Faithful visualization and dimensionality reduction on graphics processing unit

Information visualization is a process of transforming data, information and knowledge to the geometric representation in order to see unseen information. Dimensionality reduction (DR) is one of the strategies used to visualize high-dimensional data sets by projecting them onto low-dimensional space where they can be visualized directly. The problem of DR is that the straightforward relationship between the original highdimensional data sets and low-dimensional space is lost, which causes the colours of visualization to have no meaning. A new nonlinear DR method which is called faithful stochastic proximity embedding (FSPE) is proposed in this thesis to visualize more complex data sets. The proposed method depends on the low-dimensional space rather than the high-dimensional data sets to overcome the main shortcomings of the DR by overcoming the false neighbour points, and preserving the neighbourhood relation to the true neighbours. The visualization by our proposed method displays the faithful, useful and meaningful colours, where the objects of the image can be easily distinguished. The experiments that were conducted indicated that the FSPE is higher in accuracy than many dimension reduction methods because it prevents as much as possible the false neighbourhood errors to occur in the results. In addition, in the results of other methods, we have demonstrated that the FSPE has an important role in enhancing the low-dimensional space which are carried by other DR methods. Choosing the worst efficient points to update the rest of the points has helped in improving the visualization information. The results showed the proposed method has an impacting role in increasing the trustworthiness of the visualization by retrieving most of the local neighbourhood points, which they missed during the projection process. The sequential dimensionality reduction (SDR) method is the second proposed method in this thesis. It redefines the problem of DR as a sequence of multiple DR problems, each of which reduces the dimensionality by a small amount. It maintains and preserves the relations among neighbour points in low-dimensional space. The results showed the accuracy of the proposed SDR, which leads to a better visualization with minimum false colours compared to the direct projection of the DR method, where those results are confirmed by comparing our method with 21 other methods. Although there are many measurement metrics, our proposed point-wise correlation metric is the better. In this metric, we evaluate the efficiency of each point in the visualization to generate a grey-scale efficiency image. This type of image gives more details instead of representing the evaluation in one single value. The user can recognize the location of both the false and the true points. We compared the results of our proposed methods (FSPE and SDR) and many other dimension reduction methods when applied to four scenarios: (1) the unfolding curved cylinder data sets; (2) projecting a human face data sets into two dimensions; (3) classifing connected networks and (4) visualizing a remote sensing imagery data sets. The results showed that our methods are able to produce good visualization by preserving the corresponding colour distances between the visualization and the original data sets. The proposed methods are implemented on the graphic processing unit (GPU) to visualize different data sets. The benefit of a parallel implementation is to obtain the results in as short a time as possible. The results showed that compute unified device architecture (CUDA) implementation of FSPE and SDR are faster than their sequential codes on the central processing unit (CPU) in calculating floating-point operations, especially for a large data sets. The GPU is also more suited to the implementation of the metric measurement methods because they do a large computation. We illustrated that this massive speed-up requires a parallel structure to be suitable for running on a GPU

Preparation, Structural and Optical Characterization of ZnO/Ag Thin Film by CVD

Zinc Oxide thin films doped with Ag have been synthesized by CVD technique. By increasing the dopant from 0 to 10 % Ag in ZnO thin films were found to lead to pronounced changes in their morphology. From optical properties the band gap energy of pure ZnO thin film was 3.25 eV, with the increasing of Ag doping from 1 to 10% it is not affected. X-ray diffraction has shown that the maximum intensity peak corresponds to the (101) predominant orientation for ZnO and ZnO:Ag. SEM images show that more crystalline behavior by increasing the doping. EDXA analysis showed that the structure of ZnO film contains Zn and O elements and Ag, Cu, Si for doping at 10 % Ag

Trustworthy dimension reduction for visualization different data sets

A new nonlinear dimension reduction (DR) method which is called Trustworthy Stochastic Proximity Embedding (TSPE) is introduced in this paper to visualize different types of data sets. TSPE overcome the main shortcomings of the DR by sending the false neighbour points to the correct locations, and preserving the neighbourhood relation to the true neighbours, which are inside the local neighbourhood. The visualization of our proposed method displays the trustworthy, useful and meaningful colours, where the objects of the image can be easily distinguished. The performances of TSPE and 20 dimension reduction methods are compared, and the efficiency of the proposed method in both visualization accuracy and computational cost is shown. The results showed the ability of our method in preserving neighbourhood relation, where they revealed more interested information. In real data set, the efficiency of the visualization of tensor images data sets by TSPE might help the specialist to make a good decision about a patient�s treatment. The comparison with experimental data set, as three dimensions of curved cylinder, showed the ability of TSPE to unfold this complex data set efficiently whilst preserving most information of the original data set

Вплив домішки Au на структурні та оптичні властивості тонких плівок ZnO, отриманих методом CVD

