Coherent optical frequency transfer via 972-km fiber link

We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.

个性化导航模板辅助S2AI置钉与徒手置钉的对比

目的探讨3D打印导航模板辅助经后路第2骶椎髂骨(S2AI)螺钉置入的可行性与准确性。方法回顾性分析2017年9月至2019年9月接受初次S2AI置钉患者30例。其中男14例,女16例;年龄42~74岁。根据治疗方法的不同将其分为导板组和徒手组,每组15例。导板组患者术前行骨盆CT三维重建,设计导航模板并在术中使用,徒手组采用常规手术徒手置钉。所有患者术后复查骨盆CT,三维重建后观察螺钉与皮质的关系,并对比两组患者术后CT在矢状面上尾向偏角(SA)、横断面与正中线夹角(TA)、进钉点与骶正中嵴的距离(HD)以及与第1骶后孔下缘的垂直距离(VD)。记录并比较两组手术S2AI置钉时间、术中置钉所需透视C型臂次数。结果导板组15例患者共置入S2AI钉30枚,所有螺钉均穿过骶髂关节,无侵犯及穿出皮质。徒手组15例患者共置入S2AI钉30枚,所有螺钉均穿过骶髂关节,无侵犯及穿出皮质。导板组患者术后SA(30.00±3.49)°、TA(40.43±2.10)°、HD(19.44±0.85)mm、VD(4.97±0.43)mm,与徒手组患者术后SA(30.72±3.34)°、TA(39.71±2.12)°、HD(19.15±1.31)mm、VD(5.02±0.53)mm比较,差异无统计学意义(均P>0.05)。导板组测量置钉时间(19.60±1.30)min、透视次数(4.20±0.41)次低于徒手组测量置钉时间[(52.93±9.22)min]、透视次数[(13.80±2.81)次],差异有统计学意义(均P<0.05)。结论成人骨盆固定中,应用3D打印导板与徒手置钉的准确性无明显差异,但3D导板组手术时间更短,术中透视次数也更少。

Plasma Treatment Induced Chemical Changes of Alkali Lignin to Enhance the Performances of Lignin-Phenol-Formaldehyde Resin Adhesive

Alkali lignin was processed by plasma and then used in modification of phenol formaldehyde resin in this study.Chemical structural changes of lignin which was processed by plasma as well as bonding strength,tensile property,curing performance and thermal property of the prepared phenol formaldehyde resin which was modified by the plasma processed lignin were analyzed.Results demonstrated that:(1)Alkali lignin was degraded after the plasma processing.The original groups were destroyed,and the aromatic rings collected abundant free radicals and oxygen-containing functional groups like hydroxyls,carbonyls,carboxyls and acyls were introduced into increase the reaction activity of lignin significantly.(2)The introduction of alkali lignin decreased the free formaldehyde content and increased bonding strength and toughness of the prepared phenol formaldehyde resin,especially after the introduction of lignin treated with plasma.(3)The introduction of alkali lignin led to high curing temperature for the prepared phenol formaldehyde resin,but that was reduced by the plasma processed alkali lignin.(4)The introduction of alkali lignin could also increase thermal stability of phenol formaldehyde resin,but that was modified by plasma processed alkali lignin was better than the unprocessed lignin.Based on the results,the plasma processed lignin was used to modify phenol formaldehyde resin,which could increase the strength and toughness of phenol formaldehyde resin significantly.

Exploratory use of ultrasound to determine whether demyelination following carpal tunnel syndrome co-exists with axonal degeneration

Carpal tunnel syndrome （CTS） accompanied by secondary axonal degeneration cannot be clearly dis- criminated using the current cross-validated ultrasound severity classification system. This study aimed at exploring cut-off values of ultrasound parameters, including wrist cross-sectional area （W-CSA）, wrist perimeter （W-P）, ratio of cross-sectional area （R-CSA） and perimeter （R-P）, changes of CSA and P from wrist to one third distal forearm （△CSA＆AP） for differentiation. Seventy-three patients （13 male and 60 female） were assigned into group A （demyelination only, n = 40） and group B （demyelination with secondary axonal degeneration, n = 33） based on the outcomes of nerve conduction studies （NCS）. Receiver Operative Characteristics （ROC） curves were plotted to obtain sensitivity, specificity, and accuracy of cut- off values for all the ultrasound parameters. The overall identified cut-off values （W-CSA 12.0 mm2, W-P 16.27 mm, R-CSA 1.85, R-P 1.48, △CSA 6.98 mm2, △P 5.77 mm） had good sensitivity （77.1-88.6%）, fair specificity （40-62.2%） and fair-to-good accuracy （0.676-0.758）. There were also significant differences in demographics （age and severity gradation, P 〈 0.001）, NCS findings （wrist motor latency and conduction velocity, P 〈 0.0001; wrist motor amplitude, P 〈 0.05; distal sensory latency, P 〈 0.05; sensory amplitude, P 〈 0.001） and ultrasound measurements （W-CSA, W-P, R-CSA, R-P, △CSA＆△P, P 〈 0.05） between groups. These findings suggest that ultrasound can be potentially used to differentiate demyelinating CTS with sec- ondary axonal degeneration and provide better treatment guidance.

