Semiconductor Fab Scheduling with Self-Supervised and Reinforcement Learning

Semiconductor manufacturing is a notoriously complex and costly multi-step process involving a long sequence of operations on expensive and quantity-limited equipment. Recent chip shortages and their impacts have highlighted the importance of semiconductors in the global supply chains and how reliant on those our daily lives are. Due to the investment cost, environmental impact, and time scale needed to build new factories, it is difficult to ramp up production when demand spikes. This work introduces a method to successfully learn to schedule a semiconductor manufacturing facility more efficiently using deep reinforcement and self-supervised learning. We propose the first adaptive scheduling approach to handle complex, continuous, stochastic, dynamic, modern semiconductor manufacturing models. Our method outperforms the traditional hierarchical dispatching strategies typically used in semiconductor manufacturing plants, substantially reducing each order's tardiness and time until completion. As a result, our method yields a better allocation of resources in the semiconductor manufacturing process

Dust Devil Tracks

Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns

Chronique de droit maritime

Tassel Yves, Chaumette Patrick. Chronique de droit maritime. In: Revue juridique de l'Ouest, 1989-1. pp. 99-107

Facteurs d'Émission des Véhicules Récents

FEVER project aims at improving the vehicle exhaust gaz sampling conditions in order to determine emission factors for regulated and non-regulated pollutants and to assess impacts of post-treatment technologies and pollution standard evolution on pollutant emissions (Euro 4 and Euro 5 gasoline and Diesel vehicles). Moreover, the size distribution of fine and ultrafine particle has been characterized.Dans le cadre du projet FEVER, nous proposons d'améliorer les conditions d'échantillonnage et de prélèvement des gaz d'échappement des Îhicules légers, afin de déterminer les facteurs d'émissions pour les polluants réglementés et non réglementés et ainsi évaluer l'impact des nouvelles technologies de post-traitement et de l'évolution des réglementations (Îhicules Euro 4 et Euro 5 Diesel et essence). De plus, la distribution granulométrique de particules très fines et ultrafines est caractérisée

Real-world European driving cycles, for measuring pollutant emissions from high- and low-powered cars

Pollutant emissions from cars are usually measured on a test bench using driving cycles. However, the use of one unique set of driving cycles to test all cars can be seen as a weak point of emission estimation, as vehicles could conceivably be tested differently depending on their performance levels and usage characteristics. A specific study was then conducted to characterize driving conditions and vehicle usage as a function of vehicle categories, as well as to derive driving cycles specially designed for high- and low-powered cars which have significantly different driving conditions. Pollutant emissions were measured on a sample of 30 passenger cars, using on the one hand the three real-world ARTEMIS driving cycles (urban, rural road and motorway), representative of European driving, and on the other hand specific driving cycles. The comparison of the resulting aggregated emissions demonstrates that the usual test procedure (i.e. with a unique set of driving cycles) can lead to strong differences in emissions, particularly for the most recent vehicle categories

Operating conditions of buses in use in the Ile-de-France region of France for the evaluation of pollutant emissions. In : 12th International Symposium, Transport and Air Pollution

This study is intended to link the pollutant emissions from buses to their driving conditions and to the urban context. Envisaged in the case of the Ile-de-France region of France, this procedure constitutes a methodological basis for characterising bus networks by using geographic and bus operation databases. Firstly, the bus routes are characterised by linking analyses of bus operating conditions and urban characteristics collected and managed by a Geographic Information System. This multidimensional analysis provides bus-route profiles according to the types of areas served. Secondly, one vehicle of a bus route from each of the categories thus defined was instrumented in order to measure its operating parameters during commercial use. The parameters measured include engine operation, the speed and location of the vehicle, passenger load, load linked to the road profile, and electrical and pneumatic loads. After outlining the methodological approach to network characterisation, a description is given of the instrumental protocol followed by the general results of the experiments. In all, over 25,000 km were recorded over 1600 h of driving, for which the main operating parameters were measured at time intervals of 1 s. Preliminary analyses (characterisation of urban areas) and the localisation of the recordings enable linking bus operating conditions with local specificities. The bus operating conditions (speeds, congestion, load, etc.) are analysed as a function of the routes and the geographical and urban specificities of the areas served.This data is then analysed in order to formulate driving cycles representative of real traffic conditions and that serve as the basis for measuring the real pollutant emissions of buses on a vehicle test bench. These driving cycles will then enable associating pollutant emissions with the corresponding driving conditions and geographical areas

PAH, BTEX, carbonyl compound, black-carbon, NO2 and ultrafine particle dynamometer bench emissions for Euro 4 and Euro 5 diesel and gasoline passenger cars

