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1.
The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30%, and 40%) of mineral admixtures. Five repeated loadings were applied to concrete specimens using a WHY series fully automatic testing machine. The maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c). Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results showed that the replacement percentages of mineral admixtures, the curing time and repeated loading had a significant effect on chloride migration through concrete. The transport number of chloride through concrete cured for 28 d increased with increasing FA replacement and markedly decreased with extension of the curing time. 20% and 30% GGBFS replacement decreased the transport number of chloride through concrete, but 40% GGBFS replacement increased the transport number. Five repeated loadings at 40% or 80% f′c increased the transport number of chloride for all mixes.  相似文献   

2.
Ba0.6Sr0.4TiO3 （BST） thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage current of BST thin films were focused. The dielectric constant of BST thin films increased and then decreased with the increase of HfO 2 thickness, while the dielectric relaxation was gradually improved. The loss tangent and leakage current under positive bias decreased with the HfO 2 thickness increasing. The leakage current analysis based on the Schottky emission indicated an improvement of the BST/Pt interface with HfO 2 buffer layer. The loss tangent, tunability and figure of merit of optimized HfO 2 buffered BST thin film achieved 0.009 8, 21.91% （E max = 200 kV/cm）, 22.40 at 10 6 Hz, respectively.  相似文献   

3.
The effect of magnetic field on α-amylase was studied. Under the experimental conditions, α-amylase solution was treated by 0.15 T, 0.30 T and 0.45 T static magnetic fields for a known period of time, then the activity, kinetic parameters, and the secondary conformation were investigated. The results showed that there was a considerable effect of the magnetic exposure on the α-amylase. The activity was increased by 27%, 34.1%, 37.8% compared with the control. It was also found that both kinetic parameters K m and V m could be decreased due to the increasing magnetic field, K m decreased from 2.20×10?2 to 0.87×10?2, whereas V m decreased from 2.0×10?3 g/min to 1.1×10?3 g/min. At the same time, there were some irregular changes in α-amylase secondary conformation.  相似文献   

4.
Systematic studies of the transport properties of La0.67Ca0.33Mn1?xFe x O3 (x=0–0.3) systems showed that with increasing Fe-doping contentx the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe3+ doping, which easily forms Fe3+?O2??Mn4+ channel, suppressing the double exchange Mn3+?O2??Mn4+ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.  相似文献   

5.
Objective： To study the effect of levobupivacaine and bupivacaine on the contractility of isolated uterine muscle strips from pregnant and non-pregnant female rats. Methods： Full-thick myometrial strips were prepared from 18- to 2 l-day pregnant （n=8） and non-pregnant rats （n=7）. After contractions became regular, strips were exposed to cumulative concentrations of the two drugs from 10^-8 to 10^-4 mol/L, amplitude and frequency of the uterine contraction was recorded. Results： Two local anesthetics caused a concentration dependent inhibition on contractility of myometrial strips from pregnant and non-pregnant rats. In the myometrium from non-pregnant rats, -log/C50 of levobupivacaine and bupivacaine were 4.85 and 4.25 respectively. In the myometrium from pregnant rats, similar concentrations of levobupivacaine and bupivacaine were observed, -log/C50 were 2.7 and 2.9 respectively. Levobupivacaine produced an increase in amplitude of contractions, while bupivacaine showed an increased trend in frequency. Conclusion： These results demonstrate that levobupivacaine and bupivacaine may inhibit myometrium contractility. The inhibitory effect of levobupivacaine or bupivacaine is not enhanced by gestation in rat. Levobupivacaine may have more positive influence than bupivacaine in pregnant myometrium.  相似文献   

6.
Four groups of 16 rats were trained in a go-no go discrimination with symmetrical negative reinforcement (active-passive avoidance task). A 2 by 2 design was used with stimulus combinations as one factor [light-go, noise/light-no go, (L+ NL?) vs noise-go, light/noise-no go (N+ LN?)] and noise intensity as the other factor (90 dB, high, vs 70 dB, low). The two N+ LN? groups learned both active and passive avoidance responses much more rapidly than the L+ NL? groups. In later phases of training, high noise intensity facilitated passive avoidance in the L+ NL? condition and exerted a slight effect in the opposite direction in the other condition. While the differences in active avoidance learning were the same as in previous work on light and noise CSs, the interactions between stimuli of different modalities appeared to be more important than stimulus modality or stimulus intensity per se in determining rate of passive avoidance learning.  相似文献   

