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Two feeding trials were conducted to evaluate the influence of dietary curcumin level on fish meal replacement with poultry by-product (PBM) in a largemouth bass (Micropterus salmoides) diet. In trial I, the reference diet (R) contained 400 g/kg fish meal, and PBM replaced 60 and 80% of the fish meal (P16 and P8). In trial II, the diet containing 80 g/kg fish meal (P8) served as control (C), and curcumin was added at 5000 and 10000 mg/kg (C5 and C10), respectively. Replacement of fish meal with PBM significantly influenced feed intake, phosphorus retention efficiency (PRE), body lipid content, the ratio of fish meal consumption to fish production (RCP), and wastes of carbon and phosphorus but did not result in significant alternation in weight gain, feed conversion ratio (FCR), retention efficiencies of nitrogen (NRE), carbon (CRE) and energy (ERE), viscerosomatic index (VSI), hepatosomatic index (HSI), and body composition. The RCP, body lipid content, and phosphorus waste were higher in fish fed diet R than in fish fed diets P16 and P8. Curcumin supplementation influenced weight gain, feed intake, FCR, carbon waste, and RCP, but did not result in significant alternation in CRE, NRE, PRE, ERE, condition factor, VSI, HSI, body composition, and nitrogen and phosphorus wastes. The weight gain and feed intake were higher in fish fed diet C10 than in fish fed diet C, while the carbon waste was higher in fish fed diets C5 and C10 than in fish fed diet C. Overall, the minimum dietary fish meal level for largemouth bass could be dropped to 80 g/kg when PBM was used as an alternative ingredient, and 10000 mg/kg curcumin could obviously improve growth of fish fed diet containing 80 g/kg fish meal.

Massive multiple-input and multiple-output (MIMO) is considered as an advanced technique in wireless communication due to its high spectral efficiency, data rates, and transmission reliability. However, the large number of antennas makes it challenging to design efficient detectors since computational complexity is much higher. Thus, conventional linear methods like minimum mean square error (MMSE) detection suffer from prohibitive complexity. To balance complexity and performance, a class of iterative linear methods are considered to approach MMSE performance with $\mathcal {O}({N_{T}}^{2})$ complexity, where $N_{T}$ is the number of transmit antennas. Among them, successive over relaxation (SOR) detector is promising since it achieves near MMSE performance with affordable complexity and fast convergence. However, error performance of previously proposed SOR detectors is sensitive to a relaxation factor $\omega $ , especially when the channel varies. To address this issue, two detectors are proposed in this paper: non-adaptive SOR (NA-SOR) detector (with fixed $\omega $ ) and adaptive SOR (A-SOR) detector (with iteratively changed $\omega $ ). Compared to prior SOR detectors, the performance of the NA-SOR detector is more robust to $\omega $ , and the A-SOR detector achieves better performance, especially in highly correlated channels. An efficient pipelined hardware architecture of the A-SOR detector is proposed. Implementation results show advantages when compared to the state-of-the-art (SOA).

We design and numerically investigate a broadband tunable terahertz polarization converter based on graphene metamaterial. The converter presents a broad conversion band with high polarization conversion ratio (>0.95) in terahertz frequency over a bandwidth which is 25.8% of the central frequency. The converter can be dynamically tuned by varying the Fermi Energy of the graphene without changing the geometric structure. The converter shows high conversion ratio for a wide range of incident angles from 0 to 40°. By the scaling of the proposed structure, the broadband properties of the converter can be easily spread to other frequency. The proposed metamaterial offers an approach in the manipulation of the light polarization and has potential applications in imaging, sensing and communications.

A tunable external cavity diode laser (ECDL) system with narrow line-width emission at 410 nm is presented. Based on a commercially available laser diode and a Littrow arranged reflective holographic grating, a maximum output power over 500 mW with line-width of about 50 pm is achieved at the rated current. The power efficiency is over 85% and the threshold decreases over 20% compared to the free-running laser diode. Manual tuning range over 5 nm is achieved around threshold condition and over 2 nm at high injection currents up to 500 mA with side mode suppression ratio larger than 20 dB.

Massive multiple-input multiple-output (MIMO) is considered as one of the key techniques in today's 5G wireless communication systems. Though massive MIMO can achieve higher data rate and spectral efficiency compared with small-scale MIMO, its high complexity becomes a problem when hundreds of antennas are equipped. For uplink massive MIMO detection, conventional schemes like zero forcing (ZF) and minimum mean square error (MMSE) are prohibitive due to the unaffordable complexity. To this end, successive over relaxation (SOR) detection is proposed, which iteratively approaches the performance of MMSE with much lower complexity. However, the performance of SOR is often unsatisfactory enough especially in some ill channel conditions. For a better compromise between performance and complexity, Chebyshev-SOR detection is proposed in this paper. Using Chebyshev acceleration, the proposed method can achieve faster convergence and better performance than conventional SOR, especially in ill channel conditions. Numerical results with different channel conditions are given in detail, which show that Chebyshev-SOR method achieves 5dB gain with little complexity overhead. Computational complexity comparison is also given in this paper.

