Frontal Surfaces Research Articles

Effective scaled heat loss coefficient for translucent coatings of flat plate water-heating solar collectors

We study how heat losses through translucent coatings are affected by the partial absorption and heat transformation of the total solar radiation passing through the transluscent coatings of flat plate water-heating solar collectors; the radiation is incident on the frontal surfaces of the translucent coatings of their casings and is reflected from the antireflective surfaces of the heat-exchange panels of diffuse solar radiation collectors; the radiation is incident on the rear surfaces of the considered translucent walls. To allow for this factor in thermal engineering calculations for the “antireflective heat-exchange panel-translucent coating” system of the considered type of flat plate solar collectors, we introduce the effective coefficient of heat loss from the antireflective surface of a heat-exhange panel via the given translucent coating. We propose a calculation technique and the corresponding formula for determining the effective heat loss coefficient through the transluscent walls of flat plate water-heating solar collectors and present a practical calculation example for determining its value.

Features of producing an ohmic contact to frontal surfaces of photoconversion structures

This paper describes a technique for producing mechanically strong and high-temperature ohmic multilayer metal contacts to silicon photoconverters.

The impact of aerodynamics on fuel consumption in railway applications

The main consequence of on air flow surrounding a moving train resides in the aerodynamic drag and a certain pressure distribution on the frontal and lateral surfaces of the vehicle. The actual value of the aerodynamic drag (if pre-determined) may lead to a more accurate design of the whole locomotive power transmission. The aerodynamic drag may be estimated by using two specific experiments: the traction method and the free launch method. While the first one uses highly complex equipment, the second is easier to use due to the relative low number of devices required. The present work's main goal is to illustrate the importance of aerodynamic design of the railway vehicles, as their performances are influenced by the aerodynamic drag. In order to illustrate the influence of the aerodynamic shape of o locomotive body, we have chosen the latest diesel model available on the local market, the Class 621 EGM locomotives, currently in service at the national passenger railway operator, CFR Calatori SA.

Ictal barking as a manifestation of temporal lobe epilepsy

Ictal nonspeech vocalizations have been described as manifestations of either frontal or temporal epileptogenicity originating mainly from the dominant hemisphere. Ictal barking, particularly, has been considered a manifestation of mesial frontal epilepsy.A 42-year-old right-handed male with posttraumatic drug-resistant complex partial epilepsy manifested ictal barking near electrographic onset. Extraoperative electrocorticography with subdural electrode coverage of the right frontoparietal and temporal and left frontal surfaces provided surveillance of ictal origin and propagation.Ictal origin was identified in the right mesial temporal lobe with barking vocalization manifesting within 3s of electrographic onset. No subsequent spread of activity was noted beyond the temporal lobe. Resection of the mesial temporal structure resulted in seizure freedom. Pathology identified hippocampal sclerosis. This case supports the notion that an intrinsic, intralobar epileptogenic neural network in either hemisphere can act as a conduit into the limbic and memory circuits without a laterality bias to manifest as barking.

Local and non-local effects on surface-mediated stereoscopic depth

The magnitude and precision of stereoscopic depth between two probes is often determined by the disparity each has to a common background. If stereoscopic slant of the background is underestimated, a bias is introduced in the PSE of the probes (G. Mitchison & G. Westheimer, 1984). Using random dot stimuli, we show here how more remote surfaces can influence probe PSE via their influence on perceived background surface slant. The bias was reduced when frontal flanking surfaces were placed above and below the background surface, increasing its perceived slant. In a similar experiment, the flankers were slanted and the central background surface was frontal. For flankers alone, probe bias did not diminish up to a 4.4° separation of flankers and probes. When the central surface was present, the effect of the flankers on probe bias was mediated by this surface and diminished with flanker separation, presumably because of the diminishing contrast slant of the background surface. Stereoscopic depth between probes is thus influenced by a common background surface, by neighboring surfaces acting (contiguously or non-contiguously) on the background surface, and by distant surfaces acting directly on the probes.

