• Korean Journal of Materials Research
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• v.4 no.3
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• pp.253-258
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• 1994

The effect of hole size and hole-to-hole distance in the braided and laminated composite was studied in terms of tensile strength, pin bearing strength, and flexural strength of S2-glass fiber braided polyester. The tensile strength reduction with hole size was well fitted with he Whitney and Nuismer's prediction for the laminated composite. The characteristic distance was measured to be about 1.6mm for braided composite and 1.8mm for laminated one. The effect of distance between the centers of two circu lar holes on tensile strength was negligible when the distance between these two holes was larger than 4 times of the diameter of circular hole for both braided and laminated composite. The side effect was diminished when the center of hole was located 3 times farther than the diamet.er of the hole. The pin bearing strengths was decreased with the size of pin hole for both braided and laminated composite.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.665-674
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• 1996

This study was designed to evaluate the effect of processing method and surface design on the transverse strength of repaired denture base resin. Three heat-cured denture base resins(Vertex, Lucitone, Lang), one cold-cured resin(Lang), and one light-cured resin(Dentacolor gingiva material) were used for repair purpose. The specimens for 3-point flexure test were fabricated by five processing methods such as self-curing, pressure pot, boiling water, processing, and light curing. Finally to evaluate the effect of surface designs for repaired resin, three surface designs(butt, bevel, inverse bevel) were tested. Within the limit of this study, following conclusions were drawn. 1. Lucitone denture base material showed highest flexural strength of $131.37{\pm}2.15MPa$, and there were significant differences in stength between Lucitone and other resins. 2. Between two different self curing methods, self curing repair resin, Lang, cured by pressure pot method showed highest flexural strength, $58.49{\pm}4.89MPa$. 3. Among the heat cured repair resins, maximum transverse strength value of $88.69{\pm}16.60MPa$ was recorded in Lucitone group cured by processing method. 4. Inverse bevel joint design showed significantly higher bond strength than butt joint group, Maximum bond strength was $59.36{\pm}1.33MPa$ in inverse bevel joint design group.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.590-597
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• 1994

The chemical behavior of the trivalent lanthanide$(Pr^{3+}, Eu^{3+}, Gd^{3+} 그리고 Yb^{3+})$complexes with organo-ligand (2,2,6,6-tetramethyl-3,5-heptanedione) has been investigated by the use of UV/Vis-spectrophotometric, magnetics, and electrochemical method. The two or three energy absorption bands are observed by the spectra of these complexes. The magnetitude of crystal field splitting energy, the spin pairing energy and bond stength was obtained from the spectra of the complexes. These are found to be localization, low-spin (or high-spin state, and strong bonding strength. The magnetic dipole moment are found to be diamagnetic complexes (or paramagnetic). The electrochemical behavior of complexes was observed by the use of cyclic voltammetry in aprotic media. These reduction peaks were irreversible two and three step reduction processes by electron transfer.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.61-72
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• 1991

This study was carried out to research the strength drop of concrete in dry environment. The mixing ratio of cement-fine aggregate was 1: 1, 1 : 2, 1: 3 and 1 : 4. The curing was compared standard curing with dry curing immediately after casting. It is analysis of strength change by water-proof mixing. The curing age of cement mortar was 3days, 7days, l4days and 28days. The result obtained from this study are summarized as follows. 1. The compressive and bending strength change by increasing the curing age, dry curing mortar the increasing rate of strength was decreased than standard curing mortar. 2. The compressive and bending strength change in early curing, strength difference between standard curing mortar and dry curing motar was gradually closed by increasing the W/C. 3. The dry curing mortar was decreased than standard curing mortar in decreasing rate of compressive and bending strength by increasing the W/C. 4. The compressive strength of water-proof mortar in early curing, liquid water-proof mortar was shown high strength in dry curing than standard curing. The powder and liquid water-proof mortar have a small effect in dry environment. The liquid water-proof mortar was high strength without relation change of curing age in dry environment than standard curing. 5. The compressive strength of liquid water-proof mortar in poverty mix, dry curing was shown high strength than standard curing. 6. The bending strength was increased than compressive strength by decreasing the volume of cement in early curing. The increasing rate of bending strength was decreased to compressive stength by increasing the curing age.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.4
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• pp.43-50
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• 2001

In this paper, the discharge phenomena and electromagnetic waves caused by discharge with insertion of a solid insulator and flame between sphere-sphere electrodes in air ware investigated. The surface discharge light and patterns of flame generated on a solid insulator surface were observed by using a CCD(Charged Coupled Device) camera. Also, the radiated electromagnetic waves were measured by using a biconical antenna and a spectrum analyzer. The surface discharge light generated on the solid insulator surface was larger and the size of flame was smaller by increasing allied voltages. Also, voltage distortion by voltage drop was strongly revealed when a insulator surface was polluted. When a solid insulator surface was not polluted, the electric field stength of electromagnetic waves was 10∼17[dBuV/m] higher than a polluted solide insulator, and 5∼9[dBuV/m] higher than a polluted solide insulator and flame.

