Polarization observables in π-d scattering

Exact calculations of vector and tensor polarizations are presented for the reaction $\text{π +}\text{d}\text{→ π +}\text{d}$ at T_π = 142 MeV. They are aimed at meeting the apparent demand raised by upcoming pertinent experiments. The effects of (i) deuteron D state, (ii) participating π-N partial waves and (iii) coupling of different π-d orbital angular momenta are found to be very important.     

A model for rational abandonments from invisible queues

We propose a model for abandonments from a queue, due to excessive wait, assuming that waiting customers act rationally but without being able to observe the queue length. Customers are allowed to be heterogeneous in their preferences and consequent behavior. Our goal is to characterize customers' patience via more basic primitives, specifically waiting costs and service benefits: these two are optimally balanced by waiting customers, based on their individual cost parameters and anticipated waiting time. The waiting time distribution and patience profile then emerge as an equilibrium point of the system. The problem formulation is motivated by teleservices, prevalently telephone- and Internet-based. In such services, customers and servers are remote and queues are typically associated with the servers, hence queues are invisible to waiting customers. Our base model is the M/M/m queue, where it is shown that a unique equilibrium exists, in which rational abandonments can occur only upon arrival (zero or infinite patience for each customer). As such a behavior fails to capture the essence of abandonments, the base model is modified to account for unusual congestion or failure conditions. This indeed facilitates abandonments in finite time, leading to a nontrivial, customer dependent patience profile. Our analysis shows, quite surprisingly, that the equilibrium is unique in this case as well, and amenable to explicit calculation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ionization cross sections and rate coefficients for the ground state of AsI-like ions

Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct ionization and excitation-autoionization of AsI-like ions in the 3d ¹⁰4s ²4p ³ (⁴S_3/2) ground state have been performed. The cross sections are presented in the energy range near the threshold for the five ions Mo⁹⁺, Xe²¹⁺, Pr²⁶⁺, Dy³³⁺ and W⁴¹⁺. The rate coefficients are given for all the ions from Sr⁵⁺ to U⁵⁹⁺ in the AsI sequence at the seven electron temperatures (k T _e = 0.1E _I ,0.3E _I ,0.5E _I ,0.7E _I ,E _I ,2E _I and 10E _I , where E _I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the Distorted Wave (DW) approximation for the 4s ? nl, 3d ? nl and 3p ? nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the AsI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 6.5 is predicted for instance for Dy³³⁺ (Z = 66) at electron temperature of coronal equilibrium maximum abundance.     

Mass spectrometry as a diagnostic tool for 5-hydroxysteroids

The mass spectra of twelve 5-hydroxysteroids (1–12), indicate that a common feature is the formation of the ion a by loss of the four ring A C atoms 1, 2, 3, and 4, with the H atoms and other substituents attached.     

An algorithm to assign pedestrian groups dispersing at public gatherings based on pedestrian-traffic modelling

The minimization of weighted pedestrian and vehicle times for pedestrians dispersing at public gatherings is considered. An algorithm to solve this problem and to assign each pedestrian group to a unique selected path is developed. This algorithm considers general network where its arc values are dependent on pedestrian/traffic modelling and its nodes (intersections) have penalties.The algorithm is followed by a case study which exhibits possible pedestrian/traffic models. These experimental models yield some deterministic functional dependency between pedestrians' speed and sidewalk concentration, pedestrians' street concentration, and sidewalk concentration, and vehicles' speed and pedestrians' street concentration. If such and realistic models serve as an input to the algorithm it might contribute to reduce pedestrian/traffic conflicts and interference and hence to increase the overall safety of these two travel modes.     

Using time-reversal symmetry for sensitive incoherent matter-wave Sagnac interferometry

We present a theory of the transmission of guided matter-waves through Sagnac interferometers. Interferometer configurations with only one input and one output port have a property similar to the phase rigidity observed in the transmission through Aharonov-Bohm interferometers in coherent mesoscopic electronics. This property enables their operation with incoherent matter-wave sources. High rotation sensitivity is predicted for high finesse configurations.     

