• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.260-265
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• 2004

LTCC(Low temperature co-fired ceramic) is being recognized as a significant packaging material of electrical devices for the advantages such as relatively low temperature being needed for process, low conductor resistance and high printing resolution. In the process of LTCC electrical devices, the punched via-hole quality is one of the most important factors on the performance of the device. However, its mechanism is very complicated and optimization of the process seems difficult. In this paper, to clarify the process, via-hole punching experiments were carried out and the punched holes were examined in terms of their burr formation. The effects of thickness of PET sheet and ceramic sheet and punch-to-die clearance on via-hole quality were also discussed. Optimum process conditions are proposed and a factor k is introduced to express effect of the process variables.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.560-563
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• 2004

Invar is a compound metal of Fe-Ni system and contain 36％ Ni. The most distinction characteristic of Invar is the coefficient of thermal expansion is 1.0 10$^{-6}$ /$^{\circ}C$. That is a tenth of general steel material. This low thermal expansion characteristic of Invar is applied to the missile, aircraft, monitor CRT and frontier display's shadow mask such as FED and OLED. The usage of the Invar shadow mask for display is increasing due to the requirement of larger size and flatness monitor. The Invar shadow mask is machined by two ways electro-forming and laser now. However the electro-forming takes a too long time and the laser machining is accompanied with Burr. In this study, PEMM(pulse electrochemical micro machining) is conducted to machine the micro hole to the Invar and 80${\mu}{\textrm}{m}$ hole was machined.

• Journal of Korean Neurosurgical Society
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• v.60 no.6
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• pp.701-709
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• 2017

Objective : Chronic subdural hematoma is a common and relatively benign disease. However, recurrence is common after surgical treatment, and the recurrence rate varies from 5% to 33%. The aim of this study was to investigate the predictive factors for recurrence of chronic subdural hematoma. Methods : We analyzed data from 248 patients with chronic subdural hematoma who were treated by burr-hole craniostomy with a closed drainage system for hematoma evacuation in this five-year retrospective study. Results : Thirty-one (12.6%) patients underwent re-operation for recurrence of chronic subdural hematoma. Univariate analysis revealed that anticoagulation (p=0.0279), headache (p=0.0323), and preoperative midline shifting (p=0.0321) showed significant differences with respect to recurrent chronic subdural hematoma. We performed a multivariate logistic regression analysis and found that diabetes mellitus (odds ratio [OR], 2.618; 95% confidence interval [CI], 1.0899-6.2898; p=0.0314), anticoagulation (OR, 6.739; 95% CI, 1.1287-40.2369; p=0.0364), headache (OR, 2.951; 95% CI, 1.1464-7.5964; p=0.0249), and preoperative midline shifting (OR, 1.0838; 95% CI, 1.0040-1.1699; p=0.0391) were independent predictive factors for recurrence of chronic subdural hematoma. Conclusion : We showed that diabetes mellitus, anticoagulation, headache, and preoperative midline shifting were independent predictors of recurrence of chronic subdural hematoma.

• Journal of Korean Neurosurgical Society
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• v.37 no.2
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• pp.96-100
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• 2005

Objective: The brain computed tomography(CT) is an important tool throughout the clinical course of chronic subdural hematoma(CSDH). In CT findings, the density of CSDH is different in each case. We analyze management options and results according to the density of CSDH. Methods: Seventy one patients with CSDH, who had been managed in our institute from August 2001 to December 2003, were reviewed retrospectively. The authors divided the patients into six groups according to the density of hematoma; Group A-hypodense rather than the brain parenchyma, group B-isodense, group C-hyperdense, group D-mixed with hypodense and hyperdense, group E-mixed with isodense and hypodense and group F-mixed with isodense and hypersdense. In each group, the operation method, the duration of the indwelling catheter and prognosis were analyzed. Results: The patients who showed mixed density were 39 and, those who showed single density were 32. All the patients underwent burr hole drainage for the primary choice. There was only two cases that needed additional craniotomy. The average duration of indwelling catheter was $5.40{\pm}1.91$ days. Statistically the duration was not different in each group(p-value<0.05, $x^2$ test). Three cases recurred, one in group C, another in group D, and the last in group E. It had no statistical significance due to low incidence of recurrence. Conclusion: We conclude that burr hole drainage is an acceptable primary treatment option for CSDH even though the density of hematoma is different in every single case.

• Journal of Korean Neurosurgical Society
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• v.65 no.2
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• pp.255-268
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• 2022