A stable external cavity diode laser coupled with volume Bragg grating for metastable argon atoms pumping is presented. The measured maximum output power of the continuous wave is 6.5 W when the spectral width (FWHM) is less than 21 pm around 811.53 nm and the power efficiency is 68%. The tuning range of the emission wavelength is bigger than 270 pm. The calculated deviation in relative absorption efficiency caused by the fluctuations of wavelength and power is less than 4%.

For massive multiple-input multiple-output (MIMO) detection, minimum mean square error (MMSE) method can achieve close-to-optimal performance. However, its computational complexity is proportional to the third power of antenna elements due to the inevitable matrix inversion operation. Especially when the number of transmitting antennas is very large, exact MMSE detection method becomes disabled owing to the excessive complexity. In this paper, an adaptive damped Jacobi (DJ) method is proposed firstly to iteratively realize MMSE performance without the intractable matrix inversion. By automatically updating the optimal relaxation factor w with the increase of iterations, the adaptive scheme does not require careful selection of initial relaxation factor compared to the conventional fixed-w DJ method. Simulation results have shown that the proposed adaptive DJ is more applicable to the correlated MIMO channels for its great flexibility of relaxation factor ω. Additionally, the hardware architecture design is also presented in this paper.

With low-density parity-check (LDPC) code and polar code selected as the standard codes for 5G eMBB scenario, one challenge is how to improve the hardware efficiency when both decoders are required by one system. Since LDPC and polar codes can be decoded with belief propagation (BP) algorithms, this similarity allows us to design a reconfigurable decoder, which can decode both codes at the cost of only one decoder. Numerical and implementation results are also given in this paper to show that the proposed decoder achieves higher hardware efficiency than stand-alone LDPC or polar decoder, without harming the error performance.

Low-density parity-check (LDPC) coded massive multiple-input and multiple-output (MIMO) scheme is getting increasingly popular and sophisticated in today's wireless communication systems, since it can highly improve the spectral efficiency, data rates, and error performance. In this paper, a novel iterative detection and decoding (IDD) method for LDPC-coded massive MIMO systems is proposed. Based on successive over relaxation (SOR) MIMO detection, LDPC decoding process is carried out after every detection iteration when applying IDD method. In other words, SOR detection iteration and LDPC decoding iteration are executed serially in every IDD iteration. With this method, the error performance is highly improved. When BER = 4×10−4, the proposed IDD method can achieve more than 5 dB gain compared with non-IDD method. Details of simulation, computational complexity, and hardware implementation are also shown in this paper.

By adopting multiple-input multiple-output (MIMO) technique, the spectral efficiency and data rate of wireless communication systems can be highly improved. To fully take the advantages of MIMO, belief prorogation (BP) detection methods are considered as a way in balancing the hardware complexity and error performance. Also with BP methods, polar code, which has been adopted by 3GPP eMBB control channel, can achieve high reliability and throughput. In this paper, a graph merged detection and decoding (GMDD) method for polar-coded MIMO systems is proposed. When the factor graphs of MIMO detection and polar decoding are merged, the GMDD methods can help to achieve better error performance with nearly no additional cost of hardware and latency compared with the conventional separated detection and decoding (SDD) method, which has been verified by numerical results. The hardware architecture of the proposed GMDD method is given in this paper as well.

Both massive multiple-input multiple-output (MI-MO) technique and low-density parity-check (LDPC) codes have been considered as indispensable parts of 5G wireless. To improve the hardware efficiency and flexibility, a uniform belief propagation (BP) processor which can take care of both massive MIMO detection and GF(2n) LDPC decoding is proposed. To this end, the unified BP representation for BP detection and decoding is first proposed. Folding technique has been considered for further improvement of hardware efficiency and flexibility. For better illustration, a folded prototype of (8, 4) GF(2) LDPC coded 2×2 4-QAM MIMO system is implemented with FPGA. Numerical simulations and implementation results have demonstrated the feasibility of the proposed design methodology.

Graphene has attracted much attention due to its unique optical properties as a new kind of plasmonic metamaterial in the terahertz regime. Here, we theoretically investigated a wavelength tunable plasmon induced transparency (PIT) device based on graphene metamaterials which is composed of periodically patterned graphene nanostructures. The interactions and coupling between plasmonic modes are investigated in detail by analyzing the field distributions and spectral responses. The coupled Lorentz oscillator models are used to explain the physical mechanism of the PIT. The finite-difference-time-domain (FDTD) method is used to investigate the tunable properties of the structure. It is shown that the coupling strength between the bright mode and dark mode is tuned by the coupling distance between the elements of the proposed structure. By varying the Fermi level of graphene, the PIT resonant frequency can be dynamically tuned. Furthermore, we demonstrate numerically that tunable slow light can be realized in our patterned graphene metamaterials.

Raman spectroscopy is a powerful diagnostic technique in gas analysis. Based on a home-made narrow line-width high power violet external cavity diode laser and a parabolic sample cell, sensitive Raman gas analysis is achieved. A 3 σ limit of detection of 39.5 ppm is demonstrated for C2H4 with exposure time of 100 s.

