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Char particle fragmentation and its effects on unburned carbon during pulverized coal combustion. Quarterly report, January 1, 1995--March 31, 1995

This document is the tenth quarterly status report of work on a project concerned with the fragmentation of char particles during pulverized coal combustion that is being conducted at the High Temperature Gasdynamics Laboratory at Stanford University. The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The work is pertinent to the char oxidation phase of coal combustion and focuses on how the fragmen… more

Date: August 1, 1995

Creator: Mitchell, R.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The dihadron fragmentation function and its evolution

Dihadron fragmentation functions and their evolution arestudied in the process of e+e- annihilation. Under the collinearfactorization approximation and facilitated by the cut-vertex technique,the two hadron inclusive cross section at leading order (LO) is shown tofactorize into a short distance parton cross section and a long distancedihadron fragmentation function. We provide the definition of such adihadron fragmentation function in terms of parton matrix elements andderive its DGLAP evolutio… more

Date: February 24, 2004

Creator: Majumder, Abhijit & Wang, Xin-Nian

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Using the Lonsdorf model for estimating habitat loss and fragmentation effects on pollination service

Article examining the effects of habitat loss and fragmentation on pollination separately according to the Lonsdorf model. Results show that the effects of habitat loss and fragmentation on pollination are completely different at the landscape and farm levels. This article shows that using the Lonsdorf model could lead to confusing results for the landscape ecologists and farmers who want to reduce the adverse effects of fragmentation on their products by creating new forest patches.

Date: March 22, 2021

Creator: Rahimi, Ehsan; Barghjelveh, Shahindokht & Dong, Pinliang

Item Type: Article

Partner: UNT College of Liberal Arts & Social Sciences

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Quark fragmentation in e/sup +/e/sup -/ annihilation

Experimental data that provide information on parton fragmentation are reviewed. The data are compared with the internal fragmentation (IF) model, color string fragmentation (LUND) model, QCD-cluster models, and Gottschalk model. The LUND model is used most often. The general features of the data are well described by all models. Differences between independent fragmentation and string fragmentation appear clearly in detailed studies of three-jet events. The string fragmentation model fits the … more

Date: September 1, 1984

Creator: Barbaro-Galtieri, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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BOLIDE FRAGMENTATION PROCESSES : SINGLE-BODY MODELING VERSUS THE CATASTROPHIC FRAGMENTATION LIMIT.

The catastrophic 'pancake' fragmentation process, proposed as being generally applicable to very large meteoroid entry in the early 1990's by a number of workers, has been carefully examined. In this effort, the transition from the traditional single-body dynamics and energetics model to a catastrophic 'pancake' fragmentation process has been delineated. The key parameters are the {mu} parameter originally proposed by Levin and the fragmentation scale height, Hf, which we have derived from {mu}… more

Date: January 1, 2001

Creator: ReVelle, D. O. (Douglas O.)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Scaling issues in dynamic fragmentation

A set of relations which would allow the experimental results of impact fragmentation experiments conducted under the controlled environment of a testing laboratory to be confidently scaled to realistic system dimensions would be an effective tool in the developments toward a predictive capability in full scale applications involving fragmentation. Here some of the issues governing scaling relations in dynamic fragmentation are discussed. Dimensional arguments are pursued. Some of the consequen… more

Date: March 1995

Creator: Grady, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fragmentation properties of metals

In the present study we are developing an experimental fracture material property test method specific to dynamic fragmentation. Spherical test samples of the metals of interest are subjected to controlled impulsive stress loads by acceleration to high velocities with a light-gas launcher facility and subsequent normal impact on thin plates. Motion, deformation and fragmentation of the test samples are diagnosed with multiple flash radiography methods. The impact plate materials are selected to… more

Date: June 1, 1996

Creator: Grady, D. E. & Kipp, M. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Spin Effects in the Fragmentation of Transversely Polarized and Unpolarized Quarks.

