AutoBar: Automatic Barrier Coverage Formation for Danger Keep Out Applications in Smart City.

Barrier coverage is a fundamental application in wireless sensor networks, which are widely used for smart cities. In applications, the sensors form a barrier for the intruders and protect an area through intrusion detection. In this paper, we study a new branch of barrier coverage, namely warning barrier coverage (WBC). Different from the classic barrier coverage, WBC has the inverse protect direction, which moves the sensors surrounding a dangerous region and protects any unexpected visitors by warning them away from the dangers. WBC holds a promising prospect in many danger keep out applications for smart cities. For example, a WBC can enclose the debris area in the sea and alarm any approaching ships in order to avoid their damaging propellers. One special feature of WBC is that the target region is usually dangerous and its boundary is previously unknown. Hence, the scattered mobile nodes need to detect the boundary and form the barrier coverage themselves. It is challenging to form these distributed sensor nodes into a barrier because a node can sense only the local information and there is no global information of the unknown region or other nodes. To this end, in response to the newly proposed issue of the formation of barrier cover, we propose a novel solution AutoBar for mobile sensor nodes to automatically form a WBC for smart cities. Notably, this is the first work to trigger the coverage problem of the alarm barrier, wherein the regional information is not pre-known. To pursue the high coverage quality, we theoretically derive the optimal distribution pattern of sensor nodes using convex theory. Based on the analysis, we design a fully distributed algorithm that enables nodes to collaboratively move toward the optimal distribution pattern. In addition, AutoBar is able to reorganize the barrier even if any node is broken. To validate the feasibility of AutoBar, we develop the prototype of the specialized mobile node, which consists of two kinds of sensors: one for boundary detection and another for visitor detection. Based on the prototype, we conduct extensive real trace-driven simulations in various smart city scenarios. Performance results demonstrate that AutoBar outperforms the existing barrier coverage strategies in terms of coverage quality, formation duration, and communication overhead.

The influence of Na+ and Ca2+ on the migration of colloids or/and ammonia nitrogen in an unsaturated zone medium.

This experiment was conducted with an indoor sand-column device, the migration of colloids with the presence of Na+ and Ca2+ and the migration of ammonia nitrogen with the presence of Na+, Ca2+ or/and colloids was studied. The results showed that the migration of colloids was influenced by the ion valence state, different ions with different valence could block the migration of colloids. In addition, the blocking effect of bivalent ions was more obvious than that of monovalent ions. In the presence of Na+ and Ca2+, the Rd value of the ammonia-nitrogen migration process were 1.01 and 1.41, respectively, which indicated that bivalent ions have a greater blocking effect on ammonia-nitrogen migration than monovalent ions. Colloids could also block the ammonia-nitrogen migration, and Rd value in the ammonia-nitrogen migration process was 1.17. Moreover, the presence of Na+/colloids and Ca2+/colloids could enhance the blocking effect on the ammonia-nitrogen migration, and resulting the Rd values at 1.20 and 1.52, respectively. The cohesion of colloids caused by the compaction of its electric double layer with those ions added maybe the key causes of those blocking.

[Effects of water temperature and feeding on respiratory metabolism of juvenile Salvelinus fontinalus].

The oxygen consumption and ammonia excretion rates of juvenile brook trout (Salvelinus fontinalus) under satiation and starvation were measured at different levels of water temperature [(5.5 +/- 0.5), (8.5 +/- 0.5), (11.5 +/- 0.5), (14.5 +/- 0.5), (17.5 +/- 0.5) degrees C], aimed to study the effects of water temperature and feeding on the respiratory metabolism of the fish. Under satiation, the oxygen consumption and ammonia excretion rates of juvenile S. fontinalus at the five temperature levels increased rapidly to the maximum, and then decreased gradually to the initial state. The regression equations of oxygen consumption rate (OR) and ammonia excretion rate (NR) to water temperature (t) were OR = -0.0601 t4 + 2.5542 t3 - 39.256 t2 + 276.26 t - 598.75 (R2 = 1, 4.5 degrees C < t < 17.5 degrees C) and NR = - 0.0020 t4 + 0.0826 t3 - 1.2318 t2 + 8.6186 t - 18.838 (R2 = 1, 4.5 degrees C < t < 17.5 degrees C), respectively. Under starvation, the regression equations were OR = 13.723 t(0.9738) (R2 = 0.9974, 4.5 degrees C < t < 17.5 degrees C) and NR = 0.1687 t(1.0896) (R2 = 0.9977, 4.5 degrees C < t < 17.5 degrees C), respectively. The optimal temperature range was 11.5 degrees C-14.5 degrees C. The juvenile S. fontinalus in starvation was heavily depended on fat and carbohydrates.