Sylke Boyd, Physics

Nasir Siddiqui	Atmospheric Contrail Detection with a Deep Learning Algorithm, UROP spring 2020
Spencer Graff	Analysis of Total Sky Imager records (TSI) from the Southern Great Plains ARM site, McNair scholar, Summer 2019
Jamin Stagg	Optical depth of snow, UROP Spring and Fall 2018
	Optical scattering by bullet ice crystals, Summer 2017
Brittney Ferrian	Construction of a prototype cloud lidar (collaboration with Dr Kevin Boyd), HHMI Summer 2015, UROP Spring 2016
Morton Greenslit	Image analysis program, cloud and halo detection (HHMI Summer 2015, UROP Spring 2016)
Michelle King	Image analysis program for all-sky recordings, halo detection (UROP Spring 2015, UROP Spring 2016)
Shelby Richard	Image analysis program for all-sky recordings, halo detection (HHMI Summer 2014)
Jieying Jin	Development of a 3d ray tracing program in Mathematica (HHMI Summer 2014)
James Froberg	Development of a ray tracing program for halo simulations in Matlab (Summer 2013, UROP Spring 2014)
Stephen Sorensen	Halo observations with the All-sky camera (Summer 2013, UROP Spring 2014)
Zach Klassen and Josef Wieber	Climate variability and land use - and analysis of long-term weather records in the upper Midwest (HHMI, Summer 1013)
Robert Smith	RDX elastic constants in RDX and the influence of voids on the elasticity tensor (Summer 2012, UROP Spring 2013)
Chad Reverman	Bulk modulus of RDX and the influence of voids (Summer 2012, UROP Spring 2013)
Matthew Kroonblawd	Energy distribution in RDX during shock (Summer 2010, UROP spring and summer 2011)
Jerry Kessler	Statistical analysis of 90-year longitudinal weather record in Morris (UROP Spring 2010)
Johanna Martin	Water droplet formation in clouds (MAP 2008/9)
Anna Schliep	Dislocations in RDX (GIA, URS 2007 poster)
	Sound generation by wind in Strings (UROP, finished, presented as poster at MAAPT Fall 2006 meeting, URS 2007 poster)
Sam Geller	Monte Carlo Simulations of Vacancies in a Crystal (GIA, active, presented as poster at MAAPT Fall 2006 meeting)
Matt Gravelle	Point defects in RDX (UROP and GIA, finished, presented posters at URS and CCTCC, coauthor of publication)

If you are interested to collaborate in a research project please do not hesitate to stop by or drop a line by e-mail.

Research Interests:

In recent years, my interest has shifted toward atmospheric physics. Droplet formation, cloud formation, ice crystal growth, the use of optical phenomena to observe and measure aerosols, in particular droplets and ice crystals are at the center. Assessment of cirrus cloud coverage belongs to one of the more difficult problems in data collection. Spatial as well as temporal resolution is limited due to their optical properties, the restrictions of terrestrial observations and the evasiveness of cirrus in satellite images. Cirrus clouds often cause ice halos, in particular 22-degree halos. Other halo features, such as parhelia and various other subspecies of complex halo displays can be seen as well. Collecting data on these halos will, as a longitudinal set, allow assessment about the frequency, type and diurnal distribution of cirrus clouds. Hence, an all-sky camera is creating a continuous image record of sky conditions. Software is being developed to analyse these images with respect to cloud presence, cloud classification and in particular for the presence of ice halos. In addition, a lidar prototype is being developed which may add a third dimension to the observational data on the presence of ice crystals.

Previously, my research interest has been in computer simulations of materials, including force field development, molecular dynamics and Monte Carlo simulations. Materials modeling allows to address questions that are either hard to access experimentally, or for which experimental results are in need of explanation. To some degree, reliable models can have predictive power, but also provide insight into the mechanisms of otherwise inaccessible phenomena. A successful computer model for a materials problem rests is based on three elements:

The physics of the problem: The question must be relevant, aspects of it not answerable by other means, and backed up with sufficient experimental data.
The software: the success of the model is constrained by computing efficiency. The faster the algorithm, the larger the model, and the longer the times the model can access. A typical molecular dynamics simulation can span a few nanoseconds with sample sizes of a few nanometers. However, many physical problems involve processes on larger time and length scales - limits that need to be pushed. It is crucial to implement parallel computing if helpful, as well as employ other means of pushing these limits, for example by employing a multi-scale approach.
The hardware: We are using the Minnesota Supercomputing Institutes facilities. Some simulations are performed on a Beowulf cluster with currently 32 CPUs, dedicated exclusively to this purpose.

