共查询到10条相似文献,搜索用时 147 毫秒
1.
Te Li YongQiang Ning ErJuan Hao JinJiang Cui Yan Zhang GuangYu Liu Li Qin Yun Liu LiJun Wang DaFu Cui ZuYan Xu 《中国科学F辑(英文版)》2009,52(7):1266-1271
According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of
the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width
and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed with
Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consists of 30 pairs
P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02 μm and the uniformity
doping concentration is 2.5×1018cm−3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concentration
is 2×1018cm−3. Its reflectivity is 99.3%. The I–V curve shows that the series resistance of the device is about 0.05 Ω. According to the theory of DBR, with the P-type DBR
as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure
with various graded region widths and doping densities. The width and doping density of graded region are decided through
a comparative study. The P-type DBR of 980 nm VCSELs is designed, with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consist of 30 pairs
P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02 μm and the uniformity
doping concentration is 2.5×1018cm−3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concentration
is 2×1018cm−3. Its reflectivity is 99.3%. The I–V curve shows that the series resistance of the device is about 0.05 Ω.
Supported partially by the National Natural Science Foundation of China (Grant Nos. 60636020, 60676034, 60577003, 60706007) 相似文献
2.
R. Murillo M. H. Siekman T. Bolhuis L. Abelmann J. C. Lodder 《Microsystem Technologies》2007,13(2):177-180
The thermal dependence and distribution of the switching fields of arrays of magnetic Co50Ni50/Pt nanodots has been studied. These dots, with a diameter of 90 nm, are arranged in a hexagonal pattern with a periodicity of 300 nm. Field-dependent magnetic force microscopy was used to measure the switching field distribution of the array, which was found to range from 80 to 192 kA/m, a value which is confirmed by vibrating sample magnetometer measurements. Additionally, the temperature dependence on the collective behaviour of the switching fields of the array has been investigated. The energy barrier at zero field was estimated to have a value in between 1.8×10−19 and 2.1×10−19 J. Combining this value with the effective anisotropy determined by torque measurements, the switching volume can be estimated to lie in between 1.2×103 and 1.4×103 nm3. 相似文献
3.
Y. Boiko 《Optical Memory & Neural Networks》2008,17(1):30-36
Volume hologram recording is implemented experimentally in the bulk of diarylethene dyedoped polymeric host-guest material.
A wide range of reciprocity for holographic imaging is demonstrated, ranging from as low as 0.55 mW/cm2 up to more than 200 mW/cm2. At a dye concentration of 2 × 10−3 M and spatial frequency of 2000 mm−1, refractive index modulations Δn of 2 × 10−5 at λ = 514.5 nm and 1 × 10−5 at λ = 830 nm were attained. Increasing the dye concentration to 3.8 × 10−2 M resulted in higher Δn values of 3.8 × 10−4 at λ = 514.5 nm and 2.1 × 10−4 at λ = 830 nm. The high fatigue resistance of the dye allows multiple record/erase cycles without degradation. The thermal
stability of the dye allows for durability of the recording material at temperatures above 115°C. At temperatures above 57°C,
the hologram is found to exhibit thermal degradation at a rate far exceeding that caused by thermochromism. It is suggested
that diffusion of the dye in the polymer matrix is responsible for the increased sensitivity of the hologram to elevated temperatures,
which may be applied in reusable holographic thermal sensors.
The text was submitted by the author in English. 相似文献
4.
Christian Glaßer Katrin Herr Christian Reitwießner Stephen Travers Matthias Waldherr 《Theory of Computing Systems》2010,46(1):80-103
We investigate the complexity of equivalence problems for {∪,∩,−,+,×}-circuits computing sets of natural numbers. These problems were first introduced by Stockmeyer and Meyer (1973). We
continue this line of research and give a systematic characterization of the complexity of equivalence problems over sets
of natural numbers. Our work shows that equivalence problems capture a wide range of complexity classes like NL, C
=
L, P,Π2P, PSPACE, NEXP, and beyond. McKenzie and Wagner (2003) studied related membership problems for circuits over sets of natural numbers. Our results also have consequences for these membership problems: We provide an
improved upper bound for the case of {∪,∩,−,+,×}-circuits. 相似文献
5.
This paper describes the development of metallic bipolar plate fabrication using micro-electroforming process for mini-DMFC
(direct methanol fuel cell) stacks. Ultraviolet (UV) lithography was used to define micro-fluidic channels using a photomask
and exposure process. Micro-fluidic channels mold with 300 μm thick and 500 μm wide were firstly fabricated in a negative
photoresist onto a stainless steel plate. Copper micro-electroforming was used to replicate the micro-fluidic channels mold.
Following by sputtering silver (Ag) with 1.2 μm thick, the metallic bipolar plates were completed. The silver layer is used
for corrosive resistance. The completed mini-DMFC stack is a 3.5 × 3.5 cm2 fuel cell stack including a 1.5 × 1.5 cm2 MEA (membrane electrode assembly). Several MEAs were assembly into mini-DMFC stacks using the completed metallic bipolar
plates. All test results showed the metallic bipolar plates suitable for mini-DMFC stacks. The maximum output power density
is 9.3 mW/cm2 and current density is 100 mA/cm2 when using 8 vol.% methanol as fuel and operated at temperature 30°C. The output power result is similar to other reports
by using conventional graphite bipolar plates. However, conventional graphite bipolar plates have certain difficulty to be
machined to such micro-fluidic channels. The proposed micro-electroforming metallic bipolar plates are feasible to miniaturize
DMFC stacks for further portable 3C applications. 相似文献
6.
