Use Of Force Research Articles

Thermally Induced Knudsen Forces for Contactless Manipulation of a Micro-Object.

In this paper, we propose that thermally induced Knudsen forces in a rarefied gas can be exploited to achieve a tweezer-like mechanism that can be used to trap and grasp a micro-object without physical contact. Using the direct simulation Monte Carlo (DSMC) method, we showed that the proposed mechanism is achieved when a heated thin plate, mounted perpendicularly on a flat substrate, is placed close to a colder object; in this case, a beam. This mechanism is mainly due to the pressure differences induced by the thermal edge flows at the corners of the beam and the thermal edge flow at the tip of the thin plate. Specifically, the pressure on the top surface of the beam is smaller than that on its bottom surface when the thin plate is above the beam, while the pressure on the right side of the beam is smaller than that on its left side when the thin plate is located near the right side of the beam. These differences in pressure generate a force, which attracts the beam to the plate horizontally and vertically. Furthermore, this phenomenon is enhanced when the height of the beam is shorter, such that the horizontal and vertical net forces, which attract the beam to the plate, become stronger. The mechanism proposed here was also found to depend significantly on the height of the beam, the temperature difference between the thin plate and the beam, and the Knudsen number.

Causes and factors responsible for Operation Zarb-e-Azb: perspective of internally displaced persons of North Waziristan, Pakistan

After 9/11 incident, the US and NATO forces entered Afghanistan to defeat Al-Qaida and its affiliated militant group–Taliban. The NATO forces invasion pushed militants from Afghanistan to take refuge in nearby places. Due to close proximity and vulnerable borders, many of these militants entered Pakistan’s erstwhile Federally Administered Tribal Areas (FATA), which resulted in the growth of militancy and extremism in the region. Pakistan launched a series of operations to counter terrorism and its facilitators. Operation Zarb-e-Azb was the continuation of those operations, started as a last vengeance in North Waziristan Agency with the aim to evacuate common people and then to extinguish militants. Resultantly, operation started in the mid of June, 2014 and the people of North Waziristan Agency started migration to the adjacent areas i.e., Bannu, Lakki Marwat and Karak etc. with worries and miseries in their hearts. Operation Zarb-e-Azb has been discussed in the literature. However, the perspective of IDPs has been overlooked. The study is descriptive-exploratory which is accomplished on a mixed study approach. This research article aimed to assess the perception of IDPs camped in Lakki Marwat from 2014-17 regarding the operation's causes and factors and the problems IDPs faced during displacement.

Terminal force soft sensing of hydraulic manipulator based on the parameter identification

Focusing on accurately measuring the terminal force of the hydraulic manipulator without the force sensor, a soft-sensing method of terminal force based on the dynamic model and the fusion of multiple pressure/encoder feedback information is presented. Compared with the direct estimation method (DEM) which calculates the force in terms of the computer-aided design (CAD) model, the dynamic model in the presented method is identified by employing the recursive least square method to increase the soft-sensing precision. To decrease the deviations of identified dynamic parameters in the high reachable workspace, an optimal excitation trajectory based on the finite Fourier series model is designed, ensuring that the condition number of the regression matrix is at a minimum under the motion constraints. Then, the hydraulic manipulator operates without load by this excitation trajectory to establish an online soft-sensing model. The constant and variable load forces are utilized to conduct the experiment verification.

“Stop Resisting or You’re Gonna Get It Again”: Police Use of Force in a Canadian Crime Reality Television Show

Extant research suggests that crime reality television advances biased narratives about offenders, police officers, and the nature of crime. This study contributes to the literature by investigating the prevalence, severity, and proportionality of police use of force in Under Arrest, a Canadian crime reality television show. Using a content analysis of all 65 Under Arrest episodes, research reveals that police use of physical force is portrayed in nearly half of vignettes, and over half of force used is excessive force. Logistic regression indicates that the racial composition of the suspect pool does not predict use of force when controlling for other relevant variables. However, suspect race is the strongest predictor of excessive force even when controlling for initial crime seriousness, gender, suspect intoxication, and weapon possession. Results indicate that Under Arrest contributes to law and order ideology by portraying police use of force as a necessary and justified tool for controlling crime committed by racialized suspects.

