Development of control technology for HTTR hydrogen production system with mock-up test facility: System controllability test for loss of chemical reaction

The Japan Atomic Energy Agency has been planning the demonstration test of hydrogen production with the High Temperature Engineering Test Reactor (HTTR). In a HTTR hydrogen production system (HTTR-H2), it is required to control a primary helium temperature within an allowable value at a reactor inlet to prevent a reactor scram. A cooling system for a secondary helium with a steam generator (SG) and a radiator is installed at the downstream of a chemical rector in a secondary helium loop in order to mitigate the thermal disturbance caused by the hydrogen production system. Prior to HTTR-H2, the simulation test with a mock-up test facility has been carried out to establish the controllability on the helium temperature using the cooling system against the loss of chemical reaction. It was confirmed that the fluctuations of the helium temperature at chemical reactor outlet, more than 200 K, at the loss of chemical reaction could be successfully mitigated within the target of ±10 K at SG outlet. A dynamic simulation code of the cooling system for HTTR-H2 was verified with the obtained test data.     

基于溶胶-凝胶技术结合多壁纳米碳管化学修饰电极的方法制备高灵敏葡萄糖生物传感器的研究

基于多壁纳米碳管修饰铂电极与二氧化硅溶胶-凝胶(sol-gel)固定化酶相结合的技术制备了葡萄糖氧化酶传感器,充分利用了溶胶-凝胶固定化酶稳定的优点和纳米碳管的高灵敏电催化作用,优化了该酶传感器的制备过程,提高了传感器的电流响应和反应线性.结果表明,sol-gel构建的优化条件是:H2O:TEOS为2.5～3.5,TritonX-100浓度为5%,pH值为5.5.在本实验条件下,多壁纳米碳管的最适固定量为5μl(0.25g/L),溶胶-凝胶与酶的优化体积比为3:2.工作电位 0.55V、pH 6.5、25℃为制备传感器的最适工作条件.该传感器对葡萄糖在0.5～6 mmol/L呈线性响应,响应时间为20 s,检出限为0.05mmol/L,45天时的响应值仍保持90%.     

Nanocellulose as a natural source for groundbreaking applications in materials science: Today’s state

Nanocelluloses are natural materials with at least one dimension in the nano-scale. They combine important cellulose properties with the features of nanomaterials and open new horizons for materials science and its applications. The field of nanocellulose materials is subdivided into three domains: biotechnologically produced bacterial nanocellulose hydrogels, mechanically delaminated cellulose nanofibers, and hydrolytically extracted cellulose nanocrystals. This review article describes today’s state regarding the production, structural details, physicochemical properties, and innovative applications of these nanocelluloses. Promising technical applications including gels/foams, thickeners/stabilizers as well as reinforcing agents have been proposed and research from last five years indicates new potential for groundbreaking innovations in the areas of cosmetic products, wound dressings, drug carriers, medical implants, tissue engineering, food and composites. The current state of worldwide commercialization and the challenge of reducing nanocellulose production costs are also discussed.     

Protonic Conduction in Perovskite-type Oxide Ceramics Based on LnScO3 (Ln=La, Nd, Sm or Gd) at High Temperature

Ionic transport properties of perovskite-type oxides based on LnScO₃, Ln_{1- x}Ca_xScO_3- (Ln=La, Nd, Sm and Gd) and LaSc_1-xMg_xO_3- were studied using an electrochemical method at elevated temperatures. Conductivity in these oxide systems increased by more than three orders of magnitude upon doping with divalent atoms such as Ca or Mg. However, when x0.1, conductivities are almost independent of x in La_{1- x}Ca_{xScO_3-} and LaSc_{1- x}Mg_xO_3-. Gd_0.9Ca_0.1ScO_3- showed lower conductivity than Ln_1-xCa_xScO_3- (Ln=La, Nd and Sm). Protonic conduction in these oxides under hydrogen containing atmospheres was confirmed by emf measurements of hydrogen concentration cells and by electrochemical hydrogen pumping using these oxides as a diaphragm. In LaSc_1-xMg_xO_3- the transport number of protons under hydrogen containing atmosphere was unity, suggesting that electronic conduction never became dominant, even under strong reducing conditions. Under condition of high oxygen partial pressure, the transport number of ions was less than 0.1, suggesting that the majority conductive carriers under such conditions were holes.     

