bluuebunny/crossref_metadata_2025 huggingface dataset:
Mortalidade de motociclistas com lesões traumáticas resultantes de acidentes de trânsito na cidade de São José dos Campos, em 2015: estudo de coorte
Authors: Silva Caroline de Lima Neto , Lopes Maria Carolina Barbosa Texeira , Thomaz Rosimey Romero , Whitaker Iveth Yamaguchi
Published: November 2020

Resumo Objetivo: Analisar fatores associados à mortalidade por lesões traumáticas entre motociclistas. Métodos: Coorte prospectiva, conduzida no Hospital Municipal de São José dos Campos, Brasil, 2015. Foram incluídos motociclistas com lesões traumáticas, ≥14 anos de idade, hospitalizados. Analisaram-se as variáveis sociodemográficas do acidente e da hospitalização, por modelo de regressão de Poisson, apresentando-se risco relativo (RR) e intervalos de confiança de 95% (IC95%). Resultados: Entre 190 motociclistas, 161 (84,7%), jovens do sexo masculino, revelaram 422 (41,8%) lesões em extremidades inferiores e superiores. A incidência de óbito foi maior na medida do aumento da gravidade do trauma, fisiológica (RR=9,67 [IC95% 1,46;64,26]; e RR=4,71 [IC95% 1,36;16,26]) e anatômica (RR=31,49 [IC95% 3,72;266,38]); e mostrou-se menor em até uma semana de internação (RR=0,39 [IC95% 0,15;0,98]). Conclusão: A gravidade do trauma e o tempo de internação associaram-se ao óbito de motociclistas, mas novos estudos devem ser conduzidos para confirmar esses achados e analisar essas relações mais detalhadamente.
Mapping the landscape of Artificial Intelligence applications against COVID-19
Authors: Bullock Joseph , Luccioni Alexandra , Hoffman Pham Katherine , Sin Nga Lam Cynthia , Luengo-Oroz Miguel
Published: November 2020

COVID-19, the disease caused by the SARS-CoV-2 virus, has been declared a pandemic by the World Health Organization, which has reported over 18 million confirmed cases as of August 5, 2020. In this review, we present an overview of recent studies using Machine Learning and, more broadly, Artificial Intelligence, to tackle many aspects of the COVID19 crisis. We have identified applications that address challenges posed by COVID-19 at different scales, including: molecular, by identifying new or existing drugs for treatment; clinical, by supporting diagnosis and evaluating prognosis based on medical imaging and non-invasive measures; and societal, by tracking both the epidemic and the accompanying infodemic using multiple data sources. We also review datasets, tools, and resources needed to facilitate Artificial Intelligence research, and discuss strategic considerations related to the operational implementation of multidisciplinary partnerships and open science. We highlight the need for international cooperation to maximize the potential of AI in this and future pandemics.
Biocementation of soft soil by carbonate precipitate and polymeric saccharide secretion
Authors: Rao Sudhakar M , Sukumar Reshma , Joshua Rita Evelyne , Mogili Nitish Venkateswarlu
Published: November 2020

This study utilised native denitrifiers of cattle manure to oxidise its organic matter and induce calcium carbonate cementation in a synthetic soft soil. The soft soil is prepared by remoulding a 50% kaolinite + 50% sand mix with ultra-pure water at 21% water content. The prepared specimen is classified as soft soil based on its low unconfined compression strength of 16 kPa. Extraneous calcium nitrate provides nitrate ions (electron acceptors) for the metabolism of denitrifying bacteria and calcium (Ca2+) ions for calcium carbonate formation. The facultative anaerobe community peaks and declines between 7 and 14 days. A small addition of magnesium oxide balances the pH reduction caused by acetic acid formation during microbial degradation of cattle manure. Acetic acid serves as a carbon substrate for the metabolic activities of denitrifying bacteria. The CO2 (gas) released during the metabolic activities of bacteria dissolves in water and forms bicarbonate ions. The anion combines with calcium ions in the alkaline environment to form calcium carbonate cement. In addition, the native extracellular polysaccharide (EPS)-secreting bacteria in cattle manure facilitate EPS bonding of soil aggregates. Soil structure, interfacial frictional resistance mobilised by cattle manure fibres, EPS bonding and calcium carbonate cementation enhance the compression strength of the stabilised specimen by 720%.
Behaviour of steel beams retrofitted with anchored carbon-fibre-reinforced polymer strips
Authors: Mercimek Ömer , Ghoroubi Rahim , Baran Mehmet , Anil Özgür
Published: November 2020

Steel bridge beams can be damaged due to increased traffic loads and environmental impacts. An experimental study on the use of bonded and mechanically anchored carbon-fibre-reinforced polymer (CFRP) strips was undertaken to assess the retrofitting of such steel beams. The number of mechanical anchors used in the ends of the bonded strips was varied from zero to eight. The steel beam samples were tested under four-point loading. Loading was applied as an increasingly high static load and a low repetitive fatigue load. The load–displacement behaviour under the effects of static and fatigue loading and the strain distributions along the strips were measured and interpreted. The results showed that retrofitting cracked steel beams with CFRP strips is an effective method. In addition, retrofitting with anchored strips increased the performance of cracked beams under the effects of both static and fatigue loading.
Collapse safety assessment of plan-irregular buildings considering ductility and damage
Authors: Rokhsati Moeinoddin , Emami Ali R.
Published: November 2020

