Low Spatial Density Research Articles

A new approach for the optimization of the thermo-mechanical behaviour of dry-running clutches using fibre-optic sensing technology with high spatial measurement density

Measuring temperature in tribological contacts remains being a huge challenge. The present paper proposes a new approach to analyze and optimize the thermo-mechanical behaviour of a dry-running clutch without affecting the real interacting surfaces. Using fibre-optic sensing technology makes it possible to gain a very detailed view of temperature distribution in the system. The interpretation of the measurements for different load situations has shown that the behaviour in the first 0.8 s is very similar. But after 0.8 s slip-time, the temperature distribution varies considerably according to the load situations. This behaviour is linked to the clutch engagement parameters and the resulting slip time. Non-lubricated clutches are still subject to numerous investigations in order to determine their dynamic behaviour, especially the dynamic behaviour. Measuring the temperature distribution in the friction contact would deliver a more detailed view of the live friction process. Main restriction remaining to establish this information is the low spatial measurement density of conventional thermal measurement facilities. On this account, fibre-optic sensing technology has been used at the IPEK to measure the temperature distribution with high spatial resolution in a pressure plate of a clutch system. One sensing fibre offers not less than 700 measurement points, divided across 28 measurement sections belonging to the pressure plate. In addition to the very high spatial measurement density, there are two more advantages. Through the low thermal mass of the optical fibre, fast variations of the temperature can be measured. By using only one sensing fibre, with a low capacity to transfer heat in itself, the heat dissipation through the sensor is very low. By means of this measurement method, it is possible to analyze the thermo-mechanical behaviour of a friction system with a high level of details. This method enables the control of temperature distribution in the counter plate. This parameter is an indicator of the load capacity of the system as an optimal homogenization leads to the elimination of local temperature peaks and so to wear reduction. Another topic is the specific adaptation of a system to its working area. The investigation of the influence on the thermo-mechanical behaviour of parameters such as friction energy or power allows the system to be optimally designed regarding to its working area. Another field of application is the validation of the thermal CAE-models.

Debris flow activity and gully propagation: Glen Docherty, Wester Ross

Investigation into debris flow activity was undertaken in Glen Docherty. Both the historical and recent records of debris flow activity in the glen are outlined. While the glen’s psammites have a low debris flow spatial density relative to that recorded in areas underlain by other rock types, the volumes involved are high. Debris flow gully propagation, as it occurs on both vegetated and non-vegetated talus, is examined. Evidence from recent events calls into question whether debris flows are effective agents of flow channel scour. Progressive slope failure is proposed as a possible mechanism in gully propagation. Fluvial activity was also found to play an important role in debris flow processes including gully development.

Tracking surface glycans on live cancer cells with single-molecule sensitivity.

Using a combination of metabolically labeled glycans, a bioorthogonal copper(I)-catalyzed azide-alkyne cycloaddition, and the controlled bleaching of fluorescent probes conjugated to azide- or alkyne-tagged glycans, a sufficiently low spatial density of dye-labeled glycans was achieved, enabling dynamic single-molecule tracking and super-resolution imaging of N-linked sialic acids and O-linked N-acetyl galactosamine (GalNAc) on the membrane of live cells. Analysis of the trajectories of these dye-labeled glycans in mammary cancer cells revealed constrained diffusion of both N- and O-linked glycans, which was interpreted as reflecting the mobility of the glycan rather than to be caused by transient immobilization owing to spatial inhomogeneities on the plasma membrane. Stochastic optical reconstruction microscopy (STORM) imaging revealed the structure of dynamic membrane nanotubes.

Tracking Surface Glycans on Live Cancer Cells with Single‐Molecule Sensitivity

AbstractUsing a combination of metabolically labeled glycans, a bioorthogonal copper(I)‐catalyzed azide–alkyne cycloaddition, and the controlled bleaching of fluorescent probes conjugated to azide‐ or alkyne‐tagged glycans, a sufficiently low spatial density of dye‐labeled glycans was achieved, enabling dynamic single‐molecule tracking and super‐resolution imaging of N‐linked sialic acids and O‐linked N‐acetyl galactosamine (GalNAc) on the membrane of live cells. Analysis of the trajectories of these dye‐labeled glycans in mammary cancer cells revealed constrained diffusion of both N‐ and O‐linked glycans, which was interpreted as reflecting the mobility of the glycan rather than to be caused by transient immobilization owing to spatial inhomogeneities on the plasma membrane. Stochastic optical reconstruction microscopy (STORM) imaging revealed the structure of dynamic membrane nanotubes.

