The application of fuzzy control to fed-batch fermentation

Bibliography: pages 101-105.Fermentation processes are highly nonlinear and subject to variability. The fermentation's states are not readily available on-line and therefore the application of closed loop control schemes have been hindered. It was decided to investigate fuzzy control as it is able to deal with systems whose operation does not easily fit into the mathematical framework of traditional control approaches such as fermentations where the systems are highly nonlinear. The fermentation of lysine is an emergent industry in South Africa and it was therefore decided to focus on this fermentation. The control of penicillin fermentation was also investigated as it closely resembles the fermentation of lysine. A review of the types of control and estimation techniques used in the literature for biosystems was done to assess state of art in biocontrol. This covered optimal control techniques, neural networks, fuzzy controllers and adaptive control techniques. The operation and properties of fuzzy controllers were investigated. A specific form of fuzzy controller, presented in the literature, which was shown to correspond to a PI controller with a nonlinear gain was discussed. The effect of the number of output sampling points was analysed and it was found that the number of output sampling points used has an effect on the output and input response. It was also found that a higher number of sampling points results in a nonlinear integral constant and a non linear gain which has more resolution. The fuzzy controller's output response equations were found to be of a PI form with a possible bias term irrespective of the number of sampling points. The fuzzy controller was shown to yield better output and input response to that of an equivalently tuned linear PI controller for a first, second and third order system because it is able to take advantage of its nonlinear form. It was also shown that it is possible to obtain less severe input action for relatively the same value of SSE (sum of squared errors) when a higher number of sampling points is used for a first order system with dead time

The Discriminating Characteristics of For-Profit versus Not-For-Profit Freestanding Psychiatric Inpatient Facilities

This study examines the characteristics that discriminate between ownership types among private, freestanding psychiatric inpatient facilities in the United States. Use of data from the Inventory of Mental Health Organizations (NIMH, 1983, 1986), revealed that not-for-profits provide more services and serve more of the underinsured, while for-profits serve the better insured, concentrate primarily on inpatient services, and serve more children, adolescents, and substance abusers. A surplus bed capacity among for-profit psychiatric hospitals is presumed to contribute to lower occupancy rates and less turnover in the for-profit sector. Not-for-profit psychiatric facilities are also found to be more involved in professional training and to be more accessible through emergency services. However, the misclassification test in the discriminant procedure reveals that a significant group of not-for-profit facilities looks more like its for-profit counterpart group than like other not-for-profits. Study findings are interpreted both in terms of debates over the tax-exempt status of not-for-profit hospitals and the potential negative services effects of proprietization

Supportive Housing for Homeless People with Severe Mental Illness

Research suggests that as many as 110,000 single adults with severe mental illness (SMI) are homeless on any given day in the United States. The combination of mental illness and homelessness make this population especially hard to reach through either housing or mental health programs alone. Supportive housing programs, which provide independent housing along with health and social services, hold great promise for this population, but are costly to launch and maintain. This Issue Brief highlights a landmark study that examines the extent to which supportive housing costs are offset by reductions in the use of public services for health, corrections, and shelter

Public Service Reductions Associated with Placement of Homeless Persons with Severe Mental Illness in Supportive Housing

This article assesses the impact of public investment in supportive housing for homeless persons with severe mental disabilities. Data on 4,679 people placed in such housing in New York City between 1989 and 1997 were merged with data on the utilization of public shelters, public and private hospitals, and correctional facilities. A series of matched controls who were homeless but not placed in housing were similarly tracked. Regression results reveal that persons placed in supportive housing experience marked reductions in shelter use, hospitalizations, length of stay per hospitalization, and time incarcerated. Before placement, homeless people with severe mental illness used about $40,451 per person per year in services (1999 dollars). Placement was associated with a reduction in services use of$16,281 per housing unit per year. Annual unit costs are estimated at $17,277, for a net cost of$995 per unit per year over the first two years

UNDERSTANDING CAPTURE EFFICIENCY IN FLUIDIZED BEDS

This paper describes an experimental study on the extent of capture efficiency in a fluidized bed system under controlled conditions. Using aerosols as tracer compound, the capture efficiency in a fluidized bed was quantitatively measured as a function of contact distance (time). The paper presents the experimental technique as well as the results relating the capture efficiency to the bed hydrodynamic. A theoretical model was developed to describe the influence of operating variables on the overall capture efficiency. Dominant mechanisms enabling the capture of the fine aerosols are elucidated

Prevalence of Treated Behavioral Disorders among Adult Shelter Users: A Longitudinal Study

