Density Of Use Research Articles

ВІДНОВЛЕННЯ ШТОКІВ СИЛОВИХ ГІДРОЦИЛІНДРІВ АВТОМОБІЛІВ ЛЕКТРОЛІТИЧНИМ ХРОМУВАННЯМ

The quality of the repair of parts of military equipment and the increase of their service life largely depends on how it is organized and in what ways the restoration of malfunctioning or damaged parts is carried out. To restore the full functionality of the damaged parts, it is necessary to return them to their initial dimensions, geometric shape, hardness, corrosion resistance and other properties. One of the progressive methods of restoring the working rods of hydraulic cylinders is the application of electrolytic coatings on their working surface. The purpose of the study is to improve the method of restoration of hydraulic cylinder rods by electrolytic chroming with the aim of intensifying the process, improving operational properties and obtaining electrolytic chromium deposits of uniform thickness on the restored rods. The scientific and practical direction of the work consists in the fact that for the first time the technology of process intensification, improvement of the quality of coatings and obtaining of electrolytic chromium deposits uniform in length with the use of an ejector anode design has been considered. The research methodology is to identify the influence of the chrome plating process parameters on the uniformity, microhardness and microcracking of chrome coatings made of universal (250 г/л – СrO3; 2,5 г/л – H2SO4) та кріолітового (10 г/л – Na3AlF6; 250 г/л – СrO3; 2,5 г/л – H2SO4) of electrolytes by the ejector method. The results of the study are the establishment of the dependence of uniformity, microhardness and microcracking on the parameters of the ejector chromium plating process in standard and cryolite electrolytes and the determination of the optimal temperature and current density for use in restoring the rods of hydraulic cylinders of military equipment. The value of the conducted research is that for the first time an ejector anode is used as a positive electrode, which ensures obtaining high-quality and uniform electrolytic coatings directly in the chrome plating bath. Anode-ejector provides height-adjustable suspension suction of gaseous products of electrolysis and renewal of electrolyte in the interelectrode space due to the ejector effect in the anode tubes when the electrolyte is passed under pressure in the jet tubes. Keywords: stom density, anode-cathode distance, uniformity, cracking, microhardness, electrolyte temperature, anode-ejector.

The use of the Roben Jig for preparation of clean coal samples of Western Canadian coals via density separation

ABSTRACT This study compared a water-based and a solvent-based method for removing ash (washing) from coal: jigging coal in water using the Roben Jig and the float/sink method using conventional organic liquids (naphtha, perchloroethylene, methylene bromide), respectively. Clean coal curves from the two processes were compared for six coal types from British Columbia, Canada. The clean coal curve for the Roben Jig deviated from that of the organic liquids when the near-density material content was high. Also, particles were misplaced within the jigging column; however, a simple “rejig” process was capable of further cleaning the coal. The Roben Jig was used to create a clean coal sample of at least 400 kg by washing coal in batches. The clean coal curves for the jig were similar. Minor differences could be attributed to the occurrence of misplaced particles. Although the Roben Jig does not provide perfect separation of coal based on density for use in wash plant design studies, previous work has established that it is capable of creating representative clean coal composites without the use of organic liquids.

Applying the Theory of Grammatical Metaphor to Two English Short Stories

This paper identifies and describes the textual densities of ideational metaphors through the application of GM theory (Halliday, 1994) to the textual analysis of two twentieth century English short stories: one American (The Mansion (1910-11), by Henry Jackson van Dyke Jr.), and one British (Home (1951), by William Somerset Maugham). One aim is to get at textually verifiable statistical evidence that attests to the observed dominance of GM nominalization in academic and scientific texts, rather than to fiction (e.g. Halliday and Martin (1993). Another aim is to explore any significant differentiation in GM’s us by the two short- story writers. The research has been carried out by identifying, describing, and statistically analysing the frequencies of ideational GM structures in both fiction texts to get at their comparative textual densities in terms of word-counts. The obtained results have shown that GM structures – though used in both the American and British short stories – are statistically quite infrequent in both texts, accounting for a tiny (0.0064%) of the total text-wording in T1. against (0.0137%) for T2. Such very low rates of frequency (well below the threshold of even 1% of each text volume) corroborates the previously observed dominance of GM nominalization in academic and scientific texts, rather than in fiction. These same low densities of use does not allow drawing significant inference differentials in GM’s use by the two writers.

