The Global Search for Liquid Water on Mars from Orbit: Current and Future Perspectives

Due to its significance in astrobiology, assessing the amount and state of liquid water present on Mars today has become one of the drivers of its exploration. Subglacial water was identified by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard the European Space Agency spacecraft Mars Express through the analysis of echoes, coming from a depth of about 1.5 km, which were stronger than surface echoes. The cause of this anomalous characteristic is the high relative permittivity of water-bearing materials, resulting in a high reflection coefficient. A determining factor in the occurrence of such strong echoes is the low attenuation of the MARSIS radar pulse in cold water ice, the main constituent of the Martian polar caps. The present analysis clarifies that the conditions causing exceptionally strong subsurface echoes occur solely in the Martian polar caps, and that the detection of subsurface water under a predominantly rocky surface layer using radar sounding will require thorough electromagnetic modeling, complicated by the lack of knowledge of many subsurface physical parameters. Higher-frequency radar sounders such as SHARAD cannot penetrate deep enough to detect basal echoes over the thickest part of the polar caps. Alternative methods such as rover-borne Ground Penetrating Radar and time-domain electromagnetic sounding are not capable of providing global coverage. MARSIS observations over the Martian polar caps have been limited by the need to downlink data before on-board processing, but their number will increase in coming years. The Chinese mission to Mars that is to be launched in 2020, Tianwen-1, will carry a subsurface sounding radar operating at frequencies that are close to those of MARSIS, and the expected signal-to-noise ratio of subsurface detection will likely be sufficient for identifying anomalously bright subsurface reflectors. The search for subsurface water through radar sounding is thus far from being concluded

A Compact Hardware Implementation of CCA-Secure Key Exchange Mechanism CRYSTALS-KYBER on FPGA

Post-quantum cryptosystems should be prepared before the advent of powerful quantum computers to ensure information secure in our daily life. In 2016 a post-quantum standardization contest was launched by National Institute of Standards and Technology (NIST), and there have been lots of works concentrating on evaluation of these candidate protocols, mainly in pure software or through hardware-software co-design methodology on different platforms. As the contest progresses to third round in July 2020 with only 7 finalists and 8 alternate candidates remained, more dedicated and specific hardware designs should be considered to illustrate the intrinsic property of a certain protocol and achieve better performance. To this end, we present a standalone hardware design of CRYSTALS-KYBER, amodule learning-with-errors (MLWE) based key exchange mechanism (KEM) protocol within the 7 finalists on FPGA platform. Through elaborate scheduling of sampling and number theoretic transform (NTT) related calculations, decent performance is achieved with limited hardware resources. The way that Encode/Decode and the tweaked Fujisaki-Okamoto transform are implemented is demonstrated in detail. Analysis about minimizing memory footprint is also given out. In summary, we realize the adaptive chosen ciphertext attack (CCA) secure Kyber with all selectable module dimension k on the smallest Xilinx Artix-7 device. Our design computes key-generation, encapsulation (encryption) and decapsulation (decryption and reencryption) phase in 3768/5079/6668 cycles when k = 2, 6316/7925/10049 cycles when k = 3, and 9380/11321/13908 cycles when k = 4, consuming 7412/6785 LUTs, 4644/3981 FFs, 2126/1899 slices, 2/2 DSPs and 3/3 BRAMs in server/client with 6.2/6.0 ns critical path delay, outperforming corresponding high level synthesis (HLS) based designs or hardware-software co-designs to a large extent

Treatment of AC dislocation by reconstructing CC and AC ligaments with allogenic tendons compared with hook plates

Abstract Background The purpose of this study was to compare outcomes between allograft reconstruction and hook plate fixation for acute dislocation of the acromioclavicular joint with a minimum 2-year follow-up. Methods A retrospective comparative study of patients treated for acute acromioclavicular joint dislocation from February 2010 to December 2014 in our hospital, consisting of 16 patients who were followed-up, was performed. Eight patients were treated for acute AC dislocation and underwent surgical reconstruction as follows: the coracoclavicular and acromioclavicular ligaments were reconstructed with the allogenic tendon. The other eight patients were treated with hook plates to maintain the AC joint reset. At the latest follow-up, radiographic analysis and the Constant and University of California-Los Angeles (UCLA) scores were used to evaluate shoulder function. The satisfaction of the patients in terms of the efficacy and visual analog scale (VAS) data were also recorded. Results After an average follow-up of 30.3 months (range 24–46 months), no patient had dislocated their joint again at the final follow-up based on X-ray examination. The Constant score was 94.4 for the allogenic tendon group and 93.8 for the hook plate group (P = 0.57). According to the UCLA scale (P = 0.23) or VAS (P = 0.16), we found no significant difference between the two groups. All patients reported that they were very satisfied or satisfied with the outcome of surgery, and no significant difference (P = 0.08) was found between the two groups. Conclusions The use of allogenic tendon for reconstruction of the coracoclavicular and acromioclavicular ligaments shows excellent outcomes in terms of the recovery of clinical function or radiographic outcomes for acute AC dislocation. Compared with the hook plate, the hardware did not need to be removed

Flow Field, Temperature Field, and Inclusion Removal in a New Induction Heating Tundish with Bent Channels

