Earticle

The aim of this study is to determine whether concentric and eccentric isokinetic training performed at certain angular velocities in sedentary individuals is effective only in the angular velocities and contraction type where the training is performed, or at other angular velocities and contraction types that are not being trained. Twenty-eight sedentary in-dividuals (matched according to weight, age and gender) volunteered to participate in this case study. The study was conducted on a total of 56 extremities belonging to 28 individuals (14 women, 14 men) aged be-tween 24 and 60 years. Concentric and eccentric strength tests were performed at 30-60-90-120-150-180°/sec. The participants were random-ly divided into two groups as concentric training group and eccentric training group, through stratified randomization matching. The training was done 3 days a week for a total of 6 weeks. At the end of the study, no difference was found between the pre- and posttraining measure-ments in the concentric training group (P>0.05). In the eccentric training group, the eccentric muscle strength of the knee flexors and extensors at angular velocity of 90°/sec, the eccentric strength of the knee exten-sors at angular velocity of 120°/sec, and the eccentric muscle strength of the knee flexors at angular velocity of 180°/sec were found to be dif-ferent and an increase was seen after the training (P=0.032, P=0.049, P=0.041, P=0.032). These results demonstrate that eccentric training may be preferred in cases where muscle strength increase is needed in short time.

The purpose of this study was to investigate the effect of surface coefficient of restitution on vertical ground reaction force, joint angular velocity and muscle activity during landing with ankle, knee and hip joint angle limitation. 10 men were recruited as a subjects but only one person was excluded due to personal reason therefore a total of 9 men participated in this measurement. The participants were performed 30cm height drop landing on three different surface with randomized control and cross-over design. All subjects were performed four weeks drop landing to limit the joint angle during landing. Three-dimensional motion analysis equipment and surface EMG was used to measure ground reaction force, joint angles, joint angular velocity and muscle activity of lower limb. Collected data were statically analyzed by repeated one-way analysis of variance and alpha was set at .05. As a results, there were no significant difference between ground reaction force and joint angular velocity but there were significant difference in muscle activity and on wood had highest activity level than others. Based on the results of this study, further study needs to kinematic analysis and hormonal responses about a variety of surface coefficient and drop landing height followed by jump.

무선통신 기술의 발전으로 인해 디지털 라디오 시스템은 아날로그 방송으로 대체되고 있다. In-band 디지털라디오 시스템은 기존의 아날로그 라디오 주파수를 사용하기 때문에, 기존 방송과의 간섭이 발생할 수 있다. 따라서 디지털 방송을 위해 효과적인 간섭분석은 매우 중요하다. 이 논문에서는 디지털 라디오 시스템의 SINR과 BEP(bit error probability)를 분석하기 위해 각도 효과를 고려한 방법을 제안한다. 여기서 각도 효과는 송신기 주변에 다양한 방향에 수신기가 위치해 있을 때 간섭을 분석할 수 있는 방법을 의미한다. 분석 결과들은 디지털라디오 방송망을 배치하기 위한 기본 정보로 활용될 수 있다.

In the current wireless communication technology, the digital radio system replaces the analog radio broadcasting. Since the in-band digital radio systems are used in the existing analog radio frequency band, interference problems of digital radio are caused. It is important to effectively analyze the interference. In this paper, to analyze SINR and BEP (bit error probability) of digital radio system, we propose the analysis method considering angular effect. The angular effect means a method to analyze the interference when the receiver is located in different directions around the transmitter. These results are able to give basic information for the allocation of digital radio networks.

Purpose: The purpose of this study was to analyze the effect of normal timing according to angular motion in PNF patterns on electromyography (EMG) activity in rectus abdominis, internal oblique abdominal muscle, external oblique abdominal muscle, and erector spinae. Methods: Ten healthy adults volunteered to participate in this study. The participants were required to complete following two PNF extremity patterns; upper extremity extension- adduction-internal rotation pattern with 180°, 90°, 30°and lower extremity flexion- adduction-external rotation pattern with 0°, 60°, 90°. A paired t-test was used to determine the influence of the two PNF patterns on muscle activity in each muscle. Descriptive statistics were used to determine the ratio of local muscle activity to global muscle activity. Results: In terms of their effect on applied normal timing, the upper and lower extremity pattern significantly affected the rectus abdominis, internal oblique, external oblique, and erector spinae (p < .05). The upper extremity pattern (at an extension angle of 30°) and the lower extremity pattern ((at a flexion angle of 90°) influenced the rectus abdominis, internal oblique, external oblique, and erector spinae (p < .05). Conclusion: The effect of the upper and lower extremity patterns on applied normal timing was significant in that these patterns increased trunk muscle activation. The upper extremity pattern (at an extension angle of 30°) and the lower extremity pattern (at a flexion angle of 90°) increased trunk muscle activation. Normal timing is required to increase trunk muscle strength and extremity movement.

