• The Korean Journal of Ecology
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• 제12권4호
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• pp.257-284
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• 1989

This study was carried out to characterize pinus densiflora forests in middle province (Mt. Seolag, Mt. Taebaik) south province (Mt. Sokli, Mt. Jiri) and south-coast province (Mt. Daedun) of Korea. The appearance species in the P. densiflora alliance included 325 taxa and varied according to the direction of slopes. The steeper the slope was, the fewer number of taxa were observed. The floristic composition of south-coast province was gradually changing to the south hemispheric factors. Dominant species groups of P. densiflora alliance were classified into P. densiflora, Quercus serrata ( layer), Rhus trichocarpa ( layer), Lespedeza maximowiczii var. tomentella (S layer), Artemisia keiskeana, Carex humilis var. nana, Spodiopogon sibiricus (K layer). Quercus variabilis, Fraxinus sieboldiana and Styrax japonica association were formed under the P. densiflora alliance. Quercus, Rhus, Lespedeza and Rhododendron groups maintained high ecological relationships one another. The soil factors (pH, organic matters, and water field capacity)and relative light intensity tended to show negative correlation, which were significantly different among provinces. The P. densiflora forests of Korea were classified into one alliance and four associations, that is, pinion densiflorae Suz.-Tok. 1966, Quercetum variabilae ass. nov., Quercetum mongolicae ass. nov. Fraxinetum sieboldianae ass. nov. and Styraxetum japonicae ass. nov.

• 대한화학회지
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• 제36권3호
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• pp.442-445
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• 1992

용액의 굴절율이 비중에 따라 달라지는 현상을 이용하여 광학식 비중계를 제작하였다. 이 비중계는 비중에 따른 빛의 반사량을 전기신호로 출력하므로 용액의 비중 변화를 계속 관찰하거나, 용액의 비중을 자동으로 조절하고자 할 때 유용하다. 빛의 매개체로 U자형 유리봉을 사용하였으며 빛의 양을 정확히 측정하기 위하여 위상 감별 검출법을 사용하는 전자회로를 고안하였다. 이 비중계를 사용하여 황산의 비중을 측정한 결과, 비중에 따른 출력신호의 직선성이 매우 좋았다.

• 대한기계학회논문집B
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• 제25권3호
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• pp.356-365
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• 2001

Heat (mass) transfer characteristics have been investigated on the endwall of a large-scale linear turbine cascade. Its profile is based on the mid-span of the first-stage rotor blade in a industrial gas turbine. By using the naphthalene sublimation technique, local heat (mass) transfer coefficients are measured for two different free-stream turbulence intensities of 1.3% and 4.7%. The results show that local heat (mass) transfer Stanton number is widely varied on the endwall, and its distribution depends strongly on the three-dimensional vortical flows such as horseshoe vortices, passage vortex, and corner vortices. From this experiment, severe heat loads are found on the endwall near the blade suction side as well as near the leading and trailing edges of the blade. In addition, the effect of the free-stream turbulence on the heat (mass) transfer is also discussed in detail.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3013-3018
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• 2008

Supercharging system was adopted to investigate the influence of boost pressure on operating range, brake specific fuel consumption (BSFC) and exhaust emissions by using a supercharger at low temperature diesel combustion (LTC) condition in a 5-cylinder 2.7 L direct injection diesel engine. The experimental parameters such as injection quantity, injection timing, injection pressure and exhaust gas recirculation (EGR) rate were varied to find maximum operating range. The result showed that operating range with boost was expanded up to 41.9% compared to naturally aspirated LTC condition due to increased mixing intensity. The boosted LTC engine showed low BSFC value and dramatically reduced soot emission under all operating range compared with high speed direct injection (HSDI) mode. Finally, this paper presents the boosted LTC map of emission and the strategy of improved engine operating range.

• 한국화재소방학회논문지
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• 제27권4호
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• pp.56-60
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• 2013

본 연구에서는 소방방열복 착용시 작업강도가 신체에 미치는 영향을 조사하여 소방공무원의 안전을 위한 기초자료 제공을 목적으로 하며 연구에서 얻어진 결과를 제시하면 다음과 같다. 작업종료시(20분)에 작업강도가 4 METs에서 8METs로 증가함에 따라 평균피부온도차(33.3 %), 고막온도차(57.1 %), 심박수(32.5 %), 운동자각도(75.6 %) 등은 통계적으로 유의하게 높게 나타났으며, 온냉감과 체중감소는 유의한 차이가 나타나지 않았다. 이상의 결과 소방방열복 착용시 작업강도의 증가는 신체에 많은 영향을 미치는 것으로 판단된다.

