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Stiffness Enhancement of Piecewise Integrated Composite Beam using 3D Training Data Set (3차원 학습 데이터를 이용한 PIC 보의 강성 향상에 대한 연구)

  • Ji, Seungmin;Ham, Seok Woo;Choi, Jin Kyung;Cheon, Seong S.
    • Composites Research
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    • v.34 no.6
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    • pp.394-399
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    • 2021
  • Piecewise Integrated Composite (PIC) is a new concept to design composite structures of multiple stacking angles both for in-plane direction and through the thickness direction in order to improve stiffness and strength. In the present study, PIC beam was suggested based on 3D training data instead of 2D data, which did offer a limited behavior of beam characteristics, with enhancing the stiffness accompanied by reduced tip deformation. Generally training data were observed from the designated reference finite elements, and preliminary FE analysis was conducted with respect to regularly distributed reference elements. Also triaxiality values for each element were obtained in order to categorize the loading state, i.e. tensile, compressive or shear. The main FE analysis was conducted to predict the mechanical characteristics of the PIC beam.

An experimental investigation into the mechanism of the refrigerator contraction-expansion noise (냉장고 수축팽창 소음의 발생기구에 대한 실험적 규명)

  • Lee, Yeong-Gyu;Kim, Won-Jin
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.4
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    • pp.389-396
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    • 2022
  • This paper aims to identify the causes and mechanisms of contraction-expansion noise in refrigerators and proposes noise reduction methods. Contraction-expansion noise generated in refrigerators is mainly due to stick-slip phenomenon occurring on the contact surface between inner parts. Friction experiments were conducted to identify the factors causing the stick-slip phenomenon. Furthermore, the vibration level of the internal components was measured to determine the characteristics and location of the contraction-expansion noise. Based on the experimental results, experiments have been conducted to verify the noise characteristics for each factor. From this, it was confirmed that the friction experiment and the refrigerator contraction-expansion noise generation location and frequency were the same. The vibration level also increased as the vertical force was increased due to load loading. Also, it was confirmed that the contraction-expansion noise was reduced when the surface roughness was increased. Therefore, it was concluded that increasing the surface roughness of the contact surface in the same way as the results of the friction experiment was the method of reducing contraction-expansion noise.

Development of a Korean version of the Bereavement Care Confidence Scale (K-BCCS) (한국형 사별돌봄자신감 척도 개발)

  • Kwon, So-Hi;Kim, Young-Joo
    • The Journal of Korean Academic Society of Nursing Education
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    • v.27 no.2
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    • pp.197-209
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    • 2021
  • Purpose: The purpose of this study is to evaluate the validity and reliability of the Korean Bereavement Care Confidence Scale (K-BCCS). Methods: The Perinatal Bereavement Care Confidence Scale (PBCCS) was translated into Korean according to an algorithm of cultural adaptation process and excluded six items which were specific to perinatal bereavement. A total of 229 clinical nurses participated in the study. Construct validity, convergent validity, discriminant validity, and group comparison validity were evaluated, and Cronbach's α was calculated to estimate the reliability of the K-BCCS. Results: The K-BCCS consisted of 31 items in 7 factors, including knowledge and skills for bereavement care (12 items), organizational support (6 items), awareness of the needs (3 items), interpersonal skills (3 items), workload influence (2 items), continuous education (2 items), and understanding the grief process (3 items). The factor loading of 31 items within the 7 factors ranged from .60 to .86. For the convergent validity, the construct reliability (CR) ranged from .74 to .94, and the average variance extracted (AVE) ranged from .49 to .73, which is considered acceptable. The discriminant validity showed that the AVEs of the subscales were greater than the square of the correlation coefficient r. The nurses who had experience providing bereavement care (t=4.94, p<.001) or had received bereavement education (t=6.64, p<.001) showed higher K-BCCS values those without experience. The Cronbach's α of 31 items was .93 and ranged from .60 to .94 per subscale. Conclusion: The K-BCCS is a valid and reliable tool for evaluating nurses' confidence in bereavement care.

