Numerical simulation and experimental validation of cavitating flow in a multi-hole diesel fuel injector

This study assesses the predictive capability of the ZGB (Zwart-Gerber-Belamri) cavitation model with the RANS (Reynolds Averaged Navier-Stokes), the realizable k-epsilon turbulence model, and compressibility of gas/liquid models for cavitation simulation in a multi-hole fuel injector at different cavitation numbers (CN) for diesel and biodiesel fuels. The prediction results were assessed quantitatively by comparison of predicted velocity profiles with those of measured LDV (Laser Doppler Velocimetry) data. Subsequently, predictions were assessed qualitatively by visual comparison of the predicted void fraction with experimental CCD (Charged Couple Device) recorded images. Both comparisons showed that the model could predict fluid behavior in such a condition with a high level of confidence. Additionally, flow field analysis of numerical results showed the formation of vortices in the injector sac volume. The analysis showed two main types of vortex structures formed. The first kind appeared connecting two adjacent holes and is known as “hole-to-hole” connecting vortices. The second type structure appeared as double “counter-rotating” vortices emerging from the needle wall and entering the injector hole facing it. The use of RANS proved to save significant computational cost and time in predicting the cavitating flow with good accuracy.

A Novel Hyperspectral Endoscopic Imaging Method Based on Broad- and Overlapped-Band Filters

In medical domain, hyperspectral imaging (HSI) [1] offers a hybrid modality of optical diagnostics that obtains spectral information and renders the information in image form, thus it has great potential for noninvasive disease diagnosis and surgical guidance [2]. Masood [3] explored a series of research problems for classification of hyperspectral (HS) colon biopsy images, and concluded that HSI has enough discriminatory power to distinguish normal and malignant biopsy tissues. However, HS illumination is always with low intensity and signal-to-noise (SNR) ratio is low for HS images. The reason is that sensors of endoscopic systems, such as charged-couple-device (CCD), work by converting photons into electrons which are then stored in each pixel. The number of electrons stored in each pixel well is proportional to the number of photons that struck that pixel, although in actual pixel well, electrons are not only generated when receiving photons, but also due to physical processes within CCD itself, such as thermal noise which generates additional electrons dependent to temperature [4,5]. At the same time, dispersive device such as monochromators (such as prism and grating), and optical filters (including interference filters and tunable filters) are commonly used for HS imaging. Using these traditional filtering approaches, only a low fractions of photons are transmitted into the sensor. Moreover, due to the requirements of safety and keeping the working time per frame as short as possible for in-vivo and real-time application in medical domain, common methods which could improve SNR, such as using cooled sensor or high exposure time, are not applicable for HS endoscopy systems. To overcome this drawback, we proposed this novel HS imaging method based on broad- and overlapped-band filters [6].

Mesospheric gravity wave characteristics and identification of their sources around spring equinox over Indian low latitudes

We report OI557.7 nm night airglow observations with the help of a charged-couple device (CCD)-based all-sky camera from a low-latitude station, Gadanki (13.5° N; 79.2° E). Based on the data collected during March and April over 3 years, from 2012 to 2014 (except March 2013), we characterize the small-scale gravity wave properties. During this period, 50 gravity wave events were detected. The horizontal wavelengths of the gravity waves are found to ranging from 12 to 42 km with the phase velocity 20–90 m s−1. In most cases, these waves were propagating northward with only a few occurrences of southward propagation. In the present novel investigation from the Indian sector, each of the wave events was reverse-ray-traced to its source. The outgoing longwave radiation (OLR) suggested that tropospheric convection was a possible source for generation of the observed waves. It was found that approximately 66 % of the events were triggered directly by the convection.

The Emerging Use ofIn VivoOptical Imaging in the Study of Neurodegenerative Diseases

The detection and subsequent quantification of photons emitted from living tissues, using highly sensitive charged-couple device (CCD) cameras, have enabled investigators to noninvasively examine the intricate dynamics of molecular reactions in wide assortment of experimental animals under basal and pathophysiological conditions. Nevertheless, extrapolation of thisin vivooptical imaging technology to the study of the mammalian brain and related neurodegenerative conditions is still in its infancy. In this review, we introduce the reader to the emerging use ofin vivooptical imaging in the study of neurodegenerative diseases. We highlight the current instrumentation that is available and reporter molecules (fluorescent and bioluminescent) that are commonly used. Moreover, we examine howin vivooptical imaging using transgenic reporter mice has provided new insights into Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), Prion disease, and neuronal damage arising from excitotoxicity and inflammation. Furthermore, we also touch upon studies that have utilized these technologies for the development of therapeutic strategies for neurodegenerative conditions that afflict humans.

