Design Optimization of a Speed Reducer Using Deterministic Techniques

The optimal design problem of minimizing the total weight of a speed reducer under constraints is a generalized geometric programming problem. Since the metaheuristic approaches cannot guarantee to find the global optimum of a generalized geometric programming problem, this paper applies an efficient deterministic approach to globally solve speed reducer design problems. The original problem is converted by variable transformations and piecewise linearization techniques. The reformulated problem is a convex mixed-integer nonlinear programming problem solvable to reach an approximate global solution within an acceptable error. Experiment results from solving a practical speed reducer design problem indicate that this study obtains a better solution comparing with the other existing methods

General Polytropic Magnetofluid under Self-Gravity: Voids and Shocks

We study the self-similar magnetohydrodynamics (MHD) of a quasi-spherical expanding void (viz. cavity or bubble) in the centre of a self-gravitating gas sphere with a general polytropic equation of state. We show various analytic asymptotic solutions near the void boundary in different parameter regimes and obtain the corresponding void solutions by extensive numerical explorations. We find novel void solutions of zero density on the void boundary. These new void solutions exist only in a general polytropic gas and feature shell-type density profiles. These void solutions, if not encountering the magnetosonic critical curve (MCC), generally approach the asymptotic expansion solution far from the central void with a velocity proportional to radial distance. We identify and examine free-expansion solutions, Einstein-de Sitter expansion solutions, and thermal-expansion solutions in three different parameter regimes. Under certain conditions, void solutions may cross the MCC either smoothly or by MHD shocks, and then merge into asymptotic solutions with finite velocity and density far from the centre. Our general polytropic MHD void solutions provide physical insight for void evolution, and may have astrophysical applications such as massive star collapses and explosions, shell-type supernova remnants and hot bubbles in the interstellar and intergalactic media, and planetary nebulae.Comment: 21 pages, 15 figures, accepted for publication on New Astronom

Self-Similar Polytropic Champagne Flows in H II Regions

We explore large-scale hydrodynamics of H II regions for various self-similar shock flows of a polytropic gas cloud under self-gravity and with quasi-spherical symmetry. We formulate cloud dynamics by invoking specific entropy conservation along streamlines and obtain global self-similar "champagne flows" for a conventional polytropic gas with shocks as a subclass. Molecular cloud cores are ionized and heated to high temperatures after the onset of nuclear burning of a central protostar. We model subsequent evolutionary processes in several ways and construct possible self-similar shock flow solutions. We may neglect the mass and gravity of the central protostar. The ionization and heating of the surrounding medium drive outflows in the inner cloud core and a shock travels outwards, leading to the so-called "champagne phase" with an expanding outer cloud envelope. Complementarily, we also consider the expansion of a central cavity around the centre. As the inner cloud expands plausibly due to powerful stellar winds, a cavity (i.e., `void' or `bubble') can be created around the centre, and when the cavity becomes sufficiently large, one may neglect the gravity of the central protostar. We thus present self-similar shock solutions for "champagne flows" with an expanding central void. We compare our solutions with isothermal solutions and find that the generalization to the polytropic regime brings about significant differences of the gas dynamics, especially for cases of n<1, where n is a key scaling index in the self-similar transformation. We also compare our global polytropic self-similar solutions with numerical simulations on the expansion of H II regions.Comment: 17 pages, 10 figures, accepted for publication by MNRA

Diffuse X-ray Emissions from Dynamic Planetary Nebulae

We present theoretical results of a piecewise isothermal shock wind model devised for predicting the luminosity and surface brightness profile of diffuse X-ray emissions primarily from the inner shocked downstream wind zone of a planetary nebula (PN) surrounded by self-similar shocked dense shell and outer slow AGB wind envelope involving self-gravity and compare/fit our computational model results with available observations of a few grossly spherical X-ray emitting PNe. Matching shocked piecewise isothermal self-similar void (ISSV) solutions with self-gravity of Lou & Zhai (LZ) for the outer zone and a stationary isothermal fast tenuous wind with a reverse shock for the inner zone across an expanding contact discontinuity, we can consistently construct dynamic evolution models of PNe with diffuse X-ray emissions. On the basis of such a chosen dynamic wind interaction model, both X-ray luminosity and radial X-ray brightness profile are determined by three key parameters, namely the so-called X-ray parameter $X$, two radii $R_{rs}$ and $R_c$ of the reverse shock and the contact discontinuity. We find that morphologies of X-ray emissions would appear in the forms of either a central luminous sphere or a bright ring embedded within optically bright shells. In contrast to previous adiabatic models, the X-ray brightness peaks around the reverse shock, instead of the contact discontinuity surface just inside the outer shocked dense shell. Diffuse X-ray emissions of a few observed PNe appear to support this wind-wind dynamic interaction scenario.Comment: 13 pages, 8 figures, accepted by Mon. Not. R. Astron. Soc. Accepted 2010 June 2. Received 2010 May 28; in original form 2010 May

New Self-Similar Solutions of Polytropic Gas Dynamics

We explore semi-complete self-similar solutions for the polytropic gas dynamics involving self-gravity under spherical symmetry, examine behaviours of the sonic critical curve, and present new asymptotic collapse solutions that describe `quasi-static' asymptotic behaviours at small radii and large times. These new `quasi-static' solutions with divergent mass density approaching the core can have self-similar oscillations. Earlier known solutions are summarized. Various semi-complete self-similar solutions involving such novel asymptotic solutions are constructed, either with or without a shock. In contexts of stellar core collapse and supernova explosion, a hydrodynamic model of a rebound shock initiated around the stellar degenerate core of a massive progenitor star is presented. With this dynamic model framework, we attempt to relate progenitor stars and the corresponding remnant compact stars: neutron stars, black holes, and white dwarfs.Comment: 17 pages, 11 figures, Accepted for publication in MNRA

