Publikationen an der Fakultät für Mathematik und Naturwissenschaften ab 2019

Anzahl der Treffer: 873
Erstellt: Thu, 28 Mar 2024 23:08:02 +0100 in 0.0731 sec


De Santis, Marianna; Eichfelder, Gabriele
A decision space algorithm for multiobjective convex quadratic integer optimization. - In: Computers & operations research, ISSN 0305-0548, Bd. 134 (2021), 105396, S. 1-13

We present a branch-and-bound algorithm for minimizing multiple convex quadratic objective functions over integer variables. Our method looks for efficient points by fixing subsets of variables to integer values and by using lower bounds in the form of hyperplanes in the image space derived from the continuous relaxations of the restricted objective functions. We show that the algorithm stops after finitely many fixings of variables with detecting both the full efficient and the nondominated set of multiobjective strictly convex quadratic integer problems. A major advantage of the approach is that the expensive calculations are done in a preprocessing phase so that the nodes in the branch-and-bound tree can be enumerated fast. We show numerical experiments on biobjective instances and on instances with three and four objectives.



https://doi.org/10.1016/j.cor.2021.105396
Fabrici, Igor; Harant, Jochen; Mohr, Samuel; Schmidt, Jens M.
Circumference of essentially 4-connected planar triangulations. - In: Journal of graph algorithms and applications, ISSN 1526-1719, Bd. 25 (2021), 1, S. 121-132
Sonstige Körperschaft: Technische Universität Hamburg

http://nbn-resolving.de/urn:nbn:de:gbv:830-882.0120423
Nasori, Nasori; Cao, Dawei; Wang, Zhijie; Farahdina, Ulya; Rubiyanto, Agus; Lei, Yong
Tunning of templated CuWO4 nanorods arrays thickness to improve photoanode water splitting. - In: Molecules, ISSN 1420-3049, Bd. 26 (2021), 10, 2900, insges. 14 S.
Im Titel ist "4" tiefgestellt

The fabrication of the photoanode of the n-type CuWO4 nanorod arrays was successfully carried out through electrochemical deposition using anodic aluminum oxide (AAO) control templates and for the first time produced distinct gaps between the nanorod arrays. The effectiveness and efficiency of the resulting deposition was shown by the performance of the photoelectrochemical (PEC) procedure with a current density of 1.02 mA cm^-2 with irradiation using standard AM 1.5G solar simulator and electron changed radiation of 0.72% with a bias potential of 0.71 V (vs. Ag/AgCl). The gap between each nanorod indicated an optimization of the electrolyte penetration on the interface, which resulted in the expansion of the current density as much as 0.5 × 1024 cm^-3 with a flat band potential of 0.14 V vs. Ag/AgCl and also a peak quantum efficiency of wavelength 410 nm. Thus, also indicating the gaps between the nanorod arrays is a promising structure to optimize the performance of the PEC water splitting procedure as a sustainable energy source.



https://doi.org/10.3390/molecules26102900
Chang, Shilei; Hou, Minjie; Xu, Bowen; Liang, Feng; Qiu, Xuechao; Yao, Yaochun; Qu, Tao; Ma, Wenhui; Yang, Bing; Dai, Yongnian; Chen, Kunfeng; Xue, Dongfeng; Zhao, Huaping; Lin, Xiaoting; Poon, Fanny; Lei, Yong; Sun, Xueliang
High-performance quasi-solid-state Na-air battery via gel cathode by confining moisture. - In: Advanced functional materials, ISSN 1616-3028, Bd. 31 (2021), 22, 2011151, insges. 9 S.

https://doi.org/10.1002/adfm.202011151
Chen, Liangzhi; Hotz, Thomas; Zhang, Haizhang
Admissible kernels for RKHS embedding of probability distributions. - In: Statistical papers, ISSN 1613-9798, Bd. 62 (2021), 3, S. 1499-1518

Similarity measurement of two probability distributions is important in many applications of statistics. Embedding such distributions into a reproducing kernel Hilbert space (RKHS) has many favorable properties. The choice of the reproducing kernel is crucial in the approach. We study this question by considering the similarity of two distributions of the same class. In particular, we investigate when the RKHS embedding is "admissible" in the sense that the distance between the embeddings should become smaller when the expectations are getting closer or when the variance is increasing to infinity. We give conditions on the widely-used translation-invariant reproducing kernels to be admissible. We also extend the study to multivariate non-symmetric Gaussian distributions.



https://doi.org/10.1007/s00362-019-01144-5
Nozdrenko, Dmytro; Abramchuk, Olga; Prylutska, Svitlana; Vygovska, Oksana; Soroca, Vasil; Bogutska, Kateryna; Khrapatyi, Sergii; Prylutskyy, Yuriy; Scharff, Peter; Ritter, Uwe
Analysis of biomechanical parameters of muscle soleus contraction and blood biochemical parameters in rat with chronic glyphosate intoxication and therapeutic use of C60 fullerene. - In: International journal of molecular sciences, ISSN 1422-0067, Bd. 22 (2021), 9, 4977, S. 1-11

https://doi.org/10.3390/ijms22094977
Wang, Shouzhi; Zhao, Huaping; Lv, Songyang; Jiang, Hehe; Shao, Yongliang; Wu, Yongzhong; Hao, Xiaopeng; Lei, Yong
Insight into nickel-cobalt oxysulfide nanowires as advanced anode for sodium-ion capacitors. - In: Advanced energy materials, ISSN 1614-6840, Bd. 11 (2021), 18, 2100408, insges. 9 S.

