• 산업공학
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• 제14권1호
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• pp.95-105
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• 2001

Previous work measurement methods need much time and effort of time study analysts because they have to measure required time through direct observations. In this study, we propose a method which efficiently measures standard times without involvement of human analysts using digital image processing techniques. This method consists of two main steps: motion representation step and cycle segmentation step. In motion representation step, we first detect the motion of any object distinct from its background by differencing two consecutive images separated by a constant time interval. The images thus obtained then pass through an edge detector filter. Finally, the mean values of coordinates of significant pixels of the edge image are obtained. Through these processes, the motions of the observed worker are represented by two time series data of worker location in horizontal and vertical axes. In the second step, called the cycle segmentation step, we extract the frames which have maximum or minimum coordinates in one cycle and store them in a stack, and calculate each cycle time using these frames. In this step we also consider methods on how to detect work delays due to unexpected events such as operator's escapement from the work area, or interruptions. To condude, the experimental results show that the proposed method is very cost-effective and useful for measuring time standards for various work environment.

• Smart Structures and Systems
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• 제15권5호
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• pp.1329-1344
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• 2015

The stiffness of a structure is one of several structural signals that are useful indicators of the amount of damage that has been done to the structure. To accurately estimate the stiffness, an equation of motion containing a stiffness parameter must first be established by expansion as a linear series model, a Taylor series model, or a power series model. The model is then used in multivariate autoregressive modeling to estimate the structural stiffness and compare it to the theoretical value. Stiffness assessment for modeling purposes typically involves the use of one of three statistical model refinement approaches, one of which is the efficient Akaike information criterion (AIC) proposed in this paper. If a newly added component of the model results in a decrease in the AIC value, compared to the value obtained with the previously added component(s), it is statistically justifiable to retain this new component; otherwise, it should be removed. This model refinement process is repeated until all of the components of the model are shown to be statistically justifiable. In this study, this model refinement approach was compared with the two other commonly used refinement approaches: principal component analysis (PCA) and principal component regression (PCR) combined with the AIC. The results indicate that the proposed AIC approach produces more accurate structural stiffness estimates than the other two approaches.

• Clinical Pain
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• 제18권2호
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• pp.107-110
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• 2019

Flexor carpi radialis (FCR) muscle is located in the forearm anteriorly that runs through a synovial fibro-osseous tunnel in the forearm. We described a case of FCR tendon rupture due to repetitive overuse injury. A 55-year-old man, right-hand dominant, presented with right forearm pain and swelling which started 3 days ago while playing amateur golf. Focal tenderness and bruising over volo-ulnar region of the right forearm were examined. Plain radiographs showed soft tissue edema around lesion area and no detectable fracture. Ultrasonography showed multiple hypoechoic lesions suspected as hematoma of the flexor muscle group. After done magnetic resonance imaging, he was diagnosed with rupture of FCR tendon at proximal origin and strain of flexor digitorum superficialis and palmaris longus muscle. He received compressive dressing and restriction of wrist range of motion for three weeks. Two months later, remaining traces of lesions were observed at the follow-up ultrasonography and the pain disappeared.

• Tribology and Lubricants
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• 제39권5호
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• pp.212-215
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• 2023

Diaphragm compressors play a crucial role in safely compressing large volumes of high-purity hydrogen gas without contamination or leakage, thereby ensuring quality and reliability. Diaphragm compressors use a thin, flat, triple-layered diaphragm plate that is subjected to repetitive piston pressure for compression. They are usually made of metallic materials such as stainless steel or Inconel owing to their high-pressure resistance. However, since they are consumable components, they fail due to fatigue from repetitive pressure and vibration stress. This study aims to evaluate the scratch characteristics of diaphragms in operational environments by conducting tests on three different samples: Inconel 718, AISI 301, and Teflon-coated AISI 301. The Inconel 718 sample underwent a polishing process, the AISI 301 sample used raw material, and the Teflon coating was applied to the AISI 301 substrate at a thickness of 50 ㎛. To assess the scratch resistance, reciprocating motion friction tests were performed using a tribometer, utilizing 220 and 2000 grit sandpapers as the counter materials. The results of the friction tests suggested that the Teflon-coated sample exhibited the lowest initial friction coefficient and consistently maintained the lowest average friction coefficient (0.13 and 0.11 with 220 and 2000 grit, respectively) throughout the test. Moreover, the Teflon-coated diaphragm showed minimal wear patterns, indicating superior scratch resistance than the Inconel 718 and AISI 301 samples. These findings suggest that Teflon coatings may offer an effective solution for enhancing scratch resistance in diaphragms, thereby improving compressor performance in high-pressure hydrogen applications.

• Journal of Korean Neurosurgical Society
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• 제59권6호
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• pp.647-649
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• 2016

The device for intervertebral assisted motion (DIAM) is a dynamic implant that consists of a silicone bumper enveloped by a polyethylene terephthalate (PET) fiber sack. Silicone and PET were used because of their biological inertness, but repetitive motion of the spine can cause wear on the implant nonetheless. The purpose of this study is to report a case of foreign body reaction (FBR) against a DIAM. A 72-year-old female patient presented with lower back pain and both legs radiating pain. She had undergone DIAM implantation at L4-5 for spinal stenosis 5 years previously. The intervertebral disc space of L4-5, where the DIAM was inserted, had collapsed and degenerative scoliosis had developed due to left-side collapse. MRI showed L3-4 thecal sac compression and left L4-5 foraminal stenosis. The patient underwent removal of the DIAM and instrumented fusion from L3 to L5. During surgery, fluid and granulation tissue were evident around the DIAM. Histopathology showed scattered wear debris from the DIAM causing chronic inflammation due to the resulting FBR. A FBR due to wear debris of a DIAM can induce a hypersensitivity reaction and bone resorption around the implant, causing it to loosen.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1998년도 춘계학술대회논문집
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• pp.31-35
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• 1998

