Search Results (21)

This paper focuses on a fractional crystallization methodology using a rotating and internally gas-cooled crystallizer to purity crude selenium. Experiments using a rotating and gas-cooled crystallizer (cooled finger) were performed. The distribution coefficients of the main impurities (Pb, Fe and Hg) in selenium were presented as a polynomial function of concentration. The experimental parameters such as crystallization temperature and rotation rate were determined and discussed. The appropriate crystallization temperature is 222 °C and the rotation rates are 120 and 300 rpm, respectively. The purity of crude selenium increased from 99.9% to over 99.997%. Compared with the traditional method such as zone melting, this method only takes less than one day to complete several purifications, and the purification effect is better than the former. The removal rates of Hg, Pb and Fe in Se are 28.70%, 97.63% and 96.28%, respectively. The direct yield of Se purified is 92.5%. This study provides an efficient process for high-purity selenium, which has important industrial applications. Full article

The increasing demand for ultra-high purity aluminum for technological applications has led to the improvement of refining methods in recent decades. To achieve ultra-purity levels (>5N), the common industrial way is to firstly purify aluminum from 2N8 up to 4N8 via three-layer electrolysis, followed by fractional crystallization (usually zone melting). Since both of these methods are very cost- and time-intensive, this paper aims at providing other alternatives of purification. For this purpose, here, the purification of some selected impurities through cooled-finger fractional crystallization method and vacuum distillation have been the focus of this investigation. Both processes are more environmentally friendly than three-layer electrolysis and require less time than zone melting. In this paper, both methods were explored for the aluminum purification. Moreover, the effect of process parameters on the purification efficiency of iron, zinc, and silicon has been investigated. At the end, the effectiveness of the two processes was compared and advantages and disadvantages were summarized. The results showed that the cooling finger process effectively removed iron and silicon impurities, but the removal efficiency of zinc was low. The vacuum distillation process successfully removes zinc in the first stage of distillation. Iron and silicon removal requires additional distillation stages to achieve lower impurity levels. Full article

Background: Chilblains/perniosis is a non-freezing cold injury causing painful inflammatory skin lesions. Its pathogenesis remains poorly understood because it is often studied as secondary to other underlying conditions. Methods: We systematically investigated the population characteristics, symptoms, and predisposing factors of chilblains in healthy adults exposed to cool/cold environments. We screened PubMed, Embase, and Cochrane Library, and we adopted PRISMA reporting guidelines (PROSPERO: CRD42021245307). The risk of bias was assessed by two independent reviewers (RTI item bank). Random-effects model meta-analyses were performed to calculate the pooled prevalence of histopathological features. Mixed-effects meta-regressions were used to assess other sources of between-study heterogeneity. Results: Thirteen studies (477 patients) were included. Chilblains affect more women than men, up to 12% of the body skin surface, and most frequently, the hands and fingers. Meta-analyses of nine studies (303 patients) showed a frequent presence of perivascular lymphocytic infiltrate (81%), basal epidermal-cell layer vacuolation (67%), papillary dermal edema (66%), and perieccrine lymphocytic infiltrate (57%). Meta-regressions (p ≤ 0.05) showed that smoking and frequent occupational exposure to water increase the likelihood of histopathological features. Conclusions: The population characteristics, symptoms, and predisposing factors of chilblains revealed in this analysis should be incorporated in medical care to improve the condition’s diagnosis and management. Full article

The dynamic behavior of droplet impingement is one of the most important processes of spray cooling. Although refrigerants with a low boiling point have been widely used in spray cooling, their high volatility makes it difficult to generate a stable droplet under atmospheric pressure, and thus the dynamic behavior of droplet impingement is rarely reported. Therefore, it is of great significance to study the behavior of refrigerant droplet impingement to fill the relevant research gaps. In this paper, an experimental system for single refrigerant droplet generation and impingement at atmospheric pressure has been established. By means of high-speed photography technology, the morphology and dynamics of R1336mzz(Z) droplet impingement on grooved carbon steel walls have been studied. Phenomena such as a truncated sphere, boiling, and finger-shaped disturbance were observed, and the reasons responsible for them were analyzed. The effects of Weber number (We) and surface roughness (Ra) on droplet spreading factor (β) were investigated quantitatively. Higher We always causes a larger β_max, while Ra has a different influence on β_max. The Cassie–Wenzel transition occurs when Ra increases from 1.6 μm to 3.2 μm, leading to a rapid decrease in β_max. An empirical formula has been proposed to predict β_max under different conditions. Full article

