Giovanni Tapang - Profile on Academia.edu (original) (raw)
Journal Papers by Giovanni Tapang
Optics Letters, Vol. 39, Issue 7, pp. 2036-2039 (April 2014)
We present a method of reshaping light in three dimensions via phase modulation. The method calcu... more We present a method of reshaping light in three dimensions via phase modulation. The method calculates the target computer generated hologram individually and adds to it an appropriate transfer function to translate the reconstruction to any location in space. We are able to simultaneously generate independently controlled arbitrary patterns at diff erent positions using a single laser beam.
International Journal of Modern Physics C (Accepted)
Co-occurrence language networks based on Bible translations and the Universal Declaration of Huma... more Co-occurrence language networks based on Bible translations and the Universal Declaration of Human Rights (UDHR) translations in different languages were constructed and compared with random text networks. Among the considered network metrics, the network size, N, the normalized betweenness centrality, BC, and the average k -nearest neighbors, knn, were found to be the most preserved across translations. Moreover, similar frequency distributions of co-occurring network motifs were observed for translated texts networks.
International Journal of Modern Physics C, 2010
Word adjacency networks constructed from written works reflect differences in the structure of pr... more Word adjacency networks constructed from written works reflect differences in the structure of prose and poetry. We present a method to disambiguate prose and poetry by analyzing network parameters of word adjacency networks, such as the clustering coefficient, average path length and average degree. We determine the relevant parameters for disambiguation using linear discriminant analysis (LDA) and the effect size criterion. The accuracy of the method is 74.9 ± 2.9% for the training set and 73.7 ± 6.4% for the test set which are greater than the acceptable classifier requirement of 67.3%. This approach is also useful in locating text boundaries within a single article which falls within a window size where the significant change in clustering coefficient is observed. Results indicate that an optimal window size of 75 words can detect the text boundaries.
International Journal of Modern …, 2012
We identify the di®erent styles of texting in Filipino short message service (SMS) texts and anal... more We identify the di®erent styles of texting in Filipino short message service (SMS) texts and analyze the change in unigram and bigram frequencies due to these styles. Style preference vectors for sample texts were calculated and used to identify the style combination used by an average individual. The change in Shannon entropy of the SMS text is explained in light of a coding process.
Proceedings of The National Academy of Sciences, 2003
Numerical investigations of escape panic of confined pedestrians have revealed interesting dynami... more Numerical investigations of escape panic of confined pedestrians have revealed interesting dynamical features such as pedestrian arch formation around an exit, disruptive interference, self-organized queuing, and scale-free behavior. However, these predictions have remained unverified because escape panic experiments with real systems are difficult to perform. For mice escaping out of a water pool, we found that for a critical sampling rate the escape behavior exhibits the predicted features even at short observation times. The mice escaped via an exit in bursts of different sizes that obey exponential and (truncated) power-law distributions depending on exit width. Oversampling or undersampling the mouse escape rate prevents the observation of the predicted features. Real systems are normally subject to unavoidable constraints arising from occupancy rate, pedestrian exhaustion, and nonrigidity of pedestrian bodies. The effect of these constraints on the dynamics of real escape panic is also studied.
International Journal of …, 2012
Complex networks have been proven useful in characterizing written texts. Here, we use networks t... more Complex networks have been proven useful in characterizing written texts. Here, we use networks to probe if there exist a similarity within, and difference across, era as reflected within the poem's structure. In literary history, boundary lines are set to distinguish the change in writing styles through time. We obtain the network parameters and motif frequencies of 845 poems published from 1522 to 1931 and relate this to the writing of the Elizabethan, 17th Century, Augustan, Romantic and Victorian eras. Analysis of the different network parameters shows a significant difference of the Augustan era (1667-1780) with the rest. The network parameters and the convex hull and centroids of the motif frequencies reflect the adjectival sequence pattern of the poems of the Augustan era.
