视觉语言多模态预训练综述

在多模态机器学习领域,为特定任务而制作的人工标注数据昂贵,且不同任务难以进行迁移,从而需要大量重新训练,导致训练多个任务时效率低下、资源浪费。预训练模型通过以自监督为代表的方式进行大规模数据训练,对数据集中不同模态的信息进行提取和融合,以学习其中蕴涵的通用知识表征,从而服务于广泛的相关下游视觉语言多模态任务,这一方法逐渐成为人工智能各领域的主流方法。依靠互联网所获取的大规模图文对与视频数据,以及以自监督学习为代表的预训练方法的进步,视觉语言多模态预训练模型在很大程度上打破了不同视觉语言任务之间的壁垒,提升了多个任务训练的效率并促进了具体任务的性能表现。本文总结视觉语言多模态预训练领域的进展,首先对常见的预训练数据集和预训练方法进行汇总,然后对目前最新方法以及经典方法进行系统概述,按输入来源分为图像—文本预训练模型和视频—文本多模态模型两大类,阐述了各方法之间的共性和差异,并将各模型在具体下游任务上的实验情况进行汇总。最后,总结了视觉语言预训练面临的挑战和未来发展趋势。     

Microstructure and Impact Resistance Analysis of 7075 Aluminum Alloy Modified by FSP

Abstract

The hot rolled 7075 aluminum alloy was modified by friction stir processing (FSP) technology, and the effects of different processing parameters on impact toughness and microstructure of machining region were analyzed. The results showed that the impact toughness of machining region was 2.3 times that of the base metal when the rotation velocity was 1200 r/min and the feed rate was 60?mm/min, which much higher than base metal. The fracture morphology was observed by using scanning electron microscope and found that the morphology of fracture dimple was uniform and smooth. The grains in the weld nugget zone were obviously refined after friction stir processing, and the grain refinement effects were not the same in different processing parameters.     

工程结构试验技术专业硕士课程教学改革研讨

针对专业型硕士的授课特点,在总结多年结构试验技术领域的科研成果和教学经验的基础上,根据重庆大学硕士课程教学改革要求,从课程特色及存在的主要问题、教学内容调整、教学方式和考核方法方面进行了教学研究和探讨,提出了结合项目教学法、理论联系实践的课程教学方案和具体实施方法。     

安岳气田60×10~8m~3/a地面工程建设模块化技术

四川盆地安岳气田磨溪区块下寒武统龙王庙组气藏天然气储藏量大,是典型的"三高"(高温、高压、高产量)含硫酸性气田,该项目60×10~8 m~3/a地面工程单列装置处理量大、工艺控制复杂、工程建造工作量大、建设场地受限、工期紧,传统工程建设模式很难在16个月内完成项目设计和建设。为此,引入了装置大型化及模块化的设计理念,全面推行"标准化设计、规模化采购、工厂化预制、模块化施工",形成了大型地面工程建设模块化技术:(1)根据工艺流程合理布置模块化装置的位置;(2)模块化设备布置采用多层框架进行空中叠加;(3)把操作工况、介质特性、功能特征、安装要求相同或相似的设备集中布置并构成模块;(4)专门设置了安全逃生通道;(5)预留了大型设备的安装、检维修操作空间;(6)充分考虑了模块的运输和吊装要求。采用该技术提高了设计质量,有效缩短了设计周期,减少了现场工作量,降低了现场安装的安全管理风险,提高了生产效率,节约了占地,减少了投资,为类似大型项目地面工程模块化建设提供了借鉴。     

井漏失返条件下的吊灌作业安全时间计算方法

"吊灌"作业是在井漏失返条件下保持井内压力动态平衡、获得安全作业时间的重要措施。但在实施吊灌作业时,由于反映井筒内环空液面变化规律的动态数模分析方法缺失,不能为工程实践提供吊灌的合理依据,使其基本处于"盲吊"状态。为此,笔者根据"吊灌"技术实际工况,首次采用井筒漏失动态分析方法,建立起吊灌安全作业时间数学模型,给出了多种漏失速率的积分结果,并结合现场实例对计算结果进行了验证。结果表明:(1)利用计算实例对数学模型的可靠性进行检验,计算结果与实际数据高度吻合;(2)适当增加吊灌量可以增加安全作业时间;(3)适当减少吊灌钻井液密度也可以增加安全作业时间。结论认为:该成果可以从根本上解决"吊灌"技术的安全作业时间准确计算问题,对于规避井漏失返条件下的井控安全风险、实现"吊灌"技术优化、降低工程费用等都具有重要意义。     

