• The Journal of Advanced Prosthodontics
• /
• v.6 no.4
• /
• pp.245-252
• /
• 2014

PURPOSE. To present a literature review on implant overdentures after a brief survey of bone loss after extraction of all teeth. MATERIALS AND METHODS. Papers on alveolar bone loss and implant overdentures have been studied for a narrative review. RESULTS. Bone loss of the alveolar process after tooth extraction occurs with great individual variation, impossible to predict at the time of extraction. The simplest way to prevent bone loss is to avoid extraction of all teeth. To keep a few teeth and use them or their roots for a tooth or root-supported overdenture substantially reduces bone loss. Jaws with implant-supported prostheses show less bone loss than jaws with conventional dentures. Mandibular 2-implant overdentures provide patients with better outcomes than do conventional dentures, regarding satisfaction, chewing ability and oral-health-related quality of life. There is no strong evidence for the superiority of one overdenture retention-system over the others regarding patient satisfaction, survival, peri-implant bone loss and relevant clinical factors. Mandibular single midline implant overdentures have shown promising results but long-term results are not yet available. For a maxillary overdenture 4 to 6 implants splinted with a bar provide high survival both for implants and overdenture. CONCLUSION. In edentulous mandibles, 2-implant overdentures provide excellent long-term success and survival, including patient satisfaction and improved oral functions. To further reduce the costs a single midline implant overdenture can be a promising option. In the maxilla, overdentures supported on 4 to 6 implants splinted with a bar have demonstrated good functional results.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.10
• /
• pp.2409-2416
• /
• 2015

This paper presents an orientation-based adaptive prediction method for effective lossless image compression. For a robust prediction, the proposed method estimates the directional information and the property near the current pixel in a support region-based fashion, not a pixel-based one which is sensitive to a small variation. We improve the prediction performance effectively by selection of the prediction pixel adaptively according to the similarity between support regions of the current pixel and the neighboring pixels. Comprehensive experiments demonstrate that the proposed scheme achieves excellent prediction performance measured in entropy of the prediction error compared to a number of conventional prediction methods such as MED, GAP, and EDP. Moreover the complexity of the proposed algorithm measured by average execution time is low compared to MED which is the simplest prediction method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.261-264
• /
• 2008

IPv6 has been proposed and deployed to cater the shortage of IPv4 addresses. It is expected to foresee mobile phones, pocket PCs, home devices and any other kind of network capable devices to be connected to the Internet with the introduction and deployment of IPv6. This scenario will bring in more challenges to the existing network infrastructure especially in the network security area. Firewalls are the simplest and the most basic form of protection to ensure network security. Nowadays, firewalls' usage has been extended from not only to protect the whole network but also appear as software firewalls to protect each network devices. IPv6 and IPv4 are not interoperable as there are separate networking stacks for each protocol. Therefore, the existing states of the art in firewalling need to be reengineered. In our context here, we pay attention only to the IPv6 firewalls configuration anomalies without considering other factors. Pre-evaluation of security risk is important in any organization especially a large scale network deployment where an add on rules to the firewall may affect the up and running network. We proposed a new probabilistic based model to evaluate the security risks based on examining the existing firewall rules. Hence, the network administrators can pre-evaluate the possible risk incurred in their current network security implementation in the IPv6 network. The outcome from our proposed pre-evaluation model will be the possibilities in percentage that the IPv6 firewall is configured wrongly or insecurely where known attacks such as DoS attack, Probation attack, Renumbering attack and etc can be launched easily. Besides that, we suggest and recommend few important rules set that should be included in configuring IPv6 firewall rules.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.11
• /
• pp.1043-1051
• /
• 2007

The digital sun sensor calculates the incident sunlight angle using the sunlight image registered on a CMOS image sensor. In order to accomplish this, an exact center of the sunlight image has to be determined. Therefore, an accurate estimate of the centroid is the most important factor in digital sun sensor development. The most general method for determining the centroid is the thresholding method, and this method is also the simplest and easy to implement. Another centering algorithm often used is the image filtering method that utilizes image processing. The sun sensor accuracy using these methods, however, is quite susceptible to noise in the detected sunlight intensity. This is especially true in the thresholding method where the accuracy changes according to the threshold level. In this paper, a template method that uses the sunlight image model to determine the centroid of the sunlight image is suggested, and the performance has been compared and analyzed. The template method suggested, unlike the thresholding and image filtering method, has comparatively higher accuracy. In addition, it has the advantage of having consistent level of accuracy regardless of the noise level, which results in a higher reliability.

