Effect of thermal alkaline pretreatment on the anaerobic digestion of wasted activated sludge

The effect of alkaline pretreatment of waste-activated sludge, using two models to study the sequential hydrolysis rates of suspended (Sanders' surface model) and dissolved (Goel's saturation model) solids, on the mesophilic and thermophilic anaerobic digestion rate is evaluated. The pretreatment, which reduces the size of the solids, increases the reaction rate by increasing the surface area and the specific surface hydrolysis constant (K(SBK)); at thermophilic conditions from 0.45 x 10(-3) kg m(-2) d(-1) for the fresh sludge to 0.74 x 10(-3) kg m(-2) d(-1) for the pretreated sludge and at mesophilic conditions these values are 0.28 x 10(-3) kg m(-2) d(-1) and 0.47 x 10(-3) kg m(-2) d(-1) confirming the usefulness of a pretreatment for solids reduction. But for soluble solids, the thermoalkaline pretreatment decreases the reaction rates by inducing a competitive inhibition on the thermophilic anaerobic digestion rate while in the mesophilic range, a non-competitive inhibition is observed. A mathematical simulation of the consecutive reactions, suspended solids to dissolved solids and to methane in staged anaerobic thermophilic-mesophilic digestion, shows that with 4% suspended solids concentration it is better not to use a thermoalkaline pretreatment because overall solids reduction and total methane production are not as good as without pretreatment.     

Consumer perspectives on the African sharptooth catfish in rural and urban areas of the Northern Province

This study evaluated consumer behavioural patterns in relation to meat products, with special reference to the African sharptooth catfish, in the Northern Province. Personal interviews were conducted in rural Ga‐Mamphaka and urban Giyani. The major meat type purchased was found to be chicken (71 per cent in the rural and 46 per cent in the urban community). The sharptooth catfish was found to be acceptable to the majority of respondents, both urban (69 per cent) and rural (57 per cent). Most respondents also indicated that they would like to purchase canned catfish. A potential market for catfish would seem to exist at a price competitive with that of chicken.     

The analysis of determinants of going concern audit report

Going concern is one of essential things for user to make a financial decision. This research aims to explore factors that caused the issuance of going concern audit report by auditor. This research adds two new variables, audit size and audit committee, besides the other factors that cause auditor issue a going concern audit report. This research uses a regression logistic analysis to determine the relationship of each variable （liquidity, solvability, profitability, cash flow, audit firm size and audit committee） to going concern audit report. Different from previous researches, the results of this research show that liquidity, profitability, cash flow, and audit committee are not significant to influence the issuance of audit opinion. Audit size has a more significant relationship to audit opinion, while solvability is the most significant factor.     

Decentralization and the search for policy solutions

We use mathematical and computational models to analyze theability of federated organizations to solve difficult problems.Federated organizations may have some inherent advantages forsolving difficult problems since they can empower multiple subunitsto search for policy solutions in parallel and exploit and combinethe mutual information discovered by the subunits to revealeven better solutions. We find that the benefits of these methodsof experimentation first increase and then decrease as the problemof finding good policies increases in difficulty.     

GLOBALIZATION,TRADE, AND WAGES: WHAT DOES HISTORY TELL US ABOUT CHINA?

Newly assembled data show that, as China opened up to global trade during the early 20th century, its exports became more unskilled‐intensive and its imports more skill‐intensive. Difference‐in‐differences estimates show that World War I dramatically increased Chinese exports, raising the relative demand for the unskilled workers producing them. When the war ended, trade costs declined and China's terms of trade increased, further stimulating exports. A simulation of a dynamic general equilibrium model demonstrates that the effects of the war on China's terms of trade produces a decline in the skill premium similar to what China experienced in the 1920s.     

晚清铁路建设与市场发展

1881—1911年中国兴起了铁路建设的浪潮。我们从史料中整理了这一时期的小麦价格,将府间价格差对铁路建设进行回归,发现铁路造成铁路连接的府的价格离散程度下降了3.8%,占当时整个价格离散程度下降的约40%,控制铁路建设的内生性以后结果依然显著。我们还发现,铁路提高了沿线府间与邻近铁路府间的市场整合程度。与此同时,铁路削弱了与其平行的传统商路沿线府间的市场整合程度,却提高了铁路与传统商路联运网络中府间的市场整合程度。     

浅析证券市场税制的完善

文章对我国证券市场税制存在的问题作了比较客观的分析,并提出了完善证券市场税制的目标和原则,在此基础上结合我国实际有针对性地谈了完善我国证券市场税制的几点设想.     

The legacy of the Separate Amenities Act: Perceptions of recreation and future planning in the Northern Province,South Africa

Since 1990, South Africa has been undergoing a socio‐political transformation from apartheid to non‐racial democracy. This transformation culminated in April 1994, with the first‐ever general election in which people of all races participated. However, in this period of change there has not been much integration of previously separate recreational spaces, especially in more conservative regions such as the Northern Province. This article examines the perceptions, knowledge and awareness of urban blacks with regard to outdoor recreation. It also explores their expectations under the new political dispensation, as envisaged by the Reconstruction and Development Programme (RDP) of the new government. Finally, it looks at five key aspects of planning and development for deprived communities, namely education, marketing, structural constraints, public participation in development, and the development of tourism.     

Desegregation in Pietersburg after the repeal of the Group Areas Act

Since the Group Areas Act was repealed in 1991, black people have for the first time become legal home‐owners in previously whites‐only areas of South African cities. This survey is concerned with residential changes in Pietersburg between June 1991 and May 1993. The residential location of black people was monitored and mapped, and the first new black home‐owners were interviewed to determine their reasons for moving to Pietersburg. The survey shows that only blacks in the middle‐ and high‐income groups made the move, and that property values were not a deciding factor in the purchase of a home.