On Low Complexity Detection for QAM Isomorphic Constellations

Despite of the known gap from the Shannon's capacity, several standards are still employing QAM or star shape constellations, mainly due to the existing low complexity detectors. In this paper, we investigate the low complexity detection for a family of QAM isomorphic constellations. These constellations are known to perform very close to the peak-power limited capacity, outperforming the DVB-S2X standard constellations. The proposed strategy is to first remap the received signals to the QAM constellation using the existing isomorphism and then break the log likelihood ratio computations to two one dimensional PAM constellations. Gains larger than 0.6 dB with respect to QAM can be obtained over the peak power limited channels without any increase in detection complexity. Our scheme also provides a systematic way to design constellations with low complexity one dimensional detectors. Several open problems are discussed at the end of the paper.Comment: Submitted to IEEE GLOBECOM 201

Code Design for Non-Coherent Detection of Frame Headers in Precoded Satellite Systems

In this paper we propose a simple method for generating short-length rate-compatible codes over $\mathbb{Z}_M$ that are robust to non-coherent detection for $M$-PSK constellations. First, a greedy algorithm is used to construct a family of rotationally invariant codes for a given constellation. Then, by properly modifying such codes we obtain codes that are robust to non-coherent detection. We briefly discuss the optimality of the constructed codes for special cases of BPSK and QPSK constellations. Our method provides an upper bound for the length of optimal codes with a given desired non-coherent distance. We also derive a simple asymptotic upper bound on the frame error rate (FER) of such codes and provide the simulation results for a selected set of proposed codes. Finally, we briefly discuss the problem of designing binary codes that are robust to non-coherent detection for QPSK constellation.Comment: 11 pages, 5 figure

Constellation Design for Channels Affected by Phase Noise

In this paper we optimize constellation sets to be used for channels affected by phase noise. The main objective is to maximize the achievable mutual information of the constellation under a given power constraint. The mutual information and pragmatic mutual information of a given constellation is calculated approximately assuming that both the channel and phase noise are white. Then a simulated annealing algorithm is used to jointly optimize the constellation and the binary labeling. The performance of optimized constellations is compared with conventional constellations showing considerable gains in all system scenarios.Comment: 5 pages, 6 figures, submitted to IEEE Int. Conf. on Communications (ICC) 201

Firms' Histories and Their Capital Structures

This paper examines how cash flows, investment expenditures and stock price histories affect corporate debt ratios. Consistent with earlier work, we find that these variables have a substantial influence on changes in capital structure. Specifically, stock price changes and financial deficits (i.e., the amount of external capital raised) have strong influences on capital structure changes, but in contrast to previous conclusions, we find that their effects are subsequently at least partially reversed. These results indicate that although a firm's history strongly influence their capital structures, that over time, financing choices tend to move firms towards target debt ratios that are consistent with the tradeoff theories of capital structure.

Optical properties of SiGe single crystals grown by liquid phase diffusion

In this article, we present measurements for the pseudo-optical functions of germanium-rich SixGe1-x (0.000<x<0.100) single-crystals(grown by Liquid Phase Diffusion; LPD) using spectroscopic ellipsometry and photo reflectance techniques in the energy range of 1.72–3.20 eV. The E1 interband transition energies are obtained from numerically differentiated optical spectra for various crystal compositions. It was shown that the values of E1 interband transition energy determined by both the ellipsometric and photo reflectance measurements for germanium-rich SixGe1-x single-crystals are in agreement with those of bulk SiGe crystals reported in the literature[21–24].The interband transition energies are found to be in the range of 2.100 and 2.215 eV for the composition values of 0.000<x0.100. The surface morphology of the crystals assayed via atomic force microscopy shows fibrous surfaces with the average grain size of 250 nm. The measured root-mean-square (rms) roughness and maximum height are in the range of 3.78–5.40 and 32.42–67.84 nm, respectively, with increasing germanium composition

Theological-ethics and epistemology: the euthyphro dilemma and the metaethics of almāturīdī

