求一篇.关于美学基础的论文.什么内容不限，什么题材也...

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浅论悲剧美

亚里士多德最初在解释悲剧时指出：悲剧是人生中严肃的事情,它不是悲哀、悲惨、悲痛、悲观或死亡、不幸的同义语,它与日常语言中的“悲剧”一词的含义并不完全相同.作为美学对象的悲剧,必须是能使人奋发兴起,提高精神境界,产生审美愉快的.悲剧通过丑对美的暂时的压抑,却强烈地展示了美的最终和必然的胜利.所以实际上悲剧美所显示的审美特性必然体现出一种崇高之美,更具有震撼人心的力量.比如被称为悲剧典范之作的古希腊悲剧《被缚的普罗米修斯》,作品所表现的普罗米修斯为正义而甘受酷刑的不屈不挠的精神,展示出一种可歌可泣的悲壮崇高之美.

早在公元前五世纪,古希腊就留下了悲剧创作的辉煌成果,出现了埃斯库罗斯、索福克勒斯和欧里庇得斯等著名的大悲剧家.这时的悲剧,大都取材于神话、传说和史诗.《被缚的普罗米修斯》就是著名的代表作.到了文艺复兴时期,莎士比亚将悲剧艺术发展到了空前的壮大,这时的悲剧作品大都以人文主义观点宣扬新兴资产阶段的政治理想和生活愿望.其内容已离开了神话传说,而多以历史故事为体裁,如《哈姆雷特》《奥赛罗》等.19世纪的欧洲,在浪漫主义和批判现实主义的思潮推动下,出现了雨果的《欧尼娜》,小仲马的《茶花女》,奥斯特罗夫斯基的《大雷雨》等一批优秀的悲剧.

在中国的戏剧发展史上,王国维在1921年才使用悲剧这个术语.但这不等于是说中国是从那个时候才开始悲剧创作.如关汉卿的《窦娥冤》,无名氏的《孔雀东南飞》等都是较早出现的悲剧作品,在世界广为流传.

在希腊传统的悲剧创作中,人物的命运做为悲剧的最重要的因素,那是英雄人物在命运面前的无力所体现的,而观众也能够从这种无法言传的力量中得到一种命运无常的压迫感.首先要认识到这种最原初的创造往往是代表了人们的一种基本的渴求的.之后在亚里士多德的悲剧理论中则把悲剧的模式以及人们所欣赏悲剧的心理是怎么样的联系起来,他的两条重要理论便是：一、悲剧的主角是和我们相类似的人,他们并不是道德最完善的人,因此他们便会有过错,在悲剧中人们看到他们由于某种很小的过失所引起的巨大悲惨后果,从而引起悲剧的效果.二、人们在欣赏悲剧的时候,悲剧引起了哀怜和恐惧,从而导致这些情绪的净化,这种过分强烈的情绪宣泄使得恢复心灵的平静从而保持心理的健康.很显然亚里士多德把悲剧的形成和所引起的心理的效果降低到了普通人的层次上,一种人与人之间的命运的互相怜悯于是体现在悲剧的审美活动之中.之后莱辛对于悲剧理论又做了扩展,他认为观众在欣赏悲剧时候所表现的哀怜和恐惧不是作用在自己或者悲剧中人物的身上,而是把自己的命运和人类的命运结合起来,认为这样的悲剧是可能发生在任何的一个人的身上,这是最为悲惨的事情了.

中国古代并没有专门关于悲剧的理论,但是就产生人悲剧的心理的效果来看,中国的悲剧一直在发展着.二十年代鲁迅先生也曾提出过一个悲剧的著名命题：“悲剧将人生有价值的东西毁灭给人看.”这里揭示的悲剧艺术的特征是“人生有价值的东西”,而不是生活中一般的悲哀、悲痛和悲惨.悲剧的审美价值是以人生的社会价值作为基础的,而其表现的手段则是“毁灭给人看”,美好的有价值的东西遭到毁灭,它给人的感受应该是极具震撼的.这是鲁迅悲剧观的核心.也成为中国现代文学悲剧理论最有代表性的观念.

中国的比较著名的“悲剧”,比如我国古代文学史上最早、最优秀的长篇叙事诗《孔雀东南飞》就比较有代表性.诗歌所表现的悲剧艺术大致体现在三个方面：第一、故事在情节的叙述中创造一种悲剧气氛.原题目的设定、开头的起兴和情节发展中气氛的渲染,都在极力营造爱情的悲苦情调.第二、人物的悲剧美,是最富有感染力的悲剧力量.主人公刘兰芝的姿容、心灵和人格,都被塑造得完美无缺.人物形象愈是完美,其悲剧效果愈为突出.因此,刘兰芝的悲剧实际上是社会的悲剧.而焦仲卿由于受封建礼教束缚而不敢大胆反抗的软弱性格是造成他悲剧的主要原因.第三、艺术手法强化了悲剧效果.赋、比、兴等传统表现手法增加了悲剧的情绪浓度；反衬、烘托突出了人物形象的美学效果；细节描写、多层次渲染等手法,清晰有序地将悲剧气氛凝为一体.主人公因生命遭到毁灭而成就了精神生命的永恒价值,从而激起悲壮之情而使人们的心灵得以净化,精神得以提升.这就是悲剧的美学力量所在.

另外还有像《窦娥冤》.这种悲剧的力量主要来自善良又无力的小人物在不公的社会中所遭受的悲惨命运.这种悲剧情景在以上西方的传统悲剧理论中是不符合的,首先窦娥并没有在剧中表现出过失,其次窦娥在地层社会中代表的是一种典型的性格,她所遭遇的是一种黑暗力量的折磨,并不能代表一种社会的普遍力量,换言之传统的西方悲剧理论具有一种贵族性,而中国的这种下层的悲剧则代表了一种现实性.

