共查询到20条相似文献,搜索用时 15 毫秒
1.
《Solid-State Circuits, IEEE Journal of》2008,43(12):2787-2797
2.
《Solid-State Circuits, IEEE Journal of》2009,44(11):2922-2934
3.
《Solid-State Circuits, IEEE Journal of》2009,44(9):2426-2436
4.
《Solid-State Circuits, IEEE Journal of》2008,43(8):1846-1858
5.
《Solid-State Circuits, IEEE Journal of》2009,44(2):436-449
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.
Aredes M. Akagi H. Watanabe E.H. Vergara Salgado E. Encarnacao L.F. 《Power Electronics, IEEE Transactions on》2009,24(4):924-933
This paper presents a comparative analysis between results from applications of the p-q and the p-q-r theories in shunt active power filters for three-phase four-wire systems, discussing aspects related to the influence of the system voltage in the control methods that calculate the compensating currents. It is shown that in some cases, a preprocessing of the system voltage is required if the goal is to achieve sinusoidal compensated currents. On the other hand, when the goal is to compensate zero-sequence current, the need of energy storage elements in the active filter is discussed. In this case, if zero-sequence components are present simultaneously in the system voltage and load current, they produce zero-sequence power flow, and the control methods based on both theories must contain additional calculations to allow the elimination of energy storage elements in the active filter. A control strategy based on the p-q theory is proposed to eliminate the neutral current without the need of energy storage elements, with the advantage of avoiding the extra transformation from alphabeta0 to pqr coordinates that is needed in the p-q-r theory. Simulation results are presented for the purpose of comparing the performance of both control methods. 相似文献
8.
Tchamov N.T. Broussev S.S. Uzunov I.S. Rantala K.K. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2007,54(3):277-281
A dual-band LC voltage-controlled oscillator (VCO) architecture suitable for GSM/PCS/DCS applications is presented. The VCO utilizes a fourth-order resonance tank and avoids quality-factor-deteriorating switches. The paper outlines the design tradeoffs and the VCO when using a fourth-order resonator. The 0.8-GHz/1.8-GHz test chip was fabricated in the 0.5-mum IBM-5AM SiGe process and has achieved phase noise of -134 dBc/Hz at a 1-MHz frequency offset from the carrier, with 56-MHz and 121-MHz tuning ranges in the corresponding bands. The VCO core consumes 15 mW from a 2.5-V power supply 相似文献
9.
《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
10.
《IEEE transactions on medical imaging》2010,29(1):44-54
11.
《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2008,96(7):1071-1072
Considers how different our present state of technological prowess would be if wireless systems had not been discovered and implemented, then forecasts where we are headed in the real world and what the role of government and regulators may be. 相似文献
12.
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
13.
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
14.
《Microwave Theory and Techniques》2009,57(2):344-351
15.
《Power Electronics, IEEE Transactions on》2009,24(5):1321-1329
16.
Bahmani F. Serrano-Gotarredona T. Sanchez-Sinencio E. 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(4):745-756
This paper presents a scheme to accurately tune the quality factor of second-order LC bandpass filters. The information of the magnitude response at the center and one of the cutoff frequencies is used to tune both the amplitude and the quality factor of the filter using two independent yet interacting loops. Furthermore, the synergic interaction between the loops makes the proposed scheme stable and insensitive to the mismatch between the input amplitudes. A chip prototype was implemented in a 0.35-mum CMOS process and consumes 4.3 mA from a single 1.3-V supply. Measurement results show that at 1.97 GHz the quality factor is tunable from 60 to 220 while the amplitude is tunable between -15 and 0 dBm with worst case quality factor and amplitude tuning accuracies of 10% and 7%, respectively 相似文献
17.
《Industrial Electronics, IEEE Transactions on》2009,56(2):389-399
18.
Ahuja A.K. Behrend M.R. Kuroda M. Humayun M.S. Weiland J.D. 《IEEE transactions on bio-medical engineering》2008,55(6):1744-1753
Epiretinal prostheses are being developed to bypass a degenerated photoreceptor layer and excite surviving ganglion and inner retinal cells. We used custom microfabricated multielectrode arrays with 200-mum-diameter stimulating electrodes and 10-mum-diameter recording electrodes to stimulate and record neural responses in isolated tiger salamander retina. Pharmacological agents were used to isolate direct excitation of ganglion cells from excitation of other inner retinal cells. Strength-duration data suggest that, if amplitude will be used for the coding of brightness or gray level in retinal prostheses, shorter pulses (200 mus) will allow for a smaller region in the area of the electrode to be excited over a larger dynamic range compared with longer pulses (1 ms). Both electrophysiological results and electrostatic finite-element modeling show that electrode-electrode interactions can lead to increased thresholds for sites half way between simultaneously stimulated electrodes (29.4 plusmn 6.6 nC) compared with monopolar stimulation (13.3 plusmn 1.7 nC, < 0.02). Presynaptic stimulation of the same ganglion cell with both 200- and 10- m-diameter electrodes yielded threshold charge densities of 12 plusmn 6 and 7.66 plusmn 1.30 nC/cm2, respectively, while the required charge was 12.5 plusmn 6.2 and 19 plusmn 3.3 nC. 相似文献
19.
Shibasaki T. Tamura H. Kanda K. Yamaguchi H. Ogawa J. Kuroda T. 《Solid-State Circuits, IEEE Journal of》2008,43(3):610-618
Quadrature injection-lockedLC dividers with either a Miller topology or an injection-lockedLC VCO topology are coupled with transconductors to enhance their locking range. The effect of the transconductance coupling is analyzed theoretically and through circuit simulation. Both topologies were fabricated by 90-nm CMOS technology with a target input center frequency of 20 GHz and output frequency of 10 GHz. The measured locking range for the Miller topology with transconductance coupling is 25.3%, compared to 20.9% without coupling. The measured locking range for the injection-locked LC VCO topology with transconductance coupling is 18.1%, compared to 12.9% without coupling. Moreover, power consumption for both dividers is 6.4 mW with a 1.2-V supply. 相似文献
20.
《IEEE transactions on circuits and systems. I, Regular papers》2010,57(2):495-505