Lecterns are essential tools in presentations that provide structure for presenters to boost their confidence. The available lecterns in the university classrooms are not height adjustable and are without in-built presentation aid hence it requires the use of a third party computer and as such has failed to satisfy all the usersâ choice. With the aid of a Quality Function Deployment technique, the usersâ choice were analyzed and rated. With the ratings we desire to create a system that can accommodate the needs of all people, with or without disabilities. It should make the individual as independent as possible with as few adaptations possible, while maintaining a high level of functionality and grandeur. This report details the entire design process that was used to develop the manually adjustable lectern with electronic presentation aid. The main function of the final lectern design that allows it to accommodate the widest range of users is its height adjustability. It can adjust to heights ranging from approximately 113mm to 1336mm. Additional features designed to accommodate the needs of the user include a tilt adjustable touch screen presentation aid. The developed lectern improved both studentsâ performance and lecturerâs syllabus content coverage. Students in year five had average performance of 96% in practical course representing 37.1% compared with their performance using the conventional lectern.
In this investigation, the effect of time on variation of oil tank thickness using the geographic information systems (GIS) and geostatistical analysis. The variograms were created to describe the spatial variability of the tank thickness. The chosen models were used to create a corrosion map through creating many layers using GIS. ArcInfo 9.3 software package was used to achieve this study.
Determination of lateral earth pressure plays a vital role in retaining wall design. Failure surfaces are very effective in active lateral earth pressure acting on cantilever retaining walls. Calculations of lateral earth thrusts vary for two different cases, namely short heel or long heel, based on the intersection of T type cantilever wall and failure surface. In this study, the effect of heel length on an active failure mechanism was examined with numerical simulation based on FEM. The results of the numerical analyses were compared with the results of small-scale model tests and an analytical method. In comparison, the inclination angle of active failure surfaces was taken into account. An earth thrust maximization code suggested in the literature was used to determine failure surface inclination angles analytically. In order to determine failure inclination experimentally, results of small scale tests were used. In the tests, failure surfaces were determined using particle image velocimetry technique (PIV). Numerical analysis was performed using commercially available finite element program Plaxis 2D. The same material properties are used in all numerical models. As a result of the study short heel-long heel cases and effective parameters on the inclination angles of the failure surfaces are explained elaborately.
Graphene has been recently introduced as a promising material for various applications due to its outstanding mechanical, electrical, and thermal properties. It is classified as an allotropic form of carbon with the size of a single layer of graphite. This paper provides an extensive review regarding different critical applications of graphene including three categories namely: energy harvesting, strain sensors technology, and steel industry. The paper highlights what has been traversed in each category and provides an insight for researchers on what still needs to be investigated, which would open new horizons for scientific research and industrial applications. This field of research is expected to yield results that will have a considerable advance specially in 3D strain sensing technology. Also a special attention is given to the application of graphene in steel coating, steel welding, and lubrication.
Regenerated cellulosic fibers are obtained by chemical processing of cellulose-based raw materials. They are similar to cotton in terms of their structural properties, but their performance characteristics have changed with the processes they have applied. The principle of vortex spinning is a spinning technique that has become very popular in recent years in terms of production speed and yarn quality. In the study, with the production principle of regenerated cellulose fibers (viscose, modal, bamboo, tencel) and cotton fibers were made into yarn by vortex spinning technique. From these yarns, 18 jersey fabrics with different loop lengths produced by circular knitting machine. In this paper, the structural properties and drapeabilities of the obtained samples were tested and the results were compared mathematically and statistically. Results show that the effect of raw material is more effective parameter than the loop length on the drapeability of plain knitted fabrics.
Lithium-ion batteries have become one of the most commercially preferred energy storage devices because of their high energy density, low self-discharge rate, and the ability to be cycled many times with slow capacity fading in comparison with other rechargeable batteries. They have been applied on a wide variety of electrical devices and systems such as consumer electronics, power tools, electric vehicles and aerospace equipment. The characteristics of Li-ion batteries are mainly determined by the materials used for its components which can be categorized into four parts: anode and cathode electrodes, separator, and electrolyte. Over the last decade, there has been a significant increase in the number of studies evaluating battery performance based on various materials used in each battery component. However, few attempts have been made to evaluate materials of Lithium-ion batteries. Thus, in this study, we aim to evaluate different materials for cathode electrode in terms of four main criteria: cost, performance, safety and service life using two methods; AHP and interval type-2 fuzzy sets. It is shown that more reliable results are obtained for selecting the best cathode material of Li-ion battery and based on comparison of two methods, same rank is achieved for both approaches.
In this study, effects of tensile properties of epoxy adhesive with nano silica on the glass epoxy laminates adhesively bonded single strap repairs are investigated. Nano slica particles were added to the epoxy resin with an amount of 1,2,3 wt%. Single strap repairs were used as different patch ratio (D/d=2,and D/d= 3 ). Patchs were opened by CNC machine having 10 mm diameter. Tensile tests were carried out to the specimens and their load carrying capacities were measured. Experiments show that load carry capacity increases with increasing nano slica in epoxy.
