Structural relaxation in Morse clusters: Energy landscapes

We perform a comprehensive survey of the potential energy landscapes of 13-atom Morse clusters, and describe how they can be characterized and visualized. Our aim is to detail how the global features of the funnel-like surface change with the range of the potential, and to relate these changes to the dynamics of structural relaxation. We find that the landscape becomes rougher and less steep as the range of the potential decreases, and that relaxation paths to the global minimum become more complicated.Comment: 21 pages, 3 tables, 5 figure

Thermodynamics and the Global Optimization of Lennard-Jones clusters

Theoretical design of global optimization algorithms can profitably utilize recent statistical mechanical treatments of potential energy surfaces (PES's). Here we analyze the basin-hopping algorithm to explain its success in locating the global minima of Lennard-Jones (LJ) clusters, even those such as \LJ{38} for which the PES has a multiple-funnel topography, where trapping in local minima with different morphologies is expected. We find that a key factor in overcoming trapping is the transformation applied to the PES which broadens the thermodynamic transitions. The global minimum then has a significant probability of occupation at temperatures where the free energy barriers between funnels are surmountable.Comment: 13 pages, 13 figures, revte

The double-funnel energy landscape of the 38-atom Lennard-Jones cluster

The 38-atom Lennard-Jones cluster has a paradigmatic double-funnel energy landscape. One funnel ends in the global minimum, a face-centred-cubic (fcc) truncated octahedron. At the bottom of the other funnel is the second lowest energy minimum which is an incomplete Mackay icosahedron. We characterize the energy landscape in two ways. Firstly, from a large sample of minima and transition states we construct a disconnectivity tree showing which minima are connected below certain energy thresholds. Secondly we compute the free energy as a function of a bond-order parameter. The free energy profile has two minima, one which corresponds to the fcc funnel and the other which at low temperature corresponds to the icosahedral funnel and at higher temperatures to the liquid-like state. These two approaches show that the greater width of the icosahedral funnel, and the greater structural similarity between the icosahedral structures and those associated with the liquid-like state, are the cause of the smaller free energy barrier for entering the icosahedral funnel from the liquid-like state and therefore of the cluster's preferential entry into this funnel on relaxation down the energy landscape. Furthermore, the large free energy barrier between the fcc and icosahedral funnels, which is energetic in origin, causes the cluster to be trapped in one of the funnels at low temperature. These results explain in detail the link between the double-funnel energy landscape and the difficulty of global optimization for this cluster.Comment: 12 pages, 11 figures, revte

Advanced modulation technology development for earth station demodulator applications. Coded modulation system development

A jointly optimized coded modulation system is described which was designed, built, and tested by COMSAT Laboratories for NASA LeRC which provides a bandwidth efficiency of 2 bits/s/Hz at an information rate of 160 Mbit/s. A high speed rate 8/9 encoder with a Viterbi decoder and an Octal PSK modem are used to achieve this. The BER performance is approximately 1 dB from the theoretically calculated value for this system at a BER of 5 E-7 under nominal conditions. The system operates in burst mode for downlink applications and tests have demonstrated very little degradation in performance with frequency and level offset. Unique word miss rate measurements were conducted which demonstrate reliable acquisition at low values of Eb/No. Codec self tests have verified the performance of this subsystem in a stand alone mode. The codec is capable of operation at a 200 Mbit/s information rate as demonstrated using a codec test set which introduces noise digitally. The measured performance is within 0.2 dB of the computer simulated predictions. A gate array implementation of the most time critical element of the high speed Viterbi decoder was completed. This gate array add-compare-select chip significantly reduces the power consumption and improves the manufacturability of the decoder. This chip has general application in the implementation of high speed Viterbi decoders

An Intensive Cultural Resources Survey For Goforth Road Between IH-35 And Kyle Parkway, Kyle, Hays County, Texas

