• Steel and Composite Structures
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• v.25 no.6
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• pp.649-661
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• 2017

This paper is motivated by the lack of studies in the technical literature concerning to the influence of carbon nanotubes (CNTs) waviness and aspect ratio on the vibrational behavior of functionally graded nanocomposite annular sector plates resting on two-parameter elastic foundations. The carbon nanotube-reinforced (CNTR) plate has smooth variation of CNT fraction based on the power-law distribution in the thickness direction, and the material properties are also estimated by the extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Parametric studies are carried out to highlight the influence of CNTs volume fraction, waviness and aspect ratio, boundary conditions and elastic foundation on vibrational behavior of FG-CNT thick sectorial plates. The study is carried out based on three-dimensional theory of elasticity and in contrary to two-dimensional theories, such as classical, the first- and the higher-order shear deformation plate theories, this approach does not neglect transverse normal deformations. The annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. For an overall comprehension on 3-D vibration of annular sector plates, some mode shape contour plots are reported in this research work.

• Computers and Concrete
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• v.25 no.4
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• pp.293-302
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• 2020

Connections play a significant role in strength of structures against earthquake-induced loads. According to the post-seismic reports, connection failure is a cause of overall failure in reinforced concrete (RC) structures. Connection failure results in a sudden increase in inter-story drift, followed by early and progressive failure across the entire structure. This article investigated the cyclic performance and behavioral improvement of shape-memory alloy-based connections (SMA-based connections). The novelty of the present work is focused on the effect of shape memory alloy bars is damage reduction, strain recoverability, and cracking distribution of the stated material in RC moment frames under seismic loads using 3D nonlinear static analyses. The present numerical study was verified using two experimental connections. Then, the performance of connections was studied using 14 models with different reinforcement details on a scale of 3:4. The response parameters under study included moment-rotation, secant stiffness, energy dissipation, strain of bar, and moment-curvature of the connection. The connections were simulated using LS-DYNA environment. The models with longitudinal SMA-based bars, as the main bars, could eliminate residual plastic rotations and thus reduce the demand for post-earthquake structural repairs. The flag-shaped stress-strain curve of SMA-based materials resulted in a very slight residual drift in such connections.

• Clinical and Experimental Reproductive Medicine
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• v.48 no.4
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• pp.316-321
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• 2021

Objective: Amino acids can protect sperm structure in cryopreservation due to their antioxidant properties. Therefore, the present study aimed to investigate the protective effect of L-carnitine (LC) and N-acetyl cysteine (NAC) on motility parameters, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA damage, and human sperm intracellular reactive oxygen species (ROS) during vitrification. Methods: Twenty normal human sperm samples were examined. Each sample was divided into six equal groups: LC (1 and 10 mM), NAC (5 and 10 mM), and cryopreserved and fresh control groups. Results: The groups treated with LC and NAC showed favorable findings in terms of motility parameters, DNA damage, and MMP. Significantly higher levels of intracellular ROS were observed in all cryopreserved groups than in the fresh group (p≤0.05). The presence of LC and NAC at both concentrations caused an increase in PMI, MMP, and progressive motility parameters, as well as a significant reduction in intracellular ROS compared to the control group (p≤0.05). The concentrations of the amino acids did not show any significant effect. Conclusion: LC and NAC are promising as potential additives in sperm cryopreservation.

• International Journal of Contents
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• v.15 no.3
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• pp.32-38
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• 2019

We usually suffer from difficulties in treating or managing Big Data generated from various digital media and/or sensors using traditional mining techniques. Additionally, there are many problems relative to the lack of memory and the burden of the learning curve, etc. in an increasing capacity of large volumes of text when new data are continuously accumulated because we ineffectively analyze total data including data previously analyzed and collected. In this paper, we propose a general-purpose classifier and its structure to solve these problems. We depart from the current feature-reduction methods and introduce a new scheme that only adopts changed elements when new features are partially accumulated in this free-style learning environment. The incremental learning module built from a gradually progressive formation learns only changed parts of data without any re-processing of current accumulations while traditional methods re-learn total data for every adding or changing of data. Additionally, users can freely merge new data with previous data throughout the resource management procedure whenever re-learning is needed. At the end of this paper, we confirm a good performance of this method in data processing based on the Big Data environment throughout an analysis because of its learning efficiency. Also, comparing this algorithm with those of NB and SVM, we can achieve an accuracy of approximately 95% in all three models. We expect that our method will be a viable substitute for high performance and accuracy relative to large computing systems for Big Data analysis using a PC cluster environment.

