bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly Efficient Ruthenium‐Catalyzed Semi‐hydrogenation of Urea Derivatives to Formamides
Authors: Zhu Jun , Zhang Yue , Wen Zeyu , Ma Qiyi , Wang Yongtao , Yao Jia , Li Haoran
Published: March 2023

The utilization of CO2as a non‐toxic and cheap feedstock for C1 is a desirable route to achieve high value‐added chemicals. In this context, we report a highly efficient ruthenium‐catalyzed semi‐hydrogenation reaction of CO2‐derived ureas. Various alkyl and aryl urea derivatives were successfully hydrogenated to obtain the corresponding recyclable amines and formamides (up to 97 % yield), highlighting the good substrate applicability of this method, which makes this method a sustainable alternative for the hydrogenation of CO2to formamides in the presence of amines. In the meantime, we have discovered a new pathway that enables rapid hydrogenation of urea derivatives even at lower H2pressure (<5 bar). This methodology might provide a new insight into the reduction functionalization of CO2under mild pressure to form new C−N bond. Based on the control experiments and the observed intermediate products, we clarify the mechanism for selective semi‐hydrogenation of ureas.
Lessons from a soybean collection
Authors: Nelson Randall
Published: March 2023

The United States Department of Agriculture (USDA) Soybean Germplasm Collection was established in 1949. Growth of the collection has been uneven throughout its history. Restrictions on germplasm exchanges and collections will likely prevent rapid growth of the collection in the foreseeable future. Because the USDA Soybean Germplasm Collection has limited opportunities to grow and is well evaluated and characterized for both phenotypic and genotypic traits, it is a mature collection. Mature collections will require fewer resources for acquiring, documenting, evaluating, and characterizing accessions which will permit an emphasis on research that will foster increased utilization. Pure lining accessions of self‐pollinated species is superior for maintaining genetic diversity. Genetic drift, natural selection, and sample contamination are problems for mixed seed lots. We document unintended changes for this type of accession. Mixed seed lots also limit meaningful evaluation. Research is a critical part of effective germplasm curation. We report successful research within the USDA Soybean Germplasm Collection that identified exotic accessions that contributed haplotypes that increase the yield of the highest yielding cultivars and are absent from the commercially used gene pool of the northern United States. Crosses with wild soybean produced lines that yielded more than the soybean parent. We developed procedures to produce fertile progenies from crosses between soybean and Glycine tomentella and identified derived lines that exceeded the yield of the soybean parent. Research on accessions within the National Plant Germplasm system is critical if the preserved germplasm is to be used to its fullest potential.
Electrolyte Engineering Stabilizes Photoanodes Decorated with Molecular Catalysts
Authors: Jenewein Ken J. , Wang Yuanxing , Liu Tianying , McDonald Tara , Zlatar Matej , Kulyk Nadiia , Benavente Llorente Victoria , Kormányos Attila , Wang Dunwei , Cherevko Serhiy
Published: March 2023

Invited for this month′s cover is the group of Dunwei Wang from Boston College and Serhiy Cherevko from the Helmholtz Institute Erlangen‐Nürnberg for Renewable Energy. The image illustrates the impact of different electrolyte environments on the stability of hematite decorated with an iridium molecular catalyst used for solar water splitting. The Research Article itself is available at 10.1002/cssc.202202319.
An efficient artificial rabbits optimization‐based user association problems in ultradense network using deep learning model
Authors: M Phemina Selvi , N Shobanadevi
Published: March 2023

The ability of high splitting gain of dense small cells contributed to the rapid establishment of ultradense networks (UDNs). Its higher efficiency to deal with high traffic data demand made UDN a most‐promising technology for the future 5G environment. However, the UDN creates concern about user association, which causes more complexities in providing a high data transmission rate and low latency rate. To tackle these complexities, in this paper, the ambient intelligence exploration multi‐delay deep deterministic policy gradient‐based artificial rabbits optimization (AEMDPG‐ARO) algorithm is proposed for resolving data rate and the issues of latency in the small base station (SBS) and macro base station (MBS) of the wireless sensor network. The complexity in attaining lower latency and higher data rate is achieved through a novel technique AEMDPG‐ARO. The ambient intelligence exploration multi‐delay (AIEM) is combined with deep deterministic policy gradient (DDPG) for overcoming the local optimum and diversity issues of DDPG. The data sample for this study is obtained through the WINNER channel model. The proposed AEMDPG‐ARO algorithm's efficiency is compared to varied state of art methods. The performance evaluation is carried out with regard to network lifetime, end‐to‐end delay, packet delivery ratio, sum rate overall energy consumption, latency, and minimum rate and maximum rate of the network. The proposed AEMDPG‐ARO algorithm gives better performance with reduced time complexity and better metrics rate in the result analysis. The minimum latency achieved by the proposed AEMDPG‐ARO algorithm is about 0.1 s.
Scheduling strategy for networked control system based on variable sampling period and deadband feedback
Authors: Lian Lian
Published: March 2023

