Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifi...Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point （AP） is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming （BF） and UAV path planning. First of all, we study a dual-hop amplify-and-forward （AF） wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station （BS）. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal^to-noise ratio （SNR） of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability （OP） expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.展开更多
A multi-objective optimization based robust beamforming(BF)scheme is proposed to realize secure transmission in a cognitive satellite and unmanned aerial vehicle(UAV)network.Since the satellite network coexists with t...A multi-objective optimization based robust beamforming(BF)scheme is proposed to realize secure transmission in a cognitive satellite and unmanned aerial vehicle(UAV)network.Since the satellite network coexists with the UAV network,we first consider both achievable secrecy rate maximization and total transmit power minimization,and formulate a multi-objective optimization problem(MOOP)using the weighted Tchebycheff approach.Then,by supposing that only imperfect channel state information based on the angular information is available,we propose a method combining angular discretization with Taylor approximation to transform the non-convex objective function and constraints to the convex ones.Next,we adopt semi-definite programming together with randomization technology to solve the original MOOP and obtain the BF weight vector.Finally,simulation results illustrate that the Pareto optimal trade-off can be achieved,and the superiority of our proposed scheme is confirmed by comparing with the existing BF schemes.展开更多
Two clean liquid–phase cyclohexanone oxidation routes catalyzed by DHBEA and HTS zeolites, in the absence of organic solvents, have been developed for producing high value-added chemical intermediates. Under optimize...Two clean liquid–phase cyclohexanone oxidation routes catalyzed by DHBEA and HTS zeolites, in the absence of organic solvents, have been developed for producing high value-added chemical intermediates. Under optimized conditions,the cyclohexanone conversion reaches up to 60%, and the selectivity of total target products(ε-caprolactone, 6-hydroxyhexanoic acid and adipic acid) is over 90% achieved by the HTS zeolite; while both cyclohexanone conversion and the 6-hydroxyhexanoic acid selectivity are over 95% obtained on the DHBEA zeolite. Both the Lewis and Br鰊sted acid sites of DHBEA zeolite can preferentially activate the carbonyl group of cyclohexanone without any impact on H_2O_2 molecules.Meanwhile, the HTS zeolite can predominantly make H_2O_2 more reactive, which agrees well with the molecular calculation results. Hence, two different Baeyer-Villiger oxidation mechanisms based on the activation of H_2O_2 and cyclohexanone are proposed. Then, 6-hydroxyhexanoic acid is formed via the ring-opening of ε-caprolactone. However, C-OH groups cannot be reactivated by DHBEA zeolite, leading to insignificant adipic acid formation, while the selectivity of adipic acid is 28.5% obtained on the HTS zeolite. Consequently, the higher catalytic performance of the DHBEA zeolite is ascribed to its larger amount of active sites and greater diffusion features than those of HTS zeolite.展开更多
The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A ...The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.展开更多
To solve the problem of energy transmission in the Internet of Things(IoTs),an energy transmission schedule over a Rayleigh fading channel in the energy harvesting system(EHS)with a dedicated energy source(ES)is consi...To solve the problem of energy transmission in the Internet of Things(IoTs),an energy transmission schedule over a Rayleigh fading channel in the energy harvesting system(EHS)with a dedicated energy source(ES)is considered.According to the channel state information(CSI)and the battery state,the charging duration of the battery is determined to jointly minimize the energy consumption of ES,the battery's deficit charges and overcharges during energy transmission.Then,the joint optimization problem is formulated using the weighted sum method.Using the ideas from the Q-learning algorithm,a Q-learning-based energy scheduling algorithm is proposed to solve this problem.Then,the Q-learning-based energy scheduling algorithm is compared with a constant strategy and an on-demand dynamic strategy in energy consumption,the battery's deficit charges and the battery's overcharges.The simulation results show that the proposed Q-learning-based energy scheduling algorithm can effectively improve the system stability in terms of the battery's deficit charges and overcharges.展开更多
