Communication-Efficient Distribution-Free Inference Over Networks

Consider a star network where each local node possesses a set of distribution-free test statistics that exhibit a symmetric distribution around zero when their corresponding null hypothesis is true. This paper investigates statistical inference problems in networks concerning the aggregation of this general type of statistics and global error rate control under communication constraints in various scenarios. The study proposes communication-efficient algorithms that are built on established non-parametric methods, such as the Wilcoxon and sign tests, as well as modern inference methods such as the Benjamini-Hochberg (BH) and Barber-Candes (BC) procedures, coupled with sampling and quantization operations. The proposed methods are evaluated through extensive simulation studies.Comment: Accepted to the Asilomar Conference on Signals, Systems, and Computers (2023

Free Convection Heat Transfer of Alumina-Water Nanofluid in an Enclosure: Assessment of Viscosity and Conductivity Models

In this paper, the free convection heat transfer of Al2O3-Water nanofluid in a square cavity is simulated, employing the finite volume technique. The homogeneous model is utilized to determine the influence of nanoparticles. The obtained results are compared with the experiment. At higher Rayleigh numbers, higher agreement between the results is observed. The nanofluid average Nusselt number increases with the Rayleigh number. For a concentration of 0.1%, the average Nusselt number increases, and for higher concentrations, it decreases, as compared with the pure fluid. Different viscosity and conductivity models were evaluated. It was found that the viscosity correlation, which takes into account the Brownian motion effect, produces more accurate results. The results obtained using different conductivity correlations were almost the same

Free Convection Heat Transfer of Alumina-Water Nanofluid in an Enclosure: Assessment of Viscosity and Conductivity Models

In this paper, the free convection heat transfer of Al2O3-Water nanofluid in a square cavity is simulated, employing the finite volume technique. The homogeneous model is utilized to determine the influence of nanoparticles. The obtained results are compared with the experiment. At higher Rayleigh numbers, higher agreement between the results is observed. The nanofluid average Nusselt number increases with the Rayleigh number. For a concentration of 0.1%, the average Nusselt number increases, and for higher concentrations, it decreases, as compared with the pure fluid. Different viscosity and conductivity models were evaluated. It was found that the viscosity correlation, which takes into account the Brownian motion effect, produces more accurate results. The results obtained using different conductivity correlations were almost the same

Study of Droplet Impact on a Wall using a Sharp Interface Method and Different Contact Line Models

In this research, droplet impact on a surface is simulated by using a sharp method for interface modeling. The level-set method along with the ghost fluid method is used to model interface in a sharp fashion. Different contact line models are compared and evaluated at both low and high impact velocities. On a hydrophobic surface, dynamic models developed by Hoffman and Jiang represent a more accurate prediction of droplet behavior during the impact process than the static and molecular kinetic dynamic models, especially at rebounding stage. At lower impact velocities, the Hoffman’s model represents better predictions. However, at higher impact velocities, the Jiang’s model is somewhat more accurate. The molecular dynamic model is not appropriate for high impact velocities. On a hydrophilic surface, at low impact velocities, the Jiang’s model represents satisfactory results, whereas the static and the Hoffman’s models cannot produce accurate results, after initial stages of the impact process. At high impact velocities, the static model shows considerable deviation from the experimental results. The effect of the contact angle on the dynamic behavior of the droplet is investigated. At contact angles lower than 900, the droplet only spreads on the surface after impact. However, at contact angles higher than 900, the droplet starts to recoil after spreading. In this case, it is possible that droplet rebounds from surface after recoiling. Maximum spreading radius of the droplet decreases by an increase in contact angle. At higher contact angles, less time is needed for the droplet to rebound from surface

Comparing the therapeutic effects of 6-gingerol and hydro-alcoholic extract of ginger on polycystic ovary syndrome in Wistar rat

