LightGBM, short for Light Gradient-Boosting Machine, is a free and open-source distributed gradient-boosting framework for machine learning, originally developed by Microsoft. It is based on decision tree algorithms and used for ranking, classification and other machine learning tasks. The development focus is on performance and scalability. == Overview == The LightGBM framework supports different algorithms including GBT, GBDT, GBRT, GBM, MART and RF. LightGBM has many of XGBoost's advantages, including sparse optimization, parallel training, multiple loss functions, regularization, bagging, and early stopping. A major difference between the two lies in the construction of trees. LightGBM does not grow a tree level-wise — row by row — as most other implementations do. Instead it grows trees leaf-wise. It will choose the leaf with max delta loss to grow. Besides, LightGBM does not use the widely used sorted-based decision tree learning algorithm, which searches the best split point on sorted feature values, as XGBoost or other implementations do. Instead, LightGBM implements a highly optimized histogram-based decision tree learning algorithm, which yields great advantages on both efficiency and memory consumption. The LightGBM algorithm utilizes two novel techniques called Gradient-Based One-Side Sampling (GOSS) and Exclusive Feature Bundling (EFB) which allow the algorithm to run faster while maintaining a high level of accuracy. LightGBM works on Linux, Windows, and macOS and supports C++, Python, R, and C#. The source code is licensed under MIT License and available on GitHub. == Gradient-based one-side sampling == When using gradient descent, one thinks about the space of possible configurations of the model as a valley, in which the lowest part of the valley is the model which most closely fits the data. In this metaphor, one walks in different directions to learn how much lower the valley becomes. Typically, in gradient descent, one uses the whole set of data to calculate the valley's slopes. However, this commonly used method assumes that every data point is equally informative. By contrast, Gradient-Based One-Side Sampling (GOSS), a method first developed for gradient-boosted decision trees, does not rely on the assumption that all data are equally informative. Instead, it treats data points with smaller gradients (shallower slopes) as less informative by randomly dropping them. This is intended to filter out data which may have been influenced by noise, allowing the model to more accurately model the underlying relationships in the data. == Exclusive feature bundling == Exclusive feature bundling (EFB) is a near-lossless method to reduce the number of effective features. In a sparse feature space many features are nearly exclusive, implying they rarely take nonzero values simultaneously. One-hot encoded features are a perfect example of exclusive features. EFB bundles these features, reducing dimensionality to improve efficiency while maintaining a high level of accuracy. The bundle of exclusive features into a single feature is called an exclusive feature bundle.
Boundary vector field
The boundary vector field (BVF) is an external force for parametric active contours (i.e. Snakes). In the fields of computer vision and image processing, parametric active contours are widely used for segmentation and object extraction. The active contours move progressively towards its target based on the external forces. There are a number of shortcomings in using the traditional external forces, including the capture range problem, the concave object extraction problem, and high computational requirements. The BVF is generated by an interpolation scheme which reduces the computational requirement significantly, and at the same time, improves the capture range and concave object extraction capability. The BVF is also tested in moving object tracking and is proven to provide fast detection method for real time video applications.
