• 한국항해항만학회지
• /
• 제32권10호
• /
• pp.759-764
• /
• 2008

활주형선이 수면 위를 활주하여 고속이 가능하기 위해서는 특별하게 설계되어 진다. 대부분의 활주형선은 충격하중을 줄이고 황요, 종요 등의 운동성능을 개선시키기 위하여 스프레이 스트립을 설치하며, 고속에서는 파형개선과 양력발생으로 스프레이저항과 마찰저항이 감소되는 것으로 알려져 있다. 이에, 본 논문에서는 모형시험을 통하여 스프레이 스트립의 부착 유무에 따른 고속 활주형선의 저항특성을 비교, 분석하였으며, 시험결과, 스프레이 스트립 부착 고속 활주형선이 미 부착 선형에 비해서 $3.0{\sim}5.0%$의 저항감소 효과를 확인할 수 있었다.

• 한국분말재료학회지
• /
• 제2권3호
• /
• pp.201-207
• /
• 1995

In general, the characteristics of plasma spray coating are strongly dependent on process conditions. In this paper, Mo and Co alloy coating layers were made by plasma spraying with different spray parameters and characterized using X-ray diffraction, scanning electron microscopy(SEM), hardnass test, and wear test. It was found that the coating characteristics were mainly affected by phase composition of the powder, spray distance, arc current, and gas flow rate.

• 한국분무공학회지
• /
• 제11권2호
• /
• pp.81-88
• /
• 2006

The spray characteristics of the rotating fuel injection system were investigated. The special test rig was devised to get the spatial and momentary droplet information. This experimental apparatus consists of a high-speed motor, a shaft, a rotating fuel nozzle and an acrylic case. Spray droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and instantaneous velocity field was measured by 1'IV (Particle Image Velocimetry) system. At the same time, spray visualization was performed by using ND-YAG laser-based flash photography. From these two different laser diagnostic techniques, we could get spatial and instantaneous spray information fur rotating fuel injection system. The results presented in this paper indicate that spray characteristics such as droplet size, velocity and spray pattern were strongly influenced by rotational speed.

• Corrosion Science and Technology
• /
• 제12권5호
• /
• pp.209-214
• /
• 2013

In the industry, accelerated corrosion test is used for the life time prediction. When anti-corrosion test proceeds in real environments, it is difficult that we predict and evaluate the corrosion life time because of the long test time such as 10 years or more time. Accelerated corrosion test and Salt spray test are able to test corrosion life time of products in the laboratory instead of outdoor corrosion test. Experimental procedure is selected for the corrosion standard specimen, exposure of the specimens, measurements of the mass loss and evaluating the mass loss data. As a result, the acceleration factor of the accelerated corrosion test to the outdoor corrosion test is 414.8. Therefore we can predict the corrosion life time of carbon steel during a short time period.

• 한국분무공학회지
• /
• 제28권1호
• /
• pp.32-42
• /
• 2023

In this study, spray characteristics of n-heptane and propane were investigated under different injection pressure using various imaging techniques such as Mie-scattering, DBI (diffuse back-illumination), and Schlieren imaging techniques. NI compact RIO system was used to control a test injector. Spray penetration length, length-to-width ratio and number of black pixels were calculated by using MATLAB software to compare spray characteristics of each fuel. Longer spray penetration length and higher length-to-width ratio were observed in propane spray because of flash boiling caused by high saturated vapor pressure. Spray collapse occurred in propane spray due to the high plume-to-plume interaction. Moreover, rapid evaporation occurred in propane spray, so that nozzle tip wetting could not be observed. Rapid evaporation of propane also caused fewer residual droplets compared to n-heptane spray. Therefore, propane is advantageous in reducing the generation of soot emission from large droplets that are not atomized. However, additional evaluation should be conducted considering combustion efficiency and the possibility of deposits by nozzle tip icing during fuel injection.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.1349-1352
• /
• 2005

This paper is to investigate a defect for thermal barrier coating layers by acoustic emission method in 4-point bending test. The two-layer thermal barrier coating is composed of $150\mu{m}\;CoNiCrAlY\;bond\;coating\;by\;vacuum\;plasma\;spray(VPS)\;process\;and\;250\mu{m}\;ZrO_2-8wt%Y_2O_3$ ceramic coating layer by air plasma spray(APS) process on Inconel-718. The specimen prepared by cyclic thermal test(500, 1000, 2000cycle) at $1050^{\circ}C$ The AE monitoring system is composed of PICO type sensor, a wide band pre-amplifier(40dB), PC and AE DSP(16/32 PAC) board. The AE event, amplitude, Cumulative energy and count of coating specimens is evaluated according to cyclic thermal test.

