Showing papers by "Tel Aviv University published in 1990"
TL;DR: The diffusion of an innovation traditionally has been defined as the process by which that innovation iscommunicated through certain channels over time among the members of a social system.
Abstract: The diffusion of an innovation traditionally has been defined as the process by which that innovation is “communicated through certain channels over time among the members of a social system” (Rogers, 1983, p. 5). As such, the diffusion process consists of four key elements: innovation, communication channels, time, and the social system.
2,535 citations
TL;DR: Some new, general and simple procedures are discussed and demonstrated by two examples from the medical literature: the neuropsychologic effects of unidentified childhood exposure to lead, and the sleep patterns of sober chronic alcoholics.
Abstract: The problem of multiple comparisons is discussed in the context of medical research. The need for more powerful procedures than classical multiple comparison procedures is indicated. To this end some new, general and simple procedures are discussed and demonstrated by two examples from the medical literature: the neuropsychologic effects of unidentified childhood exposure to lead, and the sleep patterns of sober chronic alcoholics.
2,473 citations
TL;DR: In this article, the authors propose an elaboration of the Diamond model that permits multiple, locally stable stationary states, and this multiplicity is due to increasing social returns to scale in the accumulation of human capital.
Abstract: Standard one-sector growth models often have the counterfactual implication that economies with access to similar technologies will converge to a common balanced growth path. We propose an elaboration of the Diamond model that permits multiple, locally stable stationary states. This multiplicity is due to increasing social returns to scale in the accumulation of human capital.
2,070 citations
01 Feb 1990
TL;DR: The use of credit cards today is an act of faith on the p a t of all concerned as discussed by the authors, and each party is vulnerable to fraud by the others, and the cardholder in particular has no protection against surveillance.
Abstract: The use of credit cards today is an act of faith on the p a t of all concerned. Each party is vulnerable to fraud by the others, and the cardholder in particular has no protection against surveillance.
1,031 citations
TL;DR: This paper proposes to use as a building block the more robust Lax-Friedrichs (LxF) solver, and compensates for the excessive numerical viscosity typical to the LxF solver by using high-resolution MUSCL-type interpolants.
1,028 citations
TL;DR: A new interpolatory subdivision scheme for surface design is presented that is designed for a general triangulation of control points and has a tension parameter that provides design flexibility.
Abstract: A new interpolatory subdivision scheme for surface design is presented. The new scheme is designed for a general triangulation of control points and has a tension parameter that provides design flexibility. The resulting limit surface is C1 for a specified range of the tension parameter, with a few exceptions. Application of the butterfly scheme and the role of the tension parameter are demonstrated by several examples.
872 citations
TL;DR: A necessary and sufficient condition for blind deconvolution (without observing the input) of nonminimum-phase linear time-invariant systems (channels) is derived and several optimization criteria are proposed, and their solution is shown to correspond to the desired response.
Abstract: A necessary and sufficient condition for blind deconvolution (without observing the input) of nonminimum-phase linear time-invariant systems (channels) is derived. Based on this condition, several optimization criteria are proposed, and their solution is shown to correspond to the desired response. These criteria involve the computation only of second- and fourth-order moments, implying a simple tap update procedure. The proposed methods are universal in the sense that they do not impose any restrictions on the probability distribution of the (unobserved) input sequence. It is shown that in several important cases (e.g. when the additive noise is Gaussian), the proposed criteria are essentially unaffected. >
843 citations
TL;DR: A description of quantum systems at the time interval between two successive measurements is presented, and how this approach leads to a new concept: a weak value of an observable.
Abstract: A description of quantum systems at the time interval between two successive measurements is presented. Two wave functions, the first preselected by the initial measurement and the second postselected by the final measurement, describe quantum systems at a single time. It is shown how this approach leads to a new concept: a weak value of an observable. Weak values represent novel characteristics of quantum systems between two measurements. They are outcomes of a standard measurement procedure that fulfills certain requirements of ``weakness.'' We call it weak measurement. Physical meaning, underlying mathematical structure, and prospects of practical usage of weak measurements are explored.
701 citations
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TL;DR: In this paper, the authors examine one channel through which the trade regime might affect growth in the long run, and they derive the implications of this for the relationship between trade and growth, and argue that local knowledge capital is likely to vary positively with the extent of contact between domestic agents and their counterparts in the international research and business communities.
