large scale and
Large scale and environmentally friendly preparation of micro-submicron spherical silica and their surface effect in resin materials
Changchun Ai a ,Yong Xiao a ,Wen Wen b ,Liangjie Yuan a ,?
a College of Chemistry and Molecular Science,Wuhan University,Wuhan 430072,China b
College of Chemical Engineering,Wuhan Textile University,Wuhan 430074,China
a b s t r a c t
a r t i c l e i n f o Article history:
Received 20January 2011
Received in revised form 25March 2011Accepted 3April 2011
Available online 9April 2011Keywords:
Turbulent ?ow cycle Spherical silica Surface effect Epoxy materials
Amorphous micro-submicron spherical silica powders with different particle sizes and surface properties were prepared by turbulent ?ow cycle method and characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES),inductively coupled plasma mass spectrometry (ICP-MASS),X-ray diffraction (XRD),particle size distribution (PSD),speci ?c surface area (SSA)analysis and scanning electron microscopy (SEM).The effects of particle size and surface property of different spherical silica on the ?uidity of resin materials were conducted.The result showed that the spherical silica with the characterization of D 50=2.5μm and the ratio of experimental speci ?c surface area and calculated speci ?c surface area is 2.38,played a better role in the ?ow ability of epoxy materials.So it may be a better choice for the preparation of epoxy materials used in IC packaging area and other high-tech ?elds.
?2011Elsevier B.V.All rights reserved.
1.Introduction
Silica (SiO 2)is one of the basic raw materials in aerospace,infor-mation industry,automobile,metallurgy,chemical industry,con-struction,energy and other areas.In order to improve the mechanical and electrical properties of resin materials as electronic information materials,many kinds of silica powder were considered and the effects of their particle shape,particle size distribution and crystal type were also investigated [1–4].
Due to the controllability of particle size,speci ?c surface area,high purity,crystal type,low content of radioactive elements,spherical SiO 2is widely used in the photo-electronic information materials,special engineering plastics and daily chemicals.As raw materials used in electronic packaging materials,the technical indications of spherical SiO 2,such as particle size distribution,morphology and speci ?c surface area (SSA),impurities and radioactive element content,linear expansion coef ?cient (CET),tap density,electrical conductivity and pH value of water extract solution should be strictly controlled.In a word,the batch preparation technology of spherical silica particles is of dif ?culties.And so far,spherical silica powder is prepared by the method of high temperature melting sputtering [5,6],vapor phase synthesis [7],the combustion and atomization of metal silica,sol-gel process [8]and the hydrolysis of TEOS,TMOS [9–11]or silicon tetrachloride [12],etc.The former methods are of high-energy
consumption and high emissions of carbon dioxide.The raw materials TEOS,TMOS are expensive and silicon tetrachloride will cause heavy chemical pollution.
In this paper,an environmentally friendly and low cost method was designed for the preparation of spherical silica,by which the spherical shape,particle size and surface area of silica powder can be well controlled.Further investigation on the effect of particle size and surface property in resin material was carried out and a method of choosing spherical silica used in epoxy materials was obtained.
2.Experimental procedures 2.1.Preparation of spherical silica
The spherical hydration silica (SiO 2·nH 2O)was prepared in the reactor with turbulent ?ow cycle assembly parts (Fig.1)from silica sol (20wt.%SiO 2),sodium silicate solution (20–25wt.%SiO 2in Na 2-O·3.0SiO 2)and diluted sulfuric acid (15–20wt.%).The speed of the turbulent ?ow cycle ranged from 1500to 2500rpm.The pH value of reaction solution is about 5.0.20kg of spherical SiO 2·nH 2O can be obtained for each batch at room temperature and normal pressure.After washing with pure water,drying with cyclone separation and surface treating at the suitable temperature,?ve kinds of silica powders SS1,SS2,SS3,SS4and SS5were obtained.The method is low cost and environmentally friendly because the ?ltrate solution from the washing process can be reused by membrane ?ltration technology and Na 2SO 4concentrated from the ?ltrate solution has become a kind of valuable by-product.
Powder Technology 210(2011)323–327
?Corresponding author at:College of Chemistry and Molecular Science,Wuhan University,Wuhan 430072,China.Tel.:+862768752800;fax:+862768754067.
E-mail address:ljyuan@https://www.sodocs.net/doc/1811491820.html, (L.
