• Journal of Korean Neurosurgical Society
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• v.62 no.4
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• pp.450-457
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• 2019

Objective : Anterior cervical discectomy and fusion (ACDF) is commonly used surgical procedure for cervical degenerative disease. Among the various intervertebral spacers, the use of allografts is increasing due to its advantages such as no harvest site complications and low rate of subsidence. Although subsidence is a rare complication, graft collapse is often observed in the follow-up period. Graft collapse is defined as a significant graft height loss without subsidence, which can lead to clinical deterioration due to foraminal re-stenosis or segmental kyphosis. However, studies about the collapse of allografts are very limited. In this study, we evaluated risk factors associated with graft collapse. Methods : We retrospectively reviewed 33 patients who underwent two level ACDF with anterior plating using allogenous bone graft from January 2013 to June 2017. Various factors related to cervical sagittal alignment were measured preoperatively (PRE), postoperatively (POST), and last follow-up. The collapse was defined as the ratio of decrement from POST disc height to follow-up disc height. We also defined significant collapses as disc heights that were decreased by 30% or more after surgery. The intraoperative distraction was defined as the ratio of increment from PRE disc height to POST disc height. Results : The subsidence rate was 4.5% and graft collapse rate was 28.8%. The pseudarthrosis rate was 16.7% and there was no association between pseudarthrosis and graft collapse. Among the collapse-related risk factors, pre-operative segmental angle (p=0.047) and intra-operative distraction (p=0.003) were significantly related to allograft collapse. The cut-off value of intraoperative distraction ${\geq}37.3%$ was significantly associated with collapse (p=0.009; odds ratio, 4.622; 95% confidence interval, 1.470-14.531). The average time of events were as follows: collapse, $5.8{\pm}5.7months$; subsidence, $0.99{\pm}0.50months$; and instrument failure, $9.13{\pm}0.50months$. Conclusion : We experienced a higher frequency rate of collapse than subsidence in ACDF using an allograft. Of the various preoperative factors, intra-operative distraction was the most predictable factor of the allograft collapse. This was especially true when the intraoperative distraction was more than 37%, in which case the occurrence of graft collapse increased 4.6 times. We also found that instrument failure occurs only after the allograft collapse.

• Journal of Environmental Health Sciences
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• v.47 no.2
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• pp.175-181
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• 2021

Objectives: The correlation between the size of a leak hole, the volume of the leakage, and the range of influence was investigated for a hydrochloric acid tank-lorry. Methods: For the case of a tank-lorry chemical accident, KORA (Korea Off-site Risk Assessment Supporting Tool) was used to predict the leak rate and the range of influence according to the size of the leak hole. The correlation was studied using R. Results: As a result of analyzing the leak rate change according to the leak hole size in a 35% hydrochloric acid tank-lorry, as the size of the leak hole increased from 1 to 100 mm, the leak rate increased from 0.008 to 83.94 kg/sec, following the power function. As a result of calculating the range of influence under conditions ranging from 1 to 100 mm in size and 10 to 60 minutes of leakage time, it was found that the range spanned from a minimum of 5.4 m to a maximum of 307.9 m. As a result of multiple regression analysis using R, the quadratic function model best explained the correlation between the size of the leak hole, the leak time, and the range of influence with an adjected coefficient of determination of 0.97 and a root mean square error of 22.33. Conclusion: If a correlation database for the size of a leak hole is accumulated for various substances and under various conditions, the amount of leakage and the range of influence can easily be calculated, facilitating field response activities.

• Journal of Soil and Groundwater Environment
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• v.27 no.5
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• pp.10-17
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• 2022

Inorganic acids such as HCl, HNO₃, and H₂SO₄ have been commonly applied to soil washing of heavy metals-contaminated soil due to their cost-effectiveness. However, implementing the 'Chemical Substance Control Act' requires off-site risk assessment of the chemicals used in the soil washing. Therefore, in this study, organic acids or Fe(III)-based washing agents were evaluated to replace commonly used inorganic acids. Ferric removed heavy metals via H⁺ generated by hydrolysis, which is similar to the HCl used in the control group. Oxalic acid and citric acid were effective to remove Cu, Zn, and Cd from soil. Organic acids could not remove Pb because they could form Pb-organic acid complexes with low solubility. Furthermore, Pb could be adsorbed onto the iron-organic acid complex on the soil surface. Ferric could remove exchangeable-carbonate, Fe-Mn hydroxide, and organic matter and sulfides bound heavy metals (F1, F2, and F3). Organic acids could remove the exchangeable-carbonate and Fe-Mn hydroxide bound metals (F1&F2). Therefore, this research shows that the fractionation of heavy metals in the soil and the properties of washing agents should be considered in the selection of agents in the process design.

• Fire Science and Engineering
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• v.33 no.4
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• pp.112-120
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• 2019

Benzene is a class 4 hazardous material according to the Act on the Safety Control of Hazardous Substances. This study qualitatively evaluated the damage size of a "toxic" accident and "pool fire" accidents based on benzene in a virtual scenario of a fire and leakage accident during unloading at a port facility. The KORA program was used as an evaluation method, which is supported as a universal program by the National Institute of Chemical Safety. The range of damage effects of a benzene-induced fire and leakage accident was predicted. In the case of toxic damage range, the accident's damage effect range for the "worst case scenario" was reduced by up to 5.11% with a decrease in the size of the leakage hole. In the case of the leakage time, the damage effect range increased to 145.12% with a 10 min leakage time compared to that of a 5 min leakage time and went up to 20 min (212.29%) with a 20 min leakage time. In the case of pool-fire-induced damage, the damage effect range by radiant heat in the "worst case scenario" was 228.8 m in radius from the center of the handling facility. In the "alternative scenario," the damage effect range by radiant heat was reduced by up to 8.26% compared to that in the "worst case scenario" since the size of the leakage hole was decreased by reducing the cross-sectional area of the pipe.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.7-13
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• 2021

Various research has been done on fires and explosions at gas stations at home and abroad. However, only studies of off-site damage in the event of fire at the gas station were conducted, and research on fire at the auxiliary facilities in the gas station was insufficient. The gas station is a place where anyone can easily access dangerous goods. As the risk of fire increases due to the recent increase of auxiliary facilities such as convenience stores and car repair shops in gas stations, it is important to detect the effects of fire on the main oil refinery in case of fire and to verify the validity of existing regulations. In this thesis, we conducted a study to find out the effect of radiation heat on the separation between fixed and fixed oil reactors in the event of fire at an auxiliary facility. Simulation was modelled using FDS 5.5.3 Version, and the size of the fire source was configured with 13 fire assessment devices and the heat emission rate per unit area was entered. Simulation shows that the separation distance of 2 m does not secure the safety of the gas pump in the event of fire at the auxiliary facilities, and radiation heat does not damage at the separation distance of at least 4 m. Accordingly, facilities that can block radiant heat in the event of fire at auxiliary facilities, and measures to limit the use of auxiliary facilities or to re-impose the separation between buildings and fixtures will be needed.