Damping Index Research Articles

Evaluation of portal hypertension esophageal varices (moderate to severe) via liver ultrasound hemodynamic parameters

Objective To evaluate the application of liver ultrasound hemodynamic parameters in diagnosing moderate to severe esophageal varices(EV) among patients suffering from portal hypertension.Methods The control group consisted of twenty nine patients without EV.Sixty patients with EV diagnosed by endoscopy were divided into two groups equal in number according to grade of EV.One being mild,the other was moderate to severe.All patients underwent color Doppler flow imaging and contrastenhanced ultrasound,and the dynamic angiography data were collected.Time intensity curves were drawn by software to acquire the arrive time of hepatic artery (HAAT),hepatic vein (HVAT) and portal vein (PVAT).Then HV-HA interval time,PV HA interval time and PV-HV interval time were calculated.The quantitative parameters including HV-HA,PV-HA,PV-HV,damping index (DI) of hepatic vein and portal vein velocity(PVV) were compared.ROC curve was used to assess the value of the parameters above in predicting moderate to severe esophageal varices.Results The difference of PV-HV,PV HA,HV-HA,PVV,DI between the control and the moderate to severe group were statistically significant (P =0.000).PV-HV,PV-HA,HV-HA,DI in moderate to severe group showed statistically significant compared with mild group (P =0.000,P =0.002,P =0.000,P =0.002),however,PVV had no significant (P ＞0.05) difference between the two groups.Mild group contrasted to the control group,the differences of PV-HA and HV-HA were statistically significant (P =0.000),whereas PV-HV,DI,PVV displayed no significant (P ＞0.05) difference.The areas under ROC curve of PV-HV,PV-HA,HV-HA,PVV,DI were 0.952,0.775,0.847,0.699,0.808 respectively.The best cutoff value of PV-HV for diagnosing moderate to severe EV was 0.5 second,with sensitivity and specificity of 86.2％ and 94.8％ respectively.Conclusions The liver ultrasound hemodynamic parameters is helpful in the diagnosis and evaluation of moderate to severe esophageal varices,which is expected to become a new noninvasive method. Key words: Ultrasonography; Microbubbles ; Liver ; Hemodynamic phenomena ; Esophageal varices

Modeling And Control Of Excitation And Governor Based On Particle Swarm Optimization For Micro Hydro Power Plant

This paper presents the modeling and control of the excitation system via the automatic voltage regulator (AVR) and governor system through the automatic generation control (AGC) or frequency load control (FLC) to improve stability on a micro hydro power plant (MHPP). Three main parts of the generation system are synchronous generator, AVR-excitation, AGC modelled linearly. Generator is modelled by a single machine connected to infinite bus (SMIB) which is equipped by AVR and excitation linear model. Excitation control system made by optimizing the gain of the AVR (K A ) and the governor with the gain of the AGC (K i ). Optimization is done using the method improved particle swarm optimization (IPSO). The main purpose of setting the gain of the AVR-AGC is to stabilize the oscillation frequency of the MHPP which is connected to an infinite bus. Simulations are conducted by inputting step function with 5% load fluctuations as a representation of dynamic load. The simulation results show that the proposed method effectively raises the level of electromechanical damping oscillations the SMIB by generating the comprehensive damping index (CDI) is minimum.

Brillouin spectroscopy of a novel baria-doped silica glass optical fiber

Presented here for the first time to the best of our knowledge is a detailed Brillouin spectroscopic study of novel, highly-BaO-doped silica glass optical fibers. The fibers were fabricated utilizing a molten-core method and exhibited baria (BaO) concentrations up to 18.4 mole %. Physical characteristics such as mass density, acoustic velocity, visco-elastic damping, and refractive index are determined for the baria component of the bariosilicate system. It is found that, of each of these parameters, only the acoustic velocity is less than that of pure silica. The effect of temperature and strain on the acoustic velocity also is determined by utilizing estimates of the strain- and thermo-optic coefficients. The dependencies are found to have signs opposite to those of silica, thus suggesting both Brillouin-frequency a-thermal and a-tensic binary compositions. Via the estimate of the strain-optic coefficient and data found in the literature, the Pockels' photoelastic constant p(12) is estimated, and both a calculation and measured estimate of the Brillouin gain versus baria content are presented. Such novel fibers incorporating the unique properties of baria could be of great utility for narrow linewidth fiber lasers, high power passive components (such as couplers and combiners), and Brillouin-based sensor systems.

