• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.4
• /
• pp.365-375
• /
• 2009

Statement of problems: Stress analysis on implant components of the combined screw- and cement-retained implant prosthesis has not investigated yet. Purpose: The purpose of this study was to assess the load distribution characteristics of implant prostheses with the different prosthodontic retention types, such as cement-type, screw-type and combined type by using 3-dimensional finite element analysis. Material and methods: A 3-dimensional finite element model was created in which two SS II implants (Osstem Co. Ltd.) were placed in the areas of the first premolar and the first molar in the mandible, and three-unit fixed partial dentures with four different retention types were fabricated on the two SS II implants. Model 1 was a cement-retained implant restoration made on two cement-retained type abutments (Comocta abutment; Osstem Co. Ltd.), and Model 2 was a screw-retained implant restoration made on the screw-retained type abutments (Octa abutment; Osstem Co. Ltd.). Model 3 was a combined type implant restoration made on the cement-retained type abutment (Comocta abutment) for the first molar and the screw-retained type abutment (Octa abutment) for the first premolar. Lastly, Model 4 was a combined type implant restoration made on the screw-retained type abutment (Octa abutment) for the first molar and the cement-retained type abutment (Comocta abutment) for the first premolar. Average masticatory force was applied on the central fossa in a vertical direction, and on the buccal cusp in a vertical and oblique direction for each model. Von-Mises stress patterns on alveolar bone, implant body, abutment, abutment screw, and prosthetic screw around implant prostheses were evaluated through 3-dimensional finite element analysis. Results: Model 2 showed the lowest von Mises stress. In all models, the von Mises stress distribution of cortical bone, cancellous bone and implant body showed the similar pattern. Regardless of loading conditions and type of abutment system, the stress of bone was concentrated on the cortical bone. The von-Mises stress on abutment, abutment screw, and prosthetic screw showed the lower values for the screw-retained type abutment than for the cement-retained type abutment regardless of the model type. There was little reciprocal effect of the abutment system between the molar and the premolar position. For all models, buccal cusp oblique loading caused the largest stress, followed by buccal cusp vertical loading and center vertical loading. Conclusion: Within the limitation of the FEA study, the combined type implant prosthesis did not demonstrate more stress around implant components than the cement type implant prosthesis. Under the assumption of ideal passive fit, the screw-type implant prosthesis showed the east stress around implant components.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.1
• /
• pp.29-38
• /
• 2009

Statement of problem: A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist. Purpose: The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture. Material and methods: Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar. Results: The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area. Conclusion: The design of retentive groove that limits number of retentive groove for metal thickness and increases the depth of retentive groove for retention is highly recommended.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.5
• /
• pp.2711-2717
• /
• 2016

Background: Through search the possible randomized control trials, we make a renewed meta-analysis in order to assess the impact of aspirin in preventing the recurrence of colorectal adenoma. Materials and Methods: The Medicine/PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Chinese biomedical literature service system (SinoMed) databases were searched for the related randomized controlled trials until to the April 2016. Three different authors respectively evaluated the quality of studies and extracted data, and we used the STATA software to analyze, investigate heterogeneity between the data, using the fixed-effects model to calculate and merge data. Results: 7 papers were included the renewed meta-analysis, among these studies, two pairs were identified as representing the same study population, with the only difference being the duration of follow-up. Thus there were only five papers included our meta-analysis, and one Chinese paper were also included the work. Results were categorized by the length of follow-up, different kinds of people, varied dose of oral aspirin. The relative of adenoma in patients taking aspirin vs placebo were 0.73 (95% CI 0.55-0.98, P=0.039) with 1 year follow up; 0.84 (95% CI 0.72-0.98, P=0.484) with greater than 1 year follow up; for the advanced adenoma, the RR 0.68 (95% CI 0.49-0.94, P=0.582),for one year; RR=0.75 (95% CI 0.52-1.07, P=0.552) for greater one year. Furthermore the white population could divided into two subgroups according to the different length of follow-up time. When the length of follow-up time less than 3-year, The RR of two subgroups respective were RR=0.86 (95% CI 0.76-0.98, P=0.332), $I^2=0%$, RR=0.68 (95% CI 0.47-0.98, P=0.552), $I^2=64.6%$, But with the extension of follow-up time greater than 2-year, with the white, oral aspirin without considering dose had no efficacy on preventing the recurrence of any adenoma, the RR was 0.86 (95% CI 0.71-1.05, P=0.302), $I^2=16.4%$. Conclusions: This meta-analysis indicated that oral aspirin is associated with a remarkable decrease in the recurrence of any adenoma and advanced adenomas in patients follow-up for 1 year without concerning the dose of aspirin, but with the extension of follow-up time for greater than 1 year, oral aspirin can be effective on preventing the recurrence of any adenoma, but for the advanced adenoma, the result indicated that oral aspirin had no efficacy, According to the inclusion of ethnic groups, we also divided relevant papers into two subgroups as the yellow and white group. Then the follow-up time was less than 3 years, oral aspirin without considering the dose, had an significant efficacy on preventing the recurrence of any adenoma. But with the follow-up greater than 2 years, oral aspirin had no effect in the white.

