Showing papers by "Worcester Polytechnic Institute published in 1976"

Transient diffusion in solids with a bipore distribution

Abstract: Transient diffusion of n-butane, iso-butane, and 1-butene in synthetic CaX(Na) spherical pellets is studied in a constant volume, well-stirred system. The intracrystalline diffusion coefficients are in the order of 10−14 cm2/s, and the activation energy is about 7.0 Kcal/g-mole. Experimental data agree well with a mathematical model developed to describe transient diffusion.

Geotechnical properties of deep sea sediments: Bermuda rise

Abstract: The Giant Piston Corer has been used to obtain good quality sediment samples from several sedimentological/acoustic regimes in the northwestern Atlantic. A total of 185 m of sediment were recovered in nine cores with lengths ranging from 6.5 to 30.5 m. Sediment types include calcareous ooze, pelagic brown clay, organic‐rich gray‐green silty clay, and graded sand. Data are presented from three of these cores, taken from three different acoustic provinces. Seismic profiles and 3.5 kHz records from our study area on the eastern Bermuda Rise (4–5 km water depth) reveal marked differences in acoustic characteristics that are consistent with physical property variations at three of the core sites. This area contains three major features: (l)a broad, gently rolling plateau covered with about 300 m of sediment containing numerous conformable reflectors; (2) a slope region with maximum slope angle of 0.275 rad (16°), which is underlaid by acoustically transparent sediments; and (3) a region at the toe of ...

A Model for Generative CAI and Concept Selection.

Abstract: This paper describes a model for generative computer-assisted instruction. This model has served as the basis for the design of a CAI system used to teach problem-solving in an introductory course in digital systems design. The system individualizes the instruction which each student receives in accordance with its record of his past performance. In addition, a heuristic technique is used to determine the best path for each student through the tree of course concepts. The refinement of this method of concept selection is described. An evaluation of the GCAI system and results of classroom usage are also presented.

Laboratory instruments in the history of psychology.

Abstract: The importance of laboratory instruments as sources for the writing of the history of psychology is stressed, and illustrated through the use of examples where their study has been profitable. Most importantly, the role of the Hipp chronoscope in the reaction-time experiment is discussed, and the importance of various changes introduced into its design by James McKeen Cattell is shown. A photograph, first exhibited by the Department of Psychology of Clark University at the 1893 World's Columbian Exposition in Chicago is included, and further illustrates the importance of these instruments to historians.

Metal Flow in Two-Die Swaging

Abstract: A study of materials subjected to reductions in area by two-die swaging shows that non-uniform hardening occurs. The amount of cold work strengthening on the surface is the same as that for a similar reduction in area by cold rolling. The center hardness, however, is significantly greater. Cracks at the center of specimens are frequently observed. These effects are attributed to redundant working since successive blows strike new areas around the periphery but every blow affects the center.

A Technique for the Preparation of Specimens of Loose Layered Silts

Abstract: A brief review of previously published results of shear strength testing of silty soils is presented. It is noted that, due to their highly porous structure and the resultant unfavorable effects derived from sampling, natural silts are among the least studied deposits in the world. When found in glaciated regions, these deposits are often laminated, usually contain small amounts of clay, and, when laminated, are invariably anisotropic. A typical naturally occurring silt, prevalent in the area of Providence, Rhode Island, is described in terms of its geologic origin and its in situ index properties. An experimental procedure which entails laboratory sedimentation, consolidation under small load increments, and laboratory freezing to obtain a soil specimen which may be handled without densification, is described. It is shown that these laboratory produced specimens duplicated the in situ varved structure and index properties of the natural silt. Although the paper reports in detail on the production of cylindrical triaxial specimens, the method may be readily adapted to produce specimens of virtually any size or shape. In conclusion, it is pointed up that, in utilizing this technique, specimens may be prepared with virtually any angular relationship between the inclination of the layers and the directions of the applied principal stresses, facilitating the investigation of anisotropic strength effects.

Conceptual rmc/time synthesis

Abstract: A model is developed for synthesizing the logistics of construction projects in the early stages of design. It is based on the Bar Chart that is subsequently expanded into the RMC Chart, the RMC Demand Chart, and the Cumulative RMC Demand Chart. Resources and monetary corrollatives can now be estimated quantitatively and chronologically from the budget estimate and typical ratios of maximum to average demand. The inevitable apparent lag of construction value in place compared to elapsed time is explained. Many other resource/monetary/time relationships are equated to yield a valuable model for preliminary planning. A worked-out example of labor demand and cash flow for the entire life of a project is included. The significance of these solutions is that they evolve from a minimal amount of information. A General Progress Control Chart is developed for monitoring construction progress.

Flat Coils

Abstract: Air core coils can be made in a flat configuration with thickness of about two diameters of the conducting atrand plus insulation. They can be wound of wire (WPI's: wound planar inductors) or made on printed circuit boards (PPI's: printed planar inductors). The area of these flat coils for a given inductance is equal to the projected area of the comparable helix plus the area of one turn of that helix. Advantages over conventional belical coils include greatly reduced bulk, increased mechanical aid electrical stability because of flat supporting mounting, high coefficients of coupling, the possibility of making them by etched circuit methods. Distributed capacitances are bigher and Q's slightly lower than for comparable helixes.

Dynamics and stability of a delay-locked loop

Abstract: We discuss the transient behavior of a delay-locked loop which is designed to generate a delay-error signal that is proportional to the difference in the autocorrelation function of the input signal at two points separated by a fixed time 2\tau_{1} . When the input signal is a sine wave, we present an exact solution which shows that the system is stable and achieves a delay lock with an ambiguity of an integral number of periods. The second input considered is that of a stationary, ergodic, and band-limited Gaussian signal. In this case we present an approximate analysis which predicts that for times long compared to the inverse bandwidth of the random signal that the delay error is log-normally distributed. For this case we develop the almost sure sample stability criterion [1]. When this criterion is met, the system sample solutions are stable with probability one independant of the system amplification. We also develop stability criteria which limit the system amplification for stability of the first and second moments of the time delay.