• Rapid Communication in Photoscience
• /
• 제5권1호
• /
• pp.8-10
• /
• 2016

The potential curves of OH bonds of liquid water are inhomogeneous because of a variety of interactions with other molecules and this leads to a wide distribution of vibrational frequency which hampers our understanding of the structure and dynamics of water molecules. Mixed quantum/classical (QM/CM) calculation methods are powerful theoretical techniques to help us analyze experimental data of various vibrational spectroscopies to study such inhomogeneous systems. In a type of those approaches, the interaction energy between OH bonds and other molecules is approximately represented by the interaction between the charges located at the appropriate interaction sites of water molecules. For this purpose, we re-calculated the values of charges by comparing the approximate interaction energies with quantum chemical interaction energies. We determined a set of charges at the TIP4P charge sites which better represents the quantum mechanical potential curve of OH bonds of liquid water.

• Journal of Pharmaceutical Investigation
• /
• 제39권5호
• /
• pp.333-337
• /
• 2009

We aimed to optimize the formulation of porcine placental extract (PPE)-loaded liposomes for intramuscular administration and to investigate the effect of surface charges on the muscular retention in mice. PPE-loaded liposomes were formulated to have neutral, anionic, or cationic surface charges. The in vitro release profiles were studied by spectrofluorometry. In vivo distribution patterns at mice were studied using molecular imaging technology. Among the three types of liposomes, 1,2-dioleoyl-3-trimethylammonium-propane and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-based cationic liposomes showed the most prolonged in vitro release profile. Consistent with the in vitro results, the in vivo distribution study revealed that the cationic liposomes were retained at the site of administration for the longest period. Our results suggest the potential of cationic PPE-loaded liposomes for sustained release of the components after intramuscular administration.

• 한국항해학회지
• /
• 제8권1호
• /
• pp.103-125
• /
• 1984

All over the world, one finds different types of dues, charges and fees imposed for the use of port facilities. The positiion is further confused by the fact that different names are often used for the same charge in different ports and again the same name can be used for different types of charge. For instance, in some places "tonnage" dues can be dues on cargo tonnage and in others are dues on shipping tonnage. Charges made by port authorities can be of two kinds; charges on ships and charges on goods. One of the abiding complaints of all port tariffs is that they are too complicated. The plea is for simplicity and comprehension. The purpose of this study is to elucidate and to criticize principles for guiding port pricing policy.ng policy.

• 한국정보통신학회논문지
• /
• 제17권9호
• /
• pp.1975-1985
• /
• 2013

우리나라 가계의 통신비는 꾸준히 증가하여 왔다. 이에 따라 이동통신요금의 적정성에 대한 문제가 제기되고 있으나 실효성 있는 해결책은 제시되지 않고 있다. 우리나라의 이동전화보유율은 99%로 세계에서 가장 높고 요금은 상대적으로 비싸다. 이는 근본적으로 정부가 이동통신 3사체제를 유지해오면서 사실상 최저가격제를 용인하고 MVNO의 도입을 늦추었기 때문으로 풀이된다. 정부는 서비스생산비용이 타당하게 반영되는 요금구조로 유도할 수 있으며 시장지분확보만을 위한 마케팅비용을 일정한 범위로 제한할 수 있다. 또 과도하게 복잡한 요금제에 따른 거래비용을 억제함으로써 소비자의 소비선택권을 보장하고 요금부담을 줄일 수 있다. 이동통신요금의 적정화를 위해서는 MVNO의 활성화를 통한 이동통신시장구조의 개선, 마케팅 비용의 적정수준인정을 통한 요금의 인하가 필요하다. 바람직한 시장구조와 정책운용이 뒷받침된다면 이동통신요금은 30%정도의 하향조정은 가능할 것으로 보인다. 이동통신 요금은 데이터 사용량에 따른 종량제를 기본으로 하는 것이 바람직할 것이다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제3권3호
• /
• pp.132-138
• /
• 2003

We investigated the polarization retention characteristics of ferroelectric capacitors with $Pb(Zr,Ti)O_3$ (PZT) thin films which were fabricated by different deposition methods. In thermally-accelerated retention tests, PZT films which were prepared by a chemical solution deposition (CSD) method showed rapid decay of retained polarization charges as the thickness of the films decreased down to 100 nm, while the films which were grown by metal organic chemical vapor deposition (MOCVD) retained relatively large non-volatile charges at the corresponding thickness. We concluded that in the CSD-grown films, the thicker interfacial passive layer compared with the MOCVD-grown films had an unfavorable effect on retention behavior. We observed the existence of such interfacial layers by extrapolation of the total capacitance with thickness of the films and the capacitance of these layers was larger in MOCVD-grown films than in CSD-grown films. Due to incomplete compensation of surface polarization charges by the free charges in the metal electrodes, the interfacial field activated the space charges inside the interfacial layers and deposited them at the boundary between the ferroelectric layer and the interfacial layer. Such space charges built up an internal field inside the films, which interfered with domain wall motion, so that retention property at last became degraded. We observed less imprint which was a result of less internal field in MOCVD-grown films while large imprint was observed in CSD-grown films.

