• Corrosion Science and Technology
• /
• v.7 no.6
• /
• pp.319-323
• /
• 2008

The polarization resistance of mild steel in 0.5M hydrochloric acid has been evaluated by using impedance (Z) and linear polarization (LPR) techniques and compared to the noise resistance obtained from electrochemical noise data. The degree of localization of this general corrosion has also been discussed by evaluating localization index and power spectral density. Polarization resistance obtained by LPR technique ($28\Omega$) was higher than that obtained by impedance technique ($15\Omega$). Noise resistance ($11\Omega$) was much lower than polarization resistance measured by both of above techniques. Higher polarization resistance obtained by LPR technique is generally caused by passivation effect in the presence of scales or deposits which can introduce an increased resistance as can low conductivity electrolytes. The reason why noise resistance is lower than polarization resistance is the effect of background noise detected by using three platinum electrodes cell in 0.5M hydrochloric acid. Slope($-\beta$) of power spectral density (PSD) obtained from analysis of noise data ($-\beta$ = 3.3) was much higher than 2 which indicates mild steel corroded uniformly. Localization index (LI) calculated from statistical analysis (LI=0.08) is much lower than 1 which indicates that mild steel did not corroded locally. However, LI value is still higher than $1x10^{-3}$ and this indicates that mild steel corroded locally in microscopic point of view.

• Computers and Concrete
• /
• v.20 no.5
• /
• pp.563-572
• /
• 2017

Ordinary reinforced concrete (RC) and prestressed concrete bridges are two popular and typical types of short- and medium-span bridges that accounts for the vast majority of all existing bridges. The cost of maintaining, repairing or replacing degraded existing RC bridges is immense. Detecting the abnormality of RC bridges at an early stage and taking the protective measures in advance are effective ways to improve maintenance practices and reduce the maintenance cost. This study proposes a systematic method from influence line (IL) identification to damage detection with applications to RC bridges. An IL identification method which integrates the cubic B-spline function with Tikhonov regularization is first proposed based on the vehicle information and the corresponding moving vehicle induced bridge response time history. Subsequently, IL change is defined as a damage index for bridge damage detection, and information fusion technique that synthesizes ILs of multiple locations/sensors is used to improve the efficiency and accuracy of damage localization. Finally, the feasibility of the proposed systematic method is verified through experimental tests on a three-span continuous RC beam. The comparison suggests that the identified ILs can well match with the baseline ILs, and it demonstrates that the proposed IL identification method has a high accuracy and a great potential in engineering applications. Results in this case indicate that deflection ILs are superior than strain ILs for damage detection of RC beams, and the performance of damage localization can be significantly improved with the information fusion of multiple ILs.

• Smart Structures and Systems
• /
• v.23 no.6
• /
• pp.653-667
• /
• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• Korean Journal of Veterinary Research
• /
• v.37 no.1
• /
• pp.167-176
• /
• 1997

The present investigation was focussed mainly on the development of the tumors and proliferating cells on the intestinal tracts of 1, 2-dimethyl-hydrazine(DMH)-treated young or adult rats. 26 rats(Wistar, 14 young rats weighting approximately 130~180gm and 12 adult rats weighting approximately 500~550gm) were given subcutaneously once weekly with 20mg of DMH/kg body weight(BW)/week for 8~22 weeks. Individual body weight were recorded weekly at the same day and time. The rats were killed at 8, 13, 15. 17, 19, 21 and 22 weeks. The intestinal tracts were opened longitudinally and carefully examined for tumors. The localization, number, and size of tumors were noted. Tumor-bearing areas were dissected out and fixed on neutral buffered 10% formalin and normal-looking mucosa from 8~22 weeks rats were also taken for fixation. Paraffin sections were stained by H-E for histopathological examination or with immunohistochemical stain for bromodeoxyuridine(Brdur) positive cells. 1. The growth proportion of body weight appeared to be decreased in the DMH-treated young rats than in control young rats and body weight of DMH-treated adult rats appeared to be 13.4% or less lower than weighted on 0 week. 2. Macroscopically, the developed tumors in the intestinal tracts were not observed as early as the 13 weeks after DMH treatment. The number of developed tumors per rat was found to be 14.3, 18.8, 22.3 in 15, 17 and 22 weeks. The numbers of tumors in intestinal regions per rat were 2.1, 4.3, 5.4, 2.5 in duodenum, jejunum, ilium and colon on 15 weeks, 2.3, 6.4, 7.8, 2.3, on 17 weeks, and 2.7, 9.3, 9.0, 1.3 on 22 weeks, respectively and the ileum and jejunum were higher in appearance rate of tumors and tumor types are dome shapes and diameter of largest tumor were 6.3mm. 3. Histopathologically, intestinal mucosa were thickened by the irregular distorted and distended crypts following hyperplasia. The tumors developed on the mucosa and submucosa and were recognized to be adenocarcinoma. 4. Immunohistochemically, the labeling index(LI) was calculated as the ratio of the number of Brdur-labeled cells to the total number of column cells of the crypts with longitudinal axis. LI of Brdur positive cells per crypt were 5.6%, 8.0% on small intestine of control and 22 week group, respectively and 3.7%, 12.7% on large intestine of control and 22 week group, respectively and were appeared to be increase in 22 week group than in control group and to be more number of proliferating cells in 22 week group than in control group. 5. LI of Brdur positive cells in 1, 2, 3, 4, 5 segments of crypt column were 11.7%, 10.7%, 3.8%, 0.6%, 0% in small intestine of control group and 23.5%, 11.8%, 2.3%, 2.4%, 0.8% in small intestine of 22 week group, and 5.4%, 7.4%, 3.8%, 1.0%, 0.4% in large intestine of control group and 29.5%, 20.3%, 5.9%, 6.3%, 1.3% in large intestine of 22 week group respectively. So results indicate that the number of proliferating cells by DMH treatment increase and were concentrated on the 1, 2 segments of crypt columns.