• 천문학논총
• /
• 제15권spc2호
• /
• pp.37-44
• /
• 2000

Two different types of plasma probes have been developed and are currently in operation on board the KOMPSAT-l. One is the cylindrical Langmuir Probe (LP) that measures the electron density and temperature from its current-voltage characteristics in thermal plasmas, and the other is the Electron Temperature Sensor (ETS) which directly gives the information of the ambient electron temperatures. These plasma probes provide the electron properties of the local nighttime ionosphere at the KOMPSAT-l altitudes. In this paper we briefly describe the probes and the initial results obtained from these probes since the beginning of their normal operation in April, 2000.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권2호
• /
• pp.252-258
• /
• 1999

As an effective means to convey crushed materials from seabed to on board ship and to raise hazardous or abrasive liquids air-lift pump provides a reliable mechanism due to its simple config-uration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newto-nian liquids. it is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates and furthermore attachment of downcomer gives little effects on riser performance the conveyed liquid flow rate increases with larger submergence rate.

• Journal of the Korean Data Analysis Society
• /
• 제20권6호
• /
• pp.2771-2779
• /
• 2018

The recent financial crises cause the co-movement and transmit the risk across different markets and assets. It is well known that market fear affects the quality of credit in the financial markets. In this context, this study examines the co-movement between the volatility index (VIX) of the Chicago Board Options Exchange (CBOE), or VIX, and six emerging countries' credit default swaps (CDSs), by implementing wavelet coherence. Our research aims at revealing whether the VIX can be used to hedge against the bubble behavior of the CDS market in different investment holding periods (short-run, medium-run, and long-run), as well as whether either market can be used to manage and hedge overall market downside risks. The wavelet coherence results show a high degree of co-movement between the VIX and CDS during the 2007-2009 global financial crisis, across the 16-64 weeks' frequency band. In addition, we observe that the positive correlation between the VIX and the CDS markets, implying that the market turmoil intensifies the co-movement between the VIX and CDS markets.

• 수산해양기술연구
• /
• 제27권4호
• /
• pp.278-285
• /
• 1991

현재 사용되고 있는 전개판의 성능을 보다 향상시키기 위한 방안으로 비행기의 익이론에 기초를 두고, 전개판의 경계층을 흡입하거나 제거하는 방법 중에서 역류역을 흡입하는 슬롯(slot)을 전개판에 적용하였다. 성능분석을 위해서 단순만곡형전개판에 슬롯이 없는 기준형과 슬롯의 위치에 따른 5종의 모형전개판에 대하여 성능실험과 가시화실험을 통하여 그 성능과 유체역학적 특성을 비교해 보았다. 실험결과를 요약하면 다음과 같다. \circled1 최대전개력계수는 0.6C, 0.4C, 기준형, 0.8C, 0.2C의 순으로, 슬롯의 위치 0.6C인 전개판이 영각 27$^{\circ}$에서 1.59로 가장 우수하였다. \circled2 항력계수는 슬롯의 위치가 후연으로 갈수록 감소하며, 슬롯을 준 경우가 기준형보다 작게 나타났다. \circled3 양항비는 0.6C, 0.4C, 0.8C, 0.2C, 기준형의 순으로 모두 기준형보다 높게 나타났다. \circled4 0.2C, 0.4C 및 0.6C의 전개판이 기준형과 0.8C의 전개판보다 박리가 후연에서 발생하였다. \circled5 전개판의 전.후면에서 유속차는 영각 15$^{\circ}$~25$^{\circ}$까지는 점차 증가하고, 30$^{\circ}$에서는 감소하는 것으로 나타났다. \circled6 박리역의 크기는 0.6C의 전개판에서 가장 적게 나타났다.

