• The Journal of Advanced Prosthodontics
• /
• v.14 no.3
• /
• pp.162-172
• /
• 2022

PURPOSE. The present study aims to analyze the effect of abutment neck taper and types of cement on the amount of undetected remnant cement of cement-retained implant prostheses. MATERIALS AND METHODS. Three neck taper angles (53°, 65°, 77°) and three types of cement (RMGI: resin-modified glass ionomer, ZPC: zinc phosphate cement, ZOE: zinc oxide eugenol cement) were used. For each group, the surface percentage was measured using digital image and graphic editing software. The weight of before and after removing remnant cement from the abutment-crown assembly was measured using an electronic scale. Two-way ANOVA and Duncan & Scheffe's test were used to compare the calculated surface percentage and weight of remnant cement (α = .05). RESULTS. There were significant differences in remnant cement surface percentage and weight according to neck taper angles (P < .05). However, there were no significant differences in remnant cement surface percentage and weight on types of cement. No interaction was found between neck taper angles and types of luting cement (P > .05). The wide abutment with a small neck taper angle showed the most significant amount of remnant cement. And the types of luting cement did not influence the amount of residual cement. CONCLUSION. To remove excess cement better, the emergence profile of the crown should be straight to the neck taper of the abutment in cement-retained implant restoration.

• Journal of the Society of Naval Architects of Korea
• /
• v.59 no.3
• /
• pp.149-156
• /
• 2022

In order to study the open-water test and analysis techniques for pumpjet propulsors in the Large Cavitation Tunnel (LCT), at the Korea Research Institute of Ships and Ocean Engineering, a set of test equipment was designed and manufactured. The pumpjet propulsor is composed of rotor, stator and duct resulting in the strong interaction between the components. A ring-shaped sensor was developed to measure the thrust and torque for duct and stator. The test equipment including the pumpjet is installed on an existing POW dynamometer in the reverse direction. The results from the reverse POW test setup were validated against those from the conventional POW test setup in the Towing Tank (TT) as well as in the LCT. The pumpjet open-water test was conducted at the Reynolds number of around 1.0×106, at which the obtained experimental data became stable in the Reynolds number effect test. The open-water test for the rotor (rotor-only) was conducted to study whether the duct and stator should be considered as a part of the hull or the propulsor. On the basis of the test results, it was shown that the duct and stator could be included in the propulsor. The total thrust, combined thrust of rotor, duct, and stator was used for the pumpjet open-water test analysis. As the whole pumpjet is defined as a propulsor, it is thought that the self-propulsion test and analysis could be conducted in the same way as that of the conventional propeller.

• Journal of the Korean Wood Science and Technology
• /
• v.50 no.3
• /
• pp.149-158
• /
• 2022

To realize the infinite possibilities of materials derived from wood, it is necessary to overcome the weak moisture stability of wood. Thus, the development of an eco-friendly hydrophobic coating agent is essential, and of these, woody biomass-based materials are strongly attractive as coatings. In this study, eco-friendly hydrophobic wood coatings were prepared using carnauba wax purified from palm leaves and sprouts, and kraft lignin. The physicochemical properties of the carnauba wax/lignin blends according to the ratio of carnauba wax and lignin were observed by morphology and functional group change. In addition, the coating performance of carnauba wax/lignin blend coatings was confirmed by measuring the contact angle change. It was found that the addition of lignin could accelerate the atomization of wax particles, and that micro-roughness can be realized when applied to the actual wood surface, to ensure that the coating effect over time lasts longer. In addition, it was confirmed that the addition of lignin increases the hydrogen-bond-based interaction with the wood of the coating, thereby providing better coating stability and increasing the durability of the coating solvent under friction. The carnauba wax/lignin paint developed in this way is eco-friendly because all components are made of wood-based raw materials and have an excellent affinity with wood surfaces. Therefore, it is expected to be applicable to the coating process of wood-plastic composites and timber composites.

