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Design and Provision of Traffic Grooming for Optical Wireless Data Center Networks
摘要： Traditional wired data center networks (DCNs) suffer from cabling complexity, lack flexibility, and are limited by the speed of digital switches. In this paper, we alternatively develop a top-down traffic grooming (TG) approach to the design and provisioning of mission-critical optical wireless DCNs. While switches are modeled as hybrid optoelectronic cross-connects, links are modeled as wavelength division multiplexing (WDM) capable free-space optic (FSO) channels. Using the standard TG terminology, we formulate the optimal mixed-integer TG problem considering the virtual topology, flow conversation, connection topology, non-bifurcation, and capacity constraints. Thereafter, we develop a fast yet efficient sub-optimal solution which grooms mice flows (MFs) and mission-critical flows (CFs) and forward on predetermined rack-to-rack (R2R) lightpaths. On the other hand, elephant flows (EFs) are forwarded over dedicated server-to-server (S2S) express lightpaths whose routes and capacity are dynamically determined based on the availability of wavelength and capacity. To prioritize the CFs, we consider low and high priority queues and analyze the delay characteristics such as waiting times, maximum hop counts, and blocking probability. As a result of grooming the sub-wavelength traffic and adjusting the wavelength capacities, numerical results show that the proposed solutions can achieve significant performance enhancement by utilizing the bandwidth more efficiently, completing the flows faster than delay sensitivity requirements, and avoiding the traffic congestion by treating EFs and MFs separately.
关键词： intensity allocation,delay analysis,lightpath provisioning,mission-critical data centers,wavelength assignment,hybrid cross-connect,Wavelength routing,blocking probability analysis
更新于2025-09-04 15:30:14
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Periodic TiO2 Nanostructures with Improved Aspect and Line/Space Ratio Realized by Colloidal Photolithography Technique
摘要： This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures—in this case, hexagonally arranged nanopillars—printed in a layer of directly photopatternable sol-gel TiO2. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a re?ective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar’s cross section. The theoretical analysis is carried out by rigorous modelling of the photonics nanojet underneath the microspheres and by optimizing the experimental conditions. Aspect ratios (structure height/lateral structure size) greater than 2 are predicted and demonstrated experimentally for structure dimensions in the sub micrometer range, as well as line/space ratios (lateral pillar size/distance between pillars) greater than 1. These nanostructures could lead for example to materials exhibiting ef?cient light trapping in the visible and near-infrared range, as well as improved hydrophobic or photocatalytic properties for numerous applications in environmental and photovoltaic systems.
关键词： TiO2,sub-wavelength structures,sol-gel,colloidal photolithography
更新于2025-09-04 15:30:14
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A new methodology for the determination of silicon in plants by wavelength dispersive X-ray fluorescence
摘要： Silicon is an important element for plants at their structure and physiology and plays an important role in bone mineralization and soft tissue development in human beings. Furthermore, its determination is being requested more frequently due to nutritional requirements. However, the methods found in the literature to determine silicon in this type of samples require a sample preparation step, which makes them time‐consuming and provides high uncertainties. In this paper, a method for the determination of silicon in plants by wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry has been developed. Horsetail (Equisetum arvense L.) and nettle leaf (Urtica dioica) have been used as a source of silicon due to its medical use. Sample preparation involved calcining the sample at 700°C and preparing fused beads from the calcined sample. Calibration standards for WD‐XRF measurement were prepared by mixing certified reference materials and chemical products to reproduce the samples matrix. The linear range for silicon concentration ranges from 6 to 55 wt% SiO2. The validation of the method was performed measuring a reference material (NCS DC73349 Bush branches and leaves) and comparing the results obtained by WD‐XRF with those obtained by an independent method by atomic absorption spectrometry. The developed methodology is rapid and accurate, provides low uncertainties, and is environmentally friendly, as it does require the use of less hazardous reagents.
