• The Journal of the Korean dental association
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• v.57 no.11
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• pp.672-678
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• 2019

AIM: The purpose of this study was to evaluate and compare the torsional fracture resistances, cyclic fatigue resistance, and bending stiffness of two nickel-titanium (NiTi) rotary instruments made of different heat-treated alloy: Aurum Blue (heat-treated) and Aurum Pro (conventional). Methods: Forty-five Aurum Blue and Aurum Pro NiTi files were selected for the three mechanical tests (n=15). For the torsional resistance test, 3 mm file tip was fixed and the shaft was driven clockwise at 2 rpm until fracture occurred by using a customized device. Cyclic fatigue resistance was evaluated by rotating instruments in artificial canal with dynamic mode. Bending stiffness was tested by observation of the bending moment on attaining a 45° bend. The results were analyzed by student-t tests at a significance level of 95%. The fractured surface of each groups were examined under a scanning electron microscope (SEM). Results: Aurum Blue showed significantly higher toughness, ultimate strength, distortion angle, and number of cycles to failure than those of Aurum Pro (p < 0.05). However, Aurum Blue and Aurum Pro did not differ significantly in terms of bending stiffness. SEM showed typical topographic appearances of the cyclic fatigue and torsional fracture. Conclusions: Under the limitations of this study, heat-treated instruments showed higher flexibility and fracture resistances than conventional NiTi instruments.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.149-156
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• 2019

A stretchable thermoelectric module consisting of 5 pairs of Bi₂Te₃-based hot-pressed p-n thermoelectric legs was processed by filling the module inside with polydimethylsiloxane (PDMS) and removing the top and bottom substrates. Its stretchable characteristics and power generation properties were measured. The integrity of the module was kept well even after 10 strain cycles ranging from 0 to 0.1. With increasing the tensile strain to 0.2, the module circuitry became open because of joint failure between Cu electrodes and thermoelectric legs. The stretchable thermoelectric module exhibited an open circuit voltage of 4.6 mV with a temperature difference of 2.2K across both ends of thermoelectric legs, and changes in its open circuit voltage were below 5% for tensile strains of 0~0.1. Being elongated for a strain of 0.1, it exhibited the maximum output power of 18.5 ㎼ with the temperature difference of 2.2K across its both ends.

• Restorative Dentistry and Endodontics
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• v.42 no.3
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• pp.224-231
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• 2017

Objectives: To determine the actual revolutions per minute (rpm) values and compare the cyclic fatigue life of Reciproc (RPC, VDW GmbH), WaveOne (WO, Dentsply Maillefer), and TF Adaptive (TFA, Axis/SybronEndo) nickel-titanium (NiTi) file systems using high-speed camera. Materials and Methods: Twenty RPC R25 (25/0.08), 20 WO Primary (25/0.08), and 20 TFA ML 1 (25/0.08) files were employed in the present study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which has an artificial stainless steel canal with a $60^{\circ}$ angle of curvature and a 5-mm radius of curvature. The files were divided into 3 groups (group 1, RPC R25 [RPC]; group 2, WO Primary [WO]; group 3, TF Adaptive ML 1 [TFA]). All the instruments were rotated until fracture during the cyclic fatigue test and slow-motion videos were captured using high-speed camera. The number of cycles to failure (NCF) was calculated. The data were analyzed statistically using one-way analysis of variance (ANOVA, p < 0.05). Results: The slow-motion videos were indicated that rpm values of the RPC, WO, and TFA groups were 180, 210, and 425, respectively. RPC ($3,464.45{\pm}487.58$) and WO ($3,257.63{\pm}556.39$) groups had significantly longer cyclic fatigue life compared with TFA ($1,634.46{\pm}300.03$) group (p < 0.05). There was no significant difference in the mean length of the fractured fragments. Conclusions: Within the limitation of the present study, RPC and WO NiTi files showed significantly longer cyclic fatigue life than TFA NiTi file.

