Ceramics in the system (Bi0.5K0.5)TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium (Nb) is carried out to reduce the conductivity of (Bi0.5K0.5)TiO3-BiFeO3. Powders of composition 0.4(K0.5Bi0.5)Ti1−xNbxO3-0.6BiFe1−xNbxO3 (x = 0, 0.01 and 0.03) are prepared by the mixed oxide method and sintered at 1050 °C for 1 h. The effect of Nb doping on the structure is examined by X-ray diffraction. The microstructure is examined by scanning electron microscopy. The variation in relative permittivity with temperature is measured using an impedance analyzer. Ferroelectric properties are measured at room temperature using a Sawyer Tower circuit. Piezoelectric properties are measured using a d33 meter and a contact type displacement sensor. All the samples have high density, a rhombohedral unit cell and equiaxed, micron-sized grains. All the samples show relaxor-like behavior. Nb doping causes a reduction in conductivity by one to two orders of magnitude at 200 °C. The samples have narrow P-E loops reminiscent of a linear dielectric. The samples all possess bipolar butterfly S-E loops characteristic of a classic ferroelectric material. Nb doping causes a decrease in d33 and Smax/Emax.
Tetanus is a fatal disease caused by the infection Clostridium tetani found in animal feces and soil. It is a vaccine-preventable disease and rarely occurs in developed countries. However, approximately 30 cases still occur annually in South Korea. Tetanus, commonly called lockjaw, cause contraction of the masseter muscles in the early stage, resulting in trismus as the first symptom. As it progresses, spasm extends to various muscles in the face, neck, shoulder, and back, leading to distorted facial expression, dysphagia, backward arching of the body, dyspnea, and even death. Early diagnosis of tetanus is critical because it can quickly become fatal if left untreated. We present a case of trismus caused by tetanus and emphasize the importance of early diagnosis of acute trismus.
Color has a close relationship with multi-disciplinary art and also for a long time. The four seasons of our country are clearly distinguished so that the seasonal experience can be shared with the sense of all colors. So it is sometimes called seasonal color. A typical seasonal color palette was created using representative photographs of the four seasons taken by the researcher. In addition, when the viewer selects the season in the hologram system produced by the researcher, it is possible to experience a hologram image combining colors representing the seasons. We expect that this study will be the foundation for developing various contents with color and hologram.
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