Open Access
Refine
Year of publication
Document Type
- Article (141)
- Conference Proceeding (72)
- Bachelor Thesis (12)
- Master's Thesis (12)
- Report (7)
- Doctoral Thesis (3)
Language
- English (247) (remove)
Keywords
- virtual reality (9)
- Business Process Management Systems (4)
- Fuzzy Logic (4)
- visualization (4)
- Myopia (3)
- Assignment Automation (2)
- Augmented Reality (2)
- Business Process Modeling Notation (2)
- Git (2)
- Studie (2)
Institute
The direct ophthalmoscope is a retinal screening tool that has been in existence and development for more than 150 years, yet, the rapid influence of technological evolution in screening tools, has left the direct ophthalmoscope untouched. The main purpose of this master thesis is to determine if the direct ophthalmoscope has reached its maximum potential of development and, additionally, to determine if a further development, including a more electronic input, would be feasible.
Soft magnetic Fe-Al alloys have been a subject of research in the past. However, they never saw the same reception in technical applications as the Fe-Si or Fe-Ni alloys, which is, to some extent, due to a low ductility level and difficulties in manufacturing. Additive manufacturing (AM) technology could be a way to avoid issues in conventional manufacturing and produce soft magnetic components from these alloys, as has already been shown with similarly brittle Fe-Si alloys. While AM has already been applied to certain Fe-Al alloys, no magnetic properties of AM Fe-Al alloys have been reported in the literature so far. Therefore, in this work, a Fe-12Al alloy was additively manufactured through laser powder bed fusion (L-PBF) and characterized regarding its microstructure and magnetic properties. A comparison was made with the materials produced by casting and rolling, prepared from melts with an identical chemical composition. In order to improve the magnetic properties, a heat treatment at a higher temperature (1300 °C) than typically applied for conventionally manufactured materials (850–1150 °C) is proposed for the AM material. The specially heat-treated AM material reached values (HC: 11.3 A/m; µmax: 13.1 × 103) that were close to the heat-treated cast material (HC: 12.4 A/m; µmax: 20.3 × 103). While the DC magnetic values of hot- and cold-rolled materials (HC: 3.2 to 4.1 A/m; µmax: 36.6 to 40.4 × 103) were not met, the AM material actually showed fewer losses than the rolled material under AC conditions. One explanation for this effect can be domain refinement effects. This study shows that it is possible to additively manufacture Fe-Al alloys with good soft magnetic behavior. With optimized manufacturing and post-processing, further improvements of the magnetic properties of AM L-PBF Fe-12Al may still be possible.
Purpose: The aim is to be able to advise patients on the choice of sports and exercises regarding the effects on the intraocular pressure.
Methods: The search engines Google Scholar and PubMed were used to search for suitable studies. The studies were summarized, and the most important data were collected in one table for each study. The effect on the IOP was extracted or, if not given in the article, calculated by the difference of means of the IOP after or during exercise, and the baseline IOP before, whenever these values were available.
Findings: A total of 47 studies out of the years 1990 to 2020 that investigated the influence on the IOP of the most popular sports actively practiced in Germany were reviewed and summarized: twelve for running, sixteen for fitness/ weight training, one for swimming/diving, twelve for cycling, four for hiking, and two for yoga.
Conclusions: Throughout all studies and sports it was seen that physical fitness stabilized the IOP. Higher
intensity of exercise led to higher fluctuations of the IOP. Moderate endurance training keeps the IOP fluctuations low and may lead to a lower baseline IOP if practiced on a regular base. Fitness and weight training lead to fluctuations of the IOP in a pronounced manner when performed at moderate and high intensity. Therefore, only a moderate training can be recommended if there is need to keep the IOP stable. Isometric exercise is not recommended as it provokes a rise of the IOP even when performed with light loads. The Valsalva Maneuver should always be avoided as it leads to additional fluctuations of the IOP. Also, the IOP behaved more stable during resistance training when higher fitness was present.
Purpose
The purpose of this study was to evaluate the validity of the iPad Aniseikonia Test for
measurement size lens-induced aniseikonia. The iPad Aniseikonia Test is a new
computer-based test designed for measuring aniseikonia in vertical direction. The iPad
Test uses red-green anaglyphs.
Methods
Aniseikonia was induced in 21 subjects by means of afocal size lenses. Resulting
aniseikonia was measured in vertical direction by the iPad Aniseikonia Test. The
measurement was performed in dark condition with appropriate correction of refractive
error. All subject were patients with normal vision with no anisometropia or other
ocular problem.
