In CATOL, the test process unified description language CATOL-PR is used to describe the test flows which face spacecraft testers directly. Testers use this language to write test programs which can be executed automatically by running the test application software. By analyzing requirements of spacecraft automatic test, this article summarizes the characteristics which spacecraft automatic test should have and defines the elements of CATOL-PR language based on the researches of a spacecraft automatic test system. Similar to traditional test language, testers can use the language to compile the test program. But besides the general command and execution control command, spacecraft test process language should provide the functional statement for the spacecraft test, e.g. telemetry statement, and so on.
Here, we define the main components of the language and give the syntax of CATOL-PR. In addition, in order to ensure the accuracy of test procedures, we use the semantic model[16-17] to abstract the practical implementation of CATOL-PR, so designers and users of the language have the same understanding for the language.
5.1. Syntax of CATOL-PR
The components of CATOL-PR can be divided into two categories. The first is the procedural language elements used for the algorithm and behavioral descriptions, which mainly consist of variable assignment statement, sequence statement, condition statement and loop statement, etc. The second is the language elements used for spacecraft test and reflects real-time characteristics, which mainly consist of operational statement, data statement, time statement and control statement.
The following is a subset of CATOL-PR, which embodies the core components of the spacecraft test process and contains the two major language elements described above.
To denote the CATOL-PR, we use BNF which is a formal mathematical way to describe the language.
The determination of fracture parameters is a diffi cult and critical part of reservoir fracture evaluation. In this paper, with wavelet transformation of the conventional log curves, the wavelet decomposed signal which best matched the fractures was found. However the fractures cannot be indicated completely by an appropriate mother wavelet transform of conventional well logs. The combination of wavelet transform and differential curve forms a generalized fracture indicator curve to make up for this drawback to some extent, improves the reliability of calculating fracture density, and provides a basis for classifying the fracture density.
The fracture indicator curve can calculate the fracture density suffi ciently well but it is also a relatively better indication of the fractures owing to fracture distribution characteristics such as randomness, inhomogeneity, and special filtration. The research on five wells in the Changling fault depression in north-eastern China shows that the proposed method is effective when the fracture density is greater than 1 and it shows good correspondence between the calculated fracture density and the density from image logs.
Deuterium fluoride( DF) lasers have been under development since about 1970． The spectral regions of DF laser are from 3. 5 μm to 4. 1 μm，which is a good atmospheric transmission window as well as the absorption band of air pollutants( hydrocarbons，sulfur dioxide，nitrogen oxides，etc． ) ． Its intrinsic ability to store high levels of energy makes this type of laser attractive to the researcher for producing high power levels for an air and missile defense weapon system． Besides，it can be used in laser radar transmitters，infrared fiber-optic communications and atmospheric detecting．
Pulsed DF chemical lasers based on the electrical dissociation of SF6 are very attractive because they used gases easy to handle，while they are not corrosive and unlike F2 and F2 mixtures there is no risk of premature ignition［1］． The chain DF laser is driven by burning the gas mixture in combustor，and is comprised of a combustor，a nozzle bank，optics，a diffuser and a ejector． The chain DF laser uses F2 as the oxidizer so it has the explosion possibility when F2 reacts with D2 or deuterocarbons． Compared with the chain DF laser，there is no risk of corrosion and explosion，and the structure is compact and easy to handle． For all these advantages，the non-chain DF laser becomes an attractive research object．However，the DF laser is different from other gas lasers or chemical lasers for its distinctive discharge characteristics and working mechanism． Electric discharged non-chain DF laser usually uses mixtures of F atoms ( contained in SF6 ) and D atoms( from deuterocarbons) as active media． The discharge is used to cause chemical reactions in order to achieve population inversion and then generate laser． Relative to other gases that can form stable negative ions by attaching electrons，SF6 is a strongly electronegative gas． Its strong electro negativity makes SF6 molecule dissociation very hard，so it is important to choose a suitable type of discharge． The uniformity of discharge should be concerned for it is one of the key factors to decide whether we can obtain laser output．
Mixture ratio technology is also very important．D atoms are from deuterocarbons，such as D2，C6D12 and C2 D6．For choosing different deuterium donors，the expense and laser output will be different．The by-products and heat generated during the chemical reaction and discharge process would reduce the laser quality，such as output powers，energy and pulse widths，so the recirculating and cooling technology seems important also． The following section describes the key technologies in more details．