This study presents the angular effects of virtual vertices inserted for effective treatment of the boundary edge laid on an infinite conducting surface in a half-space scattering problem. We investigated the angular effects of virtual vertices by first computing the radar cross section (RCS) of a specific scatterer; i.e., a tilted conducting plate in contact with the ground surface, by inserting the virtual vertex in half-space. Here, the electric field integral equation is used to solve this problem with various virtual vertex angles (${\theta}_{\nu}$) and conducting plate inclination angles (${\theta}_r$) ranging from $0^{\circ}$ to $180^{\circ}$. The effects of the angles ${\theta}_{\nu}$ and ${\theta}_r$ on the RCS computation are clearly shown with numerical results with and without the virtual vertices in free- and half-spaces.

Weld reinforcements play vital role in controlling different formation of inherent strains in the heat-affected zone in arc welded joints. It is desirable to have adequate weld reinforcements on both the top and bottom sides of butt joint such that shrinkage force effects of both the reinforcements would be cancelling the angular distortion. In this study, it has been established by experiments that acceptable top and bottom weld reinforcements can be achieved and angular distortion can be controlled in square butt joints through submerged arc welding (SAW) done from both the sides with accurate control of welding process parameters. Such process does not require use of costly backing strip and instead a flux bed can be used for the purpose. Modeling of the process was also carried out using 3-D thermomechanical finite element (FE) analysis. Moving distributed heat source, weld reinforcements on top and bottom side, weld deposition in each welding pass and temperature dependent thermos-physical properties were used in the thermomechanical analysis for predicting the temperature profiles and angular distortion patterns The numerically predicted temperature distribution and distortion patterns indicated close agreement with the experimentally observed results.

The effect of annealing on the pitting corrosion resistance of anodized Al-Mg alloy (AA5052) processed by equal-channel angular pressing (ECAP) was investigated by electrochemical techniques in a solution containing 0.2 mol/L of $AlCl_3$ and also by surface analysis. The Al-Mg alloy was annealed at a fixed temperature between 473 and 573 K for 120 min in air after ECAP. Anodizing was conducted for 40 min at $100-400A/m^2$ at 293 K in a solution containing 1.53 mol/L of $H_2SO_4$ and 0.0185 mol/L of $Al_2(SO_4)_3$. The internal stress generated in anodic oxide films during anodization was measured with a strain gauge to clarify the effect of ECAP on the pitting corrosion resistance of anodized Al-Mg alloy. The time required to initiate the pitting corrosion of anodized Al-Mg alloy was shorter in samples subjected to ECAP, indicating that ECAP decreased the pitting corrosion resistance. However, the pitting corrosion resistance was greatly improved by annealing after ECAP. The time required to initiate pitting corrosion increased with increasing annealing temperature. The strain gauge attached to Al-Mg alloy revealed that the internal stress present in the anodic oxide films was compressive stress, and that the stress was larger with ECAP than without. The compressive internal stress gradually decreased with increasing annealing temperature. Scanning electron microscopy showed that cracks occurred in the anodic oxide film on Al-Mg alloy during initial corrosion and that the cracks were larger with ECAP than without. The ECAP process of severe plastic deformation produces large internal stresses in the Al-Mg alloy; the stresses remain in the anodic oxide films, increasingthe likelihood of cracks. It is assumed that the pitting corrosion is promoted by these cracks as a result of the higher internal stress resulting from ECAP. The improvement in the pitting corrosion resistance of anodized AlMg alloy as a result of annealing appears to be attributable to a decrease in the internal stresses in anodic oxide films

최근 초고압 케이블 절연체로 XLPE(가교 폴리에틸렌)이 널리 사용되어 지면서 XLPE의 여러 물리 화학적 특성에 따른 절연 성능에 관한 연구가 활발히 이루어지고 있다. 이러한 XLPE 절연층은 제조과정에서 압출과정을 거쳐 도체를 감싸게 되는데 이 과정에서 흐름 패턴으로 나타나는 비등방성(anisotropy)을 띠게된다. 본 논문에서는 초고압 XLPE 케이블에서 시계 방향으로 나타나는 비등방성(anisotropy)이 나타내는 기계-전기적 특성을 인장강도(tensile strength), 트리 개시전압 및 개시시간을 측정한 결과를 토대로 고찰해 보았으며, 이러한 비등방성이 초고압 XLPE 케이블의 절연 성능에 영향을 주는 인자로 고려되어야 함을 알 수 있었다.