Optics Communications, 2009
We report parallel two-photon photopolymerization of microgear patterns by exposing a photoresist... more We report parallel two-photon photopolymerization of microgear patterns by exposing a photoresist to holographically generated optical vortices. The optical vortices are created by imparting a helical pitch onto the incident light using a programmable lithographic phase mask realized with a computer addressable phase-only spatial light modulator. By varying the phase levels of the spatial light modulator, the truncated helical phase of an optical vortex results in output intensity patterns that typifies that of microgears instead of perfect doughnut beams. Our experiments and simulations are in good agreement implying a more efficient and highly parallel two-photon photopolymerization scheme that can be subsequently used for non-scanning fabrication of microgears.
IEEE Transactions on Circuits and Systems Ii: Analog and Digital Signal Processing, 2002
A technique is demonstrated for extending the dynamic range of 1-bit analog-to-digital converters... more A technique is demonstrated for extending the dynamic range of 1-bit analog-to-digital converters (ADCs) that sample at the maximum rate using a sinusoid reference ( ) = cos(2 ). The ADC has a detection limit = 1, where 2 is the base-clock period, and 1 = sampling interval = 1 2 2 . Optimal sampling is achieved at 1 = 2 , but with large quantization errors found in the sampled representation of the input signal ( ). Dithering with noise ( ) of appropriate variance 2 is utilized to measure a subthreshold ( ) where ( ) for all . Both uniform white noise (UWN) and Gaussian white noise (GWN) are utilized. With UWN dithering at = , we could reduce the errors to levels that are produced by an equivalent -bit amplitude-sampling (bipolar) ADC by observing the dithered signal ( ) + ( ) over a time duration of [(0 116 )(2 1)] 0 995 , where is the sampling period, and are the ADC supply voltages. With GWN dithering at = 0 5 , the duration required is [(0 109 )(2 1)] 0 996 . Index Terms-1-bit analog-to-digital conversion (ADC), crossing sampling, noise dithering.
Applied Optics, 2002
We study the behavior of the point-spread function ͑PSF͒ of the confocal scanning optical microsc... more We study the behavior of the point-spread function ͑PSF͒ of the confocal scanning optical microscope ͑CSOM͒ when the available optical energy density from the sample plane is low ͑Ͻ7.5 microJoule͞ micrometers 2 ͒. The PSF profile is analyzed under three photon-limited imaging conditions: ͑1͒ reflection-type CSOM with a weak source and a perfectly reflecting sample, ͑2͒ reflection-type CSOM with a strong illumination source and a weak sample, and ͑3͒ fluorescence CSOM with a weak fluorescent sample. Linfoot's image quality criteria of fidelity, structural content, and correlation quality are used to assess the reproducibility of the PSF profile as a function of the photon number. Low photon numbers yield a PSF profile that is difficult to maintain from one location in the sample plane to another. The optical sectioning capability of the CSOM was found to deteriorate more quickly against light power reduction than its transverse resolving power. The signal-to-noise ratio of the scanned CSOM image improves exponentially with the photon number from the sample plane. The noise that is generated by an unstable PSF has an average amplitude that decreases exponentially with the photon number and is significant only at low photon numbers. The CSOM image quality deteriorates because of spurious high-frequency components, degradation in the PSF dynamic range, and varying resolving power.
Physica A 312 (2002) 609–618
We analyze the exit dynamics of pedestrians who are initially confined in a room. Pedestrians ar... more We analyze the exit dynamics of pedestrians who are initially confined in a room. Pedestrians are modeled as cellular automata and compete to escape via a known exit at the soonest possible time. A pedestrian could move forward, backward, left or right within each iteration time depending on adjacent cell vacancy and in accordance with simple rules that determine the compulsion to move and physical capability relative to his neighbors. The arching signatures of jamming were observed and the pedestrians exited in bursts of various sizes. Power-law behavior is found in the burst-size frequency distribution for exit widths w greater than one cell dimension (w > 1). The slope of the power-law curve varies with
w from −1.3092 (w= 2) to −1.0720 (w= 20). Streaming which is a diffusive behavior, arises in large burst sizes and is more likely in a single-exit room with w = 1 and leads to a counterintuitive result wherein an average exit throughput Q is obtained that is higher than with w = 2, 3, or 4. For a two-exit room (w= 1), Q is not greater than twice the yield of a single-exit room. If the doors are not separated far enough (< 4w), Q becomes even significantly less due to a collective slow-downthat emerges among pedestrians crossing in each other’s path (disruptive interference effect). For the same w and door number, Q is also higher with relaxed pedestrians than with anxious ones.
