牙鲆‘鲆优2号’的引进、示范养殖与建议

为了改善天津地区养殖牙鲆种质落后、疾病频发的现状,规范养殖生产技术,促进渔民增产增收,分别从山东省海阳市引进‘鲆优2号’牙鲆新品种,河北省秦皇岛市购入普通牙鲆苗种,通过8个月的实地养殖对比试验,获得新品种牙鲆平均体重为539.79±83.52 g,成活率为91.00%,普通牙鲆平均体重为455.62±91.08 g,成活率为69.40%,结合本市现有养殖条件,提出牙鲆新品种养殖操作建议,形成适于本地区的养殖技术。养殖试验表明,牙鲆‘鲆优2号’新品种较普通苗种生长速度快且成活率高,适合天津地区养殖推广。

杂交黄颡鱼新品种试养效果评估

为了改良天津地区养殖黄颡鱼种质,提高经济和生态效益,本研究于2019年引进杂交黄颡鱼新品种‘黄优1号’,采用性状比较的方法,系统研究了试验鱼的生长、抗病和产氮、磷情况。结果表明:杂交黄颡鱼幼鱼生长速度、增重率显著高于普通黄颡鱼(P<0.05),饵料系数低于普通黄颡鱼,但差异不明显(P>0.05);杂交黄颡鱼的主要死亡病因为体表溃烂和烂鳃,体表溃烂发病情况与普通黄颡鱼无明显差别(P>0.05),烂鳃发病情况明显重于普通黄颡鱼(P<0.05),而其他疾病发病情况明显小于普通黄颡鱼(P<0.05),试验总成活率显著高于普通黄颡鱼;实验鱼体重增加1 kg,杂交黄颡鱼实验组尾水中氨氮、亚硝酸盐、总磷的增量均显著低于普通黄颡鱼(P<0.05),总氮的增量虽然也小于普通黄颡鱼实验组,但比较结果差异不显著(P>0.05)。因此,本研究认为杂交黄颡鱼‘黄优1号’的生长、抗病和单位增重产氮、磷量等性能较普通黄颡鱼优良,适合在天津地区推广养殖。

Development Strategy of Soundscape in Rural Tourism Based on Tourist Perception:A Case Study of Some Villages in Jiangxi Province

In the context of the development of rural tourism,through the field investigation of several rural tourism destinations in Jiangxi,and from the perspective of tourist perception,this paper discusses the development strategy of soundscape in rural tourism,so as to promote the inheritance and development of rural soundscape design.

Analysis of Comprehensive Utilization of Coconut Waste

This paper describes and analyzes the coconut cultivation in China,and the current comprehensive utilization of waste resources generated during cultivation and processing of coconut.The wastes generated in the process of cultivation include old coconut tree trunk,roots,withered coconut leaves,coconut flower and fallen cracking coconut,mainly used for biogas extraction,direct combustion and power generation,brewing,pharmacy,and processing of building materials;the wastes generated during processing include coconut water,coconut coat,coconut shell and coconut meal,mainly used for processing beverages,pharmaceutical products,activated carbon,medium and feed.This paper analyzes and explores some problems in the process of comprehensive utilization of coconut waste in China,such as insufficient understanding,inadequate development and lack of research efforts,and finally puts forth the corresponding development countermeasures.

Rooting Regional Characteristic Culture and Cultivating Students Design Consciousness:Taking the Teaching Reform of Architectural Landscape Design as an Example

China has a vast territory and numerous ethnic groups,forming various regional cultures with different styles.However,the architectural design education in colleges and universities of China used to learn from the West,and there is homogeneity in teaching mode,teaching content,and curriculum system construction,lacking regional cultural characteristics.In the context of regional culture,combined with the cultivation of students'innovation ability,the teaching of the course of Architectural Landscape Design is discussed in this article,in order to promote the inheritance and development of regional culture in landscape design teaching and promote students to truly understand the artistry and practicality of regional cultural resources.

Analysis on the Status Quo of the Public Space in Dashiyuan Community in Nanchang City and Its Renewal Strategies from Multiple Perspectives

From the perspective of big data such as Baidu heat map and GIS kernel density analysis,this paper analyzed the gathering situation of residents of Dashiyuan at different times and the use of public service facilities,as well as problems existing in the old community of Dashiyuan in Nanchang City,and put forward targeted recommendations.

