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171.
A micromachined hot-film anemometer on a high-pressure stable substrate is demonstrated to be suitable for "on-board" measurements of various injection quantities, which are needed in modern direct injection systems for optimum performance of diesel, as well as gasoline, engines. To estimate the velocity profile in the injection nozzle during the injection pulse, two-dimensional finite element method calculations are performed. To consider the substrate effect on the performance of the thermal injection rate sensor, an IR imaging system is used to determine the heat loss via the robust glass ceramic substrate up to thin-film temperatures of 450 K in air. Using both the numerical and the experimental results, the temperature sensitivity and velocity sensitivity of hot-film anemometers, operated in the constant current mode in a fuel atmosphere, can be modeled analytically. Finally, an overview about the results of the latest injection rate measurements at fuel pressures up to 60 MPa and drive pulse lengths between 0.2-5 ms is given. Comparing these signals of the thermal thin-film sensor to injection volume measurements, performed with an injection amount indicator at a high-pressure hydraulic test bench, the mass flow measurements can be calibrated. One empiric parameter is necessary, which is the exponent of a power law dependence on the maximum sensor amplitude during injection. 相似文献
172.
In this study, a new surfactant-solvent system was described for the preparation of periodic stripe patterns of zeolite A on solid substrates. The evaporation induced self-assembly of zeolite A particles was due to the stick-slip dynamics of the three-phase contact line of the colloid solutions in acetone containing 10% (v/v) poly(dimethylsiloxane) (PDMS) fluid (2 cst.). In order to investigate the possible effects of particle size and the particle concentration on the stick-slip dynamics, three types of zeolite A samples with different particle sizes (zeolite A-I: 250-500 nm, zeolite A-II: 100-250 nm and zeolite A-III: 0-100 nm) were utilized to prepare 0.007-0.06% (w/v) colloidal dispersions. Zeolite A micropatterns were self-assembled on the surface of glass, high density polyethylene (HDPE) and poly(tetrafluoroethylene) (PTFE) substrates, which were placed vertically inside the colloid solutions and held against the wall of the cylindrical vial during the evaporation of acetone. The stripe patterns of zeolite A particles were analyzed with field emission scanning electron microscope (FE-SEM) and optical microscope. The widths of microstripes and the distance between the stripes were found as 2-20 μm and 40-60 μm respectively depending on the particle concentration. By using the stick-slip dynamics of colloids, the linear micropatterns of zeolite A nanocrystals were prepared with low cost and low energy. 相似文献
173.
Raab W. Bruels N. Hachmann U. Harnisch J. Ramacher U. Sauer C. Techmer A. 《Design & Test of Computers, IEEE》2003,20(1):8-15
New generations of automobiles will include driver assistance systems requiring powerful, low-cost processors to handle video/camera applications and to enable fast, convenient application development. Shrinking feature sizes on processors already in development will bring substantial increases in system speed and functionality. 相似文献
174.
M. Hädrich N. Lorenz H. Metzner U. Reislöhner S. Mack M. Gossla W. Witthuhn 《Thin solid films》2007,515(15):5804-5807
In this paper, we describe our new baseline for CSS-CdTe-CdS solar cells on 10 × 10 cm2 substrates. The deposition of the p-n junction and all the following steps were performed at the Institut für Festkörperphysik (IFK) in Jena. Using the new baseline, we are already able to produce solar cells with similar properties as commercial ones. In the batch type process, all manufacturing steps can be investigated separately. We employ Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and external quantum efficiency (EQE) measurements to characterise the structure of the bulk materials and interfaces. It is demonstrated that by RBS the front contact becomes accessible for thinned CdTe films. At the back contact, RBS spectra show a tellurium accumulation which is due to etching. This tellurium rich layer is confirmed by XRD with Rietveld refinement. The intermixing at the CdS-CdTe interface caused by the activation step is quantified by a bandgap determination based on EQE measurements. From the bandgap energy of the CdTe1 − xSx compound, we calculated the sulphur fraction x at the interface. XRD measurements imply that the activation step induces a (111) texture in CdTe. With regard to an improved manufacturing process, our cells are compared to industrial cells produced by Antec Solar Energy. 相似文献
175.