Spatial density and ambient scent: effects on consumer anxiety

Purpose – This replication and extension of Hirsch and Gruss examines the impact of spatial density and ambient scent on consumers' spatial perception and anxiety. The paper aims to discuss these issues. Design/methodology/approach – A 2 (spatial density: high, low)×3 (ambient scent: no scent, scent associated with spaciousness, scent associated with enclosed spaces) between-participants experimental design was implemented in a laboratory setting. A pretest determined scent selection and manipulation checks were successful. Findings – Spatial perception was influenced by spatial density, but not ambient scent. Ambient scent and spatial density interacted, such that consumers' anxiety levels significantly increased under conditions of low spatial density combined with an ambient scent associated with spaciousness, and directionally increased under conditions of high spatial density combined with ambient scent associated with enclosed space. Research limitations/implications – This research was conducted in a laboratory setting in order to increase experimental control. An exploration of the strength of the observed effects in a field (retail) setting would be insightful. Practical implications – Results of this study suggest that retailers need to consider both spatial density and choice of ambient scent carefully in order to reduce consumers' anxiety levels. Originality/value – This research is one of the few to consider the impact of spatial density and ambient scent on consumers' anxiety levels. The use of a between-participants design and the experimental manipulation of both spatial density and ambient scent results in a more rigorous test of the scent – anxiety relation observed in previous research.

Small Interfering RNA Nunchucks with a Hydrophobic Linker for Efficient Intracellular Delivery

The high stiffness and low spatial charge density of siRNA limit the effectiveness of the electrostatic condensation of siRNA with cationic polyelectrolytes. Here, a facile method to stabilize nanoscale siRNA/polyelectrolyte complexes by introducing a reductively cleavable alkyl chain to siRNA as a hybrophobic linker of dimeric siRNA conjugates is reported. The increased length of the hydrophobic linker increases the intracellular translocation and gene silencing activity of the dimeric siRNA conjugates when they are complexed with linear polyethylenimine (LPEI). The results suggest that the introduction of a hydrophobic linker in the dimeric siRNA conjugates can facilitate the intracellular delivery of siRNA through effective condensation with cationic polyelectrolytes.

Nanostructure study of the coalescence growth of GaN columns with molecular beam epitaxy

We investigate the structural properties of molecular-beam-epitaxy coalescence overgrowth of GaN columns at the nanoscale with transmission electron microscopy and other characterization techniques. Two samples grown over nanocolumns of different widths and spatial densities (columns/area) are compared. It is found that columns with a larger cross section (~500 nm) and correspondingly lower spatial density normally lead to un-coalesced overgrown domains ranging 5-8 μm in size. On the other hand, the overgrowth on the columns of a smaller cross section (~100 nm) and correspondingly higher density results in coalesced domains ranging from 1 to 5 μm in size. It is believed that among the smaller, more closely spaced columns the strain distribution resulting from overgrowth is more effective in leading to the uniformity of crystalline orientation, and hence successful coalescence. The optical characterization leads to the conclusion that the defect density in the sample grown on smaller columns is lower when compared with that grown on larger columns.

