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按学科门类筛选，可继续下钻到具体专业与课程；内容为各课程复习要点，用于面谈与笔试备考。
互换性与技术测量（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i learned about the concept and effect of interchangeability(互换性), shaft-hole fit and choice of fit system(孔轴配合与配合副的选用), geometric tolerance(几何公差) and surface roughness.
Explanation of concepts:
Interchangeability:
The interchangeability is an ability that the size or the function of one product or part can be replaced by another product or part.
Effect of the interchangeability: it is very convenient for the products’ design, manufacture maintain and the production efficiency will be higher and it will reduce the workers’ work, save the cost.
Shaft-hole fit and choice of fit system:
There are three types of fit: clearance fit(间隙配合), transition fit(过渡配合), interference fit(过盈配合).
Dmax and dmax are named upper limit size(上极限尺寸).
Dmin and dmin are named lower limit size(下极限尺寸).
D is the ideal size.
ES=Dmax-D es=dmax-D
EI=Dmin-D ei=dmin-D
ES and es is named upper limit deviation(上极限偏差).
EI and ei is named lower limit deviation(下极限偏差).
If the Dmin≥dmax, EI≥es, then the hole tolerance zone is above the shaft tolerance zone, then this fit is the clearance fit.
Max clearance is Xmax=Dmax-dmin=ES-ei;
min clearance is Xmin=Dmin-dmax=EI-es.
If the Dmax≤dmin, ES≤ei, then the shaft tolerance zone is above the hole tolerance zone, then this fit is the interference fit.
Max interference is Ymax=Dmax-dmin=ES-ei;
Min interference is Ymin=Dmin-dmax=EI-es.
If the Dmax>dmin and Dmin<dmax , ES>ei and EI<es, then this fit is the transition fit.
Hole-basic system(基孔制)
The lower limit deviation of the hole is zero.
Shaft-basic system(基轴制)
The upper limit deviation of the shaft is zero.
Usually we choose the hole-basic system. Because the size of the hole is easy to ensure and to measure. In some special situation, we choose the shaft-basic system, such as in some special structure, we already have a shaft to assemble with several holes. IT is the standard tolerance grades. The alphabet is the basic deviation.
For example,
is the hole-basic system. is the shaft-basic system. H/h is the base.
In the hole-basic system, a~h is the clearance fit, js/j/k/m/n is the transition fit, p~zc is the interference fit.
In the shaft-basic system, A~H is the clearance fit, JS/J/K/M/N is the transition fit, P~ZC is the interference fit.
Geometric tolerance:
After the processed, the actual geometric elements and the ideal geometric elements have some difference in the shape, direction and the position, these difference is the geometric tolerance.
There are four types of geometric tolerance: shape tolerance, direction tolerance, position tolerance and run-out tolerance.
Type of the
tolerance
name
symbol
Shape tolerance
Straightness(直线度)
—
Flatness(平面度)
424815109855
Roundness(圆度)
45085069850
Cylindricity(圆柱度)
Direction tolerance
parallelism（平行度）
Verticality（垂直度）
Slope（倾斜度）
Position tolerance
Position degree（位置度）
Coaxiality（同轴度）
Concentricity（同心度）
degree of symmetry （对称度）
Run-out tolerance
Circular Runout（圆跳动）
Total runout（全跳动）
Closed loop:
09525The dimension chain(尺寸链): when we machine a workpiece, the dimensions of the workpiece will connect as a loop, the finial cimension which is not be labeled is called closed loop.
When the other dimension don’t change, only change one dimension , it its increasing causes the closed loop increasing, it is a increasing link or it is a decreasing link.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：互换性与技术测量
分子生物学
核心内容
· 复制（DNA Replication，DNA复制）
· 时期：有丝分裂间期（interphase）和减数第一次分裂前的间期
· 场所：主要在细胞核（nucleus）中
· 条件（缺一不可）
· 模板（template）：亲代DNA的两条母链
· 原料：四种脱氧核苷酸（deoxynucleotide）
· 能量：ATP
· 一系列酶（enzymes）
· 过程
· 解旋（unwinding）：在解旋酶（helicase）作用下，利用细胞提供的能量将两条螺旋双链解开
· 合成子链：以解开后的母链为模板，以游离脱氧核苷酸为原料，在有关酶作用下按碱基互补配对原则（complementary base pairing）合成互补子链；随解旋进行子链不断延长，每条子链与对应母链盘绕成螺旋结构
· 形成新的DNA分子
· 特点：边解旋边复制；半保留复制（semi-conservative replication）
· 结果：一个DNA分子复制一次形成两个完全相同的DNA分子
· 意义：使亲代遗传信息传给后代，保持遗传的连续性
· 准确复制的原因
· DNA独特的双螺旋结构（double helix）为复制提供模板
· 碱基互补配对能力保证复制准确无误
· 核酸（Nucleic Acid）
· 两大类：核糖核酸（RNA）与脱氧核糖核酸（DNA）
· DNA（脱氧核糖核酸）
· 组成：由脱氧核苷酸（deoxyribonucleotide）聚合而成的大分子；脱氧核苷酸 = 碱基 + 脱氧核糖（deoxyribose）+ 磷酸
· 碱基4种：腺嘌呤（A, adenine）、鸟嘌呤（G, guanine）、胸腺嘧啶（T, thymine）、胞嘧啶（C, cytosine）
· 结构：两条多脱氧核苷酸链围绕共同中心轴盘绕，构成双螺旋结构
· 功能：遗传信息的载体；为生物基因信息的转录提供模板
· RNA（核糖核酸）
· 组成：由核糖核苷酸（ribonucleotide）组成的长链状分子；核糖核苷酸 = 磷酸 + 核糖（ribose）+ 碱基
· 碱基4种：A、G、C、U（尿嘧啶, uracil），其中U取代DNA中的T
· 分类：mRNA、tRNA、rRNA
· 功能：mRNA为蛋白质合成提供模板，含有遗传密码（genetic code）
· 转录（Transcription）
· 定义：遗传信息从DNA流向RNA的过程
· 模板：双链DNA中确定的一条链（模板链用于转录，编码链不用于转录）
· 原料：A、U、C、G四种核糖核苷酸
· 催化酶：RNA聚合酶（RNA polymerase）
· 产物：RNA
· 翻译（Translation，蛋白质的生物合成）
· 模板：mRNA
· 场所/作用因子：核糖体（ribosome）
· 机制：由tRNA将mRNA上的核苷酸序列转换为氨基酸序列，合成多肽链（polypeptide chain）
参考：来源：分子生物学.png｜专业：生物科学｜课程：分子生物学
工程材料与热处理（英文要点·大三大四）
核心内容
Basic concepts:
In the course i learned the metal structure and metal crystal, iron-carbon alloy and heat treatment of steel.
