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Quadratic criterion-based iterative learning control (QILC) was applied to a numerical reactive batch distillation process, in which methacrylic anhydride (MAN) is produced through the reaction of methacrylic acid with acetic anhydride. The role of distillation is to shift the equilibrium conversion toward the direction of the product by removing acetic acid (AcH), a by-product of the reaction. Two temperatures at both ends of the column were controlled by individual control loops. A nonlinear PID controller manipulating the reflux ratio was employed to regulate the top temperature at the boiling point of AcH. A constrained QILC was used for the tracking of the reactor temperature. A time-varying reference trajectory for the reactor temperature that satisfies the target conversion and purity of MAN was obtained through repeated simulations and confrimation experiments in the pilot plant. The QILC achieved satisfactory tracking in several batch runs with gentle control movements, while the PID control as a substitute of the QILC in a comparative study exhibited unacceptable performance.
Purpose: Since the 1990s, it has been well known that orchiopexies should be performedby no later than 2 years of age. Nevertheless, studies from other countries report a substantialnumber of delayed orchiopexies. On the basis of an analysis of a tertiary carehospital database, we aimed to investigate the incidence of delayed orchiopexies performedin patients after 5 years of age and to understand the causes of such delays andthe possible consequences. Materials and Methods: We retrospectively analyzed the surgical database of SeoulNational University Hospital between 2004 and 2012 and detected patients who underwentorchiopexy later than 5 years of age. Reasons for delayed orchiopexies were studiedand the possible consequences of delayed orchiopexies were assessed with respect tosurgical difficulty and testicular volume. Results: We found 160 cases of delayed orchiopexies, which accounted for about 15%of all orchiopexies performed. Two major reasons for delay were related to the parentsof the child: parental delay and parental request for the treatment of persistent retractiletestis. Acquired cryptorchidism was found in 21 cases (13.1%), mainly associatedwith hypospadias. Surgical difficulty, especially owing to a short testicular cord,was encountered in 48 cases (30.2%), and a comparison with age-matched normativevalues showed substantially smaller testicular volume. Conclusions: Despite well-established guidelines for the optimal age of surgery, 15%of orchiopexies were not performed at a proper time. Improved propagation of an optimalage limit is necessary to reduce the rate of delayed orchiopexies considering increasesin surgical difficulty and potential testicular growth retardation.
A few previous reports have described cases wherein electrical wire cables were inserted into the male urethra and bladder. Electrical wire cables are available at home and are easy to insert. However, after they coil in the patient’s bladder, they are difficult to remove. In February 2013, a 30-year-old man presented to the emergency room of SMG-SNU Boramae Medical Center with a urethral foreign body. He had inserted an electrical wire cable into his urethra for the purpose of masturbation, despite having a regular sex partner and no underlying disease. A kidney-ureter-bladder radiography showed a tangled wire in his bladder and urethra. On the next day, we tried to remove the wire cystoscopically, but this proved to be impossible because of complex coiling and the slippery surface of the wire. A Pfannenstiel incision was made to remove the foreign body. No postoperative complications were noted.