耻脐入路单孔腹腔镜后鞘后技术在脐疝修补术中的应用

目的探讨耻脐入路单孔腹腔镜后鞘后修补术治疗脐疝的临床应用价值。方法回顾性研究2021年6月至2023年8月,上海中医药大学附属普陀医院微创外科收治的18例实施耻脐入路单孔腹腔镜后鞘后疝修补术的脐疝患者,根据临床病例资料、手术操作的技术细节及术后随访情况,分析该术式的临床效果及获益。结果18例患者均顺利完成手术,无中转开放手术,平均手术时间(106.67±28.49)min,术后6~8 h下床活动,术后8、24 h视觉模拟评分分别为2.94、2.50分,术后平均住院时间为(2.02±0.63)d;术后均无出血、肠梗阻、肠瘘、脐部坏死等严重并发症;随访时间为3~28个月,随访率100%,无复发。结论耻脐入路行单孔腹腔镜下后鞘后脐疝修补术安全可行,隐瘢痕效果好,术后疼痛轻,恢复快,可作为腹腔镜下脐疝修补的一种选择术式。

Hole surface strengthening mechanism and riveting fatigue life of CFRP/aluminum stacks in robotic rotary ultrasonic drilling

Carbon fiber reinforced plastic(CFRP)and aluminum stacks are widely used in aviation industry due to light weight and high performance.Millions of rivet holes need to be drilled on body materials,and more than 80%of fatigue cracks occur at the connection holes,so the damage and residual stress of hole surface have crucial effect on the riveting fatigue life of CFRP/aluminum stacks and the flight performance.Recently,robotic rotary ultrasonic drilling(RRUD)technology is a promising method to machine the stacks.However,the hole surface strengthening mechanism in RRUD and the service performance of the riveting joint are not verified.Thus,in this paper,the hole surface strengthening mechanism of RRUD for CFRP/aluminum stacks is investigated,a theoretical residual stress model is established,and the fatigue life experiment of riveted joints is conducted.Firstly,analysis on residual stress in RRUD is carried out with consideration of strengthening force and cutting temperature.Residual stress model is established based on the calculation of elastic stress,plastic stress and stress release.Validation experiment results show that ultrasonic vibration changes residual stress from tensile stress to compressive stress.At the same time,comparative damage analysis of CFRP hole exit and hole surface in robotic conventional drilling(RCD)and RRUD is presented.Finally,fatigue strength experiments of riveted joints are conducted for performance verification.Experimental results indicate that fatigue life of single-hole riveted joints is increased by 68%with ultrasonic vibration,and four-hole riveted joint arranged according to aerospace design standards is increased by more than 86%.

Chatter stability of robotic rotary ultrasonic countersinking

In recent years,industrial robots have received extensive attention in manufacturing field due to their high flexibility and great workspace.However,the weak stiffness of industrial robots makes it extremely easy to arouse chatter,which affects machining quality inevitably and generates noise pollution in severe cases.Compared with drilling,the chatter mechanism of robotic countersinking is more complex.The external excitation changes with cutting width and depth in countersinking.This characteristic results in time-varying and nonlinearity of robotic countersinking dynamics.Thus,it is urgent to propose a new method of chatter suppression and provide an accurate stability analysis model.As a new special machining technology,rotary ultrasonic machining has been proved to improve robotic drilling and milling stability effectively.Based on this,robotic rotary ultrasonic countersinking(RRUC)is proposed to improve the robotic countersinking stability in this paper.A three-dimensional stability domain method of RRUC is established.First,the countersinking process was divided intoρparts.The dynamic model of every unit was constructed based on ultrasonic function angle(γ)and dynamic chip area.Then,the stability region of RRUC is obtained based on the semi-discrete method(SDM).Compared with the robotic conventional countersinking(RCC),RRUC improves the stability by 27%.Finally,the correctness and effectiveness of the stability region model are proved by robotic ultrasonic countersinking experiments.

