• Structural Engineering and Mechanics
• /
• v.74 no.4
• /
• pp.567-576
• /
• 2020

Considerable controversy surrounds the choice of the best abutment type for implant prosthetics. The two most common structures are hex and non-hex abutments. The non-hex abutment typically furnishes a larger contact area between itself and the implant than that provided by a hex structure. However, when a hex abutment is loaded, the position of its contact area may be deeper than that of a non-hex abutment. Hence, the purpose of this study is to determine the different biomechanical behaviors of an internal bone-level implant based on the abutment type-hex or non-hex-and clinical crown length under static and cyclic loadings using finite element analysis (FEA). The hex structure was found to increase the implant and abutment stability more than the nonhex structure among several criteria. The use of the hex structure resulted in a smaller volume of bone tissues being at risk of hypertrophy and fatigue failure. It also reduced micromovement (separation) between the implant components, which is significantly related to the pumping effect and possible inflammation. Both static and fatigue analyses, used to examine short- and long-term stability, demonstrated the advantages of the hex abutment over the non-hex type for the stability of the implant components. Moreover, although its impact was not as significant as that of the abutment type, a large crown-implant ratio (CIR) increased bone strain and stress in the implant components, particularly under oblique loading.

• Ocean Systems Engineering
• /
• v.6 no.3
• /
• pp.265-287
• /
• 2016

The change of the global performance of a turret-moored FPSO (Floating Production Storage Offloading) with DP (Dynamic Positioning) control is simulated, analyzed, and compared for two different internal turret location cases; bow and midship. Both collinear and non-collinear 100-yr GOM (Gulf of Mexico) storm environments and three cases (mooring-only, with DP position control, with DP position+heading control) are considered. The horizontal trajectory, 6DOF (degree of freedom) motions, fairlead mooring and riser tension, and fuel consumptions are compared. The PID (Proportional-Integral-Derivative) controller based on LQR (linear quadratic regulator) theory and the thrust-allocation algorithm which is based on the penalty optimization theory are implemented in the fully-coupled time-domain hull-mooring-riser-DP simulation program. Both in collinear and non-collinear 100-yr WWC (wind-wave-current) environments, the advantage of mid-ship turret is demonstrated by the significant reduction in heave at the turret location due to the minimal coupling with pitch mode, which is beneficial to mooring and riser design. However, in the non-collinear WWC environment, the mid-turret case exhibits unfavorable weathervaning characteristics, which can be reduced by employing DP position and heading controls as demonstrated in the present case studies. The present study also reveals the plausible cause of the failure of mid-turret Gryphon Alpha FPSO in milder environment than its survival condition.

• Geomechanics and Engineering
• /
• v.15 no.2
• /
• pp.721-728
• /
• 2018

The surrounding rock mass contains cracks and joints which are distributed randomly around tunnels, and in the process of tunnel blasting excavation, radial cracks could also be induced in the surrounding rock mass. In order to clearly understand the impact of radial cracks on tunnel stability, tunnel model tests and finite element numerical analysis were implemented in this paper. Two kinds of materials: cement mortar and sandstone, were used to make tunnel models, which were loaded vertically and confined horizontally. The tunnel failure pattern was simulated by using RFPA2D code, and the Tresca stresses and the stress intensity factors were calculated by using ABAQUS code, which were applied to the analysis of tunnel model test results. The numerical results generally agree with the model test results, and the mode II stress intensity factors calculated by ABAQUS code can well explain the model test results. It can be seen that for tunnels with a radial crack emanating from three points on tunnel edge, i.e., the middle point between tunnel spandrel and its top with a dip angle $45^{\circ}$, the tunnel foot with a dip angle $127^{\circ}$, and the tunnel spandrel with $135^{\circ}$ with tunnel wall, the tunnel model strength is about a half of the regular tunnel model strength, and the corresponding tunnel stability decreases largely.