• Design & Manufacturing
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• v.15 no.4
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• pp.51-56
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• 2021

Piercing is the process of shearing a circular hole in sheet metal, whose high shear force makes it difficult to secure the durability of tools. In addition, uneven clearance between tools due to poor alignment of the piercing punch causes accelerated die wear and breakage of the tool. This study reviewed the feasibility of in-situ determining alignment failure during the piercing process by analyzing the signal deviation of a bolt-type piezo sensor installed inside the tool whose alignment level was controlled. Finite element analysis was performed to select the optimal sensor location on the piercing tool for sensitive detection of process signals. A well-aligned piercing process results in uniform deformation in the circumferential direction, and shearing is completed at a stroke similar to the sheet thickness. Afterward, a sharp decrease in shear load is observed. The misaligned piecing punch leads to a gradual decrease in the load after the maximum shear load. This gradual decrease is due to the progressive shear deformation that proceeds in the circumferential direction after the initial crack occurs at the narrow clearance site. Therefore, analyzing the stroke at which the maximum shear load occurs and the load reduction rate after that could detect the misalignment of the piercing punch in real-time.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1003-1015
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• 2022

The new methodologies to derive discharge limits considering operational flexibility according to international safety standards were developed to help reduce the environmental releases of radioactive effluents from nuclear power plants (NPPs). To overcome the limitations of the two existing methods to set up discharge limits assuming a specific statistical distribution of the effluent discharge, two modified equations were newly proposed to directly derive a particular discharge limits corresponding to the target 'compliance probability' based on the actual annual discharge data for a specific NPP and radionuclide groups. By applying these to the actual yearly discharge data of 14 Korean NPPs for 7 radionuclide groups for the past 20 years, the applicability of two new methodologies to actual cases was demonstrated. The 'characteristic value' with approximately a 90% compliance probability for each Korean NPP and radionuclide group was proposed based on the results. The new approaches for setting up the discharge limits and the characteristic values developed in this study are expected to be effectively utilized to foster operator's efforts to progressively reduce the environmental releases of radioactive effluents of NPPs relative to the previous discharge data considering operational flexibilities.

• Computers and Concrete
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• v.31 no.5
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• pp.371-384
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• 2023

Precast roofing systems employing prestressed elements often serve as smart structural solutions for the construction of industrial buildings. The precast concrete elements usually employed are highly engineered, and often consist in thin-walled members, characterised by a complex behaviour in fire. The present study was carried out after a fire event damaged a precast industrial building made with prestressed beam and roof elements, and non-prestressed curved barrel vault elements interposed in between the spaced roof elements. As a consequence of the exposure to the fire, the main elements were found standing, although some locally damaged and distorted, and the local collapse of few curved barrel vault elements was observed in one edge row only. In order to understand and interpret the observed structural performance of the roof system under fire, a full fire safety engineering process was carried out according to the following steps: (a) realistic temperature-time curves acting on the structural elements were simulated through computational fluid dynamics, (b) temperature distribution within the concrete elements was obtained with non-linear thermal analysis in variable regime, (c) strength and deformation of the concrete elements were checked with non-linear thermal-mechanical analysis. The analysis of the results allowed to identify the causes of the local collapses occurred, attributable to the distortion caused by temperature to the elements causing loss of support in early fire stage rather than to the material strength reduction due to the progressive exposure of the elements to fire. Finally, practical hints are provided to avoid such a phenomenon to occur when designing similar structures.

• Journal of Oral Medicine and Pain
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• v.48 no.3
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• pp.112-117
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• 2023

Coronoid process hyperplasia (CPH) of the mandible is a rare condition in which abnormal elongation of the coronoid process leads to chronic mandibular hypomobility. CPH causes impingement or impedance of the coronoid process on the inner surface of the frontal part of the zygomatic bone during mouth opening. The lack of significant symptoms makes the diagnosis difficult. Its etiology remains inconclusive despite several theories being suggested. In this report, three reviewed cases are presented. All three patients visited our clinic with limited mouth opening as the chief complaint. Standard clinical and radiographic examinations were conducted under the initial impression of temporomandibular disorders (TMDs), and restricted jaw movements were confirmed in all cases. The absence of improved signs and symptoms following conservative treatment for TMDs or the indeterminate plain radiographs required the attending clinicians to consider three-dimensional imagery. Computed tomography revealed bilateral coronoid hyperplasia in all cases and impingement on the zygomatic bone in two of the three cases. After concluding that this condition caused the patients' limited mouth opening, the patients were referred to the Department of Oral and Maxillofacial Surgery for possible bilateral coronoidectomy or coronoidotomy. CPH usually presents no symptoms apart from a progressive reduction of mouth opening over time. Diagnosis is often delayed, and patients may undergo unnecessary treatment procedures. Clinicians should be aware of this condition and exercise caution in the differential diagnosis of patients with chronic mandibular hypomobility.

