Side Dimension Research Articles

The experimental study of natural convection within the space of a bundle of rectangular sections

Bundles of rectangular steel sections are examples of porous charge that can be found in the industrial practice of heat treatment. Due to voids within the sections, this type of charge is characterized by porosity even exceeding 85%. This makes the thermal properties of these elements, as expressed by the effective thermal conductivity, kef, are totally different from the thermal conductivity of the solid steel. The value of the kef coefficient is determined, inter alia, by the intensity of gas convection within the sections. In view of the geometry of the system under examination, this phenomenon should be treated as convection in horizontal gaps.The presented paper describes experimental studies concerned with the qualitative and quantitative analysis of natural convection occurring within the space of unidirectionally heated rectangular steel sections. For qualitative examination, the Schlieren method was used. While for quantitative examination, was a Poensgen apparatus employed.The primary goal of the studies was to determine the natural convection occurring within the space of heated section bundles and the effect of this phenomenon on the intensity of overall heat flow. The tests were performed for square sections, dimensions 40×20mm, wall thickness 2mm. The quality tests, despite the fact that the critical value of the Rayleigh number was exceeded in the heated sections, did not demonstrate a proceeding convection. This situation was confirmed by the quantitative tests. The latter showed that the direction of the section heating, which determines the possible occurrence of the convection phenomenon or its lack, does not affect the intensity of the total heat flow. It was also pointed out that, for the range of the Rayleigh number which occurs during the heating of square sections of the side dimensions up to 80mm in a chamber furnace, the heat flow related to the occurrence of free convection can be expressed as an intensification of the thermal conductivity in the liquid. For that purpose, one can apply a simple criterion dependence resulting from the similarity theory and the dimensional analysis.

ANATOMICAL VARIATION OF FRONTAL SINUSES EVALUATED BY CT SCAN IN RELATION TO AGE AND SEX IN SULAIMANI CITY

Background
 There are considerable variations in the shape, capacity, and symmetry of the frontal sinuses. Hence, knowledge of frontal sinus anatomy and its variations is important for the diagnosis of sinus pathologies and prior to relevant surgical procedures.
 Objectives
 This study was undertaken to determine the presence of the anatomical variations and morphological characteristics of the frontal sinuses in a population aged between (20-85) years in Sulaimani city.
 Methods
 A review the CT scans of paranasal sinuses, which were taken in axial and coronal sections, of 100 individuals (58 males and 42 females), in the radiology department Sulaimani Teaching Hospital between April 1st 2009 to June 30th 2009.
 Results
 All measurements tended to be larger on the left side and were significantly larger in males than females. There was a significant difference in the anteroposterior dimensions of right and left sides in both sexes.
 Conclusion
 Morphometric features differed significantly in the two sexes at different ages and comparison with previous studies presented great regional variability.

Butterfly gardens

The May problem scenario has students explore what happens to the area of a two-dimensional shape as the side dimensions change but the perimeter remains the same. A fourth-grade teacher from North Carolina explored the task and uncovered her students' misconceptions concerning the corner tiles of the rectangle.

Synthesis and X-Ray Diffraction Analyses of Calcium Hydroxide Nanoparticles in Aqueous Suspension

Calcium hydroxide nanoparticles in aqueous suspensions (also called nanolime) were successfully employed in Cultural Heritage conservation thanks to the ability of favoring readhesion of the pictorial layer on original carbonatic substrates or allowing to a better superficial cohesion and protection of treated stones. In this work, we have synthesized nanolime particles in aqueous suspension by two different methods. The produced particles were characterized in the laboratory, in terms of structural and morphological features, by means of X-Ray diffraction powder (XRD) and by transmission electron microscopy (TEM), respectively. Nanoparticles were crystalline, regularly shaped, hexagonally plated and with side dimensions generally ranging from 300 nm to 30 nm or less. Crystal structure of nanolime particles directly in the aqueous suspension, has been also analyzed by synchrotron diffraction from X-ray synchrotron radiation (SR-XRD); data have been analyzed by means of the Rietveld method and we have investigated the structure of Ca(OH)2 particles in suspension in terms of cell parameters, atomic coordinates, bond lengths and angles.

