Optical Properties of Wurtzite InN and Related Alloys

In dieser Arbeit werden die optischen Eigenschaften von Wurtzitstruktur InN und verwandten ternären InGaN und AlInN, sowie quaternären AlInGaN Legierungen untersucht. Der Schwerpunkt wird auf die Charakterisierung mittels spektroskopischer Ellipsometrie gelegt. Die auf Si(111) Substraten gewachsenen InN-Proben und die Kohlstoff dotierten InN-Proben sind im Spektralbereich vom mittleren Infrarot bis hin zum Vakuum-Ultraviolett untersucht worden. Die Elektronenkonzentration für die InN-Proben wird durch selbstkonsistentes Lösen (der Ellipsometriedaten Analyse im Infrarotbereich und der Anpassung des Absorption Ansatz) bestimmt. Die intrinsische spannungsfreie Bandlücke für InN Proben wird unter Berücksichtigung von Vielteilcheneffekten wie der Bandlückenrenormierung und der Burstein-Moss-Verschiebung, sowie dem Einfluss der Verzerrung für die Bandlücke bestimmt. Die k*p-Methode wird verwendet, um die Verschiebung der Bandlücke (beeinflusst durch Verzerrung) zu berechnen. Es wird demonstriert, dass eine Erhöhung des Kohlenstofftetrabromid (CBr4) Drucks während des Wachstumsprozess, die Elektronenkonzentration in den InN-Proben erhöht. Die Indium-verwandten Legierungen wurden im Spektralbereich des nahen Infrarot bis zum Vakuum-Ultraviolett untersucht. Das analytische Modell, der dielektrichen Funktion im Spektralbereich 1-10 eV, für die Indium-verwandte Legierungen wird präsentiert. Durch die Anpassung des analytischen Modells an die experimentellen dielektrischen Funktionen, werden die Bandlücke und die Übergangsenergien im Hochenergie-Bereich evaluiert. Die Bowing-Parameter der spannungsfreien Bandlücke für die ternären Systeme InGaN und AlInN werden bestimmt. Es wird demonstriert, dass der Bowing-Parameter für AlInN von der Komposition der Legierung abhängig ist. Die Kenntnis von Bowing-Parametern für die ternären Legierungen ermöglicht die Entwicklung einer empirischen Gleichung, zur Berechnung der Bandlücke in quaternären Legierungen. Alle experimentell durch Ellipsometrie bestimten Bandlücken der untersuchten Legierungen werden durch ab-initio Daten unterstützt.In this work, optical properties of wurtzite structure InN and related ternary InGaN and AlInN, as well as quaternary AlInGaN alloys were investigated. The spectroscopic ellipsometer was used as the main characterization tool for the analysis of the optical properties. The InN samples grown on Si(111) substrates, as well as carbon doped InN samples were investigated from mid-infrared up to vacuum-ultraviolet spectral range. The electron concentration for InN samples were evaluated by solving a self-consistent problem that includes the IR-SE ellipsometry data analysis and the imaginary dielectric function around the band gap calculation. The intrinsic strain-free band-gap was estimated after taking into consideration a band-gap renormalization and Burstein-Moss shift, as well as a strain influence on the band gap. The k*p method was used to calculate the strain induced band-gap shift. From the analysis, it was shown that for the carbon doped InN samples the electron concentration increases linearly by increasing the CBr4 dopant pressure during the MBE growth process. The In-related alloys were investigated from near-infrared up to vacuum-ultraviolet spectral range. The analytical model of the dielectric function in the spectral range 1-10 eV was presented. From the fit of the analytical model to the experimental dielectric functions, the band gaps and high-energy inter-band transitions were estimated. The strain-free band-gap bowing parameters for ternary InGaN and AlInN alloys were obtained. It was demonstrated, that the bowing parameter for AlInN is composition dependent. With the knowledge of the bowing parameters of ternary alloys, it was possible to develop an empirical equation that allows to estimate the band gap for a quaternary AlInGaN alloy. All experimentally obtained band gaps are in good agreement with the ab-initio calculated values

Pasyvumo problemos tyrimas Baltijos šalių akcijų rinkose

The Baltic States equity market is a challenge for investors and financial analysts. Unfortunately strong  assivity is observed in ``young\u27\u27 markets, therefore any (Gaussian, α-stable etc) distribution fitting tests (Anderson–Darling, Kolmogorov–Smirnov, etc.) are poorly applicable. Improvement based on mixed distributions is proposed and its adequacy in the Baltic States market is tested. In this paper we use Koutrouvelis goodness-of-fit test and modified χ2 test.Baltijos šalių vertybinių popierių ir ypač akcijų rinkų tyrimai kelia daug iššūkių investuotojams bei analitikams. Jaunose ir besivystančiose rinkose yra pastebimas didesnis, nei įprasta, pasyvumas, todėl tinkamo dėsnio, kuris pakankamai gerai modeliuotų duomenų pasiskirstymą nustatymas, yra įdomi ir aktuali problema. Darbe siūlomas mišrusis modelis ir atliekama jo tinkamumo Baltijos šalių rinkoje analizė. Mišrusis modelis apjungia tolydžiuosius ir diskretinius dėsnius, o standartiniai suderinamumo kriterijai keičiami Koutrouvelio ir modifikuotu χ2 metodais

