• Geomechanics and Engineering
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• v.17 no.4
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• pp.333-342
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• 2019

Geological dynamic hazards during coal mining can be caused by the failure of a composite system consisting of roof rock and coal layers, subject to different loading rates due to different advancing velocities in the working face. In this paper, the uniaxial compression test simulations on the composite rock-coal layers were performed using $PFC^{2D}$ software and especially the effects of loading rate on the stress-strain behavior, strength characteristics and crack nucleation, propagation and coalescence in a composite layer were analyzed. In addition, considering the composite layer, the mechanisms for the advanced bore decompression in coal to prevent the geological dynamic hazards at a rapid advancing velocity of working face were explored. The uniaxial compressive strength and peak strain are found to increase with the increase of loading rate. After post-peak point, the stress-strain curve shows a steep stepped drop at a low loading rate, while the stress-strain curve exhibits a slowly progressive decrease at a high loading rate. The cracking mainly occurs within coal, and no apparent cracking is observed for rock. While at a high loading rate, the rock near the bedding plane is damaged by rapid crack propagation in coal. The cracking pattern is not a single shear zone, but exhibits as two simultaneously propagating shear zones in a "X" shape. Following this, the coal breaks into many pieces and the fragment size and number increase with loading rate. Whereas a low loading rate promotes the development of tensile crack, the failure pattern shows a V-shaped hybrid shear and tensile failure. The shear failure becomes dominant with an increasing loading rate. Meanwhile, with the increase of loading rate, the width of the main shear failure zone increases. Moreover, the advanced bore decompression changes the physical property and energy accumulation conditions of the composite layer, which increases the strain energy dissipation, and the occurrence possibility of geological dynamic hazards is reduced at a rapid advancing velocity of working face.

• Journal of Korean Neurosurgical Society
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• v.47 no.6
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• pp.442-445
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• 2010

Objective : The purpose of this study was to examine the efficacy and safety of microvascular decompression (MVD) for hemifacial spasm (HFS) in elderly patients. Methods : Between 1997 and June 2008, 1,174 patients had undergone MVD for HFS at our institute. Among these, 53 patients were older than 65 years. We retrospectively reviewed and compared the complication and the cure rates of these patients with those of younger patients. Results : There were 38 females and 15 males. The mean duration of symptoms of HFS of these patients was 94.6 months (range, 12-360 months), compared with 67.2 months (range, 3-360 months) in the younger group. The overall cure rate in elderly patients who underwent MVD for HFS during this period was 96.2%. Permanent cranial nerve dysfunctions, such as hearing loss and facial palsy, were seen in 2 patients (3.8%, 2/53) in the elderly group and 19 patients (1.7%, 19/1121) in the younger group. The difference in permanent cranial nerve dysfunction between the two groups was not statistically significant. There was no operative mortality in either group. Conclusion : Microvascular decompression is the most effective surgical modality available for the treatment of HFS. Results of this study indicate that such technique can be performed in the elderly without higher rates of morbidity or mortality. Any patient with HFS, whose general health is acceptable for undergoing general anesthesia, should be considered as a candidate for MVD.

• KSBB Journal
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• v.25 no.5
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• pp.471-477
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• 2010

In order to improve bio-ethanol productivity by various cultivation methods in this paper, the culture modes using food wastes, such as batch culture, high-cell-density fermentation, SSF (simultaneous saccharification and fermentation) by fill & draw, continuous culture by fill & draw were performed and their productivities were compared. SSFs by fill & draw were performed by continuous decompression using 1 L evaporator system, and by 10 L bioreactor without decompression. In addition, the continuous cultures by fill & draw mode using SFW (saccharafied food wastes) medium were performed by changes of 40% culture broth with intervals of 12 h (0.03 $h^{-1}$), 6 h (0.07 $h^{-1}$), 3 h (0.13 $h^{-1}$). Consequently, productivities of bio-ethanol were 2.52 g/L-h and 1.30 g/L-h in batch culture and high- cell-density fermentation, respectively. The productivities of SSF by fill & draw showed 2.24 g/L-h and 2.03 g/L-h in continuous decompression with 1 L evaporator and 10 L bioreactor without decompression, respectively. Also, the productivities in continuous culture by fill & draw modes showed 2.02 g/L-h, 4.07 g/L-h and 6.25 g/L-h by medium change with intervals of 12 h, 6 h, and 3 h, respectively. In conclusion, the highest ethanol productivity was obtained in the continuous culture mode by fill & draw with dilution rate of 0.13 $h^{-1}$.

