On the assessment of economic risk: factorial design versus Monte Carlo methods

The feasibility of large investment projects (such as gas transmission and power system projects) has many aspects. Usually, this problem cannot be modeled as a single optimization problem; instead, the multiple aspects (demand, supply, prices, investment costs) are modeled separately. Each aspect may require a large, nonlinear submodel. The results of such a submodel can often be summarized by one or a few variables, which combine all the submodel's information; for example, total demand is the sum of the demand per customer type, each type being modeled separately. Traditionally, the feasibility of the investment project is then judged by combining the results of the various submodels for the ‘base case’ values of all model inputs.This base case information, however, is not sufficient for the decision makers; they also like to know the economic risk they are taking. To assess this risk on the project level (Hertz, D. B., Risk analysis in capital investment. Harvard Business Review, 1964, 95–106) developed a method known as risk analysis. This method is based on the estimated probability distribution of a project's net present value (NPV). This distribution is obtained by introducing distributions for the model inputs. The project's economic risk is then. expressed as the probability of a negative NPV exceeding a critical value (say) α. Nowadays this approach is becoming popular, because many software packages (such as @RISK and Crystal Ball) facilitate such a risk analysis. Although Hertz's risk analysis is appealing, it has a number of theoretical and practical flaws, which may lead to wrong conclusions. These flaws are discussed in this paper.From a modelling point of view, Hertz's risk analysis is similar to analysing the technological or operational risk of an investment. However, economic risk and technological risk are different concepts that require different analyses. In this paper these differences are discussed and it is shown that Hertz's risk analysis does not measure what is normally meant by a project's economic risk. Furthermore, the information requirements for the application of risk analysis to large investment projects are formidable; this makes the results of Hertz's investment analysis unreliable. Less information is required by sensitivity analysis based on the statistical design of experiments (such as 2^k−P designs); this analysis is more robust, and leads to results that better satisfy the information needs of decision makers.     

Current situation on regulations for mycotoxins. Overview of tolerances and status of standard methods of sampling and analysis

A worldwide enquiry was undertaken in 1986-1987 to obtain up-to-date information about mycotoxin legislation in as many countries of the world as possible. Together with some additional data collected in 1981, information is now available about planned, proposed, existing or absence of legislation in 66 countries. Details about tolerances, legal bases, responsible authorities, prescribed methods of sampling and analysis and disposition of commodities containing inadmissible amounts of mycotoxins, are given. The information concerns aflatoxins in foodstuffs, aflatoxin M1 in dairy products, aflatoxins in animal feedstuffs, and other mycotoxins in food- and feedstuffs. In comparison with the situation in 1981, limits and regulations for mycotoxins have been expanded in 1987 with more countries having legislation (proposed or passed) on the subject, more products, and more mycotoxins covered by this legislation. The differences between tolerances in the various countries are sometimes quite large, which makes harmonization of mycotoxin regulations highly desirable.     

Comparison of the critical liquid volume fraction to rectilinear-diameter methods for prediction of the critical density of ethylene and oxygen

A comparison of the prediction of the critical density for ethylene and oxygen from available coexistence density values using three methods is presented. The conventional rectilinear diameter, the rectilinear diameter with an additional term to represent the postulated curvature near the critical point, and the critical liquid volume fraction were each utilized to predict critical density values for ethylene and oxygen. The correlating functions and fitted constants for the three techniques are given for different ranges of saturation density values. The accepted saturation lines for ethylene and oxygen calculated from new correlations of thermodynamic properties for these fluids were used in this study. The critical density of ethylene was predicted using coexistence density values from 220 to 230 K and from 220 to 282.34 K. Similarly, the critical density for oxygen was predicted using coexistence densities from 100 to 116 K, from 100 to 154.004 K, and from 100 to 154.571 K. Values of the critical density predicted using the three methods are compared with the accepted critical density values for these fluids. The ability of the three methods to predict accurate critical density values using saturation densities at temperatures removed from the critical point is assessed.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Polychlorinated biphenyl equilibria in an estuarine system

The stability of the partition of polychlorinated biphenyl (PCB) congeners between water and the compartments of particulate matter (seston), surface sediment, net-plankton and mussels has been investigated for 1.5 years. Samples were regularly obtained from four stations, representing River Rhine, brackish and saline estuarine and stagnant saline conditions. In spite of the PCB gradients, from freshwater to seawater, and time variations in concentrations, the partition coefficients Kd (distribution coefficients) were very stable for each of the congeners. This demonstrates that the partition between water and the other compartments is due to processes which reach their equilibrium within weeks, independent of the local variations in concentrations. This confirms the non-foodchain accumulation concept of Schneider [1] for aquatic organisms.     

Corrections for range restriction in structured interview ethnic group differences: The values may be larger than researchers thought.

