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On-line Writing of Fiber Bragg Grating Array on a Two-mode Optical Fiber for Sensing Applications
摘要： On-line fabricated fiber Bragg grating (FBG) array and its sensing potentials have attracted plenty of attention in recent years. In this paper, FBG arrays are written on-line on a two-mode fiber, and this two-mode fiber Bragg grating (TM-FBG) is further experimentally investigated for temperature and curvature sensing. The responses of this sensor were characterized by 11.2 pm/°C for temperature and ?0.21 dB/m?1 for curvature, respectively. Based on the measurements, a dual-parameter fiber sensing system was developed, which can realize the quasi-distributed, simultaneous detection of temperature and curvature, making it suitable for structural health monitoring or perimeter security.
关键词： on-line grating writing,fiber Bragg grating,two-mode fiber,curvature sensing,temperature sensing
更新于2025-11-28 14:23:57
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Narrow-line InGaN/GaN green laser diode with high-order distributed-feedback surface grating
摘要： We demonstrate narrow-line green laser emission at 513.85 nm with a linewidth of 31 pm and side-mode suppression ratio of 36.9 dB, operating under continuous-wave injection at room temperature. A high-order (40th) distributed-feedback surface grating fabricated on multimode InGaN-based green laser diodes via a focused ion beam produces resolution-limited, single-mode lasing with an optical power of 14 mW, lasing threshold of 7.27 kA cm?2, and maximum slope efficiency of 0.32 W A?1. Our realization of narrow-line green laser diodes opens a pathway toward efficient optical communications, sensing, and atomic clocks.
关键词： InGaN/GaN,green laser diode,distributed-feedback,narrow-line,surface grating
更新于2025-11-28 14:23:57
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[IEEE 2018 IEEE PES/IAS PowerAfrica - Cape Town (2018.6.28-2018.6.29)] 2018 IEEE PES/IAS PowerAfrica - Estimation of Inverter-Based Solar PV Penetration on Medium Voltage Networks Using Grid Impedance
摘要： Installation and control of connecting inverter-based generation to medium voltage networks are constrained by network grid structure and by technical regulations that limits its penetration into the network. Medium voltage networks form the backbone to which low-voltage inverter-based generation such as solar PV systems are connect to. However, these networks generally have inconsistent impedances that vary with line lengths, conductor types and load distribution and therefore make them not as flexible and cost effective to efficiently allow adequate penetration of solar PV type distributed generation (capacity in kW) to be integrated. A generic model that mimics a medium voltage network is analyzed in this paper to determine how inverter-based generation can be maximized on the network in terms of its location by focusing on line impedance ratios to achieve voltage regulation.
关键词： voltage regulation,Inverter-based generation,line impedance ratio,conductor type,medium voltage,line lengths
更新于2025-09-23 15:23:52
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Extended analysis of FTIR high resolution spectra of HD32S and HD34S in the region of the ν2 band: Positions and strengths of individual lines
摘要： The high resolution infrared spectra of deuterated hydrogen sulfide HDS were recorded with a Bruker IFS125HR Fourier transform infrared spectrometer (Zurich prototype ZP2001) and analyzed in the ν2 fundamental band region, 690–1510 cm?1. 2684 transitions with maximum values of the quantum numbers Jmax.=25 and Kmax.a=17 were assigned in the experimental spectra to the ν2 band (compared to Jmax.=22 and Kmax.a=10 in the preceding analogous studies) of HD32S. On this basis, 415 upper ro–vibrational energies were obtained, which were used then in the weighted fit of the Watson Hamiltonian parameters. 33 parameters obtained from the fit reproduce the 415 initial energy values with a root mean square deviation drms=1.1×10?? cm?1. An analysis of 418 experimental ro–vibrational line intensities of the ν2 band of HD32S was made using the Hartmann–Tran profile of individual lines, and results were applied in the fit of parameters of the effective dipole moment operator. Isotopic relations for the dipole moment parameters were derived and used for the fit procedure. The obtained 'model' parameters reproduce the initial line strengths with the drms=4.7%. A list of 2684 experimental transitions of HDS is generated together with the presentation of their individual line strengths predicted on the basis of the obtained effective dipole moment parameters. An analogous analysis was fulfilled for the ν2 band of the HD3?S isotopologue.
关键词： HD32S,isotopic substitution,FTIR,ν2 band,line positions,HD34S,high resolution spectra,line strengths,spectroscopic parameters
更新于2025-09-23 15:23:52
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Wide-bandwidth thru-reflect-line calibration for empty substrate-integrated coaxial line with grounded coplanar transitions
摘要： Empty coaxial structures built with printed circuit boards have low radiation, low losses, high quality factor and non-dispersive features. The full integration of empty substrate-integrated coaxial line (ESICL) in a planar substrate is nowadays a fact thanks to a grounded coplanar transition. To properly characterize and measure this new ESICL family of devices, a low cost and easy to manufacture thru-reflect-line calibration kit is proposed to de-embed not only the connectors and feeding lines, but also the ESICL transitions.