Yuan).0032-5910/$–see front matter ?2011Elsevier B.V.All rights reserved.doi:
10.1016/j.powtec.2011.04.003
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2.2.Characterization
Thermogravimetric analysis (TGA)of the spherical hydration (SiO 2·nH 2O)silica was carried out by NETZSCH STA 449C at the heating rate of 10K·min ?1in air.The morphologies of silica powder were observed by scanning electron microscopy (SEM,FEI QUANTA 200).The powder X-ray diffraction patterns (XRD)of the products were conducted by Shimadzu XRD-6000diffractometer with Cu K α1radiation (λ=1.54056?)at the scanning speed of 4°·min ?1(2θ).The scanning scope is 10–40°at tube voltage of 40kV and tube current of 40mA.The element contents of the products were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES,model IRIS,TJA,USA)and the uranium element content was measured by inductively coupled plasma mass spectrometry (ICP-MASS,Agilent,model 7500a,USA).The electric conductivity,pH value and Na +K +Ca 2+Mg 2+Cl ?contents of the extracted solutions of all products were measured by DDS-12A Digital Conductivity Meter (Yulong,China),pHS-3C Digital pH Meter (Shiji-Fangzhou,China)and DX-120Ion Chromatograph Meter (Dionex,USA).Speci ?c surface area (SSA)and total pore volume (TPV)were measured and carried out with Gemini 2360analyzer (Micromeritics,USA)by the Brunauer –Emmett –Teller (BET)method.The particle size distribu-tions of the products were measured by Mastersizer 2000(Malvern,UK).The true densities and bulk densities were tested by the pyc-nometric method and vibration method.
2.3.Preparation of epoxy materials ?lled with spherical silica
The chemical structure of epoxy resin and hardener used in this study were exhibited in Scheme 1.
The silica powders SS1,SS2,SS3,SS4,SS5and SS6(SS6sample was obtained by mixing with SS1,SS3and SS5according to the close packing theory [13,14])were treated with silane coupling agent (γ-Glycidoxypropyl trimethoxysilane,WD-60;1wt.%of silica)in the high-speed mixer.All the epoxy resins and hardeners are composed of the same equivalent weight ratio (1:1)of epoxy and hydroxyl group and the content of catalyst is 1wt.%(TPP)of epoxy resin.Epoxy resin,hardener (PF8010),silica powder and micro capsulated catalysts (TPP-MMA)were well mixed at 120°C [15,16].The ?ller loading is 73wt.%in biphenyl epoxy (NC3000)materials and they were signed with N1,N2,N3,N4,N5and N6respectively.The ?ller loading is 65wt.%in o-cresol formaldehyde novolac epoxy (EOCN1020)materials and 70wt.%in 3,3′,5,5′-tetramethyl-4,4′-diglycidyl biphe-nyl epoxy (YX4000)materials.Materials made from EOCN1020were signed with E1,E2,E3,E4,E5and E6respectively and materials made from YX4000were signed with Y1,Y2,Y3,Y4,Y5and Y6respectively.The spiral ?ow of these epoxy materials were measured by a reaction injection molding machine and a spiral mold.The ma-terials were preheated at 120°C and the molding temperature was 175°C.The injection pressure is (70±2)kg·cm ?2and the pressure hold time is 10s.
SS1,SS2,SS3,SS4and SS5samples (50wt.%of total)were treated with silane coupling agent in the same way and mixed with alicyclic epoxy resin (UVR6110),hardener (MeHHPA)and imidazole catalyst at room temperature by ARE-310model Planetary Centrifugal Mixer (Thinky,Japan).These alicyclic epoxy materials were signed with A1,A2,A3,A4and A5respectively,and the viscosities were measured by NDJ-8S Rotational Viscometer at 25°C.3.Results and discussion
There exist two types of water in SiO 2·nH 2O:one is the adherent water,the other is the bound water formed by silanol groups (≡Si –OH)bonding with water.There is a clear stage of weight loss in the TG curve of SiO 2·nH 2O (Fig.2)from room temperature to 300°C due to the loss of adherent water.The small weight loss stage from 300to 700°C is corresponding to the removing of bound water.The weight loss is approaching to zero above 800°C.
The calcined temperature has a great impact on the surface structure of the silica powder.The surface property of the powder calcined at different temperatures can be signi ?cantly observed in H 2O media at room temperature.The powder calcined at 700°C for 2h could absorb amount of water and immediately became very viscous silica gel.While the powder obtained at 900°C for 2h
was
Fig.1.The diagram of turbulent ?ow cycle assembly parts.
O
O
O
O
O O
O
H 3C
(methylhexahydrophthalic anhydride, MeHHPA)
(3,4 - epoxy cyclohexyl methyl -3,4 - epoxy
cyclohexyl carboxylate, UVR6110)
H 2C
H 2C
H
n H 2C
H 2C
OH
OH
OH
n
O
O O
O (4, 4'-diglycidyl biphenyl novolac
epoxy resin, NC3000)
(3,3 ,5,5 -tetramethyl-4,4 -diglycidyl biphenyl
epoxy resin, YX4000)
O
O
H 2C
C H 2
CH 3
CH 3
CH 3
O
O O
O
n (o-cresol formaldehyde novolac epoxy
resin, EOCN1020)
CH 3
H 3C H 3C
CH 3
O
O O
O
(Phenolic resin, PF8010)Scheme 1.Chemical structure of epoxy resins and hardeners.