• Journal of Korean Neurosurgical Society
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• v.62 no.1
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• pp.46-52
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• 2019

Objective : The aim of this nationwide study was to analyze the current state of patients with newly diagnosed metastatic spine tumors according to surgical methods. Methods : Data was extracted from the Korean Health Insurance Review and Assessment Service database. Surgery was categorized into three methods : fusion, decompression, and vertebroplasty. Data included patient age, sex, health insurance type, and co-morbidities. Survival rates of metastatic spine tumor patients according to each surgical method were evaluated. Results : Among 1677 patients who had an operation, 823 patients were treated by fusion, 141 patients underwent decompression, and 713 patients were treated by vertebroplasty. The three most prevalent primary tumor sites were the lung, breast, and liver & biliary. On the other hand, the three most prevalent primary tumor sites of patients who underwent surgery were the lung, liver & biliary, and the prostate. The median survival periods for each surgical method in the metastatic spine tumor patients were 228 days for those who underwent surgery, 249 days for decompression, and 154 days for vertebroplasty. Age, sex, and comorbidities significantly affected survival rate. Conclusion : For every primary tumor site, decompression was the least common surgical method during the study period. Although the three surgical methods did not significantly affect the survival period, patients with a poor prognosis tended to undergo vertebroplasty.

• Journal of Korean Neurosurgical Society
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• v.42 no.3
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• pp.184-190
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• 2007

Objective : The authors retrospectively analyzed clinical and radiographic features of patients who developed symptomatic adjacent segment degeneration (ASD) that required re-operation. Methods : From 1995 to 2004, among 412 patients who underwent posterior lumbar fusion surgery, the authors experienced twenty-six patients who presented symptomatic ASD. Records of these patients were reviewed to collect clinical data at the first and second operations. Results : The patients were 9 males and 17 females whose mean age was $63.5{\pm}8.7$ years. Among 319 one segment and 102 multi-segment fusions, 16 and 10 patients presented ASD, respectively. Seventeen ASDs were noticed at the cephalad to fusion (65%), eight at the caudad (31%), and one at the cephalad and caudad, simultaneously (4%). All patients underwent decompression surgery. Nine patients underwent additional fusion surgeries to adjacent degenerated segments. In 17 patients who underwent only decompression surgery without fusion, the success rate was 82.4%. In fusion cases. the success rate was observed as 55.5%. There were no statistically significant factors to be related to development of ASD. However, in cases of multi-level fusion surgery, there was a tendency toward increasing ASD. Conclusion : Multi-segment fusion surgery could be associated with a development of ASD. In surgical treatment of symptomatic ASD, selective decompression without fusion may need to be considered as a primary procedure, which could reduce the potential risk of later occurrence of the other adjacent segment disease.

• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.159-166
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• 2002

The purpose of this study was to review the knowledge related to historic background, causes, symptoms, etiology and rehabilitation methods related to this disease and suggest some ways to reduce complications from it. The importance of underwater pressure disease was not emphasized, therefore, there is a need for continuous research on treatment methods and prevention for it. As one goes into the deeper water, they will be affected by the hydraulic pressure rather then the atmospheric pressure, and it will be increased 1mmHg by 10meters. Underwater pressure disease can be occurred when one comes out of deeper water too quicked. This results the imbalance of the composition rate of nitrogen in blood. However, there is not enough facilities to treat this disease and these facilities are located in limited areas. Therefore, there is an urgent need to set up a medial center that is specialized in prevention and treatment of underwater pressure disease.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.3
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• pp.232-240
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• 2019

Approximately 80% of the world's sea cucumbers Apostichopus japonicas are processed into dried sea cucumbers. The hot air-drying method is currently used in industry, but it has many problems, such as a short drying time, severe browning, high nutrition loss, and low recovery. In this study, the moisture absorption rate, dry recovery rate, and lipid nutrient composition of sea cucumber dried by heat pump decompression and with a hybrid dryer were investigated. The moisture absorption rates for hybrid-dried sea cucumbers at 24, 48, 72, 96, and 120 h were 241.3%, 427.7%, 652.0%, 721.0%, and 742.2%, respectively. The moisture absorption rates for hot air-dried sea cucumbers were 155.8%, 240.0%, 390.3%, 655.5%, and 667.4%, respectively. Thus, moisture absorption was faster and greater with hybrid drying than with hot air drying. The dry recovery rate at 24 h was greater for hybrid-dried sea cucumber (70.7%) than for hot air-dried sea cucumber (59.8%). Saturated fatty acid contents of the hybrid- and hot air-dried sea cucumbers were 30.0% and 37.5%, respectively. Moreover, greater ${\Sigma}n-3$ polyunsaturated fatty acid content was found in hybrid-dried sea cucumber (15.8%) than in hot air-dried sea cucumber (11.7%).