New anatomical profile of the nasal musculature: Dilator naris vestibularis, dilator naris anterior, and alar part of the nasalis

The aim of this study was to clarify the morphology and topography of the dilator naris vestibularis, dilator naris anterior, and alar part of the nasalis. Anatomical variations in the topographic relationships are also described to provide critical data for understanding nasal muscular functions. Anatomical and histological examinations were performed on 40 specimens of embalmed Korean adult cadavers. The dilator naris vestibularis muscle (named by the present authors) was located between the external and vestibular skin of the alar lobule. The muscle fibers radiated along the dome-shaped nasal vestibule. The dilator naris anterior muscle originated from the frontal surfaces of the lateral half of the lateral crus and the accessory alar cartilage adjacent to the lateral crus. The extent of the lower insertion of the dilator naris anterior muscle was at the alar groove. The alar part of the nasalis originated with the transverse part of nasalis from the maxilla. It ascended to attach to the alar crease and the adjacent deep surface of external skin of the alar lobule. These findings may provide anatomical knowledge required to understand the structure and function of these nasal muscles such as during rhinoplasty or other surgery of the face.

An angio-tomographic approach to the study of the variation of the middle meningeal artery in humans

Introduction . The middle meningeal artery usually enters the endocranial cavity through the foramen spinosum, running within the dura mater and developing a vascular network on the frontal, parietal, and occipital surfaces of the brain. Little information is available on its morphogenesis and variation in human populations or within primates (Falk 1993). Its imprints on the endocranial walls can be recognised on fossil specimens, allowing inferences on the evolution of this vascular system. While extinct human species display a limited reticulation of this vessels, Homo sapiens shows a definite increase of its complexity (Bruner et al., 2005). Current hypotheses on the evolution of a complex meningeal vascularisation in our species include biomechanical protection and thermoregulation of the brain surface (Bruner et al., 2011). Taking into account the limited knowledge on the variation of this arterial network, this study is aimed at quantifying individual differences in the branching patterns, as well as at investigating the spatial relationships between middle meningeal arteries, cerebral arteries, and neurocranial bones. Methods . Angio-tomography and digital anatomy are used to reconstruct in vivo the meningeal vascular system in 37 individuals with age spanning from 20 to 85 years. Three-dimensional reconstructions of the cerebral and meningeal vascular systems have been computed by using Mimics 11.1 (Materialise Software). Variations in basic branching patterns have been described by standard anatomical approaches, as well as by using standard morphometrics. Complexity of the branching pattern has been quantified also by using fractal approaches (Zamir 1999). Results . Anatomical descriptions and metrics are reported for different age classes, sexes, and hemispheres, providing mean values and ranges of distribution accounting for the vascular patterns. Conclusions . Although the middle meningeal network shows a variable and complex geometry, its spatial organization can be quantified in terms of branching patterns and topological relationships with the neurocranial elements. This information allows to test evolutionary hypothesis by quantifying individual or between-groups differences. At the same time this information is helpful in biomedical and neurosurgical context, providing statistical values for the position and distribution of the vessels.

Factors Associated With Fouling in the Process Industry

This study evaluates the feasibility of using surface coatings on commonly used process surfaces to minimize/delay the effect of fouling. The materials considered here are stainless steel and copper with AgION and Xylan coatings. Sample plates were placed vertically in test tanks and then exposed to untreated lake water for various time periods. Results are presented that compare surface roughness over time. Additional results show transient deposit weight gain. The progressive change in surface appearance with increasing immersion times is also presented and gives a visual representation of the surface at a specific time. This review includes observations on the fouling of coated process surfaces. All coated samples showed some deposit accumulation with no change in surface appearance for the periods of immersion considered. Conclusions and observations regarding the material coatings for surfaces that are commonly used in designs where fouling may be a concern are presented here. Fouling rates, transient surface roughness values, and transient photographs of the frontal surfaces of the materials are given for typical conditions.