Current Projects:

Halo Phenomena: Halo phenomena are caused by ice crystals in upper air layers, and in summer are associated with the presence of cirrostratus clouds. In winter, blowing snow near the ground may contribute to their appearance. Most commonly, the 22-degree halo is seen, but also circumzenithal arcs, circumhorizontal arcs, perhaps 46-degree halos may be observed in our location. A variety of Parry arcs may also occur. During the winter months, other features, such as sun dogs, different parry arcs, pillars and additional Parry arcs are often observed.

Left to right: 22-degHalo and parhelia; 22-deg and 46-deg halos, parhelia and upper-tangent arc; sun pillar and a Parry arc; Light pillars above campus; 22-deg halo in cirrus(photos by S. Boyd); ray tracing in a hexagonal platelet (James Froberg, MATLAB)

Ice crystal: hexagonal plate, refractive scattering (animation)

Ice crystal: bullet rosette with 4 arms (animation)

These optical phenomena are caused by refraction and reflection in ice crystals that form in the air. Ice crystals may form as hexagonal platelets, columns, pencils, needles, hollow columns and a wide variety of combination forms. Their shapes are related to temperature and supersaturation conditions in their local environment. Observing and interpreting Halo phenomena can give us information about atmospheric conditions in elevated layers without direct probing. This project addresses two questions: (1) How frequent are halo phenomena, and which kinds are observed in our local area? (2) Which ice crystal shapes would favor particular halo appearances in the sky? Such observations and studies are performed throughout locations all over the world, as a means of passive remote sensing, and a pathway to understand cloud composition as it relates to the origin of the clouds. A new allsky camera is currently in the testing phase. It will be installed on the roof of the science building in January 2014.

Stephen Sorensen has been working on controls for the allsky to allow recording images of sky conditions throughout the daylight hours. He will work on the development of an image-processing program to recognize and categorize various halo appearances. James Froberg has developed a MATLAB program that runs statistics on optical rays through ice crystals and provides an angular distribution of the exiting intensity. He will expand this program to 3d ice crystals and to allow for variation in orientation of the crystals through the academic year 13/14.

In Summer of 2014, the camera was installed on the roof of the science building, and is recording. Shelby Richard has developed the image analysis algorithm for halo detection. The program continues to be refined. Jieying Jin has developed a Mathematica code to visualize and manipulate ray paths in hexagonal ice crystals.

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The findings and the halo detection algorithm have been presented at the Gordon Research Conference on Radiation and Climate at Bates College in Lewiston, Maine, July 2015. UMM student Michelle King was able to participate in the conference as well. Here is our poster.

2. Weather and climate: I am interested in using long-term weather records to assess local climate variability. After Jerry Kesslers analysis of a 90-year temperature record taken in Morris MN (2010) it appeared that the minimum temperatures have increased dramatically throughout the record period, while other climate markers were variable and showed no significant trends. Results of the analysis are given here. One could speculate about an increase of water vapor due to an intensification of agriculture throughout the period. The data only included monthly mins, maxes and averages, and were limited to 90 years. During summer of 2013, Zachary Klassen and Josef Wieber conducted an extensive study on twelve locations throughout the Midwest, using daily data and up to 130 years of record-keeping. It is a search process for possible correlations in land-use and variations in climate markers. It appears that the increase in minimum temperatures is a trend observed in all land forms.

Maps of the trends in February minimum temperatures, the August daily temperature range and the January mean temperature. Circle size relates to slope (max +-8 degC/100yrs); colored = +, white =-; all plots use the same scale. Winter minimum temperatures have increased everywhere. The daily range has decreased in rural areas, and slightly increased in urban areas. The January mean temperatures have small and varied trends.