关键词： silicon,WD‐XRF,wavelength dispersive X‐ray fluorescence,sample preparation,plants,fused beads
更新于2025-09-04 15:30:14
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Archaeological applications of spectroscopic measurements. Compatibility of analytical methods in comparative measurements of historical Polish coins
摘要： The ED-XRF (energy-dispersive X-ray fluorescence) compact system was used to analyze selected Polish historical coins. The compact X-ray tube developed in the National Centre for Nuclear Research (NCBJ) was used as an X-ray source in the system designed for the ED-XRF studies. The XRF spectra were recorded with the Amptek SDD spectrometer. The elemental compositions of the coins have been determined using above mentioned system and the results were compared to those obtained with WD-XRF method. Other techniques such as SEM-EDX and XRD were also included into this work for comparison. The experimental data show that the X-ray system with transmission type X-ray tube with silver anode operating at 50 kV/30 mA which was developed in NCBJ together with the Amptek SDD spectrometer is an effective tool for chemical composition analyze of historical coins and can be successfully used in archaeometry.
关键词： Elemental composition,Energy-dispersive X-ray fluorescence,X-ray powder diffraction,Scanning electron microscope with Energy Dispersive X-Ray Spectroscopy,Wavelength-dispersive X-ray fluorescence
更新于2025-09-04 15:30:14
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Rapid determination of phytosterols by NIRS and chemometric methods
摘要： Phytosterols have been extensively studied because it plays essential roles in the physiology of plants and can be used as nutritional supplement to promote human health. We use a rapid method by coupling near-infrared spectroscopy (NIRS) and chemometric techniques to quickly and efficiently determine three essential phytosterols (β-sitosterol, campesterol and stigmasterol) in vegetable oils. Continuous wavelet transform (CWT) method was adopted to remove the baseline shift in the spectra. The quantitative analysis models were constructed by partial least squares (PLS) regression and randomization test (RT) method was used to further improve the models. The optimized models were used to calculate the phytosterol contents in prediction set in order to evaluate their predictability. We have found that the phytosterol contents by the optimized models and Gas Chromatography/Mass Spectrometry (GC/MS) analysis are almost consistent. The root mean square error of prediction (RMSEP) and ratio of prediction to deviation (RPD) for the three phytosterols are 525.7590, 212.2245, 65.1611 and 4.0060, 4.7195 and 3.5441, respectively. The results have proved the feasibility of the proposed method for rapid and non-destructive analysis of phytosterols in edible oils.
关键词： phytosterol,vegetable oil,near-infrared spectroscopy,partial least squares,wavelength selection
更新于2025-09-04 15:30:14
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Hybrid transmission of unicast and broadcast signals without optical filter for WDM systems
摘要： This paper proposes and experimentally demonstrates the hybrid transmission of unicast and broadcast signals without using optical filters for the WDM systems. The dual-wavelength generated from a laser source are modulated by a phase modulator (PM) with a broadcast signal. Then, the central carriers and side-bands are separated by using a polarization beam splitter (PBS) and modulated with unicast data using Mach-Zender modulator (MZM). After combining side-bands (broadcast data) and central carriers (unicast data) using PBS, the hybrid data are transmitted through 25 km single mode fiber (SMF) to the remote node (RN). By probably adjusting the polarization controller (PC), the central carriers and side-bands are separated by PBS into two orthogonal polarization states. After transmission over 25 km SMF, the measured bit error rate (BER) curves and eye diagrams show that the performance of the proposed system is excellent to simultaneously transmit both unicast and broadcast signals. Moreover, only two modulators are required, which is cost-effective and also FBG or optical filter is not required due to sensitivity to temperature that decreases the system stability.
