A Theoretical Analysis of Two-Stage Recommendation for Cold-Start Collaborative Filtering

In this paper, we present a theoretical framework for tackling the cold-start collaborative filtering problem, where unknown targets (items or users) keep coming to the system, and there is a limited number of resources (users or items) that can be allocated and related to them. The solution requires a trade-off between exploitation and exploration as with the limited recommendation opportunities, we need to, on one hand, allocate the most relevant resources right away, but, on the other hand, it is also necessary to allocate resources that are useful for learning the target's properties in order to recommend more relevant ones in the future. In this paper, we study a simple two-stage recommendation combining a sequential and a batch solution together. We first model the problem with the partially observable Markov decision process (POMDP) and provide an exact solution. Then, through an in-depth analysis over the POMDP value iteration solution, we identify that an exact solution can be abstracted as selecting resources that are not only highly relevant to the target according to the initial-stage information, but also highly correlated, either positively or negatively, with other potential resources for the next stage. With this finding, we propose an approximate solution to ease the intractability of the exact solution. Our initial results on synthetic data and the Movie Lens 100K dataset confirm the performance gains of our theoretical development and analysis

Rearing of the native Pacific Coast oyster larvae, Ostrea lurida Carp., under controlled laboratory conditions

Fisheries Laboratory during 1952, in the rearing of the native Pacific Coast oyster, Ostrea lurida Carp., in small containers. The decline of the oyster fishery in Yaquina Bay, Oregon, has been attributed in part to the lack of adequate spat-falls. Investigations were begun in 1947 to devise methods of artificially rearing oyster larvae under controlled conditions which might later be extended in producing seed oysters in adequate numbers for the commercial production of the native oyster. Adult oysters from which larvae were obtained for the rearing tests were Longed from the native oyster beds near Oysterville on Yaquina Bay. The larvae were taken from the adult oyster by two methods. The adult oysters were placed in five-gallon wide-mouth jars and the temperature raised to 200 C. until natural swarming occurred, or the adult oysters were opened manually and the larvae were taken from the gravid oysters. These methods apply during the natural spawning season of the native oyster which occurs in late spring and summer. The rearing containers used were five-gallon wide-mouth jars and 12-gallon crocks. The larger containers gave better results. A filtering device was installed in each container to accomplish the water change without loss of larvae. A rearing temperature of 18 to 200 C. was maintained by controlling the room temperatures. All salt water used in rearing experiments was sand filtered to remove organisms that may prey on the larvae or take food in competition with them. Larval food consisted of plankton which measures less than 9 microns. These organisms were cultured in small containers and 25 ml. of the media was introduced into the rearing containers every 48 hours. Rearing containers with various larval concentrations received the same amount of media and the results showed no indications of over or under feeding. A salinity range of 26 to 32 parts per thousand yielded satisfactory results. The upper and lower limits were not determined. When the bay salinity exceeded 34 parts per thousand, the salinity was reduced by adding fresh water. This resulted in larval mortality. The reason for this mortality was not determined but it is possible that the fresh water used was toxic. The water in the rearing containers was changed every other day in the early experiments. A less frequent water change was tried which yielded satisfactory results. A water change once or twice during the larval free-swimming period appears to be adequate. The larval growth rate was measured and a daily growth of 4 to 5 microns is considered satisfactory. The rate of growth appears to be a reliable indication of the condition of the larvae. The larvae set out on a cultch after a 15 to 25 day free-swimming period. Setting began when the larvae measured about 260 microns. The spat received the same care as the free-swimming larvae and considerable 2 shell growth was evident. During the winter months, induced spawning was investigated. Adult oysters were taken from the bay and held in the laboratory at a temperature of 18 to 200 C. The water was changed occasionally and media was added. Some spawning occurred after the oysters were held for 6 to 8 weeks. The larvae thus obtained were successfully reared to the setting stage

Notes on Oyster Aquaculture

This report is a brief overview of the status of Oregon’s oyster aquaculture in the mid to late 1970s, including discussions of trends in harvests and research into oyster breeding

Wafer scale manufacturing of high precision micro-optical components through X-ray lithography yielding 1800 Gray Levels in a fingertip sized chip

