The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical...The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical simulation was also employed to investigate the nugget formation process. The results showed that for the RSW of two aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece(W/W) interface and grew along the radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of three aluminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial direction and radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after which the nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW of aluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showed that the simulation results agreed well with the experimental results.展开更多
The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted main...The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.展开更多
Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical pr...Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.展开更多
With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the con...With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical simulation.展开更多
The in-process changes of weld nugget growth during the Resistance Spot Welding were investigated based on the resistance of input electrical impedance. To compute the time varying resistance of input electrical imped...The in-process changes of weld nugget growth during the Resistance Spot Welding were investigated based on the resistance of input electrical impedance. To compute the time varying resistance of input electrical impedance, the welding voltage and current signals are measured simultaneously and then converted into complex-valued signals by using Hilbert transform. Comparing with the dynamic contact resistance as reported in literature, it showed that the time varying resistance of input electrical impedance can be accurately correlated with the physical changes of weld nugget growth. Therefore, it can be used to characterize the in-process changes of weld nugget growth. Several new findings were reported based on the investigation of spot welds under no weld, with and without weld expulsion conditions.展开更多
Sizes of nuggets are often used to evaluate spot weld quality in production. This paper presents a neural estimator used to carry out non-destructive on-line analysis of spot weld quality in which trained ANN function...Sizes of nuggets are often used to evaluate spot weld quality in production. This paper presents a neural estimator used to carry out non-destructive on-line analysis of spot weld quality in which trained ANN functions to map dynamic resistance characteristics into sizes of spot weld nuggets and results confirm the validity of neural network for this type of application.展开更多
Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><sp...Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><span><span style="font-family:;" "=""> chicken</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">wings and dehydrated shellfish to produce chicken nuggets rich in protein, minerals and vitamins.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">The proximate composition, nutritional value, physical and sensorial properties were evaluated. The different</span></span></span><span><span><span style="font-family:;" "="">ly</span></span></span><span><span><span style="font-family:;" "=""> prepared chicken nuggets </span></span></span><span><span><span style="font-family:;" "="">were </span></span></span><span><span><span style="font-family:;" "="">supplemented with dehydrated shellfish CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. There was </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">significantly reduction </span></span></span><span><span><span style="font-family:;" "="">in </span></span></span><span><span><span style="font-family:;" "="">moisture and </span></span></span><span><span><span style="font-family:;" "="">an </span></span></span><span><span><span style="font-family:;" "="">increasing in protein content (<i>P</i> < 0.05) in all Chicken Nuggets (CN) in comparison to the control. Fat content was significantly higher in CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% than CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. Ash content was increasing with added dehydrated shellfish, while </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">reduction in carbohydrates and total calories of the different chicken nuggets were noticed with </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">significant gradual rise in pH values, TBA values showed no significant difference (<i>P</i> < 0.05) between chicken nuggets. Results showed that using dehydrated shellfish in preparing chicken nuggets caused a marked rise in its content of Ca, Fe, Na, K, Zn, Mg and Mn levels, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% had the lowest concentration of all minerals, and had lower value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had higher value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D. Control Nuggets (CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%) had the lowest value of yellowness and highest value of lightness but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest value of yellowness and, </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">lowest value of lightness. </span></span></span><span><span><span style="font-family:;" "="">The </span></span></span><span><span><span style="font-family:;" "="">redness had </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">slightly reduction. All samples showed slight changes in</span></span></span><span><span><span style="font-family:;" "=""> hardness, cohesiveness, springiness, gumminess and chewiness were noticed. </span></span></span><span><span><span style="font-family:;" "="">An </span></span></span><span><span><span style="font-family:;" "="">increase in WHC, pick-up, and cooking loss of chicken nuggets with dehydrated shellfish was noticed. Panelists accepted all prepared chicken nuggets and the chicken nuggets CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest score compared with other chicken nuggets prepared.展开更多
Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framew...Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym ＆ Pines, the glitch sizes（the relative increases of spin-frequencies during glitches） △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets（SNs） which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ？？/？ are smaller than those in the standard starquake model（with larger amounts of released energy）. Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches（e.g.,by the Square Kilometre Array）.展开更多