The current study focuses on seismic fragility analysis and collapse safety assessment of reinforced concrete buildings with re-entrant corner irregularity. This is conducted in a probabilistic framework on the case studies of moment-frame building archetypes with a typical L-shaped plan. A three-dimensional perspective for ductility and damage distributions is addressed for the non-linear models developed. Multi-directional pushover procedures and incremental dynamic analyses have been performed by applying ten near-field and ten far-field earthquake records for each building model. The median collapse capacity is established through developing fragility curves in terms of several earthquake intensity measures and spatially distributed displacement, ductility and damage indices. Available and acceptable collapse margin ratios (CMRs) are measured to judge the safety margin against collapse at the maximum considered earthquake shaking level. The statistics indicate that when the collapse capacity is defined in terms of the drift, ductility or damage, instead of an intensity measure, the collapse uncertainty decreases. Thus, the median collapse capacity is calculated precisely with less variability, resulting in available CMRs that exceed acceptable CMRs. With the perspective of this methodology, a satisfactory collapse safety margin was anticipated in the seismic force-resisting system by the design requirements for the targeted building class.
Using steel slag aggregate to strengthen self-compacting concrete durability
Authors: Abendeh Raed M. , Bani Baker Mousa
Published: November 2020

The aim of this study is to produce durable self-compacting concrete (SCC) using different fractions of recycled steel slag aggregates (SSA) by replacing natural aggregate. For this purpose, a series of nine mixing proportions were designed with a constant water-to-cement ratio of 0.34 and a change of SSA ratio replacing natural coarse or fine aggregates by weight from 0 to 50% (increments of 12.5%). For freshly mixed SCC, the flowability, passing and filling abilities, segregation and viscosity were observed by slump flow, slump-flow time (T500), L-box and V-funnel empirical tests. Mechanical properties were tested for compressive and flexural strengths, while the durability characteristics were conducted for water absorption and permeability, sulfate attack and freeze–thaw action (F/T). Non-destructive measurement approaches (i.e. ultrasonic pulse velocity and resonance frequency) were involved in the F/T testing. The test results indicate that the incorporation of SSA in SCC is suitable and improves the mechanical strength and durability properties, and that enhancement is more pronounced at higher SSA increments, especially when replacing the coarse natural aggregate partially by coarse SSA.
The Effect of Travel Agency’s Ticket Commission Policy on Perceived Fairness and Purchase Intention: A Moderated Mediation Effect of Ticket Commission Understanding
Authors:   The Tourism Sciences Society Of Korea, Hur Uh-Jin , Kim Sun-Jae , Ko Young-Dae
Published: November 2020

Travel agency's ticket commission have become a rising issue with COVID-19. The present study examined the relationship between consumers' perceived fairness and purchase intention following the travel agency's ticket commission policy. We explored if the consumer's ticket commission understanding has moderation effect and moderated mediation effect. The results show that perceived fairness and purchase intention are affected by the refund and notice policy. In addition, it was found that indirect effect on purchase intention through perceived fairness according to the notice policy was affected by the consumer’s ticket commission understanding. The implications derived from this study are as follows. First, travel agency can generate additional revenue by setting higher ticket commission as long as they do not affect the total ticket price. Second, travel agency can improve purchase intension by implementing a reasonable ticket commission policy that refunds the ticket commission when there are no defects attributed to the consumer, or by clearly informing the consumer of the additional services offered compared to direct ticket purchases through airline. Third, in order to ensure that consumers are not unnecessarily damaged, relevant organizations must take legal and institutional measures to clarify the notice of ticket commission from travel agency.
Natural and artificial scents do not increase egg rejection rates of model brood parasitic eggs by American robins (Turdus migratorius)
Authors: Hauber Mark Erno
Published: November 2020

Hosts of obligate avian brood parasites can diminish or eliminate the costs of parasitism by rejecting foreign eggs from the nests. A vast literature demonstrates that visual and/or tactile cues can be used to recognize and reject natural or model eggs from the nests of diverse host species. However, data on olfaction-based potential egg recognition cues are both sparse and equivocal: experimentally-applied, naturally-relevant (heterospecific, including parasitic) scents do not appear to increase egg rejection rates in two host species, whereas unnatural scents (human and tobacco scents) do so in one host species. Here I assessed the predictions that (i) human handling of mimetically-painted model eggs would increase rejection rates, and (ii) applying unnatural or natural scents to mimetically or non-mimetically painted model eggs alters these eggs’ respective rejection rates relative to controls. I studied wild American Robins (Turdus migratorius), a robust rejecter species of the eggs of obligate brood parasitic Brown-headed Cowbirds (Molothrus ater). There was no statistical evidence to support either prediction, whereas poorer color-mimicry was still a predicted cause of greater egg rejection in this data set. Nonetheless, future studies could focus on this and other host species and using these and different methods to apply and maintain the scenting of model eggs to more directly test hosts’ use of potential olfactory cues in the foreign-egg rejection process.
Является ли Интернет сберегающим здоровье фактором в России?
Authors: Калабихина Ирина Евгеньевна , Колотуша Антон Васильевич
Published: November 2020

