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Given a real vector alpha =(alpha1 ; : : : ; alpha d ) and a real number E > 0 a good Diophantine approximation to alpha is a number Q such that IIQ alpha mod Zk1 ", where k \Delta k1 denotes the 1-norm kxk1 := max 1id jx i j for x = (x1 ; : : : ; xd ). Lagarias [12] proved the NP-completeness of the corresponding decision problem, i.e., given a vector ff 2 Q d , a rational number " ? 0 and a number N 2 N+ , decide whether there exists a number Q with 1 Q N and kQff mod Zk1 ". We prove that, unless ...
We address to the problem to factor a large composite number by lattice reduction algorithms. Schnorr has shown that under a reasonable number theoretic assumptions this problem can be reduced to a simultaneous diophantine approximation problem. The latter in turn can be solved by finding sufficiently many l_1--short vectors in a suitably defined lattice. Using lattice basis reduction algorithms Schnorr and Euchner applied Schnorrs reduction technique to 40--bit long integers. Their implementation needed several hours to compute a 5% fraction of the solution, i.e., 6 out of 125 congruences which are necessary to factorize the composite. In this report we describe a more efficient implementation using stronger lattice basis reduction techniques incorporating ideas of Schnorr, Hoerner and Ritter. For 60--bit long integers our algorithm yields a complete factorization in less than 3 hours.
A rather disillusioned observation was recently made during a pan-Africa conference: Africa women consider new information and communication technologies as "futuristic" rather than a tool for development to be used today. If initiatives are not taken now to thwart this attitude, activities by women in Africa to promote sustainable development that also benefit them will take event longer. This will be especially true in regions on the continent where English is not the common language.
The goals of Zionism today
(1998)
This paper surveys the growth and various phases of and influences on the concept of democracy in the Islamic political thought of the last two centuries. Among the thinkers covered in the survey are Rifa'a Tahtawi (1801-73), Khairuddin at-Tunis (1810-99), Jamal ad-Din al-Afghani (1838-97), Muhammad Abduh (1849-1905), Abdurrahman al-Kawakibi (1849-1903), Rashid Rida (1865-1935), Hasan al-Banna (1904-49), Ali Abd Ar-Raziq (1888-1966), Sayyid Qutb (1906-66), Sa'id Hawwa, and Malik Bennabi (1905-73). Reference is made to the influence of Sayyid Mawdudi (1903-79), on the thought of Sayyid Qutb. The paper traces also the bearing of Bennabi's thought on Rachid Ghannouchi and on the Islamic movements of our times.
In Belhare (Sino-Tibetan, Nepal), consonant prothesis at morpheme boundaries and deletion of stem "augments" is found if either metrical or morphological parsing would violate the bimoraic trochee pattern that underlies the stress system of the language. This finding corroborates Dresher & Lahiri’s (1991) "Principle of Metrical Coherence" and provides new evidence for the cross-linguistic applicability of Crowhurst’s (1994) "Tautomorphemic Foot" constraint. The data also support a view of the Prosodic Hierarchy as weakly layered, allowing consonants to be directly dominated by the foot or word node if they are prothetic and do not therefore need feature licensing within the syllable canon.
Central wage bargaining and local wage flexibility : evidence from the entire wage distribution
(1998)
We argue that in labor markets with central wage bargaining wage flexibility varies systematically across the wage distribution: local wage flexibility is more relevant for the upper part of the wage distribution, and flexibility of wages negotiated under central wage bargaining affects the lower part of the wage distribution. Using a random sample of German social-security accounts, we estimate wage flexibility across the wage distribution by means of quantile regressions. The results support our hypothesis, as employees with low wages have significantly lower local wage flexibility than high wage employees. This effect is particularly relevant for the lower educational groups. On the other hand, employees with low wages tend to have a higher wage flexibility with respect to national unemployment.
To preserve the required beam quality in an e+/e- collider it is necessary to have a very precise beam position control at each accelerating cavity. An elegant method to avoid additional length and beam disturbance is the usage of signals from existing HOM-dampers. The magnitude of the displacement is derived from the amplitude of a dipole mode whereas the sign follows from the phase comparison of a dipole and a monopole HOM. To check the performance of the system, a measurement setup has been built with an antenna which can be moved with micrometer resolution to simulate the beam. Furthermore we have developed a signal processing to determine the absolute beam displacement. Measurements on the HOM-damper cell can be done in the frequency domain using a network analyser. Final measurements with the nonlinear time dependent signal processing circuit has to be done with very short electric pulses simulating electron bunches. Thus, we have designed a sub nanosecond pulse generator using a clipping line and the step recovery effect of a diode. The measurement can be done with a resolution of about 10 micrometers. Measurements and numerical calculations concerning the monitor design and the pulse generator are presented.
