Cyclocarya paliurus  as a natural antioxidant for meat products (Frankfurters). The results showed that flavonoid extracts from C. paliurus had strong antioxidant and antibacterial activity. This is proportional to concentration, and the addition of extracts could significantly (p < 0.05) delay the lipid oxidation in the samples. In addition, we did not observe hazardous effects on the samples’ pH and texture as a result of adding flavonoid extracts. We observed that flavonoid extracts from C. paliurus at concentrations of 0.06% and 0.12% did not affect the color and sensory evaluation of the samples. At a concentration of 0.18% and 0.24%, the flavonoid extracts had a negative impact on the color and sensory evaluation of the samples, likely due to the yellow-brown color of the extract itself. The findings showed that a low concentration of 0.12% flavonoid extracts from C. paliurus in meat products could effectively prevent lipid oxidation without affecting the sensory quality.Oxidation is one of the most common causes of the deterioration of meat and meat products. At the same time, synthetic antioxidants are becoming less accepted by consumers due to the potential health hazards they might cause. Therefore, a new trend to substitute these synthetic antioxidants with natural antioxidants has emerged. This study adds flavonoid extracts from  Lipid oxidation has long been recognized as the leading cause of undesirable effects on meat and meat products’ quality, acceptability, and shelf-life. Lipid oxidation results in oxidative off-flavor, discoloration, and spoilage of meat and meat products ,2. The oNatural antioxidants are mainly derived from spices, plants, fruits, and vegetable skin residue extracts. Numerous studies have evaluated natural substances as antioxidant additives in meat products and proved their effectiveness. Estevez et al. found that adding rosemary essential oil to frankfurters delayed oxidation problems and reduced tenderness during refrigeration . Tran etCyclocarya paliurus  Iljinskaja , commonly known as the “sweet tea tree”, is a well-known edible and medicinal plant cultivated in the misty highlands of southern China. In recent years, C. paliurus has gained increasing interest due to its wide range of biological activities and antioxidant effects, such as antihypertensive activity, hypolipidemic, hypoglycemic activity, enhancement of mental efficiency, and antioxidant activity [C. paliurus leaves, such as flavonoids, polysaccharides, triterpenoids, steroids, saponins, and phenolic acid compounds [C. paliurus leaves. Xie et al. found that the DPPH radical scavenging ability of flavonoids (at the concentration of 0.1–0.8 mg/mL) from C. paliurus was always better than that of butylated hydroxytoluene (BHT) [C. paliurus had inhibited effects on Staphylococcus aureus, Salmonella, and Escherichia coli [activity ,16,17. Tompounds . Amongstne (BHT) . Regardihia coli . Furtherhia coli . Consumers expect meat products to be nutritious, safe, convenient, and of good sensory quality. In the meat industry, there is growing interest in using innovative processing methods to reformulate products and replace synthetic additives with natural bioactive compounds to minimize health concerns and improve the overall organoleptic, nutritional, and health properties of processed meats. Frankfurters are an emulsion-type meat product containing 20~30% of fat, unfermented, and consumed worldwide. They have a short shelf life as lipids are vulnerable to oxidative damage from reactive oxygen species (ROS), particularly when exposed to light ,23. The C. paliurus have specific antioxidant and antibacterial properties that could be used in the meat processing industry as a natural function antioxidant. This study aimed to assess the possibility of adding flavonoid extracts from C. paliurus at different concentrations  as a natural antioxidant to improve the physicochemical and sensory properties of cooked meat product (Frankfurters) over a refrigerated storage period of 21 days. The flavonoid extracts from C. paliurus, a brown-yellow fine powder soluble in water has the unique flavor of C. paliurus, which were purchased from Lanzhou Waters Biotechnology Co., Ltd. ; Sodium D-isoascorbate was purchased from Shiyao Group Weisheng Pharmaceutical (Shijiazhuang) Co., Ltd. ; Pig hind leg and pig back fat was purchased from Jiangsu Nanjing Yurun Group. White granulated sugar, salt, white pepper powder, and nutmeg powder were all food-grade and commercially available, sodium tripolyphosphate was purchased from Shanghai Taixin Industry Co., Ltd. , and collagen casing (22 mm) was purchased from Liu Zhou Honsen Collagen Casing Co., Ltd. . Anhydrous ethanol and methanol were purchased from Sinopharm Chemical Reagent Co., Ltd. . Flavonoid extracts from C. paliurus flavonoid extracts and prepared liquid samples with the concentration of 0.6 mg/mL, 1.2 mg/mL, 1.8 mg/mL, and 2.4 mg/mL with ultrapure water, and 0.025% sodium D-isoascorbate was prepared. Following that, we take two 1 mL centrifuge tubes for each group, add 400 μL of liquid sample, 600 μL of 80% methanol for one as the control group, and 600 μL of working solution for the other as the test group. We also add 400 μL, 80% methanol, and 600 μL working solution into the blank tube as the blank control. All treatment groups were covered to avoid light for 30 min, then 200 μL were absorbed into 96 healthy enzyme standard plates, and the absorbance was measured at 517 nm. The DPPH radical scavenging rate (%) was calculated using the following Equation (1): A1 is the absorbance of the test group, A2 is the absorbance of the control group, and A0 is the absorbance of the blank group. All measurements were performed in triplicate.The DPPH free radical scavenging rate was determined by following the instructions of the DPPH free radical scavenging capacity kit (Nanjing Jiancheng Bioengineering Research Institute). First, we take one working solution powder, add 40 mL of pure ethanol, shake it well, and store it at 4 °C away from the light. Then, we weighed the precise amount of C. paliurus) have been added. All the elements were chopped with a chopping machine  and poured into 22 mm collagen casings with a sausage machine , tied at every 10 cm, and steamed in a fuming and boiling machine to maturity. The steam frankfurters were cooled to below 15 °C, then vacuum packed in a vacuum packaging machine , sterilized, and stored in a 4 °C refrigerated warehouse. Group C contained no antioxidants as a negative control. Group VC contained 0.025% sodium D-isoascorbate as a positive control. Groups T1, T2, T3, and T4 contained 0.06%, 0.12%, 0.18%, and 0.24% flavonoid extracts from C. paliurus as different treatments, respectively. All samples were evaluated on the 1st, 7th, 14th, and 21st days.To prepare the cooked meat product (frankfurters), pork hindquarter and pig back fat were purchased, the fascia was removed, separately ground in a meat grinder, and organized into six treatment groups . The composition of frankfurters is listed in g for 10 min at 4 °C with a centrifuge , the supernatant was taken and placed on ice until tested; ③ take a 1.5 mL centrifuge tube, accurately absorb 0.3 mL reagent 1 and 0.1 mL supernatant into the test tube, mix well, and water bath at 95 °C for 30 min; ④ placed the mixed liquid in the ice water for cooling down, and centrifuge at 10,000 g for 10 min; ⑤ 200 μL of the supernatant was put into a 96-well plate, and the absorbance was measured at 532 nm and 600 nm. An automatic biochemical analyzer detected the total protein concentration . Take an appropriate amount of supernatant and use the automatic biochemical analyzer to detect the total protein concentration of the sample . MDA content was calculated using the following Equation (2): A = A532-A600 and Cpr is the sample protein concentration (mg protein/mL). All measurements were performed in triplicate.Thiobarbituric acid reactive substances are one of the most intuitive indicators of lipid oxidation. The oxidative stability of the frankfurters was based on measurements of the malondialdehyde (MDA) concentration by a malondialdehyde detection kit . The content of MDA was determined following the steps of the detection kit manual: ① weigh 0.2 g of meat sample into a 5 mL centrifuge tube, add 2 mL of extract, and homogenized in an ice water bath; ② the homogenate was centrifuged at 8000 10 CFU·g−1. Escherichia coli was determined following the national food safety standard GB4789.2-2016 [Escherichia coli was inoculated on the respective nutrient medium and incubated at 37 °C for 24 h of frankfurters samples with different antioxidants on days 0, 7, 14, and 21. All measurements were performed in triplicate.The total viable counts (TVC) were determined per the national food safety standard GB4789.2-2016 using the aerobic plate counting method . Plates 9.2-2016 . EscheriA portable digital pH meter  was used to detect the pH of the frankfurters. Before measurements, a standard buffer solution  was used for a two-point calibration. The pH value was measured on the 1st, 7th, 14th, and 21st days. All measurements were performed in triplicate.L*, a*, and b* were recorded. The color difference was measured on the 1st, 7th, 14th, and 21st days. The previous study has indicated that a total color difference (ΔE) of approximately 1 is discriminable by consumers [L*, Δa*, Δb* were calculated by the difference between stored samples and 1st day samples. All measurements were performed in triplicate.The color difference is measured by a portable color difference meter with an 8 mm aperture and D65 light source . The colorimeter was calibrated with a standard whiteboard  before use, and the frankfurter was cut into columns 1 cm high and 22 mm in diameter. Each frankfurter was measured twice at the front and rear, and the values for onsumers . The totThe determination of texture was referred to the method of Zhou et al. for appropriate modification . We tookThe method of sensory reference method has been amended appropriately for our previous experiment . A panelSAS 9.4 software was used for statistical analysis of the collected data, and unidirectional ANOVA and multiple Duncan comparisons were used to test the significance of the differences. The results were presented as mean ± standard deviation.C. paliurus are a natural extract that has been proven to have certain antioxidant properties [C. paliurus, the more efficient the DPPH scavenging activity is. The DPPH scavenging ability of the extract was significantly increased (p < 0.05) and enhanced rapidly when the concentration increased from 0.06% to 0.12%, the growth rate of DPPH scavenging ability was slowed down when the concentration from 0.12% to 0.24% and with no difference between T3 and T4 (p > 0.05). Sodium D-isoascorbate has an excellent antioxidant effect and is widely used in meat products [C. paliurus was more effective at DPPH scavenging activity than 0.025% sodium D-isoascorbate.To investigate the effects and influence of different antioxidants on meat products, the DPPH scavenging activity of different antioxidants has been determined. The DPPH free radical scavenging rate can effectively show the total antioxidant activity in natural products . Flavonooperties . To deteproducts . DPPH haE could be reflected in the changes in the overall color of frankfurters during storage. L* exhibits the degree of lightness and represents the brightness intensity. a* exhibits the degree of redness and represents the redness intensity, and b* exhibits the degree of yellowness and represents the yellowness intensity. L*, a*, and b* of frankfurters on the 1st, 7th, 14th, and 21st days, and ΔE was calculated on the 7th, 14th, and 21st days of storage in various test groups. Over the storage period, ΔE was increased and then declined apart from the C group. On the 7th day, ΔE was more than 1 in groups C and T4 but lower than 1 in groups VC, T1, T2, and T3. The result showed that adding antioxidants delayed the color change of frankfurters in the early storage period. On the 14th day, ΔE was more than 1 in six groups, groups C and T4 with the lowest ΔE, followed by groups T2, VC, T3, and T1, which may be caused by fat oxidation and a dark brown color of extract. On the 21st day, ΔE showed a downward trend in five treatment groups. Over the storage period, L* increased initially and then declined apart from the T2 group. Compared to group T1, groups T2, T3, and T4 maintained low L*, possibly due to the enhanced water-holding capacity (WHC) of frankfurters, which reduces light reflection [L* of frankfurters. Meanwhile, fat oxidation also adversely affects meat color. Throughout the storage period, group VC consistently maintained the highest a* value, significantly different (p < 0.05) from other test groups except on day 1. The result indicated that adding sodium D-isoascorbate could better maintain the color stability of meat products than other test groups. Among groups T1, T2, T3, and T4, a* initially increased, then declined as the concentration of flavonoid extracts increased; group T2 has the highest a* value, indicating that flavone extract may have a significate contribution in color protection; however, this color protection did not show a trend of increasing with the concentration of flavonoid extracts. Except for group T4, the higher the extract concentration, the greater the b* value. The b* value for all treatment groups increased throughout the storage period. On the 1st day, b* of frankfurters showed a trend of increasing with the concentration of flavonoid extracts, due to the influence of extracts’ color. On the 14th day, the b* value of group T1 was lower than group C but gradually increased and eventually exceeded group C with the added extract concentration. Compared to other groups, excluding group VC, b* in group T1 was the lowest, possibly due to the higher antioxidant effect of the extracts. Flavonoid extracts inhibited fat and protein oxidation, maintaining the color stability of frankfurters [b* gradually decreased during the whole storage period [a* and higher b* in the test groups may be due to the yellow-brown color of the flavone extract affecting the color of the frankfurters.Color is one of the most important meat quality attributes when consumers are concerned . ΔE coulflection . Therefoflection . In addiflection . Phenolikfurters . Manzoore period . Neverthe period . The lowp > 0.05). The pH of the group VC samples was always the highest over the storage period, which was significantly higher (p < 0.05) than the other five test groups. On the first day, all treatment groups showed a higher pH than group C except group T4, which may be related to a higher concentration of polyphenols contained in the extract, which may be decreased the pH of frankfurters. Meanwhile, microbial fermentation will also reduce the pH due to the presence of microorganisms in group T4. Compared with the 1st day, the pH of the samples on the 7th day declined; the pH of the group VC samples was the highest, with an average value of 6.34. In addition, the pH of group C was significantly different from those samples from groups tested with flavone extract, except for group T1 (p < 0.05). On the 14th day, the pH of groups T1 and T4 samples was lower, averaging 6.25 and 6.24, respectively. On the 21st day, all treatment groups showed little change in pH compared with the 14th day except group T4. In addition, as storage time increased, the pH value of each test group gradually decreased and then increased except for group T4, which may be caused by the higher antioxidant effect of the extract led to higher oxidation stability of frankfurter samples and reducing the oxidation [C. paliurus had no significant (p > 0.05) effect on pH. Rapid reprocessing micro-organisms can increase pH during storage in the samples at the later stage field [xidation ,39. All ge field .p > 0.05), indicating that antioxidant supplementation had no significant impact on springiness or chewiness except for samples in group T4. There were significant differences in firmness between each test group after 7 days of storage, and group C always had the highest firmness during storage time. The previous study showed that phenolic compounds extracted from plants could reduce the firmness of cooked meat products during cold storage. This allows the meat to obtain better emulsion stability through the antioxidant effects of the plant extracts on the lipids and proteins [Textural analysis was performed throughout the storage period to determine whether the addition of flavonoid extracts affected the frankfurters’ final firmness, springiness, and chewiness. The result is presented in proteins . Furtherproteins ,41. Our p < 0.05). On the 7th day of storage, MDA content in group C was drastically increased and considerably higher than the other four test groups with different concentrations of C. paliurus extracts (p < 0.05). Compared to other treatment groups, groups T3 and T4 always have the lower MDA content, which showed that the higher concentration of flavonoid extracts, the more effective the antioxidant activity of meat products. On the other hand, MDA content also increased in all the test groups with different concentrations of flavonoid extracts during the process, which is consistent with the results from the Zhang et al. study [MDA analysis was performed throughout the whole storage to determine whether adding flavonoid extracts impacts lipid oxidation during the storage period. The result is presented in l. study . This cal. study . Our resEscherichia coli (E. coli.) was not observed in the analyzed samples during the entire testing period, indicating no secondary contamination of E. coli during the experiment. The total number of colonies  increased over time while in storage in all treatment groups. Some colonies were detected in groups T3 and T4 on the first day may be caused by incomplete sterilization. On the 7th and 14th day, no colonies were detected in group VC; group C had the highest mean values for TVC, the values of TVC in groups T3 and T4 were significantly higher than in groups T1 and T2 (p < 0.05), might be caused by the initial colonies. In contrast, although the total number of initial colonies in groups T3 and T4 were higher, the trend of TVC values increase was slower than in group T1 and T2 in the storage period, suggesting that the higher concentration of extracts, the better antimicrobial ability. The growth rate of TVC values in the treatment groups with the addition of extracts and antioxidants was slower than that in group C, indicating that the antioxidant and flavonoid extract from C. paliurus had specific antibacterial activity [C. paliurus can be used as natural antibacterial agents in meat products.The microbiological test was performed on all samples on the 1st, 7th, 14th, and 21st days. The result is presented in activity . It can The sensory quality of the product is one of the most important considerations for consumers. Adding additives may change the flavor, color, and taste of products, affecting customer satisfaction. Frankfurters were evaluated on days 1, 7, 14, and 21 of storage . The objC. paliurus affect the overall quality, fat oxidation, TVC, and sensory of vacuum-packed cooked meat products (Frankfurters) over 21 days of storage. The DPPH scavenging activity showed that flavonoid extracts were an effective antioxidant, and the greater the concentration, the greater the antioxidant capacity. Compared to the negative control group C, the four different extract concentrations can significantly reduce the MDA concentration in samples (p < 0.05). The antioxidant effect of the low-concentration extract (0.06% and 0.12%) is equivalent to sodium D-isoascorbate. In comparison, the antioxidant effect of the high-concentration extract (0.18% and 0.24%) is significantly higher than that of sodium D-isoascorbate, indicating that the antioxidant capacity of flavonoid extracts is related to the concentration. The flavonoid extracts from C. paliurus had a certain antibacterial effect, and the higher concentration of extracts, the better the antimicrobial ability. Adding flavonoid extracts help to improve the tenderness of frankfurters during storage. When extracts were added, no harmful effects were observed on the quality and pH value. In the sensory evaluation towards the storage period, samples with low extract concentration had better color and appearance parameters scores. Samples with flavonoid extracts at concentrations of 0.18% and 0.24% had lower color and sensory evaluation scores, which might be caused by the yellow-brown color of the extract itself. The findings conclude that the low concentration (0.12%) of flavonoid extracts from C. paliurus in meat products could effectively inhibit lipid oxidation without affecting sensory quality.Our study observed how different concentrations of flavonoid extracts from


