opus htw (Hochschule für Technik und Wirtschaft Berlin)
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Performancevergleich von PostgreSQL und Neo4j in typischen eCommerce-Webseiten
No full textDiese Arbeit vergleicht die Leistungs- und Ressourceneffizienz eines relationalen Datenbanksystems (PostgreSQL 17, Normal- und indexoptimiert) mit einer Graphdatenbank (Neo4j 5, eins-zu-eins-Portierung und traversal-optimiert) in realitätsnahen eCommerce-Workloads. Eine vollständig automatisierte Benchmark-Pipeline führt die vier Modellierungsvarianten in identischen Docker-Containern aus. Getestet wurden CRUD-Operationen (Create, Read, Update, Delete) und Leseabfragen in vier Komplexitätsstufen, bei drei Datenmengen (1.000 /10.000 / 100.000 Entitäten) und bis zu zehn gleichzeitigen Clients. Pro Lauf wurden Latenz, CPU-Last, Arbeitsspeicherbedarf und belegter Festplattenspeicher gemessen (insgesamt 57.600 Messungen).
Die Ergebnisse zeigen einen klaren Vorsprung für PostgreSQL in allen transaktions- und leseintensiven Szenarien. Selbst ohne Tuning liegt die mittlere Latenz mindestens eine Größenordnung unter der von Neo4j. Zusätzliche Indizes verkürzen die Zeiten um bis zu 60 Prozent, erfordern jedoch mehr RAM (Random Access Memory) und Speicherplatz. Neo4j überzeugt nur bei Abfragen, die tiefe Beziehungspfade traversieren, verbraucht dabei aber deutlich mehr CPU (Central Processing Unit). Daraus lassen sich praxisnahe Leitlinien ableiten: Ein gut indexiertes relationales Schema deckt typische Shop-Funktionen am effizientesten ab, während ein spezialisierter Graph-Store erst bei stark beziehungsorientierten Analysen wirtschaftlich wird.This paper compares the performance and resource efficiency of a relational database system (PostgreSQL 17, baseline and index-optimized) with a graph database (Neo4j 5, one-to-one port and traversal-optimized) under realistic ecommerce workloads. A fully automated benchmark pipeline runs all four modeling variants in identical Docker containers. CRUD operations (Create, Read, Update, Delete) and read queries were tested at four complexity levels, across three data sizes (1,000 / 10,000 / 100,000 entities), and with up to ten concurrent clients. Each run measures latency, CPU load, memory footprint, and disk usage, yielding a total of 57,600 measurements.
The results show a clear advantage for PostgreSQL in all transaction- and read-heavy scenarios. Even without tuning, its average latency is at least one order of magnitude lower than Neo4j’s. Adding indexes further cuts response times by up to 60 percent, at the cost of increased RAM (Random Access Memory) and storage requirements. Neo4j only excels in queries that traverse deep relationship paths, and even then, incurs significantly higher CPU (Central Processing Unit) usage. From this, we derive practical guidelines: a well-indexed relational schema is the most efficient choice for typical shop functions, whereas a dedicated graph store becomes economical only when heavily relationship-driven analyses dominate
Implementation_of_Multichannel_Systems_on_a_Zynq-Based_System-on-Module_for_Terahertz_Spectroscopy
No full textThe Terahertz Sensors and Systems group at Fraunhofer HHI has developed a single channel continuous wave terahertz spectrometer. This spectrometer utilizes photoconductive antennas to convert an optical beat signal, generated by two lasers operating at different wavelengths, into the THz frequency range. Its potential for real-world applications is demonstrated through thickness measurements of multilayer dielectric samples. Scaling the system to a multichannel configuration would enable simultaneous measurements at multiple spatial points, enhancing imaging resolution and expanding it to industrial applications, such as radar-based object tracking and detection in autonomous vehicles and drone navigation.
This thesis investigates two innovative approaches for scaling the single channel terahertz spectrometer to a multichannel configuration using the RedPitaya STEMLab 125-14. The RedPitaya board consists of a Zynq7020 System on Chip (SoC), a dual channel Analog-Digital-Converter (ADC) and a dual channel Digital-Analog-Convert (DAC). The first approach explores channel expansion through an external 8 channel ADC (ADC20Click), utilizing the Linux kernel’s SPI driver for communication. The second approach implements a synchronized cluster of multiple RedPitaya devices in a master-slave architecture, leveraging their integrated ADCs and distributed clock synchronization.
