共查询到20条相似文献,搜索用时 31 毫秒
1.
《Microwave Theory and Techniques》2008,56(10):2356-2365
Elevation of intracranial pressure is one of the most important issues in neurosurgery and neurology in clinical practice. The prevalent techniques for measuring intracranial pressure require equipments that are wired, restricted to a hospital environment, and cause patient discomfort. A novel method for measuring the intracranial pressure is described. A wireless completely implantable device, operating at an industrial-scientific-medical band of 2.4 GHz, has been developed and tested. In-vitro and in-vivo evaluations are described to demonstrate the feasibility of microwave pressure monitoring through scalp, device integrity over a long period of time, and repeatability of pressure measurements. A distinction between an epidural and sub-dural pressure monitoring techniques is also described. Histo-pathological results obtained upon a long-term device implantation favor the utilization of the sub-dural pressure monitoring method. On the other hand, in-vivo studies illustrate a maximum pressure reading error of 0.8 mm middot Hg obtained for a sub-dural device with a capacitive microelectromechanical system sensor compared to 2 mm middot Hg obtained for an epidural device with a piezoresistive sensor. 相似文献
2.
《Industrial Electronics, IEEE Transactions on》2009,56(2):389-399
3.
《Mechatronics, IEEE/ASME Transactions on》2009,14(6):658-666
4.
《Power Electronics, IEEE Transactions on》2009,24(6):1444-1452
5.
《IEEE transactions on circuits and systems. I, Regular papers》2009,56(2):327-336
6.
Cheolkyun Kim O'Rourke A.P. Mahvi D.M. Webster J.G. 《IEEE transactions on bio-medical engineering》2007,54(7):1177-1185
Cryoablation is a widely used method for the treatment of nonresectable primary and metastatic liver tumors. A model that can accurately predict the size of a cryolesion may allow more effective treatment of tumor, while sparing normal liver tissue. We generated a computer model of tissue cryoablation using the finite-element method (FEM). In our model, we considered the heat transfer mechanism inside the cryoprobe and also cryoprobe surfaces so our model could incorporate the effect of heat transfer along the cryoprobe from the environment at room temperature. The modeling of the phase shift from liquid to solid was a key factor in the accurate development of this model. The model was verified initially in an ex vivo liver model. Temperature history at three locations around one cryoprobe and between two cryoprobes was measured. The comparison between the ex vivo result and the FEM modeling result at each location showed a good match, where the maximum difference was within the error range acquired in the experiment (< 5 degC). The FEM model prediction of the lesion size was within 0.7 mm of experimental results. We then validated our FEM in an in vivo experimental porcine model. We considered blood perfusion in conjunction with blood viscosity depending on temperature. The in vivo iceball size was smaller than the ex vivo iceball size due to blood perfusion as predicted in our model. The FEM results predicted this size within 0.1-mm error. The FEM model we report can accurately predict the extent of cryoablation in the liver. 相似文献
7.
Do Q.-T. Blekker K. Regolin I. Prost W. Tegude F.J. 《Electron Device Letters, IEEE》2007,28(8):682-684
Metal-insulator field-effect transistors (FETs) are fabricated using a single n-InAs nanowire (NW) with a diameter of d = 50 nm as a channel and a silicon nitride gate dielectric. The gate length and dielectric scaling behavior is experimentally studied by means of dc output- and transfer-characteristics and is modeled using the long-channel MOSFET equations. The device properties are studied for an insulating layer thickness of 20-90 nm, while the gate length is varied from 1 to 5 mum. The InAs NW FETs exhibit an excellent saturation behavior and best breakdown voltage values of V BR > 3 V. The channel current divided by diameter d of an NW reaches 3 A/mm. A maximum normalized transconductance gm /d > 2 S/mm at room temperature is routinely measured for devices with a gate length of les 2 mum and a gate dielectric layer thickness of les 30 nm. 相似文献
8.
