CIRCUIT - Grup de Recerca en Circuits i Sistemes de Comunicació
http://hdl.handle.net/2117/3801
Thu, 30 Mar 2017 18:54:40 GMT2017-03-30T18:54:40ZAnharmonicity in multifrequency atomic force microscopy
http://hdl.handle.net/2117/102988
Anharmonicity in multifrequency atomic force microscopy
Santos Hernandez, Sergio; Barcons Xixons, Víctor
In multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.
Tue, 28 Mar 2017 15:50:13 GMThttp://hdl.handle.net/2117/1029882017-03-28T15:50:13ZSantos Hernandez, SergioBarcons Xixons, VíctorIn multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.Deconstructing the governing dissipative phenomena in the nanoscale
http://hdl.handle.net/2117/102982
Deconstructing the governing dissipative phenomena in the nanoscale
Santos Hernandez, Sergio; Amadei, Carlo Alberto; Tang, Tzu-Chieh; Barcons Xixons, Víctor; Chiesa, Matteo
An expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.
Tue, 28 Mar 2017 15:04:11 GMThttp://hdl.handle.net/2117/1029822017-03-28T15:04:11ZSantos Hernandez, SergioAmadei, Carlo AlbertoTang, Tzu-ChiehBarcons Xixons, VíctorChiesa, MatteoAn expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.Wearing a single DNA molecule with an AFM tip
http://hdl.handle.net/2117/102976
Wearing a single DNA molecule with an AFM tip
Santos Hernandez, Sergio; Barcons Xixons, Víctor; Font Teixidó, Josep; Thomson, Neil H.
While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.
Tue, 28 Mar 2017 14:10:14 GMThttp://hdl.handle.net/2117/1029762017-03-28T14:10:14ZSantos Hernandez, SergioBarcons Xixons, VíctorFont Teixidó, JosepThomson, Neil H.While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
http://hdl.handle.net/2117/101717
A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
Palà Schönwälder, Pere; Miró Sans, Joan Maria
The problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.
Tue, 28 Feb 2017 15:34:46 GMThttp://hdl.handle.net/2117/1017172017-02-28T15:34:46ZPalà Schönwälder, PereMiró Sans, Joan MariaThe problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.An explicit method for modeling lossy and dispersive transmission lines
http://hdl.handle.net/2117/100927
An explicit method for modeling lossy and dispersive transmission lines
Palà Schönwälder, Pere; Miró Sans, Joan Maria
In this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.
Mon, 13 Feb 2017 14:26:09 GMThttp://hdl.handle.net/2117/1009272017-02-13T14:26:09ZPalà Schönwälder, PereMiró Sans, Joan MariaIn this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
http://hdl.handle.net/2117/98495
A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
Bonet Dalmau, Jordi; Palà Schönwälder, Pere
We present a direct method for the steady-state and stability
analysis of autonomous circuits with transmission lines and generic non-
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re-
spect to the samples of the unknowns is described. Without any modifica-
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.
Fri, 16 Dec 2016 16:30:04 GMThttp://hdl.handle.net/2117/984952016-12-16T16:30:04ZBonet Dalmau, JordiPalà Schönwälder, PereWe present a direct method for the steady-state and stability
analysis of autonomous circuits with transmission lines and generic non-
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re-
spect to the samples of the unknowns is described. Without any modifica-
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.Stability analysis of periodic solutions in non-linear autonomous circuits: a discrete time approach
http://hdl.handle.net/2117/97804
Stability analysis of periodic solutions in non-linear autonomous circuits: a discrete time approach
Miró Sans, Joan Maria; Palà Schönwälder, Pere; Mas Casals, Orestes Miquel
Steady-state methods have been devised to compute periodic wave-forms without having to integrate the
autonomous circuit equations until the transients die out. Stability analysis of the computed solutions is the
next topic to be addressed by a steady state circuit simulator. Shooting methods based on Newton's iteration
are expensive in terms of computing time, because each iteration step requires integration of the variational
equation, but directly provide information on the stability of the final On the other hand, when
making use of harmonic balance methods, the stability of the computed solutions is typically investigated
from a continuation point of view.4 Recently a discrete time approach (DTA) was proposed for the analysis
and optimization of non-linear autonomous circuits.' This letter describes how the stability of the
computed periodic wave-forms may be easily determined (I posteriori with no modification to the DTA
solution method.
