Thermoplastic modification of urea–formaldehyde wood adhesives to improve moisture resistance

Urea–formaldehyde (UF) resins are prone to hydrolytic degradation, which limits their use to indoor applications. This study examined the modification of UF resin with various thermoplastics as a means to increase the moisture resistance of the adhesive. UF adhesives were modified in situ with various hydrophobic and hydrophilic thermoplastic formulations, using either polar or nonpolar initiators. Unmodified and modified UF resins were characterized in terms of viscosity, pH, and gel time in their prepolymer suspension state. Cured solid UF resin plaques were prepared to isolate moisture sorption effects of the cured UF resin from that of the wood component in composites, which dominates their moisture uptake. Relative crosslink density and moisture sorption tests were run on cured UF resin plaques. Results indicated that viscosity increased after modification in most cases, with higher viscosities resulting from formulations using an acidic (polar) initiator. In all cases, activation energies of the curing reactions of thermoplastic‐modified UF suspensions were lower than the unmodified UF. High relative crosslink density compared to the unmodified UF was found for one sample, which correlated well with lower overall moisture sorption. Higher relative crosslink density of cured UF resin plaques appeared to be an indicator of lower moisture uptake. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4222–4229, 2006     

Electrochemical Atomic Layer Processing

Atomic layer processing with electrochemical control is discussed. A method for the electrodeposition of compound semiconductors based on the principles of atomic layer epitaxy (ALE) is reported, with specific reference to the formation of ZnTe. This method is referred to as electrochemical atomic layer epitaxy (ECALE). A number of II-VI compounds have been formed using this method, including: CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS and HgSe. Initial studies of GaAs and PbSe have also been pursued. A computer-controlled electrochemical flow deposition system is described. The system has been constructed to form thin-films of the compounds listed above using the ECALE methodology. In addition, an analogous digital electrochemical etching procedure has been developed, and used to etch CdTe substrates. The etching cycle consists of oxidizing off the top atomic layer of Cd atoms at a relatively positive potential, followed by reducing off the top layer of Te atoms at a relatively negative potential. Atomic Force Microscopy (AFM) has been used to image the resulting features. ECALE and the digital electrochemical etching process are both based on selecting potentials where an atomic layer of an element is deposited, or removed, in a surface limited reaction. The potentials used are referred to as underpotentials in the electrochemical literature. The atomic layer deposition process is referred to as underpotential deposition (UPD).     

构造独特的8051(下)

设计对比 　　回顾图1和图2,图1中FPGA上的大多数PIO引脚用于扩展8032的总线.因此,相当一部份逻辑和布线资源须用于总线存取/路由和地址解码.由于RF模块接口采用UART模式且8032仅有一个UART,必须用软件实现一个由定时器中断驱动的软UART.为节省FPGA有限的I/O引脚资源,该设计使用了串行接口的键盘.图1中用到的LCD模块基本上是一个内带LCD通用驱动器、LCD段驱动日历和LCD控制器的图形显示模块.为使8032能驱动此图形LCD模块,首先需执行到FPGA的地址写操作.而后,FPGA将在随后向LCD模块的写操作中发出LCD_WR-和LCD_CS-信号.如果FPGA不能自动将图形位图从SDRAM传送至LCD模块,就会利用MCU带宽从SDRAM向MCU逐字节传输,而后再从MCU传送至LCD模块.因此,设计也实现了从SDRAM向LCD模块自动传输数据的逻辑功能.在完成LCD位图传送或检测到有按键按下时,FPGA产生向MCU的中断信号.MCU读取FPGA内中断目标寄存器,了解中断产生的原因并执行适当的程序.……     

Synthesis of o-phenylenediamine functionalized graphite

Here is reported the synthesis of o-phenylenediamine functionalized graphite (OPDFG) using the phosphorus trichloride surface modified graphite (PCl₃-SMG) and the o-phenylenediamine (OPD). PCl₃-SMG was obtained via chlorophosphorylation of graphite for the study. PCl₃-SMG and OPDFG were analyzed using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). UV-Vis analysis shows that OPDFG have higher absorbance than graphite and PCl₃-SMG. According to FTIR analysis, PCl₃-SMG has –PCl₂ functional groups, which shows that PCl₃ reacts with sp² C-H groups on graphite's edge planes during the formation of PCl₃-SMG. Synthesis of OPDFG can be explained by a replacement reaction of amine groups of OPD with –PCl₂ groups. XRD data show that after modification of graphite with PCl₃ and after amine treatment of PCl₃-SMG, crystallite sizes of PCl₃-SMG and OPDFG decrease. SEM analysis shows that both PCl₃-SMG and OPDFG have layered structures similar to graphite.     

