• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.5
• /
• pp.313-319
• /
• 2016

It is very important to understand and control the sloshing in a liquid container that is partially filled with liquid. Previous studies focused primarily on the sloshing and resonance caused by sinusoidal excitations, while the present study focuses on understanding and suppressing sloshing in a container that moves rapidly from a given point to another in industrial applications. To achieve this, we first numerically predict the two-phase flow induced by the horizontal movement of a rectangular container. Then we analyze the effects of container-velocity profile (in particular acceleration/deceleration duration) on sloshing. Results show that sloshing is significantly suppressed when the acceleration/deceleration duration is a multiple of the 1st-mode natural period of sloshing.

• Journal of Biomedical Engineering Research
• /
• v.19 no.6
• /
• pp.585-593
• /
• 1998

In Fourier magnetic resonance imaging (MRI), the number of phase encoded signals is often reduced to minimize the duration of the studies and maintain adequate signal-to-noise ratio. However, this results in the well-known truncation artifact, whose effect manifests itself as blurring and ringing in the image domain. In this paper, we propose a new regularization method in the context of a Bayesian framework to reduce truncation artifact. Since the truncation artifact appears in t도 phase direction only, the use of conventional piecewise-smoothness constraints with symmetric neighbors may result in the loss of small details and soft edge structures in the read direction. Here, we propose more elaborate forms of constraints than the conventional piecewise-smoothness constraints, which can capture actual spatial information about the MR images. Our experimental results indicate that the proposed method not only reduces the truncation artifact, but also improves tissue regularity and boundary definition without oversmoothing soft edge regions.

• Clinics in Shoulder and Elbow
• /
• v.23 no.3
• /
• pp.144-151
• /
• 2020

Background: This study was designed to evaluate characters of the rotator cuff tear (RCT) recognized after primary shoulder dislocation in patients older than 40. Methods: From 2008 to 2019, patients who visited two hospitals after dislocation were retrospectively reviewed. Inclusion criteria were patients over 40 who had dislocation, with magnetic resonance imaging (MRI) undergone. Exclusion criteria were patients who lost to follow-up, combined with any proximal humerus fracture, brachial plexus injury, and previous operation or dislocation history in the ipsilateral shoulder. Also patients who had only bankart or bony bakart lesion in MRI were excluded. We evaluated RCTs that were recognized by MRI after the primary shoulder dislocation with regard to tear size, degree, involved tendons, fatty degeneration, the age when the first dislocation occurred, and the duration until the MRI was evaluated after the dislocation. Results: Fifty-five RCTs were included. According to age groups, the tear size was increased in coronal and sagittal direction, the number of involved tendons was increased, and the degree of fatty degeneration was advanced in infraspinatus muscle. Thirty-two cases (58.2%) conducted MRI after 3 weeks from the first shoulder dislocation event. This group showed that the retraction size of the coronal plane was increased significantly and the fatty accumulation of the supraspinatus muscle had progressed significantly. Conclusions: Age is also a strong factor to affect the feature of RCT after the shoulder dislocation in patients over 40. And the delay of the MRI may deteriorate the degree of tear size and fatty degeneration.

• Korean Journal of Radiology
• /
• v.21 no.4
• /
• pp.483-493
• /
• 2020

Objective: To evaluate the distribution and characteristics of peripheral nerve abnormalities in chronic inflammatory demyelinating polyneuropathy (CIDP) using magnetic resonance neurography (MRN) and to examine the diagnostic efficiency. Materials and Methods: Thirty-one CIDP patients and 21 controls underwent MR scans. Three-dimensional sampling perfections with application-optimized contrasts using different flip-angle evolutions and T1-/T2- weighted turbo spin-echo sequences were performed for neurography of the brachial and lumbosacral (LS) plexus and cauda equina, respectively. Clinical data and scores of the inflammatory Rasch-built overall disability scale (I-RODS) in CIDP were obtained. Results: The bilateral extracranial vagus (n = 11), trigeminal (n = 12), and intercostal nerves (n = 10) were hypertrophic. Plexus hypertrophies were observed in the brachial plexus of 19 patients (61.3%) and in the LS plexus of 25 patients (80.6%). Patterns of hypertrophy included uniform hypertrophy (17 [54.8%] brachial plexuses and 21 [67.7%] LS plexuses), and multifocal fusiform hypertrophy (2 [6.5%] brachial plexuses and 4 [12.9%] LS plexuses) was present. Enlarged and/or contrast-enhanced cauda equina was found in 3 (9.7%) and 13 (41.9%) patients, respectively. Diameters of the brachial and LS nerve roots were significantly larger in CIDP than in controls (p < 0.001). The largest AUC was obtained for the L5 nerve. There were no significant differences in the course duration, I-RODS score, or diameter between patients with and without hypertrophy. Conclusion: MRN is useful for the assessment of distribution and characteristics of the peripheral nerves in CIDP. Compared to other regions, LS plexus neurography is more sensitive for CIDP.

