Technische Universität Chemnitz
  • Chemnitz, Saxony, Germany
Recent publications
Background and purpose: Breast cancer can be a significant challenge for those affected. Knowledge of physical function, social-emotional challenges, and perceived cognitive function based on the cancer treatment regimens may help to inform adequate support. Methods: For this prospective observational pilot study, we collected data of seventy-nine women (mean age 54.6 ± 9.5 years) before (T0) and after (T1) initial breast cancer treatment. Functional Assessment of Cancer Therapy-Breast (FACT-B) and Functional Assessment of Cancer Therapy-Cognitive-Function (FACT-Cog) were used to collect data of four treatment subgroups: SCR = Surgery + Chemotherapy + Radiation Therapy; SC = Surgery + Chemotherapy; SR = Surgery + Radiation Therapy; S = Surgery. A mixed ANOVA and posthoc analysis (Tukey, Games-Howell) were used to detect interactions (group by time) and the main effect. A repeated-measures ANOVA displayed individual group differences (time). Results: Significant interaction showed more deterioration was experienced with SC and SCR than SR and S for FACT-B (p < 0.01) and FACT-Cog (p < 0.001). The longitudinal comparison between T0 and T1 indicated a significant group main effect on all subscales (p < 0.001) except for Emotional Well-Being. Significant reductions (p < 0.05) in FACT-B, (- 19%); FACT-Cog, (- 21%) with most pronounced effect in Physical Well-Being (- 30%), Functional Well-Being (- 20%), Breast Cancer Subscale (- 20%), Perceived Cognitive Impairments (- 18%) and Impact of Cognitive Impairments on Quality of Life (- 39%) were detected for SCR. Conclusion: Our study showed that the extent of change in health-related quality of life (HRQoL) and perceived cognitive function (PCF) depends on the treatment regimen. Multidisciplinary support initiated early in breast cancer therapy is needed, especially for women undergoing combined cancer treatment. Routine assessment of patient-reported outcomes (PROs) in oncology practice may increase the transparency of patients' perceived circumstances, leading to personalized and optimized acute and survivorship care.
Leishmaniasis is a group of contagious diseases having high surveillance among dogs. According to World Health Organization (WHO), ninety-two territories were infected around the world in 2018. One billion dogs live in areas endemic for Leishmaniasis and are at risk of infection. Almost one million cases are reported annually. The dog's population is categorized into five classes like susceptible (S), latent (L), infectious (I), uninfected (R), and infected (Q). The Leishmaniasis delayed model is developed to analyze and control its spread. Equilibria, positivity, boundedness, reproduction number, and parameter sensitivity are the model's essential features. The stability of the model is investigated in a local and global sense with the help of the Routh Hurwitz criterion and Lyapunov theory. In the end, simulations are presented to verify the theoretical analysis of the delayed model.
Surgical face masks reduce the spread of airborne pathogens but also disturb the flow of information between individuals. The risk of getting seriously ill after infection with SARS-COV-2 during the present COVID-19 pandemic amplifies with age, suggesting that face masks should be worn especially during face-to-face contact with and between older people. However, the ability to accurately perceive and understand communication signals decreases with age, and it is currently unknown whether face masks impair facial communication more severely in older people. We compared the impact of surgical face masks on dynamic facial emotion recognition in younger (18–30 years) and older (65–85 years) adults (N = 96) in an online study. Participants watched short video clips of young women who facially expressed anger, fear, contempt or sadness. Faces of half of the women were covered by a digitally added surgical face mask. As expected, emotion recognition accuracy declined with age, and face masks reduced emotion recognition accuracy in both younger and older participants. Unexpectedly, the effect of face masks did not differ between age groups. Further analyses showed that masks also reduced the participants’ overall confidence in their emotion judgements, but not their performance awareness (the difference between their confidence ratings for correct and incorrect responses). Again, there were no mask-by-age interactions. Finally, data obtained with a newly developed questionnaire ( attitudes towards face masks, atom ) suggest that younger and older people do not differ in how much they feel impaired in their understanding of other people’s emotions by face masks or how useful they find face masks in confining the COVID-19 pandemic. In sum, these findings do not provide evidence that the impact of face masks on the decoding of facial signals is disproportionally larger in older people.
