Aperture Rim Research Articles

Performance assessment of a parabolic trough solar collector using nanofluid and water based on direct absorption

In this investigation, a parabolic trough solar concentrating collector with an evacuated tube was fabricated with an aperture area, collector length, breadth, and rim angle, inner and outer diameter of absorber as 2.45 m2, 2.1 m, 1.2 m, 90 deg, 0.0286 m, and 0.03058 m, respectively. A copper oxide (CuO) and water-based nanofluid was employed as the working fluid. Different mass fractions (0.05%, 0.075%, and 0.1%) and volume flow rates (70 lit/hr and 140 lit/hr) of nanofluid were taken, and performance of an evacuated tube parabolic trough collector was analysed. When CuO–H2O nanofluid of varying concentrations (0.05%, 0.075%, and 0.1%) is used in place of H2O (DI), it has been observed that the solar collector's efficiency increases. The efficiency of the collector increases in direct proportion to the working fluid's volume flow rate increment. The maximum heat transfer coefficients for CuO–H2O based nanofluid were 280.68 W/m2-K and 466.8 W/m2-K while the maximum convective heat transfer coefficients for water as working fluid were 268.11 W/m2-K and 488.7 W/m2-K at 70 lit/h and 140 lit/h, respectively. An efficiency increase of 45.15%, 51.19% and 53.26% for 70 lit/h and 59.61%, 63.56% and 69.07% for 140 lit/h mass flow rate has been observed for different nanoparticle's concentrations, respectively. Economic studies showed that the cost of the experiment (for 0.05% CuO dispersion) has increased by 1.08% for 70 lit/h mass flow rate when compared to the water based direct cooling method.

Assessment of the Stirling engine performance comparing two renewable energy sources: Solar energy and biomass

The paper addresses the assessment of the Stirling engine performance by comparing biomass and solar energy as external renewable energy sources. A program-code was developed in the MatLab® to solve the thermal model of an alpha-Stirling engine, accounting for the limitations in the heat transfer processes in the regenerator and the losses due to pumping effects. The solar energy source was modelled as a concentric solar dish collector, considering a receiver located at the focal point and designed to absorb the maximum possible of the solar radiation. Regarding the biomass system, the temperature of the flue gases leaving the bed is computed through an energy balance, considering the fuel energy introduced into the bed, the energy that is provided by the bed and the incident radiation in the bed. The simulation results show that the biomass-fuelled Stirling engine provided 87.5% more power output than the solar energy source, with an efficiency of 46.67%. Also, the average receiver temperature from the solar source is about 775 K, whereas, in the boiler bed, the temperature reaches the value of 1288 K. In the solar-dish modelling, the reflected radiation that passes into the cavity receiver depends on the aperture ratio and rim angle. It was proved that a rim angle of at least 45° is required to ensure lower focal distances. Otherwise, the Stirling receiver needs to be far from the surface of the dish, resulting in higher thermal losses and lower temperature inside the receiver cavity. In biomass-fuelled system, it was shown that the temperature of the flue gases increases with the increasing the radiation flux, and decreases for higher split percentages between the primary and secondary air. The study also revealed the need to investigate the combustion stability regarding the particle emission in the flue gas, which can reduce the temperature close to the hot cylinder of the Stirling engine. The LCoE for the solar-power system is of about 1658 €/kWh, which is 52% higher when compared with the biomass-fuelled system (0.109 €/kWh). In conclusion, biomass-fuelled Stirling engines are able to provide a higher power output with higher thermal efficiency, avoiding the problems usually related to solar energy intermittency.

