A Study of Walkway Safety and Evaluation of Tribological Test Equipment

A walkway tribometer measures the coefficient of friction between flooring material and a test foot. The value of the coefficient of friction is an indicator as to whether the flooring surface is slippery and has a propensity to cause slip and falls. This study determined that one style of tribometer, an XL Tribometer, mimics the heel-to-floor interaction of the human heel strike. High speed video footage revealed that the test foot strikes the surface and rotates so that full engagement occurs before sliding thus mimicking the affect of a human ankle. The test foot accelerates forward as would be expected during a human slip event. The manufacturer’s reported impact speed of 11 in/s, when set to the operating pressure of 25psi, was found to be much lower than measured speeds of three calibrated tribometers. Three XL tribometers were tested and provided a range of impact speeds from 17.4 to 22.7 in/s (n=540) when set to the operating pressure of 25 psi. The pressure setting was found to have a significant effect on the impact speed while the mast angle had an insignificant affect. A review of human walking studies revealed a range of pedestrian heel impact speeds on the order of 19.4 to 45.3 in/s during normal human ambulation activities. These tribometers fell on the low side of this speed range. A sensitivity study showed that the measured value of the coefficient of friction tends to decrease with a higher impact speed. This COF decrease was on the order of 0.02 and below the machine resolution and considered inconsequential within the walkway safety community

Alien Registration- Baker, Henry W. (Van Buren, Aroostook County)

https://digitalmaine.com/alien_docs/33302/thumbnail.jp

Shallow Binding in LISP 1.5

Key Words and Phrases: LISP 1.5, environment structures, FUNARGs, shallow and deep binding, multiprogramming, cache. CR Categories: 4.13, 4.22, 4.32 This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0522.Shallow binding is a scheme which allows the value of a variable to be accessed in a bounded amount of computation. An elegant model for shallow binding in LISP 1.5 is presented in which context-switching is an environment structure transformation called "re-rooting". Re-rooting is completely general and reversible, and is optional in the sense that a LISP 1.5 interpreter will operate correctly whether or not re-rooting is invoked on every context change. Since re-rooting leaves (ASSOC X A) invariant, for all variables X and all environments A, the programmer can have access to a re-rooting primitive, (SHALLOW), which gives him dynamic control over whether accesses are shallow or deep, and which effects only the speed of execution of a program, not its semantics. So long as re-rooting is an indivisible operation, multiple processes can be active in the same environment structure. The re-rooting scheme is compared to a cache scheme for shallow binding and the two are found to be compatible. Finally, the concept of re-rooting is shown not to depend upon LISP's choice of dynamic instead of lexical binding for free variables; hence it can be used in an Algol interpreter, for example.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

A Note on the Optimal Allocation of Spaces in MACLISP

Key Words and Phrases: garbage collection, list processing, virtual memory, storage management, storage allocation, LISP. CR Categories: 3.50, 3.60, 3.73, 3.80, 4.13, 422, 4.32, 4.33, 4.35, 4.49 This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0522.This note describes a method for allocating storage among the various spaces in the MACLISP Implementation of LISP. The optimal strategy which minimizes garbage collector effort allocates free storage among the various spaces in such a way that they all run out at the same time. In an equilibrium situation, this corresponds to allocating free storage to the spaces in proportion to their usage. Methods are investigated by which the rates of usage can be inferred, and a gc-daemon interrupt handler is developed which implements an approximately optimal strategy in MACLISP. Finally, the sensitivity of this method to rapidly varying differential rates of cell usage is discussed.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

Laws for Communicating Parallel Processes

Key Words and Phrases: parallel processes, parallel or asynchronous computations, partial orders of events, Actor theory. CR Categories: 5.21, 5.24, 5.26. This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0522.This paper presents some laws that must be satisfied by computations involving communicating parallel processes. The laws are stated in the context of the actor theory, a model for distributed parallel computation, and take the form of stating plausible restrictions on the histories of parallel computations to make them physically realizable. The laws are justified by appeal to physical intuition and are to be regarded as falsifiable assertions about the kinds of computations that occur in nature rather than as proven theorems in mathematics. The laws are used to analyze the mechanisms by which multiple processes can communicate to work effectively together to solve difficult problems. Since the causal relations among the events in a parallel computation do not specify a total order on events, the actor model generalizes the notion of computation from a sequence of states to a partial order of events. The interpretation of unordered events in this partial order is that they proceed concurrently. The utility of partial orders is demonstrated by using them to express our laws for distributed computation.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

The Kennebecker : July 16, 1829

https://digitalmaine.com/kennebecker/1003/thumbnail.jp

The Kennebecker : December 24, 1829

https://digitalmaine.com/kennebecker/1022/thumbnail.jp