Telligent Community is a community and collaboration software platform developed by Telligent Systems and was first released in 2004. Telligent Community is built on the Telligent Evolution platform, with a variety of core applications running on top of it such as blogs, forums, media galleries, and wikis. Additional applications from third parties using the API's and REST stack can be installed or integrated with the platform. Telligent Community is built with ASP.NET, C#, and Microsoft SQL Server. It is available as downloadable software that can be installed on a web server or via hosting providers. The current version is Verint Community 12.0 which was released February 2012. The product used to be named Community Server before being rebranded as part of the 5.0 release. == History == Telligent Systems was founded by Rob Howard in 2004, who was previously part of Microsoft's ASP.NET team. Telligent introduced its first product, Community Server, in the fall of 2004. Community Server was one of the first integrated community platforms that brought together blogs, photo galleries, wikis, forums, user profiles and more. Community Server was based on the merger of three then-widely used open source ASP.NET projects: the ASP.NET Forums, nGallery photo gallery, and .Text blog engine. The people behind those projects (Scott Watermasysk, Jason Alexander, and Rob Howard) joined together as Telligent Systems and along with several other software developers created Community Server 1.0. Between 2004 and 2009 Community Server steadily grew in scope, features, and capabilities. In 2008 Telligent Systems released a second version of Community Server that targeted as an Enterprise Social Software platform used to create and manage internal employee communities and intranets. Originally branded as Community Server Evolution this was later renamed Telligent Enterprise. Telligent also announced a new Enterprise Reporting platform at its first Community Server Developers Conference in 2008, which was later renamed Harvest. It was one of the first analytics suites for enterprise collaboration software, and provides social analytics including sentiment analysis, social fingerprints, and buzz analysis on social networking sites such as Twitter. Telligent rebranded all of its products on June 23, 2009 at the Enterprise 2.0 conference when it launched its new Evolution platform product suite. Community Server became known as Telligent Community, Community Server Evolution became known as Telligent Enterprise and the underlying platform that both run on is now referred to as Telligent Evolution. The Social Analytics suite was renamed Telligent Analytics.
International Conference on Language Resources and Evaluation
The International Conference on Language Resources and Evaluation is an international conference organised by the ELRA Language Resources Association every other year (on even years) with the support of institutions and organisations involved in Natural language processing. The series of LREC conferences was launched in Granada in 1998. == History of conferences == The survey of the LREC conferences over the period 1998-2013 was presented during the 2014 conference in Reykjavik as a closing session. It appears that the number of papers and signatures is increasing over time. The average number of authors per paper is higher as well. The percentage of new authors is between 68% and 78%. The distribution between male (65%) and female (35%) authors is stable over time. The most frequent technical term is "annotation", then comes "part-of-speech". == The LRE Map == The LRE Map was introduced at LREC 2010 and is now a regular feature of the LREC submission process for both the conference papers and the workshop papers. At the submission stage, the authors are asked to provide some basic information about all the resources (in a broad sense, i.e. including tools, standards and evaluation packages), either used or created, described in their papers. All these descriptors are then gathered in a global matrix called the LRE Map. This feature has been extended to several other conferences.
Open Sound Control
Open Sound Control (OSC) is a protocol for networking sound synthesizers, computers, and other multimedia devices for purposes such as musical performance or show control. OSC's advantages include interoperability, accuracy, flexibility and enhanced organization and documentation. Its disadvantages include higher bandwidth requirements, increased load on embedded processors, and lack of standardized messages/interoperability. The first specification was released in March 2002. == Motivation == OSC is a content format developed at CNMAT by Adrian Freed and Matt Wright comparable to XML, WDDX, or JSON. It was originally intended for sharing music performance data (gestures, parameters and note sequences) between musical instruments (especially electronic musical instruments such as synthesizers), computers, and other multimedia devices. OSC is sometimes used as an alternative to the 1983 MIDI standard, when higher resolution and a richer parameter space is desired. OSC messages are transported across the internet and within local subnets using UDP/IP and Ethernet. OSC messages between gestural controllers are usually transmitted over serial endpoints of USB wrapped in the SLIP protocol. == Features == OSC's main features, compared to MIDI, include: Open-ended, dynamic, URI-style symbolic naming scheme Symbolic and high-resolution numeric data Pattern matching language to specify multiple recipients of a single message High resolution time tags "Bundles" of messages whose effects must occur simultaneously == Applications == There are dozens of OSC applications, including real-time sound and media processing environments, web interactivity tools, software synthesizers, programming languages and hardware devices. OSC has achieved wide use in