Snow water equivalent in the Sierra Nevada: Blending snow sensor observations with snowmelt model simulations

We estimate the spatial distribution of daily melt‐season snow water equivalent (SWE) over the Sierra Nevada for March to August, 2000–2012, by two methods: reconstruction by combining remotely sensed snow cover images with a spatially distributed snowmelt model and a blended method in which the reconstruction is combined with in situ snow sensor observations. We validate the methods with 17 snow surveys at six locations with spatial sampling and with the operational snow sensor network. We also compare the methods with NOAA's operational Snow Data Assimilation System (SNODAS). Mean biases of the methods compared to the snow surveys are −0.193 m (reconstruction), 0.001 m (blended), and −0.181 m (SNODAS). Corresponding root‐mean‐square errors are 0.252, 0.205, and 0.254 m. Comparison between blended and snow sensor SWE suggests that the current sensor network inadequately represents SWE in the Sierra Nevada because of the low spatial density of sensors in the lower/higher elevations. Mean correlation with streamflow in 19 Sierra Nevada watersheds is better with reconstructed SWE (r = 0.91) versus blended SWE (r = 0.81), snow sensor SWE (r = 0.85), and SNODAS SWE (r = 0.86). On the other hand, the correlation with blended SWE is generally better than with reconstructed, snow sensor, and SNODAS SWE late in the snowmelt season when snow sensors report zero SWE but snow remains in the higher elevations. Sensitivity tests indicate downwelling longwave radiation, snow albedo, forest density, and turbulent fluxes are potentially important sources of errors/uncertainties in reconstructed SWE, and domain‐mean blended SWE is relatively insensitive to the number of snow sensors blended.

A Novel Visual Data Mining Module for the Geographical Information System gvSIG

The exploration of large GIS models containing spatio-temporal information is a challenge. In this paper we propose the integration of scientific visualization (ScVis) techniques into geographic information systems (GIS) as an alternative for the visual analysis of data. Providing GIS with such tools improves the analysis and understanding of datasets with very low spatial density and allows to find correlations between variables in time and space. In this regard, we present a new visual data mining tool for the GIS gvSIG. This tool has been implemented as a gvSIG module and contains several ScVis techniques for multiparameter data with a wide range of possibilities to explore interactively the data. The developed module is a powerful visual data mining and data visualization tool to obtain knowledge from multiple datasets in time and space. A real case study with meteorological data from Villa Clara province (Cuba) is presented, where the implemented visualization techniques were used to analyze the available datasets. Although it is tested with meteorological data, the developed module is of general application in the sense that it can be used in multiple application fields related with Earth Sciences.

Estimation of a semi-physical GLBE model using dual EnKF learning algorithm coupled with a sensor network design strategy: Application to air field monitoring

In this paper, we present the fusion of two complementary approaches for modeling and monitoring the spatio-temporal behavior of a fluid flow system. We also propose a mobile sensor deployment strategy to produce the most accurate estimate of the true system state. For this purpose, deterministic and statistical information was used. We adopted a filtering method based on a semi-physical model which derives from a fluid flow numerical model known as lattice Boltzmann model (LBM). The a priori physical knowledge was introduced by the Navier–Stokes equations which were discretized by the lattice Boltzmann approach. Moreover, its multiple-relaxation-time (MRT) variant not only improved the stability, but also enabled the introduction of additional degrees of freedom to be estimated like the synaptic weights of a neural network. The statistical knowledge was then introduced into the model by performing a sequential learning of these parameters and an estimation of the speed field of the fluid flow starting from measurements. The low spatial density of measurements, the large amount of data inherent to environmental issues and the nonlinearity of the generalized lattice Boltzmann equations (GLBEs) enjoined us to use the ensemble Kalman filter (EnKF) for the recursive estimation procedure. A dual state-parameter estimation which results in a significantly reduced computation time was used by combining two filters consecutively activated in the same iteration. Finally, we proposed to complete the lack of spatial information of the sparse-observation network by adding a mobile sensor, which was routed to the location where the cell-by-cell output estimation error was the highest. Experimental results in the context of the standard lid-driven cavity problem revealed the presence of few zones of interest, where fixed sensors can be deployed to increase performances in terms of convergence speed and estimation quality. Finally, the study showed the feasibility of introducing some additional parameters which act as degrees of freedom, to perform large-eddy simulation of turbulent flows without numerical instabilities.

