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1. chinaXiv:201803.00957 [pdf]

Crop positioning for robotic intra-row weeding based on machine vision

Li, Nan; Zhang,Chunlong; Chen, Ziwen; Ma, Zenghong; Sun, Zhe; Yuan,Ting; Li, Wei; Zhang, Junxiong
Subjects: Mechanical Engineering >> Mechanical Manufacture and Automation

A machine-vision-based method of locating crops is described in this research. This method was used to provide real-time positional information of crop plants for a mechanical intra-row weeding robot. Within the normalized red, green, and blue chromatic coordinates (rgb), a modified excess green feature (g-r>T & g-b>T) was used to segment plant material from back ground in color images. The threshold T was automatically selected by the maximum variance (OTSU) algorithm to cope with variable natural light. Taking into account the geometry of the camera arrangement and the crop row spacing, the target regions covering the crop rows were defined based on a pinhole camera model. According to the statistical variation in the pixel histogram in each target region, locations of the crop plants were initially estimated. To obtain the accurate locations of crops, median filtering was conducted locally in the bounding boxes of the crops close to the bottom of the images. For the lateral guidance of the robot, a novel method of calculating lateral offset was proposed based on a simplified match between a template and the detected crops. Field experiments were conducted under three different illumination conditions. The results showed that the accurate identification rates on lettuce, cauliflower and maize were all above 95%. The positional error as within ±15 mm, and the average processing time for a 640×480 image was 31 ms. The method was adequate to meet the technical requirement of the weeding robot, and laid a foundation for robotic weeding in commercial production system.

submitted time 2018-03-16 Hits1792Downloads1069 Comment 0

2. chinaXiv:201711.00154 [pdf]

Synthesis, Structure, Photoluminescence and Thermal Expansion of a Rare Earth Formate Oxalate Framework

Hadi Abdul Nada; LI Wei; FENG Guo-Qiang; LU Pei-Xiang
Subjects: Chemistry >> Physical Chemistry

A new lanthanide formate oxalate framework [Eu(C2O4)(HCOO)]n (1) has been synthesized via hydrothermal method and characterized by single-crystal X-ray diffraction (SC-XRD). The framework crystallizes in the orthorhombic Pnma space group, with a = 7.0984(4), b = 6.6442(3), c = 10.6793(6) ?, V = 503.68(4) ?3, Z = 3, C3HO6Eu, Mr = 285.00 g/mol, Dc = 3.7581 g/cm3, F(000) = 520.3796, μ = 12.413 mm-1, the final R = 0.0264 and wR = 0.0628 for 797 observed reflections with I > 2σ(I). The photoluminescence (PL) measurements reveal the significant red emission of the framework is dominated by the (5D0 → 7F2) electronic transition at 614 nm. Further variable-temperature powder X-ray diffraction (VT-PXRD) indicates that framework 1 shows slight negative thermal expansion (NTE) along the a-axis, and positive thermal expansion (PTE) along the b and c axes.

submitted time 2017-11-05 From cooperative journals:《结构化学》 Hits806Downloads470 Comment 0

3. chinaXiv:201708.00154 [pdf]

Comment on "Cosmological Topological Massive Gravitons and Photons"

Wei Li, Wei Song, Andrew Strominger
Subjects: Physics >> The Physics of Elementary Particles and Fields

In a recent paper (arXiv: 0801.4566) it was shown that all global energy eigenstates of asymptotically AdS3 chiral gravity have non-negative energy at the linearized level. This result was questioned (arXiv: 0803.3998) by Carlip, Deser, Waldron and Wise (CDWW), who work on the Poincare patch. They exhibit a linearized solution of chiral gravity and claim that it has negative energy and is smooth at the boundary. We show that the solution of CDWW is smooth only on that part of the boundary of AdS3 included in the Poincare patch. Extended to global AdS3, it is divergent at the boundary point not included in the Poincare patch. Hence it is consistent with the results of (arXiv: 0801.4566).

submitted time 2017-08-05 Hits1078Downloads524 Comment 0

4. chinaXiv:201708.00152 [pdf]

Chiral Gravity in Three Dimensions

Wei Li, Wei Song, Andrew Strominger
Subjects: Physics >> The Physics of Elementary Particles and Fields

Three dimensional Einstein gravity with negative cosmological constant -1/\ell^2 deformed by a gravitational Chern-Simons action with coefficient 1/\mu is studied in an asymptotically AdS_3 spacetime. It is argued to violate unitary or positivity for generic \mu due to negative-energy massive gravitons. However at the critical value \mu\ell=1, the massive gravitons disappear and BTZ black holes all have mass and angular momentum related by \ell M=J. The corresponding chiral quantum theory of gravity is conjectured to exist and be dual to a purely right-moving boundary CFT with central charges (c_L,c_R)=(0,3\ell /G).

