Search

Sketch-based image retrieval (SBIR) is a cross-domain retrieval problem whose main challenge is that sketches and images differ in many aspects, such as visual content and abstract degree. Existing approaches solve cross-domain gaps using deep neural networks (DNNs) to learn a joint global feature representation for sketches and images. To improve the retrieval effect using local features, some researchers have introduced attention mechanisms and multi-scale inputs. However, these cannot effectively locate regions of detail difference between sketch–image pairs, and the discriminative ability of these models is insufficient. Just as human observational habits range from global to local, this paper constructs a multiscale network with the help of attention modules. The network is stacked in a recurrent way and focuses stepwise on the most discriminative regions from coarse to fine through region-specific attention models. The part-aware attention module is specifically designed for each scale network to make it robust against local spatial misalignment. To address the challenges of SBIR, we extend the network into a three-channel structure that integrates the sketch, edge map, and RGB photo branches to acquire a more discriminative cross-domain feature representation. The proposed network is alternately optimized by weighted regularization triplet loss, classification loss, and pairwise ranking loss. We conduct extensive experiments on several commonly used SBIR datasets, quantitative, and qualitative results demonstrate that our network learns more fine-grained features and outperforms all baselines. [ABSTRACT FROM AUTHOR]

Backscatter noise is a key limiting factor in the performance of resonant fiber optic gyroscopes. To enhance the accuracy of resonant fiber optic gyroscopes, a gyroscope system based on sideband locking technology is proposed. In this scheme, two tunable semiconductor lasers independently provide the clockwise and counterclockwise optical paths. An optical phase-locked loop is employed to achieve independent subharmonic phase locking of the two output lights, with their optical frequency difference equaling one free spectral range (FSR). By applying sinusoidal modulation at different frequencies to generate sidebands, the sideband locking technique is used to lock the first-order sidebands of the two lights to adjacent resonant frequencies. Through the filtering effect of the fiber ring resonator, the carrier intensity of the transmitted light and other sidebands are effectively suppressed. With this signal processing technique, the influence of two types of backscatter noise is completely eliminated, and the additional suppression of laser frequency noise is achieved. Experimental results show that, based on the Allan deviation, the bias instability of the gyroscope output is 1.42°/h. This method significantly improves the detection accuracy of the resonant fiber optic gyroscope under the same parameter precision or device performance requirements. [ABSTRACT FROM AUTHOR]

In the realm of picture forensics, it might be difficult to find and locate an image-splicing forgery. To improve the accuracy of the picture forensic evaluation, we introduce a dual encoder network (DAE-Net) with an efficient channel attention (ECA) module. The ECA module creates a fusion approach with an attention mechanism that enables the model to concentrate on local objects' tampering characteristics and increases the accuracy of multi-region tampering identification. We suggest combining a dual-coding network with a multi-scale dilated convolutional feature fusion module to better detect small target tampering zones. Experimental evidence suggests that DAE-Net outperforms state-of-the-art methods. The attack experiments also demonstrate the DEA-Net model's stability and noise resistance. [ABSTRACT FROM AUTHOR]

The whispering gallery mode resonator based on a fluoride crystalline material offers the advantage of an ultrahigh quality factor, however, its fast tuning remains a challenge. We propose a tuning method for a CaF2 crystalline resonator using external pressure loading. Through our theoretical calculations and simulations, we discovered that the frequency shift induced by deformation during the pressure tuning of the crystalline resonator is greater than that induced by changes in refractive index. Both shifts were of the same order of magnitude, indicating that both factors must be considered. The experimental results show tuning rates of 1114.6 and 888.2 MHz/MPa in the transverse electric and transverse magnetic modes, respectively. The tuning system can respond to a signal frequency of up to 1.2 MHz. [ABSTRACT FROM AUTHOR]

High sensitivity magnetic sensing is proposed using a sandwich structure with polydimethylsiloxane (PDMS) flexible resonator as the core. The directional sensing feature is provided by the sandwich structure's preset magnetic field. The small Young's modulus of flexible material corresponds to larger variation, resulting in a highly sensitive magnetic response. In the unshielded environment, the experimental results demonstrate redshift sensitivity of 1.08 nm / mT and blueshift sensitivity of 1.12 nm / mT, which are attributed to a slight variation in the PDMS's Young's modulus. The directivity curve's concave point has a depth of 34.6 dB. The minimum detectable magnetic field of 0.96 nT · Hz − 1/2 is achieved at 1.4 kHz. [ABSTRACT FROM AUTHOR]

In the development of miniaturized optical gyroscopes, the resonant micro-optical gyroscope (RMOG) is the most representative sensor of new optical gyroscopes. However, in the manufacturing process of optical elements, the influence of backscattering and optical Kerr noise limits the performance of RMOG. A method of suppressing optical Kerr noise generated by the front end by compensating the optical power difference while suppressing the backscattering noise is introduced. In this method, we study the optimal strategy of double-phase modulation frequency to obtain the maximum spectral gap of clockwise and counterclockwise light, so as to suppress the error related to backscattered light. At the same time, the influence of Kerr noise on the optical path is reduced through the high-precision feedback loop of the intensity modulator. Based on Allan variance, the long-term deviation stability of RMOG reaches 0.98 deg/h. [ABSTRACT FROM AUTHOR]