Nanogap Electrode-Enabled Versatile Electrokinetic Manipulation of Nanometric Species in Fluids.

Noninvasive manipulation of nanoscopic species in liquids has attracted considerable attention due to its potential applications in diverse fields. Many sophisticated methodologies have been developed to control and study nanoscopic entities, but the low-power, cost-effective, and versatile manipulation of nanometer-sized objects in liquids remains challenging. Here, we present a dielectrophoretic (DEP) manipulation technique based on nanogap electrodes, with which the on-demand capturing, enriching, and sorting of nano-objects in microfluidic systems can be achieved. The dielectrophoretic control unit consists of a pair of swelling-induced nanogap electrodes crossing a microchannel, generating a steep electric field gradient and thus strong DEP force for the effective manipulation of nano-objects microfluidics. The trapping, enriching, and sorting of nanoparticles and DNAs were performed with this device to demonstrate its potential applications in micro/nanofluidics, which opens an alternative avenue for the non-invasive manipulation and characterization of nanoparticles such as DNA, proteins, and viruses.

Plasmonic Nanoagents in Biophysics and Biomedicine

AbstractThe significant rise in implementation and applications of plasmonic nanosystems in biophysics, biochemistry, and medicine has culminated in the emergence of refined plasmonic enabling reagents, or “nanoagents”. These are defined as tools that allow researchers to not only investigate, but also actively manipulate biological processes and complex biosystems, such as living cells, on the nanoscale. This development is based on a combination of sensing capabilities, photothermal control, and optical force manipulation offered by metallic nanoparticles. The article reviews the trajectory that plasmonic nanoagents have taken in recent years and highlights seminal recent examples of their application, such as optical sensing both in vitro and in vivo, optical control of biomolecular interactions and protein function, the manipulation of lipid membrane properties, and the possibility of guiding cellular behavior

Bidirectional Locomotion of Soft Inchworm Crawler Using Dynamic Gaits.

Inchworm-styled locomotion is one of the simplest gaits for mobile robots, which enables easy actuation, effective movement, and strong adaptation in nature. However, an agile inchworm-like robot that realizes versatile locomotion usually requires effective friction force manipulation with a complicated actuation structure and control algorithm. In this study, we embody a friction force controller based on the deformation of the robot body, to realize bidirectional locomotion. Two kinds of differential friction forces are integrated into a beam-like soft robot body, and along with the cyclical actuation of the robot body, two locomotion gaits with opposite locomotion directions can be generated and controlled by the deformation process of the robot body, that is, the dynamic gaits. Based on these dynamic gaits, two kinds of locomotion control schemes, the amplitude-based control and the frequency-based control, are proposed, analyzed, and validated with both theoretical simulations and prototype experiments. The soft inchworm crawler achieves the versatile locomotion result via a simple system configuration and minimalist actuation input. This work is an example of using soft structure vibrations for challenging robotic tasks.

Heartland, Rimland, and the Grand Chessboard Deciphering the Great Power Politics in Central Asia

