Adjustable Phase Research Articles

Temperature-sensitive and self-healing shape-stable phase change materials containing temperature adjustable ionic liquid for improving the recycling stability and the applicability in cold energy storage

Advanced shape-stable phase change materials (SSPCMs) with environment self-adaptation are becoming more meaningful in regulating temperature in diverse applications. In this manuscript, a series of self-healing SSPCMs containing ionic liquids were fabricated by temperature-responsive polymers (PNIPAM) through the free radical polymerization method. 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) ionic liquid was selected as the cooling agent and PCM. 2-ureido-4[1H]-pyrimidinone (UPy) and chitosan oligosaccharide (COS) were chosen as modifiers. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to determine the chemical structure. The surface morphology of SSPCMs was observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). A rotational rheometer and electronic universal testing machine were used to assess the self-healing effectiveness and mechanical properties of SSPCMs. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the thermal characteristics and thermal reliabilities of self-healing SSPCMs. The results indicate that the self-healing efficiency of SSPCM is 91.04 % within 5 min, and compressive strength is improved by 65.7 % by the ionic liquid. The SSPCMs perform thermo-sensitive properties, which allow SSPCMs to maintain a stable shape in response to temperature change and reduce PCMs leakage. Furthermore, the SSPCMs can quickly and effectively recover their mechanical properties after damage thanks to the excellent self-healing properties. Meanwhile, the SSPCMs have a longer lifespan for improving recycling efficiency and are more environmentally friendly. The developed SSPCMs with recycle stability have a high energy density (251.5 J/g) and adjustable phase change temperature properties. The developed SSPCMs can be made to fit various temperature applications by changing the concentration of ionic liquids in the phase change system. Overall, the SSPCMs show promising potential for cold energy storage and thermal management.

A Simple and Universal Phase Control Method for Designing Directional Couplers With Adjustable Phase Difference Slope and High Linearity

Control of phase plays an indispensable role in applications such as high-efficiency power amplifiers and broadband beamforming networks. Designs of existing radio frequency (RF) components, however, have not comprehensively considered the phase characteristics within a certain operating band, such as phase slope and linearity. In this article, a simple and universal phase control method by using a 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> transmission line with fixed impedance and a 180 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> transmission line with variable impedance is proposed for the first time. By using this phase control unit in a branch-line directional coupler, the phase difference slope can be adjusted arbitrarily by simply changing the impedance of the 180 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> transmission line. For demonstration purposes, 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> directional couplers are designed based on single-section and multisection structures, respectively. Explicit theoretical analyses are given for both directional couplers to illustrate the working principle and parameters design. For verification, three circuits with different phase slopes are designed, fabricated, and measured for each coupler. According to the definition of the phase difference slope by ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi_{\mathrm{max}}-\varphi _{\mathrm{min}})$</tex-math> </inline-formula> /( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{max}}-f_{\mathrm{min}})$</tex-math> </inline-formula> , the measured results show that the 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> directional coupler can provide adjustable phase difference slopes from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 58.5 to 34 within the operating frequency range from 3.2 to 3.8 GHz. Within the same frequency range, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> directional coupler realizes an adjustable phase difference slope from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 36.5 to 94.3. In addition to the controllable phase slopes, both couplers achieve high slope linearity and fixed phase difference at the center frequency, which validate the effectiveness of the proposed structure.

Implementation of Safety Risk Management in Aircraft Airffame Maintenance

This study analyzes the application of Safety Risk Management in the practice of aircraft maintenance at AMTO (Aircraft Maintenance Training Organization) Indonesia Aviation Polytechnic Curug. The research method used is descriptive qualitative. Starting with hazard identification, risk assessment, and continuing with mitigation actions. Risk assessment uses the Risk Matrix. The results showed that 9 hazards were at tolerable levels, namely 4 hazards in the component release phase, 3 hazards in the inspection phase, and 2 hazards in the installation and adjustment phase. Recommended mitigation measures include additional training, safety briefing, safety promotion, supervision of important phases, and periodic checks on tools and equipment. This research is then used as a document for compliance with Safety Risk Management according to the SMS Implementation Plan at the AMTO (Aircraft Maintenance Training Organization) of the Indonesian Aviation Polytechnic Curug.

