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ALFVÉNIC TURBULENCE BEYOND THE AMBIPOLAR DIFFUSION SCALE
Burkhart, Blakesley,Lazarian, A.,Balsara, D.,Meyer, C.,Cho, J. IOP Publishing 2015 The Astrophysical journal Vol.805 No.2
<P>We investigate the nature of the Alfvenic turbulence cascade in two-fluid magnetohydrodynamic (MHD) simulations in order to determine if turbulence is damped once the ion and neutral species become decoupled at a critical scale called the ambipolar diffusion scale (L-AD). Using mode decomposition to separate the three classical MHD modes, we study the second-order structure functions of the Alfven mode velocity field of both neutrals and ions in the reference frame of the local magnetic field. On scales greater than L-AD we confirm that two-fluid turbulence strongly resembles single-fluid MHD turbulence. Our simulations show that the behavior of two-fluid turbulence becomes more complex on scales less than L-AD. We find that Alfvenic turbulence can exist past L-AD when the turbulence is globally super-Alfvenic, with the ions and neutrals forming separate cascades once decoupling has taken place. When turbulence is globally sub-Alfvenic and hence strongly anisotropic, with a large separation between the parallel and perpendicular decoupling scales, turbulence is damped at L-AD. We also find that the power spectrum of the kinetic energy in the damped regime is consistent with a k(-4) scaling (in agreement with the predictions of Lazarian et al.).</P>
Modelling Growth and Yield for Intensively Managed Forests
Burkhart, Harold E. Institute of Forest Science 2008 Journal of Forest Science Vol.24 No.3
Growth and yield prediction methods, ranging from whole-stand models to individual-tree models, have been developed for forest types managed for wood production. The resultant models are used for a host of purposes including inventory updating, management planning, evaluation of silvicultural alternatives, and harvest scheduling. Because of the large investment in developing growth and yield models for improved genotypes and silvicultural practices for loblolly pine (Pinus taeda) in the Southern United States, this region serves to illustrate approaches for modelling intensively managed forests. Analytical methods and computing power generally do not restrict development of reliable growth and yield models. However, long-term empirical observations on stand development, which are time consuming and expensive to obtain, often limit modelling efforts. Given that growth and yield models are used to project present volumes and to evaluate alternative treatment effects, data of both the inventory type and the experimental type are needed. Data for developing stand simulators for loblolly pine plantations have been obtained from a combination of permanent plots in operational forest stands and silvicultural experiments; these data collection efforts are described and summarized. Modelling is essential for integrating and synthesizing diverse information, identifying knowledge gaps, and making informed decisions. The questions being posed today are more complex than in the past, thus further accentuating the need for comprehensive models for stand development.
Modelling Growth and Yield for Intensively Managed Forests
Harold E. Burkhart 강원대학교 산림과학연구소 2008 Journal of Forest Science Vol.24 No.3
Growth and yield prediction methods, ranging from whole-stand models to individual-tree models, have been developed for forest types managed for wood production. The resultant models are used for a host of purposes including inventory updating, management planning, evaluation of silvicultural alternatives, and harvest scheduling. Because of the large investment in developing growth and yield models for improved genotypes and silvicultural practices for loblolly pine (Pinus taeda) in the Southern United States, this region serves to illustrate approaches for modelling intensively managed forests. Analytical methods and computing power generally do not restrict development of reliable growth and yield models. However, long-term empirical observations on stand development, which are time consuming and expensive to obtain, often limit modelling efforts. Given that growth and yield models are used to project present volumes and to evaluate alternative treatment effects, data of both the inventory type and the experimental type are needed. Data for developing stand simulators for loblolly pine plantations have been obtained from a combination of permanent plots in operational forest stands and silvicultural experiments; these data collection efforts are described and summarized. Modelling is essential for integrating and synthesizing diverse information, identifying knowledge gaps, and making informed decisions. The questions being posed today are more complex than in the past, thus further accentuating the need for comprehensive models for stand development.
최정기,유병오,Harold E. Burkhart 한국산림과학회 2007 한국산림과학회지 Vol.96 No.2
Allometry, basal area equations, and volume equations were developed with various tremeasurement variables for the major species, Quercus mongolica and Quercus variabilis, in Korean naturalhardwood forests. For alometry models, the relationships betwen total height-DBH, crown width-DBH,height to the widest portion of the crown-total height, and height to base of crown-total height wereinvestigated. Multiple regresion methods were used to relate anual basal area growth to tree variables ofinitial size (DBH, total height, crown width) and relative size (relative diameter, relative height) as well aslive crown ratio). For tree volume equations, the combined-variable and Schumacher models were fittedwith DBH, total height and crown width for both species.
