Parallel Opportunistic Routing in Wireless Networks

We study benefits of opportunistic routing in a large wireless ad hoc network by examining how the power, delay, and total throughput scale as the number of source- destination pairs increases up to the operating maximum. Our opportunistic routing is novel in a sense that it is massively parallel, i.e., it is performed by many nodes simultaneously to maximize the opportunistic gain while controlling the inter-user interference. The scaling behavior of conventional multi-hop transmission that does not employ opportunistic routing is also examined for comparison. Our results indicate that our opportunistic routing can exhibit a net improvement in overall power--delay trade-off over the conventional routing by providing up to a logarithmic boost in the scaling law. Such a gain is possible since the receivers can tolerate more interference due to the increased received signal power provided by the multi-user diversity gain, which means that having more simultaneous transmissions is possible.Comment: 18 pages, 7 figures, Under Review for Possible Publication in IEEE Transactions on Information Theor

Fundamental Limits on Data Acquisition: Trade-offs between Sample Complexity and Query Difficulty

We consider query-based data acquisition and the corresponding information recovery problem, where the goal is to recover $k$ binary variables (information bits) from parity measurements of those variables. The queries and the corresponding parity measurements are designed using the encoding rule of Fountain codes. By using Fountain codes, we can design potentially limitless number of queries, and corresponding parity measurements, and guarantee that the original $k$ information bits can be recovered with high probability from any sufficiently large set of measurements of size $n$. In the query design, the average number of information bits that is associated with one parity measurement is called query difficulty ($\bar{d}$) and the minimum number of measurements required to recover the $k$ information bits for a fixed $\bar{d}$ is called sample complexity ($n$). We analyze the fundamental trade-offs between the query difficulty and the sample complexity, and show that the sample complexity of $n=c\max\{k,(k\log k)/\bar{d}\}$ for some constant $c>0$ is necessary and sufficient to recover $k$ information bits with high probability as $k\to\infty$

Cigarette smoking and food insecurity among low-income families in the United States, 2001

The goal of this research is to quantify the association between food insecurity and smoking among low-income families. This analysis is a retrospective study using data from the 2001 Panel Study of Income Dynamics, a longitudinal study of a representative sample of U.S. men, women, and children and the family units in which they reside. Family income is linked with U.S. poverty thresholds to identify 2,099 families living near or below 200 percent of the federal poverty level. Food insecurity (that is, having insufficient funds to purchase enough food to maintain an active and healthy lifestyle) is calculated from the eighteen core items in the food security module of the U.S. Department of Agriculture. The results indicate that smoking prevalence is higher among low-income families who are food insecure compared to low-income families who are food secure (43.6 percent versus 31.9 percent). Multivariate analysis reveals that smoking is associated with an increase in food insecurity of approximately 6 percentage points. Given our finding that families near the federal poverty level spend a large share of their income on cigarettes, perhaps it would be prudent for food assistance and tobacco control programs to work together to help low-income people quit smoking.

Peridynamic modeling for crack propagation analysis of materials

In this paper, the computer simulations are carried out by using the peridynamic theory model with various conditions including quasi-static loads, dynamic loads and crack propagation, branching crack pattern and isotropic materials, orthotropic materials. Three examples, a plate with a hole under quasi-static loading, a plate with a pre-existing crack under dynamic loading and a lamina with a pre-existing crack under quasi-static loading are analyzed by computational simulations. In order to simulate the quasi-static load, an adaptive dynamic relaxation technique is used. In the orthotropic material analysis, a homogenization method is used considering the strain energy density ratio between the classical continuum mechanics and the peridynamic. As a result, crack propagation and branching cracks are observed successfully and the direction and initiation of the crack are also captured within the peridynamic modeling. In case of applying peridynamic used homogenization method to a relatively complicated orthotropic material, it is also verified by comparing with experimental result

Two New Marine Sponges of the Genus Haliclona (Haplosclerida: Chalinidae) from Korea

Two new marine sponges, Haliclona (Haliclona) tonggumiensis n. sp. and H. (Reniera) sinyeoensis n. sp., in the family Chalinidae were collected from Ulleungdo Island and Gageodo Island, Korea from 2007 to 2009. Haliclona (Haliclona) tonggumiensis n. sp. is similar to H. (H.) simulans (Johnston, 1842) in shape, but the former differs in its ectosomal skeleton structure and spicules’ shape and size. The ectosomal skeleton of H. (H.) tonggumiensis n. sp. is absent, but that of H. (H.) simulans is very regularly arranged, and has tangential reticulation with oxea. The spicule shape of H. (H.) tonggumiensis n. sp. is slender, but that of H. (H.) simulans is short and cigar-shape. The new species have two sizes of oxea, but H. (H.) simulans has one size of oxea. Haliclona (Reniera) sinyeoensis n. sp. resembles H. (R.) tubifera (George and Wilson, 1919) in the growth form and choanosomal skeleton structure. However, the new species has two kinds of oxea in size, but H. (R.) tubifera has only one size