• Safety and Health at Work
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• v.2 no.4
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• pp.348-354
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• 2011

Objectives: This cross-sectional study was performed in the Dental School of Prince of Songkla University to ascertain noise exposure of dentists, dental assistants, and laboratory technicians. A noise spectral analysis was taken to illustrate the spectra of dental devices. Methods: A noise evaluation was performed to measure the noise level at dental clinics and one dental laboratory from May to December 2010. Noise spectral data of dental devices were taken during dental practices at the dental services clinic and at the dental laboratory. A noise dosimeter was set following the Occupational Safety and Health Administration criteria and then attached to the subjects' collar to record personal noise dose exposure during working periods. Results: The peaks of the noise spectrum of dental instruments were at 1,000, 4,000, and 8,000 Hz which depended on the type of instrument. The differences in working areas and job positions had an influence on the level of noise exposure (p < 0.01). Noise measurement in the personal hearing zone found that the laboratory technicians were exposed to the highest impulsive noise levels (137.1 dBC). The dentists and dental assistants who worked at a pedodontic clinic had the highest percent noise dose (4.60 ${\pm}$ 3.59%). In the working areas, the 8-hour time-weighted average of noise levels ranged between 49.7-58.1 dBA while the noisiest working area was the dental laboratory. Conclusion: Dental personnel are exposed to noise intensities lower than occupational exposure limits. Therefore, these dental personnel may not experience a noise-induced hearing loss.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.233-249
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• 2002

The purpose of this study was to employing MRI in the estimation of the biomechanical body segment parameters of Korean adults. for this purpose MRI study on 19 Korean living subjects were used to measurement. All the parameters that was concerned were inertial characteristics of human body mass of each segment, center of mass of them and the length of radius of gyration of them. The cross sectional images and saggital images of every 1cm interval were got using the 0.5 Tesla MRI from the top of head to the bottom of foot, whole body. And then, by tracing the images of the film and scanning them, got the area which the several tissues occupied in the image of slice. By summing the area of slice of each segment which were calculating and by multipling the density of the tissues, got the mass of segment and other inertial characteristics. The ratios of radius of gyration in both transverse axis and longitudinal axis though the segmental mass and segment length are as follow: male A : head($0.229\pm0.0029$), neck($0.256\pm0.0095$), thorax($0.374\pm0.0059$) abdomen($0.245\pm0.0020$), pelvis($0.368\pm0.0106$), thigh($0.288\pm0.0030$) shank($0.280\pm0.0043$), foot($0.277\pm0.0195$), upperarm($0.311\pm0.0074$) forearm($0.286\pm0.0051$), hand($0.253\pm0.0095$) female A : head($0.214\pm0.0032$), neck($0.254\pm0.0112$), thorax($0.295\pm0.0061$) abdomen($0.289\pm0.0021$), pelvis($0.329\pm0.0108$), thigh($0.288\pm0.0036$) shank($0.280\pm0.0047$), foot($0.243\pm0.0206$), upperarm($0.279\pm0.0083$) forearm($0.286\pm0.0048$), hand($0.229\pm0.0097$) male B : head($0.532\pm0.0006$), neck($0.533\pm0.0006$), thorax($0.658\pm0.0008$) abdomen($1.350\pm0.0022$), pelvis($0.875\pm0.0002$), thigh($0.213\pm0.0001$) shank($0.160\pm0.0001$), foot($0.152\pm0.0002$), upperarm($0.136\pm0.0002$) forearm($0.202\pm0.0002$), hand($0.273\pm0.0006$) female B : head($0.198\pm0.0002$), neck($0.335\pm0.0011$), thorax($0.238\pm0.0001$) abdomen($0.888\pm0.0001$), pelvis($1.318\pm0.0117$), thigh($0.095\pm0.0001$) shank($0.075\pm0.0001$), foot($0.181\pm0.0006$), upperarm($0.0.062\pm0.0001$) forearm($0.083\pm0.0001$), hand($0.105\pm0.0007$).

• Journal of the Korean Society of Physical Medicine
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• v.17 no.1
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• pp.41-48
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• 2022

PURPOSE: This study examined the relationship between the cervical lordosis angle (CLA) and the craniovertebral angle (CVA) and between CVA and a cross-sectional area (CSA) of the cervical muscles. METHODS: In 17 healthy college students, the CLA was measured using a posterior tangent technique. The CVA was analyzed using photographic images, and the CSA of the cervical muscles, including longus colli, longus capitis, and sternocleidomastoid, was evaluated using computerized tomography. The Pearson's correlation coefficient was used to determine the relationship between these variables and a neck disability index. RESULTS: The CVA correlated with the CLA and with a CSA of longus colli (r = .487, p = .047 and r = .592, p = .012, respectively). The CLA correlated with a CSA of longus colli (r = .578, p = .015). CONCLUSION: This study clarified the relationship between the postural, structural, and muscular changes in the cervical regions. A significant correlation was observed between the CVA and a CSA of the longus colli with the CLA and between the CVA and the CSA of the longus colli. Prescription strengthening exercises for the deep neck flexors for individuals with a forward head posture and reduced cervical lordosis are useful.