Determining optimal resource recycling boundary at regional level: A case study on Tokyo Metropolitan Area in Japan

Conventionally, material inputs to industries come from either natural resources or intermediate products. With the increasing attention on greening the industrial process, municipal solid waste (MSW) can be separated and utilized as inputs to large-scale industries. As such, waste flows need to be managed to meet the requirements of industries by considering both quality and scale. Small scales of municipal recycling centers (MRCs) for pre-treating recyclable wastes often lead to higher pre-treatment cost and lower recycling efficiencies. Theoretically, appropriate facility scale and recycling boundary should be based upon a balanced consideration between economies of scale and transportation costs. However, only a few empirical studies on recycling boundaries have been conducted. Existing modeling studies are mostly case studies for planning purposes and do not theoretically examine the mechanisms and factors that determine recycling boundary. Under such a circumstance, this paper fills such a gap by quantitatively seeking the determinants for recycling boundaries and the related mechanism. An optimization model applying on the recycling of waste plastics is developed and tested in the Tokyo Metropolitan Region (TMR) in Japan. The results indicate two determinants for recycling boundary at the regional level: spatial density of separated wastes and the ratio of unit transportation cost to unit treatment cost. Separated wastes that are collected in low spatial density and have a low ratio of unit transportation cost to unit treatment cost should be better recycled in a large region. The finding implies that regional recycling networks should have multiple layers designed for different types of wastes due to the differences in their spatial density, unit transportation cost and unit treatment cost.

Primary Care Spatial Density and Nonurgent Emergency Department Utilization: A New Methodology for Evaluating Access to Care

ObjectiveTo determine the spatial and demographic characteristics of pediatric patients who make nonurgent visits (NUVs) to an urban pediatric emergency department (ED). We hypothesized that the rate of NUVs would be inversely associated with the spatial density of primary care providers (PCPs). MethodsA retrospective, cross-sectional analysis was conducted for all visits to Washington, DC’s principal pediatric ED between 2003 and 2006. NUVs were defined by a unique algorithm combining resource allocation, ambulatory-sensitive diagnoses, and billing data. Multivariate linear regression analysis was used to determine the association of PCP density and demographic variables on the spatial rate of NUVs. ResultsOver the 4-year period, 35.1% (52,110) of the 148,314 ED visits by Washington, DC, residents were nonurgent. NUVs were most associated with neighborhood median household income <$40,000 and low spatial density of PCPs. For every 1-unit increase in PCP density, the spatial rate of NUVs decreased by 9%. The odds of a visit being nonurgent were significantly higher for African Americans and Hispanics than for whites (odds ratio [OR] 2.4, 95% confidence interval [CI] 2.19–2.64; and OR 2.6, 95% CI 2.36–2.86, respectively), for patients using public insurance versus private (OR 1.46, 95% CI 1.42–1.50), and for patients age <5 years (OR 2.66, 95% CI 2.60–2.72). ConclusionsLow spatial density of primary care is strongly associated with nonurgent ED utilization. Improving spatial distribution of primary care may decrease ED misuse and improve access to the medical home.

LOW RATES OF BINDIN CODON EVOLUTION IN LECITHOTROPHIC HELIOCIDARIS SEA URCHINS

Life-history variables including egg size affect the evolutionary response to sexual selection in broadcast-spawning sea urchins and other marine animals. Such responses include high or low rates of codon evolution at gamete recognition loci that encode sperm- and egg-surface peptides. Strong positive selection on such loci affects intraspecific mating success and interspecific reproductive divergence (and may play a role in speciation). Here, we analyze adaptive codon evolution in the sperm acrosomal protein bindin from a brooding sea urchin (Heliocidaris bajulus, with large eggs and nonfeeding or lecithotrophic larval development) and compare our results to previously published data for two closely related congeners. Purifying selection and low relative rates of bindin nonsynonymous substitution in H. bajulus were significantly different from selectively neutral bindin evolution in H. erythrogramma despite similar large egg size in those two species, but were similar to the background rate of nonsynonymous bindin substitution for other closely related sea urchins (including H. tuberculata, all with small egg size and feeding planktonic larval development). Bindin evolution is not driven by egg size variation among Heliocidaris species, but may be more consistent with an alternative mechanism based on the effects of high or low spatial density of conspecific mates.

