• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.67-81
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• 2006

Using a strain-controlled rheometer, the dynamic viscoelastic properties of aqueous xanthan gum solutions with different concentrations were measured over a wide range of strain amplitudes and then the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a broad range of angular frequencies. In this article, both the strain amplitude and concentration dependencies of dynamic viscoelastic behavior were reported at full length from the experimental data obtained from strain-sweep tests. In addition, the linear viscoelastic behavior was explained in detail and the effects of angular frequency and concentration on this behavior were discussed using the well-known power-law type equations. Finally, a fractional derivative model originally developed by Ma and Barbosa-Canovas (1996) was employed to make a quantitative description of a linear viscoelastic behavior and then the applicability of this model was examined with a brief comment on its limitations. Main findings obtained from this study can be summarized as follows: (1) At strain amplitude range larger than 10%, the storage modulus shows a nonlinear strain-thinning behavior, indicating a decrease in storage modulus as an increase in strain amplitude. (2) At strain amplitude range larger than 80%, the loss modulus exhibits an exceptional nonlinear strain-overshoot behavior, indicating that the loss modulus is first increased up to a certain strain amplitude(${\gamma}_0{\approx}150%$) beyond which followed by a decrease in loss modulus with an increase in strain amplitude. (3) At sufficiently large strain amplitude range (${\gamma}_0>200%$), a viscous behavior becomes superior to an elastic behavior. (4) An ability to flow without fracture at large strain amplitudes is one of the most important differences between typical strong gel systems and concentrated xanthan gum solutions. (5) The linear viscoelastic behavior of concentrated xanthan gum solutions is dominated by an elastic nature rather than a viscous nature and a gel-like structure is present in these systems. (6) As the polymer concentration is increased, xanthan gum solutions become more elastic and can be characterized by a slower relaxation mechanism. (7) Concentrated xanthan gum solutions do not form a chemically cross-linked stable (strong) gel but exhibit a weak gel-like behavior. (8) A fractional derivative model may be an attractive means for predicting a linear viscoelastic behavior of concentrated xanthan gum solutions but classified as a semi-empirical relationship because there exists no real physical meaning for the model parameters.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.217-236
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• 1979

The author's theory for plastic deformation was applied to superplastic alloys (Zn-Al eutectoid, Al-Cu, Pb-Sn, Sn-Bi, Mg-Al eutectics). The plastic deformation of the superplastic alloys could be described by two Maxwell models connected in parallel which represent two grain boundary flow units. The flow units are characterized by the two parameters $X_{gj}/{\alpha}_{gj}\;and\;{\beta}_{gj}$ (j=l or 2, g signifies the grain boundary) the values of which were obtained by applying our flow equation [Eq. (5)] to experiment. We confirmed that our flow equation describes the superplasticity very well. The curve of strain rate sensitivity m (=${\partial}\;In\;f/{\partial}\;In\;\dot{s})\;vs.\;-In\dot{s}$, where f and s are stress and strain rate, respectively, showed two peaks corresponding to flow unit gl and g2, the separation of the two peaks is determined by the difference between ${\beta}_{g1}\;and\;{\beta}_{g2}$. The condition of superplasticity is also determined by ${\beta}_{gj}$, which satisfies $\dot{s}_{mj}{\leqslant}1.53}{\beta}_{gj}$ [Eq.(13)], where $\dot{s}_{mj}$ is the s of the jth unit at the peak. The grain size dependence of ${\beta}_{gj}$ is described by $ln({\beta}_{gj})^{-1}$=alnx+b [Eq. (16)], where x is the grain size, and a and b are constants. The activation enthalpy for each flow unit, ${\Delta}H_{gj}^{\neq}$ was also determined from the temperature dependence of ${\beta}_{gj}$ which is proportional to the relaxation time of the j th unit. Since the superplasticity is determined by Eq. (13), and since ${\beta}_{gj}$ and ${\Delta}H_{gj}^{\neq}$ are related, we obtained the conclusion that superplasticity occurs in the system having small ${\Delta}H_{gj}^{\neq}$ values. The Aej values were equal to the activation enthalpies of grain boundary self-diffusion of the component atoms of the alloys, this accords with our proposed flow mechanism. The ${\Delta}H_{gj}^{\neq}$ value increases with grain size as expected from Eq. (16).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.1
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• pp.1-10
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• 2018

