Traveling Salesman Problem with Clustering

In the original traveling salesman problem, the traveling salesman has the task to find the shortest closed tour through a proposed set of nodes, touching each node exactly once and returning to the initial node at the end. For the sake of the tour length to be minimized, nodes close to each other might not be visited one after the other but separated in the tour. However, for some practical applications, it is useful to group nodes to clusters, such that all nodes of a cluster are visited contiguously. Here we present an approach which leads to an automatic clustering with a clustering parameter governing the sizes of the clusters.     

The Use of Radioisotopes and Radiation in USSR,Great Britain,France, and Czechoslovakia

A short survey on the radioisotope applications in the four European countries is given. This survey is based on the detailed report prepared by the group of 15 experts during their 70 day study tour organized by the International Atomic Energy Agency in Vienna, at the end of 1966. The purpose of the tour was the acquaintance with the application of radioisotopes and radiation in industry and research.Organization of industrial radioisotope work and basic forms of radioisotope applications are described.     

N-city traveling salesman problem: Optimization by simulated annealings

The problem of finding the shortest closed path connectingN randomly chosen points is one of the classicNp-complete problems. We show that the length of tour depends logarithmically on the cooling rateQ in a simulated Monte Carlo anneal. We speculate that this is a general property of allNp-complete problems.     

Effect of signals on two-route traffic system with real-time information

We study the effect of signals on the vehicular traffic in the two-route system at the tour-time feedback strategy where the vehicles move ahead through a series of signals. The Nagel–Schreckenberg model is applied to the vehicular motion. The traffic signals are controlled by both cycle time and split. The tour times on two routes fluctuate periodically and alternately. The period increases with decreasing the split. Also, the tour time on each route varies with time by synchronizing with the density. The dependences of tour times and densities on both split and cycle time are clarified.     

Tour time in a two-route traffic system controlled by signals

We study the dynamic behavior of vehicular traffic in a two-route system with a series of signals (traffic lights) at low density where the number of signals on route A is different from that on route B. We investigate the dependence of the tour time on the route for some strategies of signal control. The nonlinear dynamic model of a two-route traffic system controlled by signals is presented by nonlinear maps. The vehicular traffic exhibits a very complex behavior, depending on the cycle time, the phase difference, and the irregularity. The dependence of the tour time on the route choice is clarified for the signal strategies.     

Daedalus in Dublin: A Physicist’s Labyrinth

I describe some of the rich physical and natural-philosophy heritage of the urban center of the Irish capital Dublin (first tour) and its environs (second tour), in a two-part excursion that could take between two and eight hours in toto. In terms of history, both tours center around the nineteenth century. The first tour is located in and around Trinity College, and we encounter such personages as William Rowan Hamilton, George Fitzgerald, Ernest Walton, and Erwin Schrödinger, among others. Moving away from Trinity College, the second tour explores some of the periphery of the city. I describe the role of politics, money, and religion in shaping the emergence and development of scientific talent among the Irish people, and consequently the footprint left by physics in the city today, with its numerous sites and names that put Irish physics in an honorable place among the nations.     

尼耳斯·玻尔1937年的中国之行

文章介绍了尼耳斯·玻尔1937年的中国之行以及他此次访问所开创的中丹科学家之间的友好交流.     

Physicists and Physics in Munich

We give a tour of Munich and some outlying sites that focuses on the lives and work of the most prominent physicists who lived in the city, Count Rumford, Joseph Fraunhofer, Georg Simon Ohm, Max Planck, Ludwig Boltzmann, Albert Einstein, Wilhelm Conrad Röntgen, Wilhelm Wien, Arnold Sommerfeld, Max von Laue, and Werner Heisenberg. We close with a self-guided tour that describes how to reach these sites in Munich.     

The Stochastic Traveling Salesman Problem: Finite Size Scaling and the Cavity Prediction

We study the random link traveling salesman problem, where lengths l _ij between city i and city j are taken to be independent, identically distributed random variables. We discuss a theoretical approach, the cavity method, that has been proposed for finding the optimum tour length over this random ensemble, given the assumption of replica symmetry. Using finite size scaling and a renormalized model, we test the cavity predictions against the results of simulations, and find excellent agreement over a range of distributions. We thus provide numerical evidence that the replica symmetric solution to this problem is the correct one. Finally, we note a surprising result concerning the distribution of k th-nearest neighbor links in optimal tours, and invite a theoretical understanding of this phenomenon.     

