This paper proposes a systematic design and formation process for the asymmetric compound parabolic concentrator taking the angular acceptance range as the target function and a dielectric asymmetric ...compound parabolic concentrator (DACPC) that presents almost unity angular acceptance efficiency is got. Ray-tracing simulation and experimental characterization study were conducted to reveal the optical performance of the DACPC. It was found that the DACPC with the geometric concentration ratio of 2.4 increased the short-circuit current and the maximum power by 87.0% and 96.6% averagely within the incidence angels of 0°–85° as compared with the non-concentrating photovoltaic cell. Corresponding average simulation and actual optical efficiency of it are 93.3% and 77.9%. The angular acceptance efficiency is proposed to evaluate the annual performance potential and regional applicability for optical concentrators, which indicates that the angular acceptance efficiency of the DACPC can be up to 97.7% for simulation results and 94.4% for experiment results. The outdoor experiments on 25th June when the projected incidence angle lied in the range of 60°–89° for the DACPC were conducted. It was found that the DACPC can still increase the short-circuit current and maximum power of the photovoltaic cell by average factors of 57% and 76% respectively.
•The formation process of the DACPC was introduced.•Angular acceptance efficiency was developed to predict annual performance of DACPC.•The indoor and outdoor experimental researches were performed for the DACPC-PV.•Angular acceptance efficiency of the DACPC can be up to 97.7%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Spectral thermal radiation model based on the spectral parameters was built and validated.•Negative energy-flow region (NER) partially around the solar receiver was discovered.•Quantitative analyses ...on NER by the proposed negative energy-flow index were investigated.•A novel optimization strategy by introducing a radiation shield into the receiver was proposed.•The heat loss of the novel receiver was effectively reduced by 35.9%.
Parabolic trough solar receivers are the key heat-collecting elements (HCEs) in parabolic trough collectors (PTCs). However, the HCEs emit considerable heat loss at high operating temperature, which exerts significantly negative impact on the thermal performance of the HCE and PTC. For accurately calculating the thermal radiation in HCEs, a novel spectral thermal radiation model based on the spectral parameters was established and validated. Comparison between the simulation results and experimental data demonstrated the model yielded satisfactory consistency. Integrating the achieved spectral thermal radiation with circumferentially maldistributed solar irradiance, a rarely mentioned phenomenon of negative net heat gain and negative energy-flow region (NER) partially around the HCE were discovered. NER exercises adverse influences on the thermal performance of the HCE. In this study, quantitative analyses on the NER by the proposed negative energy-flow index (NEI) were investigated. The effects of parameters, namely, absorber temperature, solar irradiance, on the NER and HCE were studied as well. Besides, a novel optimization strategy by introducing a radiation shield for effectively reducing the heat loss was proposed. The performance of the proposed novel HCE with an inner radiation shield (NHCE-RS) was also investigated. Results showed NEI can scientifically analyze the negative net heat gain and thermal performance in NER, and NHCE-RS has superior thermal performance at higher absorber temperature and lower solar irradiance. The heat loss of the NHCE-RS was effectively reduced by 35.9% at the absorber temperature of 600 °C and solar irradiance of 500 W/m2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A spectral–spatial coupling analysis of receiver is carried out.•Negative thermal-flux region and local optimal cutoff wavelength are found.•A novel receiver using two selective coating is ...proposed.•Heat loss reduction of 41.0% is reported for the optimized receiver.•Thermal efficiency enhancements of 10.2%–40.2% of the receiver are presented.
The parabolic trough system is one of the main technological routes to achieve high-temperature solar thermal conversion. The parabolic trough system is a mature technology and can be easily coupled with distributed systems. However, the parabolic trough receiver, which is a key component of the parabolic trough system, suffer from enormous radiation heat loss at high temperature. An analytical model based on spectral-spatial coupling distributed parameters is developed. Analytical results reveal that >40% surface area of the absorber is negative thermal-flux region and exposes the widely long-term thermal performance weakness in circumferentially uniform receiver design. A local optimal cutoff wavelength is reported. Results show that the exists asymmetrical design of the receiver can reduce radiation heat loss by approximately 41.0% and improve photothermal efficiency by 10.2–42.0% as solar irradiation varies from 1000 W/m2 to 200 W/m2 at 600 °C. The asymmetric design may be a promising choice for optimization of the receiver due to the strong heterogeneity of the solar flux distribution at high temperature. The discovery of negative thermal-flux region and local optimal cutoff wavelength also leads to the optimization of other concentrated solar technologies for improving photothermal performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The demands of cooling, heating and electricity in residential buildings are varied with seasons. This article presented a seasonal solar combined cooling heating and power (CCHP) system based on ...evacuated flat-plate collectors and organic Rankine cycle. The heat collected by evacuated flat-plate collectors is used to drive the organic Rankine cycle unit in spring, autumn and winter, and drive the double-effect lithium bromide absorption chiller in summer. The organic Rankine cycle condensation heat is used to yield hot water in spring and autumn, whereas supply heating in winter. The system thermodynamic performance was analyzed. The results show that the system thermal efficiency in spring, autumn and winter, ?sys,I, increases as organic Rankine cycle evaporation temperature, T6, and evacuated flat-plate collectors outlet temperature, T2, decrease. The maximum ?sys,I of 67.0% is achieved when T6 = 80?C and T2 =100?C. In summer, the system thermal efficiency, ?sys,II, increases first and then decreases with the increment of T2. The maximum ?sys,II of 69.9% is obtained at T2 =136?C. The system output performance in Beijing and Lanzhou is better than that in Hefei. The average output power, heating capacity, hot water and cooling capacity are 50-72 kWh per day, 989-1514 kWh per day, 49-57 ton per day and 1812-2311 kWh per day, respectively. The system exergy efficiency increases from 17.8-40.8% after integrating the organic Rankine cycle unit.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A simple miniaturized microstrip lowpass filter with broad stopband is proposed. The filter comprised of four open ended stubs. Transmission zeros are generated by open ended stubs and the coupling ...with each other. For the designed lowpass filter, an insertion loss of less than -1dB from dc to 5GHz and the rejection is better than 20dB from 8GHz to 25GHz.The size of the filter is only 5.5mm×6mm.