Aerodynamic performance of low aspect-ratio flapping wing with active wing-chord adjustment

In daily life, excellent aerodynamic performance of birds and bats has been widely observed during their flying and propulsion. In the present research, a low aspect-ratio wing flapping in uniform flow with a combined heaving-pitching motion has been adopted to mimic such aerodynamic process of flapping-wing-based propulsors. Inspired by the changeable skeleton of natural bio-livings, a bio-inspired flow controlling strategy based on active wing-chord adjustment has been raised to achieve aerodynamic enhancement. Adopting an Immersed Boundary-Lattice Boltzmann Method (IB-LBM) to resolve relating fluid flow with moving boundary, the effects of stretching pattern, i.e., the amplitude and the phase of the wing-chord adjustment, on the aerodynamic performance of the wing, and the role of Aspect-Ratio (Ar) have been confirmed and investigated in detail. With the Direct Numerical Simulation to achieve the vortical flow identification, detachment delaying of Leading Edge Vortex (LEV) and enhancement of Trailing Edge Vortex (TEV) have been observed for cases with in-phase active controlling, and it has been revealed that such phenomenons correlate well with the aerodynamic enhancement of the wing. On the other hand, it has been observed that, the out-phase wing-chord adjustment dominates the LEV detachment, and further the flow separation around the leading edge of the wing. It is believed that such flow detachment, together with the TEV weakening caused by the anti-phase wing-chord controlling, leads to the performance deterioration of the wing, compared with the in-phase case. Meanwhile, the present numerical results show that, with the increase of stretching ratio, the aerodynamic performance of the flapping wing becomes susceptible with respect to the stretching phase of wing-chord. Compared with the bounded thrust enhancement caused by the LEV bursting, the lifting enhancement of the flapping wing during the reinforced wing-chord adjustment shows consistent dependency on the stretching ratio.

Accurate dynamic quantitative phase imaging using multi-wavelength multiplexing

We present a novel, accurate, full-filed, dynamic quantitative phase imaging (QPI) technique by using multi-wavelength multiplexing and multi-plane iterative phase retrieval algorithm. In our method, a liquid crystal spatial light modulator is employed to flexibly generate multiple defocus intensity images at once, using its adjustable phase modulation characteristics of different wavelengths. Then these images contained at different wavelengths are captured by two color cameras with single exposure. To achieve accurate QPI, a multi-plane iterative phase reconstruction algorithm is also proposed based on transport of intensity equation (TIE). Finally, with these multiple defocus images, an accurate dynamic phase result can be provided by our approach. In addition, the errors caused by color coupling of color camera and chromatic aberration of the optical system are both analyzed and effectively compensated. Experiments conducted on the phase plate, living human colorectal cancer cells and human red blood cells well demonstrate the accuracy, dynamic measurement ability and flexibility of our method.

Constructing bifunctional TiO2 from NH2-MIL-125(Ti) for excellent photocatalytic tetracycline degradation

The defective and phase heterojunction bifunctional TiO2 with adjustable oxygen vacancy concentration and phase junction level was successfully designed via O2/Ar atmosphere thermal treatment NH2-MIL-125(Ti). The effects of calcination temperature on the morphology, light absorption properties, charge separation, chemical composition and tetracycline removal efficiency were researched. The decreased band gaps, effective charge transfer and more active sites on the photocatalysts could be achieved when the heat treatment temperature changed from 350°C to 500°C, both of which enhanced the photocatalytic degradation performance of tetracycline under visible light. The cooperation of moderate defect concentration and optimized anatase/rutile junction level can be obtained through the suitable calcination temperature at 400°C, and showed tetracycline removal activity about 2.5 times that of the initial NH2-MIL-125(Ti). Moreover, bifunctional TiO2 photocatalyst also displayed excellent stability and reusability after four cycle tests. This job provided a wonderful tactics for increasing the application of MOFs in tetracycline treatment.

Adaptive Convex Optimization Guidance for Lunar Landing

In this paper, a novel guidance algorithm based on adaptive convex optimization is proposed to ensure robustness in the uncertainty of a lunar lander’s parameters and satisfy the constraints of terminal position, velocity, attitude, and thrust. To address the problem of parameter uncertainty in the landing process, the parameter-adaptive method is used to achieve online real-time optimal estimations of specific impulse and mass by the optimal observer, and the estimated parameters are used to realize optimal trajectory programming. To overcome the difficulty in constraining the attitude and the thrust level at the final stage in the convex optimization process, a rapid adjustment phase is added to meet the final attitude and thrust constraints; the target-adaptive method is used to adjust the target adaptively at the same time. Therefore, the position and velocity deviations caused by the rapid adjustment phase can be eliminated by the target offset. Finally, the results of numerical experiments demonstrate the effectiveness of the proposed algorithm.

