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To investigate the performance of Mask RCNN (region-based convolutional neural network) using T1WI-enhanced images and fusing with attention mechanism in recognizing acoustic neuroma and meningioma in cerebellopontine angle area, this paper retrospectively collected 116 cases of meningioma and 427 cases of acoustic neuroma confirmed by pathology or clinical diagnosis. 872 images of meningioma and 2 467 images of acoustic neuroma were adopted after image screening. These images were divided into the training set, validation set, and test set in a ratio of approximately 7:1.5:1.5. After preprocessing the images, we employed five models, namely Mask RCNN model with Resnet50, Resnet101, VGG19 as the backbone network, and Mask RCNN models Resnet101-CBAM and VGG19-CBAM fusing with the convolution attention mechanism, for the detection and lesion segmentation of acoustic neuromas and meningioma in cerebellopontine angle area. The model performance was evaluated with mean average precision (mAP) and mean average recall (mAR). The results in the test set showed that the convolution attention mechanism could improve model performance. VGG19-CBAM model outperformed other models with mAP of 0.932 in classification and 0.930 in segmentation. This indicates that Mask RCNN fusing with attention mechanism has a better performance in recognizing acoustic neuroma and meningioma in cerebellopontine angle area, and hence can improve clinical efficiency by providing a reference for the diagnosis and target area segmentation.

The study proposes a Kalman Filter Family-schemed algorithm to identify the vehicle's parameters and evaluate the road roughness simultaneously, based on the response of an adapted monitoring vehicle. The vehicle is simplified as a three-dimensional multi-body system consisting of the unsprung mass of wheels and the sprung mass of the car body, connected by springs and dampers that represent the suspension system. Accelerometers and a gyroscope measure the accelerations or angular velocity of different positions of the vehicle during vibrations. The Kalman filter (KF) with unknown inputs enables the prediction of the car body's accelerations from those of wheels. On the other hand, the Augmented KF can compute the accelerations of wheels based on the car body's accelerations. Thus, an inner-systemic objective function incorporating the vehicle's parameter is built between the predicted and measured accelerations and solved in an optimized manner with the Genetic Algorithm, so that an individual complicated impact test or bump test is avoided. The numerical examples carry out field tests on a 900 m long standardized test road under two scenarios of with and without a bump. The road roughness estimated by these two KF methods from different measurements is used to calculate the International Roughness Index (IRI) and further the Riding Quality Index, which are compared with those directly provided by a standardized laser IRI profilometer. Accordance in between confirms the accuracy of the proposed algorithm under different scenarios. The analysis underlines the measurements from unsprung wheels that contact directly with the road enable a more accurate estimation of road roughness than those from the sprung car body. In addition, a vehicle speed lower than 40 km/h can provide a better estimation of the road profiles. [ABSTRACT FROM AUTHOR]

Femtosecond lasers (fs-lasers) offer a powerful and advantageous tool for fabricating a very large variety of materials. When processing transparent dielectrics, structural defects, such as cracks and broken edges, are always present, thus restricting the precision of fs-laser processing. In this paper, the formation and suppression mechanism of fs-laser induced structural defects are systematically studied. We demonstrate a novel method to improve the processing precision of lithium niobate (LiNbO 3) by elevating the substrate temperature. A crack-free ablation hole with a smooth edge was fabricated at the substrate temperature of 1000 ° C. Our results show that the increase of absorptivity and the suppression of incubation effects are responsible for the high precision processing at a high substrate temperature, which not only inhibits the formation of defects, but also additionally increases the efficiency of fs-laser processing. This work provides a simple method to efficiently suppress the defect formation induced by fs-laser in LiNbO 3 samples, paving the way for a new technique for high precision fs-laser processing. [ABSTRACT FROM AUTHOR]

Environmental protection PPP projects (EP-PPP) are subject to uncertainty during the project cycle, setting flexible project contract terms in their contracts can help establish and maintain an effective partnership. This article aims to reveal the contract flexibility mechanism of EP-PPP projects by studying the relationship between flexible contract term setting methods and their effects. Questionnaires, case studies and structural equation modeling (SEM) are applied to conduct quantitative analysis. The research shows that although some flexible terms have been adopted in current EP-PPP contracts, there is still much room for improvement. In order to deal with unforeseen risks and challenges, it is necessary to consider: (1) List uncertainties as much as possible and set up response methods accordingly; (2) Guarantee a certain degree of flexibility in uncertainty response methods; (3) Give the project itself a certain degree of autonomous response power; (4) Leave plenty space for changes that may be needed in the future. The study results can help project practitioners enhance their understanding of flexible contract terms and help to promote contract flexibility in EP-PPP projects in a context-specific manner, thereby facilitating project success. [ABSTRACT FROM AUTHOR]

