D. Micheli - Academia.edu (original) (raw)
Papers by D. Micheli
A B S T R A C T We investigated how the electrical contact of carbon foam with metallic surface c... more A B S T R A C T We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.
Progress In Electromagnetics Research B, 2012
Reverberation chamber (RC) test facility allows to determine the absorbing cross section (ACS) of... more Reverberation chamber (RC) test facility allows to determine the absorbing cross section (ACS) of lossy materials under a random field excitation. Measurements are based on the quality factor variation produced by the sample under test presence with respect to the empty chamber condition. Simulations are based on the representation of the RC electromagnetic field by means of a random plane wave superposition. A finite-difference time-domain code is used to compute the material absorbed power and to recover a numerical ACS. The method sensibility is stressed by application to small size samples. Comparison between numerical and experimental data reveals a satisfactory agreement. Results for different materials are presented in the paper: soft foam absorbers, carbon foam sheets, and carbon/carbon sheets.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
Microwave absorbing and shielding material tiles are proposed for improving the stealthness capab... more Microwave absorbing and shielding material tiles are proposed for improving the stealthness capability of nanosatellites, by using composite materials consisting in polymeric matrix filled by carbon nanotubes. The electric permittivity of the composite nanostructured materials is measured and discussed, and the data allow the modeling algorithm to design the microwave absorbing and shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and minimization of the electromagnetic reflection coefficient. The proposed structure is experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
This research is focused on simulation, manufacturing and measuring of shell radar absorbing stru... more This research is focused on simulation, manufacturing and measuring of shell radar absorbing structure of missiles. The novelty of the work is the study of a curved radar absorbing structure. The enhancement of electromagnetic wave absorption is obtained by using carbon nanotube filler in different weight ratio with respect to the epoxy-resin adopted in shell manufacturing. The structural resistance is granted by the use of conventional fiberglass. A radar absorbing prototype of an half shell, having the section of 15 cm radius has been built and characterized. The thickness of the shell is around 6.5 mm and is made of two different loaded layers. The measurements of electromagnetic reflection coefficient has been performed for two different incidence angles of 0° and 45°. The reflection coefficient show values down to -18 dB around 3 GHz and -10 dB around 11 GHz for 0° incidence angle, and -6 dB around 3 GHz and -10 dB around 12 GHz for 45° incidence angle. An electromagnetic simulation of a flat structure having the same layering configuration of the shell shows values of reflection coefficient very similar to the measured one for 0° incidence angle.
The present research is focused on multi-layered radar absorbing structures useful in low observa... more The present research is focused on multi-layered radar absorbing structures useful in low observable unmanned aircraft systems in the frequency range 2-18 GHz. A significant enhancement of the electromagnetic absorption is obtained through the use of different kind of carbon nanomaterials uniformly dispersed within epoxy matrix and fiberglass.
Video on YOUTUBE https://www.youtube.com/watch?v=-Zy9O-qq0Ck
Engineering, 2012
In recent years there has been increasing concern about the possible consequences on human health... more In recent years there has been increasing concern about the possible consequences on human health from exposure to RF fields produced by wireless telecommunication technologies. In this work the coupling between carbon foam and composite materials made of carbon nanotubes and epoxy-resin allows to build a material able to absorb the electromagnetic field thus reducing its intensity in the environment where the mitigation of electromagnetic field is required. The Frequency range considered is 2 GHz -3 GHz which is the most common frequency band used in wireless network and microwave oven too. Two different kind of heterogeneous materials are designed, one is a layered radar absorbing material made exclusively of epoxy resin and carbon nanotube in different weight percentage, the others are porous carbon foam where the pores are supposed be filled with carbon nanotubes and epoxy-resin. Both type of materials show interesting absorption properties reaching peak of reflection coefficient between -15 dB and -45 dB for a normally incident plane wave.
The present research shows a powerful method for the design of multi-layered radar absorbing mate... more The present research shows a powerful method for the design of multi-layered radar absorbing materials useful in low observable and stealth manned or unmanned aircraft systems. The imitation of a desired behavior of the reflection coefficient allows to modeling the optimal arrangement of each layer in terms of material and thickness. A significant enhancement of the electromagnetic absorption is obtained through the use of different kind of carbon nanomaterials uniformly dispersed within an epoxy matrix. Several carbon-based nanocomposite materials are dielectrically characterized in the frequency range 2-18 GHz, and an evolutionary algorithm is used to run the mathematical model in order to find out the optimal solution in terms of the multi-layer composition. Interesting applications of the proposed design method are suggested other types of military targets in the marine and terrestrial scenario where the reduction of the radar observability is mandatory.
