Showing papers by "Worcester Polytechnic Institute published in 1978"

The Hawthorne Experiments: First Statistical Interpretation

Abstract: A guide is provided to the proceedings of the Hawthorne experiments, and experimental data are now made readily available. Data from the main experiment (that in the first relay assembly test room at Western Electric) are interpreted statistically for the first time. Quantitative analysis of this quasi experiment is accomplished by time-series multiple regression using nearly five years of data. This analysis demonstrates that experimental variables account for some 90% of the variance in quantity and quality of output, both for the group andfor individual workers. Imposition of managerial discipline, economic adversity, and quality of raw materials provide most explanation, obviating the need to draw upon less clearly definable human relations mechanisms. For decades the Hawthorne studies have provided a rationale for humane approaches in the organization of work by suggesting that considerate or participative treatment of workers led to better economic performance. The present analysis suggests, to the contrary, that humanitarian procedures must provide their own justification.

Propagation of the generalized radiance through lenses

Abstract: We prove that in a large and significant class of cases the generalized radiance is, except for transmission losses, invariant along light rays traversing a lens.

Influence of erythrocyte velocity on impedance plethysmographic measurements

Abstract: Impedance plethysmography has been widely used clinically. However, uncertainty exists concerning the source of the impedance signal. The present study was designed to indicate the relative contributions made by blood volume changes and blood flow changes. Anin vitro flow system containing a pulsatile pump, a bovine carotid artery, a rigid tube, and a terminal resis tance was assembled. Impedance recordings were made on both the expansile artery and the rigid tube. The impedance signal from the rigid tube was taken as the flow-related component. The signal from the expansile artery represented the combined effects of volume changes and flow changes. The recordings were made over the full physiological range of pulse pressures and peak flow values, using both normal saline and blood (haematocrit =26±4%). No impedance change was detected in the rigid vessel using saline as the perfusate. When blood was used, the impedance signal from the rigid tube averaged about 10% of that from the expansile vessel and its morphology was different. Changes in erthrocyte velocity produced a small but definite change in the impedance signal recorded from the artery.

Bandgap narrowing in heavily doped silicon

Abstract: A model of bandgap reduction in silicon through the stored electrostatic energy of majority-minority carrier pairs is developed and compared with the experimental results of other workers in the doping range from 3×1017to 3.3×1019/cc. at room temperature. An analytic expression for the bandgap reduction is obtained: Δe g = 3q2/(16πe) . (q2N/ekT)½having a square root dependence on the doping concentration. At room temperature the bandgap narrowing follows the relationship Δe g = 22.5 (N/1018)½meV The experimental data are in excellent agreement with this expression, the experimental coefficient being within 1% of the theoretical expression.

The use of temperature to simplify formose sugar composition

Abstract: Form ose reaction, the Ca(OH)2 catalyzed condensation of HCHO to a complex mixture of sugars, does not lose its autocatalytic nature at 98°C. The induction period is 15 sec, and then, at 18% total HCHO conversion, there was a period of approximately 3 sec duration in which the reaction had produced C6 sugars at 84.3 wt.% selectivity. Glucose amounted to 90% of those sugars, and no branched sugars were detected. Conversion was complete within 3 min. The simple nature of the product was lost at lower temperatures or higher conversions.

Restricted diffusion of liquids in microporous catalysts

Abstract: Transient diffusion and adsorption data were obtained for two sizes of ..gamma.. alumina catalysts pellets (pore volumes 0.0626 and 0.58 cc/g of catalyst), in an agitated reactor and for 21 systems involving various alkylbenzenes, n-alkanes, alkenes, and partially hydrogenated polycyclic aromatics, e.g., tetralin and acenaphthene, in cyclohexane, benzene, or toluene as solvent. The data were analyzed on the basis of a previously reported diffusion model. The results showed that the effective diffusivity for the transient diffusion processes involved in liquid diffusion in catalysts is inversely proportional to the partition coefficient. For Vertical Bar3; 0.1:1 ratio of molecular radius to average pore radius (i), at least the reduced diffusivity can be empirically related to an exponential type relationship in i/sup 3/.