The re-identification of animals can distinguish different individuals and is regarded as the premise of modern animal protection and management. The re-identification of wild animals can be inferred and judged by the difference in their coat colors and facial features. Due to the limitation of long-distance feature extraction, CNN  is not conducive to mining the relationships among local features. Therefore, this paper proposes a transformer network structure with a cross-attention block (CAB) and local awareness (CATLA transformer) for the re-identification of wild animals. We replace the self-attention module of the LA transformer with CAB to better capture the global information of the animal body and the differences in facial features, or local fur colors and textures. According to the distribution of animal body parts of the animal standing posture, we redesigned the layer structure of the local aware network to fuse the local and global features.The wildlife re-identification recognition methods based on the camera trap were used to identify different individuals of the same species using the fur, stripes, facial features and other features of the animal body surfaces in the images, which is an important way to count the individual number of a species. Re-identification of wild animals can provide solid technical support for the in-depth study of the number of individuals and living conditions of rare wild animals, as well as provide accurate and timely data support for population ecology and conservation biology research. However, due to the difficulty of recording the shy wild animals and distinguishing the similar fur of different individuals, only a few papers have focused on the re-identification recognition of wild animals. In order to fill this gap, we improved the locally aware transformer (LA transformer) network structure for the re-identification recognition of wild terrestrial animals. First of all, at the stage of feature extraction, we replaced the self-attention module of the LA transformer with a cross-attention block (CAB) in order to calculate the inner-patch attention and cross-patch attention, so that we could efficiently capture the global information of the animal body’s surface and local feature differences of fur, colors, textures, or faces. Then, the locally aware network of the LA transformer was used to fuse the local and global features. Finally, the classification layer of the network realized wildlife individual recognition. In order to evaluate the performance of the model, we tested it on a dataset of Amur tiger torsos and the face datasets of six different species, including lions, golden monkeys, meerkats, red pandas, tigers, and chimpanzees. The experimental results showed that our wildlife re-identification model has good generalization ability and is superior to the existing methods in mAP (mean average precision), and obtained comparable results in the metrics Rank 1 and Rank 5. The Convention on Biological Diversity [With human society’s industrial and agricultural development, wild animals and plants have gradually lost their living spaces. iversity  was propiversity , global In order to change the living status of animal species, we need to know their populations, distributions and behavior. The re-identification of animals can distinguish different individuals and is regarded as the premise of modern animal protection and management. Meanwhile, for animals in the zoo, re-identification can help staff to establish their archives and analyze their growth and breeding behaviors, in order to reasonably plan their daily lives. For animals in the wild, individual identification can assist researchers in knowing their health status, and studying their lifestyle and distribution, which provides a factual basis for making appropriate protection measures. Re-identification methods have been used to assess animal population size and density. For example, Shannon Gowans  recordedOver the years, camera traps  have beeIn the early years, Meek et al.  once invWith the wide application of deep learning technology in the field of image processing ,12,13, rIn order to better extract and fuse global and local information on wildlife, we first applied the transformer network structure to the re-identification of wildlife and proposed a transformer network based on a cross-attention mechanism for the re-identification of wild terrestrial animals;After partitioning the whole image into patches, in order to extract the local features of the patches and the global correlation between patches, we replaced the self-attention module of the LA transformer with CAB, which captures the global information of the animal appearance and the differences in local features, such as local fur colors and textures;At the stage of the feature fusion, the hierarchical structure of the locally aware network was redesigned according to the distribution of animal body parts in the standing posture. After fusing the weighted-average values of global and local tokens, we obtained the globally enhanced local tokens where the fused features were arranged into 7 × 28 2D distribution;To validate the generalization ability of the model, we tested different types of datasets, such as the animal trunk dataset and the animal face datasets including those of tigers, lions, golden monkeys, and other common species.Due to the limitations of long-distance feature extraction, a CNN is not conducive to mining the relationships among local features. In addition, due to the shy characteristics of wild animals and the complex field environment, it is difficult to capture whole bodies of animals from multiple angles, which also poses a challenge to the re-identification of wild animals. Transformer, as an emerging deep learning structure, can utilize multi-head self-attention to capture long-distance relationships and pay attention to local features, so it has already shone in the field of human re-identification ,23,24. HIn this section, we mainly introduce the datasets in the experiments, and the division of the training set and the testing set, then we give the pipeline of the wildlife recognition network.In order to verify the performance of our proposed model from different perspectives, we chose three public datasets that are widely used for animal re-identification. These datasets include animal trunk and face images, RGB, and gray images.The dataset ATRW  was firsThe details of the datasets are shown in As shown in P is the size of the image patch; N is the number of image blocks, which is added with the position information and input into the transformer encoder module. The cross-attention block in the transformer encoder module combines the inner-patch attention with the cross-patch attention. It cannot only capture the local differences in animal fur or facial features, but also obtain global information on animal body appearance. The multilayer perceptron block [on block  fuses thCross-attention blocks (CAB)  are the As shown in IPSA and CPSA build cross-attention by stacking basic modules. The stacking mode is shown in We calculated the weighted average of local features and global features based on the locally aware network  and thene animal .Compared with the human body, the movement of animal body parts is relatively simple. Therefore, we redesigned the layer structure of the locally aware network to reduce the intra-layer difference and broaden the inter-layer difference. After the weighted-average fusion of global and local tokens, the fused feature elements were arranged into 7 × 28 2D distributions, and the number of layers was reduced.The program used in this study was written in Pytorch and trained on a computer configured with an Intel i7-11800H CPU and NVIDIA GeForce RTX 3060 GPU. The numbers of images in the training subset and the testing subset are shown in Re-identification is generally evaluated by two metrics, cumulative matching features (CMC) and mean average precision (mAP). When calculating the evaluation index, it is necessary to divide the test set into the Query image set and the Gallery image set. The re-ID methods select an image in the Query image set and retrieve the images of the same individual from the Gallery images.We utilized CMC and mAP to evaluate our experimental results. Rank 1 and Rank 5 are often used for two standards of CMC. Take Rank 1 as an example for the explanation of CMC. Given an animal image, we compare the similarity of the Query image and the images in the Gallery image sets and rank the Gallery images according to their similarity. A function is defined to judge whether the two images (Then, when calculating Rank 1, it is only necessary to count whether all Query pictures are the same as their first returned results.We replaced the original VIT attention module with the CAB to form a new transformer model. The CAB pays more attention to the differences in animal fur patterns and facial features. Since our model can re-identify the body appearances of animals, it is not limited to re-identification based on animal faces. The model proposed by Yu et al.  is basedThe layer number of the local aware network directly affects the feature extraction performance of the model. More layers mean fewer differences between features, which will reduce the classification accuracy of the model. As shown in The datasets mainly included four categories of images: body appearance, color face, gray face, and complex face datasets. Since existing studies have conducted experiments on these datasets, in order to fairly evaluate our model from multiple perspectives, we chose the state-of-the-art models corresponding to each type of dataset for the comparison: the Yu et al. model for the ATRW dataset; the Tri-AI model for color face and gray face datasets; and PrimNet  for C-ZoAs the testing set for the ATRW dataset was not yet released, Yu et al. also used the images in the training set for experiments, which were consistent with ours. Rank 1, Rank 5, and mAP are widely recognized as the standard evaluation metrics in the existing literature. We also used Rank1, Rank5, and mAP for the ATRW dataset, and mAP and Rank 1 for the Tri-AI dataset and the PrimNet dataset, respectively. The metrics and the proportions of the training set and testing set were consistent with these models’ original studies. The experimental results are shown in As shown in Through the experiments on the above datasets, we proved that our network has good generalization ability and can be well applied to various re-identification tasks with wild terrestrial animals. The reason for this is that our model extracts the local features of small image patches and uses the cross-attention module to calculate the correlation characteristics between patches in order to construct the global information. For some wild animal species, their fur patterns and facial features have distinctive differences, so the prediction results are satisfactory. However, the faces of different chimpanzee individuals are almost the same except for their lips and ears, which increases the difficulty in identifying different individuals.With the invasion of human society to nature, the living space of wild animals is gradually decreasing. To help understand the living conditions of wild animals, we designed a novel transformer-based re-identification method for wild terrestrial animals which incorporates the cross-attention mechanism and the locally aware transformer. In addition, we fine-tuned the hierarchical structure of the locally aware network to accommodate wildlife body structures. We evaluated the model on various datasets. The experimental results showed that our model had superior performance in identifying animal individuals than the existing state-of-the-art methods, even for challenging datasets.In general, the performance of wildlife re-identification using the proposed methods significantly improved. However, not all animals’ coats have stripes or spots, which greatly increases the difficulty of animal re-identification recognition. Similar to other existing methods, our model also suffered from the problem of being unable to extract subtle differences in the faces of species with a solid fur color and similar faces, such as chimpanzees. In addition, due to the occlusion of wild vegetation, the camera only can capture a part of the animal’s body. The images can also be blurred by the influence of noise and bad weather such as strong winds, heavy fog and rain. Therefore, more in-depth research is needed for animal re-identification recognition.In future research, we will try to use counterfactual attention learning  to learn