Contributions of nearby agricultural insecticide applications to indoor residential exposures

BackgroundPesticide exposure has been associated with adverse health effects. We evaluated relationships between proximity to agricultural insecticide applications and insecticides in household dust, accounting for land use and wind direction. MethodsWe measured concentrations (ng/g) of nine insecticides in carpet-dust samples collected from 598 California homes. Using a geographic information system (GIS), we integrated the California Pesticide Use Reporting (CPUR) database to estimate agricultural use within residential buffers with radii of 0.5 to 4 km. We calculated the density of use (kg/km2) during 30-, 60-, 180-, and 365-day periods prior to dust collection and evaluated relationships between three density metrics (CPUR unit-based, agricultural land area adjusted, and average daily wind direction adjusted) and dust concentrations. We modeled natural-log transformed concentrations using Tobit regression for carbaryl, chlorpyrifos, cypermethrin, diazinon, and permethrin. Odds of detection were modeled with logistic regression for azinphos-methyl, cyfluthrin, malathion, and phosmet. We adjusted for season, year, occupation, and home/garden uses. ResultsChlorpyrifos use within 1–4 km was associated with 1 to 2-times higher dust concentrations in both the 60- and 365-day periods. Carbaryl applications within 2–4 km of homes 60-days prior to dust collection were associated with 3 to 7-times higher concentrations and the 4 km trend was strongest using the wind-adjusted metric (p-trend = 0.04). For diazinon, there were 2-times higher concentrations for the 60-day metrics in the 2 km buffer and for the CPUR and wind-adjusted metrics within 4 km. Cyfluthrin, phosmet, and azinphos-methyl applications within 4 km in the prior 365-days were associated with 2-, 6-, and 3-fold higher odds of detection, respectively. ConclusionsAgricultural use of six of the nine insecticides within 4 km is an important determinant of indoor contamination. Our findings demonstrated that GIS-based metrics for quantifying potential exposure to fugitive emissions from agriculture should incorporate tailored distances and time periods and support wind-adjustment for some, but not all insecticides.

Low-Density Particleboards Modified with Expanded and Unexpanded Fillers-Characteristics and Properties.

Reducing the density of wood-based materials is a desirable research direction in the development of the wood-based materials sector. Even though lightweight wooden particleboards have been commercially available for many years, they still have a number of disadvantages, especially their low strength parameters. The aim of this paper was to determine the possibility of producing particleboards of reduced density for use in the furniture industry, as a result of using expanded polystyrene and two types of microspheres (expanded and unexpanded) to modify the core layer of three-layer particleboards. Analysis of the results of testing the particleboards’ properties when using various types of modifiers (expanded and unexpanded fillers), urea formaldehyde (UF) glue content (high: 10%/12% and low: 8%/10%), various glue-dosing methods, and different particle sizes, allows us to conclude that the most satisfactory effect was found when using EPS. One partly positive effect was observed when using the Expancel-type 031 DU 40 as a filler; therefore, it is recommended that research be continued in this area. Using microspheres that have not been used before as a filler in the production of wood-based panels is the novelty of the presented research. The proposed technology has potential for application in the industry.

Computing x-ray absorption spectra from linear-response particles atop optimized holes.

State specific orbital optimized density functional theory (OO-DFT) methods, such as restricted open-shell Kohn-Sham (ROKS), can attain semiquantitative accuracy for predicting x-ray absorption spectra of closed-shell molecules. OO-DFT methods, however, require that each state be individually optimized. In this Communication, we present an approach to generate an approximate core-excited state density for use with the ROKS energy ansatz, which is capable of giving reasonable accuracy without requiring state-specific optimization. This is achieved by fully optimizing the core-hole through the core-ionized state, followed by the use of electron-addition configuration interaction singles to obtain the particle level. This hybrid approach can be viewed as a DFT generalization of the static-exchange (STEX) method and can attain ∼0.6eV rms error for the K-edges of C-F through the use of local functionals, such as PBE and OLYP. This ROKS(STEX) approach can also be used to identify important transitions for full OO ROKS treatment and can thus help reduce the computational cost of obtaining OO-DFT quality spectra. ROKS(STEX), therefore, appears to be a useful technique for the efficient prediction of x-ray absorption spectra.

