Wang Guang-Jun

Large magnetic entropy change near room temperature in the LaFe11.5Si1.5H1.3 interstitial compound

The LaFe11.5Si1.5H1.3 interstitial compound has been prepared. Its Curie temperature TC (288 K) has been adjusted to around room temperature and the maximal magnetic entropy change (|?S|~17.0 J?kg-1?K-1 at TC) is larger than that of Gd (|?S|~9.8 J?kg-1?K-1 at TC=293 K) by ~73.5% under a magnetic change from 0 to 5 T. The origin of the large magnetic entropy change is attributed to the first-order field-induced itinerant-electron metamagnetic transition. Moreover, the magnetic hysteresis of LaFe11.5Si1.5H1.3 under the increase and decrease of the field is very small, which is favourable to magnetic refrigeration application. The present study suggests that the LaFe11.5Si1.5H1.3 compound is a promising candidate as a room-temperature magnetic refrigerant.

Large magnetic entropy change and magnetic properties in La (Fe1-xMnx)11.7Si1.3Hy compounds

Magnetic properties and magnetic entropy change in La (Fe1-xMnx)11.7Si1.3Hy compounds have been investigated. A significant increase of the Curie temperature TC and a small increase of the saturation magnetizations µS have been observed after the introduction of interstitial H, which caused a slight volume expansion. The first-order field-induced itinerant-electron metamagnetic (IEM) transition remains and brings about a large magnetic entropy change around room temperatures for the compounds. The maximal magnetic entropy change is about 23.4, 17.7 and 15.9J/kgK under a magnetic field change from 0 to 5T for x=0.01, 0.02 and 0.03, respectively. Therefore, the compounds appear to be potential candidates for magnetic refrigerants around room temperatures.

Magnetoresistances and magnetic entropy changes associated with negative lattice expansions in NaZn13-type compounds LaFeCoSi

Magnetoresistances and magnetic entropy changes in NaZn13-type compounds La(Fe1−xCox)11.9Si1.1 (x=0.04, 0.06 and 0.08) with Curie temperatures of 243 K, 274 K and 301 K, respectively, are studied. The ferromagnetic ordering is accompanied by a negative lattice expansion. Large magnetic entropy changes in a wide temperature range from ~230 K to ~320 K are achieved. Raising Co content increases the Curie temperature but weakens the magnetovolume effect, thereby causing a decrease in magnetic entropy change. These materials exhibit a metallic character below TC, whereas the electrical resistance decreases abruptly and then recovers the metal-like behaviour above TC. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase in magnetic field leads to an increase in electrical resistance at temperatures near but above TC, which is a consequence of the field-induced metamagnetic transition from a paramagnetic state to a ferromagnetic state.

Effects of Fe–Fe bond length change in NaZn13-type intermetallic compounds on magnetic properties and magnetic entropy change

In this paper the effects of Fe-Fe bond length change on magnetic properties and magnetic entropy change have been investigated on LaFe12.4-xSixCo0.6 and LaFe12.3-xAlxCo0.7 intermetallic compounds. According to the analyses of Fe-Fe bond length change, the variation of Curie temperature and the unusual magnetic phase transition which results in the large magnetic entropy change were explained. The effects of the substitution of Co and Si for Fe on magnetic entropy change and field-induced itinerant-electron metamagnetic transition in LaFe12.4-xSixCo0.6 compounds were also studied and the considerable magnetic entropy change has been achieved.

Magnetic properties and magnetocaloric effect in NdxLa1-xFe11.5Al1.5 compounds

Effects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of NdxLa1-x Fe11.5 Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic (AFM) coupling and an enhancement of the ferromagnetic (FM) coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.5Al1.5 characterized by the occurrence of two phase transitions at ~188K (PM?AFM) and ~159K (AFM?FM). As a result, a table-like MCE (9 J/kg?K) is found in a wide temperature range (160?185 K) for a field change of 0?5T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM?FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.

Effect of Co substitution on magnetic properties and magnetic entropy changes in LaFe11.83Si0.94Al0.23 compounds

Effect of Co substitution on magnetic properties and magnetic entropy changes in LaFe11.83Si0.94Al0.23 compounds has been investigated by means of magnetization measurements. X-ray diffraction shows the prepared compounds to be single phase with the cubic NaZn13-type structure. Substitution of Co for Fe leads to an increase of Curie temperature of the material. The magnetic entropy changes in LaFe11.83Si0.94Al0.23 and LaFe11.03Co0.80Si0.94Al0.23 compounds are 21.8J/(kg.K) to 16.9J/(kg.K) under a magnetic field change of 0–5T at Curie temperature, respectively. Giant magnetic entropy changes are attributed to the higher magnetization and the rapid change in magnetization at Curie temperature.

The Motion Simulation for Freestyle Skiing Aerials

In order to simulate the angular velocity, acceleration and other kinematic parameters during the training timely for the ski athletes, we design a three-dimensional motion simulation system based on the gesture information acquisition system, which can help team coach to analyze the action and guide the team members training with the given purpose. Since it is difficult to get the accurate position parameter of the ski athlete, we integrate the ski field and physical information. The gesture information acquisition system can gain the parameter information of three-dimensional acceleration and angular velocity, which are recorded by the sensor. In this paper, we construct a three-dimensional motion simulation system to achieve the parameters of velocity, angular acceleration and angle at any time. The three-dimensional motion simulation system for freestyle skiing aerials is constructed in the OpenGL environment, and can observe the effects of posture demonstration from different views. Simulation results show that this system can record the movement information accurately and help athlete obtaining the training targets.

Change in the magnetic ground state of LaFe11.4Al1.6 compound by the substitution of Mn for Fe

The structure and magnetic properties of La(Fe1−xMnx)11.4Al1.6 (0≤x≤0.25) compounds have been studied. The NaZn13-type structure is preserved and the lattice parameter increases linearly with increasing the Mn concentration. The magnetic ground state changes from the antiferromagnetic to the spin-glass or the cluster-glass state by the substitution of Mn for Fe. Furthermore, a field-induced transition from cluster glass to ferromagnet is found for the samples with x=0.05 and 0.10.

Sports biomechanics infomation acquisition and analysis based on Miniature Inertial Measurement

To fully evaluate the quality of movement the athlete performed, sports biomechanics information acquisition and analysis at barycenter is conducted based on Miniature Inertial Measurement Unit. The methods to acquire accurate speed, key point identification and index of redundant movement of the subject are proposed. Key point detection is realized by cascaded logical analysis. Velocity estimation is derived by approximate equation. Gesture Energy index is proposed which provides quantity clue for distinguishing of sports quality based on angular velocity record from Miniature Inertial Measurement Unit corresponding to key point. Experiments of measurements on athletes are done to prove the validation of the methods put forward. The velocity results of approximate equation are comparable to the results of video analysis. Phase identification procedure and Gesture Energy index are also proven to be practicable. The methods could offer some aided information to coaches in daily training.