Parkinson’s disease (PD) is increasingly being studied using science-intensive methods due to economic, medical, rehabilitation and social reasons. Wearable sensors and Internet of Things-enabled technologies look promising for monitoring motor activity and gait in PD patients. In this study, we sought to evaluate gait characteristics by analyzing the accelerometer signal received from a smartphone attached to the head during an extended TUG test, before and after single and repeated sessions of terrestrial microgravity modeled with the condition of “dry” immersion (DI) in five subjects with PD. The accelerometer signal from IMU during walking phases of the TUG test allowed for the recognition and characterization of up to 35 steps. In some patients with PD, unusually long steps have been identified, which could potentially have diagnostic value. It was found that after one DI session, stepping did not change, though in one subject it significantly improved . After a course of DI sessions, some characteristics of the TUG test improved significantly. In conclusion, the use of accelerometer signals received from a smartphone IMU looks promising for the creation of an IoT-enabled system to monitor gait in subjects with PD. Parkinson’s disease (PD) is very suitable for the application science-intensive instrumental research methods. PD is gradually becoming a kind of “model disease” for the testing of new technologies for PD diagnostics and escorting PD subjects . For sevEarlier, we have shown that in subjects with PD that both single session of Earth-based microgravity—modeled with “dry” immersion conditions (DI) —and a prThe Timed Up-and-Go (TUG) test has proven to be reliable in many domains of neuromuscular and orthopedic pathology for assessing gait, basic mobility skill, strength, agility and balance . It consThroughout the last decade, instrumented versions of the TUG test (iTUG) were increasingly invented. In most of these versions, varied numbers and positions of miscellaneous inertial measurement unit (IMU)-based wearable sensors (accelerometers) were used to discriminate between the phases of the TUG test ,16. The There is a multitude of technological approaches for studying PD. Among them are optical motion trackers, biopotential devices, audio and video recording, and, especially, wearable sensors, such as smart glasses, hats, insole sensors of ground-reaction force and smartphones . PreviouAccording to the review by Deb et al. , wearablSmartphones are equipped with IMUs that consist of a 3-axis accelerometer, a 3-axis gyroscope and a digital magnetometer that is comparable in sensitivity to research-grade biomechanical instrumentation . In the The major hypothesis of the present study was that gait characteristics in patients with PD are responsive to the conditions of either one session of DI or a course of repeated DI sessions. To address this, we obtained up-sampled acceleration signals from smartphone-based 100 Hz IMU sensors attached to the subject’s head during a 13 m TUG test before and after single session of DI and a program of seven DI sessions.Altogether, data from six PD subjects was collected in the study. Six subjects with PD participated in the study after providing their informed consent. Their anthropometric and clinical data and the medication they use is presented in 3 of fresh, thermally comfortable water stabilized at T = 32 °C. The water in the tub was periodically filtrated and aerated to prevent bacterial contamination. The water surface was covered with a large, square waterproof film (3 × 4 m2), which was wrapped around the subject’s body. The DI session was conducted at 9:30 AM, in the condition of “on-medication” in order to synchronize the effects of DI and the anti-PD therapy. The subjects usually took their medicines 2 h before the study, at 7:30 AM. Before DI, subjects were instructed to drink 200 mL of water and urinate due to the strong diuretic effect of DI [The on-Earth microgravity was modeled using the conditions of a “dry” immersion (DI). This method of DI has already been presented in detail in our earlier papers ,8,9,10. ct of DI . Before The program of DI consisted of seven 45 min DI sessions that were conducted twice a week for 25–30 days. The total DI dose during the course was 5¼ h.The TUG test was performed in its extended form . Still, its phases were all the same: (1) standing up from a 46 cm highchair (Sit-to-Stand phase), (2) walk straight , (3) turning by 180° (U-turn), (4) walking back , and (5) sitting down (Stand-to-Sit transition with a turn). In addition, unlike the classic 3 m version, the 13 m version of the TUG test allowed for an analysis of the subject’s steps (gait)—because subjects performed up to 20 steps in one direction, which is sufficient for analyzing gait . The TUGDuring the TUG test, the acceleration and rotation rate were measured with the sensor module in the smartphone Xiaomi Mi4 . The obtained signals were further processed offline. x-, y- and z- components of the acceleration vector due to the inclination as well as the presence of linear accelerations while standing up and sitting down. For the gyroscope in a motionless state, the signal includes the sensor noise as well as the head tremor; however, it is characterized by the constancy of the mean value (measurement offset). The start and end points of the TUG test were selected manually by analyzing the change in the mean value due to the rotation of the head and body during inclination while standing up and sitting down.The subject was instructed to sit still and look forward before and after the test. In a motionless state, the shape of the accelerometer signal is formed by the current projections of the gravity vector, measurement noise and the existing zero-G offsets, as well as the head tremor. The beginning and end of the movement are characterized by a change in the The internal phases of the TUG test and step moments were determined automatically. For steps in a straight-line walk (15–17 more or less uniform steps in the middle of both the Gait-Go and Gait-Come phases), a set of gait features was calculated. Altogether, subjects performed 35–40 steps in both directions, of which 30–35 steps that were in the middle of the walk were analyzed. The sampling rate of the inertial sensors—both the accelerometer and gyroscope—of the Xiaomi Mi4 smartphone that was used in the present study was 100 Hz (the period between data samples was Δt = 10 ms), which can be regarded as neither reliably accurate nor fast. The smartphone was fixed on the back of the head of a subject with an elastic band and, additionally, a tight-knitted hat; subjects felt comfortable with this kind of fixation and the smartphone never fell out of its position. Values for the acceleration and angular velocity were collected as a time-stamped data stream. Thus, the measurements were accompanied by timestamps from the smartphone’s operating system timer. For further analysis, the accelerometer and gyroscope measurements with a time-stamp difference of less than 5 ms  were considered synchronous. In order to increase the time resolution and achieve a smoother distribution, the time series data were up-sampled to a 10-fold-higher frequency of 1 kHz (Δt’ = 1 ms) . In addi(1)x);forward Fourier transform of original signal X = F((2)x) up to new length F(y);zero-padding F((3)y) to obtain up-sampled signal y;inverse Fourier transform of F((4)y to preserve amplitudes.scaling up-sampled signal Since the analyzed signal tended to be periodic, the up-sampling, which used Fast Fourier Transform, could be applied. Furthermore, as long as the measurement signals are real-valued, the real (single-sided) FFT is suitable for conversion into the frequency domain. In the frequency domain, up-sampling means there is zero-padding at the end of the high frequency components of the signal. The up-sampling procedure included the following steps:−4 m/s2 for the x-, y- and z-axis of the accelerometer, and  × 10−5 deg/s for the gyroscope. Since the test duration is less than 1 min, the bias drifts can be neglected.A simple calibration of the zero offsets of the sensors was performed before the start of the test. To do this, we used the measurements obtained from a smartphone placed on a horizontal surface. It was noted that the sensor offsets were probably pre-calibrated by the Android OS. The bias instability and velocity/angle random walk for smartphone sensors was previously analyzed by us using the Allan variation . The biaThe orientation of the smartphone was calculated using a well-known complementary filter proposed by Robert Mahony et al.  and is eAutomatic detection of a turn was conducted by analyzing the projection of the angular velocity on the vertical axis. No additional filtering of measurements was performed. If the values of the amplitude and duration of the rotation rate exceeded certain threshold values, a rotation was considered to be detected (recorded). At the first stage, a comparison was made with the threshold value of the rotation rate (10 degrees per second). At the second stage, the rotation duration was estimated. Rotations lasting less than 1 s were discarded. If three or more turns were detected in the TUG test, the two longest turns were considered the 1st (at the U-turn phase) and 2nd (prior to sitting down on a chair) turn. According to the available experimental data, this algorithm was successful in 100% of cases for both turn events.2 were taken as the approximate time-stamp of the initial contact of the foot with the ground (T’ point).Step detection was automatically performed by analyzing the time series of the acceleration vector. Since the typical cadence of stepping is about two steps per second, the measurements were filtered with a forward–backward zero-phase low-pass filter  with a cut-off frequency of 3 Hz, which allowed us to obtain the LPF time series data. After that, peak