Total Electron Content during Recurrent and Quiet Geomagnetic Periods at the Koudougou Station in Burkina Faso

In this work, the comparative study of total electron content (TEC) between recurrent and quiet geomagnetic periods of solar cycle 24 at Koudougou station with geographical coordinates 12°15'N;- 2°20'E was addressed. This study aims to analyze how geomagnetic variations influence the behavior of TEC in this specific region. The geomagnetic indices Kp and Dst were used to select quiet and recurrent days. Statistical analysis was used to interpret the graphs. The results show that the mean diurnal TEC has a minimum before dawn (around 0500 UT) and reaches a maximum value around 1400 UT, progressively decreasing after sunset. In comparison, the average diurnal TEC on recurrent days is slightly higher than on quiet days, with an average difference of 7 TECU. This difference increases with the level of geomagnetic disturbance, reaching 21 TECU during a moderate storm. The study also reveals significant monthly variations, with March and October showing the highest TEC values for quiet and recurrent days, respectively. Equinox months show the highest mean values, while solstice months show the lowest. Signatures of semi-annual, winter and equatorial ionization anomalies were observed. When analyzing annual variations, it was found that the TEC variation depends significantly on F10.7 solar flux, explaining up to 98% during recurrent geomagnetic activity and 92% during quiet geomagnetic activity.

润滑脂对More Quiet噪声测试的影响

为研究润滑脂对More Quiet噪声测试的影响,采用608微型精密轴承进行测试,对不同工作锥入度、洁净度和纤维结构的润滑脂进行分析测试,结果表明:适当增大润滑脂的工作锥入度会提高润滑脂的噪声等级,润滑脂的洁净程度越高,纤维结构越短小均匀,噪声等级越高。静音性能优异的润滑脂具有优异的机械、胶体安定性能。

HiFi并非高不可攀：抢先预览QUIET新品

对很多期望获得好声音，但又不能像顶级发烧友那样一掷千金的消费者而言，传统HiFi产品价格不菲，相对便宜的多媒体音箱又难以达到自己的要求，这是整个行业表现出来的一个明显断层。现如今，HiFi行业逐渐走向数码娱乐化、时尚化和平民化，而QUIET这个来自意大利，由三诺公司作为国内总代理的品牌，针对这一断层提出了新兴HiFi的概念。

Early warning of coal dynamic disaster by precursor of AE and EMR"quiet period"

Efcient and accurate monitoring and early warning of coal dynamic disaster and other disasters can provide guarantee for the efcient operation of mine transportation system.However,the traditional threshold early warning method often fails to warning some accidents.To address above issues,a new early warning method was proposed based on"quiet period"phenomenon of AE and EMR during fracture.It is found that,a"quiet period"of AE and EMR was present before the load reaches the peak stress,which could be used as one of the precursors to warn the imminent failure of coal and rock specimens.MS and AE signals increased abnormally followed by the phenomenon of"quiet period"before the occurrence of coal dynamic disaster on site,and the decrease of MS events in the"quiet period"is about 57%–88%compared with that in previous abnormal increase stage.During the damage evolution of coal and rock,"quiet period"phenomenon usually occurred at 85%–90%of the peak stress,where the slope of damage parameter curve is almost zero.The"quiet period"of the AE-EMR signals and the low change rate of damage parameter before failure provide a theoretical foundation for the coal dynamic disaster warning based on the"quiet period"precursor found in MS-AE-EMR monitoring system.These fndings will help reduce the number of under-reported events and improve early warning accuracy.

Peak of Electron Density in F2-Layer Parameters Variability at Quiet Days on Solar Minimum

This study deals with Peak of electron density in F2-layer sensibility scale during quiet time on solar minimum. Peaks of electron density in F2-layer (NmF2) values at the quietest days are compared to those carried out from the two nearest days (previous and following of quietest day). The study uses International Reference Ionosphere (IRI) for ionosphere modeling. The located station is Ouagadougou, in West Africa. Solar minimum of phase 22 is considered in this study. Using three core principles of ionosphere modeling under IRI running conditions, the study enables to carry out Peak of electron density in F2-layer values during the quietest days of the characteristic months for the four different seasons. These parameters are compared to those of the previous and the following of the quietest days (the day before and following each quietest selected day) at the same hour. The knowledge of NmF2 values at the quietest days and at the two nearest days enables to calculate the relative error that can be made on this parameter. This calculation highlights insignificant relative errors. This means that NmF2 values at the two nearest days of each quietest day on solar minimum can be used for simulating the quietest days’ behavior. NmF2 values obtained by running IRI model have good correlation with those carried out by Thermosphere-Ionosphere-Electrodynamics-General Circulation Model (TIEGCM).

