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   Science & Technology Review
2011, Vol.29, No. 11-06
28 February 2011

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卷首语

Planning Water Conservancy Project Prior to Rain

Science & Technology Review. 2011, 29 (11-06): 3-3. ;  doi:
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Abstract ( 279 )
科技事件

Science & Technology Review. 2011, 29 (11-06): 7-7. ;  doi:
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Abstract ( 287 )

Science & Technology Review. 2011, 29 (11-06): 9-9. ;  doi:
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Abstract ( 279 )
排行榜

Science & Technology Review. 2011, 29 (11-06): 8-8. ;  doi:
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Abstract ( 276 )
封面说明

Science & Technology Review. 2011, 29 (11-06): 8-8. ;  doi:
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Abstract ( 286 )
科技界声音

Science & Technology Review. 2011, 29 (11-06): 10-10. ;  doi:
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Abstract ( 280 )
科技工作大家谈

Science & Technology Review. 2011, 29 (11-06): 11-11. ;  doi:
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Abstract ( 346 )
科学共同体要闻

Science & Technology Review. 2011, 29 (11-06): 12-12. ;  doi:
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Abstract ( 309 )
科技期刊亮点

Science & Technology Review. 2011, 29 (11-06): 13-13. ;  doi:
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Abstract ( 284 )
科技要闻

Science & Technology Review. 2011, 29 (11-06): 14-14. ;  doi:
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Abstract ( 298 )
Exclusive

Science & Technology Review. 2011, 29 (11-06): 15-16. ;  doi:
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Abstract ( 300 )
Articles

Strontium Isotopic Tracing of Water-Rock Interaction in Quaternary Aquifer in Beijing Plain

Science & Technology Review. 2011, 29 (11-06): 17-20. ;  doi: 10.3981/j.issn.1000-7857.2011.06.001
Full text: HTML (0 KB)  PDF  (569 KB)  ( 184 )
Abstract ( 421 )
Abstract Sampling and analysis for contents of Ca2+, Sr2+ and ratios of 87Sr/86Sr in groundwater were carried out in Quaternary aquifer in Beijing Plain. It is shown that Ca2+ and Sr2+ in groundwater mainly come from water-rock interaction, and are not closely related with the sources of groundwater; they undergo a similar hydrogeological processes, which can be used to trace the water-rock interaction processes; the samples can be divided into two groups according to the concentration of Sr2+; that with a lower concentration of Sr2+corresponds a higher ratio of 87Sr/86Sr, and that with a higher concentration of Sr2+ corresponds a lower ratio of 87Sr/86Sr; ratios of 87Sr/86Sr are mainly controlled by water-rock interactions, which are generally different from those of sea and local precipitation; Sr2+ in groundwater comes mainly from carbonate rocks, and sees age effects distinctly. The concentration of Sr2+ in groundwater in the Yongding River Basin is greater than that in the Chaobai River, and the ratios of 87Sr/86Sr in groundwater are generally increasing along the flow path.

Characteristics of Summer Wind Speed Changes over CoastalRegion of China

Science & Technology Review. 2011, 29 (11-06): 21-30. ;  doi: 10.3981/j.issn.1000-7857.2011.06.002
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Abstract ( 1170 )
Based on observational data sets of general, basic, and standard climate stations in the coastal regions of China from 1965 to 2004, summer wind speed changes are analyzed. Twenty global climate models and three regional climate models have been evaluated based on their capabilities to simulate summer wind speed for 20th century, and the results are used to project the summer wind speed changes in the coastal regions of China for the 21st century. The following conclusions are drawn: (1) in recent 50 years, both summer mean wind speed and maximum wind speed observed all show declining trends over the coastal regions of China. This changing feature of wind speed in China's offshore areas is related to the changing characteristics of typhoon frequency in China. (2) Both global climate models and regional climate models possess the certain capabilities to simulate the patterns of the summer mean wind speed. The capabilities of regional climate models are slightly better than that of global climate models. (3) Both global and regional climate models are unable to simulate the obvious decrement trend shown by the observed data. Only a few of them are able to simulate the slightly decrement trend of summer wind speed changes in China for the last 50 years. (4) Global and regional climate models all predict that the summer mean wind speed in coastal regions of China for the early 21st century decreases slightly for SRES B1 and A1B scenario. The projection of summer wind speed in China's offshore areas for the early 21st century is that the speed is slightly increasing for SRES A2 scenario than that for the 20th century. (5) It is worth noting that due to current restrictions on the scientific understanding, in either case of global climate models and regional climate models, there is a considerable uncertainty in the projection of the regional climate changes, especially in projection of the wind speed. The studies on the wind projections have just been in the beginning, a large number of tests need to be done in order to get more reliable conclusions.