В связи с растущей популярностью сети Интернет в России представляется важным выяснить, как частота его использования сказывается на состоянии здоровья людей и самосохранительном поведении. В настоящей работе мы тестируем оптимистичные гипотезы, согласно которым, при прочих равных условиях, относительно частое использование Интернета соответствует лучшему состоянию здоровья и меньшему потреблению алкогольной и табачной продукции. Опираясь на данные последних трех волн (2014, 2016, 2018 г.) Комплексного обследования условий жизни населения (КОУЖ), мы строим модели бинарного пробита с использованием инструментальных переменных для определения влияния Интернета на здоровье и тобит-модели в первых разностях для оценки его влияния на объёмы потребления алкогольной и табачной продукции. Первая группа моделей демонстрирует значимое положительное влияние Интернета на состояние здоровья для обоих полов. В остальных моделях гипотезы анализа подтверждаются частично: с повышением частоты пользования Интернетом мужчины меньше курят и пьют, больше предпочитают слабоалкогольные напитки, но на женской выборке результат не подтверждает гипотезу позитивного влияния Интернета на снижение потребления табака и алкоголя. Мы полагаем, что объяснение такого результата лежит в области качества данных, а также стадии эмансипации женщин в России. Кроме того, Интернет не является для женщин заменителем «водочного» досуга в отличие от мужчин.

Исходя из вышеизложенного, мы можем сформулировать общий вывод, что для сохранения и укрепления здоровья жителей России следует расширять возможности использования Интернета.
Changing Home: Experiences of the Indigenous when Receiving Care in Hospital
Authors: Rojas Juan Guillermo , Herrero Hahn Raquel
Published: November 2020

Objective. To understand the meaning of the experience of the indigenous when receiving care in a low-complexity hospital.

Methods. Qualitative study with ethnographic approach conducted in a hospital of Antioquia, Colombia. The study had 12 indigenous participants who underwent semi-structured interviews. Observation was carried out in hospitalization wards, emergency, and outpatient services of the institution during 40 hours. The analysis process was performed descriptively. The methodological rigor was maintained by applying criteria of confirmability, credibility, transferability, and consistency. The study was approved by the Ethics Committee and authorized by the indigenous authorities to enter the field.

Results. Five themes emerged: the context of caring for the indigenous, the need to consult the hospital, changes experienced by the indigenous in the hospital, experiences in relation with treatments, and relations established within the hospital. The meaning is constructed from a dichotomous perspective based on the favorable or unfavorable aspects of the situations and experiences, which for the indigenous is like “changing home”.

Conclusion. The meaning of the experience of receiving care in hospital for the indigenous is constructed from the context in which they live and receive health services, the changes they live in the dimension of space by virtue of their traveling from their vital space to another space that, due to their physical characteristics, results strange and different, even not healing. Upon the difficulties, the indigenous develop strategies and actions to overcome limitations, whether through adaptation and learning.
Presence of the Reflective and Critical Thinking Capacity in Nursing Curricula in Iberian America
Authors: Cárdenas Becerril Lucila , Jiménez-Gómez María Antonia , Bardallo-Porras María Dolores , López-Ortega Jesús , Monroy-Rojas Araceli , Araújo-Püschel Vilanice Alves de
Published: November 2020

Objective. The objective was to identify the presence of the capacity for reflexive-critical thinking or similar, in Nursing Curricula in Iberian America.

Methods. The article gathers the results of one of the objectives of the macro-project developed by the Iberian American Network on Nursing Education Research, titled Strategies to develop reflective and critical thinking in nursing students: Iberian America situation. To achieve this, a descriptive and exploratory research was conducted with qualitative approach. An instrument created for this project was used, along with some guiding questions to focus the information.

Results. Eight countries participated (Bolivia, Brazil, Colombia, Ecuador, Spain, Mexico, Peru, and Venezuela), which contributed information from 189 curricular plans. The R&CT was found in the majority of the curricula, although with diverse denominations. The principal learning strategies used were problem-based learning, group dynamics, reflective reading, clinical practice, and simulation laboratories. The evaluation methods used are the knowledge test, case analysis, and practical exam.

