Sharif Digital Repository

The Cu2ZnSnS4 (CZTS) quaternary compound, with suitable optical and electrical properties, is one of the most interesting materials for absorber layer of thin film solar cell. Since all constituents of CZTS, are abundant in earth’s crust and non-toxic, it is a proper replacement for the materials like CdTe and CuInSe2. The CZTS pellet was synthesized by the solid-state reaction and deposited on soda lime glass substrates by pulsed laser deposition (PLD) method. PLD technique has the advantages of offering stoichiometric preservation during the materials transformation from target to substrate and good crystallinity due to the highly energetic species. CZTS has was deposited in order to... 

The main aim of this study is to propose a new structure of compression surfaces of a supersonic inlet in order to improve target performance parameter i.e. total pressure recovery ratio. This idea resulted in developing a new type of supersonic inlet, utilizing four ramps and a cone as compression surfaces simultaneously.A prototype of this type of inlet has been designed for Mach 3 and its performance has been studied via numerical simulation in design point and off design conditions. Eventually the new inlet compared to experimental performance survey data from two cases of two-cone inlets and also analytical calculations of ideal performance of some types of supersonic inlets. Results of... 

Physical and chemical properties of tungsten oxide thin films change reversibly while exposure to hydrogen gas. This property is called gasochromic. To enhance optical properties of such films, nanostructured, amorphous and porous thin films of (WO3)1-x(MeO)x (MeO= TiO2, MoO3, NiO; x=0.09, 0.17, 0.23, 0.29, 0.33) were fabricated by Pulsed Laser Deposition. Molar percentage of Me/W (Me= Ti, Mo and Ni) was changed in films with respect to targets; for Ti and Ni always a reduction, but for Mo an enhancement for low percentages was observed. The reason is the existence of thermal ablation mechanism during deposition, in the other word is different vapor pressure effect. An increment in x for... 

The Cu2ZnSnS(e)4 (CZTS(e)) quaternary and Cu2SnS3 (CTS) ternary componds with suitable optical and electrical properties have been considered as an emerging semiconductors for fabrication of thin-fim solar cells. So far, two technologies based on CdTe and CuInGaS(e)2 absorbers have achived efficiencies above 20%. However, these compounds contain toxic element Cd and rare elements such as In and Ga which, limited the development of these solar cells.In this research a 3-stage method was used for fabrication of CZTS(e) thin Films. In the first stage, CTS layers were deposited by spray pyrolysis method, in the second one, ZnS layers were also deposited on CTS layers by spray pyrolysis method... 

Given a divisible finite field extension KjF, the structure of Br(F), the Brauer group of F, is investigated. It is shown that, if F is indivisible, then Br(F) = Z2, which generalizes the Frobenius Theorem. As a consequence, when F is indivisible, the class of all finite dimensional non-commutative F-central division algebras D having radicable multiplicative groups D is determined. In fact, it is proved that the following statements are equivalent: (1) D is radicable, (2) D contains a divisible subfield KjF, and (3) D is the ordinary quaternion division algebra and F(p 1) is divisible  

In this research, a new approach for TWS (Track While Scan) systems is introduced. Conventional TWS systems usually use target’s position (in Cartesian or polar coordinate systems), its velocity, and sometimes its acceleration (in main directions of coordinate system which is being used) as the elements of target’s state vector but the suggested algorithms use target’s velocity, course of motion and their rates of change as main tracking quantities and target’s position will be calculated after updating its velocity and course of motion. Hough transform is used as a powerful tool in detecting patterns which are identified with finite parameters (like lines, circles, ellipses, etc) to... 

In algebra, division rings or skew fields are considered one of the basic building blocks in ring theory. So, a careful study of the properties of these rings is essential for the development of ring theory. All division rings, according to whether they are finite dimensional or infinite dimensional (as vector spaces) over their centers, are broadly classified into two types of centrally finite division rings and centrally infinite division rings.Herstein's conjecture about multiplicative commutators in these rings, is one of the unsolved problems that Herstein has proved it in the case when division ring is centrally finite, or the center of division ring is uncountable, but the... 

Copper-based semiconductors have received a great deal of attention due to their high absorption coefficient, direct and adjustable energy gap with stoichiometry, low frequency and toxicity. Multicomponent nanocrystals such as CuInS2, Cu (In, Ga) (S, Se) 2, Cu2ZnSnS4 and Cu2SnS3 (CTS) have been successfully synthesized by colloidal synthesis and have shown application potentials such as energy conversion, photocatalyst, thermoelectric and biomedical. Among these, the CTS ternary semiconductor with p-type conduction is one of the most well-known compounds of group I-IV-VI, which consists of abundant and non-toxic elements. In this research, thin-film solar cells with FTO / TiO2 / In2S3 / CdS... 

The problem of guarding orthogonal art galleries with sliding cameras is a special case of the well-known art gallery problem when the goal is to minimize the number of guards. Each guard is considered as a point, which can guard all points that are in its visibility area. In the sliding camera model, each guard is specified by an orthogonal line segment which is completely inside the polygon. The visibility area of each sliding camera is defined by its line segment.Inspired by advancements in wireless technologies and the need to offer wireless ser- vices to clients, a new variant of the problems for covering the regions has been studied. In this problem, a guard is modeled as an... 

Our main purpose is introducing essential dimension and investigating properties of this concept and definition of it on different algebraic objects and proving some theories about it. In the beginning we define the concept of essential dimension on the extension fields which indeed it is expressing complexity of extension on the background field.Then with the meaning of noetherian extension which we will introduce it in the chapter three, we generalize the concept of essential dimension to finite groups. At last we investigate the connection between the essential dimension with generic polynomials and one of our important results is finding upper bounds for essential dimension of finite... 

