68 research outputs found
Group Irregular Labelings of Disconnected Graphs
We investigate the \textit{group irregularity strength} () of graphs, i.e. the smallest value of such that taking any Abelian group \gr of order , there exists a function f:E(G)\rightarrow \gr such that the sums of edge labels at every vertex are distinct. We give the exact values and bounds on for chosen families of disconnected graphs. In addition we present some results for the \textit{modular edge gracefulness} , i.e. the smallest value of such that there exists a function f:E(G)\rightarrow \zet_s such that the sums of edge labels at every vertex are distinct
Direct evidence for the magnetic ordering of Nd ions in NdMnSi and NdMnGe by high resolution inelastic neutron scattering
We have investigated the low energy nuclear spin excitations in
NdMnSi and NdMnGe by high resolution inelastic neutron
scattering. Previous neutron diffraction investigations gave ambiguous results
about Nd magnetic ordering at low temperatures. The present element-specific
technique gave direct evidence for the magnetic ordering of Nd ions. We found
considerable difference in the process of the Nd magnetic ordering at low
temperature in NdMnSi and NdMnGe. Our results are consistent
with those of magnetization and recent neutron diffraction measurements
Anomalous thermal expansion and strong damping of the thermal conductivity of NdMnO and TbMnO due to 4f crystal-field excitations
We present measurements of the thermal conductivity and the thermal
expansion of NdMnO and TbMnO. In both compounds a splitting of
the multiplet of the ion causes Schottky contributions to
. In TbMnO this contribution arises from a crystal-field splitting,
while in NdMnO it is due to the Nd-Mn exchange coupling. Another
consequence of this coupling is a strongly enhanced canting of the Mn moments.
The thermal conductivity is greatly suppressed in both compounds. The main
scattering process at low temperatures is resonant scattering of phonons
between different energy levels of the multiplets, whereas the complex 3d
magnetism of the Mn ions is of minor importance.Comment: 9 pages including 6 figure
A novel heavy-fermion state in CaCu_3Ru_4O12
We have measured susceptibility, specific heat, resistivity, and thermopower
of CaCuTiRuO and CaCuMnRuO, and
have found that CaCuRuO can be regarded as a heavy-fermion oxide
in d-electron systems. The Kondo temperature is near 200 K, and the
susceptibility (1.4 emu/Cu mol) and the electron specific heat
coefficient (28 mJ/Cu molK) are moderately enhanced. The resistivity is
proportional to at low temperatures, and satisfies the Kadowaki-Woods
relation. The heavy-fermion state comes from the interaction between the
localized moment of Cu 3d and the conduction electron of Ru 4d. An
insulator-metal transition occurs between and 4 in
CaCuTiRuO, which can be regarded as a transition from
magnetic insulator to heavy-fermion metal.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp
Teaching and Learning of Calculus
This survey focuses on the main trends in the field of calculus education. Despite their variety, the findings reveal a cornerstone issue that is strongly linked to the formalism of calculus concepts and to the difficulties it generates in the learning and teaching process. As a complement to the main text, an extended bibliography with some of the most important references on this topic is included. Since the diversity of the research in the field makes it difficult to produce an exhaustive state-of-the-art summary, the authors discuss recent developments that go beyond this survey and put forward new research questions
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