Neural plasticity secondary to carpal tunnel syndrome: a pseudo-continuous arterial spin labeling study

Conventional neuroimaging techniques cannot truly reflect the change of regional cerebral blood flow in patients with carpal tunnel syndrome.Pseudo-continuous arterial spinning labeling(pCASL)as an efficient non-invasive neuroimaging technique can be applied to directly quantify the neuronal activities of individual brain regions that show the persistent symptoms owing to its better spatial resolution and increased signal-to-noise ratio.Therefore,this prospective observational study was conducted in 27 eligible female carpal tunnel syndrome,aged 57.7±6.51 years.Psychometric tests,nerve conduction studies and pCASL neuroimaging assessment were performed.The results showed that the relevant activated brain regions in the cortical,subcrotical,and cerebral regions were correlated with numbness,pain,functionality,median nerve status and motor amplitude of median nerve(K=21–2849,r=–0.77–0.76,P<0.05).There was a tendency of pain processing which shifted from the nociceptive circuitry to the emotional and cognitive one during the process of chronic pain caused by carpal tunnel syndrome.It suggests the necessity of addressing the ignored cognitive or emotional state when managing patients with carpal tunnel syndrome.Approval for this study was obtained from the Institutional Review Board of The University of Hong Kong/Hospital Authority Hong Kong West,China(HKU/HA HKW IRB,approval No.UW17-129)on April 11,2017.This study was registered in Clinical Trial Registry of The University of Hong Kong,China(registration number:HKUCTR-2220)on April 24,2017.

Coherent Optical Frequency Transfer via a 490 km Noisy Fiber Link

We demonstrate the coherent transfer of an ultrastable optical frequency reference over a 490 km noisy field fiber link.The fiber-induced phase noise power spectrum density per-unit-length at 1 Hz offset frequency can reach up to 510 rad^(2)·Hz^(-1)·km^(-1),which is much higher than the fiber noise observed in previous reports.This extreme level of phase noise is mainly due to the fiber link laying underground along the highway.Appropriate phaselocked loop parameters are chosen to complete the active compensation of fiber noise by measuring the intensity fluctuation of additional phase noise and designing a homemade digital frequency division phase discriminator with a large phase detection range of 2^(12)πrad.Finally,a noise suppression intensity of approximately 40 d B at1 Hz is obtained,with fractional frequency instability of 1.1×10^(-14 )at 1 s averaging time,and 3.7×10^(-19) at10000 s.The transfer system will be used for remote atomic clock comparisons and optical frequency distribution over a long-distance communication network established in China.

Cascaded optical frequency transfer over 500-km fiber link using regenerative amplifier

We demonstrate a 300-km+200-km cascaded coherent phase transfer via fiber link.The transfer is divided into a 300-km span and a 200-km span with independent phase locking loops,aiming to extend the phase control bandwidth of the whole link.The phase noise and transfer instability of the cascaded transmission are investigated and compared with those in the case of a single-span 500-km transfer.We achieve the transfer instabilities of 1.8×10^-14 at 1 s,8.9×10^-20 at 104 s for the 300-km+200-km cascaded transmission,and 2.7×10^-14 at 1 s for the 500-km single-span transfer.

Novel Polarization Control Approach to Long-Term Fiber-Optic Frequency Transfer

We demonstrate a novel polarization control system based on a gradient descent algorithm,applied to a 450-km optical frequency transfer link.The power of the out-loop beat note is retrieved by controlling the polarization state of the transferred signal,with a recovery time of 24 ms,thereby ensuring the long-term evaluation of the fiber link.As a result,data utilization is enhanced from 70%to 99%over a continuous measurement period of^12 h.A fractional transfer instability of 7.2×10^-20 is achieved at an integration time of 10000 s.This work lays the foundation for the comparison of a remote optical clock system via a long-haul optical fiber link.

Buster Die Shape Design of a Track Link Forging Using FEM Based Back-Tracing Method

For the preform design of a complex track link forging, fifteen critical sections were selected for two dimensional back-tracing using FEM. The preform shapes of the critical sections are designed and integrated into an ideal 3D busting shape. The buster dies are finally designed according to the ideal busting shape with a little of modification. The 3D simulation of the busting stage is carried out.