• Journal of Audiology & Otology
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• v.24 no.4
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• pp.198-203
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• 2020

Background and Objectives: We sought to evaluate the diagnostic and prognostic value of measurable parameters of internal auditory canal (IAC) magnetic resonance imaging (MRI) in patients with idiopathic sudden sensorineural hearing loss (ISSNHL). Subjects and Methods: We retrospectively reviewed the patients with ISSNHL who underwent IAC MRI from January 2008 to March 2019. Measurable parameters of IAC MRI, such as the diameter of the IAC, bony cochlear nerve canal, and cross-sectional area of the cochlear nerve, were measured by a single examiner. These parameters were then compared between the affected and healthy sides. Inner-ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis were also evaluated. The relationship between the surveyed parameters and the diagnosis of ISSNHL was assessed. Results: A total of 208 patients with ISSNHL were included. The measured parameters of IAC MRI were not different between the affected and healthy sides and were also not associated with the diagnosis of ISSNHL. However, inner-ear abnormalities of IAC MRI in ISSNHL displayed a significant association with worse hearing before and after treatment. An age that was older than 40 years also correlated with poorer outcomes. Further, inner-ear abnormalities were more frequently detected when IAC MRI was performed early after ISSNHL onset. Conclusions: Patients with ISSNHL and inner ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis identified via IAC MRI may experience poorer hearing outcomes. To detect such abnormal findings, it is recommended to perform IAC MRI early after the onset of ISSNHL.

• Korean Journal of Audiology
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• v.24 no.4
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• pp.198-203
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• 2020

Background and Objectives: We sought to evaluate the diagnostic and prognostic value of measurable parameters of internal auditory canal (IAC) magnetic resonance imaging (MRI) in patients with idiopathic sudden sensorineural hearing loss (ISSNHL). Subjects and Methods: We retrospectively reviewed the patients with ISSNHL who underwent IAC MRI from January 2008 to March 2019. Measurable parameters of IAC MRI, such as the diameter of the IAC, bony cochlear nerve canal, and cross-sectional area of the cochlear nerve, were measured by a single examiner. These parameters were then compared between the affected and healthy sides. Inner-ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis were also evaluated. The relationship between the surveyed parameters and the diagnosis of ISSNHL was assessed. Results: A total of 208 patients with ISSNHL were included. The measured parameters of IAC MRI were not different between the affected and healthy sides and were also not associated with the diagnosis of ISSNHL. However, inner-ear abnormalities of IAC MRI in ISSNHL displayed a significant association with worse hearing before and after treatment. An age that was older than 40 years also correlated with poorer outcomes. Further, inner-ear abnormalities were more frequently detected when IAC MRI was performed early after ISSNHL onset. Conclusions: Patients with ISSNHL and inner ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis identified via IAC MRI may experience poorer hearing outcomes. To detect such abnormal findings, it is recommended to perform IAC MRI early after the onset of ISSNHL.

• Restorative Dentistry and Endodontics
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• v.28 no.6
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• pp.491-497
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• 2003

The purpose of this study was to evaluate the correlation between hybrid layer thickness and bond strength using confocal laser scanning microscope and microtensile bond strength test of two adhesive systems. The dentin surface of human molars. sectioned to remove the enamel from the occlusal surface. Either Scotchbond Multi-Purpose(3M Dental Product, St. Paul, MN, U.S.A) or Clearfil SE Bond (Kuraray, Osaka, Japan) was bonded to the surface. and covered with resin-composite. The resin-bonded teeth were serially sliced perpendicular to the adhesive interface to measure the hybrid layer thickness by confocal laser scanning microscope. The specimen were trimmed to give a bonded cross-sectional surface area of $1\textrm{mm}^2$, then the micro-tensile bone test was performed at a cross head speed of 1.0 mm/min. All fractured surfaces were also observed by stereomicroscope. There was no significant differences in bond strengths the materials(p>0.05). However. the hybrid layers of three-step dentin adhesive system, SM, had significantly thicker than self-etching adhesive system. CS(p<0.05). Pearson's correlation coefficient showed no correlation between hybrid layer thickness and bond strengths(p>0.05). Bond strengths of dentin adhesive systems were not dependent on the thickness of hybrid layer.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.12 no.1
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• pp.57-67
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• 2006