Explanation of concepts:
The metal structure and metal crystal:
This part is in the 《engineering chemistry》.
Iron-carbon alloy and iron-carbon phase diagram:
09525In different situations of different carbon contents and different temperature, what is in the iron-carbon alloy is different,too.
Left is a diagram which reflects the material states of the iron-carbon alloy in different situations.
Austenite(奥氏体): face-central cubic structure, usually is the γ-Fe +few C, without magnetism, low hardness have some toughness.
Ferrite(铁素体): a lot C add into α-Fe, body-central cubic structure, can content very little C.
Cementite(渗碳体): high hardness and very brittle.
Pearlite(珠光体):the ferrite and the cementite mixed piece by piece.
Ledeburite(莱氏体): mixture of the austenite and the cementite, hard and brittle.
GS line: when cooling down, the austenite turns into ferrite, when heat up the ferrite turns into austenite.
ES line: the solubility curve of the carbon in austenite, when the temperature is lower than this line, the carbon will separate out as Fe3C from the austenite, and the Fe3C is called secondary cementite. ES line is also called ACm line.
PQ line: it is the solubility curve of carbon in ferrite, when the ferrite cooling down from the 727℃, the solubility of the carbon becomes little. The carbon will separate from the ferrite as Fe3C, which is called tertiary cementite.
The carbon content of the technically pure iron(工业纯铁) is under 0.0218%.
The carbon content of the carbon steel(渗碳钢) is 0.0218%~2.11%.
The carbon content of the white cast iron(白口铸铁) is 2.11%~6.69%.
false
Heat treatment of steel:
Heat treatment of steel is to use hear up, keep warm and cooling to change its internal structure. They can reduce the hardness and reduce or eliminate the internal stress and make the steel have better performance.
There are four basic crafts of heat treatment: annealing(退火), quenching(淬火), normalizing(正火), tempering(回火).
Annealing and normalizing: these two are heating up the workpiece to one temperature, then cool the workpiece to reduce the hardness, eliminate the internal stress. The difference between them is normalizing is to cool the workpiece fast,but the annealing is usually to cool the workpiece slowly the hardness after normalizing is a litter higher than annealing. Normalizing is cooled in the air or blow cold air, is treat the low carbon steel. Annealing is cooled with the furnace. They are all for elimating the internal stress.
Quenching : quenching is to heat up the workpiece higher than AC1(730℃) or AC3(791℃). After the holding temperature, then put the workpiece into the water or the oil to cooling fast. It is often regard as the preparation of the tempering.
Tempering: it is after the quenching, heat up the steel to a temperature under AC1, then cool the steel to the room temperature in a proper velocity to reduce or eliminate the residual stress(残余应力).
Type of the tempering:
1,low temperature tempering: 150~250℃, keep the high hardness, HRC58~64, and high resistance of wearing, mainly for low the quenching stress and brittle. Usually for the high carbon steel workpiece, die the workpiece with high wear resistance.
2,mid temperature tempering: 350~500℃, HRC35~45, high elasticity and yield limit, treat the spring.
3,high temperature tempering:500~650℃, HRC25~35, high strength, good plasticity and toughness, usually called hardening and tempering(调质), using for treating the structure parts, such as the changeable load bars, shafts and bolts.
We once practiced the quenching when we did the engineering training. First , we put the workpiece in the box-type furnace and heat up to 810℃, after two hours of holding temperature, we toot it out and put it into the water to cooling. Then we measured the hardness of the surface of the workpiece.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：工程材料与热处理
金工实习（英文要点·大三大四）
核心内容
Basic concepts:
In this course, we mainly learned how to use several tools which are very popular in factory, such as milling lathe,numerical controlled lathe, numerical controlled milling, drilling, welding, benchwork and non-traditional-machining spark cutting, heat treatment. The numerically controlled lathe programming and numerically controlled milling programming are the key of this course.
We made a frame for candle with other craftwork. The lampstand of the frame is using the milling, drilling and benchwork. As for the body of the frame, we used the lathe.
