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Papers by martin okos

Transactions of the ASAE, 1983

T HE SLAM simulation model of multi-product sausage manufacturing (Batch/Semi-continuous Processi... more T HE SLAM simulation model of multi-product sausage manufacturing (Batch/Semi-continuous Processing) plant has been developed. An application of this computer simulation to the case study and evaluation of system performance of an existing plant is investigated. The simulation results of weekly production are within 15% of the actual data. The results further indicate that the current system is under-utilized due to certain imbalancing in grinding and blending processes. Various design modifications to improve system performance are evaluated.

SAE technical paper series, Jul 1, 1996

Drying Technology, 1993

Models to describe drying pmesses are necessary for engineering design and optimization. Many res... more Models to describe drying pmesses are necessary for engineering design and optimization. Many resenrch studies in lhe past century have had the objective of developing mathematical models to describe drying pmesses in pomus solids. This review identifies key characteristics of drying models including controlling p m m resistances, internal mechanisms of moisture movement, and melhods of model cufficient determination, model solution, and model validation. Similarities and differences between previous work are noted, and strategies for future drying model development are discussad. INTRODUCTION Development of malhemalieal models lo describe drying of porous solids has been a topic of nsearch in many fields for several decades. Models are needed to enable scientific process design and minimilation of energy and capital costs subject to quality constraints. Until general models are developed which ~c e w f u l l y predict drying rates and internal moisture and temperature profiles. the design of drying processes will remain largely an art. A sound understanding of existing drying theory together with new experimental data will enable further advances in the description of the drying phenomenon. Several review articles have recently been presented on the topic of drying. Keey (1980) describes the historical development of drying theory. Van Brake1 (1980) provides a critical review of the topic of mass transfer during convective drying. Chirife (1983). Bruin and Luyben (1980), Fortes and Okos (1980). Holdswarth (1971). Raswn and Haynknwn (1977). and Van Arsdel (1963) review drying theory as applied to food materials. King (1971) Copyright O 1992 by Mprccl Dekkcr. Inc. 2 WAANANEN. LITCHFIELD. AND OKOS reviews freeredrying of fmds, and Rown (1987) and Simpson (1983-84) review the thmry of wood drying. Fulford (1969) provides a comprehensive review of Soviet research in the drying a m. Novak and Caulman (1975) note that soil physicists and engineers have 'generally ignored each other's literature.' This review attempts to encompass and classify efforts made in all arras of drying related research. Key characteristics of drying models a n discussed including controlling process resistances, internal mechanisms of moisture movement, structural and thermodynamic assumptions, and methods of material property measurement, model solution, and model validation. CONTROLLING RESISTANCES DURING DRYING Typically drying is divided into conslant-rate and falling-rate periods. The drying rate in the former is determined by conditions external to the material k i n g dried including temperature, gas velocity. total pressure, and partial vapor pressure. The controlling resislance may be m i s l e d with the transfer of energy to the solid, or the transfer of mass away from the solid. Mass transfer during the constant-ratc period involves diffusion of w s s r vapor from the material surface through a boundary layer into the drying medium. During the falling-rate period, the drying rate ds-es with time, and the rate of internal nus transfer to the material surface typically controls the pmeess. A falling drying rate may be observed when external nus transfer resistance is eontmlling and the surface vapor pressure of the solid is dec-ing m moisture content dmps. Measurement of sample temperature during drying will help to identify whether s process is controlled by energy ar mass transfer. A sample temperature equal to the wet bulb temperature of the surrounding medium is characteristic of energy transfer control. If the sample renches the dry bulb temperature of the drying medium, mass transfer control is suggested. The importance of internal versus external mass transfer resistance can be inferred from drying studies an samples of different sile (i.e.. varying slab thickness (I) or sphere and cylinder radii (r)). The drying time required to reach a given moisture content will be pmponianal lo I or r for external mass transfer control and proportional to I' or ? for control by internal diffusion. Waananen and Okos (1989) presented procedures for analyzing drying dnls from pnsh cylinders of different sires. Vsceareu. el al. (1974) analyzed the effect of nonisothcml drying conditions on the ~u l t s obtained from samples of different thickness. When he31 transfer effects were considered for sugar beet r m l slabs, the thickness dependence of drying data was consistent with internal nus transfer control. Lilchfield and Okos (1992) CLASSIFICATION OF DRYING MODELS 3 identified internaltransfer wntrol for drying of pasts slabs by varying the velocity of the drying medium and obwwing no change in drying rates. Fulrord, O.D. 1969. A ww<)rol mcerd s w i c l m u a x h on h e d r y i q of.olid..