In this thesis we investigate identities on maximal subgroups of developed by D. Kiani and M. Mahdavi-Hezavehi . Let be a division ring with centre and a maximal subgroup of ( ) . Several group identities on M and polynomial identities on the F-linear hull where is algebraic over F are studied. We show that if is a PI-algebra, then . When is non-commutative and is infinite, we show that if satisfies a group identity and is algebraic over , then we have either where is a field and , or is absolutely irreducible. Finally for a finite-dimensional division algebra and a subnormal subgroup of we show that if is a maximal subgroup of that satisfies a group identity,... 

In this thesis we study the structure of locally solvable, solvable, locally nilpotent, and nilpotent maximal subgroups of skew linear groups. In [5] it has been conjectured that if D is a division ring and M a nilpotent maximal subgroup of , then D is commutative. In connection with this conjecture we show that if M a nilpotent maximal subgroup of , then M is an abelian group. Also we show that is a solvable maximal subgroup of real quaternions and so give a counterexample to Conjecture 3 of [5], which states that if D is a division ring and M a solvable maximal subgroup of , then D is commutative. Also we completely determine the structure of division rings with a non-abelian... 

If L is a finite-dimensional Lie algebra over the field F then the universal enveloping algebra U(L) can be embedded in a division ring D. In particular, if L is a solvable p-algebra, there is a decomposition D=KR where K and R are maximal subfields of D, K is Galois extension of the center Z of D and R is a purely inseparable extension of Z with R^p⊆Z. The present thesis is concerned with the compared structures of maximal subfields in a division D and in the division ring of rational functions D(X). We prove that maximal subfields of D(X) “generically” specialize to maximal subfields of D, and properties such as being Galois or purely inseparable over the centre also carry over... 

In this Mater thesis, we o?er a general Prime Ideal Principle for proving that certain ideals in a commutative ring are prime. This leads to a direct and uniformtreatment of a number of standard results on prime ideals in commutative algebra,due to Krull, Cohen, Kaplansky, Herstein, Isaacs, McAdam, D.D. Anderson, andothers. More signi?cantly, the simple nature of this Prime Ideal Principle enablesus to generate a large number of hitherto unknown results of the “maximal impliesprime” variety. The key notions used in our uniform approach to such prime idealproblems are those of Oka families and Ako families of ideals in a commutative ring.In chapter 2, we amplify this study by developing... 

Given a finite dimensional F-centeral simple algebra A = Mn(D), denote by A′ the derived group of its unit group A*. In this thesis, the Frattini subgroup Φ(A*) of A*for various fields F is investigated. Setting G = F* ∩ Φ(A*), when F is a local or global field the group G is completely determined. For global fields it is proved that when F is a real global field, then Φ(A*) = Φ(F*)Z(A′) otherwise Φ(A*) = ∩F*p where the intersection is taken over primes p not dividing the degree of A. Using the connection between Φ(A*) and Φ(F*) via Z(A′), Φ(A*) is also calculated for some particular division rings D.

 

Defining the structure of maps using local features is among the popular fields of study in mathematics. Therefore determining the structure of maps on rings which behave like derivations at idempotent-product elements has been getting attention recently. This subject is useful for examining the structure of rings and algebraic operators in both algebra and analysis as well. Suppose that R is a ring, d : R ! R is an additive map, z 2 R and d meets the condition below: 8a; b 2 R : d(ab) = ad(b) + d(a)b Therefore d is called a derivation on R. If for every a; b 2 R where ab = z, d(ab) = ad(b) + d(a)b then d behaves like a derivation at idempotent-product elements of ab = z. The main challenge... 

In the present thesis, we study on the structure of the solvable, supersoluble, nilpotent, and irreducible structures of the subgroups. The main purpose of the present thesis is to represent a criterion given for D to be a supersoluble (nilpotent) crossed product division algebra in terms of subgroup of the multiplicative group D* of D. It is shown that the D is supersoluble (nilpotent) crossed product, if and only if D* contains an irreducible abelian-by-supersoluble (nilpotent) subgroup. Furtetmore, we review and discuss the structure of the crossed product division algebra, D, with the solvable irreducible subgroup, D*, and finally we extend our results for the semi-cross product of the... 

Given a finite dimensional F-central simple algebra A = Mn(D),the connection between the Ferattini subgroup (A) and (F) via Z(A′), the center of the derived group of A , is investigated. Setting G = F \(A), it is shown that (F)Z(A′ ) G (\pFp)Z(A′)where the intersection is taken over primes p not dividing the degree of A. Furthermore ,when F is a local or global field, the group G is completely determined. Using the above connection, (A) is also calculated for some particular division rings D  

This thesis is a survey of results of studies and researches in theory of Division rings and multiplicative groups of division rings and relations between group strcture and algebraic structure of division rings.in this case,we emphesized on study of finitely generated,maximal,nilpotent and soluble subgroups of division rings.we also,study the Valuation theory on division rings and Reduced K-theory of division rings and relations between these theories and group structure of division rings,morever,those which is finite dimensional over their center as vector spaces.at the end,we shortly,study divisible division rings and radicable division rings  

A Weddernurn polynomial over a division ring K, is the minimal polynomial of an algebraic subset of K. Such a polynomial, always is a product of linear factors over K, but not all such products are Wedderburn polynomials, even if these linear factors are distinct. In this thesis, we give some properties and characterizatios of Wedderburn polynomials over the division ring K, which relates deeply to algebraic subsets of K. We work in the general setting of Ore skew polynomials with an indeterminate t over K, corresponding to S,D, where S is an endomorphism of K and D is an S-derivation over K. Also we give a survey of the structure of the skew polynomial ring K[t; S; D] and its relation with...