• The Journal of Korean Academy of Prosthodontics
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• v.35 no.2
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• pp.417-430
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• 1997

The purpose of this study was to compare the fracture resistance of copy-milled and conventional In-Ceram crown. Four groups of ten uniform sized all-ceramic crowns were fabricated. In-Ceram Spinell and In-Ceram Alumina crowns were fabricated as control group, Celay In-Ceram Spinell and Celay In-Ceram Alumina crowns were fabricated as test group. All specimen were cemented on stainless steel master die with resin cement, and stored in $37^{\circ}C$ water for 1 day prior to loading in Instron testing machine. Using a steel ball at a crosshead surfed of 0.5mm/min, the crowns were loaded at $30^{\circ}C$ angle until catastrophic failure occurred. The results obtained were as follows : 1. With the value of $984.8N{\pm}103.67N$, the strength of Celay In-Ceram Alumina crowns had a significantly higher fracture strength than conventional In-Ceram Alumina crowns ($876.2N{\pm}92.20N$) (P<0.05) 2. The fracture strength of Celay In-Ceram Spinell crowns($706.3{\pm}70.59N$) was greater than that of conventional In-Ceram Spinell crowns($687.4{\pm}90.26N$), but there was no significant difference(P>0.05). 3. The In-Ceram Alumina crowns had a significantly higher fracture strength than In-Ceram Spinell crowns in both methods(P<0.05). 4. Ther order of fracture strength was as followed : Celay In-Ceram Alumina, In-Ceram Alumina, Celay In-Ceram Spinell and In-Ceram Spinell crowns

• The Journal of Korean Physical Therapy
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• v.24 no.2
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• pp.163-169
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• 2012

Purpose: The present study was designed to investigate the effect of trunk control training on the labile surface on relative impulse and balance in stroke patients. Methods: A total of 21 participants were assigned to an experimental group (n=11) or a control group (n=10). In addition to conventional therapy, the experimental group received trunk control training on the swiss ball; 20 minutes, 4 times a week, for 8 weeks. Balance ability was evaluated by FRT (functional reaching test) and TUG (time up and go). In addition relative impulse in 6 areas of the foot (hallux, 1st metatarsal head, 2~3 metatasal head, 4~5 metatasal head, mid foot and heel) were measured using the F-scan system to evaluate locomotion ability during gait. Results: Significant differences in the relative impulse were observed in the areas of the 2~3 metatasal head during gait after exercise in both the control group and experimental group (p<0.05). Also, a significant increase was seen in the hallux after exercise in the experimental group (p<0.05), but no such significant increase was seen in the control group (p>0.05). Significant differences were observed in FRT and TUG in the experimental group but no such significant increase was observed in the control group (p>0.05). Conclusion: These results suggest that trunk control training on labile surface improves the balance in stroke patients and has a positive effect on locomotion ability.

• Journal of the Korean Geophysical Society
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• v.2 no.2
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• pp.100-110
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• 1999

In order to find a good seismic source for high-resolution reflection surveys on a tidal flat, characteristic features of several sources were examined through test recording by the walkaway configuration. The sources comprise portable vibrator, 1.2 kg monkey spanner, 4.7 kg sledge hammer, and weight drops with a 30 kg and a 100 kg iron ball, respectively. We analyzed raw and filtered seismic data for the resolution of individual events, then compared various seismic sources to define suitable one for the high-resolution survey in terms of energy level and frequency contents. The study reveals that the portable vibrator is the most suitable source for the detection of and imaging geologic structures less than 20-30 m deep in a tidal flat. We ascribe this to the wide frequency band and high-frequency contents of the portable vibrator. In contrast, the hammer may be an alternative where the target depth increases up to 100 m.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.81-87
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• 2004

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets. 1) The Pt or Pd $(1,\;2,\;3\;wt.\%)$ as catalyst is impregnated in the base material of $SnO_2$ by impregnation method.2) $Al_2O_3\;(0,\;4,\;12,\;20\;wt.\%),\;In_2O_3\;(1,\;2,\;3\;wt.\%),\;WO_3\;(1,\;2,\;3\;wt.\%),\;TiO_2\;(3,\;5,\;10\;wt.\%)$ or $SiO_2\;(3,\;5,\;10\;wt.\%)$ is added to $SnO_2$ by physical ball milling process. 3) ZnO $(1,\;2,\;3,\;4,\;5\;wt.\%)$ or $ZrO_2\;(1,\;3,\;5\;wt.\%)$ is added to $SnO_2$ by co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET respectively. Response characteristics are examined for simulant gases with temperature in the range 200 to $400^{\circ}C$, with different gas concentrations. These sensors have high sensitivities more than $50\%$ at 500ppb concentration for test gases and also have shown good repetition tests. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array A sensor array Identities among the four simulant gases through the principal component analysis (PCA). High sensitivity is acquired by using the semiconductor thick film gas sensors and four CWA gases are classified by using a sensor array through PCA.