To overcome the problems of fusion welding of aluminium alloys, the friction stir welding(FSW) is recognized as an alternative joining method to improve the mechanical and corrosion properties. Tool profile is one of ...To overcome the problems of fusion welding of aluminium alloys, the friction stir welding(FSW) is recognized as an alternative joining method to improve the mechanical and corrosion properties. Tool profile is one of the important variables which affect the performance of the FS weld. In the present work, the effect of tool profile on the weld nugget microstructure and pitting corrosion of AA2219 aluminium-copper alloy was studied. FSW of AA2219 alloy was carried out using five profiles, namely conical, square, triangle, pentagon and hexagon. The temperature measurements were made in the region adjacent to the rotating pin. It was observed that the peak temperature is more in hexagonal tool pin compared to the welds produced with other tool pin profiles. It is observed that the extensive deformation experienced at the nugget zone and the evolved microstructure strongly influences the hardness and corrosion properties of the joint during FSW. It was found that the microstructure changes like grain size, misorientation and precipitate dissolution during FSW influence the hardness and corrosion behaviour. Pitting corrosion resistance of friction stir welds of AA2219 was found to be better for hexagon profile tool compared to other profiles, which was attributed to material flow and strengthening precipitate morphology in nugget zone. Higher amount of heat generation in FS welds made with hexagonal profile tool may be the reason for greater dissolution of strengthening precipitates in nugget zone.展开更多
Online estimation of the double nugget diameters was performed by means of a back propagation neural network.The double nugget diameters were obtained using actual welding experiment and numerical simulation,according...Online estimation of the double nugget diameters was performed by means of a back propagation neural network.The double nugget diameters were obtained using actual welding experiment and numerical simulation,according to different characteristics of aluminum nugget and steel nugget.The input of the neural network was some key characteristic parameters extracted from dynamic power signal,which were peak point,knee point and their variation rate over time,as well as heat energy delivered into the welding system.The architecture of the neural network was confirmed by confirming the number of neurons in hidden layer through a series of calculations.The key parameters of the neural network were obtained by means of training 81 arrays of data set.Then,the neural network was used to test the remaining 20 arrays of verifying data set,and the results showed that both of the mean errors for the two nugget diameters were below 3%.In addition,corresponding analyses showed that the accuracy of two nugget diameters was higher than that of tensile-shear strength.展开更多
This research presents an innovative approach to accurately predict the nugget diameter in resistance spot welding(RSW)by leveraging machine learning and transfer learning methods.Initially,low-fidelity(LF)data were o...This research presents an innovative approach to accurately predict the nugget diameter in resistance spot welding(RSW)by leveraging machine learning and transfer learning methods.Initially,low-fidelity(LF)data were obtained through finite element numerical simulation and design of experiments(DOEs)to train the LF machine learning model.Subsequently,high-fidelity(HF)data were collected from RSW process experiments and used to fine-tune the LF model by transfer learning techniques.The accuracy and generalization performance of the models were thoroughly validated.The results demonstrated that combining different fidelity datasets and employing transfer learning could significantly improve the prediction accuracy while minimize the costs associated with experimental trials,and provide an effective and valuable method for predicting critical process parameters in RSW.展开更多
The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduc- tion experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron c...The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduc- tion experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron contai- ning iron concentrate and pulverized coal mainly, from 1 623 to 1 723 K with different heating time. The results indi- cated that iron nugget making process depends mainly on heating time and temperature. And the iron nugget and slag can separate in a clean manner at 1 673 K for 15 min. For the iron nugget, the C content is 3.57% （mass percent） and B is 0. 065~ （mass percent）. The B203 content of slag is 20.01~/00, and the boron was concentrated into one phase which is identified as suanite （Mg2BaOs） during the solidification. With an extraction ratio of 80~ under the atmospheric conditions, the activity of boron in slag is good. The boron-rich slag can be used to extract boric or boric acid and alleviate the shortage of boron resource. Through series of calculation and analysis related, it can be conclu- ded that the recovery ratio of Fe and boron are about 98% and 97% respectively. The results show that this method is feasible and effective on the utilization of paigeite ore.展开更多
In order to utilize the iron resource effectively in red mud, a laboratory experiment based on the orthogonal method was carried out. Nuggets were gotten by directly reducing the carbon-bearing pellets of red mud and ...In order to utilize the iron resource effectively in red mud, a laboratory experiment based on the orthogonal method was carried out. Nuggets were gotten by directly reducing the carbon-bearing pellets of red mud and coal. The results showed that the strongest influencing factor is temperature, and the separation between liquid iron and slag is thoroughly. The nuggets can be gotten when the pellets, in which xC/xO is 1.6 and the basicity is 1.0, were maintained in 30 min at 1 400 ℃. The nuggets have a high TFe content which is higher than that in the hot metal produced in BF. It also has a low content of Si and Mn, but a high content of S and P. The main compositions of the slag are amorphous phase mainly containing SiO;and unreduced Fe;SiO;. Of course, a little reduced iron retains in it.展开更多
基金Supported by the National Natural Science Foundation of China(No.51275342 and No.51275338)
文摘The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical simulation was also employed to investigate the nugget formation process. The results showed that for the RSW of two aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece(W/W) interface and grew along the radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of three aluminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial direction and radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after which the nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW of aluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showed that the simulation results agreed well with the experimental results.