We study the fragmentation of a transversely polarized quark into a non-collinear (k{perpendicular} {ne} 0) spinless hadron and the fragmentation of an unpolarized quark into a non collinear transversely polarized spin 1/2 baryon. These nonperturbative properties are described by spin and k{perpendicular} dependent fragmentation functions and are revealed in the observation of single spin asymmetries. Recent data on the production of pions in polarized semi-inclusive DIS and long known data on … more

Date: April 23, 2001

Creator: Anselmino, M.; Boer, D.; D'Alesio, U. & Murgia, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Quarterly report, April 1--June 30, 1995

This document is the eleventh quarterly status report of work on a project concerned with the fragmentation of char particles during pulverized coal combustion that was conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California. The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The work is pertinent to the char oxidation phase of coal combustion and focuse… more

Date: August 13, 1996

Creator: Mitchell, R. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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QGP and Modified Jet Fragmentation

Recent progresses in the study of jet modification in hotmedium and their consequences in high-energy heavy-ion collisions are reviewed. In particular, I will discuss energy loss for propagating heavy quarks and the resulting modified fragmentation function. Medium modification of the parton fragmentation function due to quark recombination are formulated within finite temperature field theory and their implication on the search for deconfined quark-gluon plasma is also discussed.

Date: April 18, 2005

Creator: Wang, Xin-Nian

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Quarterly report, October 1--December 31, 1994

The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The work is pertinent to the char oxidation phase of coal combustion and focuses on how the fragmentation of coal char particles affects overall mass loss rates and how char fragmentation phenomena influence coal conversion efficiency. The knowledge and information obtained will allow the development of engineering models that can be used to predict… more

Date: March 1, 1995

Creator: Mitchell, R.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A thermodynamic theory of dynamic fragmentation

We present a theory of dynamic fragmentation of brittle materials based on thermodynamic arguments. We recover the expressions for average fragment size and number as originally derived by Grady. We extend the previous work by obtaining descriptions of fragment size distribution and compressibility change due to the fragmentation process. The size distribution is assumed to be proportional to the spectral power of the strain history and a sample distribution is presented for a fragmentation pro… more

Date: August 1, 1993

Creator: Yew, Ching H. & Taylor, P. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Final report, March 20, 1997

This document is the final report of work on a project concerned with the fragmentation of char particles during pulverized coal combustion that was conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California. The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The overall objectives of the project were: (1) to characterize the fragmentation events as a funct… more

Date: December 31, 1997

Creator: Mitchell, R.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Coal char fragmentation during pulverized coal combustion

A series of investigations of coal and char fragmentation during pulverized coal combustion is reported for a suite of coals ranging in rank from lignite to low-volatile (lv) bituminous coal under combustion conditions similar to those found in commercial-scale boilers. Experimental measurements are described that utilize identical particle sizing characteristics to determine initial and final size distributions. Mechanistic interpretation of the data suggest that coal fragmentation is an insig… more

Date: July 1, 1995

Creator: Baxter, L. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A study of detonation timing and fragmentation using 3-D finite element techniques and a damage constitutive model

The transient dynamics finite element computer program, PRONTO-3D, has been used in conjunction with a damage constitutive model to study the influence of detonation timing on rock fragmentation during blasting. The primary motivation of this study is to investigate the effectiveness of precise detonators in improving fragmentation. PRONTO-3D simulations show that a delay time of 0.0 sec between adjacent blastholes results in significantly more fragmentation than a 0.5 ms delay.

Date: March 1, 1996

Creator: Preece, D.S. & Thorne, B.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Recent progress on perturbative QCD fragmentation functions

The recent development of perturbative QCD (PQCD) fragmentation functions has strong impact on quarkonium production. I shall summarize B{sub c} meson production based on these PQCD fragmentation functions, as well as, the highlights of some recent activities on applying these PQCD fragmentation functions to explain anomalous J/{psi} and {psi}{prime} production at the Tevatron. Finally, I discuss a fragmentation model based on the PQCD fragmentation functions for heavy quarks fragmenting into h… more

Date: May 1, 1995

Creator: Cheung, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Quarterly report, July 1, 1993--September 30, 1993

The overall objectives of the project are: (1) to correlate char particle porosity with fragmentation phenomena, (2) to determine if mineral matter in the coal affects fragmentation patterns, and (3) to relate the effects of fragmentation events to unburned carbon in ash. The knowledge obtained during the course of this project will be used to predict accurately the overall mass loss rates of coals based on the mineral content and porosity of their chars. The work will provide a means of assess… more

