• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.06a
• /
• pp.122-126
• /
• 2001

Magnetic hard disk drive is continually being pushed to reduce head-disk spacing for higher recording densities. The current minimum spacing between the air-bearing slider and disk has been reduced to under 15 nm. In this work, it was investigated if flying height could be lowered under the height of laser bumps. With the reduction of the spinning speed, the flying height was decreased under the height of laser bumps. When a head swept between landing zone and data zone, the head-disk impact was monitored using AE and friction signals. It is demonstrated that magnetic hard disk drive could be operated without tribological failures under the height of laser bumps.

• Korean Journal of Hydrosciences
• /
• v.7
• /
• pp.77-86
• /
• 1996

An air chamber is design to keep the pressure from exceeding a predetermined value, or to prevent low pressures and colum separation. Therefore, it can be used to protect against rapid transients in a pipe system following abrupt pump stoppage. In this research, an air chmber was applied to a hypthetical pipe system to analyze attenuation effect of pressure head for different air volumes, locations, chamber areas, coefficients of orifice loss and pollytropic exponents. With an increase of air volume, the maximum pressure head at pump site is decreased and the minimum pressure head is imcreased. For different locations and areas of the chamber, the attenuation effects do not show much difference. Also, as the orifice loss coefficient increases, the maximum pressure head is decreased. For different polytropic exponents, isothermal process shows lower maximum pressure head than that of the adiabatic process.

• Korean Journal of Head & Neck Oncology
• /
• v.5 no.1
• /
• pp.31-38
• /
• 1989

The result of neutron therapy on head and neck cancer using KCCH -Cyclotron neutron which had been using from October 1986 to September 1989 in the Korea Cancer Center Hospital. Among the total of 27 patients the cases of malignant salivary gland tumor were 14 and the cases of advanced head and neck cancer of AJCC stage IV were 13. The local control rate was 80% in malignant salivary gland tumor and 46.2% in advanced head and neck cancer. The 2 year survival rate was 60% in malignant salivary gland tumor and 38.5% in advanced head and neck cancer. Although there was no significant difference in prognosis according to the pathologic types, squamous cell carcinoma revealed a pattern of poor prognosis. The major complication from the neutron therapy had developed 7.1% in malignant salivary gland tumor and 23.1% in advanced head and neck cancer. In conclusion, neutron therapy is superior in the treatment of malignant salivary gland tumor and also effective in the treatment of advanced head and neck cancer when it can avoid to treat some site of low tolerance.

• Korean Journal of Head & Neck Oncology
• /
• v.10 no.2
• /
• pp.102-105
• /
• 1994

The indolent course of most thyroid papillary carcinomas, even the presence of regional lymph node metastasis, make them unique among human malignant head and neck cancers. Age, sex, extracapsular invasion and anaplastic change are known to be correlated with prognosis. The purpose of this study is to clarify the significance of DNA content analysis as a prognostic factor. Twenty five thyroid papillary carcinomas were possible to be examined by flow cytometric analysis using fresh surgical specimens and three nodular hyperplasias and seven follicular adenomas were included as control group. The results were as follows: l) All of twenty five thyroid papillary carcinomas showed diploidy. 2) S-phase fraction was $1.94{\pm}2.77%$ in normal control group and $2.60{\pm}2.66%$ in papillary carcinoma group. The proliferation index was $8.44{\pm}3.89%$ in normal control and $7.70{\pm}3.63%$ in papillary carcinoma group with even low value. 3) Age, sex, extracapsular spread and lymph node metastasis showed no significant difference. In conclusion, low proliferative activity of thyroid papillary carcinomas are thought to be related with good prognosis.

• Journal of Audiology & Otology
• /
• v.25 no.4
• /
• pp.209-216
• /
• 2021

Background and Objectives: We aimed to analyze treatment outcomes following different initial management approaches and confirm treatment regimens for acute low-tone sensorineural hearing loss (ALHL) that would yield the best results. Subjects and Methods: We retrospectively analyzed the medical records of 106 patients with ALHL who visited a university hospital's otology clinic from March 2013 to June 2019. Pure-tone averages at the initial visit and at 2 and 4 weeks after the initial visit were evaluated. Results: Forty-nine patients were enrolled in this study; of them, 41 (83.7%) exhibited complete recovery (CR) at 2 weeks and 43 (87.8%) exhibited CR at 1 month after the initial visit. Regression analysis revealed that CR at 2 weeks after the initial visit was associated with diuretic use [Exp(B): 10.309, 95% confidence interval (CI): 1.007-100]. An initial daily low-dose steroid use was marginally significant [Exp(B): 1.042, 95% CI: 0.997-1.092; p=0.066]. Isolated diuretic use [Exp(B): 25.641, 95% CI: 1.121-90.909; p=0.039] was an independent, good prognostic factor at 1 month after the initial visit. However, other treatment regimens did not affect the final results. Conclusions: A combination of initial daily administration of ≤30 mg prednisolone plus diuretics was sufficient as the first-line treatment for ALHL. High-dose steroids and salvage intratympanic steroid injections can be applied as a second choice; however, the predicted outcome would not be good in that case.

