Design of 3D Space Following Positioning System Based on ZigBee

The research on positioning system and spatial alignment is a big topic. In this paper, we proposed a design (that) studies two issues. One is the study of range positioning algorithm based on ZigBee communication system. The other one is spatial alignment platform which is controlled with two servos. Hardware and software control system was realized, which also consists of two parts, ZigBee network positioning system and automatic orientation platform.

Symmetrical Distribution of Primes and Their Gaps

Primes are of great importance and interest in mathematics partially due to their hard-to-predict distribution. A corollary of the Goldbach Conjecture is that two primes are equally distanced from a mid-point integer. Here the authors demonstrate that most primes are bilateral symmetrically distributed on the both sides of the halves of super products (or their integer multiples) of primes. This pattern suggests that greater primes may be obtained more efficiently by subtracting smaller ones from constants equal to super products (or their integer multiples) of primes.

Photoacoustic imaging principle and analysis of the images by MSOT

Photoacoustic imaging, also called optoacoustic tomography, is a non-destructive biomedical imaging technique which employs acoustic detection to image optical absorption contrast with high-resolution deep into scattering tissue. Photoacoustic imaging overcomes the limit of high light scattering in the tissue and realized in vivo high-resolution and high-contrast imaging in the deep tissue. Photoacoustic imaging technology has been rapid development in recent years and make constantly breakthrough from a technical level to the application level. This paper describes the basic principles of photoacoustic imaging technology and make an example analysis by multispectral optoacoustic tomography （MSOT）.

Nearby M subdwarfs from LAMOST data release 2

We identify 108 M subdwarfs（sd Ms） out of more than two hundred thousand M type spectra from the second data release（DR2） of the LAMOST regular survey. This sample, among which 58 members are identified for the first time, includes 33 extreme subdwarfs（esd Ms） and 11 ultra subdwarfs（usd Ms）.The selection is based on the usual ratio of absorption depth of Ca H2, Ca H3 and TiO 5 band systems.We also emphasize the use of the Ca H1 band. We provide estimates of spectral subtype（SPT）, L′epine metallicity index ζ, effective temperature and [Fe/H]. Both ζ–[Fe/H] and SPT–Teff figures show reasonable consistency; compared to PHOENIX model spectra, average rounded values of [Fe/H] for sd Ms, esd Ms and usd Ms are respectively –0.5, –1 and –1.5. The photometric distances are estimated, indicating that most sources are located within 500 pc of the Sun and 350 pc of the Galactic disk. Velocities and 3D Galactic motions are also briefly discussed. Among the 108 subdwarfs, seven stars appear to be active with a significant Hα emission line. The source LAMOST J104521.52＋482823.3 is a white dwarf- M subdwarf binary, while LAMOST J123045.52＋410943.8, also active, exhibits carbon features in red.

COVID-19 Pulmonary and Extrapulmonary Complications

To date, the coronavirus disease 2019 (COVID-19) outbreak has become a global pandemic and public health disaster. In addition to acute respiratory manifestations, patients with COVID-19 exhibit other non-respiratory manifestations, particularly in those with severe underlying disease. Few specific therapeutics are effective for COVID-19, and supportive care is the primary remedy. Here, we comprehensively surveyed the most recent reports on extrapulmonary complications of COVID-19 and their corresponding treatments, as well as the comparison of different clinical symptoms and complications of COVID-19, severe acute respiratory syndrome (SARS), and the Middle East respiratory syndrome (MERS) patients. We wish to provide a molecular and cellular understanding of the complications of COVID-19 and provide guidance for future diagnostics, therapeutics, and prognostics of COVID-19.

High pressure floating-zone growth and property characterization of Cr-doped hexagonal YMnO_3 crystals

Large crystal growth of Cr-doped h-YMnO3has been investigated by using a high pressure optical floatingzone method. The size of the grown crystals is typically 60–70 mm in length and 4–5 mm in diameter. The structure of the grown crystals is analyzed by powder X-ray diffraction and scanning electron microscopy.The defects in the as-grown crystals, including low-angle grain boundary and inclusions are studied. An off-stoichiometric phenomenon is found with a slight Cr deficiency in different parts. The relationship between defects and growth conditions during crystal growth is also discussed. The magnetic properties show spin-glass phase features with weak ferromagnetic behavior below 30 K.

