A Bandit Approach to Maximum Inner Product Search

There has been substantial research on sub-linear time approximate algorithms for Maximum Inner Product Search (MIPS). To achieve fast query time, state-of-the-art techniques require significant preprocessing, which can be a burden when the number of subsequent queries is not sufficiently large to amortize the cost. Furthermore, existing methods do not have the ability to directly control the suboptimality of their approximate results with theoretical guarantees. In this paper, we propose the first approximate algorithm for MIPS that does not require any preprocessing, and allows users to control and bound the suboptimality of the results. We cast MIPS as a Best Arm Identification problem, and introduce a new bandit setting that can fully exploit the special structure of MIPS. Our approach outperforms state-of-the-art methods on both synthetic and real-world datasets.Comment: AAAI 201

Double-sided corrugated composite tube and axle protective mechanism for railway vehicles

Structural elements in transportation vehicles are exposed to different types of dynamic loadings and impact scenarios. Protecting passengers against injury and providing mechanisms to avoid impact induced damages to the critical components are the two hot topics in crashworthiness engineering. The presented research work includes two parts. The first part is about designing a novel double-sided composite corrugated tube that can be implemented in front chassis rail of ground vehicles to improve their crashworthiness against collision and car accidents. To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the DSC tube in comparison with both SSC and classical straight (S) tubes under axial crushing. Results have shown that the total absorbed energy of the DSC aluminum tube with 14 corrugations was 330% and 32% higher than that of the SSC tube with 14 corrugations and the S-tube, respectively. The second part of this research work is about designing a novel protective mechanism for railway car axle against ballast impact. The ice detached from the train body can fall on the track and form projectiles of ice and gravel (ballast); sharp, heavy, and at high impact energy. The main preventive mechanism in many countries such as Norway is to use protective coating on the axle. But when the coating is damaged by impact, bare steel of the axle can be exposed. The corrosion of these exposed impact zones can cause pits and cavities that become points of stress concentration where fatigue cracks can develop. Due to the current problems with coating technique we suggested a novel protective mechanism and used sandwich panel to protect railway axle against impact. Our results showed that the device can dissipate more than 70 % of impact energy without introducing any damage to the axle surface. Moreover, the rebounding velocity of projectile reduced by 97 % which eliminates the risk of second impact to the other vehicle components. The suggested device can be mounted by using a simple clamping system and unmount easily for potential inspections

Double-sided corrugated composite tube and axle protective mechanism for railway vehicles

Structural elements in transportation vehicles are exposed to different types of dynamic loadings and impact scenarios. Protecting passengers against injury and providing mechanisms to avoid impact induced damages to the critical components are the two hot topics in crashworthiness engineering. The presented research work includes two parts. The first part is about designing a novel double-sided composite corrugated tube that can be implemented in front chassis rail of ground vehicles to improve their crashworthiness against collision and car accidents. To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the DSC tube in comparison with both SSC and classical straight (S) tubes under axial crushing. Results have shown that the total absorbed energy of the DSC aluminum tube with 14 corrugations was 330% and 32% higher than that of the SSC tube with 14 corrugations and the S-tube, respectively. The second part of this research work is about designing a novel protective mechanism for railway car axle against ballast impact. The ice detached from the train body can fall on the track and form projectiles of ice and gravel (ballast); sharp, heavy, and at high impact energy. The main preventive mechanism in many countries such as Norway is to use protective coating on the axle. But when the coating is damaged by impact, bare steel of the axle can be exposed. The corrosion of these exposed impact zones can cause pits and cavities that become points of stress concentration where fatigue cracks can develop. Due to the current problems with coating technique we suggested a novel protective mechanism and used sandwich panel to protect railway axle against impact. Our results showed that the device can dissipate more than 70 % of impact energy without introducing any damage to the axle surface. Moreover, the rebounding velocity of projectile reduced by 97 % which eliminates the risk of second impact to the other vehicle components. The suggested device can be mounted by using a simple clamping system and unmount easily for potential inspections