Although bolts are considered to be a well-established structural element, only general statements on the influence of the different manufacturing processes on the fatigue life are available. Detailed investigations of the in-depth residual stress path and the residual stress stability under cyclic loading have not yet been carried out. A challenge in determining the residual stresses is the complex geometry of the thread and the expected residual stress state with steep gradients close to the surface. This paper examines the influence of the manufacturing process of the main two process types on the residual stress state. The focus lies on the residual stress and material state of high tension bolts (HT) rolled before heat-treatment (RBHT) and rolled after heat-treatment (RAHT) both with hot-dip galvanization (tZn). To get detailed information about in-depth residual stresses, neutron diffraction is used. In addition, the residual stress stability under cyclic loading is examined. For the first time, in-depth residual stress distributions are determined on unloaded and loaded RAHT M 36 and RBHT M 24 bolts, tZn, grade 10.9. The results show that RAHT bolts in the unloaded state have compressive residual stresses below the surface in the thread root in the magnitude of −225 MPa. In the case of RBHT bolts, low residual stresses are present at the surface in the magnitude of −160 MPa. The different progression of the residual stresses is associated with the manufacturing process. Loaded RAHT and RBHT bolts exhibit different stress characteristics. In the loaded state, RAHT bolts have residual compressive stresses on the surface, while RBHT bolts have residual tensile stresses. This may be one reason for the significantly longer fatigue life of RAHT bolts compared to RBHT bolts.
The association between extent of chronic cannabis use (CCU-extent) and cognitive impairment among adolescents has been the subject of controversial debate. Linking DNA methylation to CCU-extent could help to understand cannabis associated changes in cognitive performance. We analyzed cognitive task performances, CpG methylation in peripheral whole-blood samples and self-reported past-year CCU-extent of n = 18 adolescents ( n = 9 psychiatric outpatients with chronic cannabis use (CCU), n = 9 without) who were matched for age, gender and psychiatric disorders. Patients with CCU were at least 24 h abstinent when cognitive tasks were performed. A Principal Component Analysis (PCA) was carried out to identify group differences in whole genome DNA methylation. Mediation analyses were performed between CCU-extent associated CpG sites and CCU-extent associated variables of cognitive tasks. PCA results indicated large differences in whole genome DNA methylation levels between the groups that did not reach statistical significance. Six CpG sites revealed reduced methylation associated with CCU-extent. Furthermore, CCU-extent was associated with lower scores in verbal learning. All six CpG sites mediated the effects between CCU-extent and verbal learning free recall. Our results indicate that CCU is associated with certain patterns in the methylome. Furthermore, CCU-extent associated impairments in memory function are mediated via differential methylation of the six CCU-associated CpG sits. Six identified CpG are located in genes previously described in the context of neurodegeneration, hippocampus-dependent learning and neurogenesis. However, these results have to be carefully interpreted due to a small sample size. Replication studies are warranted.
We report a new pathway for the synthesis of plasmonic gold nanoparticles (Au NPs) in a bio-compatible medium. A modified room temperature approach based on the standard Turkevich synthesis, using sodium citrate as a reducing and stabilizing agent, results in a highly stable colloidal suspension of Au NPs in dimethyl sulfoxide (DMSO). The mean NP size of about 15 nm with a fairly low size distribution is revealed by scanning electron microscopy. The stability test through UV-vis absorption spectroscopy indicates no sign of aggregation for months. The Au NPs are also characterized by X-ray photoelectron, Raman scattering, and FTIR spectroscopies. The stabilisation mechanism of the Au NPs in DMSO is concluded to be similar to that of NPs synthesized in water. The Au NPs obtained in this work are applicable as SERS substrates, as proved by common analytes. In terms of bio-applications, they do not possess such side-effects as pronounced antibacterial activity, based on the tests performed on non-pathogenic Gram-positive or Gram-negative bacteria.
