• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.295-301
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• 2011

Recently, the use of UHPC made of superplasticizers, silica fume, and steel fibers has been increasing worldwide. Although UHPC has a very high strength as well as an excellent durability performance due to its dense microstructures, earlyage cracks may occur due to the high heat of hydration and autogenous shrinkage caused by low W/B and high unit cement content. The early-age shrinkage cracking of UHPC can be controlled by using the shrinkage reducers and expansive admixtures having autogenous shrinkage compensation effect. In this paper, ultrasonic pulse velocity of UHPC containing shrinkage reducers and expansive agents was measured to predict its stiffness change. Also, the effect of shrinkage reducers and expansive agents on the autogenous shinkage of UHPC was investigated through the shrinkage test of UHPC specimens. Furthermore, the material coefficients of autogenous shrinkage prediction model were determined using the autogenous shrinkage values of UHPC with age. Consequently, the test results showed that, by adding shrinkage reducers and expansive agents, the stiffness of UHPC was rapidly developed at early-ages and the autogenous shrinkage was considerably reduced.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.33-42
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• 2009

A polymer-based flexible neural probe was fabricated for monitoring of neural activities from a brain. To improve the insertion stiffness, a 5 ${\mu}m$ thick biocompatible Au layer was electroplated between the top and bottom polymer layers. The developed neural probe penetrated a gel whose elastic modulus is similar to that of a live brain tissue without any fracture, To minimize mechanical residual stress and bending from the probe, two new methods were employed: (1) use of a thermal annealing process after completing the device and (2) incorporation of multiple different layers to compensate the residual stress between top and bottom layers. Mechanical bending around the probe tip was clearly removed after employing the two processes. In electrical test, the developed probe showed a proper impedance value to record neural signals from a brain and the result remained the same for 72 hours. In simple in-vitro probe characterization, the probe showed a great removal of residual stress and an excellent recording performance. The in-vitro recording results did not change even after 1 week, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.271-281
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• 2021

Purpose : This study aimed to apply muscle relaxation exercise and ultrasound therapy as an effective treatment method for tension headache patients by comparatively analyzing the muscle mechanical properties, neck disorder index, and headache impact test. Method : The subjects were classified into three groups based on the intervention received: the therapeutic ultrasound (n=15, group I), placebo therapeutic ultrasound combined with the suboccipital release (n=15, group II), and therapeutic ultrasound combined with suboccipital release (n=15, group III) groups. The intragroup and intergroup differences in muscle mechanical properties, neck disability index, and headache impact test were compared and analyzed. Result : The comparison and analyses of the changes in muscle tone and post hoc analysis revealed statistically significant intragroup decreases in the suboccipitalis and upper trapezius in groups I and III. Furthermore, statistically significant intergroup differences in the upper trapezius with a greater change in group III than in group II and suboccipitalis with greater changes in group III than in groups I and II were observed. The comparison and analyses of the changes in muscle stiffness and post hoc analysis revealed statistically significant intragroup decreases in the upper trapezius in group I and suboccipitalis in group III. Moreover, statistically significant intergroup differences in both muscles with greater changes in group III than in group II for both cases were observed. The comparison and analyses of the changes in the neck disability index and post hoc analysis revealed statistically significant intragroup decreases in all three groups and statistically significant intergroup differences with greater changes in group III than in groups I and II. The comparison and analyses of the changes in the headache impact test and post hoc analysis revealed statistically significant intragroup decreases in all three groups and a statistically significant intergroup difference with greater changes in group III than in groups I and II. Conclusion : The therapeutic ultrasound and suboccipital muscle release exercise effectively increased the flexibility of the muscles around the cervical vertebrae and reduced muscle tension and stiffness in tension-type headache patients.

• The Korea Journal of Herbology
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• v.29 no.4
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• pp.45-52
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• 2014

