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Model simulations of the first aerosol indirect effect and comparison of cloud susceptibility fo satellite measurements
Present-day global anthropogenic emissions contribute more than half of the mass in submicron particles primarily due to sulfate and carbonaceous aerosol components derived from fossil fuel combustion and biomass burning. These anthropogenic aerosols modify the microphysics of clouds by serving as cloud condensation nuclei (CCN) and enhance the reflectivity of low-level water clouds, leading to a cooling effect on climate (the Twomey effect or first indirect effect). The magnitude of the first aerosol indirect effect is associated with cloud frequency as well as a quantity representing the sensitivity of cloud albedo to changes in cloud drop number concentration. This quantity is referred to as cloud susceptibility [Twomey, 1991]. Analysis of satellite measurements demonstrates that marine stratus clouds are likely to be of higher susceptibility than continental clouds because of their lower number concentrations of cloud drops [Platnick and Twomey, 1994]. Here, we use an improved version of the fully coupled climate/chemistry model [Chuang et al., 1997] to calculate the global concentrations Of sulfate, dust, sea salt, and carbonaceous aerosols (biomass smoke and fossil fuel organic matter and black carbon). We investigated the impact of anthropogenic aerosols on cloud susceptibility and calculated the associated changes of shortwave radiative fluxes at the …
Date:
March 8, 2002
Creator:
Chuang, C.; Penner, J. E. & Kawamoto, K.
Object Type:
Article
System:
The UNT Digital Library
Luminous Infrared Galaxies as Plausible y-ray Sources for GLAST and IACTs
We argue that luminous infrared galaxies (LIGs) may constitute a newly detectable population of {gamma}-ray sources for the next generation of ground and space-based high energy telescopes. Additionally, we report for the first time upper limits on their fluxes using data obtained with the EGRET telescope.
Date:
July 8, 2004
Creator:
Torres, D. F.; Reimer, O.; Domingo-Santamaria, E. & Digel, S. W.
Object Type:
Article
System:
The UNT Digital Library
Studies of the Pulse-Line Accelerator Using a Circuit Model
This note describes a simple model developed to explore some of the properties of the pulse-line ion accelerator [1], here represented as a series of lumped elements, in the general parameter regime for the ''NDCX-1d'' experiments. The goals of this modeling are: to understand the evolution of various possible input pulses in the presence of dispersive effects and imperfect termination of the line; to examine scenarios for beam acceleration; and to explore the effects of ''beam loading'', that is, changes to the voltages along the helical line that result from the interaction of the beam's return current with the ''circuitry'' of that line. In Section 1 below, the model is described and the method of solution outlined; in Section 2, a low-current example of beam acceleration is presented; in Section 3, runs are presented showing the development of beam loading-induced voltages as model pulses are followed; in section 4, the modeling of a higher-current beam under acceleration is presented, and the effects of beam loading quantified; and in section 5, a brief summary of complementary efforts and of plans to extend the modeling is presented.
Date:
March 8, 2005
Creator:
Friedman, A
Object Type:
Report
System:
The UNT Digital Library
High-end Home Firewalls CIAC-2326
Networking in most large organizations is protected with corporate firewalls and managed by seasoned security professionals. Attempts to break into systems at these organizations are extremely difficult to impossible for an external intruder. With the growth in networking and the options that it makes possible, new avenues of intrusion are opening up. Corporate machines exist that are completely unprotected against intrusions, that are not managed by a security professional, and that are regularly connected to the company network. People have the option of and are encouraged to work at home using a home computer linked to the company network. Managers have home computers linked to internal machines so they can keep an eye on internal processes while not physically at work. Researchers do research or writing at home and connect to the company network to download information and upload results. In most cases, these home computers are completely unprotected, except for any protection that the home user might have installed. Unfortunately, most home users are not security professionals and home computers are often used by other family members, such as children downloading music, who are completely unconcerned about security precautions. When these computers are connected to the company network, they …
Date:
October 8, 2003
Creator:
Orvis, W
Object Type:
Report
System:
The UNT Digital Library
Polarized light propagation through tissue and tissue phantoms
We show that standard tissue phantoms can be used to mimic the intensity and polarization properties of tissue. Polarized light propagation through biologic tissue is typically studied using tissue phantoms consisting of dilute aqueous suspensions of microspheres. The dilute phantoms can empirically match tissue polarization and intensity properties. One discrepancy between the dilute phantoms and tissue exist: common tissue phantoms, such as dilute Intralipid and dilute 1-{micro}m-diameter polystyrene microsphere suspensions, depolarize linearly polarized light more quickly than circularly polarized light. In dense tissue, however, where scatterers are often located in close proximity to one another, circularly polarized light is depolarized similar to or more quickly than linearly polarized light. We also demonstrate that polarized light propagates differently in dilute versus densely packed microsphere suspensions, which may account for the differences seen between polarized light propagation in common dilute tissue phantoms versus dense biologic tissue.