Synthesis of Ca(OH)<sub>2</sub> Nanoparticles Aqueous Suspensions and Interaction with Silica Fume

In this work, interaction at ambient temperature between silica fume and artificially produced Ca(OH)2 nanoparticles by two different methods was analyzed. Initial products and formed hydrated phases were characterized by several investigations including X-ray diffraction, thermal analyses, transmission and scanning electron microscopy. Synthesized Ca(OH)2 nanoparticles appeared regularly shaped and hexagonally plated, with side dimensions from 200nm to less than 20nm. Characterization analyses showed that, by reducing particles dimensions, calcium silicate hydrate phase formation was evident already after 7 day of hydration and a nearly complete consuming of free Ca(OH)2 after 28 days was observed. Besides, formed hydrate phases showed a highly wrinkled layer with marked crumple and rough-edge surfaces.

Failure indentation analysis of composite sandwich plates via hierarchical models

In this study, an indentation failure analysis of sandwich composite plates via several higher-order theories is presented. The unified formulation by Carrera is adopted in order to derive displacement based or mixed, refined theories based on an equivalent single layer approach or a layerwise one. In this manner, out-of-plane normal and transverse shear stresses responsible for the indentation failure can be accurately described. A closed form, Navier-type solution is assumed. Simply supported plates made of fibre-reinforced polymeric skins and foam cores are investigated. The side-to-thickness ratio, a/ h, and the indenter side dimension are considered as analysis parameters. The effect of skins' lamination and thickness is also investigated. Failure indentation is described in terms of failure loading value and failure position. The variation of displacement and stress fields near the indentation area are also presented. The accuracy of the proposed theories is assessed towards Pagano's three-dimensional exact solution. The obtained results show that higher-order models are required to accurately describe the indentation failure of sandwich plates.

A mathematical model on lateral temperature profile of buoyant window spill plume from a compartment fire

A Gaussian-based mathematical model is theoretically brought forward to describe the lateral temperature profile (in the direction normal to the façade wall) of a spill buoyant plume from window of a compartment fire. The model is built up physically based on that this buoyant plume is conceptually produced by a rectangular fire source with characteristic side dimensions of ℓ1 (beside wall, physical length scale related to the effective area of the outflow) and ℓ2 (normal to wall, physical length scale representing the length after which the outflow turns from horizontal to vertical due to buoyancy) sitting beside an adiabatic façade wall at the neutral plane height of the window. A deduced length scale, by accounting for the entrainment of air mass flow rate into the plume from the non-constrained sides, is brought forward to characterize the effective plume thickness in the direction normal to the façade wall, which will be used in the Gaussian profile function. Experiments are carried out in an experimental device to validate the model developed for six different windows. Results show that the length scale proposed for describing the effective plume thickness can successfully collapse the experimental data of different total heat release rates for various window geometries, and the proposed Gaussian-based model can predict the lateral temperature profile measurements. Furthermore, an exponential function is proposed for the parameter β in the Gaussian profile of such a spill plume in relation to the window aspect ratio (H/W).

Gender differences in experiences of ART services in South Africa: a mixed methods study

A mixed methods study exploring gender differences in patient profiles and experiences of ART services, along the access dimensions of availability, affordability and acceptability, in two rural and two urban areas of South Africa. Structured exit interviews (n = 1266) combined with in-depth interviews (n = 20) of women and men enrolled in ART care. Men attending ART services were more likely to be employed (29%vs. 20%, P = 0.001) and were twice as likely to be married/co-habiting as women (42%vs. 22%P = 0.001). Men had known their HIV status for a shorter time (mean 32 vs. 36 months, P = 0.021) and were also less likely to disclose their status to non-family members (17%vs. 26%, P = 0.001). From both forms of data collection, a key finding was the role of female partners in providing social support and facilitating use of services by men. The converse was true for women who relied more on extended families and friends than on partners for support. Young, unmarried and unemployed men faced the greatest social isolation and difficulty. There were no major gender differences in the health system (supply side) dimensions of access. Gender differences in experiences of HIV services relate more to social than health system factors. However, the health system could be more responsive by designing services in ways that enable earlier and easier use by men.

