bluuebunny/crossref_metadata_2025 huggingface dataset:
Internet implementation in Brazilian K‐12 schools
Authors: Joia Luiz Antonio
Published: July 2002

Internet is a real phenomenon. This technology is being spread out in all fields of our society, including education. But Internet does not come alone; a new modus operandi is being deployed in the productive segments of our world. Presents a framework to implement Internet in K‐12 Brazilian Schools. Shows how to make Internet a pedagogical tool to leverage the cognitive skills of the pupils and to be an enabler to reengineering the productive processes within the schools. Outlines the main obstacles to implement Internet, considering the Brazilian educational scenario. Presents conclusions about the need of a new educational paradigm for the schools and how the Internet can be useful in defining it.
Internet use by university students: an interdisciplinary study on three campuses
Authors: Perry Timothy T. , Anne Perry Leslie , Hosack‐Curlin Karen
Published: July 2002

This study sought to determine if differences exist among various age groups regarding students’ use of the Internet. Surveys were administered to 548 students from three regional universities in the southeastern USA. Survey responses were then analyzed to determine how many students regularly use the Internet, how many hours per week regular users spend on the Internet, and what computers they use. Information was also tabulated for use of e‐mail, use of the Internet to obtain university information, and for the number of students who had home pages. Finally, survey responses were analyzed to determine which students: consider the Internet to be a fad; project their future use of the Internet to be less, the same, or more than now; and project they will use the Internet in their chosen careers.
Marketing opportunities in the digital world
Authors: Reza Kiani G.
Published: July 2002

With the birth of the World Wide Web, the current decade has witnessed tremendous evolution in the media environment, and indicates that electronic commerce, defined as the electronic exchange of information, goods, services, and payments, has finally come of age. Despite the fast‐growing popularity of electronic commerce and presence of many companies on the virtual market, the opportunities offered by this new environment are still unknown. Many marketers still approach the Web based on the traditional mass communication model. The paper addresses the opportunities offered by the Web to marketers. Its approach considers the Web as a two‐way communication model in which four different communication states can take place. The paper also suggests the necessity of new concepts and models for marketers to manage their Web sites, and then presents the opportunities supporting the marketers’ objectives in the new environment.
Electronic digests in scientific communication
Authors: Ng T.W.
Published: July 2002

There are two basic forms of scientific communication: discussion and publication. In both forms, electronic versions have appeared over the Internet to challenge the viability of traditional instruments. Gives a discourse of the tools available and explains why electronic digests appear to provide the best scope in supplanting newsletters; their traditional counterpart.
Internet technology to run workflows
Authors: von Uthmann Christoph , Speck Mario
Published: July 2002

The existing, and still evolving, Internet technologies have, up to now, only been used for paper‐free distribution and hypermedia presentation of electronic documents. But today’s business and research often require more ‐ the compilation of knowledge worked out asynchronously by different distributed knowledge holders. This is in general connected with diverse review and revise processes. Owing to awkward paper‐based information flows lacking in control, this task is often characterized by exceptionally lengthy, spontaneous, unsystematic work, high error frequency and lack of transparency, which results in a lack of quality. Coming from the initial goal of supporting a process‐oriented management of distributed editorial work in the publishing sector ‐ which is analogous to the problem outlined above ‐ INTERFYS is an innovative Internet‐based system concept for making such processes more efficient by applying the concepts of workflow management using Web technologies only. With INTERFYS not only the distribution and presentation, but also the creation process of documents is supported using Internet technologies only. The paper explains and evaluates the conceptual and technical aspects of the System INTERFYS 1.0 which has just been realized and was presented on the CeBIT 1998 in Hanover.
An Internet‐based framework for federated process support
Authors: Piccinelli Floriana Marcello Giacomo , Zugliani Gabriele
Published: July 2002

The coupling of process‐centered environments (PCEs) with distributed object architectures like COM, CORBA and Java opens up an unprecedented range of possibilities in terms of automatic process management. The human factor is still the major component of the software process but its role is changing, as is the kind of support it needs. Focusing on the interactions between different distributed PCEs (heterogeneous federation), we present an Internet‐based framework for the definition and enactment of federated processes. A CSP‐like process definition language makes distribution problems transparent to the process designer while compiler and execution engines exploit Internet technology in order to map process specifications into the actual IT infrastructure. Different solutions are investigated for both the deployment of the enactment components and their interaction with local PCEs.
Distriblets: Java‐based distributed computing on the Web
Authors: Finkel David , Wills Craig E. , Brennan Brian , Brennan Chris
Published: July 2002

Describes a system for using the World Wide Web to distribute computational tasks to multiple hosts on the Web. A programmer with a computation to distribute registers it with a Web server. An idle host uses this server to identify available computations and downloads a Java class to perform the computation ‐ we call this class a distriblet. The paper describes the programs written to carry out the load distribution, the structure of a distriblet class, and our experience in using this system.
Scientific management and social responsibility: evidence from the role of women in the New York Bureau of Municipal Research
Authors: Lauer Schachter Hindy
Published: July 2002