• Korean Journal of Plant Tissue Culture
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• v.27 no.3
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• pp.191-195
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• 2000

Adventitious shoots were induced from cotyledon and hypocotyl explants of apple hybrid seedlings (P.16$\times$ Malus prunifolia) on MS medium supplement with 2,4-D and various cytokinine (Kn. BA, TDZ) The shoot regeneration from the cotyledon culture was the highest on MS medium supplemented with 1.0 mg/L NAA and 2.0 mg/L BA. Whereas in case of hypocotyl culture, it was the highest on MS medium supplemented with 0.5 mg/L NAA and 0.5 mg/L BA. However, in the MS medium without BA there was no shoot regeneration. Hypocotyl culture seemed to be more effective than cotyledon culture in shoot regeneration. Specially, the top position of the hypocotyl found to be the best explant for shoot induction among the other segments of hypocotyls. Regenerated shoots were rooted on half-stength MS medium with 1.0 mg/L NAA. Above results suggest that Apple hybrid (P.16 $\times$ Malus prunifolia) can be multiplied via cotyledon or hypocotyl culture systems.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.4
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• pp.3931-3942
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• 1975

This study was conducted to investigate the strength of soil cement for varied curing temperatures (0,10,20,30,40,50,60$^{\circ}C$) and cement content (3,6,9,12%) in four cement-stabilized soils (KY: sand, MH: sand, SS: sandy loam, JJ:loam). The experimental results obtained from unconfined compressive strength tests were as follows: 1. According to increase of curing temperature as 30,40,50, and 60$^{\circ}C$, the unconfiened compressive strength of soil cement increased, the rate of increase in the early curing period was large, and around 120 hours was suifficient curing time to complete hardening. 2. The strength at 10$^{\circ}C$ decreased to the rate of 30 to 40 percent than that of 20$^{\circ}C$ while the strength at 0$^{\circ}C$ was very small, strength of soil cement increased in cold weather unless that the temperature was below 0$^{\circ}C$ 3. The average maximum temperature, about 30$^{\circ}C$ during July and August in Korea may be recommended for a optimum construction period to increase the strength of soil cement. 4. Accelerated curing time that strength was equivalent to 28-Day norma1 curing decreased in accordance with the increase of curing temperature, and also accelerated curing decreased the effect of cement content. Accelerated curing that strength was equivalent to 28-day normal curing for soil cement of cement content 9% and temperature 60$^{\circ}C$ was 45 hours; KY, 50 hours: MH, 40 hours; SS, 34 hours; JJ. 5. According to the increase of the percent passing of No. 200 sieve, accelerated curing times became shorter to become the required stength. 6. Relation between accelerated curing times and normal curing days was showeda linear of which slope decreased in accordance with the increase of curing temperature, it may be expressed as follows: (1). 30$^{\circ}C$ t=3.6d+6(r=0.97) (2). 40$^{\circ}C$ t=3.2d-5.1(r=0.95) (3). 50$^{\circ}C$ t=2.1d-4.0(r=0.93) (4). 60$^{\circ}C$ t=1.4d+4.0(r=0.90) in which t=accelerate curing time. d=normal curing day. 7. Accelerated curing time that the strength was equivalent to 35kg/$\textrm{cm}^2$ which was the strength of cement brick was 96 hours at temperature 30$^{\circ}C$ to SS 9%, and 120 hours at temperature 50$^{\circ}C$ to JJ 9%, Consequently, a economic soil cement brick may be made in future.

• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.111-119
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• 2016

This study aimed to analyze postures that were frequently conducted in manufacturing industry. To find grip strength and muscle activities of each posture, Maximum Voluntary Contraction (MVC) and ElectroMyoGraphy (EMG) were measured. Based on the results of this study, the most appropriate posture could be suggested and used as a basic information for preventing musculoskeletal disorders. Most work-related musculoskeletal disorders have been occurred in the fields of manufacturing industry. According to previous studies, it was reported that the rate of musculoskeletal diseases of upper extremity was higher than that of other body parts. Accordingly, there were many studies about discomfort and grip strength of upper extremity. However, these studies dealt with single selection of wrist, elbow and shoulder. So, it was insufficient for comprehensive studies about upper extremity. And in order to improve the work posture, the physiological changes being generated by the combination of wrist, elbow and shoulder postures should be observed and analyzed. In order to conduct this study, thirty university students who had no records of MSDs involved were recruited. Independent variables were postures of wrist(pronation, neutral, supination), postures of elbow(flexion $45^{\circ}$, $90^{\circ}$) and postures of shoulder(flexion $0^{\circ}$, $90^{\circ}$). And dependent variables were MVC values and EMG values. Jamar dynamometer and TeleMyo 2400T G2 was used to measure MVC and EMG. MVC and EMG for 12 postures were measured for three second and for three times. Experiment was performed randomly. A 10 minutes rest period was provided after each t. To measure muscle load, the EMG signals of eight muscles (Biceps, Medial triceps, Lateral triceps, Brachioradialis, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris and Flexor carpi radialis) were evaluated. MVC values and EMG values were analyzed using Minitab ver. 14. The results showed that MVC value was the highest at shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination. In case of wrist postures, MVC of supination is the highest. In case of elbow and shoulder postures, MVC of flexion $45^{\circ}$ and $0^{\circ}$ was the highest. It was found that there were interaction between wrist and elbow posture under shoulder flexion and between shoulder and wrist under elbow flexion $45^{\circ}$. In case of the angle of shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination, the EMG values of four muscles(Medial Triceps, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris) were the highest. Based on this study, it is worth to note that the combination postures of upper extremity have a large impact on the MVC and EMG. The optimal condition upper extremity was shoulder flexion $0^{\circ}$, elbow flexion $45^{\circ}$ and wrist supination for preventing work-related musculoskeletal disease.

• Journal of Bio-Environment Control
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• v.12 no.4
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• pp.235-239
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• 2003

This study was carried out to investigate a adequate strength of nuttient solution in production of marjoram and oregano by hydroponicsl Two herbs were grown for 40days with the strength of 0.5, 1.0, 2.0, and 3.0 dS${\cdot}m^{-1}$ in herb's nutrient solution developed by European Vegetable R & D Center, Belgium. the growth, vitamin C, and essential oil content of marjormam were higher in the treatment of 0.5 dS${\cdot}m^{-1}$ than the other treatments tested. But marjoram growtn with the sstrength of 20. and 3.0 dS${\cdot}m^{-1}$ had the highest mineral contents and essential oil content, respectively. Elevated strength of nutirent solution decreased chlorophyll content. In oregano, the growth was vest in the stength of 0.5, but withered in the strength of 3.0 The chlorophyll content was the lowest in the strength of 0.2dS${\cdot}m^{-1}$, while vitamin C contents had no statistical differences among treatments, Oregano grown with 1.0 dS${\cdot}m^{-1}$had the highest mineral and essential oil content, but the oil yield washighest in the treatment of 0.5 dS ${\cdot}m^{-1}$. In conclusion, the strength of 0.5 dS${\cdot}m^{-1}$ herb's nutrient solution was adequated in production of marjorma and oregano in hydroponicc system.

• Journal of Korean Physical Therapy Science
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• v.24 no.1
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• pp.1-13
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• 2017

Purpose: The objective of this study was compare the effect of core muscle strengthening between core exercise on stable surface and core exercise on unstable surface. Methods: Thirty-nine adults participated in this study and were randomly allocated to three groups. The stable surface exercise group and unstable surface exercise groups practiced core muscle training for $3{\times}30minute$ sessions over a 4-week period. The control group did not received therapeutic intervention except pre and post test. The following clinical tools were used to assess core muscle strength and balance: Side Plank Test, Trunk Flexion Test, Balance Error Scoring Test, Core Muscle Stength & Stability Test. Results: The stable surface exercise group showed significant improvement in trunk muscle strength of anterolateral part as revealed by the Side Plank Test and Trunk flexion Test(p<.05). The unstable surface exercise group showed significant improvement in trunk muscle strength of anterolateral part and balance ability as revealed by the Balance Error Scoring Test and Core Muscle Strength & Stability Test(p<.05). Conclusion: The results of this study, both core exercise on stable surface and core exercise on unstable surface induced core muscle strengthening and balance ability. Expecially core exercise on unstable surface more effective to core muscle strengthening and balance ability.