values of the filtered signal were detected. Moments where the acceleration magnitude reached 11 m/sthe first peak corresponding to the moment of standing up and the second peak corresponding to the moment of the first step;steps during the first U-turn;steps from the moment of the second turn until the end of the whole test.For each step, the revised time-stamp T_step of the heel strike and the corresponding maximum acceleration along the vertical axis were determined by searching for the maximum value in the ±40 ms window near the T’ point. Not all steps taken during the TUG test were taken into account for gait analysis. The following local maxima that were obtained during the step detection procedure were discarded:To estimate the duration of the entire TUG20 test and its phases, the following parameters were determined :D1 (The entire TUG test duration): the time from the very beginning of motion (the Sit-to-Stand movement) until the end of the test (sitting down on a chair).D2 : the time from the start of the lifting to the moment of the heel strike on the second step.D3 : the time to perform a 180° turn at the far turning point.D4 : the time from the beginning of the second turn until the end of the test.For the analysis of gait stability, only straight-line, uniform steps were taken into account see . The folstep moments). Before calculating the average value, two points with the largest deviation from the median value of step duration were discarded : the duration of the step (dt) was determined as the difference between consecutive time-stamps of successive steps  see .To calculate the cadence mean and standard deviation, the “instantaneous walking pace” was first estimated for each step (cadence = 60/dt); then two outliers should be discarded. Usually, these outliers were characteristic of the “transitional” moments during the TUG test . S3 .S4 .S5 The ratio of the average deviation of the two largest outliers of the step duration to the standard deviation of the step duration without taking into account the two largest outliers ;For each outlier, calculate the absolute difference from DWO_STD as the standard deviation of the step durations without outliers;Calculate DOUT/DWO_STD.Calculate LS = DS5 was calculated according to the following algorithm:The estimates of the probability density functions of the step duration and the acceleration upper/lower peaks were obtained using kernel density estimation (KDE). KDE was computed using the Python scipy.stats.gaussian_kde function . As P1, P2 and S2 values are related to the width of the target variables’ distributions, they are shown as the full width at half maximum. On the left panel, the red dots denote minimal acceleration when both feet were touching the floor, and the green dots denote heel strike. The open red and green circles represent these dots. Two outlier values are denoted with black crosses. On the right panel, the open black circles represent the individual step duration along the time course. The outlier values, denoted by red crosses (>0.7 s), represent unexpectedly longer steps right prior to U-turn. Furthermore, note that during the Gait-Come phase (upper group of open black circles), the length of the steps decreased roughly from 0.68 m to 0.6 m. For more information, see the text below; these data were obtained from Subject 6.To analyze the power (amplitude) characteristics of each step, the following parameters were estimated:2): the standard deviation of the vertical acceleration in Tstep moments. Two outliers were discarded. P1 characterizes the stability (uniformity) of the heel strike during stepping in the Gait-Go and Gait-Come phases : standard deviation of the vertical acceleration minima that corresponds to the weight transfer phase. Two outliers were discarded. P2 characterizes the stability (uniformity) of the minima values when both feet made contact with the floor during the swing phase of stepping during the Gait-Go and Gait-Come phases : the average difference between the minimum and maximum of the vertical accelerations in a series of straight steps.P3 . The values of D1–4, S1–5 and P1–3 were compared in the pairs of conditions “before-after a single DI session” and “before-after a course of DI sessions” with the non-parametric paired Wilcoxon 2, P2 increased (swing phase) from 0.50 to 0.82 m/s2, and P3 increased from 8–9 to 10–11 m/s2  DI session ; however–11 m/s2 , which p–11 m/s2 . In addi–11 m/s2 . The indUnlike with a single DI session, a course of DI sessions exerted a significant influence on a few gait parameters, namely, D4 and S5 see, , which mThe purpose of this study was (1) to test the reliability of an assessment of stepping characteristics with an up-sampled IMU-based accelerometer signal and gyroscope of a smartphone when placed on the subject’s head, and (2) with the help of the acceleration signal, to study the effect of a single DI session and a program of DI sessions on stepping in subjects with PD during a long version of the TUG test.There are plenty of studies that have demonstrated sufficient reliability of iTUG test technologies based on a smartphone’s IMU to recognize the phases of the TUG test ,30,31,32Instead, in the present study, we focused on (1) the gait analysis during the Gait-Go and Gait-Come phases with the help of (2) the extended 13 m TUG test, and (3) with a smartphone fixed to the head. It has been found that the 13 m TUG test returns information about 16–21 steps in each direction , of which 15–17 steps in the middle of the Gait-Go and Gait-Come phases of the TUG test were considered to be functionally uniform . This number of steps is reliable, as data collected from 10–20 strides (20 steps) were reported to be sufficient for the reliable characterization of the gait speed and cadence of stepping [From a technical point of view, the obtained parameters and graphical presentation of the TUG test can be regarded as reliable and demonstrative, as it allows for the tracing of individual features of the subject’s gait and the recognition of graphical patterns of the subjects by eye. Furthermore, the position of the smartphone on the head can be regarded as a reliable site for the collection of information about a human’s gait. This allows for a reduction in the number of IMUs to one that is placed on the head.2, and P3  increased by 2–3 m/s2. As a whole, these changes suggest that after a single DI session, Subject 1 walked faster, performed faster turns and stepped more firmly on the floor. All these modifications can be regarded as positive. In Subjects 2 and 3, the effect of DI conditions was negligible, probably due to the relatively good initial values of their gait parameters, for example, in Subject 3, their cadence was 145 steps/min—in comparison to 90–112 steps/min in Subjects 1 and 2. In addition, Subject 1 did not take anti-PD medicine, which means that before the DI session he stood in the “off-medication” condition. As a result, the effect of DI was not inferred by anti-PD therapy.We found that a single (“acute”) 45 min DI session exerted no effect on the studied parameters of gait across the entire group of subjects with PD, which is opposite to our original hypothesis. On the other hand, in each subject, an individual set of gait characteristics still changed. For example, in Subject 1 see , the entThe effect of a program of seven DI sessions was a bit more pronounced. At a minimum, the D4 and S5 parameters became significantly larger after a course of DI, and a change in P2 values resulted in an increase after a program of DI. The reaction to DI conditions was individually significant. Again, Subject 1 presented the most notable improvement in D1 , and almost in all other parameters. Subjects 2, 4 and 5 demonstrated moderate improvement of only some parameters, and Subject 3 demonstrated a notable improvement of gait.The Internet of Things (IoT) is comprised of interconnected devices, machines, and servers with data storage that functioning through a network ,37. A smA smartphone is always “at hand” (in the pocket), it is not heavy or cost-effective, and it is already pre-set for data transfer to cloud-based storage . SmartphData collected on the gait of PD subjects with wearable accelerometers is suitable for Artificial Intelligence (AI) or IoT decisional support ,41. AI-bThe TUG20 test accelerometer signals have a repetitive structure and contain gait features. Furthermore, there are two ways that the methods of AI could be applied. First, it can be used to collect a database of signals and split this database into two parts: the training and test sets. To increase the adequacy of the model, this approach might be applied after investigation of more than 100 PD cases, which is difficult in real life. The second way is to investigate the gait features and to understand what features are significant, i.e., to exclude insignificant features and thus decrease the dimension of the model, and then apply these data to clustering. This approach requires less studied cases, and we would prefer to follow it in the future. The major limitation of this study was the insufficient number of study subjects and measurements, which did not allow for a more precise analysis of data to be conducted. Furthermore, control groups  were not formed. In future studies, we propose that more measurements should be conducted in control groups and subjects with PD, both under “dry” immersion conditions and non-DI conditions.In conclusion, the data from smartphone-based IMU accelerometers allowed us to compute gait characteristics that are conventionally used in the field of locomotion physiology, such as step duration and cadence. Like other IMU-based analyzing systems, the presented method allowed for the recognition of the phases of the TUG test. The application of an extended version of the TUG test provided a sufficient number of steps to characterize gait, and it allowed for the visualization of the duration of individual steps during the process of locomotion. Furthermore, the presented method appears to be suitable for a fast visual evaluation of stepping patterns in PD subjects. Of note, some of the specific characteristics of Parkinsonism events were recognized with the IMU sensors—for example, unusually long steps, which were produced while walking. For the entire group, the conditions of a single 45 min “dry” immersion affected none of the studied gait parameters derived with the help of smartphone-based IMU sensors; however, in one subject there was a clear increase in cadence, gait and turning speed. After a course of repeated DI sessions, some characteristics of the TUG test were improved; however, gait speed did not significantly change. The presented method of gait analysis appears to be suitable for further instrumentation because a smartphone is perfectly suited for association in IoT-based networks.