Background and aims: PCOS (polycystic ovary syndrome) is the most common endocrine and metabolic disorder characterized by amenorrhea, hyper androgens, hirsutism, chronic anovulation and infertility. The aim of the present study was determining the effects of ginger extract, and 6-gingerol on hormonal levels and ovarian follicles in induced PCOS rats, and comparing the ameliorating effects of these two substances for treatment of PCOS. Methods: In this experimental research, 42 adult female Wistar rats weighting between 160 g-180 g were divided into six groups of 7 animals. PCOS control that received no injection. PCOS received intraperitoneal injections of 100 mg/kg of ginger extract (for 28 days). Statistical analyses with SPSS, one-way ANOVA, T-test and Duncan test were used to compare groups. Results: In comparison with PCOS control, the treatment of PCOS rats with ginger extract (100 and 200 mg/kg) and 6-gingerol (200 and 400 µg/kg) led to significant decrease in LH levels. There was a decrease in FSH levels, but the significant one was only in the 6-gingerol treated group (400 µg/kg). In PCOS treated groups with ginger extract and 6-gingerol, the serum levels of estradiol decreased significantly compared to control and PCOS control groups (P<0.001). Progesterone levels in PCOS groups injected with ginger extract and 6-gingerol showed a significant increase (P<0.05). In PCOS treated groups with ginger extract and 6-gingerol, testosterone levels decreased significantly (P<0.001, P<0.01, P<0.05). Conclusion: 6-gingerol and ginger extract may be a useful treatment for improving the PCOS through reduction of estrogen, testosterone, LH and FSH, and improvement of ovulation. In fact, because of anti-inflammatory and antioxidant properties of ginger components, especially 6-gingerol, they can cause to improve PCOS

Sivrihisar nikel laterit cevherinden ferronikel üretiminin optimizasyonu.

In this study, pyrometallurgical treatment of limonitic laterite ore from Sivrihisar region was investigated. The run-of-mine (ROM) ore contained 1.26 wt.% Ni but was initially upgraded to 1.405 wt.% Ni by screening out the +50 mm particles. Finer than 50 mm ore was crushed to -1 mm and used in the experiments. Then, the ore was calcined at different temperatures. The optimum calcination conditions were determined as 700°C and 40 min. which resulted in 10% weight loss. At the next (prereduction) stage, the calcined ore was reduced at 700-1100°C by the addition of 5.74, 8.61 and 11.48 wt.% coal under argon atmosphere. It was found that the metallization of iron was limited until 900°C but increased rapidly at higher temperatures. The metallization of nickel and cobalt initiated at much lower temperatures and increased with temperature. The results also showed that increased coal additions did not affect the iron metallization up to 900°C. At 1000°C the metallization of Fe became slightly better, but its effect was more pronounced at 1100°C. The increased coal addition increased the nickel reduction at all temperatures, while it had no effect on the metallization of cobalt. The usage of 70%N2-20%CO2-10%CO gas mixture as reducing atmosphere substantially improved the reduction process below 1000°C. Finally, the reduced ore was smelted to produce ferronickel. No coal was added at the smelting stage and the reduction reactions were completed by the unreacted coal from the previous prereduction stage. Conditions were adjusted to produce a ferronickel containing ~15% Ni. The physical and the chemical losses of nickel in the slag were directly proportional to the ferronickel grade. Colemanite was added to the charge to decrease the physical losses in the slag and to increase nickel recovery but no positive effect was observed.Ph.D. - Doctoral Progra

Variable Selection with the Knockoffs: Composite Null Hypotheses

The fixed-X knockoff filter is a flexible framework for variable selection with false discovery rate (FDR) control in linear models with arbitrary design matrices (of full column rank) and it allows for finite-sample selective inference via the Lasso estimates. In this paper, we extend the theory of the knockoff procedure to tests with composite null hypotheses, which are usually more relevant to real-world problems. The main technical challenge lies in handling composite nulls in tandem with dependent features from arbitrary designs. We develop two methods for composite inference with the knockoffs, namely, shifted ordinary least-squares (S-OLS) and feature-response product perturbation (FRPP), building on new structural properties of test statistics under composite nulls. We also propose two heuristic variants of S-OLS method that outperform the celebrated Benjamini-Hochberg (BH) procedure for composite nulls, which serves as a heuristic baseline under dependent test statistics. Finally, we analyze the loss in FDR when the original knockoff procedure is naively applied on composite tests