324 C.Ai et al./Powder Technology 210(2011)323–327
dif?cult to hydrate and the ability of surface adsorption decreased greatly.The absorption capacity of the powder obtained at1100°C for 2h was almost lost.Generally,when the calcined temperature is above900°C,the stable Si–O tetrahedral structure is formed and there is no internal stress in the particle.But in fact,the silanol functional groups still exist in the powder and can be examined by IR spectra.So in our experiments,in order to control the amount of surface hydroxyl groups,improve the tap density and reduce the moisture absorption of powders,the hydration silica(SiO2·nH2O)was calcined at1100°C for2h.
SEM images(Fig.3a)present that all the products have good spherical shapes with smooth surface,monodisperse and uniform distribution,which result in their good?uidity.All samples are amorphous like according to the XRD patterns of the products (Fig.3b)and in the nature of low coef?cient of expansion.Fig.3c shows the particle size distribution of all samples.The D50of the spherical silica SS1,SS2,SS3,SS4and SS5is1.0μm,2.5μm,3.7μm, 6.7μm and12.0μm,respectively.The distributions belong to normal distribution and the diameter of the largest particle(D max)in each kind of powder is less than45μm and can be effectively controlled.
The content of SiO2is above99.95%and uranium is0.1ppb(see Supplementary S1).Data indicates that the silica products possess high purity and very lowαrays interfering signals.The electric conductivity(EC)of the extract solutions of all samples are lower than 2μs·cm?1,pH values are about6.0,and the contents of Na+K+Ca2+ Mg2+Cl?are all below0.5ppm.What's more,the moisture of all the samples is below0.03%by weight loss method.As raw materials used in IC area,silica powder with low content of harmful ions and low moisture can enhance the moisture resistance and protect the circuits from corrosion even in high humidity environment.
The true speci?c gravity of the spherical silica is2.18–2.2g·cm?3 by pycnometric method,and the bulk densities are0.73,0.98,1.05, 1.23,1.28g·cm?3assigned to SS1,SS2,SS3,SS4and SS5.
The multipoint speci?c surface area(MSSA),singlepoint speci?c surface area(SSSA)and total pore volume(TPV)of?ve products tested by BET method are listed in Table1.For all samples the data of MSSA,SSSA and TPV are very small except SS1.It is indicated that the surface of spherical silica are very smooth and the spherical particles are monodispersed,compact and solid.As for SS1sample,there may exist tiny interfaces between the particles,so the data of MSSA, SSSA and TPV are much larger than that of the other samples.That is to say,the SS1sample with a smaller bulk density(0.73g·cm?3)is not compact enough.
Since the samples are close to true spherical(as shown in SEM),the data of the speci?c surface area can be calculated by the following formula(1)assuming all spherical silica being compact and solid. The calculated results(SSA)and the ratios of measured MSSSA and calculated speci?c surface area(SSA)are also listed in Table1.
SSA=6×1000
d?ρ
e1T
where:d is the D50of spherical silica(μm);ρis the true density of
spherical silica(2.2g·cm?3).
The level of experimental data of speci?c surface area closing to
the calculated speci?c surface area is expressed by the ratio of W
e
i
g
h
t
l
o
s
s
(
%
)
Temperature (°C)
202404606809001120
10
20
30
↓
↑
12.1%
Fig.2.TG curve of SiO2·nH2O in air.
Fig.3.SEM images(a),XRD pattern(b)and particle size distribution(c)of spherical silica.
325
C.Ai et al./Powder Technology210(2011)323–327
experimental speci?c surface area and calculated speci?c surface area (ratio(exp/cal)).The ratio(exp/cal)represents the surface property of the spherical silica powders and the surface property usually plays an important role in the performance of silica in polymer materials. It can be inferred from the ratios that SS2,SS3,SS4and SS5samples
are compact spheres with little smaller internal surface area,but SS1is relatively of much internal surface area.
The characterizations mentioned earlier have proved that all of the spherical silica samples obtained by turbulent?ow cycle method have good sphericity with very smooth surface,high purity,lowαrays,small speci?c surface area and low moisture absorption.Thus they can be used as raw material for advanced electronic information materials.
Spherical silica powders play a key role in determining the me-chanical and electrical performance of the epoxy materials[17,18]. The effects of particle size and surface property of the spherical silica on the?uidity of resin materials were studied.The spiral?ow of N series(N1,N2,N3,N4,N5and N6),Y series(Y1,Y2,Y3,Y4,Y5and Y6) and E series(E1,E2,E3,E4,E5and E6)epoxy materials and the viscosity of alicyclic epoxy materials(A series:A1,A2,A3,A4and A5) were measured and exhibited in Table2and Fig.4.As shown in the table,when the?ller loading was73wt.%in the biphenyl epoxy system,the spiral?ow of N2reached up to116cm,which was much longer than that of the other four kinds of materials.This phenomenon was also observed in the other two solid epoxy resin systems:the spiral?ow of Y2was longer than Y1,Y3,Y4and Y5and the spiral?ow of E2was also longer than the other materials?lled with SS1,SS3,SS4and SS5.In alicyclic epoxy system,the rational viscosity of A2was only580mPa·s and much lower than that of the other four kinds of materials.That is to say the material made from SS2exhibited excellent performance in mobility and viscosity in different epoxy system.It is no doubt that this phenomenon is resulted from the special properties of the spherical silica:particle size (D50=2.5μm)and special surface property(ratio(exp/cal)=2.38).It seems to imply that the spherical silica with the characterization of D50=2.5μm and ratio(exp/cal)=2.38may have better?uidity in epoxy materials.In other words,the SS2can be a better?ller in epoxy materials.
