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A Modified Multiple Depth First Search Algorithm for Grid Mapping Using Mini-Robots Khepera
El-Ghoul, Sally,Hussein, Ashraf S.,Wahab, M. S. Abdel,Witkowski, U.,Ruckert, U. Korean Institute of Information Scientists and Eng 2008 Journal of Computing Science and Engineering Vol.2 No.4
This paper presents a Modified Multiple Depth First Search algorithm for the exploration of the indoor environments occupied with obstacles in random distribution. The proposed algorithm was designed and implemented to employ one or a team of Khepera II mini robots for the exploration process. In case of multi-robots, the BlueCore2 External Bluetooth module was used to establish wireless networks with one master robot and one up to three slaves. Messages are sent and received via the module's Universal Asynchronous Receiver/Transmitter (UART) interface. Real exploration experiments were performed using locally developed teleworkbench with various autonomy features. In addition, computer simulation tool was also developed to simulate the exploration experiments with one master robot and one up to ten slaves. Computer simulations were in good agreement with the real experiments for the considered cases of one to one up to three networks. Results of the MMDFS for single robot exhibited 46% reduction in the needed number of steps for exploring environments with obstacles in comparison with other algorithms, namely the Ants algorithm and the original MDFS algorithm. This reduction reaches 71% whenever exploring open areas. Finally, results performed using multi-robots exhibited more reduction in the needed number of exploration steps.
THE FUNDAMENTAL GROUP OF THE CONNECTED SUM OF MANIFOLDS AND THEIR FOLDINGS
El-Ghoul, M.,El-Ahmady, A.E.,Rafat, H.,Abu-Saleem, M. 충청수학회 2005 충청수학회지 Vol.18 No.2
In this paper, we will introduce the folding on the connected sum of some types of manifolds which are determined by their fundamental group. Also, the fundamental group of the unfolding of the connected sum will be deduced some types of conditional foldings restricted on the elements of the fundamental groups are deduced. Theorems governing these relations will be achieved. Some applications in manufacturing are presented.
El-Ghoul, Mabrouk Salem,Basher, Mohamed Esmail 충청수학회 2005 충청수학회지 Vol.18 No.2
In this paper, we introduced the tiling, for closed plane curves ${\alpha}(s)$, and we discussed the properties of tiling. Also if ${\alpha}(s)$ was arbitrary plane closed curve equipped by tiling ${\Im}$ then we studied the effect of retraction and tiling retraction on it.
THE INVARIANT OF IMMERSIONS UNDER ISOTWIST FOLDING
El-Ghoul, Mabrouk Salam,Basher, Mohamed Esmail 충청수학회 2005 충청수학회지 Vol.18 No.1
In this paper we will introduce all types of the isotwist foldings of a manifold M into itself. The limits of the isotwist foldings of a manifold are obtained. Also the relations between conditional retraction and this type of the folding are achieved. Finally the variant and invariant of the immersion under the type of folding are deduced.
A Modified Multiple Depth First Search Algorithm for Grid Mapping Using Mini-Robots Khepera
Sally El-Ghoul,Ashraf S. Hussein,M. S. Abdel Wahab,U. Witkowski,U. Ruckert 한국정보과학회 2008 Journal of Computing Science and Engineering Vol.2 No.4
This paper presents a Modified Multiple Depth First Search algorithm for the exploration of the indoor environments occupied with obstacles in random distribution. The proposed algorithm was designed and implemented to employ one or a team of Khepera II mini robots for the exploration process. In case of multi-robots, the BlueCore2 External Bluetooth module was used to establish wireless networks with one master robot and one up to three slaves. Messages are sent and received via the module’s Universal Asynchronous Receiver/Transmitter (UART) interface. Real exploration experiments were performed using locally developed teleworkbench with various autonomy features. In addition, computer simulation tool was also developed to simulate the exploration experiments with one master robot and one up to ten slaves. Computer simulations were in good agreement with the real experiments for the considered cases of one to one up to three networks. Results of the MMDFS for single robot exhibited 46% reduction in the needed number of steps for exploring environments with obstacles in comparison with other algorithms, namely the Ants algorithm and the original MDFS algorithm. This reduction reaches 71% whenever exploring open areas. Finally, results performed using multi-robots exhibited more reduction in the needed number of exploration steps.
The Persistence of Share Repurchases, Financing, and Growth
Sadok El Ghoul,Omrane Guedhami,Hyunseok Kim,Jungwon Suh 한국재무학회 2020 한국재무학회 학술대회 Vol.2020 No.08
This study documents evidence that share repurchases have become persistent in recent years, as an increasing number of firms repurchase shares year after year. This persistence means that share repurchases are now a long-term cash flow commitment. As a result, previous notions about share repurchases—such as considering them a means of distributing transitory cash flow, or a response to undervaluation or raising the debt ratio—have little explanatory power. Instead, share repurchases are linked to fast, consistent future growth, which is reflected in the high stock valuation of share repurchasing firms. Firms use cash flow as the primary source of capital to finance share repurchases year after year. This financing has cumulatively large effects on capital structure, as share repurchasing firms experience large, steady increases in retained earnings and comparable decreases in paid-in capital over time. On average, share repurchases do not displace investment, as share repurchasing firms invest actively to generate fast growth that in turn helps finance repeated share repurchases.
The Persistence and Consequences of Share Repurchases
Sadok El Ghoul,Omrane Guedhami,Hyunseok Kim,Jungwon Suh 한국경영학회 2022 한국경영학회 통합학술발표논문집 Vol.2022 No.8
Firms primarily use cash flow to finance increasingly persistent repurchases. This internal financing gradually increases retained earnings in the capital structure and results in high (low) repurchase (investment) sensitivity to cash flow. These effects are particularly pronounced among financially mature firms. During recent decades, the repurchase–cash flow sensitivity of U.S. firms has increased steadily, with steeper increases for financially mature firms. Repurchases do not appear to be associated with underinvestment. A non-trivial number of firms would have depleted their retained earnings had they paid dividends rather than repurchased shares.
THE FUNDAMENTAL GROUP OF THE CONNECTED SUM OF MANIFOLDS AND THEIR FOLDINGS
M. El-Ghoul,A.E. El-Ahmady,H. Rafat,M.Abu-Saleem 충청수학회 2005 충청수학회지 Vol.18 No.2
In this paper, we will introduce the folding on the connected sum of some types of manifolds which are determined by their fundamental group. Also, the fundamental group of the unfolding of the connected sum will be deduced some types of conditional foldings restricted on the elements of the fundamental groups are deduced. Theorems governing these relations will be achieved. Some applications in manufacturing are presented.
Foldings and retractions of manifolds and their fundamental groups
M. El-Ghoul,A. E. El-Ahmady,H. Rafat,M. Abu-Saleem 장전수학회 2007 Proceedings of the Jangjeon mathematical society Vol.10 No.1
In this paper, we introduce the definition of the folding on the fundamental group. The folding on a wedge sum of some types of manifolds which are determine by their fundamental group are obtained. Some types of conditional foldings restricted on the elements of the fundamental groups are deduced. The effect of retraction of manifolds on the fundamental group is obtained. The folding of variation curvature of manifolds on their fundamental group are presented. Theorems governing these relations are achieved.