Frequency Difference
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Atmosphere ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 86
Author(s):  
Yongdi Wang ◽  
Xinyu Sun

A statistical downscaling method based on Self-Organizing Maps (SOM), of which the SOM Precipitation Statistical Downscaling Method (SOM-SD) is named, has received increasing attention. Herein, its applicability of downscaling daily precipitation over North China is evaluated. Six indices (total season precipitation, daily precipitation intensity, mean number of precipitation days, percentage of rainfall from events beyond the 95th percentile value of overall precipitation, maximum consecutive wet days, and maximum consecutive dry days) are selected, which represent the statistics of daily precipitation with regards to both precipitation amount and frequency, as well as extreme event. The large-scale predictors were extracted from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) daily reanalysis data, while the prediction was the high resolution gridded daily observed precipitation. The results show that the method can establish certain conditional transformation relationships between large-scale atmospheric circulation and local-scale surface precipitation in a relatively simple way. This method exhibited a high skill in reproducing the climatologic statistical properties of the observed precipitation. The simulated daily precipitation probability distribution characteristics can be well matched with the observations. The values of Brier scores are between 0 and 1.5 × 10−4 and the significance scores are between 0.8 and 1 for all stations. The SOM-SD method, which is evaluated with the six selected indicators, shows a strong simulation capability. The deviations of the simulated daily precipitation are as follows: Total season precipitation (−7.4%), daily precipitation intensity (−11.6%), mean number of rainy days (−3.1 days), percentage of rainfall from events beyond the 95th percentile value of overall precipitation (+3.4%), maximum consecutive wet days (−1.1 days), and maximum consecutive dry days (+3.5 days). In addition, the frequency difference of wet-dry nodes is defined in the evaluation. It is confirmed that there was a significant positive correlation between frequency difference and precipitation. The findings of this paper imply that the SOM-SD method has a good ability to simulate the probability distribution of daily precipitation, especially the tail of the probability distribution curve. It is more capable of simulating extreme precipitation fields. Furthermore, it can provide some guidance for future climate projections over North China.


Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 52
Author(s):  
Renata Woźniacka ◽  
Łukasz Oleksy ◽  
Agnieszka Jankowicz-Szymańska ◽  
Anna Mika ◽  
Renata Kielnar ◽  
...  