As the twenty-first century progresses, struggle for the control of Central Asia is growing, as rising China increases its economic and political clout while Russia is trying to regain its lost glory. The American presence in the region was considered as a threat not only by China, but also Russia who feared that the US is determined to carve out its sphere of influence at their expense. The recent withdrawal of the US forces from Afghanistan and Taliban re- taking Kabul further complicates the geopolitical calculations. China and Russia have been cooperating to ensure that the adjoining region, typically falling under Russian sphere of influence, may not become an American influenced area. Where China has emerged as one of the biggest trading partners of the Central Asian Republics, and Russia has signed several bilateral and multilateral security agreements to ensure its continued influence therein. Eurasia generally and Central Asia specifically, once again, is back to the limelight of great powers politics. This study traces the conceptual evolution of geopolitics, from Ratzel’s Lebensraum, Kjellen’s theory of state as an organism, to the Mahan conception of the sea power, among others. It discusses the collective geopolitical insights of Halford Mackinder, Nicholas Spykman, and Zbigniew Brzezinski who focussed on the concepts of Heartland, Rimland, and Grand Chessboard, respectively, to decipher the geopolitics of Eurasia. Keywords: Central Asia, Geopolitics, Lebensraum, Heartland, Rimland.

India at the Geopolitical Crossroads

The article refutes the widely circulated claim that India has made its geopolitical choice in favor of the USA through joining it in confront-ing China by participating in the QUAD dialogue format. While considering the factors of substantial advance in US-Indian relationship, the author points out that it was rather the geopolitical choice of the USA itself, that the Obama Administration’s “pivot” went to consolidate after quite a prolonged period of ultimately futile attempts by Washington to incorporate Beijing into its “uni-polar moment.” With China-India rivalry having definitely increased, their mechanism of regular meetings on the border problem has enabled them to put the issue outside the general context of their relationship. It facilitated the creation of possibilities for a substantial advance of relations between the two countries in trade and investment spheres, setting up the political dialogue, including at the summit level, and interaction within a number of multilateral formats. Analysis of the geopolitical concept of India’s present Foreign Minister shows, that it is based on a design to take advantage from the interest taken in obtaining India’s support by the opponents of the establishment in the Indo-Pacific region of “China’s hegemony” while avoiding “excessively antagonizing” the latter. This is confirmed by India’s care to avoid giving the QUAD the shape of a military bloc, which has been taken into account by its partners within “the four” at the current stage. Highlighted is the importance attached by India to promoting its continental geopolitical interests by enhancing its relations with Russia and participating in the SCO and the RIC, especially taking into account the disorderly withdrawal of the US forces from Afghanistan. The Indians attaching lately a place of importance in their Indo-Pacific doctrine to Russia has been taken note of. The article comes to a conclusion that India continues its geopolitical maneuvering, which remains an important part of the real picture of world politics with a potential to be used for the benefit of its positive evolution.

The Human Neck is Part of the Musculoskeletal Core: Cervical Muscles Help Stabilize the Pelvis During Running and Jumping.

SynopsisDuring locomotion, cervical muscles must be active to stabilize the head as the body accelerates and decelerates. We hypothesized that cervical muscles are also part of the linked chain of axial muscles that provide core stabilization against torques applied to the hip joint by the extrinsic muscles of the legs. To test whether specific cervical muscles play a role in postural stabilization of the head and/or core stabilization of the pelvic girdle, we used surface electromyography to measure changes in muscle activity in response to force manipulations during constant speed running and maximum effort counter-movement jumps. We found that doubling the mass of the head during both running and maximum effort jumping had little or no effect on (1) acceleration of the body and (2) cervical muscle activity. Application of horizontal forward and rearward directed forces at the pelvis during running tripled mean fore and aft accelerations, thereby increasing both the pitching moments on the head and flexion and extension torques applied to the hip. These manipulations primarily resulted in increases in cervical muscle activity that is appropriate for core stabilization of the pelvis. Additionally, when subjects jumped maximally with an applied downward directed force that reduced acceleration and therefore need for cervical muscles to stabilize the head, cervical muscle activity did not decrease. These results suggest that during locomotion, rather than acting to stabilize the head against the effects of inertia, the superficial muscles of the neck monitored in this study help to stabilize the pelvis against torques imposed by the extrinsic muscles of the legs at the hip joint. We suggest that a division of labor may exist between deep cervical muscles that presumably provide postural stabilization of the head versus superficial cervical muscles that provide core stabilization against torques applied to the pelvic and pectoral girdles by the extrinsic appendicular muscles.

