RSS-Based Target Localization in Underwater Acoustic Sensor Networks via Convex Relaxation.

The received signal strength (RSS) based target localization problem in underwater acoustic wireless sensor networks (UWSNs) is considered. Two cases with respect to target transmit power are considered. For the first case, under the assumption that the reference of the target transmit power is known, we derive a novel weighted least squares (WLS) estimator by using an approximation to the RSS expressions, and then transform the originally non-convex problem into a mixed semi-definite programming/second-order cone programming (SD/SOCP) problem for reaching an efficient solution. For the second case, there is no knowledge on the target transmit power, and we treat the reference power as an additional unknown parameter. In this case, we formulate a WLS estimator by using a further approximation, and present an iterative ML and mixed SD/SOCP algorithm for solving the derived WLS problem. For both cases, we also derive the closed form expressions of the Cramer-Rao Lower Bounds (CRLBs) on root mean square error (RMSE). Computer simulation results show the superior performance of the proposed methods over the existing ones in the underwater acoustic environment.

An Effective Scheduling Algorithm for Coverage Control in Underwater Acoustic Sensor Network.

Coverage maintenance is a bottleneck restricting the development of underwater acoustic sensor networks (UASNs). Since the energy of the nodes is limited, the coverage of UASNs may gradually decrease as the network operates. Thus, energy-saving coverage control is crucial for UASNs. To solve the above problems, this paper proposes a coverage-control strategy (referred to as ESACC) that establishes a sleep⁻wake scheduling mechanism based on the redundancy of deployment nodes. The strategy has two main parts: (1) Node sleep scheduling based on a memetic algorithm. To ensure network monitoring performance, only some nodes are scheduled to work, with redundant nodes in a low-power hibernation state, reducing energy consumption and prolonging the network lifetime. The goal of node scheduling is to find a minimum set of nodes that can cover the monitoring area, and a memetic algorithm can solve this problem. (2) Wake-up scheme. During network operation, sleeping nodes are woken to cover the dead nodes and maintain high coverage. This scheme not only reduces the network energy consumption but takes into account the monitoring coverage of the network. The experimental data show that ESACC performs better than current algorithms, and can improve the network life cycle while ensuring high coverage.

High-Quality CoFeP Nanocrystal/N, P Dual-Doped Carbon Composite as a Novel Bifunctional Electrocatalyst for Rechargeable Zn-Air Battery.

A novel composite catalyst (CoFeP@C) was constructed by high-quality CoFeP nanoparticles embedded in a N, P dual-doped carbon matrix. These CoFeP nanoparticles are rich in active sites of the oxygen evolution reaction (OER) at surfaces and provide metallic conductivity in their bulk phases. The N, P dual-doped carbon matrix provided abundant active sites of the oxygen reduction reaction (ORR) and formed a conductive network substrate. The ideal composite structure endowed CoFeP@C with highly efficient bifunctional performance for catalyzing both OER and ORR, accordingly making CoFeP@C an ideal catalyst for rechargeable Zn-air batteries. The liquid Zn-air battery of CoFeP@C has achieved a large power density of 143.5 mW/cm2 and can be charged and discharged stably for 200 h (1200 cycles). The solid-state Zn-air battery of CoFeP@C has achieved a power density of 72.6 mW/cm2 and can stably run for 20 h. This work has deepened the understanding of synergistic catalysis and paved one way for the development of high-performance bifunctional catalysts.

FeNiP nanoparticle/N,P dual-doped carbon composite as a trifunctional catalyst towards high-performance zinc-air batteries and overall water electrolysis.