• Journal of Chest Surgery
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• v.30 no.6
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• pp.585-590
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• 1997

Between December 1994 and October 1996, 57 premature infants with evidence of a hemodynamically significant PDA associated with cardiopulmonary compromise underwent indomethcin therapy(Group I, n=48) or surgical ligation(Group II, n=9) because of indomethacin failure. The gestational alee(29.6$\pm$ 3.1weeks vs. 28.1 $\pm$ 1.6weeks) and birth weight(1,413 $\pm$ 580gm, ,098 $\pm$ 235gm) showed no significant differences between the two groups. Medical management included fluid restriction, diuretics, and indomethacin therapy(one or two cycles). Surgical libation was done at the neonatal intensive care unit(NICU) without moving the patient to the operation room. There was no complication associated with the operation. There were 9 deaths in Group I(19%, 9/48) and 2 deaths in Group II(22% , 219). The main causes of deaths were persistent bronchopulmonary dysplasia with sepsis(n=8) and intrapulmonary hemorrhage(n=3). The rate of medical treatment failure including death and complication in premature infants whose body weights were less than 1500gm was higher(41%, 15/38) than in premature infants whose body weights were more than 1500gm(16%, 3/19). Early surgical ligation of PDA may be applicable in the premature infant with a large size, low birth weight(<1500 gm), or associated intracardiac anomalies. Perfoming the operation in the NICU may be safe in s ead of moving the patient to the operating room.

• Radiation Oncology Journal
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• v.13 no.2
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• pp.149-156
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• 1995

Purpose : Since February 1991 a Prospective study for non-small cell lung cancer patients who underwent radical resection and had a risk factor of positive resection margin or regional lymph node metastasis has been conducted to evaluate the effect of MVP chemotherapy and radiotherapy on the pattern of failure, disease free and overall survival. and tolerance of combined treatment. Materials and Methods: Twenty nine patients were registered to this study until Sep. 1993; of these 26 received planned therapy Within 3 weeks after radical resection, two cycles of MVP(Mitomycin C $6mg/m^2,$ Vinblastin $6mg/m^2,$ Cisplatin $60mg/m^2$) chemotherapy was given with 4 weeks intervals. Radiotherapy (5040cGy tumor bed dose and 900cGy boost to high risk area) was started 3 to 4 weeks after chemotherapy. Results: One and two year overall survival rates were $76.5\%\;and\;58.6\%$ respectively. Locoregional failure developed in 6 patients$(23.1\%)$ and distant failure in 9 patients$(34.6\%)$ Number of involved lymph nodes, resection margin positivity showed some correlation with failure pattern but T-stage and N-stage showed no statistical significance. The group of patients who received chemotherapy within 2 weeks postoperatively and radiotherapy within 70 days showed lower incidence of distant metastasis. Postoperative combined therapy were well tolerated without definite increase of complication rate, and compliance rate in this study was $90\%$. Conclusion: 1) MVP chemotherapy showed no effect on locoregional recurrence, but appeared to decrease the distant metastasis rate and 2) combined treatments were well tolerated in all patients. 3) The group of patients who received chemotherapy within 2 weeks postoperatively and radiotherapy within 70days showed lower incidence of distant metastasis. 4) Addition of chemotherapy to radiotherapy failed to increase the overall or disease free survival.

• Tuberculosis and Respiratory Diseases
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• v.69 no.4
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• pp.293-297
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• 2010

A 60-year-old man was diagnosed with stage IV squamous cell carcinoma of lung and treated with weekly doses of docetaxel and cisplatin. Tumor mass and mediastinal lymphadenopathy disappeared after 4.5 cycles of chemotherapy. At one week post final chemotherapy, the patients developed sudden shortness of breath. New, multifocal infiltrations developed on both lungs without definitive evidence of infection. Despite administration of broad spectrum antibiotics, the lung lesion did not improve, so bronchoalveolar lavage and computed tomography-guided lung biopsy were performed. The proportion of lymphocytes was increased markedly and histopathology revealed squamous cell carcinoma combined with bronchiolitis obliterans organizing pneumonia. After high dose corticosteroid therapy, dyspnea and the newly developed consolidation had decreased slightly. However, dyspnea and hypoxemia increased again because of aggravated lung cancer since chemotherapy had stopped. Chemotherapy couldn't be restarted due to the poor performance status of the patient. Later, patient died of respiratory failure from poor general condition and progression of lung cancer.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.15-23
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• 2005