In order to further improve the?uidity of biphenyl epoxy materials,sample SS6was mixed from SS1,SS3and SS5samples by simulating with Matlab software according to Dinger–Funk–Alfred particle size distribution model[19,20].The spiral?ow of N6?lled with SS6is114cm,which is much longer than that of N1,N3,N4and N5and close to that of N2.It is proved that SS2as single component of ?ller in epoxy materials can achieve the desired?ow properties.
Our experiments for liquid alicyclic epoxy system also illustrated that,as?ller,the SS2can effectively adjust the viscosity of the liquid epoxy materials.The relationship between the rotational viscosities of the liquid epoxy composite materials and the mass content of SS2is shown in Fig.5.It can be found that the viscosities of the alicyclic epoxy materials decrease with the increasing of mass content of SS2in ?llers.The viscosities reach the lowest value when the mass content of SS2is40%and SS1(SS3)is10%.So the viscosities can be controlled by the content of SS2sample.
4.Conclusions
In summary,large scale micro-submicron spherical silica were prepared by turbulent?ow cycle method with an environmentally friendly process.Due to the special particle size distribution and surface property,the spherical silica SS2(D50=2.5μm and ratio(exp/ cal)=2.38)exhibited better surface effects than the other spherical powders in epoxy resin materials and can effectively adjust the?uidity of resin materials.So the spherical silica SS2can be widely applied in photo,electronic information materials and special engineering plastics.
Table1
The surface properties of spherical silica samples.
Sample D50MSSA a SSSA b TPV c SSA d Ratio
(μm)m2·g?1m2·g?1mL·g?1m2·g?1(exp/cal)
SS1 1.023.5223.440.0152 2.738.62
SS2 2.5 2.59 2.540.0018 1.09 2.38
SS3 3.7 2.23 2.200.00150.73 3.05
SS4 6.70.650.640.00050.41 1.58
SS512.00.300.320.00030.23 1.30
a Experimental data of BET multipoint speci?c surface area;
b experimental data of BET single-point speci?
c surface area;c experimental data of total pore volume;
d calculated speci?c surfac
e area.
Table2
The?uidity properties of epoxy materials.
Filler Spiral?ow(cm)Viscosity(mPa·s) N series Y series E series A series
SS155********
SS211613788580
SS36112778730
SS483104731120
SS58596694200
SS611414092
S
p
i
r
a
l
F
l
o
w
(
c
m
)
60
70
80
90
100
110
120
130
140
50
500
1000
1500
2000
2500
3000
3500
4000
4500
Particle Size (D50) of Silica (μm)
Viscosity (mPa.s) Fig.4.The?uidity properties of different epoxy materials.
Fig.5.The viscosities of the alicyclic epoxy materials?lled with SS1,SS2and SS3(SS2 mixed with SS1as?ller A,and SS2mixed with SS3as another?ller B,the total?ller loading is50wt.%).
326 C.Ai et al./Powder Technology210(2011)323–327
Acknowledgements
The authors are grateful to the National S&T Major Project(No.02),“863”Project and the National Natural Science Foundation of China (No.20671074,21071112).
Appendix A.Supplementary data
Supplementary data to this article can be found online at doi:10.1016/j.powtec.2011.04.003.
