On the use of edge cracked short bend beam specimen for PMMA fracture toughness testing under mixed-mode I/II

In this paper an inclined edge cracked short beam specimen subjected to symmetric three-point bend loading was designed and examined for conducting mixed-mode I/II fracture toughness experiments. The aspect ratio (i.e. length to width ratio) and the loading span distance are considered much lower than the other conventional cracked bend beam samples. Crack tip parameters such as stress intensity factors and T-stress were computed numerically for this specimen by several finite element analyses and it was demonstrated that the specimen is able to produce full combinations of mode I and II including pure mode II. The practical capability of the short bend beam specimen was studied experimentally by conducting a set of mixed-mode fracture tests on PolymethylMethacrylate (PMMA) as a well-known model brittle material. The critical stress intensity factors, the direction of fracture kinking and the path of fracture trajectory were investigated both experimentally and theoretically using two stress and strain-based fracture criteria. The fracture toughness of tested PMMA was decreased by moving towards mode II case due to the effect of T-stress on the fracture mechanism of the short bend beam specimen.     

Simultaneous and Fast Detection of Anions in Snow Using Short Tube by Capillary Zone Electrophoresis

A capillary zone electrophoresis (CZE) method applied short-effective length of capillary (11 cm) and low separation voltage (5 kV) was developed for the fast and quantitative determination of Cl m , $ {\rm NO}_2^ - $ , $ {\rm SO}_4^{2 - } $ , $ {\rm NO}_3^ - $ , $ {\rm HCO}_3^ - $ in snow sample. Baseline separation of inorganic anions and organic anions was achieved within 55 s. Indirect absorbance detection of anions was accomplished with a chromate - based background electrolyte modified with cetyltrimethylammonium bromide (CTAB) and acetonitrile at pH 9.5. The effect of the pH, the concentration of electrolyte and modifiers on the resolution was investigated. The application of electrokinetic injection using butyric acid as internal standard created the described method fast, sensitive, and quantitative, with good relative standard deviation (RSD), for migration times from 0.1 to 0.3% and for peak areas from 1.8 to 4.0%. The limits of detection (LOD) were 0.03 mg L m 1 Cl m , 0.1 mg L m 1 $ {\rm NO}_2^ - $ , 0.07 mg L m 1 $ {\rm SO}_4^{2 - } $ , 0.08 mg L m 1 $ {\rm NO}_3^ - $ , 0.05 mg L m 1 F m , and 0.2 mg L m 1 $ {\rm HCO}_3^ - $ , respectively. Standard addition recoveries of Cl m , $ {\rm NO}_2^ - $ , $ {\rm SO}_4^{2 - } $ , $ {\rm NO}_3^ - $ , F m , and $ {\rm HCO}_3^ - $ in snow sample were between 91 and 104%. This method has been shown promising results for the determination of small anions in snow sample.     

Genotyping of exons 1 to 20 in Duchenne muscular dystrophy by universal multiplex PCR and short‐end capillary electrophoresis

One rapid CE method was established to diagnose Duchenne muscular dystrophy (DMD). DMD is a severe recessive inherited disorder frequently caused by gene deletions. Among them, exons 1–20 account for nearly 30% of occurrences. In this study, the universal multiplex PCR was used to enhance the fluorescently labeling efficiency, which was performed only by one universal fluorescent primer. After PCR, a short‐end injection CE (short‐end CE) speeded up the genotyping of the DMD gene. This method involved no extra purification, and was completed within 9 min. The CE conditions contained a polymer solution of 1.5% hydroxylethylcellulose in 1× TBE buffer at 6 kV for separation. This method was applied to test six DMD patients and one healthy male person. The results showed good agreement with those of multiplex ligation‐dependent probe amplification. This method can be applied for clinical diagnosis of DMD disease. Accurate diagnosis of the DMD gene is the best way to prevent the disease.     

Match statistics for sequence-based alleles in profiles from forensic PCR-mps kits

The first autosomal sequence-based allele (aka SNP-STR haplotype) frequency database for forensic massively parallel sequencing (MPS) has been published, thereby removing one of the remaining barriers to implementing MPS in casework. The database was developed using a specific set of flank trim sites. If different trim sites or different kits with different primers are used for casework, then SNP-STR haplotypes may be detected that do not have frequencies in the database. We describe a procedure to address calculation of match probabilities when casework samples are generated using an MPS kit with different trim sites than those present in the relevant population frequency database. The procedure provides a framework for comparison of any MPS kit or database combination while also accommodating comparison of MPS and CE profiles.     