关键词： Wavelength-division-multiplexing (WDM) system,Hybrid signal Transmission,Optical filter,Broadcast signal,Unicast signal
更新于2025-09-04 15:30:14
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Long Wavelength Infrared Quantum Cascade Detector
摘要： The effect of the barrier width in the photovoltaic-type quantum cascade detector structure on the responsivity and the zero-bias resistance of the device are opposite. A wide barrier can increase the zero-bias resistance but hinder the transport of photo-generated carriers and decrease the responsivity. The design of a long wave infrared cascade detector usually focuses on increasing the zero bias resistance by using wide barriers to lower the thermal noise, but the photocurrent might be low in this case. Even though the thermal noise that dominates the noise performance of a photovoltaic quantum cascade detector is very low, it is possible that effective photoresponse signals cannot be obtained when the photocurrent is as low as the noise current of measurement circuits, which might be higher than the thermal noise of the detector itself. In this work, we modified the structure of our previous long wavelength infrared quantum cascade detector by increasing the number of cascaded stages, while reducing the barrier thickness to improve the responsivity of the device. Although the device’s zero bias resistance decreases due to thinning of the barrier, the detectivity is almost unaffected due to the significant increase in response. More importantly, the operating temperature of the device is increased. Therefore, optimization of long wave infrared QCDs should consider both the resistance and the photocurrent flow.
关键词： Quantum Cascade Photodetector,Long Wavelength Infrared
更新于2025-09-04 15:30:14
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Retinal and Choroidal Imaging With 870-nm Spectral-Domain OCT Compared With 1050-nm Spectral-Domain OCT, With and Without Enhanced Depth Imaging
摘要： The purpose of this study was to compare images of the retina and choroid obtained with Spectralis 1050-nm spectral-domain optical coherence tomography (SD-OCT) with and without enhanced depth imaging (EDI) to the commercially available 870-nm SD-OCT with and without EDI. Methods: Full-length 308 line scans were obtained with both 870- and 1050-nm Spectralis OCT instruments, with and without EDI. Two trained retina physicians masked to wavelength and EDI status assessed the ability to visualize the vitreoretinal interface and full-thickness choroid, and subfoveal choroidal thickness (SFCT) was measured. Results: Included in the study were 21 eyes. The vitreoretinal interface was visualized best with 870-nm OCT without EDI and was diminished with 1050-nm OCT. Graders preferred 1050 nm with EDI over 870 nm with EDI in qualitative comparisons of the choroid; 1050 nm without EDI was slightly preferred over 870 nm with EDI but was not statistically significant. SFCT measurements correlated well among the imaging modalities except for 870 nm without EDI. Conclusions: SD-OCT with EDI at 870 nm provides good visualization of both the vitreoretinal interface and choroid, whereas 1050-nm SD-OCT with or without EDI provides more choroidal detail at the expense of visualization of the vitreoretinal interface.
关键词： longer wavelength,optical coherence tomography (OCT),choroid,retina
更新于2025-09-04 15:30:14
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Elemental Analysis of Six Mines in Erzincan Region Using Wavelength-Dispersive X-Ray Fluorescence Spectrometry
摘要： This investigation concentrated on mines in the eastern Erzincan region of Anatolia, Turkey. Wavelength-dispersive X-ray fluorescence spectrometry was used to determine elemental concentrations of the ores taken from six different mines. The presence of C, O, Mg, Al, Si, P, Cl, K, Ca, Ti, V, Cr, Mn, Zn, As, Sr and Ba elements in ores were found. The relative errors for results have been given ± 7 %.
关键词： Ore,Wavelength-dispersive X-ray fluorescence
更新于2025-09-04 15:30:14
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Wavelength dependence of high-order harmonic yields in solids
摘要： We theoretically investigate the wavelength dependence of high-order harmonic yields in solids driven by a mid-infrared laser field. By solving the three-dimensional two-band density matrix equations in the wavelength range of 2.0–7.5 μm, it is shown that, in the limit of slow dephasing (dephasing time T2 → ∞), the high-order harmonic yield from a crystal follows a scaling of λ?4 for a fixed energy interval. The λ?4 scaling is attributed to the wave-packet spreading (λ?3) for the overall yield and the energy distribution effect (λ?1) due to the increase of the cutoff. For the crystal with a finite dephasing time T2, we find that the exponential factor x of λ?x increases with a decay of T2. An apparent and rapid fluctuation on a fine wavelength mesh is also observed in the harmonic yields. The fine-scale oscillation originates from the quantum interference effect, and the corresponding modulation period δλ scales as λ?1.
关键词： high-order harmonic generation,solids,wavelength dependence,mid-infrared laser field,quantum interference
更新于2025-09-04 15:30:14