A scheduling strategy of variable sampling period combined with deadband feedback for networked control system is proposed. Variable sampling period algorithm can allocate a reasonable sampling period to each controlled loop according to the network utilization and packet transmission time. Deadband feedback algorithm can alleviate network congestion by appropriately adjusting the packets in the network when the networked control system cannot be scheduled. According to the actual overload and utilization of the network, the designed scheduling strategy dynamically adjusts the sampling period and priority, and improves the performance of the system combined with deadband feedback. Based on the TrueTime platform, the proposed scheduling strategy is verified on a three controlled loops networked control system with interference nodes and limited network resources. The simulation results demonstrate that the designed scheduling strategy can overcome the uncertainty of the upper bound of network resources, improve output control performance, reduce integral absolute error value of the controlled loop, and shorten the packet transmission time. The overall control performance of the system is improved. The designed scheduling strategy is effective.
A large‐scale field experiment of artificially caused landslides with replications revealed the response of the ground‐dwelling beetle community to landslides
Authors: Furusawa Jumpei , Makoto Kobayashi , Utsumi Shunsuke
Published: March 2023

Precipitation‐induced landslides, which are predicted to increase under the changing climate, may have large impacts on insect community properties. However, understanding of how insect community properties shift following landslides remains limited because replicated research involving landslides, which are large‐scale disturbances with stochastic natural causes, is difficult. To tackle this issue, we conducted a large‐scale field experiment by artificially causing landslides at multiple sites. We established 12 landslide sites, each 35 m × 35 m, and 6 undisturbed sites in both planted and natural forests and collected ground‐dwelling beetles 1 year later. We found that forest type (i.e., pre‐disturbance vegetation) did not affect the structure of a ground‐dwelling beetle community disturbed by a landslide (landslide community), but the structure of an undisturbed community was affected by forest type. Moreover, the structures of landslide and undisturbed communities were completely different, possibly because landslides create harsh environments that act as an ecological filter. Thus, a niche‐selection process may have a critical role in community assembly at landslide sites. There were no significant differences in species diversity between undisturbed and landslide communities, suggesting that landslides to not reduce species richness overall. However, among‐site variability in species composition was much greater at landslide sites than at undisturbed sites. This result suggests that stochastic colonization predominated at the landslide sites more than undisturbed sites. Synthesis and applications. Overall, our results suggest that both deterministic and stochastic processes are critical in community assembly, at least in the early post‐landslide stage. Our large‐scale manipulative field experiment with replications has thus resulted in new insights into biological community properties after a landslide.
Street‐level bureaucrats as policy entrepreneurs and collaborators: Findings from Israel and Germany
Authors: Lahat Lihi , Klenk Tanja , Pitowsky‐Nave Noga
Published: March 2023

This comparative paper adds to the literature by exploring the connection between policy entrepreneurship and collaboration among street‐level bureaucrats (SLBs) in two countries. We asked if SLBs, as policy entrepreneurs, promote collaborative efforts in their work. If so, in what ways? The study was based on qualitative research and in‐depth semistructured interviews with 20 SLBs in social services in Israel and Germany. Our findings suggest that as policy entrepreneurs, SLBs use diverse ways of working together, and a higher level of policy change demands a higher level of collaboration. We offer three generic types of SLB policy entrepreneurs: collaborative policy entrepreneurs, collaborative‐coordinator policy entrepreneurs, and coordinator‐cooperative entrepreneurs. We suggest administrative cultures and policy styles may shed light on the presence of types of SLB policy entrepreneurs.
Megadroughts Pose Mega-Risk to Native Fishes of the American Southwest
Authors: Gido Keith B , Osborne Megan J , Propst David L , Turner Thomas F , Olden Julian D
Published: March 2023

Climate change and a host of other human stressors on aquatic systems in the American Southwest are rapidly exceeding our ability to conserve native fish diversity. The most severe megadrought in over a millennium has compromised current management plans by exacerbating the impacts of altered hydrology, poor water quality, invasive species, and habitat fragmentation. Drought legacies are of particular concern, and existing conservation actions may not be sufficient to maintain resilient native fish populations, particularly if this drought persists. We draw examples from current literature and empirical research to support our contention that more resources and novel approaches to prioritizing environmental flows, improving ecological connectivity of populations, preventing and controlling invasive species, and establishing refuge populations are necessary to stave off extinctions. Moreover, shifts in socio-political attitudes that better recognize environmental concerns must be integrated into water resource policy and management to achieve native fish conservation goals.
Attitude, awareness, and knowledge of telemedicine among medical students: A systematic review of cross‐sectional studies
Authors: Ghaddaripouri Kosar , Mousavi Baigi Seyyedeh Fatemeh , Abbaszadeh Ali , Mazaheri Habibi Mohammad Reza
Published: March 2023

Background and Aims

The success of every new technology depends on numerous factors, including specialists' knowledge and perceptions of the concept, acquired attitude skills, and work environments. This systematic review aimed to examine medical students' knowledge, attitudes, and perceptions of telemedicine.

