Using airborne lidar to discern age classes of cottonwood trees in a riparian area

Airborne lidar (light detecting and ranging) is a useful tool for probing the structure of forest canopies. Such information is not readily available from other remote sensing methods and is essential for modern forest inventories. In this study, small-footprint lidar data were used to estimate biophysical properties of young, mature, and old cottonwood trees in the San Pedro River basin near Benson, Arizona. The lidar data were acquired in June 2004, using Optech's 1233 ALTM during flyovers conducted at an altitude of 600 m. Canopy height, crown diameter, stem dbh, canopy cover, and mean intensity of return laser pulses from the canopy surface were estimated for the cottonwood trees from the data. Linear regression models were used to develop equations relating lidar-derived tree characteristics with corresponding field acquired data for each age class of cottonwoods. The lidar estimates show a good degree of correlation with ground-based measurements. This study also shows that other parameters of young, mature, and old cottonwood trees such as height and canopy cover, when derived from lidar, are significantly different (P < 0.05). Additionally, mean crown diameters of mature and young trees are not statistically different at the study site (P = 0.31). The results illustrate the potential of airborne lidar data to differentiate different age classes of cottonwood trees for riparian areas quickly and quantitatively. Copyright © 2006 by the Society of American Foresters

Implications of quality deterioration for public foodgrain stock management and consumers in Bangladesh

In the late 1990s, government policy in Bangladesh shifted in favor of increased public foodgrain stocks, setting official minimum stock targets of 1.0 to 1.2 million tons, as compared to operational targets of about 700 to 800 thousand metric tons in the early 1990s. Because no mechanism for stock rotation involving simultaneous buying and selling grain at a wholesale level exists, higher stock levels with no increase in distribution led to an increase in average age of stocks and problems of stock quality deterioration. This paper extends earlier analyses of stock policy by focusing on a key aspect of stock management in Bangladesh: the economic costs of stock quality deterioration in storage, including the implicit costs to recipients of Public Food Distribution System (PFDS) foodgrain. Using market prices to value procurement and distribution of rice and wheat, consumer and producer subsidies accounted for 57.4 and 20.9 percent, respectively, of net outlay in 2000/01. Implicit losses to rice consumers due to quality deterioration were significant in 2000/01: about 1.05 billion Taka (about 19 million dollars), equal to 10.9 percent of total net outlay on rice of the PFDS. Analysis of the costs and benefits of alternative stock targets based on calculations of the minimum age of stock on a monthly basis indicates that moderate increases in the size of stock (e.g. 200 thousand tons), lead to only small net marginal outlays. However, unless procurement and distribution are also raised, the age and quality of the stock for distribution deteriorates, resulting in significant losses to program recipients.Grain production ,Bangladesh ,Food supply ,

Composite fermions close to the one-half filling of the lowest Landau level revisited

By strictly adhering to the microscopic theory of composite fermions for the Landau-level filling fractions nu_e = p/(2 p + 1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by Willett and co-workers concerning two-dimensional electron systems with nu_e close to 1/2. Our results imply that the electron band mass m_b, as distinct from the composite fermion mass m_*, must undergo a substantial increase under the conditions corresponding to nu_e approximately equal to 1/2. In view of the relatively low aerial electronic densities n_e to which the underlying SAW experiments correspond, our finding conforms with the experimental results by Shashkin et al. [Phys. Rev. B 66, 073303 (2002)], concerning two-dimensional electrons in silicon, that signal sharp increase in m_b for n_e decreasing below approximately 2 x 10^{11} cm^{-2}. We further establish that a finite mean-free path l_0 is essential for the observed linearity of the longitudinal conductivity sigma_{xx}(q) as deduced from the SAW velocity shifts.Comment: 5 pages, 2 postscript figure