Quiet rest ameliorates biochemical metabolism in the brain in a simple concussion rabbit model Evaluation of hydrogen proton magnetic resonance spectroscopy

The present study analyzed changes in the biochemical metabolites N-acetyl aspartate, choline, and creatine in a simple concussion rabbit model following quiet rest, hyperbaric oxygen therapy, or interference stimulation through the use of hydrogen proton magnetic resonance spectroscopy detection. Experimental findings showed that brain N-acetyl aspartate and choline peak values significantly decreased, while creatine peak values significantly increased following simple concussion. Following treatments, N-acetyl aspartate and choline peaks returned to normal levels in the quiet rest and hyperbaric oxygen therapy groups, but no changes were observed in the interference stimulation group. Results demonstrated abnormal changes in the brain biochemical metabolism environment following simple concussion. Quiet rest was shown to play an important role in restoration of biochemical metabolism following simple concussion.

Simulation of the active and quiet periods of seismicity

In this paper we simulate the repeated occurrence of strong earthquakes along a strike-slip fault by using a finite element model. The fault valve mechanism is included in the model in order to take into account the effeCt of POre fluid pressure variation. Five parameters are used to characterize the rheology of the fault, POre pressure variation, and fracture criteria. By Systematically varying these parameters and calculating a large number of models we carried out a preliminary investigation on the alternatively quiet and active periods of seismicity and their relation to model Parameters and loading conditions. Under the action of a constant-rate boundary movement, in the case of intermediate stress and pore pressure, the models display a regular quiescence-activity phenomenon with a cycle length of 1/3-1 of the recurrence pened. When the model is under high stress or high pore pressure, this phenomenon becomes irregular or inexplicit. When the model is subject to periedic boundary forces and the amplitude of force variation is not too small, it results in an alternatively quiet and active seismicity Pattern with the same Period Of the force variation.

Quiet Zone Design in Diffuse Fields Using Ultrasonic Transducers

This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondary sources to produce quiet zones. Recently ultrasonic transducers have been used for the secondary sources to control the plane wave in active noise control. However there is no research related to active noise control in diffuse fields using ultrasonic transducers. Therefore this study uses ultrasonic transducers for the secondary sources to control the diffuse fields. The quiet zone produced using ultrasonic transducers in single tone diffuse fields has been analyzed through simulations in this work. The results showed that quiet zones created using ultrasonic transducers were larger than those created using conventional loudspeakers. This is due to the fact that the audible sound pressure produced by the ultrasonic transducers decays slowly with the distance. Therefore the secondary field created by an ultrasonic transducer could fit the primary field better and the larger zone of quiet could be obtained using the ultrasonic transducer. Also the audible sound produced by the ultrasonic transducers is directional;therefore the sound pressure amplification outside the quiet zones was lower.

Aerodynamic Design of the Bleed Slot in a Hypersonic Quiet Nozzle

The bleed slot is necessary for the requirement of the hypersonic quiet flow all over the world. The aim of the bleed slot is to decrease the influence of the disturbances from the contraction of the quiet nozzle to the boundary layer downstream of the throat, so that the boundary layer of the nozzle could be maintained as laminar flow. The main parameters of the bleed slot include the distance from lip to throat (DLT) and the width of slot (WS). Various values of those parameters will affect the performance of the slot by changing the suction intensity of the bleed slot. Two kinds of the bleed slots in the world are compared in this paper and the aerodynamic design of the bleed slots is optimized based on the Purdue-type slot. The influences of the various values of those parameters to the flow field around the throat are analyzed and the optimizing results of DLT and WS are consistent with those relative data designed for the slot of the Boeing/AFOSR Ma 6 Quiet Tunnel.

Aerodynamic Optimization of the Expansion Section in a Hypersonic Quiet Nozzle Based on Favorable Pressure Effect

Maximum expansion angle is the primary parameter for the design of expansion section of hypersonic quiet nozzle. According to the quantity of maximum expansion angle, expansion section could be classified as fast expansion and slow expansion. In order to diminish the effect of instability of Görtler vortex, gradually, slow expansion was employed for quiet nozzle design. Based on the favorable pressure effect, the maximum expansion angle is optimized in this paper, and a considerable selective session of maximum expansion angle is obtained. The trend that slow expansion is employed instead of fast expansion is explained, and a new method is established for aerodynamic optimization of expansion section contour in a quiet nozzle.

Research of performance of RSW on quiet steel

The quiet steel has been favored by automobile manufacturers for its advantage in shock absorption and noise reduction.However,there is less research on the welding performance of quiet steel plates.In this paper,the welding lobe of 1.0 mm quiet steel is studied.The comprehensive evaluation of spot welded joints was carried out by evaluation methods such as metallographic structure,microhardness,shear tensile and cross-tensile.The result showed that when the welding heat input was small,the interlayer of the quiet steel plate was not completely fused,and when the heat input was enough,the composite interlayer is completely fused with the steel plate,and the mechanical properties were good.The welding lobe of the quiet steel reaches 4.2 kA with good comprehensive mechanical properties and good weldability.

