Energy Transfer in Europium Doped Potassium Chloride

Physic

Up Rooting: Sports Marketing Analytics and Attendance in Major League Baseball

Spurred by a continuous decline in Major League Baseball (MLB) ticket sales and attendance, this study examines external and internal factors affecting team financial performance. Using only secondary data, constructs for external factors (i.e. population, facility age, etc.), team offensive performance (i.e. at-bats, home runs, etc.), attendance, and revenue-based financial metrics were analyzed with PLS-SEM. The findings reveal external factors positively affect both attendance and team financials, but the relationship between a team’s offensive performance and team financials is fully mediated by attendance. The findings imply future sales growth may need to come from marketing strategies and promotional efforts beyond a team’s surrounding geographical area, and possibly through the adoption of new technology to reach their target market

Game Development for Computer Science Education (Extended Abstract)

Educators have long used digital games as platforms for teaching. Games tend to have several qualities that aren’t typically found in homework: they situate problems within a compelling alternate reality that unfolds through intriguing narrative, they draw more upon a player’s intrinsic motivations than extrinsic ones, they facilitate deliberate low intensity practice, and they emphasize a spirit of play instead of work. At ITiCSE 2016, this working group convened to survey the landscape of existing digital games that have been used to teach and learn computer science concepts. Our group discovered that these games lacked explicitly defined learning goals and even less evaluation of whether or not the games achieved these goals. As part of this process, we identified and played over 120 games that have been released or described in literature as means for learning computer science concepts. In our report, we classified how these games support the learning objectives outlined in the ACM/IEEE Computer Science Curricula 2013. While we found more games than we expected, few games explicitly stated their learning goals and even fewer were evaluated for their capacity to meet these goals. Most of the games we surveyed fell into two categories: short-lived proof-of-concept projects built by academics or closed-source games built by professional developers. Gathering adequate learning data is challenging in either situation. Our original intent for the second year of our working group was to prepare a comprehensive framework for collecting and analyzing learning data from computer science learning games. Upon further discussion, however, we decided that a better next step is to validate the design and development guidelines that we put forth in our final report for ITiCSE 2016. We extend this working group to a second year—with a mission to collaboratively develop a game with clearly defined learning objectives and define a methodology for evaluating its capacity to meet its goals

Analysis of the spectra of trivalent erbium in multiple sites of hexagonal aluminum nitride

The 12 K cathodoluminescence spectra of Er3+ doped into single crystals of aluminum nitride (2H-AlN) in the hexagonal phase are reported between 320 nm and 775 nm. The emission spectra represent transitions from the lower Stark level of 2P(3/2) to the Stark levels of the 4I(15/2), 4I(13/2), 4I(11/2), 4I(9/2), 4F(9/2), and 4S(3/2) multiplet manifolds of Er3+(4f(11)). Emission spectra from 4S(3/2) to 4I(15/2) are also reported. All observed strong line emission are accounted for in terms of two principle sites, denoted site a and site b , with a few line spectra attributed to additional sites. A parameterized Hamiltonian that includes the atomic and crystal-field terms for Er3+(4f(11)) (2S+1)L_J was used to determine the symmetry and the crystal field splitting of the a and b sites. A descent in symmetry calculation was carried out to determine if distortion due to the size difference between Er, Al and the vacancies can be discerned. Modeling results assuming C_3v and C_1h are discussed. It appears that the sensitivity to a C_1h model is not sufficient to invalidate the choice of C_3v as an approximate symmetry for both sites. The g-factors reported from an EPR study of Er3+ in single-crystal AlN are in reasonable agreement with calculated g-factors for Er3+ in the a site assuming C_3v symmetry

Site-selective excitation and polarized absorption and emission spectra of trivalent thulium and erbium in strontium fluorapatite

Polarized fluorescence spectra produced by site-selective excitation, and conventional polarized absorption spectra were obtained for Tm3+ and Er3+ ions individually incorporated into single crystals of strontium fluorapatite, Sr-5(PO4)(3)F, also known as SFAP. Substitution of the trivalent rare earth ion for divalent strontium was achieved by passive charge compensation during Czochralski growth of the fluorapatite crystals. Spectra were obtained between 1780 and 345 nm at temperatures from 4 K to room temperature on crystals having the hexagonal structure [P6(3)/m(C-6h(2))]. The polarized fluorescence spectra due to transitions from multiplet manifolds of Tm3+(4f(12)), including D-1(2), (1)G(4), and H-3(4) to manifolds H-3(6) (the ground-state manifold), F-3(4), H-3(5), H-3(4), and F-3(3) were analyzed for the details of the crystal-field splitting of the manifolds. Fluorescence Lifetimes were measured for Tm3+ transitions from D-1(2), (1)G(4), and H-3(4) at room temperature and from (1)G(4) at 16 K. Results of the analysis indicate that the majority of Tm3+ ions occupy sites having C-s symmetry. A point-charge lattice-sum calculation was made in which the crystal-field components, A(nm), were determined assuming that trivalent thulium replaces divalent strontium in the metal site having C-s symmetry. Results support the conclusion that the nearest-neighbor fluoride (F-) is replaced by divalent oxygen (O2-), thus preserving overall charge neutrality and local symmetry. Crystal-field splitting calculations predict energy levels in agreement with results obtained from an analysis of the experimental data. By varying the crystal-field parameters, B-nm, we obtained a rms difference of 7 cm(-1) between 43 calculated and experimental Stark levels for Tm3+(4f(12)) in Tm:SFAP. Absorption and fluorescence spectra are also reported for Er3+ ions in Er:SFAP. Measurement of the temporal decay of the room temperature fluorescence from the I-4(11/2) and I-4(13/2) manifolds yielded fluorescence lifetimes of 230+/-20 mu s and 8.9+/-0.1 ms, respectively. The experimental Stark levels obtained from an analysis of the spectroscopic data were compared with a crystal-field splitting calculation. The initial set of B-nm parameters for Er3+(4f(11)) was established from the three-parameter theory and the final set of B-nm parameters obtained for Tm3+(4f(12)) in Tm:SFAP. The best overall agreement between calculated and experimental Stark levels is 8 cm(-1) for 48 Stark levels, representing 12 observed multiplet manifolds of Er3+(4f(11)) in Er:SFAP