submitted time 2017-08-05 Hits800Downloads469 Comment 0

5. chinaXiv:201705.00272 [pdf]

Effect of Strip Casting on Microstructure and Magnetic Properties of 2:17 Type Sm-Co Sintered Magnets

Liu, L [Liu, Lei][ 1,2 ]; Liu, Z [Liu, Zhuang][ 1,2 ]; Chen, RJ [Chen, Renjie][ 1,2 ]; Liu, XM [Liu, Xingmin][ 1,2 ]; Yan, A [Yan, Aru][ 1,2 ]; Lee, D [Lee, Don][ 1,2,3 ]; Li, W [Li, Wei][ 1,2 ]

The 2:17 type Sm-Co sintered magnets were made with strips and ingots, separately. The phase structure and microstructure of the cast alloys and their effects on magnetic properties of the magnets have been comparatively studied. X-ray diffraction analysi

submitted time 2017-05-02 Hits606Downloads354 Comment 0

6. chinaXiv:201609.00906 [pdf]

Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

GUO Yue; WANG Liang-Liang; JU Xu-Dong; WU Ling-Hui; XIU Qing-Lei; WANG Hai-Xia; DONG Ming-Yi; HU Jing-Ran; LI Wei-Dong; LI Wei-Guo; LIU Huai-Min; OU-YANG Qun; SHEN Xiao-Yan; YUAN Ye; ZHANG Yao
Subjects: Physics >> Nuclear Physics

Considering the aging effects of existing Inner Drift Chamber (IDC) of BES\uppercase\expandafter{\romannumeral3}, a GEM based inner tracker is proposed to be designed and constructed as an upgrade candidate for IDC. This paper introduces a full simulation package of CGEM-IT with a simplified digitization model, describes the development of the softwares for cluster reconstruction and track fitting algorithm based on Kalman filter method for CGEM-IT. Preliminary results from the reconstruction algorithms are obtained using a Monte Carlo sample of single muon events in CGEM-IT.

submitted time 2016-09-13 Hits1025Downloads564 Comment 0

7. chinaXiv:201609.00888 [pdf]

The study of the aging behavior on large area MCP-PMT

WANG Wen-Wen; QIAN Sen; QI Minga XIA Jing-Kai; CHENG Ya-Ping; NING Zhe; LUO Feng-Jiao; HENG Yue-Kun; LIU Shu-Lin; SI Shu-Guang; Sun Jian-Ning; LI Dong; WANG Xing-Chao; HUANG Guo-Rui; TIAN Jing-Shou; WEI Yong-Lin; LIU Hu-Lin; LI Wei-Hua; WANG Xing; XIN Li-Wei
Subjects: Physics >> Nuclear Physics

Aging experiments of a novel type of large area MCP-PMT made by JUNO collaboration were conducted.In these aging experiments, the multi-photoelectron spectrum and single photoelectron spectrum were measured daily,as well as the MCP resistance of the second PMT before and after the experiment. Two PMTs were aged successivelyfor cross check. The first PMT was aged for 52 days, while the other one was aged for 84 days. In order to study the mechanism of the aging process, the high voltage on the second PMT was increased to accelerate its aging process when the cumulative output of charge from its anode was about 4 C. From our study, it can be known that large area MCP-PMT aging had a strong relationship with the related MCPs. In accordance with the PMT aging curve,a PMT aging model was setup and a general aging formula was given.

submitted time 2016-09-13 Hits1238Downloads721 Comment 0

8. chinaXiv:201605.01493 [pdf]

Self-Assembly of Ferritin Nanoparticles into an Enzyme Nanocomposite with Tunable Size for Ultrasensitive Immunoassay

Men, Dong; Zhou, Juan; Zhang, Zhi-Ping; Cui, Zong-Qiang; Deng, Jiao-Yu; Wang, Dian-Bing; Zhang, Xian-En; Men, Dong; Zhang, Ting-Ting; Hou, Li-Wei; Shi, Yuan-Yuan; Zhang, Jin-Li
Subjects: Biology >> Biophysics

