THE ESTIMATE AND MEASUREMENT OF LONGITUDINAL WAVE INTENSITY

Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.

Wave Intensity Analysis of Carotid Artery:A Noninvasive Technique for Assessing Hemodynamic Changes of Hyperthyroid Patients

This study examined the wave intensity (WI) of the carotid artery in patients with hyperthyroid in order to assess the hemodynamic changes of hyperthyroid patients.A total of 86 hyperthyroid patients without cardiac morphological changes and arrhythmia, and 80 healthy control subjects were enrolled in the study.Right common carotid artery (RCCA) was selected for ultrasonic imaging to obtain WI indices, including amplitude of the peak during early systole (W1), amplitude of the peak during late systole (W2), area of the negative wave during mid-systole (NA), interval between R wave of electrocardiogram and W1 (R-1st), interval between W1 and W2 (1st-2nd).The levels of serum thyroid hormones, consisting of free triiodothyronine (FT3), free thyroxin (FT4) and thyroid stimulating hormone (TSH), were measured in hyperthyroid patients.Echocardiographic indices including left ventricular ejection fraction (LVEF) and left ventricular fraction shortening (LVFS) were determined in each subject.The results showed that the W1, W2, NA, and (1st-2nd×HR) in hyperthyroid patients were significantly higher than those in healthy controls.There was no significant difference in LVEF and LVFS between the two groups.FT3 was correlated with W1, W2, NA, (1st-2nd×HR), pulse pressure (PP) and heart rate (HR) in hyperthyroid patients.Several abnormal waves on WI curves were present in 19 hyperthyroid patients during mid-systole.It was concluded that WI technique may prove a real-time, noninvasive, sensitive and convenient tool for assessing the cardiac function and hemodynamic alterations in hyperthyroid patients.

THE ESTIMATE AND MEASUREMENT OF TRANSVERSE WAVE INTENSITY

Transverse waves are a type of structural waves and should be considered in the analysis of high frequency vibration because the energy carried by transverse waves increases with the increase of frequency and becomes important at high frequencies. This paper studies the estimate theory and measuring technique of the transverse wave intensity in two-dimensional homogeneous structures. In general, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Each axial intensity component is proportional to two imaginary parts of cross spectral densities and its estimate is complicated. For the special case where transverse waves propagate in one direction, the intensity variation is zero and the estimate of the intensity is simplified. The intensity technique is formed based on the finite difference principle. Transverse wave intensity can be measured using a pair of two-transducer arrays lying in the orthogonal direction for the general case or a two-transducer array lying in the propagating direction for the special case. In order to assess the measurement accuracy of transverse wave intensify, the coupling loss factors from bending to transverse waves in building structures were measured using the intensity technique and compared with the results predicted and measured using the conventional method. It is shown that the agreement between the results measured using the intensity technique and that by the conventional method is good.

Bending wave intensity in a thick beam

In this paper the expressions are derived for estimating bending wave intensity and its components at arbitrary frequency in one-dimensional structures such as beams. There is a critical frequency fo above which there are two bending waves with different wave numbers propagating along a structure and the estimates of bending wave intensity and its components become quite complicated, and it may not be possible to measure bending wave intensity using the existing intensity techniques. The expressions are also derived for calculating approximate estimate error resulting from using the existing intensity theory. To verify the theoretical results, a series of measurements was carried out on a masonry column under laboratoryconditions.

The measurement of bending wave intensity in a two-dimensional structure

In a two-dimensional bending wavefield, the intensity vector is the sum of the effec-tive intensity vector and the intensity variation vector. The effective intensity vector gives the magnitude and direction of bending wave power flow per unit width in structures. The illtensity variation vector characterizes the circulation of local bending wave energy and varies harmon ically with space and wavenumber. This paper studies the relationship between the analysis frequency bandwidth and the measurement acctiracy of effective bending wave intensity, and ex-amines the accuracy of source localization using measured intensity vectors in two-dimensional structures. It is shown that if the analysis frequency bandwidth is wider than the sum of several one-third octave frequency bandwidths, the intensity variation can be suppressed to a negligible value in comparison with the effective intensity Moreover, a structure-borne source can be localized by measuring effective bending wave intensity vectors at a few positions, but the accuracy is dependent on the analysis frequency bandwidth, the property of the wavefield and the distance between source and measurement position. The more active the wavefield, the higher the accuracy of 8ource localization.

A Preliminary Study on the Intensity of Cold Wave Storm Surges of Laizhou Bay

Abstract Dike failure and marine losses are quite prominent in Laizhou Bay during the period of cold wave storm surges because of its open coastline to the north and fiat topography. In order to evaluate the intensity of c01d wave storm surge, the hindcast of ma- rine elements induced by cold waves in Laizhou Bay from 1985 to 2004 is conducted using a cold wave storm surge-wave coupled model and the joint return period of extreme water level, concomitant wave height, and concomitant wind speed are calculated. A new criterion of cold wave storm surge intensity based on such studies is developed. Considering the frequency of cold wave, this paper introduces a Poisson trivariate compound reconstruction model to calculate the joint return period, which is closer to the reality. By using the newly defined cold wave storm surge intensity, the ＇cold wave grade＇ in meteorology can better describe the severity of cold wave storm surges and the warning level is well corresponding to different intensities of cold wave storm surges. Therefore, it provides a proper guidance to marine hydrological analysis, disaster prevention and marine structure design in Laizhou Bay.