• 한국통신학회논문지
• /
• 제34권11B호
• /
• pp.1261-1271
• /
• 2009

경제적 가치가 급증하고 있는 주파수자원은 희소성으로 인하여 효율적으로 배분하는 것이 전파관리의 중요한 과제가 되고 있다. 특히, 지나치게 높은 수준의 주파수 할당대가는 초기 투자비용을 증대시켜 경쟁력 있는 시장 형성과 원활한 서비스 제공을 저해하는 요소가 되며, 이에 따라 소요되는 비용은 소비자 요금으로 부당하게 부과될 수 있다. 따라서 본 연구에서는 주파수 이용대가를 국가별로 비교하여 현재 우리나라의 주파수 할당대가 수준을 분석한다. 세계적으로 주파수 할당대가의 산정방법은 3세대 이동통신(3G 서비스, IMT-2000)의 사업자 선정을 기준으로 판단할 때 비교심사제도와 경매제도로 나누어 진행되어오고 있으며, 방법에 따라 주파수 이용대가의 결과는 다양하게 나타났다. 본 논문에서는 ITU, OVUM 등의 자료를 바탕으로 27개 국의 3G 서비스 주파수 할당대가 산정 결과를 정리한다. 또한 주파수 할당대가 산정 시 영향을 미치는 요인을 관련 선행연구를 토대로 선정하여 회귀분석을 실시한다.

• 한국통신학회논문지
• /
• 제34권10B호
• /
• pp.1031-1042
• /
• 2009

이동통신시장은 초기부터 경쟁을 도입하여 급격히 성장하였으며 통신시장에서 가장 큰 비중을 차지하는 시장으로 등장하였다. 그러나 이동사업자들은 착신망에서의 독점력을 이용하여 비용보다 높은 이동착신접속료를 부과함으로 초과 수익을 달성하게 되었고, 이는 시장의 경쟁 왜곡을 초래하고 소비자 효용을 축소시키는 문제를 야기하게 되었다. 이동착신접속료 규제는 이동통신시장의 핵심 과제로 EU와 호주, 미국 등 대부분의 국가에서 규제하고 있다. 각 국의 이동착신접속료 조사결과 접속료 격차가 매우 큰 것으로 나타났다. 본 논문에서는 28개국 자료를 이용하여 이동착신접속료 결정에 영향을 주는 주요 요인을 밝히기 위하여 국가환경, 시장환경, 규제환경 변수들을 고려한 실증분석을 실시하였다. 실증 연구 결과 이동착신접속료는 규제환경변수인 선불가입자비율과 규제기간에 의해서만 영향을 받는 것으로 나타났다.

• Journal of Electrical Engineering and Technology
• /
• 제10권5호
• /
• pp.2089-2098
• /
• 2015

With the continuous development in insulation of electrical equipment design, the reliability of the system has been enhanced. However, in the manufacturing process and during operation under continues stresses introduce local defects, such as voids between interfaces that can responsible to occurrence of partial discharge (PD), electric field distortion and accumulation of charges. These defects may lead to localize corrosion and material degradation of insulation system, and a serious threat to the equipment. A model of three layers of PI film with air gap is presented to understand the influence of interface and voids on exploitation conditions such as strong electrical field, PD activity and charge movement. The analytical analysis, and experimental results are good agreement and show that the lose contact between interfaces accumulate more residual charges and in consequences increase the electric field intensity and accelerates internal discharges. These residual charges are trapped charges, injected by the electrodes has often same polarity, so the electric field in cavities increases significantly and thus partial discharge inception voltage (PDIV) decreases. Contrary, number of PD discharge quantity increases due to interface. Interfacial polarization effect has opposite impact on electric field and PDIV as compare to void.

• 대한기계학회논문집B
• /
• 제21권11호
• /
• pp.1509-1517
• /
• 1997

Charged and uncharged particle motions and collection characteristics around a bipolar charged rectangular shape electret fiber are studied numerically. Particle inertia, fluid drag, Coulomb force and polarization force are considered to predict the particle motion around the electret fiber. The effects of particle sizes, flow velocities, number of charges and polarities are also systematically investigated. For small size particles, the single fiber collection efficiency is greatly dependent on the charge polarity and the number of charges on a particle. However, particles larger than 5.mu.m do not show charging effect on collection efficiencies in the flow velocity ranges from 1.5 cm/s to 150 cm/s when the maximum charges are within +5 to -10. The results show that a strong electric field gradient at the corner of the bipolar charged fiber plays a very important role on collecting particles regardless of its charge polarity because of the polarization force. It also shows that the most penetrating particle size for a single electret fiber decreases as the flow velocity increases and the number of charges of a particle decreases.

• Journal of Preventive Medicine and Public Health
• /
• 제23권2호
• /
• pp.216-223
• /
• 1990

To identify the factors influencing the charges per case of acute appendicitis and normal spontaneous vaginal delivery (NSVD), the personal data-base files and hospital-characteristics-reporting data files of Korea Medical Insurance Corporation were analyzed. One hundred and twenty-nine institutions were selected. The results of this study were as follows 1. The differences of charges per case with respect to hospital ownership, location, and equipment levels were statistically significant. 2. The results of multiple regression analysis revealed that bed capacity was the most significant variable in both diseases. 3. Ownership was significant variable in acute appendicitis. In NSVD, ownership and hospital equipment level were statistically significant. In conclusion, bed capacity was statistically the most significant variable in the analysis of charages per case. And we thought that the results of this study would influence the policy of the hospital bed supply.