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As a fast-growing commercial wood species, poplar often produces tension wood because of the leaning stems of logs, which has a great impact on the production and utilization. The gelatinous layer (G-layer) was the unique component of tension wood, almost entirely composed of cellulose, which was the main reason for the special performance of the poplar tension wood. This study used the transmission electron microscopy, Raman spectroscopy and nanoindentation to examine the ultrastructure and mechanical properties of every wall layer of the poplar cell wall in order to figure out the ultrastructure and properties of G-layer. In particular, the nanoindentation mapping was combined with manual screening to obtain the mechanical performance data of each layer. The fibers in the tension wood were gelatinous wood fibers with obvious G-layers, and the thickness was 2.53 μm, which was much larger than that of other wall layers. Compared with the wood fiber in the opposite wood, the S1 layer was thicker and the S2 layer was thinner, and the entire cell wall thickness was increased in tension wood. G-layer in tension wood had a very high cellulose content, and the Raman strength of lignin was weak. In general, the micromechanical properties of poplar tension wood were better, which was consistent with its macromechanical properties. The characteristics of G-layer, including high cellulose content, small microfibril angle and high crystallinity, made G-layer own better elastic modulus (14.08 GPa) and hardness (0.45 GPa) than other wall layers in the tension wood. Moreover, G-layer had a high proportion in the tension wood cell wall, so the average longitudinal elastic modulus and hardness of wood fiber cells in the tension wood were also higher than those in the opposite wood.

As an important commodity wood material, poplar has porous structure, which is worthy of being investigated. Especially, the lignin concentration is closely related to the formation and change of pores. Although a few studies reported the relation between the pore volume and the lignin removal of the ground wood (Stone and Scallan in J Polym Sci C Polym Symp 11(1):13–25, 1965), no information of the distribution of pore sizes versus the whole delignification process steps was reported. This study initially explored the effect of delignification level on the pore size distribution and pore structure in poplar cell walls using nitrogen absorption measurement. It was found that delignification increased the N2 adsorption amount and specific surface area of poplar. It also caused a large number of mesopores in the cell wall, mainly in the 2–10 nm pore size range, and decreased the average pore size. The whole delignification process can be roughly divided into three major phases, namely, the initial phase, the transitional phase and the stable phase, in which, the change process was not completely uniform. During the delignification, the size of poplar cell wall pores continued reducing, and finally a large number of uniform pores of about 2.1 nm was formed.

The objective of this paper is to propose an active ripple filter (ARF) using the patented DC-side direct current control for eliminating the double-line-frequency current ripple in a single-phase DC/AC conversion system. The proposed ARF and its control strategies can not only prolong the usage life of the DC energy source but also improve the DC/AC system performance. At first, the phenomena of double-line-frequency current ripple and the operation principle of the ARF are illustrated. Then, steady-state analysis, small-signal model, and control loop design of the ARF architecture are derived. The proposed control system includes: (1) a DC current control loop to provide the excellent ripple eliminating performance on the output of the DC energy source; (2) a voltage control loop for the high-side DC-bus voltage of the ARF to achieve good steady-state and transient-state responses; (3) a voltage feedforward loop for the low-side voltage of the ARF to cancel the voltage fluctuation caused by the instability of the DC energy source. Finally, the feasibility of the proposed concept can be verified by the system simulation, and the experimental results show that the nearly zero double-line-frequency current ripple on the DC-side in a single-phase DC/AC conversion system can be achieved.

Switch-capacitor battery equalizer (SCBE) is widely used because of its simple structure, small PCB area, and no inductance components. Its balance current is sawtooth or trapezoid waveform is significantly different from traditional charger’s DC waveform. From many non-DC charging literatures, it can be found that different frequency and waveform shape will cause the significantly different battery charging performance. Therefore, this paper explores the near-optimal balance current frequency and waveform shape of the SCBE from electrochemical impedance to optimize its battery balance performance. Further, the LC resonant battery equalizer (LC-RBE) is proposed to perform battery balancing with a sine wave. Experiments have shown that the better efficiency and lower battery temperature rise are obtained when the LC-RBE work with the battery minimum ac impedance frequency.

