Semi Sphere Research Articles

Studies on Reflection Hologram Technology Applied Miniature Hologram Types

Miniature holograms are frequently used for exhibition as pyramid shape. But there is a lack of studies on holograms with various shapes. This study aims to learn about the shapes of miniature holograms where reflection floating hologram technologies are applied. By analyzing the floating hologram types, it aims to verify that the reflection type of floating hologram is suitable for miniature hologram implementation and study suitable types of reflection miniature holograms that are not pyramid shapes. Apart from the pyramid shape hologram frequently used for exhibition, the author studies cone, semi sphere and cylindrical shape holograms and forms them in a vertical structure to support expansion of the screen showing the image. Reflection type f hologram posed light scattering problems in the past, but by attaching a polarization filter to the screen, the effect of light scattering is minimized. A vertical type of hologram causes distortion of image depending on the visual angle of the viewer. In the future, if it is possible to minimize the image distortions, it would be possible to implement expanded shapes.

Oscillating transient flame propagation of biochar dust cloud considering thermal losses and particles porosity

This research investigates the transient flame propagation and oscillation phenomenon in the flame speed of porous biochar dust cloud. Time-dependent mass, momentum and energy equations are solved in the spherical coordinate. The gas phase reaction includes the chemical reactions, thermodynamic properties, and multi-element transition properties. To account for the porosity effects of particles, the biochar dusts are modeled as spherical particles with unlimited number of pores (semi sphere) on the surface. The particle trajectory is governed by the equation of motion. The thermophoretic, gravitational, buoyancy and drag forces are employed in this model. In the energy equation, the absorption and radiation emissions by particles is considered. The results reveal that the inertia differences between the particles and gas causes a difference in the velocities of these two phases at the flame front—which is more evident at the early stages of flame propagation when there is a significant change in the density of dust particles. Moreover, the oscillation is further intensified by enhancing the oxygen concentration due to a higher reaction rate, and, as a result, higher velocity difference between the two phases.

Reversible Ag Electroplating Onto ITO Electrode for Smart Window

Reversible electrochromic mirror by electroplating and electrodissolution of Ag film has been investigated onto transparent ITO electrode. It’s applicable to smart window and thermal management for house and vehicle. In order to form mirror surface of Ag film, Pd nanoparticles were firstly deposited onto ITO electrode by chronopotentiometry at the constant current of -10 mA/cm2 for 0.5 s, resulting in the diameter of Pd nanoparticles of 63 nm and good dispersion from SEM observation and visible light transmittance of around 80 % from UV–vis absorption spectroscopy. Pd nanoparticles are electrochemically stable for electroplating and electrodissolution of Ag film and behave as catalyst for forming Ag film. Without Pd nanoparticles on ITO electrode, the deposited Ag film becomes white surface because of light scattering from less dispersive and quite large Ag semi sphere crystals on the ITO electrode. However, Ag mirror surface was not formed even on the Pd nanoparticle deposited ITO electrode. So, several additive regents were investigated to form Ag mirror surface. At first, as 2-hydroxypyridine (2-HP) is employed as additive, yellow color smooth Ag mirror surface was achieved at the electroplating condition of the constant current of -4 mA/cm2 for 100 s. The SEM observation indicates that Ag crystal grew up anisotropically to form planar crystal. On the other hand, eletrodissolution of Ag film at the constant current of +1 mA/cm2 for 400 s was imperfect to remain residue onto ITO electrode and the color of the Ag plating solution changed from transparent to brown due to the oxidation of 2-HP. Next, as citric acid was used as additive, smooth Ag mirror surface was created by the electroplating condition of the constant current of -4 mA/cm2 for 20 s. The SEM observation shows anisotropical Ag crystal growth as similar as that in the 2-HP additive. The time taking to form Ag mirror state becomes shorter than that in the 2-HP additive because the anisotropy ratio of citric acid would be larger than that of 2-HP. The electrodissolution of Ag film at the constant current of +4mA/cm2 for 20 s shows that it’s almost back to the transparent ITO electrode at the transmittance of ca. 70 %. Repeating property has been tried to be several times so far. We will determine the repeating limit in this system.

