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Object detection has attracted growing attention due to its extensive application prospect, in which bounding box regression is an essential component. Dedicated to collaborative learning in bounding box regression, we explore the unified framework of smooth l 1 and intersection over union, named SLIoU. On the basis of that, we propose a SLIoU loss as localization loss, which focuses on the geometric relationships of pairs of rectangular bounding boxes in overlapping degree, central position and structural shape. Furthermore, we propose a SLIoU-NMS for suppressing redundant detection boxes, which adaptively maps the evaluation value of detection boxes to meet the evaluation metric using nonlinear representation. By incorporating SLIoU loss and SLIoU-NMS into the state-of-the-art one-stage detectors, the detection performance is considerably improved.

Achieving effective detection of unexploded ordnance (UXO) is of great significance for ensuring the safety of human lives and regional economic development. Differential magnetic tensor gradient systems have strong application prospects for UXO detection because of their low orientation requirements and exceptional sensitivity to weak magnetic fields. These systems usually have a hollow ring-shaped measurable range, referred to as the “measurable area”. With the rapid advancement of the tensor measurement system, it is necessary to further analyse the measurable area performance. In this paper, a simulation method based on a target magnetic dipole revolving around such a measurement system is designed for evaluating the measurable area. An improved Frobenius norm is adopted to compare the measured tensor data, and the centre distance is used instead of the baseline distance to better describe the scale of the measurement system. The measurable areas of planar cross-shaped, square, and triangular structures are studied, as well as the corresponding influencing factors. Finally, the quantitative relationships between the measurable area performance of the three structures and the magnetic dipole moment direction, the sensor accuracy, and the centre distance of the measurement system are obtained.

A miniature magnetic gradient tensor system may be used in small spacecraft for mineral prospecting and detection of unexploded explosive ordnance. The system consists of a magneto-inductive (MI) sensors array, a signal extraction circuit, and a microcontroller. A magnetic gradient full-tensor configuration utilizes four MI sensors arranged in a planar cross structure and is employed to minimize orientation and orthogonality errors. The system's performance was checked by data validation and magnetic anomaly detection. Numerous experimental results demonstrate that the system is able to detect a low-amplitude magnetic field as low as 8.28 nT at 10 Hz, with a typical noise floor of 0.235 nT/Hz $^{1/2}$ at 1 Hz. The system can identify nearby ferromagnetic objects clearly, which indicates its feasibility for weak magnetic anomaly detection.

An Overhauser geomagnetic sensor is a precise instrument commonly employed for geomagnetic field observation, magnetic surveys, and so on. Currently, the miniaturization of the Overhauser geomagnetic sensor is limited due to the lower signal-to-noise ratio. Thus, how to effectively extract weaker free induction decay (FID) signal from a miniaturized sensor and how to improve the signal quality have become the bottleneck. To address these problems, we came up with an optimal design of the FID signal sensing coil for a miniaturized Overhauser geomagnetic sensor and propose a front-end matching circuit for the sensing coil to inhibit the attenuation of the signal amplitude caused by high impedance, further reducing the overall noise floor of the signal acquisition system. Finally, the field experimental results show that the miniaturized prototype sensor has a smaller volume and mass with an approximate performance compared with the commercial sensor.