Racial Isolation and Marginalization of Economic Research on Race and Crime

This essay examines the extent to which research on the economics of race and crime produced by Black economists or published in the flagship journal of the organization of Black economists, the Review of Black Political Economy (RBPE), is undervalued by mainstream economics. We use modern bibliometric methods to test for citation biases in the economics of crime literature. We also identify the contributions of three streams of research overlooked in the mainstream literature: identity, police use of force, and mass incarceration. We find evidence that Blacks publishing on race and crime in top economics journals are less likely to be cited than non-Blacks and that articles published in the RBPE are less likely to be cited than articles published in other journals. A review of some under-cited articles reveals that themes related to identity, police use of force, and mass incarceration hold valuable insights for policy makers and those seeking solutions to problems of persistent racial disparities in the criminal legal system. (JEL A11, A14, H75, J15, K42)

Counting Conflict: Quantifying Civilian Casualties in Afghanistan

Numbers of civilian deaths and injuries have become important measurements of conflict violence. This article analyzes the methodological and epistemological underpinnings of reports on civilian casualties by the US Forces and the United Nations Assistance Mission in Afghanistan (UNAMA) as technologies of quantification. We argue that the quantification of conflict violence relies on – but obscures – judgments about the boundaries of the phenomenon that is being counted and the evidence that is required to confirm incidents. In particular, the competing civilian casualty counts operate on the basis different concepts of who counts as a civilian, what counts as conflict violence, and what counts of evidence of civilian casualties. We illustrate this argument with four examples: the distinction between direct and indirect deaths, the boundary between civilians and non-civilians, the boundary between conflict violence and criminal violence, and hierarchies in the visibility of civilians. We also draw attention to the racialized hierarchies of credibility that shape the US military’s dismissal of the voices of Afghan survivors and witnesses of conflict violence. Civilian casualty counts are products of specific methods, epistemologies, standards of proofs, and definitions. They help constitute an understanding of armed conflict as quantifiable and manageable.

Dean flow velocity of shear-thickening SiO2 nanofluids in curved microchannels

We report the effects of a curvilinear microchannel width, height, and radius of curvature, as well as the kinematic viscosity and axial velocity of shear-thickening nanofluids, on the average Dean velocity (VDe) of the secondary flow in the microchannel. Manipulation of inertial and Dean drag forces in curvilinear microchannels has enabled high-throughput and high-resolution size-based separation of microparticles and cells in various biomedical applications. VDe plays a deterministic role in the estimation of the Dean drag force and the design of these microfluidic devices. Despite the previous numerical and experimental studies on VDe of Newtonian and shear-thinning viscoelastic fluids, VDe of shear-thickening metallic nanofluids, such as SiO2 nanoparticles in water, in curved microchannels is still unknown. Such shear-thickening fluids are being used in thermal microsystem applications and are on the verge of entering the field of inertial microfluidics for particle and cell sorting. Our investigations have shown that VDe of shear-thickening SiO2–water nanofluids scales directly with the channel width and the fluid axial velocity, while being inversely proportional with the SiO2 concentration and the channel radius of curvature. Our non-dimensional analysis has led to the development of an empirical correlation that relates VDe-based Reynolds number of the nanofluid to the Dean number and the normalized kinematic viscosity of the nanofluid. It provides a significant accuracy in estimating VDe of shear-thickening fluids, compared to application of Newtonian or shear-thinning equations in the literature, which could be useful toward future design of particle and cell sorting and washing microdevices.

