Prediction of water quality in lakes and reservoirs. Part I — Model description

A tensile stress hypothesis for the etiology of idiopathic cervical erosions of human teeth is presented. It is proposed that when occlusion is not ideal, lateral forces cause the teeth to bend. The tensile stresses created during bending disrupt the chemical bonds of the crystalline structures of enamel and dentin. Small molecules may enter between the crystals and prevent the reestablishment of the chemical bonds. As a result, the disrupted tooth structure is more susceptible to loss through dissolution and abrasion and results in the development of the typically wedge-shaped lesions. Patients with lesions typical of hundreds examined by the authors were presented to illustrate the concept. The possible consequences of the proposed hypothesis were discussed. The hypothetical conclusions made in this article will be tested by experimentation.

Possible role of tensile stress in the etiology of cervical erosive lesions of teeth.

A physically based eddy diffusion model for simulating the seasonal variation in lake temperature and evaporation is presented and validated. Because no lake-specific fitting of the parameters of the model is necessary, the model can be used to simulate evaporation in studies of climate change and lake hydrology in a variety of settings. The eddy diffusion model is used to simulate evaporation for input to a simple lake level model that is applied to reconstruct recent fluctuations in the level of Harney-Malheur lake caused by climatic variations.

Simulation of lake evaporation with application to modeling lake level variations of Harney‐Malheur Lake, Oregon

Three-dimensional finite element analysis of glass-ceramic dental crowns.

The surface energy balance (SEB) of a freshwater body must incorporate shortwave (solar) and long-wave (terrestrial) radiation, together with evaporation and sensible heat energy fluxes. For inclusion in a prognostic water quality model it is vital to be able to calculate, rather than measure, these energy terms and to relate them to routinely observed meteorological parameters such as air temperature and cloud cover. Here various formulae are analyzed and compared by using two climatologically different data bases. For shortwave radiation the formulae recommended for use, in the dearth of local observations, are those of Prescott (1940) (for temporal scales of weeks or months) and Tucker (1982) (for shorter time scales). The shortwave albedo can be given by the parametrization of Pivovarov (1972), the incoming long-wave atmospheric radiation by a blackbody representation modified by an effective atmospheric emissivity (Raphael, 1962), and the evaporative flux by the equation of Sill (1983), with the sensible heat flux being related to the evaporative energy flux via the Bowen ratio under conditions of neutral atmospheric stability.

Calculating the surface energy balance for lake and reservoir modeling: A review

The finite element method used to study stress generated in a maxillary second premolar as a result of occlusal forces. This mathematical technique has been applied extensively in structural engineering and structural mechanics. It is well suited to the analysis of stress in teeth and dental restorations because it can closely simulate the geometries, loads, and material inhomogeneities in the system being studied.

Finite element analysis of dental structures — axisymmetric and plane stress idealizations

A mathematical model is developed to study the thermal behavior of freshwater impoundments. The model is formulated to simulate thermal stratification, turnover, hypolimnetic behavior, and epilimnetic behavior. Inputs to the model include meteorological data so that an energy budget relation is included. Output from the model includes the time-varying temperature distribution for the impoundment. A 315-day simulation is made of the thermal distributions in the TVA's Fontana Reservoir using the model. The results of the simulation show excellent comparison between predicted and measured quantities.

Temperature Variations in Deep Reservoirs

Earthquake response analysis of the olive view hospital psychiatric day clinic

A method for representing the seismic response of nonductile flat-plate buildings is developed. The nonductile buildings are represented by elements with interpolated nonlinear zones that are adapted to fit with the experimental data. The load-deflection relation obtained from near-full-scale tests of the column slab connections is nearly elastic until punching failure occurs in the slab. Thereafter, there is a branch representing descending resistance associated with the punching failure. A flat-plate building represented with these elements evinces the progression of punching failures in the building. It is found that if the columns are ductile, a building of this type can remain standing after a moderate seismic event, but the damage is so extensive that the building might not be repairable.

Seismic Response of Nonductile Flat-Plate Buildings

A mathematical model is developed for the study of time-dependent behavior of reinforced concrete structures. The model is formulated to account for creep, cracking, and drying shrinkage in the concrete. The output from the model includes forces, stresses, strains, and displacements in the structure. The model is formulated on the basis of idealizations in time and geometry. The idealization of incrementing the time is an expedient for integration of the hereditary strain-stress law for concrete. A linear law in functional form provides an accurate description of concrete strain-stress behavior within design stress ranges. The geometric idealizations are made so that the stiffness of the structure may be found. The structural members are divided into length increments, and each length increment is divided into depth increments so that bending and axial stiffness of a reinforced concrete member can be evaluated. Three examples are studied using the model: axially loaded column; reinforced concrete beams; and reinforced concrete frame.

Lawrence G. Selna

Papers

Finite element analysis of dental structures — axisymmetric and plane stress idealizations

Temperature Variations in Deep Reservoirs

Earthquake response analysis of the olive view hospital psychiatric day clinic

Seismic Response of Nonductile Flat-Plate Buildings

Creep, Cracking and Shrinkage in Concrete Frame Structures