Designing healthier and acceptable diets using data envelopment analysis
Kanellopoulos, A. ; Gerdessen, J.C. ; Ivancic, Ante ; Geleijnse, J.M. ; Bloemhof-Ruwaard, J.M. ; Veer, P. van 't - \ 2020
Public Health Nutrition 23 (2020)13. - ISSN 1368-9800 - p. 2290 - 2302.
Benchmark - DEA - Diet model - Efficiency - Nutrition - public health
Objective: The objective of this research is to propose methodology that can be used to benchmark current diets based on their nutrient intakes and to provide guidelines for improving less healthy diets in a way that is acceptable for the studied population.
Design: We discuss important limitations of current diet models that use optimization techniques to design healthier and acceptable diets. We illustrate how data envelopment analysis could be used to overcome such limitations, and we describe mathematical models that can be used to calculate not only healthier but also acceptable diets.
Setting: We used data from the Nutrition Questionnaires plus dataset of habitual diets of a general population of adult men and women in The Netherlands (n 1735).
Participants: Adult population.
Results: We calculated healthier diets with substantial higher intakes of protein, fibre, Fe, Ca, K, Mg and vitamins, and substantially lower intakes of Na, saturated fats and added sugars. The calculated diets are combinations of current diets of individuals that belong to the same age/gender group and comprise of food itemintakes in proportions observed in the sample.
Conclusions: The proposed methodology enables the benchmarking of existing diets and provides a framework for proposing healthier alternative diets that resemble the current diet in terms of foods intake as much as possible.
Temperature balanced hydrogen sensor system with coupled palladium nanowires
Bent, J.F. Van Der; Puik, E. ; Tong, H.D. ; Rijn, C.J.M. Van - \ 2015
Sensors and Actuators. A: Physical 226 (2015). - ISSN 0924-4247 - p. 98 - 106.
DEA - Digital signal processing - Hydrogen sensing - Nanowire - Palladium - Temperature compensation
A temperature compensated hydrogen sensor was designed and made capable of detecting H2 within a broad range of 100-10.000 ppm while compensating instantaneously for large (±25 °C) temperature variations. Two related operational constraints have been simultaneously addressed: (1) Selective, and sensitive detection under large temperature changes, (2) Fast warning at low and increasing H2 levels. Accurate measurements of hydrogen concentrations were enabled by matching relevant time-constants. This was achieved with a microchip having two temperature coupled palladium nanowires. One of the H2 sensitive Pd nanowires was directly exposed to hydrogen, whilst the other nanowire was used as a temperature sensor and as a reference. A drop forging technique was used to passivate the second Pd wire against H2 sensing. Temperature effects could be substantially reduced with a digital signal processing algorithm. Measurements were done in a test chamber, enabling the hydrogen concentration to be controlled over short and long periods. An early response for H2 sensing is attainable in the order of 600 milliseconds and an accurate value for the absolute hydrogen concentration can be obtained within 15 s.
Analyzing the impact of investment spikes on dynamic productivity growth
Kapelko, Magdalena ; Oude Lansink, Alfons ; Stefanou, S.E. - \ 2015
Omega - International Journal of Management Science 54 (2015). - ISSN 0305-0483 - p. 116 - 124.
DEA - Dynamic Luenberger productivity growth indicator - Impulse response analysis - Investment spikes - Meat processing industry
Firm-level data usually show that a large portion of firm-level investment takes place in a few investment episodes. This paper assesses productivity growth and its components in production framework that accounts for the dynamics of capital adjustment and relates this to investment spikes using firm-level data of the Spanish meat processing industry over the period 2000-2010. Using the method of impulse responses by local projections, it is shown that investment spikes produce a significant productivity change loss of 0.7% in the first year after the spike. The worsening of technology is the main cause of the reduction of productivity growth in the first year. Technology then improves in the fifth year as a result of investment spike, resulting in the U-shape pattern of relationship. Scale inefficiency significantly improves by 0.4% and 0.5% in the first and second year after the spike has occurred, respectively. All these effects, however, largely depend on the firms' size. In particular, it is shown that the loss of technology in the first year mainly pertains to smallest firms, while larger firms experience a negative impact on the contribution of technical inefficiency change to productivity growth.