Leak behavior of SCC degraded steam generator tubings of nuclear power plant

A forced outage due to a steam generator tube leak in a Korean nuclear power plant has been reported [Kim, J.S., Hwang, S.S., et al., 1999. KAERI Internal Report (Korean). Destructive analysis on pulled tubes from Ulchin unit 1. Korea Atomic Energy Research Institute]. Primary water stress corrosion cracking has occurred in many tubes in the plant, and they were repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to understand the leak behavior of the tubes containing stress corrosion cracks. Cracked specimens were prepared using a room temperature cracking technique, and the leak rates and burst pressures of the degraded tubes were determined both at room temperature and at a high temperature. Some tubes with 100% through wall cracks did not show a leakage at 10.8 MPa, which is the typical pressure difference of the pressurized water reactors (PWRs) during a normal operation. In some tests, the leak rates of the tubes increased with time at a constant pressure. In a high temperature pressure test at 282 °C one specimen showed a very small leakage at 18.6 MPa, which stopped after a small increase in the test pressure. Because stress corrosion cracks can develop at relatively low stresses, even 100% through wall cracks can be so tight that they will not leak at a normal operating pressure.     

Period And Priority Assignment Method For Dcs Design

Distributed control systems (DCS) used in industry environments consist of sensors, actuators, and controllers that are connected with a fieldbus. It is difficult to design the DCS while guaranteeing the time‐critical requirements because of both communication delays due to the fieldbus and computation delays due to many tasks executed in one node. This paper proposes a priority assignment method and a period assignment method that find the shortest periods of control loops and guarantee the end‐to‐end constraints such as precedence constraints and timing constraints. Also, a DCS design method is presented by using the proposed two assignment methods. The presented design method considers the worst‐case response times of tasks and messages simultaneously and is applicable to a practical DCS, which consists of several constraints. The design method is validated by examples.     

Corneal topography of photorefractive keratectomy versus laser in situ keratomileusis. Summit PRK-LASIK Study Group

OBJECTIVE: This study aimed to compare qualitative patterns of corneal topography early in the postoperative course after excimer laser photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) when used for the treatment of myopia of 6.0 to 15.0 diopters. DESIGN: The study design was a prospective, multicenter, randomized clinical trial. PARTICIPANTS: A total of 64 eyes were treated with PRK and 54 eyes were treated with LASIK. INTERVENTION: Using the Summit Apex excimer laser, patients received either PRK or LASIK using a single pass, multizone excimer laser ablation. Computer-assisted videokeratography was performed at designated postoperative examinations. MAIN OUTCOME MEASURES: Videokeratography maps at 1 and 3 months after surgery were classified using a standard classification scheme. The association of topography patterns to loss of spectacle-corrected visual acuity was tested. RESULTS: At 1 month, for the PRK (n = 60) and LASIK (n = 51) groups, respectively, 63.3% and 19.6% of eyes fell into one of the four optically irregular groups (central island, keyhole, semicircular, or irregularly irregular; P < 0.001). At 3 months, for the PRK (n = 49) and LASIK (n = 39) groups, respectively, 36.7% and 10.3% of eyes fell into one of the optically irregular groups (P = 0.004). Comparing the 1- and 3-month examination results in the PRK and LASIK groups, respectively, 19 (42%) of 45 eyes and 11 (31%) of 36 eyes had a change in topography, generally to an optically smoother pattern. The irregular groups, taken together, were associated with a greater tendency toward loss of spectacle-corrected visual acuity of two or more Snellen lines (P = 0.01). There also was greater tendency toward loss of spectacle-corrected visual acuity in the PRK group that diminished with time (P < 0.01 at 1 month, P = 0.05 at 3 months). CONCLUSIONS: After treatment for moderate-to-high myopia, LASIK topography patterns generally are more regular than are PRK patterns. This may be a result either of masking of underlying topography perturbations by the lamellar corneal flap, thus mitigating induced topography changes, or differences in surface wound healing. This study suggests that more rapid return of spectacle-corrected visual acuity found in patients treated with LASIK may be a result of more regular topography patterns early in the postoperative course.     

Percutaneous radiologic drainage of pancreatic abscesses

OBJECTIVE: The purpose of our study was to review and report the patient selection, techniques, and results of percutaneous drainage of pancreatic abscesses by retrospective review. MATERIALS AND METHODS: Fifty-nine patients (46 men and 13 women) with a mean age of 44 years old had 80 pancreatic abscesses that were drained percutaneously under radiologic guidance (CT, n = 77; sonography, n = 2; and fluoroscopy, n = 1). Abscesses had a wide spectrum of causes, with alcoholic pancreatitis being most common, trauma second most common, and gallstones third. Ten patients had undergone surgery for pancreatic necrosis or abscess. Patients with pancreatic pseudocysts, necrosis, or acute fluid collections were excluded from this study. RESULTS: Of the 59 patients, 51 (86%) were cured with percutaneous drainage and antibiotic therapy. Of the patients who were not cured with percutaneous drainage, seven required surgery and one underwent repeat percutaneous drainage. In the 59 patients, complications included non-life-threatening bleeding in three patients. Ten of 59 patients (17%) had fistulas that spontaneously formed into the gastrointestinal tract. The duration of catheterization ranged from 4 to 119 days, with a mean duration of 33 days. The rate of mortality at 30 days after completion of percutaneous drainage was 8% (5 of 59). CONCLUSION: Percutaneous drainage was an effective therapy for this defined group of patients with pancreatic abscesses. Factors leading to the relatively high success rate described in this study likely included selection of patients; catheters of adequate size, number, and location; careful follow-up with appropriate catheter manipulations; and an integrated, cooperative approach whereby surgeons were willing to permit drainage to effect its benefits, rather than operating prematurely.     

