• Advances in concrete construction
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• v.5 no.4
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• pp.407-422
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• 2017

Evaluating seismic performance of urban structures for future earthquakes is one of the key prerequisites of rehabilitation programs. Irregular structures, as a specific case, are more susceptible to sustain earthquake damage than regular structures. The study here is to identify damage states of vertically irregular structures using the well-recognized Park-Ang damage index. For doing this, a regular 3-story reinforced concrete (RC) structure is first designed based on ACI-318 code, and a peak ground acceleration (PGA) of 0.3 g. Some known vertical irregularities such as setback, short column and soft story are then applied to the regular structure. All the four structures are subjected to seven different earthquakes accelerations and different amplitudes which are then analyzed using nonlinear dynamic procedure. The damage indices of the structures are then accounted for using the pointed out damage index. The results show that the structure with soft story irregularity sustains more damage in all the earthquake records than the other structures. The least damage belongs the regular structure showing that different earthquake with different accelerations and amplitudes have no significant effect on the regular structures.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.659-667
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• 2017

Rail support failure is inevitably subjected to track geometric deformations. Due to the randomness and evolvements of track irregularities, it is naturally a hard work to grasp the trajectories of dynamic responses of railway systems. This work studies the influence of rail fastener failure on dynamic behaviours of wheel/rail interactions and the railway tracks by jointly considering the effects of track random irregularities. The failure of rail fastener is simulated by setting the stiffness and damping of rail fasteners to be zeroes in the compiled vehicle-track coupled model. While track random irregularities will be transformed from the PSD functions using a developed probabilistic method. The novelty of this work lays on providing a method to completely reveal the possible responses of railway systems under jointly excitation of track random irregularities and rail support failure. The numerical results show that rail fastener failure has a great influence on both the wheel/rail interactions and the track vibrations if the number of rail fastener failure is over three. Besides, the full views of time-dependent amplitudes and probabilities of dynamic indices can be clearly presented against different failing status.

• Journal of Mechanical Science and Technology
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• v.17 no.8
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• pp.1171-1184
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• 2003

An experimental study on critical heat flux (CHF) has been performed in an internally heated vertical annulus with non-uniform heating. The CHF data for the chopped cosine heat flux have been compared with those for uniform heat flux obtained from the previous study of the authors, in order to investigate the effect of axial heat flux distribution on CHF. The local CHF with the parameters such as mass flux and critical quality shows an irregular behavior. However, the total critical power with mass flux and the average CHF with critical quality are represented by a unique curve without the irregularity. The effect of the heat flux distribution on CHF is large at low pressure conditions but becomes rapidly smaller as the pressure increases. The relationship between the critical quality and the boiling length is represented by a single curve, independent of the axial heat flux distribution. For non-uniform axial heat flux distribution, the prediction results from Doerffer et al.'s and Bowling's CHF correlations have considerably large errors, compared to the prediction for uniform heat flux distribution.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1607-1612
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• 2004

Numerical simulations are performed to investigate the characteristics of flow past a sphere in uniform shear. The Reynolds numbers considered are Re=300, 425 and 480 based on the inlet center velocity and sphere diameter. The non-dimensional shear rate K of the inlet uniform shear is varied from 0 to 0.15. At Re=300, the head of the hairpin vortex loop always locates on the high-velocity side in uniform shear, and the flow maintains the planar symmetry. At Re=425 and 480, the irregularity in the location and strength of the hairpin vortex appearing in uniform inlet flow is much reduced in uniform shear, but the flows still keep the asymmetry for most inlet shear rates. However, in the cases of K=0.075 and 0.1 at Re=425, the flows become planar symmetric and their characteristics of the evolution of the hairpin vortex loops are different from those of asymmetric flows. A hysteresis phenomenon switching from the planar symmetry to the asymmetry (or vice versa) depending on the initial condition is also observed at Re=425.

• Investigative Magnetic Resonance Imaging
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• v.22 no.2
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• pp.135-139
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• 2018

Most capitate fractures occur in association with additional carpal injuries, particularly scaphoid fractures. Isolated fractures of the capitate account for only 0.3% of carpal injuries, and stress fractures are one form of this fracture. We report the case of a 20-year-old male who had a stress fracture of the capitate after serving as an honor guard in the military. Conventional radiographs and computed tomography of the right wrist revealed a minimally displaced fracture line located at the midcarpal aspect of the right capitate. A magnetic resonance imaging scan demonstrates a subarticular capitate fracture with diffuse bone marrow edema, small osteophytes, and irregularity of the midcarpal articular cartilage. We also review the carpal kinematics which possibly caused the stress fracture. Although stress fractures of the capitate are rare, they should also be accounted for with patients who perform repetitive motions of the wrist to a considerable extent.

