• Journal of the korean academy of Pediatric Dentistry
• /
• v.44 no.1
• /
• pp.56-63
• /
• 2017

Delayed eruption of the first molar, without a generalized or localized cause, is usually associated with delayed development of the affected tooth. The aim of this study was to investigate the clinical features of the first permanent molar showing delayed development and eruption, and its association with developmental anomalies of other teeth. Panoramic radiographs of 40 healthy children showing delayed development and eruption of first permanent molars were analyzed. The clinical features of affected first molars and developmental anomalies of other teeth (except third molars) were evaluated. Delayed first molars were more frequent in the maxilla. The incidence of bilateral delayed development of first molars was greater than that of unilateral cases in female patients. In contrast, male patients showed unilateral delayed development of the first molar more frequently. A higher incidence of congenitally missing teeth was observed in patients with delayed first molar. In each case, delayed development or congenital absence was observed in the second molar adjacent to the delayed first molar. Overall, delayed first molar seems to be associated with congenital absence of additional teeth. Understanding the developmental mechanisms of this phenomenon requires further studies.

• Journal of the Korean Data and Information Science Society
• /
• v.25 no.5
• /
• pp.1057-1067
• /
• 2014

Many genetic variants have been identified to be associated with complex diseases such as hypertension, diabetes and cancers throughout genome-wide association studies (GWAS). However, there still exist a serious missing heritability problem since the proportion explained by genetic variants from GWAS is very weak less than 10~15%. Gene-gene interaction study may be helpful to explain the missing heritability because most of complex disease mechanisms are involved with more than one single SNP, which include multiple SNPs or gene-gene interactions. This paper focuses on gene-gene interactions with the survival phenotype by extending the multifactor dimensionality reduction (MDR) method to the accelerated failure time (AFT) model. The standardized residual from AFT model is used as a residual score for classifying multiple geno-types into high and low risk groups and algorithm of MDR is implemented. We call this method AFT-MDR and compares the power of AFT-MDR with those of Surv-MDR and Cox-MDR in simulation studies. Also a real data for leukemia Korean patients is analyzed. It was found that the power of AFT-MDR is greater than that of Surv-MDR and is comparable with that of Cox-MDR, but is very sensitive to the censoring fraction.

• The Journal of Korean Academy of Prosthodontics
• /
• v.52 no.4
• /
• pp.324-330
• /
• 2014

In case of implant-tooth connected prosthesis, a natural tooth tends to intrude. There are several mechanisms that explain an intrusion phenomenon. So it is reco mmended not to connect an implant with a natural tooth. A 68-year-old female had upper left $2^{nd}$ premolar and $2^{nd}$ molar extracted and underwent implant surgery on the missing area. We made an implant prosthesis and treated upper left $1^{st}$ molar with a gold crown. 2.5 year later, the patient complained about loose proximal contact and food impaction between upper left $1^{st}$ molar and $2^{nd}$ molar. Mesial side of upper left $2^{nd}$ molar implant prosthesis was soldered so that proximal contact became tight again. But after 7 months, about 2 mm intrusion of upper left $1^{st}$ molar occurred, and the patient felt periodontally originated pain on intruded upper left $1^{st}$ molar. After the gold crown on upper left $1^{st}$ molar was removed, extrusion occurred and pain was relived.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.1
• /
• pp.1-6
• /
• 2012

This study is damage evaluation for CNG fuel tank during the burst test through the analysis of acoustic emission signals. Kaiser effect until the pressure 420 bar appears, but More than 420 bar by the creep effect appears significantly damaged vessels, and 480 bar pressure, the Kaiser effect of the rising phase was missing. Resonant transducer at 540 bar than 480 bar decreased activity such as energy and count Continually, but increased wideband transducer. In addition, through the rise time or frequency analysis of composite pressure vessels in order to observe the damage mechanisms wideband transducer is more effective than resonant transducer.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.64-64
• /
• 2015

Control of plasma processing methodologies can only occur by obtaining a thorough understanding of the physical and chemical properties of plasmas. However, all plasma processes are currently used in the industry with an incomplete understanding of the coupled chemical and physical properties of the plasma involved. Thus, they are often 'non-predictive' and hence it is not possible to alter the manufacturing process without the risk of considerable product loss. Only a more comprehensive understanding of such processes will allow models of such plasmas to be constructed that in turn can be used to design the next generation of plasma reactors. Developing such models and gaining a detailed understanding of the physical and chemical mechanisms within plasma systems is intricately linked to our knowledge of the key interactions within the plasma and thus the status of the database for characterizing electron, ion and photon interactions with those atomic and molecular species within the plasma and knowledge of both the cross-sections and reaction rates for such collisions, both in the gaseous phase and on the surfaces of the plasma reactor. The compilation of databases required for understanding most plasmas remains inadequate. The spectroscopic database required for monitoring both technological and fusion plasmas and thence deriving fundamental quantities such as chemical composition, neutral, electron and ion temperatures is incomplete with several gaps in our knowledge of many molecular spectra, particularly for radicals and excited (vibrational and electronic) species. However, the compilation of fundamental atomic and molecular data required for such plasma databases is rarely a coherent, planned research program, instead it is a parasitic process. The plasma community is a rapacious user of atomic and molecular data but is increasingly faced with a deficit of data necessary to both interpret observations and build models that can be used to develop the next-generation plasma tools that will continue the scientific and technological progress of the late 20th and early 21st century. It is therefore necessary to both compile and curate the A&M data we do have and thence identify missing data needed by the plasma community (and other user communities). Such data may then be acquired using a mixture of benchmarking experiments and theoretical formalisms. However, equally important is the need for the scientific/technological community to recognize the need to support the value of such databases and the underlying fundamental A&M that populates them. This must be conveyed to funders who are currently attracted to more apparent high-profile projects.