Energy Absorption Characteristics of Interface Modified GFRP Laminates under Low Velocity Impact

The effect of modification of the ply-interfaces in glass fibre reinforced polymer (GFRP) laminates with dispersed micro-particles on its impact characteristics was investigated. The reference and modified laminates were fabricated using woven GFRP prepregs. Impact tests were conducted using an instrumented drop tower device at various incident energy levels. The results were analysed using 5 different energy terms, namely maximum energy (Emax), elastic energy (Eel), absorbed energy (Eab), energy before peal load (Ebpl), energy after peak load (Eapl) and the damping index (DI). This investigation elaborates the relationship between the different energy terms as a function of the incident impact energy and time. The analysis of the energy characteristics indicates reduction in impact damage in the modified laminates. The modified laminates show higher Ebpland lower DI when compared to the reference laminates.

Radiative damping suppressing and refractive index sensing with elliptical split nanorings

Radiative damping and refractive index sensing performances of elliptical split nanorings are investigated. The third order resonance can be viewed as two electric dipoles in opposite directions, leading to a cancellation of their dipole moments. The scattering quantum yield decreases from 0.647 to 0.183 by adjusting the outer radii, and the corresponding largest figure of merit of sensing performance is 10.6, which is 61% and 86% larger than the split and perfect rings, respectively. Radiative damping can be further suppressed by increasing the gap size; the scattering quantum yield is decreased to 0.138 when the gap size is 35 nm.

Impact Damage Resistance of CFRP Prepreg Laminates with Dispersed CSP Particles into Ply Interfaces

The effects of incorporating core shell polymer (CSP) particles within interply interfaces on the impact response of CFRP prepreg laminates are investigated. The impact tests were conducted on samples without and with CSP particles into the ply interfaces. The loads versus time curves were examined to determine the impact response and the associated energy absorption by the laminates were studied. The results indicate that both, the peak load of the laminates improved by 41% and damping index (DI) reduced by 90% with the dispersion of 51 g/m2 of CSP particles within the prepreg ply interfaces of the laminates. It was noted that the CSP particles shielded the composites from the initial severity of impact. The energy absorbing mechanisms altered the supercritical response of the laminate to subcritical due to increase in the elastic energy stored within the laminates with CSP particles thereby changing the energy absorption modes. It was observed from macroscopic observations and SEM images of the damage sites that the damage mechanism and patterns changed and the extent of damage reduced with the addition of CSP particles.

Assessment of intrahepatic blood flow by Doppler ultrasonography: Relationship between the hepatic vein, portal vein, hepatic artery and portal pressure measured intraoperatively in patients with portal hypertension

BackgroundAbnormality of hepatic vein (HV) waveforms evaluated by Doppler ultrasonography has been widely studied in patients with chronic liver disease. We investigated the correlation between changes in HV waveforms and portal vein velocity (PVVel), the hepatic artery pulsatility index (HAPI), and also the extent of abnormal Doppler HV waveforms expressed as damping index (DI), severity of portal hypertension expressed as Child-Pugh scores and portal pressure (PP) measured directly from patients with portal hypertension (PHT) to evaluate the indicative value of abnormal HV waveforms and discuss the cause of abnormal HV waveform.MethodsSixty patients who had been diagnosed with PHT and accepted surgical therapy of portosystemic shunts were investigated. PP was measured intraoperatively. Thirty healthy volunteers with no history of chronic liver disease were enrolled as the control group. HV waveforms were categorized as triphasic, biphasic or monophasic. DI was compared as the quantitative indicator of abnormal HV waveforms. Another two Doppler parameters, PVVel and HAPI were also measured. These Doppler features were compared with PP, Child-Pugh scores and histological changes assessed by liver biopsy.ResultsIn the patient group, the Doppler flow waveforms in the middle HV were triphasic in 31.6%, biphasic in 46.7%, and monophasic in 21.6% of subjects. These figures were 86.7%, 10.0%, and 3.3%, respectively, in healthy subjects. With the flattening of HV waveforms, the HAPI increased significantly (r = 00.438, p < 0.0001), whereas PVVel decreased significantly (r = -0.44, p <0.0001). Blood flow parameters, HAPI, PVVel and HV-waveform changes showed no significant correlations with Child-Pugh scores. The latter showed a significant correlation with PP (r = 0.589, p = 0.044). Changes of HV waveform and DI significantly correlated with PP (r = 0.579, r = 0.473, p <0.0001), and significant correlation between DI and Child-Pugh scores was observed (r = 0.411, p = 0.001). PP was significantly different with respect to nodule size (p < 0.05), but HV-waveform changes were not significantly correlated with pathological changes.ConclusionIn patients with PHT, a monophasic HV waveform indicates higher portal pressure. Furthermore, quantitative indicator DI can reflect both higher portal pressure and more severe liver dysfunction. Flattening of HV waveforms accompanied by an increase in the HAPI and decrease in PVVel support the hypothesis that histological changes reducing HV compliance be the cause of abnormality of Doppler HV waveforms from the hemodynamic angle.

