Search results for: rayleigh number

Authors: B. V. Murlimanju, P. J. Jiji, Latha V. Prabhu, Mangala M. Pai

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Background: The scaphoid is the most commonly fractured bone of the wrist. The fracture may disrupt the vessels and end up as the avascular necrosis of the bone. The objective of the present study was to investigate the morphology and number of the nutrient foramina in the cadaveric dried scaphoid bones of the Indian population. Methods: The present study included 46 scaphoid bones (26 right sided and 20 left sided) which were obtained from the gross anatomy laboratory of our institution. The bones were macroscopically observed for the nutrient foramina and the data was collected with respect to their number. The tabulation of the data and analysis were done. Results: All of our specimens (100%) exhibited the nutrient foramina over the non-articular surfaces. The foramina were observed only over the palmar and dorsal surfaces of the scaphoid bones. The foramina were observed both proximal and distal to the mid waist of the scaphoid bone. The foramen ranged between 9 and 54 in each scaphoid bone. The foramina over the palmar surface ranged between, 2-24 in number. The foramina over the dorsal surface ranged between, 7-36 in number. The foramina proximal to the waist ranged between 2 and 24 in number and distal to the waist ranged between 3 and 39. Conclusion: We believe that the present study has provided additional data about the nutrient foramina of the scaphoid bones. The data is enlightening to the orthopedic surgeon and would help in the hand surgeries. The morphological knowledge of the vasculature, their foramina of entry and their number is required to understand the concepts in the avascular necrosis of the proximal scaphoid and non-union of the fracture at the waist of the scaphoid.

Keywords: avascular necrosis, nutrient, scaphoid, vascular

Procedia PDF Downloads 307

Authors: Saieed Akbari, Yousef Bagheri, Amir Hossein Ghodrati, Sima Saadat Akhtar

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Let G be a simple graph with the vertex set V (G) and with the adjacency matrix A (G). The energy E (G) of G is defined to be the sum of the absolute values of all eigenvalues of A (G). Also let n and m be number of edges and vertices of the graph respectively. A regular graph is a graph where each vertex has the same number of neighbours. Given a graph G, its line graph L(G) is a graph such that each vertex of L(G) represents an edge of G; and two vertices of L(G) are adjacent if and only if their corresponding edges share a common endpoint in G. In this paper we show that for every regular graphs and also for every line graphs such that (G) 3 we have, E(G) 2nm + n 1. Also at the other part of the paper we prove that 2 (G) E(G) for an arbitrary graph G.

Keywords: eigenvalues, energy, line graphs, matching number

Procedia PDF Downloads 202

Authors: Qiong Hu, Ming Yue

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Language variation signals the newest usage of language community, which might become the developmental trend of that language. The personal pronoun we is prescribed as a plural pronoun in grammar, but its number value is more flexible in actual use. Based on the homemade Friends corpus, the present research explores the number value of the first person pronoun we in nowadays American spoken English. With consideration of the subjectivity of we, this paper used ‘we+ PCU (Perception-cognation-utterance) verbs’ collocations and ‘we+ plural categories’ as the parameters. Results from corpus data and manual annotation show that: 1) the overall frequency of we has been increasing; 2) we has been increasingly used with other plural categories, indicating a weakening of its plural reference; and 3) we has been increasingly used with PCU (perception-cognition-utterance) verbs of strong subjectivity, indicating a strengthening of its singular reference. All these seem to support our hypothesis that we is undergoing the process of further grammaticalization towards a singular reference, though future evidence is needed to attest the bold prediction.

Keywords: number, PCU verbs, personal pronoun we,

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Authors: Chenxi Zhang, Weizhong Qian, Fei Wei

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Gas solids multiphase flow is common in many engineering and environmental applications. Turbulence and multiphase flows are two of the most challenging topics in fluid mechanics, and when combined they pose a formidable challenge, even in the dilute dispersed regime. Dimensionless numbers are important in mechanics because their constancy can imply dynamic similarity between systems, despite possible differences in medium or scale. In the fluid mechanics literature, the Strouhal number is usually associated with the dimensionless shedding frequency of a von Karman wake; here we introduce this dimensionless number to investigate bubbling in gas solids fluidization. St=fA/U, which divides stroke frequency (f) and amplitude (A) by forward speed (U). The bubble behavior in a large two-dimensional bubbling fluidized bed (500mm×30mm×6000mm) is investigated. Our result indicates that propulsive efficiency is high and energy dissipation is low over a narrow range of St and usually within the interval 0.2Keywords: bubbles, Strouhal number, two-phase flow, energy dissipation