Grain Shape Analysis of Free Settling Particles in Air

Science & Technology Review. 2011, 29 (11-06): 31-34. ;  doi: 10.3981/j.issn.1000-7857.2011.06.003
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Abstract ( 465 )
Based on the Area-Perimeter Method, the fractal theory and the experiment results of free settling, the profile fractal dimensions of the free settling particles in air are calculated. Using optical microscope, the grain projection images of air particles are obtained. With an image analysis software, the grain shape of air particles and the relation between the profile fractal dimension and the settling time are obtained. An analysis is made for air particles with consideration of the special causes of their formation. It is shown that the grain shape of air particles exhibits a distinct fractal characteristic, which is getting more distinct when the grain is smaller. The profile fractal dimensions of the particle range from 0.869 to 1.048. The value of fractal dimension decreases with the increase of the sampling time, and the fractal characteristic is getting less distinct. It is found that the higher percentage of finer particles is associated with the higher profile fractal dimension value of particles. This quantitative description of the profile fractal distribution of free settling particles in air, provides a new way to predict the shape change of the grain and the adhesion force between particles.

Responses of Ecosystem's Carbon and Water Fluxes to Global Changeon the Songnen Steppe

Science & Technology Review. 2011, 29 (11-06): 35-42. ;  doi: 10.3981/j.issn.1000-7857.2011.06.004
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Abstract ( 431 )
The global warming and a changing nitrogen regime could have a profound impact on ecosystem's carbon flux, therefore, a good understanding of carbon flux responses to changing environmental conditions is critical for predicting the productivity and carbon sequestration potential of grass ecosystems during the 21st century. Measurements of photosynthetic characteristics were made in Yangcao (Leymus chinensis) grassland under a warming and nitrogen deposition soil during the period from 2006 to 2009. In situ diurnal Net Ecosystem CO2 Exchange (NEE) was measured by determining the rise in CO2 in IRGA. Analysis of CO2 fluxes during 4 years shows that the climate warming reduces NEE, Gross Ecosystem Productivity (GEP) and Evapotranspiration (ET), while increases Ecosystem Respiration (ER) and ecosystem Water-Use Efficiency (WUE). The increased N stimulates the NEE, ER, GEP and WUE. Under conditions of warming plus nitrogen, the nitrogen ameliorates the negative impacts of climatic warming on ecosystem carbon fluxes. Carbon flux responses to global change were driven overwhelmingly by gains and losses by Leymus chinensis, as the native plants in the Songnen grassland. Climate change could rapidly alter carbon fluxes in the Songnen grassland. These results provide an understanding of the future impact of the terrestrial carbon-cycle feedback on the global climate change.

Biodegradation of Cholrobenzene-contaminated Ground Water by Immobilized Microorganism

Science & Technology Review. 2011, 29 (11-06): 43-47. ;  doi: 10.3981/j.issn.100-7857.2011.06.005
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Abstract ( 411 )
To study the optimal conditions for the biodegradation of cholrobenzene(CB)-contaminated ground water by immobilized microorganism, the CB-degrading bacteria are screened out from the CB-contaminated soil. Polyving alcohol (PVA) and sodium alginate are used to encapsulate microorganisms to make immobilized bacteria beads. The optimal conditions of the immobilized beads were identified by the orthogonal experiment, with the effect factors including mechanical strength, penetrability and the removal efficiency of the CB. The factors influencing the immobilized microorganism degrading ability were studied. The results show that the removal efficiency of the immobilized beads is better than the free microorganism. When the immobilized beads are in the optomal condition with the diameter of the bead being 1mm, the concentration of bacterial suspension 8%, the initial concentration of CB 80mg/L, pH value about 7.0, the concentration of the NaCl less than 1.5%, the temperature 10℃, and the shaking table revolution 120r/min, the biodegrading performance is quite excellent.

