Showing papers by "Technion – Israel Institute of Technology published in 1980"

Safety climate in industrial organizations: theoretical and applied implications.

Abstract: A 40-item measure of organizational climate for safety was constructed and validated in a stratified sample of 20 industrial organizations in Israel. This climate reflects employees' perceptions about the relative importance of safe conduct in their occupational behavior. It can vary from highly positive to a neutral level, and its average level reflects the safety climate in a given company. It was shown that there is an agreement among employees' perceptions regarding safety climate in their company and that the level of this climate is correlated with safety program effectiveness as judged by safety inspectors. The two dimensions of highest importance in determining the level of this climate were workers' perceptions of management attitudes about safety and their perceptions regarding the relevance of safety in general production processes. It is proposed that organizational climate, when operationalized and validated as demonstrated in this article, can serve as a useful tool in understanding occupational behavior.

Structural and floristic diversity of shrublands and woodlands in Northern Israel and other Mediterranean areas

Abstract: Between 1974 and 1978 structure and diversity of shrublands and woodlands of northern Israel were studied along climatic and human-disturbance gradients using 0.1 ha vegetation samples. Diversity increased along the moisture gradient, with highest woody and herb species richness in open Pistacia shrubland on the xeric border of the Mediterranean region, and highest equitability and lowest dominance concentration in sub-humid, moderately grazed, open oak woodlands. Semi-open disturbed shrublands were rich in herbs and had much higher structural, plant species, and animal species diversities than the closed, mature, ‘climax’ maquis. Diversity showed a two-slope response to grazing with highest species numbers in heavily (but not the most severely) grazed woodlands and shrublands. These communities have some of the highest plant alpha diversities in the world; the richness of their floras (especially in annual plants) is the product of relatively rapid evolution under stress by drought, fire, grazing, and cutting. Comparative data on diversity and growth-form composition are compiled for mediterranean communities: Israeli' shrublands and woodlands, California chaparral and woodlands, Chilean matorral, South African fynbos, and Australian heath and mallee. Communities of three of these areas are of more recent (primarily Pleistocene) development and share some similarities; these threc form a sequence (California, Chile, and Old World Mediter-ranean) of increasing length of human disturbance and consequent species diversity. The southwest Australian heath or kwongan and the South African fynbos are, in contrast, derived from ancient Gondwanan heath like communities and are adapted to very old, nutrient-poor soils. The Gondwanan communities are quite different in growth-form structure and soil and nutrient relationships from communities of the three more recent mediterranean areas; the Gondwanan communities are almost lacking in annual species and are exceedingly rich in woody species. The richest temperate plant communities known — grazed Mediterranean pastures vs. fynbos and Australian heath — are in almost polar contrast in their growth-form structures and the bases of their species diversities. This study, sponsored by the U.S.-Israel Binational Science Foundation (No. 450), was carried out by Z. Naveh as principal investigator with R.H. Whittaker as American collaborator. We thank Mr. A. Mann, S. Burmil, Mrs. Chaim, and Mrs. A. Kleen for botanical field work and statistical computations, Mr. D. Feigin and S. Ben Ezrah for technical assistance, Mr. S. Asherow for identification of young plants, and the Nature Reserve Authorities, the Neve Yaar Experimental Station, the Agricultural School Kfar Hanoar Hadati, and Kibbutzim Allonim and Allone Abba for allowing us to use their land for this study. The work by R.H. Whittaker was supported by the U.S. National Science Foundation, Australian National University, and Canberra Botanic Gardens; and we thank all the collaborators in this work.

A Proof System for Communicating Sequential Processes

Abstract: An axiomatic proof system is presented for proving partial correctness and absence of deadlock (and failure) of communicating sequential processes. The key (meta) rule introduces cooperation between proofs, a new concept needed to deal with proofs about synchronization by message passing. CSP's new convention for distributed termination of loops is dealt with. Applications of the method involve correctness proofs for two algorithms, one for distributed partitioning of sets, the other for distributed computation of the greatest common divisor of n numbers.

Distributed Termination

Abstract: Discussed is a distributed system based on communication among disjoint processes, where each process is capable of achieving a post-condition of its local space in such a way that the conjunction of local post-conditions implies a global post-condition of the whole system. The system is then augmented with extra control communication in order to achieve distributed termination, without adding new channels of communication. The algorithm is applied to a problem of constructing a sorted partition.