Structuring objectives to facilitate convergence of divergent opinion in hydrogen production decisions

Achieving a sustainable energy system obviously is an important goal of all societies. However, achieving that goal is complicated by multiple players with divergent interests promoting their views in the context of numerous complex technological considerations. The research described in this paper provides insights gained from the development of a multiple criteria decision-aiding process to aid such decisions and from an evaluation of convergence in decision maker opinion achievable using the process. The ability of an interactive multicriteria decision-aiding tool to facilitate convergence of decision maker opinions was tested in three phases: (1) development of an objectives hierarchy, (2) definitional clarifications, and (3) elicitation and refinement of criteria weights using shared judgment rationales. Each of these phases was conducted via repeated interactions among a disparate group of experts. Contrary to initial expectations of greatest convergence during the second and third phases of definitional clarification and weight elicitation and refinement, it was found that most convergence occurred during the initial objectives hierarchy development phase. This result demonstrates the value of structured thinking and interaction among decision makers. The structure of the exploratory model developed in this research and the insights gained may be useful for a wide range of real-world issues.     

Polymer Nanoparticles Encased in a Cyclodextrin Complex Shell for Potential Site‐ and Sequence‐Specific Drug Release

Time‐staggered combination chemotherapy strategies show immense potential in cell culture systems, but fail to successfully translate clinically due to different routes of administration and disparate formulation parameters that preclude a specific order of drug presentation. A novel platform consisting of drug‐containing PLGA polymer nanoparticles, stably fashioned with a shell composed of drug complexed with cationic cyclodextrin, capable of releasing drugs time‐ and sequence‐specifically within tumors is designed. Morphological examination of nanoparticles measuring 150 nm highlight stable and distinct compartmentalization of model drugs, rhodamine and bodipy, within the core and shell, respectively. Sequential release is observed in vitro, owing to cyclodextrin shell displacement and subsequent sustained release of core‐loaded drug, kinetics preserved in breast cancer cells following internalization. Importantly, time‐staggered release is corroborated in a murine breast cancer model following intravenous administration. Precise control of drug release order, site‐specifically, potentially opens novel avenues in polychemotherapy for synergy and chemosensitization strategies.     

The effect of few historical data on the performance of sample average approximation method for operating room scheduling

We model the scheduling problem of a single operating room for outpatient surgery, with uncertain case durations and an objective function comprising waiting time, idle time, and overtime costs. This stochastic scheduling problem has been studied in diverse forms. One of the most common approaches used is the sample average approximation (SAA). Our contribution is to study the use of SAA to solve this problem under few historical data using families of log t distributions with varying degrees of freedom. We analyze the results of the SAA method in terms of optimality convergence, the effect of the number of scenarios, and average computational time. Given the case sequence, computational results demonstrate that SAA with an adequate number of scenarios performs close to the exact method. For example, we find that the optimality gap, in units of proportional weighted time, is relatively small when 500 scenarios are used: 99% of the instances have an optimality gap of less than 2.6 7% (1.74%, 1.23%) when there are 3 (9, many) historical samples. Increasing the number of SAA scenarios improves performance, but is not critical when the case sequence is given. However, choosing the number of SAA scenarios becomes critical when the same method is used to choose among sequencing heuristics when there are few historical data. For example, when there are only three (nine, many) historical samples, 99% of the instances have less than 25.38% (13.15%, 6.87%) penalty in using SAA with 500 scenarios to choose the best sequencing heuristic.     

UV-Absorption and Silica/Titania Colloids Using a Core–Shell Approach

Metal-oxo-colloids have been prepared using tetraethoxysilane (TEOS) oligomers with titanium tetra-i-propoxide (TIP) or titanium (di-i-propoxide) bis(acetylacetonate) (TIA) precursors. Transmission electron microscopy (TEM), FTIR, UV-Vis, and photoluminescence spectroscopy were used to investigate the composition, the size, and optical properties of the Si/Ti core–shell colloids. The presence of hetero-bonded silicate structure (Si–O–Ti) was indicated by FTIR spectroscopy. The size of Si/TIP system ranged from 55 to 120 nm and Si/TIA system ranged from 220 to 250 nm. The TEM data indicated that the size of colloids can be controlled by the TIP or TIA content. The Si/Ti system exhibited strong absorption in the UV-range, yet had excellent optical transmittance in the visible range. The Si/Ti systems exhibited a photoluminescence emission at 329 nm.