Soil Apparent Electrical Conductivity (EC<Subscript>a</Subscript>) as a Means of Monitoring Changesin Soil Inorganic N on Heterogeneous Morainic Soils in SE Norway During Two Growing Seasons

An efficient method to monitor changes in soil inorganic N content during crop growth would be a useful means to guide N fertilization to ensure high yields and low N losses to the environment. In this study, soil apparent electrical conductivity (EC_a) measured by the widely used conductivity meter EM38 was tested as an indirect measurement of available N in spring barley during two cropping seasons at two sites with morainic loam in SE Norway. The experiment was constructed to maximize soil variation. In spite of the ȁ8noiseȁ9 caused by the soil heterogeneity, concentrations of inorganic N (cN_inorg) or NO₃-N were most strongly correlated with EC_a in both years and at both locations (with one exception). The measurements of EC_a reflected well the temporal variation in inorganic N content (N_inorg), and a ranking of the treatments based on EC_a fitted very well with a ranking based on N_inorg at the first three sampling times after fertilizing. The best subset of sensor variables (i.e. variables which can be measured ȁ8on-the-goȁ9 by sensor techniques in the field) described 27–69% (average 47%) of the variation in topsoil cN_inorg. When expanding the regression models to include pH as well, the degree of explanation increased significantly. In conclusion, the method of using EC_a appears to be quite robust in terms of detecting relative differences in cN_inorg, whereas a determination of absolute levels of cN_inorg with the method is unreliable.     

Legal reasoning with subjective logic

Judges and jurors must make decisions in an environment of ignoranceand uncertainty for example by hearing statements of possibly unreliable ordishonest witnesses, assessing possibly doubtful or irrelevantevidence, and enduring attempts by the opponents to manipulate thejudge's and the jurors' perceptions and feelings. Three importantaspects of decision making in this environment are the quantificationof sufficient proof, the weighing of pieces of evidence, and therelevancy of evidence. This paper proposes a mathematical frameworkfor dealing with the two first aspects, namely the quantification ofproof and weighing of evidence. Our approach is based on subjectivelogic, which is an extension of standard logic and probability theory,in which the notion of probability is extended by including degrees ofuncertainty. Subjective Logic is a framework for modelling humanreasoning and we show how it can be applied to legalreasoning.     

Modeling the longitudinal variation of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)

Grades derived from visual assessments of sawn timber are determined by the worst part of each piece. Since grade varies longitudinally in timber, grade yield will decrease if the average length of timber increases. The variation in grade is caused by longitudinal variation in knot properties and other features as they appear on the sawn surface taken into account during grading. The objective of this study is to describe and analyze this variation in Picea abies. The study consisting of 768 boards for which all features that could lead to downgrading were recorded noting position, type and size. Based on this information, all boards were graded according to appearance by Nordic Timber, and strength by INSTA 142. Logistic regression models of grade as a function of position in the stem were developed, and the dependence between responses was taken into consideration by using General Estimating Equations (GEE). The models showed a decreasing trend in grade from the butt end toward the top end of the trees, and the effect was more pronounced in strength grading than in appearance grading. Models with binomial response and different correlation structures were tested, and it was shown that both independent and autoregressive correlation structures could be used. This suggests that a multinomial ordinal logistic regression with a GEE-approach with an independent correlation structure is appropriate for modeling grade in this study.     

Power System Planning and Operation in International Markets-Perspectives From the Nordic Region and Europe

This paper describes development and experiences from the Nordic region and the current status and trend toward an integrated and open electricity market comprising most of Europe. The paper describes practical experiences as well as theoretical investigations and modeling studies. We focus on the following subjects: Congestion management: There are a variety of arrangements for transfer across national borders and for congestion management in Europe. A common future system based on an improved version of the Nordic market splitting system can be a good alternative. Management of ancillary services: We see certain trends concerning ancillary services in the Nordic market: 1) more focus on cost effectiveness and a move toward market arrangements including cross border trade in ancillary services; 2) increased use of the demand side in the provision of ancillary services; and 3) increased flexibility in defining the demand for ancillary services. Investment incentives: Experience as well theoretical investigations indicate that investment in generating capacity is a problem in an open electricity market, where investors are exposed to high risk and uncertainty. One important conclusion from our studies is that end user response (elasticity) to electricity prices is important in an open market. We also discuss how additional incentive mechanisms can be used as a measure to achieve capacity adequacy, when the market fails to provide sufficient signals for new investments.     

Sensitivity of Phage Lambda upon Variations of the Gibbs Free Energy

We investigate the sensitivity of production rates (activities) of the regulatory proteins CI (repressor) and Cro at the right operator (O_R) of bacteriophage lambda. The DNA binding energies of CI, Cro, and RNA polymerase are perturbed to check the uncertainty of the activity, due to the experimental error, by means of a computational scattering method according to which the binding energies are simultaneously chosen at random around the literature values, with a width corresponding to the experimental error. In a grand canonical ensemble, with the randomly drawn protein-DNA binding energies as input, we calculate the corresponding activities of the promoters P_RM and P_R. By repeating this procedure we obtain a mean value of the activity that roughly corresponds to wild-type (unperturbed) activity. The standard deviation emerging from this scheme, a measure of the sensitivity due to experimental error, is significant (typically >20% relative to wild-type activity), but still the promoter activities are sufficiently separated to make the switch feasible. We also suggest a new, compact way of presenting repressor and Cro data.     

