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In this paper, we examine methods of characterizing somatosensory evoked potentials (SEP's) in both the time and frequency domains. We have found that the truncated impulse response (TIR) method produced an accurate time domain model of the SEP signals at model orders greatly reduced from the original state space matrix. The TIR method was valuable for smoothing signals that were slightly corrupted by noise. In this case, the simulated data sequence was close to the original data sequence in the mean squared error sense. For signals that were greatly corrupted by noise, the TIR method was not able to perform as well. Therefore, the TIR method was not a feature extraction method but was valuable for data simulation. In the frequency domain, we have used the autoregressive moving average model (ARMA) to parameterize the SEP signal. An overdetermined set of Yule-Walker equations was created to determine the autoregressive (AR) parameters of the original data with the model order established by the singular value decomposition. From these AR parameters, a residual time series was generated which was used to find the moving average parameters. The resulting ARMA model was used to produce a simulated data sequence. The frequency domain characteristics of the simulated sequence and the corresponding power spectral density of the ARMA filter were very close to the periodogram of the original data sequence. Accurate parameterization was achieved for the SEP waveforms at low filter lengths. 相似文献
124.
Mariana Ušáková Jozef Lukáč Rastislav Dosoudil Vladimír Jančárik Anna Grusková Elemír Ušák Jozef Sláma Jan Šubrt 《Journal of Materials Science: Materials in Electronics》2007,18(12):1183-1189
The paper is devoted to the preparation of NiZn ferrite with small substitutions of copper by means of ceramic technology.
The influence of small Cu substitution on the microstructural and magnetic properties of NiZn ferrites have been analysed
by means of various experimental methods and interpreted from the point of view of preparation technology optimisation and
possible applications of such materials. A strong correlation between the substituent content and resulting properties has
been observed, thus allowing preparation of material with the properties tailored for any particular application. 相似文献
125.
Performance of Storage Tanks in Oil Facilities Damaged by Hurricanes Katrina and Rita 总被引:1,自引:0,他引:1
Luis A. Godoy 《Canadian Metallurgical Quarterly》2007,21(6):441-449
126.
J. L. Díez J. L. Navarro A. Sala 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(10):973-983
In this work, simple modifications on the cost index of particular local-model fuzzy clustering algorithms are proposed in
order to improve the readability of the resulting models. The final goal is simultaneously providing local linear models (reasonably
close to the plant’s Jacobian) and clustering in the input space so that desirable characteristics (regarding final model
accuracy, and convexity and smoothness of the cluster membership functions) are improved with respect to other proposals in
literature. Some examples illustrate the proposed approach. 相似文献
127.
Beatriz O. Hincapie Luis J. Garces Sinue Gomez Ruma Ghosh Steven L. Suib 《Catalysis Today》2005,110(3-4):323
Copper containing faujasite has been successfully prepared for the first time using a direct synthesis method. Faujasite type zeolite can be prepared in the presence of copper species by tuning the synthesis conditions. Ammonium hydroxide was used to form a copper complex that was later mixed with the reacting gel. Sodium is required to obtain copper faujasite. The complete elimination of sodium ions from the starting gel produces amorphous material. Crystallization took place at 358 K for 11 days. Crystallization temperature of 373 K produces ANA type zeolite as an impurity. Increasing by two times the amount of copper complex added to the reacting gel increases the crystallization time of Cu-FAU from 11 to 20 days (the crystallization rate decreases). The copper containing faujasite obtained was characterized by XRD, FESEM, EDX, EPR, FT-IR, TPR, and BET. According to the XRD pattern only FAU type zeolite was obtained. According to TPR experiments, the reduction temperature for Cu2+ ions present in Cu-FAU prepared by direct synthesis was 70 K more than for Cu-FAU prepared by ion-exchange. This difference can be due to the different location of the copper ions in the supercages or in the sodalite cages of the faujasite. 相似文献
128.
J Alvarez-Sabín 《Canadian Metallurgical Quarterly》1997,25(142):919-923
Between 3.7% and 8.5% of all strokes occur before the age of 45 years old. In the population under 15 years of age, the annual incidence of strokes is 2.7 per 100,000 children, with ischaemic strokes making up 1.2 and haemorrhagic strokes 1.5 of this total. The main characteristic of ischaemic strokes in childhood is the wide variety of diagnoses involved. Some of these, such as congenital cardiopathy, are rare in adults, as are dissections and arterial dysplasias, arteritis, hereditary connective tissue disorders and disorders of metabolism. Similarly, the aetiology of haemorrhagic stroke is also very varied, with bursting of a vascular malformation or aneurysm being the commonest. Other aetiologies are disorders of haemostasis, arteritis, migraine, retarded post-traumatic phenomena and the use of drugs and sympathomimetic agents. The personal, family and social repercussions are considerable, since both ischaemic and haemorrhagic strokes have an appreciable mortality and morbidity. 相似文献
129.
Cytidine deaminase (CDA) and adenosine deaminase (ADA) were investigated in the serum and polymorphonuclear leukocytes (PMNLs) of healthy controls and ten patients with rheumatoid arthritis before and during cyclosporin therapy. CDA was significantly raised in the serum and decreased in the cells of patients. A dramatic increase (10-fold or more) in CDA activity was observed in the cells of some patients after only one month of cyclosporin therapy. Serum CDA significantly increased after three months' therapy. While the increase in serum CDA level during therapy was transient, the enzyme level in cells remained permanently raised, as shown in two patients evaluated for sixteen months. ADA in the serum of RA patients was somewhat higher as compared with healthy controls and remained almost unchanged during cyclosporin therapy. ADA activity in the cells also increased, but compared with the increase in CDA activity this increase was lower. Cyclosporin increased both CDA and ADA activities in PMNLs of RA patients. The dramatic increase in CDA observed in PMNLs of patients could be the cause of the transient increase in CDA in the serum. Further investigations will show to what extent this property of cyclosporin can reflect the immunoregulatory effect of this drug. 相似文献
130.
C Fernández Pinilla M Luque Otero N Martell Claros JM Alcázar de la Osa JL Rodicio Díaz LM Ruilope Urioste 《Canadian Metallurgical Quarterly》1993,101(5):168-171
BACKGROUND: Hypertension and hypercholesterolemia are frequently associated with this leading to considerable cardiovascular risk. METHODS: An open parallel randomized study was performed in which the effects of doxazosin, an alpha-adrenergic blocker and enalapril, an inhibitor of the angiotensin converting enzyme were compared in 70 patients with essential high blood pressure and plasma cholesterol levels greater than 240 mg/dl. Following 2-4 weeks of placebo administration the patients were randomly treated with one of the two drugs. When required doses were increased and hydrochlorothiazide added until blood pressure lower than 160/95 mmHg was achieved. After this period the patients were observed for a minimum of 8 weeks. The mean length of the study was of 22 weeks. RESULTS: Both drugs significantly reduced blood pressure without modifying cardiac frequency. Doxazosin tended to favorably modify the lipid profile of the plasma while enalapril significantly reduced the levels of cholesterol, lipids and high density lipoproteins (HDL). Upon termination of the study the total HDL/cholesterol index increased 8.6% in those treated with doxazosin and decreased 5.5% in those receiving enalapril (p < 0.05). CONCLUSIONS: Although doxazosin and enalapril are potent antihypertensive drugs, the effects on plasma lipid obtained with doxazosin indicate that a reduction in cardiovascular risk was achieved with this drug in the patients included in this study. 相似文献