Digital video recorder
A digital video recorder (DVR), also referred to as a personal video recorder (PVR) particularly in Canadian and British English, is an electronic device that records video in a digital format to a disk drive, USB flash drive, SD memory card, SSD or other local or networked mass storage device. The term includes set-top boxes (STB) with direct to disk recording, portable media players and TV gateways with recording capability, and digital camcorders. Personal computers can be connected to video capture devices and used as DVRs; in such cases the application software used to record video is an integral part of the DVR. Many DVRs are classified as consumer electronic devices. Similar small devices with built-in (~5 inch diagonal) displays and SSD support may be used for professional film or video production, as these recorders often do not have the limitations that built-in recorders in cameras have, offering wider codec support, the removal of recording time limitations and higher bitrates. == History == In the 1980s, prototype high-definition (HD) digital video recorders were developed by Fujitsu, Hitachi, Sanyo and Canon Inc. In 1985, Hitachi demonstrated a prototype digital video tape recorder (VTR) that used digital recording video tape as storage media to record digital HD video content. In 1987, the first commercial digital video recorder was the Sony DVR-1000, a digital video cassette recorder (VCR) that recorded digital video content on D-1 (Sony) digital video cassettes. === Hard-disk-based DVR === In early 1995, Tektronix introduced the "Profile" series PDR100 Video Disk Recorder, which recorded and played back video stored on hard disk as motion JPEG. In 1996, Sweden's TV4 used the PDR100 extensively in building a new facility in Stockholm, and NBC used PDR100s at the Olympic games in Atlanta Georgia. The Tektronix Profile disk recorder won an Engineering, Science & Technology Emmy Award for "Outstanding Achievement in Engineering Development" at the 1996 Primetime Emmy Awards. In 1997 the U.S. Patent Office granted Tektronix patent 5,642,497 for two claims key to Profile. In 1998, Tektronix introduced two Profile models which were combined VDRs and file servers: the PDR200 and PDR300. The PDR300 stored its compressed video as MPEG-2 (ISO/IEC 13818-2) A working disk-based DVR prototype was developed in 1998 at Stanford University Computer Science department. The DVR design was a chapter of Edward Y. Chang's PhD dissertation, supervised by Professors Hector Garcia-Molina and Jennifer Widom. Two design papers were published at the 1998 VLDB conference, and the 1999 ICDE conference. The prototype was developed in 1998 at Pat Hanrahan's CS488 class: Experiments in Digital Television, and the prototype was demoed to industrial partners including Sony, Intel, and Apple. Consumer digital video recorders ReplayTV and TiVo were launched at the 1999 Consumer Electronics Show in Las Vegas, Nevada. Microsoft also demonstrated a unit with DVR capability, but this did not become available until the end of 1999 for full DVR features in Dish Network's DISHplayer receivers. TiVo shipped their first units on March 31, 1999. ReplayTV won the "Best of Show" award in the video category with Netscape co-founder Marc Andreessen as an early investor and board member, but TiVo was more successful commercially. Ad Age cited Forrester Research as saying that market penetration by the end of 1999 was "less than 100,000". In 2001, Toshiba introduced a combination DVR that allows video recording on both DVD recordable and hard disk drive. Legal action by media companies forced ReplayTV to remove many features such as automatic commercial skip and the sharing of recordings over the Internet, but newer devices have steadily regained these functions while adding complementary abilities, such as recording onto DVDs and programming and remote control facilities using PDAs, networked PCs, and Web browsers. In contrast to VCRs, hard-disk based digital video recorders make "time shifting" more convenient and also allow for functions such as pausing live TV, instant replay, chasing playback (viewing a recording before it has been completed) and skipping over advertising during playback. Many DVRs use the MPEG format for compressing the digital video. Video recording capabilities have become an essential part of the modern set-top box, as TV viewers have wanted to take control of their viewing experiences. As consumers have been able to converge increasing amounts of video content on their set-tops, delivered by traditional 'broadcast' cable, satellite and terrestrial as well as IP networks, the ability to capture programming and view it whenever they want has become a must-have function for many consumers. === DVR tied to video service === At the 1999 CES, Dish Network demonstrated the hardware that would later have DVR capability with the assistance of Microsoft software, which also included access to the WebTV service. By the end of 1999 the Dishplayer had full DVR capabilities and within a year, over 200,000 units were sold. In the UK, digital video recorders are often referred to as "plus boxes" (such as BSKYB's Sky+ and Virgin Media's V+ which integrates an HD capability, and the subscription free Freesat+ and Freeview+). Freeview+ have been around in the UK since the late 2000s, although the platform's first DVR, the Pace Twin, dates to 2002. British Sky Broadcasting marketed a popular combined receiver and DVR as Sky+, now replaced by the Sky Q box. TiVo launched a UK model in 2000, and is no longer supported, except for third party services, and the continuation of TiVo through Virgin Media in 2010. South African based Africa Satellite TV beamer Multichoice recently launched their DVR which is available on their DStv platform. In addition to ReplayTV and TiVo, there are a number of other suppliers of digital terrestrial (DTT) DVRs, including Technicolor SA, Topfield, Fusion, Commscope, Humax, VBox Communications, AC Ryan Playon and Advanced Digital Broadcast (ADB). Many satellite, cable and IPTV companies are incorporating digital video recording functions into their set-top box, such as with DirecTiVo, DISHPlayer/DishDVR, Scientific Atlanta Explorer 8xxx from Time Warner, Total Home DVR from AT&T U-verse, Motorola DCT6412 from Comcast and others, Moxi Media Center by Digeo (available through Charter, Adelphia, Sunflower, Bend Broadband, and soon Comcast and other cable companies), or Sky+. Astro introduced their DVR system, called Astro MAX, which was the first PVR in Malaysia but was phased out two years after its introduction. In the case of digital