Hybrid Poisson and multi-Bernoulli filters

The probability hypothesis density (PHD) and multi-target multi-Bernoulli (MeMBer) filters are two leading algorithms that have emerged from random finite sets (RFS). In this paper we study a method which combines these two approaches. Our work is motivated by a sister paper, which proves that the full Bayes RFS filter naturally incorporates a Poisson component representing targets that have never been detected, and a linear combination of multi-Bernoulli components representing targets under track. Here we demonstrate the benefit (in speed of track initiation) that maintenance of a Poisson component of undetected targets provides. Subsequently, we propose a method of recycling, which projects Bernoulli components with a low probability of existence onto the Poisson component (as opposed to deleting them). We show that this allows us to achieve similar tracking performance using a fraction of the number of Bernoulli components (i.e., tracks).Comment: Submitted to 15th International Conference on Information Fusion (2012

An efficient, variational approximation of the best fitting multi-Bernoulli filter

The joint probabilistic data association (JPDA) filter is a popular tracking methodology for problems involving well-spaced targets, but it is rarely applied in problems with closely-spaced targets due to its complexity in these cases, and due to the well-known phenomenon of coalescence. This paper addresses these difficulties using random finite sets (RFSs) and variational inference, deriving a highly tractable, approximate method for obtaining the multi-Bernoulli distribution that minimises the set Kullback-Leibler (KL) divergence from the true posterior, working within the RFS framework to incorporate uncertainty in target existence. The derivation is interpreted as an application of expectation-maximisation (EM), where the missing data is the correspondence of Bernoulli components (i.e., tracks) under each data association hypothesis. The missing data is shown to play an identical role to the selection of an ordered distribution in the same ordered family in the set JPDA algorithm. Subsequently, a special case of the proposed method is utilised to provide an efficient approximation of the minimum mean optimal sub-pattern assignment estimator. The performance of the proposed methods is demonstrated in challenging scenarios in which up to twenty targets come into close proximity.Comment: Accepted, IEEE Transactions on Signal Processing, http://dx.doi.org/10.1109/TSP.2014.237094

Abstracting Asynchronous Multi-Valued Networks: An Initial Investigation

Multi-valued networks provide a simple yet expressive qualitative state based modelling approach for biological systems. In this paper we develop an abstraction theory for asynchronous multi-valued network models that allows the state space of a model to be reduced while preserving key properties of the model. The abstraction theory therefore provides a mechanism for coping with the state space explosion problem and supports the analysis and comparison of multi-valued networks. We take as our starting point the abstraction theory for synchronous multi-valued networks which is based on the finite set of traces that represent the behaviour of such a model. The problem with extending this approach to the asynchronous case is that we can now have an infinite set of traces associated with a model making a simple trace inclusion test infeasible. To address this we develop a decision procedure for checking asynchronous abstractions based on using the finite state graph of an asynchronous multi-valued network to reason about its trace semantics. We illustrate the abstraction techniques developed by considering a detailed case study based on a multi-valued network model of the regulation of tryptophan biosynthesis in Escherichia coli.Comment: Presented at MeCBIC 201

"Tough Love": implications for redistributive policy

Jason Saving explores the economic and political implications of "tough love" for redistributive policy. The American welfare system unquestionably helps support the least fortunate among us, but, in making poverty less onerous, it may discourage employment among some individuals. Traditional notions of altruism assume that compassion for the poor is measured by one's willingness to redistribute income but to the extent that more generous support for the poor actually encourages recipiency, welfare programs simultaneously mitigate and exacerbate the problem of poverty. A "new altruistic" approach that incorporates tough love would reduce the number of poor people but could only do so by worsening the living standards of those who remain in poverty.Welfare ; Employment (Economic theory) ; Unemployment ; Poverty

The effect of welfare reform and technological change on unemployment

Unemployment has fallen to its lowest level in a generation. Some welcome this development because they believe it increases the average person's ability to achieve the American dream. Others view low unemployment as a precursor to dire economic consequences. Jason Saving examines the issue of unemployment and reaches three main conclusions. First, welfare reform can significantly reduce unemployment, and the empirical evidence to date suggests the recent American welfare reform effort has caused hundreds of thousands of Americans to leave the welfare rolls and enter the labor force. Second, welfare reform can increase the official unemployment rate, but it cannot increase the number of people who are out of work. Finally, technological change can help low-skilled or disabled individuals become productive members of the labor force, and there is reason to believe it has done so during the 1990s.

European economic integration: a conflict of visions

European Union

Our Impressive Immune System: More Than a Defense

Most likely the immune system was put into place in the original human body design. We know from Exodus 20:11 and other verses that God completed His work of creation in six days. Therefore, the human body and its functional parts, including the components of the immune system, must have been part of the original creation. God said that all He had made was very good (Genesis 1:31). Since there were no pathogens (germs), parasites, or diseases prior the Edenic Fall and subsequent Curse, the immune system may have functioned differently in that world unmarred by sin and death. The immune system serves more than just to “defend” against disease. The immune system was designed to interact with microbes and cleanse the body of aged, dying, dead red blood cells and bacteria even in the Pre-Fall World. There are toll-like receptors in the immune system that have “sensory” function, as well as defense functions in animals and humans. The immune system in Peyer’s Patches in the GI tract assists the normal development of the intestine and regulates the normal microbiome. Consider a sheep dog designed to positively interact with sheep (herd them); they only “defend” with teeth when a predator (e.g. a wolf) approaches. The immune system in a pre-Fall world (Gillen and Sherwin 2013) worked to positively assist body development (as will be discussed); in the post-Fall world, they also defend against pathogens. This is how most creation biologists view the immune system. Immunology is that branch of biology that involves studying how the body is designed to protect itself from agents of disease called pathogens. The word immune comes from the Latin root word that means “freedom or protection from taxes or burdens.” This amazing system battles disease in a manner that is so complex and intricate that the most gifted imagination could not envision such incredible functions. In today’s world (post-Fall), the primary role of our immune system is to recognize pathogens and parasites, then to destroy them. Three main methods of destruction include baths of caustic digestive enzymes that cause rapid perforation with submicroscopic holes, overwhelming organisms with sticky proteins, and lastly by ingestion by macrophages (amoeba-like cells). In addition, the immune system is designed to prevent the proliferation of mutant cells, such as various cancers. When this system malfunctions or when a boundary is breached, it can result in localized or systemic infections, or worse, death