504 research outputs found
Modification of slope stability probability classification and its application to rock slopes in hydropower engineering regions
Stability assessment of rock slopes in hydropower engineering regions is an important and complex issue. Rock mass classification systems are a good approach because they thoroughly consider many factors influencing rock slope stability. The slope stability probability classification (SSPC) system is a novel method. However, it has two obvious limitations when applied to rock slopes: 1) it is only suitable for slopes less than 45 m in height, and 2) there is great subjectivity and randomness in the estimation of intact rock strength. Therefore, this study presents two modifications of the SSPC system by adopting the HoekâBrown strength criterion and an empirical formula for maximum slope height. Evaluation of results from of 34 typical rock slopes of the major hydropower engineering regions in China indicated that the accuracy rate of the modified SSPC for stability evaluation of these slopes was 61.8%, and the accuracy for stability evaluation of 10 slopes with non-structural control failure was 80%. The stability values of stable and unstable slopes obtained using the modified SSPC were different to those obtained using the Chinese Slope Mass Rating (CSMR) and modified CSMR systems. In addition, the identification accuracy rate of the modified SSPC was significantly higher than that of the CSMR and modified CSMR. Therefore, the modified SSPC can be applied to hydropower engineering regions, providing a new means of rapidly evaluating the slope stability of high rock slopes (slopes > 45 m in height) in these regions.</p
A Study on Water Utilization in Chinese Rural Areas
In China, because rural population is great and agriculture is very important in national economy, rural areas have becomes a main sphere of water consume. There exist the problems of water shortage and water waste in the countryside. The conflicts of water resource supply and demand between industry and agriculture are very conspicuous. Various factors that include ideology, finance, technology, management and policy restrict the rational and effective use of water resource. The survey on the villages of Jia Ge Zhuang and Yao Bai Zhuang in Ji County, Tianjin reflects these problems. The government tries to solve the problems by making laws and policies, as well as affording financial and technology support to towns and villages. At the same time, it is necessary for the government to make officials and farmers realize the importance of rational water usage and saving by doing propaganda, coordinating the inter-governments relations, and defining the departmentsâ duties. For realizing the objective of rational water usage, it is necessary to take measures to construct and perfect irrigation installations by both superior and local governmentsâ investment and farmersâ labor force. Key Words: Chinese Rural Areas, Water Resource, Rational Use, Farmland, Irrigation System RĂ©sumĂ©: En Chine,la population est grande et lâagriculture est trĂšs importante dans lâĂ©conomie nationale. Les rĂ©gions rurales sont devenues un sphĂšre principal de la consommation dâeau. Il existe les problĂšmes dâinsuffisance dâeau et le gaspillage dâeau dans la campagne. Les conflits sur les resources dâeau fournie et demandĂ©e entre industrie and agriculture sont trĂšs frĂ©quents. Les facteurs variĂ©s tels quâidĂ©ologie, finance, technologie, management et politique limitent lâusage rationel et effectif de ressources dâeau. LâenquĂȘte sur les villages de Jia Ge Zhuang et Yao Bai Zhuang dans le pays Ji, Tianjin reflĂšte ces problĂšmes. Le government tente de rĂ©soudres les problĂšmes par lâĂ©labortion des lois et les poliques, ainsi que le support financierl et technologique aux bourgs et villages. Au meme temps, il est nĂ©cessaire pour le government Ă render conscients les officiels et les paysans lâ importance de lâusage rationel en Ă©conomisant par la publicitĂ©, en coordonnant les relations inter-governmentaux, et en dĂ©terminant les tĂąches des dĂ©partments. Pour la realiser lâobjectif de lâusage dâeau rational, il est nĂ©cessaire de prendre des mesures pour construire et perfectionner lâ installations dâirrigation par lâinvestissement des governements supĂ©rieurs et locaux ainsi que les forces des labeurs. Mots clĂ©s: Les rĂ©gions rurales chionoises, Ressource dâeau, usage rationel, fermier, SystĂšme dâ Irrigatio
Effects of ac-field amplitude on the dielectric susceptibility of relaxors
The thermally activated flips of the local spontaneous polarization in
relaxors were simulated to investigate the effects of the applied-ac-field
amplitude on the dielectric susceptibility. It was observed that the
susceptibility increases with increasing the amplitude at low temperatures. At
high temperatures, the susceptibility experiences a plateau and then drops. The
maximum in the temperature dependence of susceptibility shifts to lower
temperatures when the amplitude increases. A similarity was found between the
effects of the amplitude and frequency on the susceptibility.Comment: 8 pages, 7 figures, Phys. Rev. B (in July 1st
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Rab25-Mediated EGFR Recycling Causes Tumor Acquired Radioresistance.
Tumor acquired radioresistance remains as the major limit in cancer radiotherapy (RT). Rab25, a receptor recycling protein, has been reported to be enhanced in tumors with aggressive phenotype and chemotherapy resistance. In this study, elevated Rab25 expression was identified in an array of radioresistant human cancer cell lines, in vivo radioresistant xenograft tumors. Clinical investigation confirmed that Rab25 expression was also associated with a worse prognosis in patients with lung adenocarcinoma (LUAD) and nasopharyngeal carcinoma (NPC). Enhanced activities of EGFR were observed in both NPC and LUAD radioresistant cells. Rab25 interacts with EGFR to enhance EGFR recycling to cell surface and to decrease degradation in cytoplasm. Inhibition of Rab25 showed synergized radiosensitivity with reduced aggressive phenotype. This study provides the clinical and experimental evidence that Rab25 is a potential therapeutic target to alleviate the hyperactive EGFR signaling and to prevent RT-acquired tumor resistance in patients with LUAD and NPC
Dielectric nonlinearity of relaxor ferroelectric ceramics at low ac drives
Dielectric nonlinear response of
(PbMgNbO)(PbTiO) (0.9PMN-0.1PT) relaxor
ceramics was investigated under different ac drive voltages. It was observed
that: (i) the dielectric permittivity is independent on ac field amplitude at
high temperatures; (ii) with increasing ac drive, the permittivity maximum
increases, and the temperature of the maximum shifts to lower temperature;
(iii) the nonlinear effect is weakened when the measurement frequency
increases. The influences of increasing ac drive were found to be similar to
that of decreasing frequency. It is believed that the dielectric nonlinearities
of relaxors at low drives can be explained by the phase transition theory of
ergodic space shrinking in succession. A Monte Carlo simulation was performed
on the flips of micro polarizations at low ac drives to verify the theory.Comment: Submitted to J. Phys.: Cond. Matte
The stabilization of fused-pentagon fullerene molecules
The isolated pentagon rule (IPR) is now widely accepted as a general rule for determining the stability of all-carbon fullerene cages composed of hexagons and pentagons. Fullerenes that violate this rule have been deemed too reactive to be synthesized. The stabilization of non-IPR endohedral fullerenes depends on charge transfer from the encapsulated metal clusters (endoclusters) to fullerene cages, the electronic properties of empty all-carbon cages, the matching size and geometries of fullerene and endocluster, as well as the strong coordination of the metal ions to fused pentagons. The stability of non-IPR exohedral fullerenes can be rationalized primarily by both the 'strain-relief' and 'local-aromaticity' principles. This Review focuses on recent work on stabilization of non-IPR fullerenes, including theoretical and empirical principles, experimental methods, and molecular structures of fused-pentagon fullerenes characterized so far. The special chemical properties of non-IPR fullerenes that distinguish them from IPR-satisfying ones are also emphasized.NNSFC 20525103,20531050,20721001
973 Program 2007CB81530
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