surface angle
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Author(s):  
Qiang Jian ◽  
Zhenlei Liu ◽  
Wanru Duan ◽  
Fengzeng Jian ◽  
Zan Chen

Purpose: To obtain the relevant morphometry of the lateral mass of the subaxial cervical spine (C3-C7) and to design a series of lateral mass prostheses for the posterior reconstruction of the stability of cervical spine. Methods: The computed tomography (CT) scans of healthy volunteers were obtained. RadiAnt DICOM Viewer software (Version 2020.1, Medixant, Poland) was used to measure the parameters of lateral mass, such as height, anteroposterior dimension (APD), mediolateral dimension (MLD) and facet joint angle. According to the parameters, a series of cervical lateral mass prostheses were designed. Cadaver experiment was conducted to demonstrate its feasibility. Results: 23 volunteers with an average age of 30.1 ± 7.1 years were enrolled in this study. The height of lateral mass is 14.1 mm averagely. Facet joint angle, APD and MLD of lateral mass averaged 40.1 degrees, 11.2 mm and 12.18 mm, respectively. With these key data, a lateral mass prosthesis consists of a bone grafting column and a posterior fixation plate was designed. The column has a 4.0 mm radius, 41 degrees surface angle and adjustable height of 13, 15, or 17 mm. In the cadaver experiment, the grafting column could function as a supporting structure between adjacent facets, and it would not violate exiting nerve root (NR) or vertebral artery (VA). Conclusion: This study provided detailed morphology of the lateral mass of subaxial cervical spine. A series of subaxial cervical lateral mass prostheses were designed awaiting further clinical application.


2022 ◽  
Vol 12 (2) ◽  
pp. 785
Author(s):  
Enze Zhu ◽  
Zhipeng Zhang ◽  
Hong Nie

The release load of holdback bar will affect the safety of catapult-assisted takeoff of carrier-based aircraft, and the accurate control of releasing the load will ensure success. The magnitude and the control accuracy of release load are important parameters which impact the takeoff performance, therefore unstable release load and insufficient release precision are the main factors affecting the takeoff safety. In this paper, mechanical models of the carrier-based aircraft in the catapult-assisted takeoff tensioning state and gliding state after release are established based on multi-body dynamics, contact mechanics and tribological theory, and the influence of the release load of the holdback bar on the catapult-assisted takeoff performance is analyzed. Furthermore, a kinetic model of the holdback bar device is established, and the kinetic characteristics of the release process of the holdback bar are studied. Based on the kinetic model and friction model of the holdback bar, the influencing factors of the sensitivity of the holdback bar release load are analyzed and the structural parameters are optimized. The results show that the released load decreases slowly with the increase of the contact surface angle of the holdback bar structure and increases rapidly when that angle reaches the critical value; besides, the release load increases slowly with the increase of the friction coefficient of the contact surface and increases faster when the critical friction coefficient is reached.


2021 ◽  
Author(s):  
Zongyu Yang ◽  
Liang Cui ◽  
Shiwu Tao ◽  
Li Wang ◽  
Fengqi Zhang ◽  
...  

Abstract BackgroundPost-traumatic ankle arthritis is increasing in young people and it is very important to preserve the ankle range of motion in young patients. This study aimed to compare ankle distraction arthroplasty versus supramalleolar osteotomy for post-traumatic ankle arthritis.MethodsThis retrospective study reviewed 32 consecutive patients who underwent surgery for post-traumatic ankle arthritis from January 2015 to December 2018 after failure of conservative treatment. Thirteen ankles that underwent ankle distraction arthroplasty were age-, sex-, and body mass index-matched with 19 ankles that underwent supramalleolar osteotomy. Patients returned for clinical and radiologic follow-up at an average of 32 (range, 24–48) months postoperatively. Outcomes were the comparison of the pre- and postoperative Visual Analog Scale (VAS) pain scores and American Orthopedic Foot & Ankle Society (AOFAS) ankle-hindfoot scores, complications, subjective patient-rated satisfaction, and ankle function.ResultsThe VAS and AOFAS scores of the two groups were significantly improved at final follow-up compared with preoperatively (p<0.05), but did not significantly differ between groups. The ankle distraction arthroplasty group had better postoperative ankle mobility than the supramalleolar osteotomy group. There was no significant difference between the two groups in the tibial anterior surface angle, talar tilt angle, tibial lateral surface angle, and other imaging parameters, but supramalleolar osteotomy was more effective in correcting the load-bearing line of the ankle and hindfoot. The complication rate was similar in both groupsConclusionsAnkle distraction arthroplasty and supramalleolar osteotomy both achieved good pain relief and improved function in patients with traumatic ankle arthritis.Level of evidence: Level III, retrospective comparative series.


2021 ◽  
Author(s):  
Jaegwi Go

Abstract The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generate various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.