Conference Presentations by Giovanni Tapang
Spatial Resolution in Photon-Limited Confocal Optical Microscopy
The behavior of photon-limited light is discussed in reference to its use in confocal microscopy.... more The behavior of photon-limited light is discussed in reference to its use in confocal microscopy. A ray-tracing based simulation of photons passing through a confocal optical imaging system is performed with the photon propagation determined by the photon distribution function at the photodetector. The formation of the image of a point source is considered with regard to how well the approximate distribution of photodetector events approaches the classical three-dimensional point spread function (PSF) as the number of detected photons increase. We find that the normalized mean-square error between the detected photon distribution function and the classical PSF (very high SNR) has a power-law behavior varying as N-1.001, where N is the number of detected photons.
Noise-induced synchronization of transverse modes in wide-aperture lasers
Nonlinear Guided Waves …, 2004
The counterintuitive effects on noise in nonlinear systems are well known [1]. In this paper, we ... more The counterintuitive effects on noise in nonlinear systems are well known [1]. In this paper, we investigate the effects of noise in the dynamics of a multi-transverse mode laser model. The complex spatiotemporal oscillations observed in such lasers are the result of the competition ...
Three-dimensional simulation of photopolymerization dynamics under broadband excitation
Frontiers in Optics, 2011
ABSTRACT We simulate the growth of a voxel in a photopolymerization reaction where the degree of ... more ABSTRACT We simulate the growth of a voxel in a photopolymerization reaction where the degree of polymerization is determined by the decrease in the photoinitiator concentration. Simulation was done for both single-photon and two-photon photopolymerization.
Three-dimensional light modulation using a piecewise implementation of the Gerchberg-Saxton algorithm
Frontiers in Optics, 2011
... After modulating the phase, the beam is passed through a lens (f = 250 mm) which performs the... more ... After modulating the phase, the beam is passed through a lens (f = 250 mm) which performs the Fourier transform. ... 9. D. Palima and V. Daria, "Holographic projection of arbitrary light patterns with a suppressed zeroorder beam," Appl. Opt. ...
Local Publications by Giovanni Tapang
Noise Enhanced Imaging of Weak Objects
Science Diliman, 2007
Spatial Resolution of Weakly Reflecting Objects in Confocal Optical Microscopy
Science Diliman, 2012
Talks by Giovanni Tapang
The release of the Commission on Audit (COA) Special Audits Office Report No. 2012-03 opened a we... more The release of the Commission on Audit (COA) Special Audits Office Report No. 2012-03 opened a wealth of data that gives us a glimpse of how the Priority Development Assistance Fund (PDAF) and the so-called Various Infrastructure, Including Local Projects (VILP) funds were used by government agencies. The report gives a government-wide Performance Audit of the PDAF and the VILP of various implementing agencies from 2007 to 2009.
On US Bases and Military Access Agreements
Papers by Giovanni Tapang
The effect of climate variability on the weekly incidence of acute bloody diarrhea, dengue and in... more The effect of climate variability on the weekly incidence of acute bloody diarrhea, dengue and influenza-like illness in the 17 regions of the Philippines is examined using correlation, mutual information and transfer entropy. Results show that the correlations between climate variables and disease incidences differ from one region to another. Interestingly, the diseases are directly correlated to each other for each region. This is explained by their common driving climate factors which are shown by large transfer entropy values. This work is important in further understanding the role of climate variability to the temporal dynamics of disease incidences.
Optics Letters, 2014
We present a method of reshaping light in three dimensions via phase modulation. The method calcu... more We present a method of reshaping light in three dimensions via phase modulation. The method calculates the target computer-generated hologram individually and adds to it an appropriate transfer function to translate the reconstruction to any location in space. We are able to simultaneously generate independently controlled arbitrary patterns at different positions using a single laser beam.
