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A multi-class multi-residue analytical method was validated in this paper for simultaneously identifying 204 veterinary drugs in pork by UPLC-QTRAP MS/MS, including sulfonamides, quinolones, β-agonists, and nitroimidazoles. MRM-IDA-EPI mode of QTRAP was used to establish a secondary mass spectrum library of these 204 veterinary drugs, which could enhance the qualitative analysis of suspect substances. The separation of substances was performed on a C18 column, with a gradient elution of 0.1% formic acid solution in water and methanol. Electrospray ionization (ESI), fast polarity switching, and scheduled MRM mode were used to collect the characterization results. Factors that affected the recovery were delicately optimized, such as solvent proportion, formic acid content, and purification method. We finally determined the extracting method with formic acid-acetonitrile-water (0.1:90:10, v:v:v) and purifying method with Cleanert LipoNo as a package for dispersive solid-phase extraction. Matrix effects on the quantitative results were also investigated. Some compounds had strong matrix inhibition or enhancement, and the matrix matching external standard method was used to quantify the compounds accurately. The correlation coefficient R2 was over 0.99 within the calibration linearity range for the detected 204 veterinary drugs. The limit of quantification (LOQ) was 0.5 ~ 5 μg/kg. The recoveries ranged from 61.4% to 118.8% with RSDs of 3.1% to 19.2% (n = 6).

Dengue infection is becoming a serious global health threat. Public awareness is a pre-requisite for the successful implementation of dengue prevention programs. The main purpose of this study was to investigate dengue-related information needs and seeking behavior of the general public in Singapore. Some areas covered by this study were: importance of dengue-related information needs, preferred channels for seeking information, and respondents’ perceptions of using dengue-related information. A questionnaire was used for data collection and 152 individuals participated in this study. Data analysis showed that the most sought after information concerned: dengue-related medicines, primary symptoms of dengue infection, and different possible treatments. The popular channels for seeking information were: websites of hospitals and other health agencies, the social media, television, and newspapers. Medical staff, such as doctors and nurses, were trusted for providing accurate information. Although credibility of social media was considered low, respondents were using it due to its easy accessibility. The findings of this study will be useful to government health departments in Singapore as well as in other countries suffering from dengue, hospitals, and public welfare agencies involved in public health awareness campaigns.

Absolute orientation estimation is one of the key steps in computer vision, and n 2D–3D point correspondences can be used to obtain the absolute orientation, which is known as the perspective-n-point problem (PnP). The lowest number of point correspondences is three if there is no other information, and the corresponding algorithm is called the P3P solver. In practice, the real scene may consist of some geometric information, e.g., the vanishing point. When scenes contain parallel lines, they intersect at vanishing points. Hence, to reduce the number of point correspondences and increase the computational speed, we proposed a fast and simple method for absolute orientation estimation using a single vanishing point. First, the inertial measurement unit (IMU) was used to obtain the rotation of the camera around the Y-axis (i.e., roll angle), which could simplify the orientation estimation. Then, one vanishing point was used to estimate the coarse orientation because it contained direction information in both the camera frame and world frame. Finally, our proposed method used a non-linear optimization algorithm for solution refining. The experimental results show that compared with several state-of-the-art orientation estimation solvers, our proposed method had a better performance regarding numerical stability, noise sensitivity, and computational speed in synthetic data and real images.

In this paper, we proposed an accurate and robust method for absolute pose estimation with UAV (unmanned aerial vehicle) using RANSAC (random sample consensus). Because the artificial 3D control points with high accuracy are time-consuming and the small point set may lead low measuring accuracy, we designed a customized UAV to efficiently obtain mass 3D points. A light source was mounted on the UAV and used as a 3D point. The position of the 3D point was given by RTK (real-time kinematic) mounted on the UAV, and the position of the corresponding 2D point was given by feature extraction. The 2D–3D point correspondences exhibited some outliers because of the failure of feature extraction, the error of RTK, and wrong matches. Hence, RANSAC was used to remove the outliers and obtain the coarse pose. Then, we proposed a method to refine the coarse pose, whose procedure was formulated as the optimization of a cost function about the reprojection error based on the error transferring model and gradient descent to refine it. Before that, normalization was given for all the valid 2D–3D point correspondences to improve the estimation accuracy. In addition, we manufactured a prototype of a UAV with RTK and light source to obtain mass 2D–3D point correspondences for real images. Lastly, we provided a thorough test using synthetic data and real images, compared with several state-of-the-art perspective-n-point solvers. Experimental results showed that, even with a high outlier ratio, our proposed method had better performance in terms of numerical stability, noise sensitivity, and computational speed.

