Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Engineering science >> Mathematics - Numerical analysis - Simulation
8 proposition(s).

Inverse reinforcement learning of a task performed by a human

DPLOIRE (CTReg)

Autre

01-01-2019

SL-DRT-19-0262

laurent.dolle@cea.fr

Learning from demonstration involves an agent (e.g., a robot) learning a task by watching another agent (e.g., a human) performing the same task. It often uses reinforcement-learning methods to improve the robot's ability to perform a task in new situations (i.e., generalization). These methods involve providing a positive reinforcement (i.e., a reward) when the outputs of the algorithms help achieving the task, but require a human designed reward function. The more the task is complex the more difficult is the reward function to design, but it can be learned from a series of examples with methods called inverse reinforcement learning. The use, jointly or not, of these techniques has shown encouraging results, but which are limited to toy examples and cannot be adapted as such to tasks more representative of the industrial environment. During the thesis, the PhD student will analyze and test state-of-the-art previous works. S/He will then propose a method, combining inverse reinforcement learning to other algorithms (e.g., generative adversarial networks, GAN), so that the robot will understand the task performed by the operator (with as little explanation from the operator as possible), and will generalize enough to make the robot robust to dynamic environments (obstacles, moving objects?). This method should be suited for a "pick and place" task in an industrial environment and ensure a reasonable enough learning period (information a priori, feedback from the operator) for tasks of medium complexity.

3D Objects discovery in 3D scene

DPLOIRE (CTReg)

Autre

01-01-2019

SL-DRT-19-0269

anthony.mouraud@cea.fr

Object detection and localization in images is a problem studied since many years. The latest technological developments now allow the real-time acquisition of depth data coupled to color data (RGBD). At the same time, modern machine computing capabilities and intelligent image processing methods have led to significant advances in the detection / localization of 2D objects with many different approaches (bounding boxes, contours, from CAD models ...). An important step is being taken in recent years with the research conducted to directly extract the volume of detected objects and their position in 3D. These works are still in their infancy, but the first results are encouraging, both from 2D images (eg DeepManta) and from 3D images (eg Deep Sliding Shapes). However, there remain several identifiable scientific / technological barriers before allowing the democratization of this type of approach for the automatic extraction of objects in potentially unknown scenes. The objective of this work is to identify the current approaches of detection / localization of 3D objects, to target their weaknesses and work on new processing technologies to mitigate them. Moreover, the object discovery in unknown environments and the inference of the operator's intention by observation / location of his attention are two areas of interest that this work aims at addressing. Beyond their applications for demonstration learning, the software bricks resulting from this project can also be reused for other applications such as augmented reality ("smart" scanning, etc.), surveillance or mobile mobility for example.

SPAD Imager for HDR ToF using multimodal data fusion

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)

Laboratoire Circuits Intégrés, Intelligents pour l'Image

01-10-2019

SL-DRT-19-0301

william.guicquero@cea.fr

Depth sensors are currently a very high trending topic. Indeed, in the fields of autonomous vehicles, portable electronic devices and the Internet of Things, new technology enablers now tend to provide handy 3D image data for future innovative end-user applications. There is a great diversity of 3D sensor types, either using passive imaging (depth from defocus, stereovision, phase pixels...) or using active imaging (ultrasounds, structured light, Time-of-Flight...). Each of these systems addresses specifications in terms of depth dynamic range (accuracy of the measurement versus maximum distance). In this thesis, we will study the specific case of Single Photon Avalanche Diodes (SPAD). Recent scientific results regarding this electro-photonic component demonstrate its relevance in the context of Time-of-Flight (ToF) imaging, especially in the case of integration in a 3D-stacked design flow exhibiting a pixel pitch of the order of ten micrometers. However, the nature of the data gathered by this type of component requires significant signal processing within the sensor to extract relevant information. This thesis will aim to revise traditional approaches related to histogram processing by directly extracting statistical features from raw data. Depending on the background and skills of the PhD candidate, two research axes would be investigated. First, on the hardware side, possible modifications of SPAD based sensor architecture in order to provide ?augmented? multi-modal information. Second, on the theoretical and algorithmic side, data fusion methods to improve the final reconstruction rendering of depth maps from sensed data.

Study and implementation of non-recurrent deep learning algorithms for temporal sequences processing

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)

Laboratoire Calcul Embarqué

01-01-2019

SL-DRT-19-0393

david.briand@cea.fr

Recurrent neural networks - and notably the Long-Short Term Memory (LSTM) variant - are today at the state of the art for solving many temporal sequence classification problems and in particular used in speech recognition applications (from 2015 for Android) and automatic translation (from 2016 at Google, Apple and Facebook). This type of algorithm is also successfully applied in various applications such as audio event recognition, denoising, language modeling, sequences generations, etc. The success of these approaches comes however with the cost of huge computing power requirements. This is why most of this algorithms are run on the Cloud, and not on the Edge. Moreover, recurrent neural networks are very sensitive to training parameters and can be difficult to converge because gradients internal to their recurrent structure can easily explode or vanish to zero. The adaptation of these algorithms for an embedded implementation is therefore not straightforward, because the recurrence requires a high precision and partially sequential (large latency) computing. Some technics for overcoming these difficulties are starting to appear, but are still in their infancy. Among them, a non-recurrent technic allowing sequence processing with less constrain than LSTM seems promising: hierarchical networks. Temporal convolution networks (TCN) are one of their application. The advantages and drawbacks of this model are studied notably in "An Empirical Evaluation of Generic Convolutional and Recurrent Networks for Sequence Modeling" (Shaojie Bai, J. Zico Kolter, Vladlen Koltun). A basic implementation of each structure showed that TCN are more efficient in almost every test cases. Internal gradients are much more stable and computation can be easily parallelized thanks to the elimination of the recurrence.

