• KIEE International Transactions on Power Engineering
• /
• v.3A no.4
• /
• pp.191-197
• /
• 2003

Accurate detection and classification of faults on transmission lines is vitally important. In this respect, many different types of faults occur, such as inter alia low impedance faults (LIF) and high impedance faults (HIF). The latter in particular pose difficulties for the commonly employed conventional overcurrent and distance relays, and if undetected, can cause damage to expensive equipment, threaten life and cause fire hazards. Although HIFs are far less common than LIFs, it is imperative that any protection device should be able to satisfactorily deal with both HIFs and LIFs. Because of the randomness and asymmetric characteristics of HIFs, their modeling is difficult and numerous papers relating to various HIF models have been published. In this paper, the model of HIFs in transmission lines is accomplished using the characteristics of a ZnO arrester, which is then implemented within the overall transmission system model based on the electromagnetic transients program (EMTP). This paper proposes an algorithm for fault detection and classification for both LIFs and HIFs using Adaptive Network-based Fuzzy Inference System (ANFIS). The inputs into ANFIS are current signals only based on Root-Mean-Square (RMS) values of 3-phase currents and zero sequence current. The performance of the proposed algorithm is tested on a typical 154 kV Korean transmission line system under various fault conditions. Test results demonstrate that the ANFIS can detect and classify faults including LIFs and HIFs accurately within half a cycle.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.39 no.5
• /
• pp.203-206
• /
• 2013

Statistics is the science of data. As the foundation of scientific knowledge, data refers to evidentiary facts from the nature of reality by human action, observation, or experiment. Clinicians should be aware of the conditions of good data to support the validity of clinical modalities in reading scientific articles, one of the resources to revise or update their clinical knowledge and skills. The cause-effect link between clinical modality and outcome is ascertained as pattern statistic. The uniformity of nature guarantees the recurrence of data as the basic scientific evidence. Variation statistics are examined for patterns of recurrence. This provides information on the probability of recurrence of the cause-effect phenomenon. Multiple causal factors of natural phenomenon need a counterproof of absence in terms of the control group. A pattern of relation between a causal factor and an effect becomes recognizable, and thus, should be estimated as relation statistic. The type and meaning of each relation statistic should be well-understood. A study regarding a sample from the population of wide variations require clinicians to be aware of error statistics due to random chance. Incomplete human sense, coarse measurement instrument, and preconceived idea as a hypothesis that tends to bias the research, which gives rise to the necessity of keen critical independent mind with regard to the reported data.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.3 no.1
• /
• pp.15-21
• /
• 2004

The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Thus, traditional ceramics are very difficult-to-cut materials. To overcome such problems, in this paper, h-BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5, 10, 15, 20, 25 and 30%. The objectives of this paper is to evaluate the fracture phenomenon of the tungsten carbide tool and the variation of surface integrity of the manufactured machinable ceramics under various cutting conditions during end mill machining With CNC machining center.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1008-1013
• /
• 2003

This paper concerns the structural characteristic analysis and evaluation on the hydrostatic guide way and feeding system of a high precision centerless grinder for machining ferrules. In order to realize the required accuracy of ferrules with sub-micron order, the axial stiffness and motion accuracy of feeding system have to become higher level than those of existing centerless grinders. Under these points of view, the physical prototype of feeding system consisted of steel bed, hydrostatic guide way and ballscrew feeding mechanism is designed and manufactured for trial. Experimental results show that the axial and vertical stiffnesses of the physical prototype are very low as compared with those design values. In this paper, to reveal the cause of these stiffness difference, the structural deformations on the virtual prototype of feeding system are analyzed based on the finite element method under experimental conditions. The simulated results illustrate that the deformation of front ballscrew support-bearing bracket is the main cause of reduction in the axial stiffness of feeding system, and the deflection of bed structure and the bending deformation of hydrostatic guide rails are the main causes of reduction in the vertical stiffness of feeding system.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.7
• /
• pp.896-903
• /
• 2004

This paper proposes the structural characteristic analysis and evaluation on the hydrostatic guide way and feeding system of a high-precision centerless grinder for machining ferrules. In order to realize the required accuracy of ferrules with sub-micron order, the axial stiffness and motion accuracy of feeding system have to become higher level than those of existing centerless grinders. Under these points of view, the physical prototype of feeding system composed of steel bed, hydrostatic guide way and ballscrew feeding mechanism is designed and manufactured for trial. Experimental results show that the axial and vertical stiffnesses of the physical prototype are very low as compared with those design values. In this paper, to reveal the cause of these stiffness difference, the structural deformations on the virtual prototype of feeding system are analyzed based on the finite element method under experimental conditions. The simulated results illustrate that the deformation of front ballscrew support-bearing bracket is the main cause of reduction in the axial stiffness of feeding system, and the deflection of bed structure and the bending deformation of hydrostatic guide rails are the main causes of reduction in the vertical stiffness of feeding system.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.5
• /
• pp.82-90
• /
• 2020

