• Korean Journal of Dental Materials
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• v.44 no.1
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• pp.69-77
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• 2017

The aim of this study was to investigate the effects of chitosan powder addition on the strengthening of conventional glass ionomer cement. Two types of chitosan powders with different molecular weight were mixed with conventional glass ionomer cement (GIC): low-molecular weight chitosan (CL; 50~190 kDa), high-molecular weight chitosan (CH; 310~375 kDa). The chitosan powders (CL and CH) were separately added into the GIC liquid (0.25-0.5 wt%) under magnetic stirring, or mixed with the GIC powder by ball-milling for 24 h using zirconia balls. The mixing ratio of prepared cement was 2:1 for powder to liquid. Net setting time of cements was measured by ISO 9917-1. The specimens for the compressive strength (CS; $4{\times}6mm$), diametral tensile strength (DTS; $6{\times}4mm$), three-point flexure (FS; $2{\times}2{\times}25mm$) with flexure modulus (FM) were obtained from cements at 1, 7, and 14 days after storing in distilled water at $(37{\pm}1)^{\circ}C$. All mechanical strength tests were conducted with a cross-head speed of 1 mm/min. Data were statistically analyzed by one-way ANOVA and Tukey HSD post-hoc test. The mechanical properties of conventional glass ionomer cement was significantly enhanced by addition of 0.5 wt% CL to cement liquid (CS, DTS), or by addition of 10 wt% CH (FS) to cement powder. The CL particles incorporated into the set cement were firmly bonded to the GIC matrix (SEM). Within the limitation of this study, the results indicated that chitosan powders can be successfully added to enhance the mechanical properties of conventional GIC.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.113-129
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• 2019

A four-variable shear deformation refined plate theory has been proposed for dynamic characteristics of smart plates made of porous magneto-electro-elastic functionally graded (MEE-FG) materials with various boundary conditions by using an analytical method. Magneto-electro-elastic properties of FGM plate are supposed to vary through the thickness direction and are estimated through the modified power-law rule in which the porosities with even and uneven type are approximated. Pores possibly occur inside functionally graded materials (FGMs) due the result of technical problems that lead to creation of micro-voids in these materials. The variation of pores along the thickness direction influences the mechanical properties. The governing differential equations and boundary conditions of embedded porous FGM plate under magneto-electrical field are derived through Hamilton's principle based on a four-variable tangential-exponential refined theory which avoids the use of shear correction factors. An analytical solution procedure is used to achieve the natural frequencies of embedded porous FG plate supposed to magneto-electrical field with various boundary condition. A parametric study is led to carry out the effects of material graduation exponent, coefficient of porosity, magnetic potential, electric voltage, elastic foundation parameters, various boundary conditions and plate side-to-thickness ratio on natural frequencies of the porous MEE-FG plate. It is concluded that these parameters play significant roles on the dynamic behavior of porous MEE-FG plates. Presented numerical results can serve as benchmarks for future analyses of MEE-FG plates with porosity phases.

• The Korean Journal of Pain
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• v.34 no.4
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• pp.454-462
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• 2021

Background: This study was performed to reveal the relationships between the cross-sectional areas (CSAs) of the paraspinal muscles and the severity of low back pain (LBP), including the level of disability. Methods: This single-center cross-sectional study was conducted on 164 patients with chronic LBP. The effects of demographic characteristics, posture, level of physical activity, disc herniation type, and sarcopenia risk on the CSAs of paraspinal muscles were evaluated along with the relationship between the CSAs and severity of pain and disability in all patients. The CSAs of paraspinal muscles were evaluated using the software program Image J 1.53. Results: A negative significant correlation was found between age and the paraspinal muscle's CSA (P < 0.05), whereas a positive correlation was present between the level of physical activity and the CSA of the paraspinal muscle at the L2-3 and L3-4 levels. The CSAs of paraspinal muscles in patients with sarcopenia risk was significantly lower than those in patients without sarcopenia risk (P < 0.05). The CSAs of paraspinal muscles at the L2-3 and L3-4 levels in obese patients were significantly higher than those in overweight patients (P = 0.028, P = 0.026, respectively). There was no relationship between the CSAs of paraspinal muscles and pain intensity or disability. Conclusions: Although this study did not find a relationship between paraspinal CSAs and pain or disability, treatment regimens for preventing paraspinal muscles from atrophy may aid pain physicians in relieving pain, restoring function, and preventing recurrence in patients with chronic LBP.

• Nano
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• v.13 no.11
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• pp.1850125.1-1850125.12
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• 2018

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.

• Clinics in Shoulder and Elbow
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• v.21 no.4
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• pp.207-212
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• 2018

Background: Delaminated rotator cuff tear is known to be a degenerative tear having a negative prognostic effect. This study undertook to compare the anatomical and clinical outcomes of delaminated tears and single layer tears. Methods: Totally, 175 patients with medium to large rotator cuff tears enrolled for the study were divided into 2 groups, based on the tear pathology: single layer tear (group 1) and delaminated tear (group 2). Preoperatively, length of the remnant tendon, muscle atrophy of supraspinatus (SS), and fatty degeneration of SS and infraspinatus (IS) muscles were assessed on magnetic resonance imaging (MRI). For follow-up, the repair integrity of the rotator cuff was evaluated by ultrasonography. Clinical outcomes were assessed by evaluating the Constant score (CS) and Korean Shoulder Score (KSS). Results: Retears were detected in 6 cases of group 1 (6.5%) and 11 cases of group 2 (13.3%). Although higher in group 2, the retear rate was significantly not different (p=0.133). Preoperative MRI revealed length of remnant tendon to be $15.46{\pm}3.60mm$ and $14.17{\pm}3.16mm$ (p=0.013), and muscle atrophy of SS (occupation ratio) was $60.54{\pm}13.15$ and $56.55{\pm}12.88$ (p=0.045), in group 1 and group 2, respectively. Fatty degeneration of SS and IS in both groups had no significant differences. Postoperatively, no significant differences were observed for CS and KSS values between the groups. Conclusions: Delaminated rotator cuff tears showed shorter remnant tendon length and higher muscle atrophy that correlate to a negative prognosis. These prognostic effects should be considered during delaminated rotator cuff tear treatment.

