模板剂对MCM-41介孔分子筛结构的影响

以微硅粉为硅源,利用水热合成法成功制备出MCM-41介孔分子筛,利用XRD、N2吸附曲线和TEM等测试方法对样品进行了表征,结果表明,模板剂的用量对样品的结构具有显著的影响,当CTAB／SiO2的摩尔比为0．15时,样品的结构有序性最高;混合模板剂可明显提高样品的比表面积和孔容,合成的MCM-41介孔分子筛比表面积从299m2／g提高到837．3m2／g,孔容从0．051cm。／g提高到0．79cm3／g。     

Digital modular control of high frequency DC–DC converters

This paper presents a solution for controlling integrated DC–DC converters with high switching frequency (>20 MHz). The increase of the switching frequency is a trend biased by output filter volume restrictions and integration demand. The control of DC–DC converters operating at high frequency presents an opportunity to speed up the converter response time but also a challenge specially for the control solution, quiescent current and to limit the sensitivity to process and operating conditions for the mixed signal circuits involved. The solution presented in this work relies on separating the duty-cycle into three parts: a load-free value that depends only on the input and output voltages, a transient fast correction contribution, and an accurate compensation for the IR drop that depends on the load current. The load-free portion of the duty-cycle has a compensation of PVT variations and the fast transient part of the duty-cycle uses a non-linear sliding mode control solution. All the analog blocks required for the implementation of the proposed solution are detailed.     

铝氮比对轿车用渗碳钢晶粒混晶的影响

在转炉长流程生产工艺条件下,研究了铝含量、氮含量和铝氮比对轿车用20Mn Cr5渗碳钢晶粒度混晶的影响。结果表明,在规定的热处理工艺条件下,20Mn Cr5渗碳齿轮钢产生混晶的主要原因是钢中氮含量偏低。当20Mn Cr5钢中铝含量≥0.025%且铝氮比≥3时,可以达到轿车渗碳钢对奥氏体晶粒度的要求。     

容器钢低温韧度偏低的原因分析

试验用低温压力容器钢由于在深冷环境下使用,对其低温韧度的要求极为严格,生产中经常出现低温韧度波动的现象,影响了成材率和交货期。为此,利用光学显微镜、扫描电镜及能谱仪等设备对不同冲击性能的容器钢试样从宏观到微观进行了枝晶偏析、组织、奥氏体晶粒度等系列对比分析。结果发现:导致低温韧度波动的主要因素为混晶,产生混晶的原因是不合适的精轧温度和道次压下率,此外发达的柱状晶及枝晶偏析遗传至钢板,对轧后的组织及低温韧度也会产生不利的影响。     

Cu~+/13X分子筛吸附分离丁烷-丁烯混合体系

采用等体积浸渍法制备了一系列负载型Cu+/13X分子筛吸附剂,利用固定床吸附装置对该系列吸附剂分离丁烷-丁烯混合体系的性能进行了评价,考察了吸附剂中Cu Cl2负载量、焙烧还原时间、吸附温度、吸附压力、再生次数等对吸附剂性能的影响,并采用TPD方法分析了碳四组分与活性中心π-络合能力的强弱。实验结果表明,Cu+/13X分子筛吸附剂是一种分离丁烷-丁烯混合体系的优良吸附剂,当Cu Cl2负载量为5.67%(w)、350℃下焙烧1.00 h、吸附温度为35~40℃时,常压下吸附效果最佳。升高吸附压力使吸附剂的穿透吸附时间缩短,且吸附压力过高时会引起吸附柱死体积内的气体体积增加,不利于分离。Cu+/13X分子筛吸附剂的再生性能良好,多次再生后仍保持较高的活性。     

Joint channel assignment and routing in multiradio multichannel wireless mesh networks with directional antennas

The aggregate capacity of a wireless mesh network (WMN) is severely affected by interflow interference. In this paper, we propose a network architecture that incorporates directional antennas with multiple orthogonal channels to effectively enhance the performance of WMNs. First, a sectored connectivity graph is introduced to model multiradio multichannel WMNs with directional antennas. Next we formulate the topology design, directional interface assignment, channel allocation, and routing mathematically as a mixed integer linear programming problem. This problem is solved using an iterated local search algorithm to obtain optimized network resource allocation. Simulation results indicate that the proposed architecture can achieve higher packet delivery ratio while providing better network fairness. Copyright © 2014 John Wiley & Sons, Ltd.     

氧化铝陶瓷局部活化及选择性化学镀铜的研究

为解决陶瓷表面局部化学镀存在的问题,研制了一种针对氧化铝陶瓷局部化学镀铜前处理用的活化胶,其由具有活化能力的银盐(或钯盐)和粘稠的复合物有机载体组成.将活化胶印于氧化铝陶瓷表面,经500℃高温烧结形成局部活化层后,可直接置于化学镀液中进行镀铜处理,得到与印刷图形一致的局部镀铜层.利用电化学工作站测定样品在化学镀铜溶液中电位随时间的变化情况,考察不同活化条件对Cu2+还原的催化活性,利用SEM/EDS进行表面形貌及成分分析,确定了活化胶中银盐和钯盐的适宜浓度.结果表明,该两种活化胶应用于氧化铝陶瓷表面化学镀铜的活化工艺,可实现敏化活化的一步化,使陶瓷表面局部化学镀工艺流程简化,成本降低,具有较高的实用价值.     

Reversibly Extracellular pH Controlled Cellular Uptake and Photothermal Therapy by PEGylated Mixed‐Charge Gold Nanostars

Shielding nanoparticles from nonspecific interactions with normal cells/tissues before they reach and after they leave tumors is crucial for the selective delivery of NPs into tumor cells. By utilizing the reversible protonation of weak electrolytic groups to pH changes, long‐chain amine/carboxyl‐terminated polyethylene glycol (PEG) decorated gold nanostars (GNSs) are designed, exhibiting reversible, significant, and sensitive response in cell affinity and therapeutic efficacy to the extracellular pH (pHe) gradient between normal tissues and tumors. This smart nanosystem shows good dispersity and unimpaired photothermal efficacy in complex bioenvironment at pH 6.4 and 7.4 even when their surface charge is neutral. One PEGylated mixed‐charge GNSs with certain surface composition, GNS‐N/C 4 , exhibits high cell affinity and therapeutic efficacy at pH 6.4, and low affinity and almost “zero” damage to cells at pH 7.4. Remarkably, this significant and sensitive response in cell affinity and therapeutic efficacy is reversible as local pH alternated. In vivo, GNS‐N/C 4 shows higher accumulation in tumors and improved photothermal therapeutic efficacy than pH‐insensitive GNSs. This newly developed smart nanosystem, whose cell affinity reversibly transforms in response to pHe gradient with unimpaired biostability, provides a novel effective means of tumor‐selective therapy.     

钛对烧结矿基础性能的影响

通过微型烧结试验研究了钛对烧结矿基础性能的影响。研究结果表明:钛对烧结矿影响较大。随着钛质量分数的升高,混合矿的连晶强度和同化性温度升高,而液相流动性和黏结相强度降低。钛在烧结过程中易与Ca O反应生成高熔点的钙钛矿,减少铁酸钙物质形成,改变烧结矿矿相结构,不利于矿粉之间结合。实际生产中,应该减少混合矿的钛质量分数,从而提高烧结矿质量。