Wiss. Zeitschriftenartikel reviewed: Listung in Master Journal List
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Effective building energy efficiency requires understanding fenestration’s role in regulating indoor temperatures. Therefore, this study investigates the impact of integrating static glazing with dynamic coatings on building energy efficiency and indoor comfort in a lightweight structure situated in a semi-arid climate. Employing a comprehensive numerical model developed using EnergyPlus and Radiance tools, various static commercial glass window configurations are evaluated to assess their effects on energy consumption, thermal and visual comfort, and economic and environmental considerations. This analysis includes assessments of thermal comfort using PMV and PPD indicators and evaluations of visual comfort based on daylighting and glare metrics. The findings highlight the advantages of incorporating thermochromic and electrochromic films, demonstrating significant improvements in building energy efficiency and interior thermal and visual comfort. Notably, double glazing emerges as the most economically efficient and environmentally viable option, resulting in a reduction of emissions by 1522.38 kgCO2/year, with a payback period of 12.86 years. Furthermore, combining thermochromic and electrochromic coatings with optimal static glazing leads to a remarkable 26 % reduction in energy consumption. These results underscore the potential of dynamic coatings to enhance building energy performance while ensuring occupant comfort. This research approach provides valuable insights into sustainable building design, emphasizing the integrated impact of glazing solutions on energy use, comfort, and environmental sustainability.
One of the major goals of total knee arthroplasty (TKA) is to restore the physiological function of the knee. In order to select the appropriate TKA design for a specific patient, it would be helpful to understand whether there is an association between passive knee kinematics intraoperatively and during complex activities, such as ascending stairs. Therefore, the primary objective of this study was to compare the anterior–posterior (AP) range of motion during simulated passive flexion and stair ascent at different conditions in the same knees using a six-degrees-of-freedom joint motion simulator, and secondary, to identify whether differences between TKA designs with and without a post-cam mechanism can be detected during both activities, and if one design is superior in recreating the AP translation of the native knee. It was shown that neither TKA design was superior in restoring the mean native AP translation, but that both CR/CS and PS TKA designs may be suitable to restore the individual native kinematic pattern. Moreover, it was shown that passive and complex loading scenarios do not result in exactly the same kinematic pattern, but lead to the same choice of implant design to restore the general kinematic behavior of the native individual knee.
Continuous Biological Ex Situ Methanation of CO2 and H2 in a Novel Inverse Membrane Reactor (IMR)
(2024)
A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor (IMR) allows for the spatial separation of the required reactant gases, hydrogen (H2) and carbon dioxide (CO2), and the degassing area for methane (CH4) output through commercially available ultrafiltration membranes, enabling a reactor design as a closed circuit for continuous methane production. In addition, the Inverse Membrane Reactor (IMR) facilitates the utilization of hydraulic pressure to enhance hydrogen (H2) input. One of the process’s advantages is the potential to utilize both carbon dioxide (CO2) from conventional biogas and CO2-rich industrial waste gas streams. An outstanding result from investigating the IMR revealed that, employing the membrane gassing concept, methane concentrations of over 90 vol.% could be consistently achieved through flexible gas input over a one-year test series. Following startup, only three supplemental nutrient additions were required in addition to hydrogen (H2) and carbon dioxide (CO2), which served as energy and carbon sources, respectively. The maximum achieved methane formation rate specific to membrane area was 87.7 LN of methane per m2 of membrane area per day at a product gas composition of 94 vol.% methane, 2 vol.% H2, and 4 vol.% CO2.
The peak-to-average power ratio (PAPR), commonly used to describe the amplitude variations of an OFDM (orthogonal frequency-division multiplex) signal, does not accurately reflect its impact on the system performance. This paper applies the mutual information as a metric to assess the effects of nonlinear PAPR reduction schemes on the performance of OFDM systems. Evaluation of the achieved mutual information shows that a significant capacity loss from clipping occurs only at high SNR (signal-to-noise ratio) and a simple compression/expansion technique is proposed to achieve close to optimal performance in this regime. The effectiveness of this method is validated through WER (word error rate) simulations with several modulation and coding schemes.