• The Korean Journal of Pain
• /
• v.25 no.2
• /
• pp.81-88
• /
• 2012

Background: In discography performed during percutaneous endoscopic lumbar discectomy (PELD) via the posterolateral approach, it is difficult to create a fluoroscopic tunnel view because a long needle is required for discography and the guide-wire used for consecutive PELD interrupts rotation of fluoroscope. A stereotactic system was designed to facilitate the determination of the needle entry point, and the feasibility of this system was evaluated during interventional spine procedures. Methods: A newly designed stereotactic guidance system underwent a field test application for PELD. Sixty patients who underwent single-level PELD at L4-L5 were randomly divided into conventional or stereotactic groups. PELD was performed via the posterolateral approach using the entry point on the skin determined by premeasured distance from the midline and angles according to preoperative magnetic resonance imaging (MRI) findings. Needle entry accuracy provided by the two groups was determined by comparing the distance and angle measured by postoperative computed tomography with those measured by preoperative MRI. The duration and radiation exposure for determining the entry point were measured in the groups. Results: The new stereotactic guidance system and the conventional method provided similarly accurate entry points for discography and consecutive PELD. However, the new stereotactic guidance system lowered the duration and radiation exposure for determining the entry point. Conclusions: The new stereotactic guidance system under fluoroscopy provided a reliable needle entry point for discography and consecutive PELD. Furthermore, it reduced the duration and radiation exposure associated with determining needle entry.

• Journal of Korean Neurosurgical Society
• /
• v.39 no.5
• /
• pp.378-381
• /
• 2006

A 65-year-old woman presented with a history of severe lower back pain on forward-flexion for 2 months duration. Magnetic resonance Imaging revealed a high signal mass with a tail on T1-weighted images at the L3 level. A total surgical resection was performed via a posterior approach with the aid of a microscope. Histopathological examination of the tumor revealed two pathological components : lipoma and myxopapillary ependymoma. The presence of dual histological components in one spinal cord tumor is rare. There are no prior reports of both types of cells [adipose and ependymal] grown simultaneously in a single tumor of the filum terminale in the medical literature. We report a unique case of the co-existence of lipoma and myxopapillary ependymoma within the same tumor located at the filum terminale and review related literature.

• Journal of Korean Neurosurgical Society
• /
• v.38 no.4
• /
• pp.320-322
• /
• 2005

A 45-year-old man presented with lower back pain and pain in the right leg of 3years duration. A plain radiographic examination revealed grade I isthmic spondylolisthesis, with instability at L4-5. Computed tomography and magnetic resonance imaging demonstrated bilateral foraminal stenosis, with soft foraminal disc herniation on the right side at the L4-5 level. He underwent anterior lumbar interbody fusion[ALIF] with percutaneous posterior fixation[PF] at the L4-5 level. Without removing the posterior bony structures, removal of foraminal disc herniation and reduction of spondylolisthesis were successfully performed using ALIF with percutaneous PF. When there is no hard disc herniation or lateral recess stenosis, ALIF with percutaneous PF can be one of the treatment options for isthmic spondylolisthesis, even in the presence of foraminal disc herniation, as in our case.

• Journal of the Korean Ceramic Society
• /
• v.34 no.4
• /
• pp.420-428
• /
• 1997

Alumino-borosilicate glasses containing nano-sized CuCl crystals for nonlinear optical application were prepared by the melting and precipitation process, and structural and optical properties were investigated by using XRD, TEM, SAXS, and optical spectroscopy. the average radius of the precipitated CuCl particles was about 2 nm. The blue shift of Z3 resonance peak with decreasing the precipitated CuCl particles size was found and the radius increased with decreasing the glass transition temperature of the matrix glass and with increasing the temperature and duration time of the precipitation heat treatment.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.05a
• /
• pp.36-37
• /
• 2015

The purpose of this study is to investigate pozzolanic reactivity of the rice straw ash. This study focused on rice straw ash properties at various burning temperature and duration as a mineral admixture for mortar and concrete, and provide the crystalline state and molecular structure of rice straw ash. X.R.D and N.M.R were performed on rice straw ashes to identify pozzolanic reactivity.

• Journal of Korean Neurosurgical Society
• /
• v.39 no.4
• /
• pp.310-313
• /
• 2006

Although lipomyelomeningocele and dermoid cyst are formed during a similar embryologic developmental stage of 'neural tube formation', they are caused by entirely different embryologic mechanisms. We encountered a case, which has not been previously reported, that had a lumbar subcutaneous dermoid cyst associated with lipomyelomeningocele. A 52-year-old man presented with a slowly growing lumbar mass of 3 years duration, which had been present since birth. Lumbosacral magnetic resonance imaging[MRI] showed lipomyelomeningocele at the L3, 4 and 5 levels and a subcutaneous cystic mass of high signal intensity on the T2 weighted image and iso or low signal intensity on the T1 weighted image. He underwent total resection of the lumbar subcutaneous mass. Intraoperative findings and histological examination were consistent with the preoperative diagnosis of a 'dermoid cyst'. We demonstrate that the formation of a dermoid cyst might coexist with lipomyelomeningocele during the embryologic developmental stage.