Additive manufacturing techniques

Additive manufacturing techniques A new category based on layer-by-layer deposition of material. Currently used for the production of a few commercial devices and is considered promising many future applications [38]. 

There are several possible reasons why a scientific study of an art work may be desirable. An obvious one is in cases where the authenticity of an object is doubted on styHstic grounds, but no unanimous opinion exists. The scientist can identify the materials, analy2e the chemical composition, and then investigate whether these correspond to what has been found in comparable objects of unquestioned provenance. If the sources for the materials can be characterized, eg, through trace element composition or stmcture, it may be possible to determine whether the sources involved in the procurement of the materials for comparable objects with known provenance are the same. Comparative examination of the technological processes involved in the manufacture allows for conclusions as to whether the object was made using techniques actually available to the people who supposedly created it. Additionally, dating techniques may lead to the estabUshment of the date of manufacture. 

Fluid catalytic cracking and hydrocracking are two additional processes that are often encountered. There are many other processes used in refineries not mentioned here. The list above is intended only to emphasize the wide diversity of processing which is common to petroleum refinuig and to introduce in a very general way some of the more important of these processes. Also it must be emphasized that only fundamental principles of refinery operations have been discussed and modern manufacturing techniques vary widely from company to company. 

In 2002 several manufacturers can provide advanced water electrolysis systems that are standardized, compact in size, need minimal operator intervention and require little maintenance. The basic electrolysis reaction has not changed. However new cell designs, materials of construction, standardized designs and manufacturing techniques have enabled manufacturers to decrease dramatically the fixed costs per unit of capacity for electrolysis technology. In addition, these new systems operate automatically and require very little maintenance, which reduces personnel costs48. 

SiC-based materials have also shown very good corrosion resistance in HI. Both sintered and chemical vapor deposition (CVD) SiC have very low corrosion rates when tested in HI at elevated temperatures. In addition, Si-infiltrated C-based materials (Si-SiC) also have good potential. This method of manufacturing may become an attractive option in the future, as it promises an extremely low-cost alternative to manufacture SiC-based corrosion-resistant materials and reduce the potential joining problems. Effort is continuing to resolve the manufacturing techniques and improve the inherent mechanical properties of these SiC-based materials. 

Majority of nanoliposome manufacture techniques either involve utilisation of potentially toxic solvents (e.g. chloroform, methanol, diethyl ether and acetone) or high shear force procedures. It has been postulated that residues of these toxic solvents may remain in the final liposome or nanoliposome preparation and contribute to potential toxicity and influence the stability of the lipid vesicles (35-38). Although there are methods to decrease the concentration of the residual solvents in liposomes (e.g. gel filtration, dialysis and vacuum), these are practically difficult and time-consuming procedures. In addition, the level of these solvents in the final formulations must be assessed to ensure the clinical suitability of the products (39). Therefore, it would be much preferable to avoid utilisation of these solvents in nanoliposome manufacture, which will also bring down the time and cost of preparation especially at the industrial scales. 

Table 2.10 shows that the isolation and purification of naturally occurring flavour chemicals and extracts from animal and plant raw materials is most important for the preparation of natural flavours. About 75% of the commercially used flavours come from such natural sources. Physico-chemical reactions of typical flavour precursors may also lead to natural flavouring substances when mild conditions ( kitchen technology ) are applied. In addition, natural flavour chemicals may be prepared by biotechnological processes. This chapter outlines the most important biotechnical manufacturing techniques. 

Unlike conventional pharmaceutical products, which are usually produced from synthetic materials by means of reproducible manufacturing techniques and procedures, herbal medicines are prepared from materials of herbal origin, which are often obtained from varied geographical and/or commercial sources. As a result it may not always be possible to ascertain the conditions to which they may have been subjected. In addition, they may vary in composition and properties. Furthermore, the procedures and techniques used in the manufacture and quality control of herbal medicines are often substantially different from those employed for conventional pharmaceutical products. 

---