With the expansion of Internet-of-Things (IoT) devices in many aspects of our life, the security of such systems has become an important challenge. Unlike conventional computer systems, any IoT security solution should consider the constraints of these systems such as computational capability, memory, connectivity, and energy consumption limitations. Physical unclonable functions (PUFs) with their special characteristics were introduced as hardware-based solutions to satisfy the security needs while respecting the mentioned constraints. They exploit the uncontrollable and reproducible variations of the underlying components for security applications such as identification, authentication, and secure boot. Since IoT devices are typically low cost, it is important to reuse existing elements in their hardware (for instance, sensors, analog-to-digital converters (ADCs), etc.) instead of adding extra costs for the PUF hardware. Micro-electromechanical system (MEMS) devices are widely used in IoT systems as sensors and actuators. In this work, for the first time, a lightweight MEMS-based circuit with a piezoresistive bridge is introduced as a weak PUF. The piezoresistive PUF leverages the uncontrollable variations in the parameters of the circuit elements to derive secure keys for cryptographic applications. The experimental results show that our proposed piezoresistive PUF is capable of generating enough entropy for a complex key generation, while its responses show stability in different environmental conditions. The manufactured piezoresistive PUF shows a uniqueness of 47.73% and a reliability of 94.19%. Moreover, the generated secret keys passed the National Institute of Standards and Technology (NIST) test suite for randomness.
Unmanned Aerial Vehicle (UAV) swarms have emerged as a promising technology for various applications, such as delivery, surveillance, and infrastructure inspection. An additional feature of deploying large UAV swarms is their use in mobile offloading networking. At the same time, this implies a key challenge in the efficient management of the computational and networking requirements for these offloading processes. This paper aims to fill this gap through a systematic literature review (SLR) analysing the research on distributed task offloading in UAV swarms. We conducted a systematic search of major scientific databases to identify relevant literature published between 2019 and 2023. A total of 63 papers were selected through a multistage screening process and their key contributions. This SLR aims to provide the current state of research on UAV swarm task offloading, including considerations for computation offloading, the role of UAV swarms, different aspects of UAV swarms, the number of UAVs in swarms impacting performance, and open issues. Our review also highlights UAV swarm offloading in various domains and discusses the challenges and limitations that must be addressed to ensure the widespread adoption of this technology. We outline the future research directions and potential applications of UAV swarm offloading, including its integration with other technologies.
4D printing is the next step in additive manufacturing. Magnetoresponsive materials facilitate the creation of gripping tools through 4D printing, allowing for structural changes in response to external stimuli. In this study, the structural change is manifested as motion, triggered by an external magnetic field. This technology offers significant advantages in medical and industrial applications, including the printing of life-like moving organ models for medical training and the development of actuators for use in explosive environments. Magnetoresponsive materials are programmed with a magnetic profile and actuated by an external magnetic field. A compound of strontium ferrite microparticles Sr Fe12 O19 (≤ 20μm) and an elastic polymer (thermoplastic copolyester) with a Hardness of Shore D 40 was produced. A star-shaped body was programmed and actuated by two permanent magnets, each of Br = 1.29 − 1.32T. As there is no analytical approach for calculating the required actuation flux density, one has been developed. The approach is verified experimentally by using a Hall probe. It is appropriate to set the field with a Helmholtz coil, despite the utilization of two permanent magnets. The use of a commercial fused filament fabrication printer for the processing of magnetoresponsive materials has been realized here for the first time. The main contributions are the short time constant (around ta = 0.1s) for actuation and the repeatability (around n = 200 actuation cycles) of the motion. The feasibility of multiple diverse reprogramming is a step forward in 4D printing. Hence, the post-print programming and the inhomogeneity of the field limit the ease of the presented method.
