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排序方式: 共有291条查询结果,搜索用时 15 毫秒
11.
Molecular spiders are nanoscale walkers made with DNA enzyme legs attached to a common body. They move over a surface of DNA substrates, cleaving them and leaving behind product DNA strands, which they are able to revisit. Simple one-dimensional models of spider motion show significant superdiffusive motion when the leg-substrate bindings are longer-lived than the leg-product bindings. This gives the spiders potential as a faster-than-diffusion transport mechanism. However, analysis shows that single-spider motion eventually decays into an ordinary diffusive motion, owing to the ever increasing size of the region of cleaved products. Inspired by cooperative behavior of natural molecular walkers, we propose a symmetric exclusion process model for multiple walkers interacting as they move over a one-dimensional lattice. We show that when walkers are sequentially released from the origin, the collective effect is to prevent the leading walkers from moving too far backwards. Hence, there is an effective outward pressure on the leading walkers that keeps them moving superdiffusively for longer times, despite the growth of the product region. Multi-spider systems move faster and farther than single spiders or systems with multiple simple random walkers. 相似文献
12.
Ivana Tomaz Luna Maslov Domagoj Stupić Darko Preiner Danijela Ašperger Jasminka Karoglan Kontić 《分离科学与技术》2016,51(2):255-268
Grape skin contains large amounts of different flavonoids so it can be used for their recovery. Optimization of enzyme-assisted extraction of flavonoids was conducted using oenological enzyme preparations with respect to enzyme dosage, temperature, extraction time, pH, and enzyme preparation. Optimal conditions were obtained using enzyme preparation Lallzyme EX-V, at the temperature of 45°C, time of 3 h, pH 2.0, and enzyme dosage of 10.52 mg/g. The new optimized extraction method is less expensive, simple, accurate, and selective for the recovery of simple flavonoids. It is based on an environmentally-friendly extraction solvent which may provide a valuable alternative to conventional methods. 相似文献
13.
Petra Jenus Darja Lisjak Danjela Kuscer Darko Makovec Miha Drofenik 《Journal of the American Ceramic Society》2014,97(1):74-80
Magneto‐electric (ME) ceramic composites of cobalt ferrite (CoF) and lead zirconate titanate (PZT) were prepared by mechanical mixing of the constituent powders followed by cosintering. The cosintering conditions for nano‐sized CoF and submicrometer‐sized PZT powders were studied in detail. It was found that the CoF powder needs to be presintered at 700°C for 2 h to minimize the differences in the sintering kinetics of the constituent powders. Despite the low cosintering temperatures (900°C–1000°C) the interdiffusion of the cations from both phases was confirmed with energy‐dispersive X‐ray analysis and X‐ray diffraction. Efforts were made to optimize the cosintering conditions to prepare dense ceramic ME composites, which showed the converse ME effect. 相似文献
14.
Hydrothermal Synthesis of Ba-Hexaferrite Nanoparticles 总被引:1,自引:0,他引:1
Miha Drofenik Matja Kristl rej nidari Darko Hanel Darja Lisjak 《Journal of the American Ceramic Society》2007,90(7):2057-2061
Barium hexaferrite BaFe12 O19 nanoparticles with a single-domain size were synthesized using a controlled hydrothermal process involving the LaMer–Dinger principle and the Ostwald ripening mechanism. Nanocrystalline particles of BaFe12 O19 were obtained when the molar ratio of the precursor composition Ba(OH)2 ·8H2 O/γ-Fe2 O3 was 0.3 and the concentration of the suspension was about 1 wt%. The as-synthesized crystalline BaFe12 O19 platelets approximately 50 nm in length and 5 nm in thickness exhibited a saturation magnetization of 40 Am2 /kg. 相似文献
15.
M.S. Callén M.T. de la Cruz S. Marinov R. Murillo M. Stefanova A.M. Mastral 《Fuel Processing Technology》2007
The electron beam technology (EBT), proven treatment for SO2 and NOx removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO2 and NOx, studying EBT effects from an organic environmental point of view. 相似文献
16.
We develop a method for determinating the relative positions of the lidar transmitter (LT) and the local oscillator (LO) frequencies in Doppler CO(2) lidars. It uses the weak spectral asymmetry of TEA CO(2) laser pulses, defined by a number of secondary peaks at the high-frequency side of the main spectrum peak. Depending on the sign of the beat frequency, these peaks may appear in the demodulated spectrum at either the high- or the low-frequency side. Each laser pulse spectrum is compared with reference spectra with two types of asymmetry, with the cross-correlation coefficients used as criteria. The performance of the method at different values of signal-to-noise ratio is analyzed numerically. The method is also applied to raw data from the lidar reference channel and demonstrates good performance at noise levels lower than the secondary peaks in the pulse spectrum or at a signal-to-noise ratio of >/=20 dB. Application of the pulse spectrum asymmetry for lidar frequency stabilization is analyzed. Lidar operation without frequency stabilization is considered as well. The method offers a simple Doppler lidar hardware for the creation of low-cost coherent lidars, velocimeters-rangefinders, etc. 相似文献
17.
18.
Miko Marinov 《Thin solid films》1977,46(3):267-274
The influence of ion bombardment on the initial stages of silver deposition onto amorphous substrates was investigated. Pronounced adatom-depleted zones arise around larger crystallites, and coalescence begins earlier in the deposition process. A defined crystal orientation appears from the beginning of the condensation. The results are explained using the assumption of enhanced surface mobilities of both adatoms and crystallites. The possibility of application of ion bombardment for surface decoration is qualitatively investigates and discussed. 相似文献
19.
Marko Hrovat Darko Belavič Zoran Samardžija Janez Holc 《Journal of Materials Science》2001,36(11):2679-2689
Some commercial thick film resistors with sheet resistivities from 1 kohm/sq. up to 1 Mohm/sq. were evaluated for strain gauge applications. Temperature coefficients of resistivity, noise indices and gauge factors (GFs) were measured. For the same resistor series GFs and noise indices increase with increasing sheet resistivity. However, both GFs and noise indices are different for resistors with the same nominal sheet resistivity but from different resistor series. The results indicated that the microstructure rather than the different chemical composition of the conductive phase in thick film resistors is the primary reason for the different gauge factors. 相似文献
20.
Darko B. Mitić Goran S. Jovanović Mile K. Stojčev Dragan S. Antić 《International Journal of Electronics》2013,100(3):362-375
Phase-synchronisers have many applications in VLSI circuit designs. They are used in CMOS RF circuits including phase (de)modulators, phase recovery circuits, multiphase synthesis, etc. In this article, a phase-synchroniser based on gm-C all-pass filter chain with sliding mode control is presented. The filter chain provides good controllable delay characteristics over the full range of phase and frequency regulation, without deterioration of input signal amplitude and waveform, while the sliding mode control enables us to achieve fast and predetermined finite locking time. IHP 0.25 µm SiGe BiCMOS technology has been used in design and verification processes. The circuit operates in the frequency range from 33 MHz up to 150 MHz. Simulation results indicate that it is possible to achieve very fast synchronisation time period, which is approximately four time intervals of the input signal during normal operation, and 20 time intervals during power-on. 相似文献