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1.
Panspermic origins notwithstanding, life, assuming that it started on Earth, may have taken root as soon as it became geologically permissible. There are multiple possibilities for early biogenesis from complex inorganic/organic geochemistry at diverse geological niches. Recent theoretical calculations have revived the possibility of Earth having a rather reduced early atmosphere, and had refueled arguments for a surface origin of life. Laboratory modeling of possible prebiotic RNA polymerization has seen interesting experimental advances, although a plausible replicator-like molecule has not yet been produced. The hydrothermal origin school of thought has also seen an interesting postulation for life’s early emergence and evolution—within contiguous, porous hydrothermal iron-sulfide (FeS) compartments, leading to a non-free living last universal common ancestor (LUCA). A confined LUCA evolving later into free-living archaebacteria and eubacteria could potentially reconcile some problems of molecular divergence between these two kingdoms. There are, however, many unresolved problems, and experimental evidence for such a scheme is lacking. Here, recent updates and refinements to the mainstay hypotheses for the emergence of life on Earth are reviewed and discussed.  相似文献   

2.
As a member of robot families, climbing robots have become one of the research hot-spots in the robotic field recently and Gekko gecko (G. gecko) has been broadly seen as an ideal model for climbing robot development. But for gecko-mimic robots, one of the key problems is how to design the robot's foot. In this paper, (1) high-speed camera recording and electrophysiological method are used to observe motion patterns of G. gecko's foot when it climbs on different oriented surfaces; (2) nerve innervations of gecko's toes to motion and reception are studied. It is found that the five toes of the G. gecko can be divided into two motion and reception divisions, and also its motion and reception are modulated and controlled hierarchically. The results provide important information and exclusive ideas for the foot design and control algorithm of gecko-mimic robots.  相似文献   

3.
Han Yunxia 《科技信息》2008,(9):142-144
Sex differences are a fundamental fact of human life and it is not surprising to find them reflected in language.It's said that women tend to use more standard forms of English,while men tend to use less standard forms of English.Over the past thirty years,and as a result of the women's movement,gender issues have become entangled with issues of language.Recent research indicates that sex may be more fundamental as an influence on sociolinguistic variation than has been recognized so far.This article will try to discuss the different language use between men and women.  相似文献   

4.
Steam reforming of methanol and gasoline is actively researched and developed as hydrogen supply methods for the fuel cells of vehicles and so on. However, these materials have the problems such as the infrastructure, toxicity, difficulty of the reforming, and so forth. Dimethyl ether (DME) does not contain the poisonous substances, and is expected as a clean fuel of the next generation. DME is able to take the place of light oil and LPG, and its physical properties are similar to those of LPG. There is possibility that DME infrastructures will be settled more rapidly than those of hydrogen and methanol, because LPG infrastructures existing are able to use for DME. Then, we have been studying on steam reforming of DME for the hydrogen production.  相似文献   

5.
Scientific big data and Digital Earth   总被引:6,自引:0,他引:6  
Big data has been a focus of research in sci- ence, technology, economics, and social studies. Many countries have already incorporated big data research into their national strategies. This paper elaborates upon the origin, connotation, and development of big data from both a spatial and temporal perspective. It proposes that scien- tific big data will become a new solution in scientific research as the paradigm changes from being model-driven to data-driven. This paper defines the concept of "scientific big data" and proposes strategies for solving "big data problems". Theoretical frameworks and data systems for Digital Earth are discussed with a clear conclusion that scientific big data is a prominent feature of Digital Earth. As an example, spatial cognition of the formation mecha- nism of China's Heihe-Tengchong Line--a geo-demo- graphic demarcation line dividing China into two parts--is discussed within the context of big data computation and analysis for Digital Earth.  相似文献   

6.
Fix a collection of polynomial vector fields on R3with a singularity at the origin,for every one of which the linear part at the origin has two pure imaginary and one non-zero eigenvalue. Some such systems admit a local analytic first integral,which then defines a local center manifold of the system. Conditions for existence of a first integral are given by the vanishing certain polynomial or rational functions in the coefficients of the system called focus quantities. In this paper we prove that the focus quantities have a structure analogous to that in the two-dimensional case and use it to formulate an efficient algorithm for computing them.  相似文献   