In December 2014, Lockwood, Andrews & Newman, Inc. (Client) contracted with Raba Kistner Environmental, Inc. (RKEI) to perform an intensive cultural resources survey along Goforth Road between Interstate Highway (IH)-35 and Kyle Parkway for the expansion of the Right-Of-Way (ROW) and the installation of storm sewer inlets, manholes and one bridge in Kyle, Hays County, Texas. The purpose of this survey was to determine whether cultural resources were located within the Area of Potential Effect (APE), and if feasible, assess their significance and eligibility for designation as State Antiquities Landmarks (SALs) and for listing on the National Register of Historic Places (NRHP). The project was sponsored by the City of Kyle and the owner of the project is the City of Kyle owns the road and its ROW. Since the ROW is owned by a political subdivision of the state, the project falls under the Antiquities Code of Texas as administered by the Texas Historical Commission (THC). The field work was carried out between December 29-30, 2014 under Texas Antiquities Committee Permit No. 7117 issued to Dr. Steve A. Tomka, who served as Principal Investigator. Mark Luzmoor was the Project Archaeologist and Kristi Nichols and Chris Murray assisted during the field work. Background research revealed that no previously recorded archaeological sites are located within the boundary of the APE. However, there are two archaeology sites, seven historical markers and four National Register Properties, within a one mile radius but outside of the APE. A total of 16 shovel tests (STs) were excavated within the APE. Surface visibility was around 10% throughout the APE. Due to extensive disturbances of the banks of Plum Creek, no backhoe trenches were excavated during the project. No artifacts were encountered in any shovel test or on surface during the pedestrian survey. Since no cultural deposits were encountered, RKEI recommends no further archaeological work within the project boundaries. All project related documents are permanently housed at the Texas Archeological Research Laboratory

Proposed Salado Creek Trail, Lions Park Lake to SE Military Drive, San Antonio, Bexar County, Texas

In December 2015, Vickrey & Associates, Inc. (Client) contracted with Raba Kistner Environmental, Inc. (RKEI), to perform an intensive pedestrian survey for a proposed 3.2 mile hike and bike trail along Salado Creek near San Antonio, Bexar County, Texas. The proposed trail is an extension of the existing South Salado Creek Greenway Trail which was installed in 2008. The project is owned by the City of San Antonio. Since the project area is currently owned by a political subdivision of the state, the project falls under the Antiquities Code of Texas as administered by the Texas Historical Commission (THC). The purpose of the survey was to determine whether historic or prehistoric cultural resources are located within the Area of Potential Effect (APE), and, if so, assess their significance and eligibility for designation as State Antiquities Landmarks (SALs) and for inclusion on the National Register of Historic Places (NRHP). The project was carried out in early January 2016 under Texas Antiquities Permit No. 7491. Dr. Steve A. Tomka served as Principal Investigator. Kristi Nichols served as the Project Archaeologist, and Mark Luzmoor served as field technician. Several circumstances delayed the completion of the survey. Construction activities for a new apartment complex hindered the survey along the northern portion. During the survey, it was noted that the trail was to be placed on portions of an already laid cart path from the Pecan Valley Golf Club that was in this area from 1963-2012. Furthermore, because the golf course had fill brought in to build up the fairways and greens, no shovel tests or backhoe trenches were placed in these areas. Right-of-Entry issues also delayed progress within the golf course as well. Weather also postponed the survey due to wet and muddy conditions. One backhoe trench (BHT) and 19 shovel tests (STs) were excavated within the APE. Surface visibility was around 90 percent throughout the APE. No buried or surface-exposed historic or prehistoric materials were encountered during the survey. All documents collected during the course of the project were returned to the RKEI Archaeological Laboratory for processing. All project related documents, are permanently housed at the RKEI Laboratory. No cultural material was collected over the course of the project

A Cultural Resources Survey Of The Proposed Water And Sewer Line Project On SH-16 Helotes, Bexar County, Texas