Analyzes the role of women in the New York Bureau of Municipal Research (BMR) in the early years of the twentieth century. It shows that early practitioners of urban‐oriented scientific management had close ties to the reform/social‐work community.
A brief history of accounting for the translation of foreign currencies
Authors: Jackson Todd , Cook Doris M.
Published: July 2002

Problems in accounting for the translation of foreign currencies are as old as money itself, as far back as the ancient Greeks. In the USA these problems have been of primary concern in the twentieth century. Interest in accounting for foreign currency translation seems to have varied directly with the instability of exchange. Of particular note is the interest created by the unsettling economic effects of the First World War, Second World War and the Vietnam War. The standard setting bodies of the accounting profession, including the Committee on Accounting Procedures of the 1930s, the Accounting Principles Board which followed, and particularly the current Financial Accounting Standards Board, have devoted significant efforts to the development of accounting principles in this area, culminating in the present FASB Statement No. 52.
Editor’s introduction and situating the appraisal of rationality
Authors: Moon Bruce
Published: July 2002

As well as explaining the basis for, and linking the thematic structure of the contributions to, the Journal of Management History ‐ Special Issue on the topic of rationality, the article appraises the philosophical trichotomisation (or three‐part division) of epistemology. Recognising that rationality is primarily a philosophical concept, but also an esteemed and iconic indicator for good reasoning, the discussion of the trichotomised epistemology is undertaken to illustrate that rationality is conceptually understood in three different forms. From the observation that rationality has to be conceived as trimorphic, the commentary then illustrates the substantive limitations for each form.
Reverse engineering of clear solids using refractive index matching
Authors: Christensen Jon , Bandyopadhyay Amit
Published: July 2002

A novel approach is used to reverse engineer polymeric parts in a low cost, non‐destructive manner. Solids created from polymers with an index of refraction matching that of an immersion liquid are reverse engineered using a CCD camera. Serial images are taken as the part is immersed into the liquid or taken out of the liquid. The images are then used to create digital solid models from the polymeric physical model. The concept of the process, the hardware as a proof‐of‐concept demonstration, and results to understand the accuracy and limitations of the process are described.
Rapid prototyping and art
Authors: Rees Michael
Published: July 2002

This article is a summary of the session topic “Art and rapid prototyping” that was part of this online conference called The Future of Rapid Prototyping. The author discusses general topics covered in the conference and elaborates on the potential for collaboration between science and art, especially as it relates to rapid prototyping. There were no formal studies conducted – only observations on the speculative nature of rapid prototyping in art.
Reliability of flip chip components soldered on FR5 board
Authors: Määttänen Jarmo , Palm Petteri , Tuominen Aulis
Published: July 2002

To achieve good reliability and high performance flip chip interconnection, process parameters and materials used in the flip chip process must be optimised. In this paper reliability of Sn37Pb solder bumped flip chips on an FR5 board, using different fluxes and underfill materials, are tested in a temperature cycling test. Also the contact pad geometry used on the FR5 board had a great influence on the reliability of the joint. The solder bumps were grown on the well‐known TiW/Au under bump metallurgy (UBM1) with an extra layer of nickel (UBM2) which gives a reliable and high performance solder joint.
Self‐managing teams in high technology manufacture: overcoming technological barriers
Authors: McCalman James
Published: July 2002

This paper examines the introduction of self‐managing teams into a high technology workplace. The paper looks at the managerial and organizational implications of developing teams in what was considered a high technology environment where the physical restrictions of manufacture were assumed to dictate working practices. The case study evidence suggests that even in an atmosphere of clean rooms and clear communication difficulties, SMTs can prosper and suggests that it is only the physical boundaries which impede the development of more flexible forms of work organization.
Pricing lease clauses – The prospect of an art becoming science
Authors: Rowland Patrick
Published: July 2002

This paper reviews the literature which models lease covenants using option‐pricing techniques, probabilistic measures of risk and the contractual misalignment of incentives. These quantitative models, in conjunction with conventional discounting mathematics, offer ways to gauge the effects on rent of changes to many lease clauses. With the exception of discounted cash flow analysis to adjust rents for leasing incentives, none appears to be used in practice yet. The program has been designed to bridge the gap between academic developments in this field and current practices in rental valuation. The program works from rental values set on benchmark or standard lease conditions in that market and adjusts for different clauses. The program displays all the stages in calculating the effects of each changed clause and operates entirely from parameters set by the user. Trials of this program are described.
The valuation of contaminated land – Methods adopted in the UK and NZ
Authors: Bond Sandy G. , Kennedy Paul J.
Published: July 2002