Mon, 05 Dec 2016 16:39:28 GMThttp://hdl.handle.net/2117/978042016-12-05T16:39:28ZMiró Sans, Joan MariaPalà Schönwälder, PereMas Casals, Orestes MiquelSteady-state methods have been devised to compute periodic wave-forms without having to integrate the
autonomous circuit equations until the transients die out. Stability analysis of the computed solutions is the
next topic to be addressed by a steady state circuit simulator. Shooting methods based on Newton's iteration
are expensive in terms of computing time, because each iteration step requires integration of the variational
equation, but directly provide information on the stability of the final On the other hand, when
making use of harmonic balance methods, the stability of the computed solutions is typically investigated
from a continuation point of view.4 Recently a discrete time approach (DTA) was proposed for the analysis
and optimization of non-linear autonomous circuits.' This letter describes how the stability of the
computed periodic wave-forms may be easily determined (I posteriori with no modification to the DTA
solution method.The Mendeleev-Meyer force project
http://hdl.handle.net/2117/96683
The Mendeleev-Meyer force project
Santos Hernández, Sergio; Lai, Chia-Yun; Amadei, Carlo Alberto; Gadelrab, Karim Raafat; Tang, Tzu-Chieh; Verdaguer Prats, Albert; Barcons Xixons, Víctor; Font Teixidó, Josep; Colchero, Jaimer; Chiesa, Matteo
Here we present the Mendeleev–Meyer Force Project which aims at tabulating all materials and substances in a fashion similar to the periodic table. The goal is to group and tabulate substances using nanoscale force footprints rather than atomic number or electronic configuration as in the periodic table. The process is divided into: (1) acquiring nanoscale force data from materials, (2) parameterizing the raw data into standardized input features to generate a library, (3) feeding the standardized library into an algorithm to generate, enhance or exploit a model to identify a material or property. We propose producing databases mimicking the Materials Genome Initiative, the Medical Literature Analysis and Retrieval System Online (MEDLARS) or the PRoteomics IDEntifications database (PRIDE) and making these searchable online via search engines mimicking Pubmed or the PRIDE web interface. A prototype exploiting deep learning algorithms, i.e. multilayer neural networks, is presented.
Tue, 15 Nov 2016 16:04:39 GMThttp://hdl.handle.net/2117/966832016-11-15T16:04:39ZSantos Hernández, SergioLai, Chia-YunAmadei, Carlo AlbertoGadelrab, Karim RaafatTang, Tzu-ChiehVerdaguer Prats, AlbertBarcons Xixons, VíctorFont Teixidó, JosepColchero, JaimerChiesa, MatteoHere we present the Mendeleev–Meyer Force Project which aims at tabulating all materials and substances in a fashion similar to the periodic table. The goal is to group and tabulate substances using nanoscale force footprints rather than atomic number or electronic configuration as in the periodic table. The process is divided into: (1) acquiring nanoscale force data from materials, (2) parameterizing the raw data into standardized input features to generate a library, (3) feeding the standardized library into an algorithm to generate, enhance or exploit a model to identify a material or property. We propose producing databases mimicking the Materials Genome Initiative, the Medical Literature Analysis and Retrieval System Online (MEDLARS) or the PRoteomics IDEntifications database (PRIDE) and making these searchable online via search engines mimicking Pubmed or the PRIDE web interface. A prototype exploiting deep learning algorithms, i.e. multilayer neural networks, is presented.Circuitos de capacidades conmutadas. Análisis frecuencial por ordenador
http://hdl.handle.net/2117/87859
Circuitos de capacidades conmutadas. Análisis frecuencial por ordenador
Puerta Notario, Antonio; Miró Sans, Joan M.; Sanz Postils, Margarita
El interés fundamental de los circuitos de condensadores conmutados radica en su aplicación a la realización de filtros monolíticos y de otros bloques funcionales para su tratamiento analógico de la señal. Resulta del máximo interés disponer de métodos de análisis y programas de simulación que permitan evaluar los resultados de las diferentes técnicas de síntesis.