Measurement of the shear properties of clear wood by the Arcan test

AbstractIn this work, the identification of the shear properties of maritime pine (Pinus pinasterAit.) wood was investigated by applying the Arcan test method. For this purpose, an ad hoc Arcan fixture was designed for which clear wood samples could be tested along all the material planes of symmetry –LR,LTandRTplanes. For the accurate evaluation of the shear moduli, correction factors taking into account the non-uniformity of the shear stress and the shear strain distributions at the gauge section were determined with finite element analyses. Experimentally, two 0/90 rosettes were glued on both frontal and back surfaces of the specimens in order to take into account any through-to-thickness shear strain variation. It was found that the Arcan test is suitable for the identification of the shear moduli of wood in all its natural planes. The failure of the Arcan specimens systematically occurred under a concentrated stress state nearby the V-notches. Nevertheless, it was shown that an accurate estimation of the shear strengths of wood can be achieved by the Arcan test.

On precision improvement by ultrasonics-aided electrodischarge machining

The paper deals with increasing the precision by electrodischarge machining, aided by ultrasonic longitudinal vibration of the electrode tool. Increasing the dimensional precision of machined surfaces is strongly related to the decrease of volumetric relative wear. This essential parameter of electrodischarge machining depends on several input parameters, which are described in detail. Several optimization conditions, concer ning the technological input parameters, are elaborated, aiming at the maximization of the dimensional precision through volumetric relative wear. These conditions address overall parameters as acoustic pressure, discharge energy level and power supply of the ultrasonic chain. Several technological solutions are elaborated like the synchronization of pulses with tool oscillation semiperiods, decreasing the supply power of the acoustic chain and working with frontal flat surfaces of electrodes by generating complex surfaces through 3D technological movements provided by CNC machines. All these can lead to up to 50% decrease of volumetric relative wear.

Experimental study of attenuation coefficient of ultrasonic waves in concrete and plaster

This study has been dedicated to the determination and comparison of ultrasound attenuation coefficient in two kinds of frequently used masonry, namely concrete and plaster. The results of this investigation can be mainly applied for optimum acoustical designing of buildings which are exposed to high-power ultrasonic waves. Another expected benefit of this investigation is determining the possibility of using ultrasonic wave emissions for finding people who are buried under ruined building materials due to an earthquake. In this paper, the attenuation coefficient of 19.7 kHz ultrasonic waves are presented for nine different concrete specimens and three different plaster specimens. For this purpose, the amplitude of vibration speed of the back and frontal surfaces of the specimens were measured by a non-contact laser sensor while the front surface was actuated by a 200-W ultrasonic transducer. The variables of concrete were weight proportion between water and cement, weight proportion between course aggregate and fine aggregate, weight proportion of cement replaced with micro-silica, and the type of cement. The variable for plaster pieces was the weight proportion of water and plaster.

Estimating mass and momentum fluxes in a line of cumulonimbus using a single high‐resolution Doppler radar

AbstractWe present a method to derive the vertical‐wind field at a scale of 1–2 km from a high‐resolution Doppler radar, by performing vertical scans in the plane of the mean wind and tracking turbulent features on a scale of several hundred metres in the radial‐velocity field between consecutive scans. The method is applied to a line of cumulonimbus clouds observed by the high‐resolution Chilbolton radar in southern England. The storm was not a squall line, since it was propagating parallel rather than perpendicular to its length. A sequence of scans was taken over an hour‐long period; from these scans we derive the u and w components of the wind. Updraughts of up to 15 m s−1 are found.From these observations, the mass flux of a ‘typical’ storm cell was estimated: over the 50 min lifetime of the cell, the total mass of air transported from the boundary layer to the upper troposphere was found to be around 50 megatonnes. The profile of hour‐averaged momentum flux against height was then calculated and compared to the vertical shear of the mean horizontal wind. It was found that above 4.5 km, the momentum flux was down‐gradient, with an equivalent eddy diffusivity of around 103 m2s−1. Below this height, however, the flux was counter‐gradient, with an equivalent eddy diffusivity of around − 103m2s−1. We propose a mechanism to explain this behaviour, involving the prevalence of precipitation cooling and descent on the downshear side of convergence lines.A synthesis of the major wind flows in the storm reveals that, despite superficial appearance, the storm did not fit the usual multi‐cell paradigm, in which gust fronts play a key roll in triggering new cells downwind. Rather, the convergence lines associated with the convection were more akin to warm frontal surfaces that remain tied to the base of each cell, new cells tending to form upwind of older cells. Copyright © 2008 Royal Meteorological Society

