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101.
Broadband wireless systems generally use orthogonal frequency division multiplexing (OFDM) with link adaptation (LA) to achieve high throughput while meeting bit error rate (BER) constraint. OFDM systems are known to be affected by non-linearity of high power amplifier (HPA) at transmitter, carrier frequency offset (CFO), symbol timing offset (STO) and channel estimation error at the receiver. The delay in feedback of channel state information (CSI) further affects the performance of LA procedures. The focus of this work is on performance analysis in presence of simultaneous affect of all these impairments on LA based OFDM systems. The results are found to be useful for threshold readjustment which is essential for successful implementation of LA scheme to counter the effects of change in operating conditions from ideal to as listed above. 相似文献
102.
103.
磁场电源是 HL-2M 装置初始等离子体放电的重要组成部分,它关系到 HL-2M 装置零场的建立,等
离子体的击穿和维持及位形控制。为实现初始等离子体放电所需的供电电压和电流,对磁场电源从主回路、控制、
测量和保护分别作了相应的调整。在此基础上进行了大量的工程调试,确保了磁场电源的控制和保护等性能达到
初始等离子体放电的需求。在磁场电源运行中,电源控制性能和输出参数的一致性、纹波质量等都有显著提高。
介绍了磁场电源在调试及 HL-2M 装置初始放电中的应用。 相似文献
104.
HL-2M 装置供电系统研制 总被引:2,自引:0,他引:2
为满足 HL-2M 装置的供电需求,须配套建设相应的供电系统。通过仿真计算 HL-2M 装置的总体供 电需求,考虑到 HL-2A 装置现有的供电系统设备,提出了兼顾 HL-2A 和 HL-2M 装置供电需求的总体配置方案。介绍了国内首台 300MVA 立式交流脉冲发电机组、磁体电源、高压电源和电源控制系统的研制情况。 相似文献
105.
Ultrasonic irradiation substantially improves the reaction of cyclohexene with I2 in aqueous dioxane in the presence of Cu(OAc)2 · H2O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na2CO3 or KOH in a sonication‐sensitive step. 相似文献
106.
Kazem D. Safa Aynaz Feyzi Maryam Allahvirdinesbat Leila Sarchami Parvaneh Nakhostin Panahi 《合成通讯》2013,43(3):382-390
An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me3Si)3CLi, prepared via metalation of (Me3Si)3CH with methyllithium in tetrahydrofuran, in excellent yields. 相似文献
107.
A. Al-Kahtani Ahmed J. Jayaraju B. S. Sherigara H. S. Naik Bhojya J. Keshavayya 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1055-1063
The miscibility of dextran (Dex)/poly(vinyl pyrrolidone) (PVP) in solution has been investigated in different percentages of the blend components by employing viscosity, density, refractive index and ultrasonic velocity methods at 30 and 50°C, respectively. Ultrasonic velocity and adiabatic compressibility against blend compositions were plotted and found to be linear. The interaction parameters μ and α have been obtained by using the viscosity data. The results indicated that the Dex/PVP blends are miscible in the entire composition range and it was further confirmed by ultrasonic velocity, density, refractive index studies. In addition, the results revealed that the change in temperature has no significant effect on the miscibility of Dex/PVP polymer blend. 相似文献
108.
活性炭载体的超声波处理对钌/活性炭氨合成催化剂催化性能的影响 总被引:2,自引:0,他引:2
利用超声波处理活性炭,并采用场发射扫描电镜、X射线能谱、N2物理吸附和CO化学吸附等表征手段,考察了超声波处理对活性炭表面形貌、化学组成、表面织构和催化剂钌分散度的影响. 以超声波处理的活性炭为载体,以钡和钾为助剂制备了一系列钌基氨合成催化剂,在10.0 MPa,10000 h-1和400 ℃的条件下进行了氨合成活性评价. 结果表明,超声波处理可有效除去活性炭表面的杂质,提高中孔比表面积占BET比表面积的比例. 超声波处理50 min的活性炭表面的杂质含量较低,中孔比表面积适中,以其为载体制备的钌基催化剂的活性较高,催化氨合成反应速率可达94.8 mmol/(g·h). 相似文献
109.
Pascal Tixador 《Physica C: Superconductivity and its Applications》2010,470(20):971-979
Europe celebrated last year (2008) the 100-year anniversary of the first liquefaction of helium by H. Kammerling Onnes in Leiden. It led to the discovery of superconductivity in 1911. Europe is still active in the development of superconducting (SC) devices. The discovery of high critical temperature materials in 1986, again in Europe, has opened a lot of opportunities for SC devices by broking the 4 K cryogenic bottleneck. 相似文献
110.
Emiliano Fernández Rebeca Hernández M. Teresa Cuberes Carmen Mijangos Daniel López 《Journal of Polymer Science.Polymer Physics》2010,48(23):2403-2412
In this article, we report on the viscoelastic and thermal properties of agarose–polyacrylamide (PAAm) interpenetrating polymer hydrogels (IPHs) and semi‐IPHs as a function of agarose concentration and PAAm crosslinking degree. The results demonstrated that the agarose is able to gel in the presence of crosslinked and linear IPHs. In addition, the reticulation of PAAm in the presence of agarose is confirmed for the case of IPHs giving rise to systems with dimensional stability at high temperatures. The formation of a fully IPH was ascertained at low agarose concentrations. A study of the morphology and nanoscale elasticity of the different systems has been carried out with atomic force microscopy/ultrasonic force microscopy (UFM). UFM data provide further evidence of interpenetration, allowing us to visualize—if present—phase‐separated domains with nanoscale resolution for the various crosslinking degrees and PAAm and agarose concentrations used during the formation of the IPHs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献