The article deals with the numerical modelling of heat and mass transfer in the counterflow wet-cooling tower fill. Due to the complexity of this phenomenon the simplified model based on the set of four ODEs [1] was chosen. The used approach is generally applicable to the simulation of the distribution of moist air temperature. water temperature, specific humidity of air and water mass flow rate. Evaluation of the distribution of heat and mass sources is also done. Boundary condition for outlet water temperature are based on experimentally obtained Merkel number correlation. Numerical solution of chosen model was performed using Dormand-Prince method combined with shooting method. Results are compared with data available in the literature. and Obsahuje seznam literatury
The xanthophyll cycle and the water-water cycle had different functional significance in chilling-sensitive sweet pepper upon exposure to chilling temperature (4 °C) under low irradiance (100 µmol m-2 s-1) for 6 h. During chilling stress, effects of non-photochemical quenching (NPQ) on photosystem 2 (PS2) in dithiothreitol (DTT) fed leaves remained distinguishable from that of the water-water cycle in diethyldithiocarbamate (DDTC) fed leaves. In DTT-fed leaves, NPQ decreased greatly accompanied by visible inhibition of the de-epoxidized ratio of the xanthophyll cycle, and maximum photochemical efficiency of PS2 (Fv/Fm) decreased markedly. Thus the xanthophyll cycle-dependent NPQ could protect PS2 through energy dissipation under chilling stress. However, NPQ had a slighter effect on photosystem 1 (PS1) in DTT-fed leaves than in DDTC-fed leaves, whereas effects of the water-water cycle on PS1 remained distinguishable from that of NPQ. Inhibiting superoxide dismutase (SOD) activity increased the accumulation of O2, the oxidation level of P700 (P700+) decreased markedly relative to the control and DTT-fed leaves. Both Fv/Fm and NPQ changed little in DDTC-fed leaves accompanied by little change of (A+Z)/(V+A+Z). This is the active oxygen species inducing PS1 photoinhibition in sweet pepper. The water-water cycle can be interrupted easily at chilling temperature. We propose that during chilling stress under low irradiance, the xanthophyll cycle-dependent NPQ has the main function to protect PS2, whereas the water-water cycle is not only the pathway to dissipate energy but also the dominant factor causing PS1 chilling-sensitivity in sweet pepper. and X.-G. Li ... [et al.].
As a stress factor, salt induces the phosphorylation of light-harvesting chlorophyll (Chl) a/b proteins (LHCII) in Dunaliella salina. In this study, we found that the salt-induced phosphorylation of LHCII was not affected by phosphatase, and that salt simultaneously regulated both the phosphorylation of LHCII and the expression of genes encoding light-harvesting Chl a/b proteins of photosystem II (lhcb) and the gene encoding Chl a oxygenase (cao) in dark-adapted D. salina. The mRNA accumulation patterns of lhcb and cao were similar, which further affected the size of LHCII and the ratio of Chl a to Chl b. Therefore, we inferred this simultaneous regulation is one of the mechanisms of D. salina to adapt to the high-salinity environment. and W. M. Chen ... [et al.].
Drought stress causes changes in vein and stomatal density. The objectives of this study were to determine (1) if the changes in vein and stomatal density are coordinated in cotton (Gossypium hirsutum L.) and (2) how these changes affect water-use efficiency (WUE). The results showed significant positive correlations between vein density and stomatal density when cotton was grown under different degrees of drought stress. WUE was significantly positively correlated with the densities of both veins and stomata. Stomatal pore area and stomatal density on the abaxial leaf side, but not the adaxial side, were significantly correlated with WUE, stomatal conductance, leaf net photosynthetic rate, and transpiration rate. In conclusion, coordinated changes in vein and stomatal density improve the WUE of cotton under drought stress. The abaxial leaf side plays a more important role than the adaxial side in WUE and gas exchange., Z. Y. Lei, J. M. Han, X. P. Yi, W. F. Zhang, Y. L. Zhang., and Obsahuje bibliografii
In this work, we study coordination control and effective deployment of thyristor-controlled series compensation (TCSC) to protect power grids against disruptive disturbances. The power grid consists of flexible alternate current transmission systems (FACTS) devices for regulating power flow, phasor measurement units (PMUs) for detecting system states, and control station for generating the regulation signals. We propose a novel coordination control approach of TCSC devices to change branch impedance and regulate the power flow against unexpected disturbances on buses or branches. More significantly, a numerical method is developed to estimate a gradient vector for generating regulation signals of TCSC devices and reducing computational costs. To describe the degree of power system stress, a performance index is designed based on the error between the desired power flow and actual values. Moreover, technical analysis is presented to ensure the convergence of the proposed coordination control algorithm. Numerical simulations are implemented to substantiate that the coordination control approach can effectively alleviate the stress caused by contingencies on IEEE 24 bus system, as compared to the classic PID control. It is also demonstrated that the deployment of TCSCs can alleviate the system stress greatly by considering both impedance magnitude and active power on branches.
