5,497 research outputs found

    On Echo Outbursts and ER UMa Supercycles in SU UMa-type Cataclysmic Variables

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    I present a variation on Osaki's tidal-thermal-instability model for SU UMa behavior. I suggest that in systems with the lowest mass ratios, the angular-momentum dissipation in an eccentric disk is unable to sustain the disk on the hot side of the thermal instability. This decoupling of the tidal and thermal instabilities in systems with q < 0.07 allows a better explanation of the `echo' outbursts of EG Cnc and the short supercycles of RZ LMi and DI UMa. The idea might also apply to the soft X-ray transients.Comment: To appear in PASP, April 2001 (6 pages, 4 figs

    Enhanced mass transfer during dwarf nova outbursts by irradiation of the secondary?

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    One of the remaining issues in the problems of dwarf novae is whether or not enhanced mass transfer due to irradiation of the secondary stars could occur during outbursts. In a previous paper (Osaki and Meyer 2003), we presented a theoretical analysis that shows no appreciable enhancement of the mass outflow rate. This conclusion is challenged by Smak (2004) who claims that equations used in our analysis were incorrect and that in systems with short orbital periods substantial enhancement could occur. In this letter, we examine the origin of such divergent conclusions. We show that Smak's solutions are unacceptable from the standpoint of the equation of continuity and that our analysis is an appropriate one to treat this problem.Comment: 4 pages, accepted by Astronomy &.Astrophysics Letter

    Reforming Japan's Capital Markets

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    The Japanese version of the Big Bang announced in November 1996 was a major plan to drastically reform the financial and capital markets in Japan through significant revisions to laws such as the Securities and Exchange Law. The Japanese Big Bang was planned because of mounting worries about the lowering of the international status of Japanese markets and deadlock of the existing financial structure which depended excessively on indirect financing, mainly of bank loans. The Japanese Big Bang was supposed to have been completed by the end of March, 2001, but in reality system reforms for financial and capital markets are still continuing including revisions of the Securities and Exchange Law and of the taxation system of securities. Reform of the financial structure -- the goal of Big Bang -- has not made notable progress, an example being that most privately held financial assets are still in the form of deposits, because of the following reasons. The first reason is that participation of individual investors in the security market has not significantly increased. This is due to lack of familiarity with security companies that broker investments in securities and lack of knowledge of the market and investments. The second reason is that the use of financial and capital markets to procure funds is being hindered by the irrational behavior of banks, an example of which is the placement of loans at interest rates which are not commensurate with the risks involved. This is particularly problematic. It is necessary to reveal the values of securities in the trading market to the maximum extent and to promote conversion of bank credit into securities in order to normalize the behavior of banks. To bring this about it is necessary to strengthen supervision to prevent unjust behavior in the market in order to raise investor confidence in the market. As a consequence of the Japanese Big Bang and subsequent reforms, the financial and capital market systems of Japan now bear comparison with those in the UK and the US, at least procedurally. However, the system reforms implemented in Japan may just become a state of tilling the ground and failing to sow if there is no change in the attitude of control that experts (including the managing authorities who design the systems) persist in maintaining and no change in the way of thinking of companies that regard procurement of funds in the market as merely being the means to make adjustments for bank borrowing.reform, Japan, capital market, Big Bang

    Forecasting median and mode dates of prevalence of Japanese encephalitis patients by electronic computer (epidemiological studies on Japanese encephalitis, 31)

