Thermal insulation of wet shielded metal arc welds
Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Sciences & Engineering, 1994.
Technologies and Practices of Underwater Welding
This paper describes the present state-of-the-art of technologies and practices of underwater welding. The first part of this paper presents a review of various underwater welding technologies. The techniques currently in use may be classified depending upon the environment in which the welding takes place—dry chamber technique, portable dry spot technique, and wet technique. Shielded metal arc (SMA), gas tungsten arc (GTA), and gas metal arc (GMA) processes are the most widely used in underwater application. Stud welding has been used to a limited degree. Studies have been made of underwater applications of various processes including submerged arc, plasma arc, etc. Although all practical applications and most of the studies so far have been on manual welding, limited efforts have been made to automate welding operations by use of remotely controlled manipulators. 
 
The later parts of this paper discuss the practical aspects of two techniques which are widely used—hyperbaric dry chamber habitat welding and wet shielded metal arc welding. The second part of this paper, on hyperbaric dry welding, is based on actual experiences obtained at the Taylor Diving and Salvage Co. The third part, on wet welding process, is based on actual experiences obtained at Sea-Con Services, Inc.
Applications of nanocomposite hydrogels for biomedical engineering and environmental protection
Nanocomposite hydrogels are polymeric networks that possess a unique property of hydration. The presence of alcohols, carboxylic acids and amides as hydrophilic moieties in structure of nanocomposite hydrogels enhances their stiffness and water-absorbing capacity. Addition of cross-linker in the synthesis of hydrogels increases their stability under extreme conditions of temperature, pH and pressure. Natural polymer-based nanocomposite hydrogels are biodegradable, highly hydrophilic and possess good mechanical strength. Gelatin, chitin, cellulose, pectin, carrageenan, starch and alginate are natural polymers commonly used to fabricate nanocomposite hydrogels. Nanocomposite hydrogels have special characteristics such as high swelling rate, selectivity and stimuli-sensitive nature. Here we review nanocomposite hydrogels for environmental protection and biomedical engineering. Applications in biomedical engineering include drug delivery agents, wound dressing, tissue engineering and antibacterials. Applications in environmental protection include ion exchangers, adsorption, photocatalysis and soil conditioning. Many nanocomposite hydrogels show excellent adsorption selectivity for heavy metal ions: Cu2+ up to 30.35 mg/g, Pb2+ up to 35.94 mg/g, and Zn2+ and Fe3+ up to 94.34 mg/g. Xanthan gum-based nanocomposite hydrogel has removed 96% dye from industrial effluent as reported. In addition, most of the nanocomposite hydrogels showed better adsorption capacity for pollutants in the pH range from 5 to 7. The nanocomposite hydrogels could also be regenerated and successfully utilized for several times. Nanocomposite hydrogels are therefore good bio-absorbent materials for environmental detoxification.