Design and experiment of anti-adhesion rototiller based on staggered double-roller scraping

In order to solve the serious problem of soil adhering blade roller in the middle and lower reaches of Yangtze River,the anti-adhesion rototiller based on staggered double-roller scraping(ARSDS)was designed by mechanical scraping methods.The volume equation for scraping the soil adhesion part with staggered rotary blades was constructed.The mechanical conditions for separation of soil adhesion part from blade roller were clarified,and the contact time between rotary blade and soil during rotary tillage was analyzed.By this way,the key parameters affecting soil adhering on and separating from the blade roller were determined,which were rotational speed,cutting pitch and tillage depth.The spatial and temporal trajectory changes for the sidelong section edge of staggered rotary blades were analyzed,so that the rotary blade arrangement was obtained.Combining the discrete element method,selecting the soil adhesion mass on the staggered blade rollers as the response value established prediction model by Box-Behnken design test.For example,taking the tillage depth of 14 cm for wheat cultivation in the middle and lower reaches of Yangtze River,the optimal combination of parameters was determined to be 230 r/min and 10 cm for rotational speed and cutting pitch,respectively.At this time,the soil adhesion mass was 4566.67 g.In the meantime,the process of soil particles adhering staggered blade rollers and rotary blades scraping off the adhering soil were clarified.Field experiments have shown that the operation quality of ARSDS met the requirements of rototiller performance indexes.In the rice stubble field of high water moisture,the soil adhesion mass was 13.455 kg and 38.215 kg for ARSDS and conventional rototiller,respectively,which indicated that ARSDS effectively reducing soil adhesion mass.The research results can provide technical support for the design of rototiller reducing soil adhesion in the agricultural areas of the middle and lower reaches of the Yangtze River.

Design and experiment of anti-vibrating and anti-wrapping rotary components for subsoiler cum rotary tiller

The commonly used subsoiling cum rotary tiller machine(SRT)in Northern China is a combination of subsoiler and horizontal rotary tiller,however backfilling of the subsoiling slot,excessive vibration and plant residue wrapping on rotary components has been rarely considered.Therefore,the rotary components and assembly were redesigned to address these issues and to an SRT fitted with IT225 short curve rotary blades behind the V-shape subsoiling slots and IIT245 long curve rotary blades between the tines.Long and short blades were fitted on a rotor in a double helix,with optimal spiral angles of 65° and 90°,and phase angle of 147°and 180°,respectively.Compared with the commonly used SRT(CSRT),the additional anti-wrapping cutting blades in the circumferential and axial direction of ASRT could remove hanging residue on the blade holders,wrapping on the rotor and formation of an isolation layer.Moreover,the cutting edge curve of anti-wrapping cutting blades was an exponential curve.Field tests demonstrated that the redesigned SRT with anti-vibrating and anti-wrapping rotary components(ASRT)had was a significant advancement over the CSRT.Moreover,the working depth of rotary tillage was more stable,while other observations confirmed that backfilling of the subsoiling slot was also improved.

Design and experiment of visual navigated UGV for orchard based on Hough matrix and RANSAC

The objective of this study was to develop a visual navigation system capable of navigating an unmanned ground vehicle(UGV)travelling between tree rows in the outdoor orchard.Thus far,while most research has developed algorithms that deal with ground structures in the orchard,this study focused on the background of canopy plus sky to eliminate the interference factors such as inconsistent lighting,shadows,and color similarities in features.Aiming at the problem that the traditional Hough transform and the least square method are difficult to be applied under outdoor conditions,an algorithm combining Hough matrix and random sample consensus(RANSAC)was proposed to extract the navigation path.In the image segmentation stage,this study used an H-component that was adopted to extract the target path of the canopy plus sky.Then,after denoising and smoothing the image by morphological operation,line scanning was used to determine the midpoint of the target path.For navigation path extraction,this study extracted the feature points through Hough matrix to eliminate the redundant points,and RANSAC was used to reduce the impact of the noise points caused by different canopy shapes and fit the navigation path.The path acquisition experiment proved that the accuracy of Hough matrix and RANSAC method was 90.36%-96.81%and the time consumption of the program was within 0.55 s under different sunlight intensities.This method was superior to the traditional Hough transform in real-time and accuracy,and had higher accuracy,slightly worse real-time compared with the least square method.Furthermore,the OPENMV was used to capture the ground information of the orchard.The experiment proved that the recognition rate of OPENMV for identifying turning information was 100%,and the program running time was 0.17-0.19 s.Field experiments showed that the UGV could autonomously navigate the rows with a maximum lateral error of 0.118 m and realize the automatic turning of the UGV.The algorithm satisfied the practical operation requirements of autonomous vehicles in the orchard.So the UGV has the potential to guide multipurpose agricultural vehicles in outdoor orchards in the future.

