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71.
针对多个固态激光雷达协同工作时,需要准确地进行外参标定的实际需求,提出一种基于点云配准的多固态激光雷达自动标定算法。该标定算法由标定物分割、初始配准和精确配准三个阶段构成。在标定物分割阶段,首先通过叠加多帧非重复扫描数据制作标定点云,再使用半径滤波和体素下采样滤波分割出纹理特征明显的目标点云。在初始配准阶段,使用3D-HARRIS算法提取关键点,并使用方向直方图(SHOT)特征描述子进行特征描述,然后匹配对应点并使用采样一致算法完成初始配准;在精配准阶段使用迭代最近邻(ICP)算法进行精确配准,从而获得精确的外参标定效果。在Bunny兔数据集和现场获得的数据上进行实验,结果表明,当保证配准平均误差小于1 mm的前提下,所提出算法的性能优于多种现有算法。 相似文献
72.
提出了一款应用于Ku波段的宽带高增益基片集成腔(Substrate Integrated Cavity,SIC)圆极化阵列天线。通过引入沿SIC口径面对角线放置的一对半月形寄生贴片和SIC底部馈电纵缝,使SIC中的TM_(211)和TM_(121)谐振模式幅值相等、相位相差90°,产生高增益圆极化辐射。同时,双寄生贴片还引入了一种背腔缝隙耦合振子圆极化辐射模式,扩宽了天线高增益圆极化辐射带宽。在此基础上,设计了一款2×2单元顺序旋转馈电的SIC圆极化阵列天线。阵列天线采用双层基片集成波导顺序相移馈电网络进行馈电,进一步增大了天线的圆极化带宽。综合考虑天线的-10 dB反射系数带宽、3 dB轴比带宽和3 dB增益带宽,测试结果表明,圆极化阵列天线的有效带宽为10.74-13.30 GHz(21.3%),在通带范围内最大增益为14.50 dBi。 相似文献
73.
74.
The hydrolysis reaction of
,
and
,
-dipalmitoylphosphatidylcholine (DPPC) catalized by bee venom phospholipase A2 was studied in spreading monolayer at the water/air interface. DPPC and the hydrolysis products, palmitic acid and
-lysophosphatidylcholine, palmitoyl were characterized at the interface by means of surface pressure, surface potential and ellipsometric measurements. Furthermore, mixed monolayers of reagents and products were investigated to ascertain their miscibility. The results show that the hydrolysis reaction can be followed by the decrease of surface pressure with time on subphases containing β-cyclodextrin, a well-known complexing agent of many amphiphilic compounds. The order of the reaction, the kinetic constant and other kinetic parameters are deduced. 相似文献
75.
In this paper the formation mechanism of iron macro-spheres in
a plasma medium is dealt with, including the conditions under which such
spheres are formed. The geometry of the spheres referred to above
depends on the main technological parameters involved in the production
of pores. Conditions under which pores occur within macro-spheres are
also established. The radii of these pores are sensitive to the velocity
distribution within the plasma jet section 相似文献
76.
We provide a quick elementary solution of the mean spherical model in a random external field. This also allows an immediate proof of the self-averaging property of the free energy. We calculate the free energy by means of the replica method, i.e., for any (not necessarily integer) replica numbern, and show that when a phase transition occurs the limits
andn 0 are not interchangeable. 相似文献
77.
Crystal structure of the title compound, Cu(phen)(H2O)2·ClO4(phen=1,10-phenanthroline), was deter-mined by X-ray crystallography. It crystallizes in the monoclinic system, space group C2/c with lattice parameters a=1.49071(4)nm, b=1.38594(4)nm, c=0.70292(1)nm, β=108.509(1)° and Z=4; The Cu(Ⅰ) ion is chelated by a phen ligand and two aqua ligands in cis arrangement and assumes a C2 symmetric square-planar geometry with the CuN2O2 core. Eight Cu(phen)(H2O)2·ClO4 molecules are interconnected by strong hydrogen bonds between coordinated water molecules and uncoordinated perchlorate anions to form a molecular scale cavities along c axis. The bond distances of Cu-N and Cu-O are 0.2003(4)nm and 0.1973(3)nm, respectively. CCDC: 197600. 相似文献
78.
