Lei Jin

Pratt & Whitney · materials process engineering

Wind energy, as the most widely distributed form of renewable energy, holds great significance in addressing the energy supply issue for micro-power electronic equipment. Therefore, this paper proposes an electromagnetic wind-induced vibration energy harvester with a resonant cavity (EWVEH). When the wind blows through the resonant cavity, the pres...

The arrangement of the induction coil influences the electromagnetic damping force and output characteristics of electromagnetic energy harvesters. Based on the aforementioned information, this paper presents a proposal for a multiple off-center coil electromagnetic galloping energy harvester (MEGEH). This study establishes both a theoretical model...

In order to improve the output characteristics of the electromagnetic energy harvester in a high-speed flow field, a spring-coupling electromagnetic energy harvester (SEGEH) is proposed, based on the galloping characteristics of a large amplitude. The electromechanical model of the SEGEH was established, the test prototype was made, and the experim...

Based on the theoretical analysis of penetrating thick concrete targets, a model of converting friction into heat and then into high-pressure gas thrust at the bottom of the projectile is proposed. Furthermore, an analysis and calculation method of deceleration after perforation is given by using thermodynamic theory. In the off-target stage of pen...

In this paper, a frequency-adjustable tuning fork electromagnetic energy harvester is introduced. The electromagnetic vibration energy harvester can adjust its natural frequency according to a change in the environmental excitation frequency without any change to the structure. In the frequency-adjustable range, it can make the energy harvester res...

The classical continuum mechanics theory cannot sufficiently describe the effect of pebbles on projectile, which leads to a large calculation error. In this paper, an orthogonal curvilinear coordinate system is constructed, which effectively describes and perfects the normal cavity expansion theory. A couple stress theory based on the normal cavity...

The circular Halbach array is of great application value in electromagnetic energy conversion. The Halbach array can be formed with multiple magnets according to a specific method. The magnetic flux intensity of the magnet array is concentrated and enhanced in a certain area. The concentrated magnetic flux intensity could lead to a higher rate of c...

Energy harvesting in multi-directional excitation for human wearable devices is a challenge. A rotating electromagnetic energy harvester(REMEH) based on an eccentric rotor structure is proposed in this paper. Two poles of the magnets in REMEH are alternately arranged in a ring. The electrical output characteristics of the energy harvester are analy...

In the view of the limitation of traditional frequency up-conversion piezoelectric energy harvesters (FUC-PEH) which has a narrow operating frequency range and is difficult to adapt to the ultralow frequency excitation, this study presents a dual impact driven FUC-PEH composed of two piezoelectric energy harvester units (PEHUs). The electromechanic...

In this paper, a novel tuning fork structure for self-frequency up-conversion is proposed. The structure has an in-phase vibration mode and an anti-phase vibration mode. The in-phase vibration mode is used to sense the environment vibration, and the anti-phase vibration mode is used for energy conversion and power generation. The low-frequency ener...

This study presents a shoe-mounted piezoelectric energy harvester (PEH) to harvest energy from human walking. The PEH realizes frequency up-conversion technology through the impact between ratchet and piezoelectric beam in the gait cycle. A piecewise force-electric coupling model of the PEH is established based on the different motion states of the...

A new micromachined vibrating ring gyroscope (VRG) architecture with low quadrature error and high-linearity is proposed, which successfully optimizes the working modes to first order resonance mode of the structure. The improved mode ordering can significantly reduce the vibration sensitivity of the device by adopting the hinge-frame mechanism. Th...

For a microelectromechanical system (MEMS) piezoelectric energy harvester consisting of double-clamped beams, the effects of both beam shape and electrode arrangement on the voltage outputs are analyzed. For two kinds of harvester structures including millimeter-scale and micro-scale, and different shapes including rectangular, segmentally trapezoi...

This paper presents the design and analysis of a new micro-electro-mechanical system (MEMS) tuning fork gyroscope (TFG), which can effectively improve the mechanical sensitivity of the gyroscope sense-mode by the designed leverage mechanism. A micromachined TFG with an anchored leverage mechanism is designed. The dynamics and mechanical sensitivity...

