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- 摘要
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Selecting Band Subsets from Hyperspectral Image Through a Novel Evolutionary-Based Strategy
摘要： Hyperspectral dimensionality reduction by optimal band selection attracts wide attention recently because a few pivotal and physically meaningful bands can not only represent the whole image cube without losing effectiveness but also mitigate the computational burden. In this paper, we construct an efficient searching strategy based on the clonal selection principle to optimize a geometry-based criterion named maximum ellipsoid volume (MEV). The main contributions are two-fold: 1) a subtle relationship that can accelerate the calculation of the criterion and 2) an evolutionary strategy to relieve the heavy computational burden of obtaining the desired bands from numerous quality candidates. The experimental result on a real hyperspectral data demonstrates that the proposed method is effective.
关键词： maximum ellipsoid volume,Band selection,hyperspectral image,clonal selection principle
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Combination of Band Selection and Weighted Spatial-Spectral Method for Hyperspectral Image Classification
摘要： In this paper we propose a new method for land cover classification in hyperspectral remote sensing images by combining band selection with weighted spatial-spectral feature fusion. Spectral information for each pixel is represented by a spectral curve over all the bands. Spatial information is represented by a Bag of visual Words model within a small region around each pixel. A cluster-based band selection method is used before spatial feature extraction to reduce the computation complexity. Then spectral and spatial feature weights are learnt under a Support Vector Machine framework, obtaining a balance between the two basis features for each class. Classification results on three popular hyperspectral remote sensing images demonstrate that the proposed method can yield a higher accuracy and a lower false alarm rate compared with the other similar classifiers.
关键词： bag of words,Hyperspectral image,spatial-spectral,classification,band select
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Applied and Engineering Mathematics (ICAEM) - Taxila, Pakistan (2018.9.4-2018.9.5)] 2018 International Conference on Applied and Engineering Mathematics (ICAEM) - Characterization of Shaping Filter Employed in All-Optical Generation of UWB Pulses
摘要： In this paper, we investigate the effect of varying the bandwidth of shaping filter on bit error rate (BER) performance of ultra-wide band over fiber (UWBoF) system. UWB mono-cycle pulses are all-optically generated by exploiting the cross-phase modulation effect in highly non-linear fiber (HNLF) followed by phase modulation (PM) to intensity modulation (IM) conversion and then transmitted over 20 km single mode fiber (SMF) towards remote radio access unit (RAU) where the pulses are photo-detected. By varying the bandwidth of shaping filter from 25 GHz up to 125 GHz in steps of 25 GHz, corresponding BER plots are obtained. Simulation results show that performance degrades in terms of minimum receiver sensitivity while increasing the bandwidth of the shaping filter. We further investigate the dependence of width tuning of generated UWB mono-cycle pulses on chirp swing and shaping filter bandwidth. Simulation results show that width tuning saturates when chirp swing exceeds the bandwidth of the shaping filter.
关键词： cross-phase modulation,non-linear chirp,width tuning,mono-cycle pulses,Ultra-wide band
更新于2025-09-09 09:28:46
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Lattice considerations for the use of an X-band transverse deflecting structure (TDS) at SINBAD, DESY
摘要： An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented.
关键词： DESY,slice energy measurements,X-band TDS,3D charge density reconstruction,electron bunch,longitudinal properties,SINBAD
更新于2025-09-09 09:28:46
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Compact Circularly Polarized Wearable Button Antenna with Broadside Pattern for U-NII Worldwide Band Applications
摘要： A novel circularly polarized button antenna is proposed. The antenna is constructed on a disc shaped FR-4 substrate. This disc is located on top of a textile layer and supported by a feeding probe. The antenna works in the 5.47-5.725 GHz U-NII world wide band, with over 14% relative impedance bandwidth and over 7% relative axial ratio bandwidth. A prototype has been fabricated and measured. A good agreement is found between measured and simulated results.
关键词： Wearable,Button antenna,U-NII band,Axial ratio,Circular polarization
更新于2025-09-09 09:28:46
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Floquet topological transition by unpolarized light
摘要： We study Floquet topological transition in irradiated graphene when the polarization of incident light changes randomly with time. We numerically confirm that the noise-averaged time-evolution operator approaches a steady value in the limit of exact Trotter decomposition of the whole period during which incident light has a different polarization at each interval of the decomposition. This steady limit is found to coincide with the time-evolution operator calculated from the noise-averaged Hamiltonian. We observe that at the six corners (Dirac K point) of the hexagonal Brillouin zone of graphene random Gaussian noise strongly modifies the phase band structure induced by circularly polarized light, whereas in the zone center ((cid:2) point) even a strong noise is not able to do the same. This can be understood by analyzing the deterministic noise-averaged Hamiltonian, which has a different Fourier structure as well as a lower number of symmetries compared to the noise-free one. In one-dimensional systems noise is found to renormalize only the drive amplitude.
