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41.
Most speech enhancement methods based on short-time spectral modification are generally expressed as a spectral gain depending on the estimate of the local signal-to-noise ratio (SNR) on each frequency bin. Several studies have analyzed the performance of a priori SNR estimation algorithms to improve speech quality and to reduce speech distortions. In this paper, we concentrate on the analysis of over- and under estimation of the a priori SNR in speech enhancement and noise reduction systems. We first show that conventional approaches such as the decision-directed approach proposed by Ephraïm and Malah lead to a biased estimator for the a priori SNR. To reduce this bias, our strategy relies on the introduction of a correction term in the a priori SNR estimate depending on the current state of both the available a posteriori SNR and the estimated a priori one. The proposed solution leads to a bias-compensated a priori SNR estimate, and allows to finely estimating the output speech signal to be very close to the original one on each frequency bin. Such refinement procedure in the a priori SNR estimate can be inserted in any type of spectral gain function to improve the output speech quality. Objective tests under various environments in terms of the Normalized Covariance Metric (NCM) criterion, the Coherence Speech Intelligibility Index (CSII) criterion, the segmental SNR criterion and the Perceptual Evaluation of Speech Quality (PESQ) measure are presented showing the superiority of the proposed method compared to competitive algorithms. 相似文献
42.
Yufei Zu Guoqing ChenXuesong Fu Keguang LuoChunguang Wang Shiping SongWenlong Zhou 《Ceramics International》2014
This study investigated the densification behaviors and microstructural evolution of Al2O3–ZrO2 (3Y) composite ceramics doped with four different amounts of TiO2 (0, 1, 4, and 8 wt%; denoted as 0T, 1T, 4T, and 8T, respectively) to clarify the effect of TiO2 dopants on densification. The shrinkage rate during densification increased with the increase in the amount of TiO2. The development of grain boundary feature was also examined. The undoped ceramic showed clean grain boundaries. Thin liquid grain boundary phases were observed in 1T, whereas large liquid phases were found on the grain boundary and at the junction pockets in 4T and 8T. The results were discussed in terms of the relationship between densification and grain boundary feature. 相似文献
43.
先进节能换热器技术在硫酸工业的应用回顾与展望 总被引:1,自引:0,他引:1
介绍了折流板管壳式换热器、空心环管壳式换热器、旋流网板支撑急扩加速流缩放管管壳式换热器及壳程多通道换热器结构、技术特点。回顾20多年来国内硫酸行业气体换热器技术进展,叙述了其技术起源、理念与解决的关键问题。对今后先进节能换热器技术在硫酸工业的发展趋势进行了展望,提出了技术发展方向。 相似文献
44.
Viktor Dan’ko Katerina Michailovska Ivan Indutnyi Petro Shepeliavyi 《Nanoscale research letters》2014,9(1):165
We investigated plasmon-assisted enhancement of emission from silicon nanoparticles (ncs-Si) embedded into porous SiO
x
matrix in the 500- to 820-nm wavelength range. In the presence in the near-surface region of gold nanoisland film, ncs-Si exhibited up to twofold luminescence enhancement at emission frequencies that correspond to the plasmon resonance frequency of Au nanoparticles. Enhancement of the photoluminescence (PL) intensity was attributed to coupling with the localized surface plasmons (LSPs) excited in Au nanoparticles and to increase in the radiative decay rate of ncs-Si. It has been shown that spontaneous emission decay rate of ncs-Si modified by thin Au film over the wide emission spectral range was accelerated. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretched exponential model. The observed increase of the PL decay rate distribution width for the Au-coated nc-Si-SiO
x
sample in comparison with the uncoated one was explained by fluctuations in the surface-plasmon excitation rate.
PACS
78. 67. Bf; 78.55.-m 相似文献45.
受森林分布广、覆盖厚及矿体隐伏等因素制约,大兴安岭成矿带突泉地区铀找矿进展缓慢。航空伽玛能谱数据蕴含有丰富的铀矿化信息,除地表矿化信息外,亦含有部分深部铀矿化弱信息。在典型铀矿点地质特征及伽玛能谱特征分析的基础上,利用K、U、Th元素含量之间的地球化学特征差异,构建了3个航放参数模型(U高场、△U高值晕、N高值晕),增强航放微弱异常信息。在航放异常信息提取、优选的基础上,结合地质、化探等找矿有利信息,预测铀成矿远景区9处。其中4处远景区成矿地质条件优越,异常线索丰富,尚属铀矿空白区,在进一步工作中应引起重视。 相似文献
46.
47.
John H. Collins Seong-Hoon Yoon Deepak Musale Jian Feng Kong Jeroen Koppes Suma Sundararajan Shih-Perng Tsai G. Anders Hallsby Philippe Cachia & Karen Kronoveter 《Water and Environment Journal》2006,20(1):43-47
Recently developed polymeric membrane performance enhancer product, MPE50, was tested in various pilot‐ and full‐scale membrane bioreactors (MBRs). The Initial MPE50 dosage was determined by visual jar tests and by using various bench‐top filtration tests. Different amounts of MPE50 were dosed, and the particle size and supernatant clarity of the mixed liquor were monitored visually. Bench‐top filtration tests were also conducted. A 50% higher MPE50 dosage is recommended to be added to the pilot/full‐scale bioreactors because, based on experience, some of the soluble microbial products in the mixed liquor do not completely react with polymer during the relatively short bench‐test mixing time interval. With the addition of 400 mg/L MPE50 to a pilot MBR, the design flow was increased twofold without any significant transmembrane pressure (TMP) increase for 1 day. The control TMP surged within a few hours without MPE50. Long‐term field trials in a full‐scale plant also showed a substantial flux increase. In addition to flux enhancement, MPE50 helped to remove foam from the bioreactors and improved plant aesthetics, safety and general operating performance. 相似文献
48.
光催化技术在建筑环境与设备中的应用及研究现状 总被引:3,自引:0,他引:3
简述了光催化技术在建筑环境与设备领域中的研究和应用,目前研究开发的热点是利用光催化技术改善室内空气质量、光催化材料的杀菌作用、光催化材料的自清洁和防雾功能、利用光催化材料强化空调与制冷换热设备的传热性能;对其应用研究现状进行了分析,并指出需要进一步研究的问题。 相似文献
49.
50.
礼貌在大多数人看来,意味着好的礼节,得体的言谈举止。实际上礼貌所涉及的问题非常深奥、复杂。本文在分析礼貌内涵的基础上,从面子需求以及文化观念二方面详细阐述了礼貌用语重要性的原因。 相似文献