ملخص البحث :

High Data Rate Operation and The Bit Error Rate Performances of OFDM System JNTUH 6 ABSTRACT One of the main challenges of the 4th Generation wireless systems is to provide high data rates in mobile environments. In these 4G products, WiMax (worldwide interoperability for microwave access) and LTE (Long Term Evolution) will be the platform technologies. The rapid development of the Internet with new services and applications has created new challenges for the development of mobile communications systems. Many wireless systems offer high data rate services (IEEE 802.11n, IEEE 802.15.3 and IEEE 802.16). Possible migration of 3G to 4G (LTE) will increase data rates throughput in the range of 100Mbps. These high data rate applications may be difficult to support with the required quality-of-services (QoS) in high mobility environment. For example , the mobile WiMax can be used at mobile speeds of 60 km/h to 120 km/h sufficient for car applications but not for high speed trains. One possible solution is to use a main router for each coach connected with a single antenna to the external broadband network and to distribute the signal inside the coaches thanks to a repeater. An other architecture consider direct transmission to mobile cellular telephone networks using the 3G technology such as the HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access) allow high-speed data rates, opening the door to a range of mobile usage. All these future and advanced systems are mainly based on orthogonal frequency division multiplexing (OFDM) known to be resistant to various impairments in the mobile channels. In this paper, a transmission system based on OFDM technique and a solution for channel estimation is proposed. The main results will be presented in the case of high mobility context.

ملخص البحث :

ملخص البحث :

High Data Rate Operation and The Bit Error Rate Performances of OFDM System JNTUH 6 ABSTRACT One of the main challenges of the 4th Generation wireless systems is to provide high data rates in mobile environments. In these 4G products, WiMax (worldwide interoperability for microwave access) and LTE (Long Term Evolution) will be the platform technologies. The rapid development of the Internet with new services and applications has created new challenges for the development of mobile communications systems. Many wireless systems offer high data rate services (IEEE 802.11n, IEEE 802.15.3 and IEEE 802.16). Possible migration of 3G to 4G (LTE) will increase data rates throughput in the range of 100Mbps. These high data rate applications may be difficult to support with the required quality-of-services (QoS) in high mobility environment. For example , the mobile WiMax can be used at mobile speeds of 60 km/h to 120 km/h sufficient for car applications but not for high speed trains. One possible solution is to use a main router for each coach connected with a single antenna to the external broadband network and to distribute the signal inside the coaches thanks to a repeater. An other architecture consider direct transmission to mobile cellular telephone networks using the 3G technology such as the HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access) allow high-speed data rates, opening the door to a range of mobile usage. All these future and advanced systems are mainly based on orthogonal frequency division multiplexing (OFDM) known to be resistant to various impairments in the mobile channels. In this paper, a transmission system based on OFDM technique and a solution for channel estimation is proposed. The main results will be presented in the case of high mobility context.

ملخص البحث :

ملخص البحث :

ملخص البحث :

Recently there has been major attention towards waste materials for converting them into useful materials. This study is aimed to investigate the possibility of utilizing waste clay bricks and waste lightweight concrete blocks as suitable materials for partial replacing of the fine aggregate in the production of cement mortar. In mortar mixes, waste clay bricks constitute 10%, 20%, 30%, and 40% of fine aggregate. On the other hand, the second line (waste lightweight concrete blocks) has contained 10%, 20%, and 30% of the natural sand produced. Some mixes have contained the combination of two types of waste materials together (20% clay bricks with 10% lightweight concrete block, 10% clay bricks with 20% lightweight concrete block, and 15% clay bricks with 15% lightweight concrete block respectively). The effects of the wastes aggregate on flow and engineering properties (i.e., density, compressive strength, flexural strength, and water absorption) of mortar have been also investigated at 7, 28, and 360 days. The results have presented a reduction in the flow of mortar when using a waste aggregate and a significant increase in compressive and flexural strength when using waste clay bricks aggregate at different percent. Utilizing lightweight concrete blocks aggregate has a clear effect on mortar density.

ملخص البحث :

Concrete is a brittle material, so it is reinforced with fibers (such as steel, glass and nylon fibers) to improve its ductility. On the other hand, the use of fibers resulting from waste is an interesting issue to avoid the negative impact of these wastes on the environment as well as converting them from useless to other valuable materials. Limited studies addressed the mechanical and structural performance of the locally produced waste rope fibers (WRF) and their reuse in concrete. As a result, the goal of this research is to see how different percentages of WRF (0%, 0.25%, 0.5% and 1% by weight of concrete) affect the workability, mechanical (such as compressive and flexural strength, ultrasonic pulse velocity and bulk density) and structural (such as load deflection, crack width and propagation, and ductility index) properties of concrete. Results indicated that WRF improved the compressive and flexural strength of concrete by up to 22% and 4.3%, respectively. Furthermore, the width of cracks of reinforced concrete beams was considerably reduced and the ductility index of WRF-based beams was 3.07–3.24 compared to 1.45 for fiber-free beams.

ملخص البحث :

Concrete is a brittle material, so it is reinforced with fibers (such as steel, glass and nylon fibers) to improve its ductility. On the other hand, the use of fibers resulting from waste is an interesting issue to avoid the negative impact of these wastes on the environment as well as converting them from useless to other valuable materials. Limited studies addressed the mechanical and structural performance of the locally produced waste rope fibers (WRF) and their reuse in concrete. As a result, the goal of this research is to see how different percentages of WRF (0%, 0.25%, 0.5% and 1% by weight of concrete) affect the workability, mechanical (such as compressive and flexural strength, ultrasonic pulse velocity and bulk density) and structural (such as load deflection, crack width and propagation, and ductility index) properties of concrete. Results indicated that WRF improved the compressive and flexural strength of concrete by up to 22% and 4.3%, respectively. Furthermore, the width of cracks of reinforced concrete beams was considerably reduced and the ductility index of WRF-based beams was 3.07–3.24 compared to 1.45 for fiber-free beams.

ملخص البحث :

ملخص البحث :

The study aims in light of the goals of corporate sustainability to compare the costs and benefits of using different methods to determine costs; namely, the quantitative methods (multiple regression in particular) versus the activity-based costing (ABC) methods for assigning indirect costs on products in Iraqi companies as they still depend on traditional cost systems that face difficulties in computing accurate unit costs due to the failure to determine the appropriate amount of indirect costs. In order to achieve the study goal, the researchers reviewed the theoretical literature and previous studies to compare these methods and identify the advantages and disadvantages of each. The researchers also adopted the applied approach to compare these two methods based on the monthly costs data of the KDD production company to distribute costs according to both the activity-based method and the multiple regression. The study concluded that the design and implementation of the ABC method to determine costs requires lengthy and more expensive steps, especially in Iraqi companies that lack an integrated cost system, which requires additional costs to train employees and decision-makers to understand the steps of the system and its outputs and how to use them in the decision-making process in light of achieving Sustainability goals that require focusing on customer needs and product profitability rather than activities. On the other hand, the multiple regression method was easy to apply and inexpensive. Its results were more related to the products and the variables affecting them, thus it's more understanding for managers and helps in rationalizing decisions. Accordingly, the researchers recommended that Iraqi companies switch to the statistical method in distributing indirect costs instead of relying on a technique that increases the cost of products and makes them unable to compete and achieve growth and sustainability