On trust and privacy in context-aware systems

Recent advances in networking, handheld computing and sensors technologies have led to the emergence of context-aware systems. The vast amounts of personal information collected by such systems has led to growing concerns about the privacy of their users. Users concerned about their private information are likely to refuse participation in such systems. Therefore, it is quite clear that for any context-aware system to be acceptable by the users, mechanisms for controlling access to personal information are a necessity. According to Alan Westin "privacy is the claim of individuals, groups, or institutions to determine for themselves when, how and to what extent information is communicated to others"1. Within this context we can classify users as either information owners or information receivers. It is also acknowledged that information owners are willing to disclose personal information if this disclosure is potentially beneficial. So, the acceptance of any context-aware system depends on the provision of mechanisms for fine-grained control of the disclosure of personal information incorporating an explicit notion of benefit

Dynamic trust models for ubiquitous computing environments

A significant characteristic of ubiquitous computing is the need for interactions of highly mobile entities to be secure: secure both for the entity and the environment in which the entity operates. Moreover, ubiquitous computing is also characterised by partial views over the state of the global environment, implying that we cannot guarantee that an environment can always verify the properties of the mobile entity that it has just received. Secure in this context encompasses both the need for cryptographic security and the need for trust, on the part of both parties, that the interaction is functioning as expected. In this paper we make a broad assumption that trust and cryptographic security can be considered as orthogonal concerns (i.e. an entity might encrypt a deliberately incorrect answer to a legitimate request). We assume the existence of reliable encryption techniques and focus on the characteristics of a model that supports the management of the trust relationships between two entities during an interaction in a ubiquitous environment

ASSESSING SPATIAL BREAK-EVEN VARIABILITY IN FIELDS WITH TWO OR MORE MANAGEMENT ZONES

Farmers are interested in knowing whether applying inputs at variable rates across a field is economically viable. The answer depends on the crop, the input, their prices, the cost of variable rate technology (VRT) versus uninform rate technology (URT), and the spatial and yield response variability within each field. Methods were investigated for determining the range of spatial variability over which the return to VRT covers its additional cost compared with URT in fields with multiple management zones. Models developed in this article, or variants thereof, could be used to help farmers make the VRT adoption decision.management zones, nitrogen, precision farming, site-specific management, spatial break-even variability proportions, spatial variability, variable rate technology, yield response variability, Farm Management,

Risk and Return for Bioenergy Crops under Alternative Contracting Arrangements

This study evaluated the potential to supply biomass feedstocks under alternative contract arrangements for a northwest Tennessee 2,400 acre grain farm. The four potential types of contracts analyzed in this study offer different levels of biomass price, yield, and production cost risk sharing between the representative farm and the processor.Farm Management, Resource /Energy Economics and Policy,

Trust-based model for privacy control in context aware systems

In context-aware systems, there is a high demand on providing privacy solutions to users when they are interacting and exchanging personal information. Privacy in this context encompasses reasoning about trust and risk involved in interactions between users. Trust, therefore, controls the amount of information that can be revealed, and risk analysis allows us to evaluate the expected benefit that would motivate users to participate in these interactions. In this paper, we propose a trust-based model for privacy control in context-aware systems based on incorporating trust and risk. Through this approach, it is clear how to reason about trust and risk in designing and implementing context-aware systems that provide mechanisms to protect users' privacy. Our approach also includes experiential learning mechanisms from past observations in reaching better decisions in future interactions. The outlined model in this paper serves as an attempt to solve the concerns of privacy control in context-aware systems. To validate this model, we are currently applying it on a context-aware system that tracks users' location. We hope to report on the performance evaluation and the experience of implementation in the near future

Valuing National Forest Recreation Access: Using a Stratified On-Site Sample to Generate Values Across Activities for a Nationally Pooled Sample

