• 한국작물학회지
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• 제44권4호
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• pp.309-315
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• 1999

Rice seedling test was conducted to check the loging tolerance at ripening stage through evaluating the root characters. Thirteen Korean and foreign rice cultivars with direct seeding adaptable or high quality characteristics were grown in a cell pot and under submerged paddy. The root characters and pushing resistance of rice hill were determined at seedling and ripening stage, respectively. The diameter of crown root at the 7th and 8th leaf stages was thicker in lodging tolerance cultivars than those of others and showed significant-positive correlation with both pushing resistance and crown root diameter of mature plants. Also, the tensile strength of crown root at the 7th and 8th leaf stage showed highly positive correlation with the tensile strength of crown root of mature plants. The number of crown root at 7th leaf stage was significant-positively correlated with that of mature plant. The diameter of seminal root was not significantly correlated with the diameter of crown root throughout the whole growth stage. These results indicate that the diameter, tensile strength and number of crown root associated with root lodging tolerance can be detected with the seedling at about 7th or 8th leaf stage, and the seedling test using the cell pot is an useful and practical method to select lodging tolerant cultivars or lines of rice based on root characters, especially diameter of crown root.

• 한국환경복원기술학회지
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• 제1권1호
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• pp.54-62
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• 1998

This study measured the shearing resistance of the roots of the Sasamorpha purpurascens, Miscanthus sinensis, Lespedeza cyrtobotrya by the tensile strength gained through their individual tensile test for the Root Reinforcement Model. The results to have measured this stress by experiment are as follows. 1) The mean root diameter of the Lespedeza cyrtobotrya used for this experiment was 2.19mm and the mean tensile stress was calculated as $929.489kgf/cm^2$. As for the Sasamorpha purpurascens, its mean root diameter was 1.727mm, and the mean tensile stress was $292.069kgf/cm^2$. And as for the Miscanthus sinensis, its mean root diameter was 0.814mm, and the mean tensile stress was $696.947kgf/cm^2$. And so, it was grasped that Lespedeza cyrtobotrya was highest in tensile stress. 2) ${\Delta}Cr(kg/cm^2)$ of the shearing resistance calculated by estimating the areal ratio of roots at $10^{-3}$ is $1.069kg/cm^2$ in Lespedeza cyrtobotrya, $0.336kg/cm^2$ in Sasamorpha purpurascens, and $0.801kg/cm^2$ in Miscanthus sinensis. That is, Lespedeza cyrtobotrya has the highest shearing resistance. However, since a precise analysis of the controlled factors of the slope analyses are demanded for more accurate dynamic analyses, the future demands a study on this.

• 한국산림과학회지
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• 제97권4호
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• pp.392-397
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• 2008

산불피해지역의 소나무림을 대상으로 4년 동안 뿌리의 강도 특성변화를 시간의 경과에 따라 만능재료시험기를 이용하여 소나무 뿌리의 직경급별로 인장력과 인장강도를 측정 분석하였다. 그 결과 뿌리 직경급에 따른 산불발생 후 년차별 인장강도의 변화는 뿌리의 직경급이 큰 경우보다는 직경급이 작은 뿌리에서 강도저하폭이 큰 것으로 나타났다. 특히, 조사된 모든 직경급에서 2년차에 가장 많은 강도저하율을 나타냈고, 평균적으로는 약 61%의 인장강도가 저하되는 것으로 나타났다. 또한 시간변화에 따른 소나무뿌리의 직경급별 인장강도저하를 미분방정식을 통해 모델링한 결과, 모든 뿌리 직경급대에서 산불발생 후 2년 이내에 50%이상의 인장강도저하가 발생하는 것으로 분석되었다.

• Restorative Dentistry and Endodontics
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• 제20권1호
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• pp.142-151
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• 1995

The purpose of this study was to compare and estimate the physical properties of five root canal sealers classified Calciobiotic root canals sealer as calcium hydroxide based sealer, Apatite root sealer type II as calcium phosphate based sealer, AH-26 as resin based sealer, Canals and Pulpdent root canals sealer as zinc oxide eugenol based sealer. The author investigated dimensional change and flow rate of canal sealers, diametral tensile strength and shear bond strength of sealers to dentin to evaluate the physical properties on affect of complete obturation of root canal and performed the total 100 specimens of each 25 sealers under the condition of root temperature according to manufacturer's instructions. All specimens were stored at $37{\pm}1^{\circ}C$ in 100 % relative humidity. A microscope for measurement of micro distance is used for the dimensional change test and evacuation methods using vaccum were used for the flow rate test. The result differed by the storage time measured on the tests of diametral tensile strength and shear bond strength to dentin. The following results were obtained ; 1 On the test of dimensional change, Canals and Pulpdent expanded slightly, AH-26 and Apatite showed the severe shrinkage after 48 hours. 2. AH-26 and Apatite were the excellent with each 24.59mm, 31.19mm after 3 minutes in the aspect of flow property. 3. On the diametral tensile strength, Calciobiotic root canals sealer showed the highest strength with 27.13kg/$cm^2$ after 48 hours, Apatite root sealer type II showed highest strength with 84.57kg/$cm^2$ after 120 hours. 4. On the shear bond strength to dentin, AH-26 was most excellent with 55.73kgf/$cm^2$ after 24 hours and with 134.71kgf/$cm^2$ after 120 hours.

