Octagonal Shape Research Articles

Attenuation Correction Using Template PET Registration for Brain PET: A Proof-of-Concept Study.

NeuroLF is a dedicated brain PET system with an octagonal prism shape housed in a scanner head that can be positioned around a patient's head. Because it does not have MR or CT capabilities, attenuation correction based on an estimation of the attenuation map is a crucial feature. In this article, we demonstrate this method on [18F]FDG PET brain scans performed with a low-resolution proof of concept prototype of NeuroLF called BPET. We perform an affine registration of a template PET scan to the uncorrected emission image, and then apply the resulting transform to the corresponding template attenuation map. Using a whole-body PET/CT system as reference, we quantitively show that this method yields comparable image quality (0.893 average correlation to reference scan) to using the reference µ-map as obtained from the CT scan of the imaged patient (0.908 average correlation). We conclude from this initial study that attenuation correction using template registration instead of a patient CT delivers similar results and is an option for patients undergoing brain PET.

Effect of Structural Shape on Seismic Response of Air Traffic Control Tower

Air Traffic Control Towers (ATCT) is one of the obligatory infrastructures for the airport to control the takeoff and landing of airplanes. The primary purpose of ATCT is to prevent collisions and shape the flow of air traffic. Due to a lack of adequate information about the seismic analysis, the performance of ATCT is generally considered to be the same as that of normal structures. However, the performance and demands of ATC towers differ significantly from common structures. In the present study, the analysis of ATCT for different structural shapes (viz., Hexagonal, Octagonal, Pentagonal, Square) with a height of 55m has been investigated. The structural performance of these models has been studied by different time history analysis using commercial software ETABs. The results exhibited that the performance of octagonal and hexagonal configurations was effectively better for seismic loads as compared to the pentagonal and square configuration in respect of story displacement, story drifts, story shear, and time periods. The seismic analysis also shows that the octagonal shape attracted larger base shear than pentagonal, hexagonal, and square shaped ATCT. However, due to more lateral resisting capacity, the drifts and displacements are found to be least.

Performance evaluation of composite concrete-filled steel tube columns by steel fibers and different cross-section shapes: Experimental and numerical investigations

Increasing the load-bearing capacity of columns without increasing their dimensions has become an essential issue for engineers. Concrete-filled steel tube (CFST) column is one of the common techniques used in different constructions. This study aims to assess the influence of steel fibers (SF) on the uniaxial performance of CFST columns to improve their behavior. 27 specimens are produced and tested under a uniaxial compressive load. Specimens are made with three cross-section shapes: circular, rectangular, and octagonal. Also, steel fibers are added at the three-volume percentages of 0%, 1%, and 2%. Low, normal, and high-strength concrete is used to manufacture concrete columns to consider the influence of compressive strength. The bearing capacity, load-axial shortening curves, and axial-hoop strain performance of columns are measured. Also, the obtained outcomes are compared with the requirements of current design codes and previous models. Based on the obtained results, new models are developed to predict the uniaxial bearing capacity of CFST columns with different concrete core compressive strengths, cross-section shapes, and SF contents. The results indicated that adding SF led to changing the softening behavior of the column to the hardening behavior due to raising the axial compressive strength of the concrete core. Nonetheless, this impact is more significant in CFST columns with octagonal and square cross-section shapes. Additionally, the proposed formulas in this study, with high accuracy, could be employed to predict the uniaxial bearing capacity of CFST columns with different concrete core compressive strengths, cross-section shapes, and SF contents.

EFFECT OF VERTICAL POSITION OF HEATED SQUARE OBSTACLE ON NATURAL CONVECTION IN POROUS CAVITIES SATURATED BY A NANOFLUID USING BUONGIORNO’S TWO PHASE MODEL