Conclusion. Significant stress exists in the discourse and curricular organization. Incongruences were found and a clear inclination toward the formation of professionals with broad technical skills under a traditional, memory, banking and knowledge accumulation education.
Comprensión de textos escritos: reconceptualizaciones en torno a las demandas del siglo XXI
Authors: Parodi Sweis Giovanni , Moreno-de-León Tomás , Julio Cristobal
Published: November 2020

El vertiginoso avance de los desarrollos tecnológicos a inicios del siglo XXI ha impuesto desafíos inmensos para los investigadores de la comprensión de textos escritos desde un enfoque de alfabetizaciones múltiples, tanto académicas como profesionales. Ahora se hace apremiante examinar las exigencias que implica la comprensión lectora no solo en los formatos en papel, sino también en diversos soportes electrónicos y con propósitos de lectura diversos. Asimismo, es perentorio analizar la comprensión de múltiples textos y géneros eventualmente heterogéneos y multimodales. En la actualidad, debido al acceso inmediato y a la disponibilidad en línea de una creciente cantidad de información, tanto general como especializada, la comprensión de estos textos impone demandas incrementales para el sistema cognitivo humano. Este artículo busca abordar dicha complejidad, atendiendo, en un primer momento, a la conceptualización del macroproceso de la comprensión, con foco en un único texto eminentemente verbal, hasta considerar el procesamiento de múltiples textos multimodales y multimediales, los géneros del discurso académico y profesional, y los textos que caracterizan el siglo XXI, incluyendo los desafíos que este trae para los lectores en la actualidad y en el futuro.
Solvent Contamination Determined by UV Reflection
Authors: Murphy Edward
Published: November 2020

Commercial organic cleaning solvents, unless specially prepared, may increase contamination of an item rather than clean it. A simple test to determine the presence or absence of a contaminant in a solvent can be performed by using ultraviolet-reflection spectroscopy. The procedure consists of immersing a quartz-paper coupon in a small quantity of the solvent to be tested, then evaporating the solution to dryness in a vent hood at room temperature. Prior to immersion, clean quartz paper typically reflects 70 to 90% of the ultraviolet in a range from 200 to 360 nm. If the filaments of the quartz-paper coupon have had any contaminant from the solvent deposited on their surfaces, the multi reflections produce an extensive ultraviolet absorption.
Scientists Debate Nuclear Source Terms
Authors: Graham John
Published: November 2020

The nuclear source term, defined as the quantity, timing, and characteristic of the release of radioactive material to the environment following a core-melt accident, was thoroughly debated in 1985. This debate, summarized here, turns on the Nuclear Regulatory Commission's (NRC) source term for radioactive iodine, which is postulated as potentially the most life-threatening radionuclide that might escape in a nuclear power-plant accident. A generic radioiodine source term has been used by NRC as the surrogate for all others; thus, it has become one of the bases on which nuclear-safety regulations are founded. Following the Three Mile Island (TMI) accident, from which only traces of radioiodine escaped, scientists began arguing that nuclear regulations based on source-term calculations are erroneous and should be modified. The American Nuclear Society (ANS) and industry researchers have concluded that warranted reductions in the NRC source terms could range from a factor of ten to several factors of ten in most accident scenarios. The American Physical Society (APS), after agreeing with a large body of the conclusions from the other research groups, has told NRC that its source-term data base is still inadequate because of the existence of a number of uncertainties it found therein. Although APS presented no such conclusion, its findings made clear to NRC that an early reduction of all source terms is not warranted. The anti-nuclear lobby agrees with APS. The NRC has taken a cautious, conservative approach to the revision of its regulations based on new source-term data, although it too concedes that its old methodologies and conclusions must be revised and ultimately superceded.
Surface Contamination Measurement and Control by Nondestructive Techniques
Authors: Arora Arvind
Published: November 2020

This paper presents a new technique to measure thin layer contamination on the surface of a material. The technique uses low wavelength ultraviolet irradiation to generate optically stimulated electron emission, also known as photo electron emission, which can be used to evaluate surface cleanliness or surface chemical state. Limited data is presented to show application of this technique to wafer processing, disk lubricant thickness measurement and quality control of printed circuit boards.
Operational and Technical Results from the Spent Fuel Test-Climax
Authors: Patrick Wesley
Published: November 2020

The technical feasibility of short-term storage and retrieval of spent nuclear fuel assemblies has recently been demonstrated in a test of deep geologic storage at the U.S. Department of Energy Nevada Test Site (NTS). Handling systems and procedures developed and deployed on this test functioned safely and reliably to emplace eleven intact spent-fuel assemblies and retrieve them three years later. Three exchanges of spent fuel were conducted at regular intervals during the storage period to maintain the proficiency of personnel and the readiness of the handling system.

Technical data was collected using nearly 1,000 instruments. These data show that the mechanical and thermal properties of granites are compatible with nuclear waste isolation objectives. Measured and calculated temperatures are in excellent agreement, confirming the adequacy of available heat transfer codes. Radiation transport calculations were of high quality, exceeding the accuracy of available long-term dosimetry techniques which were used on the test. We also found good agreement between measured and calculated displacements within the rock mass.
Control of Microorganisms of Public Health Concern in Water
Authors: Geldreich Edwin
Published: November 2020

