• 대한금속재료학회지
• /
• 제49권8호
• /
• pp.635-641
• /
• 2011

The effect of high shear speed on shear force, shear energy and fracture surface was investigated for the solder joint of a $Sn-_{3.0}Ag-_{0.5}Cu$ ball. For both ENIG and OSP pads, the shear force increased with an increase in shearing speed to 0.3 m/s. However, for an ENEPIG pad, the shear force increased with an increase in shear speed to 0.6 m/s and kept almost constant afterward. The shear energy decreased with an increase in shearing speed for ENIG and OSP pads. For the ENEPIG pad, however, the shear energy almost remained constant in a shearing speed range 0.3-3.0 m/s. The fracture mode analysis revealed that the amount of brittle fracture for the ENIG and the OSP pads increased with shearing speed, and a complete brittle fracture appeared at 1.0 m/s for ENIG and 2.0 m/s for OSP. However, the ENEPIG pad showed only a ductile fracture until 0.25 m/s, and a full brittle fracture didn't occur up to 3.0 m/s. The fracture mode matched well with the shear energy. The results from the high speed shear test of SAC305 were similar to those of SAC105.

• 한국전문물리치료학회지
• /
• 제28권1호
• /
• pp.65-71
• /
• 2021

Background: The hamstring is a muscle that crosses two joints, that is the hip and knee, and its flexibility is an important indicator of physical health in its role in many activities of daily living such as sitting, walking, and running. Limited range of motion (ROM) due to hamstring tightness is strongly related to back pain and malfunction of the hip joint. High-frequency diathermy (HFD) therapy is known to be effective in relaxing the muscle and increasing ROM. Objects: To investigate the effects of HFD on active knee extension ROM and hamstring tone and stiffness in participants with hamstring tightness. Methods: Twenty-four participants with hamstring tightness were recruited, and the operational definition of hamstring tightness in this study was active knee extension ROM of below 160° at 90° hip flexion in the supine position. HFD was applied to the hamstring for 15 minutes using the WINBACK device. All participants were examined before and after the intervention, and the results were analyzed using a paired t-test. The outcome measures included knee extension ROM, the viscoelastic property of the hamstring, and peak torque for passive knee extension. Results: The active knee extension ROM significantly increased from 138.8° ± 9.9° (mean ± standard deviation) to 143.9° ± 10.4° after the intervention (p < 0.05), while viscoelastic property of the hamstring significantly decreased (p < 0.05). Also, the peak torque for knee extension significantly decreased (p < 0.05). Conclusion: Application of HFD for 15 minutes to tight hamstrings immediately improves the active ROM and reduces the tone, stiffness, and elasticity of the muscle. However, further experiments are required to examine the long-term effects of HFD on hamstring tightness including pain reduction, postural improvement around the pelvis and lower extremities, and enhanced functional movement.

• Physical Therapy Rehabilitation Science
• /
• 제10권1호
• /
• pp.16-21
• /
• 2021

Objective: To control the rate at which body weight drops, forefoot initiates floor contact with the limb relatively extended at each joint. However, when the knee joints could not extend enough with going down the stairs, the forefoot cannot be contact initially. The purpose of this study was to investigate the differences between forefoot and whole foot in initial contract on soleus and tibialis anterior for health young adults when descending stairs. Design: A cross-sectional observational study design. Methods: Fifteen healthy young adults participated in this study. To compare between forefoot and whole foot in initial contact when going down the stairs, this study measured muscle activation on soleus and tibialis anterior. This study used the paired t-test to analyze the collected data and compare the supporting conditions. Results: After analyzing, the muscle activation of soleus was not statistically significant difference as 25.16% at forefoot initial contact and 24.37% at whole foot initial contact when descending stairs (p>0.05). However, the muscle activation of tibialis anterior muscle was significantly difference was 49.19% at forefoot contact and 71.55% at whole foot contact. Conclusions: The results of this study was that the muscle activation of the tibialis anterior was a higher at whole foot contact than that at fore foot contact when descending stairs. This study suggests that the landing strategy of the initial contact is a beneficial effect at the forefoot contact to maintain the postural balance and the muscle performance effectively when descending stairs in individuals with healthy young adults.

