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991.
A Colorimetric Hydrocarbon Sensor Employing a Swelling‐Induced Mechanochromic Polydiacetylene 下载免费PDF全文
Dong‐Hoon Park Jaesung Hong In Sung Park Chan Woo Lee Jong‐Man Kim 《Advanced functional materials》2014,24(33):5186-5193
Exceptional challenges have confronted the rational design of colorimetric sensors for saturated aliphatic hydrocarbons (SAHCs). The main reasons for this difficulty are the extremely nonpolar nature of these targets and their lack of functional groups that can interact with probes. By taking advantage of a mechanochromic conjugated polydiacetylene (PDA) and the hydrocarbon‐induced swelling properties of polydimethylsiloxane (PDMS), a sensor film that enables simple, colorimetric differentiation between a variety of C5 to C14 aliphatic hydrocarbons is fabricated. The unprecedented PDA–PDMS composite sensor undergoes a blue‐to‐red colorimetric transition on a timescale that is dependent on the chain length of the hydrocarbon target. In addition, the development of the red color is directly proportional to the swelling ratio of the film. This straightforward approach enables naked‐eye differentiation between n‐pentane and n‐heptane. The versatility of the sensor system is demonstrated by using it for the colorimetric determination of kerosene in adulterated diesel oil. Finally, the observation that a PDA microcrystal in the film undergoes significant expansion and tearing in concert with a blue‐to‐red colorimetric transition during the swelling process provides direct evidence for the mechanism for the mechanochromic behavior of the PDA. 相似文献
992.
Transmission efficiency in radio channels can be considerably improved by using multiple transmit and receive antennas and employing a family of schemes called space-time (ST) coding. Both extended range and/or improved bandwidth efficiency can be achieved, compared with a radio link with a single transmit and receive antenna. Bit-interleaved coded modulation schemes give diversity gains on fading channels with higher order modulation constellations combined with conventional binary convolutional codes also for the case of a single transmit and receive antenna radio link. In this paper, we study a family of flexible bandwidth-efficient ST coding schemes which combine these two ideas in a narrowband flat-fading channel and single-carrier modems. We address receiver complexity for the case of a large number of transmit antennas and higher order modulation constellations. Especially, we focus on practical configurations, where the number of transmit antennas is greater than that of receive antennas. Simplified receivers using tentative decisions are proposed and evaluated by means of simulations. Tradeoffs between complexity reduction and performance loss are presented. We emphasize systems that are of particular interest in applications where the number of transmit antennas exceeds the number of receive antennas. A system with four transmit antennas with an eight-fold complexity reduction and a performance loss of about 1 dB is demonstrated 相似文献
993.
In this paper, we rigorously investigate the energy minimization problem for wireless packet networks with automatic repeat request (ARQ) capability. We first formulate the problem for the single-hop case under constrained packet delay and reliability and derive the necessary and sufficient condition for the optimal transmission power at each ARQ stage. We formulate a global rule of optimal transmission power control that achieves optimality regardless of the delay and reliability constraints. Then we extend it to encompass the multi-hop case by dividing the overall problem into two subproblems-energy determination for each ARQ stage and energy distribution among the constituent nodes. We show that the optimality condition established for the single-hop case is also applicable to solve the energy determination problem in the multi-hop case, rendering an optimal solution to the energy distribution problem. Numerical examples reveal that a significant amount of energy is saved by adopting the optimal transmission power and the performance gain is strongly correlated with the decreasing property of the frame error rate 相似文献
994.
Jong Pil Kim Woo Young Choi Jae Young Song Sang Wan Kim Jong Duk Lee Byung-Gook Park 《Electron Devices, IEEE Transactions on》2007,54(11):2969-2974
A novel asymmetric MOSFET with no lightly doped drain on the source side is simulated on bulk Si using a device simulator (SILVACO). To overcome the problems of the conventional asymmetric process, a novel asymmetric MOSFET using a mesa structure and a sidewall spacer gate is proposed, and it provides a self-alignment process, aggressive scaling, and better uniformity. First of all, we have compared the simulated characteristics of the asymmetric and symmetric MOSFETs. Basically, both asymmetric and symmetric MOSFETs have an n-type channel and the same physical parameters. Compared with the symmetric MOSFET, the asymmetric MOSFET shows better device performance. Moreover, we have successfully fabricated 50-nm asymmetric NMOSFETs based on simulation results and investigated its operation and characteristics. 相似文献
995.
S. Liu A. L. Briseno S. C. B. Mannsfeld W. You J. Locklin H. W. Lee Y. Xia Z. Bao 《Advanced functional materials》2007,17(15):2891-2896
A method of patterning large arrays of organic single crystals is reported. Using single‐walled carbon nanotube (SWNT) bundles as patterned templates, several organic semiconductor materials were successfully patterned, including p‐type pentacene, tetracene, sexiphenylene, and sexithiophene, as well as n‐type tetracyanoquinodimethane (TCNQ). This study suggests that the selective growth of crystals onto patterned carbon nanotubes is most likely due to the coarse topography of the SWNT bundles. Moreover, we observed that the crystals nucleated from SWNT bundles and grew onto SWNT bundles in a conformal fashion. The dependence of the number of crystals on the quantity of SWNT bundles is also discussed. The crystal growth can be directly applied onto transistor source‐drain electrodes and arrays of organic single‐crystal field effect transistors are demonstrated. The results demonstrate the potential of utilizing carbon nanotubes as nucleation templates for patterning a broad range of organic materials for applications in optoelectronics. 相似文献
996.
