THE STOCHASTIC UNIT COMMITMENT PROBLEM: A CHANCE CONSTRAINED PROGRAMMING APPROACH CONSIDERING EXTREME MULTIVARIATE TAIL PROBABILITIES

Reliable power production is critical to theprofitability of electricity utilities. Power generators (units) need to be scheduled efficiently to meet the electricity demand(load). This dissertation develops a solution method to schedule units for producing electricity while determining the estimated amount of surplus power each unit should produce taking into consideration the stochasticity of the load and its correlation structure. This scheduling problem is known as the unit commitment problem in the power industry. The solution method developed to solve this problem can handle the presence of wind power plants, which creates additional uncertainty. In this problem it isassumed that the system under consideration is an isolated one such that it does not have access to an electricity market. In such a system the utility needs to specify the probability levelthe system should operate under. This is taken into consideration by solving a chance constrained program. Instead of using a set level of energy reserve, the chance constrained model determines the level probabilistically which is superior to using an arbitrary approximation. In this dissertation, the Lagrangian relaxation technique is used to separate the master problem into its subproblems, where a subgradient method is employed in updating the Lagrange multipliers. To achieve this a computer program is developed that solves the optimization problem whichincludes a forward recursion dynamic program for the unit subproblems. A program developed externally is used to evaluate high dimensional multivariate normal probabilities. To solve thequadratic programs of period subproblems an optimization software is employed. The results obtained indicate that the load correlation is significant and cannot be ignored while determining a schedule for the pool of units a utility possesses. It is also concluded that it is very risky to choose an arbitrary level ofenergy reserve when solving the unit commitment problem. To verify the effectiveness of the optimum unit commitment schedules provided by the chance constrained optimization algorithm and todetermine the expected operation costs, Monte Carlo simulations are used where the simulation generates the realized load according to the assumed multivariate normal distribution with aspecific correlation structure

Risk factors of pneumothorax and chest tube placement after computed tomography-guided core needle biopsy of lung lesions : a single-centre experience with 822 biopsies

Purpose: To determine the risk factors of pneumothorax and chest tube placement after computed tomography-guided core needle lung biopsy (CT-CNB). Material and methods: Variables that could increase the risk of pneumothorax and chest tube placement were retrospectively analysed in 822 CT-CNBs conducted with 18-gauge non-coaxial CT-CNB in 813 patients (646 men and 167 women; range: 18-90 years; mean: 59.8 years). Predictor variables were age, gender, patient position, severity of pulmonary emphysema, lesion size and localisation, contour characteristics, presence of atelectasis, pleural tag and fissure in the needle-tract, length of the aerated lung parenchyma crossed by the needle, needle entry angle, number of pleural punctures, experience of the operator, and procedure duration. All variables were investigated by ×2 test and logistic regression analysis. Results: The overall incidence of pneumothorax was 15.4% (127/822). Chest tube placement was required for 22.8% (29/127) of pneumothoraxes. The significant independent variables for pneumothorax were lesions smaller than 3 cm (p = 0.009), supine and lateral decubitus position during the procedure (p < 0.001), greater lesion depth (p = 0.001), severity of pulmonary emphysema (p < 0.001), needle path crossing the fissure (p < 0.001), and a path that skips the atelectasis (p < 0.001) or pleural tag (p < 0.001); those for chest tube placement were prone position (p < 0.001), less experienced operator (p = 0.001), severity of pulmonary emphysema (p < 0.001), and greater lesion depth (p = 0.008). Conclusions: The supine and lateral decubitus position, a needle path that crosses the fissure, and a path that skips the atelectasis or a pleural tag are novel predictors for the development of pneumothorax. Key words: computed tomography (CT), CT-guided core needle lung biopsy (CT-CNB), pneumothorax, chest tube, pulmonary lesion

Comparison of thermal performances of plywood shear walls produced with different thermal insulation materials

Shear walls are one of the envelopes of light-frame wooden buildings where thermal insulation is most required. The thermal performance of shear walls can vary according to the type, properties and thickness of the wood and insulation materials used in their production. In this study, it was aimed to compare the thermal performances of plywood shear walls produced with different thermal insulation materials. For this aim, the archetype walls with properties similar to commonly used plywood shear walls were designed and produced for each thermal insulation material type and wood specie. The shear wall groups were formed by using Scots pine (Pinus sylvestris), black pine (Pinus nigra) and spruce (Picea orientalis) as wood species and cellulose, flax, felt, XPS, EPS, sheep’s, rock and glass wool as thermal insulation materials. Thermal conductivity of the shear wall groups was determined according to the ASTM C518-04 standard. Thermal resistance and other thermal performance parameters were calculated using the thermal conductivity values. As a result of the study, rock wool was the best thermal insulation material among the Scots pine shear wall groups while glass wool was the best thermal insulation material among the black pine and spruce shear wall groups. The shear walls produced with EPS foam boards indicated the worst thermal performance among all group

Antimicrobial, anti-biofilm and cytotoxic properties of methallyl functionalized benzimidazolium-derived Ag(I)-Nheterocyclic carbene complexes