Date:
February 8, 2000
Creator:
Sankaran, V; Walsh, J T JR & Maitland, D J
Object Type:
Article
System:
The UNT Digital Library
Oracle Log Buffer Queueing
The purpose of this document is to investigate Oracle database log buffer queuing and its affect on the ability to load data using a specialized data loading system. Experiments were carried out on a Linux system using an Oracle 9.2 database. Previous experiments on a Sun 4800 running Solaris had shown that 100,000 entities per minute was an achievable rate. The question was then asked, can we do this on Linux, and where are the bottlenecks? A secondary question was also lurking, how can the loading be further scaled to handle even higher throughput requirements? Testing was conducted using a Dell PowerEdge 6650 server with four CPUs and a Dell PowerVault 220s RAID array with 14 36GB drives and 128 MB of cache. Oracle Enterprise Edition 9.2.0.4 was used for the database and Red Hat Linux Advanced Server 2.1 was used for the operating system. This document will detail the maximum observed throughputs using the same test suite that was used for the Sun tests. A detailed description of the testing performed along with an analysis of bottlenecks encountered will be made. Issues related to Oracle and Linux will also be detailed and some recommendations based on the findings.
Date:
December 8, 2004
Creator:
Rivenes, A S
Object Type:
Report
System:
The UNT Digital Library
PROTON AND ANTI-PROTON DISTRIBUTIONS AT RHIC.
Properties of transverse momentum spectra and rapidity dependence of protons and anti-protons in Au-Au collisions at {radical}(s{sub NN}) = 200 GeV are discussed. The net-proton yields are approximately constant at |y| < 1 and increases towards y {approx} 3. The mean rapidity loss is estimated to be in the range of 1.9 < {delta}y < 2.4.
Date:
February 8, 2003
Creator:
VIDEBAEK,F. FOR THE BRAHMS COLLABORATION
Object Type:
Article
System:
The UNT Digital Library
Development of a Quantitative Approach to Incorporating Stakeholder Values into Total Maximum Daily Loads: Dominguez Channel Case Study
The federal Clean Water Act (CWA) Section 303(d)(1)(A) requires each state to conduct a biennial assessment of its waters, and identify those waters that are not achieving water quality standards. The result of this assessment is called the 303(d) list. The CWA also requires states to establish a priority ranking for waters on the 303(d) list of impaired waters and to develop and implement Total Maximum Daily Loads (TMDLs) for these waters. Over 30,000 segments of waterways have been listed as impaired by the Environmental Protection Agency (EPA). The EPA has requested local communities to submit plans to reduce discharges by specified dates or have them developed by the EPA. An investigation of this process found that plans to reduce discharges were being developed based on a wide range of site investigation methods. The Department of Energy requested Lawrence Livermore National Laboratory to develop appropriate tools to assist in improving the TMDL process. The EPA has shown support and encouragement of this effort. Our investigation found that improving the stakeholder input process would facilitate many of the TMDL processes, given the resources available to the interested and responsible parties. The first model that we have developed is a stakeholder allocation …
Date:
June 8, 2004
Creator:
Stewart, J.
Object Type:
Article
System:
The UNT Digital Library
The Effect of Organic Ligand Binding on the Growth CdSe Nanoparticles Probed by Ab-Initio Calculations
None
Date:
October 8, 2004
Creator:
Puzder, A.; Williamson, A. J.; Zaitseva, N.; Galli, G.; Manna, L. & Alivisatos, A. P.
