World Journal of Engineering and Technology

Journal Information
ISSN / EISSN : 2331-4222 / 2331-4249
Published by: Scientific Research Publishing, Inc. (10.4236)
Total articles ≅ 597
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Latest articles in this journal

Lianjun Zhang, Zhongqi Fan, Gang Liu
World Journal of Engineering and Technology, Volume 09, pp 300-308; doi:10.4236/wjet.2021.92021

The light extraction efficiency caused by total internal reflection is low. Based on the analysis of the existing technology, a new design scheme is proposed in this paper to improve the light extraction efficiency. The air gap photonic crystal is embedded on the GaN-based patterned sapphire substrate, which can reduce line misalignment and improve light extraction efficiency. The internal structure of the GaN-based LED epitaxial layer is composed of an electron emission layer, a quantum well in the light-emitting recombination region, and an electron blocking layer. Experimental results show that this method significantly improves the extraction efficiency of LED light.
Xinyu Li, Zhongxian Han, Peng Li, Lei Wang
World Journal of Engineering and Technology, Volume 09, pp 1-14; doi:10.4236/wjet.2021.91001

The organic Rankine cycle is widely used in industrial waste heat, engine waste heat and other waste heat recovery applications, and as a key component of the system, it affects the efficiency and output power of the system. In this paper, a centripetal turbine is designed for the organic Rankine cycle, using vehicle exhaust gas as the heat source. Numerical simulations are performed to analyze the effect of the ratio of the number of guide vane blades to the number of impeller blades (vane number ratio) on the turbine performance and flow field. The results show that the effect of the number of impeller blades on the turbine entropy efficiency, the average exit velocity and the temperature of the guiding grate becomes less and less as the ratio of the number of blades increases. The optimum turbine performance is obtained when the number of impeller blades and the ratio of the number of blades are 17 and 1.5882, respectively, and the expansion performance of the guide impeller is improved and the isentropic efficiency of the turbine is improved by 3.84% compared with the preliminary number of blades.
Brice Poumegne Kouam, Didier Fokwa, Dieunedort Ndapeu, Médard Fogue
World Journal of Engineering and Technology, Volume 09, pp 15-25; doi:10.4236/wjet.2021.91002

The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towards the axial direction. The phenomenon of damage is very often observed during such loading. The present study on raffia aims to analyze this phenomenon through cyclical stresses as usual. From the results obtained, it was observed in the stress-strain plane, that the area of the hysteresis loops and the residual strain evolve with two parameters: the number of cycles and the stress peaks. The study of energy dissipation has shown that it evolves according to an exponential law as a function of the number of cycles. The distribution of the energy rate along a stem shows that the samples from the zone close to the base store twice (0.0412 MJ/m3) more energy than the samples taken from the top of the foliage (0.019 MJ/m3).
Elysé Masengesho, Ji Wei, Nadine Umubyeyi, Rosette Niyirora
World Journal of Engineering and Technology, Volume 09, pp 109-127; doi:10.4236/wjet.2021.91009

Both in developed and in developing countries, the construction industry is regarded as an economic investment activity without forgetting its significant relationship with national economic development due to its great contributions to the national gross domestic product (GDP) of the country. Concerning construction processes, both risk management (RM) and value engineering (VE) techniques have commonalities from the beginning up to the completion of the project due to enhancing the project value/quality, meeting the project deadline, and reducing overall project cost. VE includes resolving the uncertainty of project objectives and ensuring that the project is delivered in a value for money way. The key point of RM is to solve the uncertainty of the project itself and its results to ensure that the specifications are achieved within the prescribed time, cost, and quality constraints. This review work is comparatively and collectively focused on assessing the role of RM and VE tools for project successful delivery. It studies the points of difference and common features of the two aspects in terms of construction project delivery. So, this study concluded that in construction RM tool cannot be the chief aim of the all parties involved in the project execution because sometimes it produces itself negative results and reduces project management success. Therefore, RM needs a strong combination with VE due to the dependence of the target in identifying and assessing risks by considering the highest performance and lowest cost. The integration of RM and VE combination in a single study would avoid duplication of work and deliver better value for money thereby leading to better project outcomes.
Neyva Maria Lopes Romeiro, Eliandro Rodrigues Cirilo, Paulo Laerte Natti, Letícia Mayumi Doy Okamoto, Tainá Julianotti
World Journal of Engineering and Technology, Volume 09, pp 173-193; doi:10.4236/wjet.2021.91013

This work proposes a way of modelling two-dimensional complex meshes using elliptic equations, which the computational grid coincides with the problem geometry, making computational processing more suitable. A multiblock technique was used in order to achieve a better representation of the problem domain. In this way, numerical simulations of the movement and dispersion of pollutant emissions in the atmosphere are presented in the generated domains, using the Navier-Stokes pollutant transport equations. The curvilinear coordinates and the finite difference method are used for the discretization. The model was verified in two tests. In the first test, three cases were proposed, with geometries containing a chimney followed by an obstacle, using different chimney heights, and the obstacle height was fixed. The test aims to verify the vortices appearance, in the blocks, to obtain agreement with as presented in the literature. In the second test, the geometry is described by a chimney and an obstacle that represents one of the mountains in the valley. The performed tests made possible to verify that the height of the chimney can be considered a determining factor to describe the dispersion of pollutants, as well as their concentration in the proximity of industrial areas.
Hongbing Wang, Chunhua Sun
World Journal of Engineering and Technology, Volume 09, pp 92-99; doi:10.4236/wjet.2021.91007