China's Tianwen-1 Mars rover carries a laser-induced breakdown spectroscopy (LIBS) payload named MarSCoDe to analyze the mineral and rock composition on Mars. MarSCoDe is expected to experience a wide working temperature range of about 100 °C, which will lead to a spectral shift of up to ∼40 pixels (∼8.13 nm). Even worse, drastic changes in temperature and environment may cause a loss or increase of some spectral lines of an on-board calibration Ti target. An elastic particle swarm optimization (PSO) approach is proposed to fulfill the on-board spectral calibration of MarSCoDe under this harsh condition. Through establishing a standard wavelength set (SWS) and an individual particle wavelength set (PWS), and further elastically selecting a part of PWS to compare with SWS, the problem of spectral shift and number mismatch can be solved gradually with the evolution of the particle swarm. Some tests of standard lamps and Ti with MarSCoDe, placed in a Mars simulation environment chamber (MSEC) in a temperature range of 70 °C, were completed. Compared with the standard spectrum of the Ti target (obtained at 20 °C), the spectral shifts of the first, second, and third channels are approximately 0.33 nm (5 pixels), 0.85 nm (6.4 pixels), and 8.09 nm (39.8 pixels), respectively, at -40 °C before correction; after PSO correction, the spectral shifts are greatly reduced to up to 0.015 nm, and specially for the 626.28 nm line, the spectral shift is reduced from 8.09 nm to about 0 nm. Experimental results demonstrate that the PSO-based approach can not only correct the on-board spectral shift but also solve the number mismatch of spectral lines of MarSCoDe in the harsh working environment of Mars. Further, it can be extended to the on-board calibration of other spectral payloads for deep space exploration.

The outliers of the magnetic sensor that are inevitable in special aeromagnetic surveys reduce the robustness of ordinary least-squares (OLS), which are widely used for aeromagnetic compensation. To address this problem, we propose an aeromagnetic compensation algorithm based on the Huber loss method that is robust to outliers. In the proposed method, different weights are assigned to the inliers and outliers using an iteratively reweighted least-squares technique. Although the OLS performs similarly to the proposed method when only 1% of the data are outliers, it is theoretically verified that the proposed method can increase the goodness-of-fit to 0.9963, from 0.6618 in the case of OLS, in the presence of 10% outliers. An experimental platform was constructed to record real magnetic data, with special measures taken to ensure the presence of outliers in the collected data. The results of a flight test using this experimental platform demonstrate that the proposed method increases the improvement ratio to 4.14 from 2.46 when using the OLS.

A series of rice straw hydrochars were produced through a microwave-assisted hydrothermal treatment method, characterized and used for the adsorption of three organics and two heavy metals from aqueous solutions. The hydrochars have carbon contents from 37.44% to 43.31%, are rich in oxygen containing functional groups, and the equilibrium of hydrothermal carbonization reactions could be reached rapidly in microwave environment. The hydrochars can effectively adsorb the model pollutants, the maximum adsorption capacities of Congo red, berberine hydrochloride and 2-naphthol at 298 K and initial concentration of 0.5 mg/mL were 222.1, 174.0 and 48.7 mg/g, respectively, and those of Zn2+ and Cu2+ were 112.8 and 144.9 mg/g, respectively. Adsorption thermodynamic parameters were calculated. These results suggest that microwave-assisted hydrothermal treatment is an effective method for the rapid production of hydrochars, and rice straw hydrochars are promising adsorbents for the removal of water pollutants such as organics and heavy metals.

Vegetable oils provide high nutritional value in the human diet. Specifically, extra virgin olive oil (EVOO) possesses a higher price than that of other vegetable oils. Adulteration of pure EVOO with other types of vegetable oils has attracted increasing attentions. In this work, a stimulated Brillouin scattering (SBS) combined with visible absorption spectroscopy method is proposed for authentication of vegetable oils and detection of olive oil adulteration. The results provided here have demonstrated that the different vegetable oils and adulteration oils exhibit significant differences in normalized absorbance values of two relevant wavelengths (455 and 670 nm) and frequency shifts of SBS. The normalized absorbance values of all spectra at the two relevant wavelengths of 670 nm and 455 nm linearly decrease with the increase of the adulteration concentration. The Brillouin frequency shifts exponentially increase with the increase of the adulteration concentration. Due to non-destructive and requiring no sample pretreatment procedure, this method can be effectively employed for authentication and detection of oils adulteration.