Replicating the mechanical behavior of human bones, especially cancellous bone tissue, is challenging. Typically, conventional bone models primarily consist of polyurethane foam surrounded by a solid shell. Although nearly isotropic foam components have mechanical properties similar to cancellous bone, they do not represent the anisotropy and inhomogeneity of bone architecture. To consider the architecture of bone, models were developed whose core was additively manufactured based on CT data. This core was subsequently coated with glass fiber composite. Specimens consisting of a gyroid-structure were fabricated using fused filament fabrication (FFF) techniques from different materials and various filler levels. Subsequent compression tests showed good accordance between the mechanical behavior of the printed specimens and human bone. The unidirectional fiberglass composite showed higher strength and stiffness than human cortical bone in 3-point bending tests, with comparable material behaviors being observed. During biomechanical investigation of the entire assembly, femoral prosthetic stems were inserted into both artificial and human bones under controlled conditions, while recording occurring forces and strains. All of the artificial prototypes, made of different materials, showed analogous behavior to human bone. In conclusion, it was shown that low-cost FFF technique can be used to generate valid bone models and selectively modify their properties by changing the infill.
Unlike conventional mechanisms, compliant mechanisms produce the desired deformations by exploiting elastic strain. The mobility of a conventional mechanism is the number of independent coordinates needed to define a configuration of the mechanism. The corresponding concept applicable to compliant mechanisms is the so-called pseudo-mobility defined as the number of scalar parameters needed to identify one single desired deformation of a compliant mechanism. In the case of compliant mechanisms with multiple pseudo-mobility, only synthesis approaches for relatively simple mechanisms exist so far, while systems for more complex tasks like shape adaptation are not covered. In addition, only a limited choice of transverse loads are considered in those approaches. In this paper, a novel optimization algorithm is presented that addresses these two shortcomings. This algorithm is based on a two-step iterative procedure in which the load-case dependency of the deformation is minimized and desired deformations are imposed. The algorithm is tested on mechanisms of different complexity. It could be demonstrated that the new procedure is well suited for the synthesis of different types of compliant mechanisms.
With $$\vec {\Delta }_j\ge 0$$ Δ → j ≥ 0 is the uniquely determined self-adjoint realization of the Laplace operator acting on j -forms on a geodesically complete Riemannian manifold M and $$\nabla $$ ∇ the Levi-Civita covariant derivative, we prove among other things a Gaussian heat kernel bound for $$\nabla \mathrm {e}^{ -t\vec {\Delta }_j }$$ ∇ e - t Δ → j , if the curvature tensor of M and its covariant derivative are bounded, an exponentially weighted $$L^p$$ L p -bound for the heat kernel of $$\nabla \mathrm {e}^{ -t\vec {\Delta }_j }$$ ∇ e - t Δ → j , if the curvature tensor of M and its covariant derivative are bounded, that $$\nabla \mathrm {e}^{ -t\vec {\Delta }_j }$$ ∇ e - t Δ → j is bounded in $$L^p$$ L p for all $$1\le p<\infty $$ 1 ≤ p < ∞ , if the curvature tensor of M and its covariant derivative are bounded, a second order Davies-Gaffney estimate (in terms of $$\nabla $$ ∇ and $$\vec {\Delta }_j$$ Δ → j ) for $$\mathrm {e}^{ -t\vec {\Delta }_j }$$ e - t Δ → j for small times, if the j -th degree Bochner-Lichnerowicz potential $$V_j=\vec {\Delta }_j-\nabla ^{\dagger }\nabla $$ V j = Δ → j - ∇ † ∇ of M is bounded from below (where $$V_1=\mathrm {Ric}$$ V 1 = Ric ), which is shown to fail for large time, if $$V_j$$ V j is bounded. Based on these results, we formulate a conjecture on the boundedness of the covariant local Riesz-transform $$\nabla (\vec {\Delta }_j+\kappa )^{-1/2}$$ ∇ ( Δ → j + κ ) - 1 / 2 in $$L^p$$ L p for all $$1\le p<\infty $$ 1 ≤ p < ∞ (which we prove for $$1\le p\le 2$$ 1 ≤ p ≤ 2 ), and explain its implications to geometric analysis, such as the $$L^p$$ L p -Calderón-Zygmund inequality. Our main technical tool is a Bismut derivative formula for $$\nabla \mathrm {e}^{ -t\vec {\Delta }_j }$$ ∇ e - t Δ → j .