fields including musical expression, robotics, video performance interfaces, distributed music systems and inter-process communication. The TUIO community standard for tangible interfaces such as multitouch is built on top of OSC. Similarly the GDIF system for representing gestures integrates OSC. OSC is used extensively in experimental musical controllers, and has been built into several open source and commercial products. The Open Sound World (OSW) music programming language is designed around OSC messaging. OSC is the heart of the DSSI plugin API, an evolution of the LADSPA API, in order to make the eventual GUI interact with the core of the plugin via messaging the plugin host. LADSPA and DSSI are APIs dedicated to audio effects and synthesizers. In 2007, a standardized namespace within OSC called SYN, for communication between controllers, synthesizers and hosts, was proposed. == Design == OSC messages consist of an address pattern (such as /oscillator/4/frequency), a type tag string (such as ,fi for a float32 argument followed by an int32 argument), and the arguments themselves (which may include a time tag). Address patterns form a hierarchical name space, reminiscent of a Unix filesystem path, or a URL, and refer to "Methods" inside the server, which are invoked with the attached arguments. Type tag strings are a compact string representation of the argument types. Arguments are represented in binary form with four-byte alignment. The core types supported are 32-bit two's complement signed integers 32-bit IEEE floating point numbers Null-terminated arrays of eight-bit encoded data (C-style strings) arbitrary sized blob (e.g. audio data, or a video frame) An example message is included in the spec (with null padding bytes represented by ␀): /oscillator/4/frequency␀,f␀␀, Followed by the 4-byte float32 representation of 440.0: 0x43dc0000. Messages may be combined into bundles, which themselves may be combined into bundles, etc. Each bundle contains a timestamp, which determines whether the server should respond immediately or at some point in the future. Applications commonly employ extensions to this core set. More recently some of these extensions such as a compact Boolean type were integrated into the required core types of OSC 1.1. The advantages of OSC over MIDI are primarily internet connectivity; data type resolution; and the comparative ease of specifying a symbolic path, as opposed to specifying all connections as seven-bit numbers with seven-bit or fourteen-bit data types. This human-readability has the disadvantage of being inefficient to transmit and more difficult to parse by embedded firmware, however. The spec does not define any particular OSC Methods or OSC Containers. All messages are implementation-defined and vary from server to server.
Are We Dating The Same Guy?
Are We Dating The Same Guy?, also abbreviated AWDTSG is a series of over 200 individual Facebook groups where women share dating profiles of men they matched with on dating networks to seek the opinion of other women who may have dated the same man in the past. The first group was created by Paola Sanchez and aimed at women living in the New York City environs. The groups have over 3.5 million members as of January 2024. The group's function is to post screenshots of a man's dating profile to that city's designated Facebook group, after which the poster asks "any tea?". Other users in the group will then share information about the man and share warnings. The groups are moderated by volunteers, and have been described as a feminist group. The groups have rules saying that personal information such as addresses must not be included in the Facebook posts. Users attempting to join the group are also examined to prevent fake profiles. The group is mainly for straight women. According to Vice, the men being posted about have no way to defend against accusations made about them, and on the other hand, posters cannot prove their stories unless backed up by others. Often times, members post pictures alongside personal information such as names, which may infringe on subjects' legal right to privacy. Lawyers have said these issues can lead to defamation lawsuits, and members can make false allegations and create fabricated stories. If members tell a man that he's been talked about on the group, the "snitch" will be banned and be "exposed to the whole group". == History == The first Are We Dating The Same Guy group was created by Paola Sanchez. The first group was created in March 2022 in New York City. A male counterpart, named "Are We Dating the Same Girl NYC" was created for New York, with mostly the same guidelines and rules to the original. When the original Are We Dating The Same Guy group found it, they denounced the new group. == Operations == Administrators are told not to respond to men asking to have posts about them removed, and to not remove said posts. The people being posted about have reported being questioned by their employers about things they have not done. Members of the groups sometimes criticise the physical appearance of the men being posted about. According to the Evening Standard, the groups "frequent[ly] mock" the appearance or dating profiles of the men who are posted about, despite being against the rules. For this behaviour, women are sometimes kicked out, or the group is disciplined en masse by admins. The groups have rules against hate towards men, but the rules can be difficult to enforce in large groups, with some having over 100,000 members. Some men have also been able to join the groups without being noticed. == Reception == In October 2023, Sera Bozza of Body+Soul wrote that consistently using Are We Dating The Same Guy can "affect your real-world view". She wrote that "A few stories of cheating may persuade you to believe that all men are unfaithful". Some lawyers and commentators have expressed concern that