Uncertainty analysis of ship model vertical center of gravity and transverse moment of inertia test

The usability of test results of ship model vertical center of gravity and transverse moment of inertia is generally depends on its uncertainty. Referring to the guidelines for uncertainty analysis in examination of liquid dynamic recommended by International Towing Tank Conference （ ITTC）, the results were analyzed, bias limits and precision limits were calculated and total uncertainty was estimated. The total uncertainty of six tests on ship model vertical center of gravity is is 0. 16% of the mean value, and the total uncertainty of six tests on ship model transverse moment of inertia is 5.66% of the mean value. The test results show that the total uncertainty of both the multiple tests and the single test is from the precision limits of ship model vertical center of gravity and transverse moment of inertia tests. Thus, the improved measurement system stability can enormously decrease the total uncertainty of multiple tests and the single test.

A Content Analysis of Hospitality Reports from the Center of Hospitality Research in Cornell University: 2001-2014

This article analyzes 186 hospitality reports from the Center of Hospitality Research in Cornell University. Objectives of the study are to (a) profile the content of hospitality report of the Center of Hospitality Research;(b) identify differences between the findings of hospitality journals research and the results of hospitality reports in the Center of Hospitality Research;and (c) derive emerging trends and make suggestions on future directions regarding hospitality research with industry professionals in the Center of Hospitality Research. Content analysis results showed that the differences between hospitality reports in the Center of Hospitality Research and other journal exit in the research theme and unit of analysis. Finance in the Center of Hospitality Research was increasingly popular, while human resources in other journal were emphasized. The Center of Hospitality Research focused on individual behavior, as well as organizational behavior, while other journal mainly focused on individual behavior. According to the results, hospitality reports in the Center of Hospitality Research will lay more emphasis on finance and decline the research of human resources. Multiple-authorship and collaboration with industry professionals and scholars from other universities will be popular in the Center of Hospitality Research.

A Review of the Logistic Regression Model with Emphasis on Medical Research

This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on medical research. Thirty seven research articles published between 2000 and 2018 which employed logistic regression as the main statistical tool as well as six text books on logistic regression were reviewed. Logistic regression concepts such as odds, odds ratio, logit transformation, logistic curve, assumption, selecting dependent and independent variables, model fitting, reporting and interpreting were presented. Upon perusing the literature, considerable deficiencies were found in both the use and reporting of LR. For many studies, the ratio of the number of outcome events to predictor variables (events per variable) was sufficiently small to call into question the accuracy of the regression model. Also, most studies did not report on validation analysis, regression diagnostics or goodness-of-fit measures;measures which authenticate the robustness of the LR model. Here, we demonstrate a good example of the application of the LR model using data obtained on a cohort of pregnant women and the factors that influence their decision to opt for caesarean delivery or vaginal birth. It is recommended that researchers should be more rigorous and pay greater attention to guidelines concerning the use and reporting of LR models.

Research and Evaluation on Key Technological Indicators for Airborne and Shipborne Gravimetry

Gravimetry technical guides are the scientific basis for air-sea gravimetry. However, the existing technical guides in China are behind the application requirements. This study analyzed the most important indicators of air-sea gravimetry, including the density of survey lines, gravimetry accuracy and space resolution, stability and reliability of the air-sea gravimeter, and proposed a gravimetry accuracy assessment system consisting of gravity RMS of error, systematic error and mean error, and an assessment system for the gravimeter stability consisting of the relative accuracy of the scale value, monthly zero-drift, RMS of the monthly nonlinear zero-drift variation and the threshold of the monthly nonlinear zero-drift variation. The mathematic models for the measurement point determination in shipborne gravimetry, E tv s correction for airborne gravimetry, platform tilt correction and evaluation air-sea gravimetry were also analyzed and modified. This work will provide technology support for the composition of the military-civil air-sea gravimetry technical guides.

Exact Bayesian and Fiducial Limits for the Mean of Lognormal Distribution

In this paper, the exact Bayesian limits, taking conjugate and noninformative prior distribution, and the exact fiducial limits for the mean of the lognormal distribution are presented. They can be found iteratively by one-dimension integral on a finite interval. The new algorithm is very convenient and with high accuracy. It can meet the practical engineering need excellently. However, the primitive algorithm is rather cumbersome. By the way, the very close approximate limits with a simple algorithm are derived. They can be applied immediately to engineering. Otherwise, they can also be used as a search interval to find the root of equation for the exact limits.

