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排序方式: 共有441条查询结果,搜索用时 15 毫秒
61.
Tipaluck Krityakierne Taimoor Akhtar Christine A. Shoemaker 《Journal of Global Optimization》2016,64(3):417-431
This paper presents a canonical dual approach for solving a nonconvex global optimization problem governed by a sum of 4th-order polynomial and a log-sum-exp function. Such a problem arises extensively in engineering and sciences. Based on the canonical duality–triality theory, this nonconvex problem is transformed to an equivalent dual problem, which can be solved easily under certain conditions. We proved that both global minimizer and the biggest local extrema of the primal problem can be obtained analytically from the canonical dual solutions. As two special cases, a quartic polynomial minimization and a minimax problem are discussed. Existence conditions are derived, which can be used to classify easy and relative hard instances. Applications are illustrated by several nonconvex and nonsmooth examples. 相似文献
62.
63.
The removal efficiency of chestnut shells for selected pesticides from aqueous solutions 总被引:3,自引:0,他引:3
The removal of selected pesticides such as carbofuran (CF) and methyl parathion (MP) using low-cost abundant sorbent chestnut shells from aqueous solutions has been investigated in the present study. The sorption parameters, i.e., contact time, pH, initial pesticide solution concentration and temperature have been studied. Maximum percent sorption (99+/-1%) was achieved for (0.38-3.80) x10(-4) and (0.45-4.5) x10(-4) mol dm(-3) of MP and CF pesticide solutions respectively, using 0.4 g of sorbent in 100 ml of solution for 30 min agitation time at pH 6. The Freundlich, Langmuir and Dubinin-Radushkevich (D-R) models have been applied, and their constants for methyl parathion and carbofuran, sorption intensity 1/n (0.55+/-0.02 and 0.54+/-0.04), multilayer sorption capacity C(m) (28.3+/-0.5 and 16.4+/-0.7) x10(-3) mol l(1-1/n)dm(3/n)g(-1), monolayer sorption capacity Q (22.5+/-0.5 and 10.8+/-0.3) x10(-6) mo lg(-1), binding energy, b (2.9+/-0.2 and 5.2+/-0.5) x10(4) dm(3)mol(-1), and sorption energy E (11.2+/-0.1 and 11.5+/-0.2 kJ mol(-1)) have been evaluated respectively. Lagergren, Morris-Weber and Reichenberg equations were employed to study kinetics of sorption process. Thermodynamic parameters DeltaH (-5.09+/-0.1 and 22.8+/-0.4 kJ mol(-1)), DeltaS (-4.33+/-0.0003 and 0.09+/-0.001 kJ mol(-1)K(-1)) and DeltaG((303K)) (-2.9 and -3.8 kJ mol(-1)) have been calculated for methyl parathion and carbofuran, respectively. The developed sorption procedure has been employed to environmental samples. 相似文献
64.
Inayat-Ur-Rahman Khan MA Arfan M Akhtar G Khan L Ahmad VU 《Natural product research》2007,21(3):243-253
One new 14-membered frangulanine-type cyclopeptide alkaloid, oxyphyl line-A (1) has been isolated from the stem bark of Zizyphus oxyphylla together with the known 13-membered cyclopeptide, nummularine R (2). The structure was established on the basis of spectral studies particularly 2D NMR. 相似文献
65.
Compression tests followed by tension tests after re-machining were performed on annealed oxygen-free-high-conductivity copper cylinders. These tests were conducted at nine levels of maximum strain ranging from 5 to 50%. From this data, isotropic and kinematic hardening were calculated using 50, 1000 and 2000 microstrain offset definitions. Both isotropic and kinematic hardening were found to depend on the yield definition. Isotropic hardening, which increased with plastic strain with no signs of saturation, also increased with larger offset definition of yield. Kinematic hardening, which increased to 40% strain and appeared to saturate thereafter, decreased with higher offset definitions of yield. 相似文献
66.
Bin Yang Marina Lledos Riaz Akhtar Giuseppe Ciccone Long Jiang Emanuele Russo Sunil Rajput Chunyu Jin Maria Galini Faidra Angelereou Thomas Arnold Jonathan Rawle Massimo Vassalli Maria Marlow Dave J. Adams Mischa Zelzer 《Chemical science》2021,12(42):14260
Controlling supramolecular self-assembly across multiple length scales to prepare gels with localised properties is challenging. Most strategies concentrate on fabricating gels with heterogeneous components, where localised properties are generated by the stimuli-responsive component. Here, as an alternative approach, we use a spiropyran-modified surface that can be patterned with light. We show that light-induced differences in surface chemistry can direct the bulk assembly of a low molecular weight gelator, 2-NapAV, meaning that mechanical gel properties can be controlled by the surface on which the gel is grown. Using grazing incidence X-ray diffraction and grazing incidence small angle X-ray scattering, we demonstrate that the origin of the different gel properties relates to differences in the architectures of the gels. This provides a new method to prepare a single domain (i.e., chemically homogeneous) hydrogel with locally controlled (i.e., mechanically heterogeneous) properties.A mechanical pattern is created in a hydrogel film by pre-patterning the underlying surface chemistry. This allows spatial variation of the viscous component of the gel, controlling dissipative forces in the gel film without altering gel chemistry. 相似文献
67.
