Micro-persistence and difficulty in a game-based learning environment for computational thinking acquisition

Persistence has been identified as a crucial quality of learning. However, it is hard to attain in online game-based environments as the drive to progress in the game may influence the ability to achieve the learning goals. This study aimed to examine the associations between micro-persistence, that is, the tendency to complete an individual task successfully, and task difficulty while acquiring computational thinking (CT). We further explored whether contextual or personal attributes better explain micro-persistence. We analysed data of 111 school students who used the CodeMonkey platform. We took a learning analytics approach for analysing the platform's log files. We found that micro-persistence is associated with task difficulty and that students who demonstrated an aptitude to learn new material are motivated to achieve the best solution. We also found that contextual variables better-explained micro-persistence than personal attributes. Encouraging micro-persistence can improve CT acquisition and the learning processes involved.     

Bit transposition for very large scientific and statistical databases

Conventional access methods cannot be effectively used in large Scientific/Statistical Database (SSDB) applications. A file structure (called bit transposed file (BTF)) is proposed which offers several attractive features that are better suited for the special characteristics that SSDBs exhibit. This file structure is an extreme version of the (attribute) transposed file. The data are stored by vertical bit partitions. The bit patterns of attributes are assigned using one of several data encoding methods. Each of these encoding methods is appropriate for different query types. The bit partitions can also be compressed using a version of the run length encoding scheme. Efficient operators on compressed bit vectors have been developed and form the basis of a query language. Because of the simplicity of the file structure and query language, optimization problems for database design, query evaluation, and common subexpression removal can be formalized and efficient exact solution or near optimal solution can be achieved. In addition to selective power with low overheads for SSDBs, the BTF is also amenable to special parallel hardware. Results from experiments with the file structure suggest that this approach may be a reasonable alternative file structure for large SSDBs.     

Effective deadlock resolution with self-interested partially-rational agents

This paper pertains to distributed deadlock resolution in settings populated with self-interested bounded-rational autonomous agents. In particular it reports the results of extensive experimentation with 66 agents, each using a deadlock resolution strategy developed and maintained throughout the experiment by a different human decision maker. While from the game-theoretic perspective a simple equilibrium-based solution can be engineered for the problem, it is shown that such a solution fails to hold with bounded-rational agents, even when its principles are thoroughly explained to the individuals that maintain the agents’ strategies. Instead, we show that the system converges to a steady-state, in which the agents use a rich set of different strategies, varying in their performance, as each of them has a different belief regarding its ability to improve, based on the behaviors of the others. To improve system performance, we develop and implement a restructuring heuristic that changes the input each agent receives, as a means of affecting the agents’ decisions to better align with the desired solution. The restructured deadlock presented to each agent is based on former deadlocks it had experienced. Our experiments demonstrate the effectiveness of the restructuring heuristic in facilitating a new steady-state in which the system as a whole substantially improves its performance. The efficiency of the method, in terms of the size of the set of former experiences required for effectively restructuring the agents’ input, is demonstrated through a comparison with a neural network implementation of input restructuring, showing a substantial advantage to the restructuring heuristic.     

The effectiveness of Light Rail transit in achieving regional CO<Subscript>2</Subscript> emissions targets is linked to building energy use: insights from system dynamics modeling

