Publications related to Experiment

Identification of parameters affecting the outcome of biochemical methane potential (BMP) tests

Anaerobic digestion of organic waste to methane gas (CH4) is an attractive method to produce renewable energy. Due to the trend towards the reuse of waste and away from fossil energy sources, this technology saw a worldwide development in the recent years. A fundamental parameter in this domain is the Biochemical Methane Potential (BMP), which defines the amount of CH4 which can be produced out of a certain organic substrate. Such information is essential in order to plan and optimise anaerobic digestion plants, and to evaluate the reactor feed with a new substrate or a new substrate combination (co-digestion). BMPs are assessed in batch test, which can be regarded as the simulation of a full-scale biogas plant. Two experiments are required, the test in which the test substrate is digested on the inoculum, and the blank, in which the inoculum is digested alone. The part of the inoculum which can be digested is called endogenous substrate. Since the test experiment produced not only on the test substrate but only on the endogenous substrate, the CH4 production on the test substrate alone is obtained by the subtraction of the test production minus the blank production. The units of a BMP are generally indicated in litre of CH4 per gram of volatile solids (VS) test substrate [L/gVS]. Despite the importance and the wide application of this parameter, its exact determination remains a challenging issue and results are often not consistent in between (inter-) and within (intra-) laboratories. Experimental protocols exist but do not lead to a satisfactory BMP tests consistency neither. The aim of this study was to identify parameters affecting the outcome of BMP tests, based on the investigation of two different data sets. An inter-laboratory study of BMP tests providing the final BMP values of 327 experiments and information about 40 related experimental parameters, and a second data set containing the complete CH4 production curves of 136 BMP experiments provided by one single laboratory. The method consisted in graphical and statistical analysis (Mixed Effect Modelling), using [R] programming language and software environment. This study found out, that a significant part of the inter-laboratory BMP inconsistency can be explained by an imprecise assessment of the VS, which was not expected. As the VS of the substrate are directly implied in the computation of the BMP, the impact was significant and therefore the BMP were corrected regarding the VS imprecision. With these data, up to 70% of the inconsistency of BMPs could be explained by inter-laboratory effects. The statistical analysis led to the conclusion that the concentration of the endogenous substrate and the moisture content in the digestate would be the principal factors affecting the outcome of BMP tests. An effort was made to identify and correct errors contained in CH4 production curves, which turned out to be delicate for certain cases. Also indications regarding the precision and the reliability of BMPs were formulated. Further, the investigation of the CH4 production curves led to the development of a new method in order to compute the BMP result. This method was based on the fact, that a certain inoculum reaches always the same slope toward the end of the experiment, no matter what was digested before. The advantage of this method would be that the experiment end-point could be set clearly and that the concentration of the endogenous substrate would not have an impact on the outcome of a BMP test. According to the findings of this report, it was proposed to add the following requirements into experimental protocols for BMP tests: Tests, blanks and the analysis of VS should be carried out in triplicates and their standard deviation should be indicated for each of them, together with the BMP result If triplicates contain set-up errors, these experiments must be repeated, including the corresponding blank/test In the annex: An experimental protocol for the TS and VS analyses An indication of a required moisture content of the digestate (mechanism to investigate in detail first) An indication of the range of required VS concentrations or a maximal production rate for blank tests according to certain experimental conditions (mechanism to investigate in detail first). This report identified several parameters, which contribute to the inter-laboratory inconsistency of BMPs. These findings should be investigated further in order to prove and quantify their impact. An effort should be made to demonstrate the newly developed BMP-computation-method, which could eventually lead to more consistent results. The limitation of this study was, that a relatively low amount of data was available compared to their characteristics. Consequently, the findings could only be proven on a few examples and should therefore only be seen as evidences. Further, this led also to the risk of overfitting, since a relative high amount of parameters needed to be included into the statistical model.

2012

A PROOF-OF-PRINCIPLE ECHO-ENABLED HARMONIC GENERATION EXPERIMENT AT SLAC

Pierre-Louis Pernet

In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harmonic generation (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC.We present the design considerations and the technical details of the experiment.

2010

Experimental study of the lateral resistance of timber shear walls

Jonas Knöri

2022

A Python package for audio signal processing

Sidney Barthe

A Python package for room acoustics. This package would allow us to simulate sound propagation in a closed room allowing us to predict a situation, compare it with experimental results or apply calculations for various signal processing applications.

2015

Demonstration of the echo-enabled harmonic generation technique for short-wavelength seeded free electron lasers

Pierre-Louis Pernet

We report the first experimental demonstration of the echo-enabled harmonic generation technique, which holds great promise for generation of high-power, fully coherent short-wavelength radiation. In this experiment, coherent radiation at the 3rd and 4th harmonics of the second seed laser is generated from the so-called beam echo effect. The experiment confirms the physics behind this technique and paves the way for applying the echo-enabled harmonic generation technique for seeded x-ray free electron lasers. © 2010 The American Physical Society.