• Cartoon and Animation Studies
• /
• s.6
• /
• pp.152-171
• /
• 2002

This study analyses the avatar service, which is recognized as an alternative strategy of animation industry. The research questions of this study are following: (1) How have the avatar services been developed and what are the present dominant types? (2) Which structural characteristics of e-business environment are needed for the success of avatar services? (3) What is the economic characteristics of avatar business model? To solve these research questions, the basic conditions and the structural characteristics of avatar services have been investigated. In the first place, two forms of avatar service are classified. One is the internet service site whole primary service is to provide chatting service based on avatar service. The other is the portal site in which many kinds of products and services are presented as bundles to meet the needs of internet users. So avatar service is one of bundles which those portal sites are providing with. In this study, the big five internet service sites are selected based on the profits they earned through the sales of avatar service. The result of analysis is that the pricing strategy of those big five sites is very different from those of traditional off-line markets. The pricing mechanism are based on the value which internet users endow with the avatar items, not based on the costs of making the products. Avatar is the representative informative goods. The informative goods have the original cost structures, constant fixed costs and zero marginal costs, so the providers of avatar services make much of the subjective values of consumers. The sayclub, which is the most successful avatar service site and earn the average sales of 3 billing won a month, takes the aggressive strategy of pricing avatar items at highest price in the industry. The avatar service providers which make lots of profits are planning of making differentiate the services, introducing well-known brand items and star-named items. Nevertheless, the fact that the members of the sayclub are not decreasing means that the network effect of the site is so strongly manifest. Moreover, the costs the members have paid for the avatar items are so big not as to switch from one site to the other site, it can be very costly. These switching costs are endemic in high-technology industries and digital contents industries. It can be so large that switching suppliers is virtually unthinkable, a situation known as 'lock-in'. When switching costs are substantial, competition can be intense to attract new customers, since, one they are locked in, they can be a substantial source of profit. The consumers of avatar items have switching costs if they subscribe for the new avatar service site. The switching costs can be subscription costs as well as the costs of giving up the items they already paid for. One common example of switching costs involves specialized supplies, as with inkjet printer cartridges. In this example, the switching cost is the purchase of a new printer. The market is competitive ex ante, but since cartridges are incompatible, it is monopolized dx post. So the providers of printer/cartridges set pricing printer so cheap and cartridges expensive. On the contrary, since the avatar service can be successful with the strong network effect, the providers of avatar services have to compete aggressively for new customers. So they allow the subscription at a low price(almost marginal cost) in the early market. The network effect can be maximized when the members are sufficiently growing. The providers which have the monopoly power with sufficient subscribers. begin to raise the prices over the lifetime of the product and make profits.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.42 no.2
• /
• pp.131-138
• /
• 2009

