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Plasma Paste Boronizing법에 의한 Ni-Cr-Mo강의 붕화물층 생성거동과 내 토사마모특성에 관한 특성
조재현,박학균,손근수,윤재홍,김현수,김창규,Cho J. H,Park H. K,Son K. S,Yoon J. H,Kim H. S,Kim C. G 한국재료학회 2004 한국재료학회지 Vol.14 No.1
The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973~1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000~2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973~1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.
조재현(J. Cho),박종진(J. J. Park) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Large load is required in forging of large-scale components, which becomes a critical restriction in practice. However, the load can be greatly reduced by adopting incremental forging technologies. In the present study, two methods of incremental forging were investigated for the purpose of reducing the load required. One was to use nine strokes with a flat die and the other was to use three strokes with a curved die. The die moves vertically in the former while it moves vertically as well as rolls horizontally in the latter. Deformation of the slab in each case was analyzed by rigid-plastic finite element method and as a result, variations of load and distributions of effective strain were predicted.
최규영 ( Kyu Young Choi ),안석진 ( Seok Jin Ahn ),김현근 ( Hyun Keun Kim ),이세한 ( Se Han Lee ),유창민 ( Chang Min Yu ),조재현 ( Jae Hyun Cho ),유지원 ( Ji Won Yoo ),서승오 ( Seong O Suh ),김은실 ( Eun Sil Kim ),정준오 ( Jun Oh J 대한내과학회 2010 대한내과학회지 Vol.78 No.2
Background/Aims: The most common type of syncope in young adults is neurocardiogenic in origin, which is not related to organic problems and has a benign nature. Therefore, there have been few reports regarding syncope in young Korean adults. Here, we examined the causes of syncope and its clinical characteristics in young combat and auxiliary police in Korea. Methods: We performed a retrospective study of the medical records of 193 combat and auxiliary police in Korea admitted to the National Police Hospital for syncope or presyncope between January 2004 and December 2007. Results: The subjects` mean age was 21±1.2 years, and there were 2.8±2.9 episodes of syncope (mean±SEM). The first syncope occurred after enlistment in the police in 102 patients (52.8%). Basic diagnostic studies showed two cases of elevated creatine phosphokinase and one case of anemia to be related to syncope. Syncope-related traumatic injuries occurred in 38 patients (19.7%), and syncope was more prevalent in the summer. Head-up tilt test was performed in 175 of the 193 patients, and 123 showed a positive response. Other evaluations, including brain magnetic resonance imaging, electroencephalography, and echocardiography, were not helpful for diagnosis. Syncope was neurocardiogenic in origin in the majority of cases. Other causes of syncope were exhaustion (n=2), hyperventilation syndrome (n=2), Meniere`s disease (n=1), anemia (n=1), and psychiatric problems (n=5). The causes of syncope could not be identified in 59 patients (30.5%). Conclusions: Neurocardiogenic syncope was the most common type in our study population. More than half of our patients experienced their first episode after enlisting with the police. Further studies in these groups are necessary. (Korean J Med 78:198-206, 2010)