Laminar flow, heat transfer and mass transfer of nanofluid in a porous medium have been studied using Buongiorno’s two phase model. The porous medium in place is a non-uniform octagonal shape. In order to increase the rate of heat transfer within the porous cavity, it has been equipped with a heated square at different vertical positions from position 1 (P1) to position 5 (P5). The left wall of this cavity is maintained at a high temperature and a unit volume fraction; whereas the right wall is exposed to a low temperature and a canceled volume fraction, and the other walls have been assumed to be adiabatic. The purpose of this paper is to highlight the effect of the heated square at different vertical positions on the evolution of the hydrodynamic, thermal and mass profiles taking into account the influence of certain parameters, such as: Rayleigh number (102≤Ra≤104), Darcy number (10-6≤Da≤10-2), thermophoresis ratio (0.1 ≤ Nt ≤ 1), buoyancy ratio (0.1 ≤ Nr ≤ 1), Brownian motion ratio (0.1 ≤ Nb ≤ 1) and Lewis number (0.1 ≤ Le ≤ 1). The physical phenomenon studied is governed by the Navier-Stokes equations coupled with the energy equation and the mass conservation equation (continuity of nanoparticles). These differential equations of boundary conditions are solved using the finite element method. The results show that an increase in the Rayleigh number and the Darcy number improves natural convection, leading to an increase in the Nusselt number at the square. It is also found that the lowest values of the Nusselt number are located at the extremities of the cavity while the highest are located at the intermediate position between the positions P3 and P4 regardless of the values of the different parameters. On the other hand, an increase in the Darcy number leads to an increase in the vertical and horizontal velocity where the highest values are located at position P4.

Numerical study on the flow characteristics of pressurized hydrogen leaking into the confined space through different shaped orifices

The safety concerns associated with accidental hydrogen leakage remain a challenge. Although numerous studies have been carried out on the flow behavior of compressed hydrogen leaking in unconfined spaces, the knowledge of the flow characteristics when it leaks into confined spaces through irregular holes is lacking. Therefore, this study uses the three-dimensional Large-Eddy Simulation (LES) model to simulate high-pressure hydrogen leakage in a confined space. Effects of the leakage hole shape on the flow features are investigated, including the circle, square, and triangle with the same equivalent area. Results indicate that the Mach disk shows circular, hexagonal, and octagonal shapes depending on the leakage port geometry. When the leak hole shape is square and triangular, the distribution of pressure waves deflects 45° and 60° near the hole, respectively. It means that non-circular holes affect the pressure distribution after hydrogen leakage. In addition, changing the shape of the leak hole results in a difference in hydrogen jet morphology. Compared to circular jets, in square and triangular jets, the jet boundary narrows along the diagonal plane and the gravity plane, respectively. It indicates that leakage ports with sharp corners can complicate the flow. Therefore, it is essential to consider the influence of the leakage port shape when performing a risk assessment of high-pressure hydrogen leaks in confined spaces.

Morphological Analysis of Laser Surface Texturing Effect on AISI 430 Stainless Steel.

Laser surface texturing (LST) is a method to obtain micro-structures on the material’s surface for improving tribological performances, wetting tuning, surface treatment, and increasing adhesion. The material selected for LST is AISI 430 ferritic stainless steel, distinguished by the low cost in manufacturing, corrosion resistance, and high strength at elevated temperature. The present study addresses the morphology of new pattern designs (crater array, ellipse, and octagonal shapes). The patterns are applied on the stainless-steel surface by a non-contact method with high quality and precision nanosecond pulsed laser equipment. The investigation of laser parameter influence on thermal affected area and micro-structures is accomplished by morphological and elemental analysis (SEM + EDX). The parameters of the laser micro-patterning have a marked influence on the morphology, creating groove-type sections with different depths and recast material features. From the SEM characterization, the highest level of recast material is observed for concentric octagon LST design. Its application is more recommended for the preparation of the metal surface before hybrid welding. Additionally, the lack of the oxygen element in the case of this design suggests the possible use of the pattern in hybrid joining.

THE IDENTITY OF THE HYBRIDITY OF THE CHINESE MUSLIM MOSQUE IN SEMPUSARI, JEMBER (CHARLES SANDERS PIERCE SEMIOTIC ANALYSIS)

Abstract: Religion and culture are two things that are always interesting to observe. It is difficult to imagine religion without culture or vice versa, culture without religion. In human history, religion and culture work hand in hand to preserve society with various legal arrangements. In Islam contains a number of teachings that are not limited to aspects of civilization. One example is the Muhammad Cheng Hoo mosque in Sempusari Jember, whose architecture is combined with Chinese, Javanese and Arabic culture. The Chinese identity was reborn after a post-reformation that was lost for decades. This study aims to describe the architectural meaning in the Cheng Hoo mosque in Sempusari Jember. To get the desired results, this research uses qualitative research with a descriptive approach, based on observation, interview, and documentation techniques. Meanwhile, to find out the existing cultural values, the writer uses the theory of cultural semiotics by Sander Pierce. The findings obtained from this study are a study of the meaning of cultural semiotics in the Cheng Hoo mosque architecture in Sempusari Jember including (a) the colors used. (b) An octagonal shape located in the middle of the Cheng Hoo Mosque. (c) Tower consisting of 5 flats. (d) the meaning of the lantern. (e) The shape on the walls of the mosque on the part of the imam and pulpit. (f) Flower motif. (g) the writing on the door of the mosque in Roman kanji style.