Vector Symbolic Architectures combine a high-dimensional vector space with a set of carefully designed operators in order to perform symbolic computations with large numerical vectors. Major goals are the exploitation of their representational power and ability to deal with fuzziness and ambiguity. Over the past years, several VSA implementations have been proposed. The available implementations differ in the underlying vector space and the particular implementations of the VSA operators. This paper provides an overview of eleven available VSA implementations and discusses their commonalities and differences in the underlying vector space and operators. We create a taxonomy of available binding operations and show an important ramification for non self-inverse binding operations using an example from analogical reasoning. A main contribution is the experimental comparison of the available implementations in order to evaluate (1) the capacity of bundles, (2) the approximation quality of non-exact unbinding operations, (3) the influence of combining binding and bundling operations on the query answering performance, and (4) the performance on two example applications: visual place- and language-recognition. We expect this comparison and systematization to be relevant for development of VSAs, and to support the selection of an appropriate VSA for a particular task. The implementations are available.
Fibre metal laminates (FML) are a group of materials consisting of layers of both metals and fibre reinforced composites. In this paper, the authors analyse the behaviour of fibre metal laminates with unusual thermoplastic matrices in composite layers under flexural loading. A three-point bending test is used to determine the flexural behaviour and interlaminar shear stress (ILSS). Two configurations of a specimen are taken into account – with fibre parallel to the specimen (A) and with fibre perpendicular to it (B). Numerical simulations using the finite element method are carried out. A model with cohesive elements is applied to model damage and a model with a continuum shell is used to determine ILSS. Both approaches can be successfully used for specimens group A. This proves that obtained previously material data is proper to use in the analysis of more complicated structures. In the case of group B, other causes than only interface damage need to be included. To investigate this, analysis of the acoustic signals is used to describe phenomenon occurring during bending for group A and B specimens. Conclusions based on AE support the hypothesis based on the optical remarks and results from numerical modelling.
The authors report on the use of a burst-mode ultrashort pulsed laser source with an emitting wavelength of 1030 nm on to micro-machining plane areas of glass with different pulse durations, burst energies, and number of sub-pulses per burst with intra-burst rates of 65 MHz and 2.5 GHz. In the investigated parameter range, the maximum specific removal rates are obtained with 11.2μm3/μJ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$11.2\,\upmu \text{m}^{3}/\upmu \text{J}$$\end{document} for MHz bursts and 27.0μm3/μJ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$27.0\,\upmu \text{m}^{3}/\upmu \text{J}$$\end{document} for GHz bursts, being up to four times higher compared to the non-burst regime. The depth per scan and the surface roughness increase at higher burst energies and at a higher number of sub-pulses per burst, respectively. Furthermore, a significant difference in the resulting surface topography between MHz and GHz bursts is shown by SEM images, mainly depending on the number of sub-pulses per burst.
In previous publications, we showed that the incremental process of the chaotic diffusion of dissipative solitons in a prototypical complex Ginzburg-Landau equation, known, e.g., from nonlinear optics, is governed by a simple Markov process leading to an Anti-Persistent Random Walk of motion or by a more complex Hidden Markov Model with continuous output densities. In this article, we reveal the transition between these two models by examining the dependence of the soliton dynamics on the main bifurcation parameter of the cubic-quintic Ginzburg-Landau equation, and by identifying the underlying hidden Markov processes. These models capture the non-trivial decay of correlations in jump widths and sequences of symbols representing the symbolic dynamics of short and long jumps, the statistics of anti-persistent walk episodes, and the multimodal density of the jump widths. We demonstrate that there exists a physically meaningful reduction of the dynamics of an infinite-dimensional deterministic system to one of a probabilistic finite state machine and provide a deeper understanding of the soliton dynamics under parameter variation of the underlying nonlinear dynamics.
The tilt of semiconductor dies is a common issue during assembly in power electronics as, e.g. die bonding during silver sintering caused by inhomogeneous thicknesses of applied die-attach material, problems with a homogeneous force application, uneven substrates etc. This tilt usually leads to reliability problems later during testing or operation in the field. A weakly sintered layer will be formed with voids larger than 1–2 μm in major numbers and more importantly will lead to insignificantly developed interfaces. None of them can be detected by SoA failure analytical techniques like scanning acoustic microscopy (SAM) or pulsed infrared thermography (PIRT), since both will still provide a sufficient phonon coupling, indistinguishable to well sintered layers. However, the undetected weak interfaces will lead to severe reliability problems and can only be detected indirectly by thickness measurement without a cross section. In this work, we present a scanning system based on confocal polychromatic distance sensors, which can scan a fully loaded tray of bonded dies on the substrate for industry-grade inline integration. We demonstrate the novel system on different bonded power dies on active metal braze substrate (AMB) under industrial production conditions. We achieve this in the required accuracy of about 2–3 μm in an environment with strong vibration influence. The in-line capability has been proven by using a setup, which is independent of mechanical vibrations and uses only optical fibers to transfer measuring signals within future smart production environments.