• Korean Journal of Clinical Pharmacy
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• v.21 no.4
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• pp.364-375
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• 2011

Given that single blockade with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) can achieve only partial and undurable suppression of the Renin Angiotensin System (RAS), it has been hypothesized that dual blockage would be more beneficial in the management of blood pressure (BP) reduction and prevention of progressive chronic kidney disease (CKD) than either agent alone. Thus, it has been suggested that the combination of an ACEI and an ARB might provide renal benefits to hypertensive patients over and above BP reduction. However, this might also expose patients to additive or synergistic side effects. We attempted to conduct a systematic review to evaluate the benefits and harms of combination therapy in hypertensive patients with or without kidney diseases. MEDLINE and KoreaMed were searched for relevant randomized clinical trials in adult hypertensive patients with or without diabetes (restricted to 1997, limited to trials published in English). Results were summarized using the random-effects model, and between-studies heterogeneity was estimated with $I^2$. A final analysis of ten trials (23,928 patients) revealed that the combination of an ACEI and an ARB reduced blood pressure (SBP/DBP) by 3.95/2.02 mmHg (95% confidence interval [CI], -4.38 to -3.53/-2.33 to -1.71) compared with ACEI monotherapy, and 2.83/2.64 mmHg (95% CI, -3.25 to -2.41/-4.95 to -0.33) compared with ARB monotherapy. Eight trials (391 patients) demonstrated a significant reduction in 24h-proteinuria (weighted mean difference, 0.16 g/day, 95% CI, -0.26-0.05), but they did not translate into an improvement in GFR. Tests for heterogeneity showed no difference in effect among the studies. The combination therapy reduced proteinuria by 30% (95% CI, 23% to 37%) and 39% (95% CI, 31% to 48%) compared with ACEI monotherapy and ARB monotherapy, respectively. However, in patients who had proteinuria more than 0.5 g/day, the combination therapy failed to show significant reduction in urinary protein excretion. The current cumulative evidence suggests that diabetic patients with proteinuria on dual RAS blockade have an increase risk of adverse events such as hyperkalemia, hypotension, and so on, compared with ACEI or ARB alone. It is, therefore, proposed that the combination therapy should not be routinely used for the treatment of hypertension with or without compelling indications.

• Journal of Korean Academy of Nursing Administration
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• v.5 no.1
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• pp.149-167
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• 1999

This study was designed and carried out to investigate the effect of Assertiveness Training on the stress response and assertive behavior of emergency room nurses from September 22, to December 21. 1997. The subjects were 45 emergency room nurses of three general hospitals of Korea University Medical Center; 25 assigned for the experimental and 20 for the control group. The Assertive Training Program was composed of cognitive training, behavioral training and progressive muscle relaxation. The subjects of the experimental group carried out the 15-minute progressive muscle relaxation according to recorded-tape once a day for 6 weeks. The cognitive and the behavioural training were conducted by the investigator for 5-8 subjects at a time for 9 series, at an interval of 4-5 days. Post-measurement were administered to all sujects in two groups three weeks after the last session. The level of general stress (Cline, 1992), job stress (Kim & Koo, 1984), physiological response to stress (cortisol, epinephrine, norepinephrine), symptoms of stress (Lee, 1984) and assertive behavior (Kim, 1982) were measured before the first and after the last experiments. Data were analysed by x2, t, paired t, Wilcoxon signed rank tests Wilcoxon rank sums tests. The results are as follows : 1. The level of general stress of the experimental group was lower than that of the control group, however, no significant difference between the two groups (P=0.234) was revealed. 2. A significant reduction of job stress was revealed in the experimental group (P=0.017). 1) A significant reduction of interpersonal conflicts in the experimental group was revealed (P=0.018). 3. The physiological stress-response were analyzed as follows : 1) A decrease of Cortisol in both the experimental and the control groups was noticed, however, the difference between the two groups was not statistically significant (P=0.991). Pre-and post-measurement of the level of Corti sol revealed that a notable decrease in the experimental group and an increase in the control group with no significant difference in the day-day subjects (P=0.765), a significant decrease was noted on the level of Cortisol of the experimental group in the night-night nurses (P=0.036). 2) An increase of Epinephrine in both groups was noticed, however, a difference was not statistically significant between the two groups (P=0.082). Pre-and post-measurement of the level of Epinephrine revealed that a notable decrease in the experimental group and an increase in the control group with no significant difference in the day-day subjects (P=0.136). increases were noted on the level of Epinephrinel of both groups in the night-night nurses (P=0.136), 3) The level of Norepinephrine of the experimental group was significantly decreased (P=0.020). Pre-and post-measurement of the level of Norepinephrine revealed that a notable decrease in the experimental group and an increase in the control group with no significant difference in the day-day subjects (P=0.073). a significant decrease was noted on the level of Norepinephrine of the experimental group in the night-night nurses (P=0.036), 4. Symptoms of stress were reduced in both groups, with no significant differences between the groups (P=0.127). 1) The physical stress symptoms were reduced in both groups, with no significant difference (P=0.386), 2) The cognitive-behavioral stress symptoms were significantly reduced in the experimental group (P=0.037). 3) The emotional stress symptoms were reduced in both groups with no significant difference between the groups (P=0.110). 5. The assertive behavior was significantly increased in the experimental group (P=0.000). This study signified the Assertiveness Training as an effective mean of self intervention for the reduction of stress of nurses assigned to emergency rooms.