Methods

Studies were obtained from the PubMed, Embase, Scopus, and Web of Science databases on June 9, 2022. We followed the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. Cross‐sectional studies that examined medical students' knowledge, attitude, and perceptions of telemedicine approaches were considered inclusion criteria. Titles and abstracts were independently screened based on eligibility criteria. Articles that did not meet the inclusion criteria were excluded from this review. After that, the complete texts were retrieved and screened by two separate researchers based on the eligibility criteria. Disputes were resolved by discussion. The same checklist was used for data extraction. To assess the quality of the studies entering this study, the Joanna Briggs Institute Critical Appraisal Checklist for analytical cross‐sectional studies was used.

Results

In total, 10 eligible articles were found through this review. The sample size of the studies ranged from 60 to 3312 participants, or 6172 participants on the whole. The medical students' attitudes toward telemedicine were evaluated in eight included studies. Many of these studies (seven cases) reported positive and promising perspectives on telemedicine. However, in one study, participants revealed moderate attitudes toward online health information and online health experience sharing (p < 0.05). Students' knowledge of the telemedicine approach was evaluated in eight included studies. Many of these studies (five cases) reported that students possessed an extensively poor knowledge of telemedicine's uses. In three other studies, two reported moderate and one disclosed desirable levels of students' knowledge. All the included studies attributed medical students' poor knowledge to the lack of, and thus failure of, educational courses in this field.

Conclusion

The evidence obtained from this review reveals that medical students possess positive and promising attitudes toward telemedicine technology for education, treatment, and care. However, their knowledge levels were extremely insufficient, and many had not passed any educational courses in this respect. Such results can foreground the health and education policymakers' obligations for planning, training, and empowering digital health and telemedicine literacy among medical students as the primary players in social health.
Evaluation of overweight control applications with cognitive‐behavioral therapy approach: A systematic review
Authors: Ebrahimi Negin , Mohammadzadeh Niloofar , Ayyoubzadeh Seyed Mohammad
Published: March 2023

Background and Aims

Overweight and obesity lead to the development of physical diseases. Cognitive factors play a vital role in controlling one's weight. Currently, cognitive‐behavioral therapy (CBT) interventions are recognized as a subcategory of lifestyle modification programs that can be implemented to control weight and modify eating patterns as well as physical activity. Nowadays, smartphone‐based applications are utilized to implement behavioral interventions. The main purpose of this study is to evaluate the quality of CBT‐based smartphone applications available on Google Play and the App Store in the field of overweight control.

Methods

Smartphone‐based utility applications available on Google Play and App Store were identified in March 2021. Weight control smartphone applications were obtained based on inclusion and exclusion criteria. The app name, platform, version, number of downloads, password protection, affiliations, and features of retrieved apps were tabulated. The Mobile Application Rating Scale was utilized to evaluate the quality of the identified apps.

Results

Seventeen CBT‐based weight control smartphone apps were retrieved. The average engagement, functionality, aesthetics, and information quality scores were 3.65, 3.92, 3.80, and 3.91, respectively. Also, the average score in an aspect containing the usefulness of the app, frequency of using the application, cost, and user satisfaction was 3.5.

Conclusion

Future applications related to this field can be improved by providing a personalization program according to the needs of users and the possibility of online chatting with the therapist. Further improvements can be achieved by improving the areas of engagement, aesthetics, and subjective quality as well as having appropriate privacy policies.
Friction reducing ability of a poly‐l‐lysine and dopamine modified hyaluronan coating for polycaprolactone cartilage resurfacing implants
Authors: Damen A. H. A. , van Donkelaar C. C. , Sharma P. K. , Wan H. , Cardinaels R. , Schmidt T. A. , Ito K.
Published: March 2023

Frictional properties of cartilage resurfacing implants should be sufficiently low to limit damaging of the opposing cartilage during articulation. The present study determines if native lubricious molecule proteoglycan 4 (PRG4) can adsorb onto a layer‐by‐layer bioinspired coating composed of poly‐l‐lysine (PLL) and dopamine modified hyaluronic acid (HADN) and thereby can reduce the friction between implant and articular cartilage. An ELISA was developed to quantify the amount of immobilized human recombinant (rh)PRG4 after exposure to the PLL‐HADN coating. The effect on lubrication was evaluated by comparing the coefficient of friction (CoF) of bare polycaprolactone (PCL) disks to that of PLL‐HADN coated PCL disks while articulated against cartilage using a ring‐on‐disk geometry and a lubricant solution consisting of native synovial fluid components including rhPRG4. The PLL‐HADN coating effectively immobilized rhPRG4. The surface roughness of PCL disks significantly increased while the water contact angle significantly decreased after application of the coating. The average CoF measured during the first minute of bare PCL against cartilage exceeded twice the CoF of the PLL‐HADN coated PCL against cartilage. After 60 min, the CoF reached equilibrium values which were still significantly higher for bare PCL compared to coated PCL. The present study demonstrated that PCL can effectively be coated with PLL‐HADN. Additionally, this coating reduces the friction between PCL and cartilage when a PRG4‐rich lubricant is used, similar to the lubricating surface of native cartilage. This makes PLL‐HADN coating a promising application to improve the clinical success of PCL‐based cartilage resurfacing implants.
Review of the Utility of Extended Recovery Room Observation after Adenotonsillectomy
Authors: Hazkani Inbal , Serino Maeve A. , Thompson Dana M. , Lavin Jennifer
Published: March 2023

