980 research outputs found
k.p Theory for Wurtzite InGaN Quantum Dot Arrays with Application to Ratchet Band Solar Cells
No full textThis thesis presents advancements on the modeling of quantum dots using Fourier-space k.p theory and on the use of InGaN quantum dots for ratchet band solar cells. Fourier-space based methods have generally assumed sharp material interfaces for electronic structure, strain and piezoelectric potential calculations in quantum dot systems. Additionally, standard Fourier-space methods have often assumed uniform elastic and dielectric constants for the strain and piezoelectric potential calculations. We present generalized methods to include smoothly varying alloy profiles for the quantum dots, including spatially varying elastic and dielectric constants for the strain and piezoelectric potential calculations. For the case of InGaN/GaN quantum dots, we show that the elastic and dielectric constants corrections are important for accurate strain, piezoelectric potentials, and electronic structure. The smooth alloy profiles are constructed by convolving sharp alloy profiles with a Gaussian, and we show that the electronic structure strongly depends on the smoothing kernel, indicating the need for precise alloy profiles for accurate electronic structures. We also present a new method that facilitates the coupling of strain into the k.p Hamiltonian when considering isolated dots, greatly reducing the computational costs of calculating the Hamiltonian matrix elements. Using the methods, we investigate the use of InGaN/GaN quantum dot superlattices as ratchet band solar cells, where we propose to use the piezoelectric potential to generate a ratchet. The piezoelectric potential can spatially separate confined electron and hole states, creating a spatial ratchet in order to reduce recombination. From our quantum dot k.p model, we calculate optical light absorption cross sections and present an improved method to calculate bound-to-continuum absorption, where electrons are excited out of the dots. In this method, we approximate the continuum states as bulk k.p states for GaN. By coupling our k.p model absorptions into a detailed balance model, we predict power conversion efficiencies. We find that a large number of QD layers is necessary to achieve sufficiently strong absorption as to reach high efficiencies, highlighting one of the key issues of QD-based solar cells. We consider systems which consists of up to 131000 layers of quantum dots and an ideal Lambertian back reflector with two different QD geometries. The first geometry possesses a strong spatial ratchet and can reach a maximum efficiency of 36% under a 1-sun 6000 K black-body spectrum. We verify the existence of the spatial ratchet through the optical properties of the system, showing that it truly has the potential to block recombination. We also present an efficiency optimized system that reaches a 42% detailed balance efficiency but does not have a spatial ratchet
Tele-operated climbing and mobile service robots for remote inspection and maintenance in nuclear industry
No full textA Time-Efficient Competitive Pokemon Team-Building Algorithm
No full textThe Pokemon video game franchise is based on players, also known as trainers, capturing and battling with fictitious creatures called Pokemon. Competitive Pokemon battling is a complicated business. Before even stepping into the arena, a trainer must design a competitively viable team of six Pokemon to battle with. This task is a difficult one because there are currently 721 species of Pokemon to construct a team from, and new Pokemon are revealed every year. The author therefore developed the Score-Based Pokemon Analysis algorithm, also known as SBPA, to aid users in easily and quickly designing new Pokemon teams. The SBPA algorithm relies heavily on user interaction, and therefore requires the user to have already chosen at least one Pokemon to build his/her team around. The algorithm then analyzes the Pokemon the user has already chosen and returns a selection of Pokemon that would best further the development of the team. The user then chooses another team member, and the process is repeated until the user has developed his/her team. The SBPA algorithm analyzes the inputted team using three factors: Base Statistics, Typing, and the Popularity Factor. These three factors are then combined to determine the best potential team members per iteration. The algorithm focuses not only on user interactivity, but also on time efficiency in order to provide valuable information to the user in a time frame that would be impossible to a technologically unaided trainer. As a cost for its speed and user-friendliness, SBPA is less accurate in determining the absolutely optimal team than certain other algorithms. However, when considering the target market of the algorithm, the author found these compromises worthwhile.Electrical Engineering, Mathematics and Computer ScienceDelft Institute of Applied Mathematic