《西厢记》《牡丹亭》等等,这些代表的是一种人物内心的强烈冲突以及社会的普遍力量的压制,这里可以看到人的情欲的力量和社会压力之间的冲突.

士大夫的悲剧.这在文学作品中并不是直接的表达的,但是他们的生平,对理想的追求,对完美人格的实现则代表了中国所特有的一种悲剧气质,那便是一种“知其不可为而为之”“虽万折吾往矣”的理想人格,这种理想人格的悲剧性在于现实精神的缺失,在面对现实的复杂和矛盾尖锐的时候不能够从一种务实的角度来实现较好的结果,而是以个体的毁灭来实现理想人格的实现.例如屈原、文天祥等.

《红楼梦》所代表的更为复杂的悲剧.它即表现了人在命运无常面前的脆弱无力,也表现了个人理想与社会普遍力量的冲突,同时也具有小人物在残酷现实中的悲惨命运,而这一切则集中表达了一种深切的人生幻灭感.

根据上述实例,我大致归纳了悲剧的四种类型.一、命运的无常（希腊悲剧、红楼梦）.二、人生理想与普遍力量的冲突（红楼梦贾宝玉、苏格拉底、黑格尔的悲剧理论）.三、理想人格的实现（中国士大夫精神）.四、平凡的人在黑暗中的悲惨命运.（窦娥冤、莱辛的悲剧论）.而这些悲剧在人心中所产生的心理效果也可以说是并不一样的,有同情,有设身处地的恐惧和哀怜,有命运的共鸣,有并未发生于自身的安全感（类似崇高）,还有黑格尔所提到的心灵的愉悦.但是应该说不论哪一类型的悲剧,都是一种美的体现.生命是有限的,而追求不朽.悲剧在将人生中最残酷的一面呈示给我们,引起我们惊悚的时候,更激发我们一种对美好的生活的追求、一种对悲剧美更深层次的认知.

参考书目：

1 《美学原理》蒋孔阳编 华北师范大学出版社1999年版

2 《唐弢文集》第九卷 《〈孔雀东南飞〉的现实主义》社会科学文献出版社1995年版

3 《中国文学史（一） 》 游国恩主编人民文学出版社1983年版

其他类似问题

问题1：英语翻译如题要英文的 题目要翻译好 只要是电气专业类别的都可以[英语科目]

用于分布式在线UPS中的并联逆变器的一种无线控制器

A Wireless Controller for Parallel Inverters in Distributed Online UPS Systems

Josep M. Guerrero', Luis Garcia de Vicufia", Jose Matas'*, Jaume Miret", and Miguel Castilla"

. Departament #Enginyeria de Sistemes, Automatica i Informhtica Industrial. Universitat Polithica de Catalunya

C. Comte d'Urgell, 187.08036 -Barcelona. Spain. Email: josep.m.guerrero@upc.es .. Departament #Enginyeria Electrbnica. Universitat Polit6cnica de Catalunya

AV. Victor BaLguer s/n. 08800I - Vilanova i la Geltrh. Spain

Absiract - In this paper, a novel controller for parallelconnected

online-UPS inverters without control wire

interconnections is presented. The wireless control technique is

based on the well-known droop method, which consists in

introducing P-oand Q-V schemes into the inverters, in order to

share properly the power drawn to the loads. The droop method

has been widely used in applications of load sharing between

different parallel-connected inverters. However, this method

has several drawbacks that limited its application, such as a

trade-off between output-voltage regulation and power sharing

accuracy, slow transient response, and frequency and phase

deviation. This last disadvantage makes impracticable the

method in online-UPS systems, since in this case every module

must be in phase with the utility ac mains. To overcome these

limitations, we propose a novel control scheme, endowing to the

paralleled-UPS system a proper transient response, strictly

frequency and phase synchronization with the ac mains, and

excellent power sharing. Simulation and experimental results

are reported confirming the validity of the proposed approach.

1. INTRODUCTION

The parallel operation of distributed Uninterruptible Power

Supplies (UPS) is presented as a suitable solution to supply

critical and sensitive loads, when high reliability and power

availability are required. In the last years, many control

schemes for parallel-connected inverters has been raised,

which are derived from parallel-schemes of dc-dc converters

[I], such as the master-slave control [2], or the democratic

control [3]. In contrast, novel control schemes have been

appeared recently, such as the chain-structure control [4], or

the distributed control [ 5 ] . However, all these schemes need

control interconnections between modules and, hence, the

reliability of the system is reduced since they can be a source

of noise and failures. Moreover, these communication wires

limited the physical situation ofthe modules [6].

In this sense, several control techniques has been proposed

without control interconnections, such as the droop method.

In this method, the control loop achieves good power sharing

making tight adjustments over the output voltage frequency

and amplitude of the inverter, with the objective to

compensate the active and reactive power unbalances [7].

This concept is derived from the power system theory, in

which the frequency of a generator drops when the power

drawn to the utility line increases [8].

0-7803-7906-3/03/$17.00 02003 IEEE. 1637

However, this control approach has an inherent trade-off

between voltage regulation and power sharing. In addition,

this method exhibits slow dynamic-response, since it requires

low-pass filters to calculate the average value of the active

and reactive power. Hence, the stability and the dynamics of

the whole system are hardly influenced by the characteristics

of these filters and by the value of the droop coefficients,

which are bounded by the maximum allowed deviations of

the output voltage amplitude and frequency.

Besides, when active power increases, the droop

characteristic causes a frequency deviation from the nominal

value and, consequently, it results in a variable phase

difference between the mains and the inverter output voltage.