Background

Our institution implemented a post‐anesthesia care unit (PACU) extended‐stay model (Grey Zone model), where the post‐operative level of care for high‐risk adenotonsillectomy patients (general care vs. intensive care unit) was decided based on the clinical course of 2–4 h of PACU admission.

Objective

To assess the correlation between post‐tonsillectomy respiratory compromise and the need for respiratory support during an extended stay at PACU. To identify comorbidities associated with a need for intensive care after extended observation.

Methods

A retrospective cohort study of high‐risk children who underwent adenotonsillectomy and were admitted to the Grey Zone following surgery.

Results

274 patients met inclusion criteria. 262 (95.6%) met criteria for general care unit transfer (mean oxygen saturation 94.4 ± 5.1%). Twelve (4.4%) patients were transferred from the PACU to the ICU due to respiratory distress (mean oxygen saturation 86.8 ± 11%). Of the patients admitted to general care, 4 (1.5%) secondarily developed respiratory compromise, requiring escalation of care. Three of these maintained oxygen saturation ≥95% throughout the PACU period. There was no difference between the groups with respect to demographic data, rates of morbid obesity, and severity of obstructive sleep apnea. Neuromuscular disease, chronic lung disease, seizure disorder, and gastrostomy‐tube status were more prevalent in those requiring ICU level of care compared to the general care unit.

Conclusions

The Grey Zone model accurately identifies patients requiring ICU‐level care following adenotonsillectomy, allowing for a safe reduction in the utilization of ICU resources. Due to rare delayed respiratory events, overnight observation in this cohort is recommended.

Level of Evidence

4 Laryngoscope, 133:3582–3587, 2023
The Effect of Chinese Herbal Medicine on Traumatic Anosmia: A Prospective, Randomized Clinical Trial
Authors: Jiang Rong‐San , Yan Karen , Chiang Yi‐Fang , Chiang Pei‐Jung
Published: March 2023

Objective

Chinese herbal medicine (CHM) has been implemented as a form of treatment for olfactory dysfunction. In this study, we aimed to use a tailored Guizhi decoction for the treatment of traumatic olfactory dysfunction.

Methods

Patients who had lost olfactory function after experiencing head trauma and whose olfactory function was anosmic were selected. The eligible patients were randomly assigned to two groups. In the CHM group, a tailored Guizhi decoction was prescribed, with patients also undergoing olfactory training (OT). In the OT group, patients performed OT only. The olfactory function of each patient was evaluated by both the phenyl ethyl alcohol (PEA) odor detection threshold test and the traditional Chinese version of the University of Pennsylvania Smell Identification Test (TC‐UPSIT), at both 3 and 6 months after the completion of treatment.

Results

A total of 38 patients in the CHM group and 40 in the OT group completed the study. The TC‐UPSIT scores of patients slightly rose after treatment in both the CHM and OT groups. Nevertheless, there were no significant differences in TC‐UPSIT scores before and after treatment in both groups. However, the PEA thresholds improved significantly in both CHM and OT groups (p = 0.005 and 0.016, respectively). Of note, there were no significant differences in threshold or identification scores between the CHM and OT groups.

Conclusion

Our results show that adding a tailored Guizhi decoction to OT conferred a limited benefit to the olfactory function of patients experiencing traumatic anosmia.

Level of Evidence

2 Laryngoscope, 133:1473–1479, 2023
Development of new electromagnetic suspension–based high‐speed Maglev vehicles in China: Historical and recent progress in the field of dynamical simulation
Authors: Ding Sansan , Eberhard Peter , Schneider Georg , Schmid Patrick , Kargl Arnim , Cui Yong , Martin Ullrich , Liang Xin , Huang Chao , Bauer Markus , Dignath Florian , Zheng Qinghua
Published: March 2023

High‐speed Maglev is a cutting‐edge technology brought back into the focus of research by plans of the Chinese government for the development of a new 600 km/h Maglev train. A Chinese‐German cooperation with industrial and academic partners has been established to pursue this ambitious goal and bring together experts from multiple disciplines. This contribution presents the joint work and achievements of CRRC Qingdao Sifang, thyssenkrupp Transrapid, CDFEB, and the ITM of the University of Stuttgart, regarding research and development in the field of high‐speed Maglev systems. Furthermore, an overview is given of the historical development of the Transrapid in Germany, the associated development of dynamical simulation models, and recent developments regarding high‐speed Maglev trains in China.
Law schools clearly affirming their missions
Authors: Elfman Lois
Published: March 2023