Comparison of transient elastography to Doppler indices in prediction of hepatitis C induced liver fibrosis and cirrhosis

ObjectivesThe aim of our study was to examine the efficiency of transient elastography (TE) and Doppler indices, namely hepatic vein damping index (DI) and splenic artery pulsatility index (SAPI) for evaluating the degree of hepatic fibrosis in chronic hepatitis C (CHC) patients. Patients and methodsOne hundred and ten CHC patients were enrolled. Hepatic vein DI, SAPI, and TE were performed to all patients before liver biopsy. Fibrosis was assessed on semi quantitative scoring system (METAVIR score). We examine the efficiency of each test in differentiating different stages of hepatic fibrosis and their diagnostic accuracy in predicting significant fibrosis F⩾2 and cirrhosis. ResultsTE showed the best results in differentiating different stages of fibrosis (p<0.001), TE had the best diagnostic accuracy for prediction of significant fibrosis and cirrhosis (AUROCs: for F⩾2 TE 0.92 vs. SAPI 0.74, DI 0.75; for cirrhosis TE 0.95 vs. DI 0.80, SAPI 0. 79). At a cut-off of 7kPa, TE predicted significant fibrosis with 87% sensitivity and 86% specificity, it correctly classified 87% of patients vs. 71% for DI and 68% for SAPI. For prediction of cirrhosis, TE at 16.5kPa had 87% sensitivity and 91% specificity it correctly classified 90% of patients vs. 70% for DI and 68% for SAPI. ConclusionTE is a non-invasive technique to accurately detect the presence of significant fibrosis and cirrhosis in patients with CHC. While the ability of Doppler tests was limited.

Changing Waveform During Respiration on Hepatic Vein Doppler Sonography of Severe Portal Hypertension

The purposes of this study were to assess retrospectively whether the waveform change during respiration on hepatic vein Doppler sonography is a parameter of severe portal hypertension as estimated by the hepatic venous pressure gradient (HVPG) and to compare with a hepatic vein damping index (DI) at expiration. Spectral Doppler sonography of the hepatic vein was performed on 22 consecutive patients who underwent HVPG measurement for portal hypertension with liver cirrhosis. From the maximum and minimum velocities of systolic hepatofugal venous flow on Doppler sonography, 3 parameters were derived: damping index at expiration (DI(exp)), damping index ratio (DI(ratio)), and damping index difference (ΔDI) between inspiration and expiration. Considering an HVPG level of 12 mm Hg or higher as the threshold level for high-grade portal hypertension, we assessed the diagnostic capability of these Doppler sonographic parameters to discriminate using receiver operating characteristic curve analysis. Area under the curve values for the DI(ratio) and ΔDI (0.875 and 0.889, P = .807 and .682, respectively) were slightly higher than the area for the DI(exp) (0.861; respectively). When the DI(exp) was greater than 0.56, the sensitivity and specificity for high-grade portal hypertension were 66.7% and 100.0%, respectively. In the case of the DI(ratio), the sensitivity and specificity were 77.8%, and 100.0% at greater than 0.69. The corresponding sensitivity and specificity at a value of 0.25 or less for the ΔDI were 83.3% and 100.0%. The ratio and difference of the DI of the hepatic vein waveform are helpful parameters in assessing the severity of portal hypertension as well as using the existing DI on its own.