A composite catalyst with a novel construction of bimetallic phosphide FeNiP nanoparticles embedded in an N,P double-doped carbon matrix was prepared. It was demonstrated to be a trifunctional catalyst that can efficiently catalyze the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It was found that the introduction of oleylamine during the preparation can adjust the catalytic sites and finally lead to ideal catalytic performances. The obtained catalyst exhibited efficient ORR catalytic performance that surpassed the commercial Pt/C catalyst, with the OER performance comparable to that of RuO2 as well as excellent HER performance. The ORR half-wave potential is 0.879 V (vs. RHE) in 0.1 M KOH solution, while the OER overpotential at a current density of 10 mA cm-2 is only 280 mV in 1 M KOH solution. The potential gap between the ORR and OER was only 0.700 V in 0.1 M KOH solution. This trifunctional catalyst was further evaluated in energy devices including zinc-air batteries and water electrolysis. The liquid zinc-air battery assembly achieved a power density of 169 mW cm-2 and stably undergoes charge-discharge cycles for 210 hours. The solid-state zinc-air battery achieved a power density of 70 mW cm-2 and stably undergoes charge-discharge cycles for 40 hours. These performances surpassed the batteries assembled with a Pt/C-RuO2 mixed catalyst. This work established a foundation of composite catalysts coupled with bimetallic phosphide and hybrid carbon substrates, which will promote the development of high-performance multifunctional catalysts and their application in energy devices.

Correction of astigmatism after penetrating keratoplasty by relaxing incision with compression suture: a comparison between the guiding effect of photokeratoscope and of computer-assisted videokeratography.

PURPOSE: To report the results of astigmatism correction after penetrating keratoplasty by relaxing incision with compression suture and to compare the guiding ability of a photokeratoscope with that of computer-assisted videokeratography. METHODS: In the two independent retrospective series, 11 eyes received a relaxing incision with compression suture guided by photokeratoscope or computer-assisted videokeratography. RESULTS: In 22 eyes, the relaxing incision with compression suture showed a mean 56% reduction in astigmatism and 78% reduction in vector-calculated astigmatism. The mean postoperative visual acuity was improved 2.92 Landolt lines. The 11 eyes in which treatment was guided by photokeratoscope demonstrated a mean reduction of 50% and 71% in astigmatism and vector-calculated astigmatism, respectively, and visual acuity increased 2.44 Landolt lines. Another 11 eyes in which treatment was guided by computer-assisted videokeratography achieved a mean reduction of 67% and 90% in astigmatism and vector-calculated astigmatism, respectively, together with 3.41 Landolt lines improvement in visual acuity. There were no significant differences in astigmatism correction and visual acuity improvement between the two groups. CONCLUSION: The results demonstrate that the relaxing incision with compression suture is an effective and safe procedure for correcting high astigmatism after penetrating keratoplasty. The two instruments have no significant difference in their guiding capacities for this procedure.

Eyelid tumors in southern Taiwan: a 5-year survey from a medical university.

This retrospective case analysis investigated the epidemiology of eyelid tumors in a subtropical area. The study assessed the proportion of all eyelid tumors that were malignancies, the accuracy of diagnosis, and surgical results. We retrospectively collected all cases of eyelid tumors in the Department of Ophthalmology, Kaohsiung Medical University, Taiwan, between January 1994 and December 1998. Among the 144 cases collected, about half of the tumors were located in the upper eyelids and the other half in the lower eyelids. Nearly 50% of cases underwent tumor resection with eyelid reconstruction. When followed up to April 1999, 97% of patients were satisfied with the surgical results. There were 18 cases (12.5%) of malignant tumors, including 14 basal cell carcinomas, three sebaceous carcinomas, and one squamous cell carcinoma. Before surgery, two malignancies were presumed to be benign tumors while another two were thought to be different malignant tumors. The benign tumors included 38 nevi, 15 squamous papillomas, 13 cysts, 11 verrucae, 10 seborrheic keratoses, four hemangiomas, and others. All tumors that were thought to be malignancies were treated using complete resection with margin monitoring by frozen section. At the end of follow-up, no recurrence was noted. More than 10% of cases of eyelid tumors in this subtropical teaching hospital were malignant. All surgeons should be alert to this phenomenon when they operate on an eyelid tumor. The best policy is to send all specimens for pathologic examination.