The foot arches are responsible for proper foot loading, optimal force distribution, and transmission throughout the soft tissues. Since the foot arch is an elastic structure, able to adapt to forces transmitted by the foot, it was reported that low arch is related to excessive foot pronation, while high arched foot is more rigid and inflexible. Therefore, it is also probable, that foot arch alterations may change the force transmission via myofascial chains. The objective of this study was to evaluate the effect of symmetrical and asymmetrical excessive feet arching on muscle fatigue in the distal body parts such as the lower limbs, trunk, and head. Seventy-seven women (25.15 ± 5.97 years old, 62 ± 10 kg, 167 ± 4 cm) were assigned to three groups according to the foot arch index (Group 1—both feet with normal arch, Group 2—one foot with normal arch and the other high-arched, Group 3—both feet with high-arch). The bioelectrical activity of the right and left hamstrings muscles, erector spine, masseter, and temporalis muscle was recorded by sEMG during the isometric contraction lasting for 60 s. The stable intensity of the muscle isometric contraction was kept for all the time during the measurement. Mean frequency difference (%), slope (Hz), and intercept (Hz) values were calculated for muscle fatigue evaluation. No differences were observed in fatigue variables for all evaluated muscles between the right and left side in women with symmetrical foot arches, but in the group with asymmetric foot arches, the higher muscle fatigue on the normal-arched side compared to the high-arched side was noted. Significantly greater values of the semitendinosus—semimembranosus muscle frequency difference was observed on the normal-arched side compared to the high-arched side (p = 0.04; ES = 0.52; −29.5 ± 9.1% vs. −24.9 ± 8.4%). In the group with asymmetric foot arches, a significantly higher value of lumbar erector spinae muscle frequency slope (p = 0.01; ES = 1.32; −0.20 ± 0.04 Hz vs. −0.14 ± 0.05 Hz) and frequency difference (p = 0.04; ES = 0.92; −7.8 ± 3.1% vs. −4.8 ± 3.4%) were observed on the high-arched foot side compared to the side with normal foot arching. The thoracic erector spine muscle frequency slope was significantly larger in women with asymmetrical arches than in those with both feet high-arched (right side: p = 0.01; ES = 1.25; −0.20 ± 0.08 Hz vs. −0.10 ± 0.08 Hz); (left side: p = 0.005; ES = 1,17; −0.19 ± 0.04 Hz vs. −0.13 ± 0.06 Hz) and compared to those with normal feet arches (right side: p = 0.02; ES = 0.58; −0.20 ± 0.08 Hz vs. −0.15 ± 0.09 Hz); (left side: p = 0.005; ES = 0.87; −0.19 ± 0.04 Hz vs. −0.14 ± 0.07 Hz). In the group with asymmetric foot arches, the frequency difference was significantly higher compared to those with both feet high-arched (right side: p = 0.01; ES = 0.87; −15.4 ± 6.8% vs. 10.4 ± 4.3%); (left side: p = 0.01; ES = 0.96; 16.1 ± 6.5% vs. 11.1 ± 3.4%). In the group with asymmetric foot arches, a significantly higher value of the masseter muscle frequency difference was observed on the high-arched side compared to the normal-arched side (p = 0.01; ES = 0.95; 6.91 ± 4.1% vs. 3.62 ± 2.8%). A little increase in the longitudinal arch of the foot, even though such is often not considered as pathological, may cause visible changes in muscle function, demonstrated as elevated signs of muscles fatigue. This study suggests that the consequences of foot high-arching may be present in distal body parts. Any alterations of the foot arch should be considered as a potential foot defect, and due to preventing muscle overloading, some corrective exercises or/and corrective insoles for shoes should be used. It can potentially reduce both foot overload and distant structures overload, which may diminish musculoskeletal system pain and dysfunctions.


2021 ◽  
Author(s):  
Yue Li

This dissertation investigates adaptive decision feedback equalizers for high-speed serial data links.<div>An adaptive data-transition decision feedback equalizer (DT-DFE) was developed. The DT-DFE boosts the eye-opening of the high-frequency components of data without attenuating their low-frequency counterparts. Reference voltages were obtained by transmitting consecutive 1s and 0s and measuring the output of the continuous-time linear equalizer using a pair of successive approximation register analog-to-digital converters in a training phase. It uses loop unrolling to detect data transitions, activate tap-tuning, launch DFE, and combat timing constraints. The performance of the DT-DFE and its advantages over commonly used data-state DFE were validated using the schematic-level simulation results of 5 Gbps backplane links.<br></div><div>A new adaptive DT-DFE with edge-emphasis (EE) taps and raised references was developed. Loop-unrolling was further developed for DT-DFE with EE-taps. The reference voltages were raised beyond that set by the low-frequency components of data to increase vertical eye-opening. Clock and data recovery was performed using 4x oversampling. The DT-DFE was validated using the schematiclevel simulation results of 10 Gbps backplane links.<br></div><div>A pre-skewed bi-directional gated delay line (BDGDL) bang-bang frequency difference-to-digital converter and a BDGDL integrating frequency difference-todigital converter (iFDDC) were proposed for clock and data recovery. Both frequency difference detectors feature all-digital realization, low power consumption, and high-speed operation. The built-in integration of iFDDC results in a zero static frequency error and the first-order noise-shaping of the quantization errors of the BDGDL and digitally-controlled oscillators. Their effectiveness was validated using schematic-level simulation results of 5-GHz frequency-locked loops.<br></div><div>All systems validating the proposed adaptive DFE and frequency-difference detectors were designed in TSMC’s 65 nm CMOS technology and analyzed using Spectre from Cadence Design Systems. <br></div>