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Authors: B. R. S. Babu, E. Prasad, P. V. Laveen, A. M. Vinodkumar

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Searching the “Island of stability” is a topic of extreme interest in theoretical as well as experimental modern physics today. This “island of stability” is spanned by superheavy elements (SHE's) that are produced in the laboratory. SHE's are believed to exist primarily due to the “magic” stabilizing effects of nuclear shell structure. SHE synthesis is extremely difficult due to their very low production cross section, often of the order of pico barns or less. Stabilizing effects of shell closures at proton number Z=82 and neutron number N=126 are predicted theoretically. Though stabilizing effects of Z=82 have been experimentally verified, no concluding observations have been made with N=126, so far. We measured and analyzed the total evaporation residue (ER) cross sections for a number of systems with neutron number around 126 to explore possible shell closure effects in ER cross sections, in this work.

Keywords: super heavy elements, fusion, evaporation residue, compund nucleus

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Authors: Minho Bang, Seok Min Choi, Jun Su Park, Hokyu Moon, Hyung Hee Cho

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Present study investigates the effect of unsteady wakes on heat transfer in blade tip. Heat/mass transfer was measured in blade tip region depending on a variety of strouhal number by naphthalene sublimation technique. Naphthalene sublimation technique measures heat transfer using a heat/mass transfer analogy. Experiments are performed in linear cascade which is composed of five turbine blades and rotating rods. Strouhal number of inlet flow are changed ranging from 0 to 0.22. Reynolds number is 100,000 based on 11.4 m/s of outlet flow and axial chord length. Three different squealer tip geometries such as base squealer tip, vertical rib squealer tip, and camber line squealer tip are used to study how unsteady wakes affect heat transfer on a blade tip. Depending on squealer tip geometry, different flow patterns occur on a blade tip. Also, unsteady wakes cause reduced tip leakage flow and turbulent flow. As a result, as strouhal number increases, heat/mass transfer coefficients decrease due to the reduced leakage flow. As strouhal number increases, heat/ mass transfer coefficients on a blade tip increase in vertical rib squealer tip.

Keywords: gas turbine, blade tip, heat transfer, unsteady wakes

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Authors: S. Amanpour, F. Mohamadian, S. A. Tabatabai

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With the number of accidents and fatalities in recent years can be concluded that Iran is the status of road accidents, remains in a crisis. Investigate the causes of such incidents in all countries is a necessity. By doing this research, the results of the number and type of accidents and the location of the crash will be available. It is possible to prioritize economic and rational solutions to fix the flaws in the way of short-term the results are all the more strict rules about the desire to have black spots and cursory glance at the change of but results in long-term are desired to change the system or increase the width of the path or add extra track. In general, the relationship between the analysis of the accidents and near police statistics is the number of accidents in one year. This could prove the accuracy of the analysis done.

Keywords: traffic, IHSDM, crash, modeling, Khuzestan

Procedia PDF Downloads 254

Authors: G. Sarojamma, K. Vendabai

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An analysis is carried out to investigate the effect of magnetic field and heat source on the steady boundary layer flow and heat transfer of a Casson nanofluid over a vertical cylinder stretching exponentially along its radial direction. Using a similarity transformation, the governing mathematical equations, with the boundary conditions are reduced to a system of coupled, non –linear ordinary differential equations. The resulting system is solved numerically by the fourth order Runge – Kutta scheme with shooting technique. The influence of various physical parameters such as Reynolds number, Prandtl number, magnetic field, Brownian motion parameter, thermophoresis parameter, Lewis number and the natural convection parameter are presented graphically and discussed for non – dimensional velocity, temperature and nanoparticle volume fraction. Numerical data for the skin – friction coefficient, local Nusselt number and the local Sherwood number have been tabulated for various parametric conditions. It is found that the local Nusselt number is a decreasing function of Brownian motion parameter Nb and the thermophoresis parameter Nt.