the groups fail to acknowledge the legal right to privacy and users can create false allegations and fabricated stories, and cyberbully men without them being able to defend themselves. This may lead to civil lawsuits against the author for defamation, harassment, and other related privacy torts. Netsafe, an online safety organisation in New Zealand, advises users of a similar group to familiarise themselves with the Harmful Digital Communications Act to ensure that posts do not lead to "harmful consequences". The Independent reported that men who have been posted on the dating groups have felt violated, and that even if reviewed positively by potentially thousands of strangers, the men being discussed about may have their reputation slightly decreased due to the association with being on the groups. The Independent also reported that some men believe that the groups are created to spread lies or mock them. Mashable reported that the growth of AWDTSG in recent years has led to the rise of a small industry of online reputation and content removal services, as increasing numbers of men seek assistance. A co-founder of Maximatic Media, one such agency offering these removal services, stated that many of the men contacting the firm do so in a state of panic after learning that allegations about them have circulated among tens of thousands of participants without their knowledge. Mashable similarly reported that the growing visibility of AWDTSG and similar platforms has contributed to what commentators describe as a "public trial" dynamic, where subjective accounts about dating behavior are interpreted as factual assessments and can influence a person's reputation among large audiences within their locale. The Oklahoman reported that anonymous, unverified claims in these groups have led some men to experience social and dating repercussions, although legal analysts argue that the benefits of community-based safety networks still outweigh these concerns in modern, app based dating environments. UTV/ITV News reportedly spoke to a man who was posted who alleged he attempted suicide, was clinically dead for three minutes, and spent three weeks in a psychiatric hospital as a result of the posts made about him. Many other men have talked about malicious false claims made about them. Self-described men’s rights activists have taken a dislike to these groups and have gotten multiple North American groups shut down by running campaigns, threatening lawsuits, and mass Facebook reporting. They also have Reddit communities dedicated to getting rid of such groups. Women who have posted in the groups have felt that they have put their safety at risk, with some having been confronted by the men they posted about. The group has been noted for exposing men who use dating apps while already in a relationship, misrepresent their ages, or repeatedly stand up the women they meet through apps, among other bad dating behaviors. For example, some members of the group had matched on a dating site with a man who had, several years prior, killed a stranger while having a mental break. After this information came to light, members of the group were warned. The group has also been noted to be complimentary of some men. == Lawsuits == In 2023, a 41-year-old man sued the administrators of the London group for $35,000 under defamation, alleging that the group "called names, accused of sending lewd photos and of being a bad parent". In January 2024 a man sued Meta, the owner of Facebook, along with Patreon, GoFundMe, and the AWDTSG website, as well as almost 30 group members due to alleged defamation, emotional distress, and invasion of privacy. Claiming that the groups violate anti-doxxing laws and do not fact check, seeking $75,000 in damages. He claims that the group shared fake images of him sending women texts containing harassment, his name and photo. His attorneys claim that if the images were real, they would fall under free speech in the First Amendment. By February, groups had raised $80,000. The Washington Post said that this case caused AWDTSG to "explode into public view". The case was dismissed in 2025 by the United States District Court for the Northern District of Illinois. On May 15, 2026, the United States Court of Appeals for the Seventh Circuit declined to renew the case in D'Ambrosio v. Meta Platforms Inc., et al. The plaintiff and his attorneys, Marc Trent and Aaron Walner of Trent Law Firm, were sanctioned "for frivolously appealing the dismissal of the claims," "misrepresentations of law," in connection with falsified citations included in the plaintiff's brief, and " disputing at oral argument without any evidentiary basis that [the plaintiff] client sent the text message she attributed to him." == By country == === Australia === In Australia, there are groups for multiple cities including Sydney, Melbourne, Adelaide, Perth, Brisbane and Rockhampton with many having several thousand members. The Sydney group has 30,000 members. In March 2023, the Adelaide version of the group, which had 7,000 members, was shut down. In 2024, groups titled "Sis, Are We Dating The Same Guy" stopped accepting new posts after an admin was sued for defamation and had to pay over AU$20,000 in legal fees. The case was settled out of court. The administrator announcing these closures cited a 2021 defamation High Court case involving detainee Dylan Voller, which led to the High Court saying that owners of Facebook groups can be held liable for defamatory comments, even if they did not know the comments had been made. === Canada === In 2023, a group was started for Ottawa. The founder previously was in a relationship full of "cheating and lies", which prompted her to creating the Facebook community. In 2023, the group for Vancouver and British Columbia was shut down after concerns about men being unable to protect themselves against fa
Are We Dating The Same Guy?