7.
A Pr-doped TiO2-NTs/SnO2-Sb electrode was prepared by a simple method, cyclic voltammetry(CV). The methyl orange(MO)aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO2-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseodymium oxide was successfully doped into the SnO2-Sb film by CV method. Due to the doped Pr, the oxygen evolution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The C t /C 0 (φ) was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.  相似文献   

8.
A feeding trial was conducted for nine weeks to investigate the effects of partially replacing Ca(H2PO4)2 with neutral phytase on the growth performance, phosphorus utilization, nutrient digestibility, serum biochemical parameters, bone and carcass mineral composition, and digestive-enzyme-specific activity in crucian carp (Carassius auratus). The diets prepared with 0.8%, 0%, and 1.8% Ca(H2PO4)2 (1%=1 g/100 g) supplements were regarded as the P1E0, negative control (NC), and positive control (PC) groups, respectively; the other three experimental diets were prepared with the addition of 200, 300, and 500 U/kg of neutral phytase, respectively, based on the P1E0 group. Three hundred and eighty-four fish ((1.50±0.01) g) were randomly distributed in the six treatments with four replicates each. The fish were initially fed with 2%–3% diets of their body weight per day, with feeding twice daily (08:00 and 16:00), under a 12-h light/12-h dark cycle at the temperature of (27.56±0.89) °C. The results showed that supplemental phytase at different levels in the diet improved the final body weight, average daily gain, feed conversion ratio, phosphorus utilization, and protein efficiency ratio of crucian carp (P<0.05). Phytase supplementation increased the mineral content in serum (P), bone (P, Ca), and carcass (P, Ca, Zn, Na, and Mg) (P<0.05); the trypsin and chymotrypsin activity soared when fed with the phytase-supplemented diets (P<0.05). We may conclude that supplemental dietary neutral phytase improved the growth performance, phosphorus utilization as well as nutrient utilization in crucian carp, and it can be considered an important nutritional replacement for Ca(H2PO4)2.  相似文献   

9.
With the straification theory we have proved the transversal layer s03,k(D) of complete equations for mixed fluid is not an empty set: s03,k(D)≠φfor all k(k≥1). Based on this conclusion and the "secondary equation" of s03,k(D), this paper fully presents the expressions of coefficients in all local analytic solutions of the equations. Therefore we provide the calculation formulas by which we can get the numerical solutions to any desired accuracy.  相似文献   

10.
This study used a large-scale cluster randomized longitudinal experiment (N = 719; 35 schools) to investigate the effects of online mathematics mini-games on primary school students’ multiplicative reasoning ability. The experiment included four conditions: playing at school, integrated in a lesson (Eschool), playing at home without attention at school (Ehome), playing at home with debriefing at school (Ehome-school) and, in the control group, playing at school mini-games on other mathematics topics (C). The mini-games were played in Grade 2 and Grade 3 (32 mini-games in total). Using tests at the end of each grade, effects on three aspects of multiplicative reasoning ability were measured: knowledge of multiplicative number facts, skills in multiplicative operations, and insight in multiplicative number relations and properties of multiplicative operations. Through path analyses it was found that the mini-games were most effective in the Ehome-school condition, where both students’ skills and their insight were positively affected as compared to the control group (significant ds ranging from 0.22 to 0.29). In the Eschool condition, an effect was only found for insight in Grade 2 (d = 0.35), while in the Ehome condition no significant effects were found. Students’ gameplay behavior (time and effort put in the games) was in some cases, but not always, related to their learning outcomes.  相似文献   

