• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.386-392
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• 2018

Turner syndrome (TS) is a chromosomal disorder caused by monosomy of the X chromosome, with complete or partial absence of the second sex chromosome. Anomalies of root morphology have been found to occur more often in patients with TS, which make endodontic treatment challenging and requires special handling. The patients with TS may also have systematic problems such as cardiac or renal malformations, so in treating these patients it is important for clinicians not only to be aware of the characteristic intraoral findings, but also to make the patients have regular dental check-ups to prevent oral complications in advance. An 12-year-old girl who had been diagnosed with TS at the age of 10 years was referred due to discomfort in the bilateral mandibular premolar regions. Dens evaginatus and taurodontism were detected in all the mandibular premolars characteristically. The bilateral mandibular first premolars had three roots and the bilateral mandibular second premolars had periapical lesion with two roots. Due to the complexity of the root canal anatomy, root canal treatment were completed with a dental microscope to ensure adequate visualization. After 2 years of regular follow-up examinations, there were no clinical sign or symptom associated with the teeth, and no periapical lesion, was found. This case report describes the characteristic oral features and dental management of TS patients.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.229-238
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• 2007

Sensor networks consist of many tiny sensor nodes that collaborate among themselves to collect, process, analyze, and disseminate data. In sensor networks, sensor nodes are typically powered by batteries, and have limited computing resources. Moreover, the redeployment of nodes by energy exhaustion or their movement makes network topology change dynamically. These features incur problems that do not appear in traditional, wired networks. Security in sensor networks is challenging problem due to the nature of wireless communication and the lack of resources. Several efforts are underway to provide security services in sensor networks, but most of them are preventive approaches based on cryptography. However, sensor nodes are extremely vulnerable to capture or key compromise. To ensure the security of the network, it is critical to develop suity mechanisms that can survive malicious attacks from "insiders" who have access to the keying materials or the full control of some nodes. In order to protect against insider attacks, it is necessary to understand how an insider can attack a sensor network. Several attacks have been discussed in the literature. However, insider attacks in general have not been thoroughly studied and verified. In this paper, we study the insider attacks against routing protocols in sensor networks using the Ad-hoc On-Demand Distance Vector (AODV) protocol. We identify the goals of attack, and then study how to achieve these goals by modifying of the routing messages. Finally, with the simulation we study how an attacker affects the sensor networks. After we understand the features of inside attacker, we propose a detect mechanism using hop count information.

• Journal of Korean Neurosurgical Society
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• v.30 no.1
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• pp.33-40
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• 2001

Objective : Aneurysms of vertebral artery and its branches make up approximately 3% of all intracranial aneurysms. As the aneurysm have an intimate relationship with lower cranial nerves and medulla, surgical management of the aneurysms are one of the challenging neurosurgical problems. The authors analyzed the management outcomes for aneurysms arising from vertebral artery and its branches. Methods : At the authors' institution between May 1989 and Jan. 2000, 42 patients were treated with transcranial and endovascular surgery for aneurysms of vertebral artery and its branches. The medical records and neuroimaging studies of the patients were reviewed retrospectively. Results : Forty two patients were comprised of 28 female and 14 male patients aged from 26-80 year old(mean : 51.8). Of the 42 patients, 37 patients(88%) had subarachnoid hemorrhage. Of the 37 patients with subarachnoid hemorrahge, 35 patients(95%) were in good neurological status(Hunt Hess grade I-III), 2 patients(5%) in poor grade(H-H grade IV-V) before operation. Location of the aneurysm were 16 in vertebral artery, 12 in vertebro-PICA junction, and 14 in the peripheral PICA. Twenty nine patients were treated with transcranial surgery and 13 patients with endovascular surgery. The management outcome of the transcranial surgery was : Glasgow outcome scale(GOS) I and II ; 24, GOS III ; 2, GOS IV ; 1 and GOS V(death) ; 2. The causes of mortality related to transcranial surgery were rebleeding after failure in clipping in one and suspected brainstem infarct in one. Morbidity was attributed to vasospasm(3), lower CN palsy(7, including temporary dysfunction) and pseudomeningocele(1). The management outcome of the endovascular surgery was : Glasgow outcome scale(GOS) I-II ; 9, GOS III ; 1, GOS IV ; 1, and GOS V(death) ; 2. The causes of mortality related to endovascular surgery were sepsis from pneumonia(1) and vasospasm(1). There were one cerebellar infarct and one lateral medullary syndrome. Conclusion : Excellent and good surgical results can be expected in 80% of the patients with aneurysms of vertebral arery and its branches. The outcomes of endovascular surgery in treating vertebral artery aneurysm were satisfactory and endovascular surgery may offer a therapeutic alternative especially in vertebral dissecting aneurysm.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.4
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• pp.83-96
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• 2020