7.
Carbide slag was used as the calcareous materials for the first time to prepare xonotlite via dynamic hydrothermal synthesis. The effects of influential factors including different calcination temperatures, pretreatment methods of the carbide slag and process parameters of hydrothermal synthesis on the microstructure and morphology of xonotlite were explored using XRD and SEM techniques. The results indicate that the carbide slag after proper calcination could be used to prepare pure xonotlite; and different calcination temperatures have little effect on the crystallinity of synthesized xonotlite, but have great impact on the morphology of secondary particles. The different pretreatment methods of the carbide slag pose great impact on the crystallinity and morphology of secondary particles of xonotlite. Xonotlite was also synthesized from pure CaO under the same experimental conditions as that prepared from calcined carbide slag for comparison. Little amount of impurities in carbide slag has no effect on the mechanism of hydrothermal synthesizing xonotlite from carbide slag.  相似文献   

8.
There has been an increasing need to migrate legacy systems to new hardware technologies and software development paradigms because the legacy systems present problems such as low effectiveness and high maintenance. If organizations want to remain competitive in today‘s fast changing business and technological environment, they must overcome these problems. Middleware is a valuable technology in that it provides convenient methods to construct system infrastructure, so it can be used to migrate the legacy systems. This paper gives a case study on using middleware technologies for the implementation of reengineering distributed arid heterogeneous bank legacy system in Anhui branch of China Construction Bank. Using middleware to migrate legacy system has proved to be good choice in practice.  相似文献   

9.
There has been much heated discussion on College English Test for non-English majors Band 4 and Band 6 because it has exerted great influence on English teaching in Chinese universities. This essay is intended to explore the reliability, validity, practicality and washback of this large-scale test by focusing on CET Band 4. The author of this report discusses the merits as well as some existing problems of this test and offers some suggestions at the end of the essay.  相似文献   

10.
Based on the existing data concerning the evolution of the sexual reproduction, it is argued that the processes of sex differentiation and interactions play a key role in evolution. From the beginning environment and organism are unified. In a changing dynamic environment life originates and the interaction between life and environment develops from simple to more complex organisms. Sexual reproduction is introduced after the origin of meiosis and is a key process in evolution. The asexual reproduction process prepares to dispersal. Sexual reproduction process adds the genome renewal and the gamete-gamete interaction. Reproduction and dispersal are connected and the process of reproduction has similarities between asexual and sexual reproduction. Unicellular algae develop the physiological and morphological sex differentiation. Sex differentiation is connected with the way of dispersal. The step to multicellular plants introduces cell isolation after meiosis and by the stay on the mother plant within a cell or organ, plant-cell apoplastic interaction originates and by prolonged stay the plant-plant interaction. This stay influences the type of dispersal. A life cycle with alternation of generations and two moments of dispersal permits plants to go on land. In ferns a shift in the moment of sex differentiation to meiospore happens and the stay of the macrospore leads to the seed plants. In water all types of sexual reproduction, interactions and the alternation of generations are prepared and these are used to conquest land. On land the biotic dispersal is realized. The phylogeny of sexual reproduction reveals that the sex differentiation and interaction are the main causes in the evolution of sexual reproduction. Sexual reproduction shows interactions during gamete fusion, between organism and environment and in multicellular plants between organisms. With respect to other types of interaction as in symbiosis or the nutrient chain, interaction is considered as an important action which is based on a persisting cooperation and points to a push during evolution. The push is expressed as communication: the driving force in the evolution. Based on the interactions between organisms and interactions between organisms and the dynamic environment, communication is considered as a driving force leading to the evolution as explained in the development of plant reproduction. Consequences for reproduction, its regulation and the process of evolution are discussed.  相似文献   

11.
The evaluation algorithm and the application of the influence diagram were surveyed, which argues that to construct an explicit,compact and objective influence diagram is of the most importance. There are two suggested ways for realization of the influence diagram: introducing the achievements of the modern psychology, cognitive science, behavior science, and so on to represent and solve uncertainty to build a well-constructed influence diagram; based on the observed data to build an influence diagram. Also, the limitations of the influence diagram were analyzed, such as that it cannot deal with asynunetric problems efficiently, cannot picture dynamic problems,cannot model the problems with a limitless horizon, and ther is no highly efficient algorithm. And some potential methods to overcome these limitations were pointed out.  相似文献   

