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排序方式: 共有315条查询结果,搜索用时 187 毫秒
51.
Kärber E Raadik T Dedova T Krustok J Mere A Mikli V Krunks M 《Nanoscale research letters》2011,6(1):359
Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km. 相似文献
52.
Kristina Hoffmann Tatjana Friedrich Bernd Tieke 《Polymer Engineering and Science》2011,51(8):1497-1506
Polyelectrolyte blend films and membranes were prepared upon alternating electrostatic adsorption of polyallylamine hydrochloride (PAH) and mixtures of polystyrene sulfonate (PSS) and polyacrylic acid (PAA) in different ratio on solid supports. Infrared studies indicated that the PSS‐PAA blend composition of the films always differed from the mixture composition in the dipping solution, PSS being preferentially adsorbed. Films deposited on porous supporting membranes (polyacrylonitrile/polyethylene terephthalate) were studied on their ion permeation under diffusion dialysis conditions, and their flux and salt rejection under nanofiltration and reverse osmosis (RO) conditions. Blend membranes prepared at pH 1.7 exhibit a significantly improved anion separation and salt rejection, the ideal separation factor α(NaCl/Na2SO4) of a membrane prepared from a PSS:PAA mixture of 1:1 (w/w) being 197 ± 10 (pure PAH/PSS: 45). The NaCl and Na2SO4 rejections under RO conditions are 85 and 97% (pure PAH/PSS: 15 and 27%), respectively. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers 相似文献
53.
Ljerka Prester Jelena Macan Veda Marija Varnai Tatjana Orct Jelena Vukušić Dubravka Kipčić 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(3):355-362
Whole Atlantic mackerel (Scomber scombrus), sardine (Sardina pilchardus) and Mediterranean hake (Merluccius merluccius) from the Croatian Adriatic were stored at 22 °C and changes in histamine, putrescine, tyramine and cadaverine levels were monitored in relation to bacterial endotoxin. After 12 h, histamine levels in sardine were above the legal limit of 50 mg kg?1, set by the US Food and Drug Administration, and an increase in putrescine content preceded the increase in histamine. After 24 h, histamine contents in mackerel and sardine reached 1090 ± 101 and 577 ± 275 mg kg?1, respectively, which exceeded the toxic threshold of 500 mg kg?1. At the same time, the putrescine content was also high in both fish (353–420 mg kg?1). The time-course of endotoxin production was similar in all fish species stored at 22 °C. A high correlation was found between endotoxin and histamine, and between endotoxin and putrescine in mackerel and sardine. On the other hand, high endotoxin levels in hake, after 24 h, were associated with the low histamine and putrescine content (40–60 mg kg?1). 相似文献
54.
Layne Christopher M.; Pynoos Robert S.; Saltzman William R.; Arslanagi? Berina; Black Mary; Savjak Nadezda; Popovi? Tatjana; Durakovi? Elvira; Mu?i? Mirjana; ?ampara Nihada; Djapo Nermin; Houston Ryan 《Canadian Metallurgical Quarterly》2001,5(4):277
Results of a preliminary effectiveness evaluation of a school-based postwar program for war-exposed Bosnian adolescents are described. The evaluation centered on a manualized trauma/grief-focused group psychotherapy protocol for war-traumatized adolescents based on 5 therapeutic foci: traumatic experiences, trauma and loss reminders, postwar adversities, bereavement and the interplay of trauma and grief, and developmental impact. Fifty-five secondary school students (81% girls; age range?=?15–19 years, M?=?16.81) from 10 Bosnian schools participated in the evaluation. Students completed pregroup and postgroup self-report measures of posttraumatic stress, depression, and grief symptoms and postgroup measures of psychosocial adaptation and group satisfaction. The evaluation yielded preliminary but promising results, including reduced psychological distress and positive associations between distress reduction and psychosocial adaptation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Milica V. Carević Nadica D. Abazović Tatjana D. Savić Tatjana B. Novaković Dejan J. Pjević Mirjana I. Čomor 《Journal of the American Ceramic Society》2018,101(4):1420-1431
Solvothermal synthesis of ZrO2–TiO2 binary oxides and pure counterparts at 150°C in water/isopropanol media is presented. Titanium (IV) isopropoxide and zirconium (IV) propoxide were used as precursors. XRD and TEM techniques were used for structural and morphological characterization of obtained samples. XPS spectra of mixed oxide samples were compared in order to correlate composition of samples with surface properties and presence of defects. Relative positions of defect states within band‐gaps of semiconductors were estimated from UCPL spectra. UV‐Vis DRS spectra revealed that both pure oxides experienced red shift of absorption thresholds compared to reference data. Photocatalytic activities of all samples were probed under simulated Solar light on three model compounds: phenol, 4‐chlorophenol (4‐CP) and 2, 4, 6‐trichlorphenol (TCP). Pure TiO2 showed the highest photocatalytic activity in the case of phenol. However, pure ZrO2 and binary oxides showed higher photoactivity in degradation of 4‐CP and TCP. The activity of wide band‐gap semiconductors under simulated Solar light in photodegradation of phenol and its derivatives is most probably the consequence of formation of charge transfer complexes between pollutant molecules and semiconductors surface. 相似文献
56.
Tina-Tini S. Trofimova Tatjana N. Ostanina Vjacheslav S. Nikitin Valentin M. Rudoi Nickolaj I. Ostanin Aleksej A. Trofimov 《International Journal of Hydrogen Energy》2021,46(32):16857-16867
Hydrogen used as an energy carrier can be obtained by water electrolysis. To improve the energy efficiency of this process porous nickel catalysts are often used. The paper investigates the electrodeposition regularities and the porous nickel deposits morphology and the properties of nickel foams toward the hydrogen evolution reaction. During electrodeposition at high current density, nickel deposits with macro- and micropores are formed. The dependence between the fraction of macropores on the deposit surface and the electrolysis time is described by the empirical equation. Total porosity of loose nickel deposits is much higher than the porosity of foams. However, the surface macropores fraction of deposits studied is approximately the same, while the microporosity of loose deposits is significantly higher. The values of nickel deposits total porosity calculated by the model agree with the values obtained by experimental data. The highest density of macropores on the surface is observed for the foam thickness of 100 μm. These data correlate with the results of polarization measurements. When the foam thickness increases up to 100 μm, hydrogen evolution overvoltage in the alkali solution decreases and the efficiency of nickel foam as a cathode material increases. 相似文献
57.
58.
Goran Lj Djordjevic Mile K. Stojcev Tatjana R. Stankovic 《Microelectronics Journal》2004,35(12):945-952
This paper presents a cost-effective, non-intrusive technique of partially self-checking combinational circuits design. The proposed technique is similar to duplication with comparison, wherein duplicated function module and comparator act as a function checker that detects any erroneous response of the original function module. However, instead of realizing checker with full error-detection capability, we select a subset of erroneous responses to implement partial, but simplified function checker. A heuristic procedure that tries to find the optimal sum-of-product expression for partial function checker that minimizes its area while providing specified error coverage is described here. Effectiveness of the technique is evaluated on a set of MCNC 91 benchmark combinational circuits. 相似文献
59.
60.
We characterize the images of Szilard languages under decreasing homomorphisms using so-called label grammars and show that each -free label language is in fact the coding of some Szilard language. This result shows that decreasing homomorphisms do not have more generating power on Szilard languages than codings, except that they generate the empty word. Label grammars naturally define a subclass of labelled Petri nets for which, unlike in the general case, it is now possible to eliminate -labelled transitions. 相似文献