We review arguments for and against reserve requirements and conclude that the main question is whether a distinction between money creation and intermediation can be made. We argue that such a distinction can be made in a money-in-advance economy and show that if the money-in-advance constraint is universally binding then reserve requirements on checkable accounts have no effect on intermediation. We then proceed to show that in a model in which trade is uncertain and sequential, a fractional reserve banking system gives rise to endogenous monetary shocks. These endogenous monetary shocks lead to fluctuations in capacity utilisation and waste. When the money-in-advance constraint is universally binding, a 100% reserve requirement on checkable accounts can eliminate this waste.
For the efficient management of large image databases, the automated characterization of images and the usage of that characterization for searching and ordering tasks is highly desirable. The purpose of the project SEMACODE is to combine the still unsolved problem of content-oriented characterization of images with scale-invariant object recognition and modelbased compression methods. To achieve this goal, existing techniques as well as new concepts related to pattern matching, image encoding, and image compression are examined. The resulting methods are integrated in a common framework with the aid of a content-oriented conception. For the application, an image database at the library of the university of Frankfurt/Main (StUB; about 60000 images), the required operations are developed. The search and query interfaces are defined in close cooperation with the StUB project “Digitized Colonial Picture Library”. This report describes the fundamentals and first results of the image encoding and object recognition algorithms developed within the scope of the project.
The prevention of credit card fraud is an important application for prediction techniques. One major obstacle for using neural network training techniques is the high necessary diagnostic quality: Since only one financial transaction of a thousand is invalid no prediction success less than 99.9% is acceptable. Due to these credit card transaction proportions complete new concepts had to be developed and tested on real credit card data. This paper shows how advanced data mining techniques and neural network algorithm can be combined successfully to obtain a high fraud coverage combined with a low false alarm rate.
The redeemers of the land
(1999)
The bedouin in Israel
(1999)
Following on the ADEA/APNET study on inter-African Book trade that was commissioned in 1999, ADEA tasked APNET to facilitate the production of national book industry updates in each country. The updates are aimed at encouraging commercial development of inter-African book trade and to make available to the public, total systematic and current situations on the book trade in each country.
Let G be a finite cyclic group with generator \alpha and with an encoding so that multiplication is computable in polynomial time. We study the security of bits of the discrete log x when given \exp_{\alpha}(x), assuming that the exponentiation function \exp_{\alpha}(x) = \alpha^x is one-way. We reduce he general problem to the case that G has odd order q. If G has odd order q the security of the least-significant bits of x and of the most significant bits of the rational number \frac{x}{q} \in [0,1) follows from the work of Peralta [P85] and Long and Wigderson [LW88]. We generalize these bits and study the security of consecutive shift bits lsb(2^{-i}x mod q) for i=k+1,...,k+j. When we restrict \exp_{\alpha} to arguments x such that some sequence of j consecutive shift bits of x is constant (i.e., not depending on x) we call it a 2^{-j}-fraction of \exp_{\alpha}. For groups of odd group order q we show that every two 2^{-j}-fractions of \exp_{\alpha} are equally one-way by a polynomial time transformation: Either they are all one-way or none of them. Our key theorem shows that arbitrary j consecutive shift bits of x are simultaneously secure when given \exp_{\alpha}(x) iff the 2^{-j}-fractions of \exp_{\alpha} are one-way. In particular this applies to the j least-significant bits of x and to the j most-significant bits of \frac{x}{q} \in [0,1). For one-way \exp_{\alpha} the individual bits of x are secure when given \exp_{\alpha}(x) by the method of Hastad, N\"aslund [HN98]. For groups of even order 2^{s}q we show that the j least-significant bits of \lfloor x/2^s\rfloor, as well as the j most-significant bits of \frac{x}{q} \in [0,1), are simultaneously secure iff the 2^{-j}-fractions of \exp_{\alpha'} are one-way for \alpha' := \alpha^{2^s}. We use and extend the models of generic algorithms of Nechaev (1994) and Shoup (1997). We determine the generic complexity of inverting fractions of \exp_{\alpha} for the case that \alpha has prime order q. As a consequence, arbitrary segments of (1-\varepsilon)\lg q consecutive shift bits of random x are for constant \varepsilon >0 simultaneously secure against generic attacks. Every generic algorithm using $t$ generic steps (group operations) for distinguishing bit strings of j consecutive shift bits of x from random bit strings has at most advantage O((\lg q) j\sqrt{t} (2^j/q)^{\frac14}).