• 한국세라믹학회지
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• 제35권11호
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• pp.1190-1196
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• 1998

Ultrafine ${\beta}$-SiC powders were synthesized by the vapor phase reaction of TMS[Si(CH3)4] in hydrogen The reaction temperature and TMS concentration were varied from 1000 to 1400$^{\circ}C$ and from 1 to 10% respectively. The average particle size and phase of the powders were analyzed by TEM and XRD. Ultrafine ${\beta}$-SiC powders were synthesized above 1000$^{\circ}C$ and the crystallinity of the powders increased with increasing reaction temperature. Shape of the particles were spherical and had average size of about 20 nm which showed no difference as the reaction temperature and TMS concentration increased. From the FT-IR analysis the absorption bands of Si-C of the powders shifted to higher wavenumber as the reaction temperature increased,. Under the condition of total gas flow above 1500cc/min ${\beta}$-SiC and poly-Si powders were obtained simultaneously. The Si-O bond intensity was increased under the condition of total gas flow rate above 1000cc/min which might be due to oxidation formed on poly-Si.

• 한국세라믹학회지
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• 제50권4호
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• pp.280-287
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• 2013

Plate-type phosphor is a promising substitute in overcoming the issues related to the powder phosphor paste mixed with resin. In this research, $Ca-{\alpha}-SiAlON:Eu^{2+}$ plate phosphor ($Ca_xSi_{12-(m+n)}Al_{m+n}O_nN_{16-n}:Eu_y$) was investigated for the varied compositions (m,n) of the host crystal with the fixed Eu content (y). Densification was promoted for the compositions with increasing 'm' values for the m=2n relationship. Dictated by the Eu concentration inside the phosphor crystal, photoluminescence intensity was stronger in ${\alpha}2$ specimen (m = 3.0, n = 1.5) containing the second phases when compared to ${\alpha}1$ specimen (m = 1.5, n = 0.75) comprising a single-phase ${\alpha}$-SiAlON. The concentration of Eu in the non-emitting amorphous interfacial glass phase was 2~4 times of the designed Eu concentration inside the ${\alpha}$-SiAlON crystal.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.718-722
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• 2011

In this work, we investigated to the etching characteristics of the TiN thin film in He/$BCl_3/Cl_2$ plasma. The etch rate was measured by the gas mixing ratio, the RF power, the DC bias voltage and the process pressure. The maximum etch rate in He/$BCl_3/Cl_2$ plasma was 59 nm/min. The etch rate increased as the RF power and the DC-bias voltage was increased. The chemical reaction on the surface of the etched the TiN thin films was investigated with X-ray photoelectron spectroscopy (XPS). The intensity of Ti 2p and N 1s peaks are varied during etching process. A new peak was appeared in He/$BCl_3/Cl_2$ plasma. The new peak was revealed Ti-$Cl_x$ by Cl 2p peak of XPS wild scan spectra analysis.

• 한국연소학회지
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• 제9권3호
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• pp.10-18
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• 2004

An experimental study of the effect of operating conditions on the behavior of a lean premixed laboratory combustor operating on natural gas has been conducted. Measurements were made characterizing the pressure fluctuations in the combustor and the flame structure over a range of inlet temperatures, inlet velocities and equivalence ratios. In addition the fuel distribution at the inlet to the combustor was varied such that it was an independent parameter in the experiment. Inlet temperature, inlet velocity and equivalence ratio were all found to have an effect on the stability characteristics of the combustor. The nature of this effect, however, depended on the fuel distribution. For example, with one fuel distribution the combustor would become unstable when the temperature was increased, whereas with a different fuel distribution the combustor would become unstable when the temperature was decreased. Similarly, the operating conditions had an effect on the flame structure. For example the intensity-weighted center of mass of the flame was found to move closer to the center body as either the temperature or equivalence ratio increased. It was interesting and somewhat surprising to note, however, that as the location of the center of mass changed with operating conditions it did so by moving along a line of constant flame angle.

• 한국조경학회지
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• 제23권2호
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• pp.213-222
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• 1995

To increase the night use level, this study was analyzed perception of users about the public safety, and extracted main variables which were influencing public safety. The public safety was evaluated by the actual (on site) and nonactual users (off site) and the Delphi method. The night users of female and the elders were relatively more than male and the young respectively as compared with day. Walking was predominant in approaching means. In public safety ratings, $\boxDr$vuknerability to violence$\boxUl$varied accoding to sex, income, education, marriage, job, age. $\boxDr$crowding, $\boxDr$noise$\boxUl$ were important variables in satisfying users at night. $\boxDr$Lack of surveillance, $\boxDr$harassment of other person$\boxUl$, $\boxDr$rowdy behavior in poorer visibility$\boxUl$, $\boxDr$fear in lower intensity of light$\boxUl$ and $\boxDr$vulnerability to violence$\boxUl$stood high , so it is required guarantee of security guard to enhance the park use at night Although the ratings between field and indoor evaluation were somewhat different the variables had so similiar rant.