The SPI communication between the RedPitaya and the ADC20Click, operating on a Linux-based system, faced challenges in achieving synchronized data acquisition due to the non-deterministic nature of OS scheduling. Consequently, the sampling rate varied between 5 ksps to 8 ksps. Given the current system architecture, this variability makes the approach unsuitable for integration. However, for other THz applications that can tolerate lower sample rates and non-synchronized operation, this method could still be a viable option. In contrast, the approach utilizing multiple RedPitaya boards in a cluster successfully achieved synchronized data acquisition across multiple ADC channels.
This was accomplished by generating and distributing clock and synchronization signals from the master device to the connected slave devices. A constant delay between sample acquisitions across devices was observed, which could be compensated using a delay unit with configurable delay lengths.
The system maintained a unified and scalable hardware architecture. Integrating the new approach into the existing THz spectrometer, it demonstrated synchronized measurements across three channels, utilizing one ADC channel from each RedPitaya board in the cluster. Compared to the current system, the RedPitaya cluster managed to achieve a similar dynamic range of 60 dB for a single shot measurement, enabling the development of a multi-channel CW spectrometer using the proposed approach
Perspective: fluorescence lifetime imaging and single-molecule spectroscopy for studying biological condensates
No full textBiological condensates, often formed via liquid-liquid phase separation (LLPS), are membraneless compartments organizing biochemical reactions. Recent advances have shifted the focus from identifying condensates to elucidating their dynamic biological functions, such as buffering concentrations, mediating reactions, and regulating signaling. These are critical for cellular processes and implicated in diseases like cancer and neurodegeneration. Advanced microscopy techniques, including fluorescence lifetime imaging microscopy (FLIM), FLIM-FRET, and fluorescence correlation spectroscopy (FCS), enable quantitative, real-time investigations of condensate composition, dynamics, material properties, and their responses to environmental stimuli in live cells. This perspective highlights the utility of time-resolved fluorescence and single-molecule spectroscopy techniques for shedding light on condensate functions, properties, and interactions with membranes, offering insights into cellular physiology and pathology
Virtual body image exercises for people with obesity – results on eating behavior and body perception of the ViTraS pilot study
No full textBackground: A negative body image can have an impact on developing and maintaining obesity. Using virtual reality (VR) to conduct cognitive behavioral therapy (CBT) is an innovative approach to treat people with obesity. This multicenter non-randomized pilot study examined the feasibility and the effect on eating behavior and body perception of a newly developed VR system to conduct body image exercises.
Methods: Participants with a body mass index (BMI) ≥ 30.0 kg/m 2 without severe mental diseases attended three study visits in an interval of one to four weeks to receive virtual (VR intervention) or traditional (non-VR intervention) body image exercises. Data on anthropometrics, eating behavior (Dutch Eating Behavior Questionnaire, DEBQ), body perception (Body Shape Questionnaire, BSQ; Multidimensional Assessment of Interoceptive Awareness, MAIA), and satisfaction (standardized interview and questionnaire) were collected.
Results: In total, 66 participants (VR intervention: 31, non-VR intervention: 35) were included. The majority was female (52/66, 78.8 %), the mean age was 45.0 ± 12.8 years, and the mean BMI was 36.8 ± 4.3 kg/m 2 . Both intervention groups showed non-significant body weight reduction (VR intervention: 1.7 ± 3.3 %, non-VR intervention: 0.9 ± 3.0 %) and showed no statistically significant difference between the groups ( p = 0.35). Scores of DEBQ, BSQ, and MAIA showed over time no statistically significant changes neither between the two groups nor within the groups (all p ≥ 0.05). The overall satisfaction of the VR group with the two virtual body image exercises was high (4.1 ± 0.8 on a 5-point Likert scale).
