Plateau characteristics of Geiger Counters with respect to different gas mixtures and pressures

The section of a Geiger Counter is characterized by the so-called plateau curve. In this curve the counting rate of a given counter is plotted as a function of voltage, when the gas which it contains and the radiation to which it is exposed are both kept the same. These curves are characterized by a rapid rise beyond the starting potential (potential at which the counter begins to respond) until a more or less flat region is reached. This flat region is called the plateau of the curve. The slope and width of the plateau curve are dependent upon the kind of gas used to fill the counter, the pressure of the gas, and the mechanical construction of the counter. The plateau slope of a perfect counter would be zero, and the counting rate would be independent of voltage fluctuations, but zero slope is not possible because of the occurrence of spurious counts which originate inside the counter. The term selfquenching counter has been applied in recent years to the types of Geiger Counters in which the discharge terminates because of a process inside the counter. These counters do not go into continuous discharge except at high voltages. In order that a counter may operate as the selfquenching type it must be filled with a certain minimum amount of a polyatomic gas as a constituent. The purpose of this study is to examine the effect of filling a counter with various polyatomic gases and helium. A search was made for a gas mixture to fill the counter which would give a high count per minute and still have desirable plateau characteristics --Introduction, page 1-2

Superconducting nanowire single-photon detectors with non-periodic dielectric multilayers

We present superconducting nanowire single-photon detectors (SSPDs) on non-periodic dielectric multilayers, which enable us to design a variety of wavelength dependences of optical absorptance by optimizing the dielectric multilayer. By adopting a robust simulation to optimize the dielectric multilayer, we designed three types of SSPDs with target wavelengths of 500 nm, 800 nm, and telecom range respectively. We fabricated SSPDs based on the optimized designs for 500 and 800 nm, and evaluated the system detection efficiency at various wavelengths. The results obtained confirm that the designed SSPDs with non-periodic dielectric multilayers worked well. This versatile device structure can be effective for multidisciplinary applications in fields such as the life sciences and remote sensing that require high efficiency over a precise spectral range and strong signal rejection at other wavelengths

When Gravity Fails: Local Search Topology

Local search algorithms for combinatorial search problems frequently encounter a sequence of states in which it is impossible to improve the value of the objective function; moves through these regions, called plateau moves, dominate the time spent in local search. We analyze and characterize plateaus for three different classes of randomly generated Boolean Satisfiability problems. We identify several interesting features of plateaus that impact the performance of local search algorithms. We show that local minima tend to be small but occasionally may be very large. We also show that local minima can be escaped without unsatisfying a large number of clauses, but that systematically searching for an escape route may be computationally expensive if the local minimum is large. We show that plateaus with exits, called benches, tend to be much larger than minima, and that some benches have very few exit states which local search can use to escape. We show that the solutions (i.e., global minima) of randomly generated problem instances form clusters, which behave similarly to local minima. We revisit several enhancements of local search algorithms and explain their performance in light of our results. Finally we discuss strategies for creating the next generation of local search algorithms.Comment: See http://www.jair.org/ for any accompanying file

Gradient design of metal hollow sphere (MHS) foams with density gradients

This is the post-print version of the final paper published in Composites Part B: Engineering. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.Metal hollow sphere (MHS) structures with a density gradient have attracted increasing attention in the effort to pursue improved energy absorption properties. In this paper, dynamic crushing of MHS structures of different gradients are discussed, with the gradients being received by stacks of hollow spheres of the same external diameter but different wall thicknesses in the crushing direction. Based on the dynamic performance of MHS structures with uniform density, a crude semi-empirical model is developed for the design of MHS structures in terms of gradient selections for energy absorption and protection against impact. Following this, dynamic responses of density graded MHS foams are comparatively analyzed using explicit finite element simulation and the proposed formula. Results show that the simple semi-empirical model can predict the response of density gradient MHS foams and is ready-to-use in the gradient design of MHS structures.The National Science Foundation of China and the State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology

Vehicular traffic flow at an intersection with the possibility of turning

We have developed a Nagel-Schreckenberg cellular automata model for describing of vehicular traffic flow at a single intersection. A set of traffic lights operating in fixed-time scheme controls the traffic flow. Open boundary condition is applied to the streets each of which conduct a uni-directional flow. Streets are single-lane and cars can turn upon reaching to the intersection with prescribed probabilities. Extensive Monte Carlo simulations are carried out to find the model flow characteristics. In particular, we investigate the flows dependence on the signalisation parameters, turning probabilities and input rates. It is shown that for each set of parameters, there exist a plateau region inside which the total outflow from the intersection remains almost constant. We also compute total waiting time of vehicles per cycle behind red lights for various control parameters.Comment: 8 pages, 17 eps figures, Late

An Analytical Relation Derivation for Threshold Voltage as a Function of Operation Time for Self-Quenching GM Counters

At normal temperatures, it is known that The threshold voltage of GM counter tubes, which are filled mixture of inert gas and quenched organic gas, was shifted toward higher voltages during operation time because of  disintegration of quenched organic molecules. While threshold voltage of GM counter tubes, which are filled mixture of inert gas and quenched halogen, was shifted towards lower voltages during operation time because of  reaction of quenched halogen molecules with anode and cathode.  In this article, assuming that the counter tube operates at constant temperature and constant activity exposure, we have derived an analytical relation of Geiger threshold voltage as function of operation time. This relation indicates that the Geiger threshold voltages of the tubes which contain organic gas are exponentially increased during operation time. the Geiger threshold voltages of the tubes which contain halogen are exponentially decreased during operation time. Keywords:  analytical relation ,threshold voltage, operation time, GM counter

07021 Abstracts Collection -- Symmetric Cryptography

From .. to .., the Dagstuhl Seminar 07021 ``Symmetric Cryptography\u27\u27 automatically was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available