bluuebunny/crossref_metadata_2025 huggingface dataset:
Ignition properties of mechanical sparks and hot surfaces in dust/air mixtures
Authors: Bruderer R. E.
Published: June 2004

Up to now it was believed that mechanically generated sparks caused most of the dust explosions in industry. Such belief was not confirmed through extensive testing involving combustible dust and selected flammable gases. The steel grinding, friction and impact sparks were capable of igniting fuel/air mixtures under certain conditions. However, from additional tests it was found that hot surfaces which are generated by rubbing steel against steel are capable of easily starting dust explosions independent of the ignition behavior of the fuels.
Analysis of a dust deflagration
Authors: Britton Laurence G. , Kirby David C.
Published: June 2004

This paper outlines the events leading to a successfully vented deflagration in a storage bin for a granular material. The hazard of particle size classification during conveying and loading operations is also illustrated.
Preventing explosions during chemicals and materials storage
Authors: Fauske Hans K.
Published: June 2004

Simple passive means are considered for preventing explosions in connection with storage of non‐reactive and reactive materials. For high‐pressure storage, special attention is given to the elimination of BLEVEs. Cost‐effective passive features are proposed to accommodate both global and local fire impingement conditions. For atmospheric pressure storage, passive features are considered to accommodate potential fire exposure and prevent runaway scenarios for reactive systems.
Safe handling of organic peroxides: An overview
Authors: McCloskey Chester M.
Published: June 2004

Organic peroxides are widely used today, and yet their properties and the procedures for their safe handling remain a mystery to many. After many years of hard work, the fog lifted considerably with the adoption, in 1986, of NFPA, 43B Code “Storage and Handling of Organic Peroxide Formulations [1]. A U.N. committee is also making a contribution by developing recommendations for the worldwide transport of organic peroxides [2]. This has had a secondary benefit in providing a forum for comparing and evaluating test methods and classifications worldwide. However, there is still much to be done.
Safety and loss prevention concerns for engineers in polymer facilities
Authors: Sullivan H. C.
Published: June 2004

Safety related problems encountered in the production and handling of materials using monomers in water based polymerization reactions are covered. It must be noted that the author's experience is specifically in acrylic monomers.
Experience with a simulator for training ammonia plant operators
Authors: Mani S. , Shoor S. K. , Pedersen Hans S.
Published: June 2004

A computer‐based simulator was used for training operators prior to the start‐up of a new fertilizer complex which includes a 1,350‐MTPD ammonia plant, two 1,100‐MTPD urea plants, and a steam and power generation plant with two 18‐MW gas turbines. The simulator offered many benefits, which can be used for continued education of operators and engineering studies.
Application of the DIERS methodology to the study of runaway polymerization: Validation of the DIERS methodology using blow‐down tests
Authors: Kirch Larry S. , Magee Joseph W. , Stuper Wayne W.
Published: June 2004

The Design Institute for Emergency Relief Systems (DIERS) and more recently the DIERS Users Group have been investigating various aspects of emergency relief for more than 12 years. The DIERS programs have given rise to an in‐depth understanding of the basic mechanism of how runaway thermal reactions are safely vented. In concert with the development of the understanding of the venting mechanism, DIERS also developed experimental procedures and computational techniques for estimating emergency vent sizes.
Preventing fires with high temperature vaporizers
Authors: Bowman James W. , Perkins Rowan P.
Published: June 2004

In 1986 one of Du Pont's plants experienced a damaging fire in and around a vaporizer containing a high‐temperature heat transfer medium (HTHTM). There were no injuries, but there was considerable property damage and lost production. A review of HTHTM history showed other plants and companies had experienced both damaging fires and incidents of severe damage to the vaporizer with no accompanying fire. This suggested a study in more depth than usually associated with one specific incident.
Turbulence effects on dust explosion venting
Authors: Tamanini Francesco
Published: June 2004

The ability to estimate the intensity of accidental dust explosions is an essential prerequisite of methodologies intended to provide design guidelines for the protection of equipment and buildings where combustible dusts are being handled. In general, the severity of an explosion depends on the type of dust involved, its physical properties (such as particle size and moisture content), the characteristics of the interested volume (size, shape, presence of vents, and blockages), the strength and type of the ignition source, and the conditions of the environment (air flow, turbulence).
Explosive decomposition of ethylene oxide
Authors: June R. K. , Dye R. F.
Published: June 2004

The purpose of this work was to obtain data on explosive limits for ethylene oxide (EtO) in nitrogen beyond the published data range. Tests were conducted at temperatures from 60°‐190°C and pressures in the range 10 to 80 psig. Initial measurements showed that the limits for the EtO/N2 system are unusually dependent on the details of the ignition source. Hot wire ignition gave very erratic responses. Induction coil sparks were not satisfactory due to inadequate energy and uncertain gap breakdown at elevated pressure. However, high‐energy capacitive discharge across an exploding bridge element tuned to the ignitive process gave responses that were reproducible and judged to be true and conservative. Graphite filament was used as the exploding bridge “wire” to avoid contamination of the test mixture. (Carbon is a product of EtO explosions.)

