• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.975-981
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• 2013

A robust optimization is only one of the ways to minimize the effects of variances in design variables on the objective functions at the preliminary design stage. To predict the variances and to formulate the probabilistic constraints are the most important procedures for the robust optimization formulation. Though several methods such as the process capability index and the six sigma technique were proposed for the prediction and formulation of the variances and probabilistic constraints, respectively, there are few attempts using a percent defective which has been widely applied in the quality control of the manufacturing process for probabilistic constraints. In this study, the robust optimization for a lower control arm of automobile vehicle was carried out, in which the design space showing the mean and variance sensitivity of weight and stress was explored before robust optimization for a lower control arm. The 2nd order Taylor expansion for calculating the standard deviation was used to improve the numerical accuracy for predicting the variances. Simplex algorithm which does not use the gradient information in optimization was used to convert constrained optimization into unconstrained one in robust optimization.

• Steel and Composite Structures
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• v.35 no.6
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• pp.799-813
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• 2020

Fatigue cracks of rib-to-deck (RD) joints have been frequently observed in the orthotropic steel decks (OSD) using conventional U-ribs (CU). Thickened edge U-rib (TEU) is proposed to enhance the fatigue strength of RD joints, and its effectiveness has been proved through fatigue tests. In-depth full-scale tests are further carried out to investigate both the fatigue strength and fractography of RD joints. Based on the test result, the mean fatigue strength of TEU specimens is 21% and 17% higher than that of CU specimens in terms of nominal and hot spot stress, respectively. Meanwhile, the development of fatigue cracks has been measured using the strain gauges installed along the welded joint. It is found that such the crack remains almost in semi-elliptical shape during the initiation and propagation. For the further application of TEUs, the design curve under the specific survival rate is required for the RD joints using TEUs. Since the fatigue strength of welded joints is highly scattered, the design curves derived by using the limited test data only are not reliable enough to be used as the reference. On this ground, an experiment-numerical hybrid approach is employed. Basing on the fatigue test, a probabilistic assessment model has been established to predict the fatigue strength of RD joints. In the model, the randomness in material properties, initial flaws and local geometries has been taken into consideration. The multiple-site initiation and coalescence of fatigue cracks are also considered to improve the accuracy. Validation of the model has been rigorously conducted using the test data. By extending the validated model, large-scale databases of fatigue life could be generated in a short period. Through the regression analysis on the generated database, design curves of the RD joint have been derived under the 95% survival rate. As the result, FAT 85 and FAT 110 curves with the power index m of 2.89 are recommended in the fatigue evaluation on the RD joint using TEUs in terms of nominal stress and hot spot stress respectively. Meanwhile, FAT 70 and FAT 90 curves with m of 2.92 are suggested in the evaluation on the RD joint using CUs in terms of nominal stress and hot spot stress, respectively.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.78-86
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• 2005

This study considers the magnitude of the harmonic components radiated from the ultrasonic contrast agents (UCA) activated by a typical diagnostic ultrasound. The nonlinear dynamic response of UCA to a 2 MHz diagnostic ultrasound pulse was predicted using Gilmore Model. The elastic property of the shell membrane of the UCA was ignored in the numerical model. Simulation was carried out for the UCA varying from 1 - 9 $\mu$m in its initial radius and the driving diagnostic ultrasound whose mechanical index (MI) ranges from 0.125 to 8. The powers of the sub. ultra and second harmonics of the acoustic signal from the UCA activated were compared with that of the fundamental component. The results show that. if the UCA is bigger than its resonant size (2 $\mu$m in radius for the present case) the sub harmonic power was much bigger than the fundamental. In particular, the 2nd harmonic component currently used as an imaging parameter for the harmonic imaging, was predicted to be lower in power than both the sub and the ultra harmonic component. This study indicates that, for obtaining harmonic imaging with UCA, the sub or ultra harmonics could be taken as imaging parameters better than the 2nd harmonic component.

• Tunnel and Underground Space
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• v.14 no.5
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• pp.327-338
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• 2004

The purpose of this research is to establish a concept of the factor of safety of tunnels which is a quantitative estimate of the stability of tunnels. Based on this concept, a numerical technique which calculates the factor of safety of tunnels was developed. To obtain the safety factor of a tunnel, the strength reduction technique in which a series of analyses are repeated with reduced ground strength until the tunnel collapses were employed. With this technique, the failure plane, as well as the factor of safety, can be obtained without prescribing the trial failure plane. Analyses were conducted with FLA $C^{2D}$(ver3.3), a geotechnical analysis program which is based on the finite difference method. From the result, the location of plastic zones, the maximum convergence and the maximum stress generated in the support system were also analyzed. The result shows that factors of safety are higher for the 1st and 2nd rock classes, and lower for the lower rock classes. Furthermore, factor of safety is higher when $K_{0}$ =0.5 compared to at in case of $K_{0}$ =2.0. Through this research, it is found that the factor of safety defined in this research can be used as a good quantitative index representing the stability of tunnels. Also, close examination of the results can help adjustment of the quantity and location of additional supports.s.