《Solid-State Circuits, IEEE Journal of》2008,43(12):2706-2715
9.
Davis C.E. Dickherber A.J. Hunt W.D. May G.S. 《Electronics Packaging Manufacturing, IEEE Transactions on》2008,31(4):273-284
Variable-frequency microwave (VFM) curing can perform the same processing steps as conventional thermal processing in minutes, without compromising intrinsic material properties. With increasing demand for novel dielectrics, there is a corresponding demand for new processing techniques that lead to comparable or better properties than conventional methods. VFM processing can be a viable alternative to conventional thermal techniques. However, current limitations include a lack of reliable temperature measuring techniques. This research focuses on developing a reliable temperature measuring system using acoustic techniques to monitor low-k polymer dielectrics cured on silicon wafers in a VFM furnace. The acoustic sensor exhibits the capability to measure temperatures from 20degC to 300degC with an attainable accuracy of plusmn2 degrees. 相似文献
10.
《Microwave Theory and Techniques》2009,57(2):344-351
11.
Tsung-Yu Chiang Tien-Sheng Chao Yi-Hong Wu Wen-Luh Yang 《Electron Device Letters, IEEE》2008,29(10):1148-1151
In this letter, for the first time, we have successfully fabricated silicon-oxide-nitride-oxide-silicon (SONOS) devices with embedded silicon nanocrystals (Si-NCs) in silicon nitride using in situ method. This process is simple and compatible to modern IC processes. Different Si-NCs deposition times by in situ method were investigated at first. SONOS devices with embedded Si-NCs in silicon nitride exhibit excellent characteristics in terms of larger memory windows (> 5.5 V), lower operation voltage, high P/E speed, and longer retention time (> 108 s for 13% charge loss). 相似文献
12.
《IEEE transactions on circuits and systems. I, Regular papers》2010,57(2):495-505
13.
Yi Pei Vampola K.J. Zhen Chen Rongming Chu DenBaars S.P. Mishra U.K. 《Electron Device Letters, IEEE》2009,30(5):439-441
AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (ITO) transparent gate electrodes have been fabricated. The transparent gate electrodes enable the investigation of photon, electron, and phonon behaviors in active regions in HEMTs using optical characterizations such as electroluminescence, photoluminescence, and Raman spectroscopy technologies. Leakage current, on/off ratio, and transparency have been compared for transistors using Ni/Au/Ni, ITO, and Ni/ITO stacks as gate electrodes. Compared to the Ni/Au/Ni gate transistor, the ITO gate device shows a comparable current gain cutoff frequency (f T) but a much lower power gain cutoff frequency (f max) due to the low conductivity of ITO. 相似文献
14.
Huafeng Liu Pengcheng Shi 《IEEE transactions on bio-medical engineering》2009,56(2):378-389
In addition to its technical merits as a challenging nonrigid motion and structural integrity analysis problem, quantitative estimation of cardiac regional functions and material characteristics has significant physiological and clinical value. We developed a stochastic finite-element framework for the simultaneous recovery of myocardial motion and material parameters from medical image sequences with an extended Kalman filter approach, and we have shown that this simultaneous estimation strategy achieves more accurate and robust results than separated motion and material estimation efforts. In this paper, we present a new computational strategy for the framework based upon the maximum a posteriori estimation principles, realized through the extended Kalman smoother, that produces a sequence of kinematics state and material parameter estimation of the entire myocardium, including the endocardial, epicardial, and midwall tissues. The system dynamics equations of the heart are constructed using a biomechanical model with stochastic parameters, and the tissue material and deformation parameters are jointly estimated from the periodic imaging data. Noise-corrupted synthetic image sequences with known kinematics and material parameters are used to assess the accuracy and robustness of the framework. Experiments with canine magnetic resonance tagging and phase-contrast image sequences have been conducted with very promising results, as validated through comparison to the histological staining of postmortem myocardium. 相似文献
15.