The radioprotect effects of fractinated fucoidan, derived from Undaria pinnatifida sporophylls, were examined in lung injured rats treated with partial body irradiation. The right lung of Sprague-Dawley rats, eight separately grouped by including radiation only control group (ROG) and fucoidan+radiation treated group (FRG), were treated with various fraction of Undaria-derived fucoidan every other day by intraperitoneal injection 6 days prior to irradiation and during monitoring at 24 hours, 48 hours, 2 weeks, 4 weeks and 12-weeks post-irradiation of 6 Mev/2 Gy. The rats were euthanized at completion of the treatment. Tissue samples from the injured lung, fixed in formaldehyde using lung perfusion prior to extraction, were H/E stained for histological analysis using optical microscopy. Interstitial congestion (IC), hemorrhage in alveolar sac (HM), number of macrophage (MP) and alveolar wall thickness (AWT) as a measure of early indication of fibrosis were measured. AWTs in 24 hrs post-irradiation rats increased in comparison with $2.49{\pm}0.06{\mu}m$ of control group by $3.67{\pm}0.09{\mu}m$, $3.21{\pm}0.08{\mu}m$ (p=0.013), $2.98{\pm}0.08{\mu}m$ (p=0.00) in ROG, F1-fucoidan+radiation, and F3-fucoidan+radiation group, respectively. AWT of the ROG was further increased by $4.30{\pm}0.13{\mu}m$ in the 12 weeks post-irradiation group, but AWT on average was $2.56{\pm}0.05{\mu}m$ in the FRG. MP in the 24 hrs post-irradiation group markedly increased in comparison with $2.6{\pm}0.34/0.14\;mm^2$ of the control group by $8.0{\pm}1.48/0.14\;mm^2$ in the ROG, but it was only $3.6{\pm}0.48/0.14\;mm^2$ in F3-FRG. MP in the 12 weeks post-irradiation group was $7.2{\pm}1.28/0.14\;mm^2$ in ROG, but it was $2.8{\pm}0.37/0.14\;mm^2$ or $2.4{\pm}0.4/0.14\;mm^2$ (p<0.05) in the FRG. In addition, increased IC and HM in ROG were relatively smaller in FRG of the 24 hr and 12 weeks post-irradiation rats. In conclusion, Undaria pinnatifida sporophylls-derived fucoidan fractions exhibited radioprotectant activity on injured rat lung subjected to X-ray irradiation. However, success was variable according to the fractions and also time of injection post injury.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.7
• /
• pp.4081-4086
• /
• 2014

Cellulose acetate butyrate (CAB) is a biodegradable resin with excellent optical properties, but it is difficult to apply film process. In this study, an attempt was made to improve the processability of CAB using polyactic acid and the mechanical properties using an impact modifier. Polylacitc acid (PLA)/Cellulose acetate butyrate (CAB) blends with an impact modifier were prepared using a twin screw extruder. The temperature range was $140^{\circ}C$ to $200^{\circ}C$, and the screw speed was fixed to 200 rpm. To evaluate the miscibility of impact modified CAB/PLA, the glass transition behavior and morphology were observed by DSC and FE-SEM. The mechanical properties were investigated by dynamic mechanical analysis (DMA) and a Universal Testing Machine (UTM). In addition, the effect of an impact modifier in the polymer matrix was determined using a notched Izod impact strength tester. Finally, the PLA/CAB/impact modifier 75/25/10 ratio was found to be a compatible system. In the 10wt.% impact modifier, the sample had a 4 times higher izod impact strength than the non-toughening composition.

• Korean Journal of Digital Imaging in Medicine
• /
• v.15 no.2
• /
• pp.45-53
• /
• 2013

Purpose : Fixed way of mAs previously Low Extremity Computed Tomography Angiography(LECTA) examination were used. Automatic Current Selection(ACS) to use for the purpose of reducing the dose when Low Extremity Computed Tomography Angiography examining patients. Materials and methods : Were analyzed from July 2011 to July 2012 MDCT examination of Dose Length Product(DLP) LECTA 116 Case. It was defined as previous inspection methods(Old protocol). CT workstation is set to 100 mAs and 150 mAs protocol based on the patient's weight 70kg examined by LECTA. We defined as 'New protocol' that applies to ACS. The data collection period are 76 cases from October 2012 to January 2013 Results : 1. Average Total DLP of 'Old protocol' is 3602.943 $mGy^*cm$. 2. Average Total DLP of 'New protocol' is 1762.977 $mGy^*cm$. 3. Due to the 'New Protocol' use of Total DLP was reduced by approximately 51 %. Phase-specific dose reduction is as follows. Pre(33.62 %), Artery(64.63 %), Delay(49.0 %) 4. Using One way ANOVA Analysis of fluctuations obtained DLP is as follows. 'Old protocol', 'New protocol' a value of P < 0.001, P = 0.882 values were obtained. Conclusions : Dose reduction of 51 % is a useful study that proves. The results obtained using the ACS, the effects of a dose reduction of 51 % was obtained. Therefore, it has been proven to be a useful way. Statistics using SPSS version came out of the 'Old protocol' P-value P < 0.0001. This result means that the DLP a large difference values. On the other hand, The results of the 'New protocol' was P = 0.882. These results means to that small and regularly was fluctuations of the dose. The use of ACS, you can get a reduction of the dose and will able to get the effect of reducing the dose errors.