Utilizing social science data from river recreationists to inform river management

AbstractRiver recreation often contributes to ecological degradation – a primary concern for river management professionals. Using social science data to inform ecological management helps mitigate recreational impacts, particularly at sites that experience high recreation use. This paper demonstrates the utility of an approach to collect, display, and use social data based on an indicators and thresholds approach at Buffalo National River in Arkansas (BUFF). Specifically, we presented a series of digitally manipulated photographs to river recreationists at BUFF that depicted varying levels of use, or density of use, to identify social thresholds – the levels of use deemed unacceptable by river users. We coupled the photos with quantitative questionnaires and found that paddlers, anglers, and campers thought that moderate to high‐density levels were unacceptable. Pairing such data with empirical evidence of ecological degradation born from recreation use (e.g., erosion, water quality issues) provides a robust and defensible justification for a range of management actions, including altering use levels and river access. The research methods presented in this paper are transferable to a range of high‐use rivers and waterways, and thus provide a blueprint for river professionals who by design or default interface with recreation and ecological resources. In the end, combining social and ecological data can fortify management decisions and decrease associated conflicts among important groups of river recreationists.

Alcohol hydroxides regulate the growth of Ni-Co layered double hydroxides on carbon fiber cloth as supercapacitor electrode materials

There is a need to design and fabricate Ni-Co layered double hydroxides (Ni-Co LDHs) with high specific capacity, rate capability, and energy density for use as supercapacitor electrode materials. In this study, Ni-Co LDHs are directly grown on the flexible carbon fiber cloth (CFC) substrate by low-carbon alcohol/water solvothermal method. It is found that the morphology of Ni-Co LDHs changes from a wire-like structure to a lamellar structure because of the increased number of alcoholic hydroxyl groups, and the wire-like structure is more favorable for charge transfer and ion diffusion. The number of alcoholic hydroxyl groups has a greater impact on the morphological and electrochemical properties of Ni-Co LDHs compared with the n-propanol content. The Ni-Co LDH@CFC with well cycling stability can be obtained at a n-propanol/water volume ratio of 6:4 and a Ni/Co molar ratio of 1:1. The specific capacity reaches 1102 C g−1 at 2 A g−1 and 70% of the initial capacitance can be retained at 30 A g−1. A button-type asymmetric supercapacitor (ASC) Ni-Co LDH@CFC//AC with an energy density of 39 Wh kg−1 and a power density of 1450 W kg−1 has been successfully fabricated. This work may provide insights into the preparation of high-performance electrode materials with tunable architectures by regulating the number of alcoholic hydroxyl groups.

Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

Validation of a Microstructure-Based Model for Predicting the High Strain Rate Flow Properties of Various Forms of Additively Manufactured Ti6Al4V(ELI) Alloy

To increase the acceptance of direct metal laser sintered Ti6Al4V(Extra Low Interstitial—ELI) in industry, analytical models that can quantitatively describe the interrelationships between the microstructural features, field variables, such as temperature and strain rate, and the mechanical properties are necessary. In the present study, a physical model that articulates the critical microstructural features of grain sizes and dislocation densities for use in predicting the mechanical properties of additively manufactured Ti6Al4V(ELI) was developed. The flow stress curves of different microstructures of the alloy were used to obtain and refine the parameters of the physical model. The average grain size of a microstructure was shown to influence the athermal part of yield stress, while the initial dislocation density in a microstructure was seen to affect the shape of the flow stress curve. The viscous drag effect was also shown to play a critical role in explaining the upturn of flow stress at high strain rates. The microstructure-based constitutive model developed and validated in this article using experimental data showed good capacity to predict the high strain rate flow properties of additively manufactured Ti6Al4V(ELI) alloy.