We finished out work all in the engineering training center of our school. And teacher ave us grade based on our theoretical exam and our production.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：金工实习
分子生物学实验
核心内容
· 课程定位：分子生物学实验，核心为植物核酸（RNA/DNA）的提取、纯化与检测三大环节。
· 一、植物总RNA的提取、纯化与检测
· 原理
· RNA极易降解，提取关键为最大限度抑制内源性（endogenous）与外源性（exogenous）核糖核酸酶（RNase）对RNA的降解。
· 高浓度强变性剂异硫氰酸胍（guanidinium isothiocyanate）可溶解蛋白质、破坏细胞结构、使核酸酶失活，使RNA从细胞中释放。
· 辅助试剂：SDS、酚（phenol）、氯仿（chloroform）等。
· 步骤（Trizol法）
1. 100 mg叶片，液氮研磨；加1 ml Trizol试剂，用力摇15秒；15–30℃温育5分钟。
2. 4℃、12000 g离心10分钟，溶液分三相，取上层水相（aqueous phase）转移至新离心管，加200 μl氯仿，振荡15秒。
3. 上清加0.5 ml异丙醇（isopropanol），颠倒混匀，15–30℃温育10分钟。
4. 4℃、12000 g离心10分钟，得RNA沉淀；去上清。
5. 用水溶解RNA，加等体积5 M NaCl和4 M（（原扫描件字迹不清）），-20℃温育10分钟。
6. 弃上清，用无水乙醇洗一次。
7. 260 nm测OD值，计算（浓度/纯度）。
· 注意事项（左侧注释）
· 戴手套、使用RNase-free耗材、DEPC处理水（DEPC-treated water）。
· 分光光度法检测RNA纯度：A260/A280比值。
· 二、植物基因组DNA的提取、纯化与检测
· 原理
· 从植物组织提取DNA是下游操作的必要前提。
· 高盐低pH法：利用高盐、低pH的提取缓冲液使DNA溶解于上清，去除蛋白质等杂质，最后用无水乙醇或异丙醇沉淀得到DNA。
· 步骤
1. 叶片（约1 g）置研钵中，加液氮研磨成粉末，加约1 ml提取缓冲液。
2. 取约300 μl上清，加入2倍体积预冷无水乙醇。
3. 从沉淀中挑出DNA，溶解，用分光光度法测定。
4. 4000 g离心。
5. 含洗沉淀、干燥、溶解等步骤（编号1~13，（原扫描件字迹不清））。
· 注意事项（右侧注释）
· DNA提取注意事项与浓度检测：OD260/280。
· 三、通用检测要点（易考点）
· 分光光度法（spectrophotometry）为RNA/DNA纯度与浓度检测的核心手段。
· RNA纯度指标：A260/A280；DNA纯度指标：OD260/280。
· 关键操作条件：4℃低温离心、12000 g（RNA）、4000 g（DNA）、液氮研磨、异丙醇/无水乙醇沉淀。
· 防降解核心：RNase-free耗材、DEPC水、手套、强变性剂（异硫氰酸胍）。
参考：来源：分子生物学实验.png｜专业：生物科学｜课程：分子生物学实验
MATLAB 基础及应用（英文要点·大三大四）
核心内容
Basic concepts:
Matlab is a software, we can use it to program and draw the diagrams. It is similar to the C language. In this course, we learned some simple programs of the Matlab.
Explanation of concepts:
We can write the program in some files and then save the files, and when we want to use it. We can use it directly in Matlab. For example, we can write a program in a file,
And we open the Matlab and type in
-6096049530>>program1 → we only need to type
radius= in the file name.
1
area=3.1416 → it can figure out the
result.
Also, it can draw some diagrams. The order bar can dram the bar chart. The order pie can draw the pie chart. The order area can draw the line chart. The order stem can draw the stem chart. For example,
Application: we can use the tool box of Matlab to solve mechanical optimization design, linear programming problems and nonlinear programming problems.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：MATLAB 基础及应用
动植物野外实习
核心内容
· 课程定位：动植物野外实习，核心为物种识别（recognition）与标本制作（specimen preparation）两大模块。
· 一、动物部分
· 常见昆虫识别
· 凤蝶科（Papilionidae）：鳞翅目（Lepidoptera）代表类群。
· 螳螂目（Mantodea）：捕食性昆虫代表。
· 昆虫标本制作（5 步流程）
· 标本回软：用水蒸气湿润虫体，使其回软，便于后续操作。
· 针插固定：昆虫针从虫体背部中央稍右位置插入（从中胸背板处进针）。
· 展翅整姿：用镊子将翅膀展开，用大头针固定在展翅板上定型。
· 干燥保存：置于通风阴凉处风干。
· 贴签保存：标签注明昆虫名称等信息，贴于标本下方。
· 小型哺乳动物（老鼠）标本制作（5 步流程）
· 用解剖刀小心剥下老鼠表皮。
· 在表皮内涂防腐剂。
· 用铁丝插入体内支撑固定表皮。
· 用棉花填充表皮内部。
· 固定到木板上，置阴凉处干燥保存。
· 二、植物部分
· 常见植物识别
· 银杏（Ginkgo biloba）。
· 金线松（原文如此，名称待核实）。
· 植物标本制作（3 步流程）
· 采集与清洗：寻找并挖出完整植物体，小心清洗表面。
· 压制干燥：将植物摊开于两张白纸之间，再移入报纸中，使之尽快干燥、压平。
· 装订与记录：将干燥标本粘到新白纸上，在纸张右下角写明植物名称等信息。
· 易考点
· 昆虫针插的进针位置（背部中央稍右、中胸背板）。
· 昆虫标本与植物标本干燥条件的区别（均需阴凉/通风，植物强调尽快压平干燥）。
· 动物标本防腐与支撑填充材料（防腐剂、铁丝、棉花）。
· 标签信息与粘贴位置（昆虫贴下方、植物写右下角）。
参考：来源：动植物野外实习.png｜专业：生物科学｜课程：动植物野外实习
数控技术（英文要点·大三大四）
核心内容
Basic concepts:
In this course, I mainly learned the classification of digit control system, digital controlled lathe programming, digital controlled milling machine programming and the interpolation calculation principle(插补原理).
Explanation of concepts:
Digit control technology is a kind of method using of digital information to control the machine movement and machining process. It has high accuracy and high efficiency. And it is very suitable for the mass production(大量生产).
Classification of digit control system:
The digit control system mainly can be divided into three kinds:
1, open loop serve system(开环);
2, closed loop serve system(闭环);
3, semi-closed loop serve system(半闭环/半开环).
There is no feedback and no position measuring element in the open loop serve system. The system has the one-way instruction flow(单向指令流), it is cheep, convenient and the structure of it is simple.The simplified structure is following:
As for the closed loop serves system, it has feedback and position measuring element.the position measuring device is installed on the operating platform. When it measures the actual displacement of the operating platform, it will feedback the signal to the comparator to compare with the command signal, then control the serve drive motor with the difference valve until the difference value turn into zero. This kind serves system has very high accuracy,but expensive of course.
As for the semi-closed loop serve system, the measuring device is not to measure the displacement of the operating platform directly, but by measuring the angular displacement of the motor or the screw to measure the displacement of the operating platform indirectly. And the operating platform is out of the feedback loop. Lower accuracy than the closed loop serve system,but easy to equipment install and trial run, and the cost is lower,too.
Digital controlled lathe programming:
We use FANUC programming language, which is widely used in china.
For example,
In FANUC, we use the G code to write the program.
First, we need to know that in G code, the code start with G is the preparatory function(准备功能), F is the feed function(进给功能), S is the speed function(速度功能), T is the tool function(刀具功能), M is the auxiliary function(辅助功能).