Antibacterial activity of enrofloxacin loaded gelatin-sodium alginate composite nanogels against intracellular Staphylococcus aureus small colony variants

  • Luo, Wanhe;Liu, Jinhuan;Algharib, Samah Attia;Chen, Wei
    • Journal of Veterinary Science
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    • v.23 no.3
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    • pp.48.1-48.12
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    • 2022
  • Background: The poor intracellular concentration of enrofloxacin might lead to treatment failure of cow mastitis caused by Staphylococcus aureus small colony variants (SASCVs). Objectives: In this study, enrofloxacin composite nanogels were developed to increase the intracellular therapeutic drug concentrations and enhance the efficacy of enrofloxacin against cow mastitis caused by intracellular SASCVs. Methods: Enrofloxacin composite nanogels were formulated by an electrostatic interaction between gelatin (positive charge) and sodium alginate (SA; negative charge) with the help of CaCl2 (ionic crosslinkers) and optimized by a single factor test using the particle diameter, zeta potential (ZP), polydispersity index (PDI), loading capacity (LC), and encapsulation efficiency (EE) as indexes. The formation mechanism, structural characteristics, bioadhesion ability, cellular uptake, and the antibacterial activity of the enrofloxacin composite nanogels against intracellular SASCVs strain were studied systematically. Results: The optimized formulation was comprised of 10 mg/mL (gelatin), 5 mg/mL (SA), and 0.25 mg/mL (CaCl2). The size, LC, EE, PDI, and ZP of the optimized enrofloxacin composite nanogels were 323.2 ± 4.3 nm, 15.4% ± 0.2%, 69.6% ± 1.3%, 0.11 ± 0.02, and -34.4 ± 0.8 mV, respectively. Transmission electron microscopy showed that the enrofloxacin composite nanogels were spherical with a smooth surface and good particle size distributions. In addition, the enrofloxacin composite nanogels could enhance the bioadhesion capacity of enrofloxacin for the SASCVs strain by adhesive studies. The minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration were 2, 4, 4, and 8 ㎍/mL, respectively. The killing rate curve had a concentration-dependent bactericidal effect as increasing drug concentrations induced swifter and more radical killing effects. Conclusions: This study provides a good tendency for developing enrofloxacin composite nanogels for treating cow mastitis caused by intracellular SASCVs and other intracellular bacterial infections.

Marine phytoplankton improves recovery and sustains immune function in humans and lowers proinflammatory immunoregulatory cytokines in a rat model

  • Sharp, Matthew;Wilson, Jacob;Stefan, Matthew;Gheith, Raad;Lowery, Ryan;Ottinger, Charlie;Reber, Dallen;Orhan, Cemal;Sahin, Nurhan;Tuzcu, Mehmet;Durkee, Shane;Saiyed, Zainulabedin;Sahin, Kazim
    • Korean Journal of Exercise Nutrition
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    • v.25 no.1
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    • pp.42-55
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    • 2021
  • [Purpose] This study investigated the effects of marine phytoplankton supplementation (Oceanix®, Tetraselmis chuii) on 1) maximal isometric strength and immune function in healthy humans following a oneweek high-intensity resistance-training program and 2) the proinflammatory cytokine response to exercise in a rat model. [Methods] In the human trial, 22 healthy male and female participants were randomly divided into marine phytoplankton and placebo groups. Following baseline testing, participants underwent a 14-day supplement loading phase before completing five consecutive days of intense resistance training. In the rat model, rats were randomly divided into four groups (n=7 per condition): (i) control, (ii) exercise, (iii) exercise + marine phytoplankton (2.55 mg/kg/day), or (iv) exercise + marine phytoplankton (5.1 mg/kg/day). Rats in the exercising groups performed treadmill exercise 5 days per week for 6 weeks. [Results] In the human model, marine phytoplankton prevented significant declines in the isometric peak rate of force development compared to placebo. Additionally, salivary immunoglobulin A concentration was significantly lower following the resistance training protocol in the placebo group but not in the marine phytoplankton group. Marine phytoplankton in exercising rats decreased intramuscular levels and serum concentrations of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) and intramuscular concentrations of malondialdehyde. [Conclusion] Marine phytoplankton prevented decrements in indices of functional exercise recovery and immune function. Mechanistically, these outcomes could be prompted by modulating the oxidative stress and proinflammatory cytokine response to exercise.

