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61.
62.
63.
The oxidation behavior of a normalized 2.25Cr-1Mo steel tempered previously for 10 hr at different temperatures between 873 and 1023 K has been studied up to a maximum duration of 1000 hr in air at 773–973 K. The oxidation resistance of the steel was found to decrease significantly with the temperature of tempering. Tempering of this steel is reported to cause microstructural changes involving precipitation of Cr as carbides and a decrease in the effective (free) Cr contents, that could influence the oxidation resistance of the Cr-containing alloys. Relative compositions across the thickness of the oxide scales, as analyzed by SEM/EDX and SIMS, suggest that a less Cr-rich (and less protective) and thicker scale on the steel formed because previous tempering caused extensive depletion of free Cr. 相似文献
64.
以往在水库大坝发生白蚁危害病情后,方采取工程措施进行除险加固。为把白蚁控制在危害之前,本文结合工程典型实例,根据气候、土壤、植被等建坝外部环境条件和白蚁生存需具备的土、水、食料基本因素,考虑白蚁具有喜温好湿、畏光避风、蔓延等生物特性,通过填筑坝料土质分析,研究了水库蓄水坝体浸润性、坝土级配及湿度与白蚁生存之间的关系,并提出相应对策以达到防患于未然。结果表明,坝体结构设计时,通过截断白蚁吸水水源,增加坝体干燥区,缩限白蚁生存空间;通过调整坝料级配,防止白蚁筑巢;合理采用护坡,切断白蚁食源。同时,结合水库运行管理,采取"预防为主,综合防治"的措施,使坝体周边一定范围内成为无蚁区,防止白蚁蔓延至坝,维护水库大坝的安全。 相似文献
65.
在立洲水电站大坝高边坡开挖过程中,其坝肩边坡马道层与层之间的高差达30 m,通过30 m孔深一次预裂爆破,达到了技术要求,同时提高了施工进度及经济效益。30 m深孔预裂爆破在该工程的成功运用,给同类工程提供了参考和借鉴。 相似文献
66.
为掌握三峡水库175 m试验性蓄水过程中库区水位、流量、含沙量变化过程,通过三峡库区寸滩、清溪场、万县、朱沱(三)水文站实测的水位、流量、含沙量、水面比降资料,分析了蓄水过程中三峡库区沿程水面比降、库区水文站的水位流量关系、含沙量变化、库区冲淤变化等。分析结果为认识掌握三峡水库175 m蓄水后库区水文泥沙的变化规律积累了资料,对探索三峡库区水文泥沙的监测方式和分析研究将具有积极作用。 相似文献
67.
Masatsune Kato Takaaki Aoki Takashi Noji Yasuhiro Ono Yoji Koike Tomoyuki Hikita Yoshitami Saito 《Journal of Superconductivity》1994,7(1):37-38
We have investigated the relation between the crystal structure and superconductivity in La1.9Bi0.1CuO4+
, in which the phase separation observed in La2CuO4+
is suppressed. A phase diagram in theT– plane is given for La1.9Bi0.1CuO4+
with excess oxygen. For very small values, the crystal structure is orthorhombic, and an orthorhombic-tetragonal phase transition occurs markedly at 0.03 in the measured temperature range between 13 and 293 K. Superconductivity is observed in the range of 0.04<<0.11. This is clear evidence thathigh-T
c
superconductivity also appears in the tetragonal phase. 相似文献
68.
69.
Sergio F. León-LuisAuthor VitaeUlises R. Rodríguez-MendozaAuthor Vitae Emmanuel LallaAuthor VitaeVíctor LavínAuthor Vitae 《Sensors and actuators. B, Chemical》2011,158(1):208-213
The temperature dependence of the green upconverted emission from the two thermally coupled 2H11/2 and 4S3/2 levels of the Er3+ ion in a fluorotellurite glass has been analyzed as a function of the optically active ion concentration in order to check its availability as a temperature sensor. The infrared-to-green upconverted emission have been observed by the naked eyes after a cw laser diode excitation at 800 nm. The fluorescence intensity ratio between the thermally coupled emitting levels as well as the temperature sensitivity has been experimentally obtained up to 540 K. A better behaviour as a temperature sensor has been obtained for the less Er3+ concentrated glass with a maximum sensitivity of 54 × 10−4 K−1 at 540 K, one of the highest found in rare-earth doped transparent materials. 相似文献
70.
Chvátal-Gomory cuts are among the most well-known classes of cutting planes for general integer linear programs (ILPs). In
case the constraint multipliers are either 0 or
, such cuts are known as
-cuts. It has been proven by Caprara and Fischetti (Math. Program. 74:221–235, 1996) that separation of
-cuts is
-hard.
In this paper, we study ways to separate
-cuts effectively in practice. We propose a range of preprocessing rules to reduce the size of the separation problem. The
core of the preprocessing builds a Gaussian elimination-like procedure. To separate the most violated
-cut, we formulate the (reduced) problem as integer linear program. Some simple heuristic separation routines complete the
algorithmic framework.
Computational experiments on benchmark instances show that the combination of preprocessing with exact and/or heuristic separation
is a very vital idea to generate strong generic cutting planes for integer linear programs and to reduce the overall computation
times of state-of-the-art ILP-solvers. 相似文献