Fast UAV path planning in urban environments based on three-step experience buffer sampling DDPG

The path planning of Unmanned Aerial Vehicle(UAV)is a critical issue in emergency communication and rescue operations,especially in adversarial urban environments.Due to the continuity of the flying space,complex building obstacles,and the aircraft's high dynamics,traditional algorithms cannot find the optimal collision-free flying path between the UAV station and the destination.Accordingly,in this paper,we study the fast UAV path planning problem in a 3D urban environment from a source point to a target point and propose a Three-Step Experience Buffer Deep Deterministic Policy Gradient(TSEB-DDPG)algorithm.We first build the 3D model of a complex urban environment with buildings and project the 3D building surface into many 2D geometric shapes.After transformation,we propose the Hierarchical Learning Particle Swarm Optimization(HL-PSO)to obtain the empirical path.Then,to ensure the accuracy of the obtained paths,the empirical path,the collision information and fast transition information are stored in the three experience buffers of the TSEB-DDPG algorithm as dynamic guidance information.The sampling ratio of each buffer is dynamically adapted to the training stages.Moreover,we designed a reward mechanism to improve the convergence speed of the DDPG algorithm for UAV path planning.The proposed TSEB-DDPG algorithm has also been compared to three widely used competitors experimentally,and the results show that the TSEB-DDPG algorithm can archive the fastest convergence speed and the highest accuracy.We also conduct experiments in real scenarios and compare the real path planning obtained by the HL-PSO algorithm,DDPG algorithm,and TSEB-DDPG algorithm.The results show that the TSEBDDPG algorithm can archive almost the best in terms of accuracy,the average time of actual path planning,and the success rate.

Enhancing corrosion resistance of 7150 Al alloy using novel three-step aging process

The effects of a novel three-step aging process （T76＋T6） on the electrochemical corrosion behavior of 7150 extruded aluminum alloy were evaluated and compared with those of the conventional retrogression and re-aging process （T77）. The open circuit potential （OCP）, cyclic polarization and electrochemical impedance spectra （EIS） of the A1 alloys were measured after treatment in three solutions （3.5% NaCl （mass fraction）; 10 mmol/L NaCl ＋ 0.1 mol/L Na2SO4; 4 mol/L NaCl ＋ 0.5 mol/L KNO3 ＋ 0.1 mol/L HNO3）. The parameters including the corrosion potential, pitting potential, pit transition potential and steepness, and potential differences were extensively discussed to evaluate the corrosion behavior of the Al alloys. The electrochemical and scanning electron microscopy （SEM） data show that compared with the 7150-T77 Al alloy, the T76 ＋ T6 aged 7150 A1 alloy exhibits better resistance to pitting corrosion, inter-granular corrosion （IGC） and exfoliation corrosion, which is attributed to further coarsening and inter-spacing of the grain boundary particles （GBPs） as revealed by transmission electron microscopy. Furthermore, the hardness tests indicate that an attractive combination of strength and corrosion resistance was obtained for the 7150 Al alloy with T76 ＋ T6 treatment.

Effect of three-step homogenization on microstructure and properties of 7N01 aluminum alloys

The effect of different homogenization treatments on the microstructure and properties of the 7N01 aluminum alloy was investigated using hardness measurements, electrical conductivity measurements, tensile and slow strain rate tests, electron probe microanalysis, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results revealed that three-step homogenization improved the uniformity of Zr distribution by eliminating segregation of the main alloying elements. During the second homogenization step at 350 °C for 10 h, coarse and strip-like equilibrium η phases formed which assisted the nucleation of Al3Zr dispersoids and reduced the width of the precipitate-free zone of A13Zr dispersoids. As a result, coarse recrystallization was greatly reduced after homogenization at 200 °C, 2 h ＋ 350 °C, 10 h ＋ 470 °C, 12 h, which contributed to improving the overall properties of the 7N01 aluminum alloys.

