Strategic Topological Formation for Wireless Control Systems.

The excessive use of nodes and communication links in a wireless control system (WCS) causes unnecessary utilization of resources. In this article, a strategic topological formation is studied for a WCS, where a previously proposed topology consisting of a plant system, a controller system, and an intermediate network system is further developed. More specifically, this article presents a modeling framework and a design procedure for the topology that results in the utilization of a reduced number of nodes and communication links. It also discusses several conditions for the connectivity of the nodes under different topological scenarios. This article uses a four-tank process system as an application example to demonstrate the strategic topological formation of its WCS.

Design of a Wireless Control System With Unreliable Nodes and Communication Links.

Unlike a traditional topology of a control system with feedback connected plant and controller systems, this paper discusses a new topology that uses an intermediate network system between the plant and controller systems. More specifically, this paper presents modeling frameworks as well as computational procedures for the design of the closed-loop control system when the nodes of the plant, controller, and network systems fail to operate and the communication links fail to transfer information between communicating nodes. It also discusses conditions required for the synthesis of the controller and network systems, and characterizes the maximum number of unavailable nodes and the maximum probability of unavailable communication links. The aim of the presented results is to provide a more practical approach to the design of the new topology. Also, a four-tank process system is used to demonstrate details of the presented modeling frameworks and computational procedures.

Evaluation of whether intracameral dexamethasone predisposes to glaucoma after pediatric cataract surgery.

PURPOSE: To evaluate the effect of intracameral dexamethasone during pediatric cataract surgery on the incidence of postoperative glaucoma. SETTING: Clinical and Academic Department of Ophthalmology, Great Ormond Street Hospital, London, United Kingdom. DESIGN: Retrospective case series. METHODS: This case-note review comprised all infants who had cataract surgery with intraocular lenses between January 1, 2007, and December 31, 2008, and were given preservative-free intracameral dexamethasone intraoperatively. The definition of glaucoma was an intraocular pressure (IOP) of 21 mm Hg or greater on more than 2 occasions or moderate or firm digital IOP with 1 of the following: myopic shift, increased cup-to-disc ratio, increased horizontal corneal diameter, or corneal edema. RESULTS: Eighteen patients (24 eyes) were included. The median age at surgery was 3 months (mean 4 months ± 3 (SD); range 1 to 11 months). The median follow-up was 38 months (mean 34 ± 10 months; range 20 to 48 months). In 4 eyes, transient postoperative antihypertensive medication was used; however, no eye developed glaucoma during the follow-up period. Fifteen eyes had a second procedure to clear the visual axis due to posterior visual axis opacification a mean of 6.4 ± 3.5 months postoperatively (median 4.8 months; range 3.5 to 14.5 months); however, no eye developed anterior membranes. CONCLUSION: Intracameral preservative-free dexamethasone in infantile cataract surgery did not seem to cause an increased risk for glaucoma and appeared to protect against anterior membrane formation.