The self-assembly of nanoparticles into larger superstructures is a powerful strategy to develop novel functional nanomaterials, as these superstructures display collective properties that are different to those displayed by individual nanoparticles or bulk samples. However, there are increasing bottlenecks in terms of size control and multifunctionalization of nanoparticle assemblies. In this study, we developed a self-assembly strategy for construction of multifunctional nanoparticle assemblies of tunable size, through rational regulation of the number of self-assembling interaction sites on each nanoparticle. As proof-of-principle, a size-controlled enzyme nanocomposite (ENC) was constructed by self-assembly of streptavidin-labeled horseradish peroxidase (SA-HRP) and autobiotinylated ferritin nanoparticles (bFNP). Our ENC integrates a large number of enzyme molecules, together with a streptavidin-coated surface, allowing for a drastic increase in enzymatic signal when the SA is bound to a biotinylated target molecule. As result, a 10000-fold increase in sensitivity over conventional enzyme-linked immunosorbent assays (ELISA) methods was achieved in a cardiac troponin immunoassay. Our method presented here should provide a feasible approach for constructing elaborate multifunctional superstructures of tunable size useful for a broad range of biomedical applications.

submitted time 2016-05-12 Hits1408Downloads819 Comment 0

9. chinaXiv:201605.01478 [pdf]

Impaired maturation of large dense-core vesicles in muted-deficient adrenal chromaffin cells

Hao, Zhenhua; Feng, Yaqin; Ma, Jing; Li, Wei; Hao, Zhenhua; Wei, Lisi; Chen, Xiaowei; Zhou, Zhuan; Chen, Liangyi; Wei, Lisi; Chen, Xiaowei; Zhou, Zhuan; Chen, Liangyi; Feng, Yaqin; Du, Wen; Li, Wei
Subjects: Biology >> Biophysics >> Cell Biology

The large dense-core vesicle (LDCV), a type of lysosome-related organelle, is involved in the secretion of hormones and neuropeptides in specialized secretory cells. The granin family is a driving force in LDCV biogenesis, but the machinery for granin sorting to this biogenesis pathway is largely unknown. The mu mutant mouse, which carries a spontaneous null mutation on the Muted gene (also known as Bloc1s5), which encodes a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), is a mouse model of Hermansky-Pudlak syndrome. Here, we found that LDCVs were enlarged in mu adrenal chromaffin cells. Chromogranin A (CgA, also known as CHGA) was increased in mu adrenals and muted-knockdown cells. The increased CgA in mu mice was likely due a failure to export this molecule out of immature LDCVs, which impairs LDCV maturation and docking. In mu chromaffin cells, the size of readily releasable pool and the vesicle release frequency were reduced. Our studies suggest that the muted protein is involved in the selective export of CgA during the biogenesis of LDCVs.

submitted time 2016-05-12 Hits2236Downloads1369 Comment 0

10. chinaXiv:201605.01400 [pdf]

Core component EccB1 of the Mycobacterium tuberculosis type VII secretion system is a periplasmic ATPase

Zhang, Xiao-Li; Zhang, Xian-En; Zhang, Xiao-Li; Li, De-Feng; Fleming, Joy; Wang, Li-Wei; Zhou, Ying; Wang, Da-Cheng; Zhang, Xian-En; Bi, Li-Jun; Zhang, Xiao-Li; Li, De-Feng; Fleming, Joy; Wang, Li-Wei; Zhou, Ying; Wang, Da-Cheng; Zhang, Xian-En; Bi, Li-Jun; Zhang, Xiao-Li
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology

Pathogenic mycobacteria transport virulence factors across their complex cell wall via a type VII secretion system (T7SS)/early secreted antigenic target-6 of kDa secretion system (ESX). ESX conserved component (Ecc) B, a core component of the T7SS architecture, is predicted to be a membrane bound protein, but little is known about its structure and function. Here, we characterize EccB1, showing that it is an ATPase with no sequence or structural homology to other ATPases located in the cell envelope of Mycobacterium tuberculosis H37Rv. We obtained the crystal structure of an EccB1-DN72 truncated transmembrane helix and performed modeling and ATP docking studies, showing that EccB1 likely exists as a hexamer. Sequence alignment and ATPase activity determination of EccB1 homologues indicated the presence of 3 conserved motifs in the N- and C-terminals of EccB1-DN72 that assemble together between 2 membrane proximal domains of the EccB1-DN72 monomer. Models of the EccB1 hexamer show that 2 of the conserved motifs are involved in ATPase activity and form an ATP binding pocket located on the surface of 2 adjacent molecules. Our results suggest that EccB may act as the energy provider in the transport of T7SS virulence factors and may be involved in the formation of a channel across the mycomembrane.

submitted time 2016-05-12 Hits1636Downloads1010 Comment 0

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