Wyniki wyszukiwania - Biblioteka Nauki

1

Synchronization and stability of an elastically coupled tri-rotor vibration system

100%

Hou Y. , Du M. , Fang P. , Zhang L.

Journal of Theoretical and Applied Mechanics

|

2017

|

tom Vol. 55 nr 1

227--240

EN

A new mechanism, an elastically coupled tri-rotor system, is proposed to implement synchronization. It is composed of a rigid body, three induction motors, coupling unit and springs. According to the Lagrange equation, the model of the system is established. The average method of small parameters is applied to study the synchronization characteristics of the system, therefore, the balance equation and stability criterion of the system can be obtained. Obviously, many parameters affect the synchronous state of the rotors, especially the spring stiffness, the stiffness of the coupling unit and the installation location of the system. Finally, computer simulations are used to verify the correctness of theoretical analysis.

2

Synthesis, Spectroscopic and Structural Characterization of Cobalt(II) Complex with Bis(3,5-dimethyl-1-pyrazolyl)methane and Its Application in Catalytic Alkanes Oxidation with tert-Butyl Hydroperoxide

100%

Zhang L. , Liu Q. , Peng F. , Du M.

Polish Journal of Chemistry

|

2005

|

tom Vol. 79 / nr 4

655-661

EN

A novel cobalt complex, [Co(bdpm)(OBz)](ClO4) (bdpm = bis(3,5-dimethyl-1-pyrazolyl) methane, OBz = benzoate), was synthesized and characterized by elemental analysis, UV-Vis, IR spectroscopy and X-ray diffraction. The complex crystallizes in the trigonal system, space group P3121 with a = 19.2583(9), b = 19.2583(9), c = 25.5269(17) A and gamma = 120 graduate. The complex can catalyze the selective oxidation of alkanes to corresponding alcohols and ketones, and a presumptive mechanism was proposed.

3

Assisted and Protected Effects of Methanol Molecules on Intramolecular Proton Transfer in Formamide Studied with the Density Functional Theory

100%

Du M. , Qin M. , Fu A. , Zhou Z.

Polish Journal of Chemistry

|

2007

|

tom Vol. 81, nr 3

369-380

EN

Methanol assisted and protected proton transfers from the amide nitrogen to carbonyl oxygen atom inmodel peptide compound formamide have been investigated employing the B3LYP/6-311++G(d,p) level of theory. In the vicinity of formamide (F) and formamidic acid (FA), three different regions are considered to form hydrogen bond with methanol. Methanol molecule only in one of them can assist the proton transfer reaction while in other two sites can protect formamide from tautomerization. Totally, 27 geometries, including nine important transition states, were optimized, and their geometric parameters have also been discussed in detail. The thermodynamic and kinetic parameters, such as tautomeric energies, equilibrium constants, barrier heights, and rate constants have been predicted, respectively. In addition, the factors influencing the thermodynamic and kinetic parameters, such as temperature dependences, and solvent effects have also been explored qualitatively. Computational results show that the lowest proton transfer barrier heights are 83.30 (61.61) kJ/mol without (with) ZPVE correction for the assistance of two methanol molecules, which are also lower than that of the water-assisted process. Nonspecific solvent effects have also been taken into account by using the IPCM model of methanol. The tautomerization energies and the barrier heights are increased for these proton transfer systems because of the bulk solvent, which imply that the tautomerization of F becomes less favorable in the polar medium.

4

Associations of traffic-related air pollution with children’s attention spans: a factor analysis

100%

Wang S. , Zhang J. , Yao J. , Du M.

Polish Journal of Environmental Studies

|

2016

|

tom 25

|

nr 4

EN

To evaluate the associations between traffic-related air pollution (TRAP) and children’s attention spans, an analysis was performed in a cross-sectional epidemiological study. Two primary schools were chosen based on the levels of traffic density and ambient air pollutants. School A is located in a clean area and School B in a polluted area. Two-hundred and eighty-two students from three third-grade classes (9-10 years of age) (School A, 136; School B, 146) participated in five computerized-based neurobehavioral tests. Neurobehavioral test results were used as the independent variables for component extraction by factor analysis, and two main compositions – visual memory factor and attention factor – were extracted. After controlling the potential confounding factors, we found that children from School B at the polluted area had lower scores of attention factor than those from School A in the clean area (β = -0.300, p = 0.016), and girls obtained higher scores than boys (β = 0.317, p = 0.011). In conclusion, exposure to TRAP was significantly associated with decreased attention score of school-aged urban children, and the association was significantly more evident in boys than girls.

5

Response of alpine plant community to simulated climate change : two-year results of reciprocal translocation experiment (Tibetan Plateau)

75%

Zhang F. , Li Y. , Cao G. , Wang S. , Zhao X. , Du M. , Wang Q.