For a piezoelectric energy harvester composed of a doubly-clamped beam with arbitrary width shapes and a proof mass, the influence of beam shapes and electrode arrangements on different electric outputs is analyzed. The output performances of piezoelectric energy harvesters with rectangular shape, concave trapezoidal shape, and concave parabolic sh...

Quasi-static and dynamic experiments were carried out to examine the influence of liquid nitrile rubber (LNBR) on the compressive behavior of epoxy resin. The quasi-static tests were performed on an electronic universal machine under strain rates of 10⁻⁴/s and 10⁻³/s, while a Split Hopkinson Pressure Bar (SHPB) system was adopted to conduct the dyn...

The concept of vibratory energy harvesting has flourished in recent years as a possible alternative to provide a continuous power supply. Most work focusing on changing the configuration of piezoelectric energy harvester has concentrated on cantilevered beams at resonance using harmonic excitation. This work is mainly devoted to obtain the effects...

At present, frequency up-converted piezoelectric energy harvesters are disadvantaged by their narrow range of operating frequencies and low efficiency at ultralow-frequency excitation. To address these shortcomings, we propose herein an impact-driven frequency up-converted piezoelectric energy harvester composed of two driving beams and a generatin...

In this paper, a piezoelectric energy-harvesting structure based on the torsional vibration in the second mode is presented, which is composed of a thin-walled cantilever beam with PZT piezoelectric material and an eccentric proof mass. It has some advantages, such as small displacement amplitudes, uniform strain, and lower natural frequency. First...

In order to improve the performances of out-of-plane electret-based vibration energy harvesters (E-VEHs) in practical environment, we investigated the dependence of output power, resonance frequency and half power bandwidth on the load resistance for E-VEHs theoretically, numerically and experimentally. A linear analytical model is presented to des...

Dy2Cu2O5 nanoparticles with perovskite structures were synthesized via a simple solution method (SSM) and a coordination compound method (CCM) using [DyCu(3,4-pdc)2(OAc)(H2O)2]•10.5H2O (pdc = 3,4-pyridinedicarboxylic acid) as precursor. The as-prepared samples were structurally characterized by X-ray diffraction (XRD), scanning electron microscopy...

In this work, for an arbitrary shape (i.e. the width can be described by an arbitrary function) beam, analytical models for vibrations and electrical output are established. And experiments are conducted to verify the models. In fact, for a rectangular beam, it can be found both theoretically and experimentally that the total output charges are ind...

Thanks to miniaturization, it is now possible to imagine self-powered systems that can harvest energy from the environment to produce electrical energy. Out-of-plane electret-based vibration energy harvesters (E-EVHs) are an effective and inexpensive energy harvester type that has attracted much attention. Increasing the capacitance of variable cap...

The expansion of wireless sensor networks in our daily environment and the rapid development of low power consumption devices and MEMS devices have been driving research on energy harvester. In this paper, based on the designed hybrid harvest structure, the equivalent vibration model and the governing electromechanical equations of PE-EM hybrid har...

In this paper, a stiffness match method is proposed to reduce the vibration sensitivity of micromachined tuning fork gyroscopes. Taking advantage of the coordinate transformation method, a theoretical model is established to analyze the anti-phase vibration output caused by the stiffness mismatch due to the fabrication imperfections. The analytical...

Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) biodiesel catalysts were prepared by a coprecipitation method followed by an overnight reflux. High fatty acid methyl ester (FAME) yield (>95%) was achieved under mild reaction conditions (<100 °C). The FAME yields of the catalysts were investigated as a function of temperature and catalyst w...

Harvesting ambient vibration energy through piezoelectric (PE) means is a popular energy harvesting technique. The merit of applying PE means to supply energy for microelectronic devices is that they can reduce the battery weight and possibly make the device self-powered by harvesting mechanical energy. This investigation will examine the energy ge...