• Journal of Korean Neurosurgical Society
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• v.64 no.6
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• pp.966-974
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• 2021

Objective : To explore the clinical efficacy and safety of microvascular decompression (MVD) combined with internal neurolysis (IN) in the treatment of recurrent trigeminal neuralgia (TN) after MVD. Methods : Sixty-four patients with recurrent TN admitted to the hospital from January 2014 to December 2017 were divided into two groups according to the surgical method. Twenty-nine patients, admitted from January 2014 to December 2015, were treated with MVD alone, whereas 35 admitted from January 2016 to December 2017 were treated with MVD+IN. The postoperative efficacy, complications, and pain recurrence rate of the two groups were analyzed. Results : The efficacy of the MVD+IN and MVD groups were 88.6% and 86.2%, and the cure rates were 77.1% and 65.5% respectively. There was no statistically significant difference between the two groups (p>0.05). The cure rate (83.3%) of patients in the MVD+IN group, who were only found thickened arachnoid adhesions during the operation that could not be fully released, was significantly higher than that of the MVD group (30.0%) (p<0.05), while the efficacy (91.7% vs. 70%) of the two groups was not statistically different (p>0.05). For patients whose arachnoid adhesions were completely released, there had no significant difference (p>0.05) in the efficacy (87% vs. 94.7%) and recurrence rate (5.0% vs. 11.1%). The incidence of postoperative facial numbness (88.6%) in the MVD+IN group was higher than that in the MVD group (10.3%) (p<0.01). The long-term incidence of facial numbness was not statistically significant (p>0.05). In the 18-36 months follow-up, the recurrence rate of patients in the MVD+IN group (9.7%) and in the MVD group (16%) were not statistically different (p>0.05). Conclusion : A retrospective comparison of patients with recurrent TN showed that both MVD and MVD combined with IN can effectively treat recurrent TN. Compared with MVD alone, MVD combined with IN can effectively improve the pain cure rate of patients with recurrent TN who have only severe arachnoid adhesions. The combination does not increase the incidence of long-term facial numbness and other complications.

• Journal of Korean Neurosurgical Society
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• v.46 no.1
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• pp.5-10
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• 2009

Objective: The purpose of this study is to evaluate the effectiveness of unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis. Methods: The study group comprises consecutive 16 patients who underwent unilateral decompression and bone cement augmented pedicle screw fixation from May 2003 to January 2006. The patients were evaluated by visual analog scale (VAS) for pain and the scoring system of the Japanese Orthopedic Association (JOA) for low back pain. The result of surgery was also evaluated with McNab's classification. Excellent or good outcome was considered as successful. The patients were followed at postoperative 1 month, 3 month, 6 month, and 1 year with standing AP and lateral films. Results: The average VAS and JOA score of the 16 patients were 7.8(range, 6-9) and 5.8(range, 3 - 10) before surgery and 2.2(range, 0 - 5)and 12.3(range, 9 - 15) at the time of last follow up. Both VAS and JOA score improved significantly after the surgery (p<0.05, t-test). All patients improved after the operation and no revision surgery was required. No metal failure or pseudoarthrosis was observed during the follow-up. The success rate was 87.5%. Conclusion: Our data suggest that unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis is an effect method for obtaining satisfactory clinical outcome. Its possible advantage is shorter operation time and reduced surgical extent. We believe that the reduced stiffness of unilateral fixation was compensated by pedicle screw augmentation and interbody fusion.

• Journal of Korean Neurosurgical Society
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• v.52 no.2
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• pp.85-91
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• 2012

Objective : Hemifacial spasm (HFS) caused by vertebrobasilar dolichoectasia (VBD) is very rare, and in theses cases, it is difficult to decompress the nerve from its vascular compression. The objective of this study was to investigate the outcome of microvascular decompression (MVD) for HFS caused by VBD. Methods : There were 10 patients of HFS caused by VBD at our hospital between September 1978 and September 2008. We evaluated magnetic resonance angiography (MRA) and time of flight magnetic resonance imaginge (TOF MRI) findings using the criteria for VBD. We compared the clinical outcomes of MVD for the 10 patients with VBD with the overall outcomes of the total 2058 MVDs performed for HFS. Results : The results of MVD for HFS caused by VBD were successful in 90.9% of cases. The postoperative complication rate in VBD was 45.5%. Offending vessels in patients with VBD were identified visually during surgery. Adverse effects after MVD were found in 4 patients. We found that the diameter of VBD was significantly greater in patients with complications than in those with no complications (p=0.028). Conclusion : Our data shows that MVD may be a good treatment modality for HFS caused by VBD but care must be taken to avoid adverse effects from the procedure. It is important to detach the dolichoectatic artery from its surrounding structures sufficiently to allow it to be easily movable. In addition, attempts should be made to lessen the retraction of the cerebellum during release of the dolichoectatic artery.