We describe a compact, ultra-clean device used to deploy radioactive sources along the vertical axis of the KamLAND liquid-scintillator neutrino detector for purposes of calibration. The device ...worked by paying out and reeling in precise lengths of a hanging, small-gauge wire rope (cable); an assortment of interchangeable radioactive sources could be attached to a weight at the end of the cable. All components exposed to the radiopure liquid scintillator were made of chemically compatible UHV-cleaned materials, primarily stainless steel, in order to avoid contaminating or degrading the scintillator. To prevent radon intrusion, the apparatus was enclosed in a hermetically sealed housing inside a glove box, and both volumes were regularly flushed with purified nitrogen gas. Finally, an infrared camera attached to the side of the housing permitted real-time visual monitoring of the cable’s motion, and the system was controlled via a graphical user interface.
The removal of radioactivity from liquid scintillator has been studied in preparation of a low background phase of KamLAND. This paper describes the methods and techniques developed to measure and ...efficiently extract radon decay products from liquid scintillator. We report the radio isotope reduction factors obtained when applying various extraction methods. During this study, distillation was identified as the most efficient method for removing radon-born lead from liquid scintillator.
This paper reviews data from the International Technology Roadmap for Semiconductors to establish where dc-dc converters are headed in the first decade of the new millennium. It focuses on the high ...performance computing (high current, fast response, high power density) and portable/handheld (low profile) sectors. Magnetics and power device packaging technologies needed to allow power supplies to move to operating frequencies in the 1-10 MHz region are discussed. It introduces the concept of magnetic components fully embedded (windings and core) in PCB and silicon offering low profile and low losses at high frequency. It also reviews developments in wirebond-free power packaging such as flip-chip assembly that offer low profile, reduced parasitics and increased thermal performance. Finally, consideration is given to the changes in the power electronics industry that may need to be addressed to enable these new technologies to play a strategic role.
This paper presents the electrical performances of the fabricated microtransformers. Measurements for open-circuit and short-circuit impedance up to a frequency of 100 MHz are presented. The measured ...results are compared with predictions obtained from models based on an analytical approach. The use of a microtransformer in a 2-MHz dc-dc converter is reported. An efficiency of 40% for a power density of 1.2 W/cm/sup 2/ was measured.
The lamination of the core in thin film magnetic components is necessary to reduce the eddy current losses of the structure at high frequencies. The usual way to achieve lamination of the core is by ...physical vapor deposition (PVD) techniques. These methods are however costly and the deposition of layers is non selective. In this article, an almost entirely aqueous-based electrochemical process for the lamination of magnetic cores is presented. The process uses an electrodepositable photoresist Eagle 2100 ED codeposited with a catalyst (palladium). The Eagle layer is left as an insulator and the catalyst allows the activation of the layer for subsequent metallization. The process can be reproduced as many times as required for producing the multilayers. It is also selective: it does not require multiple photolithography steps. As a demonstration of the multilayer process, a core constituted of two layers of Ni/sub 80/Fe/sub 20/ (6 /spl mu/m each layer), separated by an Eagle insulating layer, electroplated over three-dimensional structures, was produced.
One of the many challenges associated with sensor networks is how to transmit data and power the sensors. Sensing multiple parameters in the environment requires miniaturized sensor nodes, relatively ...powerful programming platforms to interface with and process the data, and reliable long-term power solutions. Batteries provide the most obvious power source as long as the modules are reasonably big (a few square centimeters), easily accessible, and few in number so that the batteries can be easily replaced or recharged. In the vision of ubiquitous computing, where modules are embedded into everyday objects, computer hardware should be invisible and replacing batteries isn't compatible with this vision. Several solutions to the power problem exist, such as reducing power consumption to the point where batteries can last the module's lifetime. Another solution is energy scavenging - that is, extracting energy from ambient sources such as vibrations, hear, light, and water. A new approach provides a power source and fast communication for miniaturized modules' sensor nodes using a 13.56 MHz carrier. Although its powering range is limited, this method is well suited for applications in which communication must be fast but the sensor modules are hard to access.
The impact of different geometrical parameters on the performance of printed circuit board (PCB) integrated inductors with electroplated magnetic cores is investigated in this paper. The parameters ...of winding and core structures are limited only by PCB design rules for this novel type of integrated magnetic component. The performance of the resulting structures are compared in terms of achievable inductance, flux confinement in the core, and power handling. Initial design recommendations are presented for different power applications.
Adaptive neural network processing of phased-array antenna received signals promises to decrease antenna manufacturing and maintenance costs while increasing mission uptime and performance between ...repair actions. We introduce one such neural network which performs aspects of digital beamforming with imperfectly manufactured, degraded, or failed antenna components. This paper presents measured results achieved with an adaptive radial basis function (ARBF) artificial neural network architecture which learned the single source direction finding (DF) function of an eight-element X-band array having multiple, unknown failures and degradations. We compare the single source DF performance of this ARBF neural network, whose internal weights are computed using a modified gradient descent algorithm, with another radial basis function network, Linnet, whose weights are calculated using linear algebra. Both networks are compared to a traditional DF approach using monopulse.
Modeling of high-frequency micro-transformers Ningning Wang; Hauser, H.; O'Donnell, T. ...
IEEE transactions on magnetics,
07/2004, Letnik:
40, Številka:
4
Journal Article, Conference Proceeding
A dynamic model has been developed to predict the efficiency of a micro-transformer, operating at 5 MHz. The model includes a core hysteresis model, core eddy current model and winding copper loss ...model. Measurements and finite element analysis were carried out in order to validate the model.
Metabotropic glutamate receptors (mGluR) are classified into group I, II, and III mGluR. Group I (mGluR1, mGluR5) are excitatory, whereas group II and III are inhibitory. mGluR5 antagonism potently ...reduces triggering of transient lower esophageal sphincter relaxations and gastroesophageal reflux. Transient lower esophageal sphincter relaxations are mediated via a vagal pathway and initiated by distension of the proximal stomach. Here, we determined the site of action of mGluR5 in gastric vagal pathways by investigating peripheral responses of ferret gastroesophageal vagal afferents to graded mechanical stimuli in vitro and central responses of nucleus tractus solitarius (NTS) neurons with gastric input in vivo in the presence or absence of the mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP). mGluR5 were also identified immunohistochemically in the nodose ganglia and NTS after extrinsic vagal inputs had been traced from the proximal stomach. Gastroesophageal vagal afferents were classified as mucosal, tension, or tension-mucosal (TM) receptors. MPEP (1-10 microM) inhibited responses to circumferential tension of tension and TM receptors. Responses to mucosal stroking of mucosal and TM receptors were unaffected. MPEP (0.001-10 nmol icv) had no major effect on the majority of NTS neurons excited by gastric distension or on NTS neurons inhibited by distension. mGluR5 labeling was abundant in gastric vagal afferent neurons and sparse in fibers within NTS vagal subnuclei. We conclude that mGluR5 play a prominent role at gastroesophageal vagal afferent endings but a minor role in central gastric vagal pathways. Peripheral mGluR5 may prove a suitable target for reducing mechanosensory input from the periphery, for therapeutic benefit.
