Quadrature Amplitude Modulation(QAM)

Quadrature Amplitude Modulation(QAM) DVB system as the digital modulator sle equipment, receiving from encoders, multiplex, DVB, gateway, and video server, and other equipment TS flow, undertake RS code, convolution code and QAM digital Modulation and the output can be directly in rf signal transmission cable network, also can choose according to need intermediate frequency output. With its flexible configuration and superior performance indicators, widely used in digital cable TV transmission fields and digital MMDS system.

introduction

Orthogonal amplitude keying is a kind of two kinds of amplitude modulated signal (2ask and 2psk) rendezvous methods of single channel, so will double expansion effective bandwidth. Quadrature am is used to pulse amplitude, especially in the wireless network applications.

Quadrature am signals have two of the same frequency carrier phase difference, but a quarter of 90 degrees (from integral term), cycle. A signal that I signal, another signal that Q signals. A signal from mathematical Angle can be expressed as the sine, another is expressed as cosine. Two were prepared in the carrier launch has been mixed. Arrive destination, carrier was separated, data were extracted and then and primitive modulation information phase blend.

With two road QAM is independent of baseband signal two interrelated with orthogonal to undertake inhibition frequency modulated carrier wave amplitude, use this bilateral belt already adjustable signal spectrum in the same bandwidth, realize the orthogonality within two road parallel digital information transmission. The modulation mode usually have binary QAM (4QAM), four disables QAM (l6QAM), octal QAM 64QAM),... ( , the corresponding spatial signals vector map called constellation chart, endpoint there were 4, 16, 64,... A vector endpoints. Level several m and the relationship between signal state m for 4QAM, when two is equal to signal amplitude road, which produces, demodulation, performance and phase with the same. 4PSK vector are

principle

Orthogonal amplitude modulation in QAM (by), the data signals are orthogonal two carrier wave amplitude variation said. Analog signal phase modulation and digital signal PSK (phase shift keying) can be considered amplitude unchanged, only the phase change of orthogonal amplitude modulation special. Therefore, analog signal phase modulation and digital signal PSK (phase shift keying) can also be considered QAM exceptions, because they essentially phase modulation. Here mainly discuss the QAM digital signals, although the analog signal QAM also has a lot of applications, such as NTSC and PAL systems using orthogonal system of TV of sub-carrier different color component. QAM

QAM is a kind of vector modulation, the input bit first mapping (generally USES gray yards) to a complex plane (constellation), forming a plural modulation symbols, then will I, Q component of symbols (corresponding after plane of reality department and the imaginary part, also is the horizontal and vertical direction) adopt corresponding modulation amplitude modulation, in the mutual orthogonal (the time of two carrier (orthogonal) coswt and sinwt). Such and amplitude modulation (AM), its spectrum efficiency compared will increase 1 times. Joint QAM modulation amplitude, phase is the technology, it also used the carrier of the amplitude and phase to transfer information bit, so in minimum distance under the same conditions can achieve higher utilization ratio, the band has reached 1024 - the highest QAM QAM (1,024 sample points). Sample point number, the more its transmission efficiency, such as the higher with 16 sample point of 16 - QAM signal, each sample point represents a vector state, 16 - QAM has 16 states, every four binary number one of 16 states stipulates the normal, 16 - specified in QAM 16 carrier and phase combination, 16 - each symbols and cycle QAM transmit 4 bits.

The principle of QAM modulator is sending data in bits/symbols encoder (i.e. string - and converter) in into two road, each for the original two way signal 1/2, then respectively and a pair of orthogonal modulation components after factor, summation output. The receiver complete opposite process, orthogonal demodulation out two opposite streaming, equalizer compensation caused by channel, ruling device recognition distortion of plural signals and mapping back into the original binary signals. As shown in figure 4-2 shows is QAM modulation 16 - schematic. As the modulated signal input binary data flow through string - and transform into four road after concurrent data flow. These four route data, combining the two opposite respectively, converted into two multilevel converters road 4 level data. For example, 00 convert - 3,01 convert - 1,10 convert 1,11 converted into three. The two ways 4 level data g1 (t) and the g2 (t) on carrier cos2 respectively sin2 PI PI FCT has grown and on modulation, and add FCT has grown, can get 16 - QAM signal.