This fact can be a problem when the bypass switch must

connect the utility line directly to the critical bus in stead of

its phase difference. In [9], two possibilities are presented in

order to achieve phase synchronization for parallel lineinteractive

UPS systems. The first one is to locate a particular

module near the bypass switch, which must to synchronize

the output voltage to the mains while supporting overload

condition before switch on. The second possibility is to wait

for the instant when phase matching is produced to connect

the bypass.

However, the mentioned two folds cannot be applied to a

parallel online-UPS system, since maximum transfer time

ought to be less than a % of line period, and all the modules

must be always synchronized with the mains when it is

present. Hence, the modules should be prepared to transfer

directly the energy from the mains to the critical bus in case

of overload or failure [lo].

In our previous works [11][12], we proposed different

control schemes to overcome several limitations of the

conventional droop method. However, these controllers by

themselves are inappropriate to apply to a parallel online-

UPS system. In this paper, a novel wireless control scheme is

proposed to parallel different online UPS modules with high

performance and restricted requirements. The controller

provides: 1) proper transient response; 2) power sharing

accuracy; 3) stable frequency operation; and 4) good phase

matching between the output-voltage and the utility line.

Thus, this new approach is especially suitable for paralleled-

UPS systems with true redundancy, high reliability and

power availability. Simulation and experimental results are

reported, confirming the validity of this control scheme.

Fig. 1. Equivalenl cimuif ofan invener connecled 10 a bus

t"

Fig. 2. P-odraop function.

11. REVlEW OF THE CONVENTIONAL DROOP METHOD

Fig. 1 shows the equivalent circuit of an inverter connected

to a common bus through coupled impedance. When this

impedance is inductive, the active and reactive powers drawn

to the load can be expressed as

EVcosQ - V2 Q=

where Xis the output reactance of an inverter; Q is the phase

angle between the output voltage of the inverter and the

voltage of the common bus; E and V are the amplitude of the

output voltage of the inverter and the bus voltage,

respectively.

From the above equations it can be derived that the active

power P is predominately dependent on the power angle Q,

while the reactive power Q mostly depends on the outputvoltage

amplitude. Consequently, most of wireless-control of

paralleled-inverters uses the conventional droop method,

which introduces the following droops in the amplitude E

and the frequency U of the inverter output voltage

u = w -mP (3)

E = E ' - n Q , (4)

being W* and E' the output voltage frequency and amplitude

at no load, respectively; m and n are the droop coefficients

for the frequency and amplitude, respectively.

Furthermore, a coupled inductance is needed between the

inverter output and the critical bus that fixes the output

impedance, in order to ensure a proper power flow. However,

it is bulky and increase:; the size and the cost of the UPS

modules. In addition, tho output voltage is highly distorted

when supplying nonlinezr loads since the output impedance

is a pure inductance.

It is well known that if droop coefficients are increased,

then good power sharing is achieved at the expense of

degrading the voltage regulation (see Fig. 2).

The inherent trade-off of this scheme restricts the

mentioned coefficients, which can be a serious limitation in

terms of transient response, power sharing accuracy, and

system stability.

On the other hand, lo carry out the droop functions,

expressed by (3) and (4), it is necessary to calculate the

average value over one line-cycle of the output active and

reactive instantaneous power. This can be implemented by

means of low pass filters with a smaller bandwidth than that

of the closed-loop inverter. Consequently, the power

calculation filters and droop coefficients determine, to a large

extent, the dynamics and the stability of the paralleledinverter

system [ 131.

In conclusion, the droop method has several intrinsic

problems to be applied 1.0 a wireless paralleled-system of

online UPS, which can he summed-up as follows:

Static trade-off between the output-voltage regulation

(frequency and amplitude) and the power-sharing

accuracy (active an4d reactive).

2) Limited transient response. The system dynamics

depends on the power-calculation filter characteristics,

the droop coefficients, and the output impedances.

Lost of ac mains synchronization. The frequency and

phase deviations, due to the frequency droop, make

impracticable this method to a parallel-connected

online UPS system, in which every UPS should be

continuously synchronized to the public ac supply.

1)

3)

111. PROPOSED CONTROL FOR PARALLEL ONLINE UPS

INVERTERS

In this work, we will try to overcome the above limitations

and to synthesize a novel control strategy without

communication wires that could be appropriate to highperformance

paralleled industrial UPS. The objective is to

connect online UPS inverters in parallel without using

control interconnections. This kind of systems, also named

inverter-preferred, should be continuously synchronized to

the utility line. When an overload or an inverter failure

occurs, a static bypass switch may connect the input line to

the load, bypassing the inve:rter [14][15].

Fig. 3 shows the general diagram of a distributed online

UPS system. This system consists of two buses: the utility

bus, which is connected lo the public ac mains; and the

secure bus, connected to the distributed critical loads. The

interface between these buses is based on a number of online

UPS modules connected in parallel, which provides

continuously power to the: loads [16]. The UPS modules

include a rectifier, a set of batteries, an inverter, and a static

bypass switch.

1

1638

Q ac mains

utility bus

I I I

j distributed loads !

Fig. 3. Online distributed UPS system.

syposr /

I 4

(4

Fig. 4. Operation modes of an online UPS.

(a) Normal operation. (b) Bypass operation. (c) Mains failure

The main operation modes of a distributed online UPS

1) Normal operation: The power flows to the load, from

the utility through the distributed UPS units.

2) Mains failure: When the public ac mains fails, the

UPS inverters supply the power to the loads, from the

batteries, without disruption.

Bypass operation: When an overload situation occurs,

the bypass switch must connect the critical bus

directly to the ac mains, in order to guarantee the

continuous supply of the loads, avoiding the damage

of the UPS modules.

For this reason, the output-voltage waveform should be

synchronized to the mains, when this last is present.

system are listed below (see Fig. 5):

3)

Nevertheless, as we state before, the conventional droop

method can not satisfy the need for synchronization with the

utility, due to the frequency variation of the inverters, which

provokes a phase deviation.

