Semiconductor Heterostructure Design For Non-linear Optical Process For Quantum Information Technologies

Quantum information technologies require reliable sources of correlated/entangled photons. To realize and use these technologies in real life rather than just in laboratory, high efficiency and stable sources of entangled photons are needed. This work considers the design of various semiconductor heterostructures, based on Al$_x$Ga$_{1-x}$As/GaAs, that rely on intersubband transitions in the conduction or in the valence band, to deliver the second order nonlinear process, known as spontaneous parametric down-conversion (SPDC). The second-order SPDC can produce Bell state entangled photons. Second harmonic generation (SHG) is a well known and broadly discussed process, and using the fact that SHG is the reverse process of SPDC, initial studies of SHG are used to support the validity and accuracy of the methodology employed for nonlinear susceptibility calculations. In designing the heterostructures, genetic optimization is used to reduce the computational cost in finding the best structure. The heterostructures designed by considering the intersubband transitions in the conduction band constitute good sources of spectrally entangled photons. The efficiency of the process is estimated and the Schmidt number calculation shows that the structure can produce twin photons with a reasonably good degree of entanglement. Alternatively, using intersubband transitions in the valence band can deliver the polarization entangled photons, which cannot be achieved with conduction intersubband transitions. The genetic optimization is again used to design the best structures for this purpose, and the efficiency of the process is also calculated. We then extend our work to multiparticle entangled states, also known as Greenberger-Horne-Zeilinger (GHZ) states, by considering the third order nonlinear SPDC (TOSPDC) process in designing the heterostructures for this purpose. This designed structure can be a good candidate as a direct TOSPDC source, since the second order nonlinearity is here suppressed by considering symmetric structures only. The efficiency of the process is also calculated and discussed in the thesis

Polarization-entangled mid-infrared photon generation in p-doped semiconductor quantum wells

The optimal design of double quantum well structures for generation of polarization-entangled photons in the mid-infrared range, based on the valence intersubband transitions spontaneous parametric downconversion, is considered. The efficiency and frequency selectivity of the process are also estimated

Optimization of Automotive Manufacturing Layout for Productivity Improvement / Muhamad Magffierah Razali ...[et al.]

This paper deal with an optimization of automotive manufacturing layout by using meta-heuristics approach aided with discrete event simulation (WITNESS Simulation). The objective of this study is to balance the workload, increase line efficiency, and improve productivity by optimizing assembly line balancing (ALB) using Genetic Algorithm. The current assembly line layout operated under the circumstance where idle time is high due to unbalance workload. After the optimization process takes place, the workload distribution in each workstation has shown a significant improvement. Furthermore, productivity improvement was gained after the optimization followed by increment in term of line efficiency by 18%. In addition, the number of workstation needed to assemble the product can be reduced from current layout (17 workstations) to an improved layout (14 workstations). The current study contributes to the implementation of Genetic Algorithm in ALB to improve productivity of related automotive manufacturing industry

Ab initio Investigation of the structure and electronic properties of normal spinel Fe2SiO4

Transition metal spinel oxides have recently been predicted to create efficient transparent conducting oxides for optoelectronic devices. These compounds can be easily tuned by doping or defect to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still subject to controversy. We propose a complete density functional theory investigation of fayalite (Fe2SiO4) spinel, using Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA) in order to explain the electronic and structural properties of this material. A detailed study of their crystal structure and electronic structure is given and compared with experimental data. The lattice parameters calculated are in agreement with the lattice obtained experimentally. The band structure of Fe2SiO4 spinel without Coulomb parameter U shows that the bands close to Fermi energy appear to be a band metal, with four iron d-bands crossing the Fermi level, in spite of the fact that from the experiment it is found to be an insulator

Effectiveness of a musical-based learning approach on knowledge and happy index related to anatomy syllabus: a quasi-experimental pilot study

Introduction: Musical-based education has been linked with improved students’ academic performance and mental wellbeing. This study aimed to evaluate a musical-based anatomy learning module using the combination of music, choreographed movements and 3D anatomy illustrations on muscles of the hand. Methods: A 5-minute duration video on muscles of the hand was developed through series of discussions with expert panels to incorporate the three stated components, emphasizing on the use of catchy music and simple terms to assist memorization skills. A single arm quasi-experimental pilot study was conducted with pre- and post-intervention measurement of knowledge, perception, stress and happy index related to learning anatomy. A total of 157 medical students were recruited and exposed to a total of 20 minutes video duration over three days. The effectiveness of the intervention was investigated using paired t-test and was interpreted based on the pre- and post-measured exposure mean differences. Results: The newly developed musical-based anatomy learning module had effectively improved knowledge and happy index related to learning anatomy, with significant mean differences were observed on the total mean scores for knowledge (MD= 2.707, p< 0.001) and happy index (MD=3.256, p< 0.001), as well as significant reduction of the mean scores for the negative items for perceptions and stress. Conclusion: The improved knowledge and happy index related to learning anatomy reflecting the positive impact of music used in combination choreographed movements and 3D illustrations to strengthen memorizing skills of medical students as well as instilling positive mood

A Review of Two-sided Assembly Line Balancing Problem

Assembly line balancing (ALB) is concerned with assigning tasks within an assembly line to meet the required production rate for optimization purposes. On the other hand, two-sided ALB performs double-sided assembly operation on a single assembly line. In this paper, we have focused the survey on two-sided assembly line balancing (2S-ALB) research problems. The numerous factors mentioned in 2SALB literature were actually based on problem resolutions, and this paper will quote any preferred literature considering the frequent citation. In particular, this review explores in detail the ALB problems, optimization methods, objective functions, and specific constraints used in solving 2S-ALB problems. Among the purposes of ALB problems is that it traditionally focuses on simple ALB with various engaging approaches. General ALB comes second because of its complexity and nondeterministic polynomial (NP)-hard-classified problems. However, due to the current manufacturing issues, GALB problems, such as 2S-ALB, are forced to be examined and this comprehensive literature will specify anything necessary for the optimization purposes. Finally, future research direction has been discovered and put forward as the suggestion

Mathematical Modelling of Mixed-Model Assembly Line Balancing Problem with Resources Constraints

Modern manufacturing industries nowadays encounter with the challenges to provide a product variety in their production at a cheaper cost. This situation requires for a system that flexible with cost competent such as Mixed-Model Assembly Line. This paper developed a mathematical model for Mixed-Model Assembly Line Balancing Problem (MMALBP). In addition to the existing works that consider minimize cycle time, workstation and product rate variation, this paper also consider the resources constraint in the problem modelling. Based on the finding, the modelling results achieved by using computational method were in line with the manual calculation for the evaluated objective functions. Hence, it provided an evidence to verify the developed mathematical model for MMALBP. Implications of the results and future research directions were also presented in this paper

Modelling of Two-sided Assembly Line Balancing Problem with Resource Constraints

Two-sided assembly line balancing (2S-ALB) problems is practically useful in improving the production of large-sized high-volume products. Many published papers have proposed various approaches to balance this well-known ALB problem. However, little attention is given in formulating the 2S-ALB problems. In this paper, 2S-ALB is modelled with four different objective functions comprising minimization of workstations, mated- workstation, idle time and resource constraints. In different with existing model, this paper also considers resource constraint with a mathematical modelling formulation in solving the 2S- ALB problems. The modelling procedures are present for each objective functions with a simple 2S-ALB example problem. Then, the anticipated performance solution is obtained from the test problem