• International Journal of Concrete Structures and Materials
• /
• 제8권1호
• /
• pp.1-14
• /
• 2014

In the present paper, a behavioral model is proposed for study of the individual contributions to shear capacity in shear-critical reinforced concrete members. On the basis of the relationship between shear and bending moment (V = dM/dx) in beams subjected to combined shear and moment loads, the shear resistant mechanism is explicitly decoupled into the base components-beam action and arch action. Then the overall behavior of a beam is explained in terms of the combination of these two base components. The gross compatibility condition between the deformations associated with the two actions is formulated utilizing the truss idealization together with some approximations. From this compatibility condition, the ratio of the shear contribution by the tied arch action is determined. The performance of the model is examined by a comparison with the experimental data in literatures. The results show that the proposed model can explain beam shear behavior in consistent way with clear physical significance.

• Industrial Engineering and Management Systems
• /
• 제12권1호
• /
• pp.41-45
• /
• 2013

Age replacement policy is a commonly policy in maintenance management of spare part. It means that a spare part is always replaced at failure or fixed time after its installation, whichever occurs first. An optimal age replacement policy of spare parts concerns with finding the optimal replacement time determined by minimizing the expected cost per unit time. The age of the part was generally assumed to be a random variable in the past literatures, but in many situations, there are few or even no observed data to estimate the probability distribution of part's lifetime. In order to solve this phenomenon, a new uncertain age replacement policy has been proposed recently, in which the age of the part was assumed to be an uncertain variable. This paper discusses the optimal age replacement policies by dealing with the parts' lifetimes as different distributed uncertain variables. Several results on the optimal age replacement time are provided when the lifetimes are described by the uncertain linear, zigzag and lognormal distributions.

• 한국멀티미디어학회논문지
• /
• 제13권6호
• /
• pp.865-874
• /
• 2010

Recently, Hao et al. proposed a privacy preservation protocol based on group signature scheme for secure vehicular communications to overcome a well-recognized problems of secure VANETs based on PKI. However, although efficient group signature schemes have been proposed in cryptographic literatures, group signature itself is still a rather much time consuming operation. In this paper, we propose a more efficient privacy preservation protocol than that of Hao et al. In order to design a more efficient anonymous authentication protocol, we consider a key-insulated signature scheme as our cryptographic building block. We demonstrate experimental results to confirm that the proposed protocol is more efficient than the previous scheme.

• Journal of Korean Neurosurgical Society
• /
• 제39권1호
• /
• pp.32-35
• /
• 2006

Objective : Hemangiopericytoma is known as a malignant tumor originating from pericytes and rarely occurs in the central nervous system. We present 6 cases of pathologically confirmed meningeal hemangiopericytoma. Methods : Retrospective study was done based on patient's recordings including radiological studies. Each case of tumors was treated surgically and postoperative radiotherapy was done. Results : There were 5 cases of intracranial and 1 case of spinal hemangiopericytomas. Three of 5 intracranial hemangiopericytomas were located at tentorial region. Total tumor removal was done in 4 cases and postoperative local recurrence (or regrowth) was noted in 3 cases despite of postoperative external radiation therapy, 2 of which had died. Conclusion : Our cases show more frequent tentorial locations and poor clinical outcomes of hemangiopericytomas compared with meningiomas.

• Journal of Korean Neurosurgical Society
• /
• 제30권4호
• /
• pp.509-513
• /
• 2001

Sacral schwannoma is a rare lesion with a tendency to reach large proportions. The benign schwannoma rarely involves the vertebral bodies extensively. The authors report a case of giant intrasacral schwannoma in 30-year-old woman who had intermittent lower back pain during 3 years period. CT and MRI showed a destructive mass lesion within the upper part of sacrum with a large mass extending into the presacral space. The patient underwent combined surgery consisted of anterior transabdominal approach and posterior sacral laminectomy and total removal of tumor. The characteristics of the lesion were discussed with a review of literatures.

• Journal of Korean Neurosurgical Society
• /
• 제30권1호
• /
• pp.110-113
• /
• 2001

The cerebral arteriovenous malformation(AVM) rarely coexists with primary intracranial tumor. The authors experienced a patient with intracerebral hematoma due to AVM rupture in whom intracranial meningioma and intracranial aneurysms coexisted. The meningioma was located at convexity of right frontal lobe, and arteriovenous malformation at temporo-occipital lobe of same hemisphere with feeding from right middle cerebral artery, and three intracranial aneurysms exist at the cavernous portion of right internal carotid artery, AVM feeding artery, and intranidal of the AVM. The authors report a rare case of coexisted intracranial AVM, meningioma and aneurysms with review of literatures.

• Journal of Korean Neurosurgical Society
• /
• 제30권1호
• /
• pp.85-88
• /
• 2001

Intraorbital pseudotumors are inflammatory lesions of the orbit of unknown etiology, which initially mimic an orbital neoplasm. The authors report a case of intraorbital pseudotumor presenting with painful exophthalmos. A 45-year-old male patient had a two-week history of acute progressive exophthalmos and diplopia. Right orbit was explored through transcranial route and the mass was biopsied, which revealed dense inflammatory cells and fibrosis. He subsequently underwent corticosteroid therapy and symptoms improved gradually. The literatures were reviewed.

• Journal of Korean Neurosurgical Society
• /
• 제29권2호
• /
• pp.286-290
• /
• 2000

A case of symptomatic Rathke's cleft cyst, which recurred five months after drainage of the cyst using transs-phenoidal approach, is presented. Symptomatic recurrence after surgery of Rathke's cleft cyst is very rare and nine cases have been reported in the literatures. The radiological and pathologic features and clinical course of this unusual case are described. Recent concepts about embryological pathogenesis and clinical behavior mimicking craniopharyngioma are discussed with the review of literature.

• Journal of Korean Neurosurgical Society
• /
• 제52권3호
• /
• pp.243-245
• /
• 2012

It is well known that spontaneous thrombosis in giant cerebral aneurysm is common. However, spontaneous obliteration of a non-giant and unruptured cerebral aneurysm has been reported to be rare and its pathogenic mechanism is not clear. We describe a case with rare vascular phenomenon and review the relevant literatures.

• Journal of Korean Neurosurgical Society
• /
• 제45권4호
• /
• pp.249-252
• /
• 2009

We report on a case of thrombosis of the left common iliac artery following anterior lumbar interbody fusion (ALIF) of L4-5 in a 79-year-old man with no previous medical problems, including peripheral vascular disease. After completing the ALIF procedure, the surgeon could not feel the pulsation of the left dorsalis pedis artery, and the oxygen saturation ($SaO_2$) had fallen below 90% from pulse oxymetry on the left great toe. Thrombectomy was successfully performed after confirming the thrombus in the left common iliac artery using Computed Tomography (CT) angiography. Thrombosis of the common iliac artery is very rare following ALIF. However, delayed diagnosis can lead to disastrous outcome. Although elderly patients have no cardio-vascular disease or vessel calcification in pre-op evaluation, the possibility of a complication involving L4-5 should be considered.