Acs Symposium Series, Jan 18, 1983

Transactions of the ASAE, 1984

Transactions of the ASAE, 1990

The rate of gaseous SO2 sorption by com was modeled as an insulated cylinder with one end open fo... more The rate of gaseous SO2 sorption by com was modeled as an insulated cylinder with one end open for diffusion. This was chosen to represent the flow of material from the kemel tip cap upward. The diffusion coefficient for SO2 was found to be independent of vapor pressure and moisture content (above 20%) and had an Arrhenius activation energy of 30.9 kJ-mol"^. At 14° C the diffusion coefficient was 1.88x10""^ cm^-s"^. Sulfur dioxide equilibrium isotherms for the whole kernels were independent of moisture content over the range of 15% to 38% m.c. (w.b.) and were modeled by a second-order polynomial in temperature and vapor pressure. The germ was found to hold 3 times more SO2 (38,000 ppm) and the hulls 50% more SO2 (20,(X)0 ppm) than the endosperm at equilibrium for conditions of 760 mm/Hg SO2, 25° C, and 30% (w.b.) com moisture content. LITERATURE REVIEW Sulfur dioxide has been used in the steeping of com during the wet milling process to control fermentation, to soften the kemel for grinding, to facilitate disintegration of the protein matrix around the starch granules, and to remove solubles from the germ. Fan et al. (1965) found that the uptake of the sulfurous acid (H2SO3) could be modeled using Pick's second law equation with a Article has been reviewed and approved for publication by the Food and Process Engineering Inst, of ASAE.

Transactions of the ASAE, 1988

F AILURE properties for kernels of one hybrid of corn were experimentally determined. Uniaxial co... more F AILURE properties for kernels of one hybrid of corn were experimentally determined. Uniaxial compressive tests of core specimens were performed at moisture levels of 9.7, 14, 17, 21 an 26% dry basis (db), at each of the temperature levels of 25, 55, 85 and 100°C. Failure stress and the slope of the linear portion of the stress-strain curve decreased with an increase in kernel moisture content and temperature. Failure strain increased as the moisture content and temperature increased. The modulus of toughness decreased with an increase in temperature. For a fixed temperature, the modulus of toughness increased to a maximum at a moisture content of approximately 16% dry basis, and then decreased as the moisture content was further increased.

Journal of Agricultural and Food Chemistry, Jul 1, 1983

A method is presented for the rapid measurement of water-extractable sulfur dioxide in corn. The ... more A method is presented for the rapid measurement of water-extractable sulfur dioxide in corn. The method differs from standard alkali or distillation procedures in that bound SO2 is not measured. Sulfur dioxide in ground corn samples is extracted in a buffer solution and titrated with iodine directly, without filtration. Average standard deviation of the method was 21.3 ppm, as determined from samples containing SOz levels ranging from 162.3 to 1197.0 ppm (weight basis). The method requires no specialized equipment and is suitable for control or research purposes. Direct comparison was made with the distillation procedure of the Manufacturing Confectioners' Alliance and the FMF (Pearson, 1977). Treatment of high-moisture shelled corn with small amounts of sulfur dioxide inhibits microbial growth during low-temperature grain drying (Eckhoff et al., 1980; Van Cawenberge et al., 1982). The procedure, called the trickle-S02 procedure, involves the intermittent injection of SOz into the drying air which is carried into the bin where it acts upon the indigenous microflora. In order t o develop appropriate SOz application procedures and to