Results:
Afocal size lenses of known magnification were used to induce aniseikonia. 5
measurements were taken in each subject, ranging from zero to 7 % magnification.
When using the regression analysis, the slope of the fitted line significantly differs from
1. The average slope of regression line is 0,58.
Conclusions:
Only moderate accuracy was found for tested target size and orientation. In all cases the
iPad Aniseikonia Test underestimates the level of aniseikonia. However for gross
assessment of anisometropia in clinical practice it could be successfully used. Further
study with different target size should be addressed.
Purpose: Recent studies found a reduction of myopia progression with multifocal contact lenses, however, with yet unclear mechanism. This raises the hypothesis that the addition zones of the multifocal contact lenses induce myopic defocus on the retina, which consequentially leads to choroidal thickening and therefore inhibited eye growth. We tested the effect of the optical design of multifocal contact lenses on choroidal thickness.
Methods: 18 myopic students wore four different contact lenses ((1) single-vision lens corrected for distance, (2) single-vision lens with +2.50 D full-field defocus, (3) “Multifocal center-distance” design, addition +2.50 D, (4) “Multifocal center-near” design, addition +2.50 D) for each 30 minutes on their right eye. Automated analysis of the macular choroidal thickness, vitreous chamber depth and eccentric photorefraction were performed before and after each contact lens.
Results: Choroidal thickness and vitreous chamber depth showed no significant differences to baseline with none of the contact lenses. Choroidal thickness increased the most with the “Multifocal center-distance” and the full-field defocus lens, followed by the “Multifocal center-near” and the single-vision contact lens (+2.1 ± 11.1 μm, +2.0 ± 11.1 μm, +1.6 ± 11.3 μm, +0.9 ± 11.2 μm, respectively). The “Multifocal center-distance” design showed an overall more myopic refractive profile than the other lenses. Changes of vitreous chamber depth occurred in anti-phase to these of choroidal thickness.
Conclusion: Multifocal contact lenses have no significant influence on choroidal thickness and after short-term wear. Therefore, it is assumed that it is not the main contributor to the protective effect of multifocal contact lenses in myopia control.
The effect of personality and gender on individuals' propensity for corruption and corrupt behavior
(2020)
The Dimensional Accuracy of Thin-Walled Parts Manufactured by Laser-Powder Bed Fusion Process
(2020)
In this study, we investigate the use of artificial neural networks as a potentially efficient method to determine the rate capability of electrodes for lithium-ion batteries with different porosities. The performance of a lithium-ion battery is, to a large extent, determined by the microstructure (i.e., layer thickness and porosity) of its electrodes. Tailoring the microstructure to a specific application is a crucial process in battery development. However, unravelling the complex correlations between microstructure and rate performance using either experiments or simulations is time-consuming and costly. Our approach provides a swift method for predicting the rate capability of battery electrodes by using machine learning on microstructural images of electrode cross-sections. We train multiple models in order to predict the specific capacity based on the batteries’ microstructure and investigate the decisive parts of the microstructure through the use of explainable artificial intelligence (XAI) methods. Our study shows that even comparably small neural network architectures are capable of providing state-of-the-art prediction results. In addition to this, our XAI studies demonstrate that the models are using understandable human features while ignoring present artefacts.
Production processes in Industry 4.0 settings are usually highly automated. However, many complicated tasks, such as machine maintenance, must be executed by human workers. In current smart factories, such tasks can be supported by Augmented Reality (AR) devices. These AR tasks rely on high numbers of contextual factors like live data from machines or work safety conditions and are mostly not well integrated into the global production process. This can lead to various problems like suboptimal task assignment, over-exposure of workers to hazards like noise or heat, or delays in the production process. Current Business Process Management (BPM) Systems (BPMS) are not capable of readily taking such factors into account. There- fore, this contribution proposes a novel approach for context- integrated modeling and execution of processes with AR tasks. Our practical evaluations show that our AR Process Framework can be easily integrated with prevalent BPMS. Furthermore, we have created a comprehensive simulation scenario and our findings suggest that the application of this system can lead to various benefits, like better quality of AR task execution and cost savings regarding the overall Industry 4.0 processes.