In the process of ocean exploration, highly accurate and sensitive measurements of seawater temperature and pressure significantly impact the study of seawater's physical, chemical, and biological processes. In this paper, three different package structures, V-shape, square-shape, and semicircle-shape, are designed and fabricated, and an optical microfiber coupler combined Sagnac loop (OMCSL) is encapsulated in these structures with polydimethylsiloxane (PDMS). Then, the temperature and pressure response characteristics of the OMCSL, under different package structures, are analyzed by simulation and experiment. The experimental results show that structural change hardly affects temperature sensitivity, and square-shape has the highest pressure sensitivity. In addition, with an input error of 1% F.S., temperature and pressure errors were calculated, which shows that a semicircle-shape structure can increase the angle between lines in the sensitivity matrix method (SMM), and reduce the effect of the input error, thus optimizing the ill-conditioned matrix. Finally, this paper shows that using the machine learning method (MLM) effectively improves demodulation accuracy. In conclusion, this paper proposes to optimize the ill-conditioned matrix problem in SMM demodulation by improving sensitivity with structural optimization, which essentially explains the cause of the large errors for multiparameter cross-sensitivity. In addition, this paper proposes to use the MLM to solve the problem of large errors in the SMM, which provides a new method to solve the problem of the ill-conditioned matrix in SMM demodulation. These have practical implications for engineering an all-optical sensor that can be used for detection in the ocean environment. [ABSTRACT FROM AUTHOR]

Significant developments have been made in the navigation of autonomous mobile robots within indoor environments; however, there still remain challenges in the face of poor map construction accuracy and suboptimal path planning, which limit the practical applications of such robots. To solve these challenges, an enhanced Rao Blackwell Particle Filter (RBPF-SLAM) algorithm, called Lidar-based RBPF-SLAM (LRBPF-SLAM), is proposed. In LRBPF, the adjacent bit poses difference data from the 2D Lidar sensor which is used to replace the odometer data in the proposed distribution function, overcoming the vulnerability of the proposed distribution function to environmental disturbances, and thus enabling more accurate pose estimation of the robot. Additionally, a probabilistic guided search-based path planning algorithm, gravitation bidirectional rapidly exploring random tree (GBI-RRT), is also proposed, which incorporates a target bias sampling to efficiently guide nodes toward the goal and reduce ineffective searches. Finally, to further improve the efficiency of navigation, a path reorganization strategy aiming at eliminating low-quality nodes and improving the path curvature of the path is proposed. To validate the effectiveness of the proposed method, the improved algorithm is integrated into a mobile robot based on a ROS system and evaluated in simulations and field experiments. The results show that LRBPF-SLAM and GBI-RRT perform superior to the existing algorithms in various indoor environments. [ABSTRACT FROM AUTHOR]

The two-stage suspension system (TSSS) is designed for the fiber optic vector hydrophone (FOVH) to isolate the vibration from the mooring rope. The acceleration transmissibility of the TSSS is studied theoretically and experimentally. The results show that the TSSS has a major advantage over the traditional one-stage suspension system (OSSS). Typically, the vibration isolation of the TSSS is demonstrated to be over 25 dB higher than that of the OSSS at 100 Hz. Meanwhile, it is demonstrated that the TSSS has little negative influence on the in-band acceleration response of the FOVH. The TSSS has the prospect of reducing the mechanical noise of the FOVH, which is conducive to suppressing the self-noise and enhancing the ability of weak signal detection. [ABSTRACT FROM AUTHOR]

A theoretical and experimental study on the stimulated Brillouin scattering (SBS) threshold for optical pulse in the presence of modulation instability (MI) in long optical fiber is presented. The effects of MI on the SBS gain and threshold are analyzed based on the coupled-wave equation. An analytic expression is obtained to calculate the SBS threshold in the presence of MI. Numerical simulation is conducted to study the effects of the repetition rate and amplified spontaneous emission (ASE) noise on the SBS threshold for optical pulses. An experiment is conducted, and the results agree well with the theoretical analysis. The results clearly reveal how MI affects the Brillouin gain and SBS threshold of optical pulses in long optical fiber. The SBS threshold is affected by the ASE noise level and the repetition rate of the optical pulse. The study is helpful for the power evaluation of interferometric fiber sensing systems and optical power transmission systems. [ABSTRACT FROM AUTHOR]