Mixtures of coal/waste tires, coal/waste plastics and coal/waste cotton were pyrolyzed in the laboratory pyrolytical unit built in IRSM AS CR Prague. Non-caking hard coal (mine Lazy) and its mixtures with some organic wastes were pyrolyzed in a quartz reactor inserted in a vertical tube furnace. The main product yields (coke, tar, gas and reaction water) documented exhibit entirely different influence of added waste. Results demonstrated that co-pyrolysis is meaning full in case of waste tiers and plastics. However, in case of co-processing with waste cotton (natural textile), the results are not promising., Vlastimil Kříž and Zuzana Brožová., and Obsahuje bibliografii
We argue that the correction coefficients used to calculate Young’s modulus from resonant frequency of flexural vibration obtained by Štubňa and Trník (Journal of Mechanical Engineering - Strojniški vestnik. 52, 2006, p. 317) can be applied with very good precision only when Poisson’s ratio μ = 0.25 ± 0.05. We revise their results and propose more accurate correction coefficients for the first overtone and a prismatic sample with a square cross-section when their discrepancy is most evident. and V príspevku poukazujeme na to, že korekčné koeficienty, ktoré použili štubňa a trník na výpočet Youngovho modulu z rezonančnej frekvencie ohybových kmitov (Journal of Mechanical Engineering - strojniški vestnik. 52, 2006, p. 317), je možné použiť s veľmi dobrou presnosťou iba ak Poissonovo číslo μ = 0.25 ± 0.05. Po preskúmaní ich výsledkov navrhujeme presnejšie hodnoty korekčných koeficientov pre prvú vyššiu frekvenciu a hranolovú vzorku so štvorcovým prierezom, kedy je ich nesúlad najzjavnejší.
We analyzed several approaches dealing with the components of non-photochemical energy dissipation and introduced improved versions of the equations used to calculate this parameter. The usage of these formulae depends on the conditions of the sample (acclimation to dark or irradiation, presence or absence of the "actinic light"). The parameter known as "excess" cannot be used as a component of energy partitioning. In reality, this parameter reflects the differences between potential and actual quantum yields of photochemistry. and D. Kornyeyev, A. S. Holaday.
We compared photoinhibition sensitivity to high irradiance (HI) in wild-type barley (wt) and both its chlorina f104-nuclear gene mutant, that restricts chlorophyll (Chl) a and Chl b synthesis, and its f2-nuclear gene mutant, that inhibits all Chl b synthesis. Both Fv/Fm and ΦPS2 decreased more significantly in f2 than f104 and wt with duration of HI exposure. Chl degraded more rapidly in the f2 than in either f104 or wt. Most sensitivity to photoinhibition was exhibited for f2, whereas there was little difference in response to HI between the f104 and wt. The highest de-epoxidation (DES) value at every time point of exposure to HI was measured for f2, whereas the wt had the lowest value among the three strains. There were two lifetime components resolved for the conversion of violaxanthin (V) to zeaxanthin plus antheraxanthin (Z + A). The most rapid lifetime was around 6 min and the slower lifetime was >140 min, in both the mutants and wt. However, the wt and f104 both displayed larger amplitudes of both de-epoxidation lifetimes than f2. The difference between the final de-epoxidation state (DES = [Z + A]/[V + A + Z]) in the light compared to the dark expressed as ΔDES for wt, f104, and f2 was 0.630, 0.623, and 0.420, respectively. The slow lifetime component and overall larger ΔDES in the wt and f104 correlated with more photoprotection, as indicated by relatively higher Fv/Fm and ΦPS2, compared to the f2. Hence the photoprotection against photoinhibition has no relationship with the absolute DES value, but there is a strong relationship with de-epoxidation rate and relative extent or ΔDES. and Chang-Lian Peng ... [et al.].