Transactions of the ASAE, 1981

Springer eBooks, 1989

This paper presents a comprehensive experimental study of thermal properties of various alkali-ac... more This paper presents a comprehensive experimental study of thermal properties of various alkali-activated binders at ambient and elevated temperatures. The binders were prepared using alkali-activated low calcium fly ash/ground granulated blast-furnace slag at ratios of 100/0, 90/10, 50/50 and 0/100 wt%. These binders can be considered as a composite of solid, water and air. Accordingly, a three-phase model is applied to predict thermal conductivity of the binders at ambient temperature. At elevated temperatures, the Hashin-Shtrikman model is used to estimate the bounds of thermal conductivity for alkali-activated binders containing of fly ash. To validate the above models, a transient plane source measurement technique was applied to measure the thermal conductivity and heat capacity at temperatures ranging from 23 to 600°C. Data generated is then utilised to develop analytical expressions for estimating thermal properties as a function of temperature. The simplified relationships can be used for estimating the fire resistance of structural elements made from alkali-activated cementitious materials.

Transactions of the ASAE, 1981

Transactions of the ASAE, 1985

M ORE ethanol can be produced from whole-plant corn silage than from the grain portion alone. The... more M ORE ethanol can be produced from whole-plant corn silage than from the grain portion alone. The conventional ensilement process involves conversion of soluble carbohydrates to organic acids. Preservation of corn silage sugars with sulfur dioxide (S0 2) was studied using S0 2 dosage levels between 0.0% and 3.0% (% weight/weight), and storage temperatures between 2°C and 32°C. S0 2 dosages of 0.3% and higher were sufficient to prevent microbial growth in silage during 3 to 6 months storage in culture tubes at these temperatures. A dosage of 0.6% was required to preserve silage over 8 months in larger bags at room temperatures. The calorific value of the remaining material increased during conventional ensilement. The structural components of corn silage were not noticeably hydrolysed by 1.5% S0 2 during 8 months of storage.

Springer eBooks, 1998

A model has been developed to predict the moisture and stress profiles in shrinking biopolymers d... more A model has been developed to predict the moisture and stress profiles in shrinking biopolymers during drying. The shrinkage is expressed in the form of a non-equilibrium deformation viscosity, a property that is inherently dependent on the glass transition temperature (T a) of the matrix and on the temperature of drying (T). The difference between these temperatures, i.e. T – T g, controls the rate at which shrinkage occurs during drying.

CRC Press eBooks, Oct 19, 2010

Transactions of the ASAE, 1980

T HREE thermal storage media; water, saturated soil, rock and phase change materials, were tested... more T HREE thermal storage media; water, saturated soil, rock and phase change materials, were tested to determine their feasibility as a media for a thermal storage to be used for grain drying. The thermal effectiveness of phase change material, rock and saturated soil was found to be 0.79, 0.38 and 0.31, respectively. A dimensionless thermal storage parameter is derived to aid in comparing and designing thermal storage devices.

Transactions of the ASAE, 1981

L OW-TEMPERATURE, in-bin wheat drying has been studied through use of computer simulation and on-... more L OW-TEMPERATURE, in-bin wheat drying has been studied through use of computer simulation and on-farm drying experiments involving in-bin drying with unheated and solar heated air. The simulation used is based on mathematical models which define moisture and heat transfers. A GASP IV computer program simulates drying of a bin of grain by thin-layers in discrete time steps by simultaneous solution of a set of four nonlinear equations. Experimentally obtained drying data were used to validate the simulations. The simulations predicted moisture contents for most observations within 1 percent for the solar heated drying case and within 2 percent for the natural air drying case. Analyses indicate that slight variations in airflow and air moisture content appreciably affect drying.

