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Planar cellular lattice structures subject to axial compression may undergo elastic bending or buckling of the unit cells. If sufficient compression is applied, the columns of adjacent cells make contact. This changes the topology of the lattice by establishing new load paths. This topology change induces a corresponding shift in the effective stiffness characteristics of the lattice — in particular, the shear modulus undergoes a step-change. The ability to embed adaptive stiffness characteristics through a topology change allows structural reconfiguration to meet changing load/operational requirements efficiently. The concept, of topological reconfiguration, can be exploited across a range of length scales, from (meta-)materials to components. Here we focus on macroscopic behaviour presenting results obtained from finite element analysis that shows excellent correlation with the observed response of 3D-printed PLA lattices. Through a parametric study, we explore the role of key geometric and stiffness parameters and identify desirable regions of the design space. The non-linear responses demonstrated by this topology morphing lattice structure may offer designers a route to develop bespoke elastic systems.

Empirical studies of the relationship between school inputs and test scores typically do not account for the fact that households will respond to changes in school inputs. This paper presents a dynamic household optimization model relating test scores to school and household inputs, and tests its predictions in two very different low-income country settings -- Zambia and India. The authors measure household spending changes and student test score gains in response to unanticipated as well as anticipated changes in school funding. Consistent with the optimization model, they find in both settings that households offset anticipated grants more than unanticipated grants. They also find that unanticipated school grants lead to significant improvements in student test scores but anticipated grants have no impact on test scores. The results suggest that naïve estimates of public education spending on learning outcomes that do not account for optimal household responses are likely to be considerably biased if used to estimate parameters of an education production function.

The practical viability of performance-based pay programs for teachers depends critically on the extent of support the idea will receive from teachers. We present evidence on teacher opinions with regard to performance-based pay from teacher interviews conducted in the context of an experimental evaluation of a program that provided performance-based bonuses to teachers in the Indian state of Andhra Pradesh. We report four main findings in this paper: (1) over 80% of teachers had a favorable opinion about the idea of linking a component of pay to measures of performance, (2) exposure to an actual incentive program increased teacher support for the idea, (3) teacher support declines with age, experience, training, and base pay, and (4) the extent of teachers' stated ex-ante support for performance-linked pay (over a series of mean- preserving spreads of pay) is positively correlated with their ex-post performance as measured by estimates of teacher value addition. This suggests that teachers are aware of their own effectiveness and that implementing a performance-linked pay program could not only have broad-based support among teachers but also attract more effective teachers into the teaching profession.

Performance pay for teachers is frequently suggested as a way of improving education outcomes in schools, but the theoretical predictions regarding its effectiveness are ambiguous and the empirical evidence to date is limited and mixed. We present results from a randomized evaluation of a teacher incentive program implemented across a large representative sample of government-run rural primary schools in the Indian state of Andhra Pradesh. The program provided bonus payments to teachers based on the average improvement of their students' test scores in independently administered learning assessments (with a mean bonus of 3% of annual pay). At the end of two years of the program, students in incentive schools performed significantly better than those in control schools by 0.28 and 0.16 standard deviations in math and language tests respectively. They scored significantly higher on "conceptual" as well as "mechanical" components of the tests, suggesting that the gains in test scores represented an actual increase in learning outcomes. Incentive schools also performed better on subjects for which there were no incentives, suggesting positive spillovers. Group and individual incentive schools performed equally well in the first year of the program, but the individual incentive schools outperformed in the second year. Incentive schools performed significantly better than other randomly-chosen schools that received additional schooling inputs of a similar value.

A temperature compensation method is proposed for CNT-composite strain sensors. CNT-composite sensors are fabricated on an elastic polymer substrate having known thermo-mechanical properties to introduce thermo-mechanical strain and further calibration of the sensor. Strain is induced on the sensor by bending the substrate as a cantilever configuration. Response of the sensor is measured using a bridge circuit method. Induced strain in the beam is determined using beam theory. The sensors are characterized for different CNT concentrations and at various temperatures. A model based temperature compensation scheme is proposed and verified experimentally. The result proves the ability of CNT-nanocomposite strain sensors to be used under varying temperature applications. A method is proposed to determine the strain and temperature simultaneously. The CNT sensors are simple to fabricate in complex patterns with excellent repeatability and do not require bonding layer.

