Optimal design of trusses by approximate compatibility

Optimal design of elastic trusses is formulated as an approximate linear programming problem. Using the force method of analysis, the redundant forces are expressed in linearized terms of the design variables. The solution of the resulting linear programming problem can be viewed as an exact optimum for a truss with different displacements corresponding to the unknown redundants. The latter displacements, computed directly from the linear programming solution, indicate the degree of not satisfying the compatibility conditions. This information can be used to introduce imaginary displacements in subsequent iteration cycles.An iterative procedure of solution is proposed in which both the design and the imaginary displacements are modified until the compatible optimal solution is reached. Each iteration cycle requires the solution of a linear programming problem. The proposed procedure provides more flexibility in the solution process than the usual algorithms based on a sequence of linear programs and may improve the convergence. Numerical examples illustrate the application of this procedure in optimal design of simple trusses.     

Estimating the agricultural demand for electricity in the presence of measurement error in the data

This paper begins by discussing some of the problems frequently encountered in obtaining demand elasticity estimates. To these problems is added that associated with inaccuracy in the measurement of the dependent variable and one or more of the independent variables that impact upon the quantity demanded. Two diagnostics — the regression coefficient bounds and the bias correction factor — are introduced to assess the effect that such a measurement error has on the estimated coefficients of demand relationships. Use of these diagnostics aids in assessing the integrity of the estimates obtained. In considering the demand for electricity for irrigation and the demand for electricity for other (non-irrigation) uses by farmers in the USA, both the quantity demanded and the unit price data available for demand model estimation purposes contain measurement errors. The regression coefficient bounds diagnostic is used to indicate a range over which the true price responsiveness of farmers to changes in energy prices lies. The results suggest that each 1% increase (decrease) in the price of energy will result in between a 0·51 and 0·35% decrease (increase) in the quantity of electricity demanded for irrigation and between a 0·43 and 0·17% decrease (increase) in the quantity of electricity demanded for other uses. The bias correction factor is computed to evaluate the magnitude of the under-estimation of the responsiveness of the quantity of electricity demanded for irrigation and electricity for other uses to a change in the number of acres irrigated and the number of acres planted. For electricity for irrigation, the under-estimation was 14·1% while, for electricity for other uses, it was 13·9%.     

An analysis of the proposed Btu tax on the us economy

This paper examines the impacts of a Btu tax on energy on the United States economy. The analytical approach used in the analysis consisted of a general equilibrium model composed of fourteen producing sectors, fourteen consuming sectors, six household categories classified by income and a government. The effects of imposing a tax on natural gas, coal, and nuclear power of 25.7 cents per million Btu and a tax on refined petroleum products of 59.9 cents per million Btu on prices and quantities are examined. The results are revealing. For example, a Btu tax on energy imposed at the point of production will result in lower output by the producing sectors (by about $122.4 billion), a decrease in the consumption of goods and services (by about $64.6 billion), and a reduction in welfare (by about $66.6 billion). The government would realize an increase in revenue of about $50.5 billion. In the case of the Btu tax being imposed at the point of consumption, there will be lower output by the producing sectors (by about $83.7 billion), a reduction in the consumption of goods and services (by about $48.3 billion), and a reduction in welfare (by about $49.5 billion). The government would realize an increase in revenue of $41.3 billion. Finally, when subjected to a sensitivity analysis, the results are reasonably robust with regard to the assumption of the values of the substitution elasticities.     

Impact of energy on employment in manufacturing

This paper endeavours to study the changes in the distribution of aggregate employment variation among manufacturing industries. Within the structure developed, estimates of the effects of energy on the distribution of employment and on the distribution of changes in employment between various manufacturing industries are made. The evidence indicates that changes in energy have had a significant impact on employment patterns. Energy has had the effect of decreasing the share of projected employment and increasing vulnerability to cyclical changes in employment in industries with a high relative dependence on energy.     

Demand for gasoline and diesel fuel by farmers in the USA

This study endeavours to determine whether farmers in the USA adjust their consumption of gasoline and diesel fuel in response to changes in the relative prices of different types of energy. A demand model is specified and estimated. The conclusions suggest that the price of gasoline (diesel fuel) is a factor impacting the quantity of gasoline (diesel fuel) demanded by farmers, but there is no indication that other types of energy are substitutes for gasoline (diesel fuel). Additionally, the level of farming activity is a very important factor driving the demand for gasoline (diesel fuel). Finally, the estimated models of gasoline and diesel fuel demand are structurally stable over the period 1971–1988.     

Energy demand and interfuel substitution in the transportation sector

The analysis in this paper is directed at examining the effect of energy prices on the quantity of energy demanded in the transportation sector in the United States. For motor gasoline, the suggestion is that vehicle miles travelled as well as the stock of automobiles respond to changing motor gasoline prices. For other fuels consumed in this sector, the quantity of energy consumed does respond to energy prices as well as the level of economic activity. The magnitude of the response is typically small.     

The demand for electrical energy in Korean industry

There is no question that energy is an important ingredient in the development of any country. Unfortunately, the ability of less developed countries to respond to the particular nuances of the energy market is not well understood. This paper endeavors to look at one aspect of this potential responsiveness in one country (Korea). After establishing an empirical relationship between the consumption of electrical energy in various industries and the price of electrical energy, the price of petroleum, and the price of coal, estimates of the magnitudes of the relationships are obtained. Finally, the stability of the estimated relationship is examined with the resultant suggestion that industries' demand for electrical energy was fairly stable over the decade of the seventies.     

The demand for electrical energy in Korean industry

There is no question that energy is an important ingredient in the development of any country. Unfortunately, the ability of less-developed countries to respond to the particular nuances of the energy market is not well understood. This paper endeavors to look at one aspect of this potential responsiveness in one country—Korea. After establishing an empirical relationship between the consumption of electrical energy in various industries and the prices of electrical energy, petroleum and coal, estimates of the magnitudes of the relationships are obtained. Finally, the stability of the estimated relationship is examined with the resultant suggestion that industrial demand for electricity was fairly stable during the decade of the 1970s.     

Ion-exchanged waveguide lasers in Er3+/Yb3+ codoped silicate glass

We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 mum. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 mum. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 mum were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.