Through wafer via holes manufacturing by variable isotropy Deep RIE process for RF applications

This paper reports a method on the manufacturing of through silicon wafer via holes with tapered walls by Deep Reactive Ion Etching using the opportunity to change the isotropy in the DRIE equipments during processing. By using consecutively anisotropic and isotropic etching steps it is possible to enlarge the dimension of via holes on one side of the wafer, while on the other side dimension is set by the initial etching window. The optimized process was used to obtain via’s with a good control over the walls angles for two etching windows sizes (100 and 20 μm respectively) on 300 μm thick silicon wafers. After process optimization, a deviation smaller than 10% of the manufactured via holes across the wafers was observed for the designed walls angles of 11.3° and 21.8°. Barrier and seed layers were deposited in via’s performed by Physical Vapor Deposition techniques with a very good coverage of the walls. Finally, gold electroplating was used to fill the narrow part of via’s.

EQUIVALENT CIRCUIT ANALYSIS OF RIDGE-LOADED FOLDED-WAVEGUIDE SLOW-WAVE STRUCTURES FOR MILLIMETER-WAVE TRAVELING-WAVE TUBES

In this paper, a new simple equivalent circuit model for analysis of dispersion and interaction impedance characteristics of ridge-loaded folded-waveguide slow-wave structure is presented. In order to make the computational results more accurately, the efiects of the presence of the beam-hole and discontinuity due to the waveguide bend and the narrow side dimension change of this kind of structure were considered. The dispersion characteristics and the interaction impedance are numerical calculated and discussed. The analytical results agree very well with those obtained by the 3-D electromagnetic high-frequency simulation software. It is indicated that the equivalent circuit methods are reliable and high e-ciency.

Two-dimensional manipulation of micro particles by acoustic radiation pressure in a heptagon cell

An acoustic particle manipulation system is presented, using a flexible printed circuit board formed into a regular heptagon. It is operated at 4 MHz and has a side dimension of 10 mm. The heptagonal geometry was selected for its asymmetry, which tends to reduce standing wave behavior. This leads to the possibility of having fine control over the acoustic field by varying the output phases of the transducer elements. Configurations with two and three active transducers are demonstrated experimentally. It is shown that with two transducers, the particles align along straight lines, the position of which can be moved by varying the relative excitation phases of the two transducers. With three active transducers, hexagonal-shaped patterns are obtained that can also be moved, again according to the phase of the excitation signals. Huygens' principle-based simulations were used to investigate the resultant pressure distributions. Good agreement was achieved between these simulations and both Schlieren imaging and particle manipulation observations.

Synthesis of Ca(OH)2 nanoparticles with the addition of Triton X-100. Protective treatments on natural stones: Preliminary results

a b s t r a c t Calcium hydroxide is typically used in Cultural Heritage conservation for superficial protective treatments thanks to its conversion into calcium carbonate. Calcium carbonate is, in fact, compatible with many carbonate-based architectonic surfaces, because its characteristics are similar to those of the restored materials. In order to improve calcium hydroxide treatments, Ca(OH)2 particles with sub-micrometric dimensions (nanolimes), are synthesised by a chemical precipitation process: a sodium hydroxide solu- tion, used as precipitator, is added, drop by drop, to a calcium chloride one. In this paper, a nanometric calcium hydroxide, to be used in stones treatment, is produced adding in the initial solutions a surfac- tant agent (Triton X-100); the solutions are then mixed together simultaneously, drastically reducing the time needful for preparation. Different contents of surfactant are employed, and the influence on particles dimension and carbonatation process is analysed too. The obtained Ca(OH)2 nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffrac- tion (ED). The Ca(OH)2 nanoparticles are regularly shaped, hexagonally plated and with side dimensions less than 200 nm: in particular, increasing the surfactant content, the particle dimension reaches values until 20 nm. Comparing nanolime suspensions obtained without and with the addition of the surfac- tant agent, the last ones have comparable, if not better, performances in terms of average particle size and morphology, crystallinity and reactivity. Afterwards, the alcoholic nanolime suspension obtained by using Triton X-100 is applied on some natural stones; in fact, the aim of this section is to compare the obtained results with those achieved using a nanolime synthesised without the surfactant agent. To eval- uate the treatment effectiveness in a preliminary way, standard tests are performed and compared with the same tests previously obtained by the nanolime synthesised without the surfactant agent: Scotch Tape Test and capillarity test.