Aim Patrick J. Caroline and Mark P. Andre first reported about soft lens orthokeratology in 2005. In a number of articles in the past five years, they reported about their research on this topic and their new findings. The aim of this study was to continue the research of Patrick J. Caroline and Mark P. Andre and to collect more information about the outcome of the technique. Methods Ten subjects with low myopia from -0.25 D to -1.25 D and a refractive astigmatism from plano to -0.75 D were fitted with a -10.00 D CIBA VISION AIR OPTIX® NIGHT&DAY® silicone hydrogel contact lens and were told to wear the lenses over night and everted. Corneal topography and refraction measurements were taken after one night, one week and one month of contact lens wear. Results Eight out of ten subjects finished the study, six female and two male. The mean age of the subjects was 23.9 years. With the eight subjects who finished the study, the mean change in subjective refraction was about +1.00 D in the sphere and +0.22 D in the cylinder, with maximum changes of +1.75 D sphere and +0.75 D cylinder. The mean apical power change, measured with the topographer, was 1.11 D. Changes in K - readings ranged from slight corneal steepening in both of the meridians to 0.23 mm of corneal flattening in the horizontal meridian and 0.27 mm of corneal flattening in the vertical meridian. Corneal eccentricity decreased about 0.65 on average. The main complaints and problems were the high minus power and the decentration of the contact lens and the occurrence of ghosting at night. Conclusion The results of this study show that everted wear of a high minus silicone hydrogel contact lens can lead to orthokeratology - such as changes in corneal topography and subjective refraction. These changes range from plano to +1.75 D sphere and +0.25 D to +0.75 D cylinder but are unpredictable and vary from subject to subject. Additional studies regarding the contact lens decentration and the unpredictability of the outcome need to be done to optimize the process.
Enterprise Architecture (EA) Frameworks (EAFs) have attempted to support comprehensive and cohesive modeling and documentation of the enterprise. However, these EAFs were not conceived for today’s rapidly digitalized enterprises and the associated IT complexity. A digitally-centric EAF is needed, freed from the past restrictive EAF paradigms and embracing the new potential in a data-centric world. This paper proposes an alternative EAF that is digital, holistic, and digitally sustainable - the Digital Diamond Framework. D2F is designed for responsive and agile enterprises, for aligning business plans and initiatives with the actual enterprise state, and addressing the needs of EA for digitized structure, order, modeling, and documentation. The feasibility of D2F is demonstrated with a prototype implementation of an EA tool that applies its principles, showing how the framework can be practically realized, while a case study based on ArchiSurance example and an initial performance and scalability characterization provide additional insights as to its viability.
Relevance and Adoption of AI technologies in German SMEs – Results from Survey-Based Research
(2021)
This research project is of particular importance since there is a lack of adequate data on pediatric eye and vision disorders in Russia, particularly in the Volga region. In the present study, we estimate the prevalence of vision disorders among school-aged children who participated in a vision screening program in Samara, Russia. The relationship between learning-related visual dysfunctions is explored in depth, such to illustrate the connection between vision and learning. Hence, a key feature in this study is the inclusion of binocular vision disorders among the conditions tested.
Preliminary study: Polishing force measurement by viscosity - the return of ketchup polishing
(2021)
Potentials of Digital Business Models – Empirical investigation of data driven impacts in industry
(2018)
Potential Benefits of Enterprise Architecture Management in the Digital Transformation Process
(2020)
Organizational Aspects of Cyber Security in Family Firms – an Empirical Study of German Companies
(2021)
One Single Click is enough – an Empirical Study on Human Threats in Family Firm Cyber Security
(2021)
The over-expression and aggregation of α-synuclein (αSyn) are linked to the onset and pathology of Parkinson's disease. Native monomeric αSyn exists in an intrinsically disordered ensemble of interconverting conformations, which has made its therapeutic targeting by small molecules highly challenging. Nonetheless, here we successfully target the monomeric structural ensemble of αSyn and thereby identify novel drug-like small molecules that impact multiple pathogenic processes. Using a surface plasmon resonance high-throughput screen, in which monomeric αSyn is incubated with microchips arrayed with tethered compounds, we identified novel αSyn interacting drug-like compounds. Because these small molecules could impact a variety of αSyn forms present in the ensemble, we tested representative hits for impact on multiple αSyn malfunctions in vitro and in cells including aggregation and perturbation of vesicular dynamics. We thereby identified a compound that inhibits αSyn misfolding and is neuroprotective, multiple compounds that restore phagocytosis impaired by αSyn overexpression, and a compound blocking cellular transmission of αSyn. Our studies demonstrate that drug-like small molecules that interact with native αSyn can impact a variety of its pathological processes. Thus, targeting the intrinsically disordered ensemble of αSyn offers a unique approach to the development of small molecule research tools and therapeutics for Parkinson's disease.
