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Comment Re:Define "crash". (Score 3, Insightful) 168

However, considering how many firmware bugs there are in modern SSDs and HDs which cause out-of-order writes, shorn writes, and various other random corruptions and bad behaviour during a power failure or system reset, what would be more interesting is how the file system could cope with one of those.

Comment Re:I volunteer as tribute. (Score 1) 381

>Based on study: >http://ajph.aphapublications.o... [aphapublications.org]

I should point out that this study did not look at the rate of "cure" of obesity. However, it has been widely misreported as such.

This study examined the rate of weight loss within a population of obese people - i.e. the sample was not limited to those who were trying to lose weight, but was the population in general. In this case it was about 0.5% for men and 1% for women, with much lower rates for those with morbid obesity.

Comment Re:oracle db (Score 1) 54

Oracle has been the favoured database backend for a lot of healthcare software that I've ended up procuring.

What has been quite interesting is that two of our software vendors have just delivered updates as part of the contract. In both cases, part of the upgrade was to "upgrade" the database from Oracle Enterprise to Postgres. From the cost of licensing, there's no surprise why the application vendors are doing this. Not being adequately experienced with SQL, I don't really know enough about postgres to know if technically this is a good idea.

Comment Re:OK, but... (Score 1) 161

True. But these dongles are in widespread use (e.g. by insurance companies selling insurance on a per-mile basis, or high risk policies for younger drivers; fleet managers who wish to track the movements and driving style of the their vehicles, etc.)

Because these dongles are intended to be accessible over cellular networks, any defects in authentication or validation of query data can be troublesome. In this case, these dongles intended to monitor driving behavior and forward it to an authorised viewer, appear to blindly forward data received over a cellular network to the vehicle's internal network.

Comment Re:Already propagating (Score 1) 663

It is potentially explicable. Modern refined carbohydrates and even modern varieties of unrefined starchy foods (e.g. potatoes) are extremely calorie dense. More importantly, consumption of carbohydrates, particularly unrefined carbohydrates, has an inhibitory effect on the brain's satiety response. Whereas satiety is triggered by consumption of fat, especially saturated fat, and to a lesser extent protein, carbohydrates inhibit satiety.

The hypothesised evolutionary biological explanation is that most natural sources of carbohydrates are bulky and have poor calorie density, but carbs are an excellent energy source, so there is a role for inhibiting satiety to ensure a good carb load in a hunter-gatherer type lifestyle. At the same time, there is not a single naturally occurring (wild) foodstuff that contains both fat *and* carbohydrates in meaningful quantities, so in the event of fatty food becoming available, then the satiety response is useful to limit calorie intake in a single sitting, especially as fat is slightly less desirable as an energy source.

One of the (multiple) reasons why low carb diets are so effective at inducing weight loss is that they don't inhibit the satiety response, so the natural instinctive behaviour is to limit calorie intake. As a result, considerably less will-power is needed to stick to such a diet than simply following an "eat less" diet. It is also an explanation for why people tend to overindulge on fast foods, and rich sweet foods (cakes, cookies, etc.). By packaging high quantities of fat and highly refined carbs together, you create an extremely calorie dense foodstuff which causes limited satiety, and because of the high insulin spikes and fluctuations in blood sugar may instead trigger a hunger response.

The other point you hint on, is that "metabolic syndrome" (i.e. insulin resistance, high cholesterol, low HDL, etc.) is less about what you eat, but the total calorie load. Although, to some extent, toxins which disrupt glucose metabolism and insulin sensitivity (alcohol and high doses of fructose - i.e. refined sugar and HFCS).

Comment Re:Already propagating (Score 1) 663

You miss the point of soft drinks. Soft drinks are carefully formulated to be addictive and not quench thirst.

For example, a can of regular coke contains about 0.15 grams of salt. This is deliberately added to reduce the thirst quenching capability so that you drink more. Similarly, the caffeine which is so common in sodas, is added because it is physically and psychologically addictive and because it is a diuretic and makes you thirsty and drink more.

The sugar/sweetener then has to be added to hide the taste of the salt and bitterness of caffeine. This is why most sodas are so incredibly sweet - they have to be.

