Compact tri‐band MIMO antenna based on quarter‐mode slotted substrate‐integrated‐waveguide cavity

A compact tri‐band multiple‐input‐multiple‐output (MIMO) antenna based on a quarter‐mode slotted substrate‐integrated‐waveguide (SIW) cavity is proposed. By etching a wide slot, a single SIW cavity is divided into two sub‐cavities with the same size. They are fed by coaxial ports to form two MIMO elements and high antenna isolation can be achieved by this slot. To obtain multi‐band operations, two narrow slots are cut in the upper sub‐cavity and the other two slots are etched in the lower sub‐cavity. Three eighth‐mode resonances with different areas can simultaneously occur in these antenna elements. A prototype with the overall size of 0.34λ₀ × 0.34λ₀ has been fabricated. The measured center frequencies of three operating bands are 2.31, 2.91, and 3.35 GHz, respectively. The measured gain at above frequencies is 4.52, 4.29, and 4.57 dBi, respectively. Moreover, the measured isolation is higher than 16.7 dB within the frequency of interest.     

邻苯二胺基环三磷腈阻燃剂在EVA材料中的性能及机理研究

应用混料设计实验方法研究了邻苯二胺基环三磷腈(HACTP)和聚磷酸铵(APP)、蒙脱土(MMT)复配阻燃剂对乙烯-醋酸乙烯酯共聚物(EVA)材料阻燃和力学性能的影响,并利用锥形量热仪及电子扫描显微镜研究了不同配方下阻燃EVA的热释放性能和燃烧后膨胀炭层的微观形貌,探讨阻燃机理.结果 表明:在HACTP质量分数为32.8...     

无毒增塑剂柠檬酸三(2-乙基)己酯的合成

以柠檬酸和2-乙基己醇为原料,用氧化二正丁基锡为催化剂合成了无毒增塑剂柠檬酸三(2-乙基)己酯,考察了反应温度、催化剂用量、醇酸摩尔比、反应时间等因素对反应结果的影响,对合成的产品进行了红外光谱分析。实验结果表明,氧化二正丁基锡催化合成柠檬酸三(2-乙基)己酯的最佳反应条件为n(柠檬酸)∶n(2-乙基己醇)=1∶3.60,催化剂用量为柠檬酸质量的0.5%,反应时间为120min,反应温度为150～160℃,在最佳反应条件下,柠檬酸三(2-乙基)己酯收率在98%以上。     

Tri‐band Microstrip Bandpass Filter Using Dual‐Mode Stepped‐Impedance Resonator

This letter presents a compact dual‐mode tri‐band bandpass filter by using a short‐circuited stub‐loaded stepped‐impedance resonator (SIR) and a short‐circuited stub‐loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short‐circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even‐odd mode theory. For demonstration purposes, a tri‐band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.     

A technique to dispose waste plastics in an ecofriendly way - Application in construction of flexible pavements

Waste plastics, littered both by domestic and industrial sectors was found to be a source of raw material for the flexible pavement. Waste plastics, mainly used for packing are made up of PE, PP and PS, their softening point varies between 110 °C and 140 °C and they do not produce any toxic gases during softening. But the softened plastics have a tendency to form a film like structure over the aggregate, when it is sprayed over the hot aggregate at 160 °C. The formed PCA is a better raw material for the construction of flexible pavement. PCA was then mixed with hot bitumen of different types and the mixes were used for road construction. PCA + bitumen mix showed improved binding property and poor wetting property. The sample showed higher Marshall Stability value in the range of 18-20 kN and the load bearing capacity of the road is increased by 100% and there is no pothole formation. The roads laid since 2002 using PCA + bitumen mixes are performing well. A detailed studies on the performances of these roads shows that the PCA bitumen mix roads are performing well. This is an eco friendly and economic process too.     

Numerical characterization of compact pipe specimen for stretch zone width assessment

Present work focuses on evaluating the suitability of newly proposed compact pipe (CP) fracture specimen geometry for determining critical SZW. The effect of varying the parameter of CP specimen (outer diameter, thickness, a/W ratio and straight and radial crack front) on critical SZW have been studied. It is found that SZWc values decreases slightly with the increase in outer diameter of CP specimen. In CP specimen, thickness greater than a specified value is to be used for geometry independent evaluation of SZWc. Critical SZW shows significant variation with a/W ratio, straight and radial crack front. The CP specimen and Three Point Bend (TPB) specimen also compared in terms of stress tri‐axiality.     

阻燃剂赛克三硅酸二氯丙酯的合成

以SiCl4、三(2-羟乙基)异氰尿酸酯(赛克)和环氧氯丙烷为原料合成了有机硅酸酯阻燃剂三[2-三(二氯丙氧基)硅酰氧基乙基]异氰尿酸酯(简称赛克三硅酸二氯丙酯)。考察了溶剂种类、反应温度和反应物配比对合成反应的影响,得到了最佳的反应条件,并采用FTIR、1H NMR、TG-DTA分析及极限氧指数等技术表征了产物的结构和性能。最佳的反应条件为:n(SiCl4)∶n(环氧氯丙烷)∶n(赛克)=3∶9.8∶1,SiCl4先与环氧氯丙烷在50℃下反应2 h,再与赛克在90℃下反应9 h,最后与环氧氯丙烷于90℃下反应6 h。在此条件下,赛克三硅酸二氯丙酯的收率为93.7%。性能测试结果表明,该产物阻燃效能高,与聚氯乙烯的相容性好,适合用作聚氯乙烯等材料的阻燃剂。     

泡沫级THEIC改性蜜胺树脂的研究

以三(2-羟乙基)异氰尿酸酯作为改性剂对蜜胺树脂进行改性,采用旋转黏度计测量反应体系动力黏度,根据动力黏度变化定性表征缩聚产物相对分子质量和反应速率快慢,考察了改性树脂的聚合工艺条件(如物料配比、反应时间、改性剂添加量、固含量等)对体系聚合反应的影响;并通过IR光谱、TG-DSC等对改性树脂的结构、热稳定性进行了表征....     

电喷雾-质谱法测定两种有机磷酸

采用电喷雾电离质谱(ESI)和质谱(MS)-质谱(MS)技术分析了两种工业有机磷酸--氨基三亚甲基膦酸和羟基亚乙基二磷酸。用ESI-MS技术获得了有机磷酸产品及主要副产品的准分子离子峰,用ESI-MS-MS技术获得了其碎片信息,为检验产品及主要副产品的结构提供了证据。     

切削液防锈剂的研究

以硼酸酯、取代苯甲酸乙醇胺盐、葡萄糖酸钠三者为混合防锈剂应用于切削液中，其中硼酸酯和取代苯甲酸乙醇胺盐有明显的协同效应。实际配方中硼酸酯、取代苯甲酸乙醇胺盐、葡萄糖酸钠的含量分别为10％、6％和1％。所得切削液有较好的防锈性能，使用寿命长，适合于多种金属材料的多种加工工艺。