Studies on the application of a parabolic reflector in spontaneous Raman scattering for low background Raman analysis of gas samples are reported. As an effective signal enhancing sample cell, photonic bandgap fiber (HC-PBF) or metallined capillary normally result in a strong continuous background in spectra caused by the strong Raman/fluorescence signal from the silica wall and the polymer protective film. In order to obtain enhanced signal with low background, a specially designed sample cell with double-pass and large collecting solid angle constructed by a parabolic reflector and a planar reflector was applied, of which the optical surfaces had been processed by diamond turning and coated by silver film and protective film of high-purity alumina. The influences of optical structure, polarization characteristic, collecting solid-angle and collecting efficiency of the sample cell on light propagation and signal enhancement were studied. A Raman spectrum of ambient air with signal to background ratio of 94 was acquired with an exposure time of 1 sec by an imaging spectrograph. Besides, the 3σ limits of detection (LOD) of 7 ppm for H 2 , 8 ppm for CO 2 and 12 ppm for CO were also obtained. The sample cell mainly based on parabolic reflector will be helpful for compact and high-sensitive Raman system.

A compact Raman system constructed by a parabolic sample cell and an imaging spectrograph, which has good capability for enhancing a Raman signal and compressing a continuous background, has been put forward. In the Raman spectra of ambient air acquired by this system, the signal level of Nsub2/subwas enhanced up to 14 times compared with free space, and the related signal to background ratio was increased nearly to 96. With an integration time of 10 s, the rotational fine structure of Osub2/suband Nsub2/subwere clearly recognized. Besides, a standard analytic gas mixture consisting of Hsub2/sub, COsub2/sub, and CO was also tested, and the 3σ LODs of 68 ppm for Hsub2/sub, 54 ppm for COsub2/suband 116 ppm for CO were obtained.

Spectroscopy applications of free-running laser diodes (LD) are greatly restricted as its broad band spectral emission. And the power of a single blue-violet LD is around several hundred milliwatts by far, it is of great importance to obtain stable and narrow line-width laser diodes with high efficiency. In this paper, a high efficiency external cavity diode laser (ECDL) with high output power and narrow band emission at 405 nm is presented. The ECDL is based on a commercially available LD with nominal output power of 110 mW at an injection current of 100 mA. The spectral width of the free-running LD is about 1 nm (FWHM). A reflective holographic grating which is installed on a home-made compact adjustable stage is utilized for optical feedback in Littrow configuration. In this configuration, narrow line-width operation is realized and the effects of grating groove density as well as the groove direction related to the beam polarization on the performances of the ECDL are experimentally investigated. In the case of grating with groove density of 3600 g/mm, the threshold is reduced from 21 mA to 18.3 mA or 15.6 mA and the tuning range is 3.95 nm or 6.01 nm respectively when the grating is orientated in TE or TM polarization. In addition, an output beam with a line-width of 30 pm and output power of 92.7 mW is achieved in TE polarization. With these narrow line-width and high efficiency, the ECDL is capable to serve as a light source for spectroscopy application such as Raman scattering and laser induced fluorescence.

Spontaneous Raman scattering is an effective technique in gas analysis, but the detection of minor constituents is difficult because of the low signal level and the usually existed background. Imaging spectrometer can provide highly spatial resolved spectra, so it should be much easier to pick up Raman signal of minor constituents from the Raman/fluorescence background of the sample cell and transporting optics compared with the widely used fiber-coupled spectrometers. For this reason, an imaging spectrometer was constructed from transmitting volume phase holographic grating, camera lenses and CCD detector. When it was used to analyze the gas sample in metal-lined capillary, which is a sample cell believed with great enhancement of Raman signal, the background was compressed obviously. When it was used to analyze the gas in a sample cell including a parabolic reflector, only weak background signal was observed, as the wide separation between the collecting zone (the focus point of the parabolic surface) and the wall of sample cell benefitted to the analysis by imaging spectrometer. By using the last sample cell, the signal from CO 2 in ambient air was able to be found by an exposure time about 20 sec, and limits of detection for H 2 , CO 2 and CO were estimated as 60 ppm, 100 ppm and 300 ppm respectively by the results of a longer exposure time. These results show that an imaging spectrometer paired with a well-arranged sample cell will lower the detecting limit effectively.

Sensitive Raman gas analysis based on a home-made high power 410 nm Littrow-arranged external cavity diode laser (ECDL) and a parabolic sample cell is presented. Using a commercially available violet laser diode and a reflective holographic grating, the ECDL achieves a maximum output power of 505 mW with line-width about 50 pm. Spontaneous Raman scattering of ambient air is acquired with this ECDL, in which an imaging Raman spectrometer is applied. Strong Raman signals of O2, N2 and H2O are observed with 1 s exposure time; a limit of detection (LOD) of CO2 about 210 ppm is achieved with an exposure time of 100 s; and a 3.5-fold enhancement to the signal level is also demonstrated compared with a 532 nm green laser with the same exciting power. The results show that violet diode laser can be an attractive excitation source for Raman gas analysis.