Development of a 250 kW Electric Power Generation System for a More Electric Aircraft

This paper describes the design process of a 250 kW power generation system with high energy density for use in a more electric aircraft. This task is considered in terms of developing a starter-generator, a transformer-rectifier unit, as well as selecting voltage in order to minimize the cables mass passing on board the aircraft. The analysis of the efficiency of the structures of power generation systems on board the aircraft has been carried out. Their advantages and disadvantages are considered. With the help of analytical methods and computer modeling methods, three different topologies of starter-generators have been calculated, and the most suitable option in terms of weight and dimensions has been selected. In addition, a market analysis has been made and it has showed that there is a very limited amount of mass-produced transformer-rectifier units with the required voltage. Therefore, it has been decided to design a transformer-rectifier unit for this voltage class. In order to verify the calculations, experimental studies of the starter-generator, as the main element of the studied system in various operating modes, have been carried out. Experimental studies have been carried out in idle mode, under load at constant and variable speed, temperature measurements have been taken. The results of the experimental studies have confirmed the correctness of the calculation methods. The paper may be of interest to researchers and engineers involved in the creation of aviation power supply systems, aircraft electrical machines, and technologies for a more electric and fully electric aircraft.

Contributions of nearby agricultural insecticide applications to indoor residential exposures

BACKGROUND AND AIM: Pesticide exposure has been associated with adverse health effects; individuals may be exposed to pesticide drift from nearby agricultural fields. We evaluated relationships between agricultural insecticide applications and insecticide levels in carpet dust. METHODS: We measured concentrations (ng/g) of allethrin, azinphos-methyl, carbaryl, chlorpyrifos, cyfluthrin, cypermethrin, deltamethrin, diazinon, malathion, permethrin, phosmet, propoxur, tetramethrin in carpet-dust samples collected from 558 California homes. After using the California Pesticide Use Reporting database (reporting unit: ~2.59km2) to estimate agricultural insecticide use within buffers with radii of 0.5-, 1-, 2-, 3-, and 4km around each home, we calculated the density of use (kg/km2) during 30-, 60-, 180-, and 365-day periods prior to dust collection and evaluated relationships between insecticide density and concentrations in dust. We modeled natural-log transformed dust concentrations using Tobit regression for insecticides with 40% detection. For insecticides detected ≤40%, odds of detection were modeled with logistic regression. Models were adjusted for season, year, occupation, and home/garden uses. RESULTS:Detection frequencies ranged from 10% for allethrin, azinphos-methyl, and malathion to 80% for diazinon, chlorpyrifos, and permethrin. Chlorpyrifos applications within 1-4km of the residence during all time periods were associated with higher dust concentrations compared to homes without nearby applications. Carbaryl applications within 2-4km of homes 30- and 60-days prior to dust collection were associated with higher concentrations (30-days/2km, β any applications vs. none=8.2, 95%CI 1.8-37.6; 60-days/4km, β median density vs. none=4.2, 95%CI 1.1-15.7). Cyfluthrin and phosmet applications 180- and 365-days prior to dust collection were associated with higher odds of detection (365-days/4km, highest density vs. none: OR=2.2, 95%CI 1.2-4.0 and 6.2, 95%CI 3.3-12.0, respectively) compared to homes with no nearby use. CONCLUSIONS:Agricultural insecticide use within 4km of a home could be an important determinant of indoor contamination. Our findings provide valuable information for the development of exposure metrics for epidemiologic health studies. KEYWORDS: Pesticides, Exposures, Exposure assessment, Environmental epidemiology, Children's environmental health

Spatially-Explicit Prediction of Capacity Density Advances Geographic Characterization of Wind Power Technical Potential

Mounting interest in ambitious clean energy goals is exposing critical gaps in our understanding of onshore wind power potential. Conventional approaches to evaluating wind power technical potential at the national scale rely on coarse geographic representations of land area requirements for wind power. These methods overlook sizable spatial variation in real-world capacity densities (i.e., nameplate power capacity per unit area) and assume that potential installation densities are uniform across space. Here, we propose a data-driven approach to overcome persistent challenges in characterizing localized deployment potentials over broad extents. We use machine learning to develop predictive relationships between observed capacity densities and geospatial variables. The model is validated against a comprehensive data set of United States (U.S.) wind facilities and subjected to interrogation techniques to reveal that key explanatory features behind geographic variation of capacity density are related to wind resource as well as urban accessibility and forest cover. We demonstrate application of the model by producing a high-resolution (2 km × 2 km) national map of capacity density for use in technical potential assessments for the United States. Our findings illustrate that this methodology offers meaningful improvements in the characterization of spatial aspects of technical potential, which are increasingly critical to draw reliable and actionable planning and research insights from renewable energy scenarios.

