Impedance Change Rate Research Articles

Classification of human tauopathy using blood: Detection of tau isoforms in patients’s blood with a magnetic bead‐based gap sensor

AbstractBackgroundTau protein, which is deposited or phosphorylated in the brains of patients with neurodegenerative progression, has six isoforms that include or exclude N‐terminal exons 2 and 3 and Exon 10, which is a microtubule binding region. Especially, 3R‐ and 4R‐tau, which are distinguished by inclusion or exclusion of exon 10, are known to be balanced in normal adults. However, in case of tauopathy such as progressive supranuclear palsy, the balance is disrupted and 4R‐tau becomes dominant in the patient’s brain. In this regard, some tauopathies can be classified through comparison of tau isoforms in the blood or cerebrospinal fluid (CSF) of neurodegenerative patients.MethodFirst, magnetic beads were coated with each antibody that specifically interact with 3R‐ or 4R‐tau protein, respectively. The prepared samples were reacted with patient’s blood samples from 1) healthy control (HC), 2) Alzheimer’s disease (AD), and 3) 4R‐tau dominant tauopathy (4RDT). Samples incubated with 3R‐ and 4R‐tau antibodies, respectively, were placed between two metal electrode arrays surrounded by the SU‐8 well structure and their impedance changes were measured by electrochemical method (Figure 1).ResultIn the case of HC and AD, 3R‐ and 4R‐tau are known to be in balance, but as a result of measuring the impedance change rate, it was found that the impedance change rate of 4R‐tau is larger than that of 3R‐tau. For the 4R‐tau, HC group exhibits a larger impedance change rate than the AD group (Figure 2). The 4RDT group is currently measuring. Based on reference (Acta Neuropathol., 131, 267 (2016)), the impedance change rate of 4R tau in blood will be large, while that of 3R tau is expected to be negligible.ConclusionWe used a magnetic bead‐based gap sensor to detect/compare tau isoforms in blood samples collected from living patients. Although slightly different from the expectation, the HC group showed a larger impedance change rate than the AD group for the 4R‐tau. The 4RDT group data have not yet been included, but are expected to be similar to those from CSF, and blood measurements can be used to classify tauopathies.

Transformer winding deformation accompanied by magnetic flux leakage field distribution variation and its diagnostic analysis of deformation degree

During the transformer winding deformation process, the leakage magnetic field around the winding will change accordingly. Therefore, it is an effective method to monitor and track the change of the leakage magnetic field and then analyze and judge the state of the transformer. This paper firstly uses Comsol Multiphysics software to establish a 110 kV transformer electromagnetic simulation calculation model. Based on the simulation results of magnetic leakage distribution, an installation plan for the internal magnetic leakage sensor of a 110 kV true transformer is determined. The measurement results of the true single short-circuit test under different working conditions verify the accuracy of the simulation model. Subsequently, a number of B-phase high-centered three-phase short circuit (H-M B) true type tests were carried out, and the relationship between the magnetic leakage distribution characteristics and the impedance change rate after each impact was analyzed. The results show that before the transformer is seriously deformed due to multiple short circuit shocks, the sensitivity of the impedance change rate to the winding deformation is low, and the first five shocks only increase from 0.11% to 0.39%. However, the difference ratio between the simulation value and the test value of magnetic flux leakage (MFL) has obvious changes in each small deformation. BX3 increases from 1.77% to 5.62%, and BX4 increases from 2.08% to 6.55%. The difference ratio of four shocks before winding deformation is more than 6%. Therefore, by monitoring the flux leakage magnetic induction intensity, when the difference ratio is greater than 6%, strengthen the vigilance, which can provide a certain basis for winding monitoring before serious deformation.

Polynomial analysis as a new way of describing dynamic impedance spectra – Differential and relative impedance spectra

Model measurements of an equivalent electrical system were carried out using the technique of Dynamic Electrochemical Impedance Spectroscopy. The measurement took the form of potentiodynamic changes imposed on the tested system. Using the possibility of continuous impedance measurements, an attempt was made to develop an original and innovative method of analyzing impedance spectrograms, which is termed polynomial analysis. As a result of this approach, it is possible to generate two novel impedance spectra from the primary impedance spectrogram. The innovation lies in the use of simple polynomials to describe a set of spectra, and then performing differential and division operations, which result in differential- and relative-impedance spectra. Among other things, differential spectra have the ability to track the rate of change in impedance as a function of an independent variable. By contrast, relative impedance spectra eliminate surface influence, which opens the way to the direct comparison of physicochemical processes and more.