11.
The copolymerization of CO and styrene catalyzed by Pd/C toward the formation of polyketones(PK)was studied in the N-valeronitrile-N'-methylimidazolium hexafluorophosphate([C4CNmim]+PF-6) medium. The synthesized PK was characterized by Fourier transform infrared(FTIR), elemental analysis, 13C-nuclear magnetic resonance(13C-NMR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and gel permeation chromatography(GPC). The supported ionic liquid film on the surface of Pd/C catalyst can prevent the products from covering the hole of active carbon due to its chemical stability and weak coordination ability with metal ions, and thus efficiently improve the catalytic activity. The effects of different amounts of ionic liquid on the catalytic activity and reusability of the catalyst and the molecular weight of PK were discussed. When the usage of ionic liquid is 10wt%(0.1 g ionic liquid / 1 g active carbon carrier) and the theoretical content of Pd2+ is 5wt%(0.05 g Pd2+/ 1 g active carbon carrier), the highest catalytic activity 2 963.64 gSTCO/(gPd·h) is achieved with the molecular weight and polydispersity index of PK as Mn=9 684, Mw=13 452 and Mw /Mn=1.389.  相似文献   

12.
For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μa and the reduced scattering coefficient μs′ of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μa and μs′ of different parts of the kiwifruit were 0.031–0.308 mm?1 and 0.120–0.946 mm?1, respectively. The results showed significant differences among the μa and μs′ of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits.  相似文献   

13.

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO3 ?:NH4 +) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO3 ?:NH4 + while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO3 ?:NH4 + ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO3 ?:NH4 + ratio was more beneficial for L0917. On the contrary, a lower NO3 ?:NH4 + ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO3 ?:NH4 + ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO3 ?:NH4 + ratio conditions.
  相似文献   

14.
RH和RH-KTB精炼过程中钢液流动和混合特性的研究   总被引：7，自引：0，他引：7  
The flow and mixing characteristics of molten steel during the vacuum circulation refining,including RH(Ruhrstahl-Heraeus) and RH-KTB(Ruhrastahl-Heraeus-Kawasaki top blowing) processes,were investigated on a 1/5 linear scale water model of a 90t multifunction RH degasser,The circulation rate was directly and more accurately determined,using a new method by which the more reliable results can be obtained.The fluid flow pattern and flow field in the ladle were demonstrated,observed and analyzed.The mixing time of liquid in the ladle was measured using electrical conductivity method.The residence time distribution in the RH model was obtained by tracer response technique.The influence of the main technological and geometric factors,including the gas top blowing*(KTB) operation,was examined.The results indicated that the circulation rate of molten steel in the RH degasser can be fairly precisely calculated by the formula:Q1p=0.0333Qg^0.26Du^0.69Dd^0.80(t/min),where Qg-the lifting gas flow rate(NL/min);Du and Dd-the inner diameters of the up and down-snorkels(cm),respectively.The maximum value of circulation rate of molten steel in the case of the 30cm diameters either of the up-and down-snorkels for the RH degasser(the “Saturated” rate) is approximately 31 t/min.the corresponding gas flow rate is 900NL/min.Blowing gas into the vacuum chamber through the top lance like KTB operation does not markedly influence the circulatory flow and mixing charateristics of the RH process under the conditions of the present work.There exist a major loop and a large number of small vortices and eddies in the ladle during the RH refining process.A liquidliquid two-phase flow is formed between the descnding stream from the down-snorkel and the liquid around the stream.All of these flow situation and pattern will strongly influence and determine the mixing and mass transfer in the ladle during the refining.The correlation between the mixing time and the stirring energy density is τmε^0.50 for the RH degasser.The mixing time rapidly shortens with an increase in the lifting gas flowrate.At a same gas flow rate,the mixing times with the up-and down-snorkel diameters either of 6 and 7cm are essentially same.The 30cm diameters either of the up-and down-snorkels for the RH degasser would be reasonalble.The concentration-time curve showed that three circulation cycles are at least needed for complete mixing of the liquid steel in the RH degasser.  相似文献   