• Imaging Science in Dentistry
• /
• v.52 no.4
• /
• pp.399-408
• /
• 2022

Purpose: The purpose of this study was to compare volume measurements obtained using 2 image software packages on Digital Imaging and Communications in Medicine (DICOM) images acquired from 1 multidetector computed tomography and 5 cone-beam computed tomography devices, using different protocols for physical volume measurements. Materials and Methods: Four pieces of bovine leg were prepared. Marrow was removed from 3 pieces, leaving cortical bone exposed. The resulting space of 1 piece was filled with water, another was filled with propylene glycol, and the third was left unfilled. The marrow in the fourth sample was left fully intact. Volume measurements were obtained after importing DICOM images into the Dolphin Imaging 11.95 and ITK-SNAP software programs. Data were analyzed using 3-way analysis of variance with a generalized linear model to determine the effects of voxel size, software, and content on percentage mean volume differences between tomographic protocols. A significance level of 0.05 was used. Results: The intraclass correlation coefficients for intraobserver and interobserver reliability were, respectively, 0.915 and 0.764 for the Dolphin software and 0.894 and 0.766 for the ITK-SNAP software. Three sources of statistically significant variation were identified: the interaction between software and content (P=0.001), the main effect of content (P=0.014), and the main effect of software (P=0.001). Voxel size was not associated with statistically significant differences in volume measurements. Conclusion: Both content and software influenced the accuracy of volume measurements, especially when the content had gray values similar to those of the adjacent tissues.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.3
• /
• pp.136-144
• /
• 2023

PURPOSE. The study objective was to evaluate the influence of the type of resin cement on the flexural strength and load to fracture of two chairside CADCAM materials after aging. MATERIALS AND METHODS. A polymer-infiltrated ceramic network (PICN) and a nanoceramic resin (RNC) were used to produce the specimens. Two types of dual-cure resin cements, a self-adhesive and a universal, were investigated. Bilayer specimens were produced (n = 10) and aged for 6 months in a humid environment before the biaxial flexural strength test (σ_f). Bonded specimens were subjected to a mechanical aging protocol (50 N, 2 Hz, 37℃ water, 500,000 cycles) before the compressive load test (L_f). σ_f and L_f data were analyzed using two-way ANOVA and Tukey tests (α = .05). Chi-square test was used to analyze the relationship between failure mode and experimental group (α = .05). RESULTS. The type of resin cement and the interaction between factors had no effect on the σ_f and L_f of the specimens, while the type of restorative material was significant. RNC had higher σ_f and L_f than PICN. There was a significant association among the type of cracks identified for specimens tested in L_f and the restorative material. CONCLUSION. The type of resin cement had no effect on the flexural strength and load to fracture of the two investigated CAD-CAM chairside materials after aging.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.47 no.3
• /
• pp.202-216
• /
• 2024

In today's rapidly changing business environment, rapid decision making and effective project management are essential for business growth. This study examines how project manager competencies and organizational structures affect business performance. Successful project execution depends on the strategic use of project managers' skills and organizational resources to maximize performance. An empirical study was conducted with 475 participants from the construction and engineering sectors. The applied analyses included multiple regression analysis and two-way ANOVA to assess how project manager competencies and organizational types affect business performance. The results of the study show that project manager competencies significantly improve business performance, especially when combined with appropriate organizational types. Effective use of organizational frameworks leads to better financial results, increased market competitiveness, and greater innovation. The results of the study are as follows: First, project manager competencies were found to have a significant positive effect on business performance. Second, the use of functional, project, and matrix organizations had a significant positive effect on business performance. This suggests that aligning organizational structures with business objectives is important for achieving optimal performance. Overall, this study provides valuable insights into the academic literature and practical applications of project management and organizational research. In addition, if we can select organizational members based on the learning effects of previous projects when operating new projects in the future, it will help reduce risks. Ultimately, it will improve the project manager's competency level, promote the individual abilities and knowledge sharing of team members, and provide opportunities for the company to build efficient new systems. This will be evaluated as a valuable study in terms of academic and practical productivity.

• 한국생물공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.428-433
• /
• 2003

We measured the effect of wettability of six MPSs for RGP(rigid gas permeable) lens. The used MPSs(multipurpose solutions) were OPTI-SOAK(ALCON), SOLO care hard(CIBA Vision), Total care(ALLERGAN), Simplicity(BOSTON), Wetting and Soaking Sol.(Bausch & Lomb) and Aquas-multi(Saehan). These MPSs keeps hydrophilic property of lens surface and increase the effect of cleaning or increase the effect of preservative effect. To compare with the effect of wettability we followed the way of contact angle measurement which was general way to measure wettability and compared lens which was conducted by each MPS made by different companies. As a control, 0.9% NaCl solution and artificial tears were used. The degree of the effect of wettability was decided by contact angle. It is hydrophilic property nearby $0^{\circ}$ of contact angle and it is closed by hydrophobic property as it increases. The results showed that every lens was nearby hydrophilic property within $25\;^{\circ}-36\;^{\circ}$. Also, it was differed by various factors. The surface tension showed various differences between 19.8 and 31.3 mN/m. In the viscosity, MPSs represented the highest viscosity between $4^{\circ}C$ and $20^{\circ}C$. It was much higher than compared with the viscosity of soft lens MPS. This experiment could be used to grasping the interaction between solutions used to MPS and the natural endowments of lens and to considering the relations of different factors effecting the wettability.