Purpose
The purpose of this study was to investigate the correlation of measured visual acuity
(VA) both static and dynamic obtained with static and dynamic measuring tests, as well
as, response time to visual stimulus and analysis of its influence on dynamic visual
acuity. The aim was to compare the results gathered for the three age groups and
analyze the possible differences.
Methods
The test groups consisted of 75 subjects between 10 and 60 years old, categorized in
three age groups. The measurements of static and dynamic visual acuity and reaction
time were conducted. The set of nine tests (five with radial magnification speed and four
simulating driving condition at 72 km/h and 130 km/h) was designed in order to measure
dynamic visual acuity and the set of two tests for reaction time measurement.
Results
Compared to static visual acuity in both tests, the results obtained with measurements
of dynamic visual acuity resulted in lower values depending on Landolt ring size and
magnification speed of animation. In average, the dynamic visual acuities in tests with
different magnification speeds were lower than static by 0.4 visual acuity units, or 31%
and the average of dynamic visual acuity after subtracting motoric component (reaction
time) was for 0.2 visual acuity worse than static or 15%. In the second test simulating
driving conditions at 72 km/h the average drop in dynamic visual acuity was 33% while
at 130 km/h average drop for younger and middle age groups was 37% and for older
group was 44% and after subtracting motor component values for 72 km/h speed
simulation average drop in visual acuity values was 23% for all three groups; for 130
km/h speed simulation younger and middle aged group average drop of visual acuity
was 20% and with older group it was 24%.
Conclusion
The tests used in this study were simple and fast and revealed significant difference
between static and dynamic visual acuity and influence of reaction time on dynamic
Nataša Vujko Muždalo Abstract
2
visual acuity values. It is hoped that this thesis will be a positive contribution in testing
and training of dynamic visual and sensory response skill with drivers, sportsmen and
people with visual-motor dysfunction.
Keywords: Dynamic visual acuity (DVA), static visual acuity (SVA), reaction time (RT),
motoric component, dynamic visual acuity test, reaction time test, radial increase in size
Future lunar exploration will be based on in-situ resource utilization (ISRU) techniques. The most abundant raw material on the Moon is lunar regolith, which, however, is very scarce on Earth, making the study of simulants a necessity. The objective of this study is to characterize and investigate the sintering behavior of EAC-1A lunar regolith simulant. The characterization of the simulant included the determination of the phase assemblage, characteristic temperatures determination and water content analysis. The results are discussed in the context of sintering experiments of EAC-1A simulant, which showed that the material can be sintered to a relative density close to 90%, but only within a very narrow range of temperatures (20–30 °C). Sintering experiments were performed for sieved and unsieved, as well as for dried and non-dried specimens of EAC-1A. In addition, an analysis of the densification and mechanical properties of the sintered specimens was done. The sintering experiments at different temperatures showed that the finest fraction of sieved simulant can reach a higher maximum sintering temperature, and consequently a higher densification and biaxial strength. The non-dried powder exhibited higher densification and biaxial strength after sintering compared to the dried specimen. This difference was explained with a higher green density of the non-dried powder during pressing, rather than due to an actual influence on the sintering mechanism. Nevertheless, drying the powder prior to sintering is important to avoid the overestimation of the strength of specimens to be fabricated on the Moon.
Lower bounds on the sum of 25th-powers of univariates lead to complete derandomization of PIT
(2020)
Novel myopia control spectacle lenses induce peripheral contrast reduction via optical diffusion. It is suggested, that the contrast reduction alters retinal processes in the low-level neural circuity, leading to an inhibition of eye growth. The purpose of this thesis is to evaluate the influence of full-field contrast reduction on low-level neural processing of the retina, described by the edge contrast sensitivity.
Leveraging Augmented Reality to Support Context-Aware Tasks in Alignment with Business Processes
(2021)
The seamless inclusion of Augmented Reality (AR) with Business Process Management Systems (BPMSs) for Smart Factory and Industry 4.0 processes remains a challenge. Towards this end, this paper contributes an approach integrating context-aware AR into intelligent business processes to support and guide manufacturing personnel tasks and enable live task assignment optimization and support task execution quality. Our realization extends two BPMSs (Camunda and AristaFlow) and various AR devices. Various AR capabilities are demonstrated via a simulated industrial case study.
