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🔗 Trains 🔗 Trains/Operations

Signalling block systems enable the safe and efficient operation of railways by preventing collisions between trains. The basic principle is that a route is broken up into a series of sections or "blocks". Only one train may occupy a block at a time, and the blocks are sized to allow a train to stop within them. That ensures that a train always has time to stop before getting dangerously close to another train on the same line. The block system is referred to in the UK as the method of working, in the US as the method of operation, and in Australia as safeworking.

In most situations, a system of signals is used to control the passage of trains between the blocks. When a train enters a block, signals at both ends change to indicate that the block is occupied, typically using red lamps or indicator flags. When a train first enters a block, the rear of the same train has not yet left the previous block, so both blocks are marked as occupied. That ensures there is slightly less than one block length on either end of the train that is marked as occupied, so any other train approaching that section will have enough room to stop in time, even if the first train has stopped dead on the tracks. The previously-occupied block will only be marked unoccupied when the end of the train has entirely left it, leaving the entire block clear.

Block systems have the disadvantage that they limit the number of trains on a particular route to something fewer than the number of blocks. Since the route has a fixed length, increasing the number of trains requires the creation of more blocks, which means the blocks are shorter and trains have to operate at lower speeds in order to stop safely. As a result, the number and size of blocks are closely related to the overall route capacity, and cannot be changed easily because expensive alterations to the signals along the line would be required.

Block systems are used to control trains between stations and yards, but not normally within the yards, where some other method is used. Any block system is defined by its associated physical equipment and by the application of a relevant set of rules. Some systems involve the use of signals while others do not. Some systems are specifically designed for single track railways, on which there is a danger of both head-on and rear-end collision, as opposed to double track, on which the main danger is rear-end collisions.

The Object Oriented Role Analysis and Modeling (OOram) is a method, based on the concept of role, for performing object-oriented modeling.

Originally (1989) coined Object Oriented Role Analysis, Synthesis and Structuring (OORASS), the method focuses on describing patterns of interaction without connecting the interaction to particular objects/instances. OOram was originally developed by Trygve Reenskaug (1996), a professor at the University of Oslo and the founder of the Norwegian IT company Taskon. The use of "roles" in OOram is similar in application to that of Agent-oriented programming.

Enterprise models created according to OOram may have a number of views, with each view presenting certain aspects of a model. The following ten views are proposed:

1. Area of concern view: Textual description of a phenomenon represented in the role model.
2. Stimulus-response view: Describes how environment roles may trigger activities in the organization (stimulus), together with the effect (response).
3. Role list view: List describing all roles of a role model together with attributes and textual explanation.
4. Semantic view: Describes meaning of roles and relationships between roles.
5. Collaboration view: Describes patterns of roles and message paths.
6. Interface view: Describes all messages that can be sent along a message path.
7. Scenario view: Provides a sample sequence of messages flowing between roles (a concrete example).
8. Process view: Describes data flow between roles and associated activities performed by the roles.
9. State diagram view: For each role, the legal states can be described together with messages that trigger transitions.
10. Method specification view: Describes what messages to send for each method belonging to a role. May also specify procedures to perform.

OOram suggests a varied mix of formal and informal notations and languages for representing and communicating models. Which view to use depends upon the needs in a particular situation.

🔗 Television 🔗 Science Fiction

Ark II is an American live-action science fiction television series, aimed at children, that aired on CBS from September 11 to December 18, 1976 (with reruns continuing through November 13, 1977) as part of its weekend line-up. It returned again in rerun from September 16, 1978 through August 25, 1979. Only 15 half-hour episodes were ever produced. The program's central characters were created by Martin Roth; Ted Post helped Roth develop its core format.

🔗 Computer science

The polyhedral model (also called the polytope method) is a mathematical framework for programs that perform large numbers of operations -- too large to be explicitly enumerated -- thereby requiring a compact representation. Nested loop programs are the typical, but not the only example, and the most common use of the model is for loop nest optimization in program optimization. The polyhedral method treats each loop iteration within nested loops as lattice points inside mathematical objects called polyhedra, performs affine transformations or more general non-affine transformations such as tiling on the polytopes, and then converts the transformed polytopes into equivalent, but optimized (depending on targeted optimization goal), loop nests through polyhedra scanning.

🔗 Astronomy 🔗 Central Asia 🔗 Museums 🔗 Central Asia/Uzbekistan

The Ulugh Beg Observatory is an observatory in Samarkand, Uzbekistan. Built in the 1420s by the Timurid astronomer Ulugh Beg. Islamic astronomers who worked at the observatory include Al-Kashi, Ali Qushji, and Ulugh Beg himself. The observatory was destroyed in 1449 and rediscovered in 1908.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Physics

The hafnium controversy is a debate over the possibility of 'triggering' rapid energy releases, via gamma ray emission, from a nuclear isomer of hafnium, ^178m2Hf. The energy release is potentially 5 orders of magnitude (100,000 times) more energetic than a chemical reaction, but 2 orders of magnitude less than a nuclear fission reaction. In 1998, a group led by Carl Collins of the University of Texas at Dallas reported having successfully initiated such a trigger. Signal-to-noise ratios were small in those first experiments, and to date no other group has been able to duplicate these results. Peter Zimmerman described claims of weaponization potential as having been based on "very bad science".

🔗 Computing 🔗 Crime 🔗 Computer Security 🔗 Computer Security/Computing 🔗 Business 🔗 Computing/Software

A scandal erupted in 2005 regarding Sony BMG's implementation of copy protection measures on about 22 million CDs. When inserted into a computer, the CDs installed one of two pieces of software that provided a form of digital rights management (DRM) by modifying the operating system to interfere with CD copying. Neither program could easily be uninstalled, and they created vulnerabilities that were exploited by unrelated malware. One of the programs would install and "phone home" with reports on the user's private listening habits, even if the user refused its end-user license agreement (EULA), while the other was not mentioned in the EULA at all. Both programs contained code from several pieces of copylefted free software in an apparent infringement of copyright, and configured the operating system to hide the software's existence, leading to both programs being classified as rootkits.

Sony BMG initially denied that the rootkits were harmful. It then released an uninstaller for one of the programs that merely made the program's files visible while also installing additional software that could not be easily removed, collected an email address from the user and introduced further security vulnerabilities.

Following public outcry, government investigations and class-action lawsuits in 2005 and 2006, Sony BMG partially addressed the scandal with consumer settlements, a recall of about 10% of the affected CDs and the suspension of CD copy-protection efforts in early 2007.

🔗 Marketing & Advertising 🔗 Brands 🔗 Graffiti

Reverse graffiti is a method of creating temporary or semi-permanent images on walls or other surfaces by removing dirt from a surface. It can also be done by simply removing dirt with the fingertip from windows or other dirty surfaces, such as writing "wash me" on a dirty vehicle. Others, such as graffiti artist Moose, use a cloth or a high-power washer to remove dirt on a larger scale.

Reverse graffiti has been used as a form of advertising, although this usage has been controversial, as its legality varies depending on jurisdiction.