• Structural Engineering and Mechanics
• /
• v.67 no.4
• /
• pp.347-358
• /
• 2018

The main aim of this research was to investigate the shear strength of non-prismatic steel fiber reinforced concrete beams under monotonic loading considering different parameters. Experimental program included tests on fifteen non-prismatic reinforced concrete beams divided into three groups. For the first and the second groups, different parameters were taken into consideration which are: steel fibers content, shear span to minimum depth ratio ($a/d_{min}$) and tapering angle (${\alpha}$). The third group was designed mainly to optimize the geometry of the non-prismatic concrete beams with the same concrete volume while the steel fiber ratio and the shear span were left constant in this group. The presence of steel fibers in concrete led to an increase in the load-carrying capacity in a range of 10.25%-103%. Also, the energy absorption capacity was increased due to the addition of steel fibers in a range of 18.17%-993.18% and the failure mode was changed from brittle to ductile. Tapering angle had a clear effect on the shear strength of test specimens. The increase in tapering angle from ($7^{\circ}$) to ($12^{\circ}$) caused an increase in the ultimate shear capacity for the test specimens. The maximum increase in ultimate load was 45.49%. The addition of steel fibers had a significant impact on the post-cracking behavior of the test specimens. Empirical equation for shear strength prediction at cracking limit state was proposed. The predicted cracking shear strength was in good agreement with the experimental findings.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.3
• /
• pp.1411-1414
• /
• 2014

Background: Hepatitis B and C are the leading causes of liver diseases worldwide. For hematological and solid malignancy patients undergoing chemotherapy, increases in HBV DNA and HCV RNA levels can be detected which may result in reactivation and hepatitis-related morbidity and mortality. The aim of this study was to determine the seroprevalence of Hbs ag and Anti HCV positivity in patients with solid malignancies undergoing chemotherapy and consequences during follow-up. Materials and Methods: The files of 914 patients with solid malignancies whose hepatitis markers were determined serologically at diagnosis were reviewed retrospectively. All underwent adjuvant/palliative chemotherapy. For the cases with HBV and/or HCV positivity, HBV DNA and HCV RNA levels, liver function tests at diagnosis and during follow-up and the treatment modalities that were chosen were determined. Results: Of 914 cases, Hbs Ag, anti Hbs and anti HCV positivity were detected in 40 (4.4%), 336 (36.8%) and 26 (2.8%) of the cases respectively. All of the Hbs ag positive patients received prophylactic lamuvidine before the start of chemotherapy. In the Hbs ag and anti HCV positive cases, liver failure was not detected during chemotherapy and a delay in chemotherapy courses because of hepatitis was not encountered. Conclusions: Just as with hematological malignancies, screening for HBV and HCV should also be considered for patients with solid tumors undergoing chemotherapy. Prophylactic antiviral therapy for HBV reduces both the reactivation rates and HBV related mortality and morbidity. The clinical impact of HCV infection on patients undergoing chemotherapy is still not well characterized.

• The Journal of Industrial Distribution & Business
• /
• v.10 no.5
• /
• pp.59-66
• /
• 2019

Purpose - Many studies show that dissatisfied customers are silent rather than expressing complaints directly to firms. Although silent voices are pervasive in service failure, they have received little attention from researchers. Silence implies a multidimensional nature, not just the opposite of voice. This study focuses on two types of silent students in higher education: acquiescent silence and defensive silence. This study also proposes cognitive trust and affective trust as variables affecting student silence. The objective of this study is to analyse the effects of trust types on student silence and exit intention. Research design, data, and methodology - To test the proposed model, this study conducted a survey with undergraduate students who selected silence in a dissatisfied relationship with a professor. Respondents were asked to respond to the questionnaire, recalling the dissatisfaction at that time. A total of 300 students was surveyed from whom 275 completed questionnaires was obtained. The structural equation model analysis was used for the hypothesis test. Results - First, cognitive trust was negatively related to acquiescent and defensive silence. Second, affective trust was negatively related to acquiescent and defensive silence. Third, cognitive trust was negatively exit intention, but affective trust didn't significantly reduce exit intention. Forth, acquiescent silence was positively related to exit intention, but defensive silence didn't have a significant positive impact on exit intention. Thus, a key result of this analysis was that acquiescent silence enhances exit intention. Conclusions - The findings of the study provide a better understanding of the types of silence, and the role of trust, thus furthering the implication of student reactions to dissatisfaction. In particular, this study is meaningful in that it confirms the value of student silence in the context of complaint management. Acquiescent silence should be more importantly managed because it has stronger negative motive than defensive silence. Acquiescent silence is reduced through various channels(mail, telephone, counseling) that can express complaints. Cognitive trust and affective trust are a essential factors in reducing silence. Also, in explaining exit intention, cognitive trust plays a more important role than affective trust.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.12
• /
• pp.701-707
• /
• 2016

This study surveyed 150 men aged 30 to 50, a demographic which seborrheic dermatitis is common. The time of day one shampoos and recurrent fatigue were found to have a statistically significant impact on symptoms contributing to the main causes of seborrhea, including itchiness, excessive oil, acne, and redness on the scalp (p<0.01). Study results confirm lifestyle and shampoo habits, such as the frequent sense of fatigue, a routine work schedule, susceptibility to stress, the time of day one uses shampoo, and whether hair styling products are used, affects seborrheic scalp disease. This study found seborrheic scalp disease for office workers primarily resulted from shampoo habits, rashes were predominantly caused by a failure to rinse shampoo and dry hair completely, while secondary aggravating factors included irregular work schedules, recurrent tiredness, and chronic stress.