Charge response function and a novel plasmon mode in graphene

Polarizability of non-interacting 2D Dirac electrons has a 1/\sqrt{qv-\omega} singularity at the boundary of electron-hole excitations. The screening of this singularity by long-range electron-electron interactions is usually treated within the random phase approximation. The latter is exact only in the limit of N -> infinity, where N is the ``color'' degeneracy. We find that the ladder-type vertex corrections become crucial close to the threshold as the ratio of the n-th order ladder term to the same order RPA contribution is (\ln|qv-\omega|)^n/N^n$. We perform analytical summation of the infinite series of ladder diagrams which describe excitonic effect. Beyond the threshold, qv>\omega, the real part of the polarization operator is found to be positive leading to the appearance of a strong and narrow plasmon resonance.Comment: 4 pages, 3 figures,typos correcte

Otoritas Wahyu dan Kreativitas Akal dalam Penetapan Hukum Islam (Tinjauan Epistemologis terhadap Hukum Islam)

Penelitian ini bet'tujuan menelaah adanya kreativitas akal dalam penetapan hukum Islam yang bersumber dati ototitas wahyu Tuhan, baik yang langsung teredaksikan dalam AI-Quran, maupun dalam Hadits Nabi. Penelitian berangkat dari permasalahan bahwa hukum Islam bersumbet· dati wahyu Tuhan yang sifatnya mutlak. Di sisi lain produk hukum tersebut dipemntukkan bagi manusia dengan segenap kemampuan akalnya. Maka, bagaimana keduanya dikompromikan. Hipotesisnya adalah bahwa hukum Islam sebenarnya mempakan sistem ilmu yang bersumber datiototitas wahyu, namun demikian kreativitas akal mengambil peran interpretasi dan rekonstmksi dalam pembakuannya.Penelitian dilakukan dengan cara menempatkan hukum Islam sebagai objek yang ditelaah, dan epistemologi atau filsafat pengetahuan menjadi sudut pandangnya. Dalam proses analisis ini unsur metodis penelitian filsafat seperti diskriptif, analisis, dan sintesis dipergunakan.Istimbath hukum Islam pada hakikatnya adalah proses pemahaman akal terhadap firman Tuhan. Sebagai sebuah ciptaan Tuhan, hukum Islam memuat ptinsipptinsip atura'n yang sifatnya tetap dan abadi, namun pengakuan terhadap eksistensi akal menjamin pelaksanaannya bersifat fleksibel. Pada wilayah inilah fiqh dipahami sebagai wujud upaya ilmiah manusia untuk mengkaji dan menyusun ptinsip-prinsip Tuhan itu ke dalam sistem hukum yang manusiawi. Kreativitas akal (ar-rayu) dipergunakanansebagai sumber pengetahuan hukum Islam ketiga setelah sumber utamasecara hatfiah tidak memuat ketentuan hukum yang diperlukan. Ar-ra'yu dibutuhkan untuk mengetahui hukum yang tersirat di Balik suatu redaksi AI-Quran yang memerlukan pengkajian lebih, mendalam. Latar belakang dari diakuinya peranan akal ini adalah Kenyataan berkembangnya kehidupan masyarakat yang diikuti oleh berbagai permasalahan hidup yang tidak ditemui jawabannya secara halfiah dalam AI-Quran maupun AI-Hadits

Structural analysis of long arm excavator boom for optimization performance under maximum breakout condition