In this paper, we have proposed an all-silicon and compact transverse electric (TE)-pass polarizer with large bandwidth and high polarization extinction ratio (PER), where the polarizer uses a semi-arc waveguide to cause polarization-dependent bending loss (PDBL). The combination of the subwavelength grating (SWG) and double adiabatic tapers serve as an equivalent cladding to get strengthened PDBL. The parameters of SWG and double adiabatic tapers are analyzed in detail to improve the performance of the device. In the proposed TE-pass polarizer, the injected fundamental TE mode (i.e., TE0) gets protection and the injected fundamental transverse magnetic mode (i.e., TM0) lets out. The footprint is only about 6 μm × 10 μm, which is substantially reduced compared with the previous counterparts. From the results, its bandwidth is as high as 228 nm (from 1.482 to 1.710 μm) with PER > 39 dB and low excess loss (EL < 1 dB), and it has an ultra-high PER of 42.5 dB and a low EL of 0.1 dB at 1.55 μm. In addition, large fabrication tolerances of 20 nm (± 10 nm) to the key structural parameters are analyzed. [ABSTRACT FROM AUTHOR]

Microwave chips dependent devices constitute the cornerstone of many classical and emerging quantum technologies. To meet the demand for high-resolution, lossless, and fast wide-field imaging of microwave devices, we propose a wide-field microwave imaging method based on diamond nitrogen-vacancy center ensembles by combining continuous wave optically detected magnetic resonance technology with optical wide-field imaging technology. First, the optimal selection of laser parameters is achieved by measuring different laser powers. Then the accuracy of the wide-field microwave imaging technique is demonstrated by measuring the near-field imaging of the antenna surface at different microwave input powers and different microwave input frequencies. The spatial resolution of the imaging system is 5 μm over a field of view of 2400 μm × 1350 μm, and the optimal microwave precision measurement sensitivity is 5.6 μT / Hz1/2. The above results are expected to provide a practical reference for applications such as fault diagnosis of highly integrated microwave circuits, antenna radiation profiling, and electro magnetic compatibility testing of integrated microwave circuits. [ABSTRACT FROM AUTHOR]

In this study, a polarization-maintaining fiber optical gyro (PMFOG) with orthogonal-polarization states is constructed, and the non-reciprocity error induced by varying temperatures has been studied. Compared with the traditional optical gyro system based on single-polarization, theory and experiments have shown that the non-reciprocity error induced by varying temperatures is more evident in the PMFOG with orthogonal-polarization states. It is approximately five times larger than that of the traditional PMFOG. To decrease the non-reciprocity error induced by varying temperatures, we proposed an innovative structure in this study, which enhances the symmetry of the light path without the addition of redundant optical devices. The clockwise and counterclockwise light beams experience the same change of refractive index along the fast and slow axes of the fiber, and the non-reciprocity error induced by varying temperatures can be reduced to zero when the whole gyro is heated up nearly uniformly. This research, which overcomes a design limitation in PMFOGs with orthogonal-polarization states, is significant for the miniaturization and optimization of the environmental adaptability of fiber optic gyroscopes. [ABSTRACT FROM AUTHOR]

The demand for nucleic acid detection is increasing worldwide as people are impacted by infectious diseases. Digital polymerase chain reaction (dPCR), which is a revolutionized nucleic acid absolute quantitative analysis technology, plays a significant role in the detection of genetic material. However, the traditional threshold-based methods fail to obtain high-accuracy segmentation results and real-time performance from dPCR fluorescence images with uneven illumination. Therefore, we proposed a robust two-stage automatic thresholding method to deal with dPCR fluorescence images. This method adopts the background subtraction method and the improved Otsu method to extract reaction chambers of dPCR images in two stages. Especially for the second stage, the peak-weaken method based on the improved Otsu method greatly improves the real-time segmentation of uneven illumination regions. Our method significantly improves the accuracy and processing speed of the dPCR image segmentation compared to several mainstream methods. This method could effectively segment the reaction chambers of dPCR images in complex environments. The average precision rate is 99.71%, the execution time is 0.139 s. Experimental results demonstrate that our proposed strategy has superior segmentation performance for high-throughput dPCR fluorescence images with uneven illumination. [ABSTRACT FROM AUTHOR]

A self-injection locking method for resonant micro-optical gyroscope (RMOG) is proposed. The resonator is used as the sensitive element of the gyroscope and the device of light compression locking. The fiber and waveguide ring resonator (WRR) are designed and fabricated, consecutively. Both of the resonators can narrow the linewidth by three orders of magnitude, and the phase noise and the relative intensity noise can be reduced to −120 and −150 dBc / Hz, respectively. By evaluating the locking effect, WRR is more suitable for optical locking of a resonant micro-optical gyroscope (RMOG) light source, and its theoretical locking accuracy can reach 6.02 deg/s. [ABSTRACT FROM AUTHOR]