Dissolution of salts crystallised in building materials using ultrasound: an alternative to NORMAL (1983) standard methodology.
Our aim in the present work is to extract salts from ornamental stone using a faster and less tedious method than the customarily used NORMAL method [NORMAL, Dosaggio dei Sali Solubili, CNR-ICR, Roma, Italy (1983) 13/83]. For extraction in aqueous medium, the latter method requires shaking for 72 h at a temperature of 60 degrees C. Our aim is to attempt to shorten this time to less than 1 h using ultrasound. The results of the present study indicate that there is a good correlation between the amount of salts extracted applying the method described in the NORMAL (1983) normative and the amounts extracted with the method proposed here, subjecting the material to ultrasound (50 KHz) for 45 min.
Construction of mathematical model of dissolution process of solids under action of ultrasound
An influence of the ultrasound beam on the process, dissolution of solids in liquid solvents is considered: influence of frequency, intensity, velocity of acoustic vibrations, cavitation and acoustic flows on mass transfer process. Experimental researches show that the intensification of dissolution process of solids in liquid solvents under action of ultrasound is influenced by acoustic flows, microflows and under influence of cavitation bubbles. Development of new efficient equipment for solution requires the development of calculation methods of dissolution processes of solids in liquid solvents under conditions of ultrasonic irradiation. Such methods should take into account the characteristics of ultrasonic generators, irradiation frequency of ultrasonic vibrations, power and intensity of ultrasonic vibrations. Mathematical model of dissolution process of the granule is constructed. It identifies the change of size of the granule over time under influence of the source of ultrasonic irradiation. Mathematical model consists of three differential equations used to calculate depending on the ratio of the granule size and the maximum turbulence scale of acoustic flows and for cavitation. The mathematical model will enable use in conducting numerous studies as a basis of equipment calculation methods for dissolution process of granular material.
Migration, Labor Mobility, and Relocation Assistance: The Case of the American Indian
This article, an example of "indirect" program evaluation, utilizes a 1/100 public use sample of American households from the 1970 U.S. census to examine family welfare levels among three categories of Indian families: (1) nonmigrant families living in traditional areas of Indian population concentration; (2) families in areas not receiving relocation assistance through the Bureau of Indian Affairs (BIA); and (3) migrant families moving to urban areas with BIA relocation assistance. The article concludes that the population of migrants receiving relocation assistance has a substantially higher level of economic welfare in both absolute and relative terms and that earnings are the principal source of increased welfare. It is suggested that such assistance might be utilized on a wider basis to assist other migrating populations.