Some results on 2n−m2^{n-m} designs of resolution IV with (weak) minimum aberration

It is known that all resolution IV regular $2^{n-m}$ designs of run size $N=2^{n-m}$ where $5N/16<n<N/2$ must be projections of the maximal even design with $N/2$ factors and, therefore, are even designs. This paper derives a general and explicit relationship between the wordlength pattern of any even $2^{n-m}$ design and that of its complement in the maximal even design. Using these identities, we identify some (weak) minimum aberration $2^{n-m}$ designs of resolution IV and the structures of their complementary designs. Based on these results, several families of minimum aberration $2^{n-m}$ designs of resolution IV are constructed.Comment: Published in at http://dx.doi.org/10.1214/08-AOS670 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Climate Change and Crop Yield Distribution: Some New Evidence From Panel Data Models

This study examines the impact of climate on the yields of seven major crops in Taiwan based on pooled panel data for 15 prefectures over the 1977-1996 period. Unit-root tests and maximum likelihood methods involving a panel data model are explored to obtain reliable estimates. The results suggest that climate has different impacts on different crops and a gradual increase in crop yield variation is expected as global warming prevails. Policy measures to counteract yield variability should therefore be carefully evaluated to protect farmers from exposure to these long-lasting and increasingly climate-related risks.Yield response, Climate change, Panel data, Unit-root test

Effects of Fruit Temperature, Calcium, Crown and Sugar Metabolizing Enzymes on the Occurrence of Pineapple Fruit Translucency

The role of preharvest fruit temperature, calcium, crown and sugar metabolizing enzymes in the occurrence of pineapple fruit translucency was studied. In Hawai‘i, pineapple fruit translucency began to appear 4 to 2 weeks before commercial harvest. Pineapple fruit flesh became very susceptible to high temperature 6 to 4 weeks before harvest as flesh cell electrolyte leakage increased. High fruit temperature during the last stage of pineapple fruit development decreased titratable acidity and increased translucency. The calcium concentration in pineapple fruit flesh declined with fruit development, possibly due to a decrease in the proportion of water imported via the xylem compared to the phloem. Mature fruit flesh tissue had a significantly reduced ability to bind divalent cations. Spraying calcium during pineapple fruit development decreased translucency occurrence at harvest. Removing the crown either at an early or late stage of pineapple fruit development did not cause any significant effect on the fruit weight and translucency, suggesting that the crown did not play a significant role in pineapple fruit development and translucency occurrence. Defoliation conducted 4 or 3 weeks before harvest did not significantly reduce the pineapple fruit weight, but did significantly reduce the total soluble solids and fruit translucency, suggesting that the photoassimilate partitioning during the last stage of fruit development played an essential role in the occurrence of translucency. Sucrose began to accumulate rapidly in pineapple fruit flesh 6 weeks before harvest, while the activities of three invertases and sucrose synthase were low. The activity of celliv wall invertase (CWI) increased in the fruit flesh again 4 weeks before harvest, followed by the occurrence of translucency. There was a positive correlation between the CWI activity and translucency severity in pineapple fruit flesh, suggesting that the high CWI activity, that favored apoplastic phloem unloading, may be one of the causes inducing pineapple fruit translucency

Is Contract Farming More Profitable and Efficient Than Non-Contract Farming-A Survey Study of Rice Farms In Taiwan

Trade liberalization and globalization has modernized the food retail sector in Taiwan, affecting consumers, producers and trade patterns. These changes have placed significant pressures on farmers and processors including more stringent quality control and product varieties. The government has launched a rice production-marketing contract program in 2005 to assist rice farmers and the agro-business sector to work together as partners. The minimum scale for each contract is 50 hectares of adjacent rice paddies with 50 participants including rice farmers, seedling providers, millers and marketing agents. In order to evaluate the outcome of this program, a survey is conducted in the summer of 2005 after the first (spring) crop is harvested. Information of price and value of output and major variable and fixed inputs are collected along with characteristics of the farmers and farms. The survey results show that the average revenue of a contract farm is about 11 percent higher than an average non-contract farm. The per hectare cost of production in a contract farm is about 13 percent lower and as a result the average profit margin under contract is more than 50 percent above those without contract. A swtiching regression profit frontier model is adopted to further investigate their efficiency performance. The result indicates that an average contract farms is 20 percent more efficient than an average non-contract farm in a comparable operating environment. The result also suggests that although contract farming has potential to improve the profit of smallholders, it is not a sufficient condition for such improvement.Land Economics/Use,