Background: Cold-induced vasodilation (CIVD) is a phenomenon that refers to a paradoxical increase in finger temperature that sometimes occurs during cold exposure. The aim of this study was to compare CIVD responses between women and men, during exposure to different environmental conditions. Methods: Seven men and seven women participated in a matched controlled study consisting of a familiarization protocol followed by three experimental sessions (cool (10.8 °C WBGT), thermoneutral (17.2 °C WBGT), and hot (27.2 °C WBGT)). In each session, participants were asked to immerse their left hand and foot in warm water (35 ± 1 °C) for five minutes. Thereafter, the left hand and foot were immersed in cold water (8 ± 1 °C) for 40 min. After that, the left hand and foot were removed from the water and participants remained seated for five minutes. Results: For a matched thermal stress, women experienced an elevated cardiovascular strain (heart rate and in some cases mean arterial pressure) and higher frequency of CIVD reactions (men: 31 vs. women: 60) in comparison to their male counterparts. Conclusions: The present study demonstrated that women experienced elevated cardiovascular strain and higher frequency of CIVD reactions, particularly in the toes, compared to their male counterparts during cold-water immersion. Full article

This study uses the universal thermal climate index (UTCI) and whole-body and local cooling assessment to determine the thermal benchmarks and cold risk for children in China’s severe cold regions. The relevant measurements and survey were conducted in four open spaces at a children’s park in Harbin, China. The findings of the study are as follows: (1) In winter, solar radiation and global temperature affects winter thermal sensation in male and female children the most. (2) Female children have a lower neutral UTCI (6.0 °C) than male children (7.3 °C), and female children have lower upper and lower thresholds of the neutral UTCI range (−1.3–13.4 °C) than male children (0.6–14.1 °C). (3) Children who engaged in light-intensity activities, were exposed to cold winds, and touched cold surfaces with their bare fingers are at risk of whole-body and local cooling. (4) Children prefer exercising (P_Female = 35.5%, P_Male = 48.3%) and moving to sunshine for thermal adaptation (P_Female = 31.1%, P_Male = 26.4%). (5) Winter travel guidelines, cold-risk-prevention measures, and safety guidelines for winter outdoor activities are proposed. The results provide references for the design of open spaces in urban parks in China’s severe cold regions. Full article

Miniaturization of electronics devices is often limited by the concomitant high heat fluxes (cooling load) and maldistribution of temperature profiles (hot spots). Thermal energy storage (TES) platforms providing supplemental cooling can be a cost-effective solution, that often leverages phase change materials (PCM). Although salt hydrates provide higher storage capacities and power ratings (as compared to that of the organic PCMs), they suffer from reliability issues (e.g., supercooling). “Cold Finger Technique (CFT)” can obviate supercooling by maintaining a small mass fraction of the PCM in a solid state for enabling spontaneous nucleation. Optimization of CFT necessitates real-time forecasting of the transient values of the melt-fraction. In this study, the artificial neural network (ANN) is explored for real-time prediction of the time remaining to reach a target value of melt-fraction based on the prior history of the spatial distribution of the surface temperature transients. Two different approaches were explored for training the ANN model, using: (1) transient PCM-temperature data; or (2) transient surface-temperature data. When deployed in a heat sink that leverages PCM-based passive thermal management systems for cooling electronic chips and packages, this maverick approach (using the second method) affords cheaper costs, better sustainability, higher reliability, and resilience. The error in prediction varies during the melting process. During the final stages of the melting cycle, the errors in the predicted values are ~5% of the total time-scale of the PCM melting experiments. Full article

Objective: The objective of this study was to develop a new strategy for rapid diagnosis of the source of low back pain (LBP) for treatment with cooled radiofrequency ablation (RFA). Materials: Patients suffering from facet joint (FJ) or sacroiliac joint (SIJ) pain for more than 3 months were included. Two methods, Technetium Tc99m methylene diphosphonate single photon emission tomography/computed tomography (^99mTc-MDP SPECT/CT) and a modified Fortin finger test were used to identify the source of LBP for treatment with cooled RFA. The visual analog scale (VAS) and Oswestry disability index (ODI) were used to assess the patients’ pain levels and disabilities respectively. These two measures were recorded at baseline and 1-week, 1-month, 3-month, and 6-month follow-up visits. Results: A total of 40 patients with LBP were included in this study. Our results demonstrated that the patients with LBP identified by our new strategy had significant improvements in VAS or ODI score at 1-week to 6-month follow-up visits (p < 0.001) after receiving cooled RFA. Similar results were also found in patients with FJ pain and those with FJ and SIJ pain respectively. Among all the patients, over 70% had greater than or equal to 50% reduction in VAS and ODI scores. No serious adverse events were observed after treatment. Conclusions: This new strategy could be successfully adopted for rapid diagnosis of the source of comprehensive LBP. Full article