In November 2014, LNV Engineers (CLIENT) contracted with Raba Kistner Environmental, Inc. (RKEI) to perform an intensive cultural resources survey along State Highway (SH) 16 for a proposed water and sewer line project in Helotes, Bexar County, Texas. The project occurred within the existing SH-16 Rightof Way (ROW). The purpose of this survey was to locate surface exposed or buried cultural deposits with the project area. The project is sponsored by the City of Helotes. Therefore, the proposed project falls under the Antiquities Code of Texas as administered by the Texas Historical Commission (THC). The project was carried out between November 24-26, 2014 under Texas Antiquities Committee Permit No. 7087 issued to Dr. Steve A. Tomka, who served as Principal Investigator. Mark Luzmoor served as the Project Archaeologist and Chris Murray served as the field technician. Background research carried out prior to the fieldwork revealed no known archaeological sites within or in the vicinity of the Area of Potential Effect (APE). One historical marker is present within the APE. Although there are no archaeological sites within the boundary of the APE, there are ten sites, three historical markers, and one National Register Property within a one mile radius of the project area. A total of 26 shovel tests (ST) were excavated within the APE. Due to the lack of deep soils within the APE, no backhoe trenches were excavated. No buried artifacts were encountered during shovel testing and none were noted on surface during the pedestrian survey. Since no cultural deposits were encountered, RKEI does not recommend that further archaeological investigations within the project boundaries and the proposed project can proceed as planned. All documents generated during the course of the project are permanently housed at the Texas Archeological Research Laboratory (TARL)

Archaeological Investigations and Monitoring of the Installation of a Water Line along Cunningham Avenue Near the Joint Base San Antonio-Fort Sam Houston, San Antonio, Bexar County, Texas

In the fall of 2016, Raba Kistner Environmental Inc. (RKEI) contracted with K Friese & Associates (CLIENT) to monitor the installation of a San Antonio Water System (SAWS) waterline along Cunningham Avenue (Ave.), between Broadway Street (St.) and N. Pine St., along the northern fence line of Joint Base San Antonio-Fort Sam Houston (JBSA-FSH) and the old Playland Park property. SAWS plans to install waterlines along four distinct locations surrounding JBSA-FSH. Of the four proposed waterlines, only one waterline has the potential of impacting a recorded archaeological site. The proposed waterline warranting archaeological investigation is located along Cunningham Ave. and is projected to intersect the known route of the Acequia de Valero (Acequia de Valero) also known as archaeological site 41BX8. As the utility installation is located on land owned by the City of San Antonio, a political subdivision of the State, and funding will be partially derived from public sources; the project is subject to review under the Antiquities Code of Texas (Texas Natural Resource Code, Title 9, Chapter 191) which protects historic resources found on state lands or lands owned by a political subdivision of the state. Additionally, the project is subjected to review by the City of San Antonio under the City of San Antonio’s Preservation Ordinance (Article VI, Historic Preservation and Urban Design, City of San Antonio, Unified Development Code). All work was performed in accordance with the Council of Texas Archeologists (CTA) and Texas Historical Commission (THC) Survey Standards, under Texas Antiquities Committee Permit No. 7833. Kristi Miller Nichols served as Principal Investigator and Mark Luzmoor served as Project Archaeologist. Assistant City Archaeologist, Matt Elverson was present during the exposure and documentation of the acequia. The Acequia de Valero was the first irrigation canal excavated by the Spanish colonists in the upper San Antonio River drainage. The construction of the canal began in January of 1719 for the purpose of transporting water to the agricultural fields of Mission San Antonio de Valero. Previous research conducted by RKEI within the former Playland Park property, south of the current project area, revealed a portion of the Acequia de Valero. Due to the potential of the acequia extending into the project area, the City of San Antonio’s Office of Historic Preservation (COSA-OHP) requested that RKEI monitored the mechanical excavation of a 1,000-foot portion of the waterline along Cunningham Ave., specifically focusing on an approximately 66-feet (20 meter [m]) area where the project route of the Acequia de Valero intersects Cunningham Ave. Prior to the installation of the SAWS waterline, the COSA-OHP requested that a Ground Penetrating Radar (GPR) survey be conducted to determine if the acequia alignment is still present within the project area. Additionally, the COSA-OHP requested that an exploratory trench be excavated in the area where the acequia crosses the APE, in an attempt to identify and document the acequia. On November 28, 2016, Kristi Miller Nichols and Cynthia Dickey conducted the GPR survey; however, no distinguishable anomalies were detected within in the GPR data. Therefore, on March 7, 2017, monitoring of the exploratory trenching began of an approximately 20 m long trench. The purpose of excavation of the trench was to determine if remnants of the acequia existed within the project area, prior to installation of the waterline. Due to the many layers of fill within the acequia at this location, it was difficult to identify the channel during excavation of the trench. After sections of the trench were excavated, an archaeologist entered the trench and cleared the trench walls to carefully inspect each profile for any signs of the acequia. Approximately 140 m to the east of the intersection of Broadway/Cunningham Ave., there appeared to be an outline of a ditch. Based on the location of the alignment of the acequia on historic maps and further investigations of the profiles, it was determined to be the Acequia de Valero. The north wall profile of the trench revealed the acequia to be approximately 4.15 m wide at the top of the channel and 70 centimeters (cm) wide at its base. The base of the acequia was 1.24 m below the top of the asphalt and neither the base nor its walls were lined. The south wall profile of the trench revealed that the acequia had been partially impacted on this southern edge as it was only 2.9 m wide. The southern wall profile revealed that the eastern end of the acequia was offset from the northern wall, approximately 60 cm to the east, indicating that the trench crosscut the acequia at an angle. Some similarities were noticed between this portion of the acequia and that uncovered within Playland Park, although, the Playland Park portion appears to have been truncated. Similarities between the two sections included the soil types encountered (i.e. the dark soil with cultural material). Once the documentation of the trench walls was complete the trench was filled in. After consultation with the THC and COSA-OHP, SAWS was permitted to install the waterline in the already excavated trench. No further investigations are recommended for this project as long as excavations did not further impact the acequia. All field records and photographs produced during investigations were curated at the Center for Archaeological Research at the University of Texas at San Antonio