A towed Overhauser marine geomagnetic magnetometer used for weak magnetic anomaly detection in severe ocean conditions is studied to investigate means to reduce the negative effect of dynamic behavior and magnetic noise associated with ocean waves. For the dynamic effect, a continuous polarization workflow is proposed to enhance the free-induction-decay signal, and then, a multi-angle pickup coil and a self-tracking programmable amplifier are used to further reduce the adverse effect caused by uncontrollable changes in the towfish attitude on the signal quality. Furthermore, to achieve adaptive suppression of magnetic noise in different ocean conditions and areas, a modified adaptive Kalman algorithm is assessed. In addition, an optimized Overhauser sensor and a towfish were developed. Overall, the experimental results show that the sensor can effectively suppress the dynamic effect and magnetic noise. Regarding the magnetic sensitivity, uncertainty and range are 12 pT/Hz1/2@1Hz and 0.21 nT and 20 000 nT-100 000 nT, respectively. Moreover, underwater testing was performed to verify the function and the detection of the magnetic anomaly.

In the top-down approaches of multi-person pose estimation, a human detector is adopted first to generate a set of human bounding boxes, then crop these human body and perform a single-person pose estimation model to get the final result. However, some body part of another person on the cropped image will interfere the single-person pose estimation model leading to an inaccuracy result. In order to model the relationship between adjacent keypoints effectively to alleviate this problem, we propose and attention module that could let the model get global receptive field at the shallow layer of the network and pay more attention to the key areas which is more important to pose estimation. Experiment results show that our method achieves 73.9% mAP with 2.4% absolute improvement compared to our baseline on the COCO test-dev dataset.

Peony seed oil (PSO) is a new woody nut oil which is unique to China. Its unsaturated fatty acids are over 90% and are rich in α - linolenic acid. Although the PSO industry is in its infancy, it is bound to become a top vegetable oil food material because of its own advantages. The potential high commercial profit of its adulteration with cheap vegetable oil will be an important factor hindering the healthy development of PSO industry. It is of great significance to study the adulteration of PSO for preventing large-scale adulteration. In this study, the qualitative and quantitative analysis of PSO was realised based on Raman spectroscopy combined with chemometrics analysis, and the fatty acid composition of PSO was analysed according to Raman characteristic peaks. The technology can be applied to routine analysis and quality control of PSO.

How to quickly and safely identify blood species has always been an urgent problem for scientists. Smear test method has the risk of blood contamination, and the blood itself may carry some unknown viruses or pathogens, which will bring health risks to the testing personnel. Therefore, in order to meet the urgent needs of rapid and safe detection of blood, a technology which can detect dynamic confocal Raman spectroscopy of flowing blood in bionic blood vessel was proposed. The blood, which was sealed in the bionic blood vessel, flowed through the focus gaze area of laser by the microfluidic pump, to detect the dynamic blood Raman spectrum. Human blood and cattle blood were selected as experimental objects, and the experiments were carried out under the same parameters. Combined with PCA-LDA (principal component analysis and linear discriminate analysis) classification model, the predictive classification of the two species without error recognition was realized. The hidden weak Raman signals were mined by derivative spectra, and the fundamental differences of Raman spectra of two species were compared. Then the biochemical information that caused the differences was also analyzed. The results show the method can meet the detection requirements of sealed blood, and the Raman spectra of flowing blood is more representative than those of static blood.

Two mesoporous carbons were synthesized via a hydrothermal treatment approach, characterized and evaluated for adsorption properties of berberine hydrochloride and matrine from water. The mesoporous carbons have BET specific surface areas of 1568.1 and 769.3 m2/g, pore volumes of 1.44 and 0.89 cm3/g, average pore diameters of 3.75 and 8.22 nm, and few O-containing functional groups on the surfaces. Both the mesoporous carbon adsorbents can effectively adsorb berberine hydrochloride and matrine from aqueous solutions, the higher equilibrium adsorption capacities of berberine hydrochloride and matrine at 298 K are 385, and 275 mg/g at 0.10 mg/mL, respectively. Adsorption enthalpy, entropy and free energy of berberine hydrochloride and matrine on the selected mesoporous carbon (with higher BET specific surface area and pore volume) were calculated. The adsorption of berberine hydrochloride and matrine on the selected carbon sample is fast at 298 K, 95% of the adsorption equilibrium could be achieved within 180 and 120 min, respectively. The dynamic adsorption capacities on the selected adsorbent are calculated to be 343.1 and 383.4 mg/g for berberine hydrochloride and matrine, respectively; and 70.8% of the adsorbed berberine hydrochloride and 79.2% of the adsorbed matrine could be desorbed by a 70% alcohol solution. These results provide a reference to the large-scale industrial production and application of mesoporous carbons as potential adsorbents in purification of alkaloids from herbal plant extracts.

