3.2-kW 9.7-GHz Polarization-maintaining Narrow-linewidth All-fiber Amplifier

Hang Liu,Yujun Feng,Xiaobo Yang,Yao Wang,Hongming Yu,Jue Wang,Wanjing Peng,Yanshan Wang,Yinhong Sun,Yi Ma,Qingsong Gao,Chun Tang 한국광학회 2024 Current Optics and Photonics Vol.8 No.1

We present a Yb-doped narrow-linewidth polarization-maintaining (PM) all-fiber amplifier that achieves a high mode-instability (MI) threshold, high output power, and 9.7-GHz spectral linewidth. Six wavelength-multiplexed laser diodes are used to pump this amplifier. First, we construct a high-power fiber amplifier based on a master oscillator-power amplifier (MOPA) configuration for experiments. Subsequently, we examine the MI threshold by individually pumping the amplifier with wavelengths of 976, 974, 981, 974, and 981 nm respectively. The experimental results demonstrate that the amplifier exhibits a high MI threshold (>3.5 kW) when pumped with a combination of wavelengths at 974 and 981 nm. Afterward, we inject an optimized phase-modulated seed with a nearly flat-top spectrum into this amplifier. Ultimately, laser output of 3.2 kW and 9.7 GHz are obtained.

Numerical Research on Suppression of Thermally Induced Wavefront Distortion of Solid-state Laser Based on Neural Network

Liu, Hang,He, Ping,Wang, Juntao,Wang, Dan,Shang, Jianli Optical Society of Korea 2022 Current Optics and Photonics Vol.6 No.5

To account for the internal thermal effects of solid-state lasers, a method using a back propagation (BP) neural network integrated with a particle swarm optimization (PSO) algorithm is developed, which is a new wavefront distortion correction technique. In particular, by using a slab laser model, a series of fiber pumped sources are employed to form a controlled array to pump the gain medium, allowing the internal temperature field of the gain medium to be designed by altering the power of each pump source. Furthermore, the BP artificial neural network is employed to construct a nonlinear mapping relationship between the power matrix of the pump array and the thermally induced wavefront aberration. Lastly, the suppression of thermally induced wavefront distortion can be achieved by changing the power matrix of the pump array and obtaining the optimal pump light intensity distribution combined using the PSO algorithm. The minimal beam quality β can be obtained by optimally distributing the pumping light. Compared with the method of designing uniform pumping light into the gain medium, the theoretically computed single pass beam quality β value is optimized from 5.34 to 1.28. In this numerical analysis, experiments are conducted to validate the relationship between the thermally generated wavefront and certain pumping light distributions.

Landau-level mixing, floating-up extended states, and scaling behavior in a GaAs-based two-dimensional electron system containing self-assembled InAs dots

Liu, Chieh-Wen,Liu, Chieh-I,Liang, C-T,Kim, Gil-Ho,Huang, C F,Hang, D R,Chang, Y H,Ritchie, D A Institute of Physics 2017 Semiconductor science and technology Vol.32 No.8

<P>Temperature-driven flow lines are studied in the conductivity plane in a GaAs-based two-dimensional electron system containing self-assembled InAs dots when Landau level filling factor <I>ν</I> = 2-4. In the insulator-quantum Hall (I-QH) transition resulting from the floating-up of the extended states, the flow diagram shows the critical behavior and we observed the expected semicircle in the strongest disorder case. By decreasing the effective disorder, we find that such flow lines can leave the I-QH regime and correspond to the plateau–plateau transition between <I>ν</I> = 4 and 2. The evolution of the conductivity curve at low magnetic fields demonstrates the importance of Landau-level mixing to the semicircle when the extended states float up.</P>

Optimal Strategies for Cooperative Spectrum Sensing in Multiple Cross-over Cognitive Radio Networks

( Hang Hu ),( Youyun Xu ),( Zhiwen Liu ),( Ning Li ),( Hang Zhang ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

To improve the sensing performance, cooperation among secondary users can be utilized to collect space diversity. In this paper, we focus on the optimization of cooperative spectrum sensing in which multiple cognitive users efficiently cooperate to achieve superior detection accuracy with minimum sensing error probability in multiple cross-over cognitive radio networks. The analysis focuses on two fusion strategies: soft information fusion and hard information fusion. Under soft information fusion, the optimal threshold of the energy detector is derived in both noncooperative single-user and cooperative multiuser sensing scenarios. Under hard information fusion, the optimal randomized rule and the optimal decision threshold are derived according to the rule of minimum sensing error (MSE). MSE rule shows better performance on improving the final false alarm and detection probability simultaneously. By simulations, our proposed strategy optimizes the sensing performance for each cognitive user which is randomly distributed in the multiple cross-over cognitive radio networks.