Optics Letters, Vol. 39, Issue 7, pp. 2036-2039 (April 2014)
We present a method of reshaping light in three dimensions via phase modulation. The method calcu... more We present a method of reshaping light in three dimensions via phase modulation. The method calculates the target computer generated hologram individually and adds to it an appropriate transfer function to translate the reconstruction to any location in space. We are able to simultaneously generate independently controlled arbitrary patterns at diff erent positions using a single laser beam.
International Journal of Modern Physics C (Accepted)
Co-occurrence language networks based on Bible translations and the Universal Declaration of Huma... more Co-occurrence language networks based on Bible translations and the Universal Declaration of Human Rights (UDHR) translations in different languages were constructed and compared with random text networks. Among the considered network metrics, the network size, N, the normalized betweenness centrality, BC, and the average k -nearest neighbors, knn, were found to be the most preserved across translations. Moreover, similar frequency distributions of co-occurring network motifs were observed for translated texts networks.
International Journal of Modern Physics C, 2010
Word adjacency networks constructed from written works reflect differences in the structure of pr... more Word adjacency networks constructed from written works reflect differences in the structure of prose and poetry. We present a method to disambiguate prose and poetry by analyzing network parameters of word adjacency networks, such as the clustering coefficient, average path length and average degree. We determine the relevant parameters for disambiguation using linear discriminant analysis (LDA) and the effect size criterion. The accuracy of the method is 74.9 ± 2.9% for the training set and 73.7 ± 6.4% for the test set which are greater than the acceptable classifier requirement of 67.3%. This approach is also useful in locating text boundaries within a single article which falls within a window size where the significant change in clustering coefficient is observed. Results indicate that an optimal window size of 75 words can detect the text boundaries.
International Journal of Modern …, 2012
We identify the di®erent styles of texting in Filipino short message service (SMS) texts and anal... more We identify the di®erent styles of texting in Filipino short message service (SMS) texts and analyze the change in unigram and bigram frequencies due to these styles. Style preference vectors for sample texts were calculated and used to identify the style combination used by an average individual. The change in Shannon entropy of the SMS text is explained in light of a coding process.
Proceedings of The National Academy of Sciences, 2003
Numerical investigations of escape panic of confined pedestrians have revealed interesting dynami... more Numerical investigations of escape panic of confined pedestrians have revealed interesting dynamical features such as pedestrian arch formation around an exit, disruptive interference, self-organized queuing, and scale-free behavior. However, these predictions have remained unverified because escape panic experiments with real systems are difficult to perform. For mice escaping out of a water pool, we found that for a critical sampling rate the escape behavior exhibits the predicted features even at short observation times. The mice escaped via an exit in bursts of different sizes that obey exponential and (truncated) power-law distributions depending on exit width. Oversampling or undersampling the mouse escape rate prevents the observation of the predicted features. Real systems are normally subject to unavoidable constraints arising from occupancy rate, pedestrian exhaustion, and nonrigidity of pedestrian bodies. The effect of these constraints on the dynamics of real escape panic is also studied.
International Journal of …, 2012
Complex networks have been proven useful in characterizing written texts. Here, we use networks t... more Complex networks have been proven useful in characterizing written texts. Here, we use networks to probe if there exist a similarity within, and difference across, era as reflected within the poem's structure. In literary history, boundary lines are set to distinguish the change in writing styles through time. We obtain the network parameters and motif frequencies of 845 poems published from 1522 to 1931 and relate this to the writing of the Elizabethan, 17th Century, Augustan, Romantic and Victorian eras. Analysis of the different network parameters shows a significant difference of the Augustan era (1667-1780) with the rest. The network parameters and the convex hull and centroids of the motif frequencies reflect the adjectival sequence pattern of the poems of the Augustan era.
Optics Communications, 2009
We report parallel two-photon photopolymerization of microgear patterns by exposing a photoresist... more We report parallel two-photon photopolymerization of microgear patterns by exposing a photoresist to holographically generated optical vortices. The optical vortices are created by imparting a helical pitch onto the incident light using a programmable lithographic phase mask realized with a computer addressable phase-only spatial light modulator. By varying the phase levels of the spatial light modulator, the truncated helical phase of an optical vortex results in output intensity patterns that typifies that of microgears instead of perfect doughnut beams. Our experiments and simulations are in good agreement implying a more efficient and highly parallel two-photon photopolymerization scheme that can be subsequently used for non-scanning fabrication of microgears.
