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Study of Gamma Ray Detector Efficiencies and Integral Parameters Using Stochastic Simulations and Analytical Techniques

Thesis Info

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External Link

Author

Rehman, Shakeel Ur

Program

PhD

Institute

Pakistan Institute of Engineering and Applied Sciences

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2010

Thesis Completion Status

Completed

Subject

Mathemaics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1942

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727373174

Similar


Shakeel ur Rehman, PhD, Department of Physics & Applied Mathematics, PIEAS, July 2010. “Study of gamma-ray detector efficiencies and integral parameters using stochastic simulations and analytical techniques”; Supervisor: Dr. Nasir M. Mirza; Co-Supervisor: Dr. Sikander M. Mirza; Department of Physics & Applied Mathematics, PIEAS, Nilore 45650, Islamabad. In this work a novel primary-interaction based methodology has been developed for Monte Carlo based calculations of the detector efficiency which accelerate the computations and yields converged results with much shorter computer time. The proposed methodology has been first implemented in a MATLAB based computer program PIMC and later implemented in the state-of-the-art GEANT4 Monte Carlo simulation toolkit. The methodology has been used for point isotropic sources and thin disk sources at axial locations as well as off-axial locations with respect to the detector axis, excellent agreement has been found between the predictions of the PIMC code with the corresponding results obtained by using hybrid Monte Carlo as well as by analytical techniques and experimental measurements over a wide range of γ-ray energy values. Using the PIMC program, the energy dependent detector efficiency has been found to approach an asymptotic profile by increasing either thickness or diameter of scintillator while keeping the other fixed. The variation of energy dependent total efficiency of a 3" × 3" NaI(Tl) scintillator with axial distance has been studied using the PIMC code. About two orders of magnitude change in detector efficiency has been observed for zero to 50 cm variation in the axial distance. For small values of axial separation, a similar large variation has also been observed in total xviiefficiency for 137 Cs as well as for 60 Co sources by increasing the axial-off set from zero to 50 cm. The results for disk sources show a gradual decreasing trend in the total efficiency as disk source radius increases. For coaxial thin disk sources, the total detection efficiency has been found to approach a corresponding maximum value as length is increased in 1–20 cm range for various values of radii of disk sources and γ-ray energy while keeping the diameter of the detector fixed at 3” (7.62 cm). A similar behavior is observed when the radius of the detector is increased from 1–20 cm while keeping the length of detector fixed at 3” (7.62 cm), for various values of radii of disk sources and γ-ray energy. Then Monte Carlo simulations were carried out for the determination of photo peak- to-total ratio using the GEANT4 based detector model for various gamma ray energies and detector materials. The effect of variation of length and radius of the detector, while keeping the other fixed, was studied for various gamma ray energies. Mathematical curves for peak- to-total ratio were derived for various detector materials.
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جس شخص کے لہجے میں ہی تاثیر نہیں ہے

جس شخص کے لہجے میں ہی تاثیر نہیں ہے
کر سکتا کسی دل کو وہ تسخیر نہیں ہے

کیوں آس مری ایک بھی پوری نہیں ہوتی
کیوں میرے کسی خواب کی تعبیر نہیں ہے

اجمال سے اشکوں نے بیاں کر تو دیا ہے
کامل یہ مرے حال کی تصویر نہیں ہے

اب جائو مسیحا کو مرے ڈھونڈ کے لائو
اب اور مرے بچنے کی تدبیر نہیں ہے

جکڑا ہے زمانے کی رسومات نے ہم کو
ٹوٹے گی کبھی ایسی یہ زنجیر نہیں ہے

دکھ درد ہیں تائبؔ مرا سرمایۂ ہستی
ان جیسی کوئی دوسری جاگیر نہیں ہے

دلالة التركيز في قوله تعالى: فلا تقل لهمآ أفٍ

The Qur’ān is the divine renewed miracle in which the divine systemic rules stand for the collective good of humanity, the importance of caring for its reading and the significance of the meanings according to time and place and the new circumstances that man lives in. This research stands for analysis the significance contents mentioned in the Qur’ānic verse ﴿فَلا تقل لهمآ أُفٍ﴾. The dimensions include in the verse in terms of rules, judgments, and traditions are detailed in three main themes: firstly, is to read and explore the verse in terms of being a source of fundamentalist rules in the Islamic jurisprudence, which has a multiplicity of Schools of Islamic jurisprudence, in which it recognizes the concept of obedience to parents. Secondly, this verse is a reference to the social norms that governs the behavior of the individual and the society as evidence from the signs of discipline, whose meanings are interpreted by the fact of the children's respect for the parents and the establishment of a successful and balanced society based on family relations. Lastly, inspired from the existence of the significance in this verse to stand on the reality according to the concept of running this significance in the structure of Islamic law, which means the care of the individual and the society based on honor and human dignity. Thoroughly, it is concluded with recommendations in understanding the miraculous meaning of the verse, which ensures the implementation of the rules that the verse included in preserving the feelings of the parents according to the modern concepts of social care and services to preserve the existence of societies based on family relations.

Combinatorial Generation Algorithms for Subgraphs

The field of computer science has greatly benefitted from the advances in combina- torial algorithms in the last few decades. This is because the advent of high speed computers has made it possible to generate lists of combinatorial objects in a practi- cal amount of time. In areas such as genome science and data mining the problems are often vaguely defined, and researchers have to look for meaningful information in huge datasets. In this thesis, efficient generation algorithms for subgraphs such as bicliques and paths in cliques are developed. Cliques and bicliques are used to model various real-world problems encountered in bio-informatics, data mining and networks. We consider two variations of bicliques: pseudo-bicliques and c-isolated bicliques. Pseudo- bicliques relax the rigid connectivity requirement of bicliques to cater for missing and noisy data. On the other hand, the c-isolated bicliques enforce a restriction on the external connectivity of the vertices in a biclique to model cohesive communities. This thesis presents an algorithm based on reverse search to list all pseudo-bicliques in a graph G. The algorithm takes linear time on average to generate each pseudo- biclique. On the other hand, our generation algorithm for c-isolated bicliques exploit underlying properties of an isolated biclique to trim the input graph. Furthermore, the algorithm deploys the vertex cover enumeration algorithm based on fixed point tractability (FTP) and lists all isolated bicliques in linear time, in the case where c is constant. The performance of the proposed algorithms is evaluated on random graphs and real-world problems. The results are quite promising and confirm our theoretical findings. In this research work, we also explore another combinatorial object called a clique. A constant amortized time algorithm is proposed to generate all spanning paths and all paths in a clique in minimal change order (an ordering in which successive elements differ in a small way)