• Tribology and Lubricants
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• v.35 no.2
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.281-291
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• 2021

This study aimed to measure the quantitative changes in images according to the use of compressed sensing in expressing the slow flow rate in TOF MRA test using magnetic resonance imaging. This study set different blood flow rate sections by using auto-injector and flow phantom and compared changes in the SNR, CNR, SSIM, and RMSE measurements by different CS factors between TOF with CS and TOF without CS. One-way ANOVA was performed to test the effect on the image induced by the increase of the CS factor. The results revealed that TOF MRA with CS significantly decreased scan time without significantly affecting SNR and CNR compared to TOF MRA with CS. On the other hand, the differences in SSIM and RMSE between TOF with CS and TOF without CS increased as the CS factor increased. Therefore, it is necessary to efficiently reduce scan time by adapting the CS technique while considering the appropriate range of the CS factor. Additionally, more studies are needed to evaluate CS factors and the similarity precision of images further.

• Journal of Korean Physical Therapy Science
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• v.28 no.3
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• pp.42-52
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• 2021

Background: The purpose of this study was to investigate the effects of the severity and direction of lumbar disc herniation (LDH) on the facet joints and paraspinal muscles. Design: Cross-sectional design. Methods: The subjects were divided according to the diagnosis for severity of unilateral herniation of L4-L5 disc. The groups consisted of disc protrusion group (n=15), disc extrusion group (n=15), and no disc herniation group (n=15). The asymmetry and angle of facet joints and the cross-sectional area of paraspinal muscles were analyzed and compared using magnetic resonance imaging (MRI). Results: The results showed that the angle of facet tropism was larger in disc extrusion group than the disc protrusion group and the difference was found to be significant difference (p<0.01). In addition, when both left and right angles of patients with unilateral disc herniation were measured, the results showed larger facet joint angle in the herniated area of the disc extrusion group than in the disc protrusion group. When paraspinal muscles were measured according to the severity of disc herniation and the degree of facet joint asymmetry, there was no difference in paraspinal muscles between the disc protrusion and disc extrusion groups. Meanwhile, the multifidus muscle was smaller in the group with facet tropism than the group without facet tropism (p<0.03), while there were no significant differences in the erector spinae and psoas muscles. Conclusion: Progression of disc herniation resulted in increased facet joint tropism, increased angle of the facet joints in the direction of disc herniation, and decreased size of the multifidus muscle.

• The Journal of Internal Korean Medicine
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• v.43 no.4
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• pp.751-760
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• 2022

Objective: To show a decrease in tumor recurrence and improvement in quality of life in patients with recurrent cervical cancer. Method: A 58-year-old female patient diagnosed with recurrent cervical cancer in February 2021 was treated for 14 months with integrative cancer treatment (ICT) to decrease the tumor size and improve chemotherapy-induced peripheral neuropathy (CIPN) and nausea. The patient underwent chemotherapy or concomitant chemoradiation therapy (CCRT) with ICT. Radiologic outcomes were assessed by abdomen & pelvis computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT) based on the Response Evaluation Criteria in Solid Tumors (RECIST) protocol. Clinical outcomes were assessed by the National Cancer Institute Common Terminology Criteria for Adverse Event (NCI-CTCAE), Eastern Cooperative Oncology Group (ECOG), and a numeric rating scale (NRS). Result: During the 14 months of treatment, the size and metabolic activity of the recurrent tumor decreased and underwent partial remission based on RECIST. The NRS scores for CIPN and nausea were improved, and the ECOG score improved from grade 2 to 1. No serious side effects of grade 3 or higher were noted on the NCI-CTCAE test. Conclusion: This case suggests that ICT may have a synergetic effect with chemotherapy or radiotherapy for recurrent cervical cancer.

• Journal of Acupuncture Research
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• v.39 no.3
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• pp.151-158
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• 2022

Changes in symptoms and dysfunction related to meniscus tears following the use of Korean medicine for ≥ 4 days were studied. The medical charts of 53 cases of diagnosed meniscus tears (magnetic resonance imaging) with an admission Numeric Rating Scale (NRS) score ≥ 4, between 2017 and 2022 were retrospectively reviewed. Treatments included acupuncture, pharmacopuncture, herbal treatment, Chuna therapy, and physiotherapy. The NRS, Western Ontario and McMaster Universities Osteoarthritis Index, and European Quality of Life 5 Dimensions were performed at admission and discharge. There were 42 females and 11 males in this study. Patients were more likely to be in their 60s (38.18%), have an unknown etiology (81.13%), and have complex tears (50.94%). After receiving a combination of alternative Korean medicine during hospitalization, the mean NRS score improved from 6.82 ± 1.19 to 3.66 ± 1.83 (p < 0.001), the Western Ontario and McMaster Universities Osteoarthritis Index score improved from 46.47 ± 20.99 to 37.98 ± 19.23 (p < 0.001), and the mean European Quality of Life Five Dimensions score improved from 0.61 ± 0.18 to 0.68 ± 0.14 (p < 0.001) after treatment. These results suggest that Korean medicine treatment of meniscus tears alleviated pain and improved physical function.