Carbon, 2014
ABSTRACT We investigated how the electrical contact of carbon foam with metallic surface can redu... more ABSTRACT We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.
Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics, Parts A and B, 2006
The present work presents a novel approach for the optimised design of small gas turbine combusto... more The present work presents a novel approach for the optimised design of small gas turbine combustors, that integrates a 0-D code. CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the 0-D code is a baseline design of the combustor, ...
Journal of Thermal Science, 2009
The present work presents an approach for the optimized design of small gas turbine combustors, t... more The present work presents an approach for the optimized design of small gas turbine combustors, that integrates a 0-D code, CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the 0-D code is a baseline design of the combustor, given the required fuel characteristics, the basic geometry (tubular or annular) and the combustion concept (i.e. lean premixed primary zone or diffusive processes). For the optimization of the baseline design a simplified parametric CAD/mesher model is then defined and submitted to a CFD code. Free parameters of the optimization process are position and size of the liner holes arrays, their total area and the shape of the exit duct, while different objectives are the minimization of NO x emissions, pressure losses and combustor exit Pattern Factor. A 3D simulation of the optimized geometry completes the design procedure. As a first demonstrative example, the integrated design process was applied to a tubular combustion chamber with a lean premixed primary zone for a recuperative methane-fuelled small gas turbine of the 100 kW class.
American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI, 2002
ABSTRACT The present paper deals with several problems arising in the stabilisation of surge in c... more ABSTRACT The present paper deals with several problems arising in the stabilisation of surge in compression systems. From a theoretical standpoint the system requires a high gain type controller to be stabilised. On the other hand, the real system is affected by persistent measurement noise whose negative effect on stability is strongly amplified by the high gain. Therefore, a suitable filtering of the system output is necessarily required. The bandwidth of the filter is subject to opposite constraints: if it is too large it affects the attenuation property; if it is too narrow, the large phase-lag introduced at low frequencies may compromise the system stabilisation, which requires a fast actuator reaction. This paper analyses all these aspects concurring in the stabilisation problem and the consequent trade-off in the control design. The results of experimental and numerical studies are provided with reference to the active control of surge in a multistage centrifugal compressor.
ABSTRACT The first phase of the development of an automatic methodology for the design process of... more ABSTRACT The first phase of the development of an automatic methodology for the design process of small gas turbine recuperators is presented. The different software tools are selected in order to be managed, in a successive step of the research, by means of a design-optimization platform, according to the concept of Multi Disciplinary Optimization (MDO). The methodology has been developed integrating a geometrical parametric model of the heat transfer surfaces, built inside an industrial CAD, a three dimensional meshing tool and a CFD solver. Final objectives of the research will be an optimization process designed to maximize the heat exchange rate and to minimize costs and fluid dynamics losses. The paper deals with the parameterization technique and the numerical model validation.
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2006
ABSTRACT This paper reports the results of an extensive study concerning surge instability in an ... more ABSTRACT This paper reports the results of an extensive study concerning surge instability in an industrial compression system and its dynamic suppression. Both numerical simulations and experiments have been used to analyse the system behaviour under unstable operating conditions and to compare different control devices for surge suppression. First, the characterization of surge is performed over the whole unstable operating range of a compression system based on a four-stage centrifugal compressor. The unsteady energy associated with the surge cycle is employed as an index of the surge intensity to allow for a quantitative approach to the problem. Subsequently, the behaviour and performance of a passive-type control system and of an active-type one are analysed and compared. The former consists of an innovative device based on an oscillating water column, whereas the latter is a high-gain type of feedback device implemented digitally. Experimental data show that the proposed passive device is effective not only in inhibiting surge development, but also in suppressing fully developed instability. The active device turns out to be more effective than the passive one, but under severe conditions it may fail because of actuator limitations and noise amplification. Finally, the relative merits and limitations of the two control systems are discussed with reference to their effectiveness range, flexibility, steady-state performance, installation, maintenance, and costs.