Klauzula odpowiedniego stosowania przepisów na gruncie art. 300 k.p. a modyfikacja dyspozycji przepisów kodeksu cywilnego
No full textThe article includes deliberations on the issue of proper application of provisions of the Polish Civil Code to matters relating to relationship of employment, which are not regulated by labour law provisions. Among numerous issues and doubts arising in relation to functions of Article 300 of the Polish Labour Code in the legal system, the author has distinguished significance of a reservation of proper application of the provisions for the purposes of the labour law and, in particular, in the context of admissible modification of provisions of the Polish Civil Code. The analysis of opinions of the doctrine and review of the case law of the Supreme Court have made it possible to formulate a critical opinion on the possibility to amend provisions of the Polish Civil Code in the progress of application of the same in connection with article 300 of the Polish Labour Code. The conclusions have been extended by indicated threats arising from modification of provisions applied after fulBlment of prerequisites of article 300 of the Polish Labour Code as well as several trends of modifications, which would aim at limitation or elimination of any doubts and divergences as regards interpretation.Artykuł zawiera rozważania skupione wokół zagadnienia odpowiedniego stosowania przepisów Kodeksu cywilnego do nieunormowanych przepisami prawa pracy spraw ze stosunku pracy. Wśród wielu problemów i wątpliwości narosłych wokół funkcjonowania w systemie prawnym art. 300 k.p. autorka wyróżnia znaczenie zastrzeżenia odpowiedniego stosowania dla potrzeb prawa pracy, zwłaszcza w kontekście dopuszczalności modyfikacji dyspozycji przepisów Kodeksu cywilnego. Analiza poglądów doktryny oraz przegląd orzecznictwa SN pozwoliły na sformułowanie krytycznego stanowiska wobec możliwości dokonywania zmian w obrębie dyspozycji przepisów Kodeksu cywilnego w toku ich stosowania w związku z art. 300 k.p. Wnioski wzbogacone zostały o wskazanie zagrożeń płynących z modyfikowania dyspozycji przepisów stosowanych po spełnieniu przesłanek z art. 300 k.p. oraz o kilka uwag o kierunkach zmian, których celem byłoby ograniczenie bądź zniwelowanie wskazanych wątpliwości i rozbieżności interpretacyjnych
Raken of niet raken, dat is de vraag
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Analysi
k.p theory of freestanding narrow band gap semiconductor nanowires
No full textWe report on a theoretical study of the electronic structures of freestanding nanowires made from narrow band gap semiconductors GaSb, InSb and InAs. The nanowires are described by the eight-band k.p Hamiltonians and the band structures are computed by means of the finite element method in a mixture basis consisting of linear triangular elements inside the nanowires and constrained Hermite triangular elements near the boundaries. The nanowires with two crystallographic orientations, namely the [001] and [111] orientations, and with different cross-sectional shapes are considered. For each orientation, the nanowires of the three narrow band gap semiconductors are found to show qualitatively similar characteristics in the band structures. However, the nanowires oriented along the two different crystallographic directions are found to show different characteristics in the valence bands. In particular, it is found that all the conduction bands show simple, good parabolic dispersions in both the [001]- and [111]-oriented nanowires, while the top valence bands show double-maximum structures in the [001]-oriented nanowires, but single-maximum structures in the [111]-oriented nanowires. The wave functions and spinor distributions of the band states in these nanowires are also calculated. It is found that significant mixtures of electron and hole states appear in the bands of these narrow band gap semiconductor nanowires. The wave functions exhibit very different distribution patterns in the nanowires oriented along the [001] direction and the nanowires oriented along the [111] direction. It is also shown that single-band effective mass theory could not reproduce all the band state wave functions presented in this work
Aesop's Fables
No full textThis mid-sized (7? x 9½) paperback contains 112 numbered fables on 134 pages. There is a T of C on 3-4. Each fable has a black-and-white drawing, some -- like the Bull and Gnat on 66 -- reminiscent of Rackham. The Fox and the Cat (24) finishes with this sentence from the cat: My only trick is indeed worthwhile than the many tricks of the poor fox! Can Indian English drop comparatives? Monkey and Cat (85) has a picture that imitates a traditional image for this fable. SW on 129 starts with the two as friends. Each fable has a circled moral at its end. I have one other of the four books in this series: Panchatantra Stories.Retold by Rashmi Jaiswa