Due to the complicated shape of the spider, the production method was changed from cold to warm forging. Finite element analysis was performed to predict the forging load and shape using the enclosed hydraulic die set. As the forging load increases due to the spider die volume, die stress analyses were performed to optimize the die design in order to reduce the die stress in various conditions. Large deformation while producing the complicated forging parts induces high forging load, which is one of the main parameters of the forging surface defects. The forging process was analyzed to find out the root cause of the surface defects generated during the spider production for various parameters, thereby revealing that the radius of die in the defect zone influenced the air trap depth, being the root cause of the surface defect. It was verified that die life was increased and the surface defect was eliminated by changing the die design during the mass production test.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.20
• /
• pp.241-265
• /
• 2003

The purpose of this paper is to examine the customs clearance impediment and trade parties breaches of international sales contract by the impediment. Customs clearance impediment arises when (a)clearance is not permitted, (b) importation goods are confiscated, (c)clearance delay without expectation, and (d) additional excessive trade cost caused in the process of clearance. This kind of clearance impediment may cause the breach of international sales contract. And it depends on its contents of contract and causal sequence i.e. cause and effect respectively in determining who is liable for it. If one party exemptions by Article 79 CISG, next three elements must be proved. (a)The failure was due to an impediment beyond his control; (b)the impediment was reasonably unforeseeable at the time of the conclusion of the contract, and (c)the impediment was reasonably impossible to overcome. But the customs clearance impediment is not easy to prove these three elements, the party who is responsible the customs clearance may not be exemptions by Article 79 CISG. And, according to review, it is concluded that the buyer, rather than seller, is liable for the damage which is caused in the process of clearance. It is also confirmed that the seller is sometimes liable for depending on clauses of contracts i.e. quality conditions.

• Korean Journal of Head & Neck Oncology
• /
• v.29 no.2
• /
• pp.83-86
• /
• 2013

Some clinical diseases, such as granulomatous thyroiditis, tuberculosis, and sarcoidosis can cause granulomatous inflammation in thyroid, and theses have various clinical presentations. Granulomatous thyroiditis is an inflammation of thyroid gland, and may be painful and tender in case of infection, radiation, or trauma. Otherwise, autoimmune conditions, medications, or an idiopathic fibrosis may cause to be a painless thyroididtis. It is self-limited, possibly viral, inflammatory thyroid disorder usually presented with thyroid pain and systemic symptoms. Tuberculosis of the thyroid occurs only rarely and the patient may be asymptomatic. In thyroid sarcoidosis, most common findings are painless, progressive enlargement of the thyroid with normal function. We have experienced a case of chronic granulomatous inflammation of thyroid gland presenting as a painless thyroid nodule and report it with a review of literature.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.415-418
• /
• 2011

Thermal fatigue is one of the life-limiting damage mechanisms in the nuclear power plant conditions. The turbulent mixing of fluids of different temperatures induces rapid temperature changes to the pipe wall. The successive thermal transients cause varying cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack nucleation and growth similar to the cyclic mechanical stresses. The aim of this study was to fulfil the need by developing an real crack manufacturing method, which would produce realistic cracks. The test material was austenitic STS 304, which is used as pipelines in the reactor coolant system of a nuclear power plants. In order to fabricate thermal fatigue crack similar to realistic crack, successive thermal transients were applied to the specimen. Thermal transient cycles were combined with heating (60sec) and cooling cycle (30sec). And, In order to identify ultrasonic characteristic, it was performed the ultrasonic reflection measuring method for the fabricated specimen. From the results of ultrasonic reflection measuring testing, it was conformed that A-scan results(average 83% of real crack depth) for the TFC reference specimen was more enhanced NDT reliability than results(average 38% of real crack depth) for the EDM notch reference specimen.

• The Journal of Korean Obstetrics and Gynecology
• /
• v.15 no.4
• /
• pp.238-246
• /
• 2002

Recently we observed and treated a 49-year-old postmenopausal female with enlarged uterine myoma who taking through the hormone replacement therapy(H.R.T). We regard the cause of this case as insufficiency of kidney-yin(腎陰虛), stagnation or the phlegm and pathologic blood(痰瘀阻滯) and H.R.T. ln general cases, myomas grow in size if estrogen and progesterone is present and do not increase in size if estrogen and progesterone levels are low. So if a woman can get to menopause without having symptoms from the myomas, then it is likely that she will never have problems from the growths that require treatment. But Taking postmenopausal estrogen and progestin replacement therapy can cause myomas to grow. So we recommended her to stop the H.R.T. gave herbal-medicine and acupuncture therapy. Thus we could get a good result as follows. The uterine myomas were significantly declined but no change on it's characters. Hot flush and general conditions were also significantly improved And body weight was lessened for about 4.7kg. But vaginal dryness was appeared, So we planed another therapy for that symptom.