Shape memory polymers used in 4D printing only had one permanent shape after molding,which limited their applications in requiring multiple reconstructions and multifunctional shapes.Furthermore,the inherent stability...Shape memory polymers used in 4D printing only had one permanent shape after molding,which limited their applications in requiring multiple reconstructions and multifunctional shapes.Furthermore,the inherent stability of the triazine ring structure within cyanate ester(CE)crosslinked networks after molding posed significant challenges for both recycling,repairing,and degradation of resin.To address these obstacles,dynamic thiocyanate ester(TCE)bonds and photocurable group were incorporated into CE,obtaining the recyclable and 3D printable CE covalent adaptable networks(CANs),denoted as PTCE1.5.This material exhibits a Young's modulus of 810 MPa and a tensile strength of 50.8 MPa.Notably,damaged printed PTCE1.5 objects can be readily repaired through reprinting and interface rejoining by thermal treatment.Leveraging the solid-state plasticity,PTCE1.5 also demonstrated attractive shape memory ability and permanent shape reconfigurability,enabling its reconfigurable 4D printing.The printed PTCE1.5 hinges and a main body were assembled into a deployable and retractable satellite model,validating its potential application as a controllable component in the aerospace field.Moreover,printed PTCE1.5 can be fully degraded into thiol-modified intermediate products.Overall,this material not only enriches the application range of CE resin,but also provides a reliable approach to addressing environmental issue.展开更多
Abstract Test Cases(ATCs)have been widely used in practical scenarios such as combinatorial testing.When the set of ATCs is constructed,Test Case Prioritization(TCP)is applied to improve the testing quality.Among the ...Abstract Test Cases(ATCs)have been widely used in practical scenarios such as combinatorial testing.When the set of ATCs is constructed,Test Case Prioritization(TCP)is applied to improve the testing quality.Among the many TCP approaches for ATCs,one intuitive and well-studied approach is Interaction Coverage Based Prioritization(ICBP),which greedily identifies one element as the next ATC such that it covers the largest number of uncoveredτ-wise parameter-value combinations.When aτ-wise value combination,vc,has been covered by the already-selected ATCs,it is generally believed that it may have no further role to play in the ICBP process.However,each already-covered vc may provide some potential contributions for the interaction coverage of the strength higher thanτ.Motivated by this,we propose a new TCP approach to prioritize ATCs,Weighted Interaction Coverage Based Prioritization(WICBP).WICBP attempts to assign a weight to eachτ-wise value combination that has already been covered.The experimental results show that when using the same prioritization strength,WICBP is more effective than ICBP but maintains comparable testing efficiency.In addition,WICBP with lower prioritization strengths achieves surprisingly competitive(even better)performance compared with ICBP with higher prioritization strengths.展开更多
String validation routines have been widely used in many real-world applications,such as email validation and postcode validation.String test cases are adopted to test these validation routines,to identify potential d...String validation routines have been widely used in many real-world applications,such as email validation and postcode validation.String test cases are adopted to test these validation routines,to identify potential defects and security risks.Random Testing(RT)is a well-known testing approach to randomly generate string test cases from the input domain(i.e.,the set of all possible test inputs),which is simple to implement at a low cost.However,its testing effectiveness may be unsatisfactory for string validation routines.The main reason for this is that RT may have a high probability to generate invalid rather than valid string test cases,due to its randomness property.This research proposes a new RT approach based on the output types(i.e.,valid and invalid strings)for string validation routines,namely Output-type-guided Random Testing(RTO),which attempts to randomly generate both valid and invalid string test cases with a certain probability.This research performed an empirical study involving several real-world string validation routines collected from ten Java open-source projects,to investigate and compare testing performances of RT-O against the previous two widely-used RT methods.The results show that the generated string test cases by RT-O outperform test cases generated by other RT methods.展开更多
Polylactide(PLA)is an outstanding sacrificial template material for the manufacture of microchannels in a thermosetting matrix.However,the initial thermal degradation temperature of pure PLA is relatively high(about ...Polylactide(PLA)is an outstanding sacrificial template material for the manufacture of microchannels in a thermosetting matrix.However,the initial thermal degradation temperature of pure PLA is relatively high(about 280℃),which limits its use as a sacrificial template.In this report,we found that TBD,an organic base catalyst,can significantly reduce the thermal degradation temperature of PLA.TBD has higher catalytic activity for the thermal degradation of PLA compared with Tin(II)oxalate(Sn(Oxa)),one catalyst reported in the literature.Moreover,the gaseous products catalyzed by TBD for PLA thermal degradation are mainly lactide,and the formation temperature of the monomer is lower and the yield is higher,which may have potential value for PLA recycling.A combined catalyst,S8T2,was composed of 80%low activity catalyst Sn(Oxa)and 20%high activity catalyst TBD,which can catalyze the rapid degradation of PLA without greatly damaging the mechanical properties of PLA.PLA-S8T2 sacrificial fibers can form high-precision one-dimensional microchannels in the epoxy resin matrix,and 3D-printed PLA-S8T2 sacrificial templates can be used to form three-dimensional microchannels in a thermosetting matrix by vaporization of sacrificial components process(VaSC).These features highlight the great potential of PLA-S8T2 as sacrificial template material for the preparation of the complicated microchannels in the thermosetting matrix.展开更多