• Korean Journal of Dental Materials
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• v.44 no.1
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• pp.69-77
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• 2017

The aim of this study was to investigate the effects of chitosan powder addition on the strengthening of conventional glass ionomer cement. Two types of chitosan powders with different molecular weight were mixed with conventional glass ionomer cement (GIC): low-molecular weight chitosan (CL; 50~190 kDa), high-molecular weight chitosan (CH; 310~375 kDa). The chitosan powders (CL and CH) were separately added into the GIC liquid (0.25-0.5 wt%) under magnetic stirring, or mixed with the GIC powder by ball-milling for 24 h using zirconia balls. The mixing ratio of prepared cement was 2:1 for powder to liquid. Net setting time of cements was measured by ISO 9917-1. The specimens for the compressive strength (CS; $4{\times}6mm$), diametral tensile strength (DTS; $6{\times}4mm$), three-point flexure (FS; $2{\times}2{\times}25mm$) with flexure modulus (FM) were obtained from cements at 1, 7, and 14 days after storing in distilled water at $(37{\pm}1)^{\circ}C$. All mechanical strength tests were conducted with a cross-head speed of 1 mm/min. Data were statistically analyzed by one-way ANOVA and Tukey HSD post-hoc test. The mechanical properties of conventional glass ionomer cement was significantly enhanced by addition of 0.5 wt% CL to cement liquid (CS, DTS), or by addition of 10 wt% CH (FS) to cement powder. The CL particles incorporated into the set cement were firmly bonded to the GIC matrix (SEM). Within the limitation of this study, the results indicated that chitosan powders can be successfully added to enhance the mechanical properties of conventional GIC.

• The Journal of Advanced Prosthodontics
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• v.11 no.4
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• pp.193-201
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• 2019

PURPOSE. The aim of the present study was to evaluate the color changes of an autopolymerizing PMMA resin used for interim fixed restorations, reinforced with $SiO_2$ nanoparticles. MATERIALS AND METHODS. Silica nanoparticles were blended with the PMMA resin powder through high-energy ball milling. Four shades of PMMA resin were used (A3, B3, C3, D3) and total color differences were calculated through the equations ${\Delta}E_{ab}=[({\Delta}L*)^2+({\Delta}a*)^2+({\Delta}b*)^2]^{1/2}$ and ${\Delta}E_{00}=[(\frac{{\Delta}L^{\prime}}{K_LS_L})^2+(\frac{{\Delta}C^{\prime}}{K_CS_C})^2+(\frac{{\Delta}H^{\prime}}{K_HS_H})^2+R_T(\frac{{\Delta}C^{\prime}}{K_CS_C})(\frac{{\Delta}H^{\prime}}{K_HS_H})]^{1/2}$. Statistically significant differences between ${\Delta}E_{ab}$ and the clinically acceptable values of 3.3 and 2.7 and those between ${\Delta}E_{00}$ and the clinically acceptable value of 1.8 were evaluated with one sample t-test (P<.05). Differences among the different shades were assessed through One-Way ANOVA and Bonferroni multiple comparison tests. RESULTS. Significantly lower values were detected for all groups concerning ${\Delta}E_{ab}$ compared to the intraorally clinical acceptable values of 3.3 and 2.7. Significantly lower mean values were detected for groups B3, C3, and D3, concerning ${\Delta}E_{00}$ compared to the intraorally clinical acceptant value of 1.8. Color pigments in red-brown (A3) and red-grey (D3) shades affect the total color change to a greater extent after the reinforcement with $SiO_2$ nanoparticles compared to the red-yellow (B3) shade. CONCLUSION. Within the limitations of this in vitro study, it can be suggested that reinforcing PMMA with $SiO_2$ nanoparticles at 0.25 wt% slightly affects the optical properties of the PMMA resin without being clinically perceivable.

• Journal of the Korean Society of Physical Medicine
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• v.19 no.2
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• pp.91-98
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• 2024

PURPOSE: This study aimed to provide basic clinical data by investigating the impact of Activities of daily living-related dual-task intervention on lung function, balance, and Activities of daily living of stroke patients. METHODS: After sampling 40 stroke patients who met the selection criteria, this study randomly assigned 20 patients who received dual-task exercise intervention to the experimental group and 20 patients who received single exercise intervention to the control group by drawing lots. Next, the study pre-tested their lung function, balance, and activity of daily living. All interventions were conducted for 30 minutes, 3 times a week for 4 weeks, and when all interventions were completed after 4 weeks, lung function, balance, and activity of daily living were re-measured in the same way as the pre-test. RESULTS: In comparing changes in lung function, balance, and activity of daily living within each of the experimental and control groups, statistically significant improvement were found in the experimental group only (p < .01). Statistically significant improvement were also found in lung function, balance, and activities of daily living between the groups (p < .05) (p < .01). CONCLUSION: A statistically significant improvements were found in lung function, balance, and activities of daily living only in the experimental group and statistically significant differences were found between groups. Because they take arm exercises by maintaining balance in a standing position on a labile surface and through dual-task exercise such as folding a towel, moving a cup, and throwing and catching a ball, muscles related to lung function were stimulated and lung function and balance were improved. This helped activities of daily living to be improved. Thus, it is considered that dual-task exercise should be utilized for stroke patients' smooth everyday life.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.97-103
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• 2014

