Performance optimization algorithms based on potentials for semi-Markov control processes

Optimization algorithms are studied for a class of semi-Markov control processes (SMCPs) with compact action set. Both the long-run average and discounted cost problems are considered. Formulas of performance potentials and optimality equations for SMCPs are derived. A policy iteration algorithm and a value iteration algorithm are proposed, which can lead to an optimal or suboptimal stationary policy in a finite number of iterations. The convergence of these algorithms is established, without the assumption of the corresponding iteration operator being a span-contraction. In addition, an online policy iteration optimization algorithm based on a single sample path is provided to escape ‘curse of dimensionality’. In the end, a numerical example is provided to illustrate the application of the algorithms.     

A very low-noise CMOS preamplifier for capacitive sensors

A CMOS preamplifier optimized for piezoelectric transducers is presented. The extensive use of CMOS-compatible lateral bipolar transistors (CLBTs) and careful layout leads to a very low noise along with good untrimmed DC and AC characteristics. These features make it competitive with bipolar and JFET realizations. In addition, long coaxial lines can be driven without significant alteration of performance using the two uncommitted on-chip buffers. This circuit was fabricated in a standard 3-μm p-well CMOS technology, opening perspectives to monolithic integration of data acquisition subsystems     

Tunable Parametric All-Fiber Short-Wavelength IR Transmitter

In this paper, the performance of an all-fiber short-wave IR (SWIR) transmitter with wideband tunability and high peak power is reported. Transmitter construction relied on parametric process in highly nonlinear fiber to convert a seed laser at 1260 nm to 2155 nm SWIR channel with record 39 dB efficiency and translation over 900 nm spectral range. We demonstrated 61 W of peak converted power at 2 $mu$m and 26 W at 2.15 $mu$ m. Efficient conversion was made possible by engineered fourth-order dispersion of the highly nonlinear fiber and construction of a low-noise pump source in a 1550 nm band.      

Two-dimensional synthetic aperture images over a land surface scene

The Soil Moisture and Ocean Salinity (SMOS) space mission is currently undergoing phase-B studies at the European Space Agency. The SMOS payload is an L-band interferometric radiometer based on a two-dimensional aperture synthesis concept. This paper presents the first images obtained by a demonstrator of the SMOS instrument over land surfaces at the Avignon test site in 1999     

Reconfigurable Hardware for High-Security/ High-Performance Embedded Systems: The SAFES Perspective

Embedded systems present significant security challenges due to their limited resources and power constraints. This paper focuses on the issues of building secure embedded systems on reconfigurable hardware and proposes a security architecture for embedded systems (SAFES). SAFES leverages the capabilities of reconfigurable hardware to provide efficient and flexible architectural support for security standards and defenses against a range of hardware attacks. The SAFES architecture is based on three main ideas: (1) reconfigurable security primitives; (2) reconfigurable hardware monitors; and (3) a hierarchy of security controllers at the primitive, system and executive level. Results are presented for reconfigurable AES and RC6 security primitives and highlight the value of such an architecture. This paper also emphasizes that reconfigurable hardware is not just a technology for hardware accelerators dedicated to security primitives as has been focused on by most studies but a real solution to provide high-security and high-performance for a system.     

Thin dielectric reliability assessment for DRAM technology with deep trench storage node

The reliability results of thin gate oxide and nitride–oxide film development for application in dynamic random access memories are presented. Data and observations from this technology development are embedded in general state-of-the-art review. Therein features of lifetime extrapolation models are discussed. Process and test structures as well as the stress procedure are briefly described. Among the data presented are long term stress results supporting the anode hole injection model down to 5 V, breakdown propagation results and the soft breakdown of 6 nm oxide, which allows detection of device degradation due to Fowler–Nordheim stress. Furthermore the dependence of the voltage acceleration on oxide thickness is shown for the range of less than 2–10 nm oxide thickness. The importance of physical failure analysis is emphazised.     

Network Topology Inference Based on End-to-End Measurements

We consider using traceroute-like end-to-end measurement to infer the underlay topology for a group of hosts. One major issue is the measurement cost. Given N hosts in an asymmetric network without anonymous routers, traditionally full N(N-1) traceroutes are needed to determine the underlay topology. We investigate how to efficiently infer an underlay topology with low measurement cost, and propose a heuristic called Max-Delta. In the heuristic, a server selects appropriate host-pairs to measure in each iteration so as to reveal the most undiscovered information on the underlay. We further observe that the presence of anonymous routers significantly distorts and inflates the inferred topology. Previous research has shown that obtaining both exact and approximate topology in the presence of anonymous routers under certain consistency constraints is intractable. We hence propose fast algorithms on how to practically construct an approximate topology by relaxing some constraints. We investigate and compare two algorithms to merge anonymous routers. The first one uses Isomap to map routers into a multidimensional space and merges anonymous routers according to their interdistances. The second algorithm is based on neighbor router information, which trades off some accuracy with speed. We evaluate our inference algorithms on Internet-like and real Internet topologies. Our results show that almost full measurement is needed to fully discover the underlay topology. However, substantial reduction in measurements can be achieved if a little accuracy, say 5%, can be compromised. Moreover, our merging algorithms in the presence of anonymous routers can efficiently infer an underlay topology with good accuracy     

Pilot power minimization with coverage and locatability constraints in CDMA systems

Position location (PL) of a UE requesting E-911 services should be provided by wireless communication service providers, according to the Federal Communications Commission (FCC) regulations. Raising pilot power fraction can improve the system locatability, while it may also cause pilot pollution and increase interference to UEs in neighboring cells. In this letter we find the optimal pilot power allocation subject to coverage and locatability constraints. The results have shown that with new localization techniques such as idle period downlink (IPDL) and cumulative virtual blanking (CVB), the coverage and locatability constraints can be satisfied without requiring long integration time and large pilot power fraction.     

A new concept toward computer-aided medical diagnosis - a prototypeimplementation addressing pulmonary diseases

The original concept that led to the structuring of a computer-based medical decision support system (DSS) that is able to support a physician's diagnosis is introduced in this paper. The concept's implementation modeled a generic DSS, the core of which are an integrated knowledge/information base (KIB) along with the inference properties of a data evaluator. The KIB encapsulates the necessary medical knowledge and experience in the form of rules and constraints, preemptive tasks and actual patients' clinical data. The data evaluator handles approved medical subjective and objective criteria for assessing the KIB's data. The data evaluator incorporates a medical standard data gathering and decision process, structured upon the principles of the clinical differential diagnosis methodology, and has been integrated in the system by means of both algorithmic and artificial intelligence techniques. The novel model and the resulted computer-based package have been extensively tested at the Pulmonary Department of the University Regional Hospital Patras, Greece     

Design and fabrication of ridge waveguide folded-cavity in-planesurface-emitting lasers

A 45° angled reactive ion etching combined with an in situ monitoring technique was used to fabricate ridge waveguide folded-cavity in-plane surface-emitting lasers. This laser structure, with two 45°C angle-etched internal total-reflection mirrors and an epitaxially grown distributed Bragg reflector, is very promising for OEIC applications. Laser-structure design and laser fabrication are addressed. A continuous-wave threshold current of 8 mA, the lowest reported in the literature, was achieved on 3-μm-wide, 350-μm long devices