An Integrated Method for Coding Trees, Measuring Tree Diameter, and Estimating Tree Positions

Accurately measuring tree diameter at breast height (DBH) and estimating tree positions in a sample plot are important in tree mensuration. The main aims of this paper include (1) developing a new, integrated device that can identify trees using the quick response (QR) code technique to record tree identifications, measure DBH, and estimate tree positions concurrently; (2) designing an innovative algorithm to measure DBH using only two angle sensors, which is simple and can reduce the impact of eccentric stems on DBH measures; and (3) designing an algorithm to estimate the position of the tree by combining ultra-wide band (UWB) technology and altitude sensors, which is based on the received signal strength indication (RSSI) algorithm and quadrilateral localization algorithm. This novel device was applied to measure ten 10 × 10 m square plots of diversified environments and various tree species to test its accuracy. Before measuring a plot, a coded sticker was fixed at a height of 1.3 m on each individual tree stem, and four UWB module anchors were set up at the four corners of the plot. All individual trees\u27 DBHs and positions within the plot were then measured. Tree DBH, measured using a tree caliper, and the values of tree positions, measured using tape, angle ruler, and inclinometer, were used as the respective reference values for comparison. Across the plots, the decode rate of QR codes was 100%, with an average response time less than two seconds. The DBH values had a bias of 1.89 mm (1.88% in relative terms) and a root mean square error (RMSE) of 5.38 mm (4.53% in relative terms). The tree positions were accurately estimated; the biases on the x-axis and the y-axis of the tree position were -8.55-14.88 cm and -12.07-24.49 cm, respectively, and the corresponding RMSEs were 12.94-33.96 cm and 17.78-28.43 cm. The average error between the estimated and reference distances was 30.06 cm, with a standard deviation of 13.53 cm. The device is cheap and friendly to use in addition to its high accuracy. Although further studies are needed, our method provides a great alternative to conventional tools for improving the efficiency and accuracy of tree mensuration

Time Variation of Fine-Structure Constant Constrained by [O III] Emission-Lines at 1.1<z<3.7

[O III]$\lambda\lambda$4960,5008 doublet are often the strongest narrow emission lines in starburst galaxies and quasi-stellar objects (QSOs), and thus are a promising probe to possible variation of the fine-structure constant $\alpha$ over cosmic time. Previous such studies using QSOs optical spectra were limited to $z<1$. In this work, we constructed a sample of 40 spectra of Ly$\alpha$ emitting galaxies (LAEs) and a sample of 46 spectra of QSOs at $1.09<z<3.73$ using the VLT/X-Shooter near-infrared spectra publicly available. We measured the wavelength ratios of the two components of the spin-orbit doublet and accordingly calculated $\alpha(z)$ using two methods. Analysis on all of the 86 spectra yielded $\Delta\alpha/\alpha=(-3\pm6)\times10^{-5}$ with respect to the laboratory $\alpha$ measurements, consistent with no variation over the explored time interval. If assuming a uniform variation rate, we obtained $\alpha^{-1}{\rm d}\alpha/{\rm d}t = (-3\pm6)\times10^{-15}$ yr$^{-1}$ within the last 12 Gyrs. Extensive tests indicate that $\alpha$ variation could be better constrained using starburst galaxies' spectra than using QSO spectra in future studies.Comment: 24 pages, 22 figures. Accepted for publication in MNRA

Discovery of An Active Intermediate-Mass Black Hole Candidate in the Barred Bulgeless Galaxy NGC 3319

We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy $\rm NGC~3319$. The point X-ray source revealed by archival Chandra and XMM-Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy distribution derived from the unresolved X-ray and UV-optical flux is comparable with active galactic nuclei (AGNs) rather than ultra-luminous X-ray sources, although its bolometric luminosity is only $3.6\times10^{40}~\rm erg~s^{-1}$. Assuming an Eddington ratio range between 0.001 and 1, the black hole mass (M_\rm{BH}) will be located at $3\times10^2-3\times10^5~M_{\odot}$, placing it in the so-called IMBH regime and could be the one of the lowest reported so far. Estimates from other approaches (e.g., fundamental plane, X-ray variability) also suggest M_\rm{BH}\lesssim10^5~M_{\odot}.Similar to other BHs in bulgeless galaxies, the discovered IMBH resides in a nuclear star cluster with mass of $\sim6\times10^6~M_{\odot}$. The detection of such a low-mass BH offers us an ideal chance to study the formation and early growth of SMBH seeds, which may result from the bar-driven inflow in late-type galaxies with a prominent bar such as $\rm NGC~3319$.Comment: ApJ accepted, 2 tables, 6 figure