Double-loop sigma-delta modulation with DC input

A discrete-time model having a two-bit (2-b) quantizer is analyzed exactly, and an analytical expression for the quantizer noise sequence is found. Rigorous answers are then provided to two fundamental questions for a double-loop sigma-delta modulation system with DC input: (1) What is the long-term statistical behavior of the internal quantizer noise? (2) How does the asymptotic mean square sigma-delta quantization error vary as a function of the oversampling ratio?     

Achievability proof of some multiuser channel coding theorems usingbackward decoding

New and simpler achievability proofs that are based on the backward decoding technique are presented for the well-known coding theorems for the multiple-access channel (MAC) with perfect feedback and the degraded relay channel. A class of MACs with different generalized feedback signals is also considered, and achievable-rate regions that are larger than those previously presented in the literature are established     

An Algorithm for Vector Quantizer Design

An efficient and intuitive algorithm is presented for the design of vector quantizers based either on a known probabilistic model or on a long training sequence of data. The basic properties of the algorithm are discussed and demonstrated by examples. Quite general distortion measures and long blocklengths are allowed, as exemplified by the design of parameter vector quantizers of ten-dimensional vectors arising in Linear Predictive Coded (LPC) speech compression with a complicated distortion measure arising in LPC analysis that does not depend only on the error vector.     

Proximate composition,provitamin A retention,and shelf life of extruded orange‐fleshed sweet potato and bambara groundnut‐based snacks

Evaluating the effect of processing on nutrient content and shelf life is important when developing new products. Six formulations of orange‐fleshed sweet potato (OFSP) and bambara groundnut were extruded at a feed rate of 10.15 kg/hr, screw speed of 30 rpm and at 100 and 130 °C in first and second zones respectively. Proximate composition was determined using standard methods. Provitamin A was determined using high‐performance liquid chromatography. An untrained panel (n = 73) was used to determine consumer acceptability. Shelf life was predicted by using peroxide values. Concentration of OFSP or bambara groundnut significantly (p < .05) affected proximate composition of the snacks. Moisture (4.79–8.34 g/100 g), carbohydrates (55.53–78.99 g/100 g) and provitamin (0.54–17.33 mg/100 g) contents increased with increase in proportion of OFSP. Protein (4.08–15.03 g/100 g), fat (4.20–12.74 g/100 g), fiber (5.29–6.46 g/100 g), ash (0.09–4.80 g/100 g), and energy (366.13–396.9 kcal/100 g) increased with increasing proportion of bambara groundnut in the formulation. Extrusion significantly (p < .05) reduced provitamin A content from 0.90–20.73 to 0.54–17.33 mg/100 g. Presence of OFSP improved provitamin A retention and consumer acceptability. Predicted shelf life (ranged from 118 to 150 days at room temperature) was inversely proportional to the concentration of bambara groundnut.

Practical applications

Vitamin A deficiency (VAD) is the leading cause of preventable blindness affecting many children and women of reproductive age globally. Provitamin A enriched foods can be developed from locally available provitamin A‐rich foods and their consumption promoted to help prevent VAD. In this study, recipes incorporating orange‐fleshed sweet potatoes and bambara groundnut were used to develop acceptable and shelf stable vitamin A enriched extruded snacks. The formulations and process used in this study can be adopted at commercial level to produce affordable snacks that can contribute towards reducing the burden of VAD. The results from this study can also be used in similar studies to develop nutrient enhanced extruded snacks.