In early December, the University of Washington School of Law became one of a growing number of U.S. law schools that have decided to end their participation in the U.S. News and World Report rankings process.
An Eulerian time‐stepping scheme for a coupled parabolic moving domain problem using equal‐order unfitted finite elements
Authors: von Wahl Henry , Richter Thomas
Published: March 2023

We consider an unfitted Eulerian time‐stepping scheme for a coupled parabolic model problem on a moving domain. In this model, the domain motion results from an ordinary differential equation coupled to the bulk via the forces acting on the moving interface. We extend our initial work (von Wahl & Richter, 2022) to allow for equal‐order finite element discretisations for the partial differential equation and Lagrange multiplier spaces. Together with the BFD2 time‐stepping scheme, the lowest‐order case of this equal‐order method then results in a fully balanced second‐order scheme in space and time. We show that the equal‐order method has the same stability properties as the method in our initial work.

Numerical results validate this observation.
Structure‐preserving integrators for constrained mechanical systems in the framework of the GGL principle
Authors: Kinon Philipp Lothar , Betsch Peter
Published: March 2023

Simulating multi‐body systems often requires an appropriate treatment of the differential‐algebraic equations (DAEs). The recently proposed GGL principle considers constraints both on configuration and on velocity level and embodies an index‐reduction technique in the spirit of the often‐applied GGL stabilization. In sharp contrast to the original formulation, the Euler‐Lagrange equations of the GGL principle, fit into the Hamiltonian framework of mechanics. Therefore, the GGL principle facilitates the design of structure‐preserving integrators. Due to the close relationship of the GGL principle to optimal control, previously developed direct methods can be used to obtain variational integrators for constrained mechanical systems. Furthermore, slight modifications can be applied to obtain second‐order energy‐momentum consistent integrators emanating from the GGL principle, which represent another important class of structure‐preserving time‐stepping schemes. The newly devised schemes circumvent issues of standard methods and provide more realistic results by accounting for velocity level constraints.
Space‐time phase‐field fracture optimal control computations
Authors: Khimin Denis , C. Steinbach Marc , Wick Thomas
Published: March 2023

In this work, we undertake additional computational performance studies of a recently developed space‐time phase‐field fracture optimal control framework. Therein, the phase‐field forward problem is formulated in a monolithic fashion. The optimal control problem is formulated with the help of the reduced approach in which the state variable is represented with a solution operator applied to the control. To this end, a Newton algorithm in the control variable is formulated for which auxiliary equations must be solved. Two numerical experiments demonstrate the capabilities of our framework.
Phase‐field modeling of crack propagation based on multi‐crack order parameters considering mechanical jump conditions
Authors: Schöller Lukas , Schneider Daniel , Prahs Andreas , Nestler Britta
Published: March 2023

The phase field method is commonly used for the crack propagation modeling in modern material science, as they allow for an implicit tracking of the crack surface. However, most of these crack propagation models are for homogeneous materials, and there exist only a few approaches for heterogeneous systems. Recently, Schöller et al. [1] presented a novel phase‐field model for multiphase materials, e.g. composites, based on multi‐crack crack order parameters. Despite the quantitative advantages of the model, it is based on a simple scheme for the underlying homogenization problem. In this work, a more advanced homogenization scheme based on mechanical jump condition is applied to the model. Consideration of these jump conditions yields phase‐specific stresses and strains. Therefore, the mechanical driving force for crack propagation can be modeled as more independent of the elastic properties of other physical regions. Volume elements of a fiber reinforced polymer are used to demonstrate the limitations of the simple scheme, as well the improvement if considering mechanical jump conditions. Thereby, the contrast in the crack resistance of the two materials is varied. It is shown that the simple linear interpolation does not lead to reasonable crack paths for contrary contrasts of elastic modulus and crack resistance. Taking into account the mechanical jump conditions instead yields still reasonable results. For both the final crack paths and the stress‐strain curves of the system, the novel model is less sensitive to a change in fiber crack resistance. While the result of the simple scheme depend on the selected fiber crack resistance, although failure of the matrix is expected.
A geometrical parameter study of the analytical stress calculation in adhesive joints with thick bonding layers
Authors: Methfessel Thomas S. , Becker Wilfried
Published: March 2023

Strength and failure analyses are critical to the safe and sustainable design of any structure. In the case of adhesively bonded joints, particular attention must be paid to the adhesive layer, which is comparably compliant and subject to high stresses. Determining the stresses in the adhesive layer is essential to identify critical areas in the joint and prevent the formation of cracks. In most applications, bonded joints have thin adhesive layers that can already be accounted for with highly simplified analytical models. However, for the consideration of thicker adhesive layers, advanced models are required that take the adhesive layer into account in more detail.