Calculation of parameters of drawing-out the half-sphere parts in the stamp with an elastic element

The method of forming parts of a half-sphere type in a stamp, where a die is the generatrix of the part, is presented. This is attained due to the use of an elastic steel element arranged along the puncheon contour in the stamp design. This process scheme makes it possible to combine drawing out and calibration in one stamp. Calibration when drawing out spherelike parts is necessary because of the fact that a large segment free of contact with the puncheon and a die, on which the billet losses stability and starts to corrugate, is formed in a billet. An elastic element made of spring steel and arranged along the contour of a rigid puncheon calibrates the part at the final drawing-out stage. The schematic of stamping for a half-spherical part with relative thickness S' = S/D0 × 100% = 1.5–0.15 is presented in the article. In that work calculations of elastic element’s geometrical parameters were made. To develop semi sphere part from aluminum alloy 5056 with thickness elastic element made of steel 1060 was designed. Dimension of gap between punch and elastic element was determined as well. Maximum values of strengths happened in elastic element during stamping were calculated. It was investigated that elastic element do not have plastic flow deformation. Use of elastic element helps to produce parts with accurate geometrical dimensions and compensate elastic restitution. Also due to increase of friction elastic element allows block weakest section.

SPIRAL PARABOLIC DOME: HISTORICAL STUDIES OF IRANIAN ARCHITECTURE

Ancient Dezful city is located in the SW of Iran (5000BC-2016AC) near Dez River. This spiral domes are used to demonstrate the symbolic special constructions which is similar to the construction of Denial’s holy shrine, the Jewish messenger (500BC), the Lion King Yaghob Saffari’s tomb (800AD) and the Rood-band Syd’s burial place (1409AD). These structures are made by simple local materials. The common materials used are bricks and Sarooj mixture. Sarooj is the main mortar, a man-made concrete. After thousands of years, it still stands all kinds of tension, pressure, wind, rain, conflicts and wars, weapons and rockets effects (1980-1988), and sewage exposure. All bricks were set to demonstrate the cubic elements around the spiral curve. It turns around circles with variable radiuses on the spiral path-line which makes a conic parabolic sharp dome. Two domes constructed in each parabolic dome. The first dome is fixed between the supports that are called the inner dome. It was erected on the semi sphere space. The second dome is constructed by the parabolic conic section to demonstrate a beautiful, cultural and architectural masterpiece of engineering. The Main materials are bricks, dolomite, canes, stone blocks and Sarooj, a special mortar. The height of the Spiral Parabolic Dome (SPD) is about 10m and the radius of the inner dome is measured about 2 m with a ratio of 2.5 that would vary with the Geo-technical conditions and the architectural considerations.

Study of functional characteristics for safety system check valve using scaled model

The paper provides results of experimental scale model studies of functional characteristics of a check valve used in the safety system of a liquid metal cooled reactor. The proposed check valve design with a hollow ball as a blocking element has a number of substantial advantages compared with the most widely spread valves with disc type flaps used as blocking elements. The advantages are valve operation independent of functioning of other safety systems and absence of friction pairs. The need to conduct experimental studies is determined both by the novelty of the proposed check valve design and by absence of verified computational validation methods for functioning of this type of valves. In this connection, the paper presents a computational validation method for hydrodynamic parameters of the proposed check valve design and similitude parameters describing hydrodynamic characteristics of the check valve – numeric values of the similitude parameters were obtained through calculations made by the ANSYSCFX commercial hydrodynamic code. The paper describes the experimental model of the check valve with two alternative options for the blocking element – one in the form of a hollow ball in a support bowl; and another one, in the form of a semi sphere on a guide rod going through the support sleeve on the valve spindle. Provided is a brief description of the test facility. Hydrodynamic characteristics of the check valve model obtained in experimental studies are shown in diagrams as functions of some design and operation parameters of the model.