The ‘even‐electron rule’

Abstract: Many (>170) exceptions to the ‘even-electron rule from the literature (unrecognized in most cases) and from the authors’ Laboratory are presented and discussed. The large number of violations suggests that although the generalization may be a helpful guide for the explanation of mass spectral behaviour of many organic compounds, the term ‘rule’ seems to be unjustified. THE RULE The ‘even-electron rule’ is an oft-quoted generalization important for the understanding and prediction of mass spectral behaviour of organic compounds. ’-’ It states that odd-electron cations (such as molecular ions or fragments formed by rearrangements) may eliminate either a radical or an even-electron neutral species, but even-electron ions (such as protonated molecules or fragments formed by a single bond cleavage) will not usually lose a radical to form an oddelectron cation. It can be summarized in the following scheme:

Determination of the critical slip surface in slope stability computations

Abstract: The analysis of the stability of slopes using limiting equilibrium considerations necessitates the determination of the critical slip surface which yields the minimal factor of safety. The numerous methods currently available for slope stability analysis provide a procedure for assigning a factor of safety to a given slip surface, but do not consider the problem of identifying the critical conditions. This paper presents an effective minimization procedure based on dynamic programming by which the minimal factor of safety, and the corresponding surface, are determined simultaneously. This procedure SSDP (Slope Stability by Dynamic Programming), couples the minimization scheme with Spencer's method of slope stability analysis. It may be applied to slopes of any geometry, layering, pore pressure and external load distributions. No arbitrary restrictions are placed on the shape of the slip surfaces, and the analysis satisfies all equilibrium equations. Application of the procedure to slope stability problems reported in the literature shows that for a given slip surface the procedure yields factors of safety which are almost identical to those reported, but in every case a more critical slip surface, with a lower factor of safety, may be found.

Stability properties of Smith dead-time compensator controllers

Abstract: The special stability properties of SISO systems incorporating Smith dead-time compensator controllers are investigated. It is shown that the conventional approach to the design of such systems may lead to practical instabilities. Necessary conditions for practical stability and sufficient conditions guaranteeing certain sensitivity and relative stability properties are stated and proven. The inaccuracies in the models are measured by means of an ' ignorance function '. Sufficient conditions expressed in terms of this function, from which conservative estimates on allowed mismatches in the models may be found, are stated. Illustrative examples demonstrating the main results are presented.

The deformation and fracture of Ti3Al at elevated temperatures

Abstract: The tensile properties of the intermetallic compound Ti3Al have been determined in air at several temperatures within the range of 25 to 900 °C. The dislocation structures produced by the various testing conditions were studied in the electron microscope and the fracture modes were studied in the scanning electron microscope. These microstructural observations were correlated with the mechanical properties. The results indicate that Ti3Al has only limited ductility even at 900 °C. The apparent ductile-brittle transition which occurs above 600 °C is due to increasing amounts of intergranular cracking. Some increase in ductility above 600 °C is due to the onset of dislocation cross slipping. The fracture mode up to 600 °C is entirely cleavage. Above 600 °C the fracture shows increasing evidence of plasticity; however, cleavage remains the main fracture mode up to 900 °C.

Deadlock Avoidance in Store-and-Forward Networks--I: Store-and-Forward Deadlock

Abstract: Store-and-forward deadlock in store-and-forward networks may be avoided by forwarding messages from buffer to buffer in accordance with a loop-free directed buffer graph which accommodates all the desired message routes. Schemes for designing such buffer graphs are presented, together with methods for using them to forward the messages in an efficient and deadlock-free manner. These methods can be implemented by a set of counters at each node. Such an implementation increases the efficiency of buffer use, and simplifies jumping between normal lowoverhead operation when deadlock is far and more careful operation when deadlock is near. The proposed deadlock avoidance mechanism works for any network topology and any finite routing algorithm.

Second-order and related extremality conditions in nonlinear programming

Abstract: This paper is concerned with the problem of characterizing a local minimum of a mathematical programming problem with equality and inequality constraints. The main object is to derive second-order conditions, involving the Hessians of the functions, or related results where some other curvature information is used. The necessary conditions are of the Fritz John type and do not require a constraint qualification. Both the necessary conditions and the sufficient conditions are given in equivalent pairs of primal and dual formulations.