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Euthyprhon Dilemması, bu değerin kaynağını nereden aldığını sorarak ahlaki bir değere sahip bir tanrıya inanan teistlerin karşılaştığı kafa karıştırıcı bir duruma dikkat çekmektedir. Platon'un kendi adını taşıyan diyalog, tanrının ahlakın kaynağı olduğu şeklindeki tanrı merkezli iddianın bariz sorunlarını tartışır ve ahlakın rasyonel bir biçimde tamamlayıcı bir tanımına dair bir arayış sergiler görünür. Bununla birlikte diyalog, genellikle ne böyle bir tanıma başarılı bir temel sağlamış ne de tanrı merkezli iddiayı kesin olarak çürütmüş kabul edilmez. Akıl merkezli düşünme ve tanrı merkezli düşünme tutumları arasında meydana gelen çekişmede, tamamıyla farklı epistemolojilerin tarafların kendi tutumlarının belirleyicisi olduğuna ve dolayısıyla belli kabullerle yola çıktıklarına dair bir varsayım var görünmektedir. Sonuç olarak, tartışmaya karar verebilmek için dilemmanın sınırlarının dışından olumlu bir desteğe ihtiyaç gerekli görünmektedir. Akıl merkezlilik-tanrı merkezlilik ikilemi, İslam teolojik-etik geleneğinde sırasıyla Mu'tezile ve Eş'arî kelam ekolleri tarafından benimsenen bakış açılarıyla paralellik arz etmektedir. Her bir ekol kendi uzmanlık ilgileri nedeniyle kısmen farklı bir epistemoloji kullanmaktadır. Māturīdī, hem tanrı merkezli hem de akıl merkezli tutumların boyutlarını birleştiren sofistike bir orta yol sergiler. Onun teolojik-etiği, tanrıyı ahlakın nihai kaynağı olarak sunar, ancak bir bütün olarak alemin tanzim edilmiş olması ve insanın ahlaki değerleri idrak etmesinin temel vasıtası olması temelinde akla referansta bulunur. Māturīdī'nin sofistike bir metaetiği oluşturmasında tecrübeye dayalı ve akli unsurları bir araya getirişine Jacques Derrida'nın epistemolojik çalışmasının olumlu bir destek sağladığını fark ettim. Bu ise yaratılışın, tanrının mutlak hakimiyetinin göstergesi olmaya devam ederken nasıl vahiyden bağımsız olarak objektif ahlaki bir değer kazandığını açıklamaya yardımcı olmaktadır.The Euthyprho Dilemma highlights the perplexing situation that confronts theists who believe in a God in possession of moral significance, as it asks where the origin of this significance lies. Plato's eponymous dialogue discusses apparent problems with the theocentric claim that God is the source of morality and seems to present a search for a rationally integral definition of piety. However, the dialogue is generally acknowledged to neither successfully establish the grounds for such a definition nor conclusively refute the theocentric claim. In the ensuing debate between ratiocentric and theocentric positions, there appears to be an assumption of radically different epistemologies that are determinant of the respective positions, which hence assume what they set out to prove. As a result, the need for positive support from outside the confines of the dilemma appears to be required in order to decide the debate. The ratiocentric-theocentric dichotomy is paralleled in the Islamic tradition of theological ethics (theological-ethics), with the respective stances held by the Mu'tazilī and Ash‛arī schools of kalām. Each school utilizes a different epistemology, in part due to their professional concerns. Al-Māturīdī represents a sophisticated middle position that combines aspects of both the theocentric and ratiocentric stances. His theological-ethics presents God as the ultimate source of morality, but refers to reason as the basis upon which creation as a whole is ordered and as the ultimate means by which human beings come to comprehend moral values. I find that the epistemological work of Jacques Derrida offers positive support for al-Māturīdī's juxtaposition of empirical and rational elements in the creation of a sophisticated metaethics. It helps explain how creation acquires objective moral significance independently of revelation, while remaining indicative of God's total sovereignty