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排序方式: 共有174条查询结果,搜索用时 125 毫秒
1.
Summary ESCA is used to characterize ion beam irradiated P(p-ClPhMA)-samples. The results show a chlorine abstraction. The experimental
findings are in accordance with a recently proposed model for a crosslinking mechanism of halogenated aromatic polymers. 相似文献
2.
Lampe L.H.-J. Schober R. Fischer R.F.H. 《Wireless Communications, IEEE Transactions on》2003,2(3):582-590
In this paper, powerful coding techniques for differential space-time modulation (DSTM) over Rayleigh flat fading channels and noncoherent detection without channel state information at the receiver are investigated. In particular, multilevel coding, bit-interleaved coded modulation, and so-called hybrid coded modulation (HCM) are devised and compared. For improved noncoherent reception multiple-symbol differential detection (MSDD) is adapted to DSTM. In order to reduce the computational effort required for MSDD, a low-complexity version of MSDD is applied. Evaluating the ergodic channel capacity for the different schemes as appropriate performance measure, HCM with simplified MSDD is shown to offer a favorable tradeoff between complexity and achievable power efficiency. Simulation results employing turbo codes in properly designed HCM schemes confirm the predictions from information theory. 相似文献
3.
In polynomial form, necessary and sufficient conditions are given that provide for existence of a discrete controller stabilizing a multivariable sampled-data system. 相似文献
4.
This paper considers the L 2-optimization problem for a standard sampled-data system with generalized hold of an arbitrary order. The original problem is reduced to the minimization problem of a degenerate quadratic functional, where solution appears nonunique. And finally, the authors propose a polynomial procedure for constructing a set of optimal discrete causal controllers and establish some relevant properties of L 2-optimal systems in the context of applications. 相似文献
5.
Sinharoy S Buhay H Burke MG Lampe DR Pollak TM 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1991,38(6):663-671
The growth of ferroelectric BaMgF(4) thin films on Si(100), sapphire, and other substrates under ultrahigh vacuum (UHV) conditions is reported. Microstructural characterization of the films using transmission electron microscopy (TEM) revealed that they were oriented crystalline films, although not epitaxial. Ferroelectric hysteresis measurements yielded spontaneous polarization and coercivity values of almost 1.0 muC/cm(2) and 160 kV/cm, respectively. The discrepancy with the bulk ferroelectric values were attributed to the electrical contacts, impurities in the film, and lack of polar axis orientation. Preliminary capacitance-voltage (C-V) hysteresis measurements on a 480-nm-thick BaMgF(4) film yielded a 10.8-V threshold shift (memory window) in response to a +/-10-V programming voltage for a MIS gate structure similar to that of the ferroelectric memory field-effect transistor (FEMFET). 相似文献
6.
Daniel S. Camarda Matthew J. Lampe Alan J. Lesser Philippe Desbois Klaus Stoll Claus Gabriel Rupert Konradi 《应用聚合物科学杂志》2021,138(41):51203
The creation of graft copolymers by selectively grafting a second polymer to the amorphous fraction of a semi-crystalline polymer in supercritical CO2 is demonstrated herein. The graft copolymer is synthesized by free radical polymerization of a vinyl monomer within the semi-crystalline polymer below its melt temperature. Such conditions afford selective grafting on the amorphous regions (block “B”) while leaving the crystalline domains (block “A”) unmodified. Accordingly, unique A-B, A-B-A, A-B-A-B-A, and so forth. block structures are formed. In this work, styrene is polymerized within polyamide 6, polyethylene terephthalate, and isotactic polypropylene. Purification of these material is performed to remove the un-grafted homopolymer, allowing for determination of the graft yield, the portion of polymer which covalently bonds to the semi-crystalline matrix. Grafting yields achieved in polyamide 6, polyethylene terephthalate, and isotactic polypropylene were 98%, 59%, and 15%, respectively. Property enhancements were observed upon further characterization of polystyrene-polyamide 6 copolymers, including high glass transition temperatures, the ability to be remelted, and tunable grafting molecular weight. Additionally, hydrophobicity is controlled by varying polystyrene composition. The remarkable range of accessed properties demonstrates this as a potential route to upcycling plastics. 相似文献
7.
Peter Frolkovič Michael Lampe Gabriel Wittum 《Computing and Visualization in Science》2016,18(1):17-29
When a realistic modelling of radioactive contaminant transport in flowing groundwater is required, very large systems of coupled partial and ordinary differential equations can arise that have to be solved numerically. For that purpose, the software package \(r^3t\) is developed in which several advanced numerical methods are implemented to solve such models efficiently and accurately. Using software tools of \(r^3t\) one can treat successfully nontrivial mathematical problems like advection-dominated system with different retardation of transport for each component and with nonlinear Freundlich sorption and/or precipitation. Additionally, long time simulations on complex 3D geological domains using unstructured grids can be realized. In this paper we introduce and summarize the most important and novel features of numerical simulation for radioactive contaminant transport in porous media when using \(r^3t\). 相似文献
8.
Viehweg P Heinig A Lampe D Buchmann J Heywang-Köbrunner SH 《Magma (New York, N.Y.)》1998,7(3):141-152
Purpose The aim of this study was to assess the value of contrast-enhanced (c.-e.) MRI in the follow-up of patients with conservatively
treated breast cancer since detection and exclusion of malignancy may interfere significantly with posttherapeutic changes
within the treated breast.
Material and methods A total of 207 patients with a history of limited surgery and radiation therapy underwent MR imaging, 40 patients were examined
0–12 months and 167 patients were examined later than 12 months after radiotherapy. Suspicious or indeterminate findings were
suggested by clinical examination or conventional imaging in 80 studies. In 127 women, MRI was performed within breast tissue
that was difficult to assess due to scarring or dense breast tissue.
Results Recurrent carcinoma was confirmed in 27 patients by surgical biopsy. All 27 carcinomas, except for one with a slow signal
increase, demonstrated early rise of signal intensity on dynamic T1-weighted contrast enhanced images. During the first year
after therapy, the diagnostic accuracy could not be improved by additional use of c.-e. MRI. Differentiation between posttherapeutic
changes and recurrent carcinoma was frequently not possible because of strong and sometimes early and ill-circumscribed enhancement.
Later than 12 months after therapy enhancement decreased significantly, thus the false positive calls could be reduced from
49 (conventional imaging) to 12 (conventional imaging plus MRI). A total of 12 of 26 recurrences and multifocality in 4/5
cases were diagnosed by MR imaging alone at this time interval.
Conclusion In the first year after therapy, c.-e. MRI is only indicated in selected cases. The results later than 12 months emphasize
that c.-e. MRI may contribute significant additional information. It allows better distinction of posttherapeutic fibrosis
from recurrent carcinoma and proved to be able to detect recurrent disease more sensitive and at an earlier stage. 相似文献
9.
B. P. Lampe E. N. Rosenwasser 《Journal of Computer and Systems Sciences International》2013,52(4):542-570
A frequency-polynomial H 2-optimization method for sampled-data systems with generalized hold functions and delay is proposed, which is based on the application of the concept of a parametric transfer matrix. A number of general properties of H 2-optimal systems that must be taken into account in solving practical design problems are established. 相似文献
10.
Standard multivariable sampled-data system with generalized hold of arbitrary order is investigated. An algorithm for design
of H
2-optimal digital controller is presented. Some qualitative properties of the H
2-optimal system are described, which are important in applications. 相似文献