This paper considers an optimal sequential inspection schedule for a second-hand product after that the free nonrenewable warranty is expired. The length of warranty is prespecified and during the warranty period, the...This paper considers an optimal sequential inspection schedule for a second-hand product after that the free nonrenewable warranty is expired. The length of warranty is prespecified and during the warranty period, the product is minimally repaired by the dealer when it fails. Following the expiration of the non-renewing warranty, the product is inspected and upgraded sequentially a fixed number of times at the expenses of the customer.At each inspection, the failure rate of the product is reduced proportionally so that the product is upgraded. The product is assumed to deteriorate as it ages and the replacement of the product occurs when a fixed number of inspections are rendered. In addition,the intervals between two successive inspections are assumed to decrease monotonically. The main objective of this paper is to determine the optimal improvement level to upgrade the product at each inspection so that the expected maintenance cost during the life cycle of the product is minimized from the perspective of the customer. Under the given cost structures, we derive an explicit formula to obtain the expected maintenance cost incurred during the life cycle of the product and discuss the method to find the optimal level of the improvement analytically in case the failure times follow the Weibull distribution. Numerical results are analyzed to observe the impact of relevant parameters on the optimal solution.展开更多
A 70-year-old female with poorly controlled diabetes developed sudden visual loss, ptosis and complete ophthalmoplegia of the right eye. Funduscopic examination showed the pale retina and the cherry red spot in the ri...A 70-year-old female with poorly controlled diabetes developed sudden visual loss, ptosis and complete ophthalmoplegia of the right eye. Funduscopic examination showed the pale retina and the cherry red spot in the right eye. Fluorescein angiography and indocyanine green angiography demonstrated the absence of retinal arterial filling and choroidal perfusion in the right eye even 20 minutes after injecting the dye. The patient was diagnosed with right ophthalmic artery occlusion. Computed tomography (CT) showed diffuse mucosal thickening in the right ethmoidal sinus. Based on the clinical findings and endoscopic biopsy result, mucormycosis was confirmed. Amphotericin B (40 mg/day) and ceftriaxone (2 g/day) were intravenously administered. Despite the improvement of the right ethmoidal sinusitis and the right proptosis, the patient deteriorated into a comatose state after 19 days of systemic amphotericin B therapy. Although the previous CT showed no cerebral aneurysm, a repeated CT showed newly developed posterior communicating artery aneurysm and the subarachnoid hemorrhage. Despite the amphotericin B treatment and the improvement of the sinusitis, mucormycosis could cause sudden cerebral aneurysm rupture and subarachnoid hemorrhage resulting in coma.展开更多
基金supported by the Research Base Construction Fund Support Program funded by Chonbuk National University in 2013the Mid-career Research Program(2016R1A2B4010080)through NRF Grant funded by MEST
文摘This paper considers an optimal sequential inspection schedule for a second-hand product after that the free nonrenewable warranty is expired. The length of warranty is prespecified and during the warranty period, the product is minimally repaired by the dealer when it fails. Following the expiration of the non-renewing warranty, the product is inspected and upgraded sequentially a fixed number of times at the expenses of the customer.At each inspection, the failure rate of the product is reduced proportionally so that the product is upgraded. The product is assumed to deteriorate as it ages and the replacement of the product occurs when a fixed number of inspections are rendered. In addition,the intervals between two successive inspections are assumed to decrease monotonically. The main objective of this paper is to determine the optimal improvement level to upgrade the product at each inspection so that the expected maintenance cost during the life cycle of the product is minimized from the perspective of the customer. Under the given cost structures, we derive an explicit formula to obtain the expected maintenance cost incurred during the life cycle of the product and discuss the method to find the optimal level of the improvement analytically in case the failure times follow the Weibull distribution. Numerical results are analyzed to observe the impact of relevant parameters on the optimal solution.
文摘A 70-year-old female with poorly controlled diabetes developed sudden visual loss, ptosis and complete ophthalmoplegia of the right eye. Funduscopic examination showed the pale retina and the cherry red spot in the right eye. Fluorescein angiography and indocyanine green angiography demonstrated the absence of retinal arterial filling and choroidal perfusion in the right eye even 20 minutes after injecting the dye. The patient was diagnosed with right ophthalmic artery occlusion. Computed tomography (CT) showed diffuse mucosal thickening in the right ethmoidal sinus. Based on the clinical findings and endoscopic biopsy result, mucormycosis was confirmed. Amphotericin B (40 mg/day) and ceftriaxone (2 g/day) were intravenously administered. Despite the improvement of the right ethmoidal sinusitis and the right proptosis, the patient deteriorated into a comatose state after 19 days of systemic amphotericin B therapy. Although the previous CT showed no cerebral aneurysm, a repeated CT showed newly developed posterior communicating artery aneurysm and the subarachnoid hemorrhage. Despite the amphotericin B treatment and the improvement of the sinusitis, mucormycosis could cause sudden cerebral aneurysm rupture and subarachnoid hemorrhage resulting in coma.