The data from this study show the EtO explosive range becomes wider with increasing pressure at the low end of the temperature range examined than previously understood from literature data. At modest pressures, the directly‐measured limits at elevated temperature agree with extrapolations of earlier reported data. Because of the pressure nonlinearity, the system is deemed safer at 80 psig and high temperature than had been predicted from the linear treatment.
Predicting liquid jet breakup and aerosol formation during the accidental release of pressurized hydrogen fluoride
Authors: Tilton James N. , Farley Carl W.
Published: June 2004

The safe production and handling of toxic chemicals is an issue of growing importance for public officials, legislators and petrochemical plant managers. Industrial and academic research is improving the understanding of a variety of phenomena related to risk assessment, and communicating these risks to concerned parties. Several groups are investigating the behavior and mitigation of accidental releases of anhydrous hydrofluoric acid. Forthcoming results of these studies will include the key issue of aerosol formation.
Catalyst explosion: A case history
Authors: De Haven E. S. , Dietsche T. J.
Published: June 2004

In May, 1979, an explosive rupture of a vessel took place during preparation of a catalyst solution at the Pittsburg, California plant of Dow Chemical U.S.A. About fifty contractor employees were injured, including two fatalities. Property damage amounted to two million dollars.

The operation consisted of chlorination of powdered iron suspended in an agitated mixture of chlorinated aromatic heterocyclics to produce a ferric chloride solution for use elsewhere. The operation had been subjected to then current reactive chemicals screening tests and to a number of pilot plant runs; these tests and runs did not reveal any potential for explosion. Today's tests, including the CSI‐ARC, properly conducted and analyzed, would have revealed potential difficulties.
Management of quantitative risk assessment in the chemical process industry
Authors: Arendt J. S.
Published: June 2004

Growing concern about the risk of major chemical accidents in the U.S. has led both government and industry to find new ways to identify and evaluate potential hazards. Among the most promising (and misunderstood) approaches is a collection of techniques called quantitative risk assessment (QRA). Adapted primarily from probabilistic risk assessment approaches developed in other industries, the use of QRA is spreading rapidly through the U.S. chemical industry. Of equal importance, legislators and regulatory agencies at the state and federal level are making QRA an integral part of their proposals for mandatory accident prevention measures.

This paper summarizes a workshop on QRA that was presented at the International Conference and Workshop on Process Safety Management, sponsored by the AIChE Center for Chemical Process Safety, in Toronto during May 1990. It is based on A Manager's Guide to QRA [1] developed for the Chemical Manufacturers Association. This paper gives an overview of the Guide and discusses important implications concerning the increasing acceptance of QRA as a chemical regulatory tool.
Process safety management within Dupont
Authors: Burk Arthur F. , Smith William L.
Published: June 2004

This paper presents and discusses the principles and essential features of a process safety management system which if practiced and implemented will prevent industrial catastrophes. The importance of the corporate mission/philosophy and of establishing that sense of operating discipline are also discussed. The corporate mission/philosophy provides the leadership and foundation for a process safety management system. Operating discipline is what takes a process safety management effort from a “paper” program to an “action” program!
A comprehensive test method for inline flame arresters
Authors: Roussakis N. , Lapp K.
Published: June 2004

The certification test standards that presently exist for flame arresters are highly inadequate for inline applications. A proper flame arrester test method should ensure that a unit will work with any flame front conditions that it could be exposed to in actual use. When evaluating flame arrester performance, it is just as dangerous to neglect deflagration testing as detonation testing. The comprehensive inline flame arrester test method outlined here involves exposing a unit to the entire flame propagation pressure spectrum. This includes low, medium and high pressure deflagrations as well as overdriven and stable detonations. The test method also takes into account the following factors: flow restriction on the protected side of the flame arrester, flame propagation through a flowing gas, initial system pressure and temperature, and specified gas mixture. Flow restriction on the protected side of the flame arrester has a very significant effect on performance and has not previously been given consideration in flame arrester testing. Besides moving flame front test, endurance burn testing and hydrostatic pressure testing are also discussed here. Major regulatory organizations have recently adopted these findings as the basis for new standards proposed to cover an inline flame arrester test method.
Specification of flame arresting devices for manifolded low pressure storage tanks
Authors: Piotrowski Thomas C.
Published: June 2004

The current regulations and accepted recommended practices relating to the use of mechanical flame arresting devices on low pressure, flammable liquid storage tanks will be reviewed. The applicability of these recommendations to typical manifolded tank and closed piping vapor recovery systems, as opposed to the more common “stand alone”, venting to atmosphere storage tanks, will be examined with particular emphasis on the widely varying service conditions that mechanical flame arresting devices may encounter. The limitations placed on the use of commercially available Factory Mutual Approved and Underwriters Laboratories Listed flame arresters will be explained.
Using thermodynamic availability to determine the energy of explosion
Authors: Crowl Daniel A.
Published: June 2004

Current methods to determine the thermodynamic energy of explosion are based on the Helmholtz free energy. The Helmholtz free energy represents the maximum work available from a system during a constant temperature process. For many real explosions, the material is initially at a temperature or pressure higher than the ambient environment. Thus, the Helmholtz free energy does not account for all of the energy sources.