Keywords: casson nanofluid, boundary layer flow, internal heat generation/absorption, exponentially stretching cylinder, heat transfer, brownian motion, thermophoresis

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Authors: Munnujahan Ara

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In this paper, we investigate the effect of friendly jamming power allocation strategies on the achievable average secrecy rate over a bank of parallel fading wiretap channels. We investigate the achievable average secrecy rate in parallel fading wiretap channels subject to Rayleigh and Rician fading. The achievable average secrecy rate, due to the presence of a line-of-sight component in the jammer channel is also evaluated. Moreover, we study the detrimental effect of correlation across the parallel sub-channels, and evaluate the corresponding decrease in the achievable average secrecy rate for the various fading configurations. We also investigate the tradeoff between the transmission power and the jamming power for a fixed total power budget. Our results, which are applicable to current orthogonal frequency division multiplexing (OFDM) communications systems, shed further light on the achievable average secrecy rates over a bank of parallel fading channels in the presence of friendly jammers.

Keywords: fading parallel channels, wire-tap channel, OFDM, secrecy capacity, power allocation

Procedia PDF Downloads 481

Authors: Seyed Habib Shojaei, Reza Eivazi, Mir Sajad Shojaei, Alireza Akbari, Pooria Mazloom, Seyede Mitra Sadati, Mir Zeinalabedin Shojaei, Farnaz Farbakhsh

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To study the genetic diversity in rapeseeds and agronomic traits, an experiment was conducted using multivariate statistical methods at Agricultural Research Station of Kashmar in 2012-2013.In this experiment, ten genotypes of rapeseed in a Randomized Complete Block designs with three replications were evaluated. The following traits were studied: seed yield, number of days to the fifty percent of flowering, plant height, number of pods on main stem, length of the pod, seed yield per plant, number of seed in pod, harvest index, weight of 100 seeds, number of pods on lateral branch, number of lateral branches. In analyzing the variance, differences between cultivars were significant. The average comparative revealed that the most valuable variety was Licord regarding to the traits while the least valuable variety was Opera. In stepwise regression, harvest index, grain yield per plant and number of pods per lateral branches were entering to model. Correlation analysis showed that the grain yield with the number of pods per lateral branches and seed yield per plant have positive and significant correlation. In the factor analysis, the first five components explained more than 83% of the variance in the data. In the first factor, seed yield and the number of pods per lateral branches were of the highest importance. The traits, seed yield per plant, and pod per main stem were of a great significance in the second factor. Moreover, in the third factor, plant height and the number of lateral branches were more important. In the fourth factor, plant height and one hundred seeds weight were of the highest variance. Finally, days to fifty percent of flowering and one hundred seeds weight were more important in fifth factor.

Keywords: rapeseed, variance analysis, regression, factor analysis

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Authors: Abhisek Dash

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This study had three neural networks, one for number segmentation, one for number detection and one for number recognition all of which are coupled to one another. All networks were trained on the MNIST dataset and were convolutional. It was assumed that the images had lighter background and darker foreground. The segmentation network took 28x28 images as input and had sixteen outputs. Segmentation training starts when a dark pixel is encountered. Taking a window(7x7) over that pixel as focus, the eight neighborhood of the focus was checked for further dark pixels. The segmentation network was then trained to move in those directions which had dark pixels. To this end the segmentation network had 16 outputs. They were arranged as “go east”, ”don’t go east ”, “go south east”, “don’t go south east”, “go south”, “don’t go south” and so on w.r.t focus window. The focus window was resized into a 28x28 image and the network was trained to consider those neighborhoods which had dark pixels. The neighborhoods which had dark pixels were pushed into a queue in a particular order. The neighborhoods were then popped one at a time stitched to the existing partial image of the number one at a time and trained on which neighborhoods to consider when the new partial image was presented. The above process was repeated until the image was fully covered by the 7x7 neighborhoods and there were no more uncovered black pixels. During testing the network scans and looks for the first dark pixel. From here on the network predicts which neighborhoods to consider and segments the image. After this step the group of neighborhoods are passed into the detection network. The detection network took 28x28 images as input and had two outputs denoting whether a number was detected or not. Since the ground truth of the bounds of a number was known during training the detection network outputted in favor of number not found until the bounds were not met and vice versa. The recognition network was a standard CNN that also took 28x28 images and had 10 outputs for recognition of numbers from 0 to 9. This network was activated only when the detection network votes in favor of number detected. The above methodology could segment connected and overlapping numbers. Additionally the recognition unit was only invoked when a number was detected which minimized false positives. It also eliminated the need for rules of thumb as segmentation is learned. The strategy can also be extended to other characters as well.