Communication-Efficient Distributed Multiple Testing for Large-Scale Inference

The Benjamini-Hochberg (BH) procedure is a celebrated method for multiple testing with false discovery rate (FDR) control. In this paper, we consider large-scale distributed networks where each node possesses a large number of p-values and the goal is to achieve the global BH performance in a communication-efficient manner. We propose that every node performs a local test with an adjusted test size according to the (estimated) global proportion of true null hypotheses. With suitable assumptions, our method is asymptotically equivalent to the global BH procedure. Motivated by this, we develop an algorithm for star networks where each node only needs to transmit an estimate of the (local) proportion of nulls and the (local) number of p-values to the center node; the center node then broadcasts a parameter (computed based on the global estimate and test size) to the local nodes. In the experiment section, we utilize existing estimators of the proportion of true nulls and consider various settings to evaluate the performance and robustness of our method.Comment: Accepted to the 2022 IEEE International Symposium on Information Theory (ISIT

Sivrihisar Nikel Laterit Cevherinden Ferronikel Üretiminin Optimizasyonu Ve Nikel Verimini Artırmak İçin Bor Bileşiklerinin Kullanımı

Türkiye’de mevcut nikel cevherleri laterit denilen oksitli türde nikel cevherleridir. Gördes ve Çaldağ bölgesi nikel cevherlerinden nikel eldesine yönelik çeşitli çalışmalar yapılmaktadır. Cevherin karakteristiğine ve proses ekonomisine bağlı olarak hidrometalurjik veya pirometalurjik yöntemler uygulanabilmektedir. Sivrihisar bölgesi cevherlerinden pirometalurjik metotla ferronikel eldesine yönelik çeşitli çalışmalar yapılmakta ve adı geçen bölgede bir ferronikel tesisinin kurulması planlanmaktadır. Konvansiyonel yöntemlerle ferronikel eldesinin düşünüldüğü bu tesiste prosesin doğası gereği kalsinasyon, önindirgeme, ergitme & rafinasyon aşamaları gerçekleştirilecektir. Ferronikel ergitme aşaması elektrik ark ocaklarında gerçekleştirilmektedir. Ergitme sonucunda metal ve curuf fazları elde edilmekte, metalin içerisindeki çeşitli safsızlıkların eliminasyonu ise bir sonraki aşama olan rafinasyonda sağlanmaktadır. Rafinasyon işlemi genel olarak OBM türü konvertörlerde ya da pota ocaklarında yapılmaktadır. Ferronikel ergitme işleminde, cevherlerin yapısı ve kullanılan katkılar sebebiyle yüksek hacimde curuf elde edilmektedir. Kıymetli element olan nikelin bu curufa kaybedilmemesi proses verimi açısından oldukça önemlidir. Curufa nikel kayıpları, nikel oksit olarak curufta yer alan nikel ile curuf içinde askıda kalan ve nikel içeren ferronikel metal damlacıklarının toplamı olarak ifade edilebilir. Curuf kimyası, metal-curuf reaksiyonları ve curuf akışkanlığı gibi çeşitli faktörlere bağlı olarak curuftaki nikel kayıpları artıp azalabilir. Bor bileşiklerinin (kolemanit gibi) kullanılabileceği en önemli sektörlerin başında demir-çelik sektörü gelmektedir. Kolemanitin çelik üretim aşamasında curuf akışkanlığını artırıcı özelliği bu alanda -çeşitli proseslerde ve çeşitli koşulların sağlanması şartıyla- kullanımını mümkün kılmaktadır. Benzer şekilde, söz konusu bileşiklerin ferronikel üretiminde kullanımının da ciddi bir alternatif olabileceği düşünülmektedir. Ferronikel ergitme yönteminde demir-çelik üretimindekilere kıyasla curuf hacmi oldukça fazladır. Curuf hacmi fazlalaştıkça curuf içerisinde askıda kalabilecek metal/alaşım parçacıklarının artma olasılığı da yüksektir. Curuf akışkanlığının artırılması suretiyle metal-curuf ayrışması daha efektif şekilde gerçekleşebileceğinden, curuf içerisinde kalan kıymetli metal/alaşım tanecikleri de azalabilecektir. Bu sayede nikel kayıplarının azaltılabileceği düşünülmektedir. Gerçekleştirilecek laboratuvar çaplı deneylerden elde edilecek sonuçlara göre adı geçen bileşiklerin ferronikel üretiminde kullanılabilirliği değerlendirilecektir