Well known PS-VA technology has been extensively used for TV application, but the image sticking issue is still a concern. In order to improve the image sticking performance of PS-VA TV panel, the condition of both UV1 and UV2 process are investigated to find out the relationship between the residual amount of RM and the image sticking performance. It shows that the image sticking performance is related to the RM residual amount. As we know, ion density is a factor of image sticking issue. Based on analysis on the relationship between ion density and RM residual amount, we develop a new technology to reduce the image sticking issue in PS-VA mode. Furthermore, another method is provided in this work to improve the image sticking performance by designing a new LC host mixture which has lower residual amount of RM. The technical data is obtained including ion density data measured by Toyo 6254 and surface profile investigation by SEM and AFM.

The utilization of liquid CO2 for enhanced coalbed methane recovery has great environmental and commercial potential to sink greenhouse gas emissions and enchance CH4 extraction. A comprehensive understanding of mechanical properties and micro-scale changes to coal saturated with liquid CO2 would fill the knowledge gap regarding CO2 utilization and be greatly beneficial to industry. The present study employed extensive experimentation using uniaxial compression test, acoustic emission (AE) monitoring, Brazilian splitting test, scanning electron microscopy, and energy dispersive X-ray diffraction spectrometry to determine the damage features of coal microstructure, mechanical characteristics, failure modes, and minerals variation between original and liquid CO2-saturated coal samples. The pre-existing cracks were enlarged and more cracks were generated in the saturated coal samples than in the raw samples. The liquid CO2-saturated coal samples exhibited larger plastic deformation and lower compressive strength in unstable crack propagation stage and more AE counts in rupture stage than those of unsaturated samples. The average compressive strength and tensile strength of the saturated samples were 21% and 27% lower than that of the raw samples. More ragged failure cracks were formed in the liquid CO2-saturated coal specimens than in the unsaturated coal samples. The failure modes of the saturated coal samples were inclined to ductile fracture as opposed to brittle fracture in the unsaturated coal samples. The width and number of micro-cracks on the saturated samples were both increased, and the amount of partial minerals that filled in the micro-cracks reduced after liquid CO2 saturation, which indicated an interaction between minerals in coal and liquid CO2 during the saturation process.

In this paper, the ac impedance analysis is used to explore the optimal discharging frequency for a Li-ion battery. Experiments indicate that the optimal discharging frequency is at the minimum ac impedance frequency fZmin for a conventional pulse-current (PC) discharging. In addition, a sinusoidal current (SC) discharging strategy is also proposed to achieve better performances. This SC discharging strategy improves the discharging capacity, discharging efficiency, and rising temperature of the Li-ion battery by about 1.3%, 1.32%, and 41.9%, respectively, as compared with the traditional constant-current discharging.

In this paper, a phase-locked bidirectional converter (BC) (PLBC) with pulse charge function is proposed to improve the battery charge efficiency. The circuit topology of the proposed PLBC is the same as that of the current-pump phase-locked loop (CP-PLL). Using CP-PLL inherent characteristics, a pulse current with bidirectional flow can be automatically implemented. A design example for a 42-V/14-V dual-voltage PowerNet is built to assess the PLBC's performance. Compared with the conventional BC, the battery charge efficiency ηb is improved by about 2.8%. Moreover, the battery increased temperature is reduced by about 5.7 °C simultaneously.

The spectral compression performance of the fundamental soliton in a dispersion-increasing fiber is investigated through numerically solving the generalized nonlinear Schrdinger equation.The influence of the input peak power on the output spectral width and the output center wavelength is analyzed,and the evolution of the pulse width,the spectral width and the chirping in the fiber are described.The calculation results show that spectral compression from 12.6 nm to 5.2 nm,i.e.spectral compression rate of 2.42,can be realized for the fundamental soliton with the pulse width of 200 fs and the center wavelength of 1 550 nm propagating in the dispersion-increasing fiber with the length of 100 m whose group-velocity dispersion parameter linearly varies from -1 ps2/km to -11 ps2/km.

To study the dynamic process excited by femtsecond laser,a carrier model with three energy level and trap is constructed,with which the electron rate equation is obtained.The numerical simulation is used to calculate the electron number change of each energy level and the differentiated absorbtion rate as the time goes by.With the change of the electron's absorption cross-section,differentiated absorbtion rate will have a ultrafast change process.Compared with the experimental result of Fanxin Wu,the differentiated absorbtion rate curves are basically the same,which shows the model have some rationality.