Increasing litigation involving land contamination and an escalation in the number of incidents where property owners have suffered financial losses from these cases has resulted in negative impacts on property values and greater risks associated with investments in contaminated property. To date, there has been little systematic research on the valuation methodology that accounts for these risks. To help address this, two similar surveys were undertaken within New Zealand (NZ) and the United Kingdom (UK), the results of which are summarised here. The survey instruments were designed to determine what the respondents are currently doing when providing advice or producing valuations to account for the financial risks associated with investing in contaminated properties. It is hoped that the survey results will aid the process of developing “best practice” methodologies for use by valuers.
Prepayment risk and holding period for residential mortgages in Singapore ‐ Evidence from condominium transactions data
Authors: Eng Ong Seow
Published: July 2002

Prepayment risk is a key concern in securitized real estate. Using repeat sales in transaction data to proxy for holding period and prepayment, this paper provides the first rigorous analysis of residential mortgage prepayment in Singapore. The prepayment rate for new condominiums is increasing in the holding period and exhibits spikes in the fourth and sixth years. The likelihood of observing a subsequent sale and the prepayment rate increases in floor level, sentiment and other investment return, but decreases in floor area and mortgage rate hikes. Appreciation in the property price also tends to increase the probability and rate of prepayment. In contrast, owners of larger property units and HDB upgraders are less likely to resell their properties. The evidence also suggests that the likelihood of prepayment is lowered after the anti‐speculation measures were introduced in May 1996.
COBISS: National Union Catalogue Online bibliography and gateway to other resources
Authors: Seljak Marta , Seljak Tomazo
Published: July 2002

In 1987, a shared cataloguing system as the common basis for the library information system of the former Yugoslavia was designed. Before Yugoslavia’s disintegration in 1991, the shared cataloguing system was renamed COBISS – the Co‐operative Online Bibliographic System & Services. It later became the synonym for the library information system of Slovenia. Today it connects over 220 Slovenian libraries. It provides the libraries with conditions necessary for shared cataloguing at a national level, including bibliographies and the automation of local functions. COBISS/OPAC enables the users to access information sources in the wider Internet environment. While COBISS software is used by some of the libraries in the territory of the former Yugoslavia, in Bosnia and Herzogovina too, COBISS/BIH, an independent co‐operative library system, was established in 1998. The COBISS system is an example of how to develop an efficient co‐operative library system as one of the vital segments of the information society in an environment primarily occupied with current problems of transition.
Improving access in bilingual, biscript catalogues through Arabised authority control
Authors: Vassie Roderic
Published: July 2002

Describes some of the information retrieval issues faced by Arab libraries with bilingual (Arabic/English), biscript (Arabic/Latin) catalogues. Reviews earlier published work on multiscript bibliographic databases before focusing on controlled name and subject access points, including suggestions for how best to serve the information needs of a group of end‐users who are predominantly native Arabic‐speakers.
Estimation of the Thermodynamic Properties of Branched Hydrocarbons
Authors: He Hui , Metghalchi Mohamad , Keck James C.
Published: July 2002

A simple model has been developed to estimate the sensible thermodynamic properties such as Gibbs free energy, enthalpy, heat capacity, and entropy of hydrocarbons over a wide range of temperatures with special attention to the branched molecules. The model is based on statistical thermodynamic expressions incorporating translational, rotational and vibrational motions of the atoms. A method to determine the number of degrees of freedom for different motion modes (bending and torsion) has been established. Branched rotational groups, such as CH3 and OH, have been considered. A modification of the characteristic temperatures for different motion mode has been made which improves the agreement with the exact values for simple cases. The properties of branched alkanes up to 2,3,4,-trimthylpentane have been calculated and the results are in good agreement with the experimental data. A relatively small number of parameters are needed in this model to estimate the sensible thermodynamic properties of a wide range of species. The model may also be used to estimate the properties of molecules and their isomers, which have not been measured, and is simple enough to be easily programmed as a subroutine for on-line kinetic calculations. [S0195-0738(00)00902-X]
Cavitation Nuclei and Bubble Formation—A Dynamic Liquid-Solid Interface Problem
Authors: Mo̸rch Knud A.
Published: July 2002

A model of the formation of cavitation nuclei is developed assuming local detachment of the liquid at locations of concave solid surface topography. The detachment is attributed to diffusion of gas molecules into the interfacial liquid, where the liquid-solid bonds are strained due to interfacial tension in the liquid. Calculations indicate that attached interfacial voids may grow into stabilized cavitation nuclei as a consequence of broad-band resonance, excited by external sources of noise or vibration in the whole range of frequencies up to the MHz regime. The gas content in the liquid and the amplitude and frequency of the sound field determine a balance between rectified diffusion of gas into the void and diffusion out of it due to the excess pressure in the void. In strong acoustic fields and in supersaturated liquids the voids may grow into bubbles that detach and form free gas bubbles. [S0098-2202(00)01503-0]
Moment-Based Load and Response Models With Wind Engineering Applications
Authors: Winterstein Steven R. , Kashef Tina
Published: July 2002

A general method is shown here to model wind loads and responses for reliability applications. This method characterizes the short-term loads and responses by a few summary statistics: specifically, by a limited number of statistical moments. A suite of moment-based models are derived and applied here, illustrating how this statistical moment information can best be utilized. Two examples are shown: the fatigue analysis of a wind turbine component, and the vibration response of a fixed structure to nonlinear wind drag loads. [S0199-6231(00)00702-4]
Thermal Management of Surface Mount Power Magnetic Components
Authors: Refai-Ahmed G. , Yovanovich M. M.
Published: July 2002