Research status and development of extraction process of zinc-bearing dust from ironmaking and steelmaking—a critical review

Almost 29.57–38.46 million tons of zinc-bearing dust were produced in Chinese iron and steel enterprises annually.The recovery of Zn and other metals in zinc-bearing dust from ironmaking and steelmaking could improve economic efficiency.However,zinc-bearing dust was classified as hazardous waste,and the volatile metals(like Zn,Na,Pb,etc.)in zinc-bearing dust limited the direct reusing in a blast furnace.Therefore,the formation process,fundamental characteristics,and current extraction process of Zn from zinc-bearing dust,associated with thermodynamics and kinetics of the pyrometallurgical process,hydrometallurgical process,and pyro-hydrometallurgical process,were analyzed.It is indicated that industrialized pyrometallurgical processes are undergoing high energy consumption and pollution such as rotary kiln and rotary hearth furnace process.The vacuum carbothermal reduction process can realize low carbon emission and no waste produced in the process.The hydrometallurgical leaching processes in strong acid,strong alkali,and ammonium solutions result in serious liquid pollution and equipment corrosion.The pyrometallurgical process involves complex kinetics and lacks kinetic research on semi-industrialization and industrialization.Water-soluble components in zinc-bearing dust can be removed by water leaching.The kinetics of the strong acid leaching is mainly controlled by the leaching kinetics of Fe_(2)O_(3) and ZnFe_(2)O_(4),while the alkali leaching and weak acid leaching are controlled by the kinetics of ZnO leaching.Zn in the zincbearing dust can be extracted by a low-temperature sodium roasting–weak acid leaching process that reduces equipment corrosion and environmental pollution.

Detection method for the cucumber robotic grasping pose in clutter scenarios via instance segmentation

The application of robotic grasping for agricultural products pushes automation in agriculture-related industries.Cucumber,a common vegetable in greenhouses and supermarkets,often needs to be grasped from a cluttered scene.In order to realize efficient grasping in cluttered scenes,a fully automatic cucumber recognition,grasping,and palletizing robot system was constructed in this paper.The system adopted Yolact++deep learning network to segment cucumber instances.An early fusion method of F-RGBD was proposed,which increases the algorithm's discriminative ability for these appearance-similar cucumbers at different depths,and at different occlusion degrees.The results of the comparative experiment of the F-RGBD dataset and the common RGB dataset on Yolact++prove the positive effect of the F-RGBD fusion method.Its segmentation masks have higher quality,are more continuous,and are less false positive for prioritizing-grasping prediction.Based on the segmentation result,a 4D grab line prediction method was proposed for cucumber grasping.And the cucumber detection experiment in cluttered scenarios is carried out in the real world.The success rate is 93.67%and the average sorting time is 9.87 s.The effectiveness of the cucumber segmentation and grasping pose acquisition method is verified by experiments.

儿童寰椎椎弓根螺钉最佳进钉点及进钉方法

目的探讨儿童寰椎椎弓根螺钉理想进钉点及进钉角度。方法选取在2017年1月至2020年6月于郑州大学第一附属医院接受颈椎64层CT扫描的2~6岁儿童,从中筛选出153例符合标准的儿童,每个年龄段中23~45例,平均30例,将符合要求的儿童按性别分为两组,男100例,女53例。测量双侧寰椎椎弓根螺钉在不同内倾角度时可利用间隙宽度。以及在可利用间隙宽度用达到最宽时的椎弓根螺钉钉道长度、进钉点到侧块与后弓内缘交点的水平距离,以及内倾角度。通过Sudentt检验分析性别差异是否存在统计学意义。结果当钉道内倾角度与前后弓交点所在直线平行时,螺钉可利用间隙宽度最大(8.02±1.06)mm。钉道与侧块和前后弓内缘交点的连线平行时,钉道长度为(24.75±3.34)mm,进钉点距侧块与后弓内缘交点水平距离为(5.70±1.10)mm,最佳内倾角角度为(20.93±3.07)°。不同性别,患儿椎弓根螺钉钉道长度(P>0.05),进钉点至侧块与后弓内缘交点水平距离(P>0.05),进钉最佳内倾角度(P>0.05)差异均无统计学意义。结论6岁以下儿童寰椎椎弓根螺钉时,选择距侧块与后弓内缘交点水平距离为(5.70±1.10)mm做垂线与后弓水平中线交点为进钉点是安全可行的,钉道内倾角度选为钉道与前后弓交点所在直线平行(20.93±3.07)°时为进行儿童寰椎椎弓根螺钉固定的最佳内倾角度。