Variations of Indoor Environment and the Prevalence of Sick House Syndrome over Three-Year Period in Detached Houses in Sapporo

The purpose of this study was to investigate annual variations in indoor environmental chemical, fungal and dust mite allergen levels, with regards to variations in sick house syndrome (SHS) symptoms over a three-year period. Detached houses were randomly selected from a building plan approval application, and a questionnaire survey was conducted in 2003 in Sapporo, Japan. Indoor environmental measurements and a self-administered questionnaires survey were conducted on the selected houses in 2004, 2005 and 2006. The same protocol was used for the three-year period to measure the levels of chemicals, fungi and dust mite allergens. A personal questionnaire to assess SHS was distributed to all inhabitants of the dwellings along with one questionnaire to assess housing characteristics. In 2004, 2005 and 2006, the owners of 104, 64 and 41 houses, respectively, agreed to participate in this study. Forty-one houses and the 127 inhabitants who participated in this three-year survey period were included in the analysis to evaluate the associations between differences in environmental measurements and SHS. The levels of formaldehyde, acetone, toluene, Alternaria and Cladosporium tended to decrease, whereas those of limonene and Aspergillus tended to increase over the three-year period. Increasing levels of Cryptococcus and the dampness index in individual houses correlated with increasing SHS symptom scores in the inhabitants after mutual adjustment. Although the average levels of chemicals and fungi were relatively low, the results show the relationship between annual variations in indoor environmental measurements and variations in SHS symptom scores.

Prevalence of Asthma, Atopic Dermatitis, and Rhinitis and MVOC Exposure in Single Family Homes—A Survey in 6 Cities of Japan

PP-29-136 Background/Aims: Microbial volatile organic compounds (MVOC) are a range of volatile organic compounds produced by microorganisms. According to previous reports, exposure to various MVOC at school was associated with asthmatic symptoms in pupils and a history of asthma among school employees. However, the relationship between MVOC exposure at home and allergies in inhabitants remains unknown. The aim of this study was to investigate the relationship between allergic symptoms and selected MVOC exposure in single family homes. Methods: This study is based on a survey conducted in 2006. Subjects were 624 inhabitants of 182 detached houses in 6 cities of Japan. Air samples were collected using diffusive samplers for 48 hours, and the concentrations of 8 selected compounds were analyzed by Gas Chromatograph-Mass Spectrometer (SIM). All inhabitants of the dwellings were given a self-administered questionnaire on age, sex, and medications for bronchial asthma, atopic dermatitis, and allergic rhinitis within the past 2 years. Adult inhabitants were also asked to fill out questions regarding housing characteristics. Results: The most frequently detected MVOC was 1-pentanol at a median concentration of 0.60 μg/m3. Among the 609 subjects who completed questions about allergies, the prevalence of asthma, atopic dermatitis, and allergic rhinitis was 4.8%, 9.9%, and 18.2%, respectively. No difference was found among genders, but a higher prevalence was obtained among younger subjects. A significant association between rhinitis and 1-octen-3-ol (per log10-unit: odds ratio, 2.02; 95% confidence interval: 1.05–3.87) was obtained after adjusting for age, sex, environmental tobacco smoke, and dampness index. No MVOC was related to asthma or atopic dermatitis after adjustment. Conclusion: According to the results of experimental volunteer 1-octen-3-ol exposure, mucosal irritation of airways was observed. Although indoor air concentrations of 1-octen-3-ol in this study were relatively low, exposure may cause irritation in inhabitants and evoke a rhinitis.

Dampness, food habits, and sick building syndrome symptoms in elementary school pupils

We investigated dampness/mold in schools and dwellings, and food habits and subjective symptoms in elementary school pupils, in order to clarify the effect of dampness and food habits on subjective symptoms in elementary school pupils. Questionnaires were used to investigate dampness in classrooms and dwellings in Hokkaido, Japan, and its effect on subjective symptoms in 1,077 pupils in 8 elementary schools. We used a dampness index for both the home and classroom; the index was the sum of the presence of four dampness indicators: (1) visible mold, (2) moldy odor, (3) water leakage, and (4) condensation on windowpanes. The questionnaire also contained queries about food habits, as follows: the frequency of eating breakfast, whether the energy provided by the school lunch was sufficient, and whether eating too many snacks and/or sweets were consumed. Adjusted logistic regression was used to determine whether dampness and food habits were related to the subjective symptoms. In fully adjusted models, the home dampness index was significantly related to cough, general symptoms, and having at least one symptom; the classroom dampness index was significantly related to nasal symptoms. In addition, usually not eating breakfast was significantly related to eye symptoms, and too many snacks and/or sweets was significantly related to eye, nasal, and general symptoms. Both home and classroom dampness can affect pupils' health. Home dampness, in particular, was significantly related to cough and general symptoms, and classroom dampness was significantly related to nasal symptoms. Furthermore, favorable food habits have a positive effect on pupils' subjective symptoms.