A numerical and experimental study of conduction heat transfer from low power magnetic components with gull wing leads was conducted to determine the effects of distributing the power loss between the core, the winding and the thermal underfill on the thermal resistance. The numerical study was conducted in the power loss ratio range of 0.5⩽PR⩽1.0, where the only active power loss was from the winding at PR=1. In addition, the effect of the thermal underfill material between the substrate and the lower surface of the magnetic package on the thermal performance of the magnetic device was also examined. For comparison, a test was conducted on a magnetic component at PR=1, without thermal underfill. This comparison revealed good agreement between the numerical and experimental results. Finally, a general model was proposed for conduction heat transfer from the surface mount power magnetic packages. The agreement between the model and the experimental results was within 8 percent. [S1043-7398(00)00704-0]
Effects of Tip Clearance on Hot Streak Migration in a High-Subsonic Single-Stage Turbine
Authors: Dorney Daniel J. , Sondak Douglas L.
Published: July 2002

Experimental data have shown that combustor temperature nonuniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location, or clocking, of the first-stage vane airfoils can be used to minimize the adverse effects of the hot streaks due to the hot fluid mixing with the cooler fluid contained in the vane wake. In addition, the effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have been quantified. In the present investigation, three-dimensional unsteady Navier–Stokes simulations have been performed for a single-stage high-pressure turbine geometry operating in high subsonic flow to study the effects of tip clearance on hot streak migration. Baseline simulations were initially performed without hot streaks to compare with the experimental data. Two simulations were then performed with a superimposed combustor hot streak; in the first the tip clearance was set at the experimental value, while in the second the rotor was allowed to scrape along the outer case (i.e., the limit as the tip clearance goes to zero). The predicted results for the baseline simulations show good agreement with the available experimental data. The simulations with the hot streak indicate that the tip clearance increases the radial spreading of the hot fluid, and increases the integrated rotor surface temperature compared to the case without tip clearance. [S0889-504X(00)02204-2]
Analytical Solution for W-N Criteria for the Prediction of Notched Strength of an Orthotropic Shell
Authors: Kumar R. Ramesh , Jose S. , Venkateswara Rao G.
Published: July 2002

Analytical solution for the tangential stress distribution ahead of a hole is needed for the theoretical prediction of notched strength of brittle laminate using the well-known W-N criteria. In the present study, tangential stress distribution in an orthotropic circular cylindrical shell under uniaxial loading with a circular hole is obtained intuitively with the use of a stress function. A good agreement is obtained for the stresses around and ahead of the circular hole in 0deg4±30degs and 90 deg laminates with the finite element results.
Heat, Mass, and Fluid Flow in a Solar Reactor for Fullerene Synthesis
Authors: Guillard T. , Flamant G. , Laplaze D.
Published: July 2002

Experimental results with a 2 kW solar furnace, in a wide range of vaporization rates (0.1–4 g/h), under variable pressure and flow rate of argon, are used with numerical simulation to define key parameters for large scale synthesis of fullerenes with solar energy. The vaporization process is controlled by diffusion in the temperature and pressure ranges 3000-3700 K and 70-250 hPa respectively. In the solar reactor, fullerene yield is governed by the dilution of carbon vapor in argon and the temperature gradient in the cooling zone. Criteria for both parameters are suggested. Consequently, these data, combined with a validated numerical model of the reactor, may be used for the design of large-scale solar process.
Laser-Doppler Measurements of Velocities Just Downstream of a Collapsible Tube During Flow-Induced Oscillations
Authors: Bertram C. D. , Diaz de Tuesta G. , Nugent A. H.
Published: July 2002

The flow field less than one diameter downstream of the end of a collapsible tube executing self-excited oscillations was examined using a two-component fiber-optic laser-Doppler anemometer. The time-averaged Reynolds number of the flow was 11,000. With the tube oscillating periodically, results obtained during many cycles of oscillation were combined to yield surface plots of the axial component over the cross section at 16 phases of the cycle. By combining measurements obtained with the laser probe in two different orientations, secondary flow vectors over the cross section were likewise constructed for 16 phases. The measurements showed strongly phasic turbulence intensity, with the phase of high intensity coinciding with the time of maximal tube collapse. Reverse flow occurred during much of the cycle, at places in the cross section that agree with our previous observations of laminar and turbulent steady flow through a rigid simulated collapsed tube.
Film-Cooled Turbine Endwall in a Transonic Flow Field: Part I—Aerodynamic Measurements
Authors: Kost Friedrich , Nicklas Martin
Published: July 2002