Although implementing Diesel particulate filters (DPF) and other novel aftertreatment technologies makes it possible to achieve significant reductions in particle mass emissions, it may induce the release of ultrafine particles and emissions of many other unregulated compounds. This paper focuses on (i) ultrafine particles, black carbon, BTEX, PAH, carbonyl compounds, and NO2 emissions from Euro 4 and Euro 5 Diesel and gasoline passenger cars, (ii) the influence of driving conditions (e.g., cold start, urban, rural and motorway conditions), and (iii) the impact of additive and catalysed DPF devices on vehicleemissions. Chassis dynamometer tests were conducted on four Euro 5 vehicles and two Euro 4 vehicles: gasoline vehicles with and without direct injection system and Diesel vehicles equipped with additive and catalysed particulate filters. The results showed that compared to hot-start cycles, cold-start urban cycles increased all pollutant emissions by a factor of two. The sole exception was NO2, which was reduced by a factor of 1.3e6. Particulate and black carbon emissions from the gasoline engines were significantly higher than those from the Diesel engines equipped with DPF. Moreover, the catalysed DPF emitted about 3e10 times more carbonyl compounds and particles than additive DPF, respectively, during urban driving cycles, while the additive DPF vehicles emitted 2 and 5 times more BTEX and carbonyl compounds during motorway driving cycles. Regarding particle number distribution, the motorway driving cycle induced the emission of particles smaller in diameter (mode at 15 nm) than the urban cold-start cycle (mode at 80e100 nm). The results showed a clear positive correlation between particle, black carbon, and BTEX emissions, and a negative correlation between particles and NO2

Primary particle emissions and atmospheric ageing from road traffic.

10th International Conference on Future Environment and Energy, KYOTO, JAPON, 07-/01/2020 - 09/01/2020Road traffic is a significant source of atmospheric aerosols, which are important pollutants (class 1 carcinogens for Humans). It contributes to primary and secondary particles in the atmosphere, depending on the presence of particle precursors such as volatile, intermediate-volatility, and semi-volatile organic compounds (VOCs, IVOCs, SVOCs). However, lack of knowledge exists on the sampling methodology, which depends on dilution and available deposition surface. Moreover, the physicochemical and photochemical processes leading to secondary aerosols are complex, and often studied in specific experimental conditions. Therefore, contribution of transportation on aerosol pollution is under-estimated in air-quality models. This study presents particle, black-carbon (BC) and IVOC emissions on a chassis dynamometer under controlled conditions (10 diesel and gasoline passenger-cars, Euro 1 to Euro 6) and in-situ (open urban area and tunnel). Particles and BC were measured with optical devices; IVOCs were sampled on sorbent tubes and analyzed with mass-spectroscopy. IVOC emissions are 2 to 2500 times higher in-situ than for chassis dynamometer experiments. Results show that sampling conditions influence significantly IVOC concentrations, mainly due to temperature and dilution effects on gas-particle partitioning. IVOCs can also nucleate to form new particles, or condensate onto pre-existing particles, and play an important role on particle atmospheric ageing

Euro 3 and Euro 5 Diesel vehickes' particle evolution in ageing chamber

23rd International Transport and Air Pollution Conference, THESSALONIQUE, GRECE, 15-/05/2019 - 17/05/2019This study focuses on the evolution in an ageing chamber of the particles emitted by two Diesel vehicles: a Euro 5 with a Diesel Particle Filter (DPF) and a Euro 3. Both vehicles were tested on a chassis dynamometer with Artemis urban cold start (UC) and Artemis motorway (MW) cycles. Exhaust gas was injected in a 8-cubic-meter dark ageing chamber through a stainless steel line heated at 120°C, during 16 to 25 minutes. The evolution of the particles was monitored during 10 hours. Moreover, exhaust gas was sampled at emssion from the heated line on sorbent tunes, which were then analyzed with ATD-GC-MS. For the Euro 5 DPF vehicle, particle mass (PM) concentrations are below 2µg/m3 (UC/MW) and remain stable during 10h. For the Euro 3 Diesel vehicle, PM concentrations start at 270µg/m3 (UC) and 2200µg/m3 (MW). PM increases of 29% during the first 90min and then stays stable until the end for the MW. For the UC, PM increases of 125% during 10h. This indicates the formation of new particulate matter, which might in part be explained by condensation of Semi-Volatile Organic Compounds (SVOCs). Moreover, condensation would also explain the increase of the mean particle size from 250 to 500nm. Particle number (PN) concentration is close to the background for the Euro 5 DPF UC condition. For MW conditions, the particle mean size is around 20nm. For the Euro 3 Diesel UC and MW conditions, larger particles are emitted and the initial mean particle size is around 120-150nm. Moreover, the total PN decreases and the mean particle size increases with time. This could be explained by coagulation processes. Furthermore, small particles around 30nm are formed during the first hour for Euro 5 DPF MW conditions, probably by nucleation processes. Finally, different SVOCs - such as alkane, alkene, cyclo, and aromatic compounds - were followed with C numbers between C12 and C30 at emission and during the first 6h of ageing. Considering their relatively low volatilities, these SVOCs could play a role in secondary particle formation through physicochemical interactions