television, there is no encoding necessary in the DVR since the signal is already a digitally encoded MPEG stream. The digital video recorder simply stores the digital stream directly to disk. Having the broadcaster involved with, and sometimes subsidizing, the design of the DVR can lead to features such as the ability to use interactive TV on recorded shows, pre-loading of programs, or directly recording encrypted digital streams. It can, however, also force the manufacturer to implement non-skippable advertisements and automatically expiring recordings. In the United States, the FCC has ruled that starting on July 1, 2007, consumers will be able to purchase a set-top box from a third-party company, rather than being forced to purchase or rent the set-top box from their cable company. This ruling only applies to "navigation devices", otherwise known as a cable television set-top box, and not to the security functions that control the user's access to the content of the cable operator. The overall net effect on digital video recorders and related technology is unlikely to be substantial as standalone DVRs are currently readily available on the open market. In Europe Free-To-Air and Pay TV TV gateways with multiple tuners have whole house recording capabilities allowing recording of TV programs to Network Attached Storage or attached USB storage, recorded programs are then shared across the home network to tablet, smartphone, PC, Mac, Smart TV. === Introduction of dual tuners === In 2003 many Satellite and Cable providers introduced dual-tuner digital video recorders. In the UK, BSkyB introduced their first PVR Sky+ with dual tuner support in 2001. These machines have two independent tuners within the same receiver. The main use for this feature is the capability to record a live program while watching another live program simultaneously or to record two programs at the same time, possibly while watching a previously recorded one. Kogan.com introduced a dual-tuner PVR in the Australian market allowing free-to-air television to be recorded on a removable hard drive. Some dual-tuner DVRs also have the ability to output to two separate television sets at the same time. The PVR manufactured by UEC (Durban, South Africa) and used by Multichoice and Scientific Atlanta 8300DVB PVR have the ability to view two
DBOS
DBOS (Formerly Database-Oriented Operating System, now just DBOS) is an open source durable workflow execution software library written for the Python, TypeScript, Java, and Go programming languages. DBOS arose from a joint open source project from MIT and Stanford, after a discussion between Michael Stonebraker and Matei Zaharia on how to scale and improve scheduling and performance of millions of Apache Spark tasks. Today it is a commercial company that offers an open source system to add durable computing to any software, built on concepts derived from the joint research project. == History == === 2020: Academic R&D Project === DBOS originated in 2020 as a joint open source project between MIT, Stanford, and Carnegie Mellon. The project explored the idea of operating system services built atop a distributed database - a database-oriented operating system meant to simplify and improve the scalability, security and resilience of large-scale distributed applications. The basic concept was to run a multi-node multi-core, transactional, highly-available distributed database, such as VoltDB, as the only application for a microkernel, and then to implement scheduling, messaging, file systems and other operating system services on top of the database. The architectural philosophy is described by this quote from the abstract of their initial preprint: All operating system state should be represented uniformly as database tables, and operations on this state should be made via queries from otherwise stateless tasks. This design makes it easy to scale and evolve the OS without whole-system refactoring, inspect and debug system state, upgrade components without downtime, manage decisions using machine learning, and implement sophisticated security features. A prototype was built with competitive performance to existing systems. ==
Power cycling
Power cycling is the act of turning a piece of equipment, usually a computer, off and then on again. Reasons for power cycling include having an electronic device reinitialize its set of configuration parameters or recover from an unresponsive state of its mission critical functionality, such as in a crash or hang situation. Power cycling can also be used to reset network activity inside a modem. It can also be among the first steps for troubleshooting an issue. == Overview == Power cycling can be done manually, usually using the power switch on the device, or remotely, through some type of external device connected to the power input. In the data center environment, remote control power cycling can usually be done through a power distribution unit, over the network. In the home environment, this can be done through home automation powerline communications. Most Internet service providers publish a "how-to" on their website showing their customers the correct procedure to power cycle their devices. Power cycling is a common diagnostic procedure usually performed first when a computer system freezes. However, frequently power cycling a computer can cause thermal stress. Reset has an equal effect on the software but may be less problematic for the hardware as power is not interrupted. == Historical uses == On all Apollo missions to the moon, the landing radar was required to acquire the surface before a landing could be attempted. But on Apollo 14, the landing radar was unable to lock on. Mission control told the astronauts to cycle the power. They did, the radar locked on just in time, and the landing was completed. During the Rosetta mission to comet 67P/Churyumov–Gerasimenko, the Philae lander did not return the expected telemetry on awakening after arrival at the comet. The problem was diagnosed as "somehow a glitch in the electronics", engineers cycled the power, and the lander awoke correctly. During the launch of the billion dollar AEHF-6 satellite on 26 March 2020 by an Atlas V rocket from Cape Canaveral Space Force Station in Florida, a hold was called at T-46 seconds due to hydraulic system not responding as expected. The launch crew turned it off and back on, and the launch proceeded normally. In 2023 the Interstellar Boundary Explorer spacecraft stopped responding to commands after an anomaly. When gentler techniques failed, NASA resorted to rebooting the spacecraft with the remote equivalent of a power cycle.