Thermodynamic and aerodynamic measurements were carried out in a linear turbine cascade with transonic flow field. Heat transfer and adiabatic film-cooling effectiveness resulting from the interaction of the flow field and the ejected coolant at the endwall were measured and will be discussed in two parts. The investigations were performed in the Windtunnel for Straight Cascades (EGG) at DLR, Go¨ttingen. The film-cooled NGV endwall was operated at representative dimensionless engine conditions of Mach and Reynolds number Ma2is=1.0 and Re2=850,000 respectively. Part I of the investigation discusses the aerodynamic measurements. Detailed aerodynamic measurements were carried out in the vicinity of a turbine stator endwall using conventional pressure measurements and a Laser-2-Focus (L2F) device. The L2F served as a velocimeter measuring 2D-velocity vectors and turbulence quantities and as a tool to determine the concentration of coolant ejected through a slot and through holes at the endwall. Pressure distribution measurements provided information on the endwall pressure field and its variation with coolant flow rate. Pressure probe measurements delivered cascade performance data. Oil flow visualization and laser velocimetry gave a picture of the near endwall flow field and its interference with the coolant. A strikingly strong interaction of coolant air and secondary flow field could be identified. The measurement of coolant concentration downstream of the ejection locations provided a detailed picture of the coolant flow convection and its mixing with the main flow. The relative coolant concentration in the flow field is directly comparable to the adiabatic film-cooling effectiveness measured by thermal methods at the wall.
Comparison Between Spring Balancer and Gravity Balancer in Inertia Force and Performance
Authors: Kobayashi Kazuo
Published: July 2002

In either a gravity balancer or spring balancer, the forces required to move a weight in the direction of gravity consist of inertia force and frictional force generated in the system. This report derives a general equation of inertia force for both a gravity balancer and spring balancer and compares the two. It also clarifies the conditions for decreasing inertia force and achieving a compact and light configuration in a spring balancer. In addition, a general equation of frictional force is derived for each type of balancer enabling frictional force to be predicted at the design stage.
Analysis of Feed Errors in Tapping by Contact Stress Model
Authors: Dogra Ajit Pal S. , DeVor Richard E. , Kapoor Shiv G.
Published: July 2002

One of the most common tapping errors, mismatch of tap feed rate and the thread pitch, has a significant effect on the tapping thrust signal and the resultant thread profile. The underfeed of the tap leads to an upward pull on the workpiece and overfeed causes a downward push. Tapping experiments are conducted with intentionally magnified feed errors to study the phenomenon and aid in the model development. Using contact stress theory for elastic materials, a model for tap-workpiece interaction is developed and integrated with the mechanistic force model developed earlier to predict the tapping forces. In most cases there was a good agreement between the simulations of combined model (contact stress model coupled with mechanistic model) and the experimental results. Tap tooth design with relief on the flank has been shown to significantly reduce the tapping thrust sensitivity to the feed error, thereby affecting the tool life and improving the thread quality.
Toward Improved Film Cooling Prediction
Authors: Medic G. , Durbin P. A.
Published: July 2002

Computations of flow and heat transfer for a film-cooled high pressure gas turbine rotor blade geometry are presented with an assessment of several turbulence models. Details of flow and temperature field predictions in the vicinity of cooling holes are examined. It is demonstrated that good predictions can be obtained when spurious turbulence energy production by the turbulence model is prevented.
First-Passage Failure of Quasi-Integrable Hamiltonian Systems
Authors: Zhu W. Q. , Deng M. L. , Huang Z. L.
Published: July 2002

The first-passage failure of quasi-integrable Hamiltonian systems (multidegree-of-freedom integrable Hamiltonian systems subject to light dampings and weakly random excitations) is investigated. The motion equations of such a system are first reduced to a set of averaged Ito^ stochastic differential equations by using the stochastic averaging method for quasi-integrable Hamitonian systems. Then, a backward Kolmogorov equation governing the conditional reliability function and a set of generalized Pontryagin equations governing the conditional moments of first-passage time are established. Finally, the conditional reliability function, and the conditional probability density and moments of first-passage time are obtained by solving these equations with suitable initial and boundary conditions. Two examples are given to illustrate the proposed procedure and the results from digital simulation are obtained to verify the effectiveness of the procedure.
Interfacial Thermal Stress Analysis of Anisotropic Multi-Layered Electronic Packaging Structures
Authors: Xie Weidong , Sitaraman Suresh K.
Published: July 2002

The presence of dissimilar material systems and thermal gradients introduce thermal stresses in multi-layered electronic assemblies and packages during fabrication and operation. The high stress gradients near the free edge of bonding interfaces of such structures may cause cracking and delamination leading to the failure or malfunction of electronic assemblies and packages. A simple but accurate engineering approach for the calculation of interlaminar thermal stresses due to thermal mismatch in multi-layered structures is needed so that designers can determine interlaminar thermal stresses easily without much computational efforts. A few approaches based on the generalized deformation theory have been published but most of them are only suitable for structures with symmetric layers. For electronic packages and assemblies, unsymmetric layers are often used. An improved approach, Classical Laminate Theory-Edge Stress Shape (CLT-ESS), for prediction of interlaminar thermal stresses that can be applied to multi-layered structures with unsymmetric layers is presented. Comparisons are made with finite element analysis results and are found to be favorable. The proposed approach provides an efficient way for the calculation of interlaminar thermal stresses. [S1043-7398(00)00901-4]
Turbulent Three-Dimensional Air Flow and Trace Gas Distribution in an Inhalation Test Chamber
Authors: Longest, P. W. , Kleinstreuer C. , Kinsey J. S.
Published: July 2002