Single-photon emission from the natural quantum dots in the InAs/GaAs wetting layer

Time-resolved microphotoluminescence study is presented for quantum dots which are formed in the InAs/GaAs wetting layer. These dots are due to fluctuations of In composition in the wetting layer. They show spectrally sharp luminescence lines with a low spatial density. We identify lines related to neutral exciton and biexciton as well as trions. Exciton emission antibunching (second order correlation value of g^2(0)=0.16) and biexciton-exciton emission cascade prove non-classical emission from the dots and confirm their potential as single photon sources.

Spatial and temporal trends in soil salinity for identifying perched and deep groundwater systems

AbstractCharacterization of spatial and temporal variability in water flow and solute transport to foster better land management in salt‐affected landscapes requires direct hydrological observation, for example using suites of nested piezometers and dip wells. Such methods are costly to install and produce data with low spatial density, so are not ideal for supporting within‐field scale land management decisions. We present a new methodology to characterize water‐flow systems in salt‐affected landscapes using trends in shallow (&lt;1 m) down‐profile soil salinity based on electrical conductivity of saturated paste extract (ECse) and salts (that is the water extractable major ions of Ca, K, Mg, Na, P, Cl and S mg/kg) from a range of topographic settings. This involved coupling seasonal (late winter and late summer) salinity trends with clay percent (for soil morphology) and terrain patterns to understand the connectivity between perched and deep groundwater systems in a 120 ha catchment in the Mount Lofty Ranges, South Australia. From investigations at 19 sites in the catchment comprising toposequences or paired sites (in close proximity, but in different topographic settings), soil salinity trends revealed four hydro‐pedological systems: (i) a perched freshwater system with no hydraulic connectivity to the deep groundwater in upper slopes, (ii) an intermediate system comprising perched freshwater connected to a deep groundwater system in mid and upper slopes, (iii) a deep groundwater system in upper slopes, and (iv) a deep groundwater system in lower slopes. Although most of the 19 sites proved non‐saline, seasonal changes in ECse and ion concentration along with topography and soil morphology were sufficient to characterize the hydro‐pedological systems. We assigned these systems to a newly developed salinity classification based on dominant soil‐regolith‐hydrological processes and designed to support land management decisions. Conceptual hydro‐pedological models for each system were constructed to illustrate and explain the important interactions in each and how these relate to the new salinity classification. We propose that the methodology based on seasonal monitoring offers a new approach to landscape‐based hydro‐pedological characterization without reliance on the traditional groundwater monitoring methods. The new method offers wider access to catchment hydro‐pedological information to support better land management decisions in sloping landscapes subject to salinity.

Single-photon emission from InGaAs quantum dots grown on (111) GaAs

In this letter, we demonstrate that self-organized InGaAs quantum dots (QDs) grown on GaAs (111) substrate using droplet epitaxy have great potential for the generation of entangled photon pairs. The QDs show spectrally sharp luminescence lines and low spatial density. A second order correlation value of g(2)(0)&amp;lt;0.3 proves single-photon emission. By comparing the power dependence of the luminescence from a number of QDs we identify a typical luminescence fingerprint. In polarization dependent microphotoluminescence studies a fine-structure splitting ranging ≤40 μeV down to the determination limit of our setup (10 μeV) was observed.

Nonuniform Slip Rate and Millennial Recurrence Interval of Large Earthquakes along the Eastern Segment of the Kunlun Fault, Northern Tibet

The Kunlun fault is a major, active, left-lateral strike-slip fault upon the Tibet Plateau. Analysis of the long-term behavior of the fault is important in understanding the tectonic behavior of strike-slip faults and in assessing the mode of continental deformation and nature of seismic hazards upon the Tibet Plateau. However, our knowledge of the paleoseismicity and seismic behavior of the Kunlun fault remains limited and controversial because of difficult access, lack of field data, and the low spatial density of modern monitoring instruments. This study involved field investigations, fault-trench excavations, and an analysis of remote sensing images of the eastern (Maqen-Maqu) segment of the Kunlun fault near the town of Maqu in Gansu Province, China, revealing systematic deflections of rivers and gullies and mole track structures along the fault. Trench excavations revealed horizons of fluvial sand–gravel and silt–soil deposits, containing organic soil and peat, deformed by and offset along the fault. Based on the distribution of faulted and unfaulted sediments, fault-related structures, and ![Graphic][1] age data, nine paleoseismic surface-faulting events are identified over the past 9000–10,000 yr, of which the youngest event is constrained to the past 1000–1500 yr. A millennial recurrence interval of large earthquakes is estimated with an average slip of ∼3 m. An average Holocene slip rate of 3 mm/yr is estimated for this portion of the Kunlun fault. These results, together with those of previous studies, demonstrate that the along strike-slip rate is nonuniform, diminishing toward the east at an average gradient of 1 mm/100 km. This is in contrast to previous findings that the slip rate along the Kunlun fault is uniform and on the order of 11.5±2 mm/yr. [1]: /embed/inline-graphic-1.gif