We process the workpiece from right to left, and we use the external turning
Tool. We choose the workpiece coordinate system origin at the centre of the left end surface of the workpiece. The cutting starting at the point (200,350), the speed of main shaft is 630r/min, and the feed velocity is 0.15 mm/r.
Following is the program:
O0020 --- program name
N01 F50 X200 Z350 --- G50 tool offset(刀具偏置)
N02 S630 T0101 M03 --- M03 main shaft start to rotate
clockwise; S630 the speed of main
shaft is 630 r/min
N03 G00 X50 Z76 --- move near to the workpiece
N04 G00 X50 Z75 --- G00 point location fast moving
N05 G01 X80 Z60 --- G01 linear interpolation
N06 Z50
N07 G02 X80 Z40 R70 --- G02 clockwise circular interpolation
the X and Z is the end point coordinate
N08 G01 X80 Z30 linear interpolation
N09 X85 --- the diameter of workpiece is Ф85
N10 G00 X200 Z350 M05 T0100 --- make the tool goes back to the start
To the start and stop the main shaft
Tool retract
Digital controlled milling machine programming:
The workpiece is 180*90*120mm
A(0,0) B(0,40)
C(15,70)D(45,70)
E(100,60) F(150,40)
G(170,40) H(170,0)
We choose point A as the workpiece coordinate system origin. The three holes are already finished and we can use the two small ones to locate the workpiece, and compress the workpiece with the big hole. We choose the milling cutter with diameter is 10mm. The adjusted cutter point is (-25,10,40). The move path:
adjusted cutter point---B---C---D---E---F---G---H---A---adjust cutter point
Following is the program:
O0020 program name
N01 G92 X-250 Y10 Z40 ---G92 present register
N02 G90 G00 Z-16 S300 M03 ---G90 absolute coordinate
G00 point location
M03 main shaft start to rotate clockwise
N03 G41 G01 X0 Y40 F100 D01 ---G41 cutter radius left compensation
Loot at the direction of the tool moving,
the tool is on the left of the workpiece
D01 all the diameter of the cutter from the
system data which we saved before start
N04 X15 Y70
N05 X45
N06 G02 X100 Y60 R40 ---G02 clockwise circular interpolation
The number follow the R is the radius
N07 G03 X150 Y40 R60 ---G03 anti-clockwise circular interpolation
The X and Y is the end point coordinate
N08 G01 X170
N09 Y0
N10 X0
N11 G00 G40 X-25 Y10 Z40 ---G40 cancel the cutter compensation
The cutter back to the origin point
N12 M30 ---M30 stop the program and return
the cutter compensation(刀补):
The system can calculate the path of the cutter center as the cutter has radius. So we can program directly without considering the radius of the cutter if we use the cutter compensation.
G41 is the left cutter compensation.
G42 is the right cutter compensation.
Interpolation calculation principle(插补计算原理):
When the machine process the workpiece, the oblique line and the circle which the tool move is not smooth, it is fold line(折线), the interpolation calculation principle is help us know how can we get the fold line.
Point-by-point compare method(逐点比较法):
the Xe and Ye is the point we want to get.
We can bring the x and y into the formula and get the F.
If F≥0, then the x=△x+1, y=y;
If F≤0, then the x=x, y=△y+1.
Digital differential analyzer(DDA数字积分法):
First, we should define the register digit, then we define the change value of the x and y. The principle of DDA is when the valve in the register is larger than the register digit, it will overflow(溢出), and the accumulator(累加器) will add a change value of the x or y. For example,
The register digit is 8 , the start point is (0,0), end point is (4,6), and the change value is 2.
time
x
△x
y
△y
point
1
0+4=4<8
0+6=6<8
(0,0)
2
4+4=8+0
+2
6+6=8+4
+2
(2,2)
3
0+4=4<8
4+6=8+2
+2
(2,4)
4
4+4=8+0
+2
2+6=8+0
+2
(4,6)
The DDA is easy to realize multicoordinate(多座标) linkage, easy to realize the interpolation of high order curve, and speed of operation is high.
Circular interpolation principle(圆弧插补原理):
Start point A(x0,y0), end point(xe,ye), radius R, present point(xm,ym).
We can calculate the curve according to the above pictures.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：数控技术
动物学
核心内容
· 动物学（Zoology）定义：研究动物的形态结构、分类、生命活动与环境的关系以及发生发展规律的科学
· 基本方法：①观察描述法 ②比较法 ③实验法 ④历史法
· 生物的基本特征：
· 具有共同的物质基础和结构基础——物质基础：蛋白质、核酸；结构基础：细胞
· 有新陈代谢作用
· 具有应激性
· 有生长发育生殖现象
· 有遗传和变异的特征
· 能适应一定的环境
· 分类等级（由高到低）：界(Kingdom)、门(Phylum)、纲(Class)、目(Order)、科(Family)、属(Genus)、种(Species)
· 动物分类（各门/纲特征与举例）：
· 原生动物门：
· 特征：整个身体由一个细胞组成
· 举例：藻类、草履虫
· 软体动物门(Mollusca)：
· 特征：身体柔软而不分节
· 举例：蜗牛、河蚌、乌贼、章鱼
· 节肢动物门：
· 特征：身体两侧对称，由一列体节构成，可分为头、胸、腹三部分
· 举例：虾、蟹、蜘蛛、蜈蚣
· 鱼纲：
· 特征：用鳃呼吸、用鳍运动的脊椎动物(Vertebrate)
· 举例：各种鱼；易考点：鲸鱼、海豚不是鱼类，而是哺乳动物
· 哺乳纲(Mammal)：
· 特征：多数身体被毛；体温恒定；胎生(viviparous)和哺乳
· 举例：dog、cat、human
参考：来源：动物学.png｜专业：生物科学｜课程：动物学
机电传动控制与 PLC（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly learned the load characteristic of the electric mechanical drive system, the conditions of electric mechanical system stable operation, mechanical characteristic of mechanical machinery, mechanical characteristic of separately excited DC electric motor(他励直流电机including starting characteristic, speed control characteristic,braking characteristic),mechanical characteristic of three-phase asynchronous electric motor,basic structure of the PLC, ladder diagram and some basic instruction list programming language.