• Journal of Forest and Environmental Science
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• 제26권3호
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• pp.193-202
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• 2010

To analyze the effects of tree roots on the stability of damage slope, distributional and physical properties of five-year Pinus densiflora roots were investigated. In the composition of roots, the proportion of main root to lateral root was 1 to 9 in slope condition. Root tensile force was increased in accordance with increased proportion to diameter of Pinus densiflora roots. However, tensile strength was decreased in proportion to diameter of roots. Root shear strength showed that soil containing Pinus densiflora roots was higher than that of non-treated soils. This result shows that Pinus densiflora roots significantly stabilize the surface-soil rather than sub-soil in damage slopes.

• 한국환경생태학회지
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• 제25권1호
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• pp.31-36
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• 2011

본 연구는 사면안정해석에 필요한 기초자료를 제공하고자 잣나무, 낙엽송, 소나무, 신갈나무, 오리나무를 대상으로 교목류 뿌리의 인장력 및 인장강도를 측정 분석하였다. 그 결과 인장력은 대부분 뿌리 직경의 거듭제곱의 형태로 증가하는 것으로 나타났다. 또한 뿌리의 평균 인장강도는 잣나무 $165.38kgf/cm^2$, 낙엽송 $172.78kgf/cm^2$, 소나무 $176.25kgf/cm^2$, 오리나무 $214.29kgf/cm^2$, 신갈나무 $224.19kgf/cm^2$로 나타났으며, 뿌리의 직경이 커질수록 인장강도가 감소하는 경향을 나타냈다. 측정 분석된 인장강도를 기초자료로 토양의 전단강도 증가값을 산출한 결과 잣나무 $0.099kgf/cm^2$, 낙엽송 $0.104kgf/cm^2$, 소나무 $0.106kgf/cm^2$, 오리나무 $0.129kgf/cm^2$, 신갈나무 $0.135kgf/cm^2$인 것으로 나타났다.

• 한국조경학회지
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• 제27권5호
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• pp.80-93
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• 2000

This study measured the shearing resistance of the roots of the Pinus Koraiensis by the tensile strength gained through their individual tensile test for the Root Reinforcement Model. On the basis of the shearing resistance value calculated through such a process the factor of safety(Fs) was comparatively presented by using the simplified Janbu Method in PCSTABL5M, the slop-analyzing software which had been developed in Purdue University of the U.S.A according to the shape of a slope and the type of soil. The results to have measured a stress and the factor of safety(Fs) by experiment are as follows. 1) The mean root diameter of the Pinus Koraiensis used for this experiment was 2.483mm and the mean tensile stress was calculated as 422.846(kgf/$\textrm{cm}^2$). In the strain ratio of material and the elastic modulus was measured 7.8%, 9,291.92(kgf/$\textrm{cm}^2$). 2) The shearing strength including the resistance of soil and root is expressed as Rt=C+Cr+$\sigma$.tan . ΔCr(kg/$\textrm{cm}^2$) of the shearing resistance calculated by estimating the areal ratio of roots at 10 is 0.253(kgf/$\textrm{cm}^2$). 3) As the result of making an analysis of the natural slope stability by the soil parameter, the factor of safety(Fs) was calculated at 1.795 in CL, and the stability analysis of the root reinforcement slope, Fs was calculated at 1.952. However, since a precise analysis of the controlled factors of the slope analyses are demanded for more accurate dynamic analyses, the future demands a study on this.

• Computers and Concrete
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• 제14권3호
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• pp.233-245
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• 2014

In this paper, a rule based Mamdani type fuzzy logic model for prediction of slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes were discussed. In the model steel rebar diameters and development lengths were used as inputs. The FL model and experimental results, the coefficient of determination R2, the Root Mean Square Error were used as evaluation criteria for comparison. It was concluded that FL was practical method for predicting slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes.

• 대한기계학회논문집
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• 제18권5호
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• pp.1126-1133
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• 1994

When designing an internal gear. the bending strength around pitch point as well as that at tooth root fillet should be considered because the bending stress around pitch point may occur as high as that at tooth root fillet. In this study, including stress state around pitch point, the bending strength (tensile side and compressive side) of internal gear tooth is investigated by the use of the finite element method(FEM) with regarding many influencing factors of cutter and gear geometries. Then, the critical sections around pitch point and at tooth root fillet are determined, and the simple formulae based on nominal stresses(bending, compressive, and shear) are derived for the calculations of actual stresses as the functions of tooth thicknesses and radii of curvatures of involute and fillet curve at those critical sections. The stresses calculated by the formulae agree well with those by the FEM. And the bending stresses around pitch point and at tooth root are easily estimated by the use of those formulae, therefore, those formulae are useful for the purpose of the design or the bending strength estimation of internal gear.

• Journal of Biosystems Engineering
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• 제1권1호
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• pp.64-72
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• 1976

This experimental work was carried out to investigate the fatigue bending strength on various shapes and sizes of notches of the domestically manufactured steel plate. The notch types tested were a circular hole, U-and V-notches. The S-N diagram for different notch shapes were discussed in relation to plan bending strength and stress concentration factor of notches .The results of the experiments are summarized as follows : (1) The difference between stress concentration factor and notch factor was greater as the radium of notch root became smaller, and these values approached to an identical value as the radium of notch root increased. (2) It was shown that the plane bending fatigue limit of bar without notch for the hotrolled steel having the tensile strength of 33.1kg/$mm^2$was 17.0kg/$mm^2$. (3) U-and V-notch had a greater effect of stress concentration factor on the endurance limit, but O-hole showed the same effect only for $\o\pm2mm$. (4) For the same radius of notch root, U-notch showed a lower value of fatigue limit compared to V-notch and O-hole.