Adopt QAM modulation technology, channel bandwidth at least equal to code for timing recovery rate, $, need another bandwidth, need to increase 15% or so. Compared with other modulation technology QAM coding, with can make full use of bandwidth, anti-noise ability strong, etc. But QAM modulation technology used for ADSL's main problem is how to adapt to the different between the performance of the phone lines bigger difference. To obtain a more ideal job characteristics, QAM receiver need a and the sending end with the same frequency spectrum and corresponding characteristics of the input signal is used for decoding, QAM receiver using adaptive equalizer to compensate for transmission process signal, so the method of distortion of ADSL system's complexity QAM from its adaptive equalizer.

When the demand for data transmission rate above 8 - can offer PSK once, use QAM modulation method. Because QAM constellation points than PSK constellation points more dispersed, constellation points distance between so bigger, so can provide better transmission performance. But QAM constellation points of amplitude is not exactly the same, so it can simultaneously correct the modem need testing phase and amplitude, unlike PSK demodulation need only testing phase, this increases the complexity of QAM modem. 

Remote Access

Remote access is integrated "routing and remote access" part of the service, used for remote office staff, going personnel, as well as monitoring and managing multiple department office server administrator provide remote network.

Specific application

Have run Windows computer and network connecting users can dial-up remote access their network to get services, such as file and printer sharing, electronic mail, plans and SQL database access.

User classification

Usually need to undertake remote access people have two kinds, one kind is administrator, another kind is the common user.

System administrators usually require remote access enterprise network network equipment or server, remote configuration management operation. At the current product development perspective, most of enterprise-level network equipment or server, usually provide remote configuration management interface or function, the administrator can Telnet, SSH, through web GUI and even remote management software terminals of ways, from enterprise network into a network management side WAN maintenance.

Ordinary users remote access requirements, usually remote office staff, going personnel, especially those executives need to be on business often and ERP, CRM often need operation, HR etc of the informationized management system, examination and approval, bill of lading operation. In enterprise informatization unceasingly progress today, more and more such remote access requirements gradually become the focus of enterprise IT administrators. far

Remote access needs classification

The remote access for ordinary users demand, at present relatively common means has 3 kinds.

The first kind is the internal applications directly open port, allowing external IP directly access, through application system itself account verification mechanism preventing illegal users.

The second type is using Windows Server 2003 and updated versions of the terminal service function provided in external PC running Windows remote desktop, first connected to the terminal Server, the connection through the Server proxy access to network application system.

The third kind is to use VPN technology realization and enterprise network, and the remote connections in VPN access network application system.

The first category: open port mode

Firewall open directly in the port internal applications. For example a company ERP system application 7001 ~ 7006 port is, can be in firewalls configuration will be forwarded to 7001 ~ 7006 port connection ERP server IP address. Telecommuting personnel can go out or via TCP/IP access enterprise lo-fi 7001 ~ 7006 port, directly into ERP system. In the ERP system itself through the identity authentication, then he shall enter ERP system operation. This way is very simple, for the realization of technical ability is limited, especially limited budget enterprise, is a common solution. But its threat is obvious. Directly to the public network open ERP server port, would bring network attack, hackers and other security risk. Especially in the virus and attack increasingly stormy today, which will no doubt for internal application system and application system server security pose a serious threat.

The second: using Windows remote desktop technology

Windows XP, Vista on all the versions of the remote desktop terminals are integrated, just open application system server terminal service function, and open fire wall 3389 port (i.e. remote desktop technical dedicated port), go out or telecommuting researchers can, through their own PC remote desktop terminal server system, connected to the application, and the application system running related procedure.

The plan for universal and become common Windows. Several anubis: solutions

1, through remote desktop access application system, which is equivalent to the operating system application server client program, or to the terminal server connection PC identity access to the internal application system, generated file default is stored in the server. If need to save in the distal PC, or in the distal PC connected on the printer to print, still need further configuration terminal service disk mapping function, as well as in server installation remote printer driver etc complicated Settings.

2, remote desktop technology itself needs identity authentication, more than the first kind of scheme verification mechanism, a heavy security than the first kind of scheme. Inevitably

3, external through remote desktop PC to connect to the network server, you still need to lo-fi, because open 3389 ports open port caused by the attacks and invasion of server risks still exist.

4, remote desktop technology itself wrong the transmission, encrypted data in the network if someone deliberately using caught tool, is totally possible to transmit data recovery, causing the should belong to enterprise internal information, or even commercial secrets of leakage.