Cities worldwide face the challenges of accommodating a growing population, while reducing emissions to meet climate mitigation targets. Public transit investments are often proposed as a way to curb emissions while maintaining healthy urban economies. However, cities face a system-level challenge in that transportation systems have cascading effects on land use and economic development. Understanding how an improved public transit system could affect urban growth and emissions requires a system-level view of a city, to anticipate side effects that could run counter to policy goals. To address this knowledge gap, we conducted a case study on the rapidly growing Research Triangle, North Carolina (USA) region, which has proposed to build a Light Railway by 2026 along a heavily used transportation corridor between the cities of Durham and Chapel Hill. At the same time, Durham County has set a goal of lowering greenhouse gas emissions by 30% from a 2005 baseline by 2030. In collaboration with local stakeholders, we developed a system dynamics model to simulate how Light Rail transit and concurrent policies could help or hinder these sustainable growth goals. The Durham–Orange Light Rail Project (D–O LRP) model simulates urban–regional dynamics between 2000 and 2040, including feedbacks from energy spending on economic growth and from land scarcity on development. Counter to expectations, model scenarios that included Light Rail had as much as 5% higher regional energy use and CO₂ emissions than business-as-usual (BAU) by 2040 despite many residents choosing to use public transit instead of private vehicles. This was largely due to an assumption that Light Rail increases demand for commercial development in the station areas, creating new jobs and attracting new residents. If regional solar capacity grew to 640 MW, this would offset the emissions growth, mostly from new buildings, that is indirectly due to Light Rail. National trends in building and automobile energy efficiency, as well as federal emissions regulation under the Clean Power Plan, would also allow significant progress toward the 2030 Durham emissions reduction goal. By simulating the magnitude of technology and policy effects, the D–O LRP model can enable policy makers to make strategic choices about regional growth.     

冶炼烟气净化：所有步骤在一台设备内完成

介绍Kimre公司的SXF^TM半错流洗涤器的结构、优点和应用。该洗涤器采用卧式并流气液接触方式,可根据需要分隔成不同操作段,在由交织单丝构成的纤维介质上完成气体的冷却、净化和除沫。与传统立式逆流填料塔相比,该洗涤器的优点为：高度低,泵、阀门、控制器等可在地面安装,容易操作和维修;液气比范围宽;可进行多级操作,包括在一台设备内完成多个化学过程。如用于冶炼烟气净化,所有步骤可在一台设备内完成。列举了化肥厂造粒塔气体净化、磷酸厂气体除氟和硫酸厂干燥塔除沫等应用实例。     

用于弹性机织物的双组分丝

今天,人们对休闲活动的热情与日俱增.随之而来的是对用功能性强的高性能织物制作的服装的需求的增长,这种服装使穿着者在肘部、肩部、胯部、股部和膝部(在服装的长度或宽度方向上)都能伸展自如.这种服装耐用、轻便、时尚,穿用者能够移动、赛跑、骑车、跳跃、行走和攀爬.     

On controllability and trajectory tracking of a kinematic vehicle model

This paper presents some further results concerning the issues of controllability and trajectory tracking regarding a front-wheel drive vehicle kinematic model. A simple procedure for computing an open-loop control strategy that transfers the system between given initial and final states, is presented. In particular, the input function is computed by means of a set of linear algebraic equations. The resulting motion planning procedure allows us to present a control scheme for solving the trajectory (a time-parameterized reference signal) tracking problem. Various applications of the approach in forward and backward motions are considered, and simulation results are presented.     

Lymphangiomatosis with splenic involvement

Severe splenomegaly and anemia developed in a 5-year-old girl with diffuse lymphangiomatosis of the upper part of the body. Radioisotope scanning and celiac angiography demonstrated lymphangiomatosis of the spleen, a rare but diagnosable condition. Intractable infection in areas of ulcerated skin led to her death from overwhelming sepsis.     

A 3-D fracture mechanics approach to the strength of composite materials

The first ply failure in composite laminates are studied by 3-D fracture mechanic approach. The fracture model is based on a crack embedded in one of the inner layers. Numerical results for the case of “angle ply” laminates are based on a general 3-D finite difference program.Stress intensity factors and fracture energy are evaluated by the $\text{J-}\text{integral}$ 2-D and 3-D methods as well as by the stresses and energy balance. It was found that the $\text{J(2-}\text{D}\text{)}$ method can be applied to 3-D problems while the $\text{J(3-}\text{D}\text{)}$ method is not suitable for the numerical computation.The influence of geometrical properties of the crack and the layers on the various stress intensity factors is presented and discussed. Change in failure mechanism of the weakest ply was proved by experiments to fit with numerical results. It was found that the weakest layer is strengthened by the others, a fact which has been verified experimentally and hasn't been explained by other approaches.