Poly(dodecano-12-lactam)  is one of the most resourceful materials used in the selective laser sintering (SLS) process due to its chemical and physical properties. The present work examined the influence of two SLS parameters, namely, laser power and hatch orientation, on the tensile, structural, thermal, and morphological properties of the fabricated PA12 parts. The main objective was to evaluate the suitable laser power and hatching orientation with respect to obtaining better final properties. PA12 powders and SLS-printed parts were assessed through their particle size distributions, X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), a scanning electron microscope (SEM), and their tensile properties. The results showed that the significant impact of the laser power while hatching is almost unnoticeable when using a high laser power. A more significant condition of the mechanical properties is the uniformity of the powder bed temperature. Optimum factor levels were achieved at 95% laser power and parallel/perpendicular hatching. Parts produced with the optimized SLS parameters were then subjected to an annealing treatment to induce a relaxation of the residual stress and to enhance the crystallinity. The results showed that annealing the SLS parts at 170 °C for 6 h significantly improved the thermal, structural, and tensile properties of 3D-printed PA12 parts. Additive manufacturing (AM), also known as 3D printing or direct digital manufacturing, has become an alternative technology that competes with more mature technologies such as casting and forging in different industrial fields including aerospace, automotive, and biomedical fields ,2,3,4. Ic) and melting temperature (Tm). Therefore, printing at a temperature slightly below Tm enables the densification of the SLS powder without reaching its melting point, thus limiting the parts’ distortion. Moreover, by maintaining the temperature above Tc, the sintered structure remains in an amorphous phase to prevent rapid crystallization, making the powder material more suitable for the production of the final part. Therefore, the parts need to be maintained within the processing window during the build process and slowly cooled down to room temperature to avoid any deformation and crack formation [SLS polymers are selected based on the presence of a super-cooling processing window in which there is a large space between the crystallization temperature , ,22 PolyaSLS is a complex process that usually requires great effort and control in terms of powder and post processing after fabrication to achieve successful printing and high-quality parts. During the SLS process, the material should be kept at an elevated temperature in the build chamber to avoid any deformation of the printouts. The laser provides the necessary energy to exceed the sintering point, making it possible to form the part with the desired geometry . For SLSOn the other hand, powder spreading is a crucial step of the SLS process. Controlling the powder quality on the bed affects the quality of the tested parts. The powder should have a good flowability in order to enable the consistent deposition of thin dense layers of powder. Decreasing the porosity content will increase the mechanical properties. The layer thickness of the SLS process is typically between 100–150 μm. Smooth particles with a high sphericity are thus preferable to obtain parts with a desirable microstructure after sintering ,39 and aHofland et al.  studied The present work aims to analyze the impact of the hatch orientation and laser power on the mechanical, microstructural, and morphological properties of 3D-printed PA12 parts. The effect of the heat treatment on the mechanical properties will also be evaluated and compared to the as-built samples2 laser. In this study, a Polyamide 12 (PA12) powder (Precimid1171™) from TPM3D with a density of 0.95 g/cm3 was used, as it is one of the most widely used materials due to its chemical and physical properties. The chemical structure of PA12 (PA 2200) is shown in All samples were printed on a P3200HT SLS system from TPM3D (Stratasys company) equipped with a 60W COThe software ‘’VisCAM RP’’ was used to prepare the build volume and slice models into individual layers before uploading the data to the SLS machine. The main printing parameters used to produce PA12 powder samples are shown in As shown in A dynamic image analysis measurement was performed to characterize both the size distribution and particle shape of the PA12 powder used. This analysis was performed using a Camsizer XT equipped with two digital cameras, including one optimized for the analysis of fine particles. Such a setup enables measurement of particles ranging between 2 µm and 8 mm in diameter.Two PA12 powders were analyzed for comparison: one was the as-received powder, while the second was the un-sintered powder taken from the build volume after only one fabrication. The particle size distribution (PSD) of PA12 powder was identified as a function of percent volume. Furthermore, sphericity was chosen as a shape factor to describe the shape of particles of PA12 powder.−1; spectral resolution of 4 cm−1.Fourier Transform Infrared spectroscopy (FTIR) was used in this work to analyze functional groups of SLS PA12 samples and collect infrared spectra for the structural analysis. This analysis was carried out using a NICOLET™ IS50 attenuated total reflection (ATR) spectrometer. The conditions of measurement were as follows: spectral region of 4000–400 cmc, was calculated using the equation bellow:−1 [Differential scanning calorimetry (DSC) is a common tool used for characterizing materials for laser sintering because it determines the crystallinity and quantifies the melting temperature of printed parts. This analysis was carried out on a 6.6 ± 0.1 mg powder sample using a TA Instruments DSC Q20. The measurements were carried out under a nitrogen atmosphere at a flow rate of 50 mL/min. The crystallinity, X.3 J.g−1 .−1 from room temperature to the annealing temperature Ta ;Heating ramp of 2 °C minHold at Ta during the annealing time ta (6 h);−1 from Ta to the room temperature (25 °C);Cooling ramp of 2 °C min−1 to 220 °C for characterization.Heating ramp of 10 °C minThe annealing process was performed as follows:a, sample parts were placed directly in a natural convection oven  for annealing before mechanical testing.After determination of the appropriate annealing temperature T−1.XRD is a powerful tool used to analyze the atomic or molecular structure of materials. XRD was used here to identify the phase constituent of SLS PA12 powder and samples. Examination of powder and 3D-printed samples was carried out at different laser powers using a XRD X’PERT PRO MPD. Data were acquired over the range of (2θ) 0–90° with a step size of 0.0017 and a scan rate of 7°. min−1 was used.A tensile test was used to establish tensile properties of 3D-printed SLS-PA12 specimens, including tensile strength, Young’s modulus, and deformation at break. The specimens used were designed according to the ASTM D638-14 “Standard Test Method for tensile properties of plastics”. Three runs were conducted in series to study different laser power and different build orientation as well. Each series comprised six specimens of the D638 type-5 geometry as shown in The information obtained by the software were used to enable the calculation of tensile strength, Young’s Modulus, and deformation at break, using the following equations:Microstructure of both powder and fracture surface was evaluated by scanning electron microscopy (SEM) using a Quanta 200 ESEM  configured with an EDAX (TSL) EDS/EBSD system for phase identification at high pressures. As-received PA12 powder, used-once SLS powder, and 3D-printed samples cryogenically fractured in liquid nitrogen were coated with a thin layer of electrically conducting gold (Au) to prevent surface charging. Layer arrangement and powder morphology were observed at an acceleration voltage of 5 kV in high-vacuum mode.The particle size distribution (PSD) has a significant impact on the quality of SLS powder, with an ideal diameter between 20 and 80 µm. However, a large number of small diameter particles gives the powder a sticky character that limits its application in the SLS process . HoweverThis particle size decrease was confirmed through a comparison of the percentile values  for both powders , where aThe ATR-FTIR spectra of the PA12 samples were recorded to provide information about the infrared bands and their roles. 