Usability of non-standard lower anchor configurations for child restraint system (CRS) installation

Abstract

Objectives: The objective of this study was to determine whether the amount of tension required for proper child restraint system (CRS) installation varies with lower anchor spacing and to determine whether nonexperts can produce adequate tension on wider-than-standard lower anchor configurations.

Methods: CRSs were installed by certified child passenger safety technicians (CPSTs; n?=?6 subjects, n?=?72 installations) and nonexperts (n?=?30 subjects, n?=?120 installations) on a mock-up vehicle seat fixture with lower anchors set at 11 (standard), 15, 19, and 23 in. apart from one another. Each CPST installed a rear-facing (RF) infant base, RF convertible, and forward-facing (FF) convertible into each of the 4 spacing configurations in random order. The CPSTs were instructed to tighten the lower connector strap until the tension was exactly at the threshold between passing and failing the 1-in. test. Each nonexpert installed one CRS model into all 4 spacing conditions in random order. Nonexperts were instructed to install the CRS to the best of their ability. The tension produced on the lower connector strap was recorded via load cell in the lower anchor assembly of the vehicle seat. Resultant tension magnitudes were compared across spacing conditions using matched pair t-tests. The CPSTs’ mean 1-in. test threshold values were compared to tensions produced by nonexperts. Installations were visually evaluated for errors and qualitative usability feedback was collected via survey.

Results: CPSTs installed the infant base with higher tensions in the 15-, 19-, and 23-in. configurations compared to the standard 11-in. configuration (P = .034, .032, and .003, respectively). The nonexperts installed the infant base with higher tension in the 15- and 23-in. configurations compared to the 11-in. configuration (P = .004 and .026, respectively). The RF convertible and FF convertible installations showed no significant differences in tension among any of the spacing configurations for either group. Only 19% of the nonexperts’ installations were tight enough to pass CPST thresholds, and the pass rate did not vary with respect to lower anchor spacing. In feedback surveys, the nonexpert group did not show a consistent preference for either standard or wider-than-standard lower anchor configurations.

Conclusions: The amount of tension required to pass the 1-in. rule did not vary with lower anchor spacing configurations for the RF and FF convertible CRS, but the infant base required more tension in wider anchor configurations. Nonexperts tended to produce less than ideal tension in all configurations, although their tension magnitudes increased for the infant base in wider configurations.     

Polynomial Surrogates for Open-Channel Flows in Random Steady State

Assessing epistemic uncertainties is considered as a milestone for improving numerical predictions of a dynamical system. In hydrodynamics, uncertainties in input parameters translate into uncertainties in simulated water levels through the shallow water equations. We investigate the ability of generalized polynomial chaos (gPC) surrogate to evaluate the probabilistic features of water level simulated by a 1-D hydraulic model (MASCARET) with the same accuracy as a classical Monte Carlo method but at a reduced computational cost. This study highlights that the water level probability density function and covariance matrix are better estimated with the polynomial surrogate model than with a Monte Carlo approach on the forward model given a limited budget of MASCARET evaluations. The gPC-surrogate performance is first assessed on an idealized channel with uniform geometry and then applied on the more realistic case of the Garonne River (France) for which a global sensitivity analysis using sparse least-angle regression was performed to reduce the size of the stochastic problem. For both cases, Galerkin projection approximation coupled to Gaussian quadrature that involves a limited number of forward model evaluations is compared with least-square regression for computing the coefficients when the surrogate is parameterized with respect to the local friction coefficient and the upstream discharge. The results showed that a gPC-surrogate with total polynomial degree equal to 6 requiring 49 forward model evaluations is sufficient to represent the water level distribution (in the sense of the \(\ell _2\) norm), the probability density function and the water level covariance matrix for further use in the framework of data assimilation. In locations where the flow dynamics is more complex due to bathymetry, a higher polynomial degree is needed to retrieve the water level distribution. The use of a surrogate is thus a promising strategy for uncertainty quantification studies in open-channel flows and should be extended to unsteady flows. It also paves the way toward cost-effective ensemble-based data assimilation for flood forecasting and water resource management.     

Singular Spectrum Analysis of Hydroecological Parameter Dynamics of Lake Naroch’ in the Years 1978–2015

Singular Spectrum Analysis (SSA) has been used to decompose continuous series of data on certain characteristics of Lake Naroch’ ecosystem during the vegetative seasons of years 1978–2015 into a long-time trend, a periodic component, and a residue not amenable to decomposition. The contribution of each component to changes in this variable has been assessed. The trends accounted for 78–97% of parameter variability, and the periodic components accounted for 2.5–15%. The fluctuations of phytoplankton and zooplankton biomass dynamics were the most diverse, and the contribution of these components was the greatest (15 and 8%, respectively). The periodic components in the changes of all parameters could be divided into four groups according to period duration (17–22, 7–15, 4–7, and less than 4 years). Multidimensional factor analysis of seven biotic parameters was performed in order to identify fluctuations in the ecosystem. Five major factors accounting for 93.6% of ecosystem changes together were identified, and each factor variable was subjected to SSA analysis. The period durations were similar for the oscillatory components identified. The first factor was interpreted as a trophic status of the water body, the second was taken to be the geographical location that defines the amount of solar radiation energy available, the third was taken to be the availability of biogenic elements (phosphorus in particular), and the fourth was interpreted as specific developmental cycles of live components of the ecosystem.     

