Demystifying endodontic diagnosis

Hygienic evaluation covered work conditions on 4 gold mines including 3 ones for gold and arsenic and one "arsenic-free". The mines demonstrated similar occupational factors, but differed in arsenic content of the ore extracted and therefore in arsenic concentrations in air of the workplaces. Miners engaged into extraction of the arsenic-containing ore, especially those exposed to vibration and arsenic concentrations over the MAC, manifest extensive arsenic accumulation in the hair and excretion with the urine, higher morbidity with transitory disablement, more prevalent vibration disease and mortality with malignancies. Vibration disease in those subject has more severe course, serious vegetative and sensory polyneuropathy, that is believed to result from co-action of vibration and arsenic.     

Analysis of pathological vocal fold vibrations using high-speed digital imaging

There have been various methods devised to monitor vocal fold vibration. Stroboscopy provides clinically-celevant information concerning pathology of the vocal folds. However, slow motion observation is based on the regularity of the vibration, and this ignores the role of irregularity of the vocal fold vibration in pathological cases. In order to know more about the nature of the vocal fold vibratory pattern, it is essential to monitor the vibration on a cycle by cycle basis. We analysed vocal fold vibrations of 22 pathological larynges using a computer-assisted high-speed digital imaging technique. Observed items included symmetry, regularity, phase difference, glottal closure, amplitude, mucosal wave and periodicity difference. Vibratory patterns were classified by location of lesion, severity of disease, expiratory pressure and laryngeal modulation. Analyses of pathological vocal fold vibrations using high-speed digital imaging techniques are providing the theoretical support for voice therapy and elucidating the causes of hoarseness.     

Problem of orthostatic intolerance in astronauts and perspectives for its pharmacological prevention

The article presents results of immunologic studies in 111 vibration disease sufferers with variable exposure, age, sex and severity of disease. The examinees were proved to have depressed cellular immunity--lower E-RFC count with decreased number of active E-RFC and levamisole--correctable modifications of T-cells; inhibited humoral immunity--lower levels of IgM, IgG, IgA; contradictory changes of neutrophils functions--depressed phagocytosis and metabolic activity with pronounced rosette formation; halted immune factors of saliva.     

Lymphoedema and chylo-ascites; an unusual complication of lymphography

The authors carried out experiments on animals (40 white male rats) which were subjected to daily a two-hour action of the common vertical sinusoidal vibrations with a frequency of 20 Hr (I group) and 50 Hr (II group) with acceleration of 22,0 m/sec2 for a period of ten days (I group--A and second group--A) and 30 days (I group--B and II group--B). Histomorphological and histochemical methods were used and the authors found changes in microcirculation and structure of the intestinal wall manifested in the animals of the II group. The obtained results were in support of the clinical data on the disturbances in intestinal function in patients with vibration disease and corresponded to the experimental data on the occurrence of vascular and dystrophic changes in the internal organs under vibration action.     

振动布料机入口流量及其最佳激振力

 针对钢铁厂固体废料综合利用处理系统中振动布料系统的激振力与入口流量不匹配时易造成球团矿在振动箱体内逐步堆积或者输送效果不理想这一问题,根据振动布料机的结构参数、入口流量、球团矿参数及转底炉参数,建立了入口流量与激振力的数学模型,进而求得了不同入口流量的最佳激振力,并进行了试验验证。试验结果表明：在给定布料厚度下,小于最佳激振力时,球团矿在振动箱体内会逐步堆积;大于最佳激振力时,球团矿在振动箱体内分布疏松,效果不理想;采用最佳激振力时,球团矿在振动箱体内分布较为均匀,输送稳定,与理论计算结果相符。     

1580热连轧机F2精轧机振动综合测试与分析

 针对迁钢1580热连轧生产线F2轧机在轧制薄规格产品时频繁出现的异常振动现象,组织了对其扭振、垂振及水平振动的综合测试。分析表明:轧机扭振和垂振是受迫振动,激励来自工作辊水平振动,工作辊轴承座衬板与机架衬板间间隙过大是造成轧机振动的直接原因,提出了减小工作辊轴承座与机架间间隙的振动抑制方案。现场对工作辊轴承座分别加装0.3和0.7mm两种规格的衬板垫片进行了试验,测试信号显示异常振动明显减弱甚至消失,效果令人满意。     

基于无线传感器扭矩检测的轧机扭振前馈控制

 针对轧机轧辊反复正反转咬钢抛钢受到突然强有力的冲击时扭振现象极为严重的情况,研究采用扭矩无线传感器实时采回负载干扰值,解决了现有的扭振抑制方法中采用扭振预估器计算扭振时容易出现偏差的问题;利用前馈能在扰动发生时提前做出干扰补偿的原理,在大型轧机交交变频调速系统定子转矩电流与转速双闭环的基础上,在转矩控制器的输入端加入负载扭矩扰动补偿,提前控制定子电流转矩分量而达到控制扭振的目的,并用Simulink对上述过程进行仿真。结果表明：基于无线传感的扭振前馈抑制方式对扭振的控制效果非常明显,几乎可以彻底消除扭振,更贴近实际。     