Anti-Electromagnetic Interference Design of Rail Transit Vehicles Based on the Magnetic Induction and Magnetoelectric Characteristics of Ferroelectric Ceramics

The various properties of ferroelectric ceramics bring extremely rich colors to life. Its various properties such as dielectric properties, electromagnetic properties, and anti-magnetic interference properties have been successively studied in various fields, except for stone carvings, outdoor environmental sculptures, ornamental ceramics, etc. Because of its superior performance, it can also be used in aircraft manufacturing, anti-interference materials for train tracks, and can even realize unmanned driving, workshop networks and other environments, which can meet the normal operation of electronic equipment in the car under the state of preventing external electromagnetic interference. This requires the superior electromagnetic properties of ferroelectric ceramics. Dielectric properties, dielectric relaxation, and ferromagnetic effects all need to be optimized. This article first introduces the performance test methods of ferroelectric ceramics, and describes the dielectric relaxation through Debye equation He phenomenon, test dielectric loss and dipole interaction, magnetic coupling effect and multiferrocity, and carry out electromagnetic coexistence, based on MATLAB/Simulink rail vehicle dynamics model, composed of sensors, control center and bogie, forming a coupling The functioning anti-roll structure makes the magnetic potential energy evenly distributed in the track span, forming a single suspended electromagnet modular transportation train dynamic model, which can carry the load force of the air and the gravity of the module itself. The traditional solid-phase method is used to dope at the A site. As the doped sample gradually increases, the peak value of the derivative peak changes, causing the original diamagnetic sample to carry a certain degree of ferromagnetism, and the doping amount and ferromagnetism are positively correlated. Then, experiments were performed on the composite ferroelectric ceramic materials doped with ion pairs, and the tests were carried out at different temperatures and different doping amounts. The conclusions about the coupling of dielectric constant, dielectric loss, magnetic properties and magneto electric properties were obtained and obtained the anti-magnetic interference ability. The application in the anti-magnetic interference of rail trains has a certain guiding effect. The results show that when the doping amount reaches m = 0.02, the dielectric loss is reduced by 22.58 times. The impedance change rate of the ferroelectric ceramic material with no doped Al3 +-Li + ion pair under 9 kOe is 3.95%, while at m = 0.015 Al3+ With -Li + doping, the impedance change rate of ferroelectric ceramics is 14.45%, which is 3.17 times the original.

Analysis of Electrical Impedance Myography Electrodes Configuration for Local Muscle Fatigue Evaluation Based on Finite Element Method

Local muscle fatigue (LMF) is a common physiological phenomenon that occurs in daily exercise training and medical rehabilitation. Without timely treatment it can easily lead to muscle spasm, ligament rupture, and even stress fractures. Electrical impedance myography (EIM) is a noninvasive bioelectrical impedance technique suitable for the wearable LMF monitoring anytime and anywhere. In this paper, a novel EIM electrode configuration was proposed by establishing a four-layer simulation model of the human upper arm in FEM software. Sensitivity parameters were introduced to optimize muscle selectivity. The effect of fat thickness on impedance change rate was explored to reduce the influence of individual fat differences on EIM results. Dynamic and static contraction experiments of muscle fatigue were performed on the biceps brachii muscles of 10 volunteers to verify the effectiveness and feasibility of the proposed electrode configuration. The proposed electrode configuration reduced the measurement area by 25%, whereas the impedance amplitude and sensitivity remained the same. The influence of individual fat differences on EIM results was significantly reduced. When the fat thickness increased from 6 mm to 18 mm, the impedance change decreased by 31.78% compared with the traditional electrode configuration. When the muscles were extremely exhausted, the decrease in resistance varied around $10~\Omega $ and within 10−1 order of magnitude in different volunteers. In a word, the proposed electrode configuration effectively evaluated the degree of LMF, providing more feasibility for the design of wearable devices.

Giant Magneto-Impedance (GMI) Effect in Single-Layer Soft Magnetic Film Under Stress.

