优化流水线速度

过去我们讨论了通过适当激增及其他一些方法来优化生产流水线.受最近的一些咨询经验的启发让我们思考一下最佳生产线速度和返工的问题.     

Quantitative liver ADC measurements using diffusion-weighted MRI at 3 Tesla: evaluation of reproducibility and perfusion dependence using different techniques for respiratory compensation

Object

Diffusion weighted imaging (DWI) of the liver suffers from low signal to noise making 3 Tesla (3 T) an attractive option, but 3 T data is scarce. It was the aim to study the influence of different b values and respiratory compensation methods (RCM) on the apparent diffusion coefficient (ADC) level and on ADC reproducibility at 3 T.

Materials and methods

Ten healthy volunteers and 12 patients with malignant liver lesions underwent repeated (2–22 days) breathhold, free-breathing and respiratory triggered DWI at 3 T using b values between 0 and 1,000 s/mm².

Results

The ADCs changed up to 150 % in healthy livers and up to 48 % in malignant lesions depending on b value combinations. Best ADC reproducibility in healthy livers were obtained with respiratory triggering (95 % limits of agreement: ±0.12) and free-breathing (±0.14). In malignant lesions equivalent reproducibility was obtained with less RCM dependence. The use of a lower maximum b value (b = 500) decreased reproducibility (±0.14 to ±0.32) in both normal liver and malignant lesions.

Conclusion

Large differences in absolute ADC values and reproducibility caused by varying combinations of clinically realistic b values were demonstrated. Different RCMs caused smaller differences. Lowering maximum b value to 500 increased limits of agreement up to a factor of two. Serial ADC changes larger than approximately 15 % can be detected confidently on an individual basis in both malignant lesions and normal liver parenchyma at 3 T using appropriate b values and respiratory compensation.     

An approximate model for three-dimensional alternating current potential drop analyses using a commercial finite element code

Alternating current potential drop (ACPD) is an established technique for non-destructive testing and materials characterisation. Finite element (FE) simulation is a very useful tool for the optimisation of probes and the prediction of test results, but three-dimensional models of ACPD problems are computationally intensive. This paper presents a new, simple model in which frequency-related effects are taken into account by appropriately modifying the geometry of the modelled structure: a DC analysis can then be performed on a smaller domain, thus reducing the computational power required. The results of experimental tests for the validation of the model are also presented and discussed.     

MRI of human hair

Introduction  Hair care for humans is a major world industry with specialised tools, chemicals and techniques. Studying the effect of hair care products has become a considerable field of research, and besides mechanical and optical testing numerous advanced analytical techniques have been employed in this area. In the present work, another means of studying the properties of hair is added by demonstrating the feasibility of magnetic resonance imaging (MRI) of the human hair. Materials and methods  Established dedicated nuclear magnetic resonance microscopy hardware (solenoidal radiofrequency microcoils and planar field gradients) and methods (constant time imaging) were adapted to the specific needs of hair MRI. Results  Images were produced at a spatial resolution high enough to resolve the inner structure of the hair, showing contrast between cortex and medulla. Quantitative evaluation of a scan series with different echo times provided a value of 2.6 ms for the cortex and a water content of about 90% for hairs saturated with water. Conclusion  The demonstration of the feasibility of hair MRI potentially adds a new tool to the large variety of analytical methods used nowadays in the development of hair care products.     

Anthocyanin composition in Cabernet Sauvignon red wine vinegar obtained by submerged acetification

Vinegars elaborated from white wine can be characterized by their phenolic composition. Indeed, for authenticity purpose, phenolic composition can be used to identify Sherry and Balsamic vinegars. However, the phenolic composition of red wine vinegars has scarcely been studied. Anthocyanin compounds in particular remain largely unknown. This study focuses on the analysis of anthocyanin compounds in red wine vinegar and the effect of acetification with submerged culture on such vinegars.The vinegar used in this study was produced from a young Cabernet Sauvignon wine in a laboratory-scale fermenter. Subsequent analyses of both wine and vinegar included their anthocyanin profile (by LC/MS), and their non-anthocyanin phenolic profile (by LC/DAD). In addition, wine and vinegar anthocyanin extracts were fractionated by CCC to determine the contribution of the fractions to overall antioxidant activity (AA), using ORAC, FRAP and DPPH assays.A total of 20 anthocyanin compounds were identified in the vinegar. As far as we know, this is the first time that anthocyanin-derived pigments (pyranoanthocyanins and ethyl-linked compounds) have been identified in red vinegar in such detail. Moreover, an original contribution of this study is the identification for the first time of catechyl-pyranocyanidin-3-glucoside in vinegar and wine, as well as two anthocyanin compounds not previously reported in vinegar or Cabernet Sauvignon wine: acetyl vitisin B and coumaroyl vitisin B. After the acetification process, vitisin-type and ethyl-linked compounds increased and monomeric anthocyanins, phenolic acids (ferulic acid, caffeic acid and caftaric acid) and flavan-3-ol ((+)-catechin) decreased.Although the proportion by weight of the polymeric compound fraction is similar in wine and vinegar, the AA of these polymers in vinegar is significantly greater (p < 0.05). We have also determined for the first time an approximate value of AA for malvidin-3-(6-acetyl)-glucoside isolated from vinegar.     

Compensation of magnetic disturbances improves inertial and magnetic sensing of human body segment orientation.

This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error, and magnetic disturbance error are estimated. The filter was tested under quasi-static and dynamic conditions with ferromagnetic materials close to the sensor module. The quasi-static experiments implied static positions and rotations around the three axes. In the dynamic experiments, three-dimensional rotations were performed near a metal tool case. The orientation estimated by the filter was compared with the orientation obtained with an optical reference system Vicon. Results show accurate and drift-free orientation estimates. The compensation results in a significant difference (p < 0.01) between the orientation estimates with compensation of magnetic disturbances in comparison to no compensation or only gyroscopes. The average static error was 1.4 degrees (standard deviation 0.4) in the magnetically disturbed experiments. The dynamic error was 2.6 degrees root means square.     

A/B-Ratio and Transport Properties of (La0.85Sr0.15)sCoO3−δ Perovskites

The perovskites (La_0.85Sr_0.15)_0.98CoO_{3 –} and (La_0.85Sr_0.15)_1.00CoO_{3 –} have been investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical conductivity relaxation (ECR). This system was chosen in order to investigate the influence of cation vacancies on the transport properties in the materials. From ECR-measurements it is concluded that no difference in the chemical diffusion coefficient for oxide ions between the two samples can be found. The activation energy for the chemical diffusion coefficient has been found to be 107 ± 5 kJ mol^{– 1}. However, the surface exchange coefficient differs between the two samples. The Co-rich sample has a significantly higher surface exchange coefficient than the A/B-stoichiometric sample. For both samples the surface exchange coefficient was almost independent of the temperature. At all temperatures the Co-rich sample had a significantly higher electrical conductivity. The difference in electrical conductivity between the two samples diminished when going to higher temperatures. Both materials can be assigned to a single phase hexagonal perovskite. An annealed sample of (La_0.85Sr_0.15)_0.98CoO_{3 –} did however contain an unidentified secondary phase on the surface.