Relation of Dampness to Sick Building Syndrome in Japanese Public Apartment Houses

The effect of dampness on sick building syndrome (SBS) symptoms has not been fully investigated in Japan. The purpose of this study is to elucidate the possible effects of dampness on SBS symptoms among residents in Japanese public apartment houses. A questionnaire was used to investigate the degree of dampness in public apartment houses in Asahikawa, Japan, and its effect on SBS symptoms, involving 480 residents in 64 buildings. Dampness indicators were as follows: condensation on the windowpanes, condensation on the walls and/or closets, visible mold in the bathrooms, visible mold on the walls, window frames, and/or closet, moldy odor, slow drying of the wet towels in bathrooms, water leakage, and bad drainage in bathrooms. All dampness indicators except for visible mold in bathrooms had significantly higher odds ratios (ORs) for all or any SBS symptoms after adjustment. The dampness index, the number of positive dampness indicators, was significantly related to all SBS symptoms after adjustment. There are serious problems relating to dampness in Japanese public housing, which affects the health of residents. There is a need to educate the residents about the relationship between dampness and SBS, and building problems should be rectified.

Relationship between sick building syndrome and indoor environmental factors in newly built Japanese dwellings

Indoor air contaminants and dampness in dwellings have become important environmental health issues. The aim of this study is to clarify which factors are related to sick building syndrome (SBS) in newly built dwellings at Hokkaido, Japan, through a comprehensive evaluation of the indoor environment and validated sick building symptom questionnaires. The symptoms of 343 residents in 104 detached houses were surveyed by standardized questionnaires, and the concentrations of formaldehyde, acetaldehyde, volatile organic compounds (VOCs), airborne fungi, and dust mite allergen in their living rooms were measured. By summing the presence or absence of the five dampness indicators (condensations, mold growth, moldy odor, high air humidity of the bathroom, water leakage), a dampness index was calculated. SBS symptoms were found in 21.6% of surveyed individuals. In a fully adjusted multivariate logistic regression analysis, the dampness index [odds ratio (OR) = 1.50; 95% confidence interval (CI): 1.06-1.11], log formaldehyde (OR = 23.79, 95% CI: 2.49-277.65), and log alpha-pinene (OR = 2.87, 95% CI: 1.36-6.03) had significantly higher ORs for SBS symptoms. However, other VOCs, airborne fungi, and dust mite allergen did not have significantly higher ORs. Dampness, formaldehyde, and alpha-pinene were significantly related to SBS symptoms in newly built dwellings. We should, therefore, take measures to reduce the chemicals and dampness in dwellings.

Regional differences in residential environments and the association of dwellings and residential factors with the sick house syndrome: a nationwide cross-sectional questionnaire study in Japan

This study was conducted to clarify regional differences in residential factors and the association of those factors with dwellings having sick house syndrome (SHS) problems. The survey was conducted in six areas of northern and southern Japan. In terms of regional differences, dampness was not as severe in the dwellings in Sapporo as compared with that in areas in the south. SHS was defined using five categories of nasal, throat and respiratory, skin and general symptoms, which appeared frequently or not frequently and improved upon leaving the home. The dampness index was estimated by the sum of the presence of several indicators: condensation on the window panes and/or wall, visible mold growth, moldy odor, slow-drying wet towels in the bathroom, and water leakage. The dwellings where inhabitants showed any symptoms of SHS comprised 3.7% of all surveyed dwellings. We found significant associations between SHS and dampness index, odors, and stuffiness of the air. For dampness, the adjusted odds ratio (OR) increased with increased dampness index, adjusting for the age of the house, pets indoors, stuffiness of the air, and odors. These results showed an increased risk when several dampness indicators appeared simultaneously. To evaluate the associations of residential environments and Sick House Syndrome (SHS), this cross-sectional questionnaire study was conducted on 2297 dwellings in six areas in Japan from 2003 to 2004. The dwellings where inhabitants showed any of nasal, throat and respiratory, skin and general symptoms comprised 3.7% of all surveyed dwellings, and an increased risk for SHS was found when several dampness indicators, 'condensation', 'visible mold growth', 'moldy odor', 'slow drying wet towels in the bathroom' and 'water leakage', appeared simultaneously.