The reappearance of a classical epidemic of infectious hepatitis in worcester, massachusetts

Abstract: Worcester, MA, experienced an outbreak of hepatitis during 1969-1970, an expected event which had occurred previously at eight-year intervals since reporting of the disease began in 1950. Other Massachusetts communities of similar character and the nation did not experience an epidemic during that same period. An extensive epidemiologic study of the disease illustrated that the epidemic followed the classical pattern in which individuals 5-14 years old were most affected irrespective of sex. During the interepidemic years from 1968-1972 in Worcester, and in all years (1968-1972) in both New Bedford and Springfield, MA, those primarily affected were young adults 15-30 years old, with male cases predominating. Sociodemographic statistical analyses also indicated the classical pattern of the less affluent, less educated, and sometimes the more crowded populations being at greater risk of contracting the disease. This outbreak of hepatitis was comparable to another in Greenland two years later in which immunologic methods differentiated between type A and type B viral infections. The data from both studies support the conclusion that the type B virus, often associated with parenteral drug use, is the predominate infectious agent during the interepidemic (endemic) periods. The type A virus is most likely responsible for the periodic epidemics.

Synthetic carbohydrates from formaldehyde

Abstract: Chemical food synthesis research is currently in progress as part of the US-USSR Research Collaboration in Catalysis for closed loop production of glycerol as a source of carbohydrates in sustained space flight and for direct synthesis of carbohydrates. Experimental results are presented which show the feasibility of producing not only glycerol but also potentially edible sugars from formaldehyde by means of the autocatalytic formose condensation reaction. The speculative possibility of large scale food refineries producing edible carbohydrates and purifying them by chromatographic methods is considered, as well as economically growing single cell protein, using formose sugars as substrate. If protein derived from synthetically produced carbohydrate can eventually be used for animal feed, farmland can be released for human foods.

Optimum Number of Crews

Abstract: Experience curve theory is used to determine the time and manpower requirements to construct labor intensive projects. In essence, according to this theory, one man working 100 hr is more productive than 100 men working 1 hr or any other analogously paired data. This leads to the conclusion that an extended construction timetable may be economical. However, as the duration of a project increases, so does the cost of job overheads that are time-dependent. This leads to the contrary conclusion that a contracted timetable is preferred. These two contending circumstances are formulated, related mathematically, and then solved to find the optimum manpower and the optimum construction time that minimizes costs. Several graphs are included that mechanize the solution. An illustrative example ties theory to practice. This paper is a continuation of another by the same writers.

Theorem on the uniqueness of the generalized radiance.

Abstract: We study the consequences of requiring that the generalized radiance depend linearly on the cross-spectral density, be zero wherever the field amplitude is zero, and can be defined independently of coordinate translations. We show that these requirements determine the generalized radiance uniquely, and that the resulting definition is independent of coordinate rotations.

The project experience in undergraduate computer science education

Abstract: In 1970 Worcester Polytechnic Institut e embarked on a new educational progra m which recognizes the balanced importanc e of a depth of knowledge, the interpla y of separate technical disciplines, a s well as the interplay of science , technology, society,. and th e humanities. This educational program. widely known as the WPI Plan, has fou r degree requirements : 1. a major qualifying project an d 2. a competency examination. both in a major field of study. and whic h require an understanding o f fundamental concepts of science an d technology. their relationships an d application ; 3. an interactive qualifying project an d 4. a minor in the humanities, whic h provide an awareness of th e interaction of basic knowledge, th e applications of technology. socia l consequences, social needs and huma n values. The projects. especially, provide a n experience in which students must lear n on their own. bring their learning t o bear on significant problems. an d communicate their ideas, methods. an d solutions to other students. faculty , business. industry. and governmen t representatives. Each qualifyin g project is equivalent in terms of effor t and credit to approximately nin e semester hours of course work and i s usually carried out over a time perio d of seven to twenty-one weeks dependin g on the percentage of time devoted to th e project, although other schedulin g arrangements for the projects can b e easily made. The projects are usuall y undertaken in a student ' s third o r fourth year and are often preceded b y prequalifying projects and seminar s which prepare the student for th e selection, planning, and management of a project as well as to introduce th e student to a different educationa l experience based on self-learning , self-motivation, and professiona l maturity. The project experience bring s together a project team of student an d faculty advisor. and often. a team o f several students. from the same o r different disciplines. several faculty. and advisors from off-campu s organizations. The advisors monitor th e progress of the project, give genera l guidance. and evaluate the project whe n it is completed. Course work an d independent study provide the backgroun d knowledge and skills which are needed t o bring the student to a level o f expertise where the …

