Search Results

1 - 10 of 12 items

  • Author: Ke Wang x
Clear All Modify Search

Abstract

The most attractive structural feature of the three-dimensional (3D) angle-interlock woven structure is that the straight weft yarns are bundled by the undulated warp yarns, which induces the overall good structural stability and a stable fabric structure. Thus the 3-D angle-interlock woven composite (3DAWC) prepared by the vacuum-assisted resin transfer molding (VARTM) curing process has excellent mechanical properties by using the fabric and epoxy resin as the reinforcement and matrix, respectively. The low-velocity impact damage properties of the composites under different drop-weight energies (70, 80, and 100 J) were tested experimentally. The load–displacement curves, energy–time curves, and the ultimate failure modes were obtained to analyze the performance of resistance to low-velocity impact, as well as the impact energy absorption effect and failure mechanism, especially the structural damage characteristics of the 3DAWC subjected to the low-velocity impact of drop weight. By analyzing the obtained experimental results, it is found that the fabric reinforcement is the primary energy absorption component and the impact energy mainly propagates along the longitudinal direction of the yarns, especially the weft yarn system, which is arranged in a straight way. In addition, as the impact energy increases, the energy absorbed and dissipated by the composite increases simultaneously. This phenomenon is manifested in the severity of deformation and damage of the material, i.e., the amount of deformation and size of the damaged area.

Abstract

In recent years, shortage of nurses, high turnover rate, low self-worth, and team instability have become increasingly serious. With the development of positive psychology, more and more nursing managers have begun to attach great importance to the mental health of nurses. Self-esteem, as one of the core indicators of individual mental health, has received extensive attention from researchers in different fields since its inception. This paper reviews and summarizes the research status and development trends of nurses’ self-esteem considering the aspects of self-esteem as a concept, assessment tools, significance, and intervention methods. At the same time, it also puts forward problems that need to be solved by undertaking research into nurses’ self-esteem, in order to provide a reference for further studies on nurses’ self-esteem.

We tested the hypothesis that dietary fi bre (DF) has protective effects against manganese (Mn)-induced neurotoxicity. Forty-eight one-month old Sprague-Dawley rats were randomly divided into six groups: control, 16 % DF, Mn (50 mg kg-1 body weight), Mn+ 4 % DF, Mn+ 8 % DF, and Mn+ 16 % DF. After oral administration of Mn (as MnCl2) by intragastric tube during one month, we determined Mn concentrations in the blood, liver, cerebral cortex, and stool and tested neurobehavioral functions. Administration of Mn was associated with increased Mn concentration in the blood, liver, and cerebral cortex and increased Mn excretion in the stool. Aberrations in neurobehavioral performance included increases in escape latency and number of errors and decrease in step-down latency. Irrespective of the applied dose, the addition of DF in forage decreased tissue Mn concentrations and increased Mn excretion rate in the stool by 20 % to 35 %. All neurobehavioral aberrations were also improved. Our fi ndings show that oral exposure to Mn may cause neurobehavioral abnormalities in adult rats that could be effi ciently alleviated by concomitant supplementation of DF in animal feed.

Abstract

High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

Abstract

A model is developed to describe the pressure dependence of the band gap energy for the dilute nitride GaNxAs1–x. It is found that the sublinear pressure dependence of E is due to the coupling interaction between E+ and E. We have also found that GaNxAs1−x needs much larger pressure than GaAs to realize the transition from direct to indirect band gap. It is due to two factors. One is the coupling interaction between the E+ and E. The other is that the energy difference between the X conduction band minimum (CBM) and the G CBM in GaNxAs1−x is larger than that in GaAs. In addition, we explain the phenomenon that the energy difference between the X CBM and the G CBM in GaNxAs1−x is larger than that in GaAs. It is due to the impurity-host interaction.

