623 research outputs found
Accounting for exogenous influences in a benevolent performance evaluation of teachers
Students’ evaluations of teacher performance (SETs) are increasingly used by universities and colleges for teaching improvement and decision making (e.g., promotion or tenure). However, SETs are highly controversial mainly due to two issues: (1) teachers value various aspects of excellent teaching differently, and, to be fair, (2) SETs should be determined solely by the teacher’s actual performance in the classroom, not by other influences (related to the teacher, the students or the course) which are not under his or her control. To account for these two issues, this paper constructs SETs using a specially tailored version of the popular non-parametric Data Envelopment Analysis (DEA) approach. In particular, in a so-called ‘Benefit of the doubt’ model we account for different values and interpretations that teachers attach to ‘good teaching’. Within this model, we reduce the impact of measurement errors and a-typical observations, and account explicitly for heterogeneous background characteristics arising from teacher, student and course characteristics. To show the potentiality of the method, we examine teacher performance for the Hogeschool Universiteit Brussel (located in Belgium). Our findings suggest that heterogeneous background characteristics play an important role in teacher performance.Teacher performance, Data envelopment analysis, Conditional efficiency, Education.
To publish or not to publish? On the aggregation and drivers of research performance
This paper presents a methodology to aggregate multidimensional research output. Using a tailored version of the non-parametric Data Envelopment Analysis model, we account for the large heterogeneity in research output and the individual researcher preferences by endogenously weighting the various output dimensions. The approach offers three important advantages compared to the traditional approaches: (1) flexibility in the aggregation of different research outputs into an overall evaluation score; (2) a reduction of the impact of measurement errors and a-typical observations; and (3) a correction for the influences of a wide variety of factors outside the evaluated researcher’s control. As a result, research evaluations are more effective representations of actual research performance. The methodology is illustrated on a data set of all faculty members at a large polytechnic university in Belgium. The sample includes questionnaire items on the motivation and perception of the researcher. This allows us to explore whether motivation and background characteristics (such as age, gender, retention, etc.,) of the researchers explain variations in measured research performance
Engineered valley-orbit splittings in quantum confined nanostructures in silicon
An important challenge in silicon quantum electronics in the few electron
regime is the potentially small energy gap between the ground and excited
orbital states in 3D quantum confined nanostructures due to the multiple valley
degeneracies of the conduction band present in silicon. Understanding the
"valley-orbit" (VO) gap is essential for silicon qubits, as a large VO gap
prevents leakage of the qubit states into a higher dimensional Hilbert space.
The VO gap varies considerably depending on quantum confinement, and can be
engineered by external electric fields. In this work we investigate VO
splitting experimentally and theoretically in a range of confinement regimes.
We report measurements of the VO splitting in silicon quantum dot and donor
devices through excited state transport spectroscopy. These results are
underpinned by large-scale atomistic tight-binding calculations involving over
1 million atoms to compute VO splittings as functions of electric fields, donor
depths, and surface disorder. The results provide a comprehensive picture of
the range of VO splittings that can be achieved through quantum engineering.Comment: 4 pages, 4 figure
Lifetime enhanced transport in silicon due to spin and valley blockade
We report the observation of Lifetime Enhanced Transport (LET) based on
perpendicular valleys in silicon by transport spectroscopy measurements of a
two-electron system in a silicon transistor. The LET is manifested as a
peculiar current step in the stability diagram due to a forbidden transition
between an excited state and any of the lower energy states due perpendicular
valley (and spin) configurations, offering an additional current path. By
employing a detailed temperature dependence study in combination with a rate
equation model, we estimate the lifetime of this particular state to exceed 48
ns. The two-electron spin-valley configurations of all relevant confined
quantum states in our device were obtained by a large-scale atomistic
tight-binding simulation. The LET acts as a signature of the complicated valley
physics in silicon; a feature that becomes increasingly important in silicon
quantum devices.Comment: 4 pages, 4 figures. (The current version (v3) is the result of
splitting up the previous version (v2), and has been completely rewritten
Spin Wave Response in the Dilute Quasi-one Dimensional Ising-like Antiferromagnet CsCo_{0.83}Mg_{0.17}Br_3
Inelastic neutron scattering profiles of spin waves in the dilute
quasi-one-dimensional Ising-like antiferromagnet CsCo_{0.83}Mg_{0.17}Br_3 have
been investigated. Calculations of S^{xx}(Q,omega), based on an effective spin
Hamiltonian, accurately describe the experimental spin wave spectrum of the 2J
mode. The Q dependence of the energy of this spin wave mode follows the
analytical prediction
omega_{xx}(Q)=(2J)(1-5epsilon^{2}cos^{2}Qa+2epsilon^{2})^{1/2}, calculated by
Ishimura and Shiba using perturbation theory.Comment: 13 pages, 4 figure
Enhancing workflow-nets with data for trace completion
The growing adoption of IT-systems for modeling and executing (business)
processes or services has thrust the scientific investigation towards
techniques and tools which support more complex forms of process analysis. Many
of them, such as conformance checking, process alignment, mining and
enhancement, rely on complete observation of past (tracked and logged)
executions. In many real cases, however, the lack of human or IT-support on all
the steps of process execution, as well as information hiding and abstraction
of model and data, result in incomplete log information of both data and
activities. This paper tackles the issue of automatically repairing traces with
missing information by notably considering not only activities but also data
manipulated by them. Our technique recasts such a problem in a reachability
problem and provides an encoding in an action language which allows to
virtually use any state-of-the-art planning to return solutions
A hybrid double-dot in silicon
We report electrical measurements of a single arsenic dopant atom in the
tunnel-barrier of a silicon SET. As well as performing electrical
characterization of the individual dopant, we study series electrical transport
through the dopant and SET. We measure the triple points of this hybrid double
dot, using simulations to support our results, and show that we can tune the
electrostatic coupling between the two sub-systems.Comment: 11 pages, 6 figure
Stark tuning of the charge states of a two-donor molecule in silicon
Gate control of phosphorus donor based charge qubits in Si is investigated
using a tight-binding approach. Excited molecular states of P2+ are found to
impose limits on the allowed donor separations and operating gate voltages. The
effects of surface (S) and barrier (B) gates are analyzed in various voltage
regimes with respect to the quantum confined states of the whole device.
Effects such as interface ionization, saturation of the tunnel coupling,
sensitivity to donor and gate placement are also studied. It is found that
realistic gate control is smooth for any donor separation, although at certain
donor orientations the S and B gates may get switched in functionality. This
paper outlines and analyzes the various issues that are of importance in
practical control of such donor molecular systems.Comment: 8 pages, 9 figure
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