The one-pot synthesis of 6-hydroxyhexanoic acid from cyclohexanone via the integrated Baeyer-Villiger oxida-tion and ring opening reaction catalyzed by dealuminated HBEA zeolite has been developed. Under optimized con...The one-pot synthesis of 6-hydroxyhexanoic acid from cyclohexanone via the integrated Baeyer-Villiger oxida-tion and ring opening reaction catalyzed by dealuminated HBEA zeolite has been developed. Under optimized conditions,the cyclohexanone conversion and 6-hydroxyhexanoic acid selectivity are over 95%, respectively. The excellent catalyticperformance is attributed to the activation of carbonyl group of cyclohexanone and the fast hydrolysis and ring opening ofs-caprolactone by both Lewis acid and Br0nsted acid sites under aqueous conditions.展开更多
基于“预训练+微调”范式的实体关系联合抽取方法依赖大规模标注数据,在数据标注难度大、成本高的中文古籍小样本场景下微调效率低,抽取性能不佳;中文古籍中普遍存在实体嵌套和关系重叠的问题,限制了实体关系联合抽取的效果;管道式抽取...基于“预训练+微调”范式的实体关系联合抽取方法依赖大规模标注数据,在数据标注难度大、成本高的中文古籍小样本场景下微调效率低,抽取性能不佳;中文古籍中普遍存在实体嵌套和关系重叠的问题,限制了实体关系联合抽取的效果;管道式抽取方法存在错误传播问题,影响抽取效果。针对以上问题,提出一种基于提示学习和全局指针网络的中文古籍实体关系联合抽取方法。首先,利用区间抽取式阅读理解的提示学习方法对预训练语言模型(PLM)注入领域知识以统一预训练和微调的优化目标,并对输入句子进行编码表示;其次,使用全局指针网络分别对主、客实体边界和不同关系下的主、客实体边界进行预测和联合解码,对齐成实体关系三元组,并构建了PTBG(Prompt Tuned BERT with Global pointer)模型,解决实体嵌套和关系重叠问题,同时避免了管道式解码的错误传播问题;最后,在上述工作基础上分析了不同提示模板对抽取性能的影响。在《史记》数据集上进行实验的结果表明,相较于注入领域知识前后的OneRel模型,PTBG模型所取得的F1值分别提升了1.64和1.97个百分点。可见,PTBG模型能更好地对中文古籍实体关系进行联合抽取,为低资源的小样本深度学习场景提供了新的研究思路与方法。展开更多
基金supported by the National Natural Science Foundation of China (Nos. 61202351, 61271255)the Natural Science Foundation of Jiangsu Province (No. BK20131068)+2 种基金the Open Research Fund of National Mobile Communications Research Laboratory in Southeast University (No. 2012D15)the Funding of Jiangsu Innovation Program for Graduate Education (No. CXLX11_0202)the Fundamental Research Funds for the Central Universities
文摘Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point （AP） is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming （BF） and UAV path planning. First of all, we study a dual-hop amplify-and-forward （AF） wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station （BS）. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal^to-noise ratio （SNR） of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability （OP） expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.
基金supported by the Key International Cooperation Research Project(61720106003)the National Natural Science Foundation of China(62001517)+2 种基金the Shanghai Aerospace Science and Technology Innovation Foundation(SAST2019-095)the NUPTSF(NY220111)the Foundational Research Project of Complex Electronic System Simulation Laboratory(DXZT-JC-ZZ-2019-009,DXZTJC-ZZ-2019-005).
文摘A multi-objective optimization based robust beamforming(BF)scheme is proposed to realize secure transmission in a cognitive satellite and unmanned aerial vehicle(UAV)network.Since the satellite network coexists with the UAV network,we first consider both achievable secrecy rate maximization and total transmit power minimization,and formulate a multi-objective optimization problem(MOOP)using the weighted Tchebycheff approach.Then,by supposing that only imperfect channel state information based on the angular information is available,we propose a method combining angular discretization with Taylor approximation to transform the non-convex objective function and constraints to the convex ones.Next,we adopt semi-definite programming together with randomization technology to solve the original MOOP and obtain the BF weight vector.Finally,simulation results illustrate that the Pareto optimal trade-off can be achieved,and the superiority of our proposed scheme is confirmed by comparing with the existing BF schemes.