Effect of a novel three-step aging on strength, stress corrosion cracking and microstructure of AA7085

The influence of a novel three-step aging on strength, stress corrosion cracking(SCC) and microstructure of AA7085 was investigated by tensile testing and slow strain rate testing combined with transmission electron microscopy(TEM). The results indicate that with the increase of second-step aging time of two-step aging, the mechanical properties increase first and then decrease, while the SCC resistance increases. Compared with two-step aging, three-step aging treatment improves SCC resistance and the strength increases by about 5%. The effects of novel three-step aging on strength and SCC resistance are explained by the role of matrix precipitates and grain boundary precipitates, respectively.

Short-term efficacy of robotic and laparoscopic spleen-preserving splenic hilar lymphadenectomy via Huang’s three-step maneuver for advanced upper gastric cancer: Results from a propensity scorematched study

BACKGROUND Robotic surgery has been considered to be significantly better than laparoscopic surgery for complicated procedures.AIM To explore the short-term effect of robotic and laparoscopic spleen-preserving splenic hilar lymphadenectomy(SPSHL)for advanced gastric cancer(GC)by Huang’s three-step maneuver.METHODS A total of 643 patients who underwent SPSHL were recruited from April 2012 to July 2017,including 35 patients who underwent robotic SPSHL(RSPSHL)and 608 who underwent laparoscopic SPSHL(LSPSHL).One-to-four propensity score matching was used to analyze the differences in clinical data between patients who underwent robotic SPSHL and those who underwent laparoscopic SPSHL.RESULTS In all,175 patients were matched,including 35 patients who underwent RSPSHL and 140 who underwent LSPSHL.After matching,there were no significant differences detected in the baseline characteristics between the two groups.Significant differences in total operative time,estimated blood loss(EBL),splenic hilar blood loss(SHBL),splenic hilar dissection time(SHDT),and splenic trunk dissection time were evident between these groups(P<0.05).Furthermore,no significant differences were observed between the two groups in the overall noncompliance rate of lymph node(LN)dissection(62.9%vs 60%,P=0.757),number of retrieved No.10 LNs(3.1±1.4 vs 3.3±2.5,P=0.650),total number of examined LNs(37.8±13.1 vs 40.6±13.6,P=0.274),and postoperative complications(14.3%vs 17.9%,P=0.616).A stratified analysis that divided the patients receiving RSPSHL into an early group(EG)and a late group(LG)revealed that the LG experienced obvious improvements in SHDT and length of stay compared with the EG(P<0.05).Logistic regression showed that robotic surgery was a significantly protective factor against both SHBL and SHDT(P<0.05).CONCLUSION RSPSHL is safe and feasible,especially after overcoming the early learning curve,as this procedure results in a radical curative effect equivalent to that of LSPSHL.

Auxiliary principle and three-step iterative algorithms for generalized set-valued strongly nonlinear mixed variational-like inequalities

An auxiliary principle technique to study a class of generalized set-valued strongly nonlinear mixed variational-like inequalities is extended. The existence and uniqueness of the solution of the auxiliary problem for the generalized set-valued strongly nonlinear mixed variational-like inequalities are proved, a novel and innovative three-step iterative algorithm to compute approximate solution is constructed, and the existence of the solution of the generalized set-valued strongly nonlinear mixed variational-like inequality is shown using the auxiliary principle iterative sequences generated by the algorithm technique. The convergence of three-step is also proved.

ZnO micro-nano composite hydrophobic film prepared by the three-step method

The hydrophobicity of the lotus leaf is mainly due to its surface micro-nano composite structure. In order to mimic the lotus structure, ZnO micro-nano composite hydrophobic films were prepared via the three-step method. On thin buffer films of SiO2, which were first fabricated on glass substrates by the so,gel dip-coating method, a ZnO seed layer was deposited via RF magnetron sputtering. Then two different ZnO films, micro-nano and micro-only flowerlike structures, were grown by the hydrothermal method. The prepared films have different hydrophobic properties after surface modification. The structures of the obtained ZnO films were characterized using x-ray diffraction and field-emission scanning electron microscopy. A conclusion that a micro-nano composite structure is more beneficial to hydrophobicity than a micro-only structure was obtained through research into the effect of structure on hydrophobic properties.

