扁平绕带式低温高压容器绝热性能分析和计算

扁平绕带式低温高压容器是一种新型低温液体贮存设备 ,由内外两层容器组成 ,内筒体的外壁焊有液氮预冷夹套。平均蒸发率是衡量扁平绕带式低温高压容器绝热性能的重要指标。文中在分析其传热过程和壁厚温差影响因素的基础上 ,提出了一种计算其蒸发率的工程方法 ,并结合1 0 m3液氢储罐设计实例进行了计算。结果表明扁平绕带式低温高压容器具有良好的绝热性能 ,适用于重要介质的低温贮运     

A column generation approach for determining optimal fleet mix,schedules, and transshipment facility locations for a vessel transportation problem

This paper presents a column generation approach for a storage replenishment transportation-scheduling problem. The problem is concerned with determining an optimal combination of multiple-vessel schedules to transport a product from multiple sources to different destinations based on demand and storage information at the destinations, along with cost-effective optimal strategic locations for temporary transshipment storage facilities. Such problems are faced by oil/trucking companies that own a fleet of vessels (oil tankers or trucks) and have the option of chartering additional vessels to transport a product (crude oil or gasoline) to customers (storage facilities or gas stations) based on agreed upon contracts. An integer-programing model that determines a minimum-cost operation of vessels based on implicitly representing feasible shipping schedules is developed in this paper. Due to the moderate number of constraints but an overwhelming number of columns in the model, a column generation approach is devised to solve the continuous relaxation of the model, which is then coordinated with a sequential fixing heuristic in order to solve the discrete problem. Computational results are presented for a range of test problems to demonstrate the efficacy of the proposed approach.     

Linearized iterative method for determining effects of vessel attitude error on single-beacon localization

Single-beacon localization is an advanced (and relatively new) acoustic localization technique. The traditional single-beacon uses non-linear trajectories to localize underwater vessels, which has notable drawbacks in actual underwater operations. To mitigate the limitations associated with non-linear trajectories, we developed an innovative single-beacon localization with linear trajectories. The traditional linearized least square method is not suited to linear trajectories, so we developed a linearized iterative method that includes a virtual long baseline array to analyze the effects of vessel attitude error on single-beacon localization results. We simulated the forward velocity, number of beacons, distance measurement period, and vessel heading impact on horizontal localization. The results showed that according to the proposed analysis method, localization precision is strongly dependent on vessel attitude error.     

Multi-sensor approach in vessel magnetic wake imaging

Wake is the hydrodynamic footprint of a vessel at sea. The Earth’s magnetic field makes these footprints visible using magnetic sensors. Magnetic wakes induced by the motion of vessels may extend several kilometers and stay up long hours under certain conditions. From remote sensing point of view, in this work physical properties of this magnetic pattern are studied. A mathematical model is derived to simulate the magnetic wakes in a finite depth sea. Estimation of vessel traveling direction using single airborne sensors is reviewed and some problems in this method are remarked. A multi-sensor arrangement of magnetic transducers is proposed to remove these limitations. Estimation of vessel traveling direction with the proposed sensor configuration is performed. Robustness of the proposed method in dealing with Gaussian white noise and various target cutting angles is shown.     

青铜器有害锈变温XRD及热分析

根除或有效控制氯化亚铜（CuCl）是青铜器保护的关键技术.根据铜的氯化物在一定温度下易分解或挥发这一性质,本文利用热分析仪及X射线衍射（XRD）手段,对CuCl粉末进行了分析,结果表明在大气环境中加热到420--430℃熔融后易挥发,实验结果将为寻找通过局部加热消除青铜基体内有害锈“病灶体”的合适方法提供依据.     

ITER装置中IWS装配仿真设计及研究

内中子屏蔽层(IWS-In Wall Shielding)是国际热核聚变实验装置(ITER)中核心装置-真空室(VVVacuum Vessel)的重要组成部分.由于真空室结构复杂,各项性能要求高,根据ITER国际组织要求,其所有结构必须结构设计与装配模拟研究同步进行,通过对其装配过程的动态模拟,确定其各部件的装配关系,...     

Automated vessel segmentation using cross-correlation and pooled covariance matrix analysis

Time-resolved contrast-enhanced magnetic resonance angiography (CE-MRA) provides contrast dynamics in the vasculature and allows vessel segmentation based on temporal correlation analysis. Here we present an automated vessel segmentation algorithm including automated generation of regions of interest (ROIs), cross-correlation and pooled sample covariance matrix analysis. The dynamic images are divided into multiple equal-sized regions. In each region, ROIs for artery, vein and background are generated using an iterative thresholding algorithm based on the contrast arrival time map and contrast enhancement map. Region-specific multi-feature cross-correlation analysis and pooled covariance matrix analysis are performed to calculate the Mahalanobis distances (MDs), which are used to automatically separate arteries from veins. This segmentation algorithm is applied to a dual-phase dynamic imaging acquisition scheme where low-resolution time-resolved images are acquired during the dynamic phase followed by high-frequency data acquisition at the steady-state phase. The segmented low-resolution arterial and venous images are then combined with the high-frequency data in k-space and inverse Fourier transformed to form the final segmented arterial and venous images. Results from volunteer and patient studies demonstrate the advantages of this automated vessel segmentation and dual phase data acquisition technique.     

舰船噪声听觉节奏特征

舰船噪声调制包络能反映舰船噪声听觉节奏特征,但在对其进行谱分析和特征提取过程中会损失部分信息。直接将舰船噪声包络可视化,并采用简单的人机交互提取特征量,对噪声分析和识别是有利的。包络分析采用多子带融合方法,将"最优"调制包络看作一种随机过程,并将舰船噪声的多子带检波信号看作是对"最优"调制包络的一次观测,对其作循环相关,用有限次观测的集种平均作为"最优"包络的估计,从而得到多子带融合包络,舰船噪声实测数据验证了该方法的有效性。     

Mapping of the cationic starch adsorbed on pulp fibers by ToF-SIMS

Cationic starch (CS) is routinely used in the papermaking process to improve the dry strength or printability of paper. The effectiveness depends on the distribution of the starch on the pulp fiber, and in this study, time-of-flight secondary ion mass spectrometry was used to investigate this distribution. The characteristic peak at 58m/z was applied to map the CS. Based on the imaging analysis of the handsheets with the CS as an internal additive, the distribution of CS became more uniform with decreasing freeness. The amount of adsorbed CS increased with increasing fiber length and was lower on vessels than on other fibers. These results were related to fibrillation. From the analysis of handsheets with CS as an external additive, the penetration depth of the starch into base paper increased with decreases in the sizing degree of the base paper.     

开放式微波消化-ICP-MS法快速测定食品中多种微量元素

开放式微波消解系统消化食品样品 ,以 45Sc、89Y、1 1 5In、2 0 9Bi作内标元素抑制分析信号的动态漂移 ,加入 1 %异丙醇消除 C元素对 As、Se等元素的干扰 ,建立食品中多种元素同时测定的ICP- MS方法。对 4类食品 (奶粉、鹅肝酱、水果片、燕麦片 )中的 1 2种元素 (Al、Cr、Ni、Ge、As、Se、Ag、Cd、Sn、Sb、Pb、Hg)进行了直接测定 ,绝大部分回收率在 85 %— 1 1 0 %之间 ;线性相关系数均大于 0 .999;精密度 (RSD)值 <1 0 %。对国家标准物质 (SRM)进行了分析 ,测得值与标准参考值相吻合。该法灵敏度、精密度和准确度都能满足有关标准的要求 ,具有多元素同时分析、样品前处理简单、干扰少、测定快速准确 ,省事省力等优点。