Time-adaptive quantile-copula for wind power probabilistic forecasting

This paper presents a novel time-adaptive quantile-copula estimator for kernel density forecast and a discussion of how to select the adequate kernels for modeling the different variables of the problem. Results are presented for different case-studies and compared with splines quantile regression (QR). The datasets used are from NREL’s Eastern Wind Integration and Transmission Study, and from a real wind farm located in the Midwest region of the United States. The new probabilistic prediction model is elegant and simple and yet displays advantages over the traditional QR approach. Especially notable is the quality of the results achieved with the time-adaptive version, namely when evaluated in terms of prediction calibration, which is a characteristic that is advantageous for both system operators and wind power producers.     

Unexplained site variance in machine strength grading of Norway spruce structural timber

The aim of the study was to assess site effects in terms of unexplained site variance in machine strength grading of Norway spruce structural timber. The site effects were estimated for grading based on axial resonance frequency and timber length, and for grading based on dynamic modulus of elasticity. Timber was collected from 14 sites in Norway, and linear mixed models were developed based on 1188 boards. The study showed that strength grading based on axial resonance frequency and timber length leaves out effects of site that are related to altitude, latitude and site index. The variance could be reduced when the grading was based on dynamic modulus of elasticity. For both grading methods, the site effects were smaller for bending strength than for modulus of elasticity and density. Major parts of the site effects were explained by mass density, and simulations showed that it is possible to fulfil the requirements of the strength classes with a higher yield when the sorting is based on a combination of exclusion by mass density and exclusion by the frequency-based indicating property.     

Wind power forecasting uncertainty and unit commitment

In this paper, we investigate the representation of wind power forecasting (WPF) uncertainty in the unit commitment (UC) problem. While deterministic approaches use a point forecast of wind power output, WPF uncertainty in the stochastic UC alternative is captured by a number of scenarios that include cross-temporal dependency. A comparison among a diversity of UC strategies (based on a set of realistic experiments) is presented. The results indicate that representing WPF uncertainty with wind power scenarios that rely on stochastic UC has advantages over deterministic approaches that mimic the classical models. Moreover, the stochastic model provides a rational and adaptive way to provide adequate spinning reserves at every hour, as opposed to increasing reserves to predefined, fixed margins that cannot account either for the system’s costs or its assumed risks.     

System-wide emissions implications of increased wind power penetration

This paper discusses the environmental effects of incorporating wind energy into the electric power system. We present a detailed emissions analysis based on comprehensive modeling of power system operations with unit commitment and economic dispatch for different wind penetration levels. First, by minimizing cost, the unit commitment model decides which thermal power plants will be utilized based on a wind power forecast, and then, the economic dispatch model dictates the level of production for each unit as a function of the realized wind power generation. Finally, knowing the power production from each power plant, the emissions are calculated. The emissions model incorporates the effects of both cycling and start-ups of thermal power plants in analyzing emissions from an electric power system with increasing levels of wind power. Our results for the power system in the state of Illinois show significant emissions effects from increased cycling and particularly start-ups of thermal power plants. However, we conclude that as the wind power penetration increases, pollutant emissions decrease overall due to the replacement of fossil fuels.     

A liquefied energy chain for transport and utilization of natural gas for power production with CO2 capture and storage – Part 1

A novel transport chain for stranded natural gas utilized for power production with CO₂ capture and storage is developed. It includes an offshore section, a combined gas carrier, and an onshore integrated receiving terminal. Due to utilization of the cold exergy both in the offshore and onshore processes, and combined use of the gas carrier, the transport chain is both energy and cost effective. In this paper, the liquefied energy chain (LEC) is explained, including novel processes for both the offshore field site and onshore market site. In the offshore section, natural gas (NG) is liquefied to LNG by liquid carbon dioxide (LCO₂) and liquid inert nitrogen (LIN), which are used as cold carriers. The LNG is transported in a combined gas carrier to the receiving terminal where it is used as a cooling agent to liquefy CO₂ and nitrogen. The LCO₂ and LIN are transported offshore using the same combined carrier. Pinch and Exergy Analyses are used to determine the optimal offshore and onshore processes and the best transport conditions. The exergy efficiency for a thermodynamically optimized process is 87% and 71% for the offshore and onshore processes, respectively, yielding a total efficiency of 52%. The offshore process is self-supported with power and can operate with few units of rotating equipment and without flammable refrigerants. The loss of natural gas due to power generation for the energy requirements in the LEC processes is roughly one third of the loss in a conventional transport chain for stranded natural gas with CO₂ sequestration. The LEC has several configurations and can be used for small scale (<0.25 MTPA LNG) to large-scale (>5 MTPA LNG) transport. In the example in this paper, the total costs for the simple LEC including transport of natural gas to a 400 MW_net power plant and return of 85% of the corresponding carbon as CO₂ for a total sailing distance of 24 h are 58.1 EUR/tonne LNG excluding or including the cost of power. The total power requirements are 319 kWh/tonne, hence the energy costs are 31.9 EUR/tonne LNG adding up to 90.0 EUR/tonne LNG. The exergy efficiency for this energy chain including power production and CO₂ capture is 46.4% with a total cost of 20.4 EUR/MWh for the produced electricity. The total emissions (in CO₂ equivalents) in the chain are 1–1.5% of the transported CO₂.