Bioresorbable Composite Stents for Enhanced Response of Vascular Smooth Muscle Cells

Formation of arterial plaque and stenosis is one of the main cardiovascular disease risk factors. Stenting is a popular approach to increase the inner diameter of the artery and provide an acceptable lumen gain. This is achieved by applying internal pressure to the arterial wall. Despite the desirable outcomes of this procedure, there are complexities and challenges that are being discussed among scholars in this area. Restenosis is one of these complications, in which smooth muscles cell start proliferation and remodeling in response of induced mechanical stresses. Another important issue is the placement of the stent and possible migration due to the continuous deformation and special contact state between tissue and stent struts. Finally, the mechanical properties of the stent and application of novel materials in order to improve its performance are the critical topics that also have been elaborated in the current research work. First of all, we developed a multi-scale model which is able to calculate load distribution in RVE scale and can be useful to assess the mechanical stresses experienced by smooth muscle cells. Moreover, stent migration has been simulated by using finite element modeling, and the effect of stent structure on this complication has been explained. Finally, the application of novel nano composite materials in stent design has been discussed. Developing 3D printed steel-PLLA and MgPLLA particle composites and the effect of added phases in micromechanical properties of composites has been evaluated. Advisor: Linxia G

VerdictDB: Universalizing Approximate Query Processing

Despite 25 years of research in academia, approximate query processing (AQP) has had little industrial adoption. One of the major causes of this slow adoption is the reluctance of traditional vendors to make radical changes to their legacy codebases, and the preoccupation of newer vendors (e.g., SQL-on-Hadoop products) with implementing standard features. Additionally, the few AQP engines that are available are each tied to a specific platform and require users to completely abandon their existing databases---an unrealistic expectation given the infancy of the AQP technology. Therefore, we argue that a universal solution is needed: a database-agnostic approximation engine that will widen the reach of this emerging technology across various platforms. Our proposal, called VerdictDB, uses a middleware architecture that requires no changes to the backend database, and thus, can work with all off-the-shelf engines. Operating at the driver-level, VerdictDB intercepts analytical queries issued to the database and rewrites them into another query that, if executed by any standard relational engine, will yield sufficient information for computing an approximate answer. VerdictDB uses the returned result set to compute an approximate answer and error estimates, which are then passed on to the user or application. However, lack of access to the query execution layer introduces significant challenges in terms of generality, correctness, and efficiency. This paper shows how VerdictDB overcomes these challenges and delivers up to 171$\times$ speedup (18.45$\times$ on average) for a variety of existing engines, such as Impala, Spark SQL, and Amazon Redshift, while incurring less than 2.6% relative error. VerdictDB is open-sourced under Apache License.Comment: Extended technical report of the paper that appeared in Proceedings of the 2018 International Conference on Management of Data, pp. 1461-1476. ACM, 201

Examine the Lung Role in Acute Respiratory Distress Syndrome and COVID-19-Disease with Focus on Transpulmonary Gradient of the Inflammatory Biomarkers