T. Erb U. Zhokhavets G. Gobsch S. Raleva B. Stühn P. Schilinsky C. Waldauf C.J. Brabec 《Advanced functional materials》2005,15(7):1193-1196
We investigate thin poly(3‐hexylthiophene‐2,5‐diyl)/[6,6]‐phenyl C61 butyric acid methyl ester (P3HT/PCBM) films, which are widely used as active layers in plastic solar cells. Their structural properties are studied by grazing‐incidence X‐ray diffraction (XRD). The size and the orientation of crystalline P3HT nanodomains within the films are determined. PCBM crystallites are not detected in thin films by XRD. Upon annealing, the P3HT crystallinity increases, leading to an increase in the optical absorption and spectral photocurrent in the low‐photon‐energy region. As a consequence, the efficiency of P3HT/PCBM solar cells is significantly increased. A direct relation between efficiency and P3HT crystallinity is demonstrated. 相似文献
176.
Two-step channel selection-a novel technique for reconfigurable multistandard transceiver front-ends
Pui-In Mak Seng-Pan U Martins R.P. 《IEEE transactions on circuits and systems. I, Regular papers》2005,52(7):1302-1315
This paper starts with a review of the prevailing channel-selection techniques utilized so far in the design of wireless transceiver analog front-ends before describing a novel two-step channel-selection technique, which handles the traditionally unwanted image, in radio frequency-to-intermediate frequency (RF-to-IF) or IF-to-RF frequency conversion, as a useful adjacent channel of the desired one, and selects deliberately either of them from IF to baseband (or baseband to IF). Thus, one more channel-selection possibility is created for both low-IF receivers and two-step-up transmitters. The consequential benefits of introducing channel selection at IF consist of two. First, many design specifications (such as phase noise and settling time) of the RF frequency synthesizer and local oscillator can be substantially relaxed. Second, a low-IF/zero-IF reconfigurable receiver and a direct-up/two-step-up reconfigurable transmitter can be synthesized to match better with narrowband-wideband-mixed multistandard systems. The operating principles of such architectures are presented in easy-to-understand complex-signal spectral-flow illustrations, and their practicability is demonstrated in the design of a Bluetooth/IEEE 802.11FH/HomeRF multistandard receiver. SPECTRE simulation results validate the reconfigurable functionalities mainly implemented by a triple-mode channel-select filter and a multifunctional sampling-mixer scheme. 相似文献
177.
The effect of side chain length of π-conjugated poly(9,9-dialkylfluorene)s has been studied in semi-dilute (10 mg/mL) toluene solutions using small-angle neutron scattering (SANS) and 1H and 2H NMR spectroscopies. Under these conditions, SANS data indicate that poly(9,9-dinonylfluorene) and poly(9,9-dioctylfluorene) are dissolved down to the molecule level and appear as elongated one-dimensional chains (length >20-30 nm). In contrast, the shorter side chain polymers exhibit a self-association so that poly(9,9-diheptylfluorene) forms thin sheet-like (∼1 nm) and poly(9,9-dihexylfluorene) thin (∼1 nm) and thick sheet-like (>6 nm) aggregates. 1H NMR data, together with the density functional theory (DFT) calculations, however, show that this occurs without changes in the conformation of the polymer backbone. 相似文献
178.
U. Bodenhofer 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2003,7(4):220-227
This paper is devoted to a general concept of openness and closedness with respect to arbitrary fuzzy relations – along with
appropriate opening and closure operators. It is shown that the proposed framework unifies existing concepts, in particular,
the one for fuzzy preorderings as well as the triangular norm-based approach to fuzzy mathematical morphology.
The author acknowledges support of the K
plus Competence Center Program which is funded by the Austrian Government, the Province of Upper Austria, and the Chamber of Commerce
of Upper Austria. 相似文献
179.
Negative refraction is a wave phenomenon beyond geometrical optics - it depends on the way waves behave when their phase velocity reaches a zero. Various forms of linear wave processes in media can be concisely described in one wave equation that is inspired by the interpretation of a medium as an effective space-time geometry. Depending on the conformal factor of the effective metric, the waves may show positive or negative refraction. For electromagnetic waves in two-dimensional dielectrics the conformal factor corresponds to the impedance. 相似文献
180.