Traditionally social problems had been largely left to be handled by non-profit organizations, not because of lack of interests in social causes but mostly because of lack of innovative ideas to solve them in commercially viable ways. This market failure has recently been fixed by social enterprises, which manage to provide both solutions for social issues and commercially viable business models. As a result, we have been witnessing a sudden spike of public interests in these social enterprises as well as a call for empirical investigation on social enterprises by prior studies. However, empirically investigating a social enterprise has been a challenging endeavor mostly due to the insufficient number of successful social enterprises. Answering to the call in this study, we empirically investigate Goyohan Taxi, a successful social enterprise that partners with visually impaired cabdrivers and offers a taxi service, by both longitudinally interviewing the founder and adopting in vivo observation throughout the entrepreneurial journey of Goyohan Taxi. Based on the single case study method, we find that Goyohan Taxi adopts two distinctive decision-making mechanisms, the de-escalation of commitment and the orthogonality of commercial and social goals. Although generalizability of the our finding is minimal due to the limitation of single case study method, our finding contributes to the research of social entrepreneurship by offering new avenue of research in decision-making process of social entrepreneurs.

• Journal of Korea Multimedia Society
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• v.13 no.11
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• pp.1715-1727
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• 2010

Although a hand haptic interaction which provides direct and natural sensation is the most natural way of interacting with VR environment, the hand haptic interaction has still limitations with respect to the complexity of articulated hand and related hardware capabilities. Particularly, virtual assembly simulation which refers to the verification process of digital mockup in product development lifecycle is one of the most challenging topics in virtual reality applications. However, hand haptic interaction is considered as a big obstacle, because difficulty initial grasping and non-dextrous manipulation remain as unsolved problems. In this paper, we propose that common hand haptic interactions involves two separate stages with different aspects. We present the hand haptic interaction method enables us to stably grasp a virtual object at initial grasping and delicately manipulate an object at task operating by one's intention. Therefore, proposed method provides the robustness using grasping quality and dextrous manipulation using physically simulation. We conducted experiments to evaluate the effectiveness of our proposed method under different display environments -monoscopic and stereoscopic. From 2-way ANOVA test, we show that the proposed method satisfies two aspects of hand haptic interaction. Finally, we demonstrated an actual application of various assembly simulation for relatively complex models.

• Journal of KIISE:Information Networking
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• v.36 no.6
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• pp.492-504
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• 2009

The delivery of multimedia that efficiently adapts its bit-rate to changing network characteristics and conditions is one of the important challenging tasks in the design of today's real-time multimedia streaming systems such as IPTV, Mobile IPTV and so on. In these work, the primary focus is on network congestion, to improve network stability and inter-protocol fairness. However, these existing works have problems which do not support QoE (Quality of Experience), because they did not consider essential characteristics of contents playback such as the media continuity. In this paper, we propose a novel rate control scheme for improving the QoE of multimedia streaming service in the Internet congestion, called NCAR (Network and Client-Aware Rate control), which is based on network-aware congestion control and client-aware flow control scheme. Network-aware congestion control of the NCAR offers an improving reliability and fairness of multimedia streaming, and reduces the rate oscillation as well as keeping high link utilization. Client-aware flow control of NCAR offers a removing the media discontinuity and a suitable receiver buffer allocation, and provides a good combination of low playback delay. Simulation results demonstrate the effectiveness of our proposed schemes.