Partitioning <i>H</i>-minor free graphs into three subgraphs with no large components

Liu, Chun-Hung,Oum, Sang-il Elsevier 2018 Journal of combinatorial theory. Series B Vol.128 No.-

<P><B>Abstract</B></P> <P>We prove that for every graph <I>H</I>, if a graph <I>G</I> has no (odd) <I>H</I> minor, then its vertex set V ( G ) can be partitioned into three sets <SUB> X 1 </SUB> , <SUB> X 2 </SUB> , <SUB> X 3 </SUB> such that for each <I>i</I>, the subgraph induced on <SUB> X i </SUB> has no component of size larger than a function of <I>H</I> and the maximum degree of <I>G</I>. This improves a previous result of Alon, Ding, Oporowski and Vertigan (2003) stating that V ( G ) can be partitioned into four such sets if <I>G</I> has no <I>H</I> minor. Our theorem generalizes a result of Esperet and Joret (2014) , who proved it for graphs embeddable on a fixed surface and asked whether it is true for graphs with no <I>H</I> minor.</P> <P>As a corollary, we prove that for every positive integer <I>t</I>, if a graph <I>G</I> has no <SUB> K t + 1 </SUB> minor, then its vertex set V ( G ) can be partitioned into 3<I>t</I> sets <SUB> X 1 </SUB> , … , <SUB> X 3 t </SUB> such that for each <I>i</I>, the subgraph induced on <SUB> X i </SUB> has no component of size larger than a function of <I>t</I>. This corollary improves a result of Wood (2010) , which states that V ( G ) can be partitioned into ⌈ 3.5 t + 2 ⌉ such sets.</P>

Proteomic analysis of amino acid metabolism differences between wild and cultivated Panax ginseng

Hang Sun,Fangbing Liu,Liwei Sun,Jianzeng Liu,Manying Wang,Xuenan Chen,Xiaohao Xu,Rui Ma,Kai Feng,Rui Jiang 고려인삼학회 2016 Journal of Ginseng Research Vol.40 No.2

Background: The present study aimed to compare the relative abundance of proteins and amino acid metabolites to explore the mechanisms underlying the difference between wild and cultivated ginseng (Panax ginseng Meyer) at the amino acid level. Methods: Two-dimensional polyacrylamide gel electrophoresis and isobaric tags for relative and absolute quantitation were used to identify the differential abundance of proteins between wild and cultivated ginseng. Total amino acids in wild and cultivated ginseng were compared using an automated amino acid analyzer. The activities of amino acid metabolism-related enzymes and the contents of intermediate metabolites between wild and cultivated ginseng were measured using enzyme-linked immunosorbent assay and spectrophotometric methods. Results: Our results showed that the contents of 14 types of amino acids were higher in wild ginseng compared with cultivated ginseng. The amino acid metabolism-related enzymes and their derivatives, such as glutamate decarboxylase and S-adenosylmethionine, all had high levels of accumulation in wild ginseng. The accumulation of sulfur amino acid synthesis-related proteins, such as methionine synthase, was also higher in wild ginseng. In addition, glycolysis and tricarboxylic acid cycle-related enzymes as well as their intermediates had high levels of accumulation in wild ginseng. Conclusion: This study elucidates the differences in amino acids between wild and cultivated ginseng. These results will provide a reference for further studies on the medicinal functions of wild ginseng.