Značilnosti stabilizacij trigonometričnih točk na Primorskem

An analysis of the present-day geodetic marks representing trigonometric points of the 2nd and 3rd order was carried out in the area of Slovenia that was part of the Kingdom of Italy between 1920 and 1947. By reviewing topographies, photographs on hribi.net and sample field surveys, we identified, among the 52 2nd order points, 16 points that had the Italian type of geodetic marks and 6 points with even older types of geodetic marks, dating back to the Austro-Hungarian Monarchy. Among the 407 3rd order points, we identified 68 Italian geodetic marks and 15 even older ones. The so-called Italian type of geodetic mark can be recognised as a concrete pillar with a square or octagonal shape, about 1 m high, with a diameter of 40 to 70 cm. The even older geodetic marks are carved from natural stone. These often have the dual function of being a trigonometric point mark and a land cadastral mark, indicating the boundary of cadastral municipalities. We also investigated the eccentric metal target signals erected in 1996, and those between 1995 and 1997, which were an additional post- consolidation of the existing granite trigonometric marks installed after the Second World War. Finally, we highlight the potential of these old geodetic marks in the design and planning of new measurements in the future.

Effect of Structural Shape on Seismic Response of Air Traffic Control Tower

Abstract: Air Traffic Control Towers (ATCT) is one of the obligatory infrastructures for the airport to control the takeoff and landing of airplanes. The primary purpose of ATCT is to prevent collisions and shape the flow of air traffic. Due to a lack of adequate information about the seismic analysis, the performance of ATCT is generally considered to be the same as that of normal structures. However, the performance and demands of ATC towers differ significantly from common structures. In the present study, the analysis of ATCT for different structural shapes (viz., Hexagonal, Octagonal, Pentagonal, Square) with a height of 55m has been investigated. The structural performance of these models has been studied by different time history analysis using commercial software ETABs. The results exhibited that the performance of octagonal and hexagonal configurations was effectively better for seismic loads as compared to the pentagonal and square configuration in respect of story displacement, story drifts, story shear, and time periods. The seismic analysis also shows that the octagonal shape attracted larger base shear than pentagonal, hexagonal, and square shaped ATCT. However, due to more lateral resisting capacity, the drifts and displacements are found to be least. Keywords: Air Traffic Control Tower, Structural shape, Structural configurations, Time history Analysis

Crashworthiness comparison of two-dimensional cellular sandwich cores under axial compression load

Structures that absorb energy efficiently have applications in many fields. In this paper, thin-walled structures with hexagonal, circular, X-type, square and octagonal cross-sectional shapes subjected to quasi-static compression are analyzed using FEM simulation. The results showed that the shape of the cross section has a significant effect on the mechanical properties and energy absorption capability. All structures of various cross-sectional shapes show almost the same specific stiffness, but the specific strength varies with the corner numbers. For energy absorption, the hexagonal structure exhibits the best specific energy absorption and crush stress efficiency among all considered structures.

The Philosophy of Mixed Martial Arts

Mixed Martial Arts (MMA) is a combat sport incorporating techniques from other combat sports (such as boxing and Muay Thai) and from traditional martial arts (karate, jiu-jitsu, etc.). It is a recent sport, dating only to the early 1980s, although there are historical antecedents in ancient Greece and elsewhere. As originally conceived MMA had relatively few constraints on the techniques that fighters could use. (Only biting, eye gouging, and groin strikes were forbidden.) The sport was sometimes marketed as “no holds barred” fighting, or a close approximation of street fighting. Gradually more rules were introduced, both for reasons of safety and to broaden the sport’s appeal. Fighters wear specialized gloves and other protective gear, and fights take place in a ring or enclosed area that is sometimes (but not always) an octagon shape. Professional MMA fighters have typically trained in a number of different fighting systems or martial arts. In...

