• International Journal of Highway Engineering
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• v.9 no.4
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• pp.93-104
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• 2007

This study evaluates the mechanical properties of steel fiber reinforced porous concrete for pavement according to content of slag aggregate and fly ash to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. As a result, void ratio and permeability coefficient of porous concrete for pavement increased a little as mixing rate of slag aggregates increased. Void ratio and permeability coefficient increased a lot as mixing rate of fly ash decreased. As fly ash was mixed, national regulation of permeable concrete for pavement(8% and 0.1 cm/sec) was met. Compressive strength and flexural strength decreased as mixing rate of slag aggregates increased, but they increased a lot as mixing rate of fly ash increased. Even when slag aggregates were mixed 50% with 5% fly ash mixed, national regulation of pavement concrete(18MPa and 4.5MPa) was met. In addition, compared to non-mixture, flexural strength increased about 22.8% when 0.75vol.% of steel fiber was added. Regarding sliding resistance, BPN increased as mixing rate of slag aggregates increased. But BPN decreased as fly ash was mixed. Compared to crushed stone aggregates, abrasion resistance and fleers-thaw resistance decreased as mixing rate of slag aggregates increased. When fly ash was mixed, abrasion resistance and freeze-thaw resistance improved remarkably. Compared to non-mixture, 10% mixture of fly ash improved abrasion resistance and freeze-thaw resistance about 5.6% and 14.3 respectively.

• Journal of Surface Science and Engineering
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• v.46 no.4
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• pp.168-174
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• 2013

In this study, low-cost, high-speed deposition, excellent processability, high mechanical strength and electrical conductivity, chemical stability and corrosion resistance of stainless steel to meet the obsessive-compulsive (0.1 mm or less) were selected CrN thin film. new price reduction to sputter deposition causes - the possibility of sublimation source for inductively coupled plasma Cr rods were attempts by DC bias. 0.6 Pa Ar inductively coupled plasmas of 2.4 MHz, 500 W, keeping Cr Rod DC bias power 30 W (900 V, 0.02 A) is applied, $N_2$ flow rate of 0.5, 1.0, 1.5 sccm by varying the characteristics of were analyzed. $N_2$ flow rate increases, decreases and $Cr_2N$, CrN was found to increase. In addition to corrosion resistance and contact resistance, corrosion resistance, electrical conductivity was evaluated. corrosion current density than $N_2$ 0 sccm was sure to rise in all, $N_2$ 1 sccm at $4.390{\times}10^{-7}$ (at 0.6 V) $A{\cdot}cm^{-2}$, respectively. electrical conductivity process results when $N_2$ 1 sccm 28.8 $m{\Omega}/cm^2$ with the lowest value of the contact resistance was confirmed that came out. The OES (SQ-2000) and QMS (CPM-300) using a reactive deposition process to add $N_2$ to maintain a uniform deposition rate was confirmed that.

• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.189-196
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• 2008

The pulsatile flow of blood through a stenosed artery under the influence of external periodic body acceleration is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as a Casson fluid. The non-linear coupled equations governing the flow are solved using perturbation analysis assuming that the Womersley frequency parameter is small which is valid for physiological situations in small blood vessels. The effect of pulsatility, stenosis, body acceleration, yield stress of the fluid and pressure gradient on the yield plane locations, velocity distribution, flow rate, shear stress and frictional resistance are investigated. It is noticed that the effect of yield stress and stenosis is to reduce flow rate and increase flow resistance. The impact of body acceleration is to enhance the flow rate and reduces resistance to flow.

• Transactions of Materials Processing
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• v.8 no.6
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• pp.576-582
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• 1999

The high temperature behavior of Al 6061 alloy was characterized by the hot torsion test in the temperature ranges of 400∼550℃ and the strain rate ranges of 0.05∼5/sec. To decide optimum deformation condition, three types of deformation maps were individually made from the critical strain (εc). deformation resistance(σp) and deformation efficiency (η). The critical strain(εc) for dynamic recrystallization (DRX) which was decided from the inflection point of strain hardening rate(θ) - effective stress (σ) curve was about 0.65 times of peak strain (εp). The relationship among deformation resistance (peak stress, σp), strain rate (ε), and temperature (T) could be expressed by ε=2.9×1013[sinh(0.0256σp]7.3exp (-216,000/RT). The deformation efficiency (η)which was calculated on the basis of the dynamic materials model (DMM) showed high values at the condition of 500∼550℃, 5/sec for 100% strain. The results from three deformation maps were compared with microstructures. The best condition of plastic deformation could be determined as 500℃ and 5/sec.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.58-65
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• 1999

The effect of specimen thickness on fatigue crack growth rate was studied. The objective of the present study is to investigate the effect of specimen thickness on the fatigue crack growth behavior at various stress intensity factor ranges and also the variation of material restance to fatigue crack growth. The fatigue crack growth resistance was treated as a spatial stochastic process, which varies randomly on the crack path, Compact tension specimens with a LT orientation for structural steel were used. All testing was done at a constant stress intensity level. The experimental data were analyzed for the size effect to determine the Weibull distributions of the material resistance.

• Corrosion Science and Technology
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• v.5 no.3
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• pp.112-116
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• 2006

This study has been conducted to monitor the corrosion rate of cathodically protected structure and corrosion inhibited system using multi-line thin-film electrical resistance (TFER) sensor in various environments. The field test data of TFER sensor for the corrosion monitoring of cathodically protected underground pipeline in soil environments and of corrosion inhibited gas heaters were also presented. The sensor was found to be a powerful method to commit the sensitive pick-up of small corrosion rate which can be observed in the cathodically protected and corrosion inhibited systems.