2010

Thermal management of components for high energy physics experiments and space applications

Timothée Robert Sophus Frei

High-energy physics (HEP) experiments and space missions share a common challenge: thermal management in harsh environments. The severe constraints in both fields make cooling of electronic components a major design concern. This thesis aims to develop high thermal conductivity, radiation hard devices for thermal management in HEP and space application with the help of micro-technologies.Continuous advances in micro-engineering have opened the door to the development of smaller and more efficient cooling devices capable of handling increasing power densities with minimum mass and volume penalties. In this respect, previous works have focused on the use of microchannels etched in single crystal silicon (ScSi) wafers to circulate a cooling fluid. However, whilst this technique represents the state-of-the-art for thermal management of silicon detectors, it poses several challenges, particularly those associated with the fluidic interconnections, compatibility with high operating pressures and coverage of large areas. A cooling scheme relying on two independent fluidic loops is proposed to overcome these limitations. The two cooling loops, referred to as the primary and the secondary cooling loops (i.e. PCL and SCL respectively), are connected through thermal and mechanical interfaces but do not share any fluidic interface. Both circuits work together to remove heat and control the temperature of multiple electronic components. The SCL transfers the heat generated at the source to the PCL, which transports it further away and dissipates it to the environment.The present thesis investigates the use of micro-oscillating heat pipes (uOHPs) to implement the secondary cooling loops. These devices offer great potential, particularly if embedded in silicon substrates. However, a better understanding of the mechanisms responsible for their self-actuated, two-phase flow is essential to produce high performance devices which meet the stringent requirements of particle detectors and spacecraft. Two types of dual-diameter uOHPs were microfabricated: the first version used a glass wafer to close trenches etched in a silicon substrate, while an all-silicon construction was adopted in the second type. The thermocompressed interface used to bond the two silicon wafers yielded excellent pressure resistance. The thermal performance of the of uOHPs was studied for different working fluids, charging ratios, orientations, and heat inputs, taking advantage of the transparent cover in the glass devices to monitor the two-phase flow for the different conditions. The results revealed that the performance of the proposed uOHPs was orientation-independent. Furthermore, under certain conditions the equivalent thermal conductivity of acetone-charged devices exceeded that of an equivalent copper strip.Finally, an innovative technique for charging and sealing the micro-cooling heat pipes was developed. It offers a low-volume, small-footprint solution to enclose working fluids in the devices. The proposed technique, which relies on a compressed Indium preform to seal the inlet charging port, yield very good leak-tightness results.

EPFL2021

,

The plasticity of the dense hydrous magnesium silicate (DHMS) phase A, a key hydrous mineral within cold subduction zones, was investigated by two complementary approaches: high-pressure deformation experiments and computational methods. The deformation experiments were carried out at 11 GPa, 400 and 580 degrees C, with in situ measurements of stress, strain and lattice preferred orientations (LPO). Based on viscoplastic self-consistent modeling (VPSC) of the observed LPO, the deformation mechanisms at 580 degrees C are consistent with glide on the (00 01) basal and (01 1 0) prismatic planes. At 400 degrees C the deformation mechanisms involve glide on (211 0) prismatic, (0001) basal and {1 1 21} pyramidal planes. Both give flow stresses of 2.5-3 GPa at strain rates of 2-4 x 10(-5) s(-1). We use the Peierls-Nabarro-Galerkin (PNG) approach, relying on first-principles calculations of generalized stacking fault (gamma-surface), and model the core structure of potential dislocations in basal and prismatic planes. The computations show multiple dissociations of the 1/3 [2 (1) over bar(1) over bar0] and [01 (1) over bar0] dislocations (< a >) and < b > dislocations) in the basal plane, which is compatible with the ubiquity of basal slip in the experiments. The gamma-surface calculations also suggest 1/3 [2 (1) over bar(1) over bar3] and [0 (1) over bar 11] dislocations (< a + c > or < c - b > directions) in prismatic and pyramidal planes, which is also consistent with the experimental data. Phase A has a higher flow strength than olivine. When forming at depths from the dehydration of weak and highly anisotropic hydrated ultramafic rocks, phase A may not maintain the mechanical softening antigorite can provide. The seismic properties calculated for moderately deformed aggregates suggest that S-wave seismic anisotropy of phase A-bearing rocks is lower than hydrous subduction zone lithologies such as serpentinites and blueschists. (C) 2015 The Authors. Published by Elsevier B.V.