Disk scheduling: FCFS vs.SSTF revisited

Abstract: We report on a rather extensive simulation effort directed at evaluating the merits of two scheduling strategies, FCFS and SSTF, for moving-arm disks under stationary request arrival process. For First-Come-First-Served (FCFS) scheduling, analytic results for the mean waiting time are also given (in a closed form). If the objective of a schedule is to minimize the mean waiting time (or queue size) and its variance, the results seem to confirm the overall superiority of Shortest-Seek-Time-First (SSTF), particularly for medium and heavy traffic. This holds also when the input is highly correlated or addresses the cylinders nonuniformly. These results contradict some statements published in recent years. The domain of policies where SSTF is optimal is considered. The simulation methodology is described in some detail.

Construction Planning for Linear Projects

Abstract: A method is proposed for planning the construction process for a linear project consisting of a series of production lines, each of which comprises a series of sequential activities (e.g., pipelines, roads, bridges, etc.). The method is based on an input including labor requirement for each activity and the feasible crew sizes for each production line. Dynamic programming is used for determination of the quantity of resources (therefore also activity durations) per line and the start time of each activity, with a view to work continuity within the line and to minimum overall project duration.

Internal Layout Design of a Warehouse

Abstract: Two configurations of shelves, in a homogeneous or a zoned warehouse, are compared. Handling costs as well as costs associated with the warehouse area and perimeter are taken into consideration. From these, expressions for optimal design parameters are developed. It is shown that, depending on ratios between the relevant costs, some general preference rules for the two layouts examined can be laid down.

Fourier optics described by operator algebra

Abstract: Fresnel diffraction is described by replacing the Fresnel-Kirchhoff integral, the lens transfer factor, and other operations by operators. The resulting operator algebra leads to the description of Fourier optics in a simple and compact way, bypassing the cumbersome integral calculus. Aberration effects and Gaussian beam illumination are also treated as a simple extension of the present theory.

Controlled Destruction and Temperature Distributions in Biological Tissues Subjected to Monoactive Electrocoagulation

Abstract: An analysis of the temperature fields developed in a biological tissue undergoing a monoactive electrical coagulating process is presented, including thermal recovery following prolonged heating. The analysis is performed for the passage of alternating current and assumes a homogeneous and isotropic tissue model which is uniformly perfused by blood at arterial temperature. Solution for the one-dimensional spherical geometry is obtained by a Laplace transform and numerical integrations. Results obtained indicate the major role which blood perfusion plays in determining the effects of the coagulating process; tissue temperatures and depth of destruction are drastically reduced as blood perfusion increases. Metabolic heat generation rate is found to have negligible effects on tissue temperatures whereas electrode thermal inertia affects temperature levels appreciably. However, electrodes employed in practice would have a low thermal inertia which might be regarded as zero for all practical purposes. It is also found that the depth of tissue destruction is almost directly proportional to the electrical power and duration of application. To avoid excessively high temperatures and charring, it would be advantageous to reduce power and increase the time of application. Results of this study should be regarded as a first approximation to the rather complex phenomena associated with electrocoagulation. They may, nevertheless, serve as preliminary guidelines to practicing surgeons applying this technique.

Promoting Increased Use of Ear Protectors in Noise Through Information Feedback

Abstract: Workers in a noisy department of a metal fabrication plant took hearing tests before and at the end of their workshifts to ascertain the extent of temporary hearing losses that occurred with and without earplugs being worn. This information was fed back to individual workers as a means for motivating greater use of ear protectors issued for hearing conservation purposes. Subsequent observations of earplug users in this department for 5 months showed a steady increase, attaining a level of 85 -90%. No more than 10% of the workers in another noisy department in the same plant, serving as a control group, wore earplugs over the same 5-month period after being given a standard lecture on hearing conservation in noise, later augmented by disciplinary threats. The effectiveness of the feedback technique in promoting earplug usage was explained as a two-stage process involving individual reinforcement, and subsequent group adoption of new norms for accepted behavior.

A stochastic model of bin-packing

Abstract: Recent research in combinatorial bin-packing models is extended to a stochastic model in which an arbitrary distribution of piece sizes is assumed. The asymptotic expected bin occupancy is obtained for a simple on-line algorithm. Convergence properties are also presented so that, for a given set of pieces, this measure can be related to the expected number of bins required relative to an optimization rule.