• Journal of Science Education
• /
• v.41 no.3
• /
• pp.281-296
• /
• 2017

The purpose of this study is to explore the science learning motivation of technical high school students through comparison with general high school students. 596 high school students and 1063 general high school students participated in the study. Three statistical methods were used for data analysis: two-way ANOVA, independent sample t-test, and Pearson correlation analysis. The results showed that the interaction between school type and grade had a significant effect on the difference of students' motivation for science learning. There was a significant difference in learning motivation among general high school students according to academic year, while there was no significant difference between first and second grader of technical high school students. Especially, technical high school students showed low level of science learning motivation compared to the students in general high school. The correlations among five motivational factors of science learning motivation were also significantly lower than that of general high school students. Lastly, the result of correlation analysis between science motivation and academic achievement showed that second year students in technical high school had less correlation coefficients than the first year students. Given these results, it is necessary to develop a educational strategy for enhancing science learning motivation of technical school students. We will discuss the direction of science education for technical high school based on our findings.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.3
• /
• pp.73-85
• /
• 2014

As the importance of big data analysis increases to improve the competitiveness of a corporate, a unified big data project development methodology is required in order to study the problem of a corporate in a systematic way and evaluate the problem w.r.t. a business value after solving the problem. This paper propose Scientific Data Anslysis and Development methodology(SDAD) which are integrated methodology of software development and project management for easier application into a field project. SDAD consisits of 6 stages(problem definition stage, data preparation stage, model design stage, model development stage, result extraction stage, service development state), each stages has detailed processes(47) and productions(93). SDAD, furthermore, unified previous ISP, DW, SW development methodologies in terms of the data analysis and can easily interchange the productions with them. This paper, lastly, introduces a way to assign responsible persons for each process and provide communication procedures in RACI chart to improves the efficiency of the interaction among professionals from different subjects. SDAD is applied to a Bigdata project in Korea Employment Information Services institution and the result turned out to be acceptable when evaluated by the supervision.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.2 no.2
• /
• pp.161-172
• /
• 1969

Ten experimental tuna long line fishing operations were performed with the long lines A and B, in combination casting orders of BA and AB. The long line B differs from A in its additional main line length per basket and its greater depth of submersion (Table 1). The BA casting order results in an AB hauling order, so that the long line B is casted at an earlier time of a day and fishes for a longer period than A line (fig. 2). The number of fish caught was divided into subclasses in order to be subjected to $x^2-tests$ (Table 2). The first series of $x^2-tests$ were calculated using the hooking rates of two subclasses with other factors pooled (Table 3). The second series of $x^2-tests$ were calculated to obtain the interactions between two subclasses when other factors differed (Table 4). Attention was paid to the extremely small interactions as well as to the large interactions in order to find out whether a factor functions in the same way or in a contradictory way when the other factors involved differ. The test result is summarized in Table 5. The relationship between the hook casting time (relative to the sunrise time) and the hooking rates reveals the feeding behavior of particular species (fig. 3) A high hooking rate for yellowfin tuna shown in the period from one hour before sunrise to the moment of sunrise suggests that they feed actively in that period. Their poor hooking rate on earlier casted hooks suggests that they do not feed well under conditions of darkness and that they feed best while the hooks are sinking. Furthermore it is likely that yellowfin tuna maintain a shallow depth in the daytime, for the $x^2$ interaction between the line casting order BA and AB shows their persistant preferance of the long line A regardless of line casting order. Bigeye tuna show their feeding behavior under conditions of darkness, and show a preference for the sea's deeper layer. Alepisaurus borealis (Gill) show their feeding behavior under conditions of darkness more significantly than the bigeye tuna and their preferance for deep layers is also more significant. Marlins (mainly Makaria mazara) show a feeding behavior which is similar to the yellowfin tuna. The author emphasizes that certain variations of the hooking rates in relation to the line easting time were caused by an inadequate fishing depth as well as by the fish preference for a particular feeding time. When the part of the line casted in pre-dawn hours and hauled in the pre-sunset hours show a significantly lower hooking rate than other parts of the line, then it is concluded that tile hooks settled in a sea layer too deep for feeding.