The effect of aging time on mechanical and microstructure properties of aa6061 joints welded by gas tungsten arc welding

This research examines the influence of heat treatment on mechanical properties and microstructure of AA6061 aluminium alloy welded with butt groove method, by using Gas Tungsten Arc Welding (GTAW) method. Welded samples were divided into two; heat treated (PWHT) and as-welded (AW) joints samples. For PWHT welded samples, the heat treatment applied were solution heat treatment at a temperature of 5300C for 1 h, followed by cooling water and artificial aging process at a temperature of 1600C for 18, 20 and 22 hours. Tensile test was performed based on standard ASTM E8 04, while the hardness test was taken at 3 different locations along the cross section of the weld zone of upper, middle and lower sections. Fracture surface at AW and PWHT welded samples were investigated by using Scanning Electron Microscopy (SEM) and the microstructure of the samples was analyzed by using Optical Microscopy (OM). From the results, the PWHT welded samples increased the tensile strength, hardness, and micro structural characteristics of welded joints aluminium AA6061 alloy

Laser ignition of an optically sensitised secondary explosive by a diode laser

As a green technology, laser ignition of a relatively insensitive secondary explosive has been experimentally investigated. The explosive, hexanitrostilbene (HNS), was doped with one of two optical sensitizers, carbon black or a laser absorbing dye, and a continuous-wave (CW) infrared diode laser was used as the igniting source. The ignition sensitivities of HNS with each of the two optical sensitizers were analysed and compared in terms of: optical power threshold for ignition, ignition delay and full burn delay at various laser powers. The results have shown that both the chemical dye and carbon black optically sensitize the explosive with similar efficiencies. In contrast to the carbon black, the dye provides wavelength specificity and selectivity in the laser ignition process and its solubility in some specific solvents improves the coating of the explosive material. It was therefore concluded that the laser absorbing dye is a better candidate for optical sensitization in laser ignition than the commonly used carbon black. The combination of laser ignition sensitivity with wavelength selectivity potentially offers higher reliability and safety at a low optical power for future ignitors of secondary explosives

Resource Allocation for Energy-Efficient Device-to-Device Communication in 4G Networks

Device-to-device (D2D) communications as an underlay of a LTE-A (4G) network can reduce the traffic load as well as power consumption in cellular networks by way of utilizing peer-to-peer links for users in proximity of each other. This would enable other cellular users to increment their traffic, and the aggregate traffic for all users can be significantly increased without requiring additional spectrum. However, D2D communications may increase interference to cellular users (CUs) and force CUs to increase their transmit power levels in order to maintain their required quality-of-service (QoS). This paper proposes an energy-efficient resource allocation scheme for D2D communications as an underlay of a fully loaded LTE-A (4G) cellular network. Simulations show that the proposed scheme allocates cellular uplink resources (transmit power and channel) to D2D pairs while maintaining the required QoS for D2D and cellular users and minimizing the total uplink transmit power for all users.Comment: 2014 7th International Symposium on Telecommunications (IST'2014

Worst-Case Robust Distributed Power Allocation in Shared Unlicensed Spectrum

This paper considers non-cooperative and fully-distributed power-allocation for selfish transmitter-receiver pairs in shared unlicensed spectrum when normalized-interference to each receiver is uncertain. We model each uncertain parameter by the sum of its nominal (estimated) value and a bounded additive error in a convex set, and show that the allocated power always converges to its equilibrium, called robust Nash equilibrium (RNE). In the case of a bounded and symmetric uncertainty region, we show that the power allocation problem for each user is simplified, and can be solved in a distributed manner. We derive the conditions for RNE's uniqueness and for convergence of the distributed algorithm; and show that the total throughput (social utility) is less than that at NE when RNE is unique. We also show that for multiple RNEs, the social utility may be higher at a RNE as compared to that at the corresponding NE, and demonstrate that this is caused by users' orthogonal utilization of bandwidth at RNE. Simulations confirm our analysis

Information System Ordering Online Restaurant Menu at Hover Cafe

The rapid development of technology requires every business person to upgrade his technology to more sophisticated. Many business people have upgraded their systems to be computerized and even online, one of the business people is in the culinary field. The culinary field which is meant for example is the cafe One thing that can support the quality of ordering in a cafe is the ordering process. In the hover cafe the menu ordering system is still conventional, using a menu book. This of course can be a problem because the menu book used can be damaged or lost so that it can slow down the ordering process, not to mention if the customer requests additional orders, the waiter must come to the customer's table to record additional orders again. The method used in this research is the method of data collection, the method of observation, the method of interviewing, and the method of literature study conducted to obtain accurate data. Then the data are analyzed with SWOT to find out the company's weaknesses and strengths. In describing the flow of the system using UML (Unified Modeling Language) and PHP (Hypertext Preprocessor) as a programming language with a MySQL database as a database. Therefore we need a ordering media that utilizes information technology as a medium for selecting food and beverage (E-Menu) which can provide information about order menu details to facilitate customers in making and ordering food or beverage menus