Three-step acupuncture and cupping therapy:an effective approach to treat cervicogenic headache

As early as 1983,Sjaastad proposed the concept of cervicogenic headache(CH)in the World Headache Conference,that is,the pain from upper cervical joints and muscles can be referred to the head.CH is a group of syndromes mainly caused by dysfunction of the upper cervical spine and its component muscles,ligaments,bony,vertebral arteries and/or soft tissue elements,usually not accompanied by neck pain.Therefore,the treatment strategy of CH focuses on pain relief and repair cervical lesions.Patients with painful disorders of upper cervical zygapophysial joints showed significant headache relief after directly treated at disordered cervical joints[1].

Three-Step Difference Scheme for Solving Nonlinear Time-Evolution Partial Differential Equations

In this paper, a special three-step difference scheme is applied to the solution of nonlinear time-evolution equations, whose coefficients are determined according to accuracy constraints, necessary conditions of square conservation, and historical observation information under the linear supposition. As in the linear case, the schemes also have obvious superiority in overall performance in the nonlinear case compared with traditional finite difference schemes, e.g., the leapfrog(LF) scheme and the complete square conservation difference(CSCD) scheme that do not use historical observations in determining their coefficients, and the retrospective time integration(RTI) scheme that does not consider compatibility and square conservation. Ideal numerical experiments using the one-dimensional nonlinear advection equation with an exact solution show that this three-step scheme minimizes its root mean square error(RMSE) during the first 2500 integration steps when no shock waves occur in the exact solution, while the RTI scheme outperforms the LF scheme and CSCD scheme only in the first 1000 steps and then becomes the worst in terms of RMSE up to the 2500th step. It is concluded that reasonable consideration of accuracy, square conservation, and historical observations is also critical for good performance of a finite difference scheme for solving nonlinear equations.

JOINT RANDOM OPTIMIZED THREE-STEP SEARCH ALGORITHM BASED-ON GRAY AND CHROMATIC INFORMATION

In this letter, an improved three-step search algorithm is presented, which uses both gray and chromatic information to boost the performance with random optimization and converge the motion vectors to global optima. Experimental results show that this algorithm can efficiently improve the PSNR after motion compensation.

First Exploratory Summary for Four-corresponding and Six-method Massage

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General Convergence Analysis for Three-step Projection Methods and Applications to Variational Problems

First a general model for a three-step projection method is introduced, and second it has been applied to the approximation solvability of a system of nonlinear variational inequality problems in a Hilbert space setting. Let H be a real Hilbert space and K be a nonempty closed convex subset of H. For arbitrarily chosen initial points x0, y0, z0 ∈ K, compute sequences xn, yn, zn such thatT ： K→ H is a nonlinear mapping onto K. At last three-step models are applied to some variational inequality problems.

A new three-step procedure for pancreatic head carcinoma with invasion of superior mesenteric artery

Pancreatic head carcinoma is characterized by high malignancy and a low survival rate and its mortality ranks fourth for malignant tumors with a 5-year survival rate of only 5%[1].Treatment of this cancer relies on surgical resection.However,the resection rate is only about 20%,because majority of the patients are classified as unresectable when diagnosed due to distant metastasis or