A computational investigation on flexural response of laminated composite plates using a simple quasi-3D HSDT

  • Draiche, Kada;Selim, Mahmoud M.;Bousahla, Abdelmoumen Anis;Tounsi, Abdelouahed;Bourada, Fouad;Tounsi, Abdeldjebbar;Mahmoud, S.R.
    • Steel and Composite Structures
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    • v.41 no.5
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    • pp.697-711
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    • 2021
  • In this work, a simple quasi 3-D parabolic shear deformation theory is developed to examine the bending response of antisymmetric cross-ply laminated composite plates under different types of mechanical loading. The main feature of this theory is that, in addition to including the transverse shear deformation and thickness stretching effects, it has only five-unknown variables in the displacement field modeling like Mindlin's theory (FSDT), yet satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without requiring a shear correction factor. The static version of principle of virtual work was employed to derive the governing equations, while the bending problem for simply supported antisymmetric cross-ply laminated plates was solved by a Navier-type closed-form solution procedure. The adequacy of the proposed model is handled by considering the impact of side-to-thickness ratio on bending response of plate through several illustrative examples. Comparison of the obtained numerical results with the other shear deformation theories leads to the conclusion that the present model is more accurate and efficient in predicting the displacements and stresses of laminated composite plates.

Stability investigation of symmetrically porous advanced composites plates via a novel hyperbolic RPT

  • S.R. Mahmoud;E.I. Ghandourah;A.H. Algarni;M.A. Balubaid;Abdelouahed Tounsi;Abdeldjebbar Tounsi;Fouad Bourada
    • Steel and Composite Structures
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    • v.46 no.4
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    • pp.471-483
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    • 2023
  • This paper presents an analytical hyperbolic theory based on the refined shear deformation theory for mechanical stability analysis of the simply supported advanced composites plates (exponentially, sigmoidal and power-law graded) under triangular, trapezoidal and uniform uniaxial and biaxial loading. The developed model ensures the boundary condition of the zero transverse stresses at the top and bottom surfaces without using the correction factor as first order shear deformation theory. The mathematical formulation of displacement contains only four unknowns in which the transverse deflection is divided to shear and bending components. The current study includes the effect of the geometric imperfection of the material. The modeling of the micro-void presence in the structure is based on the both true and apparent density formulas in which the porosity will be dense in the mid-plane and zero in the upper and lower surfaces (free surface) according to a logarithmic function. The analytical solutions of the uniaxial and biaxial critical buckling load are determined by solving the differential equilibrium equations of the system with the help of the Navier's method. The correctness and the effectiveness of the proposed HyRPT is confirmed by comparing the results with those found in the open literature which shows the high performance of this model to predict the stability characteristics of the FG structures employed in various fields. Several parametric analyses are performed to extract the most influenced parameters on the mechanical stability of this type of advanced composites plates.

Seismic performance of CFS shear wall systems filled with polystyrene lightweight concrete: Experimental investigation and design methodology

  • Mohammad Rezaeian Pakizeh;Hossein Parastesh;Iman Hajirasouliha;Farhang Farahbod
    • Steel and Composite Structures
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    • v.46 no.4
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    • pp.497-512
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    • 2023
  • Using light weight concrete as infill material in conventional cold-formed steel (CFS) shear wall systems can considerably increase their load bearing capacity, ductility, integrity and fire resistance. The compressive strength of the filler concrete is a key factor affecting the structural behaviour of the composite wall systems, and therefore, achieving maximum compressive strength in lightweight concrete while maintaining its lightweight properties is of significant importance. In this study a new type of optimum polystyrene lightweight concrete (OPLC) with high compressive strength is developed for infill material in composite CFS shear wall systems. To study the seismic behaviour of the OPLC-filled CFS shear wall systems, two full scale wall specimens are tested under cyclic loading condition. The effects of OPLC on load-bearing capacity, failure mode, ductility, energy dissipation capacity, and stiffness degradation of the walls are investigated. It is shown that the use of OPLC as infill in CFS shear walls can considerably improve their seismic performance by: (i) preventing the premature buckling of the stud members, and (ii) changing the dominant failure mode from brittle to ductile thanks to the bond-slip behaviour between OPLC and CFS studs. It is also shown that the design equations proposed by EC8 and ACI 318-14 standards overestimate the shear force capacity of OPLC-filled CFS shear wall systems by up to 80%. This shows it is necessary to propose methods with higher efficiency to predict the capacity of these systems for practical applications.

