893 research outputs found
Singular perturbation of an infinite interval linear state regulator problem in optimal control
No full textAbstractThe corresponding problem on a finite interval has been studied by O'Malley and Kung using two different methods, namely: (1) the two-point boundary value method (O'Malley and Kung, SIAM J. Control 13 (1975), 327–337) and (2) The Riccati gain method (O'Malley and Kung, J. Differential Eqs. 16 (1974), 413–427). For the infinite interval, the two-point boundary value method is no longer relevant. However, the Riccati gain method can be applied. The conditions are changed slightly from those for the finite interval case. Some conditions are eliminated and some new conditions are added
Precise boron isotopic determination by negative thermal ionization mass spectrometry
No full text[[abstract]]我們已經成功的發展出一套新的BO2 負離子源質譜術，此方法同時測量BO2 在質量42、43、44和45處之波峰強度，並藉由18O/16O (=I45/I43)的系統性變化，修正質譜儀過程中因溫度所造成的同位素分化效應；實驗結果顯示(1)質量分化效果導致11B16O18O/10B16O16O 及11B16O16O/10B16O16O隨11B16O18O/11B16O16O呈直線性變化；(2)利用固定18O/16O 比值將11B16O18O/11B16O16O標準化修正後，可得NBS 951 硼酸11B/10B值為4.0429±0.0003 (2σm=0.11‰, n=29)與世界公認值完全一致；(3)三個實驗室配製且具不同10B富化程度的標準溶液，利用共同18O/16O (=0.002145)修正後，也獲得相一致性的結果。此技術不但保存原有BO2質譜術的高靈敏度和高離子化率，且改善分析精確度5至10倍，可與Cs2BO2+ 質譜術結果相比擬。另一方面，質譜過程的溫度分化效應對11B/10B 比值有重大影響，可超過10千分單位(‰)，而傳統質譜術卻忽略相關問題的嚴重性。此新分析技術的確立，將對一些須要高精確度樣品之測定具有重要意義，例如利用有孔虫殼體硼同位素的變化，探討古海洋海水酸鹼值等研究。
We have successfully developed a technique for precise boron isotopic analyses using the thermal ionization mass spectrometry (TIME). This new method measures four BO2 peaks at masses 42, 43, 44, and 45 simultaneously and subsequently normalizing the 11B/10B ratio to an empirical 18O/16O (=I45/I43) value for removing any possible mass fractionation artifacts. The results show that (1) mass fractionation causes both 11B16O18O/10B16O16O and 11B16O16O/10B16O16O to vary linearly with 11B16O18O/11B16O16O; (2) By normalizing 11B16O18O/11B16O16O to a fixed 18O/16O value, a mean 11B/10B value of 4.0429±0.0003 (2σm=0.11‰, n=29) is obtained for NBS 951, which agrees with the certified ratio; (3) Excellent agreement also demonstrated for three other 10B enriched solutions, where a common 18O/16O value of 0.002145 is used for normalization. This new technique not only maintains the high ionization efficiency and sensitivity of the traditional BO2 negative-TIMES, but also improves the analytical precision more than 5times to a similar level as the Cs-borate positive-TIMES. Additionally the observed fractionation artifacts are rather large (of more than 10‰ in some cases), but was neglected in the traditional studies. The ability to resolve a small change of boron isotopic compositions in nature samples (e.g., foraminiferal shells or corals) is critical for detailed evaluation of oceanic pH variation in the past.[[fileno]]2010101010026[[department]]物理
Yen Tsun, Ho-shang-kung, and Wang Pi's Studies of Lao Tsu
No full text本文由方法學的角度討論嚴遵、河上公、王弼三家的《老子》注文。藉由他們對「道」與「言意問題」的不同意見，說明三家注本不同的詮釋型態。三家注中，王弼有《老子指略》一文說明他的詮釋方法，而嚴遵及河上公的詮釋方法則必須由注文中尋繹重建。王弼視「道」為被詮釋的對象，關心於「名言」如何識「道」的問題，因而強調道的「整全性」及其語言世界與心靈世界的「解蔽」功能。嚴遵、河上公與王弼不同，他們不把「道」視為一可被詮釋的對象，而以為道有確信的內涵。在型態上嚴遵強調「道」有「反復交感」與「對立同源」的二種特性；而河上公則強調「道」能主宰、能經營變化的功能。了解三家在詮釋型態上的不同，除了能清楚掌握他們對《老子》的理解外，或許也可以對目前關於《老子》的不同版本系統，提供學術史研究上的合理推測。This paper discusses the different methodologies used by Yen Tsun, Ho-shang-kung, and Wang Pi in their commentaries on Lao Tsu. Specifically, we will differentiate their interpretations of Lao Tsu in terms of their approaches towards Tao and the use of language to signify that concept. To understand Wang Pi's approach, we may consult his “Lao Tsu Chih Lueh”; however, for the other two authors we are left to infer their approaches based on their commentaries on the Lao Tsu. In this paper we shall show that inasmuch as Wang treats Tao as an object to be interpreted, he must resolve the problem of how language can be used to convey “Tao”. As a result, he emphasized Tao's “cmpleteness” and its role in “removing obstacles” in the linguistic and psycho-spiritual realms. Yen Tsun and Ho-shang-kung's approach to Lao Tsu differ from Wang's in the sense that they do not see Tao as an object