• Journal of Microbiology and Biotechnology
• /
• 제7권6호
• /
• pp.391-396
• /
• 1997

Two series of carbon sources, linear primary $C_1$~$C_9$ alcohols and linear $C_2$~$C_{10}$ monocarboxylic acids were tested for PHA synthesis in Paracoccus denitrificans. The results showed that the growth-associated synthesis of PHA could be referred only to the carbon sources with odd number of carbon except methanol. For all carbon sources with even number of carbon, nitrogen limitation was required to induce PHA synthesis in P. denitrificans. Poly(3-hydroxyvalerate)[P(3HV)] homopolymer was synthesized from $C_5$, $C_7$, and $C_9$ while growing in the presence of nitrogen, but the nitrogen depletion in the later growth period incorporated 3-hydroxybutyrate(3HB) unit into the polymer chain. The optimum C/N ratio for P(3HV) homopolymer production was found to be 10 when the strain was grown on 10 ml/l of valeric acid for 96 h. P. denitrificans synthesized P(3HB-co-3HV) copolymers from n-hexanoic and n-octanoic acid. The microstructural characterics of the P(3HB-co-3HV) copolymer from n-propanol was investigated using $^13C$-nuclear magnetic resonance spectroscopy, showing a structural heterogeneity.

• Structural Engineering and Mechanics
• /
• 제24권5호
• /
• pp.543-560
• /
• 2006

In this paper, first, the equations of motion for a rectangular isotropic plate have been derived. This derivation is based on the Von Karmann theory and the effects of shear deformation have been considered. Introducing an Airy stress function, the equations of motion have been transformed to a nonlinear coupled equation. Using Galerkin method, this equation has been separated into position and time functions. By means of the dimensional analysis, it is shown that the orders of magnitude for nonlinear terms are small with respect to linear terms. The Multiple Scales Method has been applied to the equation of motion in the forced vibration and free vibration cases and closed-form relations for the nonlinear natural frequencies, displacement and frequency response of the plate have been derived. The obtained results in comparison with numerical methods are in good agreements. Using the obtained relation, the effects of initial displacement, thickness and dimensions of the plate on the nonlinear natural frequencies and displacements have been investigated. These results are valid for a special range of the ratio of thickness to dimensions of the plate, which is a characteristic of the Multiple Scales Method. In the forced vibration case, the frequency response equation for the primary resonance condition is calculated and the effects of various parameters on the frequency response of system have been studied.

• Structural Engineering and Mechanics
• /
• 제46권2호
• /
• pp.153-177
• /
• 2013

Pendulums can be used as passive vibration control devices in several structures and machines. In the present work, the nonlinear behavior of a pendulum-tower system is studied. The tower is modeled as a bar with variable cross-section with concentrated masses. First, the vibration modes and frequencies of the tower are obtained analytically. The primary structure and absorber together constitute a coupled system which is discretized as a two degrees of freedom nonlinear system, using the normalized eigenfunctions and the Rayleigh-Ritz method. The analysis shows the influence of the geometric nonlinearity of the pendulum absorber on the response of the tower. A parametric analysis also shows that, with an appropriate choice of the absorber parameters, a pendulum can decrease the vibration amplitudes of the tower in the main resonance region. The results also show that the pendulum nonlinearity cannot be neglected in this type of problem, leading to multiplicity of solutions, dynamic jumps and instability. In order to improve the effectiveness of the control during the transient response, a hybrid control system is suggested. The added control force is implemented as a non-linear variable stiffness device based on position and velocity feedback. The obtained results show that this strategy of nonlinear control is attractive, has a good potential and can be used to minimize the response of slender structures under various types of excitation.

• 한국압력기기공학회 논문집
• /
• 제16권1호
• /
• pp.30-36
• /
• 2020

In SMART, the flow mixing header assembly (FMHA) is used to mix the coolant flowing into the reactor core to maintain a uniform temperature. The FMHA is designed to have enough stiffness so the resonance with reactor internal structures does not occurs during the pipe break and the seismic accidents. Since the gap between the FMHA and the core support barrel assembly is very narrow compared with the diameter of FMHA, the hydrodynamic mass effect acting on the FMHA is not negligible. Therefore the hydrodynamic mass characteristics on the FMHA are investigated to consider the fluid and structure interaction effects. The result of modal analysis for the dry and underwater conditions, the natural frequency of primary vibration mode for the horizontal direction is reduced from 136.67 Hz to 43.76 Hz. Also the result of frequency response spectrum seismic analysis for the dry and underwater conditions, the maximum equivalent stress are increased from 13.89 MPa to 40.23 MPa. Therefore, reactor internal structures located in underwater condition shall consider carefully the hydrodynamic mass effects even though they have sufficient stiffness required for performing its functions under the dry condition.

• Journal of Korean Neurosurgical Society
• /
• 제43권4호
• /
• pp.194-197
• /
• 2008

Primary cerebellar glioblastoma multiforme (GBM) is a rare tumor in adults that accounts for just 1% of all cases of GBM. Due to their rarity, cerebellar GBMs are not yet completely understood about the pathogenesis and the prognosis. Here, we present a case of GBM in a 69-year-old man. Neurologic examination revealed the presence of cerebellar signs. Magnetic resonance imaging (MRI) showed a 4.5${\times}$3.6 cm-sized, ill-defined, heterogeneously enhancing mass in the left cerebellum and two patchy hyperintense lesions in the right cerebellum with minimal enhancement. After operation, glioblastoma was histologically confrimed. Postoperative radiotherapy with concomittent and adjuvant temozolomide chemotherapy was subsequently followed. Here, a case of unusual GBM in the cerebellum is reported with review of literature regarding the pathogenesis, the differential diagnosis and prognosis. There was no evidence of recurrence during postoperative one year. This patient showed a good prognosis in spite of the multiple lesions.