IEEE Transactions on Circuits and Systems Ii: Analog and Digital Signal Processing, 2002
A technique is demonstrated for extending the dynamic range of 1-bit analog-to-digital converters... more A technique is demonstrated for extending the dynamic range of 1-bit analog-to-digital converters (ADCs) that sample at the maximum rate using a sinusoid reference ( ) = cos(2 ). The ADC has a detection limit = 1, where 2 is the base-clock period, and 1 = sampling interval = 1 2 2 . Optimal sampling is achieved at 1 = 2 , but with large quantization errors found in the sampled representation of the input signal ( ). Dithering with noise ( ) of appropriate variance 2 is utilized to measure a subthreshold ( ) where ( ) for all . Both uniform white noise (UWN) and Gaussian white noise (GWN) are utilized. With UWN dithering at = , we could reduce the errors to levels that are produced by an equivalent -bit amplitude-sampling (bipolar) ADC by observing the dithered signal ( ) + ( ) over a time duration of [(0 116 )(2 1)] 0 995 , where is the sampling period, and are the ADC supply voltages. With GWN dithering at = 0 5 , the duration required is [(0 109 )(2 1)] 0 996 . Index Terms-1-bit analog-to-digital conversion (ADC), crossing sampling, noise dithering.
Applied Optics, 2002
We study the behavior of the point-spread function ͑PSF͒ of the confocal scanning optical microsc... more We study the behavior of the point-spread function ͑PSF͒ of the confocal scanning optical microscope ͑CSOM͒ when the available optical energy density from the sample plane is low ͑Ͻ7.5 microJoule͞ micrometers 2 ͒. The PSF profile is analyzed under three photon-limited imaging conditions: ͑1͒ reflection-type CSOM with a weak source and a perfectly reflecting sample, ͑2͒ reflection-type CSOM with a strong illumination source and a weak sample, and ͑3͒ fluorescence CSOM with a weak fluorescent sample. Linfoot's image quality criteria of fidelity, structural content, and correlation quality are used to assess the reproducibility of the PSF profile as a function of the photon number. Low photon numbers yield a PSF profile that is difficult to maintain from one location in the sample plane to another. The optical sectioning capability of the CSOM was found to deteriorate more quickly against light power reduction than its transverse resolving power. The signal-to-noise ratio of the scanned CSOM image improves exponentially with the photon number from the sample plane. The noise that is generated by an unstable PSF has an average amplitude that decreases exponentially with the photon number and is significant only at low photon numbers. The CSOM image quality deteriorates because of spurious high-frequency components, degradation in the PSF dynamic range, and varying resolving power.
Physica A 312 (2002) 609–618
We analyze the exit dynamics of pedestrians who are initially confined in a room. Pedestrians ar... more We analyze the exit dynamics of pedestrians who are initially confined in a room. Pedestrians are modeled as cellular automata and compete to escape via a known exit at the soonest possible time. A pedestrian could move forward, backward, left or right within each iteration time depending on adjacent cell vacancy and in accordance with simple rules that determine the compulsion to move and physical capability relative to his neighbors. The arching signatures of jamming were observed and the pedestrians exited in bursts of various sizes. Power-law behavior is found in the burst-size frequency distribution for exit widths w greater than one cell dimension (w > 1). The slope of the power-law curve varies with
w from −1.3092 (w= 2) to −1.0720 (w= 20). Streaming which is a diffusive behavior, arises in large burst sizes and is more likely in a single-exit room with w = 1 and leads to a counterintuitive result wherein an average exit throughput Q is obtained that is higher than with w = 2, 3, or 4. For a two-exit room (w= 1), Q is not greater than twice the yield of a single-exit room. If the doors are not separated far enough (< 4w), Q becomes even significantly less due to a collective slow-downthat emerges among pedestrians crossing in each other’s path (disruptive interference effect). For the same w and door number, Q is also higher with relaxed pedestrians than with anxious ones.
