• 대한화학회지
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• 제37권5호
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• pp.483-490
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• 1993

무거운 란탄족 금속이온의 전기화학적 거동을 acetonitrile 용액에서 직류 및 펄스차이 폴라로그래피 및 순환전압전류법으로 연구하였다. $Gd^{3+}, Tb^{3+}, Dy^{3+}, Ho^{3+}, Er^{3+}, Tm^{3+} 및 Lu^{3+} 은 0.1M TEAP 지지전해질에서 3전자 전비가역반응이었으며, Yb^{3+}는 단계적인 환원반응으로 나타났다. 순환전압전류법에서 Yb^{3+}의 첫번째 환원반응은(Yb^{3+}$ ＋ $e^-\Leftrightarrow Yb^{2+})$ 유사가역적 거동을 나타냈으며, 두번째 환원반응은 전비가역적 거동을 나타냈다. 환원봉우리전류는 짙은 농도범위에서 주사속도가 저속일수록 흡착특성을 나타냈다. 물-acetonitrile 혼합용매에서 무거운 란탄이온은 물의 부피비가 증가할수록 음전위 이동하였으며 환원전류는 감소하였다. 이같은 현상은 acetonitrile보다 주개수가 큰 물의 용매화 능력이 증가하는 것으로 생각된다. 또한 Yb(Ⅲ)의 첫번째 환원과는 몰 부피비가 증가함에 따라 유사가역적 거동에서 벗어나는 현상이었다.

• 생태와환경
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• 제37권1호통권106호
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• pp.47-56
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• 2004

영양염 (N, P, Si, Fe) 결핍이 팔당호내 서로 다른 3개지점의 식물플랑크톤 군집(>10 ${\mu}m$)에 어떠한 영향을 미치는지 파악하기 위하여 채수한 현장수를 결핍배지에서 일정시간 배양한 후 대조군과 비교 조사하였다. 조사결과, 현장수는 공히 영양물질과 현장수 증류에 따라 서로 다른 종 천이 및 생물량을 나타냈다. 영양염 결핍에 따른 천이는 N, P, Si 결핍군에서는 속(genus)수준에서, Fe결핍에서는 종(species) 수준에서 일어났다. 특히 Fe결핍에서 남조 Microcystis aeruginosa, N 결핍에서 Anabaena의 발달은 매우 흥미로운 결과이다. 또한 모든 결핍군에서 뚜렷한 성장저해 현상을 보였으나 Si 결핍군에서는 생물량 변동이 거의 없었다. 식물플랑크톤 군집은 영양염결핍과 채수지점에 따라 차이를 보였는데, 전체적으로 N,P 결핍군에서는 우점도 감소 및 다양도 증가를 보였으며,Si,Fe 결핍군과는 반대 결과를 보였다. 따라서 영양염 결핍은 조사지점에 따라 다소 차이를 보였으나 식물플랑크톤 종 천이, 생물량 변동 등의 뚜렷한 군집변화를 유도함으로서 수계내 문제조류의 근본적 해결의 가능성을 시사해 주었다.

• 한국운동역학회지
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• 제24권1호
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• pp.19-26
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• 2014

This study investigated foot pressure patterns between experienced skiers and intermediate skiers during alpine skiing. Five experienced skiers and five intermediate skiers participated in this study. Foot pressure measurement system was used to measure vertical ground reaction force (vGRF) and contact area under the six plantar regions. Each participant was asked to perform basic parallel turns and carved turns on a $18^{\circ}$ groomed slope. Each right turn was divided into the initiation phase, the steering phase 1 and 2. For the initiation phase of the basic parallel turns, significantly greater contact area was found on the LRF and RRF of the intermediate skiers (p<.05) and significantly greater vGRF was found on the LRF of the intermediate skiers (p<.05). Also significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at the steering phase 1 (p<.05) and on the LRF of the intermediate skiers at the steering phase 2 (p<.05). For the carved turns, significantly greater vGRF and contact area were found on the LRF and RRF of the intermediate skiers at all three phase (p<.05). On the other hand, significantly greater vGRF was found on the RFF of the experienced skiers at the steering phase 1 (p<.05). Also significantly greater vGRF and contact area were found on the RMF of the experienced skiers at the steering phase 2 (p<.05). In order to increase performance, we suggest that the intermediate skiers should be unweighted at the initiation phase and shift the body weight to the forefoot of the outer foot at the steering phase 1. Also, the outer ski should be loaded more than the both skis at the steering phase 1 and 2.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.446-452
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• 2003

