Optimization problems for consecutive-2-out-of-n:G system

Abstract

This paper considers the optimization problems for a consecutive-2-out-of-n:G system where n is considered to be fixed or random. When the number of components is constant, the optimal number of components and the optimal replacement time are discussed by minimizing the expected cost rates. Furthermore, we focus on the above discussions again when n is a random variable. We give an approximate value of MTTF and propose the preventive replacement policy, respectively.     

The COVID‐19 Pandemic and Families in Japan

This paper, which is authored by members of the Japanese Association of Family Therapy (JAFT), describes the COVID‐19 pandemic in Japan from a family systems perspective. The authors are active members of JAFT and include current and past presidents and officers. We describe the course of the pandemic and the ways in which government policies to mitigate the pandemic have affected Japanese families. Challenges that affect Japanese families include the inability to participate in family and social rituals, prescribed gender roles that specifically affect women, high suicide rates, and prejudice against those who are at risk of spreading the infection. The need to shelter in place has also forced family homes to function as a workplace for parents, classrooms for children, and day care services for frail elders, which has resulted in psychological distress among individuals and conflicts among families. We discuss ways that therapists have worked with Japanese families using online therapy.     

Is Corporate Social Responsibility in Japanese Firms at the Theoretically Derived Achievable Level? An Analysis of CSR Inefficiency Using a Stochastic Frontier Model

The purposes of this study are to investigate whether current corporate social responsibility (CSR) is at the theoretically derived achievable level (hereinafter referred to simply as achievable level), to introduce “CSR inefficiency” as the difference between actual and achievable levels of CSR, and to specify its determinants. We established that the achievable level of CSR activity is determined by a range of keiretsu group, government, sector, and resource factors, and choosing specific activities can affect the priority levels of social contributions. CSR inefficiency is affected by its own factors such as internal management, which are different from those of CSR activity. Our study suggests the importance of the differences between the achievable levels of CSR among firms. For example, firms in machinery, electrical equipment, public utilities, and service industries have greater inefficiency in environmental CSR than the other industries. Conversely, the achievable levels of construction and petroleum and gum industries for environmental CSR are higher. Service firms can achieve higher level of environmental CSR, although their emissions and wastes are not as large as those of manufacturing firms in general. In retail industries, the achievable level of environmental CSR is lowest among all industries, while those for labor issues and social contribution are as high as those of other industries. Public utilities have large CSR inefficiency compared with other industries, while construction, steel and nonferrous metals have small CSR inefficiency.     

Urban shade as a cryptic habitat: fern distribution in building gaps in Sapporo,northern Japan

Urban Ecosystems - Biodiversity conservation and restoration in cities is a global challenge for the 21st century. Unlike other common ecosystems, urban landscapes are predominantly covered by...     

Sequential Hypothesis Tests for Identifying the Minimum Dose with a Threshold Effect

We propose a procedure to identify a lowest dose having greater effect than a threshold dose under the assumption of monotonicity of dose mean response in dose response test. So, we use statistics based on contrasts among sample means and apply a group sequential procedure to our procedure to identify effectively the dose. If we can identify the dose at an early step in the sequential test, since we can terminate the procedure with a few observations, the procedure is useful from an economical point of view. In a simulation studies, we compare the superiority among these procedures based on three contrasts.     

Estimation of firm-specific technological bias,technical change and total factor productivity growth: a dual approach

This paper deals with modeling firm-specific technical change (TC), and technological biases (inputs and scale) in estimating total factor productivity (TFP) growth. Several dual parametric econometric models are used for this purpose. We examine robustness of TFP growth and TC among competing models. These models include the traditional time trend (TT) model and the general index (GI) model. The TT and the GI models are generalized to accommodate firm-specific TC and technological bias (in inputs and output). Both nested and non-nested tests are used to select the appropriate models. Firm-level panel data from the Japanese chemical industry during 1968- 1987 is used as an application.     

Fluctuations of grasshopper populations on aMiscanthus sinensis grassland

Summary Population densities of the three grasshopper species onMiscanthus sinensis grassland in the Kawatabi IBP Area, Japan,Parapleurus alliaceus, Mongolotettix japonicus andChorthippus latipennis, were estimated principally by the release-and-recapture method for five years from 1968 to 1972. The total number of individuals of all three grasshopper species was about 42 per 100m² in August. The number of individuals ofP. alliaceus adult, the dominant species on this grassland, showed a tendency to decline during the five years, though the amplitude was not so large. The number of eggs laid was, however, nearly constant and the mortality from the second nymphal instar to adult was relatively low and constant during the survey period. The weather conditions during the periods of egg and the first instar, such as snowfall and temperature decreasing, are suggested to be one of the factors causing variation in numbers. Contributions from JIBP-CT No. 145. A part of this study was supported by the special project, “Studies on the dynamic status of biosphere”, sponsored by the Ministry of Education.     

Adult population parameters and life tables of an epilachnine beetle (Coleoptera: Coccinellidae) feeding on bitter cucumber in Sumatra

Summary The population dynamics of an epilachnine beetle, which is closely related toEpilachna sparsa Dieke (henceforth called “sp. C”) and feeds on bitter cucumberMomordica charantia, was studied by mark-recapture of adults and the construction of life tables. The study was repeated three times, i.e., March–May, July–September and October–December in 1982, in Padang, Sumatra, Indonesia. After the establishment of the host plants, adults of “sp. C” soon colonized, and each study period ended in the death of the plants due to defoliation by the larvae and adults. The estimated mean length of residence of adults ranged from 6–11 days, but this was probably much shorter than the actual longevity, because the adults were so active that they flew away, or dropped off the plants, when they were approached or slightly disturbed. Life tables indicated that egg mortality ranged from 17.8–53.9%, and a parasitic waspTetrastichus sp. B made up 41.1–64.2% of egg mortality. Two wasps,Tetrastichus sp. C andPediobius foveolatus killed 1.2–19.4% (7.6–100%)^* of 4th instars and only the latter species attacked the pupae, killing 24.6–59.1% (45.1–72.4%). Parasitism and starvation by overcrowding contributed most to the total mortality from egg to adult emergence, which ranged from 89.4–99.5%. “Sp. C” had a higher diversity and level of parasitism than the Japanese species,E. vigintioctopunctata. The high dispersal power of “sp. C”, coupled with the prolongedl _x−m_x schedules shown under laboratory conditions, was advantageous for exploiting the food plant which was available throughout the year, but was rather patchily distributed in space.