Effect of intermediate layer in photocurrent improvement of three-layer photoanodes using WO3 and Fe2O3

Sol–gel method was applied to synthesize WO3/Fe2O3 three-layer films in order to improve the generated photocurrent under UV–vis light irradiation. The films were deposited on FTO glass substrates through doctor bladding method. The samples were then calcined at 500 °C. The photocurrents of the synthesized photoanodes were evaluated by measuring the electric current and voltage under UV–vis light at room temperature. Scanning electron microscopy (SEM) revealed unique surface morphologies owing to the presence of the intermediate layers. At an applied potential of 1300 mV, the WO3\Fe2O3\WO3 and Fe2O3\WO3\Fe2O3 photoanodes exhibited photocurrent densities up to 0.1 mA/cm2 and 0.6 mA/cm2, respectively. It was found that porous films with easy accessibility to the inner surface reveal high photocurrents. The intermediate layer of WO3 demonstrated higher values of photocurrent due to roughness enhancement on the upper surface with columnar tree-growth particles. However, a compact state was observed on the cross section of Fe2O3 growth. A comparison was also drawn between the two and three-layer photoanodes using Fe2O3 andWO3. The films were characterized by XRD, SEM/EDX, and UV–vis irradiation to determine the photocurrent densities

On Filter Bank Based MIMO Frequency Multiplexing and Demultiplexing

The next generation satellite communication networks will provide multimedia services supporting high bit rate, mobility, ATM, and TCP/IP. In these cases, the satellite technology will act as the internetwork infrastructure of future global systems and assuming a global wireless system, no distinctions will exist between terrestrial and satellite communications systems, as well as between fixed and 3G mobile networks. In order for satellites to be successful, they must handle bursty traffic from users and provide services compatible with existing ISDN infrastructure, narrowcasting/multicasting services not offered by terrestrial ISDN, TCP/IP-compatible services for data applications, and point-to-point or point-to-multipoint on-demand compressed video services. This calls for onboard processing payloads capable of frequency multiplexing and demultiplexing and interference suppression. This thesis introduces a new class of oversampled complex modulated filter banks capable of providing frequency multiplexing and demultiplexing. Under certain system constraints, the system can handle all possible shifts of different user signals and provide variable bandwidths to users. Furthermore, the aliasing signals are attenuated by the stopband attenuation of the channel filter thus ensuring the approximation of the perfect reconstruction property as close as desired. Study of the system efficient implementation and its mathematical representation shows that the proposed system has superiority over the existing approaches for Bentpipe payloads from the flexibility, complexity, and perfect reconstruction points of view. The system is analyzed in both SISO and MIMO cases. For the MIMO case, two different scenarios for frequency multiplexing and demultiplexing are discussed. To verify the results of the mathematical analysis, simulation results for SISO, two scenarios of MIMO, and effects of the finite word length on the system performance are illustrated. Simulation results show that the system can perform frequency multiplexing and demultiplexing and the stopband attenuation of the prototype filter controls the aliasing signals since the filter coefficients resolution plays the major role on the system performance. Hence, the system can approximate perfect reconstruction property by proper choice of resolution

Contributions to Reconfigurable Filter Banks and Transmultiplexers

A current focus among communication engineers is to design flexible radio systems to handle services among different telecommunication standards. Thus, lowcost multimode terminals will be crucial building blocks for future generations of multimode communications. Here,  different bandwidths, from different telecommunication standards, must be supported. This can be done using multimode transmultiplexers (TMUXs) which allow different users to share a common channel in a time-varying manner. These TMUXs allow bandwidth-on-demand. Each user occupies a specific portion of the channel whose location and width may vary with time. Another focus among communication engineers is to provide various wideband services accessible to everybody everywhere. Here, satellites with high-gain spot beam antennas, on-board signal processing, and switching will be a major complementary part of future digital communication systems. Satellites provide a global coverage and customers only need to install a satellite terminal and subscribe to the service. Efficient utilization of the available limited frequency spectrum, calls for on-board signal processing to perform flexible frequency-band reallocation (FFBR). This thesis outlines the design and realization of reconfigurable TMUX and FFBR structures which allow dynamic communication scenarios with simple software reconfigurations. In both structures, the system parameters are determined in advance. For these parameters, the required filter design problems are solved only once. Dynamic communications, with users having different time-varying bandwidths, are then supported by adjusting some multipliers, commutators, or a channel switch. These adjustments do not require hardware changes and can be performed online. However, the filter design problem is solved offline. The thesis provides various illustrative examples and it also discusses possible applications of the proposed structures in the context of other communication scenarios, e.g., cognitive radios