Pharmacological Research, 1992
Pharmacological Research, 1989
Journal of Turbomachinery, 2002
ABSTRACT The present paper considers the suppression of surge instability in compression systems ... more ABSTRACT The present paper considers the suppression of surge instability in compression systems by means of active control strategies based on a high-gain approach. A proper sensor-actuator pair and a proportional controller are selected which, in theory, guarantee system stabilization in any operating condition for a sufficiently high value of the gain. Furthermore, an adaptive control strategy is introduced which allows the system to automatically detect a suitable value of the gain needed for stabilization, without requiring any knowledge of the compressor and plant characteristics. The control device is employed to suppress surge in an industrial compression system based on a four-stage centrifugal blower. An extensive experimental investigation has been performed in order to test the control effectiveness in various operating points on the stalled branch of the compressor characteristic and at different compressor speeds. On one hand the experimental results confirm the good performance of the proposed control strategy, on the other they show some inherent difficulties in stabilizing the system at high compressor speeds due to the measurement disturbances and to the limited operation speed of the actuator.
Journal of Turbomachinery, 1995
The paper presents the results of an experimental investigation on a four-stage centrifugal blowe... more The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometric configurations. Actually, the test plant allows one to change the turbomachinery characteristics assembling one, two, three, or four stages and three different types
Journal of Pharmacy and Pharmacology, 1993
The time-course of dihydropyridine receptor occupancy by lacidipine and its relationship with pha... more The time-course of dihydropyridine receptor occupancy by lacidipine and its relationship with pharmacological activity has been studied in spontaneously hypertensive rat (SHR), as measured by the inhibition of specific (+)-[3H]PN 200-110 binding in-vivo. After oral administration of doses active in reducing blood pressure, lacidipine did not show tissue target differences in respect to binding sites labelled by (+)-[3H]PN 200-110 in cerebral cortex, heart, ileum, bladder and thoracic aorta. The relative occupancy of receptors in heart 60 min after oral administration of 1 mg kg-1 lacidipine was 75%. After 12 h, when lacidipine was still effective in reducing blood pressure in SHR, a low (15%) but detectable proportion of receptors was still occupied by the drug. The percentage decrease of blood pressure was linear with the percentage of receptor occupancy obtained by different doses of lacidipine; that is, there was a close correspondence between ED25 for decrease in blood pressure (0.33 mg kg-1) and ED25 for inhibition of (+)-[3H]PN 200-110 specific binding in the heart (0.36 mg kg-1). The long-lasting effect of lacidipine on blood pressure might be explained by its selective interaction with dihydropyridine binding sites labelled in-vivo by (+)-[3H]PN 200-110.
A B S T R A C T We investigated how the electrical contact of carbon foam with metallic surface c... more A B S T R A C T We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.
Progress In Electromagnetics Research B, 2012
Reverberation chamber (RC) test facility allows to determine the absorbing cross section (ACS) of... more Reverberation chamber (RC) test facility allows to determine the absorbing cross section (ACS) of lossy materials under a random field excitation. Measurements are based on the quality factor variation produced by the sample under test presence with respect to the empty chamber condition. Simulations are based on the representation of the RC electromagnetic field by means of a random plane wave superposition. A finite-difference time-domain code is used to compute the material absorbed power and to recover a numerical ACS. The method sensibility is stressed by application to small size samples. Comparison between numerical and experimental data reveals a satisfactory agreement. Results for different materials are presented in the paper: soft foam absorbers, carbon foam sheets, and carbon/carbon sheets.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
Microwave absorbing and shielding material tiles are proposed for improving the stealthness capab... more Microwave absorbing and shielding material tiles are proposed for improving the stealthness capability of nanosatellites, by using composite materials consisting in polymeric matrix filled by carbon nanotubes. The electric permittivity of the composite nanostructured materials is measured and discussed, and the data allow the modeling algorithm to design the microwave absorbing and shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and minimization of the electromagnetic reflection coefficient. The proposed structure is experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
This research is focused on simulation, manufacturing and measuring of shell radar absorbing stru... more This research is focused on simulation, manufacturing and measuring of shell radar absorbing structure of missiles. The novelty of the work is the study of a curved radar absorbing structure. The enhancement of electromagnetic wave absorption is obtained by using carbon nanotube filler in different weight ratio with respect to the epoxy-resin adopted in shell manufacturing. The structural resistance is granted by the use of conventional fiberglass. A radar absorbing prototype of an half shell, having the section of 15 cm radius has been built and characterized. The thickness of the shell is around 6.5 mm and is made of two different loaded layers. The measurements of electromagnetic reflection coefficient has been performed for two different incidence angles of 0° and 45°. The reflection coefficient show values down to -18 dB around 3 GHz and -10 dB around 11 GHz for 0° incidence angle, and -6 dB around 3 GHz and -10 dB around 12 GHz for 45° incidence angle. An electromagnetic simulation of a flat structure having the same layering configuration of the shell shows values of reflection coefficient very similar to the measured one for 0° incidence angle.
