2,102 research outputs found

    Data Mining of the Thermal Performance of Cool-Pipes in Massive Concrete via In Situ Monitoring

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    Embedded cool-pipes are very important for massive concrete because their cooling effect can effectively avoid thermal cracks. In this study, a data mining approach to analyzing the thermal performance of cool-pipes via in situ monitoring is proposed. Delicate monitoring program is applied in a high arch dam project that provides a good and mass data source. The factors and relations related to the thermal performance of cool-pipes are obtained in a built theory thermal model. The supporting vector machine (SVM) technology is applied to mine the data. The thermal performances of iron pipes and high-density polyethylene (HDPE) pipes are compared. The data mining result shows that iron pipe has a better heat removal performance when flow rate is lower than 50 L/min. It has revealed that a turning flow rate exists for iron pipe which is 80 L/min. The prediction and classification results obtained from the data mining model agree well with the monitored data, which illustrates the validness of the approach

    Boolean-Based Surface Procedure for the External Heat Transfer Analysis of Dams during Construction

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    The external heat transfer of dams during construction is complex because such transfer is location specific and time varying. An external thermal model is developed in this paper. Five types of external heat flux are considered in the mathematical model: air-side convection, electromagnetic radiation, absorbed solar input, water-side convection, and surface insulation effect. A method for extracting and classifying the external surfaces of dams on the basis of Boolean operations is proposed. Heat transfer conditions can be automatically set up for each step according to the proposed method, and the method can be used as a preprocessing facility for finite element analysis. A 285 m high arch dam in Southwest China is examined as a study case. The model is implemented and found to correctly identify different types of external surfaces. Simulation result agrees well with the monitored temperatures

    Numerical Analysis on Temperature Rise of a Concrete Arch Dam after Sealing Based on Measured Data

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    The thermal boundary conditions in the construction and operation phases of a concrete arch dam are always complex. After sealing, differences between the arch dam temperature and its sealing temperature can cause compressive or tensile stresses. Based on measured temperature of an arch dam located in China, a temperature rise phenomenon (TRP) is found in the after-sealed regions of the arch dam. By mining and analyzing the temperature data of various monitoring apparatus embedded in the arch dam, higher environment temperature is considered to be the main cause for the occurrence of the TRP. Mathematical methods for complex thermal boundary conditions, including external boundary conditions and internal heat source conditions, are proposed in this paper. A finite element model is implemented with the concern of the construction phase and operation phase of the arch dam. Results confirm good agreement with the measured temperature and verify the conjecture that the TRP occurs mainly because the external temperature of the arch dam is higher than its sealing temperature

    Therapeutic effect and safety of vincamine in anterior non-arteritic ischemic optic neuropathy

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    AIM:To observe the clinical efficacy and safety of vincamine sustained release capsules on non-arteritic anterior ischemic optic neuropathy(NAION).METHODS:Patients who were diagnosed with monocular onset NAION in acute stage from January to September 2015 were divided into two groups. Routine treatment such as steroid pulse therapy and neurotrophic treatment were given to all the patients. Vincamine was added to the treatment group patients with 30mg twice a day for 3mo. The best corrected visual acuity(BCVA), mean deviation(MD)of visual field, retinal nerve fiber layer(RNFL), ganglion cell complex(GCC), pattern visual evoked potential(PVEP)and OCT results were analyzed before and after the treatment.RESULTS: Totally 42 eyes of 42 patients were enrolled in our study. There were 27 patients in the treatment group, aged from 33 to 79 years old, the average value was 55.55±11.83 years old. The control group has 15 patients, aged from 40 to 70 years old, the average value was 55.71±10.06 years old. There were no statistical differences between the two groups in the baseline. After 3mo of the treatment, MD value of the two groups were lower compared with the baseline, the difference was statistically significant in the treatment and control group respectively(t=2.342, 2.692; P=0.027, 0.041). The difference of PVEP amplitude and potential of the two groups before and after the treatment were not statistically significant. The thickness of retinal nerve fiber layer and the ganglion cell complex were all lower than the baseline, and the difference was statistically significant(PCONCLUSION: Vincamine is helpful in the treatment of non-arteritic anterior ischemic optic neuropathy

    Fluctuations in the Ionizing Background During and After Helium Reionization

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    The radiation background above the ionization edge of HeII varies strongly during and after helium reionization, because the attenuation length of such photons is relatively short (<40 Mpc) and because the ionizing sources (quasars) are rare. Here we construct analytic and Monte Carlo models to examine these fluctuations, including, for the first time, those during the reionization era itself. In agreement with detailed numerical simulations, our analytic model for the post-reionization Universe predicts order-of-magnitude fluctuations in the HeII ionization rate. Observations of the hardness ratio between HeII/HI show even larger fluctuations, which may be due to more complicated radiative transfer effects. During reionization, the fluctuations are even stronger. In contrast to hydrogen reionization, our model predicts that regions with strong HeII Lyman-alpha forest transmission should be reasonably common even during the beginning stages of reionization, because of strong illumination from bright quasars. Partly due to this, the mean ionizing background does not evolve strongly during and after helium reionization; it is roughly proportional to the filling fraction of HeIII regions. On the other hand, regions full of HeII and also "fossil" ionized regions that contain no (or few) active sources appear as strong IGM absorbers. Their presence exaggerates the evolution of the hardness ratio, making it evolve faster than naively expected during the reionization era.Comment: 16 pages, 9 figures, in press at ApJ; comparison to observations significantly improve
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