Тонкі плівки оксиду цинку, леговані Au, синтезували методом CVD. Збільшення легуючої домішки від 0 до 15 мас. % Au в тонких плівках ZnO призводить до виражених змін морфології плівок. З оптичних властивостей витікає, що ширина забороненої зони чистої тонкої плівки ZnO становить 3.28 еВ, і при збільшенні легуючої домішки Au від 5 до 15 мас. % вона не змінюється. Рентгенівська дифракція показала, що пік максимальної інтенсивності відповідає переважній орієнтації (101) для плівок ZnO при 15 мас. % Au. Зображення SEM показують, що збільшення кристалів відбувається за рахунок збільшення концентрації легуючої домішки. Аналіз EDX показав, що нелегована плівка ZnO містить елементи Zn і O, а плівка, легована 15 мас. % Au, додатково до елементів Zn і O містить елементи Au і Cu. Усі дифракційні піки можна віднести до кристалічного ZnO з гексагональною структурою. Крім цих піків, з'явилися два нових піки (111) і (200), які обумовлені золотом. Вивчення морфології плівок ZnO вказує на наявність однорідних зерен, тоді як при додаванні атомів Au зерна не однорідні і мають різні розміри. Аналіз EDX для чистого ZnO демонструє два сильних піки, які відповідають Zn і O, що підтверджує високу чистоту тонких плівок ZnO. А в легованих тонких плівках (15 мас. % Au) спостерігається поява елемента Au з високою інтенсивністю, також два сильні піки, що відповідають елементам Cu і Zn, і наявність піків з низькою інтенсивністю за рахунок елементів Au, Cu і Zn.Thin zinc oxide films doped with Au have been synthesized by CVD technique. Increase in the dopant from 0 to 15 wt. % Au in ZnO thin films led to pronounced changes in the film morphology. It follows from the optical properties that the band gap of pure ZnO thin film is 3.28 eV, and with increasing Au dopant from 5 to 15 wt. % it does not change. X-ray diffraction has shown that the peak of the maximum intensity corresponds to the preferred orientation (101) for ZnO films at 15 wt. % Au. SEM images show that crystal growth is due to an increase in the dopant concentration. EDX analysis showed that the undoped ZnO film contains Zn and O elements, and the film doped with 15 wt. % Au in addition to the Zn and O elements contains Au and Cu elements. All diffraction peaks can be attributed to crystalline ZnO with a hexagonal structure. In addition to these peaks, two new peaks (111) and (200) appear due to gold. Study of the morphology of ZnO films indicates the presence of homogeneous grains, while when Au atoms are added, the grains are not homogeneous and have different sizes. EDX analysis for pure ZnO shows two strong peaks corresponding to Zn and O, which confirm the high purity of ZnO thin films. And in doped thin films (15 wt. % Au), the appearance of high-intensity Au element, as well as the two strong peaks corresponding to the Cu and Zn elements, and the presence of low-intensity peaks due to the Au, Cu and Zn elements, are observed

Конструювання Al:ZnO/p-Si сонячного елемента з гетеропереходом за допомогою програми для моделювання SCAPS

Тонка плівка ZnO є потенційним кандидатом для використання в якості буферного шару в силіконовій сонячній батареї. У роботі досліджено вплив концентрації Al (1, 5, 10 мас. %) на ефективність перетворення сонячних елементів з тонких плівок Al:ZnO/Si за допомогою програми для моделювання SCAPS. Було виявлено, що основні фотоелектричні параметри, такі як напруга розімкнутого ланцюга, щільність струму короткого замикання, коефіцієнт заповнення, ефективність перетворення, квантова ефективність та коефіцієнт ідеальності зростали в міру збагачення плівки Al. При 10 мас. % Al оптимальна ефективність перетворення становила приблизно 7 %, максимальне значення коефіцієнта ідеальності складало 17,51, а значення ширини смуги – 3,56 еВ. Крім того, для всіх вимірювань визначали питомий опір, концентрацію носія та рухливість. Встановлено, що зменшення коефіцієнта Холла призвело до збільшення концентрації носія із збільшенням вмісту Al, тоді як збільшення рухливості відбувалося через зменшення електричного опору. Квантова ефективність сонячного елемента, виміряна на довжині хвилі в діапазоні 400-1000 нм, знаходилася в межах 0,4-0,5.ZnO thin film is a prominent candidate to be used as a buffer layer in silicon solar cells. In this paper, the effect of Al concentrations (1, 5, 10 wt. %) on the conversion efficiency of Al:ZnO/Si thin film solar cells has been investigated through simulation by SCAPS program. It has been found that the main photovoltaic parameters such as open-circuit voltage, short-circuit current density, fill factor, conversion efficiency, quantum efficiency and ideality factor increased as Al enrichment occurred. At 10 wt. % of Al the optimum conversion efficiency was approximately 7 %, the maximum value of the ideality factor was 17.51, and the bandgap value was 3.56 eV. Additionally, the resistivity, carrier concentration and mobility were determined for all measurements. It has been found that a decrease in the Hall coefficient led to an increase in the carrier concentration with increasing Al content, while an increase in the mobility occurred due to a decrease in the electrical resistivity. The quantum efficiency of the solar cell measured at a wavelength in the range of 400-1000 nm was between 0.4-0.5