Background: The main function of the lungs is respiration, however there are a few studies about other metabolic functions of the lungs, i.e. production of the angiotensin converting enzyme and thus participate in the metabolism of angiotensin. There is also data on the metabolism of some drugs through the lungs. 100% of the cardiac output flows through the lungs. In principle, this results in the prerequisites that the lungs also intervene in metabolic processes or significantly change the blood concentration of biomarkers i.e. inflammatory mediators. We hypothesize that numerous metabolites of the blood are changed passing through the lung or the lung secrete certain inflammatory mediators into the blood. The present work compares the transpulmonary gradient of inflammatory cytokines, mentioned as delta value through the work, among three different groups: healthy individuals, pneumonia / ARDS patients and COVID-19 patients. The delta values are defined as the difference of biomarkers concentrations found in serum taken from arterial blood (oxygenated, after passing through the lungs) and biomarkers concentration found in serum taken from the central venous blood (deoxygenated, before entering the lungs). Methods: Men from January 2019 to April 2020 were included in our study. The samples were collected at the Saarland University Hospital (UKS). Three groups were included: patients from surgery department as control group (sample size n = 26), pneumonia / ARDS group (n = 23) and COVID-19 group (n = 10). To collect samples, blood was drawn from the central venous catheter (CVC) and peripheral arterial catheter. The statistical evaluation was carried out using the program SPSS Version 26 (IBM 2019). Results: The age distribution ranged from 34 to 93 years old, with the mean age being 62.17 ± 12.69 years old. According to the Shapiro-Wilk test (p> 0.05), the age distribution of the subjects was normal. The survival of patients was also documented. No one from control group died. From the “pneumonia / ARDS” group, 3 out of 23 patients died and from the “COVID-19” group 5 out of 10 patients died in the course of the disease. We tested 76 different cytokines and biomarkers, in both arterial and venous circulatory system. 4 biomarkers differed significantly in their delta value between the COVID-19 and control groups, 2 biomarkers between the pneumonia / ARDS and the control groups and 3 biomarkers between the pneumonia and COVID-19 groups. The delta values of nine biomarkers correlated significantly with the intensive care medicine scores SAPS (Simplified Acute Physiology Score) and TISS (Therapeutic Intervention Scoring System) in pneumonia / ARDS group. In contrast, a correlation between the biomarkers in COVID-19 group and the intensive medicine scores could not be detected. The comparison between the survived and deceased COVID-19 patients revealed a significant difference in the delta values of 3 biomarkers. Conclusions: Cytokines and biomarkers can make statements about the disease and the course of COVID-19 and pneumonia / ARDS patients. In our study the transpulmonary gradient of some pro- and anti-inflammatory biomarkers were statistically significant among the three groups including IgM, IL-1RA, IL-10 among others. The transpulmonary gradient of these biomarkers were the lowest in COVID-19 group, however comparing the venous and arterial samples within each group, COVID-19 group had the highest venous and arterial concentration of theses biomarkers. This might be an indicator for a higher inflammation state in COVID-19 in comparison to other types of ARDS. Furthermore, we could show a correlation between the transpulmonary gradient of two cellular adhesion molecules and outcome of our COVID-19 patients.Die Hauptfunktion der Lunge ist der Austausch der Atemgase, jedoch es gibt ein Paar Studien über die andere metabolische Funktionen der Lungen, z. B. die Produktion des Angiotensin-Converting Enzymes und somit Beteiligung am Stoffwechsel von Angiotensin. Weiterhin gibt es Daten zur Metabolisierung einiger Pharmaka durch die Lunge. Die