Comment Re: COMAPRISON REQUIRED (Score 1) 64

It should be clarified that a "surgical robot" is not some sort of autonomous device. It is effectively a manipulator arm, with a degree of "intelligence"

The idea is that the "robot" provides the surgeon with a greater degree of control; for example, reducing movement sizes allowing micromanipulation, provides enhanced force feedback, can cross reference a pre-surgical CT scan onto which "no touch" areas have been drawn so that if the operator attempts to cut into a "no touch" structure, the robot provides feedback as if the instrument had hit a brick wall and the instrument will not go.

Comment Re:Why bother with installed capacity? (Score 1) 259

> Really? Every grid-tie inverter, ever, has this built in.

Exactly. This is why it has been a problem. In the event of a grid disturbance, a large amount of grid-tie inverters falsely detected an island and tripped out simultaneously.

> Pointer to the UK issue you're referring to?

http://www2.nationalgrid.com/a...

Although the initiating cause was 2 large thermal plants tripping, the rapid reduction in grid frequency caused approximately 300 MW of grid-tie inverters to trip simultaneous, accelerating a grid frequency collapse event.

National grid has recommended new grid-tie inverter firmware configurations, which should be present in new inverters, but this reduces the sensitivity to true islanding, but this is now considered a lesser issue than loss of embedded generation.

Comment Re:Why bother with installed capacity? (Score 3, Informative) 259

It depends on the nuclear plant design, but in general a LWR nuclear plant has better load following characteristics than a coal plant (the compact core has low thermal mass compared with the large furnaces and boilers of a coal plant). Load following, however, may not be permitted under regulatory regimes (for example, in the US). The availability characteristics of a typical LWR are not much different to coal - there are longer, less frequent maintenance/refuelling periods.

A 100 MW wind farm is not a perfectly good substitute for a 100 MW coal plant. Typically the load factor for wind is in the 25-35% range, with off-shore wind being higher. However, the "firm capacity" (i.e. the capacity that can be relied upon) is poor - about 2% in the UK, whereas for coal it is about 85%.

Both wind and solar have very poor load following capacity - as they cannot automatically respond significantly to changes in grid frequency (except in the case of overfrequency), whereas most thermal plants have the capacity to automatically increase power, provided they are not at capacity, in response to a drop in grid frequency. Im Germany, this is partly mitigated by requiring that rooftop solar installations be electronically limited to 70% of their nominal capacity and/or be able to receive remote configuration updates from the utility, so that there is frequency reserve margin.

Small scale embedded generation (i.e. rooftop solar) has an additional problem which is that of grid failure detection and anti-islanding (i.e. the embedded generators must not be allowed to supply energy to the local area in the event of failure of grid connection). The problem is that grid instability is not easily discriminated from grid islanding, hence there is a tendency for a severe grid imbalance to trigger cascading disconnections of small generators, which makes the imbalance worse.... This has happened in the UK, and very nearly caused a country-wide blackout. It was only arrested when underfrequency protection started blacking out regions of the country in an attempt to reduce load on the grid.

Comment Re:Good god. (Score 1) 253

Except in an aircraft you have multiple redundant engines, so the idea of dropping a faulty engine to idle is not that unreasonable.

The problem here was 3 faulty engines, for which there was insufficient redundancy - in this case a "common cause" failure that's a much more difficult problem to deal with.

Comment Re:Good god. (Score 3, Insightful) 253

My guess is that rather than "files" per se, these are look-up tables which were statically linked into the binary.

On this type of safety critical application, it's a key design aim to avoid code which might fail or throw an exception at runtime. So, rather than load data from a file, which could fail due to a memory allocation failure, a file system failure, etc. the relevant data is static linked, so if the executable successfully launches, it cannot fail to have the data available.

I don't know what these tables might have been mapping, but conceivably if they torque tuning parameters, the engine might still have run if the data was all NULLs, but delivered the incorrect torque in response to control inputs. Of course, if the missing data was things like fueling data, then the engine may have failed to start.

Comment Re:Hack piece (Score 3, Informative) 126

There was a big change in design philosophy. Early reactor designs were intended to prevent meltdown and had limited mitigation. More recent designs now include substantial mitigation as well as more robust prevention strategies.