External force estimation for robot manipulator based on a LuGre-linear-hybrid friction model and an improved square root cubature Kalman filter

PurposeThe sensorless external force estimation of robot manipulator can be helpful for reducing the cost and complexity of the robot system. However, the complex friction phenomenon of the robot joint and uncertainty of robot model and signal noise significantly decrease the estimation accuracy. This study aims to investigate the friction modeling and the noise rejection of the external force estimation.Design/methodology/approachA LuGre-linear-hybrid (LuGre-L) friction model that combines the dynamic friction characteristics of the robot joint and static friction of the drive motor is proposed to improve the modeling accuracy of robot friction. The square root cubature Kalman filter (SCKF) is improved by integrating a Sage Window outer layer and a nonlinear disturbance observer (NDOB) inner layer. In the outer layer, Sage Window is integrated in the square root Kalman filter (W-SCKF) to dynamically adjust noise statistics. NDOB is applied as the inner layer of W-SCKF (NDOB-WSCKF) to obtain the uncertain state variables of the state model.FindingsA peg-in-hole contact experiment conducted on a real robot demonstrates that the average accuracy of the estimated joint torque based on LuGre-L is improved by 4.9% in contrast to the LuGre model. Based on the proposed NDOB-WSCKF, the average estimation accuracy of the external joint torque can reach up to 92.1%, which is improved by 4%–15.3% in contrast to other estimation methods (SCKF and NDOB).Originality/valueA LuGre-L friction model is proposed to handle the coupling of static and dynamic friction characteristics for the robot manipulator. An improved SCKF is applied to estimate the external force of the robot manipulator. To improve the noise rejection ability of the estimation method and make it more resistant to unmodeled state variable, SCKF is improved by integrating a Sage Window and NDOB, and a NDOB-WSCKF external force estimator is developed. Validation results demonstrate that the accuracy of the robot dynamics model and the estimated external force is improved by the proposed method.

Police accounts of critical incidents: a descriptive and empirical assessment

ABSTRACT Data from body-worn cameras (BWCs) have emerged as a new approach to measuring police activity. These data, in the form of video footage, represent a new method to systematically examine how critical incidents involving police unfold. Recently, law enforcement agencies have begun documenting and releasing elements of video and other data to offer the public their accounts of critical incidents involving police-citizen encounters. These include officer-involved shootings, use of force, and police activity involving protests and demonstrations. The current research analyzes these critical incidents in three interrelated ways: First, we describe the extent to which BWC footage is used in the critical incident accounts. Second, we assess the quality of the audio and video within the BWC footage that is released. Third, we closely code and analyze the data for patterns of police use of force and citizen resistance within the context of extant theories of use of force. The implications for policy and research, and the utility and limitations of this method for future research are considered.

Pathway mapping as a tool to address police use of force in behavioral health crisis

Police use of force is a significant problem in many communities, particularly related to episodes of behavioral health crisis where police are called to respond. Fragmentation of the behavioral health care system creates a revolving door where many residents with behavioral health challenges cycle in and out of the system, often accessing services via the 9-1-1 emergency system during a crisis episode. This work leverages ethnographic and participatory techniques to build a pathway map in order to represent and characterize the behavioral health crisis system in metropolitan Phoenix, Arizona, United States. Map findings illustrate that many nominally existing connections are functionally distant when viewed through the lens of a clinical handoff. The resulting pathway map can be used as a planning and confirmatory tool for community members, practitioners, and policymakers to address challenges in behavioral health and public safety.

Criticism does not constrain: testing for evidence of de-policing following the murder of George Floyd

PurposeFollowing the shooting of Michael Brown, much scholarly attention has been paid to the so-called “Ferguson effect” resulting from rhetoric that public scrutiny of the police will lead to de-policing. The present study tests this effect due to similar rhetoric that has re-emerged in public and media dialogue in response to Black Lives Matter protests following the killing of George Floyd in May 2020.Design/methodology/approachUsing Open Minneapolis' Police Use of Force dataset, the study employs interrupted time series analysis models of weekly use of force events against all citizens, as well as use of force against Black citizens specifically. Two models for each population are conducted due to data concerns: a set from January 2019 to June 2021, and a set from January 2019 to September 2020, with the week of George Floyd's death as the interruption point.FindingsBoth models using September 2020 as the cutoff show no statistically significant variance in police use of force against subjects overall or against Black citizens following the immediate aftermath of protests. However, both models using June 2021 as the cutoff demonstrate a statistically significant rise in use of force against both populations following the interruption point.Originality/valueThis study is among the first to examine de-policing following the George Floyd protests, and among the first to examine use of force rates beyond fatal force. Implications for research and practice are discussed, such as data availability and quality, as well as diverse perspectives surrounding de-policing and their implications for police practice.