New Constructions of Zero-Correlation Zone Sequences

In this paper, we propose three classes of systematic approaches for constructing zero correlation zone (ZCZ) sequence families. In most cases, these approaches are capable of generating sequence families that achieve the upper bounds on the family size ($K$) and the ZCZ width ($T$) for a given sequence period ($N$). Our approaches can produce various binary and polyphase ZCZ families with desired parameters $(N,K,T)$ and alphabet size. They also provide additional tradeoffs amongst the above four system parameters and are less constrained by the alphabet size. Furthermore, the constructed families have nested-like property that can be either decomposed or combined to constitute smaller or larger ZCZ sequence sets. We make detailed comparisons with related works and present some extended properties. For each approach, we provide examples to numerically illustrate the proposed construction procedure.Comment: 37 pages, submitted to IEEE Transactions on Information Theor

Efficiency and Returns to Scale Measurements with Shared Inputs in Multi-Activity Data Envelopment Analysis: An Application to Farmers' Organizations in Taiwan

This paper addresses the question how team production promotes efficiency of a firm when some inputs can be rewarded on the basis of outputs but some cannot because they are shared among outputs and non-separable. A multi-activity DEA model with variable returns to scale is proposed to provide information on the efficiency performance for organizations with inputs shared among several closely related activities. The model is applied to study the case of 279 farmers' associations in Taiwan. The result suggests that it is important to improve the efficiency of the non-profit oriented activities to improve their overall performances. Three out of four departments of TFAs can gain from economies of scale through expansion, while the remaining one gains through contraction. Thus, policies promoting structural adjustment and consolidations of TFAs would not be inconsistent with public interests.multi-activity DEA, shared inputs, efficiency measure, directional distance function, Productivity Analysis,

ON THE EQUIVALENCE OF IMPORT TARIFF AND QUOTA: THE CASE OF RICE IMPORT IN TAIWAN

This paper extends the existing theory on the equivalence of import tariff and quota. If the equivalence is defined on the domestic price level (weak equivalence), then either the zero conjectural variation for domestic country or a perfectly competitive market will be sufficient to support this equivalence. If the equivalence is defined both on the same domestic price level as well as tariff rate (strong equivalence), then the conditions are that either domestic country acts as a Cournot competitor and foreign country is a price taker, or both domestic and foreign country are price takers. An empirical spatial-equilibrium trade model is constructed to simulate the impacts of import tariff and quota. Using Taiwan¡¦s rice import as an example, the empirical results show that if Taiwan switches from the quota system to tariff system, the domestic rice price as well as total social welfare can be increased given the same import volume.International Relations/Trade,

INTRA-INDUSTRY TRADE BETWEEN TAIWAN AND ASEAN-5 IN THE AGRO-FOOD SECTOR: PATTERNS AND DETERMINANTS

This paper attempts to identify the patterns and determinants of the levels of IIT between Taiwan and ASEAN-5 during the past three decades. Our empirical results confirm the belief that IIT between Taiwan and ASEAN-5 in the agro-food sector has been growing over time. Although industry-specific factors like market size and product differentiation have desirable impacts on IIT, taste overlaps do not. No deterministic conclusion can be drawn from the effect of trade liberalization as implied by removing trade barriers when shaping the future development of IIT. However, the indirect effect arising from income and consumer preferences' convergence may be the main determinant in promoting intra-industry agro-food trade among the Asian countries.International Relations/Trade,