A Comparison Between Linear Backprojection (Transpose) And Layergram Backprojection Methods For Image Reconstruciton In Charged–Couple Device (CCD) Based Optical Tomography

Proses pembinaan semula imej untuk tomografi optik berasaskan CCD dengan empat unjuran dibincangkan dalam kertas kerja ini. Deria imej linear CCD yang digunakan dalam projek ini adalah Sony ILX551A yang mempunyai 2048 piksel dengan saiz piksel 14–mikron. Susunan piksel yang digunakan dalam sistem ini adalah gabungan piksel berbentuk oktagon dan segi empat sama untuk memastikan bahawa cahaya merentasi bilangan baris piksel yang sama pada keempat-empat unjuran. Dua kaedah pembinaan semula imej dibincangkan dan dibandingkan dalam kertas kerja ini – kaedah transpose dan kaedah layergram. Kaedah transpose melibatkan pendaraban dan pembalikan matriks manakala kaedah layergram adalah penambahan nilai–nilai attenuation coefficient. Didapati bahawa kaedah layergram menghasilkan imej yang lebih baik daripada kaedah transpose, dari segi kualiti dan kuantiti (nilai α). Namun, kaedah transpose memerlukan masa pemprosesan yang lebih singkat berbanding kaedah layergram. Kata kunci: Optik; tomografi; CCD; pembinaan semula imej The image reconstruction process for CCD–based optical tomography with four projections is discussed in this paper. The CCD linear image sensor used in the study is a Sony ILX551A which has 2048 pixels with a pixel size of 14-microns. The pixel arrangement used in the system is a combination of octagonal and square pixels to ensure that light passes through the same number of pixel rows on all four projections. Two image reconstruction methods are discussed and compared in the paper – the transpose method and the layergram method. The transpose method involves the multiplication and inversion of matrices while the layergram method is simply the addition of the values of attenuation coefficients. The layergram method was found to produce better images than the transpose method, qualitatively and quantitatively (values of α). However, the transpose method requires a shorter processing time than the layergram method. Key words: Optical; tomography; CCD; image reconstruction

Measuring the Cell-Induced Deformation of Collagen Matrix Detected With Digital Holographic Microscopy

A modified Mach-Zender set-up in reflection is applied to record and reconstruct holographic amplitude and phase images. A charged couple device (CCD) is used to record a hologram and numerical reconstruction algorithms are then applied to rebuild the hologram for obtaining both phase and amplitude information. One could also focus on multiple focal planes from a single hologram, similar to the focusing control of a conventional microscope. The morphology and behavior of mammalian cells is determined by an interaction between signals from the intracellular matrix and the cellular responses. It is important to note that the physical aspect of the extracellular matrix is as significant as the chemical nature of it. Specifically the stresses, mechanical forces, and the profile of the external environment have major effects on cell behavior. The mechanical and physical characteristics of a tissue are greatly dependent on a hierarchical spatial arrangement of its extra-cellular matrix components. A key player in the ECM is collagen which exhibits significant tensile strength on the cellular scale. Digital holographic microscopy (DHM) is applied to study the deformation of collage matrix in response to cell migration.

Macro Imaging with Digital Cameras

Advances in charged couple device (CCD) design, low cast processor power, cheap memory and dropping prices of digital cameras over the last few years have made the CCD digital camera art attractive alternative to the film camera for many imaging applications. This is especially true in macro imaging where it appears likely that digital cameras will replace film cameras (curiously, Long (2001), says otherwise). As will be described here, a digital camera equipped with a quality macro-zoom lens, generates images with a depth of field (e.g., Fig. 1) that greatly surpass images produced by a film camera with a comparable lens system.

Evaluation of an Imaging Platform during the Development of a FRET Protease Assay

Synthetic peptide substrates labeled with a fluorescent donor and quenching moiety flanking an enzyme cleavage site provide a reliable method for monitoring enzyme activity. The dye pair Mca/Dnp has been widely used for this purpose, but poor solubility characteristics, combined with fluorescence emission in the region of the spectrum associated with interference from bi-ologicals and library compounds, can limit the usefulness of Mca/Dnp substrates in a high-throughput screening (HTS) environment. Peptide Mca-Arg-Pro-Lys-Pro-Val-Glu-Nva-Trp-Arg-Lys(Dnp)-NH2 is a matrix-metalloproteinase 3 (MMP-3) enzyme substrate that the authors have labeled with a CyDye pair, Cy3/Cy5Q. The Mca/Dnp- and CyDye-labeled substrates were compared during the development of an MMP-3 inhibitor assay. The results obtained showed that although the peptide substrates behaved similarly throughout the development of the MMP-3 assay, during a test screen of 934 compounds randomly selected from a collection of more than 70,000 compounds, the CyDye substrate was considerably more reliable. Screen Z factor values of 0.84 and 0.15 were obtained using the CyDye and Mca/Dnp peptides respectively, and the authors found that although < 1% of the test compounds were auto-fluorescent at Cy3 wavelengths, > 10% could not be screened using the Mca/Dnp substrate because of compound auto-fluorescence and interference. During this study, the authors used a PMTbased fluorescence plate reader and at the same time evaluated a charged couple device (CCD)—based imaging platform specifically optimized for use with CyDye reagents. The imaging platform gave improved read accuracy and faster plate processing times compared with the PMT reader. Overall, the results presented here highlight the potential benefit of employing the red-shifted CyDye reagents and imaging technology during the development and execution of HTS protease screens. (Journal of Biomolecular Screening 2003:72-80)