Global Robust Sliding Mode Control for Time-Delay Systems with Mismatched Uncertainties

A novel robust sliding mode control method for time-delay systems with mismatched uncertainties is presented, taking into consideration of both the norm-bounded mismatched uncertainties in the input matrix and the unknown input disturbance. First of all, an original time-delay system is changed into a new form without time delay via a nonsingular transformation, based on which, an integral sliding mode controller is then designed in the form of linear matrix inequalities, to guarantee the existence of the sliding motion from the initial time. In order to estimate the upper bound of unknown input disturbance, a new adaptive law is also proposed. Finally, a numerical simulation case is given to show the effectiveness of the proposed method.     

全相位-混合基FFT在相量测量装置中的实现

传统的傅里叶变换在测量非整周期的数据时会出现频谱泄露的现象,而快速傅里叶变换(FFT)只能对长度为2的整次幂(基-2)的数据进行处理,无法对非基-2的其他数据计算。为了解决以上问题,提出了一种全相位-混合基FFT算法。并详细介绍了全相位FFT、混合基FFT的原理以及全相位-混合基FFT在DSP中的实现过程。通过测试表明全相位-混合基FFT在电压、频率的测量精度较传统FFT有一定优势。将该算法应用到以DSP为核心的相量测量装置当中,对电网的状态进行实时监测,实测结果证明该算法准确可靠,在电力系统运行当中有一定实用价值。     

22SiMn2TiB钢淬火与回火过程中的组织演变

以超高强度钢 22SiMn2TiB 为对象,研究了在淬火、回火和配分状态下组织的演变规律.采用光学金相显微镜(OM)、扫描电镜(SEM)和 X 射线衍射技术(XRD)研究了不同处理状态下组织的演变规律.实验表明,回火或配分温度低于 320 ℃,板条马氏体组织形貌没有明显变化,且不随回火和配分时间的变化而变化;在此温度以上进行配分,不论配分时间的长短,组织皆转变为回火组织.表明 320 ℃为该钢材的临界回火、配分温度.随着回火温度的升高,位错密度下降;且 320 ℃以下温度回火或配分,马氏体衍射峰的半峰宽 FWHM 只是略有减少,表明虽然板条马氏体的组织形貌没有明显变化,但板条内的位错密度和内应力降低.     

Photochromic diarylethene for polarization holographic optical recording

Photochromic diarylethene, 1,2-bis[2-methyl-5-(3-fluorophenyl)-3-thienyl] perfluorocylcopentene (1a), was synthesized. The compound showed good photochromic reactions both in solution and in PMMA matrix by photo-irradiation. Using the diarylethene 1b/PMMA film as recording medium and a He-Ne laser for recording and readout, four types of polarization holographic optical recording were accomplished for the first time. The results show that the orthogonal circular polarization recording is the best method for holographic optical recording when the target photochromic diarylethene is used as recording material.     

Feasibility investigation of oily wastewater treatment by combination of zinc and PAM in coagulation/flocculation

Poly-zinc silicate (PZSS) is a new type of coagulant with cationic polymer synthesized by polysilicic acid and zinc sulfate. It has been used in several sorts of wastewaters treatment, but not used in oily wastewater treatment. In this study, we investigated the coagulation/flocculation of oil and suspended solids in heavy oil wastewater (HOW) by PZSS and anion polyacrylamide (A-PAM). The properties of PZSS cooperated with A-PAM were compared with PAC and PFS in dosages, PAMs amount, settling time, pH value and flocs morphology. The results showed that PZSS was more efficient than PAC and PFS. Under the optimum experimental conditions of coagulation/flocculation (dosage: 100mg/L, A-PAM dosage: 1.0mg/L, settling time time: 40min and pH 6.5-9.5), more than 99% of oil was removed and suspended solid value less than 5mg/L by using PZSS cooperated with A-PAM, which could satisfy the demands of the pre-treatment process for HOW to be reused in the steam boiler or recycled into the injecting well.