Agricultural production by smallholders is crucial for ensuring food provision in China.However,smallholders face a series of challenges on their farms including high-to-excess resource inputs,low use efficiency,as we...Agricultural production by smallholders is crucial for ensuring food provision in China.However,smallholders face a series of challenges on their farms including high-to-excess resource inputs,low use efficiency,as well as negative environmental impacts,which may be unfavorable for sustainable agriculture production.This study developed a county-level sustainability assessment of maize production in Hebei,China,by applying multiple data sources in combination with emergy,carbon footprint,nitrogen footprint and costbenefit analyses.Scenario analysis was applied to explore the localized implementation strategies to achieve the sustainable farming system.The results show that the average emergy sustainability index(ESI)of maize at 2.31 is relatively low.The average greenhouse gas(GHG)emissions and reactive nitrogen(Nr)losses are 0.15 g·kcal^(−1) CO_(2)-eq and 3.75 mg·kcal^(−1) N,respectively.The average cost and net income are 12,700 and 4340 CNY·ha^(−1),respectively.These results indicate a great potential to improve the environmental-economic sustainability of the maize production system of smallholders.In addition,the environmental and economic indicators calculated from the maize production show a substantial spatial heterogeneity among counties,indicating a requirement for different optimization strategies to improve the environment-economy sustainability at a finer scale.Based on the multiple scenario analysis,optimal strategies targeting each county are proposed.By adopting the optimal strategies,the average ESI and net income could increase by 32%and 83%,respectively,and the average GHG emissions and Nr losses reduce by 33%and 35%,respectively.These findings provide an important reference for adopting different strategies to achieve environmenteconomy sustainability for smallholders production systems with diverse landscapes in North China and propose a transition pathway toward achieving agriculture sustainability for smallholders worldwide.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52473080,52403167 and 52173079)the Fundamental Research Funds for the Central Universities(Nos.xtr052023001 and xzy012023037)+1 种基金the Postdoctoral Research Project of Shaanxi Province(No.2024BSHSDZZ054)the Shaanxi Laboratory of Advanced Materials(No.2024ZY-JCYJ-04-12).
文摘Shape memory polymers used in 4D printing only had one permanent shape after molding,which limited their applications in requiring multiple reconstructions and multifunctional shapes.Furthermore,the inherent stability of the triazine ring structure within cyanate ester(CE)crosslinked networks after molding posed significant challenges for both recycling,repairing,and degradation of resin.To address these obstacles,dynamic thiocyanate ester(TCE)bonds and photocurable group were incorporated into CE,obtaining the recyclable and 3D printable CE covalent adaptable networks(CANs),denoted as PTCE1.5.This material exhibits a Young's modulus of 810 MPa and a tensile strength of 50.8 MPa.Notably,damaged printed PTCE1.5 objects can be readily repaired through reprinting and interface rejoining by thermal treatment.Leveraging the solid-state plasticity,PTCE1.5 also demonstrated attractive shape memory ability and permanent shape reconfigurability,enabling its reconfigurable 4D printing.The printed PTCE1.5 hinges and a main body were assembled into a deployable and retractable satellite model,validating its potential application as a controllable component in the aerospace field.Moreover,printed PTCE1.5 can be fully degraded into thiol-modified intermediate products.Overall,this material not only enriches the application range of CE resin,but also provides a reliable approach to addressing environmental issue.
基金supported by the Science and Technology Development Fund of Macao,Macao SAR(Nos.0021/2023/RIA1 and 0046/2021/A)a Faculty Research Grant of Macao University of Science and Technology(No.FRG-22-103-FIE)the National Natural Science Foundation of China(Nos.61872167 and 61502205).
文摘Abstract Test Cases(ATCs)have been widely used in practical scenarios such as combinatorial testing.When the set of ATCs is constructed,Test Case Prioritization(TCP)is applied to improve the testing quality.Among the many TCP approaches for ATCs,one intuitive and well-studied approach is Interaction Coverage Based Prioritization(ICBP),which greedily identifies one element as the next ATC such that it covers the largest number of uncoveredτ-wise parameter-value combinations.When aτ-wise value combination,vc,has been covered by the already-selected ATCs,it is generally believed that it may have no further role to play in the ICBP process.However,each already-covered vc may provide some potential contributions for the interaction coverage of the strength higher thanτ.Motivated by this,we propose a new TCP approach to prioritize ATCs,Weighted Interaction Coverage Based Prioritization(WICBP).WICBP attempts to assign a weight to eachτ-wise value combination that has already been covered.The experimental results show that when using the same prioritization strength,WICBP is more effective than ICBP but maintains comparable testing efficiency.In addition,WICBP with lower prioritization strengths achieves surprisingly competitive(even better)performance compared with ICBP with higher prioritization strengths.