• Journal of Acupuncture Research
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• v.33 no.1
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• pp.103-116
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• 2016

Objectives : This study was performed to assess the effectiveness of conservative Korean traditional medical treatment on lumbar intervertebral disc herniation in 12 adolescents. Methods : Data were collected from adolescent patients diagnosed with lumbar intervertebral herniation by MRI, hospitalized at Jaseng Korean Medicine Hospital from January 1, 2014 to December 31, 2015. A total of 12 patients were included in the study. Patients were treated by acupuncture, pharmacopuncture, electroacupuncture, herbal medicine, chuna manual therapy, physical therapy during hospitalization period. To measure treatment outcomes, a verbal numerical rating scale (VNRS), Oswestry disability index (ODI), range of motion (ROM), Straight leg raising test (SLR), and EQ-5D were used. Results : The average age of the participants was $16.05{\pm}1.62$. The average of duration of symptom was $19.25{\pm}26.83(weeks)$ and the average length of hospitalization was $23.8{\pm}16.4(days)$. 2 patients (17 %) suffered from only lumbar pain, while 10 patients (83 %) suffered from lumbar and leg pain. No participant suffered from only leg pain. 8 patients (67 %) were diagnosed with disc herniation in one segment, and 4 patients (33 %) were diagnosed with disc herniation in multiple segments. A total of 17 disc segments (28 %) were herniated. The most herniated lumbar level was L4-5. 3 segments were diagnosed with bulging (17 %), 6 with protrusion (35 %), and 8 with extrusion (47 %). Extrusion was the most frequent herniated type. After treatment, the average VNRS of lumbar pain significantly decreased from $5.58{\pm}1.62$ to $2.91{\pm}1.56$ (p<0.001) and the average VNRS of leg pain significantly decreased from $5.16{\pm}2.51$ to $3.08{\pm}1.8$ (p<0.001). ODI significantly decreased from $48.87{\pm}18.72$ to $28.57{\pm}15.05$ (p<0.05), and EQ-5D significantly increased $0.58{\pm}0.31$ to $0.80{\pm}0.12$ (p<0.05). Range of flexion significantly improved from $61.25{\pm}32.62$ to $68.33{\pm}26.22$ (p<0.05). Conclusion : Conservative Korean Traditional Medical Treatment may be effective in the treatment of lumbar intervertebral disc herniation in adolescence. However, more case reports and clinical research are needed.

• Journal of Oral Medicine and Pain
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• v.33 no.2
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• pp.133-145
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• 2008

The purpose of this study was to investigate the taste sensitivity in patients with oral mucosal diseases(Oral lichen planus(OLP), Recurrent apthous ulcer(RAU)) using electrogustometer. One hundred and seventy three subjects were included for the study and they were categorized into 2 groups(control 100, patient 73) and patient group was investigated in the Department of Oral Medicine, Pusan National University Hospital from April, 2005 until January, 2007. Control group was investigated in the clinics at Inchen Metroplitan city and Cheongju city from February to August, 2006. The electrical taste thresholds were measured by using an electrogustometer for the 4 different sites(tongue tip, tongue lateral, circumvallate papilla and soft palate) in oral cavity. The results were as follows ; 1. The electrical taste threshold in patient group was significantly decreased than that in the control group(p<0.001). 2. The electrical taste threshold, in terms of the chronicity and lesion multiplicity, was not significantly changed in patient group. 3. The electrical taste threshold was not significantly changed in Dexan only and Dexan+Prs combination treated group. 4. The electrical taste threshold, in terms of treatment progress(no response vs half response vs complete response), was not significantly changed. However subjective index which was determined by NAS(Numerical Analogy Scale) was significantly increased in no response group but significantly decreased in complete response group(p<0.001)

• Journal of Acupuncture Research
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• v.32 no.4
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• pp.157-165
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• 2015

