Optimal control of thermal power plants

Application of optimal control system to thermal power plants is introduced Introduction In a large capacity high-pressure high-temperature boiler for electric power generation, deviations of steam temperatures at the boiler outlet must be kept within one or two percent of their rated values in order to maintain the nominal operating efficiency and insure the safety and the maximum equipment life of the plant. The main purpose of the boiler control is to allow the increase or decrease of steam generation as fast as possible in response to the load command from the power system's dispatch center, while satisfying the above-mentioned operating conditions. However, since a modern thermal power plant usually includes many control loops with significant mutual interactions within the boiler process, it is not easy under the conventional PID controller to fully compensate for these interactions to satisfy the required steam conditions for large and fast changes in plant load. To solve this problem the authors considered the use of the LQ (Linear Quadratic) regulator to the newly constructed plants. The first difficulty encountered was how to obtain a state equation representing plant dynamics properly in a rather simple procedure. The statistical approach using an AR (Autoregressive) model which had been proposed by Akaike [1] and successfully applied to a cement kiln control seemed appropriate for this purpose. Experimental results using a power plant model confirmed the validity of the statistical approach. After a series of elaborate experiments using various types of power plant simulation models, an optimal control system named ADC (Advanced Digital Control) system [2] by the authors was established

A Case of Fisher Syndrome Complicated by Maxillary Sinus Cysts

Fisher syndrome (FS) is an autoimmune peripheral neuropathy that occurs in 1 person per 2 million population. The present report is of a patient with FS who presented with diplopia and discomfort of the right cheek and in whom differentiation from maxillary sinus cysts was necessary. The patient was a 43-year-old man with a history of radical surgery of the right maxillary sinus, so we suspected that his symptoms were due to postoperative maxillary sinus cysts. Although computed tomography demonstrated right maxillary sinus cysts, these cysts were not likely to be the cause of the patient\u27s diplopia. Close neurological examination revealed external ophthalmoplegia, cerebellar ataxia, and the absence of a deep tendon reflex; on this basis, a diagnosis of FS was made. Diplopia is caused by various disorders and FS should be taken into consideration when making a differential diagnosis

CT Findings of Atypical Adenomatous Hyperplasia in the Lung

OBJECTIVE: The aim of this study was to analyze the computed tomographic (CT) findings of atypical adenomatous hyperplasia (AAH) in the lung. MATERIALS AND METHODS: The CT findings of AAHs in eight patients were retrospectively reviewed. The CT findings of each AAH lesion were evaluated for multiplicity, location, shape, size and internal density of the lesion, the interface between the normal lung and the lesion, the internal features within the lesion and any change of the lesion on the follow-up CT scans (range: 33 to 540 days; average: 145.3 days). RESULTS: The eight patients consisted of three men and five women (age range: 43-71 years). Six of eight patients were asymptomatic. Four of them (50%) had synchronous malignancies in the lung: adenocarcinoma of the lung (n = 3), and metastatic squamous cell carcinoma from the uterus (n = 1). We could identify and evaluate eleven AAH nodules in seven patients on the CT scans. Three patients had multiple AAHs. Seven of the 11 lesions (64%) were located in the upper lobe. All the AAHs showed a well-defined oval or round shape and pure ground-glass opacity (GGO) without any solid component (size: 3.9x3 mm to 19x17 mm; internal attenuation: -467 to -785 HU). All the AAHs showed no change of their size and internal density on the follow-up CT scans. CONCLUSION: Atypical adenomatous hyperplasia is often associated with malignancy. This tumor is shown on CT as persistent well-defined oval or round nodular GGOs without solid components, and it does not change on the follow-up CT.This study is supported by KISTEP, Ministry of Science and Technology, Korea

Cervical Sympathetic Chain Schwannomas

Surgery for cervical sympathetic chain schwannomas may result in postoperative Horner\u27s syndrome. Thus, appropriate informed consent and adequate surgical experience are required to prevent any decrease in patients\u27 quality of life (QOL) following such surgery. Here we report three cases of cervical sympathetic chain schwannomas, focusing on diagnosis and postoperative neuroparalysis. A schwannoma is suspected on pre-operative imaging when the common carotid artery (internal and external carotid artery) and internal jugular vein are located in front of or alongside the tumor, and cases in which the artery and vein are not separated are considered to be of sympathetic nerve origin. Since the origin nerve comes from the back anatomically, great care is needed during surgery. None of the patients in this study had symptoms of nerve paralysis postoperatively