We constructed a product network based on the sales data collected and provided by a Fortune 500 speciality retailer. The structure of the network is dominated by small isolated components, dense clique-based communities, and sparse stars and linear
chains and pendants. We used the identified structural elements (tiles) to organize products into mini-categories -- compact collections of potentially complementary and substitute items. The mini-categories extend the traditional hierarchy of retail products (group - class - subcategory) and may serve as building blocks towards exploration of consumer projects and long-term customer behavior.
Abundant examples of complex transaction-oriented networks (TONs) can be found in a variety of disciplines, including information and communication technology, finances, commodity trading, and real estate. A transaction in a TON is executed as a sequ
ence of subtransactions associated with the network nodes, and is committed if every subtransaction is committed. A subtransaction incurs a two-fold overhead on the host node: the fixed transient operational cost and the cost of long-term management (e.g. archiving and support) that potentially grows exponentially with the transaction length. If the overall cost exceeds the node capacity, the node fails and all subtransaction incident to the node, and their parent distributed transactions, are aborted. A TON resilience can be measured in terms of either external workloads or intrinsic node fault rates that cause the TON to partially or fully choke. We demonstrate that under certain conditions, these two measures are equivalent. We further show that the exponential growth of the long-term management costs can be mitigated by adjusting the effective operational cost: in other words, that the future maintenance costs could be absorbed into the transient operational costs.
In the past decade, blogging web sites have become more sophisticated and influential than ever. Much of this sophistication and influence follows from their network organization. Blogging social networks (BSNs) allow individual bloggers to form cont
act lists, subscribe to other blogs, comment on blog posts, declare interests, and participate in collective blogs. Thus, a BSN is a bimodal venue, where users can engage in publishing (post) as well as in social (make friends) activities. In this paper, we study the co-evolution of both activities. We observed a significant positive correlation between blogging and socializing. In addition, we identified a number of user archetypes that correspond to mainly bloggers, mainly socializers, etc. We analyzed a BSN at the level of individual posts and changes in contact lists and at the level of trajectories in the friendship-publishing space. Both approaches produced consistent results: the majority of BSN users are passive readers; publishing is the dominant active behavior in a BSN; and social activities complement blogging, rather than compete with it.
Instant quality feedback in the form of online peer ratings is a prominent feature of modern massive online social networks (MOSNs). It allows network members to indicate their appreciation of a post, comment, photograph, etc. Some MOSNs support both
positive and negative (signed) ratings. In this study, we rated 11 thousand MOSN member profiles and collected user responses to the ratings. MOSN users are very sensitive to peer ratings: 33% of the subjects visited the researchers profile in response to rating, 21% also rated the researchers profile picture, and 5% left a text comment. The grades left by the subjects are highly polarized: out of the six available grades, the most negative and the most positive are also the most popular. The grades fall into three almost equally sized categories: reciprocal, generous, and stingy. We proposed quantitative measures for generosity, reciprocity, and benevolence, and analyzed them with respect to the subjects demographics.
The power of networks manifests itself in a highly non-linear amplification of a number of effects, and their weakness - in propagation of cascading failures. The potential systemic risk effects can be either exacerbated or mitigated, depending on th
e resilience characteristics of the network. The goals of this paper are to study some characteristics of network amplification and resilience. We simulate random Erdos-Renyi networks and measure amplification by varying node capacity, transaction volume, and expected failure rates. We discover that network throughput scales almost quadratically with respect to the node capacity and that the effects of excessive network load and random and irreparable node faults are equivalent and almost perfectly anticorrelated. This knowledge can be used by capacity planners to determine optimal reliability requirements that maximize the optimal operational regions.
In this paper, I present the design and implementation of Clown--a simulator of a microprocessor-based computer system specifically optimized for teaching operating system courses at undergraduate or graduate levels. The package includes the simulato
r itself, as well as a collection of basic I/O devices, an assembler, a linker, and a disk formatter. The simulator architecturally resembles mainstream microprocessors from the Intel 80386 family, but is much easier to learn and program. The simulator is fast enough to be used as an emulator--in the direct user interaction mode.
In this paper, we study certain geometric and topological properties of online social networks using the concept of density and geometric vector spaces. Moi Krug (My Circle), a Russian social network that promotes the principle of the six degrees of
separation and is positioning itself as a vehicle for professionals and recruiters seeking each others services, is used as a test vehicle.