Participatory Design means recognizing that those who will be affected by a future technology should have an active say in its creation. Yet, despite continuous interest in involving people as future users and consumers into designing novel and innovative future technology, participatory approaches in technology design remain relatively underdeveloped in the German HCI community. This article brings together the diversity of voices, domains, perspectives, approaches, and methods that collectively shape Participatory Design in Germany. In the following, we (1) outline our understanding of participatory practice and how it is different from mere user involvement; (2) reflect current issues of participatory and fair technology design within the German Participatory Design community; and (3) discuss tensions relevant to the field, that we expect to arise in the future, and which we derived from our 2021 workshop through a speculative method. We contribute an introduction and an overview of current themes and a speculative outlook on future issues of Participatory Design in Germany. It is meant to inform, provoke, inspire and, ultimately, invite participation within the wider Computer Science community.
The authors present results of ablation on silicon with ultrafast laser radiation featuring burst pulses using an amplified burst-mode solid-state laser, featuring an emitting wavelength of 1030 nm to generate single burst cavities on silicon. Laser parameter are varied for different pulse durations from 270 fs up to 10 ps, burst fluences, and number of sub-pulses per burst in the respective burst regime with sub-pulse repetition rates of 65 MHz and 5 GHz. The resulting ablated volume per burst and per sub-pulse in a burst as well as the topography are investigated and discussed.
A fundamental equation of state is presented for 1-hexene. It is explicit in the reduced Helmholtz energy and depends on the independent variables temperature and density. It is valid in the fluid region at temperatures from the triple–point temperature Ttr = 133.39 K to Tmax = 535 K with a maximum pressure of pmax = 245 MPa. All thermodynamic properties can be determined from the Helmholtz energy and its derivatives with respect to temperature and density. The equation of state is validated by comparison with experimental data, along with an assessment of correct physical and extrapolation behavior. The available data base is further extended by measurements of the homogeneous density with a vibrating-tube densimeter in the temperature range from 300 K to 362 K and pressures of up to 92 MPa. Speed of sound measurements are conducted with two independent apparatuses at temperatures of 215 K and 500 K and pressures of up to 151 MPa, applying the double-path-length pulse-echo technique.
In this contribution, advanced modeling of thermo-mechanical effects in machine tools with nonlinear machine components is investigated using the example of a feed axis. Strategies of model order reduction for this coupled thermo-mechanical model with nonlinear subsystem are presented. Numerical investigations of the performance of the resulting reduced-order model compared to the original one conclude this article.
Aircraft design must be lightweight and cost-efficient on the condition of aircraft certification. In addition to standard load cases, human-induced loads can occur in the aircraft interior. These are crucial for optimal design but difficult to estimate. In this study, a simple bipedal spring-mass model with roller feet predicted human-induced loads caused by human gait for use within an end-to-end design process. The prediction needed no further experimental data. Gait movement and ground reaction force (GRF) were simulated by means of two parameter constraints with easily estimable input variables (gait speed, body mass, body height). To calibrate and validate the prediction model, experiments were conducted in which 12 test persons walked in an aircraft mock-up under different conditions. Additional statistical regression models helped to compensate for bipedal model limitations. Direct regression models predicted single GRF parameters as a reference without a bipedal model. The parameter constraint with equal gait speed in experiment and simulation yielded good estimates of force maxima (error 5.3%), while equal initial GRF gave a more reliable prediction. Both parameter constraints predicted contact time very well (error 0.9%). Predictions with the bipedal model including full GRF curves were overall as reliable as the reference.
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Carsten Deibel
  • Institute of Physics
Marcel Lichters
  • Faculty of Economics and Business Administration
Stefan Huesig
  • Faculty of Economics and Business Administration
Alexey Shaporin
  • Department of Electrical Engineering and Information Technology
Diana Armbruster
  • Institute of Psychology
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Straße der Nationen 62, 09111, Chemnitz, Saxony, Germany
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http://www.tu-chemnitz.de/