An Evaluation of Manure Management Strategies, Phosphorus Surface Runoff Potential and Water Usage at an Arkansas Discovery Dairy Farm

Manure management is an essential component of dairy production. Nutrient-laden, field-applied dairy manure often serves as a fertilizer source, but can also pose environmental threats if not properly managed. The Haak dairy farm, located in Decatur, Arkansas, was granted a permit by the Arkansas Department of Environmental Quality (ADEQ) to employ a unique method in treating and storing cattle manure generated during the milking process. This method includes minimizing water use in wash water, dry scraping solids to combine with sawdust for composting and pumping effluent underground into a sloped concrete basin that serves as secondary solid separator before transporting the manure effluent into an interception trench and an adjacent grassed field to facilitate manure nutrient uptake and retention. The Arkansas Discovery Farm program (ADF) is conducting research to evaluate the environmental performance of the dairy’s milk center wash water treatment system (MCWW) by statistical analysis, characterization of phosphorus (P) migration in soil downslope from the inception trench, temperature measurements, and nutrient analysis of a stored dry stack manure/sawdust mixture. Goals included determining possible composting effectiveness along with comparisons to untreated dairy manure and quantifying the use of on-farm water. Results from this research demonstrated that: 1) The MCWW was effective at retaining manure-derived nutrients and reducing field nutrient migration as the MCWW interception trench had significantly higher total nitrogen (TN) (804.2 to 4.1), total phosphorus (TP) (135.6 to 1.5), and water extractable phosphorus (WEP) (55.0 to 1.0) concentrations in milligrams per liter (mg⋅L-1) than the downhill freshwater pond respectively;2) temperature readings of the manure dry stack indicated heightened levels of microbial and thermal activity, but did not reach a standard composting temperature of 54°C;3) manure dry stack nutrient content was typically higher than untreated dairy manure when measured on a “dry basis” in ppm, but was lower on an “as is basis” in ppm and kg/metric ton;and 4) water meter readings showed that the greatest use of on-farm water was for farm-wide cattle drinking (18.77), followed by water used in the milking center (3.45) and then followed by human usage (0.02) measured in cubic meters per day (m3⋅d-1). These results demonstrate that practical innovations in agricultural engineering and environmental science, such as the Haak dairy’s manure treatment system, can effectively reduce environmental hazards that accompany the management of manure at this dairy operation.

Research on the natural meshing mechanism and testing analysis of scroll profiles for refrigeration scroll compressor

In the design theory of scroll profiles for refrigeration scroll compressor,a mechanism principle of scroll profiles based on the center of natural temporal involutes and meshing region is presented,by which the performance characteristics of the various involutes are studied. Profiles type selection is very important for scroll compressor. Through analyzing the characteristic geometry,natural meshing mechanism is discovered in the study of scrolls. And a novel method for scroll profiles based on natural meshing mechanism is proposed. The result shows that the meshing region angle of odd regular polygon involutes is half of the characteristic-geometry exterior angle,and that of even regular polygon involutes is equal to the exterior angle to the moment. The corresponding meshing region angle is reduced increasingly with the increase of the edge number of characteristic geometry. The performance characteristics of scroll compressor tend towards the best correspondingly. Aiming at the existing problems of profile design for scrolls,we developed a novel methodology to study scroll profile. Originality research was done for the further study of scroll profile. It is the fundamentality factor representing essence character of scroll profiles function itself.

Meta-analysis研究方法述评

整合分析是一种用效应值对某一问题的定量研究进行综合、整合和解释的研究方法。介绍了整合分析的概念、历史、研究步骤和心理学中常见的数据报告形式的效应值的计算以及在我国的应用现状。并对整合分析这种研究方法进行了简要的评价。

Tianjin Automotive Test Center & National Passenger Car Quality Supervision and Inspection Center——A State Testing and Universality Techniques Research Base in China

Tianiin Automotive Test Center has a test capability as well as a capability of conducting universality techniques research. With fixed assets of around RMB 76.44 million yuan and an architectural area of 11,200 sqm, test labs mainly include: auto emission test lab, full-scale vehicle crash test lab, auto safety test lab, auto lighting and view field test lab, engine test lab,

创新培训模式助力实验技术队伍建设与发展

该文介绍了高校分析测试中心将全国分析检测人员能力培训委员会(NTC)能力培训与校内培训相结合,形成了科学、系统的培训计划,结合先进教学方法,为实验技术人员提供了综合学习平台,持续推动校内实验技术人员的专业培训。文章详述了这一培训模式的实施过程,以及实验技术人员在个人能力、实验教学和科学研究等方面取得的成效。