Three‐Dimensional Infraorbital Foramen Location Relative to Facial Landmarks: Preliminary Results

Infraorbital nerve block injections are performed by either an intraoral approach per the oral vestibule or an extraoral approach through the skin near the infraorbital foramen. Many studies have assessed the location of the IOF relative to bony landmarks, teeth, as well as soft tissue landmarks with mixed results. Few studies have assessed the location of the IOF in three dimensions. This study analyzed the location of the IOF relative to a midpoint between the inferolateral nasal aperture and inferolateral orbital rim via three‐dimensional models rendered from 18 adult crania. The distance from the midpoint to the IOF averaged 4.16±1.43 mm (mean±SD) on the left and 3.93±1.43 mm on the right. Wilcoxon matched‐pairs signed rank tests revealed no significant difference among sides (p=0.325). This report also addresses differences among the x, y, and z axes. These preliminary data demonstrate the utility of three‐dimensional analysis for the assessment of IOF location. Understanding the location of the IOF in three dimensions may aid in determining the best patient‐specific approach for infraorbital nerve block.Support or Funding InformationWV Research Challenge Fund [HEPC.dsr.17.06] and [HEPC.dsr.14.13]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Minimally invasive medial maxillectomy and the position of nasolacrimal duct: the CT study

Several minimally invasive modifications of endoscopic medial maxillectomy have been proposed recently, with the least traumatic techniques utilizing the lacrimal recess as a route to enter the sinus. The aim of the study was to analyze the anatomy of medial maxillary wall in the region of nasolacrimal canal and, thus, to determine the capability of performing minimally invasive approach to the maxillary sinus leading through the lacrimal recess. The course of nasolacrimal canal and the distance between the anterior maxillary wall and the nasolacrimal canal (the width of lacrimal recess) were evaluated in 125 randomly selected computed tomography (CT) head examinations. The proportion of cases with unfavorable anatomical conditions (lacrimal recess too narrow to accept a 4 mm optic) to perform minimally invasive middle maxillectomy was assessed. The width of lacrimal recess, measured at the level of the inferior turbinate attachment, varied between 0 and 15.2 mm and was related to slanted course of nasolacrimal canal. The more perpendicular the axis of the canal to the nasal flor, the narrower the lacrimal recess. In about 16% of cases, lacrimal recess width was less than 4 mm and in 14.4% it was missing. The endoscopic approach to maxillary sinus leading through lacrimal recess is possible in about 70% of patients. In the remaining group of patients when the lacrimal recess is too narrow, this type of approach may be difficult to perform without damaging the piriform aperture rim or bony framework of nasolacrimal duct, or it may be impracticable when lacrimal recess is missing.

The Nasal Complex of Neanderthals: An Entry Portal to their Place in Human Ancestry

Neanderthals are one of the most intensely studied groups of extinct humans, as aspects of their phylogeny and functional morphology remain controversial. They have long been described as cold adapted but recent analyses of their nasal anatomy suggest that traits formerly considered adaptations may be the result of genetic drift. This study performs quantitative and qualitative analysis of aspects of the nasal complex (NC) in Neanderthals and other later Pleistocene fossils from Europe and Africa. A geographically diverse sample of modern human crania was used to establish an anatomical baseline for populations inhabiting cold and tropical climates. Nasofrontal angle, piriform aperture dimensions, and relative maxillary sinus volume were analyzed along with qualitative features of the piriform aperture rim. Results indicate that Neanderthals and other later Pleistocene Homo possessed NC's that align them with tropical modern humans. Thus comparison of Neanderthal nasal morphology with that of modern humans from cold climates may not be appropriate as differences in overall craniofacial architecture may constrain the narrowing of the piriform apertures in Neanderthals. They retain primitively long, low crania, large maxillary sinuses, and large piriform aperture area similar to mid-Pleistocene Homo specimens such as Petralona 1 and Kabwe 1. Adaptation to cold climate may have necessitated other adaptations such as bony medial projections at the piriform aperture rim and, potentially, midfacial prognathism. Nasal complex components of the upper respiratory tract remain a critical but poorly understood area that may yet offer novel insight into one of the greatest continuing controversies in paleoanthropology.

