A.J. van Genderen
Please Note
33 records found
1
Two configurations were investigated, namely a spouted bed and a bubbling fluidized bed, where the bubbling fluidized bed produced the best results. Additionally, the fluidized bed was equipped with motor speed control, and with sensors for the measurement of ozone concentration, temperature, humidity, air speed, and ion density. These sensors were integrated in an easy readout system using displays, making the system ready for testing of disinfection performance.
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Two configurations were investigated, namely a spouted bed and a bubbling fluidized bed, where the bubbling fluidized bed produced the best results. Additionally, the fluidized bed was equipped with motor speed control, and with sensors for the measurement of ozone concentration, temperature, humidity, air speed, and ion density. These sensors were integrated in an easy readout system using displays, making the system ready for testing of disinfection performance.
Plasma DBD Electrodes
For a Seed Disinfection Fluidized Bed Reactor
Mechanism to detect mismatches and provide recommendations about the users' preference in negotiation support systems
A case study about issue weight mismatches with the pocket negotiator
Agar/NaCl tissue phantom mimicking electrical properties of human body in low frequency spectrum
A Brain-Computer Interface Inside Your Earphones
The electrical properties of biological tissue are referred to as the conductivity Ο and permittivity Ξ΅ and denote the ability for a material to conduct and trap electric charge respectively. These properties are frequency dependent and particularly for EEGs, a frequency range of 1-1000 Hz is of interest (with some added leeway). Wet skin hereby has a conductivity of around 0.1 Siemens to 0.2 Siemens in the 1-1000 Hz frequency range whereas the permittivity ranges from 5.7 * 10^5 to 5.2 * 10^5. Different agar and agar/NaCl solutions are created to try and obtain solutions with the mentioned electric properties. Specifically, NaCl is added to improve the conductivity and obtain a non-linear frequency response similar to that of human skin. The electrical properties of the phantoms were verified/measured using the parallel plate method. This method is essentially sandwiching a material under test (MUT) (in this case the fabricated gel-like agar and agar/NaCl solutions) between two conducting plates. This method is most suited for measurements in the lower frequency spectrum.
The skin phantom consisting of 3.04 mass fraction weight (wt.%) agar and 0.539 wt.% NaCl shows the closest similarity to the conductivity of wet skin. Namely, a conductivity of ~ 0.1 Siemens to 0.45 Siemens in the frequency range of 1-1000 Hz. A decrease of 0.250 wt.% NaCl will most likely achieve the desired conductivity response of 0.1 Siemens to 0.2 Siemens in the frequency range of 1-1000 Hz. The skin phantom consisting of 3.00 wt.% agar and 1.02 wt.% NaCl showed the permittivity closest to that of wet skin, but might have been a noisy outlier. Its permittivity ranges from 10 * 10^6 and 7.5 * 10^6. This is still a large error margin from the desired 5.7 * 10^5 to 5.2 * 10^5. Additional fillers like glycine or Al powder need to be added to the solutions to obtain a permittivity close to that of wet human skin. Multi-day and difference in applied pressure measurements are performed to check the sensitivity and reproducibility of the phantoms. Applied pressure hereby has little to no influence whereas a longer life-span of the fabricated phantom shows a drastic decrease of the electrical properties of the phantoms after day 1. The changes then seem to settle. Worth mentioning is that the change is only drastic when the solution has a high conductivity. This is generally not the case for solutions with conductivities close to wet skin. ...
The electrical properties of biological tissue are referred to as the conductivity Ο and permittivity Ξ΅ and denote the ability for a material to conduct and trap electric charge respectively. These properties are frequency dependent and particularly for EEGs, a frequency range of 1-1000 Hz is of interest (with some added leeway). Wet skin hereby has a conductivity of around 0.1 Siemens to 0.2 Siemens in the 1-1000 Hz frequency range whereas the permittivity ranges from 5.7 * 10^5 to 5.2 * 10^5. Different agar and agar/NaCl solutions are created to try and obtain solutions with the mentioned electric properties. Specifically, NaCl is added to improve the conductivity and obtain a non-linear frequency response similar to that of human skin. The electrical properties of the phantoms were verified/measured using the parallel plate method. This method is essentially sandwiching a material under test (MUT) (in this case the fabricated gel-like agar and agar/NaCl solutions) between two conducting plates. This method is most suited for measurements in the lower frequency spectrum.
The skin phantom consisting of 3.04 mass fraction weight (wt.%) agar and 0.539 wt.% NaCl shows the closest similarity to the conductivity of wet skin. Namely, a conductivity of ~ 0.1 Siemens to 0.45 Siemens in the frequency range of 1-1000 Hz. A decrease of 0.250 wt.% NaCl will most likely achieve the desired conductivity response of 0.1 Siemens to 0.2 Siemens in the frequency range of 1-1000 Hz. The skin phantom consisting of 3.00 wt.% agar and 1.02 wt.% NaCl showed the permittivity closest to that of wet skin, but might have been a noisy outlier. Its permittivity ranges from 10 * 10^6 and 7.5 * 10^6. This is still a large error margin from the desired 5.7 * 10^5 to 5.2 * 10^5. Additional fillers like glycine or Al powder need to be added to the solutions to obtain a permittivity close to that of wet human skin. Multi-day and difference in applied pressure measurements are performed to check the sensitivity and reproducibility of the phantoms. Applied pressure hereby has little to no influence whereas a longer life-span of the fabricated phantom shows a drastic decrease of the electrical properties of the phantoms after day 1. The changes then seem to settle. Worth mentioning is that the change is only drastic when the solution has a high conductivity. This is generally not the case for solutions with conductivities close to wet skin.