Goran T. Vladisavljevi? Isao Kobayashi Mitsutoshi Nakajima 《Microfluidics and nanofluidics》2011,10(6):1199-1209
Uniformly sized droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and n-tetradecane with a Sauter mean diameter of d
3,2 = 26–35 μm and a distribution span of 0.21–0.25 have been produced at high throughputs using a 24 × 24 mm silicon microchannel
plate consisting of 23,348 asymmetric channels fabricated by photolithography and deep reactive ion etching. Each channel
consisted of a 10-μm diameter straight-through micro-hole with a length of 70 μm and a 50 × 10 μm micro-slot with a depth
of 30 μm at the outlet of each channel. The maximum dispersed phase flux for monodisperse emulsion generation increased with
decreasing dispersed phase viscosity and ranged from over 120 L m−2 h−1 for soybean oil to 2,700 L m−2 h−1 for n-tetradecane. The droplet generation frequency showed significant channel to channel variations and increased with decreasing
viscosity of the dispersed phase. For n-tetradecane, the maximum mean droplet generation frequency was 250 Hz per single active channel, corresponding to the overall
throughput in the device of 3.2 million droplets per second. The proportion of active channels at high throughputs approached
100% for soybean oil and MCT oil, and 50% for n-tetradecane. The agreement between the experimental and CFD (Computational Fluid Dynamics) results was excellent for soybean
oil and the poorest for n-tetradecane. 相似文献
7.
S. M. Sohel Murshed Say Hwa Tan Nam Trung Nguyen Teck Neng Wong Levent Yobas 《Microfluidics and nanofluidics》2009,6(2):253-259
This paper reports experimental investigations on the droplet formation and size manipulation of deionized water (DIW) and
nanofluids in a microfluidic T-junction at different temperatures. Investigations of the effect of microchannel depths on
the droplet formation process showed that the smaller the depth of the channel the larger the increase of droplet size with
temperature. Sample nanofluids were prepared by dispersing 0.1 volume percentage of titanium dioxide (TiO2) nanoparticles of 15 nm and 10 nm × 40 nm in DIW for their droplet formation experiments. The heater temperature also affects
the droplet formation process. Present results demonstrate that nanofluids exhibit different characteristics in droplet formation
with the temperature. Addition of spherical-shaped TiO2 (15 nm) nanoparticles in DIW results in much smaller droplet size compared to the cylindrical-shaped TiO2 (10 nm × 40 nm) nanoparticles. Besides changing the interfacial properties of based fluid, nanoparticles can influence the
droplet formation of nanofluids by introducing interfacial slip at the interface. Other than nanofluid with cylindrical-shaped
nanoparticles, the droplet size was found to increase with increasing temperature. 相似文献
8.
Stefan Palzer Emmanuel Moretton Francisco Hernandez Ramirez Albert Romano-Rodriguez Jürgen Wöllenstein 《Microsystem Technologies》2008,14(4-5):645-651
Functional micro- and nanosized metal oxide thin film structures are very promising candidate for future gas-sensors. Their
reduced size offers an increased surface to volume ratio thus improving sensitivity and sensor performance. Whilst most experimental
nanostructures are produced using a bottom-up approach, a top-down sputtering technique for structuring nano-sized gas sensitive
metal oxide areas is presented in this letter. Oxidised silicon wafers were used as substrates. The silicon dioxide film of
1 μm thickness was prepared by thermal oxidation in order to insulate the gas sensing elements from the substrate. The sensor
chips had an overall size of (1.5 × 1.5) mm2 onto which a Ta/Pt film (20/200 nm thickness) was deposited and patterned to act as electrodes, heater and temperature sensor.
In a second step micro-scaled tin dioxide layers (60 nm thick, 5 μm width) were deposited by sputtering techniques and photolithographical
patterning between the platinum micro-electrodes (4 μm gap). Finally, the width of the stripes was reduced using focused ion
beam technology to obtain the desired size and structure. This enables the control of the dimensions of the structures down
to the resolution limit of the FIB-system which is about 10 nm. The structural and electrical characterisation of the sensors
and their responses during exposure to several test gases including O2, CO, NO2 and H2O are presented as well. 相似文献
9.
In this paper, we consider the implementation of a product c=A
b, where A is N
1×N
3 band matrix with bandwidth ω and b is a vector of size N
3×1, on bidirectional and unidirectional linear systolic arrays (BLSA and ULSA, respectively). We distinguish the cases when
the matrix bandwidth ω is 1≤ω≤N
3 and N
3≤ω≤N
1+N
3−1. A modification of the systolic array synthesis procedure based on data dependencies and space-time transformations of
data dependency graph is proposed. The modification enables obtaining both BLSA and ULSA with an optimal number of processing
elements (PEs) regardless of the matrix bandwidth. The execution time of the synthesized arrays has been minimized. We derive
explicit formulas for the synthesis of these arrays. The performances of the designed arrays are discussed and compared to
the performances of the arrays obtained by the standard design procedure. 相似文献
10.
It is shown, that tubuline informative biomacromolecule has two-well structure potential energy relief for an electron responsible
for the switching between conformations of molecules. Therefore the system of conformational excitation in informative biomacromolecules
must be described as a two-level quantum system. The energy of the basic electron state ɛ+ = 1.2 eV and frequency of electron tunneling ω = (6 × 1013–6 × 1011) s−1 in a tubuline molecule were calculated. The possibility of data recording by directly collapse of wave function in a two-level
cell was shown, thus coherence of quantum state collapses only.
The article is published in the original. 相似文献