Objectives : The purpose of this study was to evaluate the efficacy of HT008 on pain relief and functional improvement in participants with mild knee osteoarthritis (OA) in comparison with that of glucosamine sulfate. Methods : This randomized double-blind trial was conducted at Kyung Hee University Medical Center in Seoul where participants with knee pain for more than 6 months and degenerative osteoarthritis were enrolled. The 100 participants were received either HT008 or glucosamine sulfate 750 mg twice daily for 8 weeks and evaluated at baseline, 4 and 8 weeks after the treatment. We primarily evaluated the differences between two groups with respect to changes in the visual analogue score (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score from baseline to week 8. Secondarily the difference between and within two groups with respect to changes in WOMAC stiffness and physical function score, and Lequesne Functional Severity Index (LFI) were also evaluated. Results : At week 8, treatment with HT008 resulted in a significant reduction of the VAS for pain and WOMAC pain scores compared to the glucosamine sulfate (both p=0.003). Patients receiving HT008 experienced statistically significantly greater improvements in WOMAC physical function scores and LFI (p = 0.014 and p=0.016, respectively) than glucosamine sulfate-treated group. The within-group change in WOMAC physical function and stiffness, and LFI during the 8-week intervention revealed significant improvements in HT008-treated group. Conclusions : HT008 treatment allows significant pain reduction and functional improvement compared with glucosamine sulfate. These data confirm HT008 as an effective and safe symptomatic drug for knee OA.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.667-674
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• 2022

In this study, the correlation between the damage type and operating conditions of the sleepers was analyzed based on the design data and visual inspection results for the concrete sleepers of the sleeper floating track (STEDEF) that have been in operation for more than 20 years. It appeared in the form of cracks, breakages, and breaks in the concrete at the center and tie bar contact and buried areas. As a result of the numerical analysis, it was analyzed that the change in the left and right spring stiffness of the sleeper resilience pad increases the maximum stress, tensile stress, compressive stress, and displacement of the concrete sleeper, and stress concentration in the concrete at the tie bar contact area. It was proved analytically that the sleeper resilience pad can affect the damage of the concrete sleeper. Therefore, damage of concrete sleepers in the sleeper floating track in urban transit could be caused by changes in spring stiffness of sleeper resilience pads. It was reviewed that preventive maintenance such as improvement and timely replacement of sleeper resilience pads was necessary.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.94-103
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• 2023

Built in urban ares tunnels is necessary to accurately grasp not only the above-ground environment of the tunnel but also the below-ground environment of the tunnel for design and construct. However, fully coupled analysis of stress and flow is very difficult due to the limited function of the tunnel numerical analysis program and difficulty in using program. This can lead to excessive design that increases the construction cost or occur problems that can lead to accidents during construction. In particular, in the case of an urban tunnel has a low layer soil section above the tunnel and the groundwater level exists in the upper layer of the tunnel. Therefore, a reduction in the groundwater level during underground construction may increase the effective stress of the upper layer and cause the ground to subsidence. So It is necessary to design after accurately evaluating the change in the groundwater level. In this study, the tunnel's behavioral characteristics were analyzed through fully coupled analysis of stress and flow according to the drainage type for an urban underground tunnel.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.1
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• pp.18-26
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• 1997

There are two types of phonetic study, acoustic and physiologic, for differentiating the three manner categories of Korean stop consonants. On the physiologic studies, there are endoscopic, electromyographic(EMG), electroglottographic(EGG) and aerodynamic studies. In this study, I tried to investigate general features of Korean stops using EGG study for the open quotient of vocal fold and baseline shift during speech, and aerodynamic characteristics for e subglottal air pressure, air flow and glottal resistance at consonants. On the aerodynamic study, the glottalized and aspirated stops may be characterized by e increasing subglottal pressure comparing with lenis stop at consonants. The airflow is largest in the aspirated stops followed by lenis stops and glottalized. The glottal airway resistance (GAR) showed highest in the glottalized followed by the lenis, but lowest in e aspirated during e production of consonants, and showed highest in e aspirated, but low in the glottalized and lenis during the production of vowel. The glottal resistance at consonant showed significant difference among consonants and significant interaction between subject and types of consonant. The glottal resistance at vowel showed significant difference among consonants, and e interaction occured between subject and types of consonant. The electroglottography(EGG) has been used for investigating e functioning of e vocal folds during its vibration. The EGG should be related to the patterns of the vocal fold vibration during phonation in characterizing the temporal patterns of each vibratory cycle. The purpose of this study is to investigate the dynamic change of EGG waveforms during continuous speech. The dynamic changes of EGG waveforms fir the three-way distinction of Korean stops were characterized that the aspirated stop appears to be characterized by largest open quotient and smallest glottal contact area of the vocal folds in e initial portion of vocal fold vibration ; the lenis stop by moderate open quotient and glottal contact area ; but the glottalized stop by smallest open quotient and largest glottal contact area. There may be close relationship between the OQ(open quotient) in the initial voice onset and the glottal width at the time of consonant production, the larger glottal width just before vocal fold vibration results in the smaller OQ of the vocal fold vibration in the initial voice onset. The EGG changes of baseline shift during continuous speech production were characterized by the different patterns for the three types of Korean consonants. The small and less stiffness change of baseline shift was found for the lenis and the glottalized, and the largest and stiffest change was found for the aspirated. On the baseline shift for the initial voice onset, they showed so similar patterns with for the consonant production, larger changed in the aspirated. for the lenis and the glottalized during the initial voice onset, three subjects showed individual difference each other. I suggest at s characteristics were strongly related with articulatory activity of vocal tract for the production of consonant, especially for the aspirated stop. The suspecting factors to affect EGG waveforms are glottal width, vertical laryngeal movement and the intrapharyngeal pressure to neighboring tissue during connected spech. So the EGG may be an useful method to describe laryngeal activity to classify pulsing conditions of the larynx during speech production, and EGG research can be controls for monitoring the vocal tract articulation, although above factors to affect EGG would have played such a potentially role on vocal fold vibratory behavior obtained using consonant production.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.543-552
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• 1994