Voxelwise rs-fMRI representation learning
A non-linear variational approach
We propose to apply non-linear representation learning to voxelwise rs-fMRI data. Learning the non-linear representations is done using two versions of a variational autoencoder (VAE). The first version is a vanilla VAE with 3D residual blocks in both its encoder and decoder. The second version is based on the identifiable VAE and uses a time-dependent prior. The models train to reconstruct the original input data from latent variables it infers. Three predictive models then evaluate the predictive power of the latent variables on an age regression, a sex classification, and a schizophrenia classification task. Each of the predictive models performs predictions for each of the three tasks. The predictive models are a support vector machine (SVM), a k-nearest neighbor (k-NN) model, and a long short-term memory (LSTM) neural network.
We show that our method performs exceptionally well on the age regression and sex classification tasks without any supervision. These results imply that VAEs can model predictive variations in their latent spaces for demographic variables. The models, however, do not do well on the schizophrenia classification task, even when the models are pretrained. Despite the lower performance on the schizophrenia classification task, the overall results are encouraging and pave the way for future work on voxelwise representation learning. ...
We propose to apply non-linear representation learning to voxelwise rs-fMRI data. Learning the non-linear representations is done using two versions of a variational autoencoder (VAE). The first version is a vanilla VAE with 3D residual blocks in both its encoder and decoder. The second version is based on the identifiable VAE and uses a time-dependent prior. The models train to reconstruct the original input data from latent variables it infers. Three predictive models then evaluate the predictive power of the latent variables on an age regression, a sex classification, and a schizophrenia classification task. Each of the predictive models performs predictions for each of the three tasks. The predictive models are a support vector machine (SVM), a k-nearest neighbor (k-NN) model, and a long short-term memory (LSTM) neural network.
We show that our method performs exceptionally well on the age regression and sex classification tasks without any supervision. These results imply that VAEs can model predictive variations in their latent spaces for demographic variables. The models, however, do not do well on the schizophrenia classification task, even when the models are pretrained. Despite the lower performance on the schizophrenia classification task, the overall results are encouraging and pave the way for future work on voxelwise representation learning.
The novel approach is compared to an existing solution method based on policy rollout and Monte Carlo sampling. Through simulations of dynamic multi-target tracking scenarios in which the cost and computational complexity of different approaches are compared, it was shown that the computational complexity is greatly reduced while the resulting resource allocation results remain similar. ...
The novel approach is compared to an existing solution method based on policy rollout and Monte Carlo sampling. Through simulations of dynamic multi-target tracking scenarios in which the cost and computational complexity of different approaches are compared, it was shown that the computational complexity is greatly reduced while the resulting resource allocation results remain similar.
Gathering a Machine Learning dataset for object detection from a satellite-platform
On bandwidth-efficient gathering of a Machine Learning dataset for Object Detection with Faster-RCNN from a satellite-platform
What Humans Consider Good Object Detection
Analysis on how automatic object detectors align with what humans consider good object detection
Designing a wireless communication system for smart sensor shorts in football
Using lossless data compression and pattern diversity
Utilizing a tagged architecture based on the RISC-V architecture, color labeling assigns colors (denoting a security domain) to individual memory words, cache lines, registers and peripherals. Using a simple set of hardware enforced policies, data protection is ensured. Control flow integrity is maintained with the
help of additional tag bits that denote code and valid jump addresses. New instructions have been added for functions that handle data residing in multiple security domains.
Software support is implemented in the Rust compiler. The compiler is enhanced with macros to support the coloring concept via source level annotations. Incorrect use of labels is reported during compilation. An external tool is used to generate tag information and generate a security report with information on
variable coloring and special function use and construction. Using the external tool keeps the changes to the compiler minimal, thereby reducing the maintenance burden and the required trust in the compiler as well. The report can be used in a security audit.
The concept is implemented on an instruction set architecture simulator. The toolchain modifications and the concept itself have been tested on this simulator. Testing showed the concept can prevent cross-security domain information leaks under several common attack patterns. The overhead due to the execution of additional instructions in the executable code depends on the actual code. Tests with the typical target application OpenVPN-NL showed a less than 5% increase in instruction count for the most commonly called functions.
By designing or redesigning software specifically for color labeling, this overhead can possibly be further reduced. Further testing, specifically on an actual hardware implementation is recommended.
Due to timing constraints, the concept has not been implemented in hardware. However, the hardware performance costs are estimated to be negligible. The area requirements are substantial: implementing the concept in the RISC-V softcore requires double the external memory capacity and FPGA resource utilization is estimated to require 14% more ALMs and 74% more internal memory blocks. ...