Panchatantra Stories
No full textThis mid-sized (7? x 9½) paperback contains 67 numbered fables on 162 pages. There is a T of C on iv. One finds a curious printer's note on the bottom of the title-page. The stories are told here separately; there is no frame story connecting them. I have usually seen The Foolish Monkeys (25) stressing the foolish bird that butted into the monkeys' foolish attempt to make fire from red fruits. I find story #13, The Great Sacrifice, surprising. In it two doves dive into the fire to provide a meal for a hungry hunter. Here is a surprise: 34 is printed backwards! I am surprised to find GGE represented as from the Panchatantra (45). In this version, the wife disagrees with her husband and kills the hen. I am also surprised to find MSA here in the Panchatantra (141). The usual story of the bedbugs here has them try at first not to allow the visiting mosquito to stay (54). The Lion and the Woodcutter is new to me (56). Suspecting the lion's friends -- crow and fox -- means giving up the friendship of the lion. The art of the quarter-page black-and-white illustrations is primitive and graphic. Notice, for example, the snake emerging from the mouth and even stomach of the sleeping prince on 112. I have one other of the four books in this series: Aesop's Fables, and it was published in 2001.Retold by Rashmi Jaiswa
Oil and Challenges of Trade Policy Making In Sudan in a Globalizing Arena
No full textAbstract The purpose of this study is to examine the potential impact of oil revenues on the economy of Sudan and the challenges facing the Government in policy making, particularly trade policy and allocation of oil revenues for long-run development and diversification of the production and export structure of the economy. The exploitation of oil resources has been accompanied by impressive liberalization of the economy by the Government of Sudan. Since then the country has been integrating into the world economy rapidly based on oil revenues. Yet, little has been achieved so far in integrating various sectors of the domestic economy despite relatively rapid GDP growth based on oil revenues. Rapid economic growth and diversification of the economy are among the main objectives of the Government. Therefore, the challenge facing the Government is to design and implement a long-term development strategy in order to build up a solid industrial and agricultural sector for sustainable development and expansion of non-oil exports. In such a strategy the design, and implementation, of trade and industrial policies and the way oil revenues are allocated, takes, inter alia, importance. Developing a conceptual framework of analysis, the author will argue that while export of petroleum provides financial resources for the acceleration of investment and growth, prospects for sustained growth and diversification will be still limited by some physical and institutional bottlenecks which can not be easily overcome by ample oil revenues. Trade in oil itself may have some detrimental socio-economic effects, including the attitude and policies of the Government, on the prospects for development and diversification of the economy in the long-run. Therefore, the Government policies, particularly trade policies, and the way oil revenues are allocated may not be necessarily conducive to long-run development and diversification of production and export structure. Proposing an alternative long-run trade and industrial policy for the country, the author will also outline the practical problems of its implementation under current international trade rules. ---------- *The author is a development economist with D.Phil from Oxford Univsity. He is currently an international consultant affiliated to the Institute of Economic Research, University of Neuchatel, Switzerland. He is the former Head, Macroeconomic and Development Policies Branch, UNCTAD and the author of a large number of articles, published in international journals, on trade and industrial policies, economic reform and other development policy issues. His latest book is: Trade Policy at the Crossroads; the recent experience of developing countries, Macmillan, 2005. This paper is developed on the basis of a part of a study undertaken for the World Bank under a DTSI project financed by the same Organization. The author benefited from interviews with Government authorities and comments from Mr. P. Shuler to whom goes his thanks. Comments are welcome and can be sent to author: [email protected] economies, trade policy, Sudan, economic development, diversification
PFA and ω1-free compact spaces
No full textThe Proper Forcing Axiom implies that compact Hausdorff spaces are either first-countable or contain a converging ω1-sequence.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Analysi
- …