Purpose: To investigate the antimicrobial, antibiofilm, and cytotoxicity properties of methallyl substituted benzimidazolium-based, silver-bound N-heterocyclic carbene (Ag(I)-NHC) complexes, with respect to their potential to act as antimicrobial agents.Methods: The antimicrobial, antibiofilm, and cytotoxicity properties of the four complexes, the synthesis and characterization of which were carried out previously, were investigated. The antimicrobial properties were tested using the broth microdilution method, while their antibiofilm potential were determined by microtiter plate assay. The L-929 cell line was used for cytotoxic studies.Results: Strong antibiofilm and antimicrobial effects were produced by Ag(I)-NHC complexes. Compounds 2 and 3 showed potent activities against E. coli strain, with effects similar to that of positive control antibiotic, while compounds 1 and 4 exhibited antimicrobial activity at a concentration of 31.2 μg/mL. The compounds were effective against biofilms formed at concentrations in the range of 32 – 84 %, and degraded mature biofilms at a concentration range of 14 - 66 %. Compounds 1 and 2 did not significantly affect cell survival (p &gt; 0.05), while compounds 3 and 4 significantly reduced cell survival, when compared with untreated cells in the control group (p &lt; 0.001).Conclusion: This study may be one of the few studies on benzimidazolium-derived NHCs. The compounds which produced antimicrobial, antibiofilm, and cytotoxic properties in this study may be valuable and novel antimicrobial agents. Therefore, there is need for further in vivo and in vitro studies on these compounds

Mini Review: A Note on Nonoscillatory Solutions for Higher Dimensional Time Scale Systems

In this paper, we focus on nonoscillatory solutions of two (2D) and three (3D) dimensional time scale systems and discuss nonexistence of such solutions

Broadband, Stable, and Non-Iterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method

A broadband, stable, and non-iterative free-space method is proposed for dielectric constant ε′r determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of non-disperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and Polyoxymethylene samples (9–11 GHz) are carried out to examine the accuracy of our method. IEE

Effects of finite source rupture on landslide triggering: the 2016 Mw 7.1 Kumamoto earthquake

The propagation of a seismic rupture on a fault introduces spatial variations in the seismic wave field surrounding the fault. This directivity effect results in larger shaking amplitudes in the rupture propagation direction. Its seismic radiation pattern also causes amplitude variations between the strike-normal and strike-parallel components of horizontal ground motion. We investigated the landslide response to these effects during the 2016 Kumamoto earthquake (Mw 7.1) in central Kyushu (Japan). Although the distribution of some 1500 earthquake-triggered landslides as a function of rupture distance is consistent with the observed Arias intensity, the landslides were more concentrated to the northeast of the southwest–northeast striking rupture. We examined several landslide susceptibility factors: hillslope inclination, the median amplification factor (MAF) of ground shaking, lithology, land cover, and topographic wetness. None of these factors sufficiently explains the landslide distribution or orientation (aspect), although the landslide head scarps have an elevated hillslope inclination and MAF. We propose a new physics-based ground-motion model (GMM) that accounts for the seismic rupture effects, and we demonstrate that the low-frequency seismic radiation pattern is consistent with the overall landslide distribution. Its spatial pattern is influenced by the rupture directivity effect, whereas landslide aspect is influenced by amplitude variations between the fault-normal and fault-parallel motion at frequencies <2 Hz. This azimuth dependence implies that comparable landslide concentrations can occur at different distances from the rupture. This quantitative link between the prevalent landslide aspect and the low-frequency seismic radiation pattern can improve coseismic landslide hazard assessment

Parameter Retrieval of Samples on a Substrate From Reflection-Only Waveguide Measurements

A microwave method has been proposed for constitutive parameters' extraction of samples on a known substrate. The advantage of this method is that it relies on noniterative reflection-only (air- and metal-backed) scattering (S-) parameters so that it is a good candidate for the characterization of samples when only one-port measurements are available. It is validated by the X-band (8.2-12.4 GHz) waveguide S-parameter measurements. A sensitivity analysis is followed to evaluate and improve the performance of our method. IEE

Effect of Needle-Tract Bleeding on Pneumothorax and Chest Tube Placement Following CT Guided Core Needle Lung Biopsy

Background: Bleeding in the biopsy tract has been studied for its ability to decrease the risk of pneumothorax with indefinite results in the previous studies. Purpose: To investigate the risk factors for needle-tract bleeding (NTB) and the possible effect of NTB on the pneumothorax and resultant chest tube placement after CT-guided cutting needle biopsy (CT-CNB) of pulmonary lesions. Methods: Predictive variables for NTB and the effect of NTB on the development of pneumothorax and consequent chest tube placement were retrospectively determined in 416 patients who had undergone an 18-gauge non-coaxial CT-CNB (338 men and 78 women; average age, 59.3 years). Patient-related parameters were age, gender, patient position, and severity of pulmonary emphysema. Lesion-related variables were size, localization, and contour characteristics of the lesion. Procedure-related variables were the presence of atelectasis, pleural tag, and fissure in the needle-tract, length of the aerated lung parenchyma crossed by needle, needle entry angle, number of pleural punctures, the experience of the operator, and procedure duration. All variables were analyzed by x2 test and logistic regression analysis. Results: NTB was demonstrated in 142 of 421 (33.7%) procedures. The predictive variables of NTB were smaller lesion size (p = 0.011) and greater lesion depth (p = 0.002). In patients without emphysema around the lesion, the pneumothorax developed in 44/190 cases (23.1%) without NTB and in 12/95 procedures (12.6%) with NTB (p < 0.001). Conclusion: NTB may have a preventive effect on pneumothorax development, particularly in the absence of emphysema around the lesion