Indoor Simulation Test on Characteristic Parameters of Expansive Soil Embankment Under the Different Weather Conditions

Science & Technology Review. 2011, 29 (11-06): 48-53. ;  doi: 10.3981/j.issn.100-7857.2011.06.006
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Abstract ( 424 )
In order to explore the basic laws of the characteristics parameters of expansive soil moisture, soil pressure, temperature, vertical expansion and contraction deformation in the different climatic conditions, the weak expansive soil and the medium expansive soil which frequently appears in highway construction in Hunan Province were selected as the test samples. According to 90% of the compaction degree to fill, in different drainage boundary conditions, two groups of expansive soil embank simulation experiment was taken in four different climate conditions, the results indicate that the water content, soil pressure, temperature, and swelling and shrinkage deformation of expansive soil embankment are all governed by atmospheric effects, and are close related to the embankment soil type, density, drainage boundary conditions: (1) The shallower subgrade buried, the greater impact of atmosphere on water content changes is . The higher water content, the clearer impact of climate conditions is. (2) The changes of earth pressure in expansive soil embankment are caused by the moisture content and expansive soils pressure in different climatic conditions and different moisture content. (3) The biggest infection factor is successive sunshine, followed by rain; cloudy day only has a minimal impact. (4) Vertical expansion and contraction change mainly occur in the top water phase of road embankment foundation. Thus, in specific construction projects, anti-seepage and moist maintenance and rational design of drainage system are the key technologies for the prevention and treatment of expansive soil damage

Evaluation of Mechanical Properties of Structural Larch Sawn Lumber by Machine Stress Rating

Science & Technology Review. 2011, 29 (11-06): 54-56. ;  doi: 10.3981/j.issn.1000-7875.2011.06.007
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Abstract ( 375 )
Elastic properties of 384 full-size Chinese larch (Larix gmelinii) sawn lumber (32mm×120mm×3900mm) were tested based on the NDT technique Machine Stress Rating (MSR) and three-point bending test are defined and implemented according to the American Society for Testing and Materials (ASTM) D 4761-05 standard. It is shown that the mean value of EMSR/GPa is 3.45% (0.56 GPa), which is greater than ES. Statistical linear regression analyses indicate that a relationship exists among dynamic and static elastic properties (at the significance level of 0.01), with a correlation coefficient of 0.9423 between EMSR and ES. Therefore, it may be concluded that the MSR technique can be used as an effective tool to predict static properties of full-size structural lumber. In addition, with a high degree of automation and the advantage of continuous batch detection, the MSR technique is very suitable for industrial applications today. So, a wide application of the mechanical stress grading technology in wood processing enterprises is surely possible.

Effect of the Shape of Wheel Spokes on Vehicle Aerodynamic Performance

Science & Technology Review. 2011, 29 (11-06): 57-61. ;  doi: 10.3981/j.issn.1000-7857.2011.06.008
Full text: HTML (0 KB)  PDF  (1741 KB)  ( 237 )
Abstract ( 422 )
The complex separated flow induced by wheel and wheel cavity has a great impact on the exterior flow field, and also is one of the major causes of aerodynamic drag. In the present paper, the exterior flow field of a whole car model including wheel is simulated using the computational fluid dynamics method. The related experiments were carried out in HD-2 wind tunnel to validate the reliability of the simulation method. In order to get the accurate flow around rotating wheel and wheel cavity, two different boundary conditions of wheel are compared with those in literature. Then, the influence of the number and size of holes in wheel spoke on the aerodynamic drag coefficient was investigated using the same type wheel. The results show that the rotating wall boundary condition is more reasonable than the MRF; the wheel's drag coefficient increases with the hole open size when the hole number is a constant, while the whole car's drag coefficient is first increased and then decreased; when the single-hole size is fixed but the opening number is increased, the rear wheel's drag coefficient increases, while the front wheel's and the vehicle's drag coefficients are increased first and then decreased. This work can provide a reference for wheel design in the future

Sequence Stratigraphic Study of Paleogene and Neogene Salt Lake, Southwestern Qaidam Basin

Science & Technology Review. 2011, 29 (11-06): 62-67. ;  doi: 10.3981/j.issn.100-7857.2011.06.005.009
Full text: HTML (0 KB)  PDF  (2909 KB)  ( 299 )
Abstract ( 618 )
Sequence stratigraphic study of the salt lake with lately started and weak foundations in Qaidam Basin is important in many respects. In order to analyze the sequence stratigraphy in Paleogene and Neogene in southwestern Qaidam Basin and provide a foundation for lithologic hydrocarbon reservoir exploration, this paper studies the sequence boundary identification and the sequence classification in Paleogene and Neogene in southwestern Qaidam Basin by using sequence stratigraphic method, and applying outcrop data, core, drilling data and seismic data. It is shown that the classification in terms of 13 long-term circles is reasonable, and there are 4 sequence developing patterns: gentle slope zone, abrupt slope zone, low uplift zone and Lake Basin. And it is also shown that the sequence circle structure plays a significant role in controlling the lithologic trap, the development of sandstone reservoir is closely related to the mid-term circle, and favorable reservoirs mainly develop at the bottom of the circle structure with a trend of "becoming deeper upward".

