Abstract: A method of dewatering sludge is provided herein. In some embodiments, the method includes introducing micronized dry water soluble polymer (DWSP) particles into a sludge, wherein the sludge includes water and solids; separating water of the sludge from solids of the sludge using the micronized DWSP particles; and collecting a wet solid including water and solids of the sludge, wherein a concentration of solids in the wet solid is higher than a concentration of solids in the sludge, wherein the micronized DWSP particles comprise a DWSP wherein the DWSP is selected from the group consisting of a dry anionic water soluble polymer, a dry cationic water soluble polymer, a dry nonionic water soluble polymer, and mixtures thereof, and wherein a mean particle size of the micronized DWSP particles ranges from about 100 to about 300 microns.

Abstract: A method of dewatering sludge is provided herein. In some embodiments, the method includes introducing micronized dry water soluble polymer (DWSP) particles into a sludge, wherein the sludge includes water and solids; separating water of the sludge from solids of the sludge using the micronized DWSP particles; and collecting a wet solid including water and solids of the sludge, wherein a concentration of solids in the wet solid is higher than a concentration of solids in the sludge, wherein the micronized DWSP particles comprise a DWSP wherein the DWSP is selected from the group consisting of a dry anionic water soluble polymer, a dry cationic water soluble polymer, a dry nonionic water soluble polymer, and mixtures thereof, and wherein a mean particle size of the micronized DWSP particles ranges from about 100 to about 300 microns.

Abstract: Methods are provided for reducing friction during fracturing of a subterranean formation. In some embodiments, a method includes introducing micronized dry water soluble polymer (DWSP) particles into a fracturing liquid to form a mixture; and pumping the mixture into a subterranean formation to fracture the subterranean formation, the micronized DWSP particles include a DWSP, DWSP is selected from the group consisting of dry anionic, dry cationic, dry nonionic water soluble polymer, and mixtures thereof, mean particle size of the micronized DWSP particles ranges from about 115 to about 225 microns.

Abstract: A dimmable light-emitting diode (LED) lamp and a dimmable LED lighting apparatus thereof are provided. The dimmable LED lamp includes a bridge rectifier, a toggle detector, a sustain voltage supply circuit, a counter, an LED light source, and an LED lighting driver. The bridge rectifier receives a source alternating current (AC) voltage through a wall switch and provides a rectified direct current (DC) voltage. The toggle detector monitors a toggle action of the wall switch. The sustain voltage supply circuit provides a sustain voltage. The counter receives the sustain voltage for operation. Moreover, the counter stores and provides an counting value that changes when the toggle detector detects the toggle action. The LED lighting driver converts the rectified DC voltage to a constant current to drive the LED light source. The LED lighting driver also provides multi-level dimming to the LED light source according to the counting value.

Abstract: A light-emitting diode (LED) driver circuit is provided, which includes a transistor, a current regulator, a release diode, and a voltage clamping device. The transistor is coupled in series with an LED string. The LED string is coupled between the transistor and a bus voltage. The current regulator is coupled to the transistor for regulating the current through the transistor and the LED string to a predetermined current. The release diode has an anode coupled between the LED string and the transistor. The voltage clamping device is coupled to the cathode of the release diode for clamping the voltage level at the cathode of the release diode to a predetermined voltage. The voltage clamping device protects the transistor from breakdown when the transistor is turned off for dimming control.

Abstract: A method of preparing and using a subterranean formation stabilization agent. The stabilization agent includes a guanidyl copolymer and may be admixed with a fracturing fluid and optionally brine. The stabilization agent is effective in preventing and/or reducing, for example, clay swelling and fines migration from a subterranean formation contacted with the stabilization agent.

Abstract: A light-emitting diode (LED) driver circuit is provided, which includes a transistor, a current regulator, a release diode, and a voltage clamping device. The transistor is coupled in series with an LED string. The LED string is coupled between the transistor and a bus voltage. The current regulator is coupled to the transistor for regulating the current through the transistor and the LED string to a predetermined current. The release diode has an anode coupled between the LED string and the transistor. The voltage clamping device is coupled to the cathode of the release diode for clamping the voltage level at the cathode of the release diode to a predetermined voltage. The voltage clamping device protects the transistor from breakdown when the transistor is turned off for dimming control.

Abstract: A dimmable light-emitting diode (LED) lamp and a dimmable LED lighting apparatus thereof are provided. The dimmable LED lamp includes a bridge rectifier, a toggle detector, a sustain voltage supply circuit, a counter, an LED light source, and an LED lighting driver. The bridge rectifier receives a source alternating current (AC) voltage through a wall switch and provides a rectified direct current (DC) voltage. The toggle detector monitors a toggle action of the wall switch. The sustain voltage supply circuit provides a sustain voltage. The counter receives the sustain voltage for operation. Moreover, the counter stores and provides an counting value that changes when the toggle detector detects the toggle action. The LED lighting driver converts the rectified DC voltage to a constant current to drive the LED light source. The LED lighting driver also provides multi-level dimming to the LED light source according to the counting value.