Convective heat transfer around a triangular cylinder in an air cross flow

Two dimensional laminar forced convection heat transfer around horizontal triangular cylinder in air is investigated numerically. Equilateral triangular cylinder of different side dimensions and configurations are examined under laminar conditions (Re ≤ 200). Two configurations of the triangular cylinders are considered; one when the vertex of the triangle facing the flow and the other when the base of the triangle facing the flow. The computational procedure is based on the finite volume technique. Results are presented in the form of streamline and temperature contour plots around the circumference of the cylinder. Comprehensive discussion is also reported about the development of wakes at the rear of the cylinder for both configurations. Critical Reynolds number for both vertex facing and base facing flow are obtained as 38.03 and 34.7 respectively. Furthermore, heat transfer data are generated and presented in terms of the average Nusselt numbers versus the Reynolds numbers. The drag coefficient is also presented versus Reynolds number and validated by comparison with the available data in the literature. General correlations of Nusselt numbers are obtained for Re ≤ 200 to cover the two investigated triangular configurations. A general correlation for each configuration is obtained and compared with the previous available results.

Multifunctional nanocomposite membrane for chemomechanical transducer

We fabricated a novel chemomechanical transducer by using the multilayered nanocomposite membrane composed of layer-by-layer assembled polymers and single-walled carbon nanotubes (SWNTs). The nanomembrane with SWNT layer embedded in it plays multifunctional roles in chemomechanical sensing such as deformable structure under surface stress, electrode for capacitance measurement, and self-heating for biochemical reactions. The thickness of the nanomembrane is 26 nm and it can be suspended over a large square opening with the side dimension of 120 μm. The fabrication is entirely based on the conventional micromachining without any cumbersome processes such as floating and picking up nanomembranes. The nanomembrane transducer integrated with sensor components for capacitive readout and microfluidic channels is utilized to detect anthrax DNA. The nanomembrane transducer is able to selectively detect up to 0.1 μM of target DNA. The assay platform of the nanomembrane transducer offers valuable attributes such as short detection time (a few hundred seconds) and portability. It is demonstrated that the nanomembrane transducer has an applicability to a fast and portable DNA detection platform with self-heating capability for chemical and biological reaction.

Convective coherent structures in a Hele-Shaw cell

Convective processes related to the onset of chaotic flows in a Hele-Shaw cell have been theoretically and experimentally studied. The properties of various modifications of a specific pulsation regime, in which certain characteristics exhibit chaotization with increasing Rayleigh number while the flow pattern remains statistically reproducible and retains a regular character, have been determined for the cavities with various ratios of the dimensions of wide sides. An analogy is established that allows pulsating vortices in the flow to be treated as simple coherent structures of a convective nature.

Lignin and carbohydrate variation with earlywood, latewood, and compression wood content of bent and straight ramets of a radiata pine clone

Abstract Changes in lignin and carbohydrate content with radial direction, growth-layer number, compression wood (CW) severity, and earlywood (EW) and latewood (LW) origin are described for one near-ground position in each of a severely bent and a nominally straight ramet (tree) of a clone (genotype) of Pinus radiata. Bark-to-bark strips were taken through the pith and the longest radial dimension of the CW side of the discs. Separate EW and LW samples were obtained for most growth layers, yielding a total of 95 samples. Differences in lignin and carbohydrate content between EW and LW were large where CW formation was moderate and small where it was severe. Mannose content was consistently different in the EW and LW of opposite wood (OW) and CW. Results suggested that the inner juvenile wood of OW rings might contain either a galactose-rich galactoglucomannan or a β-1,4-galactan. Consideration of all 95 samples showed that although the contents of galactose, lignin, glucose, and mannose were linearly and strongly correlated with one another, their relationship with xylose and arabinose content was non-linear.

