• Korean Security Journal
• /
• no.32
• /
• pp.123-150
• /
• 2012

The purpose of this study was to seek practical intelligences for certain persons who wish to be a guard by studying for what practical public guards' recognition of organization and vocation is. The results of this study were as follows. First, Six study participants presented 'Respect within members', 'Atmosphere like family', 'Premium members', and 'Economic compensation & wealth of budget' as essential requirements for the best guard organization. Second, they also presented 'Systematic daily task & training', 'Exact selection system', and 'Strong cohesion & teamwork' as strong points of their organization. Third, they mentioned 'Internal evaluation system', 'Lack of education contents', and 'Limited position circulation' as weak points of their organization. Fourth, they mentioned that they feel encouraged itself as they work in the best guard organization, while they were skeptical when the citizens did not cooperate with them and they were not fully rewarded for their injury. Fifth, they expressed 'Difficulty of business cooperation', 'Unstable living patterns', 'Inconsistent assessment', and 'Continuing tension' as difficulties for performing the duties and stress causes. Lastly, they recognized of job security and self-esteem as they work in the best guard organization as advantages of a job, while they recognized of controlled life, low salaries and welfare level compared to duty importance and risks as disadvantages of a job. Consequently, students who wish to be a guard should consider job and organization attributes and set their career goals refer to these results.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.52.1-52.1
• /
• 2011

최근에 에너지 자원의 고갈이 다가오는 상황에서 태양전지 분야가 주목받고 있으며 이에 대한 시장이 급격하게 확대되고 있다. 그러나 현재의 태양전지는 주를 이루고있는 실리콘태양전지의 경우 원재료 수급이 불안정하여 가격 변동이 심하다. 따라서 이를 대체할 2세대 태양전지인 박막형 태양전지의 연구가 활발히 이루어지고 있다. 박막형 태양전지 중에서도 주목받고 있는 것은 Cu(In,Ga)$Se_2$(CIGS)박막 태양전지이다. CIGS는 Ga의 농도에 따라 1.02~1.68eV의 다양한 에너지 밴드갭을 갖는 직접천이형 반도체 물질이다. 또한 $1{\times}10^5cm^{-1}$의 높은 광흡수계수를 가지고 있으며, $450{\sim}590^{\circ}C$의 고온공정에서도 매우 안정하여 열화현상이 거의 보이지 않아 박막형 광흡수층 재료로서 적합하다. 흡수층을 제조하는 방법은 여러 가지가 있지만, 본 연구에서는 균일성이 뛰어나고 원료사용효율이 높은 sputtering 방법을 사용하였다. 그리고 결정화하기위해서 유독기체를 사용하는 셀.렌.화. (selenization) 방법 대신 전자빔을 조사하는 방법을 채택하였다. sputtering을 통한 CIGS precursor을 제조하기위해 2~3개의 화합물target을 사용하는데, 대표적인 방법으로 동시에 sputtering하는 co-sputtering 방법과 각각의 단일 층을 쌓아 제조하는 stack형으로 분류된다. 본 연구는 CIGS precursor를 제조하기 앞서 CuGa 단일 층만을 제조하여 공정조건에 따른 박막을 제조하였다. 제조된 CuGa 단일층은 전자빔 처리에 따른 영향을 알아보기 위해 전자빔의 세기와 공정시간을 달리하여 특성을 알아보았다. 실험에서는 Cu:75wt%,Ga:25wt% 조성의 target을 사용하여 공정 압력을 각각 10~1mTorr로 변화시키며 실험을 실시하였으며 공정 power는 50W, 70W, 100W로 변화 시키며 실험을 실시하였다. 이때 실험의 초기진공은 turbo-molecular pump를 이용하여 $1{\times}10^{-6}torr$ 이하로 하였으며, Target과 기판사이의 거리는 모두 같은 조건으로 고정하여 실험을 실시하였다. 박막의 균일성을 증가시키기 위하여 5 rpm의 속도로 기판을 회전하였으며 기판 온도는 가열하지 않고 상온에서 전구체를 증착하였다. 그 후 전자빔의 세기를 고정 시킨 후 전자빔 조사 시간을 조절하여 전자빔 조사 전후의 특성을 각각 분석하였다. 전기적특성은 Hall effect, 4-point probe, 구조적 특성은 SEM,EDS, XRD, XRF 를 이용하여 분석하였다.