Early structural change detection as an optimal stopping problem: solution theorem and its proof using reduction to absurdity

The change point detection (CPD) problem in a time series is when it is found that the structure of the data being generated has changed at some time and for some reason. We have formulated structural change detection in a time series as an optimal stopping problem using the concept of dynamic programming (DP), and we present the optimal solution and its correctness by numerical calculations. In this article, we present the solution theorem and its proof using reduction to absurdity.     

Reversible Computation and Reversible Programming Languages

A reversible programming language supports deterministic forward and backward computation. This tutorial focuses on a high-level reversible programming language Janus. In common with other programming paradigms, reversible programming has its own programming methodology. Janus is simple, yet powerful, and its constructs can serve as a model for designing reversible languages in general.     

Deposition characteristics and properties of iron nitride films by CVD using organometallic compound

Iron nitride films were prepared by chemical vapour deposition from the gas mixture of Fe(C₅H₅)₂-NH₃-H₂-CO₂. The effects of deposition parameters on the deposition characteristics were investigated. Iron nitride films were deposited above 500 ° C and the films of -Fe₄N single phase were deposited above 700 ° C. At 700 ° C and under the total gas flow rate from 1 to 8 l min^–1, the deposition rate of the film may be controlled by the transport of Fe(C₅H₅)₂ molecules to the surface of the deposits. At 700 °C and under the total gas flow rate of 4 l min^–1, the phases and nitrogen contents of the films were determined bypNH₃/pH₂ ^3/2, the controlling factor of the nitrogen contents of the films. Decreasing of the total gas flow rate and increasingpCO₂ increased the nitrogen contents of the films and phases with higher nitrogen were deposited. On the other hand, increasingpFe(C₅H₅)₂ and the absence ofpCO₂ increases the carbon contents of the films, and the phase with a greater solubility in carbon, i.e. -Fe₂N, was codeposited with -Fe₄N. The saturation magnetization of the films deposited at 700 ° C was in good agreement with that reported for the bulk iron nitride, which depended not on the deposition conditions but on the nitrogen contents of the films.     

Preparation of Fe-N films by r.f. sputtering

Fe-N films over a wide compositional range have been prepared by the reactive sputtering method. Fe-N sputtered films were composed of a single or two phases such as-Fe₂N,-Fe_3.02N,-Fe_3.82N,-Fe₄N and-Fe; however, an unknown phase was observed at a higher nitrogen pressure. A remarkable preferred orientation of the-Fe_3.02N (110) plane parallel to the film surface was observed. The Curie temperature of the sputtered -Fe_3.82N sample was 490° C, which was almost the same as that of-Fe₄N prepared by metal nitriding. The saturation magnetization, _s, of the sputtered Fe-N samples decreased from 151.8 to 42.4 e.m.u.g^–1 with increasing nitrogen content from 7.94 to 24.87 at%, and its coercive force,₁ H _c was found to lie in the range 150 to 600 Oe in the powder form at room temperature.     

High-temperature sulfidation of Fe-Mn alloys

The complete range of binary Fe-Mn alloys were sulfidized in pure sulfur vapor (1 atm) at 700–1000°C. It was found that the corrosion kinetics could be divided into four groups, depending upon the alloy concentration. The first group, up to 11 w/o Mn, had a constant corrosion rate. The second group, up to about 63 w/o Mn, had an exponentially decreasing rate of corrosion with increasing manganese content. In the third group, about 63–80 w/o Mn alloys, the corrosion rate did not follow the parabolic law. The corrosion rates became constant above 80 w/o Mn. These corrosion kinetics were explained by considering the scale structure and alloy substrate.