The concept of microbial barriers in water supply and wastewater treatment involves a variety of processes other than disinfection. Many of these treatment processes have evolved from the enhancement of some factors associated with natural self-purification (sedimentation, aeration, nutrient limitations, water pH, etc.). Utilizing the multiple barrier concept in treatment of wastes before discharge to receiving waters and the further refinement possible by natural self-purification processes in the stream are beneficial in optimizing the quality of this raw water resource prior to further processing into drinking water supplies. A flow diagram based on typical percent removals in various treatment processes illustrates how water contaminated with fecal wastes can be improved in quality to protect downstream users from microbial hazards.
Pre-Earthquake Planning for Post-Earthquake Rebuilding (PEPPER)
Authors: Spangle William
Published: November 2020

This paper describes results of research in process on the feasibility of Pre-Earthquake Planning for Post-Earthquake Rebuilding (PEPPER).
Environmental Stress Screening—Some Misconceptions
Authors: Pennington Duane
Published: November 2020

Recent shipbuilding contracts and requests for proposals have specified Environmental Stress Screening (ESS) for electronics equipment. As with any new requirement, misconceptions have hindered the implementation of a viable ESS program within the shipbuilding industry. This paper addresses several of these misconceptions to provide an understanding of the objectives and advantages of a cost-effective ESS program applied to the shipbuilding industry.
The Importance of Media Refractive Index in Evaluating Liquid and Surface Microcontamination Measurements
Authors: Knollenberg Robert
Published: November 2020

This work describes the results of theoretical and laboratory studies of the effects of media refractive index on the amount of light scattered by particles. The media examined include liquids and surfaces. Exact solutions are given for a number of microcontaminant/liquid binaries. Approximate solutions are given for scattering by surfaceborne contaminants. The results of this study suggest methods of limiting errors associated with both liquidborne and surfaceborne microcontaminants.
Tailoring in the Context of Acquisition Streamlining
Authors: Greene Kurt
Published: November 2020

The presentation defines the objectives and discusses the major policy issues and concepts imbedded in the acquisition streamlining initiative (DoD Directive 5000.43). The inherent attributes of specifications and standards is explored, together with effective ways to utilize these documents to achieve the full potential benefits of acquisition streamlining.
Proposed Application of Automated Biomonitoring for Rapid Detection of Toxic Substances in Water Supplies for Permanent Space Stations
Authors: Morgan Eric , Young Richard , Smith Michael , Eagleson Kenneth
Published: November 2020

The objective of this study was to present proposed design characteristics and applications of automated biomonitoring devices for real-time toxicity detection in drinking water supplies on-board permanent space stations. Tests in transmissions of automated biomonitoring data to earth-receiving stations were simulated using satellite data linkage from remote earth-based stations.

Automated biomonitoring can provide real-time physiological response information resulting from cause/effect relationships between toxicants and selected aquatic animals. Because the reliability of information from a single-species or from specific physical/chemical water quality parameters may not provide comprehensive protection from a wide variety of potentially toxic compounds, a computer-assisted multiple species biosensing system designed for water quality monitoring was developed. Emphasis was placed on developing methods for detecting species-specific bioelectric potentials produced by unrestrained bivalve mussels and other sedentary invertebrates since these animals are presumably more easily maintained in near zero gravity than fish. In achieving this objective, differential amplifiers were constructed for measuring a wide range of response signals induced by various biological activities from fish and invertebrate subjects. Specific responses were detected as discrete analog signals, each converted to a digital voltage, and filed in computer storage. A management program provided various means for data gathering, filing, and retrieval.
A Method of Structural Analysis for Small Items in a Random Vibration Environment, Part II
Authors: Allen Hilary
Published: November 2020

To perform engineering analyses in the most cost-effective manner, engineers must eliminate non-critical design items from a detailed analysis program and concentrate on the marginal and critical design items. This paper shows an approach to accomplishing this objective through the use of a rapid single-degree-of-freedom analysis. Part I develops equations for determining dynamic stresses on structural items modeled as simple beams and presents a non-dimensional method for determining the equivalent spring rate of a variable-stiffness beam. Part II presents a step-by-step example that provides the deflection, equivalent stiffness, frequency and dynamic stress on two different beam configurations with their predicted times-to-failure. In addition, the deflection and frequency results from a finite-elementmodel analysis of two tapered brackets are compared with the results from the non-dimensional variable-stiffness beam method developed previously.
Development of a New Continuous Monitor for Nonvolatile Solute in Ultrapure Water by Atomization
Authors: Kousaka Y. , Niida T. , Tanaka Y. , Sato Y. , Kano H. , Fukushima N. , Sato H.
Published: November 2020

A new monitoring system has been developed for continuously measuring the concentration of total nonvolatile impurities in ultrapure water. The measuring method is based on the principle of determining the Residue After Evaporation (RAE) of atomized droplets, taking account of the particle deposition loss. The system consists of a water atomizing unit, a droplet evaporating and drying unit, an air diluter, a fine particle counter, etc. For the particle counter, a Condensation Nucleus Counter (CMC) is used; this counter is a mixing type, able to detect particles larger than 0.01 μm. It is verified from both the theoretical analysis and the experimental results that this monitor can rapidly detect very low impurity concentrations by counting the number concentration of aerosol particles.
A New Method for Measuring Nonvolatile Residue for Ultrapure Solvents
Authors: Blackford David , Belling Katherine , Sem Gilmore
Published: November 2020

A quantitative method is described for measuring the nonvolatile residue of ultrapure solvents. Results are presented that show reasonable agreement with an alternative gravimetric method.