Conclusions: The intervention with the developed VR system was feasible and the virtual and traditional body image exercises resulted in statistically non-significant weight loss. It seems that single focus on body image is not successful in improving eating behavior and body perception in people with obesity. Long-term human intervention studies with larger sample sizes are necessary to examine the efficacy of integrating this kind of VR system into standard obesity therapy
Biokunststoffe als Nachhaltigkeitsversprechen
No full textBiokunststoffe haben sich als ein Hoffnungsträger für nachhaltige Alternativen zu herkömmlichen, erdölbasierten Kunststoffen etabliert. Biokunststoffe geben ein Nachhaltigkeitsversprechen, die Probleme von Kunststoffen – Abfallbelastung, Emissionen sowie Erdölabhängigkeit – technisch zu lösen. Das macht sie zu einem technological fix, der für schwierige Herausforderungen relativ einfache technische Lösungen empfiehlt, dabei jedoch die komplexe Wirklichkeit außer Acht zu lassen droht. Der Beitrag zeigt empirisch, dass die Enttäuschungen der Biokunststoffe nicht nur technische Ursachen haben, sondern auch aus vernachlässigten gesellschaftlichen, sozialen, ökonomischen oder ökologischen Faktoren resultieren. Diese reichen von materiellen Eigenschaften der frühen Biokunststoffe, Monokulturen und Flächenkonkurrenz nachwachsender Rohstoffnutzung bis zu ihrer ökonomischenWettbewerbsfähigkeit. Aus technischem Nachhaltigkeitsversprechen und enttäuschten Erwartungen der Biokunststoffe wird deutlich: Ein technological fix scheitert, denn er ist an die Pfadabhängigkeiten fossiler Kunststoffe gebunden. Ohne soziale Innovationen der gesellschaftlichen Kunststoffnutzung sind diese Pfade kaum zu verlassen.Bioplastics have emerged as a beacon of hope for sustainable alternatives to conventional, petroleum-based plastics. They promise sustainability by technically addressing the issues associated with plastics – waste burden, emissions, and dependence on oil. This makes them a »technological fix,« recommending simple technical solutions to complex challenges but overlooking the intricate reality. The article empirically demonstrates that the disappointments with bioplastics are not solely due to technical reasons but stem from neglected societal, social, economic, or ecological factors. These factors range from the material properties of early bioplastics, monocultures and land competition for the use of renewable resources, to their economic competitiveness. From the technological promise of sustainability and the dashed hopes for bioplastics, it becomes clear: The technological fix fails because it is tied to the path dependencies of fossil plastics. Without social innovations in societal use of plastics, these paths can hardly be left
Evaluating Material Parameter Influence on Drapability Using VStitcher †
No full textThe goal of 3D simulation in the apparel industry is highly relevant in terms of sustainability, as the realistic visualization of textile drape and the drapability of textile surfaces plays a crucial role in reducing textile waste and optimizing resource use. It is a matter not only of generating photo-realistic images in 3D garment simulations, but also of making reliable predictions about the physical behavior of textile materials in order to achieve realistic outcomes. The prerequisite for 3D garment simulation is the correct application of standardized simulation programs, which is rarely accomplished in practice because the providers of 3D simulation software do not disclose their simulation algorithms, making accurate analysis difficult. In this study, an objective image comparison is carried out using the VStitcher simulation program as an example, which allows an assessment of the value of the relevant material parameters. A drape test is used as a validation method and the drape coefficient is calculated. Depending on the material and parameter settings, drape coefficients between 0.1 and 10% and between 0.7 and 70% are determined. By modifying the bending stiffness, the drape coefficient increases the most. By systematically varying and comparing these parameters, a deeper understanding of their influence can be obtained. The most significant effect on the drape coefficient (DC) is seen with increased bending stiffness, while changes in thickness, elongation, and shear stiffness have a minimal effect. Increased fabric thickness has a greater effect on appearance than on deformation. The digital parameters affect the simulation in much the same way as the physical textile parameters affect the real material. With VStitcher, the desired fabric changes are more effectively achieved by adjusting the bending stiffness and mass per area, while changes in thickness, elongation, and shear stiffness have little effect
The System Admin's Perspective: A Discussion on AI in Education with LMS Admins
No full textMany higher education institutions (HEIs) are implementing or reviewing the implementation of predictive Learning Analytics to improve learning processes, identify students at risk or provide personalized learning paths. The responsibility for selecting, reviewing, implementing and supporting those systems falls on system administrators, an under-researched stakeholder group of Artificial Intelligence in higher education. In this paper, we summarize qualitative insights from a workshop with system administrators in German HEIs. We find that the system administrators are highly aware not only of system requirements but also of the needs of various shareholder groups such as institutional leadership, learners and educators and that they put high emphasis on ethical, transparent and compliant system use. We conclude that system administrators should be involved more in research on the use of technology in education and that AI systems used in education need to provide possibilities to sufficiently test the system, including anonymous yet realistic test scenarios and data