To obtain the required performance, we present a transient

P-w droop without frequency-deviation in steady-state,

proposed previously by OUT in [ 111

w=o -mP (5)

where is the active power signal without the dccomponent,

which is done by

. -

I t -1s

P= p ,

( s + t - ' ) ( s + o , )

being zthe time constant of the transient droop action.

The transient droop function ensures a stable frequency

regulation under steady-state conditions, and 'at the same

time, achieves active power balance by adjusting the

frequency of the modules during a load transient. Besides, to

adjust the phase of the modules we propose an additional

synchronizing loop, yielding

o=w'-m%k,A$, (7)

where A$ is the phase difference between the inverter and the

mains; and k, is the proportional constant of the frequency

adjust. The steady-state frequency reference w* can be

obtained by measuring the utility line frequency.

The second term of the previous equality trends to zero in

steady state, leading to

w = w' - k4($ -@'), (8)

being $and $* the phase angles of the output voltage inverter

and the utility mains, respectively.

Taking into account that w = d $ / d t , we can obtain the

next differential equation, which is stable fork, positive

d$ *

dt dt

- + km$ = - + k,$' . (9)

Thus, when phase difference increases, frequency will

decrease slightly and, hence, all :he UPS modules will be

synchronized with the utility, while sharing the power drawn

to the loads.

IV. CONTROLLIEMRP LEMENTATION

Fig. 5 depicts the block diagram of the proposed

controller. The average active power P , without the dc

component, can be obtained by means of multiplying the

output voltage by the output current, and filtering the product

.

io

",.

L

Sj'nchronirorion loop

.

Fig. 5. Block diagram of the proposed controller.

using a band-pass filter. In a similar way, the average

reactive power is obtained, hut in this case the output-voltage

must be delayed 90 degrees, and using a low-pass filter.

In order to adjust the output voltage frequency, equation

(7) is implemented, which corresponds to the frequency

mains drooped by two transient-terms: the transient active

power signal term; and the phase difference term, which

is added in order to synchronize the output voltage with the

ac mains, in a phase-locked loop (PLL) fashion. The outputvoltage

amplitude is regulated by using the conventional

droop method (4).

Finally, the physical coupled inductance can be avoided by

using a virtual inductor [17]. This concept consists in

emulated an inductance behavior, by drooping the output

voltage proportionally to the time derivative of the output

current. However, when supplying nonlinear loads, the highorder

current-harmonics can increase too much the outputvoltage

THD. This can be easily solved by using a high-pass

filter instead of a pure-derivative term of the output current,

which is useful to share linear and nonlinear loads [I 1][12].

Furthermore, the proper design of this output inductance can

reduce, to a large extent, the unbalance line-impedance

impact over the power sharing accuracy.

v. SIMULATION AND EXPERIMENTARELS ULTS

The proposed control scheme, (4) and (7), was simulated

with the parameters listed in Table 1 and the scheme shown

in Fig. 6, for a two paralleled inverters system. The

coefficients m, n, T, and kv were chosen to ensure stability,

proper transient response and good phase matching. Fig. 7

shows the waveforms of the frequency, circulating currents,

phase difference between the modules and the utility line,

and the evolution of the active and reactive powers. Note the

excellent synchronization between the modules and the

ACmiiinr 4 j. ...L...I.P...S...1... .B...u...n...r.r..r..e..s... . i

Fig. 6. Parallel operation oftwa online UPS modules,

mains, and, at the same time, the good power sharing

obtained. This characteristik let us to apply the controller to

the online UPS paralleled systems.

Two I-kVA UPS modules were built and tested in order to

show the validity of the proposed approach. Each UPS

inverter consisted of a single-phase IGBT full-bridge with a

switching frequency of 20 kHz and an LC output filter, with

the following parameters: 1. = 1 mH, C = 20 WF, Vi" = 400V,

v, = 220 V, I50 Hz. The controllers of these inverters were

based on three loops: an inner current-loop, an outer PI

controller that ensures voltage regulation, and the loadsharing

controller, based on (4) and (7). The last controller

was implemented by means of a TMS320LF2407A, fixedpoint

40 MHz digital sigrial processor (DSP) from Texas

Instruments (see Fig. 8), using the parameters listed in Table

I. The DSP-controller also includes a PLL block in order to

synchronize the inverter with the common bus. When this

occurs, the static bypass switch is tumed on, and the droopbased

control is initiated.

1640

big 7 Wa\cfc)rms for twu.invencr, ;mnectcd in parallel. rpchrontred io Ihc ac mdnl.

(a) Frequencics ufhoth UPS (b) Clrculattng currcni among modulcs. (CJ Phmc d!Nercn;: betucen ihc UPS a#>dth e ai mum

(d) Ikiril uf the phze diNmncc (e) md (0 Activc and rcactlw pouerr "I ooih UPS

Note that the iimc-acs arc deliheratcly JiNercni due in thc disiinct timuion*uni) ofthe \ inrblrr

1641

TABLEI.

PARAMETEROSF THE PARALLELESDYS TEM.

Filter Order I I

Filter Cut-off Frequency I 0, I 10 I rags

Fig. 8 shows the output-current transient response of the

UPS inverters. First, the two UPS are operating in parallel

without load. Notice that a small reactive current is circling

between the modules, due to the measurement mismatches.

Then, a nonlinear load, with a crest factor of 3, is connected

suddenly. This result shows the good dynamics and loadsharing

of the paralleled system when sharing a nonlinear

load.

Fig. 8. Output current for the two paralleled UPS, during the connection of B

common nonlinear load with a crest factor of 3. (Axis-x: 20 mddiv. Axis-y:

5 Mdiv.).

VI. CONCLUSIONS

In this paper, a novel load-sharing controller for parallelconnected

online UPS systems, was proposed. The controller

is based on the droop method, which avoids the use of

control interconnections. In a sharp contrast with the

conventional droop method, the controller presented is able

to keep the output-voltage frequency and phase strictly

synchronized with the utility ac mains, while maintaining

good load sharing for linear and nonlinear loads. This fact let

us to extend the droop method to paralleled online UPS.

