• Journal of Chest Surgery
• /
• v.29 no.10
• /
• pp.1102-1110
• /
• 1996

Between Oct. 1985 and July 1995, 230 patients underwent mitral valve replacement. There were 77 men and 153 women whose mean age was 35.7 years, range 9 to 62 The concomitant operations were 40 aortic valve replacements(17.4%), 25 tricuspid annuloplasties(10.4%), 8 aortic valve replacements & tricuspid annuloplasties(3.5%), 2 tricuspid valve replacements(0.9%) and others, We used 139 mechanical (76 51. Jude medical, 33 CarboMedics, 30 Sorin) and 91 tissue 386 Carpentier-Edwards, 5 lonescu-Shiley) valves. The early postoperative complications occurred in 28 cases. There were 8 low cardiac output syndrome, 5 pleural effusion, 3 significant arrhythmia, 2 cardiac rupture and others. There were 6 early hospital deaths (2.6%) due to low cardiac output syndrome(2), arrhythmia(2) and ventricul r rupture(2). The cuAmulative notal follow-up period was 764. 4 patient-years with a mean of 4).9 months. The long term follow-up information was available for 212 patients(94.6%). There were 21 cases of valve-related complications. Prosthetic valve failure(10), anti-coagulation related bleeding (5), prosthetic valve endocarditis (4), and thromboembolism (2) occurred at rates of 1.3, 0.7, 0.5, and 0.3%Ipt-yr respectively. Late death occurred In 5 cases (0.7%/pt-yr) associated with prosthetic valve endocarditis (2), heart failure (2) and anti-coagulation related bleeding (1). There was no difference in the rate of freedom from prosthetic valve failure between the mechanical and tissue valve group at 6 years (100%), but there was significant difference at 9 years between the tissue (34.4%) and mechanical valve (100%) group (p=0.032). Actuarial survival rates were 98. 8% in tissue valve. 9).7% in mechanical valve group and 96.6% in total patients at 9 years.

• Journal of the Korean Magnetics Society
• /
• v.20 no.3
• /
• pp.89-93
• /
• 2010

We study the giant magneto-resistance (GMR), coercivity and their dependence on the ferromagnetic layers adjacent to the nonmagnetic layer in a spin-valve structure, [Pd/ferromagnetic] multilayers with perpendicular anisotropy. We fabricated a basic spinvalve structure of $[Pd/Co]_2$/ferro-magnetic layer/nonmagnet/ferro-magnetic layer/$[Pd/Co]_2$/FeMn and investigated the dependence of its GMR and magnetic properties such ad coercivity on the ferromagnetic material to reduce the coercivity of the free layer. We try to reduce the freelayer coercivity by controlled the anisotropy, we insert the material NiFe, $Co_8Fe_2$, $Co_9Fe_1$ to ferromagnetic layers adjacent to the Cu layer. Then, we have been able to reduce the coercivity as low as 100 Oe, and also achieved 6.7% of magneto-resistance ratio when the ferromagnetic layer thickness was 0,7 nm.

• Journal of Chest Surgery
• /
• v.29 no.3
• /
• pp.331-336
• /
• 1996

Four operative cases of aortic valvuloplasty with leaflet extension technique using glutaraldehyde preserved tautologous pericardium are described. All patients had severe aortic regurgitation on preoperative echocardiogram, and Grade W AR on oath-angiogram. The causes of aortic regurgitation were rheumatic fever in 2 cases, degenerative change in 1 case, and 1 case of unknown cause. The autologous pericardium was fixed In a 0.625% glutaraldehyde solution for 15 minutes and rinsed in saline for an additional 15 minutes. Leaflet extension technique varied in 4 patients depending on the site and the extent of the leaflet size and lesion. There was no hospital mortality and no thromboembolic episode without anticoagulation. Post-operative cardiac size was reduced on simple chest film in all cases, and LVESD and LVEDD were reduced on folio w- up echo cardi o gram . This experience permits us to conclude that leaflet extension technique is simple and safe in valve r construction, allowing repair of aortic valves that need to be replaced.

