Hierarchical Compound Poisson Factorization

Non-negative matrix factorization models based on a hierarchical Gamma-Poisson structure capture user and item behavior effectively in extremely sparse data sets, making them the ideal choice for collaborative filtering applications. Hierarchical Poisson factorization (HPF) in particular has proved successful for scalable recommendation systems with extreme sparsity. HPF, however, suffers from a tight coupling of sparsity model (absence of a rating) and response model (the value of the rating), which limits the expressiveness of the latter. Here, we introduce hierarchical compound Poisson factorization (HCPF) that has the favorable Gamma-Poisson structure and scalability of HPF to high-dimensional extremely sparse matrices. More importantly, HCPF decouples the sparsity model from the response model, allowing us to choose the most suitable distribution for the response. HCPF can capture binary, non-negative discrete, non-negative continuous, and zero-inflated continuous responses. We compare HCPF with HPF on nine discrete and three continuous data sets and conclude that HCPF captures the relationship between sparsity and response better than HPF.Comment: Will appear on Proceedings of the 33 rd International Conference on Machine Learning, New York, NY, USA, 2016. JMLR: W&CP volume 4

Flow field and mixing in stirred vessels with regular and fractal impellers

The goal of this thesis is to explore the potential benefits of fractal objects in dynamic mixing applications. To this end, the performance of an impeller with fractal blades was evaluated and compared to the one with regular, rectangular-shaped blades. Direct Numerical Simulations (DNS) were performed to compute the flow and passive scalar fields inside an unbaffled stirred vessel in the transitional flow regime. It was observed that at Re=1600 the mean power consumption decreases by ca. 8% when the regular blades are replaced by fractal ones. The physical explanation for this reduction was provided by comparing several characteristics of the flows generated by the two types of impellers, such as the pressure distribution on blade surfaces, the time-average recirculation pattern and the trailing vortex system in wake of the blades, the radial transport of angular momentum and the distribution of energy dissipation inside the tank. Furthermore, fluctuations were observed in the power consumption with a peak frequency at ca. three times the impeller rotational speed, for both impeller types. It was discovered that these fluctuations are associated with a periodic event in the wake of the blades, which involves alternating growth and decay of the upper and lower cores of the trailing vortex pair as well as up-and-down swinging motion of the radial jet. Moreover, the mixing time required to homogenize an injected passive scalar was evaluated for both impeller types, at Sc=1. It was observed that the fractal impeller can lead to a shorter mixing time by 10-12%. This result was explained by the differences in characteristics of flow and scalar fields generated by regular and fractal blades. A simple mathematical model was suggested which is able to approximate the decay rate of the passive scalar fluctuations integrated over the tank volume.Open Acces

Reduced power consumption in stirred vessels by means of fractal impellers

Earlier studies have shown that the power consumption of an unbaffled stirred vessel decreases significantly when the regular blades are replaced by fractal ones. In this paper, the physical explanation for this reduction is investigated using Direct Numerical Simulations at Re = 1600. The gaps around the fractal blade perimeter create jets that penetrate inside the recirculation zone in the wake and break up the trailing vortices into smaller ones. This affects the time‐average recirculation pattern on the suction side. The volume of the separation region is 7% smaller in the wake of the fractal blades. The lower torque of the fractal impeller is equivalent to a decreased transport of angular momentum; this difference stems from the reduced turbulent transport induced by the smaller trailing vortices. The major difference in the turbulent dissipation is seen in the vicinity of trailing vortices, due to fluctuations of velocity gradients at relatively low frequencies

Neopterin and Soluble Urokinase Type Plasminogen Activator Receptor as Biomarkers in Dogs with Systemic Inflammatory Response Syndrome