In order to study the flow field, temperature field, and inclusion removal in a new induction heating tundish with bent channels, a three-dimensional (3D) transient mathematical model is established. The effects of both the channel radius and heating power on the multi-physical field and inclusion removal in the bent channels’ induction heating tundish are investigated. The results show that the tundish with the channel radius of 3 m shows better flow characteristics than those with the channel radii of 4 m and 2 m. With the increase of channel length, the heating efficiency increases at first, and then decreases, while the radius of 3 m is the best one for heating efficiency. After all the inclusions are placed into the tundish, the radii of 3 m and 2 m show good efficiency regarding inclusion removal, while it is poor when the radius is 4 m. Therefore, 3 m is the optimal radius of the channel in this work. Under the optimal channel radius, the heating power of 800 kW seems better than those of 600 kW and 1000 kW on flow characteristics control in the tundish. The temperature in the receiving chamber rises gradually and distributes quite uniformly with the increasing heating power, and the removal rate of inclusions increases with the increasing heating power

Mechanical Fault Diagnosis of an On-Load Tap Changer by Applying Cuckoo Search Algorithm-Based Fuzzy Weighted Least Squares Support Vector Machine

To improve adaptability, feature resolution, and identification accuracy when diagnosing mechanical faults in an on-load tap changer (OLTC) of a transformer, in the present research, wavelet packet energy entropy is used to describe the information comprising vibration signal in the switch process of an OLTC, and a fuzzy weighted least squares support vector machine (CSA-fuzzy weighted LSSVM) model based on the cuckoo search algorithm is proposed to identify mechanical fault types. Specifically, according to the different importance of the sample data in different periods, the idea of fuzzy weighting of training samples is proposed. The cuckoo search algorithm is used to optimise regularisation parameters, kernel function width, and weight control factor of CSA-fuzzy weighted LSSVM. Finally, the real experimental platform for typical mechanical faults of an OLTC is established, and the vibration signals of several typical mechanical faults under different degrees of fatigue are obtained. The results show that the new method achieves a higher accuracy rate of fault identification compared with other common methods. It can better deal with small sample and nonlinear prediction problems and shows higher fitting accuracy than CSA-LSSVM, single LSSVM, and radial basis neural network methods and is thus better suited for mechanical fault diagnosis in OLTCs. This paper presents a new intelligent diagnosis scheme for mechanical faults of on-load tap changers, which can achieve noninterruption and nonintrusive detection. The proposed diagnosis method would change the traditional diagnosis method of the on-load tap changer and improves the power supply quality and the detection efficiency under the premise of ensuring the safety of the staff

Early Warning of High-Voltage Reactor Defects Based on Acoustic–Electric Correlation

Traditional high-voltage reactor monitoring and diagnosis research has problems such as high sampling demand, difficulty in noise reduction on site, many false alarms, and lack of on-site data. In order to solve the above problems, this paper proposes an acoustic–electric fusion high-voltage reactor acquisition system and defect diagnosis method based on reactor pulse current and ultrasonic detection signal. Using the envelope peak signal as the basic detection data, the sampling requirement of the system is reduced. To fill the missing data with partial discharge (PD) information, a method based on k-nearest neighbor (KNN) is proposed. An adaptive noise reduction method is carried out, and a noise threshold calculation method is given for the field sensors. A joint analysis method of acoustic and electrical signals based on correlation significance is established to determine whether a discharge event has occurred based on correlation significance. Finally, the method is applied to a UHV reactor on the spot, which proves the effectiveness of the method proposed in this paper

Pitfalls in GPR Data Interpretation: False Reflectors Detected in Lunar Radar Cross Sections by Chang'e-3

Chang'e-3 (CE-3) has been the first spacecraft to soft land on the moon since the Soviet Union's Luna 24 in 1976. The spacecraft arrived at Mare Imbrium on December 14, 2013, and the same day, Yutu lunar rover separated from lander to start its exploration of the surface and the subsurface around the landing site. The rover was equipped, among other instruments, with two lunar penetrating radar systems having a working frequency of 60 and 500 MHz. The radars acquired data for about two weeks while the rover was slowly moving along a path of about 114 m. At navigation point N0209, the rover got stacked into the lunar soil and after that only data at a fixed position could be collected. The low-frequency radar data have been analyzed by different authors and published in two different papers, which reported totally controversial interpretations of the radar cross sections. This paper is devoted to resolve such controversy by carefully analyzing and comparing the data collected on the moon by Yutu rover and on earth by a prototype of LPR mounted onboard a model of the CE-3 lunar rover. Such analysis demonstrates that the deep radar features previously ascribed to the lunar shallow stratigraphy are not real reflectors, rather they are signal artifacts probably generated by the system and its electromagnetic interaction with the metallic rover

Pitfalls in gpr data interpretation: false reflectors detected in lunar radar cross sections by Chang'e-3

Chang'e-3(CE-3) has been the first spacecraft to soft-land on the Moon since the Soviet Union's Luna 24 in 1976. The spacecraft arrived at Mare Imbrium on December 14, 2013 and the same day, Yutu lunar rover separated from lander to start its exploration of the surface and the subsurface around the landing site. The rover was equipped, among other instruments, with two Lunar Penetrating Radar systems (LPR) having a working frequency of 60 and 500 MHz. The radars acquired data for about two weeks while the rover was slowly moving along a path of about 114 m. At Navigation point N0209 the rover got stacked into the lunar soil and after that only data at fixed position could be collected. The low frequency radar data have been analyzed by different authors and published in two different papers, which reported totally controversial interpretations of the radar cross sections. The present study is devoted to resolve such controversy carefully analyzing and comparing the data collected on the Moon by Yutu rover and on Earth by a prototype of LRP mounted onboard a model of the CE-3 lunar rover. Such analysis demonstrates that the deep radar features previously ascribed to the lunar shallow stratigraphy are not real reflectors, rather they are signal artefacts probably generated by the system and its electromagnetic interaction with the metallic rover