The effects of non-insulin-dependent diabetes mellitus on the kinetics of onset of insulin action in hepatic and extrahepatic tissues

The mechanism(s) of insulin resistance in non-insulin-dependent diabetes mellitus remains ill defined. The current studies sought to determine whether non-insulin-dependent diabetes mellitus is associated with (a) a delay in the rate of onset of insulin action, (b) impaired hepatic and extrahepatic kinetic responses to insulin, and (c) an alteration in the contribution of gluconeogenesis to hepatic glucose release. To answer these questions, glucose disappearance, glucose release, and the rate of incorporation of 14CO2 into glucose were measured during 0.5 and 1.0 mU/kg-1 per min-1 insulin infusions while glucose was clamped at approximately 95 mg/dl in diabetic and nondiabetic subjects. The absolute rate of disappearance was lower (P < 0.05) and the rate of increase slower (P < 0.05) in diabetic than nondiabetic subjects during both insulin infusions. In contrast, the rate of suppression of glucose release in response to a change in insulin did not differ in the diabetic and nondiabetic subjects during either the low (slope 30-240 min:0.02 +/- 0.01 vs 0.02 +/- 0.01) or high (0.02 +/- 0.00 vs 0.02 +/- 0.00) insulin infusions. However, the hepatic response to insulin was not entirely normal in the diabetic subjects. Both glucose release and the proportion of systemic glucose being derived from 14CO2 (an index of gluconeogenesis) was inappropriately high for the prevailing insulin concentration in the diabetic subjects. Thus non-insulin-dependent diabetes mellitus slows the rate-limiting step in insulin action in muscle but not liver and alters the relative contribution of gluconeogenesis and glycogenolysis to hepatic glucose release.     

Multitask bilateral learning for real‐time image enhancement

Nowadays, deep neural networks (DNNs) for image processing are becoming more complex; thus, reducing computational cost is increasingly important. This study highlights the construction of a DNN for real‐time image processing, training various image processing operators efficiently through multitask learning. For real‐time image processing, the proposed algorithm takes a joint upsampling approach through bilateral guided upsampling. For multitask learning, the overall network is based on an encoder‐decoder architecture, which consists of encoding, processing, and decoding components, in which the encoding and decoding components are shared by all the image processing operators. In the processing component, a semantic guidance map, which contains processing information for each image processing operator, is estimated using simple linear shifts of the shared deep features. Through these components, the proposed algorithm requires an increase of only 5% in the number of parameters to add another image processing operator and achieves faster and higher performance than that of deep‐learning‐based joint upsampling methods in local image processing as well as global image processing.     

Effect of substrate temperature on structural, optical and electrical properties of ZnO thin films deposited by pulsed laser deposition

ZnO thin films were grown by the pulse laser deposition (PLD) method using Si (100) substrates at various substrate temperatures. The influence of the substrate temperature on the structural, optical, and electrical properties of the ZnO thin films was investigated. All of the thin films showed c-axis growth perpendicular to the substrate surface. At a substrate temperature of 500 °C, the ZnO thin film showed the highest (002) peak with a full width at half maximum (FWHM) of 0.39°. The X-ray Photoelectron Spectroscopy (XPS) study showed that Zn was in excess irrespective of the substrate temperature and that the thin film had a nearly stoichiometrical composition at a substrate temperature of 500 °C. The photoluminescence (PL) investigation showed that the narrowest UV FWHM of 15.8 nm and the largest ratio of the UV peak to the deep-level peak of 32.9 were observed at 500 °C. Hall effect measurement systems provided information about the carrier concentration, mobility and resistivity. At a substrate temperature of 500 °C, the Hall mobility was the value of 37.4 cm²/Vs with carrier concentration of 1.36 × 10¹⁸ cm⁻³ and resistivity of 2.08 × 10⁻¹ Ω cm.     

Influence of SnO2 addition on the thermoelectric properties of Zn1 − xSnxO (0.01 ≤ x ≤ 0.05)

The grain size and the density of the Zn_1 − xSn_xO (0 ≤ x ≤ 0.05) samples decreased with increasing SnO₂ content. The addition of a small amount of SnO₂ (x ≤ 0.01) to ZnO led to an increase in both the electrical conductivity and the absolute value of the Seebeck coefficient, resulting in a significant increase in the power factor. The thermoelectric power factor was maximized to a value of 1.25 × 10⁻³ Wm⁻¹ K⁻² at 1073 K for the Zn_0.99Sn_0.01O sample.     

Direct vapor phase growth process and robust photoluminescence properties of large area MoS2 layers

There has been growing research interest in the use of molybdenum disulfide in the fields of optoelectronics and energy harvesting devices, by virtue of its indirect-to-direct band gap tunability. However, obtaining large area thin films of MoS2 for future device applications still remains a challenge. In the present study, the amounts of the precursors （S and MOO3） were varied systematically in order to optimize the growth of highly crystalline and large area MoS2 layers by the chemical vapor deposition method. Careful control of the amounts of precursors was found to the key factor in the synthesis of large area highly crystalline flakes. The thickness of the layers was confirmed by Raman spectroscopy and atomic force microscopy. The optical properties and chemical composition were studied by photoluminescence （PL） and X-ray photoelectron spectroscopy. The emergence of strong direct excitonic emissions at 1.82 eV （A-exciton, with a normalized PL intensity of -55 × 10^3） and 1.98 eV （B-exciton, with a normalized PL intensity of -5 × 10^3） of the sample at room temperature clearly indicates the high luminescence quantum efficiency. The mobility of the films was found to be 0.09 cm^2/（V.s） at room temperature. This study provides a method for the controlled synthesis of high-quality two-dimensional （2D） transition metal dichalcogenide materials, useful for applications in nanodevices, optoelectronics and solar energv conversion.