• 대한기계학회논문집
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• 제14권5호
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• pp.1356-1364
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• 1990

본 연구에서는 단열해석에 재생기효율을 고려함으로써 보다 합리적인 예비설 계조건을 도출하고자 함이다. 스터링기관용 재생기의 특성검토를 통하여 예비설계에 적합한 재생기효율을 정립하며, 기 발표된 단열모델에 대한 해석적 근사해에 적용하는 방법으로 접근한다. 재생기효율이 고려될 경우 기관의 기본형태와 연관된 위상각, 행정체적비, 불용체적비, 압축비등 설계인자의 최적조건에 관하여 취급하며 온도비, 비열비등 부여조건의 변화에 따른 영향을 검토한다.

• 한국약용작물학회지
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• 제24권3호
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• pp.237-245
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• 2016

Background: Cyanazine is used as a pre-emergent herbicide once during the growing season to control weeds of many upland crops worldwide. This study aimed to establish a method to determined cyanazine residue levels in major medicinal crops by using high performance liquid chromatography-UV detection/mass spectometry (HPLC-UVD/MS). Methods and Results: Cyanazine residue was extracted with acetone from the raw products of four representative medicinal plants - Scutellaria baicalensis, Paeonia lactiflora, Platycodon grandiflorum and Angelica gigas. The extract was diluted with a large volume of saline water and directly partitioned into dichloromethane to remove polar co-extractives in the aqueous phase. It was then purifined using optimized Florisil column chromatography. HPLC analysis conducted using an octadecylsilyl column allowed the successful separation of cyanazine from co-extractives of the samples, and the amount was sensitively quantified by ultraviolet absorption at 225 nm with no interference. The accuracy and precision of the proposed method were validated by conducting recovery experiments on each medicinal crop sample fortified with cyanazine at two concentration levels per crop in triplicate. Conclusions: The mean recoveries ranged from 91.2% to 105.3% for the four representative medicinal crops. The coefficients of variation were less than 10%, irrespective of the sample types and fortification levels. The limit of quantification of cyanazine was 0.02 mg/kg as verified by the recovery experiment. A confirmatory method was performed by liquid chromatography/MS using selected-ion monitoring technique to clearly identify the suspected residue.

• Ocean and Polar Research
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• 제38권1호
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• pp.21-33
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• 2016

Gametogenesis of the comb pen shell, Atrina pectinata (Linnaeus, 1767) (Bivalvia: Pinnidae) on the southern coast of Ulleungdo Island, Korea was assessed monthly (November 2013 to October 2014) using histology. Gametogenesis commenced in January when the surface water temperature was $12.6^{\circ}C$ and pen shells evidenced an early development phase with small oogonia from January to April, although few females exhibited ripe eggs in their follicular epithelium. In April, the oocyte diameter increased rapidly, and fully mature eggs appeared in May. First spawning males and females were observed in June as the surface water temperature reached $19.3^{\circ}C$ and July ($23.2^{\circ}C$) respectively. The spawning activity continued until the end of September. Histology indicated that the spawning peak of the females in Ulleungdo Island was July to August. During October to January, most of the pen shells were in spent and resting stages. Our data suggested that A. pectinata is a summer spawner, and their annual gametogenesis is closely associated with the seasonal variation in the surface water temperature. The present study is the first provided fundamental information on the life history of A. pectinata in Ulleungdo Island, and this can be put to good use in the management of this pen shell in the study area.

• 한국대기환경학회지
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• 제21권1호
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• pp.15-26
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• 2005

An experimental investigation of the gas-phase photooxidation of toluene-NO$_{x}$-air mixtures at sub-ppm concentrations has been carried out in a 6.9 m3, indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NO$_{x}$ experiments included $O_3$, NO, NO$_2$, NO$_{x}$, CO, SO$_2$ toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NO$_{x}$ in ppbC/ppb was in the range of 5～20. It was found that the variation of gaseous species with irradiation time caused by the photooxidation of toluene-NO$_{x}$-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NO$_{x}$. The dependency of initial toluene concentration on the photooxidation of toluene-NO$_{x}$-air mixtures for toluene/NO$_{x}$=5～6 seemed to be opposite to that for toluene/NO$_{x}$=10～11. The arriving time at maximum ozone concentration depended on both initial toluene concentration and initial concentration ratio of toluene/NO$_{x}$. However, the maximum concentration of ozone formed by photooxidation depended only on the initial toluene concentration.luene concentration.