A Multimode 28 GHz CMOS Fully Differential Beamforming IC for Phased Array Transceivers

A 28 GHz fully differential eight-channel beamforming IC (BFIC) with multimode operations is implemented in 65 nm CMOS technology for use in phased array transceivers. The BFIC has an adjustable gain and phase control on each channel to achieve fine beam steering and beam pattern. The BFIC has eight differential beamforming channels each consisting of the two-stage bi-directional amplifier with a precise gain control circuit, a six-bit phase shifter, a three-bit digital step attenuator, and a tuning bit for amplitude and phase variation compensation. The Tx and Rx mode overall gains of the differential eight-channel BFIC are around 11 dB and 9 dB, respectively, at 27.0–29.5 GHz. The return losses of the Tx mode and Rx mode are &gt;10 dB at 27.0–29.5 GHz. The maximum phase of 354° with a phase resolution of 5.6° and the maximum attenuation of 31 dB, including the gain control bits with an attenuation resolution of 1 dB, is achieved at 27.0–29.5 GHz. The root mean square (RMS) phase and amplitude errors are &lt;3.2° and &lt;0.6 dB at 27.0–29.5 GHz, respectively. The chip size is 3.0 × 3.5 mm2, including pads, and Tx mode current consumption is 580 mA at 2.5 V supply voltage.

The Elite Construction Post-Authoritarianism Suharto

Suharto's New Order rule has ended with various political and economic dynamics and a vision of progressive development every five years. Suharto's New Order government became authoritarian for the sake of stability built in all regions of Indonesia, utilizing various power networks such as the military, businessmen, and oligarchs, and using Golkar as a political “boat” in every election. After the fall of Suharto, the remnants of elements of power and the oligarchs still existed in the reform era until the current Jokowi administration. The data was obtained through a literature study, a literature review, and in-depth interviews with a qualitative approach. The number of informants who were met was four informants. In addition, the views of scholars who are referred to are also to strengthen the arguments of the ideas that are designed and compiled. In analyzing, this article emphasizes inductive patterns or patterns of relationships between theoretical, conceptual, and empirical relationships. This article identifies how the transformation of the political and business elites, or the classical oligarchy that once lived forever in the New Order era, adjusted the situation and conditions of the political regime. In addition, this paper also shows that there is a phase of elite adjustment that impacts the emergence of a new style of authoritarianism in Indonesia. This article is to see how the elites adjusted themselves after the “Reformasi” in Indonesia with various political maneuvers, either involving themselves in the government or becoming trend setters outside the government until the Jokowi administration era.

Development of an asthenopia survey questionnaire for general surveys

Objective: To design a visual fatigue questionnaire that can be used for population surveys. Methods: This was a cross-sectional study that involved three stages of subjects' recruitment. In the first stage, by convenience sampling, 150 individuals who complained of visual fatigue were selected at public places in Wenzhou City in May 2016. The 19-Item Asthenopia Survey Questionnaire (ASQ-19) was used to conduct the survey, and the questionnaire was adjusted. In the second stage, 200 outpatient participants were recruited from Wenzhou Medical University Affiliated Eye and Optometry Hospital from June 2016 to May 2017 and were divided into a visual fatigue group and a control group based on clinical diagnosis. The adjusted visual fatigue questionnaire was used for validation. In the third stage, 64 outpatient participants who met the inclusion criteria were continuously recruited from the Wenzhou Medical University Affiliated Eye and Optometry Hospital in July 2022. They were tested using the adjusted visual fatigue questionnaire and retested one week later. During the questionnaire adjustment stage, factor analysis and feedback were used to adjust the scoring method and items of the ASQ-19 questionnaire. The adjusted questionnaire was then analyzed for reliability, validity, accuracy, and subject acceptance during the validation and retest stages. Results: A total of 403 participants were included, and 456 questionnaires were distributed. Eventually, 432 valid questionnaires were collected from 379 participants, resulting in a valid response rate of 94.7%. During the questionnaire adjustment phase, there were 140 valid questionnaires from 140 participants consisting of 56 males and 84 females with an average age of (35.2±12.4) years. In the questionnaire validation phase, there were 186 valid questionnaires from 186 participants. Sixty-two participants had visual fatigue and 124 were controls. During the questionnaire retesting phase, 53 participants yielded 106 valid questionnaires. The group consisted of 20 males and 33 females with an average age of (22.8±4.9) years. After factor analysis, the symptom severity graded as none, mild, moderate, severe, and very severe was scored as 0, 1, 2, 3, and 4 points, respectively. The total score was 44, and the final questionnaire consisted of 11 items (numbered 1, 2, 3, 5, 6, 8, 10, 15, 17, 18, and 19). The 11-Item Asthenopia Survey Questionnaire (ASQ-11) had a Cronbach's α coefficient of 0.89, a split-half reliability of 0.82, and a test-retest Pearson correlation coefficient of 0.90 (P<0.001). The structural validity was 51.26%, and the discriminative validity was a t-value of 9.19 (P<0.001). On average, it took (2.82±0.43) minutes for participants to complete the questionnaire. The receiver operating characteristic curve had a cutoff value of 8.5, with a sensitivity of 74.19% and a specificity of 80.65%. Conclusion: The ASQ-11, with fewer items and a shorter completion time, is easy for participants to use and is suitable for screening or self-assessment of visual fatigue in the general population. Additionally, it is convenient for clinical and epidemiological studies related to visual fatigue.