关键词： unpolarized light,noise-averaged Hamiltonian,Floquet topological transition,irradiated graphene,phase band structure
更新于2025-09-09 09:28:46
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Design of Dual-Band Bandpass Filter With Multiple Transmission Zeros Using Transversal Signal Interaction Concepts
摘要： In this letter, a compact dual-band bandpass ?lter (BPF) based on the transversal signal interaction concepts is presented. The center frequencies of dual-band BPF are centered at 3.8 and 4.8 GHz with 3-dB fraction bandwidths of 11.3% and 10.7%, respectively. Transversal ?ltering structure is introduced in the proposed dual-band BPF, which provides two signal propagation paths from input to output. Thus, a dozen of transmission zeros are yielded to obtain wide stopband suppression ranging from 5.2 to 16 GHz. To validate the design scheme, a dual-band BPF with high selectivity, compact size, independently controllable bandwidth, and wide stopband suppression is fabricated and measured.
关键词： Bandpass ?lter (BPF),transmission zeros,dual band,transversal signal interaction (TSI)
更新于2025-09-09 09:28:46
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An over 20-W/mm S-band InAlGaN/GaN HEMT with SiC/Diamond-Bonded Heat Spreader
摘要： This letter reports on an InAlGaN/GaN high-electron-mobility transistor (HEMT) employing a SiC/diamond-bonded heat spreader with a record high output power density of 22.3 W/mm. A quaternary In-added InAlGaN barrier enabled both the large current of over 1 A/mm and high breakdown voltage of 257 V. The drain bias was increased as high as 100 V for the S-band load-pull measurement, leading to high power operation. Furthermore, the thermal resistance was reduced by 60%, from 18.8°C/W to 7.2°C/W, by employing the SiC/diamond heat spreader. This large heat dissipation effect was clearly observed in the output power density for the load-pull measurement. Our results demonstrate that the GaN HEMT with In-added barrier layer is promising not only for millimeter wave applications but also for high output power microwave amplifiers.
关键词： InAlGaN,HEMTs,Wide band gap semiconductors,GaN,Microwave transistors
更新于2025-09-09 09:28:46
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Interleaved Silicon Nitride AWG Spectrometers
摘要： Interleaved arrayed waveguide gratings (AWGs) have a great potential in providing large channel counts and narrower channel spacings for many applications, including optical communication, spectroscopy, and imaging. Here, a 75-channel silicon nitride based interleaved AWG was experimentally demonstrated. The design is comprised of a 3-channel primary AWG with 1 nm of resolution and three 25-channel secondary AWGs each with 3 nm of resolution. The final device has a spectral resolution of 1 nm over 75 nm bandwidth centered at 1550 nm. Its performance is compared with a conventional AWG spectrometer with 75 nm of bandwidth and 1 nm of resolution. The interleaved AWG demultiplexer showed lower crosstalk and better uniformity in addition to being two times smaller than the conventional design.
关键词： interleaver,C-band,arrayed waveguide grating,silicon nitride,demultiplexer,Integrated optics
更新于2025-09-09 09:28:46
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Differential quenching of the angular momentum of the B and Q bands of a porphyrin as a result of extended ring π-conjugation
摘要： A novel porphyrin, whose p-system has been extended via the presence of two additional carbon–carbon triple bonds on opposite meso-positions and by fusion of a single naphthalene unit simultaneously bridging the third meso-position and the b-carbon of one of the pyrroles, has been synthesized in good yield. Absorption, magnetic circular dichroism, emission, and theoretical spectra are reported for the fused and unfused trans-naphthalene free base and zinc porphyrins. The fusing of one of the naphthalene moieties results in significant changes to the absorption spectrum and, very unusually, the bridged meso-b-pyrrole fusion results in quenching of the MCD Faraday pseudo-A term in the porphyrin’s B band (S2). This unique effect was interpreted as resulting from the origin of the electronic structure of the second excited state (the B state). The x and y polarizations are completely mixed by the electronic effects of the non-symmetric extended conjugation of the p ring. Analysis of the origin of the MCD signal indicates that the presence of this novel mixed polarization leads to negligible angular momentum in the important B state. To our knowledge, this is the first report in which the magnetic moment in a porphyrin’s intensely absorbing B band has been quenched while the angular momentum in the Q band, the first excited state, remains as normal. This implies that the photophysical properties of the B state are likely very different than those of the Q state, which has novel and significant implications for applications, especially in non-linear spectroscopy.
关键词： TD-DFT calculations,Extended porphyrin,Magnetic Circular Dichrosim (MCD),Q band,B band,angular momentum
更新于2025-09-04 15:30:14