Contributions to Flexible Multirate Digital Signal Processing Structures

A current focus among communication engineers is to design flexible radio systems in order to handle services among different telecommunication standards. Efficient support of dynamic interactive communication systems requires flexible and cost-efficient radio systems. Thus, low-cost multimode terminals will be crucial building blocks for future generations of multimode communication systems. Here, different bandwidths, from different telecommunication standards, must be supported and, thus, there is a need for a system which can handle a number of different bandwidths. This can be done using multimode transmultiplexers (TMUXs) which make it possible for different users to share a common channel in a time-varying manner. These TMUXs allow bandwidth-on-demand so that the resulting communication system has a dynamic allocation of bandwidth to users. Each user occupies a specific portion of the channel where the location and width of this portion may vary with time. Another focus among communication engineers is to provide various wideband services accessible to everybody everywhere. Here, satellites with high-gain spot beam antennas, on-board signal processing, and switching will be a major complementary part of future digital communication systems. Satellites provide a global coverage and if a satellite is in orbit, customers only need to install a satellite terminal and subscribe to the service. Efficient utilization of the available limited frequency spectrum, by these satellites, calls for on-board signal processing to perform flexible frequency-band reallocation (FFBR). Considering these two focuses in one integrated system where the TMUXs operate on-ground and FFBR networks operate on-board, one can conclude that successful design of dynamic communication systems requires high levels of flexibility in digital signal processing structures. In other words, there is a need for flexible digital signal processing structures that can support different telecommunication scenarios and standards. This flexibility (or reconfigurability) must not impose restrictions on the hardware and, ideally, it must come at the expense of simple software modifications. In other words, the system is based on a hardware platform and its parameters can easily be modified without the need for hardware changes. This thesis aims to outline flexible TMUX and FFBR structures which can allow dynamic communication scenarios with simple software reconfigurations on the same hardware platform. In both structures, the system parameters are determined in advance. For these parameters, the required filter design problems are solved only once. Dynamic communications, with users having different time-varying bandwidths, are then supported by adjusting some multipliers of the proposed multimode TMUXs and a simple software programming in the channel switch of the FFBR network. These do not require any hardware changes and can be performed online. However, the filter design problem is solved only once and offline

Reconfigurable two-stage Nyquist filters utilizing the Farrow structure

This paper introduces reconfigurable two-stage finite-length impulse response (FIR) Nyquist filters. In both stages, the Farrow structure realizes reconfigurable lowpass linear-phase FIR Nyquist filters. By adjusting the variable multipliers of the Farrow structure, various FIR Nyquist filters and integer interpolation/decimation structures are obtained, online. However, the filter design problem is solved only once, offline. Design examples illustrate the method

Complexity reduction in low-delay Farrow-structure-based variable fractional delay FIR filters utilizing linear-phase subfilters

This paper proposes a method to design low-delay fractional delay (FD) filters, using the Farrow structure. The proposed method employs both linear-phase and nonlinear-phase finite-length impulse response (FIR) subfilters. This is in contrast to conventional methods that utilize only nonlinear-phase FIR subfilters. Two design cases are considered. The first case uses nonlinear-phase FIR filters in all branches of the Farrow structure. The second case uses linear-phase FIR filters in every second branch. These branches have milder restrictions on the approximation error. Therefore, even with a reduced order, for these linear-phase FIR filters, the approximation error is not affected. However, the arithmetic complexity, in terms of the number of distinct multiplications, is reduced by an average of 30%. Design examples illustrate the method