Spatial Resolution in Photon-Limited Confocal Optical Microscopy
The behavior of photon-limited light is discussed in reference to its use in confocal microscopy.... more The behavior of photon-limited light is discussed in reference to its use in confocal microscopy. A ray-tracing based simulation of photons passing through a confocal optical imaging system is performed with the photon propagation determined by the photon distribution function at the photodetector. The formation of the image of a point source is considered with regard to how well the approximate distribution of photodetector events approaches the classical three-dimensional point spread function (PSF) as the number of detected photons increase. We find that the normalized mean-square error between the detected photon distribution function and the classical PSF (very high SNR) has a power-law behavior varying as N-1.001, where N is the number of detected photons.
Noise-induced synchronization of transverse modes in wide-aperture lasers
Nonlinear Guided Waves …, 2004
The counterintuitive effects on noise in nonlinear systems are well known [1]. In this paper, we ... more The counterintuitive effects on noise in nonlinear systems are well known [1]. In this paper, we investigate the effects of noise in the dynamics of a multi-transverse mode laser model. The complex spatiotemporal oscillations observed in such lasers are the result of the competition ...
Three-dimensional simulation of photopolymerization dynamics under broadband excitation
Frontiers in Optics, 2011
ABSTRACT We simulate the growth of a voxel in a photopolymerization reaction where the degree of ... more ABSTRACT We simulate the growth of a voxel in a photopolymerization reaction where the degree of polymerization is determined by the decrease in the photoinitiator concentration. Simulation was done for both single-photon and two-photon photopolymerization.
Three-dimensional light modulation using a piecewise implementation of the Gerchberg-Saxton algorithm
Frontiers in Optics, 2011
... After modulating the phase, the beam is passed through a lens (f = 250 mm) which performs the... more ... After modulating the phase, the beam is passed through a lens (f = 250 mm) which performs the Fourier transform. ... 9. D. Palima and V. Daria, "Holographic projection of arbitrary light patterns with a suppressed zeroorder beam," Appl. Opt. ...
Noise Enhanced Imaging of Weak Objects
Science Diliman, 2007
Spatial Resolution of Weakly Reflecting Objects in Confocal Optical Microscopy
Science Diliman, 2012
The release of the Commission on Audit (COA) Special Audits Office Report No. 2012-03 opened a we... more The release of the Commission on Audit (COA) Special Audits Office Report No. 2012-03 opened a wealth of data that gives us a glimpse of how the Priority Development Assistance Fund (PDAF) and the so-called Various Infrastructure, Including Local Projects (VILP) funds were used by government agencies. The report gives a government-wide Performance Audit of the PDAF and the VILP of various implementing agencies from 2007 to 2009.
On US Bases and Military Access Agreements
The effect of climate variability on the weekly incidence of acute bloody diarrhea, dengue and in... more The effect of climate variability on the weekly incidence of acute bloody diarrhea, dengue and influenza-like illness in the 17 regions of the Philippines is examined using correlation, mutual information and transfer entropy. Results show that the correlations between climate variables and disease incidences differ from one region to another. Interestingly, the diseases are directly correlated to each other for each region. This is explained by their common driving climate factors which are shown by large transfer entropy values. This work is important in further understanding the role of climate variability to the temporal dynamics of disease incidences.
Optics Letters, 2014
We present a method of reshaping light in three dimensions via phase modulation. The method calcu... more We present a method of reshaping light in three dimensions via phase modulation. The method calculates the target computer-generated hologram individually and adds to it an appropriate transfer function to translate the reconstruction to any location in space. We are able to simultaneously generate independently controlled arbitrary patterns at different positions using a single laser beam.
Development of a Microcontroller-based Wireless Accelerometer for Kinematic Analysis
Journal of Mechatronics, Electrical Power, and Vehicular Technology, 2015
Parametric study of axial trapping forces on an elliptically symmetric dielectric in the ray optics regime
International Conference on Photonics Solutions 2015, 2015
Zero Order Diffraction Suppression in a Phase-only Spatial Light Modulator via the GS Algorithm
Frontiers in Optics 2014, 2014