The stress-induced magnetic anisotropy can significantly affect giant magneto-impedance (GMI) effect of the soft magnetic film. This paper is devoted to the GMI effect of the single layer soft magnetic film implied without and with a stress. By simulating a physical model with MATLAB and COMSOL software, the impedance expression of the single layer soft magnetic film and the relation between external magnetic field and magnetic permeability are deduced. We observed that, without a stress, the sensitive region increased firstly and then decreased with the increasing of the excitation current frequency from 1 MHz to 200 MHz. While the film was subjected to the stress in the direction of the current with one end stressed, the stress on the film was gradually reduced from stressed end to free end. Also, the impedance change rate of the film changed when the stress was added, which is similar to the effect of adding a bias magnetic field on the film. More importantly, the addition of stress σ can induce the bias of the GMI measurement range and improve its sensitivity near zero magnetic fields. This may provide a new way for designing a GMI sensor with higher sensitivity and adjustable measurement range.

Hemodynamic effects of epinephrine in rats: evaluation by impedance cardiography.

This study was aimed to examine how inotropic effects of intravenously injected epinephrine change thoracic impedance measurements and to reveal the possible effects of this change on other hemodynamic parameters by using the technique of impedance cardiography. 10 male Wistar Albino rats were divided into two equal groups: control and epinephrine. 0.2 mg/kg of epinephrine was administered to the rats in the epinephrine group via the tail vein. All hemodynamic parameters obtained by impedance cardiography [the base impedance (Z0), the maximum rate of change in impedance (dZmax/dt), the left ventricular ejection time (LVET), stroke volume (SV), cardiac output (CO), contractility index (IC), thoracic fluid content (TFC), heart rate (HR)] were recorded using the EBI 100C, DA 100 and ECG modules in the BIOPAC MP100 system. CO (p ≤ 0.05), HR (p ≤ 0.001), dZmax/dt (p ≤ 0.05) and IC (p ≤ 0.05) increased statistically significantly in the epinephrine group compared to the control group. However, LVET (p ≤ 0.001) decreased statistically significantly in the epinephrine group compared to the control group. Tachycardia was detected in the epinephrine group. There was an inverse correlation between LVET and dZmax/dt and IC. This is based on the fact that epinephrine increases inotropic effect (Tab. 2, Fig. 4, Ref. 30).

The EIS‐based Kohonen neural network for high strength steel coating degradation assessment

Electrochemical impedance spectroscopy (EIS) method is used for a long‐term and in‐depth study on the failure analysis of polymer coatings. With the assistance of neural networks, a deeper insight into the changing states of corrosion during certain exposure circumstances has been investigated by applying specific Kohonen intelligent learning networks. The Kohonen artificial network has been trained by using 4 sets of samples from sample 1# to sample 4# with unsupervised competitive learning methods. Each sample includes up to 14 cycles of EIS data. The trained network has been tested using sample 0# impedance data at 0.1 Hz. All the sample data were collected during exposure to accelerated corrosion environments, and it took the changing rate of impedance of each cycle as an input training sample. Compared with traditional classification, Kohonen artificial network method classifies corrosion process into 5 subprocesses, which is refinement of 3 typical corrosion processes. The 2 newly defined subprocesses of corrosion, namely, premiddle stage and postmiddle stage were introduced. The EIS data and macro‐morphology for both subprocesses were analyzed through accelerated experiments that considered general atmospheric environmental factors such as UV radiation, thermal shock, and salt fog. The classification results of Kohonen artificial network are highly consistent with the predictions based on impedance magnitude at low frequency, which illustrates that the Kohonen network classification is an effective method to predict the failure cycles of polymer coatings.

Kohonen Neural Network Classification for Failure Process of Metallic Organic Coating in Corrosion Environment

A deeper insight into the changing states of corrosion during certain exposure circumstances has been investigated by applying Kohonen networks. The Kohonen network has been trained by four sets of samples and tested using another sample. All the sample data were collected during accelerated corrosion experiments and the network took the changing rate of impedance of each cycle as an input. Compared with traditional classification, the Kohonen artificial network method classifies corrosion process into five sub-processes which is a refinement of three typical corrosion processes. The two newly defined sub-processes of corrosion—namely, pre-middle stage and post-middle stage—were introduced. The EIS data and macro-morphology for both sub-processes were analyzed through accelerated experiments. The classification results of the Kohonen artificial network are highly consistent with the predictions based on impedance magnitude at low frequency, which illustrates that the Kohonen network classification is an effective method for predicting the failure cycles of polymer coatings.