Objectives : This study was designed to compare the effect of Shinbaro pharmacopuncture treatment and Jakyakgamcho Decoction pharmacopunture treatment in patients with low back pain caused by traffic accidents. Methods : This study was conducted on 64 cases of patients with low back pain caused by traffic accidents, who were admitted to Bucheon Jaseng Hospital of Korean Medicine from May 3rd, 2015 to October 31th, 2015. The patients were divided into two groups : Shinbaro pharmacopuncture treatment group and Jakyakgamcho Decoction pharmacopunture treatment group. We measured the efficacy of treatment with a numerical rating scale(NRS) and Oswestry disability index(ODI). The NRS which was checked at pre-tretment and after 4th and 8th treatments, and the ODI which was checked at pre-treatment and after 8th treatment were collected and analyzed. Results : In both Shinbaro and Jakyakgamcho Decoction group, NRS and ODI decreased significantly. However there was no statistically significant difference between the groups. At the 4th treatment, However, the Jakyakgamcho Decoction group showed a greater decrease in NRS with a statistically significant difference. Conclusions : In a short period of time, Jakyakgamcho Decoction Pharmacopuncture is more efficient than Shinbaro pharmacopuncture in reducing the pain of patients with low back pain caused by trafficic accidents, but in the end there is no statistically significant difference between the groups.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.7 no.2
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• pp.53-61
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• 2012

Objectives : The Purpose of this study is to compare the effect of ShinBaro Pharmacopuncture Treatment and Bee Venom Pharmacopuncture Treatment of low back pain and radicular pain caused by spondylolisthesis. Methods : From January 1st,2012 to September 30th, 2012, 30 Low back pain and radicular pain patients with spondylolisthesis who were admitted to Bu-Cheon Jaseng Hospital of Oriental Medicine were divided into two groups. ShinBaro group was treated by ShinBaro Pharmacopuncture Treatment and Bee Venom group was treated by Bee Venom Pharmacopuncture Treatment. We evaluated the treatment effect of each group with numerical rating scale(NRS) and Oswestry disability index(ODI). The evaluations performed at admission day and 14th day after admission. Results : In both ShinBaro group and Bee Venom group, NRS and ODI decreased significantly in ststistics as treatment was perfomed. Though ShinBaro group showed a decreasing ODI score compared to BV group and BV group showed a decreasing NRS score compared to Shinbaro group, There is no statistical significance on NRS and ODI score after the treatment in both groups. Conclusions : The result sugguest that both ShinBaro pharmacopuncture treatment and Bee Venom pharmacopuncture treatment is considered to be effective and useful on low back pain and radicular pain caused by spondylolisthesis, although further study is needed.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.7 no.2
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• pp.63-74
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• 2012

Objectives : The purpose of this study was to evaluate the effect of Oriental medical treatment in patients with Spondylolisthesis and lumbar Herniated Intervertebral Disc(HIVD). Methods : This clinical study was carried out on 39 patients with Spondylolisthesis and lumbar Herniated Intervertebral Disc(HIVD), who had been admitted from Jan. 2012 to Nov. 2012. All of 39 patients were treated with acupuncture, Chuna treatment and herbal medicine during the whole admission period. Verbal numerical rating scale(VNRS) and Oswestry disability index(ODI) were used to evaluated the effectiveness of the Oriental medical treatment. Results : 1. Significant improvement of the symptoms of low back pain and leg pain on 39 patients with Spondylolisthesis and lumbar Herniated Intervertebral Disc(HIVD) was seen when evaluated with VNRS and ODI. 2. There was no significant difference of improvement by herniated type when evaluated with VNRS and ODI.. 3. There was no significant difference of improvement by spondylolisthesis type(degenerative and spondylolytic) when evaluated with VNRS and ODI. Conclusions : These results suggest that in the case of low back pain and lower limb numbness caused by Spondylolisthesis and HIVD, conservative treatments can be considered as one of the options of treating the symptoms beside surgical way.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.7 no.2
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• pp.119-129
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• 2012

Objectives : The purpose of this study was to evaluate the effect of electro-acupuncture treatment for low back pain and radicular pain in patients diagnosed with Lumbar HIVD. Methods : This clinical study was carried out on 92 patients with low back pain and radicular pain diagnosed with HIVD, who had been admitted from Mar. 2011 to Dec. 2011. 60 patients were divided into two groups, group A and group B, of 46 patients each. Group A was treated with electro-acupuncture treatment and general acupuncture treatment twice per day for more than 2 weeks. Group B was treated with general acupuncture treatment twice per day for more than 2 weeks. Verbal numerical rating scale(VNRS) and Oswestry disability index(ODI) were used to evaluated the effectiveness of the Oriental medical treatment. Results : In both two groups, VNRS, ODI, patient's condition grade decreased significantly in ststistics as treatment was perfomed. Between the two groups there was no significant difference in the VNRS, patient's condition grade. But there was significant difference in the ODI. Conclusions : These results suggest that both electro-acupuncture and general acupuncture were effective in reducing low back pain and radicular pain caused by HIVD. More systematic clinical stuty on electro-acupuncture is needed.