The thermodynamic availability provides a general approach to determine the maximum work available from any process. Furthermore, the availability provides a much more formal and structured method for performing the calculations.

This paper provides the formal basis, demonstrates the application of availabilty using a number of examples, and provides a table of availability data.
The use of spreadsheets in modelling accidental releases of toxic chemicals
Authors: Freeman R. A. , Shaw D. A.
Published: June 2004

Many hazardous industrial chemicals are stored as liquidfied compressed gases. To evaluate the possible consequences of a pipeline rupture, hose break, or tank puncture, the safety or process engineer needs a means to estimate the two‐phase (liquid and gas) flow rate. Recent technical advances by the American Institute of Chemical Engineers Design Institute of Emergency Relief Systems (DIERS) have produced methods that can be used to compute the two‐phase flow rate. These methods are simple and can be completed using a personal computer and a standard spreadsheet program such as Excel (Macintosh) or Lotus (DOS based). This paper presents the two‐phase flow rate calculation method and shows how spreadsheets can be used for these calculations.
Chemical accident prevention under the clean air act amendments of 1990
Authors: Craig Matthiessen R.
Published: June 2004

The Clean Air Act Amendments of 1990 enacted recently contain provisions for the prevention of chemical accidents under Title III—Hazardous Air Pollutants. Some of these provisions include: a general duty clause, preparation of a list of substances and thresholds, requirements for the preparation of risk management plans by industry, specific accident prevention regulations, establishment of a Chemical Safety and Hazard Investigation Board, and requirements for the Occupational Safety and Health Administration (OSHA) to promulgate a process safety management standard. These provisions, approaches with respect to process safety management by the Environmental Protection Agency (EPA), and coordination with OSHA will be discussed.
Analysis of titanium/carbon steel heat exchanger fire
Authors: Prine Brenda A.
Published: June 2004

In the past fifteen years two serious titanium fires have occurred at scrap dealer facilities. Both incidents involved the cutting of titanium/carbon steel heat exchangers by scrap metal dealers. This paper reviews the properties of titanium and carbon steel under extreme conditions and the oxy‐acetylene cutting process relevant to its potential for initiating titanium fires. The probable modes of propagation involved in these specific incidents are considered. The formation of low melting eutectic mixtures and the Thermite reaction are both felt to contribute to the incident once initiated. Alternate methods of cutting titanium/carbon steel exchangers are discussed.
Deflagration protection of pipes
Authors: Chatrathi Kris
Published: June 2004

The potential for gas and dust explosions in the process industries has been historically recognized. Potentially explosible materials, both organic and inorganic, are handled in large quantities on a daily basis. These hazardous materials are processed in vessels and/or pipes: that is volumes with small length to diameter (L/D) ratios or volumes with large length to diameter ratios. It has also been historically recognized that explosions have different characteristics in different volumes. This difference becomes critically important when explosion protection methods are being designed.
Mitigation of hazardous emergency release source terms via quench tanks
Authors: Fauske Hans K. , Grolmes Michael A.
Published: June 2004

Analyses and test data indicate that for many hazardous materials the use of a passive quench tank can effictively eliminate airborne releases. New test data on quench tank performance indicate similarities between condensation, absorption and neutralization reactions. Both two‐phase and all‐gas releases are considered.
Predicting and controlling flammability of multiple fuel and multiple inert mixtures
Authors: Hansel James G. , Mitchell John W. , Klotz Herbert C.
Published: June 2004

Le Chatelier's Rule is in wide use for predicting the flammability of mixtures with multiple fuels present. The rule does not conveniently handle multiple inerts or elevated temperatures and pressures. This paper describes an alternate method, developed at Air Products, called FLAMCHEKTM, which conveniently handles these variables. This method for predicting flammability is based upon the commonality of the adiabatic flame temperature of a wide variety of fuels at their upper and lower flammable limits. The method, if PC based, can be extended to automatically control the addition of inerts, fuels, or oxidizers in order to avoid flammable conditions. The concept may be extended to more involved applications, such as within an oil well with fuel gas mixtures containing oxygen. In this case, the location from which a gas sample is obtained for analysis (wellhead) may have a different fuel analysis and flammability condition than the location where an explosion is likely to initiate (bottom of well). Hence a correction of the fuels analysis is required.
Acceptable risk—an overview
Authors: Philley Jack O.
Published: June 2004