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗThe systemic inflammatory response syndrome (SIRS) is a common cause of mortality in dogs. This study aims to investigate the diagnostic value of markers C-reactive protein (CRP), soluble urokinase-type plasminogen activator receptor (suPAR) and neopterin in dogs with SIRS. The materials of the study consist of 30 dogs with SIRS and 15 healthy dogs that show no clinical symptom, 45 dogs in total. CRP, suPAR and neopterin levels of the serum samples were determined by ELISA using commercial kits. In the study, it was found that CRP, suPAR and neopterin levels of dogs with SIRS were significantly higher (P < 0.001, P < 0.01 and P < 0.01, respectively) than those in the healthy group. The cut-off values for the healthy dogs and dogs with SIRS for CRP, suPAR and neopterin were determined to be 11.20 mg/L, 223.68 ng/L and 3.23 nmol/mL, respectively. At these cut-off values, sensitivity levels were determined as high (92.90%) for CRP, moderate (63.30%) for neopterin, and low (53.30%) for suPAR, and high specificities (93.30%) were determined for all. In conclusion, it was determined that CRP showed the best performance for the detection of systemic inflammatory response in dogs and neopterin and suPAR could be used as an alternative to CRP. It was also argued that further studies were necessary in order to determine diagnosis and prognosis of diseases

Neopterin and Soluble Urokinase Type Plasminogen Activator Receptor as Biomarkers in Dogs with Systemic Inflammatory Response Syndrome

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗThe systemic inflammatory response syndrome (SIRS) is a common cause of mortality in dogs. This study aims to investigate the diagnostic value of markers C-reactive protein (CRP), soluble urokinase-type plasminogen activator receptor (suPAR) and neopterin in dogs with SIRS. The materials of the study consist of 30 dogs with SIRS and 15 healthy dogs that show no clinical symptom, 45 dogs in total. CRP, suPAR and neopterin levels of the serum samples were determined by ELISA using commercial kits. In the study, it was found that CRP, suPAR and neopterin levels of dogs with SIRS were significantly higher (P &lt; 0.001, P &lt; 0.01 and P &lt; 0.01, respectively) than those in the healthy group. The cut-off values for the healthy dogs and dogs with SIRS for CRP, suPAR and neopterin were determined to be 11.20 mg/L, 223.68 ng/L and 3.23 nmol/mL, respectively. At these cut-off values, sensitivity levels were determined as high (92.90%) for CRP, moderate (63.30%) for neopterin, and low (53.30%) for suPAR, and high specificities (93.30%) were determined for all. In conclusion, it was determined that CRP showed the best performance for the detection of systemic inflammatory response in dogs and neopterin and suPAR could be used as an alternative to CRP. It was also argued that further studies were necessary in order to determine diagnosis and prognosis of diseases

Modelling of the Turkish Catastrophe Insurance Pool data, 2000-2003.

The devastating 1999 Marmara and Duzce earthquakes lead to a significant increase in the earthquake studies in Turkey in geological, engineering and financial aspects. The start of the Turkish Catastrophe Insurance Pool (TCIP) in September 2000 brought the mandatory earthquake insurance scheme in Turkey. Since then, many claims have been made after the earthquakes. In this study, the earthquake insurance claims data of the TCIP is used to model the number of claims, Ni, and the total claim size (amount). Si, as response variables with time and other covari- ates considering earthquake risk zone 1 and zone 2 in Turkey. The special functions, which are the exponential and the power kernel functions, are used for the modelling purposes to represent the sudden jumps in the number of claims after a disaster. The methods to estimate the related model parameters are presented and the results are used in the modelling process. The total claim amount (or the aggregate claims) process, S(t), is a main tool to calculate the risk process and the expectation of the total claim amount, E(S(t)) =??(t), gives an idea to calculate the necessary aount of the TCIP reserves. Therefore, the estimates of the suggested Ni and Si models are used to predict the necessary reserves of the Turkish Catastrophe Insurance Pool for selected zones. Afterwards, some examples of existing disaster management programs in different countries are given and the features of the Turkish Catastrophe Insurance Pool are discussed. Then, a hypothetical financial vulnerability analysis for Turkey in 10-,50-, 100- and 500- years is presented with suggested solutions in case of a financial gap