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基因芯片数据处理流程与分析介绍
基因芯片数据处理流程与分析介绍 关键词：基因芯片数据处理 当人类基因体定序计划的重要里程碑完成之后，生命科学正式迈入了一个后基因体时代，基因芯片(microarray) 的出现让研究人员得以宏观的视野来探讨分子机转。不过分析是相当复杂的学问，正因为基因芯片成千上万的信息使得分析数据量庞大，更需要应用到生物统计与生物信息相关软件的协助。要取得一完整的数据结果，除了前端的实验设计与操作的无暇外，如何以精确的分析取得可信数据，运筹帷幄于方寸之间，更是画龙点睛的关键。 基因芯片的应用 基因芯片可以同时针对生物体内数以千计的基因进行表现量分析，对于科学研究者而言，不论是细胞的生命周期、生化调控路径、蛋白质交互作用关系等等研究，或是药物研发中对于药物作用目标基因的筛选，到临床的疾病诊断预测，都为基因芯片可以发挥功用的范畴。 基因表现图谱抓取了时间点当下所有的动态基因表现情形，将所有的探针所代表的基因与荧光强度转换成基本数据(raw data) 后，仿如尚未解密前的达文西密码，隐藏的奥秘由丝丝的线索串联绵延，有待专家抽丝剥茧，如剥洋葱般从外而内层层解析出数千数万数据下的隐晦含义。 要获得有意义的分析结果，恐怕不能如泼墨画般洒脱随兴所致。从raw data 取得后，需要一连贯的分析流程(图一)，经过许多统计方法，才能条清理明的将raw data 整理出一初步的分析数据，当处理到取得实验组除以对照组的对数值后(log2 ratio)，大约完成初步的统计工作，可进展到下一步的进阶分析阶段。
图一、整体分析流程。基本上raw data 取得后，将经过从最上到下的一连串分析流程。(1) Rosetta 软件会透过统计的model，给予不同的权重来评估数据的可信度，譬如一些实验操作的误差或是样品制备与处理上的瑕疵等，可已经过Rosetta error model 的修正而提高数据的可信值；(2) 移除重复出现的探针数据；(3) 移除flagged 数据，并以中位数对荧光强度的数据进行标准化(Normalized) 的校正；(4) Pearson correlation coefficient (得到R 值) 目的在比较技术性重复下的相似性，R 值越高表示两芯片结果越近似。当R 值超过0.975，我们才将此次的实验结果视为可信，才继续后面的分析流程；(5) 将技术性重复芯片间的数据进行平均，取得一平均之后的数据；(6) 将实验组除以对照组的荧光表现强度差异数据，取对数值(log2 ratio) 进行计算。 找寻差异表现基因 实验组与对照组比较后的数据，最重要的就是要找出显著的差异表现基因，因为这些正是条件改变后而受到调控的目标基因，透过差异表现基因的加以分析，背后所隐藏的生物意义才能如拨云见日般的被发掘出来。 一般根据以下两种条件来筛选出差异表现基因：(i) 荧光表现强度差异达2 倍变化(fold change 增加2 倍或减少2倍) 的基因。而我们通常会取对数(log2) 来做fold change 数值的转换，所以看的是log2 ≧1 或≦-1 的差异表现基因；(ii) 显著值低于0.05 (p 值< 0.05) 的基因。当这两种条件都符合的情况下所交集出来的基因群，才是显著性高且稳定的差异表现基因。
通信接口介绍
一IIC通信 现今，在低端数字通信应用领域，我们随处可见IIC (Inter-Integrated Circuit) 和SPI (Serial Peripheral Interface)的身影。原因是这两种通信协议非常适合近距离低速芯片间通信。Philips （for IIC）和Motorola（for SPI）出于不同背景和市场需求制定了这两种标准通信协议。 IIC 开发于1982年，当时是为了给电视机内的CPU和外围芯片提供更简易的互联方式。电视机是最早的嵌入式系统之一，而最初的嵌入系统是使用内存映射（memory-mapped I/O）的方式来互联微控制器和外围设备的。要实现内存映射，设备必须并联入微控制器的数据线和地址线，这种方式在连接多个外设时需大量线路和额外地址解码芯片，很不方便并且成本高。 为了节省微控制器的引脚和和额外的逻辑芯片，使印刷电路板更简单，成本更低，位于荷兰的Philips实验室开发了‘Inter-Integrated Circuit’，IIC 或IIC ，一种只使用二根线接连所有外围芯片的总线协议。最初的标准定义总线速度为100kbps。经历几次修订，主要是1995年的400kbps，1998的3.4Mbps。 有迹象表明，SPI总线首次推出是在1979年，Motorola公司将SPI总线集成在他们第一支改自68000微处理器的微控制器芯片上。SPI总线是微控制器四线的外部总线（相对于内部总线）。与IIC不同，SPI没有明文标准，只是一种事实标准，对通信操作的实现只作一般的抽象描述，芯片厂商与驱动开发者通过data sheets和application notes沟通实现上的细节。IIC(INTER IC BUS) IIC的数据输入输出用的是一根线，但是由于IIC的数据线是双向的，所以隔离比较复杂，SPI则比较容易。所以系统内部通信可用IIC,若要与外部通信则最好用SPI带隔离（可以提高抗干扰能力）。但是IIC和SPI都不适合长距离传输。 