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    For the purpose of forecasting the prevalence ofJapanese encephalitis in Japan, we tried to find out the correlation of factors between median and mode dates of epidemic time curve of prevalence on one hand, and average atmospheric temperatures of prefectures in June and July (T6,7 in short) (X&#185;), the time when HI reaction of swine became positive to the degree of 50 per cent (D. pos. swine in short) (X&#178;), the latitude (x&#179;) and longitude (x4) in respective prefectures (in 1965 and 1967). On the other we also estimated the median and mode dates of this epidemic curve of the prevalence in 1968 and 1969, from the regression equation of one variable and multiple regression equation from the above factors using an electronic computer. The usefulness of adding factors concerned with mosquitoes to the above four factors is proven by the accuracy of estimation. And the following results were obtained. 1) Phenomenally speaking, the prevalence of Japanese encephalitis follows the principle of &#34;advancing of prevalence towards the north and east&#34; and essentially speaking, it depends upon high atmospheric temperature and the outbreak of many hazardous mosquitoes by the high atmospheric temperature. 2) To estimate median date (y) and mode rate (z) of the epidemic time curve of the prevalence, we can use the next equations; The regression equations to estimate y and z from T 6,7(X) are as follows. y = - 3. 75X&#185; + 144.47 &#963; = 12.4.路. [1] z = - 3. 80X&#185; + 157 .26 &#963; = 14.9.. 路 [1]' The regression equation from D. pos. swine (X&#178;) are as follows. y = 0. 68X&#178; + 31. 82 &#963; = 9.2路 .. [2] z=0. 76X&#178; +40. 71 &#963;= 12.0 .. 路 [2]' The multiple regression equation from T6 ,7 and D. pos. swme are as follows. y = -1. 07X&#185; +0 .62x&#178; +59. 37 &#963;= 9.7 ... [3] z= -0. 79x&#185; +0. 71x&#178; +61.02 &#963;= 12.0路 .. [3]' The multiple regression equations from T 6鈥7, D. pos. swine, latitude and longitude are as follows Y= -1.01x&#185; +0.58x&#178; -0.26x&#179;+0 .37x4 + 18.50 &#963;= 9.8&#65381;&#65381;&#65381; [4] z = -0. 32x&#185; +0. 52x&#178; +2 .05x&#179; +0 .54x4 -87. 81 &#963;= 11.8 [4]' 3) We Obtained the estimated value of median date in 17 prefectures in Kyushu, Chugoku, Shikoku, Kinki and Kanto provinces in 1968 and in 13 prefectures in 1969 from [l] or [2] or [3] or [4] equation. Nine prefectures out of 17 by [l], 12 prefectures by [2], 13 by [3J and [4] in 1968. [4] could be estimated with about 10 days error or less. And in 1969, 9 out of 13 by [3] and 7 out of 13 by [4] could be accurately esti路 mated. The estimation by the multiple regression equation using many factors is most useful for the calculation. 4) The time when the number of patients increases at maximum can be pointed out by the lower limit of prediction region obtained from data in each prefecture. And the lower limit was the estimated median value minus about 20 days by [1] and about 16 days by [2] or [3] or [4] under the next condition; &#945; = 0. 1, N= 75. 5) The mode dates in 17 prefectures out of 19 were estimated by [1]', [2]', [3]' and [4]'. 12 prefectures out of 17 by [1]', 7 by [2]', 10 by [3]' and 13 by [4]' could be estimated with about 12 days error or less in 1968 and 9 out of 13 was correctly estimated by [3]' and [4]' in 1969. The estimation by the regression line of one factor was s~mewhat different from each other, but when multiple regression line of four factors was used the estimation became more correct. Judging from these results, it is adequate to use the multiple regression equation of [4] and [4]' when we want to forecast the median date or mode date ofJapanese encephalitis time cure. 6) In the case of adding two factors concerned with mosquitoes to T6,7 (X&#185;), D. pos. swine (x&#178;), latitude (x&#179;), longitude (x4), multiple regression equations become as follows. y= -1.46x&#185;+0.14X&#178;+0.068x5+89.03 &#963;= 6.9.. 路[5] z= -3. 29x&#185;+0 .13x&#178;-0. 010x5+ 143.63 &#963;= 18.6路路路 [5]' y=-4.20x&#185;+0.35x&#178;+0.29x6 + 53.70 &#963;= 4.2 .. 路[6] z=-2.56x&#185;-0.0lx&#178;-0.02x6 +128.96 &#963;=11.4 [6]' y= 4.76x&#185;+0.41x&#178;+0.13x5+0.22x6-72.78 &#963;= 4.5 [7] z = - 2. l0x&#185; + 0. 05x&#178;+ 0. 11 x5 - 0. 08x6+ 113.4 &#963;= 10. 7.. 路 [7]' where x5 is the time when the number of mosquitoes (C. T. collected by light trap reached the maximum and X6 is the time when hazardous mosq uitoes were dected. In the case of median date, 5 prefectures out of 6 prefectures by [5], 2 out of 6 by [6] and 2 out of 5 by [7], and in the case of mode date, 5 out of 6 by [5]', 4 out of 5 by [6]' and 4 out of 5 by [7]' could be accurately estimated in 1969.</p