A data driven robust optimization model for scheduling near-zero carbon emission power plant considering the wind power output uncertainties and electricity-carbon market

Under the carbon peak and neutrality targets, the power generation industry in China is facing an urgent demand for a low carbon transition and participation in the electricity-carbon market. This paper novelty proposes a near-zero carbon emission power plant (NZCEP) integrating gas turbines, wind turbines, power-to-gas and the carbon capture, utilization and storage system. And a two-stage Data-driven Set based robust optimization (DSRO) model, including a day-ahead dispatching phase and a real-time adjustment phase, is conducted to ensure the consumption of renewable energy resources and to develop the optimal operating strategy for NZCEP participation under the electricity-carbon market. The results demonstrated the following outcomes: (1) NZCEP shows better environmental benefits by reducing carbon emissions and consuming renewable energy resources. (2) the DSRO model can resist the interference of wind power output uncertainties and address the issue of traditional robust models being overly conservative. (3) under the electricity-carbon market, NZCEP shows better economic benefits, which can generate additional revenue from selling surplus carbon emission allowances (CEA). Moreover, when the annual average CEA price reaches 355 CNY/t, the NZCEP will achieve full capital cost recovery.

Coherent manipulation of nitrogen-vacancy centers in diamond via frequency multiplication

Nitrogen-vacancy (NV) centers in diamond as ideally individual spin quantum systems can be coherently manipulated by microwave fields. Compared to the traditional method using the IQ (In-phase/Quadrature) mixer with a local oscillator and intermediate-frequency (IF) signals, we report an effective and technically simple method to generate the required microwave field by frequency multiplication and realize coherent manipulation of the NV center’s electron spin. After frequency multiplication, the IF signal can be directly converted to the high-frequency microwave field with adjustable pulse width, frequency, phase, and amplitude. A series of spin dynamics applications such as Rabi oscillation, free induction decay, and spin-locking are executed, which verified its performance and feasibility. Frequency multiplication can overcome the problem of clock synchronization between the local oscillator and IF signal and greatly reduce the complexity of the experimental system. The method can be easily used to realize a more complex quantum control sequence such as dynamic decoupling and extended to a wide range of spin-based quantum information applications in the future.

A customized two-stage parallel computing algorithm for solving the combined modal split and traffic assignment problem

Efficiently solving the traffic assignment problem (TAP) for large-scale transport networks is a critical problem for transportation studies. Most of the existing algorithms for TAP are serial ones based on single-computer mode, which has inherently limited the computational efficiency, compared with parallel computing methods. Thus, this paper aims to propose an efficient distributed multi-computer cluster resource allocation method for the parallel computing of TAP. Previous studies on the parallel computing of TAP are mainly based on a single-mode, which is extended to a more complex combined modal split and traffic assignment (CMSTA) case in this paper. In order to decompose the CMSTA problem, we proposed a block-decomposed model for solving the CMSTA problem. Then we designed an optimal parallel computing resource schedule for solving each block problem more quickly on the huge transportation network. Therefore, we implemented a customized two-stage parallel (TP) algorithm that can fully use parallel resources. The first parallel stage of the TP algorithm is used in the path generation phase, and the second parallel stage is used in the path flow adjustment phase. Besides, the parallel slowdown is uncovered in calculating each block problem of the path flow adjustment phase by using parallel resources. Numerical examples are taken to validate the efficiency and robustness of the proposed TP algorithm.

COVID-19 impact on the decision process of the Italian Medicine Agency: a quantitative assessment.

