• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.80-87
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• 2017

The performance of a pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor explosives. In this research, a micro Kapton flyer was accelerated by an exploding foil initiator (EFI) to figure out shock sensitivity of hexanitrostilbene (HNS) to impact. The averaged shock pressure and duration imparted to the explosive by flyer impact are measured by using a velocity interferometer for any reflector (VISAR) and impedance matching technique. Consequently, this research shows the possibility to determine the critical flyer velocity for initiating the miniaturized pyrotechnic unit by determining the relations between the impact velocity, the amplitude and width of impact loading.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.35-40
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• 2007

The pull strength and fracture mechanism were investigated to evaluate the reliability and compatibility of Sn-8Zn-3Bi joints, the solder paste on lead and lead-free plating under thermal shock conditions. At the Sn-8Zn-3Bi solder joint, no crack initiation was observed during thermal shock test. After 1000 cycles, the strength of the solder joint decreased not sharply but reduced gradually compared with initial conditions. The decrement of strength was affected by ${\gamma}-Cu_5Zn_8$ IMC growth which caused the IMC fracture on the fracture surface and a change in fracture mode and initial crack point. Clearly, the Sn-8Zn-3Bi solder shows good reliability properties and compatibility with lead-free plated Cu LF under thermal shock temperatures between 248K and 423K.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.11-18
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• 1991

A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics, and the effects of stress-induced phase transformation of ZrO2 on thermal shock behavior of Al2O3-ZrO2 ceramics were investigated. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent. Metal hydroxides were obtained by single precipitation(process A) and co-precipitation(process B) method at the condition of pH=7, and the composition of Al2O3-ZrO2 composites was fixed as Al2O3-15v/o ZrO2(+3m/o Y2O3). Critical temperature difference showing rapid strength degradation by thermal shock showed higher value in Al2O3/ZrO2 composites(process A : 20$0^{\circ}C$, process B : 215$^{\circ}C$) than in Al2O3(175$^{\circ}C$). The improvement of thermal shock property for Al2O3/ZrO2 composites was mainly due to the increase of strength at room temperature by adding ZrO2. The strength degradation was more severe for the sample with higher strength at room temperature. Crack initiation energies by thermal shock showed higher values in Al2O3/ZrO2 composites than in Al2O3 ceramics due to increase of fracture toughness by ZrO2.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.5
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• pp.283-288
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• 2016

A non-lethal weapon is a device that can subdue targets without causing death or mortal wounds. A high-intensity flash generator can negate electro-optical sensors and cause temporal flash blindness with a high intensity of light. In this study, we derive the design parameters of an explosive-driven high-intensity flash generator that uses the interaction of plasma caused by the detonation of explosives with surrounding inert gas. To determine the design parameters of the flash generator, we analyze test results measured using optical sensors. The experimental results show that the light intensity of xenon gas is about four times higher than that of air. In addition, the intensity increases with the weight of the explosive, and the inert gas cross-sectional area encountered a shock wave in the airframe. The light intensity caused by a double-initiation generator is about two times higher than that of the single-initiation generator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1089-1096
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• 1997

In this paper, Rancho Seco transient which is reported as a typical pressurized thermal shock event is postulated to be occuring in the Kori unit 1 plant, the oldest nuclear power plant in Korea. For the given material properties, transient history such as temperature and pressure, and postulated flaw, the stress distribution is obtained to calculate stress intensities for a wide range of assumed crack sizes. The stress intensities are compared with the fracture toughness, which is determined using the material properties and the distribution of the nil ductility transition temperature, to determine if cracking is expected to occur during the transient. The allowable operating year for the transient is determined and the evaluation results are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.417-420
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• 2009

The purpose of the present study is to evaluate high temperature fracture toughness through the experimental and analytical method. The analysis method is proposed to simulate the fracture toughness of high temperatures. Load-COD curves of compact test specimen acquired by finite element method analysis using hypo elastic model are simulated to determine the crack initiation load on high temperatures. The results of experimental work are in accord with analysis in thermal shock test.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.615-620
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• 2010

During braking of railway vehicles the repetitive thermal shock leads to thermal cracks on disc surface, and the lifetime of brake disc is dependent on the number of trimming works for removing these thermal cracks. Many tries for development of high heat resistant brake disc to extend the disc life and to warrant reliable braking performance has been continued. In present study, we carry out the computational fatigue analysis for thermal fatigue test in three candidate materials which were made to develop new high heat resistant material. Using FEM, we simulate thermal fatigue test in three candidate materials and conventional disc material. We then estimate the number of cycle to thermal crack initiation based on data from mechanical fatigue tests, and the results are compared with each material. For each material, the correction factor for $N_{f-40}$ which is the number of cycles when crack over $40{\mu}m$ was observed in thermal fatigue test is decided. From this study, we can verify the performance of thermal fatigue test system and suggest a qualitatively comparative method for heat resistance by FEM analysis of thermal shocking phenomenon.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.1-14
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• 2019

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.3929-3937
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• 2016

Gastric cancer (GC) is a major health problem worldwide and is one of the ten most commonly diagnosed cancers in Jordan. GC is usually diagnosed at late aggressive stages in which treatment options are limited. Recently, heat shock proteins (HSPs) were found to be overexpressed in a wide range of malignancies have been considered as promising candidate biomarkers for GC. The aim of this study was to investigate pathogenic roles of a panel of cytosolic HSPs including HSP90, HSP70, HSP60 and HSP27 in GC. Immunohistochemistry was used to assess the level of expression of these proteins in archived tumor samples (N=87) representing various pathological characteristics of GC. HSP90, HSP60 and HSP27 were expressed abundantly in gastric tumors. On the other hand, HSP70 was reduced significantly and also found to be associated with Helicobacter pylori infection in tissues collected from GC patients. Furthermore, HSP27 was found to be associated with the level of differentiation. Our findings indicate a role of HSP70 as a potential prognostic biomarker, patients harboring positive HSP70 expression displaying worse disease free survival than those with negative HSP70 expression. Differential expression of HSPs may play crucial roles in the initiation and progression of GC, and could be exploited as future therapeutic targets.

• Journal of Chest Surgery
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• v.52 no.2
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• pp.70-77
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• 2019

Background: Extracorporeal life support (ECLS) is used as a bridge to revascularization in high-risk patients with ischemic heart disease. We reviewed our experiences of coronary artery bypass grafting (CABG) after ECLS in patients with cardiac arrest or refractory cardiogenic shock. Methods: We retrospectively reviewed 4,616 patients who underwent CABG at our institution between May 2006 and February 2017. We identified patients who underwent CABG following ECLS for cardiogenic shock or cardiac arrest. Twenty-three patients (0.5% of all CABG cases) were enrolled in the analysis. Their median age was 65 years (Q1-Q3, 58-77 years). Nine patients (39.1%) were diagnosed with ST-elevation myocardial infarction. Mechanical complications after acute myocardial infarction, including acute mitral regurgitation, left ventricular rupture, and ventricular septal defect, occurred in 9 patients (39.1%). Results: The median time from cardiopulmonary resuscitation to ECLS initiation was 25 minutes (Q1-Q3, 18.5-28.5 minutes). Conventional CABG was performed in 10 patients (43.5%) who underwent concomitant intracardiac procedures. Postoperative ECLS was required in 16 patients (69.5%). The rate of successful ECLS weaning was 91.3% (n=21). There were 6 early mortalities (26.1%). Conclusion: CABG after ECLS was very rare in real-world circumstances. Although the early mortality rate was high, the risk of mortality may be acceptable under such devastating circumstances.