Transactions of the ASAE, 1983

U NIAXIAL tension tests at constant rates of elongation (0.02, 0.05, 0.1 and 0.2/min) were used t... more U NIAXIAL tension tests at constant rates of elongation (0.02, 0.05, 0.1 and 0.2/min) were used to determine the relaxation behavior for moisture and temperature equilibrated specimens of extruded durum semolina. Moisture contents ranged from 0.12 to 0.25 dry basis and temperatures 42 to 58 °C. Linear viscoelastic, thermo-and hydro-rheologically simple behavior were validated for experimental conditions. Data reduced for time-temperature and time-moisture equivalence was fitted to Maxwell models and used to express behavior over extended time scale. Expressions determined for the temperature and moisture shift factors using constant strain rate data were used to reduce the failure stresses with good results. The scatter of failure points about the reduced line had a standard deviation of 0.3 logarithmic units.

Annals of the New York Academy of Sciences, May 1, 1990

INTRODUCTION AND THEORETICAL CONSIDERATIONS Conclusions of previous investigations have led us to... more INTRODUCTION AND THEORETICAL CONSIDERATIONS Conclusions of previous investigations have led us to focus on Pichia stipitis as a yeast with high potential for producing ethanol from xylose-rich, wood-processing wastes. l-S Given 150 giL xylose in complex medium, strain Y-7124 functions optimally at 25-26°C and pH 4-7 to accumulate 56 giL ethanol with negligible xylitol by-production. 6 In a past report, we cited the need for an optimal bioreactor system; toward this end, we put oxygen uptake, growth, and death kinetics into mathematical form.) The present report builds on our previous work as the pathways and stoichiometry of xylose metabolism are examined and models of xylose uptake and ethanol production are identified. Yeasts begin xylose metabolism with the sequence, xylose-+ xylitol-+ xylulose-+ xylulose 5-phosphate. 8 In balanced form, this sequence is:

A literature review has been completed and pertinent data from previous food drying studies, info... more A literature review has been completed and pertinent data from previous food drying studies, information on available and developing sensors for control and monitoring of dryers, production rates and values of various food products has been obtained. This information was used to select the food products to be studied. The areas reviewed in detail include (a) Fundamental Drying Studies, (b) Quality of Foods, (c) Viscoelastic Properties of Grains and Food, (d) Thermal Properties of Porous Foods, (e) Energy Efficient Dryer Designs and (f) Density Independent Moisture Measurement.

Transactions of the ASAE, 1983

T HE SLAM simulation model of multi-product sausage manufacturing (Batch/Semi-continuous Processi... more T HE SLAM simulation model of multi-product sausage manufacturing (Batch/Semi-continuous Processing) plant has been developed. An application of this computer simulation to the case study and evaluation of system performance of an existing plant is investigated. The simulation results of weekly production are within 15% of the actual data. The results further indicate that the current system is under-utilized due to certain imbalancing in grinding and blending processes. Various design modifications to improve system performance are evaluated.

