• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.1-9
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• 2017

Shot peening is a cold surface treatment employed to induce residual stress field in a metallic component beneficial for increasing its fatigue strength. The experimental investigation of parameters involved in shot peening process is very complex as well as costly. The most attractive alternative is the explicit dynamics finite element (FE) analysis capable of determining the shot peening process parameters subject to the selection of a proper material's constitutive model and numerical technique. In this study, Ansys / LS-Dyna software was used to simulate the impact of steel shots of various sizes on an aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The influence of shot velocity and size on the plastic deformation, compressive residual stress and force-time response were investigated. The results exhibited that increasing the shot velocity and size resulted in an increase in plastic deformation of the aluminium target. However, a little effect of the shot velocity and size was observed on the magnitude of target's subsurface compressive residual stress. The obtained results were close to the published ones, and the numerical models demonstrated the capability of the method to capture the pattern of residual stress and plastic deformation observed experimentally in aluminium alloys. The study can be quite helpful in determining and selecting the optimal shot peening parameters to achieve specific level of plastic deformation and compressive residual stress in the aluminium alloy parts especially compressor blades.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.100-108
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• 1998

Morison formula has been used in the determination of wave forces acting on vertical cylindrical piles of ocean structures. The formula, however, can be applied to mildly varying varying incident waves with symmetrical shapes. The breaking waves impinge on structures with very high impact forces, which completely differ from the inertia and drag forces of the Morison formula in both magnitudes and characteristics. In the present study, a boundary element method is applied to determine the water particle velocity and acceleration under the breaking waves. A numerical model is then developed to determine breaking wave forces utilizing those water particle kinematics. The results of the model is then developed to determine breaking wave forces utilizing those water particle kinematics. The results of the model agree well with existing experimental data, giving maximal wave forces 3 times and maximal moments 5 times larger than the Morison formula does.

• Journal of Korean Academy of Nursing
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• v.54 no.1
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• pp.18-31
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• 2024

Purpose: This study aimed to investigate the impact of anthropometric indices of obesity (body mass index [BMI], waist circumference, waist hip ratio, and body fat percentage) on the incidence of hypertension in adults with prehypertension. Methods: A longitudinal study design using secondary data form the Korean Genome and Epidemiology Study was employed. The study included 1,838 adults with prehypertension tracked every two years from 2001 to 2018. Statistical analyses, including frequency assessments, number of cases per 1,000 person-years, log-rank tests, Kaplan-Meier curves, and Cox's proportional hazards regression, were conducted using SPSS version 25. Results: Over the observation period (15,783.6 person-years), 1,136 individuals developed hypertension. The incidence of hypertension was significantly higher in the obesity groups defined by BMI (hazard ratio [HR] = 1.33), waist circumference (HR = 1.34), waist hip ratio (HR = 1.29), and body fat percentage (HR = 1.31) compared to the non-obese group. These findings indicate an increased risk of hypertension associated with obesity as measured by these indices. Conclusion: The study underscores the importance of avoiding obesity to prevent hypertension in individuals with prehypertension. Specifically, BMI, waist circumference, waist hip circumference, and body fat percentage were identified as significant risk factors for hypertension. The results suggest the need for individualized weight control interventions, emphasizing the role of health professionals in addressing the heightened hypertension risk in this population.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1412-1419
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• 2002

Dynamic shear tests for the tough-pitch copper at high strain and high strain rate was performed. The Split Hopkinson Pressure Bar (SHPB) compression test system was modified to yield a shear deformation in the specimen. Hat-shaped specimens for the tough-pitch copper were adopted to generate high strain of γ=3～4 and high strain-rate of γ= 10$^4$/s. The dynamic analysis by ABAQUS 5.5/EXPLICIT code verified that shear zone can be localized in hat-shaped specimens. A proper impact velocity and the axial length of the shear localization region wert determined through the elastic wave analysis. The displacement in a hat-shaped specimen is limited by a spacer ring which was installed between the specimen and the incident bar. The shear bands were obtained by measuring the direction of shear deformation and the width of deformed grain in the shear zone. The decrease of specimen length has been measured on the optical displacement transducer. Dynamic shear stress-strain relations in the tough-pitch copper were obtained at two strain-rates.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.3
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• pp.120-123
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• 2013

Leukemia in pregnancy was first reported by Virchow in 1845, and acute Leukemia that occurs with pregnancy is extremely rare. About 350 pregnancies with leukemia have been reported in literature. The incident of acute leukemia during pregnancy has been reported in one case per 100,000 pregnancies case. A 40-year-old patient with 30 weeks of pregnancy, (by promyelocyte which is contained granules and auer rods in the bone marrow and biopsy) was diagnosed with acute promyelocyte leukemia WITH t (15;17) (q22;q12); PML-RARA. (M3) in peripheral blood and bone marrow examination, and gave a birth to the fetus normally, January 24, 2013, after receiving the complete remission decision from the bone marrow, complete blood cell count, PML-RARA PCR test, showed normal findings until March 2013. The treatment of acute leukemia during pregnancy should be considered as treatment of a pregnant mother and the impact on the fetus. Decisions about when and how birth takes place is difficult and has to consider both mother and fetus. It is preferable to start immediate treatment without delay so that the treatment time to achieve complete remission or full recovery of the pregnant mother is longer.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.291-294
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• 2007