Steady incompressible turbulent air flow and transient carbon monoxide transport in an empty Rochester-style human exposure chamber have been numerically simulated and compared with experimental data sets. The system consisted of an inlet duct with a continuous carbon monoxide point source, 45- and 90-degree bends, a round diffuser, a round-to-square transition, a rectangular diffuser, the test chamber, a perforated floor, and again transition pieces from the chamber to an outlet duct. Such a configuration induced highly nonuniform vortical flow patterns in the chamber test area where a pollutant concentration is required to be constant at breathing level for safe and accurate inhalation studies. Presented are validated momentum and mass transfer results for this large-scale system with the main goals of determining the development of tracer gas (CO) distributions in the chamber and analyzing the contributions to CO-mixing. Numerical simulations were conducted employing a k-ε model and the latest available RNG k-ε model for air and CO-mixing. Both models predict similar velocity fields and are in good agreement with measured steady and transient CO-concentrations. It was found that secondary flows in the inlet section and strong vortical flow in the chamber with perforated flooring contributed to effective mixing of the trace gas at breathing levels. Specifically, in the height range of 1.4 m<h<2.0 m above the chamber floor, predicted CO-concentrations rapidly reached a near constant value which agrees well with experimental results. This work can be extended to analyze trace gas mixing as well as aerosol dispersion in occupied test chambers with or without flow redirection devices installed in the upstream section. A complementary application is particle transport and deposition in clean rooms of the electronic, pharmaceutical, and health care industries. [S0098-2202(00)01702-8]
Carbon (as Graphite, Buckminsterfullerene, and Diamond) by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

XPS spectra were acquired for highly ordered pyrolytic graphite, a single crystal diamond, and a C60 film. Carbon 1s and valence band spectra are included in the electronic record.
In situ measurement of thickness dependent electrical resistance of ultrathin Co films on SiO2/Si(111) substrate
Authors: Li M. , Zhao Y.-P. , Wang G.-C.
Published: July 2002

Ultrathin Co films of thicknesses from 1 to 19 monolayers (ML) were grown on native oxide covered Si(111) surfaces near room temperature by thermal evaporations in ultrahigh vacuum. The thickness dependent total electrical sheet resistance R (Ω/□) at room temperature was measured in situ by a four-point probe. The total sheet resistance as a function of thickness first increased and then decreased suggesting that the Co film morphology changed from discontinuous islands of 1 or 2 ML thick to continuous films for thickness d>3 ML. The sheet resistance RCo of Co was extracted from the total sheet resistance assuming that the Co and SiO2/Si are two parallel resistors. The value of RCo gradually levels off to 31.5 (Ω/□) which corresponds to resistivity of 10.5 μΩ cm at ∼ 19 ML. The thickness dependent resistivity was fitted by models including surface, interface, grain boundary scatterings, and surface roughness. The surface roughness obtained from atomic force microscopy is consistent with that used in Namba's model to improve the fit of resistivity in a few ML thick regime.
Influence of Substrate Temperature on the Condensation of Vacuum Evaporated Films of MgF2 and ZnS
Authors: Ritter Elmar , Hoffmann Rolf
Published: July 2002

The influence of substrate temperature on the condensation and properties of thin films of MgF2 and ZnS was investigated. The properties of films on heated substrates were compared with the properties of films on unheated substrates. In both cases a decrease of film thickness with increasing substrate temperature was observed. In the case of MgF2 the packing density of the films changes from 0.80 to 0.95 with increase of substrate temperature from 40° to 365° C. This change in packing density explains the thickness differences observed. In the case of ZnS, which dissociates during evaporation, the decrease of thickness is due to a decrease of the condensation coefficient of Zn. For the adsorption energy of Zn on ZnS, 4.2 kcal/mol were calculated from the experimental data.
A Survey of Optical and Electrical Properties of Thin Films of II–VI Semiconducting Compounds
Authors: Ludeke R.
Published: July 2002

A review of the work in recent years is presented. The effects of the known physical state of the film on the optical properties, near and above the fundamental gap, and on the electrical transport properties are discussed. The transport parameters in films of II–VI compounds are largely dominated by crystalline defects. The intercrystalline barrier model is used to describe many of the observed transport properties. Mobilities limited by ionized impurity scattering have been observed in some films of CdS and CdSe. Scattering by polar optical modes possibly limits the mobilities of some illuminated CdS and CdSe films at high temperatures. Intrinsic-like behavior of the conductivity has been observed in compensated films of ZnS, CdO, and CdTe. The optical properties of II–VI films are affected to a lesser degree by impurities and crystalline defects, and bulklike behavior may be observed. The reflection and transmission spectra of most of the II–VI compounds, including films of sphalerite CdS, CdSe, and HgS (metastable phases), are discussed in relation to their band structure. The effect of strains on the optical spectra of CdTe films is briefly discussed.
Use of Auger Electron Spectroscopy and Inert Gas Sputtering for Obtaining Chemical Profiles
Authors: Palmberg P. W.
Published: July 2002