基金supported by National Natural Science Foundation of China(51275204)
文摘The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.
基金the Coordinación de la Investigación Científica(CIC)of the Universidad Michoacana de San Nicolás de Hidalgo(UMSNH-México)for the support during this project(CIC-UMSNH-1.8)sponsored by the National Council on Science and Technology(Consejo Nacional de Ciencia y Tecnología-México)and would like to thank for the support during this project N.B.254928
文摘Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.
基金Supported by National Natural Science Foundation of China (No. 50175080)
文摘With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical simulation.
文摘The in-process changes of weld nugget growth during the Resistance Spot Welding were investigated based on the resistance of input electrical impedance. To compute the time varying resistance of input electrical impedance, the welding voltage and current signals are measured simultaneously and then converted into complex-valued signals by using Hilbert transform. Comparing with the dynamic contact resistance as reported in literature, it showed that the time varying resistance of input electrical impedance can be accurately correlated with the physical changes of weld nugget growth. Therefore, it can be used to characterize the in-process changes of weld nugget growth. Several new findings were reported based on the investigation of spot welds under no weld, with and without weld expulsion conditions.
文摘Sizes of nuggets are often used to evaluate spot weld quality in production. This paper presents a neural estimator used to carry out non-destructive on-line analysis of spot weld quality in which trained ANN functions to map dynamic resistance characteristics into sizes of spot weld nuggets and results confirm the validity of neural network for this type of application.
文摘Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><span><span style="font-family:;" "=""> chicken</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">wings and dehydrated shellfish to produce chicken nuggets rich in protein, minerals and vitamins.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">The proximate composition, nutritional value, physical and sensorial properties were evaluated. The different</span></span></span><span><span><span style="font-family:;" "="">ly</span></span></span><span><span><span style="font-family:;" "=""> prepared chicken nuggets </span></span></span><span><span><span style="font-family:;" "="">were </span></span></span><span><span><span style="font-family:;" "="">supplemented with dehydrated shellfish CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. There was </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">significantly reduction </span></span></span><span><span><span style="font-family:;" "="">in </span></span></span><span><span><span style="font-family:;" "="">moisture and </span></span></span><span><span><span style="font-family:;" "="">an </span></span></span><span><span><span style="font-family:;" "="">increasing in protein content (<i>P</i> < 0.05) in all Chicken Nuggets (CN) in comparison to the control. Fat content was significantly higher in CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% than CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. Ash content was increasing with added dehydrated shellfish, while </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">reduction in carbohydrates and total calories of the different chicken nuggets were noticed with </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">significant gradual rise in pH values, TBA values showed no significant difference (<i>P</i> < 0.05) between chicken nuggets. Results showed that using dehydrated shellfish in preparing chicken nuggets caused a marked rise in its content of Ca, Fe, Na, K, Zn, Mg and Mn levels, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% had the lowest concentration of all minerals, and had lower value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had higher value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D. Control Nuggets (CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%) had the lowest value of yellowness and highest value of lightness but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest value of yellowness and, </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">lowest value of lightness. </span></span></span><span><span><span style="font-family:;" "="">The </span></span></span><span><span><span style="font-family:;" "="">redness had </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">slightly reduction. All samples showed slight changes in</span></span></span><span><span><span style="font-family:;" "=""> hardness, cohesiveness, springiness, gumminess and chewiness were noticed. </span></span></span><span><span><span style="font-family:;" "="">An </span></span></span><span><span><span style="font-family:;" "="">increase in WHC, pick-up, and cooking loss of chicken nuggets with dehydrated shellfish was noticed. Panelists accepted all prepared chicken nuggets and the chicken nuggets CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest score compared with other chicken nuggets prepared.
基金supported by the National Natural Science Foundation of China (11203018)the West Light Foundation (XBBS-2014-23)+1 种基金the Science Project of Universities in Xinjiang (XJEDU2012S02)the Doctoral Science Foundation of Xinjiang University (BS120107)
文摘Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym ＆ Pines, the glitch sizes（the relative increases of spin-frequencies during glitches） △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets（SNs） which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ？？/？ are smaller than those in the standard starquake model（with larger amounts of released energy）. Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches（e.g.,by the Square Kilometre Array）.