CMV retinitis: ganciclovir/monoclonal antibody

Points of subjective equality between continuous vibration and shock-type vibration (repeated vibration) were examined in hand-transmitted vibration to find a tendency of human response to shock-type vibration (repeated vibration with short duration). On time and off time of the repeated vibrations were changed from 10 ms to 5s. Each adjustment involved a 10 second exposure to the repeated vibration and subsequent 10 second exposure to the continuous vibration. Frequencies of the vibrations were 8, 16, 31.5 and 100 Hz. Subjective magnitude of the shock-type vibrations (repeated vibrations) decreased with increase of off-time and with decrease of on-time of the repeated vibrations. Results of this experiment were compared with calculated r.m.s. values, r.m.q. values and other quantity. R.m.s. values underestimated the repeated vibration and r.m.q. values overestimated the vibration compared with human responses.     

2160 mm热连轧机组F2精轧机振动机理及测试

针对2160 mm热连轧机组第2架精轧机（F2）在轧制薄规格产品时频繁发生振动的问题,对该轧机开展了综合测试。介绍了振动现象,分析了振动类型。考虑轧制界面动特性,建立了新的轧制界面摩擦力模型,表征了界面的正负阻尼作用。在此基础上,考虑上下辊系不同运动状态构建了轧机扭转和水平方向的耦合振动模型。基于上述模型,模拟了轧机的自激振动,仿真结果表明,轧机振动形式为上下工作辊扭转和水平方向均反向运动,振动频率为扭转一阶固有频率,与现场测试现象相符合。最后分析了轧制工艺参数对轧机自激振动的影响,并提出了相应的可行抑振方案。     

热连轧机水平振动及其与轧制参数影响关系

 研究了热连轧机轧辊水平振动机制、水平振动与轧制过程参数间的影响关系。考虑间隙、轧辊偏移距和非线性阻尼等影响因素,建立了板带轧机工作辊水平振动非线性动力学模型,同时建立了轧机水平振动与轧制过程参数的关系模型。对某厂热连轧机F2机座进行水平振动测试试验,工作辊水平振动剧烈,中后期振幅达到4.5 g,甩尾时超过5 g,振动优势频率为40和118 Hz;同时对振动过程进行仿真,研究了轧件厚度、轧制速度和张应力参数对水平振动的影响。结果表明：仿真分析水平振动加速度幅值达到4.8 g,对比仿真和实测的振动曲线,可知仿真与实测结果相符;轧件的厚度越薄,对轧辊振动影响越大;轧制速度变化对水平振动影响较大;相比其他因素,张力对轧机水平振动的影响较小。     

Evaluating the effectiveness of gloves in reducing the hazards of hand-transmitted vibration

OBJECTIVES: A method of evaluating the effectiveness of gloves in reducing the hazards of hand-transmitted vibration is proposed. METHOD: The glove isolation effectiveness was calculated from: (a) the measured transmissibility of a glove, (b) the vibration spectrum on the handle of a specific tool (or class of tools), and (c) the frequency weighting indicating the degree to which different frequencies of vibration cause injury. With previously reported tool vibration spectra and glove transmissibilities (from 10-1000 Hz), the method was used to test 10 gloves with 20 different powered tools. RESULTS: The frequency weighting for hand-transmitted vibration advocated in British standard 6842 (1987) and international standard 5349 (1986) greatly influences the apparent isolation effectiveness of gloves. With the frequency weighting, the gloves had little effect on the transmission of vibration to the hand from most of the tools. Only for two or three tools (those dominated by high frequency vibration) did any glove provide useful attenuation. Without the frequency weighting, some gloves showed useful attenuation of the vibration on most powered tools. CONCLUSIONS: In view of the uncertain effect of the vibration frequency in the causation of disorders from hand-transmitted vibration, it is provisionally suggested that the wearing of a glove by the user of a particular vibratory tool could be encouraged if the glove reduces the transmission of vibration when it is evaluated without the frequency weighting and does not increase the vibration when it is evaluated with the frequency weighting. A current international standard for the measurement and evaluation of the vibration transmitted by gloves can classify a glove as an antivibration glove when it provides no useful attenuation of vibration, whereas a glove providing useful attenuation of vibration on a specific tool can fail the test.     