SAE technical paper series, Jul 1, 1996

Drying Technology, 1993

Models to describe drying pmesses are necessary for engineering design and optimization. Many res... more Models to describe drying pmesses are necessary for engineering design and optimization. Many resenrch studies in lhe past century have had the objective of developing mathematical models to describe drying pmesses in pomus solids. This review identifies key characteristics of drying models including controlling p m m resistances, internal mechanisms of moisture movement, and melhods of model cufficient determination, model solution, and model validation. Similarities and differences between previous work are noted, and strategies for future drying model development are discussad. INTRODUCTION Development of malhemalieal models lo describe drying of porous solids has been a topic of nsearch in many fields for several decades. Models are needed to enable scientific process design and minimilation of energy and capital costs subject to quality constraints. Until general models are developed which ~c e w f u l l y predict drying rates and internal moisture and temperature profiles. the design of drying processes will remain largely an art. A sound understanding of existing drying theory together with new experimental data will enable further advances in the description of the drying phenomenon. Several review articles have recently been presented on the topic of drying. Keey (1980) describes the historical development of drying theory. Van Brake1 (1980) provides a critical review of the topic of mass transfer during convective drying. Chirife (1983). Bruin and Luyben (1980), Fortes and Okos (1980). Holdswarth (1971). Raswn and Haynknwn (1977). and Van Arsdel (1963) review drying theory as applied to food materials. King (1971) Copyright O 1992 by Mprccl Dekkcr. Inc. 2 WAANANEN. LITCHFIELD. AND OKOS reviews freeredrying of fmds, and Rown (1987) and Simpson (1983-84) review the thmry of wood drying. Fulford (1969) provides a comprehensive review of Soviet research in the drying a m. Novak and Caulman (1975) note that soil physicists and engineers have 'generally ignored each other's literature.' This review attempts to encompass and classify efforts made in all arras of drying related research. Key characteristics of drying models a n discussed including controlling process resistances, internal mechanisms of moisture movement, structural and thermodynamic assumptions, and methods of material property measurement, model solution, and model validation. CONTROLLING RESISTANCES DURING DRYING Typically drying is divided into conslant-rate and falling-rate periods. The drying rate in the former is determined by conditions external to the material k i n g dried including temperature, gas velocity. total pressure, and partial vapor pressure. The controlling resislance may be m i s l e d with the transfer of energy to the solid, or the transfer of mass away from the solid. Mass transfer during the constant-ratc period involves diffusion of w s s r vapor from the material surface through a boundary layer into the drying medium. During the falling-rate period, the drying rate ds-es with time, and the rate of internal nus transfer to the material surface typically controls the pmeess. A falling drying rate may be observed when external nus transfer resistance is eontmlling and the surface vapor pressure of the solid is dec-ing m moisture content dmps. Measurement of sample temperature during drying will help to identify whether s process is controlled by energy ar mass transfer. A sample temperature equal to the wet bulb temperature of the surrounding medium is characteristic of energy transfer control. If the sample renches the dry bulb temperature of the drying medium, mass transfer control is suggested. The importance of internal versus external mass transfer resistance can be inferred from drying studies an samples of different sile (i.e.. varying slab thickness (I) or sphere and cylinder radii (r)). The drying time required to reach a given moisture content will be pmponianal lo I or r for external mass transfer control and proportional to I' or ? for control by internal diffusion. Waananen and Okos (1989) presented procedures for analyzing drying dnls from pnsh cylinders of different sires. Vsceareu. el al. (1974) analyzed the effect of nonisothcml drying conditions on the ~u l t s obtained from samples of different thickness. When he31 transfer effects were considered for sugar beet r m l slabs, the thickness dependence of drying data was consistent with internal nus transfer control. Lilchfield and Okos (1992) CLASSIFICATION OF DRYING MODELS 3 identified internaltransfer wntrol for drying of pasts slabs by varying the velocity of the drying medium and obwwing no change in drying rates. Fulrord, O.D. 1969. A ww<)rol mcerd s w i c l m u a x h on h e d r y i q of.olid..

Acs Symposium Series, Jan 18, 1983

Transactions of the ASAE, 1984

Transactions of the ASAE, 1990

The rate of gaseous SO2 sorption by com was modeled as an insulated cylinder with one end open fo... more The rate of gaseous SO2 sorption by com was modeled as an insulated cylinder with one end open for diffusion. This was chosen to represent the flow of material from the kemel tip cap upward. The diffusion coefficient for SO2 was found to be independent of vapor pressure and moisture content (above 20%) and had an Arrhenius activation energy of 30.9 kJ-mol"^. At 14° C the diffusion coefficient was 1.88x10""^ cm^-s"^. Sulfur dioxide equilibrium isotherms for the whole kernels were independent of moisture content over the range of 15% to 38% m.c. (w.b.) and were modeled by a second-order polynomial in temperature and vapor pressure. The germ was found to hold 3 times more SO2 (38,000 ppm) and the hulls 50% more SO2 (20,(X)0 ppm) than the endosperm at equilibrium for conditions of 760 mm/Hg SO2, 25° C, and 30% (w.b.) com moisture content. LITERATURE REVIEW Sulfur dioxide has been used in the steeping of com during the wet milling process to control fermentation, to soften the kemel for grinding, to facilitate disintegration of the protein matrix around the starch granules, and to remove solubles from the germ. Fan et al. (1965) found that the uptake of the sulfurous acid (H2SO3) could be modeled using Pick's second law equation with a Article has been reviewed and approved for publication by the Food and Process Engineering Inst, of ASAE.

