Search Results (3)

Rare species at the edge of their range often persist after range contractions, yet basic information is typically lacking. We created species distribution models (SDMs) to guide field surveys for a disjunct population of Sessileflower Indian parsley (Cymopterus sessiliflorus; Apiaceae). We used historical observations to produce an initial model that guided field surveys in 2023. We refined the model using new observations from these surveys and the best predictors were shrubs, rock outcrops, mean monthly precipitation of the warmest quarter and rock type (area under the curve = 0.97). Suitable habitat (moderate-high and high classes) was predicted in <2% of Wyoming. We discovered 11 new populations over 2 summers. We collected 17 bee genera (n = 272 individuals) during C. sessiliflorus flowering suggesting diverse potential pollinators may transport pollen. Our model highlighted other areas predicted suitable and surveys in these areas may reveal new populations of this rare plant. The SDMs demonstrated how sparse historical data on rare species can be used to direct surveys in an efficient and effective manner. The information we gathered provided basic data for a rare plant at the periphery of its range where the most robust populations may occur making them critical for conservation efforts. Full article

Path coverage attracts many interests in some scenarios, such as object tracing in sensor networks. However, the problem of how to conserve the constrained energy of sensors is rarely considered in existing research. This paper studies two problems in the energy conservation of sensor networks that have not been addressed before. The first problem is called the least movement of nodes on path coverage. It first proves the problem as NP-hard, and then uses curve disjunction to separate each path into some discrete points, and ultimately moves nodes to new positions under some heuristic regulations. The utilized curve disjunction technique makes the proposed mechanism unrestricted by the linear path. The second problem is called the largest lifetime on path coverage. It first separates all nodes into independent partitions by utilizing the method of largest weighted bipartite matching, and then schedules these partitions to cover all paths in the network by turns. We eventually analyze the energy cost of the two proposed mechanisms, and evaluate the effects of some parameters on performance through extensive experiments, respectively. Full article

In this work, micro-modified polyvinylidene fluoride (PVDF) and its copolymer poly(vinylidene-trifluoroethylene) (P(VDF-TrFE)) with salient enhancement in current output are demonstrated. The influence of surface-modified structure characteristics on electrical properties of energy harvester is systematically analyzed based on the finite element method. For vertical load mode, eight structures consisting of banded and disjunctive groups are compared to evaluate the voltage performance. The cylinder is proved to be the best structure of 3.25 V, compared to the pristine structure of 0.99 V (P(VDF-TrFE)). The relevant experiment has been done to verify the simulation. The relationship between radius, height, force and distance to the voltage output of the cylinder allocation is discussed. For periodical changing load mode, the cylinder modified structure shows a conspicuous enhancement in current output. The suitable resistance, current–voltage and frequency, the relationship between loading speed and current, and the ductility of current loading are studied. For 30 kHz, the peak current is 20 times larger than the flat plate structure. Tip shape mode and fusiform shape mode are found, which show the different shapes of the peak current-frequency curves. Four electrical loading circuit properties are also discussed: the suitable resistance of the system, synchronism of current and voltage, time delay nature of energy harvester and current-loading relationship. The simulation results can provide some theoretical basis for designing the energy harvester and piezoelectric nanogenerator (PENG). Full article