Integrable SU(m|n) supersymmetric electronic models of strong correlations

We generalize the SU(2|2) supersymmetric extended Hubbard model of 1/r2 interaction to the SU(m|n) supersymmetric case. Integrable models may be defined on both uniform lattice and non-uniform one dimensional lattices. We study both cases in detail and present the ground state wavefunctions and energy spectra of these models.Comment: 24 pages, Late

Thermal Modeling and Experimental Validation in the LENS™ Process

Several aspects of the thermal behavior of deposited stainless steel 410 (SS410) during the Laser Engineered Net Shaping (LENSTM) process were investigated experimentally and numerically. Thermal images in the molten pool and surrounding area were recorded using a two-wavelength imaging pyrometer system, and analyzed using ThermaVizTM software to obtain the temperature distribution. The molten pool size, temperature gradient, and cooling rate were obtained from the recorded history of temperature profiles. The dynamic shape of the molten pool, including the pool size in both travel direction and depth direction, was investigated and the effect of different process parameters was illustrated. The thermal experiments were performed in a LENSTM 850 machine with a 3kW IPG laser for different process parameters. A three-dimensional finite element model was developed to calculate the temperature distribution in the LENS process as a function of time and process parameters. The modeling results showed good agreement with the experimental data.Mechanical Engineerin

Sunday Friends: The Working Alternative to Charity

Sunday Friends is a non-profit organization in San José, California, that provides multiple activities for families who are in need of financial support. Given the particular location of the program, most families are Latino and bilingual. Participants and program volunteers form a community at an elementary school on a couple of scheduled Sundays each month. When family members participate in activities designed to educate, improve skills, and to give back to the larger community, they earn tickets that they can redeem for items that they need and want from the Sunday Friends store. Activities include healthy cooking projects, “Thank You Letter” writing, English-as-a-Second-Language programs, crafts, and education in nutrition and financial literacy. The program’s central focus is to empower families to break out of poverty. A specific guiding principal is the developmental assets approach promoted by the Search Institute in Minneapolis (http://www.search-institute.org/). This approach encourages individuals and organizations to work together toward a common goal of supporting the healthy development of all children and youth. Healthy development is conceptualized as consisting of the development of external assets (i.e., support, empowerment, boundaries and expectations, constructive activities) and internal assets (i.e., commitment to learning, positive values, social competencies, and positive identity). The 2009 evaluation’s primary focus was on whether Sunday Friends was succeeding at fostering developmental assets for children. Other relevant indicators of success were perceptions of program effectiveness, regard for program activities, and nutrition and healthy eating habits. Data were gathered from family members (adults and minors) during program activities using written surveys administered by volunteers to the research team (most of whom were bilingual). The families were recruited in person by program staff onsite. The questionnaires were written in English and Spanish (with the choice made by respondents). Sunday Friends volunteers were recruited to the study via email by Sunday Friends staff. They completed questionnaires through an online survey platform. In all, 74 parents or guardians, 67 children or youth, and 45 volunteers participated in the data collection. Across the three sets of surveys (parents or guardians, children or youth, and volunteers), there are fairly consistent results. The families and volunteers in the Sunday Friends program believe that Sunday Friends is effectively engaging them and meeting its goals. Overall, children and youth report positive experiences at Sunday Friends. On every dimension of psychological well-being, connectedness with others, and self-efficacy, the answers provided by children and youth indicate that Sunday Friends is promoting developmental assets. In addition, parents and guardians report that Sunday Friends has positive influences on their lives. The majority of measures, whether questions about self-efficacy, the effect of Sunday Friends on their children, or improved nutrition for their family, indicate that Sunday Friends is meeting its goals. Finally, volunteers agree that the program makes an important contribution to the lives of both children and adults. They also feel that Sunday Friends enhances their awareness of the community and contributes to making their personal lives more meaningful. The survey results presented here should be interpreted with caution because all persons surveyed were continuing participants in the program, and the cross-sectional data could not detect changes over time. Despite this caution, each group’s data and triangulation across family and volunteer surveys reveal that milestones are accomplished at Sunday Friends. It is safe to conclude that Sunday Friends’ community-based approach to empowering parents and youths is achieving its goals

Basis set generation and optimization in the NISQ era with Quiqbox.jl

In the noisy intermediate-scale quantum era, ab initio computation of the electronic structure problem has become one of the major benchmarks for identifying the boundary between classical and quantum computational power. The single-particle basis set plays a key role in the electronic structure methods implemented on both classical and quantum devices. To investigate the consequences of the single-particle basis set, we propose a framework for more customizable basis set generation and basis set optimization. This framework allows configurations of composite Gaussian-type basis functions to go beyond typical Gaussian-type basis set frameworks such as the atomic orbitals and floating basis sets. Such basis set generations set the stage for more flexible variational optimization of basis set parameters. To realize this framework, we have developed an open-source electronic structure package named ``Quiqbox'' in the Julia programming language. Both the Hartree--Fock procedure and Gaussian-based electronic integral computations are implemented in this package. We compare Quiqbox with the basis set optimization package DiffiQult and find faster convergence of the basis set optimization with lower run time. We also demonstrate the additional customizability Quiqbox brings for more systematic basis set research with an example of constructing and optimizing delocalized orbitals.Comment: 15 pages, 7 figures, 5 tables, 1 listin

Thermoelectric transport with electron-phonon coupling and electron-electron interaction in molecular junctions

Within the framework of nonequilibrium Green's functions, we investigate the thermoelectric transport in a single molecular junction with electron-phonon and electron-electron interactions. By transforming into a displaced phonon basis, we are able to deal with these interactions non-perturbatively. Then, by invoking the weak tunneling limit, we are able to calculate the thermoelectricity. Results show that at low temperatures, resonances of the thermoelectric figure of merit ZT occur around the sides of resonances of electronic conductance but drops dramatically to zero at exactly these resonant points. We find ZT can be enhanced by increasing electron-phonon coupling and Coulomb repulsion, and an optimal enhancement is obtained when these two interactions are competing. Our results indicate a great potential for single-molecular-junctions as good thermoelectric devices over a wide range of temperatures.Comment: 7+ pages, 3 figures, with updated appendix. Accepted by PR