Preparation, Characterization, and Microwave Dielectric Properties of Sr2La3Nb1−x Ta x Ti4O17 (0 ≤ x ≤ 1) Ceramics

Sr₂La₃Nb_1?x Ta _x Ti₄O₁₇ (0 ≤ x ≤ 1) ceramics were processed via a solid-state mixed oxide route. Sr₂La₃Nb_1?x Ta _x Ti₄O₁₇ (0 ≤ x ≤ 1) solid solutions were single phase in the whole range of x values within the x-ray diffraction (XRD) detection limit. The microstructure comprised elongated and needle-shaped grains. The ceramics exhibit relative permittivity (ε _r) of 73 to 68.6, product of unloaded quality factor and resonant frequency (Q _u f ₀) of 7100 GHz to 9500 GHz, and temperature coefficient of resonant frequency (τ _f) of 78.6 ppm/°C to 56.6 ppm/°C.     

Thermoelectric Properties of Ca3−x Ag x Co3.95Fe0.05O9+δ (0 ≤ x ≤ 0.3)

Polycrystalline samples of Ca_3?x Ag _x Co_3.95Fe_0.05O_9+δ (x = 0.0, 0.1, 0.2, and 0.3) have been prepared by conventional solid-state synthesis. The x-ray diffraction patterns reveal that all the samples are single phase. The thermopower of all the samples is positive, indicating that the predominant carriers are holes over the entire temperature range. The electrical resistivity and thermopower simultaneously decrease with increasing Ag content. The highest power factor (2.66 μW cm^?1 K^?2 at 150 K) is reached for the Ca_2.8Ag_0.2Co_3.95Fe_0.05O_9+δ , representing an improvement of about 16 % compared to the undoped sample. These results suggest that the Ag is an effective doping element for enhancing the thermoelectric properties of Ca₃Co_3.95Fe_0.05O_9+δ.     

Superstructured ordering in Al x Ga1 − x As and Ga x In1 − x P alloys

Epitaxial heterostructures produced on the basis of Al _x Ga_{1 ? x} As and Ga _x In_{1 ? x} P ternary alloys by metal-organic chemical vapor deposition are studied. The composition parameter x of the alloys was ～0.50. By X-ray diffraction studies, scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy, it is shown that superstructured ordered phases with the stoichiometry composition III_{1 ? η}III_{1 + η}V₂ can be formed. As a consequence of this effect, not only does the cubic crystal symmetry change to the tetragonal type in the new compound, but also the optical properties become different from those of disordered alloy with the same composition.     

GSM 1x技术与GSM 1x全球网关的应用

GSM 1x技术提出的主要目标是为GSM用户提供基于CDMA1x的高速无线数据服务,采用此技术是中国联通发挥双网运营优势迈出的第一步.主要介绍GSM 1x技术在现网中的实际应用.     

cdma 1x终端测试

本文主要介绍了目前行业内对cdma 1x终端的测试要求.     

cdma2000 1x与1x EV-DO双网切换和信息交互

首先介绍了HRPD网络结构及其各个接口的功能,然后重点介绍了接入终端的类型和状态．最后以实例描述了cdma2000 1x与cdma2000 1x EV-DO双网切换过程及使用空中接口应用层定义的方法。     

cdma2000 1x与cdma2000 1x EV-DO的互操作及实施

本文首先介绍了cdma2000 1x与cdma2000 1x EV-DO互操作的4种解决方案,然后对它们进行了分析对比,最后给出多厂家供货条件下cdma2000 1x运营商的互操作规划策略。     

Room-Temperature Quantum Cascade Laser: ZnO/Zn1−x Mg x O Versus GaN/Al x Ga1−x N

A ZnO/Zn_1?x Mg _x O-based quantum cascade laser (QCL) is proposed as a candidate for generation of THz radiation at room temperature. The structural and material properties, field dependence of the THz lasing frequency, and generated power are reported for a resonant phonon ZnO/Zn_0.95Mg_0.05O QCL emitting at 5.27 THz. The theoretical results are compared with those from GaN/Al _x Ga_1?x N QCLs of similar geometry. Higher calculated optical output powers [ $ {P}_{\rm{ZnMgO}} $  = 2.89 mW (nonpolar) at 5.27 THz and 2.75 mW (polar) at 4.93 THz] are obtained with the ZnO/Zn_0.95Mg_0.05O structure as compared with GaN/Al_0.05Ga_0.95N QCLs [ $ {P}_{\rm{AlGaN}} $  = 2.37 mW (nonpolar) at 4.67 THz and 2.29 mW (polar) at 4.52 THz]. Furthermore, a higher wall-plug efficiency (WPE) is obtained for ZnO/ZnMgO QCLs [24.61% (nonpolar) and 23.12% (polar)] when compared with GaN/AlGaN structures [14.11% (nonpolar) and 13.87% (polar)]. These results show that ZnO/ZnMgO material is optimally suited for THz QCLs.     

