一种三相电路通用电流综合检测方法

提出了一种新的实时检测三相三线制或三相四线制电力系统的基波正序分量、负序分量、谐波分量、有功分量、无功分量的方法。在理论分析的基础上，用MATLAB 6.1对两种电路进行了仿真，理论分析和仿真结果证实了所采用方法的有效性。此方法可广泛应用于有源电力滤波器(APF)和统一电能质量调节器(UPQC)的谐波检测电路。     

一种抗三次谐波干扰的单相锁相环

单相锁相环是电网并机和单相有源滤波器工作的重要环节,在孤立微电网中,由于电流的影响,电网电压常含有大量三次谐波,具有较大畸变。因此,检测母线电压的相位比较困难,从而导致瞬时无功算法和并机算法难以进行。为解决此类问题,本文提出一种单相抗三次谐波锁相环算法,采用DQ正交解耦方法,将三次谐波和基波分离,从而分析各次谐波电压的相位与幅值。通过仿真和试验,证明了算法有效可行,并能完整无误差地跟踪基波电压。     

有源电力滤波器在污水处理厂中的应用

为减少污水处理设备产生的各次谐波,通过确定主要谐波源,检测和计算谐波分量,采用有源电力滤波器进行谐波治理,大幅降低了电力系统中的三相电流畸变率,提高了电能质量;抑制了谐波分量,减少了由谐波引起的电气设备故障,保证了电力系统的正常运行。     

并联型有源电力滤波器线电压控制

有源电力滤波器是一种新型的谐波电流、无功功率和不平衡分量动态补偿设备,由于设备本身高电压大电流高频率控制运行,设备功耗大,稳定温度高.为了保证设备稳定可靠运行,本文定量分析有源电力滤波器功耗,提出改进的线电压控制方法,降低有源电力滤波器的等效控制开关频率,提高了直流侧电压利用率.     

真空自耗电弧炉动态无功补偿和谐波抑制系统

真空自耗电弧炉在熔炼过程中,功率因数低、谐波含量高,严重影响电弧炉稳定生产和电网电能质量。针对真空自耗电弧炉生产过程和熔炼电源特点,开发研制了基于静止无功发生器(SVG)与晶闸管投切滤波器(TS-HPF)混合的动态连续无功补偿和谐波抑制系统。系统智能补偿综合控制器采用数字信号处理器(DSP),通过CAN总线对TS-HPF与SVG的混合投切控制,实现对电弧炉熔炼全过程动态连续无功功率补偿和谐波抑制。实际运行表明,系统可以有效抑制谐波,提高功率因数,改善电网电能质量,对真空自耗电弧炉安全稳定生产具有重要意义。     

大功率整流机组滤波器的参数设计方法

研究了电解铝厂大功率可控整流系统功率因数低下的原因,分析了这种整流机组网侧谐波电流和基波感性电流。根据系统功率因数要求,给出了整流变第三线圈加装PLC型结构的滤波器中电阻、电感、电容三个参数的计算方法,在参数计算方法中着重强调了品质因数Q的选取原则。根据给出的计算公式,计算了某电解铝公司两系列整流机组滤波器参数,并与两个系列整流机组的实践效果进行了对比,从而证明了计算方法的正确性。     

鞍钢17Mn阻尼钢4 ~ 100 mm板的研制

鞍钢研制的 17Mn 阻尼钢(/% ：0.02C, 0.08Si, 17.53Mn, 0.014P, 0.002S, 0.005Als) 4 ~ 100 mm 板,其 屈服强度311 ~4O7 MPa,15~100 mm板-20°C. V型缺口冲击吸收能量113-144 J,焊接后焊接接头抗拉强度651 ~ 654 MPa,焊接后-20 °C V型缺口冲击吸收能量66~84JO 17Mn阻尼钢组织为残余奥氏体和e马氏体,使用动态机 械热分析仪检测其阻尼性能。在30 °C ,50 Hz双悬臂应变扫描条件下,不同厚度阻尼钢阻尼值均大于0.02;在100 Hz 下测试不同厚度阻尼钢阻尼值均大于0.05,阻尼值高于传统的低合金结构钢Q235、Q345(0.008和0.010 ~0.013)。     

有色金属加工企业谐波的产生与治理

滤波器是治理电力系统谐波污染的有效装置。企业装设的滤波器一般有三种，即单调谐滤波器、高通滤波器和C型滤波器。文中分析了各种滤波器的工作特性，认为C型滤波器在有功损耗和对高次谐波的抑制方面有较好的效果。     

电弧炉的谐波抑制措施研究

针对电弧炉在实际应用过程中产生的谐波会对电网造成影响这一问题,围绕电弧炉谐波的产生展开研究,提出采用晶闸管投切电容器（TSC）+有源电力滤波器（APF）综合补偿器来抑制电弧炉谐波,并利用MATLAB搭建仿真模型,分析了TSC+APF在电弧炉谐波抑制效果。     