Timely and credible species recognition of wildlife at their habitats is helpful for ecological monitoring. Thanks to the powerful feature extraction ability of convolutional neural networks(CNN), the performance of species identification has been significantly improved. However the CNN based approach still does not achieve their full potential. The cluttered backgrounds and rich feature changes of wild environment bring great challenges to wildlife recognition. In this paper, we propose a novel approach to improve the anti-occlusion ability of CNN model, which is achieved by training a improved anti-occlusion loss function. The anti-occlusion constraint in our proposed loss function works to reduce the distance of feature expression before and after a sample has been occluded. We validated the effect of occlusion based on public dataset cifar-10, which confirms that its necessary to improve the anti-occlusion ability of CNN model. Based on single-labeled training dataset and generalization dataset, comprehensive comparative evaluation proves that our proposed loss can effectively improve the generalization ability of CNN model during the identification of wildlife.

The traditional electromagnetic nondestructive testing probe structure includes magnets and yokes, and forms an excitation circuit with the wire rope. The wire rope is excited to a near-saturation state. The magnetic sensor is used for qualitative or quantitative detection of leakage flux from defects. The yoke is essential in the traditional excitation circuit. However, the use of a yoke in a detection probe of such an excitation mechanism has a large volume and is heavy. Through simulation, we improved the magnetization direction and installation position of the permanent magnets. Without a yoke, the permanent magnets were placed in the direction of co-extrusion. The wire rope was excited to near saturation in the permanent-magnet part. However, there was no excitation in the center of the two permanent magnets. The magnetic sensor was placed in the center of two permanent magnets to pick up the magnetic-flux-leakage signal for nondestructive testing of the steel wire rope. This method simplifies the permanent-magnet magnetization. The excitation probe with the yoke removed was also reduced in volume and weight. Through experimental testing, it was proven that the proposed shoving-magnetic-field structure and the traditional detection structure have the same detection effect.

Extra virgin olive oil (EVOO) is both edible oil and health care product. Adulteration in high quality vegetable oil is a ubiquitous fraud, especially in the market of EVOO. Spectroscopy is an effective means to realize the rapid detection of adulteration in EVOO, but the accuracy of quantitative analysis is the short board of spectral detection. Traditional Raman spectroscopy is used to detect the adulteration of EVOO by analyzing the content of monounsaturated fatty acids. However, high oleic acid content is not unique to EVOO. Confocal Raman and Fluorescence Spectroscopy (CRFS) was employed to characterize EVOO along with potential adulterant oils based on their Oleic acid and photosensitive substances content. Statistical analysis of these Oleic acid and photosensitive substances using Multiple Linear Regression (MLR) allowed for a rapid approach to determine EVOO authenticity. The quantitative analysis model of adulteration in EVOO was established using this approach, and the RMSE was 0.0068, and the R-Squaredof external Prediction was 0.9996. In addition, Fluorescence quenching which interfered with the quantitative analysis of chlorophyll was found in the adulteration experiment of EVOO. Compared to traditional Raman methods, CRFS with MLR involves minimal sample preparation combined with fast analysis.