The large-scale expansion of primary schooling in developing countries has led to the increasing use of non-civil-service contract teachers who are hired locally by the school, are not professionally trained, have fixed-term renewable contracts, and are paid much lower salaries than regular civil-service teachers. This has been a controversial policy, but there is limited evidence on the effectiveness of contract teachers in improving student learning. We present experimental evidence on the impact of contract teachers using data from an 'as is' expansion of contract-teacher hiring across a representative sample of 100 randomly-selected government-run rural primary schools in the Indian state of Andhra Pradesh. At the end of two years, students in schools with an extra contract teacher performed significantly better than those in comparison schools by 0.16σ and 0.15σ, in math and language tests respectively. Contract teachers were also much less likely to be absent from school than civil-service teachers (18% vs. 27%). Combining the experimental reduction in school-level pupil-teacher ratio (PTR) induced by the provision of an extra contract teacher, with high-quality panel data estimates of the impact of reducing PTR with a regular civil-service teacher, we show that contract teachers are not only effective at improving student learning outcomes, but that they are no less effective at doing so than regular civil-service teachers who are more qualified, better trained, and paid five times higher salaries.Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

We present experimental evidence on the impact of a programme that provided low-stakes diagnostic tests and feedback to teachers, and low-stakes monitoring of classroom processes across a representative set of schools in the Indian state of Andhra Pradesh. We find teachers in treatment schools exerting more effort when observed in the classroom but students in these schools do no better on independently-administered tests than students in schools that did not receive the programme. This suggests that though teachers in the programme schools worked harder while being observed, there was no impact of the feedback and monitoring on student learning outcomes.

This study evaluates the impact of a community-based information campaign on school performance from a cluster randomized control trial. The campaign consisted of eight to nine public meetings in each of 340 treatment villages across three Indian states to disseminate information to the community about its state mandated roles and responsibilities in school management. The findings from the first follow-up 2-4 months after the campaign show that providing information through a structured campaign to communities had a positive impact in all three states. In two states there was a significant and positive impact on reading (14-27 percent) in one of the three grades tested; in the third state there was a significant impact on writing in one grade (15 percent) and on mathematics in the other grade tested (27 percent). The intervention is associated with improvement in teacher effort in two states. Some improvements occurred in the delivery of certain benefits entitled to students (stipend, uniform, and mid day meal) and in process variables such as community participation in each of the three states. Follow-up research needs to examine whether there is a systematic increase in learning when the impact is measured over a longer time period and whether a campaign sustained over a longer time is able to generate greater impact on school outcomes.

This paper presents findings from baseline surveys on student learning achievement, teacher effort and community participation in three Indian states, Karnataka, Madhya Pradesh and Uttar Pradesh. Results indicate low teacher attendance and poor student learning. Parents and school committees are neither aware of their oversight roles nor participating in school management. However, there is substantial heterogeneity in outcomes across states. Karnataka has better student and teacher outcomes as well as higher levels of community awareness and participation than the other two states. The authors find substantial variation in teacher effort within schools, but most observable teacher characteristics are not associated with teacher effort. One reason for low teacher effort may be lack of accountability. Regression analysis suggests low rates of teacher attendance are only part of the problem of low student achievement. The gains in test scores associated with higher rates of attendance and engagement in teaching are small in the states of Madhya Pradesh and Uttar Pradesh, suggesting teachers themselves may not be effective. Ineffective teaching may result from lack of accountability as well as poor professional development of teachers. Further research is needed to examine not only issues of accountability but also professional development of teachers.

This study investigates the dynamic properties of a sandwich beam with magnetorheological (MR) fluid as a core material between the two layers of the continuous elastic structure. Timoshenko beam theory has been employed to derive the governing differential equation of motion in the finite element form for the transverse vibration response of MR fluid sandwich beam. The validation of the developed finite element formulation is demonstrated by comparing the results in terms of natural frequencies evaluated with those of available literature. Various parametric studies are also performed in terms of variations of the natural frequencies and loss factor as functions of the applied magnetic field and thickness of the MR fluid layer for various boundary conditions.