Since the COVID-19 pandemic has placed more attention on drugs' approval process and the importance of rapid decision-making in the healthcare sector, it is crucial to assess how time to market (TTM) of drugs varied. To estimate the impact of the COVID-19 pandemic on TTM of drugs in Italy. An IQVIA database was used to retrieve information on drugs that obtained positive opinion from the Committee for Medicinal Products for Human Use between January 2015 and December 2021. The available observations were divided into three groups (Pre COVID, Partially COVID, and Fully COVID) according to the timing of their negotiation process. Differences in average TTM among the three groups were analyzed in three steps: (1) descriptive statistics; (2) univariate analysis; (3) multivariate analysis, using a matching estimator. A total of 363 unique combinations of molecule and indication met the inclusion criteria: 174 in the Pre COVID group, 69 in the Partially COVID group, and 123 in the Fully COVID group. Descriptive statistics and univariate analysis found a statistically significant difference in TTM among the three periods, with average TTM increasing during the pandemic (+136 days, p = 0.00) and then decreasing afterward (-23 days, p = 0.09). In the matching analysis, results for the Partially COVID period were confirmed (+108 days, p = 0.00) while results for the Fully COVID period lost significance but maintained a negative sign. The results suggest that after an adjustment phase in the Partially COVID period, a return to the status quo was reached.

Atomic and Electronic Reconstruction in Defective 0D Molybdenum Carbide Heterostructure for Regulating Lower‐Frequency Microwaves

Abstract0D nanomaterials with high efficiency of atom utilization possess extraordinary tunability over bulk materials. Precise reconstruction of atoms in a 0D nanoparticle toward tuning of crystalline phases and defects is highly desirable but remains a grand challenge. In this study, a crystallization rate‐controlled strategy is reported to achieve controllable reconstruction of atoms in situ, which inducts a series of monodisperse 0D molybdenum carbide nanoparticles (MoxC NP) that anchor on a carbon matrix with adjustable crystalline phases and atom vacancies. Aberration‐corrected transmission electron microscopy, electron paramagnetic resonance technique, density functional theory calculation, and electron holography jointly reveal the atomic reconstruction process and confirm its remarkable effects of optimizing the local electronic states and enhancing the heterointerface interactions. As a result, the optimized MoC/Mo2C heterostructure on the carbon matrix is shown to enable the promoted dielectric response and generate more than 90% absorption of lower‐frequency microwaves (the current 5th‐generation communication band). The control of atomic reconstruction may provide an effective pathway for unlocking tunable dielectric properties of 0D nanomaterials toward various technological applications.

A 48 Gb/s PAM-4 Receiver With Pre-Cursor Adjustable Baud-Rate Phase Detector in 40 nm CMOS

This article presents a 48-Gb/s four-level pulse amplitude modulation (PAM-4) receiver with a Baud-rate clock and data recovery (CDR) suitable for multi-level signaling. By deriving the relation between the vertical eye margin (VEM) and the ratio of main-cursor to pre-cursor, the proposed Baud-rate phase detector (BRPD) adjusts the pre-cursor and finds the lock point with targeted vertical eye opening. Thus, the BRPD offers a unique lock point when used with an adaptive decision feedback equalizer (DFE) where post-cursor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h_{1}$</tex-math> </inline-formula> is removed. Otherwise, the lock point could drift with the conventional Mueller–Müller phase detector (PD). Furthermore, a summer loading of the DFE reduces the input loading of the DFE by embracing the RZ sampler output instead of the conventional NRZ output, which adds to the delay associated with an RS latch. A prototype chip fabricated in 40-nm CMOS technology consists of an analog front-end (AFE), a phase rotator (PR), a current digital-to-analog converter (DAC), and synthesizable digital logic (SDL), occupying a total active area of 0.24 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> . The proposed PAM-4 receiver achieves a bit-error rate (BER) of less than 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-11}$</tex-math> </inline-formula> at 48 Gb/s and offers an energy efficiency of 2.42 pJ/b.