Therefore, in this work, an analytical model with a higher‐order displacement approach is presented to account for more complex deformation behavior in the adhesive layer. The applied advanced displacement approach is particularly suitable for joints with thicker adhesive layers. In addition, the model enables the calculation of stresses and strains in bonded joints for a wide range of joint configurations and applications. A parameter study is carried out to evaluate the effect of different thicknesses of the adhesive layer and to show the advantages of the current model compared to other existing ones. For verification, all analytical results were compared with corresponding Finite Element Analyses.
Optimizing Color of Particulate Products
Authors: Uihlein Andrian , Pflug Lukas , Stingl Michael
Published: March 2023

Optical properties of nanoparticles largely depend on their shape and material distribution. Given any such property, e.g., a desired color, the aim is to design an optimal nanoparticle, whose properties best match these targets. The corresponding nonlinear optimization problem is challenging due to numerous difficulties: The objective function is given by a multi‐dimensional integral over wavelengths, directions of incoming light rays and nanoparticle design distributions, where the integrand depends on the extinction cross section of the nanoparticle design.

Thus, classical full gradient schemes based on numerical integration prove ineffective due to their tremendous computational cost. On the other hand, known stochastic gradient descent methods cannot deal with the nonlinear fashion in which the design variables enter the objective function. Therefore, we introduce the continuous stochastic gradient (CSG) method, which does not compute a full gradient, but instead uses information from previous iterations in an optimal way to learn the exact gradient during the optimization process. Hence, CSG thematically lies in between a stochastic optimization scheme and a full gradient method, combining both the low computational cost of SG due to very few partial gradient evaluations (small “batch size”) as well as step size rules and line search techniques known from full gradient descent.
Forward coupling approach to model time periodic piezoelectric problems
Authors: Papst Alexander , Toth Florian , Kaltenbacher Manfred
Published: March 2023

Micro electro‐mechanical systems (MEMS), such as piezoelectric loudspeakers are widely used for ultrasound applications. Designing advanced MEMS can be challenging, since nonlinear physical effects may have a significant impact. Piezoelectricity couples the mechanical and electrostatic field directly via the material law, which is often nonlinear and hysteretic. In many applications, only the steady‐state solution is of interest. The nonlinear electrostatic response to periodic forcing can be found directly in the frequency domain with the help of harmonic balancing and an alternating time frequency scheme. For certain problems and boundary conditions it might be sufficient to only assume forward coupling, i.e. one first computes the nonlinear hysteretic electrostatic field and then, use the resulting electric field and polarization to define piezoelectrically induced strains that excite the mechanical system. There are several ways to incorporate the piezoelectrically induced strains into the mechanical system. One way is to use a constant piezoelectric coupling tensor, which is used in Voigt's linear piezoelectric model. We use a phenomenological model for the piezoelectric coupling tensor, linearly scaling the coupling tensor based on the magnitude of the polarization. In this model, we neglect mechanical depolarization under the assumption that the prevailing mechanical stresses are small and a strong applied electric field enforces a certain polarization. The errors made by the forward coupling are estimated and compared with Voigt's linear piezoelectric model, for which direct coupling is used. The result of the forward coupling approach agrees well with the directly coupled results, and it needs less computational effort. Due to the phenomenological model for the piezoelectric coupling tensor, the response of the mechanical system changes and reflects the influence of nonlinear electrostatics.
Development of a simple substitute model to describe the normal force of fluids in narrow gaps
Authors: Bilz Raphael , de Payrebrune Kristin M.
Published: March 2023

Fluids in narrow gaps are employed frequently in many applications. The motivation for their use is diverse and ranges from hydrodynamic lubrication in plain bearings to the transport of hard particles into the working gap for the purpose of machining workpiece surfaces in lapping processes. Depending on the focus of the analysis, it may be useful to investigate the entire pressure field or to calculate only individual quantities. For example, in sophisticated simulations it may be of interest to know the resulting force of a fluid as a function of the external system state in order to describe its damping characteristics. Especially for the simulation of flows in narrow gaps, the Reynolds equation is a convenient choice, which, in contrast to the more general Navier‐Stokes equations, can lead to considerable savings in computational time because no three‐dimensional discretization is required, but only a two‐dimensional discretization. However, if not a highly detailed pressure field is of interest, but only simple relations such as the resulting force as a function of distance and velocity, and if this relation to be evaluated many times for different parameter combinations over a wide range of values, the use of a robust substitute model is a good choice. This article deals with the creation of such a substitute model based on the Reynolds equation taking cavitation into account.
Physically constrained deep recurrent neural network for stiffness computation of plate structures
Authors: Tandale Saurabh Balkrishna , Markert Bernd , Stoffel Marcus
Published: March 2023

In the present study, we introduce two Neural Network (NN) enhanced methods to approximate the local tangent stiffness matrix and the internal force computation for a 2D Finite Element. The proposed model is based on Long‐Short Term Memory (LSTM), which inherently captures the required path‐dependent behavior through its internal parameters. Furthermore, we propose an enhanced training algorithm where an additional loss term corresponding to the derivative of the NN following the Sobolev training procedure is introduced. Such a learning algorithm combines the data‐driven approach with the necessary physical constraint to train the NN. Thus, the present work focuses on introducing the NN at an element level for plate structures taking physical non‐linearities into account. The performance of the proposed methods is demonstrated in an academic example showing a maximum of 90.564% boost in simulation speed.
Simulations of the snap‐through behavior of a fiber reinforced elastomer structure for the design of a simple clamping mechanism
Authors: Schasching Marius M. , Duy Robert , Todt Melanie , Pettermann Heinz E.
Published: March 2023

