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This paper proposes a new method to determine the droop of the inverter-based distribution generations (DGs). Conventionally, inverter-based DGs have droop controller with fixed slope according to their capacity. Some additional control methods have been proposed in order to enforce the maximum or minimum limit of a unit. However, in some severe cases, the frequency deviation during the islanded mode becomes larger with the existing methods. To overcome this problem, the proposed method, namely “variable droop,” determines the droop of DGs according to their operating points. Using the proposed method, the frequency can be maintained within the predetermined limits and the load demand can be properly shared by the DGs. The effectiveness of the method is verified by the PSCAD/EMTDC simulation.

This paper presents a grid-connected photovoltaic (PV) system with the new operation method considering voltage regulation in distribution system. In proposed system, PV system adjusts real power and reactive power injection at connection point, in order to maintain the overall system voltage within acceptable range and improve power quality. It consists of modeling of PV array, inverter and inverter controller using PSCAD/EMTDC, and development of operation method of PV generation for voltage regulation in distribution system. PV array modeling is accomplished using 2-diode model which is generally used, and inverter with control system is implemented using proposed operation method based on instantaneous power theory and hysteresis current control. Proposed operation method consists of 3 stages control and using that operation method, overall system effectiveness is improved. To validate the effectiveness of the proposed system, it is compared with system with conventional operation under variable case such that connection, disconnection, load changes and voltage sag using PSCAD/EMTDC.

By introducing the concept of simulated annealing into the conjugate gradient algorithm, we propose a stochastic conjugate gradient algorithm which has an increased probability of obtaining a global minimum, and the determination of the weights of the cost function becomes easier due to the wider feasible scope of its parameters. We apply the proposed algorithm to an optimal task partitioning and compare the scope of the parameters and the probability of obtaining a global minimum with those of the Boltzmann machine. Simulation results show characteristics in favor of the proposed algorithm. We also present a hardware for the proposed algorithm.

Adequate distention of the gastrointestinal tract is essential for the best quality image in abdominal computed tomography. We introduce a new technique for per-rectal administration of contrast material with the use of an automatic injector. With this technique, more contrast material can be inserted and thus adequately distend the colon, including the proximal colon.

Pott's puffy tumor is an extremely rare and potentially life-threatening complication of frontal sinusitis. We report a case of a 64-year-old man who presented at our emergency department with mild tenderness on the glabellar area and diplopia. Computed Tomography (CT) revealed frontal sinusitis and osteomyelitis of the frontal bone. Following sinus trephination and long-term antibiotic therapy, the patient achieved a complete recovery.

Creutzfeldt-Jakob disease (CJD) is one of the transmissible spongiform encephalopathies, which is mediated by what has been known as “prion”. It is a rare and fatal progressive neurodegenerative disease that affects the middle and old aged. There are a number of subtypes of CJD, one of which is the sporadic type characterized by rapidly progressing clinical symptoms, including progressive dementia, myoclonic jerk, and pyramidal or extrapyramidal syndrome. Patients usually end up dying within 1 to 2 years of contacting the disease. We report an autopsy-proven case of sporadic CJD with clinical symptoms that progressed within several days, along with dramatic changes on diffusion weighted magnetic resonance images.

Human tail is a rare congenital anomaly in which a lesion protrudes from the lumbosacrococcygeal region. We encountered a case of human tail involving an intradural lipoma and tethered cord, occurring in a 1-day -old female who presented with an 8 cm-sized tail shown by MRI to arise from the S3-4 level. The cauda equina and film terminale were entrapped by the lipoma, but there were no bony abnormalities.

Sclerosing stromal tumor of the ovary is a rare benign neoplasm, with distinctive clinical and pathologic features. It occurs predominantly in females during the second and third decades of life. Histologically, it is composed of cellular and acellular collagenized areas, and edematous stromal areas, and at ultrasonography and computed tomography is seen as a distinctive mixed solid and cystic mass lesion. We report a case of sclerosing stromal tumor of the ovary in a 15-year-old girl with a history of menorrhagia since menarche. Ultrasonography revealed the tumor as a well-defined, lobulated, heterogenous echogenic pelvic mass, while at CT, a huge pelvic mass 9x9x10 cm in size, was seen. This comprised a well-enhanced internal solid portion, a capsule, septa, and a non-enhanced cystic portion.