In this paper, a novel MEMS tuning fork gyroscope with anchored coupling mechanism is designed to analyze the mode ordering and vibration sensitivity. The proposed TFG prioritizes anti-phase drive-mode by using a levered mechanism while the sense-mode is prioritized utilizing an anchored coupling ring spring linked by four linear beams, which elimi...

The comb-shaped capacitive micro-machined gyroscope employing an electrostatic comb drive and capacitive sensing structure is a typical type of MEMS sensor. Because of design and processing limitation and other factors, there are problems related to parallelism, dimensional accuracy and shape accuracy of the fabricated comb capacitor. These problem...

A low frequency energy harvesting structure was studied, describing the process of its manufacture. The natural frequency was obtained by modal analysis of the structure. It obtained the relationship between the magnitudes of the voltage generated from the piezoelectric energy harvesting device and the size parameters of structure, so that the ener...

Package is one of the key technologies for micro-accelerometer. This paper researched the influence of package on the sensitivity of self-designed piezoresistive accelerometer. Based on the designed package method, the effect of thickness and elastic modulus of die adhesive, package shell materials and signal connection wires on the sensitivity of...

As an important part of MEMS, the micro-comb electrostatic driving structure is the main source of mechanical movement in many MEMS devices. Its reliability will directly affect the using performance of the MEMS devices. The electrostatic driving system of micro-comb capacitive micro-machined gyroscope can be equivalent to a second order system. If...

Selective conversion of biomass derived carbohydrates into fine chemicals is of great significance for the replacement of petroleum feedstocks and the reduction of environmental impacts. Levulinic acid, 5-hydroxymethyl furfural (HMF) and their derivatives are recognized as important precursor candidates in a variety of different areas. In this stud...

The micro-machined gyroscope is a kind of typical micro-electro-mechanical sensor, its typical working mode is electrostatic drive and comb capacitive detection. As for as the transverse detection capacitance structure now commonly used, we find out that the relationship between capacitance variation and displacement is nonlinear through analyzing...

The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. Therefore, the coupled system of a structure and the occupants can hardly be described with its basic dynamic characteristics considering only the mass of the occupants. Depending on the natural frequency of the empty str...

The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. In a simplified approach active persons can be modeled as external loads. While this approach may be sufficient for an activity like jumping, it has been shown already that for a bobbing person some interaction effects ma...

The search for solid state materials with high catalytic activities and with no leaching into the reaction medium is one of the key steps toward reducing the cost of producing biodiesel. We report a high biodiesel yield (> 95%) in less than 5 min under mild reaction conditions (< 100 degrees C) on a ZnO/La2O2CO3 heterogeneous catalyst, showing no c...

The stability and accuracy of the drive mode are important for the performance of vibrating MEMS gyroscope. At present, the PI-like controller is always used in the control of the drive mode of vibrating MEMS gyroscope. The PI-like control has good effect on rejecting the literal disturbance, but it can’t reject the time-dependent disturbance well....

Titanium containing γ-MnO2 octahedral molecular sieves having hollow sphere structures are successfully prepared for the first time using a one-step synthesis method. Titanium cations are used as structure-directing agents in the synthesis process. The assembly of the hollow spheres is carried out at the beginning of the process. Various techniques...

The comb capacitive micromachined gyroscope is a kind of typical MEMS sensor. Electrostatic driving and comb capacitive detection are its typical working mode. Recently, researchers have found that the narrow space between two combs can result in comb adhesion easily because of micro scaling effect. In this paper, some micro forces such as capillar...

A facile single-step method was developed for synthesizing todorokite-type manganese oxide octahedral molecular seieves (OMS-1) and 2 x 4 tunnel structured manganese oxide (OMS-5) materials. Selection of starting materials and initial pH conditions in the syntheses are crucial.

Preparation of TiO2 nanoscale shell/fiber superstructure: 10mg of as-synthesized microspherical cryptomelane MnO2 was mixed with 13 mL of TiOSO4 solution (2.5mM) in H2SO4 (0.1 M) solution; the mixture was then transferred to a 23mL Teflon-lined autoclave and reacted at 100 °C for 1 day using a rotary hydrothermal treatment. The product was rinsed w...