We present a novel x-ray lithography based micromanufacturing methodology that offers scalable manufacturing of high precision optical components. It is accomplished through simultaneous usage of multiple stencil masks made moveable with respect to one another through custom made micromotion stages. The range of spectral flux reaching the sample surface at the LiMiNT micro/nanomanufacturing facility of Singapore Synchrotron Light Source (SSLS) is about 2 keV to 10 keV, offering substantial photon energy to carry out deep x-ray lithography. In this energy range, x-rays penetrate through resist materials with only little scattering. The highly collimated rectangular beam architecture of the x-ray source enables a full 4″ wafer scale fabrication. Precise control of dose deposited offers determined chain scission in the polymer to required depth enabling 1800 discrete gray levels in a chip of area 20 mm$^{2}$ and with more than 2000 within our reach. Due to its parallel processing capability, our methodology serves as a promising candidate to fabricate micro/nano components of optical quality on a large scale to cater for industrial requirements. Usage of these fine components in analytical devices such as spectrometers and multispectral imagers transforms their architecture and shrinks their size to pocket dimension. It also reduces their complexity and increases affordability while also expanding their application areas. Consequently, equipment based on these devices is made available and affordable for consumers and businesses expanding the horizon of analytical applications. Mass manufacturing is especially vital when these devices are to be sold in large quantities especially as components for original equipment manufacturers (OEM), which has also been demonstrated through our work. Furthermore, we also substantially improve the quality of the micro-components fabricated, 3D architecture generated, throughput, capability and availability for industrial application. Manufacturing 1800 Gray levels or more through other competing techniques is either limited due to multiple process steps involved or due to unacceptably long time required owing to their pencil beam architecture. Our manufacturing technique presented here overcomes both these shortcomings in terms of the maximum number of gray levels that can be generated, and the time required to generate the same

Hatchery manual for the Pacific oyster

Published December 1975. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Cationic vacancy induced room-temperature ferromagnetism in transparent conducting anatase Ti_{1-x}Ta_xO_2 (x~0.05) thin films

We report room-temperature ferromagnetism in highly conducting transparent anatase Ti1-xTaxO2 (x~0.05) thin films grown by pulsed laser deposition on LaAlO3 substrates. Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), proton induced x-ray emission (PIXE), x-ray absorption spectroscopy (XAS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) indicated negligible magnetic contaminants in the films. The presence of ferromagnetism with concomitant large carrier densities was determined by a combination of superconducting quantum interference device (SQUID) magnetometry, electrical transport measurements, soft x-ray magnetic circular dichroism (SXMCD), XAS, and optical magnetic circular dichroism (OMCD) and was supported by first-principle calculations. SXMCD and XAS measurements revealed a 90% contribution to ferromagnetism from the Ti ions and a 10% contribution from the O ions. RBS/channelling measurements show complete Ta substitution in the Ti sites though carrier activation was only 50% at 5% Ta concentration implying compensation by cationic defects. The role of Ti vacancy and Ti3+ was studied via XAS and x-ray photoemission spectroscopy (XPS) respectively. It was found that in films with strong ferromagnetism, the Ti vacancy signal was strong while Ti3+ signal was absent. We propose (in the absence of any obvious exchange mechanisms) that the localised magnetic moments, Ti vacancy sites, are ferromagnetically ordered by itinerant carriers. Cationic-defect-induced magnetism is an alternative route to ferromagnetism in wide-band-gap semiconducting oxides without any magnetic elements.Comment: 21 pages, 10 figures, to appear in Philosophical Transaction - Royal Soc.

The use of heated sea water for farming oysters and salmon

For oysters, "The objective of these studies was to determine the biological feasibility of using the heated effluent from coastal nuclear power plants for culturing the Pacific oyster, Crassostrea gigas." (p.1) Work included oyster growth experiments, seasonal growth experiments and closed system studies. For salmon, "The objective of these studies was to determine the biological feasibility of using the heated effluent from coastal nuclear power plants for culturing chum salmon, Oncorhynchus keta, and, to a lesser extent, pink salmon 0. gorbuscha." (p.3) Work included temperature vs. growth experiments, temperature x ration factorial experiments, and disease control studies

Intensive culture of the Pacific oyster, Crassostrea gigas (Thunberg), in heated effluents

Published November 1978. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Enhancing topology adaptation in information-sharing social networks

The advent of Internet and World Wide Web has led to unprecedent growth of the information available. People usually face the information overload by following a limited number of sources which best fit their interests. It has thus become important to address issues like who gets followed and how to allow people to discover new and better information sources. In this paper we conduct an empirical analysis on different on-line social networking sites, and draw inspiration from its results to present different source selection strategies in an adaptive model for social recommendation. We show that local search rules which enhance the typical topological features of real social communities give rise to network configurations that are globally optimal. These rules create networks which are effective in information diffusion and resemble structures resulting from real social systems