• Journal of Chest Surgery
• /
• v.37 no.4
• /
• pp.328-334
• /
• 2004

There are only limited numbers of reports about long-term results of tricuspid valve replacement(TVR) with bioprosthetic and mechanical prostheses. We analyzed risk factors for tricuspid valve replacement and compared long-term clinical results of bioprosthetic and mechanical valves in tricuspid position. Material and Method: We reviewed 77 cases of TVR, which were performed between October 1978 and December 1996. Mean age was 38.8 15.9 years. Bioprostheses were implanted in 26 cases and mechanical prostheses were implanted in 51 cases. Result The operative mortality was 15.6% and late mortality was 12.3%. Survival for bioprosthetic and mechanical valve group at 5, 10 and 13 years was 81.3% vs. 100%, 66.1% vs. 100%, 60.6% vs. 100% (p=0.0175). Free from valve related re-operation for bioprosthetic and mechanical valve group at 5, 10 and 13 years was 100% vs. 93.9%, 100% vs. 93.9% and 58.3% vs. 93.9% (p=0.3274). Linealized incidences of valve related re-operation for bioprosthetic and mechanical valve group was 2.27 %/patient-years and 1.10 %/patient-years. Risk factor analysis showed that presence of preoperative ascites, hepatomegaly larger than 2 finger breaths, poor preoperative NYHA functional class and number of tricuspid valve replacement were risk factors for early mortality, and the use of bioprosthetic valve and number of open heart surgery were risk factors for late mortality. Conclusion: Long-term survival of mechanical valve was superior to bioprosthetic valve in tricuspid position. We recommend mechanical valve in tricuspid position if the patient can be closely followed up.

• Journal of the Korean earth science society
• /
• v.37 no.1
• /
• pp.11-20
• /
• 2016

Diatoms were studied from the trench sediments around Bangudae petroglyphs in order to better understand the depositional environment before and after the construction of Sayeon dam in Ulsan. There were no diatoms produced from the sediments before the dam construction while the diatoms were produced from the sediments (depth of trench 228 cm) after the construction of the dam. Seventy-five species of diatoms of 27 genera were identified in the trench sediments. The number of diatom valves per gram of dry sediment ranged from $0.2-5.8{\times}10^5g^{-1}$. Four diatom assemblage zones were identified according to the frequency of critical taxa as follows: assemblage zone I, from 228 to 150 cm; assemblage zone II, from 150 to 122 cm; assemblage zone III, from 122 to 62 cm; and assemblage zone IV, from 62 to 0 cm. In addition, based on the environmental indicator species, an analysis was carried out to measure eutrophication, acidity and $Cl^-$ value. Results of the eutrophication and $Cl^-$ values were as follows. Based on the lower 74 cm horizons, the degree of eutrophication middle-high to $Cl^-$ values were lower, upper horizons appeared to eutrophication in the low, and $Cl^-$ values were high. Acidification from low horizons of 122 cm showed a neutral-alkaline degree whereas it exhibited acid in the upper part. In particular, regarding nutrients (TP and TN), the index taxa showed a higher TP value at 175 cm while higher TN value at 62 cm.

• Korean Chemical Engineering Research
• /
• v.53 no.1
• /
• pp.16-21
• /
• 2015

The body structure of diaphragm type preaction valve was improved in order to reduce the pressure drop. The pressure drop must be kept within 20.7 kPa to pass the revised (2012. 2. 9) standard for alarm valve and preaction valve. The pressure drop test was carried out by KFI (Korea Fire Institute) standard. The pressure drop of a preaction valve was higher than that of an alarm valve. Causes for increasing the pressure drop were investigated with the fluid flow in the valve. The preaction valve had more pressure drop factors (changes in velocity and direction) compared with the alarm valve. Inner structure of the preaction valve was changed to the clapper type to remove the pressure drop factors. In 80A and 100A size of preaction valves, the pressure drop was reduced from 80.9 and 171.0 kPa to 14.4 and 14.2 kPa respectively, after the change of the structure.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.17 no.4
• /
• pp.447-455
• /
• 1995

