The zero-inflated Poisson regression model is a special case of finite mixture models that is useful for count data containing many zeros. Typically, maximum likelihood (ML) estimation is used for fitting such models. However, it is well known that the ML estimator is highly sensitive to the presence of outliers and can become unstable when mixture components are poorly separated. In this paper, we propose an alternative robust estimation approach, robust expectation-solution (RES) estimation. We compare the RES approach with an existing robust approach, minimum Hellinger distance (MHD) estimation. Simulation results indicate that both methods improve on ML when outliers are present and/or when the mixture components are poorly separated. However, the RES approach is more efficient in all the scenarios we considered. In addition, the RES method is shown to yield consistent and asymptotically normal estimators and, in contrast to MHD, can be applied quite generally. Copyright (c) 2009 Board of the Foundation of the Scandinavian Journal of Statistics.

Summary Length–weight and length–length relationships are reported for 32 fish species belonging to seven families and 26 genera from the Tian‐e‐zhou Oxbow in the middle reach of Yangtze River, near Shishou City, China. The weight (W) ‐ length (L) relationships were estimated using the logarithmic form of the equation W = aLb. The exponent b varied from 2.60 to 3.65 (mean ± SE: 3.12 ± 0.25). The 14 weight–length relationships, 13 length–length relationships, and seven maximum lengths are presented to FishBase for the first time.

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This paper is a progress report on geochemical studies of the Pre-Khuff Paleozoic Sequence in Saudi Arabia, summarizing current laboratory results from both Saudi Aramco and U.S. Companies and their preliminary interpretations. Oil-oil and oil-source rock correlations indicate that Pre-Khuff Paleozoic oils and condensates are closely related to each other because they have a common source, the "hot shale" at the base of the Qusaiba shale Member of the Qalibah Formation. Oils and condensates in the Hawtah trend have been generated from highly mature Qusaiba shales. Since Paleozoic source rock maturities are no more than marginal in the producing trend, hydrocarbons must have migrated generally westward from the presently overmature Udaynan depocenter of the Rub-Al-Khali Embayment. Indeed, maturity measurements and computer-assisted maturity modeling clearly indicate that oil generation and updip migration commenced as long as about 160 million years ago (MA). Residual oil was cracked into condensate and gas when the depocenter passed into a higher temperature regime beyond the oil window, approximately 90 MA. Thus, the light hydrocarbons produced in the Hawtah trend can be considered the result of a "natural refinery" process at depths in excess of approximately 13,000 ft. (3962m) and temperatures around 350°F (177°C). Late stage non-hydrocarbon gases should be co-generated in the very overmature depocenter (over 2% Ro) at present. The likely source for such gases is pyrobitumen, the residue of cracked oil. Pyrobitumen is found in many deep wells where it has a pore-plugging effect. Advantageously all of the hydrocarbons are sulfur-poor because the initial kerogen was sulfur-poor. This difference between Saudi Arabian Paleozoic and Mesozoic oils is extremely important economically!

Climbing robots have been widely used to inspect smooth walls. However, a good adsorption method has not been found for the inspection of a cliff surface and a dusty high-altitude surface with small vibration, both of which are made of coarse concrete, square brick, or rock. In this article, first, we analyzed the bionic structure of the cockroach legs and observed their morphological characteristics of the spiny claws on these legs. We also studied the interaction theory of the bionic claw with the bulges on the rough wall surfaces and deduced the mechanical criteria of the claws grabbing steadily these bulges. Then, an initial mechanical structure of a wall-climbing robot was proposed based on a grasping claw and a climbing model. Furthermore, a mathematical model was established to reflect the relationship between sharp hooks and bulges on the rough wall. Finally, we performed several laboratory experiments to verify the grasping stability.

The lacustrine dolomicrites of Unit II of the lower Xingouzui Formation deposited in the southern part of the Qianjiang Depression provide a good "tight carbonate" hydrocarbon reservoir. The dolomicrites are typically interbedded with and sourced from organic-rich argillite, which together form a source-reservoir assemblage characterized by thin single-layer thicknesses, far lateral extent and continuous lateral distribution. Systematic sedimentological and geochemical studies indicate that the depositional environment and organic matter evolution of the dark argillites (with TOC of 0.5-2%) are favorable for formation of the dolomicrites. The dolomicrite was mainly formed in a shallow-water evaporative environment; crystals are anhedral under SEM, in non-surface contact, and include a number of honeycomb intergranular micropores associated with replacement. The dolomicrite shows orange-orangered light by cathodoluminescence, indicative of association with minor terrigenous debris; X-ray diffraction results indicate that the dolomicrite is characterized by high calcium content (CaCO 3 molar contents of 52.28-52.28%), low degree of orders of 0.2-0.4), and high content of Fe. The dolomicrite has δ 18 O values of 2.47-2.47‰ PDB, more positive than micrite, and δ 13 C values as moderately negative as 9.4-4.21‰ PDB, similar to micrite. Both values indicate the dolomicrite formed in a low-temperature genetic zone. Together, these characteristics indicate that the dolomicrite in the study area was formed in a high-salinity, confined lake basin, characterized by low temperature, shallow burial, and rapid nucleation and crystallization. The dolomicrite experienced a contemporaneous period with formation of dark mudstone, shale and calcite, and a penecontemporaneous period with formation of dolomicrite via seepage-reflux and a diagenetic period when ferrodolomite was formed via burial.