IIC总线是双向、两线(SCL、SDA)、串行、多主控（multi-master）接口标准，具有总线仲裁机制，非常适合在器件之间进行近距离、非经常性的数据通信。在它的协议体系中，传输数据时都会带上目的设备的设备地址，因此可以实现设备组网。 IIC通信:是两根线，发送的开始状态和结束状态都与SCL有关，SDA上先发送设备地址，后发送寄存器地址和数据。硬件简单，软件协议稍微多点，比如开始状态，结束状态，数据变化状态对时序都有严格要求 IIC 是多主设备的总线，IIC没有物理的芯片选择信号线，没有仲裁逻辑电路，只使用两条信号线——‘serial data’(SDA) 和‘serial clock’(SCL)。IIC协议规定： 1.每一支IIC设备都有一个唯一的七位设备地址； 2. 数据帧大小为8位的字节； 3. 数据（帧）中的某些数据位用于控制通信的开始、停止、方向（读写）和应答机制。IIC 数据传输速率有标准模式（100 kbps）、快速模式（400 kbps）和高速模式（3.4 Mbps），另外一些变种实现了低速模式（10 kbps）和快速+模式（1 Mbps）。 物理实现上，IIC 总线由两根信号线和一根地线组成。两根信号线都是双向传输的，参考下图。IIC协议标准规定发起通信的设备称为主设备，主设备发起一次通信后，其它设备均为从设备。
芯片485通信
RS－485串行总线接口标准以差分平衡方式传输信号，具有很强的抗共模干扰的能力，允许一对双绞线上一个发送器驱动多个负载设备。工业现场控制系统中一般都采用该总线标准进行数据传输，而且一般采用RS－485串行总线接口标准的系统都使用8044芯片作为通信控制器或各分机的CPU。8044芯片内部集成了SDLC，HDLC等通信协议，并且集成了相应的硬件电路，通过硬件电路和标准协议的配合，使系统的通讯准确、可靠、快速。8044在市场上日渐稀少，虽然有8344可替代，但几百元的价位与普通单片机几元至几十元的价位相差甚远，用户在开发一般的单片机应用系统时，都希望能用简单的电路和简单的通信协议完成数据交换。譬如：利用单片机本身所提供的简单串行接口，加上总线驱动器如SN75176等组合成简单的RS－485通讯网络。本文所述的方法已成功地应用于工程项目，一台主机与60台从机通讯，通讯波特率达64KBPS。 2总线驱动器芯片SN75176 常用的RS－485总线驱动芯片有SN75174，SN75175，SN75176。SN75176芯片有一个发送器和一个接收器，非常适合作为RS－485总线驱动芯片。 SN75176及其逻辑如图1所示。 图1SN75176芯片及其逻辑关系 3RS－485方式构成的多机通信原理 在由单片机构成的多机串行通信系统中，一般采用主从式结构：从机不主动发送命令或数据，一切都由主机控制。并且在一个多机通信系统中，只有一台单机作为主机，各台从机之间不能相互通讯，即使有信息交换也必须通过主机转发。采用RS－485构成的多机通讯原理框图，如图2所示。
图2采用RS－485构成的多机通讯原理框图 在总线末端接一个匹配电阻，吸收总线上的反射信号，保证正常传输信号干净、无毛刺。匹配电阻的取值应该与总线的特性阻抗相当。 当总线上没有信号传输时，总线处于悬浮状态，容易受干扰信号的影响。将总线上差分信号的正端A+和+5电源间接一个10K的电阻；正端A+和负端B-间接一个10K的电阻；负端B-和地间接一个10K的电阻，形成一个电阻网络。当总线上没有信号传输时，正端A+的电平大约为3.2V，负端B-的电平大约为1.6V，即使有干扰信号，却很难产生串行通信的起始信号0，从而增加了总线抗干扰的能力。 4通信规则 由于RS－485通讯是一种半双工通讯，发送和接收共用同一物理信道。在任意时刻只允许一台单机处于发送状态。因此要求应答的单机必须在侦听到总线上呼叫信号已经发送完毕，并且没有其它单机发出应答信号的情况下，才能应答。半双工通讯对主机和从机的发送和接收时序有严格的要求。如果在时序上配合不好，就会发生总线冲突，使整个系统的通讯瘫痪，无法正常工作。要做到总线上的设备在时序上的严格配合，必须要遵从以下几项原则： 1) 复位时，主从机都应该处于接收状态。 SN75176芯片的发送和接收功能转换是由芯片的RE*，DE端控制的。RE*=1，DE=1时，SN75176发送状态；RE*=0，DE=0时，SN75176处于接收状态。一般使用单片机的一根口线连接RE*，DE端。在上电复位时，由于硬件电路稳定需要一定的时间，并且单片机各端口复位后处于高电平状态，这样就会使总线上各个分机处于发送状态，加上上电时各电路的不稳定，可能向总线发送信息。因此，如果用一根口线作发送和接收控制信号，应该将口线反向后接入 SN75176的控制端，使上电时SN75176处于接收状态。 另外，在主从机软件上也应附加若干处理措施，如：上电时或正式通讯之前，对串行口做几次空操作，清除端口的非法数据和命令。 2) 控制端RE*，DE的信号的有效脉宽应该大于发送或接收一帧信号的宽度。 在RS－232，RS－422等全双工通讯过程中，发送和接收信号分别在不同的物理链路上传输，发送端始终为发送端，接收端始终为接收端，不存在发送、接收控制信号切换问题。在RS －485半双工通讯中，由于SN75176的发送和接收都由同一器件完成，并且发送和接收使用同一物理链路，必须对控制信号进行切换。控制信号何时为高电平，何时为低电平，一般以单片机的TI，RI信号作参考。
基因表达谱芯片的数据分析