Dual-Series Solution to EM-Wave Scattering by a Circular Slit PEC Cylinder Enclosing Multiple Dielectric Cylindrical Rods

A cylindrical structure composed of a circular, PEC cylinder, having a longitudinal slot and enclosing an arbitrary number of eccentric, dielectric cylinders, embedded in a dielectric sheath, is considered in this paper. Excitation is provided by a plane wave, normally incident upon the structure. Both TE and TM polarizations are considered for the incident wave. The scattered wave, as well as the electromagnetic (EM) field within the scatterer, are determined by using a dual-series approach combined with the translational addition theorem for cylindrical wave functions. The Abel integral-transform method is applied in order to regularize the dual-series equations to a matrix Fredholm equation of the second kind. The resulting infinite set of linear algebraic equations (i.s.l.a.e.) is truncated and solved numerically. The solution inherently contains the behavior of the field near the aperture rim, as required by Meixner's edge condition. The numerical application manifests how the internal structure of the scatterer and the polarization of the incident wave affect backscattering by the cylindrical cavity.

HYDROBIA AS "JONAH IN THE WHALE": SHELL REPAIR AFTER PASSING THROUGH THE DIGESTIVE TRACT OF SHELDUCKS ALIVE

In the Wadden Sea, shell repair frequency in the small gastropod Hydrobia ulvae varied from 2.8% to 11.2%. On tidal flats of the Mok, a small bay on the island of Texel, The Netherlands, in the Wadden Sea, higher repair frequencies varying from 11.8% to 41.8% were measured. The shelduck, Tadorna tadorna, a predator of Hydrobia, occurs here in densities far above average densities for the Wadden Sea. Shelducks ingest their prey whole and crush the shells of H. ulvae internally. Live specimens of H. ulvae were collected from shelduck feces. Those with intact operculum and only a damaged outer aperture rim of the shell were kept in aquaria and repaired their shell rapidly. This indicates that predators that ingest shelled prey can also leave repair scars on shells. Such scars, however, are indistinguishable from those resulting from failed predation by predators using such pre-ingestive shell breakage as decapod crustaceans.

Tibial Tunnel Aperture Irregularity After Drilling With 5 Reamer Designs

Background: There is limited information in the literature on comparisons of antegrade versus retrograde reaming techniques and the effect on the creation of anterior cruciate ligament (ACL) tibial tunnel entry and exit apertures. Hypothesis: Proximal and distal apertures of ACL tibial tunnels, as created with different reamers, will be affected by type of reamer design. Study Design: Controlled laboratory study. Methods: Forty skeletally mature porcine tibias with bone mineral density values comparable with a young athletic population were included in this study. Five 9-mm reamer models were used (3 antegrade: A1, smooth-bore reamer; A2, acorn-head reamer; A3, flat-head reamer; 2 retrograde: R1, retrograde acorn reamer; R2, single-blade retrograde reamer), and a new reamer was used for each tibia (8 reamer-tibia pairs per reamer model). All specimens underwent micro–computed tomography scanning, and images were reconstructed and analyzed using 3-dimensional image analysis software. Aperture rim fractures were graded on a 0-IV scale that described the proportion of the fractured aperture circumference. Specimens with incomplete apertures were also recorded. Because of the unique characteristics of various tunnels, intratunnel characteristics were observed and recorded. Results: In sum, 1 proximal and 7 distal aperture rim fractures were found; 3, 0, and 4 distal aperture rim fractures were found with groups A1, A2, and A3, respectively. Incomplete apertures were more commonly found at the distal aperture (n = 15) than the proximal aperture (n = 8); there were no tibias with this finding at both apertures. All incomplete distal apertures occurred with the retrograde technique, and all incomplete proximal apertures occurred with the antegrade technique, most commonly with reamer design A3. An added finding of tunnel curvature at the distal aspect of the tunnel was observed in all 8 tibias with R1 reamers and 5 tibias with R2 reamers. This phenomenon was not observed in any of the tibias reamed with the antegrade technique. Conclusion: Anterior cruciate ligament tibial tunnel aperture characteristics were highly dependent on reamer design. Optimal proximal aperture characteristics were produced by the retrograde reamers, whereas optimal distal aperture characteristics were obtained with the antegrade reamers. In addition, a phenomenon of tunnel curvature in retrograde-type reamers was found, which may have effects on ACL graft or screw fixation. Clinical Relevance: Differences in tunnel aperture shapes and fractures depend on reamer design. This information is important for the creation of ACL reconstruction tunnels with different reamer designs.

