The fast and cost-efficient home delivery of goods ordered online is logistically challenging. Many companies are looking for new ways to cross the last-mile to their customers. One technology-enabled opportunity that recently has received much attention is the use of a drone to support deliveries. An innovative last-mile delivery concept in which a truck collaborates with a drone to make deliveries gives rise to a new variant of the traveling salesman problem (TSP) that we call the TSP with drone. In this paper, we model this problem as an IP and develop several fast route first-cluster second heuristics based on local search and dynamic programming. We prove worst-case approximation ratios for the heuristics and test their performance by comparing the solutions to the optimal solutions for small instances. In addition, we apply our heuristics to several artificial instances with different characteristics and sizes. Our experiments show that substantial savings are possible with this concept in comparison to truck-only delivery.

This study investigated the hypothesis that background television affects interactions between parents and very young children. Fifty‐one 12‐, 24‐, and 36‐month‐old children, each accompanied by 1 parent, were observed for 1 hr of free play in a laboratory space resembling a family room. For half of the hour, an adult‐directed television program played in the background on a monaural television set. During the other half hour, the television was not on. Both the quantity and quality of parent–child interaction decreased in the presence of background television. These findings suggest one way in which early, chronic exposure to television may have a negative impact on development.

This experiment tests the hypothesis that background, adult television is a disruptive influence on very young children's behavior. Fifty 12-, 24-, and 36-month-olds played with a variety of toys for 1 hr. For half of the hour, a game show played in the background on a monaural TV set. During the other half hour, the TV was off. The children looked at the TV for only a few seconds at a time and less than once per minute. Nevertheless, background TV significantly reduced toy play episode length as well as focused attention during play. Thus, background television disrupts very young children's play behavior even when they pay little overt attention to it. These findings have implications for subsequent cognitive development.

clinicaltrials.gov Identifier: NCT01565161.

Objective To examine the extent to which infant television viewing is associated with language and visual motor skills at 3 years of age. Measures We studied 872 children who were participants in Project Viva, a prospective cohort. The design used was a longitudinal survey, and the setting was a multisite group practice in Massachusetts. At 6 months, 1 year, and 2 years, mothers reported the number of hours their children watched television in a 24-hour period, from which we derived a weighted average of daily television viewing. We used multivariable regression analyses to predict the independent associations of television viewing between birth and 2 years with Peabody Picture Vocabulary Test III and Wide-Range Assessment of Visual Motor Abilities scores at 3 years of age. Results Mean daily television viewing in infancy (birth to 2 years) was 1.2 (SD: 0.9) hours, less than has been found in other studies of this age group. Mean Peabody Picture Vocabulary Test III score at age 3 was 104.8 (SD: 14.2); mean standardized total Wide-Range Assessment of Visual Motor Abilities score at age 3 was 102.6 (SD: 11.2). After adjusting for maternal age, income, education, Peabody Picture Vocabulary Test III score, marital status, and parity, and child's age, gender, birth weight for gestational age, breastfeeding duration, race/ethnicity, primary language, and average daily sleep duration, we found that each additional hour of television viewing in infancy was not associated with Peabody Picture Vocabulary Test III or total standardized Wide-Range Assessment of Visual Motor Abilities scores at age 3. Conclusion Television viewing in infancy does not seem to be associated with language or visual motor skills at 3 years of age.