Showing papers by "International Institute for Applied Systems Analysis published in 1988"

Household composition choices of older unmarried women.

Abstract: This article extends previous research on the household composition of older unmarried women, using a statistical model that treats each of a woman’s surviving children as a distinct potential provider of a shared household. Additional possibilities— living alone, living with other nuclear-family relatives, and living with others— are also recognized, providing a varied range of household-structure opportunities for older women. The approach allows us to identify individual child attributes associated with the propensity to coreside with the older unmarried mother. The results confirm earlier findings regarding the importance of income, age, and disability status as determinants of the household composition of older women. We find, however, that unmarried children, especially sons, are more likely to share a household with an elderly mother than are married children. Working reduces the likelihood that a married daughter will live with her older mother. Overall, the findings suggest that the attributes, more so than the sheer numbers, of living children influence the household structure of their mothers.

Changes in valued "Capacities" of soils and sediments as indicators of nonlinear and time-delayed environmental effects.

Abstract: This paper discusses the buffering, oxygen-donating, and sorption capacities of soils and sediments as an inter-connected system for regulating the retention and release of chemical pollutants. In this context, the author discusses the chemical conditions under which sediments may serve as a source or a sink for toxic materials, and conditions under which soils may retain or release them. It is demonstrated that nonlinear, time-delayed ecological transformations in soils and sediments often can be understood in terms of the interlinked system. The author discusses some possible future long-term environmental problems that might beset Europe, and some implications for a monitoring strategy for foresseing such problems. Because the release of adsorbed toxic chemicals from heavily polluted sediments and soils can occur suddenly owing to changes in oxygen status (i.e., redox potential) or acidity, strategies for preventing the long-term release of such materials should not only consider current conditions of pH and redox potential, but also, how those conditions might change in the future.

Carbon dioxide emissions in a methane economy

Abstract: Increasing reliance on natural gas (methane) to meet global energy demands holds implications for atmospheric CO2 concentrations. Analysis of these implications is presented, based on a logistic substitution model viewing energy technologies like biological species invading an econiche and substituting in case of superiority for existing species. This model suggests gas will become the dominant energy source and remain so for 50 years, peaking near 70 percent of world supply. Two scenarios of energy demand are explored, one holding per capita consumption at current levels, the second raising the global average in the year 2100 to the current U.S. level. In the first (‘efficiency’) scenario concentrations peak about 450 ppm, while in the second (‘long wave’) they near 600 ppm. Although projected CO2 concentrations in a ‘methane economy’ are low in relation to other scenarios, the projections confirm that global climate warming is likely to be a major planetary concern throughout the twenty-first century. A second finding is that data on past growth of world per capita energy consumption group neatly into two pulses consistent with longwave theories in economics.

Stochastic Optimization Models for Lake Eutrophication Management

Abstract: We develop a general framework for the study and the control of the eutrophication process of shallow lakes The randomness of the environment variability in hydrological and meteorological conditions is an intrinsic characteristic of such systems that cannot be ignored in the analysis of the process or by management in the design of control measures

The design of integrated monitoring systems to provide early indications of environmental/ecological changes.

Abstract: One of the important goals of the next several decades is to achieve and maintain ecologically sustainable development of the biosphere However, the management of ecological systems is rather difficult, largely because of uncertainties in long-term predictions of environmental and ecological behaviour Thus, one of the objectives for integrated monitoring should be to provide early indications of impending changes so that mitigative actions can be taken This paper includes a discussion of the factors to be considered in the design of early-warning monitoring systems, and gives some examples One approach that appears to be particularly promising is that of identifying, quantifying and monitoring the stresses, feedbacks and component lags in the environmental-ecological system being studied

Physicochemical properties in tungsten films deposited by radio‐frequency magnetron sputtering

Abstract: The microstructure, reflectivity, resistivity, and oxygen contamination of thin tungsten films (<250 nm) deposited by rf magnetron sputtering on silicon substrates are reported. Three structural stages, depending on the operating conditions, are found to occur during the deposition: (i) In the range of the rf applied power density studied (<6 W cm−2), an amorphous structure is always observed when the film thickness does not exceed ∼80 nm. The resistivity remains at a fairly high level (≂1.3 μΩ m). (ii) Upon further deposition and if the power density is <0.6 W cm−2, the β‐W phase is detected. (iii) A thermally activated transformation of the β‐W phase into pure α–W occurs for a critical temperature ∼150 °C during depositions carried out at higher powers(≥1 W cm−2). The resulting β‐W or α‐W films consist of small grains (5–20 nm) which present a low dislocation density. Resistivity and reflectivity are mainly related to the oxygen content of the films. When the rf deposition power density is low (≤0.6 W c...