Keywords: convolutional neural networks, OCR, text detection, text segmentation

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Authors: Wei Kunkun, Cao Wanyang, Xu Yujie, Qiao Yuzhi, Liu Yingning

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The reasonable design of bus parking spaces can improve the traffic capacity of the station and reduce traffic congestion. In order to reasonably determine the number of berths at BRT (Bus Rapid Transit) stops, it is based on the actual bus rapid transit station observation data, scheduling data, and passenger flow data. Optimize the number of station berths from the perspective of optimizing the balance of supply and demand at the site. Combined with the classical capacity calculation model, this paper first analyzes the important factors affecting the traffic capacity of BRT stops by using SPSS PRO and MATLAB programming software, namely the distribution of BRT stops and the distribution of BRT stop time. Secondly, the method of calculating the number of the classic human capital management (HCM) model is optimized based on the actual passenger demand of the station, and the method applicable to the actual number of station berths is proposed. Taking Gangding Station of Zhongshan Avenue Bus Rapid Transit Corridor in Guangzhou as an example, based on the calculation method proposed in this paper, the number of berths of sub-station 1, sub-station 2 and sub-station 3 is 2, which reduces the road space of the station by 33.3% compared with the previous berth 3 of each sub-station, and returns to social vehicles. Therefore, under the condition of ensuring the passenger flow demand of BRT stations, the road space of the station is reduced, and the road is returned to social vehicles, the traffic capacity of social vehicles is improved, and the traffic capacity and efficiency of the BRT corridor system are improved as a whole.

Keywords: urban transportation, bus rapid transit station, HCM model, capacity, number of berths

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Authors: Hejun Guo, Shenghua Liu

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Five palm oil ether monoesters utilized as novel biodiesels were synthesized and structurally identified in the paper. Investigation was made on the effect of ether species on physicochemical properties of the palm oil ether monoesters. The results showed that density, kinematic viscosity, smoke point, and solidifying point increase linearly with their CH2 group number in certain relationships. Cetane number is enhanced whereas heat value decreases linearly with CH2 group number. In addition, the influencing regularities of volumetric content of the palm oil ether monoesters on the fuel properties were also studied when the ether monoesters are used as diesel fuel additives.

Keywords: biodiesel, palm oil ether monoester, ether species, physicochemical property

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Authors: N. Larbi, F. Debbat

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Wireless communication systems have changed dramatically and shown spectacular evolution over the past two decades. These radio technologies are engaged in a quest endless high-speed transmission coupled to a constant need to improve transmission quality. Various radio communication systems being developed use code division multiple access (CDMA) technique. This work analyses a hybrid honey bees mating optimization algorithm (HBMO) applied to multiuser detection (MuD) in CDMA communication systems. The HBMO is a swarm-based optimization algorithm, which simulates the mating process of real honey bees. We apply a hybridization of HBMO with simulated annealing (SA) in order to improve the solution generated by the HBMO. Simulation results show that the detection based on Hybrid HBMO, in term of bit error rate (BER), is viable option when compared with the classic detectors from literature under Rayleigh flat fading channel.

Keywords: BER, DS-CDMA multiuser detection, genetic algorithm, hybrid HBMO, simulated annealing

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Authors: El-Ghalia Filali, Cherif Gadouche, Mohamed Tahar

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A three-dimensional numerical simulation of flow through mini and microchannels with designed roughness is conducted here. The effect of the roughness height (surface roughness), geometry, Reynolds number on the friction factor and the Nusselt number is investigated. The study is carried out by employing CFD software, CFX. Our work focuses on a water flow inside a circular mini-channel of 1 mm and microchannels of 500 and 100 μm in diameter. The speed entry varies from 0.1 m/s to 20 m/s. The general trend can be observed that bigger sizes of roughness element lead to higher flow resistance. It is found that the friction factor increases in a nonlinear fashion with the increase in obstruction height. Particularly, the effect of roughness can no longer be ignored at relative roughness height higher than 3%. A significant increase in Poiseuille number is detected for all configurations considered. The same observation can be done for Nusselt number. The transition zone between laminar and turbulent flow depends on the channel diameter.