基因表达谱芯片的数据分析(2012-03-13 15:25:58)转载▼ 标签：杂谈分类：生物信息 摘要 基因芯片数据分析的目的就是从看似杂乱无序的数据中找出它固有的规律, 本文根据数据分析的目的, 从差异基因表达分析、聚类分析、判别分析以及其它分析等角度对芯片数据分析进行综述, 并对每一种方法的优缺点进行评述, 为正确选用基因芯片数据分析方法提供参考. 关键词: 基因芯片; 数据分析; 差异基因表达; 聚类分析; 判别分析 吴斌, 沈自尹. 基因表达谱芯片的数据分析. 世界华人消化杂志2006;14(1):68-74 https://www.sodocs.net/doc/1811491820.html,/1009-3079/14/68.asp 0 引言 基因芯片数据分析就是对从基因芯片高密度杂交点阵图中提取的杂交点荧光强度信号进行的定量分析, 通过有效数据的筛选和相关基因表达谱的聚类, 最终整合杂交点的生物学信息, 发现基因的表达谱与功能可能存在的联系. 然而每次实验都产生海量数据, 如何解读芯片上成千上万个基因点的杂交信息, 将无机的信息数据与有机的生命活动联系起来, 阐释生命特征和规律以及基因的功能, 是生物信息学研究的重要课题[1]. 基因芯片的数据分析方法从机器学习的角度可分为监督分析和非监督分析, 假如分类还没有形成, 非监督分析和聚类方法是恰当的分析方法; 假如分类已经存在, 则监督分析和判别方法就比非监督分析和聚类方法更有效率。根据研究目的的不同[2,3], 我们对基因芯片数据分析方法分类如下: (1)差异基因表达分析: 基因芯片可用于监测基因在不同组织样品中的表达差异, 例如在正常细胞和肿瘤细胞中; (2)聚类分析: 分析基因或样本之间的相互关系, 使用的统计方法主要是聚类分析; (3)判别分析: 以某些在不同样品中表达差异显著的基因作为模版, 通过判别分析就可建立有效的疾病诊断方法. 1 差异基因表达分析(difference expression, DE) 对于使用参照实验设计进行的重复实验, 可以对2样本的基因表达数据进行差异基因表达分
通信接口介绍
IIC 通信 现今，在低端数字通信应用领域，我们随处可见IIC (Inter-Integrated Circuit) 和SPI (Serial Peripheral Interface) 的身影。原因是这两种通信协议非常适合近距离低速芯片间通信。Philips (for IIC )和Motorola (for SPI ) 出于不同背景和市场需求制定了这两种标准通信协议。 IIC开发于1982年，当时是为了给电视机内的CPU和外围芯片提供更简易的互联方式。电视机是最早的嵌入式系统之一，而最初的嵌入系统是使用内存映射( memory-mapped I/O) 的方式来互联微控制器和外围设备的。要实现内存映射，设备必须并联入微控制器的数据线和地址线，这种方式在连接多个外设时需大量线路和额外地址解码芯片，很不方便并且成本高。 为了节省微控制器的引脚和和额外的逻辑芯片，使印刷电路板更简单，成本更低，位于荷兰的Philips 实验室开发了‘Inter-Integrated Circuit '，IIC 或IIC ，一种只使 用二根线接连所有外围芯片的总线协议。最初的标准定义总线速度为100kbps。经历几次 修订，主要是1995年的400kbps，1998的。 有迹象表明，SPI总线首次推出是在1979年，Motorola公司将SPI总线集成在他们第一支改自68000 微处理器的微控制器芯片上。SPI 总线是微控制器四线的外部总线(相对于内部总线)。与IIC不同，SPI没有明文标准，只是一种事实标准，对通信操作的实现只作一般的抽象描述，芯片厂商与驱动开发者通过data sheets 和application notes 沟通实现上的细节。 IIC(INTER IC BUS) IIC 的数据输入输出用的是一根线，但是由于IIC 的数据线是双向的，所以隔离比较复杂，SPI则比较容易。所以系统内部通信可用IIC,若要与外部通信则最好用SPI带隔离 (可以提高抗干扰能力)。但是IIC和SPI都不适合长距离传输。 IIC 总线是双向、两线(SCL、SDA)串行、多主控(multi-master )接口标准，具有总线仲裁机制，
基因芯片数据功能分析
生物信息学在基因芯片数据功能分析中的应用2009-4-29 随着人类基因组计划(Human Genome Project)即全部核苷酸测序的即将完成，人类基因组研究的重心逐渐进入后基因组时代(PostgenomeEra)，向基因的功能及基因的多样性倾斜。 通过对个体在不同生长发育阶段或不同生理状态下大量基因表达的平行分析，研究相应基因在生物体内的功能，阐明不同层次多基因协同作用的机理，进而在人类重大疾病如癌症、心血管疾病的发病机理、诊断治疗、药物开发等方面的研究发挥巨大的作用。它将大大推动人类结构基因组及功能基因组的各项基因组研究计划。生物信息学在基因组学中发挥着重大的作用,而另一项崭新的技术——基因芯片已经成为大规模探索和提取生物分子信息的强有力手段，将在后基因组研究中发挥突出的作用。基因芯片与生物信息学是相辅相成的，基因芯片技术本身是为了解决如何快速获得庞大遗传信息而发展起来的，可以为生物信息学研究提供必需的数据库，同时基因芯片的数据分析也极大地依赖于生物信息学，因此两者的结合给分子生物学研究提供了一条快捷通道。 本文介绍了几种常用的基因功能分析方法和工具： 一、GO基因本体论分类法 最先出现的芯片数据基因功能分析法是GO分类法。Gene Ontology（GO，即基因本体论）数据库是一个较大的公开的生物分类学网络资源的一部分，它包含38675个Entrez Gene注释基因中的17348个，并把它们的功能分为三类： 分子功能，生物学过程和细胞组分。在每一个分类中，都提供一个描述功能信息的分级结构。这样，GO中每一个分类术语都以一种被称为定向非循环图表（DAGs）的结构组织起来。研究者可以通过GO分类号和各种GO数据库相关分析工具将分类与具体基因联系起来，从而对这个基因的功能进行描述。在芯片的数据分析中，研究者可以找出哪些变化基因属于一个共同的GO功能分支，并用统计学方法检定结果是否具有统计学意义，从而得出变化基因主要参与了哪些生物功能。