A qualitative method for measuring nonvolatile residue is also described. This method has the potential to monitor the residue contamination level in large-volume, deionized water production facilities.
Naval Weapons Center's Live-Ordnance Environmental, Safety and Nondestructive Test and Evaluation Facilities
Authors: Parmenter W.
Published: November 2020

The live-ordnance environmental, safety and nondestructive test and evaluation facilities at the Naval Weapons Center are described. These facilities are unique for performing tests on all-up weapons containing explosive materiel during development programs.
Optimized Environmental Stress Screening of U.S. Army Electronic Hardware
Authors: Huizinga Marvin
Published: November 2020

Systems analysis techniques employed by the U.S. Army provide engineering guidelines to optimized Environmental Stress Screening (ESS) considering inhouse manufacturing and field costs. Optimized ESS offers an improved quality product with significant cost savings. This article covers the systems analysis techniques and the results achieved. The development of a computer program to enable engineers (menu-driven user-friendly) to review and input inplant variables, plant capacity, test effectiveness, test integration yields, and field failure costs has enabled quality engineers to recommend optimized ESS screens. The results of these studies have identified the potential of $1.1 billion in life-cycle costs savings.
Computer Simulation of Airflow and Particle Transport in Cleanrooms
Authors: Kuehn Thomas
Published: November 2020

Numerical procedures are well developed for simulating simple fluid flows and associated heat and mass transfer processes. Steady isothermal airflow in either a vertical laminar flow cleanroom or a tunnel cleanroom can be predicted accurately by using currently available simulation codes. The effects of items such as shields, process equipment, robot components, and bench design on the cleanroom airflow can be investigated by performing simulation experiments on a computer rather than physical experiments on a mockup. Design and operating parameters can be readily varied in the simulation to demonstrate their influence on the cleanroom performance. A review of existing airflow and particle transport simulation methods is presented and some recent applications to cleanroom airflow prediction are described. Advantages of computer simulation over experimental measurements and limitations are discussed, and future directions of cleanroom modeling are presented.
Particle Deposition Onto a Flat Surface from a Point Particle Source
Authors: Stratmann Frank , Fissan Heinz , Peterson Thomas
Published: November 2020

A series of two-dimensional calculations are performed to determine particle fluxes to wafers in a stagnation flow configuration. Mechanisms that influenced particle deposition included convection, diffusion, sedimentation, and thermophoresis. Particle deposition patterns resulting from a uniform freestream concentration are compared with deposition patterns from a narrow particle beam.
Deposition of Submicron Aerosol Particles During Integrated Circuit Manufacturing: Experiments
Authors: Wu Jin , Miller Robert , Cooper Douglas , Flynn James , Delson Douglas , Teagle Robert
Published: November 2020

Measurements of airborne concentrations and surface concentrations of submicron particles were made in two different semiconductor manufacturing cleanrooms. These measurements, made with an optical particle counter, a condensation nucleus counter, and a surface contamination optical monitor were used to determine the particle fluxes and the particle deposition velocities. The measurement data were compared with theoretical predictions of deposition due to gravity, diffusion, and electrostatic effects.
Availability Analyses of HVAC Systems In Cleanrooms and Other Critical Applications
Authors: Reed Thomas , Brader William
Published: November 2020

The operational and functional criteria of heating, ventilation, and air conditioning (HVAC) systems and associated control systems for cleanrooms and other similar critical applications impose very demanding requirements on both the installed systems and the system designers. Designers and facility operators often compromise original reliability criteria due to rule-of-thumb decision making processes. These processes do not usually include a truly determinant method of evaluating, in a quantitative manner, the advantages and disadvantages of alternative HVAC and control systems with respect to redundancy, reliability, and availability. A methodology as proposed here should help to enhance the decision making processes associated with defining availability criteria and predicting the effects of alternative HVAC and control systems on critical facility operations.
ESS Quantification for Complex Systems
Authors: Perlstein Howard , Littlefield John , Bazovsky Igor
Published: November 2020

Quantification of screen duration permits controlled purification of systems by the elimination of early failures to a predetermined degree of purity, consistent with reliability requirements at time of delivery for field use, or consistent with budgetary cost constraints, or both.

In an earlier paper the authors developed a method for quantifying screen duration of Environmental Stress Screening (ESS) of homogeneous parts or component populations.1 This is briefly summarized under "Case of a Parts Population" and extended under "Mixed Parts Systems," to systems consisting of a mix of many different parts with different failure rates.

In the case of parts, each failure constitutes the end of life of that part, while in the case of systems, a failure usually results in repair or "renewal" and the system continues operation (except for one-time systems). For parts, time-to-failure is observed, while for systems, times-between-failures is observed.