Dynamic-Subarray With Fixed Phase Shifters for Energy-Efficient Terahertz Hybrid Beamforming Under Partial CSI

Terahertz (THz) communications are regarded as a pillar technology for the 6G systems, by offering multi-ten-GHz bandwidth. To overcome the huge propagation loss, THz ultra-massive MIMO systems with hybrid beamforming are proposed to offer high array gain. Notably, the adjustable phase shifters considered in most existing hybrid beamforming studies are power-hungry and difficult to realize in the THz band. Moreover, due to the ultra-massive antennas, full channel-state-information (CSI) is challenging to obtain. To address these practical concerns, in this paper, an energy-efficient dynamic-subarray with fixed phase shifters (DS-FPS) architecture is proposed for THz hybrid beamforming. To compensate for the spectral efficiency loss caused by the fixed phase of FPS, a switch network is inserted to enable dynamic connections. In addition, by considering the partial CSI, we propose a row-successive-decomposition (RSD) algorithm to design the hybrid beamforming matrices for DS-FPS. A row-by-row (RBR) algorithm is further proposed to reduce the computational complexity. Extensive simulation results show that, the proposed DS-FPS architecture with the RSD and RBR algorithms achieves much higher energy efficiency than the existing architectures. Moreover, the spectral efficiency of the DS-FPS architecture with the proposed algorithms is robust to the CSI error.

Arbitrary Current Harmonic Decomposition and Regulation for Permanent Magnet Synchronous Machines

This paper contributes a novel solution for the regulation of arbitrary current harmonics in a permanent magnet synchronous machine (PMSM) system by introducing a virtual three-phase system. The inverter nonlinearity, back-EMF harmonics, and the asymmetry among phases, are considered to derive a comprehensive electrical model of PMSMs. Compared to the conventional harmonic analysis, the derived model indicates that more new current harmonics can exist in the PMSM system. To regulate the current harmonics with arbitrary orders, a virtual three-phase system is established. By properly shifting the spatial and time phase angles between the virtual three-phase system and the original physical three-phase system, the selected current harmonics can be decomposed from the phase current. A simple proportional-integral regulator with adjustable phase compensation angle is designed based on the proposed model to regulate the decomposed current harmonics in the corresponding harmonic synchronous reference frame. The implementation details and experimental results are provided to illustrate the feasibility and correctness of the proposed control strategy.

Magnetic and magnetocaloric properties of R55Co30Al10Si5 (R = Ho, Dy) metallic glass ribbons

Metallic glass alloys are suitable systems for the development of magnetocaloric refrigerated materials due to the stable physical properties and the adjustable magnetic phase transition temperature. Here, the glass formation ability (GFA), magnetic properties and magnetocaloric effects of R55Co30Al10Si5 (R = Ho, Dy) amorphous ribbons prepared by the melt-spinning technique were investigated. The X-ray diffraction and DSC measurement indicated that the metallic glass alloys have a completely amorphous structure and excellent glass formation ability. The amorphous ribbons were demonstrated to undergo a second-order magnetic phase transition (ferromagnetic to paramagnetic) around Tc ∼ 18 K for Ho55Co30Al10Si5, ∼34 K for Dy55Co30Al10Si5, respectively. The maximum magnetic entropy change (-ΔSMmax) and the corresponding refrigerant capacity (RC) values are 12.7 J/kg K, 343 J/kg for Ho55Co30Al10Si5, 9.1 J/kg K, 334 J/kg for Dy55Co30Al10Si5 under a field change ΔH= 5 T. The large -ΔSMmax and high RC suggest that R55Co30Al10Si5 (R = Ho, Dy) amorphous ribbons have potential applications in low temperature magnetic refrigeration.

Hydrate salt/fumed silica shape-stabilized composite phase change material with adjustable phase change temperature for radiant floor heating system

Radiant floor heating system combined with hydrate salt phase change materials (PCMs) can obtain energy savings along with improving thermal comfort. However, the inappropriate phase change temperature and the leakage of PCM limit its further applications. Here, sodium acetate trihydrate (SAT)-potassium chloride (KCl)-urea composite phase change material (CPCM) was composited with fumed silica (SiO2) to prepare shape-stabilized CPCM (SSCPCM) with adjustable phase change temperature for use in floor radiant heating. The effects of the mass fraction of SiO2 on phase change properties, and shape-stabilized ability of SSCPCM were emphatically studied. Besides, the morphology, porous structure analysis and chemical compatibility and related thermal properties of SSCPCM were discussed detailedly. The results manifested that SiO2 could not only regulate the melting temperature of SAT-KCl-urea CPCM, but also stabilize CPCM into its porous structure with large surface area and high porosity. Meanwhile, SSCPCM with 30 wt% SiO2 exhibited a good shape stability, and melted at 40.85 °C with high latent heat of 132.6 J/g, low supercooling degree of 0.29 °C as well as good thermal stability and thermal reliability. The result comparison of two test rooms confirmed that phase change floor radiant heating system can effectively increase the duration of indoor thermal comfort. All good thermal properties of SSCPCM make it prospective potential in radiant floor heating system for building energy efficiency.