Object Type:
Article
System:
The UNT Digital Library
Experimental study of 351-nm and 527-nm laser-initiated surface damage on fused silica surfaces due to typical contaminants
Optics damage under high-intensity illumination may be the direct result of laser light interaction with a contaminant on the surface. Contaminants of interest are small particles of the materials of construction of large laser systems and include aluminum, various absorbing glasses, and fused silica. In addition, once a damage site occurs and begins to grow, the ejecta from the growing damage site create contamination on nearby optic surfaces and may initiate damage on these surfaces via a process we call ''fratricide.'' We report on a number of experiments that we have performed on fused silica optics that were deliberately contaminated with materials of interest. The experiments were done using 527-nm light as well as 351-nm light. We have found that many of the contaminant particles are removed by the interaction with the laser and the likelihood of removal and/or damage is a function of both fluence and contaminant size. We have developed an empirical model for damage initiation in the presence of contaminants.
Date:
November 8, 2004
Creator:
Honig, J.; Norton, M. A.; Hollingsworth, W. G.; Donohue, E. E. & Johnson, M. A.
Object Type:
Article
System:
The UNT Digital Library
Disabling Radiological Dispersal Terror
Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.
Date:
November 8, 2002
Creator:
Hart, M.
Object Type:
Article
System:
The UNT Digital Library
RIA Fragmentation Line Beam Dumps
The Rare Isotope Accelerator project involves generating heavy-element ion beams for use in a fragmentation target line to produce beams for physics research. The main beam, after passing through the fragmentation target, may be dumped into a beam dump located in the vacuum cavity of the first dipole magnet. For a dump beam power of 100 kW, cooling is required to avoid excessive high temperatures. The proposed dump design involves rotating cylinders to spread out the energy deposition and turbulent subcooled water flow through internal water cooling passages to obtain high, nonboiling, cooling rates.
Date:
August 8, 2003
Creator:
Stein, W.
Object Type:
Article
System:
The UNT Digital Library
Exploring the Potential of Table-Top X-Ray Lasers and Capillary Discharge for Applications
The advantages of using of table top x-ray lasers (XRLs) for different applications have been described. Examples of the first successful use of XRLs, the current efforts in applying them and the potential applications where an XRL can be used in future have been discussed. Modeling results showing the possibility of 3-4 times shorter wavelength capillary discharge x-ray lasers and calculated spectrum of Xe capillary EUV source are presented.
Date:
May 8, 2003
Creator:
Shlyaptev, V. N.; Dunn, J.; Smith, R. F.; Moon, S. J.; Fournier, K. B.; Nilsen, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Preliminary Evaluation of Techniques to Fabricate Beryllium, Polyimide, and Ge-doped CH/CD Ablator Materials
This report including appendices provides information to complete this deliverable. It summarizes the important features of each ablator material, with particular focus to its usefulness for ignition capsules. More detailed discussions of each ablator type are in the Appendix. Included at the end of each separate discussion in the Appendix is a list of all published work with an ICF focus on that ablator type. This report is organized into Be based and polymer (C) based ablators. We summarize status, outstanding issues, and how we plan to address them. Details are in the Appendix. For Be there are two fabrication routes, one by machining bulk pieces into hemi-shells which are then bonded together, and the other by sputtering Be with Cu dopant onto spherical plastic mandrels to build up a wall. This method allows for radial variation in the Cu dopant concentration, while the machining approach is best suited to a uniform doping level. For plastic, we have already made a down select, eliminating polyimide because its performance as an ablator has been seen to be significantly different from that predicted by simulations. The other polymer, GDP (glow discharge polymer or sometimes called plasma polymer) comes in both a normal …
Date:
November 8, 2004
Creator:
Cook, Bob; Letts, Steve; Nikroo, Abbas; Nobile, Art; McElfresh, Mike; Cooley, Jason et al.
Object Type:
Report
System:
The UNT Digital Library
Innovative Technologies to Protect Water Supplies
None
Date:
July 8, 2004
Creator:
Newmark, R. L.