The section titled "A Numerical Example" contains an example of calculating screen duration (Ts) for different predetermined degrees of purity, characterized by the screen residues that constitute the complements of purity. The Appendix describes the computer program used for the numerical solutions.
Virtual Impactor Aerosol Concentrator for Cleanroom Monitoring
Authors: Wu Jin , Cooper Douglas , Miller Robert
Published: November 2020

Particles equal to or larger than 1 μm in size can significantly reduce the yield in the microelectronics industry. This is particularly evident in the packaging stage of manufacturing when chips are inter-connected, because of the relatively large areas that must be kept contamination-free during this process. Monitoring is usually done with optical particle counters. The low particle concentrations in clean-rooms, however, result in low counts and high variability. This article presents a monitoring system that uses a virtual impactor to concentrate particles between 0.65 to 2.5 μm dia and counts them with a 0.3 L/min (lpm) particle counter. Theoretical concentration enhancement ratios versus particle size are given. The use of the virtual impactor in a clean environment is demonstrated. Tests show that the transition between the concentrated sizes is sharp. The dependence of the ratios versus particle size is in qualitative agreement with theory. An aerosol concentrator could be used to give more accurate micron-size particle concentrations through a data inversion process, if experimental calibration curves are provided.
Principal Component Analysis for Particulate Source Resolution in Cleanrooms
Authors: Tian Yi , Biswas Pratim , Pratsinis Sotiris , Hsieh Walter
Published: November 2020

Principal component analysis (PCA) is applied to particulate size distributions measured at receptor sites in two cleanrooms. The principal components are determined by evaluating the rotated component patterns. Each component is then assigned to a source by comparing the principal components to the particle size distributions emitted by the sources. Hence, sources of particulate contamination in the cleanrooms are determined. Particle volume concentration balances are used to quantitatively apportion the contaminant levels at the receptor sites to each source. PCA can thus be used to identify contaminant particle sources and to develop strategies for improvement of the cleanroom cleanliness class.
LIGO Vacuum System Study
Authors: Livas Jeffrey , Moore Boude
Published: November 2020

A laser interferometer gravitational wave observatory (LIGO) is being developed with sensitivities that will have a high probability of detecting gravitational waves from astrophysical sources. Detectors are also planned by others in Europe and eventually in space. A major component of the proposed LIGO is a total of 16 km (10 miles) of 1.2 m (48 in.) dia tube at a pressure of less than 10-8torn It will be of 304 L stainless steel procured directly from the steel mills with the initial hydrogen content specially reduced. (Target is 1 ppm by weight.) Projections of the outgassing rates of hydrogen and of water vapor as a function of time will be given and the uncertainties discussed. Based on these, a preliminary analysis of the vacuum system will be presented.
Surface Properties and Cleanability: A Rational Correlation
Authors: Nagarajan Ramamurthy
Published: November 2020

Failures in disk drives are frequently induced by particulate contamination present in the head/disk assembly (HDA). The sources and characteristics of debris vary with component material within the HDA. The inherently contaminating nature of manufacturing component parts requires that those parts be carefully cleaned and that their cleanliness be evaluated against a specified standard. Ultrasonic cleaning of substrate surfaces, and turbidity/liquid-particle-count (LPC) measurement of extracted-contaminant concentration and size distribution are popular techniques in this regard.

Two factors can be used to determine the suitability of ultrasonic surface cleaning. The first is defined here as the maximum cleaning potential, that is, how clean the surface can get when subjected to a multistage-extraction process. And the second concerns the first-stage cleanability of the surface, that is, what fraction of the total cleaning action occurs in the first ultrasonic stage. These two fundamental cleaning parameters described here are closely linked to the nature of adhesive interaction between the contaminant particle, the substrate surface, and any intervening liquid. A predictive procedure to rank various materials with respect to their maximum cleaning potential and their first-stage cleanability is presented. Turbidity/LPC data, obtained at IBM San Jose laboratories for several metallic and polymeric parts, are used to develop useful correlations in terms of relevant physical properties of these surfaces. The implications of this predictive model for future design and optimization of ultrasonic cleaning/monitoring processes are also discussed.
Influence of Temperature on the Fatigue of CC/PWB Joints
Authors: Solomon Harvey
Published: November 2020

This is a study of the low cycle fatigue of chip carrier/ printed wiring board joints tested at -55° C (-67° F) and 125° C (257° F). It is contrasted to a previous study where the joints were tested at 35° C (95° F). The behavior at 35° C and 125° C was the same. Differences were noted, however, at -55° C. The hysteresis loops were distorted. The slopes of the displacement vs. fatigue life curves were slightly lower and the fatigue lives were longer. These differences were especially significant when the change in joint resistance was used to define failure.
Use and Application of MIL-HDBK- 217
Authors: Morris Seymour
Published: November 2020

This paper addresses misconceptions and frequently asked questions about the proper use and application of MIL-HDBK-217, "Reliability Prediction of Electronic Equipment." Included in this paper are discussions of the purpose of the handbook, supporting data base, failure rate models, reliability predictions, and handbook limitations, along with supporting references. Current status and future plans are also highlighted.
Contamination Control Program for the Cosmic Background Explorer: An Overview
Authors: Barney Richard
Published: November 2020

