• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.426-432
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• 2000

The development of a low-pollution burner is important for saving energy and preserving the environment. A low-pollution burner can be produced by lean-mixture combustion and general combustion technology. The flammable limit of premixed flame is narrower than that of diffusion flame. Producing a lean mixture of fuel results in an effective combustion condition, which in turn produces high load and low pollution. In this study, it was found that the influx of $Q_2$ had an effect on extending the lean flammable limits and flame stabilization in a doubled jet burner. And the flame, consisting of small eddies, can be stabilized by the nozzle neck phenomena.

• 한국분말재료학회지
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• 제22권4호
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• pp.247-253
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• 2015

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

• 국제물리치료학회지
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• 제10권2호
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• pp.1803-1809
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• 2019

Background: Cervical mobilization has been applied mainly for the improvement of arm and neck movements and pain reduction, and little research has been done to improve the executive function. Since this kind of so-called mechanical neck pain is one of most common symptoms, there are controversial issues about this with spine alignment. Posteroanterior (PA) mobilization from the Maitland concept is a process of examination, assessment, and treatment of neuromusculoskeletal disorder by manipulative physical therapy. Objective: To examine the short-term benefits of mobilization for patients with non-specific neck pain. Design: Dual-group Pretest-Posttest Design from the Quasi-Experimental research Methods: Fourteen participants (male 8, female 6; 20's of their age) with non-specific neck pains which are distributed all the unilateral or bilateral body side were recruited. Participants were categorized to Neck Pain with Movement Coordination Impairments (NPMCI) and Neck Pain with Mobility Deficits (NPMD) groups according to the results of physical examination. Professional physical therapist who has over 15-years-of clinical experience applicated manipulative therapy for the neck pain, an occupational therapist only conducted evaluations; K-NDI (Korean version of the Neck Disability Index), VAS (Visual Analog Scale), BDS-K (Korean version of Behavioral Dyscontrol Scale) for decreasing possible adverse effects; there were no person who reported other symptoms followed 4 weeks from the trial. Results: In the NPMCI group, data analysis indicated statistical differences between the PA mobilization interventions in NDI and BDS-K; even though, pain was reduced in VAS, this is not a significantly differ. In the NPMD group, data analysis represented statistical differences between the PA mobilization interventions in NDI, VAS and BDS-K; the scores were represented to be increased or the pain got relief. Conclusions: PA mobilization techniques according to Maitland concept have beneficial effects in patients with neck pain and other clinical positive effects which included neck disability, pain itself and motor function of upper extremity.

• International Journal of Automotive Technology
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• 제6권2호
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• pp.161-169
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• 2005

Neck injuries sustained during low speed rear impact are the most commonly sustained traffic injury. Therefore, the analysis of neck injury mechanisms and methods for mitigating and reducing neck injuries during low speed rear impact are a very important issue in the vehicle safety field. In order to find a method to absorb the shock that is transmitted to the occupant, the response of frontal and rear dummy due to the motion of the struck vehicle and the rotational angular displacements of dummies' necks during rear impact at 12km/h speed were investigated using a Working Model 2D. The results suggest that the shock absorption system should be equipped in the bottom of the seat of the vehicle to reduce shock and mitigate neck injury to the occupants.

• 한국가시화정보학회지
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• 제21권1호
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• pp.94-102
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• 2023

Three design parameters were considered in this study: outlet nozzle angle (30°, 60°, 80°), neck length (1 mm, 3 mm), and flow rate (0.5, 0.6, 0.7, 0.8 lpm). A neck diameter of 0.5 mm induced cavitation flow at a venture nozzle. A secondary transparent chamber was connected after ejection to increase bubble duration and shape visibility. The bubble size was estimated using a Gaussian kernel function to identify bubbles in the acquired images. Data on bubble size were used to obtain Sauter's mean diameter and probability density function to obtain specific bubble state conditions. The degree of bubble generation according to the bubble size was compared for each design variable. The bubble diameter increased as the flow rate increased. The frequency of bubble generation was highest around 20 ㎛. With the same neck length, the smaller the CV number, the larger the average bubble diameter. It is possible to increase the generation frequency of smaller bubbles by the cavitation method by changing the magnification angle and length of the neck. However, if the flow rate is too large, the average bubble diameter tends to increase, so an appropriate flow rate should be selected.