Aluminum and aluminum-based alloys have been used for many years. In view of the increase in material purity requirements of advanced technology products, research regarding high-purity aluminum has gained significant attention in recent years. In this review, we seek to describe the fundamental purification principles and the mechanisms of various segregation techniques used to produce high-purity aluminum. Moreover, we aim to provide an overview of high-purity aluminum production, with particular emphasis on: (a) principles on how to produce high-purity aluminum by layer- and suspension-based segregation methods; (b) discussion of various influencing process parameters for each technique, including three-layer electrolysis, vacuum distillation, organic electrolysis, suspension-based segregation, zone melting, Pechiney, Cooled Finger, and directional solidification; as well as (c) investigations of fundamental working principles of various segregation methods and corresponding reported end-purification for the production of HP-Al. Eventually, the end-reported product purity, and advantages and disadvantages of various purification methods and technologies are summarized. By analyzing and comparing the characteristics of different methods, we put forward suggestions for realizing efficient and environmentally friendly production of high-purity aluminum in the future. Full article

As one of the most important prosthetic implants for amputees, current commercially available prosthetic hands are still too bulky, heavy, expensive, complex and inefficient. Here, we present a study that utilizes the artificial tendon to drive the motion of fingers in a biomimetic prosthetic hand. The artificial tendon is realized by combining liquid crystal elastomer (LCE) and liquid metal (LM) heating element. A joule heating-induced temperature increase in the LCE tendon leads to linear contraction, which drives the fingers of the biomimetic prosthetic hand to bend in a way similar to the human hand. The responses of the LCE tendon to joule heating, including temperature increase, contraction strain and contraction stress, are characterized. The strategies of achieving a constant contraction stress in an LCE tendon and accelerating the cooling for faster actuation are also explored. This biomimetic prosthetic hand is demonstrated to be able to perform complex tasks including making different hand gestures, holding objects of different sizes and shapes, and carrying weights. The results can find applications in not only prosthetics, but also robots and soft machines. Full article

In this work, we investigate sea surface temperature (SST) cooling under binary typhoon conditions. We particularly focus on parallel- and cross-type typhoon paths during four typhoon events: Tembin and Bolaven in 2012, and Typhoon Chan-hom and Linfa in 2015. Wave-induced effects were simulated using a third-generation numeric model, WAVEWATCH III (WW3), and were subsequently included in SST simulations using the Stony Brook Parallel Ocean Model (sbPOM). Four wave-induced effects were analyzed: breaking waves, nonbreaking waves, radiation stress, and Stokes drift. Comparison of WW3-simulated significant wave height (SWH) data with measurements from the Jason-2 altimeter showed that the root mean square error (RMSE) was less than 0.6 m with a correlation (COR) of 0.9. When the four typhoon-wave-induced effects were included in sbPOM simulations, the simulated SSTs had an RMSE of 1 °C with a COR of 0.99 as compared to the Argos data. This was better than the RMSE and COR recovered between the measured and simulated SSTs, which were 1.4 °C and 0.96, respectively, when the four terms were not included. In particular, our results show that the effects of Stokes drift, as well as of nonbreaking waves, were an important factor in SST reduction during binary typhoons. The horizontal profile of the sbPOM-simulated SST for parallel-type typhoon paths (Typhoons Tembin and Bolaven) suggested that the observed finger pattern of SST cooling (up to 2 °C) was probably caused by drag from typhoon Tembin. SST was reduced by up to 4 °C for cross-type typhoon paths (Typhoons Chan-hom and Linfa). In general, mixing significantly increased when the four wave-induced effects were included. The vertical profile of SST indicated that disturbance depth increased (up to 100 m) for cross-type typhoon paths because the mixing intensity was greater for cross-type typhoons than for parallel-type typhoons. Full article