Are We Dating The Same Guy?, also abbreviated AWDTSG is a series of over 200 individual Facebook groups where women share dating profiles of men they matched with on dating networks to seek the opinion of other women who may have dated the same man in the past. The first group was created by Paola Sanchez and aimed at women living in the New York City environs. The groups have over 3.5 million members as of January 2024. The group's function is to post screenshots of a man's dating profile to that city's designated Facebook group, after which the poster asks "any tea?". Other users in the group will then share information about the man and share warnings. The groups are moderated by volunteers, and have been described as a feminist group. The groups have rules saying that personal information such as addresses must not be included in the Facebook posts. Users attempting to join the group are also examined to prevent fake profiles. The group is mainly for straight women. According to Vice, the men being posted about have no way to defend against accusations made about them, and on the other hand, posters cannot prove their stories unless backed up by others. Often times, members post pictures alongside personal information such as names, which may infringe on subjects' legal right to privacy. Lawyers have said these issues can lead to defamation lawsuits, and members can make false allegations and create fabricated stories. If members tell a man that he's been talked about on the group, the "snitch" will be banned and be "exposed to the whole group". == History == The first Are We Dating The Same Guy group was created by Paola Sanchez. The first group was created in March 2022 in New York City. A male counterpart, named "Are We Dating the Same Girl NYC" was created for New York, with mostly the same guidelines and rules to the original. When the original Are We Dating The Same Guy group found it, they denounced the new group. == Operations == Administrators are told not to respond to men asking to have posts about them removed, and to not remove said posts. The people being posted about have reported being questioned by their employers about things they have not done. Members of the groups sometimes criticise the physical appearance of the men being posted about. According to the Evening Standard, the groups "frequent[ly] mock" the appearance or dating profiles of the men who are posted about, despite being against the rules. For this behaviour, women are sometimes kicked out, or the group is disciplined en masse by admins. The groups have rules against hate towards men, but the rules can be difficult to enforce in large groups, with some having over 100,000 members. Some men have also been able to join the groups without being noticed. == Reception == In October 2023, Sera Bozza of Body+Soul wrote that consistently using Are We Dating The Same Guy can "affect your real-world view". She wrote that "A few stories of cheating may persuade you to believe that all men are unfaithful". Some lawyers and commentators have expressed concern that the groups fail to acknowledge the legal right to privacy and users can create false allegations and fabricated stories, and cyberbully men without them being able to defend themselves. This may lead to civil lawsuits against the author for defamation, harassment, and other related privacy torts. Netsafe, an online safety organisation in New Zealand, advises users of a similar group to familiarise themselves with the Harmful Digital Communications Act to ensure that posts do not lead to "harmful consequences". The Independent reported that men who have been posted on the dating groups have felt violated, and that even if reviewed positively by potentially thousands of strangers, the men being discussed about may have their reputation slightly decreased due to the association with being on the groups. The Independent also reported that some men believe that the groups are created to spread lies or mock them. Mashable reported that the growth of AWDTSG in recent years has led to the rise of a small industry of online reputation and content removal services, as increasing numbers of men seek assistance. A co-founder of Maximatic Media, one such agency offering these removal services, stated that many of the men contacting the firm do so in a state of panic after learning that allegations about them have circulated among tens of thousands of participants without their knowledge. Mashable similarly reported that the growing visibility of AWDTSG and similar platforms has contributed to what commentators describe as a "public trial" dynamic, where subjective accounts about dating behavior are interpreted as factual assessments and can influence a person's reputation among large audiences within