Abstract: In this paper, we examine one channel through which the trade regime might affect growth in the long run. We model endogenous technological progress that results from profit maximizing investments by far-sighted entrepreneurs. Productivity in the research lab depends upon the "stock of knowledge capital", a variable reflecting the state of scientific, engineering and industrial know-how in the local economy. We argue that local knowledge capital is likely to vary positively with the extent of contact between domestic agents and their counterparts in the international research and business communities, and that the number of such contacts increases with the level of commercial exchange. We derive the implications of this for the relationship between trade and growth.
671 citations
TL;DR: In this paper, the interplay between the macroscopic driving force associated with the phase transition and the microscopic interfacial dynamics was studied, leading to complex patterns which are generically similar to those found in viscous fingering, aggregation and electrochemical deposition.
Abstract: Crystal growth under non-equilibrium conditions can give rise to complex patterns which are generically similar to those found in processes such as viscous fingering, aggregation and electrochemical deposition. Recent theoretical understanding focuses on the interplay between the macroscopic driving force associated with the phase transition and the microscopic interfacial dynamics.
652 citations
TL;DR: In this paper, the authors examined the desirability and implications of new venture financing within a principal-agent framework that captures the essence of the relationship between entrepreneurs and venture capitalists.
Abstract: A number of issues that relate to the desirability and implications of new venture financing are examined within a principal-agent framework that captures the essence of the relationship between entrepreneurs and venture capitalists. The model suggests: 1 As long as the skill levels of entrepreneurs are common knowledge, all will choose to involve venture capital investors, since the risk sharing provided by outside participation dominates the agency relationship that is created. 2 The less able entrepreneurs will choose to involve venture capitalists, whereas the more profitable ventures will be developed without external participation because of the adverse selection problem associated with asymmetric information. 3 If a costly signal is available that conveys the entrepreneur's ability, some entrepreneurs will invest in such a signal and then sell to investors; these entrepreneurs, however, need not be the more able ones. The implications for new venture financing of these and other findings are discussed and illustrated by example.
TL;DR: This paper analyzes the effects of different deterioration schemes and derive optimal scheduling policies that minimize the expected makespan, and, for some models, policies that minimizing the variance of the makespan.
Abstract: N jobs are to be processed sequentially on a single machine. While waiting for processing, jobs deteriorate, causing the random processing requirement of each job to grow at a job-specific rate. Under such conditions, the actual processing times of the jobs are no longer exchangeable random variables and the expected makespan is no longer invariant under any scheduling strategy that disallows idleness. In this paper, we analyze the effects of different deterioration schemes and derive optimal scheduling policies that minimize the expected makespan, and, for some models, policies that minimize the variance of the makespan. We also allow for random setup and detaching times. Applications to optimal inventory issuing policies are discussed and extensions are considered.
TL;DR: Using the analytical logic underlying the classical adopter categorization approach proposed by Rogers, the authors suggest that adopter categories for a product innovation can also be developed by product innovation start-up companies.
Abstract: Using the analytical logic underlying the classical adopter categorization approach proposed by Rogers, the authors suggest that adopter categories for a product innovation can also be developed by...
11 Mar 1990
TL;DR: In this article, an equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented, and a simple first-order approximation for the line current distortion and phase shift caused by 120 Hz duty cycle variations is derived.
Abstract: An equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented. This simple model correctly describes the basic power processing properties of the converter, including input port resistor emulation, output port power source characteristics, and control characteristics. Based on this model, steady-state design equations are described and are used in a design example. Design of the slow output voltage feedback loop is also considered. A small-signal AC model is developed for both the resistive load and the DC-DC converter-voltage regulator load cases. In addition, a simple first-order approximation for the line current distortion and phase shift caused by 120 Hz duty cycle variations is derived. >
TL;DR: The authors analyzes the trade-off between the policies that maximize their chances of reelection and their most preferred policies (or the policies most preferred by the constituency which they represent) in a dynamic electoral model in which the voters are not fully informed about the preferences of the incumbent.
Abstract: Politicians face a trade-off between the policies that maximize their chances of reelection and their most preferred policies (or the policies most preferred by the constituency which they represent). This paper analyzes this trade-off in a dynamic electoral model in which the voters are not fully informed about the preferences of the incumbent. First, we show that the incumbent follows a policy which is intermediate between the other party's ideal policy and his own ideal policy. Second, we show that, often, the incumbent has an incentive to choose procedures which make it difficult for voters to pinpoint his preferences with absolute precision. Thus, politicians may prefer to be "ambiguous."
TL;DR: In this paper, the question of whether competitive acquisition of firms by their rivals can result in complete or partial monopolization of a homogeneous product industry is modeled in terms of two distinct three-stage non-coopera-tive games.