• 한국해양환경ㆍ에너지학회지
• /
• 제14권3호
• /
• pp.205-211
• /
• 2011

해수 중의 수소이온농도(pH)와 총알칼리도(TA) 측정 방법에 대한 선상 비교 연구가 동해 표층에서 저층에 이르는 약 550개의 실제 해수 시료에 대해 이루어졌다. 분광광도법과 전위차법에 대한 pH의 비교가 이루어졌으며, 두 방법에 의한 해수의 pH는 전반적으로 잘 일치하였으나, pH가 낮은 심층의 경우 피펫을 사용한 분광법에 의한 값이 전위차법 보다 높은 값을 보였다. 그러나 피펫을 사용하지 않은 분광법과는 두 방법의 정밀도 내에서 동일한 값을 보였다. 이는 피펫에 의해 해수 내의 이산화탄소가 제거되면서 시료 내의 pH를 증가시키는 것으로 판단된다. TA 측정법의 비교를 위해 폐쇄 용기를 이용한 전위차법과 개방 용기를 이용한 전위차법이 사용되었으며, 개방형 용기를 사용했을 때의 값이 폐쇄형 용기를 사용했을 때의 값에 비해 약 5~10 ${\mu}mol\;kg^{-1}$ 작은 값을 보인다. 이는 폐쇄형 용기를 사용했을 때, 적정 도중에 발생하는 이산화탄소가 용액 속에 남아 적정액인 염산 이외의 산을 용액 속에 추가하는 효과를 내기 때문으로 판단된다. 따라서 pH혹은 TA의 분석에 있어서 본 연구에서 비교한 어느 방법을 사용할 수도 있지만 각각의 방법에 대해 특별히 요구되는 주의를 기울일 때 만족할 만한 분석결과를 얻을 수 있다.

• 한국포장학회지
• /
• 제28권2호
• /
• pp.143-149
• /
• 2022

PCS needs to freely switch AC and DC to connect the battery, external AC loads and renewable energy in both directions for energy efficiency. Whenever converting happens, power loss inevitably occurs. Minimization of the power loss to save electricity and convert it for usage is a very critical function in PCS. PCS plays an important role in the ESS(Energy Storage System) but the importance of stabilizing semiconductors on PCB(Printed Circuit Board) should be empathized with a risk of failure such as a fire explosion. In this study, the temperature variation inside PCS was reviewed by cooling fan on top of PCS, and the vibration characteristics of PCS were analyzed during truck transportation for reliability of the product. In most cases, a cooling fan is mounted to control the inner temperature at the upper part of the PCS and components generating the heat placed on the internal aluminum cooling plate to apply the primary cooling and the secondary cooling system with inlet fans for the external air. Results of CFD showed slightly lack of circulating capacity but simulated temperatures were durable for components. The resonance points of PCS were various due to the complexity of components. Although they were less than 40 Hz which mostly occurs breakage, it was analyzed that the vibration displacement in the resonance frequency band was very insufficient. As a result of random-vibration simulation, the lower part was analyzed as the stress-concentrated point but no breakage was shown. The steel sheet could be stable for now, but for long-term domestic transportation, structural coupling may occur due to accumulation of fatigue strength. After the test completed, output voltage of the product had lost so that extra packaging such as bubble wrap should be considered.

• 무역상무연구
• /
• 제34권
• /
• pp.77-108
• /
• 2007

The traditional name given to the insurance of third party liabilities and certain contractual liabilities which arise in connection with the operation of ships is protection and indemnity(P & I) insurance. P & I insurance is very different from traditional hull and machinery insurance in that shipowners' hull and machinery insurance is designed primarily to protect the assured against losses to his vessel, whereas P & I insurance seeks to indemnify an shipowner in respect of the discharge of legal liabilities he has incurred in operating his own vessels. This study is to examine the background of establishment of British P & I clubs md, therefore, the identity of P & I insurance. The present British P & I clubs are the remote descendants of the many small and local hull mutual insurance clubs that were formed by British shipowners in the end of 18th century. At that time, British shipowners were dissatified with the state of marine insurance market and, therefore, established clubs together in mutual hull insurance clubs. After the removal of the company monopoly in 1824, greater competition had a good effect on the rates, terms of cover and service offered by the commercial marine insurance market and by Lloyd's underwriters, and the hull clubs became less necessary and went into decline. The burden of British shipowners on liabilities to third parties was steadily increased after the middle of the 19th century, but the amount insured under hull policy was limited in the insured value of the ship. Eventually, the first protection club, that is, the Shipowners' Mutual Protection Society was formed in 1855. It was designed to like past mutual hull clubs, but to cover liabilities for loss of life and personal injury and also the collision risks excluded from the current marine policies, particularly the excess above the limits in hull policies. In 1870, the risks of liability for loss of or damage to cargo carried on board the insured ship was first awarded by the British shipowners. After 1874, many protection clubs formed indemnity club to cover the risk of liability for loss or damage to cargo. As mentioned above, British P & I clubs have been steadily changed according to the response of shipowners under the rapidly changing law of British shipowners' liability, and so on in the future.