Cavernous sinus thrombosis is one of the major complications of abscesses of the maxillofacial region. The initial symptoms of CST are usually pain in the eye and tenderness to pressure. this is associated with high fluctuating fever, chills, rapid pulse, and sweating. Venous obstruction subsequently causes edema of the eyelids, lacrimation, proptosis, chemosis and retinal hemorrhages. Blindness is sometimes an accompaniment of cavernous sinus thrombosis when the infection also involves the orbit. There is also cranial nerve involvement (oculomotor, troclear, abducence) and ophthalmoplegia, diminished or absent corneal reflex, ptosis, and dilation of the pupil occur. The terminal stages bring signs of advanced toxemia and meningitis. Infections of the face can cause a septic thrombosis of the cavernous sinus. Furunculosis and infected hair follicles in the nose are frequent causes. Extractions of maxillary anterior teeth in the presence of acute infection and especially curettage of the sockets under such circumstances can cause this condition. The infection is usually staphylococcal. The inflection may spread directly through the pterygoid plexus of veins and the pterygomaxillary space and then ascend into the sinus or it may spread directly from the pterygopalatine space to the orbit. This is possible because of the absence of valves in the angular, facial, and ophthalmic veins. The treatment is empirical antibiotic therapy followed by specific anbibiotic therapy based on blood or pus culture. The inflection usually involves one side, however, it may easily spread to the opposite side through the circulus sinus. Unless it is treated early, the prognosis is poor even in this doses. Occasionally the antibiotics will not adequately resolve the septic thrombus, and death ensues. the use of anticoagulants to prevent venous thrombosis has been recommended, but the efficacy of such therapy has not been substantiated. Surgical access through eye enucleation has been suggested. We report a case which demonstrates cavernous sinus thrombosis by the infection after the functional neck dissection and the intraoral reconstruction with auriculomastoid fascio-cutaneous island flap.

• Journal of the HCI Society of Korea
• /
• v.1 no.2
• /
• pp.19-26
• /
• 2006

This paper presents a novel pneumatic tactile display that can deliver some useful information. The air-jet display forms 5 by 5 arrays and features air nozzles with an external diameter of 2.4mm and internal diameter of 1.5 mm. In comparison with other tactile displays such as vibrotactile, there is little concrete psychophysical data relating to pneumatic displays, a fact which hinders their adoption. This paper addresses this challenge, and presents brief psychophysical studies examining localization rate, the two point threshold, stimulus intensity and the temporal threshold of cues produced by pneumatic air jets. Two groups of subjects were used in these studies, subsequently termed groups A and B. Both were comprised of eight participants. In the case of localization study we obtained 58.13% and 85.9% of localization rates each for dense display and sparse display. Two-points threshold test showed the length of gap between two air-jet stimuli which subjects can detect. However, it was formidable to find out precise temporal resolution of PTI owing to the limitation of capability of the pneumatic valves. Lastly, the results of stimulus intensity study suggest that by varying the size of a pneumatically created tactile stimulus, we can effectively vary its perceived magnitude.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1261-1265
• /
• 2003

Axial piston pumps of bent axis have been commonly used in hydraulic systems because of high pressure level. best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the axial piston pumps of bent axis require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the axial piston pumps of bent axis was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a paralle linel could reduce the discharge pressure wave of the pump well. The analysis model of the axial piston pumps of bent axis developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.10
• /
• pp.681-687
• /
• 2016

It is essential for micro jet injectors in the biomedical sector to operate under high pressure. High pressure injection, however, is accompanied by high volumes. On/Off valves that can be operated at high speeds have been used to address this problem. In this research, piezoelectric actuators which have a response frequency of the order of hundreds of kilohertz were used as the On/Off valve and experiments were applied. Researchers developed a controller to precisely manipulate the piezoelectric valve with various waveforms. They also fabricated five types of nozzles to consider the effect of nozzle type on injection. This allowed researchers to manipulate and confirm factors that can affect the injection volume and force. Results of this experiment have shown how to decrease the injection volume and increase the injection force. and it is predicted that the optimized injection volume and force value can be determined depending on the skin type.