This paper offers an overview of the concept of acceptable risk. Variations in the definition of risk are addressed as well as criteria for measuring and evaluating risk. Risk acceptance depends on many factors, some of which are highlighted. The myth of zero risk is addressed with relevant examples such as dioxin and the U.S. space program. Practical applications of acceptable risk concepts are discussed, featuring the RISK MATRIX from system safety MIL‐STD‐882. Some sample guidelines and benchmarks are offered.
Disengagement predictions via drift flux correlation vertical, horizontal and spherical vessels
Authors: Sheppard Charles M.
Published: June 2004

The behavior of an open system is modeled. Thus, for special cases, the void fraction is predicted as a function of location and time. The open system may be an open vessel or a vessel with an open relief device. A single governing equation is derived based on combining the material and energy balances with the churn‐turbulent drift flux relationship and assuming no radial gradients. This partial differential equation is not solved. It is, however, bounded by homogeneous and all vapor venting. These special cases are solved. In homogeneous venting the key variable is time. In all vapor venting under pseudo‐steady‐state conditions the key variable is location. The solution of the partial differential equation is also discussed.

Under pseudo‐steady‐state and churn‐turbulent conditions, the open system is modeled. The minimum void fractions (corresponding to a maximum liquid inventory) with all vapor venting, for vertical, horizontal, and spherical vessels are predicted and compared. Analytical expressions for the local and average void fractions in a vertical vessel and non‐unity distribution parameters are presented. Void fraction profiles are compared for three cases: 1. vertical cylinders with distribution parameters (Co values) of unity and 1.5, 2. horizontal and vertical cylinders with varying L/D ratios, and 3. spheres with inscribed vertical cylinders having constant gas production to bubble rise ratio (Ψ′ value). The vertical cylinder average void fraction for non‐unity distribution parameters can now be calculated analytically. The horizontal cylinder average void fraction predicted by turning it upright results in an over prediction of at most 4%. The sphere average void fraction predicted via an inscribed vertical cylinder, with the same Ψ′ value, is consistenly high by at most 8%.
New aspects of electrophylic aromatic substitution mechanism: Computational model of nitration reaction
Authors: Sokolov Alexey V.
Published: June 2004

Systematic studies of reaction of nitronium with substituted benzenes (Alk‐, X‐Ph‐, CH3O‐, Cl‐, ‐COOCH3, ‐NO2, and other) were performed using semiempirical methods Austin model 1 and Solvation model v. 2.1 (SM2.1). Reaction path and maps of potential energy surface were investigated, including charge and thermodynamic properties of transition states and intermediate σ‐complexes. Main factors of reactivity—deformation energy and orbital and coulomb interaction—were considered by means of energy partitioning procedure, theory of Perturbation of Molecular Orbitals (PMO), etc. Firm correlation between calculated activation barriers and enthalpies of σ‐complex formation was found. It was found that the above‐mentioned factors successfully joined in enthalpy of protonation of aromatic substrates; thus, this parameter appeared to be ideal index of reactivity of arenes in nitration reaction. Coulomb interaction of nitronium and substituent in transition states explained cases of abnormally high reactivity of ortho position (e.g., in substituted biphenyls). © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Kontrolle ohne Löcher — Der Sarbanes‐Oxley‐Act (SOX) und seine Auswirkungen auf die IT‐Sicherheit
Authors: Hammes Sigrid , Kob Timo
Published: June 2004

Ob KontraG, KWG oder Basel II — kaum eine Vorschrift, die nicht von Sicherheitsberatern und Produktherstellern benutzt wird, um auf die Bedeutung der IT‐Sicherheit im Allgemeinen und die sich aus den Vorschriften zwingend ergebenden Anforderungen im Speziellen zu verweisen. Da kommt mit dem Sarbanes‐Oxley Act (SOX) die nächste Vorgabe gerade recht. Doch was ist dran? Welche Aussagen lassen sich wirklich aus SOX in Bezug auf die IT‐Sicherheit ableiten und für wen sind diese von Belang?
Was ist der „Cash Flow at Risk”︁?
Authors: Hager Peter
Published: June 2004

At‐Risk‐Modelle gehören heute fast schon zur Grundausstattung eines ordentlichen Kaufmanns. Value‐at‐Risk‐Verfahren (vgl. RISKNEWS 02/2004, S. 50 f.) erfreuen sich großer Beliebtheit in der Finanzwelt, da sie der Messung potenzieller Barwertverluste dienen. Für Industrieunternehmen erscheint eine Risiko‐Definition in Form der Abweichung von einem erwarteten Cash Flow praxisnäher als ein potenzieller Barwertverlust.
Stream regulation and nitrogen dynamics in sediment interstices: comparison of natural and straightened sectors of a third‐order stream
Authors: Lefebvre S. , Marmonier P. , Pinay G.
Published: June 2004