Isolated Word Recognition by Recursive HMM Parameter Estimation Algorithm

Automatic speech recognition (ASR) technologies enable humans to communicate with computers. Isolated word recognition (IWR) is an important part of many known ASR systems. Minimizing the word error rate in cases of incremental learning is a unique challenge for developing an on-line ASR system. This paper focuses on on-line IWR using a recursive hidden Markov model (HMM) multivariate parameter estimation algorithm. The maximum likelihood method was used to estimate the unknown parameters of the model, and an algorithm for the adapted recursive EM algorithm for HMMs parameter estimation was derived. The resulting recursive EM algorithm is unique among its counterparts because of state transition probabilities calculation. It obtains more accurate parameter estimates compared to other algorithms of this type. In our experiment, the algorithm was implemented and adapted to several datasets for IWR. Thus, the recognition rate and algorithm convergence results are discussed in this work

Matricinė diskretinio logaritmo problema

In this paper the discrete logarithm problem in matrix in finite fields is formulated, possible ways of solution are given.Santraukos nėra

Reactive Oxygen Species Production in Peripheral Blood Neutrophils of Obstructive Sleep Apnea Patients

Obstructive sleep apnea (OSA) as well as obesity is associated with increased production of reactive oxygen species (ROS). Neutrophils produce great amounts of ROS. The aim was to evaluate peripheral blood neutrophils ROS production in men with OSA and to establish relations with disease severity and obesity. Methods. Forty-six men with OSA and 10 controls were investigated. OSA was confirmed by polysomnography (PSG), when apnea/hypopnea index was >5/h. Body mass index (BMI) was evaluated. Neutrophils were isolated from peripheral blood in the morning after PSG. Dihydrorhodamine-123 was used for ROS detection. Data is presented as median (25th and 75th percentiles). All subjects were divided into four groups: nonobese mild-to-moderate OSA, obese mild-to-moderate OSA, nonobese severe OSA, and obese severe OSA. Results. Neutrophil ROS production was higher in nonobese severe OSA group compared to nonobese mild-to-moderate OSA (mean fluorescence intensity (MFI) 213.4 (89.0–238.9) versus 44.5 (20.5–58.4), P<0.05). In obese patient groups, ROS production was more increased in severe OSA compared to mild-to-moderate OSA group (MFI 74.5 (47.9–182.4) versus 31.0 (14.8–53.8), P<0.05). It did not differ in the groups with different BMI and the same severity of OSA. Conclusion. Increased neutrophil ROS production was related to more severe OSA but not obesity

Key Agreement Protocol (KAP) Based on Matrix Power Function

* Work is partially supported by the Lithuanian State Science and Studies Foundation.The key agreement protocol (KAP) is constructed using matrix power functions. These functions are based on matrix ring action on some matrix set. Matrix power functions have some indications as being a one- way function since they are linked with certain generalized satisfiability problems which are potentially NP- Complete. A working example of KAP with guaranteed brute force attack prevention is presented for certain algebraic structures. The main advantage of proposed KAP is considerable fast computations and avoidance of arithmetic operations with long integers

Distributed Software Development Tools for Distributed Scientific Applications

This chapter provides a new methodology and two tools for user‐driven Wikinomics‐oriented scientific applications’ development. Service‐oriented architecture for such applications is used, where the entire research supporting computing or simulating process is broken down into a set of loosely coupled stages in the form of interoperating replaceable Web services that can be distributed over different clouds. Any piece of the code and any application component deployed on a system can be reused and transformed into a service. The combination of service‐oriented and cloud computing will indeed begin to challenge the way of research supporting computing development, the facilities of which are considered in this chapter

Rakto apsikeitimo protokolas begalinės pusgrupės įvaizdžio lygmenyje

Matrix decomposition problem over integer ring is presented. Solving methods are discussed and it is showed, that this problem is hard computational problem regard to computer memory resources. A key agreement protocol based on matrix decomposition problem is presented

Įkalinimas Lietuvoje: praktika ir prasmė

The aim of the article is to analyse the practice of sentencing in Lithuania, its changes and tendencies. The incanceration rates in Lithuania are one of the highest among the European Countries despite the minor difference in reported crime rates. The questions the dominant "corrective" conception and suggest that clearly defined purpose of re-socialization could the grounds to reform the system of imprisonment.Straipsnyje baudžiamuoju politiniu ir tarptautiniu aspektu analizuojama įkalinimo praktika Lietuvoje, esminiai pokyčiai ir tendencijos. Kalinių skaičiumi Lietuva lenkia didžią ją dalį Europos valstybių, ir to priežastimi nėra išskirtinis užregistruotų nusikaltimų lygis. Aiškus resocializacijos tikslo laisvės atėmimo bausmei iškėlimas padėtų tinkamai sustyguoti visą įkalinimo sistemą, o vis dar tebevyraujanti asmens „pataisos“ koncepcija atrodo nepagrįsta jokiais socialiniais, kriminologiniais ar teisiniais argumentais