Lunge wird von 100 % des Herzzeitvolumens durchströmt. Dadurch ergeben sich prinzipiell die Voraussetzungen, dass die Lunge auch in metabolische Prozesse eingreift bzw. die Blutkonzentration von beispielsweise Entzündungsmediatoren deutlich verändert. Wir hypothetisieren hier, dass zahlreiche Metabolite des Blutes im Rahmen der Lungenpassage verändert werden beziehungsweise die Lunge bestimmte Entzündungsmediatoren ins Blut abgibt. Die vorliegende Arbeit Vergleich die transpulmonale Gradienten der Entzündungsmediatoren, der in dieser Arbeit als Delta-Wert bezeichnet wird, zwischen drei verschiedenen Gruppen ab: Gesunde, Patienten mit Pneumonie / ARDS und Patienten mit COVID-19 Erkrankung. Die Delta-Werte sind definiert als die Differenz der Biomarkerkonzentration im Serum aus arteriellem Blut (oxygeniert, nach Durchtritt durch die Lunge) und der Biomarkerkonzentration im Serum aus dem zentralvenösen Blut (desoxygeniert, bevor es in die Lunge gelangt). Methoden: In unsere Studie wurden männliche Patienten von Januar 2019 bis April 2020 eingeschlossen. Die Proben wurden am Universitätsklinikum des Saarlandes, Deutschland gesammelt. Es wurde zwischen drei Gruppen unterschieden. Zum einen die Operationspatientengruppe als Kontrollgruppe (Stichprobengröße n = 26), die Pneumonie- / ARDS-Gruppe (n = 23) und die Gruppe mit COVID-19-Patienten (n = 10). Um die einzelnen Proben einer Person zu sammeln, wurde Blut aus dem zentralen Venenkatheter (ZVK) und dem peripheren arteriellen Katheter entnommen. Die statistische Auswertung erfolgte mit Hilfe des Programms SPSS Version 26 (IBM 2019). Ergebnisse: Die Altersverteilung über die gesamte Studie reichte von 34 bis 93 Jahren, wobei das Durchschnittsalter 62,17 Jahre mit einer Standardabweichung von 12,69 Jahren betrug. Laut Shapiro-Wilk-Test (Signifikanz p > 0,05) war die Altersverteilung der Probanden normal. Auch das Überleben der Patienten wurde dokumentiert. Es zeigte sich, dass kein Patient der „gesunden“ Gruppe starb. Aus der Gruppe „Pneumonie“ starben 3 von 23 Patienten und aus der Gruppe „COVID-19“ starben 5 von 10 Patienten im Krankheitsverlauf. Insgesamt wurde das jeweilige Blut auf 76 verschiedene Zytokine und Biomarker, sowohl arteriell wie auch venös, getestet. Die Hauptergebnisse waren, dass sich insgesamt 4 Biomarker in ihrem Delta-Wert zwischen den COVID-19-Patienten und Patienten mit gesunden Lungen signifikant unterschieden. Im Vergleich dazu wurde bei insgesamt 2 Biomarkern ein signifikanter Unterschied zwischen den Pneumonie- bzw. ARDS-Patienten und den gesunden Probanden gefunden. Die Pneumonie- und COVID-19-Patienten unterschieden sich hingegen in insgesamt 3 Biomarkern. Die Blutkonzentration der restlichen Biomarker unterschied sich beim Durchgang durch die Lunge nicht statistisch signifikant. Für die intensivmedizinischen Scores SAPS und TISS konnten für die Gruppe der Pneumoniepatienten 9 korrelierte Marker bestimmt werden. Ein Zusammenhang zwischen COVID-19-Patienten und den Scores konnte hingegen nicht nachgewiesen werden. Der Vergleich zwischen den überlebenden und verstorbenen COVID-19-Patienten ergab einen signifikanten Unterschied in den Serumkonzentrationen für 3 Biomarker. Schlussfolgerungen: Anhand der Zytokin- und Biomarkerwerte können Aussagen über die Erkrankung und den Verlauf von COVID-19- und Pneumonie/ARDS-Patienten getroffen werden. In unserer Studie waren die transpulmonalen Gradientenunterschiede einiger pro- und antiinflammatorischer Biomarker zwischen den drei Gruppen einschließlich IgM, IL-1RA, IL-10 statistisch signifikant. Der transpulmonale Gradient dieser Biomarker war in der COVID-19-Gruppe am niedrigsten, aber beim Vergleich der venösen und arteriellen Proben innerhalb jeder Gruppe wies die COVID-19-Gruppe die höchste Konzentration dieser Biomarker in beiden Proben auf. Dies könnte ein Indikator für einen höheren Entzündungszustand bei COVID-19 im Vergleich zu anderen Arten von ARDS sein. Darüber hinaus konnten wir eine Korrelation zwischen dem transpulmonalen Gradienten zweier zellulärer Adhäsionsmoleküle und dem Outcome von COVID-19-Patienten aufzeigen