Intracardiac impedance after cardiac resynchronization therapy is a novel predictor for worsening of heart failure.

Intrathoracic impedance measured by cardiac resynchronization therapy (CRT) varies because several factors other than pulmonary congestion may affect this parameter. Therefore, we hypothesized that changes in intracardiac impedance between the right and left ventricular leads would be more accurate to identify worsening heart failure in patients with CRT. The study enrolled21 patients with CRT defibrillator (15 males, 70 ± 12years). During the follow-up period (12 ± 7months), the subjects experienced 37 fluid index threshold (60 ohm-days) crossing events. These events were divided into two groups whether hospitalization due to worsening heart failure was required (group-H, n = 14) or not (group-NH, n = 23). Based on the intracardiac impedance at the beginning of increasing fluid index (BI) and the crossing of 60ohm-days (CI), the rate of impedance change (BI-CI/BI) was estimated. Then, the time elapsed from BI to CI (T) was evaluated. We calculated the rate of intracardiac impedance change per day (BI-CI/BI × T) in each group. The rate of intrathoracic impedance change per day was also determined using the same method. The median rate of intracardiac impedance change per day was 0.27 (IQR 0.22-0.54) %/day in group-H, and 0 (IQR 0-0.08) %/day in group-NH with a significant difference (P < 0.0001), whereas the rate of intrathoracic impedance change per day was similar between the two groups. By receiver operating characteristic curve for identification of hospitalization due to worsening heart failure, the best cutoff value of the rate of intracardiac impedance change per day was 0.20%/day (sensitivity 92%, specificity 88%, and AUC 0.98). In contrast, the best cutoff value of the rate of intrathoracic impedance change per day was 0.19%/day (sensitivity 86%, specificity 43%, and AUC 0.68). These results suggest thatincreased rate of change of decreasing intracardiac impedance measured by CRT is a novel useful predictor for worsening heart failure.

Simulation research on gastric emptying measurement experiment by electrical impedance tomography with three-layer electrodes

Objective To verify the effectiveness of electrical impedance tomography (EIT) with multi-layer electrodes in gastric emptying measurement by simulation experiments using EIT with three-layer electrodes. Methods Firstly, EIT system with three-layer electrodes and gastric emptying measurement simulation equipment was designed and constructed to simulate gastric emptying process and obtain EIT reconstruction images. Secondly, the region where the electrical characteristic of gastric changes was selected as region of interest. Finally, the relative impedance change rate in region of interest for every image obtained from all three layers was consecutively recorded, then the gastric emptying curve was formed and gastric emptying time was calculated. Results There are obvious differences among the sharp of impedance change curves of interested region for three layers, and the gastric emptying time and process of each layer is also different from one another. It is suggested that the passing path and emptying manner of food in gastric emptying process reflected by EIT images varied from layer to layer. Therefore, the necessity and feasibility of using EIT with three-layer electrodes in gastric emptying measurement study is verified. Conclusions EIT with three-layer electrodes can provide more abundant information of gastric motility function associated with gastric emptying pathology and physiology state. It is likely to be a noninvasive, convenient and effective imaging method for the detection and evaluation research on gastric emptying and gastric motility. Key words: Electrical impedance tomography; Three-layer imaging; Gastric emptying; Simulation experiments

Predictive impact of the decreasing rate of intrathoracic impedance in worsening chronic heart failure

Intrathoracic impedance monitoring is useful for heart failure (HF) management in patients with cardiac resynchronization therapy (CRT). However, more accurate identification of worsening chronic HF (CHF) is required in the clinical setting. We investigated this issue by estimating changes in impedance. We studied 38 CHF patients (29 males, mean age 67 years) with CRT-defibrillator capable of impedance monitoring. During the follow-up period (20.7 ± 7.8 months), the subjects experienced a total of 129 fluid index threshold (60 ohm·days) crossing events. These events were divided into two groups: HF events (n = 70) and no HF events (n = 59). Based on the impedance at the beginning of increasing fluid index (S) and at the crossing of 60 ohm·days (E), the rate of impedance change (S - E / S) was estimated. In addition, the elapsed time from S to E (T) was evaluated. Then, we calculated the rate of impedance change per day (S - E / S × T) in each group. The rate of impedance change per day was significantly higher in HF events than in no HF events (0.86 ± 0.48 vs. 0.37 ± 0.22%/day, P < 0.01). By receiver operating characteristic curve for identification of HF events, the best cutoff value of the rate of impedance change was 0.48%/day (sensitivity 80%, specificity 81%, and area under the curve 0.85). These results suggest that a faster drop in intrathoracic impedance reflected worsening CHF in patients with CRT-defibrillator. Thus, intrathoracic impedance monitoring based on the rate of impedance change may provide a more accurate identification of worsening CHF.