A Cultural Resources Survey Of The Proposed Town Creek/Haeckerville Road Levee Project, Cibolo, Guadalupe County, Texas

In December 2014, Vickery and Associates (Client) contracted with Raba Kistner Environmental, Inc. (RKEI) to perform an intensive cultural resources survey of approximately 111-acres for the proposed Town Creek/Haeckerville Road Levee Project in Cibolo, Guadalupe County, Texas. The City of Cibolo is proposing improvements to the floodplain of Town Creek in Guadalupe County, Texas. The project consists of approximately 1.5 miles of drainage improvements, channel modifications, and minor levee or earth embankment construction along Town Creek. The project also will involve the reconstruction of Haeckerville Road and modifications to Schaeffer Road from S. Main to Haeckerville Road. The project easement is owned by a mix of City and private landowners. The archaeological crews investigated all but one private property for which no Right-of-Entry was secured prior to the field work. The purpose of this survey was to determine whether historic or prehistoric cultural resources are located within the Area of Potential Effect (APE), and if so, assess the significance and eligibility for designation as State Antiquities Landmarks (SALs) and for inclusion in the National Register of Historic Places (NRHP). The project was carried out between January 5 and 8, 2015 under Texas Antiquities Permit No. 7123. Dr. Steve A. Tomka served as Principal Investigator. Kristi Miller Nichols served as the Project Archaeologist and Mark Luzmoor, Chris Murray and Cyndi Dickey served as field technicians. A total of 34 shovel tests (STs) and three backhoe trenches were excavated within the APE. Surface visibility was around 90% throughout the APE. No buried or surface-exposed prehistoric materials were encountered during the survey. A historic homestead, 41GU169, was documented near the southern terminus of the project area. Two shovel tests excavated within the boundaries of the site were positive for historic materials. The historic site is a farmstead that likely was constructed circa 1920s. It is recommended that the site is potentially eligible for listing on the NRHP and for formal designation as a State Antiquities Landmark. Proposed project plans call for the acquisition of an access-easement thorough the site. This easement may impact one dilapidated outbuilding found on the site. No other negative impacts are expected. A second historic farmstead may be present on the property that could not be accessed during the survey. No detailed information exists on the condition of this site and therefore its eligibility cannot be assessed. With regards to the remainder of the project area, RKEI recommends that since construction activities will extend to a depth of 20 feet below surface, construction monitoring be carried out to document any cultural materials that may be buried below the reach of the current project activities (i.e. 1.5 meters or 5.5–feet). All project related documents, are permanently housed at the Texas Archeological Research Laboratory. No cultural material was collect over the course of the project