Eleven mesoporous carbon adsorbents were synthesized and characterized, and the adsorption properties of berberine hydrochloride on these adsorbents were investigated. The mesoporous carbon adsorbents have high BET specific surface areas (1051.2 to 1554.9 m2 g−1), large pore volumes (1.42 to 2.31 m3 g−1), and their average pore radii range from 1.53 nm to 3.28 nm. The adsorption capacities of berberine hydrochloride on these adsorbents strongly depend on the BET specific surface areas and pore volumes of the mesoporous carbons. The mesoporous carbon sample with the highest BET specific surface area was selected as the most promising adsorbent for adsorption of berberine hydrochloride because of its high adsorption capacities (415 mg g−1 at 298 K, 0.10 mg mL−1). The adsorption thermodynamic parameters of berberine hydrochloride on the selected adsorbent were calculated. The adsorption equilibrium of berberine hydrochloride on the selected adsorbent could be established within 240 minutes at 298 K. The dynamic adsorption capacity of berberine hydrochloride on the selected adsorbent is close to the theoretical maximum adsorption capacity; and 72.4% of the adsorbed berberine hydrochloride could be desorbed by a 70% alcohol aqueous solution. The excellent adsorption/desorption properties make the mesoporous carbons promising adsorbents for adsorption of berberine hydrochloride from aqueous solutions.

Ahstract─ Road geometric parameters such as turning radius, roadway width, deflection angle and direction are all the constraints when robots passing through a road. When robots know the geometric parameters of the whole road, the control input could be designed in advance and the trajectory could be planned based on the whole road. In this paper, we present an approach to mathematical formulation of a free road which contains multiple curves. We designed a construction to present a free path with the combination of three parts: straight line, spiral and circular arc. Then add the width of the transverse and construct a free road model oriented to robot. Second, we establish the relationship between the trajectory curvature and the velocity which combined the presented road model and the dynamic model of a four-wheeled differential robot. Third, simulation and actual experiments have been carried out to verify the road model and proved that the model can be used to control the robot.

In order to characterize the radium distribution and submarine groundwater discharge (SGD) in the Bohai Sea area, the three isotopes 223Ra, 224Ra and 228 Ra in different water bodies were measured in a 4-year period with the radium-delayed coincidence counting (RaDeCC) system. The results indicated that radium activities take an order of groundwater > coastal seawater > river water > central seawater. The radium activities of groundwater were controlled by the lithology , human activities and salinity . Groundwater in aquifers with higher content of Th and U like igneous and metamorphic has higher radium activities, high salinity and oil exploitation which leads to groundwater contamination can also cause the higher radium activities. The radium isotopes of offshore waters were controlled by their respective onshore groundwater and SGD flux rates . The relative level of radium Ra isotope activity of coastal groundwater and nearshore seawater is determined by the interaction between groundwater and seawater. It is concluded that smaller radium mass transport from bottom sediments and the majority radium were supplied from landward groundwater from horizontal and vertical distribution of Ra isotope. The seasonal investigation showed that the seawater radium activities of 223Ra, 224Ra and 228Ra in autumn were higher than that in spring. Based on the seasonal variation of radium activities and the mass balance of radium, SGD of the Bohai Sea during rainy season were calculated to be 1.43 × 108 m3/d (3.73 × 10−3 m3/m2/d) in northern region and 2.84 × 107 (1.76 × 10−3 m3/m2/d) in western region by 228Ra.

The use of visual methods to explore the terrain in the wild has drawn more and more attention. Structure from motion techniques have been extensively employed to 3D topographic reconstruction from videos. Conventional 3D reconstruction of the large scene area requires the aircraft to carry the camera to photograph, but need a lot of time. As a result, it needs to plan the keyframes and matching. In this paper, a keyframe matching topological graph selection strategy is proposed for effective 3D reconstruction. First, plan the scene traversal photographic mode by Terrain elevation information. A photography constraint method, which conforms to the orthographic and equidistant projection, is proposed. After that, the selection of the key frame is performed using the planning information and the DEM information. Finally, establish the matching relationships between the frames. We verify the efficacy of our method on a mountain terrain, and demonstrate that our method is able to greatly reduce the reconstruction time and improve the reconstruction accuracy.

