Effect of Sea Level Variation on Tidal Characteristic Values for the East China Sea

Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is compared with the harmonic analysis result of hourly sea level data from 19 tide gauges for more than 19 years. It is indicated that the long-term mean sea level variation affects notably tidal waves in this region. Generally, the tidal amplitude increases when the mean sea level rises, but this relationship may be inverse for some sea areas. The maximal variation of tidal amplitude takes place in the zones near the Fujian coast and the Zhejiang coast, rather than the shallowest Bohai Sea. The maximum increase of M2 amplitude can exceed about 15 cm corresponding to the 60 cm rise of the mean sea level along the Fujian coast. The other regions with large variations of tidal amplitude are those along the Jiangsu coast, the south-east coast of Shandong, and the south-east coast of Dalian. The propagation of tidal waves is also related to mean sea level variation, and the tidal phase-lag decreases generally when the mean sea level rises. Almost all the regions where the tidal phase-lag increases with rising mean sea level are close to amphidromic points, meanwhile the spatial area of such regions is very small. Because the influence of mean sea level variation upon tidal waves is spatially marked, such spatial effect should be considered in calculation of the tidal characteristic value and engineering water level. In the region where the amplitudes of the major tidal constituents increase, the probable maximum high water level becomes higher, the probable maximum low water level becomes lower, and both design water level andcheck water level increase obviously. For example, the design water level at Xiamen increases by 13.5 cm due to the variation of tidal waves when the mean sea level rises 60 cm, the total increase of design water level being 73.5 cm.

Surface tidal currents in the open sea area to the east of the Zhoushan Islands measured with high frequency surface wave radar

Based on the quasi-harmonic analysis of 11 d vector ocean currents obtained from two high frequency sur- face wave radars located at Zhujiajian Island and Shengshan Island, the spatial distribution characteristics of surface tidal currents in the open sea area to the east of the Zhoushan Islands of Zhejiang Province, China are studied. The following conclusions are drawn from the analysis： the tidal current pattern in the open sea area to the east of Zhoushan Islands is primarily regular semidiurnal, which is significantly affected by the shallow water constituents. The directions of the major axes of tidal current ellipses of M2 lie approx- imately in the NW-SE direction. With the increasing of distance away from the coast, the directions of the tidal current ellipses gradually shift toward the E-W direction. The tidal currents are mainly reversing cur- rents. The spatial distribution of probable maximum current velocities decreases gradually from northeast to southwest which is basically in accordance with the spatial distribution of measured maximum current velocities. The residual currents near the coast are larger than those far away from the coast. The directions of the residual currents are basically north by east, and the angle to the due north increases gradually with the increasing distance away from the coast. The topography shows a certain impact on the spatial distri- bution of shallow water constituents, the rotation of tidal currents, the probable maximum currents and the residual currents.

Spatial Distribution Characteristics of Surface Tidal Currents in the Southwest of Taiwan Strait

This study was conducted on the spatial distribution characteristics of surface tidal currents in the southwestern Taiwan Strait based on the quasi-harmonic analysis of current data obtained by two high frequency surface wave radar(HFSWR) systems. The analysis shows that the tidal current pattern in the southwestern Taiwan Strait is primarily semi-diurnal and influenced significantly by shallow water constituents. The spatial distribution of tidal current ellipses of M2 is probably affected by the interaction between two different systems of tide wave, one from the northern mouth of Taiwan Strait and the other from the Bashi Channel. The directions of the major axes of M2 tidal current ellipses coincide roughly with the axis of the Taiwan Strait. The spatial distribution of the magnitudes of the probable maximum current velocity(PMCS) shows gradual increase of the velocity from northeast to southwest, which is in accordance with the spatial distribution of the measured maximum current velocity(MMCS). The directions of the residual currents are in accordance with the direction of the prevailing monsoon wind at the Taiwan Strait and the direction of the Taiwan warm current during summer. The bathymetry also shows a significant effect on the spatial distribution characteristics of tidal currents.

On electro-acoustic characteristics of a marine broadband sparker for seismic exploration

The construction of major marine infrastructure projects and the exploration and development of deep-sea mineral resources require fine imaging of seabed strata and structures.The highresolution marine seismic exploration based on a high broadband sparker source is an important approach to reveal seabed stratum and reservoir structure,and identify geohazard.To optimize the performance of sparker seismic source,we investigated the electro-acoustic characteristics of spark discharge under conditions of different charging voltages and electrode numbers.Results show that the sound source level increased with the increase of the charging voltage,whereas the main frequency decreased when the charging voltage increases.In addition,it was found that the charging capacitance had more obvious influence on the main frequency than the sound source level did.Although the load energy decreased with increasing electrode number,the sound source level still increased but the main frequency decreased.Meanwhile,the primary to bubble(P/B)ratio increased with the increase of the electrode number.To gain a deeper insight into the electro-acoustic characteristics,we investigate the relationship between sound source level and power peak,from which a good correlation was observed.A more practical statistical analysis on the rise rate of current was processed,and a perfect logarithmic function was derived.Furthermore,we found that the main frequency was most possibly subjected to the electrical energy,especially the charging energy per electrode.The results indicate that the charging energy per electrode less than 10 J could increase the main frequency to above 300 Hz.At last,the main frequency could be reduced to 20 Hz when the charging energy of a single-electrode discharge was enhanced to over 4 kJ.This study shall be helpful in developing a sparker seismic source and improving the performance for marine engineering exploration and geohazard assessment.