Relation of dampness to sick building syndrome in Japanese public apartment houses

The effect of dampness on sick building syndrome (SBS) symptoms has not been fully investigated in Japan. The purpose of this study is to elucidate the possible effects of dampness on SBS symptoms among residents in Japanese public apartment houses. A questionnaire was used to investigate the degree of dampness in public apartment houses in Asahikawa, Japan, and its effect on SBS symptoms, involving 480 residents in 64 buildings. Dampness indicators were as follows: condensation on the windowpanes, condensation on the walls and/or closets, visible mold in the bathrooms, visible mold on the walls, window frames, and/or closet, moldy odor, slow drying of the wet towels in bathrooms, water leakage, and bad drainage in bathrooms. All dampness indicators except for visible mold in bathrooms had significantly higher odds ratios (ORs) for all or any SBS symptoms after adjustment. The dampness index, the number of positive dampness indicators, was significantly related to all SBS symptoms after adjustment. There are serious problems relating to dampness in Japanese public housing, which affects the health of residents. There is a need to educate the residents about the relationship between dampness and SBS, and building problems should be rectified.

사장교 케이블의 감쇠성능 향상을 위한 댐퍼의 비선형성 연구

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigates the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a potential energy loss ratio of cable vibration, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, three types of multi-mode patterns such as ambient vibration, support excitation and rain-wind induced vibration are assumed. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5 and in case of support excitation or rain-wind induced vibration it is between 0.5 and 1.0.

Damping index of Doppler hepatic vein waveform to assess the severity of portal hypertension and response to propranolol in liver cirrhosis: a prospective nonrandomized study

Alterations in the Doppler hepatic vein (HV) waveform are associated with cirrhosis and portal hypertension. We prospectively evaluated the correlation between the extent of abnormal Doppler HV waveforms expressed as damping index (DI) and the hepatic venous pressure gradient (HVPG) and response to propranolol in patients with cirrhosis. In 76 patients with cirrhosis (69 men and seven women), both DI of Doppler HV waveform and HVPG were measured, and the relationship between them was analysed. DI was calculated by the minimum velocity/maximum velocity of the HV waveform. An HVPG>12 mmHg was defined as severe portal hypertension. In a subgroup of 19 patients receiving propranolol, changes in both DI and HVPG were evaluated after propranolol administration for 3 months. One author (S. K. B.) performed all DI of Doppler HV waveform studies. Abnormal HV waveforms were seen in 66 of 76 patients (86.8%). DI significantly correlated with the grade of HVPG, i.e. with higher HVPG increased DI was observed (P<0.01). By logistic regression analysis, DI>0.6 was significantly more likely to be severe portal hypertension (odds ratio: 14.19, 95% confidence interval: 4.07-49.55). Receiver-operating characteristic curve according to the value of 0.6 of DI showed a sensitivity of 75.9% and a specificity of 81.8% for the presence of severe portal hypertension. In 19 patients of the propranolol subgroup, change of DI following propranolol treatment also significantly correlated with that of HVPG (P<0.01). Damping index of the HV waveform by Doppler ultrasonography might be a non-invasive supplementary tool in evaluating the severity of portal hypertension and in responding to propranolol in patients with liver cirrhosis.

The stiffness degradation and damping ratio evolution of Taipei Silty Clay under cyclic straining

The non-linear behavior of Taipei Silty Clay under cyclic strain loading was investigated through a series of undrained cyclic strain-controlled tests. The Ramberg–Osgood equation was used with our proposed stiffness degradation model to calculate degraded secant moduli. The proposed degradation model is simple in that it has only one more component than Idriss's model, the modulus ratio for the first cycle, which reflects the effects of the previous cyclic strain history and the current level of the cyclic strain amplitude, and can be used to describe softening and hardening behavior under irregular cyclic straining. It was found that the Ramberg–Osgood equation successfully predicts the damping ratio for small to medium strains. However, it overestimates the damping ratio for larger strains, so we suggest it can be corrected with a damping ratio index. In addition, the proposed equation for describing the evolution of the damping ratio provides the means to assess the variation for Taipei Silty Clay in the measured damping ratio with both the number of cycles and the strain amplitude.

Transformations in machining. Part 2. Evaluation of machining quality and detection of chatter in turning by using s-transformation

S-transformation is proposed to evaluate the quality of completed turning operations. The calculated time–frequency–amplitude plot of an accelerometer or cutting force signal indicates the vibration level at different frequencies and helps the operator to identify the problems. Time–frequency–damping index plots were obtained by using the s-transformation. Variance of damping index in a narrow band around the natural frequency of the workpiece was found as a very descriptive feature of chatter for inspection after machining of a long slender bar. Use of fuzzy logic controllers was proposed for automatic detection of chatter. Integration of the data collection, computation, and dissemination processes by using the local area network is proposed to store the vibration history of machining for critical parts and reporting the results to the operators with wireless devices.