R语言在基因芯片数据处理中的应用
1.R语言安装：官方网站安装软件。 2. 所需要的软件包： 2.1 affy数据处理相关的程序包 在R中复制source("/biocLite.R") biocLite("affy") 2.2 热度图相关程序包 Gplots（）：install.packages("gplots") 3.获取基因表达数据 3.1 读取基因芯片数据（cel.files） the.filter <- matrix(c("CEL file (*.cel)", "*.cel", "All (*.*)", "*.*"), ncol = 2, byrow = T) cel.files <- choose.files(caption = "Select CEL files", multi = TRUE, filters = the.filter, index = 1) raw.data <- ReadAffy( = cel.files) 3.2 sampleNames(raw.data)ang #先看看原样品名称的规律
7. 选取目的基因 在上确定探针，选取数据；汇总到excel表格中，保存为csv格式。 8.热度图 cipk=read.csv("c:/users/suntao/desktop/TaCIPK affx arry log.csv") https://www.sodocs.net/doc/1811491820.html,s(cipk)=cipk$genename cipk <- cipk[,-1] cipk_matrix=data.matrix(cipk) library(gplots) heatmap.2(cipk_matrix,Rowv=FALSE,Colv=FALSE,col=greenred(75),key=TRUE,keysize=0.8,trace="n one",https://www.sodocs.net/doc/1811491820.html,="none",symkey=FALSE,revC=FALSE,margins=c(10,10),denscol=tracecol,distfun=dist, hclustfun=hclust,dendrogram="none",symm=FALSE) heatmap.2颜色选择函数col=colorRampPalette(c("black","red")) 中10个是当地固有个体(old)，另外10个是新迁入的个体(new)，old和new个体两两随机配对，分别用不同颜色染料（波长分别为555和647nm）标记后，在同一张基因芯片上杂交；此外，每个基因在每张芯片上都重复点样3次，因此此数据是有3个replicates及10张芯片的双通道芯片。数据是样点的信号强度值，没有经过标准化处理的。
通信接口介绍
一 IIC通信 现今，在低端数字通信应用领域，我们随处可见IIC (Inter-Integrated Circuit) 和SPI (Serial Peripheral Interface)的身影。原因是这两种通信协议非常适合近距离低速芯片间通信。Philips（for IIC）和Motorola（for SPI）出于不同背景和市场需求制定了这两种标准通信协议。 IIC 开发于1982年，当时是为了给电视机内的CPU和外围芯片提供更简易的互联方式。电视机是最早的嵌入式系统之一，而最初的嵌入系统是使用内存映射（memory-mapped I/O）的方式来互联微控制器和外围设备的。要实现内存映射，设备必须并联入微控制器的数据线和地址线，这种方式在连接多个外设时需大量线路和额外地址解码芯片，很不方便并且成本高。 为了节省微控制器的引脚和和额外的逻辑芯片，使印刷电路板更简单，成本更低，位于荷兰的Philips实验室开发了‘Inter-Integrated Circuit’，IIC 或 IIC ，一种只使用二根线接连所有外围芯片的总线协议。最初的标准定义总线速度为100kbps。经历几次修订，主要是1995年的400kbps，1998的3.4Mbps。 有迹象表明，SPI总线首次推出是在1979年，Motorola公司将SPI总线集成在他们第一支改自68000微处理器的微控制器芯片上。SPI总线是微控制器四线的外部总线（相对于内部总线）。与IIC不同，SPI没有明文标准，只是一种事实标准，对通信操作的实现只作一般的抽象描述，芯片厂商与驱动开发者通过data sheets和application notes沟通实现上的细节。 IIC(INTER IC BUS) IIC的数据输入输出用的是一根线，但是由于IIC的数据线是双向的，所以隔离比较