The change in physical properties of bell metal due to ternary addition of Al and quaternary addition of Zr has been reported. Cast samples are aged both isochronally and isothermally. Investigation on the age hardening property reveals that due to the formation of intermetallic precipitates, significant hardening takes place in case of Al added alloys and Zr addition enhances the thermal stability of the alloy. The comparative acoustic response study discloses that heat-treatment improves the sound quality of all three bell metal alloys. The base alloy shows highest decibel values for differently aged temperatures. The ternary Al added alloy and quaternary Zr added alloy show continuous increase in decibel values with increasing ageing temperature. However, the acoustic response curve of the alloys almost followed the similar pattern of hardness curve with the ageing temperature. Spectral reflectance study reveals that the ternary Al added alloy shows better percent reflectance with the increase of wavelength of incident light. The quaternary Zr added alloy is also seen to retain its superior optical properties for all ageing conditions. It is found from microstructural analysis that ternary Al addition creates a new microstructure with relatively large dendritic arms and the quaternary addition of Zr refines the grain structure. The base alloy attained almost full recrystallization state after ageing at 300°C for 60 minutes while the ternary Al added alloy was also recrystallized at elevated temperature of 500°C but the quaternary Zr added alloy did not attain recrystallization and maintained its grain structure due to thermal stability.
In this study EN-AC 43200 Aluminum alloy was subjected to secondary or interrupted aging following a T6 heat treatment. The 43200 alloy is a used widely in automotive industry for lowering weights of vehicles by substituting with ferrous alloys. This study covers the substitution of an automotive company’s part. 4320 Al alloy was melted under Argon atmosphere with an induction furnace, and cast into graphite molds. The samples were homogenized at 500 oC for 96 hours. Solutionizing treatment also done at 500 oC for 14 hours, following water quenching, T6 treatment was done at 250 oC for 2 hours ended with a water quench. Secondary aging trials were done at 100, 150 and 200 oC for 2, 4, 6 and 8 hours for each temperature range respectively. Tensile tests and microhardness tests were applied to for cast, T6 condition, and secondary aged samples. The samples were polished and observed for microstructure under optical microscope. Maximum strength value of 370 MPa, and hardness 113 Hv was obtained from samples aged secondarily at 150 oC for 6 hours.
One of the major drawbacks of fiber reinforced composite laminates is the poor impact damage resistance. Several effective techniques to improve impact damage resistance have been proposed in the literature, among which, fiber hybridization technique has been taken considerable investigation. However, little attention has, as yet, been received for the improvement of impact behavior of basalt fiber reinforced composite laminates by fiber hybridization. The objective of this study is to assess the effect of glass fiber hybridization on Charpy impact behavior of basalt fiber reinforced composite laminates. For this purpose, a series of Charpy impact tests have been performed on composite laminates made of basalt and glass fiber reinforced epoxy resin matrix in five different stacking sequences. Hybrid composite laminates have been fabricated using vacuum assisted resin transfer molding method. The test results show that the absorbed impact energy and impact strength are significantly influenced by the hybridization.
Penetration is the most critical concept in ballistic studies. Penetration is defined as the ability to penetrate the target. Penetrator tip geometry and velocity are the most important factors in terms of the penetration. There are many limitations in increasing the velocity of the penetrator. Therefore, projectile geometry can be studied in this field. So, in this study, six different tip geometry of bullet are investigated in terms of the ballistic impact performance. Numerical simulations are performed in ANSYS program, which is the finite element program. Explicit dynamics toolbox is used to perform the numerical study. Six different tip geometry of bullet was modeled in 3D modeling program. The geometries are transferred to the ANSY workbench program. Initial velocity is accepted as 300 m/s for all conditions. Within this study, the impact energy performance of six different bullet tip geometry was obtained. In addition, stress and deformation results on the target were also compared.
In relation to other materials such as concrete, plastic, steel and aluminum, wood has a number of advantages, such as beauty, high mechanical resistance to mass, good thermal insulation and easy workability. Still, wood presents environmental advantages when compared to other building materials (cement, concrete, steel and aluminum), beause it is recyclable, renewable, biodegradable and requires low energy needs for its processing. Taking so many advantages of the wooden use, itâs necessary to aim a rational use for this raw material, as an example, there are the physical and mechanical properties, which are important for the structural use of the species in the design of wood structures. This work aimed to characterize the wood species Clarisia racemosa (Oiticica-Amarela), objectifying its viable use for structural purposes. The tests to obtain the physical and mechanical properties were carried out according to the recommended established by Brazilian Standard ABNT NBR 7190 (1997), allowing the classification of such species in strength class C60 (hardwoods), as well as evaluating the possibility of estimation (linear, exponential, geometric and logarithmic models) of the physical and mechanical properties in function of the apparent density. The results obtained from the regression models implied the possibility of estimating only the mechanical property of compressive strength parallel to the fibers (fc0) as a function of the apparent density (Ïap, 12%).