Keywords: hydrodynamics, heat transfer, minichannel, microchannel, roughness

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Authors: Dia I. Abu-Al-Nadi, M. J. Mismar, T. H. Ismail

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A technique for estimating the direction-of-arrival (DOA) of unknown number of source signals is presented using the eigen-approach. The eigenvector corresponding to the minimum eigenvalue of the autocorrelation matrix yields the minimum output power of the array. Also, the array polynomial with this eigenvector possesses roots on the unit circle. Therefore, the pseudo-spectrum is found by perturbing the phases of the roots one by one and calculating the corresponding array output power. The results indicate that the DOAs and the number of source signals are estimated accurately in the presence of a wide range of input noise levels.

Keywords: array signal processing, direction-of-arrival, antenna arrays, Eigenvalues, Eigenvectors, Lagrange multiplier

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Authors: I Gede Puja Astawa, Yoedy Moegiharto, Ahmad Zainudin, Imam Dui Agus Salim, Nur Annisa Anggraeni

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Performance of Orthogonal Frequency Division Multiplexing (OFDM) system can be improved by adding channel coding (error correction code) to detect and correct the errors that occur during data transmission. One can use the convolution code. This paper presents performance of OFDM using Space Time Block Codes (STBC) diversity technique use QAM modulation with code rate 1/2. The evaluation is done by analyzing the value of Bit Error Rate (BER) vs. Energy per Bit to Noise Power Spectral Density Ratio (Eb/No). This scheme is conducted 256 sub-carrier which transmits Rayleigh multipath channel in OFDM system. To achieve a BER of 10-3 is required 30 dB SNR in SISO-OFDM scheme. For 2x2 MIMO-OFDM scheme requires 10 dB to achieve a BER of 10-3. For 4x4 MIMO-OFDM scheme requires 5 dB while adding convolution in a 4x4 MIMO-OFDM can improve performance up to 0 dB to achieve the same BER. This proves the existence of saving power by 3 dB of 4x4 MIMO-OFDM system without coding, power saving 7 dB of 2x2 MIMO-OFDM system without coding and significant power savings from SISO-OFDM system.

Keywords: convolution code, OFDM, MIMO, QAM, BER

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Authors: Nirmal Kant Singh, Anshuman Pratap Singh

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In this study the augmentation of heat transfer in a channel with delta winglet type vortex generators is evaluated. Three-dimensional numerical simulations are performed in a rectangular channel with longitudinal triangular vortex generators (LVGs). The span wise averaged Nusselt number and mean temperature are compared with and without vortex generators in the channel. The effect of variation of blade angle (15°, 30°, 45°, and 60°) is studied at a Reynolds number of 10000. The numerical results indicate that the application of LVGs effectively enhances heat transfer in the channel. The Nusselt number and mean outlet temperature were found to be greater using LVGs than in the channel without LVGs. It is observed that heat transfer increases with increase in blade angle at the same Reynolds number.

Keywords: heat transfer, rectangular channel, longitudinal vortex generators, effect of blade angle

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Authors: Mohammed Abdullah Alrajhi

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The rapid growth in the number of mobile phone subscribers has resulted in an increased number of mobile base stations all over the world. Generally, mobile base stations are existing in huge numbers in populated areas than in non-populated ones to serve the largest number of users. The total number of mobile subscriptions in the Kingdom of Saudi Arabia reached around 50 million at the end of 2014, with a penetration rate of 165.1% according to the quarterly electronic newsletter issued by the Communications and Information Technology Commission. The current investigation was conducted primarily to measure the level of electromagnetic fields emitted from 400 mobile base stations for the purpose of environmental safety and radiation protection in light of national guidelines for public exposure as well as the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The outcomes of this investigation provide valuable comments and recommendation for safety and protection of electromagnetic fields emitted from mobile base stations.