• Journal of Korean Neurosurgical Society
• /
• 제58권6호
• /
• pp.550-553
• /
• 2015

A 67-year-old male presented with left temporal hemianopsia and left hemiparesis. A contrast-enhanced magnetic resonance image revealed a $4.5{\times}3.5{\times}5.0cm$ rim-enhancing mass with central necrosis and associated edema located in the left occipital lobe. Of positron emission tomography and abdominal computed tomography, a 9-cm mass with poor enhancement was found in the right hepatic lobe. Craniotomy and right hemihepatectomy was performed. The resected specimen showed histological features and immunochemical staining consistent with a metastatic neuroendocrine tumor (NET). Four months later, the tumors recurred in the brain, liverand spinal cord. Palliative chemotherapy with etoposide and cisplatin led to complete remission of recurred lesions, but the patient died for pneumonia. This is the first case of a metastatic brain NET originating from the liver. If the metastatic NET of brain is suspicious, investigation for primary lesion should be considered including liver.

• Journal of Korean Neurosurgical Society
• /
• 제53권1호
• /
• pp.46-48
• /
• 2013

Chondrosarcoma is a very uncommon malignant primary bone tumor, especially, it occurs extremely rare in the spine. A 52-year-old man was admitted to the emergency room with sudden paraplegia. Twelve hours prior to a paraplegic event, he visited an outpatient clinic with discomfort and tenderness around the medial border of the right scapular, and his neurologic status was absolutely intact. Magnetic resonance imaging showed a lobulated soft tissue mass from T3 to T5, which extended to the epidural space. Computed tomography scans showed soft tissue mass on the spinal posterior arch and osteolytic change of the adjacent bony structures. Emergent surgery was performed and the lesion was removed. Dark reddish blood and gel-like material were encountered around the dura and posterior arch during the operation. Multiple pulmonary nodules were found on a chest CT scan and a biopsy of one of them had been proven to be a metastasis of chondrosarcoma. The histologic examination showed dedifferentiated chondrosarcoma. The patient's neurologic deficit was improved slowly from ASIA A to ASIA D. Chondrosarcoma in the spine is extremely rare, even more with acute hemorrhage and sudden expansion into the epidural space. We named it chondrosarcoma apoplexy. We should consider the possibility of a hemorrhagic event when the patient's neurologic deficit worsens suddenly with spinal bone tumor.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
• /
• pp.93-95
• /
• 2005

Coupling capacitor voltage transformers (CCVT) are widely used in high voltage power systems to obtain standard low voltage signal for protective relaying and measuring instruments. To obtain high accuracy, capacitances and inductances are tuned to the power system frequency, making a parallel resonant circuit. When no fault occurs, no distortion of the secondary voltage is generated. However, when a fault occurs, harmonics generated break the resonance between capacitances and inductance, which generates the distortion of the secondary voltage. This paper proposes an algorithm for compensating the secondary voltage of the CCVT. With the values of the secondary voltage of the CCVT, the secondary currents, the primary currents and the voltages across the capacitors and inductor are calculated. Test results indicate that the proposed algorithm can compensate the distorted secondary voltage of the CCVT, and is irrespective of the fault distance, the fault inception angle and the burden.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.266-267
• /
• 2006

A coupling capacitor voltage transformer (CCVT) is used in extra high voltage and ultra high voltage transmission systems to obtain the standard low voltage signal for protection and measurement. To obtain the high accuracy at the power system frequency, a tuning reactor is connected between a capacitor and a voltage transformer (VT). Thus, no distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has some errors due to the transient components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of the CCVT in the time domain. With the values of the secondary voltage of the CCVT, the secondary and the primary currents are obtained; then the voltage across the capacitor and the tuning reactoris calculated and then added to the measured secondary voltage. The proposed algorithm includes the effect of the non-linear characteristic of the VT and the influence of the ferro-resonance suppression circuit. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the CCVT irrespective of the fault distance, the fault inception angle and the fault impedance.

• Imaging Science in Dentistry
• /
• 제44권2호
• /
• pp.165-169
• /
• 2014

An osteolytic lesion with a small central area of mineralization and sclerotic borders was discovered incidentally in the clivus on the cone-beam computed tomography (CBCT) of a 27-year-old male patient. This benign appearance indicated a primary differential diagnosis of non-aggressive lesions such as fibro-osseous lesions and arrested pneumatization. Further, on magnetic resonance imaging (MRI), the lesion showed a homogenously low T1 signal intensity with mild internal enhancement after post-gadolinium and a heterogeneous T2 signal intensity. These signal characteristics might be attributed to the fibrous tissues, chondroid matrix, calcific material, or cystic component of the lesion; thus, chondroblastoma and chondromyxoid fibroma were added to the differential diagnosis. Although this report was limited by the lack of final diagnosis and the patient lost to follow-up, the incidental skull base finding would be important for interpreting the entire volume of CBCT by a qualified oral and maxillofacial radiologist.