12MW凝汽式汽轮机组振动分析与处理

针对莱钢12MW汽轮发电机组的振动问题,通过振动信号的现场数据采集与分析技术,找出机组振动的根本原因并对其处理,从而将振动控制在合格范围之内。     

CSP轧机垂振对水平振动影响仿真研究

CSP轧机振动问题是世界范围内轧制领域的重大难题之一。使用快速反应遥测系统对轧机进行了振动综合测试,捕捉到了振动的特征及规律。利用ANSYS的谐响应分析模块及瞬态分析模块对轧机进行了仿真研究,确定了垂振对水平振动的影响,得出了有益的结论。     

灰色关联分析法在爆破震动监测中的应用

以国内某大型露天矿山15组爆破设计参数和爆破震动测量数据为依据,基于灰色关联分析法理论基础,计算得出爆破特征变量震动速度、震动主频、震动时间与爆破设计参数最大单段药量、总药量、爆心距之间的灰色关联度,成功预测各参数对爆破震动影响的主次关系。该矿山爆破影响震动速度和震动时间的主要因素为爆心距,影响震动主频的主要因素为最大单段药量。预测结果可为该矿山今后控制爆破震动提供理论依据。     

爆破振动影响下人体舒适度振动台试验及其评价体系构建

针对现有爆破振动影响下人体舒适度评价体系中人体主观感受的不确定性,通过振动台模拟爆破振动开展人体振动反应试验,结合人体心电指标,分析爆破振动参数、心电指标以及人体主观感受的量化关系,构建爆破振动影响下人体舒适度评价体系.研究结果表明:竖直方向是影响人体舒适度的主要振动方向,且振动对人体的影响与人体主要震感部位有关,主要震感部位从脚部到头部上移时,影响也逐渐增大;随着振动频率和速度的增加,人体心电指标相邻RR间期之差的均方根(RMSSD)在竖直方向振动下呈现出先减小后增大的趋势,在水平方向振动下则一直减小,但减小的幅度有限;RMSSD的下降比例与爆破振动参数以及人体主观感受之间存在定量关系,利用三者之间的定量对应关系可实现爆破振动影响下的人体舒适度定量评价;爆破施工时,可将0.7 cm·s^-1的地表竖直方向振动速度和80 Hz的振动频率作为邻近人群密集区域爆破工程的控制阈值.     

Haemodynamic changes in ipsilateral and contralateral fingers caused by acute exposures to hand transmitted vibration

OBJECTIVES: To investigate changes in digital circulation during and after exposure to hand transmitted vibration. By studying two frequencies and two magnitudes of vibration, to investigate the extent to which haemodynamic changes depend on the vibration frequency, the vibration acceleration, and the vibration velocity. METHODS: Finger skin temperature (FST), finger blood flow (FBF), and finger systolic pressure were measured in the fingers of both hands in eight healthy men. Indices of digital vasomotor tone-such as critical closing pressure and vascular resistance-were estimated by pressure-flow curves obtained with different hand heights. With a static load of 10 N, the right hand was exposed for 30 minutes to each of the following root mean squared (rms) acceleration magnitudes and frequencies of vertical vibration: 22 m.s-2 at 31.5 Hz, 22 m.s-2 at 125 Hz, and 87 m.s-2 at 125 Hz. A control condition consisted of exposure to the static load only. The measures of digital circulation and vasomotor tone were taken before exposure to the vibration and the static load, and at 0, 20, 40, and 60 minutes after the end of each exposure. RESULTS: Exposure to static load caused no significant changes in FST, FBF, or indices of vasomotor tone in either the vibrated right middle finger or the non-vibrated left middle finger. In both fingers, exposure to vibration of 125 Hz and 22 m.s-2 produced a greater reduction in FBF and a greater increase in vasomotor tone than did vibration of 31.5 Hz and 22 m.s-2. In the vibrated right finger, exposure to vibration of 125 Hz and 87 m.s-2 provoked an immediate vasodilation which was followed by vasoconstriction during recovery. The non-vibrated left finger showed a significant increase in vasomotor tone throughout the 60 minute period after the end of vibration exposure. CONCLUSIONS: The digital circulatory response to acute vibration depends upon the magnitude and frequency of the vibration stimulus. Vasomotor mechanisms, mediated both centrally and locally, are involved in the reaction of digital vessels to acute vibration. The pattern of the haemodynamic changes in the fingers exposed to the vibration frequencies used in this study do not seem to support the frequency weighting assumed in the current international standard ISO 5349.     

