A statistical approach to the inverse problem in magnetoencephalography

Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic field outside the human head produced by the electrical activity inside the brain. The MEG inverse problem, identifying the location of the electrical sources from the magnetic signal measurements, is ill-posed, that is, there are an infinite number of mathematically correct solutions. Common source localization methods assume the source does not vary with time and do not provide estimates of the variability of the fitted model. Here, we reformulate the MEG inverse problem by considering time-varying locations for the sources and their electrical moments and we model their time evolution using a state space model. Based on our predictive model, we investigate the inverse problem by finding the posterior source distribution given the multiple channels of observations at each time rather than fitting fixed source parameters. Our new model is more realistic than common models and allows us to estimate the variation of the strength, orientation and position. We propose two new Monte Carlo methods based on sequential importance sampling. Unlike the usual MCMC sampling scheme, our new methods work in this situation without needing to tune a high-dimensional transition kernel which has a very high cost. The dimensionality of the unknown parameters is extremely large and the size of the data is even larger. We use Parallel Virtual Machine (PVM) to speed up the computation.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS716 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

HOW SUCCESSFUL ARE GOVERNMENT INTERVENTIONS IN FOOD MARKETS? INSIGHTS FROM THE PHILIPPINE RICE MARKET

We investigate the Philippine government’s price stabilization policy for rice. Seemingly Unrelated Regressions are used to examine the effectiveness of the program at regional and national levels over a 21-year period (January 1983 to December 2003). Results of the regional analysis indicate some NFA-induced spatial and temporal differences in terms of producer prices. The NFA successfully increased producer prices in 5 of 13 regions through stock accumulation and paddy rice purchase at floor prices. NFA stock releases do not correlate strongly with retail prices at the national level, although results from the regional model indicate that NFA stock releases reduced retail prices in five regions, leading to perceptible spatial and temporal differences between regions. Although the NFA support price appears to have been moderately successful in increasing producer prices at a national level, on average, the support price led to an increase in consumer prices in ten regions and contributed little to price stabilization. Overall, therefore, our results indicate very limited success on the part of the NFA to achieve its major objectives at either regional or national level. We suggest the NFA should concentrate its resources in the poorest areas of the country, where it might exert greater and more useful influence in smaller and locally thin rice markets.Philippines, rice, price supports, markets, commodity storage, food policy

Development Strategy of Organic Agriculture in China: A Case of Rural Urbanization in Xingyi

China’s development focus has been on rural development since 2000, as the country tries to upgrade the rural areas’ infrastructure and economy system. Different development methods had been applied with limited sustainability in terms of lifting the income of rural residents, who are primarily farming-based group. In this paper, we will introduce a real case study on an on-going rural urbanization project taking place in rural China, while primarily focusing on how this non-governmental project utilize organic farming to try to shape a possible method to sustainably upgrade the income of the local residents in rural China in the process of a complex rural urbanization development. Rural urbanization movement has been one of China’s most significant social and economic tasks since 1979, as the majority of China’s population was in rural. In 2013. China’s urban population surpasses rural population for the first time in the past 5,000 years. As urban population continues to grow, rural areas also continue to undergo urbanization process to withstand the excess urban population whom the current urban areas cannot sustain. The growth of urban population generates three key issues that require effective methods of rural urbanization to alleviate. First of all, urban area’s lack of physical space to withstand the increased population coming from rural areas has forced the city to expand to a degree that exceeds its original designed capability to provide an efficient living quality for its residents. Secondly, the lack of suitable career opportunity for the new urban residents that come from the rural areas, as these “new” residents’ professional background mainly surrounds labor-intensive industries such as agriculture and construction- neither has much prospect in earning enough salary for the relative workers to support a reasonable lifestyle in urban areas. Lastly, the unbalanced resources and infrastructure development distribution between rural and urban areas caused rural work force to abandon their rural homes and move to urban area, leaving rural areas with insufficient work force to develop its own industry effectively. One of the main elements of China’s national-level development strategy to rural urbanization is to explore an effective set of rules and regulations to utilize private capital in developing rural areas. A typical rural urbanization development process on the government side involves rural residential land rearrangement and consolidation, real estate development, courting and attracting of business investments, and local economic system development. Each of these development processes requires significant financial input and a long-term strategic development plan in order to allow both the private capital and local development to head into a sustainable better future together. Looking back the past 30 plus years, China has been conducting different experiments on bringing in different development models into rural development, none of them had been proven to be sustainably efficient in terms of benefiting both sides (the participating private companies, investors and rural residents). Rural residential land rearrangement and consolidation and real estate development takes up the biggest portion in terms of monetary investment at the initial stage of a typical rural urbanization project. The main purpose of land rearrangement and consolidation process is to ensure that, after urbanization process is completed, each rural urbanization development does not result in loss of farmland in terms of area, as China has imposed a strict limit in maintaining the size of farmland at 1.8 billion mu (about 1,200,000 square kilometer) nationwide. Due to the fact that each of the local residents has the decision power on determine the cost of each piece of land involving in rearrangement, the budget of completing the rearrangement and consolidation process is growing unpredictably high. As the initial cost of real estate development depends largely on the cost of the land rearrangement, the local residents’ personal willingness in cooperating with the rearrangement process become the first key element in affecting the investment efficiency and the cash flow in a rural urbanization development project