Nuclear balance and the initiation of nuclear crises: Does superiority matter?

The nuclear competition school, an emerging theoretical perspective on the political effect of nuclear weapons, argues that a favorable nuclear balance can significantly reduce one’s expected costs of nuclear war and therefore affect the interaction between nuclear-armed states, such as deterrence and crisis outcomes. This new perspective also presents a wide array of empirical evidence demonstrating the significant effect of the nuclear balance of power on political outcomes, thereby challenging the theory of the nuclear revolution, which argues that the nuclear balance of power produces no meaningful effects on political outcomes because no state can escape costly nuclear destruction. Little attention, however, has been paid to systematically exploring the effect of the nuclear balance on the initiation of nuclear crises. This is surprising, given that observable factors, such as the nuclear balance, should have a powerful effect at the crisis initiation stage because countries can observe military balance and assess the costs and benefits of entering a crisis. This article tests a core argument of the nuclear competition school regarding the effect of the nuclear balance on the initiation of nuclear crises. With original data on strategic nuclear balance, my statistical analysis shows that having a superior nuclear arsenal than another nuclear-armed opponent does not lead to a reduced likelihood of nuclear crisis initiated by the opponent. These core findings hold after conducting a series of robustness tests with various measures of the balance of nuclear forces. They encourage us to reconsider the persuasiveness of the nuclear competition school and offer implications for US nuclear policy and force size.

Strategic Unpredictability: Assessing the Doctrine from Nixon to Putin

During the 2016 US presidential campaign, candidate Donald Trump suggested the United States could benefit from a more unpredictable foreign policy. The assassination of Iranian Major-General Qasem Soleimani by US forces in 2020 during the Trump administration may be the best recent example of this doctrine in action. Other American presidents, including John F. Kennedy, Richard Nixon and Bill Clinton, have applied it in different ways. Historical comparisons of its use in the Cuban Missile Crisis and the conflicts in Vietnam and Kosovo suggest that the expected liabilities of the strategy outweigh any likely gains. Russian President Vladimir Putin appears to be seeking to establish strategic unpredictability by threatening NATO with nuclear escalation should it interfere heavily in Russia’s war in Ukraine. This threat, however, has not deterred NATO from providing effective assistance to Ukraine. Policymakers should be deeply sceptical about the benefits of strategic unpredictability.

Implementation of flexible virtual microchannels based on optically induced dielectrophoresis

Micro-nano particle manipulation methods in liquid environments have been widely used in the fields such as medicine, biology and material science. Nevertheless, the methods usually rely on pre-prepared physical microfluidic channels. In this work, virtual electrodes based on the optically induced dielectrophoresis (ODEP) method were used as virtual microchannels instead of traditional physical microfluidic channels. Virtual microchannels with different shapes were implemented by the designs of projected light patterns, which made the virtual microchannels have great flexibility and controllability. The theory of ODEP was verified by simulation and analysis of electric field distributions. The relationship between the manipulation force and the alternating current (AC) voltage or the AC frequency exerted on the cells was assessed. The experimental results indicated that the manipulation force was increased with the increase of the AC voltage, and it was reduced with the increase of the AC frequency. Moreover, different virtual microchannels were designed to carry out the transportation, aggregation and sorting of yeast cells and rat basophilic leukemia cells (RBL-2H3 cells) and the survival rate of the cells was evaluated. This work shows that the virtual microchannels can be flexibly realized by ODEP in liquid environments.