• Tunnel and Underground Space
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• v.9 no.4
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• pp.315-327
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• 1999

Rock fracture mechanics has been widely applied to blasting, hydraulic fracturing, rock slope and many other practical problems in rock engineering. But a measuring method for the fracture toughness of rock, one of the mort important parameters in fracture mechanics as an intrinsic property of rock, has not been yet well established. To obtain mode I rock fracture toughness, the more favorable disc-typed specimens such as CCNBD, SCB, chevron-notched SCB and BDT were used in this study. Rock fracture toughness under mixed-mode and mode II conditions was measured by using the STCA applied to the CCNBD specimen. Size effects such as specimen thickness, diameter and notch length on fracture toughness were investigated. From the mixed-mode results, fracture envelops were obtained by applying various regression curves. The mixed-mode results were also compared with three mixed-mode failure criteria. In each fracture toughness test, acoustic emission was measured to get the data for determining the load levels of different crack propagation patterns.

• Journal of Chest Surgery
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• v.28 no.5
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• pp.453-463
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• 1995

During 42 month period 91 consecutive patient underwent coronary artery bypass surgery. The mean age of these patient was 57 years [range from 28 to 78 years . There were 57 men and 34 women. The preoperative risk factors that include beyond the 50 % of total patients were male sex, obesity, hypo-high-density lipoproteinemia, smoking, hypercholesterolemia, hyper-low-density lipoproteinemia, hypertriglyceridemia and hypertension. Preoperatively 27 patients had stable angina pectoris and 39 patients of unstable angina pectoris. Twenty five patients had previous myocardial infarction history. The patterns of disease were 8 patients of single vessel involvement, 18 patients of double vessel involvement, 54 patients of triple vessel involvement and 11 patients of left main coronary artery disease. Fifty five patients were in Canadian Cardiovascular Society functional class III. Myocardial revascularization was performed under emergency conditions in 5 patients. Nine percent of patients had previous PTCA history. We performed 16 cases of sequential anastomosis, internal mammary artery harvest in 86 percent of total patients and total 284 distal anastomoses[mean 3.1 anastomosis per patient . The mean ACC time was 60.5 minutes and ECC time was mean 110 minutes. The combined surgeries were 16 cases of endarterectomy, 2 cases of LV aneurysmectomy, 1 case of Bentall operation, 1 case of repair of sinus of Valsalva, 1 case of ligation of coronary AV fistula and 1 case of excision of breast mass. The most common complication was wound infection[12 cases, 13 % . There was one hospital death due to postoperative respiratory failure and low output syndrome in patient with postinfarction VSD, LV aneurysm. Postoperative 88 patients were in Functional class I or II. The 99mTc-MIBI myocardial perfusion scan that used as evaluation of postoperative state was well correlated with patient`s symptoms instead of some disadvantages.

• Structural Engineering and Mechanics
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• v.39 no.3
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• pp.427-447
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• 2011

The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.

• Steel and Composite Structures
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• v.27 no.5
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• pp.577-598
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• 2018

The imperfect steel-concrete interface bonding is an important deficiency of the concrete-filled double skin tubular (CFDST) columns that led to separating concrete and steel surfaces under lateral loads and triggering buckling failure of the columns. To improve this issue, it is proposed in this study to use longitudinal and transverse steel stiffeners in CFDST columns. CFDST columns with different patterns of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes were analyzed under constant axial force and reversed cyclic loading. In the finite element modeling, the confinement effects of both inner and outer tubes on the compressive strength of concrete as well as the effect of discrete crack for concrete fracture were incorporated which give a realistic prediction of the seismic behavior of CFDST columns. Lateral strength, stiffness, ductility and energy absorption are evaluated based on the hysteresis loops. The results indicated that the stiffeners had determinant role on improving pinching behavior resulting from the outer tube's local buckling and opening/closing of the major tensile crack of concrete. The lateral strength, initial stiffness and energy absorption capacity of longitudinally stiffened columns with fixed-free end condition were increased by as much as 17%, 20% and 70%, respectively. The energy dissipation was accentuated up to 107% for fixed-guided end condition. The use of transverse stiffeners at the base of columns increased energy dissipation up to 35%. Axial load ratio, hollow ratio and concrete strength affecting the initial stiffness and lateral strength, had negligible effect of the energy dissipation of the columns. It was also found that the longitudinal stiffeners and transverse stiffeners have, respectively, negative and positive effects on ductility of CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.1-10
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• 2007