The multistate life table with duration‐dependence

Abstract: A method for generalizing the multistate, or increment‐decrement, life table to include rates which depend upon duration of exposure to risk, as well as upon age, is proposed. The method is built upon the linear approximation, called the linear integration hypothesis, developed mainly by Rogers and his colleagues. Although the use of rates indexed by duration categories leads to a substantial increase in the state space of the model, it is possible to arrange the rates in such a way that matrices to be inverted are no larger than those encountered in the usual multistate life table. In the more general approach it is possible to derive several new summary indices of the life‐table cohort's history, such as the mean and median time in current status, at any age. The method is illustrated using a simple four‐state marital‐status model which has appeared often in the literature; here, rates of divorce and widowhood vary by duration of marriage as well as age.

Linear metabolism-repair systems

Abstract: Metabolism-repair systems represent a formal mathematical framework for representing characteristic properties of living systems such as repair, replication, adaptation and so forth. In this paper, the concrete realization of such structures is developed in the case when the system “metabolism” is linear. Explicit results are given to show when system repair operations can counteract environmental and metabolic fluctuations. Additional results pertaining to the replication operation and the possibility for ‘Lamarckian” inheritance are also given, together with a formal demonstration of the increase in complexity as we proceed from the processes of metabolism to repair to replication. The paper concludes with a discussion of several application areas, together with a consideration of several conceptual and mathematical questions requiring attention for further development of this non-Newtonian systems paradigm

On stochastic filtering approximations of estimation problems for systems with uncertainty

Abstract: This paper considers estimating the state of a discrete-time linear system in which the values of an unobserved disturbance process are only known to lie in certain prescribed sets. By introducing additional stochastic disturbances it is shown that this problem can be approximated to arbitrarily high accuracy by the solution of a Kalman filtering problem

Smallholder Vulnerability and Response to Drought

Abstract: Previous sections have outlined the drought climatology of the Kirinyaga-Embu-Machakos area and the results of several agroclimatic models that indicate agricultural and livestock potentials in different climatic scenarios. Even using very simple models, it is clear that climate and weather are the primary variables in determining potential productivity (and its temporal and spatial patterns) in the area. The next step is to trace the importance of variability in agricultural and livestock production to smallholder agriculturalists. Over 80% of the population of Kenya resides in the rural areas, and the majority are smallholder farmers. Development policy in Kenya has long recognized the importance of drought in planning agricultural and livestock development. It must also incorporate consideration of the smallholders’ vulnerability to drought and their means of coping with recurrent droughts of various magnitudes and durations.

Introduction: Drought as a Policy and Planning Issue in Northeast Brazil

Abstract: The Nordeste or Northeast Brazil (NEB) has been a focus of major concern for governments, planners, social scientists and other experts over the last century, principally because of recurrent droughts and the poverty that affects the majority of the population in its semi-arid zone.

Ecosystem Theory Required to Identify Future Forest Responses to Changing CO2 and Climate