Shengshan——A Remote and Quiet Island

An Island Further East than'Dongji Island'Located at the northeastern part of the Zhoushan Islands and the eastern part of the Shengsi Islands,Shengshan Island is China’s farthest island in the east.It deserves the name of'Farthest island to the east'as it was described in the Chinese film'Continent.'Also known as'Jinshan'。

Comparative Study of foF2 during Quiet Geomagnetic Activity with URSI and CCIR Predictions during the Phase Minimum of Solar Cycle 22

This paper investigates the performance of the latest International Reference Ionosphere model to predict the critical frequency at low latitudes in the African region. The variability of the critical frequency of the F2 layer of the ionosphere (foF2) is studied for the different seasons of the phase minimum of solar cycle 22 during quiet geomagnetic activity at the Ouagadougou station. The data used are those provided by the ionosonde and the predictions of the two subprograms: International Radio Consultative Committee (CCIR) and International Radio-Scientific Union (URSI) of the 2016 version of the International Reference Ionosphere model. This study shows that, in general, URSI and CCIR of the IRI-2016 model are able to reproduce fairly well the variability of the critical frequency of the F2 layer of the ionosphere at low latitudes during the phase minimum at the Ouagadougou station. However, the model shows an almost homogeneous overestimation of the foF2 during the four seasons studied. The good response is observed between 0700 TL and 1900 TL for the available data. The agreement between the subroutine responses and the observed results is between reasonable and poor. The best match state response is obtained in winter with the CCIR subroutine. These results show that there is a need to improve both CCIR and URSI subroutines of the IRI-2016 model in low latitudes in the African region.

Quiet Steel材料在洗碗机噪声控制上的应用研究

洗碗机通常采用内胆和内门粘贴阻尼片的方式来降噪,但增加阻尼片的同时会造成整机能耗的增加。Quiet Steel材料是一种新型的降噪材料,可用于制作洗碗机内门内胆等结构部件,且具有良好的降噪效果。本文就其在洗碗机噪声控制上的应用做了一些试验研究,得出使用Quiet Steel材料的部件与贴有2mm厚度阻尼的普通材料的部件可达到相同的降噪效果,并可使整机能耗有一定的降低。

与世隔绝是一种什么样的体验？Bose Quiet Comfort35

大兄弟，你想多了，我并没有发掘出另外一个桃花源。但是如果你有幸试用一下Bose新出的QuietComfort 35（型号实在太长了，就用QC35取代之）的话，

只属于你的消噪体验 聆听Bose QuietComfort 消噪耳塞Ⅱ

Bose在消费级音频产品上向来走的是“少而精”的路线,每条产品线的产品数量不多,但每出一款新品都是经过精心打磨,在同类市场中竞争力颇强。在这几年最火的音频细分市场—真无线市场中,它的主力Bose消噪耳塞已面世两年,虽然消噪表现依旧出色,但面对层出不穷的新品也需要在其他方面有所改变。这不,最近它的接班人来了!这就是Bose QuietComfort消噪耳塞Ⅱ(下文简称Bose QC消噪耳塞Ⅱ)。

QUIET品牌专访 打造HiFi音质

欧洲的音乐大环境如何？ M答：从东西方音乐历史上看，无论是西方还是东方都是具有非常深厚的文化底蕴和音乐气氛，从风格上来说也自成一派。西方乐器多以钢琴、提琴、管弦为主，而东方则是具有显著民族特别的弹拨、吹拉的乐器，其历史都相当久远。

给你安静的听音空间BOSE Quiet Comfort25有源消器耳机

QuietComfort25采用折叠收纳的方式让收纳盒小了一大圈，这样的设计让携带变的更为方便，收纳盒内的专属备用电池和航空适配器收纳位，让用户无需担心电池续航和航空适配器无处存放的问题，最重要的是QC25拥有无源情况下依然可以聆听的重大变革，这使得Bose QuietComfort系列消噪耳机全面具备了无源播放功能，让QC25的使用范围变得更为广泛。

降噪旗舰蓝牙耳机再升级!Bose Quiet Comfort Earbuds Ⅱ体验

降噪蓝牙耳机产品相信大家都耳熟能详,无论是国外还是国产品牌都基本会有代表作。不过可能大家印象最深的还是BOSE旗下的降噪蓝牙耳机QuietComfort Earbuds,其上市后的出色表现,让大家都一度认为降噪蓝牙耳机就应如此。今日,BOSE也推出了其全新第二代产品Bose QuietComfort Earbuds Ⅱ,官方介绍其全新搭载定制独立降噪芯片,并加入全新的智能耳内音场调校技术,让降噪更加优秀,下面一起来体验。