Abstract

Triethyl citrate (TEC) was applied in the preparation of cigarette filter rods by two approaches. One was to utilize TEC as a plasticizer sprayed onto the surface of cellulose acetate (CA) fibers. The other was to apply TEC as an additive coated onto the cellulosic paper of acetate-paper dual filters. Three types of cigarette filter rods, namely, triethyl citrate-cellulose acetate (TEC-CA) filter rods, triethyl citrate-cellulose acetate-paper (TEC-CA-paper) dual filter rods and cellulose acetate-paper-triethyl citrate (CA-paper-TEC) dual filter rods, were manufactured. In order to promote the curing of CA rods, high-frequency radiation was introduced into the procedure of filter manufacture. Then Virginia type cigarettes, combined with the three kinds of prepared filter rods were manufactured and the removal efficiency of phenols from the cigarette mainstream smoke was investigated. The results revealed that no matter where the triethyl citrate was applied as plasticizer or coating additive, the content of phenol, o-, m-and p-cresol in cigarette mainstream smoke could be greatly reduced. The optimal removal efficiency for phenol was 50% compared with the control. [Beitr. Tabakforsch. Int. 26 (2014) 176-182]

Abstract

Because face images are naturally two-dimensional data, there have been several 2D feature extraction methods to deal with facial images while there are few 2D effective classifiers. Meanwhile, there is an increasing interest in the multilinear subspace analysis and many methods have been proposed to operate directly on these tensorial data during the past several years. One of these popular unsupervised multilinear algorithms is Multilinear Principal Component Analysis (MPCA) while another of the supervised multilinear algorithm is Multilinear Discriminant Analysis (MDA). Then a MPCA+MDA method has been introduced to deal with the tensorial signal. However, due to the no convergence of MDA, it is difficult for MPCA+MDA to obtain a precise result. Hence, to overcome this limitation, a new MPCA plus General Tensor Discriminant Analysis (GTDA) solution with well convergence is presented for tensorial face images feature extraction in this paper. Several experiments are carried out to evaluate the performance of MPCA+GTDA on different databases and the results show that this method has the potential to achieve comparative effect as MPCA+MDA.

Abstract

Three-dimensional angle-interlock woven composites (3DAWCs) are widely used for their excellent mechanical properties. The most significant feature is the existence of the undulated warp yarns along the thickness direction, which makes it interesting to study the mechanical properties in the warp direction. The quasi-static tensile behavior of a layer-to-layer 3DAWC along the undulated warp direction was studied by experimental and finite element analysis (FEA) methods. Based on the experimental results, the typical failure mode involving fibers, resin, and their interfaces was found. According to the FEA results, the stress concentration effect, key structural regions, and microstructural (yarn and resin) damage mechanism were obtained, which provided effective guidance for structural optimization design of the 3DAWC with stronger tensile resistance performance. In addition, the three-step progressive failure process of the 3DAWC under quasi-static tensile load was also described at the “yarn–resin” microstructural level.

Abstract

The quasi-static tensile damage behavior of one type of layer-to-layer 3-Dimensional Angle-interlock Woven Composite (3DAWC) was tested and analyzed in this paper. Incorporated with the acoustic emission (AE) events monitoring, the mechanical behavior of the 3DAWC under tensile loading condition was characterized. The Load-Extension curve, Load/AE events-Time curves occurred during the entire testing process and tensile damage modes were recorded to characterize and summarize the mechanical properties and damage mechanism of the 3DAWC subjected to tensile loading. It was found that the tensile damage of the 3DAWC could be summarized into 3 steps. And each step has a distinct primary damage mode. Moreover, the resin cracks, resin-yarn interface debonding and yarn breakages were the main damage modes for the 3DAWC.

Abstract

Objective

The aim of this study was to explore the characteristics of and preventive management strategies for suicidal inpatients in a general hospital.

Methods

A total of 54 suicide victims were drawn from a patient safety adverse event network reporting system during hospitalization in a general hospital from November 2008 to January 2017.

Results

Subjects who committed suicide in the general hospital were women and those who suffered from malignant neoplasms during general hospital treatment. Furthermore, most of the patients who committed suicide used more violent suicide methods. The most common and lethal means was jumping from heights at the windowsill.

Conclusions

It is concluded that management strategies for suicide prevention can be provided from the aspects of patients, medical staff and the hospital environment. It is not only urgent but also feasible to reduce the suicide rate of inpatients and further improve hospital safety management.