Practical studies on rockfall simulation by DDA

In this paper,simulations of real rockfall by discontinuous deformation analysis (DDA) are conducted.In the simulations,the energy losses of rockfall are categorized into three types,i.e.the loss by friction,the loss by collision,and the loss by vegetation.Modeling of the energy loss using absolute parameters is conducted by the DDA method.Moreover,in order to verify the applicability and validity of the proposed DDA,field tests on rockfall and corresponding simulations of rockfall tests by DDA are performe...     

Self-diffusion Measurements of Liquid Sn Using the Shear Cell Technique and Stable Density Layering

Metallurgical and Materials Transactions B - By utilizing the shear cell technique and achieving stable density layering with the addition of an alloying element Bi, the self-diffusion coefficients...     

Phase separation in poly(vinyl alcohol)/gelatin blend systems

Blends of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and gelatin obtained from collagen were prepared by mixing aqueous solutions of both samples under various conditions. For the blend hydrogels, the depression of melting temperatures was observed at high PVA content. Similarly to the a-PVA/silk fibroin (SF) system, when the degrees of polymerization of PVA increased, the microphase separation region in a phase diagram of the blend films increased for the a-PVA/gelatin system. In the IR spectra of the blend films, no absorption bands corresponding to a conformational change of gelatin appeared. Comparison of the mechanical properties of the a-PVA/gelatin and a-PVA/SF systems, showed the interaction between PVA and gelatin molecules to be smaller than that between PVA and SF molecules. © 1999 Society of Chemical Industry     

Single-phase line current compensator based on line current detection

We propose the three-phase active filter designed to control the ripple power based on instantaneous ac line power detection. We show that the proposed system has many excellent features such as simple construction, high accuracy, high efficiency, and so on. In this paper, we apply this control principle to single-phase power line compensators such as active filters and reactive power compensators. In this case, we must control the instantaneous current waveform instead of the ripple components of two-axis quantities of the three-phase current or power. The proposed system can be easily constructed and controlled by merely detecting the ac line side current and the dc side voltage of the PWM converter. The system combines many functions, such as a PWM converter, an active filter, a reactive power compensator, without any modifications. In this paper, we compare the proposed system with conventional systems and confirm the feasibility of the system by simulation and experimental results. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 65–73, 1998     

基于缸压的船用柴油机燃烧闭环控制策略研究

针对柴油机全寿命过程中动力性下降及各缸工作不均匀的问题,以MAN 6L16/24型船用柴油机为研究对象,模拟因各缸喷油器老化而引起柴油机动力性下降和各缸工作不均匀,对比分析开环、转速闭环和燃烧闭环等不同控制策略对改善柴油机动力性、工作均匀性的效果及动态控制性能,针对燃烧闭环控制转速滞后性较大的问题,提出转速-燃烧闭环协同控制策略,分析了该控制策略对轨压波动和进气流道阻塞干扰因素的鲁棒性。仿真结果表明协同控制策略可有效改善柴油机各缸工作不均匀和转速响应快速性。     

羊乳高F值肽酶解工艺优化

目的 探究通过生物酶解技术有效得到羊乳高F值肽的关键工艺.方法 以新鲜山羊乳为原料,采用两种酶分步水解法制备高F值肽,以蛋白质水解度和F值为指标,通过单因素试验和响应面分析法分别确定两步酶解的最佳条件,酶解液经活性炭静态吸附去除游离芳香族氨基酸,对脱去芳香族氨基酸后的酶解液进行氨基酸组成分析并测定F值.结果 水解羊乳蛋...     

Composition Regulation by Flow Copolymerization of Methyl Methacrylate and Glycidyl Methacrylate with Free Radical Method

It is important to match the feeding ratio of comonomers to the composition ratio in the resulting copolymers as closely as possible in industrial production, where the goal is often to produce more a homogeneous composition in copolymers. In this study, a flow copolymerization system with a conventionally initiated free radical method, together with randomly selected polymerization conditions is investigated. It is succeeded in achieving a closer match between the composition ratio and feeding ratio than previously reported in the copolymerization of styrene with methyl methacrylate and of glycidyl methacrylate with methyl methacrylate, which will widen the range of applications, by precisely controlling the mixing and heating in a flow polymerization apparatus. This is confirmed by the fact that the estimated values of reactivity ratios, r₁ and r₂, which are used in the reaction kinetics of copolymerization, are close to 1.     

The α/β Hydrolase AzpM Catalyzes Dipeptide Synthesis in Alazopeptin Biosynthesis Using Two Molecules of Carrier Protein-Tethered Amino Acid

During the biosynthesis of alazopeptin, a tripeptide composed of two molecules of 6-diazo-5-oxo-L-norleucine (DON) and one of alanine, the α/β hydrolase AzpM synthesizes the DON-DON dipeptide using DON tethered to the carrier protein AzpF (DON-AzpF). However, whether AzpM catalyzes the condensation of DON-AzpF with DON or DON-AzpF remains unclear. Here, to distinguish between these two condensation possibilities, the reaction catalyzed by AzpM was examined in vitro using a DON analogue, azaserine (AZS). We found that AzpM catalyzed the condensation between AZS-AzpF and DON-AzpF, but not between AZS-AzpF and DON. Possible reaction intermediates, DON-DON-AzpF and AZS-AZS-AzpF, were also detected during AzpM-catalyzed dipeptide formation from DON-AzpF and AZS-AzpF, respectively. From these results, we concluded that AzpM catalyzed the condensation of the two molecules of DON-AzpF and subsequent hydrolysis to produce DON-DON. Thus, AzpM is an unprecedented α/β hydrolase that catalyzes dipeptide synthesis from two molecules of a carrier protein-tethered amino acid.     

Identification and Analysis of the Biosynthetic Gene Cluster for the Indolizidine Alkaloid Iminimycin in Streptomyces griseus

Indolizidine alkaloids, which have versatile bioactivities, are produced by various organisms. Although the biosynthesis of some indolizidine alkaloids has been studied, the enzymatic machinery for their biosynthesis in Streptomyces remains elusive. Here, we report the identification and analysis of the biosynthetic gene cluster for iminimycin, an indolizidine alkaloid with a 6-5-3 tricyclic system containing an iminium cation from Streptomyces griseus. The gene cluster has 22 genes, including four genes encoding polyketide synthases (PKSs), which consist of eight modules in total. In vitro analysis of the first module revealed that its acyltransferase domain selects malonyl-CoA, although predicted to select methylmalonyl-CoA. Inactivation of seven tailoring enzyme-encoding genes and structural elucidation of four compounds accumulated in mutants provided important insights into iminimycin biosynthesis, although some of these compounds appeared to be shunt products. This study expands our knowledge of the biosynthetic machinery of indolizidine alkaloids and the enzymatic chemistry of PKS.