Molecular solid RDX: This is a powerful explosive with the caveat of a high sensitivity. The project originates from an initiative from Lawrence Livermore National Lab, trying to solve the problem of stockpile of weapons from the cold-war era. The weapons are aging, and need to be dealt with. Rather than experiment with these stockpiles, a computational initiative has been started to model the materials and their behavior, hence helping to decide the best course of action. In addition, RDX is a material of choice for terrorists due to its large energetic density. Its was used by the shoe bomber Michael Reid in the infamous 2001 air plane incident, but also in the attack on the Marriot hotel in Islamabad, Pakistan, in September 2008. It is important to find inconspicuous methods of detection for such chemicals, and one possibility is the use of Terahertz spectroscopy. This method analyses the spectrum of long-wave infrared radiation in a part of the spectrum that is associated with thermal vibrations of the crystal lattices in conjunction with molecular modes of motion. Our computer model is one of only very few that is able to investigate such coupled modes and predictively model and explain the vibrational spectrum of the substance. Currently my work focuses on the vibrational properties of the substance under various circumstances, such as the presence of large defects and an electric field. In addition, defects in the crystalline lattice provide places at which detonations seem to originate due to their energetically predisposed position. Experimentally, the crystals are produced from solution, and often defects are incorporated during the crystal growth. Limiting the amount of defects can help lower the sensitivity, hence our model studied how the defects are formed, which geometry they have, how easily they heal or diffuse, and how growth conditions influence their concentration. Work has been done on point defects in the molecular solid RDX, voids and dislocations. The project is a collaboration with the group of Peter Politzer at the University of New Orleans. Take a look at the vibrational properties of the RDX molecule. Several research students have made great contributions to this project throughout the recent years. Robert Smith and Chad Reverman worked intensely on an exploration of the elastic properties of RDX throughout the summer 2012 and the following academic year. Robert successfully detailed the cohesive energy surface and analyzed the elements of the elastic tensor. Chad focused on a determination of the bulk modulus and its dependence on the temperature of the material. Matthew Kroonblawd set up a computer experiment to analyse the energy dissipation of shockwaves in RDX, and look for pathways of energy transfer from lattice modes to intramolecular modes. He presented his work at a conference in Germany in Spring of 2011.
Interfaces under normal and shear stress. Friction is a dissipative phenomenon that has relevance in very many applications as well as in various environmental problems. Static friction is the force which keeps surfaces in contact under stress from sliding relative to each other, while dynamic friction sets in when the surfaces actually move. The transition from static to dynamic friction occurs when the shear stress increases beyond a critical point, detachment occurs, and the contacting surfaces start to slip past each other. The subsequent sliding will easily be maintained by a much lower shear force. Applications in robotics, construction and engineering fields, even processes in geological systems face the challenge of the unpredictability of the onset of sliding. During my research leave in Fall 2008, I am working to develop a comprehensive, multi-scale computer model of frictional processes in order to study the physical processes surrounding the so-called stick-slip transition. I expect that students can work on this project beginning in the spring semester of 2009. This project has ties to the group of Thomas Frauenheim at the Bremen Center for Computational Materials Science in Bremen, Germany.
Water droplet formation in clouds. Water droplets form if the partial pressure of water in the air supersedes the saturation pressure. However, the mechanisms of initial condensation is more complicated and involves nucleation. After the initial droplets are formed, they grow either by continued condensation on their surface, or by merging with other droplets - so-called coalescence. However, in warm cumulus clouds there often is not much time between the initial formation of the cloud and the onset of precipitation, which means that those large rain drops must have formed very fast. The problem is, that the speed of droplet growth in cumulus clouds can not be explained by either one of the two mechanisms above alone. This makes the prediction of the onset and type of precipitation from these clouds difficult - there must be mechanisms beyond condensation and coalescence. Questions of turbulence surrounding a droplet appear to play a role as mechanisms for delivery of additional moisture for condensation. There is a very active area of research, focused on the fluid dynamics involved furthering or limiting droplet growth. This project is developing a computer model for constant-pressure constant-temperature molecular dynamics simulations of water droplets embedded in an air atmosphere. We are studying questions of nucleation, growth rates and coalescence. The model is based on a Lennard-Jones model of water, embedded in a soft hard-sphere fluid (air). This allows to includes the dissipative influence of the air, as well as to study the effect of a droplet with terminal speed onto this medium.