关键词： calibration,grounded coplanar,thru-reflect-line,empty substrate-integrated coaxial line
更新于2025-09-23 15:23:52
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Inspecting human colon adenocarcinoma cell lines by using terahertz time-domain reflection spectroscopy
摘要： Techniques to inspect and analyze human colorectal cancer cell lines by using terahertz time-domain attenuated total reflection spectroscopy (THz TD-ATR) were investigated. The characteristics of THz absorption spectra of two colorectal cancer cell lines DLD-1 and HT-29 in aqueous solutions with different concentrations were studied. Different spectral features were observed compared to normal cell line. Identification results based on different parameters including absorption coefficient, refractive index, real and imaginary parts of complex permittivity, dielectric loss tangent were discussed. This research may be promising for quick and instant inspection of liquid samples by using THz time-domain spectroscopy in medical applications.
关键词： Absorption coefficient,Dielectric loss tangent,Terahertz time-domain attenuated total reflection spectroscopy,DLD-1 cell line,Cancer identification,HT-29 cell line
更新于2025-09-23 15:23:52
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Development of a novel noninvasive system for measurement and imaging of the arterial phase oxygen density ratio in the retinal microcirculation
摘要： Purpose This study was conducted in order to develop a novel noninvasive system for measurement and imaging of the arterial oxygen density ratio (ODR) in the retinal microcirculation. Methods We developed a system composed of two digital cameras with two different filters, which were attached to a fundus camera capable of simultaneously obtaining two images. Actual measurements were performed on healthy volunteer eyes (n = 61). A new algorithm for ODR measurement and pixel-level imaging of erythrocytes was constructed from these data. The algorithm was based on the morphological closing operation and the line convergence index filter. For system calibration, we compared and verified the ODR values in arterioles and venules that were specified in advance for 56 eyes with reproducibility. In 10 additional volunteers, ODR measurements and imaging of the arterial phase in the retinal microcirculation corresponding to changes in oxygen saturation of the peripheral arteries at normal breathing and breath holding were performed. Results Estimation of incident light to erythrocytes and pixel-level ODR calculation were achieved using the algorithm. The mean ODR values of arterioles and venules were 0.77 ± 0.060 and 1.02 ± 0.067, respectively. It was possible to separate these regions, calibrate at the pixel level, and estimate the arterial phase. In each of the 10 volunteers, changes in the arterial phase ODR corresponding to changes in oxygen saturation of the peripheral arteries were observed before and after breath holding on ODR images. The mean ODR in 10 volunteers was increased by breath holding (p < 0.05). Conclusions We developed a basic system for arterial phase ODR measurement and imaging of the retinal microcirculation. With further validation and development, this may provide a useful tool for evaluating retinal oxygen metabolism in the retinal microcirculation.
关键词： Retinal microcirculation region,Arterial phase,Line convergence index filter,Oxygen density ratio,Morphological closing operation
更新于2025-09-23 15:23:52
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Studying the Absolute Intensities of the Absorption Lines of 2ν7 and ν2 Bands of the CH2 = CD2 Molecule in the Region 1450–1650 cm–1
摘要： As a result of analysis of the high-resolution Fourier spectrum, the absolute intensities of absorption lines of the CH2 = CD2 molecule are measured for the first time.
关键词： CH2 = CD2 molecule,ethylene,absorption line intensities
更新于2025-09-23 15:23:52
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In-band phase deviation minimization method for wideband tunable phase shifter
摘要： This article provides a novel approach to analyze and design wideband tunable reflection-type phase shifter (RTPS) with low in-band phase deviation (IBPD) error. The proposed RTPS consists of coupled lines where through and coupled ports are terminated with varactor diodes. The coupled lines can minimize the parasitic elements of varactor diode to achieve high phase shift range (PSR). In addition, the measured frequency-dependent capacitance of varactor diode was used in the analytical analysis to obtain minimum IBPD error and high PSR. For experimental demonstration, phase shifter was fabricated at the center frequency of 2.5 GHz. The measured results show that the fabricated circuit achieved 126.85° PSR with ±6.48° IBPD error for 500 MHz bandwidth (BW). In addition, the measured maximum insertion loss variation and input/output return losses are within ±0.34 dB and higher than 16.85 dB within 500 MHz BW, respectively.
关键词： varactor diode,coupled line,low in-band phase deviation error,wideband tunable reflection-type phase shifter
更新于2025-09-23 15:23:52
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Monodimensional enlargement of resolved field of view in line scan cameras by a single doubly symmetric mirror
摘要： The geometry of the sensed and thus optically relevant area in the image plane of line scan cameras suggests that improvement of the overall system is possible, by joint design of optics and electronics. By a technique named Linear Fovea (LF) proposed in this paper, the optical contrast along the Line-of-Interest (LOI) in the image plane i.e. the location of the opto-electronic sensor, is optimized at the expense of contrast elsewhere. In the LF method, employing a single doubly symmetric surface, the resolved ?eld of view (RFOV) as the merit function, is maximized, by ?nding appropriate Zernike coe?cients describing that surface. The technique is applied on a proof-of-concept single mirror telescope and both MTF analysis and standard target imaging simulation are performed. Results show that by this technique, the RFOV can be doubled, or alternatively the illumination can be increased 2.5 times keeping RFOV unchanged. Furthermore, a rather uniform response is kept along the LOI.
关键词： Foveated imaging,Aberration compensation,Lens design,Wide ?eld angle lenses,Free form optics,Line scan cameras
更新于2025-09-23 15:23:52