• Korean Journal of Audiology
• /
• v.25 no.4
• /
• pp.209-216
• /
• 2021

Background and Objectives: We aimed to analyze treatment outcomes following different initial management approaches and confirm treatment regimens for acute low-tone sensorineural hearing loss (ALHL) that would yield the best results. Subjects and Methods: We retrospectively analyzed the medical records of 106 patients with ALHL who visited a university hospital's otology clinic from March 2013 to June 2019. Pure-tone averages at the initial visit and at 2 and 4 weeks after the initial visit were evaluated. Results: Forty-nine patients were enrolled in this study; of them, 41 (83.7%) exhibited complete recovery (CR) at 2 weeks and 43 (87.8%) exhibited CR at 1 month after the initial visit. Regression analysis revealed that CR at 2 weeks after the initial visit was associated with diuretic use [Exp(B): 10.309, 95% confidence interval (CI): 1.007-100]. An initial daily low-dose steroid use was marginally significant [Exp(B): 1.042, 95% CI: 0.997-1.092; p=0.066]. Isolated diuretic use [Exp(B): 25.641, 95% CI: 1.121-90.909; p=0.039] was an independent, good prognostic factor at 1 month after the initial visit. However, other treatment regimens did not affect the final results. Conclusions: A combination of initial daily administration of ≤30 mg prednisolone plus diuretics was sufficient as the first-line treatment for ALHL. High-dose steroids and salvage intratympanic steroid injections can be applied as a second choice; however, the predicted outcome would not be good in that case.

• Korean Journal of Head & Neck Oncology
• /
• v.18 no.1
• /
• pp.46-49
• /
• 2002

Background: Free flaps have become a very important role in the ablative head and neck surgery with functional preservation of defect sites. The forearm free flap has many advantage of lack of bulk, ease of dissection, vascularity, and malleability. Patients and Methods: A review of 51 radial forearm free flaps performed between may 1990 and feburary 2001 at the Korea University was undertaken to determine outcome. Patient age ranged 27 to 72 years (mean 56). There were 44 men and 7 women. The most prevalent neoplasm was squamous cell carcinoma. Results: The tans verse cervical artery and the external jugular vein were the most frequent receipient sites for microvascular anastomosis. Total flap loss occurred in 2 cases (4%) and other complications were seen in 42%. Fifteen patients received preoperative irradiation and the complication was higher than non-irradiation patients, but statistically not significant. Conclusion: The radial forearm free flap offers a variety of reconstructive options for head and neck. Its low flap loss and complication rates offer the best choice for reconstruction of defect of head and neck malignancy.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1999.06a
• /
• pp.53-60
• /
• 1999

As the flying height decreased, it is essential that hard disk drives perform reliable under various environmental conditions. In this paper the tribological characteristics of a head/disk interface are investigated under various temperature, relative humidity, altitude and outgas conditions. Specially, Contact-Start-Stop(CSS) tests were performed to assess the stiction, acoustic emission, slider take-off behavior, and track average amplitude(TAA). It is shown that the surface damage and head failure are accelerated by high temperature and humidity as well as low ambient pressure.

• Tribology and Lubricants
• /
• v.17 no.1
• /
• pp.1-9
• /
• 2001

Hard disk drives operate in various environmental conditions. Thus, it is necessary to assess the reliability of the head/disk interface under these conditions. In this work, stiction and acoustic emission signals were investigated under different temperature, humidity, and ambient pressure conditions. Also, track average amplitude was observed for disk failure in N$_2$environment. It is shown that failure of the head/disk interface occurs more readily at high temperature and low ambient pressure conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1998.10a
• /
• pp.131-138
• /
• 1998

It is essential that hard disk drives perform reliable under various temperature, humidity, and ambient pressure conditions. In this paper the tribological characteristics of a head/disk interface are investigated under various environmental conditions. Specially, Contact-Start-Stop(CSS) tests were performed to assess the stiction and slider take-off behavior. It is shown that the surface damage is accelerated by high temperature and humidity as well as low ambient pressure.