Long Arm Excavators are widely used in the construction site for excavating deep holes or trenches. However, due to the often-severe work conditions, such as large lifting loads, poor ground conditions to sustain the machine’s self-weight, Long Arm Excavator parts are subjected to constant wear and tear, incurring downtime losses and safety issues. The boom is considered the most critically affected part of the machine in these work conditions, where the high forces and unpredictable elements at the worksite could severely affect the machine’s overall performance. A potential solution is the reinforcement of the boom to improve its robustness. As an industrial collaborative project, the present study examines the performance of an existing machine with simulated improvement of the boom with such an approach, i.e. incorporation of stiffener reinforcement. Simulation works were carried out with Ansys Workbench 19.2 to assess the boom’s performance in terms of resulting stress, strain and deformation under a series of improved conditions, which include varying the dimensions and positions of the stiffeners on the boom. The improved conditions were Improvement I: stiffeners thickness reduction to 10mm, Improvement II: a combination of different stiffeners thickness reduction which 10mm and 8mm at critical and non-critical part of the boom, Improvement III: removal of half intermediate stiffeners thickness 12mm and Improvement IV: removal of half intermediate stiffeners thickness 8mm. Structural analysis was conducted based on the maximum breakout condition in which the excavator generates maximum digging force. From the analysis, it was found that the maximum equivalent stress of the boom decreased with the number of stiffeners. The combination of different stiffeners thickness could also increase the boom’s strength while decreasing the maximum equivalent stress. The lowest maximum equivalent stress of the boom was achieved via Improvement II with a reduction of 26.1% maximum equivalent stress. Removal of non-critical part stiffeners also kept stress values under the designated stress limits against fatigue failure, i.e. 44.49 MPa and 42.47 MPa (Improvement III and IV). In summary, the optimal design could be obtained with improvement II. This would effectively save on the manufacturing costs while maximizing the machine’s performance on-site, simultaneously reducing downtime and hence operating costs and time

Riparian vegetation classification from airborne laser scanning data with an emphasis on cottonwood trees

The high point density of airborne laser mapping systems enables achieving a detailed description of geographic objects and the terrain. Growing experience indicates, however, that extracting useful information directly from the data can be difficult. In this study, small-footprint lidar data were used to differentiate between young, mature, and old cottonwood trees in the San Pedro River Basin near Benson, Arizona, USA. The lidar data were acquired in June 2003, using the Optech Incorporated ALTM 1233 (Optech Incorporated, Toronto, Ont.), during flyovers conducted at an altitude of 750 m. The lidar data were preprocessed to create a two-band image of the study site: a high-accuracy canopy altitude model band, and a near-infrared intensity band. These lidar-derived images provided the basis for supervised classification of cottonwood age categories, using a maximum likelihood algorithm. The results of classification illustrate the potential of airborne lidar data to differentiate age classes of cottonwood trees for riparian areas quickly and accurately. © 2006, Taylor & Francis Group, LLC. All rights reserved

Infrared identification of high-mass X-ray binaries discovered by INTEGRAL

Since it started observing the sky, the INTEGRAL satellite has discovered new categories of high mass X-ray binaries (HMXB) in our Galaxy. These observations raise important questions on the formation and evolution of these rare and short-lived objects. We present here new infrared observations from which to reveal or constrain the nature of 15 INTEGRAL sources, which allow us to update and discuss the Galactic HMXB population statistics. After previous photometric and spectroscopic observing campaigns in the optical and near-infrared, new photometry and spectroscopy was performed in the near-infrared with the SofI instrument on the ESO/NTT telescope in 2008 and 2010 on a sample of INTEGRAL sources. These observations, and specifically the detection of certain features in the spectra, allow the identification of these high-energy objects by comparison with published nIR spectral atlases of O and B stars. We present photometric data of nine sources (IGR J10101-5654, IGR J11187-5438, IGR J11435-6109, IGR J14331-6112, IGR J16328-4726, IGR J17200-3116, IGR J17354-3255, IGR J17404-3655, and IGR J17586-2129) and spectroscopic observations of 13 sources (IGR J10101-5654, IGR J11435-6109, IGR J13020-6359, IGR J14331-6112, IGR J14488-5942, IGR J16195-4945, IGR J16318-4848, IGR J16320-4751, IGR J16328-4726, IGR J16418-4532, IGR J17354-3255, IGR J17404-3655, and IGR J17586-2129). Our spectroscopic measurements indicate that: five of these objects are Oe/Be high-mass X-ray binaries (BeHMXB), six are supergiant high-mass X-ray binaries (sgHMXB), and two are sgB[e]. From a statistical point of view, we estimate the proportion of confirmed sgHMXB to be 42% and that of the confirmed BeHMXB to be 49%. The remaining 9% are peculiar HMXB.Comment: Accepted for publication in A&A (in press