On-orbit assembly using superquadric potential fields

The autonomous on-orbit assembly of a large space structure is presented using a method based on superquadric artificial potential fields. The final configuration of the elements which form the structure is represented as the minimum of some attractive potential field. Each element of the structure is then considered as presenting an obstacle to the others using a superquadric potential field attached to the body axes of the element. A controller is developed which ensures that the global potential field decreases monotonically during the assembly process. An error quaternion representation is used to define both the attractive and superquadric obstacle potentials allowing the final configuration of the elements to be defined through both relative position and orientation. Through the use of superquadric potentials, a wide range of geometric objects can be represented using a common formalism, while collision avoidance can make use of both translational and rotation maneuvers to reduce total maneuver cost for the assembly process

Design and Improvement of Convection Cooling for Parallel Plate Duct Flow

In this paper a new examinations of the effect of micro channel geometry on high-pressure dispersion and emulsification were carried out.  Forced convection heat transfer from arrays of micro channels was regarded for fixed volume and fixed pressure drop constraints. Order of magnitude relationships were advanced for the optimal dimension of a number of original duct shapes containing the parallel plate channel with rectangular, square, rhombus, isosceles right triangle, circular duct and elliptic duct. Using the exact examination technique to generate a rounded expression for the optimal duct shape was advanced for all ducts regarded, where rounded analytical results demonstrate that the optimal shape is the parallel plate channel duct array but with addition a triangular or rectangular duct to the parallel plate. Comparison of the approximate results with exact results from the conventional design illustrates outstanding acceptance for the optimal duct dimensions.   Keywords: micro channel, forced convection, optimal geometry

Liability of the Maritime Carrier towards Passengers

Transport is undoubtedly of great importance in passenger’s lives. Not only because it is a legal phenomenon, but also a socio-economic phenomenon across all societies. This search deals with this topic; it is divided into two sections, the first deals with Cases of the Passengers Carrier’s Liability and its Basis, while the second deals with Area of Responsibility of the Maritime Carrier of Passengers under both of the Egyptian Law and Athens Convention relating to the Carriage of Passengers and their Luggage by Sea

Corporate Bankruptcy Requirements & Impacts “Under the Egyptian Law

The term “Merchant” does not only make reference to a natural person, but can also mean a moral person and, more precisely, corporations. As firms acquire commercial capacity, they become subject to the same legal regulations governing individual merchants. They can then be declared bankrupt just at the moment that they stop paying their commercial debts. While much emphasis has been placed on the provisions of bankruptcy generally in jurisprudence and legislation, the bankruptcy provisions of corporations are somehow overlooked, although such provisions are those which should have been given due attention, for two reasons: First, the role of a trading corporation is far more significant than that performed by individual merchants in the business field. Trading corporations bring together all efforts and savings of individuals into one whole. They undertake large-scale economic projects that individuals alone can not complete, irrespective of their abilities and potentials, making them the perfect tool for economic advancement. And so, with the growth of such significance, these corporations, and particularly joint venture companies, gained power that only the power of the state prevails over. They are recognized as a social and economic power, which are held in great respect by their country that feels like it is its duty to watch over them so that they continue on the right path, in order not to become a tool for social exploitation or political control[1]. Second, corporation bankruptcy has the most dangerous effect on national economy and the greatest influence on trade credit. The capital of these firms is, in most cases, quite as huge as their debts. What is more, not only does the bankruptcy of a corporation influence the life of such corporation, but also affects the creditors, partners, administrative structure, and even the employees whose number could reach thousands in some cases. And this will unquestionably culminate in affecting the national economy system in general. In light of the ancient commercial codification, texts only contained very few provisions concerning partnerships. These include: Article 198, which provides for the determination of the names of joint partners as well as their domicile in the “cessation of payment” report submitted by the company, and Article 241, which requires affixation of seals upon bankruptcy of partnerships or commandite companies on the “headquarters of the company and the other separate branches of each of the joint partners, as well as Article 341 that authorizes conciliation, upon bankruptcy of a partnership, with one or more joint partners, and Article 408 detailing the conditions for a joint partner to regain capacity (to be discharged of bankruptcy) upon bankruptcy. With respect to non partnerships, such as joint venture companies, texts made no mention of such companies[2]. The fifth and last chapters of the new commercial law are devoted to bankruptcy. The law also deals with corporate bankruptcy in the seventh section of this chapter. Article 698 of chapter 7 stipulated that the provisions set forth in this chapter and the following rules shall apply to corporate bankruptcy. That is to say, the rules provided for in section 7 of chapter 5 shall first apply when it comes to corporate bankruptcy. Where such rules make no mention of corporate bankruptcy, the rules set out in the fifth chapter concerning bankruptcy generally shall apply, in consistency with the nature and confidentiality of the company, factors that distinguish it from individual merchants. [1] Dr. Mohsen Shafiq, Intermediate in Commercial Law, Chapter I, 3rd Edition, 1957, page 329, Dr. Aktham Al Khawli, Comparative Lebanese Commercial Law, Chapter II, Commercial Companies, 1968, page 2, Clause 1, Dr. Mohamed Fareed Al Areeni, Commercial Companies, Collective Commercial Project Between Unity of Legal Framework and Plurality of Forms, Dar El Gamaa El Gadida, 2011, page 7. [2]. Dr. Mohsen Shafiq, Egyptian Commercial Law, Chapter II, Dar Al Thaqafa, 1949, page 1058

Robot motion planning using hyperboloid potential functions

A new approach to robot path planning using hyperboloid potential functions is presented in this paper. Unlike parabolic potential functions, where the control force increases with distance from the goal and is unbound, and conic potential functions where a singularity occurs at the goal, hyperboloid potential functions avoid both these drawbacks. However, they do combine the advantages of both parabolic and conic potentials as the asymptotic property of the hyperbolic function ensures bounded control forces, while stability and smooth contact are guaranteed at the goal point

Free flyer manoeuvring round a space station

One of the most critical processes of a free-flying autonomous robot is investigated in this paper using artificial potential fields. Close navigation round The International Space Station could not be established with the potential functions without representing the station using a superquadric model. The final configuration is defined as the global minimum of a function which includes the goal parameters and the station structure. An error quaternion representation is used to define both attractive and repulsive potentials to enable the formulation of a position-orientation dependent controller. Coupling between translational and rotational motions leads to better controller performance. Its elegancy and simplicity minimize the computational power needed for the free-flyer on-board computer

A review on solar cells from Si-single crystals to porous materials and quantum dots

AbstractSolar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-porous materials. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe–TiO2 architecture have been developed