• YAKHAK HOEJI
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• v.34 no.1
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• pp.54-63
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• 1990

These studies were made to assess the present stage of resistance of Shigella species to antibiotics and to find characteristics of R-plasmid of these bacteria. From 1986 to 1988, 125 strains of Shigella species were isolated from patients specimens collected in Chung Cheong-do Hospital, Kyunghee Medical Center, city an provincial health & environmental institutes. These specimens were tested for resistance to 12 kinds of antimicrobial agents by agar dilution method. Using Muller-Hinton agar for the assay of drug resistance and Trypticane Soy Broth as propagating medium for conjugation. All the strains (100%) were resistant to one or more antibiotics. Drug resistance patterns of isolated strains were found as the highest resistance to ampicillin (98%) in 1986, to tetracycline (98%) in 1987, to tetracycline (100%) in 1988, all strains were sensitive to gentamicin, amikacin, tobramycin. Chronologically, resistance decreased gradually as it was shown in relation to kanamycin, rifampicin in 1986, 1987 and 1988, (4%, 2%) (4%, 2%) (0%, 0%) respectively. But, resistance was increased year by year as it was shown in relation to tetracycline, nalidixic acid, streptomycin in 1986, 1987, 1988 (89%, 19%, 45%) (98%, 46%, 71%) and (100%, 58%, 88%). The resistance in correlation to more than 5 drugs, which was 13 strains among 47 strains in 1986, 38 strains among 87 strains in 1987, 23 strains among 26 strains in 1988, was increased gradually. In the transfer test of drug resistance by conjugation methods, the rate which was 3 strains (50%) in 1986, 8 strains (62%) in 1987, 3 strains (100%) in 1988, was increased gradually. When the donor strains were conjugated with the recipient strains, the conjugation rate was high in the multiple resistant strains. The relationships of transferring patterns of drug resistance and molecular weight of R-plasmid were variable. However, only a plasmid which has more than 35 Mgd was transferred.

• The Plant Pathology Journal
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• v.35 no.4
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• pp.321-329
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• 2019

Ascochyta blight caused by Ascochyta rabiei (Pass.) Lab. (Telomorph: Didymella rabiei) (Kov.) is one of the most important fungal diseases in chickpea worldwide. Knowledge about pathogen aggressiveness and identification resistance sources to different pathotypes is very useful for proper decisions in breeding programs. In this study, virulence of 32 A. rabiei isolates from different part of Iran were analyzed on seven chickpea differentials and grouped into six races based on 0-9 rating scale and susceptibility/resistant pattern of chickpea differentials. The least and most frequent races were race V and race I, respectively. Race V and VI showed highly virulence on most of differential, while race I showed least aggressiveness. Resistance pattern of 165 chickpea genotypes also were tested against six different A. rabiei races. ANOVA analysis showed high significant difference for isolate, chickpea genotypes and their interactions. Overall $chickpea{\times}isolate$ (race) interactions, 259 resistance responses (disease severity ${\leq}4$) were identified. Resistance spectra of chickpea genotypes showed more resistance rate to race I (49.70%) and race III (35.15%), while there were no resistance genotypes to race VI. Cluster analysis based on disease severity rate, grouped chickpea genotypes into four distinct clusters. Interactions between isolates or races used in this study, showed the lack of a genotype with complete resistance. Our finding for virulence pattern of A. rabiei and newly identified resistance sources could be considerably important for integration of ascochyta blight resistance genes into chickpea breeding programs and proper decision in future for germplasm conservation and diseases management.

• Tuberculosis and Respiratory Diseases
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• v.59 no.6
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• pp.619-624
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• 2005

Background : The drug resistance rate in tuberculosis patients with history of chemotherapy is an important indicator of for evaluation of appropriateness of treatment regimens and compliance of patients. This study examined the long-term changes in the drug resistance rates among TB patients failed in treatment or reactivated. Methods : The results of drug susceptibility testing data from patients registered in health centers from 1981 to 2004 were analyzed. Results : The rate of resistance to isoniazid decreased from 90% to 20%, and the resistance to ethambutol decreased from 45% to 6%. The rate of resistance to rifampicin varied from 13% to 28% and the resistance to pyrazinamide was 5% to 10%. Multidrug resistance was about 2-3% lower than any rifampicin resistance rates. The second-line drug resistance was ranged from 1% to 3%. There was no difference between patients' genders. Patient numbers per 100,000 population increased with age. The regional distribution was even at 4-6 patients per 100,000 population, and drug resistance rates were significantly lower in big city areas than in small towns and rural areas. Conclusion : The rates of resistance of Mycobacterium tuberculosis isolated from TB patients with history of chemotherapy to isoniazid, rifampin, ethambutol, and isoniazid plus rifampin were significantly decreased during over two decades.

• Food Science and Preservation
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• v.20 no.3
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• pp.289-295
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• 2013

The capacity of a pressure fan can be designed based on the air flow resistance of containers packed with fruits and vegetables in a pressure cooling system. This study was conducted to develop an air flow resistance model that was dependent on changes in the air flow rate and the method of stacking containers. The air flow resistance of a container packed with uniformly shaped balls was 1.5 times greater than the sum of the air flow resistance of a vacant container and that of a wire net container packed with only balls. In addition, the air flow resistance increased exponentially as the width of the stacks increased; however, the air flow resistance did not increase greatly as the length and height of the stacks increased, which indicates that the air flow resistance is primarily influenced by the width of the stack in the air flow direction. The air flow resistance in two lines of stacking was up to 17% less than that of the width of the stack. It was also possible to determine the air flow resistance using a function of the air flow resistance through a single container and develop a prediction model. A prediction model of air flow resistance that is dependent on the stacking method and the air flow resistance of a single container was developed.