At high speeds dolphins save energy by leaping

Abstract: An observer may wonder whether a school of ‘running’ dolphins, consisting of numerous, wildly splashing individuals, is using the most efficient mode of locomotion, because splashing wastes energy. Dolphins exhibit at least three modes of swimming. In leisurely, unhurried motion, they break the surface briefly and gently, often showing little more than the blowhole. At a faster, ‘cruising’ speed, frequently at 3–3.5 ms−1 (6–7 knots), the animals are seen swimming primarily just beneath the surface, and there is still little splashing. (Behaviour and speeds of dolphin schools were observed from a helicopter and will be described elsewhere by D. A. and W. Ferryman.) Swimming speeds in this mode have been measured up to 4.6 ms−1 (9.3 knots). But in the fastest ‘running’ mode, the animals clear the water in sequential, parabolic leaps, accompanied by considerable splashing on exit and re-entry (Fig. 1). Leaps are interspersed with relatively brief, subsurface swimming. This swimming is common when dolphins are alarmed by vessels approaching within 500 m. We have examined dolphin swimming in terms of energy required per unit distance travelled and report here that beyond a certain ‘crossover’ speed, leaping must be more efficient than swimming.

Single trial analysis of evoked potentials to noxious thermal stimulation in man

Abstract: Thermal (laser) evoked responses were obtained from 13 male volunteers. A single trial analysis technique with a latency adjusting adaptive filter was used to analyze evoked response amplitudes. Significant and substantial within-subject linear correlations were found between the magnitude (A) of the primary waveform (RMS muV of the P200--N300-P400 complex ) and subjective pain response (R) as well as stimulus intensity (S). Since subjective pain response was strongly correlated with stimulus intensity, the partial correlation coefficients were calculated for R vs. A with S controlled, and S vs. A with R controlled, for each subject. The partial correlations revealed a much stronger relationship between subjective response and the evoked response amplitude, suggesting that the primary complex may measure neural events in the pain perception process rather than transduction and transmission of the stimulus event.

A new, sensitive and simple bioluminescence test for mutagenic compounds

Abstract: A spontaneous dark variant of the luminous bacterium Photobacterium leiognathi was isolated. The reversion frequency of this variant to genetic-hereditary luminescent cells is greatly increased by nanogram quantities of different base-substitution and frameshift agents. This makes it possible to detect mutagenic compounds at concentrations 100 times lower than that detected by the Ames Test. Curing agents, such as acridine dyes, ethidium bromide and sodium dodecyl sulfate, are also very active in the reversion of this dark variant to the luminous state, but fail to revert it to a genetic-hereditary luminescent type. The nature of the primary mutation in the dark variant, and the potential use of this luminescence system for detecting different classes of carcinogenic chemical, are discussed.

Three-dimensional optimal pursuit and evasion with bounded controls

Abstract: The missile-aircraft pursuit-evasion problem is formulated by a three-dimensional linearized kinematic model with bounded control. The formulation is valid both for the optimal control (against a known adversary strategy) and the zero sum differential game versions. Assuming perfect information, the linearized kinematic model yields for both versions a solution which can be impletemented in real time for airborne application. The avoidance of a known pursuer by an evader who has no state information is solved by a stochastically optimal periodical maneuver. Other examples of imperfect information are briefly discussed.

Characterization of Pareto and Lexicographic Optimal Solutions

Abstract: Two important solution concepts in the theory of multicriteria decision making are Pareto optimum and Lexicographic optimum.

Operators which are annihilated by analytic functions and invariant subspaces

Abstract: In what follows the term operator will mean a bounded linear operator T which acts on some infinite dimensional complex Banach space B. The spectrum of T will be denoted by g(T). An invariant subspace for T will always mean here a closed subspace M c B such that T M c M. We say that M is hyperinvariant for T if it is invariant for every operator tha t commutes with T. A subspace M is called nontrivial if M ~ { 0 ) and M ~ B . J. Wermer [27] proved that if T is an invertible operator which satisfies

Ferromagnetic Superconductors: A Vortex Phase in Ternary Rare-Earth Compounds

Abstract: It is shown that the generalized Ginzburg-Landau free-energy functional of Blount and Varma admits self-consistent solutions with quantized-flux vortices, magnetized in a region about the cores. There is a temperature range where the new phase has a lower free energy than either the pure superconducting or pure ferromagnetic phases; it represents true coexistence of ferromagnetism and superconductivity. The main features of the specific heat and magnetic properties of some rare-earth ternary compounds can be explained qualitatively.