A steady-state controllable M/G/1 queueing model operating under the (TN) policy is considered where the (TN) policy is defined as the next busy period will be initiated either after T time units elapsed from the end of the previous busy period if at least one customer arrives at the system during that time period, or the time instant when Nth customer arrives at the system after T time units elapsed without customers’ arrivals during that time period. After deriving the necessary system characteristics such as the expected number of customers in the system, the expected length of busy period and so on, the total expected cost function per unit time in the system operation is constructed to determine the optimal operating policy. To do so, the cost elements associated with such system characteristics including the customers’ waiting cost in the system and the server’s removal and activating cost are defined. Then, the optimal values of the decision variables included in the operating policies are determined by minimizing the total expected cost function per unit time to operate the system under consideration.

본 연구는 2004년 12월 1일부터 2012년 8월 31일까지 원?달러선물환율과 역외선물환율을 이용하여 서로간의 정보이전효과를 규명하는 데 있다. 대칭적 정보이전효과를 검정하기 위해 VEC모형의 그랜즈 인과관계검정, 충격반응함수 및 분산분해를 이용하였다. 또한 변동성에 대한 대칭적 정보이전효과를 검정하기 위해 GARCH(1,1)-M모형을 변동성에 대한 비대칭적 정보이전효과를 검정하기 위해 GJR-GARCH(1,1)-M모형을 사용하였다. 주요분석결과는 다음과 같다. 그랜즈 인과관계검정에서 원?달러선물시장과 역외선물시장 사이에는 서로간의 피드백(feedback)적인 선도-지연효과가 존재하는 것으로 나타났다. 이러한 관계를 충격반응함수를 통해 분석한 결과에 의하면 5일 이상 지속되는 것으로 나타났다. 충격의 크기를 추정하기 위한 분산분해의 결과에서는 원?달러선물환율의 분산 중에 약 62%에서 76%는 자기 자신의 것이며 38%에서 24%는 역외선물환율의 분산변화에 의한 것으로 나타났다. 또한 역외선물환율의 분산은 약 82% 이상이 자기 자신의 분산변화에 의한 것이며 18% 정도는 선물환율변화의 분산에 의해설명되는 것으로 나타났다. 마지막으로 변동성에 대한 대칭적 정보이전효과와 비대칭적 정보이전효과를 검정하기 위해 GARCH(1,1)-M모형과 GJR-GARCH(1,1)-M모형을 도입하였다. 조건부 평균방정식을 통해 원?달러선물시장과 역외선물시장간에는 대칭적 정보이전효과가 존재함을 보였으며, 조건부 분산방정식에서도 양 선물환율 사이에 대칭적 정보이 전효과가 존재하는 것으로 나타났다. 마지막으로 GJR-GARCH(1,1)-M모형의 검정결과에서도 원?달러선물환 율과 역외선물환율 사이에는 악재정보(bad news)뿐만 아니라 호재정보(good news)에 의한 비대칭적 정보이전 효과가 존재하는 것으로 나타났다.

Competitive ELISA methods were used to measure the level of aflatoxin M1 (AFM1) from urine in 1008 Korean adults. Subjects were selected by random sampling in all areas of Korea, except Cheju-do. The recovery rate of AFM1 using this method was 105% (73-124%). The geometric mean of urinary AFM1 in all subjects was 3.43 pg/mL (3.67 ng/g creatinine). The level of AFM1 in males was statistically higher, compared with female subjects. However, the levels of AFM1 did not differ according to age. Subjects in Chungbuk-do showed the highest urinary AFM1 concentration, whereas subjects in Kyeongnam-do showed the lowest concentration. Assuming an excretion rate of 5%, this AFM1 excretion corresponds to approximately 0.1 microgram/day in Korean adults.

