The tipping point: F-score as a function of the number of retrieved items

One of the best known measures of information retrieval (IR) performance is the F-score, the harmonic mean of precision and recall. In this article we show that the curve of the F-score as a function of the number of retrieved items is always of the same shape: a fast concave increase to a maximum, followed by a slow decrease. In other words, there exists a single maximum, referred to as the tipping point, where the retrieval situation is ‘ideal’ in terms of the F-score. The tipping point thus indicates the optimal number of items to be retrieved, with more or less items resulting in a lower F-score. This empirical result is found in IR and link prediction experiments and can be partially explained theoretically, expanding on earlier results by Egghe. We discuss the implications and argue that, when comparing F-scores, one should compare the F-score curves’ tipping points.     

Heat transfer in packed bed heat recuperators-II. The film coefficient for dry sorbent solids

An elaborate experimental set up is described that was used to measure the thermal expiration curves of heat recuperators, that had been constructed with guard heaters and vacuum insulation to minimize heat losses. A much more general model is used along with a precision numerical analysis technique to show that a film coefficient correlation of the Dittus-Boelter type did an excellent job of representing the results from 162 runs in which three feed gas temperatures, two flow rates, two particle size ranges, one bed diameter and five desciccants were used. For comparison sake the reported film coefficient correlation is finally assembled in a table along with others found in the literature.     

Re及Ma对边界层的影响分析

本文分析了跨音速流中Ma及Re对边界层的影响,结论为Ma的增加使得激波强度增加,流向逆压梯度增加,边界层厚度增加较快,容易分离;Re的增加有两个效应：一是使得转捩提前,二是使得边界层变薄。R e增加使得激波后机翼表面压力降低,升力损失减小。跨音速范围内,Re对边界层与外流的干扰十分显著。     

An effective splitting-and-recombination micromixer with self-rotated contact surface for wide Reynolds number range applications

It is difficult to mix two liquids on a microfluidic chip because the small dimensions and velocities effectively prevent the turbulence. This paper describes two 2-layer PDMS passive micromixers based on the concept of splitting and recombining the flow that exploits a self-rotated contact surface to increase the concentration gradients to obtain fast and efficient mixing. The designed micromixers were simulated and the mixing performance was assessed. The mixers have shown excellent mixing efficiency over a wide range of Reynolds number. The mixers were reasonably fabricated by multilayer soft lithography, and the experimental measurements were performed to qualify the mixing performance of the realized mixer. The results show that the mixing efficiency for one realized mixer is from 91.8% to 87.7% when the Reynolds number increases from 0.3 to 60, while the corresponding value for another mixer is from 89.4% to 72.9%. It is rather interesting that the main mechanism for the rapid mixing is from diffusion to chaotic advection when the flow rate increases, but the mixing efficiency has not obvious decline. The smart geometry of the mixers with total length of 10.25 mm makes it possible to be integrated with many microfluidic devices for various applications in μ-TAS and Lab-on-a-chip systems.     

The measures precision,recall, fallout and miss as a function of the number of retrieved documents and their mutual interrelations

In this paper, for the first time, we present global curves for the measures precision, recall, fallout and miss in function of the number of retrieved documents. Different curves apply for different retrieved systems, for which we give exact definitions in terms of a retrieval density function: perverse retrieval, perfect retrieval, random retrieval, normal retrieval, hereby extending results of Buckland and Gey and of Egghe in the following sense: mathematically more advanced methods yield a better insight into these curves, more types of retrieval are considered and, very importantly, the theory is developed for the “complete” set of measures: precision, recall, fallout and miss.     

The non-molecular structure of solids

To sum up our argument then: It is shown, in the first place, that the arrangement of the atoms in certain crystals, as determined by the X-ray spectra, indicates definitely that in these crystals there is no molecular structure.In extending the argument to all solid matter it is pointed out, from the dependence of crystal form on chemical composition, from a consideration of the Dulong-Petit law and of the nature of cohesion, and from the evidence of X-rays as to certain crystals, that each atom in a solid oscillates about a definite position of stable equilibrium.From a further examination of the nature of cohesion and of the forces concerned in chemical combination and especially from the general relation found between the atomic heat of formation of a substance and its melting-point it is found that the forces holding the atoms in their positions of stable equilibrium are of the same nature and comparable in magnitude with the forces binding together a chemical molecule.It is seen further that the atoms in a solid are very close together so that they often come in contact. And, since an atom attracts equally all atoms of another kind which are in contact with it, an atom cannot remain combined for more than an infinitesimal interval with any other particular atom ordinary temperatures.Finally, it was shown that, since in the solid state each atom has three degrees of translational freedom and is strongly attracted by atoms other than those of its own “molecule,” it must, on the average, exert equal attractions on all the neighboring atoms.From this the conclusion is drawn that in the particular molecules cannot be definitely defined.When those properties of solid matter which have been explained by molecules are considered, nothing is found which indicates at all definitely a molecular structure.We feel justified in concluding, therefore, that the structure of solid matter is not molecular.     