their locale. The Oklahoman reported that anonymous, unverified claims in these groups have led some men to experience social and dating repercussions, although legal analysts argue that the benefits of community-based safety networks still outweigh these concerns in modern, app based dating environments. UTV/ITV News reportedly spoke to a man who was posted who alleged he attempted suicide, was clinically dead for three minutes, and spent three weeks in a psychiatric hospital as a result of the posts made about him. Many other men have talked about malicious false claims made about them. Self-described men’s rights activists have taken a dislike to these groups and have gotten multiple North American groups shut down by running campaigns, threatening lawsuits, and mass Facebook reporting. They also have Reddit communities dedicated to getting rid of such groups. Women who have posted in the groups have felt that they have put their safety at risk, with some having been confronted by the men they posted about. The group has been noted for exposing men who use dating apps while already in a relationship, misrepresent their ages, or repeatedly stand up the women they meet through apps, among other bad dating behaviors. For example, some members of the group had matched on a dating site with a man who had, several years prior, killed a stranger while having a mental break. After this information came to light, members of the group were warned. The group has also been noted to be complimentary of some men. == Lawsuits == In 2023, a 41-year-old man sued the administrators of the London group for $35,000 under defamation, alleging that the group "called names, accused of sending lewd photos and of being a bad parent". In January 2024 a man sued Meta, the owner of Facebook, along with Patreon, GoFundMe, and the AWDTSG website, as well as almost 30 group members due to alleged defamation, emotional distress, and invasion of privacy. Claiming that the groups violate anti-doxxing laws and do not fact check, seeking $75,000 in damages. He claims that the group shared fake images of him sending women texts containing harassment, his name and photo. His attorneys claim that if the images were real, they would fall under free speech in the First Amendment. By February, groups had raised $80,000. The Washington Post said that this case caused AWDTSG to "explode into public view". The case was dismissed in 2025 by the United States District Court for the Northern District of Illinois. On May 15, 2026, the United States Court of Appeals for the Seventh Circuit declined to renew the case in D'Ambrosio v. Meta Platforms Inc., et al. The plaintiff and his attorneys, Marc Trent and Aaron Walner of Trent Law Firm, were sanctioned "for frivolously appealing the dismissal of the claims," "misrepresentations of law," in connection with falsified citations included in the plaintiff's brief, and " disputing at oral argument without any evidentiary basis that [the plaintiff] client sent the text message she attributed to him." == By country == === Australia === In Australia, there are groups for multiple cities including Sydney, Melbourne, Adelaide, Perth, Brisbane and Rockhampton with many having several thousand members. The Sydney group has 30,000 members. In March 2023, the Adelaide version of the group, which had 7,000 members, was shut down. In 2024, groups titled "Sis, Are We Dating The Same Guy" stopped accepting new posts after an admin was sued for defamation and had to pay over AU$20,000 in legal fees. The case was settled out of court. The administrator announcing these closures cited a 2021 defamation High Court case involving detainee Dylan Voller, which led to the High Court saying that owners of Facebook groups can be held liable for defamatory comments, even if they did not know the comments had been made. === Canada === In 2023, a group was started for Ottawa. The founder previously was in a relationship full of "cheating and lies", which prompted her to creating the Facebook community. In 2023, the group for Vancouver and British Columbia was shut down after concerns about men being unable to protect themselves against fa
EM algorithm and GMM model