Biochars from chlorine-rich feedstock are low in polychlorinated dioxins, furans and biphenyls
(2024)
Chlorinated aromatic hydrocarbons like polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) and polychlorinated biphenyls (PCB) are omnipresent in the environment due to historic production, use, and (unintended) release. Nowadays, their emission and maximum concentration in environmental compartments is strictly regulated. During biochar production, PCDD/F and PCB may be formed and retained on the solid pyrolysis product. Industrial biochars certified, e.g., under the European Biochar Certificate (EBC), exhibit concentrations that were always well below threshold values for soil application and even animal feed. However, this has not been sufficiently tested for chlorine (Cl) rich organic material such as marine biomass or polyvinyl chloride (PVC) contaminated feedstock. Here, we analyzed PCDD/F and PCB contamination in biochars produced at different temperatures from different biomasses with comparatively high Cl contents in the range from 0.2 % to 3.8 % (w/w, seagrass, two types of saltwater macroalgae, tobacco stalks, and PVC contaminated wood). All of the biochars produced showed PCDD/F and PCB contents well below the applicable threshold values given by the EBC (< 20 ng TEQ kg−1 for PCDD/F and < 2×105 ng kg−1 for PCB). The EBC thresholds were undershot by a minimum of factor 1.5 for PCDD/F (mostly factor 20) and by a minimum of factor 90 for PCB. Between 1 and 27 ppb of feedstock Cl were transformed to Cl bound in PCDD/F and PCB in the biochars. No consistent correlation between biomass Cl contents and contents of PCDD/F and PCB were found but higher Cl contents in the feedstock led to a more diverse PCDD/F congener pattern in the biochars. Pyrolysis of PVC-amended wood resulted in consistently higher contamination of PCDD/F and PCB in the biochars compared to pyrolysis of the other biomasses, potentially due to differences in Cl speciation in the feedstocks i.e., Cl in PVC is already covalently bound to an organic carbon backbone. A high contamination in PCDD/F and PCB in biochar was intentionally triggered by separation of pyrogas and biochar in the reactor at < 300 °C to promote condensation of contaminants on the solid product. Between 20 % and 80 % of feedstock Cl was released via the pyrogas, i.e., neutralization of HCl in burnt pyrogas might be necessary when pyrolyzing Cl-rich feedstock in industrial biochar production. Our results indicate that biochars produced from Cl-rich feedstocks with proper biochar production process control are conform with European certification guidelines for PCDD/F and PCB contamination. The results open the opportunity to exploit and valorize so far non-used marine or otherwise Cl enriched biomasses for the production of biochar and carbon sinks.
The natural polymer chitin is an abundant source for valuable N-acetylchitooligosaccharides and N-acetylglucosamine applicable in several industries. The endochitinase Chit36-TA from Trichoderma asperellum was recombinantly expressed in Komagataella phaffii for the enzymatic degradation of chitin from unused insect exuviae into N-acetylchitooligosaccharides. Chit36-TA was purified by Ni–NTA affinity chromatography and subsequently biochemically characterized. After deglycosylation, the endochitinase had a molecular weight of 36 kDa. The optimum pH for Chit36-TA was 4.5. The temperature maximum of Chit36-TA was determined to be 50 °C, while it maintained > 93% activity up to 60 °C. The chitinase was thermostable up to 45 °C and exhibited ~ 50% activity after a 15 min incubation at 57 °C. Chit36-TA had a maximum specific enzyme activity of 50 nkat/mg with a Km value of 289 µM with 4-methylumbelliferyl-N,N′,N″-triacetyl-β-chitotrioside as substrate. Most tested cations, organic solvents and reagents were well-tolerated by the endochitinase, except for SDS (1 mM), Cu2+ (10 mM) and Mn2+ (10 mM), which had stronger inhibitory effects with residual activities of 3, 41 and 28%, respectively. With a degree of hydrolysis of 32% applying colloidal shrimp chitin (1% (w/v)) and 12% on insect larvae (1% (w/v)) after 24 h, the endochitinase was found to be suitable for the conversion of colloidal chitin as well as chitin from black soldier fly larvae into water-soluble N-acetylchitooligosaccharides. To prove scalability, a bioreactor process was developed in which a 55-fold higher enzyme activity of 49 µkat/l and a tenfold higher protein expression of 1258 mg/l were achieved.
A novel, unsupervised, artificial intelligence system is presented, whose input signals and trainable weights consist of complex or hypercomplex values. The system uses the effect given by the complex multiplication that the multiplicand is not only scaled but also rotated. The more similar an input signal and the reference signal are, the more likely the input signal belongs to the corresponding class. The data assigned to a class during training is stored on a generic layer as well as on a layer extracting special features of the signal. As a result, the same cluster can hold a general description and the details of the signal. This property is vital for assigning a signal to an existing or a new class. To ensure that only valid new classes are opened, the system determines the variances by comparing each input signal component with the weights and adaptively adjusts its activation and threshold functions for an optimal classification decision. The presented system knows at any time all boundaries of its clusters. Experimentally, it is demonstrated that the system is able to cluster the data of multiple classes autonomously, fast, and with high accuracy.