Estimating trail use and visitor spatial distribution using mobile device data: An example from the nature reserve of orange county, California USA

Monitoring visitor use in parks and protected areas (PPAs) provides essential information for managers of PPAs to evaluate aspects of the visitor experience and balance the ecological disturbance that use creates. Traditional methods for quantifying visitation and spatial use of PPAs are resource intensive and thus are conducted infrequently or at cost-effective intervals which may fail to capture the dynamic nature of modern visitor use trends. This paper provides an addition to a growing literature using mobile-device data to quantify visitation and spatial density of use of urban-proximate PPAs in Orange County, California, USA using the analysis platform Streetlight, Inc. The results of our analysis compared favorably with well-established automatic trail counting and GPS-based monitoring methods, and illustrate several advantages of mobile device data to inform the management of PPAs. Mobile device data provide reliable estimates of visitation and spatial density of use and can augment and compliment existing social and resource monitoring for PPA management and planning.

Shared streets, park closures and environmental justice during a pandemic emergency in Denver, Colorado

IntroductionDuring the COVID-19 pandemic many municipalities closed or limited access to parks. A few also added new shared streets for citizens to recreate. This large and unprecedented change in the ability of residents to use green space provides an important case for assessing how emergency planning processes might differentially impact minority groups. MethodsUsing the case of park closures and shared streets expansion in Denver, Colorado in March and April of 2020, this analysis evaluates how walking time and density of use at parks changed for different minority and income groups based on estimating park visits for residential blocks. ResultsThe analysis demonstrates that minority and low income groups were not disproportionately impacted by initial closures. Shared streets provide net decreases across the city in terms of travel time and density for recreational space usage, though there is some indication benefits were not equally distributed. ConclusionThe result emphasizes the importance of modern planning efforts and community engagement in ensuring equitable urban resilience while highlighting the potential for shared streets to provide more recreational accessibility if they can be equitably located.

On the Importance of Li Metal Morphology on the Cycling of Lithium Metal Polymer Cells

Lithium metal anodes have recently earned greater attention in the context of the development of lithium batteries with high power and energy density for use in both the automotive industry and in portable electronic devices. Lithium metal is indeed an ideal anode for lithium batteries due to its high specific capacity (3860 mAh g−1). However, the growth of dendrites under high charge currents restricts the use of lithium anode in rechargeable batteries until solid electrolytes that can mechanically hamper dendrite growth can be developed. Efforts are currently dedicated to solving these problems by focusing on either improving the shear modulus of the electrolyte, or on the modification of the lithium-electrolyte interface. The electrochemical stability of novel solid electrolytes towards lithium is commonly determined by galvanostatic cycling of Li-Li symmetric cells. However, important characteristics of the lithium foil used in most studies are seldom provided, hence making comparisons between materials trivial. This paper demonstrates the importance of a thorough electrode characterization for the cycling of symmetric cells. In this study, two types of lithium foils are used with polyethylene oxide-based (PEO-based) electrolyte. A detailed characterization of the morphological and physico-chemical properties of the metallic electrodes is first performed by PeakForce Tunneling Atomic force microscopy (PeakForce-TUNA™), and X-ray photoelectron spectroscopy (XPS), followed by an evaluation of the interface with PEO-based electrolyte. It is demonstrated that lithium foil morphology is a key factor in the electrochemical performance of the cell and a novel electrochemical pre-treatment program is presented. This type of pre-treatment, still unreported in the existing literature, results in a longer life for lithium symmetrical cells.