The present research is focused on multi-layered radar absorbing structures useful in low observa... more The present research is focused on multi-layered radar absorbing structures useful in low observable unmanned aircraft systems in the frequency range 2-18 GHz. A significant enhancement of the electromagnetic absorption is obtained through the use of different kind of carbon nanomaterials uniformly dispersed within epoxy matrix and fiberglass.
Video on YOUTUBE https://www.youtube.com/watch?v=-Zy9O-qq0Ck
Engineering, 2012
In recent years there has been increasing concern about the possible consequences on human health... more In recent years there has been increasing concern about the possible consequences on human health from exposure to RF fields produced by wireless telecommunication technologies. In this work the coupling between carbon foam and composite materials made of carbon nanotubes and epoxy-resin allows to build a material able to absorb the electromagnetic field thus reducing its intensity in the environment where the mitigation of electromagnetic field is required. The Frequency range considered is 2 GHz -3 GHz which is the most common frequency band used in wireless network and microwave oven too. Two different kind of heterogeneous materials are designed, one is a layered radar absorbing material made exclusively of epoxy resin and carbon nanotube in different weight percentage, the others are porous carbon foam where the pores are supposed be filled with carbon nanotubes and epoxy-resin. Both type of materials show interesting absorption properties reaching peak of reflection coefficient between -15 dB and -45 dB for a normally incident plane wave.
The present research shows a powerful method for the design of multi-layered radar absorbing mate... more The present research shows a powerful method for the design of multi-layered radar absorbing materials useful in low observable and stealth manned or unmanned aircraft systems. The imitation of a desired behavior of the reflection coefficient allows to modeling the optimal arrangement of each layer in terms of material and thickness. A significant enhancement of the electromagnetic absorption is obtained through the use of different kind of carbon nanomaterials uniformly dispersed within an epoxy matrix. Several carbon-based nanocomposite materials are dielectrically characterized in the frequency range 2-18 GHz, and an evolutionary algorithm is used to run the mathematical model in order to find out the optimal solution in terms of the multi-layer composition. Interesting applications of the proposed design method are suggested other types of military targets in the marine and terrestrial scenario where the reduction of the radar observability is mandatory.
Carbon, 2014
ABSTRACT We investigated how the electrical contact of carbon foam with metallic surface can redu... more ABSTRACT We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.
Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics, Parts A and B, 2006
The present work presents a novel approach for the optimised design of small gas turbine combusto... more The present work presents a novel approach for the optimised design of small gas turbine combustors, that integrates a 0-D code. CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the 0-D code is a baseline design of the combustor, ...
Journal of Thermal Science, 2009
The present work presents an approach for the optimized design of small gas turbine combustors, t... more The present work presents an approach for the optimized design of small gas turbine combustors, that integrates a 0-D code, CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the 0-D code is a baseline design of the combustor, given the required fuel characteristics, the basic geometry (tubular or annular) and the combustion concept (i.e. lean premixed primary zone or diffusive processes). For the optimization of the baseline design a simplified parametric CAD/mesher model is then defined and submitted to a CFD code. Free parameters of the optimization process are position and size of the liner holes arrays, their total area and the shape of the exit duct, while different objectives are the minimization of NO x emissions, pressure losses and combustor exit Pattern Factor. A 3D simulation of the optimized geometry completes the design procedure. As a first demonstrative example, the integrated design process was applied to a tubular combustion chamber with a lean premixed primary zone for a recuperative methane-fuelled small gas turbine of the 100 kW class.
American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI, 2002
ABSTRACT The present paper deals with several problems arising in the stabilisation of surge in c... more ABSTRACT The present paper deals with several problems arising in the stabilisation of surge in compression systems. From a theoretical standpoint the system requires a high gain type controller to be stabilised. On the other hand, the real system is affected by persistent measurement noise whose negative effect on stability is strongly amplified by the high gain. Therefore, a suitable filtering of the system output is necessarily required. The bandwidth of the filter is subject to opposite constraints: if it is too large it affects the attenuation property; if it is too narrow, the large phase-lag introduced at low frequencies may compromise the system stabilisation, which requires a fast actuator reaction. This paper analyses all these aspects concurring in the stabilisation problem and the consequent trade-off in the control design. The results of experimental and numerical studies are provided with reference to the active control of surge in a multistage centrifugal compressor.