Distraction Osteogenesis of Nasal Bone Including Piriform Aperture Rim for Syndromic Craniosynostosis

Torikai, Katsuyuki MD; Nishikori, Nagi MD; Naganishi, Hiroki MD; Yamamoto, Mayumi MD; Kijima, Takeshi DDS; Yonemitsu, Ikuo DDS; Shimazaki, Kazuo DDS; Watanabe, Keiichiro DDS; Tanaka, Eiji DDS; Moriyama, Keiji DDS; Omura, Susumu DDS

Solar Stirling Dish Power Generation Atlas of India

In this article, an atlas of solar electricity potential of Stirling dishpower generation system is presented. Important parameters neededfor solar power generation modeling are direct solar insolation, ambienttemperature, wind speed, concentrator aperture area, rim angle, mirrorreflectance, working fluid, operating temperature, receiver insulatingmaterial and intercept factor. The input data values averaged over a10-year period is obtained from India Meteorological Department, Pune.The useful energy delivered by a collector is evaluated with consider-ation for various heat losses. An average value of solar electricity po-tential of a 25.3 kW parabolic dish collector is found to be maximum of15.3 kW for Jodhpur and minimum of 12.7 for Calcutta. Maps of annualvariation of solar electricity potentials, comparison of electricity poten-tials of Indian cities for different months, average electricity potentialsand annual electrical energy generation for various Indian cities havebeen developed. To produce 25 kW of electrical power on all the daysof a year, three different dishes are recommended for the Indian citiesof Jodhpur, Trivendrum and Calcutta. This atlas provides knowledgeand aids in exploitation of solar electricity generation for Indian climaticconditions.

Anatomical Consideration of the Congenital Nasal Pyriform Aperture Stenosis: Localized Dysostosis Without Interorbital Hypoplasia

Congenital nasal pyriform aperture stenosis may be isolated or associated with other midline anomalies. The aim of the study was to describe the measurements and features of the interorbital structure and midface in congenital nasal pyriform aperture stenosis. The computed tomography scans of eight patients (two girls and six boys) were retrospectively reviewed. Several distances were obtained at the orbital and midface levels and compared with normative data. The average width of the pyriform aperture was 5.5 mm +/- 1.6, and there was overgrowth of the pyriform aperture rim (nasal process of the maxilla). No skeletal anomalies were present other than the congenital nasal pyriform aperture stenosis. It was associated with a single median maxillary central incisor in two cases. The anterior and lateral interorbital distances were normal (17.4 mm and 65.4 mm, respectively). The midface was not hypoplastic. There was no brain malformation. Congenital nasal pyriform aperture stenosis is a localized dysostosis of the pyriform aperture rim without interorbital or midface hypoplasia. It may be associated with a single median maxillary central incisor but cannot be viewed as a minor form of holoprosencephaly.

Shock wave-inertial microbubble interaction: methodology, physical characterization, and bioeffect study.