2021 ◽  
Author(s):  
Yue Li

This dissertation investigates adaptive decision feedback equalizers for high-speed serial data links.<div>An adaptive data-transition decision feedback equalizer (DT-DFE) was developed. The DT-DFE boosts the eye-opening of the high-frequency components of data without attenuating their low-frequency counterparts. Reference voltages were obtained by transmitting consecutive 1s and 0s and measuring the output of the continuous-time linear equalizer using a pair of successive approximation register analog-to-digital converters in a training phase. It uses loop unrolling to detect data transitions, activate tap-tuning, launch DFE, and combat timing constraints. The performance of the DT-DFE and its advantages over commonly used data-state DFE were validated using the schematic-level simulation results of 5 Gbps backplane links.<br></div><div>A new adaptive DT-DFE with edge-emphasis (EE) taps and raised references was developed. Loop-unrolling was further developed for DT-DFE with EE-taps. The reference voltages were raised beyond that set by the low-frequency components of data to increase vertical eye-opening. Clock and data recovery was performed using 4x oversampling. The DT-DFE was validated using the schematiclevel simulation results of 10 Gbps backplane links.<br></div><div>A pre-skewed bi-directional gated delay line (BDGDL) bang-bang frequency difference-to-digital converter and a BDGDL integrating frequency difference-todigital converter (iFDDC) were proposed for clock and data recovery. Both frequency difference detectors feature all-digital realization, low power consumption, and high-speed operation. The built-in integration of iFDDC results in a zero static frequency error and the first-order noise-shaping of the quantization errors of the BDGDL and digitally-controlled oscillators. Their effectiveness was validated using schematic-level simulation results of 5-GHz frequency-locked loops.<br></div><div>All systems validating the proposed adaptive DFE and frequency-difference detectors were designed in TSMC’s 65 nm CMOS technology and analyzed using Spectre from Cadence Design Systems. <br></div>


2021 ◽  
Vol 132 ◽  
pp. 103974
Author(s):  
Dongho Jeon ◽  
Min Kyoung Kim ◽  
Hayoung Woo ◽  
Yeounung Jeong ◽  
Jae Eun Oh ◽  
...  

2021 ◽  
Author(s):  
Yongdi Wang ◽  
Xinyu Sun

Abstract A statistical downscaling method based on SOM which named SOM-SD is used over North China. It’s applicatibility by downscaling daily precipitation is evaluated. Indices are selected which represent the statistics of daily precipitation with regard to both precipitation amount (Prtot, SDII) and frequency (nr001), as well as extreme event (P95T, CWD, CDD). The large-scale predictors were extracted from the daily NCEP reanalysis data, while the predictand was high resolution gridded daily observed precipitation. A downscaling method based on SOM named SOM-SD was presented and evaluated. In evaluating, the frequency difference of wet-dry nodes is defined. And it is confirmed that there was a significant positive correlation between frequency difference and precipitation. The SOM-SD method displayed a high skill in reproducting the climatologic statistical properties of the observed precipitation. The value of BS is between 0 and 1.5×10-4. Sscore is between 0.8 and 1. The bias ranges are -7.4% and -11.6% for Prtot and SDII, -3.1days for nr001, +3.4% for P95T, -1.1 days for CWD and +3.5 days for CDD. Therefore, SOM-SD method works reasonably well.


Photonics ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 436
Author(s):  
Yuhe Wang ◽  
Yudong Lian ◽  
Shiwei Han ◽  
Yang Yu ◽  
Xuan Qi ◽  
...  

A scheme for controlling the frequency difference of output pulse pair with double frequency shift loops is proposed. The frequency shift system includes two loop elements of 20 and 200 MHz. The first one carries out a single selective positive frequency shift of 1–20 MHz, and the second one can satisfy a single fixed positive frequency shift of 200 MHz. The reverse cascade technology of two acousto-optic crystals is introduced to solve the limitation of the small frequency shift of crystal size. A multichannel synchronization signal completes the time domain control of each acousto-optic modulator. Finally, the frequency shift difference of the output pulse pair ranges of 0–2 GHz, and the frequency shift accuracy is 5 MHz.


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