Raynaud’s phenomenon (RP) is characterized by the episodic whitening of the fingers upon exposure to cold. A recently described thermographic algorithm was proposed as a diagnostic replacement of the currently applied finger systolic pressure (FSP) test. The aim of the study was to evaluate the performance of the thermographic algorithm when applied in patients suspected of having RP. Forty-three patients were examined using thermographic imaging after local cooling of the hands in water of 10 °C for 1 min. The thermographic algorithm was applied to predict the probability of RP. The performance of the algorithm was evaluated with different cut-off levels. A new algorithm was proposed based on patients from the target population. The performance of the tested algorithm was noninferior to the FSP test, when a cut-off level of 0.05 was applied, yielding a sensitivity and specificity of 69% and 58%, respectively. The accuracy was 66%. The FSP test had a sensitivity and specificity of 77% and 37%, respectively, and the accuracy was 59%. The thermographic method proved useful for detecting RP and was able to replace the FSP test as a diagnostic test. The alternative algorithm revealed that other thermographic variables were more predictive of the target population, but this should be verified in future patients. Full article

The soft robots actuated by pressure, cables, thermal, electrosorption, combustion and smart materials are usually faced with the problems of poor portability, noise, weak load capacity, small deformation and high driving voltages. In this paper, a novel pneumatic generator for soft robots based on the gas-liquid reversible transition is proposed, which has the advantages of large output force, easy deformation, strong load capacity and high flexibility. The pressure of the pneumatic generator surges or drops flexibly through the reversible transformation between liquid and gas phase, making the soft actuator stretch or contract regularly, without external motors, compressors and pressure-regulating components. The gas-liquid reversible-transition actuation process is modeled to analyze its working mechanism and characteristics. The pressure during the pressurization stage increases linearly with a rate regulated by the heating power and gas volume. It decreases exponentially with the exponential term as a quadratic function of time at the fast depressurization stage, while with the exponential term as a linear function of time at the slow depressurization stage. The drop rate can be adjusted by changing the gas volume and cooling conditions. Furthermore, effectiveness has been verified through experiments of the prototype. The pressure reaches 25 bar with a rising rate of +3.935 bar/s when 5 mL weak electrolyte solution is heated at 800 W, and the maximum depressurization rate in air cooling is –3.796 bar/s. The soft finger actuated by the pneumatic generator can bend with an angular displacement of 67.5°. The proposed pneumatic generator shows great potential to be used for the structure, driving and sensing integration of artificial muscles. Full article

Fused deposition modeling (FDM) is one of the most often-used technologies in additive manufacturing. Several materials are used with this technology, such as poly(lactic acid) (PLA), which is most commonly applied. The mechanical properties of 3D-printed parts depend on the process parameters. This is why, in this study, three-point bending tests were carried out to characterize the influence of build orientation, layer thickness, printing temperature and printing speed on the mechanical properties of PLA samples. Not only the process parameters may affect the mechanical properties, but heat after-treatment also has an influence on them. For this reason, additional samples were printed with optimal process parameters and characterized after pure heat treatment as well as after deformation at a temperature above the glass transition temperature, cooling with applied deformation, and subsequent recovery under heat treatment. These findings are planned to be used in a future study on finger orthoses that could either be printed according to shape or in a flat shape and afterwards heated and bent around the finger. Full article

Raynaud’s phenomenon (RP) is characterized by the episodic whitening of the fingers upon exposure to cold. Verification of the condition is crucial in vibration-exposed patients. The current verification method is outdated, but thermographic imaging seems promising as a diagnostic replacement. By investigating patients diagnosed with RP, the study aimed at developing a simple thermographic procedure that could be applied to future patients where verification of the diagnosis is needed. Twenty-two patients with primary RP and 58 healthy controls were examined using thermographic imaging after local cooling of the hands for 1 min in water of 10°C. A logistic regression model was fitted with the temperature curve characteristics to convey a predicted probability of having RP. The characteristics time to end temperature and baseline temperature were the most appropriate predictors of RP among those examined (p = 0.004 and p = 0.04, respectively). The area under the curve was 0.91. The cut-off level 0.46 yielded a sensitivity and specificity of 82% and 86%, respectively. The positive and negative predictive values were 69% and 93%, respectively. This newly developed thermographic method was able to distinguish between patients with RP and healthy controls and was easy to operate. Thus, the method showed great promise as a method for verification of RP in future patients. Trial registration: ClinicalTrials.gov NCT03094910. Full article