Nitrogen dynamics were studied in the interstitial environment (i.e. hyporheic zone) of a sandy‐bottom stream in a rural landscape. A third‐order stream in Brittany (France) was studied at 11 stations (riffles) to evaluate spatial patterns of water exchange between surface and interstitial habitats. More intensive sampling was conducted in three riffles selected according to their hydrological characteristics. Chemical characteristics (especially nitrogen) and microbial denitrification were studied at 12.5 and 25 cm depth upstream, and 25 cm depth downstream of each riffle. This study confirms that the interstitial habitat of a N‐rich stream acts as a sink for the nitrate‐nitrogen. Experimental manipulation of sediment cores indicates that denitrification is limited by carbon in surface (i.e. benthic) and by nitrate in hyporheic sediments. River regulation increases inputs of fine sediments, modifies river channel location, and generates changes in the spatial patterns of biogeochemical processes, water origins, and hydrologic exchanges. Copyright © 2004 John Wiley & Sons, Ltd.
Acute exposure to gas‐supersaturated water does not affect reproductive success of female adult chinook salmon late in maturation
Authors: Gale William L. , Maule Alec G. , Postera Ann , Peters Mary H.
Published: June 2004

At times, total dissolved gas concentrations in the Columbia and Snake rivers have been elevated due to involuntary spill from high spring runoff and voluntary spill used as a method to pass juvenile salmonids over dams. The goal of this project was to determine if acute exposure to total dissolved gas supersaturation (TDGS) affects the reproductive performance of female chinook salmon late in their maturation. During this study, adult female spring chinook salmon were exposed to mean TDGS levels of 114.1% to 125.5%. We ended exposures at first mortality, or at the appearance of impending death. Based on this criterion, exposures lasted from 10 to 68 h and were inversely related to TDGS. There was no effect of TDGS on pre‐spawning mortality or fecundity when comparing treatment fish to experimental controls or the general hatchery population four to six weeks after exposures. Egg quality, based on egg weight and egg diameter, did not differ between treatment and control fish. Fertilization rate and survival to eyed‐stage was high ( > 94%) for all groups. With the exception of Renibacterium salmoninarum (the causative agent of bacterial kidney disease; BKD), no viral or bacterial fish pathogens were isolated from experimental fish. The prevalence (about 45%) and severity of R. salmoninarum did not differ among the groups or the general hatchery population. We conclude that these acute exposures to moderate levels of gas‐supersaturated water—perhaps similar to that experienced by immigrating adult salmon as they approach and pass a hydropower dam on the Columbia River—did not affect reproductive success of female chinook salmon late in their maturation. These results are most applicable to summer and fall chinook salmon, which migrate in the summer/fall and spawn shortly after reaching their natal streams. Published in 2004 by John Wiley & Sons, Ltd.
Determinants of software volatility: a field study
Authors: Zhang Xiaoni , Windsor John , Pavur Robert
Published: June 2004

Although technology advances have provided new tools for maintaining software, maintenance costs remain the largest component of software life cycle cost. A basic factor claimed to be one of the driving factors in the cost of maintenance is software volatility. The objective of this research is to investigate the relationship between certain software attributes and software volatility. In this study, software volatility refers to the frequency or number of enhancements per unit of application over a specified time normalized. However, this metric is divided by the number of source lines of code (SLOC) to obtain a measure that takes into account the size of the software application. The research model is built on previous research concerning software volatility. Three factors are examined to determine their influence on software volatility normalized for SLOC: age, software complexity, and software complexity normalized for SLOC. In addition, we introduce the notion that mean time between software enhancements moderates the relationship of age, complexity, and complexity normalized for SLOC with software volatility. A field study at a major corporation allowed for the collection of data from a 13‐year‐time period. These data are used to empirically test the hypotheses presented in this study. As a moderator variable, mean time between enhancements significantly contributes to the explanatory power of a prediction model for software volatility adjusted for SLOC. Software administrators may wish to use the proposed model in their decision‐making plans to control for software costs. Copyright © 2003 John Wiley & Sons, Ltd.
Queering high school biology textbooks
Authors: Snyder Vicky L. , Broadway Francis S.
Published: June 2004

As teachers committed to educating all students, we need to learn more about how instructional materials shape representations of sexuality and gender. Through its insistent deconstruction of the norms that structure practice and belief, queer theory offers perspectives from which science educators can question assumptions embedded in textbooks. This article applies queer theory to analyze eight biology textbooks used in the United States. Specifically, we ask how biology textbooks address sexuality outside the heterosexual norm and if they propagate heteronormative attitudes. The textbooks examined offer deafening silences, antiseptic factoids, socially sanitized concepts, and politically correct binary‐gendered illustrations. In these textbooks, the termhomosexualitywas used only in the context of AIDS where, along with iv drug users, they were identified as an affected group. The pervasive acceptance of heteronormative behavior privileges students that fit the heterosexual norm, and oppresses through omission and silence those who do not. We offer implications for practice to help science educators broaden their perspectives on the constructs of sexuality and gender to construct new ways of knowing and understanding differences in science classrooms and the natural world. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 617–636, 2004
Debate over the ocean bomb radiocarbon sink: Closing the gap
Authors: Peacock Synte
Published: June 2004