Stability analysis of robotic longitudinal-torsional composite ultrasonic milling

Currently,industrial robots are considered as an alternative towards traditional machine tools.Especially for the large-scale parts milling,robotic flexibility and low cost make it possess the irreplaceability.However,the milling chatter caused by its weak rigidity hampers robotic application and promotion severely in aviation industry.Rotary ultrasonic milling(RUM)technology with one-dimensional axial vibration has been proven and approved on avoiding robotic chatter.Based on this,the research of project team demonstrates that longitudinal-torsional composite ultrasonic milling(CUM-LT)involving separation characteristic has a greater advantage than RUM in terms of chatter suppression.Thereby,the CUM-LT as a new means is applied to avoid processing vibration of robotic milling system.And its influence mechanism on stability improvement of weak stiffness processing system is clarified.Meanwhile,the approaches to strengthen separation effect are provided innovatively.Moreover,a new analysis method of robotic CUM-LT(RCUM-LT)stability is proposed on the basis of ultrasonic function angles.The simulation and experimental results indicate that compared with robotic RUM(RRUM),stability regions of separated RCUM-LT(SRCUM-LT)and unseparated RCUM-LT(URCUM-LT)are improved by 124.42%and39.20%,respectively.The addition of torsional ultrasonic energy has a wonderful effect on the milling chatter suppression of low stiffness robots.

An intelligent self-sustained RAN slicing framework for diverse service provisioning in 5G-beyond and 6G networks

Network slicing is a key technology to support the concurrent provisioning of heterogeneous Quality of Service(QoS)in the 5th Generation(5G)-beyond and the 6th Generation(6G)networks.However,effective slicing of Radio Access Network(RAN)is very challenging due to the diverse QoS requirements and dynamic conditions in the 6G networks.In this paper,we propose a self-sustained RAN slicing framework,which integrates the self-management of network resources with multiple granularities,the self-optimization of slicing control performance,and self-learning together to achieve an adaptive control strategy under unforeseen network conditions.The proposed RAN slicing framework is hierarchically structured,which decomposes the RAN slicing control into three levels,i.e.,network-level slicing,next generation NodeB(gNodeB)-level slicing,and packet scheduling level slicing.At the network level,network resources are assigned to each gNodeB at a large timescale with coarse resource granularity.At the gNodeB-level,each gNodeB adjusts the configuration of each slice in the cell at the large timescale.At the packet scheduling level,each gNodeB allocates radio resource allocation among users in each network slice at a small timescale.Furthermore,we utilize the transfer learning approach to enable the transition from a model-based control to an autonomic and self-learning RAN slicing control.With the proposed RAN slicing framework,the QoS performance of emerging services is expected to be dramatically enhanced.

Resource allocation schemes in multi-vehicle cooperation systems

With the rapid development of smart driving and communications technologies,an increasing number of vehicles are cooperating with each other to improve traffc effciency and travel safety.This paper conducts a comprehensive survey of multi-vehicle cooperation from the aspects of control and communication.Firstly,three typical multi-vehicle cooperation scenarios are summarized.Communication issues relating to multi-vehicle cooperation are then introduced,including communication types,requirements,and potential solutions.To address the control requirements,a general resource allocation solution for multi-vehicle cooperation is formulated;speci cally,two types of resource allocation scheme for intersection management are proposed.Finally,performance of the proposed schemes is evaluated and compared.

旋转超声加工碳纤维复合材料研究现状与展望

碳纤维复合材料因其轻量化、耐高温、耐腐蚀等优异性能在多种极端服役环境得到了广泛的应用,在航空航天装备中的占比逐年提升。旋转超声加工技术在提高碳纤维复合材料去除效率、减小切削力和改善加工质量等方面具有显著优势,是当前难加工材料制造领域的研究热点。近年来,国内外学者在碳纤维复合材料的旋转超声钻削、铣削和磨削等方面展开了大量的研究工作并取得了丰硕的成果,然而,不同加工方式下多种形式超声振动能量的摄入对其切削效果的影响机理存在显著差异。此外,针对多种碳纤维复合材料表面完整性和使役性能研究的深度和广度仍存在较大的提升空间。为此,对材料去除机理、切削特性、表面质量研究及实际工程应用的国内外文献进行了总结和凝练,并展望了旋转超声加工碳纤维复合材料的发展趋势。