ALTERATIONS IN JOINT KINEMATICS AND KINETICS DURING DOWNHILL RUNNING

The purpose of this investigation was to find how joint kinematics and kinetics during downhill running change compared to level running. Fifteen recreational runners ran on a force plate imbedded treadmill with three different slopes (0 º, -6º, and -9º) at a controlled speed of 3.2 m/s. Ten steps on each slope were selected for analysis. Increased knee flexion with decreased ankle plantar-flexion and hip flexion was found during downhill running compared to level running. Decreased peak propulsive ground reaction force and posterior impulse were found during downhill running compared to level running. Additionally, increased extension moment with increased negative joint power at the knee and decreased plantar-flexion moment with decreased negative joint power at the ankle were found during downhill running compared to level running

SPRINTING CHARACTERISTICS OF WOMEN’S 100 METER FINALS AT THE IAAF WORLD CHAMPIONSHOPS DAEGU 2011

This study analyzed the sprinting characteristics of the finalists during the women's 100 m event in the IAAF World Championships Daegu 2011 in order to provide important information to track and field coaches and athletes. Five high speed cameras (Casio, Japan) with a sampling frequency of 300 Hz were used to calculate the number of steps, step length, and stride frequency of the eight sprinters in the women’s final event. There was a tendency to show a better performance time with a high number of steps (p=0.13) and shorter stride length (p=0.14) among the eight sprinters. Furthermore, stride frequency and performance time were negatively correlated as a higher stride frequency had a positive impact on performance time (p=0.02). Based on the relationship between COM velocity and lower extremity joint angles, the 4 top ranked sprinters showed the different strategies to maintain a high COM velocity during the mid portion of the race

Evaluation of a Sodium–Water Reaction Event Caused by Steam Generator Tubes Break in the Prototype Generation IV Sodium-cooled Fast Reactor

AbstractThe prototype generation IV sodium-cooled fast reactor (PGSFR) has been developed by the Korea Atomic Energy Research Institute. This reactor uses sodium as a reactor coolant to transfer the core heat energy to the turbine. Sodium has chemical characteristics that allow it to violently react with materials such as a water or steam. When a sodium–water reaction (SWR) occurs due to leakage or breakage of steam generator tubes, high-pressure waves and corrosive reaction products are produced, which threaten the structural integrity of the components of the intermediate heat-transfer system (IHTS) and the safety of the primary heat-transfer system (PHTS). In the PGSFR, SWR events are included in the design-basis event. This event should be analyzed from the viewpoint of the integrities of the IHTS and fuel rods. To evaluate the integrity of the IHTS based on the consequences of the SWR, the behaviors of the generated high-pressure waves are analyzed at the major positions of a failed IHTS loop using a sodium–water advanced analysis method-II code. The integrity of the fuel rods must be consistently maintained below the safety acceptance criteria to avoid the consequences of the SWR. The integrity of the PHTS is evaluated using the multidimensional analysis of reactor safety-liquid metal reactor code to model the whole plant

Microscopic Features of Fractured Fragment of Nickel-Titanium Endodontic Instruments by Two Different Modes of Torsional Loading

This study compared the microscopic features of the fractured endodontic nickel-titanium (NiTi) rotary instruments by two different torsional loadings: repetitive torsional loading (RTL) and single torsional loading (STL) based on the International Organization for Standardization (ISO). ProTaper Next, HyFlex EDM, and V-Taper 2 were compared in this study. In the STL method, the torsional load was applied after fixing the 3 mm tip of the file, by continuous clockwise rotation (2 rpm) until fracture. In the RTL method, a preset rotational loading (0.5 N·cm) was applied and the clockwise loading to the preset torque and counterclockwise unloading to original position were repeated at 50 rpm until the file fractured. Fractured fragments by two methods were compared under a scanning electron microscope (SEM) to examine the topographic features of the fractured surfaces and longitudinal aspects. SEM examinations showed significantly different features according to the loading methods. Specimens from the RTL method showed ruptured aspects on cross sections, with multiple areas of initiated cracks while the STL method showed the typical features of torsional failure, such as circular abrasion marks and fatigue dimples. This study suggested a new repetitive torsional loading method which is much more clinically relevant and may result in a different fracture feature from STL method

Low Grade Fibromyxoid Sarcoma in Thigh

A low grade fibromyxoid sarcoma is a rare soft tissue tumor that has a tendency to develop in the deep soft tissue of young adults and the potential for local recurrence or distant metastasis. There have been several case reports and sporadic reports in the literature. However, only 1 case has been reported in Korea but without a follow-up result. We describe a 54-year-old female patient with a low-grade fibromyxoid sarcoma of the thigh that had been growing slowly for 34 years. A marginal resection of this tumor was performed. Currently, the patient is doing well without evidence of local recurrence or distant metastasis at 5 years after surgery