There has over recent years emerged a controversy as to how much of the radiocarbon released into the atmosphere by nuclear weapons testing has been taken up by the ocean. Hesshaimer et al. [1994] made a case based on stratospheric and tropospheric measurements coupled with estimates of total bomb radiocarbon yield that it was not possible to explain both atmospheric observations and existing ocean‐based bomb radiocarbon uptake estimates [Broecker et al., 1985, 1995]. They therefore proposed that estimates of the oceanic sink should be revised downward by about 25%. One reason for concern over this discrepancy is that the widely used wind speed dependent air‐sea gas exchange parameterization of Wanninkhof [1992] is scaled to give an average exchange rate matching that given by the ocean bomb‐radiocarbon budget. An example of an application of the Wanninkhof [1992] parameterization is in estimating ocean CO2 uptake based on direct measurements of the air‐sea pCO2 difference [Takahashi et al., 1997]. Such estimates scale linearly with the air‐sea gas exchange coefficient. Further, as has been highlighted by the Hesshaimer et al. [1994] study, an understanding of the global budget of radiocarbon is an important issue in and of itself. In this paper, a number of new approaches to assessing the size of the ocean bomb radiocarbon sink are explored, and estimates are given for the total ocean bomb radiocarbon inventory during both the mid‐1970s and the mid‐1990s. The revised estimates of bomb‐radiocarbon ocean uptake yield a mid‐1970s inventory in closer agreement with that proposed by Hesshaimer et al. [1994] than the inventory obtained by the Broecker et al. [1995] study.
Constraining the exhumation and burial history of the SAFOD pilot hole with apatite fission track and (U‐Th)/He thermochronometry
Authors: Blythe A. E. , d'Alessio M. A. , Bürgmann R.
Published: June 2004

The San Andreas Fault Observatory at Depth (SAFOD) pilot hole traverses the upper 2 km of a site 1.8 km west of the San Andreas fault (SAF) near Parkfield, California. In order to evaluate the burial and exhumation history of the site and its relationship to the kinematics and mechanics of the SAF, we use 15 apatite fission‐track (FT) and 5 (U‐Th)/He analyses from pilot hole samples to document their thermal history. Sample ages decrease with depth: FT and (U‐Th)/He ages range from ∼60 and ∼31 Ma, respectively, in the upper 800 m of the hole to ∼3 and 1 Ma at the base of the hole (2.2 km depth, 93°C).Thermal modeling of the distribution of FT lengths indicates three events in the last 80 Ma: 1) cooling and exhumation of >60°C that culminated at ∼30 Ma; 2) reheating of ∼50°C from ∼30 to 8–4 Ma, probably as the result of basin subsidence and burial by 1–1.5 km of sediments; and 3) cooling of ∼30°C and estimated Coast Range exhumation of ∼1 km since 8–4 Ma.
High‐rate real‐time GPS network at Parkfield: Utility for detecting fault slip and seismic displacements
Authors: Langbein John , Bock Yehuda
Published: June 2004

A network of 13 continuous GPS stations near Parkfield, California has been converted from 30 second to 1 second sampling with positions of the stations estimated in real‐time relative to a master station. Most stations are near the trace of the San Andreas fault, which exhibits creep. The noise spectra of the instantaneous 1 Hz positions show flicker noise at high frequencies and change to frequency independence at low frequencies; the change in character occurs between 6 to 8 hours. Our analysis indicates that 1‐second sampled GPS can estimate horizontal displacements of order 6 mm at the 99% confidence level from a few seconds to a few hours. High frequency GPS can augment existing measurements in capturing large creep events and postseismic slip that would exceed the range of existing creepmeters, and can detect large seismic displacements.
Shear wave attenuation and dispersion in melt‐bearing olivine polycrystals: 1. Specimen fabrication and mechanical testing
Authors: Jackson Ian , Faul Ulrich H. , Fitz Gerald John D. , Tan Ben H.
Published: June 2004

Five melt‐bearing polycrystalline olivine aggregates have been newly prepared by hot isostatic pressing and tested at high temperature and pressure with torsional forced‐oscillation and microcreep methods. Cylindrical specimens, varying in average grain size from 7 to 52 μm, were annealed and then tested during slow staged cooling under 200 MPa pressure from maximum temperatures of 1240–1300°C where they contained basaltic melt fractions ranging from ∼0.0001 to 0.037. For temperatures ≥1000°C, pronounced departures from elastic behavior are evident in strain energy dissipation Q−1 and associated dispersion of the shear modulus G. In marked contrast with the high‐temperature viscoelastic behavior of melt‐free materials, a broad dissipation peak is observed for each of the melt‐bearing specimens ‐ superimposed upon a melt‐enhanced level of monotonically frequency‐ and temperature‐dependent “background” dissipation. The oscillation period at which the peak is centered decreases systematically with increasing temperature. A “global” model comprising an Andrade‐pseudoperiod background plus Gaussian peak accounts adequately for the variation of Q−1 with frequency, temperature, average grain size and melt fraction. In the following paper (Part II) a microstructural explanation for the observed viscoelastic behavior is sought and the global model is used to extrapolate the experimental data to the conditions of teleseismic wave propagation in the Earth's upper mantle.
Imaging the fault zones of the 2000 western Tottori earthquake by a new inversion method to estimate three‐dimensional distribution of the scattering coefficient
Authors: Asano Youichi , Hasegawa Akira
Published: June 2004

