On the Accuracy Problem for Pendulum Clock on a Vibrating Base

2018 ◽  
Vol 53 (5) ◽  
pp. 573-583 ◽  
Author(s):  
A. P. Markeev
Keyword(s):  
Pendulum Clock ◽  
Accuracy Problem

Harrison Decoded

2020 ◽  
Keyword(s):  
Theoretical Approach ◽  
Environmental Conditions ◽  
Collaborative Research ◽  
Electronic Equipment ◽  
The Public ◽  
Royal Observatory ◽  
The Subject ◽  
Written Descriptions ◽  
Pendulum Clock

This volume centres on a clock, known as Clock B, built in the mid-1970s that achieved considerable acclaim after an extraordinary performance in a 2015 peer-reviewed public trial at the Royal Observatory, Greenwich. The clock was built according to an understanding of John Harrison’s unique theoretical approach to making precision pendulum clocks, which defies the standard approaches to making accurate clocks. The clock represents the culmination of over forty years of collaborative research into Harrison’s writing on the subject, which is scattered across a number of manuscripts and a book, printed shortly before his death. Ostensibly, Harrison set out to describe how to make his precision pendulum clock, but it is a mixture of his peripheral interests. Horological information is almost completely lost among vitriolic sentiments relating to his experiences with the Board of Longitude. However, as one reviewer surmised: ‘we are sorry to say that the public will be disappointed’ and another concluded that ‘it can only be excused by superannuated dotage’. The chapters provides contextual history and documentation of the analysis and decoding of the cryptic written descriptions. It presents this in parallel to the modern horological story of making, finishing, and adjusting Clock B; the process of testing, using electronic equipment to monitor the its performance and reaction to changes in environmental conditions, and, indeed, the mechanics behind the various compensating features of the design.

Revisiting the accuracy problem in network analysis using a unique dataset

2021 ◽  
Vol 66 ◽  
pp. 1-9
Author(s):  
Steven R. Corman ◽  
Elena Steiner ◽  
Jeffrey D. Proulx ◽  
Arindam Dutta ◽  
Alex Yahja ◽  
...  
Keyword(s):  
Network Analysis ◽  
Accuracy Problem ◽  
Unique Dataset

Rollover Warning of Articulated Vehicles Based on a Time-To-Rollover Metric

1999 ◽  
Author(s):  
Bo-Chiuan Chen ◽  
Huei Peng
Keyword(s):  
Real Time ◽  
The Other ◽  
Roll Angle ◽  
Vehicle Speed ◽  
Time Model ◽  
Whole Process ◽  
Articulated Vehicles ◽  
Articulated Vehicle ◽  
The One ◽  
Accuracy Problem

Abstract A Time-To-Rollover (TTR) metric is proposed as the basis to assess rollover threat for an articulated vehicle. Ideally, a TTR metric will accurately “count-down” toward rollover regardless of vehicle speed and steering patterns, so that the level of rollover threat is accurately indicated. To implement TTR in real-time, there are two conflicting requirements. On the one hand, a faster-than-real-time model is needed. On the other hand, the TTR predicted by this model needs to be accurate enough under all driving scenarios. An innovative approach is proposed in this paper to solve this dilemma and the whole process is illustrated in a design example. First, a simple yet reasonably accurate yaw/roll model is identified. A Neural Network (NN) is then developed to mitigate the accuracy problem of this simplified real-time model. The NN takes the TTR generated by the simplified model, vehicle roll angle and change of roll angle to generate an enhanced NN-TTR index. The NN was trained and verified under a variety of driving patterns. It was found that an accurate TTR is achievable across all the driving scenarios we tested.

On the steady-state accuracy problem in multivariable control

1977 ◽  
Vol 10 (6) ◽  
pp. 81-87
Author(s):  
M. Nougaret ◽  
P.R. Bélanger ◽  
M. St-Val
Keyword(s):  
Steady State ◽  
Multivariable Control ◽  
Accuracy Problem

scholarly journals Stokes' law, viscometry, and the Stokes falling sphere clock

2020 ◽  
Vol 378 (2179) ◽  
pp. 20200214
Author(s):  
Julyan H. E. Cartwright
Keyword(s):  
Clock Synchronization ◽  
History Of Physics ◽  
Theme Issue ◽  
Fluid Medium ◽  
Stokes Drag ◽  
200Th Anniversary ◽  
Falling Sphere ◽  
History Of ◽  
Pendulum Clock

Clocks run through the history of physics. Galileo conceived of using the pendulum as a timing device on watching a hanging lamp swing in Pisa cathedral; Huygens invented the pendulum clock; and Einstein thought about clock synchronization in his Gedankenexperiment that led to relativity. Stokes derived his law in the course of investigations to determine the effect of a fluid medium on the swing of a pendulum. I sketch the work that has come out of this, Stokes drag, one of his most famous results. And to celebrate the 200th anniversary of George Gabriel Stokes’ birth I propose using the time of fall of a sphere through a fluid for a sculptural clock—a public kinetic artwork that will tell the time. This article is part of the theme issue ‘Stokes at 200 (part 2)’.

scholarly journals VIII. The distribution of blue-violet light in the solar corona on August 30, 1905. as derived from photographs taken at Kalaa-es-Senam, Tunisia

1908 ◽  
Vol 207 (413-426) ◽  
pp. 307-339
Keyword(s):  
Solar Corona ◽  
Focal Length ◽  
The Other ◽  
Automatic Apparatus ◽  
Violet Light ◽  
Royal Dublin Society ◽  
End To End ◽  
Pendulum Clock

The object of my expedition to Kalaa-es-Senam, Tunisia, was to obtain a series of photographs from which might be determined the distribution of light in the corona. In designing my apparatus, I was led by two considerations: (1) the photographs had to be taken automatically, as I had to work without assistance, (2) standardising of the photographs was to be avoided. All the photographs were therefore taken on the two halves of a whole plate placed end to end and developed in the same tray during the same time. The automatic apparatus gives 10 exposures, and it is governed electrically by a pendulum clock. I employed two cameras, one with a Cooke triple achromatic 3½ lens of inches aperture and 58·5 inches focal length, which belongs to the Glasgow spectrograph, the other with a Ross portrait lens of 2 inches aperture and 12 inches focal length. The pictures obtained with the larger camera are so much superior to the small size ones of the portrait lens that I have not made use of the latter in this paper. The cameras were fed by a cœlostat of 8 inches aperture, which had been kindly lent to me by the Royal Dublin Society. In front of the two object-glasses, and about an inch from them, a rotating shutter was mounted which served both cameras. The rotating shutter has four oblong apertures, 90 degrees apart (its back view is shown at D 2 , fig. 1); it is rotated by clockwork driven by a spring, and its motion is governed by the armature of an electro-magnet ( f ). When the armature is attracted, the shutter rotates through about 45 degrees until it presses against one of the four stops d and brings an opening opposite the object-glasses, and when the armature is released the shutter turns again 45 degrees, as far as one of the stops c , and shuts off the light. The contacts are made by a pendulum clock, and they are so devised that make or break can occur only when the pendulum is at or near its position of rest.

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