to be interpreted, although they do believe that Tao has a definite nature. In his discussion of Tao, Yen Tsun empha-sizes two concepts, a sort of “continual mutual interaction” and “dualism springing from a common source.” Ho-shang-kung, on the other hand, stresses Tao's role as “being able to control” and “responding to change.” By delineating these different interpretative attitudes among these three commentators, we can not only better understand their approaches to the text itself, but may also be in a better position to offer a reasonable explanation for the different textual traditions of the Lao Tsu over the ages
Katalog der Musikbibliothek Peters ...
No full textClassified, with author indexes.Preface signed: C.F. Peters. Dr. Emil Vogel, bibliothekar.Abth. 1. Theoretische Werke.--Abth. 2. Praktische Werke.Mode of access: Internet
Motion of quantum vortex lines near realistic rough boundaries
No full textWe numerically solve the three--dimensional, time--dependent Gross--Pitaevskii equation to model a superfluid flowing over a realistic rough boundary. Our model for the boundary is based on the atom--force microscope image of a NbTi vibrating wire used to generate turbulence in actual experiments. We find that near the boundary a dense region of quantum vortices is created, which forms a kind of `superfluid boundary layer'
Wave excitations in adjacent vortex filaments
No full textThe interactions of the nearest neighbour vortices are argued to play a significant role in the crossover range of scales that lies between the Kolmogorov-Richardson cascade and the Kelvin wave driven cascade in superfluid turbulence. In this work, we study how a wave excitation (a Kelvin wave or a soliton) on a vortex affects a nearby straight vortex. Our numerical simulations reveal that coherent excitations can hop from one vortex filament to another whilst retaining their coherent properties
Spectral properties of Andreev reflection from quantum turbulence in 3He-B: What do they tell about turbulent fluctuations?
No full textOne of the experimental techniques developed to measure quantum turbulence at low temperatures in 3He-B utilizes the Andreev reflection of thermal quasiparticle excitations from quantized vortices and vortex structures. We present the results of theoretical, numerical, and experimental study of Andreev scattering from quantum turbulence in 3He-B. We analyze the spectral properties of the Andreev reflection and compare these with the spectral properties of superfluid turbulence, and discuss the physical mechanisms responsible for the scaling of spectral densities. Finally, we discuss the relation between our findings and related observables in ordinary turbulence
Is Strong Reciprocity a Maladaptation? On the Evolutionary Foundations of Human Altruism
Full text linkIn recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically unrelated strangers. We provide ethnographic and experimental evidence suggesting that ultimate theories of kin selection, reciprocal altruism, costly signaling and indirect reciprocity do not provide satisfactory evolutionary explanations of strong reciprocity. The problem of these theories is that they can rationalize strong reciprocity only if it is viewed as maladaptive behavior whereas the evidence suggests that it is an adaptive trait. Thus, we conclude that alternative evolutionary approaches are needed to provide ultimate accounts of strong reciprocity.
A Fuzzy-based Scoring Rule for Author Ranking: an alternative to h-index
No full textThe measurement of the quality of research has reached nowadays an increasing interest not only for scientific reasons but also for the critical problem of researchers' ranking, due to the lack of grant assignments. The most commonly used approach is based on the so-called h-index, even if the current literature debated a lot about its pros and cons. This paper, after a brief review of the h-index and of alternative models, focuses on the characterization and the implementation of a modified scoring rule approach by means of a fuzzy inference system a là Sugeno
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