Chemical and microbiological changes occurring in wheat silage maintained under modified atmospheres

In wheat silage maintained for 21 days at 26°C and 9-9 kPa water vapour pressure under a continuous flow of modified atmospheres (MAs) containing 20% v/v O₂ and different concentrations of CO₂ (from 20 % v/v to 80 % v/v) there was a significant increase in pH and in the colony-forming units (CFU) of aerobic bacteria, yeasts and moulds. In addition, water-soluble carbohydrates (WSC) and acetic and lactic acids decreased considerably. Similar results were obtained with a continuous flow of 90 %, 95 % and 99 % v/v CO₂ (supplemented to 100 % v/v with O2) and with 100 % v/v pure O₂ Only with silage kept in an atmosphere of 100 % v/v CO₂ or of 100 % v/v N₂ were no changes observed.     

Public online pool—a method for managing online direct access space

This paper describes a software system, implemented at the Weizmann Institute of Science Computer Center, for managing online direct access space in a heavy batch/time sharing environment. Appropriate background discussion of the problem is presented in general, yet practical, terms. We describe the ‘ideal’ solution along with its shortcomings as we see them, followed by the solution as implemented at our installation and successfully operating for 5 years. Finally, we point out the effect this system had on our installation and show where future efforts could be rewarding. The work this paper describes won the 1975 prize of the Information Processing Association of Israel.     

A unified sequential identification structure based on convergence considerations

This paper presents a unified approach to sequential identification methods, via identification-convergence considerations, such that a fixed-structure identifier of stable and unstable processes is derived. It is shown that various identification algorithms can be derived by a proper choice of identifier parameters subject to simple constraints. Specifically, stochastic approximation and sequential learning identification algorithms are shown to be special cases of the above unified sequential structure, as are other algorithms.     

Mixed-mode fracture angle and fracture locus of materials subjected to compressive loading

The incipient fracture angle and fracture loci of prenotched brittle-like material subjected to compressive loading are investigated analytically and experimentally.The analysis of the problem includes parameters whose effects on fracture were pronounced via laboratory tests, namely: notch-tip curvature, subcritical microcracks emanating from the notch and crack closure process. Such considerations, jointly with the well-established fracture criteria in tensile loading (like the critical energy release rate, the critical energy density, J-integral and critical maximum stress used in this work) yielded an associated fracture locus for each criterion. Due to the mixed mode nature of the situation (K₁ and K₂) preevaluation of the fracture angle was instrumental.Data on critical (far-field) compressive load along with measured fracture angles performed on PMMA and Tungsten Carbide specimens are used to depict the most suitable fracture locus and thus to distinguish between the various fracture criteria when extended to fracture under compressive loading. An exact expression for the threshold load for complete closure of 2D elliptical cracks is used to delimit the fracture locus.     

Post Transmission Digital Video Enhancement for People with Visual Impairments

Image enhancement has been shown to improve the perceived quality of images and videos for people with visual impairments. The MPEG coding scheme makes spatial filtering, likely to help those with such impairments, possible at the decoding stage. We implemented a real-time platform for testing and improving contrast enhancement algorithms for MPEG video, with controls appropriate for the target population. The necessary additional processing runs efficiently on a general-purpose PC and can be integrated easily into existing MPEG-2 decoders. The system has enabled us to substantially improve the previous filtering algorithm; reducing artifacts exhibited in the previous implementation and should facilitate individual user-selection of enhancement parameters in evaluation studies.     

Online auctions enabling the secondary computer market

The Internet is enabling new forms of commerce and novel markets. One example is the secondary computer market, facilitating exchange between quality sensitive sellers, oftentimes businesses, and price sensitive buyers. As this market does not have a viable physical counterpart with reference prices, it is developing via online auctions. One question of interest in the evolution of this market is the determinants of prices. Using a dataset of 2,000 laptop auctions in a seven-month period, this research provides support for accepted auction theory while raising questions that deserve further explanation. The negative relationship between supply and auction price supports standard supply and demand theory, while higher prices for better features is consistent with vertical differentiation. Even within accepted theory this research broadens the understanding of auction behavior. There is clear support for the “price decline anomaly” where prices in sequential auctions decline, violating the “law of one price.” One result that deserves further attention is that midweek auctions realize higher prices. A second is that price changes over time are not monotonic. Future research should replicate and explain these results, as well as extend them to other auction settings. As the secondary computer market evolves it will impact the primary computer market.     

Free vibration analysis of a steel T-Shape frame including semi-rigid Khorjini connection with continuous beam

This article deals with the free vibration analysis and determination of seismic parameters of a T-Shape frame which consists of a continuous beam and a column connected to each other by means of a semi-rigid Khorjini connection. The individual members of the frame are assumed to be governed by the transverse vibration theory of an Euler-Bernoulli beam and the semi-rigid Khorjini connection is modeled employing a rotational spring. First of all, a closed-form solution is proposed and then, a numerical analysis is performed for some comparison and validation purposes. The closed-form solution is developed by solving the frame equations of motion, directly. For this reason, some mathematical techniques such as Fourier transform and the well-known complementary solutions are utilized. In this process, some differential equations must be solved, and several boundary conditions should be satisfied. Afterward, the free vibration parameters of the frame are attained. These parameters are also obtained using finite element method as a numerical analysis and it is observed that the results obtained by this approach are completely coincident with the result of closed-form solution. Also, seismic parameters of the frame and seismic behavior of the semi-rigid Khorjini connection for different cases are investigated and their results are compared. Finally, two special cases are presented and, furthermore, the connection mass effect on system frequency is investigated.     

Neutrino astronomy and gamma-ray bursts

The construction of large-volume detectors of high energy, greater than 1TeV, neutrinos is mainly driven by the search for extragalactic neutrino sources. The existence of such sources is implied by the observations of ultra-high-energy, greater than or equal to 1019eV, cosmic rays, the origin of which is a mystery. In this lecture, I briefly discuss the expected extragalactic neutrino signal and the current state of the experimental efforts. Neutrino emission from gamma-ray bursts (GRBs), which are probably sources of both high-energy protons and neutrinos, is discussed in some detail. The detection of the predicted GRB neutrino signal, which may become possible in the coming few years, will allow one to identify the sources of ultra-high-energy cosmic rays and to resolve open questions related to the underlying physics of GRB models. Moreover, detection of GRB neutrinos will allow one to test for neutrino properties (e.g. flavour oscillations and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.