HEDP-capped Terbium Orthophosphate Nanoparticles as Sensitive Luminescent Probes for the Detection of Pb2＋ Ions

Terbium orthophosphate nanoparticles were synthesized using 1-hydroxy ethylidene-l,l-diphosphonic acid（HEDP） as a capping ligand under hydrothermal conditions at 80 ℃. These HEDP-capped TbPO4 nanoparticles owned a hexagonal phase structure according to the powder X-ray diffraction（XRD） results and were spherical monodispersed particles with a diameter of about 10 nm confirmed by transimission electron microscope（TEM） images. Interestingly, the luminescent intensities of the HEDP-capped TbPO4 nanoparticles decreased obviously in the presence of Pb2＋ ions and such a quenching behavior of luminescence was well fitted by the Stern-Volmer equation.

A chaotic coverage path planner for the mobile robot based on the Chebyshev map for special missions

We introduce a novel strategy of designing a chaotic coverage path planner for the mobile robot based on the Che- byshev map for achieving special missions. The designed chaotic path planner consists of a two-dimensional Chebyshev map which is constructed by two one-dimensional Chebyshev maps. The performance of the time sequences which are generated by the planner is improved by arcsine transformation to enhance the chaotic characteristics and uniform distribution. Then the coverage rate and randomness for achieving the special missions of the robot are enhanced. The chaotic Chebyshev system is mapped into the feasible region of the robot workplace by affine transformation. Then a universal algorithm of coverage path planning is designed for environments with obstacles. Simulation results show that the constructed chaotic path planner can avoid detection of the obstacles and the workplace boundaries, and runs safely in the feasible areas. The designed strategy is able to satisfy the requirements of randomness, coverage, and high efficiency for special missions.

ECG quality assessment based on a kernel support vector machine and genetic algorithm with a feature matrix

We propose a systematic ECG quality classification method based on a kernel support vector machine(KSVM) and genetic algorithm(GA) to determine whether ECGs collected via mobile phone are acceptable or not. This method includes mainly three modules, i.e., lead-fall detection, feature extraction, and intelligent classification. First, lead-fall detection is executed to make the initial classification. Then the power spectrum, baseline drifts, amplitude difference, and other time-domain features for ECGs are analyzed and quantified to form the feature matrix. Finally, the feature matrix is assessed using KSVM and GA to determine the ECG quality classification results. A Gaussian radial basis function(GRBF) is employed as the kernel function of KSVM and its performance is compared with that of the Mexican hat wavelet function(MHWF). GA is used to determine the optimal parameters of the KSVM classifier and its performance is compared with that of the grid search(GS) method. The performance of the proposed method was tested on a database from PhysioNet/Computing in Cardiology Challenge 2011, which includes 1500 12-lead ECG recordings. True positive(TP), false positive(FP), and classification accuracy were used as the assessment indices. For training database set A(1000 recordings), the optimal results were obtained using the combination of lead-fall, GA, and GRBF methods, and the corresponding results were: TP 92.89%, FP 5.68%, and classification accuracy 94.00%. For test database set B(500 recordings), the optimal results were also obtained using the combination of lead-fall, GA, and GRBF methods, and the classification accuracy was 91.80%.

New cross-matching algorithm in large-scale catalogs with ThreadPool technique

We introduce an algorithm to solve the block-edge problem taking advantage of the two different sky splitting functions： HTM and HEALPix. We make the cross-match with the two functions, and then we obtain the union set of the two different sets. We use the ThreadPool technique to speed up the cross-match. In this way improved accuracy can be obtained on the cross-match. Our experiments show that this algorithm has a remarkable performance superiority compared with the previous ones and can be applied to the cross-match between large-scale catalogs. We give some ideas about solving the many-for-one situation occurred in the cross-match.