A novel dsign of UWB microstrip high-pass filter Huijun Feng; Honglun Yang; Weiqin Chen
2015 16th International Conference on Electronic Packaging Technology (ICEPT),
08/2015
Conference Proceeding
This paper presents a ultra-wideband (UWB) micro-strip structure high-pass filter with multi-stubs. The proposed filter was designed using a combination of 4 short-circuited stubs and an ...open-circuited stub in the form of micro-strip lines. The short-circuited stubs are to realize a high-pass filter with a bad band rejection. In order to achieve a steep cutoff, a transmission zero can be added thus an open-circuited stub is used. The passband is 5-19 GHz. The insertion loss is greater than -2dB and the return loss is less than -10dB, while the suppression of the modified filter is better than 30 dB below 4.2GHz.
In this paper, a new type suspended substrate stripline highpass filter with simple structure is presented. The filter consists of 50 ohm input and output, one Y type short stub on the top layer and ...two similar to T type short stubs on the bottom layer. It will introduce coupling capacitances by put sheetmetals close to each other. The coupling capacitances and inductances will compose the series resonators to produce transmission zeros. Thus the filter has a good restraint outside the passband. The simulation has a good result. The passband is from 5 GHz to 25 GHz, insertion loss is greater than -2 dB and return loss is less than -12 dB. At the same time, there are two transmission zeros at the low frequency.
Design of a new type micro-tri-mode filter Honglun Yang; Huan Xin; Yuzhu Wang
2015 16th International Conference on Electronic Packaging Technology (ICEPT),
08/2015
Conference Proceeding
In this paper, a new type micro-tri-mode filter with simple structure is presented. On the basis of the square ring dual-mode filter, it can introduce the third mode by loading the open stubs in the ...center of the square ring dual-mode filter. Adjusting the size of the open stubs can reduce the resonant frequency of the third mode, so it can form a micro-tri-mode filter. Meanwhile, through the introduction of capacitive coupling between the source and the load, so that this filter has three transmission zeros and can be adjusted by the direct coupling between the source and the load to change location of transmission zeros. The results of simulation are very good. The passband is 2.85 ~ 3.15 GHz. The insertion loss is greater than -2dB and the return loss is less than -12dB, and there are two transmission zeros at 2.45 GHz and 3.45 GHz.
The sun (~6000 K) and outer space (~3 K) are the original heat source and sink for human beings on Earth. The energy applications of absorbing solar irradiation and harvesting the coldness of outer ...space for energy utilization have attracted considerable interest from researchers. However, combining these two functions in a static device for continuous energy harvesting is unachievable due to the intrinsic infrared spectral conflict. In this study, we developed spectral self-adaptive absorber/emitter (SSA/E) for daytime photothermal and nighttime radiative sky cooling modes depending on the phase transition of the vanadium dioxide coated layer. A 24-hour day-night test showed that the fabricated SSA/E has continuous energy harvesting ability and improved overall energy utilization performance, thus showing remarkable potential in future energy applications.
Mycotoxins exposure from foodstuffs can trigger serious health hazards (e.g. cancers, deformity and mutation), which has been a global public health concern.
In recent years, large-scale poisoning ...incidents and international trade disputes caused by fungal contamination are extremely common. Unremitting efforts have been devoted to the investigations on classification, toxicity and occurrence of mycotoxins. Monitoring mycotoxins is highly important to ensure human health. Pretreatment technologies offer a pre-analytical separation process for reducing the instruments contamination, signal interference and matrix effects of complex foodstuffs.
In this review, the classification, toxicity and occurrence of mycotoxins were concisely summarized. We then concentrated our attentions on the methods of extraction, clean-up, separation and determination of mycotoxins. Especially, the rapid development of nanotechnology has brought many opportunities for sample pretreatment. We have also summarized the available and advanced adsorbents based on the emerging nanomaterials for pretreatment of mycotoxins in foodstuffs. At the end of the article, future opportunities and challenges in the field of mycotoxins research are tentatively proposed.
Key Findings and Conclusions: This review comprehensively summarized the latest achievements and improvements in the classification, toxicity, occurrence and detection approaches of mycotoxins. Impressively, the sample pretreatment and detection methods applied for mycotoxins determination in foodstuffs have been summarized, regarding the novel nanomaterial-based pretreatment technologies as well as the development of chromatographic and sensing technologies in the last six years. Furthermore, the current trends and the future perspectives in the toxicity and detection method of mycotoxins are tentatively proposed.
•Classification, toxicity and occurrence of mycotoxins were concisely summarized.•New methods of extraction, separation and determination of mycotoxins were reviewed.•Future opportunities and challenges of mycotoxins research are tentatively proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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