On the other hand, the proposed controller emulates a

special kind of impedance, avoiding the use of a physical

coupled inductance. Th.e results reported here show the

effectiveness of the proposed approach.

问题2：求一篇高中一般水平的作文,600字,题材不限最好不要太好或太烂,一般就可以了,题材不限

友谊

友谊是什么?友谊是我们哀伤时的缓和剂,激情时的舒解剂；是我们压力的流泄口,灾难时的庇护所；是我们犹疑时的商议者,蒙浑时的清新剂,是我们思想的散发口,也是我们沉思的锻炼和改进.

我生活在快乐之中,从未感到孤独,是因为我有很多朋友.记得看过这样一篇文章《一点六公理以内你有几个朋友》,因为在这个范围之内,饭后闲步即可到达,无需预约,无需费力,喝杯清茶几句闲语,轻松而又自然.

真正感觉到朋友的温情是在我一次高烧这后,记得那天半夜我烧到四十度,妈妈急的手足无措,就给医院的一个朋友打了求助电话,那位阿姨带着所需药物直奔而来,给我打了退烧针之后,还一直给我进行物理降温,正因为她的到来,让妈妈放下心来,我也在她的细心照顾之下进入了梦乡.第二天我也因为未能到校,同学看我上午没去上学,得知是生病之后中午就来看望我,他进门就问好些没有,虽然年龄小不会说什么安慰的话语,但他的关怀溢于言表,使我深深感到了友情的温暖.

去年我转到一所新的学校,环境的变化让我感到局促、压抑,再加上天性内向,在校内便难免形影孤单.在一次语文课上,老师要求同学们讨论问题,而我坐在那里左顾右盼,不知该如何张口,正在我不知所措的时候,两位同学邀请了我,正因为他们伸出了友谊之手,才使我很快融入到班集体,让我交到了更多的朋友,走出了一人世界.友谊就是这样神奇,它让人面对现实,对未来充满希望.

友谊是什么,友谊是寒冷时的暖流,是骄傲时的清风,是慌乱时的重心.友谊是什么,是那种“海内存知已,天涯若比邻”的相依,是“桃花潭水深千尺,不及王伦送我情”的深沉,也是那“我寄愁心与明月,随风直到夜朗西”的轻叹.请大家相信,只要我们维护友谊,为对方着想,那么,我们的友谊就会地久天长,希望大家都能得到很多知心朋友,在朋友的关爱中感受生活的美好.让我们谛造友谊,共同走向美好的明天,愿友谊地久天长!

问题3：急需一篇初二物理小论文（内容不限）,谢谢![物理科目]

1.为什么夏天吃冰糕时冰糕会冒汽.答：因为空气中的气体状态的水分在冰糕周围遇冷液化成液体状态的水,这就使我们看到了冒的汽.

2.为什么把水倒进滚烫的油里会发生飞溅.答：因为水的密度比油的大,所以水在到进油中时会在油的上面,而滚油的温度远大于水的沸点,水遇热沸腾飞溅.

3.把糖放到热水里为什么溶化的快比在凉水里快.答：因为由分子动理论可知温度越高分子做无规则的运动的速率越快,这样热水中的水分子和糖分子的运动速率要快,互相的融合越快,也就融化的越快.

4.为什么冬天下完大雪后要在路上撒盐.答：撒盐使雪熔点降低,这样可以在较低的温度下使雪融化,尽快恢复交通.

5.为什么把手机放到铁箱中会没有信号.答：因为铁箱是由铁这种导体材料构成的,所以铁箱在磁场下会产生屏蔽作用,致使手机收不到网络信号.

6.俗语"坐地日行八万里"是什么意思? 答：是由于地球自转的原因,每天地球自转一周,即时人不动也由地球自转使人一天会相对与太空运动.

7.为什么天是蓝色的.答：因为空气中各种物质整体吸收的红橙光和绿光等光线较多,使蓝光很大部分被折射或反射到我们眼中,从而我们看到的天是蓝色的.

8.为什么铁路拐弯处的两跟铁轨不是一般高,有一定倾角而此倾角还有国家标准规定.答：因为这样可以提高火车的速度,倾角使重力的分力和铁轨对火车的压力一起提供的向心力比单纯的靠铁轨压力提供的向心力更大,这样能够满足火车更大的速度所需的向心力；轨道最大的压力是固定的,而倾角会影响提供一部分向心力的重力的分力,这就影响了向心力的大小,从而决定了速度的大小,因此国家规定倾角的大小就规定了火车的最大速度.

9.为什么宇航员在近入太空和返回地球时会出现短暂的昏迷.答：直白的说是由于超重和失重的影响,使过多或过少的血液流入大脑,使人晕迷.

10.喷气式飞机的最基本动力原理是什么? 答：运用的是动量守恒原理：飞机喷出的高温气体相对于飞机运动方向相反,即公式：0=(M-m)v-mv',M为原始飞机重量,m为喷出气体重量,v为喷出气体后飞机速度,v'为喷出气体的速度.

摘要：物理是一门历史悠久的自然学科.随着科技的发展,社会的进步,物理已渗入到人类生活的各个领域； 物理学存在于物理学家的身边；物理学也存在于同学们身边；在学习中,同学们要树立科学意识,大处着眼,小处着手,经历观察、思考、实践、创新等活动,逐步掌握科学的学习方法,训练科学的思维方式,不久你就会拥有科学家的头脑,为自己今后惊叹不已的发展,为今后美好的生活打下扎实的基础.