ABSTRACT The first phase of the development of an automatic methodology for the design process of... more ABSTRACT The first phase of the development of an automatic methodology for the design process of small gas turbine recuperators is presented. The different software tools are selected in order to be managed, in a successive step of the research, by means of a design-optimization platform, according to the concept of Multi Disciplinary Optimization (MDO). The methodology has been developed integrating a geometrical parametric model of the heat transfer surfaces, built inside an industrial CAD, a three dimensional meshing tool and a CFD solver. Final objectives of the research will be an optimization process designed to maximize the heat exchange rate and to minimize costs and fluid dynamics losses. The paper deals with the parameterization technique and the numerical model validation.
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2006
ABSTRACT This paper reports the results of an extensive study concerning surge instability in an ... more ABSTRACT This paper reports the results of an extensive study concerning surge instability in an industrial compression system and its dynamic suppression. Both numerical simulations and experiments have been used to analyse the system behaviour under unstable operating conditions and to compare different control devices for surge suppression. First, the characterization of surge is performed over the whole unstable operating range of a compression system based on a four-stage centrifugal compressor. The unsteady energy associated with the surge cycle is employed as an index of the surge intensity to allow for a quantitative approach to the problem. Subsequently, the behaviour and performance of a passive-type control system and of an active-type one are analysed and compared. The former consists of an innovative device based on an oscillating water column, whereas the latter is a high-gain type of feedback device implemented digitally. Experimental data show that the proposed passive device is effective not only in inhibiting surge development, but also in suppressing fully developed instability. The active device turns out to be more effective than the passive one, but under severe conditions it may fail because of actuator limitations and noise amplification. Finally, the relative merits and limitations of the two control systems are discussed with reference to their effectiveness range, flexibility, steady-state performance, installation, maintenance, and costs.
Pharmacological Research, 1992
Pharmacological Research, 1989
Journal of Turbomachinery, 2002
ABSTRACT The present paper considers the suppression of surge instability in compression systems ... more ABSTRACT The present paper considers the suppression of surge instability in compression systems by means of active control strategies based on a high-gain approach. A proper sensor-actuator pair and a proportional controller are selected which, in theory, guarantee system stabilization in any operating condition for a sufficiently high value of the gain. Furthermore, an adaptive control strategy is introduced which allows the system to automatically detect a suitable value of the gain needed for stabilization, without requiring any knowledge of the compressor and plant characteristics. The control device is employed to suppress surge in an industrial compression system based on a four-stage centrifugal blower. An extensive experimental investigation has been performed in order to test the control effectiveness in various operating points on the stalled branch of the compressor characteristic and at different compressor speeds. On one hand the experimental results confirm the good performance of the proposed control strategy, on the other they show some inherent difficulties in stabilizing the system at high compressor speeds due to the measurement disturbances and to the limited operation speed of the actuator.
Journal of Turbomachinery, 1995
The paper presents the results of an experimental investigation on a four-stage centrifugal blowe... more The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometric configurations. Actually, the test plant allows one to change the turbomachinery characteristics assembling one, two, three, or four stages and three different types
Journal of Pharmacy and Pharmacology, 1993
The time-course of dihydropyridine receptor occupancy by lacidipine and its relationship with pha... more The time-course of dihydropyridine receptor occupancy by lacidipine and its relationship with pharmacological activity has been studied in spontaneously hypertensive rat (SHR), as measured by the inhibition of specific (+)-[3H]PN 200-110 binding in-vivo. After oral administration of doses active in reducing blood pressure, lacidipine did not show tissue target differences in respect to binding sites labelled by (+)-[3H]PN 200-110 in cerebral cortex, heart, ileum, bladder and thoracic aorta. The relative occupancy of receptors in heart 60 min after oral administration of 1 mg kg-1 lacidipine was 75%. After 12 h, when lacidipine was still effective in reducing blood pressure in SHR, a low (15%) but detectable proportion of receptors was still occupied by the drug. The percentage decrease of blood pressure was linear with the percentage of receptor occupancy obtained by different doses of lacidipine; that is, there was a close correspondence between ED25 for decrease in blood pressure (0.33 mg kg-1) and ED25 for inhibition of (+)-[3H]PN 200-110 specific binding in the heart (0.36 mg kg-1). The long-lasting effect of lacidipine on blood pressure might be explained by its selective interaction with dihydropyridine binding sites labelled in-vivo by (+)-[3H]PN 200-110.