Transactions of the ASAE, 1988

F AILURE properties for kernels of one hybrid of corn were experimentally determined. Uniaxial co... more F AILURE properties for kernels of one hybrid of corn were experimentally determined. Uniaxial compressive tests of core specimens were performed at moisture levels of 9.7, 14, 17, 21 an 26% dry basis (db), at each of the temperature levels of 25, 55, 85 and 100°C. Failure stress and the slope of the linear portion of the stress-strain curve decreased with an increase in kernel moisture content and temperature. Failure strain increased as the moisture content and temperature increased. The modulus of toughness decreased with an increase in temperature. For a fixed temperature, the modulus of toughness increased to a maximum at a moisture content of approximately 16% dry basis, and then decreased as the moisture content was further increased.

Journal of Agricultural and Food Chemistry, Jul 1, 1983

A method is presented for the rapid measurement of water-extractable sulfur dioxide in corn. The ... more A method is presented for the rapid measurement of water-extractable sulfur dioxide in corn. The method differs from standard alkali or distillation procedures in that bound SO2 is not measured. Sulfur dioxide in ground corn samples is extracted in a buffer solution and titrated with iodine directly, without filtration. Average standard deviation of the method was 21.3 ppm, as determined from samples containing SOz levels ranging from 162.3 to 1197.0 ppm (weight basis). The method requires no specialized equipment and is suitable for control or research purposes. Direct comparison was made with the distillation procedure of the Manufacturing Confectioners' Alliance and the FMF (Pearson, 1977). Treatment of high-moisture shelled corn with small amounts of sulfur dioxide inhibits microbial growth during low-temperature grain drying (Eckhoff et al., 1980; Van Cawenberge et al., 1982). The procedure, called the trickle-S02 procedure, involves the intermittent injection of SOz into the drying air which is carried into the bin where it acts upon the indigenous microflora. In order t o develop appropriate SOz application procedures and to

Transactions of the ASAE, 1981

Springer eBooks, 1989

This paper presents a comprehensive experimental study of thermal properties of various alkali-ac... more This paper presents a comprehensive experimental study of thermal properties of various alkali-activated binders at ambient and elevated temperatures. The binders were prepared using alkali-activated low calcium fly ash/ground granulated blast-furnace slag at ratios of 100/0, 90/10, 50/50 and 0/100 wt%. These binders can be considered as a composite of solid, water and air. Accordingly, a three-phase model is applied to predict thermal conductivity of the binders at ambient temperature. At elevated temperatures, the Hashin-Shtrikman model is used to estimate the bounds of thermal conductivity for alkali-activated binders containing of fly ash. To validate the above models, a transient plane source measurement technique was applied to measure the thermal conductivity and heat capacity at temperatures ranging from 23 to 600°C. Data generated is then utilised to develop analytical expressions for estimating thermal properties as a function of temperature. The simplified relationships can be used for estimating the fire resistance of structural elements made from alkali-activated cementitious materials.

Transactions of the ASAE, 1981

Transactions of the ASAE, 1985

M ORE ethanol can be produced from whole-plant corn silage than from the grain portion alone. The... more M ORE ethanol can be produced from whole-plant corn silage than from the grain portion alone. The conventional ensilement process involves conversion of soluble carbohydrates to organic acids. Preservation of corn silage sugars with sulfur dioxide (S0 2) was studied using S0 2 dosage levels between 0.0% and 3.0% (% weight/weight), and storage temperatures between 2°C and 32°C. S0 2 dosages of 0.3% and higher were sufficient to prevent microbial growth in silage during 3 to 6 months storage in culture tubes at these temperatures. A dosage of 0.6% was required to preserve silage over 8 months in larger bags at room temperatures. The calorific value of the remaining material increased during conventional ensilement. The structural components of corn silage were not noticeably hydrolysed by 1.5% S0 2 during 8 months of storage.

