Innovative Opportunities for Elementary and Middle School Teachers to Maintain Currency in Mathematics and Science: A Community College-School System Partnership

Since 1992 the Manassas Campus of Northern Virginia Community College – in response to requests from local school systems – has developed four innovative methods of assisting elementary, secondary and middle school teachers to enhance their content knowledge in science and mathematics, as well as integrate curriculum units for classroom presentation. These methods are based on the assumptions that: - While teachers at this level have fundamental understanding of math and science, if they wish to incorporate new concepts or technologies from these fields, graduate level content courses are generally beyond their background level. - Community College faculty can often provide a bridge that connects advanced content in science and mathematics with the applications that can be adapted to elementary/middle school curriculum. - Presenting content to a mixed audience of teachers from K-8 allows teachers to see how content can be adapted to grade levels above and below. - Content delivery methods must be interactive and must be responsive to the multiple demands on these teachers’ time. This requires flexibility in scheduling and course requirements

Development of a low-cost, electricity-generating Rankine cycle, alcohol-fuelled cooking stove for rural communities

This article describes a novel design and construction of a helical tube flash boiler that uses a 2kW nominal methylated spirit burner to heat an approximately 2.5m long coil of copper pipe fed by a nominal 8 bar electrically operated solenoid water pump. The final embodiment is for superheated steam to be converted to electricity and the waste exit heat from the generator used either for cooking or for ethanol pro duction for low-income families in developing countries. The performance of the flash boiler has been evaluated experimentally based on the well-known “Direct-Method”; by carefully measuring both the flow of the fuel and the steam. It found that the pressure inside the pipe can reach up to 7.4 bar and the temperature of the steam released by the flashing process can reach 255°C utilising a low-cost water pump. The research results prese nted in this paper demonstrate that flash boiler stove has a great potential for generating high-temperature steam for developing a low-cost cooking stove

Power law burst and inter-burst interval distributions in the solar wind: turbulence or dissipative SOC ?

We calculate for the first time the probability density functions (PDFs) P of burst energy e, duration T and inter-burst interval tau for a known turbulent system in nature. Bursts in the earth-sun component of the Poynting flux at 1 AU in the solar wind were measured using the MFI and SWE experiments on the NASA WIND spacecraft. We find P(e) and P(T) to be power laws, consistent with self-organised criticality (SOC). We find also a power law form for P(tau) that distinguishes this turbulent cascade from the exponential P(tau) of ideal SOC, but not from some other SOC-like sandpile models. We discuss the implications for the relation between SOC and turbulence.Comment: 3 pages, 1 figure. Submitted to PRL on 25th February 2000. Revised version re-submitted on 9th May 2000. Second revised version submitted Phys. Rev. E on 26th June, 200

Using Monte Carlo Search With Data Aggregation to Improve Robot Soccer Policies

RoboCup soccer competitions are considered among the most challenging multi-robot adversarial environments, due to their high dynamism and the partial observability of the environment. In this paper we introduce a method based on a combination of Monte Carlo search and data aggregation (MCSDA) to adapt discrete-action soccer policies for a defender robot to the strategy of the opponent team. By exploiting a simple representation of the domain, a supervised learning algorithm is trained over an initial collection of data consisting of several simulations of human expert policies. Monte Carlo policy rollouts are then generated and aggregated to previous data to improve the learned policy over multiple epochs and games. The proposed approach has been extensively tested both on a soccer-dedicated simulator and on real robots. Using this method, our learning robot soccer team achieves an improvement in ball interceptions, as well as a reduction in the number of opponents' goals. Together with a better performance, an overall more efficient positioning of the whole team within the field is achieved

A note on leapfrogging vortex rings

In this paper we provide examples, by numerical simulation using the Navier-Stokes equations for axisymmetric laminar flow, of the 'leapfrogging' motion of two, initially identical, vortex rings which share a common axis of symmetry. We show that the number of clear passes that each ring makes through the other increases with Reynolds number, and that as long as the configuration remains stable the two rings ultimately merge to form a single vortex ring

The Influence of Heat Input Ratio on Electrical Power Output of a Dual-Core Travelling-Wave Thermoacoustic Engine

This paper presents an analytical and experimental investigation of an electricity generator that employs a two-stage looped tube travellin -wave thermoacoustic prime-mover to deliver acoustic power from heat energy, a loudspeaker to extract electricity from sound energy and a tuning stub to compensate the changes in the acoustic field within the engine to enable close to travelling wave operation at the loudspeaker. Furthermore, the paper explains how to enhance the output power utilizing different heat input ratios through the engine cores. A well-known thermoacoustic design tool called Delta EC is used to simulate the wave propagation through the different parts of the system. The electrical power predicted from the low-cost prototype was 24.4 W acoustic power which confirms the potential for developing low-cost thermoacoustic electricity generator for heat recov ery from low-grade heat sources. The electrical power can be increased to 31.3 W using different heating power percentages through the two units. The verified experimental data shows good agreement with DeltaEC results

Sensitivity of mixing layers to three-dimensional forcing

It is well known that turbulent mixing layers are dominated by large scale, fairly coherent structures, and that these structures are related to the stability characteristics of the flow. These facts have led researchers to attempt controlling such flows by selectively forcing certain unstable modes, which can in addition have the effect of suppressing other modes. Much of the work on controlling the mixing layer has relied on forcing 2-D instabilities. The results of forcing 3-D instabilities are addressed. The objectives of the work are twofold: to understand how a mixing layer responds to 3-D perturbations, and to test the validity of an amplitude expansion in predicting the mixing layer development. The amplitude expansion could be very useful in understanding and predicting the 3-D response of the flow to a variety of initial conditions

CHROMOSOME NUMBERS OF RELEASED CULTIVARS OF SWITCHGRASS, INDIANGRASS, BIG BLUESTEM, AND SAND BLUESTEM

Chromosome numbers of cultivars of switchgrass (Panicum virgatum L.), indiangrass (Sorghastrum nutans L.) and the tall bluestem complex of big bluestem (Andropogon gerardi Vitman.) and sand bluestem (Andropogon hallii Hack.) were determined. Ploidy levels of these cultivars have not been reported previously even though these grasses have been reported to have two or more ploidy levels. Switchgrass cultivars \u27Pathfinder\u27, \u27Blackwell\u27, and \u27Nebraska 28\u27 were hexaploids (2n = 54), while \u27Summer\u27 and \u27Kanlow\u27 were tetraploids (2n = 36). Indiangrass cultivars \u27Nebraska 54\u27, \u27Oto\u27, \u27Osage\u27, and \u27Holt\u27 were all tetraploids (2n = 40). Big bluestem cultivars \u27Pawnee\u27 and \u27Kaw\u27 and the sand bluestem cultivar \u27Goldstrike\u27 were hexaploids (2n = 60). Meiosis was normal with bivalent pairing for most plants examined from all three grasses