高次滤波及SVC装置选型方向和注意的问题

简要介绍了相关滤波装置的功能和作用,针对电力网中谐波问题,提出了高次滤波器和静止型动态无功补偿装置(SVC)的选型方向和注意问题。     

Frequency discrimination of stylized synthetic vowels with a single formant

Just-noticeable differences (jnd's) in the center frequency of bandlimited harmonic complexes were measured for normal-hearing subjects. A triangular and a rounded spectral envelope were used. The center frequency ranged from 500 to 600 Hz in a region representing the first formant of vowels, and from 2000 to 2100 Hz in a second formant region. The slope of the spectral envelope was either 50 or 100 dB/oct for the first formant region and 100 or 200 dB/oct for the second formant region. For the fundamental frequency of the complexes 100 and 200 Hz were used. The jnd's were determined for various phase relations between the individual components of the complexes. For comparison we also determined jnd's for a Gaussian white noise that was filtered with the same spectral envelopes as the harmonic complexes. A three-interval, three-alternative forced-choice task was used. All measurements were performed with roving stimulus level. The jnd's found for center frequencies that were halfway between two harmonics were smaller than those found for center frequencies that coincided with a harmonic. The jnd's for the noise bands were mostly between those of the two aforementioned groups. Except for a small group of stimuli, the phase relations had little effect on the jnd's. The majority of the results for both the harmonic and the noise band stimuli can be described by a model using a spectral profile comparison. Most of the remaining data can be explained in the temporal domain from changes in the temporal envelope of the stimuli.     

谐波对硅钢片磁性能的影响

针对电机实际运行过程中存在的谐波环境,对不同谐波条件下无取向硅钢片的磁性能进行了研究。采用w(Si)为3%的高牌号无取向硅钢,在磁性测量设备上设置不同次数的谐波,对其磁性能进行了测试。试验结果表明,相对于正弦波条件下的磁性能,3次谐波能造成铁损明显上升;随着谐波次数的增加,谐波引起的铁损会降低并逐渐趋向稳定,但单次谐波对磁感无明显影响;复合多次谐波增加铁损最为显著,并且降低低场下的磁感。     

Stimulus-induced gamma oscillations: harmonics of alpha activity?

Event-related changes of spectral power of the EEG were studied for each integer frequency between 5 and 100 Hz in three subjects during memory storage and retrieval. Spectra were calculated for successive, overlapping time epochs in seven channels. In one subject a stimulus-locked increase of power was observed at 12 Hz, while in the other two alpha power decreased at the individual peak frequencies of 9 and 11 Hz, respectively. In all subjects corresponding changes of power appeared at frequencies which were integer multiples of the individual dominant alpha frequencies. An analysis of the cross covariance of the alpha, beta and gamma activity revealed high coefficients for harmonic frequencies only while all other covariances were negligibly small. It is argued that event-related gamma activity may be an epiphenomenon of event-related changes within the alpha band.     

Tissue harmonic imaging: why does it work?

The recent utilization of harmonic frequencies in the imaging of both tissue and contrast agents has dramatically improved echocardiographic image quality. In contrast harmonics, the harmonic frequency energy is generated on reflection from the microbubble contrast agent. In tissue harmonics, the harmonic frequency energy is generated gradually as the ultrasonic wave propagates through the tissue. Critical to the utility of tissue-generated harmonic frequencies is their origin beyond the chest wall and their nonlinear relation to the fundamental frequency energy strength. These two characteristics of tissue-generated harmonics ensure that the echoes most likely to produce artifact are least likely to produce harmonic waves. Armed with an understanding of how these images are produced and with data emerging as to their clinical utility, we anticipate that harmonic imaging will become the standard for assessing regional and global left ventricular function in technically difficult studies.     

Simultaneous changes of rhythmic organization in brainstem neurons, respiration, cardiovascular system and EEG between 0.05 Hz and 0.5 Hz

Several neurons from different regions of the brainstem of anesthetized dogs were simultaneously recorded, together with various parameters of the cardiovascular system, respiration, efferent sympathetic neural activities and cortical activity. Often rhythmic changes of activity in the range 0.05-0.5 Hz could be observed in the simultaneously recorded signals. The rhythms were analysed in time domain and by power spectra and their changes depicted over the time. The most striking rhythms between 0.05 Hz and 0.5 Hz are the respiratory rhythm and those rhythms that originate in reticular neurons of the common brainstem system as well as their respective harmonics, i.e. the ranges around the integer multiple frequencies of these basic rhythms. The observed oscillations can vanish and reappear at times. Frequencies of basic oscillations and harmonics and their amplitudes are subject to distinct slow modulations. These modulations can have irregular as well as regular courses. The different rhythms can appear separately or simultaneously in the single signals. The most important phenomenon to be observed is that the rhythms mutually influence their frequencies, which follows the rules of 'relative coordination' as described by E. v. Holst. Such changes of rhythmic activities generally also concern the ranges of harmonics of the basic rhythms. Rhythmic influences on peripheral functional systems, e.g. the cardiovascular system, are most distinct at times when the different rhythms overlap in their frequency ranges. This holds not only for the ranges of basic frequencies, but also for the ranges of their harmonics. Further it was found that rhythms with the same basic frequencies may not only appear simultaneously, but also at various times in the different functional systems. The temporal course of changes of these rhythms, their interactions and their influence on the processing of cardiac rhythmic neuronal discharge patterns is demonstrated. The meaning of the mutually influencing rhythms for the functional organization of central nervous structures is discussed.     