关键词：物理 渗入 人类生活 各个领域 存在 物理学家 同学们 身边 科学意识 科学学习方法 科学思维方式

物理是一门历史悠久的自然学科,物理科学作为自然科学的重要分支,不仅对物质文明的进步和人类对自然界认识的深化起了重要的推动作用,而且对人类的思维发展也产生了不可或缺的影响.从亚里士多德时代的自然哲学,到牛顿时代的经典力学,直至现代物理中的相对论和量子力学等,都是物理学家科学素质、科学精神以及科学思维的有形体现.随着科技的发展,社会的进步,物理已渗入到人类生活的各个领域.例如,光是找找汽车中的光学知识就有以下几点：

1． 汽车驾驶室外面的观后镜是一个凸镜

利用凸镜对光线的发散作用和成正立、缩小、虚像的特点,使看到的实物小,观察范围更大,而保证行车安全.

2． 汽车头灯里的反射镜是一个凹镜

它是利用凹镜能把放在其焦点上的光源发出的光反射成为平行光射出的性质做成的.

3． 汽车头灯总要装有横竖条纹的玻璃灯罩

汽车头灯由灯泡、反射镜和灯前玻璃罩组成.根据透镜和棱镜的知识,汽车头灯玻璃罩相当于一个透镜和棱镜的组合体.在夜晚行车时,司机不仅要看清前方路面的情况,还要还要看清路边持人、路标、岔路口等.透镜和棱镜对光线有折射作用,所以灯罩通过折射,根据实际需要将光分散到需要的方向上,使光均匀柔和地照亮汽车前进的道路和路边的景物,同时这种散光灯罩还能使一部分光微向上折射,以便照明路标和里程碑,从而确保行车安全.

4． 轿车上装有茶色玻璃后,行人很难看清车中人的面孔

茶色玻璃能反射一部分光,还会吸收一部分光,这样透进车内的光线较弱.要看清乘客的面孔,必须要从面孔反射足够强的光透射到玻璃外面.由于车内光线较弱,没有足够的光透射出来,所以很难看清乘客的面孔.

5． 除大型客车外,绝大多数汽车的前窗都是倾斜的

当汽车的前窗玻璃倾斜时,车内乘客经玻璃反射成的像在国的前上方,而路上的行人是不可能出现在上方的空中的,这样就将车内乘客的像与路上行人分离开来,司机就不会出现错觉.大型客车较大,前窗离地面要比小汽车高得多,即使前窗竖直装,像是与窗同高的,而路上的行人不可能出现在这个高度,所以司机也不会将乘客在窗外的像与路上的行人相混淆.

再如下面一个例子：

五香茶鸡蛋是人们爱吃的,尤其是趁热吃味道更美.细心的人会发现,鸡蛋刚从滚开的卤汁里取出来的时候,如果你急于剥壳吃蛋,就难免连壳带“肉”一起剥下来.要解决这个问题,有一个诀窍,就是把刚出锅的鸡蛋先放在凉水中浸一会,然后再剥,蛋壳就容易剥下来.

一般的物质（少数几种例外）,都具有热胀冷缩的特性.可是,不同的物质受热或冷却的时候,伸缩的速度和幅度各不相同.一般说来,密度小的物质,要比密度大的物质容易发生伸缩,伸缩的幅度也大,传热快的物质,要比传热慢的物质容易伸缩.鸡蛋是硬的蛋壳和软的蛋白、蛋黄组成的,它们的伸缩情况是不一样的.在温度变化不大,或变化比较缓慢均匀的情况下,还显不出什么；一旦温度剧烈变化,蛋壳和蛋白的伸缩步调就不一致了.把煮得滚烫的鸡蛋立即浸入冷水里,蛋壳温度降低,很快收缩,而蛋白仍然是原来的温度,还没有收缩,这时就有一小部分蛋白被蛋壳压挤到蛋的空头处.随后蛋白又因为温度降低而逐渐收缩,而这时蛋壳的收缩已经很缓慢了,这样就使蛋白与蛋壳脱离开来,因此,剥起来就不会连壳带“肉”一起下来了.

明白了这个道理,对我们很有用处.凡需要经受较大温度变化的东西,如果它们是用两种不同材料合在一起做的,那么在选择材料的时候,就必须考虑它们的热膨胀性质,两者越接近越好.工程师在设计房屋和桥梁时,都广泛采用钢筋混凝土,就是因为钢材和混凝土的膨胀程度几乎完全一样,尽管春夏秋冬的温度不同,也不会产生有害的作用力,所以钢筋混凝土的建筑十分坚固.

另外,有些电器元件却是用两种热膨胀性质差别很大的金属制成的.例如,铜片的热膨胀比铁片大,把铜片和铁片钉在一起的双金属片,在同样情况下受热,就会因膨胀程度不同而发生弯曲.利用这一性质制成了许多自动控制装置和仪表.日光灯的“启动器”里就有小巧的双金属片,它随着温度的变化,能够自动屈伸,起到自动开启日光灯的作用.

这样的例子举不胜举,物理是一门实用性很强的科学,与工农业生产、日常生活有着极为密切的联系.物理规律本身就是对自然现象的总结和抽象.

谈到物理学,有些同学觉得很难；谈到物理探究,有同学觉得深不可测；谈到物理学家,有同学更是感到他们都不是凡人.诚然,成为物理学家的人的确屈指可数,但只要勤于观察,善于思考,勇于实践,敢于创新,从生活走向物理,你就会发现：其实,物理就在身边.正如马克思说的：“科学就是实验的科学,科学就在于用理性的方法去整理感性材料”.物理不但是我们的一门学科,更重要的,它还是一门科学.