Date: October 1, 1993

Creator: Diaz, R. & Mitchell, R. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Impact failure and fragmentation properties of metals

In the present study we describe the development of an experimental fracture material property test method specific to dynamic fragmentation. Spherical test samples of the metals of interest are subjected to controlled impulsive stress loads by acceleration to high velocities with a light-gas launcher facility and subsequent normal impact on thin plates. Motion, deformation and fragmentation of the test samples are diagnosed with multiple flash radiography methods. The impact plate materials ar… more

Date: March 1, 1998

Creator: Grady, D. E. & Kipp, M. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Employment and Training Programs: Opportunities Exist for Improving Efficiency

Testimony issued by the Government Accountability Office with an abstract that begins "This testimony discusses the findings from our recent work on fragmentation, overlap, and potential duplication in federally funded employment and training programs and our prior work on the Workforce Investment Act of 1998 (WIA). We recently issued two reports addressing fragmentation, overlap, and potential duplication in federal programs--one that outlined opportunities to reduce potential duplication acro… more

Date: April 7, 2011

Creator: United States. Government Accountability Office.

Item Type: Text

Partner: UNT Libraries Government Documents Department

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Opportunities to Reduce Potential Duplication in Federal Teacher Quality Programs

Testimony issued by the Government Accountability Office with an abstract that begins "This testimony discusses the findings from our recent work on fragmentation, overlap, and potential duplication in federally funded programs that support teacher quality. We recently issued a report addressing fragmentation, overlap, and potential duplication in federal programs that outlined opportunities to reduce potential duplication across a wide range of federal programs, including teacher quality progr… more

Date: April 13, 2011

Creator: United States. Government Accountability Office.

Item Type: Text

Partner: UNT Libraries Government Documents Department

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Measurement of fragmentation and functionalization pathways in the multistep heterogeneous oxidation of organic aerosol

The competition between the addition of polar, oxygen-containing functional groups (functionalization) and the cleavage of C-C bonds (fragmentation) has a governing influence on the change in volatility of organic species upon atmospheric oxidation, and hence on the loading of tropospheric organic aerosol. However the branching between these two channels is generally poorly constrained for oxidized organics. Here we determine functionalization/fragmentation branching ratios for organics spannin… more

Date: March 10, 2009

Creator: Kroll, Jesse H.; Smith, Jared D.; Che, Dung L.; Kessler, Sean H.; Worsnop, Douglas R. & Wilson, Kevin R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Multiple parton scattering in nuclei: Heavy quark energy loss andmodified fragmentation functions

Multiple scattering, induced radiative energy loss and modified fragmentation functions of a heavy quark in nuclear matter are studied within the framework of generalized factorization in perturbative QCD. Modified heavy quark fragmentation functions and energy loss are derived in detail with illustration of the mass dependencies of the Landau-Pomeranchuk-Migdal interference effects and heavy quark energy loss. Due to the quark mass dependence of the gluon formation time, the nuclear size depen… more

Date: November 20, 2004

Creator: Zhang, Ben-Wei; Wang, Enke & Wang, Xin-Nian

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Catalysis and co-catalysis of bond cleavages in coal and coal analogs. Quarterly report, November 1, 1991--January 31, 1992

Catalytic hydrogenolysis and thermal fragmentation of coal-related compounds are covered in this report. Data are tabulated for the following processes: (1) Transfer Hydrogenolysis in Tetralin at 450{degrees}C in Stainless Steel Reactors; (2) Effects of Diphenylamine on Fragmentation of 1,1-Dibenzyl-1,4-dihydronaphthalene at 150{degrees}C; (3) Effect of Diphenylamine on Rate of Fragmentation of 1,1-Di-p-tolyl-1,4-dihydronaphthalene at 150{degrees}C; (4) Fragmentation of 1,1-Di-(4-chlorobenzyl)-… more

Date: May 1, 1992

Creator: Miller, B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Inclusive hadronic production of the B{sub c} meson via heavy quark fragmentation

The author summarizes the studies on the hadronic production of S- and P-wave ({bar b}c) mesons via direct fragmentation of the bottom antiquark as well as the Altarelli-Parisi induced gluon fragmentation.

Date: March 1, 1995

Creator: Cheung, K.

Item Type: Report

Partner: UNT Libraries Government Documents Department