An Experimental and Computational Fluid Dynamic Study of Axis-Symmetric Coanda Configuration for VTOL MAV Applications

This project is designed to find out a proper shape for the Coanda effect and use them for helping a vertical takeoff vehicle to create additional lift. Experiment and numerical calculations were conducted. The model was set up by placing a propeller at 10 cm above the surface. Shape, height and model with a hold at the center were investigated by ANSYS Fluent. Propeller was simulated by applying actuator disk. First shape is a semi sphere with 50 cm diameter. Second, surface in invert parabolic shape with 50 cm diameter with varying height 15, 25 and 35 cm are considered. The last shape is similar to the second case with 15 and 35 cm height, but it is made hollow by varying the hold's diameter as 7, 11 and 15 cm. The total number of the entire cases is 10. The result shows that the best shape for the Coanda effect is a semi sphere shape but total lift of all models without a hole in the middle, in the first and the second cases, are negative and tend to decline when the height of the shape increases. For the third case, the shape with a height of 35 cm and 15 cm hold diameter has the least negative lift.

Stress State of a Radial Inhomogeneous Semi Sphere under the Vertical Uniform Load

There is a solution of the problem of stress-strain state determining in the radially inhomogeneous concrete semi sphere. The inhomogeneity is induced by the temperature field. The problem reduces to a differential equation system with variable coefficients. The allowance for the variable Young's module lets to arrive to a more accurate solution.

An Investigation into the Use of Industrial Robots for Machining Soft and Low Density Materials with HSM Technique

The needs to comply with an increasingly competitive international market lead industries to some innovative solutions, such as the use of robotic arms as machine tools. Although these solutions present some well known drawbacks, there are some advantages and niches of application where success is possible. The present work investigates the use of such pieces of equipment to machine aluminum alloys AA2024 applying high speed machining (HSM) technique, assessing surface finishing as a function of different orientation angles between end mill and machined surface. It also tests the best condition to machine foam for prototyping applications. Results indicate that the directions close to the normal are the best compromises because of dynamic stability of the robot arm structure and roughness as low as 4 µm Ra are possible to be achieved in aluminum alloys. A complex shape such as a semi sphere can be easily machined in foam for rapid and accurate prototype machining. Surface finishing can be very smooth and well suitable for industrial applications in such materials.

Evaluation and comparison of nasal airway flow patterns among three subjects from Caucasian, Chinese and Indian ethnic groups using computational fluid dynamics simulation

Nasal airflow is one of the most important determinants for nasal physiology. During the long evolution of human beings, different races have developed their own attributes of nasal morphologies which result in variations of nasal airflow patterns and nasal functions. This study evaluated and compared the effects of differences of nasal morphology among three healthy male subjects from Caucasian, Chinese and Indian ethnic groups on nasal airflow patterns using computational fluid dynamics simulation. By examining the anterior nasal airway, the nasal indices and the nostril shapes of the three subjects were found to be similar to nasal cavities of respective ethnic groups. Computed tomography images of these three subjects were obtained to reconstruct 3-dimensional models of nasal cavities. To retain the flow characteristics around the nasal vestibules, a 40 mm-radius semi sphere was assembled around the human face for the prescription of zero ambient gauge pressure. The results show that more airflow tends to pass through the middle passage of the nasal airway in the Caucasian model, and through the inferior portion in the Indian model. The Indian model was found with extremely low flow flux flowing through the olfactory region. The sizes of vortexes near the anterior cavity were found to be correlated with the angles between the upper nasal valve wall and the anterior head of the nasal cavity.

COLLECTION CHARACTERISTICS OF THE SPECIAL FORMS OF THE RETURNED FLOW TYPES OF THE CYCLONE DUST COLLECTORS

Up to this time there have been many papers concerning theoretical and experimental investigations of the collection efficiencies of the axial flow types and of the returned flow types of cyclone dust collectors. However it is very difficult to estimate the collection efficiencies by a numerical analysis, since an exact grasp of the three dimensional turbulent rotational flow and of the behaviours of the fine solid particles on the centrifugal field in the cyclone dust collector can not be obtained. Therefore the authors made two kinds of normal (standard) cyclone dust collectors and five kinds of special forms (cone cyclones, sphere cyclones and a semi sphere and cone combined cyclone) of the returned flow types of the cyclone dust collectors. Then in order to compare the collection efficiencies of the normal cyclone dust collectors with those of the special forms of the cyclones, fine fly-ash particles were used as a test dust. In this paper the characteristics of the collection efficiencies of the above mentioned seven cyclone dust collectors which were related to the centrifugal effect, the feed dust concentration and the feed dust mass per unit time per energy dissipation of air flow are described in detail.