摘要:
In an NMR apparatus with a system of gradient coils for the production of a magnetic field gradient within a measurement volume (1) within a field coil, the transverse gradient coils are constructed unsymmetrically with respect to the z=0 plane dividing the measurement volume (1), however largely mirror symmetric to a x=0 or y=0 plane containing the z axis, and possess only two partial coils (20', 20''; 40', 40'') whose windings each exhibit the same winding direction. The axial gradient coils are cylindrically symmetric with respect to the z axis and totally unsymmetric with respect to the z=0 plane, and consist of at least two partial coils which are arranged on differing sides of z=0 plane, whereby the partial coils on one side largely exhibit the opposite winding direction than the coils on the other side, and whereby the number of coils with a particular winding direction is not equal to the number of coils with the opposite winding direction. In each case, it is thereby achieved that the measurement volume (1) is displaced to a, relative to the z axis, axial end of the apparatus so that access to the measurement volume (1) is substantially improved.
摘要:
In a method for the production of a magnet coil arrangement which can create a predetermined magnet field B and has a minimal inductance L. The magnetic field B to be generated is expanded in spherical harmonics with coefficients C.sub.n,m and a field error .DELTA. B=f.sub.1 (C.sub.n,m) is defined fixing the deviation of the magnet field profile of the coil arrangement to be calculated from the given magnet field B within a volume and, if necessary, further parameters P=f.sub.2 (C.sub.n,m) are predefined, whereby the value of P which is calculated with a particular set of coefficients C.sub.n,m is within predetermined limits. By defining limits for technically relevant parameters and their variation as well as by giving the desired minimum inductance, the procedure achieves a high flexibility in conjunction with independent optimization of the parameters, in particular field errors, minimum inductance and current density oscillations.
摘要翻译:在用于制造可产生预定磁场B并具有最小电感L的磁体线圈装置的方法中。要产生的磁场B以系数Cn,m的球谐函数扩展,并且场误差DELTA B = 将f1(Cn,m)定义为固定要从体积内的给定磁场B计算的线圈装置的磁场分布的偏差,并且如果需要,预定义另外的参数P = f2(Cn,m) 由此用特定系数Cn,m计算的P的值在预定限度内。 通过定义技术上相关参数及其变化的限制以及给出所需的最小电感,该程序结合独立优化参数,特别是场误差,最小电感和电流密度振荡,实现了高度的灵活性。
摘要:
The windings of an NMR magnet coil are formed of at least two adjacent non-crossing conductor paths which are electrically insulated from one another. Each conductor path of a partial coil can be transformed geometrically into one respective conductor path in each partial coil through the symmetrical operations. The various conductor paths in each partial coil are coded in such a manner that the conductor paths adjacent to one another in a winding and attributed with identical successive cardinal numbers as code numbers in their geometric order. The conductor paths in the various partial coils which can be transformed into one another through symmetrical operations have the same code numbers. Each conductor path in a partial coil is electrically connected in series with one conductor path each in at least one other partial coil. These series connections of conductor paths are electrically connected to one another in parallel. The sum of the code numbers of the conductor paths connected in series in the various partial coils is identical in each case with all series connections of conductor paths which are connected in parallel. In this manner it is possible, with an extremely small number of crossings, to avoid the problem of strong current redistributions by eddy currents in the generation of magnetic fields which are rapidly variable with time.
摘要:
In a magnetic resonance (MR) apparatus comprising a main field magnet system with a tubular opening for receiving the object to be investigated and at least one tubular mechanically oscillatory component, disposed in this opening, in particular a gradient coil system, and at least one cylindrical element of electrically conducting material surrounded by the main field magnet system, which is rigidly mechanically connected to at least one of the mechanically oscillatory components or forms an integral mechanical component thereof, the sum of the products p of the electric conductivities &sgr;, the cylinder radii R and the wall thicknesses d of the cylindrical element per mechanically oscillatory component is between 1 Am/V and 10,000 Am/V, preferably between 10 Am/V and 1000 Am/V, and particularly preferred between 20 Am/V and 500 Am/V. This produces good noise damping in an inward direction.
摘要:
A gradient coil system comprises a gradient coil for generating a rapidly changing magnetic gradient field in a working volume of a magnetic resonance apparatus, with a current path guided in windings on the surface of a geometric body, the geometry of which results in the desired spatial dependence of the magnetic field of this gradient coil in the working volume. N current power supplies (NG1, NG2) can be controlled with an analog or digital control signal to each generate a time-dependent controlled electric current (i1, i2) proportional to the control signal. The current path is divided into several parallel conductor paths which are electrically insulated from one another, and which form a doubly or multiply wound transformer, wherein the inductances of the various conductor paths with respect to one another as well as the mutual inductances with respect to one another have approximately the same value L. The ends of each conductor path are each connected to one respective current power supply (NG1,NG2), and the current power supplies (NG1, NG2) can be controlled with control signals in such a manner as to supply the same current (i1, i2) to the conductor paths at all times. This enables operation of a gradient coil with several current power supplies in such a manner that, should the dependencies of the currents of the current power supplies not be precisely identical, generation of disturbing magnetic fields having a geometry which differs considerably from the desired geometry for the gradient coil is prevented.
摘要:
Novel flake feeds are described, especially for aquatic animals, such as fish, shrimps and invertebrates, characterized in that the flakes have a uniform form, a variable thickness and a water content of from 1 to 30%, as well as a process for the production thereof.
摘要:
Novel flake feeds are described, especially for aquatic animals, such as fish, shrimps and invertebrates, characterized in that the flakes have a uniform form, a variable thickness and a water content of from 1 to 30%, as well as a process for the production thereof.
摘要:
The invention concerns a call control method for IP based telephone services and a call control server providing IP based telephone services within a communication network. The call control server assigns two or more IP telephone terminals to a telephone number commonly shared by these IP telephone terminals. It stores IP address data of these IP telephone terminals in the registry of this call control server which is responsible of VoIP calls directed to this telephone number. An IP telephone terminal transmits a presence message to the call control server when a presence button of the IP telephone terminal is pressed. VoIP calls directed to the telephone number are routed to that one of the IP telephone terminals assigned to the telephone number, the call control server has received the presence message from.
摘要:
The present invention provides a medicinal feed for fish, which comprises at least one compound selected from the group consisting of thionine, nitrothiazole, nitrofuran, quinoline and acridine derivatives, compounds splitting off aldehydes, transition metal derivatives, metal colloids, hexamethylenetetramine and/or quaternary ammonium salts as active materials.
摘要:
Disclosed is a process and apparatus for separating aspherical particles from spherical particles in an admixture thereof, preferably in the preparation of a particulate carrier material for two-component developer systems for electrostatic copy devices. The process comprises directing the mixture of particles onto a surface which is inclined with respect to the horizontal; producing a relative velocity between the inclined surface and the mixture of particles, the velocity having a directional component transverse to the steepest inclination gradient of the inclined surface; and collecting a portion of the mixture of particles in a zone of the inclined surface wherein predominantly spherical particles have accummulated as a result of their greater tendency to roll in response to the relative velocity than the aspherical particles.