Analytical and finite element method for the bending analysis of the thick porous functionally graded sandwich plate including thickness stretching effect

  • Imad Benameur;Youcef Beldjelili;Abdelouahed Tounsi
    • Structural Engineering and Mechanics
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    • v.85 no.5
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    • pp.593-605
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    • 2023
  • This work presents a comparison between analytical and finite element analysis for bending of porous sandwich functionally graded material (FGM) plates. The plate is rectangular and simply supported under static sinusoidal loading. Material properties of FGM are assumed to vary continuously across the face sheets thickness according to a power-law function in terms of the volume fractions of the constituents while the core is homogeneous. Four types of porosity are considered. A refined higher-order shear with normal deformation theory is used. The number of unknowns in this theory is five, as against six or more in other shear and normal deformation theories. This theory assumes the nonlinear variation of transverse shear stresses and satisfies its nullity in the top and bottom surfaces of the plate without the use of a shear correction factor. The governing equations of equilibrium are derived from the virtual work principle. The Navier approach is used to solve equilibrium equations. The constitutive law of the porous FGM sandwich plate is implemented for a 3D finite element through a subroutine in FORTRAN (UMAT) in Abaqus software. Results show good agreement between the finite element model and the analytical method for some results, but the analytical method keeps giving symmetric results even with the thickness stretching effect and load applied to the top surface of the sandwich.

Effects of different calcium-silicate based materials on fracture resistance of immature permanent teeth with replacement root resorption and osteoclastogenesis

  • Gabriela Leite de Souza;Gabrielle Alves Nunes Freitas;Maria Tereza Hordones Ribeiro;Nelly Xiomara Alvarado Lemus;Carlos Jose Soares;Camilla Christian Gomes Moura
    • Restorative Dentistry and Endodontics
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    • v.48 no.2
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    • pp.21.1-21.15
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    • 2023
  • Objectives: This study evaluated the effects of Biodentine (BD), Bio-C Repair (BCR), and mineral trioxide aggregate (MTA) plug on the fracture resistance of simulated immature teeth with replacement root resorption (RRR) and in vitro-induced osteoclastogenesis. Materials and Methods: Sixty bovine incisors simulating immature teeth and RRR were divided into 5 groups: BD and BCR groups, with samples completely filled with the respective materials; MTA group, which utilized a 3-mm apical MTA plug; RRR group, which received no root canal filling; and normal periodontal ligament (PL) group, which had no RRR and no root canal filling. All the teeth underwent cycling loading, and compression strength testing was performed using a universal testing machine. RAW 264.7 macrophages were treated with 1:16 extracts of BD, BCR, and MTA containing receptor activator of nuclear factor-kappa B ligand (RANKL) for 5 days. RANKL-induced osteoclast differentiation was assessed by staining with tartrate-resistant acid phosphatase. The fracture load and osteoclast number were analyzed using 1-way ANOVA and Tukey's test (α = 0.05). Results: No significant difference in fracture resistance was observed among the groups (p > 0.05). All materials similarly inhibited osteoclastogenesis (p > 0.05), except for BCR, which led to a lower percentage of osteoclasts than did MTA (p < 0.0001). Conclusions: The treatment options for non-vital immature teeth with RRR did not strengthen the teeth and promoted a similar resistance to fractures in all cases. BD, MTA, and BCR showed inhibitory effects on osteoclast differentiation, with BCR yielding improved results compared to the other materials.