In statistics, EM (expectation maximization) algorithm handles latent variables, while GMM is the Gaussian mixture model. == Background == In the picture below, are shown the red blood cell hemoglobin concentration and the red blood cell volume data of two groups of people, the Anemia group and the control group (i.e. the group of people without Anemia). As expected, people with Anemia have lower red blood cell volume and lower red blood cell hemoglobin concentration than those without Anemia. x {\displaystyle x} is a random vector such as x := ( red blood cell volume , red blood cell hemoglobin concentration ) {\displaystyle x:={\big (}{\text{red blood cell volume}},{\text{red blood cell hemoglobin concentration}}{\big )}} , and from medical studies it is known that x {\displaystyle x} are normally distributed in each group, i.e. x ∼ N ( μ , Σ ) {\displaystyle x\sim {\mathcal {N}}(\mu ,\Sigma )} . z {\displaystyle z} is denoted as the group where x {\displaystyle x} belongs, with z i = 0 {\displaystyle z_{i}=0} when x i {\displaystyle x_{i}} belongs to the Anemia group and z i = 1 {\displaystyle z_{i}=1} when x i {\displaystyle x_{i}} belongs to the control group. Also z ∼ Categorical ( k , ϕ ) {\displaystyle z\sim \operatorname {Categorical} (k,\phi )} where k = 2 {\displaystyle k=2} , ϕ j ≥ 0 , {\displaystyle \phi _{j}\geq 0,} and ∑ j = 1 k ϕ j = 1 {\displaystyle \sum _{j=1}^{k}\phi _{j}=1} . See Categorical distribution. The following procedure can be used to estimate ϕ , μ , Σ {\displaystyle \phi ,\mu ,\Sigma } . A maximum likelihood estimation can be applied: ℓ ( ϕ , μ , Σ ) = ∑ i = 1 m log ( p ( x ( i ) ; ϕ , μ , Σ ) ) = ∑ i = 1 m log ∑ z ( i ) = 1 k p ( x ( i ) ∣ z ( i ) ; μ , Σ ) p ( z ( i ) ; ϕ ) {\displaystyle \ell (\phi ,\mu ,\Sigma )=\sum _{i=1}^{m}\log(p(x^{(i)};\phi ,\mu ,\Sigma ))=\sum _{i=1}^{m}\log \sum _{z^{(i)}=1}^{k}p\left(x^{(i)}\mid z^{(i)};\mu ,\Sigma \right)p(z^{(i)};\phi )} As the z i {\displaystyle z_{i}} for each x i {\displaystyle x_{i}} are known, the log likelihood function can be simplified as below: ℓ ( ϕ , μ , Σ ) = ∑ i = 1 m log p ( x ( i ) ∣ z ( i ) ; μ , Σ ) + log p ( z ( i ) ; ϕ ) {\displaystyle \ell (\phi ,\mu ,\Sigma )=\sum _{i=1}^{m}\log p\left(x^{(i)}\mid z^{(i)};\mu ,\Sigma \right)+\log p\left(z^{(i)};\phi \right)} Now the likelihood function can be maximized by making partial derivative over μ , Σ , ϕ {\displaystyle \mu ,\Sigma ,\phi } , obtaining: ϕ j = 1 m ∑ i = 1 m 1 { z ( i ) = j } {\displaystyle \phi _{j}={\frac {1}{m}}\sum _{i=1}^{m}1\{z^{(i)}=j\}} μ j = ∑ i = 1 m 1 { z ( i ) = j } x ( i ) ∑ i = 1 m 1 { z ( i ) = j } {\displaystyle \mu _{j}={\frac {\sum _{i=1}^{m}1\{z^{(i)}=j\}x^{(i)}}{\sum _{i=1}^{m}1\left\{z^{(i)}=j\right\}}}} Σ j = ∑ i = 1 m 1 { z ( i ) = j } ( x ( i ) − μ j ) ( x ( i ) − μ j ) T ∑ i = 1 m 1 { z ( i ) = j } {\displaystyle \Sigma _{j}={\frac {\sum _{i=1}^{m}1\{z^{(i)}=j\}(x^{(i)}-\mu _{j})(x^{(i)}-\mu _{j})^{T}}{\sum _{i=1}^{m}1\{z^{(i)}=j\}}}} If z i {\displaystyle z_{i}} is known, the estimation of the parameters results to be quite simple with maximum likelihood estimation. But if z i {\displaystyle z_{i}} is unknown it is much more complicated. Being z {\displaystyle z} a latent variable (i.e. not observed), with unlabeled scenario, the expectation maximization algorithm is needed to estimate z {\displaystyle z} as well as other parameters. Generally, this problem is set as a GMM since the data in each group is normally distributed. In machine learning, the latent variable z {\displaystyle z} is considered as a latent pattern lying under the data, which the observer is not able to see very directly. x i {\displaystyle x_{i}} is the known data, while ϕ , μ , Σ {\displaystyle \phi ,\mu ,\Sigma } are the parameter of the model. With the EM algorithm, some underlying pattern z {\displaystyle z} in the data x i {\displaystyle x_{i}} can be found, along with the estimation of the parameters. The wide application of this circumstance in machine learning is what makes EM algorithm so important. == EM algorithm in GMM == The EM algorithm consists of two steps: the E-step and the M-step. Firstly, the model parameters and the z ( i ) {\displaystyle z^{(i)}} can be randomly initialized. In the E-step, the algorithm tries to guess the value of z ( i ) {\displaystyle z^{(i)}} based on the parameters, while in the M-step, the algorithm updates the value of the model parameters based on the guess of z ( i ) {\displaystyle z^{(i)}} of the E-step. These two steps are repeated until convergence is reached. The algorithm in GMM is: Repeat until convergence: 1. (E-step) For each i , j {\displaystyle i,j} , set w j ( i ) := p ( z ( i ) = j | x ( i ) ; ϕ , μ , Σ ) {\displaystyle w_{j}^{(i)}:=p\left(z^{(i)}=j|x^{(i)};\phi ,\mu ,\Sigma \right)} 2. (M-step) Update the parameters ϕ j := 1 m ∑ i = 1 m w j ( i ) {\displaystyle \phi _{j}:={\frac {1}{m}}\sum _{i=1}^{m}w_{j}^{(i)}} μ j := ∑ i = 1 m w j ( i ) x ( i ) ∑ i = 1 m w j ( i ) {\displaystyle \mu _{j}:={\frac {\sum _{i=1}^{m}w_{j}^{(i)}x^{(i)}}{\sum _{i=1}^{m}w_{j}^{(i)}}}} Σ j := ∑ i = 1 m w j ( i ) ( x ( i ) − μ j ) ( x ( i ) − μ j ) T ∑ i = 1 m w j ( i ) {\displaystyle \Sigma _{j}:={\frac {\sum _{i=1}^{m}w_{j}^{(i)}\left(x^{(i)}-\mu _{j}\right)\left(x^{(i)}-\mu _{j}\right)^{T}}{\sum _{i=1}^{m}w_{j}^{(i)}}}} With Bayes' rule, the following result is obtained by the E-step: p ( z ( i ) = j | x ( i ) ; ϕ , μ , Σ ) = p ( x ( i ) | z ( i ) = j ; μ , Σ ) p ( z ( i ) = j ; ϕ ) ∑ l = 1 k p ( x ( i ) | z ( i ) = l ; μ , Σ ) p ( z ( i ) = l ; ϕ ) {\displaystyle p\left(z^{(i)}=j|x^{(i)};\phi ,\mu ,\Sigma \right)={\frac {p\left(x^{(i)}|z^{(i)}=j;\mu ,\Sigma \right)p\left(z^{(i)}=j;\phi \right)}{\sum _{l=1}^{k}p\left(x^{(i)}|z^{(i)}=l;\mu ,\Sigma \right)p\left(z^{(i)}=l;\phi \right)}}} According to GMM setting, these following formulas are obtained: p ( x ( i ) | z ( i ) = j ; μ , Σ ) = 1 ( 2 π ) n / 2 | Σ j | 1 / 2 exp ( − 1 2 ( x ( i ) − μ j ) T Σ j − 1 ( x ( i ) − μ j ) ) {\displaystyle p\left(x^{(i)}|z^{(i)}=j;\mu ,\Sigma \right)={\frac {1}{(2\pi )^{n/2}\left|\Sigma _{j}\right|^{1/2}}}\exp \left(-{\frac {1}{2}}\left(x^{(i)}-\mu _{j}\right)^{T}\Sigma _{j}^{-1}\left(x^{(i)}-\mu _{j}\right)\right)} p ( z ( i ) = j ; ϕ ) = ϕ j {\displaystyle p\left(z^{(i)}=j;\phi \right)=\phi _{j}} In this way, a switch between the E-step and the M-step is possible, according to the randomly initialized parameters.
Media preservation
Preservation of documents, pictures, recordings, digital content, etc., is a major aspect of archival science. It is also an important consideration for people who are creating time capsules, family history, historical documents, scrapbooks and family trees. Common storage media are not permanent, and there are few reliable methods of preserving documents and pictures for the future. == Paper/prints (photos) == Color negatives and ordinary color prints may fade away to nothing in a relatively short period if not stored and handled properly. This happens even if the negatives and prints are kept in the dark, because ambient light is not the determining factor, but heat and humidity are. The color degradation is the result of the dyes used in the color processes. Because color processing results in a less stable image than traditional black-and-white processing, black-and-white pictures from the 1920s are more likely to survive long-term than color films and photographs from after the middle 20th century. Black-and-white photographic films using silver halide emulsions are the only film types that have proven to last for archival storage. The determining factors for longevity include the film base type, proper processing (develop, stop, fix and wash) and proper storage. Early films used a Cellulose nitrate base which was prone to decomposition and highly flammable. Nitrate film was replaced with acetate-base films. These Cellulose acetate films were later discovered to outgass acids (also referred to as vinegar syndrome). Acetate films were replaced in the early 1980s by polyester film base materials which have been determined to be more stable than film stocks with a nitrate or acetate base. Color prints made on most inkjet printers look very good at first but they have a very short lifespan, measured in months rather than in years. Even prints from commercial photo labs will start to fade in a matter of years if not processed properly and stored in cool, dry environments. == Documents/books == With documents for which the media are not so critical as what the documents contain, the information in documents can be copied by using photocopiers and image scanners. Books and manuscripts can also have their information saved without destruction by using a book scanner. Where the medium itself needs to be preserved, for example if a document is a crayon sketch by a famous artist on paper, a complex process of preservation may be used. Depending on the condition and importance of the item this can include gluing the media onto more stable media, or protective enclosing of the media. Polyester sleeves, acid-free folders, and pH buffered document boxes are common supportive protective enclosures whose selection must match the media's chemical and physical properties. Other considerations in preserving paper/books are: Damaging light, particularly UV light, which fades and destroys media over time by breaking down the molecules. Atmosphere contains small traces of sulfur dioxide and nitric acid which turn media yellow and break the fibers down. Humidity and moisture also aid in the breakdown of media. If there is too much, the document can be attacked by bacteria, and if too little, cellulose material breaks down. Temperature, particularly elevated ones, can destroy some media. Low temperatures can cause the water to form crystals which expands destroying the structure of paper-based documents. == Online photo albums == Although there are many websites that allow the upload of photographs and videos, digital preservation for the long-term is still considered an issue. There is a lack of confidence that such websites are capable of storing data for long periods of time (ex. 50 years) without data degradation or