Utilizing a tagged architecture based on the RISC-V architecture, color labeling assigns colors (denoting a security domain) to individual memory words, cache lines, registers and peripherals. Using a simple set of hardware enforced policies, data protection is ensured. Control flow integrity is maintained with the
help of additional tag bits that denote code and valid jump addresses. New instructions have been added for functions that handle data residing in multiple security domains.
Software support is implemented in the Rust compiler. The compiler is enhanced with macros to support the coloring concept via source level annotations. Incorrect use of labels is reported during compilation. An external tool is used to generate tag information and generate a security report with information on
variable coloring and special function use and construction. Using the external tool keeps the changes to the compiler minimal, thereby reducing the maintenance burden and the required trust in the compiler as well. The report can be used in a security audit.
The concept is implemented on an instruction set architecture simulator. The toolchain modifications and the concept itself have been tested on this simulator. Testing showed the concept can prevent cross-security domain information leaks under several common attack patterns. The overhead due to the execution of additional instructions in the executable code depends on the actual code. Tests with the typical target application OpenVPN-NL showed a less than 5% increase in instruction count for the most commonly called functions.
By designing or redesigning software specifically for color labeling, this overhead can possibly be further reduced. Further testing, specifically on an actual hardware implementation is recommended.
Due to timing constraints, the concept has not been implemented in hardware. However, the hardware performance costs are estimated to be negligible. The area requirements are substantial: implementing the concept in the RISC-V softcore requires double the external memory capacity and FPGA resource utilization is estimated to require 14% more ALMs and 74% more internal memory blocks.
Hermes, a small form factor electronic module along with piezoelectric films and a 3D mount, is fabricated, tested in a wind tunnel, and in a real aircraft fuselage for its communication performance. Hermes harvests an average power of 440 νW power. Over a wide range of AoA of β10 to 30 degrees, the estimation of the wind speed is within 0.2 m/s error with 90% probability and AoA error is within 1.2 degree with 90% probability. Hermes can be used in light aircraft and long endurance UAVs as is. It can also be used in several other applications, such as windmills. Hermes is expected to open up new avenues for interdisciplinary research for aerospace applications.
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Hermes, a small form factor electronic module along with piezoelectric films and a 3D mount, is fabricated, tested in a wind tunnel, and in a real aircraft fuselage for its communication performance. Hermes harvests an average power of 440 νW power. Over a wide range of AoA of β10 to 30 degrees, the estimation of the wind speed is within 0.2 m/s error with 90% probability and AoA error is within 1.2 degree with 90% probability. Hermes can be used in light aircraft and long endurance UAVs as is. It can also be used in several other applications, such as windmills. Hermes is expected to open up new avenues for interdisciplinary research for aerospace applications.
Interactive Learning in State-space
Enabling robots to learn from non-expert humans
Advancements in Interactive Imitation Learning techniques however, have made it easier for demonstrators to train agents and improve their performance. These techniques involve demonstrators interacting with and guiding the agent as it performs the requisite task. This guidance is typically in the form of corrections or feedback on the current actions being executed by the agent.
In this thesis, a novel Interactive Learning technique is proposed that uses human corrective feedback in state-space to train and improve agent behavior. This technique is beneficial since providing guidance to the agent in terms of `changing its state' is often easier or more intuitive for the human demonstrator (as opposed to changing the actions being executed). For instance, in manipulation tasks using a robotic arm, it is easier for the demonstrator to provide state information such as the Cartesian position of the end-effector rather than low-level action information such as joint angles. Keeping such scenarios in mind, we propose our method titled: Teaching Imitative Policies in State-space (TIPS).
We evaluate the performance of TIPS for various control tasks as part of the OpenAI Gym toolkit as well as for a manipulation task using a KUKA LBR iiwa robotic arm. We show that through continuous improvement via feedback, agents trained using TIPS outperform the demonstrator and in-turn outperform conventional Imitation Learning agents. ...
Advancements in Interactive Imitation Learning techniques however, have made it easier for demonstrators to train agents and improve their performance. These techniques involve demonstrators interacting with and guiding the agent as it performs the requisite task. This guidance is typically in the form of corrections or feedback on the current actions being executed by the agent.
In this thesis, a novel Interactive Learning technique is proposed that uses human corrective feedback in state-space to train and improve agent behavior. This technique is beneficial since providing guidance to the agent in terms of `changing its state' is often easier or more intuitive for the human demonstrator (as opposed to changing the actions being executed). For instance, in manipulation tasks using a robotic arm, it is easier for the demonstrator to provide state information such as the Cartesian position of the end-effector rather than low-level action information such as joint angles. Keeping such scenarios in mind, we propose our method titled: Teaching Imitative Policies in State-space (TIPS).
We evaluate the performance of TIPS for various control tasks as part of the OpenAI Gym toolkit as well as for a manipulation task using a KUKA LBR iiwa robotic arm. We show that through continuous improvement via feedback, agents trained using TIPS outperform the demonstrator and in-turn outperform conventional Imitation Learning agents.