A method of generating in situ shock wave-inertial microbubble interaction by a modified electrohydraulic shock wave lithotripter is proposed and tested in vitro. An annular brass ellipsoidal reflector (thickness = 28 mm) that can be mounted on the aperture rim of a Dornier XL-1 lithotripter was designed and fabricated. This ring reflector shares the same foci with the XL-1 reflector, but is 15 mm short in major axis. Thus, a small portion of the spherical shock wave, generated by a spark discharge at the first focus (F1) of the reflector, is reflected and diffracted by the ring reflector, producing a weak shock wave approximately 8.5 microseconds in front of the lithotripter pulse. Based on the configuration of the ring reflector (different combinations of six identical segments), the peak negative pressure of the preceding weak shock wave at the second focus (F2) can be adjusted from -0.96 to -1.91 MPa, at an output voltage of 25 kV. The preceding shock wave induces inertial microbubbles, most of which expand to a maximum size of 100-200 microns, with a few expanding up to 400 microns before being collapsed in situ by the ensuing lithotripter pulse. Physical characterizations utilizing polyvinylidene difluoride (PVDF) membrane hydrophone, high-speed shadowgraph imaging, and passive cavitation detection have shown strong secondary shock wave emission immediately following the propagating lithotripter shock front, and microjet formation along the wave propagation direction. Using the modified reflector, injury to mouse lymphoid cells is significantly increased at high exposure (up to 50% with shock number > 100). With optimal pulse combination, the maximum efficiency of shock wave-induced membrane permeabilization can be enhanced substantially (up to 91%), achieved at a low exposure of 50 shocks. These results suggest that shock wave-inertial microbubble interaction may be used selectively to either enhance the efficiency of shock wave-mediated macromolecule delivery at low exposure or tissue destruction at high exposure.

Reducing canonical diffraction problems to singularity-free one-dimensional integrals

The oscillatory integrands of the Kirchhoff and the Rayleigh–Sommerfeld diffraction solutions mean that these two-dimensional integrals typically lead to challenging computations. By adoption of the Kirchhoff boundary conditions, the domain of the integrals is reduced to cover only the aperture. For perfect spherical (both diverging and focused) and plane incident fields, closed forms are derived for vector potentials that allow each of these solutions to be further simplified to just a one-dimensional, singularity-free integral around the aperture rim. The results offer easy numerical access to exact—although, given the approximate boundary conditions, not rigorous—solutions to important diffraction problems. They are derived by generalization of a standard theorem to extend previous results to the case of focused fields and the Rayleigh–Sommerfeld solutions.

Investigation into the thermo-viscoplastic finite element analysis of square die extrusion of square section with Lagrangian description

An analysis of three-dimensional hot extrusion through landless square dies is carried out as a nonsteady-state problem. In the problem, difficulties arise from the severe distortion and die interference of elements at the aperture rim of the die, even with a small punch travel. Finite element simulation is impossible without intermittent remeshing procedures. To overcome these difficulties, an automatic remeshing technique is proposed by employing a modular conceptual mesh structure. In the analysis of temperature distribution, conduction, convection and radiation are considered in connection with a deformation analysis of a visco-plastic material. The effect of the mesh structure on the present scheme as well as material properties and temperatures associated with punch travel is discussed. As an example, an extrusion of a square section is simulated. In order to confirm the present scheme, experiments are carved out using aluminium at the elevated temperature.

The scattering of an H‐polarized plane wave from an axially slotted infinite cylinder: A dual series approach

The azimuthal current induced by an H‐polarized plane wave with an arbitrary angle of incidence on an infinite cylinder with an infinite axial slot is considered. A system of dual series equations is derived from the modal expansions of the tangential field components by enforcing the electromagnetic boundary conditions. This dual series system is then solved for the modal coefficients with techniques borrowed from the Riemann‐Hilbert problem of complex variable theory. The resulting infinite system of linear equations for the modal coefficients can be handled in an efficient manner. A comparison of the generalized dual series solution with a purely numerical method of moments solution based upon vector and scalar potentials is made. In contrast to this method of moments solution, it explicitly contains the behavior of the solution near the aperture rim and can generate the current values in a shadow region for small to large ratios of cylinder radius to wavelength without additional special considerations.