Abstract: We address the question of whether competitive acquisition of firms by their rivals can result in complete or partial monopolization of a homogeneous product industry. This question is modeled in terms of two distinct three-stage noncoopera-tive games. Analysis of subgame perfect pure strategy Nash equilibria of these games discloses that, under simplifying assumptions, monopolization of an industry through acquisition is limited to industries with relatively few firms. Partial monopolization is either limited in scope or can be completely eliminated by prohibiting any owner from acquiring over 50 percent of the firms in the industry.
TL;DR: It is proposed that the preexposed stimulus loses its capacity to affect behavior in conditioning, even though it predicts reinforcement, because the hippocampus inhibits the switching mechanism of the nucleus accumbens via the subiculum-accumbens pathway.
Abstract: Latent inhibition (LI) refers to decrement in conditioning to a stimulus as a result of its prior nonreinforced preexposure. It is a robust phenomenon that has been demonstrated in a variety of classical and instrumental conditioning procedures and in many mammalian species, including humans. The development of LI is considered to reflect decreased associability of, or attention to, stimuli that predict no significant outcome. The fact that LI is considered to be a reflection of attentional processes has become of increasing importance to neuroscientists who see LI as a convenient tool for measuring the effects of drug treatments and lesions on attention. The present article surveys the data on brain systems, which have been studied in regard to their involvement in LI. These are reviewed and discussed separately in sections on noradrenergic, cholinergic, dopaminergic, serotonergic, and septo-hippocampal manipulations. On the basis of these data, it is concluded that the neural substrates of LI include the mesolimbic dopaminergic system, the mesolimbic serotonergic system, and the hippocampus. It is proposed that the preexposed stimulus loses its capacity to affect behavior in conditioning, even though it predicts reinforcement, because the hippocampus inhibits the switching mechanism of the nucleus accumbens via the subiculum-accumbens pathway. This action of the hippocampus is modulated by the mesolimbic serotonergic system via its interactions with the hippocampal or mesolimbic dopaminergic systems, or both.
01 Aug 1990
TL;DR: A general formulation of atonuc wzap~hot rnenzory, a shared memory partitioned into words written (apduted) by individual processes, or instantaneously read (scanned) in its entirety is introduced.
Abstract: This paper introduces a general formulation of atonuc wzap~hot rnenzory, a shared memory partitioned into words written (apduted) by individual processes, or instantaneously read (scanned) in its entirety. Thk paw’ Presents three wait-free implementations of atomic snapshot A preliminary version of this paper appeared in Proceedings of the 9th Annaa[ ACM SVmpmnwn on Plznctptes of’ Distributed Compafing (Quebec city. Quebec, A%). ACM New York, 199Q pp. 1-14. H. Attiya’s and N. Shavit’s research was partially supported by National Science Foundation grant CCR-86-1 1442, by Office of Naval Research contract NW014-S5-K-0168, and by DARPA cmltracts NOO014-83-K-0125 and NOO014-89-J1988. E. Gafni’s research was partially supported by National Science Foundation Grant DCR 84-51396 and XEROX Co. grant W8S1111. Part of this work was done while N. Shavit was at Hebrew University, Jerusalem, visiting AT&T Bell Laboratories and the Theory of Distributed Systems Group at Massachusetts Institute of Technology, and while H. Attiya was at the LaboratoV for Computer Science at Massachusetts Institute of Technology. Authors’ present addresses: Y. Afek, Computer Science Department. Tel-Aviv University, Ramat-Aviv, Israel 69978; H. Attiya, Department of Computer Science, Technion, Haifa, Israel 3~000:” D Dolev, Department of computer Science, Hebrew University, Jerusalem, Israel 91904: E. Gafni, 3732 Boelter Hall, Computer Science Department, U. C. L.A., Los Angeles. Cahfornia 90024. M. Merritt, 600 Mountain Ave., Murray Hill. NJ 07974; N. Shavit, Laborato~ for Computer Scienee, MIT NE43, 367 Technology Square, Cambridge MA 02139. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice N gwen that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. (!2 1993 ACM 0004-541 1/93/0900-0873 $01.50 Joumd of ihe Amocl.]tmn for Computmg Mdchmerv, Vd 40. No 4. Scptemhcr 1993. pp 873-89[1
01 Oct 1990
TL;DR: An efficient matching algorithm, which assumes affine approximation to the prospective viewing transformation, is proposed and was successfully tested in recognition of industrial objects appearing in composite occluded scenes.