Tidal characteristics near the Chinese Zhongshan Station in Prydz Bay, East Antarctica

A permanent tidal station was installed at the Chinese Zhongshan Station in Feb. 2010. Harmonic constants of 170 tidal constituents were obtained from harmonic analysis of the first year＇ s data. The results of the eight main constituents showed good agreement with those of two tidal models. Tidal characteristics, such as tide type, diurnal inequality, tidal range, and water levels were also analyzed.

天然气输气站管道噪声特性实验研究

为厘清天然气输气站管道噪声特性,基于一维麦克风阵列测试原理,搭建天然气输气站管道噪声测试系统,设计不同输气流量、不同管道组合下的输气工艺测试工况。通过测试对比和分析可知,输气站支路管道噪声在频域上主要分布在3个特征频段上,在沿管道输气传输方向的空间内整体呈“M”型分布;随着输气流量的增大,输气管道噪声频率特性基本保持不变,但其总声压级有所提升;不同供气支路组合下其噪声总声压最大可相差2.8 dB,因此可以通过调整输气工艺,实现相对较低的天然气输气站噪声运行环境。

数字影厅B环电声响应技术标准解析和调试方法探讨

数字影厅B环电声响应特性是指数字影院音响系统对电信号的响应情况。本文首先概述数字影厅B环电声响应特性相关技术标准,对GY/T 312—2017《电影录音控制室、室内影厅B环电声响应规范和测量》中涉及的核心技术条款进行解读,总结调试和测量过程中遇到的问题,最后提出一种合理的B环电声响应调试方法,以期为数字影厅相关调试提供技术保障,推动国内数字影厅整体还音技术良性健康有序发展。

长江口综合整治工程前后潮汐特征分析

利用改进的Godin潮汐调和分析及预报程序,对长江口北槽附近横沙和北槽中两验潮站的潮位资料进行调和分析,得到不同年份不同时段11个分潮的振幅H、迟角g、平均海平面值Z0以及各站的特征潮位.根据计算结果比较长江口综合整治工程前后横沙站和北槽中站各主要分潮(M2,S2,K1,O1)调和常数的变化,分析综合整治工程前后特征潮位的变化趋势;利用工程前的潮汐调和常数预报2002年、2003年和2006年横沙和北槽中两验潮站的潮位过程,对预报潮位过程和实测潮位过程进行比较.分析结果表明,两站主要分潮的调和常数、特征潮位以及潮位过程,在整治工程后特别是2003年和2006年发生了较明显的变化.

变化环境下的钱塘江河口潮位特性及其影响因素

利用钱塘江河口沿程的闸口、七堡、仓前、盐官、澉浦和乍浦等7个潮位站的实测资料,分析了1953～2007年各站年最高潮位、年平均高潮位、年平均低潮位的不同变化特性,并对主要的影响因素进行了分析。线性拟合结果表明,自20世纪50年代以来,钱塘江河口沿程各潮位站年最高潮位抬升幅度达0.57～1.05m,其中七堡站年最高潮位抬升值最大;年最高潮位显著抬升的时间主要发生在20世纪90年代后,该时段年最高潮位抬升值占年最高潮位总抬升值的70.5%～92.6%,极值潮位出现频率显著增加。分析表明,1990年后钱塘江围垦面积仅占总围垦面积的21.6%,因此河口围垦不是造成年最高潮位抬升的唯一因素,而影响浙江的台风频次增多及围垦造成的潮波反射加剧是造成高潮位抬升的主要原因。钱塘江河口年平均高潮位的沿程变化出现趋势性的抬升现象,各站年平均高潮位抬高幅度接近,为0.43～0.49m,但不同潮位站因与围垦河段的相对位置不同,年平均高潮位抬升的历史过程存在明显差异。河口下游段的澉浦、乍浦站年平均高潮位呈现单一的抬升趋势,且与河口逐年累计围垦面积存在很好的相关关系(相关系数大于0.95);而河口上游段的闸口—盐官河段则以1970年为界,年平均高潮位明显有两次抬升过程,受围涂进程影响的机制比较复杂。钱塘江河口年平均低潮位多年来维持在一个相对稳定的水平上,但沿程年际间平均低潮位的变化却不相同。河口上游段的潮位站受径流丰枯及其引起的江道冲淤影响,年平均低潮位年代际呈现出波动的特性;澉浦以下的潮位站年平均低潮位受潮汐控制为主,年代际变化幅度甚微。钱塘江河口不同河段因受径流、潮流、治江围垦等因素的影响程度不同,其潮位特征值沿程的变化特点也不同,需要在河口工程设计、防洪减灾与河口治理等方面引起重视。

