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101.
102.
Ionel Danut Savu Sorin Vasile Savu Nicusor Alin Sirbu 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1427-1437
Laser marking is based on the laser heating of the subjected material, the heating being below the melting temperature or thermal degradation starting point. Within and nearby the mark, the material is chemically, physically and mechanically affected. This means that the main characteristics are changing in such a way that the material is ageing. Thermal and mechanical analysis can be used to determine the modification of the material, which is important and necessary to know for predicting its use lifetime. This paper investigates the physical and mechanical modification of the polymer HDPE100, when laser marking is applied. Burst stress, elongation and relaxation modulus were determined for the base material, within the heat affected zone and within the laser burned mark. Information on the crystallization rate and on the elongation viscosity is also reported. According to the results, the polyethylene has very fast crystallization and that affects the marking process if lower than appropriate maintaining during heating process is applied. It becomes stabile after 0.23 min, when it is tested at 103 °C. The elongation viscosity was analysed and values of 105 Pa s were recorded for 10 s, which is a usual time of applying pressure. The performed analysis revealed about 10 % difference between the relaxation modulus of the irradiated and non-irradiated HDPE. 相似文献
103.
Irina Fierascu Sorin Marius Avramescu Radu Claudiu Fierascu Alina Ortan Gabriel Vasilievici Carmen Cimpeanu Lia-Mara Ditu 《Journal of Thermal Analysis and Calorimetry》2017,129(3):1377-1387
Books represent a very important part of the cultural heritage, due to their double characteristics: first, as a man-made material and secondly, due to the information they store. The characterization of book paper represents a very important step in developing solutions for better conservation procedures, as well as for fully understanding their provenance. The present paper describes the analytical and microbiological evaluation of a collection of books from the nineteenth century, belonging to the authors’ private collections. The samples consisted of four books printed in Romania and five printed in France. The analytical characterization was performed using optical microscopy, thermal analysis, spectroscopic methods (X-ray fluorescence, X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, Fourier transform infrared spectroscopy), as well as by the evaluation of the degree of polymerization and the color change. The analyses were chosen in order to be either non-destructive or, at least, micro-destructive. The fungal loading determination was performed by plating the samples on the potato dextrose agar and Sabouraud with chloramphenicol agar media, for 28 days, followed by macroscopically and microscopically identification of mold species. The present study offers a complex methodology regarding the use of non- or micro-invasive techniques for evaluating the composition, state of degradation and potential risks related to microorganism colonization of paper artifacts. 相似文献
104.
Sorin G. Gal 《Advances in Applied Clifford Algebras》2000,10(1):91-106
Based on idens in the classical complex case, in this note we present some possible ways of extension of the classical geometric
function theory to functions of quaternlonic variables. An univalence result is obtained and certain kinds of starlikeness
and of convexity are studied. 相似文献
105.
106.
Barbara Laïk Diane Ung Amaël Caillard Costel Sorin Cojocaru Didier Pribat Jean-Pierre Pereira-Ramos 《Journal of Solid State Electrochemistry》2010,14(10):1835-1839
The electrochemical and structural responses of silicon nanowires deposited by chemical vapor deposition are investigated.
Transmission electron microscopy and X-ray diffraction experiments show the electrochemical lithiation of SiNWs is not a quantitative
process in good agreement with cycling experiments performed as a function of cycling limits. The SiNWs are not deeply lithiated
as revealed by TEM micrographs. Our results suggest the existence of two well-defined lithiation steps, first at ∼0.2 V into
amorphous silicon and then into crystalline silicon at ∼0.1 V. Cycling SiNWs above 100 mV avoid the lithiation of c-Si which
preserves the silicon 3-D architecture and results in good cycling performances. A stable capacity value of ∼500 mAh g−1 is achieved over at least 50 cycles. 相似文献
107.
Sorin Dumitrescu 《Comptes Rendus Mathematique》2009,347(19-20):1183-1187
We classify complex compact parallelizable manifolds which admit flat torsion free holomorphic affine connections. We exhibit complex compact manifolds admitting holomorphic affine connections, but no flat torsion free holomorphic affine connections. To cite this article: S. Dumitrescu, C. R. Acad. Sci. Paris, Ser. I 347 (2009). 相似文献
108.
We present a simple method for determining the exact noise power spectra and related statistical properties for linear chemical reaction networks. The method is applied to reaction networks which are representative of biochemical processes such as gene expression. We find, for example, that a post-translational modification reaction can reduce the noise associated with gene expression. Our results also indicate how to coarse grain networks by the elimination of fast reactions. In this context we have discovered a breakdown of the sum rule which relates the noise power spectrum to the total noise. The breakdown can be quantified by a sum rule deficit, which is found to be universal, and can be attributed to the high-frequency noise in the fast reactions. 相似文献
109.
Some rigidity results for non-commutative Bernoulli shifts 总被引:3,自引:0,他引:3
We introduce the outer conjugacy invariants , for cocycle actions σ of discrete groups G on type II1 factors N, as the set of real numbers t>0 for which the amplification σt of σ can be perturbed to an action, respectively, to a weakly mixing action. We calculate explicitly and the fundamental group of σ, , in the case G has infinite normal subgroups with the relative property (T) (e.g., when G itself has the property (T) of Kazhdan) and σ is an action of G on the hyperfinite II1 factor by Connes–Størmer Bernoulli shifts of weights {ti}i. Thus, and coincide with the multiplicative subgroup S of generated by the ratios {ti/tj}i,j, while if S={1} (i.e. when all weights are equal), and otherwise. In fact, we calculate all the “1-cohomology picture” of σt,t>0, and classify the actions (σ,G) in terms of their weights {ti}i. In particular, we show that any 1-cocycle for (σ,G) vanishes, modulo scalars, and that two such actions are cocycle conjugate iff they are conjugate. Also, any cocycle action obtained by reducing a Bernoulli action of a group G as above on to the algebra pNp, for p a projection in N, p≠0,1, cannot be perturbed to a genuine action. 相似文献
110.
Sorin Popa 《Inventiones Mathematicae》2006,165(2):409-451
We prove that any isomorphism θ:M0≃M of group measure space II1 factors,
,
, with G0 an ICC group containing an infinite normal subgroup with the relative property (T) of Kazhdan-Margulis (i.e. G0w-rigid) and σ a Bernoulli action of some ICC group G, essentially comes from an isomorphism of probability spaces which conjugates
the actions with respect to some identification G0≃G. Moreover, any isomorphism θ of M0 onto a “corner” pMp of M, for p∈M an idempotent, forces p=1. In particular, all group measure space factors associated with Bernoulli actions of w-rigid ICC groups have trivial fundamental
group and any isomorphism of such factors comes from an isomorphism of the corresponding groups. This settles a “group measure
space version” of Connes rigidity conjecture, shown in fact to hold true in a greater generality than just for ICC property
(T) groups. We apply these results to ergodic theory, establishing new strong rigidity and superrigidity results for orbit
equivalence relations. 相似文献