An improved sample-and-hold reconstruction procedure for estimation of power spectra from LDA data

Techniques for deriving the auto or power spectrum (PSD) of turbulence from laser Doppler anemometry (LDA) measurements are reviewed briefly. The low pass filter and step noise errors associated with the sample-and-hold process are considered and a discrete version of the low pass filter for the resampled signal is derived. This is then used to develop a procedure by which the PSD estimates obtained from sample and hold measurements can be corrected. The application of the procedures is examined using simulated data and the results show that the frequency range of the analysis can be extended beyond the Nyquist frequency based on the mean sample rate. The results are shown to be comparable to those obtained using the method of Nobach et al. (1998) but the new procedures are more straightforward to implement. The technique is then used to determine the PSD of real LDA data and the results are compared with those from a hot wire anemometer.     

一种改进的线性区分分析方法及其在汉语数码语音识别上的应用

尽管汉语数码语音识别只涉及十个数字,但由于不同数字的发音存在相同或相似的声母或韵母,造成汉语数码语音之间的混淆性很大.采用通常的隐含马尔科夫模型(HMM)作为汉语数码语音识别模型难以得到很高的识别率.为了解决汉语数码之间的混淆问题,提高汉语数码语音识别性能,本文在隐含马尔科夫模型的状态层次上采用线性区分分析方法,将不同状态之间容易混淆的特征样本构成混淆模式类,针对混淆模式类进行线性区分分析.通过线性区分变换,在变换特征空间中仅保留那些能够有效区分该混淆类别的特征参数.这种基于状态的线性区分分析有效地提高了模型对混淆数码的区分能力.实验表明即使采用状态数很少的粗糙识别模型,也能很大幅度提高模型的识别性能;经过线性区分变换优化后的汉语数码识别模型,孤立汉语数码语音识别率可以达到99.32%.     

一种改进的激光二极管纵向泵浦固体激光器的腔模设计方法

以空间相关的速率方程理论为基础，提出了一种改进的激光二极管纵向泵浦固体激光器的设计方法，给出了在一定泵浦耦合方式下，激光腔模尺寸和输出耦合率最佳值的选取依据，以采用不同耦合系统的端面泵浦Ｎｄ：ＹＡＧ激光器设计实例，相应的实验结果与有理论计算符合得较好。     

Adjustment and evaluation of an LDA probe for accurate flow measurement

An LDA probe with optimized measuring volume was obtained based on repeated adjustments of a preconfigured LDA system with a calibrated spinning disc. A retriggerable pulse-width-and-time-delay module was used to trigger and freeze favorable Doppler bursts. After a repeated beam-steering procedure and a fringe-pattern analysis, we found that the variation of fringe spacing throughout the measuring volume was reduced from 3% to 0.28%, such that the adjusted probe gave more accurate measurements. To verify this applicability in velocity calibration, the fringe spacing of the adjusted LDA measuring volume was treated as a velocity coefficient, and its mean and measurement uncertainty was experimentally estimated. Analysis shows that the expanded uncertainty of the coefficient was 0.10% at the 95% level of confidence for both the components of the LDA. The results demonstrated that the adjusted LDA system was qualified to perform accurate flow measurement.     

Insights on colorectal cancer relapse by infrared microscopy from anastomosis tissues: Further analysis

The relapse rate for colorectal cancer (CRC) is high and has a significant impact on survival and quality of life. CRC relapse can be local, at the anastomosis, or distant, as evidenced by metastasis. Reducing the local recurrence of the disease may improve patient survival and quality of life. This could be achieved by determining safe surgical margins of the removed cancerous lesion during colorectal surgery. The detection of abnormal crypts is essential for diagnosis of the spread of CRC and its effective management.Our overall goal in this study is to evaluate and suggest which biological molecules in the cell contribute more to the classification procedure. This may provide clues for biologically understanding the principle of CRC recurrence. Longitudinal sections from normal anastomosis tissues obtain from CRC patients during surgery were used. Fourier transform infrared spectroscopy (FTIR) in tandem with multivariate analysis, principal component analysis (PCA), and linear discriminant analysis (LDA) were used to achieve this purpose.Colonic longitudinal sections are preferable for studying the colonic tissues quantitatively. It was possible to differentiate between the three categories: local recurrence, distant recurrence and control with a 100% success rate.     