A laboratory investigation is conducted to characterize and quantify fatigue lives of continuously reinforced concrete pavements (CRCP) with initial design parameters. Eight specimens scaled were made based on results of finite-element analyses and stress-strain curve comparisons. Static tests were firstly performed to obtain magnitudes of static failure loads and to predict crack patterns before fatigue tests. The fatigue lives measured in the study were compared based on each initial design parameter. The comparison indicates that the fatigue lives of CRCP specimens with initial cracks increases with increasing the initial crack spacing, and CRCP specimens with reinforcements at top of the concrete slab have more fatigue lives than those with reinforcements at midheight of the concrete slab. In addition, the fatigue lives were significantly affected by soil conditions under the CRCP specimens. The results obtained in the study can be used for maintenance and retrofit of the continuously reinforced concrete pavements.

• Clinical and Experimental Reproductive Medicine
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• v.20 no.2
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• pp.117-123
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• 1993

The condition of the endometrium is an important factor which may influence the success or failure in IVF-ET. This study was undertaken for evaluation of the value of endometrial growth as an early predictor for the success of IVF. Ultrasonographic endometrial measurement were performed in 43 IVF cycles that conceived, 101 cycles that did not with an IVF-ET There was no significant difference in the endometrial thickness and the serum concentration of estradiol in the pregnant versus nonpregnant group(10.4 vs. 9.9 mm: 2348 vs. 2017 pg/ml no hCG administration day). No correlation was found between the ultrasound image and serum estradiol levels around the time of hCG administration(r=0.54, p=0.13 no Day 2; r=0.45, p=0.14 no Day 1). The duration of gonadotropin treatment, number of follicles, number of oocytes retrieved, and fertilization rate were not statistically different in the two groups, however, there was a significant difference in the number of embryos in the pregnant versus nonpregnant group)p< 0.05). A higher pregnancy rate and ongoing pregnancy rate occured with an endometrial thickness over 11 mm compared with below 7mm(p< 0.05, p< 0.005). however, no significant differences were noted in the implantation rate and abortion rate among the groups that classified according to their endmetrial thickness. The endometrial growth(${\Delta}$) from hCG administration day(DO) to D6 was greater in the women who achieved pregnancy than in the nonpregnant group(p< 0.01). There were no significant differences in serum estradiol levels, implantation rate, pregnancy rate, and abortion rate among the groups that classified according to the pattern of echogenesity of endometrium, however, significantly higher ongoing pregnancy rate was noted in group A, B compared with group C.(p< 0.0001, p< 0.001) These results suggest that there were no ultrasonographically detectable differences in the patterns of endometrial growth and development around the time of hCG administration in patients who conceive versus those that do not in IVF-ET.

• Structural Engineering and Mechanics
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• v.24 no.1
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• pp.1-18
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• 2006

Strengthening of existing old structures has traditionally been accomplished by using conventional materials and techniques, viz., externally bonded steel plates, steel or concrete jackets, etc. Alternatively, fibre reinforced polymer composite (FRPC) products started being used to overcome problems associated with conventional materials in the mid 1950s because of their favourable engineering properties. Effectiveness of FRPC materials has been demonstrated through extensive experimental research throughout the world in the last two decades. However there is a need to use refined analytical tools to simulate response of strengthened system. In this paper, an attempt has been made to develop a numerical model of strengthened reinforced concrete (RC) beams with FRPC laminates. Material models for RC beams strengthened with FRPC laminates are described and verified through a nonlinear finite element (FE) commercial code, with the help of available experimental data. Three dimensional (3D) FE analysis has been performed by assuming perfect bonding between concrete and FRPC laminate. A parametric study has also been performed to examine effects of various parameters like fibre type, stirrup's spacing, etc. on the strengthening system. Through numerical simulation, it has been shown that it is possible to predict accurately the flexural response of RC beams strengthened with FRPC laminates by selecting an appropriate material constitutive model. Comparisons are made between the available experimental results in literature and FE analysis results obtained by the present investigators using load-deflection and load-strain plots as well as ultimate load of the strengthened beams. Furthermore, evaluation of crack patterns from FE analysis and experimental failure modes are discussed at the end.