loss. == Optical media - CD, DVD, Blu-ray, M-Disc == Write-once optical media, such as CD-Rs and DVD-Rs, typically contain an organic dye that distinguishes data reading from data writing based on the dye's transparency along the disc. Conventional CDs and DVDs have finite shelf-life due to natural degradation of the dye; the newer M-DISC uses inorganic material technology to produce molded DVDs and Blu-Rays (up to 3-layer 100GB BDXL) with a claimed lifespan of 100-1000 years if stored correctly with most BD & BDXL rated read/writers enabling the higher power mode for the M-Disc format after 2011. The National Archives and Records Administration lists published life expectancies to be 10 or 25 years or more for normal CDs and DVDs and conservative life expectancies to be between 2 and 5 years. Storage environments, such as temperature and humidity, as well as handling conditions such as frequency of media use and compatibility between the recorder and media, affect media shelf-life. Improvements in media storage and migrations to new recording technologies can make certain formats obsolete within their respective lifespan. Technologists have pointed to internet streaming services, where services such as video-on-demand have contributed to the 33 percent decline in DVD sales the past 5 years, as a challenge for digital preservation. == Magnetic media - video cassettes, tapes, hard drives == Magnetic media such as audio and video tape and floppy disks also have limited life spans. Audio and video tapes require specific care and handling to ensure that the recorded information will be preserved. For information that must be preserved indefinitely, periodic transcription from old media to new ones is necessary, not only because the media are unstable but also because the recording technology may become obsolete. Magnetic media also deteriorates naturally with typical shelf lives between 10 and 20 years. Magnetic tape can degrade from binder hydrolysis or magnetic remanence decay. Binder hydrolysis, also known as sticky-shed syndrome, refers to the breakdown of binder, or glue, that holds the magnetic particles to the polyester base of the tape. Tapes which have been stored in hot, humid conditions are particularly vulnerable to this phenomenon and may suffer from accelerated degradation. Severe binder can cause the magnetic material to fall off or sheds from the base, leaving a pile of dust and clear backing. Archivists can bake the tape, which evaporates water molecules on the tape, to temporarily restore the binder before making a copy. Magnetic tape can also be destabilized by magnetic remanence decay, which refers to the weakening of the tape's magnetization over time. This weakens the affected tape's readability, leading to reduced sound clarity and volume or picture hue and contrast. Baking the tape will not restore magnetization. Media at risk include recorded media such as master audio recordings of symphonies and videotape recordings of the news gathered over the last 40 years. Threats to media that must be considered when archiving important record media include accidental erasure, physical loss due to disasters such as fires and floods, and media degradation. Along with the actual media being degraded over the years, the machines that are available to play back or reproduce the audio sources are becoming archaic themselves. Manufacturers and their support (parts, technical updates) for their machines have disappeared throughout the years. Even if the medium is vaulted and archived correctly, the mechanical properties of the machines have deteriorated to the point that they could do more harm than good to the tape being played. Many major film studios are now backing up their libraries by converting them to electronic media files, such as .AIFF or .WAV-based files via digital audio workstations. That way, even if the digital platform manufacturer goes out of business or no longer supports their product, the files can still be played on any common computer. There is a detailed process that must take place previous to the final archival product now that a digital solution is in place. Sample rates and their conversion and reference speed are both critical in this process. In floppy disks, the lubricants inside the plastic jackets of many older floppies promote the decay of the magnetic medium. Also, the alignment of the magnetic particles of the disk substrate may gradually degrade, leading to a loss of formatting and data. Early laser disk media were prone to degradation as the layers of the disk substrate were bonded with an adhesive that was vulnerable to decay and would crumble over time. This would lead the different layers of the disk to peel apart, damaging the pitted data surface and rendering the disk unreadable.