• 한국대기환경학회지
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• 제21권1호
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• pp.27-38
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• 2005

An experimental investigation of the gas-phase photooxidation of toluene-NO$_{x}$-air mixtures at sub-ppm concentrations has been carried out in a 6.9 ㎥, indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NO$_{x}$ experiments included aerosol, $O_3$, NO, NO$_2$, NO$_{x}$ CO, SO$_2$ toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NO$_{x}$ in ppbC/ppb was in the range of 5～20. It was found that the variation of aerosol number concentration with irradiation time caused by the photooxidation of toluene-NO$_{x}$-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NO$_{x}$. The dependency of initial toluene concentration on the photooxidation of toluene-NO$_{x}$-air mixtures for toluene/NO$_{x}$= 5～6 seemed to be opposite to that for toluene/NO$_{x}$=10～11. The maximum number concentration of aerosols formed by photooxidation and the aerosol yield depended on both initial toluene concentration and initial concentration ratio of toluene/NO$_{x}$. In this study, the aerosol yield, defined as aerosol formed per unit toluene consumed, was found to be 0.01～0.16.und to be 0.01～0.16.

• Environmental Engineering Research
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• 제24권4호
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• pp.670-679
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• 2019

Lignin complexity molecule makes its biodegradation difficult during lignocellulosic wastes composting. So, the improvement of its biodegradation has usually been considered as an objective. This study aimed to determine the impact of Trametes trogii inoculation on organic matter and particularly on lignin and cellulose during green wastes co-composting with olive mill waste water sludge and coffee grounds. Three types of heaps (H1, H2 and H3) were investigated during 180 d. H3 and H2 were inoculated at the beginning of the process (t₀) and 120 d later (t₁₂₀), respectively while H1 was the control. Results showed the absence of pH stabilization in H3 during the first month. Also, in this period we observed a faster degradation of some easily available organic matter in H3 than in the other heaps. After 120 d, a better cellulose decomposition (25.28%) was noticed in H3 than in H1 and H2 (16%). Inoculation during the second fermentation phase induced supplementary lignin degradation in H2 with a percentage of 35% against 23 and 26% for H1 and H3, respectively. For all the runs, a Fourier Transform Infrared analysis showed aliphatic groups' decrease, OH groups' increase and lignin structural modification.

• 한국응용과학기술학회지
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• 제12권1호
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• pp.101-107
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• 1995

케탈이나 아세탈반응에 의하여 이루어진 1, 3-디옥솔란 고리가 산수용액 중에서 불안정해 쉽게 가수분해되는 성질을 이용하여 소수부로는 지방산의 탄화수소사슬을 친수부로는 소디움 카르복시산(Soap)을 도입하여 분해 후 계면활성을 띠지 않는 분해성 계면활성제이다. 이 화합물의 수용액에 대한 표면장력은 31dyne/cm였고, 임계미셀농도는 $1.0{\times}10^{-3}mol/L$이었다. 기포력은 비교적 좋지 않았으며, 유화력은 콩기름보다 벤젠에서 양호하였다. 또한 이 화합물의 산분해 특성을 1wt% 수용액과 벤젠 사이의 계면장력 변화에 의하여 측정한 결과 pH 1 ${\sim}$ 4범위에서 약 300분 안에 모두 가수분해됨을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1999년도 제13회 학술강연논문집
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• pp.27-27
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• 1999