The Interaction of Relativistic Spacecrafts with the Interstellar Medium
Hoang, Thiem,Lazarian, A.,Burkhart, Blakesley,Loeb, Abraham American Astronomical Society 2017 The Astrophysical journal Vol.837 No.1
<P>The Breakthrough Starshot initiative aims to launch a gram-scale spacecraft to a speed of nu similar to 0.2c, capable of reaching the nearest star system, alpha Centauri, in about 20 years. However, a critical challenge for the initiative is the damage to the spacecraft by interstellar gas and dust during the journey. In this paper, we quantify the interaction of a relativistic spacecraft with gas and dust in the interstellar medium (ISM). For gas bombardment, we find that damage by track formation due to heavy elements is an important effect. We find that gas bombardment can potentially damage the surface of the spacecraft to a depth of similar to 0.1 mm for quartz material after traversing a gas column of N-H similar to 2 x 10(18) cm(-2) along the path to alpha Centauri, whereas the effect is much weaker for graphite material. The effect of dust bombardment erodes the spacecraft surface and produces numerous craters due to explosive evaporation of surface atoms. For a spacecraft speed nu = 0.2c, we find that dust bombardment can erode a surface layer of similar to 0.5 mm thickness after the spacecraft has swept a column density of N-H similar to 3 x 10(17) cm(-2) assuming the standard gas-to-dust ratio of the ISM. Dust bombardment also damages the spacecraft surface by modifying the material structure through melting. We calculate the equilibrium surface temperature due to collisional heating by gas atoms as well as the temperature profile as a function of depth into the spacecraft. Our quantitative results suggest methods for damage control, and we highlight possibilities for shielding strategies and protection of the spacecraft.</P>
Park, Yong-Tae,Kim, Young-Doo,Burkhart, Richard D.,Caldwell, Norris J. Korean Chemical Society 1988 Bulletin of the Korean Chemical Society Vol.9 No.2
The Photophysical and photochemical properties of Ruthenium bipyridine with two long hydrocarbon chains, $[Ru(bipy)_2(dhbipy)]^{2+}$ and transient phenothiazine derivative cation radical $(PTD^+)$ in the cationic vesicle were studied. Transient absorption spectra of cation radical of phenothiazine derivative in the vesicle system containing the $Ru^{2+}$ complex, $[Ru(bipy)_2(dhbipy)]^{2+}$, (1) as sensitizer and phenothiazine derivative as electron donor was observed by XeCl excimer laser photolysis system. Thus the excited ruthenium complex would be quenched by phenothiazine derivative(PTD) reductively in the vesicle system. The quenching rate constant($K_Q$) of $Ru^{2+}$ with two long hydrocarbon chains in the vesicle by PTD was $9.6{\times}10^8M^{-1}S^{-1}$. The absorption decay kinetics showed that lifetime of phenothiazine derivative cation radical is a value in the 4-8m sec range.
Choi, Jung-Kee,You, Byung-Oh,Burkhart, Harold E. Korean Society of Forest Science 2007 한국산림과학회지 Vol.96 No.2
Allometry, basal area equations, and volume equations were developed with various tree measurement variables for the major species, Quercus mongolica and Quercus variabilis, in Korean natural hardwood forests. For allometry models, the relationships between total height-DBH, crown width-DBH, height to the widest portion of the crown-total height, and height to base of crown-total height were investigated. Multiple regression methods were used to relate annual basal area growth to tree variables of initial size (DBH, total height, crown width) and relative size (relative diameter, relative height) as well as competition measures (competition index, crown class, exposed crown area, percent exposed crown area, live crown ratio). For tree volume equations, the combined-variable and Schumacher models were fitted with DBH, total height and crown width for both species.
Statistical Tracing of Magnetic Fields: Comparing and Improving the Techniques
Yuen, Ka Ho,Chen, Junda,Hu, Yue,Ho, Ka Wai,Lazarian, A.,Lazarian, Victor,Yang, Bo,Burkhart, Blakesley,Correia, Caio,Cho, Jungyeon,Canto, Bruno,Medeiros, J. R. De American Astronomical Society 2018 The Astrophysical journal Vol.865 No.1