The absence of efficient dual pairs of spanning trees in planar graphs

A spanning tree T in a finite planar connected graph G determines a dual spanning tree T* in the dual graph G such that T and T* do not intersect. We show that it is not always possible to find T in G, such that the diameters of T and T* are both within a uniform multiplicative constant (independent of G) of the diameters of their ambient graphs.Comment: 7 pages, 3 figure

A study of early stopping, ensembling, and patchworking for cascade correlation neural networks

The constructive topology of the cascade correlation algorithm makes it a popular choice for many researchers wishing to utilize neural networks. However, for multimodal problems, the mean squared error of the approximation increases significantly as the number of modes increases. The components of this error will comprise both bias and variance and we provide formulae for estimating these values from mean squared errors alone. We achieve a near threefold reduction in the overall error by using early stopping and ensembling. Also described is a new subdivision technique that we call patchworking. Patchworking, when used in combination with early stopping and ensembling, can achieve an order of magnitude improvement in the error. Also presented is an approach for validating the quality of a neural network’s training, without the explicit use of a testing dataset

Improving the performance of cascade correlation neural networks on multimodal functions

Intrinsic qualities of the cascade correlation algorithm make it a popular choice for many researchers wishing to utilize neural networks. Problems arise when the outputs required are highly multimodal over the input domain. The mean squared error of the approximation increases significantly as the number of modes increases. By applying ensembling and early stopping, we show that this error can be reduced by a factor of three. We also present a new technique based on subdivision that we call patchworking. When used in combination with early stopping and ensembling the mean improvement in error is over 10 in some cases

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

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

Population Update, Report Number 3

There is more to population study than merely knowing how many people live in a geographical location. Two of the most important other aspects of demography are the age and sex composition of a population. Should planners be thinking about adding space to a grammar school or to a retirement center? By studying age and sex compositions, they will make more accurate decisions. The distribution of a population by age and sex is often shown in a pyramid. The bars in the pyramid (see inside) represent age groups spaced at 5-year intervals. The pyramid is also divided in the middle, with the males at the left and the females at the right. State pyramids for 1960, 1970, and 1975 point up interesting trends. One of the most significant is a lowered birth rate. Thus, the base of the pyramid reflecting the children is shrinking. Statewide services required for the very young may not need expansion. On the other hand, those born around 1960, when the birth rate was higher, are now young adults and form an exaggerated proportion of the state\u27s population. Jobs and higher education are their major concerns. Should we build more colleges and technical schools to accommodate these young people? Look at the age structure at the bottom of the pyramid. In 10 years who is going to fill those schools? Perhaps educators should think in terms of temporary measures to alleviate present difficulties- extension courses, night classes, and the like. Population ratios and indexes like those under the detailed state totals can also be useful. Although pyramids are not portrayed, indexes and ratios as described below are provided for each county

Population Update, Report Number 2

It might be suggested that economics are important in a reverse sort of way. No longer can urban centers offer economic opportunity to potential rural outmigrants, and these people are simply staying at home. Between 1960 and 1970, 53 of South Dakota\u27s 67 counties were losing population. At an extreme, Stanley County dropped 40%; Fall River 30%; and Clark, Harding and Jackson lost nearly one fourth of their inhabitants. In the next 5 years (1970-1975) these same counties had not only stopped losing, but were actually gaining population. While only 14 counties gained population between 1960 and 1970, 38 showed gains between 1970 and 1975. Of the 29 counties still losing population, 19 lost a smaller percentage from 1970 to 1975 than in the decade from 1960 to 1970. Only two counties that gained population between 1960 and 1970 (Yankton and Lawrence) lost population between 1970 and 1975

Goal driven optimization of process parameters for maximum efficiency in laser bending of advanced high strength steels

Laser forming or bending is fast becoming an attractive option for the forming of advanced high strength steels (AHSS), due primarily to the reduced formability of AHSS when compared with conventional steels in traditional contact-based forming processes. An inherently iterative process, laser forming must be optimized for efficiency in order to compete with contact based forming processes; as such, a robust and accurate method of optimal process parameter prediction is required. In this paper, goal driven optimization is conducted, utilizing numerical simulations as the basis for the prediction of optimal process parameters for the laser bending of DP 1000 steel. A key consideration of the optimization process is the requirement for minimal microstructural transformation in automotive grade high strength steels such as DP 1000

Metrology: Measurement Assurance Program Guidelines

The 5300.4 series of NASA Handbooks for Reliability and Quality Assurance Programs have provisions for the establishment and utilization of a documented metrology system to control measurement processes and to provide objective evidence of quality conformance. The intent of these provisions is to assure consistency and conformance to specifications and tolerances of equipment, systems, materials, and processes procured and/or used by NASA, its international partners, contractors, subcontractors, and suppliers. This Measurement Assurance Program (MAP) guideline has the specific objectives to: (1) ensure the quality of measurements made within NASA programs; (2) establish realistic measurement process uncertainties; (3) maintain continuous control over the measurement processes; and (4) ensure measurement compatibility among NASA facilities. The publication addresses MAP methods as applied within and among NASA installations and serves as a guide to: control measurement processes at the local level (one facility); conduct measurement assurance programs in which a number of field installations are joint participants; and conduct measurement integrity (round robin) experiments in which a number of field installations participate to assess the overall quality of particular measurement processes at a point in time