• 동력기계공학회지
• /
• 제6권3호
• /
• pp.24-30
• /
• 2002

The deformation and fracture behaviors of both Al2O3 and Ni 4.5wt.%Al plasma thermal spray coating were investigated by an acoustic emission method. Plasma thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, stacking of the particles makes coating. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. A bendind test is done on smooth specimens. The waveforms of AE generated from the both test coating specimens can be classified by FFT analysis into two types which low frequency(type I) and high frequency(type II). The type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• 한방안이비인후피부과학회지
• /
• 제25권3호
• /
• pp.56-64
• /
• 2012

Objectives : This study was performed in order to investigate an immediate improvement effect of nasal obstruction after having patient with chronic rhinitis use nasal spray in nasal cavity after distilling Korean medicine, satisfaction for its fragrance and irritation and its effect continuance time. Methods : A questionnaire was performed for an immediate therapeutic effect of nasal spray 1, 2 and 3 weeks later after using spray by targeting 13 patients who used Korean medicine distillate spray for over 3 weeks among the patients who visited Sangji University Korean Medicine Hospital and whose symptoms were determined as chronic rhinitis and for whom Korean medicine distillate spray was prescribed. 3 weeks later after using spray, a questionnaire was performed for fragrance, irritation and continuance effect of Korean medicine. Immediate therapeutic effect being felt right after spraying was also surveyed and symptom scores was expressed from 10 to 0 and on the assumption that nasal obstruction symptom just before spraying was 10 points, symptom score after spraying was surveyed. In case of evaluation of satisfaction, satisfaction for fragrance and irritation of nasal spray was evaluated by scale based on full score of 5 point from 'very satisfied=5', 'satisfied=4', 'average=3', 'unsatisfactory=2' and 'very unsatisfactory=1', respectively. Effect continuance time after spraying was surveyed by dividing it into within 5 minutes, within 5-10 minutes, within 10-30 minutes and over 30 minutes. All the data was statistically analyzed by Friedman Test that is non-parametric test of Paired t-test and descriptive statistics. Results : Total surveyed patients were 13 persons including 6 males and 7 females and total average age was represented to be $27.1{\pm}17.7$ years old. Score of immediate nasal obstruction improvement effect at 1st week was $6.3{\pm}2.4$ points, at 2nd week $5.7{\pm}2.5$ points and at 3rd week $5.5{\pm}2.5$ points and when comparing 1st week, 2nd week and 3rd week statistically, p value was 0.047<0.05 and from this, it could be seen that the longer spray was used, the more was improvement effect represented with slight significance. In case of fragrance and irritation, both of its score was represented to be high as average $4.0{\pm}1.08 $points and average $4.4{\pm}0.8$ points, respectively. Effect continuance time below 10 minutes was represented in 8 persons who accounted for 61.5%. Conclusions: Immediate improvement effect of nasal obstruction being felt by the patients by using Korean medicine nasal spray could be confirmed and by having the patients use such spray for 3 weeks continuously, it could be realized that such effect was sustained and satisfaction for fragrance or irritation of Korean medicine nasal spray was significant. However, rather short sustained time was considered to be unsatisfactory and this shortcomings is required to be improved in the future.

• Corrosion Science and Technology
• /
• 제12권1호
• /
• pp.56-64
• /
• 2013

An Eectrolytic Corrosion(EC) test method was evaluated by the comparison with Copper Accelerated Acetic Salt Spray(CASS) and Neutral Salt Spray(SS) tests. Those methods were applied in order to evaluate corrosion resistance of Ni-Cr plated and Zn-plated Fe substrates. The correlations between results obtained by different test methods were investigated. Results showed that the electrochemical method such as the EC test method was superior to the conventional methods such as CASS and SS, in terms of the quantitative accuracy and the test-time span. Furthermore, the EC test method provided the useful means to estimate the initiation of corrosion of each layer by monitoring the rest potentials of the coated layers such as Ni, Cr, and Zn on Fe substrate. With regard to test time spans, the EC test provided the 78 times and 182 times faster results than the CASS test in cases of $Fe+5{\mu}m$ $Ni+0.5{\mu}m$ Cr and $Fe+20{\mu}m$ $Ni+0.5{\mu}m$ Cr respectively, while the EC test was 85 times faster results than the Salt Spray test in the case of $Fe+20g/m^2$ Zn. Therefore, the EC test can be the better method to evaluate the resistance to corrosion of coated layers than the conventional methods such as the SS test and the CASS.

• 한국분무공학회지
• /
• 제18권4호
• /
• pp.182-187
• /
• 2013

This study was performed to investigate the effect of biodiesel derived from waste cooking oil on the spray behavior and macroscopic spray characteristics. To analyze quantitative characteristics of test fuels, injection quantity was measured at various injection pressures and the spray images of injected fuels in the pressurized chamber were obtained by using a high speed camera and image analysis system. Based on the measured spray images, the spray tip penetration and spray cone angle were investigated at various energizing timings and injection pressures. In this work, the experimental results showed that the injection quantity of waste cooking biodiesel indicated the higher quantities than diesel at high injection pressure. As the injection pressure was increased, the spray tip penetrations of biodiesel were higher value than diesel. The difference of penetration between biodiesel and conventional diesel fuel was reduced in accordance with the increase of injection pressure. Also, the spray angles of diesel were larger than that of biodiesel because diesel fuel has lower viscosity than biodiesel. In addition, the spray evolution processes of biodiesel fuel at various injection pressures and the elapsed time after the injection were compared to the conventional diesel fuel.