• Analytical Science and Technology
• /
• v.30 no.5
• /
• pp.287-294
• /
• 2017

As the demand for natural gas increases with industrial development, the supply of natural gas is expected to become unstable with a shortage of imported natural gas. It is hence necessary to meet this demand by introducing and developing various types of natural gas, such as pipeline natural gas (PNG) and substituted natural gas (SNG), in addition to liquefied natural gas (LNG). The components included in PNG as well as their concentrations must be measured accurately, and a standard gas should be developed to accurately measure hydrocarbons ($C_6-C_{10}$), which are trace components included in natural gas. The components in the primary standard gas mixtures (PSMs) developed in the present study were hexane, heptane, octane, nonane, and decane with concentrations of $10-30{\mu}mol/mol$ with methane as the balance gas. Standard hydrocarbon ($C_6-C_{10}$) gas mixtures were prepared in aluminum cylinders by a gravimetric method with traceability following ISO 6142 with raw material gases, for which the purity of each component was analyzed completely. The prepared standard gas mixtures were analyzed by to evaluate the preparation consistency between the standard gas mixtures, the adsorbability of the cylinders, the variation of the stability, and the uncertainty. The results showed that aluminum cylinders have little adsorptive loss on their internal surfaces with excellent long-term stability. The developed standard gas mixture, containing hexane, heptane, octane, nonane, and decane with concentrations of $10-30{\mu}mol/mol$, showed an uncertainty in a range of 0.79 % - 1.63 %.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.4
• /
• pp.343-351
• /
• 2016

Cryogenic spray characteristics of a nitrogen swirl injector operating in supercritical environment have been numerically investigated. By comparing the equation of states(EOS) used for supercritical condition, SRK EOS was applied to predict the nitrogen thermodynamic property under supercritical environment. A Chung's method was implemented for the calculation of viscosity and conductivity and Takahashi's correlation based on Fuller's Theorem was implemented for the calculation of diffusion coefficient. By injecting the nitrogen with 5 bar differential pressure into 50 bar chamber filled with nitrogen, numerical simulation has been conducted. The dynamic Smagorinsky sub-grid scale (SGS) model has been compared with the algebraic Smagorinsky SGS model using FFT frequency analysis. The instability at the liquid film and gas core inside injector and the propagation of pressure oscillation into the injector has been investigated. The spreading angle of swirl injector obtained by numerical calculation has been validated with experimental result.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.4
• /
• pp.10-18
• /
• 2018

The primary purposes of this study are to understand a fundamental aspect of current uniformity around a reinforcing bar (rebar) in cement mortar, and to develop an accurate monitoring method in a wet-dry cycling process with the alternative current (AC) impedance method. Three cement mortar specimens with two embedded rebars were prepared in the laboratory. As a main variable, the distance between two rebars was designed to be 10, 20 and 30 mm with the same thickness of 20 mm. To simulate the corrosion of rebars in concrete structures in a marine environment, three cement mortar specimens were exposed to 15 wet-drying cycles (24-hour-immersion in seawater and 48-hour-drying in a room temperature) in the laboratory. It was observed that the potential level shifted to a noble value during corrosion potential monitoring, which is attributed to acceleration of dissolved oxygen diffusion at the drying process. AC impedance was measured in a frequency range from 100 kHz to 1 mHz on a wet-drying process. A theoretical model was proposed to explain the interface condition between the rebars and cement mortar by using the equivalent circuit consisting of a solution resistance, a charge transfer resistance and a CPE (constant phase element). It was observed that the diffusion impedance appeared in a low frequency range as corrosion of rebars progresses. At the drying stage of the wet-drying cycles, the currents line for monitoring tended to be non-uniform at the interface of rebar/mortar, being phase shift, ${\theta}$, close to $-45^{\circ}$.

• Korean Chemical Engineering Research
• /
• v.46 no.6
• /
• pp.1124-1129
• /
• 2008

Cokes wastewater is one of the most toxic industrial effluents since it contains high concentrations of pollutants, such as phenol, ammonia, thiocyanate and cyanides. Although biological pre-denitrification process has been used to treat this wastewater in Korea, unexpected failure in nitrogen removal occasionally occurs during summer season. In this study, therefore, we examined inhibitory effects of phenol, ammonia, thiocyanate, ferric cyanide and free cyanide on biological denitrification according to temperature variation ($20{\sim}38^{\circ}C$). Batch experiments showed that denitrification rate was faster in summer ($38^{\circ}C$) than other seasons, and removal rates of pollutants increased with increasing temperature. Phenol, ammonia, thiocyanate and ferric cyanide did not inhibit denitrification even at its high concentration (200 mg/L). However free cyanide above 0.5 mg/L seriously inhibited the bilolgical denitrification reaction. Inhibitory effect of these pollutants was reduced with increasing temperature.

