Low filling ratio of the distal nail segment to the medullary canal is a risk factor for loss of anteromedial cortical support: a case control study

Background Anteromedial cortical support apposition (positive and/or neutral cortical relations) is crucial for surgical stability reconstruction in the treatment of trochanteric femur fractures. However, the loss of fracture reduction is frequent in follow-ups after cephalomedullary nail fixation. This paper aimed to investigate the possible predictive risk factors for postoperative loss of anteromedial cortex buttress after nail fixation. Methods A retrospective analysis of 122 patients with AO/OTA 31A1 and A2 trochanteric femur fractures treated with cephalomedullary nails between January 2017 and December 2019 was performed. The patients were classified into two groups according to the postoperative status of the anteromedial cortical apposition in 3D CT images: Group 1 with contact “yes” (positive or anatomic) and Group 2 with contact “No” (negative, loss of contact). The fracture reduction quality score, tip-apex distance (TAD), calcar-referenced TAD (Cal-TAD), Parker ratio, neck-shaft angle (NSA), and the filling ratio of the distal nail segment to medullary canal diameter in anteroposterior (AP) and lateral fluoroscopies (taken immediately after the operation) were examined in univariate and multivariate analyses. Mechanical complications were measured and compared in follow-up radiographs. Results According to the postoperative 3D CT, 84 individuals (69%) were categorized into Group 1, and 38 individuals (31%) were classified as Group 2. The multivariate logistic regression analysis showed that the poor fracture reduction quality score (P < 0.001) and decreasing filling ratio in the lateral view (P < 0.001) were significant risk factors for the loss of anteromedial cortical contact. The threshold value for the distal nail filling ratio in lateral fluoroscopy predicting fracture reduction re-displacement was found to be 53%, with 89.3% sensitivity and 78.9% specificity. The mechanical complication (varus and over lateral sliding) rate was higher in Group 2. Conclusions The fracture reduction quality score and the decreasing filling ratio of the distal nail to the medullary canal in the lateral view (a novel parameter causing pendulum-like movement of the nail) were possible risk factors for postoperative loss of anteromedial cortical support.

Study of polymer-based adhesive mortar with higher durability

This paper deals with the study and development of polymer-based adhesive with high filling ratio of secondary raw materials and waste materials. The goal of this paper is to develop adhesive mortar with the highest filling rate of secondary raw materials and waste materials as possible while preserving very high physical-mechanical properties, including flexural and compressive strength, pull-off bond strength and abrasion resistance. High-temperature fly ash, waste slag and waste packaging glass are used in this paper as fillers. The resulting mortar shows high physical-mechanical properties, including high abrasive resistance and very high bonding strength to a large variety of building materials including concrete, steel, glass, and tiles.

MIL-88B (Fe) driven Fe/Fe3C encapsulated in high-crystalline carbon for high-efficient microwave absorption and electromagnetic interference shielding

Dual-functional magnetic/dielectric Fe/Fe3C@C composites were fabricated by pyrolysis of MIL-88B (Fe) in Ar atmosphere, which was used for microwave absorption and electromagnetic interference (EMI) shielding. The Fe/Fe3C nanocrystals were completely encapsulated in crystalline carbon, which can improve the oxidation resistance capacity. Owing to the remarkable impedance matching and strong attenuation constants, Fe/Fe3C@C composites show an optimal RL value of -56.4 dB at 14.0 GHz and broad effective absorption bandwidth (RL ≤ -10 dB) of 4.8 GHz, when the filling ratio and absorber thickness are only 20 wt% and 1.9 mm, respectively. Resulted from the high conductivity of crystalline carbon, magnetic loss of Fe/Fe3C and core-shell structure, the Fe/Fe3C@C composites also show remarkable EMI shielding properties at X band, which are enhanced by increasing the filling ratio of Fe/Fe3C@C composites. When the filling ratio was 50 wt%, the EMI shielding efficiency can reach 35 dB. This work suggests that the magnetic/dielectric Fe/Fe3C@C is a good cadidate in microwave absorption and electromagnetic interference shielding.