There has been some products adopts remote desktop technology as the core, developed a convenient maintaining and managing remote access platform software. Some brand has can realize disk mapped and remote printing, and provide simple encryption functions. Safety and feasible Windows solutions rise somewhat, but more tedious installation process. And encryption, low levels of risk. Existing crack The server 3389 port by the opening of the risks are still hard to avoid.

Third class: VPN technology

VPN technology application, the biggest advantage has also lies in data transmission is all in the public network tunnel, VPN encryption of corresponding security is higher. Subdivision up to a three kinds of main VPN technology: IPSec VPN and PPTP VPN, SSL VPN.

The PPTP VPN

The PPTP is a remote dial-up technology, Windows cabin dial-up will provide the PPTP VPN dial-up. Users can through the predefined configurations good account, through the Windows cabin dial-up, remote dial PPTP VPN gateway, the enterprise, and then get the connection IP address within the identity of a PC access to the internal network application systems.

The PPTP VPN's advantage lies in the technical popularization, Windows cabin dial-up made the final users need further buy installation extra software, reduced cost and maintenance. Weakness is that, the PPTP protocol itself also provide lower levels of encryption for data transmission to provide corresponding on the public network security. But the PPTP encryption security level is not high, there is the risk of crack civic-minded individuals. And the connection, the user dial no corresponding rights management, can access to network resources, to the detriment of any internal network information security management.

IPSec VPN

IPSec VPN with its up to 168 bits encryption security, and the popularization of core technology brought by cost down, had become enterprise construct border-crossing VPN network preferred solution. Between any two network established IPSec VPN, if, as in the same local area network, can transmit data and access to any other application system.

On the market at present is the gateway router mainstream brand IPSec VPN functionality is usually support this function is also more for enterprise headquarters and branch is established between border-crossing VPN, connect to several different regions the LAN. IPSec VPN if used to solve the remote access needs, must be installed on the remote PC IPSec VPN client program. Often this client program is not free, prices ranging from hundreds of pieces to thousands of pieces of dollars. And client configuration is relatively complex, usually for enterprise employees, especially enterprise executives, there exist certain technical difficulties. Similarly, IPSec VPN also hard to do rights management, as long as connected VPN, can not restricted access any system, go against internal information security management.

The SSL VPN

The SSL VPN adopted the 128-bit encryption technology can also provide high-level data transmission safety. And SSL technology generally placed inside all kinds of mainstream browser, the average user need only HTTPS way, can visit the channel in SSL encryption transmission of data, to avoid the installation of trival, also need not additional input costs. It is due to have high safety, application is simple and the low cost advantage, SSL encryption technology has been used widely and online banking, online shopping, online payment on safety and mobility to demand higher industries.

For enterprise go out or remote office staff, need to open the browser, input enterprise the SSL VPN entrance website or IP, use individual VPN account login, can enter the connection, visit the connection of of all kinds enterprise resource. The current commercial SSL VPN products usually contain user permissions management function, some can according to user groups -- such as financial group, administrative team, etc -- are permissions Settings, management in the group all members allow or prohibit the visit to a network resources or application system. There is a minority products can even for each user permissions Settings, and executive batch set operation, greatly enhance the enterprise internal network information security management maneuverability.  

Simple thin face fuck change little face beauty

Change is not only to hongrun xiaolian beauty, with good an oval face, facial skin compact are also important. Slap the beauty is how to practice? Learn the following simple thin face movement, you can also change little face beauty!

Eliminate brow wrinkles

Time is passing, and facial wrinkles in slowly increasing. To make the face appear more attractive, will strengthen the skin tight and enhance the facial muscles oh! Below, let small make up to look at how to eliminate facial wrinkles!

Wrinkles will focus on their eyebrows and forehead YuanXinJiao position, and often cause wrinkly frowns is one of the important reasons: oh! So, want to reduce facial wrinkles, will reduce less frown, more happy!

The forefinger and middle finger with hands on both sides of the stomach to pull the eyebrows, continued for five seconds, then relax slowly, action repeat 10 times.

Eliminate eye surrounding wrinkles

Wrinkles around her eyes is also easy part. Because the muscle less eyes, near the subtle facial muscles are easy to create the eye pulled around increase wrinkles.