Tsechpenakis G. Bianchi L. Metaxas D.N. Driscoll M. 《IEEE transactions on bio-medical engineering》2008,55(5):1539-1549
The nematode Caenorhabditis elegans (C. elegans) is a genetic model widely used to dissect conserved basic biological mechanisms of development and nervous system function. C. elegans locomotion is under complex neuronal regulation and is impacted by genetic and environmental factors; thus, its analysis is expected to shed light on how genetic, environmental, and pathophysiological processes control behavior. To date, computer-based approaches have been used for analysis of C. elegans locomotion; however, none of these is both high resolution and high throughput. We used computer vision methods to develop a novel automated approach for analyzing the C. elegans locomotion. Our method provides information on the position, trajectory, and body shape during locomotion and is designed to efficiently track multiple animals (C. elegans) in cluttered images and under lighting variations. We used this method to describe in detail C. elegans movement in liquid for the first time and to analyze six unc-8, one mec-4, and one odr-1 mutants. We report features of nematode swimming not previously noted and show that our method detects differences in the swimming profile of mutants that appear at first glance similar. 相似文献
16.
Jongsik Kim Jaewook Shin Seungsoo Kim Hyunchol Shin 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(5):399-403
A pseudo-exponential capacitor bank structure is proposed to implement a wide-band CMOS LC voltage-controlled oscillator (VCO) with linearized coarse tuning characteristics. An octave bandwidth VCO employing the proposed 6-bit pseudo-exponential capacitor bank structure has been realized in 0.18-mum CMOS. Compared to a conventional VCO employing a binary weighted capacitor bank, the proposed VCO has considerably reduced the variations of the VCO gain (K VCO) and the frequency step per a capacitor bank code (f step/code) by 2.7 and 2.1 times, respectively, across the tuning range of 924-1850 MHz. Measurement results have also shown that the VCO provides the phase noise of - 127.1 dBc/Hz at 1-MHz offset for 1.752-GHz output frequency while dissipating 6 mA from a 1.8-V supply. 相似文献
17.
Cox M.P. Hongtao Ma Bahlke M.E. Beck J.H. Schwartz T.H. Kymissis I. 《Electron Devices, IEEE Transactions on》2010,57(1):174-177
We demonstrate a reflectivity-based cerebral blood volume sensor comprised of surface-mount light-emitting diodes on a flexible substrate with integrated photodetectors in a form factor suitable for direct brain contact and chronic implantation. This reflectivity monitor is able to measure blood flow through the change of the surface reflectivity and, through this mechanism, detect the cerebral-blood-volume changes associated with epileptic seizures with a signal-to-noise (SNR) response of 42 dB. The device is tested in an in vivo model confirming its compatibility and sensitivity. The data taken demonstrate that placing the sensor into direct brain contact improves the SNR by more than four orders of magnitude over current noncontact technologies. 相似文献
18.
Ghaderi J. Liang-Liang Xie Xuemin Shen 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2009,55(8):3425-3436
For a wireless network with n nodes distributed in an area A, and with n source-destination pairs communicating with each other at some common rate, the hierarchical cooperation scheme proposed in (Ozgur, Leveque, and Tse, 2007) is analyzed and optimized by choosing the number of hierarchical stages and the corresponding cluster sizes that maximize the total throughput. It turns out that increasing the number of stages does not necessarily improve the throughput, and the closed-form solutions for the optimization problem can be explicitly obtained. Based on the expression of the maximum achievable throughput, it is found that the hierarchical scheme achieves a scaling with the exponent depending on n . In addition, to apply the hierarchical cooperation scheme to random networks, a clustering algorithm is developed, which divides the whole network into quadrilateral clusters, each with exactly the number of nodes required. 相似文献
19.
《IEEE transactions on bio-medical engineering》2009,56(6):1734-1743
20.
《Power Electronics, IEEE Transactions on》2009,24(5):1321-1329