• 한국해양공학회지
• /
• 제35권4호
• /
• pp.266-272
• /
• 2021

Mooring systems are among the most important elements employed to control the motion of floating offshore structures on the sea. Considering the use of polymer material, a new method is proposed to address the creep characteristics rather than the method of using a tension load cell for measuring the tension of the mooring line. This study uses a synthetic mooring rope made from a polymer material, which usually consists of three parts: center, eye, and splice, and which makes a joint for two successive ropes. We integrate the optical sensor into the synthetic mooring ropes to measure the rope tension. The different structure of the mooring line in the longitudinal direction can be used to measure the loads with the entire mooring configuration in series, which can be defined as SMART (Smart Mooring and Riser Truncation) mooring. To determine the characteristics of the basic SMART mooring, a SMART mooring with a diameter of 3 mm made of three different polymer materials is observed to change the wavelength that responds as the length changes. By performing the longitudinal tension experiment using three different SMART moorings, it was confirmed that there were linear wavelength changes in the response characteristics of the 3-mm-diameter SMART moorings. A 54-mm-diameter SMART mooring is produced to measure the response of longitudinal tension on the center, eye, and splice of the mooring, and a longitudinal tension of 100 t in step-by-step applied for the Maintained Test and Fatigue Cycle Test is conducted. By performing a longitudinal tension experiment, wavelength changes were detected in the center, eye, and splice position of the SMART moorings. The results obtained from each part of the installed sensors indicated a different strain measurement depending on the position of the SMART moorings. The variation of the strain measurement with the position was more than twice the result of the difference measurement, while the applied external load increased step-by-step. It appears that there is a correlation with an externally generated longitudinal tensional force depending on the cross-sectional area of each part of the SMART mooring.

• Journal of Yeungnam Medical Science
• /
• 제39권3호
• /
• pp.235-243
• /
• 2022

Background: Intrahepatic cholangiocarcinoma (ICC) of the left liver often shows left-sided lymph node (LN) metastasis. If gastric lesser curvature is extensively dissected, it can induce an iatrogenic injury to the extragastric vagus nerve branches that control motility of the pyloric sphincter and lead to gastric stasis. To cope with such LN dissection-associated gastric stasis, we performed pyloroplasty preemptively. The objective of this study was to analyze our 20-year experience of preemptive pyloroplasty performed in 10 patients. Methods: We investigated clinical sequences of 10 patients with ICC who underwent preemptive pyloroplasty following left hepatectomy and extended left-sided LN dissection. Incidence of gastric stasis and oncological survival outcomes were analyzed. Results: All 10 patients were classified as stage IIIB due to T1-3N1M0 stage according to the 8th edition of American Joint Committee on Cancer staging system. The overall patient survival rate was 51.9% at 1 year, 25.9% at 2 years, and 0% at 3 years. Seven patients showed uneventful postoperative recovery after surgery. Two patients suffered from gastric stasis, which was successfully managed with supportive care. One patient suffered from overt gastric paresis, which was successfully managed with azithromycin administration for 1 month. Conclusion: We believe that preemptive pyloroplasty is an effective surgical option to prevent gastric stasis in patients undergoing extensive left-sided LN dissection. Azithromycin appears to be a potent prokinetic agent in gastroparesis.

• 한국운동역학회지
• /
• 제32권2호
• /
• pp.49-55
• /
• 2022

Objective: This study aims to verify the front squat motions using by two different surfaces, thereby elucidating the grounds for effective training environment that can minimize the risk of injury. Method: Total of 10 healthy male crossfit athletes were recruited for this study (age: 32.30 ± 3.05 yrs., height: 173.70 ± 5.12 cm, body mass: 82.40 ± 6.31 kg, 1RM: 160 ± 13.80 kg). All participants are those who know how to do front squats well with more than five years of crossfit athlete experience. All participants have sufficient experience in front squats on two types of surface which are soft surface (SS) and hard surface (HS). In each surface, participant perform 10reps of the front squat with 80% of the pre-measured 1RM. A 3-dimensional motion analysis with 8 infrared cameras and 2 channels of EMG was performed in this study. Paired sample t-test was used for statistical verification between two surfaces. The significant level was set at α=.05. Results: The significantly decreased rectus femoris muscle activation was found in SS compared with that of HS on phase 1 (p<.05). Also, ROM of ankle joint was significantly increased in the SS compare with that of HS on phase 1 (p<.05). The muscle activity ratio of gluteus maximus/rectus femoris showed a significant difference only in SS compared with that of HS on phase 1 (p<.05). Conclusion: In conclusion, Korean crossfit boxes should consider the use of hard surface, which has a relatively less risk of injury than soft surface, in selecting flooring materials. For the Crossfit athletes, they are also considered appropriate to train on a relatively hard surface.

• Genomics & Informatics
• /
• 제20권2호
• /
• pp.23.1-23.9
• /
• 2022

A survival prediction model has recently been developed to evaluate the prognosis of resected nonmetastatic pancreatic ductal adenocarcinoma based on a Cox model using two nationwide databases: Surveillance, Epidemiology and End Results (SEER) and Korea Tumor Registry System-Biliary Pancreas (KOTUS-BP). In this study, we applied two machine learning methods-random survival forests (RSF) and support vector machines (SVM)-for survival analysis and compared their prediction performance using the SEER and KOTUS-BP datasets. Three schemes were used for model development and evaluation. First, we utilized data from SEER for model development and used data from KOTUS-BP for external evaluation. Second, these two datasets were swapped by taking data from KOTUS-BP for model development and data from SEER for external evaluation. Finally, we mixed these two datasets half and half and utilized the mixed datasets for model development and validation. We used 9,624 patients from SEER and 3,281 patients from KOTUS-BP to construct a prediction model with seven covariates: age, sex, histologic differentiation, adjuvant treatment, resection margin status, and the American Joint Committee on Cancer 8th edition T-stage and N-stage. Comparing the three schemes, the performance of the Cox model, RSF, and SVM was better when using the mixed datasets than when using the unmixed datasets. When using the mixed datasets, the C-index, 1-year, 2-year, and 3-year time-dependent areas under the curve for the Cox model were 0.644, 0.698, 0.680, and 0.687, respectively. The Cox model performed slightly better than RSF and SVM.