Polish Journal of Ecology

|

2011

|

tom Vol. 59, nr 4

741-751

EN

The great sensitivity of the response of alpine plant community to climate change makes the identification of these responses important. In 2007, we conducted a reciprocal translocation experiment on 100 x 100 x 40 cm coherent turf and soil along an elevation gradient of 3200.3800 m on the south slope of Qilian Mountains northeast of the Qinghai-Tibetan Plateau. The aim was to understand the warming/cooling effects on the alpine ecosystem where treatments were simulated by donor elevations below/above receptors. Translocated vegetation comprised the Kobresia meadow at 3200 m, deciduous shrub meadow at 3400 m, forbs meadow at 3600 m, and sparse vegetation at 3800 m. The 5 x 5 cm grid method (50 x 50 cm, 100 grids) was used for surveying plant species absolute abundance in translocated quadrats. Results showed that species richness and Shannon-Weaver index of Kobresia meadow increased significantly (P <0.05) when translocated to 3400 m. Shannon-Weaver index of shrub meadow declined, while shrub species abundance responded slightly both to warming and cooling treatments. Both species richness and Shannon-Weaver index of forbs meadow and sparse vegetation were enhanced evidently at 3200 m and 3400 m. Four groups were identified by non-metric multidimensional scaling based on receptor elevation. Responses of the alpine plant community and the function group appeared to be specific to climate magnitude and specific to function type, respectively. Correlation indicated that climatic factors played a much more important role than soil in the response of the alpine plant community. Four vegetation types were sensitive to climate change, while Kobresia meadow behaved flexibly. Global warming would depress sedges but favor legumes and graminoids.

6

Study and Application of HRP-like Catalyst Copper 2-Hydroxy-1-naphthaldehyde-2-aminothiazole {Cu II-(HNATS)2]

75%

Tang B. , Yue T. X. , Du M. , Wang Y. , Chen Z. Z. , Wang H. J.

Polish Journal of Chemistry

|

2002

|

tom Vol. 76 / nr 11

1527-1535

EN

2-Hydroxy-1-naphthaldehyde-2-aminothiazole (HNATS) and its copper complex [CuII-(HNATS)2] had been synthesized. The complex of [CuII-(HNATS)2] was used to mimic the active group of horseradish peroxidase (HRP). The catalytic characteristics of this HRP-like catalyst in the H2O2-phenol- 4-AAP redox coupling reaction was studied, and the catalytic activity of [CuII-(HNATS)2] was compared with those of HRP and other Schiff base metal complexes. It was found that [CuII-(HNATS)2] exhibits a good catalytic activity and could be used as a novel catalyst in the determination of hydrogen peroxide (H2O2). The reaction mechanism, optimal experimental conditions and interferences of coexisting substances were discussed. Under the experimental conditions established, the linear relationship between the absorbance at 504 nm (A504) and H2O2 concentration was in the range of 5.6×10-6~1.1×10-4 mol/L, with a correlation coefficient (r) of 0.9990. The linear regression equation was A504 = 2540×C (mol/L) - 3.0×10-3 with a detection limit of 1.7×10-6 mol/L. In this paper, the complex [CuII-(HNATS)2] was applied successfully with catalytic spectrophotometric method to the determination of (-O-O-H) in polyethylene glycol.

7

Colour stability and lipid oxidation of beef longissimus lumborum under different packaging conditions

75%

Bonny D. S. S. , Li X. , Li Z. , Li M. , Du M. , Gao L. , Zhang D.

Polish Journal of Food and Nutrition Sciences

|

2017

|

tom 67

|

nr 4

EN

The objective of this study was to investigate the colour stability and lipid oxidation of beef under different packaging methods. The muscles longissimus lumborum were randomly packed in vacuum or modifi ed atmosphere packaging (MAP, 80% O2 , 20% CO2 ). Both packages were aged at 4°C for 7, 14 and 21 days. After each ageing time, samples were displayed in a refrigerator for 2, 4 and 6 days. Colour stability, lipid oxidation and their correlation were determined. Beef under vacuum packaging showed higher a* values on 7, 14, and 21 days of ageing and lower L* values on 14 and 21 days of ageing than beef in MAP (p<0.05). Lower a* values were observed in the samples packed in MAP, then displayed compared to samples packed in vacuum, then displayed after 21 days of ageing time on day 2, 4 and 6 of the display period (p<0.05). Thiobarbituric acid reactive substances (TBARS) increased signifi cantly in MAP compared to vacuum during 7, 14, and 21 days of ageing (p<0.05). An increase of TBARS was also observed during display after 14 and 21 days of ageing in samples packed in MAP, then displayed. Furthermore, a significant difference (p<0.05) was observed between samples packed in MAP and vacuum in peroxide value on 14 days of ageing. Lipid oxidation was observed mainly in the samples packed in MAP compared to vacuum, and positively correlated with results on colour stability.

8

Variations in carbon, nitrogen and phosphorus stoichiometry during a growth season within a Platycladus orientalis plantation

63%

Du M. , Feng H. , Zhang L. , Pei S. , Wu D. , Gao X. , Kong Q. , Xu Y. , Xin X. , Tang X.

Polish Journal of Environmental Studies

|

2020

|

tom 29

|

nr 5