Keywords: electromagnetic fields, mobile, safety, protection, ICNIRP

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Authors: D. Srinivasacharya, G. Madhava Rao

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In this article, the pulsatile flow of blood flow in bifurcated artery with mild stenosis is investigated. Blood is treated to be a micropolar fluid with constant density. The arteries forming bifurcation are assumed to be symmetric about its axes and straight cylinders of restricted length. As the geometry of the stenosed bifurcated artery is irregular, it is changed to regular geometry utilizing the appropriate transformations. The numerical solutions, using the finite difference method, are computed for the flow rate, the shear stress, and the impedance. The influence of time, coupling number, half of the bifurcated angle and Womersley number on shear stress, flow rate and impedance (resistance to the flow) on both sides of the flow divider is shown graphically. It has been observed that the shear stress and flow rate are increasing with increase in the values of Womersley number and bifurcation angle on both sides of the apex. The shear stress is increasing along the inner wall and decreasing along the outer wall of the daughter artery with an increase in the value of coupling number. Further, it has been noticed that the shear stress, flow rate, and impedance are perturbed largely near to the apex in the parent artery due to the presence of backflow near the apex.

Keywords: micropolar fluid, bifurcated artery, stenosis, back flow, secondary flow, pulsatile flow, Womersley number

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Authors: Thaline Maira P. Cruz, Debora B. Moretti, Wiolene M. Nordi, José Eurico P. Cyrino, Raul Machado-Neto

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The aim of this study was to evaluate the effect of lyophilized bovine colostrum (LBC) used as partial source of dietary protein on the histological characteristics of the intestinal epithelium of juvenile dourado (Salminus brasiliensis). Juveniles were fed with diets containing 0, 10 or 20% of lyophilized bovine colostrum (LBC) inclusion for either 30 or 60 days. For the histological study, the intestine was divided into three segments, S1, S2 and posterior intestine. In the S1 segment, interaction between treatment and period was observed in the number of goblet cells containing sialomucin, effect of treatment in the total number of goblet cells and effect of period in the number of goblet cells containing sulphomucins (P<0.05). In the S2 segment, effect of period was observed in the number of goblet cells containing acid, neutral and total mucins, sialomucins and Vv (P<0.05). In the posterior intestine, effect of period was observed in the thickness of muscle layer and number of goblet cells containing sialomucins and sulphomucins (P<0.05). Considering the aspects studied, the presence of lyophilized bovine colostrum in the diet did not significantly influence the enteric histological characteristics of juvenile dourado during the period of the study.

Keywords: carnivorous fish, goblet cells, mucins, teleost

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Authors: Shih-Yan Chen, Shin-Shin Kao

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In this paper, a thorough review about dual-cubes, DCn, the related studies and their variations are given. DCn was introduced to be a network which retains the pleasing properties of hypercube Qn but has a much smaller diameter. In fact, it is so constructed that the number of vertices of DCn is equal to the number of vertices of Q2n +1. However, each vertex in DCn is adjacent to n + 1 neighbors and so DCn has (n + 1) × 2^2n edges in total, which is roughly half the number of edges of Q2n+1. In addition, the diameter of any DCn is 2n +2, which is of the same order of that of Q2n+1. For selfcompleteness, basic definitions, construction rules and symbols are provided. We chronicle the results, where eleven significant theorems are presented, and include some open problems at the end.

Keywords: dual-cubes, dual-cube extensive networks, dual-cube-like networks, hypercubes, fault-tolerant hamiltonian property

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Authors: Mokrani Mohamed Amine

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In this paper, we have implemented successive interference cancellation algorithms in the 5G downlink. We have calculated the maximum throughput in Frequency Division Duplex (FDD) mode in the downlink, where we have obtained a value equal to 836932 b/ms. The transmitter is of type Multiple Input Multiple Output (MIMO) with eight transmitting and receiving antennas. Each antenna among eight transmits simultaneously a data rate of 104616 b/ms that contains the binary messages of the three users; in this case, the Cyclic Redundancy Check CRC is negligible, and the MIMO category is the spatial diversity. The technology used for this is called Non-Orthogonal Multiple Access (NOMA) with a Quadrature Phase Shift Keying (QPSK) modulation. The transmission is done in a Rayleigh fading channel with the presence of obstacles. The MIMO Successive Interference Cancellation (SIC) receiver with two transmitting and receiving antennas recovers its binary message without errors for certain values of transmission power such as 50 dBm, with 0.054485% errors when the transmitted power is 20dBm and with 0.00286763% errors for a transmitted power of 32 dBm(in the case of user 1) as well as with 0.0114705% errors when the transmitted power is 20 dBm also with 0.00286763% errors for a power of 24 dBm(in the case of user2) by applying the steps involved in SIC.