Countries in the world are setting up policies to implement anti-global warning measures to actively cope with the Agreement on Climate Change. Rising problems related to energy and environment prompted research and development efforts to highly efficient electric instrument and environmentally friendly products to secure resources and save energy Korea's high dependency on imported energy and its lack in natural resources make it urgently necessary to develop energy efficient instrument and equipment that can save energy. Every household now uses a transformer, which is very important instrument among others. A variety of technologies to manufacture transformers are currently used along with efforts to develop new materials. Development nit of high efficient transformers is called for by the time and has direct economic impact on suppliers and consumers. In addition, it is desirable to install a transformer that is trustworthy, secure, low on loss, anti-incident capable, small, anti-flammable, environmentally friendly, cost-efficient high-frequency resistant and easy for maintenance. To do this, it is necessary to look deeper into a highly efficient transformer that can save energy. This paper will discuss the types and characteristics of various transformers and propose ways to save energy and raise efficiency tv analyzing a environmentally friendly amorphous transformer.

• Journal of KSNVE
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• v.9 no.4
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• pp.841-848
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• 1999

In the quality assurance check process of DC motor systems, even though the overall sound pressure level is acceptable, there is an incident that subjective evaluation leads to failure in product quality due to annoying noise. This kind of problem may be originated from the manufacturing or assembly process. In this paper, the transient spectral analysis, or the time-frequency analysis is applied to the noise quality problem. For the case study, the cause of annoying noise in the wind shield wiper motor is experimentally analyzed in detail. It is concluded that the defect in the shaft causes the impact noise which is not detectable by steady spectral analysis. Also demonstrated is how the time-frequency analysis is effectively applied to the annoying noise identification of the rotor-gear system.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.307-321
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• 2015

The primary objective of this study is to investigate the feasibility of an innovative surface-mount sensor, made of a piezoelectric disc (PZT sensor), as a consistent source for surface wave velocity and transmission measurements in concrete structures. To this end, one concrete slab with lateral dimensions of 1500 by 1500 mm and a thickness of 200 mm was prepared in the laboratory. The concrete slab had a notch-type, surface-breaking crack at its center, with depths increasing from 0 to 100 mm at stepwise intervals of 10 mm. A PZT sensor was attached to the concrete surface and used to generate incident surface waves for surface wave measurements. Two accelerometers were used to measure the surface waves. Signals generated by the PZT sensors show a broad bandwidth with a center frequency around 40 kHz, and very good signal consistency in the frequency range from 0 to 100 kHz. Furthermore, repeatability of the surface wave velocity and transmission measurements is significantly improved compared to that obtained using manual impact sources. In addition, the PZT sensors are demonstrated to be effective for monitoring an actual surface-breaking crack in a concrete beam specimen subjected to various external loadings (compressive and flexural loading with stepwise increases). The findings in this study demonstrate that the surface mount sensor has great potential as a consistent source for surface wave velocity and transmission measurements for automated health monitoring of concrete structures.

• Earthquakes and Structures
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• v.15 no.4
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• pp.395-402
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• 2018

Floor location of adjacent buildings may be different in terms of height elevation, and thus, the slab may hit on the columns of adjacent insufficiently separated buildings during severe ground motions. Such impacts, often referred to as mid-column pounding, can be catastrophic. Substantial pounding damage or even total collapse of structures was often observed in large amount of adjacent low rise buildings. The research on the mid-column pounding between low rise buildings is in urgency need. In present study, the responses of two adjacent low rise buildings with unequal heights and different dynamic properties have been analyzed. Parametric studies have also been conducted to assess the influence of story height difference, gap distance and input direction of ground motion on the effect of structural pounding response. Another emphasis of this study is to analyze the near-fault effect, which is important for the structures located in the near-fault area. The analysis results show that collisions exhibit significant influence on the local shear force response of the column suffering impact. Because of asymmetric configuration of systems, the structural seismic behavior is distinct by varying the incident directions of the ground motions. Results also show that near-fault earthquakes induced ground motions can cause more significant effect on the pounding responses.

• Journal of the Korea Safety Management & Science
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• v.15 no.2
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• pp.143-149
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• 2013

Recently in the construction business construction companies has been ordered to survive in the terriblly competitive environment. Aa a result, most of the project with low-priced contract needs a speedy progress during all construction period. For the last five years major incident frequently occurs and results in the death of 189 workers at major top 6 construction builders. In most recent 10 years, the cause of major incidents happened in construction company is the speedy construction work that is affecting on the safety management. To prevent these accidents in the speedy construction work, four factors were chosed and analysed such as the personnel/organization, the working budget, the subcontractor selection and the employee motivation. The head office taked the support plan and tested it at the pilot work site. It showed a reduced accident and the harmful factors can be eliminated. It should be able to apply to the field to secure safety and prevent accidents.