A glass fiber reinforced elastomer (FRE) sheet is used to design a simple clamping mechanism for prospective engineering applications. The mechanism is based on the phenomena of snap‐through buckling of a segment of a shallow cylindrical shell. It is simply supported at the straight edges and actuated by edge moments. The main objective of such a mechanism is the resulting clamping force, being related to the response of the material under bending. Bending includes compressive stresses, and since the fibers are embedded in a very soft matrix, it is important to understand their contribution to the compressive stiffness of the FRE sheet. For this purpose, numerical simulations by means of the Finite Element Method are performed and a simulation strategy for predicting the clamping force of the mechanism is presented. The clamping forces predicted for FRE composites with and without the contribution of fibers to the compressive stiffness are compared to that of the pure elastomer. The results illustrate the potential of FRE based structures in mechanism‐like applications. If an adequate clamping force is desired, the pure elastomer is not suitable for being used in this kind of clamping mechanism and the fiber reinforcement is necessary. If the fibers contribute to the compressive stiffness, a significantly higher clamping force is predicted. Furthermore, the FRE based structure shows a complex snap‐through deformation pattern, which has to be taken into account in the design of the mechanism and which requires non‐trivial simulation strategies.
Material‐informed training of viscoelastic deep material networks
Authors: Gajek Sebastian , Schneider Matti , Böhlke Thomas
Published: March 2023

Deep material networks (DMN) are a data‐driven homogenization approach that show great promise for accelerating concurrent two‐scale simulations. As a salient feature, DMNs are solely identified by linear elastic precomputations on representative volume elements. After parameter identification, DMNs act as surrogates for full‐field simulations of such volume elements with inelastic constituents.

In this work, we investigate how the training on linear elastic data, i.e., how the choice of the loss function and the sampling of the training data, affects the accuracy of DMNs for inelastic constituents. We investigate linear viscoelasticity and derive a material‐informed sampling procedure for generating the training data and a loss function tailored to the problem at hand. These ideas improve the accuracy of an identified DMN and allow for significantly reducing the number of samples to be generated and labeled.
Hybrid Position‐Compliance Control of Redundantly Actuated Parallel Kinematic Manipulators Equipped with Serial Elastic Actuators
Authors: Kordik Thomas , Gattringer Hubert , Müller Andreas
Published: March 2023

Redundantly actuated parallel kinematic manipulators (RA‐PKM) are ideal candidates in robotic applications combining dynamic performance with high accuracy. Actuation redundancy further allows for modulation of the end‐effector (EE) stiffness. A recent trend in robotics is the use of inherently compliant and elastic components, eventually leading to soft continuum robots, which shall provide tailored solutions for human‐robot collaboration and assistance applications. One way to introduce compliance is to use serial elastic actuators (SEA). This yields two kinematically decoupled dynamic systems, the RA‐PKM mechanism and the actuation system, that are force‐coupled by (passive) elastic elements. The DOF of the actuation system exceeds the DOF of the RA‐PKM according to the degree of actuation redundancy. Due to the kinematic decoupling the RA‐PKM is underactuated. To address this issue, a flatness‐based feedback‐linearizing position control approach along with a stiffness modulation approach is proposed.
Hybrid modeling of viscoelastic and switching–induced heating in ferroelectrics
Authors: Warkentin Andreas , Ricoeur Andreas
Published: March 2023

This contribution focuses on two effects causing a temperature change in electrically loaded ferroelectrics. These materials are often subjected to cyclic loading, where viscoelasticity prevails at lower electric fields, whereas dissipative heating by domain switching dominates above the coercive field. While viscoelasticity is modeled within a phenomenological, rheological framework, the ferroelectric constitutive behaviour is described based on a microphysical model. Merging both approaches results in the hybrid model presented in this paper.
Optimization of the dimensional stability of paper‐based sandwich panels during the pressing process using design of experiments
Authors: Wei Yuting , Hirsch Franz , Süße Dietmar , Lutsch Birgit , Kästner Markus
Published: March 2023

In this contribution, the causes leading to the undesired unevenness on the exterior surface of a paper‐based sandwich structure during the manufacturing process are investigated. This provides insight into the manufacturing parameters that need to be adjusted to reduce this waviness. A finite element model of the pressing process is developed in the commercial software ABAQUS and then used to analyze the formation of the surface unevenness. The sandwich structure adopted in the model consists of a decorative layer, an intermediate layer, a corrugated core and a bottom layer. In particular, the core has a sinusoidal structure with various geometry parameters, which are adjusted in the model to investigate the effect on the waviness of the top surface. The results of the quasi‐static process simulation correlate well with the experimental results. A subsequent parameter study based on the design of experiments (DoE) shows the relationship between the material parameters of the intermediate/bottom layer and the resulting waviness.
Analysis of a phase‐field finite element implementation for precipitation
Authors: Safi Ali Reza , Chafle Rupesh , Klusemann Benjamin
Published: March 2023