Springer eBooks, 1998

A model has been developed to predict the moisture and stress profiles in shrinking biopolymers d... more A model has been developed to predict the moisture and stress profiles in shrinking biopolymers during drying. The shrinkage is expressed in the form of a non-equilibrium deformation viscosity, a property that is inherently dependent on the glass transition temperature (T a) of the matrix and on the temperature of drying (T). The difference between these temperatures, i.e. T – T g, controls the rate at which shrinkage occurs during drying.

CRC Press eBooks, Oct 19, 2010

Transactions of the ASAE, 1980

T HREE thermal storage media; water, saturated soil, rock and phase change materials, were tested... more T HREE thermal storage media; water, saturated soil, rock and phase change materials, were tested to determine their feasibility as a media for a thermal storage to be used for grain drying. The thermal effectiveness of phase change material, rock and saturated soil was found to be 0.79, 0.38 and 0.31, respectively. A dimensionless thermal storage parameter is derived to aid in comparing and designing thermal storage devices.

Transactions of the ASAE, 1981

L OW-TEMPERATURE, in-bin wheat drying has been studied through use of computer simulation and on-... more L OW-TEMPERATURE, in-bin wheat drying has been studied through use of computer simulation and on-farm drying experiments involving in-bin drying with unheated and solar heated air. The simulation used is based on mathematical models which define moisture and heat transfers. A GASP IV computer program simulates drying of a bin of grain by thin-layers in discrete time steps by simultaneous solution of a set of four nonlinear equations. Experimentally obtained drying data were used to validate the simulations. The simulations predicted moisture contents for most observations within 1 percent for the solar heated drying case and within 2 percent for the natural air drying case. Analyses indicate that slight variations in airflow and air moisture content appreciably affect drying.

Transactions of the ASAE, 1983

U NIAXIAL tension tests at constant rates of elongation (0.02, 0.05, 0.1 and 0.2/min) were used t... more U NIAXIAL tension tests at constant rates of elongation (0.02, 0.05, 0.1 and 0.2/min) were used to determine the relaxation behavior for moisture and temperature equilibrated specimens of extruded durum semolina. Moisture contents ranged from 0.12 to 0.25 dry basis and temperatures 42 to 58 °C. Linear viscoelastic, thermo-and hydro-rheologically simple behavior were validated for experimental conditions. Data reduced for time-temperature and time-moisture equivalence was fitted to Maxwell models and used to express behavior over extended time scale. Expressions determined for the temperature and moisture shift factors using constant strain rate data were used to reduce the failure stresses with good results. The scatter of failure points about the reduced line had a standard deviation of 0.3 logarithmic units.

Annals of the New York Academy of Sciences, May 1, 1990

INTRODUCTION AND THEORETICAL CONSIDERATIONS Conclusions of previous investigations have led us to... more INTRODUCTION AND THEORETICAL CONSIDERATIONS Conclusions of previous investigations have led us to focus on Pichia stipitis as a yeast with high potential for producing ethanol from xylose-rich, wood-processing wastes. l-S Given 150 giL xylose in complex medium, strain Y-7124 functions optimally at 25-26°C and pH 4-7 to accumulate 56 giL ethanol with negligible xylitol by-production. 6 In a past report, we cited the need for an optimal bioreactor system; toward this end, we put oxygen uptake, growth, and death kinetics into mathematical form.) The present report builds on our previous work as the pathways and stoichiometry of xylose metabolism are examined and models of xylose uptake and ethanol production are identified. Yeasts begin xylose metabolism with the sequence, xylose-+ xylitol-+ xylulose-+ xylulose 5-phosphate. 8 In balanced form, this sequence is:

A literature review has been completed and pertinent data from previous food drying studies, info... more A literature review has been completed and pertinent data from previous food drying studies, information on available and developing sensors for control and monitoring of dryers, production rates and values of various food products has been obtained. This information was used to select the food products to be studied. The areas reviewed in detail include (a) Fundamental Drying Studies, (b) Quality of Foods, (c) Viscoelastic Properties of Grains and Food, (d) Thermal Properties of Porous Foods, (e) Energy Efficient Dryer Designs and (f) Density Independent Moisture Measurement.