Characteristics of graphene-layer encapsulated nanoparticles fabricated using laser ablation method

Graphene layer-encapsulated Ni nanoparticles with diameters between 3 and 10 nm were fabricated by laser ablation techniques and deposited directly on the Si substrate at room temperature. It was found from the field-emission type scanning electron microscopy (FE–SEM) and transmission electron microscopy(TEM) analyses that any carbon nanotubes were not fabricated in the deposited nano-materials. High-resolution TEM observation showed the core-shell structure of Ni–C particles with crystalline nickel core surrounded by graphite-like layers. The X-ray diffraction(XRD) pattern also revealed that nanoparticles embedded in graphene capsules are crystalline nickel. With these Ni–C nanoparticles, we demonstrated the growth of vertically aligned carbon nanotubes with low spatial density on a silicon substrate by thermal CVD.

Field experiment on transpiration from isolated urban plants

AbstractThe effect of pot plant density on plant transpiration rate was examined in a series of field experiments. Three spatial densities were created using 203 nearly homogeneous pot plants; the ratios of plant separation to plant height were 0·25, 0·5, and 3 for the ‘high,’ ‘medium,’ and ‘low’ groups respectively. The daily transpiration rate of 55 pot plants was measured for 28 days. During that period, the plants were randomly rotated each day to statistically eliminate individual characteristics and to successfully ascertain the effect of plant spatial density on the transpiration rate. As a best‐case scenario, the soil for each plant was saturated at the start of each experiment. The results showed that the transpiration rate of potted plants in the ‘low’ group was about 1·5 times greater than that of the ‘high’ group. On the basis of the transpiration rate per unit of vegetation area projected on a horizontal plain, which is a general index used in meteorological modeling, the plants in the ‘low’ group evaporated 2·7 times as much water as those in the centre of the ‘high’ group. These results indicate the need for modified models that can consider the relative increase in evapotranspiration from vegetation in small‐size plants or low spatial density of vegetation to estimate latent heat flux in urban areas. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. II. 2MASS J17072343-0558249AB

We present Infrared Telescope Facility SpeX observations of the M/L binary system 2MASS J17072343-0558249. SpeX imaging resolves the system into a 101 ± 017 visual binary in which both components have red near-infrared colors. Resolved low-resolution (R ~ 150) 0.8-2.5 μm spectroscopy reveals strong H2O, CO, and FeH bands and alkali lines in the spectra of both components, characteristic of late-type M and L dwarfs. A comparison to a sample of late-type field dwarf spectra indicates spectral types M9 and L3. Despite the small proper motion of the system (0100 ± 0009 yr-1), imaging observations over 2.5 yr provide strong evidence that the two components share common proper motion. Physical association is also likely due to the small spatial volume occupied by the two components (based on spectrophotometric distance estimates of 15 ± 1 pc) as compared to the relatively low spatial density of low-mass field stars. The projected separation of the system is 15 ± 3 AU, similar to other late-type M and L binaries. Assuming a system age of 0.5-5 Gyr, we estimate the masses of the binary components to be 0.072-0.083 and 0.064-0.077 M⊙, with an orbital period of roughly 150-300 yr. While this is nominally too long a baseline for astrometric mass measurements, the proximity and relatively wide angular separation of the 2MASS J1707-0558AB pair make it an ideal system for studying the M dwarf/L dwarf transition at a fixed age and metallicity.