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.957-967
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• 1994

The purpose of this study was to evaluate the effects of different bases of ceramic brackets on shear bond strength and to observe failure patterns of bracket bondings. Lower bicuspid brackets whose bases designed for the macromechanical and silane treated chemical bonding those for silane treated chemical bonding, those for micromechanical bonding, and those for macromechanical bonding were tested as experimental groups, and foil mesh-backed metal brackets as a control group. All the brackets were bonded with $Mono-Lok\;2^{(TM)}$ on the labial surface of extracted human lower bicuspids after etching the enamel with $38\%$ phosphoric acid solution for 60 seconds. The shear bond strengths were measured on the universal test machine after 24 hours passed in the $37^{\circ}C$ water bath. The gathered data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. The shear bond strengths of brackets for macromechanical and chemical bonding, those for chemical bonding, and those for micromechanical bonding were not different (p>0.05), but showed statistically higher than those of metal bracket and those of ceramic bracket for micromechanical bonding(p<0.05). The shear bond strengths of ceramic bracket for micromechanical bonding showed statistically lower than those of metal bracket(p<0.05). The enamel fractures and/or ceramic bracket fractures were observed in the cases of higher bond strength than that of metal bracket. These results supported that silane treated base of ceramic bracket show higher shear bond strength than that of metal bracket, and suggested that micromechanical form of ceramic bracket bases show higher shear bond strength than that of macromechanical form.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.423-431
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• 2010

In this paper, a modified sum-product algorithm to correct bit errors captured within the trapping sets, which are produced in decoding of low-density parity-check (LDPC) codes, is proposed. Unlike the original sum-product algorithm, the proposed decoding method consists of two stages. Whether the main cause of decoding failure is the trapping sets or not is determined at the first stage. And the bit errors within the trapping sets are corrected at the second stage. In the modified algorithm, the set of failed check nodes and the transition patterns of hard-decision bits are exploited to search variable nodes in the trapping sets. After inverting information of the variable nodes, the sum-product algorithm is carried out to correct the bit errors. As a result of simulation, the proposed algorithm shows continuously improved error performance with increase in the signal-to-noise ratio. It is, therefore, considered that the modified sum-product algorithm significantly reduces or possibly eliminates the error floor in LDPC codes.

• Journal of Genetic Medicine
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• v.1 no.1
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• pp.51-56
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• 1997

Spermatogenesis is known to be regulated by a number of genes and several factors such as hormones, growth factors, cytokines and others. This study was done to evaluate the relationship between HSPs and DAZ genes in human spermatogenesis; we observed the expression pattern of HSP gene in azoospermia men with DAZ gene that regulated the gene expression related with human spermatogenesis. RT-PCR method was used to detect DAZ, HSP70A, and HSP70B transcripts in all RNA samples. Total RNA was extracted from 21 testis tissues using TRIZOL reagent. cDNAs were synthesized with reverse transcriptase, AMV. All PCR reaction were performed on a PCR themocycler with DAZ, HSP70A, and HSP70B-specific primers. Semen analysis, karyotyping and testis histology were performed. DAZ gene, known as a candidate gene of azoospermia factor(AZF), was deleted in 2 of 21 patients. To evaluate the only effects of HSPs in this patients, 2 DAZ deleted cases were removed. We observed the mRNA of HSP70B in 5 whereas none could be seen with regard to HSP70A. Furthermore, the sperm of these 5 men were discovered to be immature. In conclusion, HSP70B as well ad DAZ gene seem to be involved causing spermatogenic failure. We suggest that HSP70B plays an important role in spermatogenesis and it is one of factors induced sperm maturation in human.