    A Note on Sufficient Conditions of Cross Risk Vulnerability

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    This note gives sufficient conditions of cross risk vulnerability introduced by Malevergne and Rey (2005), which is the equivalent condition to guarantee that an unfair non-monetary background risk makes decision makers more risk averse. The sufficient conditions determined by this note expand the results for univariate utility function into bivariate utility functions.Background risk, cross risk vulnerabiilty, risk aversion.

    The Study on the Evaluation of the Visual Work Using the Logistic Curve

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    Display equipment has been used as communication media in the factory, office, and home. In order to communicate effectively, it is necessary to clarify the characteristics of eye movement in the case of looking at the display. The development of Eye Camera enables us to measure eye movement during work, so that we can collect the many data of eye movement during work. In this study, we proposed a method to evaluate the visual work using the distribution of visual points in X and Y axis. The cumulative distribution is approximated by the logistic curve which shows the symmetry and kurtosis by the parameter. The proposed method was applied to the three typical display models, that is, the digital meter model, reading model, and game model. In the digital meter model, the visual points were distributed symmetrically along the meters, and the symmetry and kurtosis of the distribution varied by the arranged direction of the meter. In the reading model, the visual points were distributed nearly symmetrically and uniformly in each axis and they were moved around the character and line from the period of spectrum analysis. In the game model, the visual points moved according to the target and were distributed symmetrically in the Y axis. And whether the target moved vertically or horizontally, the kurtosis of the distribution became equal in each axis

    The Cause of the Superoutburst in SU UMa Stars is Finally Revealed by Kepler Light Curve of V1504 Cygni

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    We have studied the SC (short cadence) Kepler light curve of an SU UMa star, V1504 Cyg, which extends for a period of about 630 d. All superoutbursts in V1504 Cyg have turned out to be of the precursor-main type and the superhump first appears near the maximum of the precursor. The superhumps grow smoothly from the precursor to the main superoutburst showing that the superoutburst is initiated by the tidal instability (as evidenced by growing superhump) as envisioned in the thermal-tidal instability (TTI) model proposed by Osaki (1989). We have performed power spectral analysis of the light curve of V1504 Cyg. One of outstanding features is an appearance of a negative superhump extending for around 300 d, well over a supercycle. We have found that an appearance of the negative superhump tends to reduce the frequency of occurrence of normal outbursts. Two types of supercycles are recognized in V1504 Cyg, which are similar to those of the Type L and S supercycles in the light curve of VW Hyi, a prototype SU UMa star, introduced by Smak (1985). It is found that the Type L supercycle is the one accompanied with the negative superhump and the Type S is that without the negative superhump. If we adopt a tilted disk as an origin of the negative superhump, two types of the supercycles are understood to be due to a difference in outburst intervals, which is in turn caused by a difference in mass supply from the secondary to different parts of the disk. The frequency of the negative superhump varies systematically during a supercycle in V1504 Cyg. This variation can be used as an indicator of the disk radius variation and we have found that observed disk radius variation in V1504 Cyg fits very well with a prediction of the TTI model.Comment: 17 pages, 8 figures, accepted for publication in PASJ, minor correction
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