Explanation of concepts:
The load characteristic of the electric mechanical drive system is the function relationship between the load torque and rotational speed on the motor shaft.
There are mainly four types load characteristics,constant torque type,constant power type, out-central type(离心型),linear type.
The conditions of electric mechanical system stable operation:
, the mechanical character curve of motor n=f(TM) and the load character curve n=f(TL) have intersection point.
2,when the rotate speed is larger than the speed at the balance point, if there is a disturb which makes the rotate speed n larger,when the disturb disappears, the TM<TL;if it make n smaller, when the disturb disappears ,the TM>TL.
The DC motor:
The structure of the DC electric machinery:
The working principle of the DC electric machinery:
The electric motor have two pole. The armature winding is a winding, and the two ending of the winding is connected on the two commutator bars, and the commutator bars connect with the electric brush. When the electric machinery work as the electric motor, the power source give the winding a current, and the winding is between two poles. When there is a current in the wire, and the wire is in a magnetic field, there will be a force acting on the wire, the force is called Ampere force .In the left picture, we can see the Ampere force is toward left, so the winding will rotate anticlockwise. When the winding rotates 180°, the commutator bars will change the electric brushes which they are connected with. So the current in the winding will change its direction, and make sure the Ampere force keep the winding rotating anticlockwise.
When the electric machinery works as a generator, there will be a external force making the winding rotating in a direction, and makes it cut the magnetic line of the magnetic field. So there will be a current in the winding, the electricity is generated.
Left-hand law: using the left hand, the finger towards to the direction of the current, then let the magnetic line through the palm, then the direction of the thumb is the direction of the force.
The right-hand law is about the direction of the current.
The electromotive force between the two electric brushes is always expressed as:
E--electromotive force;
Ф-- the magnetic flux(磁通量) of a couple of poles;
n--the rotating speed of the armature(电枢);
Ke-- a constant relating to the structure of the electric machinery.
The electromagnetic torque of the electric machinery:
T--electromagnetic torque(电磁转矩);
Ф--the magnetic flux of a couple of poles;
Ia--the current of the armature;
Kt--a constant relating to the structure of the electric machinery, Kt=9.55Ke.
The mechanical characteristic hardness:
The larger is β, the softer the mechanical system is .
Mechanical characteristic of DC electric machinery:
Mechanical characteristic includes intrinsic mechanical characteristic and artificial mechanical characteristic.
The intrinsic mechanical characteristic is the characteristic when the electric machinery is working under the rated voltage(额定电压) and rated magnetic flux(额定磁通量). We can get it from the parameters wrote on data plate.
The artificial mechanical characteristic means that the mechanical characteristic when the voltage and the magnetic flux are not the rated value, and there is a resistance in series with the armature circuit.
1,when there is a resistance in series with the armature circuit:
The function of the artificial mechanical characteristic is :
With the increasing of the Rad, the system is more and more soft.
2,when change the voltage of the armature:
081915
When , and change the voltage of the armature:.
3,when change the magnetic flux:
When and change the magnetic flux Ф:.
The electric motor can be divided into four kinds by the excitation method(励磁方法):the separately excited motor(他励电动机),shunt motor(并励电动机), series motor(串励电动机) and compound motor(复励电动机). We mainly learned the separately excited motor. The other three kinds are not involved.
The starting characteristic of the separately excited motor:
The starting of the separately excited motor means connect the motor into the electric circuit, make the rotator(转子) rotate and get the rated speed. The starting current is . Before the rotator rotate, there is no inductive reactance in the armature, so the current is very large, can be 10~20 times of the rated current, which may burn out the circuit. And the starting torque will be very large, which may hurt the transmission element. So the separately excited motor can not be started directly. There are mainly two starting methods, one is buck starting(降压启动) and another is external resistance starting.
The inductive reactance(感抗): when there is current through a winding, there will be a magnetic field, and the field will generate a current in the winding too, and the current generated is opposite to the original one.
1,The buck starting:
The buck starting means when we want to start the motor, we can make the voltage lower than the rated voltage, and add the voltage with the increasing of the rotating speed of the motor until the voltage meet the rated voltage.
2, The external resistance starting:
The external resistance starting means we can connect external resistance into the starting circuit, and when we want to start the motor, we make the current through the resistance, and when the rotating speed is high enough, we make the resistance cutting-out(短路), and then the rotating speed will meet the rated speed.
and we can make more resistances in series in the circuit, and make them cutting-out one by one, which will make the starting better. The normal starting have three or four step.
Such as the motor in the factories need to be started quickly, so there will be only one external resistance. But the elevator need to move smoothly, so there will be many external resistances.
Speed control characteristic:
Speed regulation of the motor is to change the stable speed of the motor under some load.
The speed regulation and the speed changing is two different concepts. The speed changing is because the change of the load. And the speed regulation is because the artificial adjusting, such as adjust the resistance in series with the armature.
A, change the resistance which is in series with the armature:
We can change the resistance in series with the armature to change the stable speed of the motor, just like the left picture. The A-B-C is the changing step.
But this way has many disadvantage:
1, when the resistance is larger , the hardness of the system is softer, and the stability of the system is lower;2, when there is no load or there is small load, the range of the changing of the speed is small;3, it is hard to realize the stepless speed regulating（无级调速）. And the starting resistance can not be the regulating resistance, or it will be burned out.
B,change the voltage of the armature:
Under the load torque TL, when we add different voltage UN, U1,U2,U3, we can get different rotating speed na,nb,nc,nd, and realize the regulation of the speed.
When the first voltage is U1, and the rotating speed is nb, the torque is TL, we add the voltage to UN, then the T will suddenly add to Lg=(UN-Eb)/Ra. Then the characteristic curve will change along the curve of UN and the rotating speed will add to na.
The characteristic of this way:
1,when the voltage change continue, can realize the stepless speed regulating, but usually the speed must lower than the rated speed.
2,the regulation characteristic of the speed is parallel with the original characteristic, so the hardness of the mechanical characteristic is not changed, the stability is high , and the speed regulation range is large.
3,when we regulate the speed, the current of the armature is not concerned with the voltage U, and the Ф=ФN, so the torque of the motor is not changed, the regulation is constant-torque regulation of speed.
4,we can start the motor by regulating the voltage of the armature.