An apparatus is described in which surface chemical analysis by Auger electron spectroscopy (AES) is carried out simultaneously with inert gas sputtering to obtain composition profiles normal to the solid–vacuum interface. Chemical profiles are presented for as-evaporated and air-heated nichrome thin film resistors.
Growth Effects on Stress in Nickel Films
Authors: Springer R. W. , Hoffman R. W.
Published: July 2002

Intrinsic stress dam of 2000-Å Ni films evaporated by an electron beam gun onto Ni substrates has been obtained as a function of temperature. The choice of the substrate material has reduced differential thermal expansion effects, to less than 108 dyn/cm2 for a total stress of 109–1010 dyn/cm2. This figure includes possible temperature gradient effects through the thickness of the substrate. The cantilevered beam technique, with deflection determined by a modified microbalance, was used to measure the stress. External circuitry was added to the microbalance to determine the Young's modulus of each substrate in vacuum at temperature preceeding the stress measurement. The stress in the initial 800 Å of film growth is very sensitive to the cleaning technique used on the substrate. The instataneous stress appears constant with increasing thickness above 800 Å at constant temperature, and it decreases slowly with temperature above 100 °C.
Inelastic Tunneling in Pb–Zn or ZnS–Oxide–Pb Junctions
Authors: Wyatt P. W. , Barker R. C. , Yelon A.
Published: July 2002

A series of tunneling measurements using Pb–Zn or ZnS–oxide–metal thin film junctions in the normal state is reported. The samples are prepared by depositing a film of Zn or ZnS on top of the first Pb film prior to oxidation. For both dopants a metallic Zn layer of monolayer thickness is present between the Pb and the insulator. A fraction of a monolayer of Zn is sufficient to substantially enhance the structure usually attributed to electrode phonons and to eliminate that usually attributed to PbOx barrier phonons. The latter is replaced by structure which may be related to ZnO in Zn-doped junctions and ZnS in one type of ZnS-doped junctions. No barrier phonon structure whatever appears in a second type of ZnS-doped junction. The smooth background conductance is also modified by the doping. These results are discussed in terms of recent theoretical work. They suggest that the coupling to barrier and electrode phonons is at least as important in determining the tunneling characteristic as the phonon spectra themselves, and that the metal-insulator interface is critical in determining the coupling.
Range and Energy Deposition Enhancement of a Fast Electron Beam by External Electric Fields
Authors: Bowden C. M. , Perkins J. F. , Shatas R. A.
Published: July 2002

The electrode configuration in electron-beam preionized electrical discharge pumped molecular gas lasers can be arranged such that the drift field of the pump accelerates the fast electrons which are concurrently scattered. In designing lasers with output pulses beyond the kJ energy level, one uses the drift field to extend the range and to enhance the energy deposition of the fast electron beam. Although scattering and energy loss of electrons penetrating into matter without an external field is well known, electrical fields of the order of kV cm−1 at atmospheric pressures substantially affect both the range and the energy deposition of the primaries. We report numerical results in range and differential and integral energy deposition enhancement for 100 keV to 2 MeV electron beams in external fields up to 10−16 V cm2 electric field to number density (ε/N) ratio, for Zeff=6 gas mixtures obtained by Monte Carlo calculations of transport of fast electrons in thick absorbers modified to include the effects of an external electrical field applied across the scatterer. Detailed results are given in the form of graphs directly usable by the designer.
Precision Electron Beam Microfabrication
Authors: Ozdemir F. S. , Perkins W. E. , Yim R. , Wolf E. D.
Published: July 2002

A computer-controlled electron beam microfabrication system has been used to fabricate complex, high-frequency acoustic surface wave devices. System hardware and software, fabrication process, and results are described.
Electrical characteristics of metal–ferroelectric (PbZrxTi1−xO3)–insulator(Ta2O5)–silicon structure for nonvolatile memory applications
Authors: Sze Chi-yuan , Lee Joseph Ya-min
Published: July 2002

A metal–ferroelectric–insulator–silicon (MFIS) structure using lead–zirconate–titanate (PZT) as the ferroelectric layer and Ta2O5 as the insulator layer is fabricated. This structure is studied for the potential application of nonvolatile memory devices. The Ta2O5 layer is used as a buffer layer to minimize the out diffusion of silicon atoms during heat treatment processes. High frequency capacitance–voltage measurements show a flat band voltage shift of 13 V under a ±15 V writing pulse. The interface-trap density Dit is measured by the conductance method. The MFIS capacitors are shown to have a fatigue lifetime of 1×1011 cycles and 5×107 cycles for 11.4 and 15 V writing pulses, respectively.
Thin SiO2 layers on Si(111) with ultralow atomic step density
Authors: Oliver Antonio C. , Blakely Jack M.
Published: July 2002