Melatonin in palate tonsils with recurrent acute tonsillitis and tonsillar hypertrophy

In this study we present a method of monitoring the forces under the knees of preterm infants lying in the prone position. Dual force sensing resistor transducers, connected to optically-isolated amplifiers, were used to monitor the forces. A thermistor airflow sensor was used for the parallel monitoring of the respiratory signal. The measurements were made on ten preterm infants. The average forces were 0.51 and 0.50 N for the left and right knees, respectively. In the frequency domain, the basic harmonic of the force traces was 1.27 Hz approximately, corresponding to the respiratory rhythm. Additional, smaller harmonics, were detected in the force traces at 2.54 and 3.81 Hz. A rather notable power signal could also be seen around 0.1 Hz. The results obtained indicate that the system developed is highly sensitive for providing data on the amplitudes, periods and sequences of oscillations and symmetry of load bearing in preterm infants. Knowledge of the normal and abnormal reaction force patterns may assist in the early diagnosis of abnormal neurodevelopment.     

Strategies for harmonic structure discrimination by zebra finches

We trained zebra finches on a go/no-go operant conditioning procedure to discriminate between two harmonic structures that differed only by the presence or absence of the second harmonic. Test sessions revealed that the birds responded to probe stimuli based on the presence or absence of the second harmonic regardless of the other frequency components. Some of the birds also tended to use the fundamental frequency as a discriminative cue when the number of harmonics was few. These results indicate that birds use multiple strategies for this type of harmonic structure discrimination.     

Sequential stream segregation in the absence of spectral cues

This paper investigates the cues used by the auditory system in the perceptual organization of sequential sounds. In particular, the ability to organize sounds in the absence of spectral cues is studied. In the first experiment listeners were presented with a tone sequence ABA ABA ..., where the fundamental frequency (f0) of tone A was fixed at 100 Hz and the f0 difference between tones A and B varied across trials between 1 and 11 semitones. Three spectral conditions were tested: pure tones, harmonic complexes filtered with a bandpass region between 500 and 2000 Hz, and harmonic complexes filtered with a bandpass region chosen so that only harmonics above the tenth would be passed by the filter, thus severely limiting spectral information. Listeners generally reported that they could segregate tones A and B into two separate perceptual streams when the f0 interval exceeded about four semitones. This was true for all conditions. The second experiment showed that most listeners were better able to recognize a short atonal melody interleaved with random distracting tones when the distracting tones were in an f0 region 11 semitones higher than the melody than when the distracting tones were in the same f0 region. The results were similar for both pure tones and complex tones comprising only high, unresolved harmonics. The results from both experiments show that spectral separation is not a necessary condition for perceptual stream segregation. This suggests that models of stream segregation that are based solely on spectral properties may require some revision.     

Timbre control in zebra finch (Taeniopygia guttata) song syllables.

Zebra finch (Taeniopygia guttata) song syllables often include harmonically related frequency components. These harmonics may be suppressed, and this differential emphasis varies between the syllables in a song and between individual birds' songs. These patterns of harmonic suppression are timbre. Individual syllables' patterns of harmonic suppression are constant within adult males' songs. Young males that imitate the songs of older males also imitate their patterns of harmonic suppression. Syringeal denervation distorts these patterns, which suggests that they are produced through active control of the vocal organ. The selective suppression and emphasis of some harmonics creates a great number of possible timbre variants for any one syllable. These add signal diversity to the limited array of frequency modulations and range of fundamental frequencies found in zebra finch song. Analyses of bird song that disregard timbre may overlook a feature that is important in vocal communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The surface epithelium of recurrent infected palatine tonsils is rich in gammadelta T cells

Thresholds for detecting alterations in the timbre and harmonicity of complex harmonic signals were measured in zebra finches, budgerigars, and humans. The stimuli used in this experiment were designed to have particular salience for zebra finches by modeling them after natural zebra finch calls. All 3 species showed similar abilities for detecting an amplitude decrement in a single component of a harmonic complex. However, zebra finches and budgerigars were extraordinarily sensitive to the mistunings of single harmonics and exhibited significantly lower thresholds compared with humans at 2 different fundamental frequencies, 570 Hz and 285 Hz. Randomizing relative phases of components in a harmonic stimulus resulted in a significant increase in threshold for detecting mistunings in zebra finches but not in humans. Decreasing the duration of mistuned harmonic stimuli resulted in higher thresholds for both birds and humans. The overall superiority of birds in discriminating inharmonicity suggests that birds and mammals may use different strategies in processing these complex harmonic sounds.