Added value as a function of purchases of information services

Abstract

In this paper, an analysis is provided of data to evaluate the extent to which investment in information resources can be demonstrated to have direct value in greater industrial profitability. Specifically, it examines the statistical relationship between “added value” for the manufacturing industries of the country and the investment they make in purchased information services.

A review is presented of the context of evaluation of the value of information, with anecdotal evidence concerning its role. We review the theoretical background for the analysis and describe the data on which the analysis is based. The discussion of data covers the sources, the nature, and the structure of the data sets and provides a detailed listing of the data itself. We also present the results of the analysis, discuss the implications, and conclude with a commentary on potential problems due to the heterogeneous character of the data, including the analysis of a range of alternative models all of which produce the same qualitative results that were obtained in the basic regression.

We apply a Cobb‐Douglas model to value added as a function of labor, capital, purchases of information services, and purchases of other input. We do a regression analysis for that model on 50 manufacturing industries, using data from 1967, and 51 industries, using data from 1972. The theory states that, if industry is operating in an optimal manner, the marginal return from the external purchases (whether for information services or for other input), as expressed by the coefficient in the regression, should be zero. If the coefficient is positive, industry is not using enough of the external resource; if negative, industry is using too much of it.

Our results show that there is a demonstrable relationship between increased added value (and therefore profitability) and investment in information resources. Beyond that, the evidence suggests that manufacturing industry is using far less than the optimal amount of information resources than should be optimal.     

Sierpinski电阻网络的等效电阻

求出了多节点的星形-网形变换公式,用其计算了Sierpinski电阻网络的等效电阻。与文献[1,2]相比,思路更为直观简洁。     

政府IT变革阻力与人口特征变异系数的关联分析

分析了政府IT变革阻力的形成机制与测度方法,并采用模糊综合评判法,结合层次分析法对政府IT变革阻力进行了定量评估。通过相关及偏相关分析,证明政府IT变革阻力与年龄、服务年限和教育程度等人口特征变异系数之间存在显著的正相关。因此,组织人口特征趋同,特别是教育程度在较高水平上趋同,是降低政府IT变革阻力的有效途径。     

Methods for estimating the number of relevant documents in a collection

Several statistical sampling methods are evaluated for estimating the total number of relevant documents in a collection for a given query. The total number of relevant documents is needed in order to compute recall values for use in evaluating document retrieval systems. The simplest method considered uses simple random sampling to estimate the number of relevant documents. Another type of random sampling, which assigns unequal selection probabilities to the individual documents in the collection, is also investigated. An alternative approach considered uses curve fitting and extrapolation, where a smooth curve is developed which relates precision to document rank. Another curve relates a function of precision to the query-document score. In either case, the curve is extrapolated to the total number of documents in order to estimate the number of relevant documents. Empirical comparisons are made of all three methods.     

High-throughput single-cell manipulation system for a large number of target cells

A sequential and high-throughput single-cell manipulation system for a large volume of cells was developed and the successive manipulation for single cell involving single-cell isolation, individual labeling, and individual rupture was realized in a microhydrodynamic flow channel fabricated by using two-dimensional simple flow channels. This microfluidic system consisted of the successive single-cell handlings of single-cell isolation from a large number of cells in cell suspension, labeling each isolated single cell and the lysate extraction from each labeled single cell. This microfluidic system was composed of main channels, cell-trapping pockets, drain channels, and single-cell content collection channels which were fabricated by polydimethylsiloxane. We demonstrated two kinds of prototypes for sequential single-cell manipulations, one was equipped with 16 single-cell isolation pockets in microchannel and the other was constructed of 512 single-cell isolation pockets. In this study, we demonstrated high-throughput and high-volume single-cell isolation with 512 pocket type device. The total number of isolated single cells in each isolation pocket from the cell suspension at a time was 426 for the cell line of African green monkey kidney, COS-1, and 360 for the rat primary brown preadipocytes, BAT. All isolated cells were stained with fluorescence dye injected into the same microchannel successfully. In addition, the extraction and collection of the cell contents was demonstrated using isolated stained COS-1 cells. The cell contents extracted from each captured cell were individually collected within each collection channel by local hydrodynamic flow. The sequential trapping, labeling, and content extraction with 512 pocket type devices realized high-throughput single-cell manipulations for innovative single-cell handling, feasible staining, and accurate cell rupture.