264 research outputs found
How big is that? Reporting the Effect Size and Cost of ASSISTments in the Maine Homework Efficacy Study
Optical difference engine for defect inspection in highly-parallel manufacturing processes
Traditional defect inspection for highly-parallel manufacturing processes requires the processing of large measurement datasets, which is often not fast enough for in-situ inspection of large areas with high resolution. This study develops an all-optical difference engine for fast defect detection in highly-parallel manufacturing processes, where the detection of defects (differences from nominal) is performed optically and in real-time. Identification of defects is achieved through an optical Fourier transform and spatial filtering, detecting differences between two real objects by nulling information that is repeated in each object. The developed prototype device is demonstrated using geometric patterns of similar scale to components in printed electronic circuit
Diamond machining of freeform-patterned surfaces on precision rollers
Rapid development of freeform surfaces faces the challenges of not only higher form accuracy and smoother surface finishing, but also high machining efficiency and lower manufacturing cost. Combining diamond turning and roll-to-roll embossing technologies is a promising solution to fulfil these requirements. This paper presents a generic method to design and machine freeform surfaces on precision rollers. The freeform surface designed on the flat substrate is first transferred onto the cylindrical roller surface. The freeform-patterned roller surface is then diamond turned using the toolpath generated by a purposely developed toolpath generator. With the proposed method, the complex freeform surfaces designed on flat substrate can be transferred to and precisely machined on the cylindrical roller surfaces. A cutting experiment has been conducted to demonstrate the capability of the proposed method. In the experiment, a sinusoidal surface was designed and diamond turned on a precision roller. The results demonstrate that the proposed method is accurate and effective. The proposed method provides guidance for the design and precision manufacturing of freeform-patterned surfaces on precision rollers
Hybrid algorithms to solve linear systems of equations with limited qubit resources
The solution of linear systems of equations is a very frequent operation and
thus important in many fields. The complexity using classical methods increases
linearly with the size of equations. The HHL algorithm proposed by Harrow et
al. achieves exponential acceleration compared with the best classical
algorithm. However, it has a relatively high demand for qubit resources and the
solution is in a normalized form. Assuming that the
eigenvalues of the coefficient matrix of the linear systems of equations can be
represented perfectly by finite binary number strings, three hybrid iterative
phase estimation algorithms (HIPEA) are designed based on the iterative phase
estimation algorithm in this paper. The complexity is transferred to the
measurement operation in an iterative way, and thus the demand of qubit
resources is reduced in our hybrid algorithms. Moreover, the solution is stored
in a classical register instead of a quantum register, so the exact
unnormalized solution can be obtained. The required qubit resources in the
three HIPEA algorithms are different. HIPEA-1 only needs one single ancillary
qubit. The number of ancillary qubits in HIPEA-2 is equal to the number of
nondegenerate eigenvalues of the coefficient matrix of linear systems of
equations. HIPEA-3 is designed with a flexible number of ancillary qubits. The
HIPEA algorithms proposed in this paper broadens the application range of
quantum computation in solving linear systems of equations by avoiding the
problem that quantum programs may not be used to solve linear systems of
equations due to the lack of qubit resources.Comment: 22 pages, 6 figures, 6 tables, 48 equation
Online Mathematics Homework Increases Student Achievement
In a randomized field trial with 2,850 seventh-grade mathematics students, we evaluated whether an educational technology intervention increased mathematics learning. Assigning homework is common yet sometimes controversial. Building on prior research on formative assessment and adaptive teaching, we predicted that combining an online homework tool with teacher training could increase learning. The online tool ASSISTments (a) provides timely feedback and hints to students as they do homework and (b) gives teachers timely, organized information about students’ work. To test this prediction, we analyzed data from 43 schools that participated in a random assignment experiment in Maine, a state that provides every seventh-grade student with a laptop to take home. Results showed that the intervention significantly increased student scores on an end-of-the-year standardized mathematics assessment as compared with a control group that continued with existing homework practices. Students with low prior mathematics achievement benefited most. The intervention has potential for wider adoption
Symmetric or asymmetric glide resistance to twinning disconnection?
Successive gliding of twinning disconnections (TDs) creates three-dimensional twins in parent crystal and accommodates shear deformation. It is generally recognized that TD is subject to the same Peierls stress as it glides forward or backward because of its dislocation character and the twofold rotation symmetry of the twin plane. Based on atomistic simulations, we demonstrate that the glide of TDs may be subject to a symmetric or asymmetric resistance corresponding to step character, symmetric resistance for A/A type steps but asymmetric resistance for A/B type steps, where A and B represent crystallographic planes in twin and matrix. Furthermore, we experimentally demonstrate that the asymmetric resistance results in asymmetric propagation and growth of twins in Mg alloys
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