In this paper, the theoretical analysis and simulating calculation were conducted for a basic two-stage semiconductor thermoelectric module, which contains one thermocouple in the second stage and several thermocouples in the first stage. The study focused on the configuration of the two-stage semiconductor thermoelectric cooler, especially investigating the influences of some parameters, such as the current I1 of the first stage, the area A1 of every thermocouple and the number n of thermocouples in the first stage, on the cooling performance of the module. The obtained results of analysis indicate that changing the current I1 of the first stage, the area A1 of thermocouples and the number n of thermocouples in the first stage can improve the cooling performance of the module. These results can be used to optimize the configuration of the two-stage semiconductor thermoelectric module and provide guides for the design and application of thermoelectric cooler.

In this paper, a variable frequency pulse charge system (VFPCS), that can detect and dynamically track the optimal charge frequency, is proposed to improve the battery-charge response. To assess the system performance, a prototype of the VFPCS for 600-mAh lithium-ion battery is designed and implemented. Compared with the standard constant-current and constant-voltage charge system, the charge speed of the proposed VFPCS is improved above 24%, while the proposed VFPCS is improved above 10% compared with the conventional fixed-frequency pulse charge system. The results indicate that the VFPCS can actually provide pulse with optimal frequency to charge the battery and the charge response is improved

This paper proposes a new Reflex™ charging strategy mainly suitable for the 18650 lithium ion battery. This new charging strategy current consists of a forward current, a short break time, and a reverse current. The interval of break time not only provides the buffer time for uniforming electrolyte ions distribution, but also achieves the purpose of delaying cell polarization. As a result, the charging efficiency of a battery is improved. To validate the charging performance of the proposed Reflex™ charging strategy, the charging capacity of the proposed strategy was compared to the conventional constant current charging strategy during the same period of charging time. The experimental results show that a 0.73%charge capacity is increased when implementing this new charging strategy.

This paper proposes a fast measurement method to estimate the state of charge (SOC) of Li-ion battery based on AC impedance. The AC impedances of an 18650 lithium-ion battery related to various states of charge are measured firstly using a commercial AC impedance analyzer to form a database. Using the relationships between the state of charge and the AC impedance, the proposed method can obtain the battery state of charge quickly. To validate the accuracy of the proposed method, SOC 0%, 50%, and 100% are tested and compared in this paper. The results show that the error is 8.636%, 2.604%, and 0.6%, respectively.

Finite element analysis plays an important role in dental implant design. The objective of this study was to show the effect of the overall geometry of dental implants on their biomechanics after implantation. In this study, 12 dental implants, with the same length, diameter and screw design, were simulated from different implant systems. Numerical model of right mandibular incisor bone segment was generated from CT data. The von-Mises stress distributions and the total deformation distributions under vertical/lateral load were compared for each implant by scores ranking method. The implants with cylindrical shapes had highest scores. Results indicated that cylindrical shape represented better geometry over taper implant. This study is helpful in choosing the optimal dental implant for clinical application and also contributes to individual implant design. Our study could also provide reference for choice and modification of dental implant in any other insertion sites and bone qualities.

In the present article, the effects of Al, Zn, Fe, Ni, and Cu powders on the thermal degradation of waste polystyrene were studied. The results show that the catalytic effects of metal powders have a relationship with their activities. The catalytic effects increase with the increasing activities of metals. It is suggested that polystyrene degrades through a transient intermediate in the presence of metal powders, and the degradation of the transient intermediate is the rate-determining step. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1139–1143, 1999

In this paper, the AC impedance analysis is used to explore the optimal discharging frequency for a Li-ion battery. Experiments indicate that the optimal discharging frequency is at the minimum AC impedance frequency f Zmin for a conventional pulse current (PC) discharging This PC discharging strategy improves the discharging time, the discharging efficiency, and the minimum rising temperature of the Li-ion battery by about 0.9%, 0.9%, and 15.8%, respectively, as compared with the traditional constant-current (CC) discharging.