C,change the main magnetic flux of the motor:
We know that under a load power PL, change the main magnetic flux can change the rotating speed, and realize the regulation of the speed.
The regulation step is like the left picture.
When we want the speed down, it will change along c-d-b. When we want the speed up, it will change along b-e-c.
The characteristic of this way:
1,can realize smooth stepless regulating speed, but can only adjust the speed higher than the rated speed.
2, the regulation characteristic of the speed is a little softer, and limited by the direction-change condition of the motor, the speed of simple separately excited motor can not higher than the 1.2 times of the rated speed, so the regulating range is not big. If we use special material to product regulation motor, the range can be larger, but this kind of motor is big and expensive.
3, this kind regulation method does change the power, so this is constant-power regulation of speed.
Braking characteristic(制动特性):
This part is not important, and we only learned some concepts of it.097155
There are mainly three kinds of braking method:
1,feedback braking(反馈制动): feedback the mechanical energy of the motor absorbing to the power grid(电网) or resistors. Save energy, but not safe.
2,reverse connection braking(反接制动): change the direction of the supply voltage, can make it stop quickly.
3,dynamic braking(耗能制动): change the supply voltage to 0, then in series a resistor to consume the energy. Safe and high accuracy.
Mechanical characteristic of three-phase asynchronous motor(三相异步电动机):
The structure of the three-phase asynchronous motor:
The work principle of the three-phase asynchronous motor:
The working principle of the treephase asynchronous motor is similar to the DC electric machinery, but the what the three-phase asynchronous motor using is the three-phase alternating current(三相交变电流). There are 120-degree phase difference between each of the current of the phase:
It is also the Ampere force makes the rotor rotate.
The direction of the rotating of the rotor and the magnetic field is the same, but the speed of the rotor n can’t be the same as the magnetic field n0, n<n0. So the slip ratio is showing the difference degree of the n and n0: .
Electromagnetic torque and mechanical characteristic of the three-phase asynchronous motor:
The electromagnetic torque:
It is one of the most important parameter of the three-phase asynchronous motor, it is generated by the effect of magnetic flux of each pole and the current of rotor I2. The phase of the current of the rotor I2 is behind the electromotive force E2 at φ2, so the electromagnetic torque is:
KT is a coefficient which is relative with the structure of the motor.
Mechanical characteristic:
Under a certain power source voltage U1 and the resistor R2, the curve of relationship between the electromagnetic torque and the slip ratio(转差率) T=f(s) or the curve of the relationship between the rotating speed and the electromagnetic torque n=f(T) is called the mechanical characteristic curve.
The function of the torque T:
P2 is the mechanical power of the main shaft of the motor;
N is the rotating speed of the main shaft of the motor.
The rated torque is .
The max torque is .
X20 is the inductive reactance(感抗).
The starting torque is .
The starting of the the three-phase asynchronous motor:
There are two methods of the starting of the the three-phase asynchronous motor: direct starting and the buck starting.
Direct starting:
If we start the motor directly, the method is easy, but the starting current is very large and it make the voltage of the starting is very small, which may affect the work of the motor.
Buck starting:
The direct starting make the voltage of the circuit go down a lot, so we can choose the buck starting, to reduce the starting current. There is a very useful starting method of buck starting: star-delta starting.
If the motor is working under the delta winding(三角形绕组), then when we start the motor we can change the winding into the star winding(星形绕组), which can make the voltage of each phase is the square root of 1/3 times of the normal voltage, and the current is 1/3 of the normal current. But this way only fit the non-load starting or the light-load starting. When we start the motor, we connect the Q3 and Q1, when the speed is near the rated speed, we cut off the Q3 and connect the Q2.
The speed control of the three-phase asynchronous motor:
There are mainly three speed control method of the the three-phase asynchronous motor, frequency control speed regulation,pole-changing speed regulation and variable slip ratio speed regulation.
The frequency control speed regulation is usually used in air conditioner, fridge and the washing machine.
The pole-changing speed regulation is usually used in milling machine and some other manufacturing machine.
The variable slip ration speed regulation is usually used in erecting equipment (起重设备).
The braking of the three-phase asynchronous motor:
There are mainly three method of the braking of the three-phase asynchronous motor, feedback braking(反馈制动), the reverse connection braking(反接制动) and the dynamic braking(耗能制动). They are similar to the braking of the DC electric machine.
PLC:
Basic structure of PLC:
We mainly used the S7-1200 type PLC, so this part are all based on this type PLC.
,CPU: central processing unit, including microprocessor (chip) and memorizer.
CUP constantly gathers the input signal, execute the user programs,refresh the output of the system. The memorizer is used to store the programs and data.
2,the input module and the output module:
The input module is used to receive and gather the input signal, such as the signal of switch, current and voltage signal.
The output module is used to control the electromagnet(电磁铁), electromagnetic valve(电磁阀), indicator light(指示灯) or numerical display device.
The input and the output module together are called I/O module. The digital input and digital output module are called DI and DO module. The analog input and analog(模拟输入和模拟输出) are called AI and AO module. They are all called signal module, and SM for short.
3,communication module:
The PLC can add three communication module at most, can use ASCII communication protocol, USS drive protocol,Modbus RTU master protocol and Modbus RTU slave station protocol.
4,programming software, used to writing the program of the PLC.
The characteristics of PLC:
1, the method of programming is easy to learn.
2, have many function, and the ratio of the performance and the cost is high.
3, hardware is complete, easy to use, and can fit different situation.
4, high reliability, good capacity of resisting disturbance(抗干扰能力).
5, need less work to operate it.
6, less work to fix it, easy to fix.
7, small volume, small energy consumption.
Application of the PLC:
Logical control, motion control, communication and networking.
Ladder diagram:
Ladder diagram is a widely used PLC programming language. It is audio-visual and easy to understand. It consists of contact(触点),coil(线圈) and order, expressed by the box square frame.
The contact represents the input signal, such as the switching signal.
The coil represents the output result, such as the indicator light.
The square frame represents the command, such as the timer and counter.
The analysis order is pom up to down, from left to right.
For example,
This is a typical circuit, the start-retention-stop electric circuit(起保停电路).
The | | is normally open contact(常开触点).