Aiming at the gate design problem of a mobile phone panel, the plastic forming analysis software Moldflow and drop simulation were used to optimize the gate design. Six different gate design schemes were compared and studied, and the weld lines positions and injection molding results under each gate scheme were analyzed.Through the simulation analysis of the falling process of the mobile phone panel by the display dynamics analysis software ANSYS Workbench LS-DYNA, five analysis schemes were set according to the falling angle, and the stress distribution at the weld lines positions of the mobile phone panel in each scheme was studied. The reasonable gate scheme was given by synthesizing the force condition, the mold flow analysis and the drop simulation results of the mobile phone panel in use. Based on the results of die flow analysis and drop simulation the optimal gate design scheme 2 is found, and the weld line position avoids the lower part of the elliptical hole, which is the weak part of the structure. The research results had certain reference significance for the optimization of injection process of plastic products.
Kaili Liu, Hongshu Jin
World Journal of Engineering and Technology, Volume 09, pp 241-249; doi:10.4236/wjet.2021.92017

This paper is aiming to obtain an arm-root curve function performing the human arm-root size and shape realistically. A gypsum replica of upper arm for young male was made and scanned for extracting the 3D coordinates of 4 feature points of shoulder point, the anterior/posterior armpit point and the axillary point describing the real arm-root shape under the normalized definitions, and the 5 landmarks were confirmed additionally for improving the fitting precision. Then, the wholly and piecewise fitting of arm-root curve with 9 feature points and mark points in total were generated respectively based on least square polynomial fitting method. Comparing to the wholly fitting, the piecewise fitted function segmented by the line between anterior and posterior axillary points showed a high fitting degree of arm-root morphology with R-square of 1, the length difference between fitted curve and gypsum curve is 0.003 cm within error range. And it provided a basic curve model with standard feature points to simulate arm-root morphology realistically by curve fitting for accurate body measurement extraction.
Dragana Savić, Milan Tumara, Milutin Petrović
World Journal of Engineering and Technology, Volume 09, pp 250-267; doi:10.4236/wjet.2021.92018

In most cases, copper ore deposits occur at great depths, so the optimization of excavation costs is of utmost importance to identify the most cost effective and productive mining methods, such as block caving or similar methods specifically developed for these deposits. To be able to apply such methods, it is necessary to have a detailed knowledge of the rock mass in terms of its geomechanical, engineering geological and hydrogeological characteristics. This research aims to reduce geological and geotechnical unknowns, analyze in detail the geological environment, and predict geotechnical conditions for the construction of the shaft. This paper uses the example of Borska Reka Copper Deposit, located in Serbia to illustrate the importance of geotechnical investigation to enable best practice in design and construction of shafts that are over 1000 m deep.
R. David Case, D. Chuckravanen
World Journal of Engineering and Technology, Volume 09, pp 374-383; doi:10.4236/wjet.2021.92026

The research aim of this work is to analyse the characteristics of R. David Case Sound waves that are posited to have positive effects on people suffering from tinnitus. Moreover, the participants who listened to these sound wave files using specific headsets or headphones of the Koss models (ktx Pro, ksc-75) showed improved health condition such as alleviating tinnitus that they are suffering from. Therefore, these discoveries have encouraged R. David Case to pursue positively his journey into finding out what is special about those sounds when being listened specifically with Koss models. In this research, we focus mainly on the technical aspects of R. David Case sound signals which he has recorded. These specific sound waves were analysed using time domain, frequency domain as well as the effect of using the Koss Pro headphone frequency response characteristics applied to the sound. Results obtained from the analysis demonstrated that the generation of ultrasound can be the underlying reason for the treatment of the tinnitus.
Lei Zhao
World Journal of Engineering and Technology, Volume 09, pp 346-356; doi:10.4236/wjet.2021.92024

With the development of integrated circuit, the content of digital circuit experiment course is constantly updated. In order to keep up with the development trend of the Times and make students’ professional knowledge meet the needs of the industry, the school adopts the FPGA experimental platform to carry out teaching reform from the two aspects of platform and experiment, and carry out reasonable experimental planning to enrich the experimental content. In this paper, the traditional knowledge points of logic algebra, trigger, timer, counter, decoder and digital tube are organically combined, and the digital clock system is designed and realized. The practice shows that the combination of modern design method and traditional digital circuit teaching method can play a good teaching effect. In this way, students can also fully learn, understand and skillfully use the new technology in the experiment, and in the process of building a comprehensive understanding of digital circuits.
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