物理学存在于物理学家的身边.勤于观察的意大利物理学家伽利略,在比萨大教堂做礼拜时,悬挂在教堂半空中的铜吊灯的摆动引起了他极大的兴趣,后来反复观察,反复研究,发明了摆的等时性；勇于实践的美国物理学家富兰克林,为认清“天神发怒”的本质,在一个电闪雷鸣、风雨交加的日子,冒着生命危险,利用司空见惯的风筝将“上帝之火”请下凡,由此发明了避雷针；敢于创新的英国科学家亨利?阿察尔去邮局办事.当时身旁有位外地人拿出一大版新邮票,准备裁下一枚贴在信封上,苦于没有小刀.找阿察尔借,阿察尔也没有.这位外地人灵机一动,取下西服领带上的别针,在邮票的四周整整齐齐地刺了一圈小孔,然后,很利落地撕下邮票.外地人走了,却给阿察尔留下了一串深深的思考,并由此发明了邮票打孔机,有齿纹的邮票也随之诞生了；古希腊阿基米德发现阿基米德原理；德国物理学家伦琴发现X射线；……研究身边的琐事并有大成就的物理学家的事例不胜枚举.

物理学也存在于同学们身边.学了测量的初步知识,同学们纷纷做起了软尺.有位同学别出心裁,用透明胶把制好的牛皮纸软尺包扎好,这样更牢固.然后,用大大卷泡泡糖的包装盒作为软尺的外壳,在盒的中心利用铁丝做一摇柄中心轴,软尺的末端固定在轴上,这样一个可以收拾并反复使用的卷尺诞生了.同时,这位同学受软尺自作的启示,用实验解决了一道习题：用软尺测量物体长度时,若把软尺拉长些,测量值是偏大还是偏小?他做了这样一个模拟实验：在白纸上画一条直线,标上刻度,然后用透明胶粘贴,再扯下来,便做成了“软尺”,用“软尺”不仅找到了上题的答案,而且还清楚地看到分度值变大了,知其然,并知其所以然；学了电学的有关知识后,同学们对蚯蚓能承受的最大电压进行了探究：当给它加上1.5V的电压时,蚯蚓迅速分泌粘液,且奋力挣扎,从瓶内跳出瓶外.当给它加上3V的电压时,蚯蚓被电为两截；有同学在测量“2.4V、0.5A”的小灯泡的功率,并研究其发光情况时,不满足于给灯泡加上2.4V的电压,而是用自己早已准备好的小灯泡做破坏性实验,不断加大灯泡两端的电压,直至电压高达9V、灯泡灯丝烧断,才停止探究；有同学在学习蒸发的知识时,不厌其烦地座在桌旁观察相同的两滴水（其中一滴水滩开）,进行聚精会神地观察,然后进行分析、对比,得出影响蒸发的因素；……同学们捕捉身边的琐事进行探究的事例屡见不鲜.

身边的事物是取之不尽的,对与现实生活联系很紧密的物理学科来说,更是时时会用到的,用身边的事例去解释和总结物理规律,学生听起来熟悉,接受起来也就容易了.只要时时留意,经常总结,就会不断发现有利于物理教学的事物,丰富我们的课堂,活跃教学气氛,简化概念和规律.新课标告诉我们“义务教育阶段的物理课程应贴近学生生活,符合学生认知特点,激发并保持学生的学习兴趣,通过探索物理现象,揭示隐藏其中的物理规律,并将其应用于生产生活实际,培养学生终身的探索乐趣、良好的思维习惯和初步的科学实践能力.”

今天,人类所有的令人惊叹不已的科学技术成就,如克隆羊、因特网、核电站、航空技术等,无不是建立在早年的科学家们对身边琐事进行观察并研究的基础上的.在学习中,同学们要树立科学意识,大处着眼,小处着手,经历观察、思考、实践、创新等活动,逐步掌握科学的学习方法,训练科学的思维方式,不久你就会拥有科学家的头脑,为自己今后惊叹不已的发展,为今后美好的生活打下扎实的基础.

问题4：一篇想象作文,450字,题材不限只要是450字以上,并是想象作文,

星星和月亮

曾几何时,月亮和行星相依为伴,星星将全部感情寄放在月亮上,他们是那样的快乐,令空中的其他天体羡慕不已,星星感到幸福的味道特别甜美.

可是,幸福的味道总是那么短暂.宇宙星际时时都在变化着,正如凡间的人际关系一样,飘忽不定.夜空里的天体实在太多了,而且并不缺少漂亮的,温柔的,聪慧的,贤淑的,年轻的更是层出不穷.这不是谁的错,不能怪星星,也不能怪月亮,只能怪夜太长,生活太单调,时间变化太快,人心总是太难满足.

月亮不要星星了,他有了另一个亲爱的.于是星星流泪了,但月亮并不知道,因为月亮不是行星的鱼缸,也不是行星的鸟笼,他感觉不到星星的眼泪.

星星的泪在默默地流,化作清晨漫山遍野的露珠,透明的,闪烁着,她想用这些晶莹的露珠唤回月亮那颗散漫的心.可是,无数个孤独的夜晚之后,无数个期待与失望并存的夜晚之后,星星接受了“不在乎天长地久,只求曾经拥有”.

星星笑了,虽然是挂着泪的.她懂得,有时候放弃也是一种美丽,不是自己的留也留不住,如果是自己的,谁也抢不走.生活的美丽不在于昨天,而在于今天,更在于明天. 星星甜甜地睡了,梦里有一位仙人轻轻的告诉她：“孩子,不要伤心,总有一天,会有一轮只属于你的月亮,他将伴你一生一世,永远不分离.”星星笑了,泪珠飘向太空,像会说话的眼睛,向宇宙告白着星星那颗纯洁的心灵.

