Abstract: A sever including a chassis, at least one first tray, at least one second tray, a power supply module, multiple input/output interface circuit boards, and multiple mother boards is provided. The first and second trays are slidably disposed in the chassis, and the first and second trays can be drawn out of the chassis in opposite directions. The power supply module is disposed on a bottom plate of the chassis. The input/output interface circuit boards are disposed on the first tray, respectively. The power supply module is located between two input/output interface circuit boards. Each input/output interface circuit board has multiple input/output interfaces. The mother boards are disposed on the second trays, respectively. The input/output interface circuit boards and the power supply module are correspondingly electrically connected to the mother boards.

Abstract: A sever including a chassis, at least one first tray, at least one second tray, a power supply module, multiple input/output interface circuit boards, and multiple mother boards is provided. The first and second trays are slidably disposed in the chassis, and the first and second trays can be drawn out of the chassis in opposite directions. The power supply module is disposed on a bottom plate of the chassis. The input/output interface circuit boards are disposed on the first tray, respectively. The power supply module is located between two input/output interface circuit boards. Each input/output interface circuit board has multiple input/output interfaces. The mother boards are disposed on the second trays, respectively. The input/output interface circuit boards and the power supply module are correspondingly electrically connected to the mother boards.

Abstract: Tools for investigating an earth formation in the presence of either oil-base or water-base mud include a circuit which induces current into the formation in a focused manner, and a sensor electrode which is isolated from the circuit, at least partially surrounded by the circuit, and located in the area in which the current is focused. The current inducing circuit may be an oppositely polarized double-dipole circuit to which voltage is applied with the two dipoles sharing a common radiating element over which a focused area is formed. Insulators separate the outer electrodes of the double-dipole circuit from the common radiating element. Alternatively, the current inducing circuit is a coil arranged in a partial toroidal configuration in an insulated area that at least partially surrounds the focused area and which separates the focused area from return electrodes.

Abstract: Tools for investigating an earth formation in the presence of either oil-base or water-base mud are provided and includes a circuit which induces current into the formation in a focused manner, and a sensor electrode which is isolated from the circuit, at least partially surrounded by the circuit, and located in the area in which the current is focused. The current inducing circuit may be an oppositely polarized double-dipole circuit to which voltage is applied with the two dipoles sharing a common radiating element over which a focused area is formed. Insulators are provided that separate the outer electrodes of the double-dipole circuit from the common radiating element. Alternatively, the current inducing circuit is a coil arranged in a partial toroidal configuration in an insulated area that at least partially surrounds the focused area and which separates the focused area from return electrodes.