Keywords: 5G, NOMA, QPSK, TBS, LDPC, SIC, capacity

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Authors: Feyza Eda Akyurek, Bayram Sahin, Kadir Gelis, Eyuphan Manay, Murat Ceylan

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Turbulent forced convection heat transfer and pressure drop characteristics of Al₂O₃–water nanofluid flowing through a concentric tube heat exchanger with and without coiled wire turbulators were studied experimentally. The experiments were conducted in the Reynolds number ranging from 4000 to 20000, particle volume concentrations of 0.8 vol.% and 1.6 vol.%. Two turbulators with the pitches of 25 mm and 39 mm were used. The results of nanofluids indicated that average Nusselt number increased much more with increasing Reynolds number compared to that of pure water. Thermal conductivity enhancement by the nanofluids resulted in heat transfer enhancement. Once the pressure drop of the alumina/water nanofluid was analyzed, it was nearly equal to that of pure water at the same Reynolds number range. It was concluded that nanofluids with the volume fractions of 0.8 and 1.6 did not have a significant effect on pressure drop change. However, the use of wire coils in heat exchanger enhanced heat transfer as well as the pressure drop.

Keywords: turbulators, heat exchanger, nanofluids, heat transfer enhancement

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Authors: Roghayyeh Motallebzadeh, Shahin Hajizadeh, Mohammad Reza Ghasemi

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Laminar mixed convection heat transfer of a nanofluid with prescribed constant heat flux on the inner wall of horizontal annular tube has been studied numerically based on two-phase mixture model in different Rayleigh numbers and Azimuth angles. Effects of applying of different volume fractions of Al2O3 nanoparticles in water as a base fluid on hydrodynamic and thermal behaviours of the fluid flow such as axial velocity, secondary flow, temperature, heat transfer coefficient and friction coefficient at the inner and outer wall region, has been investigated. Conservation equations in elliptical form has been utilized and solved in three dimensions for a steady flow. It is observed that, there is a good agreement between results in this work and previously published experimental and numerical works on mixed convection in horizontal annulus. These particles cause to increase convection heat transfer coefficient of the fluid, meanwhile there is no considerable effect on friction coefficient.

Keywords: buoyancy force, laminar mixed convection, mixture model, nano-fluid, two-phase

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Authors: Hamidreza Bayat, Arash Mirabdolah Lavasani, Meysam Bolhasani, Sajad Moosavi

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Heat transfer from flat tube is studied numerically. Reynolds number is defined base on equivalent circular tube which is varied in range of 100 to 300. In these range of Reynolds number flow is considered to be laminar, unsteady, and incompressible. Equations are solved by using finite volume method. Results show that increasing l/D from 1 to 2 has insignificant effect on heat transfer and Nusselt number of flat tube is slightly lower than circular tube. However, thermal-hydraulic performance of flat tube is up to 2.7 times greater than circular tube.

Keywords: laminar flow, flat tube, convective heat transfer, heat exchanger

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Authors: Pratibha, Jyoti Kori

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Particles in industry, harvesting, coal mines, etc. may not necessarily be spherical in shape. In general, it is difficult to find perfectly spherical particle. The prediction of movement and deposition of non spherical particle in distinct airway generation is much more difficult as compared to spherical particles. Moreover, there is extensive inflexibility in deposition between ducts of a particular generation and inside every alveolar duct since particle concentrations can be much bigger than the mean acinar concentration. Consequently, a large number of particles fail to be exhaled during expiration. This study presents a mathematical model for the movement and deposition of those non-spherical particles by using particle aspect ratio and shape factor. We analyse the pulsatile behavior underneath sinusoidal wall oscillation due to periodic breathing condition through a non-Darcian porous medium or inside pulmonary region. Since the fluid is viscous and Newtonian, the generalized Navier-Stokes equation in two-dimensional coordinate system (r, z) is used with boundary-layer theory. Results are obtained for various values of Reynolds number, Womersley number, Forchsheimer number, particle aspect ratio and shape factor. Numerical computation is done by using finite difference scheme for very fine mesh in MATLAB. It is found that the overall air velocity is significantly increased by changes in aerodynamic diameter, aspect ratio, alveoli size, Reynolds number and the pulse rate; while velocity is decreased by increasing Forchheimer number.