• Korean journal of applied entomology
• /
• v.29 no.1
• /
• pp.31-42
• /
• 1990

Storage ecosystems of rough rice, brown rice and polished rice were analyzed form Feb. 1987 to Nov. 1988 to investigate structures and ecological successions in the arthropod communities as well as changes in energy of the systems. The changes in temperature of stored rice showed high degree dependence on the temperature of storage room with time lag of about four weeks. Moisture content of rough rice, brown rice and polished rice during the period were in the range of 12.7$\pm$0.4, 13.1$\pm$0.4 and 13.5$\pm$0.3%, respectively. The arthropod communities in rough rice, brown rice and polished rice were qualitatively and quantitatively different. In rough rice, dominant species changed from Leptinotus reticulatus Endlein to Liposcelisentomophilus Endlein, while in brown rice from Pyralis farinalis L. to Sitophilus oryze (L.), unidentified parasitic wasps, Anisopteromalus calandrae Howard and Tribolium castaneum Herbst and finally to S. oryzae. In polished rice, the arthropod community showed an ecological succession similar to that in brown rice except for a transient dominance of two psocidspecies. Thearthropod community in rough rice was rather simple and unstable in comparison with those in brown rice and polished rice. The 1000 kernel weight of brown rice decreased slightly during the period when the arthropods were active (summer season), while that of rough rice and polished rice remained at the similar level. However, the ash content per unit volume of brown rice as well as rough rice and polished rice showed no increase during the period.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.4
• /
• pp.85-93
• /
• 2011

A parametric study is conducted for the design of segmented arc plasma torch with the input power and current of 0.4 MW and 300 A, respectively. For this purpose, we use the analytical relationship between input power, current condition, plasma temperature, inner diameter (R) and length (L) of the torch constrictor based on arc channel model. The results reveal that arc plasma temperatures increase monotonically as ��L increases or R decreases for the ranges of R ${\leq}$ 7.5 mm and L ${\leq}$ 1.25 m. For larger valuse of ��R and L than 7.5 mm and 1.25 m, respectively, however, they show non-linear behavior corresponding to the variations of ��L, which stands for the generation of unstable arc plasma. From this parametric study, optimum ranges of R and L are suggested as 5.5 mm ${\leq}$ R ${\leq}$ 7.5 mm and 0.25 m ${\leq}$ L ${\leq}$ 0.5 m for 0.4 MW class segmented arc plasma torch, under which stable arc plasma can be achieved at the input currents of ~300 A.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.2
• /
• pp.140-145
• /
• 2018

This paper deals with the dynamical analysis of a two-point mooring vessel under surge excitations. The characteristics of nonlinear behaviors are investigated completely including bifurcation and limit cycle according to particular input parameter changes. The strong nonlinearity of the mooring system is mainly caused by linear and cubic terms of restoring force. The numerical simulation is performed based on the fourth order Runge-Kutta algorithm. The bifurcation diagram and several instability phenomena are observed clearly by varying amplitudes as well as frequencies of surge excitations. Stable periodic solutions, called the periodic windows, can be obtained in succession between chaotic clouds of dots in case of frequency ${\omega}=0.4rad/s$. In addition, the chaotic region is unexpectedly increased when external forcing amplitude exceeds 1.0 with the angular frequency of ${\omega}=0.7rad/s$. Compared to the cases for ${\omega}=0.4$, 0.7rad/s, the region of chaotic behavior becomes more fragile than in the case of ${\omega}=1.0rad/s$. Finally, various types of steady states including sub-harmonic motion, limit cycle, and symmetry breaking phenomenon are observed in the two-point mooring system at each parameter value.