It is difficult to predict the early-age cracks of strain restrained concrete members due to environmentally sensitive parameters. A new method is proposed to predict the cracks by test of autogenous deformation and self-induced restrained stress of specimens which simulates early-age crack state by hydration heat of the'Wall-On-Foundation'members. For this purpose, thermal analysis of entire structure considering the environmental condition is performed at first, and the specimens are set up where hydration heat was electronically controlled according to the analysis results. By measuring free deformation and force to compensate the autogenous strain including relaxation, feasibility of cracks can be estimated. The proposed method can predict the occurrence of cracks better than the material test of the early age concrete which has large variance. The method of this study is particularly useful when it is used as a preliminary experiments to predict the crack more precisely before full-scale concrete placement in construction of large structures.

• YAKHAK HOEJI
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• v.41 no.6
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• pp.802-816
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• 1997

In order to investigate the pharmacological properties of New Woohwangehungsimwon Pill (NWCH). Effects of Woohwangehungsimwon Pill (WCH) and NWCH were compared using various experimental models. In isolated rat aorta, NWCH and WCH showed the relaxation of blood vessels in maximum contractile response to phenylephrine ($10^{-6}$M) without regard to endothelium containing or denuded rings of the rat aorta. Furthermore, the presence of the inhibitors of NO synthase and guanylate cyclase did not affect significantly the relaxative effects of NWCH and WCH. NWCH and WCH inhibited the vascular contractions induced by acethylcholine, prostaglandin endoperoxide or peroxide in a dose-dependent manner. In conscious spontaneously hypertensive rats(SHRs), NWCH and WCH decreased significantly heart rate. These, at high doses, had a negative inotropic effect that was a decrease of LVDP and (-dp/dt)/(+dp/dt) in the isolated perfused rat hearts, and also decreased the contractile force and heart rate in the isolated rat right atria. In excised guinea-pig papillary muscle, these had no effects on parameters of action potential at low doses, whereas inhibited the cardiac, contractility at high doses. Furthermore, these had a significant inhibitory effects on heart acceleration in normotensive rats and SHRs. These results suggested that NWCH and WCH have weak cardiovascular effects, and that there is no significant differences between two preparations.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.605-609
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• 2004

Blood pressure (BP) is one of the important physiological parameters for diagnosing cardiovascula diseases by means of noninvasive method. Existing noninvasive methods for measuring arterial BP have to use cuff and difficult in measuring arterial BP continuously. Systolic blood pressure (SBP) and pulse transit time (PTT) have a kind of inverse relationship. We acquired PTT data when subjects were in relaxation and also after exercise. We performed the linear regression analysis for making the regression equations for each subject and the regression equation for all subjects. We compared the estimated SBP with the measured SBP to check the accuracy of our regression equations. From the result, the regression equations for each subject was appropriate according to the American National Standards Institute of the Association of the Advancement of Medical Instrument (ANSI/AAMI) which says that BP devices should have ±5mmHg mean of error and 8mmHg standard deviation of error. However, the regression equation for all subjects was not proper to ANSI/AAMI recommendation. The result means that, without cuff, we can continuously estimate each subject's SBP through PTT and indivisual calibration.