The cover picture shows electron microscopy images of the produced nanoscale shell/fiber superstructure TiO2 on cryptomelane MnO2 (OMS-2) in a single-step aqueous reaction. Control of the nanostructure and orientation of materials is important but complicated in current nanotechnological applications. The discovery of size, shape, and array control...

Molecular adsorption and oxidation at manganese oxide/liquid interfaces has attracted increased interest due to its importance in the development of heterogeneous catalysts, microbial fuel cells, and selective adsorption materials. Here we report the adsorption and oxidation of phenolic compounds on Cu(2+), Co(3+), and Ce(4+) doped K-OMS-2 nanofibe...

The cover picture shows the reaction scheme for the dehydrogenation of ethane over the octahedral molecular sieve OMS-2 in the presence of carbon dioxide. This reaction is put into action by Suib et. al. in their Communication on page 441 ff., with high ethane and carbon dioxide conversions and high selectivity towards the product ethylene. The rea...

A breath of fresh air: The octahedral molecular sieve (OMS-2) catalyst shows outstanding catalytic activity, selectivity, and stability in the dehydrogenation of ethane into ethylene in the presence of CO2. This process can be extended for other alkanes, giving an ideal feedstock for any process involving alkene carbonylation, as a greenhouse gas,...

The capacitive structure of comb capacitive micromachined gyroscope is a kind of important structure. The mechanical properties of micro inertia sensor material had changed when the structures experienced high temperature boron diffusion, lithography and etching et.al. micromachined process. Therefore, it is necessary to measure the basic mechanica...

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With the in-depth researches on MEMS sensors, a lot of mechanical problems are encountered inevitably. Especially for the comb capacitive micro-machined gyroscope, a typical MEMS inertia sensor, the speciality of its structure and micro size determines the characteristics of the mechanical environment. With the reduction of structural size, the rat...

ZnO materials with a range of different morphologies have been synthesized via a simple solvothermal method with different solvents. Zinc acetylacetonate was used as the zinc source in such solvothermal syntheses for the first time. XRD data showed that single-phase ZnO with the wurtzite crystal structure was obtained for all the solvents used. FE-...

CuO is an important transition metal oxide with a narrow bandgap (Eg = 1.2 eV). CuO has been used as a catalyst, a gas sensor, in anode materials for Li ion batteries. CuO has also been used to prepare high temperature superconductors and magnetoresistance materials. In this paper, CuO with urchin-like morphologies has been synthesized via a simple...

A synthesized γ-MnO2 octahedral molecular sieve was characterized and used to catalyze solvent-free atmospheric oxidation of toluene with molecular oxygen. The γ-MnO2 showed excellent catalytic activity and good selectivity under the mild atmospheric reflux system at a low temperature (110 °C). Under optimized conditions, a 47.8% conversion of tolu...

For a non-linear system excited by a stochastic load which is expressed as a time series, a recursive method based on the Z-transform is presented. To identify the obtained response time series, a discrete wavelet transform (DWT) technique is proposed.

Based on the equations which describe the dynamic behavior of material under high-velocity and high-pressure shock, corresponding equations at shock front whose surface is general space curve surface were established. For concrete material, a normal expansion theory was proposed by which some deceleration about time history of the projectile can be...

By means of the ultimate-density theory, the dynamic cavity-expansion theory and the stress-wave theory, the dynamic responses especially the deceleration curves of a projectile perforating multi-plates concrete targets are analyzed and calculated, the principles of scabbing on the rear surface of target plate are analyzed and illustrated. To verif...

An iteration method of statistic linearization (IMSL) is presented. By this method, an equivalent linear term was formed in geometric relation and then an equivalent stiffness matrix for nonlinear term in vibration equation was established. Using the method to solve the statistic linear vibration equations, the effect of geometric nonlinearity on t...