星星醒来了,她发现身旁一片明亮,啊,是月亮在愧疚的看着星星,眼睛里闪烁着悔恨的泪珠,面庞有些消瘦.这是真的吗?是在梦里吗?星星瞪大眼睛,用手揉了揉,不,不是梦,真的是月亮回到了自己身旁.月亮告诉星星,在远离星星的日子里,内心很孤独.虽然夜空中的天体很多,但真正理解月亮的只有星星.他穿梭在宇宙之间,找不到一个可以倾吐心声的人,他们要的只是月亮的光芒,而不是月亮的心.没有友谊的夜空是寂寞的,没有亲情的夜空是恐怖的,没有爱情的夜空是冰凉的.月亮很累,很苦,很心痛.他决定回到星星的身边,哪怕是每天看星星一眼也满足了.

星星没有怀疑月亮的话,因为她读懂了月亮的眼睛.

夜深了,星星有些困了,慢慢地睡在了月亮的怀里.月亮虔诚的守候着星星,静静地看着星星娇美的脸庞.星星呢,睡得很香,因为有月亮在身边,会很踏实,很安全.星星做了一个梦,笑容浮现在脸上.

月亮也会心地笑了……

问题5：急需一篇爱国的作文,题材不限,450字以上急需啊………………[语文科目]

我爱我的祖国 时间曾凝聚在1949年10月1日,当巍峨的华表披上曙光,当雄伟的天安门迎来新一轮的太阳,当无数先烈用鲜血染红的五星红旗在天安门广场冉冉升起,伟大的领袖毛主席洪亮的声音传遍了全世界：中华人民共和国成立了!中国人民从此站起来了!这一时刻,对于一个饱经忧患、受尽欺凌的民族来说是多么宝贵啊!中国,一个响亮的名字；一个让世界震撼的名字；一个让无数华夏儿女为之骄傲与自豪的名字,从此诞生了.这一激动人心的日子到来时,亿万华夏儿女为之雀跃.沉睡了百年的东方“雄狮”终于昂首立于世界之林.这是一个沸腾上升的祖国；这是一个如日中天的祖国!

再翻开五千年的历史,我发现祖国的生命精髓长城——那道伤痕,记载了多少沧桑,又表现得如此顽强,那是一种标识,更是一种力量,一种精神,一种向往!长江——那是祖国的脉搏吧!跳跃着永不枯竭的悸动,挥洒着无边无际的情伤.黄河——那是祖国的血液,沸腾着、沸腾着,奔涌着,奔涌着,无力不摧,昂着向前,何等的自信和骄傲啊!五岳——那是你的手掌,指着苍凉的天,戳着悲怆的地,怒斥着丑陋的奸佞……

当侵略者的铁碲践踏我们美丽山河的时候,每一个有良知的中国人脸上流着泪,心中淌着血.为了心中神圣不可侵犯的祖国,他们在黑暗中摸索,在屈辱中抗争.

闻一多拍案而起,横眉冷对暗杀者的手枪；吉鸿昌高挂写有“我是中国人”标语的木牌,走在一片蓝眼睛、黄头发的洋人之中；张学良,杨虎城将军为了挽救民族危亡,毅然发动了西安事变……

我想说又不愿说,我也曾看到祖国的孱弱,在圆明园烧焦的废墟之上,我看祖国是一滩血；在邓世昌勇猛的“致远舰”上,我看祖国是一团火.但我的祖国没有沉没,在亚细亚的东部,用宽厚的臂膀,挽起高山大海,将炎黄子孙揽于怀中,用茅草和土砖修复残缺的岁月,用野菜和稀粥喂养饥饿的生活.中山先生,在黑夜里开始规划治国方略,毛泽东,在贫瘠的土地上,支撑民族的血肉与骨骼；邓小平,把饱经沧桑的瞳仁放大,指引多灾多难的祖国,从世纪的风雨中神奇地走过!英雄长已矣!古往今来,一曲曲悲歌,一个个惊天动地泣鬼神的故事,都讲述一个简单而朴素的信念,祖国在我心中.

正是这千千万万的赤子,才撑起了我们民族的脊梁,祖国的希望;正是他们,在自己的“今天”,用满腔的热血,谱写了无愧于时代的《义勇军进行曲》,才使得我们今天的共和国国歌响彻神州,那么气势磅礴,那么雄壮嘹亮.

站在时代的今天,我们回望：一个民族要独立,要发展,不仅需要坚实的物质基础,还需要强烈的民族自信心与自尊心,需要一种更为博大深沉的民族精神.黄河在我们的血脉中流淌,长城让我们永远刚强,“神舟”载人飞船使我们的天地无限宽广.“团结统一、爱好和平、勤劳勇敢、自强不息”,传承了五千年的民族精神,正等待我们去发扬光大,使我们的明天更加辉煌.为了祖国的繁荣、民族的兴旺,我们会用激情点燃希望之火,用青春汗水浇灌成功之花.未来属于我们,世界属于我们,让我们刻苦学习、顽强拼搏,时刻准备着为中华民族的伟大腾飞而努力奋斗.

耻辱和不幸已经成为过去,中华民族迎来了新的辉煌.改革开放三十年来,在广大劳动人民的辛勤耕耘下,无论军事、科技、政治、体育,我们都取得了长足的进展.刚刚结束的雅典奥运会上,体育健儿凭借自己的“十年磨剑”,使中国首度跃身体育强国之列.五星红旗一次次高高飘扬在雅典的上空,雄浑激昂的中华人民共和国国歌让无数的华夏儿女心潮澎湃,热泪盈眶.

亲爱的祖国,五千年的蕴涵和积淀,六十年的扬弃和继承,一个东方巨人到了可以说“不!”可以发言的时候.你聚集当今世界上最多最广最大的人气和景气,不管风吹浪打胜似闲庭信步,和平与发展是您热切表达的心声!你不卑不亢不躁不惊,以坦荡豁达和深邃、闲静,阔步在新世纪的黎明