Fields of Cooperation between Latvia and Korea in Art and Culture

Bakalaura darba nosaukums ir “Latvijas un Korejas sadarbības veidi kultūras un mākslas jomās, Darba mērķi ir izpētīt iespējas ciešākai diplomātiskai sadarbībai ar Dienvidkoreju, kultūras un mākslas jomās. Analizēt paveikto abu valstu kultūras un mākslas jomās veiktās popularizēšanas metodes un rezultātus. Saprast kādēļ, neskatoties uz pēdējo gadu strauji augušo Latvijas un Dienvidkorejas diplomātisko un ekonomisko attiecību uzlabošanos, Korejas kultūra un māksla mūsu sabiedrībā paliek plaši neizzināta. Kā arī iemeslus tam, kāpēc mūsu valsts popularizēšana Korejā nav sasniegusi mums vēlamos rezultātus. Šobrīd mēs dzīvojam interesantā laikā. Visā pasaulē notiek globalizācijas procesi, aizvien vairāk sabiedrību kļūst multikulturālas un plaši pieejamie elektroniskie informācijas līdzekļi mums sniedz iespējas būt informētiem par procesiem kas norisinās ikkatrā kultūrā. Abu valstu sadraudzības programmas ir viena no iespējām uzzināt vairāk par citu kultūru, valodu un iegūt jaunas draudzīgas attiecības, kas, bez daudziem pozitīviem aspektiem, stiprina demokrātiskos principus un pat ekonomisko izaugsmi iesaistītajām pusēm. Darbs sastāv no trijām daļām. Pirmajā daļā tiks izskatīta Eiropas savienības un Dienvidkorejas diplomātiskā vēsture, kā arī atsevišķi un detalizētāk aprakstītas Latvijas un Korejas savstarpējās attiecības. Kā arī ieskats Korejas kultūrpolitikas vēsturē ar uzsvaru uz 20/21. gadsimtu. Otrajā daļā tiks veikta Latvijas un citu Āzijas valstu organizāciju sadraudzības projektu analīze, lai izvērtētu tajās izmantotos kultūras apmaiņas mehānismus un to efektivitāti ar perspektīvām tos izmantot nākotnē, Korejas un Latvijas sadraudzības projekta izveides ietvaros. Šajā daļā tiks apskatītas tādas organizācijas un institūcijas, ar kuru starpniecību jau ir tikusi veikta Latvijas un Korejas sadarbība kultūras jomā, vai tās, kuras sniedz vislabākās iespējas. Trešajā daļā tiks apskatītas pārējās organizācijas un projekti, kas var potenciāli veidot sadarbības līgumus starp Latvijas un Dienvidkorejas institūcijām, bet veiksmīgas sadarbības izveidošanai būs nepieciešami lielāki pūliņi. Balstoties uz iepriekš iegūtās informācijas, tiks apkopoti secinājumi par kopējo situāciju abu valstu kultūras un mākslas apmaiņā, kā arī nākotnes perspektīvas.The title of this Bachelors thesis is “Fields of cooperation between Latvia and Korea in art and culture. Objective of this work is to explore opportunities for closer diplomatic relations with South Korea in art and culture fields. To analyse the progress of the two countries methods and results in cultural and arts promotion's. To understand why, in spite of the recent years of rapidly growing Latvian-South Korea diplomatic and economic relations, the Korean culture and art in our society remains widely unknown area. As well as the reasons why our country's culture promotion in Korea has not reached the desired results. Currently we live in interesting times. Throughout the world, globalization processes take place, societies are becoming increasingly multicultural and widely accessible electronic media provides us with opportunities to be informed about the processes that are happening in every culture imaginable. Latvia and Korea cooperation programs is one of the possibilities to learn more about other cultures, languages and gain new friendships, which, besides many positive aspects although strengthen democratic principles and even economic growth of the parties concerned. The work consists of three parts. The first part will deal with the European Union and South Korea's diplomatic history, as well as separately and in more detail describe Latvian-Korean relations timeline. And an insight in Koreas culture policy history with accent on 20/21th century. The second part will be an analysis of the Latvian and other Asian countries cooperation projects analysis to evaluate those mechanisms used for cultural exchange and their efficiency with prospects for using them in the future within the framework of the establishing Korean and Latvian cooperation projects. In this part we will look into those institutions and organizations where Latvian and Korean cultural exchange has already been made or has the best perspectives. In the third part, we will look at those organizations, where there is perspectives for establishing cooperation in art and culture fields between our countries, however it would require more actions to be taken in order of successful cooperation establishment. A summary of thoughts about overall situation between Latvia and Korea cultural and art exchange will be written. Including thoughts about future perspectives on this issue

A farrow-structure-based multi-mode transmultiplexer

This paper introduces a multi-mode transmultiplexer (TMUX) consisting of Farrow-based variable integer sampling rate conversion (SRC) blocks. The polyphase components of general interpolation/ decimation filters are realized by the Farrow structure making it possible to achieve different linear-phase finite-length impulse response (FIR) lowpass filters at the cost of a fixed set of subfilters and adjustable fractional delay values. Simultaneous design of the subfilters, to achieve overall approximately Nyquist (Mth-band) filters, are treated in this paper. By means of an example, it is shown that the subfilters can be designed so that for any desired range of integer SRC ratios, the TMUX can approximate perfect recovery as close as desired.Original publication: Amir Eghbali, Håkan Johansson and Per Löwenborg, A farrow-structure-based multi-mode transmultiplexer, 2008, Proceedings of IEEE International Symposium on Circuits and Systems, Seattle, Washington, USA, May. 18-21, pp3114-3117. http://dx.doi.org/10.1109/ISCAS.2008.4542117. Copyright: IEEE, http://www.ieee.org</p

A Multimode Transmultiplexer Structure

This paper introduces a multimode transmultiplexer (TMUX) structure capable of generating a large set of user-bandwidths and center frequencies. The structure utilizes fixed integer sampling rate conversion (SRC) blocks, Farrow-based variable interpolation and decimation structures, and variable frequency shifters. A main advantage of this TMUX is that it needs only one filter design beforehand. Specifically, the filters in the fixed integer SRC blocks as well as the subfilters of the Farrow structure are designed only once. Then, all possible combinations of bandwidths and center frequencies are obtained by properly adjusting the variable delay parameter of the Farrow-based filters and the variable parameters of the frequency shifters. The paper includes examples for demonstration. It also shows that, using the rational SRC equivalent of the Farrow-based filters, the TMUX can be described in terms of conventional multirate building blocks which may be useful in further analysis of the overall system.Original publication: Amir Eghbali, Håkan Johansson and Per Löwenborg, A Multimode Transmultiplexer Structure, 2008, IEEE Transactions on Circuits and Systems II, (55), 3, 279-283. http://dx.doi.org/10.1109/TCSII.2008.918934. Copyright: IEEE, http://www.ieee.or