• Journal of Korean Society for Atmospheric Environment
• /
• v.28 no.5
• /
• pp.581-594
• /
• 2012

The goal of this study is to investigate the effects of the chemical lateral boundary conditions (CLBCs) on Community Multi-scale Air Quality (CMAQ) simulations of tropospheric ozone for East Asia. We developed linking tool to produce CLBCs of CMAQ from Goddard Earth Observing System-Chemistry (GEOS-Chem) as a global chemistry model. We examined two CLBCs: the fixed CLBC in CMAQ (CLBC-CMAQ) and the CLBC from GEOS-Chem (CLBC-GEOS). The ozone fields by CMAQ simulation with these two CLBCs were compared to Tropospheric Emission Spectrometer (TES) satellite data, ozonesonde and surface measurements for May and August in 2008. The results with CLBC-GOES showed a better tropospheric ozone prediction than that with CLBC-CMAQ. The CLBC-GEOS simulation led to the increase in tropospheric ozone concentrations throughout the model domain, due to be influenced high ozone concentrations of upper troposphere and near inflow western and northern boundaries. Statistical evaluations also showed that the CLBC-GEOS case had better results of both the index of Agreement (IOA) and mean normalized bias. In the case of IOA, the CLBC-GEOS simulation was improved about 0.3 compared to CLBC-CMAQ due to the better predictions for high ozone concentrations in upper troposphere.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.21 no.2
• /
• pp.24-33
• /
• 2018

DSM and orthoimage, which are representative results of UAV photogrammetry, are high-quality spatial information data and are widely used in various fields of spatial information industry in recent years. However, the UAV photogrammetry has a problem that the quality of the output of the UAV deteriorates due to the altitude of the UAV, the camera calibration, the weather conditions at the time of shooting, the performance of the GPS / IMU and the number of the ground reference points. The purpose of this study is to analyze the location accuracy of unmanned aerial photogrammetry according to the change of the number if ground control points. Experiments were made with fixed wing, and the shooting altitude was set at 130m and 260m. The number of ground reference points used was 9, 8, 5, and 4, respectively. Ten checkpoints were used. XY RMSE for orthoimage and Z RMSE for DSM were compared and analyzed. In addition, the resolution of the orthoimage was determined to affect the judgment of the operator in the verification of the planimetric position accuracy, and the visual resolution was analyzed using the Siemens star target. As a result of the analysis, the variation of the vertical position accuracy is larger than the variation of the planimetric position accuracy when the number of the ground reference points are different. Also The higher the flying height, the greater the effect of change of ground control points on position accuracy.

• Clean Technology
• /
• v.21 no.3
• /
• pp.200-206
• /
• 2015

In order to investigate the effect of cerium oxide addition, Cu-ZnO-CeO₂ catalysts were prepared using co-precipitation method for water gas shift (WGS) reaction. A series of Cu-ZnO-CeO₂ catalyst with fixed Cu Content (50 wt%, calculated as CuO) and a given ceria content (e.g., 0, 5, 10, 20, 30, 40 wt%, calculated as CeO₂) were tested for catalytic activity at a GHSV of 95,541 h^-1, and a temperature range of 200 to 400 ℃. Cu-ZnO-CeO₂ catalysts were characterized by using BET, SEM, XRD, H₂-TPR, and XPS analysis. Varying composition of Cu-ZnO-CeO₂ catlysts led the difference characteristics such as Cu dispersion, and binding energy. The optimum 10 wt% doping of cerium facilitated catalyst reduction at lower temperature and improved the catalyst performance greatly in terms of CO conversion. Cerium oxide added catalyst showed enhanced activities at higher temperature when it compared with the catalyst without cerium oxide. Consequently, ceria addition of optimal composition leads to enhanced catalytic activity which is attributed to enhanced Cu dispersion, lower binding energy, and hindered Cu metal agglomeration.