Study on Adaptive Distance Relay to Prevent Cascading Trips in Complex Power Grid

Cascading trips caused by flow transferring are the crucial reason for a lot of well-known blackouts. Aiming at the distance relay which is most applied in power grid, this paper puts forward an adaptive setting scheme to prevent cascading trips in complex power grid. In this paper, using two-port network model to fast calculating apparent impedance, and than calculating the apparent impedance change rate which is caused by flow transferring. According to the apparent impedance change rate modify the setting value which would contract the range of the impedance circle. After accomplishing the contraction, the relay action check will start. Through the process of modification and checking, the adaptive setting scheme which is not affected by the flow transferring will be formed. Taking the New England 10-unit 39-bus system which also used this method as the example, in this case, this method is confirmed by the BPA simulation.

Drilling Electrode for Real-Time Measurement of Electrical Impedance in Bone Tissues

In order to prevent possible damages to soft tissues, reliable monitoring methods are required to provide valuable information on the condition of the bone being cut. This paper describes the design of an electrical impedance sensing drill developed to estimate the relative position between the drill and the bone being drilled. The two-electrode method is applied to continuously measure the electrical impedance during a drill feeding movement: two copper wire brushes are used to conduct electricity in the rotating drill and then the drill is one electrode; a needle is inserted into the soft tissues adjacent to the bone being drilled and acts as another electrode. Considering that the recorded electrical impedance is correlated with the insertion depth of the drill, we theoretically calculate the electrode-tissue contact impedance and prove that the rate of impedance change varies considerably when the drill bit crosses the boundary between two different bone tissues. Therefore, the rate of impedance change is used to determine whether the tip of the drill is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue. In vitro experiments in porcine thoracic spines were performed to demonstrate the feasibility of the impedance sensing drill. The experimental results indicate that the drill, used with the proposed data-processing method, can provide accurate and reliable breakthrough detection in the bone-drilling process.

The measurement of peripheral blood volume reactions to tilt test by the electrical impedance technique after exercise in athletes

We have investigated the distribution of peripheral blood volumes in different regions of the body in response to the tilt-test in endurance trained athletes after aerobic exercise. Distribution of peripheral blood volumes (ml/beat) simultaneously in six regions of the body (two legs, two hands, abdomen, neck and ECG) was assessed in response to the tilt-test using the impedance method (the impedance change rate (dZ/dT). Before and after exercise session cardiac stroke (CSV) and blood volumes in legs, arms and neck were higher in athletes both in lying and standing positions. Before exercise the increase of heart rate and the decrease of a neck blood volume in response to tilting was lower (p <0.05) but the decrease of leg blood volumes was higher (p<0.001) in athletes. The reactions in arms and abdomen blood volumes were similar. Also, the neck blood volumes as percentage of CSV (%/CSV) did not change in the control but increased in athletes (p <0.05) in response to the tilt test. After (10 min recovery) the aerobic bicycle exercise (mean HR = 156±8 beat/min, duration 30 min) blood volumes in neck and arms in response to the tilting were reduced equally, but abdomen (p<0.05) and leg blood volumes (p <0.001) were lowered more significantly in athletes. The neck blood flow (%/CSV) did not change in athletes but decreased in control (p<0.01), which was offset by higher tachycardia in response to tilt-test in controls after exercise. The data demonstrate greater orthostatic tolerance in athletes both before and after exercise during fatigue which is due to effective distribution of blood flows aimed at maintaining cerebral blood flow.