Among various lead-free solders, the Sn-58Bi solders have been considered as a highly promising lead-free solders because of its low melting temperature and high tensile strength. However, Sn-58Bi solder has the poor ductility. To enhance the mechanical property of Sn-58Bi solder, epoxy-enhanced Sn-58Bi solders have been studied. This study compared the microstructures and the mechanical properties of Sn-58Bi solder and Sn-58Bi epoxy solder with aging treatment. The solders ball were formed on the printed circuit board (PCB) with organic solderability preservative (OSP) surface finish, and then the joints were aged at 85, 95, 105 and $115^{\circ}C$ for up to 100, 300, 500 and 1000 hours. The shear test was conducted to evaluate the mechanical property of the solder joints. $Cu_6Sn_5$ intermetallic compound (IMC) layer grew with increasing aging time and temperature. The IMC layer for the Sn-58Bi epoxy solder was thicker than that for the Sn-58Bi solder. According to result of shear test, the shear strength of Sn-58Bi epoxy solder was higher than that of Sn-58Bi solder and the shear strength decreased with increasing aging time.

• Fire Science and Engineering
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• v.30 no.4
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• pp.121-127
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• 2016

This study analyzed the structural and electrical characteristics of an iron fittings type Corrugated Stainless Steel Tubing (CSST) damaged by the Primary Current Injection Test System (PCITS). CSST consists of cladding, tube, nuts, clamp ring, flare cap, socket, and ball valve. For an evaluation of the dielectric withstand voltage, the area between the live part and non-live part of the CCST shall withstand a voltage of 220 V AC for one minute. For an evaluation of the insulation performance by 500 V DC, it is required that the insulation exceed more than $1M{\Omega}$ before the temperature rise test, $0.3M{\Omega}$ after the test. Although the average resistance of the product was $11.5m{\Omega}$, that of the product damaged at a current of 130 A by the PCITS was $11.50m{\Omega}$. Furthermore, parts of the cladding were melted and black smoke appeared when a current of 130 A applied for 10 s. After 60 s, most parts were heated and turned red. At 120 s, the parts that turned red had widened. Although it did not form a normal distribution because the P value was 0.019 with a confidential interval of 95%, it revealed outstanding characteristics with an AD (Anderson-Darling) value of 0.896 and a standard deviation of 0.5573.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.65-80
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• 1980

Processing conditions of the krill products such as paste food, krill protein concentrate, seasoned dried krill, powdered seasoning, meat ball, and snack have been examined and the quality was evaluated chemically and organoleptically. In the processing of paste food, krill juice was yielded $71\%$ and krill scrap $29\%$. The yields of paste and broth from the krill juice showed $53\%$ and $43\%$, respectively. In amino acid composition of the krill paste, proline, glutamic acid, aspartic acid, lysine, and leucine were abundant, while histidine, methionine, tyrosine, serine and threonine were poor. The optimum condition for solvent extraction in the processing of krill protein concentrate was the 5 times repetitive extraction using isopropyl alcohol at $80^{\circ}C$ for 5 mins. The yield of krill protein concentrate when used fresh frozen materials was $10.2\%$ in isopropyl alcohol solvent and $8.8\% in ethyl alcohol, and when used preboiled frozen materials, the yield was $13.0\%$ in isopropyl alcohol and $11.8\%$ in ethyl alcohol. Amino acid composition of krill protein concentrate showed a resemblance to that of fresh frozen krill meat. In quality comparison of the seasoned dried krill, hot air dried krill was excellent as raw materials and sun dried krill was slightly inferior to hot air dried krill, but preboiled frozen krill showed the poorest quality. The result of quality evaluation for seasoning made by combination of dried powdered krill, parched powdered sesame, salt, powdered beef extract, monosodium glutamate, powdered red pepper and ground pepper showed that the hot air dried krill was good in color and sundried krill was favorable in flavor. When krill meat ball was prepared using wheat flour, monosodium glutamate and salt as side materials, the quality of the products added up to $52\%$ of krill meat was good and the difference in quality upon the results of the organoleptic test for raw materials was not recognizable between fresh frozen and preboiled frozen krill. In the experiment for determining the proper amount of materials such as dried Powdered krill, $\alpha-starch$, sweet potato starch, sugar, salt, monosodium glutamate, glycine, potassium tartarate, ammonium bicarbonate, and sodium bicarbonate in processing krill snack, sample B(containing $7.7\%$ of dried powdered krill) and sampleC (containing $10.8\%$ of dried powdered krill) showed the most palatable taste from the view point of organoleptic test. Sweet potato starch in testing side materials was good in the comparison of suitability for processing krill snack. Corn starch and kudzu starch were slightly inferior to sweet potato starch, while wheat flour was not proper for processing the snack. In the experiment on frying method, oil frying showed better effect than salt frying and the suitable range of frying temperature was $210-215^{\circ}C$.