As far as possible to face eyes see, then slowly rising, narrowed eyes until, finally looks straight ahead, this can help you intensify an eye surrounding skin muscle, remove wrinkle oh! Movement repeats 10 times can.

Reduce facial ministry fat

Eyes look straight ahead, and then slammed the face of meat to suck, lasts 10 seconds, repeat act 10 times. This action will help reduce facial ministry adipose, long-term insist to shape face are of great help!

Stepping up facial muscles

How much of the facial muscles not only with the elasticity of the skin with face is concerned, inseparable. So, tightening the facial muscle exercise is molding perfect face important step!

1, eyes look straight ahead, closed mouth, a smiling state.

2, eyes look straight ahead, closed mouth, then to the left of the mouth cape to face up to the left, the movement for 10 seconds.

Three, eyes look straight ahead, closed mouth, then to the left of the mouth cape to face up to the left, then close your left eye movements, hold for 10 seconds.

4, eyes look straight ahead, closed the corners of the mouth, then the right to face up, then right close your right eye, action for 10 seconds.

Compact facial muscles, molding perfect shape

Let the facial muscles to more tightening is to eliminate facial wrinkles and molding perfect face important parts. So, want to have v-shaped face facial muscles, the relaxation of words is not allowed!

1, eyes try to face look, then slowly rising, narrowed eyes, until last look straight ahead.

2, the stomach with both hands to pull the eyebrows on both sides, this can help you intensify an eye surrounding skin muscle, remove wrinkle oh! Movement lasts 15 seconds can. 1 and the mouth closed and eyes look straight ahead, keep smile appearance, then both sides mouth slightly to rise, the movement lasts 20 seconds.

2 and the mouth closed and eyes look straight ahead, keep smile appearance, then both sides to rise as the corners of the mouth, the movement lasts 20 seconds.

1 and the mouth closed and eyes look straight ahead, keep smiling state.

2, bulges gills help, then slammed the face of meat to suck, movement repeats 10 times.

Shaping V type chin

V type chin is little face beauty sign, so, how to thin out V type face? Neck line and chin shaping are linked together cheek by jowl, want to thin out V type line of words, will remember to you recommend the following facial exercise cough up!

1, mouth closed, show smile appearance, then looked up and let jaw and neck into a straight line shape, eyes toward the ceiling look, movement lasts 15 seconds.

2, raise head, let jaw and neck into a straight line shape, eyes toward the ceiling look, slightly spit 1:00 tongue, the movement lasts 15 seconds.

3, raise head, let jaw and neck into a straight line shape, eyes toward the ceiling look, mouth go toward outside expiratory, action repeated 15 times. 

The big stomach male to play office shape gymnastics

The big stomach male to play office shape gymnastics

In some of the men of white-collar employees, because usually do not pay attention to exercise, riotously too frequently, therefore belly fat daily hoarding, formed the conspicuous "beer belly". Some men still appear hip hypertrophy, thighs brawny, etc. The posture of lossy image Here for yourself afore-mentioned bad shape men a prescription, recommend a set of foreign popular, in the office of the special aerobics practice. As long as the time doing 15 minutes a day, insist on about a month, waist and abdomen and words of hip "stay" excess fat will gradually disappear, a full of male charm posture will be reflected in your body.

Flexor arm movement

Will the telephone directory for certain weight within, and then something into handbag, hand holding the bag, the handle of the flexor arm repeatedly in the forms, from the waist began to mention on shoulder position, or so, each arm back and forth alternating 30 times do.

This movement can effectively stimulating biceps, make its strong developed. Flexor arm sports can exercise your upper body, farewell single book, thin upper body, solid got strong arms and rich in the chest.

Push-ups sports A

Will both hands respectively from shoulder about a flat outside the fist interval two chair, the body try to keep a straight line, then do push-ups. This movement can exercise upper arms triceps

Push-ups sports B

The preparation before posture and movement, but to increase A similar exercise intensity, will double foot frame on the table. Do push-ups. Slowly unbend arm, so that the outside of the muscles are stimulated, gradually becomes a steel.

Squat movement

With legs apart, about and shoulder are the same as wide, legs slightly outward, pointed legs slightly bent, after hands cling to the brain. Then, make hip slowly underground crouchs, till ham and ground flat so far. Then, slowly healing, careful not to unbend the knee joint.