Ahmad Umar M. Shaheer Akhtar Hassan Algadi Ahmed A. Ibrahim Mohsen A. M. Alhamami Sotirios Baskoutas 《Molecules (Basel, Switzerland)》2021,26(15)
Herein, we have developed a novel sensing electrode to detect the eco-toxic 4-nitrophenol (4-NP). Ag-doped-ZnO nanoflowers were synthesized by facile hydrothermal method and examined by several characterization techniques in order to understand the morphology, crystal structure, composition, and surface properties. Morphological results were confirmed by the formation of Ag-doped ZnO nanoflowers decorated with nanosheets. Ag-doped ZnO/glassy carbon electrode (GCE) electrode-material-matrix was used for electrochemical sensing of toxic 4-NP. Under optimized conditions, Ag-doped ZnO/GCE modified electrode exhibits high-sensitivity and selectivity compared to the bare GCE electrode. The Ag-doped ZnO/GCE modified electrode exhibits high electrocatalytic oxidation towards 4-NP. Anodic peak current of 4-NP is increased linearly by increasing the concentration of nitrophenol. Additionally, Ag-doped ZnO/GCE shows a wide range of sensitivity from 10 µM to 500 µM, and a linear calibration plot with a good detection limit of 3 µM (S/N = 3). The proposed Ag-doped ZnO/GCE modified electrode showed high sensing stability. In addition, the oxidation mechanism was studied. The obtained results revealed that the Ag-ZnO/GCE electrode could be the promising sensing electrode for 4-NP sensing. 相似文献
68.
Samina Rubnawaz Waqas Khan Kayani Nosheen Akhtar Rashid Mahmood Asif Khan Mohammad K. Okla Saud A. Alamri Ibrahim A. Alaraidh Yasmeen A. Alwasel Bushra Mirza 《Molecules (Basel, Switzerland)》2021,26(16)
Ajuga bracteosa Wall. ex Benth. is an endangered medicinal herb traditionally used against different ailments. The present study aimed to create new insight into the fundamental mechanisms of genetic transformation and the biological activities of this plant. We transformed the A. bracteosa plant with rol genes of Agrobacterium rhizogenes and raised the regenerants from the hairy roots. These transgenic regenerants were screened for in vitro antioxidant activities, a range of in vivo assays, elemental analysis, polyphenol content, and different phytochemicals found through HPLC. Among 18 polyphenolic standards, kaempferol was most abundant in all transgenic lines. Furthermore, transgenic line 3 (ABRL3) showed maximum phenolics and flavonoids content among all tested plant extracts. ABRL3 also demonstrated the highest total antioxidant capacity (8.16 ± 1 μg AAE/mg), total reducing power, (6.60 ± 1.17 μg AAE/mg), DPPH activity (IC50 = 59.5 ± 0.8 μg/mL), hydroxyl ion scavenging (IC50 = 122.5 ± 0.90 μg/mL), and iron-chelating power (IC50 = 154.8 ± 2 μg/mL). Moreover, transformed plant extracts produced significant analgesic, anti-inflammatory, anticoagulant, and antidepressant activities in BALB/c mice models. In conclusion, transgenic regenerants of A. bracteosa pose better antioxidant and pharmacological properties under the effect of rol genes as compared to wild-type plants. 相似文献
69.
70.
This paper describes an experimental observation of post oxidation annealing (POA) treatment on current-voltage and capacitance-voltage
characteristics of Ni/SiO2/4H-SiC system with varying oxide thickness. The leakage current of fabricated structures shows an asymmetric behavior having
noticeable effect of POA with the polarity of gate bias (+V or −V at the anode). When compared with the conventional wet oxidation,
the POA processes greatly reduce interface-state density and enhance reliability of devices. An extensive increment in the
barrier height at SiO2/4H-SiC interface was observed due to POA, which resulted into lower forward leakage current. A significant improvement in the
oxide charges are also demonstrated using C-V characteristics of POA treated structures. 相似文献