Keywords: deposition, interstitial lung diseases, non-Darcian medium, numerical simulation, shape factor

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Authors: Younes El Khchine, Mohammed Sriti

Abstract:

A parametric study has been conducted to analyse the flow around S809 airfoil of wind turbine in order to better understand the characteristics and effects of laminar separation bubble (LSB) on aerodynamic design for maximizing wind turbine efficiency. Numerical simulations were performed at low Reynolds number by solving the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations based on C-type structural mesh and using γ-Reθt turbulence model. Two-dimensional study was conducted for the chord Reynolds number of 1×105 and angles of attack (AoA) between 0 and 20.15 degrees. The simulation results obtained for the aerodynamic coefficients at various angles of attack (AoA) were compared with XFoil results. A sensitivity study was performed to examine the effects of Reynolds number and free-stream turbulence intensity on the location and length of laminar separation bubble and aerodynamic performances of wind turbine. The results show that increasing the Reynolds number leads to a delay in the laminar separation on the upper surface of the airfoil. The increase in Reynolds number leads to an accelerate transition process and the turbulent reattachment point move closer to the leading edge owing to an earlier reattachment of the turbulent shear layer. This leads to a considerable reduction in the length of the separation bubble as the Reynolds number is increased. The increase of the level of free-stream turbulence intensity leads to a decrease in separation bubble length and an increase the lift coefficient while having negligible effects on the stall angle. When the AoA increased, the bubble on the suction airfoil surface was found to moves upstream to leading edge of the airfoil that causes earlier laminar separation.

Keywords: laminar separation bubble, turbulence intensity, S809 airfoil, transition model, Reynolds number

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Authors: Tanapon Suklim, Prachaya Intaphrom, Noppadol Poomvises, Anchalee Kongsuk

Abstract:

The relationship between shear wave velocity (Vs30) and blow count Number from Standard Penetration Tests (NSPT) was investigated on specified embankment dam to find the solution which can be used to estimate the value of N. Shear wave velocity, Vs30 and blow count number, NSPT were performed at three specified dam sites. At each site, Vs30 measurement was recorded by using seismic survey of MASW technique and NSPT were measured by field Standard Penetration Test. Regression analysis was used to derive statistical relation. The relation is giving a final solution to applicable calculated N-value with other earthen dam. Dam engineer can use the statistical relation to convert field Vs30 to estimated N-value instead of absolute N-value from field Standard Penetration Test. It can be noted that the formulae can be applied only in the earthen dam of specified material.

Keywords: blow count number, earthen dam, embankment, shear wave velocity

Procedia PDF Downloads 217

Authors: R. M. Kashim

Abstract:

The study investigated primary school teachers’ conceptual and procedural knowledge of rational numbers and its effects on pupil’s achievement in rational numbers. Specifically, primary school teachers’ level of conceptual knowledge about rational numbers, primary school teachers’ level of procedural knowledge about rational numbers, and the effects of teachers conceptual and procedural knowledge on their pupils understanding of rational numbers in primary schools is investigated. The study was carried out in Bauchi metropolis in the Bauchi state of Nigeria. The design of the study was a multi-stage design. The first stage was a descriptive design. The second stage involves a pre-test, post-test only quasi-experimental design. Two instruments were used for the data collection in the study. These were Conceptual and Procedural knowledge test (CPKT) and Rational number achievement test (RAT), the population of the study comprises of three (3) mathematics teachers’ holders of Nigerian Certificate in Education (NCE) teaching primary six and 210 pupils in their intact classes were used for the study. The data collected were analyzed using mean, standard deviation, analysis of variance, analysis of covariance and t- test. The findings indicated that the pupils taught rational number by a teacher that has high conceptual and procedural knowledge understand and perform better than the pupil taught by a teacher who has low conceptual and procedural knowledge of rational number. It is, therefore, recommended that teachers in primary schools should be encouraged to enrich their conceptual knowledge of rational numbers. Also, the superiority performance of teachers in procedural knowledge in rational number should not become an obstruction of understanding. Teachers Conceptual and procedural knowledge of rational numbers should be balanced so that primary school pupils will have a view of better teaching and learning of rational number in our contemporary schools.

Keywords: conceptual, procedural knowledge, rational number, pupils

Procedia PDF Downloads 428