2021-2022年江阴市公共场所微生物检测结果分析

目的分析旅店、洗浴中心、超市的微生物检测结果。方法根据《公共场所卫生监测技术规范》和《公共场所卫生标准监测检验方法》要求,对3类公共场所(旅店、洗浴中心、超市)共2372份样品进行微生物检测。结果通过对2021年-2022年空气和公共用品用具微生物检测结果进行分析后,2021年共计检测1124份样本,其中合格样本1110份,合格率为98.75%;2022年共计检测1248份样本,其中合格样本为1248份,合格率为100.00%。2022年空气和公共用品用具微生物检测结果高于2021年(x^(2)值=13.586,P<0.05)。结论与2021年相比,2022年江阴市公共场所微生物检测合格率有较高的提升。然而,需要保持警惕,加强卫生管理,以确保公共场所的环境卫生和人员健康。

高校分析测试中心实验室安全管理体系的构建

高校分析测试中心是实验教学、科研和社会服务的重要场所,是大型仪器共享平台的重要基地,因此,学校对分析测试中心实验室的安全管理提出了更高的要求。文章针对分析测试中心实验室的特点及安全管理现状进行分析,从管理制度的建立、安全教育培训的强化、定期监督巡查以及应急响应体系的建立等方面去探讨分析测试中心实验室安全管理体系的构建,并提出实验室安全管理持续改进的措施,为其他高校分析测试中心实验室安全管理提供参考。

高校国家知识产权信息服务中心建设研究(一):现状、问题及成因分析

本文运用多种调研方法,对高校国家知识产权信息服务中心进行调研。从发展现状、机构设立、人员配备、建章立制、全链条协同优化、业务开展、资源配置、馆员理论研究等方面进行统计分析,发现问题,并从宏观政策、思想观念、微观运行等层面分析问题成因。

高校分析测试中心仪器维修维护现状调查与思考

高校分析测试中心作为教学科研的重要阵地,大型高端设备的数量逐年增加,然而,高校分析测试中心大型仪器设备运行维护水平和快速增长的仪器设备存量间存在一定差距。文章通过调研国内70家高校分析测试中心运行维护情况,分析了高校分析测试中心在制度体系、仪器厂商服务、仪器国产替代及运维成本方面存在的问题和需求,从完善制度体系、探索第三方维护维修方案以及依托高校分析测试协会组织优势建立沟通平台几个方面提出了解决方案,以期能够推动建立对供应商服务的评价机制,提升仪器运行维护水平。

移动式高比刚度桁架四通优化设计研究

针对移动式大口径光管,完成了高比刚度桁架四通的详细优化设计。采用有限元法,分析了32组方钢管对应四通的最大形变、最大应力、一阶模态频率、整体质量、光轴偏移角与壁厚的关系,再结合设计指标成功筛选出了最优方钢管的规格型号。同时采用控制变量法,保证质量相同的情况下将桁架式四通与板式四通进行了对比分析,结果表明桁架式相比板式在光轴偏移角上减小了1.15%,一阶模态频率上提高了89.19%,证明了桁架式结构的优越性。通过振动敲击实验测得桁架式四通的一阶模态频率为60.264 Hz,与仿真获得的63.385 Hz基本一致,证明了理论设计与仿真的准确性。通过长距离实际道路稳定性实验证明了该四通可以完全胜任项目的工程需求。