Activation of Small GTPases RhoA and Rac1 Is Required for Avian Reovirus p10-induced Syncytium Formation

Hung-Jen Liu,Ping-Yuan Lin,Ling-Rung Wang,Hsue-Yin Hsu,Ming-Huei Liao,Wen-Ling Shih 한국분자세포생물학회 2008 Molecules and cells Vol.26 No.4

The first ORF of the ARV S1133 S1 segment encodes the nonstructural protein p10, which is responsible for the induction of cell syncytium formation. However, p10-dependent signaling during syncytium formation is fully unknown. Here, we show that dominant negative RhoA, Rho inhibitor C3 exoenzyme, ROCK/Rho-kinase inhibitor Y-27632 and Rac1 inhibitor NSC23766 inhibit p10-mediated cell fusion. p10 over-expression is concomitant with activation and membrane translocation of RhoA and Rac1, but not cdc42. RhoA and Rac1 downstream events, including JNK phosphorylation and transcription factor AP-1 and NF-B activation, as well as MLC expression and phosphorylation are simultaneously activated by p10. p10 point mutant T13M possessed 20% fusion-inducing ability and four p10 fusion-deficient mutants V15M, V19M, C21S and L32A reduced or lost their ability to activate RhoA and Rac1 signaling. We conclude that p10-mediated syncytium formation proceeds by utilizing RhoA and Rac1-dependent signaling.

High-Speed Four-Parallel 64-Point Radix-2⁴ MDF FFT/IFFT Processor for MIMO-OFDM Systems

Hang Liu,Hanho Lee 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7

This paper presents a design and implementation result of a high-speed, low-complexity four data-path 64-point radix-2⁴ FFT/IFFT processor for high-throughput MIMO-OFDM wireless LAN system. The proposed FFT/IFFT processor can provide a higher throughput rate and low hardware complexity by using a four-parallel datapath scheme and a multipath delay feed-back (MDF) structure. The proposed four data-path 64-point MDF FFT/IFFT processor has a throughput rate of up to 600 M sample/s at 150 ㎒ while requiring much smaller hardware complexity satisfying IEEE 802.11n standard requirements.

Occupational Neurotoxic Diseases in Taiwan

Liu, Chi-Hung,Huang, Chu-Yun,Huang, Chin-Chang Occupational Safety and Health Research Institute 2012 Safety and health at work Vol.3 No.4

Occupational neurotoxic diseases have become increasingly common in Taiwan due to industrialization. Over the past 40 years, Taiwan has transformed from an agricultural society to an industrial society. The most common neurotoxic diseases also changed from organophosphate poisoning to heavy metal intoxication, and then to organic solvent and semiconductor agent poisoning. The nervous system is particularly vulnerable to toxic agents because of its high metabolic rate. Neurological manifestations may be transient or permanent, and may range from cognitive dysfunction, cerebellar ataxia, Parkinsonism, sensorimotor neuropathy and autonomic dysfunction to neuromuscular junction disorders. This study attempts to provide a review of the major outbreaks of occupational neurotoxins from 1968 to 2012. A total of 16 occupational neurotoxins, including organophosphates, toxic gases, heavy metals, organic solvents, and other toxic chemicals, were reviewed. Peer-reviewed articles related to the electrophysiology, neuroimaging, treatment and long-term follow up of these neurotoxic diseases were also obtained. The heavy metals involved consisted of lead, manganese, organic tin, mercury, arsenic, and thallium. The organic solvents included n-hexane, toluene, mixed solvents and carbon disulfide. Toxic gases such as carbon monoxide, and hydrogen sulfide were also included, along with toxic chemicals including polychlorinated biphenyls, tetramethylammonium hydroxide, organophosphates, and dimethylamine borane. In addition we attempted to correlate these events to the timeline of industrial development in Taiwan. By researching this topic, the hope is that it may help other developing countries to improve industrial hygiene and promote occupational safety and health care during the process of industrialization.

A Performance Analysis of 2-Parallel MB-OFDM UWB Receiver

Hang Liu,Hanho Lee,Duk Kyung Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

This paper investigates the performance of the high speed 2-parallel MB-OFDM ultra-wideband (UWB) receiver. Achieving high speed and low complexity become a challenge of UWB system design. In our solution, a highspeed low-complexity 2-parallel MB-OFDM UWB system with fixed point data type will be described and simulated.