Modulation instability (MI) is the main limitation factor of the maximum optical power in long-haul phase-sensitive optical time domain reflectometry (Φ-OTDR), and induces signal fading and serious phase noise. In this paper, a method of coherent seed injection is proposed to suppress the MI-induced phase noise in long-haul Φ-OTDR. The spontaneous MI is suppressed by stimulating induced MI in an optical fiber. The visibility of the signal in Φ-OTDR is enhanced and the phase noise is suppressed significantly. This paper offers an effective method to increase the maximum input power with the MI-induced phase noise suppressed in the long-haul Φ-OTDR system. As a result, the maximum input power and sensing distance can be potentially increased, which is greatly beneficial to the enhancement of the performance of long-haul Φ-OTDR. [ABSTRACT FROM AUTHOR]

The phase-generated-carrier (PGC) method is one of the popular interrogation methods for the interferometric fiber-optic sensor systems. Among varieties of specifications, the noise characteristic is a key one that determines the minimum detectable signal. However, the mechanism of the noise transfer process in the PGC-based interferometric fiber-optic sensor has not been reported to the best knowledge. In this paper, the influences of three different types of noise sources on the noise floor of the PGC-based interferometric fiber-optic sensor system are studied systematically. On the basis of that, the phase noise transfer model is built and verified experimentally. The results depict that the theoretical model can well predict the experimental result. With the proposed theoretical model, the prediction and analysis of the output phase noise in the PGC-based interferometric fiber-optic sensor is available. In addition, the proposed model provides a potential support for locking the initial phases to suppress the common-mode noise in the PGC-based system. In this sense, the proposed model is a significant tool for the noise-target design and construction of the PGC-based in terferometric fiber-optic sensor system. [ABSTRACT FROM AUTHOR]

The evaluation of road roughness plays a critical role in the life-long maintenance of the highway system. This study proposes a Kalman Filter-based scheme to evaluate the road roughness indirectly from the response of a moving adapted monitoring vehicle. Key feature of the scheme is the use of measurements from dynamic tire pressure of unsprung mass components that directly interact with roads. Combination of ideal gas law and elastic contact model results in a nonlinear relationship between the tire pressure and the contact force, in which the parameters are calibrated by the Extended Kalman Filter. Identification of vehicle's physical parameters adopts the power spectrum method with a known-size bump test. Subsequently, the road roughness is treated as unknowns in the vehicle's state-space equation and solved by the Discrete Kalman Filter with unknown inputs. The estimated road roughness profiles are then used to calculate the International Roughness Index and compared with that provided by the standardized laser profilometer, an outer-systematic comparison. On the other hand, available measurements are split into groups that measurements of tire pressure are used to predict the accelerations of the car body and wheels and compared with these accelerations directly measured from accelerometers, an inner-systemic comparison. Field tests are carried out on a 900 m long standardized road under two scenarios of with and without the bump and four different vehicle running speeds from 20 to 50 km/h. Consistence of comparison from different perspectives proves the reliability of the proposed scheme. In addition, the results unveil that the scenario with a lower running speed can offer a better estimation of road roughness. [ABSTRACT FROM AUTHOR]

To adapt to the complex application of polyurethane bearings, it is feasible to improve the tribological performance of single polyurethane-based friction materials through the synergistic effect produced by multi-component-lubricating fillers. In this context, rather than using tungsten disulfide (WS2), which has demonstrated excellent self-lubricating performance as a lubricating oil additive, this paper proposes that WS2 and single-walled carbon nanotubes (SWNTs) can be designed for addition into a polyether 4,4′-diphenylmethane diisocyanate (MDI) polyurethane matrix as self-lubricating fillers so as to explore the synergistic effect of micro- and nano-lubricating fillers on the tribological performance of polyurethane matrix materials. Through a series of characterizations and tests, it was found that the dispersion of two-component-lubricating additives in a polyurethane matrix is improved when the ratio of WS2 to SWNTs is roughly 2:1. In this case, the tribological performance of polyurethane matrix composites is more satisfactory than at other ratios. In addition, compared with the blank sample, the tribological performance of the synergistically modified polyurethane composites under dry friction is more significantly improved with the increase in contact load, while there is no significant improvement under water lubrication. Aside from contributing to the idea of exploring the synergistic effect of WS2 and other micro or nanofillers, this method also opens up the possibility of practically applying WS2 in the field of friction. [ABSTRACT FROM AUTHOR]