STUDI EKSPERIMEN PENGARUH BEBAN KALOR TERHADAP UNJUK KERJA TERMAL MODEL LOOP HEAT PIPE

Sistem pendingin pasif sangat diperlukan sebagai redundance apabila sistem pendingin aktif pada instalasi nuklir mengalami kegagalan operasi. Konspe teknologi sistem pendinginan pasif yang potensial digunakan dalam menyerap dan membuang kalor dengan baik adalah loop heat pipe (LHP). Diharapkan LHP menjadi solusi manajemen termal dalam keselamatan pengoperasian instalasi nuklir. Tujuan studi eksperimen ini adalah untuk mengetahui fenomena perpindahan kalor yang terjadi di dalam model LHP yang dibuat sendiri dan bagaimana unjuk kerja termalnya dalam menyerap dan melepas kalor. Metode yang digunakan adalah dengan melakukan eksperimen model LHP pada variasi beban kalor pada suhu air panas 35°C, 45°C, 55°C, dan 65°C. Fluida kerja di dalam evaporator menggunakan air demineral dengan filling ratio 200 %. Pembuangan kalor pada bagian condenser menggunakan udara dengan laju pendinginan sebesar 2 m/s. Model LHP divakum dengan tekanan sebesar -74 cm Hg. Hasil studi eksperimen menunjukkan bahwa didapatkan fenomena overshoot, zigzag, dan stable seperti fenomena umum perpindahan kalor yang terjadi pada LHP. Unjuk kerja termal terbaik didapatkan dengan hambatan termal terkecil sebesar 0,0017 ºC/W, yaitu diperoleh pada saat model LHP dioperasikan pada beban kalor 65°C. Kesimpulan dari penelitian ini menunjukkan bahwa semakin tinggi beban kalor yang diterima oleh evaporator menyebabkan semakin kecilnya nilai hambatan termal model LHP.

STUDI PENGARUH FILLING RATIO PADA MODEL LOOP HEAT PIPE

Pembuangan panas sisa hasil peluruhan pada saat sistem pendingin aktif mengalami kegagalan masih menjadi permasalahan termal. Loop heat pipe (LHP) sebagai salah satu teknologi sistem pendingin pasif berpotensi untuk dimanfaatkan dalam menangani permasalahan termal tersebut. Tujuan studi ini adalah untuk mengetahui pengaruh filling ratio terhadap unjuk kerja termal model LHP yang dibuat pada berbagai variasi filling ratio yang diberikan dan fenomena perpindahan kalor yang terjadi di dalamnya. Metode eksperimen dilakukan dengan cara mengoperasikan LHP pada filling ratio 100 %, 150 % dan 200%. Dalam eksperimen ini, laju aliran udara di condenser diberikan sebesar 2 m/s, beban kalor sebesar 35, 45, 55, dan 65oC. Model LHP divakum dengan tekanan awal -74 cm Hg. Hasil eksperimen yang diperoleh menunjukkan bahwa LHP memiliki unjuk kerja termal terbaik ketika dioperasikan pada filling ratio 200%, yaitu dengan nilai hambatan termal sebesar 0,0017 oC/W. Fenomena perpindahan kalor yang didapatkan berupa distibusi suhu di dalam LHP yaitu overshoot, zigzag dan stable. Kesimpulan studi menunjukan bahwa filling ratio terbesar yang diberikan pada LHP memberikan unjuk kerja termal terbaik, karena semakin banyak fluida kerja yang ada didalam model LHP menyebabkan semakin agresifnya pendidihan dan semakin besar transfer kalor pada LHP.

STUDI PENGARUH LAJU ALIRAN UDARA PENDINGIN PADA CONDENSER TERHADAP DISTRIBUSI SUHU MODEL LOOP HEAT PIPE

Penggunaan sistem pendingin pasif perlu ditingkatkan dalam rangka meningkatkan keselamatan operasi instalasi nuklir. Salah satu teknologi sistem pendingin pasif yang berpotensi untuk digunakan adalah loop heat pipe (LHP). Tujuan studi eksperimen ini adalah mempelajari pengaruh besarnya laju aliran udara pendingin terhadap pembuangan kalor oleh model LHP, dan mempelajari fenomena perpindahan kalor yang terjadi di dalamnya. Dalam studi ini peneliti melakukan eksperimen dengan mengoperasikan model LHP pada berbagai variasi laju aliran pendinginan udara sebesar 0 m/s, 1 m/s, 1,5 m/s dan 2 m/s. Pemberian beban kalor pada evaporator digunakan dengan memvariasikan suhu air panas pada 35°C, 45°C, 55°C, dan 65°C. Model LHP diisi dengan fluida kerja berupa air demineral pada filling ratio 200%. Model LHP divakum dengan tekanan awal -74 cm Hg. Hasil studi menunjukkan bahwa model LHP memiliki hambatan termal terendah sebesar 0.0017 °C/W pada saat diberikan laju aliran pendingin 2 m/s. Kesimpulan studi menyebutkan bahwa semakin besar laju aliran pendingin di condenser dapat meningkatkan unjuk kerja termal model LHP.

Global Sensitivity Analysis of Attenuation Zones of 2D Periodic Foundations

In this paper, global sensitivity analyses of attenuation zones of 2D periodic foundations are conducted. Global sensitivity analyses of upper bound frequency and lower bound frequency of the 1st attenuation zone of 2D periodic foundation are conducted considering four input parameters, i.e., initial stress ratio, filling ratio of core, filling ratio of resonator and periodic constant. Interactions and relative importance of input parameters are calculated.