Open-Ended Circular Waveguide with a Curved Corrugated Disk at its Aperture as a Diathermy Applicator

A direct-contact type of diathermy applicator consisting of an open-ended circular waveguide loaded with a curved (concave) corrugated disk at its aperture is described. The waveguide is dimensioned to support the dominant TE/sub 11/ mode. Performance characteristics of this applicator are compared with those of an identical structure having a flat corrugated disk at the aperture rim [1]. Also, the superiority of the proposed applicator in respect of improved beam symmetry and reduced edge-diffraction effect (leakage) is indicated. Experimental results on the near-field distributions in the principal planes of a test applicator are presented and are compared with relevant results obtained from a flat-disk loaded applicator [1] of identical dimensions. Also, to get improved input VSWR performance (VSWR less than 1.6), off-setting the corrugated disk (flat or curved) behind the aperture is suggested and is also demonstrated experimentally. Furthermore, as a design flexibility and to simplify fabrication, filling the corrugation grooves with a suitable dielectric material is suggested and explained. Lastly, the feasibility of using a simple corrugated circular waveguide as an alternative direct-contact type of applicator is discussed.

Minimum-noise maximum-gain telescopes and relaxation method for shaped asymmetric surfaces

For future low-noise receivers, future radio telescopes must avoid the pickup of ground radiation, and for obtaining the maximum gain with a given diameter, they should be shaped two-mirror systems. A configuration with a double asymmetry is suggested, which would improve the signal-to-noise ratio by a factor of two to three. The asymmetric shaping problem is solved by a method of iterative relaxation. Starting with an original paraboloid-hyperboioid system, the primary surface is changed in each iteration for a gradual approach to the illumination demand, including the boundary condition that the circular aperture rim is represented by an exact circle of the feed pattern, and an exactly focussing secondary mirror is calculated in each iteration. The well-documented Fortran program can be obtained from the National Radio Astronomy Observatory (NRAO). All calculated examples, for various strongly asymmetric configurations, converged after 6-10 iterations (within a few minutes of computer time) to an aperture efficiency of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\eta \geq 99.97</tex> percent (for geometrical optics). The maximum change of the primary surface, from the original paraboloid to its final shape, was always less than 3 percent of the aperture diameter.

Cost of paraboloidal collectors for solar to thermal electric conversion

Much is underway concerning technical and design aspects of solar collectors and associated costs of point designs. But little has been published on the tradeoffs between alternative designs and large-scale manufacturing possibilities. To fill this gap, close interchange is needed among those versed in technical and systems design, manufacturing and costing. The solar to thermal electric power study funded by the National Science Foundation and carried out by Colorado State University and Westinghouse Electric Corporation has led to the assembly of such a team. This team is obtaining new data on large-scale production of concentrating collectors of widely varying parameters. Investment and other costs of paraboloidal collectors with various aperture widths, reflectivities, rim angles, and accuracies of contour and tracking are reported herein. In studying alternative design-cost-performance relationships, emphasis is placed on breadth of coverage rather than on detailed accuracy. Alternative aperture widths led to preferences for different production processes that are not particularly sensitive to changes in rim angle or reflectivity. Significant cost relationships in the manufacture, installation and maintenance of collectors were found; other relationships are less certain. Besides the above, study results indicate directions for further study.

The diffraction of an electromagnetic wave by a large aperture

With the aid of methods previously developed, an approximate expression is obtained for the difference from unity of the transmission coefficient for plane waves at normal incidence of a large aperture of rather general form in a plane perfectly-conducting screen. The coefficient is expressed in the form of one or more line integrals taken around all (or part) of the aperture rim. These may be evaluated analytically in certain cases, e.g. a circular or elliptical aperture. In the former case the result agrees with that derived elsewhere; the ellipse is considered in some detail in the present paper, and the transmission coefficient is evaluated for a range of eccentricities. The results appear to be in qualitative agreement with the limited experimental data available.