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61.
Dr. Maning Liu Hannu Pasanen Dr. Harri Ali-Löytty Dr. Arto Hiltunen Dr. Kimmo Lahtonen Syeda Qudsia Dr. Jan-Henrik Smått Prof. Mika Valden Prof. Nikolai V. Tkachenko Assoc. Prof. Paola Vivo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22301-22309
Colloidal lead-free perovskite nanocrystals have recently received extensive attention because of their facile synthesis, the outstanding size-tunable optoelectronic properties, and less or no toxicity in their commercial applications. Tin (Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions. Here, we propose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals, demonstrating the role of Ge2+ in stabilizing Sn2+ cation while enhancing the optical and photophysical properties. The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies, reducing the surface traps and leading to a longer excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices show the highest efficiency of 4.9 %, enhanced by nearly 60 % compared to that of pure Sn nanocrystals-based devices. 相似文献
62.
Lea H?m?l?inen Kimmo Smolander P?ivi Karttunen 《Fresenius' Journal of Analytical Chemistry》1988,330(2):107-110
Summary Silver was determined in 20 different geological samples by electrothermal AAS with and without (NH4)2HPO4 matrix modifier after aqua regia leach. The results were compared with those obtained after total dissolution of samples.The ashing temperature can be 300 °C higher and the atomising temperature 100°C lower when matrix modifier is used. The sensitivity of the method for Ag was 25% better with modifier. The detection limit, calculated in relation to the original solid sample, was 0.01 g/g with modifier.The results were systematically lower with matrix modifier, the mean value of recovery being 91.2% with modifier and 97.2% without. The ranges of the recovery values were noticeably different: from 84.5 to 99.5 with matrix modifier and from 63.4 to 110.2 without. The matrix modifier tended to even out the differences in the effects of geological matrices.
Direkte Silberbestimmung in geologischem Referenzmaterial mit Hilfe der Graphitofen-AAS mit Matrixmodifikation (nach Auslaugen mit Königwasser)相似文献
63.
In this paper, new nonlinear dynamic formulations for belt drives based on the three-dimensional absolute nodal coordinate formulation are developed. Two large deformation three-dimensional finite elements are used to develop two different belt-drive models
that have different numbers of degrees of freedom and different modes of deformation. Both three-dimensional finite elements
are based on a nonlinear elasticity theory that accounts for geometric nonlinearities due to large deformation and rotations.
The first element is a thin-plate element that is based on the Kirchhoff plate assumptions and captures both membrane and bending stiffness effects. The other three-dimensional
element used in this investigation is a cable element obtained from a more general three-dimensional beam element by eliminating degrees of freedom which are not significant in
some cable and belt applications. Both finite elements used in this investigation allow for systematic inclusion or exclusion
of the bending stiffness, thereby enabling systematic examination of the effect of bending on the nonlinear dynamics of belt
drives. The finite-element formulations developed in this paper are implemented in a general purpose three-dimensional flexible
multibody algorithm that allows for developing more detailed models of mechanical systems that include belt drives subject
to general loading conditions, nonlinear algebraic constraints, and arbitrary large displacements. The use of the formulations
developed in this investigation is demonstrated using two-roller belt-drive system. The results obtained using the two finite-element
formulations are compared and the convergence of the two finite-element solutions is examined. 相似文献
64.
65.
Filler-nanocellulose substrate for printed electronics: experiments and model approach to structure and conductivity 总被引:1,自引:0,他引:1
Antti Penttilä Jenni Sievänen Katariina Torvinen Kimmo Ojanperä Jukka A. Ketoja 《Cellulose (London, England)》2013,20(3):1413-1424
Composites made of inorganic filler particles and cellulose nanofibres can be applied as substrates for printed electronics. We have studied the structural properties of these substrates both experimentally and with particle-level modeling approach. Our model describes the skeleton structure formed by pigment particles of varied shapes and size distributions. Nanocellulose is assumed to fill voids of the structure. The model simulations predict quite well the relative changes in measured density, porosity and roughness for kaolin and precipitated calcium carbonate (PCC) pigments. Measured roughness turns out to be higher for kaolin than for PCC. Yet, the measured conductivity of printed lines on kaolin surface is higher than the conductivity on the PCC surface. The simulations reveal a more open surface pore structure for PCC than for kaolin, which leads to stronger absorption of the silver ink, and thus explains the differences in the measured conductivities. 相似文献
66.
Kimmo Hakala Tuulamari Helaja Barbro Lfgren 《Journal of polymer science. Part A, Polymer chemistry》2000,38(11):1966-1971
Copolymerizations of ethylene with 10‐undecen‐1‐ol, 10‐undecenyl methyl ether, 10‐undecenyl trimethyl silyl ether, and 1‐undecene were performed with rac‐ethylene‐bis(1‐indenyl)zirconium dichloride as a catalyst and methylaluminoxane as a cocatalyst. All three oxygen‐functional comonomers copolymerized with ethylene, although the activity of the catalyst decreased considerably compared with the homopolymerization of ethylene. The conversions of the comonomers varied from 17 to 40%, depending on the amount of comonomer in the feed. Under the same conditions, the conversion of 1‐undecene was 50–75%. The incorporation (0.7–3.6 mol %, depending on the feed) and the effect on the activity of the catalyst were on the same level for all the functional comonomers, which indicates that trimethylsilyl or methyl groups do not act as effective protecting groups for oxygen atoms. According to NMR and Fourier transform infrared analyses, the final functional group in the copolymers of the trimethylsilyl ether comonomer was hydroxyl. In contrast, the methyl ether group remained untouched in the copolymer, which suggests that the formation of aluminum alkoxides via a reaction with a cocatalyst is not a prerequisite for comonomer incorporation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1966–1971, 2000 相似文献
67.
Kimmo Hakala Barbro Lfgren Mika Polamo Markku Leskel 《Macromolecular rapid communications》1997,18(8):635-638
The use of two kinds of tantalum(V) aminopyridinato complexes, bis(2-benzylaminopyridinato)trichlorotantalum(V) and trichlorobis[2,6-di(phenylamino)pyridinato-N,N′]-tantalum(V), activated by methylaluminoxane was studied in polymerization of ethylene. The activities of these homogeneous catalyst systems are comparable to those of metallocenes. The weight-average molecular weights (M̄w) of the produced polyethylenes are between 60 000 and 200 000 and M̄w/M̄n ≈ 2. 相似文献
68.
We consider the TU version of Gale and Shapley's roommate game. We find several results that are analogous to known results
for the NTU game, such as a characterization of stable outcomes by forbidden minors, a characterization of the extreme points
of the core, and a median property of stable outcomes. The TU roommate game is a special case of the TU partitioning game
of Kaneko and Wooders. Bondareva and Shapley's balancedness condition for the core of such games is the starting point for
our forbidden minors approach.
Received: April 1999/Revised version: November 2000 相似文献
69.
Kimmo Himber Erkki Sippola Frank David Pat Sandra 《Journal of separation science》1993,16(11):645-650
In chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart-cut window. Very often the reliability of this positioning is ensured by applying relatively large heart-cuts; this reduces the intrinsic selectivity offered by the technique. The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precisely. 相似文献
70.
We prove a finite version of the well-known theorem that says that the number of partitions of an integer N into distinct parts is equal to the number of partitions of N into odd parts. Our version says that the number of lecture hall partitions of length n of N equals the number of partitions of N into small odd parts: 1,3,5, ldots, 2n-1 . We give two proofs: one via Bott's formula for the Poincaré series of the affine Coxeter group
, and one direct proof. 相似文献