Musculoskeletal neck dysfunction syndromes are common in outpatient musculoskeletal pain practice. The underlying musculoskeletal and neurologic causes of pain are variable. In the management of these patients, it is important to accurately identify and treat these pain generators to optimize patient outcome. It is the purpose of this review to discuss three main categories of functional anatomy, the role of superficial/deep muscular system and the scientific evidence for optimal physical therapy intervention for cervical dysfunction. Specifically there is evidence of lowered microcirculation in the upper trapezius muscle, morphological signs of disturbed mitochondrial function which appears to be limited to type I fibers and an increased cross-sectional area of type I muscle fibers despite a lower capillary to fiber area ratio. In acute neck pain syndrome, changes in muscle activity of painful muscles may result from segmental and supraspinal inhibitory effects. Muscle activation is closely related to the control of joint movements and postures and it is difficult to separate the influence of the two components. Both the altered muscle recruitment patterns and altered kinematics appear to be a poor adaptation for pain of the head - neck region, as they are likely to result in increased compressive loading in the cervical spine, affecting muscles, articular structures such as zygapophyseal joints, connective tissues and neural tissues which are all peripheral generators of referred pain. The rectus capitus posterior minor muscle shows that it is one of the most important muscles of the suboccipital region. In this article, i reviewed the anatomy, neurophysiology, function and dysfunction as well as the treatment of cervical dysfunction.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.649-655
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• 2006

Waves progressing into the coastal area can be amplified, swashed and overtopped by a wave overtopping control structure, and it converts the kinetic energy of the waves to the potential energy with a hydraulic head above the mean sea level by conserving the overflow in a reservoir. Then the potential energy in the form of hydraulic head can be converted to electric power utilizing extremely low-head hydraulic turbine. This study aims to find the most optimal shape of wave overtopping structure which maximizes overtopping volume rate of sea water. Laboratory experiments for the performance evaluation of wave overtopping control structures were carried out in three dimensional wave tank, and the three dimensional structure models with planar wave concentration shapes(B/b) were manufactured into five classes, which were optimized by cross sectional parameters of the structure, ie, length of ramp(l), gradient of inclined ramp($cot{\phi}$) and freeboard height of the wave overtopping structure($h_e$) proposed by Shin and Hong(2005). The wave overtopping discharges were investigated with 20 incident wave conditions and wave directions of $0^{\circ},\;15^{\circ},\;30^{\circ}$.

• ETRI Journal
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• v.27 no.3
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• pp.304-311
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• 2005

We report on the fabrication of an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) using a dielectric-defined process. This process was utilized to fabricate $0.12\;{\mu}m\;{\times}\;100 {\mu}m$ T-gate PHEMTs. A two-step etch process was performed to define the gate footprint in the $SiN_x$. The $SiN_x$ was etched either by dry etching alone or using a combination of wet and dry etching. The gate recessing was done in three steps: a wet etching for removal of the damaged surface layer, a dry etching for the narrow recess, and wet etching. A structure for the top of the T-gate consisting of a wide head part and a narrow lower layer part has been employed, taking advantage of the large cross-sectional area of the gate and its mechanically stable structure. From s-parameter data of up to 50 GHz, an extrapolated cut-off frequency of as high as 104 GHz was obtained. When comparing sample C (combination of wet and dry etching for the $SiN_x$) with sample A (dry etching for the $SiN_x$), we observed an 62.5% increase of the cut-off frequency. This is believed to be due to considerable decreases of the gate-source and gate-drain capacitances. This improvement in RF performance can be understood in terms of the decrease in parasitic capacitances, which is due to the use of the dielectric and the gate recess etching method.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.1 no.1
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• pp.64-72
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• 2008

Compression neuropathy around elbow and wrist are one of the common disturbing problems in the upper extremity. The understanding of normal nerve architectures and pathophysiologic changes in compression neuropathy is important to interpret the ultrasonographic images correctly. Compression neuropathies have characteristic ultrasonographic imaging features of flattened nerve at compression and hypoechoic swollen nerve with loss of fascicular patterns at proximal segments. Dynamic ultrasonographic imagings on motion can show dymanic subluxation of ulnar nerve and medial head of triceps muscle over the medial epicondyle in snapping triceps syndrome. Dynamic compression of median nerve also can be visualized in pronator teres syndrome by dynamic imaging studies. A quantitative measures of cross sectional area or compression ratio can be helpful to diagnose compression neuropathies, such as carpal tunnel syndrome or cubital tunnel syndrome. With the clinical features and electeophysiologic studies, the untrasonographic imagings are useful tool for evaluation of the compression neuropathies in the upper extremities.