We developed an inversion method to estimate the spatial variation of scattering coefficient from observed envelopes of S coda waves. Synthetic envelopes are calculated on the basis of the single scattering theory, assuming double‐couple sources and a one‐dimensional depth‐dependent velocity structure. In our algorithm, we evaluated scattering attenuation taking spatial variation of scattering coefficient into consideration in order to model energy attenuation by passing through the localized anomalous zones with high scattering coefficients. The inversion method was applied to the seismograms in and around the focal area of the 2000 western Tottori earthquake with M 7.3. Obtained results show that there exist several zones with large scattering coefficient zones (LSZs). One of the most predominant LSZ is located along and around the fault zone of the M 7.3 earthquake in the upper crust. This LSZ suggests the existence of damaged zones in the main shock fault. Within this LSZ, an exceptionally small scattering coefficient area was detected. This area corresponds to an asperity with a large amount of coseismic slip of the main shock. Other prominent LSZs are detected in the mid to lower crust below the northwestern part of the main shock fault. In addition, LSZs are distributed in a seismic low‐velocity zone, near Quaternary volcanoes, and near hypocenters of deep low‐frequency microearthquakes. Some of the imaged LSZs are probably related to local concentration of fluid in the crust.
Nearshore sandbar migration predicted by an eddy‐diffusive boundary layer model
Authors: Henderson Stephen M. , Allen J. S. , Newberger P. A.
Published: June 2004

We simulated the erosion and accretion of a natural beach using a wave‐resolving eddy‐diffusive model of water and suspended sediment motion in the bottom boundary layer. Nonlinear advection was included in this one‐dimensional (vertical profile) model by assuming that waves propagated almost without change of form. Flows were forced by fluctuating pressure gradients chosen to reproduce the velocity time series measured during the Duck94 field experiment. The cross‐shore flux of suspended sediment beneath each field‐deployed current meter was estimated, and beach erosion (accretion) was calculated from the divergence (convergence) of this flux. Horizontal pressure forces on sediment particles were neglected. The model successfully predicted two bar migration events (one shoreward bar migration and one seaward) but failed to predict a third (seaward migration) event. Simulated seaward sediment transport was due to seaward mean currents. Simulated shoreward sediment transport was due to covariance between wave‐frequency fluctuations in velocity and sediment concentration and was mostly confined to the wave boundary layer. Predicted seaward (shoreward) bar migration was driven by a maximum in the current‐generated (wave‐generated) flux over the sandbar. A wave‐generated downward flux of shoreward momentum into the wave boundary layer contributed to shoreward sediment transport and often had a local maximum over the bar crest. Second‐order nonlinear advection of sediment, mostly representing shoreward advection by the Stokes drift, also often had a local maximum over the bar crest. Together, wave‐generated momentum fluxes and the Stokes drift substantially increased shoreward transport and were essential to predictions of shoreward bar migration.
Atmospheric methane during the last four glacial‐interglacial cycles: Rapid changes and their link with Antarctic temperature
Authors: Delmotte M. , Chappellaz J. , Brook E. , Yiou P. , Barnola J. M. , Goujon C. , Raynaud D. , Lipenkov V. I.
Published: June 2004

Atmospheric methane (CH4) recorded in Antarctic ice cores represents the closest ice proxy available for Greenland temperature changes beyond times when Greenland climate records are available. The record over four climatic cycles from the Vostok ice core offers the opportunity to study the phase relationship between Greenland and Antarctic climate changes through detailed CH4 profiles. Combining American and French analytical efforts, we have improved the time resolution of the existing CH4 record from Petit et al. [1999]. Spectral analyses reveal high‐ and low‐frequency variability (including a strong precessional component). The phase relationship between CH4 and the Antarctic temperature proxy (δD) shows a systematic lag of CH4 versus temperature by 1100 ± 200 years, on long timescales (50–400 kyr) and a more complex behavior over shorter timescales (i.e., ≤25 kyr), suggesting that Dansgaard/Oeschger‐type of climatic variability and associated interhemispheric linkage are robust features of late Quaternary climate.
Spatial variability in water content at the cold‐temperate transition surface of the polythermal Storglaciären, Sweden
Authors: Pettersson Rickard , Jansson Peter , Blatter Heinz
Published: June 2004