The purpose of this study was to evaluate effect of aging and thermocycling on the tensile strength of restorative composite resins. Eight commercially available light-cured restorative composites (Heliomolar: HM, Palfique Estelite: PE, Spectrum: ST, UniFil-F: UF, Z100: ZH, Clearfil AP-X: CA, P60: PS, and Palfique Toughwell: PT) were selected as experimental materials. Rectangular-shaped tensile test specimens were fabricated in a teflon mold giving 5 mm in gauge length and 2 mm in thickness. All samples were stored in distilled water at $37^{\circ}C$ for 100 days. Every 10 days, specimens were thermocycled for 1,000 cycles with 15 seconds of dwelling time in each $5^{\circ}C$ and $55^{\circ}C$ water baths. Tensile testing was carried out at a crosshead speed of 0.5 mm/min and fracture surfaces were observed with a scanning electron microscope. The results obtained were summarized as follows; 1. The strength degradation of thermocycled group was severer than that of the aged group (P<0.01). 2. The tensile strength of the CA and ST groups were significantly higher than that of other groups after thermocycling treatment (P<0.05). 3. Fracture surfaces showed that the composite resin failure developed along the matrix and the filler/resin interface region.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.15-24
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• 2017

A comparative study was performed on the passivating abilities of surface films generated on lithium titanate (LTO; $Li_4Ti_5O_{12}$) electrodes during pre-cycling at two different rates. The surface film deposited at a faster pre-cycling rate (i.e., 0.5 C) is irregularly shaped and unevenly covers the LTO electrode. Owing to the incomplete coverage of the protective film, this LTO electrode exhibits poor passivating ability. Additional electrolyte decomposition and concomitant film deposition occur during subsequent charge/discharge cycles. As a result of the thick surface film, severe cell polarization occurs and eventually causes cell failure. However, pre-cycling the Li/LTO cell at a slower rate (0.1 C) improves cell polarization and capacity retention; this occurs because the surface film uniformly covers the LTO electrode and provides strong passivation. Accordingly, there is no significant film deposition during subsequent charge/discharge cycling. Additionally, self-discharge is reduced during high-temperature storage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1027-1035
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• 2016

In this study, a strain-controlled fatigue test of widely-used 316L stainless steel with excellent corrosion resistance and mechanical properties was conducted, in order to assess its fatigue life. Low cycle fatigue behaviors were analyzed at room temperature, as a function of the strain amplitude and strain ratio. The material was hardened during the initial few cycles, and then was softened during the long post period, until failure occurred. The fatigue life decreased with increasing strain amplitude. Masing behavior in the hysteresis loop was shown under the low strain amplitude, whereas the high strain amplitude caused non-Masing behavior and reduced the mean stress. Low cycle fatigue life prediction based on the cyclic plastic energy dissipation theory, considering Masing and non-Masing effects, showed a good correlation with the experimental results.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.11-20
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• 2014

The Concrete Capacity Design(CCD) method has been used in the design of anchor since 2001 and Korean design code specify that concrete breakout capacity of CIP anchor under seismic load shall be taken as 75% of static capacity. In this study, an experimental study was performed to evaluate the concrete breakout capacity of unreinforced CIP anchors under dynamic shear force. For the purpose, three static and dynamic shear-loading tests were conducted using 20mm diameter anchors, respectively. The edge distance of 120mm was considered in the tests. In the dynamic tests, 15 cycles pulsating load with 1Hz speed was applied and the magnitude of loading step was increased until concrete breakout failure occurs. From the tests, the concrete breakout capacity under dynamic shear loading showed nearly same capacity by static loading.