Comparative Analysis of Variation in Ecological Forms of Altai Osman, <Emphasis Type="Italic">Oreoleuciscus potanini</Emphasis> (Cyprinidae), in Lakes Ayrag,Khyargas, and Nogon (Western Mongolia)

Analysis of variation in morphological characters of Potanin Altai osman, Oreoleuciscus potanini, from two freshwater and one brackish water lakes of Western Mongolia has shown that specimens of different ecological forms—herbivorous and piscivorous—form two integral and, at the level under consideration, internally indivisible units in the system of phenetic diversity of the species O. potanini.     

Spatial Distribution of Heavy Metals and <Superscript>137</Superscript>Cs in Spruce Forest Soil under Conditions of Regional Pollution

The influence of horizontal structure of spruce forest on the spatial distribution of acid-soluble Zn, Cd, Pb compounds and ¹³⁷Cs in the litter and the humus horizon of soddy podzolic soil has been studied in the territory with the regional background level of industrial fallout. It has been found that the distribution pattern of Zn in the forest litter is a result of biogeochemical processes. The litter in fern–wood sorrel microplots contains increased amounts of Zn and Cd, while the contents of Pb and ¹³⁷Cs are decreased. The distribution patterns of Pb and ¹³⁷Cs in the litter are positively correlated with each other, since both elements are deposited from the atmosphere, and similar mechanisms account for their redistribution in the spruce forest ecosystem.     

Variation in the Composition of Secondary Metabolites in <Emphasis Type="Italic">Flavocetraria</Emphasis> Lichens from Western Siberia

The composition and contents of secondary metabolites in Flavocetraria lichens from Eastern Siberia were analyzed using herbarium specimens. Based on the composition of identified metabolites, three F. cucullata chemotypes and two F. nivalis chemotypes were distinguished. Distinct geographic differentiation between the F. cucullata chemotypes was revealed, probably reflecting their adaptation to environmental conditions. The content of usnic acid in F. cucullata thalli was found to correlate with the latitude of growing region. This may be regarded as evidence for a protective role of this metabolite in lichens growing at high latitudes and exposed to excess solar irradiation during the polar day.     

Holocene Dynamics of Vegetation and Ecological Conditions in the Center of the East European Plain

Changes in the vegetation and fire regimes in the central East European Plain during the second half of the Holocene have been reconstructed based on the results of paleobotanical analysis and radiocarbon dating of material from a section of peat deposit in the Mordovia State Nature Reserve. It has been shown that birch–pine forests were widespread in the region between 7000 and 5000 yr BP, with the frequency of fires in that period being high (the fire return interval ranged from 10–20 to 100 years). Beginning from 5000 yr BP and to the early 20th century, broadleaf forests were dominant, with the fire return interval increasing to 300–500 years or longer.     

Assessment of the State of Lung Lichen, <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> (L.) Hoffm., in Forest Communities with Different Times Since Disturbance in the Northeast of European Russia

Quantitative parameters of cenopopulations of Lobaria pulmonaria, an endangered cyanolichen, have been studied in spruce phytocenoses of Karelia recovering after disturbance through the successional stage of aspen stands for a period ranging from 80 to 450 years. The results show that, as the time since disturbance increases, the total number of L. pulmonaria thalli and the number of colonized substrate units increase as well, with no stabilization of these parameters being observed in the series of communities studied. The total area of thalli in the phytocenoses is restored within approximately 200 years after the last disturbance. In old-growth forests (>400 years), L. pulmonaria thalli colonize a broad spectrum of tree species in different life states, including lower branches of young spruce trees. Even if they serve as temporary substrates, this can markedly strengthen the potential of the species for further expansion within the community in case of shortage in the main phorophyte (aspen). Thus, the proportion of regressive populations decreases, while that of colonizing populations increases, which is indicative of successful reproduction of the species.     

A Mathematical Model for the Effects of Fertilization on Nitrogen Concentrations in Unsaturated Soil on Blueberry Farms in Southern New Jersey

Nitrogen is commonly known as a food source for crops. However, the nitrogen compounds used in crop fertilizers, most commonly nitrate (NO₃) and ammonium (NH₄), are not widely understood. Blueberry plants do not take up these compounds as efficiently as organic nitrogen so varying amounts of leaching into the soil and groundwater will occur. A biogeochemical model consisting of ordinary and partial differential equations is implemented to computationally predict the concentrations of nitrate and ammonium in unsaturated soil of blueberry plants, specifically in the southern region of New Jersey. The model takes into account the type of soil of the region, the nitrate uptake of the plant, the water content in the roots region, the pressure heads in the soil pores, and the application rates of fertilizers containing nitrate, ammonium, and organic nitrogen. Computational simulations demonstrate that the model accounts for natural processes and, in addition, show that commonly used fertilizer application rates cause unnecessarily high concentrations of both nitrate and ammonium in the unsaturated soil level. Further, simulations show that decreasing nitrate fertilizer applications by 85.7% in annual and 91.8% in bi-annual schedules provides an optimal system for safe reapplication.