変形するノズルから流出する噴流

The purpose of this study is to control the jet diffusion by using the deforming nozzle. The shape of polypropylene nozzle can change from square shape into the cruciform shape or the octagonal shape smoothly. The velocity measurement of the jet flow was performed using X-type hot wire sensors and the constant temperature anemometer. The mean flow properties of the jet flow, such as the velocity distribution and the half value width were obtained. Moreover, to catch the flow feature of the jet near the nozzle the flow visualization was conducted by using the Laser Light Sheet and the high speed video camera. As a result, it has been found that the diffusion of the jet issuing from the deforming nozzle is promoted, comparing with the case of the square nozzle jet

Flow Visualization of Jet Flow Issuing from Pentagonal Duct

The purpose of this study is to control the jet diffusion by using the deforming nozzle. The shape of polypropylene nozzle can change from square shape into the cruciform shape or the octagonal shape smoothly. The velocity measurement of the jet flow was performed using X-type hot wire sensors and the constant temperature anemometer. The basic characteristics of the jet flow, such as the velocity distribution and the half value width were obtained. Moreover, to catch the flow feature of the jet near the nozzle the flow visualization was conducted by using the Laser Light Sheet and the high speed video camera. As a result, it has been found that the diffusion of the jet issuing from the deforming nozzle is promoted, comparing with the case of the square nozzle jet.

Optimization of single point incremental forming process through experimental investigation on SS 304 DDQ steel

Sheet Metal Single Point Incremental Forming (SPIF) is a flexible novel forming process to meet the growing demands of the manufacturing industry and the development of latest sheet metal based products. The SPIF process is used for rapid prototyping and sheet metal forming in batch production and is more economical than traditional stamping processes. The current study looks into the effects of process variables such as rpm, feeds, and step size on forming time, surface quality, and formed part thinning. Octagonal shape of part is formed from SS 304 DDQ steel sheet of 1 mm thickness. This process is performed by the CNC Vertical Machining Center (VMC). For this task, the fixture used for forming and tools with hemispherical edges are designed and manufactured. Experiments are performed based on design of experiments using orthogonal L9 arrays with Taguchi methods. The ideal process factors on response, such as forming time, surface roughness, and formed part thinning, were determined using analysis of variance (ANOVA). To determine the optimal level of process parameters, the signal-to-noise ratio (S/N) is used. The results show that step size has the greatest impact on forming time, followed by feed rate and a minimal effect from rotational speed. The feed rate has been found to have the greatest impact on the part's surface roughness, followed by speed and step size. Furthermore, the most important parameter that affects thinning of the created portion is step size, which is followed by rate of feedand spindlespeed in controlling overall variability.

Damage Detection of CFRP Filament Wound Tubes Using Electrical Resistance Measurement

The electrical resistance measurement method was used for damage detection of Carbon Fiber Reinforced Polymer (CFRP) tubes during torsion and flexural loading. The symmetrical convex octagon shape specimens were manufactured using a filament winding technology. The specimens were manufactured with Integrated Loop Technology (ILT) joints at the ends in a single production step. This configuration of tubes with ILT joints allows very effective load transfer and it is also efficient from the manufacturing point of view. This type of components could be used in construction of robotic arms for automated processes. Possible collisions and resulting overloading can cause damage to the composite tubes. Such damage could be overlook due to cabling, coating and casing covering the surface of the robotic arms. In addition to the above, the requirement for a smooth surface must also be met. Therefore, possible way how to easily detect serious damage of CFRP tubes was investigated, together with a testing of a novel approach to an electrical contact manufacturing. The electrical contacts for damage monitoring were made of carbon fiber tows with electrically connected endings. They were integrated to the composite structure during filament winding process. Four specimens were loaded by flexural loading and two specimens were loaded by torsional loading. All specimens were loaded by three cycles of operational loading and then loaded to final fracture. It was shown that the presented type of electrical connection to the structure is feasible, does not disturb the surface of the sample and does not affect the ultimate strength of the specimen. According to our measurements, operational loading could be monitored only to a limited extend using the electrical resistance measurement. This is because the fracture damage caused significant change in measured electrical resistance of the specimen for both torsional and flexural loading. The presented measurement configuration with electrodes made of integrated carbon fibers is suitable for further investigation in the field of fracture damage detection of carbon fiber wound profiles.

Crushing behavior of multi-cell tubes with a novel pattern of design for their cross-section under multiple crushing angles

Crushing behavior of multi-cell tubes with a novel pattern of design for their cross-section is investigated under axial and oblique loads. The tubes have hexagonal, octagonal and decagonal shapes. According to SAW method, the tubes of H-1, O-1 and D-1 show better crushing performance, and the decagonal tube of D-1 is found as the best energy absorber. Multi-objective optimization design of the D-1 is finally provided using NSGA-II and RBF metamodels. The optimal decagonal tube provides on average of 248% and 61% higher SEA and CFE, respectively, compared to the D-0. However, it offers 11% higher PCF than the D-0.