To illustrate the global variation of the droplet mean diameters and the turbulent flow characteristics in counterflowing internal mixing pneumatic nozzle, the experimental measurements at five axial downstream locations(i.e., at Z=30, 50, 80, 120, and 170mm) were made using a PDPA(Phase Doppler Particle Analyzer) under the different air injection pressures ranging from 40 ㎪ to 120 ㎪. A nozzle with axi-symmetric tangential-drilled four holes at an angle of 15$^{\circ}$ has been designed and manufactured. The distributions of velocities, turbulence intensities, turbulence kinetic energy, turbulent correlation coefficients, spray angle, droplet mean diameters, volume flux, number density are quantitatively analyzed. It is possible to discern the effects of increasing air pressure. It indicates that the strong axial momentum in spite of more or less disparity between the velocity components means more reluctant to disperse radially, and that axial fluctuating velocities are substantially higher than those of radial and tangential ones, suggesting that the disintegration process is enhanced under higher air assist. The larger droplets are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup at farther axial locations are attributed to the internal mixing type nozzle characteristics. Despite of the strong axial momentum, the poor atomization around the centre close to the nozzle exit is attributed to the lower rates of spherical particles which are not subject to instantaneous breakup. As it goes downstream, however, substantial increases in SMD(Sauter Mean Diameter) from the central part toward spray periphery are understandable because the droplet relative velocity is too low to bring about any subsequent disintegration.

• 한국지구과학회지
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• 제35권5호
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• pp.313-323
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• 2014

We secured the high dispersion spectra of the symbiotic star CI Cyg. The HI, HeI, and HeII line profiles were analyzed using the relatively long exposure data including 1800 sec (Sep. 12, 1998, phase=0.90), 3600 sec (Aug. 12, 2002, ${\phi}=0.47$), and 1800 sec (Oct. 21, 2009, ${\phi}=0.54$). Although a minor outburst was reported in 2008, our three observation periods were generally known to be quiescent in earlier photometric studies. With the help of hydrodynamic simulations, we identified the two emission zones responsible for the blue- and red-shifted line components: (a) an accretion disk around a hot white dwarf star which consists of the outer cool HeI emission zone and the inner hot HeII emission part, and (b) a high density zone near the inner Lagrangian point responsible for the HeI line flux variation and the broadening of its line profile. The HeII line fluxes indicate that the HeII emission zone of the accretion disk is relatively stable, implying a constant gas inflow from the giant star throughout the quiescent period. The 2002 HeI data showed that the notable mass flow activity through the inner Lagrangian point occurred during this period and its flux intensity became strongest, whereas the HeII line width in the same period indicates that its flow activity forced the accretion disk to expand. The [OIII] lines were observed in 1998 but not detected in 2002 and 2009, implying the disappearance of the low density zone. Based on our kinematical studies upon the line profiles, we conclude that CI Cyg was stable in 1998 among the three observation periods selected in this research.

• 한국통신학회논문지
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• 제23권8호
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• pp.1963-1970
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• 1998

본 논문에서는 위상천이가 없이 발진기간의 결합을 통해 빔을 주사하는 이차원 발진기형 능동 위상배열 안테나의 결합소자로 이차원 슬롯라인 결합구조를 제안하여 실험을 통해 그 특성을 고찰하였다. 제안된 이차원 슬롯라인 결합구조는 방사소자인 마이크로스트립 패치 안테나의 E-면과 H-면을 각각 결합하기 위하여 방사소자의 뒷면인 접지면에 $|{=}|$ 형태의 슬롯라인으로 구성되어졌으며, 슬롯라인의 폭, 실이 그리고 개수등에 의한 결합정도를 조사하여 최적의 결합구조를 제안하고 이를 $2{\times}5$ 소자 배열 안테나에 적용하여 실험하였다. 실험을 통하여, 2개의 소자가 배열된 H-면은 빔폭이 약 $42^{\circ}$이고 5개의 소자가 배열된 E-면은 빔폭이 약 $15^{\circ}$이며, 빔이 브로드사이드로부터 $-20^{\circ}$에서 $15^{\circ}$까지 주사함을 확인하였다. 따라서, 이차원 슬롯라인 결합을 이용한 발진기형 능동 위상배열 안테나가 실제로 이차원 평면배열 안테나로의 응용이 가능하다는 것을 알 수 있다.