• Journal of Korea Trade
• /
• 제24권6호
• /
• pp.1-18
• /
• 2020

Purpose - This study investigates whether a listing effect exists in cross-border M&As and whether the effect can be attributed to the uncertainty of the GDP growth rate in the target firm's home country. We apply a joint variable analysis using M&A announcement data from the Korea Exchange (KRX), Shanghai Stock Exchange (SSE), and the Taiwan Stock Exchange (TWSE) from 2004 to 2013. We also conduct an event study using the measure of the uncertainty of the GDP growth rate (based on IMF statistics) in 55 target countries. Design/methodology - We measure the abnormal return (AR) using the market-adjusted model. We test the significance of the AR and the cumulative abnormal return (CAR) using a one-sample t-test. We examine the characteristics of the CARs depending on whether the target company is listed by applying a difference analysis using CAR as a test variable. In addition, we set CAR (-5, +5) as a dependent variable to identify the cause of the listing effect, and test both the financial characteristic variables of the acquirer and the collective characteristic variables of the merger as independent variables in the multiple regression analysis. Findings - First, we find the listing effect of cross-border M&As in the KRX, SSE, and TWSE, which represent the capital markets in Korea, China, and Taiwan, respectively. This listing effect persists during the global financial crisis and has a negative effect on the wealth of acquiring shareholders, especially when the target countries are emerging markets. Second, greater uncertainty regarding the target countries' economic growth in cross-border M&As has a negative effect on the wealth of acquiring firms' shareholders. Third, our empirical analysis demonstrates that the listing effect is attributable to the fact that firms listed in a target country with greater uncertainty of economic growth are more directly and greatly exposed to uncertain capital markets through stock markets, than are unlisted firms. Originality/value - This study is significant in that it presents a new strategic perspective in the study of cross-border M&As by demonstrating empirically that the listing effect is attributable to the uncertainty regarding the economic development of the target firms' home countries.

• 한국전문물리치료학회지
• /
• 제29권1호
• /
• pp.64-69
• /
• 2022

Background: Gluteus medius muscle is important for the stability of hip joint. The sufficient core stability can be contributed to the performance of gluteus medius muscle in standing position. In addition, the external support may affect core stability in standing position. Objects: The purpose of this study was to investigated the effectiveness of the external support on the strength and muscle activity of hip abductor muscle during hip abduction in standing position in subjects without core stability. Methods: Fifteen subjects participated in this study. The subjects were evaluated by using the double-leg lowering with bent knees to measure the core stability. The strength and muscle activity of hip abductors was measured in standing position with the condition with and without external support using the tensiometer sensor and the surface electromyography. The paired t-test was used to investigate the difference between hip abductor strength and activity according to external support. The level of statistical significance was set at α = 0.05. Results: The hip abductor strength and muscle activity of gluteus medius muscle with external support were significantly greater than those without external support during hip abduction in standing position (p < 0.05). Conclusion: During hip abduction in standing position, the external support may be contributed to the improvement of the hip abductor strength and muscle activity of gluteus medius especially in the subjects without core stability.

• 센서학회지
• /
• 제31권5호
• /
• pp.307-311
• /
• 2022

With the development of Internet of Things (IoT) technologies, numerous people worldwide connect with various electronic devices via Human-Machine Interfaces (HMIs). Considering that HMIs are a new concept of dynamic interactions, wearable electronics have been highlighted owing to their lightweight, flexibility, stretchability, and attachability. In particular, wearable strain sensors have been applied to a multitude of practical applications (e.g., fitness and healthcare) by conformally attaching such devices to the human skin. However, the stretchable elastomer in a wearable sensor has an intrinsic stretching limitation; therefore, structural advances of wearable sensors are required to develop practical applications of wearable sensors. In this study, we demonstrated a 3-dimensional (3D), porous, and piezoelectric strain sensor for sensing body movements. More specifically, the device was fabricated by mixing polydimethylsiloxane (PDMS) and polyvinylidene fluoride nanoparticles (PVDF NPs) as the matrix and piezoelectric materials of the strain sensor. The porous structure of the strain sensor was formed by a sugar cube-based 3D template. Additionally, mixing methods of PVDF piezoelectric NPs were optimized to enhance the device sensitivity. Finally, it is verified that the developed strain sensor could be directly attached onto the finger joint to sense its movements.