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As the concentration of environmental samples was generally very low and existing analytical instruments had limited sensitivity, developing mini pre-treatment systems for effectively concentrating the components was very important and necessary. The purposed of this paper is to develop mini pretreatment system integrated with micro pre-concentrator and micro GC column.

In this work, a mini pre-treatment system integrated with a micro pre-concentrator and a micro gas chromatograph (GC) column was proposed. The micro pre-concentrator filled with single-walled carbon nanotubes as adsorbent materials was able to effectively concentrate the trace environmental sample, which dramatically improved the response of detectors. In addition, instead of conventional columns, micro GC columns were able to effectively separate gas mixtures, which are able to overcome low resolution and poor anti-interference ability of portable instruments.

The results demonstrated that the proposed pre-treatment system was able to concentrate the trace sample with a concentration factor of 15 and effectively separate the gas mixtures with a resolution over 1.5.

A mini pre-treatment system integrated with a micro pre-concentrator and a micro GC column was proposed.

The main purpose of the paper is to examine the truth behind allegations of neo-colonialism performed by China toward Africa, which was raised due to the growing relationship between China and Africa that enhanced the debate between supporters of the notion of neo-colonialism or mutual beneficial relationship. In addition to the growing number of arguments are on the dominance of PRC in Africa over the western powers as European Union or United States in the Continent.

The paper investigates the claims of neo-colonialism practiced by China toward Africa through the lenses of international political economy using the Interdependence theory of neoliberalists. Egypt was selected as a case study due to the emphases that Egypt gives to China as a strategic partner and as rising economic power as well as representing a way of diversifying Egypt's foreign policy and an additional economic partner beside the western ones. The research relied on two interwoven indicators to investigate the main argument: Trade and Development Aid.

The two pillars of analysis indicate that the growing relationship between Egypt and China is a form of interdependent relationship that is expected to get further complex in the future, which is relatively indicated among other things in the synergy Egypt has made between its Vision 2030 and China's Belt and Road Initiative. In reference to development aid, China uses different techniques that is not commonly used by the donors of Official Development Assistance (“ODA”), and due to unpublished actual data on China's aid figures, any indication of dominance is hard to attain regardless a solo incident of debt trap in Africa, the model of China's aid is provided through low-interest loans for development projects that is highly important for developing countries.

The paper tried to engage in the ongoing debate and examine the truth behind the neo-colonial allegations from the perspective of international political economy, which is an added value to the literature in this regard as the data provided are prepared for the present research purpose.

Lapping is a vital flattening process to improve the quality of processed semiconductor wafers such as single-crystal sapphire wafers. This study aims to optimise the lapping process of the fixed-abrasive lapping plate of sapphire wafers with good overall performance [i.e. high material removal rate (MRR), small surface roughness (Ra) of the wafers after lapping and small lapping plate wear ratio (η)].

The influence of process parameters such as lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed on MRR, Ra and η of lapping-processed sapphire wafers was studied, and the results were combined with experimental data to establish a regression model. The multi-evaluation index optimisation problem was transformed into a single-index optimisation problem via an entropy method and the grey relational analysis (GRA) to comprehensively evaluate the performance of each parameter.

The results revealed that lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed had different influence degrees on MRR, Ra and η. Among these parameters, lapping time, lapping speed and abrasive size had the most significant effects on MRR, Ra and η, and the established regression equations predicted the response values of MRR, Ra and η to be 99.56%, 99.51% and 93.88% and the relative errors between the predicted and actual measured values were <12%, respectively. With increased lapping time, MRR, Ra and η gradually decreased. With increased abrasive size, MRR increased nearly linearly, whereas Ra and η initially decreased but subsequently increased. With an increase in abrasive concentration, MRR, Ra and η initially increased but subsequently decreased. With increased lapping pressure, MRR and η increased nearly linearly and continuously, whereas Ra decreased nearly linearly and continuously. With increased lapping speed, Ra initially decreased sharply but subsequently increased gradually, whereas η initially increased sharply but subsequently decreased gradually; however, the change in MRR was not significant. Comparing the optimised results obtained via the analysis of influence law, the parameters optimised via the entropy method and GRA were used to obtain sapphire wafers lapping with an MRR of 4.26 µm/min, Ra of 0.141 µm and η of 25.08, and the lapping effect was significantly improved.

Therefore, GRA can provide new ideas for ultra-precision processing and process optimisation of semiconductor materials such as sapphire wafers.