Fouling surface finish evaluation

Fouling of a surface takes place as the result of a series of complex reactions that cause deposits to form on process surfaces. For many conditions, fouling can be reduced but not necessarily eliminated. The materials considered here are: carbon steel, stainless steel, and aluminium with typical finishes. Sample plates were placed vertically in tanks and exposed to untreated lake water for various time periods. Results are presented that compare surface roughness over time, for the materials/surfaces considered. The progressive change in surface appearance with increasing immersion times is also presented. Stainless steel samples showed a relatively small change in surface appearance for most periods of immersion, with a small increase in surface deterioration for increasing immersion times. Brite aluminum, an aluminium alloy with an anodized surface film, performs similar to stainless steels. Cold rolled carbon steel has the largest variation of surface appearance over time. This review includes observations on fouling and process surface materials/finishes. Conclusions and observations regarding the materials that are commonly used in designs when fouling may be a concern are presented here. Photographs of material frontal surfaces and transient surface roughness are given for a variety of surfaces.

On the spatial localization of the laminar boundary layer in a non-Newtonian dilatant fluid

In dilatant fluids the shear perturbation propagation rate is finite, in contrast to Newtonian and pseudoplastic fluids in which it is infinite [1]. Therefore, in certain dilatant fluid flows, frontal surfaces separating regions with zero and nonzero shear perturbations may be formed. Since, in a sense, the boundary layer is a “time scan” of the nonstationary shear perturbation propagation process, in dilatant fluids the boundary layer should definitely be spatially localized. This was first mentioned in [2] where, however, it was mistakenly asserted that boundary layer spatial localization does not take place in all dilatant fluids and is absent in so-called “hardening” dilatant fluids. In [3], the solutions of the laminar boundary-layer equations for speudoplastic and “hardening” dilatant fluids were investigated qualitatively. The formation of frontal surfaces in dilatant fluid flows is usually mathematically related with the existence of singular solutions of the corresponding differential equations [4]. However, since the analysis performed in [3] was inaccurate, in that study singular solutions were not found and it was incorrectly concluded that in “hardening” dilatant fluids there is no spatial boundary layer localization. The investigation performed in [5] showed that in fact in “hardening” dilatant fluids boundary layers are spatially localized, since there exist singular solutions of the corresponding differential equations. Subsequently, this result was reproduced in [6], where an attempt was also made to carry out a qualitative investigation of the solutions of the laminar boundary-layer equations for other types of dilatant fluids. The author did not find singular solutions in this case and mistakenly concluded that in these fluids there is no spatial boundary layer localization. This misunderstanding was due to the fact that in [6] it was not understood that in dilatant fluid flows the formation of frontal surfaces can be mathematically described not only in relation to the existence of singular solutions.