Some new nanohybrid materials have been synthesized by intercalating the oxotitanium(IV) meso-tetrakis(4- sulfonatophenyl) porphyrin$(O=Ti^{(IV)} TSPP)$ into the Zn/Al layered double hydroxides (LDHs), and their structures and photophysical properties have been investigated by various laser spectroscopic techniques. According to the XRD pattern of the synthesized nanohybrid materials, the macrocycle plane of $O=Ti^{(IV)}$ TSPP are grafted perpendicular to the LDH layers. The $O=Ti^{(IV)}$ TSPP-intercalated LDH exhibits band broadening of the absorption spectrum and a blue shift of Q-band as compared to that observed in solution. Resonance Raman spectral measurements demonstrate that the positively charged LDHs give rise to a slight decrease of the electronic density of the porphyrin ring accompanying a small change of the electronic distribution of the $O=Ti^{(IV)}$ TSPP. Consequently the LDH environment affects the energies of the two highest occupied molecular orbitals (HOMOs) of the $O=Ti^{(IV)}$) TSPP, $a_{1u}$ and $a_{2u}$, producing a mixed orbital character. Being consistent with these electronic structural changes of $O=Ti^{(IV)}$ TSPP in LDH, both the fluorescence spectral change and the fsdiffuse reflectance transient measurements imply that the photoexcitation of the $O=Ti^{(IV)}$ TSPP intercalated into LDH undergoes fast relaxation to the O=Ti(IV) $TSPP^+-LDH^- $charge transfer (CT) state within a few picoseconds, followed by a photoinduced electron transfer between the O=Ti(IV) TSPP and LDHs with a rate constant greater than %1×10^{10}S^{-1}$. No evidence is found for back electron transfer. In conclusion, the $O=Ti^{(IV)}$ TSPP intercalated LDH seems to be a possible candidate for an artificial reaction center for an efficient solar energy conversion system.

• 대한화학회지
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• 제63권6호
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• pp.453-458
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• 2019

Synthesis of ZnCo₂O₃ oxide is performed by sol-gel method via nitrate-citrate route. Powder X-ray diffraction (XRD) study shows monoclinic unit cell having lattice parameters: a = 5.721(1) Å, b = 8.073(2) Å, c = 5.670(1) Å, β = 93.221(8)°, space group P_2/m and Z = 4. Average crystallite sizes determined by Scherrer equation are the range ~14-32 nm, whereas SEM micrographs show nano-micro meter size particles formed in ZnCo₂O₃. Endothermic peak at ~798 K in the Differential scanning calorimetric (DSC) trace without weight loss could be due to structural transformation and the endothermic peak ~1143 K with weight loss is due to reversible loss of O₂ in air atmosphere. Energy Dispersive X-ray (EDX) analysis profile shows the presence of elements Zn, Co and O which indicates the purity of the sample. Magnetic measurements in the range of +12 kOe to -12 kOe at 10 K, 77 K, 120 K and at 300 K by PPMS-II Physical Property Measurement System (PPMS) shows hysteresis loops having very low values of the coercivity and retentivity which indicates the weakly ferromagnetic nature of the oxide. Observed X-band EPR isotropic lineshapes at 300 K and 77 K show positive g-shift at g_iso ~2.230 and g_iso ~2.217, respectively which is in agreement with the presence of paramagnetic site Co²⁺(3d⁷) in the oxide. DC conductivity value of 2.875 ×10^-8 S/cm indicates very weakly semiconducting nature of ZnCo₂O₃ at 300 K. DRS absorption bands ~357 nm, ~572 nm, ~619 nm and ~654 nm are due to the d-d transitions ⁴T_1g(⁴F)→²E_g(²G), ⁴T_1g(⁴F)→⁴T_1g(⁴P), ⁴T_1g(⁴F)→⁴A_2g(⁴F), ⁴T_1g(⁴F)→⁴T_2g(⁴F), respectively in octahedral ligand field around Co²⁺ ions. Direct band gap energy, E_g~ 1.5 eV in the oxide is obtained by extrapolating the linear part of the Tauc plot to the energy axis indicates fairly strong semiconducting nature of ZnCo₂O₃.

