title: Balanced diagonals in frequency squares

authors: Cavenagh, Nicholas J.

subjects: Science & Technology

abstract: We say that a diagonal in an array is λ-balanced if each entry occurs λ times. Let L be a frequency square of type F (n; λ); that is, an n ✕ n array in which each entry from {1, 2, …, m=n / λ } occurs  λ times per row and  λ times per column. We show that if m≤3 , L contains a λ -balanced diagonal, with only one exception up to equivalence when m=2. We give partial results for m≥4 and suggest a generalization of Ryser’s conjecture, that every Latin square of odd order has a transversal. Our method relies on first identifying a small substructure with the frequency square that facilitates the task of locating a balanced diagonal in the entire array.

text: Balanced diagonals in frequency squares We say that a diagonal in an array is λ-balanced if each entry occurs λ times. Let L be a frequency square of type F (n; λ); that is, an n ✕ n array in which each entry from {1, 2, …, m=n / λ } occurs  λ times per row and  λ times per column. We show that if m≤3 , L contains a λ -balanced diagonal, with only one exception up to equivalence when m=2. We give partial results for m≥4 and suggest a generalization of Ryser’s conjecture, that every Latin square of odd order has a transversal. Our method relies on first identifying a small substructure with the frequency square that facilitates the task of locating a balanced diagonal in the entire array.

year: 2018

title: Speed regulation of model railway controllers: A comparison of technologies

authors: Scott, Jonathan B.

abstract: In this manuscript the relative performance of a variety of model railway controllers is tested in real-world conditions. Model railway locomotives use permanent-magnet, brushed, dc motors. Series resistance in armature windings, brushes and the rail, and magnetic losses in the armature all contribute to non-ideal operation. This manifests most annoyingly as moment by moment variation in locomotive speed. The effect is more noticeable in smaller scales. It is more noticeable on vintage models. Speed regulation performance is compared for a number different controllers using different technologies. Some interesting conclusions are drawn.

text: Speed regulation of model railway controllers: A comparison of technologies In this manuscript the relative performance of a variety of model railway controllers is tested in real-world conditions. Model railway locomotives use permanent-magnet, brushed, dc motors. Series resistance in armature windings, brushes and the rail, and magnetic losses in the armature all contribute to non-ideal operation. This manifests most annoyingly as moment by moment variation in locomotive speed. The effect is more noticeable in smaller scales. It is more noticeable on vintage models. Speed regulation performance is compared for a number different controllers using different technologies. Some interesting conclusions are drawn.

year: 2021

title: Changing genes: Science and being Maori

authors: Hudson, Maui

subjects: ethics

abstract: This commentary follows tangential lines of reason stimulated by Hook‟s thought- provoking paper, “Warrior genes” and the disease of being Māori (2009), to question the ethical responsibilities of scientists to the public in modern society.

text: Changing genes: Science and being Maori This commentary follows tangential lines of reason stimulated by Hook‟s thought- provoking paper, “Warrior genes” and the disease of being Māori (2009), to question the ethical responsibilities of scientists to the public in modern society.

year: 2009