12.
We have made a new investigation on the vertical profiles of tritium and helium isotopes in Lakes Van and Nemrut (Eastern Turkey), using experimental data from the reference by Kipfer et al. for study of long-term vertical mixing and deep water renewal in Lake Van. Lakes Van and Nemrut are crater lakes. Lake Nemrut is at the western border of Lake Van. The ^3He and ^4He are injected at the bottom of Lakes Van and Nemrut, and the both helium isotopes are confirmed from the mantle source. From ^3H (tritium) data in Lakes Van and Nemrut, we have observed "^3H anomaly" at the vertical profile of ^3H concentrations in Lake Nemrut. The ^3H concentration at the lake bottom is 10% higher than at the surface. The difference of ^3H concentrations between surface and bottom is about 3.7±1.2 TU. This excess ^3H should be injected from the lake bottom. An investigation on the origin of the injected tritium has been made. The results show the conventional origins are excluded, such as residence of precipitation tritium from nuclear testing in the early 1950s--1960s and tritium from known nuclear reactions. Based on the correlation of excess ^3H with ^3He and heat flow in Lake Nemrut, we infer that the ^3He and ^3H might be all from the mantle source, and produced by the supposed natural-nuclear-fusion, which might occur in an environment rich in water (H) and (U + Th) at high temperature and high pressure in the deep Earth. Detection of tritium in the Earth's interior is a key evidence for exploration of natural nuclear fusion in the deep Earth. Based on the published data, we have found that the excess ^3He and ^3H injected at the bottom of Lake Laacher (Germany) were also released from the mantle source. The present work will be helpful to the further study of mechanism of natural nuclear fusion in the Earth's interior.  相似文献   

13.
Truck scheduling and storage allocation, as two separate subproblems in port operations, have been deeply studied in past decades. However, from the operational point of view, they are highly interdependent. Storage allocation for import containers has to balance the travel time and queuing time of each container in yard. This paper proposed an integer programming model handling these two problems as a whole. The objective of this model is to reduce congestion and waiting time of container trucks in the terminal so as to decrease the makespan of discharging containers. Due to the inherent complexity of the prob-lem, a genetic algorithm and a greedy heuristic algorithm are designed to attain near optimal solutions. It shows that the heuristic algorithm can achieve the optimal solution for small-scale problems. The solutions of small-and large-scale problems obtained from the heuristic algorithm are better than those from the genetic algorithm.  相似文献   

14.
Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formarion of oxalates. Oxalates are most readily detected using Raman spectroscopy. A comparative study of a suite of natural oxalates including weddellite, whewellite, moolooite,humboldtine, glushinskite, natroxalate and oxammite has been undertaken using Raman spectroscopy. The minerals are characterised by the Raman position of the CO stretching vibration which is cation sensitive. The band is observed at 1468 cm^-1 for weddellite, 1489 cm^-1 for moolooite, 1471cm^-1 for glushinskite and 1456 cm^-1 for natroxalate. Except for oxammite, the infrared and Raman spectra are mutually exclusive indicating the minerals are bidentate. Differences are also observed in the water OH stretching bands of the minerals. The significance of this work rests with the ability of Raman spectroscopy to identify oxalates which often occur as a film on a host rock. As such Raman spectroscopy has the potential to identify the existence or pre-existence of life forms on planets such as Mars.  相似文献   

15.
A new unsupervised feature extraction method called similar component analysis (SCA) is proposed in this paper. SCA method has a self-aggregation property that the data objects will move towards each other to form clusters through SCA theoretically, which can reveal the inherent pattern of similarity hidden in the dataset. The inputs of SCA are just the pairwise similarities of the dataset, which makes it easier for time series analysis due to the variable length of the time series. Our experimental results on many problems have verified the effectiveness of SCA on some engineering application.  相似文献   

16.
We have made a new investigation on the vertical profiles of tritium and helium isotopes in Lakes Van and Nemrut(Eastern Turkey),using experimental data from the reference by Kipfer et al.for study of long-term vertical mixing and deep water renewal in Lake Van.Lakes Van and Nemrut are crater lakes.Lake Nemrut is at the western border of Lake Van.The 3He and 4He are injected at the bottom of Lakes Van and Nemrut,and the both helium isotopes are confirmed from the mantle source.From 3H(tritium) data in Lakes Van and Nemrut,we have observed "3H anomaly" at the vertical profile of 3H concentrations in Lake Nemrut.The 3H concentration at the lake bottom is 10% higher than at the surface.The difference of 3H concentrations between surface and bottom is about 3.7±1.2 TU.This excess 3H should be injected from the lake bottom.An investigation on the origin of the injected tritium has been made.The results show the conventional origins are excluded,such as residence of precipitation tritium from nuclear testing in the early 1950s-1960s and tritium from known nuclear reactions.Based on the correlation of excess 3H with 3He and heat flow in Lake Nemrut,we infer that the 3He and 3H might be all from the mantle source,and produced by the supposed natural-nuclear-fusion,which might occur in an environment rich in water(H) and(U Th) at high temperature and high pressure in the deep Earth.Detection of tritium in the Earth's interior is a key evidence for exploration of natural nuclear fusion in the deep Earth.Based on the published data,we have found that the excess 3He and 3H injected at the bottom of Lake Laacher(Germany) were also released from the mantle source.The present work will be helpful to the further study of mechanism of natural nuclear fusion in the Earth's interior.  相似文献   