Electrospinning Poly(acrylonitrile) (PAN) Nanofiber Mats with Mushroom Mycelium Powder
No full textElectrospinning is a technique to produce nanofiber mats for diverse applications. In biomedicine in particular, the addition of an antibacterial agent can be advantageous. Here, we report on the needleless electrospinning of nanofiber mats using poly(acrylonitrile) (PAN) blended with different mushroom mycelium powders, which have antibacterial and other functional properties. While PAN blended with Pleurotus ostreatus (oyster mushroom) powder could be electrospun well, PAN blended with Ganoderma lucidum (reishi mushroom) powder was nearly impossible to spin. The PAN/ P. ostreatus nanofiber mats showed a morphology after electrospinning similiar to pure PAN; however, the carbon yield was lower. This indicates the possibility of embedding P. ostreatus powder in PAN nanofiber mats for biotechnological or biomedical applications
Using N-Version Architectures for Railway Segmentation with Deep Neural Networks
No full textAutonomous trains require reliable and accurate environmental perception to take over safety-critical tasks from the driver. This paper investigates the application of N-version architectures to rail track detection using Deep Neural Networks (DNNs) as a means to improve the safety of machine learning (ML)-enabled perception systems. We combine three different neural network architectures (WCID, VGG16-UNet, MobileNet–SegNet) in a 3M1I configuration. In this configuration, we apply two fusion methods to increase accuracy and to enable error detection: Maximum Confidence Voting (MCV), combining the DNN predictions at the image level, and Pixel Majority Voting (PMV), a novel approach for combining the predictions at the pixel level. In addition, we implement a new method for evaluating and combining prediction confidence values in the N-version architecture during runtime. We adjust the overall prediction confidence according to the conformity of all individual predictions, which is not possible with an individual network. Our results show that the N-version architecture not only enables a detection of erroneous predictions by utilizing those adjusted confidence values, but it can also partially improve the predictions by using the PMV combination algorithm. This work emphasizes the importance of model diversity and appropriate thresholds for an accurate assessment of prediction safety. These approaches can significantly improve the practical applicability of ML-based systems in safety-critical domains such as rail transportation
Vergleich zugelassener Verfahren zur Bewertung der Tages-lichtverfügbarkeit gemäß den Zertifizierungsanforderungen der DGNB: Eine Untersuchung von Berechnungs-, Mess- und Simulationsverfahren
No full textDie Verfügbarkeit von Tageslicht ist ein entscheidender Faktor bei der Bewertung der Gebäudequalität und Nachhaltigkeit gemäß den Kriterien der Deutschen Gesellschaft für Nachhaltiges Bauen (DGNB). Die Bewertung der Tageslichtverfügbarkeit kann dabei durch Berechnungen, Simulationen und Messungen erfolgen, die sich teilweise auf un-terschiedliche normative Grundlagen stützen. Ziel dieser Arbeit ist es, diese Verfahren systematisch miteinander zu vergleichen und ihre Eignung im Kontext der DGNB-Zerti-fizierungsanforderungen zu analysieren. Ein zentraler Schwerpunkt der Untersuchung liegt darauf, zu bewerten, ob und in wel-chem Umfang mögliche Abweichungen in den Ergebnissen der verschiedenen Verfah-ren die Bewertung des Indikators und damit den Zertifizierungsprozess beeinflussen können. Zur Klärung dieser Fragestellung werden insgesamt 15 Räume anhand von vier unter-schiedlichen Untersuchungsvarianten analysiert. Die Analyse umfasst eine Betrachtung sowohl der theoretischen Grundlagen als auch der praktischen Anwendung der Verfah-ren, wobei besonderes Augenmerk auf die Genauigkeit und Vergleichbarkeit der Ergeb-nisse gelegt wird.The availability of daylight is a decisive factor in the assessment of building quality and sustainability in accordance with the criteria of the „Deutsche Gesellschaft für nachhalti-ges Bauen“ (DGNB). Daylight availability can be assessed using calculations, simulati-ons and measurements, some of which are based on different normative principles. The aim of this work is to compare these methods systematically and to analyze their suita-bility in the context of the DGNB certification requirements. A central focus of the study is to evaluate whether and to what extent possible deviations in the results of the different procedures can influence the evaluation of the indicator and thus the certification process. To clarify this question, a total of 15 rooms are analyzed on the basis of four different examination variants. The analysis includes a consideration of both the theoretical prin-ciples and the practical application of the procedures, with particular attention being paid to the accuracy and comparability of the results