Protein extraction solutions such as aqueous solutions of sodium hydroxide (0.1 and 0.2 %), sodium lauryl sulfate (SLS, 1.2 %) containing sodium sulfite (0.12 %), and dodecylbenzene sulfonate (DoBS, 1.2 %) containing sodium sulfite (0.12 %) were compared in their protein removal efficiencies during isolation of starch from a rice flour (Ilpumbyo, a nonwaxy Korean rice variety). In addition, the pasting properties of the isolated starch was compared. More than 80 % of the flour protein was extracted in 1 h by stirring the dispersion (1:3, w/v) at room temperature. Repeating the extractions (1 or 2 h for each step) with fresh solution significantly increased the protein removal efficiency. When the extraction in 0.2 % NaOH was repeated four times (1 h for each step) at 25°C, the residual protein content in the isolated rice starch was 0.9 % (DB), equivalent to 86 % removal of the rice protein. Raising the extraction temperature slightly increased the protein solubility, but starch loss also became significant. Among the solutions, DoBS was most effective in removing rice protein whereas SLS was least. The residual protein content had a critical role in determining the pasting characteristics of the isolated starch, showing a negative correlation to the peak viscosity of the starch paste, but a positive correlation to the pasting temperature. 相似文献
997.
Quantitative x-ray diffraction topography techniques have been used to measure the residual strain magnitude and uniformity
of deposition for Mo and W sputtered films on Si(100) substrates. High sensitivity rocking curve measurements were able to
determine differential strains for films as thin as 2.5 nm; while Bragg angle contour mapping had similar sensitivity and
was also able to assess coating uniformity and stress distribution over areas covering a whole wafer. Measurements of strain
versus film thickness over a range of 2.5 nm to 80 nm showed that a critical thickness exists for maximum residual strain.
Growth beyond this range produces stress relaxation. This non-destructive type of analysis could be employed on a wide range
of film-substrate combinations. 相似文献
998.
Lee J.-C. Strojwas A.J. Schlesinger T.E. Milnes A.G. 《Electron Devices, IEEE Transactions on》1991,38(3):447-454
The characteristics of n-semi-insulating-n (n-si-n) structures that dictate the design rules for electrical isolation between active devices of GaAs integrated circuits fabricated on semi-insulating substrates are studied by one-dimensional and two-dimensional numerical simulations. It is found that the I -V characteristics of these structures are characterized by sharp current-rising regions which result from a potential barrier lowering effect caused by the punchthrough phenomenon. Simplified expressions are derived for quick evaluation of the punchthrough voltages for both one-dimensional and two-dimensional analyses. For a given operating voltage, the one-dimensional calculation gives a larger spacing between n regions in a n-si-n structure for onset of large current flow than does the two-dimensional analysis. Therefore, the spacing obtained from one-dimensional results can be used as a conservative design criterion for device isolation. For more aggressive electrical isolation design, two-dimensional simulation is necessary since it provides more accurate results 相似文献
999.
G.R. Olbright R.P. Bryan W.S. Fu R. Apte D.M. Bloom Y.H. Lee 《Photonics Technology Letters, IEEE》1991,3(9):779-781
The authors report the measurement of the laser linewidth, wavelength tunability, and generation of microwave frequencies between individually addressable elements of a vertical-cavity GaAs quantum-well surface-emitting laser diode array (lasing in the wavelength range 850-865 nm). Using heterodyne techniques, the authors obtain a deconvolved 65 MHz laser linewidth from the 109 MHz beat signal. The laser linewidth corresponds to a semiconductor laser linewidth enhancement factor alpha =5.7, which is in excellent agreement with that obtained independently from optical gain measurements and corresponding calculated refractive index changes. The authors measured heterodyne beat frequencies of 2-20 GHz. The bandwidth was limited by the microwave amplifiers. A simple calculation shows that a tuning range of 65 MHz to 3 THz can be achieved.<> 相似文献
1000.
J.S. Yoo H.H. Lee P.S. Zory 《Photonics Technology Letters, IEEE》1991,3(7):594-596
Relationships obtained by F. Kappeler et al. (1982) are utilized to assess the effect of facet passivation on the output intensity limit in terms of surface recombination velocity. The results show a trend that the output intensity limit increases in an exponential manner with decreasing recombination velocity once the velocity is reduced by a factor of 2 from that for an unpassivated laser. They also indicate that the output intensity is not likely to be limited by nonradiative recombination at the facet when the recombination velocity is reduced by a factor of 4.<> 相似文献