Abstract: A buck converter LED driver circuit is provided. The driver circuit includes a buck power stage, a rectified AC voltage source, a voltage waveform sampler, and a control circuit. The buck power stage includes at least one LED and provides a first signal directly proportional to the current through the LED. The rectified AC voltage source is coupled to the buck power stage for driving the buck power stage. The voltage waveform sampler is coupled to the rectified AC voltage source for providing a second signal directly proportional to the voltage provided by the rectified AC voltage source. The control circuit is coupled to the voltage waveform sampler and the buck power stage for turning on and turning off the buck power stage according to a comparison between the first signal and the second signal.

Abstract: A digital communication network including several receivers and a communication method for the digital communication network are provided. Each of the receivers includes a first port and a second port. The first port of the first receiver is coupled to the microcontroller. The first port of each of the receivers except the first receiver is coupled to the second port of the previous receiver. Each receiver further includes a chain register. The chain registers of the receivers are mutually connected through the first ports and the second ports, forming a virtual global queue. By utilizing the characteristics of the virtual global queue, the system and the method achieve bi-directional, single-wire, serial communication without the encumbrance of assigning addresses or identification codes to the receivers.

Abstract: A synchronous rectifier DC/DC converter is provided. The synchronous rectifier DC/DC converter includes a power transformer, a first diode, a first MOSFET, and a first controller. The power transformer includes a core, a primary winding, a secondary winding, and a sense winding. The primary winding is wrapped around the core and receives an input voltage of the synchronous rectifier DC/DC converter. The secondary winding is wrapped around the core and provides the energy of an output current of the synchronous rectifier DC/DC converter. The sense winding is wrapped around the core and provides a sense signal. The first diode is coupled to the secondary winding for rectifying the output current. The first MOSFET is coupled in parallel with the first diode. The first controller is coupled to the sense winding and the first MOSFET for turning on and turning off the first MOSFET according to the sense signal.

Abstract: A buck converter LED driver circuit is provided. The driver circuit includes a buck power stage, a rectified AC voltage source, a voltage waveform sampler, and a control circuit. The buck power stage includes at least one LED and provides a first signal directly proportional to the current through the LED. The rectified AC voltage source is coupled to the buck power stage for driving the buck power stage. The voltage waveform sampler is coupled to the rectified AC voltage source for providing a second signal directly proportional to the voltage provided by the rectified AC voltage source. The control circuit is coupled to the voltage waveform sampler and the buck power stage for turning on and turning off the buck power stage according to a comparison between the first signal and the second signal.

Abstract: A circuit and a method for controlling the rotating speed of a brushless direct current (BLDC) motor are provided, whose goal is solving the stall problem encountered by conventional BLDC motors driven by pulse width modulation (PWM). The circuit includes a closed-loop control mechanism for adjusting the duty cycle of the motor current of the BLDC motor, thus controlling the rotating speed of the motor. The closed-loop control is based on the comparison of a signal proportional to the actual rotating speed and another signal proportional to the predetermined target rotating speed.

Abstract: A circuit and a method for controlling the rotating speed of a brushless direct current (BLDC) motor are provided, whose goal is solving the stall problem encountered by conventional BLDC motors driven by pulse width modulation (PWM). The circuit includes a closed-loop control mechanism for adjusting the duty cycle of the motor current of the BLDC motor, thus controlling the rotating speed of the motor. The closed-loop control is based on the comparison of a signal proportional to the actual rotating speed and another signal proportional to the predetermined target rotating speed.

Abstract: An active power factor correction (PFC) circuit and its controlling method are provided. The method comprises the following steps. Drive the power switch of the circuit so that the average inductor current waveform follows the rectified input voltage waveform. Suspend the operation of the power switch at a first moment in a first line cycle of the rectified input voltage and then resume the operation of the power switch at a second moment in a second line cycle of the rectified input voltage. The first moment is when the phase angle of the rectified input voltage exceeds a predetermined angle and the switching frequency of the power switch exceeds a predetermined frequency. The time span from the first moment to the end of the first line cycle is substantially as long as the time span from the beginning of the second line cycle to the second moment.

Abstract: Methods and systems for generating and validating value-bearing documents include an issuer module that receives requests for value-bearing documents. The issuer module communicates the requests to a guarantor module. The requests may include a desired security level and/or a target validator. The guarantor module generates value-bearing documents for each request and randomly or pseudo-randomly selects an encryption key from a set of encryption keys to encrypt the value-bearing document. The set of encryption keys may be a key space selected based on the target validator and/or requested security level. The guarantor module encrypts the value-bearing document using the selected encryption key and forwards the document to the issuer. The issuer forwards the encrypted value-bearing document to the requester. When the requester desires to redeem the document, the requester presents the value-bearing document to a validator.

Abstract: There are disclosed several embodiments of a disc brake caliper assembly in which adjustment is made for wear on the pads by a non-rotating linearly expandable and retractable linkage arranged between a brake actuator and the pads. The linkage includes inner and outer members coaxially reciprocal without rotation with respect to one another, one member having surfaces which extend at acute angle with respect to the axis and opposite surfaces on the other member which extend parallel to the axis. Circumferentially spaced wedges are disposed in the space between the angled and parallel surfaces, and springs between the first member and wedges yieldably urge the wedges in the first longitudinal direction toward the angled surfaces, the second member being movable during the braking cycle in a second longitudinal direction and thus relatively to the first member, whereby the linkage is caused to expand in order to adjust for wear.