基金financially supported by the National Basic Research Program of China (973 Program, 2006CB202508)the Research Program of China Petrochemical Corporation (SINOPEC Group 20673054)the National Key Research and Development Program of China (2017YFB0306800)
文摘Two clean liquid–phase cyclohexanone oxidation routes catalyzed by DHBEA and HTS zeolites, in the absence of organic solvents, have been developed for producing high value-added chemical intermediates. Under optimized conditions,the cyclohexanone conversion reaches up to 60%, and the selectivity of total target products(ε-caprolactone, 6-hydroxyhexanoic acid and adipic acid) is over 90% achieved by the HTS zeolite; while both cyclohexanone conversion and the 6-hydroxyhexanoic acid selectivity are over 95% obtained on the DHBEA zeolite. Both the Lewis and Br鰊sted acid sites of DHBEA zeolite can preferentially activate the carbonyl group of cyclohexanone without any impact on H_2O_2 molecules.Meanwhile, the HTS zeolite can predominantly make H_2O_2 more reactive, which agrees well with the molecular calculation results. Hence, two different Baeyer-Villiger oxidation mechanisms based on the activation of H_2O_2 and cyclohexanone are proposed. Then, 6-hydroxyhexanoic acid is formed via the ring-opening of ε-caprolactone. However, C-OH groups cannot be reactivated by DHBEA zeolite, leading to insignificant adipic acid formation, while the selectivity of adipic acid is 28.5% obtained on the HTS zeolite. Consequently, the higher catalytic performance of the DHBEA zeolite is ascribed to its larger amount of active sites and greater diffusion features than those of HTS zeolite.
基金The author thanks for the financial support of SINOPEC Corporation(S413108).
文摘The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.
基金The National Natural Science Foundation of China(No.51608115).
文摘To solve the problem of energy transmission in the Internet of Things(IoTs),an energy transmission schedule over a Rayleigh fading channel in the energy harvesting system(EHS)with a dedicated energy source(ES)is considered.According to the channel state information(CSI)and the battery state,the charging duration of the battery is determined to jointly minimize the energy consumption of ES,the battery's deficit charges and overcharges during energy transmission.Then,the joint optimization problem is formulated using the weighted sum method.Using the ideas from the Q-learning algorithm,a Q-learning-based energy scheduling algorithm is proposed to solve this problem.Then,the Q-learning-based energy scheduling algorithm is compared with a constant strategy and an on-demand dynamic strategy in energy consumption,the battery's deficit charges and the battery's overcharges.The simulation results show that the proposed Q-learning-based energy scheduling algorithm can effectively improve the system stability in terms of the battery's deficit charges and overcharges.
基金supported by the National Basic Research Program of China(973 Program,2006CB202508)the China Petrochemical Corporation Program(SINOPEC Group ST417004)the National Key Research and Development Program of China(2017YFB0306800)
文摘The one-pot synthesis of 6-hydroxyhexanoic acid from cyclohexanone via the integrated Baeyer-Villiger oxida-tion and ring opening reaction catalyzed by dealuminated HBEA zeolite has been developed. Under optimized conditions,the cyclohexanone conversion and 6-hydroxyhexanoic acid selectivity are over 95%, respectively. The excellent catalyticperformance is attributed to the activation of carbonyl group of cyclohexanone and the fast hydrolysis and ring opening ofs-caprolactone by both Lewis acid and Br0nsted acid sites under aqueous conditions.
文摘基于“预训练+微调”范式的实体关系联合抽取方法依赖大规模标注数据,在数据标注难度大、成本高的中文古籍小样本场景下微调效率低,抽取性能不佳;中文古籍中普遍存在实体嵌套和关系重叠的问题,限制了实体关系联合抽取的效果;管道式抽取方法存在错误传播问题,影响抽取效果。针对以上问题,提出一种基于提示学习和全局指针网络的中文古籍实体关系联合抽取方法。首先,利用区间抽取式阅读理解的提示学习方法对预训练语言模型(PLM)注入领域知识以统一预训练和微调的优化目标,并对输入句子进行编码表示;其次,使用全局指针网络分别对主、客实体边界和不同关系下的主、客实体边界进行预测和联合解码,对齐成实体关系三元组,并构建了PTBG(Prompt Tuned BERT with Global pointer)模型,解决实体嵌套和关系重叠问题,同时避免了管道式解码的错误传播问题;最后,在上述工作基础上分析了不同提示模板对抽取性能的影响。在《史记》数据集上进行实验的结果表明,相较于注入领域知识前后的OneRel模型,PTBG模型所取得的F1值分别提升了1.64和1.97个百分点。可见,PTBG模型能更好地对中文古籍实体关系进行联合抽取,为低资源的小样本深度学习场景提供了新的研究思路与方法。