The volume fraction of liquid water in temperate glacier ice is important not only for the flow of glaciers and the analysis and processing of ground penetrating radar data from glaciers but also for the stability of the thermal layering in polythermal glaciers. However, little is known about the spatial variations of water content in glaciers. We use relative backscatter strength of ground‐penetrating radar signals to estimate the spatial distribution of water content close to the cold‐temperate transition on Storglaciären, northern Sweden, in an area close to the equilibrium line. The values of relative backscatter strength are calibrated using determinations of absolute water content from temperature measurements across the cold‐temperate transition and the thermodynamic boundary condition at the freezing front. The results show a water content of 0.80%, 0.75%, and 0.58% at three calibration points and a mean water content of 0.8% with a standard deviation of ±0.26% for the extrapolated water content. The extrapolated water content shows a distinct pattern, with lower water content on one side of the glacier center line and higher water content on the other side, with higher water content on the northern side. We hypothesize that the different water contents result from the fact that the ice on either side of the center line originates from different cirques, thus implying spatial variations in the entrapment of water in the firn‐ice transition process in the different cirques.
A drought early warning system on real‐time multireservoir operations
Authors: Huang Wen‐Cheng , Yuan Lun‐Chin
Published: June 2004

A color‐coded early warning system is developed and proposed for drought management on the real‐time reservoir operation. The system consists of three essential elements, namely, (1) drought watch, (2) water consumption measure, and (3) policy making. A new drought alert index is used to characterize the alert level of drought severity. For demonstration the drought warning procedures were effectively applied to a real‐world two‐parallel‐reservoir region in northern Taiwan. The implementation of such a system proves that the decision support‐like system can help the water authorities concerned take a timely action while confronting drought threats.
A minimal substorm model that explains the observed statistical distribution of times between substorms
Authors: Freeman M. P. , Morley S. K.
Published: June 2004

A minimal model for the evolution of the global dynamical state of the magnetotail during the substorm has been developed, involving only three simple rules and one free parameter D – the period between substorms under constant solar wind driving. The model is driven with a power input derived from solar wind observations from the Wind spacecraft between 1995 and 1998, to derive a sequence of simulated substorm onsets. For values of D between 2.6 h and 2.9 h, the probability distribution of waiting times between successive simulated substorm onsets is not significantly different to an empirical distribution derived from energetic particle observations at geostationary orbit in 1982‐3. Similar results are obtained using solar wind data from the ACE spacecraft between 1998 and 2002. Thus, we argue that the minimal substorm model provides a useful statistical and physical description of the timing of substorm onsets and possibly other substorm properties.
Groundwater‐induced vertical movements observed in Tsukuba, Japan
Authors: Munekane H. , Tobita M. , Takashima K.
Published: June 2004

The anomalous vertical movements observed in Tsukuba and their relevance to groundwater level changes are investigated. First, we investigated the vertical coordinate time series of an IGS station TSKB w.r.t. a nearby stable site and found that the time series has a strong correlation with the groundwater level changes of the deep wells. Next, we investigated those of the GPS antenna attached at the tip of the antenna of Tsukuba VLBI station w.r.t. TSKB. We found that the time series is decomposed into components that have 1) high correlation with the groundwater level changes of the shallow wells, and 2) high correlation with the air‐temperature. Poroelastic movements of aquifers due to groundwater level changes and thermal expansion of the VLBI antenna are likely for the mechanisms of these high correlations.
Asymmetry in the Rosenberg‐Coleman effect around solar minimum revealed by wavelet analysis of the interplanetary magnetic field polarity data (1927–2002)
Authors: Echer E. , Svalgaard L.
Published: June 2004

Interplanetary magnetic field (IMF) polarity data for the years 1927–2002 were studied by wavelet analysis technique, which permits the identification of non‐steady features in the IMF polarity data. It was found that the annual variation in the IMF polarity (the Rosenberg‐Coleman effect) is present only during the rise phase of solar cycles. This result is confirmed by the observed Bx (radial) solar wind measurements since 1964. This asymmetry could be caused by a more stable and flat heliospheric current sheet being present only in the rise phase of solar cycles, with co‐rotating high speed streams disturbing it during the descending phases. This finding bears on the generally accepted explanation of the 22‐year geomagnetic activity cycle.
Mechanisms and variations of the paleoproductivity off northern Chile (24°S–33°S) during the last 40,000 years
Authors: Mohtadi M. , Hebbeln D.
Published: June 2004

A multiparameter investigation including organic carbon, carbonate, opal, and planktic foraminifera was carried out on five sediment cores from the coastal upwelling area between 24°S and 33°S along the Peru‐Chile Current to reconstruct the history of the paleoproductivity and its driving mechanisms during the last 40,000 years. Inferred from our data, we conclude that the Antarctic Circumpolar Current as the main nutrient source in this region mainly drives the productivity by its latitudinal shifts associated with climate change. Simplified, its northerly position during the last glacial led to enhanced productivities, and its southerly position during the Holocene caused lower productivities. At 33°S the paleoproductivity was additionally affected by the southern westerlies and records highest levels during the Last Glacial Maximum (LGM). North of 33°S, several factors (e.g., position and strength of the South Pacific anticyclone, wind stress, continental runoff, and El Niño Southern Oscillation events) supplementary influenced upwelling and paleoproductivity, where maximum values occurred prior to the LGM and during the deglaciation.