A posteriori finite element output bounds with adaptive mesh refinement: application to a heat transfer problem in a three-dimensional rectangular duct

Numerical simulations based on an a posteriori finite element bound method with adaptive mesh refinement are presented for the three-dimensional convection–diffusion equation. The bound method provides relevant, quantitative, inexpensive, and rigorous lower and upper bounds to the output on a very fine discretization (“truth” discretization) at a cost close to the coarse mesh calculation (“working” discretization). To achieve a desired bound gap (i.e., difference between upper and lower bounds) at the lowest cost, an adaptive mesh refinement technique is used to refine the mesh only where needed. An optimal stabilization parameter is also applied to improve the sharpness of the bound gap. In this paper, the output of a heat transfer problem in a rectangular duct with a given velocity field is investigated. The average temperature at one section of the duct is bounded for a given inlet temperature and heat flux. For this problem, the adaptive mesh refinement strategy provides the same bound gap with only half the number of elements required by an uniform mesh refinement strategy. The hybrid flux calculation on the coarse mesh introduced for the domain decomposition approach is compared with the hybrid flux calculation on the fine mesh to analyze the contribution of the hybrid flux to the bound gap

Metal/graphene sheets as p-type transparent conducting electrodes in GaN light emitting diodes

We demonstrate the use of graphene based transparent sheets as a p-type current spreading layer in GaN light emitting diodes (LEDs). Very thin Ni/Au was inserted between graphene and p-type GaN to reduce contact resistance, which reduced contact resistance from similar to 5.5 to similar to 0.6 Omega/ cm(2), with no critical optical loss. As a result, LEDs with metal-graphene provided current spreading and injection into the p-type GaN layer, enabling three times enhanced electroluminescent intensity compared with those with graphene alone. We confirmed very strong blue light emission in a large area of the metal-graphene layer by analyzing image brightness.open281

A Case of Myxoid Dermatofibrosarcoma Protuberans

Dermatofibrosarcoma protuberans (DFSP) is a slowly growing dermal spindle cell tumor and its myxoid variant, a rare type of DFSP, is characterized by extensive myxoid degeneration. We present the case of a 69-year-old woman with a multinodular reddish plaque on her trunk. Histopathologically, the tumor was located in the dermis and consisted of uniform spindle-shaped cells, showing strongly positive reaction for CD34, and negative for both S-100 and desmin. In addition to the typical storiform pattern, prominent myxoid stromal changes were demonstrated. Herein, we report an interesting case of myxoid DFSP, rarely reported in the dermatology literature

Climatological Features of Korea-Landfalling Tropical Cyclones

The present study analyzed the interdecadal variation by applying the statistical change-point analysis to the frequency of the tropical cyclone (TC) that landed in the Korean Peninsula (KP) for the recent 54 years (1951 to 2004) and performed cluster classification of the Korea-landfall TC tracks using a Fuzzy Clustering Method (FCM). First, in the interdecadal variation analysis, frequency of TC that landed in the KP was largely categorized into three periods: high frequency period from 1951 to 1965, low frequency period from 1966 to 1985, and high frequency period from 1986 to 2004. The cluster analysis result of the Korea-landfall TC tracks produced the optimum number of clusters as four. In more detail, Cluster A refers to a pattern of landing in the southern coast in the KP starting from East China Sea followed by heading north while Cluster B refers to a pattern of landing in the west coast of the Korean Peninsula, also starting from East China Sea followed by heading north. Cluster C refers to a pattern of landing in the southern region of the west coast in the KP moving from mainland China while Cluster D refers to a pattern of landing in the mid-north region of the west coast in the Korean Peninsula, also moving from mainland China

Outcomes of Revision Surgery Following Instrumented Posterolateral Fusion in Degenerative Lumbar Spinal Stenosis: A Comparative Analysis between Pseudarthrosis and Adjacent Segment Disease

