TY  - JOUR
A1  - Akimbekov, Nuraly S.
A1  - Digel, Ilya
A1  - Tastambek, Kuanysh T.
A1  - Sherelkhan, Dinara K.
A1  - Jussupova, Dariya B.
A1  - Altynbay, Nazym P.
T1  - Low-rank coal as a source of humic substances for soil amendment and fertility management
JF  - Agriculture
N2  - Humic substances (HS), as important environmental components, are essential to soil health and agricultural sustainability. The usage of low-rank coal (LRC) for energy generation has declined considerably due to the growing popularity of renewable energy sources and gas. However, their potential as soil amendment aimed to maintain soil quality and productivity deserves more recognition. LRC, a highly heterogeneous material in nature, contains large quantities of HS and may effectively help to restore the physicochemical, biological, and ecological functionality of soil. Multiple emerging studies support the view that LRC and its derivatives can positively impact the soil microclimate, nutrient status, and organic matter turnover. Moreover, the phytotoxic effects of some pollutants can be reduced by subsequent LRC application. Broad geographical availability, relatively low cost, and good technical applicability of LRC offer the advantage of easy fulfilling soil amendment and conditioner requirements worldwide. This review analyzes and emphasizes the potential of LRC and its numerous forms/combinations for soil amelioration and crop production. A great benefit would be a systematic investment strategy implicating safe utilization and long-term application of LRC for sustainable agricultural production.
KW  - soil remediation
KW  - crop yield
KW  - soil health
KW  - soil amendment
KW  - low-rank coal
Y1  - 2021
U6  - https://doi.org/10.3390/agriculture11121261
SN  - 2077-0472
N1  - This article belongs to the Special Issue "From Waste to Fertilizer in Sustainable Agriculture"
VL  - 11
IS  - 12
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Kleefeld, Andreas
T1  - The hot spots conjecture can be false: some numerical examples
JF  - Advances in Computational Mathematics
N2  - The hot spots conjecture is only known to be true for special geometries. This paper shows numerically that the hot spots conjecture can fail to be true for easy to construct bounded domains with one hole. The underlying eigenvalue problem for the Laplace equation with Neumann boundary condition is solved with boundary integral equations yielding a non-linear eigenvalue problem. Its discretization via the boundary element collocation method in combination with the algorithm by Beyn yields highly accurate results both for the first non-zero eigenvalue and its corresponding eigenfunction which is due to superconvergence. Additionally, it can be shown numerically that the ratio between the maximal/minimal value inside the domain and its maximal/minimal value on the boundary can be larger than 1 + 10− 3. Finally, numerical examples for easy to construct domains with up to five holes are provided which fail the hot spots conjecture as well.
KW  - Numerics
KW  - Boundary integral equations
KW  - Potential theory
KW  - Helmholtz equation
KW  - Interior Neumann eigenvalues
Y1  - 2021
U6  - https://doi.org/10.1007/s10444-021-09911-5
SN  - 1019-7168
VL  - 47
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - GEN
A1  - Mayntz, Joscha
A1  - Keimer, Jona
A1  - Tegtmeyer, Philipp
A1  - Dahmann, Peter
A1  - Hille, Sebastian
A1  - Stumpf, Eike
A1  - Fisher, Alex
A1  - Dorrington, Graham
T1  - Aerodynamic Investigation on Efficient Inflight Transition of a Propeller from Propulsion to Regeneration Mode
T2  - AIAA SCITECH 2022 Forum
N2  - This paper discusses a new way of inflight power regeneration for electric or hybrid-electric driven general aviation aircraft with one powertrain for both configurations. Three different approaches for the shift from propulsion to regeneration mode are analyzed. Numerical cal-culation and wind tunnel results are compared and show the highest regeneration potential for the "Windmill" approach, where the propeller blades are flipped, and rotation is reversed. A combination of all regeneration approaches for a realistic flight mission is discussed.
Y1  - 2021
U6  - https://doi.org/10.2514/6.2022-0546
N1  - AIAA SCITECH 2022 Forum, January 3-7, 2022, San Diego, CA & Virtual
PB  - AIAA
CY  - Reston, Va.
ER  - 
TY  - BOOK
A1  - Kurz, Melanie
A1  - Schwer, Thilo
T1  - Designentscheidungen : über Begründungen im Entwurfsprozess / herausgegeben von Melanie Kurz und Thilo Schwer
T3  - Schriften / Gesellschaft für Designgeschichte
Y1  - 2021
SN  - 978-3-89986-353-6
PB  - avedition
CY  - Stuttgart
ER  - 
TY  - CHAP
A1  - Peterson, Leif Arne
ED  - Schlüter, Dominik
T1  - Holzbau
T2  - Wofür braucht man das eigentlich? Ein Handbuch für Mathematiklehrkräfte der Sekundarstufe I und II
Y1  - 2021
SN  - 978-3-7543-2606-0
SP  - 21
EP  - 23
PB  - BoD
CY  - Norderstedt
ER  - 
TY  - CHAP
A1  - Kurz, Melanie
T1  - Zur Multikausalität von Designentscheidungen - eine Beispielsammlung
T2  - Designentscheidungen: über Begründungen im Entwurfsprozess
Y1  - 2021
SN  - 978-3-89986-353-6
SP  - 22
EP  - 43
PB  - avedition
CY  - Stuttgart
ER  -