E.g. The fukushima accident occurred because of a "common cause" failure of multiple safety critical systems - the redundant diesel generators. This failure led to a "cliff edge" cascading failure of numerous safety systems, effectively meaning that core melt was inevitable. (This is in addition to the incorrect site risk assessment, where an incorrect tsunami risk was used when assessing the suitability of the site for a nuclear power plant, and the additional failure to mitigate that risk when the tsunami risk was recognised in the 1980s).

Most modern reactor designs (the EPR excepted) do not class their diesel generators as "safety critical", because they are not necessary to place the plant in a safe state and initiate adequate reactor cooling. In addition, nuclear regulators (Japan excepted) around the world started carefully investigating "cliff edge" scenarios following the 9/11 attacks, to see if deliberate sabotage could result in disproportionate failure of safety features. In the US, the NRC started mandating that "safety critical" diesel generators be heavily hardened against beyond design-basis natural events and other methods of attack, even if not originally conceived at design stage; that UPS batteries be upgraded to provide up to 24 hours of safety, in order to allow emergency assistance to be called in, and/or that additional electrical power sources (e.g. gas turbines) be installed in fortified near-site (to mitigate against local site damage) installations.

A similar set of upgraded mitigations have also been in place for a while - hydrogen catalytic recombiners (these are basically catalytic converters similar to those in a car exhaust which react hydrogen and oxygen at a low temperature and low hydrogen concentration, well below the minimum ignition level. Heat generated from the recombination is used to cause natural circulation of air through the combiner to accelerate hydrogen removal and stir up the air to ensure that hydrogen cannot pool away from the recombiners) have been installed in-containment, and in buildings close to hydrogen vent pipes. In Fukushima, no hydrogen recombiners were used, instead the main containment building was inerted with nitrogen. As a result, hydrogen (and steam) built up in the containment pressurising the building. In order to reduce pressure to prevent rupture, the containment building was vented into the main reactor building, where the hydrogen mixed with air and later ignited. More modern designs vent directly outside through filters, or vent through hydrogen recombiners.

The other complicating issue is that at Fukushima unit 1, the reactor core appears to have completely melted through the reactor vessel into the containment building, severely contaminating the water in the containment building which was being used for cooling (and also leaked through minor damage to the containment). Again, modern designs try to mitigate this. The AP1000 design fills the bottom of the reactor vessel with low-melting point, sacrificial material into which molten core material will melt, resulting in dilution, prevention of re criticality, and spreading of the decay heat. Then by flooding the containment building and submerging the reactor with water, "melt through" is prevented because of combination of external cooling water and the diluted core material, as a result the containment building itself is not contaminated. The EPR instead, has a special chamber beneath the reactor intended to spread and retain molten core material, in such a way that it would not contaminate the containment building.

Comment Re:Pointing out the stark, bleeding obvious... (Score 1) 247

The grid technical paper specifically listed multiple different sizes of OCGT and their ramp rates, so I presume that they do matter.

However, checking the specification sheet for a state of the art large turbine (GE 7HA), the ramp rate is 40 MW/min for the 275 MW model, with a manufacturer claimed startup-signal to full load time of 10 minutes.

By contrast, checking the spec sheet for the same manufacturer's small turbine, they claim that the turbine can ramp to 20 MW (45%) from idle within 5 seconds. I could well imagine that such a turbine could start, synchronize and ramp to full power within 1-2 minutes.

Comment Re:Pointing out the stark, bleeding obvious... (Score 1) 247

My figures were taken from a 2012 report by my local grid operator, based upon operational data supplied by the power plant operators.

The figures are conservative, but they are based upon the figures declared by the plant operators, based upon existing plant, but some consideration has been given to new-build plant. I accept that I omitted the issue of ramp "elbow" for CCGT, but that was for simplification.

As to the ramp rate of OCGT, it varies with size. Aero-derivative OCGT (20-60 MW range) can certainly come to full power within 3 minutes. Large frame OCGT (200 MW range) are slower. Even a state-of-the-art turbine needs at least 10 minutes to come to full power from cold shutdown. Most existing plant is slower.

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