ObjectiveTo examine the relation between the presence of penetration or aspiration and the occurrence of the clinical indicators of dysphagia. The presence of penetration or aspiration is closely related to the clinical indicators of dysphagia. It is essential to understand these relationships in order to implement proper diagnosis and treatment of dysphagia.MethodsFifty-eight poststroke survivors were divided into two groups: patients with or without penetration or aspiration. Medical records and videofluoroscopic swallowing examinations were reviewed. The occurrence of clinical indicators of dysphagia between two groups was analyzed with Cross Tabulation and the Pearson chi-square test (p<0.05).ResultsPoststroke survivors with penetration or aspiration had significantly high occurrences of delayed initiation of the swallow (p=0.04) and reduced hyolaryngeal elevation (p<0.01) than those without penetration or aspiration.ConclusionThe results of this study indicate that delayed initiation of the swallow is a strong physiological indicator of penetration or aspiration during the oral stage of swallowing in poststroke survivors. For the pharyngeal stage of swallowing, hyoid and laryngeal elevation is a key event related to occurrence of penetration or aspiration. Clinical indicators should be investigated further to allow appropriate implementation of treatment strategies for stroke survivors.

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The effects of tempering condition on the microstructure and mechanical properties of 30MnB5 hot stamping steel were investigated in this study. Before the tempering, hot-stamped 30MnB5 steel was composed of only α′-martensite microstructure without precipitates. After the tempering at 180 o C for 120 min, nano-sized ε-carbides were precipitated in the α′-martensite laths. After tempering at 250 o C for 60 min, cementite was precipitated along the α′-martensite lath boundaries. The cementite was also observed in the specimens tempered at 350 o C for 30 min and 450 o C for 6 min, respectively. The globular α-ferrite appeared at 350 o C-30 min tempering, and the volume fraction of α-ferrite increased when the tempering temperature was increased. The yield strength increased after tempering, and it reached a peak with the tempering condition of 180 o C-120 min, due to the nano-sized precipitates in the α′martensite lath. After the tempering, the steel's ultimate tensile strength (UTS) was decreased due to the reduction in dislocation density and C segregation to lath boundaries. The highest elongation was observed at the 180 o C-120 min tempering condition, due to the reduction of residual stress, and the lack of precipitates along the lath boundaries. The 180 o C-120 min tempering condition was considered to have outstanding crash performance, according to toughness and anti-intrusion calculation results. In drop tower crash tests, the 30MnB5 door impact beam tempered at 180 o C for 120 min showed better crash performance compared to a 22MnB5 door impact beam.

The hot stamping process is beneficial for fabricating high strength automotive parts without spring back. To suppress high temperature oxidation and decarburization, it is necessary to coat the hot stamping steel. In the present work, the performance of galvannealed coated (GA) hot stamped steel was evaluated. During cyclic corrosion tests, the steel substrate began to corrode after the heat treated galvannealed coating fully corroded, because a Zn alloyed coating provides cathodic protection. In order to be applied to the automotive body-in-white, GA coated hot stamped steel must overcome drawbacks such as liquid metal embrittlement (LME) due to the low melting temperature of the Zn, and low or limited weldability due to the thick surface ZnO layer. The results of this study showed that an increase in the α-Fe(Zn) phase fraction of the coating was an effective way to prevent LME. In addition, the resistance spot weldability of GA hot stamped steel can be improved by removing the thick Zn oxide layer by sand blasting.