1 chains. Therefore, PA12 can be crystalized within structures of α and γ phases, where the major γ phase acts as a stable structure [The X-ray diffraction patterns of both PA12 powders are shown in tructure . The chatructure .The patterns relative to the powder after fabrication are almost similar to the patterns for the as-received powder, which confirms the possibility of re-using the powder for SLS after a suitable recycling process.g) phase where the polymer changes to a highly elastic state [m), corresponds to the endothermic peak detected at 182 °C. During cooling, a third transition, observed at 151 °C, is attributed to the crystallization (Tc) of PA12, where a rearrangement of the molecular chains takes place to create crystalline lamellae inside the continuous amorphous structure. These results show that both types of PA12 powder are in a semi-crystalline state after the cooling process. As shown in c) must also be avoided as long as possible during processing.The DSC technique was applied to study the glass transition temperature, melting temperature range, and the degree of crystallinity of the PA12 material. ic state . The sec−1 and 48.49 J. g−1 have been measured. After melting, the as-received powder and the powder after fabrication re-solidify with peak crystallization temperatures of 151.9 °C and 149.1 °C, respectively. The solidification  temperature is significantly lower than the crystalline melting temperature of PA12; this phenomenon is common in crystalline polymers and is known as super cooling [The melting point for the as-received powder is 182.7 °C and is 183.3 °C for the powder after fabrication. The respective fusion heat values of 55.62 J. gThe tensile properties were evaluated at different levels of laser power and hatch orientations and the results are presented in While the effects of laser power on TS are obvious, those linked to hatch orientation are less evident. Such an isolation requires a comparison between the 0° and 90° TS values first, followed by the 45° and 90° TS values. As mentioned previously, the parts made at 0° and 90° XY plane orientation have a nearly identical hatching. This should result in similar TS values as no other SLS parameters differ, something not observed here. Parts made at 90° XY plane orientation exhibit TS values 2 to 10% lower compared to those at 0°, with the greatest difference observed at a low laser power. This decrease in TS for the 90° parts could be explained by their position on the build platen during fabrication relative to the 0° parts. It was shown that there was a need to operate with a powder layer of uniform temperature to achieve builds of multiple parts with similar mechanical properties ,56,57. TThe parts made at a 45° XY plane orientation exhibit the overall lowest TS values compared to other orientations made in the same conditions by as much as 7.5%. As these 45° parts were positioned at the periphery, a gradient in the powder bed temperature could partially explain this. As the 45° and 90° parts were interspersed at the periphery, both orientations should exhibit similar TS values, which was not the case here. This difference could be attributed to the hatching orientation. While hatching is conducted alternatively parallel/perpendicular to the applied load in the case of the 90° parts, hatching in 45° parts is performed at an angle relative to the applied load. In a fashion similar to this well-known effect in FDM , more loThe Elongation at break as a function of the build orientation and laser power variation was also evaluated see c. HoweveIn order to further understand the influence of laser power on the properties of SLS-PA12, the fracture surface of the SLS-PA12 samples was analyzed. (a)Differential Scanning Calorimetryg). The second thermal transition, associated with the melting temperature (Tm), is the endothermic peak detected at 176 °C. During cooling, a third exothermic transition at 146 °C is attributed to the crystallization of PA12, where a re-arrangement of molecular chains takes place to create crystalline lamellae inside the continuous amorphous structure. From these results, it can be concluded that PA12 kept its semi-crystalline property after the cooling process. A DSC analysis of the printed PA12 parts at different laser powers was performed to determine the impact of this controlling parameter on the thermal characteristics of the PA12 samples manufactured by the SLS process. m), crystallization temperature (Tc), and glass transition temperature (Tg) between the printed PA12 at different laser power. It is evident from We can notice in g from 51.7 to 44.07 °C as a result of sintering correlates strongly with the degree of crystallization of the sample. This can be attributed to the gain in the mobility of the polymer chains as they are not partly anchored inside the crystalline domain.(b)X-ray DiffractionHowever, the degree of crystallization decreased from 46.62% see  for the Many studies investigating polymeric materials have considered that using heat treatment post-processing can improve the material properties and crystallinity of SLS parts made from Nylon 12 . These hm) to characterize the melting enthalpy, and then the degree of crystallinity (Xc) generated during the annealing cycle. c and all thermal transitions were measured  were annealed for six hours at various temperatures  to allow for the relaxation of the residual stress generated during their printing process. The annealed parts were analyzed by DSC, using the first heating cycle to characterize the thermal history experienced during the annealing process. During this heating cycle, the material achieved its melting temperature , the Tg value was still higher than the unannealed printed parts. It can also be noted that raising the annealing temperature from 130 to 170 °C results in an increase in the heat flow of melting from 65.51 to 76.51 J.g−1. An increase in the relative degree of crystallinity was also observed, from 31.29% to 36.55%. This latter crystallinity enhancement could be the result of a phenomenon called secondary crystallization, which increases the lamellar form of PA12. Moreover, the increase in Tg because of annealing correlates strongly with the degree of crystallinity of the printed PA12′s parts. Annealing thus induces strong intermolecular interactions between polymer chains. Thus, this increase is attributed to the loss of mobility of polymer chains as they are partly anchored inside the crystalline region.The annealed specimens were then subjected to mechanical testing to record the Young’s modulus, tensile strength, and strain at break. From From the above results, it has been confirmed that high-temperature annealing (170 °C) yields the best improvement in Young’s modulus , tensile strength , and elongation at break  over the unannealed parts. It can be concluded from these results that annealing had a higher percent contribution to the mechanical performance over the duration of annealing. This confirms the importance of the annealing process for achieving proper chain crystallization, thus enhancing the mechanical properties of 3D parts .This study evaluated the effect of laser power and hatch orientation on the tensile properties and morphology of the SLS PA12-produced parts. The main objective was to identify the suitable laser power and hatch orientation leading to better mechanical properties and high-quality parts. Different methods were used to study the SLS parts by considering the morphological, structural, and mechanical properties using XRD, FTIR, DSC, tensile testing, and SEM characterizations.The results confirmed the significant impact of laser power, while the effects of hatching were almost unnoticeable when using a high laser power. A more significant condition is the uniformity of the powder bed temperature, a factor that is seldom considered. This needs to be accounted for because of its effects on the mechanical properties. However, the operator has little recourse with respect to these conditions, which are strongly dependent on the quality of the SLS system.Operating at a high laser power minimized the presence of spherical particles normally related to un-melted powder and yielded an improved microstructure. It was also observed that reducing the laser power to LP: 75% decreases the mechanical properties, with the parts exhibiting spherical particles and a poor microstructure. Heat treating SLS-produced PA12 parts showed the positive impact of annealing, especially at 170 °C, on the tensile properties. This can be related to changes in the microstructure of the PA12 parts.