Animations: NPT simulation of a water droplet of 4000 water molecules at 275 K and 1 atm, water particles shown only.

whole system, close-up

Recent publications and conference presentations:

Boyd, S., Sorenson, S., Richard, S., King, M., and Greenslit, M.: Analysis algorithm for sky type and ice halo recognition in all-sky images, Atmos. Meas. Tech., 12, 4241, https://doi.org/10.5194/amt-12-4241-2019, 2019. https://www.atmos-meas-tech.net/12/4241/2019/amt-12-4241-2019.html

Sylke Boyd, Stephan Sorenson, Michelle King, Shelby Richard, Morton Greenslit, Halo Identification Algorithm for Sky Images Produced in TSI Series, 99^th Annual Meeting of the American meteorological Society, Phoenix AZ Januray 6-10, 2019, poster, extended abstract

Jamin Stagg and Sylke Boyd, Simulations of the Optical Properties of Dirty Snow, 99^th Annual Meeting of the American meteorological Society, Phoenix AZ Januray 6-10, 2019, poster

Sylke Boyd, How can we use ice halos to improve our knowledge about cirroform clouds and the conditions in the upper troposphere? 2017 Gordon Conference on Radiation and Climate, Bates College, Lewiston, Maine, July 17 to 21, 2017.

Brittney Ferrian, Kevin J. Boyd, and Sylke Boyd. Construction of a low-cost LIDAR for cirrus cloud observations, March Meeting of the American Physical Society, Baltimore 2016, APS March Meeting Abstracts.

Michelle King, Morton Greenslit, and Sylke Boyd, Algorithms for ice halo detection in all-sky images. March Meeting of the American Physical Society, Baltimore 2016.In APS March Meeting Abstracts.

Sylke Boyd, Michelle King, and Morton Greenslit, Analysis of Ice Halo Appearances Using an All-Sky Camera. 2015 Gordon Research Conference on Radiation and Climate, Bates College, Lewiston, Maine, July 26-30 2015.

Shelby Richard, Jieying Jin and Sylke Boyd, Data Collection on Cirrus Coverage Using an Allsky Camera, 2014 Summer Meeting: Minneapolis, Minnesota July30 2014.

Stephen Sorenson, James Froberg and Sylke Boyd, Data collection and analysis on Halo displays using an all-sky camera, APS March Meeting 2014, March 3-7 2014, Denver, Volume 59, Number 1.

Zach Klassen, Josef Wieber and Sylke Boyd, Climate Variability and Local Land Use in the Upper Midwest, APS March Meeting 2014, March 3-7 2014, Denver, Volume 59, Number 1.

Chad Reverman and Sylke Boyd, Bulk modulus of RDX crystal, MAAPT Spring Meeting, Minneapolis, 4-27-2013.

Robert Smith and Sylke Boyd, Computational Study of elastic constants of cyclotrimethylene-trinitramine, MAAPT Spring Meeting, Minneapolis, 4-27-2013.

Matthew Kroonblawd and Sylke Boyd, Computer Study of the Effect Voids in RDX Crystals on the Dissipation of Shock Energy and on the Vibrational Eigenmode Spectrum, International Workshop Progress and Future Challenges in Computational Materials Science, Bremen Center for Computational Materials Science–BCCMS, University of Bremen, March 28th to 30th 2011.

Sylke Boyd, Jane S Murray, and Peter Politzer, Molecular dynamics characterization of void defects in crystalline (1,3,5-trinitro-1,3,5-triazacyclohexane), J. Chem. Phys. 131, 204903 (2009).

Sylke Boyd and Kevin J Boyd, A computational analysis of the interaction of lattice and intramolecular vibrational modes in crystalline alpha-RDX, J. Chem. Phys. 129, 134502 (2008).

S. Boyd, K. J. Boyd, Vibrational properties of RDX, presented as poster at the 16^th Conference on Current Trends in Computational Chemnistry (CCTCC) in Jackson, MS, November 1-2, 2007.

S. Boyd, M. Gravelle, Computer Simulations Of Point Defects In Crystalline RDX, presented as poster at the 2006 Gordon Research Conference on Energetic Materials in Tilton, NH, June 18-23, 2006.

Sylke Boyd, Matthew Gravelle, and Peter Politzer, Nonreactive molecular dynamics force field for crystalline hexahydro-1,3,5-trinitro-1,3,5 triazine, , J. Chem. Phys. 124, 104508 (2006).

M. Gravelle, S. Boyd, A computer study of point defects in the RDX crystal, presented as poster at the 14^th Conference on Current Trends in Computational Chemistry (CCTCC) in Jackson, MS, November 4-5, 2005.