Object Type:
Report
System:
The UNT Digital Library
Aspects of the Tribology of the Plastic Bonded Explosive LX-04
The coefficient of friction, {mu}, of the plastic bonded explosive (PBX) LX-04 was measured on stainless steel, aluminum, Teflon and the explosive itself as a function of temperature between ambient and 135 C at a rotational speed of 0.0025 rad/sec{sup -1}. An optical profilometer was used to analyze the mean surface roughness, R{sub a}, of the various materials. LX-04 is a composite of the explosive 1,3,5,7-tetranitroazacyclooctane (HMX) and Viton A in an 85/15 weight ratio. The average roughness of the pressed explosive surface was R{sub a} = 0.55 {micro}m. The coefficient of friction for LX-04 on stainless steel of R{sub a} = 0.40 {micro}m decreased from 0.38 at ambient to 0.18 at 95 C. Above this temperature {mu} was nearly constant to about 125 C, where the coefficient began to increase again. The opposite behavior was observed with aluminum with R{sub a} = 0.31 {micro}m. The coefficient of friction increased from about 0.3 at ambient to 0.46 at 125 C. At this temperature or above, {mu} tended to increase during the measurement, indicating that the sample may have been sticking to the counter surface. The coefficient of friction against Teflon of R{sub a} = 0.054 {micro}m was nearly constant from …
Date:
July 8, 2004
Creator:
Hoffman, D. M. & Chandler, J. B.
Object Type:
Article
System:
The UNT Digital Library
Aspects of the Tribology of the Plastic Bonded Explosive (PBX) 9404
The coefficient of friction, {mu}, of the plastic bonded explosive (PBX) 9404 was measured on stainless steel, aluminum, Teflon and the explosive itself as a function of temperature between ambient and 135 C at a rotational speed of 0.0025 rad/sec{sup -1}. An optical profilometer was used to analyze the mean surface roughness, R{sub a}, of the various materials. PBX 9404 is a composite of the explosive 1,3,5,7-tetranitroazacyclooctane (HMX) chloroethyl phosphate (CEF) and nitrocellulose in an 96/3/3 weight ratio. The average roughness of the pressed explosive surface was R{sub a} = 1.37 {micro}m. The coefficient of friction for PBX 9404 on stainless steel of R{sub a} = 0.40 {micro}m increased from 0.22 at ambient to 0.34 at 95 C. Above this temperature {mu} decreased to about 0.23 at 125 C. Similar behavior was observed with aluminum with R{sub a} = 0.31 {micro}m. The coefficient of friction increased from about 0.08 at ambient to 0.48 at 115 C. Above this temperature, {mu} tended to decrease slightly. The coefficient of friction against Teflon of R{sub a} = 0.054 {micro}m was sigmoidal, increasing from about 0.3 at ambient to about at 0.49 {+-} 0.002 above 115 C. Against a PBX 9404 counter surface, the …
Date:
July 8, 2004
Creator:
Hoffman, D. M. & Chandler, J. B.
Object Type:
Article
System:
The UNT Digital Library
Deterministic, Nanoscale Fabrication of Mesoscale Objects
Neither LLNL nor any other organization has the capability to perform deterministic fabrication of mm-sized objects with arbitrary, {micro}m-sized, 3-D features and with 100-nm-scale accuracy and smoothness. This is particularly true for materials such as high explosives and low-density aerogels, as well as materials such as diamond and vanadium. The motivation for this project was to investigate the physics and chemistry that control the interactions of solid surfaces with laser beams and ion beams, with a view towards their applicability to the desired deterministic fabrication processes. As part of this LDRD project, one of our goals was to advance the state of the art for experimental work, but, in order to create ultimately a deterministic capability for such precision micromachining, another goal was to form a new modeling/simulation capability that could also extend the state of the art in this field. We have achieved both goals. In this project, we have, for the first time, combined a 1-D hydrocode (''HYADES'') with a 3-D molecular dynamics simulator (''MDCASK'') in our modeling studies. In FY02 and FY03, we investigated the ablation/surface-modification processes that occur on copper, gold, and nickel substrates with the use of sub-ps laser pulses. In FY04, we investigated laser …
Date:
December 8, 2004
Creator:
Mariella, R., Jr.; Gilmer, J.; Rubenchik, A. & Shirk, M.
Object Type:
Report
System:
The UNT Digital Library
Texas Racing Commission Annual Report: 2004
Annual report of the Texas Racing Commission describing goals, activities, and accomplishments during fiscal year 2004
Date:
April 8, 2005
Creator:
Texas Racing Commission
Object Type:
Report
System:
The Portal to Texas History