Thermal Conductivity in Bi1−x Sb x Solid Solutions

Bi_1?x Sb _x solid solutions have attracted much attention as promising low-temperature thermoelectric materials. Previously, we observed distinct extrema in the isotherms of the transport and mechanical properties of polycrystalline Bi_1?x Sb _x and attributed their presence to the transition from diluted to concentrated solid solutions and to the reconstruction of the energy band structure under increasing Sb concentration. The goal of the present work is a detailed study of the concentration dependences of the thermal conductivity λ for Bi_1?x Sb _x polycrystalline solid solutions (x = 0 to 0.09) in the temperature range of 170 K to 300 K. It is established that the λ(x) dependences exhibit a nonmonotonic behavior: in certain concentration ranges an anomalous increase in λ with increasing x is observed. It is shown that the concentration dependences of the thermoelectric figure of merit calculated on the basis of the measured λ values are also nonmonotonic. The obtained data represent additional evidence in favor of our assumptions stated earlier about a significant effect of electronic phase transitions observed in Bi_1?x Sb _x solid solutions on the concentration dependences of their thermoelectric properties. These results should be taken into account when developing new Bi_1?x Sb _x -based materials.     

SHT1x/7x温/湿度传感器应用

介绍了基于Atmel公司的AT89C2051，Sensirion公司的SHT1x／7x温／湿度传感器完成温度、湿度监控系统的设计方法。SHT1x／7x温／湿度传感器具有精度高、稳定度好、一致性好、体积小、数字输出等特点，非常适合于对温度和湿度进行监控。     

CDMA1x数据网络优化思路

随着CDMA1x数据用户的快速增长,针对CDMA1x的数据网络优化已经迫在眉睫。由于数据和语音的优化既有不同点但也有相同点,在语音优化基础上对数据优化进行有益的尝试和探索是很有必要的。本文结合广州所做的数据优化经验,对CDMA1x数据优化的思路进行了总结。     

三星电子cdma2000 1x系统

2000年10月,韩国最大的移动通信运营商SK电信采用三星技术正式启用了cdma 2000 1x商用系统,三星cdma20001x手机也同时面世.     

朗讯科技公司cdma 1x发展现状

cdma2000近来发展非常顺利,目前美国的Verizon、韩国的SK电信和KTF以及LG-Telecom等运营商的网络已经正式投入商用,所提供的话音容量比cdmaOne高近一倍,数据业务速率可达153.6klit/s,cdma 1x手机也已经大量投产.北美、南美、亚太和欧洲的许多运营商已经开始将原有的cdmaOne系统全面升级为cdma 1x,也有许多新的运营商一开始就选用cdma 1x技术.cdma 1xEV-DO(最高速率可达2.4 Mbit/s)和lXEV-DV(最高速率可达6 Mbit/s)技术也取得了质的飞跃,朗讯科技在美国Verizon和Sprint PCS公司已开通了cdma lxEV-DO商用试验网.     

cdma2000 1x无线网络规划设计

中国联通CDMA网络二期工程,将主要铺设cdma2O00 1x(以下简称1X)网络,因此该文主要对1X网络的建网方案、基站配置、基站设置和覆盖能力进行了探讨。     

华为cdma1x网络解决方案

从1995年开始,华为公司就致力于CDMA相关技术的研究积累,1996-1998年承接了国家863项目CDMA WLL系统的开发,成功开发出CDMA原型机,掌握了CDMA的关键技术。2000年成功推出了cdma 1x移动交换系统,2001年又成功推出了基于先进的宽带分组平台的cdma 1x基站。 华为cdma 1x基站系统,是在华为公司成熟的数据通信及移动通信技术平台上开发出的新一代CDMA基站设备。空中接口遵循IS-2000-A标准,提供高质量的语音和高达153.6kbps的数据业务;A接口遵循IOS4.0标准,具有良好的开放性和兼容性。设备在设计上充分考虑我国建设CDM…     

联通CDMA 1 x全面上马

4月8日,中国联通CDMA网3个月的试运营圆满结束,这意味着CDMA网二期扩容工程开始进入紧张建设之中,二期扩容以CDMA1x网络升级为主,在CDMA 1x试验网的基础上,将在全国主要城市建成CDMA 1x网,扩容规模约为1300万～1500万户。