated to the source when the marked ECN bits are reflected back from its destination.Source rates are then updated by all sessions according to the received congestion measure.The main advantage of our scheme is its fast convergence ability and robustness;it can also provide the network with zero packet loss by properly choosing the queue threshold and provide differentiated service to users by applying different utility functions.  相似文献   

8.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

9.
A preliminary survey of estrogenic activity of the contaminant in part of waters (Ziya River and the estuary of Haihe River) in Haihe River, Tianjin has been performed with the plasma vitellogenin (Vtg) in feral fish as a biomarker for estrogenic activity. The concentrations of bisphenol A (BPA), 4-tert-octylphenol (OP) and 4-nonyl- phenol (NP) in surface water were also determined. The presence of Vtg in male fish plasma as well as that in female can be detected at different sites and different seasons. The results indicate that the water in the sampling sites was contaminated by some estrogenic compounds. Although BPA, OP and NP can be detected in all of the water samples, their concentrations were much lower than the effective concentrations for those chemicals to induce Vtg production in male fish.  相似文献   

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The mirror extending approach proposed by Zhao and Huang ^[9] in EMD method is improved in this paper.Mirror extending manner of data is kept unchanged,but the apprioach for determining envelopes is changed.When the end of data is obviously not extremum,the envelope is determined by the first inner extremum and the image value in the mirror,ignoring the value on the end.This improvement eliminates the frequency compression near the end and decreas the error.Meanwhile,tridiagonal equations are used and the calculation speed is much increased.The temporal process curve is more important in reflecting the real physical process and comparable with other phenomena,Frequency mixing in IMFs makes it impossible,A high frequency reconstruction (HFR) approach is proposed to eliminate common frequency mixing and reconstruct an IMF with all high frequency portions.By this approach,the IMFs without frequency mixing are obtained to express significative processes.The high frequency information restored in high frequency IMF can be extracted by general spectrum method,After obtainning IMFs by EMD method,some of the theoretical and technological issues still exist when using the IMFs.The consistency of IMFs with real physical process is discussed in detail.By virtue of the approach proposed in this paper,the EMD method can be widely used in various fields.  相似文献   

12.
The influence of factors on the substrate-specificity of Pst Ⅰ restriction endonuclease has been studied with the method of electrophoresis. The results show that, the specificity of Pst Ⅰ almost can not be influenced by the single alteration of the concentration of Tris*HCl, Mg2+ or Na+ in the reaction system, but it can be altered by the reduction of any two of them. The specificity can not be altered by the single alteration of pH or the replacement of Mg2+ with Mn2+. The addition of glycerol or dimethylsulphoxide (DMSO) to the reaction system results in the relaxation of the substrate-specificity of Pst Ⅰ , but dimethylmethylformide, glycol and ethyl alcohol can not bring about the alteration of Pst Ⅰ specificity. Through the method of cloning and sequencing, the nucleotides of No.1 and 6 in the recognition sequence of Pst Ⅰ have changed (1C→A or 6G→T). Used with the enzyme analysis of an artificially synthetic DNA segment containing a special sequence, the nucleotides of No.1 and 6 have both changed (1C→A and 6G→T). The recognition sequence of Pst Ⅰ is speculated to be changed from CTGCA↓G to TGCA↓.  相似文献   

13.
The origin and sedimentary environment of theLate Tertiary (Neogene) Red Clay Formation in northernChina had long been controversial. A new mollusk recordfrom the Xifeng red clay (red-earth) sequence in the centralLoess Plateau provides the biological evidence for addressingquestions of its origin and environmental implication. Thestudy of composition and preservation condition of seventymollusk fossil assemblages reveals the initial ecological con-dition of the red clay formation, avoiding the effect ofpost-deposited alteration. The result shows that all of identi-fiable mollusk species are composed of terrestrial taxa, mostof them are the common species found in the overlying Qua-ternary Ioess-paleosol sequence. Most of fossil individualspreserved in the red clay strata are in living conditions basedon the investigation of fieldwork, indicating the originalpopulation. Thus, the mollusk fossil assemblages can be usedas an indicator of primary environment of the red clay for-mation. The mollusk record from the Xifeng red clay se-quence supports the view that the red clay is an aeolian ori-gin, similar to the overlying Quaternary loess deposits. Ourdata also reveal the history of environmental changes atXifeng from 6.2--2.4 Ma, which is coupled in phase with theformation and development of the Arctic ice sheets and theprocess of the Tibetan Plateau uplift. Both may be the majorcause and forcing mechanisms of the late Tertiaryenvironmental changes in the Loess Plateau.  相似文献   

14.
Animals interact with their environments all the time, and must react to all kinds of factors present in the environments. Environmen- tal RNA interference refers to the phenomenon that exogenous RNA molecules can enter cells of certain animal species and inter- fere with gene expression of these animals. These exogenous RNAs may be molecules in animal food, or may be present in the living environment from other sources. Molecular pathways for the cell entry of environmental RNAs and further for their func- tionality in gene interference have started to be revealed in the animal model Caenorhabditis elegans. Here we highlight some known examples of environmental RNA interference (RNAi) in animals and introduce the molecular mechanisms underneath.  相似文献   