The |/| is normally closed contact(常闭出点 if we touch it , the circuit will cut off).
And the ( ) is the coil.
And we can rewrite it into instruction list programming language.
LD I0.0 LD -- load, is equal to the “| |”;
O Q0.2 O -- or;
AN I0.1 AN -- and not;
= Q0.2 = -- output;
And there are some other signals, such as,
A -- and; ON -- or not; LDN -- negation then load, is equal to the”|/|”.
So the function of this circuit is to start the motor when we push the start button and keep it run until we push the stop button.
When we push the start button, the I0.0 closed, and I0.1 is already closed, then the line is conducting, and the coil Q0.2 is electrify. This is the start function. Meanwhile , it is normally open contact Q0.2 is connect and when we relives the start button, the I0.0 is cut off, but the Q0.2 is still connecting, so through the OR gate, the circuit is also running. This is the retention function.
Until we push the stop button, the I0.1 cut off, then the coil Q0.2 and Q0.2 are both cut off, when we relives the stop button, they will still keep cutting off situation, so it will not connected, this is the stop function.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：机电传动控制与 PLC
动物学实验
核心内容
· 显微镜的使用与保护（Microscope operation & maintenance）
· 取放：小心取出显微镜并置于实验桌上；实验结束后小心放回储物盒（storage box）
· 使用流程：
· 检查镜头（lens）是否完整，开启光源（light source）并打开电源
· 将制作好的载玻片（slide）放于载物台（stage）上
· 先用低倍镜（low-power objective）寻找目标，再切换高倍镜（high-power objective）放大观察
· 观察时用眼观察，左眼用于在记录本上绘制与记录数据（原文表述如此；常规操作为右眼观察、左眼记录）
· 保护：实验结束用擦镜纸（lens paper）擦净目镜（eyepiece/ocular lens）与物镜（objective lens）
· 易考点：低倍→高倍的观察顺序；仅用擦镜纸清洁镜头，不可用手或普通纸巾
· 口腔上皮细胞切片（human oral epithelial cell smear）的制作与观察
· 属动物细胞（animal cell）临时装片制作与显微观察实验
· 与显微镜使用技能直接衔接（低倍定位、高倍观察）
· 螯虾的解剖（crayfish dissection）
· 属甲壳动物（Crustacea）代表动物的解剖观察
· 鸡的解剖（chicken dissection）
· 属鸟类（Aves）代表动物的解剖观察
· 兔子的解剖（rabbit dissection）
· 属哺乳动物（Mammalia）代表动物的解剖观察
· 课程整体结构（思维导图中心节点：动物学实验）
· 两大板块：① 显微镜使用与保护、动物标本观察；② 代表动物解剖（螯虾、鸡、兔）与细胞装片制作观察
· 解剖对象覆盖无脊椎动物（螯虾）与脊椎动物（鸡、兔），体现从低等到高等的解剖比较思路
· 易考点：各解剖对象所属分类阶元（甲壳纲/鸟纲/哺乳纲）与实验操作规范（显微镜使用顺序、镜头清洁方式）
参考：来源：动物学实验.png｜专业：生物科学｜课程：动物学实验
生产实习（英文要点·大三大四）
核心内容
Basic concepts:
In this course, we mainly visit some factories and companies to know more about the production in factory and how to design the products.
Explanation of concepts:
We mainly visited the Chery automobile company .The Chery automobile company is located in Wuhu, Anhui province.
We mainly visited the engine production workshop and the assembly workshop. In the engine production workshop , there are mainly five production lines, the cylinder production production line(引擎缸体线), the cylinder head production line(缸盖生产线), the cam rough machining production line(凸轮粗加工生产线), the cam finishing machining production line(凸轮精加工生产线) and the assembly production line(组装线). First two production lines are all form a German company named Cross Huller. The cylinder production line is a flexible production line(柔性生产线) which consists of high speed machining center(高速加工中心), cleaning machine(清洗机), assembly machine(装配机) and some other devices. It can product many kinds of cylinder which belongs to many kinds of gasoline engines(汽油机引擎) and diesel engines(柴油机引擎). As for the cylinder head production line, it can product self-contained complete cylinder heads of the cylinders. The rough machining production line consists of some Chinese product machine. The finishing machining production line is buying from a German company named Junker. And the assembly production line is buying from a Italian company named COMAU.
In the assembly workshop, the assembly production line is almost full automatic, it consists of many mechanical arms and conveyer belts. The efficiency of the assembly production line is very high.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：生产实习
基因工程（基因操作与DNA重组技术） · 基因工程（基因操作_DNA重组技术
核心内容
· 聚合酶链式反应（Polymerase Chain Reaction, PCR）
· 定义：一种用于放大扩增特定 DNA 片段的分子生物学技术；可视为生物体外的特殊 DNA 复制；最大特点是将微量 DNA 大量扩增。
· 程序：半保留复制，在合适条件下可无限扩增目标 DNA 片段。
· 三个步骤：
· 变性（denaturation）：模板 DNA 在约 95 ℃ 变性。
· 退火（annealing）：温度骤降至约 55 ℃，引物（primer）与模板 DNA 结合。
· 延伸（extension）：温度升至约 72 ℃，在 Taq DNA 聚合酶（Taq DNA polymerase）作用下延伸。
· 两个重要特性：①特异性（specificity）；②可重复循环、指数扩增（exponential amplification）。
· 应用范围：资料中未展开具体条目。
· 基因工程（gene engineering / genetic engineering）
· 定义：在生物体（胞内）对基因分子进行人工拼接（splicing）和重组（recombination），生产出目标产物，即基因克隆（gene cloning）。
· 广义：遗传工程（genetic engineering）。
· 狭义：将一种生物体（供体，donor）基因组中的目标基因转移至另一生物体（受体，recipient）中。
· 应用领域：
· 农业：转基因（transgenic）。
· 医药：基因工程药物、基因诊断、基因治疗。
· 工业：发酵。
· 环保。
· 操作对象与操作水平：
· 操作对象：基因。
· 操作水平：分子水平（基因水平）。
· 基因工程操作步骤：
· 目的基因的获得。
· 目的基因与载体的连接。
· 将重组 DNA 导入受体细胞。
· 目的基因的检测与表达。
· 基因组 DNA 技术
· 定义：资料中未展开。
· 三个基本条件：资料中未展开。
· DNA 重组技术：人工拼接、重组，是基因操作的核心。
· 易考点提示
· PCR 三步温度：95 ℃（变性）、55 ℃（退火）、72 ℃（延伸）。
· PCR 关键酶：Taq DNA 聚合酶。
· 基因工程四步流程顺序。
· 操作对象（基因）与操作水平（分子水平/基因水平）的区分。
· 基因工程应用四大领域：农业、医药、工业、环保。
参考：来源：基因工程（基因操作_DNA重组技术.png｜专业：生物科学｜课程：基因工程（基因操作与DNA重组技术）
液压与气压传动课程设计（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly made a course exercise of hydraulic transmission. The topic of my course exercise is design a hydraulic system of a water gate.