基金supported by the Science and Technology Development Fund of Macao,Macao SAR(Nos.0021/2023/RIA1 and 0046/2021/A)a Faculty Research Grant of Macao University of Science and Technology(No.FRG-22-103-FIE)supported by the National Natural Science Foundation of China(Nos.61872167 and 61502205).
文摘String validation routines have been widely used in many real-world applications,such as email validation and postcode validation.String test cases are adopted to test these validation routines,to identify potential defects and security risks.Random Testing(RT)is a well-known testing approach to randomly generate string test cases from the input domain(i.e.,the set of all possible test inputs),which is simple to implement at a low cost.However,its testing effectiveness may be unsatisfactory for string validation routines.The main reason for this is that RT may have a high probability to generate invalid rather than valid string test cases,due to its randomness property.This research proposes a new RT approach based on the output types(i.e.,valid and invalid strings)for string validation routines,namely Output-type-guided Random Testing(RTO),which attempts to randomly generate both valid and invalid string test cases with a certain probability.This research performed an empirical study involving several real-world string validation routines collected from ten Java open-source projects,to investigate and compare testing performances of RT-O against the previous two widely-used RT methods.The results show that the generated string test cases by RT-O outperform test cases generated by other RT methods.
基金supported by the National Natural Science Foundation of China(52173079 and 51873170)the National Key R&D Program of China(2019YFA0706801)+4 种基金the Shaanxi International Science and Technology Cooperation Program Project(2020kW-062)the Xi'an Scientific and Technological Achievements Transformation Project(20KYPT000108)the Key Laboratory Construction Program of Xi'an Science and Technology Bureau(201805056ZD7CG40)the Shaanxi Provincial Natural Science Basic Research Program-Shaanxi Coal Joint Fund(2021JLM-40)the One Hundred Talents Program of Shaanxi Province。
文摘Polylactide(PLA)is an outstanding sacrificial template material for the manufacture of microchannels in a thermosetting matrix.However,the initial thermal degradation temperature of pure PLA is relatively high(about 280℃),which limits its use as a sacrificial template.In this report,we found that TBD,an organic base catalyst,can significantly reduce the thermal degradation temperature of PLA.TBD has higher catalytic activity for the thermal degradation of PLA compared with Tin(II)oxalate(Sn(Oxa)),one catalyst reported in the literature.Moreover,the gaseous products catalyzed by TBD for PLA thermal degradation are mainly lactide,and the formation temperature of the monomer is lower and the yield is higher,which may have potential value for PLA recycling.A combined catalyst,S8T2,was composed of 80%low activity catalyst Sn(Oxa)and 20%high activity catalyst TBD,which can catalyze the rapid degradation of PLA without greatly damaging the mechanical properties of PLA.PLA-S8T2 sacrificial fibers can form high-precision one-dimensional microchannels in the epoxy resin matrix,and 3D-printed PLA-S8T2 sacrificial templates can be used to form three-dimensional microchannels in a thermosetting matrix by vaporization of sacrificial components process(VaSC).These features highlight the great potential of PLA-S8T2 as sacrificial template material for the preparation of the complicated microchannels in the thermosetting matrix.
基金funded by State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex(SCAPC202102)the National Natural Science Foundation of China(71904189).
文摘Agricultural production by smallholders is crucial for ensuring food provision in China.However,smallholders face a series of challenges on their farms including high-to-excess resource inputs,low use efficiency,as well as negative environmental impacts,which may be unfavorable for sustainable agriculture production.This study developed a county-level sustainability assessment of maize production in Hebei,China,by applying multiple data sources in combination with emergy,carbon footprint,nitrogen footprint and costbenefit analyses.Scenario analysis was applied to explore the localized implementation strategies to achieve the sustainable farming system.The results show that the average emergy sustainability index(ESI)of maize at 2.31 is relatively low.The average greenhouse gas(GHG)emissions and reactive nitrogen(Nr)losses are 0.15 g·kcal^(−1) CO_(2)-eq and 3.75 mg·kcal^(−1) N,respectively.The average cost and net income are 12,700 and 4340 CNY·ha^(−1),respectively.These results indicate a great potential to improve the environmental-economic sustainability of the maize production system of smallholders.In addition,the environmental and economic indicators calculated from the maize production show a substantial spatial heterogeneity among counties,indicating a requirement for different optimization strategies to improve the environment-economy sustainability at a finer scale.Based on the multiple scenario analysis,optimal strategies targeting each county are proposed.By adopting the optimal strategies,the average ESI and net income could increase by 32%and 83%,respectively,and the average GHG emissions and Nr losses reduce by 33%and 35%,respectively.These findings provide an important reference for adopting different strategies to achieve environmenteconomy sustainability for smallholders production systems with diverse landscapes in North China and propose a transition pathway toward achieving agriculture sustainability for smallholders worldwide.