Budapest: A Random Walk in Science and Culture

I give a tour of sites of historical significance in physics and related sciences in Budapest, noting their connections to Hungarian scientists, and placing them within the context of the cultural and institutional histories of Hungary and Budapest. I begin the tour in the inner districts of Budapest and then go to the outer districts.     

Physics in Novosibirsk and Akademgorodok

Novosibirsk, founded in 1893, and Akademgorodok, founded in the 1950s, are places where Soviet and Russian physicists realize long-term large-scale socially-oriented projects. This article provides a walking tour of Akademgorodok, and discusses the unique interaction between Novosibirsk University and dozens of research institutes located in and around Akademgorodok. The tour includes a visit to one of the finest technology parks in Russia.     

Green-wave control of an unbalanced two-route traffic system with signals

We introduce the preference parameter into the two-route dynamic model proposed by Wahle et al. The parameter represents the driver’s preference for the route choice. When the driver prefers a route, the traffic flow on route A does not balance with that on route B. We study the signal control for the unbalanced two-route traffic flow at the tour-time feedback strategy where the vehicles move ahead through a series of signals. The traffic signals are controlled by both cycle time and phase shift (offset time). We find that the mean tour time can be balanced by selecting the offset time successfully. We derive the relationship between the mean tour time and offset time (phase shift). Also, the dependences of the mean density and mean current on the offset time are derived.     

Physics in Berlin: A Walk Through the Historical City Center

A guided tour of significant sites pertaining to the history of physics is conducted around the area of the University of Berlin, now Humboldt University, on Unter den Linden.     

SUSY dark matter — a collider physicist’s perspective

A short tour on the supersymmetric dark matter and its connection to the collider physics.     

Peripatetic Highlights in Bern

This tour of significant scientific sites in Bern uses the local legacy of its most illustrious scientists, Albert Einstein (1879–1955) and Fritz Houtermans (1903–1966), as its guiding thread through the old town and the university district.Ann M.Hentschel is translator of the correspondence volumes of The Collected Papers of Albert Einstein and is currently employed by the Institute for the History and Philosophy of Science at the University of Bern to write the guide for a city tour of Einsteins old haunts in Bern for the coming jubilee of special relativity in 2005. For the historical companion guidebook, see Hentschel and Grasshoff, Albert Einstein (ref. 4) and the website <.     

Shipping noise in whale habitat: characteristics, sources, budget, and impact on belugas in Saguenay-St. Lawrence Marine Park hub

A continuous car ferry line crossing the Saguenay Fjord mouth and traffic from the local whale-watching fleet introduce high levels of shipping noise in the heart of the Saguenay-St. Lawrence Marine Park. To characterize this noise and examine its potential impact on belugas, a 4-hydrophone array was deployed in the area and continuously recorded for five weeks in May-June 2009. The source levels of the different vessel types showed little dependence on vessel size or speed increase. Their spectral range covered 33 dB. Lowest noise levels occurred at night, when ferry crossing pace was reduced, and daytime noise peaked during whale-watching tour departures and arrivals. Natural ambient noise prevailed 9.4% of the time. Ferry traffic added 30-35 dB to ambient levels above 1 kHz during crossings, which contributed 8 to 14 dB to hourly averages. The whale-watching fleet added up to 5.6 dB during peak hours. Assuming no behavioral or auditory compensation, half of the time, beluga potential communication range was reduced to less than ~30% of its expected value under natural noise conditions, and to less than ~15% for one quarter of the time, with little dependence on call frequency. The echolocation band for this population of belugas was also affected by the shipping noise.     

美国高校物理实验教学和管理情况考察报告

根据对美国6所大学物理实验室的实地考察情况,介绍了美国大学物理实验教学情况、实验课程设置和实验室管理等方面的一些做法和特点,讲述了考察后的收获和体会。     

Some Historical Points of Interest in Göttingen

A guided tour of sites of scientific interest in Göttingen is offered.     

Physical Science in Bologna

We provide a guide to Bologna, Italy, focusing particularly on sites of interest to physicists. Our first tour is in the city center; it begins in the Piazza Maggiore at the Palazzo d’Accursio, the Basilica di San Petronio, and the Archiginnasio (Old University) and then proceeds to the Two Towers and the Palazzo Poggi, which houses the Astronomical Observatory Museum and other important instrument and art collections; it concludes at the Physics Museum, Department of Physics and Astronomy. Our second tour again begins in the Piazza Maggiore but goes to sites beyond the city center where famous Bolognese physicists and other scientists were born, lived, and are buried. Finally, we point out important museums and other institutions on the outskirts of Bologna.