The morphologies of the oxide surface and of the Si–SiO2 interface that form on special Si(111) substrates have been studied by atomic force microscopy (AFM). The substrates are totally free of atomic steps or have very low step density. Step-free regions are formed on patterned Si(111) by thermal processing. AFM scans of the same areas prior to oxidation, after oxidation, and after chemical removal of the oxide allow the relative roughnesses to be compared. The step structure of the Si(111) substrate is translated to the oxide surface even for SiO2 layers in the 10 nm range. The lack of significant displacement of the atomic steps at the Si–SiO2 interface indicates that the oxide grows by a layer-by-layer mechanism.
Field electron emission from patterned nanostructured carbon films on sodalime glass substrates
Authors: Park Kyung Ho , Lee Kyung Moon , Choi Seungho , Lee Soonil , Koh Ken Ha
Published: July 2002

Using the hot filament chemical vapor deposition method, patterned nanostructured carbon films with excellent field emission characteristics have been deposited at the nominal substrate temperatures of 540 °C and 450°C on sodalime glass substrates. These films have demonstrated a good visual emission uniformity and good current stability during the continuous operation for 140 h. Taking advantage of the poor adhesion of the nanostructure carbon without a chrome interlayer and selective growth on the metal catalyst, the formation of the patterned nanostructured carbon films has been carried out via the prepattering of the chrome electrodes and/or metal catalyst using the conventional photolithography process. An example of the patterned emitter with high complexity is presented to demonstrate the feasibility of practical emitter fabrication using nanostructured carbon films.
Epitaxially overgrown, stable W–GaAs Schottky contacts with sizes down to 50 nm
Authors: Wernersson L.-E. , Georgsson K. , Gustafsson A. , Löfgren A. , Montelius L. , Nilsson N. , Pettersson H. , Seifert W. , Samuelson L. , Malm J.-O.
Published: July 2002

A processing scheme for the fabrication of embedded W–GaAs contacts has been established and the resulting contact characteristics have been evaluated. The main advantage of these contacts is that they are stable during high-temperature epitaxial overgrowth. The fabrication scheme is based on a liftoff process with electron beam evaporation of tungsten and subsequent epitaxial overgrowth using metalorganic vapor phase epitaxy. Various methods were used to characterize the buried contacts. First, the structural properties of GaAs surrounding embedded W features, with widths down to 50 nm, were characterized by high-resolution transmission electron microscopy. Measurements of the conductivity in individual, buried wires were performed in order to study the influence of the overgrowth process on the properties of the tungsten. We also evaluated the current–voltage characteristics for macroscopic contacts, which revealed a clear dependence on processing parameters. Optimized processing conditions could thus be established under which limited contact degradation occurred during overgrowth. Finally, we used the overgrowth technique to perform a detailed investigation of the electrical and optical properties of floating-potential embedded nano-Schottky contacts by space-charge spectroscopy.
Ion assistance effects on electron beam deposited MgF2 films
Authors: Alvisi M. , De Tomasi F. , Della Patria A. , Di Giulio M. , Masetti E. , Perrone M. R. , Protopapa M. L. , Tepore A.
Published: July 2002

Thin films of MgF2 have been deposited by the ion-assisted electron-beam evaporation technique in order to find out the ion beam parameters leading to films of high laser damage threshold whose optical properties are stable under uncontrolled atmosphere conditions. It has been found that the ion-assisted electron-beam evaporation technique allows getting films with optical properties (refraction index and extinction coefficient) of high environmental stability by properly choosing the ion-source voltage and current. But, the laser damage fluence at 308 nm was quite dependent on the assisting ion beam parameters. Larger laser damage fluences have been found for the films deposited by using assisting ion beams delivered at lower anode voltage and current values. It has also been found that the films deposited without ion assistance were characterized by the highest laser damage fluence (5.9 J/cm2) and the lowest environmental stability. The scanning electron microscopy analysis of the irradiated areas has revealed that the damage morphologies were not dependent on the deposition conditions.
Fabrication of Multilayer Dielectric Films
Authors: Behrndt K. H. , Doughty D. W.
Published: July 2002

For the fabrication of multilayer dielectric films for mirrors or filters, an evaporation system was built for attaining (1) thickness variations below ±0.5% on substrates up to 6 in. in diameter and (2) simultaneous deposition on five such substrates. During deposition, the substrates perform a planetary rotation around the source thereby greatly reducing thickness variations and angle-of-incidence effects, together with inhomogeneities in the evaporation characteristic of the source. Details of the system and the optical monitoring arrangement are given. The experimental thickness variation amounted to ±0.15% on the 6-in.-diam substrates. Reflectances of up to 99.8% could be attained with the losses due to scattering. The application of the mirrors to optical information-storage experiments is briefly described.