Data-stories about (im)patient customers in tele-queues

Credible queueing models of human services acknowledge human characteristics. A prevalent one is the ability of humans to abandon their wait, for example while waiting to be answered by a telephone agent, waiting for a physician’s checkup at an emergency department, or waiting for the completion of an internet transaction. Abandonments can be very costly, to either the service provider (a forgone profit) or the customer (deteriorating health after leaving without being seen by a doctor), and often to both. Practically, models that ignore abandonment can lead to either over- or under-staffing; and in well-balanced systems (e.g., well-managed telephone call centers), the “fittest (needy) who survive” and reach service are rewarded with surprisingly short delays. Theoretically, the phenomenon of abandonment is interesting and challenging, in the context of Queueing Theory and Science as well as beyond (e.g., Psychology). Last, but not least, queueing models with abandonment are more robust and numerically stable, when compared against their abandonment-ignorant analogues. For our relatively narrow purpose here, abandonment of customers, while queueing for service, is the operational manifestation of customer patience, perhaps impatience, or (im)patience for short. This (im)patience is the focus of the present paper. It is characterized via the distribution of the time that a customer is willing to wait, and its dynamics are characterized by the hazard-rate of that distribution. We start with a framework for comprehending impatience, distinguishing the times that a customer expects to wait, is required to wait (offered wait), is willing to wait (patience time), actually waits and felt waiting. We describe statistical methods that are used to infer the (im)patience time and offered wait distributions. Then some useful queueing models, as well as their asymptotic approximations, are discussed. In the main part of the paper, we discuss several “data-based pictures” of impatience. Each “picture” is associated with an important phenomenon. Some theoretical and practical problems that arise from these phenomena, and existing models and methodologies that address these problems, are outlined. The problems discussed cover statistical estimation of impatience, behavior of overloaded systems, dependence between patience and service time, and validation of queueing models. We also illustrate how impatience changes across customers (e.g., VIP vs. regular customers), during waiting (e.g., in response to announcements) and through phases of service (e.g., after experiencing the answering machine over the phone). Our empirical analysis draws data from repositories at the Technion SEELab, and it utilizes SEEStat—its online Exploratory Data Analysis environment. SEEStat and most of our data are internet-accessible, which enables reproducibility of our research.     

Analysis of maximum traffic flow and its breakdown on congested freeways

This study analyzes the dynamic behavior of traffic flow over time by deriving the theoretical value of flow oscillations convergence () following the breakdown of traffic flow. Modeling traffic flow fluctuations over time reflects two basic zones: the increasing demand zone that terminates approximately when the maximum flow is attained, and the oscillations zone that reflects the fluctuations of flow until its stabilization. The models in the flow-time plane introduce a new concept of “stable maximum flow” particularly for design purposes. Both converged values and observed recovery flow values represent the end of the recovery phase transition where the traffic stream approaches the free flow regime through lower flow conditions than the maximum flow conditions. A comparison between breakdown starting times and times of the maximum flow shows that in most cases, when one breakdown period (OB) is experienced, breakdown starts 21–50 min after observing the maximum flow. Modeling changes in traffic flows in the flow-time plane is emphasized for OB or multiple breakdown period (MBP) cases. The analysis of frequent OB and infrequent MBP cases allow for better controlling of the traffic flow by maintaining its flow level below maximum.     

A two-regime traffic flow model and the consistency of its parameters

An attempt is made to demonstrate the traffic behaviour and phenomena under normal morning peak period conditions, and to examine the suitability of a two-regime traffic flow model for these conditions. This paper has three main parts. First, the consistency of flow and concentration patterns of a 9-mile freeway section is examined and provides a basis for distinguishing between the free-flow and the congested-flow regimes. This distinction clearly indicates the data points obtained from traffic flow situations, which, in time-sequence, approach maximum flow conditions, congested conditions, and through a recovery process backwards to free-flow conditions.

In the second part, a car-following model for the two-regime approach is introduced. By using the analysis of driver performance as a sensitivity measurement, model parameters are defined and evaluated. An overall comparison between the proposed and known generalized car-following models emphasizes the advantages of the proposed model, particularly its simplicity and clarity at both the micro- and macroscopic levels, for the two-regime phenomenon.

In the third part, the steady-state formulation, derived from the proposed car-following model, is evaluated by using the time-sequence data points. The consistency of the two-regime model parameters is apparently well preserved regarding data sets of 3-year period (1972–1975) with respect to three independent variables: years, workdays and locations.