Elsevier2015

Behaviour of carbon-14 containing low molecular weight organic compounds in contaminated groundwater under aerobic conditions

Aislinn Ann Boylan

Short chain carbon-14 (C-14) containing organic compounds can be formed by abiotic oxidation of carbides and impurities within nuclear fuel cladding. During fuel reprocessing and subsequent waste storage there is potential for these organic compounds to enter shallow subsurface environments due to accidental discharges. Currently there is little data on the persistence of these compounds in such environments. Four C-14-labelled compounds (acetate; formate; formaldehyde and methanol) were added to aerobic microcosm experiments that contained glacial outwash sediments and groundwater simulant representative of the Sellafield nuclear reprocessing site, UK. Two concentrations of each electron donor were used, low concentration (10(-5) M) to replicate predicted concentrations from an accidental release and high concentration (10(-2) M) to study the impact of the individual electron donor on the indigenous microbial community in the sediment. In the low concentration system only similar to 5% of initial C-14 remained in solution at the end of experiments in contact with atmosphere (250-350 h). The production of (CO2)-C-14(g) (measured after 48 h) suggests microbially mediated breakdown is the primary removal mechanism for these organic compounds, although methanol loss may have been partially by volatilisation. Highest retention of C-14 by the solid fractions was found in the acetate experiment, with 12% being associated with the inorganic fraction, suggesting modest precipitation as solid carbonate. In the high concentration systems only similar to 5% of initial C-14 remains in solution at the end of the experiments for acetate, formate and methanol. In the formaldehyde experiment only limited loss from solution was observed (76% remained in solution). The microbial populations of unaltered sediment and those in the low concentration experiments were broadly similar, with highly diverse bacterial phyla present. Under high concentrations of the organic compounds the abundance of common operational taxonomic units was reduced by 66% and the community structure was dominated by Proteobacteria (particularly Betaproteobacteria) signifying a shift in community structure in response to the electron donor available. The results of this study suggest that many bacterial phyla that are ubiquitous in near surface soils are able to utilise a range of C-14-containing low molecular weight organic substances very rapidly, and thus such substances are unlikely to persist In aerobic shallow subsurface environments.

ELSEVIER SCI LTD2018

Helio-photocatalytic enhancement of the biodegradation of biorecalcitrant pollutants in water

Simeon Kenfack

The importance of the photocatalytic treatment of water is continuously growing since the 80s. In spite of the well management of the existing biological water treatment plants and the constant reinforcement of the wastewater discharge standards, the development of new water depolluting processes among which the photocatalysis is still relevant. It is recognized that certain chemicals mostly from the synthetic chemistry are not or could only be biodegradable under very critical conditions. When these "biorecalcitrant" pollutants are rejected in a biological wastewater treatment plant, they very often cross it without being degraded and thus, they accumulate in the environment and/or in the living beings. Some of them like the phthalates and the pesticides are known for their carcinogenic and mutagen effects or, they induce hormonal disruptions in the animals, including humans. In general, all the Advanced Oxidation Processes (AOP) whose characteristic is to generate hydroxyls radicals (OH) are able to degrade most of the organic molecules including the biorecalcitrant chemicals. As a technology using the photons emitted by a light source to excite a catalyst and facilitate the generation of the 'OH radicals, the photocatalysis would be a more environmental compatible and less expensive process for depolluting such chemicals, if the light source is natural: the sun. For the first time, a study of potential application in the field of helio- photocatalysis was explored in a sub-Saharan Africa country (Burkina Faso), making profitable the significant solar radiation present in that country, to validate certain results obtained using appropriated experimental and analytical methods at the Laboratory for Environmental Biotechnology (LBE) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. The main objective of this thesis was to contribute to evaluate some physicochemical and technical rules which guide the scaling up processing of the helio-photo-Fenton process. To achieve this, the work was organized in several phases of laboratory work at the EPFL and field apply work at the Ecole Inter-Etats d'Ingénieurs de l'Equipement Rural (EIER) of Ouagadougou in Burkina Faso. To mitigate the deficit of sophisticated analytical material during the field work's periods, a simple analytical method requiring relatively modest equipment was developed and validated in the laboratory and on the field. This thesis is organized in 5 chapters of which the first focuses on the problems of this research and presents the fundamental principles of the photocatalytic processes. Chapter 2 presents the systematic development of a low cost analytical method built up and validated in the laboratory for field's applied studies on three phthalates: the dimethyl phthalate (DMP), the diethyl phthalate (DEP) and the Diallyl phthalate (DAP). The chapter 3 focuses on the study of the optimal parameters influencing the helio-photodegradation of the DEP. In the chapter 4, two case studies on the enhancement of the biodegradability of some biorecalcitrants wastewaters of which, the first evaluates the possibility of integrating the photocatalysis into a global strategy of managing the effluents of a chemical industry and the other treat problem of the depollution of the water polluted by a pesticide are presented. The last chapter presents some modelling approaches allowing to evaluate the solar UVA energy (needed for the helio-photocatalysis) basing on the equation of the solar UVA irradiation which was proposed and tested with the one year solar data of Ouagadougou.

EPFL2006

2009