FastTrack Automation Studio
FastTrack Automation Studio (formerly known as FastTrack Scripting Host), often referred to as just FastTrack, is a scripting language for Windows IT System Administrators. The product’s goal is to handle any kind of scripting that might be required to automate processes with Microsoft Windows networks. == Manufacturer == FastTrack is produced by FastTrack Software, which is headquartered in Aalborg, Denmark. The product is promoted by the manufacturer as a one-stop shop for Windows script writers and its development paradigm is “one operation = one script line”. Script writers use a purpose-built editor to create scripts, inserting script lines via menus, drag’n drop, or simply typing them in. Scripts may be used out of the box, created from scratch, imported from forums or other users, or customized from product documentation. == Types of scripts == Simple scripts include: Outlook Signatures Login scripts Backup and replication scripts Inventory and asset management Automated Windows OS installation and deployment Automated application software deployment Active Directory scripts More advanced scripts include: SCCM task sequences Citrix ICA and RDP Clients built-in Deploying applications to server farms Deploying GPO MSI files SQL Server scripts == Basic structure == Under the hood, scripts comprise commands, functions, collections, and conditions. When a script is executed these components are converted into many lines of C# code, sometimes hundreds of lines, depending on the particular script operation. Scripts can be compiled into EXE files or MSI packages and treated as standalone Windows applications. == History == FastTrack Scripting Host (FastTrack) was first developed around 2006 to ease the administration burden of IT System Administrators on Windows networks. === Product idea === The idea for the product came from founder and President of FastTrack Software, Lars Pedersen, who has a background in systems administration. Previously with Telenor, Denmark’s major telephone company, Pedersen performed various roles in systems administration, programming and web development. He also worked as a consultant and developer on several major projects at various companies in Europe. Dissatisfied from his own experiences and frustrations administering Windows networks, Pederson looked for a way to make life easier for system administrators. In particular, he wanted something that could minimize the amount of time needed each day to perform routine and mundane tasks, which was a waste of time and expertise that should have been committed to other projects. === Development === Leading a small team of developers, Pedersen developed FastTrack Scripting Host to simplify and automate the routine tasks of system administrators. The resulting product is definitely a scripting language, but it can be used intuitively like a programming language, without requiring users to learn syntax or other concepts typically associated with programming languages. === Marketing === In April 2010, FastTrack Software entered into an agreement with Binary Research International Archived 2008-10-15 at the Wayback Machine, based in the city of Milwaukee, United States to market and sell the product globally. === Awards === FSH received a Windows IT Pro Community Choice award in 2012. == Versions == The first version was produced in June 2006 and contained 51 components, which are the commands, functions, conditions and collections making up FastTrack. The following table summarizes dates and components for major releases. Companies and organizations such as NOAA, Kawasaki, and Goodyear have used and implemented the FastTrack Scripting Host. == Comparison with other scripting software == FastTrack Scripting Host Kixtart PowerShell ScriptLogic VBScript
Magnetoquasistatic field
A magnetoquasistatic field is a class of electromagnetic field in which a slowly oscillating magnetic field is dominant. A magnetoquasistatic field is typically generated by low-frequency induction from a magnetic dipole or a current loop. The magnetic near-field of such an emitter behaves differently from the more commonly used far-field electromagnetic radiation. At low frequencies the rate of change of the instantaneous field strength with each cycle is relatively slow, giving rise to the name "magneto-quasistatic". The near field or quasistatic region typically extends no more than a wavelength from the antenna, and within this region the electric and magnetic fields are approximately decoupled. Weakly conducting non-magnetic bodies, including the human body and many mineral rocks, are effectively transparent to magnetoquasistatic fields, allowing for the transmission and reception of signals through such obstacles. Also, long-wavelength (i.e. low-frequency) signals are better able to propagate round corners than shorter-wave signals. Communication therefore need not be line-of-sight. The communication range of such signals depends on both the wavelength and the electromagnetic properties of the intervening medium at the chosen frequency, and is typically limited to a few tens of meters. == Physical principles == The laws of primary interest are Ampère's circuital law (with the displacement current density neglected) and the magnetic flux continuity law. These laws have associated with them continuity conditions at interfaces. In the absence of magnetizable materials, these laws determine the magnetic field intensity H given its source, the current density J. H is not everywhere irrotational. However, it is solenoidal everywhere. == Equipment design == A typical antenna comprises a 50-turn coil around a polyoxymethylene tube with diameter 16.5 cm, driven by a class E oscillator circuit. Such a device is readily portable when powered by batteries. Similarly, a typical receiver consist of an active receiving loop with diameter of one meter, an ultra-low-noise amplifier, and a band-pass filter. In operation the oscillator drives current through the transmitting loop to create an oscillating magnetic field. This field induces a voltage in the receiving loop, which is then amplified. Because the quasistatic region is defined within one wavelength of the electromagnetic source, emitters are limited to a frequency range between about 1 kHz and 1 MHz. Reducing the oscillating frequency increases the wavelength and hence the range of the quasistatic region, but reduces the induced voltage in the receiving loops which worsens the signal-to-noise ratio. In experiments carried out by the Carnegie Institute of Technology, the maximum range reported by was 50 meters. == Applications == === Resonant inductive coupling === In resonant coupling, the source and receiver are tuned to resonate at the same frequency and are given similar impedances. This allows power as well as information to flow from the source to the receiver. Such coupling via the magnetoquasistatic field is called resonant inductive coupling and can be used for wireless energy transfer. Applications include induction cooking, induction charging of batteries and some kinds of RFID tag. === Communications === Conventional electromagnetic communication signals cannot pass through the ground. Most mineral rock is neither electrically conducting nor magnetic, allowing magnetic fields to penetrate. Magnetoquasistatic systems have been successfully used for underground wireless communication, both surface-to-underground and between underground parties. At extremely low frequencies, below about 1 kHz, the wavelength is long enough for long-distance communication, although at a slow data rate. Such systems have been installed in submarines, with the local antenna comprising a wire up to several kilometers in length and trailed behind the vessel when at or near the surface. === Position and orientation tracking === Wireless position tracking is being increasingly used in applications such as navigation, security, and asset tracking. Conventional position tracking devices use high frequencies or microwaves, including global positioning systems (GPS), ultra-wide band (UWB) systems, and radio frequency identification systems (RFID), but these systems can easily be blocked by obstacles in their path. Magnetoquasistatic positioning takes advantage of the fact that the fields are largely undisturbed when in the presence of human beings and physical structures, and can be used for both position and orientation tracking for ranges up to 50 meters. To accurately determine the orientation and position of a dipole/emitter, allowance must be made not only for the field pattern generated by the emitter, but also for the eddy-currents they induce in the earth, which create secondary fields detectable by the receivers. By using complex image theory to correct this field generation from earth, and by using frequencies on the order of a few hundred kilohertz to obtain the required signal-to-noise ratio (SNR), it is possible to analyze the position of the dipole through azimuthal orientation, θ {\displaystyle \theta } , and inclination orientation, ϕ {\displaystyle \phi } . A Disney research team has used this technology to effectively determine the position and orientation of an American football, something not traceable through conventional wave propagation techniques due to human body obstruction. They inserted an oscillator-driven coil, around the diameter of the center of the ball, to generate the magnetoquasistatic field. The signal was able to pass undisturbed through multiple players.