Research on coating deterioration process under fully immersing condition by using multi-parameters

In this paper, a parameter, named as the changing rate of impedance (CRI) derived from electrochemical impedance spectroscopy (EIS) data was selected. The deterioration process of organic coating was investigated by analyzing this parameter using neural network toolbox. In addition, four parameters characterizing the coating state were fitted by appropriate equivalent circuits (ECs). Integrating all the results of CRI and the evaluation of fitted parameters, it can be deduced that three stages were presented in the entire coating deterioration process, which separately represented the process of water penetration, corrosion acceleration, and coating deterioration. Furthermore, CRI was proved to be a credible parameter to depict coating state in its entire deterioration process.

Different approaches in evaluating organic paint coatings with electrochemical impedance spectroscopy

This work presents the effectiveness of different approaches in evaluating two coatings with intermediate and poor qualities using electrochemical impedance spectroscopy (EIS) measurements. Different approaches with no errors in calculations, i.e. the breakpoint frequency, changing rate of impedance, impedance at low frequency, phase angle at high frequency, and the areas under Bode plots were used in evaluating coated samples with EIS measurements. Results from these approaches were compared with each other and with the results extracted from the equivalent electrical circuit (EEC) models. The results are in good agreement with EEC models in coating ranking point of view. It is found that the results of impedance at low frequencies, breakpoint frequency, and Bode area measurements were useful in evaluating coating performance during immersion period.

State-of-Charge Determination From EMF Voltage Estimation: Using Impedance, Terminal Voltage, and Current for Lead-Acid and Lithium-Ion Batteries

State-of-charge (SOC) determination is an increasingly important issue in battery technology. In addition to the immediate display of the remaining battery capacity to the user, precise knowledge of SOC exerts additional control over the charging/discharging process, which can be employed to increase battery life. This reduces the risk of overvoltage and gassing, which degrade the chemical composition of the electrolyte and plates. The proposed model in this paper determines the SOC by incorporating the changes occurring due to terminal voltage, current load, and internal resistance, which mitigate the disadvantages of using impedance only. Electromotive force (EMF) voltage is predicted while the battery is under load conditions; from the estimated EMF voltage, the SOC is then determined. The method divides the battery voltage curve into two regions: 1) the linear region for full to partial SOC and 2) the hyperbolic region from partial to low SOC. Algorithms are developed to correspond to the different characteristic changes occurring within each region. In the hyperbolic region, the rate of change in impedance and terminal voltage is greater than that in the linear region. The magnitude of current discharge causes varying rates of change to the terminal voltage and impedance. Experimental tests and results are presented to validate the new models.

Analysis of deterioration process of organic protective coating using EIS assisted by SOM network

Under cyclic wet–dry conditions, the deterioration process of the organic coating on carbon steel surface has been studied using electrochemical impedance spectroscopy (EIS) assisted by self-organizing feature map (SOM) network. According to the EIS characteristics, changing rate of impedance and the classification results by SOM network, the entire deterioration process can be divided into three main stages shown as follows. Stage I is the medium penetration into coatings, which is a slow process. Stage II is the corrosion initiation under coatings, which is a relatively fast transition period. Stage III is the corrosion extension which causes coating delamination and makes the coatings lose its corrosion protection eventually. Besides, the results indicate that SOM network is a very simple and effective technique for analyzing the deterioration process of organic coating.

Parameter analysis of impedance pharyngography (IPG) for assessment of swallowing function

AbstractWith steady aging of society, the number of patients with dysphagia due to esophageal cancer and to muscular and neural diseases is increasing. This tendency is a problem from the viewpoint of social welfare. We intended to develop a simple quantitative evaluation method for the swallowing function, and we propose impedance pharyngography (IPG), which can measure noninvasively the electrical impedance of the neck during swallowing. Although the swallowing function is reflected in the IPG, the effect of swallowing function degradation on the waveform varies depending on the cause of the problem, making it difficult to compare simply the IPGs of subjects with various states of the swallowing function. In this study, four parameters are defined, based on the normal IPGs of normal young subjects, in order to evaluate the waveform features representing the swallowing function, namely, the pharynx transit time, the rate of impedance change, the similarity, and the timing of the swallowing sound. Then, a method is proposed to evaluate the IPG quantitatively. IPGs of two groups, young and elderly, are analyzed in terms of these parameters, and it is shown that the degradation of the lifting speed and the lifting distance of the larynx, and also degradation of smooth activity of the organs related to swallowing, can be detected as differences in the parameters. © 2006 Wiley Periodicals, Inc. Syst Comp Jpn, 37(13): 20–27, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20588