Experimental Study of the Heat-Transfer Performance of an Extra-Long Gravity-Assisted Heat Pipe Aiming at Geothermal Heat Exploitation

The installation and operation of enhanced geothermal systems (EGS) involves many challenges. These challenges include the high cost and high risk associated with the investment capital, potential large working-fluid leakage, corrosion of equipment, and subsiding land. A super-long heat pipe can be used for geothermal exploitation to avoid these problems. In this paper, a high aspect-ratio heat pipe (30 m long, 17 mm in inner diameter) is installed vertically. Experiments are then carried out to study its heat-transfer performance and characteristics using several filling ratios of deionized water, different heating powers, and various cooling-water flowrates. The results show that the optimal filling-ratio is about 40% of the volume of the vaporizing section of the heat pipe. Compared with a conventional short heat pipe, the extra-long heat pipe experiences significant thermal vibration. The oscillation frequency depends on the heating power and working-fluid filling ratio. With increasing cooling-water flow rate, the heat-transfer rate of the heat pipe increases before it reaches a plateau. In addition, we investigate the heat-transfer performance of the heat pipe for an extreme working-fluid filling ratio; the results indicate that the lower part of the heat pipe is filled with vapor, which reduces the heat-transfer to the top part. Based on the experimental data, guidelines for designing a heat pipe that can be really used for the exploitation of earth-deep geothermal energy are analyzed.

Modeling and Analysis of the Kinetic Influence of Liquid Sloshing Characteristics on High-Clearance Sprayers

To research the influence of liquid sloshing on the driving stability of high-clearance sprayers, this paper builds an equivalent liquid sloshing mechanical model and obtains the stochastic acceleration excitation of the rectangular spray tank using the Adams kinetic model, thus obtaining the relationship between the impact force, moment, and the stochastic acceleration using Fluent numerical simulation analysis. This paper makes further calculations with MATLAB/Simulink system models, and the result from comparing these two calculations shows that the equivalent strategy proposed in this paper has a better consistency. Based on the consideration of the acting forces of the additional moment due to lateral movement of the center of mass of the liquid and the dynamic pressure due to liquid sloshing in the tank, this paper builds a mathematical model of the sprayer and researches the influence of the filling ratio and vehicle velocity on the vehicle stability through stochastic acceleration excitation. The results show that, in the case of different speeds, the liquid sloshing has a small influence on the overall roll angle; in the case of different filling ratios, the liquid sloshing has a big influence on the overall roll angle, the slip angle of the center of mass, and the yaw angular velocity; the filling ratio k = 0.85 and the speed u = 1 m/s−2 m/s are safe operation parameters of the sprayer. This research provides reference solutions for the stability control and optimization problems of the high-clearance sprayer and semitrailer.

Numerical Simulation on Motion Behavior of Inclusions in the Lab-Scale Electroslag Remelting Process with a Vibrating Electrode

In order to meet the requirement of high-quality ingots, the vibrating electrode technique in the electroslag remelting (ESR) process has been proposed. Non-metallic inclusions in ingots may cause serious defects and deteriorate mechanical properties of final products. Moreover, the dimension, number and distribution of non-metallic inclusions should be strictly controlled during the ESR process in order to produce high-quality ingots. A transient 2-D coupled model is established to analyze the motion behavior of inclusions in the lab-scale ESR process with a vibrating electrode, especially under the influence of the vibration frequency, current, slag layer thickness, and filling ratio, as well as type and diameter of inclusions. Simulation model of inclusions motion behavior is established based on the Euler-Lagrange approach. The continuous phase including metal and slag, is calculated based on the volume of fluid (VOF) method, and the trajectory of inclusions is tracked with the discrete phase model (DPM). The vibrating electrode is simulated by the user-defined function and dynamic mesh. The results show that when the electrode vibration frequency is 0.25 Hz or 1 Hz, the inclusions will gather on one side of the slag layer. When it increases from 0.25 Hz to 1 Hz, the removal ratio of 10 μm and 50 μm inclusions increases by 5% and 4.1%, respectively. When the current increases from 1200 A to 1800 A, the flow following property of inclusions in the slag layer becomes worse. The removal ratio of inclusions reaches the maximum value of 92% with the current of 1500 A. The thickness of slag layer mainly affects the position of inclusions entering the liquid-metal pool. As the slag layer thickens, the inclusions removal ratio increases gradually from 82.73% to 85.91%. As the filling ratio increases, the flow following property of inclusions in the slag layer is enhanced. The removal ratio of 10 μm inclusions increases from 94.82% to 97%. However, for inclusions with a diameter of 50 μm, the maximum removal ratio is 96.04% with a filling ratio of 0.46. The distribution of 50 μm inclusions is significantly different, while the distribution of 10μm inclusions is almost similar. Because of the influence of a vibrating electrode, 10 μm Al2O3 and MnO have a similar removal ratios of 81.33% and 82.81%, respectively.