• Korea journal of population studies
• /
• v.27 no.2
• /
• pp.1-34
• /
• 2004

최근 한국사회에서는 출산율의 저하로 인한 사회경제적 영향을 우려하여 대책방안을 강구하여야 한다는 논의가 증대되고 있다. 그런데 국가정책을 개발${\cdot}$추진하기 이전에 반드시 요구되는 것은 저출산 현상의 올바른 인식과 철저한 원인규명이다. 따라서 본 연구에서는 출산율 변화의 원인을 다각적으로 살펴보고, 향후 변화방향을 전망해 보고자 한다. 먼저 자녀출산의 변화를 결혼상태 변화와 유배우부인의 출산율 변화 부분으로 나누어 살펴본 결과, 과거와는 달리 최근의 출산율 저하는 유배우 부인에 의해서가 아니라 미혼자의 결혼연장 또는 독신생활에서 기인되는 것으로 나타났다. 이들 두 요인에 영향을 주는 변수로는 경기침체 및 직장불안정, 결혼가치관의 변화와 초혼연령의 상승, 자녀양육 관심증대, 자녀양육비 부담, 가정과 직장의 양립을 위한 사회적 인프라 부족, 여성의 자아욕구 및 사회참여 증대, 자녀효용가치 감소, 이혼 등 가족해체의 증대, 그리고 불임부부의 증대 등인 것으로 판단된다. 향후 출산율 변화를 전망해 보면, 저출산을 일찍 경험한 서구 선진국의 경우와는 달리 정책의 추진에 한계가 있어 선진국보다 더 낮은 출산율을 회복하는 데는 많은 어려움이 있을 것이라는 판단이다. 더군다나 젊은 미혼남녀의 가치관이 개인주의화 되는 경향이 있다는 점을 감안한다면 출산율 회복정책을 추진한다 하더라도 한계가 있을 수밖에 없을 것이다. 수년간 실시된 각종 실태조사를 분석한 결과에 의하면 현재의 경기침체가 회복될 경우 약 20%의 출산율 상승 가능성이 있으며, 이 때의 합계출산율은 약 1.43명 수준이 될 수 있을 것으로 예견된다. 또한 종합적 체계적 출산회복정책을 효과적${\cdot}$효율적으로 추진한다면 약 10년 후에는 합계출산율이 약 1.6 수준으로 회복될 것이라는 낙관적 견해를 가져본다. 그렇지만 정책의 강도에 따라서 회복수준은 현저하게 상이할 것이다.를 진단, 치료함에 있어 진행성 신질환의 가능성을 시사하는 예후인자가 없다면 신생검보다는 지속적이고 정기적인 추적관찰만으로도 충분할 것으로 생각된다도 등은 양군 사이에 유의한 차이가 관찰되지 않았다. 발견 당시 혈청 $C_3$치의 감소는 모두 11명(61.1%)에서 관찰되었는데, 증상군에서는 7명(87.5%), 집단뇨검사군에서는 4명(40%)으로 증상군에서 혈청 $C_3$치의 감소가 보다 현저하였다. 그러나 추적관찰 기간 동안 증상군에서는 7명 중 4명, 집단뇨검사군에서는 4명 중 1명에서 혈청 $C_3$치는 정상범위로 증가하여 최종 관찰시점에서는 6명 (33.3%)에서만 혈청 $C_3$치의 감소가 지속되고 있다. 혈청 $C_3$치의 감소를 보인 경우를 다시 병리조직학적 분류에 의해 세분하여보면 발병당시에는 I형 8명(61.5%), II형에 1명(100%), III형 2명(50%)에서 관찰되었는데, 최종 시점에서는 I형 4명(30.8%), II형 1명(100%), III형 1명(33.3%)이었다. 또한 증상군에서 세포성 반월체형성과 세뇨관위축의 빈도가 높았으며, 사구체 혈관벽 비후와 사구체 간질의 증가의 정도가 집단뇨검사군에 비해 통계적으로 유의하게 높았다. 결론: 무증상성 요이상을 가진 환자에서 신장조직검사 실시 후 MPGN으로 진단되는 증례가 증가하고 있고, 오히려 증상을 동반하는 경우보다 빈도가 증가한다는 사실은 집단뇨 검사에서 소변의 이상소견이 발견되어 신장 조직검사를 실시할 경우 혈청 $C_3$치의 감소 여부에 관계없이 MPGN도 진단적 고려 대상이 되어야 한다고 생각한다.신장 조직검사를 시행한 결과 진행성 경과를 취할 수 있는 막 증식성 사구체 신염과 매우 희귀한 증례인 신유전분증 등으로 진단됨으로써 지속성 단백뇨의 경우 정확 진단적 접근이 필수적임을 알 수