• Radiation Oncology Journal
• /
• v.32 no.3
• /
• pp.179-186
• /
• 2014

Purpose: To study the long-term outcomes and tolerance in our patients who received dose escalated radiotherapy in the early salvage post-prostatectomy setting. Materials and Methods: The medical records of 54 consecutive patients who underwent radical prostatectomy subsequently followed by salvage radiation therapy (SRT) to the prostate bed between 2003-2010 were analyzed. Patients included were required to have a pre-radiation prostate specific antigen level (PSA) of 2 ng/mL or less. The median SRT dose was 70.2 Gy. Biochemical failure after salvage radiation was defined as a PSA level >0.2 ng/mL. Biochemical control and survival endpoints were analyzed using the Kaplan-Meier method. Univariate and multivariate Cox regression analysis were used to identify the potential impact of confounding factors on outcomes. Results: The median pre-SRT PSA was 0.45 ng/mL and the median follow-up time was 71 months. The 4- and 7-year actuarial biochemical control rates were 75.7% and 63.2%, respectively. The actuarial 4- and 7-year distant metastasis-free survival was 93.7% and 87.0%, respectively, and the actuarial 7-year prostate cancer specific survival was 94.9%. Grade 3 late genitourinary toxicity developed in 14 patients (25.9%), while grade 4 late genitourinary toxicity developed in 2 patients (3.7%). Grade 3 late gastrointestinal toxicity developed in 1 patient (1.9%), and grade 4 late gastrointestinal toxicity developed in 1 patient (1.9%). Conclusion: In this series with long-term follow-up, early SRT provided outcomes and toxicity profiles similar to those reported from the three major randomized trials studying adjuvant radiation therapy.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.8
• /
• pp.3923-3927
• /
• 2016

Infection with the hepatitis C virus is a major public health concern which can lead to carcinoma and liver failure. It has been shown that single nucleotide polymorphisms can affect the level of gene activity of tumor necrosis factor (TNF) which has an important role, especially in viral infections which can lead to apaptosis of infected hepatocellular cells. We investigated the impact of three possible genotypes for rs1800629 or A/G single nucleotide polymorphism located downstream of $TNF{\alpha}$ gene promoter in groups of control (n=76) and chronic hepatitis C patients (n=89) focusing on the response to treatment among sensitive and resistant groups. Genomic DNA was extracted from $500{\mu}l$ prepheral whole blood and PCR and RFLP were used to amplify the region of interest and genotyping. With statistical analyzes a p-value <0.05 was considered meaningful. There was no significant difference in distribution of possible three genotypes among healthy individuals and patients (P=0.906, OR=1.194, CI=0.063-22.790). However, the frequency of G allele was higher in patients whereas A allele was more common among healthy individuals (p<0.0001). Further studies with more samples seem to be necessary.

• The Journal of Advanced Prosthodontics
• /
• v.5 no.4
• /
• pp.409-415
• /
• 2013

PURPOSE. The midline fracture of maxillary complete dentures is a frequently encountered complication. The purpose of this study was to assess the effect of frenulum height on midline strains of maxillary complete dentures. MATERIALS AND METHODS. A removable maxillary complete denture was fabricated and duplicated seven times. Four different labial frenulum heights were tested for stresses occurring on the palatal cameo surface. The strains were measured with strain gauges placed on 5 different locations and the stresses were calculated. To mimic occlusal forces bilaterally 100 N of load was applied from the premolar and molar region. RESULTS. A statistically significant association between the height of the labial frenulum and the calculated stresses and strains was shown (P<.05) predominantly on the midline and especially on the incisive papilla. The results showed that stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. CONCLUSION. Within the limitations of this in vitro study, it can be concluded that the stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. Surgical or mechanical precautions should be taken to prevent short-term failure of maxillary complete dentures due to stress concentration and low cycle fatigue tendency at the labial frenulum region.