杭州湾潮汐特征时空变化及原因分析

杭州湾是世界著名的强潮河口湾,一直是研究的热点。基于杭州湾口内外实测潮汐资料,对杭州湾潮汐特征及时空变化进行了系统分析,包括高潮位、低潮位、平均潮位、潮差、涨潮历时以及天文潮变化,同时分析了20世纪80年代以来潮汐特征变化的原因。结果表明:最近50年来,杭州湾年平均高潮位和海平面抬高,潮差增大;澉浦年平均低潮位抬高,涨潮历时缩短,浅海分潮增大;钱塘江河口治江缩窄是造成杭州湾潮汐变化的主要因素;浙江和邻近海域的涉海工程可能是造成浙江沿海海平面上升的主要原因之一。

设计潮位计算中若干问题探讨

针对感潮河段潮位序列的不一致现象,提出了一种通过提取序列趋势项进行资料一致性修正的方法。针对低潮位系列容易呈“负偏态”分布的事实,介绍了负偏态潮位系列的频率计算方法,提出了一种融入更多潮位过程特征信息的设计潮位过程推求方法,以长江口天生港、徐六泾、外高桥潮位站为例,采用上述方法计算了典型站的设计潮位和设计潮位过程。研究表明,所提出的方法概念清楚、计算简便、适用性强,对类似潮汐河口设计潮位和设计潮位过程计算具有参考意义。

塔河油田石炭系卡拉沙依组沉积与成因分析

综合古生物、测井、岩心、地震、地化等资料 ,对塔河油田石炭系卡拉沙依组砂泥岩段沉积特点及成因的分析表明该组砂岩总体具有向上变粗变厚的进积式沉积序列 :上部的Ⅰ -Ⅲ油组主要为河流相 ,下部Ⅳ -Ⅴ油组为受潮汐影响的扇三角洲前缘和平原相。该组受潮汐影响体现在 :(1)富含陆相轮藻化石 ,并见个别半咸水介形虫类和疑源类微体化石 ;(2 )局部有波状、透镜状层理、生物扰动层理和冲刷充填层理 ;(3)该组底部泥岩的锶钡比值介于 0 0 2 1～ 0 716 ,具半咸水 -微咸水 -淡水的变化特点 ;(4 )Ⅳ -Ⅴ油组总体处于巴楚组双峰灰岩潮坪相到Ⅰ -Ⅲ油组河流相沉积的过渡相中。

花岗岩单轴受压条件下声发射信号频率特征试验研究

研究分析破裂过程不同阶段的声发射信号频率特性,对于选出相应谐振频率的声发射传感器具有重要意义。通过单轴压缩试验,结果表明:花岗岩受压过程中主要经历3个受力阶段,声发射振铃计数率随相对应力的增加呈现出阶段性的变化规律,声发射信号优势频率主要发生在岩石破裂前塑性破坏和主破裂阶段,且集中在41～85kHz。在相对应力较低时,花岗岩声发射信号频率以低频为主,随着相对应力的增加,其高频、低频信号密集且幅值很大,因此高频高幅值声发射信号的突然增多预示花岗岩有破坏危险。

水淹对红花玉蕊幼苗生长及生理特性的影响

为揭示淹水胁迫对淡水红树植物红花玉蕊的生长及生理特性的影响,获得红花玉蕊在10‰盐水淹浸时适生的水位范围。模拟半日潮,每天在温室分别以不同水位(不淹、淹浸至地径、淹浸至枝下高、全淹)对2年生红花玉蕊实生苗进行不同水位淹浸胁迫处理6h,以不淹为对照(CK),处理后每7d调查各处理幼苗的形态指标,第10天取样测定各处理的超氧化物歧化酶(SOD)、过氧化物酶(POD)活性、丙二醛(MDA)和脯氨酸(Pro)含量,综合分析红花玉蕊的耐水淹能力。结果表明,10‰盐水淹浸幼苗10d后,红花玉蕊幼苗无死亡株,幼苗株高及地径均有所增长,淹浸至地茎、枝下高2种水位均对株高、地径、叶片的生长起促进作用,全淹时均有所抑制,不利于幼苗正常生长。在生理指标上,随着淹浸水位的不断升高,幼苗叶片的SOD酶活性逐渐增高,全淹较对照呈显著差异(P<0.05);POD酶活和丙二醛含量均是先升高后降低,脯氨酸含量先降低后急剧升高,全淹较CK呈极显著差异(P<0.01)。综合分析得知,适当水位的盐水淹浸有利于红花玉蕊的生长,其在10‰盐水淹浸胁迫下主要通过快速增加脯氨酸含量来维持细胞正常的渗透压,同时启动SOD酶、POD酶以清除活性氧对植株的损伤,而后开始适应外界淹水环境。红花玉蕊幼苗在10‰盐水环境下最佳淹水水位为淹浸至地径,适生水位范围是不淹至枝下高。