A series of drained plane strain compression tests was performed on dried samples of dense Toyoura sand and Silver Leighton Buzzard sand prepared by air-pluviation method to find out the deformation and strength characteristics on the value of confining pressure ${\sigma}{_3}^{\prime}({\sigma}{_3}^{\prime}=0.05{\sim}4.0kgf/cm^2)$. The axial and lateral strains measured in this apparatus ranged from $10^{-6}$ up to the failure of the specimen. So the stress-strain characteristics would be investigated from very small to very large strain levels. It was found that the change of the angle of internal friction ${\phi}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$ with the change of ${\sigma}{_3}^{\prime}$ is very small when ${\sigma}{_3}^{\prime}$ is lower than higher. Furthermore, the effect of confining pressure on stiffness of sands was evaluated. It was also found that for the range of shear strain ${\gamma}$ from $10^{-6}$ to those at peak, the Rowe's stress-dilatancy relation seems to be a good approximation for air-dried Toyoura sand and Silver Leighton Buzzard sand, irrespective of the change of ${\sigma}{_3}^{\prime}$.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.39-50
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• 2015

The installation of the expansion joints in a tunnel concrete lining and duct would minimize the cracking at the location of structural shape and stiffness change, differential settlement, big temperature change, and so on. However, it is difficult to determine the required spacing of the expansion joint in a tunnel concrete lining and duct quantitatively because the spacing is influenced by temperature change, structure construction condition, ground-structure interaction, and etc. Nevertheless, a highway specification (Korea Expressway Corporation, 2012) or a road design manual (Ministry of Land, Transport and Maritime Affairs, 2010) specifies that the expansion joint spacing in a tunnel concrete lining should be installed uniformly smaller than 25 m from the tunnel portals to 50 m inside of a tunnel and elsewhre 20-60 m in a tunnel (because there is no specifcation for a duct it is assumed that a duct follows the specfication of lining). This specification results in several construction and economic problems in relation with a tunnel construction. Accordingly, in order to minimize the problems, this study analyzed both domestic and foreign design standards and specifications. In addition, field test, theoretical and numerical analyses were carried out in relation to the expansion joint in a tunnel lining and duct. The purpose of this study is to reestabilish a criterion for installing the expansion joint in a tunnel concrete lining and duct.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.362-370
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• 2019

This study was conducted to investigate effects of 12 weeks of combined exercise training with blood flow restriction (BFR) on body composition (weight, %body fat, lean body mass, body mass index (BMI)) and cardiovascular responses (brachial-ankle pulse wave velocity (ba PWV) and ankle-brachial index (ABI)) in elderly women. Participants (N = 43, Females) were randomly assigned into a combined exercise with BFR (n = 14, BFR), only combined exercise (n =14, EX) or non-exercise control group (n = 15, CON). Two-way repeated measures ANOVA with contrast testing was utilized for data analysis. Alpha was set at p < 0.05. Body composition (weight, %body fat, BMI) in BFR was significantly changed, and %body fat in EX was significantly decreased, but there was no change in the CON. In addition, the right and left ba PWV values in the BFR were significantly decreased, while only the left side ba PWV in EX was significantly decreased and there was no change in the CON. Moreover, the % change and effect size of most variables in the BFR were higher than the EX. Taken together, the results indicate that even though BFR and EX groups performed the same combined exercise training, BFR had additional stimulations of the sympathetic nerve system due to blood flow restriction. Thus, BFR training is more beneficial and has greater effects on body composition and cardiovascular responses in elderly females.