• Journal of Korean Association for Spatial Structures
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• v.8 no.3
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• pp.83-90
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• 2008

It is hard to predict the mechanical characteristics of discontinuous stone masonry structures by the static analysis method, because of irregularity of face stones and also due to randomness of backfill materials. Inversely, one can estimate the mechanical characteristics by comparing the natural frequencies between measured and computed. The aim of this paper is to investigate the computational modeling method of ancient stone arch bridges in Korea and to find the factors influencing their dynamic characteristics. The results revealed that the rigidity of spandrel walls and backfill materials are the most important factors influencing the natural frequencies of stone arch bridges.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.1
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• pp.181-192
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• 1989

Loss of teeth causes the inevitable reduction of residual ridge. Among the various methods solving this problem, hydroxyapatite proved to be useful for correction of ridge defect and irregularity. The purpose of this study is to evaluate the tissue responses of two types Of hydroxyapatites and resin polymer. Calcitite 2040 (Calcitek Inc.), Interpore 200 (Interpore Int.), and HTR polymer (HTR Sciences) were implanted into the jaw of an adult dog. The procedure was designed to obtain the results of 1 week, 2 week, 4 week, and 12 week-intervals. And after 12 weeks from the first operation day, the dog was sacrificed and evaluated histologically by light microscope. The results were as follows : 1. The mucosa was healed after two weeks. 2. After 1 week, there were acute inflammatory cells, but diminished after 2 weeks and were not seen after 12 weeks. 3. The hydroxyapatites implanted in soft tissues were surrounded by fibrous connective tissue. And some foreign body giant cells were found. 4. Calcitite and Interpore particles implanted subperiosteally were surrounded by newly formed bone after 12 months. And direct contact between bone and particles was noted. 5. The HTR particles implanted in soft tissues were encapsulated by fibrous connective tissues. The sample where the particles contacted directly to bone could not obtained by some probable insufficiencies of surgical technique or care of the animal. And the residue of HTR particles was digested by macrophage.

• Journal of Korean Academy of Rural Health Nursing
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• v.5 no.1
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• pp.25-32
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• 2010

Purpose: The purpose of this study was to provide a fundamental data for improving nurses' working environment and securing quality of nursing care. Method: It was consisted of analyzing education system and employment status of nursing personnel, and focus group interviews in Cheju Island. Results: Total graduates were 4,139 by 2006 from two nursing schools in Cheju. Difficulties in working conditions from focal group interviews were classified into four categories; Lack of anonymity of nurses, the burden from performing nontraditional nursing roles due to shortage of physicians, irregularity of working schedule and too many night shifts for taking care of female colleague's condition related with pregnancy, and poor support for implementing and developing professional nursing. Conclusion: A survey revealing working condition of nursing personnel of all health care institutions in Cheju Island will provide the comparison between Cheju Island and other areas. It needs to cultivate the public opinion about the importance of quality of nursing care proceeded by the broad support for improving nurses' working environment. It is essential to support continuing education to bring professional nurses and establishing the system to utilize them to overcome the shortage of physicians in Cheju Island.

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.143-149
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• 1974

The traditional cryoscopic measurement had performed by inconvenient manual operation which accompanies various unavoidable errors. For example, the irregularity of hand stirring, difference of visual angle in reading Beckmann thermometer and furthermore, its large heat capacity acts as the decreasing effect of the sensitivity. In these studies, the author devised new automatically measuring cryoscopic apparatus with temperature recording system in which temperature variation is changed to electric current. The light beam from the galvanometer is absorbed by the photographic paper on the rotating cylinder. On the other hand, the use of sodium sulfate decahydrate in cryoscopy causes considerable error, because small crystal particles adhere on the upper wall of the measuring tube. As an improvement, anhydrous sodium sulfate is used and then the desired amount of water is added.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.283-289
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• 2004

According to continuos welded rails on a bridge, temperature changes bring about the expansion of the bridge deck adding axil forces on the track. Moreover, the ballast on the bridge deck expansion joint is moved due to the bridge deck. If bridge decks are longer, the influence is greater, loosening ballast, causing track irregularities, and deteriorating passengers' comfort. Considering structure of bridge itself and tolerance of track irregularities caused by the loosened ballast on bridges, the maximum length of a deck should be less than 80m, which is the same as the standard of the French railway. In this study, an interaction between the expansion related to the bridge length and irregularity in longitudinal level referring to measurements and maintenance works performed in the high-speed railways was analyzed. This research shows that installation of sliding plate or vertical ballast stopper is not a good option since it is difficult to install. On the other hand, installation of movable fastener or gluing is easy but its influence is insignificant. To conclude, switch tie tamping or manual tamping is more effective than others.