Abstract: New techniques are described for model-based recognition of the objects in 3-D space. The recognition is performed from single gray-scale images taken from unknown viewpoints. The objects in the scene may be overlapping and partially occluded. An efficient matching algorithm, which assumes affine approximation to the prospective viewing transformation, is proposed. The algorithm has an offline model preprocessing (shape representation) phase which is independent of the scene information and a recognition phase based on efficient indexing. It has a straightforward parallel implementation. The algorithm was successfully tested in recognition of industrial objects appearing in composite occluded scenes. >
TL;DR: The cyclic polling model, its enhancement by customer routing, and the replacement of a fixed polling order by a random polling order are reviewed.
Abstract: The cyclic polling model, its enhancement by customer routing, and the replacement of a fixed polling order by a random polling order are reviewed. Modeling of polling systems, performance improvement, and system optimization issues are discussed. Examples are given that include token rings, ARQ and time-sharing schemes, random-access protocols, robotics and manufacturing systems. Emphasis is not on the analytical derivations of polling systems but rather on the description of the capabilities and limitations of the different polling models. >
TL;DR: A thoroughly objective method for the definition, selection and tracing of Mediterranean region cyclones is presented in this paper, which is applied to the ECMWF 1982-1987 analyzed datasets to show monthly cyclone frequencies, cyclonic tracks and vertical variation of average relative vorticity.
Abstract: A thoroughly objective method for the definition, selection and tracing of Mediterranean region cyclones is presented. The method is applied to the ECMWF 1982-1987 analyzed datasets to show monthly cyclone frequencies, cyclonic tracks and vertical variation of average relative vorticity. Day-to-night changes and vertical variation of cyclonic frequencies/vorticities indicate the importance of the sea thermal effect in the eastern Mediterranean. In the western Mediterranean and to a lesser extent in the Cyprus region, the lee cyclogenetic effect is very pronounced. Monthly cyclone tracks are presented and they clearly indicate the preferred routes of cyclonic movements. DOI: 10.1034/j.1600-0870.1990.00007.x
TL;DR: The equivalence of the two approaches to quantum interference in the presence of an environment is proven and dephasing of electron interference by photon modes in coherent and thermal states and by electromagnetic fluctuations in metals is proven.
Abstract: The problem of quantum interference in the presence of an environment is considered by two approaches. One treats the problem from the point of view of the trace left by the interfering particle on its environment. The other regards the phase accumulation of the interfering waves as a statistical process, and explains the loss of interference in terms of uncertainty in the relative phase. The equivalence of the two approaches is proven for the general case. The two approaches are applied to dephasing of electron interference by photon modes in coherent and thermal states, and to dephasing by electromagnetic fluctuations in metals.
TL;DR: In this article, the authors analyze the causes and consequences of delegitimization and suggest two models that describe the role of conflict and ethnocentrism in the process of such a process.
Abstract: Delegitimization is the process of categorizing groups into extremely negative social categories and excluding them from acceptability. This paper analyzes the causes and consequences of delegitimization, and suggests two models that describe the role of conflict in delegitimization and of ethnocentrism in delegitimization. During conflict, when the ingroup perceives the negating goal(s) of an outgroup as far-reaching and evil, feelings of threat become intensified and delegitimization may be used to explain the conflict. Then, to prevent danger, the ingroup may harm the threatening group and justify the harm by delegitimization, which in turn increases perceived threat and intensifies harmful behavior toward the other group. Even mild conflicts can escalate, become violent, and lead to delegitimization as an explanation, and later, as justification. Ethnocentrism is related to this process because groups that are perceived as very different and devalued arouse feelings of fear and contempt. Their delegitimization leads to harm, and later, to intensified delegitimization to justify the harm.
22 Oct 1990
TL;DR: The authors present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent, and two of the constructions are based on bit sequences that are widely believed to possess randomness properties.
Abstract: The authors present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent. The number of bits used to specify a point in the sample space is O(log log n+k+log 1/ epsilon ), where epsilon is the statistical difference between the distribution induced on any k-bit locations and the uniform distribution. This is asymptotically comparable to the construction recently presented by J. Naor and M. Naor (1990). An advantage of the present constructions is their simplicity. Two of the constructions are based on bit sequences that are widely believed to possess randomness properties, and the results can be viewed as an explanation and establishment of these beliefs. >
TL;DR: The curvature elastic energy of bilayer vesicles formed by a mixture of two surfactants, which individually form either micelles or lamellar bilayer phases is described theoretically.