Synergetic value-driven innovation in business model of organic agriculture in China: a case study of IGARDEN

The innovation of business model is an important way for enterprises to gain competitive advantages and achieve sustainable development. With the rapid development of organic agriculture, an increasing number of scholars started to pay more attention to the research on the business model innovation of organic agriculture in recent years. However, most of the studies took the western developed countries as research objects, while research on cases of China’s local entrepreneurs are not often to be found. In order to develop Chinese organic agriculture’s business model innovation theory and to guide the practice, this thesis selects IGARDEN as the research object, and with a value-created perspective we explore the innovation process, path and essential characteristics of its business model by a case study method. Through the case study of IGARDEN, the result shows that: (1) The business model of IGARDEN follows the evolution from product-based to platform-based; (2) IGARDEN’s business model innovation follows the logic of value creation, and the core of value creation is the expression of product value, the increase of platform value and the accumulation of sustainable value; (3) The emergence of synergistic value expands the border of value creation activities, promoting the innovation process of business model. Driven by Synergetic Value, the value creation carrier of IGARDEN has thus facilitated the emergence of new business models; (4) The process of business model innovation in IGARDEN is essentially an iterative process based on value creation, value synergy and value upgrading. The research result has contributed to the potential enrichment of theories related to business model innovation through a specific scope of the business model innovation within the organic agriculture industry of China, and it can be a guide of forming business model innovation strategy for entrepreneurs facing similar business environment as described in the case.A inovação do modelo de negócios é um método importante para as empresas obterem vantagens competitivas e alcançarem o desenvolvimento sustentável. Com o rápido desenvolvimento da agricultura orgânica, um número crescente de estudiosos começou a prestar mais atenção à pesquisa sobre o modelo de negócios da agricultura orgânica nos últimos anos. No entanto, a maioria dos estudos levaram esses países ocidentais desenvolvidos como objetos de pesquisa, enquanto a pesquisa sobre casos de empreendedores locais chineses não costuma ser encontrada. Para desenvolver a teoria da inovação do modelo de negócio da agricultura orgânica chinesa e orientar a prática, esta tese seleciona o IGARDEN como objeto de pesquisa e, com uma perspectiva de valor, exploramos o processo, caminho de inovação e as características essenciais de seu modelo de negócio. Através do estudo de caso do IGARDEN, o resultado mostra que: (1) O modelo de negócio do IGARDEN segue a evolução de baseada em produto para baseada em plataforma; (2) A inovação do modelo de negócios do IGARDEN segue a lógica da criação de valor, e o núcleo da criação de valor é a expressão do valor do produto， o aumento do valor da plataforma e o acúmulo de valor sustentável; (3) O surgimento de valor sinérgico expande a fronteira das atividades de criação de valor, promovendo o processo de inovação do modelo de negócio. Impulsionado pelo Valor Sinérgico, o portador de criação de valor do IGARDEN facilitou o surgimento de novos modelos de negócios; (4) O processo de inovação do modelo de negócios no IGARDEN é essencialmente um processo iterativo baseado na criação de valor, na sinergia de valor e na atualização de valor. O resultado da pesquisa contribuiu para o potencial enriquecimento de teorias relacionadas à inovação do modelo de negócios através de um escopo específico da inovação do modelo de negócios dentro da agricultura orgânica da China, e pode ser um guia de formação de estratégia de inovação de modelo de negócios para empreendedores que enfrentam negócios semelhantes ambiente descrito neste caso

Customer retention in acquisitions : Case: A bulk liquid distribution company

Siirretty Doriast