Web application | EPFL Graph Search

A web application (or web app) is application software that is accessed using a web browser. Web applications are delivered on the World Wide Web to users with an active network connection. In earlier computing models like client-server, the processing load for the application was shared between code on the server and code installed on each client locally. In other words, an application had its own pre-compiled client program which served as its user interface and had to be separately installed on each user's personal computer. An upgrade to the server-side code of the application would typically also require an upgrade to the client-side code installed on each user workstation, adding to the support cost and decreasing productivity. In addition, both the client and server components of the application were usually tightly bound to a particular computer architecture and operating system and porting them to others was often prohibitively expensive for all but the largest applications (Nowadays, native apps for mobile devices are also hobbled by some or all of the foregoing issues). In 1995, Netscape introduced a client-side scripting language called JavaScript allowing programmers to add some dynamic elements to the user interface that ran on the client side. So instead of sending data to the server in order to generate an entire web page, the embedded scripts of the downloaded page can perform various tasks such as input validation or showing/hiding parts of the page. In 1999, the "web application" concept was introduced in the Java language in the Servlet Specification version 2.2. [2.1?]. At that time both JavaScript and XML had already been developed, but Ajax had still not yet been coined and the XMLHttpRequest object had only been recently introduced on Internet Explorer 5 as an ActiveX object. Applications like Gmail started to make their client sides more and more interactive since early 2000s. A web page script is able to contact the server for storing/retrieving data without downloading an entire web page.

Contact.engineering-Create, analyze and publish digital surface twins from topography measurements across many scales

Till Junge, Abhijeet Gujrati

The optimization of surface finish to improve performance, such as adhesion, friction, wear, fatigue life, or interfacial transport, occurs largely through trial and error, despite significant advancements in the relevant science. There are three central challenges that account for this disconnect: (1) the challenge of integration of many different types of measurement for the same surface to capture the multi-scale nature of roughness; (2) the technical complexity of implementing spectral analysis methods, and of applying mechanical or numerical models to describe surface performance; (3) a lack of consistency between researchers and industries in how surfaces are measured, quantified, and communicated. Here we present a freely-available internet-based application (available at https://contact.engineering) which attempts to overcome all three challenges. First, the application enables the user to upload many different topography measurements taken from a single surface, including using different techniques, and then integrates all of them together to create a digital surface twin. Second, the application calculates many of the commonly used topography metrics, such as rootmean-square parameters, power spectral density (PSD), and autocorrelation function (ACF), as well as implementing analytical and numerical calculations, such as boundary element modeling (BEM) for elastic and plastic deformation. Third, the application serves as a repository for users to securely store surfaces, and if they choose, to share these with collaborators or even publish them (with a digital object identifier) for all to access. The primary goal of this application is to enable researchers and manufacturers to quickly and easily apply cutting-edge tools for the characterization and properties-modeling of real-world surfaces. An additional goal is to advance the use of open-science principles in surface engineering by providing a FAIR database where researchers can choose to publish surface measurements for all to use.

IOP Publishing Ltd2022

Exploration of micro-acoustic spectrometry techniques

Florian Fernand Hartmann

This master’s thesis aimed at exploring the field of micro-acoustic spectrometry using surface acoustic waves. The objectives of this project were to design and fabricate a platform for the detection and characterization of bioentities. Design of a delay line based on the experience and knowledge of the ANEMS group and on investigation of existing solutions was performed. Different configurations and types of transducers were simulated to come up with some meaningful designs for fabrication. The devices were fabricated in the clean rooms at EPFL with a specific process flow used for the suspended structures. Extensive simulation of bidirectional and unidirectional transducers were carried out in order to understand their behavior and to be able to use them as the elements of the sensing platform. Setbacks prevented the completion of the fabrication and no real measurements could be done before the end of this project, but the simulations gave nice perspectives for the targeted application. The potential of surface acoustic waves to detect modifications in the elasticity or the density of a material could be witnessed in the last simulations.

2022

Sketches, metrics and fast algorithms

Navid Nouri

As it has become easier and cheaper to collect big datasets in the last few decades, designing efficient and low-cost algorithms for these datasets has attracted unprecedented attention. However, in most applications, even storing datasets as acquired has become extremely costly and inefficient, which motivates the study of sublinear algorithms. This thesis focuses on studying two fundamental graph problems in the sublinear regime. Furthermore, it presents a fast kernel density estimation algorithm and data structure. The first part of this thesis focuses on graph spectral sparsification in dynamic streams. Our algorithm achieves almost optimal runtime and space simultaneously in a single pass. Our method is based on a novel bucketing scheme that enables us to recover high effective resistance edges faster. This contribution presents a novel approach to the effective resistance embedding of the graph, using locality-sensitive hash functions, with possible further future applications.The second part of this thesis presents spanner construction results in the dynamic streams and the simultaneous communication models. First, we show how one can construct a

\tilde{O}(n^{2/3})

-spanner using the above-mentioned almost-optimal single-pass spectral sparsifier, resulting in the first single-pass algorithm for non-trivial spanner construction in the literature. Then, we generalize this result to constructing

\tilde{O}(n^{2/3(1-\alpha)})

-spanners using

\tilde{O}(n^{1+\alpha})

space for any

\alpha \in [0,1]

, providing a smooth trade-off between distortion and memory complexity. Moreover, we study the simultaneous communication model and propose a novel protocol with low per player information. Also, we show how one can leverage more rounds of communication in this setting to achieve better distortion guarantees. Finally, in the third part of this thesis, we study the kernel density estimation problem. In this problem, given a kernel function, an input dataset imposes a kernel density on the space. The goal is to design fast and memory-efficient data structures that can output approximations to the kernel density at queried points. This thesis presents a data structure based on the classical near neighbor search and locality-sensitive hashing techniques that improves or matches the query time and space complexity for radial kernels considered in the literature. The approach is based on an implementation of (approximate) importance sampling for each distance range and then using near neighbor search algorithms to recover points from these distance ranges. Later, we show how to improve the runtime, using recent advances in the data-dependent near neighbor search data structures, for a class of radial kernels that includes the Gaussian kernel.

EPFL2022

Sketches, metrics and fast algorithms

Navid Nouri

\tilde{O}(n^{2/3})

\tilde{O}(n^{2/3(1-\alpha)})

-spanners using

\tilde{O}(n^{1+\alpha})

space for any

\alpha \in [0,1]

EPFL2022