15.
This article gives a summary and analasis to experimental study on the restoration and giving a new lease of life to the alpine grassland vegetation along the Qinghai-Tibet Railway. Through on-the-spot investigation and vegetaion storation experimental study to the constructive fetching soil ground in Tuotuo River experiment section in the construction of the Qinghai-Tibet Railway, the result shows : after the activities of the construction, soil conditions on the fetching soil ground have changed a lot, the soil quality has obviously degraded. In order to do well the vegetaton storation and reconstruction in the process of the construction of the Qinghai-Tibet Railway, the backfilling of the surface soil should really be done well. According to the result of on -the-spot experiment, the Elymus dahuricus Turcz and Poa annua Linn are all more suitable to the fetching soil environment on the alpine grassland, the plant can normally grow in the growing season. The timing selection of the vegetation should fully use feature of both rain and heat in the same season, thus can improve the percentage of success.  相似文献   

16.
Aepyosciurinae,a new subfamily of Sciurldae,were found at the base of the early Pleistocene loess deposits in dongxiang County,Gansu Province.Its umilaterally hyp-sodont and lophodont cheek teeth are unique among the sciurids so far known all over the world.Certain degree of similarity can be observed between the cheek teeth of the new subfamily and the Anomalurinae living in tropical and subtropical forests in central and western Africa.Aepyosci-uris orientalis gen.et sp.nov.might have lived in montaneous woodland or grassland and lived on harder leaves,harks,or even grass.This tends to show that the northeastern border area of the Tibetan Plateau had been lifted considerably high in early Pleistocene(ca.2 Ma),with drier climate,becoming a suitable habitat for Aepyosciurus orientalis.  相似文献   

17.
The main-channel of the lower Yellow River is the main path of water and sediment transportation. In this paper, we put forth a suggestion that the bank-full discharge of the main-channel in the lower Yellow River should be no less than 4000 m^3/s, which is based on the demand from effective sediment transportation (or riverbed scouring), the demand of flood control on morphology of the cross section of the main-channel, and the possible riverbed-forming force of future flood. The forming of the main-channel is the process for the flood force to overcome the resistance from the riverbed. The forming of the main-channel configuration comes from the competition between riverbed-forming force of flood and resistance from the riverbed. Regarding the flood with medium or less sediment content and without floodplain inundated, the main-channel forming mechanism can be simplified as the relationship between the change of cross section area and W^αQ^β. For forming same main-channel, the needed flood force W^0.32Q^0.37 is definite, i.e., when the discharge is large, the flood volume can be smaller; if some flood is able to scour the main-channel, its force W^0.32Q^0.37 should be larger than 41. Not all floods that inundate floodplain have the function of silting in floodplain and scouring main-channel. Regarding flood with medium or less sediment content, only when the flood discharge is over 1.5 times of the relevant bankfull discharge, obvious scouring effect can occur in the main-channel.  相似文献   

18.
Nonlinear transport of intense continuous beam in the axial-symmetric electrostatic fields is analyzed with the Lie algebraic method. The K-V particle distribution is adopted in the analysis. The results obtained can be used in the calculations of the intense continuous beam dynamics in the beam optical systems consisting of drift spaces, electrostatic lenses, and DC electrostatic accelerating tubes. A computer code has been designed for practical simulations. To meet the needs of accurate calculation, all the elements are divided into many small segments, the electric fields in each segment are regarded as uniform fields, and the dividing points are treated as thin lenses. Iteration procedures are adopted in the code to obtain self-consistent solutions. The code can be used to design low energy dc beam transport systems, electrostatic accelerators, and ion implantation machines.  相似文献   

19.
A series of light-emitting conjugated polymers alternatively involving carbazole and bivinylene arylene moieties in the main chain were synthesized via Wit-tig-Horner type copolymerization.The photoinduced charge transfer process relating to these polymers was investigated by using the technique of fluorescence spectroscopy.The interaction between excited copolymers and C60 in benzene solution was studied.The fluorescence quenching can be well described by the “sphere-of-action” mechanism.It is be-lieved that two basic steps are involved in the quenching process,i.e. the diffusion of excitation within the comjugated polymers and the dissociation of the exctions trapped by fullerene,The radius of the sphere-of-action can be related to the excitation diffusion length,which depends on the lifetime of the exciton.The dynamic fluorescence quenching of the copolymers by another quencher,1,4-dicyanobenzene(DCB) was also surveyed.Copolymers with different chain confor-mations show different temperature effects in the dynamic quenching.A planar conformation is beneficial for the quenching via bimolecular collision.  相似文献   

20.
Through collecting, summarizing and effectively classifying the image resources in Daur nationality,and applying the theories and methods of costume design,ethnology and computer science,it investigates into the retrieval method and indicator system of images resources in Daur nationality in the context of digitalization. The preliminarily established application model of Daur costume design database can search out all qualified image resources from the database quickly according to the prerequisites given by users so that they can obtain information promptly. In particular,costume designers can get inspirations of creation and enlightenment on their creative thinking. Therefore,the effective integration of art and scientific researches can be realized.  相似文献   

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