Acquisition of particle processing capability in juvenile oyster Crassostrea gigas: ontogeny of gill mucocytes

Acquisition of particle processing capability in postlarval oysters depends upon the structural development of the pallial organs, as well as the development of cilia and mucocytes used (either directly or indirectly) in particle capture and transport. Mucocyte mapping was therefore used to identify mucocyte types and distributions throughout gill development in juvenile oyster Crassostrea gigas (Thunberg 1793) specimens from 2.9 mm to 2.4 cm in shell length. Three categories of gill filaments were identified: apical, lateral and principal filaments, corresponding to filament location or future location in gill plicae. Mucocyte densities were recorded per linear μm (l μm) of frontal surface, and converted to potential total volumes, using the mean volumes of each of the two major mucocyte types: acid mucopolysaccharide (AMPS)-mucocytes and mixed mucopolysaccharide (MMPS)-mucocytes. While AMPS secretions were dominant up to 1.0 cm (flat homorhabdic gill, to semi-heterorhabdic differentiation and plication), MMPS secretions increased progressively, dominating in 2.4 cm and adult specimens (fully heterorhabdic and plicated). Mucus composition, and hence mucus viscosity, thus appears to evolve in relation to the degree of enclosure of the gill frontal surfaces. Total (AMPS + MMPS) potential mucus secretion increased allometrically with juvenile growth, characterized by a sharp increase between 10 and 24 mm shell length, suggesting a marked improvement in particle processing capability. Mucocyte distributions on the gill were heterogeneous from the onset of heterorhabdic differentiation (7.5 mm): the apical filaments of the plicae contained much greater mucocyte total volumes, compared to the lateral and principal filaments. In addition to mucus composition, total potential mucus volume thus also evolved in relation to the degree of enclosure of the gill frontal surfaces. These results show that functional specialization in mucocyte distribution precedes the complete anatomical heterorhabdic differentiation. The completely functional adult gill system is thus attained in 2.4 cm juveniles. This information should be of use in understanding the dynamics of juvenile feeding, growth, and mortality, both in natural systems and in rearing operations.

Selective growth of carbon nantoubes on SiO 2/Si substrate

Three-step raising temperature process was employed to fabricate carbon nanotubes by pyrolysis of ferrocene/melamine mixtures on silica and single crystalline silicon wafers respectively. Then the morphologies, structures and compositions of obtained carbon nanotubes are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscope (EDX) and electron energy-loss spectroscopy (EELS). TEM and SEM observation shows that on silica substrate, high-oriented carbon nanotube can grow compactly to form continuous film on both frontal and cross-section surfaces, but on silicon substrate, only can form on cross-section surface. These carbon nanotubes have much irregular cup-like structure, and with outer diameter varying from 25 nm to 35 nm. At the top end of carbon nanotube there is a catalyst particle. EDX analysis reveals that the particle are iron cluster, and EELS spectrum indicates that the nanotube is composed of pure carbon. Finally, the effect of substrate surface roughness on the growth behavior of carbon nanotubes has been discussed.

Transient Evaluation of Process Surfaces Used in Fouling Applications

Fouling is an important and complex problem that affects a variety of industries. Surface fouling takes place as a result of the complex reactions that cause deposits to form on process surfaces. A number of parameters influence fouling development, including flow velocity, surface temperature, surface material/finish, surface geometry, and fluid properties. It is a transient process that begins with a clean process surface and may progress until the surface can no longer be used effectively. The event sequence of the fouling process appears in general to be universal, beginning when fluid comes into contact with a process surface. During this induction period, a conditioning film forms, and the heat transfer efficiencies do not change significantly. Conditioning film appearance may occur in weeks, days, or minutes. This stage is followed by a rapid accumulation of deposit growth. It is during this growth phase that the heat transfer across the process surface starts to dramatically change. Finally, a pseudo-steady-state period is arrived at when accumulation is almost constant. This accumulation causes heat transfer to significantly decrease and a complete cleaning of the surfaces may be required. Included here is a discussion on process surface materials used in applications where fouling may be a concern. Previous work in this area has prompted this study in order to provide better information for designs involving fouling. Conclusions and observations regarding the materials/surfaces that are commonly used in designs where fouling may be a concern are presented here. Photographs are presented of frontal surfaces and edges. Finally, transient surface roughness values are given for several materials.