The Forest Service controls vast quantities of natural resources including timber, wildlife, watersheds, air sheds, and ecosystems. For many of these resources, recreation is one of the primary uses of the natural asset. Recreation visits taken to National Forests are not "purchased" in the same type of market as other goods (e.g., timber, grazing, or housing). The price of, and ultimately benefit received from, recreation to National Forests cannot be estimated via traditional market prices and quantities. Alternate methods must be employed to estimate the value of recreation access. We use on-site survey data from the Forest Service's National Visitor Use Monitoring database (2000-2003) and stated preference demand estimation methods to model annual recreation trip-taking behavior to National Forests. We then use these models to derive estimates of per-visit net economic benefits across regions and activities. In 2000, the FS began conducting systematic research into recreation visitation levels on National Forest lands under the National Visitor Use Monitoring Project (NVUM). From 2000 to 2003 NVUM has collected data from 120 National Forests providing information on the number of annual visits, primary activity, local area expenditures, satisfaction with facilities, and limited demographic information. These data were collected using an on-site stratified random sampling scheme resulting in over 90,000 completed surveys. Using the NVUM data we estimate the net economic value (NEV) of recreation on National Forest lands. The dataset used to estimate these values contains 73,655 observations. Using a truncated negative binomial estimator, weighted by a composite factor that adjusts for the stratified, on-site nature of the data, we have estimated a series of pooled, multi-site recreation demand models and calculated net economic values for recreational visits to the National Forests for each of fourteen activities and four RPA regions (Pacific, Rocky Mountain, Northern, and Southern) on a per visit per individual value and for a per activity day per individual basis. Our results indicate that for most models and specifications, adjusting for the choice based sampling frame by using a truncated, weighted, stratified, negative binomial estimator, as well as accounting for regional and activity differences, reduces the estimate of the average per day and per activity day values. Forest managers and others involved in managing, planning, and administering resources used for recreation often need an estimate of the economic value of the resource. For many of these resources non-market analysis must be used to generate this information. For forest recreation, many of the values currently available come from secondary sources or from small samples. The values estimated using NVUM represent an improvement over many of the currently available forest recreation values because of the unique nature of the large-scale, stratified random sample.Resource /Energy Economics and Policy,

Point-of-care measurement of blood lactate in children admitted with febrile illness to an African District Hospital.

BACKGROUND: Lactic acidosis is a consistent predictor of mortality owing to severe infectious disease, but its detection in low-income settings is limited to the clinical sign of "deep breathing" because of the lack of accessible technology for its measurement. We evaluated the use of a point-of-care (POC) diagnostic device for blood lactate measurement to assess the severity of illness in children admitted to a district hospital in Tanzania. METHODS: Children between the ages of 2 months and 13 years with a history of fever were enrolled in the study during a period of 1 year. A full clinical history and examination were undertaken, and blood was collected for culture, microscopy, complete blood cell count, and POC measurement of blood lactate and glucose. RESULTS: The study included 3248 children, of whom 164 (5.0%) died; 45 (27.4%) of these had raised levels of blood lactate (>5 mmol/L) but no deep breathing. Compared with mortality in children with lactate levels of ≤ 3 mmol/L, the unadjusted odds of dying were 1.6 (95% confidence interval [CI].8-3.0), 3.4 (95% CI, 1.5-7.5), and 8.9 (95% CI, 4.7-16.8) in children with blood lactate levels of 3.1-5.0, 5.1-8.0, or >8.0 mmol/L, respectively. The prevalence of raised lactate levels (>5 mmol/L) was greater in children with malaria than in children with nonmalarial febrile illness (P < .001) although the associated mortality was greater in slide-negative children. CONCLUSIONS: POC lactate measurement can contribute to the assessment of children admitted to hospital with febrile illness and can also create an opportunity for more hospitals in resource-poor settings to participate in clinical trials of interventions to reduce mortality associated with hyperlactatemia

Effects of Demographics and Attitudes on WTP for Fuel Import Reductions through Ethanol Purchases

imported fuel, willingness to pay, Marketing,

The Variable-Rate Input Application Decision for Multiple Inputs with Interactions

Research has evaluated the relative profitability of variable-rate (VRT) versus uniform-rate (URT) application of a single input in fields with multiple management zones. This study addresses map-based VRT decisions for multiple inputs in fields with multiple management zones. The decision-making framework is illustrated for nitrogen and water applied to irrigated cotton in fields with three management zones. Results suggest traditional methods of determining VRT application of a single input may by suboptimal if interactions exist among VRT inputs and URT inputs. Implications are that a systems approach to multiple-input VRT decisions can produce increased net returns to VRT.breakeven analysis, cotton, economic feasibility, multiple-inputs, precision farming, variable-rate technology, Crop Production/Industries,