A piezoelectric transducer‐tuned microstrip‐ring resonator oscillator operating at the second resonant mode of the ring resonator

A microstrip open‐loop resonator oscillator operating at even modes is proposed. The even mode of the ring circuit can be predicted by using a simple transmission‐line model. The new oscillator has a characteristic similar to that of a push‐push oscillator. In addition, in comparison with the push‐push oscillator, the new oscillator with one active device can minimize the size and lower the cost. A voltage‐controlled piezoelectric transducer (PET) is used to vary the resonant frequencies of the ring resonator, which in turn tunes the oscillator with a good tuning range of 4.9% at around 12.1 GHz. This tuned oscillator should have many applications in wireless systems. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

A genetic fuzzy agent using ontology model for meeting scheduling system

A Genetic Fuzzy Agent (GFA) using the ontology model for Meeting Scheduling System (MSS) is presented in this paper. The ontology model includes the Fuzzy Meeting Scheduling Ontology (FMSO) and the Fuzzy Personal Ontology (FPO) that can support to construct the knowledge base of the GFA. The FMSO is utilized to record and describe the meeting scheduling domain knowledge for the GFA. In addition, we implement a FMSO editor for generating the Web Ontology Language, OWL, that will be utilized by the GFA. Furthermore, the GFA will infer the suitable meeting time slots based on the ontology model. Moreover, it also adjusts the FMSO and FPO based on the results of the genetic learning mechanism for the next meeting. The experimental results show that our approach can effectively work for MSS.     

Investigation of a solid-state detector for advanced computed tomography

Utilization of solid-state detectors for computed tomography (CT) has been the focus of many studies. Previous phantom and clinical experiments have shown that one of the important performance parameters for the solid-state detector is the primary speed and afterglow. In this paper, we present a detailed investigation on the signal decay characteristics of the HiLight (GE Medical Systems, Milwaukee, WI) scintillating detector. The detector primary speed and afterglow are modeled by a multiexponential function and fully characterized by a set of time constants and relative strengths. The sensitivity of these parameters to X-ray photon energy, detector aging, and radiation exposure is then established and analyzed. No statistically significant variation is observed in these parameters due to changes in the above external variables. The impact of various decay time constants on CT image quality, such as spatial resolution, noise, and artifacts, is subsequently illustrated with computer simulations and phantom experiments. Finally, an algorithmic correction scheme is derived to compensate for detector afterglow. The correction scheme employs a recursive filter to remove adverse effects of the detector decay on image quality. Experimental results have shown that the correction scheme successfully restores system spatial resolution, produces a more homogeneous noise pattern, and eliminates ring-band image artifacts due to detector afterglow. The effectiveness and robustness of the correction scheme are demonstrated by extensive phantom and clinical experiments.     

Tomographic reconstruction for tilted helical multislice CT

One of the most recent technical advancements in computed tomography (CT) is the introduction of multislice CT (MCT). Because multiple detector rows are used for data acquisition, MCT offers higher volume coverage, faster scan speed, and reduced X-ray tube loading. Recognizing its unique data-sampling pattern, several image reconstruction algorithms were developed. These algorithms have been shown to be adequate in producing clinically acceptable images. Recent studies, however, have revealed that the image quality of MCT can be significantly degraded when helical data are acquired with a tilted gantry. The degraded image quality has rendered this feature unacceptable for clinical usage. In this paper, we first present a detailed investigation on the cause of the image quality degradation. An analytical model is derived to provide a mathematical basis for correction. Several compensation schemes are subsequently presented, and a detailed performance comparison is provided in terms of spatial resolution, noise, computation efficiency, and image artifacts.     

Genetic Algorithm for Optimization of Infrastructure Investment Under Time-Resource Constraints

Abstract:   This work shows the infrastructure investment decision is essentially a 0-1, nonlinear, multiobjective knapsack problem. It argues that, without making substantial simplification on some of the practical considerations, a conventional mathematical optimization approach may not be suitable for solving the problem. Further, the use of explicit heuristics may sometimes be unwieldy dependent on the system parameters. An innovative approach based on the concept of genetic algorithms is proposed in the work to tackle the nonlinearity in the decision problem. Based on the experimental results, the proposed approach is capable of producing good quality results. The key success feature of the proposed approach resides in the unique and innovative modeling of system parameters by genetic coding in the algorithms .     

Coexpression of leptin receptor and preproneuropeptide Y mRNA in arcuate nucleus of mouse hypothalamus

Leptin, the protein product of the adipose tissue-specific ob (obese) gene (1), reduces the body weight, adiposity and food intake of obese ob/ob mice on peripheral or central injection (2, 3, 4). [125I]leptin binding has been detected in mouse choroid plexus (5), from which a leptin receptor gene was expression cloned (5). The gene has at least 6 splice variants (6, 7). Leptin receptor mRNA was localized in the hypothalamus by in situ hybridization being particularly abundantly expressed in the arcuate nucleus (8). There is evidence linking the physiological effects of injected leptin with hypothalamic neuropeptide Y (9, 10) (NPY), which has potent central effects on food intake and energy balance (11), and is also expressed in the arcuate nucleus. Here we report dual in situ hybridization studies for leptin receptor and NPY gene expression in the mouse arcuate nucleus, where the majority of cells examined expressed both genes. This provides the first direct evidence that leptin acts on cells that express NPY mRNA.     

Anticonvulsant and antibiotic prophylaxis in head injury

The evidence for and against the prophylactic use of anticonvulsants and antibiotics in head injury is reviewed. There is a lack of blinded placebo-controlled trials in this area. On balance there is no compelling evidence to support the use of either anticonvulsant or antibiotic prophylaxis in head injury, with the possible exception of antibiotic prophylaxis in compound depressed skull fractures and penetrating brain injuries.     

Telechelic elastomers

Telechelic elastomers, polymers with reactive terminal groups, can be prepared in emulsion and solution systems. Examples of characterization of the polymers and preparation of a mercapto telechelic copolymer in an emulsion system and of mercapto-, hydroxy-, and aziridinyl-telechelic elastomers in solution systems are given. The elastomers were cured in peroxide or sulfur-accelerator formulations. The telechelic polymers exhibited enhanced stress-strain and dynamic properties in comparision to those of the controls. In tread formulations, outstanding properties were obtained for the mercapto-and azieridinyl-telechelic butadiene-styrene copolymers.