• Journal of Information Technology Applications and Management
• /
• v.15 no.4
• /
• pp.159-188
• /
• 2008

This study suggests strategies which can enable to creation of new opportunities of competitive advantages while operating a long lasting and consistent business with major trading partners, based on interorganizational information systems (IOISs) specially established and installed for interorganizational transactions. Nowadays, IOISs based mechanism having been widely expanded as a conventional business infrastructure for the interorganizational transactions and/or exchanges, it is customary difficult to obtain any strongly sound advantage over the competitors who have adopted even the simplest deployment of the IOIS mechanisms. In this connection, this study intends to investigate the interorganizational collaborative activities conducted by under the auspicious of IOISs, focused on the prospect of the exploitation of IOISs rather than the implementation of the IOISs. In this study, we, firstly, suggest the concept of Electronic Collaboration which can be defined by the collaborative activities conducted by IOISs, compared to the ones conducted on off-line. In addition, we suggest the Electronic Collaboration as a multi-dimensional concept, constituted by three sub-constructs, the Electronic Information Sharing (EIS), the Electronic Joint Activity (EJA), and the construction of the Electronic Relational Knowledge Store (ERKS). Secondly, we empirically verify the effects of relational and environmental determinants on the Electronic Collaboration. In this study, the relational determinants relate to the variables created in interorganizational relationship like Trust, Influence, Relational Specific Asset-asset invested for the transaction-, and Continuity of the relationship. On the other hand, the environmental determinants relate to the variables surrounding the relationship which are difficult to control. We consider Product Complexity, Technological Uncertainty, and Market Variability as the domain of the environmental determinants. To test our hypotheses, we conducted both paper-based survey and online-based survey. After refining the data with missing responses, a total of 150 data was used for analysis. The results were as follows : Firstly, it is statistically significant that the Electronic Collaboration is composed of EIS, EJA, and ERKS. In particular, the results imply that the firms are able to accumulate relational knowledge base as well as to exchange information or knowledge, and to conduct joint activities through effort to further expand the Electronic Collaboration. Secondly, we have verified the individual effects of the relational and the environmental determinants on the Electronic Collaboration. Product Complexity has been revealed as the most influential variable affecting the Electronic Collaboration. Next, Interorganizational Trust and Technological Uncertainty, in that order, have been seen to have significant effects on the Electronic Collaboration. In other words, when products or services seem to be difficult to standardize, and the core technologies seem to rapidly change, the need for the Electronic Collaboration increase. In addition, the observation dictates that the interorganizational trust turns out to be a critical variable in building a relationship and in seeking further collaboration. The results, further, illustrate that the environmental determinants are relatively more effective than the relational determinants, which is not consistent with a few prior researches relational determinants emphasized. It is because this study doesn't consider the size of the firm. A few researchers have given an emphasis on the relational determinants like trust and influence, especially from the perspective of small firms in interorganizational relationship. However, in our study, where all the sizes of the firms are contained, electronic collaboration is considerably affected by the environmental determinants.

• Journal of Trauma and Injury
• /
• v.24 no.1
• /
• pp.18-24
• /
• 2011

Purpose: Missing cervical pathology after injury may lead to disability and influence long-term survival. Controversies continue to evolve concerning the initial screening methods used to predict cervical spine injury. Through a retrospective chart review, we attempted to analyze and propose factors predictive of cervical trauma. Methods: Of all the patients who had visited the Emergency Department of Korea University, from January 2009 to December 2009, a retrospective review of the clinical records of the 217 patients who had undergone cervical spine computed tomography was done. We investigated whether we could predict the need for cervical spine computed tomography shortly after presentation in trauma patients by comparing the group with fractures and group without fractures and by finding risk factors showing significant differences between the two groups that might be used as guides in decision making. Results: Of the 217 subjects who underwent cervical spine computed tomography scans, 33 were identified with fractures of the cervical spine while 184 were not. The most common mechanisms of trauma, in order, for those with fractures were falls, followed by traffic accidents. We found that the injury severity score, multiple injuries, a high-energy injury mechanism, neurologic deficit, and pain and tenderness of the cervical spine showed statistically significant differences between the two groups. Conclusion: Fractures of the cervical spine that are not observed with simple radiography occur with a relatively high frequency in trauma patients. Consideration should be given to the risk factors for cervical spine fracture, and if pertinent, cervical spine computed tomography should be performed with speed for early diagnosis of cervical spine fractures.