Abstract: The current anthropogenic disturbances in global environmental systems require immediate study and understanding. Yet, piecemeal and applied approaches to solving these interrelated problems hold little promise because the underlying processes of environmental change and ecological response are not understood. Development of an appropriate and valid body of theory is desperately needed. The nature of certain ecosystem theory requirements is revealed by model experiments on responses by forest ecosystems to future climate and CO2 effects. Increasing concentrations of atmospheric CO2 potentially could generate multiple and even opposing effects on forests. Greenhouse experiments have shown that enhanced CO2 positively affects woody seedling growth, and that these effects may also occur in saplings and mature trees under elevated CO2 concentrations. Yet, today’s close geographic correspondence between certain climate variables and forest distributions suggests that climate changes resulting from future CO2 increases could destroy many currently existing forests. The potential response of forests to these conflicting forces was examined using a computer model of tree growth and forest stand development. The model is composed of abstractions from current ecological theory and uses knowledge of forest dynamics to simulate simultaneous changes in CO2 and climate, and the known responses of forest stands to these variables. Model runs of several hundred years were constrained by a climate and CO2 scenario which changed annually, as suggested by current energy use projections. Simulation results suggest that initial forest response to both climate and CO2 changes may be minor because of tree longevity. In the long term, the positive effects on forests, simulated as CO2 fertilization, were overwhelmed by the negatve effects, simulated as drastic changes in the climatic status quo. Yet, the value of the simulations is severely diminished by weaknesses in the theoretical underpinnings of the models. Particularly (but not exclusively) constraining is the absence of a cohesive, tested theory to predict (l) forest ecosystem behavior under chronically changing environmental regulation, and (2) tree species behavior along boundaries of geographic ranges.

The assessment of impacts of possible climate changes on the results of the IIASA rains sulfur deposition model in Europe

Abstract: An analysis is made of the relationship between patterns in atmospheric circulation in Europe and the temperature regime of the Northern Hemisphere over the same period. The basis for classifying different types of atmospheric circulation or large-scale weather paterns [commonly known as Grosswettertypes (GWT-s) or Grosswetterlagen (GWL-n)] is the identification of the position of centers of cyclones, ridges and troughs. The linear regression between the frequency distribution of GWL-n and the deviation in the mean annual Northern Hemisphere extratropical temperatures from the 90-yr period (1891 to 1980) were tested. The results show that the null hypothesis, i.e. that there no linear relationship, is rejected at the 95% probability level (assuming a normal distribution) for several GWT-s and GWL-n. Changes in GWT-s and GWT-n frequency distribution associated with global warming could substantially change the long-range transport of pollutant over Europe. For example, the decrease in frequency of zonal circulation regimes and the more frequent meridional and blocked circulations (especially easterly flows) could result in a decrease of the existing net export of S pollutants from western to eastern Europe during the winter months.

Estimating hidden morbidity via its effect on mortality and disability

Abstract: The applicability of the theory of partially observed finite-state Markov processes to the study of disease, morbidity, and disability is explored. A method is developed for the continuous updating of parameter estimates over time in longitudinal studies analogous to Kalman filtering in continuous valued continuous time stochastic processes. It builds on a model of filtering of incompletely observed finite-state Markov processes subject to mortality due to Yashin et al. The method of estimation is based on maximum likelihood theory and the incompleteness in the observation of the process is dealt with by applying missing information principles in maximum likelihood estimation.

The Implications for Agricultural Policies and Planning

Abstract: In the preceding sections we have shown that Japanese agriculture is finely adjusted to the climatic conditions prevailing in different regions of the country. In northern Japan in particular, where thermal conditions are critical determinants of rice production, seemingly small temperature anomalies can result in wide variations in productivity and regional rice supply that have implications for the national rice market, itself a precarious balance of domestic heavily subsidized supply and demand.

Kinship patterns and household composition: older unmarried Hungarian women, 1984.

Abstract: Household composition of older unmarried women in Hungary is analyzed using data from the 1984 microcensus. The principal determinants of household composition investigated are kin availability — the number of living children, siblings, and parents — health status, marital status, age, and income. A multinomial logit model distinguishing among five household types reveals that number of children, severe disabilities, age and income are all strongly related to household composition. Trends in fertility and mortality patterns suggest that kinship patterns will change in coming years; these results imply that household composition will, in turn, change as well.

Ellipsoidal approximations in problems of control

Abstract: The subject of study in this paper is an adaptive control problem involving uncertainties. It is a special case of the one considered in the paper by Kurzhanski [1], in the present volume. The system is described by differential inclusions and, accordingly, its solution, a feedback control ensuring that certain feasibility constraints be fulfilled, is sought in the form of a set valued map. We apply recent results of ellipsoidal calculus to develop an easily implementable algorithm that gives approximations to the known exact formulae. The paper is therefore an attempt to carry out the program proposed in the above mentioned article.