Fully analytical solution to discrete behavior of hybrid zero dynamics in limit cycle walking with constraint on impact posture

This paper proposes a fully analytical solution to the discrete behavior of hybrid zero dynamics (HZD) in limit cycle walking with constraint on impact posture. First, we introduce a passive rimless wheel and explain the stability principle through derivations of the analytical transition functions of the state error for the stance and collision phases. Second, we consider an active rimless wheel driven by a steady control input for investigating the stability of semi-passive dynamic walking, and propose a method for analytically deriving the transition function for the stance phase without including unknown parameters. We then numerically investigate the solution accuracy and discuss how the discrete behavior of the HZD changes according to the control parameters. Furthermore, we extend the analysis to level walking of an underactuated rimless wheel with a torso and show that the discrete behavior of the HZD can be determined in the same manner.     

Hydrogeological Classification and Water Inrush Accidents in China’s Coal Mines

In 2012, China’s State Administration of Coal Mine Safety conducted a reconnaissance and statistical analysis to better understand and characterize water inrush accidents in China’s coal mines. Data collected from 12,985 mines from 26 provinces and municipalities were used to study each mine’s hydrogeological classification, water content coefficient, and the level of effort being spent in preventing and controlling these accidents. Analysis of the water inrush accidents in these mines suggests that their likelihood reflects a mine’s hydrogeological characteristics, and that they can be controlled by professionals who are specifically trained for mine water prevention and emergency responses. In terms of hydrogeological complexity, there were 78 extremely complex coal mines, 827 complex mines, 4141 moderately complex mines, and 6458 relatively simple mines. Advances in mine water control and management methods and techniques and implementation of safety standards and regulations have significantly reduced the number of people killed per ton of coal produced, but analysis of the 2013 water hazard accidents indicates that continued effort is needed to better understand hydrogeological classification and implement safe procedures in water prospecting and dewatering.     

Heavy Metals in Stream Sediments from the Coquimbo region (Chile): Effects of Sustained Mining and Natural Processes in a Semi-arid Andean Basin

Abstract.   Active sediments from the Elqui River in Chile were sampled 4 times at 10 sites during 2000. Concentrations of Ag, Ba, Cd, Co, Cr, Hg, Mn, Mo, Ni, Pb, Sr, Ti, V, Al, Ca, Fe, K, Mg, Na, P, and S were normal. Zinc levels were clearly high, and those of Cu (hundred to thousands ppm) and As (tens to hundreds ppm) were highly anomalous. Dissolved Cu (0.1-12.7 ppm) and Zn (0.2-2.2 ppm) levels were also very high. The anomalies of the upper tributaries are due to the El Indio–Tambo Au-Cu-As district and large hydrothermal alteration zones at altitudes between 3500–4500 m. Lower on the river, old and active tailing waste deposits and on-going mining operations in the Talcuna Cu (Pb) district are responsible. Partially eroded tailing deposits in the alluvial plain of the Elqui River and its tributaries, and especially in the El Indio-Tambo district, after mine closure in 2000, warrant special attention.     

Hydrogeochemistry,Elemental Flux,and Quality Assessment of Mine Water in the Pootkee-Balihari Mining Area,Jharia Coalfield,India

Ninety nine mine water discharge samples were collected and analyzed for pH, electrical conductivity (EC), major cations, anions, and trace metals in the Pootkee-Balihari coal mining area of the Jharia coalfield. The mines of the area annually discharge 34.80 × 10⁶ m³ of mine water and 39,099 t of solute loads. The pH of the analyzed mine waters ranged from 6.97 to 8.62. EC values ranged from 711 μS cm⁻¹ to 1862 μS cm⁻¹, and reflect variations in lithology, geochemical processes, and hydrological regimes in the mines. The cation and anion chemistry indicate the general ionic abundance as: Mg²⁺ > Ca²⁺ > Na⁺ > K⁺ and HCO₃ ⁻ > SO₄ ²⁻ > Cl⁻ > NO₃ ⁻ > F⁻, respectively. Elevated SO₄ ²⁻ concentrations in the Gopalichuck, Kendwadih, and Kachhi-Balihari mine waters are attributed to pyrite weathering. The water quality assessment indicated that TDS, hardness, Mg²⁺, and SO₄ ²⁻ are the major parameters of concern in the study area. Except for Fe, all of the measured metals in the mine water were well within the levels recommended for drinking water. With only a few exceptions, the mine water is of good to permissible quality and suitable for irrigation.     

Ecological Restoration of Novel Lake Districts: New Approaches for New Landscapes

Mine void pit lakes often contain water of poor quality with potential for environmental harm that may dwarf other mine closure environmental issues in terms of severity, scope, and longevity. This is particularly so when many pit lakes occur close together and thus form a new “lake district” landscape. Pit lakes that can be developed into healthy lake or wetland ecosystems as a beneficial end use provide opportunities for the mining industry to fulfil commitments to sustainability. Clearly articulated restoration goals and a strategic closure plan are necessary to ensure pit lake restoration toward a new, yet regionally-relevant, aquatic ecosystem, which can achieve sustainability as an out-of-kind environmental offset. Such an approach must also consider obstacles to development of a self-sustaining aquatic ecosystem, such as water quality and ecological requirements. We recommend integration of pit lakes into their catchments as a landscape restoration planning exercise with clearly-identified roles and objectives for each new lake habitat and its surrounds.     

Treatment of Acid Leachate from Coal Discard using Calcium Carbonate and Biological Sulphate Removal

Abstract.   An integrated approach is proposed for treating acidic coal discard leachate, consisting of CaCO₃ handling and dosing, CaCO₃-neutralization, and biological sulphate removal. It was found that: powdered CaCO₃ can be slurried to a constant density and used to neutralize the acid water, remove Fe (II), Fe (III), and Al, and partially remove the sulphate (to saturation level); biological sulphate removal can be used to lower the sulphate to less than 200 mg/L using ethanol as the carbon and energy source; CO₂ produced during calcium carbonate treatment can be used for H₂S-stripping and; H₂S gas recovered in the sulphate removal stage can be used for iron removal.     

西方教育思想及校园建筑——新校园建筑溯源

由于学校本身就是一个社会，一个小城市，所以具备社会及城市探讨的多种可能。本文将校园建筑规划设计同建筑的基本性讨论联系在一起，试图将学院建筑的新形式、新思考归结为建筑思想革新及对教育思想质疑的结果。     

Technological spillovers and the location of production in an asymmetric duopoly

We evaluate the impact of technological externalities on the location choices of duopolistic firms in a Weber triangle. Assuming technological spillover effects to be decreasing in the distance between firms, we show that each firms optimum location is independent of a demand shock when the firms distance to market is constant. When distance to market is variable, a firms optimum location will not be independent of a demand shock if one of the duopolistic firms has non-linear technology. The optimum location of an IRS (DRS) firm moves away from (closer to) the market place if the other firm is CRS and if demand is not strongly concave or convex.Received: 14 March 2002, Accepted: 5 August 2003, JEL Classification: D23, L13, R30Ping-yen Lai: I would like to thank Jacques Poot, Mike Sperr and two anonymous referees for insightful comments, which contributed to improvement of this article. All errors are my responsibility.     

Changing the way UK cities are built: The shifting urban policy and the adaptation of London’s housebuilders<Superscript>1</Superscript>

This paper summarises recent trends in UK housebuilding and tries to place them within the wider context of the changes in housing provision in the UK. Based on relevant management literature it argues that recent changes in British urban policy, related to the types of land released and types of development promoted, have significant effects on housing production in the UK. Some indications of those changes are already visible in the type of industry outputs and in the practices of emerging industry leaders.