基于PLC的环境模拟系统温度控制算法的研究与实现

针对环境模拟试验温度控制系统中被控对象存在的非线性、时滞等特点,本文采用区间限幅PID控制算法和模糊PID控制算法对传统控制方法进行了改进。首先为了解决模拟量三通粗调阀调节缓慢的缺点,建立了区间限幅PID控制算法的控制规则表,并将其在PLC中实现。其次提出用模糊PID控制算法来解决电加热器的非线性、大时滞性问题,并结合实际控制经验建立了模糊控制规则表,然后将模糊PID控制算法在PLC中进行实现。最后将限幅PID和模糊PID控制算法应用于某大型环境模拟试验控制系统,实验结果表明利用改进算法对温度控制具有良好的稳定性及精确度。     

A novel nanoscale fin field effect transistor by amended channel: Investigation and fundamental physics

The present paper proposes a new Fin Field Effect Transistor (FinFET) with an amended Channel (AC). The fin region consists of two sections; the lower part which has a rounded shape and the upper part of fin as conventional FinFETs, is cubic. The AC-FinFET devices are proven to have a lower threshold voltage roll-off, reduced DIBL, better subthreshold slope characteristics, and a better gate capacitance in comparison with the C-FinFET. Moreover, the simulation result with three-dimensional and two-carrier device simulator demonstrates an improved output characteristic of the proposed structure due to reduction of self-heating effect. Due to the rounded shape of the lower fin region and decreasing corner effects there, the heat can flow easily, and the device temperature will decrease. Also the gate control over the channel increases due to the narrow upper part of the fin. The paper, thus, attempts to show the advantages of higher performance AC-FinFET device over the conventional one, and its effect on the operation of nanoscale devices.     

The effect of short glass fibers on the process behavior of polyamide 12 during selective laser beam melting

In additive manufacturing, polymer composites are used for setting tailored properties. Short glass fibers can be used as fillers for polyamide 12 for enhancing stiffness or tensile strength as well as for reducing shrinkage. In this paper, the effects of short glass fibers on polyamide 12 concerning powder properties, process behavior and part properties in laser beam melting of polymers (SLS) are investigated. It could be shown that by increasing the short glass fiber content powder properties as well as part properties are immensely affected. By adding glass fibers, powder properties, like flowability and diffuse reflection decrease. The isothermal crystallization changes resulting in a narrower processing window. Concerning mechanical properties, short glass fibers allow for a higher stiffness until a critical limit of filler concentration within this study is reached, after which the tensile strength decreases. The elongation of break decreases by rising the filler content.     

熵驱大分子胶体粒子的柱状受限结晶

熵是物理化学的基本状态参量,在统计力学和热力学中处于核心位置.按照玻尔兹曼的微观解释,熵可以由孤立系统微观状态的数目(W)给出,即S=kBlnW,这里kB为玻尔兹曼常数[1,2].根据此公式,微观状态数越多,系统越混乱,熵越大,所以熵常被视作体系无序程度的度量.但熵增仅对应体系微观状态数的增加,与可观测的结构有序程度无关[3~5].在一些典型的软物质体系中,结构越有序熵反而越大,如胶体硬球在随机密堆积点的有序结晶[6]及描述各向异性棒状分子从各向同性相到向列相转变的Onsager原理[7].     

Characterization of sequence variation at 30 autosomal STRs in Chinese Han and Tibetan populations

Massively parallel sequencing (MPS) technologies have the ability to reveal sequence variations within STR alleles as well as their nominal allele lengths, which have traditionally been detected by CE instruments. Recently, Thermo Fisher Scientific has updated the MPS-STR panel, named the Precision ID GlobalFiler next-generation sequencing (NGS) STR Panel version 2, with primers redesigned to add two pentanucleotide tandem repeat loci and profile interpretation supported by the Converge software. Using the Ion Chef System, the Ion S5XL System, and the Converge software, genetic variations were characterized within STR repeat and flanking regions of 30 autosomal STR markers in 115 unrelated individuals from two Chinese population groups (58 Tibetans and 57 Hans). Nineteen STRs demonstrated a relative increase in diversity with the variant sequence alleles compared with those of traditional nominal length alleles. In total, 390 alleles were identified by their sequences compared with 258 alleles that were identified by length. Of these 92 sequence variants found within the STR repeat regions, 40 variants were located in STR flanking regions. Additionally, the agreement of the results with CE data was evaluated, as was the ability of this new MPS panel to analyze case-type (11 samples) and artificially degraded samples (seven samples in triplicate). The results generated from this study illustrate that extensive sequence variation exists in commonly used STR markers in the selected population samples and indicate that this NGS STR panel has the potential to be used as an effective tool for human forensics.     

Synthesis and Molecular Structure of [Ru3(CO)10(μ-dppa)] (dppa = Ph2PN(H)PPh2) Provided by Its Dioxane Solvate

The sodium benzophenone ketyl-induced reaction of [Ru₃(CO)₁₂] with bis(diphenylphosphanyl)amine Ph₂PN(H)PPh₂ (dppa) in THF resulted in the formation of the expected metal cluster [Ru₃(CO)₁₀(μ-dppa)] ( 1 ) in high yield. 1 was fully characterized by spectroscopic means and crystals of the compound suitable for X-ray diffraction were obtained from dichloromethane/dioxane. The molecular structure of 1 as its dioxane solvate was determined by X-ray crystallography. The compound crystallized in a new crystal structure of [Ru₃(CO)₁₀(μ-dppa)] in the triclinic space group P1 , whereas that compound was described in an earlier report crystallizing from chloroform in the monoclinic space group P2₁/c.