Dust clearing by radial drift in evolving protoplanetary discs

Recent surveys have revealed that protoplanetary discs typically have dust masses that appear to be insufficient to account for the high occurrence rate of exoplanet systems. We demonstrate that this observed dust depletion is consistent with the radial drift of pebbles. Using a Monte Carlo method we simulate the evolution of a cluster of protoplanetary discs, using a 1D numerical method to viscously evolve each gas disc together with the radial drift of dust particles that have grown to 100 $\mu$m in size. For a 2 Myr old cluster of stars, we find a slightly sub-linear scaling between the gas disc mass and the gas accretion rate ($M_\mathrm{g}\propto\dot{M}^{0.9}$). However, for the dust mass we find that evolved dust discs have a much weaker scaling with the gas accretion rate, with the precise scaling depending on the age at which the cluster is sampled and the intrinsic age spread of the discs in the cluster. Ultimately, we find that the dust mass present in protoplanetary disc is on the order of 10-100 Earth masses in 1-3 Myr old star-forming regions, a factor of 10 to 100 depleted from the original dust budget. As the dust drains from the outer disc, pebbles pile up in the inner disc and locally increase the dust-to-gas ratio by a factor of up to 4 above the initial value. In these high dust-to-gas ratio regions we find conditions that are favourable for planetesimal formation via the streaming instability and subsequent growth by pebble accretion. We also find the following scaling relations with stellar mass within a 1-2 Myr old cluster: a slightly super-linear scaling between the gas accretion rate and stellar mass ($\dot{M}\propto M_\star^{1.4}$), a slightly super-linear scaling between the gas disc mass and the stellar mass ($M_\mathrm{g}\propto M_\star^{1.4}$) and a super-linear relation between the dust disc mass and stellar mass ($M_\mathrm{d}\propto M_\star^{1.4-4.1}$).Comment: 18 pages, 18 figures, accepted for publication in A&

Interaction Between Solid Copper Jets and Powerful Electrical Current Pulses

The interaction between a solid copper jet and an electric current pulse is studied. Coppe

Automated control and test system for long time stess tests of microwave ovens

To be able to improve products extensive testing is required in order to find hidden flaws in the design. The earlier flaws are found the higher are the probability that they can be corrected before the product is released onto the market. If the tests could be carried out all hours of the day every day of the week, this would introduce another level of stress to the product. More stress than if the product would be tested only during working days and it may reveal issues that could be corrected to improve the product further. Although a similar test environment already exists at Whirlpool Sweden AB, there are requests to rethink and improve these tests so that the microwave ovens are tested in an environment more close to reality. This thesis will present a concept proposal of how to improve the tests. Further, the thesis will include initial construction of a machine that could perform automated tests with the ability to interpret errors and report them. In the end, the machine should press buttons on the microwave oven, look at the display with a camera, open the door and so on. The mechanics for the machine is bought, so a big part of the thesis will be electronics design. The project will include an embedded system design with a 32-bit ARM micro controller that is going to control the machine. As this part is quite big the thesis will include the hardware design, but not much programming. The hardware design of the embedded system did work as expected, without any revisions. The hardware has been verified by electrical tests and basic software to test the general functions of the hardware. In the future, the hardware needs programming and the machine has to be equipped with a mechanical finger to be able to press buttons. Keywords: Embedded system design, ARM, Cortex-M3, , Linear guide, Stepper motor

Evaluation of non-destructive testing methods for automatic quality checking of spot welds

Car bodies are today more often made of high strength steel. In high strength steel spot welds are more friable and it is necessary to have higher demands on the inspections of spot welds. Quality control of spot weld can be either destructive or non-destructive. Destructive testing is still the most common method to test spot weld. The non-destructive methods that are investigete in this project are visual inspektion (VT), penetrant testing (PT), eddy current testing (ET), ultrasonic testing (UT), magnetic paticle testing (MT) and X-ray testing (RT). Other NDT methods are acoustic emission (AE), digital sheargraphy and IR-termography (IRT). These methods are investigated with focus on the possibility to detect Lens Diameter, stick welds, expulsions, porosity and cracks. And the possibility to automation of the method with focus on size and weight of the system, protection equipment, contact or contactless, one or two sided, position accuracy, and result in real-time. Only tree NDT methods, UT, RT and IRT, can detect all discontinuities that we looking for in RSW. The thermography system has the largest potential to be a NDT system for spot weld in the future, mainly because the method is non-contact, which helps when you have the opportunity to searching on a surface instead of a specific position. The main problem with this method is that there is no software for analysing the results to obtain lens diameter.SpotLigh

Sizing Up Extracellular DNA : Instant Chromatin Discharge From Cells When Placed in Serum-Free Conditions

How do you wash cells? Three out of four of our colleagues use experimental procedures during everyday lab-bench work that can severely impair data interpretation depending on how cells are handled. We show here that a subpopulation (2–3%) of human leukocytes immediately induce a yet unclassified lytic cell death, concomitant with discharge of chromatin entities and cell elimination, when placed in protein-free solutions (i.e., PBS and HBSS). DNA release was not restricted to hematopoietic cells but occurred also in HEK293T cells. Albumin, fetal bovine serum, polyethylene glycol, and Pluronic F-68 supplements prevented chromatin discharge. Expelled chromatin was devoid of surrounding membranes but maintained its original nuclear shape, although ∼10 times enlarged. These structures differed from DNA appearance after osmotic or detergent-induced cell lysis. Besides sounding a cautionary note to the neutrophil extracellular trap (NET) research community, in which ∼50% of all published studies used protein-free media for NET-formation, our study also provides a rapid tool for analysis of chromatin organization

Automatic Inspection of Spot Welds by Thermography

The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.Funding Agencies|Vinnova (the FFI program)</p

Automated NDT cell for quality checking of spot welds

This report is written within Spotlight WP5 financed by the FFI programme within Vinnova. Thermography is a non-destructive testing method based on measurement of the heat distribution by an infrared camera. The method is suitable for automatic inspection since it is a full filed and non-contact method. A thermography system with an analysis tool developed by Termisk Systemteknik AB is investigated as an inspection method for spot weld. The system is able to detect spot welds, measure the diameter and separate a spot weld from a stick weld. The algorithms used in the analysis are rather simplified and the development opportunities are significant. A fully automated NDT-cell for spot weld inspection is presented. The automation includes a six axis industrial robot and communication for handling the information flow. This comprised the identification of the inspected spot weld and the reporting to the overall system as to the operator. A failure modes and effects analysis (FMEA) of the automated NDT-cell is accomplished and the most important actions are reported A business case for implementing a automated NDT-cell was included in the project. In this business case the most promising quality check concepts for NDT spot weld will be presented and compared with the other identified methods