Transition metal oxides have a great potential in sodium-ion capacitors (SICs) due to their pronouncedly higher capacity and low cost. However, their poor conductivity and fragile structure hinder their development. Herein, core-shell-like nickel-cobalt oxysulfide (NCOS) nanowires are synthesized and demonstrated as an advanced SICs anode. The bimetallic oxysulfide with multiple cation valence can promote the sodium ion adsorption and redox reaction, massive defects enable accommodation of the volume change in the sodiation/desodiation process, meanwhile the core-shell-like structure provides abundant channels for fast transfer of sodium ions, thereby synergistically making the NCOS electrode exhibit a high reversible sodium ion storage capacity (1468.5 mAh g^-1 at 0.1 A g^-1) and an excellent cyclability (90.5% capacity retention after 1000 cycles). The in-situ X-ray diffraction analysis unravels the insertion and conversion mechanism for sodium storage in NCOS, and the enhanced capability of NCOS is further verified by the kinetic analysis and theoretical calculations. Finally, SICs consisting of the NCOS anode and a boron-nitrogen co-doped carbon nanotubes cathode deliver an energy density of 205.7 Wh kg^-1, a power density of 22.5 kW kg^-1, and an outstanding cycling lifespan. These results indicate an efficient strategy in designing a high-performance anode for sodium storage based on bimetallic dianion compounds.



https://doi.org/10.1002/aenm.202100408
Gizatullin, Bulat; Mattea, Carlos; Stapf, Siegfried
Molecular dynamics in ionic liquid/radical systems. - In: The journal of physical chemistry, ISSN 1520-5207, Bd. 125 (2021), 18, S. 4850-4862

Molecular dynamics of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (Emim-Tf2N) with either of the four organic stable radicals, TEMPO, 4-benzoyloxy-TEMPO, BDPA, and DPPH, is studied by using Nuclear Magnetic Resonance (NMR) and Dynamic Nuclear Polarization (DNP). In complex fluids at ambient temperature, NMR signal enhancement by DNP is frequently obtained by a combination of several mechanisms, where the Overhauser effect and solid effect are the most common. Understanding the interactions of free radicals with ionic liquid molecules is of particular significance due to their complex dynamics in these systems, influencing the properties of the ion-radical interaction. A combined analysis of EPR, DNP, and NMR relaxation dispersion is carried out for cations and anions containing, respectively, the NMR active nuclei 1H or 19F. Depending on the size and the chemical properties of the radical, different interaction processes are distinguished, namely, the Overhauser effect and solid effect, driven by dominating dipolar or scalar interactions. The resulting NMR relaxation dispersion is decomposed into rotational and translational contributions, allowing the identification of the corresponding correlation times of motion and interactions. The influence of electron relaxation time and electron-nuclear spin hyperfine coupling is discussed.



https://doi.org/10.1021/acs.jpcb.1c02118
Knauer, Andrea; Kuhfuss, Danja; Köhler, Michael
Electrostatic control of Au nanorod formation in automated microsegmented flow synthesis. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 4 (2021), 2, S. 1411-1419

An automated flow rate program was applied for the synthesis of gold nanorods of different aspect ratios dependent on a two-dimensional concentration space of reducing agent and additional silver ions. It was found a regular redshift of the spectral position of the electromagnetic in-axis resonance of metal nanorods with decreasing concentration of reducing agent and increasing concentration of silver ions. The increase of resonance wavelength is strongly correlated with the aspect ratio of the formed nanorods. The experimental results agree with an electrostatic model of self-polarization due to positive excess charge of the nanorods in the presence of CTAB and confirm the crucial role of electrostatic control in the formation of nonspherical and composed nanoparticles in general.



https://doi.org/10.1021/acsanm.0c02941
Wu, Yuhan; Zhang, Chenglin; Zhao, Huaping; Lei, Yong
Recent advances in ferromagnetic metal sulfides and selenides as anodes for sodium- and potassium-ion batteries. - In: Journal of materials chemistry, ISSN 2050-7496, Bd. 9 (2021), 15, S. 9506-9534

In next-generation rechargeable batteries, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as attractive alternatives to lithium-ion batteries due to their cost competitiveness. Anodes with complicated electrochemical mechanisms determine the performance and safety of battery systems to a large degree. Among a wide range of anode materials for SIBs and PIBs, ferromagnetic metal (Fe, Co, and Ni) sulfides and selenides have captured prominent attention by virtue of their high theoretical capacities, suitable potentials, and relatively low price. Although some breakthrough results have been achieved, a few intrinsic issues stemming from the materials themselves need to be further explored and studied, especially in the field of PIBs, an emerging research interest. Herein, in this review, we highlight the pioneering investigation of typical ferromagnetic metal sulfides and selenides for application as anodes in SIBs and PIBs and overview their recent research progress. Meanwhile, the preparation methods, structural characteristics, charge storage mechanisms, and electrochemical properties are outlined. Finally, the present challenges and research perspectives are discussed.



https://doi.org/10.1039/D1TA00831E