Effects of size and location of distal tear on hemodynamics and wave propagation in type B aortic dissection

The type B aortic dissection(TBAD)is a perilous disease with high morbidity and mortality rates.The hemodynamics of TBAD in different scenarios has been widely studied by computational fluid dynamics(CFD)research.However,the flow pattern and wave propagation characteristics in the cardiovascular system with TBAD are not yet clear,and the effect of the distal tear is still unknown.In this work,a onedimensional(1D)cardiovascular system model coupling with a zero-dimensional(0D)lumped-parameter model is introduced to study the hemodynamics and wave propagation in the cardiovascular system.The results show that the proposed 0D-1D method well captures the oscillation and retrograde characteristics for the flow in the false lumen(FL),and the smaller distal tear damps the retrograde flow.Besides,the distal tear should also be paid attention to,and the wave intensity(WI)can be used as an access mark of the degree of the aortic dissection(AD).

The damage of the optical components induced by the stimulated Brillouin scattering

A theory of excitation of ultrasonic waves in the stimulated Brillouin scattering （SBS） process is presented in this paper. By using several reasonable approximations, a numerical calculation of the transient longitudinal SBS shows that large amplitude of acoustic waves can be built up by the nanosecond pulse of high-power laser, which may result in the damage of optical glasses. The maximal density change and the maximal acoustic wave intensity in optical glasses of 5cm in thickness are calculated by using different parameters of the high-energy laser, such as the intensity, the pulse width, and the wave length. The damage threshold of the optical glasses is about 80 GW/cm^2 when using a 1064 nm laser. The dynamic mechanism of SBS is the electrostriction effect of the components coupling with the high-power laser.

A preliminary study of the feasibility of using superconducting quarter-wave resonators for accelerating high intensity proton beams

The superconducting （SC） cavities currently used for the acceleration of protons at a low velocity range are based on half-wave resonators. Due to the rising demand on high current, the issue of beam loading and space-charge problems has arisen. Qualities of low cost and high accelerating efficiency are required for SC cavities, which are properly fitted by using SC quarter-wave resonators （QWR）. We propose a concept of using QWRs with frequency 162.5 MHz to accelerate high current proton beams. The main factor limiting SC QWRs being applied to high current proton beams is vertical beam steering, which is dominantly caused by the magnetic field on axis. In this paper, we intend to analyze steering and eliminate it to verify the qualification of using QWRs to accelerate high intensity proton beams.

Spin effects on the relativistic strong EM wave modes in magnetized plasma

Based on the relativistic hydrodynamic model of EM wave-spin plasmas interaction,the spin effects on the relativistic strong EM modes in magnetized plasma are investigated.The dispersion relations of the EM wave propagating parallel and perpendicular to the external magnetic field are obtained.Results show that the strong EM wave modes are affected by the time component of four-spin as well as the increase of electron effective mass.Especially in the case of EM wave propagating parallel to the external magnetic field,the time component of fourspin amplifies the influence of spin effects on the low-frequency modes obviously.

Relationship between Renying pulse augmentation index and Cunkou pulse condition in different blood pressure groups

OBJECTIVE： To explore the relationship between Renying pulse （carotid） augmentation index （AI） and Cunkou pulse condition in different blood pres- sure groups, and the clinical significance of Reny- ing and Cunkou pulse parameters to reflect vascu- lar function. METHODS： Eighty-six patients with essential hyper- tension （EH） and 52 individuals with normal blood pressure （control group） between and January 2012 were included September 2010 this study. Reny- ing pulse AI was examined by a new diagnostic tool （ALOKA ProSound Alpha 10） --wave intensity （Wl） that is calculated as the product of the deriva- tives of the simultaneously recorded blood pres- sure changes （dP/dt） and blood-flow-velocity changes （dU/dt）, while Cunkou pulse condition was detected by DDMX-100 Pulse Apparatus inboth EH and control groups. A multifactorial corre- lation analysis was performed for data analysis. RESULTS： After adjusting for potential confound- ing variables, in the EH group, AI was positively cor- related with ts, w2/t （rts=0.225, P〈0.05; rw2/t=0.230, P〈 0.05） and negatively correlated with hs, hs/hl and w2 （rhs=- 0.393,P〈0.01 ;rhs/l=- 0.444, P〈0.01 ;rw2=- 0.389, P〈0.01）. In the control group, AI was positively cor- related with t3, t4, ts and w, （rt3=0.595, P〈0.01; r,4= 0.292, P〈0.05; rt5=0.318, P〈0.05; rw1=0.541, P〈0.01） and negatively correlated with h1, h2, h3, Ad and A （rh1= - 0.368, P〈0.05; rh2= - 0.330, P〈0.05; rh3= - 0.327, P〈 0.05; rAd=- 0.322, P〈0.05; rA=- 0.410, P〈0.01）. In the total sample group （EH plus control group, n= 138）, AI was positively correlated with t, ts, w1 and w, （rt=0.257, P〈0.01; rt5=0.266, P〈0.01; rw1=0.184, P〈 0.05; rw/t=0.210, P〈0.05） and negatively correlated with hs, hs/hl, w2 and Ad （rhs= - 0.230, P〈0.01; rh5/h1= - 0.218, P〈0.05; rw2= - 0.267, P〈0.01; rAd= - 0.246, P〈0.01）. Multiple linear regression analysis was car- ried out to model the relationship （F=7.887, P〈 0.001）.CONCLUSION： Renying pulse AI can effectively pre- dict arterial stiffness in synchrony with the manifes- tations of Cunkou pulse in elderly patients with hy- pertension. Cunkou pulse apparatus is a valuable tool for evaluating AI in clinical practice, The close correlations reported above reflect the holistic con- cept of Traditional Chinese Medicine.