• Journal of Veterinary Clinics
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• v.30 no.6
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• pp.421-427
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• 2013

There are many intramuscularly injectable drugs commonly used for anesthesia in dogs and combination of drugs were used for decrease the side effects. The objective of this study was to evaluate the anesthetic and cardiopulmonary effects of butorphanol-tiletamine-zolazepam-medetomidine and tramadol-tiletamine-zolazepam-medetomidine in dogs. Ten healthy beagle dogs (intact male; mean body weight : $9.5{\pm}1.60$ kg) were used in the study. Experimental animals were divided into two groups (n=5, each) and received 0.2 mg/kg of butorphanol (BZM) and 2 mg/kg of tramadol (TZM) according to the group after injection of $Zoletil^{(R)}$ (5 mg/kg) and medetomidine (10 ug/kg). All drugs were administered intramuscularly. Anesthesia and recovery, sedation and analgesia score, cardiovascular and respiratory parameters were measured. Induction and recovery time were not significantly different between the groups. Anesthesia time was $117.4{\pm}25.64$ minute and $81.2{\pm}12.50$ minute in BZM and TZM groups, respectively. Sedation and analgesia were satisfied in both groups. In both groups, common side effects related to the medetomidine, significant bradycardia and hypertension were not observed. There were no significant changes in respiratory data. In conclusion, tiletamine-zolazepam-medetomidine in combination with either butorphanol or tramadol can be suitable anesthetic protocol for minor procedures in dogs. They produced adequate anesthesia characterized by rapid induction, adequate analgesia and muscle relaxation without remarkable side effects.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.4
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• pp.394-400
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• 2016

The b-type natriuretic peptide (BNP) values and increase on functional disorder in the ventricle, and are used as an index to diagnose heart failure and predict the prognosis. BNP values is known to be relevant to dyssystole in congestive heart failure. This study aimed to identify correlation between the BNP values and the items that indicate the diastolic function in echocardiography. The research divided 188 patients who went through the BNP test and echocardiography in the hospital into the groups with the BNP values; <100, 100-300, 301-600, 601-900, and >901 pg/mL. As the BNP values increase, there was relevance with the echocardiography items of ejection fraction, size of left atrium, E velocity, A velocity, Deceleration time, E/A ratio, E', A', S' and E/E'. In comparison on the groups divided based on the BNP values, E/E' had the highest relevance. The research also categorized 67 patients who diagnosed with heart failure. In comparison on the groups of the heart failure patients, the BNP values of the three groups of Grade I: $623.0{\pm}459.7pg/mL$, Grade II: $1013.2{\pm}1155.1pg/mL$ and Grade III: $1693.4{\pm}1544.0pg/mL$, respectively (p<0.01). As the grade was higher, there was a higher relevance with the echocardiography items of ejection fraction, size of left atrium, E velocity, A velocity, Deceleration time, E/A ratio, E', A', S' and E/E' (p<0.001). Higher BNP values had a higher relevance with the items that indicate the diastolic function in echocardiography and the BNP values of the Restrictive physiology group were the highest in echocardiography. So the BNP values was thought to be valuable to predict diastolic function of heart.

• Clinical and Experimental Pediatrics
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• v.49 no.4
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• pp.417-423
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• 2006

Purpose : The objectives of this study were to assess ventricular function by tissue Doppler imaging in children who were receiving chemotherapy or who had received chemotherapy, and to apply repeated tissue Doppler imaging to make an early assessment in cardiac toxicity studies. Methods : This study was conducted on 23 oncology patients on-treatment or off-treatment from April 2005 to July 2005 at Dongsan Medical Center, Keimyung University. All patients(group 1) were divided into two groups, fractional shortening(FS) over 29 percent(group 2) and FS under 28 percent (group 3) in the first category. These same patients were also divided into the following groups : group treated with anthracyclin(group 4) and group treated without anthracyclin(group 5). Deceleration time(DT), isovolumic relaxation time(IVRT), FS, peak early diastolic(E), and peak late diastolic (A) velocity of transmitral flow were measured by M-mode and pulsed wave Doppler. Systolic(Sm), peak early diastolic(Em), and peak late diastolic(Am) velocity in apical 4-chamber and 2-chamber views were measured by tissue Doppler imaging. The author calculated a modified Tei index, E/A, E/Em ratio by using measured values. Results : Twenty three patients were enrolled : 12 boys and 11 girls. The average age of patients was 8 years and 4 months. Thirteen out of 23 patients were in the group treated with anthracyclin (group 4) and 6 had FS under 28 percent(group 3). E/Em ratio showed a significant difference between group 1 and control group($6.46{\pm}1.85$ vs $7.06{\pm}1.64$, P<0.05). Other parameters had no difference statistically. Conclusion : This study showed that the change of cardiac function developed earlier in diastolic function than in systolic function, as E/Em ratio reflecting the mean LV diastolic pressure showed a significant difference between the control group and chemotherapy groups. Echocardiography using tissue Doppler imaging is a non-invasive, comfortable and reliable method for post-chemotherapy follow up.