Molecular Line Profiles of Collapsing Gas Clouds

Emission line profiles of tracer molecule H$_2$CO 140 GHz transition from gravitational core collapsing clouds in the dynamic process of forming protostars are calculated, using a simple ray-tracing radiative transfer model. Three self-similar dynamic inside-out core collapse models -- the conventional polytropic model, the empirical hybrid model and the isothermal model -- for star-forming molecular clouds are examined and compared. The isothermal model cannot produce observed asymmetric double-peak molecular line profiles. The conventional polytropic model, which gives flow velocity, mass density and temperature profiles self-consistently, can produce asymmetric double-peak line profiles for a core collapsing cloud. In particular, the blue peak is stronger than the red peak, consistent with a broad class of molecular line profile observations. The relative strengths of the blue and red peaks within a molecular line profile are determined by the cloud temperature gradient. The conventional polytropic model can be utilized to produce molecular line-profile templates, for extracting dynamical information from line spectra of molecular globules undergoing a gravitational core collapse. We show a sample fit using the 140 GHz H$_2$CO emission line from the central region of the molecular globule B335 by our model with $\gamma=1.2$. The calculation of line profiles and fitting processes also offer a scenario to estimate the protostellar mass, the kernel mass accretion rate, and the evolution time scale of a core collapsing cloud. Our model can be readily adapted to other tracer molecules with more or less constant abundances in star-forming clouds.Comment: 12 pages, 10 figures, accepted for publication in MNRA

Transmission of acute infectious illness among cases of Kawasaki disease and their household members

Background/purposeKawasaki disease (KD) is a disease of unknown cause and the causative agent is most likely to be infectious in nature. To investigate the household transmission pattern of infectious illness and etiology, we thus initiated a prospective case and household study.MethodsWe enrolled KD cases and their household members from February 2004 to September 2008. The KD cases and their household members accepted questionnaire-based interviews of the contact history, signs of infection, and symptoms to check whether clusters of infectious illness occurred.ResultsA total of 142 KD cases and 561 household members were enrolled. Among the 142 KD cases, 136 cases (96%) were typical KD, and six (4%) were atypical KD. Of the 561 household members, 17% were siblings, 46% were parents, 18% were grandparents, and the others were cousins or babysitters. Prior to the onset of their KD illness, 66% (94/142) KD cases had contact with ill household members. On the same day of the onset of KD cases' illness, 4% (6/142) KD cases had household members with illness. After KD cases' disease onset, 70% (100/142) KD cases had at least one other family member with illness. Overall, 61% (343/561) of all the household members had acute infectious illness during KD cases' acute stage, and 92% (130/142) of the families had clusters of infectious illness.ConclusionA total of 66% KD cases had positive contact with ill household members prior to their disease onset and 92% of families had clusters of infectious illness, so KD is strongly associated with infections

Distinct roles for dynein light intermediate chains in neurogenesis, migration, and terminal somal translocation

Cytoplasmic dynein participates in multiple aspects of neocortical development. These include neural progenitor proliferation, morphogenesis, and neuronal migration. The cytoplasmic dynein light intermediate chains (LICs) 1 and 2 are cargo-binding subunits, though their relative roles are not well understood. Here, we used in utero electroporation of shRNAs or LIC functional domains to determine the relative contributions of the two LICs in the developing rat brain. We find that LIC1, through BicD2, is required for apical nuclear migration in neural progenitors. In newborn neurons, we observe specific roles for LIC1 in the multipolar to bipolar transition and glial-guided neuronal migration. In contrast, LIC2 contributes to a novel dynein role in the little-studied mode of migration, terminal somal translocation. Together, our results provide novel insight into the LICs' unique functions during brain development and dynein regulation overall.This project was supported by National Institutes of Health grants HD40182 and GM105536 to R.B. Vallee and the Fundação para Ciência e a Tecnologia MDPhD Scholarship PD/BD/113766/2015 to J.C. Gonçalves. During the final year, T.J. Dan-tas was supported by the Porto Neurosciences and Neurologic Disease Research Initiative at Instituto de Investigação e Inovação em Saúde (Norte-01-0145-FED ER-000008

A new era for studies on cross-Strait relations: introduction

After more than half a century’s separation, interaction between China and Taiwan has increased and has progressively changed from a politico-economic interaction to a more civic interaction. Scholars working on cross-Strait relations have recently begun to pay attention to the civic influence of Taiwanese businesses on the relationship. Some emphasize the importance of sub-governmental interactions in the process of cross-Strait integration. Others assert that Taiwanese businesses can exercise economic leverage to constrain the Chinese government in cross-Strait policymaking. These scholars stress bottom–up processes by observing current phenomena, then deducing the emerging pattern of cross-Strait relations that may be influenced by business activities. Taking account of changing trends in scholarly discussions of the cross-Strait relationship, this special issue of China Information presents current research in this field. Unlike studies on top–down processes that affect political and economic interactions between China and Taiwan, several contributions in the special issue highlight bottom–up mechanisms affecting such interactions by examining the identity of Taiwanese businesspeople and migrants, as well as the activities and implications of Taiwanese charitable organizations operating in China. This issue focuses not only on the impact of China on Taiwan, but also the impact of Taiwanese investments, migrants, and exports on Chinese society