江苏海岸港口特征潮位计算与分析

利用潮汐调和分析程序对江苏海岸6个港口2001年4～6月份的高低潮位资料进行调和分析，得出了11个分潮的调和常数、平均海平面和特征潮位，并进行了一致性验证．利用预报程序预报了2000-2005年的时序潮位和高、低潮位，所得结果与潮汐表预报潮位基本一致．利用预报结果计算了工程设计高、低潮位，时序潮位累积频率99％对应的潮位与低潮位序列数据累积频率90％对应的潮位一致．根据特征潮位数据拟合出了各验潮站特征潮位间的关系表达式．

井水位的振荡与地震波

利用弹性理论和渗流理论研究了井水位振荡试验 ,给出了一种计算水井含水层频率特性参数 (固有振动周期和阻尼系数 )的新方法 ,对 5口水井进行SLUG试验 ,计算水井含水层的固有振动周期和阻尼系数 ,分析了水井对地震波响应的规律和内在联系。水井含水层系统对地震波的响应主要取决于水井含水层系统的固有振动周期和振动的阻尼系数 ,固有振动周期越是接近地震波—瑞利波的振动周期 2 0s ,振动的阻尼系数越小 ,它对地震波的响应越好 ,水井含水层系数的渗流特性越好 ,渗透系数越大 ,对水振动的阻尼系数越小 ,它对地震波的响应越好。

三角洲感潮河段洪潮水位频率分析方法的初步研究

根据珠江三角洲感潮河段年最高洪潮水位存在长期上升趋势的事实 ,提出了河口区感潮河段洪潮水位频率分析一种新的计算方法 ,新方法的分析结果表明 ,未来不同年代同频率的设计洪潮水位各不相同 ,也存在相应的长期变化趋势。以灯笼山站为例 ,新方法计算的 2 0 30年和 2 0 5 0年的百年一遇设计洪潮水位分别为 3 12m和3 2 8m ,比传统频率分析方法计算的结果分别高出 0 2 4m和 0 40m。建议有关部门在制定河口区的防洪标准时 ,根据洪潮水位的长期变化趋势作相应的动态调整 。

地铁运营引起的环境低频振动传播特征试验研究

为了分析地铁运营造成的环境低频（〈20 Hz）振动,进行试验室低频振动试验研究。通过试验获得离散频率（5-16 Hz）简谐荷载下隧道内、地表和建筑物内的振动加速度信号,并对其进行预处理和归一化处理,从时程与频谱、加速度级和传递函数3个方面,分析低频振动在隧道结构、地表和建筑物内的传播特征。结果表明：隧道结构低频振动表现为整体振动,地表低频振动以竖向为主,而建筑物内的低频振动以水平方向为主;地表竖向低频振动随着距轨道水平距离的增加而衰减较快,水平低频振动在距轨道0-40 m范围内出现放大,40 m之外衰减较缓;建筑物内的水平低频振动,在10 Hz以下随着楼层的升高而增大,而在10-16 Hz时随着楼层的升高而减小;隧道基底到地表的竖向传递函数值随着距轨道水平距离的增加而逐渐减小,但随频率变化不大,在5-16 Hz范围内的传递函数值为0-0.5。

上海洋山深水港区水文泥沙特征分析

根据现场水文测验资料,对上海洋山深水港区的潮位、流速、流向、含沙量的变化规律进行了分析,为优化工程方案和设计提供科学依据。

级联多电平逆变器的频谱分析及滤波器设计

为解决级联多电平技术过大的电压变化率和相对集中的高次谐波的问题,通过计算机仿真技术,深入比较了几种典型拓扑结构的逆变器输出电压谐波的频谱,分析了基于载波组SPWM调制技术的级联多电平逆变器输出电压的谐波特征后,针对该结构电压谐波的特点,提出一种级联多电平逆变器的LC滤波器设计方法并给出了电抗参数和电容参数的具体设计原则和方法。该方法综合考虑了滤波器频率特性和功率因数等要素,通过仿真实验证明,通过该方法选择的滤波器参数满足系统各方面的要求,达到预期的滤波效果,对于不同功率因数的负载,均有很好的滤波效果,并提高了系统的功率因数。