Gino Morisi Marina Patriarca Ferdinando Chiodo Anna Minoprio Antonio Menditto 《Mikrochimica acta》1996,123(1-4):281-290
Between 1992 and 1994, a new screening campaign for blood Pb monitoring in the Italian general population was carried out. Since the first campaign (started in 1978, in accomplishment of the European Community Directive 77/312/EEC) a working group of the Laboratory of Clinical Biochemistry at the Italian National Institute of Health (Istituto Superiore di Sanità), as the Reference Centre (RC), has coordinated the activity of various laboratories spread over the national territory. Appropriate quality assurance procedures, including an external quality assessment scheme (EQAS), were elaborated. Within the EQAS, three or four trials were carried out every year. Each laboratory participating in the trial analyzed eight control samples prepared from cow blood at different Pb concentrations. The results obtained by each peripheral laboratory and the RC between 1992 and 1994 have been compared by regression analysis. The same statistical method was adopted to compare the results obtained by each peripheral laboratory and the RC in the duplicate analysis of about 10 per cent of the human samples collected during the 1992–1994 monitoring campaign. There was no evidence of systematic differences between the regression lines obtained on control and human samples. In spite of the lower Pb concentration in the control samples analyzed during the 1992–1994 campaign, the analytical performance of the laboratories was better than that obtained in the previous screening campaign (1985–1986). Blood Pb levels observed in human samples collected between 1992 and 1994, confirm the downward time trend observed in the campaigns carried out in 1978–1979, 1980–1981 and 1985–1986. This study confirms that the results obtained in an EQAS are representative of the actual performance in the analysis of real (human) samples. 相似文献
79.
Warrener Ronald N. Malpass John R. Butler Douglas N. Sun Guangxing 《Structural chemistry》2001,12(3-4):291-304
The thermal addition of N-carbobenzyloxyisoindole (N-Z isoindole) 11a, generated by the reaction of 3,6-di(2-pyridyl)-s-tetrazine 9 with N-Z 7-azabenzonorbornadiene 8a, onto dimethyl tricyclo[4.2.1.02.5]nona-3,7-diene-3,4-dicarboxylate 17 occurred site selectively at the cyclobutene -bond to form a stereoisomeric mixture of 1 : 1-adducts 18 and 19, in which the bent-frame isomer 19 was dominant (ratio 5 : 1). In contrast, N-benzyl tetrafluoroisoindole 11c reacted with 17 only under high-pressure conditions (14 kbar, RT, 4 days) to afford 1 : 1-adducts at the cyclobutene site, in which the extended-frame isomer 18c was dominant and the accompanying bent-frame product 19c reverted to starting materials soon after isolation. These same stereoselectivities were used to prepare "windscreen wiper" compound 28c having two mobile N-benzyl substituents attached to a rigid scaffold by the reaction of N-benzyl tetrafluoroisoindole 11c with tetramethyl tetracyclo[4.4.1.0.2,5.07.10]undeca-3,8-diene-3,4,7,8-tetracarboxylate 23. Cavity bis-(cyclobutene-1,2-diester) 6 reacted with N-benzyl tetrafluoroisoindole 11c twice over to produce cavity structure 36 with two O- and two N-benzyl bridges on the inner face, whereas the narrower cavity bis-alkene 32 stopped at the 1 : 1-addition stage. The dynamics of the Z-group in the dual adducts 26a–28a are discussed briefly and key adducts and cavity systems have been structurally evaluated by X-ray crystallography, VT NMR, and molecular modeling. 相似文献
80.
A high-powered, microwave-induced nitrogen–oxygen plasma (N2–O2–MIP) generated by using an Okamoto cavity at atmospheric pressure was investigated when the observation height, the flow rate of carrier gas, and the oxygen content were varied as the experimental parameters. The emission characteristics of the plasma were evaluated with regard to the excitation temperature and the intensity ratio of atomic line to ionic line. The excitation temperature of the N2–O2–MIP was in the range of 5100–5700 K when the oxygen content was varied from 0 to 30% at the observation height of 7 mm and the carrier gas flow rate of 0.6 l/min. The intensity ratio of atomic line to ionic line was elevated with an increase in the oxygen content. 相似文献