Wastewater treatment in tsunami affected areas of Thailand by constructed wetlands.

The tsunami of December 2004 destroyed infrastructure in many coastal areas in South-East Asia. In January 2005, the Danish Government gave a tsunami relief grant to Thailand to re-establish the wastewater management services in some of the areas affected by the tsunami. This paper describes the systems which have been built at three locations: (a) Baan Pru Teau: A newly-built township for tsunami victims which was constructed with the contribution of the Thai Red Cross. Conventional septic tanks were installed for the treatment of blackwater from each household and its effluent and grey water (40 m3/day) are collected and treated at a 220 m2 subsurface flow constructed wetland. (b) Koh Phi Phi Don island: A wastewater collection system for the main business and hotel area of the island, a pumping station and a pressure pipe to the treatment facility, a multi-stage constructed wetland system and a system for reuse of treated wastewater. The constructed wetland system (capacity 400 m3/day) consists of vertical flow, horizontal subsurface flow, free water surface flow and pond units. Because the treatment plant is surrounded by resorts, restaurants and shops, the constructed wetland systems are designed with terrains as scenic landscaping. (c) Patong: A 5,000 m2 constructed wetland system has been established to treat polluted water from drainage canals which collect overflow from septic tanks and grey water from residential areas. It is envisaged that these three systems will serve as prototype demonstration systems for appropriate wastewater management in Thailand and other tropical countries.     

High-speed and large noise margin tolerance E/D logic gates withLDD structure DMTs fabricated using selective RIE technology

The authors describe a novel design concept for enhancement (E) and depletion (D) mode FET formation using i-AlGaAs/n-GaAs doped-channel hetero-MISFET (DMT) and a novel self-aligned gate process technology for submicrometer-gate DMT-LSIs based on E/D logic gates. 0.5-μm gate E-DMTs (D-DMTs) with a lightly doped drain (LDD) structure show an average V_t of 0.18 (-0.46) V, a V_t standard deviation of 22.6 (24.9) mV, and a maximum transconductance of 450 (300) mS/mm. The V_t shift is less than 50 mV with a decrease in gate length down to 0.5 μm. The gate forward turn-on voltage V_f is more than 0.9 V, i.e. about 1.6 times that for MESFETs. This superiority in V _f, preserved in the high-temperature range, leads to an improvement in noise margin tolerance by a factor of three. In addition, 31-stage ring oscillators operate with a power consumption of 20 (1.0) mW/gate and a propagation delay of 4.8 (14.5) ps/gate. Circuit simulation based on the experimental data predicts 140 ps/gate and 1 mW/gate for DMT direct-coupled FET logic circuits under standard loading conditions. DMTs and the technology developed here are very attractive for realizing low-power and/or high speed LSIs     

THE RELATIONSHIP BETWEEN HAZE AND THE SIZE OF PARTICLES IN BEER

Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values.     

Mechanism of alloying element vaporization during laser welding

Vaporization of alloying elements is a serious problem in the laser welding of many important engineering alloys. Since the available mass transfer correlations are not applicable for credible assessment of the rates of transport of vaporized species in the gas phase, the role of gas phase mass transfer in the overall vaporization of alloying elements was examined by conducting several critical experiments. The rates of transport of alloying elements in the weld pool were determined from numerically computed fluid flow fields. Since the weld pool is surrounded by plasma during laser welding, the role of plasma in the vaporization of alloying elements was physically modeled by allowing molten copper drops to vaporize isothermally both in the presence and absence of plasma. The transport of alloying elements in both liquid and gas phases was found to be rapid and the overall vaporization rates were controlled by the plasma influenced intrinsic vaporization of alloying elements at the weld pool surface. The experimentally obtained rates of vaporization of alloying elements from laser melted stainless steel weld pools were compared with the corresponding theoretically calculated values.     

Increase in laser repetition rate by spectral selection

An experimental and theoretical study into the use of Fabry-Perot etalons as static repetition rate upconverters outside the laser cavity is discussed. It is shown that the output repetition rate can be increased up to 12 times while maintaining high average power     

High speed BiCMOS current mode differential track-and-hold circuit

A new principle for a high speed BiCMOS differential track-and-hold circuit based on current mode processing is presented, and simulation results are given. The main characteristics are an acquisition time of 5.5 ns for 8 bit precision and a small-signal bandwidth of 1 GHz     

Multichannel FM-TV transmission using an engineered 1.3 μmpraseodymium-doped fluoride fibre amplifier

The authors report the first use of a praseodymium-doped fluoride fibre amplifier (PDFFA) in a 24 TV channel FM-SCM transmission experiment. Twenty-four analogue FM-SCM-TV channels were amplified by a PDFFA without any observable degradation in picture quality. By using a single PDFFA as a post-amplifier, transmission over 104 km of `standard' 1.3 μm optimised fibre was demonstrated with a total loss budget of 45 dB. By using the same PDFFA as an inline amplifier, a loss budget of 53 dB was achieved