The Minimal Automorphism-Free Tree

A finite tree $T$ with $|V(T)| \geq 2$ is called {\it automorphism-free} if there is no non-trivial automorphism of $T$. Let $\mathcal{AFT}$ be the poset with the element set of all finite automorphism-free trees (up to graph isomorphism) ordered by $T_1 \preceq T_2$ if $T_1$ can be obtained from $T_2$ by successively deleting one leaf at a time in such a way that each intermediate tree is also automorphism-free. In this paper, we prove that $\mathcal{AFT}$ has a unique minimal element. This result gives an affirmative answer to the question asked by Rupinski.Comment: 8 pages, 5 figure

We All Live in a Virtual Submarine

Our seas and oceans hide a plethora of archaeological sites such as ancient shipwrecks that, over time, are being destroyed through activities such as deepwater trawling and treasure hunting. In 2006, a multidisciplinary team of 11 European institutions established the Venus (Virtual Exploration of Underwater Sites) consortium to make underwater sites more accessible by generating thorough, exhaustive 3D records for virtual exploration

From cadaver to computer: Incorporating computers into the topographical anatomy laboratory

Traditionally, students have studied human anatomy through dissection and prosection. This requires considerable input from demonstrators, with students working mainly in large groups. Increasing student numbers, decreasing funds for staff, and a need to encourage students to develop independent learning skills that will be of value throughout their professional lives, have meant that the nature of their learning in the Topographical Anatomy Laboratory has had to change. The situation in which groups of students are guided by demonstrators has moved towards a more self‐directed learning environment. Several innovations have been introduced at University College London, including a multimedia laboratory which is the focus of this paper. The results of the evaluation and the lessons learned from the early stages of setting up a self‐directed learning environment are presented

When does an ostrich become a bird? The role of typicality in early word comprehension

Which objects and animals are are children willing to accept as referents for words they know? To answer this question, the authors assessed early word comprehension using the preferential looking task. Children were shown 2 stimuli side by side (a target and a distractory) and heard the target stimulus named. The target stimulus was either a typical or an atypical exemplar of the named category. It was predicted that children first connect typical examples with the target name and broaden the extension of the name as they get older to include less typical examples. Experiment 1 shows that when targets are named, 12-month-olds display an increase in target looking for typical but not atypical targets whereas 24-month-olds display an increase for both. Experiment 2 shows that 18-month-old display a pattern similar to that of 24-month-olds. Implications for the early development of word comprehension are discussed

Prototyping and Experimentation of a Closed-Loop Wireless Power Transmission with Channel Acquisition and Waveform Optimization

A systematic design of adaptive waveform for Wireless Power Transfer (WPT) has recently been proposed and shown through simulations to lead to significant performance benefits compared to traditional non-adaptive and heuristic waveforms. In this study, we design the first prototype of a closed-loop wireless power transfer system with adaptive waveform optimization based on Channel State Information acquisition. The prototype consists of three important blocks, namely the channel estimator, the waveform optimizer, and the energy harvester. Software Defined Radio (SDR) prototyping tools are used to implement a wireless power transmitter and a channel estimator, and a voltage doubler rectenna is designed to work as an energy harvester. A channel adaptive waveform with 8 sinewaves is shown through experiments to improve the average harvested DC power at the rectenna output by 9.8% to 36.8% over a non-adaptive design with the same number of sinewaves.Comment: accepted for publication in IEEE WPTC 201

A DYNAMIC ANALYSIS OF THE EFFECTS OF A PRICE SUPPORT PROGRAM ON PRICE DYNAMICS AND PRICE VOLATILITY

This study presents an econometric analysis of the effects of a government price support program on price dynamics and price volatility. Price support programs, a common feature of agricultural policy, provide a lower-bound censoring of the distribution of market prices. An econometric model of market prices is developed using a dynamic Tobit specification under time-varying volatility. The model is applied to the U.S. non-fat dry milk market. It is used to investigate the impact of market liberalization on price dynamics and price volatility in the presence of private and public stocks. The econometric results show how the price support program and stocks (both private and public) affect expected price volatility.Agricultural and Food Policy,