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71.
In this paper,a fifth-order fully differential interface circuit( IC) is presented to improve the noise performance for micromechanical sigma-delta( Σ-Δ) accelerometer. A lead compensator is adopted to ensure the stability of the closed-loop high-order system. A low noise capacitance detection circuit is described with a correlated-double-sampling( CDS) technique to decrease 1 /f noise and offset of the operational amplifier. This paper also proposes a self-test technique for the interface circuit to test the harmonic distortion. An electrostatic force feedback linearization circuit is presented to reduce the harmonic distortion resulting in larger dynamic range( DR). The layout of the IC is implemented in a standard 0. 6 μm CMOS technology and operates at a sampling frequency of 250 kHz. The interface consumes 20 mW from a 5 V supply. The post-simulation results indicate that the noise floor of the digital accelerometer is about- 140 dBV /Hz1 /2at low frequency. The sensitivity is 2. 5 V /g and the nonlinearity is 0. 11%. The self-test function is achieved with 98. 2 dB thirdorder harmonic distortion detection based on the electrostatic force feedback linearization. 相似文献
72.
试从词法扭曲的扭曲方式入手,分析莫言小说的扭曲性语言构造及其相关特征,进一步揭示其使用后的超常表达效果,以此来透视语言本体论提出的"约定俗成性",对语言运用及审美过程中语言灵性的遗忘与压抑。 相似文献
73.
胡新福 《四川轻化工学院学报》2014,(2):43-46
普通电子节能灯通常采用不可控整流,使得输入电流严重畸变,谐波含量多,功率因素低.针对这一现象,利用逐流高频反馈技术设计了电子节能灯.结果表明,电子节能灯中应用逐流高频反馈技术,提高了节能灯输入功率因素,降低了输入电流总谐波畸变,是一种高性价比的电子节能灯设计方案. 相似文献
74.
Hanan. M. Eyssa Mona Y. Elnaggar Magdy M. Zaky 《Polymer Engineering and Science》2021,61(11):2843-2860
Seals prepared from acrylonitrile–butadiene rubber (NBR) are primarily used in nuclear services. Nevertheless, at relatively high ionizing radiation doses, NBR seal materials may undergo radiation-induced degradation processes, leading to adverse effects on the sealing ability life. Herein, to strengthen the functional characteristics of NBR seals against radiation, graphene oxide (GO) nanoparticles were prepared and characterized by transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and ultraviolet/visible spectroscopies. Various NBR/GO composites fabricated with different ratios of GO nanoparticles and in the presence or absence of carbon black (CB) were investigated via cross-linking density, scanning electron microscopy, XRD, FTIR, and mechanical and thermal stability analyses. The synergistic effect of the simultaneous presence of GO and CB on the NBR seal sensitization to gamma radiation up to a dose of 1 MGy was studied. The physicomechanical properties were enhanced by adding GO nanosheets up to 3 phr and by incorporating 35 phr of a CB with GO until 5 phr. Further, the application of γ-irradiation resulted in an overall enhancement in the mechanical, physical, and thermal stability of the prepared composites up to 0.5 and 1 MGy with GO nanosheets in the absence or presence of CB particles, respectively. The mechanical measurements indicated significant increments by loading with GO nanosheets in the absence and presence of CB as well as by irradiation. The tensile strength elevated up to about 121%, 336%, and 366% by adding 3 phr GO, 3 GO:35 CB phr, and 5 GO:35 CB phr, respectively. 相似文献
75.
采用左旋聚乳酸(PLLA)和右旋聚乳酸(PDLA)为原料,采用熔融共混法制备了立构复合聚乳酸(SC?PLA)粉末,再通过注射成型制备了SC?PLA样条,并通过差示量热扫描仪(DSC)和热变形温度测定仪对SC?PLA粉末和样条的熔融、结晶情况和热变形性能进行了表征分析。结果表明,SC?PLA粉末的结晶能力与初始熔融状态直接相关;当熔融温度为220~230 ℃时,SC?PLA粉末的熔融稳定时间增加,有助于SC?PLA体系结晶,该温度适合SC?PLA的注射成型加工;SC?PLA样条中SC?PLA结晶度越高,均聚物PLA结晶度越低,越有助于样条热变形性能的提高;低注射温度和以SC?PLA粉末、PLLA、PDLA为原料成型有助于SC?PLA样条在220 ℃下加热再退火后获得较高的SC?PLA结晶度,其热变形温度最高可达到150 ℃以上;注射成型过程中,有利于保留更多SC?PLA晶体和提高SC?PLA结晶度的方式,有助于提高样条在退火后的热变形性能。 相似文献
76.
G. Moulin C. Mons C. Severac C. Haut G. Rautureau E. Beauprez 《Oxidation of Metals》1993,40(1-2):85-108
Nickel-base alloys, such as Astroloy, used for aeronautical turbine disks, are sensitive to time-dependent cracking in environments containing oxygen. The mosaic structure of the alloy consisting islands (200 nm average size) surrounded by the -phase (100 nm thick) induces complex oxidation phenomena. Various analytical approaches allow the delineation of all the steps from segregation to oxidation occurring on the surface of such a duplex structure. The protection of Astroloy by its outer oxide layer against oxygen penetration was studied also, using alternative
16O2
then
18O2
oxidation. In association with STEM studies, it is shown that the outer oxide scale is not a real barrier against oxygen penetration and that inner precipitation of chronium (+ aluminium and titanium)-enriched oxides, takes place especially in the structure. 相似文献
77.
A. Irretier O. Kessler F. Hoffmann P. Mayr 《Journal of Materials Engineering and Performance》2004,13(5):530-536
When precipitation-hardenable aluminum parts are water quenched, distortion occurs due to thermal stresses. Thereby, a costly
reworking is necessary, and for this reason polymer quenchants are often used to reduce distortion, with the disadvantage
that the quenched parts have to be cleaned after quenching. In opposition to liquid quenchants, gas quenching may decrease
distortion due to the better temperature uniformity during quenching. Furthermore, cleaning of the quenched parts can be avoided
because it is a dry process. For this purpose, a heat-treating process was evaluated that included a high-pressure gasquenching
step. Gas quenching was applied to different aluminum alloys (i.e., 2024, 6013, 7075, and A357.0), and tensile tests have
been carried out to determine the mechanical properties after solution annealing, gas quenching, and aging. Besides high-pressure
gas quenching, alloy 2024 was quenched at ambient pressure in a gas nozzle field. The high velocity at the gas outlet leads
to an accelerated cooling of the aluminum alloy in this case. Aluminum castings and forgings can be classified as an interesting
field of application of these quenching methods due to their near-net shape before the heat treatment. Cost savings would
be possible due to the reduced distortion, and therefore, less reworking after the precipitation hardening. 相似文献
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