Is it safer at the beach? Spatial and temporal analyses of beachgoer behaviors during the COVID-19 pandemic

Tourism localities worldwide continue to grapple with how best to sustain coastal visitation during the COVID-19 pandemic. Emerging epidemiological science illustrates the risk of disease transmission is lower outdoors than indoors, and exposure is likely lower in outdoor, coastal environments due to dispersion and dilution of respiratory droplets through regular air flow. That said, it remains unclear how beachgoer behavior affects the likelihood of disease transmission. During summer 2020, we analyzed publicly-available beachcam video data and collected unmanned aerial vehicle (UAV) imagery at the recreational beach oceanfront in Virginia Beach, U.S.A. Data were collected over 24 days, documenting tourists' and recreationists’ behaviors related to the public health guidance from the U.S. Centers for Disease Control, Commonwealth of Virginia Department of Public Health and City of Virginia Beach. Specifically, using a sample test area of beach and adjoining boardwalk, we investigated diurnal patterns of beach and boardwalk use, the location and density of use, as well as the presence of face coverings (i.e., masks) on boardwalk users. Results from beachcam analyses indicate a curvilinear trend in beach use, peaking in the mid-afternoon, while boardwalk use remained consistent throughout the day. Beachcam observations were corroborated by UAV photography and spatial analysis, indicating concentrated use of the beach adjoining shoreline above high tide, with onethird of the landward adjacent upper beach vacant. Among boardwalk pedestrians, few (8.7%) were observed wearing facial coverings. These findings point to both indirect and direct strategies coastal managers can implement to communicate when, where, and how to reduce the potential for transmission while accessing beach amenities during the COVID-19 pandemic.

Understanding the reaction mechanism and performances of 3d transition metal cathodes for all-solid-state fluoride ion batteries

Fluoride ion batteries (FIBs) are regarded as promising energy storage devices, and it is important and urgent to develop cathode materials with high energy densities for use in FIBs.

The use of engineering model‐building activities to elicit computational thinking: A design‐based research study

AbstractBackgroundComputation and computational thinking are of great interest to both engineering research and teaching communities. Effective learning environments are needed to incorporate computational thinking within the engineering disciplines. Design‐based research is uniquely positioned to address this need for designing effective learning environments.PurposeThis design‐based research study characterizes the different ways in which students used computational thinking when building computational models. The design of the model‐building activities was grounded in productive failure and model‐eliciting activities.DesignThe design‐based research study implemented the computational modeling activities within an engineering capstone course. The research question was: What types of computational thinking outcomes emerge when engineering students build computational models? Thematic analysis was applied to individual student artifacts to identify key computational thinking outcomes that were elicited as a result of the intervention.ResultsThroughout the building of the model, students demonstrated the use of computational thinking outcomes, mainly abstraction, algorithmic thinking, evaluation, generalization, and decomposition. However, the diversity and density of use for each outcome were different and unique.ConclusionsThis study shows how building computational models, when guided by current educational theories, can allow for students to practice the use of computational thinking and for educators to incorporate these key practices into their engineering classrooms.

Low background doping in AlInN grown on GaN via metalorganic vapor phase epitaxy

Nearly lattice-matched and unintentionally doped AlInN films with low background doping grown via metalorganic vapor phase epitaxy on GaN/sapphire are investigated. The lattice-matched condition is verified with x-ray diffraction (XRD), and the films exhibit typical morphological characteristics for AlInN. The optical constants (nr &k) and thicknesses of the AlInN films are determined via spectroscopic ellipsometry, finding an nr ~ 2.2 at 500 nm and a bandgap of ~4.366 eV. Temperature-dependent Hall measurements in the Van der Pauw configuration are performed for temperatures from 80 K up to 350 K, and a low background doping concentration (n ~ 3 × 1017 cm−3) and high electron mobility (μe ~ 320 cm2/V∙s) are found at room temperature. Simulations are performed to determine the influence of the 2-D electron gas (2DEG) caused by polarization fields from the GaN/AlInN interface and validate the Hall measurements. Thus, this work shows the potential of achieving high-quality AlInN films with low background doping densities for use in power electronic devices and deep-ultraviolet light-emitting diodes.