2021 ◽  
pp. 51-60
Author(s):  
Gennadii Golub ◽  
Nataliya Tsyvenkova ◽  
Anna Holubenko ◽  
Vyacheslav Chuba ◽  
Marina Tereshchuk

The results of the research on the influence of the drum type reactor design-technological parameters and the substrate`s physical-chemical parameters on the substrate`s components mixing evenness, that influence the quality of the received compost, are presented in this paper. By the method of the multifactor experiment rational values of the drum rotation speed, the blades (mounted on the inner drum surface) angle and the substrate`s moisture content are defined at which the components distribution homogeneity in the substrate reaches maximal value. The abovementioned, in turn, provides high compost quality by the agrichemical indices. The recommendations are given to pick the design parameters and operational modes of the drum type reactor.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yunbin Ke ◽  
Yun Que ◽  
Yuanshuai Fu ◽  
Zhenliang Jiang ◽  
Said Easa ◽  
...  

The in situ frost-heaving (FH) process and characteristics of the shallow layer of a residual soil slope in the intermittently frozen zone were simulated by a modified three-dimensional particle flow code (PFC3D) model, of which the mesoscopic parameters of soil and ice particles were calibrated through the indoor experiments. In this model, the in situ FH process was gradually achieved by expanding the volume of ice particles (divided into 24 times of expansion), and the process was terminated when the monitored porosity was stable. These countermeasures avoided the stress accumulation and effectively realized the simulation of the in situ FH process. The results found that the displacement occurred firstly and got the largest final value at the surface angle (SA) under the in situ FH effect, followed by that at the foot, and it gradually extended to the interior based on these two regions. The vertical tension was present at the SA, and the major force type in the lateral interlayer was pressure. In addition, the FH effect seemed to be strongly related to the frozen depth, and a sliding surface was found in a steeper slope. Finally, the smaller stone appeared to be favorable to the slope stability, but it was reduced by the larger stone to some extent.


2021 ◽  
Vol 37 ◽  
pp. 432-445
Author(s):  
Chun-Kuei Chen ◽  
Sheng-Qi Chen ◽  
Wei-Mon Yan ◽  
Wen-Ken Li ◽  
Ta-Hui Lin

Abstract The present study is concerned with the experimental impingement of two consecutive droplets on an inclined solid surface. Attention is mainly paid to the effects of impingement timing with various oblique angles (Φ) of the surface on the impact phenomena, which mainly affect the maximum droplet spreading diameter. The investigation considers four impingement scenarios differentiated by impingement timing, namely Case 1: single-droplet impingement; Case 2 of Δt1: the moment when the leading droplet starts spreading along the oblique surface; Case 3 of Δt2: the moment when the leading droplet reaches its maximum spreading; and Case 4 of Δt3: the moment when the leading droplet starts retracting. It is observed that deformation behavior of two successive droplets impacting on the inclined surface experiences a complex asymmetric morphology evolution due to the enhancement of gravity effect and various conditions of the impingement timing. The merged droplet becomes slender with increasing oblique surface angle in the final steady shape, causing the decrease in the value of front and back contact angles. The impingement timing has a significant influence on the change of the maximum height of the merged droplet. The coalesced droplet spreads to the maximum dimensionless width diameter at Δt = Δt2 and the oblique angle of Φ = 45°, but reaches the maximum dimensionless height for Δt = Δt2 at Φ = 30°. The front contact angles converge to a fixed value eventually for all conditions of impingement timing, and the values become lower with the increasing surface inclination.


2020 ◽  
pp. 107110072097093
Author(s):  
Hyuck Sung Son ◽  
Jung Gyu Choi ◽  
Jungtae Ahn ◽  
Bi O Jeong

Background: In patients with end-stage varus ankle osteoarthritis (OA), hindfoot varus malalignment resulting from the varus deformity of the ankle joint is common. Although total ankle arthroplasty (TAA) performed to correct varus deformity of the ankle joint has the effect of correcting hindfoot alignment, no reports to date have described how much hindfoot alignment correction can be achieved. The purpose of this study was to identify correlation between ankle deformity correction and hindfoot alignment change after performing TAA in patients with end-stage varus ankle OA. Methods: A total of 61 cases that underwent TAA for end-stage varus ankle OA and followed up for at least 1 year were enrolled for this study. Correlation between changes of tibial-ankle surface angle (TAS), talar tilt (TT), and tibiotalar surface angle (TTS) and changes of hindfoot alignment angle (HA), hindfoot alignment ratio (HR), and hindfoot alignment distance (HD) measured preoperatively and at postoperative year 1 was analyzed. Results: TAS, TT, and TTS changed from 83.9 ± 4.1 degrees, 5.8 ± 5.0 degrees, and 78.1 ± 5.9 degrees, respectively, before operation to 89.2 ± 2.1 degrees, 0.4 ± 0.5 degrees, and 88.7 ± 2.3 degrees, respectively, after operation. HA, HR, and HD also changed from −9.2 ± 4.6 degrees, 0.66 ± 0.18, and −11.2 ± 6.9 mm to −3.7 ± 4.1 degrees, 0.48 ± 0.14, and −5.0 ± 5.3 mm. All the changes were statistically significant ( P < .001, respectively). The regression slope of correlation was 0.390 ( R2 = 0.654) between TTS and HA; 0.017 ( R2 = 0.617) between TTS and HR; and 0.560 ( R2 = 0.703) between TTS and HD. Conclusion: In patients with end-stage varus ankle OA, changes of hindfoot alignment could be predicted based on degree of ankle deformity corrected with TAA. Level of Evidence: Level IV, case series.


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