Many reaearchers have reproted that poor body postures are associated with pains or symptoms of musculoskeletal dissoders. Therefore, the ergonomic evaluation of postural stresses as well as biomechanical stresses is important when a job such as automobile assembly tasks involves highly repetitive and/or prolonged poor body postures. A macropostural classification shema was developed to characterise various body postures occurring in automobile assembly tasks in the study. To specify a postural code and stress level to each body posture, perceived joint discomforts were subjectively evaluated in the lab experiments for the full range of motion in five human body joints. Based on the reaults, a postural classification scheme was developed where the full range of motion in each body joint was classified into several codes repressenting different stress levels. The automobile tasks were clustered into 12 types based on the result walk-in-surveillance and the possible posture codes for each task type are defined. I was exposed that the poor postural problems in automobile assembly tasks were concerned in most part with arms, trunk and neck. Application of te developed schema to seven operations in automobile assembly tasks showed that the schema can be used as a tool to identify the operations and tasks involving highly stressful body postures. The schema can also be utilised as a basis to prioritise the candidate assembly operations for redesign of work methods.

• 대한인간공학회지
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• 제24권4호
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• pp.55-62
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• 2005

This study examined the effect of ergonomic heel rest that was designed for drivers who have physical handicap in the low leg muscles or have to drive prolonged hours with frequent foot pedaling. An experiment was designed to test the ergonomic heel rest with traditional foot pedal. Forty subjects participated in the experiment. Electromyography(EMG) was used to monitor the muscle activity and fatigue of right leg, and Electro-goniometer was used to measure the ranges of motions of the knee and ankle. A simulator of driver's seat was built for the experiment and the heel rest was installed on it. In order to examine the low muscle activity and range of motion, subjects used the foot pedal for 15 minutes repetitively for each experimental condition. Another 15 minutes test without the heel rest was also performed for comparison. The Root Mean Square(RMS) and Mean Power Frequency(MPF) Shift were used to quantify the level of muscle activity and local muscle fatigue. In results, statistically significant decreases of muscle activity and fatigue were found in all the low leg muscles. The range of motion of the knee and ankle joint also decreased when the heel rest was used. The mechanism of the heel rest effect was discussed in this study. This type of heel rest can be applied to real driving situation after ensuring the safety, or overcoming the psychological discomfort possibly due to unfamiliarity.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.411-416
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• 2000

Cutting process has been automated by progress of CNC and CAD/CAM, but polishing process has been depended on only experiential knowledge of expert. To automate the polishing process, a polishing robot with w degrees of freedom which is attached to a machining center with 3 degrees of freedom has been developed. This automatic polishing robot is able to keep the polishing tool normal on the curved surface of die to improve a performance of polishing. Polishing task for a curved surface die demands repetitive operation and high precision, but conventional control algorithm can not cope with the problem of disturbance such as a change of load. In this research, a new sliding mode control algorithm is applied to the robot. The signal compression method is used to identify polishing robot system. to obtain an effect of 5 degrees of freedom motion, a synchronization between the machining center and polishing robot is accomplished by using M code of machining center. And also a trajectory for polishing the curved surface die by 5 degrees of freedom motion, a synchronization between the machining center and polishing robot is accomplished by using M code of machining center. And also a trajectory for polishing the curved surface die by 5 axes machining center is divided into data of two types for 3 axes machining center and 2 axes polishing robot. To evaluate polishing performance of the robot. various experiments are carried out.

• 대한정형도수물리치료학회지
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• 제19권1호
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• pp.79-83
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• 2013

Background: Spasmodic torticollis is a disorder that is described by sustained muscle contractions causing repetitive and twisting movements, and abnormal postures in a single body region. The purpose of this case is to describe the manual therapy for a patient with spasmodic torticollis. Methods: The patient was a 64 years old man with an 3 month history of left side laterocollis spasmodic torticollis. No known genetic history or trauma. Prior to intervention, his score on the Western Spasmodic Torticollis Rating Scale (TWSTRS) severity score was 24, disability score was 20, pain score was 11. There is a noticeable distinction between left and right side cervical range of motion. The intervention consisted of manual therapy (MET, PNF) 3 times per week for the treatment during 4 weeks. Results: After intervention for 4weeks, his TWSTRS score and range of motion was improved quite a bit before therapeutic exercise. But symptoms are not improving sufficiently fast. Conclusions: Manual therapy is that MET and PNF is effective in improving for patient had spasmodic torticollis with laterocollis of neck.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.577-584
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• 2003

Traditional ankle rehabilitation procedures are tedious, repetitive, and require therapist's help. Therefore, they do not provide patients with good motivation to actively participate in the rehabilitation exercises. In addition, objective diagnosis and evaluation of the treatment progress have been difficult because records of exercise history are made by passive instruments from time to time. The virtual reality technology can make these procedures more fun so that patients can perform everyday rehabilitation exercises more actively. Moreover, haptics technology can give active resistance to the patients ankle motion to improve strength of muscles as well as can record ankle's motion and force histories for objective diagnosis and evaluation. This paper summarizes development of a virtual environment fur reforming the conventional ankle rehabilitation procedures. First of all, conventional rehabilitation procedures have been summarized. Secondly, haptic design and control, user interface design, virtual environment contents design are described. Lastly, mutual cooperation among many developers including medical doctors and therapists and future works are commented.