Of 27,638 homeless adults admitted to Philadelphia public shelters in the years 1990 through 1992, 20.1% received treatment for a mental health disorder, and 25.3% for a substance use disorder in the years 1985 through 1993. An additional 20.7% were identified as having untreated substance use problems. Overall, a total of 65.5% of adult shelter users were identified as ever having had a mental health or substance use problem, treated or untreated

The Treated Prevalence of Mental Health and Substance Use Disorders among Adults Admitted to the Philadelphia Shelter System: Results from the Integration of Longitudinal Data on Shelter and Mental Health Services Utilization

This paper reports results from a study of the treated prevalence of mental health and substance use disorders among adults admitted to Philadelphia public shelters between 1990 and 1992 (N=28,638). Identifiers and service records from longitudinal databases on shelter and mental health services were merged, finding that 49% of single homeless adults and 33.2% of homeless adults with children had a treatment for a mental health or substance use disorder between 1985 and 1993. The rate of treatment for serious mental illness (SMI) was 10.7% (by most frequently occurring diagnosis). Single women (18.6%) had twice the rate of SMI as single men (9.9%), and single adults (12.1%) had twice the rate of SMI as adults with children (6.2%). The treatment rate of substance use disorders (25.2%) was higher than the rate of mental health disorders (20%), and was twice as high for single adults (28.6%) as for adults with children (14.6%). An additional 20% of adult shelter users were identified through shelter records as having untreated substance use problems. Veterans had comparable rates of disorders as nonveterans. Overall, 65% of adult shelter users were identified as ever having some mental health or substance use problem, treated or untreated. People with SMI were less represented among shelter users on two single day censuses than over three years, suggesting a higher rate of turnover among people with SMI, while people with substance use disorders were overrepresented by a third on the two single day censuses, suggesting a lower rate of turnover among people treated for substance abuse. Of the treated Medicaid population, 6.8% became homeless in the three year study period, representing 7.8% of the treated population with SMI, 9.5% of the treated schizophrenia population, and 20.1% of the population receiving inpatient substance abuse services. Approximately 3,000 people with SMI became homeless in the 3-year study period, with an average of 73 people with SMI entering shelter for the first time each month. An analysis of inpatient usage found that 25.7% of the SMI and 34.2% of the treated substance abuse population were hospitalized within 120 days of their first shelter admission (before or after). Fourteen percent of the SMI were also seen in an emergency room within 120 days of shelter admission (before or after)

EXPERIMENTAL QUANTIFICATION OF THE SOLIDS FLUX IN AN INTERNALLY CIRCULATING FLUIDIZED BED

Internally circulating fluidized beds (ICFBs) have been applied to a number of processes and provide a means of exchanging the bed particles from one reaction chamber to the other. Fundamental to this system is a good knowledge of the solids circulation rate (SRR). This paper summarises experimental investigations conducted using a hot tracer technique to measure the solids recirculation flux through an ICFB with a reaction and heat exchange chamber. Possible predictive models which link the bed hydrodynamics to the SRR are also evaluated

Expenditure and Revenue Patterns of State Mental Health Agencies from 1981 to 1987

This paper documents expenditure and revenue patterns of state mental health agencies from 1981 to 1987. Expenditure data show an overall decline of mental health expenditures of 4.9% over this period. States with declining overall expenditures were more likely to make deep cuts in hospital expenditures and little or no increases in community programs, while the few states with increasing expenditures showed substantial increases in community programs and contant funding for hospitals. A relatively more dramatic shift was noted across states of shifting expenditures from inpatient to ambulatory care. Revenue data reveal that federal support for state mental health agencies increased slightly during this period, but solely as a function of the introduction of the Block Grant in 1982. However, once introduced, both the Block Grant and other federal sources show steady losses against inflation. State sources also show a decline of 4% during this period, most of which was felt between 1981 and 1983, after which there has been no further decreases. Interstate variability in percapita spending on mental health is described and found to significant even beyond adjustments for costs of services. Expenditures on mental health also show relatively greater declines compared to overall state budgets and state health and welfare budgets during this period, suggesting an increasingly lower priority for mental health services in the state budget alloction process

PRESSURE BALANCE OF A MULTIPLE-LOOP CHEMICAL REACTOR

For a chemical looping (CL) process it is important to determine the optimum reactor configuration that would offer good pressure balance to ensure smooth transfer of the solids between the reactor loops as well as satisfying the oxygen carrier and heat requirements. A variation of the CL process for production of enriched hydrogen stream is investigated which adopts multiple reactor loops. A pressure balance model is developed and a methodology is proposed to find a feasible reactor configuration at an industrial scale production of hydrogen