• Journal of Korea Water Resources Association
• /
• v.48 no.3
• /
• pp.233-243
• /
• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• Membrane Journal
• /
• v.29 no.6
• /
• pp.299-307
• /
• 2019

Photocatalysis is an environment friendly technique for degrading organic dyes in water. Tungsten oxide is becoming an active area of research in photocatalysis nanomaterials for having a smaller bandgap than the previously favored titanium dioxide. Synthesis of hierarchical structures, doping platinum (Pt), coupling with nanocomposites or other semiconductors are investigated as valid methods of improving the photocatalytic degradation efficiency. These impact the reaction by creating a redshift in the wavelength of light used, effecting charge transfer, and the formation/recombination of electron-hole pairs. Each of the methods mentioned above are investigated in terms of synthesis and photocatalytic efficiency, with the simplest being modification on the morphology of tungsten oxide, since it does not need synthesis of other materials, and the most efficient in photocatalytic degradation being complex coupling of metal oxides and carbon composites. The photocatalysis technology can be incorporated with water purification membrane by modularization process and applied to advanced water treatment system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.5B
• /
• pp.365-377
• /
• 2006

We define the incomplete medium sharing system as a multi-channel shared medium communication system where any types of constraints are imposed to the set of channels that may be allocated to any transmitter-receiver node pair. A set of distributed MAC schemes are proposed, all of which are based on the CSMA/CA scheme employed in IEEE 802. 11 WLAN standards. Distributed MAC schemes are proposed in three different forms, which can be differentiated by the number and the location of back-off timers; that is, (1) one timer for all queues destined for different receiver nodes, (2) multiple timers at individual transmission queues, (3) multiple timers for individual channels. Through an extensive set of computer simulations, the performances of the proposed MAC schemes show that the MAC scheme with timers at individual transmission queues outperform the others in terms of throughput and delay for most cases considered. The complexity of the proposed schemes is also compared, and the first scheme obviously turned out to be the simplest, and the complexity of the second and third schemes depends on the number of receiver nodes and the number of channels, respectively.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.19 no.3
• /
• pp.408-414
• /
• 2009

A GPS/INS system is widely used in the UGV to estimate position during the mission. However, there are few restrictions when a GPS/INS system used alone. For example, GPS provides precise location information but easily interrupted by external factors like weather, environment, etc. INS provides continuous location data but positioning errors grew very rapidly with time. Therefore, it is necessary to integrating multi-sensors for more continuous and correct position estimation. In this paper, we propose location estimation algorithm of the UGV for GPS/INS integrated system that combines Fuzzy Inference and Unscented Particle Filter(UPF) to improve navigation. Fuzzy inference provides the simplest method integrating GPS/INS and UPF is non-linear estimation filter well suited to the correction of errors. The performance of the proposed algorithm was tested to compare with other algorithms. the results show that the proposed algorithm is more accuracy in position estimation and ensures continuous position tracking.

• Quality Improvement in Health Care
• /
• v.21 no.1
• /
• pp.36-49
• /
• 2015

In Intensive Care Units (ICUs), where severely ill patients are treated, importance of reducing Hospital Acquired Infection (HAI) cannot be overstated. One of the simplest and most effective actions against HAI is proper hand hygiene (HH) behavior of Health Care Workers (HCWs). However, compliance varies across different cultures and different job types of HCWs (physicians, residents and nurses). This study aims to understand determinants of HH behavior by HCWs' job types in Korea. Qualitative analysis was performed based on Reasoned Action Approach style interviews with staff physicians, residents and nurses across 7 teaching hospitals. We found that all HCWs strongly believe HH is important in reducing HAI. There were, however, job type-specific HH behavior modifying factors; staff physicians stated feeling pressure to be HH behavior role model. Residents identified Quality Improvement team that measured compliance as a facilitator; a notable barrier for residents was senior physicians not washing their hands, because they were afraid of appearing impudent to their seniors. Nurses designated their chief nurse as a key referent. All participants mentioned heavy workload and lack of access to alcohol-based sanitizer as situational barriers, and sore and dry hand as deterrents to HH compliance.

• The Korean Journal of Applied Statistics
• /
• v.33 no.3
• /
• pp.309-320
• /
• 2020

Bayesian networks, also known as directed acyclic graphs (DAG), are used in many areas of medicine, meteorology, and genetics because relationships between variables can be modeled with graphs and probabilities. In particular, Bayesian network classifiers, which are used to predict discrete data, have recently become a new method of data mining. Bayesian networks can be grouped into different models that depend on structured learning methods. In this study, Bayesian network models are learned with various properties of structure learning. The models are compared to the simplest method, the naïve Bayes model. Classification results are compared by applying learned models to various real data. This study also compares the relationships between variables in the data through graphs that appear in each model.