The four-wheel differentially driven mobile robot adjusts its position and orientation by controlling the rotating speeds of four wheels. Proper four wheel speed coordination is important to reach the desired speed and trajectory , and will not cause damage to the mechanical structure. In this paper, considering the robot structure parameters and path geometric constraints, we establish the relationship between turning radius, the robot's velocity at the center of gravity (COG) and the rotating speeds of four wheels. In addition, the relationship between the yaw rate and the slip angle and the above three variables is alse established. Those relations are all based on the theory of instantaneous center of rotation (ICR). Simulative results verify them correctness and will not do damage to mechanical structure.

WiFi indoor localization has attracted much attention owing to the pervasive penetration of wireless local area networks (WLANs) and WiFi enabled mobile devices. Traditional WiFi indoor localization systems rely on received signal strength (RSS), which is instability and low space distinguish ability. Recently, channel state information (CSI) has been adopted instead of RSS and proven to be an efficient method. However, CSI raw data is sensitive to environment change. In this paper, we propose an improved WiFi indoor localization system combining CSI and RSS. Firstly, this study applies a time domain filtering method to reduce CSI data dynamic range. Then, we use the coherence bandwidth for CSI dimensional reduction. Afterwards, we extract a robust positioning feature from CSI and RSS. Finally, an improved weighted k-nearest neighbor algorithm based on kernel methods is used to estimate the location. The experiments demonstrate the effectiveness of the proposed system.

Aeromagnetic surveys using unmanned aerial vehicles (UAV) can be used in low-altitude detailed detection of small-scale magnetic anomalies and offers an auxiliary means for geomagnetic survey on land. However, excessive weight of the detection instruments and strong magnetic interference remain problems. To address them, an aeromagnetic system for a multi-rotor UAV based on the Overhauser sensor was designed. To ensure aeromagnetic surveys have high precision and are omnidirectional and fast, a miniaturized Overhauser sensor and a narrow-band tuned filter were designed and a short-time high-precision measurement method was proposed. Furthermore, the ridge regression is used to reduce the adverse effects of multicollinearity and enhance the stability of the compensation coefficient estimators. Both laboratory and flight tests were conducted. Overall, the results show that the static and dynamic noise is 0.029 nT, 0.041 nT, respectively, and the improvement ratio of aeromagnetic interference is 4.38 in the dynamic tests; a test of iron pipe detection was performed to verify the overall performance of the aeromagnetic system.

A new anthracene derivative, 3-hydroxy-1-keto-3-methyl-8-methoxy-1,2,3, 4-tetrahydro-benz[alpha]anthracene, was isolated from the marine strain Streptomyces sp. W007, and its structure was established by spectroscopic analysis including mass spectra, 1D- and 2D-NMR ((1)H-(1)H COSY, HMBC, HSQC and NOESY) experiments. 3-hydroxy-1-keto-3-methyl-8-methoxy-1,2,3,4-tetrahydro-benz[alpha]anthracene showed cytotoxicity against human lung adenocarcinoma cell line A549.

If the continuous-wave electromagnetic induction (EMI) method is used to detect plastic anti-personnel (PAP) landmines in strongly mineralized soil, background noise may interfere with and further submerge the weak secondary field generated by the landmine. To analyze quantitatively the characteristics of this noise, a semi-space homogenous medium model was developed based on a cylindrical coordinate system. The results of simulation show that, in the signal of the background noise generated by the mineralized soil, the real component dominates whereas the imaginary component is insensitive to changes in the electromagnetic properties and sensor height. A noise reduction method based on the quadrature electromagnetic method is proposed. Assuming a spherical model for the ferromagnetic components of the PAP landmine, an optimal excitation frequency of the primary field was determined. By considering the phase shift in the sensor and signal processing circuit, a method was developed to determine a sensor pre-correction. In addition, an experimental platform was built that included a PCB-based double-D EMI sensor, a data acquisition card, and a three-dimensional scanning slideway. Experimental tests with a PAP landmine buried in clay, laterite, and magnetite produced results that corroborated the above theoretical analysis. The quadrature electromagnetic method is still able to detect secondary fields with high signal-to-noise ratio generated by the PAP landmine buried 15 cm deep in the magnetite.