Precipitation hardening is an essential mechanism in materials design of age‐hardenable aluminium alloys. The occurrence and distribution of nano‐sized particles in such alloys can lead to superior material properties. During thermo‐mechanical processing, these particles evolve dynamically as function of temperature and applied load. Therefore, sophisticated modelling frameworks are required to study the underlying phenomena of this microstructural evolution in depth. Phase‐field method based on the diffuse interface approach has been successfully employed in literature to study particle nucleation and growth, as well as equilibrium particle shapes. Although phase‐field models provide reliable results due to the flexible adaption of the free energy, the method is computationally expensive, requiring efficient solution schemes. The finite‐element discretization in deal.II can overcome scalability disadvantages and can outperform standard finite‐difference codes. In this work, we used adaptive mesh refinement and adaptive time‐stepping and investigate how AMR and the use of the same stiffness matrix for a certain amount of time steps affect the performance of the phase‐field model. Particle growth simulations are performed to outline the major benefits of the finite element phase‐field model. The numerical strategy is shown to be effective regardless of the initial particle shape by considering different particle morphologies. The results illustrate a significant increase in simulation performance with the applied numerical techniques.
On the numerical homogenization of real polycrystalline microstructures
Authors: Scheunemann Lisa , Schröder Jörg
Published: March 2023

The FE2 method, cf. [1], a direct micro‐macro homogenization approach, has become a standard procedure for scale‐transition applications. Therein, the modeling of a micro‐heterogeneous material described by a representative volume element (RVE) based on realistic microstructures can give rise to a barely unmanageable computational effort. Alternatively, statistically similar RVEs (SSRVEs) can be used, which are constructed based on morphological information of the real microstructure and lead to a reduction of computational cost, see [2]. In their construction, a least‐square functional is used to minimize the deviation of statistical properties, such as volume fraction, spectral density and lineal‐path function, of the SSRVE and the real microstructure. The application of SSRVEs has been shown to lead to an adequate representation of the mechanical behavior of the real microstructure. The first part of the talk will give an overview on the construction of SSRVEs and present examples of multiscale analyses using the FE2 approach with simplified microstructures in different engineering applications of steel material.

The paper also focusses on the details of the microstructure and discusses crystal plasticity models, see e.g. [3], in order to account for the material anisotropy induced by the texture of the crystalline structure of steel. It is well known that for rate independent single crystal plasticity, the ambiguity of the choice of active slip systems and linear dependency of slip criteria may cause instabilities in the algorithm. Classical perturbation methods are often used to solve the problem as well as rate dependent algorithms which model the rate independent case as the limit of vanishing viscosity. However, this leads to stiff constitutive equations and thus requires small time increments. In [4], an alternative approach has been proposed recently which is based on handling the constrained optimization problem in the framework of infeasible primal‐dual interior point methods (IPDIPM). We modify the original constrained optimization problem using slack variables in order to stabilize the algorithm and allow for temporary violation of the constraints. Numerical examples are presented for crystalline structures with face centered cubic properties.
Incorporation of thermal effects into the energy‐momentum consistent elastic model for fiber‐bending stiffness in composites
Authors: Dietzsch Julian , Kalaimani Iniyan , Gross Michael
Published: March 2023

Owing to the wide acceptance of fiber reinforced composites in the lightweight structure industry, the need to study its thermo‐elastic behavior in dynamical multi‐body systems still remains an open question. Standard continuum models, by virtue of first‐order gradient of deformation, cannot capture curvature effects and hence appropriate extensions of the standard modeling techniques are indispensable to model the accurate physical stiffness. The fiber‐bending curvature are captured by introducing a higher‐order gradient of the deformation as an independent field in the standard continuum. This work explores in detail, a further extension of this continuum to understand the thermal effects on the bending stiffness of fiber bundle in fiber‐reinforced composites. Our proposed model incorporates the temperature of the composite and its bidirectional dependency with the higher‐order gradients of the deformation into the extended mechanical continuum model. The implementation of the model is pursued in the context of multi‐field mixed finite element method and dynamic variational principle. The principle of virtual power enables our extended non‐isothermal continuum to derive an energy‐momentum scheme of higher order. The resulting time‐integrator exhibits physically consistent locking‐ free numerical behavior in dynamical simulations. Our novel approach is illustrated by simple transient dynamic simulations with a hyperelastic, transversely isotropic, polyconvex material behavior. We investigate the conservation of total energy and total momentum in the framework of thermo‐elasticity and study the spatial and temporal convergence for long‐term dynamic simulations with coarser grids and increased accurate numerical solutions.