Previous studies of standardized ethnic group differences in the employment interview have shown differences to be relatively small. Unfortunately, many researchers conducting interview studies have not considered the issue of range restriction in research design. This omission is likely to lead to underestimates of standardized ethnic group differences (d) when the interview is considered as an initial screening device or used in combination with other initial screening devices. The authors found that 2 forms of a behavioral interview were associated with standardized ethnic group differences of .36 and .56 when corrected for range restriction. These differences are substantially larger than previously thought and demonstrate the importance of considering a variety of study design characteristics in obtaining the appropriate parameter estimates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overview of solar cell technologies and results on high efficiency multicrystalline silicon substrates

Fabrication technologies for multicrystalline silicon (mc-Si) solar cells have advanced in recent years with efficiencies of mc-Si cells exceeding 18%. Intense efforts have been made at laboratory level to improve process technology, growth methods, and material improvement techniques to deliver better devices at lower cost. Deeper understanding of the physics and optics of the device led to improved device design. This provided a fruitful feedback to the industrial sector. Both screenprinting and buried-contact technologies yield cells of high performance. An increasingly large amount of research activity is also focussed on the fabrication of thin solar cells on cheap substrates such as glass, ceramic, or low quality silicon. Success of these efforts is expected to lead to high efficiency devices at much lower costs. Efforts are also being put on low thermal budget processing of solar cells based on rapid thermal annealing.     

Experienced emotion and affect recognition in adult attention-deficit hyperactivity disorder.

[Correction Notice: An erratum for this article was reported in Vol 16(3) of Neuropsychology (see record 2007-17085-001). On Page 102, in the byline and in the author note, and on page 109 in the Rapport et al. (2001) reference, Sara Friedman's middle initial incorrectly reads "L." Her correct middle initial is "R."] Emotional competence and deficits that may disrupt interpersonal interactions were evaluated in 28 adults with attention-deficit hyperactivity disorder (ADHD) and 28 demographically equivalent controls. Participants completed tasks assessing affect recognition and experienced emotional intensity. Adults with ADHD performed worse in affect recognition than did adults without the disorder; however, the impairment was unrelated to gross perceptual processes, fundamental abilities in facial recognition, or attentional aspects of affect perception. Moreover, intensity of experienced emotion moderated affect recognition: Among controls, experienced emotion facilitated affect recognition. Among adults with ADHD, who reported significantly greater intensity, experienced emotion was inversely related to affect recognition. Results are consistent with theories of ADHD as a deficit in behavioral inhibition; yet, results may merely reflect a constellation of deficits associated with the disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Insulin effects on ouabain binding in A6 renal cells

OBJECTIVES: This study sought to identify risk markers associated with the provision of new restorations in children and to investigate whether the carious status of a tooth surface is associated with the restorative decisions of dentists. METHODS: A total of 911 schoolchildren in grades one, two, and three were randomly selected from the island of Montreal, Quebec, Canada. Dental examinations were carried out in 1990, 1991, and 1992. Tooth surfaces of first permanent molars were classified as sound, noncavitated, and cavitated. The carious status of a tooth was matched with restorative decisions reported to the insurance board. RESULTS: The presence of a carious cavity was a strong risk marker for placement of new restorations (odds rations > or = 4.11). After one year, less than 2 percent of sound tooth surfaces of first permanent molars were restored and about 21 percent of noncavitated tooth surfaces were restored. When new class I restorations placed in maxillary first permanent molars within 3-6 months after the baseline examination were evaluated, we found that between 73 percent and 86 percent of these new restorations were placed in sound or noncavitated tooth surfaces. A similar trend also was observed in mandibular first permanent molars. Poor agreement between epidemiologic diagnosis and restorative decisions was found. The restorative profile of dentists was a significant risk marker for placement of new restorations. CONCLUSION: The majority of new restorations in first permanent molars were placed in sound and noncavitated tooth surfaces because of the ubiquitous prevalence of these tooth surfaces and the validity problems of current caries diagnosis methods.     

Realistic speech animation based on observed 3D face dynamics

An efficient system for realistic speech animation is proposed. The system supports all steps of the animation pipeline, from the capture or design of 3D head models up to the synthesis and editing of the performance. This pipeline is fully 3D, which yields high flexibility in the use of the animated character. Real detailed 3D face dynamics, observed at video frame rate for thousands of points on the face of speaking actors, underpin the realism of the facial deformations. These are given a compact and intuitive representation via independent component analysis (ICA). Performances amount to trajectories through this 'viseme space'. When asked to animate a face, the system replicates the 'visemes' that it has learned, and adds the necessary coarticulation effects. Realism has been improved through comparisons with motion captured groundtruth. Faces for which no 3D dynamics have been observed can be animated nonetheless. Their visemes are adapted automatically to their physiognomy by localising the face in a 'face space'.