• Journal of radiological science and technology
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• v.32 no.1
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• pp.101-106
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• 2009

Purpose of this study is to compare the signal intensity (SI) and CNR with T1 weighted image using FLASH at 3T abdominal MRI by varying flip angle (FA). Totally 20 patients (male : 12, female : 8, Age : $28{\sim}63$ years with mean : 51) were examined by 3 Tesla MR scanner (Magnetom Tim Trio, SIEMENS, Germany) with 8 channel body array coil between september and October 2008. Imaging parameters were as follows : FLASH sequence, TR : 120 ms, TE : minimum, FOV (field of view) : $360{\times}300\;mm$, Matrix : $256{\times}224$, slice : 6 mm, scan time : 15 sec and Breath-hold technique. Abdominal image, with a 50 ml syringe filled with water placed in the FOV measuring the water signal, were acquired with varying FA through $10^{\circ}$ to $90^{\circ}$ with $10^{\circ}$ interval. SI's were measured three times at liver parenchyme, water, spleen and background and averaged. The CNR's were measured between the ROIs (region of interest). Statistic analysis was performed with ANOVA test using SPSS software (version 17.0). Less than FA $30^{\circ}$, abdominal images were severely inhomogeneity. Especially, T1 effect of water signal was weak. As the flip angle increased, the signal intensity decreased at all the regions. Especially, flip angle of the highest signal intensity was observed with $40^{\circ}$ at the liver parenchyme, $20^{\circ}$ at water, $30^{\circ}$ at the spleen, respectively. The CNR between liver and water was -60.92 at FA $10^{\circ}$ and 15.16 at FA $80^{\circ}$. The CNR between liver and spleen was -3.18 at FA $10^{\circ}$ and 9.65 at $80^{\circ}$. In conclusion, FA $80^{\circ}$ is optimal for T1 weighted effect using FLASH pulse sequence at 3.0 T abdominal MRI.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.2 no.1
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• pp.30-39
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• 1999

Purpose: Anorectal manometry is a way of investigation for ano-rectal sphincters. In this paper we evaluated the usefulness of anorectal manometry in constipation patients and compared the anal spnincter function in control, constipation and encopresis patients Methods: We analysed the data of anorectal function studies in normal children (control, n=11), children with constipation (constipation group, n=20) and children with encopresis (encopresis group, n=16). Results: The specific manometric parameters in normal children were like as follows; external anal sphinter pressure $21.0{\pm}8.00$ mmHg, internal anal sphicter pressure $30.0{\pm}14.57$ mmHg, conscious rectal sensitivity threshold $11.4{\pm}4.52$ mmHg. The above results were not different from that of previous studies except conscious rectal sensitivity threshold, which was slightly lower than that of others. Internal and external anal sphincter pressure were elevated significanlty in constipation and encopresis groups than in control, which results was the same in conscious rectal sensitivity threshold. But the values of rectoanal inhibitory threshold and percent relaxation of rectoanal inhibitory reflex were not different among control group, constipation group and encopresis group. External sphincter activity was increased during the act of bearing down for defecation in none of the child in control group, in 6 of 17 children in constipation group and 5 of 12 children in encopresis group. Conclusion: With the results of above we could say that complete history taking and physical examination are important in diagnosis of constipation, and we could say also that the anorectal manometry was a valuable tool to understand the physiology of normal defecation and the pathophysiology of constipation and encopresis.