Electrochemical Performance of Polyaniline-deposited Active Carbon Electrode

Science & Technology Review. 2011, 29 (11-06): 68-71. ;  doi: 10.3981/j.issn.1000-7857.2011.06.010
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Abstract ( 478 )
Polyaniline was fabricated by Cyclic Voltammetry (CV) on the surface of active carbon electrode in organic solvent. The electrochemical characterisation of the materials was carried out by means of cyclic voltammetry, galvanostatic charge-discharge experiments and Electrochemical Impedance Spectroscopy (EIS). The experiment results show that, the PANI/AC electrode exhibits typical capacitive behavior at the voltage window range from -1.0 to 1.5V vs Ag/AgCl. The specific capacitance of the PANI/AC electrode reaches up to 276F·g-1 in comparison with a value of 92F·g-1 for the bare-carbon electrode. And the ionic charge transfer resistance of the PANI/AC electrode is 2.4Ω in comparison with a value of 4.9Ω for the active carbon electrode. The electrode also shows an excellent cyclic life. The capacitance is decayed only by 15.7% after 1000 cycles for the composite electrode. Therefore, it is demonstrated that the loading of PANI onto high surface area activate carbon can greatly improve the performance of the electrode, and the composite is a very promising electrode material for applications in supercapacitors
Reviews

Progress in Nucleating Agents for Polyamide

Science & Technology Review. 2011, 29 (11-06): 72-79. ;  doi: 10.3981/j.issn.1000-7857.2011.06.011
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Abstract ( 1600 )
Polyamide (PA) nucleating agents are used to improve the crystal structure, increase the crystallization rate, improve the physical-mechanical properties and shorten the forming period. The most common PA nucleating agents can be divided into two groups: inorganic nucleating agents and organic nucleating agents. Inorganic nucleating agents include clay (kaolin, MMT, terra-cotta and TALC etc.), oxide (nano-SiO2, nano-ZrO2, nano-TiO2, Nd2O3, MgO, ZnO crystal whisker etc.), and inorganic salts (nano-CaCO3, CaF2, MgSO4 crystal whisker etc.) , which are the earliest nucleating agents to be used. Inorganic nucleating agents have the advantages of being cheap, easy to obtain and easy to be used and they are heterogeneous in PA, and are not easy to disperse uniformly. Organic nucleating agents include low molecular compounds (such as amide, osphinate etc.) and polymer (polycarbonate, polyphenylene sulfide, carbon fiber etc.). The organics are easy to disperse in PA and enjoy good performances. Compound nucleating agents possess both the advantages of organic and inorganic nucleating agents. The synergistic effect is obvious with excellent performances. Therefore, the compound nucleating agents have a very promising future, but the nucleating mechanism and application require further studies.
书评

Science & Technology Review. 2011, 29 (11-06): 80-80. ;  doi:
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Abstract ( 326 )
科技纵横捭阖

Science & Technology Review. 2011, 29 (11-06): 81-81. ;  doi:
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Abstract ( 302 )
读者之声

Science & Technology Review. 2011, 29 (11-06): 82-82. ;  doi:
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Abstract ( 286 )
主编心语

Science & Technology Review. 2011, 29 (11-06): 83-83. ;  doi:
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Abstract ( 280 )
科学共同体介绍

Science & Technology Review. 2011, 29 (11-06): 83-83. ;  doi:
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Abstract ( 383 )
走向职场

Science & Technology Review. 2011, 29 (11-06): 84-84. ;  doi:
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Abstract ( 293 )
科技人才招聘

Science & Technology Review. 2011, 29 (11-06): 85-87. ;  doi:
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Abstract ( 285 )
全球招聘新闻

Science & Technology Review. 2011, 29 (11-06): 88-91. ;  doi:
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Abstract ( 295 )
智力休闲

Science & Technology Review. 2011, 29 (11-06): 92-92. ;  doi:
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Abstract ( 277 )

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