Preparation and luminescence characteristics of LiYF4: Tm3+/Dy3+ single crystals for white-light LEDs

Tm³⁺ /Dy³⁺ co-doped LiYF₄ single crystals were synthesized by using vertical Bridgman method in sealed Pt crucibles. When excited by a proper UV-light, the crystals show blue emission band centered at 485 nm, which overlaps between the transition of Tm³⁺ (¹G₄ → ³H₆) and Dy³⁺ (⁴F_9/2 → ⁶H_15/2) ions, and yellow band of 573 nm ascribed to Dy³⁺ (⁴F_9/2 → ⁶H_13/2) ions. Both chromaticity coordinates and photoluminescence intensity vary with the excitation wavelengths and the concentration of rare earth dopants. A white light can be achieved from Tm³⁺ (0.6 mol%), Dy³⁺ (2.25 mol%) co-doped LiYF₄ crystal with chromaticity coordinates of x ≈ 0.2836, y ≈ 0.3229, and color temperature T _c = 8419 K by the excitation of a 350 nm light. It indicates that this crystal can be a potential candidate for the UV-light excited white-light emitting diodes.     

国外冷库制冷系统节能设计的若干技术剖析

在冷库设计中,寿命周期成本分析法将能源效率合并在设计优化的评估过程。可避免仅根据初投资来设计,达到项目全寿命周期成本的最优。设计中应关注制冷系统的全年效率,我国可以从掌握系统部分负荷规律,设备选型合理配置和调节方面采取措施,提高系统的全年运行效率。冷风机阁楼式和壁龛式安装形式值得借鉴,空气除霜技术具有明显节能效果,可在全年环境温度高于0℃地区推广采用。     

Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Ammonium vanadate with bronze structure (NH4V4O10) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. Howeve...     

Analysis of Staggered OFDM Data Transmission With Reduced Complexity

ＡｎａｌｙｓｉｓｏｆＳｔａｇｇｅｒｅｄＯＦＤＭＤａｔａＴｒａｎｓｍｉｓｓｉｏｎＷｉｔｈＲｅｄｕｃｅｄＣｏｍｐｌｅｘｉｔｙＺｈａｎｇＬｉｊｕｎ（ＤｅｐａｒｔｍｅｎｔｏｆＴｅｌｅｃｏｍｍｕｎｉｃａｔｉｏｎＥｎｇｉｎｅｅｒｉｎｇ，ＮａｎｊｉｎｇＵｎｉｖｅｒ...     

探究输水建筑物基础工程施工工艺

基输水建筑物各基础工程中,严格按照设计要求完成各环节的施工工艺,是保证整个输水建筑工程质量的基础。本文以位于云南麻栗坝水库的东干渠渠首的城子渡槽工程施工为例,分别对工程概况以及施工工艺相关情况作了阐述。     

Effect of Ar annealing temperature on SiO2/4H-SiC interface studied by spectroscopic ellipsometry and atomic force microscopy

The authors have investigated the effects of different annealing temperatures in Ar atmosphere on the SiO₂/4H-SiC interfaces by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). There is a strong correlation between the annealing temperatures and the quality of SiO₂/4H-SiC interface. Annealing at 600 °C can significantly improve the quality of SiO₂/4H-SiC interface with no transition layer. The reasons for such improvement in the quality of the SiO₂/4H-SiC interface after moderate temperature annealing at 600 °C may be explained by the formation and consumption of carbon clusters and silicon oxycarbides during annealing.     

Optimal beamforming for two-way multi-antenna relay channel with analogue network coding

This paper studies the wireless two-way relay channel (TWRC), where two source nodes, S1 and S2, exchange information through an assisting relay node, R. It is assumed that R receives the sum signal from S1 and S2 in one timeslot, and then amplifies and forwards the received signal to both S1 and S2 in the next time-slot. By applying the principle of analogue network coding (ANC), each of S1 and S2 cancels the so-called "self-interference" in the received signal from R and then decodes the desired message. Assuming that S1 and S2 are each equipped with a single antenna and R with multi-antennas, this paper analyzes the capacity region of the ANC-based TWRC with linear processing (beamforming) at R. The capacity region contains all the achievable bidirectional rate-pairs of S1 and S2 under the given transmit power constraints at S1, S2, and R. We present the optimal relay beamforming structure as well as an efficient algorithm to compute the optimal beamforming matrix based on convex optimization techniques. Low-complexity suboptimal relay beamforming schemes are also presented, and their achievable rates are compared against the capacity with the optimal scheme.     

Design and fabrication of a planar patch-clamp substrate using a silicon-on-insulator wafer

noise.     

Evaluation of an ultra‐wide bandwidth wireless indoor non‐line‐of‐sight channels

In this paper, based on the analysis of the experimental data using a new post‐processing method for time‐domain channel measurements, a new double‐cluster statistical model for UWB systems with a bandwidth lower than 1 GHz in non‐line‐of‐sight (NLOS) indoor propagation environment is proposed. By using the proposed model, both the model itself and the parameter estimation of the corresponding model are simplified. By defining the polarity of a particular model parameter, the model has the flexibility to deal with both ‘soft NLOS’ and ‘hard NLOS’ indoor propagation environments. Therefore, the channel impulse responses (CIRs) generated by the proposed model ‘resemble’ the measured CIR better than the SV (Saleh‐‐Valenzuela)/IEEE 802.15.3a model not only in terms of the average values, but also in terms of the cumulative distribution functions (CDFs) of the small‐scale statistics. Copyright © 2008 John Wiley & Sons, Ltd.     

Symbol Error Rate Analysis and Power Allocation for Adaptive Relay Selection Schemes

In this paper, we analyse the symbol error rate (SER) performance of adaptive relay selection schemes (ARS) in a general dual-hop multiple-relay network. Specifically, we provide a closed-form SER expression for ARS which is tight over the whole signal-to-noise ratio (SNR) region. In addition, the derived SER can be readily extended to conventional relay selection schemes, i.e. amplify-and-forward relay selection (AF-RS), perfect decode-and-forward relay selection (PDF-RS), adaptive decode-and-forward relay selection (ADF-RS), and cooperative-maximum-ratio-combining decode-and-forward relay selection (CDF-RS). Transmit power allocation based on the simplified SER is presented to improve the system performance. The analytical results are verified by computer simulations.