Incomplete similarity of a plane turbulent wall jet on smooth and transitionally rough surfaces

This study assesses the hypothesis of incomplete similarity for a plane turbulent wall jet on smooth and transitionally rough surfaces. Typically, a wall jet is considered to consist of two regions: an inner layer and an outer layer. The degree to which these two regions reach equilibrium with each other and interact to produce the property of self-similarity remains an open question. In this study, the analysis of the outer and inner regions indicates that each region is characterised by a half-width which exhibits its own distinct dependence on the streamwise distance x from the slot, and a single self-similar structure for both regions does not exist. More specifically, the inner and outer layers of the wall jet exhibit different scaling laws, which results in two self-similar mean velocity profiles, both of which retain a dependence on the slot height H. As such, incomplete similarity of the wall jet on smooth and transitionally rough surfaces is confirmed by this study. In addition, comparison of the experimental results for the transitionally rough surface with the smooth wall case indicates that the surface roughness modifies the development of the mean velocity profile in both the inner and outer regions, although the effect on the outer region is relatively small and close to the experimental uncertainty.     

Confocal Raman microspectroscopy discriminates live human metastatic melanoma and skin fibroblast cells

Confocal Raman microspectroscopy (CRM) continues to develop as a promising technique with possible clinical applications for the diagnosis and treatment of skin cancers. CRM studies of single cells can provide information on the biochemical content of cancer cells in situ, potentially providing new biochemical signatures or markers of cancer cells. Here, we report a CRM study of single, living human metastatic melanoma cells (SK‐Mel‐2) and normal skin fibroblast cells (BJ) cultured and examined under identical experimental conditions. A total of almost 1200 Raman spectra were measured from more than 120 BJ and SK‐Mel‐2 cells using an inverted microscope with 647 nm laser excitation. Raman spectra were measured from within three distinct intracellular regions of the cells – cytoplasm, nucleoplasm, and nucleolus. When Raman spectra from each cell type were compared using principal components analysis (PCA) and linear discriminant analysis with leave‐one‐dish‐out cross‐validation (LDA‐CV), the two cell types were discriminated with 93% (cytoplasm), 98% (nucleolus), and 96% (nucleoplasm) accuracy. The main biochemical differences identified between the two cell types were higher RNA levels in the nucleoli of BJ cells and high amounts of lipid and collagen in the cytoplasm of SK‐Mel‐2 cells. For both cell types, higher levels of RNA were detected in the nucleoli versus the nucleoplasm. PCA with LDA‐CV was 98% (cytoplasm), 93% (nucleoplasm), and 73% (nucleolus) accurate in identifying the intracellular region based on the Raman spectra from both cell types. No significant trend was observed when the data were analyzed with respect to cell passage number. Thus, CRM with PCA and LDA‐CV successfully discriminated two skin cancer‐relevant cell lines while detecting different amounts of nucleic acids, lipids, and proteins in distinct intracellular regions, further underscoring its potential as a clinical diagnostic tool. Copyright © 2013 John Wiley & Sons, Ltd.     

On compressibility of osmium metal

On the basis of the high-pressure diamond anvil cell experiments on Os metal, Cynn et al. [Phys. Rev. Lett. 88, 135701-1 (2002)] have reported that this metal has lower compressibility than diamond. In the present work we have reanalysed the experimental data of Cynn et al. We find that the bulk moduli of Os and diamond are close to each other, implying that Os metal is as incompressible as diamond, but not more so. Our first principles total energy calculations using the full potential linearised augmented plane wave method on Os and diamond also suggest the same results.