Amplitudes of laser evoked potential recorded from primary somatosensory, parasylvian and medial frontal cortex are graded with stimulus intensity

Intensity encoding of painful stimuli in many brain regions has been suggested by imaging studies which cannot measure electrical activity of the brain directly. We have now examined the effect of laser stimulus intensity (three energy levels) on laser evoked potentials (LEPs) recorded directly from the human primary somatosensory (SI), parasylvian, and medial frontal cortical surfaces through subdural electrodes implanted for surgical treatment of medically intractable epilepsy. LEP N2* (early exogenous/stimulus-related potential) and LEP P2** (later endogenous potential) amplitudes were significantly related to the laser energy levels in all regions, although differences between regions were not significant. Both LEP peaks were also significantly correlated with the pain intensity evoked by the laser stimulus, excepting N2* over the parasylvian region. Peak latencies of both LEP peaks were independent of laser energy levels. N2* and P2** amplitudes of the maxima in all regions showed significant positive linear correlations with laser energy, excepting N2* over the parasylvian region. The lack of correlation of parasylvian cortical N2* with laser energy and pain intensity may be due to the unique anatomy of this region, or the small sample, rather than the lack of activation by the laser. Differences in thresholds of the energy correlation with amplitudes were not significant between regions. These results suggest that both exogenous in endogenous potentials evoked by painful stimuli, and recorded over SI, parasylvian, and medial frontal cortex of awake humans, encode the intensity of painful stimuli and correlate with the pain evoked by painful stimuli.

Cutaneous painful laser stimuli evoke responses recorded directly from primary somatosensory cortex in awake humans.

Negative and positive laser evoked potential (LEP) peaks (N2*, P2**) were simultaneously recorded from the primary somatosensory (SI), parasylvian, and medial frontal (MF: anterior cingulate and supplementary motor area) cortical surfaces through subdural electrodes implanted for the surgical treatment of intractable epilepsy. Distribution of the LEP N2* and P2** peaks was estimated to be in cortical areas (SI, parasylvian, and MF) identified by anatomic criteria, by their response to innocuous vibratory stimulation of a finger (v-SEP), and to electrical stimulation of the median nerve (e-SEP). The maximum of the LEP N2* peak was located on the CS, medial (dorsal) to the finger motor area, as determined by cortical stimulation, and to the finger somatosensory area, as determined from the e-SEP and v-SEP. This finding suggests that the generator source of the LEP N2* peak in SI was different from that of e-SEP or v-SEP in Brodmann's areas 3b or 1. In parasylvian and MF, polarity reversal was often observed, indicating tangential current sources in these regions. In contrast to e-SEP and v-SEP, the LEP N2* latency over SI was not shorter than that over the parasylvian region. The amplitude of N2* was larger over SI than over MF and the latencies of the LEP peaks in those 2 regions were different. These findings provide evidence for a significant LEP generator in the postcentral gyrus, perhaps SI cortex, that is situated outside the tactile homunculus in SI and that receives its input arising from nociceptors simultaneously with parasylvian and MF cortex.

Monocular gap stereopsis: manipulation of the outer edge disparity and the shape of the gap

A binocular stimulus that arises when two black frontal plane surfaces located at different depths have a gap between them for one eye but not for the other eye is interesting since the gap is monocular––it has no matching contours in the other eye––and yet binocular processes resolve a depth step effortlessly (Vision Research, 39, 493). In two experiments we investigate the processes and constraints underlying this depth resolution by varying the width of the solid image (the one without the gap) and the shape of the gap. The results show that the processes underlying monocular gap stereopsis can handle a situation in which the images of two surfaces in depth are effectively overlapping for one eye’s view with the other eye seeing between them and that binocular depth is seen even when there is no disparity present. We also show that under ecologically appropriate conditions, depth curvature and warping can result when the monocular gap has a curved or warped edge. Both these experiments imply that the visual system responds to the ambiguity of the stimulus by adopting a minimum slant constraint.