AIDS caregiving and health among midlife and older women

OBJECTIVES: This study investigated changes in finger circulation after different durations of exposure to hand-transmitted vibration. METHODS: Finger skin temperature (FST), finger blood flow (FBF), and finger systolic blood pressure (FSBP) were measured in the middle fingers of both hands of 10 healthy men. Finger vascular resistance was also estimated. The right hand was exposed for 7.5, 15, and 30 minutes (static load 10 N) to 125-Hz vibration (root-mean-square acceleration 87 m/s2). Static load only was used as a control. Finger circulation was measured before the vibration and static load exposure and at fixed intervals during exposure and a 45-minute recovery period. RESULTS: No significant changes were found with the static load. The FST and FSBP did not change significantly during vibration exposure, whereas vibration produced significant reductions in FBF and increases in vascular resistance at each duration when compared with preexposure and contralateral (non-vibrated) finger values. Temporary vasodilation occurred in the vibrated finger immediately after each vibration exposure. Recovery was complete for FBF and vascular resistance after the 7.5-minute vibration, whereas a progressive FBF reduction occurred in both the vibrated and the nonvibrated fingers after 15- and 30-minute exposure. The longer the duration of vibration exposure, the stronger the vasoconstriction in the vibrated finger during recovery. CONCLUSIONS: Vasoregulatory mechanisms mediated by both intrinsic (local) and extrinsic (neural or endocrine) control systems seem to be related to digital circulatory changes during 125-Hz vibration. It is concluded that, not only the frequency and magnitude of vibration, but also its duration contributes to the reaction of the digital vessels to acute vibration.     

压力管道振动原因分析及对策

本文实例分析了压力管道振动的主要原因。提出消除振动的主要对策,包括避免固有频率接近引起的谐振、减少压力脉动及接蓄能器吸收振动等。     

Proprioceptive consequences of tendon vibration during movement

1. Previous studies have used tendon vibration to investigate kinesthetic illusions in the isometric limb and end point control in the moving limb. These previous studies have shown that vibration distorts the perceptions of static joint angle and movement and causes systematic errors in the end point of movement. In this paper we describe the effects of tendon vibration during movement while human subjects performed a proprioceptively coordinated motor task. In an earlier study we showed that the CNS coordinates this motor task-a movement sequence-with proprioceptive information related to the dynamic position and velocity of the limb. 2. When performing this movement sequence, each subject sat at a table and opened the right hand as the right elbow was passively rotated in the extension direction through a prescribed target angle. Vision of the arm was prevented, and the movement velocity was changed randomly from trial to trial, leaving proprioception as the only useful source of kinematic information with which to perform the task. 3. In randomly occurring trials, vibration was applied to the tendon of the biceps brachii, a muscle that lengthens during elbow extension. In some experiments the timing of tendon vibration was varied with respect to the onset of elbow rotation, and in other experiments the frequency of vibration was varied. In each experiment we compared the accuracy of the subject's response (i.e., the elbow angle at which the subject opened the hand) in trials with tendon vibration with the accuracy in trials without tendon vibration. 4. The effect of tendon vibration depended on the frequency of vibration. When the biceps tendon was vibrated at 20 Hz, subjects opened the hand after the elbow passed through the target angle ("overshooting"). Overshooting is consistent with an underestimate of the actual displacement or velocity of the elbow. Vibration at 30 Hz had little or no effect on the elbow angle at hand opening. Vibration at 40 Hz caused subjects to open the hand before the elbow reached the target angle ("undershooting"). Undershooting is consistent with an overestimate of the actual displacement or velocity of the elbow. The size of the error depended on the velocity of the passively imposed elbow rotation. 5. The effect of tendon vibration also depended on the timing of vibration. If 40-Hz vibration began at the onset of movement, the subject undershot the target. If 40-Hz vibration started 5 s before movement onset and continued throughout the movement, the undershoot error increased in magnitude. However, if 40-Hz vibration started 5 s before movement onset and then stopped at movement onset, the subject overshot the target. When vibration was shut off during movement, a transition occurred from an over-shooting error to an undershooting error at a time that depended on the velocity of elbow rotation. 6. In a separate experiment, subjects were instructed to match either the perceived dynamic position or the perceived velocity of rotation imposed on the right elbow by actively rotating the left elbow. In both matching tasks, tendon vibration produced oppositely directed errors depending on the frequency of vibration. Vibration at 20 Hz produced a perception of decreased elbow velocity and a bias in dynamic position in the flexion direction, and vibration at 40 Hz produced the opposite perceptions. 7. We conclude that muscle spindle afferents, which are activated by tendon vibration, are an important source of the dynamic position and velocity information that the CNS uses to coordinate this movement sequence task. The observed effects of vibration timing and frequency suggest that perceptual changes evoked by vibration cannot be explained by the simple summation of sensory input evoked by movement and by vibration. Rather, the bias in perception produced by vibration appears to be related to the difference between vibration- and movement-evoked activity in muscle spindle afferents.     

考虑振动频率的爆破振动安全标准的探讨

爆破振动安全标准如果不考虑振动频率的影响,则难以准确地衡量爆破振动的危害。文中在分析爆破振动频率对爆破振动的作用后,运用分形理论对其进行定量计算,得出考虑振动频率的爆破振动速度安全判别标准。并针对现场应用。提出采用简单易行的计频允许振速代替单一的爆破质点振动速度来判别爆破安全标准。