佩戴口罩运动对心率、血氧饱和度及呼气末二氧化碳影响的Meta分析

目的:口罩是阻隔病毒最重要的防线之一,然而日常活动或运动时佩戴口罩对呼吸循环功能的影响尚存分歧。文章运用Meta分析方法综合定量评价佩戴口罩运动中的心率、血氧饱和度和呼气末二氧化碳,探讨在不同强度、时间运动中佩戴不同类型的口罩对人体呼吸循环系统的影响。方法:截至2023年2月,以“口罩,面罩,N95,训练,运动,跑步,步行,自行车”为中文检索词,以“Masks,Respiratory Protective Devices,N95 Respirators,Surgical Face Masks,Exercise,Resistance Training,Explosive training,Muscle Stretching Exercises”为英文检索词在中国知网和Web of Science、PubMed、Cochrane Library、万方网络数据库进行检索,收集佩戴口罩运动对血流动力学指标影响的试验研究。结局指标包括运动中心率、血氧饱和度和呼气末二氧化碳,共3个连续性变量,运用Stata 16.0软件对所纳入文献的结局指标进行分析,以PEDro量表作为质量评估的工具,采用漏斗图进行发表偏倚的分析。结果:共纳入25篇文献,含健康儿童及成年人共857人。PEDro量表评分6分的研究22项,7分的研究2项,8分的研究1项,总体文献方法学质量较高。Meta分析结果显示:①与对照组相比佩戴口罩进行运动对心率影响不显著(SMD=0.02,95%CI:-0.11-0.15,P=0.81),但会提高呼气末二氧化碳水平(SMD=0.60,95%CI:0.37-0.83,P=0.00),降低血氧饱和度(SMD=-0.28,95%CI:-0.47至-0.09,P=0.03);②强度与持续时间是影响研究间异质性的因素,佩戴口罩进行高强度运动会使心率显著升高(SMD=-0.20,95%CI:-0.36至-0.04,P=0.02),高强度、短时间运动对被试血氧饱和度的影响非常显著地高于其他运动(SMD=-0.40,95%CI:-0.70至-0.10;SMD=-0.25,95%CI:-0.45至-0.04);③对于呼气末二氧化碳水平而言,维持一定强度增加运动时间或进一步增加强度,该指标均会显著升高,达到中等效应量(SMD=0.61,95%CI:0.06-1.15;SMD=0.58,95%CI:0.04-1.13)。结论:①现有的证据表明,戴口罩运动可能有增加呼气末二氧化碳、降低血氧饱和度的不良影响。②不同运动测试时间、强度对3个结局指标的影响程度存在差异。③高强度运动中佩戴口罩会显著提升心率并降低血氧饱和度,维持中等强度进行长时间运动或进一步增加运动强度,均会导致呼气末二氧化碳水平增加。

新型球型钢支座耗能减震元件试验研究与数值模拟

在万向减震球型钢支座的基础上对其弹簧元件进行耗能设计,提出了一种新型耗能减震球型钢支座,采用钢板弹簧叠加耗能钢作为耗能减震元件。通过单调拉伸加载试验和循环拉伸加载试验,研究了Q295钢材的耗能能力,采用拟静力试验和数值分析相结合的方法,分析了支座耗能减震元件的滞回性能和自复位性能;将该新型球型钢支座应用于网架结构中,考察其耗能减震能力。研究结果表明,Q295钢材的滞回曲线饱满,具有一定的耗能能力;减震元件的耗能减震性能较好,并且具有一定的复位能力;相较于一般的弹性减震支座,新型球型钢支座可以吸收部分地震能量,从而进一步降低结构的动力响应。

高校分析测试中心建设、管理与运行机制的探讨

分析测试中心是高等院校开展教学科研、科技培训以及社会公共服务工作的主要平台之一。文章结合安徽理工大学分析测试中心的建立、管理与运作的具体实践,分析测试中心的经营管理模式、检测团队管理以及重大仪器设备的运用和管理工作等方面情况,研究了如何最大程度地利用高校分析测试中心的信息平台功能,以充分发挥重大仪器设备的功能,从而更好地为高校教育教学和科研工作以及为社会各界提供优良服务。

高校分析测试中心助力本科生科研兴趣培养的探索

高校作为创新型人才培养的重要基地,应以创新作为大学生培养的核心,注重理论基础的同时,培养学生的创新能力和实践能力。培养学生的科学研究兴趣是培养创新型人才的有效方式之一。高校分析测试中心是师生开展科学研究的重要保障部门,是高校大型仪器资源集中管理的科研平台,配有专业的管理和培训教师,且有涵盖多个领域研究所需的主要仪器,为本科生科学研究兴趣培养提供了优质的资源。扫描电子显微镜作为科学研究的基础表征仪器,选择生活化的实验对象设置简单的演示实验,可以快速地拉近学生与科学研究的距离,提高学生的科学研究参与度,打开学生科学研究兴趣的大门。

重切龙门镗铣加工中心结构静动态特性分析

为了在设计阶段精准评估重切龙门镗铣加工中心结构的动静态特性,建立加工中心整机结构有限元仿真模型,分析其静、动态特性。通过模态测试验证动态仿真模型的准确性和有效性,根据分析结果提出加工中心的结构优化建议。结果表明:由于滑枕的静刚度不足,导致加工中心Y方向的静刚度较低,在1 500 N切削力作用下,最大变形可达0.008 137 mm;加工中心的前6阶实测固有频率分别是41.87、55.69、88.06、103.45、129.68、159.41 Hz,前6阶固有频率的平均仿真计算误差为6.5%,立柱和滑枕位置在外部激振力作用下易发生较大的动态变形响应。