Study DesignRetrospective study.PurposeWe examined the clinical and radiological outcomes of patients who received revision surgery for pseudarthrosis or adjacent segment disease (ASD) following decompression and instrumented posterolateral fusion (PLF).Overview of LiteratureAt present, information regarding the outcomes of revision surgery for complications such as pseudarthrosis and ASD following instrumented PLF is limited.MethodsThis study examined 60 patients who received PLF for degenerative lumbar spinal stenosis and subsequently developed pseudarthrosis or ASD leading to revision surgery. Subjects were divided into a group of 21 patients who received revision surgery for pseudarthrosis (Group P) and a group of 39 patients who received revision surgery for ASD (Group A). Clinical outcomes were evaluated using the visual analogue scales for back pain (VAS-BP) and leg pain (VAS-LP), the Korean Oswestry disability index (K-ODI), and each patient's subjective satisfaction. Radiological outcomes were evaluated from the extent of bone union, and complications in the two groups were compared.ResultsVAS-LP at final follow-up was not statistically different between the two groups (p =0.353), although VAS-BP and K-ODI at final follow-up were significantly worse in Group P than in Group A (all p <0.05), and only 52% of the patients in Group P felt that their overall well-being had improved following revision surgery. Fusion rates after the first revision surgery were 71% (15/21) in Group P and 95% (37/39) in Group A (p =0.018). The rate of reoperation was significantly higher in Group P (29%) than in Group A (5%) (p =0.021) due to complications.ConclusionsClinical and radiological outcomes were worse in patients who had received revision surgery for pseudarthrosis than in those who had revision surgery for ASD. Elderly patients should be carefully advised of the risks and benefits before planning revision surgery for pseudarthrosis

Structural safety inspection of reinforced concrete structures considering failure probabilities of structural members

Regular safety inspections of existing reinforced concrete (RC) structures are required according to the regulations and criteria set by each country. In South Korea, the safety inspection regulations provided by the Korea Infrastructure Safety and Technology Corporation (KISTEC) are followed. These regulations were developed based on fuzzy theory to avoid subjective decisions, and provide standardized deterioration grades for member types, floors, and the entire structure. However, the safety inspection regulation by the KISTEC often provides unconservative evaluation results. In particular, as the importance factors of beam and slab members are set lower than those of other members, there are cases in which deteriorations occurring in beams and slabs are not properly reflected in the floor level evaluation. In this study, to overcome such limitations, case studies were carried out and modified importance factors for structural member types were proposed considering the failure probabilities of each member type based on the reliability theory. The importance modification factor was calculated based on the strength ratio of structural members so that the more dangerous the members are, the more impact they give on the evaluation. Overall, compared to the KISTEC method, the proposed method provided conservative but practical assessment results, and it was found that the proposed importance factors can be very useful to properly reflect the effects of damaged members on the deterioration status evaluation of the floors and the entire structure

Predictors of Successful Trial without Catheter for Postoperative Urinary Retention Following Non-Urological Surgery

Purpose To investigate the success rate of trial without catheter (TWOC) for postoperative urinary retention (POUR) after non-urological surgery and to determine predictors of successful TWOC. Methods A total of 104 patients who underwent non-urological surgery and were referred to the department of urology for POUR were included in this retrospective study. All eligible patients underwent indwelling catheterization as an initial treatment and then TWOC was performed 3 to 7 days later. POUR was defined as micturition difficulty with greater than 400 mL of postvoid residual (PVR) urine volume measured by catheterization after non-urological surgery. Successful TWOC was defined as voiding with less than 100 mL of PVR urine volume. Predictive factors were identified by multivariate regression analysis. All definitions corresponded to recommendations of the International Continence Society. Results The mean age of the patients was 65.2 (range, 23 to 92) years. There were 45 male and 59 female patients. Intraoperative indwelling catheterization was performed in 69 (66.3%) patients. Mean duration of indwelling catheterization for POUR was 5.0 (range, 3.0 to 7.0) days and 83 (79.8%) patients received medication with an alpha-blocker. A successful TWOC was observed in 70 (67.4%) patients. The mean age of the patients with failure of TWOC was significantly higher than that of the patients with successful TWOC. The percentages of female patients, spinal surgery, and prone position during surgery in patients with unsuccessful TWOC were higher than in those with successful TWOC. In the multivariate logistic regression analysis, age and location of surgery (spine vs. non-spine) were the independent predictors of successful TWOC for POUR. Conclusions Our data suggest that older age and spinal surgery may be important risk factors for failure of TWOC for POUR after non-urological surgery. Thus, adequate prevention measures may be necessary for POUR after non-urological surgery, especially in patients with these risk factors