Electron transport and ionization in silicon at high fields

Abstract: The saturated drift velocity measured for electrons at high fields is inconsistent with Shockley's model for impact ionization in silicon. It is explained in terms of a field-dependent mean free path for high energy phonon creation in the electric field direction, electrons creating a high energy phonon as soon as they have acquired sufficient energy from the field. Assuming that the electron wavepacket travels at the saturated drift velocity without dispersion, it can be shown that the increased scattering rate at high fields must result in a large spread in the carrier energy. If a drifted Maxwellian distribution is assumed, a unique expression can be obtained for the carrier temperature T* which is in good agreement with the measured field dependence of the ionization coefficient. In this model, a cylindrical hot carrier distribution must be assumed with the hot carrier energy in a plane perpendicular to the applied field. Exact calculations of the magneto-resistance of such a distribution can be made verifying that the drift velocity is indeed saturated.

Concreting and Formwork Logistics and Optimization

Abstract: Formulas, with correction factors, are derived for finding the pressure of concrete on formwork. The design and cost of wood formwork is analyzed to find the optimum number of uses, that is also expressed as a simple formula. The trade off between rates of pour and strength of formwork is investigated and a least-cost solution is modeled. This is expanded to find the optimum height of lifts when several forms are poured alternately rather than continuously. Other expressions are derived to find the number of sets of forms, arrival intervals and sizes of concrete trucks, and related scheduling of pours. Numerous examples, tables, and diagrams as well as a cogent review of basics will help the field engineer relate theory to practice. This is a systems engineering approach that attempts to mate and quantify the interaction between many of the variables encountered in concrete and formwork construction related to large piers and lays the foundation for analagous studies.

Optimum Location of Construction Haul Roads

Abstract: The unique function of roads that are designed and constructed for temporary use to facilitate the construction of larger projects requires an emphasis not ordinarily encountered in permanent road design. The first part of the paper develops three simple models for locating haul roads that minimize distance, time, and cost of transporting materials and temporary construction. These models are derived from elementary mathematical principles. The second part of the paper brings together several geometrical and mechanical solutions of related location problems. The mechanical solutions are static and dynamic and include the use of weights and strings, and soap films. Examples illustrate each of the models described. One example compares the rigorous solution with an intuitive solution that is not uncommon among construction engineers. The difference in cost between the two for a typical construction problem is in excess of $1,000,000. The bibliography includes some light reading that is both instructive and entertaining.

Responses of joint afferent neurons to loadings of isolated joint capsule

Abstract: Publisher Summary This chapter describes the responses of joint afferent neurons to loadings of isolated joint capsule. It describes preliminary experiments that were performed in which sections of knee joint capsule, with intact sensory innervation, were excised from the cat knee, and subjected to various loadings in vitro, similar to the experiments described by Eklund & Skoglund. Given the properties of joint afferents observed in isolated capsule sections, the problem was to devise a configuration for loading the capsule so that the stress on the inner surface could be measured and controlled. The experimental design included transverse loading with both spherical and cylindrical probes. Each capsule section was tested for a neuronal response to pure axial loading. All capsule sections were highly sensitive to transverse loading. Transverse and axial loads were confounded in these experiments as the application of the transverse load increased the axial load.