Polished photonic crystal fiber refractive index sensor based on surface plasmon resonance

A polished photonic crystal fiber sensor based on surface plasmon resonance for refractive index (RI) detection is proposed and analyzed by finite element analysis. The design of polishing can greatly increase the birefringence of photonic crystal fiber and ensure a uniform coating film, thus improving sensor performance. The outer air of the structure is arranged in half of an octagonal shape, and the inner layer is arranged in a quadrilateral shape, which can effectively improve coupling strength in the y -polarization direction. The sensor works mainly in visible and infrared wavelengths with a detection range of 1.33 to 1.38. Through analysis of external RI changes, pore structure parameters, and silver mold thickness, the maximum sensitivity is 14800 nm/RIU, maximum amplitude sensitivity is 766.7008 R I U − 1 , resolution is up to 6.7568 × 10 − 6 R I U , and maximum figure of merit is 548.1481. The sensor is suitable for biomedicine, environmental monitoring, chemistry, and other fields.

Study of Pressure Distribution on an Irregular Octagonal Plan Oval-Shape Building Using CFD

This paper aims to study the wind flow characteristics and to analyze the wind pressure distribution on the surfaces around an irregular octagonal plan shape building model. There is a central open space in plan to provide more surface area around the building for natural ventilation. Plan area of the building is 300 m2(excluding the open space) and height is 50 m. Steady state flow of wind with 5% turbulence (moderate turbulence) under atmospheric boundary layer has been taken in the study. Numerical simulation with standard k-e model using ANSYS (CFX) software has been used for the purpose. Flow characteristics has been studied in terms of flow separation, reattachment of flow, creation of wakes and vortices. The surface pressure generated around the model has been studied in terms of coefficient of pressure. The model is symmetrical about both the axes in plan. Hence, study for different wind angle of attacks from 0° to 90° @ 30° interval has been conducted. The flow characteristics and unusual or critical coefficient of pressure on surfaces of the model observed have been discussed. Doi: 10.28991/cej-2021-03091760 Full Text: PDF

The influence of the setup shape of a portable UWB system’s antennas in sport

Ultra-wide band (UWB) technology has become one of the most promising technologies of the future. It seems that the positioning of the antenna set influences the accuracy of the player’s performance. This study was aimed to assess the influence of two different antenna positioning system shapes: (i) octagonal installation and (ii) circular installation. A UWB technology was used to track a healthy and well-trained athlete’s (age: 38 years, mass: 76.34 kg, and height: 1.75 m) positioning. Overall, the data measured showed high accuracy in both shape setups in all trajectories assessed in static and dynamic conditions for all speed thresholds. However, the distance covered during jogging and sprinting showed poor accuracy for both shape setups. Moreover, the data measured showed high test-retest reliability and inter-device agreement in the static condition, regardless of the antenna setup shape. In conclusion, both the octagonal and circular antenna setup shape provided accurate data, but the measurement error associated within the setup shape seemed slightly different between the two systems.

Wind Effect Analysis of a High-rise Ancient Wooden Tower with a Particular Architectural Profile via Wind Tunnel Test

ABSTRACT Wooden architectural heritage is a symbol of architectural heritage worldwide and has high historical, cultural, and scientific values in Asia countries (e.g., China, Japan, Korea, and Nepal). Wooden pagoda (a kind of tower with multiple eaves in East Asia) serving as one important member of wooden architectural heritages suffers from damages that are caused in various natural disasters such as windstorm, fire, and earthquake due to its long-time service and considerable size. Wind caused damage is one of the most common damages caused by natural disasters, making the structural safety of high-rise wooden pagodas under wind action a major concern in architectural heritage protection. This study analyzes the wind effects on the Yingxian wooden pagoda in China by a wind tunnel test and computes the wind loads on the wooden pagoda. The wind characteristics of wooden the pagoda in a wind tunnel test are presented and compared with modern buildings and other types of wooden architectural heritages. Additionally, this study attempts to analyze the difference of the computed wind loads from the wind tunnel test and from the full-scale measurement. The results reveal that the wind pressure distribution at certain locations are similar to those of modern buildings or other ancient wooden architectures. However, the wind pressure distribution at some locations are distinctive due to the complexity of the architectural profile (e.g., the boundary of the pagoda is an octagon in bird view). The wind load from wind tunnel test are in good agreement with those in full-scale measurement with less than 14% error. This study extends the understanding of the wind effects and structural safety assessment on the high-rise wooden pagoda, providing useful guidelines for structural design (e.g., wind-resistant design) and for structural health monitoring (e.g., service maintenance) to monitor not just the specific wooden pagoda but also other high-rise pagodas, especially the those with top views of octagonal shapes.