15.
Implementation of effective teacher evaluation procedures is a global challenge in which lowering the chances that teachers receive inaccurate evaluations is a pertinent goal. This study investigates the minimum number of observations required to guarantee that teachers receive feedback with modest reliability (Eρ2 ≥ 0.70) and that any summative decisions about their professional career have high reliability (Eρ2 ≥ 0.90). A sample of 198 classroom observations by 62 colleagues of 69 teachers working at eight schools reveals that reliable feedback requires at least three lesson visits by three different observers and that reliable summative decisions require more than 10 visits. These findings mirror those reported through other observation instruments. This study accordingly offers directions for how schools can implement such procedures most cost-effectively.  相似文献   

16.
Pd77Cu6Si17 （PCS） tbin film metallic glasses （TFMGs） with high glass forming ability and hardness were selected as a hard coating for improving the surface hardness ofAZ31 magnesium alloy. Both microindentation and nanoindentation tests were conducted on specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indenta- tion depth （fl） were integrated using a quantitative model. The interaction parameters involved and relative hardness values were extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing fl ratio. In addition, specimens with thinner coatings （e.g., 200 nm） showed greater substrate-film interaction and those with thick coatings （e.g., 2000 nm） became prone to film cracking. The op- timum TFMG coating thickness in this study was estimated to be around 200 nm.  相似文献   

17.
Dorrance, Kaiser, and Zentall (1998) trained pigeons on two concurrent simultaneous discriminations (A+B?; C+D?), with interspersed single-stimulus trials in which responding to the two positive discriminanda was differentially reinforced (A+; C±). In each of four separate experiments, the birds showed a preference for stimulus B over stimulus D. Dorrance et al. concluded that the results of these experiments were best described in terms of value transfer theory (VTT; Fersen, Wynne, Delius, & Staddon, 1991). They reject the possibility that the results of these experiments might have been caused by differential nonreinforced experience with the test stimuli (B and D) on the basis of correlational analyses within each experiment. However, differences between experiments in choice of B over D are well predicted by differences in their history of reinforcement. Previous findings that were thought to favor VTT are also entirely consistent with a simpler associative analysis.  相似文献   

18.
Previous work with rats showed slower active avoidance (AA) and passive avoidance (PA) learning in a light-go/noise-light no-go task (L+NL?) than in a noise-go/light-noise no-go task (N+LN?), independently of noise intensity and of presence or absence of AA pretraining. Experiment I compared these two tasks and the corresponding discriminations with a compound AA and a simple PA signal. The latter were learned at a faster rate, with only negligible differences between the two types of stimulus arrangements (NL+L? vs LN+N?). Experiment II investigated the acquisition and reversal of four go/no-go tasks with a simple AA signal, with either a simple or a compound no-go signal and asymmetrical reinforcement, i.e., with an extinction instead of a PA contingency during the presentation of no-go signals. As in previous experiments with symmetrical reinforcement, the groups with a simple no-go signal (L+N?, N+L?) acquired AA with little or no generalization to the other stimulus. In reversal, however, the L+N? group (formerly N+L?) responded to the no-go signal much more frequently than the other (N+L?, formerly L+N?). Both the L+NL? and the N+LN? groups gave a large number of responses to the extinction signal, but the differences between the two groups were at least as large as in previous work with a PA contingency. These data show that perceptual or attentional phenomena cannot explain stimulus nonequivalences in situations with a compound no-go signal. Furthermore, the similar nonequivalences found in situations with and without differential fear conditioning (AA-extinction tests vs AA-PA tests) leads to complex, highly speculative models concerning possible interactions between response and drive-modulating properties of various stimuli.  相似文献   

19.
In this study, we used a simple impregnation method to prepare Fe–Ce–O x catalysts and tested them regarding their low-temperature (200–300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94–99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h?1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80–98% between 200 and 300 °C at a space velocity of 204,000 h?1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200–300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.  相似文献   

20.
In this paper we give a short survey on a problem on extremal quasiconformal extensions. It had been a conjecture for a long time that the dilatations K0(h) and K1(h) are equal before Anderson and Hinkkanen disproved this by constructing concrete examples of a family of affine mappings of some parallelograms. The problem also engendered many interesting results. At the end of the current paper, we discuss relationships among K0(h), H(h) and K1(h) as a concluding remark.  相似文献   

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