Learning for E-Learning
(2020)
Laser melting manufacturing of large elements of lunar regolith simulant for paving on the Moon
(2023)
The next steps for the expansion of the human presence in the solar system will be taken on the Moon. However, due to the low lunar gravity, the suspended dust generated when lunar rovers move across the lunar soil is a significant risk for lunar missions as it can affect the systems of the exploration vehicles. One solution to mitigate this problem is the construction of roads and landing pads on the Moon. In addition, to increase the sustainability of future lunar missions, in-situ resource utilization (ISRU) techniques must be developed. In this paper, the use of concentrated light for paving on the Moon by melting the lunar regolith is investigated. As a substitute of the concentrated sunlight, a high-power CO2 laser is used in the experiments. With this set-up, a maximum laser spot diameter of 100 mm can be achieved, which translates in high thicknesses of the consolidated layers. Furthermore, the lunar regolith simulant EAC-1A is used as a substitute of the actual lunar soil. At the end of the study, large samples (approximately 250 × 250 mm) with interlocking capabilities were fabricated by melting the lunar simulant with the laser directly on the powder bed. Large areas of lunar soil can be covered with these samples and serve as roads and landing pads, decreasing the propagation of lunar dust. These manufactured samples were analysed regarding their mineralogical composition, internal structure and mechanical properties.
Industry 4.0 production comprises complicated highly automated processes. However, human activities are also a crucial component of these processes, e.g., for machine main- tenance. Task assignment of human resources in this domain is challenging, as many factors have to be taken into account to ensure effective and efficient activity execution and satisfy special conditions (like worker safety). To overcome the limita- tions of current Business Process Management (BPM) Systems regarding activity resource assignment, this contribution provides a BPM-integrated approach that applies fuzzy sets for activity assignment. Our findings suggest that this approach can be easily applied to complex production scenarios, while providing efficient performance even with a large number of concurrent activity assignment requests. Additionally, our evaluation shows its potential for improved work distribution which can lead to cost savings in Industry 4.0 production processes.
Integrated laser based pre‐tempering at laser welding of AISI 1045 steel by using 3D‐scanner optics
(2021)
A good stereopsis (depth perception) is needed in everyday life, regardless whether a person is a professional driver or chef. Good estimation of distance, and of what is further and what closer, could mean the difference between a crushed and a whole car or between a bloody and a healthy finger. The main theme of this Master thesis is detect and quantify major factors in depth perception. Do the younger estimate the depth better than the older; do they have better depth perception with greater or smaller pupil distance; does depth perception depend on gender; what happens with stereopsis when vision is fogged by +0,5 and +1,0 D? These are the questions dealt with in this Master thesis.
To answer these questions measurements were made on 51 subjects (mean age 45,0 +/- 13,32 years) of whom 25 were women, mean age 45,5 +/-13,55 years (12 with PD<62 mm, mean and 13 with PD>66 mm) and 26 men, mean age 44,4 +/- 13,34 years (13 with PD<62 mm and, 13 with PD >66 mm). Each of these four groups was further divided by age (one in range 20 to 35 years and second in range 50 to 65 years).
The measurements were made with a few assumptions. The first assumption was that stereopsis is in direct correlation with visual acuity, the second assumption was that persons with bigger interpupillar distance have better stereopsis, and the third assumption was that with age the stereopsis ability decreases.
The measurements were done with modified Frisby–Davis test expanded from four geometrical shapes to twenty-five circles. The stereopsis was measured with full refractive correction at 4,5 and 3,0 meters. Later, stereopsis was measured with fogging with +0,5 and +1,0 D at the 4,5 and 3,0 meter distances.
Statistically there is no correlation (or very weak) between stereopsis and the visual acuity for whole group of 51 test persons, but if only young test persons are taken in consideration, the correlation becomes significant, r(20)=0,566, p=0,009 at 4,5 m and r(20)=0,456, p=0,043 at 3,0 m and that matches the assumption. Stereopsis is in no or weak positive correlation with pupil distance r(51)=0,059, p=0,679, which is in total contrast to the assumption. Stereopsis is in positive correlation with age at 4,5 meters measuring distance, r(51)=0,371, p=0,007, which corresponds to assumption. In addition, stereopsis is better in females than in males by 32,5%.
Based on the results it can be concluded that the stereopsis is in negative correlation with age, in positive correlation with visual acuity, females have better stereopsis than males and statistically, the correlation between stereopsis and pupil distance (PD) has not been proved. The most important conclusion is that the decreased visual acuity brings significant fall of stereopsis. A deficit in refraction of -0,50 D decreases stereo acuity by about 90% (nearly 2x) and a deficit of -1,0 D decreases stereo acuity by about 220% (about 3x).
Keywords: Stereopsis, stereo acuity, depth perception, pupil distance (PD), visual acuity (VA).