Short wave Infra Red diffuse reflectance spectroscopy for noninvasive molecular detection medical devices

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Imagerie et Systèmes d'Acquisition

01-10-2019

SL-DRT-19-0562

anne.koenig@cea.fr

Diabetes is a major public health and industrial issue, with the number of diabetics worldwide estimated at 415 million. Until recently, to control their blood glucose, patients had to prick their fingertips. To avoid this inconvenience, laboratories have recently been offering minimally invasive measurement systems that can be interrogated using a smartphone. This evolution, although major, still poses many problems, such as its cost, its size, or its invasiveness, even reduced. As such, a medical optical sensor, reliable, inexpensive would represent a major breakthrough: many players in microelectronics such Apple or Google produce an effort in this direction. In vitro, the sugar measurement can be performed by diffuse spectroscopy in the SWIR domain (wavelength range 1 - 1.7 µm). A fraction of the photons produced by an immersed light source (emitter) diffuse into the liquid and emerge from it by the interplay of multiple reflections. The sugar absorption is on a band around 1.5 µm, the fraction of light emerging and detected in this range will be as lower as the sugar concentration is high. Multispectral analysis provides realistic concentration measurements. In vivo, the results are much worse because of the heterogeneity of the biological tissues and the presence of many interferents (other absorbents). The purpose of the thesis is to remove these biases by developing a new type of optical sensor comprising on the one hand several emitters, on the other hand a plurality of detectors. This subject concerns a candidate who must have received a physicist training with a solid module dedicated to optics / photonics, interested in a work at the interface between physics and biology.

A quantum algorithm toward a practical evaluation of Worst-Case Execution Times (WCETs) for real-time tasks

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)

Laboratoire Calcul Embarqué

01-10-2019

SL-DRT-19-0568

sergiu.carpov@cea.fr

Schedulability analysis is an old research field related to both real-time systems and performance of systems. An important requirement of the schedulability analysis is the availability of upper bounds of execution times. As a consequence, the research field of Worst Case Execution Times (WCETs) started to flourish in the 90s. For safety critical real-time systems, missing a deadline can lead to catastrophic results, with important damages or even loss of human lives. As such event must be avoided, the schedulability analysis must provide a safe result. So if exact WCETs cannot be expressed, which is usually the case because they depends on too many parameters including a perfect model of inner-work of the target microprocessor, then a safe upper bound of the WCETs must be provided instead. However, if it is indeed easy to show overly pessimistic WCETs, e.g. by disabling caches, and serializing instructions in the pipeline, the usefulness of a given WCET estimation decreases as its accuracy is reduced. So a useful WCET should be both safe and as accurate as possible, which is a tricky problem because execution times in modern systems are heavily context dependent, and the mathematical models of WCETs are NP-hard problems. Within this PhD work we aim at two target objectives: The first si to find a way of modeling the evaluation of WCETs with a quantum algorithm, and the second is to open up another field of application of quantum computing outside of the usual fields of reseach.

CNN-3d-lensfree

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Imagerie et Systèmes d'Acquisition

01-09-2019

SL-DRT-19-0605

lionel.herve@cea.fr

At CEA-Leti, we are developing lensfree microscopy for the monitoring of cell culture. This technique overpass several limits of conventional microscopy (compactness, field of view, quantification, etc.). Recently we showed, for the first time, 3D+time acquisitions of 3D cell culture with a lens-free microscope. We observed cells without any labelling within the volume as large as several cubic millimeters over several days. This new mean of microscopy allowed us to observe a broad range of phenomena only present in 3D environments. However, two drawbacks are still present on the microscope prototype: a long reconstruction time (>1 hour/frame) and the reconstructed volumes present artefacts owing to the limited number of angular acquisitions. The thesis work will focus on the ability of deep learning technologies to overcome the above-mentioned limitations. Basically, a convolutional neural network will be trained on the basis of simulated 3D cell culture volume (ground truth) and simulated response of our current 3D lensfree microscope (input). This approach is expected to accelerate the reconstruction process and to allow full 3D reconstructions. Yet it poses two scientific questions: are simulated data pertinent to train a neural network and how can we assess the quality of 3D reconstruction obtained through a neural network? Profile of the candidate sought: - Engineering degree in applied mathematics or physical sciences. - Strong knowledge in image processing with skills in deep learning.

Spintronic Wake-Up Radio

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)

Laboratoire Architectures Intégrées Radiofréquences

01-09-2019

SL-DRT-19-0645

dominique.morche@cea.fr

The increasing number of wireless connected objects and smart sensors requires defining components and operational schemes that drastically reduce the power consumption. Within such communicating networks the RxTx modules are the most power consuming elements. The solution actively searched for is to switch off the main RxTx module when no communication is requested and to use a low power, degraded wake-up radio receiver WuRx that will switch on the main module when receiving an according wake-up signal. The realization of robust and ultralow power WuRx is an active field of research. The thesis proposes to explore RF spintronic devices as such a compact and low power solution. Magnetic tunnel junctions, which are the main spintronics building blocks, are capable to passively convert an RF signal into a DC signal, with frequency selectivity and at relatively high output signal levels. LETI/DACLE and INAC/SPINTEC work together on the realization of such spintroncis based WuRx and the PhD project will be at the interface of the two laboratories. While SPINTEC will realize the devices and optimize their sensitivity to low input signal levels, the thesis will be carried out at LETI/DACLE to realize the corresponding antenna networks and rf electronics. In order to establish the performance parameters the student will first spend some time at SPINTEC to get trained on the characterization of spintronic based rf components. The student will also be involved in the testing of the developed rf circuits with the spintronics components to iteratively optimize the electronic circuits and adapt it to the spintronics device performances.

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