17.
Video sensors and agricultural IoT ( internet of things) have been widely used in the informa-tionalized orchards.In order to realize intelligent-unattended early warning for disease-pest, this pa-per presents convolutional neural network ( CNN) early warning for apple skin lesion image, which is real-time acquired by infrared video sensor.More specifically, as to skin lesion image, a suite of processing methods is devised to simulate the disturbance of variable orientation and light condition which occurs in orchards.It designs a method to recognize apple pathologic images based on CNN, and formulates a self-adaptive momentum rule to update CNN parameters.For example, a series of experiments are carried out on the recognition of fruit lesion image of apple trees for early warning. The results demonstrate that compared with the shallow learning algorithms and other involved, well-known deep learning methods, the recognition accuracy of the proposal is up to 96.08%, with a fairly quick convergence, and it also presents satisfying smoothness and stableness after conver-gence.In addition, statistics on different benchmark datasets prove that it is fairly effective to other image patterns concerned.  相似文献   

18.
It is well known that fossil bird tracks are geological records of ancient birds walking on the sediments. Prior to the 1980s, little attention was paid to fossil bird tracks partly because of the difficulties of field discrimination. Over the last decade, new discoveries on the bird origin and early evolution, as well as their relation to dinosaurs[1] have greatly stimulated dinosaur and ancient bird studies.Accordingly, the paleoenvironmental, paleoecological and early evolutional significan…  相似文献   

19.
As an important part of marine hydrothermal system, hydrothermal vent faunas live in hydrothermal inorganic environment and closely interact with hydrothermal inorganic environment. Sometimes, they can participate in the mineralization process of modern hydrothermal site. Hydrothermal vent faunas, particularly vesUmentiferan and polychaete tubeworms, are occasionally preserved in the geological record. Study on the early mineralization process of hydrothermal vent fauna is significant for understanding the interaction between mineral and organism, and also the formation and preservation mechanism of geological fossil in hydrothermal environment. In this paper, the early stage of mineralization of Vestimentiferan Ridgeia piscesae tubes collected from Juan de Fuca Ridge is studied. The results showed that a lot of filamentous microorganisms were unevenly distributed on the surface of internal wall and in the interspace of the wall of tubeworm. In some cases, microorganisms aggregated as thin layers in or on the wall of tubeworm. The surfaces of microbial cells and the products of microbial degradation may play an important role in the early mineralization of tubeworm. Semitransparent thin layers of organic matter containing sulfur and sulfur granules were commonly found on the wall of tubeworm with lower degree of mineralization. The degradation production of these semitransparent thin layers may accelerate the mineralization of tube wall during the early stage. EDS results showed that on the tube walls some chemical elements such as Fe, P, Ca and Si are selectively enriched from ambient hydrothermal environment. Interestingly, P, Ca and Si covary with Fe content. Because element S originated from the bio-oxidation of H2S by symbiotic microorganism in the tissue of tubeworm, it can be considered as a biomarker when studying the mineralization process of tube wall. Based on the characteristics of tubeworms with different degrees of mineralization, we suggested that the early mineralization stage of tube wall was mai  相似文献   

20.
Here is proposed the principle of interaction between plastic volumetric and shear strains, revealing the main origin of generating the complexity and variety of deformations for geotechnical materials. Here are also explained the manners of the interaction between plastic volumetric and shear strains and the conditions of generating shear dilatancy. It is demonstrated that dependency of the stress path exists and is a combination of effects of this interaction. According to this principle, it is theoretically proved that the space critical state line exists, and is unique and independent of the stress history. Based on this principle, the constitutive models that are able completely and accurately to characterize the basic behavior features for geotechnical materials have been constructed within the framework of thermodynamics. What is determined is a general expression of the constitutive relation as well as the inequality of the dissipative potential increment for obeying the second law of thermodynamics.  相似文献   

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