The crux of his attack is based on the Over-The-Air (OTA) software updates for these cards, which are typically sent via "secure" binary SMS directly to the SIM. He claims that in 25% of the cases, the SIM will respond with a signed error message to an invalid attempt to update its code, and that for about 50% of the SIMs on the market, the signature will be encrypted with the very old and crackable Digital Encryption Standard (DES). Worse yet, the signature is signed with the same key as is used to sign code, so that once it is broken offline it can be used to send a software update to the SIM.
For some sums this is a little slow. But if you know your 1-12 times tables to the point where its not something you think about, you just see the answer and you know this method extremely thoroughly, you can work out a question like this quicker than the traditional method. It takes a shitload of practice to get so familiar with the system, but if you really want to excel at speed maths, its a great book.
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Tbh, depends on the product I think. On the cash equities desk you really need it, I work on a vanilla options desk and tbh i was great at mental math when i started and now rely on the calculator for everything. This is mainly because you get quite quick using a calculator, and its actually a bit faster because instead of focusing on mental maths you can use those seconds to think about something else, while the calculator does the work for you. You might be a bit faster mentally if you get really good, but the calculator isnt so much about speed as it is freeing up your mind. When you are pricing something you need to think about so many things (ie are we inline with divs, where is spot, where is vol, where is the skew, can i get borrow for the stock etc), that not having to think about doing mental calcs is just easier. Its a useful skill, but not essential for a lot of desks.
Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection. PMID:27171083
Charged-particle fluxes from breakdown events were studied. Methods to measure mass spectra and total emitted flux of neutral particles were developed. The design and construction of the specialized mass spectrometer was completed. Electrical breakdowns were initiated by a movable blunt contact touching the insulating surface. The contact discharge apparatus was used for final development of two different high-speed recording systems and for measurements of the composition of the materials given off by the discharge. It was shown that intense instantaneous fluxes of neutral particles were released from the sites of electrical breakdown events. A laser micropulse mass analyzer showed that visible discoloration at breakdown sites were correllated with the presence of iron on the polymer side of the film, presumably caused by punch-through to the Inconel backing. Kapton samples irradiated by an oxygen ion beam were tested. The irradiated samples were free of surface hydrocarbon contamination but otherwise behaved in the same way as the Kapton samples tested earlier. Only the two samples exposed to oxygen ion bombardment were relatively clean. This indicates an additional variable that should be considered when testing spacecraft materials in the laboratory.
In this paper, CuIn xGa (1-x) (CIGS) mini-modules are stressed under reverse bias, resembling partial shading conditions, to predict and characterize where failures occur. Partial shading can cause permanent damage in the form of 'wormlike' defects on thin-film modules due to thermal runaway. This results in module-scale power losses. We have used dark lock-in thermography (DLIT) to spatially observe localized heating when reverse-bias breakdown occurs on various CIGS mini-modules. For better understanding of how and where these defects originated and propagated, we have developed techniques where the current is limited during reverse-bias stressing. This allows for DLIT-based detection and detailedmore studying of the region where breakdown is initiated before thermal runaway leads to permanent damage. Statistics of breakdown sites using current-limited conditions has allowed for reasonable identification of the as-grown defects where permanent breakdown will likely originate. Scanning electron microscope results and wormlike defect analysis show that breakdown originates in defects such as small pits, craters, or cracks in the CIGS layer, and the wormlike defects propagate near the top CIGS interface. less 2ff7e9595c
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