• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.1280-1300
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• 2020

In the modern financial sector, interest in providing financial services that employ blockchain technology has increased. Blockchain technology is efficient and can operate without a trusted party to store all transaction information; additionally, it provides transparency and prevents the tampering of transaction information. However, new security threats can occur because blockchain technology shares all the transaction information. Furthermore, studies have reported that the private keys of users who use the same signature value two or more times can be recovered. Because private keys of blockchain identify users, private key leaks can result in attackers stealing the ownership rights to users' property. Therefore, as more financial services use blockchain technology, actions to counteract the threat of private key recovery must be continually investigated. Private key recovery studies are presented here. Based on these studies, duplicated signatures generated by blockchain users are defined. Additionally, scenarios that generate and use duplicated signatures are applied in an actual bitcoin environment to demonstrate that actual bitcoin users' private keys can be recovered.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.39-45
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• 2009

The attenuation of the fundamental non-torsional modes that propagate down buried steel water pipes has been studied. The mode shapes, mode attenuation due to leakage into the surrounding medium and the scattering of the modes as they interact with pipe joints and fittings have been investigated. In the low frequency region the mode predicted to dominate over significant propagation distances approximates a plane wave in the water within pipe. The established acoustic technique used to locate leaks in buried steel water pipes assumes that leak noise propagates as a single non-dispersive mode at a velocity related to the low frequency asymptote of this water borne mode.

• Journal of Environmental Health Sciences
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• v.35 no.4
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• pp.239-248
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• 2009

The Institute of Medicine of the National Academies of Science in the United States concluded in its 2004 report that excessive indoor dampness is a public health hazard and that its prevention should be a public health goal. Water damage in buildings, such as leaks from roofs, walls, or windows, may increase indoor moisture levels. Excessive dampness may promote microbial proliferation in indoor environments, increase occupants' exposure to microbial agents, and eventually produce adverse health effects in building occupants. Epidemiological studies to demonstrate the causal association between exposure to indoor microbial agents and health effects require reliable exposure assessment tools. In this review, I discuss various sampling and analytical methods to assess human exposure to biological agents in indoor environments, their strengths and weaknesses, and recent trends in research and practice in the USA.

• Journal of Korean Neurosurgical Society
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• v.54 no.2
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• pp.142-144
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• 2013

A 49-year-old female with a history of several neurosurgical and otolaryngologic procedures for occipital meningioma and cerebrospinal fluid leaks was diagnosed with pneumocephalus after a one hour flight on a domestic jet airliner. Despite multiple operations, the air appeared to enter the cranium through a weak portion of the skull base due to the low atmospheric pressure in the cabin. The intracranial air was absorbed with conservative management. The patient was recommended not to fly before a definite diagnostic work up and a sealing procedure for the cerebrospinal fluid leak site had been performed. Recent advances in aviation technology have enabled many people to travel by air, including individuals with medical conditions. Low cabin pressure is not dangerous to healthy individuals; however, practicing consultant neurosurgeons should understand the cabin environment and prepare high risk patients for safe air travel.

• Journal of Information Technology Services
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• v.19 no.2
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• pp.83-92
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• 2020

The current technology drain at small and medium-sized enterprises in Korea is very serious. According to the National Intelligence Service's survey data, 69 percent of technology leaks are made through employees of small and medium-sized enterprises. A document security system was introduced to compensate for the problem. However, small and medium-sized enterprises are not doing well due to their poor environment. Therefore, it proposes a document security system suitable for small businesses by developing a location information machine learning system that automatically creates a document security Green Zone through learning, and an ECM-based electronic document leakage prevention system that manages generated Green Zone information by reflecting it into the document authority system. And step by step, propose a universal solution through cloud services..

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.4
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• pp.307-317
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• 2010

The majority of financial and general business organizations have had individual damage from hacking, worms, viruses, cyber attacks, internet fraud, technology and information leaks due to criminal damage. Therefore privacy has become an important issue in the community. This paper examines various elements of the information security management system and discuss about Information Security Management System Models by using the analysis of the financial statue and its level of information security assessment. These analyses were based on the Information Security Management System (ISMS) of Korea Information Security Agency, British's ISO27001, GMITS, ISO/IEC 17799/2005, and COBIT's information security architecture. This model will allow users to manage and secure information safely. Therefore, it is recommended for companies to use the security management plan to improve the companies' financial and information security and to prevent from any risk of exposing the companies' information.

• Journal of Chest Surgery
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• v.27 no.12
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• pp.1060-1065
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• 1994

For most surgeons, stomach and colon are the first choice for reconstruction of the esophagus, as well as for bypass. When the esophagogastric or esophagocolonic anastomosis is made in the neck, cervical anastomosis site leakage is the main complication. In our most recent four patients who underwent a transhiatal & posterior mediastinal esophagogastric or esophagocolonic anastomoses following esophageal resection, we performed the cervical anastomoses with a circular EEA stapler. No leaks have developed at the anastomosis site. In these four patients the cancer was tiny and was located on the upper or middle third of the thoracic esophagus. A total esophagectomy was performed by blunt resection without thoracotomy. Surgical staplers have been used previously for esophagogastric anastomosis through a right thoracotomy with a very low rate of leakage. When the esophagogastric or esophagocolonic anastomosis is performed in the neck, the prevalence of leakage does not increase the postoperative mortality, but it can increase significantly the duration of hospitalization and morbidity. The use of the circular stapler allowed us to perform four consecutive cervical esophagogastric & esophagocolonic anastomoses without any leakage and to shorten the operating time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.950-953
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• 2002

Trepan prevents wear of an inside part of a bearing when the initial shaft rotates. It continuously contacts with the eccentric part of the shaft in rotation and is loaded repeatedly. Therefore, even if an early crack of a trepan part is small, a crack progresses by a repeated load. If a crack progresses, very small chips come out. This is pill in the rotor and prevents rotation of the compressor. There can be leaks in a microgroove and extreme wear can occur due to lack of oil on the surface contact pan. Therefore, this study was carried out to compare and investigate trepan strength and deflection characteristics between trepan locations and dimension changes using a finite element method and search a motor bearing for a model with bigger stiffness of a trepan part and the same deflection. And then. five different types of the oil groove model were chosen to prevent small crack and considered also machining ability and the analysis was carried out on oil feeding flow.

• Journal of KSNVE
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• v.10 no.5
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• pp.880-885
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• 2000

In a verical type, vibratory gyroscope, the coupled motion between the reference and sensing vibrations causes the zero-point output which means non-zero sensing vibration without angular velocity. This structural coupling leaks to an inherent discrepancy between the natural frequencies of the reference and sensing oscillations, causing the degradation of the sensing performance and dynamic stability. In this paper, the dynamic characteristics associated the coupling phenomenon are theoretically analyzed. Effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are studied. A technique to predict the existence of curve veering of crossing in frequency trajectories is introduced to apply the design of micro gyroscopes with decoupled structures.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.36-41
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• 2008

Fault detection and diagnosis(FDD) system is beneficial in equipment management by providing the operator with tools which can help find out a failure of the system. An experimental study has been performed on fault detection and diagnosis method for a water chiller. Bayes classifier, which is one of classical pattern classifiers, is adopted in deciding whether fault occurred or not. FDD algorithm can detect refrigerant leak failure, when 20% amount of charged refrigerant for normal operation leaks from the water chiller. The refrigerant leak failure caused COP reduction by 6.7% compared with normal operation performance. When two kinds of faults, such as a decrease in the mass flow rate of cooling water and temperature sensor fault of cooling water inlet, are detected, COP is a little decreased by these faults.