• 한국정보통신학회논문지
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• 제20권6호
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• pp.1154-1162
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• 2016

본 논문에서는 이진 가중치 전류 기법을 이용한 고속 디지털 LDO(Low Dropout) 레귤레이터를 제안했다. 기존의 디지털 LDO는 일정량의 전류를 한 단계씩 제어하기 때문에 응답하는데 오랜 시간이 걸리며, 링잉 문제가 발생하게 된다. 이중 가중치 전류 기법은 링잉 문제를 제거함으로써 출력전압이 빠르게 안정화되도록 한다. 출력전압이 목표 전압에 안정적으로 도달하면, 디지털 LDO의 동작을 멈추는 프리즈 모드를 추가했다. 제안된 고속 응답 디지털 LDO는 출력 전원 전압이 급격히 바뀌는 시스템에서 응답속도가 느린 DC-DC 변환기와 함께 사용되어 출력전압을 빠르게 변하도록 한다. 제안된 디지털 LDO는 기존의 양방향 시프트 레지스터보다 면적이 56% 감소했고, 리플전압이 87% 감소했다. 제안된 디지털 컨트롤러는 $0.18{\mu}F$ CMOS 공정으로 제작되었다. $1{\mu}F$의 출력 캐패시터에서 정착시간이 $3.1{\mu}F$이고, 리플전압은 6.2mV 였다.

• 한국해양공학회지
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• 제25권2호
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• pp.85-91
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• 2011

Many protection methods such as surface coating, electric protection, or other methods have been applied to the numerous steel structures widely used in continental and marine areas to control their corrosion, which is done from an economic point of view. Most of these steel structures are primarily protected by coating methods. However, some steel piles under seawater are protected by the electric protection method, that is, either using an impressed current or a sacrificial anode method. Furthermore, environmental contamination may cause a severely corrosive environment, which, in turn, causes the accelerated corrosion of steel structures. Subsequently, coated steel structures could deteriorate more rapidly than the designed lifetime because of the acid rain caused by air pollution, etc. Therefore, a coating of marine paint exposed to seawater, that is, underwater hardening painting, is increasingly required to be fast drying as well as highly corrosion resistant. In this study, five types of underwater hardening paints were prepared with different resin series and additives. Their corrosion and water resistances were investigated using electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements, etc. Even though it is generally accepted that the corrosion resistance of bare steel tends to increase with a shift of the corrosion potential in the noble direction, the corrosion resistance of a sample with a coating exhibited a relatively better tendency when it had a lower corrosion potential in this study. The corrosion current density was also decreased with a decrease in the diffusion limiting current density, which may mean that there is some relationship between corrosion and water resistance. The S sample of the ceramic resin series showed the relatively best corrosion and water resistance among those of samples, while the worst corrosion and water resistance were observed for the R sample of the epoxy resin series. The corrosion and water resistance of those samples tended to deteriorate with an increase in the immersion days, and their corrosion and water resistances were considered to be apparently improved by the types of resin and additives.

• 한국전자파학회논문지
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• 제20권8호
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• pp.701-713
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• 2009

본 논문은 LTE 상향 링크 전송에서 물리적 채널간의 전력 과도 현상으로 인한 인접 부 반송파 간섭으로 반송파간의 직교성이 손상되어 수신 신호에 성능감쇄를 초래하는 문제점을 개선하기 위한 기법을 연구하였다. 전력과도 현상에 의해 발생하는 인접 부 반송파 간섭은 도플러 효과에 의해 발생하는 인접 부 반송파 간섭과는 다른 형태로 채널의 전후에서 전력 변화의 각 주기마다 발생한다. 인접 부 반송파 간섭이 발생하는 원인은 채널간의 전력 차이, 전력 과도 구간의 길이, 다중경로 채널 지연 스프레드 그리고 부 반송파의 수에 의해서 발생한다. 본 논문에서는 위에 언급한 4가지 원인으로 인해 발생하는 인접 부 반송파 간섭을 개선하기 위한, 각 채널별 다중 탭 등화기의 탭 수를 결정하는 새로운 기법을 제시하였다. 이 기법은 정규화된 간섭(normalized interference) 즉, 정규화된 부 반송파간의 간섭이 정규화된 잡음(normalized noise)보다 클 때 다중 탭 등화기의 탭 수를 결정하는 기법이다. 모의 실험 결과에서, 수신 신호의 SNR에 따라 적응적으로 탭 수가 조절되고 비트 오류율(BER)의 성능이 향상 됨을 보였고 또한 제안한 기법의 복잡도가 전통적인(classical) 방법의 복잡도 보다 88 % 줄어듦을 보였다.