Magnesium and its alloys are attractive as light weight structural/functional materials for high performance application in automobile and electronics industries due to their superior physical properties. In order to obtain high quality products manufactured by the magnesium powders, it is important to control and understand the densification behavior of the powders. The effect of the sheath surrounding the magnesium powders on the plastic deformation and densification behavior during equal channel angular pressing was investigated in the study by experimental and the finite element methods. A modified version of Lee-Kim’s plastic yield criterion, notably known as the critical relative density model, was applied to simulate the densification behavior of magnesium powders. In addition, a new approach that extracts the mechanical characteristics of both the powder and the matrix was developed. The model was implemented into the finite element method, with which powder compaction under equal channel angular pressing was simulated.

The effect of equal channel angular pressing (ECAP) on the pitting corrosion resistance of hard anodized Al5052 alloy was investigated. The degree of internal stress generated in anodic oxide films during hard anodization was also evaluated with a strain gauge method. The pitting corrosion resistance of hard anodized Al5052 alloy was greatly decreased by ECAP. Cracks occurred in the anodic oxide film during hard anodization and these cracks were larger and deeper in the alloy with ECAP than without. The pitting corrosion was accelerated by cracks. The internal stress present in the anodic oxide films was compressive and the stress was higher in the alloys with ECAP than without, resulting in an increased likelihood of cracks. The pitting corrosion resistance of hard anodized Al5052 alloy was improved by annealing at the range of 473-573K after ECAP processed at room temperature for four passes. The compressive internal stress gradually decreased with increasing annealing temperature. It is assumed that the improvement in the pitting corrosion resistance of hard anodized Al5052 alloy by annealing may be attributed to a decrease in the likelihood of cracks due to the decreased internal stresses in anodic oxide films.

Much research efforts have been made on the structure and properties of metals deformed to severe plastic deformation (SPD). Being deformed to SPD, ultra-fine grains (UFG) are usually formed, and UFG structure exhibits fundamental differences in original physical properties. One method often used to obtain SPD is equal channel angular pressing (ECAP). In order for this technique to be exploited, it is important to understand the deformation behavior during the ECAP processing with respect to friction. The finite element method (FEM) has been used to investigate this issue.

The effect of piston geometry on in-cylinder flow during intake and compression was inv-estiated quantitatively by three-component LDV measurement. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance Particular emphasis was placed on the three dimensional turbulent kinetic energy and meas-urement of tumble ratio. This work describes a newly designed transient tumble ratio calc-ulation method for development purposes. The LDV results reveal that generating a vortical motions during the compression processes is one of the ways to achieve substantial incea-se of turbulent kinetic near TDC.

다층 용접이 적용되는 후판 조립 부재에서는 각 조립단계별로 용접변형이 필연적으로 발생되고 있으며 용접변형의 교정을 위한 추가 작업도 각 조립간계 및 후 공정에서 반복적으로 수행되고 있다. (중략)

This study aimed to analyze the effects of external load between male and female on angular velocity, moment, and absorbed energy of the lower-extremity joints during drop landing. The study subjects were 9 male($mass=70.82{\pm}4.64kg$, $height=1.71{\pm}0.04m$, $age=24.5{\pm}1.84years$), 9 female($mass=50.14{\pm}4.09kg$, $height=1.61{\pm}0.03m$, $age=23.6{\pm}2.62years$), without any serious musculoskeletal, coordination, balance, or joint/ligament problems for 1 year before the study. The angular velocity, flexion/extension and abduction/adduction moments, and absorbed energy of the lower-extremity joints were compared between the men and women during drop landing under 4 different conditions of external load(0%, 8%, 16%, and 24%) by using two-way repeated ANOVA(p < .05). The women landed with a greater peak angular velocity of the ankle joint, greater peak inversion moment, and lower peak hip-extension moment than the men did, under all 4 conditions. Additionally, the landing characteristics of the women were distinct from those of the men; the women showed a greater peak knee-adduction moment and greater absorbed energy of the knee joint. These differences indicate that anterior cruciate ligament(ACL) strain was greater in the women than in the men and therefore, women may be at a higher potential risk for noncontact injuries of the ACL with an increase in external load.

Equal channel angular pressing has been employed to produce materials with ultra-fine grains that have high strength and high corrosion resistance properties. Along with the experiments, the finite element method has been widely performed to investigate the deformation behavior of specimen and the effects of process parameters of ECAP. In general, several steps of ECAP have been repeatedly executed. In this paper, the effects of sectional shape change have been investigated during ECMAP (RouteA, RouteC) with pure-Zr by using three-dimensional finite element analysis. The results have been compared with the experimental results.

We have fabricated a novel Vertical Trench Hall-Effect Device sensitive to the magnetic field parallel to the sensor chip surface for non-contact angular position sensing applications. The Vertical Trench Hall-Effect Device is built on SOI wafer which is produced by silicon direct bonding technology using bulk micromachining, where buried $SiO_2$ layer and surround trench define active device volume. Sensitivity up to 150 V/AT is measured.