Quxi movement

Hip slightly contact chair, clasped chair edge. Let the knee easily bend, legs, and then spell on slowly to make knee, then slowly chest near the recovery.

Sideways bending movement

Armed with a proper weight handbag, the palm of the other hand posted on his head. Then, handbag like is pulled to the ground, as natural body follow together drooping sideways bending. Recovery action is: will slowly handbag and bring the body also is slowly unbend. Alternating on either side.

Music movement after

Her legs spread apart and shoulder are the same as wide, a hands on the chair, let the upper part of the body keeps fixed, then, knees forward, and the waist is quite slowly falling backwards, maintain this pose sloping, until relatively fatigue so far. This moral integrity can make big leg ministry muscle of the side robust, and consumption of coxal adipose. 

Wi-Fi Direct

Wi-Fi Direct standard allows wireless networks without the equipment can be connected through wireless router. And bluetooth technology similar to the standard allow wireless equipment, with point-to-point form, but in a transmission speed interconnect with transmission distance than bluetooth is a sharp ascent.

Initially, Wi - Fi league this new standard name "Wi - Fi peer to peer," - finally - WiFiDirect denominate is, face the various Wi - Fi equipment, from computer to computer peripherals, mobile phones, to the home appliance and so on. Meets the standard equipment without hot and routers, it can be convenient and other equipment realize directly connected, transmits data or sharing application. Wi - Fi Direct can support a pair of has been even, also can achieve multiple devices also connected, and Wi - Fi Direct standards will support all Wi - Fi equipment, from 11 / b/g to 11n, different standard Wi - Fi equipment directly between can also interconnected.

Main advantage: transmission rate is high, compatible with the original equipment

Main drawback: power consumption than high (bluetooth) 

Demilitarized zone(DMZ)

Demilitarized zone "DMZ is the abbreviation of", it is to solve after install firewall external network cannot access the internal network servers, and the establishment of a non safety system and safety system, the buffer zone between the buffer is located in the enterprise internal network and the external network of small network between area, in this small network area can be placed some must open server facilities, such as enterprise Web server, FTP server and BBS etc. On the other hand, through such a DMZ area, more effectively protect the internal network, because this kind of network deployment, than the average firewall program for the attacker is another hurdle.

introduction

Network equipment developers, use DMZ technology, to develop a corresponding firewall solutions. Say "DMZ structure model". DMZ is usually a filter subnet, internal network and the DMZ in between the external network constructed a safety.

DMZ firewall solutions to protect the internal network increases a security perimeter, usually think it is very safe. It provides a regional placed public server, which also can effectively avoid some Internet applications requiring public, and internal security strategy of contradictory situation happened. In the DMZ area often include fort host, Modem pool, and all public servers, but should notice is electronic commerce server can only used for users to connect, the real electronic business backend data need to be on internal network.

In this firewall scheme, including two firewall, external firewall against external network attack, and manage all external network to the DMZ visit. Internal firewall management DMZ for internal network access. Internal firewalls are internal network of the third security perimeter (front with external firewalls and fort host), when external firewall failure, it still can rise to protect the internal network function. And for the Internet and LAN internal by internal firewalls and visit the DMZ bastion host in control. In such a structure, a hacker must pass three separate areas (external firewall, internal firewalls and fort host) to get LAN. Attack difficulty greatly enhance the safety of network, the corresponding internal is strengthened, but investment cost is also the highest.

If your machine is not providing web site or other network services words don't setting. The DMZ is all the ports open your computer to the network.

A: what is the DMZ

Demilitarized Zone) DMZ (namely commonly known as the DMZ, and israelis and trust region corresponds, purpose is to change the WEB, E-mail, etc of external access allowed up in the port server alone, make whole needed to protect the internal network meet in trust region ports, don't allow any access, achieve internal and external nets separation, achieve user requirements. DMZ can be understood as a different from outside the special network connection network or within the DMZ regional, put up some excluding usually confidential information, such as the public server Web, E-mail, FTP, etc. So from the nets visitors can visit the DMZ service, but may not touch the company secrets or stored in a network such as private information, even if in the DMZ sabotage, also won't server to affect the confidential information network.

