Emergence of Two-Dimensional Massless Dirac Fermions, Chiral Pseudospins, and Berry's Phase in Potassium Doped Few-Layer Black Phosphorus

Thin flakes of black phosphorus (BP) are a two-dimensional (2D) semiconductor whose energy gap is predicted being sensitive to the number of layers and external perturbations. Very recently, it was found that a simple method of potassium (K) doping on the surface of BP closes its band gap completely, producing a Dirac semimetal state with a linear band dispersion in the armchair direction and a quadratic one in the zigzag direction. Here, based on first-principles density functional calculations, we predict that, beyond the critical K density of the gap closure, 2D massless Dirac Fermions (i.e., Dirac cones) emerge in K-doped few-layer BP, with linear band dispersions in all momentum directions, and the electronic states around Dirac points have chiral pseudospins and Berry's phase. These features are robust with respect to the spin-orbit interaction and may lead to graphene-like electronic transport properties with greater flexibility for potential device applications

Dealing with menstrual pain and difficulties: holistic experiences using a heating wearable device for management of menstrual pain

The main purpose of this thesis is to develop an understanding of women’s experiences during menstruation. The research questions are: how to improve the experience of using a wearable device that heats the abdomen and the back to relieve menstrual pain; what should be considered when designing such a product for relieving menstrual period pain. This thesis is based on the ‘Hottie’ project, which involved conceptually designing a skirt for menstrual pain. The skirt has two heating pads – one for the abdomen and one for the back – which can be heated up to 42 °C. A working prototype was produced for the ‘Wearable Electronics and Fashion’ summer course in 2015, so the main purpose of the research in this thesis is focused on how to make a skirt that can be worn more consistently, on a regular basis in real life. The thesis includes a study of the literature on menstrual period pain and interviews with women about their perceptions of menstrual periods in order to build a general understanding about what women experience during their periods. It continues with a brief study of wearable devices and period-related products, followed by a multi-staged study of active user involvement. The latter began with user testing of the current prototype. A co-creation workshop and a cultural probe on periods were then carried out. From the research, the ‘Blood pal’ concept and an app related to periods was introduced. User testing of these was then conducted using the inVision prototype. During the research process, a total of seven participants were involved in the qualitative research, and two participated in all the research phases of the process. As a result, the Hottie app, which controls the Hottie wearable device and functions as a holistic support for women during menstrual periods, was implemented at the prototype level. Hottie predicts the start of the menstruation cycle by measuring body temperature with an everyday sensor located in a Bluetooth earphone or a wearable device, such as Fitbit. The app includes the ‘Blood pal’ function, so women can get support from each other, e.g. sharing tampons and information about the nearest toilets, and finding deals on period-related products – from hygiene products to chocolates. It The ultimate aim to make menstruation a better experience. Valuable insights were gained throughout the research, and Six Guidelines for designing related to menstrual periods

Topology-Guided Path Integral Approach for Stochastic Optimal Control in Cluttered Environment

This paper addresses planning and control of robot motion under uncertainty that is formulated as a continuous-time, continuous-space stochastic optimal control problem, by developing a topology-guided path integral control method. The path integral control framework, which forms the backbone of the proposed method, re-writes the Hamilton-Jacobi-Bellman equation as a statistical inference problem; the resulting inference problem is solved by a sampling procedure that computes the distribution of controlled trajectories around the trajectory by the passive dynamics. For motion control of robots in a highly cluttered environment, however, this sampling can easily be trapped in a local minimum unless the sample size is very large, since the global optimality of local minima depends on the degree of uncertainty. Thus, a homology-embedded sampling-based planner that identifies many (potentially) local-minimum trajectories in different homology classes is developed to aid the sampling process. In combination with a receding-horizon fashion of the optimal control the proposed method produces a dynamically feasible and collision-free motion plans without being trapped in a local minimum. Numerical examples on a synthetic toy problem and on quadrotor control in a complex obstacle field demonstrate the validity of the proposed method.Comment: arXiv admin note: text overlap with arXiv:1510.0534