Estimating the absolute pose of a camera is one of the key steps for computer vision. In some cases, especially when using a wide-angle or zoom lens, the focal length and radial distortion also need to be considered. Therefore, in this paper, an efficient and robust method for a single solution is proposed to estimate the absolute pose for a camera with unknown focal length and radial distortion, using three 2D–3D point correspondences and known camera position. The problem is decomposed into two sub-problems, which makes the estimation simpler and more efficient. The first sub-problem is to estimate the focal length and radial distortion. An important geometric characteristic of radial distortion, that the orientation of the 2D image point with respect to the center of distortion (i.e., principal point in this paper) under radial distortion is unchanged, is used to solve this sub-problem. The focal length and up to four-order radial distortion can be determined with this geometric characteristic, and it can be applied to multiple distortion models. The values with no radial distortion are used as the initial values, which are close to the global optimal solutions. Then, the sub-problem can be efficiently and accurately solved with the initial values. The second sub-problem is to determine the absolute pose with geometric linear constraints. After estimating the focal length and radial distortion, the undistorted image can be obtained, and then the absolute pose can be efficiently determined from the point correspondences and known camera position using the undistorted image. Experimental results indicate this method’s accuracy and numerical stability for pose estimation with unknown focal length and radial distortion in synthetic data and real images.

Alien species may adversely affect not only human health, agriculture, and fisheries but also the native ecosystem. Pomacea canaliculata is one of alien harmful species (IUCN). Forest residues are a kind of renewable, cheap and secure source of primary energy. Nandina domestica Thunb. is a commonly and widely cultivated plant for city landscape construction in China. After being pruned, a large of N. domestica leaves are usually abandoned. In this work, extracts of ethanol Soxhlet (SE), ethanol immerse (EE), and water immerse (WE) were obtained from leaves of N. domestica Thunb. cv. Firepower. The molluscicidal effects of the three extracts from the leaves were evaluated against black P. canaliculata. In sand pot culture condition and pot culture with paddy soil condition, SE at concentration of 4000 mg L-1 did not affect seedlings normal growth. Plant height, seedling fresh weight (SFW), seedling dry weight (SDW) and Chlorophyll content of SE (4000 mg L-1) were not significantly different from that in DS (distilled water + seedlings). Besides, in pot culture with paddy soil condition, the SE treatment at concentration of 4000 mg L-1 inhibited P. canaliculata chewing rice seedlings effectively, which was not statistically different from the positive control {NSP, niclosamide (according to field dosage, 0.086 g m-2 ) + seedlings + P. canaliculata)}. Results from this study indicated that SE has molluscicidal effect against P. canaliculata and SE did not affect the normal growth of rice seedlings. Thus, we suggest further chemical and toxicological studies of SE.

In this paper we propose an efficient closed form solution to the absolute orientation problem for cameras with an unknown focal length, from two 2D–3D point correspondences and the camera position. The problem can be decomposed into two simple sub-problems and can be solved with angle constraints. A polynomial equation of one variable is solved to determine the focal length, and then a geometric approach is used to determine the absolute orientation. The geometric derivations are easy to understand and significantly improve performance. Rewriting the camera model with the known camera position leads to a simpler and more efficient closed form solution, and this gives a single solution, without the multi-solution phenomena of perspective-three-point (P3P) solvers. Experimental results demonstrated that our proposed method has a better performance in terms of numerical stability, noise sensitivity, and computational speed, with synthetic data and real images.