• Journal of Korean society of Dental Hygiene
• /
• v.16 no.2
• /
• pp.233-240
• /
• 2016

Objectives: The aim of this study was to evaluate the oral health status and behavior in Korean diabetic adults. Methods: The study subjects were 11,840 adults who participated in the fifth Korea National Health and Nutrition Examination Survey(2010-2012). Diabetic status was defined by doctors and fasting blood sugar(FBS) level. Oral health status was assessed by decayed-missing-filled teeth(DMFT), community periodontal index(CPI), periodontal disease, denture needs, limitation of oral function, and chewing difficulty. The oral health behavior was evaluated by oral examination within a year, brushing times a day, and use of auxiliary oral product. The data were analyzed by descriptive analysis, chi-square tests and multiple logistic regression analyses. Results: The prevalence rate of diabetes mellitus diagnosed by doctor and FBS was 8.3% and 10.2%, respectively. The prevalence rate of periodontitis was 25.4%. The proportions of $DMFT{\geq}20$, $CPI{\geq}3$, periodontal disease, denture needs, oral function limitation and chewing difficulty in the confirmed diabetic group by doctor were significantly higher than those of the non-diabetic group(p<0.05). In multiple logistic regression analysis, the adjusted odds ratio(aOR) for periodontal disease(aOR=1.73, 95% CI=1.41-2.12), presence of denture needs(aOR=1.40, 95% CI=1.06-1.84), limited oral function(aOR=1.43, 95% CI=1.15-1.78) and chewing difficulty(aOR=1.41 95% CI=1.13-1.77) in diabetic subjects were significantly higher than those of the non-diabetic subjects. There were similar associations between diabetes defined with FBS and oral health. In oral health behavior, diabetic subjects had significantly lower odds ratios for oral examination(aOR=0.76, 95% CI=0.60-0.98), brushing time ${\geq}2$ times(aOR=0.73, 95% CI=0.57-0.93), and auxiliary oral products(aOR=0.74, 95% CI=0.59-0.94). Conclusions: There was a significant relationship between oral health status and behavior in Korean diabetic adults. Further study is needed to evaluate the underlying mechanisms between diabetes mellitus and oral health status.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.5
• /
• pp.175-183
• /
• 2023

This study examines differences in satisfaction, intention to revisit, and word-of-mouth recommendations among foreign tourists, based on their nationality and factors influencing their decision to visit Korea. The study utilizes the data collected from foreign tourists who visited Korea in 2021, including information on their country of origin, factors influencing their decision to visit, satisfaction levels, intention to revisit, and willingness to recommend Korea to others. While the survey data comprises a large sample of over 8,000 respondents, only 1,398 without missing values are used for analysis. According to the analysis results, there were significant differences in satisfaction, intention to revisit, and word-of-mouth recommendations among foreign tourists based on their nationality and factors influencing their decision to visit. Notably, leisure and sports activities and distance from their home country are significant factors in making a decision to visit Korea. Countries with relatively lower tourism decision mechanisms are Japan, Singapore, China, Taiwan, Malaysia, Canada, Mongolia, and India. Based on these analysis results, this study presents strategic improvement measures to revitalize Korean tourism industry, particularly after the pandemic.

• Korean Journal of Weed Science
• /
• v.30 no.3
• /
• pp.272-281
• /
• 2010

The objective of this research was to find out the weed management techniques in environment-friendly rice paddy fields through the study on herbicidal effects and problems of various organic materials. This experiment was conducted under different conditions of weed species and weed densities in environment-friendly rice paddy fields. There was no difference in weedy efficacy on golden apple snail (GAS), paper mulching (PM), and machine weeding (MW) between low and high weed densities. However, the effect of weed control in rice bran (RB) and effective microorganism (EM) + molasses was higher in high weed density than in low weed density. In general, the effect of weed control as affected by various organic materials was in the order of GAS (97-100%) > PM (93-98%) > RB (15-80%) > EM (7-31%). GAS provided excellent control of all weed species tested except for Persicaria hydropiper. PM gave acceptable control of the weed species except for Echinochloa crus-galli, Ludwigia prostrata, and Eleocharis kuroguwai. However, MW gave fair control (70% biomass reduction) of all weed species tested. BR followed by MW or EM followed by MW treatments had similar effect on weed control compared to each treatment alone. However, BR followed by GAS or EM followed by GAS provided 100% control of weed species tested. The level of rice foliar injury caused by various organic materials was in the order of GAS and MW (10-20%) > RB (10-15%) > PM and EM (5-7%). Typical symptoms of organic materials are wilting, inhibition of growth, missing hill, and reduction of tiller. Cost for weed control of GAS, RB, EM, and PM were 2.1, 3.1, 2.3, and 13.2 times higher than that of the herbicide. These data indicate that GAS was the best method for weed management in environmentfriendly rice paddy fields. Further study is required to elucidate the mechanisms underlying the rice injury as affected by GAS.