Explanation of concepts:
In this course , we work by group, each group has about 7 student. And we have our own work to do. For me, my work is to model the 3D workpiece. I also know the step of the whole work, but i don’t know the detail of many parameters, it is a long time ,you know, and the design has been given to my teacher after the class, and my work need not to know too know every parameter. So lets talk about the step of the design.
First , we should know the data of the requirement, then choose the hydraulic pump;
Second, we have choose the hydraulic, then we should design the hydraulic circuit and draw the hydraulic principle diagram;
Third, we should choose other hydraulic elements according to the requirement and the data of the hydraulic pump;
Forth, we have know all the hydraulic elements, then we should design the hydraulic manifold block(液压集成块), this is my task.
These four steps are the whole work of this course.
As for my task, we should to know what is the hydraulic manifold block. If we use the classical way to design the hydraulic system, we should use tube, and if a system is very complicated, there will be so many kinds and amount of tubes, and arranging the tube and the hydraulic elements in the space will be a very big problem. So we can drill holes on a cubic steel block as the tubes and fix all the hydraulic elements on the surface of it. So the cubic steel block is the hydraulic manifold block. Using it can avoid the complicated tube arrangement, but we should arrange the holes on it ,too.
First, we may use more than one block, in this course, we use four block.
Second, we should redraw the hydraulic principle diagram, to rearrange the elements more suitable for the block.
Third, every block has three main holes, common pressure oil port(公用压力油口), common oil return port(公用回油口) and common leakage oil port(公用泄漏油口). We should arrange the elements on the front, back and the right side. On the right side, we always arrange the pressure control valve and the flow control valve. On the front, we always arrange the direction control valve, of course if there are too many valves on the right side, we can adjust some of them to the front. As for the back, we always arrange some direction valve which don’t need to be controlled. On the left side, we always don’t arrange valves, but some measuring devices and auxiliary oil ports.
Forth, we should arrange the other holes as the tubes connects the hydraulic elements. They should be straight as far as possible. And the position of the holes are decided by the position of them on the hydraulic elements. All the elements are standard parts , the position of the ports on them can be found on the book, we just need to look at the books and find them.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：液压与气压传动课程设计
微生物学
核心内容
· 微生物（microorganism）定义：一切肉眼看不见或看不清的微小生物的总称。
· 微生物五大共性（特点）：体积小、面积大（比表面积大）；结构简单；繁殖快；种类多；易变异；分布广；代谢强。
· 微生物三型结构分类：
· 非细胞型（acellular）：病毒（virus）。
· 原核细胞型（prokaryotic cell）：细菌（bacteria）、放线菌（actinomycetes）等。
· 真核细胞型（eukaryotic cell）：真菌（fungi）、藻类（algae）、原生动物（protozoa）。
· 病毒（virus）：
· 定义：一类非细胞型微生物，由核酸和蛋白质外壳构成。
· 特点：体积小；专性活细胞内寄生；对抗生素不敏感。
· 化学组成与结构：核酸（DNA 或 RNA）+ 蛋白质衣壳（capsid），部分具包膜（envelope）。
· 繁殖方式（复制，replication）：吸附（adsorption）→ 注入（penetration/injection）→ 复制（replication）→ 装配（assembly）→ 释放（release）。
· 举例：噬菌体（bacteriophage）、烟草花叶病毒（TMV）、流感病毒（influenza virus）。
· 微生物学（microbiology）定义：研究微生物的形态、结构、生理、分类、遗传变异、生态及与人类关系等的科学。
· 微生物学发展史关键人物：列文虎克（Leeuwenhoek）、巴斯德（Pasteur）、科赫（Koch）等（资料标注字迹不清）。
· 微生物的营养（nutrition）：
· 营养类型（按碳源与能源划分）：光能自养（photoautotroph）、光能异养（photoheterotroph）、化能自养（chemoautotroph）、化能异养（chemoheterotroph）。
· 营养要素：碳源（carbon source）、氮源（nitrogen source）、无机盐（inorganic salts）、生长因子（growth factors）、水（water）。
· 培养基（culture medium）：定义、种类（固体/液体/半固体；选择培养基 selective medium / 鉴别培养基 differential medium）；配制原则。
· 微生物的生长与繁殖（growth & reproduction）：
· 繁殖方式：二分裂（binary fission）、出芽（budding）、孢子（spore）等。
· 生长曲线（growth curve）四期：延迟期（lag phase）、对数期（log phase）、稳定期（stationary phase）、衰亡期（death phase）。
· 影响生长的因素：温度、pH、氧气、水分等。
· 细菌的结构（bacterial structure）：
· 基本结构：细胞壁（cell wall）、细胞膜（cell membrane）、细胞质（cytoplasm）、核区/拟核（nucleoid）。
· 特殊结构：荚膜（capsule）、鞭毛（flagellum）、菌毛（pilus/fimbria）、芽孢（endospore）。
· 形态：球菌（coccus）、杆菌（bacillus）、螺旋菌（spirillum）。
· 微生物的控制（control of microorganisms）：
· 基本概念：灭菌（sterilization）、消毒（disinfection）、防腐（antisepsis）、化疗（chemotherapy）。
· 物理方法：高温、辐射、过滤。
· 化学方法：消毒剂（disinfectant）、防腐剂（antiseptic）。
参考：来源：微生物学.png｜专业：生物科学｜课程：微生物学