• 융합보안논문지
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• 제13권5호
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• pp.3-10
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• 2013

김정일시대 군사협상 분석 모델인 '항일유격대식 협상모델'을 활용하여 최근에 실시된 개성공단 실무회담 분석을 통하여 김정은시대에 개최될 군사협상의 지속과 변화를 제시하고자 한다. 특히, 개성공단 실무회담 분석을 통하여 김정은 시대의 경제분야 협상에서도 군사회담과 유사한 협상행태가 진행되고 있음을 확인할 수 있었다. 이와 같은 분석을 통하여 유추할 수 있는 사항은 김정은시대 군사협상에서도 김정일시대의 군사협상 범주에서 협상이 진행될 것이라는 사실이다. 근본적으로 북한은 변화의 길을 걷겠지만 현 시점에서는 기존의 전략문화를 변경하기 보다는 그 틀 속에서 군사협상 목적을 달성하려 할 것이다. 이러한 현상은 당분간 지속될 것이다. 향후 북한은 경제난 극복을 위하여 군사협상에 변화를 꾀할 것이다. 따라서 우리 정부의 군사협상에 대한 인식의 대전환이 있어야 할 것이다. 우리정부는. 대화와 협상을 유도하기 위해서 지속적으로 노력하여야 한다. 북한의 변화를 유도하기 위해서는 군사 협상에 적용할 수 있는 통일 전선논리를 활용한 경제 분야 협상 의제를 개발하여야 한다. 이를 이용하여 북한의 군사협상 정책결정자들에게 논리체계를 형성하여 준다면 새로운 군사협상의 틀을 만들 수 있을 것이다. 북한은 변화를 통한 경제적 교류협력을 보장하는 길이 생존하고 발전하는 길임을 인식하여야 한다.

• 한국국방경영분석학회지
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• 제2권1호
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• pp.127-143
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• 1976

The purpose of this thesis is to study the optimal arrangement of aircraft instrument panels through the human factors approach. Human factors engineering is the process of effectively fitting the human component to the machine component in any man-machine system. The human factors. are especially important to an aircraft pilot who must constantly shift his attention between the instrument panel within the cockpit and the surrounding area of the aircraft. The preliminary part of this study is to find the general patterns of the Korean pilot's eye movements during their various flying maneuvers, and which instruments require the most attention while in flight. It is assumed that all pilots have a general pattern of eye movement when observing the aircraft instrument panel and that an optimum arrangement would be to minimize the eye travel distance between instruments. In this thesis the arrangements of instruments is taken to be the independent variable and the eye travel distance between instruments the dependent variable. la order to compile the information necessary for this study, sixty Korean Air Force pilots were interviewed and requested to complete information forms. These information forms listed various flying maneuvers and listed each instrument used on the instrument panel. The compilation of the information on these completed forms listed the instruments most frequently used by the pilots. The second part of this study was to determine the optimum instrument arrangement. It was necessary to study the various number of possible arrangements of instruments depending upon the number of instruments involved. Therefore, these instruments are grouped by two major functions, The flight instruments were subdivided into three groups, and the engineering instruments were subdivided into six groups. With this subdivision we arrive at the possible number of arrangements of 4,320. Through the simulation method, total eye travel distance for each of these 4,320 arrangements is calculated and the arrangement which appears to be of optimum distance between the most frequently used aircraft instruments is determined. The results of this study indicate that the optimum distance between instruments would be 33,028cm and that the corresponding distance of the instrument panel now being used is 34,288cm. Therefore, an increased efficiency of $3.8\%$ would be realized if the existing aircraft instrument panel were re-arranged according to layout proposed in this thesis.