文摘To overcome the problems of fusion welding of aluminium alloys, the friction stir welding(FSW) is recognized as an alternative joining method to improve the mechanical and corrosion properties. Tool profile is one of the important variables which affect the performance of the FS weld. In the present work, the effect of tool profile on the weld nugget microstructure and pitting corrosion of AA2219 aluminium-copper alloy was studied. FSW of AA2219 alloy was carried out using five profiles, namely conical, square, triangle, pentagon and hexagon. The temperature measurements were made in the region adjacent to the rotating pin. It was observed that the peak temperature is more in hexagonal tool pin compared to the welds produced with other tool pin profiles. It is observed that the extensive deformation experienced at the nugget zone and the evolved microstructure strongly influences the hardness and corrosion properties of the joint during FSW. It was found that the microstructure changes like grain size, misorientation and precipitate dissolution during FSW influence the hardness and corrosion behaviour. Pitting corrosion resistance of friction stir welds of AA2219 was found to be better for hexagon profile tool compared to other profiles, which was attributed to material flow and strengthening precipitate morphology in nugget zone. Higher amount of heat generation in FS welds made with hexagonal profile tool may be the reason for greater dissolution of strengthening precipitates in nugget zone.
基金This work was supported by the National Natural Science Foundation of China(No.51605103).
文摘Online estimation of the double nugget diameters was performed by means of a back propagation neural network.The double nugget diameters were obtained using actual welding experiment and numerical simulation,according to different characteristics of aluminum nugget and steel nugget.The input of the neural network was some key characteristic parameters extracted from dynamic power signal,which were peak point,knee point and their variation rate over time,as well as heat energy delivered into the welding system.The architecture of the neural network was confirmed by confirming the number of neurons in hidden layer through a series of calculations.The key parameters of the neural network were obtained by means of training 81 arrays of data set.Then,the neural network was used to test the remaining 20 arrays of verifying data set,and the results showed that both of the mean errors for the two nugget diameters were below 3%.In addition,corresponding analyses showed that the accuracy of two nugget diameters was higher than that of tensile-shear strength.
基金founded by the Construction Project of the National Natural Science Foundation(Grant No.52205377)the National Key Research and Development Program(Grant No.2022YFB4601804)the Key Basic Research Project of Suzhou(Grant Nos.SJC2022029,SJC2022031).
文摘This research presents an innovative approach to accurately predict the nugget diameter in resistance spot welding(RSW)by leveraging machine learning and transfer learning methods.Initially,low-fidelity(LF)data were obtained through finite element numerical simulation and design of experiments(DOEs)to train the LF machine learning model.Subsequently,high-fidelity(HF)data were collected from RSW process experiments and used to fine-tune the LF model by transfer learning techniques.The accuracy and generalization performance of the models were thoroughly validated.The results demonstrated that combining different fidelity datasets and employing transfer learning could significantly improve the prediction accuracy while minimize the costs associated with experimental trials,and provide an effective and valuable method for predicting critical process parameters in RSW.
基金Sponsored by National Key Technology Research and Development Program in 11th Five-Year Plan of China (2008BAB32B05)
文摘The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduc- tion experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron contai- ning iron concentrate and pulverized coal mainly, from 1 623 to 1 723 K with different heating time. The results indi- cated that iron nugget making process depends mainly on heating time and temperature. And the iron nugget and slag can separate in a clean manner at 1 673 K for 15 min. For the iron nugget, the C content is 3.57% （mass percent） and B is 0. 065~ （mass percent）. The B203 content of slag is 20.01~/00, and the boron was concentrated into one phase which is identified as suanite （Mg2BaOs） during the solidification. With an extraction ratio of 80~ under the atmospheric conditions, the activity of boron in slag is good. The boron-rich slag can be used to extract boric or boric acid and alleviate the shortage of boron resource. Through series of calculation and analysis related, it can be conclu- ded that the recovery ratio of Fe and boron are about 98% and 97% respectively. The results show that this method is feasible and effective on the utilization of paigeite ore.
基金Sponsored by National Science and Technology Support Plan of China(2012BAB14B00)
文摘In order to utilize the iron resource effectively in red mud, a laboratory experiment based on the orthogonal method was carried out. Nuggets were gotten by directly reducing the carbon-bearing pellets of red mud and coal. The results showed that the strongest influencing factor is temperature, and the separation between liquid iron and slag is thoroughly. The nuggets can be gotten when the pellets, in which xC/xO is 1.6 and the basicity is 1.0, were maintained in 30 min at 1 400 ℃. The nuggets have a high TFe content which is higher than that in the hot metal produced in BF. It also has a low content of Si and Mn, but a high content of S and P. The main compositions of the slag are amorphous phase mainly containing SiO;and unreduced Fe;SiO;. Of course, a little reduced iron retains in it.