En este artículo se presenta un programa de simulación, basado en los métodos de análisis desarrollados por los autores, que permite la obtención de las funciones de transferencia y de la respuesta frecuencial de circuitos SC. Para su realización se requiere un soporte informático reducido, lo que, junto con la facilidad de utilización, son sus características más sobresalientes.
Thu, 09 Jun 2016 15:57:23 GMThttp://hdl.handle.net/2117/878592016-06-09T15:57:23ZPuerta Notario, AntonioMiró Sans, Joan M.Sanz Postils, MargaritaEl interés fundamental de los circuitos de condensadores conmutados radica en su aplicación a la realización de filtros monolíticos y de otros bloques funcionales para su tratamiento analógico de la señal. Resulta del máximo interés disponer de métodos de análisis y programas de simulación que permitan evaluar los resultados de las diferentes técnicas de síntesis.
En este artículo se presenta un programa de simulación, basado en los métodos de análisis desarrollados por los autores, que permite la obtención de las funciones de transferencia y de la respuesta frecuencial de circuitos SC. Para su realización se requiere un soporte informático reducido, lo que, junto con la facilidad de utilización, son sus características más sobresalientes.Dynamic geometry based on geometric constraints
http://hdl.handle.net/2117/87511
Dynamic geometry based on geometric constraints
Freixas Boleda, Marc; Joan Arinyo, Robert; Soto Riera, Antoni; Vila Marta, Sebastià
Dynamic geometry systems are tools for geometric visualization. They allow the user to define geometric elements, establish relationships between them and explore the dynamic behavior of the remaining geometric elements when one of them is moved. The main problem in dynamic geometry systems is the ambiguity that arises from operations which lead to more than one possible solution. While the user is defining the geometric construction, he is responsible to resolve these ambiguities. However, when the user is dragging a geometric element, the system is responsible to choose the intended solution, that is, the same solution that the user would select if we could ask him again. Most dynamic geometry systems deal with this problem in such a way that the solution selection method leads to a fixed dynamic behavior of the system. This is specially annoying when this behavior is not the one the user intended. In this work we propose an architecture for dynamic geometry systems built upon a set of functional units which will allow to apply some well known results from the Geometric Constraint Solving field. A functional unit called emph{filter} will provide the user with tools to unambiguously capture the expected dynamic behavior of a given geometric problem.
Tue, 31 May 2016 07:28:25 GMThttp://hdl.handle.net/2117/875112016-05-31T07:28:25ZFreixas Boleda, MarcJoan Arinyo, RobertSoto Riera, AntoniVila Marta, SebastiàDynamic geometry systems are tools for geometric visualization. They allow the user to define geometric elements, establish relationships between them and explore the dynamic behavior of the remaining geometric elements when one of them is moved. The main problem in dynamic geometry systems is the ambiguity that arises from operations which lead to more than one possible solution. While the user is defining the geometric construction, he is responsible to resolve these ambiguities. However, when the user is dragging a geometric element, the system is responsible to choose the intended solution, that is, the same solution that the user would select if we could ask him again. Most dynamic geometry systems deal with this problem in such a way that the solution selection method leads to a fixed dynamic behavior of the system. This is specially annoying when this behavior is not the one the user intended. In this work we propose an architecture for dynamic geometry systems built upon a set of functional units which will allow to apply some well known results from the Geometric Constraint Solving field. A functional unit called emph{filter} will provide the user with tools to unambiguously capture the expected dynamic behavior of a given geometric problem.