Statement of problem A variety of zygomatic implantation techniques currently exist; however, a consensus regarding the most suitable method has not yet been reached. Purpose The purpose of this study was to evaluate and compare 3 zygomatic implantation techniques and to clarify the optimal number and position of zygomatic and dental implants for the reconstruction of the severely atrophied edentulous maxilla. Material and methods A 3-dimensional finite element analysis craniofacial model was constructed from the computed tomography data of a selected patient with a severely atrophic edentulous maxilla. Modeled zygomatic implants were inserted into the craniofacial model with 3 surgical techniques (classic Branemark, exteriorized, and extramaxillary), and with 3 model variations that involved the number and position of zygomatic and dental implants. The zygomatic implants were loaded with a vertical force of 150 N and a lateral force of 50 N. The stresses on and deformations of the bones and implants were then observed and compared. Results No obvious differences in the amount and distribution of stress on the external craniofacial bones were detected in the models. The lowest stresses on the zygomatic implants were observed in the exteriorized technique group. The lowest deformations of the bone that surrounds zygomatic implants and dental implants were observed in the exteriorized technique and classic Branemark technique groups. For the exteriorized technique group, the model with 1 dental implant in the site of the maxillary lateral incisor exhibited the lowest stress on the zygomatic implants and the least deformation of the bone surrounding the zygomatic and dental implants. Conclusions All 3 zygomatic implant techniques resulted in more or less homogeneous transference of force and thus could reconstruct the edentulous maxilla; however, the exteriorized technique with 1 dental implant in the lateral incisor appeared to be the most appropriate reconstruction method for the severely atrophied edentulous maxilla.

A zero-voltage switching DC/DC converter with the high circuit efficiency is presented in this paper. The structure of a full-bridge converter with the phase-shift PWM is used to achieve the zero-voltage switching in the transformer primary side for the purpose of the switching lose reduction. In order to increase the converter efficiency in the transformer secondary side, a current doublers rectifier, low current ripple, and synchronized rectifier circuits are also adopted. The detail circuit operation and mathematical analysis are presented in this paper. The measured efficiency on the prototype, a DC/DC converter 200V/24V with 6A output current, is higher than 88%.

This paper aims to explore the optimal Li-ion battery charging frequency by using AC impedance technique. The experiment proves that the optimal charging frequency is the point of the minimum AC impedance. In such a situation of the battery charged by the optimal charging frequency, the charging time and charging efficiency are improved above 30.68% and 30.6%.

In this paper, a Li-ion battery is considered as a grey system and a predictable Li-ion battery charge system is implemented using the grey prediction theory. The proposed grey-predicted Li-ion battery charge system (GP-LBCS) can decrease charge time and avoid overcharge to increase life cycle. To assess the system performance, a prototype of the GP-LBCS is implemented. Experiments shown that the GM(1,1) model can precisely predict the Li-ion battery voltage, and the charge speed is increased about 16% such that the safe charge condition is held. These experimental results are very attractive as theory predicts.

In this paper, a variable frequency pulse charge system (VFPCS), that can detect and dynamically track the optimal charge frequency, is proposed to improve the Li-ion battery charge response. To assess the system performance, a prototype of the VFPCS is implemented. In comparison with standard CC-CV charging system and conventional fixed-frequency pulse charge system, the charge time of the proposed VFPCS is improved about 25% and 10%, respectively. The results indicate that the VFPCS can actually provide pulse with optimal frequency to charge the battery and the charge response is improved as theory predicted.

Subwavelength and nanometer diameter optical fibers have the optical property of enhanced evanescent fields, which makes them very sensitive to the index change of the ambient medium. In this paper, a novel refractometric sensor based on fiber Bragg grating in micro/nano-fiber (MNFBG) is proposed, integrating the enhanced evanescent fields of micro/nano-fiber (MNF) with wavelength choice feature of FBG, and the fabrication about MNFBG is discussed. Refractive index sensing characteristics is comprehensively investigated in theories, and the simulation of sensing the variation of ambient refractive index is performed by using the software of OptiGrating. Results show the sensitivity of the MNFBG is increasing with the decrease of the radium of the MNF. MNFBG with the radius of 400nm can achieve the sensitivity as high as 993nm/RIU. This value is enhanced by 170 times over that of the FBG with etched cladding, which demonstrates that MNFBG has great potential of application in miniaturized, high-sensitivity refractometric sensors.

The Imaging theory of two-photon and multi-photon confocal scanning microscopy is presented. The three-dimensional point spread function and three-dimensional optical transfer function of two-photon confocal scanning microscopy is derived. By using the three-dimensional point spread function and three-dimensional optical transfer function theory, we have proved that the horizontal and vertical resolutions of two-photon confocal scanning microscopy are higher than those of the single photon confocal scanning microscopy, and the space resolution of multi-photon confocal scanning microscopy is higher than that of two-photon confocal scanning microscopy.

The theoretical analysis of photoacoustic Raman spectroscopy (PARS) is prese-nted The general expressions of PARS signal in solid and liquid samples are derived and the theoretical estimation is given.