Supervised Topical Key Phrase Extraction of News Stories using Crowdsourcing, Light Filtering and Co-reference Normalization

Fast and effective automated indexing is critical for search and personalized services. Key phrases that consist of one or more words and represent the main concepts of the document are often used for the purpose of indexing. In this paper, we investigate the use of additional semantic features and pre-processing steps to improve automatic key phrase extraction. These features include the use of signal words and freebase categories. Some of these features lead to significant improvements in the accuracy of the results. We also experimented with 2 forms of document pre-processing that we call light filtering and co-reference normalization. Light filtering removes sentences from the document, which are judged peripheral to its main content. Co-reference normalization unifies several written forms of the same named entity into a unique form. We also needed a "Gold Standard" - a set of labeled documents for training and evaluation. While the subjective nature of key phrase selection precludes a true "Gold Standard", we used Amazon's Mechanical Turk service to obtain a useful approximation. Our data indicates that the biggest improvements in performance were due to shallow semantic features, news categories, and rhetorical signals (nDCG 78.47% vs. 68.93%). The inclusion of deeper semantic features such as Freebase sub-categories was not beneficial by itself, but in combination with pre-processing, did cause slight improvements in the nDCG scores.Comment: In 8th International Conference on Language Resources and Evaluation (LREC 2012

Local Ice Pressures on the ODEN 1991 Polar Voyage.

In 1991 the ODEN made a voyage to the North Pole. An area in the starboard bow of the ship was instrumented with strain gauges to measure local ice pressures. The ship encountered various ice conditions in its voyage, and whenever a threshold strain was exceeded, a 6 to 12 second-long \u201cevent\u201d record of strains was made. Based on a finite element analysis of the ship structure the strains were converted to average ice pressures on a 40-sub-panel area, 10 frames wide (8.5 m) by 4 panels high (3.52 m). The bow is a \u201clanding-craft-form\u201d, sloped 22o from the horizontal. There were 784 events and for each of them average pressures on various area and shapes were determined and related to ship speed and ice conditions. A means of predicting probable ice pressures as a function of a \u201cdesign\u201d area and exposure is presented.NRC publication: Ye

Local Ice Pressures from the Louis S. St. Laurent 1994 North Pole Transit.

Ice pressure data collected from the 1994 Polar transit of the Louis S. St. Laurent were analysed to determine local average ice pressures as a function of size and shape of area of interest as well as the influence of ice thickness and ship velocity. A probabilistic approach was used to determine annual probability of exceedance of ice pressures. The results indicated a more rapid decrease in pressure with increasing area (exponent \u20130.7) compared to exponents of \u20130.4 to \u20130.5 commonly found in the literature. This is explained on the basis of more frequent loading on smaller hull areas and the definition of area, in this case a design area. areas In terms of ice thickness at the smallest hull area (0.72 m2) average ice pressure was about 1 MPa higher for ice thicker than 2 m compared to ice thinner than 2m. There was no significant affect of speed on local pressures for speeds up to 10 kts, however at speeds greater than 10 kts, the average pressure was about 20% greater.NRC publication: Ye

Tiltmeter Application at Norstr\uf6msgrund Lighthouse - STRICE Project.

The STRICE project installed load panels on half the circumference of the Norstr\uf6msgrund lighthouse in the Gulf of Bothnia to make direct measurements of ice forces. Near continuous measurements and observations of ice conditions were also made. As an adjunct to the project, a high-resolution tiltmeter capable of simultaneously measuring tilt in two orthogonal directions was installed inside the lighthouse for the 2002 winter season in order to assess an alternative means of measuring global ice force. For quasi-static ice loading, the tiltmeter provided a good representation of ice force acting on the lighthouse regardless of the direction from which the forces acted. In the case of dynamic ice loading with frequency components up to 3 Hz, a 7-second moving average "filter" provided a good representation of force components up to 0.5 Hz.NRC publication: Ye

The Local Pressure-Area Relation in Ship Impact with Ice.

The relation between pressure and area is used to describe various ice-ship interaction processes. Two types of pressure-area relations have been defined. One pressure-area relation describes the process of ship penetration into an ice feature. The other pressure-area relation describes the spatial distribution of pressure at an instant in time. The extensive local pressure data from the Louis S. St. Laurent and the Oden provide useful insights into the nature of pressure-area relations. The cases examined in this paper show that even though the two types of relations demonstrate similar trends of decreasing pressure with increasing area, they are quite different in nature. More examination of data in the context of the process pressure-relation is required before generalizations can be made. There is adequate data for describing the spatial distribution of local pressure as a function of area.NRC publication: Ye

Ice Pressure Variations during Indentation

The Japan Ocean Industry Association made available to the IAHR Ice Crushing Working Group one data file from a field test conducted February 4, 1999. An indenter 1.5 m wide by 0.5 m high, penetrated a sea ice sheet 168 mm thick at a rate of 3 mm/s for a total penetration of 1000 mm. The entire indenter face was covered with \u201ctactile\u201d sensor elements, each nominally 10 mm by 10 mm. Spatial distributions of local pressure were recorded throughout the test as well as the total load measured with a load cell. Detailed analysis of the results showed that the load cell and tactile sensors gave comparable results. The tactile sensors showed a \u201cline-like\u201d load distribution with only about 10 % of the ice edge in loadbearing contact. \u201cHot-spots\u201d of high local pressure persisted for surprisingly long periods, up to 10 s. Local pressure variations tended to be synchronous, that is largely increasing and decreasing with global load.NRC publication: Ye

Local Ice Pressures

NRC publication: Ye

Sea Ice Floe Impacts - Large Scale Basin Experiments

The impact forces produced by ice floes can be a significant factor in the design considerations for structures off the East Coast of Canada. A test program was carried out in an ice tank to investigate the force levels due to impact of isolated floes with a structure. In the tests, large floes of sea ice with a surface area of up to 60 m2 and thickness over 200 mm were grown. These floes represented actual sea ice floes, since there was no scaling of ice strength properties. These floes, with a mass up to 14 tonnes, were then accelerated to a desired speed (up 0.2 m/s) and allowed to impact against an instrumented test structure. The impact force and local pressures were measured for each impact. Impact velocity, floe mass and floe edge geometry were varied. The highest force levels measured were of the order of 50 kN at a speed of 0.2m/s. A simple analytical impact model was developed and validated with test results. It indicates that the maximum impact force was a function of the kinetic energy of the impacting floe raised to some power less than 1. The exponent and coefficient of the power relation were a function of ice floe edge geometry and the ice crushing pressure relation. Key words: ice forces, sea ice, impact.NRC publication: Ye

Probabilistic Analysis of Seasonal Ice Loads on the Molikpaq

A probabilistic analysis is made to predict the seasonal evolution of first-year ice loads on the Molikpaq offshore structure throughout a winter in the Canadian Beaufort Sea. The analysis is based solely on the failure modes of the ice, the ice thickness, and the number of weekly ice loading events. The paper illustrates the use of the probabilistic approach using these basic input values. The results of the analysis show good agreement with the measured ice loads on the Molikpaq in the Beaufort Sea.NRC publication: Ye