Each of the three state-of-the-art instruments flown aboard NASA's Cosmic Background Explorer (COBE)2 were designed, fabricated, and integrated using unique contamination control procedures to ensure accurate characterization of the diffuse radiation in the universe. The most stringent surface level cleanliness specifications ever attempted by NASA were required by the diffuse infrared background experiment (DIRBE) which is located inside a liquid helium cooled dewar along with the far infrared absolute spectrophotometer (FIRAS). The DIRBE instrument required complex stray radiation suppression that defined a cold primary optical baffle system surface cleanliness level of 100A.1.3 The cleanliness levels of the cryogenic instrument and the differential microwave radiometers (DMR) which were positioned symmetrically around the dewar were less stringent, ranging from level 300A to 500A. To achieve these instrument cleanliness levels, the entire flight spacecraft was maintained at level 500A throughout each phase of development. This paper describes the COBE contamination control program and the difficulties experienced in maintaining the cleanliness quality of personnel and flight hardware throughout instrument assembly, spacecraft integration, flight environmental qualification, and launch-site operations.
Global Impact of the CFC Phaseout
Authors: Andersen Stephen
Published: November 2020

The amendments to the Montreal Protocol and the 1990 Clean Air Act call for the accelerated reduction of fully halogenated CFCs and halons. Recent scientific data indicate that these chemicals are more damaging to the earth's ozone layer than previously thought. This ozone depletion has serious consequences for the environment and human health. These chemical compounds are scheduled for phaseout under the Montreal Protocol and Clean Air Act. Because CFC-13 and methyl chloroform are used extensively in the electronics industry worldwide, the industry and the U.S. EPA have formed a partnership to develop technically feasible, cost-effective, and environmentally sound alternatives for ozone-depleting substances.
Combined Environments Facility for Externally Carried Aircraft Stores
Authors: Rice James
Published: November 2020

Raytheon Company, Electromagnetic Systems Division (ESD), Goleta, California, has recently completed a facility that simulates the environments measured on the AN/ALQ-184 EW Jammer Pod during a series of flight tests.

The laboratory uses high-intensity acoustic excitation to duplicate the effects of turbulent aerodynamic flow, vibration exciters to drive the lower frequency air frame structural motions, temperature-conditioned air across the store to simulate the effects of frictional skin heating or frigid conditions, and temperature-conditioned coldplate fluid to create the correct thermal effect on the high voltage section of the pod (see Figure 1).

This approach to testing externally carried stores builds on the work that has been done by the Navy at the Pacific Missile Test Center (PMTC), Point Mugu, California. The primary differences are in the use of two distinct thermal profiles applied simultaneously to different portions of the test item, and the use of multiple accelerometers in the control of the vibroacoustic environment.

Special considerations had to be taken into account in the design of the test facility. Overall sound pressure levels of 155 dB were required to achieve the desired pod response. Space restrictions caused the facility to be placed within 21.3 m (70 ft) of the property boundary in an area zoned as a research park. Water restrictions in Santa Barbara County prevented the use of a water cooling system for equipment typically cooled by liquid. Both problems were addressed and successfully overcome. The completed lab is now being used for reliability growth testing and for lot sampling of the production pods.
CFC Alternative Cleaning Systems: Alternative Processing Techniques and Their Effectiveness in Precision Cleaning
Authors: Marts Ken , Howard John
Published: November 2020

A multidisciplined product team comprised of Engineering, Operations, Safety, and Environmental Management assessed the feasibility of various cleaning materials and processing equipment for precision cleaning. Precleaning using an aqueous-based cleaner followed by isopropyl alcohol spray final clean were the materials and methods selected to replace 1,1,1-trichloroethane proclean (vapor degrease) and CFC-113 final clean.
Cost-Effectiveness of Environmental Stress Screening (ESS): A Case History
Authors: Nagle Amber
Published: November 2020

AFLC Regulation 74-25 requires that all newly manufactured electronic hardware be exposed to an environmental stress screening (ESS) program. ESS is often viewed as "just another reliability program." However, the return on investment (ROI) and increased reliability that resulted from screening 20 circuit cards emphasized the need for ESS in Air Force applications at Warner Robins Air Logistics Center.
PWB Solder Joint Life Calculations Under Thermal and Vibrational Loading
Authors: Barker Donald , Dasgupta Abhijit , Peeht Michael
Published: November 2020

The goal of automating PWB solder joint fatigue life calculations into a design environment is to make reliability assessment information available to the designer as early as possible and in an easily understood and implemented manner. This paper discusses the assumptions and details of the fatigue life calculations under a combined thermal and vibrational load. A methodology is presented to evaluate the combined effects of simultaneous vibration and thermal cycling of solder joints. This combined loading situation is simulated by superposing the effects of the vibrational and thermal loads. The damage due to each load-type acting individually is determined and then superposed to assess the overall effective fatigue life of the joint. As a first order approximation. Palmgren-Miner's linear superposition rule is utilized.