The aim of the perspective-three-point (P3P) problem is to estimate extrinsic parameters of a camera from three 2D–3D point correspondences, including the orientation and position information. All the P3P solvers have a multi-solution phenomenon that is up to four solutions and needs a fully calibrated camera. In contrast, in this paper we propose a novel method for intrinsic and extrinsic parameter estimation based on three 2D–3D point correspondences with known camera position. Our core contribution is to build a new, virtual camera system whose frame and image plane are defined by the original 3D points, to build a new, intermediate world frame by the original image plane and the original 2D image points, and convert our problem to a P3P problem. Then, the intrinsic and extrinsic parameter estimation is to solve frame transformation and the P3P problem. Lastly, we solve the multi-solution problem by image resolution. Experimental results show its accuracy, numerical stability and uniqueness of the solution for intrinsic and extrinsic parameter estimation in synthetic data and real images.

With the advent of Industry 4.0, more and more investment casting enterprises are implementing production manufacturing systems, especially in the last two years. This paper summarizes three new common requirements of the digital management aspect in precision casting enterprises, and puts forward three corresponding techniques. They are: the production process tracking card technology based on the main-sub card mode; the workshop site production process processing technology based on the barcode; and the equipment data integration technology. Then, this paper discusses in detail the principle, application and effect of these technologies; to provide the reference for enterprises to move towards digital casting and intelligent casting.

The near space airships usually have a large volume. when the airship leave the boathouse, it is influenced by the near surface wind significantly, and the attitude of the airship will change, and the risk of the experiment will be increase. In this paper, the dynamics method is used to analyse the force in the mooring rope and the attitude of the airship with nosecone constraint. The kinetic equation is established. A typical near space airship is choose as an example. The Runge- Kutta method is used to solve the dynamic equation. According to calculation result, the change law of the force in the mooring rope and the attitude of the airship is given, which can provide reference for the near space airship experiment. For the airport in this paper, the force in the mooring rope near the tail in the windward side is bigger than the others. The stronger rope should be used in design.

Head movement during a dynamic brain PET/CT imaging results in mismatch between CT and dynamic PET images. It can cause artifacts in CT-based attenuation corrected PET images, thus affecting both the qualitative and quantitative aspects of the dynamic PET images and the derived parametric images. In this study, we developed an automated retrospective image-based movement correction (MC) procedure. The MC method first registered the CT image to each dynamic PET frames, then re-reconstructed the PET frames with CT-based attenuation correction, and finally re-aligned all the PET frames to the same position. We evaluated the MC method's performance on the Hoffman phantom and dynamic FDDNP and FDG PET/CT images of patients with neurodegenerative disease or with poor compliance. Dynamic FDDNP PET/CT images (65 min) were obtained from 12 patients and dynamic FDG PET/CT images (60 min) were obtained from 6 patients. Logan analysis with cerebellum as the reference region was used to generate regional distribution volume ratio (DVR) for FDDNP scan before and after MC. For FDG studies, the image derived input function was used to generate parametric image of FDG uptake constant (Ki) before and after MC. Phantom study showed high accuracy of registration between PET and CT and improved PET images after MC. In patient study, head movement was observed in all subjects, especially in late PET frames with an average displacement of 6.92 mm. The z-direction translation (average maximum = 5.32 mm) and x-axis rotation (average maximum = 5.19 degrees) occurred most frequently. Image artifacts were significantly diminished after MC. There were significant differences (P

In major public health crises, online education can play an important role in guaranteeing the continuity of education. However, whether online education can promote educational equity has been questioned widely. The COVID-19 pandemic has revealed severe challenges students face in online teaching. Based on Bourdieu's theory of cultural reproduction and 34 interviews with participants including students, parents, and teachers, this research adopted a case study approach to explore the digital divide among Chinese rural and urban secondary school students during the COVID-19 pandemic. It was found that despite measures adopted by the Chinese government, a wider digital divide has been created between urban and rural secondary schools, and the online learning result was heavily influenced by the socioeconomic status of both the individuals and the schools they attended. More specifically, compared with urban students, rural students had less access to sui digital devices and environment, quality-parental guide and supervision, effective teachers' instruction, and worse habitus and less ability in independent online learning. Overall, this study calls on policymakers, leaders, educators, and parents to take collective actions to create a more effective online educational environment for students from the vulnerable and disadvantaged groups.