Effect of shear on deflection and buckling of beams and plates

The paper deals with the influence of shear stresses on bending and buckling of beams and plates of composite materials employing the hypothesis of ‘straight line’. It is assumed that a set of points lying on a line perpendicular to the neutral surface (the mid-plane) before deformation remains on the line and this line is non-perpendicular to the neutral surface after a load's application. This non-orthogonality is caused by the presence of shear stresses. Thus, this approach does not require the section to be normal to the neutral surface as in the classic Kirchhoff hypothesis. It is shown that the latter is inconsistent with the existence of shear stresses. The corresponding differential equations are derived from the non-linear differential equations of the theory of elasticity in Cartesian coordinates. This allows well-founded simplification of the equations for different partial cases and also correct determination of the sections' rotation angles in the equations for buckling. Several solutions for bending and buckling of beams and plates are given while considering the effect of shear stresses. Formulae are derived for the Euler force of compressed beams and simply supported orthotropic plates, which allows calculation of the error resulting from the application of the Kirchhoff hypothesis. For example, it is shown that for h/b < 0.1 (h = plate thickness, b = dimension of smallest side) the error is smaller than 5% and it does not depend on the plate's aspect ratio. Also, a solution is found for bending strength of beams and orthotropic plates subjected to the arbitrarily distributed lateral pressure considering the effect of shear stresses. Formulae for the deflection in the plate's centre are derived as well as for calculating the error when the classic Kirchhoff hypothesis is applied.

E-Learning 학습자 만족도 영향요인에 관한 연구

As many universities introduce e-Learning classes as formal courses, numerous research topics relating to c-Learning such as, defining e-Learning, identifying factors affecting successful e-Learning deployment and examining relationships between the factors in e-Learning classes need to be focused on. However, most researches thai have been undertaken only consider the positive side or right functional dimension. This can result in e-Learning dissemination at universities being overlooked. In accordance with this indispensability, the negative factors, which are potentially inherent in e-Learning learner's perception and affect personnel e-Learning acceptance in university classes need 10 be acknowledged. The purpose of this study was to identify the negative factors affecting personnel e-Learning acceptance and to analyze the interrelation among the factors in this research model. The two independent variables avoidable convenience and reliant convenience, based on pilot test results, and self-efficacy and perceived playfulness, based on the relevant literature, are used to examine the research model. The research problem was tested with data collected from 446 respondents in 12 universities. This study developed and empirically analyzed a model representing the relationship by using the Structural Equation Model. The major findings of this study are, firstly, that the higher reliant convenience is negatively affecting the degree of system use and learner satisfaction, whereas avoidable convenience is only affecting the learner satisfaction. Secondly, the higher self-efficacy and stronger perceived playfulness affects the degree of system use as well as learner satisfaction. Finally, the degree of system use affects the learner satisfaction.

Various-Shaped Uniform Mn3O4 Nanocrystals Synthesized at Low Temperature in Air Atmosphere

We report a novel and facile method for the synthesis of manganese oxide (Mn3O4) nanocrystals with various sizes and shapes. Mn3O4 nanocrystals were synthesized via a reaction of manganese(II) acetate with water in xylene in the presence of surfactants at the temperature of as low as 90 °C in air atmosphere. Structural characterizations revealed that the synthesized nanocrystals were tetragonal Mn3O4 structure and that they were highly crystalline in spite of the low reaction temperature. The size and shape of the nanocrystals were readily controlled by varying the experimental conditions such as precursors, surfactants, and injection temperature of water. Nanoplates with a thickness of 5 nm and side dimensions of 9, 15, and 22 nm were synthesized using oleylamine as the surfactant. When carboxylic acid was used as the cosurfactant along with oleylamine, spherical nanocrystals were obtained with sizes of 5.5, 6.2, 7.2, 8.5, and 15 nm. Interesting anisotropic nanostructures including nanowires and nanokite...

Design Space for Low Sensitivity to Size Variations in [110] PMOS Nanowire Devices: The Implications of Anisotropy in the Quantization Mass

A 20-band sp(3)d(5)s* spin-orbit-coupled, semiempirical, atomistic tight-binding model is used with a semiclassical, ballistic, field effect transistor (FET) model, to examine the ON-current variations to size variations of [110]-oriented PMOS nanowire devices. Infinitely long, uniform, rectangular nanowires of side dimensions from 3 to 12 nm are examined and significantly different behavior in width versus height variations are identified and explained. Design regions are identified, which show minor ON-current variations to significant width variations that might occur due to lack of line width control. Regions which show large ON-current variations to small height variations are also identified. The considerations of the full band model here show that ON-current doubling can be observed in the ON-state at the onset of volume inversion to surface inversion transport caused by structural side size variations. Strain engineering can smooth out or tune such sensitivities to size variations. The cause of variations described is the structural quantization behavior of the nanowires, which provide an additional variation mechanism to any other ON-current variations such as surface roughness, phonon scattering, etc.