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Hans D. Hallen
North Carolina State University
Analytical chemistryOpticsPhysicsNear-field scanning optical microscopeRaman spectroscopy
132Publications
21H-index
2,114Citations
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Publications 130
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#1Ako Emanuel (NCSU: North Carolina State University)
#2Ernest Walker (NCSU: North Carolina State University)
Last. Hans D. Hallen (NCSU: North Carolina State University)H-Index: 21
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Self-assembly of structures that are more than a few millimeters in size is a current problem that can have broad applications in new ways to construct the objects that we use. As a step in that direction, fluidic self-alignment at the wafer-to-wafer level is demonstrated, characterized, and modeled. Although self-alignment of millimeter-sized objects has previously been shown, several physical processes become important as the structure size is increased to a whole wafer. These processes are me...
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#1Hans D. HallenH-Index: 21
The atmospheric boundary layer is typically characterized by a higher water vapor content and higher temperature than the free troposphere above it. Its height increases as the size of convection cells grow during the morning due to surface heating, stabilizes during the day, and it collapses as the energy input decreases in the evening. The marine boundary layer emphasizes these aspects. The large temperature gradients, humidity gradients and shear at the top of the boundary layer impact severa...
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High frequency signals propagate along the edges of conductors. If the conductors are electroplated, then the seed layer forms at least one edge, so care must be taken to insure the electrical quality of these layers. In this work, we study the initial quality of SAM-based seed layers that are compatible with complex surfaces including through-silicon vias (TSVs), as are used in via-last three-dimensional semiconductor device packaging. The conformal and electrical quality of the seed metal is v...
#1Ziad Ali (NCSU: North Carolina State University)
#2Alexandra Duel-Hallen (NCSU: North Carolina State University)H-Index: 17
Last. Hans D. Hallen (NCSU: North Carolina State University)H-Index: 21
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The susceptibility of millimeter-wave (mmWave) signals to physical blockage and abrupt signal strength variations presents a challenge to reliable 5G communication. This work proposes and examines the feasibility of utilizing lower-frequency signals as early-warning indicators of mobile mmWave signal blockage or recovery. A physics-based channel simulation tool incorporating Fresnel diffraction and image sources is employed to demonstrate that sub-6 GHz signals “lead” mmWave signals in reaching ...
1 CitationsSource
#1Hans D. HallenH-Index: 21
#2Brandon J. N. LongH-Index: 1
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#1Shuang Fang LimH-Index: 14
#2Janina WirthH-Index: 2
Last. Hans D. HallenH-Index: 21
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The susceptibility of millimeter-wave (mmWave) signals to physical blockage and abrupt signal strength variations presents a challenge to reliable 5G communication. This work proposes and examines the feasibility of utilizing lower-frequency signals as early-warning indicators of mobile mmWave signal blockage or recovery. A physics-based channel simulation tool incorporating Fresnel diffraction and image sources is employed to demonstrate that sub-6 GHz signals often "lead" mmWave signals in rea...
#1Hans D. Hallen (NCSU: North Carolina State University)H-Index: 21
#2Ling Li (NCSU: North Carolina State University)H-Index: 3
Last. Brandon J. N. Long (NCSU: North Carolina State University)H-Index: 1
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Methylation in DNA is a controlling factor in gene expression, embryonic development, and has been found to be important in infections and cancer. From a basic biology point of view, great heterogeneity has been found in methylation levels within tissues, so questions arises as to how and why. We show that methylated-DNA (m-DNA) can be distinguished from non-methylated (n-DNA) with nano-bowtie- and resonance- enhanced Raman spectra. By tuning the bowtie antenna to the resonance wavelength, both ...
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#1Brandon J. N. Long (NCSU: North Carolina State University)H-Index: 1
#2Wenxia Zheng (NCSU: North Carolina State University)H-Index: 11
Last. Hans D. Hallen (NCSU: North Carolina State University)H-Index: 21
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The discovery of soft structures in dinosaur bone with the morphological and molecular characteristics of blood vessels in extant vertebrates was both surprising and controversial. Mounting evidence suggests that these soft tissues are blood vessels, their preservation driven in part by reactive oxygen species derived from hemoglobin degradation. More data are needed to support this hypothesis. Raman spectroscopy, and resonance Raman in particular, can provide detailed information as to the chem...
1 CitationsSource
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