• 한국전산유체공학회지
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• 제18권4호
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• pp.69-73
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• 2013

Mass manufacturing of optical fiber includes the process of very thin glass fiber drawing by heating and softening the high purity silica preform and applying the draw tension on the softened tip of preform neck-down profile in a draw furnace. In this computational study, this process is numerically modeled with simplified geometry of the draw furnace which is comprised of essential parts such as concentric graphite heater, muffle tube, and insulation surrounding the heater. The iterative computational scheme is employed between one-dimensional model of neck-down profile prediction and two-dimensional axisymmetric thermo-fluid CFD computation of radiative heating and working gas convection. The computational results show the experimentally observed neck-down profile in heated section of preform, while yielding the reasonable values of draw tension and heater wattage. Also, this study analyzes and discusses the effects of heating conditions such as heater length and temperature on several important aspects of glass fiber drawing process.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.32-39
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• 2003

In this study we examined connections between vertebral motion and patterns of muscle activation during voluntary head tracking movements. A Rhesus (Maraca mulatta) monkey was trained to produce sinusoidal tracking movements of the head in the sagittal plane while seated. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted to record from eight neck muscles. Videofluoroscopic images of cervical vertebral motion, and EMG (electromyographic) responses were simultaneously re-corded. Experimental results demonstrated that head and vertebrae moved synchronously and that motion occurred primarily at skull-C$_1$, C$\_$6/-C$\_$7/ and Csub 7/-C$_1$. Our findings illustrate that although the biomechanical constraints of each species may limit the number of solutions available, it is the task requirements that appear to govern CNS (central nervous system) selection of movement behaviors.

• 소성∙가공
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• 제12권6호
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• pp.582-587
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• 2003

This paper is concerned with the mechanical property changes of the milli-size products manufactured by forward extrusion processes with square dies. Experiments are carried out with pure aluminum and pure copper billets. Extrusion ratio and knock-out pad are chosen as the important process parameters affecting the changes of mechanical properties such as shear strength and hardness. Shear strength tests with the extruded milli-size pin have shown the strong relation between victors hardness and shear strength in the neck of a stepped pin. As the extrusion ratio increases, the hardness on both the surface and the center line of a pin also increase. It is also noted that the hardness on the surface is a little higher than that on the center. The existence of knock-out pad in extrusion die causes the hardness in the neck of a extruded pin to increase. Finally, the approximated linear relations between shear strength and hardness of a pin are suggested.

• Korean Journal of Otorhinolaryngology-Head and Neck Surgery
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• 제61권12호
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• pp.705-709
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• 2018

It is challenging to achieve sufficient hearing gain in patients with mixed hearing loss. In chronic middle ear diseases, conventional passive reconstructive surgeries often result in suboptimal hearing gain and additional hearing aids may have limitations due to insufficient sound amplification, occlusion effect, acoustic feedback, and skin irritation. Middle ear implantation (MEI) using Vibrant Soundbridge (VSB) is another option for auditory rehabilitation in mixed hearing loss as well as sensorineural hearing loss. The floating mass transducer of VSB can be placed on various middle ear structures either directly or using different types of couplers in order to deliver vibratory mechanical energy to the cochlea. We report a patient who presented with bilateral mixed hearing loss due to chronic otitis media and had limitations using conventional hearing aids in the worse hearing ear. The patient was successfully treated with MEI using the Bell coupler together with middle ear surgery in a single step.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.132-139
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• 2005

The driving position of head restraints and the relative risk of neck injury were studied in the computer simulation. MADYMO human model with the detail neck model was used to define the magnitude and direction of internal forces acting on the cervical spine during rear-end impact and to determine the effect of the initial position of the occupant's head with respect to the head restraints. Maximum reaction forces were generated during the head contact to the restraint and relatively large forces were generated at each spinal components in lower cervical spine in proportion to backset and height distance increasement.