艾灸联合“三步六法”推拿治疗腰椎间盘突出症对患者腰椎功能的影响

目的探讨艾灸联合“三步六法”推拿治疗腰椎间盘突出症(LDH)的效果。方法选取2021年1月—2023年12月盐城市大丰中医院收治的60例LDH患者为研究对象,按随机数字表法将其分为对照组和观察组,每组30例。对照组采用常规治疗,观察组在对照组基础上采用艾灸联合“三步六法”推拿治疗。对比两组患者的疼痛程度、腰椎功能及生活质量。结果治疗后,观察组的疼痛视觉模拟评分为(1.35±0.21)分,低于对照组的(1.80±0.54)分,差异有统计学意义(P<0.05);观察组的日本矫形外科学会下腰痛评分表中主观症状、临床体征、日常活动受限评分及总分分别为(6.02±0.25)分、(4.56±0.57)分、(10.33±1.62)分、(21.28±4.07)分,均高于对照组的(5.51±0.34)分、(3.85±0.32)分、(8.12±1.46)分、(16.94±3.72)分,组间差异有统计学意义(P<0.05);观察组的世界卫生组织生存质量测定量表中心理、精神、环境、生理、社会关系、独立性、一般健康和生活质量评分分别为(70.19±5.20)分、(15.25±0.36)分、(115.40±7.26)分、(42.26±3.54)分、(41.37±3.78)分、(58.56±3.51)分、(18.12±0.74)分,均高于对照组的(64.42±5.18)分、(14.28±1.01)分、(105.77±8.95)分、(37.66±4.85)分、(35.18±4.89)分、(52.39±4.38)分、(16.55±0.57)分,组间差异有统计学意义(P<0.05)。结论艾灸联合“三步六法”推拿可减轻LDH患者的腰椎疼痛,改善腰椎功能,提高其生活质量。

血气分析酸碱失衡三步判断法在急诊科低年资护士培训中的应用效果评价

目的 :评价血气分析酸碱失衡三步判断法在急诊科低年资护士培训中的应用效果。方法 :六步法组护士和三步法组护士在培训后当天每人分析5个案例,记录判断每个案例所需的时间及正确与否。一周后两组护士再分析另外5个案例,记录同样的指标。观察两组护士对两种血气分析方法的掌握和遗忘情况。结果 :血气分析酸碱失衡三步判断法分析案例比六步法耗时短,且有统计学差异(P<0.01)。授课一周后,六步法组分析案例的错误率(11.9%)明显高于三步法组(4.8%),有统计学差异(P<0.01)。结论 :血气分析酸碱失衡三步判断法比经典六步法更适合急诊科低年资护士的培训,值得在临床推广。

“三段五步六法”教学模式在体操教学中的建立与实验研究

为了提高高师体育专业体操课教学质量，深化教学改革，使大学生的体操课学习由被动接受变为主动学习，本人经过三年的有益探索，提出了“三段五步六法”教学模式并运用于实践中，普遍受到学生的欢迎，其技能成绩有大幅度提高。

“三步六法”对膝关节骨性关节炎康复治疗的临床规范化研究

目的:客观评价"三步六法"对膝关节骨性关节炎康复治疗的有效性。方法:将120例膝关节骨性关节炎患者随机分为治疗组和对照组,分别给予"三步六法"和常规推拿手法治疗,通过治疗4周,评价两组治疗疗效。结果:治疗4周后,两组治疗前后组内及两组治疗后VAS评分比较,P<0.01,差异有统计学意义。治疗组总有效率90%,对照组总有效率81.6%,两组比较,P<0.05,差异有统计学意义。结论:"三步六法"对膝关节骨性关节炎康复的治疗安全有效,值得临床推广。

集团公司财务战略规划构建方法研究

财务战略管理是战略管理的核心,是影响企业长远发展的重大问题,是我国管理领域的一个崭新课题。传统的财务战略规划理论及构建方法存在着许多缺陷,财务战略规划的构建方法可以从定性和定量两个维度进行。不同性质的企业,因所处的内外部环境因素不同,所使用的方法也不一样,其可分为三步六分法、矩阵分析法。

突出学生主体地位 提高课堂教学效率——泰州实验学校“三环六步自主学习法”课题实验报告

本文报告了"三环六步自主学习法"课题实验的基本情况,阐述了其研究的目标和意义以及"三环六步自主学习法"的操作流程、原则、效果和实验反思。

PST理论视角下“三学六步”混合式教学模式研究与实践

以PST(教学-社会-技术)理论为指导,借助互联网信息技术和现代教育技术,从科学的教学法、适切的技术、新的交互空间三个角度关注学习者需求,将学习资源、学习目标、学习活动及学习环境相融合。以铁路信号与通信设备课程为例,借鉴操作技能教学法的先进理念,构建“三学六步”线上线下混合式教学模式,从准备阶段、要领讲解、示范操作、对标精炼、归纳总结和应用延展六个步骤来设计课堂活动,激发学生的探究兴趣,提高学生实践操作能力,实现教学效果的最大化。