• Journal of KIISE:Software and Applications
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• v.37 no.5
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• pp.341-353
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• 2010

Mobile Internet Device (MID) allows users to flexibly use various forms of wireless internet such as Wi-Fi, GSM, CDMA, and 3G. Using such Internet, MID users can utilize application services. MID usage is expected to grow due to the benefits of portability, Internet accessibility, and other convenience. However, it has resource constraints such as limited CPU power, small memory size, limited battery life, and small screen size. Consequently, MIDs are not capable to hold large-sized complex applications and to process a large amount of data in memory. An effective solution to remedy these limitations is to develop cloud services for the required application functionality, to deploy them on the server side, and to let MID users access the services through internet. A major concern on running cloud services for MIDs is the potential problems with low Quality of Service (QoS) due to the characteristics of MIDs. Even measuring the QoS of such services is more technically challenging than conventional quality measurements. In this paper, we first identify the characteristics of MIDs and cloud services for MIDs. Based on these observations, we derive a number of quality attributes and their metrics for measuring QoS of mobile services. A case study of applying the proposed quality model is presented to show its effectiveness and applicability.

• Journal of KIISE:Software and Applications
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• v.35 no.12
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• pp.780-788
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• 2008

Modeling hand poses and tracking its movement are one of the challenging problems in computer vision. There are two typical approaches for the reconstruction of hand poses in 3D, depending on the number of cameras from which images are captured. One is to capture images from multiple cameras or a stereo camera. The other is to capture images from a single camera. The former approach is relatively limited, because of the environmental constraints for setting up multiple cameras. In this paper we propose a method of reconstructing 3D hand poses from a 2D input image sequence captured from a single camera by means of Belief Propagation in a graphical model and recognizing a finger clicking motion using a hidden Markov model. We define a graphical model with hidden nodes representing joints of a hand, and observable nodes with the features extracted from a 2D input image sequence. To track hand poses in 3D, we use a Belief Propagation algorithm, which provides a robust and unified framework for inference in a graphical model. From the estimated 3D hand pose we extract the information for each finger's motion, which is then fed into a hidden Markov model. To recognize natural finger actions, we consider the movements of all the fingers to recognize a single finger's action. We applied the proposed method to a virtual keypad system and the result showed a high recognition rate of 94.66% with 300 test data.

• Membrane Journal
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• v.25 no.4
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• pp.301-309
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• 2015

Importance of pretreatment for seawater desalination is growing rapidly. Proper selection of pretreatment is critical for the successful, long-term operation in the seawater desalination plant such as seawater reverse osmosis (SWRO). The purposes of seawater pretreatment are to remove particulate, colloidal materials, organic, inorganic materials, microorganisms and their by-products present in the seawater, and thus to improve the performance of seawater desalination systems. However, pretreatment is most challenging for designing and operating seawater desalination plants because of fluctuations of water qualities, site specifications and wide ranges of target materials present in the seawater to be treated. In addition, it is also becoming evident increasingly that microscopic algae are a major cause of operational problems, for example, membrane fouling which is long-standing problem in SWRO process. Pretreatment strategies prior to the operation of seawater desalination technologies should be even more complicated by algae blooms and release of their harmful by-products in marine environment. This paper reviews the roles of various pretreatment methods in seawater desalination process. Benefits and drawbacks are described, which should be taken into account in future studies on selecting pretreatment for seawater desalination process.

• Journal of the Korean School Mathematics Society
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• v.15 no.1
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• pp.109-135
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• 2012

In December of 2009, General Curriculum Revised in 2009 was announced and research on corresponding mathematics curriculum revision has been initiated from that period. Finally, in August 2011, Mathematics Curriculum Revised in 2009 was announced. In this new curriculum, Creativity is emphasized as the ability pursued in General Curriculum Revised in 2009. Accordingly, for the purpose of fostering students with creative and challenging minds, teaching and learning methods including the objectives and content should be more carefully implemented in math class. In case of the area of Probability and Statistics closely related to real life situations, it is suggested that school curriculum in mathematics would not deal with only mathematical problems on algorithm, but rather present teaching and learning materials related to the real life in order to recognize the usefulness of the content of Probability and Statistics and to learn how to think about it. In this paper, effective guidelines for teaching and learning the content of Probability and Statistics and its activities that follows the direction on Mathematics Curriculum Revised in 2009' are suggested based on the analysis of the PISA and TIMSS international assessments items. Thus, the guidelines suggested in this study would be used efficiently and appropriately for developing instructional materials or planning curriculum revision and setting its direction in the future.