Objective : Chronic subdural hematoma (CSDH) is a common disease in neurosurgical departments, but optimal perioperative management guidelines have not yet been established. We aimed to assess the current clinical management and outcomes for CSDH patients and identify prognostic factors for CSDH recurrence. Methods : We enrolled a total of 293 consecutive patients with CSDH who underwent burr hole craniostomy at seven institutions in 2018. Clinical and surgery-related characteristics and surgical outcomes were analyzed. The cohort included 208 men and 85 women. Results : The median patient age was 75 years. Antithrombotic agents were prescribed to 105 patients. History of head trauma was identified in 59% of patients. Two hundred twenty-seven of 293 patients (77.5%) had unilateral hematoma and 46.1% had a homogenous hematoma type. About 70% of patients underwent surgery under general anesthesia, and 74.7% underwent a single burr hole craniostomy surgery. Recurrence requiring surgery was observed in 17 of 293 patients (5.8%), with a median of 32 days to recurrence. The postoperative complication rate was 4.1%. In multivariate analysis, factors associated with CSDH recurrence were separated hematoma type (odds ratio, 3.906; p=0.017) and patient who underwent surgery under general anesthesia had less recurrence (odds ratio, 0.277; p=0.017). Conclusion : This is the first retrospective multicenter generalized cohort pilot study in the Republic of Korea as a first step towards the development of Korean clinical practice guidelines for CSDH. The type of hematoma and anesthesia was associated with CSDH recurrence. Although the detailed surgical method differs depending on the institution, the surgical treatment of CSDH was effective. Further studies may establish appropriate management guidelines to minimize CSDH recurrence.

• The Journal of Internal Korean Medicine
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• v.44 no.5
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• pp.867-874
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• 2023

Introduction: Chronic subdural hemorrhage (CSDH) primarily affects the elderly, and its incidence is rising due to aging trends. Although burr-hole craniostomy is a common treatment for CSDH, it often has a high recurrence rate and can sometimes result in poor outcomes. Oryeong-san, a traditional Korean medicine, is emerging as a potential remedy, with documented cases in both Korea and Japan. Case Presentation: In March 2021, a patient was diagnosed with an intracerebral hemorrhage in the left basal ganglia. A subsequent brain computed tomography in June 2022 revealed CSDH. Given the potential need for surgery if no CSDH absorption occurred, the patient was treated with Oryeong-san. Later computed tomography scans indicated that surgery was no longer necessary. Conclusions: This study evaluated the efficacy of Oryeong-san in treating CSDH. The results demonstrated complete CSDH absorption with no observed side effects, highlighting Oryeong-san as a promising and safe therapeutic option.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.337-343
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• 2010

Current need of weight reduction in automotive part increases the application for high strength steel (HSS). The various types of high strength steels have been used to produce chassis part, control arms and trailing arms for weight reduction and increasing of fatigue durability such as dual phase steel (DP) and ferrite bainite steel (FB). But, DP and FB steels have proven to show inferiority in durability as well as press formability. Edge cracking occurred often in flange forming and hole expansion processes is the major failure encountered. This paper discussed the behavior of edge stretchability of high strength steel of DP and FB steels. Experimental works have been conducted to study the effect of punch clearance and burr direction on hole expansion ratio (HER). Also finite element simulation (FEM) has been preformed to clarify the mechanism of flange crack and support the experimental results on HER of DP and FB steels. It was simulated the whole process of blanking process following by hole expansion process and ductile fracture criterion named the modified Cockcroft-Latham model which was used to capture the fracture initiation. From the hole expansion tests and FEM simulation studies it was concluded that ferrite bainite steel showed better stretch-flangeability than dual phase steel. It was attributed to the lower work hardening rate of ferrite bainite steel than dual phase steel at the sheared edge.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.17-23
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• 2010

Titanium alloy is one of the hard processing materials made by the traditional manufacturing method because of the excellent mechanical strength. Ablation of titanium alloy is investigated by using a femtosecond laser which is a regenerative amplified Ti:sapphire laser with 1kHz repetition rate, 184fs pulse duration time and 785nm wavelength. Experiments are carried out under various ablation conditions with different pulse overlap ratios for the rectangular shape and micro hole. Test results show that the ablation characteristic according to pulse overlap ratio of titanium alloy seems to be as non-linear type at the different zone of energy fluence. The optimal condition of rectangular shape processing is obtained at the laser peak power 1.3mW, pulse overlap ratio of 90%, beam gap of $1\;{\mu}m$. The micro hole has a good quality from the pulse overlap ratio of 99% at the same laser peak power. With the optimal processing condition, the fine rectangular shape and micro hole without burr and thermal damage are achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.65-68
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• 2004

When a monolithic component of piston and rebound is produced by sintering process, some technical problems such as clogging of holes during post-machining, dimensional change around the holes, and cracking of the component edges due to concentration of mechanical stress during machining are frequently encountered. To solve these problems, we systematically evaluated and investigated the density of green compacts and sintered parts, the microstructural change around the holes, and the attenuation and durability of the sintered parts in this study. By doing so, it was able to solve above problems.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.3
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• pp.419-425
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• 2010

To machine the micro hole, laser machining system is widely used, however, the system cannot fabricate the micro hole with high aspect ratio and good surface finish. To break the obstacles, the high frequency vibration mechanism with PZT (Piezoelectric Transducers) is proposed in this paper. The mechanism will vibrate the laser beam in vertical direction so that the aspect ratio and surface finish may be higher than the conventional. The mechanism vibrates the eyepiece of laser optics. In addition to the benefits, the mechanism enables us to have high precision and flexibility. It decreases burr and debris during machining. And it is able to machine various materials of workpiece. This research include high frequency and large travel range of the proposed mechanism. The PZT motion of mechanism and analysis on the sensitivity of design parameters are extracted from a finite element method (FEM) simulation. In the analysis, the target vibration mode without parasitic motion is designated to have the target frequency and high amplitude.