Between two moments

In this short note, we draw attention to a relation between two Horn polytopes which is proved in [Chenciner-Jim\'enez P\'erez] as the result on the one side of a deep combinatorial result in [Fomin,Fulton, Li,Poon], on the other side of a simple computation involving complex structures. This suggested an inequality between Littlewood-Richardson coefficients which we prove using the symmetric characterization of these coefficients given in [Carr\'e,Leclerc].Comment: 9 pages, 3 figure

Compact Einstein-Weyl four-dimensional manifolds

We look for four dimensional Einstein-Weyl spaces equipped with a regular Bianchi metric. Using the explicit 4-parameters expression of the distance obtained in a previous work for non-conformally-Einstein Einstein-Weyl structures, we show that only four 1-parameter families of regular metrics exist on orientable manifolds : they are all of Bianchi $IX$ type and conformally K\"ahler ; moreover, in agreement with general results, they have a positive definite conformal scalar curvature. In a Gauduchon's gauge, they are compact and we obtain their topological invariants. Finally, we compare our results to the general analyses of Madsen, Pedersen, Poon and Swann : our simpler parametrisation allows us to correct some of their assertions.Comment: Latex file, 13 pages, an important reference added and a critical discussion of its claims offered, others minor modification

Ekstraksi Model Gummel Poon Dengan Metode Pencocokan Kurva

Simulator rangkaian elektronika berbasis SPICE menerapkan model Gummel Poon banyak digunakan pelajar. Perancang harus memiliki parameter model dari devais elektronika sebelum melakukan analisis dengan bantuan komputer. Jika komponen yang digunakan diperoleh dari pasar, ada kemungkinan karakteristiknya tidak sesuai dengan lembar data dan / atau model dalam pustaka SPICE. Oleh karena itu perlu dikembangkan metode ekstrasi parameter model. Metode ekstaksi model Gummel Poon menerapkan analisis regresi telah diuji dan disimulasi. Hasilnya menunjukkan bahwa faktor kualitas kurva yang dicocokkan, R2, sangat dekat dengan 1. Hasil ini cukup memuaskan dalam simulasi.Kata Kunci— Ekstraksi, Gummel Poon, karakteristik statik, kuadrat terkecil, pencocokan kurva

On the outer automorphism groups of triangular alternation limit algebras

Let $A$ denote the alternation limit algebra, studied by Hopenwasser and Power, and by Poon, which is the closed direct limit of upper triangular matrix algebras determined by refinement embeddings of multiplicity $r_k$ and standard embeddings of multiplicity $s_k$. It is shown that the quotient of the isometric automorphism group by the approximately inner automorphisms is the abelian group \ZZ ^d where $d$ is the number of primes that are divisors of infinitely many terms of each of the sequences $(r_k)$ and $(s_k)$. This group is also the group of automorphisms of the fundamental relation of $A$.Comment: 12 pages, Late

The structure of colloid-polymer mixtures

We investigate the structure of colloid-polymer mixtures by calculating the structure factors for the Asakura-Oosawa model in the PY approximation. We discuss the role of potential range, polymer concentration and polymer-polymer interactions on the colloid-colloid structure. Our results compare reasonably well with the recent experiments of Moussa\"{i}d et. al. for small wavenumber $k$, but we find that the Hansen-Verlet freezing criterion is violated when the liquid phase becomes marginal.Comment: 7 pages, 4 figures, to appear in EuroPhys. Let

A Compact 3H(p,gamma)4He 19.8-MeV Gamma-Ray Source for Energy Calibration at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) is a new 1000-tonne D2O Cerenkov solar neutrino detector. A high energy gamma-ray source is needed to calibrate SNO beyond the 8B solar neutrino endpoint of 15 MeV. This paper describes the design and construction of a source that generates 19.8-MeV gamma rays using the 3H(p,gamma)4He reaction (``pt''), and demonstrates that the source meets all the physical, operational and lifetime requirements for calibrating SNO. An ion source was built into this unit to generate and to accelerate protons up to 30 keV, and a high purity scandium tritide target with a scandium-tritium atomic ratio of 1:2.0+/-0.2 was included. This pt source is the first self-contained, compact, and portable high energy gamma-ray source (E>10 MeV).Comment: 33 pages (including 2 table, 12 figures) This is the revised manuscript, accepted for publication in NIM A. This revision relfects minor editorial changes from the previous versio

The effectiveness of integrating reading and writing to enhance students' ability to express emotions = 探討「讀寫結合」對提升學生抒情能力的成效

Adviser: Poon Wan Man Ada.Includes bibliographical references (p. 74-76).Thesis (B.Ed)--University of Hong Kong, 2010.published_or_final_versionEducationBachelorBachelor of Education in Language Educatio