We analyzed the current status of the telescope control system (TCS2) of the 1.8 m telescope in Bohyunsan Optical Astronomy Observatory (BOAO), and suggest a new TCS (TCS3) for the long term development of BOAO. The TCS2 was constructed in 1998 to replace the TCS1 which was installed with the telescope itself at the commencement of BOAO. One of the important parts of TCS is PMAC (Programmable Multi-Axis Controller), which is a general-purpose multi-axis motion controller. PMAC provides the direct interactive communication environment permitting users to command the controller directly with simple operations. This makes the setup, debugging, and diagnostics very easy. The TCS2 was operated stable for a long time, but the hardware and TCS computers have been deteriorated and are out of date now. The new TCS3 needs to be constructed based on a modern computer system. And functions such as pre-calculations of telescope limiting position, interworking with virtual observatory tools, and using GUI, etc should be added. Construction of the TCS3 will be a step creating a better observation environment for the Korean astronomical society.

Y -band is a broad passband that is centered at ~1 μm. It is becoming a new, popular window for extragalactic study especially for observations of red objects thanks to recent CCD technology de- velopments. In order to better understand the general characteristics of objects in Y -band, and to investigate the promise of Y -band observations with small telescopes, we carried out imaging observa- tions of several extragalactic fields, brown dwarfs, and high redshift quasars with Y -band filter at the Mt. Lemmon Optical Astronomy Observatory and the Maidanak observatory. From our observations, we constrain the bright end of the galaxy and the stellar number counts in Y -band. We also test the usefulness of high redshift quasar (z >6) selection via i − z − Y color-color diagram, to demonstrate that the i − z − Y color-color diagram is effective for the selection of high redshift quasars even with a conventional optical CCD camera installed at a 1-m class telescope.

KASI and Seoul National University developed the Fast Imaging Solar Spectrograph (FISS) as one of major scientific instruments for the 1.6 m New Solar Telescope (NST) and installed it in the Coude room of the NST at Big Bear Solar Observatory (BBSO) in May, 2010. The major objective of the FISS is to study the fine-scale structures and dynamics of plasma in the photosphere and chromosphere. To achieve it, the FISS is required to take data with a spectral resolution higher than 105 at the spectrograph mode and a temporal resolution less than 10 seconds at the imaging mode. The FISS is a spectrograph using Echelle grating and has characteristics that can observe dual bands (Hα and CaII 8542) simultaneously and perform fast imaging using fast raster scan and two fast CCD cameras. In this paper, we introduce briefly the whole process of FISS development from the requirement analysis to the first observations.

Using the known result of the expected busy period for a controllable M/G/1 queueing model operating under the triadic Max (N, T, D) policy, its upper and lower bounds are derived to approximate its corresponding actual value. Both bounds are represented

Us ing the known result of the expected bllsy period for the triadic Min (N, T, 0) operating po licy applied to a controllable M/GI1 queueing model, its upper and lower bounds are derived to approximate its corresponding ac tual value. 80th bounds are rep

The electrocatalytic characteristics of oxygen reduction reaction of the PtxM(1-x) (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The PtxM(1-x)/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the PtxM(1-x) particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and PtxM(1-x)/MWNTs catalysts are seen as FCC, and synthesized PtxM(1-x) crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, Pt0.77Co0.23/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or PtxM(1-x)/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and PtxM(1-x) (M = Co, Cu, Ni) catalysts, the Pt0.77Co0.23/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.

Using the results of the expected busy periods for the dyadic Min(N, D) and Max(N, D) operating policies in a controllable M/G/1 queueing model, an important relation between them is derived. The derived relation represents the complementary property betw

The long-period stacking order (LPSO) structures and stacking faults (SFs) in rapidly solidified powder metallurgy (RS P/M) Mg97Zn1Y2 alloy were investigated by high resolution transmission electron microscopy (HRTEM) observations. The 18R-type LPSO structure with a stacking sequence of ACBCBCBACACACBABAB and a period of 4.86 nm was observed in the as-extruded RS P/M Mg97Zn1Y2 alloy. After annealing at 773 K for 5 hr, the 18R-type LPSO structure was transformed to the 14H-type LPSO structure with a stacking sequence of ABABABACBCBCBC and a period of 3.64 nm. The 24R-type LPSO structure containing 24 atomic layers of ABABABABCACACACABCBCBCBC with period of 6.18 nm coexists with the 14H-type LPSO structure in the same grains. The LPSO structures contain intrinsic Type II SFs such as BCB/CABA and ABA/CBCB stacking sequences of a closely packed plane.