Halyomorpha halys, native to East Asia, has become one of the most damaging agricultural pests worldwide. After being first detected in Europe (in Switzerland), it is now widely spread throughout the European continent and many countries in Eurasia. Since its first appearance in Slovenia in 2017, it has caused extensive damage to fruit and vegetable production. Investigating the biology and behavior in local environmental conditions is the first step towards effective pest control. Information on the number of generations per year is crucial for anticipating critical phases of pest development and for adapting control measures that target the pest’s vulnerable life stages. A 3-year study (2019–2021) on the biological parameters of H. halys was performed outdoors in Nova Gorica (western Slovenia), confirming that in the sub-Mediterranean climate this pest has two overlapping generations per year. The net reproductive rates observed over the period studied indicate growing populations. The highest population growth was recorded in 2019, when the net reproductive rate of increase (R0) reached 14.84 for the summer generation and 5.64 for the overwintering generation. These findings reflect the current situation in Slovenia, where the growing populations of H. halys has been causing considerable damage to agricultural crops since 2019.The invasive brown marmorated stink bug Halyomorpha halys, native to East Asia, has become one of the most serious pests for agricultural crops worldwide. First detected in Europe (in Switzerland), the insect is now widely found across the European continent and many Eurasian countries. Since its first appearance in Slovenia in 2017 it has caused considerable damage to fruit and vegetable production. Understanding the biology and behavior in the local environmental conditions is of key importance for an effective pest management. Knowledge of the voltinism of the species is crucial to anticipate critical phases of pest development and for adapting control measures that target the vulnerable life stages of the pest. A 3-year study (2019–2021) of H. halys biological parameters was performed outdoors in Nova Gorica (western Slovenia), confirming that in the sub-Mediterranean climate this pest has two overlapping generations per year. The net reproductive rates observed in the studied period indicate growing populations. The highest population growth was recorded in 2019, when the net reproductive rate of increase (R0) reached 14.84 for the summer generation and 5.64 for the overwintering generation. These findings match the current situation in Slovenia, where increasing populations of H. halys and severe crop damage have been observed since 2019.In the last decade, the invasive brown marmorated stink bug  Halyomorpha halys  , also known as the brown marmorated stink bug, is native to East Asia and has rapidly become a globally distributed invasive species by stowing away on traded goods and people traveling  was calculated as a fraction of died individuals in a specific stage (dx) out of the total number of individuals entered in the same stage (lx).Apparent mortality (qx) = [dx/l0] was calculated as a fraction of died individuals in a specific stage (dx) out of the total number initially entering the first stage in a life table (l0).Real mortality (rx) = −log (1 − mx): the kx-values which express the intensity of mortality are the negative logarithm of ) for a factor. When only one mortality factor occurs in a stage, or where more than one occurs and they act sequentially, then the apparent mortality (qx) equals the marginal attack rate (mx).k-values (ks) is the sum of all mortality factor k-values and represents the total mortality for the generation . Ks = keggs + kN1 + kN2 + kN3 + kN4 + kN5.Generation mortality , which describes the number of times the population increases or decreases from one generation to the next [H. halys according to the formula:The net reproductive rate of increase R0 summer generation = realized progeny/number of eggs in the summer generation (l0 = 760)R0 values for growing populations are greater than 1, whereas values for declining populations are less than 1.The RThe relationships between temperature (x) and the development time (y) were determined using a simple linear regression analysis (y = kx + n) . StatistThe overwintering survival rate of adults was followed and assessed in the 2018/2019, 2019/2020 and 2020/2021 seasons. In all 3 years, some single specimens emerged from overwintering cages at the end of January and in the first week of February, respectively. However, they were unable to survive in cold weather conditions. In all 3 years, the noticeable adult emergence began at the end of March, when average daily temperatures exceeded 12 °C and peaked at the end of April, with average daily temperatures above 15 °C. Overwintering survival rates during the three following years were 39.9%, 40.3% and 36.5%, respectively. One third to one half of the adults who survived the winter died before the mating season. Total overwintering mortality of adults in the 3 years was 78.8%, 71.2%, and 80.8%. Oviposition began when average daily temperatures reached 17 °C, and the earliest was recorded in 11 May 2020. In the other 2 years, the first egg laying was observed at the end of May. The oviposition period of overwintering generations lasted 12–13 weeks. In 2020 and 2021 the last eggs were laid in the first half of August, while in 2019 the overwintering generation laid eggs from the end of May until the end of third week of August . The oviThe time elapsed between the exit from overwintering and the first egg laying  was 39.43 ± 3.28 days. The shortest time was recorded in 2020, when females needed an average of 33.2 days at an average temperature of 15.9 °C during this period. The pre-oviposition period was generally shorter at high temperatures. Females of the summer generation required 14.0 ± 1.11 to 18.6 ± 0.58 days to start oviposition after their emergence as adults , at meanThe accumulation of degree days was calculated using the lower threshold of 12.2 °C  startingn = 10) produced in total 1742 eggs, with the average lifetime fecundity of 174.2 ± 19.07 eggs per female. The females of the summer generation (n = 10) laid in total 760 eggs; the average lifetime fecundity was 76.0 ± 11.73 per female. The females of the overwintering population laid 3–11 egg masses, while the females of the summer generation laid 1–6 egg masses. Mating and oviposition were not observed among newborn adults of the summer generation, and the development of the third generation did not occur.The highest fecundity of our experimental populations was recorded in 2019, when overwintering couples  of the overwintering and summer generations were 14.84 and 5.64, respectively.The total generation mortality of the summer generation (89.86%)  was highH. halys is a recently established invasive pest in Europe, there is still a lack of basic biological knowledge in the newly invaded areas, which is essential for the development of management solutions. Three studies of H. halys biology have been carried out in Europe so far, namely Swiss research that reported the existence of one generation/year in the area of Zurich [H. halys develops two generations/year [H. halys developed two generations/year for 3 consecutive years. The favorable temperature conditions in Nova Gorica (western Slovenia) with monthly average temperatures 12 °C in April and 16.7 °C in May allowed for the early emergence of adults from the winter shelters and the early start of oviposition from mid-May to late May. Similarly, the early onset of oviposition has been reported in the province of Modena  [H. halys populations are also bivoltine. Subsequently, the development of the nymphs was driven by the high summer temperatures of June and July, which accelerated the emergence of adults. The first adults of the summer generation appeared from mid-July onwards, which is also in good agreement with the Chinese and Italian results, where the new generation adults emerged in the beginning of July. In addition to temperature, which is the main driver of insect development, photoperiod is a crucial factor in determining the developmental pattern [H. halys entry into the reproductive diapause [As f Zurich , an Italons/year  and Russons/year . The bas  , and in   , where H pattern . Haye et pattern  suggeste pattern  and othediapause ,45,46,47H. halys [H. halys [H. halys have higher overwintering mortality than univoltine populations [The overall overwintering mortality rates observed in 3-year period ranged from 71 to 81%, slightly lower than the results for northern Italy (86%), but much higher than those recorded in the Swiss survey (39%). Temperature is known to play a critical role in the biology of H. halys . Being aH. halys . AccordiH. halys  (2017) fH. halys , adults ulations . This coH. halys in our study averaged 39.43 ± 3.28 days for the overwintering population with an average 174.2 ± 19.07 eggs laid per female and 16.63 ± 1.37 days for the summer generation, with an average 76.0 ± 11.73 SE eggs laid per female. Fecundity was much lower than that observed in the native area in Asia, where a single female can produce over 480 eggs in her lifetime [H. halys was also pointed out in a study conducted by Govidan et al. [H. halys but reduces the fecundity of females, gave an additional explanation for the lower fecundity obtained in our study.The pre-oviposition period of lifetime  and evenlifetime . The higlifetime . Subsequlifetime , who foulifetime . In our lifetime , while tn et al. . Accordin et al. , differen et al. , who fouH. halys, based on the shortest development time and the highest survival obtained in the experiments. The opposite trend was observed in specimens that completed development in autumn. With decreasing temperatures, the development time was extended. The last specimens that were able to complete development, hatched in late August and molted into adults in early November. At the average temperature 16.8 °C measured during this period, it takes 67 to 81 days to complete development. The lowest temperature at which H. halys was able to complete development, as observed in our study (16.8 °C), is consistent with findings of Nielsen et al. [Here we present data on development time obtained at natural fluctuating temperatures under outdoor conditions. Over a 3-year period, developmental time and average temperature during the development period were calculated for all adults of the first and second generation. In line with the aforementioned studies, the development time from egg to adult was closely linked with temperature. In general, the development time decreased with increasing temperatures. The shortest development time recorded was 38 days, at an average temperature of 25 °C during the development period. This result is fully consistent with the findings of the laboratory experiments conducted by Nielsen et al. , who sugn et al. , Haye etn et al.  and Govin et al. , who sugH. halys Slovenian populations is comparable to the Swiss population (588.24 DD), to those of the United States where 538 DD are needed with a minimum temperature threshold of 14.14 °C [Considering the minimum temperature threshold of 12.2 °C , develop14.14 °C  and simi14.14 °C .H. halys was first found in Slovenia in 2017, increasing populations and crop damage have been observed [0) for the Slovenian populations in 2019 were 14.8 for the first generation and 5.6 for the second generation. Since the research was performed in outdoor conditions, it provided a clear view of temperature-dependent development and population growth. Considering that temperature directly affects insect population dynamics by changing rates of development, reproduction and mortality [H. halys are expected to vary within years. Although our study did not include limiting factors, such as the contribution of natural enemy-induced mortality, recent findings suggest that biological control is expected to play an important role in pest suppression over the coming years.Since observed . The preortality , the bioH. halys has only recently invaded the Slovenian territory, there is still lack of natural enemies that can effectively limit its population growth and spread. So far, the most promising natural enemies of H. halys found in Slovenia are the egg parasitoids Anastatus bifasciatus (Geoffroy) and Trissolcus mitsukurii (Ashmead) [H. halys suppression. Trissolcus mitsukurii is non-native parasitoid and currently has limited distribution in Europe, but it has a high potential to expand its range globally and help mitigate the negative effects of H. halys in invaded areas [Since Ashmead) . The fired areas .H. halys remains a very challenging task. Many researchers have worked hard over the past decade to provide alternative management tactics that are effective and environmentally acceptable as well. In this 3-year research study, key phenological data and information on the biological parameters of H. halys were obtained, which helps to optimize control measures and adapt them, especially in relation to the most vulnerable life stages of the pest. Regardless of the control method used, its effectiveness depends on an optimal timing and this must be taken into consideration both when applying pesticides or when releasing natural enemies. Knowledge of the phenology of local populations makes it possible to predict the occurrence of particular development stages of in the field. The results obtained in this work could also be applied in the development of forecasting models as important decision-making tools, contributing to a more efficient management of this globally invasive species.The present study confirmed that Slovenia has favorable climatic conditions for development of two generations per year, which causes high population growth and increases the risk of damage to agricultural production. For the above reasons, the management of