2: why need DMZ

In actual use, some hosts need foreign provides the service, in order to provide service, at the same time to effectively protect the internal network security, will these need to open the host and internal network equipment are separated by the numerous, according to the different needs, pertinently adopt corresponding measures so that they can provide friendly service in foreign maximum protection while the internal network. According to different resources provide different security levels of protection, can build a DMZ area, DMZ can provide network level for hosting environment protection, can reduce services for clients to distrust the dangerous sparked public information, was placed the best position. In a non DMZ system, internal network and host security usually don't like people expected solid, provide Internet services has produced many loopholes, make other host vulnerable to attack. But, through the configuration DMZ, we will need to protect Web application servers and database system in the connection, containing sensitive data, bear no responsibility host data access agency placed on such DMZ for application system security provided protection. DMZ make contain important data internal systems from direct exposure to external network and the attack, the attacker even if successful, still faces preliminary invasion DMZ setting new barriers.

3: DMZ network access control strategy

When planning a has the DMZ, we can clear network access relations between each network, can determine the following six access control strategy.

1. A network can access the nets

A network users clearly need to visit freely outside nets. In this strategy, firewall need to undertake the source address conversion.

2. The DMZ connection can access

This strategy is to facilitate the use and management of network users the DMZ server.

3. Outer net connection cannot access

Obviously, the network storage in a company's internal data is, these data don't allow the user to access the net.

4. The nets can access DMZ

The server is itself DMZ provide services to the outside world, so the nets must can access DMZ. Meanwhile, the DMZ need to visit by firewall net foreign address to the server completed the actual address convert.

5. The connection cannot access the DMZ

Obviously, if against this strategy, then, when the invaders DMZ, can seize further offensive to the important data connection.

6. DMZ cannot access the nets

This strategy also have exception, such as placing DMZ email server, it need access to the outer net, otherwise will not work properly. In a network, demilitarised zone (DMZ) refers to provide services for the isolated distrust system, its purpose is to segment the sensitive internal network and other provides access service network connection and separate, prevent the nets direct communication, network security to ensure. 

New international pop to receive an abdomen aerobics

Keep beautiful figure, in addition to a diet correctly, sports is the indispensable. Calisthenics experts are middle-aged designed a set of accept stomach aerobics, everyday take only 20 minutes, insist on practicing for a period of time, waist and abdomen will become fine, the body more healthy. Introduce below is foreign popular tucked up strong and handsome morning exercises.

One, the back arched movement

1, preliminary pose: trend, look up, back straight.

2, action: the back arched, lower the head, shrinkage abdominal muscle, keep pose 5 seconds, restore. Repeated 8 times. Contraction abdominal muscle, reductive when mouth only when nasal inhale.

Second, body lateral flexion movement

1, preliminary pose: legged, with her hands on her body side on the ground.

2, action: left hand to the left side slip out of his right arm, lift on the left, and bowed to the left shimmy with bowed to the left, repeatedly put four times, reduction. Change right done 4 times. Repeat twice. Lateral flexion hip motionless, action to do slow rhythm.

Three, boating

1, preliminary pose: posture, two legs are apart, arms knees before palm down, raises.

2, action: hands down on devices with forward, head to lap, restore. 6 seconds intervals do 1 times, 24 times repeated. Lumbar back straight when accept stomach. When the flexor devices, unbend inspiratory exhale.

Four, leg movement

PingWo, after his left arm, left leg unbend, extend deuce put right leg knees props up, his right arm pig body side. Back before you reach the ground, lifted, left leg left after, make both carried together. Repeat 12 times, and in the right arm, leg do 12 times. Point is to receive an abdomen, keep his back straight.

Five, twisting movement

Posture, the two arms natural prolapse, left leg, right leg knees right put up feet on knees outside left thigh. Left to right turn, i.e., your right hand on his right foot therein with eyes behind the floor, right shoulder. Maintaining a pose 20 seconds. Change direction do the same action. The repeated twice. As you roll to receive an abdomen, take a deep breath.

Six, accept stomach movement

Supine, with legs apart, waist not stick to, two arms lie body side. Tightening abdominal muscle, make the spine to the earth, maintain 6 seconds, then relax posture reduction. Repeated do 12 times. Accept stomach when expiratory, relax when inspiratory.

Seven, pretty waist movement

1, preliminary pose: supine, knees and legs back posted separately, arms lie body side.

2, action: accept abdominal muscle, slow puffed out the waist, until only the shoulder touchdown. Keep straight back four seconds. Then slowly down the waist reduction. Repeated do 12 times.