Abstract: The curvature elastic energy of bilayer vesicles formed by a mixture of two surfactants, which individually form either micelles or lamellar bilayer phases is described theoretically. In the limit of large bending elastic modulus K being much greater than the temperature T, the free energy is minimized by vesicles with different concentrations of the two surfactants in each monolayer of the bilayer. Vesicles are more stable than lameliar structures only when interactions or complexing of the two surfactants is taken into account.
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TL;DR: In this paper, the authors introduce several options of modeling the hydrodynamic parameters and pressure drop using a unified approach that is applicable for the vertical, horizontal, and inclined cases of slug flow.
Abstract: Publisher Summary Slug flow is a highly complex type of flow with an unsteady nature The prediction of pressure drop, heat, and mass transfer for such flow is often considered a difficult task The chapter deals with steady slug flow The chapter introduces several options of modeling the hydrodynamic parameters and pressure drop using a unified approach that is applicable for the vertical, horizontal, and inclined cases The chapter also reviews transient phenomena in slug flow by illustrating an example of severe slugging in a pipeline-riser system It is noted that heat transfer in slug flow is of major importance for practical applications The treatment of the two-phase flow is usually considered as a two-phase mixture The severe slugging that consists of one riser and one pipeline is one of the simplest example of slug flow under nonsteady conditions The Boe criterion differentiates between steady and cyclic operations with two exceptions At high liquid flow rates, a steady flow can also exist within the severe slugging region predicted by the Boe criterion There is a region outside the Boe criterion that is in an unsteady state and leads to unsteady oscillations
TL;DR: The cDNAs and deduced amino acid sequences, presented here, define the complete amino acids sequences of the epithelial tumor antigen and demonstrate the existence of multiple protein forms that probably localize to different cellular and extracellular compartments.
Abstract: The isolation and characterization of complementary DNAs (cDNAs) which code for an epithelial antigen aberrantly expressed in human breast tumor tissue are described here. The only information regarding the primary structure of this potentially important antigen has been a 20-amino-acid repeat motif. We now report the complete amino acid sequences of different forms of the human epithelial tumor antigen as deduced from the nucleotide sequence of isolated non-repeat cDNAs. The diversity of protein forms is generated by a series of alternative splicing events that occur in the regions located upstream and downstream to a central tandem repeat array. Isolated cDNAs coding for the upstream region show that differential usage of alternative splice acceptor sites may generate two protein forms containing putative signal peptides of varying hydrophobicities. The complexity of possible antigen forms is further compounded by alternative splicing events occurring in the region 3' to the repeat array. The isolated cDNAs 3' to the tandem repeats indicate that whereas one mRNA transcript is colinear with the gene, and defines an open reading frame (ORF) containing 160 amino acids downstream to the repeat array, a second cDNA correlates with a mRNA that is generated by a series of splicing events. The deduced amino acid sequence of the spliced cDNA contains an ORF that is identical for 149 amino acids downstream to the repeat array with the amino acid sequence of the unspliced cDNA. At this point it diverges and continues for an additional 179 amino acids. The sequence contains a highly hydrophobic 28-amino-acid peptide, located towards the carboxyl terminus, that may correspond to a transmembrane region. The cDNAs and deduced amino acid sequences, presented here, define the complete amino acid sequences of the epithelial tumor antigen and demonstrate the existence of multiple protein forms that probably localize to different cellular and extracellular compartments.
TL;DR: In this paper, the use of simple currents in constructing modular invariant partition functions and the problem of resolving their fixed points is discussed. But the fixed points are always related to some conformal field theory.
Abstract: We review the use of simple currents in constructing modular invariant partition functions and the problem of resolving their fixed points. We present some new results, in particular regarding fixed point resolution. Additional empirical evidence is provided in support of our conjecture that fixed points are always related to some conformal field theory. We complete the identification of the fixed point conformal field theories for all simply laced and most non-simply laced Kac-Moody algebras, for which the fixed point CFT’s turn out to be Kac-Moody algebras themselves. For the remaining non-simply laced ones we obtain spectra that appear to correspond to new non-unitary conformal field theories. The fusion rules of the simplest unidentified example are computed.
TL;DR: A method to obtain a superposition of time evolutions of a quantum system which correspond to different Hamiltonians as well as to different periods of time is derived.
Abstract: A method to obtain a superposition of time evolutions of a quantum system which correspond to different Hamiltonians as well as to different periods of time is derived. Its application to amplification of an effect due to the action of weak forces is considered. A quantum time-translation machine based on the same principle, utilizing the gravitational field, is also considered.